Surface Properties of Low-k Hybrid-Organic-Siloxane-Polymer (HOSP) Films Etched with Ions of Different Incident Angles i
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Surface Properties of Low-k Hybrid-Organic-Siloxane-Polymer (HOSP) Films Etched with Ions of Different Incident Angles in CHF3 Plasma Sung-Wook Hwang, Gyeo-Re Lee, Jae-Ho Min, Sang Heup Moon*, Yu Chang Kim1, Hyun-Kyu Ryu1, Yun Seok Cho1, and Jin Woong Kim1 School of Chemical Engineering and Institute of Chemical Processes, Seoul National University, San 56-1, Shillim-dong, Kwanak-ku, Seoul 151-744, Korea 1 Memory R&D Division, Hynix Semiconductor Inc., Ichon P.O. Box 1010, Ichon-si, Kyoungkido 467-701, Korea ABSTRACT Hydrido-organo-siloxane-polymer (HOSP), a typical silsesquioxane-based low dielectric constant material, was etched with ions of different incident angles in CHF3 plasma. The etch rate normalized to the rate obtained with ions incident perpendicular to the surface deviated from the general cosine dependence on the ion incident angle. That is, the rate deviated to over-cosine values at low ion angles below 70o, due to the physical sputtering of the surface by energetic ions, and to under-cosine values at high angles, above 70o, due to the redeposition of particles emitted from the bottom. The roughness of the etched surface also varied with the ion incident angle as a result of the surface etching by energetic ions and the redeposition of particles emitted from the bottom. For example, when the bias voltage was –100V, the surface roughness was different according to three angle regions: i) ion bombardment dominant region below 70o, ii) intermediate region between 70o and 85o, and iii) redeposition dominant region above 85o. The surface composition and chemical structure after etching were also affected by the ion incident angle. The F/C atomic in the surface layer was much lower at ion angles higher than 70o than below 70o because cage-like Si-O bonds were more rapidly dissociated by F atoms from fluorocarbon polymer layer than network Si-O bonds at high angles. This information obtained in this study is useful for predicting the profile and surface characteristics of interconnection patterns in microelectronics fabrication.
INTRODUCTION Hydrido-organo-siloxane-polymer (HOSP) is one of the promising candidates for intermetal dielectric (IMD) due to its low dielectric constants, thermal stability, gap filling ability, and process compatibility with silicon dioxide. However, it is reported that properties of HOSP film are considerably affected by plasma during etching process [1-3] because sidewalls in patterns, such as trench, via, and contact hole, are continually exposed to plasma. However, studies about the change of HOSP film properties in plasma etching are mostly focused on films processed with ions incident perpendicular to the surface. In this study, we etched HOSP film with ions of different incident angles in CHF3 plasma and analyzed properties, such as roughness and the chemical composition, of the etched surface using atomic force microscopy, Auger electron spectroscopy, and infrared spectroscopy. Information about the angular dependence of the surface properties will allow us to predict *
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