Using Electron Cyclotron Resonance Plasma for Depositing Epitaxial Titanium Nitride Thin Films
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Piscataway,
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murzin@aol .comn *Electrotechnical Laboratory, Applied Radiation Physics Section, 1-1-4 Umezono, Tsukuba, Ibaraki, 305 Japan
ABSTRACT We have employed a 2.45 GI-z electron cyclotron resonance (ECR) plasma source to deposit single-crystal thin films of titanium nitride onto MgO substrates of (100) orientation. During deposition the ECR plasma beam delivering a mixture of excited species of molecular and atomic nitrogen ions, strikes a substrate while an electron beam deposits on the same substrate species of titanium. We have studied the formation of films at substrate temperatures of 200, 400, and 600°C, as well as at room temperature. X-Ray diffraction (XRD) revealed that a cubic B 1 phase of titanium nitride forms predominantly at all the temperatures explored. Both channeling and Rutherford hackscattering spectroscopy (RBS) showed epitaxial layers forming at the temperature as low as 400°C. The minimum relative backscattering yield, y•,, decreased as the temperature increased, with the best result of 7.3% obtained for the film deposited at 600°C. Biasing the substrates with either negative or positive voltage at room temperature directly affects film crystallography. INTRODUCTION Deposition of epitaxial thin films for various micro- and optoelectronics devices is well known and widely established method [1]. Molecular beam epitaxy (MBE), metal-organic chemical vapor deposition (MOCVD) and other techniques have been used extensively to grow epitaxial layers at relatively high temperatures to achieve sufficient films quality [1]. Recently, several groups of researchers have reported using electron cyclotron resonance plasma in combination with traditional methods mentioned above to promote high-quality layers growth [28]. These efforts are based on such advantageous ECR features as high plasma density generation at relatively low gas pressures of 10- Pa, low energy and highly reactive plasma constituents [2]. Cho et al. studied the effects of growth temperature, nitrogen pressure, Ga cell temperature and substrate surface nitridation on crystal quality of GaN epilayers deposited with ECR MBE [3]. They reported the formation of fiat and smooth surfaces at the growth temperature of 750°C at the growth rate of 0.5 urn/h.. Ono et al. have developed an ECR plasma deposition apparatus with a sputtering capability [4]. They obtained a thickness uniformity of___5% over a 6" diameter wafers for deposition of polycrystalline TiN and Al layers at the substrate temperature of 3003 50°C. Okano et al. investigated the effect of such ECR parameters as plasma energy and power on the crystalline orientation of"AN films deposited onto the a-SiN/(l 10) Si substrates hold at 600°C [5]. The current area of interest is an application of ECR-assisted technology to growing metal or metal compound thin films. Titanium nitride is known as very hard, corrosion and erosion 527
Mat. Res. Soc. Symp. Proc. Vol. 396 © 1996 Materials Research Society
resistant, relatively inert material, which is often used as
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