"Influence of Stereochemistry on Radiation-Induced Structural ...

1 downloads 0 Views 360KB Size Report
Jun 3, 1994 - J. A. Moore and Jin 0 Choi. To Be Published ... United States Government. This document .... On formation of vinylidene groups v) in the model.
Office of Naval ResearchContract N0014-85-K-0632

10

R & TCode 413c014 Technical Report No.. 18

N N

"INFLUENCE OF STEREOCHEMISTRY ON RADIATION-INDUCED STRUCTURAL CHANGES IN PMMA"

by J. A. Moore and Jin 0 Choi

To Be Published in Polymer Preprints, Fall 1990 ACS Meeting Washington, DC Department of Chemistry Rensselaer Polytechnic Institute Troy, New York 12180-3590 .. ...

JUN May 31, 1990

W c~w"r' -. A .4

3 1994~

,

Reproduction in whole or in part is permitted for any purpose of the United States Government. This document has- been approved for public release and sale; its distribution is unlimited.,

. ... . . -

--

°--

0.

*'Jnclassif-ied

%j:YCLASSIFICA7ION OF THIS PAGE

REPORT DOCUMENTATION PAGE lb. RESTRICTIVE MARKCINGS

Ia.-REPORT SECURITY CLASSIFICATION

Unclassified_______________________ 3. DISTRIBUTION I AVAILABILITY OF REPOR

2a. SECURITY CLASSIFICATION AUTHORITY

Approved for public release distribution

unl'imi ted.

2b. DECI SSIFICATIONIDowNGRADING SCHEDULE 4. PERFORMING ORGANIZATION REPORT NUMBER(S)

5. MONITORING ORGANIZATION REPORT NUMBER(S)

j

r6b.

68. NAME OF PERFORMING ORGANIZATION

OFFICE SYMBOL

(if appkiable)

7a. NAME OF MONITORING ORGANIZATION

ON R 7b. 'ADDRESS (City. State, and ZIP Code)

6c. ADDRESS (City. State, and ZIP Code)

Department of Navy Arlington, VA 22217 Ba. %AME OF FUNDING!-SPONSORING

1 8b.

OFFICE SYMBOL

Sc. ADDRESS (City. State, and ZIP Code)

9. PROCUREMENT INSTRUMENT IDENTIFICATION NUMBOR

10. SOURCE OF FUNDING NUMBERS ITASK PROJECT PROGRAM .ELEMENT NO. INO. NO

Department of Navy Arlington, VA 222,17

g-OO014-85-K 0632

IWORK UNIT

IACCESSION

NO

625-826

11 T TLE (include Security Clazification)

TECH.

(Unclassified) REP #'18 INFLUENCE OF STEROCHEMISTRY ON RADIATION- INDUCED STRUCTURAL CHANGES IN PMM.

12 P:ERSONAL AUTHOR(S)

J.A. MOORE* AND JIN 0 CHOI 113b. TIME COVER-ED 14. DATE OF REPORT (Year, Month, Day)

13a. TYPE OF REPORT

I

Publication

e''

POLYMER PREPRINTS, POLYMER DIV./A4ER. CHEM. SOC. 17. OSAI COES FIELD

GROUP

SUB-GROUP

15S.PAGE ZOUNT

____

§.,SUBCT TRMS(Continue on reverse if ne~ess iy and idenify' by block numbe

Ho iyro

AM

:rraic4mon u LcA'm

mIl4\ctec rve &"\f teDc44

A

tzkJ-

V)r, G &QeC

ABSTRACT (Continue on revpf-eit ' necesiry and identify by block number)

We have been studying the effeihs of radiation on poly(methylmethacrylate), PMNA, which has been used as a resist in computer hip microlithography. In contrast to predictions based on solution photochemistry of related-compounds we have found by careful spectroscopic study of the irradiated polymer leads to four diffterent kinds of~double bonds. These ester cleavage reactions do not necessarily lead to ruueof the backbone, a necessary condition foreffciet ue a a esit. We find evidence thZ&p only does the state (solution vs film) upon which irradiation is carried out affec tepductdstributin bualoht the stereochemistry of PMMA (atactic vs. isotactic) plays a role2

20 DiSTRIBUTION/~AVAILABILITY OF ABSTRACT JUNCLASSIFIEDIUNLIMITED C SAME AS RPT, 22a NqAME OF RESPONSIBLE INDIVIDUAL

Kenneth J. Wynne DO FORM 1473,84MAR

21 ABSTRACT SECURITY CLASS IFICATION QO TIC USERS

Unclassified 22b. TELEPHONE (Include Area oe

22c. OFFICE SYMBOL

(202) 696-4410 83 APR edition may be used untilexhausted.

All other ecitions are obsolete.

__SECURITY

CLASSIFICATION OF THIS PAGE

ricasifie

UV Irradiations and Structural Analysis A

INFLUENCE OF STEREOCHEMISTRY CTURAL CHANGES ON RADIATION-INDUCED STRU IN PMMA

PMMA samples were exposed to light from a high pressure. 500 W. mercury-xenon lamp without a filter, ina air. The Intensity of UV light was measured with Black-RayR shortwave ultraviolet Intensity meter J-225 (UVP. Inc.. CA).

by J. A. Moore' and Jin-O Choifa -of Chiy nd a J. Morep Rensselaer Polftechnic Institute

Irradiated PMMA samples on silicone waters were: dissolved in CDCI3 and analyzed with a Varian 200 MHz: proton magnetic resonance spectrometer (XL-200). From the 1H NMR peak intensities of PMMA. which was studied. 6 the content of rr. mr. mm triad sequences in Du Pont Elvacite 2041 was 63. 33. and 4 %. and for isotactic PMMA (Polysciences. Inc.) was 9. 21. and 70 %.i

Troy. NY'12180-3590 INTRODUCTION Exposure of polv(methyl methacrylate). PMMA. to radiation sources such as ultraviolet. x-ray. electron1 and 2 weight. the reduced molecular proton beams of the generation gaseousin products. of results evolution

respectively.

3 unsaturated bonds'by the scission -of side chains. . 4 and spectra spin electron the appearence of the characteristic of radicals. 2 ' 5 These changes in PMMA films caused by iradiation with these sources increase the-solubility in the exposed area. permitting PMMA to be used as a resist in advanced microlithography. The chemical changes in irradiated PMMA films as chromatography. by gel permeation measured

program employing MM2 on a MicroVax the Macromodel 7 II computer.

Fourier-transformed infrared and UV spectroscopies demonstrated a 1:1 correspondence between the disapperance of ester groups and the generation of double bonds in the polymer chain by UV and high energy radiations (x-ray. electron and proton beams). The comparison of the ratio-of main chain scission to changes in the number of ester groups indicated that high energy radiation was about 10 times more efficient than deep UV in causing main chain scission with less ester group removal. The unsaturated bonds associated with mainl chain scission were much more pronounced in the IH 4 NMR spectra of PMMA exposed to high energy radiations.

abstraction of a primary methyl hydrogen atom by an acyl fragment to yield vinylidene groups without main chain scission. 3 This behavior is particularly apparent for UV irradiation where 90 % of the cleavage of methyl ester side chains is associated with the generation of vinylidene groups in the main chain despite the fact that reaction at the methylene sites isfavored on enthalpic and statistical, grounds.

of model isomers stable most for The withl deter-mined of MMA units were triadsconformational compounds

RESULTS AND DISCUSSION The characterization of unsaturated bonds generated in 1 irradiated atactic PMMA films by H NMR indicated that the major process leading to carbon double bonds is

On formation of vinylidene groups v) in the model sequences, the triad units, rr. mm and mr. give rise to two different types of segments trv and mv) as shown in Scheme 1. In 1 H NMR spectra of the UV-irradiated atatic PMMA (Figure 1). the new peaks appear at 0.95 and 1.14 ppm. The relative height of these two peaks is approximately the same as the ratio of rr+mr/2 to mm+mr/2 triad contents, assuming that the mr triad has the same possibility to form mv or rv segments. These two peaks are assigned to a-methyl groups next to vinylidene' groups: rv at 0.95 ppm and mv at 1.14 ppm.

In this work. we extend the analysis of our earlier results to include examination of the changes in the, stereochemical triad sequences- in the UV-irradiated PMMA In addition, structural changes in isotactic PMMA films and solutions of atactic PMMA by UV-exposures are reported. EXPERIMENTAL

!

Materials and Sample Preparation 2041. was purified byf Atactic PMMA. Du Pont Elvacite reprecipitauon from toluene into methanol and dried in a (Mn = 176x 10~5 g/mole from GPO vacuum oven measurements with polystyrene reference standards). 4 g/mole. Folysciences. Isotactlc PMMA (Mv = 2 5 x×i0 Chlorobenzenc. purificailon. any Inc ) was used without methylene chloride and acetonitrile (HPLC grade) were used for the preparation of PMMA solutions. PMMA was spin-coated onto silicone dissolved in chlorobenzene and 0 wafers and then baked at 150 C for 30 minutes to remove solvents completely.

Present address: IBM Corp.. East Flshklll Facility Hopewell Junction, NY 12533-0999

I

In the most stable conformational isomers of the PMMA triad model compounds calculated with the Macromodel• program. 7 the hydrogen atoms of the a-methyl group arel much closer to carbonyl oxygen atom than to located mr triad the rr and those of the methylene group in 96% in atactic PMMA, sequences, the content of which is This result may be one reason that the vinylidene group is C the major segment produced in the UV-irradiated atactic PMMA film. Ih the structure of the mm triad model at the minimum energy state in the MM2 program. the carbonyl ,i oxygen atom is positioned closei to the methylene hydrogen atoms than to the a-methyl hydrogen atoms. The r amplified NMR spectra of UV-irradiated isotactic PMMA (Figure 2) shows several resonances of hydrogen atoms on unsaturated bonds with peaks appearing at 4.4-5.4 ppm. which are very similar to those in atactic samples. and the other peaks at 5.5-6.5 ppm are believed to originate from the degradation of Isotactic segments.

a

K

When a solution of atactic PMMA in methylene chloride or acetonitrile was exposed to UV light, hydrogen atoms on unsaturated bonds, which are different from those, generated in solid films, appeared in the 1H NMR spectrum (Figure 2). This large difference may be explained by the fact that the degradation reaction occurs' in a cage in the solid film at the most stable, conformational structures. On the other hand. in solution. the cage effect and the probability of the degradation: reaction occuring in the most stable conformational state-

I'

J

is expected to be much d~nminshed.

REFERENCES

M

-

1C. G. Willson. in Introduction to Microlithography.l,

2. H. Hiraoka. IBM J. Res. Dev.. 21. 121 (1977). 3. J. 0. Choi. J. A. Moore. J. C. Corelli. J. P. Silverman and. H. Bakhru. J. Vac. Sci. Technol. B6(6). 2286 (1988).

(1989). 4. J. A. Moore and J. 0. Choi. Polymer Preprints. 30. 335 5. R. M. Tarro. J. T. Warden. J. C. Corelli. J. A. Moore. A. J. Steckl. and S. Kumar. Microcircuit Engineering 84. edited by A. Heuberger and H. Beneking (Academic Press. London). 1985. p. 537. 6. F. Bovey. Accounts Chem. Res.. 1. 175 (1968). 7. U. Burkert and N. L. Allinger. Molecular Mechanics. ACS Monograph 177. Washington. D. C.. 1982.

0

o~'~~~

o

',\ mm

D

, ,

'

-

l

hM

0.6

"l. I

, '

-

.... Figure 1.

1

.

'

:

H NMR Spectra (x3) of UV-Irradiated Atactic PMMA

ISOTACTIC PMMA FILM '.2 J/cm ,

/

myv

7.2 I/aii2

IyI

edited by L. F. Thompson. C. G Willson and M. J.1 Bowden. ACS Symposium Series #219. Americani

ISOTACTIC P.M..A

A

UM,

2

42A111'Cm )

A-\,Z

-It.:. 1y

I mr

vr

". ,"p!° 4

'//

ATACTIC

,

+

. %. . ?'.

o rr

I

PMMA SOLUTION in CII2CI2 (3 Y=2m)

[

.

iry 2,ATACTIC

PMMA FILM

Scheme 1. a-Methyl Groups in the Triad Sequences of Irradiated PMMA

6.5

6.2

"

.

,

,0., 5

Figure 2. 1H NMR Spectra (x25) of UV-Irradiated PMMA

7_

TECHNICAL REPORT DISTRIBUTION LIST

-

GENERAL

(2) Office of Naval Research Chemistry Division, Code 1113 800 North Quincy Street Arlington, Virginia 22217-5000

Dr. Robert Green, Director (1) Chemistry Division, Code 385 Naval Weapons Center China Lake, CA 93555-6001

(1) Commanding Officer Naval Weapons Suppoft Center Dr. Bernard E. Douda Crane, Indiana 47522-5050

(1) Chief of Naval Research Special Assistant for Marine Corps Matters Code OOMC 80&r-North Quincy Street Arlington,. V, - 222179000

(1)

(1) Dr. Bernadette Eichinger Systems Engineering Naval Ship Station Code 053 Philadelphia Naval Base Philadelphia, PA 19112

Dr. Richard W. Drisko Naval Civil Engineering Laboratory Code L52 Port Hueneme, CA 93043

David Taylor Research Center (1) Dr. Eugene C. Fischer Annapolis, MD 21402-5067

Dr. Sachio Yamamoto Naval Ocean Systems Center Code, 52 San Diego, CA 92152-5000

(M)

, 'I%

(1) Dr. James S. Murday Chemistry Division, Code 6100 Naval Research Laboratory Washington, D.C. 20375-5000

(1) Dr. Harold H. Singerman David Taylor Research Center Code 283 Annapolis, MD 21402-5067 Accession For

Defense Technical Information Center(7 Building 5, Alexandria,

Cameron Station VA 22314

-

NTIS GRA&I DTIC TAB

-

Unannounced Justification

El

By... -

n bo Diltrut Availab:iity Codes

~

+

I

0!Dist

lki

Av&i! and/or Special