In-Situ Low-Temperature Bonding for Silicon-on-Quartz Substrates

Heterogeneous integration exploits the complementary advantages of different semiconductor materials to achieve a major performance leap in manufacturing new-generation chips and devices. Bonding of silicon and quartz glass is widely used in the fabrication of MEMS devices and micro fluidic chips. In general, high bonding temperatures are required to achieve high bonding energy for interfacial reinforcement. However, for heterogeneous materials, the large mismatch in thermal expansion coefficients between heterogeneous materials can limit the bonding temperature and interface strength. In addition, non-in-situ bonding can cause manufacturing inefficiencies and interfacial defects. In this paper, we propose a strategy for low-temperature in-situ bonding of silica and quartz glass at ~150°C. The bonding is performed by mild water vapor-assisted free radical bonding. Mild water vapor-assisted radical activation increases the density of hydroxyl groups on the surface of silica and glass, which improves the surface properties. As a result, we have successfully achieved low-damage and high-strength (~1.8 J/m
²
) bonding between silicon and quartz glass for Silicon-on-Quartz (SOQ) substrates.