Laser Beam Divergence Adjustment for Stable Semiconductor Exposure
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Solution Overview
Problem
Chromatic aberration in semiconductor exposure apparatuses due to large spectral line widths of KrF and ArF excimer laser devices leads to decreased resolution, necessitating line-narrowed laser devices with line narrowing modules, but beam divergence angle changes cause vignetting and energy loss when repetition frequency or duty changes.
Innovation Solution
A laser device with an optical pulse stretcher and beam divergence angle adjuster, including an upstream and downstream lens with an optical path length changing mechanism, controlled by a processor to maintain a small beam divergence angle despite changes in repetition frequency or duty.
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 beam divergence angle changes when repetition frequency or duty changes, causing vignetting and energy loss
Solution Approach 1:
The patent applies the dynamics principle by making the optical path length adjustable through a movable mirror. The mirror position is dynamically changed based on the repetition frequency or duty cycle to maintain a constant beam divergence angle. This allows the system to adapt to different operating conditions while preserving beam quality and preventing energy loss from vignetting.
Solution Approach 2:
The patent changes the optical path length parameter in response to changes in repetition frequency or duty cycle. By adjusting the mirror position to modify the optical path length, the system compensates for beam divergence angle changes and maintains consistent beam characteristics across different operating parameters, thereby preventing energy loss.
2Productivity
If the repetition frequency or duty is increased to improve productivity, then output is improved, but the beam divergence angle changes causing vignetting and energy loss
Solution Approach 1:
The patent implements feedback control by monitoring the repetition frequency or duty cycle and automatically adjusting the mirror position to maintain the optimal optical path length. This closed-loop control ensures that the beam divergence angle remains constant even when productivity parameters change, preventing energy loss from vignetting while allowing high-output operation.
Solution Approach 2:
The system dynamically adjusts the optical path length based on the operating conditions. When productivity parameters such as repetition frequency or duty cycle change, the mirror position is automatically modified to compensate for beam divergence angle changes, enabling high-productivity operation without energy loss.
3Loss of energy
If the beam divergence angle is reduced to prevent vignetting and energy loss, then energy efficiency is improved, but additional optical components and control mechanisms are required
Solution Approach 1:
The patent makes the existing optical components multi-functional by using the movable mirror for dual purposes: beam steering and optical path length adjustment. This approach reduces the need for separate dedicated components for beam divergence control, thereby limiting the increase in device complexity while achieving the goal of preventing energy loss.
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
Stabilizes beam divergence angle, preventing vignetting and energy loss, thereby maintaining consistent exposure quality in semiconductor manufacturing.
Implementation Method 1
an optical pulse stretcher including a beam splitter and a plurality of mirrors, and configured to extend a pulse width of the pulse laser light
Implementation Method 2
a beam divergence angle adjuster including an upstream lens arranged upstream on an optical path of the pulse laser light, a downstream lens arranged downstream of the upstream lens on the optical path, and an optical path length changing mechanism for changing an inter-lens optical path length between the upstream lens and the downstream lens
Implementation Method 3
an oscillator configured to output pulse laser light having an ultraviolet wavelength
Implementation Method 4
an amplifier configured to amplify the pulse laser light
Data Source
AI summary
A laser device includes an oscillator outputting pulse laser light; an amplifier amplifying the pulse laser light; an optical pulse stretcher extending a pulse width of the pulse laser light; a beam divergence angle adjuster including an upstream lens arranged on an optical path of the pulse laser light, a downstream lens arranged downstream of the upstream lens, and an optical path length changing mechanism for changing an inter-lens optical path length between the upstream lens and the downstream lens; and a processor controlling the beam divergence angle adjuster and obtaining a repetition frequency or a duty of the pulse laser light, and to change, when the repetition frequency or the duty changes by a preset threshold or more, the inter-lens optical path length so that the beam divergence angle of the extended pulse laser light becomes small in accordance with the repetition frequency or the duty after the change.