Stress-free bonding technology with bondable thin glass layer for MEMS based pressure sensor

In the present work, an intermediate sodium-rich glass layer was deposited on silicon wafer by a PVD (Physical Vapor Deposition) process for further silicon to silicon anodic bonding. The anodic bonding process was carried out at low direct-current voltage of about 40 V-100 V and temperature from 320°C to 400°C. The concentration of alkali ion (sodium) in the deposited thin glass layer, the surface roughness of the thin film, and the bonding properties of the thin glass layer were studied in detail and later on this technology was used to fabricate a MEMS based pressure sensor (bonding voltage 40 V and bonding temperature 360°C). The infrared microscopy (IR) was used as the visual method to detect the bonding defects. The offset value was measured with varied temperature to check the stress issues. The purpose of the proposed method is to reduce the offset value for MEMS based pressure sensor by using the thin glass bonding layer. This novel method can be applied to the other type of MEMS sensors, which requires anodic bonding process to improve the performance.