Line-Narrowing Laser Mirror Mount for Thermal Beam Pointing Stability
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Solution Overview
Problem
In semiconductor exposure apparatuses, gas laser devices with wide spectral line widths, such as KrF and ArF excimer lasers, suffer from chromatic aberration due to large spectral line widths, which degrade resolution. To mitigate this, line narrowing modules are used, but thermal expansion issues cause beam pointing instability, affecting exposure quality.
Innovation Solution
A line narrowing gas laser device is designed with a wavelength dispersion element, an output coupling mirror, and a rotatable holder system that adjusts the beam pointing to compensate for thermal expansion, ensuring stable output even as temperature changes occur, thereby reducing chromatic aberration and improving resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a line narrowing module is added to narrow the spectral line width, then chromatic aberration is reduced, but thermal expansion causes beam pointing instability
Solution Approach 1:
The patent changes the physical state of the adjustment device by utilizing thermal expansion of the second holder to automatically adjust the mirror's inclination angle. As temperature changes, the holder expands or contracts, rotating the mirror to compensate for beam pointing deviations caused by thermal effects in the line narrowing module.
Solution Approach 2:
The system uses its own thermal response to automatically correct beam pointing instability. The second holder and adjustment device are configured to self-adjust the mirror angle based on temperature changes, eliminating the need for external control systems or manual intervention.
2Reliability
If the beam pointing is adjusted to compensate for thermal expansion, then beam pointing stability is improved, but the structure becomes more complex
Solution Approach 1:
The patent deliberately utilizes thermal expansion of the second holder as the driving mechanism for beam pointing adjustment. By designing the holder with appropriate thermal expansion characteristics, the system converts temperature changes into useful angular adjustments of the output coupling mirror, simplifying the overall control mechanism.
Solution Approach 2:
The system transitions from a static mirror mounting to a dynamic adjustment mechanism where the mirror angle can change in response to temperature variations. The rotatable first holder mounted on the second holder creates a flexible, adaptive optical path that automatically responds to thermal conditions.
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 effectively stabilizes beam pointing and reduces chromatic aberration, enhancing the resolution and exposure quality of the semiconductor manufacturing process by dynamically adjusting the beam alignment in response to thermal changes.
Implementation Method 1
a line narrowing device including a wavelength dispersion element
Implementation Method 2
a line narrowing device including a wavelength dispersion element
Implementation Method 3
the second holder and the adjustment device are configured to rotate the first holder in a direction in which a change in the first direction in the beam pointing of the laser light output from the output coupling mirror is suppressed by thermal expansion when temperature of the second holder and the adjustment device rises
Data Source
AI summary
A line narrowing gas laser device includes a line narrowing device, an output coupling mirror, a laser chamber arranged on an optical path of an optical resonator, a first holder which supports the output coupling mirror, a second holder which supports the first holder to be rotatable about a rotation axis of the first holder, and an adjustment device supported by the second holder and being in contact with the first holder to rotate the first holder about the rotation axis. The line narrowing device has a characteristic of changing, into a first direction, beam pointing of laser light output toward the output coupling mirror when temperature inside the line narrowing device rises. The second holder and the adjustment device rotate the first holder in a direction in which a change in the first direction in the beam pointing of the laser light is suppressed by thermal expansion.