Abstract: Bulk CMOS RF switches having reduced parasitic capacitance are achieved by reducing the size and/or doping concentration of the switch's N-doped tap (N-Tap) element, which is used to conduct a bias voltage to a Deep N-Well disposed under each switch's P-Type body implant (P-Well). Both the P-Well and the N-Tap extend between an upper epitaxial silicon surface and an upper boundary of the Deep N-well. A low-doping-concentration approach utilizes intrinsic (lightly doped) N-type epitaxial material to provide a body region of the N-Tap element, whereby an N+ surface contact diffusion is separated from an underlying section of the Deep N-well by a region of intrinsic epitaxial silicon. An alternative reduced-size approach utilizes an open-ring deep trench isolation structure that surrounds the active switch region (e.g., the Deep N-well and P-Well), and includes a relatively small-sized N-Tap region formed in an open corner region of the isolation structure.

Abstract: Methods for providing improved isolation structures in a SiGe BiCMOS process are provided. In one method, an n-type epitaxial layer is grown over a p-type high-resistivity substrate. A mask covers a first region, and exposes a second region, of the epitaxial layer. A p-type impurity is implanted through the mask, counter-doping the second region to become slightly p-type. Shallow trench isolation (STI) and optional deep trench isolation (DTI) regions are formed through the counter-doped second region, thereby providing an isolation structure. The first region of the epitaxial layer forms a collector region of a heterojunction bipolar transistor. In another method, shallow trenches are etched partially into the epitaxial layer through a mask. A p-type impurity is implanted through the mask, thereby counter-doping thin exposed regions of the epitaxial layer to become slightly p-type. The shallow trenches are filled with dielectric material and a CMP process is performed to form shallow trench isolation regions.

Abstract: Methods and structures for improved isolation in a SiGe BiCMOS process or a CMOS process are provided. In one method, shallow trench isolation (STI) regions are formed in a first semiconductor region located over a semiconductor substrate. Dummy active regions of the first semiconductor region extend through the STI regions to an upper surface of the first semiconductor region. A grid of deep trench isolation (DTI) regions is also formed in the first semiconductor region, wherein the DTI regions extend entirely through the first semiconductor region. The grid of DTI regions includes a pattern that exhibits only T-shaped or Y-shaped intersections. The pattern defines a plurality of openings, wherein a dummy active region is located within each of the openings.

Abstract: Bulk CMOS RF switches having reduced parasitic capacitance are achieved by reducing the size and/or doping concentration of the switch's N-doped tap (N-Tap) element, which is used to conduct a bias voltage to a Deep N-Well disposed under each switch's P-Type body implant (P-Well). Both the P-Well and the N-Tap extend between an upper epitaxial silicon surface and an upper boundary of the Deep N-well. A low-doping-concentration approach utilizes intrinsic (lightly doped) N-type epitaxial material to provide a body region of the N-Tap element, whereby an N+ surface contact diffusion is separated from an underlying section of the Deep N-well by a region of intrinsic epitaxial silicon. An alternative reduced-size approach utilizes an open-ring deep trench isolation structure that surrounds the active switch region (e.g., the Deep N-well and P-Well), and includes a relatively small-sized N-Tap region formed in an open corner region of the isolation structure.

Abstract: A thin Ge layer is formed between an SiGe intrinsic base and single-crystal Si extrinsic base structures to greatly simplify the fabrication of raised-base SiGe heterojunction bipolar transistors (HBTs). The fabrication process includes sequentially depositing the SiGe intrinsic base, the Ge, and Si extrinsic base layers as single-crystal structures over a patterned silicon wafer while the wafer is maintained inside a reaction chamber. The Ge layer subsequently functions as an etch stop, and protects the crystallinity of the underlying SiGe intrinsic base material during subsequent dry etching of the Si extrinsic base layer, which is performed to generate an emitter window. A wet etch then removes residual Ge from the emitter window to expose a contact portion of the SiGe layer surface without damage. A polysilicon emitter structure is formed in the emitter window, and then salicide is formed over the base stacks to encapsulate the SiGe and Ge structures.