Charged Particle Beam Writing Edge Irradiation Correction
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Solution Overview
Problem
Conventional electron beam writing methods face challenges in accurately correcting line width errors due to backscattering and forward scattering effects, particularly in middle range effect corrections, leading to insufficient irradiation at the edge portions of patterns, which results in dimensional variations and reduced writing accuracy.
Innovation Solution
A charged particle beam writing method that divides a figure pattern into shot figures, calculates correction irradiation amounts for each mesh region, and resizes shot figures based on insufficient irradiation amounts at the edges to ensure accurate irradiation, using a variable shaped beam writing apparatus with a controller that processes writing data to correct proximity and middle range effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the shot size is larger than the middle range effect correction mesh size, then the writing efficiency is improved, but the irradiation amount at the edge portion of the shot becomes insufficient, causing dimensional variation
Solution Approach 1:
The patent applies local quality by differentiating the irradiation amount calculation between edge portions and non-edge portions of shots. Specifically, the determination unit identifies whether a shot is located at an edge portion of the pattern and applies different correction strategies: for edge shots, it calculates insufficient irradiation amounts and compensates by increasing irradiation dose or extending irradiation time, while for non-edge shots, it uses standard correction amounts. This localized differentiation ensures dimensional accuracy is maintained at critical edge regions without compromising overall writing efficiency.
2Manufacturing precision
If the maximum shot size is reduced to improve edge irradiation, then the writing time becomes longer, reducing productivity
Solution Approach 1:
The patent employs parameter changes by dynamically adjusting irradiation parameters (dose, time, or intensity) based on the spatial location of each shot within the pattern. The determination unit classifies shots as either edge portions or non-edge portions, and the calculation unit subsequently modifies irradiation parameters accordingly. Edge shots receive enhanced irradiation parameters to compensate for insufficient dose, while non-edge shots use standard parameters. This selective parameter modification resolves the contradiction by maintaining precision at edge regions without requiring a global reduction in shot size that would extend overall writing time.
3Device complexity
If conventional irradiation amount correction is used, then the calculation is simplified using convolution with gaussian kernel, but residual correction occurs at shot edges due to insufficient irradiation amount
Solution Approach 1:
The patent implements preliminary action by introducing a pre-calculation step that identifies edge portions of shots before the main irradiation amount correction is applied. The determination unit预先 (in advance) classifies which shots are located at edge portions of the pattern, and this classification information is then used by the calculation unit to apply appropriate correction amounts. This preliminary identification ensures that edge shots are prepared for special correction treatment, preventing residual errors from occurring during the actual irradiation process while maintaining the computational efficiency of the convolution-based correction method.
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 improves the dimensional and positional accuracy of the written patterns by ensuring sufficient irradiation at the edges, reducing residual corrections and enhancing the overall writing precision.
Implementation Method 1
a backscattering irradiation amount is calculated, where the backscattering occurs when an electron beam, with which a photomask is irradiated, is reflected by a substrate, and a resist is exposed to the electron beam again
Implementation Method 2
electrons, with which a substrate surface is irradiated at the time electron beam writing, are scattered (forward scattered) in a resist
Data Source
AI summary
In one embodiment, a charged particle beam writing method includes dividing a figure pattern defined in writing data into a plurality of shot figures, virtually dividing a writing target substrate into a plurality of mesh regions, and calculating a correction irradiation amount to correct proximity effect and middle range effect for each of the mesh regions based on a position of the figure pattern, calculating an irradiation amount for each of the plurality of shot figures using the correction irradiation amount, calculating an insufficient irradiation amount at an edge portion of the shot figure based on the irradiation amount, resizing the shot figure based on the insufficient irradiation amount, and writing the resized shot figure on the writing target substrate using a charged particle beam in the irradiation amount.