System for instantaneous radiofrequency power measurement and associated methods

Patent metadata

Field	Value
Publication number	US-9704692-B2
Application number	US-201514789892-A
Country	US
Kind code	B2
Filing date	Jul 1, 2015
Priority date	Jul 1, 2015
Publication date	Jul 11, 2017
Grant date	Jul 11, 2017

Abstract

Each of multiple plasma processing chambers has an RF power input line connected to receive RF power from a common RF power source. An RF control module is connected to distribute RF power from the common RF power source to the RF power input lines of the multiple chambers. A voltage sensor and a current sensor are connected to a corresponding RF power input line. Each voltage sensor measures an instantaneous electrical voltage present on its RF power input line. Each current sensor measures an instantaneous electrical current present on its RF power input line. An analog multiplier module is connected to receive as inputs the instantaneous electrical voltage from its corresponding voltage sensor and the instantaneous electrical current from its corresponding current sensor. Each analog multiplier module generates an output signal that indicates an instantaneous RF power present on the corresponding RF power input line of the corresponding chamber.

First claim

What is claimed is:

1. A system for semiconductor substrate processing, comprising:
a plurality of plasma processing chambers, each of the plurality of plasma processing chambers respectively including a radiofrequency (RF) power input line through which RF power is transmitted to generate a plasma within the plasma processing chamber;
a radiofrequency (RF) power source configured to generate RF power for transmission to the plurality of plasma processing chambers;
an RF control module connected to receive the RF power generated by the RF power source and distribute a respective portion of the RF power to each RF power input line of the plurality of plasma processing chambers;
a plurality of voltage sensors respectively connected to the RF power input lines of the plurality of plasma processing chambers, such that each of the plurality of plasma processing chambers has a separate one of the plurality of voltage sensors connected to its RF power input line, each of the plurality of voltage sensors configured to output a signal indicating an instantaneous electrical voltage present on the RF power input line to which it is connected;
a plurality of current sensors respectively connected to the RF power input lines of the plurality of plasma processing chambers, such that each of the plurality of plasma processing chambers has a separate one of the plurality of current sensors connected to its RF power input line, each of the plurality of current sensors configured to output a signal indicating an instantaneous electrical current present on the RF power input line to which it is connected; and
a plurality of analog multiplier modules respectively corresponding to the plurality of plasma processing chambers, each of the plurality of analog multiplier modules connected to receive as a first input signal the signal indicating the instantaneous electrical voltage present on the RF power input line of its corresponding plasma processing chamber as output by the corresponding one of the plurality of voltage sensors, each of the plurality of analog multiplier modules connected to receive as a second input signal the signal indicating the instantaneous electrical current present on the RF power input line of its corresponding plasma processing chamber as output by the corresponding one of the plurality of current sensors, each of the plurality of analog multiplier modules configured to generate an output signal representing a product of its first and second input signals, the output signal of a given one of the plurality of analog multiplier modules indicating an instantaneous RF power present on the RF power input line of the plasma processing chamber corresponding to the given one of the plurality of analog multiplier modules.

2. The system of claim 1 , wherein the RF power source is configured to generate multiple RF signals at different frequencies.

3. The system of claim 1 , wherein the RF control module is configured to process the instantaneous RF power as indicated by the output signal of a given one of the plurality of analog multiplier modules to determine a value of a corresponding RF power parameter, and wherein the RF control module is configured to compare the value of the corresponding RF power parameter to a prescribed value for the RF power parameter for the plasma processing chamber corresponding to the given one of the plurality of analog multiplier modules and based on the comparison adjust an amount of RF power delivered to the plasma processing chamber corresponding to the given one of the plurality of analog multiplier modules.

4. The system of claim 3 , wherein the RF control module is configured to adjust the amount of RF power delivered to the plasma processing chamber by adjusting one or more settings of a variable capacitor, a variable coil inductor, or both a variable capacitor and a variable coil inductor.

5. The system of claim 1 , wherein each of the plurality of analog multiplier modules operates at a frequency at least five times greater than a highest frequency of the RF power generated by the RF power source.

6. The system of claim 1 , wherein each of the plurality of analog multiplier modules is configurable with regard to its operating frequency.

7. The system of claim 1 , wherein both the voltage sensor and the current sensor corresponding to a given one of the plurality of plasma processing chambers are connected to the RF power input line of the given one of the plurality of plasma processing chambers at a substantially same location.

8. The system of claim 1 , wherein an electrical transmission line length from the RF power input line of a given one of the plurality of plasma processing chambers to the corresponding voltage sensor is substantially equal to an electrical transmission line length from the RF power input line of the given one of the plurality of plasma processing chambers to the corresponding current sensor, and wherein an electrical transmission line length from the voltage sensor corresponding to the given one of the plurality of plasma processing chambers to the analog multiplier module corresponding to the given one of the plurality of plasma processing chambers is substantially equal to an electrical transmission line length from the current sensor corresponding to the given one of the plurality of plasma processing chambers to the analog multiplier module corresponding to the given one of the plurality of plasma processing chambers.

9. An apparatus for measuring radiofrequency (RF) power, comprising:
a voltage sensor connected to an RF power input line of a plasma processing chamber at a connection location just outside the plasma processing chamber, the voltage sensor configured to measure electrical voltage present on the RF power input line and output a signal indicative of the measured electrical voltage;
a current sensor connected to the RF power input line of the plasma processing chamber substantially near the connection location, the current sensor configured to measure electrical current present on the RF power input line and output a signal indicative of the measured electrical current; and
an analog multiplier module connected to receive as a first input signal the signal indicative of the measured electrical voltage as output by the voltage sensor, the analog multiplier module connected to receive as a second input signal the signal indicative of the measured electrical current as output by the current sensor, the analog multiplier module configured to generate an output signal representing a product of its first and second input signals, the output signal of the analog multiplier module indicating an instantaneous RF power present on the RF power input line of the plasma processing chamber,
wherein an electrical transmission line length from the RF power input line to the voltage sensor is substantially equal to an electrical transmission line length from the RF power input line to the current sensor, and wherein an electrical transmission line length from the voltage sensor to the analog multiplier module is substantially equal to an electrical transmission line length from the current sensor to the analog multiplier module.

10. The apparatus of claim 9 , wherein the analog multiplier module operates at a frequency at least five times greater than a highest frequency of any RF signal present on the RF power input line.

11. The apparatus of claim 9 , wherein the analog multiplier module is configurable with regard to its operating frequency.

12. A method for measuring instantaneous radiofrequency (RF) power, comprising:
a) measuring an electrical voltage present on an RF power input line of a plasma processing chamber as RF

Assignees

• Lam Res Corp

Inventors

• Leeser Karl F

Classifications

• G01R21/133

  by using digital technique · CPC title

• H01J2237/334

  Etching · CPC title

• H01J37/32174

  Circuits specially adapted for controlling the RF discharge · CPC title

• H01J37/32899

  Multiple chambers, e.g. cluster tools · CPC title

• H01J37/321

  the radio frequency energy being inductively coupled to the plasma · CPC title