Investigation of GMR sensor microstructural changes induced by HBM ESD using advanced microscopy approach

In theory, the microstructure of any material dictates its macroscopic properties. This study explores the microstructure of the GMR reader characterized during gradual ESD stressing and with the aid of the advanced analytical tools of AFM/MFM after enhanced imaging of GMR sensors by surface ion milling. It is known that ESD events can occur and manifest themselves exclusively either physically (melting of sensor element) or magnetically (sudden drop in electrical parameters when plotted against stress voltage) in GMR heads. A simulation study was directed using commercial HBM and dynamic electrical test machines to produce different types of ESD failure events. Preliminary results showed that ESD stressed and ESD-free GMR heads can be characterized and differentiated from one another using the simple surface technique of MFM. By using the combined analytical techniques which are particular to AFM and MFM coupled with methodical and systematic failure analysis, we are able to observe in-situ the previously unknown ESD phenomena unique to GMR heads.