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Introduction to / Status of Directed Self- Assembly

DSA Workshop, Kobe Japan, October 2010

Bill Hinsberg

IBM Almaden

Research CenterSan Jose CA 95120

[email protected]

Introduction to / Status of Directed Self-Assembly

Hinsberg / IBM Almaden Research Center DSA Workshop, Kobe Japan, October 20102

from “Bringing New Materials to Market,” ,TW Eagar, Technology Review Feb/Mar 1995, p 43

Poor communication between inventors and product designers

Inadequate/immature materials supply and production capacity

Inadequate economic incentives for user or supplier

Inflexible codes and standards

The commercialization of new materials technologies is slowed by

Twenty years from invention to commercialization…Materials Technology Date of Invention Widespread commercializationVulcanized rubber 1839 Late 1850s

Low cost aluminum 1886 Early 1900s

Teflon 1938 Early 1960s

Titanium as a structural mat’l. Mid 1940s Mid 1960s

Velcro Early1950s Early 1970s

Poly(carbonate) 1953 ~ 1970

Gallium arsenide mid 1960s Mid 1980s

Diamond-like carbon films Early 1970s Early 1990s



Outline

What is Self-assembly?What is Directed

Self-assembly?

My assessment of –Current status

–Near-term and mid-term needs

–What might a first application of DSA look like

–What might a 2nd

generation application of DSA be?



Self-assemblySpontaneous, reversible transformation of a disorganized system into regular structures or patterns

Controlled by weak interactions (van der

Waals, capillary, π − π, hydrogen bonds)

Molecular properties are important

Outcome typically controlled by thermodynamic equilibria

dimensions controlled by molecular size, magnitude of weak interactions

in contrast to microlithography…Transfer of an existing pattern into a recording medium

Controlled by strong forces (covalent bond formation/fragmentation

Properties of specific bonds are important

Outcome typically controlled by kinetics

dimensions controlled by length scales of energy deposition and kinetic processes



Biological / bio-inspired –

assembly using biomolecules

(DNA, proteins, phage-virus)

–

nanomedicine, devices, structural materials

Polymer –

block copolymers, phase separated polymers–

patterning, structured materials

Layer-by-layer –

Self-assembled monolayers–

sequential deposition of alternating layers–

bio/medical, sensors, optical devices, solar cells

Nanoparticle–

assembly can be mediated by small molecules, biomolecules, polymers, topography

–

magnetic composites, electronic devices, catalysis

DNA nanostructures

(N. Seeman / NYU)

Templated

assembly (Xia/ U Washington)

Ultrastrong

polymer

composites (Kotov/UM)

“knitting pattern”

in ABC triblock

copolymer

(Stadler/Gutenberg U)

Taxonomy of self-assembly



Block copolymer self-assembly

Block copolymers in wide commercial use (e.g. adhesives, coatings)

repulsion between dissimilar polymer chains drives microphase

separation

Pros : sublithographic

patterns, high feature density, dimensions controlled by chemical synthesis

Cons: limited pattern types, random orientation, poor long-range order

Poly-A

Poly-B

where χ

= interaction parameter

even slightly unfavorable interactioncauses phase separation



Directed

Block copolymer self-assembly

Bottom-upSelf-assembling

material

Top-down Lithographically

patterned substrate

Limited spatial resolution

Large CD variation

+

High spatial resolution

No placement control

Directed Self- assembly

=

Enhanced resolution

Reduced CD variation



Two approaches to orientation control

Segalman

et al, Adv. Mater., 13, 1152 (2001) Cheng et al, Appl. Phys. Lett., 81, 3657 (2002)Sundrani

et al., Nano Lett., 4, 273 (2004)

selective surface modification

neutral substrate surface

Rockford et al., Phys. Rev. Lett., 82, 2602 (1999)Kim et al., Nature, 424, 411 (2003)

On topographic patterns : graphoepitaxy

On surface patterns: chemical epitaxy





BCP DSA on Topographical Patterns

DSA Subdividing the trench

Cross-barStructures

Via Shrink andrectification

DSA

DSA

Guiding Lines

Organosilicate

PS-b-PEO/MSSQ

DSA on 193 nm resist Wresist = 375nm, PSA =25nm

15X Subdivision

DSA



BCP DSA on Chemical Patterns

80 nm

10

20

193 nm litho to form guide pattern

Apply BCP anneal and develop

Form trim mask by 193 nm litho,And dry etch to substrate

Strip

193 nm resist: 100 nm pitch

DSA: 25 nm pitch

NeutralizeLiftoffDSAEtch



Attributes of BCP DSA

an adjunct/assist to conventional litho practice–Pattern subdivision process analogous to sidewall image transfer

– trim mask, single CD available–Via process shares analogous to chemical shrink processes (“smart”

shrink)

able to extend capabilities of current (and future) lithographic technologies–Sublithographic

dimensions, tighten dimensional tolerances, defect reduction

Not universally applicable

Characteristics of DSA must be accounted for early in design cycle

mask design must be “DSA-aware”



Status of BCP DSA

Several process approaches have been demonstrated

compatibility with 193 nm lithographic materials established

compatible process times and coating solvents are demonstrated

PS-PMMA has been focus for process development

Staged for practical demonstrations



Near term needs for BCP DSA…

Identification and specification of initial applications by end-users

detailed examination of integration issues

Chip-scale and wafer-scale characterization in a fab

environment of CD uniformity, placement accuracy, defects, LER

Mid term …

broadening scope of application

extendibility -

smaller dimensions

improved materials –

block copolymers, surface control layers, guide pattern materials



Some candidates for first practical application of DSALamellar patterns

DSA

Multifingered

devices (Nanowire

arrays, FinFET)

Regularized patterns/gratings

Via shrink/rectification

Bit-patterned media

Cylindrical patterns

What else?

Specific target : dimensions, materials, insertion point

What are the benefits and shortcomings?

What still needs to happen to enable?

Keep in mind during the day



Potential candidates for 2nd generation applications of DSA

Multiple levels of DSA : pattern-to-pattern alignment

Complex DSA patterns : bends, jogs, tees

Imageable

BCP films

Direct patterning of device structures

Specific targets

What else?

Advantages and issues

What still needs to happen to enable these?

Keep in mind during the day



Today’s workshop

Broad spectrum of research will be described

Emphasis on BCP DSA but other forms of DSA are to be discussed

Diverse range of participants : research, tooling and materials suppliers, end-users offer a range of perspectives

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