New spider-webs test structure and characterization methodology for flash memory tunnel oxide quality

Tunnel oxide quality is a key parameter during flash memory development. A high quality tunnel oxide will result in good cell endurance characteristics. However, the conventional tunnel oxide characterization is usually based on a large area capacitor test structure with a high sheet resistance floating poly-silicon gate, and, as a result, an over-estimated oxide quality is obtained. In this study, we design a new test structure and a new characterization methodology for tunnel oxide measurement. It is found that more accurate and reliable tunnel oxide lifetime prediction can be obtained with this new approach. Besides, this measurement is correlated to flash memory endurance performance.