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Moore’s Law – the Z dimensionMoore’s Law – the Z dimension

Sergey Savastiouk, Ph.D.Sergey Savastiouk, Ph.D.savastuk@trusi.comsavastuk@trusi.com

April 12April 12, 2001, 2001

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Introduction: The next dimension is the Z dimension

Step 1: Vertical miniaturization – thinning

– Thinner is better

– Thinning and handling problems and solutions

Step 2: Vertical integration – stacking

– Thru-Silicon vias

– 3D stacking for system-in-a-chip (SIP)

Conclusion: 3D Wafer Level Packaging

Presentation Overview Presentation Overview

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Moore’s Law – the X-Y dimensions. Moore’s Law – the X-Y dimensions.

The number of components on a surface of a chip would double every 18 – 24 months.

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?Si

SiSi

Si

Si

Si

Si

Si

Moore’s Law - the Z dimensionMoore’s Law - the Z dimensionThe number of components in 3D space would double every 18 – 24 months.

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PACKAGEPACKAGE

LITHOGRAPHYLITHOGRAPHYDESIGNDESIGNRULERULE

200020001995199519851985 19901990

DIPDIP

CSPCSP

MCMMCM

TCPTCP

STACKSTACKTSOPTSOP

SOPSOP

BGABGAPGAPGA

TQFPTQFPQFPQFP

BARECHIPBARECHIP STACK MEMORY MODULESTACK MEMORY MODULE

SYSTEM ON MODULESYSTEM ON MODULE

SYSTEM ON SILICONSYSTEM ON SILICON

1M1M 4M4M 16M16M 64M64M 256M256M

2000200010001000300300200200

0.8um0.8um 0.5um0.5um 0.35um0.35um 0.25um0.25um 0.18um0.18um

PIN COUNTPIN COUNT

Packaging trendsPackaging trends

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Package and Chip ThicknessPackage and Chip Thickness

0

1000

2000

3000

4000

5000

6000

7000

1981 1986 1992 1996 1999 2002 2006 2012

PackageThicknessBare DieThickness

CSP

DIP

TQFPBGA

PDIP

STACK MODULES

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Wafer and Chip ThicknessWafer and Chip Thickness

0

100

200

300

400

500

600

700

800

900

1960 1970 1980 1990 2000 2010 2020

Year of Significant Production

Wafer Diameter, mm Wafer Thickness, um Chip Thickness, um

DIPPDIP TQFP

BGA

TSSOP

CSPSTACK MODULES

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• Step 1: Vertical miniaturization – thinning Step 1: Vertical miniaturization – thinning

Thinner is betterThinner is better

Why to thin? Why to thin?

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Thinner is betterThinner is better

WHY to thin ?

Better packaging density More flexible More reliable Better thermal resistance Better yields

50 m wafer.

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Reduction of thickness by half provides 50% reduction in height and 30% in footprint of packaging

SiH1

H2

Si

Thinning for smaller space: Why to thin?

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<100 micron thickness for improved

reliability, requires damage-free silicon

Hitachi

Thinning for flexibility: Why to thin ? Thinning for flexibility: Why to thin ?

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Numerical results for reliability: Why to thin ?Numerical results for reliability: Why to thin ?

Thick chip: u = 700 m, b = 1000 m

Thin chip: u = 50 m, b = 200 m

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Thermal Resistance vs. Thickness

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0.05

50 100 200 300

Chip Thickness (microns)

Thermal Resistance (Deg.C/Watt)

Chip

Adhesive

Chip+Adhesive

Improved Power Dissipation: Why to thin?Improved Power Dissipation: Why to thin?

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• Step 1: Vertical miniaturization – thinning Step 1: Vertical miniaturization – thinning

Thinning and handling problems Thinning and handling problems and solutionsand solutions

How to thin?How to thin?How to handle thinned wafers? How to handle thinned wafers?

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Thinning alternativesThinning alternatives

Grinding (leaves damage) Polishing (leaves some damage) Wet etching (removes damage, but wet) Dry etching (removes damage)

Silicon

Damage

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Si WAFER

•No induced electrical damage

•No vacuum pumps – excellent process control

•Etch rate suitable for mass production

Atmospheric Downstream Plasma: How to thin?Atmospheric Downstream Plasma: How to thin?

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Edge damage yield problems: How to handle?

Damaged edges cause wafers to break

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NoTouch™ wafer holding: How to thin? NoTouch™ wafer holding: How to thin?

Atmospheric Downstream

Plasma

Holding Gas

NoTouch Holder

Wafer Back Side

•Maintains planarity of flexible wafers

•No contact with bumps

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Silicon

Damage

Silicon

No damage

Damage-free wafer surface: How to thin ?Damage-free wafer surface: How to thin ?

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Damage free edges: How to thin? Damage free edges: How to thin?

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After wet spin etchingAfter grinding or polishing

Oldtechnologies

After ADP etchingNew ADP technology

Thinning alternatives: How to thin?Thinning alternatives: How to thin?

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Die strength etching vs. grind & CMP: How to Die strength etching vs. grind & CMP: How to thin?thin?

Front tensile strength Weibull plot

160um thick die (35 mm squared)

1

10

100

0 200 400 600 800 1000 1200

Tensile strength (N/mm2)

Survival probability(%)

Grind & cmp /Front side

Plasma 10um /FS

Plasma 20um /FS

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Wafer warp improvementWafer warp improvement

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Damage Free Dicing (in development)

Step 2. Controlled depth dicing

Step 3. Apply top side tape

Step 1. Grind

Individual diceStep 4. Etch the backside to singulate

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DBG vs. Damage Free DicingDBG vs. Damage Free DicingSawed die showing chipping 40 micron thin ADP etched dice,

rounded and smoothed

Chip Shifts and Cracks No Chip Shifts and Cracks

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Damage Free DicingDamage Free Dicing

SEM picturesof the edges

Die top

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• Step 2: Vertical integration – stacking Step 2: Vertical integration – stacking

How to thin and to bump on a How to thin and to bump on a backside in one step?backside in one step?

How to stack? How to stack?

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Integration: SOC vs. SOB ,SIP ? Integration: SOC vs. SOB ,SIP ?

SIP

SOB

SOC

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ADP Via Etch (continued)

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ADP thinning of via ADP thinning of via (continued)

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Thru-Silicon viaThru-Silicon via

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Back Side of a wafer with contact pad

Thru-Silicon via results

Silicon

MetalSiO2

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Thru-Silicon via resultsThru-Silicon via results

Back side of a wafer with contact pads

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Direct Chip Attach

Solder Paste Or Other Joining Material

Substrate Or PWB

Active Circuitry Front Side Passivation

Exposed ThroughHole Contact

Tru-CSP™ for front side up : project

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Opto-Electronic Devices

Optically Transparent Layer Or Optical Waveguide

Optical Signals Can Be Transmitted And Received From Either Surface

Optical Waveguide Or Other Silicon Device

Tru-CSP™ for opto-electronics: project

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Tru-CSP™ with passive interposer : project

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Tru-CSP™ face-to-face : project

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Tru- 3D Stacking Tru- 3D Stacking : project

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1997, $8m raised, ADP prototyping

1998, Ultra-thin handling prototyping

1999, $10m raised, Product development

2000, System sales and Thru-Silicon dev-t

2001, $18m raised, – Thru-Silicon dev-t hiring

process engineers: jobs@trusi.com

Conclusion: History of CompanyConclusion: History of Company

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Thinning by ADP and NoTouch handling:

– enables low cost damage free thinning

– enables low cost damage free dicing

Thinning by ADP with Thru-Silicon vias:

– enables the new generation of low cost 3D stacking

methods of chips and wafers for System-In-a-Package

– brings front-end technologies to back-end applications

Conclusion: OverallConclusion: Overall SummarySummary