A novel approach to study patterned thin film local stress for microelectronics application

A novel testing methodology to study the full-field stress distribution in patterned microstructures has been developed for microelectronics applications. The testing structure consists of a Si diaphragm, whose deformation caused by the stress due to an overlying patterned thin film is captured by a Twyman-Green interferometer. The finite element model used to analyze this structure assumes a uniform in-plane biaxial initial stress in the patterned thin film before stress relaxation occurs, and gives the Si diaphragm deflection profile which matches the measured values. Hence the full-field stress in the patterned thin film and Si diaphragm can be given. The stress distribution in an electroless Ni pad on a Si diaphragm is used as an example