Charged Particle Beam Discharge Detection for Pattern Error Control
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Solution Overview
Problem
Existing discharge detection methods in electron beam writing apparatuses struggle to accurately determine whether a discharge has caused a pattern error, leading to potential false stops or continued pattern errors due to undetected discharges.
Innovation Solution
A charged particle beam writing apparatus that includes a discharge sensor to detect changes in the electric field, a discharge detection control unit that calculates the time integral of the sensor's output over a fixed period, and determines based on this integral value whether a discharge causing a pattern error has occurred.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the output voltage is compared with a threshold value to detect discharges, then the discharge detection is simple, but false stops occur when the voltage exceeds the threshold even though no pattern error has occurred
Solution Approach 1:
The patent changes the detection parameter from simple voltage threshold comparison to time-integrated voltage accumulation. By integrating the voltage signal over time and comparing the accumulated value against a threshold, the system distinguishes between transient voltage spikes (false alarms) and sustained discharges (actual pattern errors), thereby improving detection accuracy while maintaining operational simplicity.
2Reliability
If the writing processing is stopped when the output voltage becomes greater than or equal to a predetermined threshold value, then the pattern error detection is immediate, but false stops occur reducing productivity
Solution Approach 1:
The patent transforms the detection mechanism from instantaneous voltage threshold checking to time-integrated voltage accumulation. This parameter change allows the system to tolerate brief voltage excursions without triggering false stops, while still detecting sustained discharges that cause actual pattern errors, thus maintaining both reliability and productivity.
3Reliability
If the output voltage is continuously monitored, then the discharge detection is continuous, but short-lived discharges below the threshold are missed causing pattern errors
Solution Approach 1:
The patent implements preliminary action by continuously accumulating the integrated voltage value even when it remains below the threshold. This preliminary accumulation ensures that short-lived discharges are not missed, as their voltage contributions are added to the running total. When the accumulated value eventually exceeds the threshold, the discharge is detected, maintaining detection coverage without increasing system complexity.
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 solution enables accurate detection of discharges that cause pattern errors, preventing false stops and ensuring continued writing accuracy by distinguishing between short-lived and long-lasting voltage changes.
Implementation Method 1
Changes in the electric field generated at the time of discharge affect the electric potential of the antenna, and voltage changes occur in the output of the discharge detection apparatus
Data Source
AI summary
In one embodiment, a charged particle beam writing apparatus includes a high-voltage power supply configured to apply an acceleration voltage for charged particles to an emission unit, a deflector configured to deflect a charged particle beam emitted from the emission unit, a discharge sensor configured to output an output value indicating a change in a case where a discharge occurs in a column in which the emission unit and the deflector are arranged or in the high-voltage power supply, and a discharge detection control unit configured to convert the output value from the discharge sensor into a conversion value with the same sign, calculate an integral value of the conversion value over a fixed period of time, and determine, based on the integral value, whether or not a discharge that causes a pattern error has occurred.