Aberration Measurement in Multi-Beam Lithography
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Solution Overview
Problem
Conventional electron beam lithography machines struggle with throughput in exposing high-density fine patterns due to unbalanced aberration in the exposure field, which limits the precision and efficiency of the process.
Innovation Solution
An aberration measuring machine that generates multiple charged particle beams at different incidence angles to detect and adjust aberrations, using a calculating unit to divide aberrations into components with Zernike coefficients, ensuring balanced aberration correction across the effective field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single electron beam is used for drawing, then the system is simple to operate, but the throughput is low
Solution Approach 1:
The patent divides a single electron beam into multiple beams using beam splitting optics. The single electron beam from the source is segmented into multiple beams that can simultaneously expose different regions of the sample, thereby increasing throughput while maintaining operational simplicity through centralized beam control
Solution Approach 2:
The patent transitions from one-dimensional sequential beam scanning to two-dimensional parallel beam exposure by spatially distributing multiple beams across the sample plane. This dimensional expansion allows simultaneous exposure of multiple regions, dramatically improving throughput
2Productivity
If multiple electron beams are used to increase throughput, then the exposure area is wider, but aberration balance becomes difficult to maintain across the entire exposure field
Solution Approach 1:
The patent applies local quality by measuring and correcting aberrations at different positions across the exposure field. The aberration measurement unit specifically measures spherical aberration, coma, and astigmatism at multiple field positions, and the correction system applies position-dependent corrections to maintain uniform beam quality across the entire wide exposure field
Solution Approach 2:
The patent implements a feedback mechanism where the aberration measurement unit continuously monitors beam quality at various field positions, and this measurement data feeds back to the correction system which adjusts optical elements to compensate for measured aberrations, maintaining aberration balance across the expanded exposure field
3Device complexity
If conventional aberration measurement is used, then the measurement process is simple, but only defocus and position are measured, unable to suppress aberration in balance across the entire exposure field
Solution Approach 1:
The patent segments the aberration measurement process into distinct components: spherical aberration measurement, coma measurement, and astigmatism measurement. The aberration measurement unit separately measures each type of aberration at multiple field positions, enabling comprehensive characterization of optical imperfections across the entire exposure field
Solution Approach 2:
The patent extends aberration measurement from simple one-dimensional defocus and position detection to three-dimensional aberration space by measuring spherical aberration, coma, and astigmatism components. This multi-dimensional measurement approach enables comprehensive aberration suppression across the entire exposure field
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
Enables precise measurement and adjustment of aberrations in the charged particle beam optical system, improving the throughput and precision of the exposure process by ensuring balanced aberration correction across the entire exposure field.
Implementation Method 1
a charged particle generating unit adapted to make a plurality of charged particle beams strike an object plane of the charged particle beam optical system at different incidence angles
Implementation Method 2
a detecting unit adapted to detect a position where the plurality of charged particle beams form images on an image surface of the charged particle beam optical system
Data Source
AI summary
A charged particle beam lithography machine for exposing a target exposure surface by using a plurality of charged particle beams. The machine includes a charged particle source to emit a charged particle beam, an aperture substrate which has a plurality of apertures to divide the charged particle beam from the charged particle source into a plurality of charged particle beams, a plurality of electron optical systems which have the apertures as pupils, a charged particle beam optical system which projects, to the target exposure surface, charged particle source images formed by the plurality of electron optical systems, a unit adapted to set the apertures of the aperture substrate to an aperture for exposure and an aperture for aberration measurement to make the plurality of charged particle beams strike the charged particle beam optical system at different incident angles, and a detecting unit adapted to detect a position where the plurality of charged particle beams, which have passed through the aperture for aberration measurement, form images on an image surface of the charged particle beam optical system.