Narrow and Thin Copper Linear Pattern Deposited by Vacuum Cold Spraying and Deposition Behavior Simulation

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Narrow and Thin Copper Linear Pattern Deposited by Vacuum Cold Spraying and Deposition Behavior Simulation Kai Ma1 • Chang-Jiu Li1 • Cheng-Xin Li1

Submitted: 15 April 2020 / in revised form: 21 August 2020 / Accepted: 13 September 2020 Ó ASM International 2020

Abstract Compared with ceramic materials, the fabrication of dense metal films requires higher impact velocity in vacuum cold spraying (VCS), also known as aerosol deposition method. In this study, a supersonic nozzle for the fabrication of dense, thin and narrow copper lines was designed. The acceleration behavior of gas and copper particles was investigated through CFD numerical simulation. And the impact behavior of copper particles was studied through finite element analysis. The copper lines with the width of about 200 lm and the height of about 4 lm were directly fabricated on silicon wafers at room temperature without masking. The results show that there is an optimum particle diameter for the impact velocity in particle collision deposition systems. In order to obtain a higher particle impact velocity in VCS, the substrate should be placed behind the high-pressure region of gas shock wave, so that the position of the high-pressure region of the free jet and the position of the bow shock with the substrate coincide as much as possible. Copper particles undergo plastic deformation and particle flattening upon impact and subsequent particle compaction. The width of copper line increased with increasing standoff distance, and maximum height decreased with increasing standoff distance. Keywords aerosol deposition (AD)  copper  deposition behavior  metal films  vacuum cold spraying (VCS)

& Cheng-Xin Li [email protected] 1

State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, Shaanxi Province, People’s Republic of China

Introduction With the rapid development of micro-electromechanical systems (MEMS), micro–nano-device manufacturing has attracted more and more attention. Copper, silver and other metals are often used for the electrical and heat dissipating parts of electronic devices because of their excellent electrical and thermal conductivity. Because some circuits are often used in harsh environmental conditions, such as vibration and high temperature, the materials used for conductive and thermally conductive components not only have good electrical and thermal conductivity, but also have high strength and heat resistance. In addition, environmental protection is gaining more and more attention, and it is necessary to find high-efficiency, low-cost and environmentally friendly metallization processes. The traditional methods used to prepare copper thin films include rolling, electroplating (Ref 1), magnetron sputtering (Ref 2) and chemical vapor deposition (Ref 3). It is difficult for the rolling process to prepare metal thin films under 10 microns. Electroplating has serious environmental pollution. Magnetron sputtering and chemical vapor d