Investigation of data retention window closure on logic embedded non-volatile memory

摘要

Two mechanisms of data retention (DR) are investigated on logic embedded non-volatile memory (eNVM) in Multiple-Time-Programming (MTP) application. Unlike the typically observed DR degradation after endurance test in flash memory, DR window closure of logic eNVM can be recovered at higher data retention bake temperature and longer bake time due to thermally activated electron de-trapping from interface of tunnel oxide to Si substrate. In addition, a new DR degradation mechanism called Reverse Code Effect (RCE) is shown to exhibit faster DR degradation than the original DR behaviors. RCE induced DR degradation can be attributed to the combined effect of capacitive coupling [1] in between floating gate (FG) and contact-etch-stop-layer (CESL) dipole charges and charge loss due to charge recombination in FG. We also demonstrate that RCE can be effectively suppressed by adopting low-level Si-H compositions of CESL nitride film with less dipole charges to reduce the charge loss in the FG.