Abstract:
A Hall-effect magnetic sensor comprises a p-type Hall element and an n-type epitaxial Hall element. The p-type element can be implanted directly on top of the n-type element. The merged Hall elements can be biased in parallel to provide a nearly zero-bias depletion layer throughout for isolation. Electrical contacts to the n-type element can be diffused down through the p-type element and positioned to partially obstruct current flow in the p-type element. Electrical contacts can be diffused into the p-type element. Each bias contact of the p-type element can be connected to respective bias contacts of the n-type element in a parallel fashion. Then, an output signal can be taken at the sense contacts of the n-type element in order to provide improved magnetic responsivity. Further provided is a method for manufacturing the Hall-effect magnetic sensor.

Description:
TECHNICAL FIELD 
       [0001]    Embodiments are generally related to Hall-effect elements. Embodiments are more particularly related to Hall-effect magnetic sensors with Hall-effect elements. Embodiments are also related to methods for manufacturing Hall-effect magnetic sensors. 
       BACKGROUND OF THE INVENTION 
       [0002]    With the development of the semiconductor industry, the application of well-known Hall effect elements can be utilized in various semiconductor devices, in particular Hall-effect sensors. Such integrated Hall-effect sensors can be fabricated in accordance with well-known silicon planar process technology. Integrated Hall-effect sensors can be operated based on what can be referred to in the art as “Hall-effect technology.” Such Hall-effect technology can provide solutions for reliable solid-state magnetic switching and linear magnetic sensing. Hall-effect magnetic sensors can convert energy stored in the magnetic field to an electrical signal by means of the Hall-effect in order to sense position of a moveable object. Generally, the Hall-effect can occur when a conductor carrying electrical current is placed in a magnetic field. Integrated Hall-effect sensors can be utilized for automotive, consumer, medical and industrial applications. 
         [0003]    Furthermore, the Hall element can be a basic component of the Hall-effect magnetic sensors and supplied by an electrical power source. The Hall element can be constructed from a thin sheet of conductive material with output connections perpendicular to the net direction of electrical current flow. When the magnetic field is applied normal to the plane, approximated as the thin sheet of electrical current flow through the Hall element, an electric field responds to counteract deflection of charge carriers due to the Lorentz force. The counteracting electric field is commonly referred to as the Hall field. The development of the Hall field results from the necessity of charge neutrality in the thin conducting sheet, in a direction perpendicular to the direction of current flow. The Hall field present between the output connections can be measured as a Hall voltage, which can be orthogonal to both the magnetic field and the electrical current flow. Such Hall voltage can be directly proportional to the magnetic field, in particular magnetic responsivity, and can be measured to sense magnetic flux density. 
         [0004]    Hall-effect elements can be fabricated using a semiconductor material such as silicon. A Hall-effect element can include two bias contacts and two sensing contacts that can be formed by diffusing impurities into the semiconductor body incorporating a Hall-effect element. Metal conductors can be deposited and patterned on the surface of said semiconductor body to provide electrical connections to the Hall element. The diffused impurities raise the conductivity of the silicon in the localized regions of the contacts to provide ohmic characteristics at the interface of the silicon and the metal interconnects. The high-conductivity diffused regions that facilitate the contacts act approximately as eqipotential regions within the bulk of the Hall effect element. The electric field must tend to zero along an eqipotential boundary. Accordingly, the Hall field is diminished near the high conductivity diffused regions at the contacts. Deflection of mobile charge carriers occurs, in accordance with the Lorentz force, in the region of diminished Hall field near the contacts. The diminution of the Hall field and consequential deflection of mobile charge carriers in the region of a contact can be referred to as the shorting effect, and can be quantified as the shorting factor in a mathematical description of the Hall voltage. A common technique of prior art is to minimize the area of the contacts in order to minimize the shorting factor, thereby maximizing the Hall voltage. 
         [0005]    Hall Offset can be measured as a differential voltage, at the output sensing contacts, in the absence of a magnetic field. Geometrical irregularities in the contact locations and shape can produce Hall offset. Processing tolerances effect the placement accuracy and geometry control of the contacts, so that there is a practical limit to contact size reduction imposed by Hall offset considerations. Ultimately, contact size is chosen on the basis of maximizing the Hall voltage-to-offset ratio. 
         [0006]    It is well established in the literature that no particular geometrical shape or contact configuration can improve magnetic responsivity of single-plate Hall elements that are constructed using identical processes and materials. In the prior art, maximization of the Hall voltage-to-offset ratio is limited to reducing the Hall offset through precise control of geometrical symmetry. Other techniques can be applied to reduce Hall offset such as: averaging the output signals of a plurality of Hall elements that are arranged geometrically in a common centroid layout, the use of trimming networks or by averaging output signals obtained with multiple bias configurations; the so called current spinning method. 
         [0007]    A need therefore exists for an improved Hall-effect magnetic sensor with higher magnetic responsivity, an improvement which can be provided by a parallel arrangement of two semiconducting layers, one n-type and one p-type, magnetically coupled across a nearly zero-bias depletion region. A nearly zero-bias depletion region herein includes any bias induced depletion layer that does not cause significant diffusion current to pass between the n-type and p-type layers. Such Hall-effect magnetic sensor is described in greater detail herein. 
       BRIEF SUMMARY 
       [0008]    The following summary is provided to facilitate an understanding of some of the innovative features unique to the embodiments disclosed and is not intended to be a full description. A full appreciation of the various aspects of the embodiments can be gained by taking the entire specification, claims, drawings, and abstract as a whole. 
         [0009]    It is, therefore, one aspect of the present invention to provide for an improved Hall-effect magnetic sensor with higher magnetic responsivity. 
         [0010]    It is another aspect of the present invention to provide for a method for manufacturing the Hall-effect magnetic sensor. 
         [0011]    The aforementioned aspects and other objectives and advantages can now be achieved as described herein. A Hall-effect magnetic sensor comprises a p-type Hall element and an n-type epitaxial Hall element. The p-type element can be implanted directly on top of the n-type element. The merged Hall elements can be biased in parallel to provide a nearly zero-bias depletion layer throughout for isolation. Electrical contacts to the n-type element can be diffused down through the p-type element and positioned to partially obstruct current flow in the p-type element. Bias contacts can be diffused into the p-type element. Power bias contacts of the p-type element can be connected to respective bias contacts of the n-type element in a parallel fashion. Then, an output signal can be taken at the sensor contacts of the n-type element in order to provide improved magnetic responsivity. The invention further provides a method for manufacturing the Hall-effect magnetic sensor. 
         [0012]    Furthermore, the Hall-effect magnetic sensor can also include a p-type substrate and be constructed using a standard silicon IC technology. The n-type epitaxial Hall element can be disposed on the p-type substrate. The n-and-p type Hall elements can represent a set of parallel sheets or plates that are connected to an external power source. N-type diffusions can extend through the implanted layer comprised by the p-type Hall element. Such n-type diffusions can be connected as bias terminals to supply electrical power to the n-type Hall element. These n-type diffusions can partially obstruct electrical current flow in the p-type Hall element. Such partial obstruction of current flow in the p-type Hall element can result in enhanced asymmetry of the current-flow lines, about a center line intersecting the bias contacts of the p-type Hall, upon application of an external magnetic field, and resulting from current deflection at the bias contacts of the p-type element, due to the Lorentz force. The output signal voltage of the n-type epitaxial Hall element can be enhanced by magnetic coupling between the parallel sheets of conduction currents. The parallel sheets of the Hall elements can also be formed together with a topology of n-and-p-type Hall element contacts that optimizes the output voltage of the n-type Hall element. 
         [0013]    Such Hall-effect magnetic sensor described herein can exhibit better magnetic responsivity in order to achieve higher Hall sensor performance in an optimized manner. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the embodiments and, together with the detailed description, serve to explain the embodiments disclosed herein. 
           [0015]      FIG. 1  illustrates a sectional view for a layout of a Hall-effect magnetic sensor with two parallel Hall elements, which can be adapted for use in implementing a preferred embodiment; 
           [0016]      FIG. 2  illustrates a sectional view of the Hall-effect magnetic sensor perpendicular to the sectional view as shown in  FIG. 1 , which can be implemented in accordance with a preferred embodiment; 
           [0017]      FIG. 3  illustrates a top view of the Hall-effect magnetic sensor with electrical contacts, which can be implemented in accordance with a preferred embodiment; 
           [0018]      FIG. 4  illustrates a top view of the Hall-effect magnetic sensor with electrical contacts and interconnecting conductors, which can be implemented in accordance with a preferred embodiment; 
           [0019]      FIG. 5  illustrates a flowchart of a method for manufacturing the Hail-effect magnetic sensor as shown in  FIG. 1 , which can be implemented in accordance with a preferred embodiment; 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof. 
         [0021]      FIG. 1  and  FIG. 2  represent sectional views (not to scale) of a Hall-effect device with improved magnetic responsivity. These sectional views are depicted at right angle to one another.  FIG. 1  illustrates internal structures along a section that passes through the signal output terminals of the n-type and p-type Hall elements.  FIG. 2  depicts internal structures along a section that passes through the bias terminals of the n-type and p-type Hall elements. Heavily doped n-type and p-type diffused layers are respectively indicated as n+ and p+ in  FIG. 1  and  FIG. 2 . 
         [0022]    Referring to  FIG. 1  a sectional view of a Hall-effect device with improved magnetic responsivity  100  is illustrated, which can be implemented in accordance with a preferred embodiment. The Hall-effect device  100  can be formed on a semiconductor body made of silicon, utilizing silicon integrated circuit technology. A p-type substrate  110  can be formed as a base for the Hall-effect magnetic device  100 . The Hall-effect device  100  generally includes a p-type substrate layer  110  upon which an epitaxial layer or an n-type Hall element  120  can be formed. A p-type layer or a p-type Hall element  130  can be implanted directly on top of the n-type epitaxial Hall element  120 . 
         [0023]    An isolating layer  180  bounds the entire perimeter of the n-type epitaxial Hall element  120  and surrounds the p-type Hall element  130 . The isolating layer  180  is preferably p-type silicon, and the n-type Hall element  120  is preferably formed within a region of an n-type epitaxial silicon layer that can be grown on the p-type substrate  110 . The isolating layer  180  can be formed by diffusing p-type impurities extending down through the n-type epitaxial layer and into the p-type substrate  110  and can provide electrical isolation. The isolating layer  180  can be biased with a negative voltage potential with respect to the n-type Hall element  120  to isolate Hall elements  120  and  130  from other circuit elements. Additionally, an insulating layer  190  can be formed above the n-type epitaxial layer  120 . The insulating layer  190  can be for example, silicon dioxide. 
         [0024]    An electrically conductive material can be formed on top of the insulating layer  190 . The conductive layer can be for example, mostly aluminum or polysilicon. The conductive layer can be partitioned into separate regions  170 ,  171 ,  172 ,  173  and  175 , configured to provide electrical interconnection to the Hall Effect device  100 . The insulating layer  190  can be selectively removed to respectively configure electrical contacts  160 ,  161 ,  162  and  163  between interconnection conductors  170 ,  171 ,  172  and  173  and the underlying silicon layers  140 ,  141 ,  150 ,  151 . Silicon layers  150  and  151  can be formed from heavily doped n-type diffusions to support ohmic conduction between the n-type Hall element  120  and conductors  171  and  173 . 
         [0025]    Silicon layers  140  and  141  can be formed from heavily doped p-type diffusions to support ohmic conduction between the p-type Hall element  130  and conductors  170  and  172 . Conductors  171  and  173  can be used to connect the n-type Hall element differential output signal to an electrical circuit. In one embodiment, conductors  170  and  172  can be electrically isolated or floating. In an alternate embodiment, conductors  170  and  172  can be used to connect the p-type Hall element differential output signal to an electrical circuit, to provide modulation of the n-type Hall element differential output signal. For example, and electrical signal applied to conductors  171  and  172  can be used to null the offset voltage of the n-type Hall element. Electrical connections from conductor  175  to the silicon under layers are not apparent in this sectional view. 
         [0026]    Referring to  FIG. 2  a sectional view of a Hall-effect device with improved magnetic responsivity  200  is illustrated, which can be implemented in accordance with a preferred embodiment. Descriptions of the p-type substrate layer  110 , epitaxial layer comprising the n-type Hall element  120 , p-type implanted layer  130  and isolation diffusion  180  are as in the detailed description of  FIG. 1 . An insulating layer  190  can be formed above the n-type epitaxial layer. The insulating layer  190  can be for example, silicon dioxide. 
         [0027]    An electrically conductive material can be formed on top of the insulating layer  190 . The conductive layer can be for example, mostly aluminum or polysilicon. The conductive layer can be partitioned into separate regions  174  and  175 , configured to provide electrical connection to the n-type and p-type Hall elements. The insulating layer  190  can be selectively removed to configure electrical contacts  164  and  165  between conductor  174  and the underlying silicon layers  152  and  142 . Additionally, insulating layer  190  can be selectively removed to configure electrical contacts  166 ,  167  and  168  between conductor  175  and the underlying silicon layers  143 ,  153  and  180 . 
         [0028]    Silicon layers  152  and  153  can be formed from heavily doped n-type diffusions to support ohmic conduction between the n-type Hall element  120  and conductors  174  and  175 . Silicon layers  142  and  143  can be formed from heavily doped p-type diffusions to support ohmic conduction between the p-type Hall element  130  and conductors  174  and  175 . Conductors  174  and  175  can be used to connect the n-type and p-type Hall elements to an external power source. Silicon layer  180  can be formed from a heavily doped p-type diffusion to support ohmic conduction to conductor  175 . Reverse bias can be provided across the n-type epitaxial layer and the p-type isolating layer to provide electrical isolation; conductor  174  can be biased at a voltage potential that is positive with respect to conductor  175  to isolate the two Hall elements  120  and  130  from other circuit elements. 
         [0029]    Sufficient electrical isolation between the n-type and p-type Hall elements  120  and  130  can be achieved by arranging bias connection conductors  174  and  175  to power the n-type and p-type Hall elements in parallel. This parallel bias configuration produces a nearly zero-bias depletion region between the n-type and p-type Hall elements. 
         [0030]    Referring to  FIG. 3  a schematic top view of Hall-effect device  300  with improved magnetic responsivity is illustrated, which can be implemented in accordance with a preferred embodiment. Descriptions of the epitaxial layer comprising the n-type Hall element  120 , the p-type implanted layer  130 , p-type diffusions  140 ,  141 ,  142  and  143 , n-type diffusions  150 ,  151 ,  152 , and  153 , contact openings  160 ,  161 ,  162 ,  163 ,  164 ,  165 ,  166 ,  167  and  168 , and isolation diffusion  180  are as in the detailed description of  FIG. 1  and  FIG. 2 . The sectional view in  FIG. 1  relates to a section from the lower left-hand corner to the upper right-hand corner of Hall device  300  in  FIG. 3 . The sectional view in  FIG. 2  relates to a section from the upper left-hand corner to the lower right-hand corner of Hall device  300  in  FIG. 3 . 
         [0031]      FIG. 4  illustrates an alternative schematic view of Hall-effect device  400  with improved magnetic responsivity in accordance with a preferred embodiment. Descriptions of the contact openings  160 ,  161 ,  162 ,  163 ,  164 ,  165 ,  166 ,  167  and  168 , and conductors  170 ,  171 ,  172 ,  173  and  174  are as in the detailed description of  FIG. 1  and  FIG. 2 . Interconnection conductor  175  can connect the two merged Hall elements and the isolating diffusion (see component  180  in  FIG. 1-FIG .  3 ) to the low-potential side of an external power source through contact openings  166 ,  167  and  168 . Conductor  175  can also cover the surface area of Hall device  100  that is not covered by conductors  170 ,  171 ,  172 ,  173  and  174 , to act as a field plate. Substantial surface accumulation and depletion layers can exist in lightly doped silicon layers at the silicon-insulator interface, in response to electric fields. In particular, the n-type epitaxial layer and to a lesser degree the implanted p-type layer (i.e., components  120  and  130  respectively depicted in  FIG. 1-FIG .  3 ) are susceptible to modulation of sheet conductivity due to these field induced surface layers. 
         [0032]    In the presence of locally non-uniform fields, the resulting local variation in sheet conductivity can produce error signals at the output of either the n-type or p-type Hall elements. Conductor  175  is configured to guard the underlying layers from external electric fields, thereby controlling the error signals. The field effects that remain, due to charges in the insulating layer (i.e., see component  190  in  FIG. 1-FIG .  2 ) and work function differences between the silicon and conductor  175 , are mainly uniform and so produce only small, relatively stable offset signals from the Hall elements. 
         [0033]    Referring to  FIG. 5 , a detailed flow chart of operations illustrating logical operational steps of a method  500  for constructing the Hall-effect device  100  with merged complementary structure is illustrated, which can be implemented in accordance with a preferred embodiment. Note that in  FIGS. 1-4 , identical or similar parts or elements are generally indicated by identical reference numerals. As indicated at block  510 , a p-type substrate can be provided, and at block  520  an n-type epitaxial layer can be formed upon the p-type substrate. Such n-type epitaxial Hall element  120  can be formed of thin n-doped epitaxial layer. As indicated in block  530 , a p-type layer can be diffused down through the n-type epitaxial layer to provide for electrical isolation of an area of the epitaxial layer that forms the n-type Hall element  120 . Next, as depicted at block  540 , a p-type hall element  130  can be implanted directly on top of n-type epitaxial hall element  120 . Similarly, the p-type Hall element  130  can be formed of a thin p-type implanted layer. 
         [0034]    As specified at block  550 , electrical contact regions  140 - 143  to the p-type Hall element  130  and electrical contact regions  150 - 153  to the n-type epitaxial Hall element  120  can be diffused. The diffusions can be made by doping appropriate n-type and p-type impurities into the n-type epitaxial layer and the thin p-type implanted layer. 
         [0035]    n-type contacts  150 - 153  to the n-type Hall element  120  can be diffused down through the p-type Hall element  130  and positioned to partially obstruct current flow in the p-type Hall element  130 . As displayed at block  560 , the merged Hall elements  120  and  130  can be biased in parallel to provide a nearly zero-bias depletion layer between Hall elements  120  and  130 . The nearly zero-bias depletion layer can provide isolation between the p-type Hall element  130  and the n-type epitaxial Hall element  120 . Finally, as indicated at block  570 , a differential output voltage signal can be measured at the output terminals  171  and  173  of the n-type epitaxial Hall element  120 . The present invention can provide the Hall-effect magnetic sensor  100 ,  200 ,  300  and/or  400  that is capable of precisely measuring a magnetic field in accordance with the Hall effect. In addition, such design optimizations of the Hall-effect magnetic sensor  100 ,  200 ,  300  and/or  400  can improve magnetic responsivity for achieving higher performance. 
         [0036]    It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.