National Semiconductor Corporation

Texas Instruments Corporation

Jamal Ramdani

Craig Richard Printy

Sandeep Raj Bahl

Andre Paul Labonte

Mingwei Xu

Alexei Sadovnikov

James B Wieser

Dennis M Monticelli

Michael X Maida

Lawrence Herbert Zuckerman

Monir H El-Diwany

Steven J Adler

Thanas Budri

Jeff A Babcock

Paul Mawson

Wibo Van Noort

Donald Robertson Getchell

Moulay Mohamed Ibourk

Steve Adler

Todd Thiebeault

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.

Normally-off gallium nitride-based semiconductor devices

A method includes forming a stress compensation layer over a first side of a semiconductor substrate and forming a Group III-nitride layer over a second side of the substrate. Stress created on the substrate by the Group III-nitride layer is at least partially reduced by stress created on the substrate by the stress compensation layer. Forming the stress compensation layer could include forming a stress compensation layer from amorphous or microcrystalline material. Also, the method could include crystallizing the amorphous or microcrystalline material during subsequent formation of one or more layers over the second side of the substrate. Crystallizing the amorphous or microcrystalline material could occur during subsequent formation of the Group III-nitride layer and/or during an annealing process. The amorphous or microcrystalline material could create no or a smaller amount of stress on the substrate, and the crystallized material could create a larger amount of stress on the substrate.

Backside stress compensation method for making gallium nitride or other nitride-based semiconductor devices

A method includes forming a first epitaxial layer over a semiconductor substrate and etching the first epitaxial layer to form multiple separated first epitaxial regions. The method also includes forming a second epitaxial layer over the etched first epitaxial layer. Each epitaxial layer includes at least one Group III-nitride, and the epitaxial layers collectively form a buffer. The method further includes forming a device layer over the buffer and fabricating a semiconductor device using the device layer. The second epitaxial layer could include second epitaxial regions substantially only on the first epitaxial regions. The second epitaxial layer could also cover the first epitaxial regions and the substrate, and the second epitaxial layer may or may not be etched. The device layer could be formed during the same operation used to form the second epitaxial layer.

Growth of multi-layer group III-nitride buffers on large-area silicon substrates and other substrates

An enhancement-mode GaN MOSFET with a low leakage current and an improved reliability is formed by utilizing a SiO/SiNgate insulation layer on an AlGaN (or InAlGaN) barrier layer. The SiNportion of the SiO/SiNgate insulation layer significantly reduces the formation of interface states at the junction between the gate insulation layer and the barrier layer, while the SiOportion of the SiO/SiNgate insulation layer significantly reduces the leakage current.

Enhancement-mode GaN MOSFET with low leakage current and improved reliability

Backside stress compensation for gallium nitride or other nitride-based semiconductor devices

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.

Stress compensation for large area gallium nitride or other nitride-based structures on semiconductor substrates

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.

Heart monitoring system or other system for measuring magnetic fields

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.

Magneto electric sensor with injected up-conversion or down-conversion

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.

SiGe heterojunction bipolar transistor and method of forming a SiGe heterojunction bipolar transistor

A bipolar transistor structure comprises a semiconductor substrate having a first conductivity type, a collector region having a second conductivity type that is opposite the first conductivity type formed in a substrate active device region defined by isolation dielectric material formed in an upper surface of the semiconductor substrate, a base region that includes an intrinsic base region having the first conductivity type formed over the collector region and an extrinsic base region having the second conductivity type formed over the isolation dielectric material, and a sloped in-situ doped emitter plug having the second conductivity type formed on the intrinsic base region.

Self-aligned bipolar transistor structure

A base structure for high performance Silicon Germanium:Carbon (SiGe:C) based heterojunction bipolar transistors (HBTs) with phosophorus atomic layer doping (ALD) is disclosed. The ALD process subjects the base substrate to nitrogen gas (in ambient temperature approximately equal to 500 degrees Celsius) and provides an additional SiGe:C spacer layer. During the ALD process, the percent concentrations of Germanium (Ge) and carbon (C) are substantially matched and phosphorus is a preferred dopant. The improved SiGe:C HBT is less sensitive to process temperature and exposure times, and exhibits lower dopant segregation and sharper base profiles.

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Scarborough, ME, United States of America

Jamal Ramdani