Drop-In Test Structure to Evaluate Residual Stress in Conformally Grown Films

We propose and demonstrate a drop-in test structure to visualize and measure the residual stress in the conformally deposited film. For reliable device process of microsystems (such as 3-D MEMS), the residual stress must be controlled through quantitative evaluation at each deposition step. A small drop-in test structure placed near the main sample is suitable for monitoring film characteristics. We developed a free-standing rotating beam stress sensor as the drop-in test structure to visualize and measure the residual stress in conformally deposited films with no additional processes. The dimensions of the developed drop-in test structure chips were 5 mm ×10 mm. For a demonstration, supercritical fluid deposition (SCFD) was performed over the test structure chips under a couple of conditions. The residual stresses in SCFD films were successfully extracted by equation-based analysis.