Simulation and Experiment of Wide Bandgap Material Based Nonvolatile Memory
- Author(s): LI, ZONGLIN
- Advisor(s): Liu, Jianlin
- et al.
Flash memory, primarily NAND Flash, is widely used in our daily life like mobile handsets, tablets, and laptabs to enterprise volume data storage. The huge market demand increases the market revenue from 10.6 billion dollars in 2005 to 25.1 billion dollars in 2011 and it is expected to continue the growth. The increasing demand of data transmission and data storage forms tremendous gap between the flash capacity and application demand. In order to catch the market, flash memory device has been scaled down over 18 years. Highly reliable, fast reading, programming and erasing speed, and lower cost are always pursued. In 1998, the feature size of floating gate memory is 0.7um and right now it has been shrunk to 20nm. There are fundamental issues that impede the further scaling down. Physical limitations include photolithography and small size structure formation; electrical limitation includes interference, capacitive coupling ratio, less number of electrons in the cell, and dielectric leakage.
To break the limitation from the conventional floating gate memory, a novel wide bandgap material based flash memory was proposed. Device performance including electrostatic analysis, programming and retention was studied by small signal model. GaN based nonvolatile memory was fabricated and device performance was measured. Chapter 1 introduces the conventional floating gate memory and new technology development. The advantages and disadvantages of different technology have been summarized. Motivation of the wide bandgap material based memory has also been addressed. Chapter 2 describes the wide bandgap material based memory, the advantages of wide bandgap materials and their application in this novel memory device, and the potential how this novel memory device can fit with the mainstream CMOS VLSI technology. Chapter 3 is the device simulation part. It gives a detailed explanation of device function. Memory performance like programming and retention has been studied. Chapter 4 is the experiment study of GaN based flash memory. Device fabrication process flow has been introduced and characterization result has been analyzed. Chapter 5 is the summary.