GMR heads as ESD detectors - a direct assessment of subtle ESD

In this work, we demonstrate the importance and the effectiveness of using GMR heads as ESD detectors in new tester qualifications. Traditionally, to resolve ESD concerns of a new tester, a high bandwidth digital oscilloscope and a CT1 probe are often used for ESD waveform detection. An assessment is then provided based on the observed waveform. The methodology is largely consistent with investigations in a majority of papers published recently - a giant magnetoresistive (GMR) sensor is typically seen with catastrophic failure from SEM measurements if a sizable waveform is detected. As the scale of the GMR sensors reduces with each new product, it becomes essential to locate subtle ESD transient from the tester. This kind of transient will not cause any observable damage in SEM measurements and introduces nearly no resistance change. The transient, however, degrades magnetic performance of the sensor. The focus of the work is on transients that are more difficult to measure using an oscilloscope, and their impacts to the sensors are difficult to assess without direct measurements on the sensors.