| 摘要 |
A dry etching method whereby underlying layer selectivity and anisotropy may be prevented from deteriorating due to excessive radicals in an over-etching process. In the etching chamber of an ordinary magnetically-enhanced microwave plasma etching apparatus, the so-called ECR position at which the ECR condition is established is a very small region, where ionization current has the highest density and the most uniform direction in ECR plasma. On the downstream side of the ECR position is the after-glow region of ECR plasma with a low plasma density. According to the present invention, the etching chamber is provided on part of the inner sidewall thereof with an Si-based material layer capable of consuming halogen radicals while a lifting and lowering means is provided for varying the distance between a target wafer and the ECR position. In a just-etching process, the wafer is kept close to the ECR position so that it may be etched at a high rate in an anisotropic shape by radicals with a high density and ions with a uniform direction. In an over-etching process, the wafer is kept distant from the ECR position to bring the after-glow region into contact with the Si-based material layer, which captures excessive radicals such as F* in the form of SiFx for removal from an etching reaction system. Thus, the present invention can be applied to polysilicon gate electrode processing to improve gate insulation film selectivity.
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