Apparatus and Method of Wafer Bonding Using Compatible Alloy

A method of bonding a device wafer to a second wafer, the method comprising:

• providing the device wafer with a two-dimensional array of MEMS devices;
• and
• providing the second wafer;
• depositing a metal alloy onto one or both the device wafer and the second wafer, the metal alloy being substantially CMOS fabrication compatible;
• aligning the device wafer and the second wafer;
• forming an intermediate apparatus having the metal alloy between the device wafer and the second wafer;
• heating the intermediate apparatus to within about 75 degrees C. of the metal alloy eutectic temperature between the device wafer and the second wafer;
• and
• cooling the wafers to form a plurality of conductive hermetic seal rings about the plurality of the MEMS devices on the device wafer, the seal rings bonding the device wafer to the second wafer.

A method of bonding a first wafer to a second wafer, the method comprising:

• forming a first metal layer on the first wafer, the first metal layer including one of aluminum-germanium or silicon-germanium;
• forming a second metal layer on the second wafer, the second metal layer including one of aluminum, germanium, or aluminum-germanium;
• bringing the first metal layer on the first wafer into contact with the second metal layer on the second wafer;
• heating the first and second metal layers to diffuse together the first and second metal layers to form a mechanical bond, heating being initiated either before or after bringing the first metal layer into contact with the second metal layer;
• and
• cooling the wafers to form a plurality of hermetic seal rings between the wafers.