Nanocrystalline Ge Flash Memories: Electrical Characterization and Trap Engineering
Name
AMMNS011.pdf
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980.29 KB
Format
Adobe PDF
Checksum (MD5)
2b915a01db1f0d96fa913dd9edc1baa7
Author(s)
Kan, Eric Win Hong
Koh, B.H.
Choi, Wee Kiong
Chim, Wai Kin
Antoniadis, Dimitri A.
Fitzgerald, Eugene A.
Date Issued
January 2005
Series/Report no.
Advanced Materials for Micro- and Nano-Systems (AMMNS);
Abstract
Conventional floating gate non-volatile memories (NVMs) present critical issues for device scalability beyond the sub-90 nm node, such as gate length and tunnel oxide thickness reduction. Nanocrystalline germanium (nc-Ge) quantum dot flash memories are fully CMOS compatible technology based on discrete isolated charge storage nodules which have the potential of pushing further the scalability of conventional NVMs. Quantum dot memories offer lower operating voltages as compared to conventional floating-gate (FG) Flash memories due to thinner tunnel dielectrics which allow higher tunneling probabilities. The isolated charge nodules suppress charge loss through lateral paths, thereby achieving a superior charge retention time.
Despite the considerable amount of efforts devoted to the study of nanocrystal Flash memories, the charge storage mechanism remains obscure. Interfacial defects of the nanocrystals seem to play a role in charge storage in recent studies, although storage in the nanocrystal conduction band by quantum confinement has been reported earlier.
In this work, a single transistor memory structure with threshold voltage shift, Vth, exceeding ~1.5 V corresponding to interface charge trapping in nc-Ge, operating at 0.96 MV/cm, is presented. The trapping effect is eliminated when nc-Ge is synthesized in forming gas thus excluding the possibility of quantum confinement and Coulomb blockade effects. Through discharging kinetics, the model of deep level trap charge storage is confirmed. The trap energy level is dependent on the matrix which confines the nc-Ge.
Subjects
Flash memory
nanocrystalline germanium
charge trapping
quantum dot
Vth
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