Epitaxial Wafer Pocket Offset for Edge Thickness Uniformity
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Solution Overview
Problem
Existing methods for depositing epitaxial layers on semiconductor wafers struggle to achieve uniform thickness in the edge region, especially when the substrate wafer has thickness differences along its circumference.
Innovation Solution
A method that involves measuring the edge geometry of the substrate wafer to determine thickness characteristic values, and then adjusting the position of the substrate wafer within the susceptor pocket to ensure that the thicker edge sections are closer to the pocket boundary than the thinner edge sections, thereby controlling the deposition of the epitaxial layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the substrate wafer is placed centrally in the pocket for uniform deposition, then the deposition process is simple and reproducible, but the edge thickness uniformity deteriorates when the substrate wafer has non-uniform edge geometry
Solution Approach 1:
The patent applies local quality by positioning the substrate wafer asymmetrically in the pocket based on its specific edge geometry characteristics. Instead of using a universal centered position, the wafer is placed at a location that compensates for its particular thickness variations, allowing uniform epitaxial growth despite non-uniform starting geometry. This is achieved by measuring the edge geometry and calculating an optimal offset position that accounts for the specific thickness distribution of each wafer.
Solution Approach 2:
The patent implements preliminary action by measuring the edge geometry of the substrate wafer before the epitaxial deposition process and pre-calculating the optimal positioning offset. This preliminary measurement and calculation step allows the system to compensate for thickness variations before deposition begins, ensuring uniform edge thickness in the final product without requiring complex real-time adjustments during the deposition process.
2Manufacturing precision
If the substrate wafer position is adjusted to compensate for edge thickness variations, then edge thickness uniformity improves, but the positioning process becomes more complex and time-consuming
Solution Approach 1:
The patent performs the edge geometry measurement and offset calculation as a preliminary step before deposition, allowing the positioning to be set once and remain fixed during the actual deposition process. This approach avoids time-consuming adjustments during deposition while still achieving the benefit of compensated positioning for uniform edge thickness.
Solution Approach 2:
The system performs self-service by automatically measuring the edge geometry, calculating the appropriate offset, and positioning the wafer without requiring manual intervention. This automation reduces both the time and complexity of the positioning process while maintaining high precision in achieving uniform edge thickness.
3Adaptability or versatility
If a fixed positioning method is used for all wafers, then the process is simple and fast, but it cannot accommodate wafers with different edge thickness distributions
Solution Approach 1:
The patent applies local quality by tailoring the wafer position to its specific edge geometry characteristics. Each wafer receives a customized positioning offset based on its measured thickness distribution, allowing the system to adapt to different wafer geometries while maintaining uniform deposition. The positioning system becomes adaptive rather than fixed, compensating for variations in each individual wafer.
Solution Approach 2:
The patent changes the positioning parameter (offset distance and direction) based on the measured edge geometry of each wafer. By adjusting this key parameter according to the specific thickness distribution, the system achieves adaptability to different wafer geometries. The offset value is calculated and modified for each wafer based on its unique characteristics, enabling versatile handling of various wafer types.
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 method standardizes the edge geometry of the epitaxially coated semiconductor wafer, achieving more uniform thickness in the edge region by adjusting the deposition process based on the measured edge geometry.
Implementation Method 1
A frequently used method for depositing the layer is chemical vapor deposition. The material for the layer is provided by process gas, which is passed over the side of the substrate wafer to be coated at temperatures at which a precursor compound containing the material contained in the process gas chemically cleaves.
Implementation Method 2
at temperatures at which a precursor compound containing the material contained in the process gas chemically cleaves
Data Source
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AI summary
A method for depositing an epitaxial layer onto a substrate disk from a gas phase, comprising measuring an edge geometry of the substrate disk which assigns a thickness parameter to an edge of the substrate disk depending on edge positions; depositing the substrate disk into a pocket of a susceptor of a device for depositing the epitaxial layer, wherein the pocket is surrounded by a boundary with a circular circumference; heating the substrate disk; and passing process gas over the substrate disk; characterized by depositing the substrate disk into the pocket such that the distance between the substrate disk and the boundary of the pocket is smaller at edge positions with the thickness parameter of a thicker edge than at edge positions with the thickness parameter of a thinner edge.