| 摘要 |
PURPOSE:To protect a semiconductor substrate against the influence of a thermal strain and to stabilize a thermal diffusion method by performing the temperature rise to a target diffusing temperature via the diffusing treatment to the temperature fall from the diffusing temperature in the same heat treating unit when a conductive type deciding impurity is diffused by the thermal diffusion method. CONSTITUTION:A diffusion preventive layer 3 is formed for selective diffusion on a GaAs substrate 2 grown in gas phase for GaAsP crystal 2. the layer 3 as a mask an impurity is diffused in the substrate 1 to produce a P-N junction 4 in an arbitrary depth. At this time, a spike 5 might occur due to an abnormal diffusion to the slip line in the crystal 2 due to the difference of lattice constant between the substrate 1 and the crystal 2. A strain is produced at the side of the crystal 2 due to the difference of the thermal expansion coefficient between the layer 3 and the crystal 2 at the end of the layer 3, and an abnormal diffused region 6 might be produced similarly. Accordingly, the temperature in the furnace is reduced to approx. 450 deg.C, the substrate and the impurity are filled in the furnace, and are secured at approx. 800 deg.C, and are maintained at the same heat treating unit until they are lowered to 450 deg.C. |
