Ultraprecision cutting of photoresist/gold composite microstructures

Ultraprecision cutting tests were performed on a photoresist/gold bump composite and cutting characteristics were investigated by examining the surface topography, chip formation, cutting force, and temperature. The cutting mechanisms depended significantly on the cutting speed, undeformed chip thickness, and tool geometry. At a high cutting speed, photoresist softening occurred, leading to chip adhesion on tool faces and burr formation on gold bumps. Two kinds of microfractures were identified in the photoresist cutting, and critical cutting conditions for each were obtained. The findings in this study provide process criteria for ultraprecise planarization of LSI substrates for three-dimensional chip implementing technology.