Large dynamic range RF voltage sensor and method for voltage mode RF bias application of plasma processing systems

Patent metadata

Field	Value
Publication number	US-10121641-B2
Application number	US-201514728444-A
Country	US
Kind code	B2
Filing date	Jun 2, 2015
Priority date	Jul 21, 2014
Publication date	Nov 6, 2018
Grant date	Nov 6, 2018

Abstract

A voltage sensor of a substrate processing system including a multi-divider circuit, a clamping circuit and first and second outputs. The multi-divider circuit receives a RF signal indicative of a RF voltage at a substrate. The multi-divider circuit includes dividers of respective channels and outputting first and second reduced voltages based on the received RF signal. The reduced voltages are less than the RF voltage. The clamping circuit clamps the first reduced voltage to a first predetermined voltage when the RF voltage is greater than a second predetermined voltage or the first reduced voltage is greater than a third predetermined voltage. While the received RF signal is in first and second voltage ranges, the first and second outputs output output signals based respectively on the first and second reduced voltages. The first predetermined voltage is based on a maximum value of the first voltage range.

First claim

What is claimed is:

1. A voltage sensor of a substrate processing system, the voltage sensor comprising:
a multi-divider circuit configured to receive a radio frequency (RF) signal, wherein the received RF signal is indicative of a RF voltage provided at a substrate in a plasma chamber of the substrate processing system, wherein the multi-divider circuit comprises a first divider and a second divider, wherein the first divider corresponds to a first channel and is configured to (i) receive the RF signal from an electrode, and (ii) output a first reduced voltage based on the received RF signal, wherein the second divider corresponds to a second channel and is configured to (i) receive the RF signal from the electrode, and (ii) output a second reduced voltage based on the received RF signal, and wherein the first reduced voltage and the second reduced voltage are less than the RF voltage;
a clamping circuit configured to clamp the first reduced voltage to a first predetermined voltage when (i) the RF voltage is greater than a second predetermined voltage, or (ii) the first reduced voltage is greater than a third predetermined voltage;
a first output of the first channel configured to output a first output signal based on the first reduced voltage and while the received RF signal is in at least one of a first voltage range or a second voltage range, wherein the second voltage range is higher than the first voltage range, and wherein the first predetermined voltage is based on a maximum value of the first voltage range; and
a second output of the second channel configured to output a second output signal based on the second reduced voltage and while the received RF signal is in the at least one of the first voltage range or the second voltage range.

2. The voltage sensor of claim 1 , wherein:
the first divider comprises a first capacitance connected in series with a second capacitance; and
the second divider comprises a third capacitance connected in series with a fourth capacitance.

3. The voltage sensor of claim 2 , wherein:
the first divider comprises a fifth capacitance and a first resistance connected in parallel with the second capacitance; and
the second divider comprises a sixth capacitance and a second resistance connected in parallel with the fourth capacitance.

4. The voltage sensor of claim 1 , wherein the clamping circuit comprises a pair of zener diodes.

5. The voltage sensor of claim 1 , wherein:
the first predetermined voltage is equal to the third predetermined voltage; and
the second predetermined voltage is greater than the first predetermined voltage and the third predetermined voltage.

6. The voltage sensor of claim 1 , wherein:
the second channel comprises a buffer circuit;
the buffer circuit comprises an amplifier and a voltage divider;
the amplifier receives a first input and a second input;
the first input is generated based on the second reduced voltage;
the second input is generated based on an output of the voltage divider; and
the second output signal is generated based on an output of the amplifier.

7. The voltage sensor of claim 6 , wherein the second channel further comprises a voltage circuit configured to block voltages out of the amplifier that are less than a fourth predetermined voltage.

8. The voltage sensor of claim 7 , wherein:
the voltage circuit comprises a pair of diodes; and
the fourth predetermined voltage is 0V.

9. The voltage sensor of claim 1 , wherein:
the first channel comprises a first rectifier;
the second channel comprises a second rectifier;
the first rectifier generates a first rectified signal based on the first reduced voltage; and
the second rectifier generates a second rectified signal based on the second reduced voltage.

10. The voltage sensor of claim 9 , wherein:
the first channel comprises a first buffer circuit;
the second channel comprises a second buffer circuit;
the first buffer circuit buffers the first rectified signal; and
the second buffer circuit buffers the second rectified signal.

11. A voltage controlled interface comprising:
the voltage sensor of claim 1 ; and
a controller configured to control a bias voltage supplied to a substrate support structure in the plasma chamber based on (i) the first output signal while the received RF signal is in the first voltage range, and (ii) the second output signal while the received RF signal is in the second voltage range.

12. A substrate processing system comprising:
the voltage controlled interface of claim 11 ;
the plasma chamber;
a pickup device configured to receive the RF voltage and generate the RF signal;
a chuck disposed in the plasma chamber, wherein the pickup device is connected to the chuck; and
a power source configured to supply the bias voltage to the chuck.

13. The voltage sensor of claim 1 , wherein the clamping circuit clamps the first reduced voltage to the maximum value of the first voltage range.

14. The voltage sensor of claim 1 , wherein:
an overall voltage range of the voltage sensor has a peak voltage;
the first voltage range is from zero to the maximum value;
the maximum value is less than the peak voltage; and
the second voltage range is from a voltage less than the maximum value to the peak voltage.

15. The voltage sensor of claim 14 , wherein the peak voltage is greater than or equal to 1200V.

16. The voltage sensor of claim 1 , wherein the maximum value is greater than a minimum voltage of the second voltage range and less than a maximum voltage of the second voltage range.

17. The voltage sensor of claim 1 , wherein the clamping circuit comprises:
a first diode; and
a second diode connected in series with the first diode, wherein a cathode of the second diode is connected to a cathode of the first diode.

18. The voltage sensor of claim 1 , wherein the second reduced voltage is not clamped by a clamping circuit.

19. The voltage sensor of claim 1 , wherein the second reduced voltage is not clamped by the clamping circuit.

20. A voltage controlled interface comprising:
the voltage sensor of claim 1 ; and
a controller configured to select a bias voltage to supply to a substrate support structure in the plasma chamber and determine whether to monitor either the first channel or the second channel based on the selected bias voltage,
wherein
the controller monitors the first channel while the bias voltage is in the first voltage range,
the first output signal represents the RF signal in the first voltage range,
the controller monitors the second channel while the bias voltage is in the second voltage range, and
the second output signal represents the RF signal in the second voltage range.

Assignees

• Lam Res Corp

Inventors

• Long Maolin
• Drewery John
• Paterson Alex

Classifications

• G01R15/04

  Voltage dividers · CPC title

• G01R19/0084

  Measuring voltage only · CPC title

• G01R15/26

  using modulation of waves other than light, e.g. radio or acoustic waves · CPC title

• H01J37/32577

  Electrical connecting means · CPC title

• H01J37/32935

  Monitoring and controlling tubes by information coming from the object and/or discharge · CPC title