Divot reduction in SIMOX layers

Abstract

A method of fabricating a silicon-on-insulator (SOI) having a superficial Si-containing layer that has a reduced number of tile and divot defects is provided. The method includes the steps of: implanting oxygen ions into a surface of a Si-containing substrate, the implanted oxygen ions having a concentration sufficient to form a buried oxide region during a subsequent annealing step; and annealing the substrate containing implanted oxygen ions under conditions wherein the implanted oxygen ions form a buried oxide region which electrically isolates a superficial Si-containing layer from a bottom Si-containing layer. Moreover, the annealing conditions employed are capable of reducing the number of tile or divot defects present in the superficial Si-containing layer so as to allow optical detection of any other defect that has a lower density than the tile or divot defect. The present invention also relates to the SOI substrate that is produced using the inventive method.

Having thus described our invention in detail what we claim as new and desire to secure by the Letters Patent is:  
     
         1 . A method of substantially reducing the number of tile or divot defects that are present in a silicon-on-insulator (SOI) substrate, said method comprising the steps of: 
 (a) implanting oxygen ions into a surface of a Si-containing substrate, said implanted oxygen ions having a concentration sufficient to form a buried oxide region during a subsequent annealing step; and    (b) annealing said substrate containing said implanted oxygen ions under conditions wherein said implanted oxygen ions form said buried oxide region which electrically isolates a superficial Si-containing layer from a bottom Si-containing layer, said superficial Si-containing layer having a top surface which contains a reduced number of tile or divot defects so as to allow optical detection of any other defect that has a lower density than the tile or divot defect.    
     
     
         2 . The method of  claim 1  wherein step (a) comprises a single oxygen base implant or a base oxygen implant followed by a second oxygen implant, said second oxygen implant is carried out at a temperature lower than the base oxygen implant.  
     
     
         3 . The method of  claim 2  wherein said second oxygen implant step is carried out using an oxygen dose of from about 1E14 to about 1E16 cm −2  and at an energy of about 40 keV or greater.  
     
     
         4 . The method of  claim 3  wherein said second oxygen implant step is carried out using an oxygen dose of from about 1E15 to about 4E15 cm −2  and at an energy of from about 120 to about 450 keV.  
     
     
         5 . The method of  claim 2  wherein said second oxygen implant step is carried out at a temperature of from about 4K to about 200° C. at a beam current density of from about 0.05 to about 10 mA cm −2 .  
     
     
         6 . The method of  claim 5  wherein said second oxygen implant step is carried out at a temperature of from about 25° to about 100° C. at a beam current density of from about 0.5 to about 5.0 mA cm −2 .  
     
     
         7 . The method of  claim 2  wherein said base oxygen implant comprises a high-dose oxygen implant which is carried out using an oxygen dose of about 4E17 cm −2  or greater.  
     
     
         8 . The method of  claim 7  wherein said high-dose oxygen implant is performed using an oxygen dose of from about 4E17 to about 4E18 cm −2 .  
     
     
         9 . The method of  claim 7  wherein said high-dose oxygen implant is carried out at an energy of from about 10 to about 1000 keV.  
     
     
         10 . The method of  claim 9  wherein said high-dose oxygen implant is carried out at an energy of from about 120 to about 210 keV.  
     
     
         11 . The method of  claim 7  wherein said high-dose oxygen implant is carried out at a temperature of from about 200° to about 800° C. at a beam current density of from about 0.05 to about 500 mA cm −2 .  
     
     
         12 . The method of  claim 11  wherein said high-dose oxygen implant is carried out at a temperature of from about 200° to about 600° C. at a beam current density of from about 4 to about 8 mA cm −2 .  
     
     
         13 . The method of  claim 2  wherein said base oxygen implant comprises a high-energy, high-dose oxygen implant which is carried out using an oxygen ion dose of about 4E17 cm −2  or greater and at an energy of about 60 keV or greater.  
     
     
         14 . The method of  claim 13  wherein said high-energy, high-dose oxygen implant is carried out using an oxygen ion dose of from about 5E17 to about 7E17 cm −2  and at an energy of from about 200 to about 500 keV.  
     
     
         15 . The method of  claim 13  wherein said high-energy, high-dose oxygen implant is performed at a temperature of from about 100° to about 800° C. at a beam current density of from about 0.05 to about 500 mA cm −2 .  
     
     
         16 . The method of  claim 15  wherein said high-energy, high-dose oxygen implant is performed at a temperature of from about 300° to about 700° C.  
     
     
         17 . The method of  claim 2  wherein said base oxygen implant comprises a low-dose oxygen implant which is carried out using an oxygen dose of about 4E17 cm −2  or less.  
     
     
         18 . The method of  claim 17  wherein said low-dose oxygen implant is performed using an oxygen dose of from about 1E17 to about 3.9E17 cm −2 .  
     
     
         19 . The method of  claim 17  wherein said low-dose oxygen implant is carried out at an energy of from about 20 to about 10000 keV.  
     
     
         20 . The method of  claim 19  wherein said low-dose oxygen implant is carried out at an energy of from about 100 to about 210 keV.  
     
     
         21 . The method of  claim 17  wherein said low-dose oxygen implant is carried out at a temperature of from about 100° to about 800° C.  
     
     
         22 . The method of  claim 21  wherein said low-dose oxygen implant is carried out at a temperature of from about 200° to about 650° C. at a beam current density of from about 0.05 to about 500 mA cm −2 .  
     
     
         23 . The method of  claim 1  wherein said annealing step is carried out in an ambient gas that comprises from about 0 to about 90% oxygen and from about 10 to about 100% of at least one high-surface mobility gas that hinders oxide growth, said high-mobility gas is selected from the group consisting of He, N 2 , Kr, H 2  and mixtures thereof.  
     
     
         24 . The method of  claim 23  wherein said high-surface mobility gases is N 2 .  
     
     
         25 . The method of  claim 23  wherein said high-surface mobility gas comprises 100% N 2 .  
     
     
         26 . The method of  claim 23  wherein said high-surface mobility gas is admixed with Ar.  
     
     
         27 . The method of  claim 23  wherein said annealing step is carried out at a temperature of from about 1250° C. or greater for a time period of from about 1 to about 100 hours.  
     
     
         28 . The method of  claim 27  wherein said annealing step is carried out at a temperature of from about 1300° to about 1350° C. for a time period of from about 2 to about 24 hours.  
     
     
         29 . The method of  claim 23  wherein said annealing step includes a ramp and soak-heating regime.  
     
     
         30 . The method of  claim 1  wherein said annealing step comprises the steps of: partially annealing the Si-containing substrate containing the implanted oxygen ions in oxygen so as to form a surface layer of oxygen on the Si-containing and to partially form said BOX region; stripping the surface layer of oxygen; and continuing the annealing to complete formation of said BOX region.  
     
     
         31 . The method of  claim 30  wherein said partially annealing is carried out in an ambient that comprises from about 1 to about 100% oxygen and from about 0 to about 99% inert gas.  
     
     
         32 . The method of  claim 31  wherein said inert gas comprises He, Ar, Kr, N 2  or mixtures thereof.  
     
     
         33 . The method of  claim 31  wherein said gas comprises N 2  or a mixture of N 2  and Ar.  
     
     
         34 . The method of  claim 30  wherein said partial annealing is performed at a temperature of from about 1250° to about 1400° C. for a time period of from about 1 to about 100 hours.  
     
     
         35 . The method of  claim 34  wherein said partial annealing is performed at a temperature of from about 1320° to about 1350° C. for a time period of from about 2 to about 20 hours.  
     
     
         36 . The method of  claim 30  wherein said surface layer of oxygen is removed utilizing a wet etch process that includes an etchant that has a high-selectivity for removing oxide compared with Si.  
     
     
         37 . The method of  claim 30  wherein second anneal is performed at a temperature of from about 1250° to about 1400° C. for a time period of from about 1 to about 100 hours.  
     
     
         38 . The method of  claim 37  wherein said second anneal is performed at a temperature of from about 1320° to about 1350° C. for a time period of from about 2 to about 20 hours.  
     
     
         39 . The method of  claim 30  wherein said second annealing is performed in an ambient gas that comprises from about 0 to about 90% oxygen and from about 10 to about 100% of at least one high-surface mobility gas that hinders oxide growth, said high-mobility gas is selected from the group consisting of He, N 2 , Kr, H 2  and mixtures thereof.  
     
     
         40 . The method of  claim 1  further comprising applying a patterned resist to the surface of the SOI wafer prior to oxygen implantation.  
     
     
         41 . A silicon-on-insulator (SOI) substrate comprising: 
 a buried oxide region that is sandwiched between a superficial Si-containing layer and a bottom Si-containing layer, said superficial Si-containing layer having a top surface which contains a reduced number of tile or divot defects so as to allow optical detection of any other defect that has a lower density than the tile or divot defect.    
     
     
         42 . The SOI substrate of  claim 41  wherein said buried oxide region has a uniform interface with said superficial Si-containing layer.  
     
     
         43 . The SOI substrate of  claim 41  wherein said buried oxide region has an undulating defect-containing interface with said superficial Si-containing layer.  
     
     
         44 . The SOI substrate of  claim 41  wherein said superficial Si-containing layer is smooth and has a glass-like appearance.  
     
     
         45 . The SOI substrate of  claim 41  wherein said buried oxide region is present continuously through the substrate.  
     
     
         46 . The SOI substrate of  claim 41  wherein said substrate comprises discrete and isolated buried oxide regions.  
     
     
         47 . The SOI substrate of  claim 46  wherein some of said discrete and isolated buried oxide regions have an undulating defect-containing interface with said superficial Si-containing layer.