EUV Microscope Monochromator Zone-Plate Chromatic Correction
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Solution Overview
Problem
Existing EUV mask imaging devices are highly chromatic, leading to poor resolution due to wavelength-dependent focal length, and have constrained working distances and issues with zero-order flare correction.
Innovation Solution
The use of a monochromator to further narrow the bandwidth of the EUV beam, allowing for a longer working distance and mitigating chromatic effects by integrating a zone-plate with a central stop to filter out zero-order flare.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a zone-plate microscope is used to achieve EUV mask imaging, then the device can function as a mask imaging tool, but the system suffers from severe working distance constraints and poor resolution due to chromatic effects
Solution Approach 1:
The patent changes the spectral parameter by introducing a monochromator to narrow the bandwidth of EUV light from the broadband source. This parameter change (from broadband to narrowband illumination) reduces chromatic effects in the zone-plate microscope, thereby improving resolution while allowing for a longer working distance between the zone-plate and the mask being imaged
2Measurement precision
If the focal length of the zone-plate microscope is reduced to minimize chromatic effects, then resolution improves, but the working distance becomes severely constrained
Solution Approach 1:
Instead of changing the focal length parameter, the patent changes the spectral bandwidth parameter by introducing a monochromator. This allows the system to maintain a longer focal length (and thus longer working distance) while still achieving high resolution by illuminating the zone-plate with narrowband EUV light that minimizes chromatic blurring
3Measurement precision
If a central stop is added to the zone-plate to filter out zero-order flare, then image quality improves, but the device complexity increases
Solution Approach 1:
The patent merges the central stop feature with the existing zone-plate structure, creating an integrated component rather than a separate element. The central stop is incorporated into the zone-plate itself, allowing it to filter zero-order flare while maintaining a relatively simple overall device structure. This combined design improves image quality without proportionally increasing device complexity
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 solution enables a novel EUV mask imaging tool with improved resolution, longer working distance, and reduced chromatic effects, facilitating efficient and accurate visualization and evaluation of EUV lithography masks.
Implementation Method 1
The monochromator is then used to purify the light to the level of λ/Δλ of 350 or better
Implementation Method 2
The EUV light reflected from the mask passes through a zone-plate
Implementation Method 3
The zone-plate may, optionally, include a central obscuration in order to employ first order light without overlap of zero order light
Implementation Method 4
Such emanation may originate with a laser-produced plasma, a discharged-produced plasma, and the like
Data Source
AI summary
An EUV microscope apparatus utilizing a source of EUV light. The light is sent to a collector which creates a first focused EUV beam. A monochromator module receives the first focused EUV beam and produces a second focused EUV beam that is passed to an illumination module. The output of the illumination module is reflected off a mask. The reflected beam from the mask is sent to a zone-plate and a detector to produce an image.