New High Resolution Liquid Crystal Electron Beam Resists
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R1
Experiments and Results The derivatives studied are shown in fig. 1. The first nine derivatives shown in fig. 1 form a homologous series. In the case of C5/C5 the data obtained confirms our previous report [23]. The derivatives C6/C6 and C5/C5COOH, shown in fig. 1, were also studied. All of the derivatives bar C5/CO, C5/Cl, C5/C2 and C5/C5COOH are liquid crystalline [25]. Films of the triphenylene derivatives were deposited from chloroform solution by spin coating at room temperature onto HF cleaned hydrogen terminated silicon. The film thickness, measured with a surface profiler (Dektak, Sloan), could be controlled in all cases by varying either the angular frequency of the spin coater or the concentration of the deposition solution. It was possible to produce films of thickness less than 10 nm to more than 300 nm for all of the derivatives, with the exception of C5/C5COOH, for which 10 - 60 nm thickness films were possible. (In the case of C5/C5, films as thick as 6 microns have been produced with concentrated deposition solutions). Smooth films were observed for all samples, with roughness of less than 5 nm (with the exception of the 6 micron film where the thickness variation was - 180 nm). However, the films of C5/CO, C5/Cl, C5/C2, and C5/C5COOH crystallized slowly, rendering them unusable after approximately half a day. This is probably because these derivatives are not liquid crystals. Preliminary results from small angle x-ray scattering (SAXS) analysis of the films on H-Si suggests that the film smoothness may be due ordering of the molecules on the surface. Fig. 2 shows the SAXS spectrum of C5/C5 (100 nm film on H-Si. The sharp peak indicates a well ordered film. The dspacing obtained is identical to the mesophase d-spacing [25] corresponding to the intercolumnar separation (dlOO), which implies that the molecules are ordered perpendicularly on the surface as shown in the inset to fig. 2. To measure the response of the derivatives to e-beam irradiation films were exposed to a 20 keV beam using a
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R,
R2
R, Code C5/CO C5/C1 C5/C2
C5/C3 C5/C4 C51C5 C5/C6 C5/C7 C5/C9 C5/C5 COOH C6/C6
R2
Formula R1=OCs5 H1 R1= OC5H11
Name 2,7,1 0-tri-pentyloxy-3,6, 11 -trihydroxytriphenylene 2,7,1 0-tri-pentyloxy-3,6, 11 -tri-
Rl= OC 5 H1 1
2,6,1 0-tri-pentyloxy-3,7,11 -Ai-
R2 =OH
R2 = OC1 H 3
methyloxytriphenylene
R 2 = 0C 2 H 5
ethyloxytriphenylene 2,6,1 0-tri-pentyloxy-3,7, 11 -tri-
R 2= 0C3 H 7
propyloxytriphenylene
R 2= OC 4 H9
butyloxytriphenylene
Ri= OC5HF 1
2,3,6,7,10,11-hexa-
R1= OC5H11 R1= OC5H11
2,6,1 0-tri-pentyloxy-3,7, 11-tri-
R 2= 0G 5 H11
pentyloxytriphenylene
R 2= OC6H 13
hexyloxytriphenylene
Rj= OC5H• 1
2,6,1 0-tri-pentyloxy-3,7, 11-tri-
R 2= OC 7 H15
heptyloxytriphenylene
Rl= OC5H11
2,6,1 0-tri-pentyloxy-3,7, 11-tri-
R1= OC5H• 1
R2 = 0C9 H1 9
Rl= OC5H11 R2=OCsH•oCOOH
2,6,1 0-tri-pentyloxy-3,7, 11 -trinonyloxytriphenylene 2,6,1 0-tri-pentyloxy-3,7, 11 -tri[5(carboxy)pentyloxyltriphenylene
R1 = O0C 6H13 R2 = 0C 6 H1 3
2,3,6,7,10,11-hexahexyloxytriphenylene
Fig. I El
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