Method for separating a device-forming layer from a base body

Abstract

A porous Si layer is formed on a single-crystal Si substrate, and then a p + -type Si layer, p-type Si layer and n + -type Si layer which all make up a solar cell layer. After a protective film is made on the n + -type Si layer, the rear surface of the single-crystal Si substrate is bonded to a tool, and another tool is bonded to the front surface of the protective film. Theo, the tools are pulled in opposite directions to mechanically rupture the porous Si layer and to separate the solar cell layer from the single-crystal substrate. The solar cell layer is subsequently sandwiched between two plastic substrates to make a flexible thin-film solar cell.

What is claimed is: 
     
       1. A method for separating a semiconductor layer from a substrate, comprising:
 forming a porous layer on a surface of a substrate by an anodic oxidization;   forming at least one semiconductor layer on said porous layer; and   separating said semiconductor layer from said substrate by forming a mechanical rupture in said porous layer or along an interface formed between the porous layer and the substrate or between the porous layer and the semiconductor layer.   
     
     
       2. A method for separating a semiconductor layer from a substrate according to  claim 1 , wherein said substrate is a Si substrate. 
     
     
       3. A method for separating a semiconductor layer from a substrate according to  claim 1 , wherein said porous layer is a Si porous layer. 
     
     
       4. A method for separating a semiconductor layer from a substrate according to  claim 1 , wherein the method further comprises a step of oxidizing said porous layer after forming said porous layer. 
     
     
       5. A method for separating a semiconductor layer from a substrate according to  claim 4 , wherein said porous layer is oxidized at a temperature of 400° C. to 600° C. 
     
     
       6. A method for separating a semiconductor layer from a substrate according to  claim 1 , wherein the method further comprises a step of H 2 -annealing said porous layer after forming said porous layer. 
     
     
       7. A method for separating a semiconductor layer from a substrate according to  claim 6 , wherein said porous layer is H 2 -annealed at a temperature of 950° C. to 1000° C. 
     
     
       8. A method for separating a semiconductor layer from a substrate according to  claim 1 , wherein the method further comprises the steps of: forming a oxide film on a entire surface of said semiconductor layer, said porous layer and said substrate; and removing said oxide film to form a wedge-shaped gap in an interface between said porous layer and said semiconductor layer. 
     
     
       9. A method for separating a semiconductor layer from a substrate, comprising:
 forming a porous layer on a surface of a substrate;   H 2 -annealing said porous layer;   forming at least one semiconductor layer on said porous layer;   separating said semiconductor layer from said substrate by forming a mechanical rupture within said porous layer or along an interface formed between the substrate and the porous layer or between the porous layer and said semiconductor layer.   
     
     
       10. A method for separating a semiconductor layer from a substrate, comprising:
 forming a porous layer on a surface of a substrate;   oxidizing said porous layer;   forming at least one semiconductor layer on said porous layer;   separating said semiconductor layer from said substrate by forming a mechanical rupture within said porous layer or along an interface formed between the substrate and the porous layer or between the porous layer and said semiconductor layer.   
     
     
       11. A method for manufacturing a solar cell, comprising;
 forming a porous layer on a surface of a substrate by anodic oxidization;   forming a plurality of semiconductor layers on said porous layer to form the solar cell;   separating said plurality of semiconductor layers from said substrate by forming a mechanical rupture within said porous layer or along an interface formed between the substrate and the porous layer or between the porous layer and said semiconductor layer.   
     
     
       12. A method for separating at least one semiconductor layer from a substrate, comprising the steps of:
 forming a semiconductor layer-containing structure by first forming a porous layer on a first surface of the substrate by an anodic oxidization, then forming said at least one semiconductor layer on said porous layer, said at least one semiconductor layer being composed of solar cell layers on said porous layer, and then forming a protective layer over said at least one semiconductor layer;   forming an oxide film on an entire exposed outer surface of said semiconductor layer-containing structure that includes entire exposed surfaces of said at least one semiconductor layer, said porous layer, and said substrate, and then removing said oxide film to form a wedge-shaped gap in an interface between said porous layer and said at least one semiconductor layer;   bonding a first tool to a second surface of said substrate;   bonding a second tool to a surface of said semiconductor layer-containing structure that faces away from said substrate; and   separating said at least one semiconductor layer from said substrate by forming a mechanical rupture in said porous layer or along an interface formed between said porous layer and said substrate or between said porous layer and said at least one semiconductor layer by pulling said first and second tools in opposite directions.    
     
     
       13. A method for separating at least one semiconductor layer from a substrate comprising the steps of:
 forming a semiconductor layer-containing structure by first forming a porous layer on a first surface of the substrate by an anodic oxidization, and then forming said at least one semiconductor layer on said porous layer;   forming an oxide film on an entire exposed surface of said at least one semiconductor layer, said porous layer, and said substrate, and then removing said oxide film to form a wedge-shaped gap in an interface between said porous layer and said at least one semiconductor layer;   bonding a first tool to a second surface of said substrate;   bonding a second tool to a surface of said semiconductor layer-containing structure that faces away from said substrate; and   separating said at least one semiconductor layer from said substrate by forming a mechanical rupture in said porous layer or along an interface formed between said porous layer and said substrate or between said porous layer and said at least one semiconductor layer by pulling said first and second tools in opposite directions.    
     
     
       14. The method of claim 13, comprising the further step of removing said porous layer from said separated substrate and said at least one semiconductor layer.  
     
     
       15. The method of claim 14, comprising the further step of restoring those portions of said substrate turned into said porous layer by said anodic oxidization by an appropriate material growth process.  
     
     
       16. The method of claim 13, wherein said substrate is made of single-crystal silicon.  
     
     
       17. The method of claim 13, wherein said substrate is made of polycrystalline silicon.  
     
     
       18. The method of claim 13, comprising forming a protective layer over said at least one semiconductor layer before forming said oxide film.  
     
     
       19. The method of claim 18, comprising forming said oxide film on an entire exposed surface of said semiconductor layer-containing structure including said protective layer.  
     
     
       20. The method of claim 18, comprising forming solar cell layers as said at least one semiconductor layer prior to forming said protective layer.  
     
     
       21. The method of claim 13, comprising forming solar cell layers as said at least  one semiconductor layer prior to forming said oxide film.