Plasma Processing Gas Switching via Emission Spectrum Feedback

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Solution Overview

Problem

Conventional plasma processing methods face challenges in achieving stable step switching during gas replacement in plasma processing, leading to non-negligible time lags and unexpected etching due to residual gases, making it difficult to achieve optimum processing conditions.

Innovation Solution

A plasma processing method that involves stopping the supply of one gas while introducing an inert gas, detecting the remaining gas, and then transitioning to the next gas supply based on detection results, ensuring complete gas replacement before applying radio-frequency bias power, thereby synchronizing gas supply with plasma conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If gas replacement is performed by controlling MFC with predetermined delay time, then step switching can be achieved, but the delay time varies 0.2 to 0.3 seconds making stable synchronization impossible

Engineering Contradiction:

Improvestep switching stabilityVSAvoidgas introduction delay variation

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent uses emission spectrum detection to monitor gas concentration in real-time and provides feedback to the control system. This allows the system to dynamically adjust the timing of radio-frequency power application based on actual gas replacement status, eliminating the need for fixed delay time compensation and achieving stable synchronization despite MFC response variations.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces the mechanical/MFC-based timing system with an optical detection system using emission spectrum analysis. Instead of relying on mechanical flow control timing, the system uses electromagnetic radiation detection to sense gas concentration and triggers process steps based on optical signals, achieving more precise and stable timing control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If radio-frequency power is applied based on predetermined delay time, then plasma generation can be initiated, but non-negligible time lag occurs between plasma generation and bias generation reducing processing quality

Engineering Contradiction:

Improveprocessing qualityVSAvoidtime lag between plasma and bias

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The system continuously monitors emission spectrum to detect when the process chamber is actually filled with the intended gas. The radio-frequency power application timing is dynamically adjusted based on this real-time feedback, ensuring that plasma generation and bias generation are synchronized to within a predetermined time margin, thereby eliminating processing quality degradation.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system performs preliminary detection of gas concentration using emission spectrum analysis before initiating radio-frequency power application. This preliminary action ensures that the chamber is properly filled with the correct gas and plasma conditions are optimal before bias generation begins, preventing time lag-related quality issues.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If gas concentration is detected using emission spectrum/mass spectrometer, then gas replacement timing can be identified, but the process chamber is not filled with the gas when power is applied causing suboptimal processing

Engineering Contradiction:

Improvegas concentration detectionVSAvoidprocessing optimization

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The system uses emission spectrum detection to continuously monitor gas concentration and provides real-time feedback to the control system. The radio-frequency power is applied only when the detection confirms that the process chamber is fully filled with the intended gas, ensuring that processing is always performed under optimal conditions. The feedback loop dynamically adjusts timing to maintain the chamber in the optimal state throughout the process.

Inventive Principle:

Principle #23Feedback

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 method enables highly stable step switching and precise synchronization of gas and radio-frequency power, preventing gas mixing and ensuring optimal plasma processing without residual gas effects.

Implementation Method 1

radio-frequency power supplied to an electrode substrate for generating plasma

Methodology Applied

Scientific EffectRadio-frequency power generation of plasma: Electromagnetic Induction

Implementation Method 2

emission spectrum/mass spectrometer to detect the gas concentration

Methodology Applied

Scientific EffectEmission spectrum detection: Absorption Spectroscopy

Data Source

PatentUS9899241B2Plasma processing method

Publication Date: 2018.02.20 HITACHI HIGH TECH CORP

AI summary

A plasma processing method which performs plasma processing on a sample by a plurality of steps includes a first step of stopping supply of gas of one step while supplying an inert gas and a second step stopping the supply of the inert gas of the first step while as supplying a gas of the other step after the first step. An amount of the gas of the one step remaining inside a process chamber in which the sample is plasma-processed is detected in the first step. An amount of the gas of the other step reached inside the process chamber is detected in the second step. The one step is switched to the other step based on the amount of the gas of the one step detected in the first step and the amount of the gas of the other step detected in the second step.