EUV Photomask Absorber Openings for Blistering Prevention
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Solution Overview
Problem
EUV masks degrade with usage, leading to poor pattern transfer and device/circuit failure due to issues like surface blistering and layer splitting during EUV lithography processes.
Innovation Solution
Incorporating one or more openings in the absorber layer of the EUV mask, spaced away from main pattern areas, to release hydrogen gas and reduce thermal film expansion, thereby preventing hydrogen accumulation and minimizing surface blistering and layer splitting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If EUV masks are used for lithography processes, then pattern transfer capability is improved, but mask degradation occurs leading to surface blistering and layer splitting
Solution Approach 1:
The mask structure is segmented into multiple functional layers (substrate, multi-layer structure, capping layer, absorber layer) with distinct roles. The absorber layer is further segmented to include openings spaced away from main pattern areas, creating separate functional zones that prevent hydrogen accumulation and reduce thermal stress concentration.
Solution Approach 2:
Different regions of the mask are given different properties: the main pattern areas maintain high absorption for pattern transfer, while the opening areas have reduced absorber material to facilitate hydrogen release and reduce thermal stress. The capping layer provides localized protection over the multi-layer structure in critical areas.
2Manufacturing precision
If absorber layer is made thick to improve pattern transfer, then absorption capability increases, but thermal film expansion and hydrogen accumulation worsen
Solution Approach 1:
The thickness of the absorber layer is optimized rather than maximized. In main pattern areas, sufficient thickness is maintained for absorption, while in opening areas, the absorber layer is thinner or absent. This parameter variation reduces overall thermal mass and hydrogen accumulation risk while preserving necessary absorption capability.
Solution Approach 2:
Absorber material is selectively removed in the opening areas to create pathways for hydrogen release and reduce thermal stress. This extraction of material from non-critical zones eliminates the harmful effects of thick absorber layers (hydrogen accumulation, thermal expansion) while preserving absorption function in pattern areas.
3Productivity
If continuous usage of EUV masks is increased to improve productivity, then output increases, but mask degradation accelerates
Solution Approach 1:
The mask structure is pre-configured with opening areas and capping layers during fabrication to prevent hydrogen accumulation and reduce thermal stress before they can cause damage. This preliminary structural preparation enables continuous usage without accelerated degradation, extending mask life and maintaining productivity.
Solution Approach 2:
The capping layer acts as a protective cushion over the multi-layer structure, and the opening areas serve as pressure relief zones that prevent hydrogen buildup. These features are built in advance to cushion against the harmful effects of continuous EUV exposure, allowing higher productivity without compromising mask durability.
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 high-fidelity pattern transfer to semiconductor wafers by reducing and eliminating surface blistering and layer splitting, maintaining mask integrity and enhancing lithography process reliability.
Implementation Method 1
the openings provide for reduced thermal film expansion and/or reduced and/or eliminated surface blistering and layer splitting by allowing hydrogen gas to escape
Implementation Method 2
the openings provide for reduced thermal film expansion
Data Source
AI summary
A method of fabricating a semiconductor device includes providing a first substrate and forming a resist layer over the first substrate. In some embodiments, the method further includes performing an exposure process to the resist layer. The exposure process includes exposing the resist layer to a radiation source through an intervening mask. In some examples, the intervening mask includes a second substrate, a multi-layer structure formed over the second substrate, a capping layer formed over the multi-layer structure, and an absorber layer disposed over the capping layer. In some embodiments, the absorber layer includes a first main pattern area and an opening area spaced a distance from the first main pattern area. In various examples, the method further includes, after performing the exposure process, developing the exposed resist layer to form a patterned resist layer.