Introduction

OSAKAUNIVERSITY

Conclusion

Results and Discussion

We synthesized positive-tone chemically amplified molecular resist materials based on noria derivatives (noria-CHVEs) and examined their application as EB-resist materials. The sensitivity of these resists was shown to be between 15and 18 mC/cm2 using a 125 keV EB exposure tool. Also, we found that a half pitch of 20-30 nm could be achieved in the caseof 125 keV EB exposure. Although the LWRs of the noria-CHVEs were not superior to that of a polymer resist, theirlithographic performance such as LWR has the potential to be improved by modification of the molecular structure. Also, weexamined the lithographic performances of the noria-CHVEs such as their etch durability and LWR. Their etch durability wasshown to be comparable to that of conventional resist materials such as ZEP520A and UVIII. These results demonstrate thatnoria-CHVEs have excellent potential to be used as chemically amplified molecular resists to meet the requirements of resistsfor next-generation lithography systems.

Reference

Exposure dose40 mC/cm2

Exposure dose100 mC/cm2

Exposure dose200 mC/cm2

500 nm

500 nmLWR: 6.3

500 nmLWR: 7.5

Line 80 nm, Pitch 200 nm

500 nmLWR: 9.5

500 nm

500 nm

500 nm

500 nm

500 nm

Line 40 nm, Pitch 200 nm Line 100 nm, Pitch 200 nm

Line 50 nm, Pitch 200 nm Line 50 nm, Pitch 120 nm Line 30 nm, Pitch 80 nm

Line 50 nm, Pitch 200 nm Line 40 nm, Pitch 100 nm Line 50 nm, Pitch 100 nm

LWR: 11.8

LWR: 10.3

LWR: 21.3 LWR: 7.5 LWR: 5.3

LWR: 22.3

Resist212 mJ/cm2

Resist 31 mJ/cm2

Resist47 mJ/cm2

Resist510 mJ/cm2

Resist 72 mJ/cm2

Resist 640 mJ/cm2Resist 8

11 mJ/cm2

>> >>

>> > =

Resist17 mJ/cm2

Sensitivity

LER

(11 nm)

Shot noiseAcid diffusion

Acid diffusion

Specification of DRAM ½ pitch = sub 10 nm

(5-15 mJ/cm2)

(3s = 0.9 nm)

The trade-off relationship betweensensitivity, resolution and line edgeroughness (LER) is the most seriousproblem in EUV lithography. In particular,LER is the most severe problem in resistmaterials. LER target is set to be 0.9 nmfor 11 nm DRAM half pitch. Thus, novelchemically amplified resist materials mustbe developed to meet the strictrequirement for nanolithography.

32 nm half pitch 11 nm half pitch

The plasma condition :15 sccm of CF4 gas flow

5 sccm of Ar gas flow RF power of 100W

The pressure in the process chamber was 1.0 Pa.

Study on Resist Performance of Noria Derivatives Modified with Various Protection Ratios of Acetal Moieties for EUV lithography

Hiroki Yamamoto1, Hiroto Kudo2, and Takahiro Kozawa1

1The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan2 Materials and Bioengineering, Kansai university,3-3-35, Yamate-cho, Suita, Osaka 564-8680, Japan

hiroki@sanken.osaka-u.ac.jp

Advantage

・Very small molecular size

High resolution

The origins of LER

・ Molecular size・ Molecular dispersion

Molecular resist

・ Small molecular size・ Uniform size・ Developable in TMAH・ Thermal stability・ Etching durability

With the further reduction of featuresizes, LER control requirement approachespolymer size. Therefore, molecular resistswith smaller molecular size are expected asthe next-generation resist materialsbecause they give the possibility forhigher resolution and lower LER.1-3 Also, itis necessary to improve the etch durabilityof the materials in order to use thinnerresist films.

[1] Y. Shirota, J. Mater. Chem. 10 1 (2000). [2] J. Dai et al., Chem. Mater. 18 3404 (2006). [3] T. Tada et al. Jpn. J. Appl. Phys., Part 2 35, L63 (1996). [4] F. Diederich, C. Thilgen, Science 271 317 (1996)[5] M. Yoshiiwa et al. Appl. Phys. Lett. 69, 2605 (1996). [6] J. Fujita et al. Appl. Phys. Lett. 68, 1297 (1996).[7] H. Kudo et al. Angew. Chem. Int. Ed 45 7948 (2006). [8] X. André et al. Proc. SPIE 6519 65194B (2007).[9] H. Kudo and T. Nishikubo: Polym. J. 41 569 (2009). [10] H. Kudo et al. J. Mater. Chem. 18 3588 (2008).[11] H. Kudo et al. J. Photopolym. Sci. Technol. 23(5) 657 (2010). [12] T. Nishikubo et al. J. Photopolym. Sci. Technol. 22 73 (2009). [13] H. Kudo et al. Journal of Materials Chemistry 18, 3588 – 3592 (2008). [14] N. Niina et al. Thin Solid Films 534, 459

Up to now, several different materialshave been investigated molecular resistmaterials. 4-6 Recently, Prof. Kudo succeeded inthe synthesis of a new ladder cyclic oligomernoria7 and noria derivatives.8-14 In previousstudy, we evaluated their lithographicperformance using EUV and EB exposure systemsuch as sensitivity, resolution and LWR in orderto enhance the performance of molecular resistmaterials based on cyclic oligomers. Furthermore,we also examined the etch durability ofsynthesized molecular resist materials．

AcknowledgementsThe authors wish to thank Prof. Tadatomi Nishikubo for his guidance, helpful suggestions, and warm encouragement through their research. Also, this work was partly performed under the Cooperative Research Program "Network Joint Research Center for Materials and Devices". This study was supported by the NIMS Nanofabrication Platform in the Nanotechnology Platform Project sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. It was also supported in part by a Grant-in-Aid for Scientific Research (Project No. 24656447) from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT).

Figure 1. Sensitivity curves of noria derivative resists (Resists 1-4) upon exposure to EB. The noria derivativeresists contain 10 wt% acid generator and no TOA. The postexposure baking (PEB) temperature and time were 90˚C and 60 s, respectively.

Figure 2. SEM micrographs of line and space patterns delineated on Resists 1, 2, 3, and 4. The noria derivative resists contain 10 wt% acid generator and TOA. The postexposure baking (PEB) temperature and time were 90 ˚C and 60 s, respectively.

Figure 3. (a) Estimated etching rates of noria derivative resists (Resists 1-4). The plasma conditions were a 15 sccm CF4 gas flow, a 5 sccm Ar gas flow, and an RF power of 100 W. The pressure in the process chamber was 1.0 Pa.

(b) Relative etching rates of noria derivative resists (Resists 1-4) normalized to that of PHS. PMMA, PHS, ZEP520A, and UVIII were used as reference materials.

Cyclic oligomers

･ Sample

Acid generator

Propyrene glycol methyl ether acetate(PGMEA)

Triphenylsulfonium nonaflate(TPS-nf)

Amine

Trioctylamine

Resist2Resist 3 Resist4

> ≒

Resist1

>

･ Experimental procedureEB exposure

Si

Resist1-4TPS-nfPGMEATOA

125 keV EB (ELIONIX, ELS-F125)

6. SEM observation1. Application 2. Spin coating

（ condition：3000 rpm 30 second ）

3. Exposure 4. Post exposure bake(PEB)

5. Development & Rinse

1. HMDS process

7. Development & Rinse

EUV

EB

8. Film thickness measurement

2. Application 3. Spin coating（ condition：3000 rpm 30 second ）

4. Prebake（ condition：90 ℃ 90 second ）

5. Exposure6. Post exposure bake (PEB)

Resist1-4TPS-nfPGMEA

Experimental

Also, we developed chemicallyamplified molecular resist materialsbased on cyclic oligomers such as noria,calixarene dimer, cyclodextrin, andpillar[5]arene. We clarified a smallmodification of noria resists can causea significant change in sensitivity. Inparticular, protecting groups, such as2-acetyloxy-2-methyladamantyl ester(AD) groups and ethoxy groups, can beused to improve resist sensitivity.

Exposure dose200 mC/cm2

Exposure dose300 mC/cm2

Exposure dose500 mC/cm2

500 nmLWR: 8.4 500 nmLWR: 8.0

LWR: 10.9 500 nm

500 nm

500 nm 500 nm

Line 60 nm, Pitch 200 nm Line 60 nm, Pitch 120 nm Line 80 nm, Pitch 200 nm

Line 20 nm, Pitch 100 nm Line 55 nm, Pitch 150 nm Line 40 nm, Pitch 100 nm

LWR: 6.6 LWR: 6.1

LWR: 21.4

In this study, we have explored theapplication of noria derivatives as high-resolution EUV resists by using EB. To enhancethe performance of molecular resist materialsbased on noria derivatives, we evaluated theirlithographic performances such as resolution andLWR to investigate the response of thederivatives when using EB exposure systems.Furthermore, we also examined the etchingdurability of the resist materials. In particular,we examined the physical properties of noriaderivatives with various protection ratios ofadamantyl ester groups and their patterningproperties as EB resists.

Resolution

Sensitivity

LWR

Etch durability