NASA Technical Reports Server (NTRS) 19870006978: Surface property modification of semiconductors by fluid absorption

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ADVANCED SILICON SHEET

N 87-16411

SURFACE PROPERTY MODIFICATION OF
SEMICONDUCTORS BY FLUID ABSORPTION

UNIVERSITY OF ILLINOIS AT CHICAGO
S. Danyluk

:*

Objectives

. Lubricated Cutting (wafering)
laboratory simulation
mechanism
model

. Residual Stresses in Sheet

Develop Interferometry Technique
Apply to EFG and WEB

Lubricated Cutting in Simulated Laboratory Experiments

Load, Temperature, Fluids

Surface Morphology
Hardness
Wear rate
Depth of Damage

Mechanism

Model

A

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w

ADVANCED SILICON SHEET

{

Silicon Wafer

tracks ( propagate on

c lavage planes)

— r

*

7 T T~

— ?

k damage

. _V - zoni*

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*

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1

plasticity(?)

.due to high compressive stresses

. at crack tips

. Simulate Damage

dicing (OD sawing)
indentation (Vickers dia)

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•5

Identify critical parameters
Load

i

fluid :

temperature

heatable stage

ADVANCED SILICON SHEET

OD Sawing (Dicing)

KERF + OAMAGE
(—2-3 TIMES
BLADE THICKNESS)

sioe vtw

Diamond

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Examples of Cracks at the Bottom of Grooves

ORIGINAL

OF POOR QUAUTY

310

mmmnmmkmX ^ _

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Summary of High-Speed, Elevated Cutting

Deformation Mode

Cracks at Bottom of groove

Plasticity

Fluids, Temperature — influence C, trface morphology

P

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fs*

■V

ADVANCED SILICON SHEET

Indentation Model

(space charge
field)

2D a X

n

at low P, space charge
fields influence damage

X «

n

#N S ~ finite rnaber of surface states
•N j# E JS not known but extracted fro* expt.
•lie, electrochemical potential

2D • f(N 0 .N s . E JJf n

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ADVANCED SILICON SHEET

Summary of Indentation Model

2D and x exhibit maximum at 150C
n

N s = 10 16 -10 18 /m 2

E s = 0.79 eV

tv

Doping level influences 2D

Predict T,N^ variation with 2D

Summary of Silicon Results

. Wear rate

♦ Ethanol - highest
. air - lowest

. Damage

. Aoad

plasticity.

cracks.

p 100«f
p 200gf

i

t

. temp

cracks,, damage decreases
at T 250°C

. bulk doping
. fluid

316

ADVANCED SILICON SHEET

Conclusions

Mechanisms of Wear

Wear rate and damage includes: cracks and plasticity

Laboratory simulation tests provide guidance in modifying
industrial practices.

Wear rate may be optimized and damage may be minimized

Load (below 0.98N (lOOfg)

Fluid (alcohol-based vs. water-based fluids)

Temp (200-300°C)

Model allows parameters to be identified and range to be
extrapolated.

Unresolved problems: Impact, fatigue

Residual Stresses

Interferometry is a promising NDT technique for sheet geometries

Edges - compressive
Center * tensile

• EFG - growth " 2 C * /Bin * °RS " 4JDMP *

WEB * v growth ' < * />in ' °RS * 11 *»•

. Unresolved problems: anisotropy of E, v

dendrite geometry