Caged Plasma Immersion Ion Processing for Uniform 3D Coating

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Solution Overview

Problem

Conventional plasma immersion ion processing (PIIP) techniques face challenges in uniformly coating three-dimensional objects, particularly dielectric surfaces like ceramics and polymers, as existing methods are limited to coating one side and struggle with achieving high deposition rates and uniformity.

Innovation Solution

The 'caged' PIIP method encloses workpieces in a metal mesh cage within a vacuum chamber, generating plasma through negative voltage pulses, which increases electron-neutral collisions, resulting in higher plasma density and conformal deposition, allowing for uniform coating of all surfaces, including inner and outer surfaces, without repositioning the parts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional PIIP methods are used to coat three-dimensional objects, then coating can be applied to surfaces, but deposition rate is low and coating uniformity is poor

Engineering Contradiction:

Improvedeposition rateVSAvoidcoating uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The workpiece is segmented into multiple sections, each independently biased to control plasma distribution. This allows different regions to receive optimized plasma flux, simultaneously improving deposition rate and uniformity across complex three-dimensional surfaces

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A conductive coating is applied as an intermediary layer on dielectric workpieces to enable plasma interaction. This mediator allows ions to be effectively drawn to and deposited on non-conductive surfaces, improving both deposition rate and uniformity on dielectric materials

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If high voltage is applied to draw ions to the surface, then deposition rate increases, but coating uniformity deteriorates

Engineering Contradiction:

Improvedeposition rateVSAvoidcoating uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

Different regions of the workpiece are assigned different bias voltages tailored to their specific geometric requirements. This local quality approach ensures each surface region receives optimal ion flux for uniform coating, while maintaining high overall deposition rates across the entire workpiece

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The bias voltage applied to different workpiece sections is dynamically adjusted during the coating process based on real-time plasma distribution and deposition rate monitoring. This dynamic control maintains optimal coating uniformity while maximizing deposition rate throughout the process

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 enhances deposition rates and coating uniformity, achieving higher current density and conformal plasma sheaths, enabling efficient and uniform DLC coating of complex shapes, including dielectric surfaces, with improved corrosion resistance and reduced friction.

Implementation Method 1

The plasma can be generated in a suitably designed vacuum chamber and with various plasma sources. Examples of plasma sources are an electron cyclotron resonance plasma source, helicon plasma source, capacitively coupled plasma source, inductively coupled plasma source

Methodology Applied

Scientific EffectElectron cyclotron resonance:

Implementation Method 2

Methodology Applied

Scientific EffectHelicon plasma generation:

Implementation Method 3

Methodology Applied

Scientific EffectCapacitively coupled plasma generation:

Implementation Method 4

Methodology Applied

Scientific EffectInductively coupled plasma generation: Electromagnetic Induction

Implementation Method 5

A pulsed DC glow discharge is commonly used and does not require an external source for plasma generation

Methodology Applied

Scientific EffectDC glow discharge:

Implementation Method 6

A high voltage pulsed DC or pure DC power supply is used to target the ions to a surface. The same voltage also draws positively charged ions from the plasma to the worktable and the surfaces of the workpieces

Methodology Applied

Scientific EffectIon acceleration: Lorentz Force

Implementation Method 7

The impact of the incoming ions also generates electrons (secondary electrons) from the surfaces. These electrons travel to the chamber wall, which is positive with respect to the workpieces, to complete the circuitry

Methodology Applied

Scientific EffectSecondary electron emission:

Implementation Method 8

achieving higher current density and conformal plasma sheaths, enabling efficient and uniform DLC coating of complex shapes

Methodology Applied

Scientific EffectPlasma sheath formation:

Data Source

PatentUS8252388B2Method and apparatus for high rate, uniform plasma processing of three-dimensional objects

Publication Date: 2012.08.28 SOUTHWEST RES INST

AI summary

A method of performing plasma immersion ion processing (PIIP), particularly suited for processing three-dimensional objects. One or more such objects are placed in a conductive cage having solid or mesh walls. The cage completely encloses the objects. A voltage is applied to the cage, and the plasma is generated, resulting in the plasma being contained within the cage.