Comparison of Amorphous and Polycrystalline Tungsten Nitride Diffusion Barrier for MOCVD-Cu Metallization
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CHUL SOON KWON*, DONG JOON KIM**, CHANG WOO LEE, YONG TAE KIM****, AND IN-HOON CHOI*** Semiconductor Materials Laboratory, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul, Korea * Micro Process Development, Samsung Electronics, 82-3, Dodang-Dong, Wonmi-Ku, Buchun, Kyunggi-Do, 421-130, Korea ** Department of Metallurgical Eng., Hanyang Univ., 17, Haengdang-Dong, Sungdong-Ku, Seoul, 133-791, Korea *** Department of Material Science, Korea Univ., 5-1, Anam-Dong, Sungbuk-Ku, Seoul 136701, Korea
ABSTRACT An amorphized tungsten nitride diffusion barrier is compared with that of polycrystalline tungsten nitride preventing the diffusion of copper into Si during post annealing processes at 600 - 800 'C for 30 min. Experimental evidence such as RBS, TEM, XRD measurements shows that the amorphized tungsten nitride layer perfectly blocks the expeditious diffusion of the Cu film due to the amorphous grain boundaries stuffed with N impurities. INTRODUCTION Copper (Cu) thin films are now intensively studied as a promising interconnection material
in ultra large scale integrated circuit (ULSI) metallization schemes because of the lower electrical resistivity and a higher resistance to electromigration [1]. However, the practical application of Cu metallization needs effective solutions for several problems; one of the key problems is to find a good diffusion barrier because Cu is expeditiously mobile in metals as well as in silicon. Cu can destroy shallow junction and contact during subsequent thermal treatments and Cu atoms act as electrically active defects in the bandgap. Therefore, diffusion barrier materials such as sputtered TiN, TiW, TaN and W-N have been studied to establish a thermally stable Cu contact system [2-3]. However, these diffusion barriers were inadequate in preventing Cu diffusion into Si because their thermal stabilities were low at temperature of 400 - 600 °C. Our work has been based on the fact that plasma enhanced chemical vapor deposited tungsten nitride (PECVD-Wl 00o xNx) thin film could be an effective diffusion barrier between the Si substrate and several metals such as Al, Au and Pt showing excellent thermal stability up to 800 - 850 °C [4-6]. Therefore, in this work, we have investigated the comparison of a new amorphized tungsten film which is implanted with N atoms and the conventional polycrystalline tungsten nitride after depositing Cu film on these amorphized and polycrystalline tungsten nitride diffusion barriers. *
To whom all correspondence should be addressed 441 Mat. Res. Soc. Symp. Proc. Vol. 355 01995 Materials Research Society
EXPERIMENTALS Phosphorus-doped (100) oriented Si wafers with resistivities of 5 - 6 0-cm were used as starting substrates. Si wafers were cleaned by the RCA method and spin dried. 500 A poly WooxN, films were deposited on the Si substrate in a home made parallel type cold wall PECVD reactor by using the gas flow ratio of WF 6/NH 3/H 2 fixed at 2/1/50. The total pressure in the CVD reactor was maintained at 0.5 Torr by controlling th
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