Laser grooving of multi stack material modeling: implementation of a high accuracy tool for laser-grooving and dicing application

Laser grooving is a powerful method widely used in the semiconductor industry for chip singulation because of the advantages it provides, such as high grooves profile quality, lower mechanical stresses on devices. Nevertheless, challenges related to unexpected drawbacks on process such as efficiency, quality and reliability still remain. In order to maximize control of this critical process and reduce its undesirable effects, numerical models of nano-second laser pulsed and multistack material interaction have been developed. The modeling strategy using finite elements formalism is based on the convergence of two approaches, numerical and experimental characterizations. To evaluate this interaction, several laser grooved of multilayer samples Cu/SiO2, Al/SiO2, and complete state of the art back-end-of-line (BEOL) material stack were correlated with finite elements modeling. Three different aspects were studied; phase change, thermo-mechanical sensitive parameters as well as optical sensitive parameters. The mathematical model makes it possible to highlight a groove profile (depth, width, etc.) of a single pulse or multi-pulses on BEOL wafer material. Moreover, the heat-affected zone (HAZ) has been predicted as a function of laser operating parameters (power, frequency, spot size, defocus, speed, etc.). After modeling validation and calibration, a satisfying correlation between experiment and modeling results has been observed in terms of groove depth, width and HAZ.