Lithographic Substrate Table Thermal Shielding
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Solution Overview
Problem
The existing lithographic apparatuses face challenges in accurately positioning substrates due to substrate table distortion caused by temperature variations and mechanical contact, which affects the quality of pattern formation on the substrate.
Innovation Solution
A lithographic apparatus is designed with a substrate table temperature stabilization device that controls the temperature of a cover plate separate from the substrate table, providing thermal shielding and reducing heat transfer to maintain accurate positioning and pattern quality. Additionally, a measuring system determines the substrate table's position and distortion, allowing for precise control of the substrate's position relative to the projection system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the substrate table is used to support and position the substrate, then the substrate can be held and moved during exposure, but temperature variations cause the substrate table to distort, reducing positioning accuracy
Solution Approach 1:
The support structure is divided into two separate components: the substrate table (which provides mechanical support and positioning) and the cover plate (which provides thermal shielding). This segmentation allows each component to perform its specialized function without the thermal instability affecting the positioning accuracy of the other.
Solution Approach 2:
The cover plate acts as an intermediary thermal shield between the radiation source and the substrate table. It absorbs and blocks thermal radiation before it can reach the substrate table, preventing thermal expansion and distortion of the positioning structure.
2Temperature
If a cover plate is added to provide thermal shielding, then heat transfer to the substrate table is reduced, but the device complexity increases
Solution Approach 1:
The cover plate is integrated with the substrate table to form a unified support structure. The cover plate is positioned to overhang the substrate table, creating a combined structure that provides both mechanical support and thermal shielding without requiring separate complex systems.
Solution Approach 2:
The cover plate is designed as a simple, easily manufactured component that can be made from common materials. Its straightforward geometry and integration method keep manufacturing costs and complexity low while effectively providing thermal shielding.
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
This solution improves the accuracy of substrate positioning and reduces overlay errors by stabilizing the substrate table's temperature and accounting for distortions, leading to enhanced pattern formation quality.
Implementation Method 1
It has been proposed to immerse the substrate in the lithographic projection apparatus in a liquid having a relatively high refractive index, e.g. water, so as to fill a space between the final element of the projection system and the substrate. The point of this is to enable imaging of smaller features since the exposure radiation will have a shorter wavelength in the liquid.
Implementation Method 2
Known substrate tables are subject to distortion, for example due to thermal expansion. This may have a negative impact on the quality of a pattern to be formed on the substrate.
Implementation Method 3
A measuring system may be provided which determines a position of the substrate table, for example by measuring a separation of a reflector from a reference point.
Data Source
AI summary
A lithographic apparatus with a cover plate formed separately from a substrate table and means for stabilizing a temperature of the substrate table by controlling the temperature of the cover plate is disclosed. A lithographic apparatus with thermal insulation provided between a cover plate and a substrate table so that the cover plate acts as a thermal shield for the substrate table is disclosed. A lithographic apparatus comprising means to determine a substrate table distortion and improve position control of a substrate by reference to the substrate table distortion is disclosed.