EUV Mask Glass-Ceramic Substrate Planarization
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Solution Overview
Problem
Extreme ultraviolet lithography systems face challenges with phase defects caused by scratches and surface variations on mask blanks, which are magnified due to the short wavelengths used, leading to distortions in the pattern on semiconductor wafers, and existing polishing and cleaning methods either fail to eliminate these defects or introduce new issues like pits and ripples.
Innovation Solution
A method involving the use of a glass-ceramic substrate with a planarization layer deposited via flowable chemical vapor deposition (CVD) to smooth and flatten the surface, reducing surface roughness to below 0.6 nanometers root mean square (rms), thereby eliminating imperfections such as pits and scratches, and allowing for the deposition of a multi-layer stack without removing the substrate from the vacuum chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mechanical polishing with abrasive is used to smooth the mask blank surface, then surface roughness is reduced, but scratch-dig marks are introduced which cause phase defects in EUV lithography
Solution Approach 1:
The patent replaces mechanical polishing with a chemical vapor deposition (CVD) process to planarize the mask blank surface. Instead of using mechanical abrasives that create scratch-dig marks, the CVD process deposits a planarization layer that chemically smooths the surface without introducing mechanical scratches, thereby eliminating the source of phase defects while still achieving the required surface roughness of less than 0.6 nm RMS
Solution Approach 2:
The patent changes the surface treatment parameter from mechanical removal of material (polishing) to chemical deposition and planarization (CVD). This parameter change allows the surface to be smoothed without the harmful mechanical scratches that cause phase defects, while maintaining the ultra-low surface roughness required for EUV lithography
2Object-affected harmful factors
If traditional polishing and cleaning methods are used on mask blanks, then particles are removed, but new pits and surface imperfections are introduced that magnify as phase defects
Solution Approach 1:
The patent replaces mechanical cleaning and polishing methods with a chemical vapor deposition process. The CVD planarization layer chemically treats the surface to remove particles and imperfections without creating new pits or scratches, thereby eliminating both the harmful particles and the harmful pits that result from mechanical processing
Solution Approach 2:
The patent introduces a planarization layer as an intermediary between the mask blank substrate and the multilayer coating. This intermediate layer serves multiple functions: it removes particles through the CVD process, fills in existing pits, and provides a perfectly planar surface that prevents phase defects, without introducing new surface imperfections
3Ease of manufacture
If the mask blank surface is not perfectly planar, then manufacturing is simpler, but surface variations cause phase transitions in reflected light that distort the pattern on semiconductor wafers
Solution Approach 1:
The patent performs planarization as a preliminary action before depositing the multilayer coating on the mask blank. By applying the planarization layer through CVD before the critical multilayer deposition, the surface is pre-smoothed to eliminate variations that would cause phase transitions, ensuring that subsequent manufacturing steps produce high-fidelity patterns without distortion
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 method achieves a significantly smoother and flatter surface, reducing the risk of phase defects and enabling the production of EUV masks with ultra-low defects, improving the quality and reliability of semiconductor devices by maintaining the thermal expansion properties of the glass-ceramic substrate while minimizing the introduction of new defects during the process.
Implementation Method 1
depositing a planarization layer on the glass-ceramic substrate
Data Source
AI summary
An extreme ultraviolet mask and method of manufacture thereof includes: providing a glass-ceramic block; forming a glass-ceramic substrate from the glass-ceramic block; and depositing a planarization layer on the glass-ceramic substrate.