Charged Particle Beam Drift Detection via Reflected Signal Analysis
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Solution Overview
Problem
Conventional methods for measuring beam drift in electron beam lithography are unable to detect changes in microseconds, leading to inefficiencies in positioning accuracy during pattern writing.
Innovation Solution
A method involving irradiation of a charged particle beam onto a substrate with a reference mark of different reflectance, measuring the current change from reflected particles, and using this data to calculate and correct for beam drift, allowing for rapid detection and compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods scan electron beam over reference mark to measure position, then measurement can be performed, but sampling time is approximately 0.5 milliseconds which is too slow to detect beam drift in microseconds
Solution Approach 1:
The patent replaces the mechanical scanning method with an optical detection method. Instead of physically scanning the electron beam across the reference mark to measure position, the system uses reflected electron signal intensity to detect beam position and drift. This substitution of detection mechanism enables microsecond-level sampling by eliminating the time-consuming scanning process.
Solution Approach 2:
The patent creates an optical/electrical copy of the reference mark position information through reflected electron signals. By measuring the intensity of reflected electrons from the reference mark, the system obtains position information without physical scanning, enabling rapid drift detection at microsecond intervals.
2Loss of information
If electron beam is scanned over reference mark to obtain position data, then beam drift can be measured, but the process takes 0.5 milliseconds per data point including communication time
Solution Approach 1:
The patent replaces mechanical beam scanning with direct optical/electrical detection of reflected electron signals from the reference mark. This allows position information to be obtained instantaneously through signal intensity measurement rather than through time-consuming scanning and communication processes.
Solution Approach 2:
The patent enables continuous monitoring of beam position through continuous measurement of reflected electron signal intensity. This continuous detection method eliminates the intermittent nature of scanning-based measurement, allowing uninterrupted beam drift detection at microsecond resolution throughout the writing process.
3Productivity
If beam drift is not corrected in real-time, then writing process continues without interruption, but positional accuracy deteriorates due to accumulated drift
Solution Approach 1:
The patent implements a feedback mechanism where reflected electron signal intensity is continuously measured to detect beam drift, and this information is used to correct beam positioning in real-time. The feedback loop operates at microsecond intervals, allowing the system to maintain positional accuracy while continuing the writing process without interruption or slowdown.
Solution Approach 2:
The patent performs preliminary drift detection and correction by measuring reflected electron signals before the drift significantly impacts writing accuracy. By continuously monitoring and correcting beam position in advance, the system prevents accuracy deterioration while maintaining high writing throughput.
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
Enables the detection and correction of beam drift in approximately one microsecond, significantly reducing sampling time and improving positional accuracy during pattern writing.
Implementation Method 1
the charged particle beam is irradiated on a portion that includes both the surface of a substrate and a part of a reference mark formed on the substrate and made of a material having a different reflectance than the substrate
Implementation Method 2
a charged particle beam irradiating unit that irradiates the charged particle beam onto the substrate; a reflected charged particle receiving unit that receives reflected charged particles generated when the charged particle beam is irradiated onto the substrate
Data Source
AI summary
A detector 32 measures the value of the current formed by reflected electrons generated as a result of irradiation of a reference mark on a substrate with an electron beam 54, where the reference mark is made of a material having a different reflectance than the substrate. The signal from the detector 32 is amplified by a detecting unit 33 and converted to a digital signal by an A/D conversion unit 34. A control computer 19 then performs averaging processing on the digital signal which is then used for drift compensation by a writing data correcting unit 31.