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We describe a study on wet etching of thin films of indium tin oxide (ITO) using a simple method by monitoring the resistance of the thin film in aqueous solutions of oxalic acid and hydrochloric acid. Generally three different regimes can be distinguished during etching ITO in acids: (1) initial etching, which is slow, (2) a fast etching phase and (3) slow etching stage at the end. These regimes are explained in terms of a porosity–roughness model. This porosity model has been confirmed largely by X-ray reflection measurements at grazing incidence, roughness measurements and scanning electron microscopy (SEM). A reliable method for monitoring the resistance during etching has been developed. This method is based on a 2-strips measuring jig with a very low series contact resistance. The activation energy of the etch rate of ITO films was found to be 80 ± 5 kJ/mol for oxalic acid and 56 ± 5 kJ/mol for HCl. SEM analyses in the final stage of the etching process indicate an enrichment of Sn in the residual film material. These observations are explained in terms of preferential etching of In2O3. X-ray analyses showed that the density of the ITO film decreased by etching. By adding ferric chloride to the oxalic acid solution we could accelerate the etch rate substantially.

We have shown previously that porous diamond membranes can be fabricated using a method based on growing diamond on a patterned silicon substrate. The technique used to pattern the silicon is conventional lithography. In this work we present a method for reducing the pore size using diamond post-deposition over the membrane. An important concern in this work was to determine the pore-shutting rate, considering the time post-deposition and the pore morphology.

As reported previously, porous diamond membranes can be fabricated using a method based on growing diamond on a patterned silicon surface. Protrusions on the silicon surface act as molds for forming the pores on the diamond films. This method leads to a non-negligible pore size non-uniformity. The present work is concerned with identifying the process that accounts for this, so as to minimize its effects. The approach developed here is based on the digital processing of the scanning electron microscope (SEM) images obtained from selected pores in five different membranes.

We describe here a method for fabricating free-standing diamond membranes. Diamond films were deposited on a silicon substrate by microwave plasma-assisted chemical vapor deposition and then part of the substrate chemically removed. The films described here were 15 mm in diameter with thickness of approximately 12 μm. A novel feature of our approach lies in the method used to obtain the selective dissolution of the substrate; a container with O-rings was used, instead of masks, allowing a fast and clean isotropic dissolution of part of the silicon substrate. The deposited diamond films as well as the free-standing membranes were characterized by scanning and transmission electron microscopy, electron diffraction and Raman spectroscopy.

An appropriately structured grating allows accurate measurement of the thickness of a thin film. We propose the use of this technique to measure the point-by-point evolution of plasma etching, and consequently the etching rate. We compare this real-time remote sensing technique with other available techniques. We note that this technique is suitable for measuring rapid fluctuations in plasma processes. We describe some experimental results concerning a photoresist film coated on a silicon wafer and predict the theoretical behaviour of other commonly occuring films.

An in-process optical technique is described for accurately monitoring the end point in plasma etching processes. A grating pattern is lithographed somewhere in the film to be etched. The grating modulation decreases as the film is etched out and the process may be monitored by measuring the diffraction of a low power He-Ne laser beam aimed at the grating. The etching end point is accurately detected by the disappearance of all diffracted orders. The laser beam does not need to be directed at normal incidence and so any available plasma etching equipment is suitable. The detection is carried out with low cost photovoltaic detectors but simple visual inspection is satisfactory also. Comparative experimental results are presented.

The structural characteristics of optically transparent electrically conducting thin films of SnO 2 and of In 2 O 3 deposited onto amorphous substrates and onto monocrystalline silicon substrates were studied by X-ray diffraction. The SnO 2 films, which were prepared by chemical vapor deposition, were polycrystalline with a grain size of 7–15 nm and with a marked (200) preferred orientation. The evaporated In 2 O 3 films had an average grain size of 3–10 nm but showed no preferential orientation.