Tantalum Dry-Etching Characteristics for X-Ray Mask Fabrication

概要

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Directional dry etching of Tantalum is described X-ray lithography mask absorber patterns. Experiments are carried out using both reactive ion etching in CBrF_3-based plasma and electron-cyclotron-resonance ion-stream etching in C1_2-based plasma. Ta absorber patterns with perpendicular sidewalls cannot be obtained by RIE when only CBrF_3 gas is used as the etchant. While adding CH_4 to CBrF_3 effectively improves the undercutting of Ta patterns, it deteriorates etching stability because of the intensive deposition effect of CH_4 fractions. By adding an Ar/CH_4 mixture gas to CBrF_3, it is possible to use RIE to fabricate 0.2-μm Ta absorber patterns with perpendicular sidewalls. ECR ion-stream etching is investigated to obtain high etching selectivity between Ta and SiO_2 (etching mask) / SiN (membrane). Adding O_2 to the Cl_2 etchant improves undercutting without remarkably decreasing etching selectivity. Furthermore, an ECR ion-stream etching method is developed to stably etch Ta absorber patterns finer than 0.2 μm. This is successfully applied to X-ray lithography mask fabrication for LSI test devices.
社団法人電子情報通信学会の論文
1994-02-25