IGBT RBSOA失效分析及改善方案

一种绝缘栅双极晶体管模块在做反向偏置安全工作区测试时,器件在较低的关断电流下就发生了损坏。失效分析显示失效区的位置靠近栅极条区。模拟显示失效区处元胞结构并非对称,而正常元胞结构是对称的,由此造成了该处元胞的闩锁电流密度比对称结构元胞的闩锁电流密度低。因此,元胞结构的一致性不好是RBSOA关断电流低的原因。通过修改版图设计,使工作区元胞结构一致。对改版后的芯片封装后进行RBSOA测试,结果显示安全关断电流有明显提高。

IGBT RBSOA Failure Analysis and Improvement

An Insulated Gate Bipolar Transistor （ IGBT ） module failed at a low turn off current during Reverse Biased Safe Operating Area （ RBSOA ） test. Failure analysis showed the failure area was close to the gate finger. Simulation results showed the cell structures at failure area were asymmetrical, however normal cell structures were symmetrical. The simulation also showed the latch-up current density of asymmetrical cells was lower than that of symmetrical cells. So, the bad uniformity of cell structures is the cause of the low RBSOA turn off current. By modifying layout design, all cell structures become uniform. RBSOA test results for the packaged chips with modified layout showed the turn-off current was improved obviously.