Transcript Brush

Contest and Pizza Party
June 11, 2013
Term Project on Surface Engineering (DM23757)
Objectives; Better understanding of process mechanism,
operating method and experimental results
Outline ; 상감기법 (Damascene Process) 을 응용한 창작품 제작
재료 제한 없음 (금속, 종이, 플라스틱, 세라믹, 나무 등)
Evaluation ; 1. 창의성 5
2. 기술성 3
3. 응용성 2
6월 7일까지 메일로 제출 [email protected]) 늦으면 감점 -3
Contest ; June 11
1인당 1개의 작품을 전시, 1페이지에 작품에 대한 설명 첨부
학점에 35% 반영함과 동시에 상금 (3명에 10만원씩)
Boom Boom Speaker
200821403 최혜림
• 표면에 광섬유를 상감기법으로 적용하여 음악에 맞춰 불빛이 반짝이는 스피커
- 음악의 세기에 따라 스피커에 인가되는 전력의 차이가 발생함을 이용해 LED의 광량을 조절
- 빛을 전반사 시켜 손실 없이 이동 시킬 수 있는 광섬유를 이용해 LED 빛을 스피커 표면에서 빛나게 함
1. 도안 준비
5. 스피커
가공 완료
2. 도안 부착
6. 광섬유 준비
3. 스피커 가공
7. 광섬유 부착
4. LED 연결
8. LED-광섬유
연결
Lecture 7
Cleaning Solution & Cleaner
Contents
1. What is Cleaning
2. Importance of Cleaning
3. Classification of Cleaning
4. Cleaning Solution
5. Selecting the cleaning solution
6. Development of Cleaning
7. Summary
8. Paper Review
1. What is Cleaning ?
Definition
To reduce the surface contamination to a minimum level during
semiconductor manufacturing processes in order to achieve higher yield.
Pre-Cleaning
Post-Cleaning
Contamination
Cleaning process for subsequent process. Ex) surface
preparing, cleaning before CVD and furnace
To remove the contamination induced in previous process.
Ex) post-CMP cleaning, Post PECVD
1. What is Cleaning ?
- 전체 공정의 약 25%, 100개 이상의 공정에서 세정이 이루어짐
- 습식세정은 100도 이하의 온도에서 모든 물질을 용해 혹은 액중 분산시키고, 웨이퍼 표면에 손상을
주지 않는 등의 뛰어난 특징을 가지고도 그 중요성을 확보하고 있다.
- 요구사항 (1) 아주 청정한 표면을, (2) 부작용 없이, (3) 단시간 내에, (4) 높은 재현성을 가지고,
(5) 낮은 원가로 실현.
RCA 세정법을 기본으로 한 전통적인 반도체 습식 세정법
세정액
세정목적
부작용
H2SO4/H2O2 (SPM)
유기물, 금속
미립자
NH4OH/H2O2/H2O(APM)
미립자, 유기물
금속
HCl/H2O2/H2O(HPM)
금속(표면위)
미립자
HF/H20(DHF)
산화막, 금속(산화막내부)
귀금속(Cu등), 미립자
RCA 세정의 문제점
(1)
(2)
(3)
(4)
(5)
세정 공정수가 많다.
화학액 및 초순수의 사용량이 많다.
장치가 매우 크다.
오염 재부착으로 인해 고청정화가 곤란하다.
부식으로 인해 금속재료가 노출해 있는 표면 세정에는 사용할 수 없다.
2. Importance of Cleaning
• Cleaning process must be added after each process in semiconductor
processes
• Decrease of device dimensions
• Reduction of electrical characteristics
• Yield
Cleaning Mechanism
기능 1
오염의 이탈
- 파티클 오염 (불용성/난용성의 경우) → 물리력
- 금속오염 및 유기물 오염 → 용해 및 분해 기능
기능 2
오염의 재부착방지
- 파티클 오염 → 제타 전위제어, 젖음성 제어 등
- 금속 오염 → pH 산화환원전위 제어 / 킬레이트제 활용
기능 3
하부 막의 식각
- 막 표면과 강고하게 화학 결합해 있는 오염, 막 내부에
존재하는 오염
3. Classification of Cleaning
< Mechanical Type >
Wet
Scrubber
Dry
Megasonic
Single-wafer spin
Aerosol
SCF
Noncontact
Contact
< Chemical solution >
APM
(SC-1)
HPM
(SC-2)
SPM
DHF
BOE
Ozonated / water
Metal
Metal
Heavy
organic
Oxide
Film
Oxide
Film
Oxide
Film
Metal
Metal
Particle
Metal
4. Cleaning Solution
4 -1 RCA
< SC-1 ; APM> Lift off
Au, Ag, Cu, Ni, Cd, Zn, Co, Cr
Etching the particles
Prevention of readhesion
< SC-2 ; HPM> Dissolution
HCl : H2O2 : DIW = 1:1:5 at 75~85℃
Heavy metal, Alkali ions, Metal hydroxides
Hydrophilic after the cleaning
Zeta Potential
-
+
- + - - - - +
+
Stern
+ + - +
- +
Layer
+ + +
+
+
+
- + + +- +Net- - + - + +
+
-+
negative + +
- - - + - charge - -+ + - +
-- + +
- +
+
+ - - +
- - - + + ++ + - + +
+ - +
+ +
+
+ + - +
- -+
-+
+
+ +
Diffused
- + --
+
-
+
Layer
Zeta potential
Repulsive Force
-
- Particle
-
-
-
-
-
Wafer
Attractive Force
+
-
-
+
+
-
-
4-2. HF & BOE
< HF >
• Oxide film
• Metal except noble metal as Cu, Au
• Impurity in oxide film
< BOE > ; Buffered Oxide Echant
NH4F + HF
Stable etch rate by buffer
High chemical wettability with surfactant
4-3. O3 / HF(SCROD)
SiO2 + HF  H2O + SiF4
Particle removal
Ozonated water
Oxide
removal
Oxide
By oxide
film removal
Si + O3  SiO2 +O
DHF
Metal removal
Particles
removal
5. Selecting the cleaning solution
Material of wafer
Si
Goal
Particle
Metal
Noble metal
Copper
Except
Noble metal
APM + Scrubber
SCROD
APM + Megasonic
Scrubber + DHF or HPM
Scrubber + HPM
SCROD
DHF
6. Development of Cleaning
Eco-friendly
Reduction of
process time
< IMEC >
Little light
Chemistry
3 - 1. Scrubber Mechanism
Total
Interaction
Energy
=
van der Waals Energy
(Hamaker constant
+Particle ssize
size) )
- Attractive
+
Electrostatic Energy
(Zeta Potential)
- Repulsive/Attractive
Noncontact : Hydrodynamic drag force
Contact : Rotation torque of brush
Brush force > Total interaction force
 Remove !
Brush
Brush
Noncontact
N
Brush
Partial
Contact
Removal force with SC-1
Removal force with DIW
Full
Contact
∴ Physical Force > Total Energy
Force
Scratch
Defects
Adhesion force
Removal force
Added chemical solution
Brush rpm
< 0.1㎛, Noncontact >
Surfactant
< Readhesion >
+
Physical
force Brush Brush + Brush + Brush
+
Brush
Brush out
Brush
+
+
Zeta
potential
< with surfactant >
Physical
force Brush Brush - Brush - Brush
-
Brush
Brush
-
-
Brush out
Particle Deposition Mechanism
1. Physisorption(Van Der Waals Forces) :
E= - AR / 6D
2. Electrostatic Attraction
– Surface charge : Zeta-Potential
1  exp(  H / x) 

V
(
H
)


R
2


ln

  (   ) ln( 1  exp( 2H / x)) 
–E
1  exp(  H / x) 
 
2
0
0
1
2
1
2
2
0
0
3. Chemisorption : Chemical reaction
between particles and surfaces
4. Capillary Condensation : Fc = 4πRγL
3 - 2. Megasonic
Cavitation
Acoustic streaming
Radiation force
Megasonic energy(1000-15500kHz)
< Application of Megasonic >
3 - 3. Single wafer spin
< SEZ Spin Etcher >
• Lower chemical and water
• High efficiency and short process time
• Lower scratch by particles
• With O3 / DHF / N2
< Single wafer spin >
3 - 4. Cryogenic Aerosol-based Cleaning Technology
• Physical force of Aerosol
• No surface tension
Conventional gas : CO2, Ar
 Damage of pattern in
semiconductor
N2 Gas is more light than CO2, Ar
3 - 5. SCF (Super Critical Fluid) cleaning
Damage of pattern in Wet cleaning
by surface tension
Environment problem
Dry process
SCF Cleaning
CO2 (31℃, 7.3MPa)
Super critical fluid
:Surface tension is zero
3-6. 기능수 세정
전해 환원수와 수소용해수의
세정능력 비교
전해 환원수에 의한 CMP후 세정효과
7. Summary
• Cleaning
solution is selected by slurry, wafer and kind of
removed material.
• Cleaning station must be composed of machine and
chemical solution.
• Reduction of damage by surface tension.
• Goal of cleaning solution is little light chemistry in the
future.
• Recently, many researches are progressing Cu CMP
cleaning
• As development of new materials and size reduction of
device, cleaning solution and cleaner will be important.
Paper review
A Study on Particle Removal of PVA Brush
Cleaning based on Contact Mode
2006 ITRS Road Map
2006
2008
2010
2012
Maximum Substrates Diameter (mm)
300
300
300
450
DRAM 1/2 Pitch (nm)
70
57
45
36
Particle size (nm) at front
> 90
> 90
> 65
> 45
Particle (ea/㎠) at front
> 0.17
> 0.17
> 0.17
> 0.17
Particle (ea/wafer) at front
< 116
< 120
< 115
< 265
Particle size (nm) at back
> 160
> 160
> 140
> 140
Particle (ea/wafer) at back
< 400
< 200
< 200
< 200
Production rate
= 4 times
• Cleaning process occupies more than
35% of semiconductor fabrication.
• As pattern size decrease, effect of
defect is becoming large.
• Cleaning process performance affect
directly device yield and cost.
• Eco-friendly process
Post-Cu CMP Cleaning
Metal Trench
Electroplating Cu
Via
Substrate
Damascene
Patterning
Metal Dep. &
Anneal
CMP Process
Post-Cu CMP Cleaning
Conventional Chemical Cleaning
RCA cleaning process (SC-1, SC-2)
Wet Station
Chemical
Component
Chemical
Ratio
Time
Target
Contamination
SC-1
NH4OH:H2O2:H2O
(50~90 ℃)
1:1:5~0.05:1:5
10
min~
Particle,
Organic and
Metal
SC-2
HCl: H2O2:H2O
(80~90 ℃)
1:1:6~1:2:8
10
min~
Noble Metal,
Alkaline ions
Disadvantage
Yearly chemical use / wet station
19,235 Gallon
Yearly DI water use / wet station
64,821,120 Gallon
• Waste huge chemistry and DIW
• Environment Problem
• Cross contamination
Yearly chemical cost / wet station
$ 1,136,300
• Based on 8” wafer, 96 run/day
• Data from Semiconductor International 2000
• Chemical attack (corrosion, etching)
• Non-uniform cleaning performance
Brush Cleaning
Typical physical properties of the PVA brush
Advantage
• Does not make dusts
• Good chemical stability
• Strong cleaning force
• Double side cleaning
Porosity (%)
85-95
Average pore size (㎛)
110-150
Apparent density (g/㎤)
0.7-0.11
30 % compressive stress (g/㎠)
10-110
Tensile strength (kg/㎠)
2-6
Tensile elongation (%)
200-400
Water absorption (wt%)
700-1500
Maximum allowable temperature (℃)
80 dry, 60 wet
Decomposition point (℃)
170
Disadvantage
• Pattern damage due to contact
process
• Contamination stuck
• Inducing scratch
Background
J. Taylor, “Yield Enhancement through Understanding
the Particle Adhesion and Removal Mechanisms in CMP
and Post CMP Cleaning processes”, IEEE Advanced
Semiconductor Manufacturing Conference, pp. 14-17,
2000
A. A. Busnaina, “Particle Adhesion and Removal
Mechanisms in Post-CMP Cleaning Processes”, IEEE
Transaction on Semiconductor Manufacturing, Vol. 15,
No. 4, pp. 374-382, 2002
• The boundary of partial and ideal contact is vague.
• Difficult realization of partial and ideal contact.
• While brush cleaning has been widely used, little theoretical work
has been done in the fields.
Monitoring System
Monitoring Sys’
Contact condition
Non-contact condition
Velocity
Gap between brush
and wafer
Full contact condition
Monitoring
Sys’
Particle removal
efficiency
Friction force
Re-adhesion of
particle
Scratch
AFM
lithography
Defectivity
Objective
Particle Adhesion on Different Surface
Cu
After CMP Process
PETEOS
180 nm
PETEOS
Cu
- Attractive
+ + + + + + + force
Cu
-
-
-
-------
Repulsive
force
PETEOS
 Many particles remain selectively on Cu surface, rather than on PETEOS.
 We focus on the particle removal from the Cu surface after Cu CMP process.
Experimental Setup: GnP Cleaner system
GnP Cleaner812L
Applicable Wafer Size : 8inch and 12 inch
Configuration :
Stand alone with 4 cleaning stations
- 1 Pre Cleaning with DIW Spray
- 2 Double-side Roll Brush Cleaning
- 1 Spin Rinse Dry with N2 Blow
Pre-cleaning
Brush scrubbing
Size
- 1700W 960D 1300H
- Brush size : Ø70(OD) Ø32(ID) Ø320(L)
Ø38(OD) Ø22(ID) Ø310(L)
Chemical : NH4OH ~1wt% available
Brush type : PVA brush, Both side of wafer cleaning
Brush rotation speed : Max 300rpm
Spin speed : Max 2500rpm
Spin rinse dry
Megasonic
- DI rinse / N2 blow
Control Module
- PC Monitor Interface
- Programmable Sequence
- Sequence Control: PC
Definition of Terms
1. Contact force: Contact force is defined as a force to pressurize a wafer.
Brushes
2. Friction force : Friction force is defined as a force generated
between brushes and wafer
wafer
Brushes
Brush
Brush
Brush Module
3. Brush overlap: Brush
overlap is the amount of
overlap between wafer and
brush.
Data Acquisition Program- CleanEYE
Contact
force
Contact force
Friction
force
Friction force
Contact
force
Friction
force
Experimental Condition
Parameter
Conditions
Wafer
4 inch blanket wafer (CVD Cu deposition 1㎛)
8 inch PETEOS for re-adhesion test
Slurry
TST-D2 (Techno Semichem Co.),
Mean diameter of abrasive : 60nm
pH : 10
Cleaning solution
Citric acid (0.5 wt%), BTA (0.03 wt%)
NH4OH (1 wt%)
Pre-cleaning time (s)
10
Brush scrubbing time (s)
60
Spin dry speed (rpm)
3000
Spin dry time (s)
60
Brush velocity (rpm)
240
Brush gap (㎛)
Under 10
Non-Contact Condition
Contact condition
By
10 ㎛
By
10 ㎛
Non-contact
Condition
Under
10 ㎛
Under
10 ㎛
u2
Fd  CD l
Ao
2
Brush
w
U = tip velocity
Fd
u<< U = tip velocity
Fd 

CD ld p2u 2
8
2/3


Re
24 
p

CD 
1
Re p 
6 
Ref : Busnaina et al, “Particle adhesion and removal mechanisms in postCMP cleaning process”, 2002
Results of Non-Contact Condition: Brush Velocity
60 rpm
120 rpm
240 rpm
Results of Non-Contact Condition: Brush Gap
Gap< 10 ㎛
40 ㎛ < Gap< 50 ㎛
10 ㎛ < Gap< 20 ㎛
20 ㎛ < Gap< 30 ㎛
Theoretical Mechanism of Full Contact Condition
 Johnson-Kendall-Roberts (JKR) equation.
a3 
R
{P  3WR  [6WRP  (3WR ) 2 ]1 / 2 }
K
r2
F A 2WR(1 
)
Rz 0
Ref : Fan Zhang et al, Journal of
Electrochemical Society,1999
Contact Area
P : Load R : Radius a : Contact area
W : Interaction Force
FA : Adhesion force between two material
r : Contact Radius W : Thermodynamic work of
adhesion
Small
Middle
Large
Adhesion Force Small
Middle
Large
Monitoring System for Friction Force
Friction Force Monitoring Sys
Charge
Amp.
F2
F1
A/D conv.
P
C
Results of Full Contact Condition: Friction Force
0.117kgf
0.195kgf
Scratch length
0.406kgf
0.601kgf
Scratch Test on Cu surface: Experiment
XE-100
• AFM lithography mode
• Probe  single crystal silicon
• 1000 nN ~ 6000 nN
Properties of PPP-NCHPt non-contact probe
Typical
Value
PPP-NCHPt non-contact probe
Specified
Values
Thickness (㎛)
4
3.0-5.0
Mean width (㎛)
30
22.5-37.5
Length (㎛)
125
115-135
Force constant (N/m)
42
10-130
Resonance frequency
(kHz)
330
204-497
Guaranteed tip radius of
curvature (nm)
< 10
Scratch Test on Cu surface: Results
4000
nN
5000
nN
6000
nN
Scratch Test on Cu surface: before and after
Before
After
A
A
5000 nN
B
B
6000 nN
A
B
A
B
Conclusion
10-10 ~10-11 N
10-6 ~10-7 N
Conclusion
 Contact condition was classified into two broad categories (noncontact and full contact) using monitoring system.
 In non-contact condition, removal efficiency was dominated by
velocity and gap between brush and wafer, which matched well
theoretical mechanism.
 High friction force have strong removal force, but it is poor to
defectivity.
 Through AFM scratch test, force that induced scratch could be
estimated.
 Full contact condition had re-adhesion problem by contaminating
brush.