Abstract:
At least one magnetic field sensing device and an RF transceiver are integrated in a discrete, single-chip package. Rather than requiring at least two separate chips to wirelessly transmit the device output, an integrated, single chip solution can be used. The single chip integration of the at least one magnetic field sensing device and the RF transceiver can reduce the physical space required and, therefore, allow such devices to be smaller, lighter, and possibly more portable.

Description:
FIELD  
       [0001]     The present invention relates generally to a system on a chip (SOC), and more particularly, relates to a magneto-resistive (MR) sensor integrated on a single chip with a radio frequency (RF) transceiver.  
       BACKGROUND  
       [0002]     Magnetic field sensors have applications in magnetic compassing, ferrous metal detection, position sensing, and current sensing. They may be used to detect variations in the magnetic field of machine components and in the earth&#39;s magnetic field, as well as to detect underground minerals, electrical devices, and power lines. For such applications, an anisotropic magneto-resistive (AMR) sensor, a giant magneto-resistive (GMR) sensor, a colossal magneto-resistive (CMR) sensor, a Hall sensor, a fluxgate sensor, or a coil sensor that is able to detect small shifts in magnetic fields may be used.  
         [0003]     MR sensors, for example, may be formed using typical integrated circuit fabrication techniques. Permalloy, a ferromagnetic alloy containing nickel and iron, is typically used as the magneto-resistive material. Often, the permalloy is arranged in thin strips of permalloy film. When a current is run through an individual strip, the magnetization direction of the strip may form an angle with the direction of current flow.  
         [0004]     As the magnetization direction of the strip changes relative to the current flow, its effective resistance also changes. Strip resistance reaches a maximum when the magnetization direction is parallel to the current flow and reaches minimum when the magnetization direction is perpendicular to the current flow. Such changes in strip resistance result in a change in voltage drop across the strip when an electric current is run through it. This change in voltage drop can be measured and used as an indication of the change in the magnetization direction of an external magnetic field acting on the strip.  
         [0005]     To form the magnetic field sensing structure of a MR sensor, several permalloy strips may be electrically connected together. The permalloy strips may be placed on the substrate of the MR sensor as a continuous resistor in a “herringbone” pattern or as a linear strip of magneto-resistive material, with conductors across the strip at an angle of 45 degrees to the long axis of the strip. This latter configuration is known as “barber-pole biasing.” The positioning of conductors in a “barber-pole biasing” configuration may force the current in a strip to flow at a 45-degree angle to the long axis of the strip. These magneto-resistive sensing structure designs are described in U.S. Pat. No. 4,847,584 titled “Magnetoresistive Magnetic Sensor” and assigned to the same assignee as the current application. U.S. Pat. No. 4,847,584 is hereby fully incorporated by reference.  
         [0006]     An MR sensor often includes a number of straps through which current may be applied for controlling and adjusting sensing characteristics. For example, MR sensor designs often include set, reset, and offset straps. These straps can improve the performance and accuracy of the MR sensor, but require driver circuitry for proper operation. Additionally, the MR sensor typically includes other components used for signal conditioning and electrostatic discharge protection, such as operational amplifiers, transistors, capacitors, and so on.  
         [0007]     An RF transceiver is commonly used to wirelessly transmit data. For example, RF transceivers are used in short range communication systems. Typically, the RF transceiver is connected to one or more antennas. When receiving data, the RF transceiver filters and down converts RF signals into analog or digital baseband signals. When sending data, the RF transceiver filters, up converts, and amplifies analog or digital baseband signals into RF signals.  
         [0008]     By combining the functionality of the MR sensor with that of the RF transceiver, the output of the MR sensor can be wirelessly transmitted. As a result, the output of the MR sensor can be easily obtained. For example, an MR sensor may be located on a pipeline valve to determine the position of the valve (e.g., whether the valve is open or closed). The position of the valve can be wirelessly transmitted to a pipeline control station by the RF transceiver. As a result, a pipeline operator can determine the position of the valve without having to go into the field to manually determine the position of the valve.  
         [0009]     Typically, to wirelessly transmit data from an MR sensor at least two chips are placed separately on a printed circuit board. For example, Honeywell&#39;s Radio on a Chip (part number HRF-ROC09325) along with data acquisition, data formatting, and control electronics may be used to transmit output data from one or more of Honeywell&#39;s MR sensors, such as part numbers HMC1501 and HMC1512. In some applications, multiple chips on a printed circuit board is too unwieldy and inefficient due to the physical space requirements of the RF transceiver chip, the MR sensor chip, and any additional chips required for operation of the MR sensor.  
         [0010]     Single chip designs with an MR sensor and other additional circuitry have been described. For example, U.S. Patent Application Publication No. 2004/0207400 describes the integration of an MR sensor with a SET/RESET driver, U.S. Patent Application Publication No. 2004/0207035 describes the integration of an MR sensor with a semiconductor device, and U.S. Patent Application Publication No. 2004/0254726 describes the integration of an MR sensor with a GPS receiver. These applications are assigned to the same assignee as the current application and are hereby fully incorporated by reference. Single chip packaging for an RF transceiver has also been described. However, none of these designs suggest integrating an RF transceiver on the same chip as the MR sensor.  
         [0011]     Thus, a single-chip design that would minimize the physical space required to integrate an MR sensor with an RF transceiver would be desirable.  
       SUMMARY  
       [0012]     A system and method for integrating an MR sensor with an RF transceiver on a single integrated circuit is described. The system includes at least one magnetic field sensing device and a transceiver co-located on the same integrated circuit. The at least one magnetic field sensing device is located in a first portion of the integrated circuit and the transceiver is located in a second portion of the integrated circuit.  
         [0013]     The system may also include an antenna located in first portion of the integrated circuit. In one example, the antenna is integrated with the at least one magnetic field sensing device. In another example, the at least one magnetic field sensing device is the antenna. The system may also include additional circuitry in the second portion of the integrated circuit. For example, the additional circuitry may include power conditioning electronics, MR sensing electronics, and control and I/O electronics. The system may also include a shielding layer to prevent electromagnetic fields generated in the second portion of the integrated circuit from interfering with the MR sensor operation.  
         [0014]     The at least one magnetic field sensing device may be an anisotropic magneto-resistive (AMR) sensor, a giant magneto-resistive (GMR) sensor, a colossal magneto-resistive (CMR) sensor, a Hall sensor, a fluxgate sensor, or a coil sensor. The transceiver wirelessly transmits data from the at least one magnetic field sensing device. In another example, the at least one magnetic field sensing device includes an array of magnetic field sensing devices and the transceiver wirelessly transmits data from the array magnetic field sensing devices.  
         [0015]     A method for making a single chip magnetic field sensing device integrated with a transceiver is also described. The method includes forming a transceiver underlayer that includes transceiver circuitry, forming a planar dielectric layer on the transceiver underlayer, and forming at least one magnetic field sensing device above the dielectric layer. The transceiver circuitry and the at least one magnetic field sensing device are formed as a single integrated circuit.  
         [0016]     In one example, the at least one magnetic field sensing device is formed within a metal interconnection layer located above the planar dielectric layer. In another example, the at least one magnetic field sensing device is formed between metal interconnection layers located above the planar dielectric layer. The method may also include forming an antenna within or between the metal interconnection layers. The method may also include forming additional circuitry in the transceiver underlayer. The additional circuitry may include power conditioning electronics, MR sensing electronics, or control and I/O electronics.  
         [0017]     The transceiver underlayer may be formed using at least one of complementary metal oxide semiconductor (CMOS), gallium-arsenide (GaAs), germanium, bipolar CMOS (BiCMOS), and indium phosphide (InP) technologies. The at least one magnetic field sensing device may be formed on the dielectric layer using lithography, metallization, and etch processes. The transceiver underlayer may be formed before the dielectric layer and the at least one magnetic field sensing device.  
         [0018]     These as well as other aspects and advantages will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings. Further, it is understood that this summary is merely an example and is not intended to limit the scope of the invention as claimed.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     Presently preferred embodiments are described below in conjunction with the appended drawing figures, wherein like reference numerals refer to like elements in the various figures, and wherein:  
         [0020]      FIGS. 1A-1C  are simplified block diagrams of an integrated MR sensor and an RF transceiver, according to some examples;  
         [0021]      FIGS. 2A-2C  are simplified block diagrams of an integrated MR sensor and an RF transceiver depicting shielding features, according to some examples;  
         [0022]      FIG. 3  is a side view of an MR sensor and an RF transceiver integrated in a single die, according to an example;  
         [0023]      FIG. 4  is a top view of a MR sensor with RF transceiver components, according to an example;  
         [0024]      FIG. 5  is a top view of the MR sensor with the RF transceiver components depicted in  FIG. 4  with a shield located between the MR sensor and other components, according to an example; and  
         [0025]      FIG. 6  is a top view of a MR sensor with RF transceiver components, according to another example.  
     
    
     DETAILED DESCRIPTION  
       [0026]      FIGS. 1A-1C  are block diagrams illustrating the integration of an MR sensor with an RF transceiver. The device  100  includes a first portion  102  and a second portion  104 . The first portion  102  includes the MR sensor and an antenna. The second portion  104  includes the RF transceiver and additional circuitry. The additional circuitry may include power conditioning electronics, MR sensing electronics, and control and I/O electronics. The second portion  104  may also include other circuitry, such as circuitry for electro-static discharge (ESD) protection for the MR sensor in the first portion  102 .  
         [0027]     The first and second portions  102 ,  104  are included within a single chip, so that the device  100  is a discrete, one-chip design. The term “chip” is a term of art and refers to an integrated circuit. The term “single chip” as used herein means that a single integrated circuit or die is used for fabricating the MR sensor and the RF transceiver.  
         [0028]     The first and second portions  102 ,  104  of the device  100  may be manufactured using standard fabrication processes, such as complementary metal oxide semiconductor (CMOS), which includes bulk, silicon-on-insulator (SOI) and microwave-on-insulator (MOI) technologies; gallium-arsenide (GaAs); germanium; bipolar CMOS (BiCMOS); and indium phosphide (InP). Preferably, the first portion  102  is manufactured using standard lithography, metallization, and etch processes; while the second portion  104  is preferably manufactured using Honeywell&#39;s MOI-5 0.35 micron processing or GaAs processing. While a technology like GaAs may provide advantages in operational speed, reduced power consumption might be best realized through the use of other techniques, such as those involving SOI or MOI.  
         [0029]     Integrating the MR sensor with the RF transceiver in a single chip design may be accomplished in a variety of ways. Three examples are depicted in  FIG. 1 . In  FIG. 1A , the first portion  102  and the second portion  104  are located in discrete vertical layers in a single die. Preferably, the MR sensor and antenna are located in the first portion  102 , which is fabricated on the second portion  104 , which preferably includes the RF transceiver and other circuitry. The dashed line between the first and second portions  102 ,  104  indicates that the discrete vertical layers may not be linear and may have varying dimensions.  
         [0030]     It may be advantageous to include one or more electrical connections between the first portion  102  and the second portion  104  to provide feedback, for example. For example, wiring  106  may be used to connect the MR sensor and antenna to the RF transceiver and the other circuitry. Alternatively, the first portion  102  and the second portion  104  may simply be located physically close to one another with no intentional electrical interaction.  
         [0031]      FIG. 1B  illustrates another way in which the MR sensor may be integrated with a RF transceiver. In this example, the first portion  102  and the second portion  104  are formed adjacent to each other in discrete horizontal layers on the same die. The MR sensor and the antenna are fabricated on a first portion  102 , while the RF transceiver and the other circuitry are fabricated on a second portion  104 . The dashed line between the first and second portions  102 ,  104  indicates that the discrete horizontal layers may not be linear and may have varying dimensions. In addition, the wiring  106  may be used to connect circuitry in the first portion  102  to circuitry in the second portion  104 .  
         [0032]      FIG. 1C  illustrates yet another example of a single die integration in which the first portion  102  and the second portion  104  are contained in a single die. In this example, the first portion  102  and the second portion  104  are not adjacent to each other in the integrated device  100 . The wiring may be used to connect circuitry in the first portion  102  to circuitry in the second portion  104 .  
         [0033]     The RF transceiver and some of the other circuitry located in the second portion  104  may generate electromagnetic fields significant enough to influence the operation of the MR sensor. As a result, the sensitive parts of the first portion  102  of the integrated device  100  may need to be physically separated from parts of the second portion  104  in order to provide optimal magnetic field sensing.  FIG. 1C  depicts one example in which the first portion  102  is physically separated from the second portion  104 . The amount of separation may be determined using theoretical or empirical means, for example.  
         [0034]     As an alternative to introducing physical separation between potentially interfering parts of an integrated device  200 , a shielding layer  206 - 210  may be provided.  FIGS. 2A-2C  illustrate three example configurations for such a shield. Use of a shielding layer will likely allow tighter integration of the device  200  than use of physical separation of physical parts. The shielding layer  206 - 210  may be composed of a metal or a magnetic material (e.g., NiFe film). Other materials for the shielding layer  206 - 210  may also be suitable.  
         [0035]     In  FIG. 2A , the device  200  is a single die integration of the MR sensor and the RF transceiver with a shielding layer  206  located substantially between the two portions  202 ,  204 . In this example, the first portion  202  and the second portion  204  are formed in discrete vertical layers on the same die. The shielding layer  206  may extend over some of or over the entire interface between the first and second portions  202 ,  204 , depending on the characteristics of the electromagnetic fields and the location of sensitive components.  
         [0036]      FIG. 2B  illustrates a single die integrated MR sensor and RF transceiver with a shielding layer  208  located within the second portion  204 . In this example, the first portion  202  and the second portion  204  are formed in discrete vertical layers on the same die. The shielding layer  208  is a localized shield which may be beneficial when the majority of the magnetic field effects originate from a relatively small part of the second portion  204 . The shield  208  may also be advantageous in designs having electrical connections between the first and second portions  202 ,  204 . The size and location of the shielding layer  208  may be varied as necessary to properly shield sensitive components.  
         [0037]      FIG. 2C  illustrates an integrated MR sensor and RF transceiver with a shielding layer  210  located substantially between the first portion  202  and the second portion  204 . In this example, the first portion  202  and the second portion  204  are formed in discrete horizontal layers on the same die. The shielding layer  210  may extend over some or over the entire interface between the first portion  202  and the second portion  204 , depending on the characteristics of the electromagnetic fields and the location of sensitive components.  
         [0038]      FIG. 3  is a side view of a device  300  in which an MR sensor is integrated with an RF transceiver on a single die. Shown in  FIG. 3  are CMOS/Bipolar underlayers  302  (also referred to as the RF transceiver layers), a planar dielectric layer  310 , contacts V 1 -V 3 , metal interconnection layers M 1 -M 3 , a first dielectric layer  308 , a second dielectric layer  306 , and a passivation layer  304 . The RF transceiver along with any additional circuitry, such as power conditioning electronics, MR sensing electronics, and control and I/O electronics, may be fabricated largely within the RF transceiver underlayers  302 , while an MR sensor and an antenna may be fabricated within or between the metal interconnection layers M 1 -M 3 , above the planar dielectric layer  310 . Alternatively, the MR sensor may be used as the antenna.  
         [0039]     Preferably, the RF transceiver underlayers  302  are fabricated first because its fabrication processes usually require the highest temperatures. A substantially planar dielectric layer  310  (e.g., contact glass) is then deposited on the RF transceiver underlayers  302 . The planar dielectric layer  306  provides a substantially planar surface on which the MR sensor and antenna can be fabricated, as well as electrically isolating the RF transceiver underlayers  302  from the upper layers  304 - 308 . The MR sensor and the antenna are then fabricated within or between the metal interconnection layers M 1 -M 3 . Preferably, the antenna is located within the highest interconnection layer M 3 .  
         [0040]     Layers  304 - 308  may be formed using standard lithography, metallization, and etch processes, while layers  310  and  302  may be formed using Honeywell&#39;s MOI-5 0.35 micron processing or GaAs processing. Other components of the MR sensor (such as set, reset, and offset straps; signal conditioning circuitry, and ESD protection circuitry) may be included in various locations in the layers  308 - 310  and  302 , and are not fully illustrated in  FIG. 3 .  
         [0041]      FIG. 4  illustrates a plan view of a device  400  in which an MR sensor is integrated with an RF transceiver on a single chip. The structures visible in  FIG. 4  include a MR sensing element  402 , power conditioning electronics  404 , RF electronics  406 , MR sensing electronics  408 , control and I/O electronics  410 , and an antenna  412 . More than one MR sensing element  402  may be used. For example, the RF transceiver may be designed to wirelessly transmit outputs from an array of MR sensing elements  402 .  
         [0042]     The MR sensing element  402  may be any element that can detect variations in magnetic fields, whether natural or man-made. For example, the MR sensing element  402  may be an AMR sensor, a GMR sensor, a CMR sensor, a Hall sensor, a fluxgate sensor, or a coil sensor. The MR sensing element  402  may also include one or more straps through which current may be run for controlling and adjusting the element&#39;s sensing characteristics. For example, the MR sensing element  402  may include set, reset, and offset straps.  
         [0043]     The MR sensing electronics  408  include any electronics needed to convert an output of the MR sensing element  402  to a user-recognizable output. For example, the MR sensing electronics  408  may include an analog-to-digital (A/D) converter, a processor, a memory device, and a display or other type of output device. Additionally, the MR sensing electronics  408  may include driver circuitry for controlling the set, reset, and/or offset straps.  
         [0044]     The RF electronics  406  include the circuitry needed for the RF transceiver. For example, the RF electronics  406  may include digital-to-analog (D/A) converters, low-pass filters for filtering the outputs of the D/A converters, and a modulator that performs a frequency conversion on signals received at its inputs and which is driven by a phase-locked loop (PLL) circuit that includes a reference voltage controlled oscillator (VCO) and a resonator (tank circuit). The modulator&#39;s output is fed to a power amplifier, and the amplified output is filtered with a bandpass filter and connected to the antenna  412 . RF transceiver designs are well known in the art, and any appropriate RF transceiver design may be used.  
         [0045]     The antenna  412  is incorporated with the MR sensing element  402  in the die. Preferably, the antenna  412  is a loop antenna. A loop antenna includes a multi-turn loop of less than 1/10th wavelength in length. Other antenna designs may also be used.  
         [0046]     The power conditioning electronics  404  are used to control the power to the integrated device, especially during initial startup of the device. The control and I/O electronics  410  provide control signals and input/output signal conditioning to the device. The power conditioning electronics  404  and the control and I/O electronics  410  are standard electronics and any appropriate design may be used in the device  400 .  
         [0047]      FIG. 5  illustrates a plan view of a device  500  in which an MR sensor is integrated with an RF transceiver on a single chip. The device  500  is substantially the same as the device  400 , except the device  500  includes a shield layer  514  located substantially between the MR sensing element  502  and the power conditioning electronics  504 , RF electronics  506 , MR sensing electronics  508 , and control and I/O electronics  510 . The electronics  504 - 510  cannot be fully seen in  FIG. 5  due to the location of the shield layer  514 . Preferably, the shield layer  514  does not extend over the antenna  512 . The shielding layer  514  may be composed of a metal, a magnetic material (e.g., NiFe film), or any other suitable material.  
         [0048]      FIG. 6  illustrates a plan view of a device  600  in which an MR sensor is integrated with an RF transceiver on a single chip. The structures visible in  FIG. 6  include a combined MR sensing element and antenna  602 , power conditioning electronics  604 , RF electronics  606 , MR sensing electronics  608 , and control and I/O electronics  610 . The device  600  is similar to the device  400  depicted in  FIG. 4 , but uses a larger MR sensing element that can also be used as the antenna. Additional real estate may be saved by using the MR sensing element as the antenna for the RF transceiver. Moreover, the device  600  may have a larger antenna aperture than the device  400 .  
         [0049]     The MR sensing element may be used as the antenna when the size of the MR sensing element is compatible with the resonant frequency of the wireless transmission. For example, when the MR sensing element is at ¼ or ½ wavelength resonance at the transmission frequency, the MR sensing element may be used as the radiating element/ground plane of the antenna.  
         [0050]     Table 1, below, shows a simplified exemplary process for integrating a RF transceiver with a magnetic field sensing device. It is believed that such a process is unique because, in the past, semiconductor foundries have gone to great lengths to prevent contamination of their processes with materials typically used in manufacturing magnetic sensors. In addition, companies in the magnetic industries (e.g., disk drive head manufacturers, etc.) have been separate from electronics companies, and their specialized manufacturing techniques have been kept largely separate from one another.  
                     TABLE 1                       Sample Manufacturing Process                                CMOS (bulk or SOI), Bipolar, GaAs, BiCMOS, InP, underlayers       (end front-end processing; begin back-end processing)       Deposit contact glass (if any), reflow       Form magnetic field sensing device layer (MR and additional metallization       layers)       Inspection and evaluation/test/package                  
 
         [0051]     In a preferred embodiment, the semiconductor device processing (i.e. CMOS, Bipolar, GaAs, etc.) is done at the front end, while the metal interconnect and the magnetic field sensing device are done at the back end. Table 1 is intended to be generally applicable to any manufacturing process, and thus does not include detail on how to obtain particular architectures. Additional cleaning and other steps are also implemented as appropriate.  
         [0052]     It should be understood that the illustrated embodiments are examples only and should not be taken as limiting the scope of the present invention. For example, while an MR sensor has been used to describe the invention, any magneto-resistive sensor, such as AMR, GMR, and CMR, or other magnetic field sensing device may be used. Similarly, this invention is not limited to any particular RF transceiver design. The claims should not be read as limited to the described order or elements unless stated to that effect. Therefore, all embodiments that come within the scope and spirit of the following claims and equivalents thereto are claimed as the invention.