RF signal parameter measurement in an integrated circuit fabrication chamber
An apparatus to estimate parameters of a radio frequency (RF) signal may include a voltage sensor configured to provide an indication of a voltage of the RF signal as well as a current sensor configured to provide an indication of current conducted by the RF signal. The apparatus may additionally include an analog-to-digital conversion module coupled to an output port of the voltage sensor and the current sensor, wherein the analog-to-digital converter is configured to provide digital representations of an instantaneous voltage and an instantaneous current of the RF signal. The apparatus may additionally include one or more processors configured to transform the digital representations of the instantaneous voltage and current into frequency domain representations of a complex voltage and complex current.
1. An apparatus to estimate parameters of a radio frequency (RF) signal coupled to an integrated circuit fabrication chamber, comprising:
a voltage sensor configured to provide an indication of a voltage of the RF signal;
a current sensor configured to provide an indication of a current conducted by the RF signal;
an analog-to-digital conversion module coupled to an output port of the voltage sensor and to an output port of the current sensor, the analog-to-digital converter configured to provide digital representations of an instantaneous voltage and an instantaneous current of the RF signal; and
one or more processors configured to transform the digital representations of the instantaneous voltage and the digital representations of the instantaneous current into frequency domain representations of a complex voltage corresponding to the RF signal voltage and into frequency domain representations of a complex current corresponding to the RF signal current, the one or more processors additionally configured to combine frequency domain representations of the complex voltage and the complex current to form root mean square (RMS) voltage and RMS current, wherein the frequency domain representations of the complex voltage and the frequency domain representations of the complex current each include a plurality of samples.
2. The apparatus of claim 1 , wherein at least one of the one or more processors is configured to perform a Fast Fourier Transform (FFT) of the digital representation of the instantaneous voltage of the RF signal and of the instantaneous current of the RF signal.
3. The apparatus of claim 1 , wherein the voltage sensor comprises a capacitive voltage sensor.
4. The apparatus of claim 1 , wherein the current sensor comprises an inductive current transformer.
5. The apparatus of claim 1 , wherein the analog-to-digital conversion module is configured to apply a successive-approximation technique.
6. The apparatus of claim 1 , wherein the RF signal is provided by an RF power generator that provides at least 2 frequency components.
7. The apparatus of claim 6 , wherein the at least 2 frequency components comprise a first frequency of about 400 kHz and a second frequency of about 13.56 MHz.
8. The apparatus of claim 1 , wherein the one or more processors are additionally configured to apply one or more calibration coefficients to the frequency domain representations of the complex voltage and to apply one or more calibration coefficients to the frequency domain representations of the complex current, wherein the one or more calibration coefficients represent frequency-dependent deviations from ideal scattering parameters.
9. The apparatus of claim 1 , wherein the apparatus is exclusive of a voltage divider.
10. The apparatus of claim 1 , wherein the apparatus is exclusive of a peak detector.
11. The apparatus of claim 1 , wherein the apparatus is exclusive of a buffer amplifier.
12. The apparatus of claim 1 , wherein the frequency domain representations of the complex voltage and the complex current are combined to obtain actual power delivered to a process station.
13. The apparatus of claim 12 , wherein the frequency domain representations of the complex voltage and the complex current are combined to obtain power factor at the process station.
14. An apparatus adapted to estimate radio frequency (RF) power coupled to a station of an integrated circuit fabrication chamber, comprising:
a voltage sensor configured to provide an indication of a voltage of the RF signal;
a current sensor configured to provide an indication of the current conducted by the RF signal;
an analog-to-digital conversion module coupled to an output port of the voltage sensor and to an output port of the current sensor, the analog-to-digital converter configured to provide digital representations of an instantaneous voltage and an instantaneous current of the RF signal; and
one or more processors configured to:
obtain the digital representations of the instantaneous voltage of the RF signal and the digital representations of the instantaneous current conducted by the RF signal;
transform the obtained digital representations of the instantaneous voltage of the RF signal and the instantaneous current of the RF signal into a frequency domain representation of a complex voltage corresponding to the voltage of the RF signal and into a frequency domain representation of a complex current corresponding to the current conducted by the RF signal; and
combine the complex voltage of the RF signal and the complex current of the RF signal to form root mean square (RMS) voltage and RMS current, wherein the frequency domain representation of the complex voltage and the frequency domain representation of the complex current each include a plurality of samples.
15. The apparatus of claim 14 , wherein the one or more processors is configured to transform the obtained digital representations of the instantaneous voltage of the RF signal and the instantaneous current conducted by the RF signal utilizing a Fast Fourier Transform.
16. The apparatus of claim 14 wherein the one or more processors is additionally configured to apply one or more calibration coefficients to the complex voltage of the RF signal and the complex current conducted by the RF signal, wherein the one or more calibration coefficients represent frequency-dependent deviations from ideal scattering parameters.
17. The apparatus of claim 14 , wherein the one or more processors is additionally configured to utilize the complex voltage of the RF signal and the complex current of the RF signal to obtain power delivered to a station of the integrated circuit fabrication chamber.
18. The apparatus of claim 17 , wherein the one or more processors is additionally configured to utilize the complex voltage of the RF signal and the complex current of the RF signal to obtain a ratio of power delivered to forward power at the station of the integrated circuit fabrication chamber.
19. The apparatus of claim 14 , wherein the apparatus is exclusive of a buffer amplifier.