Looking for advice on wafer bonding

Dear labmembers, 

I have been doing silicon-silicon wafer bonding for years using gold-silicon eutectic bonding.  While this is a reasonable wafer bonding method,  it leaves much to be desired.  Briefly,  the bond is not very strong - frequently even ultrasonic cleaning can break the bonded chip stack. 

I am looking for a better silicon-silicon wafer bonding process.  Factors to consider include process simplicity, bonding yield/strength, tolerance to dust particle, etc.  If every step can be performed at SNF,  it would be always better.  A lower temperature process is desirable. 

Your kind advice is greatly appreciated. 

Ben Jian