Atomic Layer Deposition at UCSB

Atomic Layer Deposition @ UCSB
• Oxford FlexAL ALD tool
• Load locked, turbo pumped unit
• System pressures below 240 mTorr
• Substrate temps up to 500C
• Configured for 6 metal-organic precursors
• 8 gas lines configured for 6 reactive gases
plus Ar (bubbling/purge) and water
• Reactive gases: O2, N2, H2, NH3, and O3
• In-situ monitoring of ALD process with
Woollam Spectroscopic Ellipsometer
• ICP Remote Plasma source (up to 600W)
• Ozone Generator and Controller recently
added

Films Grown/ Precursors Used @ UCSB
Standard “already developed” Processes
• Al2O3 growth
• Thermal: TMA + H2O
• Plasma: TMA + O2
• HfO2 growth
• Thermal: TEMAH + H2O
• Plasma: TEMAH + O2
• ZrO2 growth
• Plasma: ZrEMA + O2
• SiO2 growth
• Plasma: 3DMAS + O2
• SiNx growth
• Plasma: 3DMAS + H2/N2
• TiO2 growth
• Thermal: TTIP + H2O
• TiN growth
• Plasma: TDMAT + H2/N2
New “under development” Processes
• SiO2 growth
• Thermal: BDEAS + O3
• TiN growth
• Thermal: TDMAT + NH3
• Ru metal film growth
• Thermal: Ru(Cp)2 + O2
• Thermal: Ru(Cp)2 + O3

Ozone for “Active” Thermal Oxidation
InUSA MiniODS Ozone Source + Sci-L Controller
• Closed loop feedback control of O3 concentration
using built-in O3 monitor.
• O2 gas flows up to 1000 sccm, O3 concentration up
to 22 wt%.
• When generator is on, O3 is always flowing => need a
divert line and a process line (built-in with source)
• Divert line must be pumped since the generator
runs @ 30 psig (maintained by BPR) and the ALD
unit is low pressure.
• Process line connects to reactive gas pod of the
ALD unit => can use standard ALD valves already
in place (small modification of the FlexAL control
software was required)
• We use a small script to control the ozone source
(gas flow, O3 concentration, On/Off) directly from
the desktop of the ALD control PC
OZONE SOURCE
divert
generator
bpr
process
atmosphere
ALD unit
Gas Pod

Application: Conductive TiN Film Growth
Deposition conditions
• Substrate temp = 300C,
• TDMAT cycle: 1sec @ 15mT , Ar draw @ 50sccm;
Ar purge 4s @ 15mT; source @ 60C
• H2/N2 plasma dosing: flow, pressure, ICP power,
time are variable
Annealing conditions (resistivity stability tests)
• 60 min @ 400C in Forming Gas
1.2
1400
GR (A/cycle)
1
0.8
0.6
0.4
0.2
0
0 10 20 30 40 50
H2/N2 Plasma Time (s)
15mT, 30/10
H2/N2 400W
10o’sK uOhm-cm)
• Resistivity less sensitive to plasma time @
lower ICP Power and/or H2-N2 ratio

Capacitance ( µF / cm 2 )
Application: MIS devices on III-V
semiconductors
• Why Al2O3 To improve III-V films MIS? Grown EOT InGaAs of insulator, on InGaAs has higher need electron higher dielectric velocity and constant lower material Eg => faster => HfO2! electronics and lower power
demand.
• Deposition Found • In-situ that As Conditions HfO2 decapping would using not FlexAL deposit 50 cycles ALD cleanly TMA/H2O on InGaAs @ 300C => => use 5nm interfacial Al2O3 layer of Al2O3
Scaling • TMA(RT) requires • cycle: thin 20ms ( perfect Ar purge for ALD 7s @ 15mT; pump 2s
• Deposition Condition
Grow amorphous
uses 10 cycles
As-cap
TMA/H2O
on InGaAs
then
at the
40
end
cycles
of
TEMAH/H2O
MBE growth
@
=>
300C
surface is protected from
Major H2O cycle: issue 100ms; – maintain Ar purge low 7s @ 15mTorr; state density pump (Dit) 7s @ growth interface
• TMA(RT)/TEMAH(70C)
environment (ideal
cycle:
surface
500ms
=>
@
minimal
200mT
Dit?).
, Ar draw @ 100sccm; Ar purge 7s @ 15mT; pump 2s
• InGaAs Cleaning • H2O MIS cycle: Treatment • As- @ 500ms; UCSB cap removed prior utilizes Ar purge to growth a by gate 7s exposure @ last using 15mTorr; (dummy to 10 low cycles pump gate) power of 7s TMA/H* process.
plasma plasma (2W) @ as 300C AsH3. Cycle (2W H* plasma for
• interface TMA cycle: 5s)/(SE is exposed 40ms measurement @ to 200mT air and , Ar for processing draw 4s) until @ 100sccm; chemicals interface Ar reached. prior purge to 5s ALD @ growth 15mT; pump => high 2s Dit
• Same cleaning treatment prior to growth using 5 cycles of TMA/H* plasma @ 300C
• H* plasma • Immediate cycle: 2s oxide @ 100W growth ICP/20mT, on clean 50sccm InGaAs H2; interface Ar purge (interface 5s @ 15mTorr; is never pump exposed 2s to air!)
• Initial results promising
1.6
1.4
1.2
1
InAs
0.8
0.6 S/D
No H 2
/ TMA Cycles
“False
inversion”
“Stretch
out”
0.4
100 Hz
1 kHz
10 kHz
0.2
100 kHz
InGaAs
InAlAs Back Barrier
1 MHz
0
-3 -2 -1 0 1 2 3 -3 -2 -1 0 1 2 3
Voltage (V)
Voltage (V)
H 2
Nickel Al2O3/InGaAs Gate
Metal
1 00 nm L g
1 0 nm InGaAs Channel
STEM FET cross section, color-coded by
chemistry
+ TM A Cycles
As-cap
Low- damage process
Thermal
HfO2/Al2O3/InGaAs
gate metal
No/Low- damage plasma
• TMA/H* cycling improves interface
significantly:
• False inversion in ‘depletion’
suppressed
week)
• Transition from depletion to
accumulation rapid is sharper learning
Rapid turn- around (~2
ALD Oxide Process
Al 2 O 3 /HfO 2 Bilayer
Highly Conformal!

SiOx Deposition Rate (A/cycle)
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
BDEAS@50mTorr/3s
O3@200mTorr
O3@50mTorr
0.10
0 5 10 15 20
O3 Dose (secs)
Application: SiOx ALD Growth using
“SAM.24” and Ozone
• Standard Saturation SiOx Film aminosilane growth Growth using Rate precursor aminosilane strongly for dependent SiOx precursors film on growth requires Ozone in Pressure ALD an ‘active’ => TDMAS (or form adsorption of oxygen flux)! (CH3) 2 N N(CH3) 2
• Contains suggests 2 options three that – plasma O3 dimethyl dissociation O* source amino or is groups balanced thermal O3 by source desorption from molecularly adsorbed state. Si
• Removal Here BDEAS we adsorption investigate of first 2 amino is BDEAS pressure groups + O3 independent during thermal dissociative ALD => (preliminary irreversible chemisorption and study) complete are
H N(CH3)
thermodynamically favorable.
2
• Deposition Conditions using BDEAS/O3 cycling at 300C
• Due BDEAS(50C) to strain, cycle: removal 100% of vapor final amino flow @ group 50 or is 200 not mTorr; favorable Ar purge => issues @ 50sccm/2s; with C/N pump 3s
incorporation in film
• O3 cycle: 250sccm O2 flow/19 wt% O3 conc @ 50 or 200 mTorr; O3(g) Ar purge @ 50sccm/2s; pump 3s
• “New” aminosilane precursor (Air Liquide – SAM.24) => BDEAS
(C2H5) 2 N N(C2H5) 2
• Contains only two diethyl amino groups which are easily removed during
dissociative chemisorption
O3(a)
Si
• Cleaner SiOx films?
O2(g)+O(a)
H H
SiOx Deposition Rate @ Saturation
(A/cycle)
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
BDEAS dose = 3s,
(O3@200mTorr/10s)
O3 dose = 10s,
(BDEAS@50mTorr/3s)
0.40
50 100 150 200
Gas Pressure (mTorr)

A few more applications…
High performance N-Polar GaN-HEMTs using
5nm Al2O3 Gate Oxide– Denninghoff et. al.
Dit reduction of ALD-Al2O3 on Ga-faced GaN using
water pre-saturation of surface – X Liu et. al.
No H2O
H2O treated
Near Midgap Dit States dropped by an order of magnitude (5e11cm -2 eV -1
to 4e10 cm -2 eV -1 ) when pre-treating surface with H2O before ALD growth
1.4 A/mm, Good Turn-off, 270GHz fmax.
ALD-Al2O3 for SiO2 membrane pore size shrinking and ion-current leakage suppression for CMOScompatible
Biosensing devices – A. Uddin, etl al.
Pores
EXPERIMENTAL SETUP
I-V Characteristics of blank SiOx membrane
before and after ALD coating.