Advances in thermal laser separation: Process monitoring in a kerf-free laser-based cutting technology to ensure high yield

Thermal Laser Separation (TLS) is an ablation free and therefore kerf free laser based cutting technology. This novel dicing technology is utilized to separate microelectronic devices on semiconductor wafers. In order to broaden the use of TLS method towards smaller chips and new materials on the one side and towards an advanced process monitoring on the other side, a novel contact-free measuring method for monitoring the TLS process has been developed. This new method is based on heating the semiconductor wafer with a near-infrared (NIR) laser and analyzing the subsequent temperature gradients induced by heat diffusion with contact-less temperature measurement. Thus, the TLS-crack can be detected due to its isolating effect to heat flux. The feasibility of the method is presented and the influence of parameters like sample size, distance to the TLS-crack and the laser setup in the measurements is reported.