Vacuum Transfer Chuck for Semiconductor Wafer Isolation
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Solution Overview
Problem
Semiconductor wafer handling tools face challenges with precise and complete stopping of motion stages, mechanical vibrations, and thermal drift, which affect measurement accuracy due to large mechanical loops and thermal instability, especially when measuring small features on wafers.
Innovation Solution
A semiconductor wafer processing tool with a support structure for coarse motion positioning, using a vacuum transfer chuck with a vacuum ring that can be adhered to a top plate for precise positioning and then released to a motion stage, coupled with a kinematic alignment mechanism and vibration isolators to decouple from the larger tool's mass and noise sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a large mechanical loop is used to measure all parts of the wafer, then the measurement coverage is improved, but thermal drift and vibration noise increase
Solution Approach 1:
The system is divided into two independent parts: a large mechanical stage for coarse wafer positioning and a small isolated measurement platform for precise measurements. The measurement platform is physically separated from the large mechanical loop, creating independent measurement and positioning systems that do not interfere with each other.
Solution Approach 2:
The measurement instrument and its supporting structure are extracted from the large mechanical loop and placed on a separate vibration-isolated platform. This removes the measurement system from the source of mechanical vibrations and thermal drift associated with the large stage movements.
2Adaptability or versatility
If the mechanical stage moves the wafer over large ranges, then positioning flexibility is improved, but settling time and stopping precision deteriorate
Solution Approach 1:
The positioning function is segmented into two stages: a coarse positioning stage for large-range wafer movement and a fine positioning mechanism on the isolated platform for precise stopping. This allows the system to achieve both large movement ranges and high stopping precision by using appropriate positioning mechanisms for each range.
3Area of stationary object
If the frame structure is made large to accommodate wafer measurement, then measurement completeness is improved, but thermal expansion and vibration amplitude increase
Solution Approach 1:
The system separates the large-frame positioning function from the small-frame measurement function. The large mechanical stage provides the necessary coverage area while the small isolated measurement platform experiences minimal thermal expansion and vibration, as its size is minimized for the actual measurement task.
4Measurement precision
If vibration isolators are used to decouple the measurement head, then measurement stability is improved, but system complexity increases
Solution Approach 1:
Vibration isolators serve as intermediary elements between the large mechanical stage and the measurement platform. These isolators actively decouple vibrations while allowing the system to maintain a relatively simple overall structure by using off-the-shelf isolation components rather than complex active vibration cancellation systems.
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 solution allows for precise and vibration-free movement of wafers, maintaining sub-micron accuracy by isolating the measurement head from the mechanical stage and tool noise, and ensuring thermal stability, thereby improving measurement reliability and reducing errors.
Implementation Method 1
a vacuum ring that can be vacuum adhered to the underside of a top plate
Data Source
AI summary
A semiconductor wafer processing tool has a support structure for a coarse motion positioning system. A measurement head having a rigid super structure is supported from the support structure by vibration isolators and a top plate is mounted to the super structure. A vacuum transfer chuck is releasably carried by the coarse motion positioning system and releasably adherable to the top plate by application of vacuum. The vacuum transfer chuck supports a semiconductor wafer.