Projection Optical System Correction for Exposure Apparatus
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Solution Overview
Problem
Existing projection exposure systems struggle to accurately correct imaging characteristics due to variations in environment conditions like atmospheric pressure, temperature, and humidity, as previous methods rely on a single correction coefficient that does not account for variations in the effective light source, numerical aperture, and mask pattern conditions.
Innovation Solution
An exposure method that calculates and applies correction amounts for the projection optical system based on parameters such as the numerical aperture of the illumination and projection optical systems, and the size and pitch of the pattern, to adjust for changes in environment conditions, specifically using a calculation step and a correction step to drive optical and wafer stages accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single correction coefficient is used for atmospheric pressure changes, then the correction method is simple, but the imaging characteristics cannot be accurately corrected when effective light source, numerical aperture, or mask pattern conditions change
Solution Approach 1:
The patent applies parameter changes by making the correction coefficient variable based on multiple parameters including effective light source type, numerical aperture, and mask pattern conditions. Instead of using a fixed single coefficient, the system selects or calculates appropriate correction coefficients according to the specific combination of these parameters, thereby adapting the correction to match the actual imaging conditions and achieving accurate correction across different operational scenarios
Solution Approach 2:
The patent implements dynamics by transitioning from a static single correction coefficient to a dynamic multi-parameter correction system. The correction coefficient is no longer fixed but changes dynamically based on the effective light source, numerical aperture, and mask pattern conditions. This dynamic adjustment allows the correction system to respond to varying imaging conditions and maintain accuracy across different operational parameters
2Manufacturing precision
If correction coefficients are determined for each combination of effective light source, numerical aperture, and mask pattern, then the imaging characteristics correction accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the correction system into multiple independent correction coefficients, each corresponding to specific combinations of effective light source, numerical aperture, and mask pattern conditions. This segmentation allows the complex correction problem to be broken down into manageable segments that can be handled independently, with each segment addressing a specific set of conditions while collectively providing comprehensive correction coverage
Solution Approach 2:
The patent uses an intermediary approach by introducing a parameter-based selection mechanism that acts as a mediator between the varying imaging conditions and the appropriate correction coefficients. This intermediary system automatically selects or calculates the correct correction coefficient based on the current effective light source, numerical aperture, and mask pattern conditions, thereby managing the complexity through intelligent parameter matching rather than requiring manual configuration for each scenario
Data Source
AI summary
An exposure method comprises a calculation step of calculating a correction amount of a correction unit which corrects a change in imaging characteristics of a projection optical system based on at least one of parameters including a numerical aperture and effective light source of an illumination optical system, a numerical aperture of the projection optical system, and a size and pitch of a pattern, and an amount of change in environment condition in the projection optical system; and a correction step of making the correction unit operate in accordance with the correction amount calculated in the calculation step.