Jpn. J. Appl. Phys. 35 (1996) pp. 2488-2493  |Next Article|  |Table of Contents|
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Characterization of Highly Selective SiO₂/Si₃N₄ Etching of High-Aspect-Ratio Holes

Hisataka Hayashi, Kazuaki Kurihara and Makoto Sekine

(Received November 22, 1995; accepted for publication January 9, 1996)

The pattern size dependence of SiO₂ and Si₃N₄ etch rates of contact holes (RIE-lag) in C₄F₈+CO plasma was studied. It was found that these etch rates can be characterized by the aspect ratio, regardless of the pattern size. SiO₂ etch rate decreased with increasing aspect ratio and became 0 at an aspect ratio of 6. Si₃N₄ etch rate also decreased; however, etching still occurred at an aspect ratio of 30. From ion current measurements through capillary plates (CPs), it was deduced that etch rates decreased because of decreasing ion current. XPS analyses revealed that fluorocarbon film deposited on the Si₃N₄ surface at the bottom of a hole was more F-rich than that deposited on a flat Si₃N₄ surface. This explained why Si₃N₄ is etched even in high-aspect-ratio holes. A small amount of O₂ addition to the C₄F₈+CO plasma resolved the RIE-lag. It was found that the ion current density at high aspect ratio increased with O₂ addition, which would enhance SiO₂ etching and contribute to suppressing RIE-lag.

KEYWORDS: oxide etching, C₄F₈+CO plasma, RIE-lag
URL: http://jjap.ipap.jp/link?JJAP/35/2488/
DOI: 10.1143/JJAP.35.2488

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