Multi-Pole Beam Deflection for SEM Astigmatism Correction
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Solution Overview
Problem
In SEM measurement devices, achieving high resolution and visibility of deep grooves and holes on semiconductor wafers requires improved scanning accuracy of the primary electron beam and efficient detection of secondary beams, which is hindered by the challenge of large angular deflection causing primary beam wobbling and astigmatism issues in the projected image of the secondary electron beam.
Innovation Solution
A charged particle beam device equipped with a multi-pole electromagnetic deflector that simultaneously deflects the secondary beam and corrects astigmatism of both primary and secondary electron beams, using a control circuit to manage electric and magnetic fields for precise beam control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large angular deflection of the secondary beam is performed to improve visibility of deep grooves and holes, then detection efficiency of secondary beam is improved, but the primary beam experiences wobbling and astigmatism occurs
Solution Approach 1:
The deflection unit is segmented into multiple independent deflection units, each with its own deflection unit drive circuit. This allows separate control of secondary beam deflection from primary beam scanning, enabling large angular deflection of secondary beam without affecting primary beam stability.
Solution Approach 2:
A beam separation unit is introduced as an intermediary component between the primary beam path and secondary beam detection path. This unit separates the two beams spatially, allowing independent manipulation of each beam without mutual interference, thus enabling large secondary beam deflection while maintaining primary beam accuracy.
2Ease of operation
If high electric and magnetic fields are applied to achieve large angular deflection of secondary beam, then deflection capability is improved, but in-plane uniformity of projected image of secondary electron beam deteriorates
Solution Approach 1:
The deflection unit employs dynamic control through dedicated drive circuits that can adjust deflection parameters in real-time. This allows optimization of the balance between deflection angle and image uniformity, compensating for distortions caused by high electric and magnetic fields while maintaining large angular deflection capability.
3Measurement precision
If a multi-pole configuration is used for secondary beam deflection, then astigmatism correction capability is improved, but device complexity increases
Solution Approach 1:
The deflection unit is designed with multi-functionality, where each deflection unit serves both as a beam separator and an astigmatism corrector. By integrating multiple functions into a single component structure, the patent avoids the need for separate dedicated components, thereby reducing overall device complexity while maintaining astigmatism correction capability.
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 solution enables accurate deflection of the secondary beam while maintaining the primary beam's positional stability, enhancing measurement resolution and visibility of deep features on semiconductor wafers by correcting astigmatism and reducing beam wobbling.
Implementation Method 1
a multi-pole electromagnetic deflector that deflects a path of the secondary beam... the multi-pole electromagnetic deflector includes electric field deflectors that generate an electric field
Implementation Method 2
magnetic field deflectors of which number is the same as the number of the electric field deflectors and which generate a magnetic field
Implementation Method 3
a control circuit that controls the multi-pole electromagnetic deflector... outputs a first astigmatism correction voltage for carrying out astigmatism correction of the primary beam or the secondary beam
Data Source
AI summary
Deflection of a secondary beam, and astigmatism correction of a primary beam or of the secondary beam are carried out using a multi-pole electromagnetic deflector which deflects the path of the secondary beam toward a detector.