Nano-aperture Ion Source Chip for High Brightness Proton Beam Writing

Solution Overview

Problem

Current proton beam writing (PBW) systems are limited by low brightness ion sources, which restrict their performance in terms of spot size and throughput due to large ionization chamber dimensions and thick silicon nitride membranes, limiting the versatility and efficiency of ion species selection.

Innovation Solution

A modified nano-aperture ion source (NAIS) with a compact ionization chamber chip is developed, featuring a sub-micron ionization chamber design with reduced dimensions and a MEMS fabrication process, allowing for high brightness ion generation with a small virtual source size and low energy spread, enabling the selection of various ion species.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If conventional ion sources with large ionization chamber dimensions and thick silicon nitride membranes are used, then structural stability is maintained, but ion source brightness is limited

Engineering Contradiction:

Improveion source brightnessVSAvoidionization chamber dimension

Core Design Contradiction:

Illumination intensityVSLength of stationary object

Solution Approach 1:

The patent applies parameter changes by reducing the ionization chamber dimensions from conventional large sizes to sub-micron scales (e.g., 500 nm aperture, 200 nm membrane thickness). This dimensional parameter change enables higher ion source brightness while maintaining structural integrity through optimized geometric parameters

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent utilizes thin film technology by employing ultra-thin silicon nitride membranes (200 nm thickness) as the ionization chamber wall. This thin film approach allows the chamber to maintain structural stability while achieving the reduced dimensions necessary for high brightness ion source performance

Inventive Principle:

Principle #30Flexible shells and thin films

2Adaptability or versatility

If conventional ion sources are used, then device simplicity is maintained, but ion species selection versatility is limited

Engineering Contradiction:

Improveion species selectionVSAvoidion source structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent achieves universality by designing the nano-aperture ion source structure that can generate multiple ion species (H+, He+, Ne+, Ar+) through electron impact ionization of different gas molecules. The same physical structure and mechanism serve multiple ion generation functions, enabling versatile ion species selection without requiring separate specialized sources for each ion type

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Manufacturing precision

If conventional ion sources with thick membranes are used, then mechanical strength is maintained, but energy spread increases

Engineering Contradiction:

Improveenergy spreadVSAvoidmembrane strength

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The patent applies parameter changes by optimizing the membrane thickness parameter to 200 nm, which is thin enough to minimize energy spread (achieving 5 eV FWHM) but thick enough to maintain mechanical strength. This precise parameter optimization resolves the contradiction between membrane strength and energy spread control

Inventive Principle:

Principle #35Parameter changes

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

The modified NAIS achieves a significantly higher reduced brightness of 9.1×10^3 A/(m2srV), surpassing existing PBW systems and approaching the performance of high-brightness ion sources, while maintaining a strong electric field and low energy spread, facilitating high-throughput sub-10 nm lithography without proximity effects.

Implementation Method 1

A modified nano-aperture ion source (NAIS) with a compact ionization chamber chip is developed, featuring a sub-micron ionization chamber design with reduced dimensions and a MEMS fabrication process, allowing for high brightness ion generation with a small virtual source size and low energy spread

Methodology Applied

Scientific EffectElectron impact ionization: Photoionisation

Implementation Method 2

The modified NAIS achieves a significantly higher reduced brightness of 9.1×10^3 A/(m2srV), surpassing existing PBW systems and approaching the performance of high-brightness ion sources, while maintaining a strong electric field and low energy spread

Methodology Applied

Scientific EffectElectric field acceleration: Electric Field

Data Source

PatentUS11056315B2Ionization chamber chip for a nano-aperture ion source, method of fabrication thereof, and a proton beam writing system

Publication Date: 2021.07.06 NATIONAL UNIVERSITY OF SINGAPORE

AI summary

An ionization chamber chip, a nano-aperture ion source, a proton beam writing system, and a method of fabricating an ionization chamber chip. The method comprises the step of providing a first substrate comprising a first depression formed in a back surface thereof; providing a backing element attached at the back surface of the first substrate such that a chamber is formed comprising at least the first depression; forming a gas inlet in the first substrate in fluid communication with the chamber; and forming a first aperture structure in the first substrate in fluid communication with the chamber.