Laser Spectral Width Control for Semiconductor Exposure
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Solution Overview
Problem
In sequentially moving type exposure apparatuses, the increasing numerical aperture and finer patterns in semiconductor devices require precise control and monitoring of laser spectral width to minimize linewidth errors and ensure accurate image-forming, as changes in spectral characteristics of the laser beam can no longer be ignored.
Innovation Solution
An exposure apparatus and method that includes a laser unit with a storage unit for pattern size error-spectral characteristic information and a spectral control unit to adjust the laser beam's spectral width based on this information, ensuring accurate pattern formation without size errors, and a system with a spectroscope for precise spectral width measurement and calibration of multiple laser units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the numerical aperture of the projection optical system is increased to achieve finer patterns and higher integration of semiconductor devices, then the resolution and image-forming capability are improved, but the sensitivity of image-forming to spectral width variation increases, causing linewidth errors that can no longer be ignored
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the spectral width of the laser beam to compensate for linewidth errors. The spectral control unit modifies the spectral characteristic parameter (spectral width) based on the relationship between spectral width and linewidth error, thereby resolving the contradiction between achieving fine patterns with high NA and maintaining stability against spectral variation
Solution Approach 2:
The patent implements feedback control by measuring the actual spectral width of the laser beam and comparing it with the target spectral width. The spectral control unit uses this feedback information to adjust the spectral width, creating a closed-loop control system that maintains image-forming stability despite variations in operating conditions
2Manufacturing precision
If optical elements such as gratings or etalons are used to narrow the laser spectral width to the ultimate level, then the spectral width is reduced to meet the requirements of high N.A. projection systems, but the manufacturing error of the narrowing element and other factors cause spectral characteristic changes that affect linewidth accuracy
Solution Approach 1:
The patent uses feedback control to measure the actual spectral width and adjust it to achieve the target spectral width. This closed-loop approach compensates for manufacturing errors in narrowing elements and other sources of spectral variation, thereby maintaining both spectral width control and linewidth measurement accuracy
Solution Approach 2:
The patent performs preliminary spectral width adjustment before exposure by predicting the required spectral width based on the pattern type and exposure conditions. This preliminary action ensures that the spectral width is optimized before the actual exposure process, preventing linewidth errors from occurring in the first place
3Productivity
If multiple exposure apparatus are used in the same manufacturing line for semiconductor device production, then the productivity is improved, but the spectral characteristics of the laser beam may vary among different apparatus, causing errors in pattern formation
Solution Approach 1:
The patent implements a universal spectral control method that can be applied to multiple exposure apparatus in the same manufacturing line. By using the same spectral control strategy and target spectral width settings across all apparatus, the system achieves consistent pattern formation while maintaining high productivity through parallel processing
Solution Approach 2:
The patent adjusts the spectral width parameter to match the specific pattern type being exposed on each apparatus. By dynamically changing the spectral width parameter based on the pattern requirements and apparatus characteristics, the system maintains pattern consistency across multiple apparatus while maximizing manufacturing throughput
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 solution enables precise control of laser spectral width, reducing size errors in pattern formation and improving the precision of device manufacturing by accurately managing and calibrating the spectral characteristics of the laser beam, thereby enhancing the quality of semiconductor device production.
Implementation Method 1
a laser unit that emits a laser beam as the energy beam
Implementation Method 2
a spectral control unit that controls spectral width of the laser beam based on the pattern size error-spectral characteristic information
Data Source
AI summary
An exposure apparatus is equipped with a laser unit that emits a laser beam, a memory that stores a first information which shows a first relation indicating a relation between a linewidth error of a pattern formed on a wafer and a spectral characteristic of the laser beam emitted from the laser unit, and a main controller that controls the spectral width of the laser beam via a laser controller, based on the first information and on information related to a reticle that is to be used. Main controller performs spectral width control of the laser beam so as to suppress linewidth error, based on the first information and on the information related to the reticle that is to be used.