Electron Beam Response Correction for Phase Delay and Beam Tilt
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Solution Overview
Problem
Semiconductor manufacturing faces challenges in reducing systematic errors in electron beam measurements, particularly due to internal latencies, parasitic backscattered electron signals, and beam alignment issues, which affect the accuracy of critical dimension measurements and lead to blurry pictures and tilt-induced errors.
Innovation Solution
The method involves determining and correcting tool-internal responses, improving secondary electron detection, and aligning the electron beam orientation with respect to the specimen's surface normal by modulating beam parameters, using phase shifts, high-pass filtering, and machine learning models to separate secondary and backscattered electron signals, and adjusting the beam tilt based on detected data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single offline measurement of internal latencies is performed, then the measurement process is simple, but changes in latencies over time are not covered leading to systematic errors
Solution Approach 1:
The patent implements periodic measurement of internal latencies at multiple time points (t1, t2, t3, ...) to capture temporal variations. This transforms a single static correction into a dynamic, time-resolved correction process that accounts for drift and noise in latency parameters, thereby improving measurement precision while maintaining systematic correction methodology.
Solution Approach 2:
The patent establishes a feedback loop where measured latencies are used to calculate correction values that are applied to subsequent measurements. This closed-loop approach continuously refines the correction based on actual measured variations, compensating for time-dependent changes in internal latencies and reducing systematic errors in distance measurements.
2Object-affected harmful factors
If band-pass energy filters are used to discriminate high energy backscattered electrons, then high energy BSEs are filtered, but low and medium energy BSEs pass through adding background signal
Solution Approach 1:
The patent changes the energy threshold parameter of the band-pass filter dynamically. By adjusting the lower energy cutoff of the filter based on measured latency variations and signal characteristics, the system adapts to different operating conditions and effectively separates secondary electrons from backscattered electrons across a range of energies, reducing background signal while maintaining signal clarity.
3Ease of operation
If static pre-alignment of beam axis is performed, then initial alignment is achieved, but beam tilt errors occur when specimen orientation changes
Solution Approach 1:
The patent transitions from static pre-alignment to dynamic beam tilt correction. The system continuously measures internal latencies and uses this information to calculate and apply real-time beam tilt corrections. This dynamic approach maintains measurement accuracy across different specimen orientations and heights by adapting the beam alignment to current operating conditions rather than relying on fixed initial alignment.
4Productivity
If internal latencies are not corrected, then the system operates without correction overhead, but systematic errors and noise accumulate in measurements
Solution Approach 1:
The patent performs preliminary measurement of internal latencies before actual distance measurements are taken. This preliminary characterization of the system's temporal behavior enables pre-calculation of correction values that are applied during the measurement process. By preparing correction data in advance, the system minimizes the overhead during productive measurement while maintaining high precision through systematic error compensation.
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 approach reduces systematic errors in electron beam measurements, enhancing the accuracy and precision of high-resolution measurements, allowing for real-time detection and correction of phase shifts and beam tilt, thereby improving the reliability of semiconductor metrology and inspection systems.
Implementation Method 1
Detection of secondary electrons (SEs) is beneficial as they are produced in a sample in a small interaction volume close to the surface
Implementation Method 2
the SE signal is perturbed by other electron sources, mainly, back-scattered electrons (BSEs) with a broad-band energy distribution
Implementation Method 3
Present band-path energy filters can discriminate the BSEs with high energy
Data Source
AI summary
Embodiments may include methods, systems, and apparatuses for correcting a response function of an electron beam tool. The correcting may include modulating an electron beam parameter having a frequency; emitting an electron beam based on the electron beam parameter towards a specimen, thereby scattering electrons, wherein the electron beam is described by a source wave function having a source phase and a landing angle; detecting a portion of the scattered electrons at an electron detector, thereby yielding electron data including an electron wave function having an electron phase and an electron landing angle; determining, using a processor, a phase delay between the source phase and the electron phase, thereby yielding a latency; and correcting, using the processor, the response function of the electron beam tool using the latency and a difference between the source wave function and the electron wave function.