System and method for scanning near-field optical microscopy
A method for scanning near-field optical microscopy comprises illuminating an apertureless atomic force microscopy (AFM) probe with electromagnetic energy having a frequency in the Terahertz range, where the sample under observation includes a dielectric layer having a thickness greater than the radius of the tip of the AFM probe. A system for scanning near-field optical microscopy comprises a collimated light source for emitting collimated light, a photoconductive antenna for converting collimated light into electromagnetic energy having a frequency in the Terahertz range, an AFM probe, a sample comprising a dielectric layer, the dielectric layer having a thickness greater than the radius of the probe tip; and a detector configured to detect energy that has interacted with the sample.
1 . A method for imaging metallic patterns deposited on a surface of semiconductor materials, the method comprising:
illuminating an apertureless atomic force microscopy (AFM) probe with electromagnetic energy having a frequency in a Terahertz range, the probe having a probe tip, the probe tip having a radius, wherein the electromagnetic energy is redirected by the probe tip onto a sample, the sample comprising a dielectric layer having a thickness greater than the radius; and
detecting the electromagnetic energy that has interacted with the sample.
2 . The method of claim 1 , wherein the thickness of the dielectric layer is at least five times greater than the radius.
3 . The method of claim 2 , wherein the thickness is about 200 nm to about 400 nm.
4 . The method of claim 1 , further comprising oscillating the probe tip such that the probe tip is between about 5 nm and about 255 nm from the sample.
5 . The method of claim 4 , wherein the thickness of the dielectric layer is at least five times greater than the radius.
6 . The method of claim 5 , wherein the thickness is about 200 nm to about 400 nm.
7 . The method of claim 1 , wherein the dielectric layer overlays the metallic patterns on the surface of the semiconductor materials, and wherein the electromagnetic energy that has interacted with the sample has interacted with the metallic patterns through the dielectric layer.
8 . The method of claim 7 , further comprising: generating a topographical image of the metallic patterns from the detected electromagnetic energy that has interacted with the sample.
9 . A method for non-destructive testing using an atomic force microscope (AFM) probe, the AFM probe having a probe tip, the probe tip having a radius, the method comprising the steps of:
detecting terahertz electromagnetic energy reflected from a sample, the terahertz electromagnetic energy originating from a collimated light source, said and directed to the probe tip and a surface of the sample, the sample having a dielectric layer with a thickness greater than the radius, and wherein the probe tip oscillates at a distance of between about 5 nm and about 255 nm from the surface of the sample.
10 . The method of claim 9 , wherein the thickness is about 200 nm to about 400 nm.
11 . A system for scanning near-field optical microscopy comprising:
a collimated light source for emitting collimated light;
a photoconductive antenna for converting the collimated light into electromagnetic energy having a frequency in a terahertz range;
an atomic force microscope (AFM) probe, having a probe tip configured to scatter the electromagnetic energy from the photoconductive antenna towards a sample; and
a detector configured to:
detect the electromagnetic energy that has interacted with the sample after being scattered by the probe tip, and
based on the detected electromagnetic energy, generate a modulated signal including topographical information of a metallic pattern in the sample, wherein the metallic pattern is below a dielectric layer having a thickness greater than a radius of the probe tip.
12 . The system of claim 11 , wherein the thickness is about 200 nm to about 400 nm.
13 . The system of claim 11 , wherein the AFM probe is configured to oscillate the probe tip at a distance of between about 5 nm and about 255 nm from the sample.
14 . The system of claim 13 , wherein the thickness is about 200 nm to about 400 nm.
15 . The system of claim 11 , wherein the thickness of the dielectric layer is at least five times greater than the radius.
16 . The system of claim 11 , further comprising a demodulator for demodulating the modulated signal at a harmonic of a tapping frequency of the AFM probe.
17 . The system of claim 16 , wherein the thickness is about 200 nm to about 400 nm.
18 . The system of claim 17 , wherein the AFM probe is configured to oscillate the probe tip at a distance of between about 5 nm and about 255 nm from the sample.
19 . The system of claim 16 , further comprising:
a beam splitter configured to split the collimated light into a first portion directed to the photoconductive antenna and a second portion providing a reference signal;
a delay line configured to receive the reference signal; and
an electro-optical sampler configured to receive the electromagnetic energy that has interacted with the sample, and generate the modulated signal based on the received electromagnetic energy and the reference signal from the delay line.
20 . The system of claim 11 , wherein the probe tip comprises a metal tip composed of a platinum-iridium alloy.