Polysilicon and titanium disilicide+polycide fusion bonding for 3-D microdevices applications

Successful electrically conductive fusion bonding has been achieved for polysilicon to polysilicon and titanium disilicide+polycide to titanium disilicide+polycide coated wafers. The effects of wafer flatness and surface roughness play important roles in accomplishing direct bonding at room temperature of such deposited materials. The authors discuss the experimentally obtained estimates of minimum wafer curvature and maximum roughness for fusion bonding of these materials. For effective wafer bonding it was found experimentally that the radius of wafer curvature should be greater than 60 meters for a 500 micrometer thick wafer with a surface vertical microroughness less than 10 AA. The average microroughness was calculated from traces of a surface profilometer. The results of the bond strength measurements are presented. These wafer bonding systems can be used as an elegant technique to provide vertical interconnection for 3-D microdevices.<>