High-Energy Atomic Layer Etching for Sub-10 Nm Uniformity
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Solution Overview
Problem
Traditional etching processes face challenges in achieving precise control over the etching of sub-10 nm structures due to pitch loading, aspect ratio effects, and inefficient transport of neutrals and ions, leading to uneven surface reactions and product removal.
Innovation Solution
The method involves high energy atomic layer etching, where a substrate is modified with a gas and then exposed to energetic particles with sufficient ion energy to overcome the surface binding energy of the underlying material, using pulsed delivery of energetic particles to preferentially remove the modified surface without sputtering the underlying material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional etching processes are used, then etching can be performed on substrate surfaces, but pitch loading and aspect ratio effects cause uneven etching rates and poor control for sub-10 nm structures
Solution Approach 1:
The etching process is segmented into distinct sequential steps: surface modification with modification gas followed by removal with removal gas. This segmentation allows independent optimization of each step, enabling precise control over etching depth and rate while maintaining uniformity across structures with varying aspect ratios
Solution Approach 2:
The etching process uses periodic pulsed delivery of modification and removal gases rather than continuous flow. This periodic action enables better control over reaction timing and product removal, addressing pitch loading effects by ensuring complete reaction completion before the next pulse begins
2Productivity
If high ion energy is used to remove modified surface, then etching rate increases, but sputtering of underlying unmodified material occurs
Solution Approach 1:
The process changes the chemical state of the surface through modification gas exposure, creating a modified layer with different binding energy characteristics. This parameter change allows subsequent removal at lower ion energies that would be insufficient for unmodified material, thereby achieving selective removal without sputtering
Solution Approach 2:
The modification gas acts as an intermediary that chemically alters the surface layer, creating a distinct modified surface that serves as the target for removal. This intermediary layer enables selective etching by providing a chemical distinction between the material to be removed and the underlying material to be protected
3Ease of operation
If continuous gas delivery is used, then process simplicity is maintained, but transport of neutrals and ions to etch front becomes inefficient for high aspect ratio structures
Solution Approach 1:
The process employs periodic pulsed delivery of gases instead of continuous flow. This periodic action improves transport efficiency by allowing pressure equilibration between pulses, enabling better penetration of reactive species into high aspect ratio structures while maintaining process control
Solution Approach 2:
The gas delivery is segmented into distinct modification and removal phases with separate gas chemistries. This segmentation allows optimization of each phase independently, improving overall efficiency by ensuring complete surface modification before removal begins, thereby reducing re-deposition and enhancing net etching rate
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 enables precise, self-limiting etching of narrow features with high aspect ratios, reducing depth loading and maintaining the conformality and directionality of the etching process, while extending the energy window for atomic layer etching to accommodate a wider range of critical dimensions and aspect ratios.
Implementation Method 1
exposing a surface of the material to be etched to a modification gas to modify the surface
Implementation Method 2
exposing the modified surface to an energetic particle to preferentially remove the modified surface relative to an underlying unmodified surface, the energetic particle having an ion energy sufficient to overcome an average surface binding energy
Data Source
AI summary
Methods and apparatus for performing high energy atomic layer etching are provided herein. Methods include providing a substrate having a material to be etched, exposing a surface of the material to a modification gas to modify the surface and form a modified surface, and exposing the modified surface to an energetic particle to preferentially remove the modified surface relative to an underlying unmodified surface where the energetic particle has an ion energy sufficient to overcome an average surface binding energy of the underlying unmodified surface. The energy of the energetic particle used is very high; in some cases, the power applied to a bias used when exposing the modified surface to the energetic particle is at least 150 eV.