Thermal‐ and Plasma‐Enhanced Copper Film Deposition via a Combined Synthesis‐Transport CVD Technique

Abstract

Metallic copper thin layers are deposited by means of a modified metal-organic (MO)CVD method via passing formic acid vapor through a finely dispersed powder of a solid metal-containing reactant (Cu/CuO) under thermal and plasma activation. To characterize the copper layers obtained, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and UVvis spectroscopy, scanning electron microscopy (SEM), diffraction of synchrotron radiation (DSR) analyses, and laser interferometry, are used. The layers are found to be crystalline with a nanometer-scale grain structure, the parameters of which depend on the experimental conditions and chemical composition, with a predominant content of copper in the metallic state, Cu 0 . It is revealed that the plasma activation causes a decrease in the mean size of copper grains, as well as film thickness. Average growth rates inherent in the films obtained under thermal and plasma conditions are calculated. Based on studying the composition of a gas-phase copper complex synthesized, a schematic diagram of chemical conversion is suggested for the combined synthesis-transport process (CST).

Precise Control of Nanoscale Cu Etching via Gas-Phase Oxidation and Chemical Complexation

“…Specifically, gas-phase formic acid (HCOOH) is used here to demonstrate its capability to react preferentially with Cu oxide over Cu metal at a relatively mild temperature (80 °C). Although HCOOH has been utilized as a reducing agent for CVD and ALD of Cu, − the mechanism that leads to etching is believed to be via acid–base reaction between HCOOH and Cu oxide, resulting in the formation of gaseous neutralization products, namely, water vapor (H 2 O­(g)) and Cu­(II)-formato complexes. Decomposition of HCOOH on Cu and Cu oxide, which generally only occurs at temperatures greater than 180 °C, simply reduces the oxide back to its metallic form and does not lead to etching. , Leveraging the above-mentioned etching selectivity for the oxide, we have developed a two-step cyclic process, consisting of: (1) oxidation via exposure to O 2 plasma to form a surface copper-oxide layer and (2) selective removal of the oxide layer via etching with HCOOH vapor, leaving a pristine metal Cu surface behind.…”

Epitaxial Growth of Copper Film by MOCVD

“…The crystal is becoming more complete due to the fact that high temperature facilitate the growth of crystal and the temperature region is more suitable for crystal growth. Compared to Copper film on Mica [8], our films have smoother surface. Consequently, the surface structure will be suitable for graphene growth.…”