Continuous Atomic Layer Deposition Tunnel for High-Throughput Film Growth
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Solution Overview
Problem
Current atomic layer deposition (ALD) systems have limited throughput capacity, which is insufficient to meet the increasing demand for solar cell panels and other semiconductor applications, as they can only process about 60 wafers per hour for film thicknesses of 5-15 nm.
Innovation Solution
A continuous ALD apparatus and method that uses a process tunnel with parallel tunnel walls and segmented gas zones to deposit films on a train of substrates or continuous substrate tape, allowing for higher throughput by enabling continuous processing and arbitrary film thickness growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional single or multi-wafer ALD systems are used, then precise thickness control and conformal coating are achieved, but throughput capacity is limited to about 60 wafers per hour
Solution Approach 1:
The process tunnel is divided into multiple segments along the substrate transport direction, with each segment containing gas injection channels for precursors and purge gases. This segmentation allows different deposition cycles to occur simultaneously on different portions of the substrate train, enabling continuous processing and dramatically increasing throughput capacity from 60 to potentially 3000 wafers per hour while maintaining precise thickness control through the self-limiting nature of each segment's deposition process
Solution Approach 2:
The system enables continuous substrate transport through the process tunnel while maintaining continuous deposition action. Substrates move continuously through the tunnel in the transport direction, exposed to alternating precursor and purge gas zones without interruption. This continuous operation eliminates idle time between wafer processing cycles, achieving the target throughput improvement while preserving the conformal coating quality inherent to ALD methodology
2Manufacturing precision
If film thickness is increased to 5-15 nm for solar cell passivation, then adequate passivation is achieved, but processing time increases proportionally
Solution Approach 1:
To achieve film thicknesses of 5-15 nm while maintaining high throughput, the process tunnel contains multiple segments (e.g., 100 segments for 10 nm aluminum oxide) arranged in sequence along the transport direction. Each segment deposits a controlled fraction of the total thickness through self-limiting chemisorption reactions. The cumulative effect of passing through all segments produces the desired total thickness with atomic-layer precision, while the continuous transport through all segments simultaneously processes many substrates, achieving both precise thickness control and high productivity
Solution Approach 2:
The system controls film thickness by adjusting parameters including the number of segments, transport speed, and gas flow rates. For 5-15 nm films required in solar cell passivation, the apparatus can be configured with appropriate segment counts and exposure times to achieve the target thickness range. The self-limiting nature of each deposition step ensures precise thickness control regardless of the total number of segments, allowing flexible adjustment between quality and throughput requirements
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
The apparatus achieves significantly improved throughput capacity, potentially processing up to 3000 wafers per hour, while maintaining precise control and conformal coating, and can be adapted for various film compositions and substrate forms.
Implementation Method 1
A series of sequential steps in which a surface of the substrate is exposed to all precursors is called a deposition cycle. Each deposition cycle grows a single monolayer of film, or a fraction of a monolayer. This is due to the fact that in ALD the film growth depends on chemisorption, a process whereby a precursor molecule adheres to a substrate's surface through the formation of a chemical bond without further thermal decomposition of the precursor molecule taking place.
Implementation Method 2
Exposing the substrate to the second precursor results in a chemical reaction of the second precursor with the chemisorbed first precursor under the formation of a solid film, until all of the chemisorbed first precursor has been reacted and the substrate is covered with a layer of chemisorbed second precursor in a self-limiting manner.
Data Source
Figure 1~2
Figure 3
Figure 4A
AI summary
Atomic layer deposition apparatus for depositing a film in a continuous fashion. The apparatus includes a process tunnel, extending in a transport direction and bounded by at least a first and a second wall. The walls are mutually parallel and allow a flat substrate to be accommodated there between. The apparatus further includes a transport system for moving a train of substrates or a continuous substrate in tape form, through the tunnel. At least the first wall of the process tunnel is provided with a plurality of gas injection channels that, viewed in the transport direction, are connected successively to a first precursor gas source, a purge gas source, a second precursor gas source and a purge gas source respectively, so as to create a tunnel segment that - in use - comprises successive zones containing a first precursor gas, a purge gas, a second precursor gas and a purge gas, respectively.