Silicide resistors for integrated circuits

Thin-film resistors are useful in monolithic integrated circuits whenever high sheet resistance (ρ
s
> 1 kΩ/sq) or radiation hardness are required. Silicide resistive films (MoSi
2
, CrSi
2
, and Si-Cr) deposited by dc sputtering have been shown to be compatible with monolithic circuit production end require no protective overlayer. Si-Cr films 200-300 Å thick have ρ
s
, and temperature coefficients of resistance (TCR) ranging from about 1 kΩ/sq and +150 ppm/°C (CrSi
2
) to 20 kΩ/sq and -1400 ppm/°C (17 at % Cr). MoSi
2
is best suited for resistor applications requiring 100-200Ω/sq. MoSi
2
films are about 700 Å thick at 200 Ω/sq, compared to < 100 Å for 200-Ω/sq Ni-Cr, and their TCR is -125 ppm/°C. Typical stability for unprotected silicide resistors in TO-5 packages at 200°C, no load, is < ±3 percent during the first 200 h and < ± 0.5 percent during the next 2000 h. The films are stable during short term exposure to high temperatures as encountered during monolithic or hybrid circuit ceramic package sealing.