MOT

High resolution negative resists are needed for masked ion beam lithography (MIBL) and for the fabrication of MIBL masks by E-beam lithography (EBL). The MOTSS copolymer resists were developed to obtain the resolution of fine features that a bilevel resist can best provide. The flexibility afforded by choosing the structure of the HS, the copolymer composition, and the molecular weight allows a resist to be tailored by simple synthesis adjustments to have the particular sensitivity and etch protection which best suits the application. 

Elemental analyses were performed by Galbraith Laboratories, Inc., of Knoxville, TN. The compositions of the HS-MOTSS copolymers were derived from the average of the values calculated from the reported halogen and silicon content. The molecular weight and dispersity of the polymers were measured in tetrahydrofuran by size... 

The exposed HS-MOTSS copolymer films were dip-developed in solvent followed by baking at 50-80 °C in vacuum for about 30 min. E-beam dose matrice images were developed in chlorobenzene for 30 sec ion beam test exposures were developed in methyl isobutyl ketone for 30 sec. The thicknesses of the films were measured with a Nanospec/AFT microarea film thickness measuring system. 

Table I. The polymerization of MOTSS with various halostyrenes...

Halostyrene (HS) Temp °C Time [HS] hr M [MOTSS] M [BPO] MxlO3 % Conv. HS/MOTSS Feed Polymer ... 

The D Mw values for a series of CMS-MOTSS copolymer compositions are shown in Figure 3 with the lines calculated from the above formula using two D Mw values for the PCMS homopolymer.. Extrapolation of the experimental data suggests that the actual D Mw value for the PCMS homopolymer is 0.057, midway between our earlier value of 0.046 (Jensen, J.E. Brault, R.G. Miller, L.J. Granger, D.D. van Ast, C.I., Hughes Research Laboratories, unpublished results) and that of 0.07 used by Tanigaki et al. (11)-... 

Figure 3. The DgMw values for the CMS-MOTSS copolymers compared with theoretical values calculated by the formula of Tanigaki et al.

HS) MOTSS 90keV 125keV 75keV 250keV slope coeff. 

Halostyrene (HS) HS MOTSS 90keV Contrast (nr,) 125keV 175k eV 250keV... 

Figure 4. The effect of proton beam energy on the sensitivity (QH) of the MOTSS copolymer resists.

An earlier paper from this laboratory showed that a plot of l°g(Qe) at 20 keV against log(Qp) at 100 keV for 19 negative and positive resists had a linear least squares slope of 1.30 with a correlation coefficient of 0.909 (14). Our log-log plot of Qe against Q at 90 and 125 keV for the MOTSS copolymers is shown in Figure 7. The linear least squares fit for the 125 keV plot has a slope of 1.05 with a correlation coefficient 0.992. Those for the 175 and 250 keV protons have the same slope within experimental error, but that for the 90 keV protons is higher, 1.11, with a correlation coefficient of 0.981. The reason that the slopes derived from the HS-MOTSS data... 

Figure 7. The E-beam sensitivity (Qe) of MOTSS copolymer resists as a function of the proton beam sensitivity (Qp) with 90 and 125 keV protons.

In summary, we have shown that the proton beam sensitivity of an HS-MOTSS copolymer decreases and the contrast increases with increasing proton energy, and that the influence of the proton energy on the sensitivity of these materials is diminished with the more sensitive resists. 

L.R. Motss, Comparative thermochemical and aadation-reduction properties of lanthanides and actinides 239... 

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