Wafer Inspection Camera Positioning via Rotational Tracking
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Solution Overview
Problem
Existing wafer inspecting apparatuses using macro and micro cameras become large due to the need for separate moving mechanisms for capturing images of the surface and edge of a wafer, which complicates alignment and compactness.
Innovation Solution
A wafer inspecting apparatus with a macro camera and a micro camera, supported by a holding table that rotates and an X-axis moving mechanism, controlled by a unit that calculates center coordinates and adjusts the micro camera's position to align with the wafer's edge, allowing both surface and edge images to be captured efficiently with minimal moving parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate moving mechanisms are used for macro camera and micro camera to capture images of different areas, then image capturing capability is improved, but apparatus size increases
Solution Approach 1:
The patent combines both the macro camera and micro camera onto a single movable support structure that can be positioned to different locations. This merging of multiple cameras into one shared moving system eliminates the need for separate moving mechanisms, thereby reducing apparatus size while maintaining the capability to capture images of both the wafer surface and edge
Solution Approach 2:
The single moving support structure serves multiple functions by being able to position both the macro camera and micro camera to different locations. The support structure can move to a first location for surface inspection and to a second location for edge inspection, making it a universal positioning system that handles multiple inspection tasks
2Measurement precision
If multiple cameras with different fields of vision are used for surface and edge inspection, then inspection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple cameras with different functions (macro for surface, micro for edge) onto a single shared support and moving mechanism. This reduces the overall device complexity by eliminating redundant moving systems while preserving the specialized capabilities of each camera type for their respective inspection tasks
3Adaptability or versatility
If cameras are moved to different areas with separate moving means, then image capturing flexibility is improved, but alignment difficulty increases
Solution Approach 1:
By combining both cameras on a single movable support, the patent simplifies the alignment process. The support structure can be moved as a unified unit to predetermined locations, and the control system can coordinate both cameras' positions and focusing based on the wafer's detected position, reducing alignment complexity compared to coordinating multiple independent moving systems
Data Source
AI summary
A micro camera is placed in an appropriate image capturing position therefor on the basis of a center-to-center distance depending on a rotational angle of a holding table. Even in the case where the center C0 of a holding surface and the center C1 of a wafer are displaced out of alignment with each other, allowing a position in X-axis directions of an outer circumference of the wafer to vary as the holding table rotates, a control unit can make an image capturing range of the micro camera follow the varying position of the outer circumference of the wafer. Therefore, the image capturing range of the micro camera can be determined with ease. Both a surface of the wafer and the outer circumference of the wafer can be inspected simply when two cameras are moved along the X-axis directions by a single X-axis moving mechanism.