Pattern Inspection Apparatus Gravitational Distortion Correction
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Solution Overview
Problem
The increasing complexity of semiconductor manufacturing requires more accurate pattern inspection methods to detect defects in ultrafine patterns, but existing systems face challenges in maintaining high inspection speed while correcting for gravitational distortion, which increases costs due to the need for faster feedback operations.
Innovation Solution
A pattern inspection method that uses a support member to correct linear and secondary components of gravitational distortion in the specimen by creating a distortion map and employing an autofocusing feedback circuit to align the pattern surface uniformly, allowing for faster imaging speeds without requiring high-speed feedback operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the imaging speed is increased to improve productivity, then the inspection efficiency is improved, but the feedback operation speed must be increased which adversely increases the entire cost of the pattern inspection apparatus
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction values for gravitational distortion in a lookup table before inspection. The support heights that compensate for gravitational distortion are calculated in advance based on the relationship between support point positions and distortion amounts, allowing the inspection system to simply retrieve and apply these pre-computed values during high-speed imaging without requiring complex real-time feedback calculations.
2Measurement precision
If the feedback operation speed is increased to maintain focus during high-speed imaging, then the imaging quality is maintained, but the entire cost of the pattern inspection apparatus increases
Solution Approach 1:
The system pre-calculates correction values for gravitational distortion and stores them in a lookup table. During inspection, the system simply retrieves the appropriate correction value based on the current support point position and applies it to adjust the support heights, eliminating the need for expensive high-speed feedback operations while maintaining imaging quality.
Solution Approach 2:
The patent replaces the mechanical feedback control system with a computational approach using pre-calculated correction values. Instead of using complex real-time feedback mechanisms to maintain focus during high-speed imaging, the system uses stored correction data to predict and compensate for gravitational distortion, substituting expensive mechanical feedback with simpler computational retrieval and application of correction values.
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 accurate defect inspection at increased imaging speeds while reducing the operational costs associated with high-speed feedback, ensuring efficient and cost-effective pattern inspection for semiconductor manufacturing.
Implementation Method 1
Light having transmitted through or reflected from the specimen forms an image on a sensor via an optical system
Implementation Method 2
An autofocus function by a slit-projection mask-plane-position measurement device is used to align the surface of the mask with the imaging plane
Data Source
AI summary
A method according to an embodiment includes: mounting a reference-specimen of a same material as that of a specimen on a support member and creating a map indicating a distortion in a gravity direction of the reference-specimen; mounting the specimen on the support member and irradiating light to the specimen; correcting a linear component of a distortion in a gravity direction of the specimen between a first point on the specimen and a second point located in the first scanning direction on the specimen on a basis of a first difference in the gravity direction between the first and second points in the map, and correcting a secondary component of the distortion in the gravity direction of the specimen using a feedback circuit, when the pattern is imaged; and performing a defect inspection using an image of the pattern.