1

A simulation analysis on defect annihilation

in directed self-assembly lithography

Katsuyoshi Kodera, Hideki Kanai, Yuriko Seino, Hironobu Sato, Yusuke Kasahara, Katsutoshi Kobayashi, Hiroshi Kubota, Naoko Kihara, Yoshiaki Kawamonzen, Shinya Minegishi, Ken Miyagi, Toshikatsu Tobana, Masayuki Shiraishi, Satoshi Nomura and Tsukasa Azuma

EUVL Infrastructure Development Center

A part of this work was funded by the New Energy and Industrial Technology Development Organization (NEDO) of Japan under the EIDEC project.

2

Original simple HP 15nm L/S patterning process using PS-b-PMMA

PS short and dislocation defects are observed at the wafer center and edge after SOG etch.

average (3σ )CD (nm) 16.9 (4 .6)LWR (nm) 4.8 (1 .3)LER (nm) 3.7 (1 .5)

85 chips / waferPS short defect

6 chips (7%)

Dislocation defect

8 chips (9%)

71 chips (84%)

500 nm

OK chip

Y. Seino et al., MNE 2014

3

Outline

Grid defects Experimental behavior Simulation results acquired using

self-consistent field theory(SCFT) Simulation results acquired using

dissipative particle dynamics (DPD)

Dislocation defects

Summary

4

Outline

Grid defects Experimental behavior Simulation results acquired using

self-consistent field theory(SCFT) Simulation results acquired using

dissipative particle dynamics (DPD)

Dislocation defects

Summary

5

Characteristic DSA Defect (Grid defect)

grid

defects

short

defects

short

defects L/S with

roughness

fine L/S L/S with

roughness

open

defects

Dry development or SOG RIE Small Large

Although most of these grid defects disappeared after SOG full etching, they

could result in the degradation of etching process margin, and therefore, in line

edge roughness and open/short defects

microphase

separation dry development (PMMA removed)

SOG etched shallowly SOG full etch

PMMA PS

SOG SOC

resist PS

Grid defect

* SOG: Spin On Glass,SOC: Spin On Carbon

Seino, MNE2014

Sato, MRS2014

Kasahara, SPIE2015.

• Guide:

Width=0.5𝐿0

Pitch=3𝐿0

6

Process condition dependence

• Grid defects can be decreased with optimum neutral layer and sufficient

phase separation annealing.

• The subtle adjustment of the neutral layer toward a more neutral condition

results in the decrease of the grid defects.

250℃ 2 min 250℃ 30 min 270℃ 30 min

* contact angle: 84°

200n

m

Annealing condition dependence

Neutral layer: contact angle dependence

200

nm

Contact angle: 80.5° Contact angle: 81.9°

Contact angle: 84.4°

PS affinity PMMA

affinity

Y. Seino, MNE2014

7

Simulation model

top(air)

bottom Pinning

film thickness=1.5𝐿0

pinning height=0.68𝐿0 pinning width=0.5𝐿0 pinning period=3𝐿0

periodic condition

1.7𝐿0

• SCF simulation, masking method • BCP : 𝜒𝑁 = 20 , 𝐿0 = 30 nm (PS-b-PMMA) • top: neutral (𝜒𝑃𝑀𝑀𝐴−𝑡𝑜𝑝 = 2, 𝜒𝑃𝑆−𝑡𝑜𝑝 = 2)

• pinning: PMMA attractive (𝜒𝑃𝑀𝑀𝐴−𝑃𝐼𝑁 = 1, 𝜒𝑃𝑆−𝑃𝐼𝑁 = 2) • bottom: PMMA attractive (𝜒𝑃𝑀𝑀𝐴−𝐵𝑇𝑀 = 1.3, 𝜒𝑃𝑆−𝐵𝑇𝑀 = 2)

8

Grid defect as metastable morphology Vertical Lamellar(V L) Grid Defect (GD) Mixed lamellar (ML)

Side view

Top-down

pinning pinning pinning

3 stable/metastable morphologies including grid defect were acquired using SCFT.

most stable

quasi-hexagonal buried structures

9

Stability of grid defects

𝜒𝑃𝑀𝑀𝐴−𝐵𝑇𝑀

Fre

e e

nerg

y Δ𝐹

-0.001

-0.0005

0

0.0005

0.001

0.0015

0 0.5 1 1.5 2 2.5

GD

ML

VL

Vertical lamellar state is the most stable

Mixed lamellar state is the most stable

PMMA attractive neutral

• These simulation results agree with the experimental behavior.

mixed lamellar

grid defect

vertical lamellar

10

Conformation of BCP chains

(a)PMMA chain is parallel to the bottom.

(b) PMMA chain is vertical to the bottom

𝑛0~𝑛5

𝑛0 > 𝑛5, 𝑛9

terminal

center

junction

𝑛0

𝑛5

𝑛9

Neutral layer（PMMA-attractive bottom）

PMMA

We can acquire the information of the polymer chain conformation by evaluating n0, n5 and n9 immediately above the bottom.

11

Conformation of BCP chain (GD-state)

0

0.2

0.4

0.6

0.8

1

0 0.5 1 1.5 2 2.5 3

n0 n5

n9 nPMMA

Densi

ty

Position (𝐿0) 𝑛0 > 𝑛5, 𝑛9 immediately above the bottom

𝑛0

𝑛5

𝑛9

PMMA

𝑛0

𝑛9

𝑛5

𝑛𝑀𝑀𝐴

12

Conformation of BCP chain (GD-state)

Parallel BCP chains

Vertical PMMA blocks

Parallel PMMA blocks

PMMA blocks are nearly vertical to the bottom in the region where the vertical PMMA lamellar patterns are connected toward the bottom. This characteristic conformation of BCP chains is considered to be related with the origin of the grid defects.

中性化膜に対して垂直 Vertical PMMA blocks

↑Top-down

13

Node density biased MC method

GD-state

terminal segment

junction segment

・・・・・

Field model particle model

Computer Physics Communications 145 267-279.

• The segment density distribution acquired using SCFT was transformed into the atomic representation using the node density biased MC method.

• Using this atomic representation as initial chain conformations, we executed DPD simulations and investigated the defect annihilation dynamics.

14

DPD simulation results

Firstly, grid defects were observed. And finally, the grid defects disappeared and the simulation converged into the equilibrium lamellar state.

15

Defect annihilation dynamics

Polymer chains are partially vertical.

Polymer chains are parallel

Both vertically and horizontally oriented polymer chains appeared randomly.

The polymer chains flipped down and flopped up randomly

(b)1000 steps (Transient state)

(c)10000 steps (Equilibrium lamellar)

(a)Initial state (GD state)

Vertically oriented

horizontally oriented

The defect annihilation dynamics of the grid defects could be understood as the change of the orientation of the BCP chains.

16

Outline

Grid defects Experimental behavior Simulation results acquired using

self-consistent field theory(SCFT) Simulation results acquired using

dissipative particle dynamics (DPD)

Dislocation defects

Summary

17

Polymer conformation in dislocation defects

𝑛𝑐𝑒𝑛𝑡𝑒𝑟 =Segment density distribution of the center node 𝑛𝑡𝑒𝑟𝑚𝑖𝑛𝑎𝑙 =Segment density distribution of the terminal node

Center node Terminal node

Single dislocation

Double dislocation

Perfect state

Self-consistent field theory

𝑛𝑐𝑒𝑛𝑡𝑒𝑟 − 𝑛𝑡𝑒𝑟𝑚𝑖𝑛𝑎𝑙

18

Polymer conformation in dislocation defects

Terminal segment density is larger than the center segment density.

Terminal segment density is larger than the center segment density.

Terminal segment is localized in a specific region. The delocalization of the terminal segments is effective for defect mitigation.

19

Summary

• We have investigated the conformations of

the polymer chains in “grid defects” and

“dislocation defects”.

• In both defective states, polymer chain

conformations were found to play an

important role in formation of the defective

states.

• For practical application, it is important to

understand the origin of the defective states

more. We need the corporation of the

simulation people more and more…!