Actuator Pad Geometry for Projection Exposure Rigidity
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Solution Overview
Problem
In projection exposure apparatuses for semiconductor lithography, parasitic deformations caused by actuators lead to imaging quality issues due to loss of rigidity at the peripheries of actuator matrices, which are exacerbated by scanning operations, resulting in aberrations that negatively impact the imaging quality.
Innovation Solution
A force-fitting connection between optical elements and actuators, with the actuator designed to minimize peripheral rigidity losses by optimizing the geometry and arrangement of actuator pads and holes, and incorporating a separately controllable section to compensate for rigidity deviations, thereby reducing parasitic deformations and aberrations through a method involving FEM simulations and optical measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If actuators are adhesively connected to the rear side of mirrors to create mechanical connection for targeted deformation, then the optical element can be deformed to improve imaging quality, but loss of rigidity at the peripheries occurs causing parasitic deformations
Solution Approach 1:
The actuator is divided into multiple actuator pads arranged in an actuator matrix, with each pad independently controllable. This segmentation allows targeted deformation of specific regions while maintaining overall structural integrity and distributing mechanical stresses to minimize parasitic deformations at peripheries.
Solution Approach 2:
Different regions of the actuator are designed with different properties: the peripheral sections have reduced cumulative length parallel to scanning direction and aligned at angles thereto, while the central region provides primary deformation control. This local differentiation minimizes rigidity loss at peripheries while maintaining effective actuation capability.
2Ease of operation
If actuators are designed with holes for contacting controllers, then electrical connection is enabled, but rigidity loss occurs at the peripheries of the holes causing additional parasitic deformations
Solution Approach 1:
The holes are positioned asymmetrically within the actuator pads, specifically at corners or sides rather than at the center. This asymmetric placement minimizes the cumulative length of hole peripheries parallel to the scanning direction and reduces their impact on rigidity while maintaining effective electrical contact capability.
3Productivity
If scanning mode operation is used to improve productivity, then throughput increases, but parasitic deformations add up along scanning direction causing more pronounced imaging quality issues
Solution Approach 1:
The actuator peripheral sections are specifically designed with reduced cumulative length parallel to the scanning direction and with peripheries aligned at angles to the scanning direction. This local optimization at the actuator level counteracts the cumulative effect of parasitic deformations during scanning, maintaining imaging quality while enabling high-speed scanning operation.
4Adaptability or versatility
If different materials with different coefficients of thermal expansion are used for actuator and optical element, then functional requirements are met, but thermal expansion differences cause parasitic deformations
Solution Approach 1:
The segmented actuator pad structure with optimized peripheral sections and angular alignment distributes thermal stresses more evenly across the actuator-optical element interface. This segmentation reduces the cumulative effect of differential thermal expansion while maintaining the ability to use functionally appropriate materials for each component.
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 minimizes parasitic deformations and aberrations, improving the imaging quality by averaging out peripheral effects during scanning and allowing for real-time correction of deformations, thus enhancing the overall performance of the projection exposure apparatus.
Implementation Method 1
an actuator (32, 35, 39.1-39.6, 43, 50) for deforming the optical element (31, 117)
Implementation Method 2
the actuator (32, 35, 39.1-39.6, 43, 50) is configured to at least locally deform the optical element (31, 117)
Implementation Method 3
The force-fitting connection between the actuator and the optical element, such as a mirror, can be brought about by an adhesive connection or bonding
Implementation Method 4
some optical effects of disturbances extending perpendicular to the scanning direction, such as parasitic deformations, are averaged out by the scanning operation and thus minimized
Data Source
AI summary
A component for a projection exposure apparatus for semiconductor lithography, comprises an optical element and an actuator, which are force-fittingly connected to each other. The actuator at least locally deforms the optical element. The actuator can be configured to minimize the loss in rigidity at the peripheries delimiting the actuator on the imaging quality. A method for designing a component of projection exposure apparatus is provided.