FLEXIBLE ELECTRONICS PHYSICAL METHODS IN · PDF fileMolecules vibrate and produce specific ......

FLEXIBLE ELECTRONICS

PHYSICAL METHODS IN MATERIALS CHARACTERIZATION

L.J. MATIENZO, Ph.D.

FLEXIBLE ELECTRONICS Combining Materials into Electronic Packages (1990s)

Wire Bond

30K Circuits (CMOS)250 I/O (Chip)

0.006 inch WB Pad Pitch

Flip Chip

200 - 300 I/O (Chip)0.010 inch C4 Pitch

0.5 - 0.65mm TQFP<100 I/O

Memory TSOP30 - 40 I/O

Wire Bond300 - 500 I/O (Chip)

0.004 inch WB Pad Pitch

0.25 - 0.3mm TQFP300 - 500 I/O (Chip)

Flip Chip1000 I/O (Chip)

0.009 inch C4 Pitch

MCM's (3x3)1300 I/O (Module) Integrated Flex

Connector

Source: IBM Corp., with permission and L. Tiemann, IBM Corp.

Chip Carrier

Encapsulant

Wirebond Assembly

Chip Carrier

Underfill

Conductive Joint

Flip Chip Assembly

FLEXIBLE ELECTRONICS Dielectric Polymeric Films as Protective Device Layers

Chip Carrier

Encapsulant

Wirebond Assembly

Chip Carrier

Underfill

Conductive Joint

Flip Chip Assembly

Source: L.J. Matienzo and F.D. Egitto J. Mater. Sci, in press (2006)

Thermal Ball Grid Array (TBGA):

Light weight and flexible packagesIncreased number of I/OsExtensive use of polymeric dielectric layerMetallized areas are used to create conductors

Hyper-Ball Grid Array (Hyper-BGA):

Required for processors with increased speeds (GHz)I/O numbers in the thousandsDielectric constant of polymeric material is criticalMechanical and electrical performance is required

FLEXIBLE ELECTRONICSBall Grid Array Technologies

FLEXIBLE ELECTRONICSEarly Flexible Circuits (ca. 1990)

Flexible circuit

Source: L.J. Matienzo and F.D. Egitto Solid State Technol. 38, 99 (1995)

*Values supplied by Joseph P. Curilla, Electronics Consulting Laboratory.

Dk1.0001.00062 to 534 to 75 to 98 to 1080

MaterialVacuumAirTypical PlasticsNatural RubberGlassMica Aluminum Oxide (Alumina)Water

Table 1-Dielectric constants of Different Materials*

*Values supplied by Joseph P. Curilla, Electronics Consulting Laboratory.

Dk2.12.22.32.42.63.03.03.13.23.53.74.6

ResinPTFEPolypropylenePolyethylenePolystyreneABSPolycarbonatePETPBTPPSLCPAcetal CopolymerNylon 66

Table 2-Thermoplastic Dielectric Constants*

Source: Plastic Technology,” What we Didn’t Know about Dielectric Properties of Plastics.”K. Reignier et al. (http://www.plasticstechnology.com/articles/200406fa2.html), Feb. 02, 2006,with permission)

FLEXIBLE ELECTRONICS Dielectric Constants of Some Materials and Polymers

FLEXIBLE ELECTRONICS Effect of Dielectric Constant of LCP with Frequency and Filler Addition

Source: Plastic Technology, “What we Didn’t Know about Dielectric Properties of Plastics.”K. Reignier et al. (http://www.plasticstechnology.com/articles/200406fa2.html), Feb. 02, 2006,with permission)

FLEXIBLE ELECTRONICSOrganic Flip Chip Package: HyperBGATM

D1D2D3

D4D5D6

C4 Pads

BGA Pads SignalsVo l tage Planes

CIC Ground

soldermask

Layer Material Thickness(microns)

Outer Soldermask Epoxy Based Er=3.2

S1 and S4 signals Cu 15Voltage Cu 12

S2 and S3 signals Cu 12Ground Cu/Invar/Cu 6/38/6

PTH Barrel Cu OD= 50/ID=34Dielectric Layers D1, D2,

D5, D6PTFE Based

Er = 2.735

Dielectric Layers D3, D4 PTFE Based Er = 2.7

FLEXIBLE ELECTRONICS Combining Low Dielectric Constant Materials and Flip Chip Technologies

FLEXIBLE ELECTRONICS Enhanced Wiring Densities in Organic Packages: Hyper-ZeITM

Blind via increases wiring densities

Conductive paste interconnection enhances connectivity

Source: F.D. Egitto, EIT Corp.

FLEXIBLE ELECTRONICS The Near Future: Molecular Transistors

Gate electrode

Organic semiconductor

Gold electrode

MicroencapsulatedElectronic ink

FLEXIBLE ELECTRONICS Toward Paper-Like Displays

Source: J.A. Rogers Science 23, Feb. 23 (2001) p. 1502

FLEXIBLE ELECTRONICS Beyond Flexible Circuits and Laptops

Source: http://www.rense.com/general69/future.htm, March 27, 2006

Optical image of a Test Circuit on Ceramic:

Low magnification view:

FLEXIBLE ELECTRONICS Magnification Scales and Resulting Information

Data are collected from this area

FLEXIBLE ELECTRONICS Surface Analysis Using XPS: Dielectric and Conductive Areas

Point 2

Point 1

Cr + O

FLEXIBLE ELECTRONICS Small Spot Sampling with an Electron Beam: AES

FLEXIBLE ELECTRONICSElemental Mapping with X-rays and Electron Beams

X-ray beam

Electron beam

Point 1 on Edge of Line

SED image of line

FLEXIBLE ELECTRONICSIncreasing Magnification Scale by Electron Imaging and AES

Molecular Fluorescence Image FTIR Spectrum of Material and Aromatic Ether Sulfone(Side of metal line)

FLEXIBLE ELECTRONICSIdentification of Contaminant by CLSM and FTIR Methods

Organic contaminant

• Evaluation of working hypotheses on materials interactions• Process and scale-up definitions for products• A means of solving production problems• As part of approaches to answer questions on field returns• As a tool to evaluate competitive product analysis• As a source of documentation on patent litigations and licensing issues

FLEXIBLE ELECTRONICSRelevance of Physical Methods to Characterize Materials

FLEXIBLE ELECTRONICSThe Role of Surface Science in Flexible Circuit Applications

• Definition of sampling depth and its relevance to measured properties• Awareness of materials interactions and interfacial effects• Chemical and mechanical factors that affect interfacial strength:

– Mechanical interlocking and surface roughness – Surface wetting– Acid-base interactions– Method of measurement of interfacial strength and locus of fracture– Environmental effects on materials and interfaces for life prediction

FLEXIBLE ELECTRONICSRelationships Between Characterization Methods and Engineering

Properties of Materials

Mechanical interlocking and surface roughness:

Contact angle:

Acid-Base Interactions:

FLEXIBLE ELECTRONICSRelationships Between Characterization Methods and Engineering

Properties of Materials

Source:A. Kinlock, ed.: Durability of Structural Adhesives, Applied Science Publishers, 1983

FLEXIBLE ELECTRONICSEnvironmental Effects on Practical Adhesion

• Techniques rely on the interaction of energy and matter to produce a measurable result in a time scale (hours to femto-seconds)

• Scales of interactions are determined by range of energy available from a source or sources• Responses that are distinguished from baseline noise can be obtained and in many cases,

theoretically predicted, via models based on first principles• Responses can come from various depths of matter and contributions from various regions may

need to be conveniently separated to provide relevant information to answer a particular question

Thickness Scales Definitions:

Surface Region: 0 to 10 nmSub-Surface Region: 100 to 5 µmBulk region: > 5 µm

Representative Techniques for Analysis:

Surface Region: XPS, AES, SIMS, Reflectance FTIR, AFMSub-Surface Region: RBS, EDS, EMPA, ATR-FTIRBulk: FTIR, Chromatography, ICP, Mass spectroscopy

FLEXIBLE ELECTRONICSBasic Approaches in Materials Characterization

FLEXIBLE ELECTRONICSThe Electromagnetic Spectrum

Source: astro.uiuc.edu~kaler/

FLEXIBLE ELECTRONICSRanges of Materials Characterization Techniques and Sampling Capabilities

Image courtesy of C. Evans & Associates

Consider atoms as spheres attached to springs:

What applies:– Selection rules– Hooke’s law (F=-kx)– Harmonic (E= (½) x kx2) and anharmonic oscillator rules

Basis of Infrared Spectroscopy: Molecules vibrate and produce specific bands (infrared active modes) in their spectra

Basic Instrumental Set-Up:IR source sample Energy discriminator Detector Output

FLEXIBLE ELECTRONICS Vibrational Spectroscopy: Conventional and Fourier Transform Infrared

Types of Infrared Spectroscopy:– Conventional grating systems (original technology)– Fourier Transform systems (Michelson interferometer)– Surface sensitive techniques (reflectance spectroscopy)– Infrared microscopy (absorption and reflectance modes)

Other Useful Techniques in Microelectronic Applications:– Diffuse reflectance spectroscopy (DRIFT)– Attenuated Total Reflectance (ATR)– Photo-acoustic Spectroscopy (PAS)– Group mapping microscopy

Importance of FTIR Techniques:– Surface and bulk analyses are possible– Micro techniques can work to about 10 µm spot sizes– Useful in characterizing polymers and metal surfaces

FLEXIBLE ELECTRONICS Vibrational Spectroscopy: Conventional and Fourier Transform Infrared

FLEXIBLE ELECTRONICS FTIR Spectroscopy: Michelson Interferometer and Signal Patterns

Source: F. Anariba, Ohio State University, with permission

FLEXIBLE ELECTRONICS FTIR Microscopy

Uses of PDMS: Adhesives, lubricant additive, high temperature rubbers,mold release agent

FLEXIBLE ELECTRONICS FTIR Spectra: Fingerprinting Materials

(PDMS)

FLEXIBLE ELECTRONICS Applications of FTIR Microscopy: Transfer Material from Assembly Tool

to Chip Passivation Layer

Source: L.J. Matienzo and D.C. VanHart, EIT

FLEXIBLE ELECTRONICS FTIR Applications: Skin Residues on Gold bonding Pad in a Flexible Circuit

Optical image

EDS spectrum

SE imaging

Source: L.J. Matienzo and D.C. VanHart, EIT

Technique Sampling Probe Lower Sampling Dimension

Light microscopy light 0.2 µm

Confocal LSM light 0.2 µm

SEM electrons 1 nm

TEM electrons 0.1 nm

STM current/voltage 0.02 nm

AFM force 0.02 nm

FLEXIBLE ELECTRONICS Microscopic Techniques

FLEXIBLE ELECTRONICS Cross-Sectional View of Scanning Electron Microscope

Some Critical Considerations:

– Sample imaging requires conductive material– Two dimensional image is obtained by beam rastering at a

given beam voltage– Organic samples may be sensitive to beam damage– Interaction volume is appreciable, however, surface

topography features can be easily observed

Type of information Developed by SEM Modes:

– Secondary electrons give information on topography (SED)– Backscattering mode (BSE) highlights atoms according to their

atomic numbers

SEM and Elemental Identification:

– Coupling of SEM system with Energy Dispersive Detector (EDS) allows the collection of elemental information

– Fluorescence yields low for light atomic elements make their detection in this range less sensitive

F LEXIBLE ELECTRONICS The Scanning Electron Microscope

Primary electron beam

Secondary electrons (surface texture) Auger electrons (0.4 to 5 nm)

Backscattered electrons X-ray emission(Atomic number contrast)

Sample surface

Excitation volume(1-3 m)

FLEXIBLE ELECTRONICS Interactions of an Electron Beam and a Surface

FLEXIBLE ELECTRONICS Surface and Near-Surface Information from a Single UHV Chamber

Source: ub.rug.nl/eldoc/dis/science/n.j.m carvalho.

FLEXIBLE ELECTRONICS Secondary and Backscattering Imaging in SEM

Source: B.L. Pennnigton, EIT

Spectralresponse

10 KeV

20 KeV

FLEXIBLE ELECTRONICS Energy Dispersive Spectroscopy (EDS) in SEM

Source: B.L. Pennington, EIT

FLEXIBLE ELECTRONICS Elemental Analysis with Energy Dispersive Spectroscopy (EDS)

HeightInformation

Volume andDimensionalInformation

FLEXIBLE ELECTRONICS The Confocal Principle and Applications of CLSM

Side A

Side B

FLEXIBLE ELECTRONICSCLSM Applications: Electrical Connections in a Multilayer Flexible Board

Source: D.C. VanHart, EIT

FLEXIBLE ELECTRONICS CLSM Applications: Molecular Fluorescence in Polymer Layers

Source: D.C. VanHart., EIT

Scratches on bonding pads

Metal contact across aPolymer film

Source: http://www.beugungsbild.de/stm/stm_basics.html

Source: Department of Experimental Physics, Ulm, Denmark

FLEXIBLE ELECTRONICS Atomic Microscopies: STM and AFM

Source: Encyclopedia of Materials Characterization, C.R. Brundle, C.A. Evans, Jr, S. Wilson, eds., Butterworth-Heinemann, Boston 1992

Experimental Image Molecular Model of PMDA-ODA

FLEXIBLE ELECTRONICS STM Image of PMDA-ODA Polyimide

Source: Fujiwara, et al. JVST, B, Vol. 9, No. 2, Mar/April 1992

UV/Ozone

O2 Plasma

FLEXIBLE ELECTRONICS AFM Images of a Surface-Modified Biopolymer Film

Source: L.J. Matienzo and S.W. Winnacker, Macromolec. Mater. Eng., 287, 871(2002)

hv or e

ion He+ ion ion He+ ion

h e x-ray x-ray

XPS AES

SIMS RBS

XRF EMPA

FLEXIBLE ELECTRONICS Surface and Near-Surface Spectroscopies

Basis of technique:Collision of accelerated particle at high energy (MeV) with a nucleus induces

energy transfer to target and detection of process is done through nuclear particle detector.

FLEXIBLE ELECTRONICS Rutherford Back Scattering Spectroscopy (RBS) Fundamentals

FLEXIBLE ELECTRONICS RBS Applications: Stoichiometry of a Cermet Film

Source: L.J. Matienzo, et al., Thin Solid Films, 204, 265 (1989)

Source: L.J. Matienzo, et al., Proc. 34th Soc. Vac. Coaters Meeting, p. 247, Philadelphia, PA (1991)

FLEXIBLE ELECTRONICS RBS Applications: Copper Thickness on a Polyimide Substrate

Photo emission Shake-up Auger process X-ray fluorescence

FLEXIBLE ELECTRONICS XPS and AES: Excitation and De-Excitation Processes

Source: L. Karlsson, Department of Physics, Uppsala University, Sweden

FLEXIBLE ELECTRONICS XPS and AES: Multipurpose UHV Chamber

A, B, and C are sampled A and C are sampled C is only sampled

Slit size

FLEXIBLE ELECTRONICS Beam Size Selection and Appropriate Sampling

FLEXIBLE ELECTRONICS Surface Modified Glass Fiber with a Silane Coupling Agent

Source: L.J. Matienzo, unpublished results

Plasma treated polymer

FLEXIBLE ELECTRONICS Chemical Group Mapping with XPS: Areas of a Flex Module

Image source: www.physik.uni-jena.de/ ~layer/techniques/AES.HTML

Integratedsignals

Derivativesignals

FLEXIBLE ELECTRONICS Auger Electron Spectroscopy and Resulting Spectra

FLEXIBLE ELECTRONICS AES Point Analysis of a Complex Surface

Ethyl trifluoroacetate

C1s region,expect 4 differentcarbon environments with equivalent areas

B.E. shifts are given by different + (charge) on carbon atoms

Expect two different O1s environments with area ratios of 1-to-1

Note: Reference on XPS data is the position of C-C or C-H bonds located at 284.6 eV

Source: Siegbahn et al.Nova Acta Regiae Soc. Sci. Ups. 20:7(1967)

FLEXIBLE ELECTRONICS High Resolution XPS Spectra

2-(4-nitrobenzenesulfonamide)

N1s region contains three differentenvironments with equivalent areas

S2p region will include a single doublet

Source: Siegbahn et al.Nova Acta Regiae Soc. Sci. Ups. 20:7(1967)

FLEXIBLE ELECTRONICS High Resolution XPS Spectra

FLEXIBLE ELECTRONICS High Resolution XPS Spectra for Deposition of Dithiols on Gold Surfaces

h or e-

h or e-h or e-

Ar+ Ar+

Stationary sputtering Dynamic sputtering (Zalar)

Variable angle

FLEXIBLE ELECTRONICS Non-Destructive and Destructive Depth Profiling

FLEXIBLE ELECTRONICS Non-Destructive Depth Profiling of Aluminum Surface

65 degrees

30 degrees

15 degrees

Oxidized Al

Al metal

Oxidized Al

Al metal

Al2p region

FLEXIBLE ELECTRONICS Destructive Depth Profiling: Tantalum Oxide on Tantalum Metal

FLEXIBLE ELECTRONICSAES Imaging and Depth Profiling: Nickel Spheres on In Foil

Source: PHI, USA

FLEXIBLE ELECTRONICSAES Imaging and Depth Profiling: Nickel Spheres on In Foil

Source: PHI, USA

The incident beam can induce loss of neutral atoms and positively and negatively charged fragments

Silicon Surface

Before Bombardment After 3 x 1012 ion/cm 2

FLEXIBLE ELECTRONICSSecondary Ion Mass Spectroscopies: Static and Dynamic SIMS

Specific spectral analysis

Ion imaging

Depth profiling

FLEXIBLE ELECTRONICSThe Uses of Static and Dynamic SIMS

FLEXIBLE ELECTRONICSSecondary Ion Mass Spectroscopy : Positive and Negative Spectra of Teflon

FLEXIBLE ELECTRONICSIon Mapping of Polyvinyl Alcohol Contaminant on a PET Surface

Source: PHI, USA

Technique useful and provides:

1) Thickness of Ge layer2) Concentration of dopant (B)3) Impurities or other additives4) Depth of modification5) Good spatial resolution6) Fast rate of profiling

FLEXIBLE ELECTRONICSD-SIMS Profiling of a Si-Ge Thin Gate Structure

Source: PHI, USA

FLEXIBLE ELECTRONICSA Comparison of Surface-Sensitive Techniques for Materials Characterization

FLEXIBLE ELECTRONICSSome Applications of Physical Methods to the Characterization of

Polymeric Materials in Microelectronic Applications

• Polyimide Films in the fabrication of TBGA circuits

• Optimization of lamination processes for fluoropolymer composites

• Application of dry process modification methods to biopolymers

• Segregation, surface modification and adhesion of polyimide films

FLEXIBLE ELECTRONICS Design of a Flexible Circuit in an Electronic Package: Example 1

Attributes of Desired Final Product

• Adhesion of metal lines to polymer substrate should be 20 gm/cm as a minimum• Use of high temperature stable polymer as the dielectric layer• Use a solvent-based photo-imaging system for line definition• Copper layer should be protected by a gold overlayer applied by electro-deposition• After die attachment, the package will be encapsulated• Encapsulated package must have a minimum adhesion level of 20 gm/cm after 200 hours at

85% R.H./80°C

Cross-Sectional View of Encapsulated Circuit

Source: L.J. Matienzo and F. D. Egitto, Solid State Technol., 38, 99(1995)

FLEXIBLE ELECTRONICS Flexible Circuits in Grid Ball Array Applications

FLEXIBLE ELECTRONICS Some Flexible Circuit Manufacturing Processes

roll metallized material

Cr/Cu deposition

load vacuum chamber

Ar gas into

chamber

O2 plasma

FLEXIBLE ELECTRONICS Semi-continuous Process for Polymer Metallization

FLEXIBLE ELECTRONICS Surface Modification of a Polyimide (PMDA-ODA) Film

Source: L.J. Matienzo and F. D. Egitto, Solid State Technol., 38, 99(1995)

L.J. Matienzo and W.N. Unertl, Polyimides Fundamentals and Applications, M. Ghosh and K.L.Mittal, eds. Marcel Dekker, New York (1996) and F.D. Egitto et al., J. Adh. Sci. Technol., 8, 411 (1991)

FLEXIBLE ELECTRONICS Measuring Effectiveness of Surface Modification of Metallized Films

Weak BoundaryLayer

Microwave Plasma D.C. Glow Plasma

MechanicallyStrong Layer

FLEXIBLE ELECTRONICS Surface Modification and Integrity of Polymeric Films

Kapton Side of Peel

Source: L.J. Matienzo et al., unpublished results

FLEXIBLE ELECTRONICS Measuring Environmental Performance of Metallized Films

FLEXIBLE ELECTRONICS Characterization of Fracture Modes on Metallized Films

L.J. Matienzo et al., J. Vac Sci. Technol. A9, 1278 (1991)

No temperature Exposure

After bake in MeCl

L.J. Matienzo et al., J. Vac Sci. Technol. A9, 1278 (1991)

FLEXIBLE ELECTRONICS Failure Mechanisms of PI/Cr/Cu Metallized Films Solvent

CuCrPI

0 50 100 150 200

Distance ( m)

Potassium Ion Distribution Across Peeled Line from AES line scans (Polymer side)

FLEXIBLE ELECTRONICS Electrochemical Susceptibility of PI Films During Gold Deposition

K Based Gold Salt Ammonium Based Gold SaltK [Au (CN)4 ] (NH4) [Au (CN) 4 ]

FLEXIBLE ELECTRONICS Resulting Adhesion After Gold Deposition Using Different Gold Plating Salts

FLEXIBLE ELECTRONICSA Case Study in Process Optimization: Flexible Polyimide Circuits

• Adhesion of metal to polymer was enhanced by surface oxidation of polymer • Ion bombardment during surface modification enhanced mechanical properties of

dielectric film• Other fabrication process beyond metallization affected metal/polymer adhesion• Adhesion loss was enhanced in humid environments• Additional reactions of residual chemicals can affect overall metal/polymer adhesion• Polymers can also be altered via electrochemical reactions• Optimized engineering design of interface can yield expected specifications

(Summary of Example 1)

Surfactants andCoupling Agents

PTFE polymer chain

FLEXIBLE ELECTRONICSLamination Processes for Fluoropolymer (PTFE) Composites: Example 2

Unfilled PTFE

PTFE Composite

Source: L.J. Matienzo and D. Farquhar, unpublished results

F~~~~~~

Cr CuPTFE-SiO2Cr Cu

~~~~~~Cr CuPure PTFE Cr Cu

PTFE orPTFE-SiO2

FLEXIBLE ELECTRONICSLamination Processes for Fluoropolymer (PTFE) Composites and PTFE Films

FLEXIBLE ELECTRONICSSEM Images of Fractured Interfaces for a Composite

METAL SIDE POLYMER SIDE

354.4°C

379.4°C

300290

700690

545535

525600

Binding Energy (eV) Binding Energy (eV)

Binding Energy (eV0 Binding Energy (eV)

C1s F1s

O1s Cr2p

FLEXIBLE ELECTRONICSXPS Spectra of Fractured Interfaces: Metal Sides vs. Temperature

Increasing Temperature

300290

545535

700690

1.0 1.0

C1s F1s

Binding Energy (eV) Binding Energy (eV)

Binding energy (eV)

FLEXIBLE ELECTRONICSXPS Spectra of Fractured Interfaces: Polymer Sides vs. Temperature

Increasing Temperature

354.4°C

365.6°C

379.4°C

290280

300Nor

Binding energy (eV)

300290

composite

FLEXIBLE ELECTRONICSC1s XPS Spectra of PTFE and Composite Films at Various Temperatures

Binding energy (eV)

-C-C/-C-H

354.4 365.6 379.4

Lamination Temperature (°C)

PTFE with SiO2

Failure Strain(%)

FLEXIBLE ELECTRONICSUniaxial Tension Results for PTFE Film and Composite Film

SEM; XPS

as laminated after etching

280Binding Energy (eV)

FLEXIBLE ELECTRONICSPTFE Surface After Metal Removal (Post Lamination)

Increasing temperature

7 6 5 4 3 2 1

280 76

Binding Energy (eV)

PTFE Film

FLEXIBLE ELECTRONICSMicrotome Slice and XPS Point Analysis for Sample Laminated at 379.4°C

354.4 365.6 379.4Lamination Temperature, °C

Peelstrength

(N/m) 2628

354.4 365.6 379.4Lamination Temperature, °C

Peelstrength(N/m)

FLEXIBLE ELECTRONICSPeel Strengths for PTFE/Metal and FP-SiO2 Composite

FLEXIBLE ELECTRONICSModel for Cracking on Metal/Fluoropolymer Composite

(Summary of Example 2)

Rationale:• Alternative to petroleum derived polymers• Mixtures of this polymer and a synthetic polymer increase biodegradability• A potential for a “Green Product” from second larger biomass available• Potential model for modification of a biomaterial• Dry processes of modification offer possibility for cleaner material thanthose produced by solution modification

Source: L.J. Matienzo and S.W. Winnacker Macromolec. Mater. Eng., 287, 871(2002)

FLEXIBLE ELECTRONICSModification of a Bio-Polymer Film (Chitosan): Example 3

FLEXIBLE ELECTRONICSXPS Analysis of a Thin Chitosan Film on an Al/Si Wafer

Chitosan is a biopolymer derived from chitin with x = 0.33 and y = 0.67

FLEXIBLE ELECTRONICSA Comparison Between 13C CP-MAS NMR and C1s XPS Results

C2 + C6 + C8

C3 + C4 + C5

C1s region

Source: A.A. de Angelis et al., Macromolecules 31, 1595 (1998) and L.J. Matienzo and S.W. Winnacker Macromol. Mater. Eng. 281, 871(2002)

C1s region

20°0 10 20 30 40 50 60 70

Take-Off Angle (degrees)

102030405060708090

Estimated Polymer Thicknessvs Take-Off Angle

d = 3 sin( )

FLEXIBLE ELECTRONICSVariable Angle XPS and Overlayer Effects For a Thin Film of Chitosan

Source: L.J. Matienzo and S.W. Winnacker, Macromolec. Mater. Eng., 287, 871(2002)

FLEXIBLE ELECTRONICSModification of a Biopolymer by Dry-Processes: Non-RIE Plasma,

RIE Plasma and UV/Ozone

Source: L.J. Matienzo and S.W. Winnacker 24th Latin American Chemistry Congress Proceedings, Lima, Peru (2000)

FLEXIBLE ELECTRONICSRIE Plasma and UV/Ozone Results Followed by XPS: Chitosan

RIE Oxygen Plasma UV/Ozone

Segment x is the only one affected by UV/ozone irradiation and one would expect an enhancementof carbonyl groups as the XPS spectra of the C1sregion show. In addition, molecular weight decreasesas a function of irradiation time

FLEXIBLE ELECTRONICSMechanism of Modification by UV/Ozone Surface Reaction

FLEXIBLE ELECTRONICS Evaluating Topography of a Surface-Modified Biopolymer: AFM and SEM

UV/Ozone

O2 Plasma

Surface reaction

Oxidized region

Oxidized zone can react with asilane coupling material

CF3 CF3 CF3

SiOx barrier

Carbonyls, hydroxyl groups, etc.

FLEXIBLE ELECTRONICSChanging Hydrophobic and Hydrophilic Responses by Surface Reactions

Source: L.J. Matienzo and S.W. Winnacker 24th Latin American Chemistry Congress Proceedings,Lima, Peru (2000)

(CH3O)3SiCF3

+ SiOCF3

O+ CH3OH3

Controlled oxidation of surface silicon-containing materials

FLEXIBLE ELECTRONICSPhase Separation Approaches in Surface Modification: Example 4

Applications to the Formation of Thick Polyimide Films

• PI films are usually made by spin casting from solvents and subsequent reaction curing

• Spin casting of polyimide is typically limited to thicknesses below 1 µm•Thicker layers of polyimide over a substrate can be formed but typicaladhesion of interfaces is weak without surface modification

•Surface modification of polyimides is usually done by basic hydrolysis

Concern: Alpha emission of filler particles in materials can induce soft error rates in electronic devices

What is needed: A method by which a thick polyimide layer is formed with minimal contamination of stack and excellent inter-layer adhesion

FLEXIBLE ELECTRONICSThick Polymeric Films of Polyimide

γ PDMS = 0.024 N/m

γ PI = 0.040 N/m

Segregation of PDMS

Liquid-Applied PI

Transformation with UV/Ozone

Application and Cure of Second PI Layer

DI Water Contact Angle = 104(Undoped PI = 70 )

"Glassy" PI SurfaceDI Water Contact Angle = 5

PMDA-ODA Polyimide

R is CHR' is OH

R R RR-Si- -O-Si- -O-Si-R'

R R Rn3

Materials:

Approach: Phase separation and surface modification of resulting films

FLEXIBLE ELECTRONICS PMDA-ODA Films Modified by Various Processes: Efficiency of

Moisture Barriers

Time (min)

2 min Plasma Treatment

60 min UV/OzoneTreatment

0.01 0.1 1 10 100 1000 10000 1000000

120UV/OzonePlasma (RIE)Plasma (No Ions)

F.D. Egitto, L.J. Matienzo, and B.O. Morrison, Jr. US Patent 5693928, December 12, 1997

300 298 296 294 292 290 288 286 284 282 280 Binding Energy (eV)

1.81.61.41.21.00.80.60.40.2 0

Figure 4

C1s XPS spectra of PMDA-ODA and Blended Films with PDMS

0.75% PDMS

0.25% PDMS

0.00% PDMS

0 5 10 15 20

Time (min)

es) 0.25% PDMS

0.75% PDMS

FLEXIBLE ELECTRONICS Thick Polymeric Films of Polyimide

Advancing contact Angle as a Function of UV/Ozone Treatment

1.81.61.41.21.00.80.60.40.2 0

60 minutes

20 minutes

5 minutes

0 minutes

C1s region on PMDA-ODA/PDMS (0.25%) BLEND

C1s XPS Spectra as a Function of UV/Ozone Treatment Time

Figure 5b

15°30°65°

0.25% PDMS in PMDA-ODA

Variable Angle C1s XPS Spectra of PMDA-ODA/PDMS

Variable Angle N1s XPS Spectra of PMDA-ODA/PDMS

C1s region

N1s region

60 minutes

5 minutes

0 minutes

60 minutes

5 minutes0 minutes

C1s and N1s XPS Spectra for PI as a Function of UV/Ozone Treatment Time

116 114 112 110 108 106 104 102 100 98 96 94 Binding Energy (eV)

Si2p region

1.81.61.41.21.00.80.60.40.2 0

N1s region

60 minutes

20 minutes5 minutes

0 minutes

60 minutes

20 minutes5 minutes

0 minutes

Si2p and N1s XPS Spectra as a Function of UV/Ozone Treatment Time

C-Si-O

Si-O ∆ B.E.

400 nm 400 nm 400 nm

SEM Images for PMDA-ODA Blends Before and After Treatment in UV/Ozone

0.25% PDMS blend, no treatment 0.25% PDMS blend, 5 minutes 0.75% PDMS blend, 5 minutes

0.20.4

0.60.8

0.20.4

0.60.8

0.20.4

0.60.8

0.20.4

0.60.8

AFM Images of Films as a Function of UV/Ozone Treatment Time

0% PDMS, no treatment

0.25% PDMS, no treatment

0.25% PDMS, 5 minutes

0.25% PDMS, 60 minutes

0 0.25 0.50 0.75 1.00m

L 306.6 nmRMS 1.74 nmlc DCRa(lc) 1.24 nmRmax 7.97 nmRz 3.28 nmRz Cnt validRadius 436.1 nmSigma 7.93 nm

AFM Image Profile of Film Containing 0.25% PDMS

A -1100 adhesion promoter

silicon

polyimide blend or polyimide

new polyimide

Cross-sectional View of Samples for Adhesion Testing

pattern of cut

peel on PI-PDMS

peel on PI

pattern of cut

peel on PI-PDMS

peel on PI

(b)(a)

FLEXIBLE ELECTRONICS PHYSICAL METHODS IN · PDF fileMolecules vibrate and produce specific ......

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