• Doctoral research performed at the Department of Materials Science and Engineering at the University of Illinois at Urbana-Champaign, in collaboration with chemistry students in Dr. Gregory S. Girolami’s research group

Amount of assumed background knowledge and information:

Assumed knowledge areas: Basic chemistry and physics

Doctoral Research Overview

Teresa S. Spicer, PhD, PMPteresa.s.spicer@gmail.comhttp://www.linkedin.com/in/teresaspicer

Outline

Why are new ways of making thin layers of materials important?

Key findings

What is chemical vapor deposition?

What needs figuring out?

Why are new ways of making thin layers of materials important?

Integrated circuits have created a vital industry and enabled the telecommunications revolution

Semiconductor industry plays an important role in globalization, and therefore also in shaping our collective future.

Global Semiconductors Market Value, $ billion, 2004-2013(e)

Source: Datamonitor

J

J

J

J

J

J

J JJ

2004 2005 2006 2007 2008 2009 2010 2011 2012 2013

0

50

100

150

200

250

300

350

0

1

2

3

4

5

6

7

8

9

Mark

et

valu

e (

US

D b

illio

ns)

% G

row

th

Image from http://www.textually.org/

Miniaturization drives integrated circuit development and applications

Image from http://tunicca.wordpress.com/2009/07/21/moores-law-the-effect-on-productivity/

Integrated circuits are made layer by layer by depositing thin layers or films of materials

Every material needed for an integrated circuit needs to be deposited as a thin film.

http://www.rigalab.com/Images/cross_section.jpg

webmedia.national.com/ gallery/52/52_rgb.jpg

Materials and thin film processing are key to miniaturization

In order to continue making smaller chips, thin films of new materials are required.

2007: 30 new materials introduced into 45-nm node1

1 A Thorough Examination of the Electronic Chemicals and Materials Markets, Businesswire, August 15, 2007 Image from http://www.intel.com/pressroom/kits/45nm/photos.htm

❝The implementation of high-k and metal materials marks the biggest change in transistor technology

since the introduction of polysilicon gate MOS transistors in the late

1960s.❞Gordon Moore, Intel Co-Founder, regarding two of the 30

new materials introduced in 2007

What is chemical vapor deposition?

What is Chemical Vapor Deposition?

Substrate Thermometer

Chemical Vapor Deposition (CVD) is a way of growing thin layers of materials, also called films.

1 2Chemicalreaction

3 4 5

A main starting molecule, called

precursor, arrives at the hot growth

surface, the substrate, inside a vacuum

chamber.

The precursor molecule may ‘meet’ another molecule it

needs to react, called a reactant.

The precursor and reactant react.

Sometimes the warm surface alone can cause this step by

making the precursor decompose.

New molecules are now attached to the

substrate, one of which is hopefully the material we wanted to

grow.

Whatever isn’t the film leaves the surface.

Here we are growing a film of purple balls rather than green.

Substrate

Precursor

Precursor Reactant Atom of filmVolatile product Atom of film

A substrate up close, outside the chamber.

What needs figuring out?

The two major constraints for circuits are temperature and obtaining uniform coatings

Deep features need coating, but this is difficult to do evenly

Si Dopants

Si Dopants

Δ

http://www.pressebox.de/pressemeldungen/infineon-technologies-ag/boxid-28544.html

If dopants do not stay where they were put, the chips cease

to function.

Dopants diffuse with heat

How do you deposit the films at low temperature and do it evenly?

Deep holes need uniform coatings, but this is often slow

Pinch-off.

Conformal coating.

Conformal coating, but slow growth.

The ideal: completely uniform (conformal), fast coating.

Conformality = (ttop/tbottom)·100%

The problem: the hole ‘clogs’ at the top - pinch-off.

The impractical compromise: grow slowly so that the hole doesn’t have time to pinch off.

An opportunity exists to find a process that is fast but retains the uniformity of the coating.

} ttop

} tbottom

If the incoming molecules do not stick where they land first, conformality is possible

If the incoming molecules don’t stick immediately, coatings are more likely to be uniform.

The deposited atoms quickly

cause pinch-off.

High sticking probability Low sticking probability

Precursor molecules react or stick nearly

instantly

Precursor molecules bounce off the walls into

the trench.

Nearly conformal coverage.

Traditional CVD has a high reaction probability

Traditional CVD (at high temperatures)

Ru

C

O

C

O

CO

Traditional CVD often leads to pinch-off.

Ru

C

O

C

O

C

OC

O

CO

C

O

Ru

With the right starting molecule, temperatures can be kept low and improve the conformality

Si Dopants

Si Dopants

Dopants diffuse, ruining chip

CO

COC

O

Ru

High temperatures

Low temperature

Incoming molecules react as soon as they reach the surface, causing pinch-off

Dopants stayIncoming molecules do not react immediately enabling conformality

Precursor design is key to novel CVD process development

Enhance CVD conformality:

Low sticking probability

Precursor molecules bounce off the walls into

the trench.

Nearly conformal coverage.

Appropriate precursor stability:

Stable during handling

Reactive at low T

M LL

M

L

L M

Competitive advantage: collaboration with the Girolami chemistry group

State of the art analysis techniques at the Center of Microanalysis of Materials

Girolami group: Innovative new chemistry

Abelson group: State of the art vacuum chamber for growth

Key finding

Precursor design is key to novel CVD process development

Choose ligands purposefully: Ruthenium project

Siteblocking by ligands

Choose clever co-reactant: Manganese nitride project

Lability enables low-T CVD

+ NH3

+

Mn

t-Bu

N

t-Bu

t-Bu

t-Bu

N

H

H

Mn N

t-Bu

N

t-Bu

H

t-Bu

t-Bu

N

80 ºC and up

Ru

C

O

C

OC O

L L L