Mask Holding Apparatus for Lithography Aberration Correction
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Solution Overview
Problem
In lithography processes using high-energy light sources like KrF excimer lasers, aberration changes in the projection optical system deteriorate exposure precision by altering the pattern image surface of the mask, leading to insufficient focus margin due to the narrow depth of focus, especially when using shorter exposure wavelengths and higher numerical apertures.
Innovation Solution
A holding apparatus with a driving unit that adjusts the posture of the mask to correct aberration-induced changes, allowing precise alignment and deformation of the mask to maintain exposure precision, utilizing a dual-holding mechanism with differential pressure control to affect bending moments and relative positional changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the exposure wavelength is shortened and numerical aperture is increased to improve resolution, then the resolution is improved, but the depth of focus is narrowed
Solution Approach 1:
The mask holding apparatus employs a dynamic posture adjustment mechanism that can change the mask's orientation and position in real-time. This allows the system to adapt to the reduced depth of focus by dynamically correcting the mask posture to maintain optimal focus conditions throughout the exposure process, effectively resolving the contradiction between high resolution and narrow depth of focus.
Solution Approach 2:
The invention changes the physical parameters of the mask holding system by introducing adjustable inclination angles and positional coordinates. By varying these parameters dynamically, the system can optimize both resolution and depth of focus, transforming the fixed parameter constraint into a variable solution space.
2Productivity
If high-energy light sources are used to improve exposure efficiency, then the exposure speed is improved, but aberration changes occur in the projection optical system
Solution Approach 1:
The mask holding apparatus incorporates a feedback mechanism where the driving unit continuously adjusts the mask posture based on detected aberration changes. This closed-loop control compensates for the detrimental effects of high-energy light sources on the optical system, maintaining exposure precision while utilizing high-power light sources for improved productivity.
3Device complexity
If the mask is held in a fixed position to simplify the holding mechanism, then the device complexity is reduced, but the ability to correct aberration-induced distortions is lost
Solution Approach 1:
The holding mechanism is segmented into multiple independently controllable components: a holding unit for gripping the mask, a posture adjusting unit for inclination and position control, and a driving unit for actuation. This segmentation allows each component to perform its specific function efficiently, achieving high precision without requiring an overly complex integrated system.
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 ensures precise pattern transfer from the mask to the substrate by correcting aberration-induced distortions, maintaining exposure precision even with high-resolution, short-wavelength lithography, thereby enhancing the focus margin and overall exposure accuracy.
Implementation Method 1
utilizing a dual-holding mechanism with differential pressure control to affect bending moments
Implementation Method 2
deformation of the mask to correct aberration-induced changes
Data Source
AI summary
A holding apparatus includes a holding portion that includes a first member which contacts a portion of an object, a second member which at least a portion thereof is fixed to a base, and a connection member which is configured to connect the first and second members, and a driving unit which drives the holding portion to change at least a posture of the first member, wherein a relative positional relationship between the first member and the second member is changed via the connection member.