Thermal-resistance-processed silicon carbide back metal thickening method

Abstract

The invention relates to a thermal-resistance-processed silicon carbide back metal thickening method. The method comprises the following steps of 1) forming a metal layer on the back surface of a SiC wafer through evaporation or sputtering, and forming an ohmic contact after an annealing process; forming a stopping metal layer on the back surface ohmic contact through evaporation or sputtering; 3) applying a layer of resin onto the front surface of the SiC wafer, heating the SiC wafer in a drying oven to solidify the resin; 4) performing coating protection, wet HF corrosion, cleaning and drying on the front surface of the SiC wafer; 5) forming thickening metal on the back surface of the SiC wafer through sedimentation; 6) performing photoresist removal and scribing, and after a chip is sintered onto a carrier, performing shear assessment. The thermal-resistance-processed silicon carbide back metal thickening method has the advantages of solving the problem of infirmness of the back surface metal of a high-temperature-processed SiC power device, and by means of the stopping metal layer sputtered onto the back surface ohmic contact, which can be diffused to combine with C on the surface of the ohmic contact after the high-temperature processing process, avoiding forming a dissociative C layer and guaranteeing the firmness and reliability of the back surface thickening metal.

Description

technical field [0001] The invention relates to a back metal thickening method, in particular to a high temperature resistant silicon carbide back metal thickening method. Background technique [0002] Silicon carbide (SiC) material has a large band gap (3.2eV), high critical breakdown electric field (up to 4×10 6 V / cm above), high electron saturation velocity (2×10 7 cm / s) and high thermal conductivity (4.9W / cm.K), it has obvious advantages in high temperature, high power, radiation resistance and other working conditions, and has broad applications in communication, transportation, energy and other fields Application prospect. [0003] In silicon carbide power devices, nickel (Ni) is usually used as the ohmic contact metal, and a layer of highly doped epitaxy is grown on the surface of the silicon carbide wafer. After depositing the metal nickel, after up to 1000 o After high-temperature annealing of C, a good ohmic contact is formed, and its specific contact resistivit...

AI Technical Summary

Problems solved by technology

However, during the ohmic contact formation process of silicon carbide, due to the reaction of nickel and silicon carbide to form nickel silicon compound (Ni x Si y ), carbon (C) will be precipitated. During the ohmic annealing process, due to the short annealing time at high temperature, carbon has not diffused to the surface. Since the diffusion coefficient of carbon is proportional to time and temperature, at higher temperature and longer time, This carbon will diffuse to the ohmic contact surface to form a free carbon layer. At this time, the metal thickening process will result in very poor adhesion of the thickened metal.

[0004] In response to the appeal problem, the carbon precipitated on the back can usually be removed by wet etching and dry etching. The strong acid used for wet etching will corrode the front of the device, and the dry etching of the back of silicon carbide will damage the silicon carbide wafer and etch. The equipment cavity causes pollution. Both of these methods will damage the electrical properties of silicon carbide devices and cause potential reliability hazards. Therefore, it is very important to develop a silicon carbide back metal thickening process that does not need to remove the carbon layer and has good adhesion to the back metal. of

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