Methods for preparing a bonding surface of a semiconductor wafer

Abstract

A method for preparing an oxidized surface of a first wafer for bonding with a second wafer. The method includes treating the oxidized surface using a mix of NH 4 OH/H 2 O 2 to increase the bonding energy between the first and second wafers. The treatment parameters are chosen such that etching occurs that is sufficient to remove isolated particles from the oxidized surface, but that is sufficiently weak to smooth the surface without creating rough patches thereon. Also described is a thin layer removal process, which may advantageously be used to fabricate a semiconductor on insulator structure.

1 . A method for preparing an oxidized surface of a first wafer for bonding with a second wafer, which comprises treating the oxidized surface of the surface with a solution of NH 4 OH/H 2 O 2 , wherein treatment parameters are chosen to provide etching that is sufficient to remove isolated particles from the oxidized surface but that is sufficiently weak to smooth the surface without creating rough patches thereon to enable an increased bonding energy between the first and second wafers when those surfaces are bonded together compared to bonding without treating the oxidized surface of the fist wafer.  
   
   
       2 . The method of  claim 1 , which further comprises implanting atomic species through the oxidized surface of the first wafer prior to the treating.  
   
   
       3 . The method of  claim 1 , wherein the treatment parameters include at least one of a predetermined dose of chemical elements, a predetermined temperature, or a predetermined duration for applying the treatment.  
   
   
       4 . The method of  claim 1 , wherein the treatment parameters are chosen such that treating removes isolated surface particles having an average diameter of more than about 0.1 micrometers.  
   
   
       5 . The method of  claim 1 , wherein the treatment parameters are chosen such that after treatment any rough patches that appear are less than about 5 ÅRMS.  
   
   
       6 . The method of  claim 1 , wherein the treatment parameters are chosen such that after treatment any rough patches that appear are less than about 4 ÅRMS.  
   
   
       7 . The method of  claim 1 , wherein the etching occurs to a depth of about 10 angstroms to about 120 angstroms.  
   
   
       8 . The method of  claim 1 , wherein the etching occurs to a depth of about 10 angstroms to about 60 angstroms.  
   
   
       9 . The method of  claim 1 , wherein the solution provides a dose per unit mass of NH 4 OH/H 2 O 2  in the range from about 1/2 to about 1/1.  
   
   
       10 . The method of  claim 1 , wherein the treating occurs at a temperature in a range of between about 30° C. and about 90° C. and a cleaning duration of between about 1 and 6 minutes.  
   
   
       11 . The method of  claim 1 , wherein the treatment parameters comprise a dose per unit mass of NH 4 OH/H 2 O 2  of about 1/2, a temperature of about 50° C., and a cleaning duration of about 3 minutes.  
   
   
       12 . The method of  claim 1 , wherein the treatment parameters comprise a dose per unit mass of NH 4 OH/H 2 O 2  of about 1/2, a temperature of about 70° C., and a cleaning duration of about 3 minutes.  
   
   
       13 . The method of  claim 1 , wherein the treatment parameters comprise a dose per unit mass of NH 4 OH/H 2 O 2  of about 3/4, a temperature of about 80° C., and a cleaning duration of about 3 minutes.  
   
   
       14 . The method of  claim 2 , wherein the first wafer is a donor wafer, the second wafer is a receiving wafer, and the atomic species are implanted through the oxidized surface of the first wafer to form a weakened zone at a predetermined depth to define a thin layer for subsequent transfer; and the method further comprises bonding the donor wafer to the receiver wafer; and supplying energy to detach the thin layer from the donor wafer at the weakened zone.  
   
   
       15 . The method of  claim 14 , wherein the implanted atomic species comprise at least one of hydrogen and helium ions.  
   
   
       16 . The method of  claim 14 , further comprising conducting a thermal oxidation step prior to treating the donor wafer.  
   
   
       17 . The method of  claim 14 , wherein the thin layer and donor wafer comprise a semiconductor-on-insulator structure.