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US-12626895-B2 - RF signal parameter measurement in an integrated circuit fabrication chamber

US12626895B2US 12626895 B2US12626895 B2US 12626895B2US-12626895-B2

Abstract

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 converter 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.

Inventors

  • Sunil Kapoor
  • David French
  • Gary Lemson
  • Liang MENG

Assignees

  • LAM RESEARCH CORPORATION

Dates

Publication Date
20260512
Application Date
20210324

Claims (20)

  1. 1 . An apparatus to estimate parameters of a radio frequency (RF) signal coupled to an integrated circuit fabrication chamber comprising a plurality of stations, comprising: a plurality of voltage sensors, each configured to provide an indication of a voltage of the RF signal; a plurality of current sensors, each configured to provide an indication of a current conducted by the RF signal; a multiplexer configured to: select a voltage sensor of the plurality of voltage sensors and a current sensor of the plurality of current sensors, wherein the selected voltage sensor and the selected current sensor correspond to a selected station of the plurality of stations; and provide outputs of the selected voltage and the selected current sensor to an analog-to-digital converter, the analog-to-digital converter configured to receive outputs from the voltage sensor and the current sensor and configured to provide digital representations of the voltage of the RF signal and the current conducted by the RF signal based on the outputs from the voltage sensor and the current sensor; and one or more processors configured to determine, based on the digital representations of the voltage and the current of the RF signal: a peak voltage associated with the digital representation of the voltage, a peak current associated with the digital representation of the current, and power characteristics associated with the RF signal.
  2. 2 . The apparatus of claim 1 , wherein the one or more processors are further configured to determine phases associated with the digital representations of the voltage and the current.
  3. 3 . The apparatus of claim 2 , wherein the power characteristics are based on the determined phases.
  4. 4 . The apparatus of claim 1 , wherein the one or more processors are further configured to determine an impedance based on the peak voltage and the peak current.
  5. 5 . The apparatus of claim 1 , wherein the voltage sensor comprises a capacitive voltage sensor.
  6. 6 . The apparatus of claim 1 , wherein the current sensor comprises an inductive transformer.
  7. 7 . The apparatus of claim 1 , wherein the RF signal is provided by an RF power generator that provides at least 2 frequency components.
  8. 8 . The apparatus of claim 1 , wherein the RF signal is provided by an RF power generator that provides one frequency component.
  9. 9 . The apparatus of claim 1 , wherein the one or more processors comprise a Field Programmable Gate Array (FPGA).
  10. 10 . The apparatus of claim 1 , wherein the digital representations are at a sampling rate typically greater than about 100 MHz.
  11. 11 . The apparatus of claim 1 , wherein the power characteristics comprise a power factor.
  12. 12 . The apparatus of claim 1 , wherein the one or more processors are further configured to communicate data via a serial communication protocol, via Ethernet, or via another digital communication protocol.
  13. 13 . The apparatus of claim 1 , wherein the one or more processors are further configured to provide outputs to an Ethernet for Control Automation Technology (EtherCAT) system.
  14. 14 . The apparatus of claim 13 , wherein the EtherCAT system is configured to provide instructions to one or more elements in a matching network or other RF distribution system.
  15. 15 . The apparatus of claim 1 , wherein the one or more processors are configured to: 1) provide calibration coefficients to the voltage sensor for storage in memory associated with the voltage sensor; or 2) provide calibration coefficients to the current sensor for storage in memory associated with the current sensor.
  16. 16 . The apparatus of claim 15 , wherein the calibration coefficients are determined for a plurality of RF signal frequencies.
  17. 17 . The apparatus of claim 15 , wherein the calibration coefficients are determined using a modular calibration method that comprises: determining an effect of one or more cables that electrically couple the voltage sensor and the current sensor to the analog-to-digital converter; or determining an effect of a controller that receives outputs from the voltage sensor and the current sensor via the one or more cables.
  18. 18 . The apparatus of claim 15 , wherein the calibration coefficients are determined using an end-to-end calibration method that comprises determining transformation functions that relate outputs of the one or more processors to characteristics of the RF signal.
  19. 19 . The apparatus of any one of claim 15 , wherein: 1) the voltage sensor is configured to provide identifying information to the one or more processors; or 2) the current sensor is configured to provide identifying information to the one or more processors.
  20. 20 . The apparatus of claim 19 , wherein the identifying information comprises the calibration coefficients.

Description

INCORPORATION BY REFERENCE A PCT Request Form is filed concurrently with this specification as part of the present application. Each application that the present application claims benefit of or priority to as identified in the concurrently filed PCT Request Form is incorporated by reference herein in its entirety and for all purposes. BACKGROUND Fabrication of integrated circuit devices may involve the processing of semiconductor wafers in a semiconductor processing chamber. Typical processes may involve deposition, in which a semiconductor structure may be built on or over a substrate such as by way of a layer-by-layer process. Typical processes may also involve removal (e.g., etching) of material from certain regions of the semiconductor wafer. In commercial-scale manufacturing processes, each wafer contains many copies of a set of semiconductor devices, and many wafers may be utilized to achieve the required volumes of semiconductor devices. Accordingly, the commercial viability of a semiconductor processing operation may depend, at least to some extent, upon within-wafer uniformity and upon wafer-to-wafer repeatability of process conditions. Consequently, efforts are made to ensure that each portion of a given wafer, as well as each wafer processed in a semiconductor processing chamber, is subjected to tightly-controlled processing conditions. Variations in processing conditions can bring about undesirable variations in deposition and etch rates, which, in turn, may bring about unacceptable variations in overall fabrication processes. Such variations may degrade circuit performance which, in turn, may give rise to unacceptable variations in performance of higher-level systems that utilize the integrated circuit devices. Accordingly, techniques for monitoring semiconductor processes with increased granularity, as well as an ability to make fine adjustments to process variables during fabrication, continues to be an active area of investigation. The background description provided herein is for the purposes of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. SUMMARY In one embodiment an apparatus is utilized to estimate parameters of a radio frequency (RF) signal coupled to an integrated circuit fabrication chamber. The apparatus may include a voltage sensor configured to provide an indication of a voltage of the RF signal. The apparatus also includes a current sensor configured to provide an indication of a current conducted by the RF signal. The apparatus also includes 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 is configured to provide digital representations of an instantaneous voltage and an instantaneous current of the RF signal. The apparatus also includes 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 are additionally configured to combine frequency domain representations of a complex voltage and the complex current. In other implementations, the one or more processors of the apparatus are configured to perform a Fast Fourier Transforms (FFT) of the digital representation of the instantaneous voltage of the RF signal and of the instantaneous current of the RF signal. In another implementation, the voltage sensor of the apparatus includes a capacitive voltage sensor. In another implementation, the current sensor includes an inductive current transformer. In an implementation, the analog-to-digital conversion module is configured to apply a successive-approximation technique. In another implementation, the RF signal is provided by an RF power generator, which provides at least 2 frequency components. In an implementation, the at least 2 frequency components include a first component having a frequency of about 400 kHz and a second component having a frequency of about 13.56 MHz. In an implementation, the one or more processors of the apparatus 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. In an implementation, the one or more processors are additionally configured to aggregate the complex voltage and the complex current to form root mean square voltag