(Color online) (a) Oxygen -edge NEXAFS spectra of a HSQ thin film before (unexposed) and after (exposed) x-ray exposure (808 MGy, 520–600 eV). The differences are attributed to x-ray induced cross-linking and increase in total oxygen content. (b) Similar peak shifts and a smaller increase in oxygen content are observed for a smaller dose in a slightly thinner film. Less , more (580 eV).
(Color online) Oxygen -edge NEXAFS spectra for pure MSQ with no Si–OH compared to MSQ with incorporated Si–OH, suggesting that the peak in Fig. 1 is likewise due to Si–OH in as-spun HSQ.
(Color online) Silicon -edge NEXAFS spectra of a HSQ thin film, indicating an increase in -like structure but no loss of total Si content after x-ray exposure. The “more exposed” region received at 540 eV prior to imaging, and both spectral regions received at the Si edge (1830–1880 eV) during the image stack (approximate doses).
Dose dependence of x-ray cross-linking in an undeveloped HSQ film. (a) Equally sized features exposed with increasing x-ray dose: STXM image (transmission) and line profile at oxygen -edge (536 eV). Lighter regions indicate more transmission and higher degree of cross-linking; dark points are clusters of nanoparticles used for focusing. Line profile is the average contrast through the narrow region indicated by the gray bar and arrows. Scale . (b) Total average contrast (excluding nanoparticles) vs x-ray dose, indicating two stages of cross-linking and a maximum possible contrast of . Horizontal error bars are for the MGy axis only.
Area-dependent sensitivity in x-ray cross-linking of HSQ. (a) Increasing size features patterned at constant x-ray dose (8.6 MGy, 536 eV): STXM image (transmission) and line profile at oxygen -edge (536 eV). Scale . (b) Peak contrast values from the image above. Lower dashed line (black) is the expected contrast based on the actual exposed area. Upper curve (gray) is simulated using a single-pass line width of 360 nm, as measured. Thus, the peak degree of cross-linking increases with feature width due to spreading effects.
(a) Single-pass line at increasing dose used to quantify the extent of reaction diffusion: STXM image (transmission) and line profile at oxygen -edge (536 eV). All cross-linked materials below the dashed line are washed away by subsequent development, as shown in (b) SEM image and (c) STXM image at 536 eV (transmission intensity and line profile in OD) of these same lines after development. The developer onset occurs at 3.9 MGy. Scale .
(a) Plot of undeveloped single-pass line widths, FWHM, showing a strong dependence of width on both dose and film thickness. (b) Plot comparing developed and undeveloped widths, showing similar but slightly sharper lines after development at low doses, due to removal of partially cross-linked material below the threshold [Fig. 6(a), ]. SEM measurements of developed lines in 100 nm thick films are considerably narrower, continuing the trend of narrower lines in thinner films.
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