Study On Characteristics Of SOI Device And Ferroelectric Memory

With the rapid development of microelectronic, the feature size of semiconductor devices becomes smaller, which causes many parasitical effects such as short channel effects, latch-up effects and parasitical capacitance effects. To meet the development of Integrated Circuit (IC), kinds of improved semiconductor devices have been proposed. Among these devices, there exist two type semiconductor devices. One is the new material device such as the compound semiconductor device, phase change device and ferroelectric device. The other is the new structure devices such as silicon-on-insulator (SOI) device. In this dissertation, the SOI device and ferroelectric device are studied. SOI devices have broad application in the fields of military and aerospace, and are named as"the 21st century silicon technology"due to high speed, low power dissipation, anti-radiation and excellent high temperature properties. However, there exist many inner physic problems which constrain the development of SOI devices. For these points, the high temperature characteristic, kink effects, floating body effects and transient effects are studied in detail in this paper using the theory model and computer simulation. Ferroelectric memories have been regarded as one of the potential memories due to its non-volatility, low power consumption, high endurance, high speed writing, high density, anti-radiation and compatible with IC process. Ferroelectric memories (FeRAM) have widespread application in computer, aerospace and military industry. As one type of ferroelectric memories, ferroelectric gate field-effect transistors (FETs) have attracted considerable interest for several decades due to its potentially applications to nonvolative memory devices, because FET has a nondestructive read-out operation, a simple FET structure and obeys a scaling-down rule. Thus, ferroelectric gate field-effect transistor memory is an ideal memory suitable for ultimately memory. In our paper, theory models have been proposed to study the metal-ferroelectric-insulator-semiconductor (MFIS) device and also V5+-doped Bi3.7Dy0.3Ti3O12 (BDTV) and V5+-doped Bi3.4Yb0.6Ti3O12 (BYTV) thin films have been prepared. The experiments make clear that the ferroelectric characteristic can be enhanced using V5+ ion substituted, such as increasing the remanent polarization, reducing the leakage current and enhancing the anti-fatigue characteristic. The experiment results show that the BDTV and BYTV thin films are the ideal candidates of ferroelectric thin films. Finally, we propose a new structure device MFI-SOI by combination of SOI device and ferroelectric memories and hope that the MFI-SOI structure can possess the advantages of the two devices and offer some useful information.In chapter 1, the development and potential application of semiconductor device are introduced. The advantage, shortcoming and application of SOI device are given as well. And also the fabrication of ferroelectric memory and the new structures of this memory are included. In chapter 2, the future development of semiconductor device software, its physic mechanism and the mathematic theory are presented from the computer simulation view.In chapter 3, the temperature characteristic, threshold voltage and kink effects in SOI devices are studied. The high temperature properties of SOI device with different parameters are simulated by SILVACO software. The temperature-dependent surface potential and threshold voltage model are proposed and the short channel effects are obtained under different temperatures. The temperature-dependent current kink effects are also proposed. The models are confirmed by SILVACO simulation and good agreement with the simulation results is obtained. The transient effects of SOI device with different parameters are simulated by SILVACO software as well.In chapter 4, we develop a method to improve the floating body effects in SOI device, namely, asymmetry doping channel. Through SILVACO software simulation, we found that this new structure can suppress the floating body effects, improve current kink effects and breakdown characteristic. Also, the transient effects of this device have been simulated such as the transient effects of transfer characteristic curves, threshold voltage, and output characteristic curves.In chapter 5, theoretical models about MFIS structure have been proposed. The temperature characteristics in MFIS are studied. The results show that the temperature can cause the change of polarization in ferroelectric layer. And also we study the effects of substrate concentration, and obtain the capacitance-voltage (C-V) characteristic and current-voltage (I-V) characteristic.In chapter 6, the V5+-doped BDT and BYT thin films are deposited on Pt(111)/Ti/SiO₂/Si(100) substrates by Sol-Gel. The experimental results show that the V5+ substituted in B-site can increase the remanent polarization, decrease the leakage current, and enhance the anti-fatigue. The results make sure that the BDTV and BYTV thin films may be potential candidates for ferroelectric materials. At last, we develop a new structure device by combination of SOI device and ferroelectric device. With the development of SOI technology and ferroelectric thin film technology, this improved device can offer some helpful information in memories due to their combinative advantages of the two devices.