Adjustable Diffraction Grating for Lithography Beam Control
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Solution Overview
Problem
Current radiation beam apparatuses in lithographic systems face challenges in efficiently controlling the power and angular separation of output radiation beams, particularly at small grazing incidence angles, which affects the precision and efficiency of feature formation on substrates.
Innovation Solution
An adjustable diffraction grating mechanism with a distortion mechanism using actuators to control the shape of a periodic structure on an optical surface, allowing for precise control of output radiation beams by adjusting the pressure or shape of the diffraction grating, enabling high-speed operation and minimal power absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional radiation beam apparatuses are used to control output radiation beams, then the system structure is simple, but the control precision of output beam power and angular separation is insufficient
Solution Approach 1:
The patent employs a dynamically adjustable diffraction grating where the periodic structure on the optical surface can be modified in real-time. By changing the shape, depth, or spacing of the periodic structure through actuators, the system achieves precise control over output beam power and angular separation. This dynamic adjustment capability resolves the contradiction by providing high control precision without requiring multiple fixed apparatuses.
Solution Approach 2:
The invention changes physical parameters of the diffraction grating, such as the period, depth, or shape of the periodic structure, to control the diffraction characteristics. By adjusting these parameters, the system can precisely control the power and angular separation of output beams. This parameter-based control approach achieves high precision while maintaining a relatively simple single-element device structure.
2Adaptability or versatility
If the optical element is made movable to adjust the diffraction grating, then the control flexibility is improved, but the response time increases and high-speed operation is compromised
Solution Approach 1:
The patent segments the optical element into a rigid substrate and a separate adjustable periodic structure (such as a membrane or surface layer). The periodic structure can be independently adjusted through actuators while the main optical element remains fixed. This segmentation allows for rapid adjustment of diffraction characteristics without moving the entire optical element, thus maintaining high-speed operation capability while achieving control flexibility.
Solution Approach 2:
The invention replaces traditional mechanical movement of the entire optical element with alternative mechanisms such as piezoelectric actuators, electrostatic actuators, or thermal expansion elements that can modify the periodic structure in place. These substitution mechanisms provide faster response times and enable high-speed adjustment of diffraction properties without the inertia and mechanical complexity associated with moving heavy optical components.
3Measurement precision
If the grazing incidence angle is reduced to improve beam control, then the angular precision is improved, but the power absorption by the optical element increases
Solution Approach 1:
The patent applies local quality by creating a periodic structure with spatially varying properties (different depths, shapes, or materials) across the optical surface. This allows different regions to optimize for either angular precision or power reflection, enabling the system to achieve high angular precision at small grazing angles while minimizing overall power absorption through local optimization of the periodic structure characteristics.
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 enables precise control of output radiation beams, allowing for high-speed operation with short response times and reduced power absorption, maintaining efficiency even at small grazing incidence angles, thereby improving the precision and consistency of feature formation in lithographic processes.
Implementation Method 1
form a periodic structure on the optical surface which acts as a diffraction grating such that the input radiation beam is diffracted from the optical element to form a plurality of angularly separated sub-beams
Implementation Method 2
The closed channels may be filled with a fluid and the distortion mechanism comprises one or more actuators that are operable to control the pressure of the fluid within the plurality of closed channels
Data Source
AI summary
An adjustable diffraction grating includes: an optical element and a distortion mechanism. The optical element has an optical surface to receive an input radiation beam. The optical element is provided with a plurality of closed channels below the optical surface, above each closed channel the optical surface being formed from a membrane of material. The distortion mechanism includes one or more actuators that are operable to distort the membranes over the closed channels so as to control the shape of the optical surface and to form a periodic structure on the optical surface which acts as a diffraction grating such that the input radiation beam is diffracted from the optical element to form a plurality of angularly separated sub-beams.