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A dual temperature method has been developed for subtracting the 77 K thermally smoothed background from 4.2 K inelastic electron tunneling spectra of ultrathin dielectric metal-insulator-semiconductor junctions. A mode resolving method applied to the remaining spectrum clearly identifies electrode and insulator vibrational modes. The ability to track these relative mode positions and amplitudes shows promise as a unique interface analysis and process diagnostic method. Results are reported on polycrystalline silicon gate, 1.5-nm-thick oxide devices fabricated on 1–10 Ω cm, N-type, (100) silicon substrates by a standard industrial process sequence.

Local anodization of aluminum was studied by patterning SiO2 masks on aluminum thin films by nanoimprint lithography and subsequent electrochemical anodization. We observed the formation of isolated pores when the mask openings are of the order of the steady-state unpatterned pore spacing, which is related to the breakdown strength of the alumina and the anodization potential. Based on our observations, we have developed an empirical model describing the formation mechanism of porous aluminum oxide. The model described successfully explains the formation and shapes of pores as a function of mask aperture size.

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Alumina formed by the electrochemical anodization of bulk aluminum has a regular porous structure [1]. Sub-100 nm pores with aspect ratios as high as 1000:1 can easily be formed [2] without elaborate processing. Anodization of aluminum thus provides the basis for the inexpensive, high throughput microfabrication of structures with near vertical sidewalls [2]. In this work we explore the patterned anodic oxidation of deposited aluminum thin films, facilitating the integration of this technique with established microfabrication tools. An anodization barrier of polymethylmethacrylate (PMMA) is deposited onto 300 nm thick aluminum films. The barrier film is subsequently patterned and the exposed aluminum anodized in a 10% sulfuric acid solution. Barrier patterning techniques utilized in this study include optical exposure, ion-beam milling and nano-imprint lithography. Sharp edge definition on micron scale patterns has been achieved using optical methods. Extension of this technique to smaller dimensions by ion-beam milling and nano-imprint lithography is presented. We further report on the observation of contrast reversal of anodization with very thin PMMA barriers, which provides a novel means of pattern transfer. Potential applications and challenges will be discussed.