Some Essentials of TCB

Some Essentials of

Thermo Compression

Bonding

A Machine Vendor’s View

Hugo Pristauz

Dec-2016

(presented on the 3D-ASIP 2016 conference in San Francisco)

Introduction

TCB Core Capabilities

Accuracy

Co-planarity

Bond Control

Conclusions

Dec-2016

Adoption of 2.5D/3D Integration

3 3D-ASIP 2016

Source: Yole

TCB is still seen as the key assembly technology

for 2.5/3DI C2S, C2C or C2W (might change in the future)

Dec-2016

Challenges Which are Mastered with TCB

4 3D-ASIP 2016

warping

substrate

thin warping die

Warpage

non-wets

solder bridging

Ultra Fine Pitch small

solder volume

dielectric

cracks

Thermal Stress extra

low-k

solder climbing squish

non-wet

Dec-2016

3 Kinds of TCB Processes

5 3D-ASIP 2016

TC-NCF Process (WL applied nonconductive

film or wafer level underfill)

T F

future

killer process

enables

collective

bonding !!!

simple

bond

control

TC-NCP Process (pre-applied nonconductive

paste) T F TCB pioneer!

not good for

thin (memory)

die

simple

bond

control

TC-CUF Process (capillary underfill, or

TC-MUF: molded underfill) T F still major

volume

(material

readiness)

z hybrid bond

control

Dec-2016

Video Clips from 8800 TCadvanced

6 3D-ASIP 2016

Face-up TCB Robot handling for C2W

TC-NCF @ C2W TC-CUF @ C2S

Dec-2016

3D TSV Stacks - Done in 2014

7 3D-ASIP 2016

60 ... 80 µ pitch

Dec-2016

10µ pitch TC-NCF C2W face-up stacked die

Some Results from 2016

8 3D-ASIP 2016

Dec-2016

3D Technology Landscape

9 3D-ASIP 2016

IMEC Test Dies

• 40µ pitch

• 20µ pitch

• 10µ pitch

Now at 10µ pitch!

2µ @ 3 accuracy

3D stacked IC 3D system-on-chip True 3D IC public source:

IMEC

3D-SIC roadmap: 40µ 20µ 10µ 5µ pitch 10µ

3D stacked IC 3D system-on-chip

Dec-2016

Get Back to 3D Technology Landscape

10 3D-ASIP 2016

next target

200 nm @ 3 accuracy

source: IMEC (public)

Next step to focus:

• 1µ @ 3 pitch, needs 200 nm @ 3 placement accuracy!

3D-SOC roadmap: 5µ pitch 1µ

Introduction

TCB Core Capabilities

Accuracy

Co-planarity

Bond Control

Conclusions

Dec-2016

TCB Core Capabilities – Yield

12 3D-ASIP 2016

3 Core Capabilities

Accuracy Co-planarity Bond Control

Essential - Yield

3 core capabilities are major

responsible for making yield

Current HVM requirement:

99.8% yield per die

Introduction

TCB Core Capabilities

Accuracy

Co-planarity

Bond Control

Conclusions

Dec-2016

Breaking Up the Accuracy Chain

14 3D-ASIP 2016

2µ@3

hot

matrix

high force

real die

2µ@3 2µ @ 3

Dec-2016

Breaking Up the Accuracy Chain

15 3D-ASIP 2016

2µ@3

hot process

matrix position

high force

GoG real die

2µ@3 2µ @ 3 2µ @ 4

Dec-2016

Breaking Up the Accuracy Chain

16 3D-ASIP 2016

2µ@3

hot process

matrix position

high force low force

glass-on-glass (GoG) real die

2µ@3 2µ @ 3 2µ @ 4 2µ @ 5

Dec-2016

Breaking Up the Accuracy Chain

17 3D-ASIP 2016

2µ@3

cold proc. hot process

matrix position

low force high force

glass-on-glass aplication (GoG) real die

2µ@3 2µ @ 3 2µ @ 4 2µ @ 5 2µ @ 6

Dec-2016

Breaking Up the Accuracy Chain

18 3D-ASIP 2016

2µ@3

cold process hot process

matrix position single pos.

low force high force (250N)

glass-on-glass aplication (GoG) real die

2µ@3 2µ @ 3 2µ @ 4 2µ @ 5 2µ @ 6 2µ @ 7

0 100 200 300 400 500 600 700 800 900

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

x [

µ],

y [

µ]

@4305.77.Speck Challenge (17:04:43) [stream]: mean = 0.17/0.02, sigma = 0.16/0.12 @ x/y [µ/µ]

Cpk = 3.88/5.57, Cp = 4.24/5.62 @ x/y [2µ/2µ]

Dec-2016

A Closer Look at the Data

19 3D-ASIP 2016

2µ @ 7

required

Single position GoG application

cold (20°C), low force (30N)

2µ @ 11 sigma

achieved!

(+/- 0.55µ)

Matrix GoG application

hot (380°C), high force (250N)

0 200 400 600 800 1000 1200

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

x [

µ],

y [

µ]

Matrix GoG, T: 100->380°C, 30N [stream]: mean = 0.17/-0, sigma = 0.4/0.4 @ x/y [µ/µ]

Cpk = 1.53/1.68, Cp = 1.67/1.68 @ x/y [2µ/2µ]

2µ @ 4 required

2µ @ 5 sigma

achieved!

(+/- 1.2µ)

Temperature

Ramp

>300°C/s

Heat Up

Accuracy – Essential !

20 3D-ASIP 2016

Essential - Accuracy

Maintain position accuracy while

ramping from cold to hot state

Dec-2016

Accuracy – Essential !

21 3D-ASIP 2016

Essential - Accuracy

Maintain position accuracy while

ramping from cold to hot state

Dec-2016

single position GoG application

hot (380°C), low force (30N)

2µ @ 5 required weird

behavior !!!

1000 1500 2000 2500 3000 3500 4000 4500-10

-8

-6

-4

-2

0

2

4

6

8

10@4305.84.BMC_Test_left_heated_tool_hot (13:51:51)

time

x [µ

], y

[µ

]

Potential Issue

Or: bring accuracy

from bond head down to die

80°C

80°C

80°C->380°C

Dec-2016

The Problem with CTE

22 3D-ASIP 2016

Tool Holder: Material A

isolator

CTE = 3ppm/K

Issues: • expansion on bottom: 13.5µ/15mm

• Loss of planarity

• Thermal stress

• life time issues

(cracks after >30.000 cycles)

Solution: controlled relative movements

80°C

380°C

Benefits: • stays highly planar

• life time: >2 Mio cycles

Drawback • CTE mismatch between nozzle

& tool holder (Si: CTE = 2.6 ppm/K)

• relative movements !!!

• 15 mm Si die: 11.7µ @ 300°C

• isolator: 2.7µ @ 300°C

Tool Holder: Material B+C

isolator, CTE = 0.6 ppm/K

any, CTE = 9-12 ppm/K

380°C

70°C

80°C

Introduction

TCB Core Capabilities

Accuracy

Co-planarity

Bond Control

Conclusions

Dec-2016

Co-Planarity

24 3D-ASIP 2016

US Patent 6 651 866 B1

US Patent 2014/0030052A1

Besi: Two approaches to

achieve co-planarity

better than +/-1µ@10mm

Why? - a picture says

more than 1000 words!

Challenge: small solder volume of micro bumps is not forgiving!

Dec-2016

Co-planarity Auto Setup

25 3D-ASIP 2016

Automatic procedure for co-planarity setup

Target for tilt setup: +/- 1µ@10mm

Principle 1

implemented in

8800 TC & 8800 TC advanced

used for dynamic tilt

compensation

Co-planarity can be adjusted by

servo actuators

in spec!

Dec-2016

Co-planarity Auto Setup

26 3D-ASIP 2016

Target for tilt setup: +/- 0.5µ @ 10mm

Principle 2

More simple principle!

if dynamic tilt compensation

is not reqired!

Automatic procedure

a) spherical air bearing in bond head can be

switched from fixed to friction-less state

b) co-planarity is established while pressing

bond head to stage in friction-less state

c) after establishing co-planarity spherical

bearing is fixed

max 0.45µ

Dec-2016

Co-planarity – Essential !

27 3D-ASIP 2016

0 1 2 3 4 5 6 7 8

10

15

20

25

30

#2.56 Tilt 119G-05 (2015-01-29)

F [N

] (fo

rce

- blu

e), T

/10

[°C

] (te

mp.

- re

d), w

[µ](p

os. -

gre

en)

(C) Time t [s] - (selection by: tasks: All Tasks, types: * gantry: L layer: 0)

100

150

200

250

300

Test: Run 40 repeatable

temperature ramps

from 80°C to 300°C

0 1 2 3 4 5 6 7 8-4

-2

0

2

4

6

Residues: kinematic: std = NaNµ (Cpk = NaN), thermal: std = 0.69µ (Cpk = 0.48)

#2.56 Tilt 119G-05 (2015-01-29)

-40

-20

0

20

40

60

Improper Co-planarity Integrity

Position traces of

4 die corners

Residual analysis out of spec

0 1 2 3 4 5 6 7 8-4

-2

0

2

4

6

Residues: kinematic: std = 0.03µ (Cpk = 12.29), thermal: std = 0.09µ (Cpk = 3.8)

#2.56 Tilt 119G-05 (2015-01-29)

-40

-20

0

20

40

60

Proper Co-planarity Integrity

Position traces of

4 die corners

Residual analysis in spec +/-1µ

Essential:

Coplanarity Integrity

„Maintain co-planarity during

temperature ramp!“

Introduction

TCB Core Capabilities

Accuracy

Co-planarity

Bond Control

Conclusions

Dec-2016

TC-CUF – Most Sophisticated Bond Control

29 3D-ASIP 2016

Essential: Sophisticated Hybrid Bond Control

TC-CUF Process (capillary underfill, or

TC-MUF:molded underfill) T F

TC-CUF

sophisticated

z

• start in force control mode, switch to position control ...

• ... controlling BLT (bond line thickness) tightly within +/-1µ tolerance

• ... despite of thermal expansion movements (10-20x larger)

• ... which cannot be sensed life (in liquification phase)

Dec-2016

Bond Control for TC-CUF Process

30 3D-ASIP 2016

z (position)

T (temperature)

F (force)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5-20

-10

0

10

20

30

40

50

-200

-100

0

100

200

300

400

500

Tem

pera

ture

[°C

]

Bond Control for CUF Process

Forc

e [

N],

Positio

n [

µm

]

time [s]

high temperature

ramping rate

200°C/s

dynamic

z-control

during collapse

thermal

compensation

rapid cooling

-100°C/s

• Challenge 1: How do you teach the position control?

• Challenge 2: How do you move from one tool to another?

T (temperature)

F (force)

z (position)

position control. force

control

Dec-2016

Enhanced Bond Control for TC-CUF Process

31 3D-ASIP 2016

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5-20

-10

0

10

20

30

40

50

-200

-100

0

100

200

300

400

500

Tem

pera

ture

[°C

]

Enhanced Bond Control for CUF Process

Forc

e [

N],

Positio

n [

µm

]

time [s]

• By distributing bond control over two position axes the

complexity of the bond control is reduced

w (position)

T (temperature)

F (force)

z (position)

thermal

compensation

@ z-position-axis

w-position axis

used for

BLT control

-7µ@2s responsibility of

process engineer kinematic

compensation position control. force

control

Dec-2016

1) Start with Force Ramp

32 3D-ASIP 2016

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5-20

-10

0

10

20

30

40

50

-200

-100

0

100

200

300

400

500

Tem

pera

ture

[°C

]

Enhanced Bond Control for CUF Process

Forc

e [

N],

Positio

n [

µm

]

time [s]

w (position)

T (temperature)

z (position)

start with

force ramping

-7µ@2s

responsibility of

process engineer

bond head position (w)

reacts with elastic movement)

F (force)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5-20

-10

0

10

20

30

40

50

-200

-100

0

100

200

300

400

500

Tem

pera

ture

[°C

]

Enhanced Bond Control for CUF Process

Forc

e [

N],

Positio

n [

µm

]

time [s]

Dec-2016

2) Start Temperature Ramping

33 3D-ASIP 2016

w (position)

T (temperature)

z (position)

-7µ@2s

responsibility of

process engineer

start

temperature

ramping

bond head position (z)

will start moving due to

thermal expansion

Shortly before liquification:

switch from force to position

control (to be prepared for the

soon following force collapse)

hold force

start your compensation for

the thermal expansion

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5-20

-10

0

10

20

30

40

50

-200

-100

0

100

200

300

400

500

Tem

pera

ture

[°C

]

Enhanced Bond Control for CUF Process

Forc

e [

N],

Positio

n [

µm

]

time [s]

Dec-2016

3) Liquification Phase: Hurry up!

34 3D-ASIP 2016

w (position)

T (temperature)

z (position)

-7µ@2s

responsibility of

process engineer

temperature

exceeds

liquification

threshold

Liquification:

the bump gets

liquid and the

force breaks

down

Luckily you are already in

position mode and you can

control bond head position

for whatever you want!

Hurry up and raise the bond

head position, since by collapse

of the force your compressed

elasticities relax at sudden

don‘t forget: your materials

are thermally expanding!

Compensate with porper

bond head raise movement!

solder climbing

squish

otherwise you get these

nasty results

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5-20

-10

0

10

20

30

40

50

-200

-100

0

100

200

300

400

500

Tem

pera

ture

[°C

]

Enhanced Bond Control for CUF Process

Forc

e [

N],

Positio

n [

µm

]

time [s]

Dec-2016

4) Relax – Solder Joint Formation

35 3D-ASIP 2016

w (position)

T (temperature)

z (position)

-7µ@2s

Relax!

Adjust bond head position to

form final solder joint height

and never forget:

your materials are still

thermally expanding!

Compensate with porper

bond head raise movement!

responsibility of

process engineer

temperature

is still in a

transient

phase

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5-20

-10

0

10

20

30

40

50

-200

-100

0

100

200

300

400

500

Tem

pera

ture

[°C

]

Enhanced Bond Control for CUF Process

Forc

e [

N],

Positio

n [

µm

]

time [s]

Dec-2016

5) Bring to the End

36 3D-ASIP 2016

w (position)

T (temperature)

z (position)

-7µ@2s

Hold your solder joint thickness!

Especially during solidification

phase, otherwise you will

impact your solder joint strength

And never forget:

your materials are still

thermally expanding, later

on shrinking!

Compensate with porper

bond head movement!

run the rest of

your thermal profile.

solder joints are still

liquid until

solidification

Dec-2016

Further Essential

37 3D-ASIP 2016

Essential:

The control of each process variable

must be highly repeatable !

Keep in mind!

• There is no sensor which helps you how to do the

• thermal compensation (this is the current standard)

• The thermal compensation movement has to be identified

automatically and to be recalled from memory during bond

control

Introduction

TCB Core Capabilities

Accuracy

Co-planarity

Bond Control

Conclusions

Dec-2016

• For 2.5D/3DI C2S, C2C and C2W TCB is fully established in HVM

packaging

• Essential for TCB yield are 3 core capabilities: accuracy, co-planarity

and bond control.

• Essential for TCB is to maintain high accuracy from a cold die position

to a hot die position during rapid temperature ramps (rapid means:

>300°C/s)

• Essential for TCB is to maintain high co-planarity during whole rapid

temperature transients (heating & cooling)

• Essential for TCB is a highly repeatable bond control, especially for

TC-CUF where BLT control of +/-1µ needs to be achieved

Conclusions

39 3D-ASIP 2016

Thank You

Questions ?