Hughes Aircraft Company

USA As Represented by Secretary of the Navy

Wing Y Lum

William M Clark, Jr

Gary M Atkinson

Arthur R Clawson

James R Herring

Gerald E McWilliams

James W Roach

Frank J Scholz

A microelectronic device of the MOSFET type (20) is structured to exhibit low noise characteristics at cryogenic temperatures of less than about 40K. The device (20) comprises a doped silicon substrate wafer (22), the dopant having an ionization energy in the substrate of more than about 0.1 eV. Preferred substrate dopants include tellurium as an n-type dopant and indium as a p-type dopant. A metal-oxide-semiconductor field effect transistor (20) in the substrate wafer (22) includes a source (24), a drain ( 26 ), and a gate (30) intermediate the source (24) and the drain (26).

Low-noise cryogenic MOSFET

A high value, precision resistor (10) includes a doped region (18) having a boustrophedonic (folded or meandering) shape formed in a substrate (12). At least one section of the doped region (18) is formed by implantation using a focused ion beam. Where the entire doped region (18) is formed by the focused ion beam, the length thereof is selected to be large (10 to 100 times the width of the boustrophedonic shape) to maximize the accuracy of the resistor (10) by averaging over variations in grain size and implant dose. Alternatively, a probe resistor (32) and a plurality of similar unconnected doped sections (28) may be formed by means such as photolithography and flood ion implantation. The probe resistor (32) is measured at the desired operating temperature to determine the ratio of the measured resistance to the desired design resistance value. The unconnected doped sections (28) are then interconnected by plugs (40, 42, 44, 46), formed with a focussed ion beam, to program the fabricated resistor to exactly the designed resistance value at the desired operating temperature.

Integrated circuit resistor fabrication using focused ion beam

An improved method of liquid phase epitaxial growth of III-V compound on an nP substrate by growing the epitaxial layer in an atmosphere of H.sub.2 with 10.sup.-5 to 10.sup.-4 mole fraction PH.sub.3.

Method of liquid phase epitaxial growth

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San Diego, CA, United States of America

Wing Y Lum