Abstract:
A method for making an anisotropic dielectric layer includes the steps of: forming a fluid layer comprising a plurality of magnetizable particles, for example, in a fluid capable of solidifying to fix the configuration of the magnetizable particles in a dielectric matrix; aligning the magnetizable particles of the fluid layer in a predetermined configuration by applying a magnetic field thereto; and fixing the aligned magnetizable particles in the predetermined configuration within the dielectric matrix by solidifying the fluid. In one particularly advantageous application, the fluid layer is coated onto a surface portion of an integrated circuit, such as a fingerprint sensor, to provide mechanical protection without effecting the image resolution. In addition, the step of aligning for certain devices preferably comprises aligning the magnetizable particles in a predetermined configuration so that an impedance perpendicular to the anisotropic dielectric layer is less than an impedance parallel to the anisotropic dielectric layer. The magnetizable particles may be mixed in a curable polymer fluid, and the step of fixing the aligned magnetizable particles may comprise curing the curable polymer fluid, such as by applying heat or radiation.

Description:
RELATED APPLICATION 
     The present application is a continuation-in-part patent application of U.S. patent application Ser. No. 08/858,005 filed May 16, 1997, and the entire disclosure of which is incorporated herein in its entirety by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of materials, and, more particularly, to the field of semiconductor materials having certain dielectric properties. 
     BACKGROUND OF THE INVENTION 
     Semiconductor devices are widely used in many applications. For example, an early version of an integrated circuit fingerprint sensor produced by Harris Corporation was based upon sensing an electric field between the sensor and the ridges and valleys of a fingerprint of a user. Such a sensor may be extremely accurate in generating an image of the ridges and valleys of the fingerprint. 
     The fingerprint sensor relied on direct contact between the finger of the user and the integrated circuit. Such direct contact can lead to several difficulties with regards to the long term reliability of the sensor. For example, sodium ions from perspiration may migrate through the relatively thin outer passivation layer or layers and adversely affect the semiconductor material of the sensor. Solvents for cleaning the sensing surface may also damage the integrated circuit. 
     Typical passivation layers for integrated circuit technologies are relatively thin, since the IC is usually protected by an overall body of molded encapsulating material. The encapsulating material provides both mechanical protection, as well as protection from contamination of the semiconductor material. Unfortunately, in an application such as the electric field fingerprint sensor, the IC die itself must be exposed to direct contact. Moreover, simply increasing the thickness of passivation or protective coatings may reduce the quality of the fingerprint image. This is so because the electric fields of the individual pixel elements of the sensor tend to curve or defocus as the spacing between the elements and the finger is increased. 
     U.S. Pat. No. 4,353,056 to Tsikos discloses an early approach to sensing a live fingerprint. In particular, the patent discloses an array of extremely small capacitors located in a plane parallel to the sensing surface of the device. When a finger touches the sensing surface and deforms the surface, a voltage distribution in a series connection of the capacitors may change. Unfortunately, the resilient materials required for the sensor may suffer from long term reliability problems. Moreover, noise and stray capacitances may adversely affect the plurality of relatively small and closely spaced capacitors. 
     U.S. Pat. No. 5,325,442 to Knapp discloses another fingerprint sensor and which includes a plurality of sensing electrodes. A capacitor is effectively formed by each sensing electrode in combination with the respective overlying portion of the finger surface which, in turn, is at ground potential. The sensor may be fabricated using semiconductor wafer and integrated circuit technology. The dielectric material upon which the finger is placed may be provided by silicon nitride or a polyimide which may be provided as a continuous layer over an array of sensing electrodes. 
     Unfortunately, such conventional semiconductor related materials and their relative thinness may not be sufficient for direct contact by the finger of a user. Moreover, increasing the thickness of any coating layer may adversely affect the image accuracy or resolution. Accordingly, at present the designer needs to sacrifice robustness of the IC fingerprint sensor to obtain sufficient accuracy in the image produced. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing background, it is therefore an object of the present invention to provide a method for making a dielectric layer, such as for integrated circuits, that is relatively thick, yet which has reduced defocusing of an electric field passing therethrough. 
     It is another object of the present invention to provide integrated circuits and layers having a dielectric layer with certain desirable dielectric properties. 
     These and other objects, features, and advantages in accordance with the present invention are provided by a method for making an anisotropic dielectric layer comprising the steps of: forming a fluid layer comprising a plurality of magnetizable particles in a fluid capable of solidifying to fix the configuration of the magnetizable particles in a dielectric matrix; aligning the magnetizable particles of the fluid layer in a predetermined configuration by applying a magnetic field thereto; and fixing the aligned magnetizable particles in the predetermined configuration within the dielectric matrix by solidifying the fluid to thereby make the anisotropic dielectric layer. In one particularly advantageous application, the fluid layer is coated onto a surface portion of an integrated circuit, such as a fingerprint sensor, to provide mechanical protection without effecting the image quality or resolution. In addition, the step of aligning for certain devices preferably comprises aligning the magnetizable particles in a predetermined configuration so that an impedance in a direction perpendicular to the anisotropic dielectric layer is less than an impedance in a direction parallel to the anisotropic dielectric layer. 
     The magnetizable particles may be mixed in a curable polymer fluid, and the step of fixing the aligned magnetizable particles may comprise curing the curable polymer fluid, such as by applying heat or radiation. The magnetizable particles may be generally spherical having diameters in a range of about 1 to 3 microns. The magnetizable particles may also be generally elongate. 
     The method may also include the step of controlling a viscosity of the fluid by incorporating dielectric particles in the fluid. For example, the size and/or concentration of the dielectric particles may be controlled in the curable polymer fluid. The dielectric particles may also reduce lateral coupling of the magnetizable particles. 
     The step of aligning the magnetizable particles preferably comprises applying a substantially uniform magnetic field to the fluid layer, such as achieved by positioning a pair of opposing magnets adjacent opposite sides of the fluid layer and extending laterally outwardly beyond edges thereof. 
     An integrated circuit including the anisotropic layer preferably also comprises a substrate, and a semiconductor layer adjacent the substrate. The anisotropic dielectric layer is preferably adjacent the semiconductor layer, and the anisotropic dielectric layer preferably comprises a dielectric matrix and a plurality of aligned magnetizable particles therein. The magnetizable particles may be aligned in a predetermined direction so that the anisotropic dielectric layer has an impedance in a direction perpendicular to a surface being less than an impedance in a parallel direction. In addition, the semiconductor layer may include means for passing an electric field through the anisotropic dielectric layer, such as for sensing applications. 
     Another aspect of the invention relates to the dielectric layer. The dielectric layer preferably comprises a plurality of aligned magnetizable particles fixed in a dielectric matrix, such as to provide an impedance in a first direction which is less than an impedance in a second direction transverse to the first direction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a fingerprint sensor including the anisotropic dielectric layer as an outer surface layer in accordance with the present invention. 
     FIG. 2 is an enlarged schematic cross-sectional view of a portion of the fingerprint sensor including an anisotropic dielectric layer as shown in FIG.  1 . 
     FIG. 3 is a greatly enlarged view of a plurality of electric field sensing elements or pixels used in the fingerprint sensor shown in FIG.  1 . 
     FIG. 4 is a schematic cross-sectional view of an apparatus for carrying out the method for making the anisotropic dielectric layer in accordance with the present invention. 
     FIG. 5 is a flow chart illustrating the method for making the anisotropic dielectric layer in accordance with the present invention. 
     FIG. 6 is a schematic cross-sectional view of the fingerprint sensor including the anisotropic dielectric layer in accordance with the present invention and illustrating the focusing effect of the anisotropic dielectric layer. 
     FIG. 7 is a greatly enlarged schematic cross-sectional view of a fluid layer including spherical magnetizable particles before alignment and curing in accordance with the method of the present invention. 
     FIG. 8 is a schematic cross-sectional view of the fluid layer of FIG. 7 after alignment of the magnetizable particles and curing of the fluid material in accordance with the method of the present invention. 
     FIG. 9 is a greatly enlarged schematic cross-sectional view of a fluid layer including elongate magnetizable particles before alignment and curing in accordance with a second embodiment of the method of the present invention. 
     FIG. 10 is a schematic cross-sectional view of the fluid layer of FIG. 9 after alignment of the elongate magnetizable particles and curing of the fluid material in accordance with the second embodiment of the method of the present invention. 
     FIG. 11 is a schematic view, partially in section, of another application of the anisotropic dielectric layer in accordance with the present invention for facilitating capacitive coupling through the layer. 
     FIG. 12 is a photomicrograph of a cured fluid with the magnetizable particles in an unaligned condition. 
     FIG. 13 is a photomicrograph of the cured fluid with the magnetizable particles aligned at an angle to the viewing direction and at the same magnification as FIG.  12 . 
     FIG. 14 is a photomicrograph of the cured fluid and aligned magnetizable particles as shown in FIG. 13, but at a higher magnification. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout and prime notation is used to indicate similar elements in alternate embodiments. The scaling of various features, particularly layers in the drawing figures, have been exaggerated for clarity of explanation. 
     Referring to FIGS. 1-3, a fingerprint sensor  30  including the anisotropic dielectric layer  52  in accordance with the invention is initially described. The illustrated sensor  30  includes a housing or package  51 , the anisotropic dielectric layer  52  exposed on an upper surface of the package which provides a placement surface for the finger, and a plurality of output pins, not shown. A first conductive strip or external electrode  54  around the periphery of the dielectric layer  52 , and a second external electrode  53  provide contact electrodes for the finger  79  as described in greater detail below. The sensor  30  may provide output signals in a range of sophistication levels depending on the level of processing incorporated in the package as would be readily understood by those skilled in the art. 
     The sensor  30  includes a plurality of individual pixels or sensing elements  30   a  arranged in array pattern as perhaps best shown in FIG.  3 . As would be readily understood by those skilled in the art, these sensing elements are relatively small so as to be capable of sensing the ridges  59  and intervening valleys  60  of a typical fingerprint. As will also be readily appreciated by those skilled in the art, live fingerprint readings as from the electric field sensor  30  in accordance with the present invention may be more reliable than optical sensing, because the impedance of the skin of a finger in a pattern of ridges and valleys is extremely difficult to simulate. In contrast, an optical sensor may be deceived by a photograph or other similar image of a fingerprint, for example. 
     The sensor  30  includes a substrate  65 , and one or more active semiconductor devices formed thereon, such as the schematically illustrated amplifier  73 . A first metal layer  66  interconnects the active semiconductor devices. A second or ground plane electrode layer  68  is above the first metal layer  66  and separated therefrom by an insulating layer  67 . A third metal layer  71  is positioned over another dielectric layer  70 . In the illustrated embodiment, the first external electrode  54  is connected to an excitation drive amplifier  74  which, in turn, drives the finger  79  with a signal that may be typically in the range of about 1 KHz to 1 MHZ. Accordingly, the drive or excitation electronics are thus relatively uncomplicated and the overall cost of the sensor  30  may be relatively low, while the reliability is great. 
     An illustratively circularly shaped electric field sensing electrode  78  is on the insulating layer  70 . The sensing electrode  78  may be connected to sensing integrated electronics, such as the illustrated amplifier  73  formed adjacent the substrate  65  as schematically illustrated, and as would be readily appreciated by those skilled in the art. 
     An annularly shaped shield electrode  80  surrounds the sensing electrode  78  in spaced relation therefrom. As would be readily appreciated by those skilled in the art, the sensing electrode  78  and its surrounding shield electrode  80  may have other shapes, such as hexagonal, for example, to facilitate a close packed arrangement or array of pixels or sensing elements  30   a . The shield electrode  80  is an active shield which is driven by a portion of the output of the amplifier  73  to help focus the electric field energy and, moreover, to thereby reduce the need to drive adjacent electric field sensing electrodes  78 . 
     The sensor  30  illustratively includes only three metal or electrically conductive layers  66 ,  68  and  71 . The sensor  30  can be made without requiring additional metal layers which would otherwise increase the manufacturing cost, and, perhaps, reduce yields. Accordingly, the sensor  30  is less expensive and may be more rugged and reliable than a sensor including four or more metal layers as would be appreciated by those skilled in the art. 
     Another aspect of the present invention is that the amplifier  73  may be operated at a gain of greater than about one to drive the shield electrode  80 . Stability problems do not adversely affect the operation of the amplifier  73 . Moreover, the common mode and general noise rejection are greatly enhanced. In addition, the gain greater than one tends to focus the electric field with respect to the sensing electrode  78  as will be readily appreciated by those skilled in the art. 
     In general, the sensing elements  30   a  operate at very low currents and at very high impedances. For example, the output signal from each sensing electrode  78  is desirably about 5 to 10 millivolts to reduce the effects of noise and permit further processing of the signals. The approximate diameter of each sensing element  30   a , as defined by the outer dimensions of the shield electrode  80 , may be about 0.002 to 0.005 inches in diameter. The ground plane electrode  68  protects the active electronic devices from unwanted excitation. The various signal feedthrough conductors for the electrodes  78 ,  80  to the active electronic circuitry may be readily formed as would be understood by those skilled in the art. 
     The overall contact or sensing surface for the sensor  30  may desirably be about 0.5 by 0.5 inches—a size which may be readily manufactured and still provide a sufficiently large surface for accurate fingerprint sensing and identification. The sensor  30  in accordance with the invention is also fairly tolerant of dead pixels or sensing elements  30   a . A typical sensor  30  includes an array of about  256  by  256  pixels or sensor elements, although other array sizes are also contemplated by the present invention. The sensor  30  may also be fabricated at one time using primarily conventional semiconductor manufacturing techniques to thereby significantly reduce the manufacturing costs. 
     Turning additionally to FIGS. 4-8, the anisotropic dielectric layer or film  52  and the associated manufacturing techniques in accordance with the invention are now described. From the start at Block  90  of the flow chart  88 , magnetizable particles  93  are mixed in a hardenable or solidifiable fluid  91   a  (FIG. 7) at Block  92 . The magnetizable particles  93  may be iron or ferrous particles in one example, although those skilled in the art will appreciate that there are other material particles that may be similarly aligned by application of a magnetic field. 
     The viscosity of the fluid  91   a  may also be readily controlled by the addition or incorporation of dielectric particles  89  of predetermined sizes and/or at a predetermined concentration as will be readily appreciated by those skilled in the art. The dielectric particles  89  may also reduce undesired lateral coupling of the magnetizable particles  93  as will also be readily appreciated by those skilled in the art. 
     For the embodiment shown in FIGS. 7 and 8, the magnetizable particles  93  have a generally spherical shape and diameters in the range of about 1 to 3 μm. The hardenable fluid  91   a  may be a curable liquid, such as a polyimide, for example, or a thermoplastic or thermosetting material as will be appreciated by those skilled in the art. The solidifiable or hardenable fluid  91   a  may also be a mixture of such materials as will also be readily appreciated by those skilled in the art. 
     At Block  98  the solidifiable fluid  91   a  including the magnetizable particles  93  is applied to the upper surface portion  95  of an integrated circuit die, such as the fingerprint sensor  30 . More particularly, as shown in FIG. 4, an entire wafer  100  including a plurality of fingerprint sensing dies may be positioned in the chamber  102  of the apparatus  101 . The fluid  91   a  may be applied by conventional spin coating techniques, for example, although those of skill in the art will recognize other deposition techniques as well. 
     The apparatus  101  illustratively includes a pair of upper permanent magnets  105   a ,  105   b  and a pair of lower permanent magnets  106   a ,  106   b  to provide a sufficiently large magnetic field. The pairs of magnets are positioned in vertically spaced relation. The magnets desirably generate a substantially uniform magnetic field between them in the range of about 400 to 1000 Gauss. Of course, the strength of the magnetic field can be varied based upon spacings, materials, etc. as will be readily appreciated by those skilled in the art. In addition, as will also be appreciated by those skilled in the art, electromagnets could also be used in addition to or in lieu of the permanent magnets. The magnets  105   a ,  105   b ,  106   a  and  106   b  desirably extend past the edges of the wafer  100  so that the magnetic field will be uniform even at the edges. 
     Respective aluminum plates  107 ,  108  are positioned adjacent the upper magnet  105   a  and the lower magnet  106   a  as shown in the illustrated embodiment. A glass plate  111  is positioned on the lower aluminum plate  108 . The wafer  100  is positioned on top of the glass plate  111  in about the center of the chamber to thereby be exposed to a relatively uniform magnetic field as indicated by the dashed arrows. 
     The magnetic field aligns the magnetizable particles  93  along the magnetic field lines (Block  112 ) and as schematically illustrated in FIG. 7 (nonaligned) and FIG. 8 (after aligning). At Block  114  the fluid is cured to its final hardened state defining the solid matrix of material  91   b  as shown in FIG.  8 . As will be readily appreciated by those skilled in the art, the curing or hardening may be affected by applying heat or radiation (FIG.  8 ), such as ultraviolet or laser radiation, to any of a number of curable materials as would also be readily appreciated by those skilled in the art. Other suitable materials may be cured by application of an electric field, for example, as will also be appreciated by those skilled in the art. The solidifiable fluid  91   a  may also be a self-curing material, or one that cures upon evaporation of a solvent, although a heat-cured or radiation-cured material may be preferred for greater controllability. 
     The curable fluid  91   a  may have sufficient viscosity so that once the magnetizable particles  93  are aligned they remain in a stable position until the fluid cures and without constant application of the magnetic field. Of course, the viscosity can be controlled by the incorporation of dielectric particles  89  as explained above. In other words, for certain materials, the magnetic field may be applied, and the wafer  100  may then be removed from the chamber  102  for curing, and without effecting the alignment of the particles. Alternately, it may be desirable to cure the fluid  91   a  while the magnetic field is still applied as will be readily appreciated by those skilled in the art. Accordingly, the apparatus  101  may be fitted with a heater or radiation emitting device to effect curing in the same process while the wafer  100  is positioned in the chamber  102  and is exposed to the magnetic field. 
     Once the fluid is cured to yield the solidified matrix  91   b  (FIG.  8 ), the anisotropic dielectric layer is thus defined having a so-called z-axis anisotrophy wherein the electrical impedance in a direction perpendicular to the layer is less than an impedance parallel to the layer. By perpendicular to the layer is meant normal to the major surface of the layer as will be understood by those skilled in the art. Accordingly, for an embodiment where the curing occurs in the chamber  102 , at Block  116  the wafer  100  may be removed and subjected to further processing (Block  118 ), such as dicing into individual integrated circuits before stopping at Block  120 . 
     Referring briefly in particular to FIG. 6, a portion of the integrated circuit fingerprint sensor  30  is described with the outer layer being provided by the z-axis anisotropic dielectric layer  52 . In the illustrated embodiment, there is also a thin passivation layer  94  on the electrodes  78 ,  80  and underlying the anisotropic dielectric layer  52 . The thin passivation layer  94  may comprise a thin oxide, nitride, carbide, or diamond layer as will be appreciated by those skilled in the art. 
     As schematically illustrated by the electric field lines E, the electric field is more constrained or focused upon passing through the z-axis anisotropic dielectric layer  52 . In other words, if the layer were not an anisotropic layer, the electric field lines would diverge, and focus would be reduced. Accordingly, the resolution of the sensor  30  would suffer as will be appreciated by those skilled in the art. Typically there would be a trade-off between field focus and mechanical protection. Unfortunately, a thin film which is desirable for focusing, may permit the underlying circuit to be more easily subject to physical or chemical damage. The anisotropic dielectric layer  52  in accordance with the present invention overcomes this limitation as it provides both a relatively thick protective layer, and enhances electric focusing therethrough. 
     The anisotropic dielectric layer  52  of the present invention, for example, may have a thickness in range of about 0.0004 to 0.004 inches. Other thickness are also possible. Of course, the anisotropic dielectric layer  52  is also preferably chemically resistant and mechanically strong to withstand contact with fingers, and to permit periodic cleanings with solvents when used for the fingerprint sensor  30 . The anisotropic dielectric layer  52  may preferably define an outermost protective surface for the fingerprint sensor  30 . The anisotropic dielectric layer  52  may also be desirably softer than the passivation layer  94  to thereby absorb more mechanical activity. 
     Turning now to FIGS. 9 and 10, an alternate embodiment of magnetizable particles  98  is illustrated in the unaligned and uncured state (FIG.  9 ), and the aligned and cured state (FIG.  10 ). In this embodiment, the magnetizable particles  98  are elongate in shape, and align with the magnetic field so that their longitudinal axes align with the magnetic field lines as would be readily understood by those skilled in the art. In this illustrated embodiment, the dielectric particles are not shown, but could be readily used as will be appreciated by those skilled in the art. The other elements shown in FIGS. 9 and 10 are indicated with prime notation and are similar to those in FIGS. 7 and 8 described above. 
     Referring now to FIG. 11, another application of the anisotropic dielectric covering  52 ′ is explained. The anisotropic dielectric layer  52  may be used to completely cover and protect the entire upper surface of the integrated circuit die of the fingerprint sensor  30  and still permit connection and communication with the external devices and circuits. The third metal layer  71  (FIG. 2) may further include a plurality of capacitive coupling pads  116   a - 118   a  for permitting capacitive coupling of the integrated circuit die. Accordingly, the anisotropic dielectric covering  52  is preferably continuous over the capacitive coupling pads  116   a - 118   a  and the array of electric field sensing electrodes  78  of the pixels  30   a  (FIG.  1 ). In sharp contrast to this feature of the present invention, it is conventional to create openings through an outer coating to electrically connect to the bond pads. Unfortunately, these openings would provide pathways for water and/or other contaminants to come in contact with and damage the die. 
     A portion of the package  51  includes a printed circuit board  122  which carries corresponding pads  115   b - 118   b . A power modulation circuit  124  is coupled to pads  115   b - 116   b , while a signal modulation circuit  126  is illustratively coupled to pads  117   b - 118   b . As would be readily understood by those skilled in the art, both power and signals may be readily coupled between the printed circuit board  122  and the integrated circuit die further using the illustrated power demodulation/regulator circuit  127 , and the signal demodulation circuit  128 . The z-axis anisotropic dielectric layer  52  also advantageously reduces cross-talk between adjacent capacitive coupling pads. This embodiment of the fingerprint sensor  30  presents no penetrations through the dielectric layer  52  for moisture to enter and damage the integrated circuit die. In addition, another level of insulation is provided between the integrated circuit and the external environment. 
     In one example, a magnetic strength of about 700 Gauss on the top of the glass plates was applied to a mixture comprising 30 wt % iron powder roll milled with polyimide PI 2808. Non-magnetic and non-magnetizable substrates were used. After spin coating on the substrate, the films were placed in the apparatus  101  as described above. An infrared heat lamp gently dried the film while the specimen was exposed to the magnetic field. The heating was relatively slow, about 5 to 10 minutes with the infrared heat source at about 1 foot separation, so the surface was dried evenly. The specimen was allowed to cool before being removed from the magnetic field. The specimen was then cured as follows: heated at a rate of 3° C./min to 300° C., held at 300° C. for 60 minutes, and then allowed to cool naturally. 
     In other example, 15 wt % iron and 15 wt % aluminum oxide was used in a PI 2808 fluid. The paste coating was allowed to stand for a relatively long time period of about 5 hours to harden, so that the particles were not disturbed when being removed from between the magnets. The heat lamp was positioned at a minimum distance of about 20 cm and not applied for longer than 5 minutes. The results were that the unaligned mix seemed to be uniform and homogenous, at least as good as the roll prepared paste. The magnetically aligned coatings showed alignment of iron particles in columns. This alignment occurred both in mixes with or without dielectric particles, such as Al 2 O 3 , being added. It is believed that the dielectric particles are effective to control viscosity, while also reducing the lateral coupling of the magnetizable particles. The electrical anisotropy of the films was found to about 35:1. 
     A photomicrograph of a dielectric layer  135  including magnetizable particles in an random configuration, that is, in a cured matrix without being magnetically aligned, is shown in FIG.  12 . The surface of the film  135  illustrated particles that appear random in arrangement. In contrast, the photomicrographs of FIGS. 13 and 14 show the anisotropic dielectric layer  52  wherein the magnetizable particles have been magnetically aligned. The surface of the anisotropic dielectric layer  52  presents regular repeating grouped particles illustrating that the magnetic alignment and curing have been effective. 
     Other aspects, advantages, and features relating to sensing of fingerprints are disclosed in copending U.S. patent application Ser. No. 08/592,469 entitled “Electric Field Fingerprint Sensor and Related Methods”, and U.S. patent application Ser. No. 08/671,430 entitled “Integrated Circuit Device Having an Opening Exposing the Integrated Circuit Die and Related Methods”, both assigned to the assignee of the present invention, and the entire disclosures of which are incorporated herein by reference. Of course, the anisotropic dielectric layer and associated method of making same may be used in many other semiconductor, imaging, and/or image sensing devices. In addition, the direction of alignment of the magnetizable particles  93 ,  98  may be readily controlled to define other than z-axis anisotropy as will be readily appreciated by those skilled in the art. 
     Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.