SEM Deflector Configuration for Large Field Inspection
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Solution Overview
Problem
Scanning electron microscopes face a bottleneck in throughput during large field inspections of semiconductor patterns due to the need for repeated movement of the field of view, which causes signal electron detection rates to deteriorate as signal electrons collide with optical components, and existing deflector configurations are complex and difficult to control.
Innovation Solution
A scanning electron microscope configuration with multiple deflectors and a control unit that sets deflection fields to move the primary electron beam off-axis and correct signal electron trajectories, allowing for enlarged field of view movement without deteriorating signal electron detection rates, using a combination of magnetic and electrostatic fields to control the electron beam paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the field of view is moved by repeated stage movement for large field inspection, then the inspection coverage is improved, but the throughput is deteriorated due to the bottleneck caused by frequent stage movements
Solution Approach 1:
The patent segments the field of view movement function into two parts: stage movement for coarse positioning and beam deflection for fine positioning and scanning. This allows the stage to move less frequently while the electron beam is deflected to cover different areas, thereby improving throughput while maintaining inspection coverage.
Solution Approach 2:
The patent replaces the mechanical stage movement system with an electromagnetic beam deflection system for field of view movement. By using electromagnetic deflectors to move the electron beam instead of mechanically moving the stage, the system achieves faster and more frequent field of view changes, eliminating the throughput bottleneck caused by mechanical stage movement limitations.
2Productivity
If the beam deflection range is enlarged to reduce stage movement frequency, then the throughput is improved, but the signal electron detection rate is deteriorated due to increased collisions with optical components
Solution Approach 1:
The patent introduces a signal electron trajectory control mechanism that acts as an intermediary between the beam deflection system and the detector. By controlling the trajectory of signal electrons separately from the primary beam deflection, the system ensures that signal electrons are guided to the detector without colliding with optical components, even when the beam deflection range is enlarged.
Solution Approach 2:
The patent applies preliminary action by pre-controlling the signal electron trajectory before the electrons reach the detector. The trajectory control mechanism anticipates potential collisions with optical components and adjusts the signal electron paths in advance, ensuring that even with enlarged beam deflection, signal electrons reach the detector without collisions, maintaining detection rate while allowing larger beam deflection for improved throughput.
3Reliability
If a Wien filter is used to deflect only signal electrons without deflecting the primary beam, then the signal electron trajectory is controlled, but the device complexity is increased due to the need for superimposed electrostatic and magnetic fields
Solution Approach 1:
The patent segments the deflection function into separate components: primary beam deflection is handled by one set of deflectors while signal electron trajectory control is handled by another set. This segmentation allows each deflector system to be optimized for its specific function, avoiding the complexity of a Wien filter that requires superimposed electrostatic and magnetic fields to achieve both functions simultaneously.
Solution Approach 2:
The patent makes the deflectors universal by designing them to perform multiple functions: they deflect both the primary electron beam and control signal electron trajectories. By configuring deflectors with multiple coils that can generate different types of fields (electromagnetic and electrostatic) and controlling them with different settings, the system achieves signal electron trajectory control without requiring a separate Wien filter, thereby reducing device complexity while maintaining the desired functionality.
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 configuration enhances throughput by reducing the frequency of stage movement and maintaining signal electron detection rates, even with increased beam deflection, through precise control of signal electron trajectories and avoidance of collisions with optical components.
Implementation Method 1
a deflector that deflects a signal electron by acting with an electrostatic deflection field on the signal electron
Implementation Method 2
plural magnetic deflectors that deflect the primary electron beam passing the condenser lens
Implementation Method 3
an objective lens for focusing the primary electron beam emitted from the electron source on the specimen
Implementation Method 4
an electron source, a condenser lens and an objective lens respectively for focusing a primary electron beam emitted from the electron source
Data Source
AI summary
The present invention enlarges a range of movement of field of view by beam deflection with a simple deflector configuration and suppresses deterioration of a signal electron detection rate caused by the beam deflection. A scanning electron microscope according to the present invention is provided with a first deflection field setting module that sets plural deflectors to move a scanning area on a specimen by a primary electron beam to a position deviated from an axis extended from an electron source toward the center of an objective lens and a second deflection field setting module that sets the plural deflectors so that trajectories of signal electrons are corrected without changing the scanning area set by the first deflection field setting module. The control unit controls the plural deflectors by adding a setting value set by the second deflection field setting module to a setting value set by the first deflection field setting module.