Hughes Aircraft Company

Hughes Electronics Corporation

Minh V Le

Loi D Nguyen

Chanh N Nguyen

Nguyen Xuan Nguyen

Michael J Delaney

Jeff B Shealy

James C Loh

Jorge L Tizol

A process is provided for fabricating MODFET's in group III nitride compound semiconductors. The process precedes isolation of the MODFET structure with the use of e-beam lithography to define very narrow (e.g., .about.0.25 micrometer) gates which enhance transistor microwave cut-off frequency. Because these compound semiconductors resist chemical etchants, isolation is accomplished by etching with reactive ions to form an isolation mesa having a vertical mesa sidewall. To improve breakdown, the mesa sidewall is covered with a passivation layer prior to deposition of a gate feed that contacts the gate. To reduce parasitic gate capacitance, the gate feed is spaced from a narrow edge of the transistor's two-dimensional electron gas.

Modulation-doped field-effect transistors and fabrication processes

A structure and method for making HEMTs with a gate metal having a layer comprising titanium, a layer comprising vanadium over the layer comprising titanium, and a layer comprising gold over the layer comprising vanadium. Such HEMTs are insensitive to hydrogen.

Structure and method for making FETs and HEMTs insensitive to hydrogen

A method for hydrogen treatment of FETs for use in hermetically sealed packages is disclosed. FETs such as GaInAs HEMTs are treated before hermetic packaging by heating them in a hydrogen atmosphere until their drain currents degrade, and then continuing to heat them until their drain currents are restored. The HEMTs' drain currents are monitored and the process is continued until the currents stabilize. Thereafter the devices' temperature is lowered to the desired operating temperature and their drain currents are measured. If the drain currents after treatment are close enough to the current levels before treatment, the devices are selected; otherwise they are rejected.

Method for hydrogen treatment of field effect transistors for use in

Yields of FETs such as HEMTs are significantly improved by establishing an elongate gate contact opening in a patterning material with the patterning material overhanging the opening along both its elongate sides and its ends. A contact metal is next evaporated both into the opening and onto the adjacent patterning material, with the overhang producing a continuous gap around the periphery of the upper section of the gate contact between it and the metal on the adjacent patterning material. The adjacent metal is then lifted-off without disturbing the gate contact. The inward tapered profile in the elongate direction of the contact opening is achieved with multiple parallel e-beam scans, while a similar profile is achieved at the ends of the elongate scans by increasing the electron beam dose in the vicinity of the scan ends, preferably by scanning the beam at a substantial angle to the elongate direction near the ends of the opening.

High yield sub-micron gate FETs

Yields of FETs such as HEMTs are significantly improved by establishing an elongate gate contact opening in a patterning material with the patterning material over-hanging the opening along both its elongate sides and its ends. A contact metal is next evaporated both into the opening and onto the adjacent patterning material, with the overhang producing a continuous gap around the periphery of the gate contact between it and the metal on the adjacent patterning material. The adjacent metal is then lifted-off without disturbing the gate contact. The inward tapered profile in the elongate direction of the contact opening is achieved with multiple parallel e-beam scans, while a similar profile is achieved at the ends of the elongate scans by increasing the electron beam dose in the vicinity of the scan ends, preferably by scanning the beam at a substantial angle to the elongate direction near the ends of the opening.

Growing community of inventors

Simi Valley, CA, United States of America

Minh V Le