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A recessed source and drain structure for a gallium arsenide MESFET device is disclosed which results in a self-aligned gate structure without the requirement for tight photolithographic tolerances.
English (United States)
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Recessed Source and Drain Gallium Arsenide MESFET
A recessed source and drain structure for a gallium arsenide MESFET
device is disclosed which results in a self-aligned gate structure without the
requirement for tight photolithographic tolerances.
Figs. 1 through 3 illustrate the sequence of stages in the process of making
the device. A stripe of photoresist material 1 is patterned on the surface of the
semi-insulating gallium arsenide bulk material 2 over the location 3 where the
MESFET channel is to be formed. Approx. 500 Angstroms of material from the
surface of the gallium arsenide bulk material 2 is removed from the surface on
each side of the photoresist stripe 1. Then, an N-type dopant species is ion
implanted so as to form the region 4 shown in Fig. 1. This is followed by
depositing the layer 5 of porous silicon monoxide or a capping layer of nonporous
material on the exposed surface of the semi-insulating gallium arsenide bulk
material, on each side of the photoresist stripe 1, as shown in Fig. 2.
The photoresist is then stripped and a capless anneal applied through the
silicon monoxide and on the uncapped exposed region 3. After the anneal step, a
gate metal layer 6, capable of forming a Schottky barrier with the gallium
arsenide in the bulk material 2, is deposited with broad tolerances on the channel
region 3 and overlapping the silicon monoxide layer 5. The location of the gate
layer 6 can be asymmetrically aligned with respect to the channel 3, as...