TRENCH FORMATION METHOD FOR RELEASING A SUBSTRATE FROM A SEMICONDUCTOR TEMPLATE
A method is provided for fabricating a thin-film semiconductor substrate by forming a porous semiconductor layer conformally on a reusable semiconductor template and then forming a thin-film semiconductor substrate conformally on the porous semiconductor layer. An inner trench having a depth less than the thickness of the thin-film semiconductor substrate is formed on the thin-film semiconductor substrate. An outer trench providing access to the porous semiconductor layer is formed on the thin-film semiconductor substrate and is positioned between the inner trench and the edge of the thin-film semiconductor substrate. The thin-film semiconductor substrate is then released from the reusable semiconductor template.
1 . A method for fabrication of a thin-film semiconductor substrate, the method comprising:
forming a porous semiconductor layer on a reusable semiconductor template, said porous semiconductor layer conformal to said reusable semiconductor template;
forming a thin-film semiconductor substrate on said porous semiconductor layer, said thin-film semiconductor substrate conformal to said porous semiconductor layer;
forming an inner trench on said thin-film semiconductor substrate having a depth less than a thickness of said thin-film semiconductor substrate;
forming an outer trench on said thin-film semiconductor substrate providing access to said porous semiconductor layer and positioned between said inner trench and an edge of said thin-film semiconductor substrate; and
releasing said thin-film semiconductor substrate from said reusable semiconductor template.
2 . The method of claim 1 , wherein said thin-film semiconductor substrate is a silicon thin-film semiconductor substrate.
3 . The method of claim 1 , wherein said porous semiconductor layer is a porous silicon layer.
4 . The method of claim 1 , wherein said reusable semiconductor template is a silicon template made of a silicon wafer.
5 . The method of claim 1 , wherein said thin-film semiconductor substrate is substantially planar.
6 . The method of claim 1 , wherein said thin-film semiconductor substrate is three-dimensional.
7 . The method of claim 1 , wherein said inner trench is aligned along a crystallographic direction of said thin-film semiconductor substrate.
8 . The method of claim 1 , further comprising the step of dividing the released thin-film semiconductor substrate at said inner trench.
9 . The method of claim 1 , further comprising the step of breaking the released thin-film semiconductor substrate at said inner trench according to a mechanical snapping method using said first trench as a cleaving line.
10 . The method of claim 1 , wherein said first trench is created according to a laser cutting process.
11 . The method of claim 1 , wherein said outer trench is created according to a laser cutting process.
12 . The method of claim 1 , wherein said inner trench is created according to a mechanical scribing process.
13 . The method of claim 1 , wherein said outer trench is created according to a mechanical scribing process.
14 . The method of claim 1 , wherein said inner trench is created according to a silicon reactive ion etching (RIE) etching process.
15 . The method of claim 1 , wherein said outer trench is created according to a silicon reactive ion etching (RIE) etching process.
16 . The method of claim 1 , wherein said outer trench is located at an edge of said reusable semiconductor template and is formed according to a mechanical lapping, grinding, or polishing process.
17 . The method of claim 1 , wherein said inner trench is created according to an anisotropic silicon wet etching process.
18 . The method of claim 1 , wherein said outer trench is created according to an anisotropic silicon wet etching process.
19 . The method of claim 1 , wherein said inner trench is created according to an anodic silicon etching process.
20 . The method of claim 1 , wherein said outer trench is created according to an anodic silicon etching process.