Resistivity of linear scratches in doped (100) n-type single-crystal silicon

Abstract

Four-point probe measurements have been made on (100) n-type Czochralski silicon wafers of initial resistivities 0.016, 0.96, and 3.35 Ω cm. The probe tips straddled linear single scratches formed by a Vickers pyramid diamond. The diamond was dead-loaded with 0.25 N, and the scratches were made in a laboratory air environment with a relative humidity of 50%, as the silicon wafer was held at various elevated temperatures. The measurements show that the relative change in resistivity increases with temperature up to an optimum temperature, after which the resistivity decreases. The temperature at which the maximum occurs and at which the relative change in resistivity occurs depends on the initial resistivity of the wafers; the temperature at which the maximum change in relative resistivity occurs is 200 °C for the 0.016- and 0.96-Ω cm wafers and 250 °C for the 3.35-Ω cm wafer. The relative change between the undamaged wafer resistivity and the resistivity including the scratches for these same samples was 4%, 7%, and 9%. Scanning electron micrographs of the scratches showed that the scratch morphology also depended on the temperature; as the temperature is increased, the grooves become shallow and display evidence of ploughing. An analysis of the four-point probe geometry shows that the voltage in the four-point probe measurement depends on the size and the conductivity of the damage surrounding the scratches.