Charged Particle Beam Masking for Laser Micromachining

Solution Overview

Problem

Existing laser micromachining techniques face challenges in achieving high resolution and precision due to the inherent limitations of laser beam wavelength and material removal rates, particularly in determining the endpoint for sequential processing with charged particle beams.

Innovation Solution

A high-resolution mask is fabricated using charged particle beam processing and deposited directly on the work piece, allowing for improved lateral resolution and aspect ratios by differentiating the ablation thresholds of the mask and substrate materials, enabling precise control over laser beam exposure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If laser micromachining is used to achieve high material removal rates, then productivity is improved, but manufacturing precision deteriorates due to the longer beam wavelength limiting minimum spot size

Engineering Contradiction:

Improvematerial removal rateVSAvoidminimum spot size

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The invention segments the micromachining process into two distinct stages: a laser processing stage for rapid material removal, and a charged particle beam stage for high-precision final machining. This segmentation allows each process to operate at its optimal capability, with the laser handling bulk removal and the particle beam providing sub-wavelength precision for the final structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The laser performs preliminary action by removing the majority of material before the charged particle beam completes the micromachining. This preliminary material removal reduces the workload for the precision particle beam process, enabling it to focus on achieving the final high-precision dimensions without excessive material removal time.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If charged particle beam processing is used to achieve high resolution, then manufacturing precision is improved, but productivity deteriorates due to limited beam current

Engineering Contradiction:

ImproveresolutionVSAvoidmicromachining speed

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The invention segments the micromachining process into two distinct stages: a laser processing stage for rapid material removal, and a charged particle beam stage for high-precision final machining. This segmentation allows each process to operate at its optimal capability, with the laser handling bulk removal and the particle beam providing sub-wavelength precision for the final structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The laser performs preliminary action by removing the majority of material before the charged particle beam completes the micromachining. This preliminary material removal reduces the workload for the precision particle beam process, enabling it to focus on achieving the final high-precision dimensions without excessive material removal time.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If sequential processing with laser followed by charged particle beam is used, then both productivity and precision can be achieved, but device complexity increases due to the need for endpoint detection

Engineering Contradiction:

ImproveresolutionVSAvoidprocess control complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The invention implements feedback through real-time monitoring of secondary electron emission during charged particle beam processing. This feedback mechanism provides continuous information about the micromachining progress and material removal rate, enabling dynamic adjustment of processing parameters and automatic endpoint detection without complex external measurement systems.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The charged particle beam process serves itself by using its own secondary electron emission signal as the endpoint detection mechanism. This self-service approach eliminates the need for separate, complex endpoint detection equipment, simplifying the overall system while maintaining precise control over the sequential processing transition.

Inventive Principle:

Principle #25Self-service

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 enhances the resolution and precision of laser micromachining by creating features with improved lateral resolution and aspect ratios, addressing the limitations of conventional laser micromachining and enabling more accurate endpoint detection.

Implementation Method 1

A mask is formed on a surface of the work piece through charged particle beam processing

Methodology Applied

Scientific EffectCharged particle beam deposition: Deposition (physical)

Implementation Method 2

The work piece is exposed to a laser beam through the mask and ablated

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentUS8629416B2Charged particle beam masking for laser ablation micromachining

Publication Date: 2014.01.14 FEI CO

AI summary

An improved method for substrate micromachining. Preferred embodiments of the present invention provide improved methods for the utilization of charged particle beam masking and laser ablation. A combination of the advantages of charged particle beam mask fabrication and ultra short pulse laser ablation are used to significantly reduce substrate processing time and improve lateral resolution and aspect ratio of features machined by laser ablation to preferably smaller than the diffraction limit of the machining laser.