Sos substrate having low surface defect density

Abstract

A method of making bonded SOS substrate with a semiconductor film on or above a sapphire substrate by implanting ions from a surface of the semiconductor substrate to form an ion-implanted layer; activating at least a surface of one of the sapphire substrate and the semiconductor substrate from which the ions have been implanted; bonding the surface of the semiconductor substrate and the surface of the sapphire substrate at a temperature of from 50° C. to 350° C.; heating the bonded substrates at a maximum temperature of from 200° C. to 350° C.; and irradiating visible light from a sapphire substrate side or a semiconductor substrate side to the ion-implanted layer of the semiconductor substrate to make the interface of the ion-implanted layer brittle at a temperature of the bonded body higher than the temperature at which the surfaces were bonded, to transfer the semiconductor film to the sapphire substrate.

1 . A silicon-on-sapphire (SOS) substrate comprising a single crystal silicon film on or above a sapphire substrate, wherein a defect density of a surface of the single crystal silicon film measured by a Secco defect detection method and a selective etching defect detection method is 10 4  pieces/cm 2  or less. 
     
     
         2 . The SOS substrate according to  claim 1 , wherein the thickness of the single crystal silicon film exceeds 100 nm. 
     
     
         3 . The SOS substrate according to  claim 1 , comprising a silicon oxide film between the single crystal silicon film and the sapphire substrate. 
     
     
         4 . The SOS substrate according to  claim 1 , wherein a thickness variation of the single crystal silicon film is 20 nm or less. 
     
     
         5 . The SOS substrate according to  claim 1 , or wherein the SOS substrate is obtained by the bonding method. 
     
     
         6 . A bonded SOS substrate comprising a semiconductor film on a surface of a sapphire substrate obtained by a method comprising the steps of:
 providing the sapphire substrate and a semiconductor substrate;   implanting ions from a surface of the semiconductor substrate to form an ion-implanted layer;   activating at least a surface selected from the surface of the sapphire substrate and the surface of the semiconductor substrate from which the ions have been implanted;   bonding the surface of the semiconductor substrate and the surface of the sapphire substrate at a temperature of from 50° C. to 350° C.;   heating the bonded substrates at a maximum temperature of from 200° C. to 350° C. to form a bonded body; and   irradiating visible light from a sapphire substrate side or a semiconductor substrate side to the ion-implanted layer of the semiconductor substrate for making an interface of the ion-implanted layer brittle, while keeping a temperature of the bonded body higher than the temperature at which the surfaces of the semiconductor substrate and the sapphire substrate were bonded, so as to transfer the semiconductor film to the sapphire substrate.   
     
     
         7 . The bonded SOS substrate according to  claim 6 , wherein a step of activating comprises one or more selected from the group consisting of ozone water treatment, UV ozone treatment, ion beam treatment and plasma treatment. 
     
     
         8 . The bonded SOS substrate according to  claim 6 , wherein the temperature of the bonded body during irradiation of the visible light is from 30° C. to 100° C. higher than the temperature at which the bonded body was formed. 
     
     
         9 . The bonded SOS substrate according to  claim 6 , comprising a step of applying a mechanical impact to the interface of the ion-implanted layer to split the bonded body along the interface after the step of irradiating visible light. 
     
     
         10 . The bonded SOS substrate according to  claim 6 , comprising a step of applying a mechanical impact to a side near the interface of the bonded body before the step of irradiating visible light. 
     
     
         11 . The bonded SOS substrate according to  claim 6 , wherein the semiconductor substrate is a single crystal silicon substrate or a silicon substrate on which an oxide film has been grown. 
     
     
         12 . The bonded SOS substrate according to  claim 6 , wherein the visible light is a laser beam. 
     
     
         13 . The bonded SOS substrate according to  claim 6 , wherein the visible light is of a RTA (Rapid Thermal Anneal) including spike anneal. 
     
     
         14 . The bonded SOS substrate according to  claim 6 , wherein the visible light is flash lamp light. 
     
     
         15 . The bonded SOS substrate according to  claim 6 , wherein the implanted ions are hydrogen atom ions (H + ) and a dose amount thereof is from 1×10 16  atoms/cm 2  to 1×10 17  atoms/cm 2 . 
     
     
         16 . The bonded SOS substrate according to  claim 6 , wherein the implanted ions are hydrogen atom molecule ions (H 2   + ) and a dose amount thereof is from 5×10 15  atoms/cm 2  to 5×10 16  atoms/cm 2 . 
     
     
         17 . The bonded SOS substrate according to  claim 6 , further comprising a step of chemically etching and/or polishing a surface of the transferred semiconductor film. 
     
     
         18 . (canceled) 
     
     
         19 . The SOS substrate according to  claim 2 , comprising a silicon oxide film between the single crystal silicon film and the sapphire substrate. 
     
     
         20 . The SOS substrate according to claim or  2 , wherein a thickness variation of the single crystal silicon film is 20 nm or less. 
     
     
         21 . The SOS substrate according to  claim 2 , wherein the SOS substrate is obtained by the bonding method.