Impact of Program/Erase Cycling Interval on the Transconductance Distribution of NAND Flash Memory Devices
Yung-Yueh Chiu, Kai-Chieh Chang, Hsin-Jyun Vincent Lin, Hung-Te-En Tsai, Po-Jui Jerry Lin, Hsin-Chiao Li, Toshiaki Takeshita, Masaru Yano, R. Shirota · IEEE Transactions on Electron Devices · 2020
This study comprehensively investigates the impact of the time interval (twait) between program/erase (P/E) cycles on the oxide quality of NAND Flash memory devices. It is observed that, at room temperature, P/E cycles with a shorter twaityield a better oxide quality than those with a longer twait. The oxide charge (QT) evolution by distributed P/E cycles can be well described by an analytical equation through the extension of our previous statistical transconductance reduction (Gm,max) method. This equation is characterized by a power of the number of P/E cycles multiplied by an exponential decay term of twait. The former term is related to the QTgeneration, whereas the latter is related to the QTemission during twaitbetween cycles. This model allows to evaluate the activation energy for both QTgeneration (EA,G) and recovery (EA,R). EA,Gis revealed to be a function of the logarithmic scale of twait, decreasing from 100 to 85 meV for twaitvarying from 0.1 to 4 s. Moreover, EA,Ris approximately 0.4 eV, which is consistent with the value of electron thermal emission from traps in SiO2.