Methods and structure for improving wafer bow control

Abstract

A method for controlling bow in wafers which utilize doped layers is described. The method includes depositing a silicon-germanium layer onto a substrate, depositing an undoped buffer layer onto the silicon-germanium layer, and depositing a silicon-boron layer onto the undoped layer.

1 .- 7 . (canceled)  
     
     
         8 . A wafer comprising: 
 a substrate layer;    a silicon-germanium layer deposited onto said substrate layer;    an undoped buffer layer deposited onto said silicon-germanium layer; and    a boron doped silicon layer deposited onto said undoped buffer layer.    
     
     
         9 . (canceled)  
     
     
         10 . A wafer according to  claim 8  wherein said undoped buffer layer has a thickness between about 0.1 and about 5.0 micrometers.  
     
     
         11 . A wafer according to  claim 8  wherein said silicon-boron layer has a thickness between about 5.0 and about 50.0 micrometers.  
     
     
         12 . (canceled)  
     
     
         13 . A wafer according to  claim 8  wherein a concentration of boron in said silicon-boron layer is between about 5×10 19  and about 5×10 20  cm −3 .  
     
     
         14 . A micro-electromechanical system (MEMS) comprising: 
 a housing;    a micro-machine coupled to said housing, at least a portion of said micro-machine comprising boron-doped silicon that has been etched from a wafer which comprises a substrate layer, a silicon-germanium layer deposited onto said substrate layer, an undoped buffer layer deposited onto said silicon-germanium layer, and a silicon-boron layer deposited onto said undoped buffer layer.    
     
     
         15 . A MEMS according to  claim 14  wherein boron-doped silicon comprises proof masses, motor drive combs, and motor pick-off combs for a tuning fork gyroscope.  
     
     
         16 . A MEMS according to  claim 14  wherein a concentration of boron in said silicon-boron layer is between about 0.1 percent and about 1.0 percent.  
     
     
         17 . A MEMS according to  claim 14  wherein said silicon-boron layer has a thickness between about 5.0 and about 50.0 micrometers.  
     
     
         18 . A MEMS according to  claim 14  wherein said micro-machine comprises one or more of an accelerometer, a resonator, a pressure sensor, a temperature sensor and an air flow sensor.  
     
     
         19 . A gyroscope comprising: 
 at least one proof mass;    at least one motor drive comb; and    at least one motor pick-off comb, said proof masses, said motor drive combs, and said motor pick-off combs comprising boron-doped silicon that has been etched from a wafer which comprises a substrate layer, a silicon-germanium layer deposited onto said substrate layer, an undoped buffer layer deposited onto said silicon-germanium layer, and a silicon-boron layer deposited onto said undoped buffer layer.    
     
     
         20 .- 22 . (canceled)