Microstructural modification of metallic thin films via high-frequency alternating current treatment at room temperature

Abstract

This study comprehensively investigates the effects of high-frequency alternating current (AC) on the adhesion strength between metallic thin films and substrates as well as on the resistivity of metallic films. Under AC treatment at the optimal frequencies of 26, 37, and 38 MHz, the adhesion strengths of the Al, Cu, and Pt films to a substrate increase by 44.9%, 42.0%, and 101.8%, respectively, whereas their resistivities decrease by 22.6%, 38.4%, and 8.1%, respectively, at optimal frequencies of 30, 40, and 20 MHz. Microstructural characterization results show that the metallic films exhibit nanometer-scale crystal grains with numerous defects (i.e., disordered atoms). However, the application of high-frequency AC significantly reduces these defects and improves the crystallinity, thereby promoting adhesion enhancement and resistivity reduction. The different optimal frequencies of the Al, Cu, and Pt films are attributable to the different atomic weights and resistivities of the materials. The high-frequency AC method proposed herein is a highly efficient and energy-conserving technique with a maximum temperature increase of less than 7.1 °C. This study provides a promising alternative to conventional heat treatment methods for enhancing the reliability and durability of wiring in semiconductor components.