Showing papers by "Deirdre L. Olynick published in 2006"

Etching radical controlled gas chopped deep reactive ion etching

Abstract: A method for silicon micromachining techniques based on high aspect ratio reactive ion etching with gas chopping has been developed capable of producing essentially scallop-free, smooth, sidewall surfaces. The method uses precisely controlled, alternated (or chopped) gas flow of the etching and deposition gas precursors to produce a controllable sidewall passivation capable of high anisotropy. The dynamic control of sidewall passivation is achieved by carefully controlling fluorine radical presence with moderator gasses, such as CH 4 and controlling the passivation rate and stoichiometry using a CF 2 source. In this manner, sidewall polymer deposition thicknesses are very well controlled, reducing sidewall ripples to very small levels. By combining inductively coupled plasmas with controlled fluorocarbon chemistry, good control of vertical structures with very low sidewall roughness may be produced. Results show silicon features with an aspect ratio of 20:1 for 10 nm features with applicability to nano-applications in the sub-50 nm regime. By comparison, previous traditional gas chopping techniques have produced rippled or scalloped sidewalls in a range of 50 to 100 nm roughness.

Fabrication of 30 nm pitch imprint moulds by frequency doubling for nanowire arrays

Abstract: We report the fabrication of 30 nm pitch nanowire array imprint moulds by spatial frequency doubling a 60 nm pitch array generated by electron beam lithography. We have successfully fabricated nanowire arrays at a 30 nm pitch, which is targeted for the year 2020 by the International Technology Roadmap for Semiconductors, with an average line-width of 17 nm and a 3σ line width roughness (LWR) of 4.0 nm. In contrast to previously reported procedures, our spatial frequency doubling technique produces electrically isolated nanowires that are appropriate for crossbar circuits.

Scanning x-ray microscopy investigations into the electron-beam exposure mechanism of hydrogen silsesquioxane resists

Abstract: Electron-beam exposed hydrogen silsesquioxane cross-linking chemistry is investigated by scanning transmission x-ray microscopy (STXM) and atomic force microscopy (AFM). Using STXM, a maximum in the chemical contrast is obtained by measuring the x-ray absorption at 535.4eV, corresponding to the 1sK-edge transition in oxygen. An area-dependent and dose-dependent chemical conversion is observed for feature sizes between 150nm and 10μm and doses between 0.4 and 40mC∕cm2. The activated (cross-linked) regions extend beyond the exposure zones, especially for higher dosed exposures. With AFM, thickness changes in the latent images (e-beam exposed but undeveloped) are observed, which also display a dependence on exposed area. Potential mechanisms, involving chemical diffusion outside the exposure zone, are discussed.

A silicon-based, sequential coat-and-etch process to fabricate nearly perfect substrate surfaces.

Abstract: For many thin-film applications substrate imperfections such as particles, pits, scratches, and general roughness, can nucleate film defects which can severely detract from the coating's performance. Previously we developed a coat-and-etch process, termed the ion beam thin film planarization process, to planarize substrate particles up to approximately 70 nm in diameter. The process relied on normal incidence etching; however, such a process induces defects nucleated by substrate pits to grow much larger. We have since developed a coat-and-etch process to planarize approximately 70 nm deep by 70 nm wide substrate pits; it relies on etching at an off-normal incidence angle, i.e., an angle of approximately 470 degrees from the substrate normal. However, a disadvantage of this pit smoothing process is that it induces defects nucleated by substrate particles to grow larger. Combining elements from both processes we have been able to develop a silicon-based, coat-and-etch process to successfully planarize approximately 70 nm substrate particles and pits simultaneously to at or below 1 nm in height; this value is important for applications such as extreme ultraviolet lithography (EUVL) masks. The coat-and-etch process has an added ability to significantly reduce high-spatial frequency roughness, rendering a nearly perfect substrate surface.

Extreme ultraviolet binary phase gratings: Fabrication and application to diffractive optics

Abstract: Diffractive optics play an important role in a variety of fields such as astronomy, microscopy, and lithography. In the extreme ultraviolet region of the spectrum they have been difficult to make due to the extremely precise control required of their surface structure. We have developed a robust fabrication technique that achieves the required topographic control through the deposition of a thin film of Si on a Cr etch stop. We have fabricated binary phase gratings using this approach that have an efficiency of 80% of the theoretical maximum. This technique could be applicable to similar binary phase structures requiring precise topography control.