A new type of large-diameter semiconductor chip and molybdenum sheet bonding ohmic contact processing method

Abstract

The invention provides a novel large diameter semiconductor chip and molybdenum sheet bonding type ohmic contact processing method. A semiconductor chip and a molybdenum sheet are comprised. Contact layers between the semiconductor chip and the molybdenum sheet comprise Al electrode layer, a Ti / Pt / Au metal transition layer and an Ag solder layer. According to the invention, a number of metal transition layers and the solder layer are introduced; a metal atom micro diffusion bonding principle is used; the characteristics of low conductivity and easy bonding with other metal at a low temperature of Au and Ag are used, so that the semiconductor chip Si and the Mo sheet are firmly adhered together to form a great ohmic contact technology; the high power semiconductor chip and the molybdenum sheet form large area ohmic contact without deformation; the on-state voltage drop of a device is significantly reduced; the flow capacity, the reverse blocking characteristic and the heat radiating effect of the device are improved; the parameter consistency and the yield of the device are improved; and huge economic benefits are produced.

Description

technical field [0001] The invention relates to the technical field of manufacturing power semiconductor devices, in particular to a processing method for a high-power thyristor, a rectifier semiconductor chip and a molybdenum sheet bonding ohmic contact technology. Background technique [0002] As we all know, high-power thyristors and rectifiers are power semiconductor discrete devices, and their development direction is high-voltage and high-current power, and the chip area is relatively large. During operation, it bears high voltage and generates a lot of heat through high current, which needs to be carried away by metal electrode conduction. The tightness of the contact between the metal electrode and the semiconductor chip and the flatness of the interface determine the electrothermal resistance and flow capacity of the device. [0003] The existing contact technologies between high-power discrete device chips and molybdenum sheets (electrodes) include high-temperatur...

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Problems solved by technology

[0004] 1) Since the process temperature is as high as 700°C, the thermal expansion coefficients of Si and Mo are inconsistent, and large deformation occurs after cooling, which causes stress inside the chip, which may lead to increased pressure drop, poor contact of the electric heating circuit, and poor heat dissipation. The chip is broken when it is subjected to electric heat or mechanical shock, making the device permanently invalid

[0005] 2) Using the mutual fusion of Si and Al at high temperature, the formation of an alloy layer will consume a certain depth of silicon on the surface, unevenly change the original PN junction depth and surface concentration distribution, and deteriorate the electrical characteristic parameters

[0006] 3) In the process of high temperature, AL first turns into a liquid, which is easy to lose, resulting in edge voids and other local adhesion problems, and does not form an excellent ohmic contact, resulting in a decrease in blocking voltage, an increase in on-state voltage drop, a decrease in flow capacity, and heat dissipation. poor effect

The disadvantage is that the contact transient thermal resistance is large and the surge current is small

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