Multi-beam Calibration for Charged Particle Beam Inspection
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Solution Overview
Problem
Charged particle beam apparatuses face challenges in achieving high-speed and high-precision inspection when the layout of primary beams on a specimen surface varies, leading to issues such as unscanned regions, overlap, and reduced spatial resolution due to deflection aberration.
Innovation Solution
A method for calibrating primary multi-beams by measuring and adjusting variance in their layout using reference marks, electron optics system adjustments, and mechanical parameters to ensure optimal beam alignment and detection, even under varying inspecting conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the layout of primary beams on the specimen surface varies, then the inspection speed can be increased by using multi-beams, but unscanned regions and overlap occur leading to reduced measurement precision
Solution Approach 1:
The patent applies preliminary action by performing beam layout calibration before inspection. The system measures the actual positions of multiple primary beams on the specimen surface using reference marks, calculates variance from ideal positions, and adjusts electron optics parameters in advance. This preliminary calibration ensures that when multi-beams are used for high-speed inspection, the beams are properly aligned to cover the entire field of view without unscanned regions or excessive overlap, thus maintaining measurement precision while achieving high inspection speed.
2Area of stationary object
If the beam deflection width is increased to cover wider regions, then the inspection area can be expanded, but deflection aberration increases reducing spatial resolution
Solution Approach 1:
The patent applies dynamics by making the beam deflection width adjustable and adaptive. Instead of using a fixed large deflection width that causes aberration, the system dynamically adjusts the deflection width of each primary beam based on the calibrated layout. The electron optics system can modify deflection parameters to optimize the balance between field of view coverage and spatial resolution, allowing the beam layout to adapt to different inspection requirements while maintaining high spatial resolution even when covering wide regions.
3Reliability
If the primary beam intervals are adjusted to eliminate unscanned regions, then complete coverage is achieved, but beam overlap increases causing redundant scanning
Solution Approach 1:
The patent applies feedback by using the measured beam positions and layout variance information to optimize beam intervals. The system first measures the actual beam positions on the specimen surface, calculates the variance from ideal positions, and uses this feedback information to adjust the beam intervals and deflection widths. This feedback loop enables the system to determine the optimal beam spacing that ensures complete coverage of the field of view while minimizing redundant overlap, thus eliminating unscanned regions without excessive redundant scanning.
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 high defect detection sensitivity and inspection speed by ensuring precise beam alignment and detection, reducing unscanned regions and aberration effects, thereby enhancing the quality of scanned images and throughput.
Implementation Method 1
a charged particle beam apparatus that emits a charged particle beam (hereinafter called a primary beam) such as an electron beam and an ion beam on a specimen, acquires a signal of a generated secondary charged particle (hereinafter called a secondary beam)
Implementation Method 2
the layout of primary beams is rotated from the ideal layout on the surface of the specimen... Primary beams raster-scan the specimen in respective deflection width
Data Source
AI summary
In a multi-charged-particle-beam apparatus, when an electric field and voltage on a surface of a specimen are varied according to characteristics of the specimen, a layout of plural primary beams on the surface of the specimen and a layout of plural secondary beams on each detector vary. Then, calibration is executed to adjust the primary beams on the surface of the specimen to an ideal layout corresponding to the variation of operating conditions including inspecting conditions such as an electric field on the surface and voltage applied to the specimen. The layout of the primary beams on the surface of the specimen is acquired as images displayed on a display of reference marks on the stage. Variance with an ideal state of the reference marks is measured based upon these images and is corrected by the adjustment of a primary electron optics system and others.