Observation of Microscopic Nonuniformity during Overetch in Polysilicon Gate Etching

概要

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Microscopic uniformity during overetch has been investigated for polysilicon gate etching in electron cyclotron resonance C1_2 /0_2 plasmas, using atomic force microscopy as well as scanning electron microscopy. As the 0_2 percentage was increased in C1_2 /0_2 plasmas, the aspect-ratio dependence of the poly-Si etch rate changed from a weak reactive-ion-etching (RIE) lag to a slightly inverse RIE lag; on the other hand, the aspect-ratio dependence of the Si0_2 etch rate exhibited a strongly inverse RIE lag at high 0_2 percentages. As a result, the microscopic etchselectivity of poly-Si over Si0_2 was considerably degraded with increasing aspect ratio, giving rise to gate oxides broken in large aspect-ratio features during overetch. These results are indicative of the transport of incoming oxygen atoms in microstructures limited by neutral shadowing.
社団法人応用物理学会の論文
1997-04-15