Preparation And Application Of AIN And Ta-C Thin Films For SOI Technology

Silicon-on-insulator (SOI) is expected to become mainstream substrate for microelectronics in near future. For many applications, such as high-speed and low-power consuming ICs, SOI substrates offer numerous advantages as compared to bulk silicon, i.e. lower parasitic capacitances, improved subthreshold characteristics of transistors, and higher currert gain of amplifiers. However, application of SOI in high-temperature and high-power ICs is limited by the self-heating effect, caused by the poor thermal conductivity of the insulating SiO2 layers which will trap heat from the operating device in the operating region, then degrading operation and reducing device lifetime. Thus, to develop integrated circuit with on-chip power devices, it is important to investigate new buried insulator with good thermal conductivity.Firstly, we built electro-thermal model for the "electro-thermal-structure" analysis of novel SOI structures with different insulating materials. In the model, the device heat flow can be well represented by the current flow in an electrical transmission line approximated by an equivalert lumped circuit consisting of the heat source and lumped thermal capacitances and resistance. Therefore, the thermal model can be represented by a series of RC-networks, the dissipated power is given by Pth(t)=V(t) I(t). The topology of the thermal network and the components of RC-networks for the calculation of temperature c istribution could be obtained by the finite element method. Using model equations and collecting all temperature dependent parameters lead to an electrical-thermal model for the device. The ambient temperature is simulated by the potential of a node in the network-model.Then we studied the influence of temperature on main electrical parameters of SOI devices, such as mobility, carrier concentration, threshold voltage, drain-source current, etc. Our results show that the variety of temperature could influence the drain-source current and intrinsic carrier concer tration, and the channel mobility andthreshold voltage of the device decreased with increasing temperature. These resultsare important for further study on the influence of self-heating effect on power devices. In details, under the same temperature, channel mobility of SiO2 SOI device is lower than that of bulk silicon device and the novel insulator SOI devices.We also studied the self-heating and heat-dissipating process due to the power consumption during device operation. Due to considerable power dissipation and low thermal conductive SiO2 box layer, the temperalure in the SiO2 SOI device rises significantly. Analysis of the heat flow shows that the temperature rise AT in the device due to self-heating is given by , where R(t) is thermal resistance, which is dependent on thermal conductivity, area and thickness of every layer.To study the lattice-temperature and internal thermal-stress distribution caused by power consumption under different environment temperature, we simulated the influence of self-heating effect on different device structures through the finite element software of ANSYS v6.1. We also studied the interaction among electricity, heat and structure. To better compare with each other, we choose the same size for all the SOI structures, i.e. bulk silicon LDMOSFET, SiO2 SOI LDMOSFET, A1N SOI LDMOSFET, diamond SOI LDMOSFET and ta-C SOI LDMOSFET.For the electro-thermal model, we choose the coupled-field analysis in ANSYS v6.1, which could be divided by two parts: thermal and stress simulation. For the first part, we finished defining the element type, real constants, materials property, constrains, and creating geometry model, then began to simulate the structures, i.e. the step of "Current LS". Thus the results of thermal distribution in every structure could be obtained. For the second part, we switched the element type from "thermal" to "structure" and defined the material properties fretly, then we gave the constrains and load to the structures, i.e. readin thermal analyzing results as load, thus we could be...