Silicon-to-silicon wafer bond efficiency by sol-gel process

In this paper, a design of experiments approach is used to estimate the effects of the bonding temperatures (100 and 300°C), solution aging times (1 and 48 hours) and spin speeds (1500 and 3000 rpm) on bond efficiency of Si-to-Si wafer bonding by sol-gel process. Acid catalyzed tetraethylorthosilicate (TEOS) solution is spun on the silicon wafer surfaces before putting two wafers into contact. Eight runs are carried out to form a full 2³ factorial design. The statistic analyses show that the spin speed, bonding temperature and solution aging time are the most dominant factors, while no interaction is significant. High spinning speed, low bonding temperature and short solution aging time can improve the bond efficiency. Annealing experiments and contact angle measurements indicate that the reason causing the unbonded area at low temperature is the absence of bonding species, while that at high temperature is the decomposition of hydrocarbon species. These observed trends could be helpful to obtain general guidelines that might be beneficial in tailoring preparation condition for better bond quality.