ALDのメカニズムとプロセスの紹介
ALD mechanism and process introduction
Draft01

メルクエレクトロニクス株式会社 小林明子

2022.12.22 第１回ARIM量子・電子マテリアル領域セミナー
ALD（原子層堆積）による成膜技術

Contents
1. ALD introduction
1) ALD characteristics
2) Chemical adsorption3) Step coverage4) Reactant dose(thermal ALD & PEALD)
5) Deposition time6) Saturation process
2. ALD-SiO2 process (deposition at AIST NPF )3. Oxide and nitride ALD
4. Summary22022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

1. ALD introduction
1) ALD characteristics

Mechanism1. cycle deposition
2. 1 mono layer precursor adsorption (self-limiting)
3. saturated growth rate

Advantage

4. good step coverage
5. thin film deposition by atomic level

Disadvantage 6. low deposition rate

32022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

Atomic Layer Deposition
Cycle deposition consist some steps.

layer by layer deposition~ 1Å/cycle

precursor
reactant

CH3C2H5N
H-Si-H
OHOH

OH

initialOHOOHOH OH

precursor dose2022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

OHOHOHOHOH

purge (precursor)

reactant dose

1 cycle4OH

purge (reactant)

2)Chemical adsorption

chemical adsorptionadsorption siteOHOH OHOH

initialCH3AlCH3CH3CH3CH3AlAlAlOO

CH3CH3Precursor

CH3O

after precursor dose

AlOH* + Al(CH3)3 → [Al-O-Al(CH3)2]* + CH4.
2AlOH* + Al(CH3)3 → [Al-O-Al(CH3)]* + 2CH4
irreversible reaction
only one layer adsorption (=self limiting)5O

2022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

3) Step coverage
CVD Casepoor coverage

precursor

Why is coverage different?
good coveragemean free path >> pattern size
highprecursor collides pattern side walldesorption

depositprecursor
concentration

deposition rate
∝ precursor concentration

lowsticking probability

high → high difference concentration between top and bottom in the pattern➔ poor coverage
low → low difference.
➔ good coverage62022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

Sticking probability and coverage in ALD caseunsaturated

saturated

When precursor adsorption issaturated, precursor adsorbedconformal.

If they react with reactant, film isdeposited conformal.

unsaturated
saturated
72022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

4) Reactant dose -- Thermal ALD

react with reactant

chemical adsorption

bypAr

H2O
CH3CH3CH3 CH

CH33AlAlOO

reactant: H2OAlOO

Adsorbed precursorOHOHOAlAlOArHOHOHOAlOOReactant dose

[Al-O-Al(CH3)2]* + 2H2O → [Al-O-Al-(OH)2] + 2CH4
[Al-O-Al(CH3)]* +H2O → [Al-O-Al-OH] + CH4

thermal ALD: react with reactant by thermal energy.
82022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

byp

H2O

Reactant dose -- Plasma Enhanced ALD (PEALD)

react with reactant

chemical adsorption

O ion

O2 Plasma
CH3CH3CH3AlAlOOArO*CH3CH3OO
adsorbed precursor

OHOHO

AlAlOArHOHOHOAlAlOO

reactant dose

direct plasma ：O radical, O ion
remote plasma：O radical
PEALD : react with radical and ion
plasma energy and thermal energy
deposition at lower temperature
92022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

O ion

O*

5) Deposition timecycle number

deposition time = cycle number x cycle timeThickness is proportional to cycle number.
Deposition rate is shown by GPC:Growth Per Cycle (nm/cycle)
150C 60nm/400cy
GPC 0.15 nm/cy
Normally
GPC is around 0.1 nm/cy
1 mono layer adsorption

cycle number = thickness /GPC
Precursor DPIPID
T.Nam and et. al., applied surface science 485 (2019)381.
102022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

GPC < 0.2 nm/cy
increase GPC → decrease cycle number

Cycle time

deposition time = cycle number x cycle timeprecursor
reactant

CH3C2H5N
H-Si-HOHOHOH

initialOHOOHOH OH

0.2secpurge (precursor)

reactant dose

2sec

2sec

1 cycletotal 6.2 sec/cycle

cycle time112022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

OHOHOH

OHOH

precursor doseexOH

purge (reactant)
2sec6) Saturation process
GPC (Growth Per Cycle)：thickness on 1 cycle (nm/cycle)

GPC

GPC

GPC

CVD depositionprecursor dose (sec)Precursor adsorption saturated

plasma/reactant dose time (sec)
Reaction is saturated.

purge time (sec)
In CVD region residual precursor
or reactant react in gas phase.

Poor coverage and large non-uniformity in unsaturated region (in case).
122022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

2. ALD-SiO2
Samco ALD tool in AIST NPF

PEALD- SiO2, Al2O3, AlNx
thermal-ALD SiO2, Al2O3
precursor: BDEAS / TMA
oxidation: O2 plasma (remote and direct)
O3 or Pure O3, H2O
nitridation:NH3, N2 Plasma
4 inch Si wafer
temp.: 50~500C

k-satoh@mst.or.jp

132022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

Samco ALD toolgas lineO3 or Pure O3
O3 inlet

O2MFC

Ar

MFC

NH3MFC

H2MFC

N2

MFC

ICP1: direct RF
ICP2: remote RF

LLC

gas：lateral flow
plasmaICP1：direct
ICP2：remote

ICP1 ICP2O3 & pure O3 (>90% O3)

wafer

precursor
BDEAS (Si source)

reactor

TMA (Al source)

ALD valve

MFC
N2
carrier gas N2

TMP
sub. temp. 50~500C
BDEAS

TMAprecursor bottle
BDEAS 60℃ heated142022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

DPDP2abatement systemother gas: Ar, N2, O2, NH3, H2

ALD-SiO2 Experiment
BDEAS （Amino Silane precursor）

center condition

temp. 300℃
Press. 5~12Pa
dose time 0.2sec
direct plasma 100W 3sec

BDEAS GPC ~0.1nm/cy

other oxidation
remote plasma 100W 3sec
Pure O3 (>90% O3 2sec)
evaluation

GPC saturation curve
film property

152022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

thickness (ellipsometry)
WER (DHF 1:500 dip)

NU(non uniformity)Sequence (center condition）
precursor
RFpurgedosepurge
RFflowprecursor

1 cycle (6.1sec)
press.

stopflow

O2

RF

on
RF

off
50sccmcarrier gas
(N2)

stop
150sccmpurge gas
(N2)

stop

1 cycletime

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2022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

cycle time
center GPC

6.1 sec/cy
0.08 nm/cy

30nm ~ 400 cycle➔ 2400 sec ~~ 40min

1) GPC saturation curve
precursor dose
center cond.

dose time x precursor partial pressure (∝ flow rate)

Precursor adsorption saturates with precursor dose.
172022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

A. Kobayashi, and et. Al., thin solid films 520 (2012)3994.

Saturation curve
reactant dose (RF time)

center cond.

Oxidation saturates with RF time.
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2022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

2) Film property (WER)
RWER: Relative Wet Etch Rate
dip dHF:H2O-1:500 TOX 0.2nm/min(=RWER 1.0)
temperature

RF power
center cond.

RWER depends on RF time, RF power and temperature.
Film property depends on plasma and thermal energy.
192022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

WER at pattern

PEALD-SIO2 STD 300℃ direct RF 100W 3sec RWER11PEALD-SiO2

25nm
17nm
Δ8nm

SiN

13nm
Δ13nm

26nm

Si
as depoafter WE (dip DHF 1:500 3min)thickness (nm)WER on top is smaller than that on side.
Ion effect is smaller on side than that on top.

202022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

as depoafter WE

etchedΔTop

25178Side

2613133) Oxidation
300℃ data

GPC in the case of direct and remote PEALD are almost same.
RWER is the smallest with direct PEALD. It depends on RF power and RF time.

212022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

WER at pattern
Etched thickness

PEALD-SiO2

Δ top17nm
Δ8nm

25nm

25nm

Δ sideSiNreactant

13nm
Δ13nm

26nm

22nm

Sias depo

Direct plasma PEALD-SiO2 film on side wall haslarger WER than that on top. It is caused by ion
effect.
Radical and O3 reactant are isotropic.

radicalion
radicalwet etch

O3

25nm

25nm

ALD-SiO2
dip DHF:H2O = 1:500
300℃ pattern Etch thickness (nm)direct PE

remote PE

Pure O3

Δ top (nm)857Δ side (nm)1376

large side WER
2222nmsame level2022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

direct plasma remote plasma

O3 (thermal)
21nm

3. ALD oxide & nitride
Typical Process
precursor

Reactant

Temp.

GPC

BDEAS

O2 plasma 1)
O3 2)

>50C
>300C

0.12 nm/cy
0.1 nm/cy

TiCl4
TDMAT

O2 Plasma / H2O
O2 Plasma 5)>RTM
150℃、300C

0.05 nm/cy4) 大陽日酸技報 No. 33(2014)

TDMACpHO2 plasma 5)

150℃

0.1 nm/cy5) T. Faraz, and et. Al., ACS Appl. Mater. Interfaces 10 (2018)13158.

precursor

reactant

Temp.

GPCSiNxDCS

NH3 Plasma 3)
NH3 4)(>450C)>600C

0.05 nm/cy

TiNx

TiCl4
TDMATNH3 6)
H2 plasma 5)

400C
200℃

0.03 nm/cy
0.05 nm/cy

HfNx

TDMACpHH2 plasma 5)

450℃

0.035 nm/cy

SiO2
TiO2
HfO2

1) A. Kobayashi, and et. Al., thin solid films 520 (2012)3994.
2) H. Roh, and et. Al., Applied Surface Science 571(2022)151231

3) K.Koehler and et. Al., IOP Conf. Series: Materials Science andEngineering 41 (2012) 012006

Oxide film can be deposited easier than nitride film.
Nitride film need high energy like higher temperature and higher power plasma.
232022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

ALD-SiN
Cl included
Amino-silane
C & Cl free
Xin Meng and et. Al., Materials 2016, 9, 1007

Chlorine-containing precursor deposited with high
GPC (~0.05nm/cy).
Amino-silane precursor typically have very low GPC.

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2022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

BTBAS :SiH2(NHBu)2 + N2 plasma

ALD-SiN

DCS(SiH2Cl2)
SiH3Cl

H.C.M.Knoops and et. Al., ACS Applied Materials & Interfaces, 7, 35 (2015) 19857.

1.

K.Koehler and et. Al., IOP Conf. Series: Materials Science andEngineering 41 (2012) 012006

252022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

ALD-SiN film quality is better at high deposition temperature.
GPC @ 500 ℃
DCS (Chloride) : 0.05 nm/cy
BTBAS (amino silane) :0.01 nm/cy.

Summary・ALD is cycle deposition having good coverage with atomic level thickness control. It is
self-limiting process thanks to mono layer precursor adsorption.
・ALD-SiO2 film was deposited at AIST NPF. GPC is saturated with precursor dose and RFtime. Film property depends on RF time and power with direct plasma. Pattern WER on sidewall is larger than that on top because of ion bombardment effect.
・Several oxidants, direct, remote plasma and O3, are evaluated in ALD-SiO2 film deposition.
WER with remote plasma and O3 are similar and larger than that with direct plasma.
Pattern WER with remote and O3 are conformal.
・Nitride ALD is the next target to oxide ALD.

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2022.12.22 第１回ARIM量子・電子マテリアル領域セミナー

Thank youAIST
Dr. Arimoto, and Mr. Yamazaki for supporting ALD work at AIST.

Merck Electronics
Mr. Ishikawa, Mr. Ishii, Ms. Hasegawa, Ms. Matsuura and Mr. Aoki
for ALD work and analysis at Merck Electronics.