Future of GaN RF Technology in Europe
In the last years GaN has remained a key technology in Europe in particular, but not only, for RF Applications. After an intensive period of research and development the scope has shifted towards industrialization and product development. This is especially true for the applications up to around 20GHz where systems are now being built using European GaN-based components. At the same time, an increasing part of the research activity has moved toward higher frequencies beyond 20GHz.
Evaluation of an InAlN/AlN/GaN HEMT with Ta-based ohmic contacts and PECVD SiN passivation
An InAlN/AlN/GaN HEMT with Au-free Ta-based ohmic contacts and a high-quality PECVD SiN passivation is reported. The ohmic contacts were annealed at 550 degrees C, resulting in a contact resistance of 0.64 Omm. The gate length was 50 nm. The device performance and the process were evaluated by performing DC-, pulsed IV-, RF-, and load-pull measurements. It was observed that current slump was effectively mitigated by the passivation layer. The DC channel current density increased by 71 % to 1170 mA/mm at the knee of the IV curve, and the transconductance increased from 382 to 477 mS/mm after passivation. At the same time the gate leakage increased, and the extrinsic f(max) decreased from 207 to 140 GHz. Output powers of 4.1 and 3.5 W/mm were measured after passivation at 31 and 40 GHz, respectively.
Bevel RIE application to reduce defectivity in copper BEOL processing
Bevel etch used during wafer fabrication for semiconductor devices is discussed. In this case, the bevel etch process was utilized in middle of the line processing (MOL) to reduce back end of line (BEOL) defectivity. Tungsten and titanium nitride films, from the formation of contacts to the transistors, extend into the bevel region of the wafer and have been shown to initiate arcing. This can spread foreign material defects on the front side of the wafer in various BEOL post processing steps including subsequent reactive ion etching, SEM metrology and film depositions. The bevel etch tool confines a plasma etch to the outer edge of the front side of the wafer (which can be individually adjusted) and can remove dielectric, organic and Ti/TiN/W films using a fluorine based chemistry.