SiN Mask Blank Nitrogen Optimization for EB Defect Repair
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Solution Overview
Problem
In the manufacturing of semiconductor devices, SiN-based transfer masks face challenges with slow repair rates and surface digging during electron beam defect repair due to low nitrogen content, which affects the balance between repair rate and etching rate, and the difficulty in isolating the electron beam and fluorine-based gas application to specific defect areas.
Innovation Solution
A mask blank and transfer mask design featuring a thin film with a high nitrogen content, where X-ray photoelectron spectroscopy is used to optimize the silicon and nitrogen composition, ensuring a high repair rate and minimizing surface digging by adjusting the nitrogen content and oxygen levels in the surface and inner regions, thereby enhancing the repair rate ratio between the thin film and the transparent substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If unexcited fluorine-based gas is supplied to a black defect portion while irradiating with an electron beam to perform EB defect repair, then the black defect portion is removed through etching, but the surface of the transparent substrate near the defect portion is also affected, resulting in insufficient repair rate ratio between the transparent substrate and the thin film pattern
Solution Approach 1:
The patent changes the chemical composition parameters of the thin film by adjusting the nitrogen content to 50 atom% or more. This parameter change increases the etching rate of the thin film relative to the transparent substrate during EB defect repair, thereby improving the repair rate ratio and preventing surface digging of the substrate.
Solution Approach 2:
The patent creates a local quality difference by having the thin film contain significantly more nitrogen (50 atom% or more) compared to the transparent substrate. This localized compositional difference ensures that during EB defect repair, the thin film etches much faster than the substrate, confining the etching effect primarily to the defect area rather than causing widespread substrate damage.
2Reliability
If a thin film of SiN-based material containing a large amount of nitrogen is used to achieve the required refractive index for phase shift function, then the phase shift function is satisfied, but the repair rate of EB defect repair becomes significantly slow
Solution Approach 1:
The patent optimizes the nitrogen content parameter to be 50 atom% or more, which provides the right balance: sufficient nitrogen content to achieve the required refractive index for phase shift function, while not excessively high to prevent EB defect repair from becoming too slow. This parameter optimization simultaneously satisfies both the phase shift function requirement and maintains acceptable repair rate.
Solution Approach 2:
The patent introduces oxygen vacancies in the thin film structure, creating a somewhat porous or defective structure that enhances the etching rate during EB defect repair. This allows the thin film to maintain its phase shift function through nitrogen content while the oxygen vacancies facilitate faster repair by making the material more reactive to fluorine-based gas etching.
3Productivity
If the nitrogen content in the SiN-based thin film is increased to improve the repair rate ratio, then the etching rate increases, but the refractive index changes, affecting the phase shift function
Solution Approach 1:
The patent precisely controls the nitrogen content parameter at 50 atom% or more, which is the threshold value that simultaneously achieves both goals: sufficient etching rate improvement for fast repair and adequate refractive index for phase shift function. This specific parameter setting resolves the contradiction by finding the optimal point where both requirements are satisfied.
Solution Approach 2:
The patent creates a composite structure in the thin film by combining silicon, nitrogen (50 atom% or more), and oxygen vacancies. This composite composition allows the material to exhibit both the high etching rate needed for fast repair and the appropriate refractive index for phase shift function, as the different components contribute different properties that work together.
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 design achieves a faster and more precise repair rate for SiN-based transfer masks, reducing surface digging and improving transfer precision by optimizing the nitrogen and oxygen content, ensuring effective defect repair without excessive substrate etching.
Implementation Method 1
irradiating the black defect portion with an electron beam so as to change the black defect portion into volatile fluoride
Implementation Method 2
unexcited fluorine-based gas such as XeF2 is supplied to a black defect portion... so as to change the black defect portion into volatile fluoride for its removal
Implementation Method 3
conducting an X-ray photoelectron spectroscopy to acquire a maximum peak PSi_fi of photoelectron intensity of Si2p narrow spectrum
Data Source
AI summary
A mask blank that includes a thin film made of a material containing silicon and nitrogen for forming a transfer pattern on a transparent substrate. In conducting an X-ray photoelectron spectroscopy on a plurality of measurement locations in an inner region, which is a region excluding a vicinity region and a surface layer region of the thin film, in order to acquire an average value PSi_fi_av of maximum peaks PSi_fi of photoelectron intensity of Si2p narrow spectrum and conducting an X-ray photoelectron spectroscopy on a plurality of measurement locations in the transparent substrate to acquire an average value PSi_sb_av of maximum peaks PSi_sb of photoelectron intensity of Si2p narrow spectrum, (PSi_fi_av)/(PSi_sb_av) is 1.08 or more.