Pulsed DC Upper Electrode for Plasma Process Stability

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Solution Overview

Problem

Capacitively coupled plasma processing apparatuses with direct-current power sources face variations in plasma processing due to the influence of electrical characteristics of components on energy transfer, particularly when applying a negative direct-current voltage to the upper electrode.

Innovation Solution

The apparatus employs a direct-current power source device that generates a pulsed negative direct-current voltage, alternating between a negative voltage and zero volts, allowing energy transfer through capacitive coupling rather than direct-current coupling, with a frequency of 400 kHz or more and a duty ratio of 20% to 60%, thereby suppressing process variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a negative direct-current voltage is applied to the upper electrode through direct-current coupling, then the plasma processing can be performed, but process variations occur due to the influence of electrical characteristics of components on energy transfer

Engineering Contradiction:

Improveprocess stabilityVSAvoidetching rate consistency

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies periodic pulsed voltage instead of continuous direct-current voltage. The voltage application unit periodically applies pulsed voltage in a periodic waveform to the upper electrode, which eliminates the influence of electrical characteristics of components on energy transfer and suppresses process variations, thereby improving both process stability and etching rate consistency.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent changes the voltage waveform parameter from direct-current to periodic waveform. By changing the voltage application mode from continuous DC to periodic pulsed voltage, the system achieves more stable energy transfer and reduced process variations while maintaining effective plasma processing.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a ground block is provided in the chamber to receive direct-current current, then the direct-current power source can be implemented, but the device complexity increases

Engineering Contradiction:

Improvedirect-current power source functionalityVSAvoidchamber structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the ground block from the chamber structure. By using periodic pulsed voltage applied to the upper electrode, the system no longer requires a ground block inside the chamber to receive direct-current current, thereby reducing device complexity while maintaining direct-current power source functionality through the periodic voltage application.

Inventive Principle:

Principle #2Taking out (Extraction)

3Stability of the object's composition

If continuous direct-current voltage is applied to the upper electrode, then steady plasma processing is achieved, but energy transfer is influenced by electrical characteristics of components

Engineering Contradiction:

Improveplasma stabilityVSAvoidenergy transfer consistency

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The patent uses periodic pulsed voltage with specific duty ratios (20% to 80%) to maintain plasma stability while avoiding the influence of electrical characteristics on energy transfer. The periodic nature of the voltage application ensures consistent energy transfer to the plasma without being affected by component electrical characteristics, thereby achieving both plasma stability and energy transfer consistency.

Inventive Principle:

Principle #19Periodic action

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 stabilizes the energy transfer and reduces process variations in plasma processing, enhancing the controllability of ion behavior and maintaining consistent etching rates across the substrate, as demonstrated in experimental results.

Implementation Method 1

radio frequency power is supplied to the upper electrode or the lower electrode, whereby a gas in the chamber is excited, so that a plasma is generated

Methodology Applied

Scientific EffectPlasma generation through radio frequency excitation: Electromagnetic Induction

Implementation Method 2

allowing energy transfer through capacitive coupling rather than direct-current coupling

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Data Source

PatentUS11062882B2Plasma processing apparatus and plasma processing method

Publication Date: 2021.07.13 TOKYO ELECTRON LTD

AI summary

A plasma processing apparatus according to an exemplary embodiment includes a chamber, a substrate support, an upper electrode, a radio frequency power source, and a direct-current power source device. The substrate support includes a lower electrode. The lower electrode is provided in the chamber. The upper electrode is provided above the substrate support. The radio frequency power source generates a plasma in the chamber. The direct-current power source device is electrically connected to the upper electrode. The direct-current power source device is configured to periodically generate a pulsed negative direct-current voltage. An output voltage of the direct-current power source device is alternately switched between a negative direct-current voltage and zero volts.