Aligned Au–Si eutectic bonding of silicon structures

Abstract

A technique for precisely aligning structures before a Au–Si eutectic bond has been developed. A (100) silicon wafer is anisotropically etched to create v grooves around the periphery of the structure to be bonded. Gold is then deposited onto one of the wafers prior to dicing into individual die. Optical fibers are used as precision locating keys and align the structure when it is assembled. The entire structure is then placed onto a hot chuck at 400 °C. An ultrasonic transducer is used to aid the Au–Si bond. The fibers may be removed after bonding. Current results have shown a maximum misalignment of 5 μm for a 1 cm×1 cm die. This accuracy is achieved with the entire assembly being done by hand without the aid of a microscope or micropositioners. This technique allows a sensor die to be precisely bonded to an electronics die.