Direct Frequency Tuning for Matchless Plasma Source

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Solution Overview

Problem

Substrate processing systems face inefficiencies due to impedance mismatches between the load and drive circuit in matchless plasma sources, leading to power reflection and slow tuning speeds in existing frequency tuning methods.

Innovation Solution

A direct drive circuit with a frequency tuning circuit that calculates and adjusts the tuned frequency based on voltage, current, and impedance network configuration, eliminating the need for iterative phase offset or peak-searching methods, and utilizing a clock generator and gate driver to adjust the RF frequency in real-time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If existing frequency tuning methods are used, then the plasma source can operate at adjusted frequencies, but the tuning speed is slow due to iterative phase offset or peak-searching methods

Engineering Contradiction:

Improvetuning speedVSAvoidtime for frequency adjustment

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The system pre-calculates and stores the relationship between frequency and impedance characteristics in a lookup table during system initialization or calibration. When frequency tuning is needed, the controller directly queries the lookup table using measured voltage and current to immediately determine the optimal frequency, eliminating the need for slow iterative searching during actual operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the mechanical iterative tuning process with a direct computational approach. Instead of physically adjusting components and measuring results iteratively, the system uses a calculator that computes the optimal frequency directly from electrical measurements (voltage and current) through mathematical relationships, significantly accelerating the tuning process.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If impedance matching is not achieved, then the drive circuit can operate at any frequency, but power is reflected which is inefficient

Engineering Contradiction:

Improvefrequency adjustment capabilityVSAvoidpower reflection

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The system continuously monitors the electrical characteristics (voltage and current) at the plasma source output and uses this feedback to calculate and adjust the operating frequency in real-time. This closed-loop feedback mechanism ensures that the system maintains optimal impedance matching conditions while operating at the desired frequency, preventing power reflection and energy loss.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent dynamically changes the operating frequency parameter based on real-time measurements of voltage and current. By adjusting the frequency to match the impedance characteristics of the plasma load, the system optimizes power transfer efficiency while maintaining the ability to operate at different frequencies as needed for various processing conditions.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If a matchless plasma source is used, then the system structure is simplified, but impedance mismatch causes power reflection and inefficiency

Engineering Contradiction:

Improvesystem structureVSAvoidpower reflection

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The matchless plasma source design eliminates the need for external impedance matching networks by making the frequency adjustment capability inherent to the plasma source itself. The source automatically adjusts its operating frequency based on its own electrical characteristics, providing self-matching functionality that simplifies the overall system structure while preventing power reflection through intelligent frequency selection.

Inventive Principle:

Principle #25Self-service

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution enables efficient power delivery by directly calculating the tuned frequency, reducing power reflection and improving tuning speed, thus enhancing the efficiency of substrate processing systems.

Implementation Method 1

The inductively-coupled plasma may be generated by coils arranged outside of a processing chamber adjacent to a dielectric window. Process gas flowing inside the processing chamber is ignited to create plasma.

Methodology Applied

Scientific EffectInductive coupling: Electromagnetic Induction

Implementation Method 2

RF bias power may also be supplied to an electrode in the substrate support to generate a capacitively coupled plasma (CCP).

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Data Source

PatentUS11728137B2Direct frequency tuning for matchless plasma source in substrate processing systems

Publication Date: 2023.08.15 LAM RES CORP

AI summary

A drive circuit for providing RF power to a component of a substrate processing system includes a plasma source operating at a first frequency. A load includes the component of the substrate processing system. An impedance network connects the plasma source to the load. A current sensor senses current at an output of the plasma source. A voltage sensor senses voltage at the output of the plasma source. A controller includes a tuned frequency calculator configured to calculate a tuned frequency for the plasma source based on the voltage, the current, and a configuration of the impedance network and to adjust the first frequency based on the tuned frequency.