Substrate-Bias Assisted Hot Electron Injection Method for High-Speed, Low-Voltage, and Multi-Bit Flash Memories

Abstract

The authors present a highly efficient program method for high-speed, low-voltage, and multi-bit/cell operation in the conventional silicon/oxide/nitride/oxide/silicon structure. This method uses a forward bias for collecting the electrons into the substrate whilst both substrate and drain biases are used for injecting the electrons into the nitride layer. With an aid of the substrate bias for electron injection, we obtained a program time as short as 600 ns and an ultralow-voltage operation with a drain voltage of 2 V and a substrate voltage of -3 V. In addition, a localized charge-injection near the junction edge was confirmed with a threshold voltage difference of 1 V between the forward and reverse read.

Multi-level 2-bit/cell operation utilizing Hf-based metal/oxide/nitride/oxide/silicon nonvolatile memory with HfO2 and HfON tunneling layer

“…Generally, a CT-type NVM is able to realize the multi-level cell operation utilizing localizedcharge-trapping phenomena. [24][25][26][27][28][29][30][31][32][33][34] Typically, a channel hot electron (CHE) injection into the nitride near the electrode is utilized to localized-charge trapping phenomena. 31,32) Meanwhile, it needs a high drain voltage which causes a high leakage current and high power consumption.…”

“…31,32) Meanwhile, it needs a high drain voltage which causes a high leakage current and high power consumption. 33) To solve this problem, a 2-bit/cell operation utilizing a modulated tunneling distribution by V DS with a TaN/Al 2 O 3 /Si 3 N 4 /SiO 2 /Si structure was reported. 31,32) Compared to conventional CHE, this operation does not require charge acceleration.…”