Mask Inspection System with Position Error Correction Stripes
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Solution Overview
Problem
As semiconductor device patterns shrink to nanometer sizes, existing inspection systems face challenges in accurately detecting defects due to increased position fluctuations caused by thermal drift and air flow fluctuations, leading to measurement errors and reduced inspection efficiency.
Innovation Solution
An inspection system and method that utilize a position error correcting unit with patterns virtually divided into stripes, acquiring optical images of both the sample and the correcting unit to compare and correct position coordinates, and produce a map of position coordinate fluctuations, thereby reducing position errors and improving inspection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the inspection time is prolonged to achieve high magnification for detecting smaller pattern defects, then the measurement precision improves, but position fluctuation increases due to thermal drift and air flow changes
Solution Approach 1:
The patent implements a feedback mechanism by measuring the position of the position error correcting unit patterns during inspection, calculating position errors relative to reference positions, and using these errors to correct the optical images of the sample. This closed-loop feedback system compensates for thermal drift and air flow fluctuations, maintaining position stability during prolonged high-magnification inspection.
Solution Approach 2:
The patent introduces a position error correcting unit with known reference patterns as an intermediary standard. This intermediary provides stable reference positions that mediate between the unstable inspection environment and the measurement process, enabling accurate defect detection by comparing sample patterns against the corrected reference framework.
2Measurement precision
If high magnification is used to detect smaller pattern defects, then the measurement precision improves, but the inspection time increases
Solution Approach 1:
The patent performs preliminary action by pre-calculating position error correction values based on measurements of the position error correcting unit before inspecting the sample. This preliminary correction framework is established in advance, allowing the actual sample inspection to proceed more efficiently with real-time correction application, reducing total inspection time while maintaining high magnification precision.
3Productivity
If the pattern dimensions are reduced to increase LSI capacity, then the productivity improves, but the difficulty of detecting and measuring increases
Solution Approach 1:
The position error correcting unit serves as an intermediary measurement standard that provides stable reference positions even when inspecting nanometer-scale patterns. This intermediary framework enables accurate defect detection of ultra-fine patterns by compensating for position fluctuations, making it feasible to inspect smaller features that correspond to higher LSI capacity designs.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting position correction values based on measured errors from the position error correcting unit. This real-time parameter adjustment compensates for environmental variations during inspection, maintaining measurement capability across different pattern scales including the nanometer dimensions required for high-capacity LSI devices.
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
The system effectively corrects position errors and enhances inspection accuracy by continuously scanning the sample and position error correcting unit, allowing for precise defect detection and maintaining high inspection efficiency even with smaller pattern dimensions.
Implementation Method 1
an optical image acquiring unit configured to irradiate light onto the inspection region of the sample and onto the position error correcting unit, thereby obtaining optical images
Data Source
AI summary
An inspection region of a mask is virtually divided by stripes, and a pattern on a position error correcting unit is also virtually divided by stripes. Then, a stage is moved such that all the stripes of both the mask and the position error correcting unit are continuously scanned, so that optical images of these stripes are acquired. Fluctuation values of position coordinates of the patterns formed on the position error correcting unit are acquired from the optical images of the position error correcting unit. Based upon the fluctuation values, fluctuation values of the position coordinates of the respective patterns in the inspection region of the mask are obtained so that the position coordinates are corrected. Thereafter, a map is generated from the fluctuation values of the position coordinates of the respective patterns in the inspection region of the mask.