EUV Mask Substrate with Electrically Isolated Chucking Layer
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Solution Overview
Problem
In EUV lithography, the formation of electrical connections between the reflective layer and the chucking layer, and between the absorbing layer and the chucking layer, leads to substrate defects due to static build-up and particle attraction, which hampers the fabrication of high-quality EUV masks with fine circuit patterns.
Innovation Solution
A substrate with a reflective layer and an EUV mask blank is designed to prevent electrical connections by forming a non-conducting portion on the substrate's surface and using a chucking layer that is electrically isolated from the reflective and absorbing layers, ensuring a resistance value of 1 MΩ or higher between these layers, and employing a shielding member or partial removal of the deposited layers to prevent electrical conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conductive chucking layer is formed on the substrate to enable electrostatic chucking, then the substrate can be firmly supported during film deposition, but electrical connection between the chucking layer and reflective layer causes static build-up and particle attraction leading to substrate defects
Solution Approach 1:
The chucking layer is segmented into a conductive portion and a non-conductive portion, where the non-conductive portion is formed at the periphery to electrically isolate the reflective layer from the conductive chucking layer, preventing electrical connection while maintaining electrostatic chucking capability
Solution Approach 2:
Different portions of the substrate have different electrical properties: the central area has the conductive chucking layer for electrostatic support, while the peripheral area has the non-conductive portion to prevent electrical connection, creating local quality differentiation to resolve the contradiction
2Area of stationary object
If the reflective layer is deposited on the entire substrate surface, then complete coverage is achieved, but electrical connection to the chucking layer at the periphery causes harmful static effects
Solution Approach 1:
The reflective layer is extracted from the peripheral region where it would otherwise contact the conductive chucking layer, leaving a non-conductive portion at the periphery that prevents electrical connection and harmful static effects while maintaining coverage of the functional area
3Reliability
If a non-conductive portion is formed at the periphery to prevent electrical connection, then particle attraction is reduced, but the structure becomes more complex
Solution Approach 1:
The non-conductive portion is formed by depositing a non-conductive material layer over the conductive chucking layer at the periphery, merging the chucking layer structure with the reflective layer structure through a single deposition process, which reduces overall structural complexity despite the multi-functional design
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 configuration minimizes substrate defects and particle attraction, enabling the fabrication of EUV masks with improved dimensional accuracy and reduced defects, facilitating effective exposure processes.
Implementation Method 1
a chucking layer formed on a rear surface opposite a front surface with the reflective layer formed thereon, the chucking layer serving to chuck and support the substrate by an electrostatic chuck
Implementation Method 2
a catoptric system, i.e., a combination of a reflective photomask and a mirror, is employed in EUV light lithography
Implementation Method 3
an absorbing layer for absorbing EUV light formed thereon in this order
Implementation Method 4
The reflective layer and the absorbing layer are deposited by ion beam sputtering or magnetron sputtering
Data Source
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AI summary
There are provided a substrate with a reflective layer and an EUV mask blank, which can prevent particles from adhering to a surface of the reflective layer or an absorbing layer, or into a reflective layer or an absorbing layer during formation thereof by eliminating electrical connection between a film formed on a front surface of the substrate and a film formed on a rear surface of the substrate. A substrate with a reflective layer, which is usable to fabricate a reflective mask blank for EUV lithography, comprising a chucking layer formed on a rear surface opposite a surface with the reflective layer formed thereon, the chucking layer serving to chuck and support the substrate by an electrostatic chuck, wherein the reflective layer has no electrical connection to the chucking layer.