CN100533785C - Plating process - Google Patents
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- CN100533785C CN100533785C CNB2007101098952A CN200710109895A CN100533785C CN 100533785 C CN100533785 C CN 100533785C CN B2007101098952 A CNB2007101098952 A CN B2007101098952A CN 200710109895 A CN200710109895 A CN 200710109895A CN 100533785 C CN100533785 C CN 100533785C
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
Methods of plating electrical contacts on a photosensitive device are provided. Also provided are methods of plating electrical contacts on solar cells.
Description
Technical field
The present invention relates generally to the metal-plated field.More specifically, the present invention relates to the metal-plated field of photovoltaic device.
Background technology
Photovoltaic device, for example solar cell generally includes the semiconductor wafer that forms single big PN junction (junction).The electromagnetic radiation such as the daylight incident light to this knot produces electric charge carrier and produces electric current in device, must collect this electric current and be sent to external circuit.The electric current that is produced roughly is directly proportional with the radiation of incident.Collect described electric current with the metal pattern of the two sides ohmic contact of PN junction.This metal pattern need provide low resistance path (resistance path), so that the ohmic loss of the electric current that is produced minimizes.Must limit physical extent (physical extent), the especially physical extent on the device front surface of described metal pattern, minimize, that is to say for the purpose that produces electric current to make the energy minimization of loss so that stop the surface area of incident radiation energy.Usually, the metal pattern of front comprises the fillet of the material that conductivity is very high.
In making the panel solar battery, can be by ohmic contact layer and the barrier material that applies thin patterning, metallizing then obtains gratifying metal pattern.A kind of metallized method is a silk screen printing silver thickener, and this method provides resistance enough low thick conductor for a lot of the application.But the resistance of silver-colored thickener itself is not low to the degree that optimized solar cell properties enough is provided.Need the stronger material of conductivity, for example the silver of plating or copper minimize the ohmic loss that reduces solar battery efficiency.With silver-colored electrolytic deposition on photovoltaic device, in described device itself, produce electric current by utilizing radiant energy.In described silver-colored electrolysis method for plating, when a surface at described device applies voltage simultaneously with the facing surfaces of radiant energy irradiation device, obtain the silver layer of uniform deposition.
The conventional silver-colored electroplating bath that is used for the auxiliary plating of this light contains cyanide.Yet, use the plating bath that contains cyanide to produce many problems, for example processing, waste disposal and environmental problem.Need a kind of plating bath that does not contain cyanide that is suitable for the auxiliary photovoltaic device plating of light in the industry.United States Patent (USP) 5,882,435 (Holdermann) have disclosed the method for electroplating the solar cell that is made by crystalline silicon.This patent has exemplified uses the silver plating bath that contains cyanide.Can not use the silver plating bath that does not contain cyanide although this patent is mentioned, it is not enough that it has described the stability of silver bath under illuminate condition that does not contain cyanide.
Therefore, still need a kind of suitable metal plating bath that does not contain cyanide in the industry, especially silver plating bath, the described metal plating bath that does not contain cyanide can be used in the electro-plating method that uses the radiant energy irradiation, and this plating bath has enough stability under service condition.
Summary of the invention
The present invention has overcome above-mentioned defective, provide a kind of and go up methods of plating electrical contacts at the light-sensitive device (photovoltaic device) that shows the photovoltage effect, described method comprises provides the semiconductor wafer with at least two first type surfaces, described wafer is formed with photovoltaic junction therein, make a first type surface of working as described wafer be exposed to the light time, negative electrical charge gathers at first first type surface, and positive charge gathers at second first type surface, described wafer is contacted with the metal plating bath that does not contain cyanide, apply voltage to described plating bath, and described wafer is exposed to light with depositing metal layers on described first first type surface, wherein, described plating bath is the aqueous solution, and comprises metal ion, at least a water miscible compound that contains nitro, at least a surfactant, at least a amide compound and at least a water-soluble amino acids that is selected from, the component of water-soluble sulfonic acid and composition thereof.
In another embodiment, with described wafer with before the metal plating bath that does not contain cyanide contacts, on described second first type surface, provide metal coating.In this embodiment, metal is moved to the plating bath from the coating of described second first type surface, moves to the first electronegative first type surface more therefrom.
The metal plating bath that does not contain cyanide that the present invention is used has enough stability under the used illuminate condition of the auxiliary plating of light, to provide metal deposition satisfying on the photovoltaic device of required specification.
Description of drawings
Fig. 1 is the schematic diagram of photovoltaic device of the present invention.
Fig. 2 is the schematic diagram that metal coating is provided on photovoltaic device according to the present invention.
Embodiment
In the full text of this specification, as indicating in the literary composition, term " plating " is meant by for example electroplating or the chemical plating depositing metal layers." deposition " and " plating " is used interchangeably in this explanation in full.Indefinite article " one " is intended to comprise odd number and plural number.Unless otherwise indicated, below the implication of abbreviation is as follows: ℃=degree centigrade; The g=gram; The mL=milliliter; The L=liter; The A=ampere; The dm=decimetre; μ m=micron; The nm=nanometer.Except as otherwise noted, all percentage and ratio are all based on weight.All number ranges all comprise end points, and can any sequential combination, are 100% unless can obviously find out such number range aggregate upper.
Can use various photovoltaic devices, for example solar cell in the present invention.Usually use semiconductor chip, for example semiconductor wafer is produced this photovoltaic device.In one embodiment, solar cell is made up of monocrystalline, polycrystalline or amorphous silicon wafer.In another embodiment, solar cell is made up of polycrystalline silicon wafer.Although following description is at silicon wafer, it will be understood by those skilled in the art that the semiconductor wafer that other is fit to, for example GaAs, SiGe and germanium also can be used for the present invention.When using silicon wafer, described silicon wafer has p type matrix usually and mixes.
This wafer can be circular, foursquare or rectangular, maybe can be any shape that other is fit to.This wafer can have a variety of sizes.For example, the diameter of circular wafer can be 150nm, 200nm, 300nm, 400nm or bigger.
Can be with the back metallization of described wafer.Can the whole back of washing, the perhaps part of washing back is to form grid (grid).Can provide back metallization by multiple technologies, and this back metallization can carry out before the metallization of wafer front, perhaps carry out simultaneously with the metallization of wafer front.In one embodiment, the form with conducting paste (thickener of argentiferous for example contains the thickener of aluminium or contains the thickener of silver and aluminium) applies metal coating rearwards.This conducting paste generally includes conductive particle and the organic bond that is embedded in the glass matrix.Can pass through multiple technologies, for example silk screen printing is on conducting paste paint wafer.After applying thickener, fire wafer to remove organic bond.When use contains the conducting paste of aluminium, be diffused into the back of wafer aluminum portions, if or be used in also contain silver thickener in the time, described aluminium can form alloy with silver.The thickener that uses this class to contain aluminium can improve the resistance contact and " p+ " is provided doped region.By applying aluminium or boron earlier, then phase counterdiffusion can also produce heavily doped " p+ " type district.In one embodiment, can apply the back metal coating then with containing aluminium thickener paint back and firing.Before applying the back metal coating, can randomly remove and come from the residue of firing that contains the aluminium thickener.In another embodiment, can and pass through chemical plating or electroplate plated metal coating on described Seed Layer in the back of wafer deposition Seed Layer.Use the present invention, on the Seed Layer of the back of wafer plated metal can with carry out simultaneously at wafer front plated metal.
Can randomly carry out the texture etching (texture etching) of crystal orientation to give the light incident shape that the improvement of reflection has been reduced on described surface to the front of wafer.In order to produce semiconductor junction, phosphorous diffusion or iron implantation take place, to produce the n doped region and the wafer with PN junction is provided in the front of wafer.
Can randomly add dielectric layer to the front of described wafer.This dielectric layer not only can be used as passivation layer (passivation layer) but also can be used as antireflection layer.The dielectric layer that is fit to includes but not limited to, such as SiO
xSilicon oxide layer, such as Si
3N
4Silicon nitride layer and the combination of silica and silicon nitride layer, and silicon oxide layer and/or silicon nitride layer and such as TiO
xThe combination of titanium oxide layer.In aforesaid general formula, x is the number of oxygen atom.Can be by a variety of technology, for example various vapor deposition process deposit this dielectric layer.
The front of wafer is contained metallized pattern usually.For example, the front of wafer is made up of current collection line (currentcollecting line) and current bus bar (current busbar).The current collection line crosses bus usually, and compares with bus, and the current collection line has thinner structure (being size).
In one embodiment, use the metallize front of wafer of conducting paste, described conducting paste is identical or different with any conducting paste on the back that is used in wafer.Any conducting paste of front of wafer of being used to metallize does not contain aluminium usually.Can be in an operation or in the operation that separates any conducting paste that uses on the front that is used in wafer or the back be fired.Used temperature depended on the factors such as thickness of used concrete thickener, used any dielectric layer (or antireflection layer) during thickener was fired.In the limit of power that is chosen in those skilled in the art of this temperature.In addition, it will be understood by those skilled in the art that and to carry out described burning process in containing the atmosphere of aerobic, inert atmosphere, reducing atmosphere or in the combination of these atmosphere.For example, can fire under first temperature in the atmosphere that contains minute quantity oxygen, fire under second temperature under inert atmosphere or under the reducing atmosphere then, wherein said second temperature is higher than described first temperature.
After described burning process, randomly wafer is contacted with buffering acid solution (for example buffered hydrofluoric acid solution), to remove any oxide that in firing step, produces.Can realize this contact by solution being sprayed on the wafer or wafer being immersed in this solution or by other suitable way.
In another embodiment, with optional antireflection layer, for example silicon nitride comes the front of coated wafers.Limit channel patterns then in front.The semiconductor body that described channel patterns passes antireflective (or dielectric) layer and enters wafer.The degree of depth that described groove enters into the semiconductor body of described wafer can be the 1-25 micron.Can use darker or more shallow groove.Can use several different methods to form channel patterns, such as but not limited to laser ablation, mechanical means and photoetching method, all these methods all are well known in the art.Described mechanical means comprise saw and scrape.Typical photoetching method is included in the imageable material of deposition on the wafer surface, makes described imageable patterns of materialization to form groove, and described channel patterns is transferred to wafer, with the channel patterns depositing metal layers and remove described imageable material.In one embodiment, before step, remove described imageable material with the channel patterns depositing metal layers.In another embodiment, after step, remove described imageable material with the channel patterns depositing metal layers.When having imageable material in metal deposition step, this imageable material should avoid having in the radiation wavelength used in metal deposition step any dyestuff of absorption, for example contrast dye (contrast dye).The imageable material that exists in the plating step should contain the dyestuff that can see through the wavelength of radiation used in the plating step.
When but described image forming material is liquid, can be by any suitable technology, such as but not limited to spin coating, scraper be coated with, curtain coating and roller coat be deposited on this material on the surface of wafer.When but described image forming material is dry film, can this material be deposited on the surface of wafer by irradiation.
But, described image forming material comes the described imageable material of patterning in actinic radiation by being seen through mask exposure.But selected concrete image forming material is depended in the selection of actinic radiation.The wavelength that is fit to of actinic radiation includes but not limited to, 500nm is to being lower than 200nm, for example 430nm, 405nm, 365nm, 248nm and 193nm, and Extreme Ultraviolet (" EUV ") and electron beam.Also can use laser to come the described imageable material of patterning.
Follow the design transfer in the imageable material to wafer substrate.Use the wet chemical etch technology or use the dry-etching technology to carry out design transfer.The dry-etching technology that is fit to includes but not limited to plasma etching, for example reactive ion etching.Described channel patterns is made up of narrower line of cross sectional dimensions (being the current collection line) and the thicker line (being bus) of cross sectional dimensions usually.Described bus crosses described current collection line.
Can use any suitable polymers remover to remove described imageable material, for example those polymer removers of Rohm And Haas Electronic Mater (U.S., Massachusetts) sale.This class remover can be alkaline, acid or basic neutrality.
No matter what technology to form channel patterns with, this groove can be randomly with acid (for example hydrofluoric acid) or alkali contacts so that flute surfaces has texture or roughening.Randomly, can use n type dopant to carry out other method of diffusion, obtain " n++ " at trench region and mix.
Usually, conducting paste is deposited in the groove of wafer front.Can be before the metallization front, afterwards or with the metallization front time, the back of metallization wafer.When using conducting paste metallization back, in single step, fire the front and back usually.
Behind the front pattern and back that use conducting paste metallization wafer, depositing metal layers on the conductive pattern in front.This metal level can be any suitable conducting metal, for example gold, silver or copper, and silver normally.In one embodiment, the metal level that is deposited is made up of the metal identical with used metal in the conducting paste.For example, silver layer is deposited on the conducting paste that contains silver.
Compare with the pattern of only being made up of the conducting paste of firing, contain the metal level of deposition on the conducting paste of firing, especially the efficient of the pattern of the metal level of electro-deposition improves.In addition, on the conducting paste of firing, use the metal level that deposits to reduce the width of current collection line and bus, provide and more can be exposed to the solar cell surface of incident light, thereby produced more electric current.Less metal wire mean stop incident light on the surface metal still less.
Fig. 1 is representative photovoltaic device 5 of the present invention, for example schematic diagram of solar cell.Device 5 has semiconductor wafer 10, and described semiconductor wafer has PN junction, back 11 and front 12.Next 11 are metallized, for example by silver metallized.The metal pattern (for example silver-colored pattern) of bus 14 and current collection line 15 formations is contained in front 12.Described metal pattern is made up of the silver layer that is deposited on the argentiferous conducting paste.Described metal pattern and front 12 ohmic contact.Typically, front 12 is coated with antireflective figure layer, and for example silicon nitride or other dielectric materials are also not shown among the figure.
Prepare plating coating metal layer on the pattern of wafer front and metallized back now.In the present invention, using the plating bath depositing metal layers on the conducting paste of firing that does not contain cyanide, specifically is silver layer, shines described semiconductor wafer with incident light simultaneously.Being used for plating bath of the present invention is the aqueous solution, and contains metal ion, at least a water miscible compound of nitro, at least a surfactant, at least a amide compound and at least a component that is selected from water-soluble amino acids, water-soluble sulfonic acid and composition thereof of containing.According to the ENLIGHT of silver plating bath of the present invention available from Rohm And Haas Electronic Mater (U.S., Massachusetts)
TMSilver plating bath 600.
Metal ion in the plating bath of the present invention can provide by using any suitable solution soluble metal compound (normally slaine).This metallic compound can include but not limited to: metal halide; Metal nitrate; Metal carboxylate, for example acetate, metal formate and metal gluconate hydrochlorate; Metal amino acid complex, for example metal cysteine complex compound; Metal alkyl sulfonate, for example metal mesylate, metal esilate; Metal hydroxyalkylated sulfonic acid salt, metal toluene fulfonate and metal phenolsulfonate.Exemplary metallic compound comprises copper compound, gold compound and silver compound.In one embodiment, described metallic compound is a silver compound.Particularly, the metallic compound of Shi Heing comprises silver nitrate, silver-colored cysteine complex compound, methanesulfonic acid silver, ethyl sulfonic acid silver, propane sulfonic acid silver, silver phenolsulfonate and silver acetate.It will be understood by those skilled in the art that when metal is silver described slaine is not silver halide usually, because the solubility of this class salt is limited.Also can use the mixture of metallic compound in the plating bath of the present invention.This mixture can be the metallic compound with same metal, but be different compounds, the mixture of silver nitrate and silver-cysteine complex compound for example, or have the metallic compound of different metal, for example mixture of silver-cysteine complex compound and copper gluconate.When the mixing use has the different metal compound of different metal, the plating bath of this metal will deposit the alloy of different metal.
It is 0.1-60g/L that the amount that joins the metallic compound in the plating bath is enough to provide the concentration of metal ions in the plating bath, is more typically 0.5-50g/L, and that the most general is 1-50g/L.When described metal ion was silver ion, the concentration of silver ion was generally 2-40g/L in the plating bath.This metal compound can be commercially available from multiple source usually, for example Aldrich chemical company (state of Wisconsin, Milwaukee).
Metal plating bath of the present invention is electroplating bath and contains electrolyte.Any all can be used in the multiple electrolyte, comprise bronsted lowry acids and bases bronsted lowry in the metal plating bath of the present invention.Exemplary electrolyte includes but not limited to, alkyl sulfonic acid, for example methanesulfonic acid, ethyl sulfonic acid and propane sulfonic acid; Hydroxyalkylated sulfonic acid; Aryl sulfonic acid, for example toluenesulfonic acid, benzene sulfonic acid and phenolsulfonic acid; Contain amino sulfonic acid, amidosulfonic acid (amido sulfonic acid) for example, sulfamic acid; Mineral acid; Carboxylic acid, for example formic acid and halogenated acetic acids; Halogen acids and pyrophosphate.The salt that it will be understood by those skilled in the art that bronsted lowry acids and bases bronsted lowry also can be used as electrolyte.In addition, described electrolyte can contain the mixture of acid blend, alkali mixture or one or more acid and one or more alkali.This electrolyte can be commercially available from multiple source usually, for example Aldrich chemical company.
Although do not want to be bound by theory, it is believed that the compound that contains nitro in the plating bath of the present invention is used for stable and complexing plating bath.Can use any in the multiple water miscible compound that contains nitro.This compound that contains nitro includes but not limited to, contains carboxylic acid and the salt and the sulfonic acid and the salt thereof that contain nitro of nitro.This compound that contains nitro can contain one or more nitros.The described water miscible compound that contains nitro has at least one heterocyclic group usually.In other embodiments, the described compound that the contains nitro heterocyclic compound that is aromatics.The exemplary compound that contains nitro includes but not limited to, 2-nitrophthalic acid, 3-nitrophthalic acid, 4-nitrophthalic acid and/or p-nitrophenyl sulfonic acid.Usually, the described consumption of compound in plating bath that contains nitro is 0.1-200g/L, is more typically 0.5-175g/L, and the most general is 1-150g/L.This compound that contains nitro can be commercially available from multiple source usually, for example Aldrich chemical company.
A variety of surfactants can be used for the present invention.Can use any in anion surfactant, cationic surfactant, amphoteric surfactant and the non-ionic surface active agent.Exemplary ionic surfactant pack is drawn together succinate.In one embodiment, described surfactant is selected from cationic surfactant and amphoteric surfactant.Exemplary cationic surfactant includes but not limited to, available from the commodity of Degussa TEGOTAIN by name
TMChlorination 1,3-didecyl-glyoxal ethyline.In another embodiment, described surfactant is both sexes, for example available from the commodity of Degussa TEGOTAIN by name
TMAlkyl betaine.Can use surfactant mixtures.The amount of this surfactant in plating bath is generally 0.1-5g/L.
Randomly, vitamin can be included in the plating bath of the present invention.They can be fat-soluble or water miscible.Usually, use water miscible vitamin.The fat-soluble vitamin that is fit to comprises A, D
1, D
2, D
3, K
1, K
2And E.The water soluble vitamin that is fit to comprises C, B
1, B
2, B
3, B
6And B
12Exemplary vitamin includes but not limited to, retinol, sterol, ergocalciferol, vitamin D
3, vitamin K
1, polyisoprene menadione, α-tocopherol, β-tocopherol, ascorbic acid, thiamines, nicotinic acid, riboflavin, pantothenic acid, biotin, Cobastab
6, folic acid and Cobastab
12Particularly suitable vitamin comprises ascorbic acid, thiamines, nicotinic acid, riboflavin, pantothenic acid, biotin, vitamin B6 and folic acid.Vitamin used herein is intended to comprise the salt of vitamin.
Generally speaking, when adding vitamin in plating bath, the amount of vitamin in plating bath is 0.01-150g/L, is more typically 0.5-100g/L, and that the most general is 1-100g/L.Vitamin can be commercially available from multiple source usually, for example Aldrich chemical company.
A variety of amido compounds can be used in the plating bath of the present invention.The amide-containing compound that is fit to includes but not limited to, such as the sulfonic acid amides of butanedioic acid sulfonamide with such as the carboxylic acid amide of succinamide (succinamic acid).
Generally speaking, the amount of amido compounds in plating bath is 0.01-150g/L, is more typically 0.5-100g/L, and that the most general is 1-100g/L.Amido compounds can be commercially available from multiple source usually, for example Aldrich chemical company.In addition, but the amido compounds original position forms acid imide, for example, and succinimide.Although do not wish to be bound by theory, the acid imide that joins in the alkali plating bath is its corresponding amide compound in the plating bath temperature inversion.It is believed that it is by at imido carbon-nitrogen key (C-N) locate by hydroxyl ion (OH
-) nucleophilic attack obtains.
Any amino acid all is suitable in the plating bath of the present invention, comprises amino acid whose derivative and amino acid whose salt.Except that one or more amino, amino acid of the present invention can contain one or more sulfydryls.The amino acid whose example that is fit to includes but not limited to glycine, alanine, cysteine, methionine and 4-amino-nicotinic acid.When amino acid was used for plating bath of the present invention, its consumption was 0.1-150g/L, is more typically 0.5-150g/L, and that the most general is 0.5-125g/L.Can use amino acid whose mixture.This metallic compound can be commercially available from multiple source usually, for example Aldrich chemical company.When described metal was silver, the amount of water soluble amino acid compound surpassed the stoichiometry of silver usually.
A variety of water miscible sulfonic acid can be used in the plating bath of the present invention.Exemplary sulfonic acid comprises any sulfonic acid described in the top electrolyte.When sulfonic acid is used as electrolyte, do not need to add in addition other sulfonic acid.Usually, the amount of described sulfonic acid is 0.1-200g/L.
Randomly, plating bath of the present invention can contain one or more other component.These other components include but not limited to brightener, grain refiner, ductility reinforcing agent, rust inhibitor (anti-tarnish agent) and antifreezing agent.The compound that contains sulfone can be used as brightener.Particularly, the compound that contains sulfone of Shi Heing contains one or two aromatic ring on its sulfuryl.This aromatic ring can randomly be replaced by one or more substituting groups that are selected from nitro, amino, halogen, alkyl and metal.When existing, the described consumption of compound in plating bath that contains sulfone is generally 0.001-5g/L.
A variety of rust inhibitor can randomly be used for plating bath of the present invention.The rust inhibitor that is fit to includes but not limited to triazole, BTA, tetrazolium, imidazoles, benzimidazole and indazole.Useful especially rust inhibitor comprises (C
1-C
16) alkyl imidazole and Aryimidazole.Exemplary rust inhibitor includes but not limited to, methylimidazole, ethyl imidazol(e), propyl imidazole, hexyl imidazoles, decyl imidazoles, undecyl imidazole, 1-phenylimidazole, 4-phenylimidazole, hydroxybenzotriazole, amino BTA, 2-imidazoles carboxylic aldehyde, BTA carboxylic acid, 2-guanidine radicals benzimidazole, 2-Aminoindazole, chlorinated benzotriazole, ethoxy benzo triazole, hydroxyethyl imidazole, hydroxy benzo imidazoles and 1,2, the 4-triazole.The mixture of rust inhibitor should be used in the plating bath of the present invention.Generally speaking, when using rust inhibitor, its consumption is 0.005 to 50g/L.
In another embodiment, described metal plating bath can randomly contain buffer.Exemplary buffer includes but not limited to, borate buffer (for example borax), PB, citrate buffer agent and carbonate buffer agent.The amount of used buffer is enough to make the pH of plating bath to maintain desirable level, and this amount is that those skilled in the art's number is known.
In another execution mode, can randomly in plating bath, add alloying metal.Can use any suitable alloying metal.This alloying metal is well-known to those skilled in the art.
The pH of plating bath of the present invention in the scope of 7-14, more generally is 7-12 usually, and that the most general is 9-12.The working temperature of plating bath of the present invention is generally 10-30 ℃.When described plating bath was silver plating bath, described working temperature was generally 10-20 ℃, more generally was 15-20 ℃.Usually use cooler with the temperature maintenance of plating bath below room temperature.
Be used for the metal plating bath that does not contain cyanide of the present invention and under the auxiliary employed illuminate condition of plating of light, have enough stability, so that the metal deposit that satisfies required specification to be provided on photovoltaic device.In addition, plating bath of the present invention is compared with the photoinduced plating bath of routine has ecological dominance, because it does not contain cyanide.Another advantage of the present invention is to realize high current output on the photovoltaic device of metal-plated, thereby can reduce the energy usage in the metal plating process, thereby reduces running cost.Another advantage is that plating bath of the present invention is enough stable under photoinduced plating condition, and it can be used.
Prepare the metal level of deposition of thick on the wafer 5 of patterning now.Fig. 2 shows the device according to photoinduced electroplated metal layer of the present invention.The wafer 5 of patterning of preparation as mentioned above is immersed in the plating bath 21 that is contained in plating pond 20.The wafer 5 of patterning is the negative electrode in plating pond.Plating bath 21 as mentioned above.Placing light source 25 uses usually by the numeral 27 radiant energy irradiate wafer of representing 5.The positive terminal of power supply 24 contacts with silver anode 22, and negative terminal contacts with the back (back) or the P face of wafer 5.If the wafer of patterning 5 is silicon solar cells, the energy that light source 25 can for example be to be provided is similar to the quartz-halogen lamp of the solar spectrum of silicon solar cell institute Electrophotosensitive.Can use a variety of other light sources, include but not limited to, such as the incandescent lamp and the mercury lamp of 250 watts of lamps.Luminous energy 27 can be continuous or pulsed.Can realize pulsed exposure by interrupting light with mechanical chopper.
Plating pond 20 must be to plating bath 21 chemically inert materials and can see through luminous energy 27.Perhaps, wafer-level is placed in the plating pond 20, and from the top irradiate wafer in plating pond, in this case, plating pond 20 needs not be can printing opacity.For shown silver-plated on silicon wafer 5, quartz beaker is the plating pond 20 that is fit to.Silver anode 22, for example silver strip is dissolved in and keeps plating bath saturated by silver in the plating bath and along with plating.
By applying voltage with the front of luminous energy 27 irradiate wafer 5 and by power supply 24 to the plating pond, in the front of wafer 5 (front) and back (back) plating takes place simultaneously.The voltage that is applied can be continuous or pulsed.Collision luminous energy (impinging light energy) produces electric current in solar cell.The plating speed of the front of wafer 5 is the functions that are incident on the radiation intensity on the wafer, because the electric current that is produced is directly proportional with incident intensity.The plating speed of front surface and rear surface is controlled by regulating luminous intensity and external current densities respectively independently.For the concentrator solar cell, need the silver layer of 1-25 micron thickness usually, accurate thickness depends on various factors, for example the geometry of method of application, battery size, pattern etc.
The used voltage that applies of the present invention can have the current density of certain limit.Usually, current density is 0.1A/dm
2To 10A/dm
2, more generally be 0.1A/dm
2To 5A/dm
2Concrete current requirements depends on the concrete size of used crystal chip.If the front of irradiate wafer also is reduced to about 50 milliamperes or littler with external voltage, then usually at the continuous plating of front surface, and plating does not take place in the back of wafer.The irradiation of front improved the uniformity of back plating and overcome with from Seed Layer to away from all relevant difficult problems of the ohmmic drop of the point that electrically contacts.It will be understood by those skilled in the art that method for plating of the present invention can randomly comprise the plating step that one or more are reverse, for example the periodically reverse method for plating of pulsed.
Method above specifically having described with reference to the plating silver layer.This technology can perform well in other material of plating, for example mixture of copper, gold or tin and nickel equally.Can be by the water-bath plating tin that contains stannous chloride, nickel chloride, ammonium hydroxide and ammonium fluoride and the mixture of nickel.Described tin nickel mixture can be used as the environment inert blanket on other metal level.
Described above-mentioned embodiment, but the invention is not restricted to this limited purposes with reference to the silicon wafer that is used for solar cell.Can also use photovoltaic device, and when needs, can also suitably change, for example change the source of used luminous energy by the made beyond the silicon.But, do not have luminous point response device in the presence of, this method is inoperative.For example, when the silicon wafer that contains the silver-colored thickener pattern of firing contacts and be applied in 0.5 volt voltage with plating bath of the present invention, but when not shining, almost do not observe plating or observe few plating.In addition, will there be the flat silicon wafer of PN junction to be placed in the device shown in Figure 2 and can't on the surface of irradiation, to produce plating.When the silicon wafer that contains the silver-colored thickener pattern of firing contacts and be subjected to actinic radiation with plating bath of the present invention, but when not applying voltage, observe few plating.Yet, when silicon wafer that contains the silver-colored thickener pattern of firing and plating bath of the present invention contact and are applied in 0.5 volt voltage and be subjected to radiation, be easy to take place metal-plated.
Wish various aspects of the present invention to be described with following embodiment.
Embodiment 1
Merge following component and add enough deionizations (" DI ") water and prepare 1 liter solution, thereby make silver-colored electroplating bath.
| 8g/L is as the silver of gluconic acid silver | The 2g/L m-nitrobenzene sulfonic acid |
| 10g/L methanesulfonic acid solution (70%, neutralize) with potassium hydroxide solution | The 25g/L succinamide |
| The 4g/L methionine | 1mL/L TEGOTAIN 485 (1% aqueous solution) |
| The 20g/L borax | 0.1mL/L sulfone derivative (1% aqueous solution) |
| 20g/L butanedioic acid sulfonamide |
The pH of plating bath is remained in the scope of 9-12.The temperature of plating bath remains on 25-35 ℃.
Embodiment 2
Merge following component and add enough deionized waters and prepare 1 liter solution, thereby make silver-colored electroplating bath.
| 9g/L is as the silver of methanesulfonic acid silver | The 4g/L4-nitrophthalic acid |
| 15g/L methanesulfonic acid solution (70%, neutralize) with potassium hydroxide solution | The 15g/L niacin hydroxyacyl amine |
| The 10g/L glycine | 5mL/L TEGOTAIN 485 (1% aqueous solution) |
| The 25g/L borax |
The pH of plating bath is remained in the scope of 9.5-10.5.The temperature of plating bath remains on 25-35 ℃.
Embodiment 3
Merge following component and add enough deionized waters and prepare 1 liter solution, thereby make silver-colored electroplating bath.
| 10g/L is as the silver of methanesulfonic acid silver | 2g/L 2-nitrophthalic acid |
| 5g/L methanesulfonic acid solution (70%, neutralize) with potassium hydroxide solution | The 25g/L niacin hydroxyacyl amine |
| The 5g/L cysteine | 3mL/L TEGOTAIN 485 (1% aqueous solution) |
| The 20g/L borax | 0.1mL/L sulfone derivative (1% aqueous solution) |
The pH of plating bath is remained in the scope of 9.5-10.5.The temperature of plating bath remains on 25-35 ℃.
Embodiment 4
Repeat the step of embodiment 1, except replace methionine with oxyalkylated amino acid (amino acid derivativges).
The current collection line that having as shown in Figure 1 formed by the silver-colored thickener of firing and the wafer of bus pattern contact with the aqueous methane sulfonic acid of 25 volume %, use deionized water rinsing then.
Provide and contain silver plating bath (ENLIGHT
TMSilver plating bath 600) and the plating pond that disposes 250 watts of lamps and silver anode.The wafer of patterning is immersed in the plating bath.Apply 1-5A/dm with radiation
2Current density.Continue plating 30 minutes, and from plating bath, shifted out wafer then, and with deionized water rinsing 1 minute, drying then.On the silver-colored thickener of firing, obtain the plating silver layer of 2-3 micron thickness.
Described plating bath can use 4-5 month cycle with a large amount of wafer of plating.Routine maintenance is accepted in described plating bath, for example replaces the element that exhausts, and replaces anode etc.In this time cycle, do not observe the forfeiture of stability.
Claims (11)
1. methods of plating electrical contacts on the light-sensitive device that shows the photovoltage effect, described method comprises provides the semiconductor wafer with at least two first type surfaces, described wafer is formed with photovoltaic junction therein, make first first type surface in two first type surfaces of described wafer be exposed to the light time, negative electrical charge gathers at described first first type surface, and positive charge gathers at second first type surface of two first type surfaces; Described wafer is contacted with the metal plating bath that does not contain cyanide, and the pH of described plating bath is 7-14, and working temperature is 10-30 ℃; Apply voltage to described metal plating bath, and described wafer is exposed to light with depositing metal layers on described first first type surface, wherein, described metal plating bath is the aqueous solution, comprises metal ion, at least a water miscible compound of nitro, at least a surfactant, at least a amide compound and at least a component that is selected from water-soluble amino acids, water-soluble sulfonic acid and composition thereof of containing.
2. the method for claim 1, it is characterized in that, described method also is included in described wafer with before the described metal plating bath that does not contain cyanide contacts, the step that wafer is contacted with the solution that contains sulfonic acid, and the described metal plating bath that does not contain cyanide is the silver-colored electrolyte that does not contain cyanide.
3. method as claimed in claim 2 is characterized in that described sulfonic acid is methanesulfonic acid.
4. the method for claim 1 is characterized in that, and is described only continuous or pulsed.
5. the method for claim 1 is characterized in that, described wafer has antireflection coatings on its first first type surface.
6. method as claimed in claim 5 is characterized in that, described antireflection layer comprises one or more in the combination of silicon oxide layer, silicon nitride layer and silicon oxide layer and silicon nitride layer.
7. the method for claim 1 is characterized in that, described plating bath also comprises buffer, and the pH of described plating bath is 7-14.
8. the method for claim 1 is characterized in that, described metal level is selected from silver, Jin Hetong.
9. the method for claim 1 is characterized in that, described first first type surface comprises a plurality of contact points.
10. the method for claim 1 is characterized in that, described method also is included in described wafer with before the metal plating bath that does not contain cyanide contacts, and provides metal coating on described second first type surface.
11. the method for claim 1 is characterized in that, described plating bath also comprises one or more vitamins.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US81095406P | 2006-06-05 | 2006-06-05 | |
| US60/810,954 | 2006-06-05 | ||
| US11/588,520 | 2006-10-27 |
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| CN100533785C true CN100533785C (en) | 2009-08-26 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102725442A (en) * | 2009-11-03 | 2012-10-10 | 新南创新私人有限公司 | Photoplating of metal electrodes for solar cells |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP5216633B2 (en) * | 2008-03-19 | 2013-06-19 | ローム・アンド・ハース・エレクトロニック・マテリアルズ，エル．エル．シー． | Method for suppressing background plating |
| US8337942B2 (en) * | 2009-08-28 | 2012-12-25 | Minsek David W | Light induced plating of metals on silicon photovoltaic cells |
| DE102009051688A1 (en) * | 2009-10-23 | 2011-04-28 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Method for light-induced galvanic pulse deposition for forming a seed layer for metal contact of a solar cell and for subsequent reinforcement of this seed layer or metal contact and arrangement for carrying out the method |
| JP5996244B2 (en) * | 2011-04-19 | 2016-09-21 | ローム アンド ハース エレクトロニック マテリアルズ エルエルシーＲｏｈｍ ａｎｄ Ｈａａｓ Ｅｌｅｃｔｒｏｎｉｃ Ｍａｔｅｒｉａｌｓ ＬＬＣ | Copper plating on semiconductors |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102725442A (en) * | 2009-11-03 | 2012-10-10 | 新南创新私人有限公司 | Photoplating of metal electrodes for solar cells |
| CN102725442B (en) * | 2009-11-03 | 2015-01-28 | 新南创新私人有限公司 | Photoplating of metal electrodes for solar cells |
| US9040128B2 (en) | 2009-11-03 | 2015-05-26 | Newsouth Innovations Pty Limited | Photoplating of metal electrodes for solar cells |
| TWI486492B (en) * | 2009-11-03 | 2015-06-01 | Newsouth Innovations Pty Ltd | Photoplating of metal electrodes for solar cells |
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