Mask Blank Substrate Surface Roughness Control for EUV Lithography
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Solution Overview
Problem
In semiconductor manufacturing, high-sensitivity defect inspection tools often detect false defects on mask blank substrates and substrates with multilayer reflective films, obscuring critical defects like foreign matters and scratches, due to surface roughness issues, leading to inefficiencies and potential failures in mass production.
Innovation Solution
The development of mask blank substrates and substrates with multilayer reflective films that achieve specific surface roughness and power spectrum density levels, reducing false defect detection and enhancing the visibility of critical defects through precise surface treatment and film deposition techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-sensitivity defect inspection is used to detect critical defects, then detection sensitivity is improved, but false defects from surface roughness increase
Solution Approach 1:
The patent applies parameter changes by precisely controlling the surface roughness parameters (Rms ≤ 0.15 nm and power spectrum density ≤ 10 nm⁴ at spatial frequency ≥ 1 μm⁻¹) of the mask blank substrate. This parameter optimization allows high-sensitivity defect inspection to distinguish between critical defects and surface roughness, reducing false detections while maintaining detection sensitivity.
2Object-generated harmful factors
If surface roughness is reduced to minimize false defects, then false defect detection is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by performing surface treatment on the mask blank substrate before depositing the multilayer reflective film. This advance surface preparation (achieving Rms ≤ 0.15 nm and specific power spectrum density) ensures that the substrate is ready to minimize false defect detection, eliminating the need for complex post-deposition surface correction processes.
3Ease of manufacture
If conventional photolithography is used for pattern formation, then manufacturing simplicity is maintained, but pattern fineness is limited
Solution Approach 1:
The patent applies parameter changes by transitioning from conventional photolithography to EUV lithography, changing the exposure light wavelength parameter to enable formation of finer patterns. The optimized substrate surface parameters (Rms ≤ 0.15 nm, power spectrum density ≤ 10 nm⁴) support this wavelength change by minimizing interference from surface roughness, thereby achieving both manufacturing feasibility and enhanced pattern fineness.
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 approach significantly reduces false defect detection while ensuring critical defects are identifiable, improving the quality and efficiency of semiconductor device manufacturing by enhancing defect inspection sensitivity.
Implementation Method 1
a reflective mask has a multilayer reflective film formed on a substrate to reflect exposure light
Implementation Method 2
an absorber film patterned on the multilayer reflective film to absorb exposure light
Data Source
AI summary
Disclosed is a mask blank substrate for use in lithography, wherein the main surface on which the transfer pattern of the substrate is formed has a root mean square roughness (Rms) of not more than 0.15 nm obtained by measuring an area of 1 μm×1 μm with an atomic force microscope, and has a power spectrum density of not more than 10 nm4 at a spatial frequency of not less than 1 μm−1.