Authors: C. Brubaker, T.Matthias and M. Wimplinger Company: EV Group Inc. Date Published: 11/1/2006
IWLPC (Wafer-Level Packaging)
Abstract: In recent years, a veritable explosion of optical microdevices have entered the market place, from projection display systems such as LCD technology and Texas Instruments DLP™ systems, to optical sensing devices such as he CCD chips used in digital cameras and cell phones. The vast increase in the demand for these products (with device sales easily measured in the hundreds of millions) and highly competitive nature of the marketplace require the use of more cost effective means of creating transparent packages to protect these devices from the environment. This paper will discus the use of SU-8 to perform a wafer lever bonding process to apply the transparent package to such devices. The use of SU-8 bonding medium for this process is ideal for a variety of reasons. First, it allows accurate definition of a precise separation gap between the device and the glass cover; which also prevents any relative tilt between the cover glass and the device (very important for proper optical processing). Second, the gasket pattern can be easily defined in the SU-8 via mask aligner. Third, the bonding process itself can take place at very low temperatures (less that 150ºC), which makes it easily compatible to packaging CMOS devices. Finally, when SU- 8 is cured, it is impervious to any solvent (and virtually all chemistry that may encountered) creating effective protection for the optical device.