Solar cell contact formation process using a patterned etchant material

Abstract

Embodiments of the invention contemplate the formation of a high efficiency solar cell using novel methods to form the active region(s) and the metal contact structure of a solar cell device. In one embodiment, the methods include the use of various etching and patterning processes that are used to define point contacts through a blanket dielectric layer covering a surface of a solar cell substrate. The method generally includes depositing an etchant material that enables formation of a desired pattern in a dielectric layer through which electrical contacts to the solar cell device can be formed.

1 . A composition for etching a dielectric layer disposed on a substrate, comprising:
 ammonium fluoride; and   an amine disposed in an aqueous solution.   
     
     
         2 . The composition of  claim 1 , further comprising hydrofluoric acid. 
     
     
         3 . The composition of  claim 1 , further comprising:
 a surfactant selected from a group consisting of polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol-block-copolymer, and glycerin.   
     
     
         4 . The composition of  claim 1 , wherein the amine comprises dimethylamine, diethylamine, triethylamine or ethanolamine. 
     
     
         5 . The composition of  claim 1 , further comprising a doping material that comprises an element selected from the group consisting of phosphorous, boron, arsenic, antimony, aluminum, indium and gallium. 
     
     
         6 . The composition of  claim 5 , wherein the doping material comprises phosphoric acid (H 3 PO 4 ), phosphorous acid (H 3 PO 3 ), hypophosphorous acid (H 3 PO 2 ), ammonium phosphite (NH 4 H 2 PO 3 ), ammonium hypophosphite (NH 4 H 2 PO 2 ), boric acid (H 3 BO 3 ), or ammonium tetrafluoroborate (NH 4 BF 4 ). 
     
     
         7 . The composition of  claim 1 , wherein the amine forms a homogenous mixture with ammonium fluoride, and the composition has a pH of about 7. 
     
     
         8 . The composition of  claim 1 , further comprising a metal containing solution comprising nickel. 
     
     
         9 . The composition of  claim 8 , wherein the metal containing solution comprises nickel acetate and hypophosphorous acid. 
     
     
         10 . The composition of  claim 8 , further comprising methanol or ethanol. 
     
     
         11 . The composition of  claim 8 , further comprising a doping material that comprises an element selected from the group consisting of phosphorous, boron, arsenic, antimony, aluminum, indium and gallium. 
     
     
         12 . A composition for etching portions of a dielectric layer disposed on a substrate, comprising:
 ammonium fluoride; and   a solvent material comprising ethanolamine, wherein the etchant material has a pH of about 7 or more.   
     
     
         13 . The composition of  claim 12 , further comprising hydrofluoric acid. 
     
     
         14 . The composition of  claim 12 , further comprising:
 a surfactant selected from a group consisting of polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol-block-copolymer, and glycerin; and   
     
     
         15 . A method of forming an etchant material used for removing portions of a dielectric layer disposed on a substrate, comprising:
 mixing an amount of ammonium fluoride and an amount of ethanolamine; and   adding an amount of hydrofluoric acid to the ammonium fluoride and ethanolamine mixture to bring the pH to about 7 or more.   
     
     
         16 . The method of  claim 15 , further comprising adding an amount of polyethylene glycol. 
     
     
         17 . A method of forming a solar cell device, comprising:
 forming a dielectric layer on a surface of a substrate;   disposing an etchant material on a plurality of regions of the dielectric layer, wherein the etchant material comprises ammonium fluoride and an amine;   heating the substrate to a desired temperature to causes the etchant material to remove at least a portion of the dielectric layer in the plurality of regions to expose a plurality of regions of the surface of the substrate; and   depositing a conducting layer on the exposed regions of the surface.