Method for making a silicon substrate comprising a buried thin silicon oxide film

Abstract

A method for making a silicon substrate having a buried thin silicon oxide film is described. The method consists of: a) producing a first element having a first silicon body whereof the main surface is coated, in succession, with a buffer layer of germanium, or of an alloy of germanium and silicon, and with a thin silicon film; b) producing a second element, having a silicon body whereof a main surface is coated with a thin silicon oxide film; c) linking the first element with the second element such that the thin silicon film of the first element is in contact with the thin silicon oxide film of the second element; and d) eliminating the buffer layer to recuperate the silicon substrate having a buried thin silicon oxide film and a reusable silicon substrate. The method may be useful in making microelectronic devices such as CMOS and MOSFET devices.

1. A method of fabricating a silicon substrate comprising a thin buried silicon oxide layer, the method comprising:
 producing a first element comprising a first silicon body, wherein a main surface of the first element is coated with a buffer layer comprising germanium and a thin silicon layer, in that order;  
 producing a second element comprising a second silicon body, wherein a main surface of the second element is coated with a thin silicon oxide layer;  
 bonding the first element to the second element such that the thin silicon layer of the first element is in contact with the thin silicon oxide layer of the second element; and  
 removing the buffer layer in order to recover the silicon substrate comprising the thin buried silicon oxide layer and a reusable silicon substrate.  
 
     
     
       2. The method of  claim 1 , wherein the buffer layer comprises a silicon-germanium alloy chosen from the alloys Si 1-x Ge x (0<x<1) and Si 1-x-y Ge x C y (0<x<0.95; 0<y≦0.05). 
     
     
       3. The method of  claim 1 , wherein the buffer layer comprises a germanium-silicon alloy, and wherein the germanium-silicon alloy comprises at least 10% by weight of germanium. 
     
     
       4. The method of  claim 1 , wherein the buffer layer comprises a layer made of a silicon-germanium alloy having a germanium concentration gradient. 
     
     
       5. The method of  claim 1 , further comprising forming the buffer layer and the thin silicon layer of the first element by epitaxial deposition. 
     
     
       6. The method of  claim 5 , wherein the epitaxial deposition comprises chemical vapor deposition or molecular beam epitaxial deposition. 
     
     
       7. The method of  claim 1 , further comprising forming the silicon oxide layers by thermal oxidation. 
     
     
       8. The method of  claim 1 , wherein removing the buffer layer comprises selective dissolution of the buffer layer by an oxidizing solution or by anisotropic plasma etching. 
     
     
       9. The method of  claim 1 , wherein the buffer layer comprises a germanium-silicon alloy. 
     
     
       10. The method of  claim 1 , wherein the buffer layer comprises a germanium-silicon alloy, and wherein the germanium-silicon alloy comprises at least 30% by weight of germanium. 
     
     
       11. A method of fabricating a silicon substrate comprising a thin buried silicon oxide layer, the method comprising:
 producing a first element comprising a first silicon body, wherein a main surface of the first element is coated with a buffer layer comprising germanium, a thin silicon layer, and a first thin silicon oxide layer, in that order;  
 producing a second element comprising a second silicon body, wherein a main surface of the second element is coated with a second thin silicon oxide layer;  
 bonding the first element to the second element such that the first thin silicon oxide layer of the first element is in contact with the second thin silicon oxide layer of the second element; and  
 removing the buffer layer in order to recover the silicon substrate comprising the thin buried silicon oxide layer and a reusable silicon substrate.  
 
     
     
       12. The method of  claim 11 , wherein the buffer layer comprises a silicon-germanium alloy chosen from the alloys Si 1-x Ge x (0<x<1) and Si 1-x-y Ge x C y (0<x<0.95; 0<y≦0.05). 
     
     
       13. The method of  claim 11 , wherein the buffer layer comprises a germanium-silicon alloy, and wherein the germanium-silicon alloy comprises at least 10% by weight of germanium. 
     
     
       14. The method of  claim 11 , wherein the buffer layer comprises a layer made of a silicon-germanium alloy having a germanium concentration gradient. 
     
     
       15. The method of  claim 11 , further comprising forming the buffer layer and the thin silicon layer of the first element by epitaxial deposition. 
     
     
       16. The method of  claim 15 , wherein the epitaxial deposition comprises chemical vapor deposition or molecular beam epitaxial deposition. 
     
     
       17. The method of  claim 11 , further comprising forming the silicon oxide layers by thermal oxidation. 
     
     
       18. The method of  claim 11 , wherein removing the buffer layer comprises selective dissolution of the buffer layer by an oxidizing solution or by anisotropic plasma etching. 
     
     
       19. The method of  claim 11 , wherein the buffer layer comprises a germanium-silicon alloy. 
     
     
       20. The method of  claim 11 , wherein the buffer layer comprises a germanium-silicon alloy, and wherein the germanium-silicon alloy comprises at least 30% by weight of germanium. 
     
     
       21. A method of fabricating a silicon substrate comprising a thin buried silicon oxide layer, the method comprising:
 producing a first element comprising a silicon body, wherein a main surface of the first element is coated with a buffer layer comprising germanium, a thin silicon layer, and a thin silicon oxide layer, in that order;  
 obtaining a second element comprising a silicon body;  
 bonding the first element to the second element such that the thin silicon oxide layer of the first element is in contact with the silicon body of the second element; and  
 removing the buffer layer in order to recover the silicon substrate comprising the thin buried silicon oxide layer and a reusable silicon substrate.  
 
     
     
       22. The method of  claim 21 , wherein the buffer layer comprises a silicon-germanium alloy chosen from the alloys Si 1-x Ge x (0<x<1) and Si 1-x-y Ge x C y (0<x<0.95; 0<y≦0.05). 
     
     
       23. The method of  claim 21 , wherein the buffer layer comprises a germanium-silicon alloy, and wherein the germanium-silicon alloy comprises at least 10% by weight of germanium. 
     
     
       24. The method of  claim 21 , wherein the buffer layer comprises a layer made of a silicon-germanium alloy having a germanium concentration gradient. 
     
     
       25. The method of  claim 21 , further comprising forming the buffer layer and the thin silicon layer of the first element by epitaxial deposition. 
     
     
       26. The method of  claim 25 , wherein the epitaxial deposition comprises chemical vapor deposition or molecular beam epitaxial deposition. 
     
     
       27. The method of  claim 21 , further comprising forming the silicon oxide layers by thermal oxidation. 
     
     
       28. The method of  claim 21 , wherein removing the buffer layer comprises selective dissolution of the buffer layer by an oxidizing solution or by anisotropic plasma etching. 
     
     
       29. The method of  claim 21 , wherein the buffer layer comprises a germanium-silicon alloy. 
     
     
       30. The method of  claim 21 , wherein the buffer layer comprises a germanium-silicon alloy, and wherein the germanium-silicon alloy comprises at least 30% by weight of germanium. 
     
     
       31. A method, comprising:
   contacting a first element to a second element such that a silicon layer on a surface of the first element is in contact with a silicon oxide layer on a surface of the second element, wherein the first element includes a buffer layer comprising germanium; and        removing the buffer layer to produce a silicon substrate with the silicon oxide layer beneath the silicon layer.     
     
     
       32. The method of  claim 31 , wherein the silicon substrate comprises the second element and the silicon oxide layer beneath the silicon layer. 
     
     
       33. The method of  claim 31 , wherein the buffer layer is beneath the silicon layer on the surface of the first element. 
     
     
       34. The method of  claim 31 , wherein the first element comprises a silicon body. 
     
     
       35. The method of  claim 31 , wherein the second element comprises a silicon body. 
     
     
       36. The method of  claim 31 , wherein contacting the first element to the second element comprises bonding the surface of the first element to the surface of the second element. 
     
     
       37. The method of  claim 31 , further comprising depositing the buffer layer and the silicon layer on the first element using chemical vapor deposition and/or molecular beam epitaxial deposition. 
     
     
       38. The method of  claim 31 , further comprising forming the silicon oxide layer on the second element by thermal oxidation. 
     
     
       39. The method of  claim 31 , wherein removing the buffer layer produces a reusable silicon substrate. 
     
     
       40. The method of  claim 31 , wherein removing the buffer layer comprises selective dissolution of the buffer layer by an oxidizing solution or by anisotropic plasma etching. 
     
     
       41. The method of  claim 31 , wherein the buffer layer comprises a silicon- germanium alloy chosen from the alloys Si   1-x   Ge   x  (   0 <x< 1   )  and Si   1-x-y   Ge   x   C   y  (   0 <x< 0 . 95 ;  0 <y≦ 0 . 05   ).