The Study On Temperature Analysis Method For HBT Integrated Circuit Based On MATLAB Programming

Heterojunction bipolar transistor(HBT) has been used widely with the rapid development of modern communications technology. HBT has an extensive application in radar, mobile phones, optical communications and other fields. Compared with conventional Si CMOS device, HBT device has many advantages, such as high gain, low phase noise, high linearity, especially high cut-off frequency, making it an excellent candidate in microwave RF circuits. High power and current density of the HBT device, which result in the high temperature of it, affect the reliability of the circuit based on HBT. So it is very important to study the temperature distribution for the design of circuit based on HBT. Layout design is the key to integrated circuit design. Given the temperature distribution of devices and chips, it will help us fully consider the effects of temperature and achieve the electromagnetic heat integration analysis, and it will improve the accuracy of circuit design.We summarize the importance of studying the distribution of HBT circuit and the research status of today's IC temperature distribution in this thesis, then analyze the principle and the self-heating effects of HBT devices, and describe the relevant heat transfer numerical simulation and finite element analysis theory.Then we introduce the work of this article: based on MATLAB programming, a temperature distribution method of HBT IC layout is presented. The main steps are as follows:(1) The geometry model of the HBT in the chip is built with finite element analysis software Comsol on the basis of the foundry's process library. Next, the thermal loads and boundary are applied to the model, and the structure is meshed carefully. Finally, we can obtain the temperature distribution by solving the stationary thermal conduction equation and import temperature profile data into MATLAB for function fitting.(2) The data of power dissipation for each HBT is obtained by simulating the circuit using EDA software and it is marked on the emitter center of the layout. Then we export the layout using GDSII format and edit it with Link CAD. At last, we keep emitter and power information, and convert the layout to DXF format.(3) Finally, we extract emitter coordinate and power information automatically by MATLAB programming. Then we calculate the temperature of the center of each HBT, and draw the temperature profile and isotherm distribution.In order to verify the validity of the above method, a thermal imager is used in this work to test the circuit chip on operation. The test results obtained by this method are consistent with the overall trend of the measured temperature distribution.However, the simulated temperature of some of the region is lower than the measured temperature. We analyze reasons for this phenomenon, propose the method for correcting the layout based on the simulation results, and put forward some improvement for this method.