x-ray techniques for 3d metrology and diagnostics...

Ehrenfried Zschech | Fraunhofer IKTS Dresden | Germany | [email protected]

Zhiyong Ma | Intel Inc. Hilsboro/OR | USA | [email protected]

X-RAY TECHNIQUES FOR 3D METROLOGY AND DIAGNOSTICS – STATUS AND OUTLOOK

IRSP 2016 | Bad Schandau, 31 May 2016

Picture: NovaledPicture: Fraunhofer IPMS Picture: GLOBALFOUNDRIES

mailto:[email protected]

mailto:[email protected]

Outline

1. Today‘s and future metrology and diagnostics challenges in microelectronics, Role of X-ray techniques

2. X-ray imaging of 3D structures: From micro to nano

3. Reliability-limiting effects: Imaging of kinetic processes in microelectronic products

4. Outlook:

Hybrid metrology and inspection

Analytical X-ray microscopy with novel X-ray sources

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CM

OS

: C

PU

, M

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ory

, Lo

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130nm

90nm

65nm

45nm

32nm

22nm

Beyond CMOS

Functional Diversification: More than Moore

Analog/RF Passives HV PowerSensors

ActuatorsBiochipsFluidics

InformationProcessing

Digital content &System-on-Chip

(SoC)

Interacting with people and environment

Non-digital content & System-in-Package (SiP)

New processes and new materials

Scaling „More Moore“ and Functional Diversification „More than Moore“

From International Technology Roadmap for Semiconductors: http://www.itrs.net

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lin

g:

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re M

oo

re

Ba

seli

ne

CM

OS

: C

PU

, M

em

ory

, Lo

gic

130nm

90nm

65nm

45nm

32nm

22nm

Beyond CMOS

Functional Diversification: More than Moore

Analog/RF Passives HV PowerSensors

ActuatorsBiochipsFluidics

InformationProcessing

Digital content &System-on-Chip

(SoC)

Interacting with people and environment

Non-digital content & System-in-Package (SiP)

New processes and new materials

Scaling „More Moore“ and Functional Diversification„More than Moore“ New Processes and New Materials

Trend: Materials innovations – Increas ingnumber of new materials in microelectronic

products to fulfill performance and reliabilityneeds

for „More Moore“ and for „More than Moore“

From International Technology Roadmap for Semiconductors: http://www.itrs.net

You cannot control what you cannot measure metrology is critical!

Future Products will be Increasingly More Complex

X-ray Techniques for Metrology and Diagnostics

Integral technique covering large areas / many devices metrology

• X-ray diffraction XRD and small angle X-ray scattering SAXS (local

technique at individual structures: TEM (CBED, ENBD, Holography, … +

brightfield imaging)

• X-ray reflectometry XRR (local technique at individual structures: TEM)

• X-ray spectroscopy XRF, XAS (local technique at individual structures:

TEM/EDX+EELS)

High resolution imaging techniques diagnostics/failure analysis

• (micro) X-ray computed tomography micro-XCT

• Transmission X-ray microscopy TXM / nano X-ray computed tomography

nano-XCT

B. Bunday, SPIE Adv Litho 2013

Alain Diebold, ITRS 2011

2 parameters

Gate

Fin

HMHiK/MG

3 parameters

3 parameters

3 p

ara

mete

rs

1 parameter

>10 CD

Parameters

+ Others?

Metrology Gaps for 3D Structures

Destructive technique at individual device (TEM)

vs. nondestructive integral technique (SAXS)

Metrology

driven

demand

Tri-gateMG/HKStrain

TEM Samples

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8

199

9

200

0

200

1

200

2

200

3

200

4

200

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200

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200

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200

9

201

0

201

1

201

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201

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201

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201

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201

8

Materials Science

driven demand

Dimensional Metrology Lab Demand

(driven by 3D transistor)

Automated TEM flow as near-fab metrology solution

CDSAXS is a potential alternative

CD-SAXS: Statements at FCMN 2015 Dresden Conference

R. J. Kline, NIST:

• CD-SAXS is a potential replacement

metrology for visible and UV OCD

• Applicable to periodic test

structures, for 32nm pitch

demonstrated: resolves sub-nm

pitch changes

• Statistical limitations for FinFETs

High-brightness X-ray source

needed!

New X-ray sources are key to success

of CD-SAXS

Flux Plot

CDSAXS

Courtesy of Joe Kline, NIST

Spacer-Assisted Quadruple

Patterning (SAQP)

Pitch/walking

Height

Width

Slope

LER

Shape

3D Metrology Option - CDXAS

SAXS is the technique of

choice for FinFET metrology,

data from reciprocal space

maps

Outline




4. Outlook:



Requirements for XCT in Microelectronics

X-ray source

max energy

for highly x-ray

absorbing

samples

Diverse spectrum of sample sizes, ranging from a few millimeters

to a few inches

A means to compensate for resolution deterioration when using

large sample-to-source distances to avoid sample-source crashing

Efficient data

processing algorithms

and computing systems

for fast time to

tomographic data

No sample trimming should be required!

C4 Bump “Invisible” Defects

Best 2D

X-ray image

could not

detect the

defect!

Physical

x-section

X-ray CT

x-section viewX-ray CT

3D view

Gap ~2um

TPT 10min

X-ray CT

plane view

2D X-ray Imaging vs. 3D XCT

2D X-ray imaging is a matured and widely used analytical method for failure

analysis in microelectronics

- Demonstrated capability for defect detection

- Real time nature

- Availability of automated defect detection routines

Technical challenges for 2D X-ray imaging are:

- Development of smaller / more complex packages

- Small defect dimensions with a lot of interfering features in the FOV

- Increasingly difficult and sometimes impossible to image certain

defects in non-destructive fashion

- Samples often require preparation that may produce artifacts.

This fundamental limitation of 2D X-ray imaging technology is a

common roadblock driving X-ray CT for failure analysis in

microelectronic devices

X-ray Micro Imaging: Principle of Conventional Radiography

SDD

SOD

DF

UFProjection of the (small) specimen on a (large) screen

d > DF : Resolution is limited by size of the source

DF > 0.6 µm (thin target)

Zeiss Versa XCT 520: 0.7 mm resolution

Sub-micron X-ray Tomography for Advanced Packaging: 3D TSV Stacking

Physical Failure Analysis for Advanced Packaging: Micro-XCT of 3D Chip Stack

X-ray computed tomography (XCT): Incomplete Cu TSV filling, variation in

solder flow (AgSn) around the Cu bumps

100 µm

M. Löffler, TU Dresden/DCN, J. Gluch, E. Zschech, Fraunhofer IKTS

M. J. Wolf, Fraunhofer IZM-ASSID

EU project 3D MASTER / BMBF 3D INNOPRO

Xradia Nano-XCT: Lab-based X-ray Microscopy

Multi-chip Stack – High-resolution nano-XCT

Tomography of a partially filled Cu TSV




Multi-chip stack – High-resolution nano-XCT

Tomography of a AgSn solder bump




SEM Image of FIB X-section of Copper TSV after nano-XCT Study

1. Nondestructive failure localization: Voids ~ 100 nm size can be localized2. Destructive physical failure analysis: Validation of nano-XCT results

M. Baklanov, P. S. Ho, E. Zschech, “Advanced Interconnects for ULSI Technology”

(Eds.), John Wiley & Sons Chichester, pp. 437 - 502 (2012)

L. W. Kong, E. Zschech, et al., J. Appl. Phys. 110, 053502 (2011) DOI:10.1063/1.3629988

Cavity

Void chain

Curved bottom

Outline




4. Outlook:



G. Schneider et al., APL 81, 2535 (2002)

SEM micrograph X-ray micrograph imaged at 1.8 keV

X-rays

Cu interconnect

Cu via

Wafer

1 mm

In-situ XRM Degradation Experiment @ BESSY Berlin: Electromigration in on-chip Cu Interconnects

A

C

t = 0 h

I = 20 mA

B

D

E F

t = 8:19 h

I = 29 mA

t = 10:44 h

I = 34 mA

t = 10:58 h

I = 30 mA

t = 11:16 h

I = 30 mA

t = 12:41 h

I = 34 mA

void formation

in Cu via

void

X-ray micrographs visualizing void formation, movement and agglomeration inside the passivated vias

G. Schneider et al., APL 81, 2535 (2002)

In-situ XRM Degradation Experiment @ BESSY Berlin: Electromigration in on-chip Cu Interconnects

Mechanical Properties of Thin Film Materials Integrated in Microchips and Advanced Packaging

Chip-package interaction (CPI) is one of the major reliability concerns in leading

edge chips with low-k and/or ultra-low-k insulating material in the on-chip

interconnect stack, because of the low fracture toughness of these materials.

- To prevent chip damage as cracking, e. g. caused by dicing, so-called crack stop

structures are integrated.

- Crack pathways have to be imaged to estimate reliability risks.

Crack propagation and particularly the efficiency of the crack stop structure in an

Intel CORE i3 processor is studied.

SEM images of

cross-section with

crack stop structure

of an Intel CORE i3

processor with 12

metallization layers

Micro Double Cantilever Beam test (MicroDCB)

Scope: crack initiation and propagation

XRM investigation under load

In-situ Mechanical Testing of Multilayer Systems in the X-ray Microscope (XRM)

Force

S. Niese, PhD thesis, BTU Cottbus, 2014

Nano XCT: X-ray Microscope Setup for microDCB Test

dedicated

sample stage

(xyz-Q)

Source Condenser X-ray lens Detection system

1500 mm

Laminography

S. Niese, PhD thesis, BTU Cottbus, 2015 Talk 14: S . Niese

Micro-DCB Test in the nano-XCT Tool at Crack Stop Structures of CORE i3 Processor

Cross section view

Before crack initiation

Crack in front of crack stop

(quick intermediate tomography)

After cracking

Crack up to here

• Delamination occurred typically inside the metallization layer where it was

induced until it reached the crack stop pattern

• The crack changed the direction of propagation at the crack stop structure

Edge of chip

Crack stop region, delaminated/broken structures appear darker

Active chip area

In plane view at metal layer 8

Tomographic image (side view) of

de-lamination between metallization

layers (crack path)

Tomographic image (in plane) showing

the delaminated area (dark) within the

shown metallization layer

Poster 20: K. Kutukova

Outline




4. Outlook:



What does “Smart” Metrology look like?

Multiple vectors need industry/vendor focus

Enhanced (hybrid) in-fab metrology particularly for 3D

structures

Product/layout awareness

Evaluation and development of lab analytical capabilities for

potential in-fab use

Integration of manufacturing-worthy and cost effective near-fab

capabilities

Where required, enable the lab capability for near-fab support

A manufacturing flow that seamlessly incorporates all

of these elements

X-ray Techniques in Microelectronics

There are several industrial needs that require X-ray systems

with high-brightness X-ray sources:

o Challenges from new materials / smaller dimensions on

wafer (new gate stacks, MRAMs, …): XRD, CD-SAXS, XRF

o Challenges from advanced packaging (micro-bumps,

TSVs): micro- and nano-XCT:

o Combination of techniques (hybrid metrology and

diagnostics):

« Analytical X-ray microscope »

- high-resolution (3D) imaging (nano-XCT)

- high-resolution XRF and XRD

High-flux X-ray Sources

Joe Kline, NIST @ FCMN 2015

Linac ICS

Graves et al, . Phys. Rev. Spec. Top. - Accel. Beams 2014

www.excillum.com

Metal Jet Anode

Synchrotron ICS

www.lynceantech.com

Microstructured Anode

www.sigray.com

e-

Diamond Heat Sink

Talk 15: W. Yun

Thank you!

Contact: [email protected]

Picture: NovaledPicture: Fraunhofer IPMS Picture: GLOBALFOUNDRIES

Martin Gall, Jürgen Gluch, Sven Niese *, Kristina Kutukova,

Fraunhofer IKTS Dresden, Germany

• now with AXO Dresden, Germany

Markus Löffler, Technical University Dresden, Germany

Gerd Schneider, Helmholz Zentrum Berlin, Germany

Wening Yun, Sigray Inc. Concord/CA, US

x-ray techniques for 3d metrology and diagnostics...

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