CMOS Transistors under Uniaxial Stress on Ultra-Thin Chips for Applications in Bendable Image Sensors

In this work characteristics of CMOS transistors on ultra-thin silicon chips embedded into a polyimide foil are discussed. The thinning and the encapsulation processes are presented and the piezoresistive coefficients of both n- and pMOS transistors are experimentally determined. Moreover, the dependence of the threshold voltage and subthreshold slope on uniaxial tensile and compressive stress is examined. Keywords - flexible ultra-thin silicon chips; uniaxial stress; bending machine;piezoresistance; chip-in-foil