NSF GOALI Interactions of Plasmas/Energetic Beams with Organic Masking Materials

G. Oehrlein, D. Graves and E. Hudson DMR  - 0406120

Fig 1: Simplified schematic of problem of fabricatingnanosctructures using organic imaging materials and plasma etch for pattern transfer.

O

CH2

20C

C

O

O

CH2C

C

O

O

CH2

40C

CH3

O

40

CH3 CH3

OHO

O

MAMA

Fig. 3: Chemical structure of one model compound employed in this work, with special functional groups marked.

Model Compound Approach:Study impact of different polymer backbones/endgroups on etch and morphological stability in plasma/beam environment to identify molecular design factors required for etch and morphological stability

Fig. 2: Resists after plasma etch showingsurface/line edge roughness incompatiblewith nanoscale manufacturing

NSF GOALI Interactions of Plasmas/Energetic Beams with Organic Masking Materials

G. Oehrlein, D. Graves and E. Hudson DMR  - 0406120

0 10 20 30 40 50 60 70 80 901.30

1.35

1.40

1.45

1.50

1.55

1.60

1.65

1.70

dam

aged

laye

r re

frac

tive

inde

x

exposed time (s)

0

1

2

3

4

5

6

7

8

9

10

11

12

RM

S ro

ughn

ess

(nm

)

YB-27C

refractive index forundamaged compound

We investigate the interaction of well characterized and controlled plasmas and energetic particle beams with completely specified and flexible model compounds as well as fully developed photoresist systems to establish the key factors that give rise to surface and line edge roughening for nanoscale patterning.

Figs. 4 and 5 show changes of the optical properties and surface roughness of photoresist systems/model compounds upon plasma exposure. All materials show modifications after a few seconds of exposure consisting of densification followed by surface roughening. Introduction of surface roughness depends strongly on the nature of the polymer backbone/ endgroups.

248 nm photoresistRMS = 4.5 nmAfter 60 s exposure

193 nm photoresistRMS = 11.5 nmAfter 60 s exposure

Fig. 4: Refractive index evolution for photoresist systemsduring 60 s of plasma exposure and AFM images after 60 s.

Completely Formulated Photoresists

Model Compound

O

CH2

20C

C

O

O

CH2C

C

O

O

CH2

40C

H

O

40

CH3 CH3

OHO

O

acrylate

Fig. 5: Refractive index and AFM roughness evolution for one model compound.

Fig. 6: Chemical structure of compound YB-27C used for Fig. 5.

A first insight from comparison of different model compounds: Acrylate content (Fig. 6) improves plasma stability (Fig. 5).

0 10 20 30 40 50 601.0

1.2

1.4

1.6

1.8

2.0

dam

aged

laye

r re

frac

tive

inde

x

exposed time (s)

193 nm248 nm

248 nm undamaged

193 nm undamaged

NSF GOALI Interactions of Plasmas/Energetic Beams with Organic Masking Materials

G. Oehrlein, D. Graves and E. Hudson DMR  - 0406120 Fig. 7: Morphologies of advanced photoresist materials and model

compounds are unstable when exposed to fluorinating environment in a commercial etch reactor. Severe surface roughening is related to formation of wiggly lines with uniform width (seen for YB-27B). Without optimization of the resist systems, these wiggly lines get transferred to underlying layers resulting in unsatisfactory performance of nanoscale devices.

Similar materials modifications effects have been observed upon exposure to energetic ion beams but not after exposure to radical beams.

Material modifications can be observed by FTIR (Fig. 8), and time-of-flight SIMS.

These insights and model compound approach enables rational design of photoresists with improved morphological stability.

Broader impact Participation of Lam Research and Rohm & Haas add critical scientific,

technical and industrial expertise to this project which strongly increases the technical relevance of this work, enhances development of new photoresist materials and insures impact on industrial plasma processing.

The collaboration of the industrial partners exposes the university research groups, especially the students performing the research, to a realistic research experience that is fast-paced to impact industry in real time, and informed by commercial needs, industrial environments and approaches. This enables a unique educational and research experience. The methodologies and scientifically complex but at same time highly practical knowledge created in this project benefit all participants, the university environments and the larger technical community.

Fig. 7: SEM image of compound YB-27B after ~60s of dielectric etch processing in a commercial reactor.

Fig. 8: Normalized FT-IR spectra of C-H stretch region for compound YB-27C after 1 and 2 min. exposure to dielectric etch processing in a commercial reactor.

not an optimized process

NSF GOALI Interactions of Plasmas/Energetic Beams with Organic Masking Materials

G. Oehrlein, D. Graves and E. Hudson DMR  - 0406120

Photograph on Top: Graduate student Sebastian Engelmann discusses with undergraduate students Brian Smith and Michael Figueroa – all Materials Science and Engineering, University of Maryland, College Park - results that he has obtained in his research. Brian Smith and Michael Figuero began participating in the NSF funded research in 2005, and plan to actively contribute to the research on this topic during the final two years of their undergraduate program.

Photograph at Left: Graduate student Sebastian Engelmann working on an ultra-high vacuum surface analysis system used to characterize organic masking materials after plasma processing, while undergraduate student Brian Smith watches.