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Bernd K Appelt Business Development ASE (U.S.) Inc. April 11, 2012
Copper Wire Bonding: the Last Frontier of Cost Savings
© 2012 ASE Group. All rights reserved.
Outline
Fundamental Study
Reliability Study
Monitoring Data
Summary
2
Introduction
High Volume Implementation
© 2012 ASE Group. All rights reserved. 3
Fine wire active development since 2005 in ASE Kaohsiung
ASE Chung-Li started HVM in Sep 2008
Followed by ASE Kaohsiung, Shanghai, Malaysia, Korea and Japan.
HVM covers:
25/ 23 / 20 / 18 um Cu and Pd/Cu
wire in QFP, SO, QFN, BGA packages.
wafers from ALL foundries, ALL
nodes, with different structures.
Overall yield is around 99.85%.
Introduction – ASE Cu wire-bonding history
© 2012 ASE Group. All rights reserved. 4
M units
Introduction – ASE Production Unit Shipment
ASE Group Shipment: More than 7 Billion units up-to-date
5 8 11 24 65 159 201
363 410
575
716
956
1144 1210
1270
1620
1985
2245
0
500
1000
1500
2000
2500
Q3 2008
Q4 Q1 2009
Q2 Q3 Q4 Q1 2010
Q2 Q3 Q4 Q1 2011
Q2 Q3 Q4 Q1 2012
Q2 Q3 Q4
Units: Equivalent to LQFP14x20mm 144L
© 2012 ASE Group. All rights reserved. 5
100 200
500
1500
2400
3000 3800
4500 5400
6100
6700 7000
7500
8300
9400
10000
2% 3%
8%
20%
28%
32%
37%
41%
45% 47%
49% 50%
52% 54%
57% 59%
0%
20%
40%
60%
80%
100%
0
3000
6000
9000
12000
Q1 2009
Q2 Q3 Q4 Q1 2010
Q2 Q3 Q4 Q1 2011
Q2 Q3 Q4 Q1 2012
Q2 Q3 Q4
Cu Wire Bonder Cu Wire Bonder %
Introduction – ASE Cu wire Bonders Quantity
© 2012 ASE Group. All rights reserved.
2010 2009
aQFN/ QFN 16%
PQFP 8% LQFP
43% TQFP 8%
PBGA 4%
FBGA 7%
SOIC/PLCC 14%
aQFN/ QFN 27%
QFP 31%
BGA 16%
SOIC 16%
Discrete 10%
QFP 59%
BGA 11%
6
Introduction – Production Volumes by Package Types
aQFN/ QFN 35%
QFP 23%
BGA 14%
SOIC 20%
Discrete 8%
2011
© 2012 ASE Group. All rights reserved.
40/45 nm 1%
60/65 nm 7%
90/80 nm 14%
0.13 um 18%
0.18 um 36%
0.25um 3%
0.35 um 9%
>= 0.4um 12%
2010
65/60 nm 2%
90/80 nm 10%
0.13um 22%
0.18 um 37%
0.25 um 5%
0.35 um 10%
>=0.4um 14%
2009
7
Introduction – Production Volumes by Wafer Nodes
40/45 nm 2%
60/65 nm 11%
80/90 nm 14%
0.13 um 13% 0.18
um 42%
0.25 um 8%
0.35 um 6%
0.4 um 4%
2011
© 2012 ASE Group. All rights reserved.
Computing
20%
Consummer 48%
Comm (Cell
Phone) 24%
Auto 0.2%
Industrial 8%
2010
Computing 15%
Consumer 54%
Comm 21%
Industrial 10%
2009
8
Introduction – Production Volumes by Applications
Computing 20%
Consumer 51%
Comm 24%
Auto 0.4%
Industrial 4%
2011
© 2012 ASE Group. All rights reserved.
130nm
90 nm
65 /60nm
45/40 nm 32/28 nm
22/20 nm
2012 2011
60/50um
45/40um 40/35um 35/30um ?
50/45um
(BBP / BPO) Au wire
1.2 Au wire
1.0 Au wire
0.9 Au wire
0.8 Au wire 0.7
Au wire 0.6 Au wire
0.5
Cu wire 0.8~1.0 Cu wire
0.7 Cu wire
0.6
Cu wire 1.0~1.2
0.7 mil 17%
0.8 mil 52%
0.9 mil 12%
1.0 mil 16%
1.2 mil 2%
>2 mil 1% Wire Diameter Trend
9
Introduction – Production Volumes by Wire Diameters
2013
0.7mil 22%
0.8mil 52%
0.9mil 10%
1.0mil 13%
1.2mil 2%
>1.2mil 1% 2010 2011
2011
© 2012 ASE Group. All rights reserved.
Outline
Fundamental Study
Reliability Study
Monitor Data
Summary 10
Introduction
High Volume Implementation
© 2012 ASE Group. All rights reserved.
Cons: 1. Surface Oxidation
1. Inert gas requirement 2. Hardness Impact Al Pad 3. EFO kit requirement
Pros:
1. Lower Material Cost
2. Lower Electrical resistivity
3. Better Thermal Conductivity
4. Better Mechanical Properties
5. Slower IMC Growth.
11
Bonding Wire Au Cu
Atomic weight (g/mol) 197 64
Density (g/cm-‐3) 19.3 8.94
MelDng point 1066 °C 1085°C
Boiling point 2856 °C, 2562 °C
Electrical resisDvity (nΩ·∙m -‐20 °C-‐ )
22.1 16.8
Thermal conducDvity (W·∙m−1·∙K−1 -‐300 K-‐ )
318 401
Young's modulus (Gpa)
79 110–128
Vickers hardness (Mpa)
216 369
Cu Wire vs Au Wire : Raw Material Properties
Fundamental Study
© 2012 ASE Group. All rights reserved.
EFO Kit
Good FAB
(a) Control EFO process.
(b) Forming gas rate.
Void Unstable FAB Asymmetry
EFO kit with Forming gas:
For Stable / Symmetric FAB :
12
Process Control: Fundamental Study
© 2012 ASE Group. All rights reserved.
Source: Johnny Yeung, Challenges for Copper Wire Bonding, KnS , 2008
Cu Wire Bonding
Au Wire Bonding Cu Wire vs Au Wire : Hardness
Hardness
Au Ball
Cu Ball
Al Splash
13
Fundamental Study
© 2012 ASE Group. All rights reserved.
Cratering / Cracking Test
Remained Al thickness: 277nm
Al thickness remaining : > 100nm (min)
Al thickness remaining should > 100nm.
Cratering Crack
14
Process Control: Fundamental Study
© 2012 ASE Group. All rights reserved. 15
High energy transformation capillary. Parameter optimization. Ball shape control. Ball shear inspection.
CUP Design & LowK Wafer
• Fine Pitch • Small Pad opening • Circuit Under Pad • Cu / low K
Defect photos
Process Control: Fundamental Study
© 2012 ASE Group. All rights reserved.
Top Al Metal
(Top -1) Al Metal
CUP Layer
P1
USG
Cu wire
Al wafer design
Cu wire
Al Cap TOP Cu Metal
(Top – 1) Cu Metal
CUP Layer
P1
P2
USG or FSG
Cu wafer design
• The top 2 metal layers (Top and Top-1) can not be circuit layers
• The top 2 metal layers (Top and Top-1) must be solid layer and
must be larger than bond pad
Design Guideline : CUP Bonding
16
Fundamental Study
© 2012 ASE Group. All rights reserved.
Reliability Test Cu-Al IMC Inspection
17
© 2012 ASE Group. All rights reserved.
2004 M. Li, C. Li, F. Wang, D. Luo, and W. Zhang, Thermodynamic,Assessment of the Al- Au System, J. Alloys Compd. , 1991Oka1: H. Okamoto, Al-Au (Aluminum- Gold), J. Phase Equilib., Vol 12 (No. 1), 1991, p 114-115
Reliability Test
18
© 2012 ASE Group. All rights reserved. 19
“ Cl- ” ions reacts with IMC & creates “Al2O3” with high resistivity,
The mechanism for open failure in biased HAST test
Studies and Learning
Reliability Test Improvement
Mold Compound Cl ions - low ppm required
Cl-
Cl-
Cl-
Cl- Cl-
Inside Mold Compound
Cu Wire
Cl-
Cl- Cl-
Cl-
Inside Mold Compound
Cu Wire
Al2O3 Cl-
Cl-
Cl-
Inside Mold Compound
Cu Wire
Al2O3 Al2O3 Al2O3 Al2O3
Cu9Al4+6HCl+3O2+nH2O! 2AlCl3+2Al(OH)3* +9Cu+nH2O
© 2012 ASE Group. All rights reserved.
Outline
Fundamental Study
Reliability Study
Monitor Data
Summary 20
Introduction
High Volume Implementation
© 2012 ASE Group. All rights reserved. 21
Monitoring Data
© 2012 ASE Group. All rights reserved.
Outline
Fundamental Study
Reliability Study
Monitor Data
Summary 22
Introduction
High Volume Implementation
© 2012 ASE Group. All rights reserved.
Cu Wire Process/Package Qualifica=on (APQP)
Product Design & Development Qualifica=on Pre-‐produc=on
Monitoring HVM RFQ
3. Package / Process Qualifica=on
2. Process / Package Development
1. Design & Feasibility Study
1. Design Rules review 2. Products/Processes data
Domain: -‐ Wafer Tech & Bond Pad Structure, BOMs, Package
construc=on -‐ device groupings
3. Electrical & Stress Modeling
1. Machine Calibra=on 2. Cu Wire Process DOE & Window
Valida=on 3. Pre-‐qualificaDon & REL assessment
1. Machine C & C 2. Qualifica=on POR 3. Package REL & Extended REL
1. Machine C & C 2. Pre-‐produc=on
POR
1. Machine C & C
2. REL MON
Cu Wire Product/Process Qualifica=on Flow Overview
Bonders Calibration & Correlation Process Recipe Potability
Process Design & Development
© 2012 ASE Group. All rights reserved.
Device Groupings & Data Base
Wirebonder Calibra=on
& Correla=on
Wire Diameter
> 1 mil Diameter
< 0.9mil Diameter
-‐ BPO -‐ Wire Length -‐ MulD-‐Ders
CUP / Non CUP
Via Structure
Under-‐layer Metal Stacking
Wafer Nodes
Bondpad Structure
20um 25um
BOM Selec=on, Package StressModelling
(bHAST solu=on)
Film Materials
Al Bond Pad Cu
Silicon
Al
Mold Compound Cu Ball
Film Materials
0.45um Al thickness
© 2012 ASE Group. All rights reserved.
WB Parameters &
Control
WB WIP Staging Time Control
Cu Wire Material Controls
Gas Flow Rate control
Set-‐up/Conversion buy-‐off
• Free Air Ball(FAB) – wire type change
• WB Quality Characteris=cs
• Copper wire bonder MTMV
• Regular calibra=on & correla=on
• Forming Gas (Bare copper wire)
• N2 Gas (Pd coated wire only)
• Locked and can be adjusted within controlled range
• 1st Bond and 2nd Bond-‐ USG and Bond Force
• EFO Fire Time-‐ Control the size of FAB
• System control through MES-‐system
Integrated Controls
• Plasma to WB
• WB processing =me
Cu Wire Bond Process Control
Wirebond Process/Quality/Material Controls
Cu-‐Wire Package In High Volume Manufacturing
© 2012 ASE Group. All rights reserved. 26
More Challenges to be addressed
Advanced Nodes Legacy Products Automotive & Advanced Network
Systems New Package Technologies Collaborative Research with
Universities, suppliers, and research institutes
© 2012 ASE Group. All rights reserved.
Outline
Fundamental Study
Reliability Study
Monitor Data
Summary 27
Introduction
High Volume Implementation
© 2012 ASE Group. All rights reserved. 28
Cu Wire Technology
2009 2010 2011 2012
Cu wafer
Wafer Node 0.18um/0.15um
Wafer Node (LK) 0.13um/90nm/65nm
Wafer Node (ELK) 45nm/40nm
Al wafer CUP wafer
BPP62um/BPO55um BPP52um/BPO45um BPP45um/BPO40um BPP40um/BPO35um
Wafer Node (ELK) 28nm
Tri-tier/Quar-tier
NiAu/NiPd pad
L/F PKG Substrate PKG
Stack die
Low loop
FOW
Pad to pad
In-line/Staggered
Waf
er T
ech.
Pack
age
Tech
.
© 2012 ASE Group. All rights reserved. 29
New wafer technology overview
For BGA PKG: - Au wire MP on 40nm wafer, available on 28nm wafer technology - Cu wire MP on 40nm wafer, Qual lot build on 28nm wafer, expect Qual finish on Y2012Q1
For QFP PKG: - Au wire MP on 40nm wafer, under plan on 28nm wafer - Cu wire MP on 40nm wafer, under plan on 28nm wafer
PKG Available 2011 2012
BGA
QFP
Production
0.13 um/ 90nm /65nm/ 40nm
0.13 um/ 90nm /65nm/ 40nm
40nm
28nm Au wire
Cu wire
Au wire
Cu wire
40nm
0.13 um/ 90nm /65nm/ 40nm 40nm
2013
20 nm ELK
28 nm ELK 20 nm ELK 0.13 um/ 90nm /65nm/ 40nm
28 nm ELK
28 nm ELK
© 2012 ASE Group. All rights reserved.
Summary
Fine pitch Cu wire-bonding ramped successfully into high volume production in all sites .
Close collaboration and partnership with equipment and materials suppliers.
Devices from advanced wafer nodes from different foundries in broad spectrum of packages
ASE has 6 years experience in Cu wire-bonding, total shipment will exceeded 7 billion units at end of 2011
Reliability demonstrated to exceeded up to 6X standard JEDEC testing and is continuing.
30
© 2012 ASE Group. All rights reserved.
Thank You
www.aseglobal.com