Fabrication of nickel and nickel carbide thin films by pulsed chemical vapor deposition
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Research Letter
Fabrication of nickel and nickel carbide thin films by pulsed chemical vapor deposition Qun Guo*, Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Beijing 102600, China Zheng Guo*, School of Advanced Materials, Shenzhen Graduate School, Peking University, Shenzhen 518055, China Jianmin Shi, Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621000, China Lijun Sang, Bo Gao, Qiang Chen and Zhongwei Liu, Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Beijing 102600, China Xinwei Wang, School of Advanced Materials, Shenzhen Graduate School, Peking University, Shenzhen 518055, China Address all correspondence to Zhongwei Liu and Xinwei Wang at [email protected]; [email protected] (Received 22 January 2018; accepted 12 February 2018)
Abstract We report a new pulsed chemical vapor deposition (PCVD) process to deposit nickel (Ni) and nickel carbide (Ni3Cx) thin films, using bis(1,4-ditert-butyl-1,3-diazabutadienyl)nickel(II) precursor and either H2 gas or H2 plasma as the coreactant, at a temperature from 140 to 250 °C. All the PCVD films are fairly pure with low levels of N and O impurities. The films deposited with H2 gas at ≤200 °C are faced centered cubic-phase Ni metal films with low C content; but at ≥220 °C, another phase of rhombohedral Ni3C is formed and the C content increases. However, when H2 plasma is used, the films are always in rhombohedral Ni3C phase for the entire temperature range.
Introduction Nickel (Ni) and nickel carbide (Ni3Cx) thin films have many important applications. For instance, Ni films have been used in ultra-large-scale integrated-circuit devices for preparing lowresistivity Ni-silicide contacts.[1,2] Ni films have also been used in many microelectromechanical systems (MEMS), such as micro-cantilevers and micromechanical switches.[3–5] Also, since Ni is an important element in catalysis, synthesizing Ni and its compounds as thin films are also of great importance for catalysis applications.[6,7] Common fabrication methods for Ni and Ni3Cx thin films include physical vapor deposition (PVD), chemical vapor deposition (CVD), and atomic layer deposition (ALD). PVD is capable of fabricating high-purity films, but the step coverage of the PVD films is rather poor, which could largely limit its applications to conformal film coatings on non-flat trench or hole structures. CVD and ALD are generally better for film step coverage.[8,9] In particular, ALD is known for depositing films with high uniformity and conformality on high-aspectratio complex structures[9–15]; however, the deposition rate of ALD is comparatively slow. CVD is generally faster than ALD in the deposition rate, but the film quality relies very much on the control of the CVD parameters (e.g., gas flow control).[8] Normally, CVD processes are run in a continuous deposition mode, where the metal precursor vapor and the coreactant gas (if needed) are continuously and simultaneously * Q.G. and Z.G. contributed
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