Ralph Zoberbier Director Product Management Exposure and … · 2018-06-11 · Director Product Management Exposure and Laser Processing ... JSR WPR 5100 – 10µm thick HD8930 PBO

Excimer Laser Ablation A Novel Patterning Technology for Wafer Level Packages

Ralph Zoberbier

Director Product Management Exposure and Laser Processing

SUSS MicroTec Lithography GmbH

Advanced Packaging Market Trends and Requirements

Excimer Laser Ablation Technology

Application Examples

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Advanced Packaging Forum SEMICON Taiwan 20132

� Patterning is required for Via Formation, RDL and bumping process

� Patterning is done today by Photolithography with various solutions and technologies like Mask Aligner, UV Projection Scanner and Projection Stepper

EMERGING PACKAGING PLATFORMS


Todays Advanced Packaging Platforms

RDLRDL

BumpingBumpingBallingBalling

Wafer BondingWafer Bonding

Via FormationVia Formation

WL-Optics

WL-Capping

2.5D Interposer

3DIC

BallingBalling

WLCSPFO

WLPEmbedded

ICFlip Chip

MEMS IC

CappingIC

Sensor

MemoryLogic

3DWLCSP

Die 1 Die 2 Die 3 Die 4

Middle-End Process Steps

� Technical Constraints:� Thermal & Mechanical limitations of

photo dielectric materials

� CTE material mismatch

� Wet etch constraints at high pitch

� Challenges in stripping negative resists

� Environmental Care:� Stepping away from hazardous

chemicals

� Need for further cost reduction

APPLICATIONS AND TODAYS LIMITATIONS


Flip Chip: 200/300mm(Cu Pillar, Micro Bumping, Solder Bumping)

WLCSP: 200/300mm (RDL, Integrated Passive Devices)

Fan out WLP: >300mm(eWLB,RCP,other)

Embedded IC: >300mm(FCBGA, FCCSP)

2.5D Interposer, 3DIC:(200)/300mm

Excimer Laser Ablation




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WHAT IS EXCIMER LASER ABLATION?


� Laser ablation is the process of removing material (subtractive process) from a solid surface by irradiating it with a laser beam.

� At low laser flux, the material is heated by the absorbed laser energy and evaporates.

� At high laser flux, the material is typically converted to a plasma.



Excimer Laser Ablation Solid State Laser Ablation

Imaging Type Mask based projection Maskless, direct ablation

Imaging area Field area (i.e. 50x50mm) Single spot

Patterning Mode Direct bond breaking Material evaporation

Available wavelength 248nm, 308nm Various: 355nm, 532nm, 1064nm, etc…

Throughput +++ -

Typical applications Complex structures: Low density patterning, scribing, drilling:

Ablation of complex structures(i.e. RDL trench and vias)

Laser drilling(i.e. through glass vias)

Mask

Excimer Laser

Large-area Ablations

Solid State Laser

Spot-area Ablations

� Most similar to a UV Photolithography Stepper (ablates instead of images)

� Reticle defines the ablation pattern (up to 50x50mm)

� Resolution down to 2µm

� Ablation is direct bond breaking, “direct etch” process

� Throughput not dependent upon density of ablated pattern

� Available wavelengths - 308nm & 248nm (High power 300W;300Hz; 1000mJ)



Optical setup of Excimer laser ablation stepper:

Materials that ablate include:

� Most organic materials:� Polymers (PEN, PI, PET, etc..)

� Organic Dielectrics (HD4100, JSR WPR5100, PBO, etc…)

� Epoxy Mold Compounds (EMC - Nagase, Anjinomoto, Sumitomo)

� Photoresist

� Some in-organics:� Dielectrics (SiNx - < 1µm thick with 248nm

only)

� Thin metals (Au, Cu, Ag, Al, Ni, ITO, etc…); <1µm thick on organic material

� Conductive materials (ITO, IZO, CNT); <1µm thick on organic material



Side-wall Angle Control:

� Higher fluence: Steeper wall-angle

� Lower fluence: Shallow wall-angle

Depth Control:

� Each pulse removes a certain amount of material

� (Etch-rate = material removed/pulse)

� With a known etch-rate – the number of pulses to reach a desired depth can be predicted and controlled

EXCIMER LASER ABLATION PROCESS CONTROL


~65º ~81º

EXCIMER LASER ABLATION SAMPLES


HD8930 PBO - 13µm thickJSR WPR 5100 – 10µm thick Duramide 7310 – 10.5µm thick

� Enables use of better performing dielectrics/polymers� Non Photo Polymers exhibit better thermal, mechanical and electrical characteristics

� Improved elongation - 1 layer thick instead of 2

� Can use high Si filled dielectrics (not photo-imageable)

� Better CTE and Warp control

� Allows Embedded Structures � Cu traces more reliable – bound on 3 sides

� Lower material costs� PI has an ‘infinite’ shelf life without Photo-initiator (less waste)

� No need for expensive photo ingredient's to help drive down costs

� Less lithography steps with reduced chemical consumption

� Lower manufacturing costs� Eliminate etch chemicals & Hazardous disposal

� Eliminate process steps and complexity (compared to Photo/Wet)

� Reduced CAPEX

� Green process� Reduction of hazardous chemicals

KEY ADVANTAGES OF EXCIMER LASER ABLATION





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EXCIMER LASER ABLATION APPLICATIONS


Seed Layer Removal

Patterning of dielectrics (i.e. vias)

Patterning of trenches (RDL)

Example: Laser Patterned WLCSP/WLFO Process Flow

EXCIMER LASER ABLATION


RDL Via and Trench by Standard Photolithography

� Polyimide Apply( Photo imageable)

� Bake � Expose RDL Via� Develop � Seed Layer apply � Resist coat � Pre expose bake� Expose RDL trace� Post Expose bake� Develop resist� Cu plate RDL� Resist strip� Etch seed layer� Apply dielectric around RDL

structure� Bake (Polyimide Cure)� Descum

RDL Via and Trench by Excimer Laser Ablation

� Polyimide Apply (thickness for both Via and Trench). Can be cheap material

� Bake

� Ablate both RDL Trench and Via

� Clean/descum

� Seed layer apply

� Cu plate via and trench

� Back etch

REDUCED PROCESSING STEPS LASER ABLATION VS. PHOTOLITHOGRAPHY


� Significant cost reduction

� Eliminate ~8 process steps

� Eliminate equipment required for deleted process steps

� Eliminate operator overhead

� Eliminate yield contributing steps

Compared to typical photolithographic process, laser direct etching can reduce many of the manufacturing process steps. (~8 steps eliminated). Typical process.

� Laser etch non-photo EMC materials and take advantage of the lower CTE:

VARIOUS SI FILLED DIELECTRICS - EXCIMER ABLATED


Sumitomo ABF 9813SBA-II10µm line, 12µm deep

� ABF GX-13

Via-1 Via-1

Via-1 Via-1

ABF GX-13:- 5µm wide L/S, 10µm deep- 40µm dia vias in 40µm deep, 74°

� Ablation process breaks down the material molecular structure and debris is generated:� debris collection system for particle removal

� debris exhausted out of the building or through a filter

� laminar flow of HEPA filtered air across the substrate.

DEBRIS COLLECTION


Debris Cell

Cu Pad (~3µm)

PI (~7µm)

Debris

� Various post laser cleaning methods are used based on material being ablated.

Plasma and wet solutions shown as examples:

POST LASER CLEANING PROCESSES


CO2 Wet Spray

Non-Photo Polymer Material Metal Seed Layer

O2 Plasma

� Photochemical ablation rate 0.3 µm/pulse

� Pattern resolution of 8µm L/S or less is achievable

� Significant amount of material deposition around the ablated patterns

� Simple chemical treatment can successfully remove the residue

LASER PATTERNABLE DIELECTRICS


CYCLOTENE™ Dielectric Material

Thickness Fluence ID # of pulses Trench Depth

Trench/Pad Via (µm)

3000 Dry Etch Resin 12.0 A 22 28 6-7

Toughened Resin 10.2 A 18 24 5-6

6505 Aq. Develop. Resin 6.5 A 11 18 3-4

0.00

20.00

40.00

60.00

80.00

100.00

0 10 20 30 40

% Strain

Str

ess

(MP

a)

Source: DOW Electronic Materials - Photo- and Laser- Patternable Plating Resists and Diel ectric Materials for 3D-TSV

SUSS Technology Forum 2013 – Semicon West

TOUGHENED CYCLOTENE RESIN - TRENCH AREA


Afte

r La

ser

Pat

tern

Afte

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lean

Source: DOW Electronic Materials - Photo- and Laser- Patternable Plating Resists and Diel ectric Materials for 3D-TSV


Afte

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Pat

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Afte

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LASER PATTERNABLE DIELECTRICS

Advanced Packaging Forum SEMICON Taiwan 201322Source: DOW Electronic Materials - Photo- and Laser- Patternable Plating Resists and Diel ectric Materials for 3D-TSV





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“Excimer laser ablation is proving to be an innovative and very promising patterning technology for various Advanced Packaging applications with significant technical and cost reducing potential”

EXCIMER LASER ABLATION


SUSS ELP300


See you next time at:

SUSS TECHNOLOGY FORUM ASIA 2013

Taiwan, Hsinchu | November 13

China, Shanghai | November 15

Korea, Seoul | November 19

SÜSS MicroTec AG

Schleissheimer Str. 90

85748 Garching

www.suss.com


Documents

Ralph Zoberbier Director Product Management Exposure and … · 2018-06-11 · Director Product Management Exposure and Laser Processing ... JSR WPR 5100 – 10µm thick HD8930 PBO