IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Plasma Science Thursday Sessions
       Session PS-ThP

Paper PS-ThP34
The Influence of Ar Flow Rate on Photoresist Selectivity in High Density Plasma Etching of SiO@sub2@

Thursday, November 1, 2001, 5:30 pm, Room 134/135

Session: Plasma Etching Poster Session
Presenter: E. Haikata, Lam Research Co., Ltd, Japan
Authors: E. Haikata, Lam Research Co., Ltd, Japan
S. Sasaki, Lam Research Co., Ltd, Japan
T. Yoshida, Lam Research Co., Ltd, Japan
K. Nojiri, Lam Research Co., Ltd, Japan
Correspondent: Click to Email
As dimension of LSI becomes smaller, higher photoresist selectivity to SiO@sub2@ is required in high-aspect-ratio contact hole etching, because photoresist mask becomes thinner to get enough resolution. Although C@sub4@F@sub8@/Ar/O@sub2@ gas chemistry is widely used for SiO@sub2@ etching, the influence of Ar flow rate on photoresist selectivity is not clear. This paper presents the influence of Ar flow rate on photoresist selectivity and etching profile along with the discussion on the basis of XPS and OES analysis. In the experiment, Ar flow rate was changed from 50 sccm to 500 sccm in Transformer Coupled Plasma Etcher, with C@sub4@F@sub8@/O@sub2@ flow rate kept constant. With increasing Ar flow rate, photoresist selectivity increased because the photoresist etch rate decreased drastically, while the SiO@sub2@ etch rate decreased only slightly. In contrast, at low Ar flow rate, photoresist selectivity dropped remarkably at small diameter holes due to RIE Lag, and etch stop was observed. XPS data showed that polymer deposited on the photoresist at high Ar flow rate contained more C-C and C-CF@subx@ chain, and it was more C rich. From OES results, C@sub2@/CF@sub2@ ratio increased as Ar flow rate increased. Since C radical has higher sticking coefficient than CF@sub2@ radical, C is thought to deposit at the upper part of the contact hole and photoresist surface, leading to higher selectivity because C rich polymer has high resistance to plasma attack.On the other hand, CF@sub2@ is thought to go into inside of the hole, causing etch stop at low Ar flow rate. We conclude that high Ar flow rate has advantage of wider etch stop margin and higher photoresist selectivity.