Electroplating Solutions and Methods For Deposition of Group IIIA-VIA Films

Abstract

The embodiment described herein relate to pulse electroplating methods and solutions.

We claim: 
     
         1 . A method of forming an absorber layer over a surface of a base, the method comprising:
 forming a metal layer over the surface of the base, wherein the metal layer comprises a Group IIIA material;   co-depositing Group IIIIA and Group VA materials to form a Group IIIA-VIA layer on the metal layer using pulse electroplating that varies an electroplating pulse between a first higher value and a second lower value, wherein at the first higher value electroplating of at least one of Ga and In predominates, and wherein at the second lower value electroplating of one of Se, Te and S predominates, wherein the step of co-depositing the Group IIIA-VIA layer uses a roll-to-roll electroplating process wherein the base having the metal layer is continuously advanced within an electroplating solution held in a deposition chamber as at least one electric field is formed between at least one anode to deposit the Group IIIA-VIA layer onto the metal layer; and   reacting the metal layer and the Group IIIA-VIA layer to form the absorber layer.   
     
     
         2 . The method of  claim 1  wherein the Group IIIA-VIA layer is one of a Ga—Se alloy, In—Se and In—Ga—Se alloy. 
     
     
         3 . The method of  claim 1  wherein the Group IIIA-VIA layer is one of a Ga—Te alloy, In—Te and In—Ga—Te alloy. 
     
     
         4 . The method of  claim 1  wherein the Group IIIA-VIA layer is one of a Ga—S alloy, In—S and In—Ga—S alloy. 
     
     
         5 . The method of  claim 1  wherein the Group IIIA-VIA layer is one of a Ga—Se—Te alloy, In—Se—Te and In—Ga—Se—Te alloy. 
     
     
         6 . The method of  claim 1  wherein the Group IIIA-VIA layer is one of a Ga—Se—S, In—Se—S and In—Ga—Se—S alloy. 
     
     
         7 . The method of  claim 1  wherein the Group IIIA-VIA layer is one of a Ga—Te—S, In—Te—S and In—Ga—Te—S alloy. 
     
     
         8 . The method of  claim 1  wherein the Group IIIA-VIA layer is one of a Ga—Se—Te—S, In—Se—Te—S and In—Ga—Se—Te—S alloy. 
     
     
         9 . The method of  claim 1 , wherein the step of forming the metal layer comprises forming an In-layer. 
     
     
         10 . The method of  claim 9 , wherein the absorber layer is a CIS absorber. 
     
     
         11 . The method of  claim 1 , wherein the step of forming the metal layer comprises forming a film stack comprising: a Cu film formed on the base, a Ga film formed on the Cu film and an In film formed on the Ga film. 
     
     
         12 . The method of  claim 11 , wherein the absorber layer is a CIGS absorber. 
     
     
         13 . The method of  claim 1 , wherein the pulse electroplating technique'includes varying an electroplating voltage between a first voltage value as the first higher value and a second voltage value as the second lower value. 
     
     
         14 . The method of  claim 13  wherein a voltage range between the first voltage value and the second voltage value is in the range of 0 and 20 volts. 
     
     
         15 . The method of  claim 13  wherein each pulse of the pulse electroplating has a duration that is in the range of 1E-7-360 sec. 
     
     
         16 . The method of  claim 1 , wherein the pulse electroplating technique includes varying an electroplating current density between a first current density value as the first higher value and a second current density value as the second lower value. 
     
     
         17 . The method of  claim 16  wherein a current density range between the first current density value and the second current density value is between 0 and 200 mA/cm 2 . 
     
     
         18 . The method of  claim 1 , wherein the at least one anode includes a plurality of anodes positioned along the deposition chamber so as to apply a plurality of electric fields during the electroplating as the base having the metal layer advanced in process direction across from the plurality of anodes; 
     
     
         19 . The method of  claim 18 , wherein each anode is isolated from adjacent anodes by anode separators so as to isolate the electric field of each anode from the electric fields of the adjacent anodes. 
     
     
         20 . The method of  claim 1 , wherein the electroplating solution comprises:
 a solvent, a Group IIIA material source that provides Ga in ionic form in the solvent, a Group VIA material source that dissolves in the solvent and provides Se in ionic form, an anti-oxidant, an anti-flocculant, a pH adjuster including at least one of an organic acid, an inorganic acid, an organic base and an inorganic base, additives including at least one of an anti-oxidant, an anti-flocculant, a surface-active compound and an ionic conductivity enhancer and wherein the pH of the solution is in the range of 0.5-13.   
     
     
         21 . The method of  claim 1 , wherein the Group IIIA-VIA layer includes at least one of a mixture of the Group IIIA and Group VIA materials and an alloy of the Group IIIA and Group VIA materials. 
     
     
         22 . An electroplating solution for deposition of a Group IIIA-Group VIA thin film on a Group IIIA material surface, the electroplating solution comprising:
 a solvent;   a Group IIIA material source that provides Ga in ionic form in the solvent;   a Group VIA material source that dissolves in the solvent and provides Se in ionic form;   an anti-oxidant;   an anti-flocculant;   a pH adjuster including at least one of an organic acid, an inorganic acid, an organic base and an inorganic base;   additives including at least one of a surface-active compound, a complexing agent and an ionic conductivity enhancer;   wherein the pH of the solution is in the range of 0.5-13.   
     
     
         23 . The electroplating solution of  claim 22 , wherein the pH is in the range of 0.0.5-4. 
     
     
         24 . The electroplating solution of  claim 22 , wherein the pH is in the range of 0.0.8-2.5. 
     
     
         25 . The electroplating solution of  claim 22 , wherein the anti-oxidant includes at least one of hydroquinone, pyrocatechol, gallic acid; 4-Amino- 4 H-1,2,4-triazole, 4,5-Imidazoledicarboxylic acid; dextrose, saccharin, fructose; hydroquinone sulfonic; ethanol, methanol, glycerol and ethylenglycol. 
     
     
         26 . The electroplating solution of  claim 22 , wherein the anti-flocculant includes at least one of dipotassium phosphate, ammonium dihydrogen phosphate, ammonium hexafluorophosphate, calcium phosphate, potassium metaphosphate, potassium phosphate, potassium triphosphate, potassium hexafluorophosphate, potassium hydrogen phosphate and sodium hydrogen phosphate, diethyl dithiophosphate, diethyl dithiophosphate, ammonium salt, Tetrabutylammonium hexafluorophosphate, polyethylene glycol, 1-Hydroxyethylidenebis(phosphonic acid), methylenediphosphonic acid and diethylenediamine. 
     
     
         27 . The electroplating solution of  claim 22 , wherein the surface-active compound includes at least one of melamine, dopamine hydrochloride; (HEPES) 4-(2-Hydroxyethyl)piperazine-1-ethanesulfonic acid; 1,3,5-Triazine-2,4,6-trithiol trisodium Sodium Dodecyl Sulfate, n-Dodecylamine, Sodium n-octyl sulfate, Pluronic P123, Pluronic F127, Brij 35. 
     
     
         28 . The electroplating solution of  claim 22 , wherein the ionic conductivity enhancer includes at least one of NaCl, Na 2 SO 4 , KCl, K 2 SO 4 , H 4 ClN, and (NH 4 ) 2 SO 4 . 
     
     
         29 . The electroplating solution of  claim 22 , wherein a molar ratio of Group IIIA/Group IIIA+VIA is in the range of 0 to 1. 
     
     
         30 . The electroplating solution of  claim 22 , wherein the pH adjuster is selected from the group including sulfuric acid, hydrochloric acid, phosphoric acid, ethylenediaminetetraacetic acid, malonic acid, malic acid, nitrilotriacetic acid, succinic acid, maleic acid, oxalic acid, tartaric acid, citric acid, sulfamic acid, hydroxyethylethylenediaminetriacetic acid, NaOH, KOH, NH 4 OH, organic amines such as methylamine and trimethylamine, tetramethylammonium hydroxide and tetrabutylammonium hydroxide, pyridine, imidazole, benzimidazole, histidine and phosphazene. 
     
     
         31 . The electroplating solution of  claim 22 , wherein the complexing agent is selected from the group including tartaric acid, citric acid, acetic acid, malonic acid, malic acid, succinic acid, ethylenediamine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, and hydroxyethylethylenediaminetriacetic acid.