Study On Thermal Issues Of InP HBT Devices And Circuits

The rapid growth in demand for wireless communication and mobile devices accelerates the study of millimeter-wave devices and circuits. Especially after the 21 st century, with the improvement of the level of technology, InP HBT devices and circuits are widely used in wireless communications, radar, aerospace and other fields. Compared with conventional Si-based CMOS technology, because of high cut-off frequency, InP-based IC has developed into an important choice for RF and microwave circuit design. However, the high speed of InP HBT makes its reliability even more valued by the people, such as thermal effects, electromagnetic effects and space radiation. InP HBT easily leads to high power density and significantly increases the operating temperatures. The increasing device temperature has two undesired effects. Firstly, it limits electrical device performance through thermal instability, and secondly, increasing self-heating effects lead to early failure of the device and a shorter lifetime. In particular, the increasing density of integrated circuits and power consumption, which make the IC thermal issues become increasingly prominent. Therefore, It is essential to the analysis thermal characters of ultra-high-speed InP HBT devices and circuits.This thesis focuses on the mechanism of self-heating thermal effects and InP HBT devices and circuits, The author’s major contributions are outlined as follows:(1)The thermodynamic model used by the ISE simulation is described in detail. The model takes into account the non-linear relationship between the InP material thermal conductivity and temperature. Further more, MATLAB simulation is used to converte the exponential relationship between InP material thermal conductivity and temperature into a two order polynomial form, which determines the thermal conductivity of InP material used in the simulation model. The heat inside InP HBT is studied by establishing a two-dimensional thermodynamic model. The joule heat and temperature distribution is analyzed, and the thermal source location in InP HBT is determined by the simulation.(2) Using the international mainstream analysis-the finite element method, a three-dimensional simulation model of InP HBT is built in ANSYS, and the nonlinear relationship between thermal conductivity and temperature is taken into account. According to the simulation of InP HBT 2D electrothermal model, Joule heat peak position of the device is loaded in the position of the heat source in the finite element model. The thermal equation is solved by using the finite element method numerically, and the internal temperature distribution of the InP HBT is simulated. Then, using the model, an analysis is carried out to study the key factors affecting the device junction temperature/thermal resistance. On this condition, we propose a thermal design scheme to optimize the InP HBT.(3) The temperature of an InP HBT dynamic frequency divider circuit is analyzed. Using equivalent method, we transform chip layout into a three-dimensional electrothermal model in ANSYS to analyze the temperature distribution of the circuit, and from the perspective of the circuit propose the thermal optimization design.