Multi-Beam Optical System Adjustment via Movable Limiting Aperture

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Solution Overview

Problem

In multi-beam writing, distortion of images formed on the target object surface is significant due to deviations in the crossover position of electron beams, leading to beam loss and reduced contrast, making it difficult to achieve precise blanking control.

Innovation Solution

A method and apparatus for adjusting the multi-beam optical system by varying the crossover height position and adjusting the height of the limiting aperture substrate to minimize distortion, while restricting extra electron passage, using a shaping aperture array substrate and a limiting aperture substrate with a height position adjusting mechanism.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the crossover position is adjusted to the design position by the lens on the upstream side, then the beam size on the limiting aperture surface is reduced, but distortion of the image focused on the target object surface becomes large

Engineering Contradiction:

Improvebeam size on limiting aperture surfaceVSAvoidimage distortion

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The patent makes the limiting aperture substrate movable in the optical axis direction, allowing its position to be dynamically adjusted. This enables the system to adapt to different crossover positions without requiring fixed lens adjustments, thereby reducing image distortion while maintaining acceptable beam sizes on the aperture surface

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the position parameter of the limiting aperture substrate along the optical axis to optimize system performance. By adjusting this parameter, the system can accommodate variations in crossover position and minimize image distortion without compromising beam transmission efficiency

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If the aperture diameter of the limiting aperture is widened, then beam loss is avoided, but extra electrons pass through and image contrast decreases

Engineering Contradiction:

Improvebeam lossVSAvoidimage contrast

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The movable limiting aperture substrate allows for dynamic optimization of the aperture diameter based on actual beam conditions. The system can adjust the aperture size to match the beam size at different crossover positions, maximizing beam transmission while preventing extra electrons from degrading image contrast

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system uses distortion measurement to provide feedback on the quality of the focused image. This feedback information is used to adjust the limiting aperture position and diameter, creating a closed-loop control system that optimizes both beam transmission and image contrast

Inventive Principle:

Principle #23Feedback

3Loss of energy

If the aperture diameter of the limiting aperture is widened, then beam loss is avoided, but blanking control becomes difficult due to large blanking deflection requirements

Engineering Contradiction:

Improvebeam lossVSAvoidblanking control

Core Design Contradiction:

Loss of energyVSEase of operation

Solution Approach 1:

The movable limiting aperture substrate enables dynamic adjustment of the aperture position to optimize blanking control. By positioning the aperture at the actual crossover location, the system reduces the deflection angle required for blanking, making control easier while maintaining adequate aperture diameter to prevent beam loss

Inventive Principle:

Principle #15Dynamics

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 approach effectively reduces distortion and beam loss, maintaining image contrast and enabling precise blanking control, thus enhancing the writing process's accuracy and efficiency.

Implementation Method 1

forming multi-beams by making a region including a whole of a plurality of openings in a shaping aperture array substrate irradiated by a charged particle beam, and making portions of the charged particle beam individually pass through a corresponding one of the plurality of openings

Methodology Applied

Scientific EffectPhysical containment through aperture array: Filter (physical)

Implementation Method 2

adjusting a height position of a limiting aperture substrate which limits passage of a beam deviated from a trajectory in the multi-beams

Methodology Applied

Scientific EffectPhysical filtering of deviated particles: Filter (physical)

Data Source

PatentUS10224172B2Multi-beam optical system adjustment method, and multi-beam exposure apparatus

Publication Date: 2019.03.05 NUFLARE TECH INC

AI summary

A multi-beam optical system adjustment method includes forming multi-beams by making a region including the whole of a plurality of openings in a shaping aperture array substrate irradiated by a charged particle beam, and making portions of the charged particle beam individually pass through a corresponding one of the plurality of openings, measuring a distortion of the multi-beams while variably changing the crossover height position of the multi-beams, measuring the crossover height position of the multi-beams where the distortion of the multi-beams is smaller than the others, and adjusting the height position of a limiting aperture substrate which limits passage of a beam deviated from the trajectory in the multi-beams to the crossover height position.