Abstract: A system for forming self-aligned contacts includes electroplating a first metal contact onto a Group III-V semiconductor substrate, the first metal contact having a greater height than width and having a straight sidewall profile, etching back the semiconductor substrate down to a base layer to expose an emitter semiconductor layer under the first metal contact, conformally depositing a dielectric layer on a vertical side of the first metal contact, a vertical side of the emitter semiconductor layer and on the base layer, anisotropically etching the dielectric layer off of the semiconductor substrate to form a dielectric sidewall spacer on the vertical side of the first metal contact and providing a second metal contact immediately adjacent the dielectric sidewall spacer.

Abstract: A system for forming self-aligned contacts includes electroplating a first metal contact onto a Group III-V semiconductor substrate, the first metal contact having a greater height than width and having a straight sidewall profile, etching back the semiconductor substrate down to a base layer to expose an emitter semiconductor layer under the first metal contact, conformally depositing a dielectric layer on a vertical side of the first metal contact, a vertical side of the emitter semiconductor layer and on the base layer, anisotropically etching the dielectric layer off of the semiconductor substrate to form a dielectric sidewall spacer on the vertical side of the first metal contact and providing a second metal contact immediately adjacent the dielectric sidewall spacer.

Abstract: A system for forming self-aligned contacts includes electroplating a first metal contact onto a Group III-V semiconductor substrate, the first metal contact having a greater height than width and having a straight sidewall profile, etching back the semiconductor substrate down to a base layer to expose an emitter semiconductor layer under the first metal contact, conformally depositing a dielectric layer on a vertical side of the first metal contact, a vertical side of the emitter semiconductor layer and on the base layer, anisotropically etching the dielectric layer off of the semiconductor substrate to form a dielectric sidewall spacer on the vertical side of the first metal contact and providing a second metal contact immediately adjacent the dielectric sidewall spacer.

Abstract: A system for forming self-aligned contacts includes electroplating a first metal contact onto a Group III-V semiconductor substrate, the first metal contact having a greater height than width and having a straight sidewall profile, etching back the semiconductor substrate down to a base layer to expose an emitter semiconductor layer under the first metal contact, conformally depositing a dielectric layer on a vertical side of the first metal contact, a vertical side of the emitter semiconductor layer and on the base layer, anisotropically etching the dielectric layer off of the semiconductor substrate to form a dielectric sidewall spacer on the vertical side of the first metal contact and providing a second metal contact immediately adjacent the dielectric sidewall spacer.

Abstract: A mask layer is applied to a surface of a semiconductor structure or a seed layer deposited on the surface. The mask layer has a submicron width opening with a high aspect ratio that exposes a portion of the surface or seed layer. Conductive material is conformed to the opening, for example by plating, to form a first contact on the surface or seed layer. The mask and the top layer of the semiconductor structure, except for the portion under the first contact, are removed to expose a second layer of the semiconductor structure. An insulating layer is formed along the sidewalls of the first contact and the top layer of the semiconductor structure beneath the first contact. A mask is then applied to the second layer and a second contact is formed by selectively depositing metal only on the portion of the second layer exposed by the opening.

Abstract: A method for fabricating an HBT is 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.

Abstract: 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.

Abstract: A bipolar junction transistor (BJT) requires the fabrication of a BJT structure and of a support post which is adjacent to, but physically and electrically isolated from, the BJT structure. The BJT structure includes a semi-insulating substrate, a subcollector, a collector, a base, and an emitter. Metal contacts are formed on the subcollector and emitter to provide collector and emitter terminals. Contact to the structure's base is accomplished with a metal contact which extends from the top of the support post to the edge of the base nearest the support post. The contact bridges the physical and electrical separation between the support post and the base and provides a base terminal for the device. The base contact need extend over the edge of the base by no more than the transfer length associated with the fabrication process. This results in the smaller base contact area over the collector than would otherwise be necessary, and a consequent reduction in base-collector capacitance.

Abstract: A BJT device configuration includes an emitter finger and via arrangement which reduces emitter finger width, and is particularly suitable for use with compound semiconductor-based devices. Each emitter finger includes a cross-shaped metal contact which provides an emitter contact; each contact comprises two perpendicular arms which intersect at a central area. A via through an interlevel dielectric layer provides access to the emitter contact; the via is square-shaped, centered over the center point of the central area, and oriented at a 45° angle to the arms. This allows the via size to be equal to or greater than the minimum process dimension, while allowing the width of the emitter finger to be as narrow as possible with the alignment tolerances still being met.

Abstract: A testing apparatus for determining the etch bias associated with a semiconductor-processing step includes a substrate, a first cathode finger with a first width on the substrate, a second cathode finger with a second width on the substrate, and a cathode large area on the substrate wherein the cathode large area has a third width W″ and a length L″ that are both substantially larger than either of the first and second widths.

Abstract: A thin InGaAs contact layer is provided for the collector of a heterojunction bipolar transistor (HBT) above an InP sub-collector. The contact layer provides a low resistance contact mechanism and a high thermal conductivity path for removing device heat though the sub-collector, and also serves as an etch stop to protect the sub-collector during device fabrication. A portion of the sub-collector lateral to the remainder of the HBT is rendered electrically insulative, preferably by an ion implant, to provide electrical isolation for the device and improve its planarity by avoiding etching through the sub-collector.

Abstract: A thin InGaAs contact layer is provided for the collector of a heterojunction bipolar transistor (HBT) above an InP sub-collector. The contact layer provides a low resistance contact mechanism and a high thermal conductivity path for removing device heat though the sub-collector, and also serves as an etch stop to protect the sub-collector during device fabrication. A portion of the sub-collector lateral to the remainder of the HBT is rendered electrically insulative, preferably by an ion implant, to provide electrical isolation for the device and improve its planarity by avoiding etching through the sub-collector.

Abstract: A III-V compound planar HBT-FET device integrates field effect transistors (FETs) with heterojunction bipolar transistors (HBTs) formed on the same semiconductor substrate. An HBT fabricated on the substrate includes a collector, a base, and an emitter. The HBT emitter comprises a lightly doped layer of a first conductivity type deposited atop a heavily doped base layer of a second conductivity type, a lightly doped emitter cap layer of the first conductivity type deposited atop the emitter layer, and a heavily doped emitter contact layer of the first conductivity type deposited atop the emitter cap layer. A FET, isolated from the HBT by areas of ion implantation, is formed in the layers of material deposited during fabrication of the HBT. The FET has a source and a drain formed in the heavily doped emitter contact layer, a gate recess etched in the emitter contact layer between the source and drain, and a Schottky gate metal contact deposited on the lightly doped emitter cap layer exposed in the gate recess.