Wafer Boat Support Ring Alignment for Uniform Batch Deposition
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Solution Overview
Problem
Existing wafer boats in vertical batch furnaces often suffer from non-uniform processing due to tilting and inadequate flatness, leading to uneven material deposition, and experience heat loss through multiple contact points with the pedestal.
Innovation Solution
A wafer boat design featuring a support ring and alignment ring with protruding alignment elements and matching openings, allowing precise alignment and rotation, minimizing heat conduction by maintaining a small contact surface and ensuring flatness for uniform processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the wafer boat is placed on small cylindrical feet on the pedestal, then the structure is simple and easy to manufacture, but the contact surface is large causing heat loss and the alignment precision is insufficient leading to non-uniform processing
Solution Approach 1:
The wafer boat structure is segmented into a support ring and an alignment ring. The support ring provides structural support and defines the bottom end surface, while the alignment ring separately handles positioning and alignment functions. This segmentation allows each component to be optimized for its specific function, reducing heat conduction through the support ring while maintaining precise alignment through the alignment ring with its alignment elements.
Solution Approach 2:
The alignment ring acts as an intermediary element between the wafer boat and the pedestal. It introduces alignment elements (protrusions or openings) that mediate the positioning process, ensuring precise alignment without requiring direct contact between the support ring and the pedestal over a large area. This intermediary structure enables accurate positioning while minimizing the heat conduction path.
2Loss of energy
If the contact surface between wafer boat and pedestal is made small, then heat conduction is minimized, but achieving sufficient flatness for proper alignment becomes more difficult
Solution Approach 1:
The bottom end surface structure is segmented into the support ring and alignment ring. The support ring's bottom end surface provides a substantial flat contact area with the pedestal for stable support and heat dissipation, while the alignment ring sits atop the support ring and provides the small-contact-point alignment interface. This segmentation resolves the contradiction by separating the flatness requirement (support ring) from the minimal contact requirement (alignment ring).
Solution Approach 2:
The alignment ring is positioned in a different vertical dimension relative to the support ring. By placing the alignment ring above the support ring's contact surface, the patent creates a hierarchical structure where the support ring handles the flatness and support function at the first dimension (contact with pedestal), while the alignment ring handles precise positioning at a second dimension (above the contact surface). This dimensional separation allows both large flat contact area and small alignment contact area to coexist.
3Ease of manufacture
If the wafer boat is tilted relative to the process chamber, then the structure can accommodate manufacturing tolerances, but the deposition uniformity deteriorates
Solution Approach 1:
The alignment system with alignment elements and alignment openings provides self-aligning functionality. When the wafer boat is placed on the pedestal, the alignment elements automatically engage with the alignment openings, guiding the wafer boat into the correct aligned position without requiring external adjustment or intervention. This self-service alignment mechanism ensures that even with manufacturing tolerances in the support structure, the wafer boat automatically achieves proper alignment for uniform deposition.
Solution Approach 2:
The alignment ring and alignment elements are pre-configured with specific geometric features (protrusions or openings) that establish the correct alignment position before the actual processing begins. This preliminary alignment configuration ensures that when the wafer boat is loaded onto the pedestal, it is automatically positioned with the correct orientation and alignment relative to the process chamber, preventing tilt and ensuring uniform deposition throughout the manufacturing process.
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 design ensures precise alignment and rotation of the wafer boat, reducing heat loss and achieving uniform deposition by maintaining a single, flat contact surface, thereby enhancing processing efficiency and minimizing contamination risks.
Implementation Method 1
Either the support surface of the pedestal, or a bottom side of the alignment ring may be provided with a plurality of alignment elements respectively protruding upwards from the support surface or downwards from the alignment ring. The other one of the support surface and the alignment ring may be provided with a plurality of alignment openings configured to accommodate therein the plurality of alignment elements.
Implementation Method 2
A small contact surface may minimize heat conduction from the wafer boat to the pedestal, and thus minimize heat losses.
Data Source
AI summary
A wafer boat configured to be placed on a pedestal of a vertical batch furnace, the pedestal having a substantially flat support surface. The wafer boat comprises a support ring defining a substantially flat bottom end surface of the wafer boat, and an alignment ring substantially concentric with the support ring. Either the support surface of the pedestal, or a bottom side of the alignment ring is provided with a plurality of alignment elements respectively protruding upwards from the support surface or downwards from the alignment ring, while the other one is provided with a plurality of alignment openings configured to accommodate therein the plurality of alignment elements. The support ring downwardly protrudes beyond the alignment ring so that, when the wafer boat is placed on the pedestal, the support ring is supported on the support surface while the alignment ring is spaced from the support surface of the pedestal.