United States of America As Represented by the Secretary of the Air Force

Charles L Cerny

Tony K Quach

John L Ebel

Kenichi Nakano

James K Gillespie

James S Sewell

Charles K Havasy

Ross W Dettmer

Christopher A Bozada

G David Via

Gregory C DeSalvo

Thomas J Jenkins

Carl I Pettiford

Michael Shur

Fritz L Schuermeyer

Edgar J Martinez

An enhancement mode periodic table group III-IV semiconductor field-effect transistor device is disclosed. The disclosed transistor includes single metallization for ohmic and Schottky barrier contacts, a permanent non photosensitive passivation layer (a layer which has also been used for masking purposes during fabrication of the transistor) and a gate element of small dimension and shaped cross section as needed to provide desirable microwave spectrum electrical characteristics. The transistor of the invention is fabricated from undoped semiconductor materials disposed in a layered wafer structure and selectively doped by ion implantation to achieve either a p-channel or an n-channel transistor. The semiconductor materials may include two, one or zero buffer layers in their layer structure. The disclosed transistor is of reduced fabrication cost, increased dimensional accuracy and state of the art electrical performance.

Single layer integrated metal enhancement mode field-effect transistor

A method for fabricating an enhancement mode periodic table group III-IV metal semiconductor metal field-effect transistor is described. The disclosed fabrication arrangement uses single metallization for ohmic and Schottky barrier contacts, employs initially undoped semiconductor materials--materials selectively doped in a disclosed processing step, employs a non-alloyed ohmic contact semiconductor layer and includes an inorganic dielectric material layer providing non photosensitive masking at plural points in the fabrication sequence along with permanent surface passivation. The invention uses a combined optical and electron beam lithographic process, the latter in small dimension gate areas. These attributes are combined to provide a field-effect transistor capable of microwave frequency use, of reduced fabrication cost, low electrical energy operating requirements increased dimensional accuracy and state of the art electrical performance. Fabricated device characteristics are also disclosed.

Single layer integrated metal process for enhancement mode field-effect

A room temperature wet chemical digital etching technique for, gallium arsenide or other semiconductor material. Hydrogen peroxide and an acid are used in a two step etching cycle to remove the gallium arsenide in approximately 15 .ANG. limited increments. In the first step of the cycle, gallium arsenide is oxidized by, for example, 30% hydrogen peroxide to form an oxide layer that is diffusion limited to a thickness of, for example, 14-17 .ANG. for time periods from 15 seconds to 120 seconds. The second step of the cycle removes this oxide layer with an acid that does not attack unoxidized gallium arsenide. These steps are repeated in succession using new reactant materials and cleaning after each reactant (to prevent reactant contamination) until the desired etch depth is obtained. Experimental results are presented demonstrating the etch rate and process invariability with respect to hydrogen peroxide and acid exposure times. A method for using a Hall effect measurement to determine the achieved change in surface layer thickness of doped semiconductor material is also included.

Digital wet etching of semiconductor materials

This is a fabrication process for complementary III-V HFETs in which devices are built side-by-side in doped-areas, known as 'tubs', grown by molecular beam epitaxy on indium phosphide (InP) substrates, or other material systems such as materials grown on GaAs substrates. The layers grown are a semi-insulating buffer layer of InAlAs, a InGaAs channel, an InAlAs barrier layer and finally an InGaAs cap layer. All layers are lattice matched or pseudomorphic to the InP substrate. After mesa etching of areas around the transistor, a high temperature silicon nitride (Si.sub.3 N.sub.4) layer is deposited using chemical vapor deposition, and photoresist is deposited. Then n-well and p-well areas are formed in turn, with appropriate ion-implantation, stripping of the photoresist, and annealing to activate the dopants. Then the Si.sub.3 N.sub.4 is stripped and the samples thoroughly cleaned. Then, the refractory gate metal is sputtered, delineated with photoresist and reactive ion etch procedures. Areas for n-ohmic and p-ohmic contacts are formed, using with Si.sub.3 N.sub.4 and photoresist covering, ion implanting, and annealing. Finally the p- and n-ohmic contact metals are evaporated and alloyed. The typical n-ohmic metal system is Au/Ge/Ni while Au/Zn is used for the formation of the p-ohmic contacts. The integrated circuit is completed by depositing and patterning the interconnect metal.

Twin-tub complementary heterostructure field effect transistor fab

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Huber Heights, OH, United States of America

Charles L Cerny