Plasma Etch Waveform Synchronization for Feature Charge Neutralization
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Solution Overview
Problem
The accumulation of positive charges in high aspect ratio features during plasma processing leads to feature distortion and reduced etch rates due to local electric fields decelerating incoming ions, which is a challenge in producing next-generation semiconductor devices with atomic level precision.
Innovation Solution
A plasma processing system with synchronized pulsed-voltage (PV) and radio frequency (RF) waveforms is used to generate secondary electrons that neutralize trapped charges, control sheath voltage, and maintain a desirable ion energy distribution function (IEDF) by controlling ion and electron flux, energy, and angular distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ion assisted etching is used to form high aspect ratio features, then etching capability is improved, but positive charges accumulate in feature walls causing feature distortion and reduced etch rate
Solution Approach 1:
The patent converts the harmful accumulated positive charges into a beneficial effect by introducing a second plasma source that generates electrons. These electrons are attracted to the positive charges in the feature walls, neutralizing them and preventing feature distortion. The harmful charge accumulation is thus transformed into a mechanism for controlling plasma chemistry and improving etch uniformity.
Solution Approach 2:
The patent introduces a second plasma source as an intermediary element between the first plasma source and the substrate. This second source generates electrons that act as mediators to neutralize positive charges in the feature walls, thereby controlling the charge balance and improving both etch rate and feature fidelity without directly modifying the primary etching process.
2Productivity
If higher ion energy is used to increase etch rate, then productivity is improved, but feature distortion increases due to charge accumulation
Solution Approach 1:
The patent changes the plasma parameters by introducing a second plasma source with different characteristics (electron-rich plasma). This modifies the overall plasma environment, changing the balance between ion and electron fluxes to the substrate. The parameter change allows maintenance of high ion energy for etching while simultaneously providing sufficient electrons to neutralize charge accumulation.
Solution Approach 2:
The patent creates a composite plasma environment by combining two distinct plasma sources. The first source provides ion flux for etching, while the second source provides electron flux for charge neutralization. This composite approach allows simultaneous optimization of both etch rate and feature fidelity that cannot be achieved with a single plasma source.
3Device complexity
If conventional single plasma source is used, then device complexity is low, but charge neutralization is insufficient leading to feature distortion
Solution Approach 1:
The patent segments the plasma generation function into two separate sources: one dedicated to providing ion flux for etching and another dedicated to providing electron flux for charge neutralization. This segmentation allows independent optimization of each plasma source's characteristics, enabling effective charge control without excessive overall system complexity.
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 reduces feature distortion and improves etch rate and selectivity, enabling precise formation of high aspect ratio features suitable for next-generation semiconductor devices.
Implementation Method 1
generate secondary electrons that neutralize trapped charges
Implementation Method 2
ion energy and directionality control are key elements to desirably forming etched high aspect ratio features
Implementation Method 3
control sheath voltage, and maintain a desirable ion energy distribution function
Data Source
AI summary
Embodiments provided herein include an apparatus and methods for the plasma processing of a substrate in a processing chamber. In some embodiments, aspects of the apparatus and methods are directed to reducing defectivity in features formed on the surface of the substrate, improving plasma etch rate, and increasing selectivity of etching material to mask and/or etching material to stop layer. In some embodiments, the apparatus and methods enable processes that can be used to prevent or reduce the effect of trapped charges, disposed within features formed on a substrate, on the etch rate and defect formation. In some embodiments, the plasma processing methods include the synchronization of the delivery of pulsed-voltage (PV) waveforms, and alternately the delivery of a PV waveform and a radio frequency (RF) waveform, so as to allow for the independent control of generation of electrons that are provided, during one or more stages of a PV waveform cycle, to neutralize the trapped charges formed in the features formed on the substrate.