WO2007026931A1 - Electrochemical machining method and electrochemical machining apparatus - Google Patents

Electrochemical machining method and electrochemical machining apparatus Download PDF

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Publication number
WO2007026931A1
WO2007026931A1 PCT/JP2006/317586 JP2006317586W WO2007026931A1 WO 2007026931 A1 WO2007026931 A1 WO 2007026931A1 JP 2006317586 W JP2006317586 W JP 2006317586W WO 2007026931 A1 WO2007026931 A1 WO 2007026931A1
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WIPO (PCT)
Prior art keywords
substrate
electrolytic
barrier layer
diffusion barrier
electrolytic processing
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Application number
PCT/JP2006/317586
Other languages
French (fr)
Japanese (ja)
Inventor
Akira Kodera
Itsuki Kobata
Original Assignee
Ebara Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ebara Corporation filed Critical Ebara Corporation
Priority to US11/991,356 priority Critical patent/US20090134036A1/en
Priority to JP2007533376A priority patent/JPWO2007026931A1/en
Publication of WO2007026931A1 publication Critical patent/WO2007026931A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F3/00—Electrolytic etching or polishing
    • C25F3/02—Etching
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
    • B23H5/00—Combined machining
    • B23H5/06—Electrochemical machining combined with mechanical working, e.g. grinding or honing
    • B23H5/08—Electrolytic grinding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
    • H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
    • H01L21/7684—Smoothing; Planarisation

Definitions

  • the present invention relates to an electrolytic processing method and an electrolytic processing apparatus, and in particular, for processing metal wiring of a semiconductor integrated circuit, it is disposed for embedding a spring metal in recesses such as trenches and via holes provided on the surface of a substrate such as semiconductor wafer.
  • the present invention relates to an electrolytic processing method and an electrolytic processing apparatus used for removing excess wiring metal layers and diffusion barrier layers after damascene plating and planarizing the surface of a substrate.
  • Copper wiring is embedded by plating copper in a via hole or trench provided in an insulating film on a substrate by plating, and CMP (chemical mechanical polishing) of a diffusion barrier layer provided in advance to prevent excessive copper and copper diffusion. It is generally formed by the damascene method of removing and flattening the surface.
  • This example has a low dielectric constant insulating layer as an insulating film.
  • the Si _N barrier layer 14 As shown in FIG. 1A, on the surface of the base 3 W having the lower layer 2 made of copper formed in the lower layer insulating film 10 and the wire 12 formed on the surface, the Si _N barrier layer 14, the first low dielectric constant insulation ( Upper layer insulating film 22 consisting of L o w-k) layer 16, second low dielectric constant insulating (L o w-k) layer 18 and hard mask 20 is deposited, and the inner part of upper layer insulating film 22 Then, via holes 24 and trenches 26 are formed by, for example, lithography and etching techniques.
  • Diffusion barrier layer 28 for preventing diffusion of copper is formed on the upper layer insulating film 22, and a seed layer 30 is formed on the diffusion barrier layer 28 as an electrolytic feed layer.
  • Diffusion barrier layer 28 W, T a / T a x N Y T i X N Y , W x N Y , W x S i Y (X, Y indicate arbitrary values depending on the alloy), T a x S i Y N z, T i x S i Y N Z (X, Y, Z can be any numerical value of an alloy) metal material such as and R u are generally used.
  • copper 32 is filled in the via holes 24 and the trenches 26 of the substrate W by plating or the like, and copper 32 is deposited on the hard mask 20.
  • CMP chemical mechanical polishing
  • the substrate W Of the outermost copper film (copper 32 and seed layer 30) the substrate W Of the outermost copper film (copper 32 and seed layer 30).
  • the copper 32 is removed to the same thickness of the diffusion barrier layer 28 and the same MS depth. That is, the surface of the copper 32 filling the trench 26 is positioned lower than the surface formed by the diffusion barrier layer 28 by approximately the thickness of the diffusion barrier layer 28.
  • the diffusion barrier layer 28 is separately polished so that the surface of the copper 32 filled (embedded) in the via holes 24 and the trench 26 and the surface of the hard mask 20 are substantially flush. Finish the polishing process. As a result, as shown in FIG. 1D, a wiring (upper layer wiring) 34 made of copper 32 is formed inside the upper layer insulating film 22.
  • the above “upper surface of the substrate” means, on the surface on which the metal wiring of the substrate is processed and formed, a recessed portion for metal wire embedding such as a trench or a via hole processed portion such a recessed portion
  • M means the surface of the substrate of the portion where the M portion is not processed although there is a portion that is not subjected to stress (the metal wiring is not embedded). Also, the portion where the above-mentioned recess is processed is called "the recess of the substrate”.
  • C VD Chemical Vapor Deposition
  • S i 0 2 dielectric constant k than film be a lower L o w- k material organic-inorganic material called using Proposed.
  • L o w- k material since the many lifting one porous pores to reduce the dielectric constant, mechanical strength is lower than the C VD- S i 0 2 film. Therefore, for example, when the copper film and the diffusion barrier layer are polished away by a CMP process, if the low-k material is positioned below the hard mask, the hard mask is peeled off from the low-k material.
  • the CMP polishing pressure at this time needs to be lower than that when polishing the conventional SiO 2 film. Lowering the polishing pressure is not preferable from the viewpoint of productivity because it causes a reduction in the polishing rate. Further, among the cost for CMP process, the ratio of the abrasive slurry (abrasive liquid in which the abrasive is dispersed in an aqueous solution) accounts for a high ratio, and the reduction of the abrasive slurry is desired.
  • the excess copper 32 such as copper 32 deposited on the hard mask 20 is removed, and an electrolyte is used instead of the abrasive slurry until the surface of the diffusion barrier layer 28 is exposed. It has been proposed to accelerate the processing of the copper 32 and the seed layer 30 exclusively by performing the electrolytic processing. The purpose of this method is to process only copper film, that is, copper 32 and seed layer 30 by electrolytic processing, and attempts have been made to carry out electrolytic processing including diffusion barrier layer 28. It is not the current situation.
  • tantalum It is a surface layer of titanium or tantalum metal generally used for the diffusion barrier layer 28
  • a dielectric film oxide film
  • this dielectric film blocks current. This is because electrolytic processing becomes difficult.
  • the oxide film over all the p H region (T a 2 0 5) is formed, as long as the oxide coating is a good adhesiveness dense with respect to the metal tantalum, tantalum (T a) can behave like a noble metal, and can be treated with HC 1, H 2 S 4 4 , H 2 PO 4 and HN O 3 or aqua regia other than hydrofluoric acid and concentrated aqueous solutions. It is almost completely corrosion resistant.
  • aprotic polar to roughen the surface of a human bone or artificial tooth root, a tantalum material or a niobium material used for a capacitor.
  • a method of electrolytic processing using an organic electrolyte in which anions are dissolved in a solvent (refer to JP-A-2003-730), or by using only a radiation source, tantalum pentoxide in a fluorine-based solution
  • a method e.g., Japanese Patent Application Laid-Open No. 6-4964 and the like are known. Disclosure of the invention
  • the processing pressure is increased in the conventional CMP in order to remove the copper 32 which is deposited over the entire substrate and with unevenness on the surface with a sufficient polishing rate. It was difficult to obtain sufficient flatness of the surface. That is, if the dishing is such that the cross section of the wiring is dished down, there is a problem such as an erosion in which the insulating film is also excessively polished together with the metal such as copper.
  • a Low-k material having a dielectric constant lower than that of a conventional C VD -S i 0 2 film.
  • the low-k material is configured to be porous, that is, contain a large number of holes, and its mechanical strength is lower than that of the conventional SiO 2 film.
  • the processing pressure in the CMP process must be reduced to a low value, which reduces the processing speed. Therefore, there is a problem with productivity and it is difficult to put it to practical use.
  • the solution is a solution containing a fluoride ion, which is generally used as a solution system that dissolves metals such as tantalum, titanium, tungsten, and ruthenium, which are metals that constitute the diffusion barrier layer.
  • a fluoride ion which is generally used as a solution system that dissolves metals such as tantalum, titanium, tungsten, and ruthenium, which are metals that constitute the diffusion barrier layer.
  • Slurry reduction is also desirable because of the high proportion of slurry in the cost of the MP process and the high cost of slurry-waste treatment.
  • the purpose of the invention is to provide an electrolytic processing method and an electrolytic processing apparatus capable of reducing the
  • the surface of a substrate is brought into contact with an electrolytic solution in which an electrolyte is dissolved in an organic solvent, and a potential is applied to the surface of the substrate to electrolytically process the surface.
  • the diffusion barrier layer Even if an electrolytic solution (aqueous solution) using water as a solvent is used and a positive potential is applied to the diffusion barrier layer in the aqueous solution to carry out electrolytic processing (electrostatic polishing or polishing) of the diffusion barrier layer, the diffusion barrier Many of the types of metals used in the layer are formed by applying a positive potential in a 7 K solution to form a passive oxide film on the surface of the diffusion barrier layer and not dissolving it in a solvent as metal ions. Is impossible. This is because oxygen in water molecules, oxygen generated by electrolysis, dissolved oxygen, etc. are present in the aqueous solution.
  • the processing (polishing) speed can be increased by increasing the potential applied to the diffusion barrier layer.
  • the theoretical voltage of water is 1.33 V, and applying a potential higher than this to the diffusion barrier layer is not preferable because water early is generated to lower the evaporation efficiency. Therefore, the upper limit of the processing (polishing) speed also remains low.
  • a passive oxide film is formed on the surface of the diffusion barrier layer when a positive potential is applied to the diffusion barrier layer in the electrolyte.
  • the diffusion barrier layer can be electrolyzed exclusively, or the wiring layer such as copper can be electrolyzed simultaneously with the diffusion barrier layer.
  • the removal of the diffusion barrier layer should be initiated even on a substrate in which excess copper metal is not completely removed and part of the excess copper film remains.
  • the electrolytic processing speed can be increased, but it is also necessary to consider the decomposition voltage of the solvent as described above.
  • the partial angle voltage of propylene carbonate is +3.7 V (based on a silver-silver ion reference electrode)
  • the potential applied to the surface of the substrate is preferably less than this value.
  • the constant potential means that the potential applied to the surface of the substrate is kept constant.
  • the electrolytic processing of the diffusion barrier layer of the semiconductor substrate can be suitably performed, and furthermore, the substrate is applied to the substrate in a state in which excess copper or the like is deposited on the surface of the substrate. Copper or the like can also be electrolytically processed by controlling the potential. As a result, electrolytic processing can be performed efficiently by performing electrolytic processing consistently to removal of the diffusion barrier layer following removal of excess copper and the like using the same electrolytic cell.
  • Examples of the electrolyte solution include a solution containing at least one of a fluoride ion, a chloride ion, a bromide ion, an iodine ion, a hexafluorophosphate ion, a tetrafluoroborate ion and a hexafluoroarsenic ion.
  • hexafluorophosphate ion is preferably used for electrolytic processing because it has a high effect of binding to the metal ion used in the diffusion barrier layer and dissolving it in a solvent.
  • organic solvent examples include at least one or more of propylene carbonate, ethylene carbonate and dimethylsulfoxide.
  • Propylene carbonate, ethylene carbonate and dimethyl sulfoxide are among organic solvents. It is also more preferably used because of its high dielectric constant and its high ability to dissolve the electrolyte.
  • the dissolution ability can be indicated, for example, by the dielectric constant of the solvent, and it is known that the higher the value of the dielectric constant, the higher the dissolution ability.
  • lithium hexafluoroborophosphate tetrabutylammonium hexafluorophosphate, tetramethylammonium hexafluorophosphate, tetrabutylammonium phosphate hexafluorophosphate, ammonium tetrafluoroborate, And at least one of lithium tetrafluoroborate.
  • the electrolyte provides ions that play the role of transporting electrons in the solution during electrolytic processing, and further has the property of chemically bonding to the metal to be subjected to the electrolytic processing, that is, the metal dissolved in the solvent.
  • the power to dissolve the metal in the solvent when performing electrolytic processing It is not necessary to keep the metal in the form of ions in the worm, but it is always necessary to combine with another substance and precipitate it in the solution. For this reason, a compound capable of binding to the metal ion is selected as the electrolyte.
  • the above-mentioned early solution of electric angle further contains at least one kind of heterocyclic compound having a triazole ring, a pyrrole ring, a pyrazonol ring, a thiazole ring or a idazole ring.
  • the wiring metal such as copper also contacts the electrolytic solution, and depending on the potential applied to the surface of the substrate, the wiring metal may be dissolved in the electrolytic solution.
  • the heterocyclic compound is generally referred to as a corrosion inhibitor or inhibitor, and contains oxygen, nitrogen and sulfur atoms. Then, by specifically adsorbing these atoms to the surface of the wiring metal, a substance that causes corrosion, that is, a substance that acts to dissolve the wiring metal in the electrolytic solution directly reacts with the metal to cause corrosion. It is possible to suppress (dissolving).
  • inhibitors need to be heterocyclic compounds which do not adsorb to the diffusion barrier layer, and may be previously contained in the electrolytic solution, or before the substrate is immersed in the electrolytic solution In the phase, it may be possible to pre-apply fins on the surface of the substrate.
  • the heterocyclic compound is a nitrogen-containing heterocyclic compound, and is a benzotriazole, a piro monole, a 3- (2-che di nore) 1 1-pyrazonole, a 2 petite nore midazone, 6- It is preferred that the acid be either thioguanein or trithiocyanuric acid. These substances adsorb specifically on the surface of the wiring metal made of copper or the like, but do not adsorb on the diffusion barrier layer. Therefore, the diffusion barrier layer is selectively electroprocessed can do.
  • the surface of a substrate having a barrier layer formed of tantalum, titanium, tantalum, ruthenium or a compound thereof is processed by electrolytic processing.
  • the electrolytic processing apparatus comprises: a substrate holding portion for holding a substrate; a processing tool having a processing surface for performing electrolytic processing on the surface of the substrate; and a voltage between the surface of the substrate and the processing tool. It has an electric power source to be applied, and an electrical angle? F which holds the electrolytic solution in which the electrolyte is dissolved in an organic solvent and brings the electrolytic solution into contact with the surface of the substrate and the processing surface of the processing tool.
  • the diffusion barrier layer that appears when the excess wiring metal is removed can be suitably removed (removed) .
  • the electrolyte is, for example, hexafluorophosphate.
  • the diffusion barrier layer can be more suitably removed by using hexaflurothioate as the electrolyte.
  • the electrolytic processing apparatus further comprises a control device for adjusting the value of the electric potential marked on the surface of the substrate.
  • An excess base metal removal step which is performed after the step of damascene embedding of the wiring metal in the recess of the substrate by controlling the value of ⁇ applied to the surface of the substrate, and the diffusion which is performed after that.
  • the removal process of the barrier layer can be continuously performed using the same electrolytic cell, which can simplify the processing process and shorten the processing time.
  • the diffusion barrier layer and the diffusion barrier layer are suppressed while the processing of the wiring metal is suppressed when the surface of the substrate (the finished surface of the metal shell) on which both the diffusion barrier layer and the wiring metal such as copper are exposed is polished flat.
  • FIG. 1A to 1D are cross-sectional views showing an example of copper wiring formation in the order of steps.
  • FIG. 2 is a view showing an outline of an electrolytic processing apparatus according to an embodiment of the present invention.
  • FIG. 3 is a step diagram showing an example of copper formation in the order of steps.
  • FIG. 4 is a plan view showing an outline of an electrolytic processing apparatus according to another embodiment of the present invention.
  • FIG. 5 is a front elevational view of FIG.
  • FIG. 6 is a photograph of the surface of sample 1 after electrolytic processing in Example 1.
  • FIG. 7 is a view showing a cross-sectional profile of Sample 1 after electrolytic processing in Example 1.
  • FIG. 8 is a photograph of the surface of Sample 1 after electrolytic processing in Example 2.
  • FIG. 9 is a view showing a cross-sectional profile of Sample 1 after electrolytic processing in Example 2.
  • FIG. 1B a substrate in which copper 32 is deposited on the surface of the hard mask 20 via the diffusion barrier layer 28 while buried in the via holes 24 and the trenches 26 is performed.
  • the copper film (seed layer 30 and copper 32) as an excess wiring metal of the substrate W and the diffusion barrier layer 28 are polished and removed, as shown in FIG. 1D.
  • An example in which a copper 32 wiring 34 is formed in the inside of 2 will be shown.
  • FIG. 2 shows an electrolytic processing apparatus according to an embodiment of the present invention applied to an electrolytic polishing apparatus.
  • This electrolytic processing apparatus is an electrolytic processing apparatus designed to feed power to a conductor such as copper 32 or a diffusion barrier layer 28 provided from the peripheral portion of the substrate W to the surface (surface to be machined).
  • a conductor such as copper 32 or a diffusion barrier layer 28 provided from the peripheral portion of the substrate W to the surface (surface to be machined).
  • a disk-like substrate holding portion 40 for holding the substrate W detachably with the surface facing upward.
  • the substrate holding unit 40 rotates (rotates) along with the driving of the motor for rotation 42.
  • a seal ring 44 is disposed, which is in pressure contact with the peripheral portion of the substrate W held by the substrate holding unit 40 to seal the peripheral portion.
  • the outer surface of the seal ring 44 contacts the peripheral edge of the substrate W and the surface A feed electrode 50 for feeding a conductive film such as copper 32 is provided.
  • the feed electrode 50 is connected to a weir 3 5 5 a extending from the anode of the power supply 52.
  • An electrolytic solution supply pipe 54 for supplying an electrolytic solution 48 to the formed electrolytic cell 46 is disposed. Although not shown, the electrolytic solution in the electrolytic cell 46 after being subjected to the electrolytic treatment is sucked and removed through the vertically movable suction pipe.
  • An electrode portion 58 is disposed above the substrate holding portion 40, and the electrode portion 58 is vertically provided at a free end of a swing arm 60 which can swing in the horizontal direction.
  • the swinging arm 60 moves up and down with the drive of the up and down movement motor 62 and is connected to the upper end of a swing shaft 66 which rotates with the drive of the swing motor 64.
  • the electrode portion 58 rotates (rotates) along with the driving of the hollow motor 68 attached to the free end of the swing arm 60.
  • a counter electrode 70 is provided as a processing tool which is a processing surface for releasing the lower surface and performing electrolytic processing.
  • the counter electrode (processing tool) 70 is made of, for example, platinum, and the counter electrode 70 is a slip ring which extends from the cathode of the power source 52 and passes through a hollow portion provided on the swing shaft 66. 2, and the wire 55b passing through the hollow portion of the hollow motor 68 from this slip ring 72 is connected.
  • a controller 74 is provided which adjusts (controls) the voltage applied between the feed electrode 50 and the counter electrode 70.
  • the electrolyte solution 48 As the electrolyte solution 48, a solution in which an electrolyte is dissolved in an organic solvent is used. Thus, by using an organic solvent instead of water as a solvent, a passive acid film is formed on the surface of the diffusion barrier layer when a positive potential is applied to the diffusion barrier layer in the electrolytic solution.
  • the diffusion barrier layer can be subjected to electrolytic processing (electrolytic polishing) in such a manner that the metal constituting the diffusion barrier layer becomes ions and dissolves in the electrolytic solution.
  • the organic solvent generally has a high decomposition voltage, for example, the decomposition voltage of propylene carbonate is 6.7 V, a higher voltage should be applied to the diffusion barrier layer to sufficiently increase the electrolytic processing speed. Can.
  • organic solvent for example, acetal, acetonitrile, 1,2-dichloroethane (10. 1), sulfuryl chloride (10), thionyl chloride (9.2), acetyl chloride (15.8), tetrachloroethylene carbonate (9 .2) Benzyl chloride (23),-Tromethane (36), Dichloroethylene carbonate (31.6),-Benzene benzene (34.8), Acetic anhydride (20.7), Oxy phosphorus chloride (14) , benzonitrile (25.2), Okishi selenium chloride (46), Asetonitoriru (38), sulfolane (4 2), propylene carbonate (69), cyanide base Njiru 8.4), ethylene sulfates eye preparative (41) , Isobutyric acid ditolyl (20.4), propio-trinole (27.7), ethyl methyl carbonate, ethylene carbonate (89.1), dimethyl carbonate,
  • the values in Katsuko represent the dielectric constant.
  • propylene carbonate, ethylene carbonate and dimethyl sulfoxide are more preferably used because they have high dielectric constants and high ability to dissolve the electrolyte.
  • electrostatic 1H "Ru Anion fluorine Ion, chlorine ion, bromine ion, iodine ion, PF 6 - (to Kisafuruoro Ion phosphate), BF 4 - (Tetorafuruo port borate ion), A s F 6 - ( An alkali metal salt such as hexafluoroarsenic ion), ammonium salt, tetraalkyl ammonium salt, etc.
  • lithium hexafluorophosphate, tetrafluoroammonium phosphate, hexafluorophosphate, hexafluoromouth examples thereof include tetramethyl ammonium phosphate, hexabutyl tetrabasic ammonium, tetrafluorinated ammonium, lithium tetrafluoroborate, etc.
  • concentration of the electrolyte is generally 0.01 to 30% by mass. Preferably, it is 0.1 to 10% by mass.
  • An inhibitor composed of a heterocyclic compound containing oxygen, nitrogen and sulfur atoms is added to the electrolytic solution 48, as necessary.
  • the inhibitor is, for example, a nitrogen-containing heterocyclic compound and has a triazole ring, a pyrrolo nore ring, a pyrazonore ring, a thiazole ring, and an imidazole ring.
  • benzotriazole pyronole, 3- (2-cheunole), 1-pyrazonole, 2-peptoleimidazonore, 6-thiogguanin, trithiocyanuric acid, benzotriazole, tolyl triazole, 6-thiogguanine, 2- Examples include benzothiazole thiol, trithiocyanuric acid, and N, N-jetyldithiocarbamic acid sodium.
  • alkylamines, alanthiols, 1-hexyne Monools etc. can be used as inhibitors.
  • a predetermined amount of electrolytic solution 48 is supplied from the electrolytic solution supply pipe 54 into the electrolytic cell 46 formed on the surface of the substrate W and held. Thereafter, by moving the electrode portion 5 8 until immediately above the substrate holder 4 0, further lowered, the electrolytic solution 4 8 the underside of the counter electrode 7 0 is held in the electrolytic bath 4 6 of the electrode portion 5 8 Stop falling of the electrode unit 5 8 when reaching the predetermined position where it contacts.
  • a predetermined voltage is applied between the feeding electrode 50 and the counter electrode 70, with the feeding electrode 50 being the anode and the counter electrode 70 being the cathode, at the same time. If necessary, the substrate holding unit 40 and the electrode unit 58 are rotated (rotated), and the electrode unit 58 is swung horizontally (in a direction parallel to the processing surface of the substrate W) to diffuse Paria layer 28 Electrolytic polishing (electropolishing) is performed.
  • a potential controlled at a predetermined value less than the decomposition voltage of the organic solvent of the electrolytic solution 48 is applied between the feeding electrode 50 and the counter electrode 70, thereby performing constant potential control type electrolysis.
  • the processing For example, since the ⁇ voltage of propylene carbonate is +3.7 V (based on a silver-silver ion reference electrode), when propylene carbonate is used as the organic solvent of the electrolytic solution 48, the potential applied to the surface of the substrate is Below this value, the organic solvent (propylene carbonate) is decomposed to prevent the processing efficiency from decreasing.
  • the constant potential means that the potential applied to the surface of the substrate is kept constant.
  • the diffusion barrier layer 28 is exclusively subjected to the electrolytic processing by controlling the electric potential marked on the surface of the substrate, or the wiring barrier such as copper is simultaneously subjected to the electrolytic processing together with the diffusion barrier layer 28. It can also be done. As a result, for example, the diffusion barrier layer 28 can be removed even on a substrate in which excess copper metal or the like has not been completely removed and a part of the excess copper film remains. It can start.
  • the efficiency of the electrolytic processing is determined not only by the electrolyte solution 48 used but also by the conditions of the power supply, for example, the period of pulse voltage value / panorless, duty-to-duty ratio, diffusion barrier layer 28 serving as an anode and counter electrode 7 serving as a cathode. It varies depending on the distance between 0 and the ratio of the surface area of the exposed metal wiring layer to the total surface area of the 3 ⁇ 4 W work surface.
  • the substrate W Since the entire surface (work surface) acts as an anode, in the state where the diffusion parlia layer 28 covers the area excluding the surface of the metal base S / swell layer embedded in the recess of the substrate such as trench 26 etc.
  • the application of the HE between the feeding electrode 50 and the counter electrode 70 is released to stop the rotation (rotation) of the substrate holding portion 40 and the electrode portion 58. Then, the electrolytic solution 48 in the electrolytic cell 46 is removed, and the substrate after electrolytic processing is transported to the next step.
  • an indirect power supply system is adopted.
  • the indirect feeding method is a method in which the anode and the cathode are made to face the surface (the surface to be processed) of the substrate without contact, and the substrate is processed by applying an electric potential between the anode and the cathode.
  • a part of the electrolytic solution absorbs moisture and oxygen in the air to be decomposed, which may cause a problem that oxidation of the processing surface progresses. In such a case, such an adverse effect can be prevented by performing the electrolytic processing in an inert gas atmosphere.
  • a via hole / layer 24 and a trench 26 are formed in the upper insulating film 22 by, for example, a known lithography / etching technique (step 1).
  • a diffusion barrier layer 28 for preventing copper diffusion into the first low dielectric constant insulating layer 16 and the second low dielectric constant insulating layer 18 is formed thereon (step 2).
  • a seed layer 30 is formed thereon as a feed layer for electrolytic plating (step 3).
  • the diffusion barrier layer 28 is made of, for example, a film such as TaZTa mixed film, TiN, WN, SiTN, Ru, etc. deposited by sputtering method or ALD (Atomic Layer Deposition) method.
  • the layer 30 is made of, for example, a copper film deposited by sputtering or the like. If the diffusion barrier layer 28 is Ru and no seed layer is required, step 3 is omitted, and steps 2 to 4 are performed.
  • copper 32 is formed as a wiring metal by electrolytic plating (damascene plating) on the surface of the substrate (step 4).
  • electrolytic plating (damascene plating)
  • the via holes 24 and the trenches 26 are filled with copper 32 and also on the outermost surface of the substrate W.
  • Copper 32 is deposited, and the low dielectric constant insulating layers 16 and 18 constituting the upper insulating film 22 and the hard mask 20 are covered with copper 32 as a wiring metal.
  • Electrolytic plating (damascene plating) There are irregularities on the surface of copper 32 at the end of the process.
  • silver or an alloy of copper and silver may be used as the cold spring metal.
  • the seed layer 30 and copper 32 are integrated and function as wiring after the device is completed. Excess copper 32 is removed by CMP or electrolytic processing (electrolytic polishing). This removal is performed integrally for the seed layer 30 and the copper 32.
  • step 5 the surface of the 3 ⁇ 4 W is subjected to electrolytic corrosion using CMP or an aqueous solution as an electrolytic solution (step 5), whereby extra copper film on the diffusion barrier layer 2 8 is obtained as shown in FIG. 1C.
  • the copper 32 and the seed layer 30 are removed, and the surface of the copper 32 embedded in the trench 26 is made flush with the hard mask 20.
  • Removal of the copper film is achieved by electrolytic composite polishing, which causes relative movement while bringing the substrate and polishing member (eg, polishing pad) into contact with each other while applying a voltage between the substrate and the counter electrode through the electrolytic solution. You may go.
  • substrate and polishing member eg, polishing pad
  • the above process can be performed by the same process as the conventional process, and in the case of electrolytic processing for removing the copper film (copper 32 and seed layer 30), electrolytic processing using the organic solvent shown in FIG. It can be done using the device.
  • the subsequent removal of the unnecessary diffusion barrier layer 28 on the hard mask 20 (step 6) is performed using the electrolytic processing apparatus of the present invention shown in FIG.
  • the diffusion barrier layer on the surface of the substrate W is prepared by dissolving the electrolyte in the organic solvent and optionally adding the inhibitor (corrosion inhibitor) to the electrolyte solution 48 of the electrode reservoir 46.
  • a voltage is applied between the diffusion barrier layer 28 and the counter electrode 70 by bringing the diffusion barrier layer 28 positive and the counter electrode 70 negative.
  • Selectively polish away the diffusion barrier layer 28 without removing the film step 6 a).
  • a wire 34 made of copper is formed inside the upper layer insulating film 22.
  • the diffusion barrier layer 28 on the surface of the base feW is brought into contact with the electrolytic solution, the diffusion barrier layer 28 on the surface of the base W is previously applied by coating or the like in a solution or in the gas phase.
  • electrolytic processing may be performed using an electrolytic solution that does not necessarily contain an inhibitor (Step 6 c).
  • CMP is performed with an extremely low pressure (for example, less than 1 si (about 69 h P a)) that does not cause any defects in the substrate to Hard mask (insulation film) which completely removes the remaining diffusion barrier layer 28 without removing it (step 7), thereby completely removing the diffusion barrier layer 28.
  • Hard mask insulation film
  • the inhibitor covering 34 was also removed, and the processing was completed with the copper exposed.
  • the surface of the substrate W is brought into contact with the electrolyte solution 48 to electrolytically process the diffusion barrier layer 28 of the surface of the 3 ⁇ 4 ⁇ 4 W.
  • the mechanical action of the polishing member is added to the surface of the substrate to polish the surface. You may do it. Due to the material of the diffusion barrier layer and the thickness unevenness of the diffusion barrier layer, when the electrolytic processing is performed until the insulating film is exposed, the diffusion barrier layer may remain on the surface of the insulating film in stripes. In the electrolytic processing, generally, the processing phenomenon does not occur unless the electrical conduction can be secured.
  • the diffusion barrier layer can not be removed unless the electrical continuity can be ensured in the remaining diffusion barrier layer. Therefore, if the diffusion barrier layer remains in stripes on the surface of the insulating film, the diffusion barrier layer can not be removed by the electrolytic processing in which the surface of the base is in contact with the electrolytic solution 48. Even in such a case, the diffusion barrier layer is subjected to the electrolytic processing while adding the function of the polishing member to the diffusion barrier layer, without leaving the diffusion barrier layer on the insulating film. , Removal of diffusion barrier layer can be performed.
  • An electrolytic processing apparatus electrolytic polishing apparatus according to another embodiment of the present invention, in which a surface is polished by a die, is shown.
  • This electrolytic processing apparatus comprises: a rotatable polishing table 86 having a counter electrode 82 connected to the cathode of W 80 and a polishing member 8 4 on its upper surface; It has a flexible top ring 8 8 and a dresser 90 and an absorber 92 that condition the surface of the polishing member 84. Above the polishing tape notch 8 6, an electrolyte solution supply unit 94 having a large number of electrolyte solution supply ports 94 a for supplying the electrolyte solution to the polishing member 84 is disposed.
  • the dresser 90 has a plurality of circular projections 90a formed of hard material such as diamond pellet etc., brushes, etc., ringed on the lower surface of the peripheral portion under vertical movement and rotational self-rotation.
  • the die It is configured to be attached to the although not shown, the die It is also possible to use a dresser in which diamond abrasive grains are arranged in a ring shape on the lower surface of the peripheral portion. Also, the diameter of the dresser 90 shown in Fig. 5 is almost the same size as the tape notch radius. For example, in addition to rotation in the form of a small disk with a diameter of about ⁇ 100, it is good even if the polishing pad surface is rocked. Les. In this case, diamond abrasive is placed on the entire surface of the pad contact surface of the disk.
  • the polishing member 84 is composed of, for example, a polishing pad made of foamed polyurethane resin, and lattice grooves or concentric grooves are formed on the polishing surface 8 4 a of the surface (upper surface) of the polishing member (polishing pad) 84. It is done. Also, in order to ensure electrical continuity between the counter electrode 82 and the 3 ⁇ 4 ⁇ 4 ⁇ 4 W via the electrolytic solution supplied to the polishing member 84, inside of the polishing member 84, there are a plurality of through holes that penetrate vertically. It is formed.
  • the polishing member 84 is brought into contact with the polishing surface 8 4 a of the polishing member 84, and the substrate W and the polishing member 84 are moved relative to each other (here, both are rotational motions).
  • the electrolytic solution is supplied to the upper surface of 84, and a voltage is applied between the counter electrode 82 and the diffusion barrier layer 28 on the substrate surface to remove the diffusion barrier layer 28 on the substrate surface.
  • power is supplied to the diffusion barrier layer 28 on the substrate surface through the feed electrode 96.
  • the polishing pressure is smaller than that of the ordinary CMP (for example, less than 1 psi (about 69 h P a)).
  • the polishing surface 8 4 a of the polishing member 84 may be conditioned using a dresser 90 a.
  • the diffusion barrier layer 28 is removed by supplying the electrolytic solution while the substrate W and the polishing member (polishing pad) 84 are moved relative to each other, This is performed while applying a voltage between the counter electrode 82 and the diffusion barrier layer 28 on the substrate surface.
  • the voltage value that is marked during this polishing may be varied between the initial and the end of the polishing of the diffusion Paria layer 28.
  • the application of the voltage is stopped and the diffusion barrier layer 28 remaining only by the mechanical action of the polishing member 84 is removed. It may be removed, and this can prevent the remaining diffusion barrier layer 28 from being unable to be removed because the remaining diffusion barrier layer 28 can not be electrically conducted. Furthermore, in order to remove the inhibitor adsorbed on the wiring metal after the removal of the diffusion barrier layer 28, the application of the voltage may be stopped and the processing by only the mechanical action of the polishing member 84 may be performed.
  • Abrasive grains may be mixed in an amount of 10% or less in the electrolytic solution in the case of electrolytic composite polishing, whereby the uniformity of mechanical action increases B.
  • the present invention is suitably used for removing a diffusion barrier layer by, in particular, dissolving the metal constituting the diffusion barrier layer with an organic electrolyte in the process of forming 12 springs on a substrate such as semiconductor wafer.
  • a metal consisting of tantalum, titanium, tungsten, ruthenium or one of their compounds is generally used. Specific examples of this compound include, for example, tantalum nitride, titanium nitride, tungsten nitride and silicon tantalum nitride.
  • a silicon oxide film piece in which a Ta N sputtering film (film thickness of about 200 nm) having a uniform film thickness was formed on the surface was prepared. Then, the Ta / TaN sputtered film on the surface of this sample 1 was polished and removed using the electrolytic processing apparatus shown in FIG. The following composition was used at room temperature as an electrolytic solution.
  • Electrolyte lithium hexafluorophosphate
  • the electrolytic solution was prepared by placing at a normal temperature into a vessel filled with an appropriate amount of propylene so that each of the above six types of electrolytes had a molar concentration of 0.5 with respect to the appropriate amount of propylene carbonate as an organic solvent. The inhibitor was added at 0.1% by weight.
  • the voltage of the organic solvent must be taken into consideration when selecting the voltage, the voltage was adjusted so as not to exceed the decomposition voltage of 3.7 V (vs A g / A g + ) of propylene carbonate.
  • the Ta / TaN sputtering film was electroprocessed at 1 V (VsAg / Ag +) for about 10 minutes while masking a part of the Ta / TaN sputtering film. Show the picture after. As shown in FIG. 6, the portion (masking portion) where the masking tape is attached on the sample 1 on the right side of the curved boundary shown in the center of the photograph is not processed because it is not in contact with the electrolyte. On the left side (electrolyzed portion), it can be seen that the underlying silicon oxide film is exposed by electrolytic processing.
  • FIG. 7 shows a cross-sectional profile when the surface of sample 1 after electrolytic processing is measured by a stylus type step difference measuring device.
  • the curve drawn in the figure represents the cross-sectional shape of the sample 1, and the portion (masking portion) not processed by applying the masking tape is the portion (electrolytic processing) on the left side of FIG.
  • the electroprocessed part is shown on the right side of FIG.
  • a silicon wafer piece having a copper-clad film with a uniform film thickness (film thickness of about 1.5 ⁇ ) formed on the surface was prepared as Sample 2. Then, electrolytic processing was carried out under the same conditions as in Example 1 (about 10 minutes under IV ( VS A g / A g + )) to polish away the copper-clad film on the surface of Sample 2.
  • FIG. 8 shows a photograph of sample 2 after electrolytic processing. It can be seen from FIG. 8 that the underlying silicon film is not exposed at the portion (masking portion) which is not processed by applying the masking tape (masking portion) and the portion which contacts the electrolytic solution (electrolytic portion).
  • FIG. 9 shows a cross-sectional profile of sample 2 after electrolytic processing. From FIG. 9, it is found that the portion (masking portion) and the processing surface (electrolytic processing portion) where the masking tape is attached and not in contact with the processing fluid is almost on the same surface, and the processing of the copper plating film is suppressed. Recognize. Industrial applicability
  • damascene plating for burying wiring metal in recesses such as trenches and via holes provided on the surface of a substrate such as a semiconductor wafer is performed when processing metal wiring of a semiconductor integrated circuit. It is later used to planarize the surface of the substrate by removing excess ⁇ 2 / wire metal layer and diffusion barrier layer.

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Abstract

This invention provides an electrochemical machining method that, while suppressing the working of a wiring metal, can preferentially work a diffusion barrier layer, and consequently can omit CMP or can reduce working pressure in CMP. The electrochemical machining method comprises bringing the surface of a substrate (W) into contact with an electrolysis solution (48), prepared by dissolving an electrolyte such as lithium hexafluorophosphate in an organic solvent such as propylene carbonate and optionally adding an inhibitor of a heterocyclic compound, and applying a positive potential regulated, for example, to a value below the decomposition voltage of an organic solvent to the surface of the substrate (W) to electrochemically machine the surface of the substrate (W).

Description

明細書 電解加工方法及び電解加工装置 技術分野  Method and apparatus for electrolytic processing
本発明は、電解加工方法及び電解加工装置に関し、特に半導体集積回路の金属配 線の加工に際し、半導体ゥエーハ等の基板の表面に設けたトレンチやビアホール等 の凹部に配 f泉金属埋め込みの為のダマシンめつきを行つた後に、過剰な配線金属層 及び拡散バリァ層を除去し基板の表面を平坦化するのに使用される電解加工方法 及び電解加工装置に関する。 背景技術  The present invention relates to an electrolytic processing method and an electrolytic processing apparatus, and in particular, for processing metal wiring of a semiconductor integrated circuit, it is disposed for embedding a spring metal in recesses such as trenches and via holes provided on the surface of a substrate such as semiconductor wafer. The present invention relates to an electrolytic processing method and an electrolytic processing apparatus used for removing excess wiring metal layers and diffusion barrier layers after damascene plating and planarizing the surface of a substrate. Background art
半導体集積回路の配線金属材料として、 従来、 ァゾレミニゥムゃアルミニゥム合 金が一般に使われてきたが、 昨今では電気抵抗率が低くエレクロトマイグレーシ ヨン耐性が高い銅が用いられてきている。 銅配線は、 基板上の絶縁膜内に設けた ビアホーノレやトレンチ内にめっきによって銅を埋め込み、 過剰の銅や銅の拡散を 防止するために予め設けられた拡散バリア層を CMP (化学機械的研磨） により 除去し表面を平坦化するダマシン法により一般に形成される。  Conventionally, aluminum alloy has generally been used as a wiring metal material for semiconductor integrated circuits, but recently copper having a low electric resistivity and high resistance to electromigration has been used. Copper wiring is embedded by plating copper in a via hole or trench provided in an insulating film on a substrate by plating, and CMP (chemical mechanical polishing) of a diffusion barrier layer provided in advance to prevent excessive copper and copper diffusion. It is generally formed by the damascene method of removing and flattening the surface.
図 1 A乃至 1 Dを参照して、 銅配線形成例を説明する。 この例は、 絶縁膜とし て低誘電率絶縁層を有している。 図 1 Aに示すように、 下層絶縁膜 1 0の内部に 銅からなる下層酉 2；線 1 2を形成した基 ¾Wの表面に、 S i _Nバリア層 1 4、 第 1低誘電率絶縁 (L o w- k ) 層 1 6、 第 2低誘電率絶縁 (L o w- k ) 層 1 8 及びハードマスク 2 0からなる上層絶縁膜 2 2を堆積し、 この上層絶縁膜 2 2の 内部に、 例えばリソグラフィ ■エッチング技術により、 ビアホール 2 4とトレン チ 2 6を形成する。 そして、 上層絶縁膜 2 2の上に銅の拡散を防止する拡散パリ ァ層 2 8、 更に拡散バリア層 2 8の上に電解めつきの給電層としてシ ド層 3 0 を形成する。 拡散バリア層 2 8には、 W、 T a /T a xNY T i XNY、 WXNY、 WX S i Y (X， Yは、 合金により任意の数値を示す）、 T a x S i YNz、 T i x S i YNZ (X, Y, Zは、 合金により任意の数値） や R uなどの金属材料が一般に 用いられる。 An example of copper wiring formation will be described with reference to FIGS. 1A to 1D. This example has a low dielectric constant insulating layer as an insulating film. As shown in FIG. 1A, on the surface of the base 3 W having the lower layer 2 made of copper formed in the lower layer insulating film 10 and the wire 12 formed on the surface, the Si _N barrier layer 14, the first low dielectric constant insulation ( Upper layer insulating film 22 consisting of L o w-k) layer 16, second low dielectric constant insulating (L o w-k) layer 18 and hard mask 20 is deposited, and the inner part of upper layer insulating film 22 Then, via holes 24 and trenches 26 are formed by, for example, lithography and etching techniques. Then, a diffusion barrier layer 28 for preventing diffusion of copper is formed on the upper layer insulating film 22, and a seed layer 30 is formed on the diffusion barrier layer 28 as an electrolytic feed layer. Diffusion barrier layer 28: W, T a / T a x N Y T i X N Y , W x N Y , W x S i Y (X, Y indicate arbitrary values depending on the alloy), T a x S i Y N z, T i x S i Y N Z (X, Y, Z can be any numerical value of an alloy) metal material such as and R u are generally used.
そして、 図 1 Bに示すように、 基板 Wのビアホール 2 4及ぴトレンチ 2 6内に めっき等で銅 3 2を充填するとともに、 ハードマスク 2 0の上に銅 3 2を堆積す る。 その後、 研^^スラリーを用いた化学機械的研磨 (CMP) により、 基板 W の最表面の銅膜 （銅 3 2及ぴシード層 3 0 ) を除去する。 この時、 図 1 Cに示す ように、 トレンチ 2 6を埋め込んでいる銅 3 2にあっては、 拡散パリア層 2 8の 厚さと同禾 MSの深さまで銅 3 2を除去する。 つまり、 トレンチ 2 6を埋め込んで いる銅 3 2の表面が、 拡散バリア層 2 8が形成する表面よりもほぼ拡散バリア層 2 8の厚さ分だけ低い位置となるようにする。 続いて、 ビアホール 2 4及びトレ ンチ 2 6に充填させた （埋め込んだ） 銅 3 2の表面とハードマスク 2 0の表面と がほぼ同一平面になるように、 拡散バリア層 2 8を別途研磨して研磨工程を終了 する。 これにより、 図 1 Dに示すように、 上層絶縁膜 2 2の内部に銅 3 2からな る配線 （上層配線） 3 4を形成する。 Then, as shown in FIG. 1B, copper 32 is filled in the via holes 24 and the trenches 26 of the substrate W by plating or the like, and copper 32 is deposited on the hard mask 20. After that, the chemical mechanical polishing (CMP) using a polishing ^^ slurry, the substrate W Of the outermost copper film (copper 32 and seed layer 30). At this time, as shown in FIG. 1C, in the case of the copper 32 filling the trench 26, the copper 32 is removed to the same thickness of the diffusion barrier layer 28 and the same MS depth. That is, the surface of the copper 32 filling the trench 26 is positioned lower than the surface formed by the diffusion barrier layer 28 by approximately the thickness of the diffusion barrier layer 28. Subsequently, the diffusion barrier layer 28 is separately polished so that the surface of the copper 32 filled (embedded) in the via holes 24 and the trench 26 and the surface of the hard mask 20 are substantially flush. Finish the polishing process. As a result, as shown in FIG. 1D, a wiring (upper layer wiring) 34 made of copper 32 is formed inside the upper layer insulating film 22.
前記 "基板の最表面" とは、 基板の金属配線が加工形成される側の表面におい ては、 トレンチやビアホールなどの金属 線埋め込み用の凹部力 s加工されている 部分ど、 そのような凹部力 ¾ロェされていない (金属配線を埋め込まない)部分とが あるが、 前記 M部が加工されていない部分の基板の表面を意味する。 また前記凹 部が加工されている部分を "基板の凹部" と言う。  The above “upper surface of the substrate” means, on the surface on which the metal wiring of the substrate is processed and formed, a recessed portion for metal wire embedding such as a trench or a via hole processed portion such a recessed portion The term “M” means the surface of the substrate of the portion where the M portion is not processed although there is a portion that is not subjected to stress (the metal wiring is not embedded). Also, the portion where the above-mentioned recess is processed is called "the recess of the substrate".
絶縁材 （層間絶縁材） として、 従来の C VD (Chemical Vapor Deposition) - S i 02膜よりも誘電率 kが更に低い L o w- k材と呼ばれる有機 ·無機材料を使 用することが提案されている。 L o w- k材は、誘電率を下げるため空孔を多く持 つ多孔質からなるため、機械的強度が C VD- S i 02膜に比べて低い。このため、 例えば、 CMPプロセスによって、 銅膜及ぴ拡散バリア層を研磨除去する時に、 ハードマスクの下層に L o w- k材が位置すると、 ハードマスクが L o w- k材か ら剥離し易くなり、 このハードマスクの剥離を防止するには、 この時の CMP研 磨圧力を従来の S i 02膜を研磨する時よりも低圧力にする必要がある。 研磨圧 力を低くすることは、 研磨速度の低下をもたらすため、 生産性からは好ましくな い。 また CM P工程にかかる費用の中では、 研磨剤スラリー （研磨剤を水溶液中 に分散させた研磨液） の占める割合が高く、 研磨剤スラリーの低減が望まれてい る。 As an insulating material (interlayer insulation), conventional C VD (Chemical Vapor Deposition) - S i 0 2 dielectric constant k than film be a lower L o w- k material organic-inorganic material called using Proposed. L o w- k material, since the many lifting one porous pores to reduce the dielectric constant, mechanical strength is lower than the C VD- S i 0 2 film. Therefore, for example, when the copper film and the diffusion barrier layer are polished away by a CMP process, if the low-k material is positioned below the hard mask, the hard mask is peeled off from the low-k material. In order to prevent this hard mask peeling, the CMP polishing pressure at this time needs to be lower than that when polishing the conventional SiO 2 film. Lowering the polishing pressure is not preferable from the viewpoint of productivity because it causes a reduction in the polishing rate. Further, among the cost for CMP process, the ratio of the abrasive slurry (abrasive liquid in which the abrasive is dispersed in an aqueous solution) accounts for a high ratio, and the reduction of the abrasive slurry is desired.
そこで、 ハードマスク 2 0の上方に堆積された銅 3 2などの過剰の銅 3 2を除 去し、 拡散バリァ層 2 8の表面が露出するまで、 研磨剤スラリ一の代わりに電解 液を使用した電解加工を行うことで、 専ら銅 3 2及びシード層 3 0の加工を促進 することが提案されている。 し力 し、 この方法は、 銅膜、 即ち銅 3 2及ぴシード 層 3 0のみを電解加工で加工することを目的としており、 拡散バリア層 2 8を含 めて電解加工する試みは未だなされていないのが現状である。  Therefore, the excess copper 32 such as copper 32 deposited on the hard mask 20 is removed, and an electrolyte is used instead of the abrasive slurry until the surface of the diffusion barrier layer 28 is exposed. It has been proposed to accelerate the processing of the copper 32 and the seed layer 30 exclusively by performing the electrolytic processing. The purpose of this method is to process only copper film, that is, copper 32 and seed layer 30 by electrolytic processing, and attempts have been made to carry out electrolytic processing including diffusion barrier layer 28. It is not the current situation.
それは、 拡散バリア層 2 8に一般に用いられるチタンやタンタル系金属の表層 には、 拡散バリア層 2 8が正電位に印加された場合に、 均一な厚さの耐食†生のあ る誘電体膜 （酸化物膜） が形成され、 この誘電体膜が電流を遮るため、 電解加工 が困難となるためである。 特にタンタルの表面には、 水溶液中においては、 全て の p H領域にわたり酸化皮膜（T a 2 05)が形成され、 この酸化皮膜が金属タンタ ルに対して密着性良く緻密である限り、 タンタル (T a ) は、 貴金属のように振 舞うことができ、 弗化水素酸や濃厚アル力リ溶液以外の H C 1、 H 2 S〇4、 H2 P O 4及ぴ HN O 3また王水に対しても殆ど完全に耐食的となる。 It is a surface layer of titanium or tantalum metal generally used for the diffusion barrier layer 28 When the diffusion barrier layer 28 is applied to a positive potential, a dielectric film (oxide film) having a uniform thickness is formed, and this dielectric film blocks current. This is because electrolytic processing becomes difficult. Especially on the surface of the tantalum in the aqueous solution, the oxide film over all the p H region (T a 2 0 5) is formed, as long as the oxide coating is a good adhesiveness dense with respect to the metal tantalum, tantalum (T a) can behave like a noble metal, and can be treated with HC 1, H 2 S 4 4 , H 2 PO 4 and HN O 3 or aqua regia other than hydrofluoric acid and concentrated aqueous solutions. It is almost completely corrosion resistant.
一般的に、 このような耐食性のあるタンタルを電解加工する手法としては、 人 口骨や人工歯根、 コンデンサ一に用いられるタンタル材料やニオブ材料の表面を 粗面化するために非プロトン性の極性溶媒にァニオンを溶解した有機電解液を用 いて電解加工する方法 （特開 2 0 0 3— 7 3 9 0 0号公報参照） や、 放射源のみ を用いることで五酸化タンタルをフッ素系溶液中でェツチングする方法 （特開平 6 - 4 9 6 6 4号公報） 等が知られている。 発明の開示  Generally, as a method of electrolytically processing such corrosion-resistant tantalum, it is possible to use aprotic polar to roughen the surface of a human bone or artificial tooth root, a tantalum material or a niobium material used for a capacitor. A method of electrolytic processing using an organic electrolyte in which anions are dissolved in a solvent (refer to JP-A-2003-730), or by using only a radiation source, tantalum pentoxide in a fluorine-based solution A method (e.g., Japanese Patent Application Laid-Open No. 6-4964) and the like are known. Disclosure of the invention
図 1 Bに示すように、 トレンチ 2 6等の内部に銅 3 2等の配線金属をダマシン めっきにより確実に埋め込むため、 ハードマスク 2 0の上部 (基板の最表面上）に 過剰な銅 3 2を堆積させ、 同時に、 トレンチ 2 6やビアホール 2 4等の基板の凹 部に埋め込まれた鲖 3 2自体も基板の最表面を超えた高さにまで過剰に堆積させ るようにしている。 このようにして堆積させた銅 3 2の表面は、 基板の最表面部 分と基板の凹部に当たる部分とで高さが異なり、 凹凸状を呈し平坦面とはなりに くい。 このように基板の全体に渡って過剰に、 且つ表面に凹凸を持って堆積した 銅 3 2を、 十分な研磨速度を持って除去するため、 従来の CMPでは加工圧力を 上げていたが、 基板表面の十分な平坦性を得ることは難しかった。 つまり、 配線 の断面が皿状に窪んでしまうディッシングゃ、 銅等の金属と共に絶縁膜も余分に 研磨されるエロージョン等の不具合が発生していた。  As shown in FIG. 1B, in order to securely embed a wiring metal such as copper 32 into the interior of the trench 26 etc. by damascene plating, excess copper 32 2 on the top of the hard mask 20 (on the outermost surface of the substrate). At the same time, the crucible 32 itself embedded in the recess of the substrate such as the trench 26 and the via hole 24 is also excessively deposited to a height beyond the outermost surface of the substrate. The surface of the copper 32 deposited in this manner is different in height between the outermost surface portion of the substrate and the portion corresponding to the concave portion of the substrate, and has an uneven shape and is difficult to be a flat surface. Thus, the processing pressure is increased in the conventional CMP in order to remove the copper 32 which is deposited over the entire substrate and with unevenness on the surface with a sufficient polishing rate. It was difficult to obtain sufficient flatness of the surface. That is, if the dishing is such that the cross section of the wiring is dished down, there is a problem such as an erosion in which the insulating film is also excessively polished together with the metal such as copper.
近年、 層間絶縁材として、 従来の C VD- S i 02膜よりも誘電率の更に低い L o w- k材と呼ばれる有機 ·無機材料を使用することが提案されている。 L o w- k材は、 誘電率を下げるため、 ポーラスな、 即ち空孔を多く含む構成であり、 機 械的強度が従来の S i 02膜に比べ低い。 このため、 拡散パリア層の除去に CM Pプロセスを適用すると、拡散バリア層の下層の、例えばハードマスクが L o w- k材から剥離し易くなつて、 C M Pプロセスの適用は一般に困難である。 また C MPプロセスの際の加工圧力を低い値に抑えなければならず、 加工速度が低下す るため、 生産性に問題があり、 実用化が困難である。 In recent years, it has been proposed to use, as an interlayer insulating material, an organic / inorganic material called a Low-k material having a dielectric constant lower than that of a conventional C VD -S i 0 2 film. In order to lower the dielectric constant, the low-k material is configured to be porous, that is, contain a large number of holes, and its mechanical strength is lower than that of the conventional SiO 2 film. For this reason, when the CMP process is applied to the removal of the diffusion barrier layer, the application of the CMP process is generally difficult, as the lower layer of the diffusion barrier layer, for example, the hard mask, easily peels off from the Low-k material. In addition, the processing pressure in the CMP process must be reduced to a low value, which reduces the processing speed. Therefore, there is a problem with productivity and it is difficult to put it to practical use.
そこで、過剰の銅等を除去し拡散バリア層が露出するまでは、 CMPに代えて、 専ら銅の加工を促進するための電解液 （加工液） を用いた電解加工を行うことが 考えられる。 し力、し、 電解加工中に表層一面に露出する拡散バリア層は、 その硬 さや化学的安定性から研磨速度力 S銅等に比べ遅いため、 電解加工を継続すると、 拡散バリア層が露出した段階で銅等が優先的に加工されて、 ディッシングが生じ やすくなる。  Therefore, it is conceivable to carry out electrolytic processing using an electrolytic solution (processing liquid) exclusively for promoting processing of copper, in place of CMP, until excess copper and the like are removed and the diffusion barrier layer is exposed. Since the diffusion barrier layer exposed to the entire surface during electrolytic processing is slower than the polishing rate force S copper or the like due to its hardness and chemical stability, when the electrolytic processing is continued, the diffusion barrier layer is exposed. At the stage, copper etc. is processed preferentially, and dishing tends to occur.
このため、 拡散バリア層が露出した後に、 銅等とバリア層との加工速度が同等 の電解加工を行うことが望まれる。 し力 し、 拡散バリア層を構成している金属で あるタンタル、 チタン、 タングステン、 ルテニウムといった金属を溶解せしめる 溶液系として一般に使用されているフッ素ィオンを含む水溶液や濃厚アル力リ水 溶液を電解液に使用して電解加工を行うと、 前記のどちらの水溶液も S i系の材 料で構成されている下地のハードマスク等の絶縁膜をも溶解してしまう。 また c Therefore, after the diffusion barrier layer is exposed, it is desirable to carry out electrolytic processing with a processing speed equal to that of copper or the like and the barrier layer. The solution is a solution containing a fluoride ion, which is generally used as a solution system that dissolves metals such as tantalum, titanium, tungsten, and ruthenium, which are metals that constitute the diffusion barrier layer. When the electrolytic processing is performed using the above, both of the aqueous solutions described above dissolve the insulating film such as the underlying hard mask made of the Si-based material. C
M P工程にかかる費用の中ではスラリーの占める割合が高く、 スラリ一廃液の処 理費用も嵩むため、 スラリーの低減も更に望まれている。 Slurry reduction is also desirable because of the high proportion of slurry in the cost of the MP process and the high cost of slurry-waste treatment.
本究明は上記事情に鑑みて成されたもので、 配線金属の加工を抑制しつつ、 拡 散バリア層を優先的に加工できるようにして、 CM Pを省略したり、 CMPにお ける加工圧力を軽減したりできるようにした電解加工方法及び電解加工装置を提 供することを目的とする。  This investigation was made in view of the above-mentioned circumstances, so that the diffusion barrier layer can be processed preferentially while suppressing the processing of the wiring metal, CMP is omitted, and the processing pressure in CMP. The purpose of the invention is to provide an electrolytic processing method and an electrolytic processing apparatus capable of reducing the
上記目的を達成するため、 本発明の電解加工方法は、 有機溶媒に電解質を溶か した電解液に基板の表面を接触させ、 前記基板の表面に電位を印加して該表面の 電解加工を行う。  In order to achieve the above object, according to the electrolytic processing method of the present invention, the surface of a substrate is brought into contact with an electrolytic solution in which an electrolyte is dissolved in an organic solvent, and a potential is applied to the surface of the substrate to electrolytically process the surface. .
溶媒として水を用いた電解液 （水溶液） を使用し、 水溶液中で拡散バリア層に 正電位を印カ卩して拡散バリア層の電解加工 （電角?研磨） を行おうとしても、 拡散 バリア層に使用される金属の種類の多くは、 7K溶液中での正電位の印加により、 拡散バリア層の表面に不働態酸化皮膜が形成され、 金属イオンとして溶媒中に溶 解しないため、 電解加工が不可能となる。 これは、 水分子中の酸素や電気分解で 発生する酸素、 溶存酸素等が水溶液中に存在しているためである。 また、 7溶液 中で電解加工 （研磨） を行う場合、 拡散バリア層に印加する電位をより高くする ことで、加工（研磨）速度を速くことができる。 しかし、水の理論^ »電圧は 1 . 2 3 Vであり、 これ以上の電位を拡散バリア層に印加すると水^早が発生し、 加 ェ効率が低下するため好ましくない。 従って、 加工 （研磨） 速度の上限値も低い 値に留まる。 本発明によれば、 酸素等の影響の少ない有機溶媒を電解液の溶媒として使用す ることで、 電解液中で拡散バリァ層に正電位を印加した時に拡散バリァ層の表面 に不働態酸化皮膜が形成されることを防止し、 拡散バリァ層を構成する金属がィ オンとなって電解液中に溶解するようにして、 拡散バリア層の電解加工 （電解研 磨） を行うことができる。 また、 有機溶媒は^電圧が一般的に高く、 例えば炭 酸プロピレンの分解電圧は 6. 7 Vである。 このため、 より高い電圧を拡散パリ ァ層に印加して、 電解加工速度を十分に高めることができる。 Even if an electrolytic solution (aqueous solution) using water as a solvent is used and a positive potential is applied to the diffusion barrier layer in the aqueous solution to carry out electrolytic processing (electrostatic polishing or polishing) of the diffusion barrier layer, the diffusion barrier Many of the types of metals used in the layer are formed by applying a positive potential in a 7 K solution to form a passive oxide film on the surface of the diffusion barrier layer and not dissolving it in a solvent as metal ions. Is impossible. This is because oxygen in water molecules, oxygen generated by electrolysis, dissolved oxygen, etc. are present in the aqueous solution. When the electrolytic processing (polishing) is performed in a solution 7, the processing (polishing) speed can be increased by increasing the potential applied to the diffusion barrier layer. However, the theoretical voltage of water is 1.33 V, and applying a potential higher than this to the diffusion barrier layer is not preferable because water early is generated to lower the evaporation efficiency. Therefore, the upper limit of the processing (polishing) speed also remains low. According to the present invention, by using an organic solvent less affected by oxygen or the like as a solvent of the electrolyte, a passive oxide film is formed on the surface of the diffusion barrier layer when a positive potential is applied to the diffusion barrier layer in the electrolyte. It is possible to perform electrolytic processing (electrolytic polishing) of the diffusion barrier layer in such a manner that the metal forming the diffusion barrier layer is ionized and dissolved in the electrolytic solution. In addition, organic solvents generally have a high voltage, for example, the decomposition voltage of propylene carbonate is 6. 7 V. For this reason, a higher voltage can be applied to the diffusion barrier layer to sufficiently increase the electrolytic processing speed.
前記基板の表面に、 前記有機溶媒の分解電圧未満の所定の値に制御した正電位 を印加して、 定電位制御型の電解加工を行うことが好ましい。  It is preferable to perform constant potential control type electrolytic processing on the surface of the substrate by applying a positive potential controlled to a predetermined value less than the decomposition voltage of the organic solvent.
基板の表面に印加する電位を制御することによって、 専ら拡散バリア層を電解 加工したり、 または拡散バリア層と共に銅等の配線金属も同時に電解加工したり することもできる。 これによつて、 例えば過剰な銅等の 線金属が完全に除去さ れておらず、 一部に過剰な銅膜が残留した状態の基板に対しても、 拡散バリア層 の除去を開始することができる。  By controlling the potential applied to the surface of the substrate, the diffusion barrier layer can be electrolyzed exclusively, or the wiring layer such as copper can be electrolyzed simultaneously with the diffusion barrier layer. Thus, for example, the removal of the diffusion barrier layer should be initiated even on a substrate in which excess copper metal is not completely removed and part of the excess copper film remains. Can.
基板の表面により高い ®ϊを印加することで、 電解加工速度を速くすることが できるが、 前述の通り溶媒の分解電圧も考慮する必要がある。 例えば炭酸プロピ レンの分角電圧は、 + 3 . 7 V (銀一銀イオン参照電極基準） であるため、 基板 の表面に印加する電位はこの値未満であることが好ましい。 ここで定電位とは、 基板の表面に印加する電位を一定に保つことを意味する。  By applying a higher temperature to the surface of the substrate, the electrolytic processing speed can be increased, but it is also necessary to consider the decomposition voltage of the solvent as described above. For example, since the partial angle voltage of propylene carbonate is +3.7 V (based on a silver-silver ion reference electrode), the potential applied to the surface of the substrate is preferably less than this value. Here, the constant potential means that the potential applied to the surface of the substrate is kept constant.
本発明によれば、 半導体基板の拡散パリァ層の電解加工を好適に行うこどがで き、 さらに、 基板の表面に過剰な銅等を堆積した状態の基板に対しても、 基板に 印加する電位を制御することにより銅等を電解加工することもできる。 これによ つて、 同一の電解槽を用いて、 過剰な銅等の除去に引き続いて、 拡散バリア層の 除去まで一貫して電解加工して、 電解加工を効率的に行うことができる。  According to the present invention, the electrolytic processing of the diffusion barrier layer of the semiconductor substrate can be suitably performed, and furthermore, the substrate is applied to the substrate in a state in which excess copper or the like is deposited on the surface of the substrate. Copper or the like can also be electrolytically processed by controlling the potential. As a result, electrolytic processing can be performed efficiently by performing electrolytic processing consistently to removal of the diffusion barrier layer following removal of excess copper and the like using the same electrolytic cell.
前記電角军液の例としては、 フッ素イオン、 塩素イオン、 臭素イオン、 よう素ィ オン、 へキサフルォロりん酸イオン、 テトラフルォロほう酸イオン及びへキサフ ルォロ砒素イオンの少なくとも一つを含む溶液が挙げられる。  Examples of the electrolyte solution include a solution containing at least one of a fluoride ion, a chloride ion, a bromide ion, an iodine ion, a hexafluorophosphate ion, a tetrafluoroborate ion and a hexafluoroarsenic ion.
例えば、 へキサフルォロりん酸イオンは、 拡散バリア層に使用される金属のィ オンと結合して溶媒中へ溶解する効果が高いので、 電解加工に好ましく使用でき る。  For example, hexafluorophosphate ion is preferably used for electrolytic processing because it has a high effect of binding to the metal ion used in the diffusion barrier layer and dissolving it in a solvent.
前記有機溶媒の例としては、 炭酸プロピレン、 炭酸エチレンまたはジメチルス ルホキシドのうちの少なくとも 1種類以上が挙げられる。  Examples of the organic solvent include at least one or more of propylene carbonate, ethylene carbonate and dimethylsulfoxide.
炭酸プロピレン、 炭酸ェチレン及びジメチルスルホキシドは、 有機溶媒の中で も誘電率の値が高く、 電解質を溶解する能力が高いため、 一層好ましく使用され る。 溶解能力は、 例えば溶媒の誘電率を指標とすることができ、 誘電率の値が高 いほど溶解能力が高いことが分っている。 Propylene carbonate, ethylene carbonate and dimethyl sulfoxide are among organic solvents. It is also more preferably used because of its high dielectric constant and its high ability to dissolve the electrolyte. The dissolution ability can be indicated, for example, by the dielectric constant of the solvent, and it is known that the higher the value of the dielectric constant, the higher the dissolution ability.
前記電解質の例として、 へキサフルォロりん酸リチウム、 へキサフルォロりん 酸テトラプチルアンモニゥム、へキサフルォロりん酸テトラメチルアンモ-ゥム、 へキサフルォロりん酸テトラブチルアンモニゥム、 テトラフルォロほう酸アンモ 二ゥム、 及びテトラフルォロほう酸リチウムの少なくとも一つが挙げられる。 電解質とは電解加工時の溶液中での電子運搬の役割を担うィオンを提供し、 さ らに電解加工の対象となる金属、 即ち溶媒中に溶解してくる金属と化学結合する 性質を持ち合わせている化合物である。 電解加工を行う場合に金属を溶媒中に溶 解させる力 当該金属を戦虫でイオンとして存在させ続けるのではなく、 必ず別 の物質と結合させて溶液中に析出させる必要がある。 このため、 当該金属イオン と結合可能な化合物が電解質として選択される。  As examples of the electrolyte, lithium hexafluoroborophosphate, tetrabutylammonium hexafluorophosphate, tetramethylammonium hexafluorophosphate, tetrabutylammonium phosphate hexafluorophosphate, ammonium tetrafluoroborate, And at least one of lithium tetrafluoroborate. The electrolyte provides ions that play the role of transporting electrons in the solution during electrolytic processing, and further has the property of chemically bonding to the metal to be subjected to the electrolytic processing, that is, the metal dissolved in the solvent. Compounds. The power to dissolve the metal in the solvent when performing electrolytic processing It is not necessary to keep the metal in the form of ions in the worm, but it is always necessary to combine with another substance and precipitate it in the solution. For this reason, a compound capable of binding to the metal ion is selected as the electrolyte.
前記電角早液は、 トリァゾール環、 ピロール環、 ピラゾーノレ環、 チアゾール環ま たはィミダゾール環を有する複素環式化合物の少なくとも 1種類を更に含むこと が好ましい。  It is preferable that the above-mentioned early solution of electric angle further contains at least one kind of heterocyclic compound having a triazole ring, a pyrrole ring, a pyrazonol ring, a thiazole ring or a idazole ring.
基板表面の拡散パリァ層を電解加工で加工する時、 銅等の配線金属も電解液に 接触し、 基板の表面に印力 Uする電位によっては、 配線金属も電解液中に溶解する おそれがあるが、複素環式化合物を配線金属の表面に特異的に吸着させることで、 配線金属の電解液中への溶解を防ぐことができる。 この複素環式化合物は、 一般 的に腐食抑制剤またはインヒビターと呼ばれ、 酸素、 窒素及び硫黄原子を含んで いる。 そして、 これら原子を配線金属の表面に特異的に吸着させることで、 腐食 の要因となる物質、 即ち電解液中に配線金属を溶解させるように作用する物質が 該金属と直接反応して腐食する（溶解する）ことを抑制することができる。 これら インヒビターは、 拡散バリア層に対して吸着しない複素環式化合物である必要が あり、 電解液中に予め含ませるようにしてもよく、 また基板を電解液に浸漬させ る前に、 溶液または気相中で基板の表面にィンヒビターを予め付与するようにし てもよい。  When processing the diffusion barrier layer on the surface of the substrate by electrolytic processing, the wiring metal such as copper also contacts the electrolytic solution, and depending on the potential applied to the surface of the substrate, the wiring metal may be dissolved in the electrolytic solution. However, by specifically adsorbing the heterocyclic compound on the surface of the wiring metal, the dissolution of the wiring metal in the electrolytic solution can be prevented. This heterocyclic compound is generally referred to as a corrosion inhibitor or inhibitor, and contains oxygen, nitrogen and sulfur atoms. Then, by specifically adsorbing these atoms to the surface of the wiring metal, a substance that causes corrosion, that is, a substance that acts to dissolve the wiring metal in the electrolytic solution directly reacts with the metal to cause corrosion. It is possible to suppress (dissolving). These inhibitors need to be heterocyclic compounds which do not adsorb to the diffusion barrier layer, and may be previously contained in the electrolytic solution, or before the substrate is immersed in the electrolytic solution In the phase, it may be possible to pre-apply fins on the surface of the substrate.
前記複素環式化合物は、含窒素複素環式化合物であって、ベンゾトリァゾール、 ピロ一ノレ、 3— （ 2—チェ二ノレ） 一 1—ピラゾーノレ、 2一プチノレィミダゾーノレ、 6—チォグァユンまたはトリチオシァヌル酸のいずれかであることが好ましい。 これらの物質は、 銅等からなる配線金属の表面に特異的に吸着するが、 拡散バ リァ層には吸着しなレ、性質を持つ。 このため、 拡散バリァ層を選択的に電解加工 することができる。 The heterocyclic compound is a nitrogen-containing heterocyclic compound, and is a benzotriazole, a piro monole, a 3- (2-che di nore) 1 1-pyrazonole, a 2 petite nore midazone, 6- It is preferred that the acid be either thioguanein or trithiocyanuric acid. These substances adsorb specifically on the surface of the wiring metal made of copper or the like, but do not adsorb on the diffusion barrier layer. Therefore, the diffusion barrier layer is selectively electroprocessed can do.
本発明の好ましい一態様において、 本発明は、 タンタル、 チタン、 タンダステ ン、 ルテニウムまたはそれらの化合物からなるバリア層が形成された基板の表面 を電解加工で加工する。  In a preferred embodiment of the present invention, in the present invention, the surface of a substrate having a barrier layer formed of tantalum, titanium, tantalum, ruthenium or a compound thereof is processed by electrolytic processing.
本発明の電解加工装置は、 基板を保持する基板保持部と、 前記基板の表面に電 解加工を行う加工面を有する加工具と、 前記基板の表面と前記加工具との間に電 圧を印加する電源と、 有機溶媒に電解質を溶かした電解液を保持して該電解液に 前記基板の表面及び前記加工具の加工面を接触させる電角? fを有する。  The electrolytic processing apparatus according to the present invention comprises: a substrate holding portion for holding a substrate; a processing tool having a processing surface for performing electrolytic processing on the surface of the substrate; and a voltage between the surface of the substrate and the processing tool. It has an electric power source to be applied, and an electrical angle? F which holds the electrolytic solution in which the electrolyte is dissolved in an organic solvent and brings the electrolytic solution into contact with the surface of the substrate and the processing surface of the processing tool.
この電解加工装置によれば、 基板の凹部に酉 金属をダマシンめつきにより埋 め込んだ後に、 過剰な配線金属を除去したときに現れる拡散バリァ層を好適に加 ェ （除去） することができる。  According to this electrolytic processing apparatus, after the base metal is damascene embedded in the recess of the substrate, the diffusion barrier layer that appears when the excess wiring metal is removed can be suitably removed (removed) .
前記電解質は、 例えばへキサフルォ口りん酸ィオンである。  The electrolyte is, for example, hexafluorophosphate.
電解質としてへキサフル才ロりん酸ィオンを用いることにより、 拡散バリァ層 を一層好適に除去することができる。  The diffusion barrier layer can be more suitably removed by using hexaflurothioate as the electrolyte.
本発明の好ましい一態様において、 電解加工装置は、 前記基板の表面に印カロす る電位の値を調節する制御装置を更に有する。  In a preferred embodiment of the present invention, the electrolytic processing apparatus further comprises a control device for adjusting the value of the electric potential marked on the surface of the substrate.
基板の表面に印加する ®ΐの値を制御することで、 基板の凹部に配線金属をダ マシンめつきにより埋め込む工程の後に実行される、過剰な酉 金属の除去工程、 及びその後に行われる拡散バリァ層の除去工程を同一の電解槽を用いて連続して 行うことができ、 これによつて、 加工工程の簡素化と加工時間の短縮を図ること ができる。  An excess base metal removal step which is performed after the step of damascene embedding of the wiring metal in the recess of the substrate by controlling the value of ΐ applied to the surface of the substrate, and the diffusion which is performed after that. The removal process of the barrier layer can be continuously performed using the same electrolytic cell, which can simplify the processing process and shorten the processing time.
本発明によれば、 拡散バリァ層と銅等の配線金属とが共に露出した基板の表面 (ネ皮加工面） を平坦に研磨加工するに際して、 配線金属の加工を抑制しつつ、 拡 散パリア層を優先的に加工して除去し、 平坦性に優れた研磨面 （表面） を得るこ とができる。 また本発明によれば、 加工時に基板の表面に加える加工圧力を極め て低い値に抑えて、 デイツシングゃェロージヨンの発生を防止し、 かつ高い生産 性を維持することができる。 またスラリーを不要、 もしくはその使用量を極少量 に抑えて、 加工費用の低減に貢献することができる。 図面の簡単な説明  According to the present invention, the diffusion barrier layer and the diffusion barrier layer are suppressed while the processing of the wiring metal is suppressed when the surface of the substrate (the finished surface of the metal shell) on which both the diffusion barrier layer and the wiring metal such as copper are exposed is polished flat. Can be processed preferentially and removed to obtain a polished surface (surface) with excellent flatness. Further, according to the present invention, it is possible to suppress the processing pressure applied to the surface of the substrate at the time of processing to an extremely low value, prevent the generation of date singling and erosion, and maintain high productivity. In addition, it is possible to contribute to the reduction of processing cost by eliminating the need for slurry or keeping the amount used small. Brief description of the drawings
図 1 A乃至図 1 Dは、 銅配線形成例を工程順に示す断面図である。  1A to 1D are cross-sectional views showing an example of copper wiring formation in the order of steps.
図 2は、 本発明の実施の形態における電解加工装置の概要を示す図である。 図 3は、 銅配形成例を工程順に示すステップ図である。 図 4は、 本発明の他の実施の形態における電解加工装置の概要を示す平面図で ある。 FIG. 2 is a view showing an outline of an electrolytic processing apparatus according to an embodiment of the present invention. FIG. 3 is a step diagram showing an example of copper formation in the order of steps. FIG. 4 is a plan view showing an outline of an electrolytic processing apparatus according to another embodiment of the present invention.
図 5は、 図 4の縦断正面図である。  FIG. 5 is a front elevational view of FIG.
図 6は、 実施例 1における電解加工後の試料 1の表面を写した写真である。 図 7は、 実施例 1における電解加工後の試料 1の断面プロフィールを示す図で ある。  FIG. 6 is a photograph of the surface of sample 1 after electrolytic processing in Example 1. FIG. 7 is a view showing a cross-sectional profile of Sample 1 after electrolytic processing in Example 1.
図 8は、 実施例 2における電解加工後の試料 1の表面を写した写真である。 図 9は、 実施例 2における電解加工後の試料 1の断面プロフィールを示す図で める。 発明を実施するための最良の形態  FIG. 8 is a photograph of the surface of Sample 1 after electrolytic processing in Example 2. FIG. 9 is a view showing a cross-sectional profile of Sample 1 after electrolytic processing in Example 2. BEST MODE FOR CARRYING OUT THE INVENTION
以下、 本発明の実施の形態を図面を参照して説明する。 以下の例では、 図 1 B に示すように、 ビアホール 2 4及びトレンチ 2 6の内部に埋め込みつつ、 ハード マスク 2 0の表面に拡散バリア層 2 8を介して銅 3 2を堆積させた基板を用意し、 この基板 Wの余剰の配線金属としての銅膜（シード層 3 0及び銅 3 2 )、及び拡散 バリア層 2 8を研磨除去して、 図 1 Dに示すように、 上層絶縁膜 2 2の内部に銅 3 2カゝらなる配線 3 4を形成するようにした例を示す。  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following example, as shown in FIG. 1B, a substrate in which copper 32 is deposited on the surface of the hard mask 20 via the diffusion barrier layer 28 while buried in the via holes 24 and the trenches 26 is performed. The copper film (seed layer 30 and copper 32) as an excess wiring metal of the substrate W and the diffusion barrier layer 28 are polished and removed, as shown in FIG. 1D. An example in which a copper 32 wiring 34 is formed in the inside of 2 will be shown.
図 2は、 電解研磨装置に適用した本発明の実施の形態の電解加工装置を示す。 この電解加工装置 （電解研磨装置） は、 基板 Wの周縁部から表面 （ネ励口工面） に 設けた銅 3 2や拡散バリア層 2 8等の導電体に給電するようにした電解加工装置 で、 上面に、 表面を上向きにして基板 Wを着脱自在に保持する円板状の基板保持 部 4 0を有している。 基板保持部 4 0は、 自転用モータ 4 2の駆動に伴って回転 (自転） する。  FIG. 2 shows an electrolytic processing apparatus according to an embodiment of the present invention applied to an electrolytic polishing apparatus. This electrolytic processing apparatus (electrolytic polishing apparatus) is an electrolytic processing apparatus designed to feed power to a conductor such as copper 32 or a diffusion barrier layer 28 provided from the peripheral portion of the substrate W to the surface (surface to be machined). On the upper surface, there is provided a disk-like substrate holding portion 40 for holding the substrate W detachably with the surface facing upward. The substrate holding unit 40 rotates (rotates) along with the driving of the motor for rotation 42.
基板保持部 4 0の上方には、 基板保持部 4 0で保持した基板 Wの周縁部に圧接 して該周縁部をシールするシールリング 4 4が配置されている。 これにより、 基 板保持部 4 0で保持して基板 Wの周縁部をシールリング 4 4に圧接させることで、 基板 Wの上面にシールリング 4 4で包囲された電解槽 4 6が形成され、 この電解 槽 4 6の內部に電解液 4 8が保持される。  Above the substrate holding unit 40, a seal ring 44 is disposed, which is in pressure contact with the peripheral portion of the substrate W held by the substrate holding unit 40 to seal the peripheral portion. As a result, by holding the substrate holding portion 40 and pressing the peripheral portion of the substrate W against the seal ring 44, the electrolytic cell 46 surrounded by the seal ring 44 is formed on the upper surface of the substrate W, An electrolytic solution 48 is held at the rim of the electrolytic cell 46.
シールリング 4 4の下面には、 前述のようにして、 基板 Wの周縁部をシールリ ング 4 4でシールした時、 このシールリング 4 4の外方で基板 Wの周縁部に接触 して表面の銅 3 2等の導電膜に給電する給電電極 5 0が設けられている。 この給 電電極 5 0には、 電源 5 2の陽極から延びる酉 3；锒 5 5 aが接続される。  When the peripheral edge of the substrate W is sealed by the sealing ring 44 on the lower surface of the seal ring 44 as described above, the outer surface of the seal ring 44 contacts the peripheral edge of the substrate W and the surface A feed electrode 50 for feeding a conductive film such as copper 32 is provided. The feed electrode 50 is connected to a weir 3 5 5 a extending from the anode of the power supply 52.
基板保持部 4 0の側上方に位置して、 基板 Wの上面にシールリング 4 4で包囲 されて形成された電解槽 4 6に電解液 4 8を供給する電解液供給管 5 4が配置さ れている。 図示しないが、 電解槽 4 6内の電解処理後の電解液は、 上下動自在な 吸引管を通して吸引されて除去される。 Located on the upper side of the substrate holder 40 and surrounded by the seal ring 4 4 on the upper surface of the substrate W An electrolytic solution supply pipe 54 for supplying an electrolytic solution 48 to the formed electrolytic cell 46 is disposed. Although not shown, the electrolytic solution in the electrolytic cell 46 after being subjected to the electrolytic treatment is sucked and removed through the vertically movable suction pipe.
基板保持部 4 0の上方に電極部 5 8が配置され、 この電極部 5 8は、 水平方向 に揺動自在な揺動アーム 6 0の自由端に垂設されている。 揺動アーム 6 0は、 上 下動用モータ 6 2の駆動に伴って上下動し、 摇動用モータ 6 4の駆動に伴って回 転する揺動軸 6 6の上端に連結されている。 電極部 5 8は、 摇動アーム 6 0の自 由端に取付けた中空モータ 6 8の駆動に伴って回転 （自転） する。  An electrode portion 58 is disposed above the substrate holding portion 40, and the electrode portion 58 is vertically provided at a free end of a swing arm 60 which can swing in the horizontal direction. The swinging arm 60 moves up and down with the drive of the up and down movement motor 62 and is connected to the upper end of a swing shaft 66 which rotates with the drive of the swing motor 64. The electrode portion 58 rotates (rotates) along with the driving of the hollow motor 68 attached to the free end of the swing arm 60.
電極部 5 8の内部には、 下面を解放させて電解加工を行うための加工面とした 加工具としての対電極 7 0が設けられている。 この対電極 （加工具） 7 0は、 例 えば白金からなり、 対電極 7 0には、 電源 5 2の陰極から延び、 揺動軸 6 6に設 けられた中空部を通ってスリップリング 7 2に達し、 このスリップリング 7 2か ら中空モータ 6 8の中空部を通る配線 5 5 bが接続される。  Inside the electrode portion 58, a counter electrode 70 is provided as a processing tool which is a processing surface for releasing the lower surface and performing electrolytic processing. The counter electrode (processing tool) 70 is made of, for example, platinum, and the counter electrode 70 is a slip ring which extends from the cathode of the power source 52 and passes through a hollow portion provided on the swing shaft 66. 2, and the wire 55b passing through the hollow portion of the hollow motor 68 from this slip ring 72 is connected.
この例では、 給電電極 5 0と対電極 7 0との間に印加する電圧を調節 （制御） する制御装置 7 4が備えられている。  In this example, a controller 74 is provided which adjusts (controls) the voltage applied between the feed electrode 50 and the counter electrode 70.
次に、 電解液 4 8について説明する。 電解液 4 8として、 有機溶媒に電解質を 溶かした溶液を使用している。 このように、 溶媒として、 水の代わりに有機溶媒 を使用することで、 電解液中で拡散バリァ層に正電位を印加した時に拡散バリァ 層の表面に不働態酸ィ匕皮膜が形成されることを防止し、 拡散バリァ層を構成する 金属がイオンとなって電解液中に溶解するようにして、 拡散バリア層の電解加工 (電解研磨）を行うことができる。また、有機溶媒は、分解電圧が一般的に高く、 例えば炭酸プロピレンの分解電圧は 6 . 7 Vであるため、 より高い電圧を拡散バ リァ層に印加して、 電解加工速度を十分に高めることができる。  Next, the electrolyte solution 48 will be described. As the electrolyte solution 48, a solution in which an electrolyte is dissolved in an organic solvent is used. Thus, by using an organic solvent instead of water as a solvent, a passive acid film is formed on the surface of the diffusion barrier layer when a positive potential is applied to the diffusion barrier layer in the electrolytic solution. The diffusion barrier layer can be subjected to electrolytic processing (electrolytic polishing) in such a manner that the metal constituting the diffusion barrier layer becomes ions and dissolves in the electrolytic solution. Also, since the organic solvent generally has a high decomposition voltage, for example, the decomposition voltage of propylene carbonate is 6.7 V, a higher voltage should be applied to the diffusion barrier layer to sufficiently increase the electrolytic processing speed. Can.
有機溶媒としては、例えばァセタール、ァセトーノレ、 1, 2 -ジクロロェタン（10. 1)、 塩化スルフリル （10)、 塩化チォニル (9. 2)、 塩化ァセチル (15. 8)、 炭酸テトラ クロ口エチレン （9. 2)、 塩化べンジル （23)、 -トロメタン （36)、 炭酸ジクロロ エチレン（31. 6)、 -ト口ベンゼン（34. 8)、無水酢酸（20. 7)、ォキシ塩化りん（14)、 ベンゾニトリル （25. 2)、 ォキシ塩化セレン （46)、 ァセトニトリル （38)、 スルホ ラン （42)、炭酸プロピレン（69)、 シアン化べンジル 8. 4)、 エチレンサルフアイ ト（41)、 ィソブチ口二トリル (20. 4)、 プロピオ-トリノレ (27. 7)、 炭酸ェチルメチ ル、 炭酸エチレン (89. 1)、 炭酸ジメチル、 炭酸ジェチル、 ジフエ二ルホスホン酸 ジフロリ ド（27. 9)、 酢酸メチル、 -プチ口-トリル (20. 3)、 ェチルアルコール、 メチルアルコール、 プロピルアルコール、 ブチルアルコール、 アセトン（20. 7)、 蟻酸メチル、 蟻酸ェチル、 酢酸ェチル、 フエ-ルホスホン酸ジクロリ ド (26)、 ジ ェチルエーテル (4. 3)、テトラヒドロフラン（7. 6)、 2 -メチノレテトラヒドロフラン、 1， 3ジォキソラン、 4-メチル- 1, 3 -ジォキソラン、 3-メチルォキサゾリジノン、 1，2 -ジメ トキシェタン、 ジフエエルホスホン酸クロリ ド、 りん酸トリメチル (20. 6)、 りん酸トリプチノレ (6. 8)、 N, N-ジメチノレホルムアミ ド（26. 6)、 N， N -ジメチ ルァセトアミド（27. 8)、ジメチルスルホキシド (45)、N, N -ジェチルホルミアミド、 N, N-ジェチルァセトアミド、 ピリジン（12. 3)、へキサメチルホスホ（3)トリアミド (30)、 ヒドラジン、エチレンジァミン、 ェチルァミン、 t -ブチルァミン、 アンモ ニァ、 トリェチノレァミン、 γプチ口ラタトン等が使用される。 これらの複数種か らなる混合物を用いるようにしてもよレヽ。ここで、カツコ内数値は誘電率を表す。 これらの有機溶媒のうち、 炭酸プロピレン、 炭酸エチレン及びジメチルスルホ キシドは、 誘電率の値が高く、 電解質を溶解する能力が高いため、 一層好ましく 使用される。 As the organic solvent, for example, acetal, acetonitrile, 1,2-dichloroethane (10. 1), sulfuryl chloride (10), thionyl chloride (9.2), acetyl chloride (15.8), tetrachloroethylene carbonate (9 .2) Benzyl chloride (23),-Tromethane (36), Dichloroethylene carbonate (31.6),-Benzene benzene (34.8), Acetic anhydride (20.7), Oxy phosphorus chloride (14) , benzonitrile (25.2), Okishi selenium chloride (46), Asetonitoriru (38), sulfolane (4 2), propylene carbonate (69), cyanide base Njiru 8.4), ethylene sulfates eye preparative (41) , Isobutyric acid ditolyl (20.4), propio-trinole (27.7), ethyl methyl carbonate, ethylene carbonate (89.1), dimethyl carbonate, jetyl carbonate, diphenyl phosphonic acid difluoride (27.9), Methyl acetate, -petite-tolyl (20.3), ethyl alcohol, Chill alcohol, propyl alcohol, butyl alcohol, acetone (20.7), Methyl formate, ethyl formate, ethyl acetate, phenyldiphosphonic acid (26), diethyl ether (4.3), tetrahydrofuran (7.6), 2-methynotetrahydrofuran, 1,3 dioxolane, 4-methyl-1 , 3-Dioxolane, 3-Methyloxazolidinone, 1,2-Dimethoxetane, Diphenylphosphonic Acid Chloride, Trimethylphosphate (20.6), Tryptone Nol Phosphate (6.8), N, N- Dimethinoleformamide (26. 6), N, N-Dimethyl acetoamide (27.8), Dimethyl sulfoxide (45), N, N- Jetylformiamide, N, N- Jetyl Ascetoamide, Pyridine (12. 3) Hexamethylphospho (3) triamide (30), hydrazine, ethylenediamine, cetylamine, t-butylamine, ammonium, triethinolamine, gamma petit ratatonate, etc. are used. It is also possible to use a mixture of two or more of these. Here, the values in Katsuko represent the dielectric constant. Among these organic solvents, propylene carbonate, ethylene carbonate and dimethyl sulfoxide are more preferably used because they have high dielectric constants and high ability to dissolve the electrolyte.
電解質としては、電 1H"るァニオンがフッ素ィオン、塩素イオン、臭素イオン、 よう素イオン、 P F 6- (へキサフルォロりん酸ィオン）、 B F 4 - (テトラフルォ 口ほう酸イオン）、 A s F 6— (へキサフルォロ砒素イオン)等のアルカリ金属塩、 アンモェゥム塩、 テトラアルキルアンモニゥム塩等が使用される。 具体的には、 例えばへキサフルォロりん酸リチウム、 へキサフルォロりん酸テトラプチルアン モニゥム、 へキサフルォ口りん酸テトラメチルアンモニゥム、 へキサフルォ口り ん酸テトラプチルアンモ-ゥム、 テトラフルォロほう酸アンモニゥム、 テトラフ ルォロほう酸リチウム等が挙げられる。 電解質の濃度は、 一般には 0 . 0 1〜3 0質量％で、 好ましくは 0 . 1〜 1 0質量％である。 As the electrolyte, electrostatic 1H "Ru Anion fluorine Ion, chlorine ion, bromine ion, iodine ion, PF 6 - (to Kisafuruoro Ion phosphate), BF 4 - (Tetorafuruo port borate ion), A s F 6 - ( An alkali metal salt such as hexafluoroarsenic ion), ammonium salt, tetraalkyl ammonium salt, etc. Specifically, for example, lithium hexafluorophosphate, tetrafluoroammonium phosphate, hexafluorophosphate, hexafluoromouth Examples thereof include tetramethyl ammonium phosphate, hexabutyl tetrabasic ammonium, tetrafluorinated ammonium, lithium tetrafluoroborate, etc. The concentration of the electrolyte is generally 0.01 to 30% by mass. Preferably, it is 0.1 to 10% by mass.
電解液 4 8には、 必要に応じて、 酸素、 窒素、 硫黄原子を含む、 複素環式化合 物からなるインヒビター （腐食抑制剤） が添加される。 これにより、 これらの元 素の非共有電子対を銅等の配線金属の表面の吸着点に吸着させ、 配線金属がィォ ンとして溶解することを防ぎ、 また遅らせることができる。 インヒビターは、 例 えば含窒素複素環式化合物であり、 トリァゾール環、ピロ一ノレ環、ピラゾーノレ環、 チアゾール環、 イミダゾール環を有する。 具体的には、 ベンゾトリァゾール、 ピ ローノレ、 3— （2—チェュノレ） 一 1ーピラゾーノレ、 2—プチノレイミダゾーノレ、 6 ーチォグァニン、 トリチオシァヌル酸、 ベンゾトリァゾール、 トリルトリァゾー ル、 6—チォグァニン、 2—べンゾチアゾールチオール、 トリチオシァヌル酸、 N, N—ジェチルジチォカルバミド酸ナトリムが挙げられる。 また、 含窒素複素 環式化合物以外にもアルキルァミン類、 アル力ンチオール類、 1一へキシン一 3 一オール等がインヒビターとして使用できる。 An inhibitor (corrosion inhibitor) composed of a heterocyclic compound containing oxygen, nitrogen and sulfur atoms is added to the electrolytic solution 48, as necessary. As a result, the non-shared electron pair of these elements can be adsorbed to the adsorption point on the surface of the wiring metal such as copper, thereby preventing or delaying the dissolution of the wiring metal as ions. The inhibitor is, for example, a nitrogen-containing heterocyclic compound and has a triazole ring, a pyrrolo nore ring, a pyrazonore ring, a thiazole ring, and an imidazole ring. Specifically, benzotriazole, pyronole, 3- (2-cheunole), 1-pyrazonole, 2-peptoleimidazonore, 6-thiogguanin, trithiocyanuric acid, benzotriazole, tolyl triazole, 6-thiogguanine, 2- Examples include benzothiazole thiol, trithiocyanuric acid, and N, N-jetyldithiocarbamic acid sodium. In addition to nitrogen-containing heterocyclic compounds, alkylamines, alanthiols, 1-hexyne Monools etc. can be used as inhibitors.
次に、 この電解研磨装置による電解研磨について説明する。 先ず、 例えば図 1 Cに示す、 拡散バリア層 2 8を露出させた ¾Wを、 下降させた基板保持部 4 0 に表面を上向きにして保持する。 そして、 基板の周縁部にシールリング 4 4を圧 接させ、 これによつて、 基板 Wの表面に、 シールリング 4 4で包囲した電解槽 4 6を形成する。 同時に、 基板 Wの周縁部で給電電極 5 0を表面の拡散バリア層 2 8に接触させる。  Next, the electropolishing by this electropolishing apparatus will be described. First, for example, as shown in FIG. 1C, 3⁄4 W in which the diffusion barrier layer 28 is exposed is held with the surface thereof facing upward in the lowered substrate holding unit 4 0. Then, the seal ring 44 is pressed against the peripheral portion of the substrate, thereby forming the electrolytic cell 46 surrounded by the seal ring 44 on the surface of the substrate W. At the same time, the feed electrode 50 is brought into contact with the surface diffusion barrier layer 28 at the periphery of the substrate W.
次に、 基板 Wの表面に形成された電解槽 4 6内に電解液供給管 5 4から所定量 の電解液 4 8を供給して保持する。 しかる後、 電極部 5 8を基板保持部 4 0の直 上方まで移動させ、 更に下降させて、 電極部 5 8の対電極 7 0の下面が電解槽 4 6内に保持した電解液 4 8に接触する所定の位置に達したときに電極部 5 8の下 降を停止させる。 Next, a predetermined amount of electrolytic solution 48 is supplied from the electrolytic solution supply pipe 54 into the electrolytic cell 46 formed on the surface of the substrate W and held. Thereafter, by moving the electrode portion 5 8 until immediately above the substrate holder 4 0, further lowered, the electrolytic solution 4 8 the underside of the counter electrode 7 0 is held in the electrolytic bath 4 6 of the electrode portion 5 8 Stop falling of the electrode unit 5 8 when reaching the predetermined position where it contacts.
この状態で、 1?源 5 2力、ら、 給電電極 5 0と対電極 7 0との間に、 給電電極 5 0が陽極、対電極 7 0が陰極となる所定の電圧を印加し、同時に、必要に応じて、 基板保持部 4 0及び電極部 5 8を回転 （自転） させ、 更に電極部 5 8を水平方向 (基板 Wの被加工表面に平行な方向） に揺動させて、 拡散パリア層 2 8の電解カロ ェ （電解研磨） を行う。  In this state, a predetermined voltage is applied between the feeding electrode 50 and the counter electrode 70, with the feeding electrode 50 being the anode and the counter electrode 70 being the cathode, at the same time. If necessary, the substrate holding unit 40 and the electrode unit 58 are rotated (rotated), and the electrode unit 58 is swung horizontally (in a direction parallel to the processing surface of the substrate W) to diffuse Paria layer 28 Electrolytic polishing (electropolishing) is performed.
この時、 給電電極 5 0と対電極 7 0との間に、 電解液 4 8の有機溶媒の分解電 圧未満の所定の値に制御した電位を印カ卩して、 定電位制御型の電解加工を行う。 例えば炭酸プロピレンの^電圧は、 + 3. 7 V (銀一銀イオン参照電極基準） であるため、 電解液 4 8の有機溶媒として、 炭酸プロピレンを使用した場合、 基 板の表面に印加する電位はこの値未満として、 有機溶媒 （炭酸プロピレン） が分 解して、 加工効率が低下することを防止する。 ここで定電位とは、 基板の表面に 印加する電位を一定に保つことを意味する。  At this time, a potential controlled at a predetermined value less than the decomposition voltage of the organic solvent of the electrolytic solution 48 is applied between the feeding electrode 50 and the counter electrode 70, thereby performing constant potential control type electrolysis. Do the processing. For example, since the ^ voltage of propylene carbonate is +3.7 V (based on a silver-silver ion reference electrode), when propylene carbonate is used as the organic solvent of the electrolytic solution 48, the potential applied to the surface of the substrate is Below this value, the organic solvent (propylene carbonate) is decomposed to prevent the processing efficiency from decreasing. Here, the constant potential means that the potential applied to the surface of the substrate is kept constant.
このように、 基板の表面に印カロする電位を制御することによって、 専ら拡散バ リア層 2 8を電解加工したり、 または拡散バリア層 2 8と共に銅等の配線金属も 同時に電解加工したりすることもできる。 これによつて、 例えば過剰な銅等の配 線金属が完全に除去されておらず、 一部に過剰な銅膜が残留した状態の基板に対 しても、 拡散バリア層 2 8の除去を開始することができる。  Thus, the diffusion barrier layer 28 is exclusively subjected to the electrolytic processing by controlling the electric potential marked on the surface of the substrate, or the wiring barrier such as copper is simultaneously subjected to the electrolytic processing together with the diffusion barrier layer 28. It can also be done. As a result, for example, the diffusion barrier layer 28 can be removed even on a substrate in which excess copper metal or the like has not been completely removed and a part of the excess copper film remains. It can start.
電解加工の効率は、 使用する電解液 4 8の他に、 電源の条件、 例えばパルス電 圧値ゃパノレスの周期、 デューティ一比、 陽極となる拡散パリア層 2 8と陰極とな る対電極 7 0との間の距離、 ¾Wの被加工表面における全表面積に対する露出 した金属配線層の表面積の比率等によって変わる。 電解加工の際には、 基板 Wの 表面 （被加工面） 全体が陽極として作用するので、 拡散パリア層 2 8が、 トレン チ 2 6など基板の凹部を埋め込んだ金属酉 S/锒層の表面を除く領域を覆う状態では、 電解により多くの電流が流れ、 電解加工が促進されて、 拡散パリア層 2 8の溶解 が進む。 このとき、 金属酉锒を同時に溶解してしまうが、 電解液 4 8として、 ィ ンヒビター （腐食抑制剤） を添加したものを使用することで ほたは電解液に浸 漬する前に、予めインヒビターを基板に塗布などにより付与しておくことで)、金 属配線の溶解を防止して、 拡散バリア層 2 8のみを選択的に電解加工することが できる。 The efficiency of the electrolytic processing is determined not only by the electrolyte solution 48 used but also by the conditions of the power supply, for example, the period of pulse voltage value / panorless, duty-to-duty ratio, diffusion barrier layer 28 serving as an anode and counter electrode 7 serving as a cathode. It varies depending on the distance between 0 and the ratio of the surface area of the exposed metal wiring layer to the total surface area of the 3⁄4 W work surface. During electrolytic processing, the substrate W Since the entire surface (work surface) acts as an anode, in the state where the diffusion parlia layer 28 covers the area excluding the surface of the metal base S / swell layer embedded in the recess of the substrate such as trench 26 etc. A large amount of current flows, electrolytic processing is promoted, and dissolution of the diffusion barrier layer 28 progresses. At this time, the metal 酉 锒 will be dissolved at the same time, but by using an electrolyte 48 added with an inhibitor (corrosion inhibitor), it is possible to inhibit the inhibitor in advance before immersion in the electrolyte. Can be applied to the substrate by application or the like to prevent dissolution of the metal wiring, and to selectively electrolyze only the diffusion barrier layer 28.
電解加工終了後、 給電電極 5 0と対電極 7 0との間の HEの印加を解き、 基板 保持部 4 0及び電極部 5 8の回転（自転）を停止させる。 そして、 電解槽 4 6内の 電解液 4 8を除去して、 電解加工後の基ネ を次工程に搬送する。  After the completion of the electrolytic processing, the application of the HE between the feeding electrode 50 and the counter electrode 70 is released to stop the rotation (rotation) of the substrate holding portion 40 and the electrode portion 58. Then, the electrolytic solution 48 in the electrolytic cell 46 is removed, and the substrate after electrolytic processing is transported to the next step.
電解加工装置として、 この例のように、 基 ¾Wに直接正電位を、 対電極に負電 位をそれぞれ印加して電解加工を行う直接給電方式を採用したものの他、 間接給 電方式を採用したものを使用してもよい。 間接給電方式とは、 陽極及び陰極を基 板の表面 （被加工面） に非接触に対向させ、 陽極と陰極との間に電位を印加する ことで基板の加工を行う方式である。 また、 電解液の一部が大気中の水分や酸素 を吸収して分解し、 加工面の酸化が進行したりする不都合が生じることがある。 このような場合には、 不活性ガス雰囲気中で電解加工を行うことで、 このような 弊害を防止することができる。  As an electrolytic processing apparatus, as in this example, in addition to a direct feed system in which electrolytic processing is performed by applying a positive potential directly to the base electrode W and a negative potential to the counter electrode, an indirect power supply system is adopted. You may use The indirect feeding method is a method in which the anode and the cathode are made to face the surface (the surface to be processed) of the substrate without contact, and the substrate is processed by applying an electric potential between the anode and the cathode. In addition, a part of the electrolytic solution absorbs moisture and oxygen in the air to be decomposed, which may cause a problem that oxidation of the processing surface progresses. In such a case, such an adverse effect can be prevented by performing the electrolytic processing in an inert gas atmosphere.
次に、 図 1 A乃至 1 D及び図 3を参照して、 銅配線形成例を説明する。  Next, with reference to FIGS. 1A to 1D and FIG. 3, an example of copper wiring formation will be described.
先ず、 図 1 Aに示すように、 上層絶縁膜 2 2に、 例えば公知のリソグラフィ · エッチング技術によりビアホー/レ 2 4やトレンチ 2 6を形成する (ステップ 1 )。 次に、 この上に、 第 1低誘電率絶縁層 1 6や第 2低誘電率絶縁層 1 8内への銅拡 散防止のための拡散バリア層 2 8を形成し（ステップ 2)、更にその上に電解めつ きの給電層としてのシード層 3 0を形成する （ステップ 3 )。  First, as shown in FIG. 1A, a via hole / layer 24 and a trench 26 are formed in the upper insulating film 22 by, for example, a known lithography / etching technique (step 1). Next, a diffusion barrier layer 28 for preventing copper diffusion into the first low dielectric constant insulating layer 16 and the second low dielectric constant insulating layer 18 is formed thereon (step 2). A seed layer 30 is formed thereon as a feed layer for electrolytic plating (step 3).
拡散バリァ層 2 8は、 例えばスパッタリング法や A L D (Atomic Layer Deposition)法により堆積した T a ZT a Ν混合膜、 T i N、 WN、 S i T i N、 R u等の膜からなり、 シード層 3 0は、 例えばスパッタリング法等により堆積し た銅膜からなる。 なお、 拡散バリア層 2 8が R uでシード層が必要ない場合は、 ステップ 3を省略して、 ステップ 2からステップ 4を行う。  The diffusion barrier layer 28 is made of, for example, a film such as TaZTa mixed film, TiN, WN, SiTN, Ru, etc. deposited by sputtering method or ALD (Atomic Layer Deposition) method. The layer 30 is made of, for example, a copper film deposited by sputtering or the like. If the diffusion barrier layer 28 is Ru and no seed layer is required, step 3 is omitted, and steps 2 to 4 are performed.
次に、 基板の表面に、 電解めつき （ダマシンめつき） により、 配線金属として の銅 3 2を形成する （ステップ 4)。 これにより、 図 1 Bに示すように、 ビアホー ル 2 4及びトレンチ 2 6内に銅 3 2を充填すると共に、 基板 Wの最表面の上にも 銅 3 2を堆積させ、 上層絶縁膜 2 2を構成する低誘電率絶縁層 1 6， 1 8やハー ドマスク 2 0上を配線金属としての銅 3 2で覆う。 電解めつき（ダマシンめつき） 工程終了時点における銅 3 2の表面には凹凸が存在する。なお、酉 泉金属として、 銅の他に、 銀または銅と銀からなる合金を使用してもよい。 また、 シード層 3 0 と銅 3 2は一体となり、 デバイス完成後は配線として機能する。 また過剰な銅 3 2は、 CMPや電解加工 （電解研磨） により除去される。 この除去は、 シード層 3 0と銅 3 2について一体的に行なわれる。 Next, copper 32 is formed as a wiring metal by electrolytic plating (damascene plating) on the surface of the substrate (step 4). As a result, as shown in FIG. 1B, the via holes 24 and the trenches 26 are filled with copper 32 and also on the outermost surface of the substrate W. Copper 32 is deposited, and the low dielectric constant insulating layers 16 and 18 constituting the upper insulating film 22 and the hard mask 20 are covered with copper 32 as a wiring metal. Electrolytic plating (damascene plating) There are irregularities on the surface of copper 32 at the end of the process. In addition to copper, silver or an alloy of copper and silver may be used as the cold spring metal. In addition, the seed layer 30 and copper 32 are integrated and function as wiring after the device is completed. Excess copper 32 is removed by CMP or electrolytic processing (electrolytic polishing). This removal is performed integrally for the seed layer 30 and the copper 32.
このとき、 ¾Wの表面に CMPまたは電解液として水溶液を使用した電解カロ ェを施し（ステップ 5 )、 これによつて、 図 1 Cに示すように、拡散バリア層 2 8 上の余分な銅膜 （銅 3 2及びシード層 3 0 ) を除去し、 尚且つトレンチ 2 6内に 埋め込んだ銅 3 2にあっては、 その表面がハードマスク 2 0と同一平面になるよ うにする。  At this time, the surface of the 3⁄4 W is subjected to electrolytic corrosion using CMP or an aqueous solution as an electrolytic solution (step 5), whereby extra copper film on the diffusion barrier layer 2 8 is obtained as shown in FIG. 1C. The copper 32 and the seed layer 30 are removed, and the surface of the copper 32 embedded in the trench 26 is made flush with the hard mask 20.
電解液を通して、 基板と対電極との間に電圧を印加した状態で、 基板と研磨部 材 （例えば研磨パッド） とを互いに接触させながら相対運動をさせる電解複合研 磨によって、 銅膜の除去を行っても良い。  Removal of the copper film is achieved by electrolytic composite polishing, which causes relative movement while bringing the substrate and polishing member (eg, polishing pad) into contact with each other while applying a voltage between the substrate and the counter electrode through the electrolytic solution. You may go.
以上のプロセスは、 従来と同様のプロセスで行うことが出来るほか、 銅膜 （銅 3 2及ぴシード層 3 0 ) の除去に関して電解加工による場合は、 図 2に示す有機 溶媒を使用した電解加工装置を使用して行うことができる。 そして続いて行われ るハードマスク 2 0上にある不要な拡散バリア層 2 8の除去 （ステップ 6 ) は、 図 2に示す本発明の電解加工装置を使用して行う。  The above process can be performed by the same process as the conventional process, and in the case of electrolytic processing for removing the copper film (copper 32 and seed layer 30), electrolytic processing using the organic solvent shown in FIG. It can be done using the device. The subsequent removal of the unnecessary diffusion barrier layer 28 on the hard mask 20 (step 6) is performed using the electrolytic processing apparatus of the present invention shown in FIG.
つまり、 前述のように、 有機溶媒に電解質を溶かし、 必要に応じてインヒビタ 一 （腐食防止剤） を添加した電角槽 4 6の電角液 4 8に、 基板 Wの表面の拡散バ リア層 2 8及ぴ対電極 7 0を接触させ、拡散バリア層 2 8と対電極 7 0との間に、 拡散バリア層 2 8を正、 対電極 7 0を負とした電圧を印加して、 銅膜を除去する ことなく、拡散バリア層 2 8を選択的に研磨除去する （ステップ 6 a )。 これによ つて、 図 1 Dに示すように、 上層絶縁膜 2 2の内部に銅からなる配線 3 4を形成 する。  That is, as described above, the diffusion barrier layer on the surface of the substrate W is prepared by dissolving the electrolyte in the organic solvent and optionally adding the inhibitor (corrosion inhibitor) to the electrolyte solution 48 of the electrode reservoir 46. A voltage is applied between the diffusion barrier layer 28 and the counter electrode 70 by bringing the diffusion barrier layer 28 positive and the counter electrode 70 negative. Selectively polish away the diffusion barrier layer 28 without removing the film (step 6 a). As a result, as shown in FIG. 1D, a wire 34 made of copper is formed inside the upper layer insulating film 22.
なお、 基 feWの表面の拡散バリア層 2 8を電解液に接触させる前に、 溶液中ま たは気相中でィンヒビターを基 ¾Wの表面の拡散バリア層 2 8に予め塗布などに より付与し（ステップ 6 b )、 し力る後、インヒビターを必ずしも含まない電解液 を用いた電解加工を行う （ステップ 6 c ) ようにしてもよい。  Before the diffusion barrier layer 28 on the surface of the base feW is brought into contact with the electrolytic solution, the diffusion barrier layer 28 on the surface of the base W is previously applied by coating or the like in a solution or in the gas phase. (Step 6 b) After the force is applied, electrolytic processing may be performed using an electrolytic solution that does not necessarily contain an inhibitor (Step 6 c).
次に、 必要に応じて、 基板に不具合を発生しない程度の極低い圧力 （例えば、 1 s i (約 6 9 h P a ) 未満） による CM P加工を行って、 ハードマスク （絶 縁膜） 2 0上に除去されること無く残留している拡散バリア層 2 8を完全に除去 し（ステップ 7 )、 これによつて、拡散バリア層 2 8を完全に除去したハードマス ク （絶縁膜） 2 0を露出させる （ステップ 8 )。 これと同時に、 3 4を被覆し ていたインヒビターも除去し、 銅を露出させた状態で加工を完了する。 Next, if necessary, CMP is performed with an extremely low pressure (for example, less than 1 si (about 69 h P a)) that does not cause any defects in the substrate to Hard mask (insulation film) which completely removes the remaining diffusion barrier layer 28 without removing it (step 7), thereby completely removing the diffusion barrier layer 28. Expose the membrane 2 0 (step 8). At the same time, the inhibitor covering 34 was also removed, and the processing was completed with the copper exposed.
上記の例では、 基板 Wの表面を電解液 4 8に接触させて ¾¾Wの表面の拡散バ リア層 2 8を電解加工するようにしている。 基板の表面を電解液中で研磨部材の 表面と接触させながら、 基板と研磨部材とを相対運動をさせることで、 基板の表 面に研磨部材による機械的な作用を付加して該表面を研磨するようにしても良い。 拡散バリア層の材質や拡散バリア層の厚さムラにより、 絶縁膜が露出するまで電 解加工を施した際に、 絶縁膜の表面に縞状に拡散バリァ層が残留する可能性があ る。電解加工は、一般的に電気的導通が確保できないと加工現象が生じないため、 残留した拡散バリア層に電気的導通が確保できないと拡散パリア層は除去ができ ない。 このため、 絶縁膜の表面に縞状に拡散バリア層が残留すると、 基¾\¥の表 面を電解液 4 8に接触させるようにした電解加工では、 拡散バリァ層を除去でき なくなる。 このような場合であっても、 研磨部材による «的な作用を拡散パリ ァ層に付加しながら該拡散バリァ層の電解加工を行うことにより、 絶縁膜上へ拡 散バリァ層を残留させることなく、 拡散バリァ層の除去を行うことができる。 図 4及び図 5は、 基板の表面を電解液中で研磨部材の表面と接触させながら、 基板と研磨部材とを相対運動をさせることで、 基板の表面に研磨部材による機械 的な作用を付カ卩して該表面を研磨するようにした、 本発明の他の実施の形態の電 解加工装置 （電解研磨装置） を示す。  In the above example, the surface of the substrate W is brought into contact with the electrolyte solution 48 to electrolytically process the diffusion barrier layer 28 of the surface of the 3⁄4⁄4 W. By causing the substrate and the polishing member to move relative to each other while bringing the surface of the substrate into contact with the surface of the polishing member in the electrolytic solution, the mechanical action of the polishing member is added to the surface of the substrate to polish the surface. You may do it. Due to the material of the diffusion barrier layer and the thickness unevenness of the diffusion barrier layer, when the electrolytic processing is performed until the insulating film is exposed, the diffusion barrier layer may remain on the surface of the insulating film in stripes. In the electrolytic processing, generally, the processing phenomenon does not occur unless the electrical conduction can be secured. Therefore, the diffusion barrier layer can not be removed unless the electrical continuity can be ensured in the remaining diffusion barrier layer. Therefore, if the diffusion barrier layer remains in stripes on the surface of the insulating film, the diffusion barrier layer can not be removed by the electrolytic processing in which the surface of the base is in contact with the electrolytic solution 48. Even in such a case, the diffusion barrier layer is subjected to the electrolytic processing while adding the function of the polishing member to the diffusion barrier layer, without leaving the diffusion barrier layer on the insulating film. , Removal of diffusion barrier layer can be performed. 4 and 5 show that the substrate and the polishing member are moved relative to each other while the surface of the substrate is brought into contact with the surface of the polishing member in the electrolytic solution, whereby the surface of the substrate is mechanically acted by the polishing member. An electrolytic processing apparatus (electrolytic polishing apparatus) according to another embodiment of the present invention, in which a surface is polished by a die, is shown.
この電解加工装置は、 W 8 0の陰極に接続される対電極 8 2と研磨部材 8 4 とを上面に有する回転自在な研磨テーブル 8 6、 基板 Wを着脱自在に保持する上 下動及び回転自在なトップリング 8 8、 及び研磨部材 8 4の表面をコンディショ ユングするドレッサー 9 0及びァトマィザ 9 2を備えている。 研磨テープノレ 8 6 の上方には、 研磨部材 8 4に電解液を供給する多数の電解液供給口 9 4 aを有す る電解液供給部 9 4が配置されている。 更に、 研磨テープ/レ 8 6には、 対電極 8 2の側方に位置して、 トツプリング 8 8で表面を下向きにして保持した基板 Wを 下降させて研磨部材 8 4に接触させた時に、 基板 Wの表面に接触して通電させる 給電電極 9 6が配置されている。 この給電電極 9 6は、 電源 8 0の陽極に接続さ れる。 ドレッサー 9 0は、 例えば図 4及び図 5に示す例では、 上下動及び回転自 在で、 ダイヤモンドペレツト等の硬質部材ゃブラシ等からなる複数の円形の突起 9 0 aを周辺部下面にリング状に取付けて構成されている。 図示しないが、 ダイ ャモンド砥粒が周辺部下面にリング状に配置されたドレッサーを使用しても良い。 また、 図 5に示すドレッサー 9 0の直径はテープノレ半径とほぼ同等の大きさであ る力 例えば φ 1 0 0程度の小径のディスク形状で回転に加え、 研磨パッド面を 揺動させても良レ、。 この場合、 ダイャモンド砥粒は、 ディスクのパッド接触面の 全面に配置される。 This electrolytic processing apparatus comprises: a rotatable polishing table 86 having a counter electrode 82 connected to the cathode of W 80 and a polishing member 8 4 on its upper surface; It has a flexible top ring 8 8 and a dresser 90 and an absorber 92 that condition the surface of the polishing member 84. Above the polishing tape notch 8 6, an electrolyte solution supply unit 94 having a large number of electrolyte solution supply ports 94 a for supplying the electrolyte solution to the polishing member 84 is disposed. Furthermore, when the polishing tape / reel 86 is positioned on the side of the counter electrode 82 and the substrate W held with the surface facing downward by the top ring 8 8 is lowered and brought into contact with the polishing member 84. A feed electrode 96 is disposed which contacts the surface of the substrate W to be energized. The feed electrode 96 is connected to the anode of the power source 80. For example, in the example shown in FIG. 4 and FIG. 5, the dresser 90 has a plurality of circular projections 90a formed of hard material such as diamond pellet etc., brushes, etc., ringed on the lower surface of the peripheral portion under vertical movement and rotational self-rotation. It is configured to be attached to the Although not shown, the die It is also possible to use a dresser in which diamond abrasive grains are arranged in a ring shape on the lower surface of the peripheral portion. Also, the diameter of the dresser 90 shown in Fig. 5 is almost the same size as the tape notch radius. For example, in addition to rotation in the form of a small disk with a diameter of about φ100, it is good even if the polishing pad surface is rocked. Les. In this case, diamond abrasive is placed on the entire surface of the pad contact surface of the disk.
研磨部材 8 4は、 例えば発砲ポリウレタン樹脂製の研磨パッドから構成されて おり、 研磨部材 （研磨パッド） 8 4の表面 （上面） の研磨面 8 4 aには、 格子状 溝や同心円溝が形成されている。 また、 研磨部材 8 4に供給される電解液を介し て、 対電極 8 2と ¾¾Wとの電気的導通を確保するため、 研磨部材 8 4の内部に は、 上下に貫通する複数の貫通孔が形成されている。  The polishing member 84 is composed of, for example, a polishing pad made of foamed polyurethane resin, and lattice grooves or concentric grooves are formed on the polishing surface 8 4 a of the surface (upper surface) of the polishing member (polishing pad) 84. It is done. Also, in order to ensure electrical continuity between the counter electrode 82 and the 3⁄4⁄4⁄4 W via the electrolytic solution supplied to the polishing member 84, inside of the polishing member 84, there are a plurality of through holes that penetrate vertically. It is formed.
この例にあっては、 基; ¾Wを研磨部材 8 4の研磨面 8 4 aに接触させ、 基板 W と研磨部材 8 4とを相対運動 （ここでは共に回転運動） させた状態で、 研磨部材 8 4の上面に電解液を供給し、 対電極 8 2と基板表面の拡散バリア層 2 8との間 に電圧を印加することで、 基板表面の拡散バリア層 2 8の除去を行う。 この時、 基板表面の拡散バリア層 2 8には、 給電電極 9 6を通して給電される。 ここで、 拡散バリア層 2 8の除去は、 電解作用と賺的作用の両者で行われるため、 通常 の CMPよりも小さい （例えば 1 p s i (約 6 9 h P a ) 未満） 研磨圧力で研磨 を行うことで、 十分な研磨速度を確保することができる。 なお、 拡散バリア層 2 8の除去工程中または工程のインターバノレにおいては、 研磨部材 8 4の研磨面 8 4 aをドレッサー 9 0ゃァトマィザ 9 2を用いてコンディショニングしても良い。 この電解加工装置によれば、 拡散バリア層 2 8の除去は、 上記のように、 基板 Wと研磨部材 （研磨パッド） 8 4を互いに接触させながら相対運動させた状態で 電解液を供給し、 対電極 8 2と基板表面の拡散バリア層 2 8との間に電圧を印加 しながら行う。 この研磨時に印カロする電圧値は、 拡散パリア層 2 8の研磨の初期 と終了付近までの間で変化させても良い。 また、 絶縁膜 2 0上に拡散パリア層 2 8が縞状に残留する場合においては、 電圧の印加を停止して、 研磨部材 8 4の機 械的作用のみにより残留する拡散バリア層 2 8を除去するようにしても良く、 こ れによって、 残留した拡散パリア層 2 8に電気的導通が確保できなくなつて、 拡 散バリア層 2 8が除去できなくなることを防止することができる。 更に、 拡散バ リァ層 2 8の除去後に配線金属上に吸着したインヒビターを除去するため、 電圧 の印加を停止して、 研磨部材 8 4の機械的作用のみによる加工を行っても良い。 なお、 電解複合研磨の場合の電解液には砥粒が 1 0 %以下で混合されても良く、 これにより機械的作用の均一性が増力 Bする。 本発明は、 半導体ゥエーハ等の基板に 12泉を形成する過程で、 特に拡散バリア 層を構成する金属を有機電解液で溶解することで、 拡散バリァ層の除去のために 好適に用いられる。半導体装置の配線材料に用いられるバリァ層には、タンタル、 チタン、 タングステン、 ルテ ウムまたはそれらの化合物の 1種類からなる金属 が一般に使用される。 この化合物の具体例としては、 例えば、 窒化タンタル、 窒 化チタン、 窒化タングステン及ぴ窒化シリコンタンタルなどが挙げられる。 実施例 1 In this example, the polishing member 84 is brought into contact with the polishing surface 8 4 a of the polishing member 84, and the substrate W and the polishing member 84 are moved relative to each other (here, both are rotational motions). The electrolytic solution is supplied to the upper surface of 84, and a voltage is applied between the counter electrode 82 and the diffusion barrier layer 28 on the substrate surface to remove the diffusion barrier layer 28 on the substrate surface. At this time, power is supplied to the diffusion barrier layer 28 on the substrate surface through the feed electrode 96. Here, since the removal of the diffusion barrier layer 28 is performed by both the electrolytic action and the thermal action, the polishing pressure is smaller than that of the ordinary CMP (for example, less than 1 psi (about 69 h P a)). By doing this, it is possible to secure a sufficient polishing rate. In the process of removing the diffusion barrier layer 28 or during the process of removing the diffusion barrier layer 28, the polishing surface 8 4 a of the polishing member 84 may be conditioned using a dresser 90 a. According to this electrolytic processing apparatus, as described above, the diffusion barrier layer 28 is removed by supplying the electrolytic solution while the substrate W and the polishing member (polishing pad) 84 are moved relative to each other, This is performed while applying a voltage between the counter electrode 82 and the diffusion barrier layer 28 on the substrate surface. The voltage value that is marked during this polishing may be varied between the initial and the end of the polishing of the diffusion Paria layer 28. In the case where the diffusion barrier layer 28 remains in stripes on the insulating film 20, the application of the voltage is stopped and the diffusion barrier layer 28 remaining only by the mechanical action of the polishing member 84 is removed. It may be removed, and this can prevent the remaining diffusion barrier layer 28 from being unable to be removed because the remaining diffusion barrier layer 28 can not be electrically conducted. Furthermore, in order to remove the inhibitor adsorbed on the wiring metal after the removal of the diffusion barrier layer 28, the application of the voltage may be stopped and the processing by only the mechanical action of the polishing member 84 may be performed. Abrasive grains may be mixed in an amount of 10% or less in the electrolytic solution in the case of electrolytic composite polishing, whereby the uniformity of mechanical action increases B. The present invention is suitably used for removing a diffusion barrier layer by, in particular, dissolving the metal constituting the diffusion barrier layer with an organic electrolyte in the process of forming 12 springs on a substrate such as semiconductor wafer. In the barrier layer used for the wiring material of the semiconductor device, a metal consisting of tantalum, titanium, tungsten, ruthenium or one of their compounds is generally used. Specific examples of this compound include, for example, tantalum nitride, titanium nitride, tungsten nitride and silicon tantalum nitride. Example 1
表面に均一な膜厚の T a a Nスパッタリング膜 （膜厚約 2 0 0 n m) を形 成したシリコン酸化膜ゥエーハ片を試料 1として用意した。 そして、 この試料 1 の表面の T a /T a Nスパッタリング膜を図 2に示す電解加工装置を使用して研 磨除去した。 電解液として、 常温で以下の組成のものを使用した。  As a sample 1, a silicon oxide film piece in which a Ta N sputtering film (film thickness of about 200 nm) having a uniform film thickness was formed on the surface was prepared. Then, the Ta / TaN sputtered film on the surface of this sample 1 was polished and removed using the electrolytic processing apparatus shown in FIG. The following composition was used at room temperature as an electrolytic solution.
電解液の組成  Composition of electrolyte
電解質：へキサフルォロりん酸リチウム  Electrolyte: lithium hexafluorophosphate
テトラフルォロほう酸リチウム  Lithium tetrafluoroborate
テトラフルォロほう酸テトラェチルアンモニゥム  Tetrafluoroboronic acid tetraethyl ammonium
テトラフルォロほう酸テトラ- n -プチルアンモユウム 過塩素酸テトラェチルァンモ -ゥム  Tetrafluoroboronic acid Tetra-n-Putyl Ammoium Perchlorate Tetraethylammo-um
臭素テトラ- n-ブチルアンモニゥム  Bromine tetra-n-butyl ammonium
有機溶媒：炭酸プロピレン  Organic solvent: Propylene carbonate
インヒビター： トリチオシァヌル酸  Inhibitor: Trithiocyanuric acid
また、 対電極として、 白金を用い、 参照電極として、 A g ZA g + (銀/銀ィ オン）参照電極を用いた。電解液は、有機溶媒である炭酸プロピレン適量に対し、 上記 6種類の各電解質がそれぞれ 0. 5モル濃度になるように、 適量を満たす容 器に入れ常温で調整して作製した。 インヒビターは、 0. 1重量％添加した。 試料 1の端部の T a ZT a Nスパッタリング膜に電源（北斗電工： HS-501G) の 正極側から配線された電気的接点 （作用極用酉 2^ 2本） を接続し、 対電極側であ る白金に慰原の負極側から配線された電気的接点 （対電極用配線 1本） を接続し た。 そして、 電源の参照電極用酉線に参照電極である銀/銀ィオン電極を接続し た。 この状態で、 T aノ T a Nスパッタリング膜と対電極との間に任意の値、 例 えば、 I V ( v s A g ZA g +銀イオン参照電極） に設定した電圧を印加して 電解加工を始めた。 ただし、 電圧の選択には有機溶媒の 電圧を考慮しなけれ ばならないため、 炭酸プロピレンの分解電圧 3 . 7 V ( v s A g /A g +) を 超えないように調整した。 図 6に、 T a /T a Nスパッタリング膜の一部をマスキングしながら、 T a / T a Nスパッタリング膜を 1 V ( V s A g / A g +) で約 1 0分間電解加工し た後の写真を示す。 図 6から、 写真中央に示される曲線状の境界線より右側の試 料 1上にマスキングテープを貼付した箇所 （マスキング部） は、 電解液には接触 していないため加工は行われておらず、 同左側 （電解加工部） は、 電解加工によ り下地のシリコン酸ィヒ膜が露出していることがわかる。 In addition, platinum was used as a counter electrode, and an Ag ZA g + (silver / silver ion) reference electrode was used as a reference electrode. The electrolytic solution was prepared by placing at a normal temperature into a vessel filled with an appropriate amount of propylene so that each of the above six types of electrolytes had a molar concentration of 0.5 with respect to the appropriate amount of propylene carbonate as an organic solvent. The inhibitor was added at 0.1% by weight. Connect an electrical contact (2 ^ 2 electrodes for working electrode) wired from the positive electrode side of the power supply (Hokuto Denko: HS-501G) to the TaZTaN sputtering film at the end of sample 1, and the counter electrode side The electrical contacts (one wire for counter electrode) wired from the negative side of the source were connected to platinum. Then, a silver / silver ion electrode, which is a reference electrode, was connected to the reference electrode wire of the power supply. In this state, electrolytic processing is performed by applying a voltage set to an arbitrary value, for example, IV (vs. Ag ZA g + silver ion reference electrode) between the Ta N Ta N sputtering film and the counter electrode. I started. However, since the voltage of the organic solvent must be taken into consideration when selecting the voltage, the voltage was adjusted so as not to exceed the decomposition voltage of 3.7 V (vs A g / A g + ) of propylene carbonate. In Fig. 6, the Ta / TaN sputtering film was electroprocessed at 1 V (VsAg / Ag +) for about 10 minutes while masking a part of the Ta / TaN sputtering film. Show the picture after. As shown in FIG. 6, the portion (masking portion) where the masking tape is attached on the sample 1 on the right side of the curved boundary shown in the center of the photograph is not processed because it is not in contact with the electrolyte. On the left side (electrolyzed portion), it can be seen that the underlying silicon oxide film is exposed by electrolytic processing.
図 7は、 電解加工後の試料 1の表面を触針式段差測定器によつて測定した時の 断面プロファイルを示す。 同図に描カゝれている曲線は、 試料 1の断面形状を表し ており、 マスキングテープを貼付して加工されていない部分 （マスキング部） が 図 7の左側に、電解加工された部分（電解加工部）は図 7の右側に示されている。 両者の段差は、 約 2000A (= 2 0 0 n m) であることから、 T a N及び T aが完 全に電解加工されていることがわかる。  FIG. 7 shows a cross-sectional profile when the surface of sample 1 after electrolytic processing is measured by a stylus type step difference measuring device. The curve drawn in the figure represents the cross-sectional shape of the sample 1, and the portion (masking portion) not processed by applying the masking tape is the portion (electrolytic processing) on the left side of FIG. The electroprocessed part is shown on the right side of FIG. The difference in level between the two is about 2000 A (= 200 nm), which indicates that Ta N and Ta are completely electroprocessed.
実施例 2 Example 2
表面に均一な膜厚の銅めつき膜 （膜厚約 1 . 5 μ τα) を形成したシリコンゥェ 一ハ片を試料 2として用意した。 そして、 実施例 1と同じ条件 （I V ( V S A g /A g +) で約 1 0分間） の電解加工を行って、 試料 2の表面の銅めつき膜を 研磨除去した。 A silicon wafer piece having a copper-clad film with a uniform film thickness (film thickness of about 1.5 μτα) formed on the surface was prepared as Sample 2. Then, electrolytic processing was carried out under the same conditions as in Example 1 (about 10 minutes under IV ( VS A g / A g + )) to polish away the copper-clad film on the surface of Sample 2.
図 8に、 電解加工後の試料 2の写真を示す。 図 8から、 マスキングテープを貼 付して加工されていない部分 （マスキング部） 及び電解液に接触する部分 （電解 加工部）には、下地のシリコン膜は露出していないことがわかる。また、図 9は、 電解加工後の試料 2の断面プロファイルを示す。 図 9から、 マスキングテープを 貼付して加工液に接触させていない箇所（マスキング部） と加工面（電解加工部） はほぼ同一面にあり、 銅めつき膜の加工が抑制されていることがわかる。 産業上の利用可能性  Fig. 8 shows a photograph of sample 2 after electrolytic processing. It can be seen from FIG. 8 that the underlying silicon film is not exposed at the portion (masking portion) which is not processed by applying the masking tape (masking portion) and the portion which contacts the electrolytic solution (electrolytic portion). Further, FIG. 9 shows a cross-sectional profile of sample 2 after electrolytic processing. From FIG. 9, it is found that the portion (masking portion) and the processing surface (electrolytic processing portion) where the masking tape is attached and not in contact with the processing fluid is almost on the same surface, and the processing of the copper plating film is suppressed. Recognize. Industrial applicability
本発明の電解加工方法は、半導体集積回路の金属配線の加工に際し、 半導体ゥェ ーハ等の基板の表面に設けたトレンチやビアホール等の凹部に配線金属埋め込み の為のダマシンめつきを行った後に、過剰な酉 2/線金属層及ぴ拡散バリァ層を除去し 基板の表面を平坦化するのに使用される。  According to the electrolytic processing method of the present invention, damascene plating for burying wiring metal in recesses such as trenches and via holes provided on the surface of a substrate such as a semiconductor wafer is performed when processing metal wiring of a semiconductor integrated circuit. It is later used to planarize the surface of the substrate by removing excess 酉 2 / wire metal layer and diffusion barrier layer.

Claims

請求の範囲 The scope of the claims
1 . 有機溶媒に電解質を溶かした電解液に基板の表面を接触させ、 前記基板の表面に電位を印加して該表面の電解加工を行うことを特徴とする電 解加工方法。 1. An electrolytic processing method comprising: bringing a surface of a substrate into contact with an electrolytic solution in which an electrolyte is dissolved in an organic solvent, and applying an electric potential to the surface of the substrate to carry out electrolytic processing of the surface.
2 . 前記基板の表面に、 前記有機溶媒の分解電圧未満の所定の値に制御した 正電位を印カ卩して、 定電位制御型の電解加工を行うこと特徴とする請求項 1記載 の電解カ卩ェ方法。 2. The electrolytic processing according to claim 1, wherein a positive potential controlled at a predetermined value less than the decomposition voltage of the organic solvent is applied to the surface of the substrate to perform constant potential control type electrolytic processing. How to do it.
3 . 前記電解液として、 フッ素イオン、 塩素イオン、 臭素イオン、 よう素ィ オン、 へキサフルォロりん酸イオン、 テトラフルォロほう酸イオン及びへキサフ ルォロ砒素ィオンの少なくとも一つを含む溶液を使用することを特徴とする請求 項 1または 2記載の電解加工方法。 3. As the electrolyte, a solution containing at least one of fluorine ion, chloride ion, bromide ion, iodine ion, hexafluorophosphate ion, tetrafluoroborate ion and hexafluoroarsenic ion is used. The electrolytic processing method according to claim 1 or 2.
4 . 前記有機溶媒は、 炭酸プロピレン、 炭酸エチレンまたはジメチルスルホ キシドのうちの少なくとも 1種類以上からなることを特徴とする請求項 1または 2記載の電解加工方法。 4. The electrolytic processing method according to claim 1 or 2, wherein the organic solvent comprises at least one of propylene carbonate, ethylene carbonate and dimethyl sulfoxide.
5 . 前記電解質として、 へキサフルォロりん酸リチウム、 へキサフルォ口り ん酸テトラプチルアンモ-ゥム、 へキサフルォロりん酸テトラメチルアンモ-ゥ ム、 へキサフルォロりん酸テトラプチルアンモニゥム、 テトラフルォロほう酸ァ ンモ-ゥム、 及ぴテトラフルォロほう酸リチウムの少なくとも一つを使用するこ とを特徴とする請求項 1または 2記載の電解加工方法。 5. As the electrolyte, lithium hexafluorophosphate, tetrabutyl ammonium phosphate, tetramethyl ammonium hexafluorophosphate, tetrabutyl ammonium phosphate, hexafluorophosphoric acid ammonium tetrafluoroammonium phosphate The electrolytic processing method according to claim 1 or 2, characterized in that at least one of lithium and lithium tetrafluoride is used.
6 . 前記電解液は、 トリァゾーノレ環、 ピロ一ノレ環、 ピラゾーノレ環、 チアゾー ル環またはィミダゾール環を有する複素環式化合物の少なくとも 1種類を更に含 むことを特徴とする請求項 1または 2記載の電解加工方法。 6. The electrolytic solution according to claim 1 or 2, wherein the electrolytic solution further contains at least one heterocyclic compound having a triazonore ring, a pyrrolo noreto ring, a pyrazonole ring, a thiazolo ring or a imidazole ring. Electrolytic processing method.
7. 前記複素環式化合物は、 含窒素複素環式化合物であって、 ベンゾトリア ゾーノレ、 ピロ一ノレ、 3— ( 2一チェ二ノレ） 一 1一ピラゾーノレ、 2—ブチノレイミダ ゾール、 6—チォグァニンまたはトリチオシァヌル酸のいずれかであることを特 徴とする請求項 6記載の電解加工方法。 7. The heterocyclic compound is a nitrogen-containing heterocyclic compound, which is a benzotriazole, pyrrolo nore, 3- (2 cicho nore), 1 1 pylazonole, 2-butynoreimidazole, 6-thioguanine or trithiocyanyl. The electrolytic processing method according to claim 6, characterized in that it is any one of acids.
8 . タンタル、 チタン、 タングステン、 ノレテェゥムまたはそれらの化合物か らなるバリァ層が形成された基板の表面を電解加工で加工することを特徴とする 請求項 1または 2記載の電解力 Hェ方法。 8. The method according to claim 1, wherein the surface of the substrate on which the barrier layer formed of tantalum, titanium, tungsten, noble metal or a compound thereof is formed is processed by electrolytic processing.
9 . 基板を保持する基板保持部と、 9. A substrate holding unit for holding a substrate,
前記基板の表面に電解加工を行う加工面を有する加工具と、  A processing tool having a processing surface for performing electrolytic processing on the surface of the substrate;
前記基板の表面と前 加工具との間に を印加する 源と、  A source for applying between the surface of the substrate and the processing tool;
有機溶媒に電解質を溶かした電解液を保持して該電解液に前記基板の表面及び 前記加工具の加工面を接触させる電解槽を有することを特徴とする電解加工装置。  What is claimed is: 1. An electrolytic processing apparatus comprising: an electrolytic bath that holds an electrolytic solution in which an electrolyte is dissolved in an organic solvent and brings the surface of the substrate and the processing surface of the processing tool into contact with the electrolytic solution.
1 0 . 前記電解質は、 へキサフルォロりん酸イオンであることを特徴とする請 求項 9記載の電解加工装置。 10. The electrolytic processing apparatus according to claim 9, wherein the electrolyte is hexafluorophosphate ion.
1 1 . 前記基板の表面に印加する電位の値を調節する制御装置を更に有するこ とを特徴とする請求項 9または 1 0記載の電解加工装置。 11. The electrolytic processing apparatus according to claim 10, further comprising a control device that adjusts the value of the potential applied to the surface of the substrate.
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