Efficient gallium thin film electroplating methods and chemistries

Abstract

The present invention relates to gallium (Ga) electroplating methods and chemistries to deposit uniform, defect free and smooth Ga films with high plating efficiency and repeatability. Such layers may be used in fabrication of electronic devices such as thin film solar cells. In one embodiment, the present invention provides a solution for application on a conductor that includes a Ga salt, a complexing agent, a solvent, and a Ga-film having submicron thickness is facilitated upon electrodeposition of the solution on the conductor. The solution may further include one or both of a Cu salt and an In salt.

1 . A solution for electrodeposition of a gallium (Ga) containing film on a conductor comprising:
 a gallium (Ga) salt,   a complexing agent with at least one of a carboxylic chelating group, and an ammine chelating group, and   a solvent, and   wherein the pH of the solution is higher than 7.0.   
     
     
         2 . The solution of  claim 1  wherein the complexing agent is selected from the group consisting of a citrate, ethylenediaminetetraacetic acid (EDTA), a tartrate, an oxalate, ethylenediamine, nitrilotriacetic acid, and an amino acid. 
     
     
         3 . The solution of  claim 1  wherein the gallium (Ga) salt is selected from the group consisting of gallium (Ga)-chloride, gallium (Ga)-sulfate, gallium (Ga)-acetate and gallium (Ga)-nitrate. 
     
     
         4 . The solution of  claim 2  wherein the gallium (Ga) salt is selected from the group consisting of gallium (Ga)-chloride, gallium (Ga)-sulfate, gallium (Ga)-acetate and gallium (Ga)-nitrate. 
     
     
         5 . The solution of  claim 2  further comprising an alkali metal salt of the complexing agent. 
     
     
         6 . The solution of  claim 5  wherein the alkali metal salt of the complexing agent is one of a sodium salt of the complexing agent, a potassium salt of the complexing agent, and a lithium salt of the complexing agent. 
     
     
         7 . The solution of  claim 1  wherein the solvent is water. 
     
     
         8 . The solution of  claim 1  wherein the solvent is a mixture of water with an organic solvent. 
     
     
         9 . The solution of  claim 1  further comprising an organic additive. 
     
     
         10 . The solution of  claim 1  further comprising at least one of a copper (Cu) salt and an indium (In) salt. 
     
     
         11 . The solution of  claim 1  further comprising a pH adjustment agent that is one of NaOH and KOH. 
     
     
         12 . The solution of  claim 1  wherein the pH of the solution is within a range of 9-14.