Thermal Effects And Analysis On Analog Integrated Circuit Design
Rahman, Ardasheir Sayek
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Analog circuit design is an art of circuit designing. With technology becoming more advance and size of devices shrinking, circuit designing has becoming a real chance for the designers to meet up the demands in the market. Density of device transistor is rapidly increasing leading to thermal runaway issues and increasing operational speed of the transistors. Thus transistors are more sensitive to temperature changes, therefore requiring a more sensitive and accurate modeling of the thermal effects of the device as well as its adjacent devices. This research is on the thermal modeling of dielectric bipolar junction devices. It looks into the existing thermal models and suggests possible improvement that can be made. Dielectrically Isolated Bipolar Junction(DiBJT) devices are an essential building block of high speed IC design. Full dielectric isolation of bipolar transistors is fabricated by using trench isolation and silicon-on-insulator (SOI) technologies. These transistors have reduced parasitic capacitances, low leakage currents, latchup free and radiation hardened circuitry, which are few of the many advantages of such transistors. But a major disadvantage of full dielectric isolation bipolar junction is the poor thermal conductivity of the dielectric. The trench oxide silicon isolation as roughly 1% of the thermal conductivity than silicon. With the drive towards smaller device geometry and higher operating current density, meaning more effect of adjacent device heating and addition packaging, bipolar transistors fabricated exhibits greater sensitivity to thermal effects caused by excessive self-heating.  For the research work National Semiconductor's dielectrically isolated complementary bipolar junction has been used to extract real work results. The process for this device is called VIP10. Further analysis has been done to convert multiple pole circuit models to single pole circuit models. The effect of adjacent heating devices has also being explored.