Improved SiCr Resistor Performance by Means of Rapid Thermal Processing

Abstract

New and improved processes for fabrication of SiCr thin film resistors are desirable to achieve precision circuits. Two major draw backs to conventional single target sputtered SiCr resistors are high temperature coefficient of resistance (TCR) and low sheet rho (ρ_□). Depositing a very thin film to achieve a higher ρ_□, generally degrades the film stability, TCR and manufacturability. Annealing the film at higher temperatures by means of hot air, does increase the film sheet rho but the anneal temperature is limited to below 500°C to avoid film decomposition.

A new method of increasing the sheet rho of SiCr films has been established where the deposited film with a ρ_□ of 400Ω/□ is annealed to 1400Ω/□. Silicon substrates with thermally grown oxide were deposited with SiCr using rf sputtering. The wafers were ran through a single wafer rapid thermal processor with the chamber filled with dry nitrogen. Anneal temperatures were varied and it was found that the highest sheet rho was obtained at a temperature of 650°C and anneal time of 60 seconds. Resistors were manufactured using the annealed film and electrical characteristics of the resistors evaluated. When compared to hot air annealed SiCr resistors, the RTA SiCr resistors showed improved stability, TCR and sheet rho performance.