Abstract:
Capacitor technology that provides a high density, high reliability capacitor that is capable of operating at high temperature, for example for use in downhole tools. The capacitive cells have an insulating dielectric of crystalline diamond deposited on a substrate of silicon. Methods of manufacturing capacitor cells are also disclosed, as are stacked configurations of single die capacitors.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to EP Patent Application No. 14290286.5 filed Sep. 18, 2014, the entire contents of which is hereby incorporated by reference herein. 
       FIELD 
       [0002]    Embodiments of the present invention relate to a capacitor cell and a method for manufacturing a capacitor cell. Merely by way of example, the capacitor cell may comprise a polycrystalline diamond capacitor and a method for manufacturing such a capacitor. In some embodiments, the capacitor cells may be use in high temperature environments, for example in downhole applications in the oil and gas industries. 
       BACKGROUND 
       [0003]    Existing silicon-based capacitors have been commercialized with high density and high reliability features at high temperature. The electrical performance and reliability of such silicon-based capacitors are very attractive compared to other technologies like tantalum or ceramic capacitors. 
         [0004]    Silicon-based capacitor technology is fairly mature and uses advanced clean room processes, such as Deep Reactive Ion Etching (DRIE). Silicon-based capacitor technology is based mainly on the dielectric properties of the silicon di-oxide (SiO 2 ) or Hafnium oxide (HfO 2 ), which are currently used as dielectrics in microelectronics. 
         [0005]    However, a limitation of such technology comes from the voltage rating, which only provides for low voltages, typically below about 15 Volts (V). Additionally, the more the voltage increases, the more the density decreases in term of capacitance per surface unit, typically in the range from 25 to 250 nF/mm 2  (nanofarads per square millimetre). 
         [0006]    In recent years, three-dimensional arrangements of capacitor cells have been developed in which the density of the cell can be improved by increasing the surface area of the dielectric between the electrodes of the cell. 
         [0007]    One of the objects of the present invention is to provide capacitor cells and methods for manufacturing such capacitor cells that provide a high density, high reliability capacitor, in particular one that can operate at high temperature. In some aspects, operation may be above about 150° C., 175° C. or 200° C. Such capacitors having application in downhole tools used in the oil and gas exploration and production industries. 
       SUMMARY 
       [0008]    Aspects of the present invention provide capacitor cells and methods of manufacturing capacitor cells in which a diamond dielectric layer is used. 
         [0009]    The disclosure relates to a capacitor cell comprising a semi-conductor assembly comprising a substrate of semi-conductor material having a plurality of cavities etched into a top surface thereof; a dielectric insulator layer of crystalline diamond formed on said semi-conductor assembly; a top layer electrode formed on said diamond layer; a bottom layer electrode formed on a bottom surface of the substrate of said semi-conductor assembly ; and an insulating layer formed on said top electrode layer and having a plurality of openings to provide access to said top electrode layer. 
         [0010]    A first aspect of an embodiment of the present invention provides a capacitor cell comprising: a substrate of intrinsic semi-conductor material having a plurality of cavities etched into a top surface thereof; an inner electrode formed on said top surface; a dielectric insulator layer of crystalline diamond formed on said inner electrode; a top layer electrode formed on said diamond layer; a bottom layer electrode formed on a bottom surface of said substrate; and an insulating layer formed on said top electrode layer and having a plurality of openings to provide access to said top electrode layer. 
         [0011]    In some embodiments, the inner electrode is a layer of ion implanted n-type dopant or is metal or a multilayer metallization. 
         [0012]    A second aspect of an embodiment of the present invention provides a capacitor cell comprising: a substrate of highly doped n-type semi-conductor material having a plurality of cavities etched into a top surface thereof; a dielectric insulator layer of crystalline diamond formed on said substrate; a top layer electrode formed on said diamond layer; a bottom layer electrode formed on a bottom surface of said substrate; and an insulating layer formed on said top electrode layer and having a plurality of openings to provide access to said top electrode layer. 
         [0013]    The capacitor cells according to the above first and second aspects differ in the type of semi-conductor substrate used. In the first aspect, an intrinsic material (e.g. bulk silicon) is used. In the second aspect, a highly-doped (N++) material (e.g. highly-doped silicon) is used. In other embodiments, different semi-conductor materials may also be used, such as, for example GaN, SiC, GaAs and/or the like. 
         [0014]    As a result of the difference in substrates, the capacitor cells of the first and second aspects also differ in the provision of an inner electrode. Where the substrate is intrinsic, an inner electrode may be separately formed. Where the substrate is already highly-doped, the electrode may be directly composed of the substrate itself and not separately formed. 
         [0015]    The optional and preferred features of the capacitor cells set out below apply to both the first and second aspects set out above. 
         [0016]    In embodiments of the present invention, diamond, a carbon (poly)-crystalline material, provides a wide range of attractive intrinsic characteristics for dielectric use (e.g. Young modulus, chemically inert, thermal conductivity, dielectric strength) with good reproducibility when deposited by CVD techniques or the like. Techniques for deposition may comprise, CVD, Plasma Enhanced Chemical Vapor Deposition (PECVD), Microwave PECVD (MPECVD), High Pressure High Temperature (HPHT) crystal growth and/or the like. 
         [0017]    In embodiments of the present invention, a high capacitive energy per unit volume can be achieved in the capacitor cell by use of a diamond dielectric and the three dimensional structure of the capacitor cell. 
         [0018]    In some embodiments, the diamond dielectric layer is deposited by Chemical Vapor Deposition (CVD) techniques. In an embodiment of the present invention, CVD is used to deposit and work with synthetic diamond with respect to a large variety of substrates, environments and geometries. For instance, in some embodiments, substrate materials such as alloys, silicon wafers and conventional metals (Cu, Ag, Au, Pt and/or the like) may be used with the diamond dielectric layer. 
         [0019]    By using diamond as a dielectric layer, in accordance with an embodiment of the present invention, a capacitor cell can be provided which has high density, high reliability and is capable of operation at high temperatures (up to and above 200° C.). 
         [0020]    The geometries of the cavities can also be designed to optimize the density and reliability of the capacitor cells. Various possible geometries are set out in the detailed description below. 
         [0021]    In certain embodiments, the top layer electrode comprises a thin layer of highly doped crystalline diamond. 
         [0022]    In some embodiments, the top layer electrode is metallized to allow the connection of other contacts. 
         [0023]    The insulating layer formed on said top electrode layer protects the top electrode (particularly where metallized) from mechanical, electrical and chemical damage. In embodiments of the present invention, the layer may comprise an organic or inorganic layer and/or may comprise a multilayer structure. 
         [0024]    The capacitor cells of the above first and second aspects may include any combination of some, all or none of the above described preferred and optional features. 
         [0025]    A third aspect of an embodiment of the present invention provides a capacitor comprising a stack of capacitor cells, each cell being an identical capacitor cell according to the above first or second aspect, including some or all features of those aspects, and wherein the cells are connected by bonding the top and bottom layer electrodes of neighbouring cells in the stack to each other. 
         [0026]    In some embodiments of the present invention, by adopting a modular approach of identical capacitor cells, robust and easy stacking of individual capacitor cells within a device can be achieved. In some embodiments, the electrodes of the cells may be bonded to each other and to a substrate (which may comprise a metallized ceramic substrate with a conductive layer) by conductive attachment material, and the whole may be encapsulated in an insulating material such as silicone or other polymeric material. 
         [0027]    Another aspect of an embodiment of the present invention provides a method of manufacturing a capacitor cell, the method including the steps of providing a plurality of cavities in a top surface of a substrate of semi-conductor material. In some aspects, the cavities are produced using etching, such as deep reactive ion etching or the like. Etching methods may be used that provide deep cavities in the substrate. 
         [0028]    The substrate may be made of intrinsic semi-conductor material. 
         [0029]    The method of manufacture in accordance with an embodiment of the present invention, includes, forming an inner electrode on said top surface depositing a thin layer of crystalline diamond on said inner electrode as a dielectric insulator layer, creating an electrically conductive top layer electrode on said diamond layer, finishing said top electrode layer by thin film metallization, creating an electrically conductive bottom electrode layer on a bottom surface of said substrate, finishing said bottom electrode layer by thin film metallization, forming an insulating layer on said top electrode layer, and forming openings in said insulating layer to provide access to said top electrode layer. 
         [0030]    In some embodiments, the inner electrode is a layer of ion implanted n-type dopant or is metal or a multilayer metallization, which may be formed by sputtering, CVD, PECVD, MPECVD and/or the like. 
         [0031]    The substrate may be made of highly doped n-type semi-conductor material. 
         [0032]    The method may include the steps of: etching a plurality of cavities into a top surface of a substrate of highly doped n-type semi-conductor material with a high conductivity; depositing a thin layer of crystalline diamond on said substrate as a dielectric insulator layer; creating an electrically conductive top layer electrode on said diamond layer; finishing said top electrode layer by thin film metallization; creating an electrically conductive bottom electrode layer on the bottom side of said substrate; finishing said bottom electrode layer by thin film metallization; forming an insulating layer on said top electrode layer; and forming openings in said insulating layer to provide access to said top electrode layer. 
         [0033]    The methods according to the above fourth and fifth aspects differ in the type of semi-conductor substrate used. In the fourth aspect, an intrinsic material (e.g. bulk silicon or the like) is used. In the fifth aspect, a highly-doped (N++) material (e.g. highly-doped silicon or the like) is used. Other semi-conductor materials may also be used, such as GaN, SiC and GaAs. 
         [0034]    As a result of the difference in substrates, the method of the fourth aspect includes an additional step of forming an inner electrode. In embodiments where the substrate is intrinsic, an inner electrode needs to be separately formed. In embodiments where the substrate is already highly-doped, the electrode can be directly composed of the substrate itself and is not separately formed. 
         [0035]    The optional and preferred features of the methods set out below apply to both the fourth and fifth aspects set out above. 
         [0036]    In some embodiments, the diamond layer is deposited by CVD, PECVD, MPECVD, HPHT crystal growth or the like. In some embodiments of the present invention, use of CVD to deposit and work with synthetic diamond provides for use of a large variety of substrates, environments and generation of a broad range of geometries. For instance, substrate materials such as alloys, silicon wafers and conventional metals (Cu, Ag, Au, Pt . . . ) are compatible with diamond CVD techniques. 
         [0037]    By combining microelectronics processes, such as DRIE or the like and the use of diamond, for example deposited by CVD, as a dielectric layer, the method can produce a capacitor cell which has high density, high reliability and is capable of operation at high temperatures (above 200° C.). 
         [0038]    Scalability of the method of these aspects can be provided by ensuring a compatibility with standard clean room processes. 
         [0039]    In certain embodiments, the top layer electrode is a thin layer of highly doped crystalline diamond. 
         [0040]    In some embodiments the top layer electrode is metallized to allow the connection of other contacts. 
         [0041]    The insulating layer formed on said top electrode layer protects the top electrode (particularly where metallized) from mechanical, electrical and chemical damage. In some embodiments, the insulating layer may comprise an organic or inorganic layer and may have a multilayer structure. 
         [0042]    The methods of the above fourth and fifth aspects may include any combination of some or all features of the fourth and fifth aspects. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0043]    Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: 
           [0044]      FIGS. 1 a -1 k    illustrate a method of manufacturing a capacitive cell according to an embodiment of the present invention; 
           [0045]      FIGS. 2 a  and 2 b    illustrate finished capacitive cells according to embodiments of the present invention; 
           [0046]      FIGS. 3 a -3 d    illustrate possible geometries of the cavities in the capacitive cells; 
           [0047]      FIG. 4  shows the configuration of a capacitive cell making up a single die for use in a stacked die capacitor according to an embodiment of the invention; 
           [0048]      FIG. 5  shows a stacked die according to an embodiment of the invention using the die shown in  FIG. 4 ; 
           [0049]      FIG. 6  shows an alternative configuration of a capacitive cell making up a single die for use in a stacked die capacitor according to an embodiment of the invention; 
           [0050]      FIG. 7  shows a stacked die according to an embodiment of the invention using the die shown in  FIG. 6 ; 
           [0051]      FIGS. 8 a  and 8 b    illustrate decoupling capacitors, in accordance with embodiments of the present invention, and pull-up/pull-down resistors within the same die/chip; 
           [0052]      FIGS. 9 a  and 9 b    illustrate capacitors, in accordance with embodiments of the present invention, incorporated in resistor-capacitor (RC) filters; and 
           [0053]      FIG. 10  illustrates capacitors, in accordance with embodiments of the present invention, integrated in a circuit as by-pass capacitors/analog capacitors. 
       
    
    
       [0054]    In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label. 
       DETAILED DESCRIPTION 
       [0055]    The ensuing description provides preferred exemplary embodiment(s) only, and is not intended to limit the scope, applicability or configuration of the invention. Rather, the ensuing description of the preferred exemplary embodiment(s) will provide those skilled in the art with an enabling description for implementing a preferred exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims. 
         [0056]    Specific details are given in the following description to provide a thorough understanding of the embodiments. However, it will be understood by one of ordinary skill in the art that the embodiments maybe practiced without these specific details. For example, circuits may be shown in block diagrams in order not to obscure the embodiments in unnecessary detail. In other instances, well-known circuits, processes, algorithms, structures, and techniques may be shown without unnecessary detail in order to avoid obscuring the embodiments. 
         [0057]    Also, it is noted that the embodiments may be described as a process which is depicted as a flowchart, a flow diagram, a data flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. A process is terminated when its operations are completed, but could have additional steps not included in the figure. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination corresponds to a return of the function to the calling function or the main function. 
         [0058]    Moreover, as disclosed herein, the term “storage medium” may represent one or more devices for storing data, including read only memory (ROM), random access memory (RAM), magnetic RAM, core memory, magnetic disk storage mediums, optical storage mediums, flash memory devices and/or other machine readable mediums for storing information. The term “computer-readable medium” includes, but is not limited to portable or fixed storage devices, optical storage devices, wireless channels and various other mediums capable of storing, containing or carrying instruction(s) and/or data. 
         [0059]    Furthermore, embodiments may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. 
         [0060]    When implemented in software, firmware, middleware or microcode, the program code or code segments to perform the necessary tasks may be stored in a machine readable medium such as storage medium. A processor(s) may perform the necessary tasks. A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc. 
         [0061]    A method of manufacturing a capacitive cell according to an embodiment of the present invention is set out step-wise below (cleaning and other non-critical steps which will be readily apparent to the person skilled in the art are not listed to avoid unnecessary information), with reference to  FIGS. 1 a   - 1   k.    
         [0062]    Initial substrate ( FIG. 1 a   ). The process starts with a polycrystalline or monocrystalline substrate material  1  which is called a “wafer”. The wafer may be composed of intrinsic silicon (or bulk silicon) with low conductivity (I) or highly doped silicon with high conductivity (N++). The wafer may be composed of another intrinsic semi-conductor material or another highly doped semi-conductor material. For instance, other semi-conductor materials may be GaN, SiC, GaAs or the like. 
         [0063]    DRIE ( FIG. 1 b   ). The substrate  1  is deeply etched by DRIE (Deep Reactive Ion Etching) or the like. Possible mask geometries are set out below. This step creates a number of cavities  2  into the substrate to increase the surface of the substrate  1 . 
         [0064]    Implantation (optional) ( FIG. 1 c   ). If the polycrystalline or monocrystalline substrate  1  is an intrinsic material, a process step of doping by ion implantation of an n-type dopant is required in order to increase electrical conductivity to create an inner electrode  3 . Alternatively to such implantation, the inner electrode  3  may be a metal or a multilayer metallization deposited by thin film deposition techniques such as sputtering. 
         [0065]    Two cases are illustrated in  FIGS. 1 c  and 1 d   : full N++ ( FIG. 1 c   ) or intrinsic substrate ( FIG. 1 d   ). When the substrate  1  is a full N++ substrate (highly conductive substrate), the inner electrode is directly composed of the N++, etched substrate itself and so the implantation step is not required. 
         [0066]      FIGS. 1 e -1 k   , which illustrate the subsequent steps, will be shown for the full N++ substrate only, but the skilled person will readily appreciate that the same steps are applicable for the intrinsic substrate with the implanted inner electrode  3 . 
         [0067]    Dielectric Diamond Deposition ( FIG. 1 e   ): a thin film of polycrystalline or monocrystalline diamond  4  is deposited by CVD or the like. The dielectric diamond layer  4  is an insulating layer. 
         [0068]    Top Electrodes Deposition ( FIG. 1 f   ): a thin film of highly doped polycrystalline or monocrystalline diamond is deposited by CVD or the like, or a thin film metallization is performed with metal or alloys (Al, Au, Ti, Cr, Ag, Pd and/or the like) in order to create the top electrode layer  5 . The top electrode layer is an electrically conductive layer. Note that this layer of conductive material may not fill entirely or cover entirely the three dimensional geometry of the substrate cavities. Top electrodes deposition may be deposited on different and insulated potentials (or nets) depending on mask design. 
         [0069]    Top Electrodes Finish ( FIG. 1 g   ): a thin film metallization  6  is performed with metals or alloys (Al, Au, Ti, Cr, Ag, Pd and/or the like) in order to adapt the metallurgy with microelectronic packaging technologies, fill or cover void geometric irregularities, and increase the thickness of the top electrode  5 . Top electrode finish may be deposited on different and insulated potentials (or nets) depending on mask design. 
         [0070]    Bottom Electrodes Deposition ( FIG. 1 h   ): a thin film of highly doped polycrystalline or monocrystalline diamond is deposited by CVD or the like, or a thin film metallization is performed with typical metals or alloys (Al, Au, Ti, Cr, Ag, Pd . . . ) in order to create the contacts of the bottom electrode layer  7 . The bottom electrode layer  7  is an electrically conductive layer. Note that this layer of conductive material may not fill entirely or cover entirely three dimensional geometry of the substrate. 
         [0071]    Bottom Electrodes Finish ( FIG. 1 i   ): a thin film metallization  8  is performed with metals or alloys (Al, Au, Ti, Cr, Ag, Pd and/or the like) in order to adapt the metallurgy with microelectronic packaging technologies, fill or cover void geometric irregularities, and increase the thickness of the bottom electrode  7 . 
         [0072]    Top passivation ( FIG. 1 j   ): the top passivation  9  is an insulating layer that protects the top metallization from being damaged (mechanically, electrically, chemically . . . ). It can be an organic or an inorganic layer, and it may be composed of a multilayered structure, such as a primary passivation and a secondary passivation. 
         [0073]    Top Electrodes Opening ( FIG. 1 k   ): The passivation  9  is removed at a selected number of positions  10  depending on the mask design to provide accesses to the top electrodes  5 . 
         [0074]    The main process steps have been listed above for the manufacturing of an elementary capacitive cell according to an embodiment of the present invention. The method results in the two final configurations as shown in  FIGS. 2 a  and 2 b   .  FIG. 2 a    shows the full N++ substrate configuration,  FIG. 2 b    shows the intrinsic substrate configuration. 
         [0075]    When the substrate  1  is composed of intrinsic silicon, instead of full N++ substrate (highly conductive substrate), the bottom electrode  6  is not an active electrode and must be connected to the lowest potential/net (typically the ground potential). When the substrate  1  is composed of full N++ substrate (highly conductive substrate) instead of intrinsic silicon, the inner electrode is composed of the N++ substrate itself and it is mechanically and electrically connected to the bottom electrode  6 . 
         [0076]    The elementary capacitive cell stack-up and geometry has been defined above. In some embodiments, dimensions for each cell may be within the ranges set out below: 
         [0077]    Wafer diameter: from about 4 to 20 inches 
         [0078]    Wafer thickness: from about 200 μm to 1 mm 
         [0079]    Intrinsic doping concentration: about 10 −3  to 10 −11  cm −3    
         [0080]    N++ doping concentration: about 10 −13  to 10 −20  cm −3    
         [0081]    Cavity depth: from about 50 μm to 400 μm. In some embodiments, the depth may be about 150 μm 
         [0082]    Cavity width or diameter: from about 0.5 μm to 20 μm. In some embodiments, the width may be about 1 μm 
         [0083]    Ratio Cavity depth/Cavity width or diameter: about 10 to 100 
         [0084]    Inner electrode thickness: from 10 nm to 100 μm. In some embodiments, the thickness may be about 200 nm to 1 μm. 
         [0085]    Diamond dielectric thickness: from 10 nm to 100 μm. In some embodiments, the thickness may be about 100 nm to 1 μm 
         [0086]    Top electrode thickness: from 10 nm to 100 μm. In some embodiments, the thickness may be about 200 nm to 1 μm 
         [0087]    Top metallization thickness: from 10 nm to 100 μm. In some embodiments, the thickness may be about 500 nm to 2 μm 
         [0088]    Bottom metallization thickness: from 10 nm to 100 μm. In some embodiments, the thickness may be about 500 nm to 2 μm 
         [0089]    Passivation thickness: from 10 nm to 100 μm. In some embodiments, the thickness may be about 1 nm to 10 μm 
         [0090]    Passivation opening: about 50 nm to 500 μm length (square or rectangular opening) 
         [0091]    Single die size (from wafer cutting): about 0.2 mm to 12 mm length (square or rectangular die shape). In some embodiments, the square or rectangular chip/die may be about 1×1 mm 2  to 6×6 mm 2    
         [0092]    Single die thickness (with or without grinding): from 150 μm to 400 μm. In some embodiments, the thickness may be about 400 μm 
         [0093]    Cavity Geometries 
         [0094]    Depending on the precise mechanical and electrical optimal design, different cavity geometries may be used in embodiments of the present invention.  FIGS. 3 a -3 d    show the top view geometries (mask design) of four examples of a substrate  1  with a plurality of cavities  2 : 
         [0095]      FIG. 3 a    shows square cavities (inversed micro-post) 
         [0096]      FIG. 3 b    shows circular cavities (inversed micro-fingers) 
         [0097]      FIG. 3 c    shows hexagonal cavities (“nid d′abeille”) 
         [0098]      FIG. 3 d    shows octagonal cavities (other polygonal shapes are also possible) 
         [0099]    For each of the geometries listed above, a filling factor may be defined as the ratio from the top view between the cavity area and the elementary capacitive cell area. Merely by way of example, the filling factor may in some aspects range from about 0.1 to 0.9. 
         [0100]    Die Stacking and Microelectronics Packaging 
         [0101]    In some embodiments, by adding silicon vias (through hole cavity /metallized via) and special electrode geometries, the initial process described above may be optimized to stack dies of individual capacitor cells. Two examples of stacked die configurations according to embodiments of the present invention will now be described 
       EXAMPLE 1 
       [0102]    In this example, bottom and top electrodes are designed to be placed and metalized on each side of the die (top and bottom side) in order to stack the same die. Merely by way of example, in some aspects, the number of stacked dies within a stack may ranges from 2 to 20. 
         [0103]    The geometry and electrode design of a single die  20  is shown in  FIG. 4 . The die has top and bottom positive and negative electrodes as indicated. 
         [0104]      FIG. 5  shows a plurality of stacked dies  20  on a metalized substrate  21  which is covered by a conductor  22  which is a conductive material with appropriate plating for metallurgical compatibility with die attaches and/or wire bonding processes. 
         [0105]    The metallized substrate is a Printed Circuit Board (PCB) or a metallized ceramic substrate. In some embodiments, the materials are polyimide and FR4 for PCBs, and Al 2 O 3 , AlN or Si 3 N 4  for metallized ceramic substrates (known as DBC, DBA, AMB or 
         [0106]    HTCC ceramic substrates). 
         [0107]    In some embodiments, the dies  20  are attached to each other and to the conductor  22  by a die attach material  23 , which may be a conductive or non-conductive bonding material. In the nonconductive embodiment, the die may not be conductive and stacked dies for some hybrid assembly configurations may be connected by wire bonds (e.g. if capacitor die/chip is mounted on another which is larger, or the opposite way around. 
         [0108]    A wire bond  24  is provided which is a micro-wire that enables the electrical connection between the top of the stack and the conductor  22 . Materials for the wire bond may include Au, AuSi, AuPd, Al, Cu and/or the like. 
         [0109]    An outer encapsulation or passivation  25  may surround the stack and may comprise an insulating material to protect the assembly. The encapsulation or passivation  25  may comprise silicones, other polymers and/or epoxies. For some hermetic packaged systems, encapsulation may not be required. 
       EXAMPLE 2 
       [0110]    In this example, the stacked dies are implemented using silicon vias  26  on the edges or extremities of the dies  20 ′ as shown in  FIG. 6  which shows the geometry and electrode design of a single die  20 ′. 
         [0111]      FIG. 7  shows a plurality of stacked dies  20 ′ as shown in  FIG. 5  stacked on a metalized substrate  21 . The reference numerals used in these figures correspond to the same features as set out in respect of Example 1 above, and the stacked die shown in  FIG. 7  will not be described further here. 
         [0112]    Material Properties 
         [0113]    The following material properties are expected from diamond active layers: 
         [0000]    
       
         
               
               
               
               
               
               
               
             
           
               
                   
               
               
                   
                   
                 Dielectric 
                 Breakdown 
                   
                   
                   
               
               
                   
                   
                 constant 
                 electric 
                   
                 Bandgap 
                 Thermal 
               
               
                   
                   
                 ε r  (no 
                 fields 
                 Resistivity 
                 energy 
                 conductivity 
               
               
                 Material 
                 Function 
                 unit) 
                 (kV/mm) 
                 ρ (Ω · m) 
                 (eV) 
                 (W · m −1  · K −1 ) 
               
               
                   
               
             
             
               
                 Diamond 
                 Insulator 
                 5.7-11 
                 1000-2000 
                 10 10 -10 12   
                 5.6 
                 2000 
               
               
                 Diamond 
                 Conductor 
                 ? 
                 N/A 
                 ? 
                 N/A 
                 2000 
               
               
                 P-doped 
               
               
                   
               
             
          
         
       
     
         [0114]    Calculations of the properties of capacitors according to embodiments of the present invention are now set out. These calculations are based on specific capacitor die configurations and are provided by way of example only to demonstrate the potential electrical properties of capacitor cells and capacitors according to embodiments of the invention. 
         [0115]    Symbols: 
         [0116]    Ec_SiO2 SiO 2  Critical electric field (V/m) 
         [0117]    Ec_cd Diamond Critical electric field (V/m) 
         [0118]    εc_SiO2 SiO 2  relative permittivity 
         [0119]    εc_cd Diamond relative permittivity 
         [0120]    ε0 vaccum permittivity 
         [0121]    r_ext Cavity width or diameter with dielectric layer(m) 
         [0122]    r_int Cavity width or diameter with no dielectric layer (m) 
         [0123]    L_motif Clearance between two cavities (m) 
         [0124]    L_drie Cavity depth (m) 
         [0125]    Vbr_sio2 Voltage breakdown of SiO 2  dielectric layer (V) 
         [0126]    Vbr_cd Voltage breakdown of diamond dielectric layer (V) 
         [0127]    W_sio2 Stored energy per volume unit in SiO 2  dielectric layer (J/m 3 ) 
         [0128]    W_cd Stored energy per volume unit in diamond dielectric layer (J/m 3 ) 
         [0129]    CO_sio2 Capacitance per surface unit (F/mm 2 ) 
         [0130]    CO_cd Capacitance per surface unit (F/mm 2 ) 
         [0131]    Technology performance estimates for capacitor cells in accordance with embodiments of the present invention: 
         [0132]    Dielectric Material Properties: 
         [0133]    Ec_sio2:=2.5.10 8  εr_sio2:=4.1 Ec SiO2 theorical=6-10 MV/cm 
         [0134]    Ec_cd:=10-10 8  εr_cd:=5.68 Ec diamond theorical=10-20 MV/cm ε0:=8.854210 −12    
         [0135]    Geometry: 
         [0000]    
       
         
           
             
               
                 
                   r_ext 
                   := 
                   
                     0.5 
                     · 
                     
                       10 
                       
                         - 
                         6 
                       
                     
                   
                 
               
               
                 
                   L_motif 
                   := 
                   
                     2 
                     · 
                     
                       10 
                       
                         - 
                         6 
                       
                     
                   
                 
               
               
                 
                   N_motif 
                   := 
                   
                     
                       
                         ( 
                         
                           
                             10 
                             
                               - 
                               3 
                             
                           
                           L_motif 
                         
                         ) 
                       
                       2 
                     
                     = 
                     
                       
                         
                           
                             2.5 
                             × 
                           
                         
                       
                       
                         
                           
                             10 
                             5 
                           
                         
                       
                     
                   
                 
               
             
             
               
                 
                   r_int 
                   := 
                   
                     0.35 
                     · 
                     
                       10 
                       
                         - 
                         6 
                       
                     
                   
                 
               
               
                 
                   L_drie 
                   := 
                   
                     100 
                     · 
                     
                       10 
                       
                         - 
                         6 
                       
                     
                   
                 
               
               
                 
                     
                 
               
             
           
         
       
     
         [0136]    Electrical Parameters: 
         [0000]    
       
         
           
             Vbr_sio2 
             := 
             
               
                 Ec_sio2 
                 · 
                 
                   ( 
                   
                     r_ext 
                     - 
                     r_int 
                   
                   ) 
                 
               
               = 
               37.5 
             
           
         
       
       
         
           
             Vbr_cd 
             := 
             
               
                 Ec_cd 
                 · 
                 
                   ( 
                   
                     r_ext 
                     - 
                     r_int 
                   
                   ) 
                 
               
               = 
               150 
             
           
         
       
       
         
           
             W_sio2 
             := 
             
               
                 
                   1 
                   2 
                 
                 · 
                 ɛ0 
                 · 
                 ɛr_sio2 
                 · 
                 
                   Ec_sio2 
                   2 
                 
                 · 
                 
                   10 
                   
                     - 
                     6 
                   
                 
               
               = 
               
                 1.134 
                  
                 
                     
                 
                  
                 J 
                  
                 
                   / 
                 
                  
                 cm 
                  
                 
                     
                 
                  
                 3 
               
             
           
         
       
       
         
           
             W_cd 
             := 
             
               
                 
                   1 
                   2 
                 
                 · 
                 ɛ0 
                 · 
                 ɛr_cd 
                 · 
                 
                   Ec_cd 
                   2 
                 
                 · 
                 
                   10 
                   
                     - 
                     6 
                   
                 
               
               = 
               
                 
                   25.146 
                    
                   
                       
                   
                    
                   J 
                    
                   
                     / 
                   
                    
                   cm 
                    
                   
                       
                   
                    
                   3 
                    
                   
                     
 
                   
                    
                   C0_sio2 
                 
                 := 
                 
                   
                     
                       
                         [ 
                         
                           
                             
                               ɛ0 
                               · 
                               ɛr_sio2 
                               · 
                               2 
                               · 
                               π 
                               · 
                               L_drie 
                             
                             
                               ln 
                                
                               
                                 ( 
                                 
                                   r_ext 
                                   r_int 
                                 
                                 ) 
                               
                             
                           
                           + 
                           
                             
                               ɛ0 
                               · 
                               ɛr_sio2 
                               · 
                               
                                 ( 
                                 
                                   
                                     L_motif 
                                     2 
                                   
                                   - 
                                   
                                     π 
                                     · 
                                     
                                       r_ext 
                                       2 
                                     
                                   
                                 
                                 ) 
                               
                             
                             
                               r_ext 
                               - 
                               r_int 
                             
                           
                         
                         ] 
                       
                       · 
                       N_motif 
                     
                      
                     
                       
 
                     
                      
                     C0_sio2 
                   
                   = 
                   
                     
                       1.618 
                       × 
                       
                         10 
                         
                           - 
                           8 
                         
                       
                        
                       
                         
 
                       
                        
                       C0_cd 
                     
                     := 
                     
                         
                       
                         
                           
                             
                               [ 
                               
                                 
                                   
                                     ɛ0 
                                     · 
                                     ɛr_cd 
                                     · 
                                     2 
                                     · 
                                     π 
                                     · 
                                     L_drie 
                                   
                                   
                                     ln 
                                      
                                     
                                       ( 
                                       
                                         r_ext 
                                         r_int 
                                       
                                       ) 
                                     
                                   
                                 
                                 + 
                                 
                                   
                                     ɛ0 
                                     · 
                                     ɛr_cd 
                                     · 
                                     
                                       ( 
                                       
                                         
                                           L_motif 
                                           2 
                                         
                                         - 
                                         
                                           π 
                                           · 
                                           
                                             r_ext 
                                             2 
                                           
                                         
                                       
                                       ) 
                                     
                                   
                                   
                                     r_ext 
                                     - 
                                     r_int 
                                   
                                 
                               
                               ] 
                             
                             · 
                             N_motif 
                           
                            
                           
                             
 
                           
                            
                           C 
                            
                           
                               
                           
                            
                           0 
                            
                           _cd 
                         
                         = 
                         
                           2.242 
                           × 
                           
                             10 
                             
                               - 
                               8 
                             
                           
                         
                       
                     
                   
                 
               
             
           
         
       
     
         [0137]    Capacitance (F) and Estimated Ratings for Typical SMC Footprints: 
         [0000]    
       
         
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Cap. Ratings: 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 0603 capacitor: 
                 C0603_cd := 
                 0603-27 nF-100 V 
               
               
                 1.6 × 0.8 
                 C0_cd · 1.6 · 0.8 = 2.87 × 10 −8   
               
               
                 0805 capacitor: 
                 C0805_cd := 
                 0805-56 nF-100 V 
               
               
                 2.0 × 1.25 
                 C0_cd · 2 · 1.25 = 5.604 × 10 −8   
               
               
                 1210 capacitor: 
                 C1210_cd := 
                 1210-180 nF-100 V 
               
               
                 3.2 × 2.5 
                 C0_cd · 3.2 · 2.5 = 1.793 × 10 −7   
               
               
                 1812 capacitor: 
                 C1812_cd := 
                 1812-330 nF-100 V 
               
               
                 4.5 × 3.2 
                 C0_cd · 4.5 · 3.2 = 3.228 × 10 −7   
               
               
                   
               
             
          
         
       
     
         [0138]    Comparison: SMT Tantalum cap. 1210, rated 50V ranges from 100 nF to 1 μF 
         [0139]    In some embodiments, the capacitor cell/die may comprise more than one elementary component. In other embodiments, the capacitor cell/die may comprise one or more resistors where doping concentration may be used to change the diamond resistivity or top layer metallization. 
         [0140]    Equivalent Electrical Circuit 
         [0141]    In some embodiments, a passive network may comprise several independent capacitors and resistors may be integrated on the same die/chip. Passive networks may comprise stacked dies/chips. In some embodiments, resistors may be made from the top electrode metallization mask design. 
         [0142]    Examples of embodiments of the present invention comprising multiple components are provided in  FIGS. 8A, 8B, 9A, 9B and 10 . 
         [0143]      FIGS. 8A and 8B  illustrate decoupling capacitors, in accordance with embodiments of the present invention, and pull-up/pull-down resistors within the same die/chip. 
         [0144]      FIGS. 9A and 9B  illustrate capacitors, in accordance with embodiments of the present invention, incorporated in resistor-capacitor (RC) filters. 
         [0145]      FIG. 10  illustrates capacitors, in accordance with embodiments of the present invention, integrated in a circuit as by-pass capacitors/analog capacitors. 
         [0146]    While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the scope of the invention.