METHODS FOR TEXTURING A SEMICONDUCTOR MATERIAL

1 . A method for modifying the texture of semiconductor material, the method comprising:

a. providing a semiconductor lamina having a thickness between a first surface and a second surface;

b. performing a first texture step comprising reactive ion etching to the first surface of the lamina, wherein after the first texture step, the first surface has a random texture comprising a plurality of peaks and a plurality of valleys, and wherein at least fifty percent of the first surface has a peak-to-valley height of less than one micron and an average peak-to-peak distance of less than one micron; and

c. fabricating an electronic device, wherein the electronic device comprises the lamina.

2 . The method of claim 1 wherein the electronic device is a photovoltaic cell having a base, and wherein the base comprises the lamina.

3 . The method of claim 1 wherein the step of providing the semiconductor lamina comprises:

a) providing a donor body comprising a top surface;

b) implanting ions into the top surface of the donor body to define a cleave plane;

c) exfoliating the lamina from the donor body at the cleave plane, wherein the step of exfoliating the lamina forms the first surface of the lamina, wherein the first surface is opposite the top surface of the donor body, and wherein the top surface of the donor body becomes the second surface of the lamina.

4 . The method of claim 1 wherein the reactive ion etching comprises generating a plasma by applying a power to a flow of gas, wherein the gas comprises chlorine, oxygen, fluorine, or any combination thereof.

5 . The method of claim 4 wherein the flow of gas comprises chlorine.

6 . The method of claim 4 wherein the flow of gas comprises SF 6 , Cl 2 and O 2 at a ratio of 3.0:1:1.8 standard cubic centimeters per minute.

7 . The method of claim 4 wherein the flow of gas comprises SF 6 , Cl 2 and O 2 at a ratio of 1.0:3.0:6.0 standard cubic centimeters per minute.

8 . The method of claim 4 wherein the power is between 0.4 and 1.2 Watts/cm 2 .

9 . The method of claim 4 wherein the flow of gas has a total working pressure between 300 and 500 milliTorr.

10 . The method of claim 1 wherein the lamina is comprised of monocrystalline silicon in a <111> crystal orientation.

11 . The method of claim 1 wherein the thickness is less than 25 microns.

12 . The method of claim 10 wherein after the first texture step, greater than 50% of the first surface of the lamina is in the {111} crystal orientation.

13 . The method of claim 1 wherein the first texture step reduces the thickness of the lamina by less than 1 micron.

14 . The method of claim 1 , further comprising the step of performing a second texture step to the first surface of the lamina, wherein the second texture step rounds the corners of the peaks and valleys while removing less than 1 micron of the thickness of the lamina.

15 . The method of claim 14 wherein the second texture step comprises wet etching, plasma etching, or any combination thereof.

16 . The method of claim 14 wherein the second texture step comprises immersing the lamina in an alkaline bath.

17 . The method of claim 14 , further comprising the step of performing a third texture step to the second surface of the lamina, wherein after the third texture step, the second surface has a random texture comprising a new plurality of peaks and a plurality of valleys, and wherein at least fifty percent of the second surface has a new peak-to-valley height of less than one micron and an average new peak-to-peak distance of less than one micron.

18 . The method of claim 17 wherein the third texture step comprises reactive ion etching.