In-situ Protective Layer for Plasma Etch Selectivity
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Solution Overview
Problem
Conventional plasma etching methods face challenges in achieving high etch selectivity without compromising throughput, feature integrity, and process compatibility, particularly at smaller feature sizes where corner selectivity is critical, leading to issues like edge rounding, merged patterns, and reduced mask dimensionality.
Innovation Solution
The method involves forming an in-situ protective layer over the mask and etchable layers during plasma etching, with varying thicknesses to enhance etch selectivity, allowing for concurrent removal of the protective layer and etching of the etchable layer, thereby improving corner selectivity and maintaining throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional plasma etching processes are used to maintain throughput, then productivity is improved, but etch selectivity deteriorates leading to edge rounding and merged patterns
Solution Approach 1:
A protective layer is introduced as an intermediary between the mask layer and the etchable layer. This protective layer has higher etch selectivity than the mask layer, allowing the plasma etch process to remove protective layer material faster than mask layer material, thereby preventing mask erosion and maintaining pattern fidelity during high-speed etching
Solution Approach 2:
The etching process is segmented into multiple stages: first etching the protective layer, then etching the etchable layer through openings in the mask. This segmentation allows the protective layer to be removed selectively before the mask is significantly eroded, enabling better control over the etching process
2Manufacturing precision
If mask chemical composition is changed to increase etch selectivity, then etch selectivity is improved, but manufacturing cost increases and process compatibility is reduced
Solution Approach 1:
Instead of changing the mask material composition, a protective layer is deposited over the existing mask structure. This protective layer serves as the selective etching interface, allowing standard mask materials to be used while achieving high etch selectivity through the protective layer's material properties
Solution Approach 2:
The etch selectivity is improved by changing the parameter of layer composition - specifically by adding a protective layer with different material properties (higher selectivity to the etchant) rather than changing the mask layer composition itself. This maintains compatibility with existing mask processes
3Manufacturing precision
If ALE processes are used to improve etch selectivity, then etch selectivity is improved, but productivity deteriorates due to additional processing steps
Solution Approach 1:
The protective layer formation and etching processes are merged into a single integrated process flow. The protective layer is deposited and then etched in the same plasma reactor without breaking vacuum, combining multiple steps into one continuous operation that maintains high throughput while achieving selective etching
4Manufacturing precision
If plasma etching process is tuned for increased etch selectivity, then etch selectivity is improved, but productivity deteriorates due to longer process times
Solution Approach 1:
The protective layer acts as a sacrificial intermediary that absorbs the selective etching action. By designing the protective layer thickness and material properties appropriately, the etch process can be optimized for speed while the protective layer still provides sufficient protection to the mask, achieving both high selectivity and high throughput
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 enhances etch selectivity, reduces edge rounding, and maintains the integrity of mask features, improving pattern fidelity and throughput compared to conventional methods, while allowing for the use of continuous wave processes with good selectivity.
Implementation Method 1
Plasma processes such as plasma etching processes are commonly used to form devices in microelectronic workpieces
Implementation Method 2
forming, in the processing chamber, a protective layer over the first mask layer and the exposed regions
Data Source
AI summary
A method of plasma etching includes receiving, by a plasma processing apparatus, a substrate into a processing chamber of the plasma processing apparatus. The substrate includes an etchable layer and a first mask layer overlying the etchable layer. The first mask layer includes a plurality of openings vertically aligned with exposed regions of the etchable layer. The method further includes forming, in the processing chamber, a protective layer over the first mask layer and the exposed regions and etching, in the processing chamber, the protective layer and the exposed regions to remove the protective layer and form recesses in the etchable layer.