Aberration Corrector Power Supply Merging for SEM Stability
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Solution Overview
Problem
The high cost and instability of power supplies required for aberration correction in electron beam apparatuses, such as SEMs, make it challenging to manufacture these devices at a reasonable price while maintaining performance, especially due to the need for multiple power sources and the susceptibility of electrostatic lenses to noise.
Innovation Solution
The use of an electromagnetic multipole lens in the first stage for trajectory isolation and an electrostatic-electromagnetic complex type multipole lens in the final stage within a multistage aberration corrector structure, allowing for a reduction in the number of current sources and power supplies by sharing currents among coils and using a common voltage source, thereby improving stability and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple power supplies are provided for each pole of the aberration corrector, then the aberration correction performance is improved, but the manufacturing cost increases significantly
Solution Approach 1:
The patent merges multiple independent power supplies into a single shared power supply that serves all poles of the aberration corrector. This is achieved by providing a common voltage source and current source that are shared across all multipole lenses, thereby reducing the number of power supplies from multiple individual units to just one unified power supply system.
Solution Approach 2:
The patent makes the single power supply universal by enabling it to serve multiple functions and multiple poles simultaneously. The common voltage source and current source are designed to provide power to all multipole lenses in the aberration corrector, making one power supply unit perform the work of what would traditionally require multiple separate power supplies.
2Reliability
If electrostatic multipole lenses are used for trajectory isolation and synthesis, then the control stability is improved, but the susceptibility to noise increases
Solution Approach 1:
The patent replaces electrostatic multipole lenses with electromagnetic multipole lenses in the first and fourth stages. This substitution uses magnetic fields instead of electric fields for trajectory isolation and synthesis, thereby reducing susceptibility to noise while maintaining control stability. The electromagnetic lenses are less sensitive to electrical noise and interference compared to their electrostatic counterparts.
3Ease of manufacture
If the number of power supplies is reduced, then the manufacturing cost decreases, but the stability of the electromagnetic field generation may be compromised
Solution Approach 1:
The patent implements feedback control mechanisms in the single power supply system to maintain electromagnetic field stability. The power supply includes control circuits that monitor and adjust the voltage and current output to ensure stable operation of all multipole lenses, compensating for any variations or disturbances in real-time.
Solution Approach 2:
The patent optimizes the electrical parameters of the common power supply, including voltage levels, current characteristics, and frequency, to ensure stable electromagnetic field generation across all multipole lenses. By carefully selecting and adjusting these parameters, the system achieves both cost reduction through fewer power supplies and maintained field stability.
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 effectively minimizes beam spot size by correcting chromatic and spherical aberrations, improves operational stability, and reduces the number of power supplies required, making the technology more affordable without compromising performance.
Implementation Method 1
an electromagnetic multipole lens is used for a multipole lens in the first stage to form trajectories isolated
Implementation Method 2
an electrostatic-electromagnetic complex type multipole lens in the final stage within a multistage aberration corrector structure
Implementation Method 3
an electrostatic-electromagnetic complex type multipole lens in the final stage
Implementation Method 4
removes aberration included in the charged particle beam passing the inside thereof by generating an electric field or a magnetic field within the multiple lenses
Data Source
AI summary
When an accelerating voltage and operating distance are changed, an excitation current and a pole voltage of an aberration corrector must also be changed. Moreover, different multipole voltages or currents must be added individually for each pole in order to superpose multipoles. In view of overcoming the problems explained above, the charged particle optical apparatus of the present invention comprises an excitation device including, to give excitation to form a multipole field to each pole of the multipole lens, electromagnetic type quadrupole of four stages arranged along an optical axis of charged particle beam, electromagnetic type quadrupole of two stages for superposing distribution of voltage similar to distribution of magnetic potential of the electromagnetic type quadrupole of two stages at the center of the electromagnetic type quadrupole of four stages, and electromagnetic type octupole for superposing magnetic potential at least to three multipoles among that of four stages and also comprises a first power supply group for driving the same excitation device and a second power supply group for impressing voltages.