Dielectric-constant measurement of thin insulating films at low frequency by nanoscale capacitance microscopy

Abstract

We demonstrate a method for quantitatively probing the local low-frequency dielectric constant of thin insulating films by nanoscale capacitance microscopy. The calibrated capacitance-distance curves are measured on the dielectric film and analyzed by using a tip-sample capacitance model here proposed. Applied to SiO2 films as small as 1×1μm2 area and 20–30nm thickness, the method gives a dielectric constant on the submicron scale in agreement with the value determined on the large scale. The observed precision is set by the capacitance noise level of the instrument and the tip radius.

Nanoscale dielectric microscopy of non-planar samples by lift-mode electrostatic force microscopy

“…Among them, we can cite nanoscale capacitance microscopy [1][2][3], electrostatic force microscopy (EFM) [4][5][6][7][8][9][10], nanoscale impedance microscopy [11,12], scanning polarization force microscopy [13][14][15][16], scanning microwave microscopy (SMM) [17,18] and nanoscale non-linear dielectric microscopy [19]. These techniques have allowed measuring the electric permittivity with nanoscale spatial resolution on planar samples, such as thin oxides, polymer films and supported biomembranes [2][3][4]8,10], and on non-planar ones, such as, single carbon nanotubes, nanowires, nanoparticles, viruses and bacterial cells [20][21][22][23][24][25][26][27][28][29][30].…”

Nanoscale capacitance microscopy of thin dielectric films

“…6 we have demonstrated that by performing calibrated C͑Z͒ curves on a homogeneous and uniformly thick dielectric film ͑see Fig. 6 below͒, the ratio h / r can be extracted in a very quantitative way at the nanoscale.…”

“…The remaining contributions conform the stray capacitance contribution that can be subtracted from the experiments following an appropriate calibration procedure as previously reported. 1,6,10 In order to arrive at an analytical expression for the apex capacitance in the presence of a thin dielectric film, we will restrict ourselves to the model system depicted in Fig. 1͑b͒.…”

“…1͑a͔͒. For thin dielectric films, the power of NCM resides in the ability to quantify intrinsic properties, including film thickness 5 and dielectric constant, 6 with lateral spatial resolution well beyond the limit of conventional ellipsometry, reflectance spectroscopy, 7 and capacitance metrology. 8,9 In two recent papers, 6,10 we have demonstrated the quantitative measurement of the dielectric constant and the thickness of thin insulating films at the nanoscale.…”

High temperature conductance mapping for correlation of electrical properties with micron-sized chemical and microstructural features

“…It may be reduced further by a better screening, but this is not trivial due to the high temperature. Thus, it is not likely that the values in the aF range achieved [7,8] at room temperature can be obtained. The upper limit is set by the 1 M overload protection resistor.…”