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Suspended Fine Metal Conductors

IP.com Disclosure Number: IPCOM000060049D
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 3 page(s) / 45K

Publishing Venue

IBM

Related People

Knoedler, CM: AUTHOR

Abstract

Suspended fine metal conductors, useful in noise studies and quantum size effects, may be fabricated as a film on a sandwich substrate, a portion of which can be removed from under the film. As a specific example, a molybdenum film grown on a GaAs/AlxGal-x As/GaAs sandwich substrate is used as an illustration. A GaAs semi-insulating, substrate oriented (100) has a buffer layer of undoped GaAs grown that is about 300 nm-500 nm thick by molecular beam epitaxy (MBE) techniques or metal organic chemical vapor deposition (MOCVD). Then, in the same growth run, an AlxGal-xAs layer with .2_x_.4 about 50 nm thick is grown on top of the buffer layer and finally an undoped GaAs layer about 300 nm or greater is grown.

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Suspended Fine Metal Conductors

Suspended fine metal conductors, useful in noise studies and quantum size effects, may be fabricated as a film on a sandwich substrate, a portion of which can be removed from under the film. As a specific example, a molybdenum film grown on a GaAs/AlxGal-x As/GaAs sandwich substrate is used as an illustration. A GaAs semi-insulating, substrate oriented (100) has a buffer layer of undoped GaAs grown that is about 300 nm-500 nm thick by molecular beam epitaxy (MBE) techniques or metal organic chemical vapor deposition (MOCVD). Then, in the same growth run, an AlxGal-xAs layer with .2_x_.4 about 50 nm thick is grown on top of the buffer layer and finally an undoped GaAs layer about 300 nm or greater is grown. If the samples are grown by MBE, then a layer of Mo or W could be grown in situ on top of the GaAs by means of E-beam, electrostatic, deposition. In this way highly oriented films of Mo or W can be obtained. Otherwise, the GaAs substrate sandwich (GaAs/AlGaAs/GaAs) can be removed from the system and an appropriate metal film can be deposited by sputtering or evaporation. This film is a blanket film covering the entire substrate. Thus, the starting structure is as shown in Fig. 1. Next, the Mo is patterned using conventional optical lithographic techniques. Shown in Figs. 2 and 3 is a standard "four probe" design. The photoresist pattern forms a stencil for etching the molybdenum. The pattern is etched in the Mo using CF4+O2, fluorine chemistry, which will not etch the GaAs underneath. The exact mask dimensions can be achieved by not overetching. If finer lines, that is ones that are less wide, are desired, then the Mo can be overetched. Since the photoresist and the GaAs are not etched by the CF4+O2 under the conditions used to etch the Mo, the metal lines will have a decreased width that can be controlled by the length of time for the overetch. At this point, with the photoresist intact on the sample, the sample appears as in Fig. 4. Now, the photoresist is stripped and the oxide on the GaAs is removed by a chemical dip in...