| 摘要 |
PURPOSE:To improve yield by a method wherein a P type semiconductor region is composed of a high resistivity region and a low resistivity region respectively doped with Ga and B so that life time distribution may be uniform among the wafers constituting a diodes. CONSTITUTION:The exposed surface of Si constituting an Si substrate 1 is diffused with B for the selective formation of the first region (low resistivity region) 2a of a P type semiconductor region 2. A process follows wherein the portion, not diffused with B, of the P type semiconductor region 2 is diffused with Ga for the formation of a second region (high resistivity region) 2b. The backward voltage withstanding capability is dependent as in a conventional method on the P-N junction formed between the second region 2b diffused with Ga and an N type Si substrate 1. The dimensions of the depletion layer in th vicinity of a groove 4 surrounding the mesa is also same as in a conventional method, maintaining the withstand voltage as in said traditional method. With the centrally positioned first region 2a being richly doped with B with its radius of covalent bonding short, the Si substrate 1 can be rich in defective layers, dislocations, empty holes. Their increase facilitate the control of the diffusion of impurities into the Si substrate 1, making the control easier of life time of wafers in the Si substrate 1.
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