A MM (Machine Model) failure case study: Parasitic NPN turn-on induced by reverse recovery current

Abstract

MM (Machine Model) is an ESD test method used to test for robustness of the device against the ESD event which is induced by the running equipment in fabrication or testing procedure [1]. Due to zero resistance in the equivalent circuit, MM is difficult to simulate. In most cases, MM capability can be calculated from HBM (Human Body Model) result (MM ∼10∼20∗HBM) [2]. But in this study HBM can reach 3.5kV, but MM only achieves 50V, failing at 100V zap. A detailed study was carried out to find the root cause. It was found that parasitic NPN was turned on which is induced by reverse recovery current. One more step, the RRSOA (Reversed Recovery Safety Operation Area) [3] was tested and compared. One simple and one complicated solution were verified. MM capability can be greatly improved and a good correlation was achieved between HBM and MM.