US20030087590A1 - Method of planarization - Google Patents
Method of planarization Download PDFInfo
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- US20030087590A1 US20030087590A1 US10/288,224 US28822402A US2003087590A1 US 20030087590 A1 US20030087590 A1 US 20030087590A1 US 28822402 A US28822402 A US 28822402A US 2003087590 A1 US2003087590 A1 US 2003087590A1
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- metallic layer
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- 238000000034 method Methods 0.000 title claims abstract description 42
- 238000005498 polishing Methods 0.000 claims abstract description 73
- 239000002002 slurry Substances 0.000 claims abstract description 71
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 38
- 229910052721 tungsten Inorganic materials 0.000 claims description 31
- 239000010937 tungsten Substances 0.000 claims description 31
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 30
- 239000002245 particle Substances 0.000 claims description 16
- 239000003795 chemical substances by application Substances 0.000 claims description 15
- 239000000758 substrate Substances 0.000 claims description 15
- 235000012239 silicon dioxide Nutrition 0.000 claims description 14
- 239000000377 silicon dioxide Substances 0.000 claims description 14
- 239000007800 oxidant agent Substances 0.000 claims description 12
- 230000001590 oxidative effect Effects 0.000 claims description 12
- 239000004065 semiconductor Substances 0.000 claims description 9
- 238000000151 deposition Methods 0.000 claims description 5
- 239000003989 dielectric material Substances 0.000 claims description 4
- 150000007524 organic acids Chemical group 0.000 claims description 4
- 238000000059 patterning Methods 0.000 claims description 3
- 229910052751 metal Inorganic materials 0.000 description 14
- 239000002184 metal Substances 0.000 description 14
- 238000004519 manufacturing process Methods 0.000 description 6
- 229910052782 aluminium Inorganic materials 0.000 description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 5
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 4
- 238000005530 etching Methods 0.000 description 4
- 239000003292 glue Substances 0.000 description 4
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000007769 metal material Substances 0.000 description 4
- QGLKJKCYBOYXKC-UHFFFAOYSA-N nonaoxidotritungsten Chemical compound O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 QGLKJKCYBOYXKC-UHFFFAOYSA-N 0.000 description 4
- 229920002120 photoresistant polymer Polymers 0.000 description 4
- 229910001930 tungsten oxide Inorganic materials 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 238000007796 conventional method Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- MLIWQXBKMZNZNF-KUHOPJCQSA-N (2e)-2,6-bis[(4-azidophenyl)methylidene]-4-methylcyclohexan-1-one Chemical compound O=C1\C(=C\C=2C=CC(=CC=2)N=[N+]=[N-])CC(C)CC1=CC1=CC=C(N=[N+]=[N-])C=C1 MLIWQXBKMZNZNF-KUHOPJCQSA-N 0.000 description 2
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical group CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 2
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical group OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 238000005229 chemical vapour deposition Methods 0.000 description 2
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical group OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- XLJMAIOERFSOGZ-UHFFFAOYSA-M cyanate group Chemical group [O-]C#N XLJMAIOERFSOGZ-UHFFFAOYSA-M 0.000 description 2
- 238000001312 dry etching Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N nitrate group Chemical group [N+](=O)([O-])[O-] NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 2
- KHIWWQKSHDUIBK-UHFFFAOYSA-N periodic acid Chemical group OI(=O)(=O)=O KHIWWQKSHDUIBK-UHFFFAOYSA-N 0.000 description 2
- 125000002081 peroxide group Chemical group 0.000 description 2
- 238000001020 plasma etching Methods 0.000 description 2
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 2
- 229910052814 silicon oxide Inorganic materials 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical group O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 238000005299 abrasion Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 238000007521 mechanical polishing technique Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B37/00—Lapping machines or devices; Accessories
- B24B37/04—Lapping machines or devices; Accessories designed for working plane surfaces
- B24B37/042—Lapping machines or devices; Accessories designed for working plane surfaces operating processes therefor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B57/00—Devices for feeding, applying, grading or recovering grinding, polishing or lapping agents
- B24B57/02—Devices for feeding, applying, grading or recovering grinding, polishing or lapping agents for feeding of fluid, sprayed, pulverised, or liquefied grinding, polishing or lapping agents
-
- 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
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
- H01L21/3105—After-treatment
- H01L21/31051—Planarisation of the insulating layers
- H01L21/31053—Planarisation of the insulating layers involving a dielectric removal step
-
- 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
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
- H01L21/3205—Deposition of non-insulating-, e.g. conductive- or resistive-, layers on insulating layers; After-treatment of these layers
- H01L21/321—After treatment
- H01L21/32115—Planarisation
- H01L21/3212—Planarisation by chemical mechanical polishing [CMP]
Definitions
- the present invention relates to a method of planarization. More particularly, the present invention relates to a method of forming a metallic plug within an inter-metal dielectric layer by filling metallic material into a via, and then performing a chemical-mechanical polishing (CMP) operation to remove excess metal above the plug and surrounding areas. Once the metallic layer is polished away, metallic residues above the inter-metal dielectric layer are removed by a controlled increase in the polishing rate of the dielectric layer. Consequently, undesirable metallic residues are completely removed and a planar surface is obtained at the same time.
- CMP chemical-mechanical polishing
- CMP chemical-mechanical polishing
- the slurry normally contains a chemically active component such as an acid or a base, and a mechanically active component such as abrasive particles made from silicon dioxide.
- a chemically active component such as an acid or a base
- a mechanically active component such as abrasive particles made from silicon dioxide.
- a conventional method of forming a plug includes the steps of depositing insulating material over an integrated circuit device, and then patterning the insulating layer to form a contact hole or a via opening. Finally, conductive material is deposited to fill the hole or the via so that a vertical interconnect penetrating the insulating layer and linking electrically with a portion of the device in the substrate is formed.
- a chemical vapor deposition (CVD) method is normally used to fill the via of hole with tungsten (W).
- CVD chemical vapor deposition
- a layer of tungsten also forms over the insulating layer.
- An etching back method for example, a reactive ion etching (RIE) method, can be used to remove the tungsten above the insulating layer.
- RIE reactive ion etching
- the etching back operation can lead to over-etching, and a portion of the tungsten within the via may be removed to form a recessed cavity. Therefore, subsequently deposited aluminum layer makes poor contact with the tungsten inside the recessed cavity of the via. Furthermore, when the tungsten is etched back, microscopic particles will remain attached to the wafer surface. These attached particles can often lead to undesirable damage of the device. Hence, an alternative method of removing excessive tungsten above an insulating layer, that is, a chemical-mechanical polishing method, is often used.
- FIGS. 1A through 1D are cross-sectional views showing the progression of manufacturing steps in producing a plug according to a conventional method. Due to insufficient planarization of the inter-metal dielectric layer, recessed cavities are produced in some areas leading to device problems.
- patterned conductive lines 112 are formed above a semiconductor substrate 100 .
- the conductive lines 112 are made of aluminum or aluminum alloy.
- MOS devices and the semiconductor substrate 100 underneath the conductive lines 112 are not fully drawn.
- a dielectric layer 114 for example, a silicon oxide layer is deposited over the conductive layers 112 and the substrate 100 .
- the dielectric layer 114 is somewhat influenced by the underlying ridge pattern of the conductive lines 112 on the surface of the semiconductor substrate 100 , such that the surface of dielectric layer 114 manifests an undulated surface.
- planarization of the dielectric layer 114 is carried out.
- a chemical-mechanical polishing method is used to form a planarized dielectric layer 114 a .
- not all areas are planarized and some areas contain recessed cavities 116 .
- a photoresist layer (not shown in FIG. 1C) is formed over the dielectric layer 114 a .
- the photoresist layer exposes portions of the dielectric layer 114 a where via openings will form.
- the dielectric layer 114 a is selectively etched using an etching technique such as a dry etching method.
- a portion of each conductive line 12 is exposed, forming via openings 126 and a dielectric layer 114 b.
- a glue layer 118 conformal to the dielectric layer 114 b is formed and covers the substrate structure. Thereafter, a layer of tungsten 120 is formed over the glue layer 118 and completely fills the via openings 126 .
- a chemical-mechanical polishing operation is carried out using slurry for polishing tungsten.
- a portion of the tungsten layer 120 above the dielectric layer 114 b is removed, thereby forming tungsten plugs 120 a within the via openings 126 .
- residual tungsten 120 b is embedded, which makes its removal particularly difficult.
- the slurry for polishing tungsten has an especially slow removing rate for dielectric layer 114 b , residual tungsten 120 b entrenched inside the cavities 116 is difficult to be removed by prolonging the chemical-mechanical polishing operation.
- the residual tungsten 120 b within the cavities 116 can affect the quality of a finished device, and may lead to low yield and waste of the silicon wafer.
- the present invention provides a planarization method that utilizes a chemical-mechanical polishing operation.
- a planarization method that utilizes a chemical-mechanical polishing operation.
- this invention provides a planarization method that utilizes a chemical-mechanical polishing operation.
- a first slurry especially for polishing a metallic layer is first employed to remove a greater portion of the metallic layer.
- a second slurry for polishing a dielectric layer and having properties very similar to the metal-polishing slurry is added and mixed together so that polishing rate for the dielectric layer is increased. Consequently, metallic residues remaining on the dielectric layer are removed and a planar dielectric layer is obtained at the same time.
- the invention provides a method of planarization.
- the method includes the steps of providing a semiconductor substrate having a first metallic layer, and then forming a dielectric layer over the first metallic layer and the substrate.
- the dielectric layer is patterned to form a via opening.
- a second metallic layer is formed over the dielectric layer and fills the via opening.
- a chemical-mechanical polishing operation using a first slurry for removing metallic layer is performed to remove most of the second metallic layer above the dielectric layer.
- a second slurry for removing dielectric layer is added and mixed with the first slurry for removing metallic layer, while the chemical-mechanical polishing operation is continued. Eventually, the dielectric layer is planarized and any residual material from the second metallic layer is removed.
- FIGS. 1A through 1D are cross-sectional views showing the progression of manufacturing steps in producing a plug according to a conventional method
- FIG. 2 is a cross-sectional view showing a plug fabricated according to one preferred embodiment of this invention.
- FIGS. 3A through 3D are cross-sectional views showing the progression of manufacturing steps for producing a plug within an inter-metal dielectric layer having no embedded residual metallic material according to a second preferred embodiment of this invention.
- This invention provides a method of removing metallic residues stop an inter-metal dielectric layer and planarizing the dielectric layer at the same time.
- the method is actually a continuation of the conventional process depicted in FIGS. 1A through 1D.
- the dielectric layer 114 b (indicated in FIG. 1D) is planarized.
- a portion of the dielectric layer 114 b together with metallic residues 120 b is removed.
- FIG. 2 is a cross-sectional view showing a plug fabricated according to one preferred embodiment of this invention.
- the dielectric layer 114 b is now turned into a dielectric layer 114 c . Since the dielectric layer 114 b is probably an oxide layer, the slurry used in the chemical-mechanical polishing operation is for removing oxide. Since operations are carried forward from FIG. 1D, detailed explanations of elements in FIG. 2 are omitted because they are labeled identically.
- polishing agents within the slurries will not congeal into lumps that may scratch and damage the wafer. Furthermore, the same type of polishing agents must be used in the two types of slurries, because different polishing agents will have different polishing characteristics. If two or more non-similar types of polishing agents are used at the same time, processing instability may result.
- pH value of the slurry for removing tungsten is around 2.1-2.5, and the polishing agent is silicon dioxide particles with a size of around 200 nm.
- the slurry for removing tungsten further comprises oxidant.
- the oxidant can be ferric nitrate, hydrogen peroxide, potassium periodate or acid solution containing nitrate group, cyanate group, periodate group, peroxide group or strong oxidant, for example.
- the oxidant in the slurry reacts with the surface of the tungsten under acidic condition to form tungsten oxide and the silicon dioxide particles are used to polish away the tungsten oxide.
- the slurry for polishing a dielectric has a pH value of around 2.1-2.5, and the polishing agent is again silicon dioxide particles with a size of around 200 nm.
- the slurry for polishing the dielectric comprises organic acid group such as acetate group, citrate group and oxalate group. The hydroxide group in the slurry bonds with the silicon atoms on the surface of the dielectric to form silicon hydroxide which is easily removed by the silicon dioxide particles.
- FIGS. 3A through 3D are cross-sectional views showing the progression of manufacturing steps for producing a plug within an inter-metal dielectric layer having no embedded residual metallic material according to a second preferred embodiment of this invention.
- patterned conductive lines 312 are formed above a semiconductor substrate 300 .
- the conductive lines 312 are made of aluminum or aluminum alloy.
- MOS devices and the semiconductor substrate 300 underneath the conductive lines 312 are not fully drawn.
- a dielectric layer 314 for example, a silicon oxide layer, is deposited over the conductive layers 312 and the substrate 300 .
- the dielectric layer 314 is somewhat influenced by the underlying ridge pattern of the conductive lines 312 on the surface of the semiconductor substrate 300 , such that the surface of dielectric layer 314 manifests an undulated surface.
- planarization of the dielectric layer 314 is deferred until after the plug is formed. By this arrangement, one less chemical-mechanical polishing operation can be conducted. Therefore, some wafer processing time is saved.
- a photoresist layer (not shown in the Fig.) is formed over the unplanarized dielectric layer 314 .
- the photoresist layer exposes the area where a desired via opening is to be formed.
- the dielectric layer 314 is selectively etched to form a dielectric layer 314 a using, for example, a dry etching method. Hence, via openings 326 that expose a portion of the conductive line 312 are formed.
- a glue layer 318 conformal to the dielectric layer 314 a is formed over the substrate structure.
- a conductive layer 320 is formed over the glue layer 318 and completely fills the via openings 326 .
- the conductive layer is a tungsten layer.
- a chemical-mechanical polishing operation is carried out using slurry for removing metal.
- slurry for removing tungsten is used. Consequently, a large portion of the conductive layer 320 above the dielectric layer 314 a is removed forming plugs 320 a .
- the slurry for removing tungsten further comprises oxidant.
- the oxidant can be ferric nitrate, hydrogen peroxide, potassium periodate or acid solution containing nitrate group, cyanate group, periodate group, peroxide group or strong oxidant, for example.
- the oxidant in the slurry reacts with the surface of the tungsten under acidic condition to form tungsten oxide and the silicon dioxide particles are used to polish away the tungsten oxide. Therefore, the new tungsten surface is exposed and is oxidized by the oxidant in the slurry.
- slurry for removing dielectric material is added and mixed together with the original slurry. Subsequently, the chemical-mechanical polishing operation is continued until the dielectric layer 314 a is completely planarized and any metallic residues 320 b are removed from the dielectric 314 a surface.
- the slurry for polishing the dielectric comprises organic acid group such as acetate group, citrate group and oxalate group. The hydroxide group in the slurry bonds with the silicon atoms on the surface of the dielectric to form silicon hydroxide which is easily removed by the silicon dioxide particles.
- pH value of the slurry for removing metal is around 2.1-2.5
- the polishing agent is silicon dioxide particles with a size of around 200 nm.
- the slurry for polishing a dielectric has a pH value of around 2.1-2.5, and the polishing agent is again silicon dioxide particles with a size of around 200 nm.
- planarization using a chemical-mechanical polishing method according to this invention is capable of eliminating metallic residues above the surface of a dielectric layer as well as planarizing the dielectric layer, device quality can be greatly improved.
- a chemical-mechanical polishing technique is used for planarization. By first polishing away a large portion of a metallic layer with slurry for polishing a metal and then adding another similar slurry for polishing a dielectric, the dielectric layer is planarized and any metallic residues above the dielectric layer are removed at the same time.
- the slurry for removing metallic material and the slurry for removing dielectric material are very similar in physical properties. They both have a pH value of between 2.1-2.5, and particles of silicon dioxide with a size of around 200 nm are used as polishing agents.
- steps in forming a plug can be conducted without the need for performing a planarization operation first. Hence, one less planarization using a chemical-mechanical polishing operation is needed, and some wafer processing time can be saved.
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Abstract
A planarization method that utilizes a chemical-mechanical polishing operation. In the polishing operation, a first slurry for polishing a metallic layer is first employed to remove a greater portion of the metallic layer. Next, a second slurry for polishing a dielectric layer and having properties very similar to the metal-polishing slurry is added and mixed together with the slurry for polishing a metallic layer so that the polishing rate for the dielectric layer is increased. Consequently, metallic residues remaining on the dielectric layer are removed, and a planar dielectric layer is obtained at the same time.
Description
- This application is a continuation-in-part of prior application Ser. No. 09/182,968, filed Oct. 29, 1998.
- 1. Field of Invention
- The present invention relates to a method of planarization. More particularly, the present invention relates to a method of forming a metallic plug within an inter-metal dielectric layer by filling metallic material into a via, and then performing a chemical-mechanical polishing (CMP) operation to remove excess metal above the plug and surrounding areas. Once the metallic layer is polished away, metallic residues above the inter-metal dielectric layer are removed by a controlled increase in the polishing rate of the dielectric layer. Consequently, undesirable metallic residues are completely removed and a planar surface is obtained at the same time.
- 2. Description of Related Art
- Amongst the methods of planarizing a surface, chemical-mechanical polishing (CMP) is one of the most important techniques for the global planarization for VLSI or ULSI circuit fabrication. In the process of manufacturing integrated circuit devices, material often has to be removed from the surfaces of intermediate devices one or more times. Furthermore, material layers sometimes have to be planarized before carrying out the next operation. As the number of material removing operations or planarization increases, CMP operations are used more often. Chemical-mechanical polishing operates by pressing the front surface of a wafer down onto a rotating surface on a polishing table, and supplying slurry at the same time.
- The slurry normally contains a chemically active component such as an acid or a base, and a mechanically active component such as abrasive particles made from silicon dioxide. Although the physical mechanism of the polishing action is still not fully understood, the chemical reaction and the mechanical abrasion of its active components has satisfactorily polished and planarized various types of surfaces. Nowadays, CMP methods are frequently applied to the planarization of metallic and dielectric layers.
- A conventional method of forming a plug includes the steps of depositing insulating material over an integrated circuit device, and then patterning the insulating layer to form a contact hole or a via opening. Finally, conductive material is deposited to fill the hole or the via so that a vertical interconnect penetrating the insulating layer and linking electrically with a portion of the device in the substrate is formed.
- Since metallic conductive material such as aluminum is unable to fill the via or hole satisfactorily, a chemical vapor deposition (CVD) method is normally used to fill the via of hole with tungsten (W). In the process of depositing tungsten into the via, a layer of tungsten also forms over the insulating layer. After the via is completely filled, excess tungsten above the via needs to be removed before aluminum lines are deposited above the insulating layer and the via. An etching back method, for example, a reactive ion etching (RIE) method, can be used to remove the tungsten above the insulating layer.
- However, the etching back operation can lead to over-etching, and a portion of the tungsten within the via may be removed to form a recessed cavity. Therefore, subsequently deposited aluminum layer makes poor contact with the tungsten inside the recessed cavity of the via. Furthermore, when the tungsten is etched back, microscopic particles will remain attached to the wafer surface. These attached particles can often lead to undesirable damage of the device. Hence, an alternative method of removing excessive tungsten above an insulating layer, that is, a chemical-mechanical polishing method, is often used.
- FIGS. 1A through 1D are cross-sectional views showing the progression of manufacturing steps in producing a plug according to a conventional method. Due to insufficient planarization of the inter-metal dielectric layer, recessed cavities are produced in some areas leading to device problems.
- First, as shown in FIG. 1A, patterned
conductive lines 112 are formed above asemiconductor substrate 100. Theconductive lines 112 are made of aluminum or aluminum alloy. To simplify the drawing, MOS devices and thesemiconductor substrate 100 underneath theconductive lines 112 are not fully drawn. Next, adielectric layer 114, for example, a silicon oxide layer is deposited over theconductive layers 112 and thesubstrate 100. Thedielectric layer 114 is somewhat influenced by the underlying ridge pattern of theconductive lines 112 on the surface of thesemiconductor substrate 100, such that the surface ofdielectric layer 114 manifests an undulated surface. - Next, as shown in FIG. 1B, planarization of the
dielectric layer 114 is carried out. For example, a chemical-mechanical polishing method is used to form a planarizeddielectric layer 114 a. However, not all areas are planarized and some areas containrecessed cavities 116. - Next, as shown in FIG. 1C, a photoresist layer (not shown in FIG. 1C) is formed over the
dielectric layer 114 a. The photoresist layer exposes portions of thedielectric layer 114 a where via openings will form. Thereafter, thedielectric layer 114 a is selectively etched using an etching technique such as a dry etching method. Ultimately, a portion of each conductive line 12 is exposed, forming viaopenings 126 and adielectric layer 114 b. - In the subsequent step, a
glue layer 118 conformal to thedielectric layer 114 b is formed and covers the substrate structure. Thereafter, a layer oftungsten 120 is formed over theglue layer 118 and completely fills thevia openings 126. - Next, as shown in FIG. 1D, a chemical-mechanical polishing operation is carried out using slurry for polishing tungsten. Hence, a portion of the
tungsten layer 120 above thedielectric layer 114 b is removed, thereby formingtungsten plugs 120 a within thevia openings 126. However, due to the presence ofrecessed cavities 116 on the surface of the originaldielectric layer 114 b,residual tungsten 120 b is embedded, which makes its removal particularly difficult. - In fact, because the slurry for polishing tungsten has an especially slow removing rate for
dielectric layer 114 b,residual tungsten 120 b entrenched inside thecavities 116 is difficult to be removed by prolonging the chemical-mechanical polishing operation. Theresidual tungsten 120 b within thecavities 116 can affect the quality of a finished device, and may lead to low yield and waste of the silicon wafer. - In light of the foregoing, there is a need to improve the method of planarization.
- Accordingly, the present invention provides a planarization method that utilizes a chemical-mechanical polishing operation. Through increasing and controlling the removal rate of the inter-metal dielectric layer, recessed cavities above the dielectric layer due to an inefficient planarization technique are avoided. Therefore, device problems caused by metallic residues remaining on the dielectric surface can be reduced.
- In another aspect, this invention provides a planarization method that utilizes a chemical-mechanical polishing operation. In the polishing operation, a first slurry especially for polishing a metallic layer is first employed to remove a greater portion of the metallic layer. Next, a second slurry for polishing a dielectric layer and having properties very similar to the metal-polishing slurry is added and mixed together so that polishing rate for the dielectric layer is increased. Consequently, metallic residues remaining on the dielectric layer are removed and a planar dielectric layer is obtained at the same time.
- To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a method of planarization. The method includes the steps of providing a semiconductor substrate having a first metallic layer, and then forming a dielectric layer over the first metallic layer and the substrate. Next, the dielectric layer is patterned to form a via opening. Thereafter, a second metallic layer is formed over the dielectric layer and fills the via opening. Subsequently, a chemical-mechanical polishing operation using a first slurry for removing metallic layer is performed to remove most of the second metallic layer above the dielectric layer. Then, a second slurry for removing dielectric layer is added and mixed with the first slurry for removing metallic layer, while the chemical-mechanical polishing operation is continued. Eventually, the dielectric layer is planarized and any residual material from the second metallic layer is removed.
- It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
- The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings,
- FIGS. 1A through 1D are cross-sectional views showing the progression of manufacturing steps in producing a plug according to a conventional method;
- FIG. 2 is a cross-sectional view showing a plug fabricated according to one preferred embodiment of this invention; and
- FIGS. 3A through 3D are cross-sectional views showing the progression of manufacturing steps for producing a plug within an inter-metal dielectric layer having no embedded residual metallic material according to a second preferred embodiment of this invention.
- Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
- This invention provides a method of removing metallic residues stop an inter-metal dielectric layer and planarizing the dielectric layer at the same time. The method is actually a continuation of the conventional process depicted in FIGS. 1A through 1D. By continuing the polishing operation while adding a slurry for removing dielectric layer to the original slurry for removing metallic layer, the
dielectric layer 114 b (indicated in FIG. 1D) is planarized. At the same time, a portion of thedielectric layer 114 b together withmetallic residues 120 b is removed. - FIG. 2 is a cross-sectional view showing a plug fabricated according to one preferred embodiment of this invention. As shown in FIG. 2, the
dielectric layer 114 b is now turned into adielectric layer 114 c. Since thedielectric layer 114 b is probably an oxide layer, the slurry used in the chemical-mechanical polishing operation is for removing oxide. Since operations are carried forward from FIG. 1D, detailed explanations of elements in FIG. 2 are omitted because they are labeled identically. - Because the slurry for removing tungsten layer is present when the slurry for removing dielectric layer is added, physically similar slurries have to be selected. Physical similarity refers to the characteristic of having similar pH value. Therefore, when the two types of slurries are mixed together, unstable conditions due to a difference in pH values will not happen.
- In other words, the polishing agents within the slurries will not congeal into lumps that may scratch and damage the wafer. Furthermore, the same type of polishing agents must be used in the two types of slurries, because different polishing agents will have different polishing characteristics. If two or more non-similar types of polishing agents are used at the same time, processing instability may result.
- Hence, according to the embodiment of this invention, pH value of the slurry for removing tungsten is around 2.1-2.5, and the polishing agent is silicon dioxide particles with a size of around 200 nm. It should be noticed that the slurry for removing tungsten further comprises oxidant. The oxidant can be ferric nitrate, hydrogen peroxide, potassium periodate or acid solution containing nitrate group, cyanate group, periodate group, peroxide group or strong oxidant, for example. The oxidant in the slurry reacts with the surface of the tungsten under acidic condition to form tungsten oxide and the silicon dioxide particles are used to polish away the tungsten oxide. Therefore, the new tungsten surface is exposed and is oxidized by the oxidant in the slurry. Similarly, in order to match the slurry for polishing tungsten, the slurry for polishing a dielectric has a pH value of around 2.1-2.5, and the polishing agent is again silicon dioxide particles with a size of around 200 nm. It should be noticed that the slurry for polishing the dielectric comprises organic acid group such as acetate group, citrate group and oxalate group. The hydroxide group in the slurry bonds with the silicon atoms on the surface of the dielectric to form silicon hydroxide which is easily removed by the silicon dioxide particles.
- FIGS. 3A through 3D are cross-sectional views showing the progression of manufacturing steps for producing a plug within an inter-metal dielectric layer having no embedded residual metallic material according to a second preferred embodiment of this invention.
- First, as shown in FIG. 3A, patterned
conductive lines 312 are formed above asemiconductor substrate 300. Theconductive lines 312 are made of aluminum or aluminum alloy. To simplify the drawing, MOS devices and thesemiconductor substrate 300 underneath theconductive lines 312 are not fully drawn. Next, adielectric layer 314, for example, a silicon oxide layer, is deposited over theconductive layers 312 and thesubstrate 300. Thedielectric layer 314 is somewhat influenced by the underlying ridge pattern of theconductive lines 312 on the surface of thesemiconductor substrate 300, such that the surface ofdielectric layer 314 manifests an undulated surface. However, in this embodiment, planarization of thedielectric layer 314 is deferred until after the plug is formed. By this arrangement, one less chemical-mechanical polishing operation can be conducted. Therefore, some wafer processing time is saved. - Next, as shown in FIG. 3B, a photoresist layer (not shown in the Fig.) is formed over the unplanarized
dielectric layer 314. The photoresist layer exposes the area where a desired via opening is to be formed. Thereafter, thedielectric layer 314 is selectively etched to form adielectric layer 314 a using, for example, a dry etching method. Hence, viaopenings 326 that expose a portion of theconductive line 312 are formed. - In the subsequent step, a
glue layer 318 conformal to thedielectric layer 314 a is formed over the substrate structure. Then, aconductive layer 320 is formed over theglue layer 318 and completely fills the viaopenings 326. Preferably, the conductive layer is a tungsten layer. - Next, as shown in FIG. 3C, a chemical-mechanical polishing operation is carried out using slurry for removing metal. Preferably, slurry for removing tungsten is used. Consequently, a large portion of the
conductive layer 320 above thedielectric layer 314 a is removed formingplugs 320 a. It should be noticed that the slurry for removing tungsten further comprises oxidant. The oxidant can be ferric nitrate, hydrogen peroxide, potassium periodate or acid solution containing nitrate group, cyanate group, periodate group, peroxide group or strong oxidant, for example. The oxidant in the slurry reacts with the surface of the tungsten under acidic condition to form tungsten oxide and the silicon dioxide particles are used to polish away the tungsten oxide. Therefore, the new tungsten surface is exposed and is oxidized by the oxidant in the slurry. - Next, as shown in FIG. 3D, with the slurry for removing metal present, slurry for removing dielectric material is added and mixed together with the original slurry. Subsequently, the chemical-mechanical polishing operation is continued until the
dielectric layer 314 a is completely planarized and anymetallic residues 320 b are removed from the dielectric 314 a surface. It should be noticed that the slurry for polishing the dielectric comprises organic acid group such as acetate group, citrate group and oxalate group. The hydroxide group in the slurry bonds with the silicon atoms on the surface of the dielectric to form silicon hydroxide which is easily removed by the silicon dioxide particles. - Because the slurry for removing tungsten layer is present when the slurry for removing dielectric layer is added, physically similar slurries have to be selected. The reason for choosing physically similar slurries has already been explained in the first embodiment. Therefore, in the second embodiment, pH value of the slurry for removing metal is around 2.1-2.5, and the polishing agent is silicon dioxide particles with a size of around 200 nm.
- Similarly, in order to match the slurry for polishing a metal, the slurry for polishing a dielectric has a pH value of around 2.1-2.5, and the polishing agent is again silicon dioxide particles with a size of around 200 nm.
- Since planarization using a chemical-mechanical polishing method according to this invention is capable of eliminating metallic residues above the surface of a dielectric layer as well as planarizing the dielectric layer, device quality can be greatly improved.
- In summary, major aspects of this invention includes:
- 1. A chemical-mechanical polishing technique is used for planarization. By first polishing away a large portion of a metallic layer with slurry for polishing a metal and then adding another similar slurry for polishing a dielectric, the dielectric layer is planarized and any metallic residues above the dielectric layer are removed at the same time.
- 2. The slurry for removing metallic material and the slurry for removing dielectric material are very similar in physical properties. They both have a pH value of between 2.1-2.5, and particles of silicon dioxide with a size of around 200 nm are used as polishing agents.
- 3. After the deposition of an inter-metal dielectric layer, steps in forming a plug can be conducted without the need for performing a planarization operation first. Hence, one less planarization using a chemical-mechanical polishing operation is needed, and some wafer processing time can be saved.
- It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
Claims (12)
1. A planarization method that utilizes a chemical-mechanical polishing operation, the method comprising the steps of:
providing a semiconductor substrate that has a first metallic layer formed thereon;
forming a dielectric layer over the first metallic layer;
patterning the dielectric layer to form a via opening that exposes a portion of the first metallic layer;
forming a second metallic layer over the dielectric layer that completely fills the via opening;
performing a chemical-mechanical polishing operation, using a first slurry with an oxidant for polishing the second metallic layer, to remove the second metallic layer above the dielectric layer and form a plug inside the opening; and
adding a second slurry containing organic acid groups for polishing the dielectric material without first removing the first slurry, and then continuing the chemical-mechanical polishing operation until the dielectric layer is planarized and metallic residues of the second metallic layer are completely removed.
2. The method of claim 1 , wherein step of forming the second metallic layer includes depositing tungsten.
3. The method of claim 1 , wherein a pH value of the first slurry and a pH value of the second slurry are about the same.
4. The method of claim 1 , wherein the first slurry and the second slurry contain the same type of polishing agents.
5. The method of claim 1 , wherein the first slurry has a pH value of between 2.1-2.5, and includes a polishing agent containing silicon dioxide particles with a size of around 200 nm.
6. The method of claim 1 , wherein the second slurry has a pH value of between 2.1-2.5, and includes a polishing agent containing silicon dioxide particles with a size of around 200 nm.
7. The method of claim 1 , further comprising planarizing the dielectric layer after forming the dielectric layer.
8. A planarization method that utilizes a chemical-mechanical polishing operation, the method comprising the steps of:
providing a semiconductor substrate that has a first metallic layer formed thereon;
forming a dielectric layer over the first metallic layer;
patterning the dielectric layer to form a via opening that exposes a portion of the first metallic layer;
forming a second metallic layer over the dielectric layer that completely fills the via opening;
performing a chemical-mechanical polishing operation, using a first slurry for polishing the second metallic layer, to remove the second metallic layer above the dielectric layer and form a plug inside the opening, wherein the first slurry comprises an oxidant; and
adding a second slurry containing an organic acid for polishing the dielectric material without first removing the first slurry for polishing the second metallic layer, and then continuing the chemical-mechanical polishing operation until the dielectric layer is planarized and metallic residues of the second metallic layer are completely removed, wherein a pH value of the slurry for polishing the second metallic layer and a pH value of the slurry for polishing the dielectric layer are about the same.
9. The method of claim 8 , wherein step of forming the second metallic layer includes depositing tungsten.
10. The method of claim 8 , wherein the first slurry and the second slurry contain the same type of polishing agents.
11. The method of claim 8 , wherein the first slurry has a pH value of between 2.1 to 2.5, and includes a polishing agent containing silicon dioxide particles with a size of around 200 nm.
12. The method of claim 8 , wherein the second slurry has a pH value of between 2.1 to 2.5, and includes a polishing agent containing silicon dioxide particles with a size of around 200 nm.
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US10/288,224 US20030087590A1 (en) | 1998-10-29 | 2002-11-04 | Method of planarization |
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US09/182,968 US6609954B1 (en) | 1998-10-29 | 1998-10-29 | Method of planarization |
US10/288,224 US20030087590A1 (en) | 1998-10-29 | 2002-11-04 | Method of planarization |
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US09/182,968 Continuation-In-Part US6609954B1 (en) | 1998-10-29 | 1998-10-29 | Method of planarization |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
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US20050176253A1 (en) * | 2004-02-05 | 2005-08-11 | Atsushi Shigeta | Method of manufacturing semiconductor device |
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US20050176253A1 (en) * | 2004-02-05 | 2005-08-11 | Atsushi Shigeta | Method of manufacturing semiconductor device |
US7413989B2 (en) | 2004-02-05 | 2008-08-19 | Kabushiki Kaisha Toshiba | Method of manufacturing semiconductor device |
CN100416753C (en) * | 2004-02-05 | 2008-09-03 | 株式会社东芝 | Method of manufacturing semiconductor device |
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