2016-07-21 Accelerated Neutral Atom Beam Processing for ......Jul 21, 2016 · 1 NPC NEUTRAL...

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NPCNEUTRAL PHYSICS CORPORATION

Accelerated Neutral Atom Beam (ANAB)Processing for Atomic Layer Etch (ALE)

E. Barth, C. Huffman, F. Goodwin, S. Papa Rao, B. O’Brien, D. Steinke, M. Rodgers, B. Sapp,

S. Kirkpatrick, M. Walsh, R. Svrluga

July 25, 2016

www.neutralphysics.com© 2016 Neutral Physics Corporation. All Rights Reserved.

Accelerated Neutral Atom Beam (ANAB)

ionizationgas supersonicnozzle

Cluster formation

Chargedeflection

Acceleration

Accelerated neutral atoms

De‐clusteringby collisions

ANAB process modulation:‒ Choice of atom Ar, Xe, … with CH4, O2, Cl2, etc‒ Cluster size 500 – 10000 atoms/cluster Tunable atom energy ‒ Cluster ionization 1‐3 charges/cluster ~1 to ~100 eV/atom ‒ Cluster acceleration 10 – 50 keV‒ Atom flux 5E14 ~ 5E16 atoms/cm2/s

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Surface Modification: Silicon

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top surface

Accelerated Neutral Atom BeamANAB

ANAB treated layer2.1 nm

interface

buried oxide

ANAB treated layer

Silicon

interface

ANAB modified layer is uniform over both nano‐ and micro‐scales Interface with underlying Si crystal lattice is sharp

www.neutralphysics.com© 2016 Neutral Physics Corporation. All Rights Reserved. 25 July 2016 4

Surface Modification: Silicon Nitride

SiN surface is converted to SiOx by ANAB exposure and ambient O2

The SiOx layer thickness is uniform

SiN

SiOx


Uniformity of ANAB Oxide

Ellipsometric measurements of ANAB‐based oxide thickness show remarkable uniformity at the wafer scale

Treated

side

1.8

1.9

2.0

Si Oxide

Thickne

ss (n

m)

‐150 ‐100 ‐50 0 50 100 150Wafer Radius Y‐direction (mm)

ANAB Treated

Untreated


Modulating ANAB Layer Thickness

SiSiNAcceleration Voltage (keV)

Depth (nm)

20 keV

2

2.5

3

3.5

4

10 20 30 40 50

SiSiN

2.4 nm

20 keV

30 keV 30 keV

2.6 nm

2.9 nm 3.4 nm

50 keV 50 keV

3.2 nm 3.9 nm

ANAB layer thickness can also be modulated by changes to cluster size and ionization

Increasing neutral atom energy


Self-Limiting ANAB Layer Thickness

The nanometer‐scale modified layer is formed rapidly ANAB layer thickness is self‐limiting Layer thickness can be tailored by the process conditions utilized

0

0.5

1

1.5

2

2.5

3

3.5

0 50 100 150 200 250

ANAB

Layer Thickne

ss (nm

)

ANAB time (s)

High Energy ANAB

Low Energy ANAB

Control (native oxide)

Process Condition B

Process Condition A


ANAB Operating Regimes

Low energy ANAB: ANAB modified layer formed – no sputtering High energy ANAB: Sputtering occurs through the modified layer

ANAB layer thickness is stable

0

2

4

6

8

10

12

14

0 50 100 150 200 250

SiNThickness (nm)

ANAB exposure time per unit area (s/cm2)

High Energy

Low Energy

Increasing ANAB exposure tim

e

SiN

SiN

SiN

SiN

High EnergyANAB

SiN

Low EnergyANAB

SiN

SiN

SiN


Gas Phase SiOx Removal

Commercially available, fab‐friendly, NH4F‐based oxide removal processes remove ANAB‐formed oxide, selectively to nitride

0

5

10

15

20

25

As

dep

AN

AB

+V

apo

r A

AN

AB

+V

apo

r B

AN

AB

+d

HF

AN

AB

+V

apo

r A

AN

AB

+V

apo

r B

AN

AB

+d

HF

SiN

Th

ickn

ess

(nm

)High Energy ANAB

and SiOx removalLow Energy ANABand SiOx removal


Source Drain

Gate

HighK

Cap

Source Drain

Gate

HighK

Cap

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ANAB-Based Atomic Layer EtchStarting structure

Structure withsilicon nitride sidewall spacer

ANAB exposure forms SiOx onSiN surfaces

Vapor etch of SiOxselectively to SiN

Process is repeated 2 to 10 cycles until

targeted material is removed

Source Drain

Gate

HighK

Cap

Source Drain

Gate

HighK

Cap


Anisotropy of ANAB ALE

0

2

4

6

8

10

12

14

16

0 1 2 3 4 5

Remaining

SiN

(nm)

ANAB Cycles

Cyclic ‘HE’ ANAB Etch of SiN

Top

Sidewall

Trench

0.6 nm/cycle

2.5 nm/cycle

1.8 nm/cycle

Rates measured on 50nm line‐width, 90nm pitch structures with ~1:1 AR Similar removal rates and anisotropy observed on ~100um wide structures Anisotropy can be increased further by using O2 doped Ar ANAB coupled

with in vacuo oxide etch


Atomic Layer Etch

High energy ANAB has been used to form a sub 10nm nitride spacer structure with minimal over‐etch into the underlying oxide.

No ANAB Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5

Si

nitride

oxide

TEM overcoat material


Material Selectivity of ANAB ALE

Control Sample After 5 cycles of ANAB‐based ALE

ALDSiN

Si Si

With low energy ANAB‐based atomic layer etch, removal of SiNdemonstrated with minimal etching of the underlying Si


Hot-plate accelerated corrosion showing copper

passivation effect.

Time lapse video embedded here

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ANAB Applications to BEOL


Neutral Physics Corporation


Summary

ANAB enables Atomic Layer Etch 0.5 nm ~ 3 nm removal per cycle

ANAB‐based ALE is manufacturable: Self‐limiting ANAB layer thickness for wide process window ANAB layer thickness controllable by simple process variables Relatively benign, inexpensive chemistries for the in‐situ vapor etch step

ANAB is anisotropic – vertical sidewalls can be maintained ANAB tooling compatible with a 30‐45 wafer per hour throughput.

ANAB processes characterized on dielectrics (SiN, SiCN, etc) and metals (Cu, Co, Pt, etc)

2016-07-21 Accelerated Neutral Atom Beam Processing for ......Jul 21, 2016 · 1 NPC NEUTRAL...

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