Comparison of I/sub DDQ/ testing and very-low voltage testing

Abstract

I/sub 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/sub DDQ/ testing. To obtain a significant increase in defect coverage, one must use a supply voltage below 2/spl times/V/sub T/. In the experiments, a supply voltage of 1.5/spl times/V/sub T/ was used with relaxed timing. This makes the method more than twice as sensitive compared to 2/spl times/V/sub 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/sub DDQ/ anomalies. Therefore VLV is not suited to replace I/sub DDQ/ testing.