Structure and properties of magnetron sputtered Zr-Si-N films with a high (≥25 at.%) Si content

The Zr-Si-N films were deposited using an unbalanced dc reactive magnetron sputtering of the alloyed ZrSi2 target in a mixture of argon and nitrogen onto steel and silicon substrates. This article reports on a systematic investigation of dependences of the structure, elemental composition, mechanical properties and oxidation resistance of Zr-Si-N films with a high (≥25 at.%) Si content on the partial pressure of nitrogen pN2, magnetron discharge current Id, total sputtering gas pressure pT, substrate temperature Ts and dc and pulsed substrate bias Us. It was demonstrated that (i) ZrSi2 films sputtered in (a) a pure argon (pN2=0) and (b) Zr-Si-N films sputtered at very low values of pN2≤0.03 Pa are crystalline, electrically conductive, optically opaque and exhibit a relatively high value of the microhardness H≈17-20 GPa; (ii) Zr-Si-N films sputtered at pN2≥0.1 Pa are X-ray amorphous, electrically insulating, optically transparent and exhibit (a) a high microhardness H of about 30 GPa and (b) a low compressive macrostress σ of about −1.2 GPa; (iii) an increase in the substrate temperature Ts from 300 to 750 °C has no effect on the structure and H of as-deposited films; the structure of the Zr-Si-N film sputtered at Ts=750 °C remains X-ray amorphous and its hardness H does not decrease with increasing Ts, i.e. it is approximately the same (≈30 GPa) as that of the film sputtered at Ts=500 °C; (iv) the Zr-Si-N films with high (≥25 at.%) Si content and high H≈30 GPa can be produced in the metallic mode of sputtering, i.e. they can be produced approximately four times faster than the binary nitrides such as, for instance, the TiN films; and (v) the Zr-Si-N films with a high (≥55 vol. %) content of the a-Si3N4 phase, composed of a mixture of a-Si3N4+ZrNx>1 phases, exhibit a high oxidation resistance in flowing air, greater than 1300 °C.