Dopant profile measurement module, method and apparatus

1. An apparatus, comprising:

a first signal source;

a dopant profile measurement module (DPMM) configured to receive a portion of the signal from the first signal source;

a probe tip connected to a reflective coupler;

a load connected in parallel with the probe tip; and

a second signal source connected to the load, wherein the second signal source is configured to provide an amplitude-modulated (AM) signal to the probe tip.

2. An apparatus as claimed in claim 1 , further comprising:

a reference coupler configured to receive a signal from the first signal source, and to provide the portion of the signal to the DPMM.

3. An apparatus as claimed in claim 2 , wherein the reflective coupler is configured to receive another portion of the signal from the reference coupler.

4. An apparatus as claimed in claim 2 , wherein the DPMM further comprises a mixer configured to receive the portion of the signal from the reference coupler.

5. An apparatus as claimed in claim 4 , wherein the reflective coupler is configured to receive a reflected signal from the probe tip and to provide the reflected signal to the mixer.

6. An apparatus as claimed in claim 5 , wherein a modulation index of the reflected signal is proportional to a doping concentration.

7. An apparatus as claimed in claim 4 , wherein the portion of the signal from the reference coupler provides a local oscillator (LO) input to the mixer.

8. An apparatus as claimed in claim 1 , wherein the other portion of the signal is reflected by the probe tip and is modulated at a frequency of the AM signal.

9. An apparatus as claimed in claim 1 , wherein the probe tip contacts a sample, and the AM signal applies a voltage that changes a capacitance at the probe tip.

10. An apparatus as claimed in claim 9 , wherein the sample comprises a semiconductor comprising a doping profile.

11. An apparatus as claimed in claim 9 , wherein the AM signal has a frequency f and the change in capacitance (ΔC) results in a change in impedance equal to 1/(2πfΔC).

12. An apparatus as claimed in claim 9 , wherein the probe tip is a probe tip of an atomic force microscope (AFM).

13. In an apparatus for measuring a doping level of a sample, the apparatus, comprising: a first signal source; a dopant profile measurement module (DPMM) configured to receive a portion of a signal from the first signal source; a reflective coupler configured to receive a second portion of the signal from a reference coupler; a probe tip connected to the reflective coupler; a load connected in parallel with the probe tip; and a second signal source connected to the load, a method, comprising:

transmitting the signal from the first signal source to the reference coupler;

providing the first portion of the signal to the DPMM;

providing the second portion of the signal to the reflective coupler and to the probe tip;

providing an amplitude modulated (AM) signal to the probe tip;

modulating the second portion of the signal with the AM signal; and

reflecting the modulated portion of the signal back to the reflective coupler.

14. A method as claimed in claim 13 , further comprising:

providing the modulated portion of the signal to a mixer at the DPMM; and

mixing the modulated portion of the signal with the first portion of the signal to provide an output indicative of a doping concentration.

15. A method as claimed in claim 14 , wherein the first portion of the signal provides a local oscillator (LO) input to the mixer.

16. A method as claimed in claim 13 , further comprising contacting the sample with the probe tip whereby the AM signal applies a voltage that changes a capacitance at the probe tip.

17. A method as claimed in claim 16 , wherein the sample comprising a semiconductor comprising a doping profile.