Built-in current sensor for ΔIDDQ testing of deep submicron digital CMOS ICs

This paper presents the implementation of a built-in current sensor that includes two recently reported new techniques for I_DDQ testing to take into account the increased background current of defect-free circuits and its increased variance due to process variations. These techniques are the correlation between speed and I_DDQ, and the ΔI_DDQ testing technique. The monitor has been manufactured in a 0.18 μm CMOS technology and it is based on the principle of disconnecting the device under test from the power supply during the testing phase. The monitor has a resolution of 1 μA for a background current less than 100 μA or 1% of background currents over 100 μA to a total of 1 mA fullscale. The sensor operates at a maximum clock speed of 250 MHz. The monitor has been verified in a test chip consisting of one "DSP like" circuit of about 250,000 transistors. Experimental results prove the usefulness of our approach as a quick and effective means for detecting defects.