SRAM retention testing: zero incremental time integration with March algorithms

Testing data retention faults (DRFs), particularly in integrated systems on chip comprised of very large number of various sizes and types of embedded SRAMs is challenging and typically time-consuming due to the required pause time that needs to be introduced in the test session. This paper proposes a novel technique, referred to as pre-discharge write test mode (PDWTM), that effectively integrates the testing of DRF within "regular" March algorithms such that the rate (speed) of the latter remains unaltered. That is, the PDWTM enables DRF testing without incurring the additional cycles or pauses in the March test execution thereby enabling additional coverage at no expense in terms of overall test time. We show that DRFs can be easily detected by pre-discharging bit lines before a write operation. Here, the PDWTM is evaluated using both high-speed and low power memory cells, representing two extreme cases based on the typical memory design methodologies.