Atomic Layer Etching Directionality via Bias-Controlled Surface Modification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional etching techniques for semiconductor substrates lack fine-tuned control over uniformity and etch rate, especially as technology advances to atomic-scale devices, requiring improved directionality and atomic-scale fidelity in etching processes.
Innovation Solution
The method involves atomic layer etching (ALE) using a ligand exchange mechanism with a fluorine-containing plasma and tin-containing etchant, specifically modifying the substrate surface with fluorine plasma and exposing it to tin-(II) acetylacetonate (Sn(acac)2) vapor for self-limiting etching, allowing for controlled isotropic or anisotropic etching by adjusting bias voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional reactive ion etching is used to etch materials on semiconductor substrate, then etch rates can be controlled by modulating radio frequency plasma power, but control of etch process with atomic-scale fidelity is insufficient
Solution Approach 1:
The etching process is segmented into discrete atomic layers, with each etching cycle removing precisely one atomic layer through controlled ligand exchange reactions. This segmentation enables atomic-scale precision by breaking down the continuous etching process into quantized steps, where each step removes a specific thickness determined by monolayer dimensions rather than continuous rate control.
Solution Approach 2:
The process transitions from controlling etch rate through radio frequency plasma power modulation to controlling etch depth through the number of cyclic ligand exchange reactions. This parameter change from energy-based control to reaction-cycle-based control enables atomic-scale precision, as the etch depth is determined by the discrete number of monolayers removed in each cycle rather than continuous power adjustment.
2Manufacturing precision
If isotropic etching is performed to achieve uniform material removal, then etch uniformity is improved, but directionality control is lost
Solution Approach 1:
The process introduces asymmetry by applying a bias voltage during the plasma treatment step, which creates anisotropic ion bombardment that preferentially etches in the vertical direction. This asymmetric treatment is applied selectively during specific phases of the cyclic process, allowing the material to exhibit both isotropic uniformity (through complete surface coverage in each cycle) and anisotropic directionality (through bias-enhanced vertical preferential etching).
3Manufacturing precision
If atomic layer etching with ligand exchange mechanism is used to achieve self-limiting etching, then etch rate control is improved, but process time increases
Solution Approach 1:
The etching process employs periodic cyclic action, repeating sequences of plasma treatment and ligand exchange reactions. Each cycle is self-limiting and removes a precise amount of material, with the total etch depth controlled by the number of cycles performed. This periodic repetition enables precise control over etch rate and depth, as each cycle contributes a known, controllable amount of material removal that can be summed across multiple cycles to achieve the desired total etch depth.
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 highly controlled and uniform etching with the ability to introduce anisotropy, enabling precise etching of metal oxides like aluminum oxide, addressing the challenges of directionality and scalability in atomic-scale etching.
Implementation Method 1
modifying a surface of the material to be etched using a fluorine-containing plasma
Implementation Method 2
The substrate is then exposed to tin-(II) acetylacetonate (Sn(acac)2) vapor
Implementation Method 3
A ligand exchange reaction is sustained in a vapor deposition chamber with Sn(acac)2 vapor without plasma
Implementation Method 4
ions from the plasma are typically accelerated onto the wafer surface to etch the substrate
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A method for performing atomic layer etching (ALE) on a substrate is provided, including the following operations: performing a surface modification operation on a substrate surface, the surface modification operation configured to convert at least one monolayer of the substrate surface to a modified layer, wherein a bias voltage is applied during the surface modification operation, the bias voltage configured to control a depth of the substrate surface that is converted by the surface modification operation; performing a removal operation on the substrate surface, the removal operation configured to remove at least a portion of the modified layer from the substrate surface, wherein removing the portion of the modified layer is effected via a ligand exchange reaction that is configured to volatilize the portion of the modified layer. A plasma treatment can be performed to remove residues from the substrate surface following the removal operation.