Low Temperature Silicon Wafer Bonding By Sol-Gel Processing

Low temperature bonding of two silicon wafers with significant high bond strength has been prepared successfully using sol-gel coating as intermediate layer. The effects of bonding temperature, solution aging time and spin speed on bonding quality have been investigated by a full 23 factorial design. Under the 75% confidence level, the statistic result shows that only the interaction effect between bonding temperature and spin speed is significant. Design of experiments (DoE) is used to study the effects of key parameters on bond strength, and bonding mechanism are discussed. The possible reason for the observed high bond strength is the absence of absorbed water on the smooth coating surface, which results in the direct condensation reactions between OH groups to form strong Si-O-Si bonds even at low temperatures.