Electro-Optic Prism Wavelength Control in Excimer Lasers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Chromatic aberration in semiconductor exposure apparatuses due to the large spectral linewidth of KrF and ArF excimer laser beams leads to decreased resolution, necessitating improved wavelength control to minimize chromatic aberration.
Innovation Solution
Incorporation of an electro-optic crystal in the prism within the laser apparatus to dynamically control the wavelength of the laser beam using electro-optic effects, combined with mechanical rotation, enabling high-speed and accurate wavelength adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a line narrowing module including a line narrowing element is provided in a laser resonator to narrow the spectral linewidth, then chromatic aberration is reduced and resolution is improved, but the device complexity increases
Solution Approach 1:
The patent replaces the conventional mechanical rotation of a grating with an electro-optic crystal and prism system. The electro-optic crystal changes its refractive index in response to applied voltage, dynamically adjusting the laser beam direction and wavelength selection without mechanical movement. This substitution of mechanical systems with electro-optic systems achieves wavelength control while reducing mechanical complexity and improving response speed.
Solution Approach 2:
The patent utilizes the electro-optic effect where the refractive index of the electro-optic crystal changes in response to applied voltage. By changing the voltage parameter, the system dynamically adjusts the laser beam's propagation direction and the effective optical path, thereby controlling the selected wavelength and narrowing the spectral linewidth without mechanical intervention.
2Manufacturing precision
If a grating is used in the optical resonator for wavelength selection, then spectral linewidth is narrowed, but the response speed of wavelength adjustment is limited
Solution Approach 1:
The patent replaces mechanical grating rotation with an electro-optic crystal and prism system. The electro-optic crystal responds to voltage changes at electronic speeds, dynamically adjusting the laser beam direction and wavelength selection instantaneously. This eliminates the inertia and mechanical limitations of rotating gratings, achieving high-speed wavelength adjustment while maintaining precise wavelength control through the electro-optic effect.
Solution Approach 2:
The patent introduces dynamic control of the laser wavelength through voltage application to the electro-optic crystal. The system transitions from static or mechanically slow adjustment to dynamically responsive control where wavelength can be changed rapidly by varying the voltage parameter in real-time, enabling high-speed wavelength tuning synchronized with laser pulse generation.
3Manufacturing precision
If the spectral linewidth of the laser beam is narrowed to ignore chromatic aberration, then resolution is improved, but the device complexity and control difficulty increase
Solution Approach 1:
The patent replaces complex mechanical wavelength adjustment mechanisms with an electro-optic crystal system controlled by voltage. This substitution simplifies the control interface to electrical signals, making wavelength selection and spectral linewidth control more straightforward and easier to automate, while achieving the necessary wavelength precision to minimize chromatic aberration.
Solution Approach 2:
The patent utilizes voltage as a simple, easily controllable parameter to adjust the electro-optic crystal's refractive index. By changing the voltage parameter, the system directly controls the laser beam's propagation characteristics and wavelength selection, providing an intuitive and easily measurable control mechanism that simplifies wavelength management while maintaining narrow spectral linewidth.
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
Enhances wavelength control responsiveness and accuracy, reducing chromatic aberration and improving resolution in semiconductor manufacturing processes.
Implementation Method 1
a first electro-optic crystal that changes a direction in which the light beam travels toward the grating when voltage is applied to the second electrodes from the power supply
Implementation Method 2
The optical resonator may include an output mirror and a grating
Implementation Method 3
The first prism may be provided between the laser chamber and the grating and may expand a light beam output from the laser chamber and direct the expanded light beam toward the grating
Data Source
AI summary
A laser apparatus includes an optical resonator including an output mirror and a grating, a laser chamber disposed in an optical path of the optical resonator and including a pair of first electrodes configured to apply voltage to a laser gain medium, a power supply, and a first prism that is provided between the laser chamber and the grating and that expands a light beam output from the laser chamber and directs the expanded light beam toward the grating. The first prism includes a pair of second electrodes, and a first electro-optic crystal that changes a direction in which the light beam travels toward the grating when voltage is applied to the second electrodes from the power supply.