Two-Stage Beam Detector Apertures for Scattered Electron Blocking
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Solution Overview
Problem
Existing multi-beam writing apparatuses face challenges in accurately detecting individual beams due to reduced beam diameters and decreased pitch, leading to noise from scattered electrons and reduced detection accuracy, especially when aligning microscopic apertures.
Innovation Solution
A two-stage aperture system comprising a first aperture substrate with a micropore and a second aperture substrate with a micropore, along with a sensor, is used to detect individual beams by blocking scattered electrons, allowing precise alignment and detection through a conductive, light-permeable second aperture substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of beams is increased to improve throughput, then productivity increases, but the pitch between beams decreases making individual beam detection difficult
Solution Approach 1:
The detection system is segmented into two independent aperture stages, each with its own micropore. The first aperture substrate's micropore selectively transmits the detection target beam while blocking adjacent beams. The second aperture substrate's micropore further refines the beam selection. This segmentation allows individual beam detection even when beams are closely spaced with reduced pitch, resolving the contradiction between high throughput (many beams) and detection accuracy.
2Measurement precision
If a thin film aperture is used to detect individual beams, then beam selection is achieved, but scattered electrons from adjacent beams enter the sensor causing noise
Solution Approach 1:
The scattering problem is solved by segmenting the aperture function into two stages. The first aperture substrate's micropore performs initial beam selection, and the second aperture substrate's micropore performs secondary selection that blocks scattered electrons from reaching the sensor. This two-stage segmentation effectively filters out harmful scattered electrons while maintaining the desired beam selection capability.
Solution Approach 2:
The second aperture substrate acts as an intermediary element between the first aperture and the sensor. It mediates by blocking scattered electrons that pass through the first aperture, allowing only the primary beam to reach the sensor. This intermediary structure eliminates the noise problem caused by scattered electrons.
3Measurement precision
If a second aperture is added to block scattered electrons, then detection accuracy improves, but alignment of the two microscopic holes becomes difficult
Solution Approach 1:
The patent employs a copying approach where the micropore pattern on the second aperture substrate is replicated from the first aperture substrate. Specifically, the through-holes in the first aperture substrate are used as masks to form the micropores in the second aperture substrate. This copying method ensures precise alignment between the two apertures without requiring complex external alignment procedures, thus improving ease of manufacture while maintaining high detection accuracy.
4Productivity
If the beam diameter is reduced to increase the number of beams, then productivity increases, but individual beam detection becomes more difficult
Solution Approach 1:
The detection system uses segmented apertures with micropores that are specifically sized and positioned to detect individual reduced-diameter beams. Each micropore in the first and second aperture substrates is designed to transmit only one beam at a time, even when beams have small diameters and are closely spaced. This segmentation enables reliable individual beam detection despite the reduced beam dimensions required for high productivity.
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
Enhances beam detection accuracy by preventing scattered electrons from interfering with the sensor, enabling precise alignment and improved writing accuracy in multi-beam systems.
Implementation Method 1
a first aperture substrate including a first passage hole smaller than a pitch between beams of a multi charged particle beam
Implementation Method 2
a sensor detecting a beam current of the detection target beam which has passed through the second passage hole
Data Source
AI summary
According to one embodiment, a beam detector includes a first aperture substrate including a first passage hole smaller than a pitch between beams of a multi charged particle beam, a second aperture substrate including a second passage hole allowing one detection target beam which has passed through the first passage hole, and a sensor detecting a beam current of the detection target beam which has passed through the second passage hole. The second aperture substrate has light permeability, and includes a conductive material.