Thick PMMA films

Amount of Tia (atoms/cm2) Before Etching After Etching Etching Time (min.) PMMA Film Thickness ( im) Initial Final Etching Rate (A/min)... 

Fig. 2 shows one application of ATR depth profiling. In this case, ATR spectra were obtained as a function of angle of incidence from a polymethylmethacrylate (PMMA) film of thickness 0.5 p.m that was deposited onto a germanium hemi-cylinder [4]. The solid line represents the ATR spectrum of PMMA while the squares represent the film thickness that was recovered from the infrared spectra using four different bands. It can be observed that the recovered film thickness was very close to the measured thickness. 

More Ti was measured for longer treatment times, lower treatment temperatures and with higher background pressure in the gas functionalization cell. The increase in the thickness of Ti02 layer with longer reaction times was more pronounced in hydrophilic HB-HPR 206 and PMMA films compared to PS films. More Ti was detected in PS films at shorter reaction times, but the Ti incorporation saturated after about 1.5 min. of reaction (Figure 4). 

Electron Beam Lithography. LB PMMA films with thicknesses of 6.3 nm (7 layers) are sufficient for patterning a Cr film suitable for photomask fabrication. For ultrathin PMMA films the resolution (see Fig. 1) is limited by the smallest spot diameter available on MEBES I (1/8 pm). However, it is not possible to obtain this resolution if a thicker resist (>100 nm) is used under the same exposure and development conditions, which demonstrates that ultrathin resists are able to minimize the proximity effect. Also, since the radius of gyration of 188,100 Mw PMMA is about 10 nm in the bulk, and the thickness of the 7 layer film (6.3 nm) is less than 10 nm, it is reasonable to assume there must be an alteration of chain configuration in the ultrathin films. This will be particularly true when the post-deposition baking temperature of the multilayer films is less than the glass transition temperature (115°C), as is the case for the present experiments. In such a case, interdiffusion of PMMA chains between the deposited layers may not result in chain configurations characteristic of the bulk. 

In our previous paper (H), we introduced a novel experimental method to study the mechanistic details of solvent permeation into thin polymer films. This method incorporates a fluorescence quenching technique (19-20) and laser interferometry ( ). The former, in effect, monitors the movement of vanguard solvent molecules the latter monitors the dissolution process. We took the time differences between these two techniques to estimate both the nascent and the steady-state transition layer thicknesses of PMMA film undergoing dissolution in 1 1 MEK-isoproanol solution. The steady-state thickness was in good agreement with the estimate of Krasicky et al. (IS.). ... 

A typical time profile of the excited PMMA-Phe fluorescence intensity decay is shown in Figure 2. The MEK permeation commences at 24 sec. The SPR increases during the plasticization period until it becomes constant, the onset of the steady state. It is characterized by a linear relationship between the amount of solvent absorbed and time. It was determined from a linear regression analysis that the PMMA-Phe fluorescence intensity starts to deviate from linearity at 197 sec. This indicates a decrease in the SPR and/or the unquenched PMMA-Phe. The decrease in SPR is unexpected at this film thickness since the SPR in thicker PMMA-Phe films show no anomaly at 1 /tm. A more plausible explanation is the reduction in available PMMA-Phe, which is expected when the front end of the SCP reaches the substrate. 

It was found from the absorption spectrum that 1.1 % of the incident photons were absorbed at 2537 A by a PMMA film of 0.5 ym thickness (Fig. 5). The molecular weight distribution and the average molecular weight of the coated polymer which was irradiated for the least irradiation time required for the dissolution of polymer coating in the developer were measured by gel-permeation chromatography (Fig. 7). 

The comparison of the resistive property in the plasma etching process between PMMA itself and PMMA sensitized by 2,4,6-tri-tert-butyl phenol is shown in Fig. 12. Following the etching tim the thickness of the PMMA coating becomes thinner. The rate of the decreasing of the film thickness is proportional to the etching time in the former case, but it becomes very slow in the case of the sensitized PMMA. Therefore, the sensitized PMMA is a superior resist than PMMA itself in both properties of the sensitivity and the resistivity. This fact is true in the cases of other sensitizers. 

The effect of molecular weight of the resist on degree of planarization is shown in Figure 30a where the amplitude of fluctuation of 2 - pm thick PMMA films with average molecular weight of 500,000, 150,000, and 33,000 respectively, is plotted as a function of periodicity of 0.8 - pm high... 

Fig. 7 2D thickness-surface energy gradient library for mapping the effects of these parameters on the self-assembly of PS-b-PMMA block copolymer thin films. See text for a fuU description. Lq is the equilibrium self-assembly period and h is the film thickness. Dashed white lines delineate the neutral surface energy region, which exhibits nanostructures oriented perpendicular to the substrate plane. (Derived from [18] with permission)... 

Figure 5a is a p ttern in a film cured for 1 hour at 100°C and exposed at 2yC/cm, the residual film thickness being about a third of a micron. Figure 5b is the same film after being heated for 20 minutes at 175 C and the edge detail appears to be unchanged after this treatment. Figures 6a and 6b are patterns in a PMMA film which is also one third of a micron thick after development and has been heated in the same way (Figure 6b). The flow of the polymer film is much more extensive and has destroyed all the detail in the pattern edges.

In the cases of poly (methyl methacrylate) (PMMA) and poly (vinyl chloride-vinyl acetate) (PVC/PV Ac), these polymers generate much more gas during irradiation than polystyrene. Thus, even if the gases accumulated in microvoids, where their enhancement of creep rate might be lessened, the local gas concentration between the polymer chains should still be much higher than in the case of polystyrene. One would thus expect to see an effect of film thickness on creep rate for these polymers. 

Fig. 18. Induced open-circuit voltage in elongation plotted against amplitude at the end of film for as-cast films polypropylene (PP), high-density polyethylene (PE(H)), low-density polyethylene(PE(L)), polystyrene PS), and poly(methyl methacrylate) (PMMA). Span length = 3.6 cm. Electrode area=2.5 x 2.5 cm2. Film thickness =0.5 mm. Reproduced from Furukawa and others [J. Appl. Polym. Sci. 12, 2675 (1968)] by permission of John Wiley Sons, Inc.

The effect of constraints introduced by confining diblock copolymers between two solid surfaces was examined by Lambooy et al. (1994) and Russell et al. (1995). They studied a symmetric PS-PMMA diblock sandwiched between a silicon substrate, and silicon oxide evaporated onto the top (homopolymer PMMA) surface. Neutron reflectivity showed that lamellae formed parallel to the solid interfaces with PMMA at both surfaces. The period of the confined multilayers deviated from the bulk period in a cyclic manner as a function of the confined film thickness, as illustrated in Fig. 2.60. First-order transitions were observed at t d0 = (n + j)d0, where t is the film thickness and d0 is the bulk lamellar period, between expanded states with n layers and states with (n + 1) layers where d was contracted. Finally, the deviation from the bulk lamellar spacing was found to decrease with increasing film thickness (Lambooy et al. 1994 Russell et al. 1995). These experimental results are complemented by the phenomenologi-... 

Fig. 2.60 The period, d, of lamellae formed in symmetric

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