Method for selective under-etching of porous silicon

a technology of porous silicon and under-etching, which is applied in the field of solar cell making, can solve the problems of crystals taking an exceptionally long time to grow on silicon ingots, and the impracticality of large-scale production of solar cells from these materials

Inactive Publication Date: 2015-07-09
NAURA AKRION INC
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention describes a method for making a solar cell. The method involves depositing a sacrificial porous silicon layer on a single crystal silicon wafer, followed by the growth of a silicon-based device layer on top of the sacrificial layer. The sacrificial layer is then selectively etched to release the device layer, which is further processed to form a solar cell. The method provides improved efficiency and cost-effectiveness for solar cell production.

Problems solved by technology

However, high manufacturing costs for making single crystalline materials makes the large scale production of solar cells from these materials impractical.
This method is disadvantageous in that the crystal takes an exceptionally long time to grow on the silicon ingot.

Method used

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  • Method for selective under-etching of porous silicon
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  • Method for selective under-etching of porous silicon

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Embodiment Construction

[0019]FIG. 1 shows a composite wafer 100 used to make a silicon-based device layer used in solar cells. The composite wafer 100 includes a single crystal silicon wafer 101 and a sacrificial porous silicon layer 103 that is deposited thereon, which is referred to herein as a base wafer. The composite wafer 100 also includes a silicon-based device layer 105 that is preferably crystalline or semi-crystalline and is epitaxially grown on top of the sacrificial porous silicon layer 103.

[0020]As described above, the sacrificial porous silicon layer 103 preferably has a porosity of 30 percent or more and is several nanometers to several microns thick. The sacrificial porous silicon layer 103 is formed from any suitable porous silicon material including, but not limited to carbon doped oxide, spin-on-glass (SOG), fluoridated silicon glass (FSG) or a combination thereof.

[0021]The silicon-based device layer 105 is preferably a p-doped silicon-based device layer that has a thickness of several ...

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Abstract

A method for making a solar cell is disclosed. In accordance with the method of the present invention a composite wafer is formed. The composite layer includes a single crystal silicon wafer, a silicon-based device layer and sacrificial porous silicon sandwiched therebetween. The composite wafer is treated to an aqueous etchant maintained below ambient temperatures to selectively etch the sacrificial porous silicon and release or undercut the silicon-based layer from the single crystal silicon wafer. The released silicon device layer is attached to a substrate to make a solar cell and the released single crystal silicon wafer is reused to make additional silicon device layer.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]The present application is a continuation of U.S. patent application Ser. No. 12 / 716,785, filed Mar. 3, 2010, which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61 / 157,195, filed on Mar. 3, 2009, and titled “METHOD FOR SELECTIVE UNDER-ETCHING OF POROUS SILICON,” the entirety of which is hereby incorporated by reference.FIELD OF THE INVENTION[0002]This invention relates to a method for making solar cells. More particularly, the present invention relates to selective etching of a porous silicon layer to under-cut and release a silicon-based device layer that is then used for making solar cells.BACKGROUND OF THE INVENTION[0003]Solar cells are semiconductor devices that are usually manufactured from silicon-based material. Some solar cells are made from screen printed poly-crystalline silicon. Single crystalline wafers can be used to make very efficient solar cells. However, high manufacturing costs f...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): H01L31/18H01L31/028
CPCH01L31/028H01L31/1804H01L21/31111H01L31/068H01L31/1892Y02E10/547Y02P70/50H01L21/30604
InventorKASHKOUSH, ISMAIL I
OwnerNAURA AKRION INC