Electromagnetic Lens With Permanent Magnets for Stray Field Control
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Solution Overview
Problem
High-throughput industrial manufacturing of charged-particle beams for lithography and nano-patterning requires increased electrical current, but this leads to resolution limitations due to Coulombic interactions, and existing magnetic lenses face challenges with stray fields and precision adjustments in multi-column systems.
Innovation Solution
An electromagnetic lens with a magnetic circuit assembly using permanent magnets and electrostatic elements, featuring a sleeve insert with conductive electrodes to generate an electrostatic field, allowing for precise focal length adjustment and control of optical aberrations, while minimizing stray fields through strategically placed gaps in the magnetic circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If coil-based magnetic lenses are used to generate strong magnetic fields, then the magnetic field strength is sufficient for lens operation, but Joule heating becomes extremely large and requires inadequate space for temperature control
Solution Approach 1:
The patent replaces the electromagnetic coil system with a permanent magnet system. Instead of using electrical current through coils to generate the magnetic field, permanent magnets are arranged in a specific configuration within the housing body to produce the required magnetic field for lens operation. This substitution eliminates Joule heating while maintaining sufficient magnetic field strength.
Solution Approach 2:
The patent changes the method of magnetic field generation from electromagnetic induction (coil-based) to permanent magnet field. By altering the fundamental parameter of how the magnetic field is produced, the system achieves the same functional outcome without the associated energy loss and heating problems.
2Loss of energy
If permanent magnets are used to generate magnetic fields, then Joule heating is eliminated, but the magnetic field precision cannot be adjusted after manufacturing
Solution Approach 1:
The patent introduces electrostatic elements that can be dynamically adjusted by applying different electrical potentials. These electrostatic elements interact with the permanent magnet field to modify the effective magnetic field strength and focal properties of the lens. This dynamic adjustment capability is achieved through electrical control of the electrostatic elements while the permanent magnets provide the base field.
Solution Approach 2:
The electrostatic elements act as an intermediary between the permanent magnets and the charged particle beam. By applying electrical potentials to these intermediate elements, the system can adjust the effective magnetic field without directly changing the permanent magnet configuration, thus maintaining both energy efficiency and adjustability.
3Productivity
If the column diameter is reduced to fit multiple sub-columns on a wafer, then the throughput increases, but the space for temperature control and coil fabrication becomes insufficient
Solution Approach 1:
By replacing the coil-based magnetic lens system with a permanent magnet system, the patent dramatically reduces the space required for each sub-column. The permanent magnets are more space-efficient than coils with their required cooling infrastructure, enabling tighter packing of sub-columns on the wafer surface while maintaining adequate space for necessary control systems.
4Productivity
If electrical current is increased to improve throughput, then the manufacturing speed increases, but resolution deteriorates due to Coulombic interactions
Solution Approach 1:
The patent employs dynamically adjustable electrostatic elements that can optimize the beam focusing for different current levels. By adjusting the electrical potentials applied to these elements, the system can compensate for Coulombic interactions at higher currents and maintain resolution while achieving higher throughput through increased beam current.
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 high-precision adjustment of the charged-particle beam's optical properties, significantly improving the throughput and accuracy of multi-column systems by reducing stray fields and enhancing the precision of magnetic field control, thus addressing the limitations of existing technologies.
Implementation Method 1
the sleeve insert comprises one or more electrically conductive electrode elements, preferably at least two, which are configured to be applied respective electric potentials (with respect to the electric potential of the housing, which is identified with a ground potential) so as to generate an electrostatic field within the passage opening
Implementation Method 2
the ring magnet(s) comprising a permanent magnetic material being magnetically oriented with its two magnetic poles towards the inner yoke shell and the outer yoke shell, respectively
Implementation Method 3
an electromagnetic lens configured to modify a charged-particle beam
Implementation Method 4
an electromagnetic lens configured to modify a charged-particle beam
Data Source
Figure 1~2
Figure 3~3A
Figure 4
AI summary
A fine-adjustable electromagnetic lens (10) for a charged-particle optical apparatus (401) comprises a magnetic circuit assembly (11) including one or more ring magnets (101, 102), and a sleeve insert (12) of generally rotational symmetry around a longitudinal axis (c1). The sleeve insert (12) surrounds a passage opening (120) extending along the longitudinal axis (c1), and comprises several electrically conductive electrode elements (106, 108, 110, 112) configured to generate an electrostatic field (202) within the passage opening. The ring magnets (101, 102) are arranged circumferentially around an inner yoke shell (103) and surrounded by an outer yoke shell (104); the inner yoke shell in turn surrounds a central portion of the sleeve insert. The ring magnets are magnetized such that the two magnetic poles are oriented towards the inner and outer yoke shell, respectively. The inner and outer yoke shell together with the ring magnets form a magnetic circuit having at least one gap (14a, 14b), in order to generate a magnetic field (201) reaching inwards into the passage opening (120) and spatially overlapping with the electrostatic field (202) generated by the sleeve insert (12).