Detector Signal Sampling for Wide Dynamic Range at High Throughput
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Solution Overview
Problem
Existing multi-beam assessment apparatuses face challenges in achieving a high throughput while maintaining a wide dynamic range without increasing data transmission bandwidth.
Innovation Solution
A signal processing method that receives detection signals from a detector with multiple elements, processing sequences of ascending sample values to output values, where the output value for each detector element and sampling period is determined by selecting the Nth sample value or based on earlier sample values in the sequence, thereby managing dynamic range without reducing throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple charged particle beams are used to increase throughput, then productivity increases, but beam to beam differences and detector sensitivity variations cause loss of information in the dynamic range
Solution Approach 1:
The system performs preliminary actions by capturing multiple ascending sample values for each detector element before final output. This preliminary data collection ensures that even if saturation occurs in later samples, the earlier non-saturated samples preserve the dynamic range information, thus preventing information loss while maintaining high throughput from multi-beam operation
Solution Approach 2:
The invention changes the parameter selection dynamically by choosing different sample values from the ascending sequence based on saturation detection. When the Nth sample indicates saturation, the system transitions to using the Mth sample (where M < N) as the output value. This parameter change strategy preserves dynamic range information while accommodating the high data rates from multiple beams
2Productivity
If the Nth sample value is always used as output to maximize data utilization, then productivity is maintained, but dynamic range is reduced due to detector saturation
Solution Approach 1:
The system implements feedback by monitoring the Nth sample value for saturation conditions and using this information to determine whether to output the Nth sample or an earlier Mth sample. This feedback mechanism ensures that saturation does not compromise measurement precision, while still utilizing the latest available data when conditions permit, thus maintaining productivity
Solution Approach 2:
The invention introduces dynamics by making the output sample selection adaptive rather than fixed. The system dynamically chooses between the Nth sample and earlier Mth samples based on real-time saturation detection. This dynamic approach allows the system to maximize data utilization when possible while preserving dynamic range when saturation occurs
3Measurement precision
If earlier sample values (Mth where M < N) are used to preserve dynamic range, then measurement precision improves, but throughput is reduced due to loss of latest data
Solution Approach 1:
The system changes the output parameter selection based on saturation detection. Instead of always using the earliest non-saturated sample, the system uses the Nth sample when it hasn't saturated, and only falls back to the Mth sample when saturation is detected. This parameter change strategy preserves dynamic range when necessary while maintaining throughput by utilizing the latest data when possible
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
The method effectively increases the dynamic range of the assessment apparatus without reducing throughput or increasing data transmission, thereby improving the efficiency of defect assessment in manufacturing processes.
Implementation Method 1
detecting interaction products using a detector system having at least one detector element per charged particle beam
Data Source
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Figure 3~4
AI summary
A signal processing method comprising: receiving, from a detector, e.g. in a charged particle assessment apparatus, having a plurality of detector elements, a detection signal comprising a sequence of N ascending sample values for each detector element and for each sampling period, where N is an integer greater than 1; and outputting for each detector element and for each sampling period an output value; wherein outputting comprises: selecting, for at least one detector element and at least one sampling period, the Nth sample value in the sequence of ascending sample values of that sample period as the output value; and determining, for at least one detector element and at least one sampling period, the output value on the basis of at least an Mth sample value in the sequence of ascending sample values of that sample period, where M is an integer less than N.