Because most of these integrated circuit companies have no independent power device production line, they can only use the existing integrated circuit production technology to complete chip processing, so they basically design and produce some low-voltage chips. Compared with ordinary IC chips, high-power devices have many unique technical problems, such as chip thinning process and back surface process. To solve these problems, we need not only mature technology, but also advanced technology and equipment, which are all urgent problems in the development of China's power semiconductor industry.
from the early 198s to now, there are three types of IGBT chip internal structure design: non-punch-through (NPT), punch-through (PT) and weak punch-through (LPT), and a lot of work has been done to improve the switching performance and on-state voltage drop of IGBT. However, it is quite difficult to realize the above design in technology. In particular, the sheet technology and the back technology. The insulation passivation of the front surface and the thinning of the back surface are not very good in China. Low-temperature flux-cored tin wire
sheet technology, IGBT devices with specific withstand voltage index, the chip thickness is also specific, and it needs to be thinned to 2-1 μ m, even to 8 μ m. Now, the wafer can be thinned to 175 μ m in China, and it will not be capable if it is lower. For example, in the order of 1~2um, when the silicon wafer is so thin, the subsequent processing is more difficult, especially for large silicon wafers over 8 inches, which are easily broken and more difficult.
back surface technology includes back surface ion implantation, annealing activation, back surface metallization and other process steps. Due to the limitation of the melting point of the front metal, these back surface technologies must be carried out at a low temperature (no more than 45°C), and the step of annealing activation is extremely difficult. Back implantation and annealing, this process is not as simple as imagined. Some foreign companies can process on their behalf, but once they sign an agreement with their customers, they will no longer provide processing services to their customers in China.
in terms of module packaging technology, the traditional welding packaging technology has been basically mastered in China, among which there are many middle and low voltage module packaging manufacturers, and high voltage module packaging is mainly concentrated in CSR and CNR. Compared with foreign companies, the technical gap still exists. Based on the traditional packaging technology, foreign companies have successively developed a variety of advanced packaging technologies, which can greatly improve the power density, heat dissipation performance and long-term reliability of modules, and have initially realized commercial applications.
There is a shortage of high-end process developers, and the design level of existing R&D personnel needs to be improved. At present, there are no talents in China who systematically master the IGBT manufacturing process. Introducing from foreign advanced power device companies is a shortcut. However, it is difficult to master the whole process of IGBT manufacturing by introducing only one person, and it is too difficult to introduce a team. Many technologies in IGBT manufacturing abroad are protected by patents. At present, if you want to buy IGBT design and manufacturing technology from abroad, it also involves a lot of patents. Price of BGA solder balls in Kunming