DAC Abnormality Detection in Charged Particle Beam Writing
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Solution Overview
Problem
Existing charged particle beam writing systems face challenges in detecting abnormalities in digital-analog converter units (DAC amplifiers) in real-time, leading to defective mask manufacturing due to undetected errors during the writing process, which results in significant losses and secondary damage.
Innovation Solution
A method and apparatus that utilize a pair of DAC converter units to output synchronized plus-minus reversed values, with a judging unit detecting abnormalities by comparing the sum of their outputs to a threshold value, allowing for immediate identification of abnormal units during pattern writing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If abnormality detection is performed during writing, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the detection function with the existing writing system by using the same DAC amplifier units and deflector hardware for both writing and detection purposes. The judging unit is integrated into the control system, allowing abnormality detection to be performed during the writing process without adding separate dedicated detection hardware, thus improving manufacturing precision while minimizing device complexity increase
Solution Approach 2:
The DAC amplifier units and deflector are designed to serve dual functions: normal beam deflection during writing and abnormality detection. By making these components multi-functional, the system can detect abnormalities during writing without requiring separate dedicated detection components, resolving the contradiction between improved precision and increased complexity
2Reliability
If real-time abnormality detection is implemented, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the judging unit continuously monitors the output values from the DAC amplifier units during writing and provides real-time abnormality detection. The comparison circuit compares actual output values with expected values and feeds back abnormality information to the control system, improving reliability by enabling immediate detection and response to DAC amplifier failures without requiring complex external monitoring systems
Solution Approach 2:
The system performs self-diagnosis by using its own internal components (DAC amplifier units, deflector, and judging unit) to detect abnormalities during normal writing operations. The system monitors its own operational parameters and can identify failures without external intervention, improving reliability while avoiding the need for separate complex diagnostic equipment
3Loss of time
If abnormality detection is performed during writing, then loss of time is reduced, but measurement precision requirements increase
Solution Approach 1:
The patent performs preliminary abnormality detection during the writing process itself, before defective masks are completed and cause losses. By detecting DAC amplifier abnormalities in real-time during writing, the system can stop production immediately upon detecting a failure, preventing the time loss that would occur from producing entire batches of defective masks. The comparison circuit is designed to detect abnormalities with sufficient precision using standard measurement capabilities, resolving the contradiction between time reduction and precision requirements
Data Source
AI summary
A charged particle beam apparatus includes a plurality of digital-analog (DA) converter units configured to input digital signals, convert the digital signals into analog values, and amplify the analog values to output the analog values, a deflector configured to input at least one analog value of the plurality of analog values output from the plurality of DA converter units to deflect a charged particle beam, and a judging unit configured to judge that at least one of the plurality of DA converter units is abnormal by using the plurality of analog values output from the plurality of DA converter units.