A bilayer resist system, consisting of hydrogen silsesquioxane (HSQ) as negative tone electron (e)-beam resist top coat and hard baked novolak resist as bottom coat, has been investigated for its ability to yield high aspect ratio nanoscale structures. For comparison, single layer HSQ (hard mask) has been investigated for its resolution, contrast, and process latitude. In single layer HSQ, dense lines and spaces (1:1) have been resolved down to 20 nm and single lines have been obtained with widths less than 15 nm. Processing conditions which result in higher contrasts in HSQ also result in higher horizontal contrasts, i.e., in poorer process latitudes; this effect has previously been observed for other negative tone e-beam resists as well. In the bilayer combination, HSQ allows nanoscale structures with an aspect ratio exceeding 15 to be etched in hard baked novolak resist. Single lines with 800 nm height and 40 nm width, semidense lines and spaces (1:2) with 155 nm height and 25 nm width, and dense lines and spaces (1:1) with 130 nm height and 40 nm width have been patterned in this bilayer system. Both the single layer HSQ and the HSQ/novolak bilayer system appear to be suitable as e-beam resists for research on nanoscale gates in complementary metal–oxide–semiconductor (CMOS) and other devices.

The use of Pt–Rh-based three-way catalysts for automotive exhaust-gas control stimulated us to study various Pt–Rh alloy surfaces: well defined single-crystal surfaces and SiO₂-supported catalysts. For the sake of comparison data were also obtained for pure Pt and Rh single-crystal surfaces and catalysts. The surface composition and chemical properties have been studied using AES, FEM, TDS and XPS. The surface composition was studied under various experimental conditions, both in vacuum and in the presence of the relevant gases, NO, O₂, CO and H₂. We discuss the effects of the surface structure and the surface composition on the chemical properties of the Pt–Rh alloys. The surface composition varies easily with changing experimental conditions (temperature and gas-phase composition). Clean Pt–Rh alloy surfaces are enriched with Pt after high-temperature annealing (T 1000 K). However, the surface composition of Pt-rich Pt–Rh alloys is almost bulk-like following low-temperature equilibration (T≈ 800 K). Adsorbates can easily induce segregation of Rh or Pt to the surface, and the chemical properties of the surfaces are changed accordingly. In particular, the NO dissociation, which is often mentioned as the first step in the NO reduction with CO or hydrogen, is extremely sensitive to both the structure and the composition of the surface. For the pure metals the influence of the surface structure is different for Pt and Rh. The NO reduction and CO oxidation reactions were studied at low pressures on the single-crystal surfaces and at atmospheric pressure on the supported catalysts. We show that the chemical properties of the supported catalysts can be understood on the basis of the single-crystal results.

Hydrogen silsesquioxane (HSQ) has been shown to behave as a negative tone inorganic e-beam resist with a resolution better than 20 nm established. In this article, delay-time and aging effects on contrast and sensitivity have been investigated. The effect of a 1 week delay in air between softbake and exposure is much larger than either the aging effect or the effect of the softbake temperature. A pre-exposure delay in air seems to decrease the sensitivity and to enhance the contrast of HSQ. A general correlation between sensitivity and contrast has been established for various pre-exposure and postexposure treatments for 20, 50, and 100 kV exposures. The possible causes for the various delay-time effects are discussed.