Multi-Level RF Bias Pulsing for High Aspect Ratio Plasma Etching

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Solution Overview

Problem

Existing reactive ion etching technologies face challenges in etching high aspect ratio features due to aspect ratio dependent etch decline and iso-dense loading, where etch rate decreases with increasing aspect ratio and feature density affects processing.

Innovation Solution

Implementing multi-level pulsing schemes with sinusoidal and custom RF waveforms to control ion energy and angular distribution, using a combination of sinusoidal and non-sinusoidal waveforms to optimize etch selectivity and control over high aspect ratio features.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional RF pulsing schemes are used, then etch rate is maintained, but etch selectivity and high aspect ratio feature loading cannot be optimized simultaneously

Engineering Contradiction:

Improveetch rateVSAvoidetch selectivity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies periodic multi-level RF pulsing schemes where the bias RF signal alternates between multiple voltage levels (e.g., first level, second level, third level) with specific duty cycles. This periodic modulation of ion energy enables selective etching of different materials while maintaining overall etch rate, resolving the contradiction between productivity and manufacturing precision.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent dynamically adjusts RF voltage levels and duty cycles during the etch process. By varying the bias RF signal between multiple levels (e.g., 0V, -50V, -100V) with different duty cycles, the system adapts ion energy distribution to achieve optimal etch selectivity for different materials while maintaining high aspect ratio feature loading.

Inventive Principle:

Principle #15Dynamics

2Device complexity

If high aspect ratio features are etched, then device complexity is reduced, but etch rate declines due to aspect ratio dependent etch

Engineering Contradiction:

Improvefeature aspect ratioVSAvoidetch rate

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent changes multiple parameters simultaneously including bias RF voltage levels, duty cycles, and waveform shapes (sinusoidal and non-sinusoidal). This multi-parameter optimization enables maintenance of etch rate while etching high aspect ratio features by controlling ion energy distribution and angular spread throughout the feature depth.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite RF signal approach combining sinusoidal and non-sinusoidal waveforms with multiple voltage levels. This composite pulsing scheme creates optimized ion energy distributions that maintain etch rate while enabling penetration into high aspect ratio features, effectively resolving the contradiction between device complexity and productivity.

Inventive Principle:

Principle #40Composite materials

3Device complexity

If feature density increases, then device integration is improved, but etch processing is affected by iso-dense loading

Engineering Contradiction:

Improvefeature densityVSAvoidetch rate uniformity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent uses periodic multi-level RF pulsing with specific duty cycles to modulate ion flux and energy distribution. This periodic action compensates for iso-dense loading effects by maintaining consistent etch rates across different feature densities, enabling improved device integration while preserving etch rate uniformity.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent implements feedback control by monitoring etch rates across different feature densities and adjusting RF voltage levels and duty cycles accordingly. This feedback mechanism ensures uniform etch processing regardless of feature density variations, resolving the contradiction between device integration and manufacturing precision.

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

Achieves selective etching of multiple materials with minimal trade-offs by controlling ion energy and angular distribution, enhancing etch rate and feature loading efficiency in high aspect ratio features.

Implementation Method 1

the source RF signal is configured to generate a plasma in a plasma process region disposed between the top electrode and the lower electrode

Methodology Applied

Scientific EffectPlasma generation: Plasma

Implementation Method 2

the bias RF signal is configured to accelerate ions from the plasma towards the lower electrode

Methodology Applied

Scientific EffectIon acceleration: Lorentz Force

Data Source

PatentUS20250329514A1Customizing etch selectivity and high aspect ratio feature loading through multi-level pulsing schemes utilizing sinusoidal and custom RF waveforms

Publication Date: 2025.10.23 LAM RES CORP

AI summary

A method for performing a plasma etch process in a process chamber is provided, including: applying a source radiofrequency (RF) signal to a top electrode of the process chamber; applying a bias RF signal to a lower electrode of the process chamber; wherein the bias RF signal has two or more pulsed duty cycles, including a first duty cycle having a first sinusoidal waveform at a first frequency and pulsed at a first voltage level, and a second duty cycle having a custom waveform pulsed at a second voltage level, the custom waveform consisting of a second sinusoidal waveform at a second frequency that is combined with a non-sinusoidal waveform.