The effects of chlorine content on the properties of titanium carbonitride thin film deposited by plasma assisted chemical vapor deposition

Abstract

Wear resistant titanium carbonitride (TiCxNy) films were deposited onto high speed steel (AISI M2) by plasma assisted chemical vapor deposition using the gaseous mixture of TiCl4, CH4, N2, H2, and Ar. The effects of deposition conditions on the deposition rate and residual chlorine content were investigated. The influences of the chlorine on the crystallinity, microstructure, and mechanical properties of coatings were also studied. It was found that the residual chlorine content in the films greatly varied with the deposition conditions. Subsequently the crystallinity of the TiCxNy films deteriorated with the increase in the chlorine content. The microhardness and adhesion strength also decreased with the chlorine content. However, in spite of the low residual chlorine content, TiCxNy film deposited at high radio-frequency power shows inferior mechanical properties due to the micropore network structure.

Atom Probe Tomography investigations on grain boundary segregation in polycrystalline Ti(C,N) and Zr(C,N) CVD coatings

“…In this study, Table 1 shows that there is nearly no solubility of Cl in Ti(C,N) (as the concentration is estimated about 200 ppm inside the grain) and the chlorine is rather segregated at the GBs up to 2.2 at.%. Additionally, Ti(C,N) has a finer grain size than Zr(C,N) [3] which is consistent with the role of chlorine in refinement of the microstructure [6,10,23]. Then, it is suggested that chlorine acts as an impurity, which is adsorbed on the crystal facets during film growth and segregates, yielding finally smaller grain sizes.…”

“…In this study, deposition of Zr(C,N) is conducted at 45°C higher than Ti(C,N) since ZrCl 4 is more stable than TiCl 4 and requires higher activation energy to reach similar deposition rate as for the Ti(C,N). Therefore, it is suggested that the absence of chlorine segregation in the Zr(C,N) and its lower concentration inside the grain is due to higher temperature deposition, along with the lower metal chloride partial pressure [6], which is in this study two times lower for Zr(C,N) compared to Ti(C,N). All APT specimens obtained for this study showed consistent results with no Cl segregation at the GB of Zr (C,N).…”

“…One plausible cause for such distinct behavior could be segregation of impurities at interfaces. For low temperature CVD processes, chlorine contamination is a concern [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] , which stems from the widely used metal chloride as a precursor in CVD reactions (e.g. TiCl 4 is the most widely used inorganic precursor employed in the CVD of titanium-containing materials (TiN, TiC, TiO 2 , Ti(C,N)) [22]).…”

“…Chlorine contamination related to CVD processes, using metal chloride precursors, is well known and documented for Low Temperature (LT) CVD processes; like Plasma Assisted (PA) [4][5][6][7][8][9][10][11][12][13]23,34] and Low Pressure (LP) CVD [12,[14][15][16][17][18][19][20][21]. However, its effects on MT-CVD process are underestimated or overlooked, given that chlorine content decreases considerably with higher temperatures and at MT-CVD temperature deposition range (700~950°C) the Cl concentration is very low.…”

“…For Ti(C,N) PA-CVD, Kim et al has shown that the chlorine content decreased largely with an increase of the temperature [6], and generally there is a consensus that the main parameter controlling the chlorine contamination in LT-CVD processes using metal chloride is the temperature [5,6,10,[13][14][15][16][17]20,21,23,34]. Some authors even controlled the chlorine contamination by changing only the temperature, while keeping the other parameters constant [13,23,34].…”