r&d on integration and packaging technologies for...

© IMEC 2010

R&D on integration and packaging technologies

for wearable and implantable devices

Maaike Op de BeeckImec, Leuven, Belgium

iNEMI workshop Santa Clara, May 2011

© IMEC 2011

IMEC: independent research instituteLocations in the world

- CONFIDENTIAL - INEMI WORKSHOP MAY 2011 - MAAIKE OP DE BEECK

imecBelgium

imec The Netherlands

imecTaiwan

imec office Japan

imec office US imecChina

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© IMEC 2011

IMEC: growing research institutewith broadening research focus

PayrollNon-payroll

ICT

Healthcare

Energy

ICT

- CONFIDENTIAL - INEMI WORKSHOP MAY 2011 - MAAIKE OP DE BEECK 3

© IMEC 2011

ADVANCED MULTI-CORE RESEARCH FACILITIES

200/300mm clean room • biosensors and bioelectronics lab • organic electronics lab • SiPV/OPV pilot lines • microfluidics lab • RF lab • material/device characterization lab


© IMEC 2011

HUMAN++: merging biology and electronics for a better life

Biomolecular diagnostics and imaging

Cellular interfacing

Wearable health and comfort monitoring

Smart implants


© IMEC 20102011

HUMAN++: Packaging and Integration technologiesActivities related to wearable & implantable packaging


Hermetic and biocompatible packaging for in vivo

applications

FLEX Embedding

Hermetic chip encapsulationPhase 1:

Biocompatible device encapsulationPhase 2:

Functional layersDry electrodes

in-vivo electrodes & interconnects

STRETCH carriers

UTCP

Antenna design & integration

antennabattery

skin

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© IMEC 2011

Typical Packaging Requirements


Wearing comfort importantsmall, thinflex, stretch

Reliability: very good• mechanical properties• storage environment

life time: days ... weeks ... monthstesting: duration is long but feasible

acceleration models?

Cheap disposable device

Wearable packaging

Shape, size: small, thin, flex, biomimeticpackage for less pronounced inflammation and FBR, and higher user comfort

Reliability: extremely good over (long) lifetime

• mechanical properties• storage environment• hermeticity / diffusion barrier

properties • biocompatibility ( ~application)Testing: - duration??

- uncertainty of bio-testing- strongly dependent on

application

Cost can be higher (operation cost, insurance)

Implantable packaging

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© IMEC 20102011

Activities related to wearable & implantable packaging



applications

FLEX Embedding





STRETCH carriers

UTCP


antennabattery

skin

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© IMEC 20102011 - CONFIDENTIAL - INEMI WORKSHOP MAY 2011 - MAAIKE OP DE BEECK

2.2 µm

15.4 µm

15.9 µm

18.5 µm

Die

PI

PIrelease from carrier

Ultra-Thin Chip Package (UTCP) processing

Ultra Thin Chip Embedding in Flexboard level ‘UTCP’ process

Die thinning < 30um

Cross section

die packaging in between 2 polyimide (PI)

layers

UTCP

Top view: die & fan out

glue

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© IMEC 20102011

UTCP: ultra thin chip package

Highly flexible packageMiniaturizationChemically inert

Typical:- Si chip: 20-30µm thick- Total UTCP: 60-70µm thickPI: chemically inert


Die

PI

PI

glue

15.4 µm

15.9 µm

18.5 µm

2.2 µm

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© IMEC 20102011

Embedding of UTCP into std. multilayer flex PCB

• Thin package laminated in adhesive layer between two (large) flex PCB’s

• Chip contacting through standard via drilling & metallization process

• Only minor modifications to flex PCB processing line needed

UTCP provides 2 fan-outs :(1) Easy testing before integration(2) Compatible with std. flex substr.

(2)(1)


Dedicated test fan-out is used during

testing

After testing, test fan-out is removed

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© IMEC 20102011

UTCP integration in std. flex PCB: example


UTCP

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© IMEC 20102011

ECG demonstrator: system prior to molding


Flexibleantenna

Electrode B(at bottom)

3 UTCP’s(analog front-end UTCP

shielded from light)

Meander interconnect

Magnetic on/off switch

Electrode A (at bottom)

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© IMEC 20102011

ECG demonstrator: final system


• ECG patch can function continuously for at least 7 days

• Wireless communication

• Comfortable: flexible, stretchable, thin package

© IMEC 2010 - CONFIDENTIAL - INEMI WORKSHOP MAY 2011 - MAAIKE OP DE BEECK 15

UTCP: recent and ongoing activities

• improvement of UTCP fabrication technology towards higher yieldand throughput

• ‘lab-to-fab’ activities: developments in order to facilitate transfer of UTCP process towards larger scale production:

• purchase of dedicated tools

• adjustment of fabrication steps

• transfer of UTCP techno to company ‘HighTec’

• New technology developments related to:• fabrication of flat UCTP• stacked UCTP (vertical chip integration, very compact system)• multiple chip- UTCP (horizontal chip integration, very thin

and flexible system)

© IMEC 20102011

Reliability testing of UTCP: work in progress

• Environmental tests: very good results obtained• Hot/humidity storage at 85% rel. humidity & 85°C, up to 1000h• thermal cycling : -40/+125°C, up to 1000 cycles

More tests are still ongoing

• Functionality during and after static mechanical load /bending

• Tests are still ongoing. • Very promising results, only

for strong bending (R<10mm) some temporally artifacts have been observed on very few UTCP’s.

• Functionality during and after dynamic mechanical load

Testing just started

R

timeConnections with electrical measurement

setupUTCPcompressible substrate

Moving cylinder


© IMEC 20102011




applications

FLEX Embedding





STRETCH carriers

UTCP


antennabattery

skin

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© IMEC 20102011

SMI: stretchable mould interconnect

Stretchablematrix

Fabrication of stretchable wiring to connectIndividual components rigid/flexible component islands

stretchable wiring meander-shaped interconnects

Molding of device in silicone:to provide stretchable matrix for

• good mechanical support • corrosion resistance

Functional‘non-stretchable’

island

Fabrication of non-stretchable islands using:• conventionally packaged electronic

components• UTCP embedded in flex


© IMEC 20102011

Demonstrators SMI technology

Fitness monitor (with third party) Baby monitor (with third party)

R��

B��

Lesson learned: attention for transition stretch/flex/rigid for optimum reliability


© IMEC 20102011

Reliability characterization : detailed analysis of failure mechanisms

Design improvements based on FEM-simulation and experiments- horse shoe shape- multi-line design

Predicted failure locations after stretching

Shear strain induced local distortion

Failure mode

EXAMPLE: In-plane shear strain contour mapping @ 30% strain (In-situ stretching SEM micrograph vs. FEM modeling)

Before stretchingAfter a few stretch cycles

After many stretch cycles


© IMEC 20102011

Current focus of SMI: process optimization towards high reliability and process throughput

‘Old’ samples improved samples

Process improvements: related to flex-stretch transition

time

improved technostrongly improved lifetime!

Reliability test : cyclic strain of 2.5-10% @ 1%/s strain rate


older techno

% strain

Life

time

(# c

ycle

s)

Interconnectlifetime

vs strain

1 2 3 4 5 10 20 30

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© IMEC 20102011




applications

FLEX Embedding





STRETCH carriers

UTCP


antennabattery

skin

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© IMEC 2011

PACKAGING FOR IMPLANTABLE APPLICATIONSConventional biomedical packaging• Typical packaging for medical electronic implant: Ti can

– Well known, biocompatible safe, NDA-approved– Large container compared to ‘active’ content of packaging– Rigid package: mechanical mismatch with softer tissue

• Example: pacemaker:

• Disadvantage of large size / rigid ‘foreign’ material:– Larger implant: larger incision, more invasive for patient (short/long term)

more risk of infection, biofilm formation…more pronounced foreign body reaction (FBR)

– Rigid package risk of irritation & infection due to mechanical friction– FBR often results in malfunctioning of sensors or electrodes

More advanced package? Requirements?

- CONFIDENTIAL - INEMI WORKSHOP MAY 2011 -MAAIKE OP DE BEECK

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© IMEC 2011

PACKAGING FOR IMPLANTABLE APPLICATIONSPackage Requirements

• Biocompatibility

Proper material selectionPackage : bi-directional diffusion barrier:

no diffusion of harmful components into tissueno leaching of body fluids into implant

• Often the device needs ‘feedthroughs’ for direct contact between body and sensing part of device

Eg. electrodes, sensors, mechanical feedthroughs

Feedthroughs should also be a bi-directional diffusion barrier

at location of feedthroughs: reduce fibrous encapsulation due to FBR

small package soft, flexible, textured package biomimeticUse of functional drug containing coating

• Device should withstand common sterilization techniques

• Avoid biofilm formation: functional drug containing coating?

Biomimetic hydrogelused for scaffolds

tissue

implant

- CONFIDENTIAL - INEMI WORKSHOP MAY 2011 -MAAIKE OP DE BEECK

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© IMEC 2011

PACKAGING FOR IMPLANTABLE APPLICATIONSimec’s biocompatible packaging approach (1)

(6) electrode

(2) Rounded edges, to enhance step coverage of capping layers and

avoid damage of encapsulating material or injury of tissue after implantation

(3) first top encapsulation: biocompatible capping layers, being also a diffusion barrier

(7) Global feedthrough(for sensing)

(5) Optional: second encapsulation:

embedding in i.e. parylene,...

IC (i.e. CMOS,..)Active part of IC, microsystem,..

Passivation layer(s)

(1) Thinned die

(4) first bottom encapsulation: biocompatible capping layers, being also a diffusion barrier

Phase 1: wafer level chip encapsulationGoal: creation of a bi-directional diffusion barrier


© IMEC 2011

PACKAGING FOR IMPLANTABLE APPLICATIONSimec’s biocompatible packaging approach (2)

Phase 3: system package: .global biocompatible interconnect and embedding of various dies, battery,...

die 1 die 2 battery

Second flexible global embedding

Metallization to connect various sub-parts

Global feedthrough

main function:- mechanical support of total system- electrical connections between dies- creation of functional feedthroughsrequirements:- all materials are ‘biocompatible’- flexible package to reduce body

reaction after implantation

Phase 2: (sub-)system package / interposer:

biocompatible interconnect and embedding of various dies

die 1 die 2


© IMEC 2011

Processing of first phase

encapsulation

Conventional chips(non-biocompatible) are encapsulated.

Encapsulation layers: - biocompatible- bi-directional

diffusion barrier.

All processing is carried out at wafer level

for high throughput and hence low cost


© IMEC 2011

PACKAGING FOR IMPLANTABLE APPLICATIONSFirst Phase Encapsulation Validation: oxide step coverage

1

SEM pictures showing the excellent step coverage of a ~1.5um thick oxide used as top capping layer.

A dedicated low temperature oxide deposition process at 350°C is used.

3

oxide

copper

nitrideoxide

silicon

1.65µm

2

nitrideoxide

silicon

oxide

1.4µm

1.56µm

Thinned Si chip

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3


© IMEC 2011 - CONFIDENTIAL - INEMI WORKSHOP MAY 2011 - MAAIKE OP DE BEECK

Test tableISO10993

• = ISO Evaluation tests for consideration

F = additional tests which may be required for US submissions

1: tissue includes tissue fluids and subcutaneous spaces

2: for all devices used in extracorporeal circuits

3: depends on specific nature of the device and its component materials

ISO10993: document describing biocompatibility tests

is only a guidelineit remains difficult to

determine best testing procedure

Type of test

Type

and

dur

atio

n of

con

tact

cytotoxicity

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© IMEC 2011

Testing of biocompatibility and diffusion barrier properties?


Final device should be biocompatible

Start with cytotoxicity tests for materials used in package

tissue

biomaterial

Develop in house a test procedure based on the definition of biocompatibility, & following test descriptions in ISO 10993 std.

start with cytotoxicity tests

followed by other in vitrobiocompatibility tests

much later in vivo testing

compare the results

ask specialists in the field to test some of our materials• certified laboratory • Professor A of university X

specialized in biocompatibility• Professor B of university Y

specialized in biocompatibility

start with cytotoxicity tests

© IMEC 2011

Cytotoxicity testing by various specialists


silicon nickel copper platinum

literature

Certified laboratory

Prof. A, Univ. X

Prof. BUniv. Y

Is materialcytotoxic?

Samples: plane layers on Si substrate (Ti adhesion layer if necessary)All testing is in accordance with ISO 10993 (long term implantation is soft tissue)

© IMEC 2011

Cytotoxicity testing by various specialists


silicon nickel copper platinum

literature

Certified laboratory

L929 fibroblast cell line, 24 h elution, 48h cell culture using elution fluid

Prof. A, Univ. X

Fibroblast type cell line, various elution times incl. long periods, cell culture using elution fluid

Prof. BUniv. Y

4 different cell lines (also 3T3 fibroblasts), up to 72h. Co-culture, various evaluation methods

Is materialcytotoxic? No ??? ??? No

Samples: plane layers on Si substrate (Ti adhesion layer if necessary)All testing is in accordance with ISO 10993 (long term implantation is soft tissue)

Even cytotoxicity tests are not easy

© IMEC 2011

Biocompatibility / cytotoxicity based on ISO 10993Testing of medical devices


cytotoxicity based on ISO 10993: variables:• # of cells, growth phase of cells, cell line versus primary cells, cell type • test sample size, exposed surface area, duration of elution• duration of culture, type of culture (elution, co-culture)

▸ select suitable test with final application in mind- Don’t make tests too easy, you will pass this test but fail in a later (in-vivo) test. - Don’t make test too difficult either...

Situation is similar for other standards related to testing of medical devices or biomaterials. These standards are guidances, not a directive to follow. A lot of freedom in testing still exists. Tests have to be defined for each individual device, based on ‘purpose and intentional use of a product’ , but also with risks related to wrong usage in mind.

IEC 60601-1 standard (“General requirements for basic safety and essential performance” of an electric medical device) is recently updated (3rd edition): even more ‘freedom’ in testing is given, in order to perform best suited tests for intended use of a medical device.

Appropriate testing is a challenge (correct, efficient, according to stds)

© IMEC 2011

PACKAGING FOR IMPLANTABLE APPLICATIONSValidation: in vitro co-culture – 3T3 fibroblast

co-culture with 3T3 fibroblasts (cell line) and 1 single test dieAfter 1 week : morphology test

Control: 3T3

medium

copper

passivation

passivation + oxide

copper passivation passivation + oxide

Control: cells in good

condition

Almost no cells alive,cells in bad condition

Most cells in good condition: Cu diffusion is significantly reduced


© IMEC 2011

PACKAGING FOR IMPLANTABLE APPLICATIONSValidation: in vitro co-culture - cardiomyocytes

co-culture with neonatal cardiomyocytes (primary cells)After 5 days: live/dead cell assay with Calcein-AM

copper

passivation

passivation + oxide

Fluorescent intensityfigure of merit for amount of cells being alive

Encapsulation is functioning very well as

diffusion barrier forimplants in heart tissue


© IMEC 2011

Work ongoing - phase 2: Interposer-like package


IMEC’s board level ultra thin chip package (UTCP)

• biocompatible interconnect and embedding of various dies • might be board level (cheaper) or wafer level (higher pitch density)• biocompatible materials required

for an ‘implantable’ UTCP: - PI selection depends on application (wearable or implantable device): photopatternable PI is not biocompatible.

- metallization (now Cu) needs to be adjusted for long term implants: Pt and Au metallization is needed

die 1 die 2

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© IMEC 2011

Work ongoing - phase 3: global embedding


Only a very thin silicone layer is covering the

pressure sensor in order to realize sufficient hermeticity without loosing the sensor

functionality.

battery

Electronics on PCB

Pressure sensor

die 1 die 2 battery

silicone molding interconnect (SMI) technology using biomedical grade siliconefabrication of an implantable bladder pressure sensor:

Packaging and integration: IMEC: electronic system design: by KUL (SBO-Bioflex project)

• to embed all sub-devices• typical board level process (cost)• biocompatible and corrosion resistant materials required

IMEC’s SMI process: metallization (now Cu) needs to be adjusted for long term implants (Au, Pt)encapsulation by implantable silicones or polyurethanesfuture alternatives: biomimetic encapsulation? Drug containing encapsulation?

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© IMEC 2011

ConclusionsPackaging and integration for wearable and implantable medical devices: dedicated packaging techniques have important advantages!

wearable devices: - small flexible/stretchable package for enhanced user comfort- optimized antenna design longer battery usage / smaller battery size

implantable devices: - miniaturization for reduced foreign body reaction and enhanced user comfort- many challenges to overcome: biocompatibility, realization of bi-directional diffusion barrier, stability over (long) lifetime, power management- additional needs possible such as a drug releasing coating, an anti-microbial layer, a biomimetic surface,..

Appropriate testing of these dedicated packaging techniques is a challenge.


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