Variable Grating Incidence for Narrow-Linewidth Excimer Lasers
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Solution Overview
Problem
In semiconductor exposure apparatuses, the wide spectrum line width of KrF and ArF excimer laser beams leads to chromatic aberration, reducing resolving power due to the use of materials that transmit ultraviolet light, necessitating a method to narrow the spectrum line width of laser beams.
Innovation Solution
A laser apparatus with a grating system and an actuator system that adjusts the incident angles of optical beams on the grating, controlled by a processor to periodically vary these angles, ensuring they differ in phase or variation range, thereby achieving a narrower spectrum line width and reducing chromatic aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a projection lens is made of a material that transmits ultraviolet light (such as KrF and ArF laser beams), then the laser beam can pass through the lens, but chromatic aberration occurs due to the wide spectrum line width, reducing resolving power
Solution Approach 1:
The patent applies dynamics by making the grating incident angle variable rather than fixed. The incident angle is dynamically adjusted during laser oscillation to sweep through a range of angles, which narrows the spectrum line width and reduces chromatic aberration while maintaining UV transmission through the lens
Solution Approach 2:
The patent changes the physical parameter of the grating incident angle to control the spectrum line width. By varying the incident angle parameter, the system achieves narrower spectral output that minimizes chromatic aberration effects in the UV-transmitting projection lens
2Object-affected harmful factors
If the spectrum line width of the laser beam is narrowed using a line narrowing module, then chromatic aberration is reduced, but the device complexity increases
Solution Approach 1:
The patent makes the existing grating in the laser resonator serve multiple functions: it acts as both the wavelength-selective element and the line-narrowing element. By controlling the incident angle dynamically, the single grating component achieves spectrum narrowing without requiring an additional dedicated line narrowing module, thus reducing device complexity
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 configuration enhances the resolving power by achieving a flat-top integration spectrum waveform with a wide wavelength range, improving the imaging performance and focal point depth during semiconductor manufacturing.
Implementation Method 1
a line narrowing module (LNM) including a line narrowing element (for example, etalon or grating) is provided in a laser resonator
Implementation Method 2
a processor configured to control the actuator system to periodically vary the first and second incident angles so that the first and second incident angles are different from each other in at least one of phase and variation range
Data Source
AI summary
A laser apparatus includes a grating system; an actuator system configured to adjust a first incident angle on the grating system and a second incident angle on the grating system, the first incident angle being an angle of a first part of an optical beam incident on the grating system, the second incident angle being an angle of a second part of the optical beam incident on the grating system; and a processor configured to control the actuator system to periodically vary the first and second incident angles so that the first and second incident angles are different from each other in at least one of phase and variation range.