Surface Metallization Influence on Equivalence of Laser Simulation of Dose-Rate Effects

Pulsed laser simulation is a powerful method in studying dose-rate effects of semiconductor devices. However, blocking of the incident laser from the device layer by the surface metallization layers has always been an influencing factor affecting their equivalent relationship because the penetrations of laser light and gamma rays are different. For the quantitative study of the equivalent relationship, the conversion factor (CF) is defined as a comparison between the laser intensity and dose rate at the same equivalent basis [carrier generation rate (CGR), peak photocurrent]. The conventional models usually use CGR, and they suggest that the CF varies linearly with metallization coverage, but few of them considered the metallization distribution. In this paper, we propose a numerical simulation method for CF using the peak of transient response as the equivalent basis, and unambiguously taking into account the effects of metallization distribution. Backed up with the finite-element analysis, we find that the distribution of the metallization can lead to a significant change in the linear relation between CF and metallization coverage. Experimental data on discrete devices conform to these simulation results. In addition, the experimental verification in the classical diode structure further indicates the validity and the accuracy of the approach.