EUV Mask Flare-Suppressing Phase-Shift Layer
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Solution Overview
Problem
Existing EUV lithography techniques suffer from image contrast loss due to out-of-band (OOB) radiation, which is not effectively suppressed by current methods such as top-coating or filtering, leading to increased costs and EUV light loss.
Innovation Solution
A mask structure incorporating a reflective multilayer with a flare-suppressing absorption stack (FSAS) and a flare-suppressing-by-phase-shifting (FSbPhS) layer, which absorbs EUV light and induces destructive interference to suppress OOB radiation, specifically DUV flare, enhancing image contrast and lithography performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If top-coating or filtering methods are used to suppress OOB radiation, then image contrast loss is reduced, but EUV light loss increases and costs increase
Solution Approach 1:
The patent converts the harmful OOB radiation into a beneficial effect by using the mask structure to reflect DUV flare back toward the source, where it is absorbed by the plasma. This transforms the harmful flare into a mechanism for suppressing OOB radiation without losing EUV light, as the multilayer mirror is designed to be highly reflective at EUV wavelengths while the phase-shifting layer creates destructive interference for DUV wavelengths.
Solution Approach 2:
The patent introduces an intermediary mask structure with specific layers (multilayer mirror and phase-shifting layer) that mediates between the EUV light and OOB radiation. The multilayer mirror acts as an intermediary to reflect EUV light while the phase-shifting layer creates destructive interference for DUV flare, thereby suppressing OOB radiation without affecting EUV light transmission.
2Productivity
If conventional EUV lithography methods are used, then manufacturing is achieved, but image contrast is reduced due to OOB radiation
Solution Approach 1:
The patent converts the harmful DUV flare into a beneficial effect by using the mask structure to reflect it back toward the source. The phase-shifting layer creates destructive interference for DUV wavelengths, transforming the flare into a suppression mechanism that improves image contrast without sacrificing lithography performance.
Solution Approach 2:
The patent changes the optical parameters of the mask by introducing a phase-shifting layer with specific thickness and material properties. This layer creates a phase difference that results in destructive interference for DUV wavelengths while maintaining constructive interference for EUV wavelengths, thereby improving image contrast without affecting productivity.
3Object-affected harmful factors
If OOB radiation suppression is improved, then image contrast is enhanced, but device complexity increases
Solution Approach 1:
The patent merges the functions of OOB radiation suppression and EUV light reflection into a single mask structure. The multilayer mirror and phase-shifting layer are combined in one component, allowing the mask to simultaneously reflect EUV light and suppress DUV flare through destructive interference, thereby reducing overall device complexity.
Solution Approach 2:
The patent creates a universal mask structure that performs multiple functions: reflecting EUV light, suppressing DUV flare, and improving image contrast. The phase-shifting layer and multilayer mirror work together to provide both reflection and interference functions in a single component, reducing the need for additional separate elements.
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 proposed solution effectively suppresses a substantial portion of OOB radiation, improving aerial image contrast and lithography performance while maintaining EUV light integrity, thus enhancing the overall efficiency and cost-effectiveness of the EUV lithography process.
Implementation Method 1
absorbing a portion of the EUV light in an absorptive region of the mask
Implementation Method 2
induces destructive interference to suppress OOB radiation
Implementation Method 3
reflecting a portion of the EUV light from a reflective region of the mask
Data Source
AI summary
A system of an extreme ultraviolet lithography (EUVL) is disclosed. an extreme ultraviolet lithography (EUVL) system includes an extreme ultraviolet (EUV) reflection-type mask having a patterned flare-suppressing-by-phase-shifting (FSbPhS) layer disposed over a patterned absorption layer. The system also includes a radiation to expose the EUV mask and a projection optics box (POB) to collect and direct the radiation that reflects from the EUV mask to expose a target.