Waveform Generator With DAC Glitch Compensation for Beam Deflection
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Solution Overview
Problem
In electron-beam lithography, glitches in the tracking amplifier's output during deflection voltage control lead to beam irradiation position displacement, degrading writing accuracy due to sudden changes in voltage, especially when high-order bits are inverted in the command values.
Innovation Solution
A waveform generating device with multiple DA converters and a compensation glitch generating unit that inverts specific bits in the command values to produce a compensation glitch waveform, which is then combined with the original output to cancel out glitches, ensuring stable beam deflection and improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If continuous operation of tracking amplifier is performed to maintain beam tracking, then beam following capability is improved, but glitches occur in output voltage causing position displacement
Solution Approach 1:
The system performs preliminary detection of high-order bit inversions in the command value before they cause glitches. By predicting when glitches will occur based on bit inversion detection, the system can prepare compensation signals in advance, preventing the harmful effects before they manifest in the beam position.
Solution Approach 2:
The invention applies preliminary anti-action by generating compensation glitch waveforms that are specifically designed to counteract the harmful glitches before they affect beam positioning. The compensation signal is generated in advance based on predicted bit inversions, creating an opposing effect that neutralizes the harmful voltage changes.
2Measurement precision
If deflection voltage is changed to adjust beam position, then positioning capability is improved, but high-order bit inversion causes sudden voltage changes and glitches
Solution Approach 1:
The invention extracts the harmful glitch component from the deflection voltage by separately detecting high-order bit inversions. By identifying and isolating the specific moments when bit inversions occur, the system can extract and compensate only the harmful voltage changes without affecting the overall positioning control.
Solution Approach 2:
The system changes the parameter of voltage stability by dynamically adjusting the deflection voltage while compensating for bit inversion effects. By monitoring bit patterns and adjusting compensation based on detected inversions, the system maintains voltage stability while preserving positioning accuracy.
3Reliability
If multiple DA converters are used to generate compensation waveforms, then glitch suppression is improved, but device complexity increases
Solution Approach 1:
The invention segments the waveform generation function into multiple specialized DA converters, each handling specific aspects of the compensation process. This segmentation allows each converter to be optimized for its specific function, improving overall reliability while maintaining manageable complexity through functional decomposition.
Solution Approach 2:
The multiple DA converters are designed with multi-functionality, where each converter can operate in different modes depending on the operational requirements. This universality allows the system to achieve high reliability through redundancy and compensation while avoiding the complexity of entirely separate dedicated circuits for each function.
Data Source
AI summary
In one embodiment, a waveform generating device includes a first DA converter converting input data, a controller outputting a first signal having a command value based on the input data, and a second signal having a command value differing by a constant value from the first signal, a second DA converter converting the first signal, a third DA converter converting the second signal, and a combiner combining the output of the first DA converter, the output of the second DA converter, and the output of the third DA converter. When a value of a predetermined first high-order bit of the input data is inverted, the controller changes the command value of the first signal such that a value of the first high-order bit or a second high-order bit different from the first high-order bit is inverted.