A heterojunction bipolar transistor (HBT) is disclosed that includes successive
emitter, base and collector and sub-collector epitaxial layers and emitter, base
and collector contact metals contacting the emitter, base and sub-collector layers
respectively. A passivation material is included that covers the uncovered portions
of the layers and covers substantially all of the contact metals. The passivation
material has a planar surface and a portion of each of the contact metals protrudes
from the surface. Planar metals are included on the planar surface, each being
isolated from the others and in electrical contact with a respective contact metal.
A method for fabricating an HBT is also disclosed, wherein successive emitter,
base, collector and sub-collector epitaxial layers are deposited on a substrate,
with the substrate being adjacent to the sub-collector layer. The epitaxial layers
are etched to provide locations for contact metals and emitter, base and contact
metals are deposited on the emitter, base and sub-collector epitaxial layers, respectively.
A self-alignment material is deposited on the surface of the substrate around the
epitaxial layers and a planarization material is deposited on and covers the top
surface of the HBT. The planarization material is then etched so it has a planar
surface about the same level as the surface of the self-alignment material and
the contact metals protrude from the planar surface. The planar metals are then
deposited over the protruding portions of the contact metals.