Abstract
The flash memory devices with some advantages like low power consumption, higher device density and portable devices are more needed recently. However, as the devices scale down to few nanometers, there is limited space for planar devices to microminiaturize, which makes the process flow more difficult. Therefore, improvement of the device characteristic and how to make the process easier at the same time becomes two of the most important issues today. Some solutions have been reported like the implement of SiGe, nanowire channel structure and junctionless channel flash memory devices etc. In this thesis, we implemented the polycrystalline Ge on the nanowire channel flash memory devices, and the device electrical characteristics are investigated. In the first experiment, the poly-Ge planar flash memory device is compare with Si planar capacitor one. The poly-Si planar devices show higher P/E speeds, better endurance and similar retention compared to poly-Ge one. In the second experiment, the poly-Ge and poly-Si nanowire channel are implemented on the junctionless flash memory devices. Effects of poly-Ge channel on junctionless nanowire flash devices are studied. The results show that the junctionless nanowire devices perform well on the programming speed and reliability characteristics. Moreover, the erasing speeds of poly-Ge junctionless nanowire flash devices are faster compare to those of the poly-Ge planar capacitor ones. In the third experiment, effects of channel concentration on the characteristics of junctionless poly-Ge nanowire channel flash memory devices are investigated. It is that the heavily doped junctionless poly-Ge nanowire devices show better P/E speeds and reliable characteristics, indicating that the channel concentration is still on important parameter in the Ge nanowire channel flash memory devices. From above, the characteristics of poly-Ge flash memory device including P/E speed, endurance and retention are not good enough compare to those of the poly-Si ones. However, the electrical performance of poly-Ge flash device improved by junctionless nanowire structure shows great potential for nonvolatile memory industry in the future. It is believed that the results of poly-Ge flash memory device above are helpful to the future development memory technology.