| 摘要 |
PURPOSE:To obtain a deep Al atom-diffused region without causing Al to be separated out and alloyed, by a method wherein when Al ions are implanted into an Si substrate, Si and Ga ions are simultaneously implanted, and then diffusion thereof is effected. CONSTITUTION:An SiO2 film and an Si3N4 film are laminated on the (111) surface of a mirror-finished Si substrate, and Al, Si and Ga ions are implanted into the substrate. In this case, the accelerating voltage and implantation rate of ions of each impurity are selected so that the concentration distribution peaks of the Al, Si and Ga ions are disposed at substantially the same position in the depthwise direction of the substrate. After the implantation, the Si3N4 film is increased in thickness to prevent any outward diffusion, and diffusion is effected with a temperature raised to 1,200 deg.C at a rate of 20-30 deg.C/hr in order to reduce the stress between the Si and Si3N4 films generated in the early stages of the diffusion and prevent Al from being separated out with a high concentration in the vicinity of the concentration distribution peak. This is maintained at 1,200 deg.C for 60hr. By this constitution, it is possible to prevent Al from being separated out and alloyed, which is impossible when Al is employed solely, and accurately diffuse Al at a high concentration to form a region having a deep junction with an excellent reproducibility. |
