GB1175392A - Method of Treating Protective Coatings for Semiconductor Devices - Google Patents

Abstract

1,175,392. Semi-conductor devices. HITACHI Ltd. 4 Sept., 1967 [14 Sept., 1966], No. 40360/67. Heading H1K. In order to expose surface regions of a semiconductor body 51a through apertures 55, 56 in two superposed insulating layers, the upper of which 53 is less etchant-resistant than the lower 52, a first etching mask 54 is used to define the apertures in the upper layer 53 and a second etching mask 57 is then applied so as to protect the exposed edges of the layer 53 around the apertures 55, 56 during a second etch which penetrates the lower layer 52. As shown, the body 51a is of N-type Si having a P-type diffused base region 51b and an N-type diffused emitter region 51c to comprise a transistor. The emitter region 51c is formed by phosphorus-diffusion through an oxide mask 52, a phospho-silicate glass layer 53 being formed simultaneously. The two etching masks 54, 57 are of photoresist materials, the second of which, 57, is applied to the entire surface and subsequently washed free of the bottoms of the apertures 55, 56. The exposed edges of the easily etched glass layer 53 remain protected by the second mask 57 during the second etching stage. After exposure of the semi-conductor surface through the apertures 55, 56, the photoresist layers 54, 57 are removed and electrodes, e.g. of Al, are applied. In an alternative embodiment, the first etching mask may be completely removed from the surface between the first etching stage and the application of the second etching mask.