Hybrid plasma bonding of germanium and glass wafers at low temperature

Hybrid plasma bonding (i.e., sequentially plasma activation followed by anodic bonding) has been demonstrated for germanium and glass wafers for the first time. Void-free interface with high bonding strength has been observed at 200 °C. This improved quality is attributed to reduced surface roughness and increased hydrophilicity of sequentially activated germanium and glass. Three layers caused by reactions of OH molecules between the highly reactive surfaces after plasma activation and opposite migration of cations and anions are observed across the interface.