Wafer-level chip scale packaging for piezoresistive pressure sensors using a dry-film shielding approach

In this study, wafer-level chip scale packaging (WL-CSP) for piezoresistive pressure sensors using a dry-film shielding approach is demonstrated. A sensing-channel opening just above the silicon membrane of the pressure sensor is reserved in the package body. To protect the silicon membrane of the pressure sensors from metal-deposition contaminants, a dry-film with a redistribution pattern is used to shield the sensing-channel opening during the seed layer sputter process. Experimental results reveal that the silicon membrane of the pressure sensor is free of metal-deposition contamination and functionally operational. The packaged pressure sensor meets all of specifications of an unpackaged bare pressure sensor, holding a maximum sensing error of 1.24 kPa over an operation temperature range of 25–85 °C. The proposed pressure sensor packaging is low cost and has a tiny packaging size, making it suitable for portable consumer products.