Titanium oxide thin films were deposited at room temperature by reactive magnetron sputtering in a mixture of oxygen and argon on oxidized silicon substrates. The optimal etching characteristics of TiO 2 films by reactive ion etching (RIE) and RIE with inductively coupled plasma source (ICP) were investigated. Patterning of TiO 2 tip arrays by electron beam lithography and dry etching were developed. Different spot sizes 200 and 500 nm in diameter and with spacing 500 and 1000 nm were investigated with regards to the minimal size and the pyramidal shape. Experimental results have shown that the exposure dose optimization wa a significant parameter for controlling the tip size and its shape. We successfully fabricated the pyramidal TiO 2 tip arrays over an 1×1 mm 2 area. The TiO 2 tip array can be expected to have an important application in gas microsensors.
We report on the technology and properties of Schottky contacts on reactive-ion etched n-In 0.49 Ga 0.51 P (nϭ7.5ϫ10 17 cm Ϫ3 ). A mixture of CH 4 /H 2 was used for a controllable smooth dry etching of InGaP while a CCl 2 F 2 -based plasma was shown to enable a highly selective etching of GaAs over InGaP. Current-voltage (I -V), capacitance-voltage (C -V) methods and deep-level transient spectroscopy ͑DLTS͒ were used for diode characterization. CCl 2 F 2 -based reactive-ion etching ͑RIE͒ led to diodes with barrier heights of 0.67 eV ͑from I -V measurements͒ and ideality factors of 1.24, which are parameters that are very close to those of the reference ͑not dry etched͒ sample. Additional C -V and DLTS characterization has confirmed no detectable damage for CCl 2 F 2 -based RIE. On the other hand, hydrogenation after CH 4 /H 2 plasma led to substantial passivation of donors which were successfully reactivated after 430-470°C rapid thermal annealing ͑RTA͒. For this type of processing we measured barrier heights of 0.70-0.75 eV and ideality factors of 1.25-1.27, depending on the temperature of the RTA. DLTS on CH 4 /H 2 -RIE based diodes has shown that, in contrast to the reference sample, no bulk deep traps are generated with RTA. We point out that thermal treatment also led to changes in the interface states density which may be responsible for the diode barrier height increase.
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