RF Generator Frequency Hopping for Plasma Load Impedance Variations

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Solution Overview

Problem

RF generator systems face challenges in efficiently delivering power to plasma chambers due to intermodulation distortion (IMD) caused by periodic disturbances from bias RF generators, leading to reduced forward power and increased reflected power.

Innovation Solution

The implementation of a frequency-hopping pattern in the source RF generator, synchronized with the periodic disturbances from the bias RF generator, to minimize IMD and maintain constant power delivery.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the source RF generator operates at a fixed frequency, then the system is simple to operate, but intermodulation distortion increases causing reduced forward power and increased reflected power

Engineering Contradiction:

Improvefixed frequency operationVSAvoidforward power delivery

Core Design Contradiction:

Ease of operationVSPower

Solution Approach 1:

The patent implements dynamic frequency adjustment by hopping the source RF generator frequency across multiple discrete frequencies according to a predetermined pattern synchronized with the bias RF generator. This transforms the static fixed-frequency operation into a dynamic multi-frequency system that actively avoids intermodulation distortion while maintaining ease of operation through automated frequency selection.

Inventive Principle:

Principle #15Dynamics

2Power

If the source RF generator uses frequency hopping to reduce IMD, then power delivery efficiency improves, but the device complexity increases

Engineering Contradiction:

Improvepower delivery efficiencyVSAvoidfrequency control system

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by establishing a predetermined frequency hopping pattern before operation begins. The pattern is pre-calculated to synchronize with the bias RF generator period, allowing the source RF generator to automatically select appropriate frequencies without real-time complex calculations. This reduces operational complexity while maintaining the power delivery efficiency benefits of dynamic frequency adjustment.

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If hardware is simplified to reduce cost, then device complexity decreases, but the ability to mitigate IMD is reduced

Engineering Contradiction:

Improvehardware configurationVSAvoidintermodulation distortion

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces potential complex hardware solutions (such as multiple RF generators or complex filtering networks) with a software-controlled frequency hopping algorithm. The controller implements the frequency selection logic through programmed instructions rather than physical hardware modifications, achieving IMD mitigation while maintaining simple hardware architecture and reducing overall system cost.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS20250069853A1Apparatus and tuning method for mitigating RF load impedance variations due to periodic disturbances

Publication Date: 2025.02.27 MKS INSTR INC

AI summary

A radio frequency (RF) generator includes a power source configured to generate an RF signal applied to the load and a power controller coupled to the power source. The power controller is configured to generate a control signal to vary the RF signal, wherein the control signal adjusts a frequency of the RF signal in accordance with an external RF signal applied to the load. The frequency adjustment is variable in accordance with a cost responsive to a perturbation of the frequency of the RF signal.