Immersion Lithography Substrate Route Optimization
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Solution Overview
Problem
Immersion lithography apparatuses face defects such as trail defects due to liquid droplets or evaporation on the substrate and expose defects caused by bubbles in the immersion liquid, which reduce yield and throughput.
Innovation Solution
A lithographic apparatus with a liquid confinement structure and a positioning device that controls the substrate's motion to maintain continuous contact with the immersion liquid, using a combination of linear and curved motions to minimize liquid loss and bubble interference, while optimizing exposure routes to prevent defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the speed of movement of the substrate relative to the immersion space increases, then productivity is improved, but the rate of defects increases due to liquid droplets and evaporation
Solution Approach 1:
The liquid confinement structure is pre-configured with confinement elements positioned around the immersion space boundary before exposure begins. These elements create a potential barrier that prevents liquid droplets from escaping onto the substrate during high-speed movement, addressing the defect prevention need before the problem occurs during exposure
Solution Approach 2:
The liquid confinement structure acts as an intermediary barrier between the immersion liquid and the substrate. The confinement elements (such as gas seals or physical barriers) mediate the interaction by containing the liquid within the immersion space while allowing the substrate to move at high speeds through the exposure zone without contacting liquid droplets
2Productivity
If the substrate moves quickly through the immersion space, then productivity is improved, but trail defects occur due to liquid droplets or evaporation on the substrate
Solution Approach 1:
The harmful liquid droplets are extracted or removed from the path between the immersion space and the substrate by using confinement elements that direct liquid flow away from the substrate surface. This prevents droplets from forming trail defects during high-speed exposure
Solution Approach 2:
Gas seals or pneumatic confinement elements are used to create a gas barrier that prevents liquid from escaping the immersion space onto the substrate. The gas flow is controlled to maintain a stable barrier during substrate movement, preventing trail defects while allowing high exposure speeds
3Manufacturing precision
If bubbles are present in the immersion liquid, then exposure quality deteriorates due to expose defects, but removing bubbles increases process complexity
Solution Approach 1:
The immersion liquid circulation system is designed to automatically remove bubbles through its own operation. The liquid flow paths and confinement structure configuration create conditions where bubbles naturally rise and are carried away by the liquid circulation, eliminating the need for separate complex bubble removal systems
Solution Approach 2:
The liquid confinement structure is designed with features that prevent bubble formation and entrapment before exposure occurs. The confinement elements and liquid flow paths are configured to eliminate air pockets and allow bubbles to escape before they can interfere with the exposure process
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 reduces the occurrence of defects, thereby increasing the yield and throughput of the lithography process by ensuring consistent immersion liquid contact and minimizing bubble interference during exposure.
Implementation Method 1
a liquid confinement structure configured to confine the immersion liquid to the immersion space between the final optical element and the substrate
Implementation Method 2
a positioning device configured to position the substrate support and thereby the substrate; and a controller configured to control the positioning device so that the substrate support follows a route comprising: a first exposure motion during which the substrate is moved at a constant speed in a first direction; a first transit motion during which the substrate is accelerated in a second direction orthogonal to the first direction and decelerated in the first direction
Data Source
AI summary
A route for a substrate support that supports a substrate in an immersion lithographic apparatus is calculated to satisfy the following constraints: after the edge of the substrate first contacts the immersion space, the substrate remains in contact with the immersion space until all target portions are exposed; exposures of target portions are performed while the substrate moves in a scan direction; and all movements of the substrate between exposures are, in a plane parallel to its upper surface, either curved or only in one of the scan directions or transverse directions. In order to reduce exposure defects at the edge of the substrate the outside portion of the substrate is avoided from being exposed to the immersion liquid. The transfer routes are designed to overly the substrate surface.