A low-temperature bonding method for thyristor chips

Abstract

The invention discloses a low-temperature combination method for thyristor chips, comprising the following steps: picking a mono-crystalline silicon sheet, an aluminum silicon alloy sheet, and a molybdenum sheet; deforming the center of the molybdenum sheet by a predetermined amount of deformation; putting the mono-crystalline silicon sheet, the aluminum silicon alloy sheet and the deformed molybdenum sheet in a graphite mould in sequence, wherein the concave side of the deformed molybdenum sheet directly faces the aluminum silicon alloy sheet; and putting the graphite mould in a vacuum high-temperature furnace to melt the aluminum silicon alloy sheet, wherein the mono-crystalline silicon sheet is combined onto the molybdenum sheet to form an approximately planar thyristor chip. The method is advantageous in that the original aluminum sheet is replaced with the aluminum silicon alloy sheet of which the melting point is lower, so that the combination temperature can be reduced to 580-600 DEG C, and the deformation of the obtained thyristor chip is reduced; and the center of the molybdenum sheet is deformed in advance by a predetermined amount of deformation, and therefore, thermal expansion deformation produced by the molybdenum sheet and the pre-deformation offset each other after combination, the finally obtained thyristor chip is approximately planar, and the possibility that a silicon slice is broken during installation can be greatly reduced.

Description

technical field [0001] The invention relates to a preparation technology of a thyristor chip, in particular to a low-temperature bonding method of a thyristor chip. Background technique [0002] With the development of industrial power conversion and control devices (power electronic equipment) towards ultra-high power, it is required that the power conversion capability of the most core power electronic components in power conversion and control devices can be doubled, and this will inevitably require power electronic chips. Large diameter, super large diameter. At present, the maximum diameter of a single thyristor chip has reached 3 to 6 inches. The thyristor chip is generally made of a processed silicon wafer, which is bonded to the high-temperature resistant metal (flat molybdenum wafer) with the closest expansion coefficient under high temperature and high vacuum conditions through a metal adhesive. The molybdenum wafer is the thyristor. The chip provides electrical ...

AI Technical Summary

Problems solved by technology

This combination method has the following problems: 1) Since the linear thermal expansion coefficient of single crystal silicon is 2.5×10 -6 / °C, the linear thermal expansion coefficient of metal molybdenum is 5.2×10 -6 / °C, so when the temperature of the silicon and molybdenum sheets is finally lowered from 700 to 800°C when they are combined to room temperature, the molybdenum sheet will shrink relative to the silicon sheet, and the silicon sheet will expand relative to the molybdenum sheet, and deformation will occur between them. like figure 2 As shown; and when the temperature of high-temperature bonding is higher and the diameter of the thyristor chip is larger, the deformation is greater, and the deformation at the center of the thyristor chip of 3 to 6 inches is generally 40 to 400 μm; 2) Using this combination When the thyristor chip obtained by the method is installed and used, it is subjected to an installation pressure of 10-150KN. Under this pressure, the deformed thyristor chip is flattened, but the silicon chip in the thyristor chip produces deformation stress. When the deformation is large or the long-term The silicon chip is very easy to break, which will seriously affect the reliability of the thyristor chip; 3) The semi-closed cylindrical graphite mold used in this combination method has the characteristics of high temperature resistance, and is used for the high temperature of the thyristor chip. However, due to the poor thermal conductivity of graphite, there will be a temperature difference between the thyristor chip in the graphite mold and the furnace chamber of the vacuum high-temperature furnace, which will affect the bonding accuracy and uniformity, and it is very easy to make the bonding between the silicon wafer and the molybdenum wafer. A poorly bonded void is formed in the center, which will eventually affect the electrical conductivity and heat dissipation of the thyristor chip

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