Switched Capacitor Impedance Matching for Pulse Plasma RF

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Solution Overview

Problem

Conventional impedance matching devices in plasma processing systems face challenges in rapidly adjusting capacitance due to mechanical driving means, leading to difficulties in matching plasma impedance, especially during high-speed pulse mode RF power supply, resulting in variations in plasma density and process results.

Innovation Solution

An adjustable capacitor with a plurality of capacitors grouped into N sets, connected in parallel, and controlled by switches, allowing for precise capacitance adjustment via a controller, enabling rapid and fine-tuned impedance matching, even during pulse mode RF power supply.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If mechanical driving means (stepping motor and gear stage) is used to adjust capacitor interval, then capacitance can be adjusted, but adjustment time becomes longer and fine control becomes difficult

Engineering Contradiction:

Improvecapacitance control precisionVSAvoidadjustment time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces the mechanical driving means (stepping motor and gear stage) with an electrical switching system. Multiple capacitors with different capacitance values are connected in parallel, and electronic switches control which capacitors are connected to the circuit. This substitution eliminates mechanical movement, enabling instantaneous capacitance adjustment without time delays, while achieving fine control through selective combination of discrete capacitor values.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If mechanical driving means is used to adjust capacitance, then impedance matching is achieved, but rapid adjustment during high-speed pulse mode becomes difficult

Engineering Contradiction:

Improveimpedance matching capabilityVSAvoidadjustment speed

Core Design Contradiction:

Adaptability or versatilityVSSpeed

Solution Approach 1:

The patent replaces the slow mechanical adjustment system with fast electronic switching. Electronic switches can change state almost instantaneously compared to mechanical motors and gears. This enables the impedance matching device to rapidly adapt to changing plasma impedance conditions during high-speed pulse mode RF power supply, maintaining effective impedance matching across different operating conditions.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If conventional adjustable capacitor is used, then impedance matching is possible, but reflected power increases during pulse mode off state due to remaining power

Engineering Contradiction:

Improveimpedance matching stabilityVSAvoidreflected power

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent uses electronic switches that can be precisely controlled to disconnect capacitors from the circuit. During pulse mode off state, the controller can quickly discharge or disconnect the capacitor network, preventing remaining power from being supplied to the process chamber. This reduces reflected power and energy loss while maintaining impedance matching stability during the on state.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

This solution allows for rapid and precise adjustment of capacitance, minimizing time delays and reflected power, ensuring consistent plasma density and improved process results by effectively matching plasma impedance in plasma processing systems.

Implementation Method 1

the plurality of switches being switched on/off according to the control signal so that capacitance of the adjustable capacitor is adjusted

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS20120168081A1Adjustable Capacitor, Plasma Impedance Matching Device, Plasma Impedance Matching Method, And Substrate Treating Apparatus

Publication Date: 2012.07.05 SYSTEM ENGINEERING MEGA SOLUTION CO LTD

AI summary

Disclosed is a substrate treating apparatus which comprises a process chamber; an electrode configured to generate plasma from a gas supplied into the process chamber; an RF power supply configured to output an RF power; a transmission line configured to transmit the RF power to the electrode from the RF power supply; an impedance matching unit connected to the transmission line and configured to match plasma impedance; and a controller configured to output a control signal to the impedance matching unit, wherein the impedance matching unit comprises an adjustable capacitor having a plurality of capacitors and a plurality of switches corresponding to the plurality of capacitors, the plurality of switches being switched on/off according to the control signal so that capacitance of the adjustable capacitor is adjusted.