Electrical and colorimetric properties of TiN thin films prepared by DC reactive sputtering in a facing targets sputtering (FTS) system

The aims of the present work are twofold: first, to confirm the condition for obtaining gold-yellow TiN films without bias application; second, to examine the quantitative relationship between the colorimetric properties and electrical resistivity of these films. For the first aim, TiN films were prepared by DC reactive sputtering under a no-bias condition in the facing targets sputtering (FTS) apparatus, in which discharge is maintained even at a low gas pressure of less than 0.3Pa. For the second aim, the color of the films was evaluated by means of the chromaticity coordinates, x and y, and the luminance factor Y, which is an index of the brightness based on a CIE standard colorimetric system. Gold-yellow TiN films having low resistivity were obtained, and a study of their electrical and colorimetric properties has provided the following conclusions. (i) The colorimetry of the films is affected by both the mixing ratio and total gas pressure. In particular, the brightness (the luminance factor) Y varied greatly with a change in total gas pressure. (ii) Even without bias application, a gold-colored TiN film with higher brightness Y has been obtained by deposition at an appropriate mixing ratio of N₂/Ar and also under lower total gas pressure (ρ=0.31μΩm and Y=49 for the films deposited at 0.15Pa). (iii) As the total gas pressure was increased, the column size, the surface roughness and oxygen content showed a clear increase. Thus, the films deposited under an atmosphere higher than 0.15Pa had higher resistivity and lower brightness. (iv) Based on our results, the quantitative relationship between the resistivity and brightness of the TiN films is shown by the relation of ρ=775Y^-2.