| 摘要 |
To avoid charging effects of isolated chromium structures during the structuring of a second level of attenuated phase shift masks, a previous chromium etching step is preferably carried out in a time-controlled manner, so that a residual chromium layer, which is approximately 5-20 nm thick, remains at the bottom of the columns. The residual chromium layer connects the chromium webs, which are otherwise isolated, in a conductive manner and therefore dissipates the charge to the outside during the subsequent structuring by an electron beam. In the process steps that follow the exposure of the second level-preferably of alternating attenuated phase shift masks-two further chromium etching steps can be carried out, with a small etching depth in each case in the columns provided for the quartz etching of different phase shift.
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