Abstract: According to one exemplary embodiment, a heterojunction bipolar transistor includes a base situated on a substrate. The heterojunction bipolar transistor can be an NPN silicon-germanium heterojunction bipolar transistor, for example. The heterojunction bipolar transistor further includes a cap layer situated on the base, where the cap layer includes a barrier region. The barrier region can comprises carbon and has a thickness, where the thickness of the barrier region determines a depth of an emitter-junction of the heterojunction bipolar transistor. An increase in the thickness of the barrier region can cause a decrease in the depth of the emitter-base junction. According to this exemplary embodiment, the heterojunction bipolar transistor further includes an emitter situated over the cap layer, where the emitter comprises an emitter dopant, which can be phosphorus. A diffusion retardant in the barrier region of the cap layer impedes diffusion of the emitter dopant.

Abstract: According to one exemplary embodiment, a bipolar transistor includes an active area situated between first and second isolation regions in a substrate. The bipolar transistor further includes an epitaxial extension layer situated on the active area, where the epitaxial extension layer extends over the first and second isolation regions. The bipolar transistor further includes a base layer situated on the epitaxial extension layer, where the base layer includes an epitaxial base, and where the epitaxial base includes a usable emitter formation area. The active area has a first width and the usable emitter formation area has a second width, where the second width is at least as large as the first width.

Abstract: According to one exemplary embodiment, a heterojunction bipolar transistor includes a base situated on a substrate. The heterojunction bipolar transistor can be an NPN silicon-germanium heterojunction bipolar transistor, for example. The heterojunction bipolar transistor further includes a cap layer situated on the base, where the cap layer includes a barrier region. The barrier region can comprises carbon and has a thickness, where the thickness of the barrier region determines a depth of an emitter-junction of the heterojunction bipolar transistor. An increase in the thickness of the barrier region can cause a decrease in the depth of the emitter-base junction. According to this exemplary embodiment, the heterojunction bipolar transistor further includes an emitter situated over the cap layer, where the emitter comprises an emitter dopant, which can be phosphorus. A diffusion retardant in the barrier region of the cap layer impedes diffusion of the emitter dopant.

Abstract: According to one exemplary embodiment, a heterojunction bipolar transistor includes a base situated on a substrate. The heterojunction bipolar transistor can be an NPN silicon-germanium heterojunction bipolar transistor, for example. The heterojunction bipolar transistor further includes a cap layer situated on the base, where the cap layer includes a barrier region. The barrier region can comprises carbon and has a thickness, where the thickness of the barrier region determines a depth of an emitter-junction of the heterojunction bipolar transistor. An increase in the thickness of the barrier region can cause a decrease in the depth of the emitter-base junction. According to this exemplary embodiment, the heterojunction bipolar transistor further includes an emitter situated over the cap layer, where the emitter comprises an emitter dopant, which can be phosphorus. A diffusion retardant in the barrier region of the cap layer impedes diffusion of the emitter dopant.

Abstract: According to one exemplary embodiment, a bipolar transistor includes an active area situated between first and second isolation regions in a substrate. The bipolar transistor further includes an epitaxial extension layer situated on the active area, where the epitaxial extension layer extends over the first and second isolation regions. The bipolar transistor further includes a base layer situated on the epitaxial extension layer, where the base layer includes an epitaxial base, and where the epitaxial base includes a usable emitter formation area. The active area has a first width and the usable emitter formation area has a second width, where the second width is at least as large as the first width.

Abstract: According to an exemplary embodiment, a method for integrating bipolar and CMOS devices on a substrate, where the substrate includes bipolar and CMOS regions and has a sacrificial oxide layer situated thereon, includes removing a portion of the sacrificial oxide layer in the bipolar region of the substrate to expose a top surface of the substrate. The method includes forming a base layer on the top surface of the substrate in the bipolar region. The base layer forms a bipolar transistor base. The method further includes forming a sacrificial post on the base layer in the bipolar region and at least one gate electrode in the CMOS region of the substrate. A common mask is used to form the sacrificial post and the at least one gate electrode. The method further includes forming LDD regions adjacent to the at least one gate electrode in the CMOS region.

Abstract: According to one exemplary embodiment, a heterojunction bipolar transistor includes a base situated on a substrate. The heterojunction bipolar transistor can be an NPN silicon-germanium heterojunction bipolar transistor, for example. The heterojunction bipolar transistor further includes a cap layer situated on the base, where the cap layer includes a barrier region. The barrier region can comprises carbon and has a thickness, where the thickness of the barrier region determines a depth of an emitter-junction of the heterojunction bipolar transistor. An increase in the thickness of the barrier region can cause a decrease in the depth of the emitter-base junction. According to this exemplary embodiment, the heterojunction bipolar transistor further includes an emitter situated over the cap layer, where the emitter comprises an emitter dopant, which can be phosphorus. A diffusion retardant in the barrier region of the cap layer impedes diffusion of the emitter dopant.

Abstract: According to one exemplary embodiment, a bipolar transistor includes an active area situated between first and second isolation regions in a substrate. The bipolar transistor further includes an epitaxial extension layer situated on the active area, where the epitaxial extension layer extends over the first and second isolation regions. The bipolar transistor further includes a base layer situated on the epitaxial extension layer, where the base layer includes an epitaxial base, and where the epitaxial base includes a usable emitter formation area. The active area has a first width and the usable emitter formation area has a second width, where the second width is at least as large as the first width.

Abstract: A method for fabricating an NPN bipolar transistor comprises forming a base layer on a top surface of a substrate. The NPN bipolar transistor may be an NPN silicon-germanium heterojunction bipolar transistor. The method for fabricating the NPN bipolar transistor may further comprise a cap layer situated over the base layer. According to this embodiment, the method for fabricating the NPN bipolar transistor further comprises fabricating an emitter over the base layer, where the emitter defines an intrinsic and an extrinsic base region of the base layer. The emitter may comprise, for example, polycrystalline silicon. The method for fabricating the NPN bipolar transistor further comprises implanting germanium in the extrinsic base region of the base layer so as to make the extrinsic base region substantially amorphous. The method for fabricating the NPN bipolar transistor further comprises implanting boron in the extrinsic base region of the base layer.

Abstract: According to one exemplary embodiment, an NPN bipolar transistor comprises a base layer situated over a collector, where the base layer comprises an intrinsic base region and an extrinsic base region. The NPN bipolar transistor may be, for example, an NPN silicon-germanium heterojunction bipolar transistor. The base layer can be, for example, silicon-germanium. According to this exemplary embodiment, the NPN bipolar transistor further comprises a cap layer situated over the base layer, where a portion of the cap layer is situated over the extrinsic base region, and where the portion of the cap layer situated over the extrinsic base region comprises an indium dopant. The cap layer may be, for example, polycrystalline silicon. According to this exemplary embodiment, the NPN bipolar transistor may further comprise an emitter situated over the intrinsic base region. The emitter may be, for example, polycrystalline silicon.

Abstract: A method for fabricating an NPN bipolar transistor comprises forming a base layer on a top surface of a substrate. The NPN bipolar transistor may be an NPN silicon-germanium heterojunction bipolar transistor. The method for fabricating the NPN bipolar transistor may further comprise a cap layer situated over the base layer. According to this embodiment, the method for fabricating the NPN bipolar transistor further comprises fabricating an emitter over the base layer, where the emitter defines an intrinsic and an extrinsic base region of the base layer. The emitter may comprise, for example, polycrystalline silicon. The method for fabricating the NPN bipolar transistor further comprises implanting germanium in the extrinsic base region of the base layer so as to make the extrinsic base region substantially amorphous. The method for fabricating the NPN bipolar transistor further comprises implanting boron in the extrinsic base region of the base layer.

Abstract: According to one exemplary embodiment, an NPN bipolar transistor comprises a base layer situated over a collector, where the base layer comprises an intrinsic base region and an extrinsic base region. The NPN bipolar transistor may be, for example, an NPN silicon-germanium heterojunction bipolar transistor. The base layer can be, for example, silicon-germanium. According to this exemplary embodiment, the NPN bipolar transistor further comprises a cap layer situated over the base layer, where a portion of the cap layer is situated over the extrinsic base region, and where the portion of the cap layer situated over the extrinsic base region comprises an indium dopant. The cap layer may be, for example, polycrystalline silicon. According to this exemplary embodiment, the NPN bipolar transistor may further comprise an emitter situated over the intrinsic base region. The emitter may be, for example, polycrystalline silicon.

Abstract: According to one exemplary embodiment, a heterojunction bipolar transistor is fabricated by forming a metastable epitaxial silicon-germaniuim base on a collector. The metastable epitaxial silicon-germanium base, for example, may have a concentration of germanium greater than 20.0 atomic percent of germanium. The heterojunction bipolar transistor, for example, may be an NPN silicon-germanium heterojunction bipolar transistor. According to this exemplary embodiment, the heterojunction bipolar transistor is further fabricated by fabricating an emitter over the metastable epitaxial silicon-germanium base. The heterojunction bipolar transistor is further fabricated by doping the emitter with a first dopant. The first dopant, for example, may be arsenic.

Abstract: According to one exemplary embodiment, a heterojunction bipolar transistor comprises a base having a concentration of a first material at a first depth, where the first material impedes the diffusion of a base dopant. The first material also causes a change in band gap at the first depth in the base. According to this exemplary embodiment, the base further includes a concentration of a second material, where the concentration of second material increases at the first depth so as to counteract the change in band gap.

Abstract: According to one exemplary embodiment, a heterojunction bipolar transistor comprises a base having a top surface. The heterojunction bipolar transistor further comprises an epitaxial emitter selectively situated on the top surface of the base. For example, the epitaxial emitter may be N-type single-crystal silicon. The heterojunction bipolar transistor further comprises an etch stop layer situated on the top surface of the base, where the etch stop layer is in contact with the epitaxial emitter. The heterojunction bipolar transistor further comprises a first spacer and a second spacer situated on the etch stop layer, where the epitaxial emitter is situated between the first and second spacer. The first spacer and the second spacer, for example, may be LPCVD silicon nitride. The heterojunction bipolar transistor further comprises a dielectric layer deposited on the first and second spacers.

Abstract: According to one exemplary embodiment, a heterojunction bipolar transistor comprises a base having a concentration of germanium, where the concentration of germanium decreases between a first depth and a second depth in the base. According to this exemplary embodiment, the base of the heterojunction bipolar transistor further comprises a concentration of a diffusion suppressant of a base dopant, where the concentration of the diffusion suppressant decreases between a third depth and a fourth depth so as to counteract a change in band gap in the base between the first depth and the second depth. For example, the diffusion suppressant can be carbon and the base dopant can be boron. For example, the concentration of diffusion suppressant may decrease between the third depth and fourth depth so as to counteract the change in band gap at approximately the second depth.

Abstract: According to one exemplary embodiment, a heterojunction bipolar transistor comprises a base having a concentration of germanium, where the concentration of germanium decreases between a first depth and a second depth in the base. According to this exemplary embodiment, the base of the heterojunction bipolar transistor further comprises a concentration of a diffusion suppressant of a base dopant, where the concentration of the diffusion suppressant decreases between a third depth and a fourth depth so as to counteract a change in band gap in the base between the first depth and the second depth. For example, the diffusion suppressant can be carbon and the base dopant can be boron. For example, the concentration of diffusion suppressant may decrease between the third depth and fourth depth so as to counteract the change in band gap at approximately the second depth.

Abstract: According to one exemplary embodiment, a heterojunction bipolar transistor comprises a base having a top surface. The heterojunction bipolar transistor further comprises an epitaxial emitter selectively situated on the top surface of the base. For example, the epitaxial emitter may be N-type single-crystal silicon. The heterojunction bipolar transistor further comprises an etch stop layer situated on the top surface of the base, where the etch stop layer is in contact with the epitaxial emitter. The heterojunction bipolar transistor further comprises a first spacer and a second spacer situated on the etch stop layer, where the epitaxial emitter is situated between the first and second spacer. The first spacer and the second spacer, for example, may be LPCVD silicon nitride. The heterojunction bipolar transistor further comprises a dielectric layer deposited on the first and second spacers.

Abstract: According to one exemplary embodiment, a heterojunction bipolar transistor comprises a base having a concentration of a first material at a first depth, where the first material impedes the diffusion of a base dopant. For example, the first material can be carbon and the base dopant can be boron. The first material also causes a change in band gap at the first depth in the base. According to this exemplary embodiment, the base further comprises a concentration of a second material, where the concentration of second material increases at the first depth so as to counteract the change in band gap. For example, the second material may be germanium. The concentration of the second material, for example, may increase at the first depth by amount required to cause a decrease in band gap to be substantially equal to the increase in band gap caused by concentration of the first material.

Abstract: According to one exemplary embodiment, a heterojunction bipolar transistor comprises a base having a concentration of germanium, where the concentration of germanium decreases between a first depth and a second depth in the base. According to this exemplary embodiment, the base of the heterojunction bipolar transistor further comprises a concentration of a diffusion suppressant of a base dopant, where the concentration of the diffusion suppressant decreases between a third depth and a fourth depth so as to counteract a decrease in band gap in the base between the first depth and the second depth. For example, the diffusion suppressant can be carbon and the base dopant can be boron. For example, the concentration of diffusion suppressant may decrease between the third depth and fourth depth so as to counteract the decrease in band gap at approximately the second depth.