Ž . Thin Solid Films 324 1998 292–299 Water-induced degradation of chromium fluoride films Eunah Kim a, ) , Seungbum Hong a , John David Gorman b , Sungchul Lim c , Seong-Yong Moon a , Dae-Weon Kim a , Kwangsoo No a a Department of Materials Science and Engineering, Korea AdÕanced Institute of Science and Technology, Taejon, South Korea b Department of Applied Physics, Royal Melbourne Institute of Technology, GPO BOX 2476V, Melbourne, Victoria 3001, Australia c Samsung Electronics, Yongin-city, Kyongki-do, South Korea Received 19 August 1997; accepted 14 November 1997 Abstract As an optical film, chromium fluoride is an important material because it has good transparency in short wavelength region. However, it was found that chromium fluoride film degrades at humid condition. Therefore, we investigated the degradation phenomena of chromium fluoride films under 100% humid condition. The degraded samples were analyzed by several thin film analyzing techniques. With these results, we proposed a possible degradation mechanism consisting of multi-step reactions. First, H O molecules are permitted 2 to the porous structure in the films to percolate through numerous microchannels and microvoids. Then, the water molecules react with the chromium fluoride film to make hydroxide bonding producing HF gas. HF gas evolves and gathers at some spots, and dome structure was developed. Chromium oxide precipitates around HF gas gathered dome. After time passes, HF gas evolution occurs followed by explosion of the dome structure, and crater-like feature remains as a result around the dome. It was found that the chromium oxide ring is left around the feature. In the whole process, cracking also occurred due to the molecular volume difference between CrF and degraded x part. q 1998 Elsevier Science S.A. All rights reserved. Keywords: Chromium fluoride; Rutherford backscattering spectroscopy; X-ray photoelectron spectroscopy 1. Introduction Chromium fluoride film has been noticed in optical applications because it has excellent transparency in short Ž . wavelength Deep-UV region. Especially, there has been much research to investigate chromium fluoride as an Ž attenuated phase shifting mask material Phase shifting mask will be inserted below the exposure system and will shift incoming light’s phase to make destructive interfer- ence with the initial light, which can increase the resolu- . tion , which will play a great role in future semiconductor wx industry 1. Although chromium fluoride has suitable optical property as a PSM material for Deep-UV applica- tion, it was found that the film degrades at humid condi- tion. This phenomenon puts severe restriction on the appli- cation of chromium fluoride films to the optical films. In this paper, we tried to explain the degradation mech- anism investigating the properties of the degraded samples ) Corresponding author. and the nondegraded samples fabricated by a DC mag- netron sputtering system. Degradation condition of the films was controlled artificially to investigate the phe- nomenon quantitatively. The degraded samples were ana- Ž . lyzed by FTIR Fourier Transform Infrared spectrometer, Ž . Ž RBS Rutherford Backscattering Spectroscopy , XPS X- . Ž ray Photoelectron Spectroscopy , WDS Wavelength-dis- . Ž persive Spectrometer , and AES Auger Electron Spec- . troscopy . Also, we observed the morphology by SEM Ž . Scanning Electron Microscopy and optical microscope. 2. Experimental procedure 2.1. Apparatus The apparatus used for the deposition of CrF films is a x DC magnetron sputtering system, which consists of vac- uum system, sputtering target, DC power supply, substrate holder system and gas injection system. The schematic diagram of the magnetron sputtering system is shown in Fig. 1. In this study, we used two gas rings and stainless 0040-6090r98r$19.00 q 1998 Elsevier Science S.A. All rights reserved.