Rotating Mirror System for Semiconductor Inspection Blur Reduction
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Solution Overview
Problem
In semiconductor inspection systems, capturing images of moving substrates often results in motion blur due to the mismatch in speed between the substrate and the camera, which can limit throughput and make it difficult to capture small features clearly.
Innovation Solution
The implementation of a mirror system with a rotating or dithering mirror that moves according to a preset angular velocity profile, synchronized with the stage's movement, to counteract the linear motion of the substrate, thereby reducing relative motion between the object and the imaging system, and an image capture system that includes a stage moving at a constant speed with a camera system that matches this speed to minimize blur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the stage moves at high speed to increase throughput, then productivity improves, but motion blur increases making it difficult to capture small features
Solution Approach 1:
The patent applies the dynamics principle by making the mirror system movable rather than stationary. The mirror rotates or dithers at a controlled angular velocity that dynamically compensates for the linear motion of the stage, allowing the system to maintain image sharpness while operating at high speeds. This transforms a static optical system into a dynamic one that can adapt to motion conditions.
Solution Approach 2:
The patent implements preliminary anti-action by introducing a mirror system that preemptively counteracts the motion blur effect. The mirror rotates in a direction opposite to the stage motion, creating a compensating effect that cancels out the relative motion between the substrate and the imaging system before the blur can occur.
2Manufacturing precision
If a strobe light is used to illuminate the moving substrate, then motion blur is reduced, but the pulse speed is limited by the light bulb's physical specifications and cooling requirements
Solution Approach 1:
The patent replaces the mechanical/stroboscopic illumination system with an optical compensation system using a rotating mirror. Instead of using strobe lights to freeze motion, the system uses a continuously illuminated sensor paired with a mirror that optically compensates for motion, eliminating the need for high-speed pulsed illumination and its associated cooling constraints.
Solution Approach 2:
The rotating mirror acts as an intermediary element between the stationary imaging system and the moving substrate. It translates the linear motion of the stage into a counter-rotational motion, effectively mediating the relative motion between the object and the sensor to reduce blur without requiring high-speed strobe illumination.
3Manufacturing precision
If the camera is accelerated and deaccelerated to match the stage speed, then motion blur is reduced, but the system complexity increases
Solution Approach 1:
The patent extracts the motion compensation function from the camera system and places it in a separate, dedicated mirror system. This separates the functions of imaging and motion compensation, allowing the camera to remain simple while the mirror system handles the complex task of matching speeds and reducing blur.
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 effectively reduces motion blur in captured images by compensating for the stage's movement, allowing for sharper images and increased throughput without causing significant vibrations or reducing productivity.
Implementation Method 1
a mirror system to receive light beams from the microscope objective representative of the substrate and reflect the light beams to a tube lens
Data Source
AI summary
Disclosed herein are techniques to reduce blurring in images taken during semiconductor inspection. A stage, which holds a substrate for inspection, can move at a substantially constant speed during inspection to increase throughput. In some techniques, a mirror system can be added to the camera system for reducing blur in images. The mirror system can include a rotating or dithering mirror to translate the linear motion of the stage into a counter rotational motion in the form of deflecting beam angles thereby reducing the motion blur caused by the movement of the stage.