Abstract:
At least one magnetic field sensing device and GPS receiver integrated in a discrete, single-chip package, and a method of manufacture for the same. Rather than requiring at least two separate chips to be used to realize GPS positioning and compassing capabilities in a single device, an integrated, single chip solution can be used. A single chip integration of a GPS receiver and at least one magnetic field sensing device can reduce the physical space required to provide positioning and electronic compassing capabilities in a single device, and therefore allow such devices to be smaller, lighter, and possibly more portable.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. application Ser. No. 10/754,947, now U.S. Pat. No. ______, filed Jan. 8, 2004, which claims the benefit of U.S. Provisional Application Nos. (1) 60/475,191, filed Jun. 2, 2003, entitled “Semiconductor Device Integration with a Magneto-Resistive Sensor,” naming as inventors Lonny L. Berg and William F. Witcraft; (2) 60/475,175, filed Jun. 2, 2003, entitled “On-Die Set/Reset Driver for a Magneto-Resistive Sensor,” naming as inventors Mark D. Amundson and William F. Witcraft; and (3) 60/462,872, filed Apr. 15, 2003, entitled “Integrated GPS Receiver and Magneto-Resistive Sensor Device,” naming as inventors William F. Witcraft, Hong Wan, Cheisan J. Yue, and Tamara K. Bratland. The present application also incorporates each of these Provisional Applications in their entirety by reference herein.  
         [0002]     This application is also related to and incorporates by reference U.S. Nonprovisional Application Nos. (1) 10/754,946, Honeywell Docket No. H0004948US, filed concurrently, entitled “Semiconductor Device and Magneto-Resistive Sensor Integration,” naming as inventors Lonny L. Berg, William F. Witcraft, and Mark D. Amundson; and (2) 10/754,945, Honeywell Docket No. H0004956US, filed concurrently, entitled “Integrated Set/Reset Driver and Magneto-Resistive Sensor,” naming as inventors Lonny L. Berg and William F. Witcraft.  
     
    
     BACKGROUND  
       [0003]     1. Field of the Invention  
         [0004]     The present invention relates in general to magnetic field and current sensing, and more particularly to integrating a GPS receiver with a compassing sensor.  
         [0005]     2. Description of Related Art  
         [0006]     Magnetic field sensors have applications in magnetic compassing, ferrous metal detection, 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 effect sensor, a fluxgate sensor, or a coil sensor that is able to detect small shifts in magnetic fields may be used.  
         [0007]     Magneto-resistive 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. 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 change in the magnetization direction of external magnetic fields acting on the strip.  
         [0008]     To form the magnetic field sensing structure of a magneto-resistive sensor, several permalloy strips may be electrically connected together. The permalloy strips may be placed on the substrate of the magneto-resistive 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 discussed in U.S. Pat. No. 4,847,584, Jul. 11, 1989, to Bharat B. Pant, and assigned to the same assignee as the current application. U.S. Pat. No. 4,847,584 is hereby fully incorporated by reference. Additional patents and patent applications describing magnetic sensor technologies are set forth below, in conjunction with the discussion of  FIG. 4 .  
         [0009]     Magnetic sensors often include a number of straps through which current may be run for controlling and adjusting sensing characteristics. For example, magnetic sensor designs often include set, reset, and offset straps. These straps can improve the performance and accuracy of magnetic sensors, but require driver circuitry for proper operation. Such circuitry has typically been located off-chip from the magnetic sensor, resulting in space inefficiencies. Similarly, other components, such as operational amplifiers, transistors, capacitors, etc., have typically been implemented on a separate chip from the magnetic sensor. Both signal conditioning and electrostatic discharge circuitry, for example, are typically located off-chip. Although such off-chip circuitry is adequate for many applications, for those where physical space is at a premium it would be desirable to have necessary circuitry integrated into a single-chip magnetic sensor, thereby conserving space.  
         [0010]     One consequence of the space inefficiencies of multiple-chip magnetic sensors is the stunting of technological advances in the integration of compassing and positioning technologies. To take advantage of the functionality of both magnetic sensors and positioning technologies, at least one additional positioning chip is required. The Global Positioning System (GPS), the leading positioning technology, enables a GPS receiver to determine its position on the earth from a set of concurrently received signals transmitted by at least three of a constellation of GPS satellites. GPS receivers can also determine heading using the same signals used to determine position. However, in order to obtain an accurate heading, the GPS receiver must be moving at a speed of at least 10 mph. As a result, GPS has been successfully used for positioning in both handheld and vehicle-mounted systems, as well as for navigation in vehicle mounted systems (when traveling at a speed of at least 10 mph).  
         [0011]     By combining the functionality of a magnetic field sensing device with that of a GPS receiver, a user can determine both direction (from the magnetic field sensing device) and position (from the GPS receiver), both when stationary and when moving. However, for handheld applications, such a combination may be unwieldy and inefficient due to the physical space requirements of a GPS receiver chip, a magnetic field sensing device chip, and a potential for additional chips required for magnetic field sensing device circuitry. Thus, a single-chip design that would minimize the physical space required to integrate a GPS receiver with a magnetic field sensing device would be desirable.  
       SUMMARY  
       [0012]     One exemplary embodiment provides a single package sensor device. The single package sensor device is comprised of GPS receiver circuitry and a magnetic field sensing device adjacent to the GPS receiver circuitry. The single-package integration of the GPS receiver circuitry and the magnetic field sensing device can be accomplished in the following two ways: (1) a single-die, single package solution and (2) a multiple-die, single-package solution. Because such an integrated device may be manufactured as a single package, the user may realize advantages that include possible cost reduction, reduced size, and increased functionality, among others.  
         [0013]     These as well as other aspects and advantages of the present invention will become apparent to those of ordinary skill in the art by reading the following detailed description, with appropriate reference to the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     Preferred embodiments of the present invention are described with reference to the following drawings, wherein:  
         [0015]      FIGS. 1A-1C  are simplified block diagrams illustrating embodiments of the present invention;  
         [0016]      FIGS. 2A-2C  are simplified block diagrams illustrating embodiments of the present invention with included shielding features;  
         [0017]      FIG. 3  is a simplified block diagram illustrating a GPS receiver and a magneto-resistive sensor integrated on a single die in accordance with an embodiment of the present invention;  
         [0018]      FIG. 4  is a simplified block diagram illustrating a device-architecture for a GPS receiver and a magneto-resistive sensor integrated in a single die in accordance with an embodiment of the present invention;  
         [0019]      FIG. 5  is a simplified block diagram illustrating a magneto-resistive sensor with GPS receiver components in accordance with an exemplary embodiment of the present invention;  
         [0020]      FIG. 6  is a simplified block diagram illustrating a typical GPS receiver;  
         [0021]      FIG. 7  is a simplified block diagram illustrating an exemplary use for an integrated GPS receiver and magneto-resistive sensor in accordance with an embodiment of the present invention; and  
         [0022]      FIG. 8  is a simplified block diagram illustrating an exemplary use for an integrated GPS receiver and magneto-resistive sensor in accordance with an embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0023]     In view of the wide variety of embodiments to which the principles of the present invention can be applied, it should be understood that the illustrated embodiments are exemplary only, and should not be taken as limiting the scope of the present invention.  
         [0024]      FIGS. 1A-1C  are block diagrams illustrating an integration of a GPS receiver with a magnetic field sensing device (i.e. a magneto-resistive sensor). The device  100  of  FIGS. 1A and 1B  includes a first portion  102 , including a magneto-resistive sensor and wiring, and a second portion  104 , including GPS receiver circuitry. In a preferred embodiment, the second portion  104  also includes signal conditioning circuitry and circuitry for ESD (electro-static discharge) protection for the magneto-resistive sensor in the first portion  102 . As discussed below, the second portion  104  is particularly amenable to standard semiconductor fabrication techniques, such as those used for CMOS (complementary metal oxide semiconductor). The first and second portions  102 ,  104  are included within a single chip, so that the device  100  is a discrete, one-chip design.  
         [0025]     Prior attempts to integrate a GPS receiver and electronic compassing using a magneto-resistive sensor have typically involved at least two chips placed separately on a printed circuit board, which likely results in a larger-sized end-user device (e.g. cell phone, portable device, watch, etc.) and increased complexity. The one-chip design of device  100 , however, provides reduced sized and added functionality. This smaller size may be useful in such applications as cell phones, handheld GPS units, and watches, for example. Further, this integrated design allows a user to determine a compass heading both while stationary and while moving. GPS (and other satellite-based systems) require the GPS receiver to be moving at an approximate velocity of at least 10 m.p.h. relative to the surface of the earth in order to allow the GPS receiver to determine a compass heading, based on past and present position. Thus, if used in a cell phone, for example, the one-chip design of device  100  could allow a user to determine both position and heading while standing or walking. Other applications may include industrial or automotive uses.  
         [0026]     The first and second portions  102 ,  104  of the device  100  may be manufactured using standard RF/microwave processes, such as CMOS, gallium-arsenide (GaAs), germanium, BiCMOS (bipolarCMOS), InP (indium phosphide), SOI (silicon-on-insulator), and MOI (microwave-on-insulator). While a technology like GaAs may provide advantages in operational speed, reduced power consumption might best be realized through the use of other techniques, such as those involving SOI (Silicon on Insulator) or MOI (Microwave-On-Insulator), a variation of SOI. In a preferred embodiment, the first portion  102  is manufactured using standard lithography, metallization, and etch processes. The second portion  104  is preferably manufactured using Honeywell&#39;s MOI-5 0.35 micron processing, or another RF/microwave method, such as GaAs processing.  
         [0027]     Integrating the magnetic field sensing device with the GPS receiver in a single chip design may be accomplished in at least two ways.  FIGS. 1A  illustrates a first embodiment where a magneto-resistive sensor  102  is fabricated on a single die along with the GPS receiver  104  and possibly other circuitry, such as signal conditioning and ESD protection circuitry, for example. In the embodiment illustrated in  FIG. 1A , the GPS receiver  104  and other circuitry and the magneto-resistive sensor  102  are located in discrete layers in a single die.  
         [0028]      FIG. 1B  illustrates a second way in which a magnetic field sensing device can be integrated with a GPS receiver. In  FIG. 1B , a magneto-resistive sensor  102  is fabricated on a first die, while the GPS receiver  104  and signal conditioning circuitry are fabricated on a second die. The first die and the second die may then be placed in close proximity to one another and packaged within a single integrated circuit chip  106 . In all cases, it may be advantageous to include one or more electrical connections between the GPS receiver  104  and the magneto-resistive sensor  102  to provide feedback, for example. Alternatively, the GPS receiver  104  and magneto-resistive sensor  102  may simply be located physically close to one another with no intentional electrical interaction.  
         [0029]     Additionally,  FIG. 1C . illustrates a second embodiment of a single die integration wherein a magneto-resistive sensor  102  and a GPS receiver  104  and other circuitry are contained in a single die. However, in the embodiment illustrated in  FIG. 1C , wiring  108  and the magneto-resistive sensor  102  are contained in separate portions of the second portion of the die.  
         [0030]     Some GPS receiver circuitry and signal conditioning circuitry may generate electromagnetic fields significant enough to influence the operation of the magnetic field sensing device. 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 device operation. The amount of separation may be determined using theoretical or empirical means, for example.  
         [0031]     As an alternative to introducing physical separation between potentially interfering parts of the integrated device  100 , a shielding layer may be provided.  FIGS. 2A-2C  illustrate three exemplary configurations for such a shield. The device  200  of  FIG. 2A  is a single die integration of a magnetic field sensing device  202  and a GPS receiver  204  with a shielding layer  206  located substantially between the two. 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.  
         [0032]      FIG. 2B  illustrates a single die integrated magnetic field sensing device  202  and GPS receiver  204  with a shielding layer  208  located within the second portion  204 . Shielding layer  208  is a localized shield which might be beneficial where 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 . However, shielding layer  208  could be made less localized where necessary to properly shield sensitive components.  
         [0033]      FIG. 2C  illustrates a multiple die, integrated magnetic field sensing device  202  and GPS receiver  204  with a shielding layer  210  located substantially between the magnetic field sensing device  202  and the GPS receiver  204 . The shielding layer  210  may extend over some of or over the entire interface between the magnetic field sensing device  202  and the GPS receiver  204 , depending on the characteristics of the electromagnetic fields and the location of sensitive components. The magnetic field sensing device  202 , the GPS receiver  204 , and the shielding layer  210  are contained in a single-chip package  212 . For all embodiments, use of a shielding layer will likely allow tighter integration of the device  200  than use of physical separation of physical parts. While such a shielding layer may comprise metal or a magnetic material (e.g. NiFe film), other materials may also be suitable.  
         [0034]      FIG. 3  illustrates an exemplary architecture of a device  300 , in which a GPS receiver  302  may be implemented with a magnetic field sensing device  304  on a single die. The GPS receiver circuitry (along with any signal conditioning circuitry and drivers for set and/or offset straps associated with the magnetic field sensing device portion) may be fabricated largely within the GPS receiver underlayer  302 , while a magneto-resistive sensor  304  may be fabricated above the planar dielectric layer  306 . Also shown in  FIG. 3  are contacts  308  for connecting the GPS receiver underlayer  302  with the magneto-resistive sensor  304 . Additionally, NiFe permalloy structures  310  which are part of the magneto-resistive sensor  304  are shown.  
         [0035]     In a preferred embodiment, the GPS receiver underlayer  302  may be fabricated first. A substantially planar dielectric layer  306  (i.e. contact glass) is then deposited on the GPS receiver underlayer  302 , on top of which the magneto-resistive sensor  304  is then fabricated. The GPS receiver underlayer  302  is fabricated first because its fabrication processes usually require the highest temperatures. Additionally, the function of the planar dielectric layer  306  is to provide a substantially planar surface on which the magneto-resistive sensor can be fabricated, as well as to electrically isolate the GPS receiver underlayer  302  from the magneto-resistive sensor  304 .  
         [0036]      FIG. 4  illustrates a detailed view of an exemplary architecture of a device  400 , in which a GPS receiver may be implemented with a magnetic field sensing device on a single die. The GPS receiver circuitry (along with any signal conditioning circuitry and drivers for set and/or offset straps associated with the magnetic field sensing device portion) may be fabricated largely within the CMOS/Bipolar underlayers  402 , while a magneto-resistive sensor may be fabricated in layers  404 - 408 , above the planar dielectric layer  410 . Also shown in  FIG. 4  are various contacts V 1 -V 3  and metallizations M 1 -M 3 , NiFe permalloy structures, a 1 st  dielectric layer  408 , a second dielectric layer  406 , and a passivation layer  404 . In one embodiment, layers  404 - 408  are formed using standard lithography, metallization, and etch processes, while layers  410  and  402  are formed using Honeywell&#39;s MOI-5 0.35 micron processing, or another RF/microwave method, such as GaAs processing. Other components of the magneto-resistive sensor (such as set, reset, and offset straps; signal conditioning circuitry, and ESD protection circuitry) may be included in various locations in the layers  408 - 410  and  402 , and are not fully illustrated in  FIG. 4 .  
         [0037]     For further information on magneto-resistive sensor designs, reference may be made to the following patents and/or patent applications, all of which are incorporated by reference herein: 
        U.S. Pat. No. 6,529,114, Bohlinger et al., “Magnetic Field Sensing Device”    U.S. Pat. No. 6,232,776, Pant et al., “Magnetic Field Sensor for Isotropically Sensing an Incident Magnetic Field in a Sensor Plane”    U.S. Pat. No. 5,952,825, Wan, “Magnetic Field Sensing Device Having Integral Coils for Producing Magnetic Fields”    U.S. Pat. No. 5,820,924, Witcraft et al., “Method of Fabricating a Magnetoresistive Sensor”    U.S. Pat. No. 5,247,278, Pant et al., “Magnetic Field Sensing Device”    U.S. patent application Ser. No. 09/947,733, Witcraft et al., “Method and System for Improving the Efficiency of the Set and Offset Straps on a Magnetic Sensor”    U.S. patent application Ser. No. 10/002,454, Wan et al., “ 360 -Degree Rotary Position Sensor”       
 
         [0045]     In addition, U.S. Pat. No. 5,521,501, to Dettmann et al., titled “Magnetic Field Sensor Constructed From a Remagnetization Line and One Magnetoresistive Resistor or a Plurality of Magnetoresistive Resistors” is also incorporated herein by reference, and may provide additional details on constructing a magneto-resistive sensor.  
         [0046]      FIG. 5  illustrates a plan view of one embodiment of a device  500  in which a GPS receiver is integrated with a magnetic field sensing device on a single die. The structures visible in  FIG. 5  are attributable largely to a magneto-resistive sensor (and other circuitry, such as set/offset drivers or magnetic sensor signal conditioning circuitry formed in the underlayers of the device  500 ). Exemplary parts of the device  500  include a magneto-resistive bridge  502 , set/reset straps  504 , offset straps  506 , set/reset circuitry  508 ,  510 , laser trim sites  512  (for matching impedance of the legs of the magneto-resistive bridge  502 ), ESD protection diode  514 , operational amplifiers  516 , contacts  518 , test sites  520 , and GPS receiver components  522 . Reference may be made to the patents and patent applications incorporated above for further information.  
         [0047]      FIG. 6  is a simplified block diagram of a GPS receiver  600 . The GPS receiver  600  receives signals  602  from at least three different GPS satellites received by an antenna on the device. The received signals  602  are then usually filtered by a passive bandpass prefilter  604  to reduce out-of-band RF interference and preamplified  604 . Next, the RF signals are typically downconverted to an intermediate frequency (IF)  606 , and converted from analog to digital  606 . These signals are then sent to the digital signal processor (DSP)  608 . From the DSP  608  the signal undergoes navigation processing  610 , which yields position, velocity, and time information  612 . Because conventional processes are used, the particular GPS circuitry is not disclosed herein, as it is flexible. Thus, conventional GPS receiver designs implementable in CMOS/GaAs/BiCMOS, for example, can be utilized in accordance with the presently disclosed embodiments.  
         [0048]      FIG. 7  illustrates one application  700  for the integrated GPS receiver and magnetic field sensing device set forth herein. A user  702  is shown with a cell phone  704  having a single-chip integrated GPS receiver and magnetic field sensing device. The user  702  is able to obtain location and heading information by orienting the cell phone  704  in the direction the user  702  is facing, for example. The magnetic field sensing device is able to determine direction while the GPS receiver is able to determine the user&#39;s  702  location. The combination provides synergistic effects, such as the ability to perform database lookups to combine directions with yellow page information. For example, a user  702  could obtain a phone number for a business or residence the user is facing by causing the cell phone  704  to transmit location and heading information to a network server, which could respond with the phone number.  
         [0049]      FIG. 8  illustrates another application  800  for the integrated GPS receiver and magnetic field sensing device set forth herein. A user  802  is show with a video camera  804  having a single-chip integrated GPS receiver and magnetic field sensing device. The user  802  is able to obtain location and heading information by orienting the video camera  804  in the direction the user is facing. The magnetic field sensing device is able to tell the user  802  what direction he is facing, while the GPS receiver is able to determine the user&#39;s  802  location. The combination provides synergistic effects, such as the ability to record location and heading information which correlates to the footage being recorded by the user  802 . This could allow the user  802  to later identify buildings or other landmarks that that were recorded, as well as allow the user  802  to later find the same area where particular footage was recorded. Of course, many other uses are possible as well. Because only one chip is needed, rather than two or more, the overall size of the user&#39;s  802  device (e.g. digital camera, cell phone, portable device, watch, etc.) may be kept small.  
         [0050]     Table 1, below, shows a simplified exemplary process for integrating a GPS receiver 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, Bipolar, GaAs, BiCMOS, InP, SOI, MOI underlayers           (end front-end processing; begin back-end processing)           Deposit contact glass (if any), reflow           Form magnetic field sensing device layer           Inspection and evaluation                      
 
         [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 magnetic field sensing device manufacturing process, and thus does not include detail on how to obtain particular architectures. Additional cleaning and other steps should be implemented as appropriate.  
         [0052]     An exemplary embodiment of the present invention has been described above. Those skilled in the art will understand, however, that changes and modifications may be made to this embodiment without departing from the true scope and spirit of the present invention, which is defined by the claims.