<title>Advances in silicon-to-glass bonding with laser</title>

Abstract

In this work low temperature bonding of silicon and glass wafers for MEMS applications by the application of a Nd:YAG Laser using the transmission welding principle is examined. With this method the Laser beam is transmitted through the glass wafer and absorbed by the silicon at the silicon-glass interface. The resulting heated zone leads to locally selective bonding in spot and line shape with line width of 300 micrometers and less. The scope of the work is to characterize the Laser bonding (LB) technology and the quality of the produced silicon-glass joints. The continuous Laser power applied was between 12 and 30 W and the scribing velocity was between 50 and 500 mm/min. The measurements of the thermal load in the silicon during LB performed with micro-thermocouples show temperatures near the bonding zone around 300 degree(s)C for less than one second. The produced joints were found to have tensile strength between 5 and 10 MPa, which is comparable with other bonding methods. Hermetic tightness was proved with a helium leak detector and leak rates around 3(DOT)10-8 mbar(DOT)l(DOT)s-1 were found. Finally it will be discussed in which cases LB could be a supplement to anodic bonding, which is the state of the art bonding method for silicon-glass couples. Conclusively it can be said that locally selective LB is a novel method for MEMS packaging, with high bonding velocity, low thermal load for the joining partners and high bonding quality concerning strength and hermetic tightness.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.