Method and apparatus for determining gate capacitance
Provided is a method of determining a gate capacitance of a semiconductor device having a source, a drain, a gate, and a channel, the semiconductor device being arranged in a circuit further comprising an electrical resonator, wherein one of the source, the drain, and the gate is connected to the electrical resonator. The method comprises: measuring a resonance frequency of the circuit; and calculating, based on the resonance frequency, the gate capacitance. Since it is not necessary to pass a current through the semiconductor device, an accurate measurement of gate capacitance may be achieved. Also provided are an apparatus for determining a gate capacitance, a probe for measuring gate capacitance, and a related computer program product.
1. A method of determining a gate capacitance of a semiconductor device having a source, a drain, a gate, and a channel,
the semiconductor device being arranged in a circuit further comprising an electrical resonator, wherein one of the source and the drain is connected to the electrical resonator, and the other of the source and the drain is connected to a high-impedance contact, the high-impedance contact being selected from a tunnel junction, a resistor having a resistance greater than or equal to 1 MΩ, and a transistor in an off state;
the method comprising:
measuring a resonance frequency of the circuit based on tuning of the electrical resonator and a probe signal having a frequency sent to the circuit, wherein measuring the resonance frequency includes varying both the frequency of the probe signal and the tuning of the electrical resonator; and
calculating, based on the resonance frequency, the gate capacitance.
2. The method according to claim 1 , wherein measuring the resonance frequency comprises sending the probe signal having a frequency to the circuit, monitoring at least one parameter selected from the amplitude and phase of a response signal from the circuit, and identifying a change of the at least one parameter.
3. The method according to claim 2 , wherein the probe signal has a frequency in the range 10 MHz to 10 GHz.
4. The method according to claim 1 , including applying a gate voltage to the gate, and measuring the resonance frequency of the circuit while applying the gate voltage.
5. The method according to claim 4 , wherein the method comprises determining a gate capacitance at two or more different gate voltages.
6. The method according to claim 4 , further comprising varying the gate voltage during the measuring.
7. The method according to claim 1 , further comprising measuring a conductance of the semiconductor device.
8. The method according to claim 1 , further comprising performing an additional measurement of gate capacitance of the semiconductor device, wherein the additional measurement is selected from a capacitance bridge measurement, a coulomb blockade measurement, and a capacitance-voltage measurement.
9. The method according to claim 1 , wherein
the electrical resonator is an LC circuit comprising an inductor and a capacitance; and
the capacitance is a parasitic capacitance, or wherein the capacitance is provided by a varactor.
10. The method according to claim 1 , wherein the electrical resonator is a transmission line resonator.
11. The method according to claim 1 , wherein the electrical resonator is connected to the gate.
12. The method according to claim 1 , wherein measuring the resonance frequency comprises sending the probe signal having a frequency to the circuit; measuring a phase difference between the probe signal and a response signal received from the circuit; and calculating the resonance frequency based on the phase difference.
13. An apparatus for determining a gate capacitance of a semiconductor device, the semiconductor device having a having a source, a drain, a gate, and a channel; the apparatus comprising:
an electrical resonator connected to one of the source and the drain of the semiconductor device;
a high impedance contact connected to the other of the source and the drain of the semiconductor device;
a signal generator capable of providing a probe signal to the electrical resonator;
a sensor capable of sensing at least one of amplitude and phase of a response signal from the electrical resonator;
a processing unit operably linked to the signal generator and the sensor; and
a memory unit operably linked to the processing unit, wherein the memory unit stores computer program code, the computer program code being executable by the processing unit;
wherein the computer program code comprises:
a control module configured to cause the processing unit to control the signal generator;
an identification module configured to cause the processing unit to identify, based on an input from the sensor, a resonance frequency of the electrical resonator, the processing unit identifying the resonance frequency based on tuning of the electrical resonator and the probe signal having a frequency sent to the electrical resonator, wherein identifying the resonance frequency includes varying both the frequency of the probe signal and the tuning of the electrical resonator;
a calculation module configured to cause the processing unit to calculate, based on the resonance frequency, the gate capacitance of the semiconductor device; and
an output generation module configured to generate an output identifying the gate capacitance.
14. The apparatus according to claim 13 , wherein the electrical resonator is an LC circuit comprising an inductor and a capacitance.
15. The apparatus according to claim 13 , wherein the LC circuit includes a varactor.
16. The apparatus according to claim 13 , further comprising a first probe configured to be connected to the source of the semiconductor device, and a second probe configured to be connected to the drain of the semiconductor device.
17. The apparatus according to claim 13 , further comprising a unit for measuring conductance of the semiconductor device.
18. A computer program product embodied on a non-transitory computer readable medium, comprising computer program code which, when executed by a processor, causes the processor to:
process an input to identify a resonance frequency of a circuit comprising an electrical resonator based on tuning of the electrical resonator and a probe signal having a frequency sent to the circuit, wherein identifying the resonance frequency includes varying both the frequency of the probe signal and the tuning of the electrical resonator;
calculate, based on the resonance frequency, a gate capacitance; and
generate an output identifying the gate capacitance.