Studies Of New SOI Materials And Relevant Technologies & Applications

SOI (Silicon-on-insulator) technology is expected to replace bulk silicon technology in microelectronics industry because it possesses many advantages as compared to bulk silicon, such as easier electrical isolation, significant reduction of parasitic capacitances, excellent sub threshold slope, elimination of latch up and resistance to radiation. But it is inevitable that the buried silicon dioxide layer also thermally insulates the MOSFETs (metal-oxide-silicon field-effect transistors) from the bulk due to the low thermal conductivity. So self-heating effects becomes a critic problem for a MOSFETs built-in SOI because it would eventually degrade the device electrical characteristics under prolonged high temperature operation and limit SOI materials in application to high temperature and high power integrate circuit. At the same time, with the improvement of operation frequency and integration of radio frequency circuit, although SOI shows excellent ability of mixed process and devices and compatibility with CMOS process to incorporate digital and analog circuits on one chop, noise impact still is a serious problem. In order to resolve the problems and meet the demand of special device/circuit, there has been a strong interest in the development new SOI structures.So in this project we have made a series of investigations on the Self-heating effect of SOAN(silicon-on-aluminum nitride) device with the buried layer of AlN and the new materials of GPSOI (Ground Plane SOI) with the buried layer of WSix to reducing noise in RFIC. Besides, we have studied the new applications and advanced technologies of SOI materials.The main results acquired are drawn as follows:(1) AlN thin films were fabricated successfully on silicon substrates by pulsed laser deposition and their properties were investigated; a novel SOAN structure were prepared via Smart-cut technology; a two-dimensional numerical analysis was performed by using a device simulator called MEDICI to discuss the influence caused by all kinds of the parameters of SOI device, such as the doping concentration ofsource/drain region, the doping concentration of the channel region, the thickness of the top silicon layer, the thickness of the buried oxide layer; MEDICI also have been used to simulate the electrical characteristics and temperature distribution by comparing with those of bulk and standard SOI MOSFETs, which results suggested that A1N is a suitable alterative to silicon dioxide as a buried dielectric in SOI and expands the applications of SOI to high temperature conditions.(2) Single-crystalline Si/SiO₂/poly-WSix/Sub-Si structure has been successfully fabricated by a new method incorporating standard smart-cut technology and high temperature solid phase reaction between tungsten and silicon; The characteristics of poly-crystalline WSix (12/Al₂O₃ on ultra-thin SOI substrate via ultrahigh vacuum electron-beam evaporation and post-annealed in N₂ at 450℃ for 30min; The results of its high frequency capacitance voltage (C-V) characteristics of the fully depleted (FD) SOI MOS capacitor showed that the minority carriers determined the high frequency C-V properties and the series resistance of the SOI substrate is the determinant factor of the high frequency characteristics of the FD SOI MOS capacitors.(4) A non-source device with high-performance — CPW transmission lines on different substrates were fabricated and the characterization of their radio wastage were investigated, which showed that the depletion of CPW transmission lines on GPSOI substrate would reduce effectively.(5) ZnO nanotetrapods were synthesized by evaporating highly pure zinc pellets (99.999%) at 900℃ in air and a humidity sensors with ZnO anotetrapods as a sensing element were featured by combination of a quartz crystal as a transducer. The experimental results indicated that ZnO nanotetrapods was a potential humiditysensing material because the response of the sensors had a good sensitivity, frequency stability and reproducibility; A new structure of ZnO anotetrapods humidity sensor on SOI substrate was designed in order to develop the next investigation about SOI sensors.We hope we could develop farther the application of SOI technology and materials through the results of this project.