PMMA films

Figure Bl.22.11. Near-field scanning optical microscopy fluorescence image of oxazine molecules dispersed on a PMMA film surface. Each protuberance in this three-dimensional plot corresponds to the detection of a single molecule, the different intensities of those features being due to different orientations of the molecules. Sub-diffraction resolution, in this case on the order of a fraction of a micron, can be achieved by the near-field scaiming arrangement. Spectroscopic characterization of each molecule is also possible. (Reprinted with pennission from [82]. Copyright 1996 American Chemical Society.)...

Figure Cl.5.3. Near-field fluorescence image 4.5 p.m square) of single oxazine 720 molecules dispersed on die surface of a PMMA film. Each peak (fwhm 100 nm) is due to a single molecule. The different intensities are due to different molecular orientations and spectra. Reprinted widi pennission from Xie 11221. Copyright 1996 American Chemical Society.

Single molecules also have promise as probes for local stmcture when doped into materials tliat are tliemselves nonfluorescent. Rlrodamine dyes in botli silicate and polymer tliin films exliibit a distribution of fluorescence maxima indicative of considerable heterogeneity in local environments, particularly for the silicate material [159]. A bimodal distribution of fluorescence intensities observed for single molecules of crystal violet in a PMMA film has been suggested to result from high and low viscosity local sites witliin tire polymer tliat give rise to slow and fast internal conversion, respectively [160]. 

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. 

Figure 5 (a) Carbonyl index (at 1640 cm ) and (b) hydroxyl index (at 3550 cm ) versus irradiation time for PMMA films. X-control -DHBP A-HMBP B-HBBP O-DHBP-F A-HMBP-F and D-HBBP-F. 

Figure 9 Optical density (280 nm) versus irradiation time (hours) for PMMA films. -2,4-DHB -2H-4BB -DHBP-F A-2H-4MB A-HMBP-F and B-HBBP-F.

Figure 14 Weight loss of PMMA films versus aging time ...

Figure 6. Photodegradation rate data on Tinuvin-type UV stabilizers (A) UV-visible spectrophotometric data (B) FTIR data on PMMA films...

Fig. 14 The molecular structures of BP-BTE and DHBO above). Microsized erasable ESIPT-fluorescence photoimaging on a spin-coated BP-BTE/DHBO-loaded PMMA film and its nondestructive readout capability (a) initial open-form state (b) writing (c) erasing (d) rewriting and (e) continuous nondestructive reading under irradiation with relatively high-intensity 415 nm light (200 4W cm-2) for 30 min. The dark region represents the area irradiated with the 365 nm UV light below) (reprint from ref. [88], Copyright 2006 American Chemical Society)...

Figure 35 Top row XPS C(ls) and O(ls) band envelopes and curve-fitted components for (a) PMMA and (b) PEEK films A is untreated, B the DBD-treated at 5.7J cm-2 and C the post-treatment-aged (stored) sample. Bottom row contact angle and XPS O/C variation of (c) PMMA film and (d) PEEK film solid lines are for the freshly treated in air DBD samples, the dashed lines are for the post-process-aged films. Reprinted from Upadhyay et al. [98]. Copyright 2005, with permission of Elsevier.

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). 

To determine the number of equivalent Ti monolayers (1 equivalent Ti monolayer = 2 x 1015 Ti atoms/cm2) needed on the polymer surface to protect the underlying organic film during 02 RIE, several PMMA films were treated with TiCLt under different processing conditions. After treatment with TiCLt the films were etched in an 02 plasma for different lengths of time and the etching rates were determined. The Ti concentration in the samples was measured both before and after etching (Table II). 

Table IL O2 RIE Behavior of TiC -Treated PMMA Films as a Function of Ti on the Film Surface...

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

Figure 6. RBS spectra of a PMMA film treated with TiCU for 2 mins.

Figure 6. Scanning electron micrographs of hard-baked PMMA films before and after a 1.0-min oxygen-RIE treatment at the following conditions a, unetched and b, etched, 0.125 W/cm, 35 mTorr, -230 VDC, no thermal grease. Continued on next page.

Figure 1. Patterns in 50 nm Cr film employing a 8.1 nm (9 layers) LB PMMA film as resist, exposed with a dose of 80 i.C/cm. The linewidths of the patterns are 1/8,1/4, 3/8, and 1/2 i.m, respectively.

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. 

Figure 4. Fluorescence emission spectrum of 5 mol% PDA in monolayer LB PMMA film transferred at 7 dyn/cm. The excitation wavelength is 343 nm.

Ultrathin LB PMMA and novolac/diazoquinone films have been demonstrated to act as high resolution electron beam and optical resists, respectively. Structural rearrangements in the LB PMMA films have been observed by using fluorescence spectroscopy. However, this rearrangement did not appear to influence the lithographic performance when seven or more layers of LB PMMA films were used as the resist. A more comprehensive study of the relationship between lithographic performance and LB film structure is currently underway. 

Figure 8. Schematic of PDA dyes in monolayer Langmuir PMMA film on the water surface before and after the film collapse.

PMMA) film is quenched by permeation of methyl ethyl ketone (MEK), a good solvent for PMMA. A steady-state MEK concentration profile has been estimated from quenching data with existing sorption and light scattering data. The profile contains all the features of Case II diffusion the Fickian precursor, the solvent front, and the plateau region. However, the solvent front is not so steep as those observed in systems where penetrant diffusion is much slower. 

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.). ... 

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