Abstract:
In one aspect, an integrated circuit (IC) includes an isolation trench dividing the IC into a first section and a second section, an active electronic device disposed in the first section of the IC and a capacitor disposed in the second section of the IC and electrically isolated from the active electronic device.

Description:
BACKGROUND 
       [0001]    Techniques for integrated circuit (IC) packaging are well known in the art. In general, a semiconductor die is cut from a wafer, processed, and attached to a lead frame. As is known in the art, ICs are typically overmolded with a plastic or other material to form the package. After assembly of the IC package, the package may then be placed on a circuit board. 
         [0002]    Such ICs, for example sensors, often require passive components, such as capacitors, resistors, inductors, and diodes, to be coupled to the IC for proper operation. Magnetic sensors, for example, can require decoupling capacitors to reduce noise and enhance EMC (electromagnetic compatibility). Such passive components, which can be used in filtering and other functions, can result in the addition of a circuit board near the IC package, or additional real estate on a circuit board that may be present. 
         [0003]    In some IC packages, a passive component is coupled to the lead frame adjacent to the die, such as arrangements described in a U.S. Patent Application Publication No. 2012/0086090, which application is assigned to the Assignee of the subject application and is incorporated herein by reference in its entirety. Also known are techniques for forming a capacitor on a semiconductor die from a combination of conductive and dielectric layers, such as arrangements described in a U.S. Pat. No. 7,573,112, which patent is assigned to the Assignee of the subject application and incorporated herein by reference in its entirety. 
       SUMMARY 
       [0004]    In one aspect, an integrated circuit (IC) includes an isolation trench dividing the IC into a first section and a second section, an active electronic device disposed in the first section of the IC and a capacitor disposed in the second section of the IC and electrically isolated from the active electronic device. 
         [0005]    In another aspect, a method to fabricate a capacitor in an integrated circuit includes providing a preliminary structure having an isolation trench dividing the structure into a first section and a second section, forming a plurality of trenches into an epitaxial silicon in the second section, disposing a silicide within the trenches, disposing a dielectric material on the silicide and disposing a metal on the dielectric material. The silicide forms a bottom plate of a capacitor and the metal forms a top plate of the capacitor. The first section comprises an active electronic device. 
         [0006]    In a further aspect, an integrated circuit (IC) sensor includes an IC having a first surface and a second, opposing surface. The IC includes an isolation trench dividing the IC into a first section and a second section, an active electronic device disposed in the first section of the IC and a capacitor disposed in the second section of the IC and electrically isolated from the active electronic device. The IC sensor also includes a lead frame having a die attach area to which the IC is attached. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIGS. 1A to 1J  are cross-sectional diagrams depicting processing steps in a process to integrate a capacitor into an integrated circuit (IC). 
           [0008]      FIG. 2  is a flowchart of an example of a process to integrate the capacitor into the IC. 
           [0009]      FIG. 3A  is a cross-sectional diagram of an example of a preliminary structure that may be used as a starting point to perform the process of  FIG. 2 . 
           [0010]      FIG. 3B  is a cross-sectional diagram of an integrated circuit with an integrated capacitor using the preliminary structure of  FIG. 3A  and the process in  FIG. 2 . 
           [0011]      FIG. 4A  is a plan view of an IC sensor having a “die up” configuration. 
           [0012]      FIG. 4B  is a view of an alternative IC sensor having a flip-chip arrangement. 
           [0013]      FIG. 4C  is a cross-sectional view of another IC sensor having a lead-on-chip configuration. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Described herein are techniques to integrate a capacitor into an integrated circuit (IC) that supports one or more active electronic devices. In one example, the capacitance of the integrated capacitor ranges from 100 nf to 100 pF. By integrating a capacitor into the IC, the IC can be provided using standard assembly techniques. For example, the need of wire bonding a capacitor disposed outside of the IC to the IC is no longer needed. In another example, the need of attaching the capacitor to the IC using soldering or epoxy is no longer required. In other examples, by having an integrated capacitor, the IC may he customized to meet specific electrostatic discharge (ESD) or electromagnetic compatibility (EMC) requirements. 
         [0015]    Referring to  FIG. 1A , a preliminary structure  5  may be fabricated that includes an interlayer dielectric (ILD) oxide  10  on an epitaxial silicon (EPI)  14 . The underlying substrate and circuit components below the EPI  14  are not shown for clarity. The IC  5  includes a polysilicon gate  22  with a self-aligned silicide  18 . The gate  22  is used to control some active electronic devices. Though not shown in  FIG. 1A , active electronic devices may be formed up to the ILD oxide  10  as shown in the IC sensor embodiments of  FIGS. 4A-4G . A shallow trench isolation  34  and a trench isolation  26  formed in the EPI  14  are used to isolate the yet to be fabricated capacitor from the electronic devices on the preliminary structure  5  including the polysilicon gate  22 . In one example, the depth of the trench isolation  26  ranges from about 6 microns to about 20 microns and the width of the trench isolation  26  ranges from about 1 micron to about 5 microns. In one example, the depth of the shallow trench isolation  34  ranges from 0.5 microns to 20 microns. one example, the shallow trench isolation  34  and the trench isolation  26  are made of silicon oxide (SiO y ), including silicon dioxide (SiO 2 ). 
         [0016]      FIG. 1B  depicts the result of removing a portion of the ILD oxide  10  to form a trench  30  down to the EFI  14 . in one example, the trench  30  ranges from about 100 microns by 100 microns to about 1,000 microns by 1,000 microns. 
         [0017]      FIG. 1C  depicts the result of forming trenches  32  in the EP 1   14 . In one example, each trench  32  has a width that ranges from about one micron to about 10 microns and has a depth that ranges from about 5 microns to about 100 microns. While the trenches  32  shown are rectangular in shape, one of ordinary skill in the art would recognize that the trenches may be other type shapes including shapes having a circular or elliptical type shapes, for example. 
         [0018]      FIG. 1D  depicts the result of disposing a self-aligned silicide  42  into the trenches  32 . The silicide  42  will function as a bottom capacitor plate or lower electrode. In one example, the silicide materials may include at least one of titanium silicide (TiSi 2 ), tantalum silicide (TaSi 2 ), nickel silicide (NiSi x ), tungsten silicide (WSi x ), Molybdenum silicide (MoSi x ) or platinum silicide (PtSi x ). In other examples, a metal and/or a doped polysilicon may be used. 
         [0019]      FIG. 1E  depicts the result of depositing a dielectric material  46  in the trenches  32 . 
         [0020]    In one example, the dielectric material includes at least one of tungsten oxide (TaO x ), titanium oxide (TiO), titanium oxynitride (TiO x NO y ), silicon oxide (SiO y ), silicon nitride (Si x N y ) silicon oxynitride (Si x O y N z ) or hafnium oxide (HfO x ). In one example, the thickness of the dielectric material ranges from 50 nm to 300 mm. 
         [0021]      FIG. 1F  depicts the result of depositing a metal  43  on the dielectric material  46  and  FIG. 1G  depicts the result of patterning and etching the metal  43 . The metal  43  will function as the top plate of the capacitor or upper electrode. In other examples, a polysilicon such as a doped polysilicon may be used instead of the metal  43 . 
         [0022]      FIG. 1H  depicts the result of depositing a dielectric  48 .  FIG. 1I  depicts the result after planarization. 
         [0023]      FIG. 1J  depicts the result of adding interconnects  51   a - 51   e  and a metal contact  50  to each interconnect to allow access to electrical components such as the active elements and the capacitor. In particular, the interconnect  51   a  provides an electrical connection to the active elements, the interconnect  51   b  provides an electrical connection to the upper electrode (metal  43 ) of the capacitor and the interconnect  51   c  provides an electrical connection to the lower electrode (silicide  42 ) of the capacitor (silicide  42 ). In one example, the metal  50  is aluminum silicon (AlSi). In one example, the interconnects  51   a - 51   c  are made of tungsten. 
         [0024]    Referring to  FIG. 2 , an example of a process to generate the IC  100  is a process  200 . A preliminary structure is fabricated ( 202 ). For example, the preliminary structure  5  ( FIG. 1A ) is fabricated, in another example, the preliminary IC  5 ′ ( FIG. 3A ) is fabricated. 
         [0025]    Portions of the ILD oxide layer are removed ( 208 ). For example, a pattern and etch of the ILD oxide  10  is performed to form the trench  30  down to the EPI  14  ( FIG. 1B ). 
         [0026]    Trenches in the epitaxial silicon are formed ( 212 ). For example, a pattern and etch of the EPI  14  is performed to for trenches  32  ( FIG. 1C ). 
         [0027]    A suicide is provided within the trenches  32  ( 216 ). For example, the self-aligned suicide  42  is disposed into the trenches  32  ( FIG. 1D ). In one example, a process to provide the suicide  42  includes depositing at least one of titanium (Ti), tungsten (Ta), nickel (Ni) or platinum (Pt) into the trenches  32 , annealing at a temperature ranging from about 580° C. to about 750° C., performing a wet etch with one or more of hydrogen peroxide (H 2 O 2 ), ammonium hydroxide (NH 4 OH) and water (H 2 O), and annealing at a temperature ranging from about 900° C. to about 1100° C. 
         [0028]    A dielectric material is disposed in the trenches ( 218 ). For example, the dielectric material  46  is deposited on the silicide  42  to fill the trenches  32  ( FIG. 1E ). In one example, the dielectric material  46  is deposited using one of a Chemical vapor deposition (CVD) process, a sputtering process or a spin-on process. 
         [0029]    A metal is disposed on the dielectric material ( 222 ). For example, a metal  43  is disposed ( FIG. 1F ). A pattern and etch is performed ( 224 ) to remove portions of the metal  43  ( FIG. 1G ). 
         [0030]    A dielectric is disposed ( 226 ) and a planarization is performed ( 236 ). For example, the dielectric  48  is deposited in the trench  30  to fill the topology in the trench  30  ( FIG. 1H ) and a planarization is performed on the dielectric  48  ( FIG. 1I ), In one example, the planarization is performed using a chemical-mechanical planarization (CMP) process or a plasma etch process. 
         [0031]    Trenches are formed ( 242 ) and filled with interconnect material ( 246 ). For example, the trenches are formed by etching the ILD oxide  10  and the dielectric  48  and the trenches are filled with interconnects  51   a - 51   c  ( FIG. 1J ). 
         [0032]    A layer of metal is disposed ( 252 ) and portions of the layer of metal are removed ( 256 ). For example, the metal  50  is deposited and a pattern and etching process is performed to remove portions of the metal  50  to form the IC  100  (FIG. IS), Referring to  FIGS. 3A and 3B . an IC  100 ′ may be formed by using the process  200 . 
         [0033]    For example, the process  200  may start with the preliminary structure  5 ′. The preliminary structure  5 ′ is the same as the preliminary structure  5  except the preliminary structure  5 ′ includes a silicon oxide layer  86  at the bottom of the preliminary structure  5 ′. The result of performing the process  200  on the preliminary structure  5 ′ is the IC  100 ′ which is the same as the IC  100  except for the silicon oxide layer  86 . The silicon oxide Layer  86  provides additional isolation between the capacitor and the active electronic component. 
         [0034]    Referring also to  FIG. 4A , an IC sensor  300  includes a semiconductor die  304  in which one or more active electronic devices  308  and in which an integrated capacitor  312  of the type described above are formed. The sensor  300  further includes a lead frame  314  having a die attach area  316  to which the die  304  is attached, such as with an adhesive, and further having a plurality of leads  318 . A mold material  320  is provided, such as in the form of a plastic, to enclose the die and a portion of the lead frame  314 . 
         [0035]    The die  304  has an “active” surface in which the magnetic field sensing element  308  is formed and an opposing surface. In the embodiment of  FIG. 4A , it is the opposing surface that is attached to the die attach area. Accordingly, sensor configuration can be referred to as a “die-up” configuration. 
         [0036]    Various techniques are suitable for coupling the electronic device  308  and the capacitor  312  to leads  318 , such as the illustrated wire bonds  310 . 
         [0037]    The active electronic device  308  may take various forms, such as a magnetic field sensing element or an amplifier or other devices. The illustrative device  308  is a magnetic field sensing element and thus, the IC sensor  300  may be referred to alternatively as a magnetic field sensor. As used herein, the term “magnetic field sensing element” is used to describe a variety of electronic elements that can sense a magnetic field. The magnetic field sensing element can be, but is not limited to, a Hall effect element, a magnetoresistance element, or a magnetotransistor. As is known, there are different types of Hall effect elements, for example, a planar Hall element, a vertical Hall element, and a Circular Vertical. Hall (CVH) element. As is also known, there are different types of magnetoresistance elements, for example, a semiconductor magnetoresistance element such as Indium Antimonide (InSb), a giant magnetoresistance (GMR) element, an antisotropic magnetoresistance element (AMR), a tunneling magnetoresistance (TMR) element, and a magnetic tunnel junction (MTJ). The magnetic field sensing element may he a single element or, alternatively, may include two or more magnetic field sensing elements arranged in various configurations, e.g., a half bridge or full (Weatstone) bridge. Depending on the device type and other application requirements, the magnetic field sensing element may he a device made of a type IV semiconductor material such as Silicon (Si) or Germanium (Ge), or a type III-V semiconductor material like Gallium-Arsenide (GaAs) or an Indium compound, e.g., Indium-Antimonide (InSh). 
         [0038]    As is known, some of the above-described magnetic field sensing elements tend to have an axis of maximum sensitivity parallel to a substrate that supports the magnetic field sensing element, and others of the above-described magnetic field sensing elements tend to have an axis of maximum sensitivity perpendicular to a substrate that supports the magnetic field sensing element. In particular, planar Hall elements tend to have axes of sensitivity perpendicular to a substrate, while metal based or metallic magnetoresistance elements (e.g., GMR, TMR, AMR) and vertical Hall elements tend to have axes of sensitivity parallel to a substrate. 
         [0039]    As used herein, the term “magnetic field sensor” is used to describe a circuit that uses a magnetic field sensing element, generally in combination with other circuits. Magnetic field sensors are used in a variety of applications, including, but not limited to, an angle sensor that senses an angle of a direction of a magnetic field, a current sensor that senses a magnetic field generated by a current carried by a current-carrying conductor, a magnetic switch that senses the proximity of a ferromagnetic object, a rotation detector that senses passing ferromagnetic articles, for example, magnetic domains of a ring magnet or a ferromagnetic target (e.g., gear teeth) where the magnetic field sensor is used in combination with a back-biased or other magnet, and a magnetic field sensor that senses a magnetic field density of a magnetic field. 
         [0040]    Referring also to  FIG. 4B , an alternative IC sensor  330 , such as a magnetic field sensor, includes a semiconductor die  334  in which one or more active electronic devices  338  and in which an integrated capacitor  342  of the type described above are formed. The sensor  330  further includes a lead frame  344  having a die attach area  346  to which the die  334  is attached and further having a plurality of leads  348 . A mold material  350  is provided, such as in the form of a plastic, to enclose the die and a portion of the lead frame  344 . 
         [0041]    The die  334  has an “active” surface in which the magnetic field sensing element  338  is formed and an opposing surface. In the embodiment of  FIG. 4B , it is the active surface that is attached to the die attach area. Accordingly, sensor configuration can be referred to as a “flip-chip” configuration. In some embodiments, the die  334  is coupled to the lead frame  344  with solder bumps, solder balls, or pillar bumps  352 . 
         [0042]    The magnetic field sensor  330  is a current sensor in which current flows through interconnected leads as indicated by arrows  354 . 
         [0043]    A further alternative IC sensor  360  is shown in  FIG. 4C  to include a semiconductor die  364  in which one or more active electronic devices  368  and in which an integrated capacitor  372  of the type described above are formed. The sensor  360  further includes a lead flume  374  having a die attach area  376  to which the die  364  is attached and further having a plurality of leads  378 . A mold material  380  is provided, such as in the form of a plastic, to enclose the die and a portion of the lead frame  374 . 
         [0044]    A second mold material  384 , as may comprise a hard or son ferromagnetic material, may be provided to form a hack bias magnet or concentrator. Optionally, a further mold material  386  may be provided in a central aperture of the second mold material  384  as shown. 
         [0045]    The die  364  has an “active” surface in which the magnetic field sensing element  368  rued and an opposing surface. In the embodiment of  FIG. 4C , the active surface is attached to the die attach area, but at the “bottom” of the lead frame. Accordingly, sensor configuration can be referred to as a “lead-on-chip” configuration. Various techniques are suitable for coupling the electronic device  368  and the capacitor  372  to leads  378 , such as the illustrated wire bonds  382 . 
         [0046]    The processes described herein are not limited to the specific examples described. For example, the process  200  is not limited to the specific processing order of  FIG. 2 . Rather, any of the processing blocks of  FIG. 2  may be re-ordered, combined or removed, performed in parallel or in serial, as necessary, to achieve the results set forth above. 
         [0047]    Elements of different embodiments described herein may be combined to form other embodiments not specifically set forth above. Other embodiments not specifically described herein are also within the scope of the following claims.