Gas Separation Tunnel with Angled Sections and Rollers
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Solution Overview
Problem
Existing gas separation methods in CVD systems for coating and doping flat and/or strip-shaped substrates, particularly with amorphous silicon, are inadequate in preventing gas mixing and entrainment due to the low proportion of dopants used in successive process steps, which demands higher separation efficiency.
Innovation Solution
The arrangement features deflection devices with rollers extending across the substrate width, a central suction opening, and angled outer tunnel sections to create high flow resistance, combined with gas inlets and throttle valves to direct a controlled gas flow, ensuring effective separation between process areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gas locks with small-volume segments are used for gas separation, then the structure is simple, but the gas separation efficiency is insufficient for CVD deposition with low dopant content
Solution Approach 1:
The separation chamber is divided into multiple sections: outer tunnel sections for substrate transport and an inner tunnel section for gas separation. The deflection devices create distinct flow regions that segment the gas paths, allowing efficient separation of process gases from adjacent chambers while maintaining structural organization.
Solution Approach 2:
Different regions of the tunnel have different gas flow characteristics. The inner tunnel section between deflection devices has high flow resistance to prevent gas mixing, while outer sections allow substrate transport. Gas inlets are positioned locally to create controlled flow patterns in specific areas.
2Reliability
If the tunnel cross-section is narrowed by deflection devices, then gas separation is improved, but the substrate transport path is constrained
Solution Approach 1:
The deflection devices are positioned at specific locations along the substrate transport path, creating localized narrow sections for gas separation while maintaining adequate space in other regions for substrate movement. The separation occurs in the cross-sectional dimension at specific points without blocking the longitudinal substrate transport path.
3Reliability
If gas flow rate is increased to improve separation, then gas mixing is reduced, but energy consumption increases
Solution Approach 1:
A controlled gas flow acts as an intermediary medium between adjacent process chambers. The gas flow is directed through the inner tunnel section to create a barrier that prevents mixing of process gases from different chambers, achieving separation without requiring high energy input.
Solution Approach 2:
The system uses pneumatic principles to create gas flows that separate process areas. By controlling gas pressure and flow direction through the tunnel sections, effective gas separation is achieved using fluid dynamics rather than mechanical barriers, reducing energy consumption.
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 configuration achieves superior gas separation by minimizing gas mixing and entrainment, particularly suitable for continuous CVD deposition chambers with different doping levels, ensuring a mixing-free connection of adjacent process areas.
Implementation Method 1
a gas flow directed from the gas inlets to the central suction opening
Implementation Method 2
a suction opening centrally between these to form a gas flow directed from the gas inlets to the central suction opening
Implementation Method 3
the defined placement of the substrate on the deflection devices significantly increases the flow resistance for passing gases
Implementation Method 4
the gas inlets are equipped with throttle valves
Data Source
AI summary
In the tunnel (2), two rollers (4) are set apart at given spacing, to guide the substrate (3). They reduce the free cross section of the tunnel. Gas inlets are located between the rollers, one close to each roller. Near the centre, a suction opening (10) is connected to a vacuum pump inducing gas flow (13). The rollers extend over the full width of the substrate (3) and run in housings adjacent to the tunnel. The gap between the substrate and one tunnel wall continues around the roller housing. The central inner tunnel section runs in a straight line between rollers, with outer tunnel sections set at an angle of 5[deg] to it. Spacing between tunnel walls in the straight section between rollers is reduced to a few millimeters. It is preferably approximately 1 mm. The gas inlets each have throttling valves (11). The low-pressure gas flow conductance of the outer tunnel sections differs from that of the inner tunnel section, the ratio being 1:5. The lengths of all tunnel sections are very much greater than the free mean path lengths of the gases or gas mixtures within them.