| 摘要 |
PURPOSE:To form a hole, which has sufficiently tapered wall so that a metal wiring is not broken, in an insulating film only by anisotropic etching, by using a multilayer positive photoresist film, in which upper layers have higher optical sensitivity than that of the lower layers, as a mask for etching when the hole is formed in the insulating film. CONSTITUTION:A PSG film 2 is formed on one main surface of a semiconductor substrate 1. A three-layer photoresist film, in which the sensitivity of the upper layer film is higher than that of the lower layer film, is formed on the surface of the PSG film 2. Then, exposure and development are performed with a specified mask pattern, and a hole is formed at a specified region in the photoresist film. Because of the difference in the optical sensitivity in the photoresist films, the opening parts of the photoresist films 3, 4 and 5 become large in this order. When these parts are adequately baked, the side surface of the holes in the multilayer photoresist films becomes considerably smooth. With the tapered multilayer photoresist films 3, 4 and 5 as masks, reactive ions 7 are projected from the upper part of the substrate using an RIE method, and the PSG film 2 is etched away. The tapered part is slowly retreated, and the tapered part is formed in the hole in the PSG film.
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