Multi-physics Modelling and Experimental Investigation – An Original Approach for Laser-Dicing/Grooving Process Optimization

摘要

The highly complex technology requirements of today's integrated circuits (ICs), lead to the increasingly use of several materials types such as metal structures, brittle dielectrics, porous low-k and ultra-low-k materials which are used in both front-end-of-line (FEOL) and back-end-of-line (BEOL) process for wafer manufacturing. In order to singulate chips from wafers, a critical laser-grooving process, prior to blade dicing, is used to remove these layers of materials out of the dicing street. The combination of laser-grooving and blade dicing allows to reduce the potential risk of induced mechanical defects such micro-cracks, chipping, on the wafer top surface where circuitry is located. Nevertheless, challenges related to unexpected drawbacks on process such as efficiency, quality and reliability still remain. To maximize control of this critical process and reduce its undesirable effects, numerical models of nano-second laser pulsed and multi-stack material interaction have been developed. The modeling strategy using finite elements formalism is based on the convergence of two approaches, numerical and experimental Validation. To evaluate this interaction, several laser grooved samples were performed using IBM 14 nm technology node wafer and were correlated with finite elements modeling. Three different aspects were studied; phase change, thermo-mechanical and optical sensitive parameters. The numerical model makes it possible to simulate groove profile (depth, width, etc.) of a single pulse or multi-pulses on BEOL wafer material. Moreover, the heat-affected zone (HAZ) has been estimated as a function of laser operating parameters (power, frequency, spot size, defocus, speed, etc.). After modeling validation and calibration, a reasonable agreement between experiment and modeling results has been observed in terms of groove depth, width and HAZ