Noncontact dielectric constant metrology of low-k interconnect films   using a near-field scanned microwave probe
  We present a method for noncontact, noninvasive measurements of dielectric constant, k, of 100-nm- to 1.5-\mu m-thick blanket low-k interconnect films on up to 300 mm in diameter wafers. The method has about 10 micron sampling spot size, and provides <0.3% precision and <2% accuracy for k-value. It is based on a microfabricated near-field scanned microwave probe formed by a 4 GHz parallel strip transmission line resonator tapered down to a few-micron tip size. 
Vladimir V. Talanov, Andr\'e Scherz, Robert L. Moreland, and Andrew R.   Schwartz
cond-mat.mtrl-sci physics.ins-det