Fabrication of via-holes in multi-chip module using third harmonic generation of Nd: YAG laser

Abstract

In the fabrication of high-speed digital integrated circuits using polyimide films as insulators, especially multi-chip modules (MCMs), via-holes of 20 μm depth have to be realized for the characteristic impedance along the signal line. When a logical scale in a near-feature engineering work station (EWS) is considered, the number of via-holes does not exceed 600 in one circuit. In this work, the authors propose the possibility of applying a third harmonic generation (THG) of a Q-switched Nd:YAG laser to drill high-aspect-ratio via-holes in such a thick polyimide film. The drilled holes as well as the excimer laser exhibit excellent configurations. The THG laser system is applicable to the fabrication process of the MCM.