摘要:
A system and method are disclosed for providing an improved polyemit module for a self aligned heterojunction bipolar transistor architecture. The polyemit module of the transistor of the present invention is formed using a double layer deposition process. In the double layer deposition process, the first layer is a layer of emitter polysilicon and the second layer is a sacrificial layer of silicon germanium (SiGe). The shape and thickness of the emitter polysilicon layer of the polyemit module provides (1) a reduction in the overall resistance of the emitter and (2) an increase in the contact area between the emitter polysilicon layer and a contact structure that is more than three times the contact area that is provided in prior art polyemit modules.
摘要:
A system and method are disclosed for providing a self aligned silicon germanium (SiGe) heterojunction bipolar transistor using a mesa emitter-base architecture. The transistor of the present invention comprises a non-selective epitaxial growth (NSEG) collector, an NSEG base, an NSEG emitter and a raised external base that is formed by the selective epitaxial growth (SEG) of a doped polysilicon layer.
摘要:
A system and method are disclosed for providing a fully self aligned bipolar transistor using modified cavity formation to optimize selective epitaxial growth. A collector of a transistor is formed and at least two layers of silicon oxide are formed above the collector and covered with a polysilicon external raised base. Then an emitter window is etched through the polysilicon external raised base down to the top layer of silicon oxide. A wet etch process is performed to form a cavity in the at least two layers of silicon oxide. Different wet etch rates of the silicon layers with respect to the wet etch process cause the cavity to be formed with a shape that optimizes selective epitaxial growth in the cavity. Polysilicon rich corners and a monocrystalline silicon base are then formed within the cavity.
摘要:
A method includes forming a stress compensating stack over a substrate, where the stress compensating stack has compressive stress on the substrate. The method also includes forming one or more Group III-nitride islands over the substrate, where the one or more Group III-nitride islands have tensile stress on the substrate. The method further includes at least partially counteracting the tensile stress from the one or more Group III-nitride islands using the compressive stress from the stress compensating stack. Forming the stress compensating stack could include forming one or more oxide layers and one or more nitride layers over the substrate. The one or more oxide layers can have compressive stress, the one or more nitride layers can have tensile stress, and the oxide and nitride layers could collectively have compressive stress. Thicknesses of the oxide and nitride layers can be selected to provide the desired amount of stress compensation.
摘要:
A heterostructure semiconductor device includes a first active layer and a second active layer disposed on the first active layer. A two-dimensional electron gas layer is formed between the first and second active layers. A first gate dielectric layer is disposed on the second active layer. A second gate dielectric layer is disposed on the first gate dielectric layer. A passivation layer is disposed over the second gate dielectric layer. A gate extends through the passivation layer to the second gate dielectric layer. First and second ohmic contacts electrically connect to the second active layer. The first and second ohmic contacts are laterally spaced-apart, with the gate being disposed between the first and second ohmic contacts.
摘要:
A system includes at least one first magnetic field sensor configured to measure first and second magnetic fields. The system also includes at least one second magnetic field sensor configured to measure the second magnetic field substantially without measuring the first magnetic field. The system further includes processing circuitry configured to perform signal cancellation to generate measurements of the first magnetic field and to generate an output based on the measurements of the first magnetic field. The sensors could represent magneto-electric sensors. The magneto-electric sensors could be configured to up-convert electrical signals associated with the first and/or second magnetic fields to a higher frequency. The processing circuitry could be configured to identify one or more problems associated with a patient's heart.
摘要:
A method includes generating an electrical signal representing a magnetic field using a magnetic field sensor having alternating layers of magneto-strictive material and piezo-electric material. The method also includes performing up-conversion or down-conversion so that the electrical signal representing the magnetic field has a higher or lower frequency than a frequency of the magnetic field. The up-conversion or down-conversion is performed before the magnetic field is converted into the electrical signal. The up-conversion or down-conversion could be performed by repeatedly sensitizing and desensitizing the magnetic field sensor. This could be done using a permanent magnet and an electromagnet, an electromagnet without a permanent magnet, or a movable permanent magnet. The up-conversion or down-conversion could also be performed by chopping the magnetic field. The chopping could involve intermittently shielding the magnetic field sensor from the magnetic field or moving the magnetic field sensor with respect to the magnetic field.
摘要:
A SiGe heterojunction bipolar transistor is fabricated by etching an epitaxially-formed structure to form a mesa that has a collector region, a cap region, and a notched SiGe base region that lies in between. A protective plug is formed in the notch of the SiGe base region so that thick non-conductive regions can be formed on the sides of the collector region and the cap region. Once the non-conductive regions have been formed, the protective plug is removed. An extrinsic base is then formed to lie in the notch and touch the base region, followed by the formation of isolation regions and an emitter region.
摘要:
A method includes forming a relaxed layer in a semiconductor device. The method also includes forming a tensile layer over the relaxed layer, where the tensile layer has tensile stress. The method further includes forming a compressive layer over the relaxed layer, where the compressive layer has compressive stress. The compressive layer has a piezoelectric polarization that is approximately equal to or greater than a spontaneous polarization in the relaxed, tensile, and compressive layers. The piezoelectric polarization in the compressive layer could be in an opposite direction than the spontaneous polarization in the compressive layer. The relaxed layer could include gallium nitride, the tensile layer could include aluminum gallium nitride, and the compressive layer could include aluminum indium gallium nitride.
摘要:
One or more trenches can be formed around a first portion of a semiconductor substrate, and an insulating layer can be formed under the first portion of the semiconductor substrate. The one or more trenches and the insulating layer electrically isolate the first portion of the substrate from a second portion of the substrate. The insulating layer can be formed by forming a buried layer in the substrate, such as a silicon germanium layer in a silicon substrate. One or more first trenches through the substrate to the buried layer can be formed, and open spaces can be formed in the buried layer (such as by using an etch selective to silicon germanium over silicon). The one or more first trenches and the open spaces can optionally be filled with insulative material(s). One or more second trenches can be formed and filled to isolate the first portion of the substrate.