Abstract
3D flash technology is becoming more important, because the scaling down planar device faces challenge. In addition to high storage density, flash device with good electrical characteristic and reliability are required. In recent years, buried channel such as SiGe and Ge deposition layer applications are applied used to improve operation characteristics of flash device. Therefore, in this thesis, operation characteristics of device are improved by Ge buried channel, which can provide more injection carriers and lower energy barrier height. Operation characteristic of devices with different build-in electric field near channel and tunneling oxide interface formed by P/B doping junction are analyzed and discussed. Finally, erase speeds of flash device are enhanced by inversion mode device are compared to junctionless. In the first part, SiGe and Ge deposition buried channels are applied to poly silicon junctionless flash memory device. From experiment result, program and erase speeds of devices with SiGe and Ge buried channels are faster than those without buried channel device. This improvement can be attributed to Ge with more injection carriers by a narrower bandgap, high electric field in tunneling layer, and lower energy barrier. In addition, endurance performance of SiGe, Ge buried channel device are good because of fast program speed, namely shorter program time which reduces the damage in tunneling oxide layer. In the second part, SiGe/Ge buried channels are doped with phosphorus and boron to forms PN junction and create a built-in electric field. Although in effects of built-in electric field of PN junction formed with different doping are expected, the thickness of GeO2 in the dominant faster than our observation. From experiment at result, device with a thicker GeO2 shows faster program/erase speed and good endurance performance. Effects of the built-in electric field are minor, because operation characteristic are influence by the tunneling path. In the third part, IM flash memory device with Ge buried channel and P/B doping is studied, the program/erase speeds of devices with more GeO2 are faster and junctionless flash memory device has slower erase speed. From experiment at result, the IM device shows faster erase speed and good endurance performance.