plasma quest limited magnetic data storage materials plasma quest perspective barry holton managing...

Plasma Quest Limited

Magnetic Data Storage Materials

Plasma Quest Perspective

Barry HoltonManaging Director

January 16th 2006

Tel: +44(0) 1256 740680 www.plasmaquest.co.uk e-mail: [email protected]

http://www.plasmaquest.co.uk/

Objectives:

To tell you who we are!

To present what PQL sees as the challenges for deposition technologies

To indicate where PQL is directing its materials deposition developments

To indicate where PQL sees the potential

To listen

Introduction

PQL is a small R&D company with 7 years experience of developing, using - and promoting - Remote Plasma Sputtering as a solution to a wide range of materials and applications, providing unique solutions and benefits in most cases.

- high rate, low temperature deposition of low stress thin film coatings with near ideal physical properties

-significantly increased process scope – ‘enabling technology’

- deposition of metals, alloys, insulators and ferromagnetics*- stable reactive sputter deposition for dielectric thin films- deposition of high quality transparent conducting oxides (TCO)- deposition of DLC with high optical transmission- deposition of polycrystalline silicon for electronic devices- new waveguide materials and system options for opto-electronics

[*remote plasma allows thick (6mm+) target use]

Hard Disc Developments

Already well established with large companies and theirR&D operations investing heavily.

PQL will not look DIRECTLY at developing in this area,but it will look to promote its technologies where appropriate

Currently working with Universities of York and Manchesterin a LINK ISD programme to:

“demonstrate the potential of HiTUS technology for the production of thin films of magnetic materials and other filmssuitable for application in the field of magnetic information storage”

(a number of papers have been generated from this project)

PQL seeks to concentrate on “specialist” activities,where the key characteristics of its technology offernew opportunities, for example:

High target utilisation Sputtering from thick ferromagnetic targets Thin film properties close to bulk Ability readily to control grain size

PLUS

Readily controllable stress High rate deposition at low temperature Stoichiometric deposition from compound

targets Very smooth films High rate, stable reactive sputtering

What will PQL develop?

Plasma Density Amplification through Magnetic Confinement

Gnd

Diode Sputtering(no magnetic field)

Low ionisation efficiency

= low sputter rates, high pressureTarget current

density0.1 – 2.0 mA/cm2

Target : -ve bias


Gnd





Target : -ve bias

Gnd

‘Magnetron’ - confinement at target

High local ionisation efficiency

= high local sputter rates (‘racetrack’)

Target current density

up to 100 mA/cm2 locally

Target : -ve bias


Gnd





Target : -ve bias

Gnd

‘Magnetron’ - confinement at target

High local ionisation efficiency

= high local sputter rates (‘racetrack’)

Target current density

up to 100 mA/cm2 locally

Target : -ve bias

Gnd

Remote Plasma

High remote ionisation efficiency= high sputter rates

over full targetTarget current

densityup to 100 mA/cm2

over full target

Target : -ve bias

Standard System Schematic

Substrate Holder Assembly, Shutter,

etc.

DEPOSITION CHAMBERSIDE ARM

PLASMA SOURCE

Source Electromagnet

Target Electromagnet

Multiple IndexableTarget System

Plasma Path in

Chamber

Substrate Holder Assembly, Shutter,

etc.

DEPOSITION CHAMBERSIDE ARM

PLASMA SOURCE

Source Electromagnet


Multiple IndexableTarget System

Plasma Path in

Chamber

• External RF antenna (13.56, 40MHz) produces initial low density plasma.

• Combined RF and DC electromagnetic fields accelerate electrons; magnetic field constrains electron paths and increases average path length.

• A significant proportion of electrons are accelerated to c. 50eV (probe measurements) – optimum for ionisation of argon gas.

• Combination of long path and high ionisation efficiency results in plasma density amplification towards plasma source exit – visible by OES.

• Plasma densities in excess of 1013 cm-3 may be achieved at source exit, limited by ambient gas pressure (90% ionised by OES).

• Measurements show high ion densities, but low ion bias (tens of V) – no sputtering of unbiassed components.

• Electrodeless system, highly robust and tolerant of reactive gases.

Plasma Source Basics

• DC magnetic field produced by the Source and Target electromagnets continues to constrain electron paths, essentially ‘directing’ the plasma to the target – a ‘cascade’ generation process.

• Despite magnetic field variations (30-300G range) and increasing distance from the source, high ionisation efficiencies are maintained – producing a high density plasma in front of the target surface.

• In the absence of target bias no sputtering occurs. Increasing (negative) target bias up to ~100V draws increasing ion current from the plasma. Sputtering begins during this time for most materials.

• Above -100V bias, the ion current ‘limits’ at a value dependent on process conditions (Source Power, magnetic field strength, gas pressure). Sputter rate therefore depends on bias voltage from hereon (approx. linearly to 2kV)

• The plasma itself is unaffected by target bias – giving an inherently stable basis for the sputtering process. Independent Source and Target operation allows stable coating over 5 orders of magnitude of deposition rate.

Remote Plasma Sputtering Basics

Some Indicative Deposition Rates

Reactive Al2O3 240nm/min 200mm Ø target Reactive Ta2O5 125nm/min 100mm Ø target Reactive SiO2 100nm/min 100mm Ø target Reactive TiO2 100nm/min 100mm Ø target

Fe/Co 120nm/min 6mm x 100mm Ø target

High Density Plasma Launch System(Some Benefits)

•Plasma Densities 1010 to 1013 cm-3

•Plasma Assisted High Rate Reactive Deposition•High Target Utilisation•Control of Grain Size•Sputter from thick ferromagnetic targets•Exceptional Film Properties eg

•Low Stress Films•Refractive Index near bulk•Low absorption•Very Smooth•Stoichiometry of compound targets maintained•Control of Properties

•System retrofittable to existing vacuum processes•Deposition onto Organic Substrates•Plasma Clean Facility

AN ENABLING TECHNOLOGY

Plasma Quest’s Base Technology

Some Magnetic Materials Information

Bias Voltage (-V)200 400 600 800 1000

<D> (nm)

80

60

40

20

100

CoFe 20nm films

University of York - 2005

Origins of the films Sample reference RoughnessRa (nm)

PQL MTA-100 0.5 nm

PQL MTA-101 (A) 0.5 nm

PQL MTA-104 1.6 nm

Coey et al. Janko-Si-1 2.4 nm

Coey et al. Janko-Si-2 2.5 nm

Trinity College Dublin - 2001

-1000 -500 0 500 1000-30000

-20000

-10000

0

10000

20000

30000

sample KAP4

H (Oe)

M (

kilo

ga

uss

)

PQL/UoY 2005

120nm Fe deposited onto 25µm Kapton

-600 -400 -200 0 200 400 600-30

-20

-10

0

10

20

30M (kG)

Field (Oe)

29050501 29050502 03050501 04050501 04050502 04050503

Si /Cr /FeCo-2.5nm Cr with different voltage levels for seed

Sample BP Bias Volume Ms Ms Ms Hc mbar -V (cm3) EMU EMU/cm3 kG Oe

29050501 5.0e-6 200 2.2x10-5 4.1x10-2 1865 23.4 21

29050502 1.6e-6 250 2.1x10-5 3.68x10-2 1754 22 41

03050501 7.5e-6 300 2.0x10-5 3.71x10-2 1858 23.3 11

04050501 1.0e-6 400 2.2x10-5 3.7x10-2 1685 21.2 33

04050502 8.5e-6 500 1.5x10-5 2.63x10-2 1744 21.9 60

04050503 8.0e-6 600 2.0x10-5 3.481x10-2 1744 21.9 64

Cr seed shows good MS

AND lower HC ~ 11 Oe

• The ‘standard’ HiTUS technology requires a source of similar diameter to the target diameter to be used. Typically 7.5cm to 20cm diameter targets are used in our systems (application dependent)

• We have successfully demonstrated Plasma Source operation to 20cm diameter – potentially allowing use with 30cm targets.

• The Plasma Source requires an RF supply of similar rating to the target supply – a cost disadvantage.

• Substrate size and deposition rate trade off = bigger targets or multiple targets are required for large throughput applications. Remote Plasma systems are disadvantaged due to multiple plasma source cost implications.

Production Systems ‘Scale Up’ Issues

Trials passing the plasma ‘beam’ along a rectangular target show improved area coating as expected, but …………..

………….we also discovered that a cylindrical target can be placed within the plasma beam without compromising the beam in any way.

Substantial in-house R&D over the last year has shown that this configuration has many benefits:

• More efficient use of plasma source – one tenth the power required

• Eliminates need to scale source with target• Greatly increased coating area• Greatly increased coating rates• Retains all HiTUS advantages – improves reactive stability.

Scale Up Development – ‘Linear’ System

Cylindrical TargetSubstrate Carrier Or Web Feed (1)

Launch Electromagnet


Plasma Source

Linear System Schematic

Substrate Carrier Or Web Feed (2)

(Note: system shown rotated 90 degrees for clarity)

• Critical understanding: the plasma beam from our Plasma Source essentially comprises two regions:

• A tubular cross section ‘generation’ region• A more extensive ‘cylindrical’ cross section plasma region

• The former is the main ‘glow discharge’ that visually defines the apparent plasma ‘beam’ – this must not be obstructed.

• The latter (may be invisible) can be obstructed.

• Thus a target may be placed within the plasma generation tube and thereby surrounded by plasma without detriment to the plasma itself.

• In addition, the generation tube appears to act as a ‘conduit’ for the RF energy – plasma generation efficiency is maintained, providing a uniform plasma density for sputtering from the whole target surface.

Fundamentals of Linear Source Operation

Linear System - Target Size Comparison

20cm

10cm

Linear Source 35cm

50cm x 7.5cm dia. Linear Target System

• A wide range of thin films , from metals to dielectrics, have been successfully deposited onto 50µm Kapton and 25µm PET

• Films are low stress, controllable from tensile through to compressive

• Film properties are near ideal and unchanged from those achieved on e.g. glass, and silicon wafers

• Examples of thin film depositions onto plastics (35cm linear target):•Stainless steel – 80 nm/min at 30cm separation•Titanium – 100 nm/min at 26cm separation•Iron – 45 nm/min at 30cm separation•Aluminium – 100 nm/min at 22cm separation•Alumina – 115 nm/min at 22cm separation

• System limited – extrapolated potential rates are 2-3 times this.

• Target wall thickness ~ 1.5cm for all targets – including magnetics.

Linear System - High Rate Deposition onto Thin Plastic Sheet for Flexible Electronics

Stress control

800nm Permalloy (NiFe) on 25µm Kapton sheet

-1000 -500 0 500 1000-30000

-20000

-10000

0

10000

20000

30000

sample KAP4

H (Oe)

M (

kilo

ga

uss

)

• 15mm wall thickness low purity iron (mild steel) 35cm linear target• Target - substrate separation 30cm• Substrate : 25µm Kapton sheet• Deposition rate : 45nm/min; Total film thickness : 120nm; Deposition area : 0.2m2

• Zero stress film

Linear System - High Rate Deposition of Ferromagnetic Materials onto thin plastic film – M-H Loop Data

• Linear System uses the same ‘reactive sputtering’ technique as standard HiTUS – inherently stable process without feedback control

• Uses metallic sputtering target, e.g. Al for alumina, Si for silica. This allows high rate sputtering – and cheaper DC supplies for metallics.

• Introduce appropriate flow (and distribution) of reactive gas during the sputter process, e.g. O2 for oxides, N2 for nitrides – or appropriate mixture for oxy-nitrides.

• High density plasma assists reaction (gas phase or surface) resulting in deposition of high quality, densified dielectrics at room temperature.

• Fully reacted coatings for optimised process – no free metal inclusion.

•Coatings are generally amorphous (low light scatter).

Linear System - High Rate Dielectric Deposition

• Reactive deposition from aluminium 35cm linear target• Target - substrate separation 22cm• Substrate : 25µm PET sheet• Deposition rate : 115nm/min; Total film thickness : 1000nm; Deposition area : 0.2m2

• Very low stress film. RI = 1.7

Linear System - High Rate Deposition of Aluminaonto thin plastic film – Transmission Data

80

85

90

95

100

105

110

200 400 600 800 1000 1200

Wavelength (nm)

Tra

ns

mis

sio

n (

%)

Preliminary Results - tbc•Prototype system in test, driven by 15cm diameter Plasma Source.

• Target diameter is 7cm – this has proven undersize for the Plasma Source as expected. Estimated maximum is 12cm.

• System power limited at present (60kW target supply requirement). (RF requirement is 5kW).

• Achieving full utilisation of target length – i.e. plasma propagates over 0.5m.

• Scaling data according to prior target dependencies indicates that target rates of 400nm/min will be exceeded – potentially 900nm/min.

• Data shows expected scaling of rate with target size increase – a 10cm target could therefore further raise this rate to 1400nm/min or more.

(Separation = 25cm)

Linear System – 50cm Target Development

Concept In-Line Linear Source Coating System Schematic

Dynamic Deposition Rate > 1000nm m/min(Continuous feed, Web or carrier plates

(Batch and multi-component target systems also in development)

Plasma Sources

Carrier Plate9 off 4” dia substrates

Load Lock Deposition Chambers Load Lock

Contacts:

Professor Michael Thwaites (CEO) Tel: +44 (0) 1256 740682 e-mail: [email protected]

Barry Holton (MD) Tel: +44 (0) 1256 740680 e-mail: [email protected]

Website: www.plasmaquest.co.uk




LINK Programme Materials

Rigid Disc MaterialsCr, CoPt, FePt

Soft Magnetic Films and InterlayersCoFe

Antiferromagnetic MaterialsFeMn, IrMn, PtMn

Tunnel JunctionsAl2O3, MgO


The Hardware


No Racetrack

Copper 6mm Cobalt

Racetrack Full surface erosion

>90% UTILISATION

Magnetron HiTUS



“Driving” the HiTUS

0.0

0.2

0.4

0.6

0.8

1.0

0 200 400 600 800 1000

2.0 kW1.5 kW

1.0 kW0.5 kW

Applied target voltage (V)Applied target voltage (V)

Tar

get c

urre

nt (

A)

Tar

get c

urre

nt (

A)

Target current/voltage relationshipTarget current/voltage relationship



Range of the HiTUS

Target Voltage (V)

Tar

get

Cu

rren

t (A

)

Magnetron + HiTUS

Magnetron + HiTUS

Minimum magnetron plasma Minimum magnetron plasma striking voltage and current striking voltage and current (Not applicable to HiTUS)(Not applicable to HiTUS)

HiTUS OnlyHiTUS Only

HiTUS + MagnetronHiTUS + Magnetron

HiTUS OnlyHiTUS Only

0000

BUTBUT:: HiTUS INDEPENDENT of gas pressure !! HiTUS INDEPENDENT of gas pressure !!



Comparison of theoretical and actual transmittance vs wavelength for a 14-layer diagnostic filter

TheoreticalTheoretical

ActualActual



Waveguide action in Ta2O5


Optical Emission Spectra for Remote Plasma Source

Optical emission at antennaOptical emission at source exit

0

5000

10000

15000

20000

25000

41

5.0

41

6.5

41

8.0

41

9.5

42

1.0

42

2.5

42

4.0

42

5.5

42

6.9

42

8.4

42

9.9

43

1.4

43

2.9

43

4.4

43

5.8

43

7.3

43

8.8

420.0 nmAr

434.8 nmAr+

nnii ~ 10 ~ 101313 cmcm-3-3

EmissionIntensity(arb units)

Wavelength (nm)

plasma quest limited magnetic data storage materials plasma quest perspective barry holton managing...

Documents

films deposition

target use slide

technology deposition

low sputter rates

films of magnetic materials

deposition technologies

plasma density amplification

ve bias slide