cu wire bonding survey results

Cu Wire BondingSurvey Results

iNEMI Cu Wire Bonding Reliability

Project Team

Jan 30, 2011

Outline

• About iNEMI

• Project Overview

• Survey Mechanism

• Survey Respondents

• Survey Results– Technology Adoption Status by Device Type

– Implementation Plan by Package

– Major Concerns

– Reliability Test Challenges

– Common Failure Modes

– JEDEC Standard

– Failure Analysis Technique

– Preferred Wire Type

– Mold Compound

– Smallest Bond Pad Size & Wire Diameter

– Pad Structure Re-design

– Chip Pad Finish

– Interposer Surface Finish

– Surface Treatment

– iNEMI Project Expectation

1

About iNEMI

2

iNEMI is an industry-led consortium of more than 85 global manufacturers, suppliers,

industry associations and consortia, government agencies and universities. Visit us at

www.inemi.org.

5 Deliverables:

• Technology Roadmaps

• Deployment Projects

• Research Priorities

• Proactive Forums

• Position Papers

4 Major Focuses:

• Miniaturization

• Environment

• Alternative Energy

• Medical Electronics

Mission: Forecast and accelerate improvements in the Electronics

Manufacturing Industry for a sustainable future.

http://www.inemi.org/

Strategy Issues Graphics

Project Lead:

Project Co-Lead:

Tactics Milestones and/or Deliverables Plan Actual

Thrust Area:

Mar-11TIG:

Goal:

Strategy Issues Graphics

Project Lead:

Project Co-Lead:

Tactics Milestones and/or Deliverables Plan Actual

Thrust Area:

TIG:

Goal: Understand key issues and concerns regarding reliability of fine-pitch Cu wire bonding for semiconductors.

• 2-phased project. The first phase will focus on collecting information from the industry regarding the key processing and reliability issues pertaining to Cu wire bonding. The second phase of the project will perform necessary experimental work in the areas defined by Phase 1.

• Copper bond wires are

increasingly being used for a wide

variety of components.

• Reliability needs to be collectively

assessed by the industry in a

quantitative manner.

• Standard reliability test methods

and durations for Au wire device

may not be sufficient for Cu.Peng Su, Cisco Systems, inc.

TBD

Phase 1• 1. Industry Survey• 2. Existing Data Review• 3. DOE Plan for Phase 2Phase 2• 1. Finalize DOE• 2. Procure Materials• 3. Package Assembly• 4. Reliability Tests• 5. Failure Analysis• 6. Summary

Miniaturization

Packaging

Copper Wire Bonding Reliability Project

Initiative Launch Date

Project Inauguration - Two PS Signers

Conduct survey, analyze inputs

Plan DoE for phase 2 Mar-11 Dec-10

Jan-11Nov-10

Sep-10Sep-10

Mar-10Mar-10

3

More information at: http://www.inemi.org/cms/projects/OrgPkg/Copper_Wire.html

http://www.inemi.org/cms/projects/OrgPkg/Copper_Wire.html

Cu Wire Bonding Reliability

Project Members

4

Survey Mechanism

• The industry survey is Phase 1 of the iNEMI Cu Wire Bonding Reliability

Project.

• Survey Objectives

– Understand the key processing and reliability issues pertaining to fine pitch

Cu wire bonding

– Collect information to help outline an experimental study of reliability of

components using copper wire bonding

• Survey Process

– May – Aug 2010: Develop survey by project formation team

– Aug 23 – Sept 30, 2010: Collect inputs from industry

– Oct 1 – Nov 26, 2010: Review & analyze survey data

– Dec 3 – Dec 24, 2010: Verify significant issues with follow-up questions

– Jan 2011 : Report survey results

5

Survey Respondents

• 58 individuals from over 40 companies

completed the survey.

– Suppliers (32)

• Bonding wire manufacturers

• Interposer suppliers

• Equipment manufacturers

• Package assemblers

• IC IDM

• Total revenue ~40B USD

– OEM/EMS (20)

• System providers

• End product manufacturers

• Total revenue ~400B USD

– Others (6) came from consulting,

academia, industry organizations

• Survey data is analyzed separately for

suppliers and OEM/EMS.

6

OEM/EMS Product Segment

Respondent Statistics

15

5

119

4

8

6

OEM

ODM/EMS

Semiconductor

IC assembly house

Equipment supplier

Material supplier

Other

2

4

4

33

3

4

2Consumer/portable

Computers and PeripheralsHigh End Servers

Industrial

Netcom

Automotive

Medical

Other

* Military, Aerospace

Survey Results

7

*1st number = number of responses to question

2nd number = total responses to the survey.

0 5 10 15 20 25 30

High volume production

Low volume production

Technical qualification

Feasibility study

No plan

Memory

Logic

Analog

Low MPU/MCU

Power Devices

Technology Adoption Status by Device Type

8

Question:

Please select the current application status of Cu wire bonding of your company for different device types.

Survey Results:

• Suppliers

– Only semiconductor suppliers and assembly houses are counted. Material or equipment suppliers are not included.

– Most suppliers are in the process of technical qualification or production.

– Cu wires are used for all device types but memory devices appear to have less usage.

• OEM/EMS

– Many OEM/EMS have no plan for Cu wire bonding product introduction at this time.

– Some OEM/EMS are conducting feasibility studies.

– Small percentage in production for memory, logic and power devices.

Observation:

• Suppliers are already in the process of implementing Cu bond wires.

• OEM/EMS are just beginning to study feasibility and a few are in the early stage of production introduction.

OEM/EMS (16 of 20*)

Suppliers (20 of 32*)

0 10 20 30 40




Feasibility study

No plan

Memory

Logic

Analog

Low MPU/MCU

Power Devices

9

0 2 4 6 8




Feasibility study

No plan

High End Server

0 2 4 6 8




Feasibility study

No plan

Automotive

0 1 2 3 4 5 6




Feasibility study

No plan

Netcom

0 2 4 6 8 10 12




Feasibility study

No plan

Medical

0 1 2 3 4 5




Feasibility study

No plan

Consumer/Portable, Computer

Technology Adoption Status by Device Type – Cont.

Question:

Please select the current application status of Cu wire bonding of your company for different device types.

Survey Results: OEM/EMS in different product segments

• Memory, Logic and Power devices are in volume production for some Consumer/Portable, Computer and High End Server products.

• Not in production for Netcom, Medical, Automotive products.

• No plan for Military and Aerospace.

0 1 2




Feasibility study

No plan

Military, Aerospace

Implementation Plan by Package

Question:

What package types do you plan to adopt (or have already adopted) for Cu-wire technology?

Survey Result:

• All package types are in “planned” or “already adopted” phase for Cu wires in the industry, but may vary for each company.

• xBGA, QFN and xQFP packages have highest adoption rates.

Observation

• Slow adoption by OEMs in contrast to suppliers, most likely because of reliability concerns (refer to results later in this report).

• Less implementation for memory devices, per suppliers‟ input.

10

OEM/EMS (8 of 20)

Suppliers (24 of 32)

0

5

10

15

20

25

30

35

40

Power Devices

Low MPU/MCU

Analog Logic Memory

xSOP

xQFP

QFN

xBGA

Power package (HSOP, etc.)

0

5

10

15

20

25

30

35

40

Power Devices

Low MPU/MCU

Analog Logic Memory

xSOP

xQFP

QFN

xBGA

Power package (HSOP, etc.)

Major ConcernsQuestion:

What are the major concerns with Cu wire bonding?

– In-service reliability

– Process yield

– Throughput

– JEDEC reliability spec

– Unproven historical performance

– Manufacturing statistical process control

– Equipment and assembly process parameters

Survey Results:

• Reliability and historical performance are major concerns for the OEM community.

• Suppliers have concerns in these areas as well but to a lesser degree.

• Suppliers have additional concerns about throughput and yield.

11

OEM/EMS (18 of 20)


0

2

4

6

8

10

12

14

16

18

In-service reliability

Process yield Throughput JEDEC reliability spec.

Unproven historical

performance

Manufacturing Statistical Process Control

Equipment and assembly process

parameters

N/A High Medium Low

0

5

10

15

20

25

30

35

In-service reliability

Process yield Throughput JEDEC reliability spec.

Unproven historical

performance

Manufacturing Statistical Process Control

Equipment and assembly process

parameters

N/A High Medium Low

When “In-service Reliability” is selected, the major

reason is lack of use history (80%), followed by

“unknown or poor correlation of JEDEC testing with

in-field performance” (20%).

Reliability Test Challenges

Question:

For your current production process, which reliability tests are the most difficult to pass?

Survey Result:

• Suppliers see biased HAST as the most difficult reliability test to pass.

• OEM/EMS perceive biased HAST and thermal cycling as equally difficult.

Observation:

• HAST and thermal cycling are commonly used for package qualification. OEMs often have difficulty passing these items in qualification and would be aware of such failures.

12

OEM/EMS (10 of 20)


0%

10%

20%

30%

40%

50%

60%

HTSL Un-biased HAST

Biased HAST

PCT Thermal cycling

THB MSL3

0%

10%

20%

30%

40%

50%

60%

70%

80%

HTSL Un-biased HAST

Biased HAST

PCT Thermal cycling

THB MSL3

65% respondents made their selection based on actual

test results, while the other 35% were based on what

they expect would be difficult to pass.

Common Failure Modes

Question:

What are the most common failure modes for copper wire bonding?

Survey Result:

• Inputs from OEM/EMS and Suppliers are similar.

• Ball lift, IC damage and 2nd bond defect are the major failure modes.

• OEM/EMS also cite wire break as a common failure mode.

Observation:

• The responses for the „ball lift‟ failure mode most likely refers to ball lift defect on the bonding process, not interface cracking after acceleration tests.

13

All Respondents (38 of 58)

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

Ball lift IC damage Short Wire break 2nd bond defect

JEDEC StandardQuestion:

Are current JEDEC standard acceleration tests sufficient for system application requirements?

Survey Result:

• Both supplier and OEM/EMS responses indicate great uncertainty of the suitability of current tests.

• There are concerns on test duration, temperature range, and if current JEDEC standard can properly detect corrosion.

• A higher percentage of Suppliers believes different or new tests are needed for Cu wire device qualification.

Observation:

• The word „sufficient‟ in the question may have been interpreted differently by different companies. Some may have interpreted it as „sufficient to generate failures‟, while others may have interpreted it as „sufficient to ensure product reliability‟.

14

OEM/EMS (14 of 20)


Yes, the requirements for copper wire bonding are the same as gold wire bonding.

No. Please explain why and/or suggest what test should be added/modified.

Not sure. Please explain why not sure.

Yes, the requirements for copper wire bonding are the same as gold wire bonding.

No. Please explain why and/or suggest what test should be added/modified.

Not sure. Please explain why not sure.

Any Issue of Failure Analysis Technique ?

Question:

For Cu wire bonding, have you seen any issues for the following Failure Analysis (FA) techniques?

Survey Result:

• Suppliers indicated that Decap, IMC thickness measurement and X-ray inspection of debonding/ wire shifting are issues.

• X-ray inspection for debonding / wire shifting is an issue for OEM/EMS.

• C-SAM analysis for delamination is not an issue for either suppliers and OEM/EMS.

Observation:

• This data indicates that suppliers and OEM/EMS have seen challenges for FA.

15

OEM/EMS (12 of 20)


0

2

4

6

8

10

12

Decap IMC layer thickness

measurement

Delamination analysis (i.e. C-

SAM)

Pad cratering condition inspection

X-ray inspecion for debonding or

wire shifting

N/A No Yes

0

5

10

15

20

25

Decap IMC layer thickness

measurement

Delamination analysis (i.e. C-

SAM)

Pad cratering condition inspection

X-ray inspecion for debonding or

wire shifting

N/A No Yes

Preferred Wire Type

Question:

What's the preferred type of wire material?

Survey Result:

• More than 50% of Suppliers prefer pure Cu wire, followed by Pd coated Cu wire.

• Most OEM/EMS prefer Pd coated Cu wire

Observation:

• Choice of Pd coated or pure copper is determined by reliability performance and cost considerations .

• Some commented that Pd-coated wires have better reliability test results than bare Cu wires, while others showed opposite results.

16

OEM/EMS (8 of 20)


Pure copper

Pd coated copper

Other wire composition

Pure copper

Pd coated copper

Other wire composition

Mold Compound

Question:

Have you adopted new specifications on mold compounds for Cu wire bonding?

Survey Result:

• Some component suppliers are adopting materials (e.g. molding compound) with lower halogen content and more neutral pH.

• Others do not have special requirement on materials such as mold compound. Some (40%) stated no performance advantage was observed for materials with nominally better properties.

Observation:

• Some OEMS do not have sufficient information on package BOMs and currently can not clearly specify material property requirements.

17


0 2 4 6 8 10 12

We do not use special mold compounds for Cu

Lower specification on halogen content

Changed specification on pH

Changed specification on Tg

Reduced specification on moisture absorption/penetration

Other

Smallest Bond Pad Pitch & Wire Diameter

Question:

In your CURRENT/FUTURE PRODUCTION, what is the smallest bond pad pitch and smallest wire diameter for copper wire bonding?

Survey Result:

• General trend is moving to smaller wire diameter and pitch.

• 0.6 mil wire diameter is being considered for pitch ranging from 20 to 45 μm.

Observation:

• Fine Cu wires / fine bond pitch are already being used for current products and future trend is going toward even finer wires.

• Some data might have been mis-entered.

• E.g., Current: 65um pitch for 0.8mil wire, 40um pitch

for 1.38mil wire

• 1.0mil wire for 30um pitch would be challenging.

• Data may be scattered due to die pad design differences or specific use for big pad size.

18

Future (20 of 58)

Current (20 of 58)Pad pitch (um)

20 25 30 35 40 45 50 55 60 65 70 80 120 170

Wir

e D

iam

ete

r (m

il)

0.6

0.7 3 1 2 1

0.8 1 1 2 1 1

0.9 1

1 1 1 1

1.2

1.3

1.4 1

2 1 1

Pad pitch (um)

20 25 30 35 40 45 50 55 60 65 70 80 120 170

Wir

e D

iam

ete

r (m

il)

0.6 2 1 1 2 2

0.7 2

0.8 2 3 2

0.9 1

1 1

1.2 1

1.3

1.4

2

* Highlighted numbers in the table counts how many people input in this wire

diameter & pad pitch size.

Pad Structure Re-design Needed ?

Question:

For the same device in your application, have the bond pad and under-pad structures been re-designed for copper wire bonding?

Survey Result:

• While almost half of respondents replied no re-design was required for pad structure, some indicated the need for re-design.

• Some re-designed the structure to prevent bond pad damage.

Observation:

• Accuracy of response might have been limited by manufacturing experiences.

• Chip manufacturers might not disclose this information.

19

OEM/EMS (8)

Suppliers (23)

No

Not sure

Yes. Please explain the reason of re-design.

No

Not sure

Yes. Please explain the reason of re-design.

Chip Pad Finish

Question:

What is the preferred surface finish on the chip bond pad?

Survey Result:

• No specific preference is indicated from suppliers‟ input.

Observation:

• OEM/EMS may not have the information to make comments.

20

OEM/EMS (4 of 20)


0.0 1.0 2.0 3.0 4.0 5.0

0.8 - 1.2 um Al

1.2 - 2.0 um Al

> 2um Al

NiPd

NiPdAu

0.0 1.0 2.0 3.0 4.0 5.0

0.8 - 1.2 um Al

1.2 - 2.0 um Al

> 2um Al

NiPd

NiPdAu

Interposer Surface FinishQuestion:

For different interposer types, what is the preferred surface finish?

Survey Result:

• Wide range of surface finishes are suggested. There is no clear consensus from suppliers or OEM/EMS.

• Flex / Rigid Substrate: Au finish is preferred

• Ceramic Substrate: No clear preferred finish

• Leadframe: Ag was preferred by suppliers, but OEMs

have no clear preference.

Observation:

• Variability of OEM/EMS inputs may have been limited by small sample sizes.

• Suppliers‟ input shows similar surface finishes as presently used for Au wire bonding.

21

OEM/EMS (5 of 20)


0

5

10

15

20

25

Flex materials

Rigid substrate

Ceramic Leadframe

Electrolytic NiPd

Au

Flash Au

Ag

ENEPIG

ENEPEG

Other

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Flex materials

Rigid substrate

Ceramic Leadframe

Electrolytic NiPd

Au

Flash Au

Ag

ENEPIG

ENEPEG

Other

Surface Treatment

Question:

Have you adopted new cleaning process for Cu wire bonding (e.g. plasma clean prior to bonding process)?

Survey Result:

• Majority of respondents (75%) use the same

cleaning process for Cu wire bonding as the

current Au wire bonding process.

• The other 25% use slightly modified cleaning

process.

22

OEM/EMS (5 of 20)


No

Yes (please specify the process and why)

No

Yes (please specify the process and why)

Expectation for iNEMI Project

• Top 3 issues respondents expect iNEMI project to address:

– Reliability assessment of representative Cu wire bonding currently in production;

– Requirements for reliability testing (either new tests or modification of current standard JEDEC tests);

– Recommendations about wire materials, pad materials, and design rules for under-pad Si structures

• Several other issues were also identified as important.

23

OEM/EMS (18 of 20)


0% 10% 20% 30% 40% 50% 60% 70% 80%

Reliability assessment of representative Cu wire bonding currently in production;

Standardized requirements on packaging materials such as molding compounds;

Recommendations on wire materials, pad materials, and design rules for under-pad Si structures;

Standardized requirements on bonding process controls;

Requirements on reliability testing (either new tests or modification for current standard JEDEC tests);

Requirements on assembly quality tests;

Other (please specify)

0% 10% 20% 30% 40% 50% 60% 70%

Reliability assessment of representative Cu wire bonding currently in production;

Standardized requirements on packaging materials such as molding compounds;

Recommendations on wire materials, pad materials, and design rules for under-pad Si structures;

Standardized requirements on bonding process controls;

Requirements on reliability testing (either new tests or modification for current standard JEDEC tests);

Requirements on assembly quality tests;

Other (please specify)

24

www.inemi.org

iNEMI Contact: Haley Fu

[email protected]

cu wire bonding survey results

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