Impact of Program/Erase Cycling Interval on the Transconductance Distribution of NAND Flash Memory Devices

Yung-Yueh Chiu,Toshiaki Takeshita,Masaru Yano,Hsin-Chiao Li,Riichiro Shirota,Kai-Chieh Chang,Hung-Te-En Tsai,Po-Jui Lin,Hsin-Jyun Lin

doi:10.1109/ted.2020.3024484

Abstract

This study comprehensively investigates the impact of the time interval (t wait ) 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 t wait yield a better oxide quality than those with a longer t wait . The oxide charge (Q T ) evolution by distributed P/E cycles can be well described by an analytical equation through the extension of our previous statistical transconductance reduction (G m,max ) method. This equation is characterized by a power of the number of P/E cycles multiplied by an exponential decay term of t wait . The former term is related to the Q T generation, whereas the latter is related to the Q T emission during t wait between cycles. This model allows to evaluate the activation energy for both Q T generation (E A,G ) and recovery (E A,R ). E A,G is revealed to be a function of the logarithmic scale of t wait , decreasing from 100 to 85 meV for t wait varying from 0.1 to 4 s. Moreover, E A,R is approximately 0.4 eV, which is consistent with the value of electron thermal emission from traps in SiO 2 .

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