| 摘要 |
PURPOSE:To obtain a Zener diode whose positive direction breakdown voltage and negative direction breakdown voltage are nearly equal by a method wherein one conductivity type dopant is diffused into the one conductivity type substrate from one direction with a higher concentration than the substrate and the other conductivity type polycrystalline silicon is made to grow on the surface of the substrate on the higher dopant concentration side first and then is made to grow on the surface of the substrate on the lower dopant concentration side too. CONSTITUTION:From apertures 4a and 4b in proteotive films 2a and 2b which cover both surfaces of one conductivity type substrate 1', the other conductivity type polycrystalline silicon layers 5a' and 5b' are made to grow. in manufacture of a bidirectional Zener diode like this, one conductivity type dopant is diffused into the substrate 1' from one direct.on with a higher conentration than the substrate 1' and, at first, the polycrystalline silicon 5a' is made to grow on the surface of the substrate 1' on the higher dopant concentration side and then the polycrystalline silicon 5b' is made to grow on the surface of the substrate 1' on the lower dopant concentration side. For instance, phosphorus is diffused into an N-type semiconductor substrate from one direction to make a substrate 1' with a concentration gradient. P-type layers 3a and 3b are formed on the substrate 1' and, at first, a P-type polycrystalline silicon 5a' is made to grow on the surface of the substrate 1' on the higher phosphorus concentration side. Then, under the same heat treatment conditions, a P-type polycrystalline silicon 5b' is made to grow on the surface of the substrate 1' on the lower phosphorus concentration side. |
