Orthogonal Electromagnetic Deflector for Electron Beam Stability
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Solution Overview
Problem
In metrology apparatus using scanning electron microscopes, the separation of primary and secondary electron beams is challenging due to circuit noises causing position shifts in the primary electron beam, which affects measurement accuracy and visibility of deep grooves and holes on semiconductor wafers.
Innovation Solution
A charged particle beam device with an orthogonal electromagnetic deflection unit that includes a magnetic-field deflector and an electric-field deflector, where a common unit generates control signals for both, ensuring the magnetic and electric fields are orthogonal and overlap, reducing position shifts by canceling out noise effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a unit deflects the secondary beam towards a predetermined direction, then the detection efficiency of secondary electrons is improved, but the primary beam position shifts, lowering measurement accuracy
Solution Approach 1:
The patent divides the deflection unit into two separate functional components: an electrostatic deflector that deflects the secondary beam toward the detector, and an electromagnetic deflector that compensates for primary beam position shifts. This segmentation allows each component to perform its specific function independently, resolving the contradiction between improving detection efficiency and maintaining measurement accuracy.
Solution Approach 2:
The electromagnetic deflector acts as an intermediary that compensates for the harmful side effect (primary beam position shift) caused by the electrostatic deflector. By introducing this intermediate component, the system can maintain both high detection efficiency and measurement accuracy simultaneously.
2Manufacturing precision
If the secondary beam is deflected at a high angle, then the visibility of deep grooves and holes is improved, but the primary electron beam position shifts occur
Solution Approach 1:
The electromagnetic deflector provides a counteracting effect to compensate for the primary beam position shifts caused by high-angle deflection of the secondary beam. The electromagnetic deflector generates an opposing force that counterbalances the harmful side effects, allowing the system to achieve high visibility of deep grooves and holes while maintaining primary beam position stability.
3Device complexity
If a common unit generates control signals for both magnetic and electric field deflectors, then the device complexity is reduced, but noise cancellation becomes challenging
Solution Approach 1:
The patent merges the control signal generation for both the magnetic field deflector and electrostatic deflector into a single common unit. This integration reduces device complexity by eliminating redundant control circuits while maintaining the ability to generate coordinated control signals for both deflectors.
Solution Approach 2:
The system employs feedback mechanisms where the control unit monitors the operation of both deflectors and adjusts their control signals accordingly. This feedback enables effective noise cancellation by coordinating the operation of the magnetic and electric field deflectors to compensate for each other's harmful effects while maintaining stable beam control.
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 enables high-resolution and high-throughput measurement by effectively deflecting secondary electrons at large angles while minimizing primary electron beam position shifts, improving the visibility of deep grooves and holes on semiconductor wafers.
Implementation Method 1
a magnetic-field deflector generating a magnetic field to change a path of the charged particle beam
Implementation Method 2
an electric-field deflector generating an electric field to change the path of the charged particle beam
Implementation Method 3
an orthogonal electromagnetic deflection unit that deflects a traveling path of the secondary electrons or the reflected electrons towards the detection unit
Data Source
AI summary
A processing apparatus and a processing method are provided, which use a charged particle beam device that achieves defection of secondary electrons/reflected electrons at a large angle and cancels out noises of an electromagnetic deflector and an electrostatic deflector to suppress a position shift of a primary electron beam caused by circuit noises of a primary beam/secondary beam separation circuit. In the charged particle beam device that includes an electronic optical system radiating a concentrated electron beam onto a sample placed on a stage to perform scanning and captures an image of the sample, a reference signal and a signal generation unit of a voltage-source control signal applied to the electrostatic deflector generating the electrostatic deflector and a reference signal and a signal generation unit of a current-source control signal applied to the electromagnetic deflector generating a magnetic field are made common in an overlapping-electromagnetic-deflector control unit that controls a path of the secondary electrons/reflected electrons incident on a detector, and frequency characteristics and phase characteristics of the voltage control signal are coincident with those of the current-source control signal.