• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
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    • 专利摘要:
    The invention relates to a fingerprint sensing device comprising: a sensing chip comprising an array of sensing elements being configured to be connected to readout circuitry for detecting a capacitive coupling between each of the sensing elements and a finger placed on a sensing surface of the sensing device, wherein a surface of the sensing elements define a sensing plane; a plurality of interposer structures arranged on the sensing chip extending above sensing plane, wherein the plurality of interposer structures have substantially the same height above the sensing plane; and a protective plate attached to the sensing chip by means of an adhesive arranged on the sensing chip, wherein the protective plate rests on the interposer structures such that a distance between the protective plate and the sensing plane is defined by the height of the interposer structures.Publication fig: Fig 2B
    公开号:SE1551288A1
    申请号:SE1551288
    申请日:2015-10-07
    公开日:2016-12-09
    发明作者:Lundahl Karl
    申请人:Fingerprint Cards Ab；
    IPC主号:
    专利说明:

    FINGERPRINT SENSING DEVICE WITH INTERPOSER STRUCTURE Field of the lnvention The present invention relates to a fingerprint sensing device. lnparticular, the present invention is related to a fingerprint sensing devicecomprising an interposer structure for enhancing the performance in thesensing device, and to a method for manufacturing a fingerprint sensor comprising such an interposer structure.
    Backqround of the lnvention As the development of biometric devices for identity verification, and inparticular of fingerprint sensing devices, has lead to devices which are madesmaller, cheaper and more energy efficient, the possible applications for suchdevices are increasing. ln particular fingerprint sensing has been adopted more and more in,for example, consumer electronic devices, due to small form factor, relativelybeneficial cost/performance factor and high user acceptance.
    Capacitive fingerprint sensing devices, built based on CMOStechnology for providing the fingerprint sensing elements and auxiliary logiccircuitry, are increasingly popular as such sensing devices can be made bothsmall and energy efficient while being able to identify a fingerprint with highaccuracy. Thereby, capacitive fingerprint sensors are advantageously used forconsumer electronics, such as portable computers, tablet computers andmobile phones, e.g. smartphones.
    Afingerprint sensing chip typically comprises an array of capacitivesensing elements providing a measure indicative of the capacitance betweenseveral sensing structures and a finger placed on the surface of thefingerprint sensor. The sensing chip may further comprise logic circuitry forhandling addressing of the array of sensing elements.
    Atypical fingerprint sensor is protected so that the finger does notcome in physical contact with the sensing elements. ln particular, it may bedesirable to arrange a glass plate on top of the sensor for protecting the sensor, or to arrange the sensor behind a display glass. By arrangingelements between the sensing surface and the sensing elements, thedistance between the sensing surface and the sensing elements increaseswhich reduces the capacitive coupling between a finger placed on a sensingsurface of the device and the capacitive sensing elements.
    With increased distance and reduced capacitive coupling, anincreasing sensitivity is required of the sensing elements, i.e. the sensingelements must be able to measure a lower capacitance. With the sensingelements being pushed to the limit with regard to the minimum measurablecapacitance, it is increasingly important to ensure that the fingerprint sensormeasures uniformly over the entire sensing area of the sensor. ln view of the above, it is desirable to improve the performance of afingerprint sensor having a low capacitive coupling between a finger placedon the sensing surface and the sensing elements.
    Many attempts are made at improving the capacitive coupling, forexample, US2013/0201153 discloses a fingerprint sensing device whereelectrically conductive strands are arranged between the sensing surface andthe sensing elements of a fingerprint sensing device. An insulating material isarranged between conductive strands. However, a direct electrical contactbetween the finger and the pixel may cause problems related to electrostaticdischarge (ESD). Moreover, the metallic portions of the surface may oxidize,resulting in undesirable aesthetic effects.
    Summaryln view of above-mentioned desirable properties of a fingerprint sensing device, and drawbacks of prior art, it is an object of the presentinvention to provide a fingerprint sensing device and a method formanufacturing a fingerprint sensing device which improves capacitivemeasurements for capacitances near the limit of what is measureable.According to a first aspect of the invention, there is provided a fingerprint sensing device comprising: a sensing chip comprising an array ofsensing elements, the sensing elements being configured to be connected to readout circuitry for detecting a capacitive coupling between each of thesensing elements and a finger placed on a sensing surface of the sensingdevice, wherein a surface of the sensing elements define a sensing plane; aplurality of interposer structures arranged on the sensing chip extendingabove sensing plane, wherein the plurality of interposer structures havesubstantially the same height above the sensing plane; and a protective plateattached to the sensing chip by means of an adhesive arranged on thesensing chip, wherein the protective plate rests on the interposer structuressuch that a distance between the protective plate and the sensing plane isdefined by the height of the interposer structures.
    The sensing chip should in the present context be understood as achip comprising a plurality of sensing elements in the form of conductiveplates or pads, typically arranged in an array, which are capable of forming acapacitive coupling between each sensing element and a finger placed on anexterior surface of the fingerprint sensing device. Through readout of thecapacitive coupling for each sensing element, ridges and valleys of afingerprint can be detected as a result of the distance dependence of thecapacitive coupling. To achieve a fingerprint image with sufficient resolution,the sensing elements are typically substantially smaller than the features(ridges and valleys) of the finger. ln general, a chip may also be referred to asa die.
    The protective plate typically comprises a dielectric material in order toprovide a good capacitive coupling between a finger placed on the plate andthe sensing elements of the sensing chip. ln particular, the protective platemay advantageously comprise a glass or ceramic material, such as achemically strengthened glass, ZrOg or sapphire. The aforementionedmaterials all provide advantageous properties in that they are hard andthereby resistant to wear and tear, and in that they are dielectric therebyproviding a good capacitive coupling between a finger placed on the surfaceof the protective plate and the sensing element of the sensing device. Theprotective plate described herein commonly forms the outer surface of thefingerprint sensing device, hereinafter referred to as the sensing surface.
    The sensing chip according to various embodiments of the inventionmay subsequently be arranged on a conventional rigid PCB substrate or itmay be implemented using a flexible type of substrate comprising readoutcircuitry to form the fingerprint sensing device.
    The present invention is based on the realization that a morehomogeneous distance distribution between the sensing surface and thesensing p|ane can improve the performance of a fingerprint sensing device. lnparticular, when a protective plate is used and the distance between thesensing surface and the sensing p|ane is increasing to the degree that thedifference in capacitance between a fingerprint ridge and a valley is barelydiscernable by the sensing chip, it is increasingly important that the capacitivecoupling is as homogeneous as possible over the entire surface of thesensing device.
    Moreover, since a wafer coating material is sometimes provided on thesensing chip to protect and cover the sensing elements, it has been realizedthat the wafer coating material, if formed with a high degree of accuracy, canbe used as an interposer structure defining the distance between the sensingp|ane and the sensing surface. The thickness of the protective plate can becontrolled to a high degree of accuracy, whereas the adhesive attaching theprotective plate to the sensing chip typically is more difficult to deposit evenly,thereby exhibiting a more uneven surface. Thus, the distance between thesensing surface and the sensing p|ane has previously been defined, at leastin part, by the adhesive attaching the protective plate, which may lead tosome inhomogeneity in the distance and in subsequent readout of afingerprint image.
    According to embodiments of the present invention, interposerstructures exhibiting high thickness uniformity are provided on the sensingelements such that they have substantially the same height above thesensing p|ane. Accordingly, with the protective plate attached to the sensingchip by means of an adhesive, while resting on the interposer structures, thedistance between a finger placed on the protective plate and the sensingelements can be controlled with a high degree of accuracy. ln such a situation, optimal settings can be applied across the whole sensing areathereby facilitating acquisition of a fingerprint image with high quality.Furthermore, the interposer structures are preferably arranged and configuredto provide sufficient mechanical support for the protective plate to avoidmovement or flexing of the protective plate when the fingerprint sensor is inuse.
    The interposer structures can in principle be made from any commonlyused wafer coating material, which may refer to any material which isarranged to cover the sensing chip and in particular the sensing elements.
    According to one embodiment of the invention, a variation in heightbetween the plurality of interposer structures may advantageously be lessthan 1 um.
    According to one embodiment of the invention, the plurality ofinterposer structures may comprise parallel lines, which would provide anassembly of interposer structures which is simple to manufacture and whichcould provide sufficient mechanical support for the protective plate. Thespecific configuration of lines, such as the length, width, pitch and orientationcan be selected based on the specific configuration of the fingerprint sensor.For example the parallel lines may be aligned with an edge of the sensingchip and have a length substantially similar to the side of the sensing chip,thereby providing interposer structures which define the distance between thesensing plane and the sensing surface over the full area of the sensing chip,including at the edges of the sensing chip to avoid that any edge effectsoccur Alternatively, according to one embodiment of the invention, theplurality of interposer structures may comprise one interposer structurecentered on each of said sensing elements. Thereby, it can be ensured thatthe distance from each individual sensing element to the sensing surface iswell defined and homogeneous over the full area of the sensing chip. ltshould be noted that many different configurations of interposer structures arepossible, while still providing the advantageous effects described above. ln one embodiment of the invention, in the case where one interposerstructure is located on each of said sensing elements, the interposerstructures may be formed in a material having a dielectric constant higherthan a dielectric constant of the adhesive. An improved capacitive couplingbetween a finger and a sensing element can be achieved by providing aninterposer structure having a dielectric constant which is higher than thesurrounding adhesive. Thereby, the electric field between a finger placed onthe sensing surface and the sensing element can b focused towards therespective sensing elements by means of the difference in dielectric constant.Accordingly, a further improved fingerprint sensing device can be provided.
    According to one embodiment of the invention, the plurality ofinterposer structures may be arranged in alignment with boundaries betweenthe sensing elements, such that a central portion of each sensing element isnot covered by an interposer structure. For the above configuration ofinterposer elements, where at least a central portion of the sensing element isnot covered by the interposer structure, the interposer structures may beformed in a material having a dielectric constant lower than a dielectricconstant of the adhesive in order to achieve the above described effect ofimproved capacitive coupling between the sensing element and a finger. Theadhesive will then fill the space between interposer structures such that aninhomogeneous layer is formed with respect to the dielectric constant of thematerials, and where the higher dielectric constant of the adhesive providesthe improved capacitive coupling.
    According to one embodiment of the invention, the interposerstructures may be arranged on the sensing chip at locations outside of asensing area of the sensing chip, the sensing area being defined by the arrayof sensing elements. Thus, the interposer can be arranged to form a framepartially surrounding the array of sensing elements. The adhesive can then bearranged primarily within the frame formed by the interposer elements According to one embodiment of the invention, the plurality ofinterposer structures may comprise a photoresist. By using a photoresist, theinterposer structures can be formed using conventional photolithography and development processes, which simplifies the overall process flow. Moreover,a photoresist can easily be tailored to have a specific dielectric constant sothat a desired ratio of dielectric constants can be achieved.
    According to one embodiment of the invention, the sensing device mayfurther comprise a bond wire arranged between a bond pad on the sensingchip and a substrate on which the sensing chip is arranged, wherein a bondloop height of the bond wire is lower than the interposer structure. lt may alsobe possible to have a bond wire loop height which is slightly higher than theheight of the interposer structure, in which case the protective plate may pushdown on the bond wire when the protective plate is attached to the sensingchip. ln one embodiment of the invention, the sensing device may furthercomprise a via connection through said sensing chip to electrically connectthe sensing chip to a substrate. A via connection, commonly referred to as athrough-silicon via (TSV) connection, can be used to electrically connect thesensing chip to readout circuitry on a substrate without using wire bonding.TSV connection is for example used when wire bonding is undesirable orunpractical, such as when the desired height of the interposer structures islower than a height of the wire bond. This situation could for example occurwhen the sensor shall be utilized with a very thick protective plate such ase.g. a cover glass in a mobile phone.
    According to a second aspect of the invention, there is provided amethod for manufacturing a fingerprint sensing device, the methodcomprising; providing a sensing chip comprising an array of sensingelements, the sensing elements being configured to be connected to readoutcircuitry for detecting a capacitive coupling between each of the sensingelements and a finger placed on a sensing surface of the sensing device,wherein a surface of the sensing elements define a sensing plane; forming aninterposer layer on the sensing chip; forming a plurality of interposerstructures from the interposer layer, wherein the plurality of interposerstructures have substantially the same height above the sensing plane;providing a liquid adhesive on the sensing chip; and arranging a protective plate on the sensing chip such that the adhesive is filling out spaces betweenthe plurality of interposer structures, and such that the protective plate restson the interposer structures.
    Through the above describe manufacturing method, a fingerprintsensing device can be manufactured which exhibits the advantagesdescribed above in connection with the first aspect of the invention.
    That the adhesive is liquid should be interpreted to mean that it has afluidity which is sufficiently high to allow redistribution of the adhesive whenthe protective plate is arranged on the sensing chip. The protective plate ispressed down onto the sensing chip until it rests on the interposer structures,thereby defining the distance between the sensing elements and the sensingsurface. Through the redistribution of the adhesive it can be assured thatvoids between interposer structures are filled and that superfluous adhesive ispushed out to the sides of the sensing chip.
    According to one embodiment of the invention, the interposer layermay be deposited by spin coating or by spray coating which are methods thatallow a high degree of accuracy and thickness uniformity when depositing theinterposer layer. Moreover, spin and spray coating represent establishedmethods which are compatible with conventional CMOS processingtechnologies, thereby providing a controllable manufacturing process which iseasily integrated in existing manufacturing processes. ln one embodiment of the invention, providing the adhesive maycomprise dispensing a liquid adhesive on and in between said interposerstructures. A liquid adhesive can easily be dispensed onto the sensing chip,over and in between the interposer structures. The uniformity whendispensing the adhesive is not crucial sine the adhesive will be redistributedwhen the protective plate is pressed down onto the adhesive.
    According to one embodiment of the invention, the interposer layermay advantageously comprise a photoresist, and the plurality of interposerstructures can thus be formed using photolithography, which is a wellestablished manufacturing technique that can be performed with high accuracy, uniformity and repeatability.
    According to one embodiment of the invention, the method maycomprise the steps of depositing a hard mask on the interposer layer,patterning the hard mask, patterning the interposer layer according to thehard mask pattern, and removing the hard mask. Thereby, an alternativemanufacturing technique is provided. The hard mask can for example bemade from SiN and conventional photolithography may be used to form apattern in the hard mask which is subsequently transferred to the interposerlayer According to a third aspect of the invention, there is provided a methodfor manufacturing a fingerprint sensing device, comprising: providing asemiconductor wafer, on the semiconductor wafer forming a plurality offingerprint sensing chips, each sensing chip comprising an array of sensingelements, the sensing elements being configured to be connected to readoutcircuitry for detecting a capacitive coupling between each of the sensingelements and a finger placed on a sensing surface of the sensing device,wherein a surface of the sensing elements define a sensing plane; forming aninterposer layer on the semiconductor wafer, the interposer layer covering theplurality of fingerprint sensing chip sub-areas; forming a plurality of interposerstructures from the interposer layer, wherein the plurality of interposerstructures have substantially the same height above the sensing plane; dicingthe semiconductorwafer into a plurality of individual sensing chips; arranginga sensing chip on a substrate comprising readout circuitry; electricallyconnecting the sensing elements of the sensing chip to the readout circuitry;providing a liquid adhesive on the sensing chip; and arranging a protectiveplate on the sensing chip such that the adhesive is filling out spaces betweenthe plurality of interposer structures, and such that the protective plate restson the interposer structures.
    An advantage of the above described method is that an interposerlayer can be deposited on a full wafer with a high uniformity using establisheddeposition techniques such as spin coating, thereby providing a moreeffective manufacturing method where a large number of sensing chips canbe prepared simultaneously. Moreover, using spin coating or spray coating also allows the process to be easily modified with respect to the desiredthickness of the interposer layer.
    Further features of, and advantages with, the present invention willbecome apparent when studying the appended claims and the followingdescription. The skilled person realize that different features of the presentinvention may be combined to create embodiments other than thosedescribed in the following, without departing from the scope of the present invenüon.
    Brief Description of the Drawinqs These and other aspects of the present invention will now be describedin more detail, with reference to the appended drawings showing an exampleembodiment of the invention, wherein: Fig. 1 schematically illustrates a handheld electronic device comprisinga fingerprint sensing device according to an embodiment of the invention; Figs. 2A-B schematically illustrate a fingerprint sensing deviceaccording to an embodiment of the invention; Figs. 3A-B schematically illustrate a fingerprint sensing deviceaccording to an embodiment of the invention; Figs. 4A-B schematically illustrates fingerprint sensing devicesaccording to embodiments of the invention; Fig. 5 is a flow chart outlining the general steps of a method formanufacturing a fingerprint sensing device according to an embodiment of theinvenüon; Figs. 6A-G schematically illustrate a method for manufacturing afingerprint sensing device according to an embodiment of the invention; and Fig. 7 schematically illustrates a fingerprint sensing device according to an embodiment of the invention.
    Detailed Description of Example Embodimentsln the present detailed description, various embodiments of afingerprint sensing device according to the present invention are mainly 11 discussed with reference to a capacitive fingerprint sensing device. A methodfor manufacturing a fingerprint sensing device is also discussed.
    Fig. 1 is a schematic illustration of a handheld device 100 comprising afingerprint sensing device 102 comprising a touchscreen display 104. Afingerprint sensing device 102 can be used in for example a mobile phone, atablet computer, a portable computer or any other electronic device requiringa way to identify and/or authenticate a user.
    Fig. 2A is a schematic illustration of a fingerprint sensing device 200according to an embodiment of the invention, as seen in a top view. lnparticular, Fig. 2A illustrates the outline of a plurality of interposer structures202, where each interposer structure 202 is arranged on a sensing element204 of the sensing device 200.
    Fig. 2B illustrates the sensing device 200 in further detail where asensing chip 206 comprising an array of sensing elements 204 is shown.Here it can be seen that an adhesive 208 is arranged in the space betweeninterposer structures 202, and that a protective plate 210 is attached to thesensing device 200 by means of the adhesive 208. The protective plate 210can be manufactured with a high degree of accuracy, and the variation inthickness over the sensing area is typically less than 2um. Moreover, thedistance between the surface of the sensing elements 204 and the surface212 of the protective plate 208, is defined by the height of the interposerstructures 202. The height of the interposer structures is typically in the rangeof 5 to 50 um. The height the of the interposer structures for a specificapplication can for example be selected based on the bonding techniqueused to connect the sensing chip to a substrate, or on the type of adhesiveused. The surface plane of the sensing elements 204 is defined as thesensing plane, and the surface 212 of the protective plate 210 is defined asthe sensing surface 212.
    The protective plate 210 may also be the cover glass in a devicecomprising a touch screen, and a cover glass covering the fingerprint sensingdevice may also be covering the display and touchscreen portions of thehandheld device. ln principle, the protective plate may be any structure which 12 acts to cover and protect the sensing device while still allowing a capacitivecoupling between a finger placed on the surface of the protective plate andthe sensing elements.
    The sensing elements 204 are here shown arranged in a square array,the sensing elements having a size of about 50x50 um and a distancebetween adjacent elements is about 5 um. The sensing elements 204 areelectrically conductive, typically metallic, and can as a general approximationbe considered to act as one plate in a parallel plate capacitor, where a fingerplaced on a sensing surface 212 of the fingerprint sensing device 200represents the other plate. Each sensing element 204 is connected to readoutcircuitry (not shown) for detecting a capacitive coupling between each of saidsensing elements 204 and a finger placed on the sensing surface 212.
    Fig. 3A is a schematic illustration of a fingerprint sensing device 300according to an embodiment of the invention where the interposer structures302 are provided in the form of parallel lines, or ridges, aligned with theboundaries between sensing elements 204. ln Fig. 3B it can be seen that the adhesive is arranged to fill out thespace between the ridges 302 and to attach the protective plate 210 to thesensing chip 206.
    Fig. 4A is schematic illustration of an alternative embodiment of afingerprint sensing device 400 where interposer structures 402 are arrangedaligned with boundaries between adjacent sensing elements 204 but with agap or opening in the interposer structures 402 between adjacent sensingelements 204.
    Fig. 4B is schematic illustration of an alternative embodiment of afingerprint sensing device 410 where interposer structures 412 are arrangedon the sensing chip outside of the array of sensing elements 204, whichdefines the sensing area. Thereby, the adhesive 208 can be arranged tocompletely cover the sensing elements 204, providing a homogeneouscovering layer. As can be seen in Fig. 4B, there is a space between adjacentinterposer structures 412 enabling a liquid adhesive to flow out through thegaps formed between the structures when the adhesive is deposited. 13 Thereby, any additional adhesive can be pushed out outside of the interposerstructures 412 when the protective plate 210 is arranged on the sensingdevice 410 so that the protective plate 210 rests on the interposer structures412. lt should be noted that the configuration illustrated in Fig. 4B is one ofmany possible configurations for the interposer structures, and that manydifferent configurations of the interposer elements are possible, where themain feature is that the interposer structures are all of the same height andthat they provide mechanical support for the protective plate.
    An advantage of providing interposer structures as illustrated in Figs.2-4 above is that when a liquid adhesive is being dispensed, the adhesive caneasily flow out and fill all the spaces between interposer structures, therebyforming a homogeneous layer without air gaps, which in turn leads to a welldefined dielectric structure between the sensing elements 204 and thesensing surface 212. The adhesive may for example have the same dielectricconstant as the material from which the interposer structures are made,thereby making the layer comprising the interposer structures and theadhesive behave as a uniform layer in a dielectric perspective.
    Alternatively, it is possible to use an adhesive and an interposerstructure having different dielectric constants, in which case the difference indielectric constant can be used to focus the electric field towards the sensingelements. This requires that the material located directly above each sensingelement should have a higher dielectric constant than the surroundingmaterial. Taking the sensing device 200 of Figs. 2A-B as an example, theinterposer structures 202 would need to have a dielectric constant which ishigher than the dielectric constant of the adhesive 208 to achieve the fieldfocusing effect.
    Fig. 5 is a flow chart outlining the general steps of a manufacturingmethod according to an embodiment of the invention. The manufacturingmethod will be discussed also with reference to Figs 6A-G.
    First, in step 502 illustrated in Fig. 6A, a circularwafer 600 comprisinga plurality of sensing chips 602 is provided. The wafer 600 may for examplebe a silicon wafer where sensing chips 602 have been formed using 14 conventional CMOS-compatible processing. By using a full size circular wafer,large scale processing advantages can be achieved.
    Next 504, as illustrated in Fig. 6B, an interposer layer 604 is formed onthe surface of the wafer 600, thereby covering the sensing chips 602 to forma uniform layer on the surface of the wafer 600. The interposer layer 604,which may also be referred to as a coating layer, is formed to have a uniformthickness and to cover the entire area of the wafer 600. The interposer layer604 can for example be a photoresist deposited by spin-coating or spraycoating, and the photoresist may be either a positive or a negativephotoresist. Spin- and spray-coating are well established manufacturingtechniques which can be performed with high accuracy on wafer scale,thereby providing an interposer layer 604 having a uniform thickness over thesurface of the wafer 600. To achieve a high homogeneity in the depositedlayer, spray coating can advantageously be performed using ultrasonicnozzles. Furthermore, it is also possible to use methods such as inkjetprinting or 3D-printing to form the interposer structures. ln the next step 506, illustrated in Fig. 6C, interposer structures 606 areformed on the surface of the wafer using photolithography. Here, theinterposer structures are provided in the form of individual structures whereeach structure 606 is centered on a corresponding sensing element 608. Thecross section of the interposer structure 606 is illustrated as beingsubstantially hexagonal. However, the cross section of the interposerstructure may in principle be selected arbitrarily, and it may be circular,quadratic or have any polygonal shape there between. Moreover, it is notrequired that the interposer structure is symmetric, nor does it need to besymmetric in the vertical direction.
    As an alternative to using a photoresist to form the interposerstructures as described above, it is also possible to form the interposerstructures in another material. As an example, a hard mask may be formed onthe wafer, for example a SiN mask, after which the hard mask is patternedusing photolithography, patterning and subsequent deep reactive ion etching(DRIE). lt is also possible to use laser ablations to remove material in selected areas to form the desired patterns of interposer structures.Moreover, it is also possible to use additive techniques for the purpose offabricating the interposer structures and associated geometries, such as e.g.inkjet printing or 3D printing.
    After forming the interposer structures, the interposer layer may betreated in a plasma cleaning process in order to improve adhesion betweenthe interposer structures and the subsequently deposited adhesive. Theplasma cleaning may for example comprise oxygen mixed with an inert gassuch as nitrogen or argon.
    After forming the interposer structures 606 on the wafer, the wafer isdiced 508 into separate sensing chips 610 illustrated in Fig. 6D. Fig. 6Dfurther illustrates a bond pad 609 on the sensing chip subsequently used toelectrically connect the sensing chip 602 to a substrate. As illustrated in Fig.6E, the individual sensing chips are subsequently arranged 510 ontocorresponding substrates 612 comprising readout circuitry (not shown) forreading out the information from the sensing elements 608 of the sensing chip610 in order to form a fingerprint image. The sensing chip 610 is connected tothe substrate 612 by means of a bond wire 614 reaching from a first bond pad616 on the sensing chip to a second bond pad 618 on the substrate. Here,only one bond wire is illustrated to avoid cluttering the drawings.
    As a next step 512, illustrated in Fig. 6F, a liquid adhesive 620 isprovided 514 by dispensing the adhesive 620 onto the interposer layer so thatthe adhesive 208 fills the spaces between the interposer structures 606. ln the final step 516 as illustrated in Fig. 6G, a protective plate 210 isattached to the sensing device by means of the adhesive 208. The protectiveplate 210 is arranged onto the adhesive 620 and a certain pressure is appliedso that the adhesive 620 is redistributed to fill all the spaces betweenadjacent interposer elements 606. The protective plate is pressed down untilit rests on the interposer structures. After the step of applying the adhesive onthe sensing chip, there could be a drying step involved (sometimes referred to as beta stage curing) to partially dry the adhesive. ln case of curing, the 16 protective plate can be attached to the partially cured/dried adhesive in asubsequent assembly step by applying heat and pressure.
    Fig. 7 illustrates a sensing device where the electrical connectionbetween the sensing elements and the substrate 612 is formed using a viaconnection 702 through the sensing chip 610. Such a via connection 702 mayalso be referred to as a through silicon via (TSV) connection.
    Even though the above method is illustrated as starting from a fullwafer, it is equally possible to form the interposer structures on an alreadydiced sensing chip.
    Moreover, the protective plate may also be provided with a frame,which may also be referred to as a bezel, surrounding the sensing chip oncethe protective plate is in place. The bezel may for example help to protect thebond wires between the sensing chip and the substrate. The bezel may alsobe a conductive structure acting as a drive element for a finger, and/orfunctioning as an ESD discharge node. lt should be noted that the general aspects of the invention discussedherein are not limited to the specific dimensions and sizes disclosed in thepresent description. The above description merely provides an exampleembodiment of the inventive concepts as defined by the claims.
    Even though the invention has been described with reference tospecific exemplifying embodiments thereof, many different alterations,modifications and the like will become apparent for those skilled in the art.Also, it should be noted that parts of the device and method may be omitted,interchanged or arranged in various ways, the device and method yet beingable to perform the functionality of the present invention.
    Additionally, variations to the disclosed embodiments can beunderstood and effected by the skilled person in practicing the claimedinvention, from a study of the drawings, the disclosure, and the appendedclaims. ln the claims, the word "comprising" does not exclude other elementsor steps, and the indefinite article "a" or "an" does not exclude a plurality. Themere fact that certain measures are recited in mutually different dependent 17 claims does not indicate that a combination of these measures cannot beused to advantage.
    权利要求:
    Claims (19)
    [1] 1. A fingerprint sensing device comprising: a sensing chip comprising an array of sensing elements, said sensingelements being configured to be connected to readout circuitry for detecting acapacitive coupling between each of said sensing elements and a fingerplaced on a sensing surface of said sensing device, wherein a surface of saidsensing elements define a sensing plane; a plurality of interposer structures arranged on said sensing chipextending above sensing plane, wherein said plurality of interposer structureshave substantially the same height above said sensing plane; and a protective plate attached to said sensing chip by means of anadhesive arranged on said sensing chip, wherein said protective plate restson said interposer structures such that a distance between said protectiveplate and said sensing plane is defined by the height of said interposer structures.
    [2] 2. The sensing device according to claim 1, wherein a variation in height between said plurality of interposer structures is less than 1 um.
    [3] 3. The sensing device according to claim 1 or 2, wherein saidplurality of interposer structures comprises parallel lines.
    [4] 4. The sensing device according to claim 3, wherein said parallellines are aligned with an edge of said sensing chip and have a lengthsubstantially similar to a side of the sensing chip.
    [5] 5. The sensing device according to claim 1 or 2, wherein saidplurality of interposer structures comprises one interposer structure centeredon each of said sensing elements. 19
    [6] 6. The sensing device according to claim 5, wherein said pluralityof interposer structures are formed in a material having a die|ectric constanthigher than a die|ectric constant of said adhesive.
    [7] 7. The sensing device according to any one of claims 1 to 4,wherein said plurality of interposer structures are arranged in alignment withboundaries between said sensing elements, such that a central portion ofeach sensing element is not covered by an interposer structure.
    [8] 8. The sensing device according to claim 7, wherein said pluralityof interposer structures are formed in a material having a die|ectric constantlower than a die|ectric constant of said adhesive.
    [9] 9. The sensing device according to claim 1 or 2, wherein saidinterposer structures are arranged on said sensing chip at locations outside ofa sensing area of said sensing chip, said sensing area being defined by said array of sensing elements.
    [10] 10. The sensing device according to any one of the precedingclaims, wherein said plurality of interposer structures comprises a photoresist.
    [11] 11. The sensing device according to any one of the precedingclaims, further comprising a bond wire arranged between a bond pad on saidsensing chip and a substrate on which the sensing chip is arranged, whereina bond loop height of said bond wire is lower than said interposer structure.
    [12] 12. The sensing device according to any one of the precedingclaims, further comprising a via connection through said sensing chip toelectrically connect said sensing chip to a substrate.
    [13] 13. A method for manufacturing a fingerprint sensing device, saidmethod comprising; providing a sensing chip comprising an array of sensing elements, saidsensing elements being configured to be connected to readout circuitry fordetecting a capacitive coupling between each of said sensing elements and afinger placed on a sensing surface of said sensing device, wherein a surfaceof said sensing elements define a sensing plane; forming an interposer layer on said sensing chip; forming a plurality of interposer structures from said interposer layer,wherein said plurality of interposer structures have substantially the sameheight above said sensing plane; providing a liquid adhesive on said sensing chip; and arranging a protective plate on said sensing chip such that saidadhesive is filling out spaces between said plurality of interposer structures, and such that said protective plate rests on said interposer structures.
    [14] 14. The method according to claim 13, wherein said interposer layer is deposited by spin coating or by spray coating.
    [15] 15. The method according to claim 13 or 14, wherein providing saidadhesive comprises dispensing a liquid adhesive on and in between saidinterposer structures.
    [16] 16. The method according to any one of claims 13 to 15, whereinsaid interposer layer comprises a photoresist.
    [17] 17. The method according to claim 16, wherein said step of forminga plurality of interposer structures comprises patterning said interposer layerusing photolithography.
    [18] 18. The method according to any one of claims 13 to 16, furthercomprising the steps of depositing a hard mask on said interposer layer,patterning said hard mask, patterning said interposer layer according to saidhard mask pattern, and removing said hard mask. 21
    [19] 19. A method for manufacturing a fingerprint sensing device,comprising: providing a semiconductor wafer, on said semiconductor wafer forming a plurality of fingerprint sensingchips, each sensing chip comprising an array of sensing elements, saidsensing elements being configured to be connected to readout circuitry fordetecting a capacitive coupling between each of said sensing elements and afinger placed on a sensing surface of said sensing device, wherein a surfaceof said sensing elements define a sensing plane; forming an interposer layer on said semiconductor wafer, saidinterposer layer covering said plurality of fingerprint sensing chip sub-areas; forming a plurality of interposer structures from said interposer layer,wherein said plurality of interposer structures have substantially the sameheight above said sensing plane; dicing said semiconductor wafer into a plurality of individual sensingchips; arranging a sensing chip on a substrate comprising readout circuitry; electrically connecting said sensing elements of said sensing chip tosaid readout circuitry; providing a liquid adhesive on said sensing chip; and arranging a protective plate on said sensing chip such that saidadhesive is filling out spaces between said plurality of interposer structures,and such that said protective plate rests on said interposer structures.
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    法律状态:
    2017-07-11| NAV| Patent application has lapsed|
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    SE1550748|2015-06-08|TW105115304A| TW201643772A|2015-06-08|2016-05-18|Fingerprint sensing device with interposer structure|
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    EP16807913.5A| EP3304419A4|2015-06-08|2016-06-02|Fingerprint sensing device with interposer structure|
    PCT/SE2016/050525| WO2016200315A1|2015-06-08|2016-06-02|Fingerprint sensing device with interposer structure|
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    US15/613,741| US9805244B2|2015-06-08|2017-06-05|Fingerprint sensing device with interposer structure|
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