High-barrier Al/p-Si Schottky diodes
Sequential implantation of argon ions and low-energy hydrogen ions has been found to yield Schottky barriers of exceptionally high values on p-type silicon. The interaction of these ions in Si is quite complex, involving donor defect generation, defect passivation, and acceptor dopant neutralization. The apparent synergism of these specific implants has resulted in Al/p-Si Schottky diodes with an effective barrier height as high as 0.83 eV, among the highest value reported for any metal/p-Si contact.
On resolving the anomaly of indium-tin oxide silicon junctions
Experimental evidence is presented to resolve the anomalous rectifying behavior of indium-tin oxide (ITO)/silicon junctions. Previous work has demonstrated that the rectifying direction for this heterojunction depends on the method used to deposit the ITO. It is shown here that the cause for this is the existence of damaged surface layers in junctions subject to ion beam processing. Irrespective of the material deposited and irrespective of the doping type, ion-beam sputtering tends to cause the silicon band edges to bend downwards at the surface. It is for this reason that ion-beam deposited ITO gives a rectifying junction on p-Si and an ohmic contact on n-Si.
Edge-defined patterning of hyperfine refractory metal silicide MOS structures
Edge-defined patterning was used to obtain hyperfine (< ¼ µm) refractory metal silicide MOS structures. A patterning technique, using standard optical lithography and advanced etching technology, was developed and proven to result in submicrometer structures of controllable dimensions. Hyperfine MoSi<inf>2</inf>/SiO<inf>2</inf>/Si MOS structures were realized using a vertical aluminum step defined by CCl<inf>4</inf>plasma etching. The MoSi<inf>2</inf>patterning was performed using anisotropic planar etching in NF<inf>3</inf>. Functional relationships between Al step height (0.3- 0.9 µm), MoSi<inf>2</inf>film thickness (0.3-1.0 µm), and the resulting silicide linewidth (0.1-0.25 µm) and line height (0.3-0.9 µm) were investigated. It was found that the linewidth and height could be independently controlled.