METHOD FOR FABRICATING A THREE-DIMENSIONAL THIN-FILM SEMICONDUCTOR SUBSTRATE FROM A TEMPLATE
A method is presented for fabrication of a three-dimensional thin-film solar cell semiconductor substrate from a template. A semiconductor template having three-dimensional surface features comprising a top surfaces substantially aligned along a (100) crystallographic plane of semiconductor template and a plurality of inverted pyramidal cavities defined by sidewalls substantially aligned along a (111) crystallographic plane is formed according to an anisotropic etching process. A dose of relatively of high energy light-mass species is implanted in the template at a uniform depth and parallel to the top surfaces and said sidewalls defining the inverted pyramidal cavities of the template. The semiconductor template is annealed to convert the dose of relatively of high energy light-mass species to a mechanically-weak-thin layer. The semiconductor template is cleaved along the mechanically-weak-thin layer to release a three-dimensional thin-film semiconductor substrate from the semiconductor template.
1 . A method for fabrication of a three-dimensional thin-film solar cell semiconductor substrate from a semiconductor template, the method comprising:
anisotropically etching a semiconductor template to form three-dimensional surface features comprising a top surfaces substantially aligned along a (100) crystallographic plane of said semiconductor template and a plurality of inverted pyramidal cavities defined by sidewalls substantially aligned along a (111) crystallographic plane of said semiconductor template;
implanting a dose of relatively high energy light-mass species at a uniform depth and parallel to said top surfaces and said sidewalls defining said plurality of inverted pyramidal cavities of said template according to an ion implantation process;
annealing said semiconductor template to convert said dose of relatively high energy light-mass species to a mechanically-weak-thin layer; and
cleaving said semiconductor template at said mechanically-weak-thin layer to release a three-dimensional thin-film semiconductor substrate from said semiconductor template.
2 . The method of claim 1 , wherein said semiconductor template is a silicon template.
3 . The method of claim 1 , wherein said semiconductor template is a monocrystalline silicon template.
4 . The method of claim 1 , wherein said semiconductor template is a polycrystalline silicon template.
5 . The method of claim 1 , wherein said semiconductor template is a template selected from the group consisting of gallium, arsenide, or germanium.
6 . The method of claim 1 , wherein said semiconductor template is a reusable semiconductor template for use in multiple three-dimensional thin-film solar cell semiconductor substrate fabrication cycles.
7 . The method of claim 1 , wherein said high energy light-mass species is proton.
8 . The method of claim 1 , wherein said high energy light-mass species is helium.
9 . The method of claim 1 , wherein said ion implantation process comprises bombarding said three-dimensional surface features of said semiconductor template with high energy light-mass species generated using a Radio Frequency Quadrupole linear accelerator.
10 . The method of claim 1 , further comprising the step of forming a border definition trench defining the peripheral of the 3-D TFSS prior to cleaving said semiconductor template at said mechanically-weak-thin layer.
11 . The method of claim 10 , wherein said step of forming a border definition trench further comprises forming a border definition trench by laser ablation prior to cleaving said semiconductor template at said mechanically-weak-thin layer.
12 . The method of claim 10 , wherein said step of forming a border definition trench further comprises forming a border definition trench by mechanically grinding the edges of said semiconductor template to the depth of said mechanically-weak-thin layer prior to cleaving said semiconductor template at said mechanically-weak-thin layer.
13 . The method of claim 1 , wherein said step of cleaving said semiconductor template at said mechanically-weak-thin layer further comprises pulling said three-dimensional thin-film semiconductor substrate from said semiconductor template with an electrostatic chuck.
14 . The method of claim 1 , wherein said step of cleaving said semiconductor template at said mechanically-weak-thin layer further comprises submersing said semiconductor template in an ultrasonic water bath.
15 . The method of claim 1 , further comprising the step of cleaning said template with a selective etchant solution to reestablish the structure of the three-dimensional surface features after the release of said three-dimensional thin-film semiconductor substrate.
16 . The method of claim 1 , wherein said step of anisotropically etching a semiconductor template to form three-dimensional surface features utilizes a solution containing at least one of KOH, NaOH, or TetraMethyl-Ammonium-Hyrdoxide (TMAH) as an etchant.
17 . The method of claim 1 , further comprising the step of applying a reinforcement plate to the top surface of the three-dimensional thin-film semiconductor substrate to be released prior to the step of cleaving said semiconductor template at said mechanically-weak-thin layer.
18 . The method of claim 1 , wherein said plurality of inverted pyramidal cavities are rectangular pyramidal cavities defined by four sidewalls substantially aligned along a (111) crystallographic plane of said semiconductor template.
19 . The method of claim 1 , wherein said plurality of inverted pyramidal cavities comprise a plurality of pyramidal sizes.
20 . The method of claim 1 , wherein said plurality of inverted pyramidal cavities comprises at least one pyramidal cavity further defined by a bottom surface aligned along a (100) crystallographic orientation plane of said semiconductor template.