Comparison of IDDQ testing and very-low voltage testing

I_DDQ testing is a well-known test method to filter dies with reliability risks. However, the test method is endangered by the increase in off-state current in advanced process technologies. An alternative for detecting resistive shorts is very-low voltage (VLV) testing. This test method tests dies at a strongly reduced supply voltage. The smaller the supply voltage, the higher the sensitivity for defects. This paper investigates if VLV testing can replace I_DDQ testing. To obtain a significant increase in defect coverage, one must use a supply voltage below 2×V_T. In the experiments, a supply voltage of 1.5×V_T was used with relaxed timing. This makes the method more than twice as sensitive compared to 2×V_T and allows one to detect shorts with resistance of five times the detection limit at the nominal supply voltage. However, even with these settings we were only capable of detecting a small fraction of the I_DDQ anomalies. Therefore VLV is not suited to replace I_DDQ testing.