Selectively regrown contacts to field-effect transistors withtwo-dimensional electron-gas channels

The authors have fabricated for the first time heterostructure field-effect transistors where the two-dimensional electron gas (2-DEG) channel is directly contacted by selectively regrown epitaxial GaAs contacts. Both modulation-doped FETs (MODFETs) and semiconductor-insulator-semiconductor FETs (SISFETs) were fabricated. Contact resistances were low, as evidenced by high transconductances and improvements to the transconductance at low temperatures. The low resistance and shallow nature of the regrown contacts should permit scaling of these structures to very small dimensions     

Effect of dissolved oxygen on thermal oxidation in Ta2O5/Ta sandwiches

Chemical analysis, structural investigations, and electrical capacitance measurements have been performed on Ta₂O₅/Ta foils annealed at 753K in air for different initial concentration of oxygen in Ta. It was shown that the initial concentration of oxygen in Ta plays a crucial role in formation of thermal nonstoichiometric oxide layer between tantalum and anodic Ta₂O₅, namely only Ta with low initial oxygen content covered with thin Ta₂O₅ layer is resistant to thermal oxidation. The obtained results may explain the degradation of real capacitors made of fine Ta powders.     

Critical oxygen content in porous anodes of solid tantalum capacitors

X-ray diffraction analysis of sintered porous anodes of solid tantalum capacitors and the current-voltage (I–V) characteristics of Ta2O5 amorphous layers formed on the anode surface have been performed. A strong correlation between a sharp increase of direct current in the I–V characteristics at some critical oxygen content and the creation of a saturated solid-phase solution of oxygen in tantalum was found. The appearance of a crystalline oxide Ta2O5 phase was detected in porous anodes at oxygen contents above the critical oxygen level. The decrease of effective radius below 1 m of Ta powder particles used in sintering leads to the size effect: the oxygen content in the porous anode after sintering exceeds the solubility limit. © 1998 Kluwer Academic Publishers     

Microstructural and surface effects on electromigration failure mechanism in Cu interconnects

It is shown that changes in the microstructure of Cu interconnects lead to qualitative variation in electromigration damage kinetics - from the formation of the open circuit to continuous damage not leading to failure. Surface diffusion acting simultaneously with grain boundary mass transport is shown to be critical for damage formation. Activation energy of electromigration was measured to be 0.95 eV.