Atomic Layer Deposition (ALD) - An Enabling Technology for NASA Space Systems

Dr. Vivek H. Dwivedi,

NASA Goddard Space Flight Center Greenbelt, MD. 20771

3/26/2019

What is a Thin Film?

Thin film: thickness typically <1000nm.

Special properties of thin films: different from bulk materials, it may be –

• Not fully dense

• Under stress

• Different defect structures from bulk

• Quasi ‐ two dimensional (very thin films)

• Strongly influenced by surface and interface effects

2

Other Deposition Techniques

3

CVD Process

«) «)

«) «) «)

«)

«) «) «) «) «)«)

«) «) «)

«) Step 1«) «) «)

«) «) Step~ «) «) «)

«) • Step 7

Step 2

~~ ~ ~

Step 4 • • Step 6 _____._ 6 0

Bare Substrate

1. Precu rsor gas phase reaction 2.Diffusion 3. Adsorption 4. Surface Process 5. Desorption 6.Diffusion 7, Purge

I 00

Ar• o o O O < 0 0

·\: /I\ Vent

Sputtered Target Atom

Cryo or Turbo Pum

Air Inlet

Thin-Film Engineering

4

Vapor-phase deposition of inorganic materials

Microelectronics Solar energy Solid-state lighting

James River Semiconductor First Solar The New Ecologist

Ga phase reactions • '\ ~ lRedesorption

of fi lm precursors

0

Desorption of volatile surface

reaction products

Common Denominator

5

•Deposition only occurs on substrates that “see” the target.•Plasma process can damage the substrate•Poor thickness control•Poor Step Control•High Pressure High Temperature Environment

Step Coverage Example

Step coverage of metal over non-planar topography.(a) Conformal step coverage, with constant thickness on horizontal and vertical surfaces.(b) Poor step coverage, here thinner for vertical surfaces.

conformal non-conformal

Atomic Layer Deposition

Atomic

Layer

Deposition} A thin film“nanomanufacturing” tool that allows for

the conformal coating of materials on a myriad of surfaces with precise atomic thickness control.

Based on:

Paired gas surface reaction chemistries

Benign non-destructive temperature and pressure environment

• Room temperature -> 250 °C (even lower around 45 °C)

• Vacuum

ALD Analogy (Checkers)

Introduction of Precursor •

1 Pair Stacked Chips

Purge Excess & Reacted Speci~

Random Precursor Surface Rxn Surface Limited State

i

Surface Limited State

Purge Excess & Reacted Species

~- I t LJ Introduction of Precursor •

Random Precursor Surface Rxn

ALD Analogy Chemistry

OH+ Al(CH3)3-> O-Al(CH3)2 + CH4 1.1 A/Cycle

., ., ., .,., .,., ., O-Al(CH3)2 + 2H20-> O-Al-(OH)2 + 2CH4

ALDPrecursor A + Precursor B → Solid film + Gas by-products

Cyclic operation: A → purge → B → purge → A → purge → ···

Atomic-level thickness control ...

... equivalent to a 60 μm layer

over a city-sized wafer

ALD Advantageous Property

Epitaxial Growth

Batch Process

Substrate Independence

. ·.·•· 1 ~·---::;;;-· · • , , ' I

I

Schematic of a 30 ban:ery integrated in a Si- substrate.

in the battery stack as well as the candidiite materials.

Multilayer c:om1sting of: Al203 25nm T1N 20nm Al203 25nm

'

ALD Material Systems

• Gordon, Roy (2008). Atomic Layer Deposition (ALD): An Enable for Nanoscience and Nanotechnology. PowerPoint lecture presented at Harvard University, Cambridge, MA.• Elam, Jeffrey (2007). ALD Thin Film Materials. Argonne National Laboratory

H He 0 :0 x ide C:Carbicle 2 N:Nilricle F:Flooride

9 M:Metal D:Dopant 0 N

LI Be P: Phos phideJAs enide 8 C N 0 F Ne 3 4 S: Sulphicle/Selenicle/T elluricle 5 6 7 8 9 10

0

9 @III M @NM Na Mg 0 Oxide of this e lement has bee depos iled by the ALO, commu nily Al SI p s Cl Ar 11 12 11!1 Recipe for this mate rial is available from C NT staff or c~tomer base

p 13 14 15 16 17 18 F m C

0 0 @III M 0 0 [!]NM 9 N t'!J 9 N t'!J @N t'!J 0 N M ra @III 0 M

K Ca Sc Tl V Cr Mn Fe Co NI Cu zn 111 Ga Ge As Se Br Kr 19 20 5 21 22 s 23 24 25 s 26 27 28 29 s 30 P 31 32 3.3 34 3.5 36

F D D FI!] D

0 0 @III @III 0 N M 0 t'!J 0 M 0 t'!J 0 M @N [!] 0 M Rb Sr y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te Xe 37 3.8 s 39 40 41 42 43. 44 45 46 47 48 5 P 49 5 50 5 51 52 53 54

F D D

0 [!] @III @NM @ III t'!J 0 0 0 M 0 t'!J 0 0

Cs Ba La 5 Hf 5 Ta w Re Os Ir pt Au Hg s Tl Pb 5 131 Po At Rn 55 56 s 57 72 73 74 75 76 17 78 79 llO 81 82 83 84 as &6

F F C D

Fr Ra Ac Rf Db Sg Bh Hs Mt 87 88 89 104 105 106 1'1>7 108 1,09

0 0 0 0 0 0 0 0 9 0 0 0

Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 58 59 ,50 61 62 63 64 ,55 ,55 ,57 ,68 69 70 71

D D D D

Th Pa u Np Pu Am Cm Bk Cf Es Fm Md No Lr 90 92 93. 94 95 96 97 98 100 101 1,02 104 4 4

NASA Impacts

ISS Orbit 400 kmAtomic O Density = 1 x 108 cm-2 s-1

v = 7.2 x 105 cm s-1

-> 1 O impact nm-2 s-1

KE = 4.2 eV

Conformal, flexible, 0(100 nm), nonvolatile oxide coating

Low temperature (100 °C) deposition process

STORM XRI

NASA GSFC

direct ion of urcc-1

unrcncctcd rn)/ contribute 10 background

nick.el i clepo ·i1 on in ide o channel 10 enhanc rcncc1ivi1y

Black et a l. 2003 , arXiv

ZnO

14

UV Absorption

120

100

80

~ ~ 60

40

20

0 ---

275 775 1275 1775 2275

.......,._ Bare Quartz .......,._ 100Cycles .......,._ 250 Cycles .......,._500Cycles

ALD For Radiators - Pigments

Precu rso1r • lnjedion

I ..

lsolatihn Valv•e V.a;cuum

ProblemSpacecraft charging is the condition that occurs when a spacecraft accumulates excesselectrons or ions. For a conducting spacecraft, the excess charges are on the surface. Theterm spacecraft surface charging (absolute charging) is used to clearly denote charging onthe spacecraft surface as opposed to other charge distributions such as the voltagedifferences between electrically isolated parts of the spacecraft (differential charging).

HAZARD

If a charge builds up that is too big for the spacecraft’s material to hold, discharge arcs, which are essentially strong electrical currents, will occur.

And depending on where those arcs go, they can damage electronic components, destroy sensors, or damage important materials such as thermal control coatings.

Problem

ESA EURECA satellite solar array sustained arc damage.Credits: ESA

Arc damage in laboratory tests of the chromic acid anodized thermal control coating covering ISS orbital debris shields.Credits: NASA/T. Schneider

Radiator - Vary in Size

The space station’s radiator system, which is a critical component of the active system, consists of seven panels (each about 6 by 12 feet) Wide Field Planetary Camera 2 (WFPC2)

that was installed on the Hubble Space Telescope in December 1993, and removed during the last servicing mission in 2009

Origami Inspired

Motivation

• Most white pigments do not dissipate electrical charge without a dopant or additive

• Two most commonly used dissipative thermal coatings (Z93C55 and AZ2000) rely on indium hydroxide or tin oxide as charge dissipative additives utilizing sol gel wet chemistry

• ITO formed locally on a macroscopic scale due to seeding and ITO crystal formation on the boundaries of the pigment grains. Thickness and dispersion throughout the coating are difficult to control.

Instead of postprocessing the dissipative coating can we preprocess the dissipative coating before binding directly on the pigment itself?

Experimental Procedures

• The first set of experiments were conducted on flat substrates for the ALD of In2O3

and ITO, the films were deposited on a variety of substrates including n-type Si(100) wafers for thickness measurements and glass microscope slides for sheet resistivity determination.

• The In2O3 ALD on the particle substrates was applied to Z93P pigments provided by Alion Science and Technology; these particles had a mean size of 2 microns.

• Thickness and conformity of the ALD films on the Si wafers of In2O3 and ITO were measured using a J.A. Woollam M-2000D Spectroscopic Ellipsometer. The sheet resistivity of the ALD films on the microscope glass substrates was measured using a Lucas Signatone S-302 four-point probe

• The bulk resistivity of the ALD deposited pigment system is measured in air after the formation of a pellet of 1 in. diameter and a thickness of approximately .5 in. The pigment is compressed lightly by hand and held in place by a 3D printed electrically insulating hollow nylon/Teflon annulus spacer held on an aluminum plate. Resistivity was measured in air and vacuum.

Results

Uncoated Pigment Coated Pigment

Results

Results

Spectrum Label Zinc Oxide Particles Indium Oxide Coated

C 57.73 73.72

O 33.23 24.76

Zn 9.04 1.28

In - 0.23

XPS of Particle Composition

p1~ n3s In 3p /2 L 1s

~ ~~312 ln3p 13d3/2

60 In 3p3/2 In 3d5/2

'OKLL ln3d

50 Variable Name Pos. At% 2 - Zn Part In Coated 052418 0 15 531 .60 24.77

C 1s 284.80 73.72 Zn 2p 1021.19 1.32 In 3d5/2 444.67 0.19

40

U} a. u

30

20

10

1200 1000 800 600 400 200 Binding Energy (eV)

Results

Pressure (Torr) Sample Voltage (V) R (ohms)

7.60E+02 In2O3 ALD Z93 40 1.30E+08

Z93 40 5.10E+08

7.00E+01 In2O3 ALD Z93 40 1.60E+08

Z93 40 8.00E+10

7.00E-02 In2O3 ALD Z93 40 1.80E+08

Z93 40 1.80E+11

6.00E-02 In2O3 ALD Z93 100 7.00E+07

Z93 100 6.00E+10

As vacuum is increased the resistivity of the Z93

pigment powders increases several orders of

magnitude while the indium oxide treated Z93P

pigment remains relatively stable. This increase in

resistivity can be attributed to either the removal of

moisture within the bulk powder or the compression

of the powder filling the void space allowing for an

increased number of conduction paths.

Results

Reflectance measurements were taken on lightly compressed pellets of the untreated and

indium oxide treated Z93P pigment and show approximately one percent reflectance

differences across the solar spectrum

90

80

70

60

so

40

30

20

10

250 500 750 1000 1250 1500 1750 2000 2250

Wavelength (nm)

ISS Opportunity

MISSE-FF

The Materials ISS Experiment Flight Facility (MISSE-FF) with MISSE Sample Carriers (MSCs) in the fully open position exposing samples/experiments to the harsh environment of space in low-Earth Orbit (LEO). Image courtesy of Alpha Space.

An earlier MISSE mission

16

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Acknowledgments

Adomaitis Research Group

Mark Hasegawa