SEM BSE Overlay Target Layout for Beam Tilt Calibration
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Solution Overview
Problem
The challenge in semiconductor manufacturing lies in accurately inspecting and detecting defects in complex IC structures using scanning electron microscopes (SEMs), particularly in aligning and calibrating the SEM systems to ensure high-quality imaging and efficient detection of secondary and backscattered electrons for buried layers and surface information, which is crucial for advanced metrology and inspection.
Innovation Solution
The development of SEM targets and evaluation methods that include buried and top features with varying recess depths, allowing for determination of beam tilt angle, resolution, contrast, and overlay precision, enabling adjustment and improvement of SEM system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple electron detectors are used to simultaneously obtain high quality imaging and efficient collection of surface information from secondary electrons and buried layer information from backscattered electrons, then imaging quality and detection efficiency are improved, but device complexity increases
Solution Approach 1:
The patent employs multiple electron detectors (secondary electron detector and backscattered electron detector) that each serve specific functions but collectively enable comprehensive imaging capabilities. The secondary electron detector captures surface information while the backscattered electron detector captures buried layer information, allowing the system to perform multiple detection functions simultaneously without requiring a single complex detector to do everything.
Solution Approach 2:
The detection system is segmented into multiple specialized detectors rather than using one unified detector. Each detector is optimized for specific electron types (secondary or backscattered), allowing independent optimization of each detection channel while maintaining overall system performance through coordinated operation of the segmented detection components.
2Reliability
If SEM system alignment and calibration are monitored and qualified using traditional methods, then basic functionality is maintained, but the ability to monitor and detect IC non-idealities is limited by image quality
Solution Approach 1:
The patent implements preliminary alignment and calibration procedures using standardized targets with known geometries before actual inspection. By performing alignment and calibration in advance using reference structures with precisely defined features, the system establishes optimal detection parameters that enhance its ability to detect subtle non-idealities during subsequent production inspection.
Solution Approach 2:
The patent uses standardized alignment and calibration targets that replicate known geometric patterns and features. These reference copies with precisely defined dimensions and arrangements serve as benchmarks for evaluating and adjusting SEM system performance, enabling accurate monitoring of alignment and calibration status without requiring direct measurement of production parts.
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
Enhances SEM image quality by accurately determining beam tilt angle and overlay precision, thereby improving the alignment and calibration of SEM systems for effective defect detection and inspection in complex IC structures.
Implementation Method 1
high secondary-electron and backscattered-electron signal detection efficiencies
Implementation Method 2
Backscattered electrons have higher emission energy to escape from deeper layers of a sample
Data Source
AI summary
A method for evaluating a scanning electron microscope (SEM) system, the method including accessing an SEM image of two or more sets of overlay targets, wherein each set of overlay targets includes buried features and top features, the buried features at a buried depth, wherein, in at least one of the two or more sets of overlay targets, the top features are recessed, each of the recesses having a corresponding recess depth, wherein the recess depths for the top features of the two or more sets of overlay targets are different; and determining a beam tilt angle of a SEM system based on the SEM image of the two or more sets of overlay targets.