Optical Foreign Matter Inspection Device Synchronization
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Solution Overview
Problem
In optical foreign matter inspection devices, the non-synchronization between the charge transfer trigger signal and the light emission timing signal leads to variations in the detection signal, reducing the accuracy of foreign matter determination on semiconductor surfaces.
Innovation Solution
An optical foreign matter inspection device is configured with a light emission timing synchronizing signal that synchronizes the charge accumulation and detection processes with the light emission timing of the pulse laser, using a trigger signal generating circuit and a number-of-emitted-pulse calculating circuit to correct luminance variations across the sample surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the charge transfer trigger signal is synchronized with the stage encoder signal, then the rotation state can be accurately tracked, but the detection signal varies due to non-synchronization with the light emission timing signal
Solution Approach 1:
The patent introduces a light emission timing synchronizing signal as an intermediary that bridges the stage encoder signal and the light emission timing signal. This synchronizing signal ensures that the charge accumulation and transfer operations are synchronized with both the rotation state (via stage encoder) and the light emission timing (via laser control), thereby eliminating detection signal variations while maintaining accurate rotation tracking
Solution Approach 2:
The patent changes the synchronization parameter from solely stage encoder signal-based timing to a dual-synchronized timing that incorporates both stage encoder signal and light emission timing signal. By adjusting the trigger signal generation to reference both parameters, the system achieves consistent detection signals across different rotation positions and laser emission cycles
2Measurement precision
If the charge accumulation type sensor is used with pulse laser, then high sensitivity and multiple pixels are achieved, but variations in accumulated charge amount occur due to non-synchronized timing
Solution Approach 1:
The light emission timing synchronizing signal acts as a mediator that coordinates the charge accumulation process with the light emission timing. This ensures that each pixel accumulates charges corresponding to the same number of laser pulses regardless of rotation position, thereby maintaining luminance value consistency while preserving the high sensitivity and multi-pixel capabilities of the charge accumulation type sensor
Solution Approach 2:
The system uses feedback from both the stage encoder signal (rotation state) and the light emission timing signal to generate the trigger signal for charge accumulation. This feedback mechanism ensures that the accumulated charge amount is consistently correlated with the actual number of laser pulses incident on each pixel, eliminating variations in luminance values across different positions
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 configuration reduces or eliminates variations in detection signals, enhancing the accuracy of foreign matter inspection and determination on semiconductor surfaces by synchronizing the charge accumulation and detection processes with the light emission timing.
Implementation Method 1
Each of the imaging elements is implemented by a photodiode or the like that can capture the scattered light and convert the scattered light into charges
Implementation Method 2
a pulse laser is applied as a laser light source... a pulsed laser is applied as a laser light source
Implementation Method 3
a charge accumulation type sensor configured to detect light scattered or reflected from the surface of the sample
Data Source
AI summary
An optical foreign matter inspection device includes a rotation stage; a laser light source; a sensor that is a charge accumulation type sensor; a detecting circuit; a light emission timing signal generating circuit configured to generate a light emission timing synchronizing signal synchronized with laser emission; a trigger signal generating circuit configured to receive a first signal (a stage encoder signal) indicating a rotation state of a sample, and generate a trigger signal synchronized with the light emission timing synchronizing signal; a number-of-emitted-pulse calculating circuit configured to receive the light emission timing synchronizing signal and the first signal, and calculate the number of pulses in each period corresponding to a position in a radial direction of the sample; and a processing system configured to measure a state of each position on a surface of the sample by using a detection signal and the number of pulses.