Characteristics of Molybdenum Nitride Thin Film by N 2 + Ion Implantation
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OF MOLYBDENUM
NITRIDE THIN FILM BY N2 . ION
DONG JOON KIM", IK-SOO KIM', YONG TAE KIM' AND JONG-WAN PARK' 'Semiconductor Materials Laboratory, Korea Institute of Science and Technology, P.O.Box 131, Cheongryang, Seoul, Korea "Dept. of Metallurgical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-ku, Seoul, 133-791, Korea
ABSTRACT Molybdenum nitride thin films were prepared by N2' implantation with acceleration energy of 20 keV and the ion dose of 3x10 17 ions/cm 2. The structural property and thermal stability of the films were investigated by XRD, AES, AFM and RBS. The crystal structure of N2+ implanted molybdenum thin films (Mo-N 2+)which had microcrystalline state was transformed to y-Mo 2N phase with a preferred (111) orientation after a post-annealing at 500 'C for 30min. However, a silicide reaction was not observed even after the annealing at 700 'C, which is due to the modification of the interface between Mo thin film and Si substrate by N2' implantation. Also, Cu diffusion did not seem to be induced by the annealing at 700 'C for 30 min. The internal stress of the Mo-N 2+thin films during post-annealing at 600 'C for 30min was found to change from highly compressive stress to low tensile stress. INTRODUCTION Transition metal nitrides of group 4b, group 5b and group 6b elements have been widely studied because of their chemical stability and thermal stability. One of them, molybdenum nitride thin films have been investigated as a diffusion barrier for copper metallization as well as materials for hard coating, superconductor and aluminum diffusion barrier.[1-5] However, Cu atom has a fast diffusion along grain boundaries of diffusion barriers even at low temperatures, which is deleterious to device operation. Therefore, it is necessary to develop a diffusion barrier which is free from grain boundary diffusion of Cu atom. Recently, amorphous and microcrystalline diffusion barriers have been studied to solve these problems. One of the methods to form an amorphous or microcrytalline structure was to form a disordered structure by physical and mechanical damage such as implantation. This technique is known to be easy not only to modify the physical and mechanical properties of materials but also to control precisely impurity concentration and penetration depth.[6] Thus, in this work, Mo thin films without any chemical reaction with Cu were prepared by sputtering and amorphized by injecting N 2+ ions into the films. And their physical properties and thermal stability against Cu were investigated to evaluate the eligibility of the films for application as a diffusion barrier layer for Cu meatallization. EXPERIMENT P-type wafers were used as starting materials of which orientation and resistivity were (100) and 5-10 Qcm, respectively. Molybdenum thin films of about 65nm in thickness were deposited on Si substrates by dc magnetron sputtering using Mo metal target of 4 inch in diameter. The 45 Mat. Res. Soc. Symp. Proc. Vol. 563 c 1999 Materials Research Society
sputtering chamber was evacuated t
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