Continuous Wafer Inspection via Controlled Illumination and Shutter Timing
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Solution Overview
Problem
Current inspection methods for flat objects, such as wafers and circuit boards, are limited by slow inspection rates due to the need for multiple images and mechanical movements, especially when high resolution is required, and often compromise on resolution or suffer from inconsistent illumination.
Innovation Solution
A continuous illumination system with controlled illuminance and a shutter to limit exposure time, allowing for continuous relative movement between the camera and object without interruption, ensuring detector elements operate within their dynamic range and minimizing image blur through precise control of exposure time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple individual images are taken with mechanical movement between camera and object, then high resolution inspection is achieved, but inspection rate becomes slow
Solution Approach 1:
The patent implements continuous illumination of the object throughout the inspection process, eliminating the need to stop mechanical movement for each image capture. The camera continuously records image data while the object or camera assembly moves, transforming the previously discontinuous image acquisition process into a continuous operation that maintains high resolution while dramatically increasing inspection throughput
Solution Approach 2:
The patent replaces the traditional mechanical stopping-and-capturing system with a continuous recording system using detector arrays (such as CMOS or CCD sensors) that can capture image data continuously during movement. This substitution of mechanical interruption with electronic continuous detection allows high-speed inspection without sacrificing resolution
2Reliability
If mechanical movement is used to capture multiple images, then complete object surface inspection is achieved, but inspection time increases significantly
Solution Approach 1:
The patent transitions from capturing a limited number of two-dimensional images at discrete positions to continuously recording image data across space and time. By using detector arrays that capture information along the movement direction continuously, the system effectively adds a temporal dimension to the imaging process, allowing complete surface inspection to occur in a single continuous pass rather than through multiple discrete image captures
Solution Approach 2:
The continuous recording capability ensures that the entire object surface is inspected without interruption or repetition. The camera assembly or object moves continuously while image data is recorded throughout the entire traversal, eliminating the time losses associated with stopping, repositioning, and restarting that plague traditional multi-image inspection methods
3Productivity
If flash illumination is used during continuous movement, then image capture is possible, but illumination consistency deteriorates
Solution Approach 1:
The patent employs periodic or pulsed illumination that is synchronized with the continuous movement and recording process. Rather than using random or inconsistent flashes, the illumination is delivered in regular, controlled pulses that ensure consistent lighting conditions throughout the inspection, maintaining both high inspection rates and uniform image quality across the entire object surface
Solution Approach 2:
The system incorporates feedback control for the illumination source, monitoring and adjusting illumination parameters in real-time to maintain consistency despite variations in object position, movement speed, or environmental conditions. This feedback mechanism ensures that illumination remains uniform and reliable throughout the continuous inspection 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
This approach enables faster inspection with high resolution, maintaining detector element performance at high inspection rates and reducing image blur, allowing for efficient generation of focused images even with high movement velocities.
Implementation Method 1
the light source continuously illuminates the object
Implementation Method 2
a shutter is provided for limiting the exposure time of the imaging of the image
Data Source
AI summary
A method for inspecting wafers or other flat objects having an object surface, comprises the steps of: providing a camera assembly with a camera for recording images of said object surface or portions of said object surface during an exposure time which is limited by a shutter; generating a continuous relative movement of said camera assembly and said object without interruption, whereby a movement blur of said image during said exposure time is caused; continuously illuminating said object with an illuminance which is controlled to remain at the same value; and recording one or more images of at least one of said portions of said object surface with said camera; defining a movement blur which is acceptable for an analysis of said image wherein said exposure time is smaller than a time causing said acceptable movement blur; and performing said analysis of said image.