Hybrid DHF and N2 Jet Spray Cleaning for Silicon Nitride ... · Hybrid DHF and N 2 Jet Spray Cleaning for Silicon Nitride and Metal Layer ADepartment of Bio-Nano Technology and bMaterials

02019 SPCC, April 2-3, Oregon, USA

†[email protected]

+820314004080

Hanyang Univ., Ansan, 15588, KOREA

Kook-Hyun Ana, Dong-Kyu Leec, Hun-Hee Leec

Woo-Sik Choic, Tae-Hoon Jungc and Jin-Goo Parka, b, †

Hybrid DHF and N2 Jet Spray Cleaning for

Silicon Nitride and Metal Layer

ADepartment of Bio-Nano Technology and bMaterials Science and Chemical Engineering, Hanyang University, Korea

CSamsung Electronics, Hwaseong, Korea

THE SURFACE PREPARATION AND CLEANING

CONFERENCE (SPCC)

SPCC 2019│ Portland, Oregon, USA │ April 2-3, 2019


1. Research Background

2. Experimental Materials/Procedure

4. Summary

1) Research motivation : limitation of the current cleaning methods

2) Research objectives : diluted HF jet hybrid cleaning

1) Particle removal efficiency of HF spray process

2) Correlation of “Etch rate” and “Particle removal efficiency”

3) Surface roughness of HF spray process

4) Evaluation of patterned wafer particle removal

3. Experiment Results and Discussion


Research Background


Clean processing method conversion

• Wafer size increased from 200 mm to 300 mm

• IC circuit line width is reducing : micron(µm) → nanometer(nm)

Need to control small contaminants for yield improvement

Switch from batch to single equipment


Importance of fine particle control

• Scaling and structures are more complex

• Capacitor aspect ratio is increase

Fine particle removal much more important

DRAM device roadmap

Imec Magazine September 2018 Emerging memories for the zettabyte era

Year of early introduction

Cap

acito

r A

spect

Rat

ion

Cri

tica

l pitch

conta

ct n

ode


Current jet spray issues

Particle remove cleaning technology

• APM spray

Corrosion defect occurs when used in metal layer

Physical Cleaning

Brush

Megasonic

Nozzle type

Bar type

Skirt type

Laser CleaningLaser Shock wave

Laser Heating

Cryogenic Gas Cleaning

Jet SprayDIW spray

APM spray

Mono-dispersion Droplet

Frozen Cleaning

Gas Cluster Ion Beam

Chemical CleaningAlkali Chemical

SC1

Ammonia

Electrolytic Solution

• DIW spray

Pattern damage occurs when physical force is increased

(Pattern damage)

IP.W. Mertens st al, VLSI Taiwan 2006

.

Current issues on jet spray

• DIW spray and APM spray

Low PRE on silicon nitride film


Hideki Hirano et al., ” Damage-free ultra diluted HF/nitrogen jet spray cleaning

for particle removal with minimal silicon and oxide loss.”(2006).

Research objective

Efficiency of metal removal

• DHF : Metal contaminants removal no metal attack

Physical force vs. Particle removal efficiency

• HF spray : High PRE at silicon substrate

Evaluation and application of DHF Spray cleaning for SiN and metal wafers


Experiment Materials

And Procedure


Experimental materials

• Contamination solution: silicon powder mixed with DIW

• Wafer contamination: poured a contaminant on wafer surfaces (2 min/wafer)

• Adsorption of contaminants : store in clean room 24 hours

DIW Un-patterned wafer

(Low spin speed)

Silicon powderContamination

source

Stored in FOUP

for 24 hours

Contamination


Experimental materials

Materials

PRE evaluation

• Si wafer (p-type (100))

• 90 nm SiN on Si

Etch amount

• 90 nm thermal Oxide (SiO2)

• 90 nm poly-Si

• 60 nm TiN

• 40 nm W

Field evaluation (Patterned)

• 40 nm-scale DRAM

(Poly, SiN, TiN and W)

Analysis equipment

Unpatterned wafer defect inspection(SP-5, KLA-Tencor)

Spectroscopy ellipsometer(Aleris, KLA-Tencor)

Lens collector

Ellipsoidal collector

Polarization

WidePMT

NarrowPMT

Oblique incidence

beam


Experimental setup

Experimental parameters

• Nozzle

- Design: In-nozzle mixing

- Wafer ~ nozzle distance: 30~50 mm

• Gas

- Flow rate: 40~55 l/min

• Scan

- Speed: 40~100 mm/sec

- Frequency: 2~4 scans

- Scan profile: 170 mm 0 mm

• Wafer

- Rotation speed: 0~2000 RPM

• Liquid

- Flow rate: 30~60 cc/min

DIW Diluted APM Diluted HF

1. Temperature : 65°C

2. Concentration :

NH4OH : 0.3 ~ 1.7 wt%

H2O2 : 0.3 ~ 6.5 wt%


2. Concentration :

DHF : 0.08 ~ 1.6 wt%


Controlled parameters

300mm singe wet cleaning equipment


Experiment Results and

Discussion


Limit of physical cleaning (DIW-N2 spray Only)

Particle removal vs. pattern damage

0

20

40

60

80

100

0

20

40

60

80

100

25 30 35 40 45 50 55

Num

ber

of P

atte

rn

Dam

ages

(ea)

Par

ticl

eR

em

ova

lEffic

iency

(%)

(Si/

SiW

afer)

@>

45nm

Nozzle Height (mm)

PRE (%)

# of Damages

0

20

40

60

80

100

0

20

40

60

80

100

35 40 45 50 55 60 65

N2 Flow Rate (l/min)

PRE (%)# of Damages N

um

ber

of P

atte

rn

Dam

ages

(ea)

Par

ticl

eR

em

ova

lEffic

iency

(%)

(Si/

SiW

afer)

@>

45nm

Particle removal

Physical cleaning

events

Pattern standing

strength

Fre

quency

PRE

Pattern Damage

Events

Chemical reaction needed to

better cleaning performance


PRE on SiN film in HF spray

HT Nitride 900Å LayerParticle Source – Si Powder +DIW diluted Solution

PRE on SiN compared to other cleaning conditions

• DHF combined with N2 spray showed the best PRE

• Chemical etching is required on SiN

Before

After


Dominant factor for PRE on SiN layer

Comparison of PRE according to etch amount on SiN and oxide films

• Oxide film : No correlation between surface etch amount and PRE

• Silicon nitride film : PRE has very strong correlation with etch amount

Support the estimated mechanism

< Oxide layer > < SiN layer >


HF etch amount on metal layers

Etch amount according to HF process time

• TiN, W surface showed slight etch amount in HF

HF spray was expected to have high PRE on TiN, W films


PRE on W patterned wafer in HF spray

DRAM 4x – W Layer / Particle : Si Powder

Comparison of PRE with DIW spray & HF spray

• HF spray showed far superior PRE on W patterned wafers

• Higher PRE was achieved by slight surface etching of the films

HF SprayDIW Spray

PRE - 34.28% PRE - 90.23%


Surface roughness changes at different chemical

• SiN,Poly-Si layer : No difference between HF spray and reference

• Oxide layer : high roughness of 10.4nm after treated in HF spray

Need caution for roughness change when applying on oxide films


Process application on patterned wafers

Metal Layer

(TiN)SiN LayerPoly Layer

15.5% ↓ 11.1% ↓ 15.5% ↓ HF SprayConventional Spray

PRE results (HF spray vs. conventional spray)

• DRAM 4x – Poly-Si, SiN, TiN layer particle trend (1month, over 3000 wafers)

• SiN layer : 11.1% improvement with HF spray

• Poly-Si, TiN layer : 15.5% improvement with HF spray

Nu

mb

er

of

parti

cle

s (e

a)


Summary

Need new type of cleaning method

• Increased PRE on SiN/Metal layers

• No pattern damage on reduced design rule

• No attack on metallic films

High particle removal performance requires

• Chemical cleaning cooperated with physical force

• Slight etching of the surface on SiN/Metal films

New hybrid cleaning of “ Diluted HF/N2 jet spray” can be answer

• High PRE on SiN and Metal layer without pattern attack

Documents

Hybrid DHF and N2 Jet Spray Cleaning for Silicon Nitride ... · Hybrid DHF and N 2 Jet Spray Cleaning for Silicon Nitride and Metal Layer ADepartment of Bio-Nano Technology and bMaterials