Plasma Sheath Tuning for Uniform High-Aspect-Ratio Etching
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Solution Overview
Problem
Conventional plasma processing chambers struggle to achieve reliable control over plasma sheath characteristics, leading to non-uniform etch profiles in high aspect ratio openings during semiconductor manufacturing, which is critical for next-generation devices.
Innovation Solution
A plasma processing system with independently controllable biasing pixels and waveform generators is used to adjust plasma sheath characteristics, enabling fine-tuning of ion energy, angular distribution, and directionality through pulsed voltage waveforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma processing chambers use RF-biased etch process with sinusoidal waveform, then plasma sheath is formed and etching occurs, but the oscillating sheath voltage causes two-peak ion energy distribution function that results in non-uniform etch profiles and reduced anisotropy
Solution Approach 1:
The patent applies periodic pulsed voltage waveforms with specific duty cycles (e.g., 10-90% duty cycle where forward bias duration is shorter than reverse bias duration) to control the plasma sheath. This periodic action replaces the continuous sinusoidal RF waveform, enabling precise control over ion energy distribution and sheath thickness uniformity, thereby achieving uniform etch profiles and high anisotropy while maintaining process reliability
Solution Approach 2:
The patent changes the voltage waveform parameters from conventional sinusoidal RF to custom-designed pulsed waveforms with adjustable amplitude, frequency, and duty cycle. By optimizing these parameters (e.g., peak forward voltage, pulse width, repetition rate), the system achieves a single-peak ion energy distribution function that eliminates the two-peak distribution problem, resulting in improved etch profile uniformity and manufacturing precision
2Productivity
If higher energy ions are used to increase etch rate and anisotropy, then vertical etch profiles are achieved, but etch selectivity between masking layer and substrate material is reduced
Solution Approach 1:
The patent employs dynamically adjustable pulsed voltage waveforms that can be modified in real-time during the etching process. By dynamically changing the waveform parameters (amplitude, duty cycle, frequency), the system optimizes ion energy delivery to achieve both high etch rates and maintained selectivity, adapting the ion bombardment conditions to preserve masking layer integrity while enhancing vertical profile formation
Solution Approach 2:
The patent applies preliminary conditioning pulses before the main etching phase to prepare the plasma sheath and substrate surface. These preliminary actions (e.g., pre-biasing pulses, plasma conditioning phases) establish optimal sheath thickness and ion distribution patterns that enable subsequent high-rate anisotropic etching while maintaining selectivity, effectively pre-configuring the plasma environment for balanced productivity and precision
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 system provides improved uniformity and control over plasma sheath characteristics, resulting in consistent, high aspect ratio etch profiles and enhanced processing results across the substrate surface.
Implementation Method 1
a plasma generator assembly electrically coupled to the support base and configured to generate a plasma from processing gases
Implementation Method 2
by use of a radio frequency (RF) power
Implementation Method 3
a plasma sheath, i.e., a region depleted of electrons, is formed between the plasma and the substrate surface
Implementation Method 4
Ions are accelerated across the plasma sheath with a directionality perpendicular to the sheath boundary with the bulk plasma
Implementation Method 5
ions concurrently bombard the exposed substrate surface to increase the chemical reaction rate in the direction of ion impact
Data Source
AI summary
Embodiments herein provide plasma processing chambers and methods configured for fine-tuning and control over a plasma sheath formed during the plasma-assisted processing of a semiconductor substrate. Embodiments include a sheath tuning scheme, including plasma processing chambers and methods, which can be used to tailor one or more characteristics of a plasma sheath formed between a bulk plasma and a substrate surface. Generally, the sheath tuning scheme provides differently configured pulsed voltage (PV) waveforms to a plurality of bias electrodes embedded beneath the surface of a substrate support in an arrangement where each of the electrodes can be used to differentially bias a surface region of a substrate positioned on the support. The sheath tuning scheme disclosed herein can thus be used to adjust and/or control the directionality, and energy and angular distributions of ions that bombard a substrate surface during a plasma-assisted etch process.