Wafer-Scale Circuit Probing Test for Flexible Ultra-Thin Chips Enabled by Temporary Support

Abstract

Ultra-thin and flexible chips are essential for high-performance flexible electronic devices, whose large-scale fabrication relies on reliable ultra-thin wafers. Circuit probing test of ultra-thin wafers plays a crucial role in screening functional chips prior to packaging; however, wafer warpage and fragility pose significant challenges to such testing. In this study, the stress distribution in ultra-thin wafers temporarily supported during circuit probing is analyzed based on layered elasticity theory. A wafer failure phase diagram is subsequently established, from which a selection strategy for temporary support materials is proposed to enhance the mechanical resistance of ultra-thin wafers against probing forces. The analysis reveals that higher Young’s modulus and thinner temporary supports enable safer probing. Using the optimized support configuration, successful circuit probing tests are performed on 8-inch, 10- $\upmu $ m-thick self-made dummy wafers and pyroelectric infrared control wafers. No visible cracks are observed on the ultra-thin wafers after the test under a scanning electron microscope. The proposed strategy is expected to pave the way for the large-scale application of ultra-thin and flexible chips.