Parametric and theoretical study of hole quality in conventional micro-machining and rotary ultrasonic micro-machining of silicon

Abstract

Microhole machining for silicon is an essential process in the manufacturing of several semiconductor devices, such as solar panels, pressure and flow sensors, the stacking of micro-electromechanical systems, and complementary metal-oxide semiconductors. Due to the device miniaturization, there is a growing need for micro-machining on silicon wafers. Compared with the thermal machining processes for micro-drilling (such as laser machining), mechanical micro-machining processes can avoid the generation of heat-affected-zone, recast layers, and silicon oxidation. Conventional mechanical micro-machining (CμM) of brittle materials generates a higher cutting force and severe quality issues (such as cracking and edge chipping). To address the quality issues, drilling with rotary ultrasonic micro-machining (RUμM) has been proposed and applied. There are no reported investigations on comparisons of micro-machining quality in CμM and RUμM. In this study, the effects of ultrasonic vibration, tool diameter, and feed rate on cutting force and edge chipping were investigated experimentally. To explain machined hole quality (edge chipping) and cutting force, effects on indentation depth were also investigated. We developed the mechanistic models to describe the relationships between input variables and single abrasive indentation depth for both CμM and RUμM processes. Finally, the relationships among ultrasonic indentation, cutting force, and hole quality were established.