Geometry optimization of TMR current sensors for on-chip IC testing

In this paper, we demonstrate that tunnel magnetoresistive (TMR) elements can be used as sensitive on-chip current sensors in the microampere to milliampere range for current-based IC testing such as power-pin testing and quiescent I/sub dd/ current (IDDQ) testing. The sensor can be integrated in CMOS ICs containing magnetic random access memory. TMR current sensors with various lateral dimensions (from submicrometer to micrometer) arranged in a Wheatstone bridge have been realized and analyzed. A typical sensitivity of 2.5(mV/V)/mA and a current resolution of 5.5/spl mu/A have been observed. The influence of the sensor geometry on sensor sensitivity, hysteresis, and temperature rise due to Joule heating has been investigated.