Particle Counter Vacuum Threshold Adjustment
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Solution Overview
Problem
Conventional particle counters in semiconductor manufacturing equipment face challenges in accurately discriminating between light scattered by real particles and background noise from gas molecules, especially when the number of gas molecules is high, leading to difficulties in detecting smaller particles.
Innovation Solution
A particle counter that operates in a vacuum or near-vacuum state, incorporating a light emitter, scattered light detector, vacuum measurement means, and a threshold setting unit to adjust the discrimination threshold based on the degree of vacuum, allowing for precise differentiation between particle and background signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the discrimination threshold is set to detect small particles, then the detection sensitivity for small particles is improved, but the background noise from gas molecules causes false detections
Solution Approach 1:
The patent changes the parameter of discrimination threshold dynamically based on vacuum degree. When vacuum degree is high (fewer gas molecules), a lower threshold is used to detect smaller particles. When vacuum degree is low (more gas molecules), a higher threshold is used to avoid false detections from background noise. This resolves the contradiction by adapting the threshold parameter to current environmental conditions.
Solution Approach 2:
The patent introduces feedback by measuring the vacuum degree and using it to adjust the discrimination threshold. The vacuum measurement unit continuously monitors the measurement area, and this information feeds back to the threshold setting unit, which adjusts the threshold accordingly. This closed-loop feedback system maintains optimal detection accuracy despite changing background noise conditions.
2Quantity of substance
If the measurement area contains more gas molecules, then the background light intensity increases, but this prevents detection of small particles
Solution Approach 1:
The patent changes the discrimination threshold parameter based on the quantity of gas molecules (vacuum degree). When gas molecule density is high, the threshold is increased to filter out background noise. When gas molecule density is low, the threshold is decreased to enable detection of smaller particles. This dynamic parameter adjustment resolves the contradiction between gas molecule quantity and detection precision.
Solution Approach 2:
The patent makes the discrimination threshold dynamic rather than fixed. The threshold setting unit continuously adjusts the threshold based on real-time vacuum degree measurements. This dynamic adaptation allows the system to optimize particle detection capability under varying gas molecule densities, resolving the contradiction between background noise levels and detection sensitivity.
3Ease of operation
If a fixed discrimination threshold is used, then the device operation is simple, but accurate discrimination between particle signals and background noise becomes difficult when vacuum conditions vary
Solution Approach 1:
The patent implements self-service by automatically adjusting the discrimination threshold based on measured vacuum conditions. The threshold setting unit uses vacuum degree information to autonomously determine the appropriate threshold without requiring manual intervention. This maintains ease of operation while improving measurement precision through adaptive threshold selection.
Solution Approach 2:
The patent transitions from a static fixed threshold to a dynamic adaptive threshold. The threshold automatically adjusts its value based on real-time vacuum degree measurements, allowing the system to maintain high discrimination accuracy across varying operating conditions without increasing operational complexity. Users simply operate the device normally while the system self-optimizes the threshold.
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 background noise, enabling the detection of smaller particles by setting a lower discrimination threshold in lower vacuum conditions, thereby improving the accuracy and sensitivity of particle counting.
Implementation Method 1
a light emitter for emitting a light to a measurement area... a scattered light detector for detecting a scattered light generated when a light is delivered to the measurement area... molecules of gas such as oxygen, nitrogen, and other elements are very small particles and scatter light when irradiated
Implementation Method 2
a scattered light detector for detecting scattered light generated when a light is delivered to the measurement area and for converting into an electrical signal
Data Source
AI summary
The present invention provides a particle counter capable of accurately discriminating the signal of scattered light by real particles from the background light noise, and furthermore, capable of detecting smaller particles than conventional particle counters. The particle counter according to the present invention includes: a light irradiator for emitting light to the measurement area 40 in a vacuum state or in a near vacuum state; a scattered light detector 32 for detecting scattered light generated when the light is delivered to the measurement area 40; a discriminator 18 for determining whether or not a particle exists in the measurement area 40 by comparing the detection signal of the scattered light detector 32 and a predetermined discrimination threshold; a vacuum gauge 12 for measuring the pressure of the measurement area 40; and the threshold setting unit 16 for setting a discrimination threshold in accordance with the pressure of the measurement area 40.