Influence of Deposition and Processing Parameters on the TCR of Ni-Cr-Cu-Al ALloy Film Resistors

This paper concerns vacuum-deposited resistive films for possible use in circuits that require low-temperature-coefficient components. Films were deposited by both ordinary and "flash" techniques from an alloy of Ni, Cr, Cu, and Al with a bulk TCR of ±5 ppm/°C. The nonflash experiments showed that the film TCR's varied from + 250 ppm/°C for a film Ni/Cr ratio of 1.3 to +20 ppm/ °C for a ratio of 3.4. Films deposited onto borosilicate glass were more stable than those deposited onto soda-lime glass. The composition for the nonflash films was not as reproducible as that for the flash-deposited films. The latter were characterized by negative TCR's for resistances higher than 100Ω/ᵇ. The flash technique was of the particle-by-particle type that resulted in films having appreciable amounts of entrapped gases. Vacuum baking of these gas-laden films decreased the values of resistance and the absolute values of TCR.