Narrow-band Laser Spectral Line Width Adjustment
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Solution Overview
Problem
The variation in spectral line width, specifically E95 bandwidth, among narrow-band laser devices leads to inconsistent quality of integrated circuit patterns due to machine differences and maintenance-related changes, exceeding allowable ranges and affecting semiconductor device production.
Innovation Solution
A method to adjust the spectral line width of narrow-band lasers by setting upper and lower limits and using a spectral line width adjustment unit, such as a wavefront adjuster, cylindrical lenses, or grating curvature mechanisms, to maintain the E95 bandwidth within a common range, minimizing deviations among devices and after maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a line narrowing module is provided in the laser resonator to narrow the spectral line width, then chromatic aberration is reduced and resolution is improved, but the spectral line width varies among different laser devices and after maintenance, exceeding allowable ranges
Solution Approach 1:
The patent applies parameter changes by adjusting the curvature radius of the grating surface in the line narrowing module. By changing this geometric parameter, the spectral line width (E95 bandwidth) is controlled to fall within a specific range (0.350-0.450 pm), ensuring consistency across different laser devices and maintaining stability after maintenance operations.
Solution Approach 2:
The patent implements preliminary action by pre-adjusting the grating curvature radius during the laser device setup or maintenance phase. This preliminary adjustment ensures that when the laser is投入 into production use, the spectral line width is already within the acceptable range, preventing quality issues before they occur during semiconductor exposure operations.
2Manufacturing precision
If the spectral line width is narrowed to reduce chromatic aberration, then image formation performance is improved, but the complexity of adjusting and maintaining the laser device increases
Solution Approach 1:
The patent simplifies the adjustment mechanism by focusing on changing a single key parameter - the curvature radius of the grating surface. This approach avoids the need for complex multi-parameter adjustment systems while still achieving the desired spectral line width control and image formation performance.
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 stabilizes the quality of integrated circuit patterns by ensuring the spectral line width remains within the acceptable range, improving semiconductor device yield and reducing production and maintenance costs.
Implementation Method 1
One of techniques to change the laser light wavefront is disclosed in the Patent Document 1 (Japanese Patent Application Laid-Open No. 2000-312048) which relates to a device for changing the curvature of a grating.
Implementation Method 2
a line narrowing module having a line narrowing element (e.g. etalon or grating) is provided in a laser resonator of the gas laser device, so that the spectral line width is narrowed
Data Source
AI summary
An upper limit and a lower limit are preliminarily set for a spectral line width common to a plurality of narrow-band laser devices. When delivered or subjected to maintenance, the narrow-band laser device is caused to laser oscillate to detect its spectral line width before it is used as a light source for semiconductor exposure. A spectral line width adjustment unit provided in the narrow-band laser device is adjusted so that the spectral line width assumes a value between the upper limit and the lower limit. The present invention is able to suppress the variation in spectral line width such as E95 bandwidth caused by machine differences during the manufacture of the laser device, or by replacement or maintenance of the laser device, whereby the quality of integrated circuit patterns formed by the semiconductor exposure tool can be stabilized.