FORMATION OF INTERFACE BUBBLES IN BONDED SILICON-WAFERS - A THERMODYNAMIC MODEL

A thermodynamic model of the formation of unbonded areas or bubbles generated at the interface of bonded silicon wafers in the temperature range of 200-800-degrees-C is presented. Within this model it is assumed that the desorption of hydrocarbon contamination at the silicon wafer surfaces leads to small hydrocarbon molecules which are mobile at the bonding interface. When the vapor pressure generated by these molecules overcomes the interface bonding strength, interface bubbles are nucleated. These bubbles grow by incorporating further hydrocarbon and also possible hydrogen molecules. The model semiquantitatively explains all the essential features of interface bubble formation observed experimentally.