Electrical resistivity and luminous reflectance of TiN films prepared by D.C. reactive sputtering

We have already reported that the conditions for obtaining gold-yellow TiN films by reactive sputtering method without bias application. It is well known that the qualitative relationship between the color and the electrical resistivity of TiN films such as `the golden yellow TiN films have low resistivity'. However the reason for this relationship is not clear. The purposes of the present work are to investigate the quantitative relationship between the calorimetric properties and electrical resistivity of these films and to examine the cause for these properties. For these purposes, the color of the films was evaluated by means of the chromaticity coordinates, x and y, and the stimulus value or luminous reflectance, Y, which is an index of the brightness based on a CIE standard calorimetric system. TiN films having several kinds of properties were obtained, and a study of their electrical and calorimetric properties has provided the following conclusions: (i) The colorimetry of the films is affected by both the mixing ratio of Ar/N₂ gas and the total gas pressure. Particularly, the luminous reflectance, Y, varied greatly with a change in total gas pressure of Ar and N₂ gas. (ii) Even without bias application, a gold-colored TiN film with higher reflectance, Y, has been obtained by deposition at an appropriate mixing ratio of N₂/Ar and also under lower total gas pressure, namely, ρ = 0.31 μΩm and Y = 49% for the films deposited at 0.15 Pa. (iii) As the total gas pressure was increased, the column size, the surface roughness and oxygen content clearly showed an increase. Thus, the films deposited under an atmosphere higher than 0.15 Pa had higher resistivity and lower reflectance. (iv) Based on our results, the quantitative relationship between the resistivity, ρ, and the luminous reflectance, Y, of the TiN films is shown by the representation of ρ = 775 Y^-2.