| 摘要 |
PURPOSE:To enable a substrate to be etched deeply even if a ratio of the total area to that of the substrate is large and to improve profile of a side cross section of an etched part, by providing apertures of a mask with a large aspect ratio (depth/width). CONSTITUTION:An aspect ratio (depth/width) of an aperture is set to be 1.5 or over for controlling the profile of side cross section of an etched part. For example, about 2 mum thick masks 3a of phosphorus glass having an about 1 mum wide aperture 2 are provided on a silicon substrate 1 at positions where trenches are to be formed. A ratio of the total area of the apertures 2 to the area of the substrate 1 is about 30 % which would cause a problem of loading effect according to prior arts. Subsequently, the substrate 1 is etched selectively in the apertures 2 until about 2 mum thick trenches are formed. ln this embodiment, the aspect ratio of the apertures is about 2. If the area ratio related to the loading effect is lower than 20 %, trenching can be prevented even if the thickness of the mask 3a may be increased up to about 1.5 mum, that is, the aspect ratio of the apertures 2 may be decreased up to about 1.5.
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