Method and apparatus for etching a semiconductor article and method of preparing a semiconductor article by using the same

Abstract

With a method according to the invention, a semiconductor article such as an SOI substrate having on the surface thereof a single crystal silicon film formed on an insulator is etched by heat treatment in a hydrogen-containing reducing atmosphere in order to remove the surface by a desired height and smooth it. The method is characterized in that the single crystal silicon film is arranged opposite to silicon oxide in a furnace during the etching process.

What is claimed is:  
     
         1 . A method for etching a semiconductor article having a planar surface comprising silicon, said method comprising a step of heat-treating said silicon surface in a hydrogen-containing reducing atmosphere, with keeping said silicon surface in a state disposed opposite to a surface comprising silicon oxide with a predetermined distance separating them.  
     
     
         2 . A method for etching a semiconductor article according to  claim 1 , wherein said semiconductor article is an SOI substrate having a single crystal silicon film.  
     
     
         3 . A method for etching a semiconductor article according to  claim 1  or  2 , wherein said silicon surface has a root mean square of surface roughness of not smaller than 0.2 nm in a 1 μm square area.  
     
     
         4 . A method for etching a semiconductor article according to  claim 1  or  2 , wherein said silicon surface is an unpolished surface.  
     
     
         5 . A method for etching a semiconductor article according to  claim 1  or  2 , wherein said silicon surface has a surface roughness attributable t o a porous silicon layer.  
     
     
         6 . A method for etching a semiconductor article according to  claim 1  or  2 , wherein said silicon surface has a surface roughness attributable to micro-cavities.  
     
     
         7 . A method for etching a semiconductor article according to  claim 2 , wherein said SOI substrate having a single crystal silicon film is obtained by bonding a first silicon article containing said single crystal silicon film and a separation layer for predefining a separating position to a second article and then separating the bonded assembly at the separation layer predefining the separating position so as to transfer said single crystal silicon film onto said second article.  
     
     
         8 . A method for etching a semiconductor article according to  claim 7 , wherein said separation layer is a layer implanted with inert gas or hydrogen ions.  
     
     
         9 . A method for etching a semiconductor article according to  claim 7 , wherein said separation layer is a porous layer.  
     
     
         10 . A method for etching a semiconductor article according to  claim 2 , wherein said SOI substrate has a buried oxide layer obtained by implanting oxygen ions into and heat-treating a silicon wafer.  
     
     
         11 . A method for etching a semiconductor article according to  claim 1 , wherein the flow rate of gas running near and in parallel with said silicon surface is made lower than the flow rate of gas running perpendicularly relative to and outside the surface of the peripheral area of the semiconductor article in said etching step.  
     
     
         12 . A method for etching a semiconductor article according to  claim 11 , wherein the flow rate of gas running near and in parallel with said silicon surface is made practically equal to 0.  
     
     
         13 . A method for etching a semiconductor article according to  claim 1 , wherein a silicon wafer having a silicon oxide film on its surface is arranged opposite to the silicon surface of said semiconductor article and said semiconductor article is heat-treated until the silicon oxide film is etched out to expose the underlying silicon.  
     
     
         14 . A method for etching a semiconductor article according to  claim 1 , wherein a tray made of silicon oxide is arranged opposite to the silicon surface of said semiconductor article.  
     
     
         15 . A method for etching a semiconductor article according to  claim 1 , wherein said hydrogen-containing reducing atmosphere contains hydrogen by 100% or hydrogen and an inert gas.  
     
     
         16 . A method for etching a semiconductor article according to  claim 1 , wherein said hydrogen-containing reducing atmosphere shows a dew point not higher than −92° C.  
     
     
         17 . A method for etching a semiconductor article according to  claim 1 , wherein said semiconductor article is supported by a member containing silicon oxide at least on its surface as principal ingredient.  
     
     
         18 . A method for etching a semiconductor article according to  claim 1 , wherein said semiconductor article is arranged so as to make said silicon surface disposed perpendicularly relative to the principal flow of hydrogen-containing gas in a container.  
     
     
         19 . A method for etching a semiconductor article according to  claim 1 , wherein a plurality of semiconductor articles, each having said silicon surface, are arranged coaxially in parallel with each other at predetermined regular intervals and heat-treated in a container, with causing a hydrogen-containing gas to flow around the semiconductor articles so as to make the flow rate of gas running near and in parallel with said surface practically equal to 0.  
     
     
         20 . A method for etching a semiconductor article according to  claim 1 , wherein a quartz plate is arranged opposite to said silicon surface with a hydrogen-containing gas interposed therebetween for heat-treating said semiconductor article.  
     
     
         21 . A method for etching a semiconductor article according to  claim 1 , wherein said silicon oxide surface is a rear surface of another semiconductor article, said rear surface of another semiconductor article being arranged opposite to said silicon surface.  
     
     
         22 . A method for etching a semiconductor article according to  claim 1 , wherein said article is arranged in a container having an inner wall surface comprising silicon oxide.  
     
     
         23 . A method for etching a semiconductor article according to  claim 1 , wherein a plurality of semiconductor articles are supported by a support member having a surface comprising silicon oxide so as to be arranged in parallel with each other in a container having an inner wall surface also comprising silicon oxide.  
     
     
         24 . A method for etching a semiconductor article according to  claim 1 , wherein said silicon surface is removed by about 10 nm to 200 nm by etching.  
     
     
         25 . A method for etching a semiconductor article according to  claim 1 , wherein the rate of etching said silicon surface is between 1.0×10 −3  nm/min. and 1.0 nm/min.  
     
     
         26 . A method for etching a semiconductor article according to any of claims  1  and  23  through  25 , wherein the root mean square of surface roughness of said silicon surface is made to be not greater than 0.4 nm in a 1 μm square area.  
     
     
         27 . A method for etching a semiconductor article according to any of claims  1  and  23  through  25 , wherein said silicon oxide shows a thickness not smaller than 2.2 times of the height to be etched of said silicon surface.  
     
     
         28 . A method for etching a semiconductor article according to any of claims  1 ,  19  and  23 , wherein a plurality of semiconductor articles, each having said silicon surface, are arranged coaxially in parallel with each other at predetermined regular intervals to face a same direction and a dummy substrate or a quartz wafer substrate having a silicon oxide film on the surface is arranged foremost to face the silicon surface of the leading semiconductor article.  
     
     
         29 . A method for etching a semiconductor article according to any of claims  2  and  23  through  25 , wherein said single crystal silicon film of the silicon surface is an SOI layer formed by epitaxial growth.  
     
     
         30 . A method for etching a semiconductor article according to any of claims  2  and  23  through  25 , wherein said single crystal silicon film of the silicon surface has a film thickness between 50 nm and 500 nm before the etching process.  
     
     
         31 . A method for etching a semiconductor article according to  claim 1 , wherein a counter-surface constituting member comprising a silicon oxide film formed on the surface of a supporting material is arranged opposite to said article so as to allow said heat treatment to continue for a period of time sufficient to make the silicon oxide film to be etched out to expose the surface of the support material.  
     
     
         32 . A method for etching a semiconductor article according to any of claims  2  and  23  through  25 , wherein the single crystal silicon film of said silicon surface has a film thickness between 20 nm and 250 nm after the etching process.  
     
     
         33 . A method for etching a semiconductor article according to any of claims  2  and  23  through  25 , wherein the single crystal silicon film of said silicon surface has a film thickness selected out of a range between 50 nm and 500 nm and is etched to show a film thickness between 20 and 250 nm.  
     
     
         34 . An etching apparatus for carrying out an etching method according to  claim 1 .  
     
     
         35 . An etching apparatus according to  claim 34 , comprising a reaction furnace made of vitreous silica and adapted to contain said semiconductor article and reduce the internal pressure.  
     
     
         36 . A method of preparing a semiconductor article having a silicon film, said method comprising steps of: 
 bonding a first article containing therein a silicon film and a separation layer defining a separating position to a second article;    separating the bonded first and second articles along the layer defining said separating position to transfer said silicon film onto said second article; and    etching the surface of said silicon film transferred onto said second article by heat-treating said second article in a hydrogen-containing reducing atmosphere, with arranging a surface of silicon oxide opposite to said silicon film.    
     
     
         37 . A method of preparing a semiconductor article having a silicon film, said method comprising steps of: 
 bonding a first article comprising silicon and a second article;    removing part of said first article from said bonded first and second articles so as to leave a silicon film on said second article;    etching the surface of said silicon film left on said second article by heat-treating said second article in a hydrogen-containing reducing atmosphere, with arranging a surface of silicon oxide opposite to said silicon film.    
     
     
         38 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , further comprising a step of forming a silicon oxide film on the rear surface of said second article to provide said surface of silicon oxide.  
     
     
         39 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , further comprising a step of preparing a first article by forming a non-porous single crystal silicon film on a porous silicon layer.  
     
     
         40 . A method of preparing a semiconductor article having a silicon film according to  claim 36 , wherein said separation layer is a porous layer and said etching step is conducted after selectively etching the residual porous layer remaining on said silicon film after the separation.  
     
     
         41 . A method of preparing a semiconductor article having a silicon film according to  claim 36 , wherein said separation layer is a porous layer and said etching step is conducted with the residual porous layer remaining on said silicon film after the separation.  
     
     
         42 . A method of preparing a semiconductor article having a silicon film according to  claim 36 , wherein said separation layer is a layer implanted with inert gas or hydrogen ions and said etching step is conducted without polishing the surface of said silicon film exposed after the separation.  
     
     
         43 . A method of preparing a semiconductor article having a silicon film according to  claim 37 , wherein said first article comprises a porous layer and said removing step includes a step of removing the porous layer remaining on said silicon film.  
     
     
         44 . A method of preparing a semiconductor article having a silicon film according to  claim 37 , wherein the porous layer is remaining on said silicon film after the removing step.  
     
     
         45 . A method of preparing a semiconductor article having a silicon film according to  claim 37 , wherein the surface of said silicon film is a surface subjected to plasma etching after said removing step.  
     
     
         46 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein said silicon film surface has a root mean square of surface roughness of not smaller than 0.2 nm in a 1 μm square area.  
     
     
         47 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein said silicon surface has a surface roughness attributable to a porous silicon layer.  
     
     
         48 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein said silicon surface has a surface roughness attributable to micro-cavities.  
     
     
         49 . A method of preparing a semiconductor article having a silicon film according to  claim 36 , wherein said separation layer is a layer implanted with inert gas or hydrogen ions  
     
     
         50 . A method of preparing a semiconductor article having a silicon film according to  claim 36 , wherein said separation layer is a porous layer.  
     
     
         51 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein the flow rate of gas running near and in parallel with said silicon surface is made lower than the flow rate of gas running perpendicularly relative to and outside the surface of the peripheral area of the semiconductor article in said etching step.  
     
     
         52 . A method of preparing a semiconductor article having a silicon film according to  claim 50 , wherein the flow rate of gas running near and in parallel with said silicon surface is made practically equal to 0.  
     
     
         53 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein a silicon wafer having a silicon oxide film on its surface is arranged opposite to the silicon film of said semiconductor article and said semiconductor article is heat-treated until the silicon oxide film is etched out to expose the underlying silicon.  
     
     
         54 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein a tray made of silicon oxide is arranged opposite to the silicon film of said semiconductor article.  
     
     
         55 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein said hydrogen-containing reducing atmosphere contains hydrogen by 100% or hydrogen and an inert gas.  
     
     
         56 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein said hydrogen-containing reducing atmosphere shows a dew point not higher than −92° C.  
     
     
         57 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein said semiconductor article is supported by a member containing silicon oxide at least on its surface as principal ingredient.  
     
     
         58 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein said semiconductor article is arranged so as to make said silicon surface disposed perpendicularly relative to the principal flow of hydrogen-containing gas in a container.  
     
     
         59 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein a plurality of semiconductor articles, each having said silicon surface, are arranged coaxially in parallel with each other at predetermined regular intervals and heat-treated in a container, with causing a hydrogen-containing gas to flow around the semiconductor articles so as to make the flow rate of gas running near and in parallel with said silicon surface practically equal to 0.  
     
     
         60 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein a quartz plate is arranged opposite to said silicon surface with a hydrogen-containing gas interposed therebetween for heat-treating said semiconductor article.  
     
     
         61 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein said silicon oxide surface is a rear surface of another semiconductor article, said rear surface of another semiconductor article being arranged opposite to said silicon surface.  
     
     
         62 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein said article is arranged in a container having an inner wall surface comprising silicon oxide.  
     
     
         63 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein a plurality of semiconductor articles are supported by a support member having a surface comprising silicon oxide so as to be arranged in parallel with each other in a container having an inner wall surface also comprising silicon oxide.  
     
     
         64 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein said silicon surface is removed by about 10 nm to 200 nm by etching.  
     
     
         65 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein the rate of etching said silicon surface is between 1.0×10 3  nm/min. and 1.0 nm/min.  
     
     
         66 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein the root mean square of surface roughness of said silicon surface is made to be not greater than 0.4 nm in a 1 μm square area.  
     
     
         67 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein said silicon oxide shows a thickness not smaller than 2.2 times of the height to be etched of said silicon surface.  
     
     
         68 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein a plurality of semiconductor articles, each having said silicon surface, are arranged coaxially in parallel with each other at predetermined regular intervals to face a same direction and a dummy substrate or a quartz wafer substrate having a silicon oxide film on the surface is arranged foremost to face the silicon surface of the leading semiconductor article.  
     
     
         69 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein said single crystal silicon film of the silicon surface is an SOI layer formed by epitaxial growth.  
     
     
         70 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein said single crystal silicon film of the silicon surface has a film thickness between 50 nm and 500 nm before the etching process.  
     
     
         71 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein the single crystal silicon film of said silicon surface has a film thickness between 20 nm and 250 nm after the etching process.  
     
     
         72 . A method of preparing a semiconductor article having a silicon film according to  claim 36  or  37 , wherein the single crystal silicon film of said silicon surface has a film thickness selected out of a range between 50 nm and 500 nm and is etched to show a film thickness between 20 and 250 nm.  
     
     
         73 . A method according to  claim 1 , wherein the temperature of said heat treatment is higher than 300° C. and lower than the melting point of silicon.  
     
     
         74 . A method according to  claim 1 , wherein the temperature of said heat treatment is higher than 800° C. and lower than the melting point of silicon.  
     
     
         75 . A method according to  claim 36  or  37 , wherein the temperature of said heat treatment is higher than 300° C. and lower than the melting point of silicon.  
     
     
         76 . A method according to  claim 36  or  37 , wherein the temperature of said heat treatment is higher than 800° C. and lower than the melting point of silicon.  
     
     
         77 . A method according to  claim 1 ,  36  or  37 , wherein the flow rate of gas flowing along the outer peripheral area of said silicon film article in the furnace is not smaller than 10 cc/min.cm 2  and not greater than 300 cc/min.cm 2 .