7 June 1996 DUV resist profile improvement on TiN-deposited metal layer
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Over the past several years, there have been many publications concerning the sensitivity of chemically amplified (CA) resist to substrate contamination. Resist footing phenomena are found on SiN, BPSG, TiN...etc stack films. Many approaches, such as varying the film thickness, oxide deposition, etc., have been proposed to solve this problem, with the sacrifice of increasing process complexity. In this study, we tried to improve DUV photoresist profile on TiN/AlSiCu/BPSG stacked layers. A positive tone CA resist was used and the improvement was carried out through both thin-film and lithography treatments. Since many process parameters were optimized, Taguchi design-of-experiment method was utilized to save processing cost, time and effort. The results turned out that passivation of TiN with hydrogen can improve resist footing better than either oxygen passivation or no treatment. However, the improvement was less significant than lithography process parameters. It is believed that since HMDS serves as an interlayer between TiN substrate and DUV resist, optimizing dehydration hot baking, post baking and post-exposure baking processes apparently has a more direct and significant impact on resist profile improvement than thin-film treatments. It is suggested that in this specific problem, the optimization of lithographic parameters can result in satisfactory resist profile.
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Chia-Hui Lin, Chun-Cho Chen, Jhy-Sayang Jenq, Maaike Op de Beeck, Luc Van den Hove, "DUV resist profile improvement on TiN-deposited metal layer", Proc. SPIE 2726, Optical Microlithography IX, (7 June 1996); doi: 10.1117/12.240968; https://doi.org/10.1117/12.240968

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