The deposition rate has a great influence on the performance of the TiN film. The film prepared at a high deposition rate is denser with good hardness and bonding strength, while the thin film prepared at a lower deposition rate is looser. Deposition rate and arc source current have a great relationship, Researches had shown that the deposition rate of TiN film is proportional to the cathode current density, and its calculation formula is:
R = Jm/eρ
In the formula, R—deposition rate of thin film; J—cathode current density; m—molecular weight of TiN; e—electron charge; ρ—theoretical density of TiN
Figure 4 is a variation diagram of film thickness with the change of arc source current measured by scanning electron microscopy in this study. It can be seen that as the arc source current increases, the deposition rate and the thickness of the TiN film layer increases, which is in complete agreement with the formula. When the arc source current is 40 A, the deposition rate is very low, and the TiN film deposition rate is 625nm/h. When the arc source current is increased to 100 A, the TiN film deposition rate reaches 1857nm/h under the same conditions.
Fig. 4 The thickness of TiN film changes with arc source current
Fig. 5 Vacuum chamber temperature changes with arc source current
In addition, if the arc source current increases, both the target surface temperature and the vacuum chamber temperature will increase (Figure 5). On the one hand, there are more Ti evaporating from the target, so more Ti particles will ionize and interact with the ionized N to form the TiN film. On the other hand, in the substrate (sample) surface, due to the temperature increase, the particle diffusion process is easier, so the film deposition rate is accelerated. At the same time, due to the increase in the temperature of the vacuum chamber, from the perspective of chemical reaction, Ti and N are more likely to combine into TiN, and thus a large amount of N ions are reacted, resulting in an increase in the vacuum degree of the vacuum chamber, in a sparse plasma, The hindrance of the particles to the surface of the substrate is weakened, and more particles reach the surface of the substrate (sample) and deposit into a film, thereby the deposition rate is increased.