| 摘要 |
PURPOSE:To selectively leave a metal film on only a diffused film by applying a mask having a double layer constitution of different materials in order to perform a selective diffusion, then covering the whole surface with a metal film and chemically etching only the upper layer film of the mask. CONSTITUTION:On an N type InP substrate 1, an Si3N4 film 3 and an SiO2 film 3 are successively piled by the plasma arc coating method. The SiO2 is etched by using a mixture of HF and NH4F and the Si3N4 is plasma-etched to form an opening 4. Cd is diffused to form a P type InP layer 5. Because the plasma-formed films 2 and 3, which are piled, have no pinhole, the Cd can be diffused only in the opening 4. After an Au-Zn alloy 6 is deposited by evaporation, the film 3 is etched by using the mixture of HF and NH4F so that the alloy film 6 is left only on the diffused layer 5. Moreover, a heat treatment is applied in a nonoxidative atmosphere to accerelate alloying reaction in order to form an ohmic contact having low resistance. By said constitution, the process is largely simplified and a device having high reliability can be obtained at high yield. |
