Low-CTE Subframe Mounting for Thermally Stable Optical Columns
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Solution Overview
Problem
Thermal expansion and contraction of optical columns in lithographic projection apparatuses cause unwanted displacements and rotations, leading to errors in the lithographic process, particularly in high-precision manufacturing of semiconductor devices and other microstructures.
Innovation Solution
A system comprising an optical column supported by a frame with a first coefficient of thermal expansion (CTE) and stabilized by a subframe with a lower second CTE, anchored at multiple points to resist displacements and rotations, using materials like steel and cordierite for the frame and subframe, respectively, to minimize thermal effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the optical column is supported by a frame with high CTE for mechanical strength and ease of manufacture, then the frame provides adequate structural support, but thermal expansion causes displacement and rotation of the optical column affecting manufacturing precision
Solution Approach 1:
The support structure is divided into two separate frames: an outer frame providing mechanical support and an inner frame providing thermal stability. This segmentation allows each frame to be optimized for its specific function without compromise.
Solution Approach 2:
The inner frame acts as an intermediary between the optical column and the outer frame, isolating the optical column from thermal expansions of the outer frame while still providing necessary support and alignment.
2Stability of the object's composition
If the optical column is rigidly fixed to prevent any movement, then alignment stability is improved, but thermal expansion stresses cause deformation and potential damage to optical components
Solution Approach 1:
The support structure transitions from a single rigid connection to a dual-frame system with controlled degrees of freedom, allowing thermal expansion while maintaining alignment stability through the constrained design of the inner frame.
Solution Approach 2:
The inner frame with lower CTE serves as a protective buffer that absorbs and compensates for thermal expansion stresses before they can reach the optical column, preventing deformation and damage.
3Manufacturing precision
If multiple anchors are used to stabilize the optical column against thermal expansion, then alignment precision is maintained, but device complexity increases
Solution Approach 1:
The inner frame serves multiple functions simultaneously: it provides thermal isolation, mechanical support, alignment reference, and stress distribution, eliminating the need for separate components for each function.
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 stabilization system effectively limits displacements and rotations to less than 10 microns and 10 micro-radians, ensuring precise positioning of optical components and maintaining high precision in lithographic processes.
Implementation Method 1
stabilize the optical column against a displacement or a rotation caused by thermal expansion in the frame or the optical column
Data Source
AI summary
Systems and methods are disclosed for stabilizing an optical column. One system can include an optical column; a frame configured to support the optical column, the frame having a first coefficient of thermal expansion (CTE); and a subframe configured to be coupled to the optical column in at least two places by a first anchor and a second anchor to stabilize the optical column against a displacement or a rotation caused by thermal expansion in the frame or the optical column, the subframe having a second CTE lower than the first CTE.