Deflection Amplifier Voltage Control for Electron Beam Writing
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Solution Overview
Problem
In electron beam writing apparatuses for semiconductor lithography, precise voltage control is crucial for micropattern formation, but existing calibration methods are inefficient and prone to output strain due to overlapping voltage ranges of D/A converters.
Innovation Solution
The method involves synthesizing voltage signals from multiple D/A converters with assigned control ranges, sampling lower or upper limit values, and generating correction values to correct output voltages, ensuring linear output characteristics and precise calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple D/A converters with overlapping voltage ranges are used to control deflection electrodes, then the control flexibility and resolution are improved, but output strain occurs and calibration complexity increases
Solution Approach 1:
The voltage control range is segmented into multiple non-overlapping sub-ranges, with each D/A converter assigned to a specific sub-range. This segmentation eliminates overlapping voltage ranges and the resulting output strain, while maintaining high control precision through coordinated operation of multiple converters.
Solution Approach 2:
The invention changes the voltage range parameters of each D/A converter to be non-overlapping, transforming the system from having overlapping ranges to having adjacent, discrete ranges. This parameter change resolves the output strain issue while preserving the ability to achieve fine voltage control through the segmented approach.
2Measurement precision
If comprehensive calibration of all D/A converters is performed, then output precision is improved, but calibration time increases
Solution Approach 1:
The invention extracts and eliminates the redundant calibration requirements caused by overlapping voltage ranges. By assigning non-overlapping ranges to each D/A converter, the system removes the need for comprehensive calibration of all converters, requiring only calibration at boundary points instead.
Solution Approach 2:
The voltage range assignments are predetermined and configured before operation to be non-overlapping, which preliminarily prevents the output strain problem. This preliminary configuration eliminates the need for extensive calibration procedures that would otherwise be required to correct overlapping range issues.
3Stability of the object's composition
If D/A converters operate with overlapping voltage ranges, then continuous voltage control is improved, but output strain and non-linearity occur
Solution Approach 1:
The continuous voltage control range is segmented into multiple non-overlapping sub-ranges, with each D/A converter responsible for a specific segment. This segmentation maintains continuous voltage control capability while eliminating the output strain and non-linearity that occur with overlapping ranges.
Solution Approach 2:
The voltage range parameters of the D/A converters are changed from overlapping to adjacent non-overlapping values. This parameter change preserves the continuity of voltage control across the full range while eliminating the harmful effects of overlap, thereby improving pattern writing accuracy.
Data Source
AI summary
An output control method according to an embodiment is to control an output by a deflection amplifier that outputs a voltage signal to a deflection electrode of an electron beam writing apparatus. The voltage signal is proportional to input data, and the method includes: performing, for the voltage signal generated by synthesizing respective outputs by a plurality of D/A converters to which a control range of the voltage signal is assigned, the respective outputs by the plurality of D/A converters being proportional to respective inputs, sampling on at least either a lower limit value of the voltage signal within the control range or an upper limit value thereof; and generating a correction value to correct the output by the D/A converter based on the sampling result.