Low Stress Solution of Anodic Bonding Technology with SW-YY® Glass for Sensitive MEMS

Anodic bonding technology is a well-established industrial technique, which is reported to be the most widely used MEMS packaging method. This Paper studies residual stress issue caused by different coefficients of thermal expansion (CTE) between silicon and glass during the anodic bonding process and its influence on MEMS-based sensors. For this purpose, SW-YY
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Glass from ASAHI is selected. Firstly, the SW-YY
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glass material is characterized in the bonding temperature range from 250°C to 500°C and voltage range from 400V-800V. Secondly, a MEMS based pressure sensor and two type glass substrates (SW-YY
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, Pyrex
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7740) were fabricated and bonded to evaluate the stress issue. Results show that the offset of the pressure sensor introduced by mismatched CTE was reduced significantly with SW-YY
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glass than standard Pyrex
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®7740 glass. The proposed method can be used to reduce the influence of the internal stress caused with bonding temperature and the mismatched CTEs for stress sensitive MEMS.