Photomask Inspection Apparatus Deflection Correction
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Solution Overview
Problem
Current pattern inspection apparatuses face challenges in accurately measuring positional deviations due to deflection of the mask during inspection, which affects the precision of pattern defect detection and positional measurement, especially when the pattern forming surface is oriented downward, leading to bending and positional errors.
Innovation Solution
The apparatus includes optical image acquisition, first and second measurement units to quantify positional deviations, and a difference map generation unit to correct for deflection-induced errors by subtracting the first positional deviation from the second, allowing for precise positional deviation mapping and defect inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the pattern forming surface is oriented downward during inspection, then the mask can be supported from below and foreign substances can be prevented from adhering to the pattern surface, but the mask undergoes deflection due to gravity causing positional deviation in pattern measurement
Solution Approach 1:
The patent changes the physical parameter of the mask by attaching a rigid backing board to the rear surface of the mask. This increases the stiffness and reduces the deflection caused by gravity when the mask is held in the downward orientation during inspection, thereby maintaining measurement precision while preventing foreign substance adhesion.
2Object-affected harmful factors
If the mask is supported from the external side of the pattern forming surface, then the pattern surface can be protected, but the mask deflects due to its own weight causing bending of the pattern forming surface
Solution Approach 1:
The patent modifies the mechanical parameters of the mask system by adding a rigid backing board to the rear surface. This increases the overall stiffness and reduces gravitational deflection, maintaining the protective support configuration while minimizing pattern forming surface bending.
3Productivity
If the inspection apparatus measures both pattern defects and positional deviations using the same optical system, then inspection efficiency is improved, but measurement accuracy of positional deviation is reduced due to mask deflection
Solution Approach 1:
The patent changes the mechanical parameter of the mask by providing a rigid backing board that reduces deflection. This allows the combined inspection system to maintain high measurement accuracy for positional deviations while continuing to efficiently inspect both defects and positions using the same optical system.
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 solution enables accurate correction of positional deviations caused by mask deflection, enhancing the precision of pattern defect inspection and measurement, thereby improving the overall yield and reducing manufacturing costs in semiconductor production.
Implementation Method 1
Light transmitted through the target object or reflected therefrom is focused on a sensor through the optical system
Implementation Method 2
acquire an optical image of the pattern image on the substrate by applying laser irradiation thereto
Data Source
AI summary
An inspection apparatus includes an optical image acquisition unit to acquire an optical image of a photomask on which a plurality of figure patterns are formed, a first measurement unit to measure a first positional deviation amount in the horizontal direction at each position on the photomask accompanying deflection of the surface of the photomask generated by supporting the photomask using a support method which is used for acquiring the optical image, a second measurement unit to measure a second positional deviation amount of each of the plurality of figure patterns, by using the optical image, and a difference map generation unit to generate a difference map in which a difference value obtained by subtracting the first positional deviation amount from the second positional deviation amount is used as a map value, with respect to a region on the surface of the photomask.