Abstract

Au/Si eutectic bonding is considered to BE a promising technology for creating 3D structures and hermetic packaging in micro-electro-mechanical system (MEMS) devices. However, it suffers from the problems of a non-uniform bonding interface and complex processes for the interconnection of metal wires. This paper presents a novel Au/Si eutectic wafer bonding structure and an implementation method for MEMS accelerometer packaging. The related processing parameters influencing the Au/Si eutectic bonding quality were widely investigated. It was found that a high temperature of 400 °C with a low heating/cooling rate of 5 °C/min is crucial for successful Au/Si eutectic bonding. High contact force is beneficial for bonding uniformity, but the bonding strength and bonding yield decrease when the contact force increases from 3000 to 5000 N due to the metal squeezing out of the interface. The application of TiW as an adhesion layer on a glass substrate, compared with a commonly used Cr or Ti layer, significantly improves the bonding quality. The bonding strength is higher than 50 MPa, and the bonding yield is above 90% for the presented Au/Si eutectic bonding. Furthermore, the wafer-level vacuum packaging of the MEMS accelerometer was achieved based on Au/Si eutectic bonding and anodic bonding with one process. Testing results show a nonlinearity of 0.91% and a sensitivity of 1.06 V/g for the MEMS accelerometer. This Au/Si eutectic bonding process can be applied to the development of reliable, low-temperature, low-cost fabrication and hermetic packaging for MEMS devices.

Highlights

  • Wafer bonding is as a key technology for microelectronics and micro-electro-mechanical systems (MEMS) for creating three-dimensional (3D) structures and hermetic packaging

  • Ahlers [8] studied the effect of platinum diffusion barriers and the metallization process in Au/Si eutectic bonding

  • We developed a simple Au/Si eutectic bonding process that enabled high bonding strength and a uniform bonding interface for hermetic packaging

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Summary

Introduction

Wafer bonding is as a key technology for microelectronics and micro-electro-mechanical systems (MEMS) for creating three-dimensional (3D) structures and hermetic packaging. Ahlers [8] studied the effect of platinum diffusion barriers and the metallization process in Au/Si eutectic bonding. Errong Jing et al [9] investigated the interface of Au/Si (100) eutectic bonding with an infrared (IR) microscope and related their observations to the bond strength. There have been few reports about the influence of contact force and the heating/cooling rate on Au/Si eutectic bonding quality.

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