High-Energy Atomic Layer Etching for High Aspect Ratio Features
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional etching processes face challenges in achieving precise control over high aspect ratio features as devices shrink below the 10nm node, particularly due to pitch loading, transport of neutrals and ions, surface reaction rates, and etch product removal, which are not effectively addressed by existing atomic layer etching techniques.
Innovation Solution
The method involves performing high energy atomic layer etching by exposing a modified substrate surface to an energetic particle with sufficient ion energy to break bonds, using a bias voltage and delivering the energetic particle in temporally separated doses to maintain self-limiting etching without sputtering the underlying material, and modulating ion energy and dose during pulsing to optimize etch rates and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional etching processes are used to etch high aspect ratio features, then etching can proceed, but pitch loading effects increase and etch rate becomes uncontrolled as aspect ratio increases
Solution Approach 1:
The etching process is segmented into two distinct sequential steps: (1) surface modification step where reactant gas modifies the surface in a self-limiting manner, and (2) removal step where different gas chemistry removes the modified layer. This segmentation allows independent optimization of each step, enabling precise etch rate control while eliminating pitch loading effects that plague traditional single-step etching processes.
Solution Approach 2:
The etching process employs periodic cyclic operation with distinct phases: surface modification phase followed by removal phase. This periodic action allows the system to reset between cycles, maintaining self-limiting behavior and preventing the cumulative pitch loading effects that occur in continuous etching processes. Each cycle independently controls the etch front, enabling precise control even for high aspect ratio features.
2Manufacturing precision
If atomic layer etching is used to achieve self-limiting etching, then etch selectivity is improved, but etching of high aspect ratio features remains challenging due to transport limitations
Solution Approach 1:
The invention changes the fundamental parameters of the etching process by using very low ion energies (1-100 eV) in the removal step, which is insufficient to cause significant sputtering of unmodified material. This parameter change maintains the self-limiting nature of atomic layer etching (preserving etch selectivity) while enabling the process to handle high aspect ratio features by reducing the harmful effects of ion bombardment and transport limitations.
Solution Approach 2:
The process uses composite gas chemistry sequences, combining different gas phases with distinct functions: modification gas (e.g., SF6, CF4) followed by removal gas (e.g., CF4, NF3). This composite approach allows the modification step to create a reactive surface layer while the removal step uses different chemistry optimized for selective removal, enabling control over high aspect ratio features without sacrificing etch selectivity.
3Productivity
If high ion energy is used to increase etch rate, then productivity improves, but sputtering of underlying unmodified material occurs losing self-limiting control
Solution Approach 1:
The invention maintains continuous useful action through the cyclic repetition of modification and removal steps. Each cycle removes a controlled amount of material through the self-limiting modified layer removal mechanism, and the cycles can be repeated to achieve the desired total etch depth. This continuous cyclic operation maintains self-limiting control while achieving high productivity through optimized cycle times and multiple cycles.
Solution Approach 2:
The process dynamically adjusts between two distinct states: a modification phase with reactive gas exposure, and a removal phase with low-energy ion bombardment. This dynamic switching allows the system to optimize for different functions at different times - surface modification for selectivity, then controlled removal for rate control - thereby maintaining self-limiting behavior while achieving high overall etch rates through the combined effect of multiple cycles.
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 efficient and precise etching of narrow features with high aspect ratios, reducing lateral etch and pitch loading effects, while maintaining the self-limiting nature of atomic layer etching, thereby improving etch selectivity and control across a wide range of critical dimensions and aspect ratios.
Implementation Method 1
exposing the modified surface to an energetic particle to remove the modified surface, the energetic particle having an ion energy sufficient to overcome an average surface binding energy of the underlying unmodified surface
Implementation Method 2
The energetic particle does not significantly sputter the underlying unmodified material
Data Source
Figure 1
Figure 2
Figure 3A
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.