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Glass for Advanced Semiconductor Applications: Myths and Opportunities Peter L. Bocko Ph.D. CTO – Glass Technologies November 8, 2011
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Page 1: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

Glass for Advanced Semiconductor Applications:Myths and Opportunities

Peter L. Bocko Ph.D.CTO – Glass TechnologiesNovember 8, 2011

Page 2: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Outline

• New Roles for Glass in the Semiconductor Industry • What Is Needed for 3DS-IC Packaging• Myths about Glass• Conclusion: Glass is a an Excellent Substrate for 3DS-IC

Applications

Page 3: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Roles Of Glass In Advanced Semiconductor Packaging

flip wafer

carrier glass wafer

bond wafer thin & processwafer

debond wafer

CARRIER

Page 4: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Roles Of Glass In Advanced Semiconductor Packaging

CARRIER

glass

Back-illuminated (BSI) CMOS image sensor

INTEGRATEDCARRIER

flip wafer

carrier glass wafer

bond wafer thin & processwafer

debond wafer

Page 5: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Roles Of Glass In Advanced Semiconductor Packaging

CARRIER

glass

Back-illuminated (BSI) CMOS image sensor

glass

PWB

IC

3D System Start withGlass Interposer

INTEGRATEDCARRIER

INTERPOSER

flip wafer

carrier glass wafer

bond wafer thin & processwafer

debond wafer

Page 6: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Corning’s Strategic Intent In Semiconductor Glass

Advanced Optical Melting Fusion Sheet Forming Process

Molten glass

Pristine

Glass Sheet

FusionIsopipe

Page 7: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Corning’s Strategic Intent in Semiconductor Glass

Advanced Optical Melting Fusion Sheet Forming Process

Molten glass

Innovative AluminosilicateGlass Compositions

FusionIsopipe

Pristine

Glass Sheet

+

Page 8: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Corning’s Strategic Intent in Semiconductor Glass

Advanced Optical Melting Fusion Sheet Forming Process

Molten glass

OptimizedExpansion

Pristine Surface

ProfoundlyFlat

Thin & Strong

Innovative AluminosilicateGlass Compositions+

FusionIsopipe

Page 9: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

What is Needed for 3DS-IC Packaging

• A substrate that can support a silicon device wafer during the thinning and stacking process as a carrier

• A substrate that can be used as an interposer• Key attributes for such substrates:

– Smooth and clean surface– Low total thickness variation (TTV)– Low warp/bow– High edge strength– Strength & reliability– CTE similar to silicon– Good chemical durability

Page 10: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Glass Myths

1. Glass is weak

Page 11: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Glass Can Be Made Strong

• The strength of glass, like silicon, depends upon the defect population.

• Unlike silicon, glass failure occurs almost exclusively due to tensile stress applied to surface flaws. Glass, as an amorphous material, is not subject to failure along crystallographic planes or from crystal defects.

• If the surface were free of defects, glass strength could be very high (>10GPa). Typical, non-technical glass in every-day use has strength on the order of 10’s MPa corresponding to flaw sizes >100 . In technical glass, for example fusion formed LCD substrates with a pristine surface (flaw size in the micron range), GPa scale strength can be achieved.

• Recipe for achieving high mechanical reliability for advanced semiconductor applications: start with a pristine surface and minimize surface damage in process. Simple.

Page 12: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Glass Can Be Made Strong

• The strength of glass, like silicon, depends upon the defect population.

• Unlike silicon, glass failure occurs almost exclusively due to tensile stress applied to surface flaws. Glass, as an amorphous material, is not subject to failure along crystallographic planes or from crystal defects.

• If the surface were free of defects, glass strength could be very high (>10GPa). Typical, non-technical glass in every-day use has strength on the order of 10’s MPa corresponding to flaw sizes >100 . In technical glass, for example fusion formed LCD substrates with a pristine surface (flaw size in the micron range), GPa scale strength can be achieved.

• Recipe for achieving high mechanical reliability for advanced semiconductor applications: start with a pristine surface and minimize surface damage in process. Simple.

Page 13: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Glass Can Be Made Strong

• The strength of glass, like silicon, depends upon the defect population.

• Unlike silicon, glass failure occurs almost exclusively due to tensile stress applied to surface flaws. Glass, as an amorphous material, is not subject to failure along crystallographic planes or from crystal defects.

• If the surface were free of defects, glass strength could be very high (>10GPa). Typical, non-technical glass in every-day use has strength on the order of 10’s MPa corresponding to flaw sizes >100 . In technical glass, for example fusion formed LCD substrates with a pristine surface (flaw size in the micron range), GPa scale strength can be achieved.

• Recipe for achieving high mechanical reliability for advanced semiconductor applications: start with a pristine surface and minimize surface damage in process. Simple.

Page 14: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Glass Can Be Made Strong

• The strength of glass, like silicon, depends upon the defect population.

• Unlike silicon, glass failure occurs almost exclusively due to tensile stress applied to surface flaws. Glass, as an amorphous material, is not subject to failure along crystallographic planes or from crystal defects.

• If the surface were free of defects, glass strength could be very high (>10GPa). Typical, non-technical glass in every-day use has strength on the order of 10’s MPa corresponding to flaw sizes >100 . In technical glass, for example fusion formed LCD substrates with a pristine surface (flaw size in the micron range), GPa scale strength can be achieved.

• Recipe for achieving high mechanical reliability for advanced semiconductor applications: start with a pristine surface and minimize surface damage in process. Simple.

Page 15: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

FACT: Surface strength of thin semiconductor quality wafer glass is amazingly strong!

Probability - Weibull

Strength, MPa

Failu

re P

roba

bilit

y, %

100 2. E+ 310001.E-1

5.E-1

1

5

10

50

90

99

1.E-1

Probabilit y-W e ibull

0 .3 mm EXGW eibull-2PRRX SRM MED FMF= 56/S= 26

Data Po intsSusp PointsProbability Line

G. Scot t GlaesemannCorning Incorpora ted4/8/201111:48:23 AM

about 50% of glassexceeds 1 GPa!

Page 16: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

FACT: Glass can be engineered to have edge strength higher than silicon

160012008004000

99.99

9995

80

50

20

51

0.01

Strength (MPa)

Per

cen

t

Glass Process 1 (MPa)Glass Process 2 (MPa)Glass Process 3 (MPa)Glass Process 4 (MPa)Silicon Baseline (MPa)

V ariable

Normal - 95% CIMeasured Edge Strength after Finishing

( True for edge and notch)

Page 17: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Glass Myths

1. Glass is weak2. All glasses are the same

Page 18: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

FACT: Not all glass is created equal. Glass Composition Matters!

Properties Under Control By Glass Chemistry

• Thermal Properties (Expansion)

• Chemical Durability

• Mechanical Strength

• Surface Hardness

• Elastic Properties

• Optical Properties

• Electrical Propertiescomputer molecular model of a glass

optimized for scratch resistance

Page 19: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

FACT: Not all glass is created equal.Process matters!

Pristine

sheet of

glass

Scalable width

Molten glass

IsopipeCorning Fusion Glass• Surface formed in air

- no polishing required• Excels in thickness variation

control • Low warp/bow• Good overall uniformity (TTV)• Superior surface roughness

characteristics are not affected by shift to large or thinner sheet

• Scalable to large sizes

Page 20: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

FACT: Chemical durability is a critical attribute that differentiates candidate glasses

Competitor Glass

Haze following wet chemical etch in glass carrier wafers is a limiting factor in the recyclability of glass carriers

Other Glass

Page 21: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Glass Myths

1. Glass is weak2. All glasses are the same3. Glass is not compatible with precision semiconductor

processing

Page 22: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

FACT: Aluminosilicate glass substrates enabled the winning large area electronics platform of the LCD revolution

Page 23: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

FACT: We have developed capability to control particulate contamination on LCD substrates to the sub-µ level

S&T analysis of defect from p-Si customer process showing submicron surface anomaly ca. 1998

Page 24: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

30

Particles near and on the surface impact the surface topography

10 3

Driving to increasingly stringent levels – maximum allowable particle size has been continuously improved

Page 25: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

FACT: CTE of glass is a close match to silicon

Instantaneous CTE vs. Temperature

2.00

2.50

3.00

3.50

4.00

0 100 200 300 400

Temperature (C)

CTE

(ppm

/C)

Corning GlassSiliconb

Exact match at 200ºC

Page 26: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Wafer stack bow as a function of temperature

Wafer Stack Bow vs. Si Thickness / Temperature

-200-150-100-50

050

100150200

0.7 mm Si 0.05 mm Si 0.02 mm Si

Stack Type

Waf

er S

tack

Bow

(um

)

20 C (um)200 C (um)

Limit

Limit

ccv +

GlassAdhesiveSilicon

Page 27: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Glass Myths

1. Glass is weak2. All glasses are the same3. Glass is not compatible with precision semiconductor

processing4. Glass has to be ground and polished to meet specs

Page 28: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

FACT: Outstanding TTV & warp variation can be achievedin the as-formed (non-polish) fusion surface

Champion Wafer | 300 0.7mm | 1.352 total thickness variation | 13.8 warp

Page 29: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

FACT: Fusion surface is smooth & featureless

Roughness Measurement Results

Lap & Polish10 nm

Fusion

RMS 0.29 nm 1.46 nmRa 0.23 nm 1.13 nmZ-Range 4.23 nm 33.7 nm

Page 30: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Etching reveals subsurface damage in polished glass that is not in fusion glass.

Etch time in 1:5 Buffered HF

polishingparticle

subsurfacecracks

Polishingparticle

subsurfacecracks

Glass is re-deposited under as compression is relieved in wake of particle

Glass is dissolved as hydrous oxides under hydrostatic pressure of polishing particle

Page 31: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

© Corning Incorporated 2011

Conclusion

• Glass is a versatile and robust material with a track record & enormous future potential as an enabling material in electronics

• Corning’s capabilities in flat glass in aluminosilicate family are an excellent foundation for the development of glass for advanced semiconductor packaging

• The key attributes to be delivered are in the areas offlatness, surface quality, thermal behavior, thin & strong.

• An open & deep collaboration across the value chain isthe best path to mutual success: the right product withoptimized value will not be “off the shelf”.

Page 32: Glass for Advanced Semiconductor Applications: Myths and ...€¦ · advanced semiconductor packaging • The key attributes to be delivered are in the areas of flatness, surface

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