Component arrangement having magnetic field controlled transistor

Abstract: A controllable magnetic field generator (10) applies a magnetic field to a transistor device (5) at a particular orientation for producing a corresponding Lorentz force (F) on the flow of carriers (11) in the device to advantageously deflect the carriers to facilitate performance of a corresponding desired circuit function. Such a component arrangement is useable in a variety of circuit configurations for performing different circuit functions with a reduced number of devices and complexity relative to conventional circuit configurations. Exemplary circuit configurations for signal mixers, differential amplifiers, switches, and multiplexers and demultiplexers are possible using as little as one or two devices. According to another aspect of the invention, an inductor coil is used for the magnetic field generator and is formed on a substrate (15) containing the transistor device to provide a component arrangement having relatively compact dimensions.

Description: This invention relates to component arrangements. Modem electronic products including, for example, consumer electronics, computers, telecommunication equipment and automobile electronics use semiconductor devices, such as transistors, to perform a desired function. Exemplary functions performed by semiconductor devices in such products include electrical signals routing switches, multiplexer/demultiplexers, differential amplifiers, and signal mixers such as up and down signal converters for modulation or demodulation. Typical circuit configurations of at least four transistors, in integrated circuit form or otherwise, are used for producing a 1 x 2 signal routing switch circuit or multiplexer/demultiplexer, which is described in greater detail in, for example, N. Weste and K. Eshraghian, Principles of CMOS VLSI Design, ch. 1, pp. 4-29 (Addison-Wesley Publishing Co. 1985). Also, typical circuit configurations of at least seven transistors are used for producing an up or down signal converter circuit, such as a conventional Gilbert cell, which is described in greater detail in, P. Gray and R. Meyer, Analysis and Design of Analog Integrated Circuits, pp. 590-593 (John Wiley & Sons 1984). Also, JP-A-08 088 324 discloses a field-effect transistor configured to restrain a short-channel effect without using a buried layer. The transistor uses a coil positioned with respect to the transistor to act on the carriers in such a way that they remain confined in the channel layer. IBM Technical Disclosure Bulletin, vol. 13, no. 12, p.3633 ("Two drain FET Magnetic Field Sensor") discloses a two-drain field-effect transistor that measures the strength and direction of an applied magnetic field. The device uses the differential current to the two drains, caused by the deflection of carriers, to measure the strength of the applied magnetic field. Also, the device uses the polarity of the differential current to measure the field's direction. EP-A-0 063 209 discloses multiple-collector transistor arrangements in which carrier injection is modulated by the Lorentz field, which is produced by the application of a magnetic field. JP-A-61 188 978 discloses a semiconductor device having a magnetic field producing means sandwiched therein. Reduction in the size, complexity and cost of electronic components has been a general goal of the electronic industry. A limited reduction in the size of typical components has been achieved by reductions in the size of the fabricated devices and other circuit elements. However, the complexity and number of devices required to perform such circuit functions has not been reduced in conventional electronic components. Accordingly, a circuit configuration to perform such functions with a reduced number of devices and complexity is desirable. According to this invention there is provided a component arrangement as claimed in claim 1. The invention advantageously uses a controllable magnetic field generator at a particular position relative to a transistor device such that when carriers flow within the device, such as when the device is enabled, a magnetic field produced by the generator extends through the carrier flow and produces a Lorentz force that deflects the carriers in a desired relative direction to provide a corresponding desired circuit function. The component arrangement of this invention is useable in a variety of circuit configurations for performing different functions with a reduced number of devices and complexity relative to conventional circuits. Exemplary circuit configurations for signal mixers, up and down converters, modulators/demodulators,differential amplifiers, switches, and multiplexers/ demultiplexers are possible using as little as one or two devices. For example, it is possible for a signal mixer arrangement to use a single FET device and magnetic field generator. When the device is enabled, carriers flow forming an inversion layer under the gate, between the source and drain regions. The magnetic field generator is positioned, for example, such that it generates a corresponding magnetic field extending in a direction substantially perpendicular to the direction of the carrier flow and substantially parallel to the inversion layer. The magnetic field is then varied based on a first signal to be mixed having a frequency ƒ 1 . A second signal to be mixed having a frequency ƒ 2 is applied to the device gate which varies the formation of the inversion layer according to such frequency stimulus. As a result, carrier flow in the inversion layer is modulated by both the Lorentz force produced by the varying magnetic field according to the first signal as well as by the second signal at the device gate to produce a mixed signal with at least frequencies |ƒ 1 ± ƒ 2 | at the device drain. The controllable magnetic field generator comprises an inductor coil formed on a substrate containing the transistor device to provide a component arrangement having relatively compact dimensions. Additional features and advantages of the invention will become more readily apparent from the following detailed description and accompanying drawings. Brief Description of the Drawings FIG. 1 is a cut-away perspective representation of a component arrangement embodying the invention; FIG. 2 illustrates a schematic block diagram of an exemplary signal mixer circuit employing the component arrangement of FIG. 1; and FIG. 3 illustrates a graph of an exemplary modulated signal produced by the signal mixer circuit shown in FIG. 2. Detailed Description The invention employs a controllable magnetic field generator at a particular relative position to a transistor device such that when the device is enabled and carriers flow within the device, a magnetic field produced by the generator extends through the carrier flow and produces a Lorentz force that deflects the carriers in a desired relative direction to cause the performance of a desired circuit function. Exemplary component arrangements for performing signal mixing and routing functions using field effect transistors (FETs) are depicted in the drawing and described below for illustration purposes only and not meant to be a limitation of the invention. Moreover, it should be readily understood that it is possible to practice the invention in numerous other component arrangements for performing other circuit functions including, for example, arrangements for performing circuit functions of a differential amplifier and multiplexer/demultiplexer. An exemplary component arrangement 1 embodying the invention is shown in FIG. 1. Referring to FIG. 1, the component arrangement 1 includes a FET device 5 formed within a substrate 15, and a controllable magnetic field generator, such as inductor coil 10. It is possible for the device 5 to be a conventional ambient-temperature metal-oxide-semiconductor (MOS) FET or MOSFET. The particular type of MOS device used for the device 5 is not critical to practicing the invention and can be, for example, a NMOS, PMOS or CMOS device based on the desired operation of the component arrangement 1. Other types of FET devices useable for the device 5 include, for example, metal-semiconductor FET (MESFET) and metal-insulator-semiconductor-type FET (MISFET) devices. Further, it is possible for the device 5 to be a discrete component or part of an integrated circuit. Conventional methods for fabricating the MOSFET device 5 are described in, for example, S. M. Sze, VLSI Technology, Chap. 11, pp. 466-515 (McGraw-Hill 1988). Such conventional devices are typically formed of discrete layers of semiconductor, insulator and metal. For instance, the exemplary device 5 includes a p-type Si substrate 15 having source and drain regions 20 and 25 formed by doping with n -type impurities, such as arsenic or phosphorous for NMOS. An optional layer of silicide 30 is deposited over the source and drain regions 20 and 25 to reduce the source and drain resistance which enables greater current delivery by the device 5. A gate 35 of the device 5 includes, for example, polysilicon 40 doped with an n -type impurity such as by an implant or vapor doping. The gate polysilicon 40 is disposed on a SiO 2 spacer 45 on the substrate 15. An optional layer of silicide (not shown) can also be deposited over the gate polysilicon 40 to reduce the gate's electrical resistance. An insulating layer 50 of, for example, SiO 2 or P-glass which is an oxide doped with a phosphorus is then deposited on the transistor to provide physical protection and to facilitate electrical connection. Contact windows 55 are etched in the insulating layer 50 to expose the device gate 35 and source and drain regions 20 and 25. Leads S , G and D are connected to the source, gate and drain regions 20, 35 and 25, respectively. Although a N -channel MOSFET device has previously been described, it should be readily understood that a P -channel device is also useable for the device 5. The inductor coil 10 is formed on a surface of the insulator 50 and has leads L 1 and L 2 . Conventional methods for forming such a coil include those described in N. Nguyen and R. Meyer, "Si IC-Compatible Inductors and LC Passive Filters", IEEE J. Solid-State Circuits, vol. 25, no. 4, pp. 1028-31 (August 1990), and J. Chang, A. Abidi and M. Gaitan, "Large Suspended Inductors on Silicon and Their Use in a 2-µm CMOS RF Amplifier", IEEE Electron Device Letters, vol. 15, no. 5, pp. 246-248 (May 1993). Although an on-chip inductor coil 10 is used for the controllable magnetic field generator, it is alternatively possible to use an off-chip inductor coil, for generation of a magnetic field . For instance, a formed inductor coil supported at a distance above the substrate as described in, for example, T. Gabara, K. Tai, M. Lau, S. Pei, R. Frye and P. Sullivan, "A 27mW CMOS RF Oscillator Operating at 1.2 GHz", Proc. of 1994 IEEE Multi-Chip Module Conf. MCMC-1994, pp. 15-19(1994) is useable and enhances the quality factor of the corresponding component arrangement. During operation, an inversion layer is formed in a channel under the gate 35 of the device 5, between the source and drain regions 20 and 25 under the gate 35. An exemplary formed inversion layer is shown between the layer 45 and the dashed line 38. It is possible to form such an inversion layer in a conventional manner such as by providing a sufficient voltage on the gate lead G and a voltage difference between the source and drain leads S and D . Carriers flow in the formed inversion layer from the source region 20 to the drain region 25. Carriers refer to flow of negative or positive charges or their equivalents in a semiconductor and include, for example, electrons to convey negative charges, such as in N -channel devices, or holes to convey positive charges, such as in P -channel FET devices. Carrier flow in transistor devices is described in general in A. Grove, Physics and Technology of Semiconductor Devices, ch. 11, pp. 317-333 (John Wiley & Sons, 1967). The velocity of the carriers flowing between the source 20 and the drain 25 is represented by the vector U . The carrier flow produces a corresponding signal output at the source and/or drain leads S and D . The formation of the inversion layer which controls the carrier flow rate and corresponding output signal magnitude is typically based on a voltage magnitude present at the gate 35. Accordingly, it is possible to modulate the carrier flow by modulating the voltage on the gate lead G . However, it is also possible to further modulate the carriers reaching the drain 25 based on a magnetic field generated by the inductor coil 10. The magnitude of such a magnetic field is based on a current I L flowing in the inductor coil 10. The inductor coil 10 is positioned such that a generated magnetic field extends under the coil 10 through the produced inversion layer in a direction substantially parallel to the inversion layer and substantially perpendicular to the direction of the carrier flow U as indicated by the magnetic flux density vector B . Such a magnetic field produces a corresponding Lorentz force on the carriers in the direction indicated by the vector F . The direction and magnitude of the force F acting on the carriers is based on the expression: F = q ( E + U × B ), where the value q is the charge of the carriers and the vector E is the electric field in the MOS device caused by a Hall voltage produced in the device due to the effect of the magnetic field. Hall effect and the corresponding Hall voltage are described in, for example, S. Sze, Physics of Semiconductor Devices, pp. 27-35 (John Wiley & Sons 1981). Since the carriers are election in the N -channel device 5, the charge q has a negative value. The carriers are deflected in the direction of the produced Lorentz force F which creates a Hall voltage that varies the threshold voltage and thereby, alters the number of carriers reaching the drain region 25. As a result, the signal produced at the drain lead D is altered a respective amount compared to a conventional device that is not exposed to such magnetic field. As a result, the magnitude of the magnetic field determines the extent of the variation of the number of carriers reaching the drain region 25. The invention exploits such behavior and modulates the carrier flow reaching the drain region 25 by controlling the current signal I L flowing in the inductor coil 10. Such modulation operates substantially independent of the conventional modulation of the inversion layer depth and carrier flow rate by the voltage at the gate 35. As a consequence, the component arrangement 1 is advantageously useable for performing numerous signal mixing circuit functions, such as a modulator/ demodulator, up- or down-signal converter, and differential amplifier. An exemplary signal mixer circuit 100 using the component arrangement 1 is shown in FIG. 2, described below. The particular length L of the gate 35 or channel length in the FET device 5 also determines the distance over which flowing carriers would be subjected to the magnetic field. As a consequence, longer gate lengths enable a greater deflection of the carriers from a particular magnetic field. Gate lengths L in the approximate range of, for example, 0.25 µm to 4.0 µm, are useable according to the invention. Also, the width W of the gate 35 should be large enough for providing sufficient exposure of the carrier flow to a generated magnetic field to achieve the desired modulation effect. For instance, when an on-chip inductor coil is used for the magnetic field generator, such as that shown in FIG. 1, it is possible to employ a gate width W in the range of approximately 20 µm to 80 µm based on the size of conventional fabricated on-chip inductor coils. However, if the magnetic field generator can produce magnetic fields of greater magnitudes, then smaller gate widths are useable. In FIG. 2, the component arrangement 1 of FIG. 1 is shown by the schematic symbol indicated by like reference number 1 within the signal mixer circuit 100 for clarity. A local oscillator signal source, such as a voltage source 105, is connected to lead L 1 of the inductor coil in the component arrangement 1. The lead L 2 of the component arrangement 1 is connected to resistor R 1 that is connected to ground. The device source lead S of the component arrangement 1 is also connected to ground. The device drain lead D of the component arrangement 1 is connected to resistor R 2 which is further connected voltage source V DD . Also, an output signal V OUT is generated at the device drain lead D. The device gate lead G of the component arrangement 1 is connected to resistor R 3 which is further connected to a bias voltage source V BIAS . A DC-blocking capacitor C 1 is connected between the device gate lead G and an intermediate frequency signal source, such as voltage source 110. In operation, the voltage source V DD and bias voltage source V BIAS generates sufficient voltages to produce an inversion layer in the FET device of the component arrangement 1 and cause carriers to flow between the device source and drain in a manner previously described with respect to FIG. 1. It is possible for the voltage of the voltage sources V DD and V BIAS to be in the approximate ranges of 1.8 V to 3.6 V, and 1.0 V to 2.0 V, respectively, when a conventional MOSFET device is employed in the component arrangement 1. The voltage source 110 generates signal V IF with a frequency ƒ 1 . The generated signal V IF produces a corresponding variation in the formation of the inversion layer at the frequency ƒ 1 which causes a corresponding modulation of the carrier flow rate at that frequency. Such modulation of the carrier flow rate produces a corresponding oscillating signal variation in the output signal V OUT at the frequency ƒ 1 . The voltage source 105 generates a signal V LO having a frequency ƒ 2 . A corresponding produced current I LO through the inductor coil of the component arrangement 1 causes a corresponding magnetic field that varies in magnitude at the frequency ƒ 1 . Such variation in magnitude produces a corresponding variation of the Lorentz force upon the carriers in the device of the component arrangement 1 and correspondingly modulates the carriers reaching the device drain. As a result, the output signal V OUT is also modulated at the frequency ƒ 2 independent of the modulation at the frequency ƒ 1 due to the corresponding variation of the intermediate frequency signal V IF at the device gate lead G . As a consequence, the generated output signal V OUT possesses at least three frequency components of ƒ 1 and ƒ 2 as well as ƒ 2 +ƒ 1 and ƒ 2 -ƒ 1 . Typically, the output signal V OUT would also include frequency components based on the harmonics of the intermediate frequency ƒ 1 , such as ƒ 2 +2ƒ 1 and ƒ 2 -2ƒ 1 and ƒ 2 +3ƒ 1 and ƒ 2 -3ƒ 1 , etc., which can be removed by filtering in a conventional manner, if desired. FIG. 3 depicts an exemplary output signal V OUT of the circuit 100 as represented on a spectrum analyzer. The local oscillator and intermediate frequencies ƒ 2 and ƒ 1 employed to generate the output signal V OUT in FIG. 3 are 1.8 GHz and 1.0 MHz, respectively. Accordingly, spectral peaks occur at frequencies 1.799 GHz, 1.800 GHz and 1.801 GHz as indicated by reference numbers 150, 155 and 160. The particular signal frequencies being mixed by the component arrangement 1 is not critical to practicing the invention. Exemplary frequencies that can be provided to an inductor coil when used as the magnetic field generator can be less than 1 Hz or to a maximum that is limited by the resonance frequency of the inductor coil, which is typically on the range of 2 GHz to 7 GHz for conventional fabricated on-chip inductors. Moreover, the frequency of the signal applied to the gate lead G can be in the range from less than 1 Hz to as large as 2 to 3 GHz in conventional MOSFET devices. However, DC coupling may be required to achieve such frequency range. The exemplary circuit 100 of FIG. 2 illustrates an up-conversion signal mixing operation for illustrations purposes only and it should be readily understood that a corresponding down-conversion circuit can be produced in a substantially similar manner. Moreover, FIG. 1 depicts a single device 5 interacting with the magnetic field generator 10 for illustration purpose only, and in particular signal mixing operations including, for example, mixing of multiple signals and/or for providing greater signal strength or balanced output signals, it is possible to configure a component arrangement such that a plurality of devices are positioned within the magnetic field produced by the generator 10. Although FIG. 1 depicts a component arrangement 1 producing a magnetic field B extending parallel to the inversion layer and perpendicular to the flow of carriers U , it should be readily understood that deviation from such orientation still provides the advantageous signal mixing but with corresponding attenuated frequency components in the output signal caused by such an oriented magnetic field. It will be appreciated that many modifications can be made. For example, although the previously described embodiments employ an inductor coil disposed on the same substrate as the device, it is possible to alternatively position the inductor coil on a separate substrate positioned in close proximity to the device to provide the desired magnetic field extending through the device.

Claims: A component arrangement (1) comprising: at least one field effect transistor (FET) device (5); and a controllable magnetic field generator (10), wherein the generator is at a fixed position relative to said device such that when carriers flow within an inversion layer formed within said device, the magnetic field (B) produced by the generator extends through said carrier flow (U) in a direction parallel to said inversion layer and perpendicular to the direction of said carrier flow and produces a Lorentz force (F) on said carriers in said flow in a desired relative direction to perform a corresponding desired circuit function; characterized in that the controllable magnetic field generator has a magnetic coil whose windings lie in a plane that is parallel to said inversion layer. An arrangement as claimed in claim 1, wherein a magnitude of the generated magnetic field is controllable by a first signal to be mixed. An arrangement as claimed in claim 1, wherein said device has a plurality of drains. An arrangement as claimed in claim 1 wherein said magnetic field generator is formed on said device.

Inventors: GABARA THADDEUS JOHN, GABARA, THADDEUS JOHN
Applicants: LUCENT TECHNOLOGIES INC, LUCENT TECHNOLOGIES INC.
Application year: 1998
Main classification: H01L27
IPC codes: H01L27, H01L21, H01L25