EUV Mask Blank Spacing Layer for Phase and Intensity Control
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Solution Overview
Problem
EUV mask blanks face challenges in optimizing both intensity and phase of reflected light for improved imaging resolution, particularly due to the mask shadowing effect and the need for high reflectance in extreme ultraviolet lithography, where existing solutions like absorber thickness reduction and phase shift masks do not simultaneously optimize both parameters effectively.
Innovation Solution
The introduction of a spacing layer between the capping layer and the absorber layers, combined with a phase tuning layer in contact with one of the absorber materials, allows for independent control of intensity and phase of reflected light, optimizing imaging resolution by adjusting the thickness of these layers to achieve specific reflectance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If absorber thickness is reduced to minimize mask shadowing effect, then mask shadowing is reduced, but imaging resolution and image contrast deteriorate
Solution Approach 1:
A spacing layer is introduced as an intermediary element between the capping layer and the absorber stack. This spacing layer mediates the optical interaction by controlling the phase and intensity of reflected light, allowing the absorber thickness to be reduced for minimal shadowing while maintaining imaging resolution through the mediator's optical path control
Solution Approach 2:
The invention changes the optical parameters by introducing a spacing layer with specific thickness and refractive index properties. This parameter change allows the system to achieve optimal phase and intensity control of reflected light, resolving the contradiction between reduced absorber thickness and maintained imaging resolution
2Manufacturing precision
If phase shift mask is used to improve image contrast with thinner absorber, then image contrast improves, but intensity and phase optimization becomes complex
Solution Approach 1:
The optical control function is segmented into separate components: the spacing layer handles phase control through its optical path length, while the absorber stack handles intensity control. This segmentation simplifies the overall optimization by dividing the complex intensity and phase control into manageable separate functions
Solution Approach 2:
The spacing layer serves multiple functions simultaneously: it acts as a phase tuning element, an intensity control element, and a structural spacer. This multi-functionality reduces device complexity by consolidating multiple control functions into a single element rather than requiring separate complex mechanisms
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 enhances the imaging resolution by tuning the intensity and phase of reflected light, improving the overall performance of EUV mask blanks by achieving optimal reflectance and phase shift within the desired wavelength range, specifically at 13.53 nm, thereby reducing mask shadowing effects.
Implementation Method 1
Bragg reflectors are typically made of multilayers of alternating thin film materials of different refractive index, wherein high reflectance is one of the key attributes
Implementation Method 2
A Bragg reflector or mirror is a structure formed from a multilayer stack of alternating thin film materials with varying refractive index
Implementation Method 3
extreme ultraviolet light, which is generally in the 5 to 100 nanometer wavelength range, is strongly absorbed in virtually all materials
Implementation Method 4
a phase tuning layer in contact with one of the first material A and the second material B
Data Source
AI summary
An extreme ultraviolet reflective element comprising a multilayer stack of absorber layers on a multilayer stack of reflective layers. The element comprises spacing layer and phase tuning layer. Methods of manufacturing extreme ultraviolet reflective elements and lithography systems including extreme ultraviolet reflective elements are also described.