Research On The Reliability Of The Insulated Gate Bipolar Transistor (IGBT)

Since the birth of semiconductor devices, what comes next is the reliability of the semiconductor device. The reliability of semiconductor devices affects the device’s function, stability, and the length of longevity. Since the1950s, the reliability analysis techniques developed into an integrated technology, and it’s more matured today. With the development of society, semiconductor devices are playing more and more important role in people’s lives, and at the same time, the condition of using semiconductor devices is becoming much stricter, the reliability of semiconductor device have attracted more and more attention.The insulated gate bipolar transistor (IGBT), as a kind of power semiconductor devices, which collects the advantages of the insulated gate field effect transistor (MOSFET) and the bipolar transistor (BJT), has had a rapid development in recent years and has been used widely in industrial equipment, automotive electronics, and other fields. Because of the huge power dissipation and the complex working condition, the reliability issues of IGBT have been gradually focused and studied.The temperature of power devices, including IGBT, MOSFET, LEDs, will be greatly increased, when they are dissipating power, and the distribution of junction temperature becomes non-uniform. As we all know, the semiconductor devices is quite sensitive to the change of temperature, and high temperature may cause the function of device to be bad, make the device unstable, lead the device to burn down, and destroy the entire system at last. Therefore, it is necessary to do a research on the thermal reliability parameters (such as thermal resistance) and the distribution of junction temperature of IGBT.As one of the important thermal parameters, the thermal resistance is used to measure the cooling capability of semiconductor devices. It is meaningful to make a research on the parameters that influence the value of thermal resistance and how they influence the thermal resistance. First, this paper gives the methods of measuring the thermal resistance according to the standard of the IEC (International Electrotechnical Commission)60747-7and the standard of JEDEC (Solid-state Associations)51-1, respectively, and compares their characteristics. Second, we do some research on the parameters that influence the thermal resistance with the advanced instrument Phase11, produced by the Analysis Tech Corporation, and the results indicate that not only the power but also the voltage will affect the measurement value of thermal resistance. Furthermore, we use structure function, one kind of advanced analysis methods, to analyze the package structure of the device, and these results reflect the information of package materials of IGBT, including the thermal resistance and thermal capacity. With this method, we can screen out those devices whose packages are defective.Due to its own characteristics, the method of infrared thermal image cannot be widely used, although the method can prove the non-uniform of distribution of the junction temperature. Fortunately, the electrical method can make up the shortcomings of infrared thermal method, and this method has not developed very well until the discovery of small current excessive thermotaxis effect and the invention of the MQH Algorithm by Miao Qinghai, professor of Shandong University, at the end of20th century. Thus, using the theory above, it is successful to calculate the degree of non-uniform of junction temperature distribution, and it is become more mature to analyze the junction temperature.This paper will give a more explicit description of the theories above, and analyze the non-uniform distribution of the junction temperature of IGBT by using the theories above. In this paper, first, we give a amendment of Shockley Equation, and give the physical meaning of the parameters. Second, give the preconditions of using MQH Algorithm by deriving the theoretical model strictly, and these preconditions are described as follows.a) The area of the junction can be divided into two parts with different temperature, and temperature is uniform in each part, respectively.b) The two parts are equivalent in parallel, i.e., they have the same voltage.c) Current flows only in the part whose temperature is higher. These are continuation and development of the previous theory. In this paper, we calculated the peak junction temperature and the degree of the non-uniform distribution of PN junction successfully by measuring data from the instrument and software, designed by ourselves. This is both an affirmation of the previous theoretical and some achievements for the research of IGBT junction temperature distribution.In the end of this paper, we give a summary of the entire postgraduate research work and recast the future trends in the reliability study of the IGBT, and we also make several requests for future research work.