Plasma Processing Gas Detection via Impedance Monitoring

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Solution Overview

Problem

In plasma processing for semiconductor manufacturing, there is a challenge in accurately detecting when a second gas has reached the processing vessel, as the emission spectra of different gases may not be distinguishable, leading to inappropriate timing for supplying high-frequency power, which can affect processing efficiency.

Innovation Solution

A method that uses changes in plasma impedance parameters, such as load impedance and reflection wave coefficients, to detect the presence of the second gas, allowing for precise timing of high-frequency power supply initiation and adjusting processing times to maintain consistent processing durations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Difficulty of detecting and measuring

If emission spectrum detection is used to detect the second gas arrival, then the detection method is simple, but the detection accuracy is insufficient when emission spectra of different gases are similar

Engineering Contradiction:

Improvedetection method simplicityVSAvoidgas arrival detection accuracy

Core Design Contradiction:

Difficulty of detecting and measuringVSMeasurement precision

Solution Approach 1:

The patent changes the detection parameter from emission spectrum characteristics to plasma impedance parameters (load impedance, reflection wave coefficient). This parameter transformation allows accurate detection of gas arrival timing by monitoring impedance changes that occur when different gases are present in the processing vessel, resolving the issue of indistinguishable emission spectra.

Inventive Principle:

Principle #35Parameter changes

2Speed

If the second high frequency power is supplied immediately after gas switching control, then the power supply response is fast, but the gas may not have reached the processing vessel causing inappropriate timing

Engineering Contradiction:

Improvepower supply response speedVSAvoidprocessing timing accuracy

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

The patent implements a feedback control mechanism where the supply timing of the second high frequency power is determined based on real-time detection of plasma impedance parameters. When the detected impedance change indicates that the second gas has reached the processing vessel, the power supply is activated. This feedback loop ensures both rapid response and precise timing accuracy.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system performs preliminary detection of plasma impedance parameters continuously before the actual power supply decision. This preliminary monitoring allows the system to be ready to activate power supply immediately when the gas arrival condition is met, achieving both fast response and accurate timing.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If alternating plasma processes with different gases are performed, then processing versatility is improved, but the complexity of gas switching and power supply timing control increases

Engineering Contradiction:

Improveprocessing process varietyVSAvoidgas switching and power control system complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent employs a universal detection method using plasma impedance parameters that works for detecting the arrival of any gas type in alternating plasma processes. This single detection approach replaces the need for multiple gas-specific detection systems, reducing overall system complexity while maintaining versatility for processing with different gases.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 approach enables accurate detection of the second gas's arrival, ensuring appropriate timing for high-frequency power supply and maintaining consistent processing times, thereby improving the efficiency and accuracy of plasma processing.

Implementation Method 1

the first high frequency power from the first high frequency power supply is supplied to the first electrode or the second electrode to generate plasma

Methodology Applied

Scientific EffectPlasma generation: Plasma

Implementation Method 2

the second high frequency power from the second high frequency power supply is supplied to the second electrode when necessary

Methodology Applied

Scientific EffectIon attraction: Ion Repulsion/Attraction

Data Source

PatentUS9805917B2Plasma processing method

Publication Date: 2017.10.31 TOKYO ELECTRON LTD

AI summary

In a plasma processing method, first processes and second processes are performed alternately. In each first process, a first gas is supplied into a processing vessel from a gas supply system, and a first high frequency power is supplied from a first high frequency power supply. In each second process, the first high frequency power is supplied from the first high frequency power supply continuously from a first process which is performed just before the corresponding second process. In each second process, a gas switching signal for switching the gas from the first gas to the second gas is applied to the gas supply system. Further, a supply of a second high frequency power is begun by a second high frequency power supply when a parameter such as a load impedance exceeds a threshold value after the gas switching signal is applied to the gas supply system.