Method For Producing A Semiconductor Film

Abstract

A method is provided for producing, with high reproducibility, an SOI substrate which is flat and high in quality, and simultaneously for achieving resources saving and reduction in cost through recycling of a substrate member. For accomplishing this, a porous-forming step is performed forming a porous Si layer on at least a surface of an Si substrate and a large porosity layer forming step is performed for forming a large porosity layer in the porous Si layer. This large porosity layer forming step is performed by implanting ions into the porous Si layer with a given projection range or by changing current density of anodization in said porous-forming step. At this time, a non-porous single-crystal Si layer is epitaxial-grown on the porous Si layer. Thereafter, the surface of the porous Si layer and a support substrate are bonded together, and then separation is performed at the porous Si layer with the large porosity. Subsequently, selective etching is performed to remove the porous Si layer.

What is claimed is:  
     
         1 . A semiconductor article having a porous layer comprising two or more different layers having differing porosities, said layers being formed on a surface of a semiconductor substrate, and a semiconductor layer formed on the porous layer, wherein the semiconductor layer is capable of being peeled away from the semiconductor.  
     
     
         2 . The semiconductor article according to    claim 1   , which has a second porous layer in a first porous layer, or on a side of the first porous layer, wherein said side faces the semiconductor substrate, wherein the porosity of said second porous layer is higher than that of the first porous layer.  
     
     
         3 . The semiconductor article according to    claim 2   , which has a third porous layer between the second porous layer and the semiconductor substrate, wherein the porosity of said third porous layer is lower than that of the second porous layer.  
     
     
         4 . The semiconductor article according to    claim 1   , wherein said semiconductor layer is an epitaxial growth layer.  
     
     
         5 . The semiconductor article according to    claim 1   , wherein said porous layer is formed by anodization.  
     
     
         6 . The semiconductor article according to    claim 5   , wherein said porous layer is formed by varying current density.