Proximity Effect Correction in Electron Beam Lithography
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Solution Overview
Problem
Conventional proximity effect correction methods in electron beam writing for semiconductor lithography suffer from errors due to inaccurate calculation of back scattering energy distribution, which affects the accuracy of beam dose and pattern correction, especially as LSI integration density increases.
Innovation Solution
The method involves virtually dividing the pattern into mesh-like regions with deviated grids to distribute area values such that the center-of-gravity position remains unchanged, allowing for accurate calculation and correction of proximity effects by redistributing area values to maintain the center-of-gravity position across multiple regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If area value is concentrated on mesh center for back scattering energy calculation, then calculation is simplified, but position accuracy deteriorates causing error in energy distribution
Solution Approach 1:
The patent divides the mesh area value into multiple segments (first through fourth area values) corresponding to different regions around the pattern. Instead of concentrating all area value at the mesh center, it segments the calculation into multiple positional components that better represent the actual spatial distribution, thereby improving position accuracy while maintaining calculation feasibility.
Solution Approach 2:
The patent applies different area value calculations to different local regions around the pattern. By calculating first and second area values for one direction and third and fourth area values for the other direction, it creates locally optimized representations that accurately reflect the spatial relationship between the pattern and surrounding areas, resolving the contradiction between simplified calculation and accurate positioning.
2Productivity
If patterns are densely arranged for high integration, then productivity increases, but proximity effect error increases due to wider back scattering exposure
Solution Approach 1:
The patent calculates proximity effect corrections with local quality by determining area values in four different directions around each pattern. This directional approach accounts for the specific spatial relationships in densely arranged patterns, allowing accurate correction even when patterns are closely spaced, thus maintaining manufacturing precision while supporting high integration density.
Solution Approach 2:
The patent extends the correction calculation from a single point or isotropic approach to a multi-dimensional directional approach. By calculating area values in two orthogonal directions with four distinct measurements, it captures the anisotropic nature of back scattering in dense patterns, improving accuracy without sacrificing productivity.
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 reduces errors in back scattering energy distribution, enhancing the accuracy of proximity effect correction and improving the precision of pattern writing, particularly in high-density LSI applications.
Implementation Method 1
the electron beam used in the pattern writing passes through the resist material and is incident on the target object 340. Then, back scattering occurs. A part of the electron beam is incident on the resist material again.
Data Source
AI summary
A method for calculating area values of a pattern written by using a charged particle beam, includes virtually dividing a pattern into a plurality of mesh-like first square regions surrounded by first grids defined at intervals of a predetermined size, virtually dividing the pattern into a plurality of mesh-like second square regions surrounded by second grids defined at intervals of the predetermined size, wherein the second grids being positionally deviated from the first grids by a half of the predetermined size, distributing an area value of a sub-pattern in each of the second square regions to a plurality of apexes of each of the second square regions such that a center-of-gravity position of the sub-pattern does not change, wherein the sub-pattern being a part of the pattern, and outputting the distributed area values as area values, for correcting a proximity effect, defined at the center position of each of the first square regions.