Zero Temperature Coefficient of Resistance Bi-Film Resistor.
DEPARTMENT OF THE NAVY WASHINGTON D C
Pagination or Media Count:
A first thin-film resistor member, preferably TaN, is disposed over a second thin film member, such as NiCr, to completely cover the second member and act as a passivating layer preventing anodization of the second. The thin-film materials used for the first and second members have substantially an equal thin-film, sheet-resistance, resistance value per square ohm, with the first material being trimmable for this purpose. Also, the TCR temperature coefficient of expansion of the first material is negative while that of the second is positive. These members are coupled in parallel with substantially equal lengths but with differing widths which permit the first to completely cover the second. The arrangement permits the TCR of the parallel circuit to be brought substantially to a zero value and, in any event, a value no greater than or - 50 ppmC. Additionally, the first member anodically protects the second with the protection being assured by the formation of an oxide film formed on the first by the trimming. The bi-film system is adapted for microcircuitry in that it provides an acceptable sheet resistance without requiring excessive lengths or widths of the parallel circuit members. Author
- Electrical and Electronic Equipment