JP2009156637A - Capacitance type sensor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitance type sensor which can be manufactured of materials used for a normal LSI manufacturing process and can detect roughness formed at fine intervals on a surface, and to provide its manufacturing method. <P>SOLUTION: The capacitance type sensor comprises a plurality of sensor parts 20 arranged on a detection surface which is adjacent to or in contact with a surface of an object. Each sensor 20 includes: a first sensor electrode 10 formed below the detection surface; a second sensor electrode 13 formed so that the top end face is exposed to the detection surface; and a first insulation film 12 which is formed above the first sensor electrode 10 and between the first and second sensor electrodes 10, 13, and constitutes part of the detection surface. Side faces of the first and second sensor electrodes 10, 13 are opposed to each other across the first insulation film 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a capacitive sensor and a manufacturing method thereof.

  With the progress of the information society and changes in the social environment in recent years, interest in security technology is increasing. For example, identity recognition technology required for system construction such as electronic money has attracted a great deal of attention. In addition, research and development has been actively conducted on recognition techniques for preventing unauthorized use of credit cards, and many techniques have been proposed so far.

  As a personal authentication method, there is a method of performing personal authentication by detecting fingerprints, faces, voiceprints, irises, etc. Among them, fingerprint authentication is particularly inexpensive and is easy to downsize. Technology development is in progress.

  As a method of reading the shape of a fingerprint as data, there are an optical type provided with an optical system such as a lens and illumination, a pressure type using a pressure sensitive sheet, a semiconductor type having a sensor disposed on a semiconductor substrate, and the like. Among these, the semiconductor type is easy to downsize and has versatility.

  As a semiconductor sensor, there is a capacitance type surface shape recognition sensor using an LSI (Large-Scale Integration) manufacturing technique (for example, refer to Patent Document 1 below). This surface shape recognition sensor has a structure in which sensor elements are two-dimensionally arranged on an LSI chip, and detects a fine uneven pattern on a fingerprint surface or the like by detecting capacitance.

  FIG. 6 is a schematic plan view of a capacitive sensor according to the prior art. FIG. 6A is a partial schematic plan view of the capacitance type sensor, and FIG. 6B is an enlarged view of one sensor portion.

  As shown in FIG. 6, the capacitive sensor 110 is configured by arranging a plurality of sensor units 100 in a matrix. Each sensor unit 100 has a rectangular sensor electrode 101 at the center, and on the outside thereof, an insulating film 12 is provided for forming an electrical connection with the ground electrode 11 for preventing electrostatic breakdown and the ground electrode 11. Contact electrode 14 is formed. The ground electrode 11 is formed in the boundary region so as to divide each sensor unit 100.

  FIG. 7 shows a part of a schematic cross-sectional structure diagram when the conventional sensor unit 100 shown in FIG. 6 is cut along a line XX ′. With reference to FIG. 7, a conventional method of manufacturing a capacitive sensor will be described. In FIG. 7, only the upper layer portion of the metal wiring 15 formed as a peripheral circuit is shown.

After the metal wiring 15 as the peripheral circuit is formed by, for example, a three-layer wiring, an interlayer insulating film 16 made of, for example, a SiO ₂ film is formed, and a planarization process is performed using a CMP (Chemical Mechanical Polishing) method or the like. . Next, after forming a conductive film made of, for example, a TiN / Ti / AlCu / Ti / TiN film, patterning is performed to form the sensor electrode 101 and the ground electrode 11. Next, after forming an insulating film 12 made of, for example, a SiN film by plasma CVD or the like, a groove-shaped contact is opened on the ground electrode 11 by a photo process and an etching process. Then, after forming a conductive film made of, for example, a W film by a CVD method (Chemical Vapor Deposition) method, the contact electrode 14 is formed by filling the opening region on the ground electrode 11.

  When a finger as a measurement object approaches or comes into contact with the capacitive sensor formed in this way, the capacitance Cf between the finger surface and the sensor electrode has a dielectric constant k and a capacitor electrode area. A, where d is the distance between the sensor electrode and the finger surface, it is expressed by the following (Equation 1).

(Equation 1)
Cf = k (A / d)

  As can be seen from the above (Equation 1), in the raised (convex) portion of the finger surface, d is the film thickness of the insulating film 12, and k is determined by the dielectric constant of the insulating film 12, thereby determining the capacitance Cf. On the other hand, in the valley (concave) portion of the finger surface, the distance from the capacitor C1 where the film thickness of the insulating film 12 is d and the dielectric constant of the insulating film 12 is k to the valley portion of the finger surface from the surface of the insulating film 12 is as follows. d, Cf is determined by the combined capacitance of a capacitor connected in series with a capacitor C2 whose dielectric constant is k. That is, since the capacitance value in each region differs because the distance from the surface of the insulating film 12 to the valley portion of the finger surface varies depending on the location, the capacitance value for each region is measured by measuring the capacitance value for each region. Unevenness can be recognized.

  When detecting the capacitance, the sensor electrode is precharged with the voltage Vc, and then the finger is brought close to or in contact. As a result, the voltage Vc is divided into a capacitance between the sensor electrode and the finger and a parasitic capacitance between the sensor electrode and the wiring pattern or the Si substrate under the sensor electrode. As a result, the sensor The electrode potential decreases. This reduced voltage ΔVi is the capacitance between the sensor electrode and the finger (hereinafter referred to as “sensing capacitance”) Cf, and the parasitic capacitance between the sensor electrode and the wiring pattern or Si substrate under the sensor electrode. The voltage signal detected as Cp is expressed by the following (Equation 2).

(Equation 2)
ΔVi = Vc · Cf / (Cf + Cp)

  Since the voltage signal ΔVi is determined depending on the sensing capacitance Cf from (Equation 2), the distribution of the size of the sensing capacitance Cf for each region is recognized by measuring ΔVi for each sensor unit. It is possible to recognize the unevenness at each place.

  As apparent from the above (Equation 2), ΔVi depends not only on the sensing capacitance Cf but also on the parasitic capacitance Cp. For this reason, if the parasitic capacitance Cp shows a relatively large value with respect to the sensing capacitance Cf, the change in Cf is not sufficiently reflected in the change in the value of ΔVi, and the surface shape unevenness is recognized. Accuracy is reduced. In other words, in order to obtain a surface shape image with high accuracy, it is necessary to increase the sensing capacitance Cf and reduce the parasitic capacitance Cp.

  In particular, when a capacitive sensor is used as a fingerprint sensor, it is necessary that the fingerprint that is the object to be detected be able to authenticate to people of a wide range of age groups. It is necessary to reduce the size of the sensor electrode and increase the number of pixels. At this time, if the sensor electrode is reduced in size, the sensing capacitance Cf is reduced, so that the influence of the parasitic capacitance Cp cannot be ignored.

  As a method of increasing the sensing capacitance Cf, a method of reducing the film thickness of the insulating film 12 on the upper layer of the sensor electrode 101 is conceivable. However, if this film thickness is reduced, there is a problem that the strength of the electrode surface and the moisture resistance are reduced. Invite

  In Patent Document 2 below, as a method of increasing the sensing capacitance Cf and reducing the parasitic capacitance Cp, the dielectric constant is applied to the insulating film 12 on the upper layer of the sensor electrode 101 and the interlayer insulating film 16 on the lower layer of the sensor electrode 101 so that Cf> Cp. The use of different membranes is disclosed.

JP-A-8-305832 Japanese Patent Laid-Open No. 11-072306

  In the case of the method described in Patent Document 2, whether or not the sensing capacitance Cf can be made sufficiently larger than the parasitic capacitance Cp depends only on the dielectric constant of the material. For this reason, the material which can be used at the time of manufacture is limited, and it is difficult to manufacture flexibly.

In a general LSI manufacturing process, as described above, a SiO ₂ film is used for the interlayer insulating film 16 below the sensor electrode 101, and a SiN film is used for the protective insulating film 12 on the sensor electrode 101. It is normal. For this reason, when the method described in Patent Document 2 is used, it is necessary to prepare an insulating film made of a material different from the insulating film normally used in manufacturing, which raises a problem of increasing manufacturing costs.

  In view of the above problems, the present invention provides a capacitive sensor that can be manufactured with a material used in a normal LSI manufacturing process and that can detect surface irregularities with minute intervals, and a method for manufacturing the same. The purpose is to provide.

  In order to achieve the above object, a capacitive sensor according to the present invention is a capacitive sensor that detects the form of the surface of an object to be detected, and is a detection surface that approaches or contacts the surface of the object to be detected. A plurality of sensor units are arranged on the top, and each sensor unit is formed with a first sensor electrode formed by retreating downward from the detection surface and an upper end surface exposed to the detection surface. A second sensor electrode, an upper layer of the first sensor electrode, and a first insulating film formed between the first sensor electrode and the second sensor electrode and constituting a part of the detection surface; The first feature is that a side surface of the first sensor electrode and a side surface of the second sensor electrode are opposed to each other with the first insulating film interposed therebetween.

  According to the first characteristic configuration of the capacitive sensor according to the present invention, when the detected object is placed on the detection surface, the detected object and the second sensor electrode have the same potential. The second sensor electrode and the first sensor electrode face each other via the first insulating film on the side surface, and these form a capacitive element. For this reason, when the detected object is placed on the detection surface, the capacitive component formed between the first sensor electrode and the first sensor electrode includes an electrode body constituted by the detected object and the second sensor electrode, It is determined by the area facing one sensor electrode. That is, as compared with the case where the second sensor electrode is not present, a large capacitance (sensing capacitance) between the object to be detected and the sensor electrode (herein, the first sensor electrode) formed in the lower layer is ensured. be able to.

  Accordingly, since a large sensing capacitance can be secured, the ratio of the parasitic capacitance to the sensing capacitance can be reduced. Since the uneven pattern of the object to be detected affects the size of the sensing capacitance, the smaller the parasitic capacitance with respect to the sensing capacitance, the more accurately the sensing capacitance decrease due to the presence of the recess is recognized. can do.

  In addition, according to the above configuration, since the sensing capacitance can be sufficiently secured, in order to reduce the parasitic capacitance compared to the sensing capacitance, the dielectric constant of the lower interlayer insulating film compared to the insulating film on the upper layer of the sensor electrode There is no need to make it smaller. For this reason, since the insulating film material used in the conventional process can be used, and the usable material is not limited, the manufacturing cost can be reduced and the manufacturing can be performed flexibly. Is possible.

  In addition, with such a configuration, a sufficient sensing capacity can be ensured, so that the uneven pattern can be recognized even if the sensor electrode is made somewhat small. For this reason, when the capacitance type sensor according to the present invention is used as a fingerprint sensor, it is possible to measure a wide range of human fingerprints from infants to adults.

  In addition to the first characteristic configuration, the capacitance type sensor according to the present invention is such that the bottom surface of the second sensor electrode is formed at a position deeper than the bottom surface of the first sensor electrode. The second feature.

  According to the second characteristic configuration of the capacitive sensor according to the present invention, since all the side surfaces of the first sensor electrode are opposed to the side surfaces of the second sensor electrode, a larger sensing capacitance is ensured. Is possible.

  In addition to the first or second characteristic configuration, the capacitance type sensor according to the present invention is configured so that each sensor unit is surrounded by a ground electrode for ground connection in a plane parallel to the detection surface. The third feature is that it is surrounded.

  According to the third characteristic configuration of the capacitive sensor according to the present invention, the sensing capacitance can be recognized for each sensor unit surrounded by the ground electrode. For this reason, since each sensor unit is arranged in a matrix and is surrounded by a ground electrode, the sensing capacitance can be recognized for each coordinate specified by the sensor unit arranged in a matrix. By analyzing the capacity for each coordinate, it becomes possible to recognize the uneven pattern of the detected object based on the size of each capacity with good reproducibility.

  In addition to the third characteristic configuration, the electrostatic capacitance sensor according to the present invention is configured such that, in each of the sensor portions, the ground electrode is formed so as to surround an outer peripheral portion of the first sensor electrode. The second feature is that the two sensor electrodes are formed on the inner side of the outer periphery of the first sensor electrode.

  In order to achieve the above object, a method of manufacturing a capacitive sensor according to the present invention is a method of manufacturing a capacitive sensor having any one of the first to fourth characteristic configurations, wherein the interlayer A first step of exposing the interlayer insulating film in a predetermined region and forming a plurality of the first sensor electrodes by performing a patterning process after forming the first conductive film on the insulating film, and completing the first step Thereafter, a second step of forming the first groove portion by digging the exposed interlayer insulating film by a predetermined thickness in the depth direction, and the first groove portion is not completely filled after the second step is completed. Forming a first insulating film on the entire surface with a film thickness within a range, and forming a second groove, and filling the second groove with a second conductive film after the third step is completed. And a fourth step of forming the second sensor electrode. To.

  According to the first feature of the method of manufacturing a capacitive sensor according to the present invention, the first insulating film is formed on the outer side in the first groove formed in the second step, and the second is formed on the inner side. A conductive film is filled. For this reason, the side surface of the second conductive film and the side surface of the first conductive film face each other with the first insulating film interposed therebetween.

  Therefore, according to the capacitance type sensor manufactured according to the above characteristics, it is possible to ensure the capacitance also on the side surface as compared with the case where the sensor electrode is simply provided on the lower layer via the insulating film. Therefore, the ratio of the parasitic capacitance to the capacitance (sensing capacitance) for recognizing the uneven pattern can be reduced. Since the uneven pattern of the object to be detected affects the size of the sensing capacitance, the smaller the parasitic capacitance with respect to the sensing capacitance, the more accurately the sensing capacitance decrease due to the presence of the recess is recognized. can do.

  In addition, according to the above feature, the manufactured capacitive sensor can secure a sufficient sensing capacitance, and therefore, compared with the insulating film on the upper layer of the sensor electrode in order to reduce the parasitic capacitance compared to the sensing capacitance. There is no need to reduce the dielectric constant of the underlying interlayer insulating film. For this reason, since the insulating film material used in the conventional process can be used, and the usable material is not limited, the manufacturing cost can be reduced and the manufacturing can be performed flexibly. Is possible.

  In addition to the first feature, the method of manufacturing a capacitive sensor according to the present invention includes a fifth step of forming a metal wiring in a predetermined region before the first step, and the metal wiring. A sixth step of forming the interlayer insulating film on an upper layer, and removing the first conductive film located in an upper region of the metal wiring in the first step, thereby removing the metal wiring A second feature is that a plurality of the first sensor electrodes having a rectangular opening whose longitudinal direction is the extending direction of the metal wiring are formed in an upper region of the first wiring.

  According to the second feature of the capacitive sensor according to the present invention, since the facing area between the metal wiring and the first sensor electrode can be reduced, the parasitic capacitance generated between the two electrodes can be reduced. it can.

  In addition to the first or second feature, the method for manufacturing a capacitive sensor according to the present invention includes an outer periphery of the first sensor electrode in addition to the first sensor electrode in the first step. A ground electrode for ground connection that is separated from the first portion is formed in a boundary region of each sensor portion, and after the third step is completed and before the fourth step is started, a partial region of the first insulating film on the ground electrode upper layer Is etched to form a third groove portion so that the upper surface of the ground electrode is exposed. In the fourth step, the third groove portion is filled with the second conductive film. A third feature is that a contact electrode electrically connected to the ground electrode is formed.

  According to the third aspect of the method of manufacturing the capacitive sensor according to the present invention, the formation of the contact electrode for electrical contact connection to the ground electrode and the formation of the second sensor electrode are realized in the same process. can do.

  In addition to the third feature, the method for manufacturing a capacitive sensor according to the present invention may be configured such that, in the first step, the distance between the first sensor electrode and the ground electrode is greater than the hole diameter of the first groove portion. Patterning is performed so as to shorten the length, and in the second step, a fourth groove is formed by digging in the depth direction the interlayer insulating film exposed between the first sensor electrode and the ground electrode, In the third step, the fourth feature is that the fourth groove is completely filled with the first insulating film.

  According to the fourth aspect of the method of manufacturing a capacitive sensor according to the present invention, the gap between the ground electrode and the first sensor electrode is completely filled with the first insulating film, so that it is formed between the two electrodes. Parasitic capacitance can be reduced.

  In addition to the third feature, the method for manufacturing a capacitive sensor according to the present invention may be configured such that, in the first step, the distance between the first sensor electrode and the ground electrode is greater than the hole diameter of the first groove portion. Patterning is performed so as to be long, and in the second step, a fourth groove is formed by digging in the depth direction the interlayer insulating film exposed between the first sensor electrode and the ground electrode, In the third step, the fourth groove portion is not completely filled, and the first insulating film is formed on the bottom surface and the inner wall of the fourth groove portion, so that the first insulating film is formed in the fourth groove portion. An enclosed fifth groove is formed, and in the fourth step, the fifth groove is not completely filled, and the second conductive film is formed on a bottom surface and an inner wall of the fifth groove, After the completion of 4 steps, before being formed in the fifth groove Further comprising a eighth step of removing the second conductive film by etching the fifth aspect.

  According to the fifth feature of the method of manufacturing a capacitive sensor according to the present invention, the sensing capacitance can be increased even when the separation between the ground electrode and the first sensor electrode is required due to layout constraints. It is possible to manufacture a sufficiently secured capacitance type sensor.

  According to the configuration of the present invention, it is possible to realize a capacitive sensor that can be manufactured by a material used in a normal LSI manufacturing process and can detect surface irregularities having a fine interval.

  Hereinafter, an embodiment of a capacitance type sensor according to the present invention (hereinafter appropriately referred to as “the present invention sensor”) and a manufacturing method thereof (hereinafter referred to as “the present invention method” as appropriate) will be described with reference to the drawings. explain.

  The schematic structural diagram shown below is schematically shown, and the dimensional ratio on the drawing does not necessarily match the actual dimensional ratio. The dimension values such as thickness are examples, and are not limited to these values. The same components as those shown in FIGS. 6 and 7 are denoted by the same reference numerals.

  FIG. 1 is a schematic plan view of the sensor of the present invention. FIG. 1A is a schematic plan view of a part of the sensor of the present invention, and FIG. 1B is an enlarged view of one sensor unit.

  As shown in FIG. 1, the sensor 1 of the present invention includes a plurality of sensor units 20 arranged in a matrix. Each sensor unit 20 has a sensor electrode 10 (hereinafter referred to as “first sensor electrode 10”) in the central portion, and an insulating film 12 (hereinafter referred to as “first insulating film 12”) on the outside thereof. Thus, a ground electrode 11 for preventing electrostatic breakdown and a contact electrode 14 for forming an electrical connection with the ground electrode 11 are formed. The ground electrode 11 is formed in a boundary region so as to surround each sensor unit 20. As will be described below with reference to the cross-sectional structure diagram, the first insulating film 12 is formed so as to cover the upper layer of the first sensor electrode 10 (in FIG. 1, the first layer of the upper layer of the first sensor electrode 10). 1 is omitted).

  The first sensor electrode 10 is a rectangular electrode having a groove portion 21 in part. In FIG. 1, three groove portions 21 are illustrated, but the number of the groove portions 21 is not limited to three. In the groove portion 21, a conductive electrode 13 (hereinafter referred to as “second sensor electrode 13”) different from the first sensor electrode 10 is formed in the central portion, and the outside thereof is the first insulating film 12. Covered with That is, the first sensor electrode 10 and the second sensor electrode 13 are separated by the first insulating film 12 and are not electrically connected.

  The upper surface of the second sensor electrode 13 is formed at the height position of the upper surface of the first insulating film 12 formed in the upper layer of the first sensor electrode 10. The detection surface is constituted by the upper surface of the first insulating film 12, the upper surface of the second sensor electrode 13, and the upper surface of the contact electrode 14 formed in the upper layer of the ground electrode 11. In other words, the second sensor electrode 13 and the contact electrode 14 are exposed on the upper surface, while the first sensor electrode 10 is formed on the lower layer of the first insulating film 12 and is not exposed on the upper surface.

  Further, the bottom surface of the second sensor electrode 13 is formed at a position deeper than the bottom surface of the first sensor electrode 10. That is, the side surface of the first sensor electrode 10 is completely opposed to the side surface of the second sensor electrode 13 with the first interlayer insulating film 12 interposed therebetween.

  The first sensor electrode 10 has a width d1 of an electrode region formed between adjacent groove portions 21 of about 1.0 μm, for example, and an electrode width d2 of the second sensor electrode 13 in the groove portion 21 is about 1.3 μm. Composed. The first sensor electrodes 10 are arranged at a pitch of about 30 μm to 100 μm with the first sensor electrodes 10 of the adjacent sensor unit 20.

  Hereinafter, the manufacturing method of the sensor 1 of the present invention shown in FIG. 1 will be described with reference to the drawings. FIG. 2 schematically shows a schematic cross-sectional structure diagram in each process when the sensor of the present invention is manufactured using the method of the present invention. The process is divided into FIGS. 2A to 2E for each process. It is shown. FIG. 3 is a flowchart of the manufacturing process of the method of the present invention, and each step in the following sentence represents each step of the flowchart shown in FIG.

  The schematic cross-sectional structure diagram for each step shown in FIG. 2 is a cross-sectional view when one sensor unit 20 shown in FIG. 1 is cut along line XX ′, and is formed as a peripheral circuit. Only the upper layer portion of the metal wiring 15 is shown. Only the process after the formation of the metal wiring 15 will be described below.

As shown in FIG. 2A, after a metal wiring 15 as a peripheral circuit is formed by, for example, a three-layer wiring by a known process (step # 1), an interlayer insulating film 16 made of, for example, a SiO ₂ film is formed. Then, a planarization process is performed using a CMP (Chemical Mechanical Polishing) method or the like (step # 2). Next, after forming a conductive film composed of, for example, a TiN / Ti / AlCu / Ti / TiN film (hereinafter referred to as “first conductive film”), a patterning process is performed to expose the interlayer insulating film 16. At the same time, a plurality of first sensor electrodes 10 and ground electrodes 11 are formed (step # 3). The film thickness of the first sensor electrode 10 (and the ground electrode 11) at the end of step # 3 is preferably about 800 to 1100 nm.

  By the patterning process in step # 3, the ground electrode 11 formed in the boundary region of each sensor unit 20 and the first sensor electrode 10 for each sensor unit 20 surrounded by the ground electrode 11 are formed and patterned. The upper surface of the interlayer insulating film 16 is exposed in the formed region. The first sensor electrode 10 formed in each sensor part 20 has a rectangular outer peripheral part, and has a void part 29 in which the upper surface of the interlayer insulating film 16 is exposed. In the present embodiment, in step # 3, the distance d31 between the ground electrode 11 and the first sensor electrode 10 is set to about 0.7 μm, for example, and the hole diameter d32 of the gap 29 is set to about 1.3 μm, for example.

  In step # 3, the area where the upper surface of the interlayer insulating film 16 is exposed is located above the formation area of the metal wiring 15, so that the opposing area between the metal wiring 15 and the first sensor electrode 10 is reduced. It is suppressed to about 0.1 times the electrode area.

  Next, as shown in FIG. 2B, the interlayer insulating film 16 exposed on the bottom surface of the gap 29 is dug in the depth direction by etching (step # 4). Thereby, the depth of the gap portion 29 is increased, and a groove portion (hereinafter referred to as “first groove portion 21”) is formed. In this step # 4, the etching depth for digging the interlayer insulating film 16 is set to a depth equal to or greater than the film thickness of the first insulating film 12 formed in the next step # 5.

  Next, as shown in FIG. 2C, a first insulating film 12 made of, for example, a SiN film is formed on the entire surface by a plasma CVD method or the like (step # 5). At this time, the first insulating film 12 is formed within a film thickness range that does not completely fill the first groove portion 21, and is formed with a film thickness of, for example, about 400 to 600 nm. By this step # 5, the first insulating film 12 is formed on the upper layer of the first sensor electrode 10 and the ground electrode 11, the bottom surface and the inner side wall in the first groove portion 21, and the bottom surface and the inner side wall are the first insulating film. The groove portion surrounded by 12 (hereinafter referred to as “second groove portion 22”) is formed with a hole diameter of about 0.1 to 0.5 μm, for example.

  As described above, since the etching depth dug down in step # 4 is equal to or greater than the thickness of the first insulating film 12 formed in step # 5, it is formed after the first insulating film 12 is formed. The bottom surface of the second groove portion 22 is positioned lower than the bottom surface of the first sensor electrode 10.

  In the present embodiment, it is assumed that the gap between the ground electrode 11 and the first sensor electrode 10 is completely filled with the first insulating film 12 in step # 5 (see A in the figure).

  Next, as shown in FIG. 2D, the first insulating film 12 formed on the ground electrode 11 is etched so that the upper surface of the ground electrode 11 is exposed, and a contact hole 23 (hereinafter, referred to as “contact hole 23”) is formed. (Described as “third groove 23”) (step # 6).

  Next, as shown in FIG. 2E, a conductive film made of, for example, a W film (hereinafter referred to as “second conductive film”) is formed by a CVD (Chemical Vapor Deposition) method, and then the first By flattening by CMP until the surface of the insulating film 12 is exposed, the second groove portion 22 and the third groove portion 23 are filled with the second conductive film (step # 7). In step # 7, the second sensor electrode 13 is formed by filling the second groove 22 with the second conductive film, and the contact electrode 14 is filled by filling the third groove 23 with the second conductive film. Is formed. In this way, the sensor 1 of the present invention is formed.

  FIG. 4 is a schematic cross-sectional view showing a state where a finger, which is an object to be detected, is placed on the sensor 1 of the present invention. FIG. 4 also shows only the upper layer portion of the metal wiring 15 as in FIG.

  When the finger 18 as the detection object is placed on the detection surface, the convex portion of the finger 18, the second sensor electrode 13, and the contact electrode 14 have the same potential. Since the finger 18 is grounded, the second sensor electrode 13 and the contact electrode 14 also show a ground potential.

  At this time, the sensing capacitance Cf formed between the convex portion of the finger 18 and the first sensor electrode 10 is in addition to the capacitance Cftop between the upper surface of the first sensor electrode 10 and the finger 18 thereabove, This is a parallel capacitance of the capacitance Cfside between the side surface of the first sensor electrode 10 and the side surface of the second sensor electrode 13. In other words, the capacitive component formed between the finger 18 and the first sensor electrode 10 is determined by the facing area between the electrode body constituted by the finger 18 and the second sensor electrode 13 and the first sensor electrode 10. Is done. For this reason, sensing capacitance Cf = Cftop + Cfside, and the sensing capacitance can be increased by the amount of capacitance Cfside compared to the conventional configuration.

  Then, as described above, the first groove portion 21 is formed above the metal wiring 15 to reduce the facing area between the first sensor electrode 10 and the metal wiring 15, thereby the metal wiring and the first sensor electrode 10. Can be reduced. In addition, since the first insulating film 12 is completely filled between the first sensor electrode 10 and the ground electrode 11 on the outer periphery thereof, the second sensor electrode 13 is not buried between the first sensor electrode 10 and the first sensor electrode 10. It is possible to prevent a large parasitic capacitance from being generated between 10 and the ground electrode 11.

  According to the sensor of the present invention configured as described above, in addition to the capacitance between the conventional sensor electrode and the object to be detected above, due to the presence of the second sensor electrode 13 embedded in the groove, the first sensor electrode 13 Capacitance formed at the facing portion between the side surface of the sensor electrode 10 and the side surface of the second sensor electrode 13 can also be used. For this reason, since the change in the distance between the object to be detected and the detection surface can be sufficiently reflected in the change in the sensing capacitance Cf, it is possible to detect unevenness on the surface having a fine interval by downsizing the sensor electrode. it can.

  Further, as in the structure of the above-described embodiment, a groove is formed on the inner side of the outer periphery of the first sensor electrode 10, and the second sensor electrode 13 is realized in the groove with a high hardness W. There is also a secondary effect that the strength of can be improved.

  Another embodiment will be described below.

  <1> In the above-described embodiment, the separation between the ground electrode 11 and the first sensor electrode 10 is narrower than the hole diameter of the first groove portion 21, and the ground electrode is formed by the step of forming the first insulating film 12 according to Step # 5. 11 and the first sensor electrode 10 are completely filled, but the method of the present invention is used even when it is necessary to widen the distance between the ground electrode 11 and the first sensor electrode 10 due to layout constraints. It is possible to use.

  In the above case, as shown in FIG. 5A, the space 28 between the ground electrode 11 and the first sensor electrode 10 is a gap 29 formed in the ground electrode 11 at the end of the patterning process in Step # 3. It will be large enough compared to Thereafter, as shown in FIG. 5B, the first groove portion 21 and the groove portion 24 (hereinafter referred to as “fourth groove portion 24”) are formed by the etching process in Step # 4. Thereafter, as shown in FIG. 5C, the first insulating film forming step according to Step # 5 has a bottom surface and an inner wall surrounded by the first insulating film 12 in the first groove portion 21. 22 is formed, and in the fourth groove portion 24, a groove portion 25 (hereinafter referred to as “fifth groove portion 25”) whose bottom surface and inner wall are surrounded by the first insulating film 12 is also formed.

  When the second conductive film is formed in step # 7, the inside of the second groove portion 22 is filled with the second conductive film, and the second conductive film 18 is also formed on the bottom surface and the inner wall of the fifth groove portion 25. It is formed. Thereafter, as shown in FIG. 5D, a photoresist 19 is formed in a portion other than the fifth groove portion 25. Thereafter, the second conductive film 18 formed in the fifth groove 25 is removed by etching using the photoresist 19 as a mask, and then the groove is filled with an insulating film. Thereby, even when the separation between the ground electrode 11 and the first sensor electrode 10 is wide, the parasitic capacitance between the ground electrode 11 and the first sensor electrode 10 can be reduced.

<2> In the above-described embodiment, the case where SiO ₂ is used for the interlayer insulating film 16 and SiN is used for the first insulating film 12 has been described as an example, but of course the sensor of the present invention is limited to these materials. It is not something. In other words, by applying the technique of Patent Document 2 and using a material having a higher dielectric constant than the material of the interlayer insulating film 16 as the first interlayer insulating film 12, the metal wiring 16 and the first sensor are compared with the sensing capacitance. The parasitic capacitance with the electrode 10 can be further suppressed. However, as described above, in the case of the sensor of the present invention, the provision of the second sensor electrode 13 in the groove formed in the first sensor electrode 10 has the effect of sufficiently increasing the sensing capacity. As described in Document 2, the influence of parasitic capacitance can be greatly suppressed without necessarily using an insulating material whose dielectric constant differs greatly between the upper layer and the lower layer of the sensor electrode.

  <3> In the above embodiment, the bottom surface of the second sensor electrode 13 is formed at a position deeper than the bottom surface of the first sensor electrode 10, but the bottom surface of the second sensor electrode 13 is the first sensor. Even if it is formed at a position higher than the bottom surface of the electrode 10, the sensing capacity can be increased as compared with the conventional configuration, and the same effect can be realized. However, in order to further increase the sensing capacity, it is preferable to form the bottom surface of the second sensor electrode 13 at a position deeper than the bottom surface of the first sensor electrode 10 as in the above-described embodiment.

  <4> In the above-described embodiment, the first sensor electrode 10 is formed in a rectangular shape, the groove 21 is formed in a part thereof, the first insulating film 12 is formed on the inner wall of the groove 21, and further By forming the second sensor electrode 13 on the inner side, the side surface of the second sensor electrode 13 and the side surface of the first sensor electrode 10 face each other through the first insulating film 12 in the groove portion 21. However, the structure described above is merely an example, and each sensor unit 20 includes a first sensor electrode 10 and a second sensor electrode 13 that is not electrically connected thereto, and the side surfaces of both sensor electrodes are first insulated. The structure is not limited to the above structure as long as the structure faces the film 12.

  At this time, in order to secure a large capacitance Cfside between the side surface of the first sensor electrode 10 and the side surface of the second sensor electrode 13, the opposing area of the side surfaces of both sensor electrodes may be increased. Since the opposing area of the side surfaces of both electrodes increases in proportion to the length of the outer periphery of the first sensor electrode 10, the length of the outer periphery of the first sensor electrode 10 remaining in each sensor unit 20 in step # 3. However, the first conductive film may be patterned with a complicated patterning shape that can be secured for as long as possible. In this case, in order to make the electrode shape between the sensor units as uniform as possible, the position and shape of the gap 29 formed in each sensor unit 20 may be formed vertically and horizontally symmetrical on a plane parallel to the detection surface. preferable.

  The present invention can be applied to a capacitive sensor that places an object to be detected on a detection surface and measures the uneven pattern of the object to be detected, and can be applied to, for example, a fingerprint sensor.

Schematic plan view of a capacitive sensor according to the present invention Schematic cross-sectional structure diagram in each step when manufacturing a capacitive sensor according to the present invention The flowchart which shows the manufacturing process at the time of manufacturing the electrostatic capacitance type sensor which concerns on this invention in process order. Schematic cross-sectional structure diagram of a capacitive sensor according to the present invention Schematic cross-sectional structure diagram in each step in another embodiment when manufacturing a capacitive sensor according to the present invention Schematic plan view of a conventional capacitive sensor Part of a schematic cross-sectional view of a conventional capacitive sensor

Explanation of symbols

1: Capacitive sensor according to the present invention 10: First sensor electrode 11: Ground electrode 12: Insulating film (first insulating film)
13: Second sensor electrode 14: Contact electrode 15: Metal wiring 16: Interlayer insulating film 18: Second conductive film formed in the fifth groove 19: Photoresist 20: One of the capacitive sensors according to the present invention Sensor part 21: Groove part (first groove part)
22: 2nd groove part 23: 3rd groove part 24: 4th groove part 25: 5th groove part 29: Cavity part 100: One sensor part of the conventional capacitive sensor 101: Conventional sensor electrode 110: Conventional electrostatic capacity Type sensor

Claims (9)

A capacitance type sensor that detects the form of the surface of an object to be detected,
Comprising a plurality of sensor units arranged on a detection surface that is close to or in contact with the surface of the object to be detected;
Each sensor unit is
A first sensor electrode formed to recede downward from the detection surface;
A second sensor electrode having an upper end surface exposed to the detection surface;
An upper layer of the first sensor electrode, and a first insulating film formed between the first sensor electrode and the second sensor electrode and constituting a part of the detection surface;
A capacitive sensor, wherein a side surface of the first sensor electrode and a side surface of the second sensor electrode are opposed to each other with the first insulating film interposed therebetween.   The capacitive sensor according to claim 1, wherein a bottom surface of the second sensor electrode is formed at a position deeper than a bottom surface of the first sensor electrode.   The capacitance type sensor according to claim 1, wherein each sensor unit is surrounded by a ground electrode for ground connection in a plane parallel to the detection surface. In each of the sensor units,
The said ground electrode is formed so that the outer peripheral part of the said 1st sensor electrode may be enclosed, The said 2nd sensor electrode is formed inside the outer peripheral part of the said 1st sensor electrode, The Claim 3 characterized by the above-mentioned. The capacitance type sensor described. It is a manufacturing method of the capacitance type sensor according to any one of claims 1 to 4,
Forming a first conductive film on the interlayer insulating film and then performing a patterning process to expose the interlayer insulating film in a predetermined region and to form a plurality of the first sensor electrodes;
A second step of forming the first trench by digging the exposed interlayer insulating film by a predetermined thickness in the depth direction after the first step;
After the second step, a third step of forming the first insulating film on the entire surface with a film thickness within a range that does not completely fill the first groove portion, and forming a second groove portion;
And a fourth step of forming the second sensor electrode by filling the second groove with a second conductive film after the third step is completed. . Before starting the first step, including a fifth step of forming a metal wiring in a predetermined region, and a sixth step of forming the interlayer insulating film on an upper layer of the metal wiring,
In the first step, a part of the first conductive film located in the upper region of the metal wiring is removed, so that a rectangular shape with the extending direction of the metal wiring as a longitudinal direction is formed in the upper region of the metal wiring. 6. The method of manufacturing a capacitive sensor according to claim 5, wherein a plurality of the first sensor electrodes having openings are formed. In the first step, in addition to the first sensor electrode, a ground electrode for ground connection separated from the outer peripheral portion of the first sensor electrode is formed in a boundary region of each sensor unit,
After the completion of the third step and before the start of the fourth step, a part of the first insulating film in the upper layer of the ground electrode is etched to form a third groove so that the upper surface of the ground electrode is exposed. Having a seventh step,
7. The contact electrode that is electrically connected to the ground electrode is formed by filling the third groove with the second conductive film in the fourth step. 8. A method for manufacturing a capacitive sensor. In the first step, patterning is performed so that a distance between the first sensor electrode and the ground electrode is shorter than a hole diameter of the first groove portion,
In the second step, a fourth groove is formed by digging down the interlayer insulating film exposed between the first sensor electrode and the ground electrode in the depth direction,
The method of manufacturing a capacitive sensor according to claim 7, wherein in the third step, the fourth groove is completely filled with the first insulating film. In the first step, patterning is performed so that a distance between the first sensor electrode and the ground electrode is longer than a hole diameter of the first groove portion,
In the second step, a fourth groove is formed by digging down the interlayer insulating film exposed between the first sensor electrode and the ground electrode in the depth direction,
In the third step, the fourth groove portion is not completely filled, and the first insulating film is formed on the bottom surface and the inner wall of the fourth groove portion, so that the first insulating film is formed in the fourth groove portion. Forming an enclosed fifth groove,
In the fourth step, the second groove is not completely filled in the fifth groove, and the second conductive film is formed on the bottom surface and the inner wall of the fifth groove,
The method of manufacturing a capacitive sensor according to claim 7, further comprising an eighth step of removing the second conductive film formed in the fifth groove portion by etching after the fourth step. .

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