A TCAD approach to robust ESD design in oxide-confined VCSELs

Abstract

Electrostatic Discharge (ESD) events can cause irreversible damage during production, packaging and application of Vertical-Cavity Surface Emitting Lasers (VCSELs). Experimental investigation of those damage patterns inside a real device is a complex and expensive task. Simulation tools can provide insight into the physics during an actual discharge event. This paper aims to analyze ESD events in VCSELs with a microscopic simulation. With the help of a state-of-the art Technology Computer Aided Design (TCAD) virtual ESD tests are performed on oxide-confined VCSELs. The 2-D simulation model takes into account high-field effects and self-heating in a hydrodynamic framework that allows time-dependent spatially resolved monitoring of critical quantities (such as electric field across the oxide, temperature profile, current densities) during the ESD events. Human Body Model (HBM), Machine Model (MM) and Charged Device Model (CDM) show typical local heating and current crowding effects which may lead to irreversible damaging of the device. For slow ESD events the temperature peak is found near the center of the device. Faster pulses show maximum temperature at the interface between oxide and aperture. Physics-based explanations in terms of local electric field, heat generation and heat transport are given. Oxide aperture, thickness and its position relative to the intrinsic region strongly influence self-heating, electric fields, current density profiles and the dielectric breakdown conditions. The impact of those factors on ESD robustness are analyzed and guidelines for robust ESD design in VCSELs are presented.