My thoughts after reading "The Great Chip" (Part 1)
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Talking about semiconductors from my personal experience, in the summer of 1970, driven by the enthusiasm of the whole nation for semiconductors, my alma mater set up a school-run factory to produce planar diodes. I was fortunate to be recommended by my class teacher to participate in the preparation and construction of the school-run factory. It took nearly three months from making the production equipment to producing the first qualified 2CZ11 diode. When the first batch of tube cores was officially started, after being taken out of the sintering furnace and put under a microscope for observation, the PN junction showed an irregular hexagonal golden glow. The feeling at that time was indescribable.
After graduation, I stayed at the school to work for three years, and during these five years I gained a deeper understanding of semiconductor production.
The N-region doping of the low-power planar rectifier diode is done with a gold-antimony alloy sheet, while the P-region doping is done with pure aluminum wire. The arrangement order is to put a gold-antimony alloy sheet, a silicon wafer, and an aluminum wire in a graphite mold, and fuse them at high temperature under a high vacuum environment.
The crystal face of single crystal silicon is very particular. Different products require single crystal silicon with different crystal directions. The best single crystal silicon in China at that time was produced in Luoyang, but the price was very expensive and small enterprises could not afford it. Only small-diameter silicon crystal rods produced locally could be used, with a diameter of about 30~50mm. I remember that in the early 1970s, China imported a large number of second-hand Japanese cars. The on-board generators of Japanese cars used silicon rectifier AC generators. Because the maintenance workers did not understand the characteristics of silicon rectifier AC generators, many rectifier diodes were damaged. Spare parts could not be bought in China, and they could only be purchased from Japan with foreign exchange, but the price was expensive. We began to develop 30A automotive generator professional silicon rectifier tubes. At the beginning, the sintering method was still used to produce products with a low pass rate, which could only reach about 40~60%.
The diffusion method is used to make chips, and the product qualification rate has been greatly improved. The general process is to apply phosphorus pentoxide and boric acid solution on both sides of the silicon wafer that has been ground to the required size and then cleaned and dehydrated, and then heated and diffused in a high vacuum environment to form a PN junction. After the diffusion is completed, the silicon wafer is tested and cut into the required size, chamfered by chemical method, and a qualified tube core is made with a molybdenum sheet as the substrate. After testing, it is cleaned, dried, dehydrated, and packaged to obtain the finished product. The domestic market was opened up, so the small school-run factory became famous for a while.
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