Multi-Camera Wafer Inspection Parallel Imaging
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Solution Overview
Problem
Current inspection methods for flat objects, such as wafers, require extensive mechanical movement and numerous images, leading to prolonged inspection times, especially as resolution increases, and fail to achieve high throughput while maintaining accuracy.
Innovation Solution
A device and method utilizing a camera arrangement with multiple fixed cameras, where the object or camera arrangement rotates about a perpendicular axis, allowing simultaneous imaging of different object areas, which are combined to form a comprehensive image, reducing the need for extensive mechanical movement and fine adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple images are captured with mechanical movement to inspect the entire object surface, then measurement precision is improved, but inspection time increases significantly
Solution Approach 1:
The object surface is divided into multiple image fields, each captured by a separate camera. Instead of capturing the entire surface sequentially with one camera, multiple cameras simultaneously capture different segments (image fields) of the object, reducing the number of mechanical movements and images required while maintaining complete surface coverage and defect detection capability
Solution Approach 2:
Multiple partial images (image fields) captured by different cameras are merged into a single composite image representing the entire object surface. This combining process allows simultaneous capture of multiple object regions without requiring sequential mechanical movement, thereby reducing inspection time while preserving measurement precision through the integrated view
2Measurement precision
If resolution requirements increase to detect smaller defects, then measurement precision is improved, but inspection time increases quadratically
Solution Approach 1:
The high-resolution inspection task is segmented across multiple cameras, each capturing a specific image field at high resolution. By distributing the high-resolution capture across multiple simultaneous cameras rather than sequential single-camera captures, the system achieves high lateral resolution for small defect detection without the quadratic time penalty that would result from sequential high-resolution imaging of the entire surface
3Productivity
If the entire object surface is captured simultaneously by all cameras, then productivity is improved, but device complexity increases
Solution Approach 1:
Rather than requiring all cameras to capture the entire object surface simultaneously (which would demand an impractically large number of cameras and complex coordination), the system segments the object surface into multiple image fields, with each camera responsible for capturing its specific field. This segmentation approach achieves high productivity through parallel capture while keeping the camera arrangement and control system manageable
Solution Approach 2:
The system transitions from a single-camera sequential capture approach to a multi-camera parallel capture approach, adding the dimension of spatial parallelism. By arranging cameras in a configuration where each captures a different image field, the system achieves simultaneous multi-region capture without requiring exponential increases in camera count, thus improving productivity while controlling device complexity
4Measurement precision
If mechanical movement is used to position the object or camera for each image, then measurement precision is improved, but ease of operation deteriorates due to extensive movement control requirements
Solution Approach 1:
The system segments the imaging task across multiple fixed cameras, eliminating the need for extensive mechanical movement. Each camera remains in a fixed position capturing its designated image field, and the combination of these fixed-camera views achieves complete surface coverage without requiring precise mechanical positioning for each capture, thereby improving ease of operation while maintaining measurement precision through the segmented multi-camera approach
Data Source
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AI summary
An apparatus for inspecting flat objects, in particular wafers, containing an object holder; a camera arrangement having a camera for recording an image of at least one part of the object; and a drive arrangement for producing a relative movement between the camera arrangement and the object from a first recording position to at least one further recording position; is characterized in that the camera arrangement has at least one further camera; the object areas imaged in different cameras are at least partially different, wherein all cameras together simultaneously record only part of the total inspection area of the object; and each object point of the entire inspection area can be imaged at least once in one of the cameras as a result of the relative movement between the camera arrangement and the object, as produced with the drive arrangement.