Temperature-dependent characteristics of polysilicon and diffused resistors

The temperature-dependent characteristics of polysilicon and diffused resistors have been studied. By using 0.18-(mu)m CMOS technology, a cobalt salicide process is employed and silicide is formed at the ends of resistors. Based on a simple and useful model, some important parameters of resistors including bulk sheet resistance (R/sub bulk/) and interface resistance (R/sub interface/) are obtained at different temperature. For diffused resistors, the R/sub bulk/ and R/sub interface/ values increase and decrease with increase of temperature, respectively. Positive values of temperature coefficient of resistance (TCR) are observed. Furthermore, TCR values decrease with decreasing resistor size. For polysilicon resistors, the R/sub interface/ values decrease with increase of temperature. In addition, negative and positive TCR values of R/sub bulk/ are found in n/sup +/ and p/sup +/ polysilicon resistors, respectively. In conclusion, by comparing the studied diffused and polysilicon resistors, negative trends of TCR are observed when the resistor size decreases.