| 摘要 |
PURPOSE:To improve optical characteristics by applying positive resist to the surface of a substrate, converging ion beams into the resist so as to make the beams correspond to the shape of an optical element while changing acceleration voltage to draw a picture and executing development processing to change the film thickness of the resist. CONSTITUTION:The positive resist 6 is applied to the glass substrate 1 and an electrification preventing film 3 is vacuum deposited on the surface of the resist 6. The acceleration voltage of ion beams 5 is periodically changed from a large value to a small value or a small value to a large value so as to correspond to the shape of a grating 20 with a fixed period to converge the ion beams 5 into the resist 6 and directly draw a picture. Finally, the film 3 is removed by etching and developed, so that resist is deeply peeled on the draw portion with a high ion beam acceleration voltage and the film thickness of the resist 6 can be changed to obtain the grating 20. Thus, an excellent sectional shape can be obtained with high reproducibility and the optical characteristics can be improved.
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