| Considerable savings in cost and development time can be achieved if high-voltage ICs (HVICs) are fabricated in an existing low-voltage process. In this thesis, the feasibility of fabricating HVICs in a standard CMOS process is investigated.; The high-voltage capabilities of an existing 5 {dollar}mu{dollar}m CMOS process are first studied. High-voltage n- and p-channel transistors with breakdown voltages of 50 V and 190 V respectively, have been fabricated without any modifications to the process under consideration. SPICE models for these transistors are developed and their accuracy verified by comparison with the experimental results. In addition, the effect of the interconnect metallization on the high-voltage performance of these devices is also examined. Polysilicon field plates are found to be effective in preventing premature interconnect induced breakdown in these devices.; A novel high-voltage transistor structure, the insulated base transistor (IBT), based on a merged MOS-bipolar concept, is proposed and implemented. The device, which can be implemented using a standard CMOS process, is capable of handling high current densities without latching. The IBT exhibits a fivefold increase in the current density compared to the lateral DMOS transistor. A simple technique to improve the breakdown voltage and the switching speed of the IBT, without significantly compromising its current carrying capability, is also presented.; In order to enhance the high-voltage device capabilities, an improved CMOS-compatible HVIC process using junction isolation is developed. High-voltage lateral DMOS transistors and merged MOS-bipolar devices such as the LIGT and IBT with breakdown voltages of 400 V, have been fabricated using this process. The IBTs, which in addition to having high breakdown voltages have high current handling capabilities as well as high switching speeds, offer better performance than the LIGTs. In addition, the IBT, because it doesn't latch-up, is a more reliable device than the LIGT.; The processes and devices developed in this work have potential applications in the telecommunications and display driver fields. |
