Stealth Dicing Challenges for MEMS Wafer Applications

Abstract

In our digital world, microelectromechanical system (MEMS) are here to stay and will open the doors for the next exciting wave in the advancement of technology such as the Internet of Things (IoT). The MEMS devices in wafer forms are fabricated in minute details and eventually singulated into individual units to act as sensing or actuation elements in various applications such as accelerometer and gyroscopes for navigation, in wireless mobile and smart car applications. Handling of such MEMS device requires overcoming many challenges in both fabrication and assembly. Singulation of MEMS device with fragile and sensitive structures is one of the many assembly challenges. In fact, most devices are capped to protect its active moving components that maybe damaged when using conventional singulation method that is by mechanical dicing wherein water splashes or pressure is unavoidable. With the introduction of stealth laser dicing, where micro damage is created internally and through several layers of this damages creates a propagation to eventually separate the wafer upon forced expansion through tape, it became possible for a dry process singulation without damaging the fragile components. However, stealth dicing leverages on infrared waves being transparent only and able to penetrate through smooth surface silicon wafers and at certain resistivity or level of doping to create internal damage on the work piece. As such, stealth dicing process may have difficulty to handle saw street with metallization, heavily doped or high resistivity wafer as in the case of SOI wafer and deep trenches that may surface in some MEMS devices. This created limitations for MEMS designs, processes and materials selection that may not be limited to the active region alone but as well as on the dicing saw street. In this paper we will conduct stealth dicing study on various types of wafer configuration and thus making a clearer assembly process for next generation of mobile applications and the fast growing market of IoT.