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Versatile Lead-Free Solder Electroplating Products for Advanced Bumping Technologies

Inho Lee, Regina Cho, Lou Grippo, Yen-Lin Wang, Wayne Baldelli, Ryan Farrell, Julia Woertink, Yi Qin, Jonathan Prange, Yil-Hak Lee, Masaaki Imanari, Jianwei Dong, Jeff Calvert

Advanced Packaging Technologies 3/12/2014 IMAPS 10th International Conference and Exhibition on Device Packaging, March 10-13, 2014

www.dowelectronicmaterials.com

Presented at 2014 IMAPS

Device Packaging

Outline

Background

Introduction of the lead-free solder electroplating products

- SOLDERONTM BP TS 6000 SnAg Plating Bath –

TS 6000 SnAg process performance

TS 6000 SnAg process versatility

TS 6000 SnAg process robustness

Conclusion

2 IMAPS 10th International Conference and Exhibition on Device Packaging, March 10-13, 2014


Background

3

Graphic courtesy of Yole Developpement

Lead-free SnAg solder bumps are used

extensively in the high volume production lines for

a number of new bumping technologies

C4 bumping

Cu pillars capped with SnAg solder

3D microbumps

Traditional device manufacturers, wafer foundries

and OSAT companies are manufacturing various

and complex bumping wafers with challenging

requirements

Tightly controlled thickness uniformity

Alloy composition uniformity

Avoidance of reflow voids

To meet challenging requirements, a SnAg

plating chemistry must deliver versatile and

robust plating process

ETNA 3D chip stack with DRAM and Logic integration

IMAPS 10th International Conference and Exhibition on Device Packaging, March 10-13, 2014


Lead-free Solder Electroplating Solution components

4

Inorganic {Sn, Ag, Acid} Provide the metal source for solder

Bulk electrolyte

pH control

Organic Additives WID and WIW height uniformity

Smooth as-plated morphology

Ag% control and uniformity

Stability and compatibility



SOLDERONTM BP TS 6000 Tin-Silver Plating Chemistry

5

Focus on development of a brand new additive system

Benchtop functional testing of candidates

on challenging Dow internal test vehicle at

8 ASD, measure %WID

For WID/WIW height uniformity For Surface morphology

20 um

20 um 20 um

20 um

Candidate A Candidate B

Candidate C Candidate D

For Ag% control

Control Ag% composition in plated

solder, allow for good uniformity and

reliability, long-term bath stability

Prange, Jonathan et al. Next-Generation Lead-Free Solder Plating Products for High Speed Bumping, Capping and Micro-Capping Applications. in

IMAPS Conference Proceedings. 2013. Orlando, FL.

Full Bath Plating



I. SOLDERONTM BP TS 6000 Tin-Silver Plating Chemistry

Process Performance

- Morphology

- Bump height uniformity

- Ag% composition distribution

- Voiding



TS 6000 Process Performance: Morphology

7

Surface Morphology and Voiding as function of plating rate

4 ASD

2m/min

6 ASD

3m/min

8 ASD

4m/min

10 ASD

5m/min

As-plated

After reflow

X-ray

12 ASD

6m/min

14 ASD

7m/min

18 ASD

9m/min

Sn2+: 50g/L Sn2+: 75g/L

Consistent smooth surface morphology over the wide range of plating rate

Wafer: 300mm DOW Test vehicle

• PR thickness: 50 m, via diameter: 75 m, Pitch: 150 ~ 375 m, Open area: 15%

• Target height after reflow: 70 m, Mushroom plating



TS 6000 Process Performance: Bump Height Uniformity

8

SnAg after reflow bump height Within die uniformity as function of plating rate

0

2

4

6

8

10

4 ASD 6 ASD 8 ASD 10 ASD 12 ASD 14 ASD 18 ASD

Co-p

lan

arit

y (

%)

50 g/L of Sn2+ 75 g/L of Sn2+

1002/(%) minmax avghhhplanarityco




Uniform SnAg bump height over the wide range of plating rate



TS 6000 Process Performance: Ag% distribution

9

1.8

1.9

2.0

2.1

2.2

2.3

1 2 3 4 5 6 7 8 9

Ag

(%

)

1

2

3

4

5

6 7 8 9

Ag% composition distribution across the wafer (8 ASD)

Uniform Ag% composition across the wafer




2.01 ±0.02% (Cpk =1.5, 6 sigma level)

USL

LSL



TS 6000 Process Performance: Voiding

10

=75m

=75m =20m

C4 SnAg Bumping Cu Pillar Capping

Micro-void free performance by FIB-SEM for C4 bumping, Cu Pillar, and Cu Pillar capping

applications

Macro-void free performance by X-Ray inspection for C4 bumping, Cu Pillar, and Cu Pillar

capping applications

Macro and micro void free for 1X and 10X reflow

Macro-Void

Free

Micro-Void

Free

Cu Pillar Capping

Ni/SnAg Interface Cu/SnAg Interface

Cu/SnAg Interface

Macro-Void

Free Micro-Void

Free

Macro-Void

Free

Micro-Void

Free

Multiple reflow

1X reflow

10X reflow



II. SOLDERONTM BP TS 6000 Tin-Silver Plating Chemistry

Process Versatility

- Various applications

- Various photoresists

- Plating tool configuration



TS 6000 Process Versatility : Various Applications

12

SnAg bump size

Consistent plating performance in

the various applications

150 m100 m50 m20 m

=75 m =100m= 90m

=90 m =130 m=70 m

=100 m=50 m

Cu

SnAgCu

SnAg

=30 m=20 m

Cu

SnAg

Cu

SnAg

Platable open area

Aspect Ratio (AR)

C4 Mushroom

C4 In-via

Cu pillar

capping

Cu pillar -capping

a b

AR= b/a

60um

105um

30um

40umCu

Pillar

[As plated]

0.2 0.5 1.0 1.7

50um

105um

Ni UBM 2um

72um

[As plated]

75 um

75um

SnAg 80 um

120 um

70um

SnAg 80 um

[As plated]

AR

1% 10% 15% 20% 25%



TS 6000 Process Versatility: Various Photoresists

13

Liquid Photoresist Dry film Photoresist

Positive tone Negative tone Negative tone

Compatible with various photoresist



TS 6000 Process Versatility: Plating Tool Configuration

14

Tool A Horizontal plating

Tool B Vertical plating

Type A Agitation: Rotation

Type B Agitation: Paddle

Increasing paddle speed

Increasing rotation speed

C4 in-via

(deep via)

C4 Mushroom

=75 m

75 m

=75 m =30 m

Cu pillar capping

Compatible with various plating tool configuration



III. SOLDERONTM BP TS 6000 Tin-Silver Plating Chemistry

Process Robustness

- Performance Stability

- Electrolytic Aging



W21W19W17W15W13W11W9W7W5W3W1

7

6

5

4

3

2

1

0

Co

-pla

na

rity

(%

)

USL

TS 6000 Process Robustness

16

TS 6000 process stability Test method: One patterned wafer plated every day for a month and monitor TS 6000 process performance.

Test condition: 10 ASD, mushroom plating in 300mm horizontal tool

Test vehicle information: PR thickness: 50 m, via diameter: 75 m, Open area: 20%, Target height after reflow: 70 m

21191715131197531

75.0

72.5

70.0

67.5

65.0

Run

Sn

Ag

.B

um

p h

eig

ht

(u

m)

USL

LSL

Target

1197531

2.2

2.0

1.8

1.6

1.4

Sample

Ag

%

+0.2%

Target

-0.2%

1002/(%) minmax avghhhplanarityco

SnAg bump height Within Die height uniformity (co-planarity)

Ag% content Morphology and voiding

Run 1 Run 7 Run 14 Run 21 1 5 9 13 17 21

Consistent and repeatable plating performance



TS 6000 Process Robustness

17

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

50

55

60

65

70

75

80

85

0 20 40 60 80 100

Ag

%

Hei

gh

t (

m)

Ahr/L

0 Ahr/L 50 Ahr/L 100 Ahr/L

TS 6000 Electrolytic Aging Test method: Batch mode – only replenishment of component based on consumption rate, maintain the volume by

conducting regular bleeding of the bath

Test condition: 8 ASD, in-via plating in 300mm vertical type plating tool

Test vehicle: PR thickness 120 m, via diameter 75 m, Open area 15%, Target height after reflow: 70 m

Consistent and repeatable plating performance over 100 Ahr/L electrolytic aging



Conclusion

18

A new SnAg electroplating product, SOLDERONTM BP TS 6000 SnAg

demonstrated key performance attributes over a wide range of applications

Well controlled bump height uniformity

Tight Ag% control

Smooth surface morphology

Void free

TS 6000 SnAg chemistry is highly versatile in a number of bumping

technologies; C4 mushroom bump, C4 in-via plating, SnAg capped with Cu pillar

and with Cu -pillar

TS 6000 SnAg chemistry shows robust plating process with regard to plating

capability, electrolytic bath aging and thermal idling



Thank You

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