MEMS麦克风噪声失效分析

The analysis method of MEMS microphone noise failure

MEMS麦克风噪声主要包括MEMS芯片的机械振动噪声和ASIC芯片的电噪声,如何在非破坏性测试的情况下快速判断噪声失效的原因一直困扰着失效分析工程者。本文创造性提出在真空密闭腔体进行非破坏性电测试,可以快速确定噪声失效的主要来源。通过MEMS麦克风噪声失效具体案例分析验证此方法的可行性,快速确定噪声来源于ASIC芯片的电噪声。针对ASIC芯片级电性能及物理失效分析,成功发现噪声产生的原因是由于ASIC芯片偏置电压区域ESD保护电路中的SCR上Poly与Diffusion层位置严重偏移导致该区域存在漏电流通道。适当增加两者的物理间距,彻底解决这类问题的再次发生。

MEMS microphone＇s noise mainly includes the mechanical vibration noise of the MEMS chip and the electrical noise of the ASIC chip. How to quickly determine the cause of the kind of noise failure by non-destructive test method is becoming a hot topic in the field of Failure analysis of MEMS microphone. In this paper,it is proposed that the non-destructive electrical test in the vacuum chamber can be applied to judge the main source of noise failure. Then the feasibility of this method is verified by the case study of the MEMS microphone noise failure and it is confirmed the high noise was generated from ASIC chip. With the help of Chip level electrical and physical failure analysis method for further analysis,the root cause of the noise failure is due to the Poly and Diffusion layer offset seriously to cause the leakage path existing in SCR of the ESD protection circuit of Vbias pad. To solve this kind of problem successfully,it is recommend to increase the physical distance between Poly and diffusion layer to some extent.