A Microfabricated Near-Field Scanned Microwave Probe for Noncontact Dielectric Constant Metrology of Low-k Films

We have developed a non-contact method for quantitative measurements of permittivity, k, for low-k dielectric films of 0.1 to 1.5 mum in thickness deposited on up to 300-mm silicon wafers. It is based on a near-field scanned microwave probe formed by a microfabricated 4 GHz stripline resonator tapered down to a few-micron tip size. Probe calibration and measurements are performed at a unique tip-sample distance at which the probe resonant frequency exhibits a linear dependence on the parameter (k-1)/(k+1). The probe has about 10 micron sampling spot size and provides better than 0.3% precision and plusmn2% accuracy for k-value. Excellent correlation with mercury probe measurements is established using a variety of blanket low-k films