JPS5473557A - Aluminum diffusion method into semiconductor - Google Patents

Abstract

PURPOSE: To obtain a semiconductor device of high dielectric strength having high life time and large capacity, by heating Al of diffusion source stored in a container made of high melting point metal together with semiconductor substrate in a vacuum sealed tube in order to diffuse Al in the substrate, and heat treating in O₂ or N₂ stream.

CONSTITUTION: N type Si substrate and a container storing Al of 99.999% purity are sealed in a quartz tube of which degree of vacuum is controlled at 1×10^-6 mmHg. At this time, as the container to store Al, a metal material such as Mo and W is used, and the quantity of Al diffusion source is selected to 0.5 to 5 mg/cm³ per volume of the quartz tube. Then, heat treating at 1080°C for 10 hours, Al is diffused in the substrate, and, after cooling down, the substrate is taken out of the quartz tube. Next, in O₂ or N₂ gas of which flow rate is 1.0 l/minute, a heat treatment is performed at a higher temperature than former, 1250°C, for 25 hours. By this making, at least the life time of more than 50 μS can be obtained, so that the reverse leakage current and forward voltage drop in a semiconductor device using such constitution may be smaller.

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