A wafer-level hermetic encapsulation for MEMS manufacture application

Abstract

In order to simplify the processing complexity and cut down the manufacturing cost, a new wafer bonding technique using ultraviolet (UV) curable adhesive is introduced here for microelectromechanical systems (MEMS) device packaging and manufacturing applications. UV curable adhesive is cured through UV light exposure without any heating process that is suitable for the packaging of temperature-sensitive materials or devices. A Pyrex 7740 glass is chemically wet etched to form microcavities and utilized as the protection cap substrate. After a UV-curable adhesive is spin-coated onto the glass substrate, the substrate is then aligned and bonded through UV light exposure with a device substrate below. Electrical contact pad opening and die separation are done simultaneously by dicing. Two different testing devices, a dew point sensor and capacitive accelerometer, are built to evaluate the package strength and hermeticity. After the dicing process, no structural damage or stiction phenomenon is found in the packaged parallel capacitor. The acceleration test results also indicate that the package using the Loctite 3491 UV adhesive with 150 mu m bond width can survive more than 300 days at a 25 degrees C and 100% relative humidity working environment.