Excimer Laser Feedback Control for Speckle Contrast and Resolution
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Solution Overview
Problem
Chromatic aberration occurs in semiconductor exposure apparatuses due to the large spectral line width of KrF and ArF excimer laser devices, leading to decreased resolution, and existing methods struggle to detect speckle contrast deterioration in connected exposure apparatuses without disconnecting them.
Innovation Solution
A laser device equipped with a beam intensity distribution measurement device, beam angle distribution measurement device, pulse waveform measurement device, and spectrum measurement device, along with a laser controller to calculate speckle contrast, allowing for real-time detection and adjustment of pulse width, spectral line width, and etendue to maintain exposure quality.
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 device complexity increases
Solution Approach 1:
The patent implements feedback control by measuring actual laser parameters (spectral line width, pulse width, beam diameter) and adjusting the line narrowing element's inclination angle based on measured deviations from target values, thereby maintaining resolution without requiring overly complex mechanical structures
Solution Approach 2:
The patent replaces complex mechanical adjustment mechanisms with a control system that uses measurements from detection devices to calculate and apply appropriate adjustments to the line narrowing element, substituting mechanical complexity with computational control
2Reliability
If multiple measurement devices are added to the laser device, then speckle contrast can be detected and maintained, but the device complexity increases
Solution Approach 1:
The patent designs measurement devices that serve multiple functions: the spectral line width measurement device also provides data for pulse width control, and the beam diameter measurement device contributes to both speckle contrast calculation and beam quality assessment, thereby reducing overall system complexity through functional integration
Solution Approach 2:
The patent combines multiple measurement functions into a coordinated control system where data from spectral line width measurement, pulse width measurement, and beam diameter measurement are integrated to comprehensively assess and control speckle contrast, reducing the need for separate independent control loops
3Object-affected harmful factors
If the spectral line width is narrowed, then chromatic aberration is reduced, but the device complexity and measurement requirements increase
Solution Approach 1:
The patent uses feedback control where the spectral line width measurement device continuously monitors the actual spectral line width and the control unit adjusts the line narrowing element's inclination angle to maintain the target spectral line width, thereby minimizing chromatic aberration through active control rather than passive design
Data Source
AI summary
A laser device includes a laser oscillation device configured to output pulse laser light; a beam intensity distribution measurement device configured to measure a beam intensity distribution of the pulse laser light; a beam angle distribution measurement device configured to measure a beam angle distribution of the pulse laser light; a pulse waveform measurement device configured to measure a pulse waveform of the pulse laser light; a spectrum measurement device configured to measure a spectrum of the pulse laser light; and a laser controller configured to calculate a speckle contrast based on measurement data of each of the beam intensity distribution, the beam angle distribution, the pulse waveform, and the spectrum.