The High Temperature Application Research Of Deep Sub Micron SOI CMOS Circuits

The SOI technology exhibits many advantages over bulk silicon technology , such as the reduction of parasitic capacitances, easy to form shallow junction, elimination of latch-up, much better electrical character et al, so that it is a potential technology in the realm of deep sub-micron process. However, the buried layer thermal conductivity of conventional SOI device is very low, therefore the joule heat generated in the channel area of the device can not be easily dissipated, which results in the heat accumulation in the channel region, this self heating effect would arises some problems, such as saturation current of the device lowering, threshold voltage Vt shifting etc. Thereby, thoroughly analyzing the forming mechanism and gathering position of heat generated in SOI device and trying to bring forward effective solving method become researching hotspots on high temperature domain application of SOI technology, the application of DSM SOI technology in high temperature realm is mainly concern in this paper, and particular attention is paid on model construction, analysis of self-heating effect and comparison of several device structures that can cure the self heat effect.Based on the 100nm full depleted SOI CMOS process, the device structures of NMOS and PMOS which comprise a SOI CMOS inverter are established according to the requirement of deep sub micron realm by employing device simulator ISE TCAD. moreover, corresponding physical models are selected aiming at reflecting the proper second order effects in deep sub micron devices, and the default material parameters of AlN material in the ISE TCAD material database are also modified according to the relevant literatures. The thermal property and electrical characteristics of SOI CMOS inverter are simulated using the models established above, the results reveal that conventional SOI device would suffer serious self-heating effect when operating, the output characteristics degrade severely and the leakage current also has a sharp increase along with the rising of lattice temperature; the generating and gathering position of heat locates at drain/channel PN junction, and NMOS suffers more seriously from self-heating effect compared with PMOS. In order to eliminate the self-heating effect in conventional SOI device, the SOAN device and AlN_DSOI device are established, the comparison of on-state current and stability of threshold voltage of the above 3 devices are also conducted. The results shows that SOAN (Silicon On Aluminum Nitride) can completely eliminate the self-heating effect, and it can also elevate the driving capability of the device. Some optimization of structural and processing parameters of SOAN device are carried out in allusion to high temperature application circumstance, and their optimized values are gained. A CMOS inverter consisted of optimized SOAN NMOS and PMOS is put up, and its transient characteristic is simulated. The simulated figure demonstrates that the gate propagation delay of SOAN CMOS is 19ps and 25.5ps, when the ambient temperature is 300K and 500K; the delay of its SOI counterpart is 28.5ps and 35.5ps at the two temperature points respectively. Finally, a new SOI device structure, Air_AlN_SOI structure is brought forward, and its implementing process is proposed too. The simulation results demonstrate that not only the Air_AlN_SOI structure can enhance the dissipating capability to eliminate self-heating effect, but it can also eliminate the off-tate current rising problem invoked by DD3L (Drain Induced Barrier Lower) and DIVSB (Drain Induced Virtual Substrate Biasing)effect after including in the high thermal conductivity material AlN, the above all simulation shows that the Air_AlN_SOI device is suitable for the high temperature field application.