| 摘要 |
PURPOSE:To provide a protection film without affecting element characteristic by covering the MESA side surface with the anode oxide film. CONSTITUTION:The resist mask 6 is deposited on the GaAs epitaxial wafer (P<+> layer 3, N<-> layer 4, N<+> layer 5) providing the electrodes 1, 2 and the MESA etching is carried out in such a degree that flaw does not reach the electrode 1. The anode oxide film 11 can be formed also credibly and uniformly on the MESA side by the anode oxidation in the liquid of water + ethylene glycol + tartaric acid with the Pt used as the negative electrode. At this time, when external voltage is considered as V, breakdown voltage of p<+> n<-> junction as V1, breakdown voltage between the caustic liquid and N<-> layer 4, N<+> layer 5 as V2 and V3, the oxide films in the thicknesses proportional to V-V1, V-V2, V-V3 can be obtained on the layers 3-5. At this time, since V1 V2, the oxide films in the almost equal thickness can be formed at the sides of layers 3, 4. Finally, the resist 6 is removed. Since the anode oxidation is carried out at a low temperature, it does not cause any influence on the element characteristic and the perfect protection insulating film can be obtained at the MESA side surface. |
