Plasma Etch Uniformity via Segmented Gas Feed and Tuning
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Solution Overview
Problem
In semiconductor manufacturing, plasma etching processes often suffer from non-uniformity due to varying gas distributions and uneven by-product distribution across the wafer surface, leading to inconsistent etching rates and profile uniformity issues.
Innovation Solution
The method involves controlling gas flows in a plasma processing chamber by using separate inner and outer gas feeds with distinct flow rates and angles, allowing for convective and diffusive gas injection patterns, and applying RF power to create a dissociation pattern that separates mixing in space and time, with the option to include passivation components in the gases to control etch uniformity and by-product distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gases are introduced through a single feed mechanism, then the device complexity is reduced, but the etch uniformity across the wafer surface deteriorates
Solution Approach 1:
The gas feed system is segmented into multiple independent feeds (inner feed and outer feed) that deliver different gas compositions to different radial zones of the wafer. The inner feed delivers reactant gas to the center region while the outer feed delivers tuning gas to the edge region, enabling spatially-resolved control of etch chemistry and improving etch uniformity across the wafer surface.
Solution Approach 2:
Different gas compositions are delivered to different local regions of the wafer surface. The inner feed provides a gas mixture optimized for center region etching while the outer feed provides a different gas mixture optimized for edge region etching, creating locally-optimized chemistry that compensates for radial variations in plasma density and improves overall etch uniformity.
2Manufacturing precision
If reactant gas and tuning gas are pre-mixed before introduction, then the device complexity is reduced, but the control over dissociation patterns and etch uniformity deteriorates
Solution Approach 1:
The gas delivery system is segmented into separate channels for reactant gas and tuning gas that remain physically separated until they enter the plasma region. This segmentation allows independent control of gas flows and compositions, enabling precise control over where and how the gases mix and dissociate in the plasma, thereby improving etch uniformity.
Solution Approach 2:
The plasma region acts as an intermediary zone where the separately-delivered reactant gas and tuning gas meet and mix. By allowing mixing to occur in the plasma rather than in the gas delivery system, the invention enables controlled dissociation patterns that improve etch uniformity while avoiding the complexity of pre-mixing apparatus.
3Manufacturing precision
If diffusive flow is used for tuning gas, then the control over gas distribution and etch uniformity is improved, but the productivity is reduced due to longer mixing time
Solution Approach 1:
The gas delivery system is segmented into convective and diffusive flow paths. The inner feed uses convective flow for rapid delivery of reactant gas to the center region, while the outer feed uses diffusive flow for controlled delivery of tuning gas to the edge region. This segmentation allows each gas to be delivered by the most appropriate mechanism, balancing etch uniformity with productivity.
Solution Approach 2:
Different flow mechanisms are applied locally to different gas feeds based on their specific requirements. The reactant gas requires rapid convective delivery to maintain high etching rates, while the tuning gas benefits from slower diffusive delivery to achieve uniform distribution and control etch profiles, thereby maintaining both productivity and uniformity.
4Productivity
If convective flow is used for reactant gas, then the productivity is maintained through rapid gas delivery, but the control over gas distribution uniformity deteriorates
Solution Approach 1:
The gas delivery system is segmented into multiple independent feeds with different flow characteristics. The inner feed uses convective flow for rapid reactant gas delivery to maintain high etching rates, while the outer feed uses diffusive flow for uniform tuning gas distribution. This segmentation allows each feed to optimize for its specific function, achieving both productivity and uniformity.
Solution Approach 2:
Different flow mechanisms are applied locally to match the specific requirements of different wafer regions. The center region receives convectively-delivered reactant gas for high-speed etching, while the edge region receives diffusively-delivered tuning gas for uniform distribution, thereby maintaining both productivity and gas distribution uniformity across the wafer.
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 achieves uniform etching profiles across the wafer surface, minimizing residues and pattern dependence, while optimizing neutral-to-ion flux ratios and by-product distribution, resulting in consistent FinFET profiles without compromising productivity.
Implementation Method 1
flowing a reactant gas to the inner feed, the flowing of the reactant gas is set at a convective flow so that the reactant gas has a first flow rate and is directed perpendicular to the substrate
Implementation Method 2
the flowing of the tuning gas is set at a diffusive flow so that the tuning gas has a second flow rate and is directed at an angle between perpendicular to the substrate and parallel to the dielectric window
Implementation Method 3
The diffusive flow of the tuning gas is directed at the angle, enabling the tuning gas to be dissociated by the RF power to have mixing and dissociation separated in space and time with the reactant gas
Implementation Method 4
providing radio frequency (RF) power to the electrode so that a plasma is ignited in the plasma region over the substrate using the reactant gas and the tuning gas
Data Source
AI summary
Methods, systems, and computer programs are presented for controlling gas flow in a semiconductor manufacturing chamber. The method includes flowing a reactant gas thorough an inner feed and a tuning gas through an outer feed surrounding the inner feed, such that the gases do not mix until both are introduced in the chamber. Further, the flow of the reactant gas is convective, and the flow of the tuning gas is directed at an angle from the direction of the reactant gas, providing a delivery of the tuning gas in closer proximity to the RF power before further mixing with the reactant gas. Radio frequency power is provided to the electrode to ignite a plasma using the reactant and tuning gases. The diffusive flow of the tuning gas enables the tuning gas to be dissociated by the RF power allowing for control of the local residence time variation and preferential spatial dissociation patterns with respect to the local residence time of the reactant gas. The introduction of the gases into the chamber without pre-mixing imparts control of etch uniformity across the surface of the substrate during etching.