Electron Beam Induced Carbon Depositionand Etching
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ELECTRON BEAM INDUCED CARBON DEPOSITION AND ETCHING Y.-M. Sun, J. Eklund, Q. Wang, D. Gay and J. M. White Center for Materials Chemistry, Texas Materials Institute, University of Texas at Austin, Austin, TX 78712, USA
ABSTRACT Electron induced carbon deposition and etching was investigated by Auger electron spectroscopy in a custom designed vacuum system. The Auger electron spectrometer was used to provide a high flux electron beam to induce reactions and to monitor surface composition. During the e-beam induced deposition or etching, the gas phase pressure was 10-4 to 10-5 Torr. Several carbon precursors: benzene, cyclohexane and propane were used for deposition. The deposition rate depended on the precursor sticking coefficient and bonding structure. Among the three precursors tested, the deposition rate of carbon was cyclohexane > benzene > propane. The e-beam induced etching of carbon films was carried out in 1 x 10-4 torr oxygen ambient and the carbon film was prepared by reactive physical vapor deposition. The etching process can be divided into three stages: bulk film, interface, and substrate. For the bulk carbon film, the decrease of film thickness varies linearly with the e-beam flux, while at the interface, the film thickness shows an exponential decay with the electron flux. For the C in the Si substrate, a very slow etching rate was observed. The etching rate for bulk carbon film was ~ 0.1 nm/min under the experimental conditions, which is equivalent tp 2.4 x 10-27 cm3/electron. At the interfacial region, the cross section of carbon removal by electrons was ~ 4.6 x 10-21 cm2. Based on the change of the carbon line shape at the interface, we concluded that the etching rate is related to the chemical nature of the carbon species.
INTRODUCTION Electron induced thin film deposition has been reported using a scanning electron microscope as an electron source [1-3]. The unique feature of electron assisted deposition and etching is its high spatial resolution, because the electron beam can be focused to a very small size. In addition, electrons provide the energy for all surface reactions, and the growth or etching can be done at a lower temperature, compared to thermal methods. It has the capability to deposit or remove a small dot or dot array by computerized electron beam control. These advantages make it a very attractive and prospective technology for nano-science and microelectronics. Studies for e-beam induced carbon deposition using an electron microscope have been reported [4]. For these studies, the vacuum is usually in the 10-6 Torr region and residual gas was used as a carbon source. However, the lack of surface sensitive analytical capabilities of the scanning electron microscope makes it difficult to study the reaction process and mechanism. We have built a system for studying electron-induced surface reactions at pressures up to 10-4 Torr [5]. It uses the electron source of a single pass cylindrical mirror electron energy analyzer to both stimulate surface reactions and to analyze, by
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