Defect Inspection Apparatus with Real-Time Environmental Focus Correction
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Solution Overview
Problem
Defect inspection sensitivity in semiconductor manufacturing processes is compromised by changes in temperature and barometric pressure, leading to frequent calibration needs and reduced operating efficiency due to image defocus and sensitivity fluctuations.
Innovation Solution
A mechanism that measures temperature and barometric pressure to correct the height of the inspected substrate in real time, using pre-calculated correction values from a data table to maintain optimal imaging focus and sensitivity without requiring a thermostatic chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser beam is projected onto a semiconductor substrate to detect scattered light from particles, then defect detection sensitivity is improved, but the detection sensitivity fluctuates due to temperature and barometric pressure changes
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring temperature and barometric pressure, comparing these values against reference values stored in memory, and automatically adjusting the focal position of the laser beam based on the differences. This closed-loop control system compensates for environmental variations and maintains stable defect detection sensitivity without requiring manual intervention or a thermostatic chamber.
Solution Approach 2:
The patent changes the focal position parameter of the laser beam dynamically based on detected temperature and pressure variations. By calculating the focal position adjustment amount from the differences between current and reference environmental parameters, the system adapts the optical parameters in real-time to maintain optimal detection conditions despite environmental changes.
2Measurement precision
If the detection pixel size is reduced to enhance defect signal strength, then measurement precision is improved, but the focal depth becomes shallow causing image defocus due to temperature and pressure changes
Solution Approach 1:
The patent makes the focal position dynamic rather than fixed. The focal position is continuously adjusted based on real-time temperature and barometric pressure measurements, allowing the system to adapt to environmental changes and maintain sharp imaging focus even with reduced detection pixel size that would otherwise create shallow depth of field.
Solution Approach 2:
The system uses feedback from temperature and pressure sensors to automatically correct focal position deviations. The detected environmental parameters are compared with reference values, and the resulting differences are used to calculate and apply focal position adjustments, ensuring continuous focus accuracy without manual intervention.
3Measurement precision
If sensitivity calibration is performed frequently to maintain detection accuracy, then measurement precision is improved, but the operating rate of the apparatus decreases due to frequent calibration interruptions
Solution Approach 1:
The patent implements self-service calibration where the apparatus automatically monitors and adjusts its own focal position based on environmental conditions without requiring external intervention. The system uses onboard sensors to detect temperature and pressure changes, compares them with stored reference values, and autonomously performs focal position adjustments, eliminating the need for manual calibration operations and maintaining continuous productivity.
Solution Approach 2:
The feedback mechanism continuously monitors environmental parameters and automatically corrects focal position deviations in real-time. This eliminates the need for periodic manual calibration interruptions, as the system self-corrects focus drift caused by temperature and pressure changes, thereby maintaining both high measurement precision and continuous operating rate.
4Stability of the object's composition
If a thermostatic chamber is installed to control temperature variations, then detection sensitivity stability is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical/physical approach of using a thermostatic chamber with a software-based algorithmic solution. Instead of physically controlling temperature through heating or cooling mechanisms, the system uses software algorithms that calculate and apply focal position corrections based on detected temperature and pressure deviations, thereby achieving stability without the complexity of thermal control hardware.
Solution Approach 2:
The patent introduces environmental parameters (temperature and pressure) as intermediaries to indirectly control detection stability. Rather than directly controlling the physical temperature environment through a thermostatic chamber, the system uses these parameters as inputs to calculate focal position adjustments, achieving stability through computational mediation rather than physical environmental control.
5Measurement precision
If the focal depth is reduced to improve detection precision, then measurement precision is improved, but the system becomes more sensitive to environmental changes causing frequent refocusing needs
Solution Approach 1:
The patent uses feedback from environmental sensors to compensate for the reduced depth of field. By continuously monitoring temperature and pressure changes that cause focal drift, the system automatically adjusts the focal position in real-time, allowing the use of reduced focal depth for higher precision while mitigating the increased sensitivity to environmental variations through active compensation.
Solution Approach 2:
The system dynamically changes the focal position parameter in response to environmental conditions. By calculating and applying real-time focal adjustments based on temperature and pressure deviations, the system maintains optimal focus despite the shallower depth of field, effectively managing the trade-off between detection precision and environmental sensitivity.
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 stabilizes defect detection sensitivity, reduces calibration frequency, and maintains high detection accuracy while minimizing equipment size and cost, allowing for continuous operation without the need for a thermostatic chamber.
Implementation Method 1
an image of an inspected substrate formed on an image sensor by a detection lens
Implementation Method 2
a laser beam is projected onto a semiconductor substrate to detect scattered light generated from a particle
Implementation Method 3
a wafer is irradiated with coherent light and diffracted light produced from a repeating pattern on the wafer is removed by a spatial filter
Data Source
AI summary
A defect inspecting apparatus of the invention solves a problem that in a defect inspecting apparatus, because of improving detection sensitivity of a microscopic defect by reducing a detection pixel size, a focal depth becomes shallow, a height of imaging is varied due to environmental change and the detection sensitivity of a defect becomes unstable. This apparatus comprises an XY stage, which carries a substrate to be inspected and scans in a predetermined direction, and a mechanism having a system of irradiating a defect on the inspected substrate at a slant and detecting the defect by a detection optical system disposed on the upper side, which corrects a height of imaging in real time for change in temperature and barometric pressure in order to keep the imaging in a best condition.