Cu films by partially ionized beam deposition for ultra large scale integration metallization
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Cu films by partially ionized beam deposition for ultra large scale integration metallization Ki-Hwan Kim,a) Hong-Gui Jang, Sung Han, Hyung-Jin Jung, and Seok-Keun Koh Thin Film Technology Research Center, Korea Institute of Science and Technology, P.O. Box 131, Cheonryang, Seoul 130-650, Korea
Doo-Jin Choi Department of Ceramic Engineering, Yonsei University, Seoul 120-794, Korea (Received 10 August 1996; accepted 11 April 1997)
˚ were prepared on Si(100) Highly (111) oriented Cu films with a thickness around 1800 A at room temperature by partially ionized beam deposition (PIBD) at pressure of 8 3 1027 –1 3 1026 Torr. Effects of acceleration voltage (Va ) between 0 and 4 kV on such properties as crystallinity, surface roughness, resistivity, etc. of the films have been investigated. The Cu films deposited by PIBD had only (111) and (200) planes, and the relative intensity ratio, I(111)yI(200) of the Cu films increased from 6.8 at Va 0 kV to 37 at Va 4 kV. There was no indication of impurities in the system from Auger electron spectroscopy (AES) analyses. A large increase in grain size of the films occurred with Va up to Va 1 kV, but little increase occurred with Va . 1 kV. Surface roughness of the Cu films decreased with Va , and resistivity showed the same trends as that of the surface roughness. In the Cu films by PIBD, it is considered that changes of resistivity are mainly due to a surface scattering rather than a grain boundary scattering. The via holes, dimensions of which are 0.5 mm in diameter and 1.5 mm in depth, in the Cu films made at Va 4 kV were completely filled without voids. Interface adhesion of the Cu film on Si(100) deposited at Va 3 kV was five times greater than that of Cu film deposited at Va 0 kV, as determined by a scratch test.
I. INTRODUCTION
Metallization of future ultra large scale integration (ULSI) devices requires downward scaling of their dimensions. Current use of Al and its alloys has limitations in resistivity for applications with shrinked dimensions.1 Furthermore, Al and its alloys are susceptible to electromigration and stress failures. Cu is a promising material for interconnects in ULSI devices because of low bulk resistivity. In addition, Cu has high resistance to electromigration compared with Al and its alloys.23 Recently, much research on Cu metallization has been conducted using various deposition techniques such as metal-organic chemical vapor deposition (MOCVD),4 sputtering,5 electroless deposition,6 etc. In order to apply Cu to metallization on ULSI devices, it is important to fabricate Cu films, as the interconnects in submicron patterns, that possess high conductivity, smooth surface, good adhesion to substrate, and excellent via hole filling capability.7 Partially ionized beam deposition (PIBD) used for preparing metal thin films has many advantages such as near-bulk resistivity, good adhesion to substrates, thermal stability, and a)
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