Evaluation of directly bonded silicon wafer interface by the magic mirror method

Abstract

The magic mirror method was used to evaluate directly bonded Si wafers. An unbonded region at the silicon-to-silicon interface was detected as a bubble in an optical image by this method. The bubbles at the interface generate a locally convex distortion at the surface and this convex surface is visualized as a dark region using the magic mirror method. A comparison of the resulting effect was made with transmission X-ray topography and ultrasonic flaw detection, and good correspondence was found among the three methods, especially between the magic mirror method and transmission X-ray topography. We applied this method to the observation of changes of interface bubbles before and after thermal annealing. © 1990.