Highly Reliable 28nm Embedded Flash Process Development for High-Density and High-Speed Automotive Grade-1 Application

Based on robustness of split-gate embedded Flash (eFlash) bit-cell, 28-nm eFlash process with Flash IP (20Mb) and SRAM IP (32Mb) is developed for automotive Grade 1 (G1) application with temperature range of (−40∼150°C) for the first time. In case of single flash cell evaluation, sufficient sensing margin and tight current distribution, decent endurance and retention characteristics have been demonstrated. A new type of Flash IP scheme is introduced to compensate the degradation at high temperature, called SAPVL (Sense amp Proportional to absolute temperature and Vdd variable Load scheme) enabling reduction of load current dependency on temperature. Robust reliability (100K cycle endurance, 150oC/RT retention up to 15 years) with 20Mb eFlash IP is validated even at error-correction-code (ECC) off mode. Moreover, lower failure rate and significant improvement of high temperature reliability are achieved with rebalancing cell FET device immunity of SRAM IP (32Mb). All the requirement from AC-Q100 for automotive G1 qualification are accomplished at 28nm split-gate eFlash process.