JP2006014838A - Electrostatic capacity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve accuracy or sensitivity in detection by increasing the rate of change in capacity of an electrostatic capacity sensor. <P>SOLUTION: The electrostatic capacity sensor 10 comprises detection row wiring 34 connected to row wiring 14, detection column wiring 37 connected to column wiring 17, a first dielectric layer 15 coating the detection line wiring 34, and a second dielectric layer 16 coating the detection column wiring 37. The dielectric constant of the second dielectric layer 16 is set larger than that of the first dielectric layer 15. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique suitable for use in a capacitance sensor, a touch pad, and the like for measuring fine irregularities of a measurement object.

As a sensor for detecting fine irregularities on the surface of the object to be measured pressed against the detection surface, for example, Patent Document 1 is known as a sensor for measuring a change in capacitance between an electrode arranged in an array and the object to be detected. It has been.
In addition, as a touch pad for measuring the contact position of a finger or the like from the change in capacitance, it is assumed that the row wiring and the column wiring intersect with each other through an insulator, and the capacitance at the intersection changes depending on the object to be detected. Patent document 2 is known.
JP 2000-213908 A Japanese Translation of National Publication No. 09-51086

However, the technique described in Patent Document 1 requires a transistor to select a detection electrode. For example, when detecting a fine shape such as a fingerprint, it is necessary to dispose detection electrodes and switching transistors continuously at the pitch of 100 μm or less and throughout the entire detection range, and these are integrated on a semiconductor substrate. It is essential. Therefore, there is a problem that the cost increases when a detector having a large area is constructed.
Moreover, in the technique of Patent Document 2, it is necessary to increase the capacitance at the wiring intersection in order to ensure a certain degree of detection sensitivity. At this time, since it is necessary to increase the wiring width in order to increase the capacitance, the wiring pitch cannot be reduced. As a result, this technique has a problem that a sensor structure for detecting a fine structure such as a fingerprint with high sensitivity cannot be realized.
In addition, when detecting a change in capacitance, if the amount of change is too small with respect to the initial capacitance, the change in capacitance cannot be detected, so there has been a demand for an electrostatic detection sensor that is easier to detect. .

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a capacitance sensor that can improve detection sensitivity at low cost.

The capacitance sensor of the present invention includes a row wiring extending in a first direction with a plurality of conductors arranged in parallel on an insulating substrate, and a column wiring extending in a second direction intersecting the first direction with the plurality of conductors arranged in parallel. A capacitance sensor that detects the approach of a detected conductor based on a change in capacitance formed by the row wiring and the column wiring,
A detection row wiring connected to the row wiring;
A detection column wiring provided on the detection row wiring with a first dielectric layer interposed therebetween, laminated on the first dielectric layer and connected to the column wiring;
A second dielectric layer covering the detection column wiring is provided,
The above problem has been solved by setting the relative dielectric constant of the second dielectric layer to be larger than that of the first dielectric layer.
In the present invention, a detection region defined by a distance between adjacent wirings in the row wiring and the column wiring is provided,
In the detection region, a detection row wiring connected to the row wiring and a detection column wiring connected to the column wiring are provided, and the detection row wiring and the detection column wiring are mutually viewed in plan view. More preferably, it is formed in a comb shape so as to fill the gap.
In the present invention, the detection row wiring and the detection column wiring can be formed in an L shape so as to fill a gap between them in a plan view.
In the present invention, the detection row wirings and the detection column wirings may adopt a spiral shape so as to fill the gaps in plan view.
Further, the detection row wiring and the detection column wiring may be formed in a quadrant shape so as to fill a gap between each other in plan view.
In the present invention, the ratio between the relative dielectric constant ε1 of the first dielectric layer and the relative dielectric constant ε2 of the second dielectric layer is
3 ≦ ε2 / ε1 ≦ 3500
It is desirable that
Further, the first dielectric layer is selected from at least one of SiO ₂ , Si ₃ N ₄ , MgO, Al ₂ O ₃ , acrylic resin, polyimide, and epoxy resin,
The second dielectric layer is made of at least one selected from Ta ₂ O ₅ , ZrO ₂ , HfO ₂ , La ₂ O ₃ , Pr ₂ O ₃ , TiO ₂ , CaTiO ₃ , SrTiO ₃ , and BaTiO _3. Is possible.

  In the capacitance sensor of the present invention, the relative dielectric constant of the second dielectric layer covering the detection column wiring is higher than the relative dielectric constant of the first dielectric layer covering the detection row wiring. The first dielectric layer positioned between the detection row wiring and the detection column wiring when the capacitance is formed in an initial state where the detection target is not positioned on the surface of the capacitance sensor. The capacitance is formed between the detection column wiring and the detected object rather than the relative dielectric constant of the body layer, and the capacitance is changed between the initial capacitance and the detection column wiring and the detected object. By increasing the relative dielectric constant of the second dielectric layer, it is possible to increase the size of the capacitance that changes relative to the initial capacitance, increase the capacitance change rate, and improve detection accuracy or sensitivity. It becomes possible.

In the present invention, the detection row wiring and the detection column wiring are provided in the detection area surrounded by the adjacent row wirings and the adjacent column wirings so as to fill the detection area, thereby detecting It is possible to increase the amount by which the electrostatic capacitance formed by the row wiring and the detection column wiring changes due to the contact of a detected object (detected conductor) such as a finger. Thereby, the sensitivity in each detection cell can be improved, and the resolution at the time of detection without forming a transistor can be improved.
Here, “defined by the distance between wirings” means a range surrounded by row wiring and column wiring, or a range having an area equivalent to the range surrounded by this wiring. A range corresponding to a detection cell that operates by a set of row wiring and column wiring can be used. Further, “so as to fill the detection area” means that the detection wiring facing length is increased as will be described later.
Note that the capacitance sensor of the present invention does not need to change the distance between electrodes (wirings), and can be formed on a glass substrate or the like.

According to the present invention, when the detection row wiring and the detection column wiring fill the detection area, the detection wiring facing length (facing length) between the detection wirings is increased so as to increase the capacitance formed between these wirings. ) Increases so that the change in capacitance can be increased and the detection sensitivity can be improved.
Here, the “detection wiring opposing length (opposite length)” is a direction in which each detection wiring intersects with each other in a portion where the detection row wiring and the detection column wiring face each other to form a capacitance. It means the length dimension of each detection wiring, and the parameter that originally forms the capacitance as a physical quantity is the electrode plate area. Since this is the area for forming the capacitance between the detection wirings stacked in an L-shape, quadrant shape, etc., the actual design parameter can be recognized as the length. Each detection wiring is arranged to increase the length. In this case, the detection wirings (electrodes) forming the electrostatic capacitance are laminated in different layers.

Further, in the present invention, the detection row wiring and the detection column wiring are opposed to the detection wiring which forms the capacitance so as to increase the capacitance formed between these wirings when filling the detection region. By being positioned so that the inter-distance (inter-opposite distance) is decreased, it is possible to increase the change in capacitance and improve detection sensitivity.
Here, the “distance between opposing detection wirings (distance between opposing wirings)” means the distance between the detection row wirings and the detection column wirings in a direction intersecting the aforementioned “detection wiring opposing length (opposite length)”. In this case, the detection wirings (electrodes) forming the electrostatic capacitance are laminated in different layers. In addition, when the detection row wiring and the detection column wiring are formed in different layers, the detection wiring (detection row wiring and detection column wiring) related to actual detection may be configured not to overlap each other in plan view. preferable. This is because if the detection row wiring and the detection column wiring overlap each other like an intersection in Patent Document 2, the capacitance of the overlapping portion does not change due to contact / separation of the detection target (detected conductor). This is because the change in capacitance is small and the detection sensitivity is lowered.

  As shown in FIGS. 2 and 12 to 15, the planar pattern of the detection wiring that fills the detection region in the present invention can be comb-like, spiral, L-shaped, quadrant, etc. As a result, it is possible to increase the variation in the capacitance formed between the detection wirings by increasing the “opposing length” and decreasing the “distance between the opposing”. In this case, the detection wirings (electrodes) forming the capacitance can be adapted to a structure in which they are stacked in different layers.

  In addition, the detection column wiring is laminated on the first dielectric layer, thereby reducing the distance between the detection column wiring and the detection object at the time of detection, and between the detection object and the detection column wiring. It is possible to increase the capacity to be formed and increase the rate of change in both detections.

  In the present invention, the ratio between the relative dielectric constant ε1 of the first dielectric layer and the relative dielectric constant ε2 of the second dielectric layer is 3 ≦ ε2 / ε1 ≦ 3500. The capacitance at the time of detection formed by sandwiching the second dielectric layer relative to the initial capacitance formed by sandwiching the one dielectric layer can be made large enough to be detected, and the capacitance change rate at the time of detection Can be increased.

Further, at least one of the first dielectric layers is selected from SiO ₂ , Si ₃ N ₄ , MgO, Al ₂ O ₃ , acrylic resin, polyimide, epoxy resin and the like having a relative dielectric constant of about 10 or less. The second dielectric layer has Ta ₂ O ₅ , ZrO ₂ , HfO ₂ , La ₂ O ₃ , Pr ₂ O ₃ , TiO ₂ , CaTiO ₃ , SrTiO ₃ , BaTiO _{3, etc.} By selecting at least one of those greater than 100, the above ratio of 3 ≦ ε2 / ε1 ≦ 3500 can be realized.

  According to the present invention, the relative dielectric constant of the second dielectric layer covering the detection column wiring is set larger than the relative dielectric constant of the first dielectric layer covering the detection row wiring. As a result, the first dielectric layer positioned between the detection row wiring and the detection column wiring is mainly formed when the capacitance is formed in the initial state where the detection target is not positioned on the surface of the capacitance sensor. A capacitance is formed between the detection column wiring and the object to be detected rather than the relative dielectric constant, and is located between the detection column wiring and the detection object that has a capacitance that changes with respect to the initial capacitance. By increasing the relative dielectric constant of the dielectric layer, the magnitude of the changing capacitance is increased with respect to the initial capacitance, and the capacitance change rate is increased, thereby improving the detection accuracy or sensitivity. Can do.

Hereinafter, an embodiment of a capacitance sensor according to the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view showing an equivalent circuit of a capacitance sensor in the present embodiment, FIG. 2 is an enlarged plan view of a main part of the capacitance sensor of the present invention, and FIG. 3 is a capacitance of the present invention. It is a principal part expanded sectional view of a sensor. In the figure, reference numeral 10 denotes a capacitance sensor.

  The electrostatic sensor 10 according to the present embodiment is adapted as a fingerprint sensor, and a plurality of row wirings 14 arranged in parallel in the first direction X on a glass substrate 13 and an insulating film covering the row wirings 14. 15 and a plurality of column wirings 17 arranged in parallel in the second direction Y intersecting the first direction X and the insulating film 16 covering the row wirings 17. A region surrounded by the row wirings 14 and the column wirings 17 is a detection region 30.

The row wirings 14 are made of, for example, an ITO film having a thickness of 0.1 μm, and 200 lines are formed on a glass substrate 13 having a thickness of 0.7 mm at a pitch of 30 to 100 μm, for example, 50 μm. The insulating film 15 may be any film in which SiN _x such as Si ₃ N ₄ is laminated. Each row wiring 14 is connected to a capacitance detection circuit 22 that detects electrostatic capacitance.
The column wiring 17 is made of, for example, a 0.1 μm thick lTO film, and 200 lines are formed on the insulating film 15 at a pitch of 30 to 100 μm, for example, 50 μm. Each column wiring 17 is connected to a column selection circuit 23. Such a column selection circuit 23 connects all except the column wiring 17 selected at the time of capacitance measurement to the ground side.

  In the detection area 30, detection row wirings 34 and detection column wirings 37 are provided so as to fill the detection area 30. The detection row wiring 34 is provided at the same height as the row wiring 14, and the detection column wiring 37 is provided at the same height as the column wiring 17. Here, the height means that they are in the same layer on the glass substrate 13, and the detection row wiring 34 is provided in the insulating film (first dielectric layer) 15 with the row wiring 14. Further, the detection column wiring 37 means that the column wiring 17 is provided in the insulating film (second dielectric layer) 16.

  The detection row wiring 34 and the detection column wiring 37 are opposed to each other between the detection wirings 34 and 37 so as to increase the capacitance formed between the wirings 14 and 17 when the detection region 30 is filled. Are arranged so as to increase, and the distance between the faces forming the capacitance is reduced. Specifically, the planar pattern of the detection wirings 34 and 37 filling the detection region 30 can be comb-shaped as shown in FIG. Thus, by forming the detection wirings 34 and 37 in a comb shape so as to fill the gaps in plan view, the “opposite length” between the detection wirings 34 and 37 is increased and the “inter-opposite distance” is increased. It is possible to increase the fluctuation of the capacitance formed between the detection wirings 34 and 37.

The insulating film (first dielectric layer) 15 is provided so as to cover the detection row wiring 34, and a detection column wiring 37 is provided on the insulating film 15 so as to cover the detection column wiring 14. An insulating film (second dielectric layer) 16 is provided.
The relative dielectric constant ε2 of the upper insulating film 16 is set larger than the relative dielectric constant ε1 of the lower insulating film 15, and specifically, the ratio of the relative dielectric constant ε1 of the insulating film 15 to the insulating film 16 is set. The ratio to the dielectric constant ε2 is
3 ≦ ε2 / ε1 ≦ 3500
It is set to be in the range.

More specifically, the insulating layer 15 can be made of a material having a relative dielectric constant of about 10 or less, and the insulating layer 16 can be made of a material having a relative dielectric constant of 10 to 100 or more.
The insulating layer 15 is preferably made of at least one selected from SiO ₂ , Si ₃ N ₄ , MgO, Al ₂ O ₃ , acrylic resin, polyimide, epoxy resin, and more preferably SiO ₂ , Si ₃ N. Can consist of _four .
The insulating layer 16 is preferably made of at least one selected from Ta ₂ O ₅ , ZrO ₂ , HfO ₂ , La ₂ O ₃ , Pr ₂ O ₃ , TiO ₂ , CaTiO ₃ , SrTiO ₃ , BaTiO _{3 and the} like. More preferably, it can be made of TiO ₂ .

  When a finger or the like as the conductor to be detected F is brought into contact with the surface of the capacitance sensor 10 as described above, in the pixel corresponding to the concave portion of the fingerprint, as shown in FIG. The capacitance formed by the above and the like does not change much from the initial capacitance value where the detected conductor F is not in contact. On the other hand, in the pixel corresponding to the convex portion of the fingerprint, as shown in FIG. 5, some of the electric lines of force d of the electric lines of force D from the detection column electrodes 37 toward the detection row electrodes 34 are finger points. As a result, the capacitance formed between the detection wirings 34 and 37 is smaller than the initial capacitance value where the detection conductor F is not in contact.

  The capacitance sensor 10 of the present embodiment has a configuration as described above, and a detection region corresponding to an intersection 21 where the row wirings 14 and the column wirings 17 intersect as shown in the equivalent circuit shown in FIG. The capacitance change at 30 can be detected by the capacitance detection circuit 22. In this way, by detecting changes in the capacitance of the large number of detection regions 30 that occur when a fine uneven surface is pressed against the surface of the insulating film 16, the shape of the uneven surface of the object F to be measured is represented by signal data. Can be output as

Here, a capacitance (initial capacitance) in an initial state in which the ratio detection conductor (detected object) F does not contact the sensor surface is formed between the detection row wiring 34 and the detection column wiring 37, and the ratio detection conductor F is A change capacitance (capacitance change) in contact with the sensor surface is formed between the detection column wiring 37 and the detected conductor F. Therefore, the initial capacitance depends on the relative dielectric constant ε1 of the insulating film 15 located between the detection row wiring 34 and the detection column wiring 37, and the changed capacitance is located between the detection column wiring 37 and the relative detection conductor F. It depends on the relative dielectric constant ε2 of the insulating film 16 to be processed.
In this embodiment, by setting the relative dielectric constant ε2 of the insulating film 16 to be larger than the relative dielectric constant ε1 of the insulating film 15, the change capacity is increased with respect to the initial capacity, and the capacity change rate is increased. It becomes possible to improve detection accuracy or sensitivity.

  For example, a circuit as shown in FIG. 6 is used as the capacitance detection circuit 22, and at the time of measurement, all except the column wiring 17 selected by the column selection circuit 23 are connected to the ground side, and on the same row wiring 14. All of the capacitances not measured are input in parallel to the measurement system as parasitic capacitance, but can be canceled by connecting the electrode on the opposite side of the parasitic capacitance to the ground side. . With such a configuration, it is possible to detect a minute uneven surface, that is, to detect a minute change in capacitance with high accuracy. As a result, cost reduction can be achieved without using expensive materials such as semiconductor substrates, and even if the dot pitch is reduced, the initial capacitance of each dot and the amount of change in capacitance can be increased to increase the sensitivity of the sensor. Can be improved.

Thus, was varied the relative dielectric constant of the insulating film 16 and the insulating film 15 is, for example, in FIG. 6, the output-side voltage V _out on the input side voltage V _in,
V _out = (ΔCx / Cf) V _in (1)
In order to enable output signal processing in this state,
V _out ≧ 100 mV (2)
Is preferably, this time, the input voltage _{V in} and the initial capacitance Cf and the _V in = 3.3V
Cf = 1pF (3)
The capacity change is
ΔCx = 30 fF (4)
It becomes. Here, when the initial capacitance Cf is suppressed to 100 fF or less, the amount of change needs to be 30% or more in order to obtain Equation (4). Therefore, to satisfy this condition,
ε2 / ε1 ≧ 3 (5)
Is necessary.
Thereby, it is possible to sufficiently detect the capacitance at the time of detection formed with the insulating film (second dielectric layer) 16 sandwiched between the initial capacity formed with the insulating film (first dielectric layer) 15 interposed therebetween. It is possible to increase the capacity change rate at the time of detection.

  Such a capacitance sensor 10 is not limited in its application, but as an example in which the capacitance sensor 10 is applied to a fingerprint sensor, for example, as shown in FIG. Can be applied. In recent years, it has been considered to make payments with the mobile phone 26 or the like, but by forming the capacitance sensor 10 on the mobile phone 26, the fingerprint pressed against the capacitance sensor 10 can be accurately detected. The owner can be correctly authenticated by checking with fingerprint data registered in advance. FIG. 7 shows an example in which the mobile phone 26 is formed on a display screen 26 a such as a liquid crystal display. In this case, the wirings 14 and 17 and the detection wirings 34 and 37 are formed of transparent electrodes, and the capacitance sensor (fingerprint sensor) 10 is of a light transmission type, so that the fingerprint sensor 10 is disposed in a portion other than the display screen 26a. There is no need to do so, and miniaturization can be achieved.

Hereinafter, a second embodiment of a capacitance sensor according to the present invention will be described with reference to the drawings.
FIG. 8 is an enlarged plan view of the main part of the capacitance sensor of the present embodiment, and FIG. 9 is an enlarged cross-sectional view of the main part of the capacitance sensor of the present embodiment.

The capacitance sensor 10 of the present embodiment is different from the above-described embodiment in that a ground wiring A connected to the sensor surface 10a is provided.
That is, as shown in FIGS. 8 and 9, the ground wiring A has the same height as the ground wiring 33 provided at the same height as the row wiring 14 and the detection row wiring 34, and the same height as the column wiring 17 and the detection column wiring 37. It has a ground wiring 35 provided at this position and a ground wiring 36 provided on the sensor surface 10a. The ground wiring 33 is provided in parallel with the row wiring 14 and is at a ground potential. The ground wires 35 and 36 are connected by through holes so as to be electrically connected to the ground wires 33 and 35 on the glass substrate 13 side, respectively.

  According to the present embodiment, since the ground wiring A is provided, the detected conductor F in contact with the sensor surface 10a and the ground wiring A can be set to the same potential (ground potential). Is forcibly set to the ground potential, the capacitance change between the detection wirings 34 and 37 is increased, and the electrical noise from the detected conductor F is reduced, thereby enabling stable measurement.

Hereinafter, a third embodiment of a capacitance sensor according to the present invention will be described with reference to the drawings.
FIG. 10 is a schematic plan view of the capacitance sensor of this embodiment.

In the present embodiment, the difference from each of the embodiments described above is that there are a fine portion S in which the detection regions 30 are provided continuously and a non-definition portion T in which the detection regions 30 are provided discontinuously, This is the point where the fine part S can be switched in the operating state.
In the capacitance sensor 10 of the present embodiment, in FIG. 10, the fine portion S is located near the center, and the detection regions 30 are provided densely and continuously. Further, the non-definition part T is provided around the fine part S so that the detection region 30 becomes rough.
Further, in the fine portion S, the spacing between the wirings 14 and 17 is provided at a pitch of 256 μm, and each 256 wires is provided, and in the non-definition portion T, the spacing between the wirings 14 and 17 is 3.2 mm. It is provided one by one.

  In this embodiment, in the fine part S where the detection areas 30 are continuous, the entire operation state (authentication state) in which all the detection areas 30 are operated, and the detection area in the non-definition part T where the detection areas 30 are discontinuously arranged It is possible to switch between a partial operation state (coordinate input state) in which only the detection region 30 equal to the density (arrangement interval) 30 is in an operating state and the other detection regions 30 are in an inactive state. Specifically, the non-definition part T is used as a touch pad as a pointing device, and a part thereof is a fine part S that can be detected as a fingerprint sensor.

  In such a capacitance sensor 10, the operation of the fine part S is switched between the fingerprint sensor and the touch pad by a switching circuit unit (not shown). Specifically, the output of the non-definition part T is to detect the movement of the finger (detected conductor) on the sensor surface, and the fine part S is not in the coordinate input state for detecting this movement. In the pattern recognition state (authentication state) in which only signals from the detection region 30 having the same density as the fine portion T are output and in which fingerprint recognition is performed, all detection regions of the fine portion S are detected. 30 is set to output a signal from 30.

Further, the operation state switching of the fine part S is performed as shown in FIG.
First, as shown in S1, in a notebook personal computer or the like, when starting or canceling the standby screen, as shown in S2, the operation mode of the fine unit S is changed to the fingerprint sensor (authentication state) by the switching circuit unit. Set to Next, as shown in S3, a LOGIN screen is displayed on the screen, and a selection screen for selecting password authentication by fingerprint authentication or a keyboard is displayed. Here, when the input by the keyboard or the like is selected in S4, the operation mode is set to the touch pad (coordinate input state) as in S5, and the password input is waited. If fingerprint authentication is selected in S4, the authentication operation is entered in the fine part S as shown in S6. If it is confirmed that the fingerprint is the person's fingerprint, the fine part is shown in S7. The operation mode of S is switched to the touch pad (coordinate input state), and as shown in S8, LOGIN is completed and a normal operation is possible.

  In the present embodiment, it is possible to provide a fine portion S on a part of the touch pad T and use the fine portion S as a fingerprint sensor. Accordingly, the fingerprint sensor and the touch pad can be formed integrally, and high-definition detection as the fingerprint sensor and high-speed scan detection as the touch pad can be simultaneously performed.

In the above-described embodiment, the arrangement pattern of the detection electrodes 34 and 37 in the detection region 30 is not limited to the comb-like shape, but the spiral shape shown in FIG. 12, the L shape shown in FIG. 13, and the quadrant shown in FIG. A shape or the like is possible. In addition, as a comb, a region surrounded by the row wiring 14 and the column wiring 17 is not used as a detection region, but a region straddling the row wiring 14 may be used as the detection region 30 as shown in FIG. Is possible.
In any case, it is possible to increase the “opposite length” of the detection wirings 34 and 37 and decrease the “distance between the opposing surfaces” to increase the variation in capacitance formed between the detection wirings. Any pattern is acceptable.

  Furthermore, the electrostatic capacity sensor of the present invention can be applied as a seal reading device or the like as shown in FIG. 16 in addition to the fingerprint sensor. That is, instead of the detected conductor (finger) F, even when detecting the shape of the non-conductive detected object (seal) F2, the surface of the capacitance sensor 10 in each of the above embodiments is contacted. The conductive film F1 having the conductive film F0 or a conductive film that shakes flexibility, such as conductive rubber (not shown), is separately disposed, and a seal is placed on the film to form a shape (a seal). ) Reading can be performed.

Examples of the present invention will be described.
The change rate of the capacitance with respect to the detection region in the capacitance sensor having the same structure as that of the first embodiment was calculated. The values of the specifications of the detection wiring are shown below.

a) Influence of gap and water Detection wiring width dimension: 3 μm
Detection wiring length: 42 μm
Lower insulating layer (first dielectric layer): SiN _x
Lower insulating layer (first dielectric layer) film thickness: 300 nm
Lower insulating layer (first dielectric layer) relative dielectric constant ε1: 7
Upper insulating layer (second dielectric layer): optional Upper insulating layer (second dielectric layer) film thickness: 400 nm
Upper insulating layer (second dielectric layer) relative dielectric constant ε2: 1 to 100

Detection area: 50 μm square Detection wiring: ITO
Detection wiring film thickness: 100 nm
Detection wiring width: 3μm

Specific permittivity of glass substrate εG = 4
Water relative dielectric constant: 80

In the detection region as described above, the relative dielectric constant ε1 of the lower insulating film 15 as shown in FIG. 3 is fixed, and the relative dielectric constant ε2 of the upper insulating film 16 is changed to calculate the change rate of the capacitance. did. Table 1 shows the results and the rate of change when the surface has water.

From the results shown in Table 1, in order to increase the capacitance change rate to 30% or more in the present invention, the ratio of the relative dielectric constant ε1 of the lower insulating film 15 to the upper insulating film ε2 is 3 ≦ ε2 / ε1.
It is preferable that

b) Next, the capacitance change rate with respect to the change in the thickness of the upper and lower insulating films was calculated.
Detection wiring width dimension: 3μm
Detection wiring length: 42 μm
Lower insulating layer (first dielectric layer): TiO ₂ and SiN _x
Lower insulating layer (first dielectric layer) film thickness: 300 nm
Lower insulating layer (first dielectric layer) relative dielectric constant ε1: 7
Upper insulating layer (second dielectric layer): TiO ₂
Upper insulating layer (second dielectric layer) film thickness: 400 nm
Upper insulating layer (second dielectric layer) relative dielectric constant ε2: 65

Detection area: 50 μm square Detection wiring: ITO
Detection wiring film thickness: 100 nm
Detection wiring width: 3μm

Specific permittivity of glass substrate εG = 4
Water relative dielectric constant: 80

The results are shown in Tables 2 and 3.

  From the results in Table 2, even when the same dielectric is used for the upper and lower insulating films, the capacitance change can be increased by using a dielectric having a high relative dielectric constant, and the capacitance change rate can be increased by widening the gap G. Can be raised. However, in practice, it is preferable to reduce the parasitic capacitance and increase the volume change rate due to the performance of the detection circuit (amplifier circuit) and the influence of ambient noise. In addition, the volume change rate can be increased by widening the gap G. However, since the influence of water on the sensor surface increases, it is preferable that the gap G is kept as small as possible. Here, the state in which the sensor surface has water is considered to be a state in which the film thickness of the upper insulating film in the initial state is increased. Therefore, as shown in the results of Table 3, the relative dielectric constant ε2 of the upper insulating film is made larger than the relative dielectric constant ε1 of the lower insulating film, so that the same dielectric is used for the upper and lower insulating films. In addition, the parasitic capacitance can be reduced, the capacitance change can be increased, and the gap G can be reduced. Thus, by selecting the dielectric (relative permittivity) of the upper and lower insulating films and controlling the gap G, the capacitance change / change rate can be controlled to a value suitable for the intended use.

c) Next, the capacity change rate with respect to the film thickness change of the upper and lower insulating films was calculated.
Detection wiring width dimension: 3μm
Detection wiring length: 42 μm
Lower insulating layer (first dielectric layer): SiN _x
Lower insulating layer (first dielectric layer) film thickness: 300 nm
Lower insulating layer (first dielectric layer) relative dielectric constant ε1: 7
Upper insulating layer (second dielectric layer): TiO ₂
Upper insulating layer (second dielectric layer) film thickness: 400 nm
Upper insulating layer (second dielectric layer) relative dielectric constant ε2: 65

Detection area: 50 μm square Detection wiring: ITO
Detection wiring film thickness: 100 nm
Detection wiring width: 3μm

Specific permittivity of glass substrate εG = 4
Water relative dielectric constant: 80

The results are shown in Tables 4-10.

From the above results and the preferable value of dielectric strength is 10 kV / mm, it is preferable that the lower insulating film (first dielectric layer) has a thickness sufficiently satisfying the dielectric strength. It is preferably about 3 μm.
The upper insulating film (second dielectric film) has a thickness that functions as a passivation film and is about 0.1 μm to 3 μm because the capacitance change amount and the rate of change decrease as the film thickness increases. preferable.

  It should be noted that the contents of the present invention such as the detection wiring material and film thickness according to the present invention can also be applied to the touchpad described in Patent Document 2.

It is explanatory drawing which shows the equivalent circuit of the electrostatic capacitance sensor which concerns on this invention. It is a principal part enlarged plan view in 1st Embodiment of the electrostatic capacitance sensor which concerns on this invention. It is a principal part expanded sectional view in 1st Embodiment of the electrostatic capacitance sensor of this invention. It is explanatory sectional drawing which shows the operation | movement in 1st Embodiment of the electrostatic capacitance sensor of this invention. It is explanatory sectional drawing which shows the operation | movement in 1st Embodiment of the electrostatic capacitance sensor of this invention. It is an equivalent circuit diagram showing an example of a capacitance detection circuit. It is an external appearance perspective view which shows the mobile telephone provided with the electrostatic capacitance sensor of this invention. It is a principal part enlarged plan view in 2nd Embodiment of the electrostatic capacitance sensor which concerns on this invention. It is a principal part expanded sectional view in 2nd Embodiment of the electrostatic capacitance sensor of this invention. It is a schematic plan view in 3rd Embodiment of the electrostatic capacitance sensor which concerns on this invention. It is a flowchart which shows the operation | movement in 3rd Embodiment of the electrostatic capacitance sensor which concerns on this invention. It is a schematic diagram which shows the plane pattern of the electrostatic capacitance sensor which concerns on this invention. It is a schematic diagram which shows the plane pattern of the electrostatic capacitance sensor which concerns on this invention. It is a schematic diagram which shows the plane pattern of the electrostatic capacitance sensor which concerns on this invention. It is a schematic diagram which shows the plane pattern of the electrostatic capacitance sensor which concerns on this invention. It is a schematic cross section which shows other embodiment of the electrostatic capacitance sensor which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Capacitance sensor, 14 ... Row wiring (wiring), 15 ... 1st dielectric layer (insulating film), 16 ... 2nd dielectric layer (insulating film), 17 ... Column wiring (wiring), 30 ... Detection region 34 ... Detection row wiring (detection wiring) 37 ... Detection column wiring (detection wiring), S ... fine portion, T ... non-fine portion, F ... detected conductor

Claims (7)

A row wiring having a plurality of conductors arranged in parallel on the insulating substrate and extending in the first direction, and a plurality of conductors arranged in parallel and a column wiring extending in the second direction intersecting the first direction, A capacitance sensor that detects the approach of a detected conductor based on a change in capacitance formed by the column wiring,
A detection row wiring connected to the row wiring;
A detection column wiring provided on the detection row wiring with a first dielectric layer interposed therebetween, laminated on the first dielectric layer and connected to the column wiring;
A second dielectric layer covering the detection column wiring is provided,
A capacitance sensor, wherein a relative dielectric constant of the second dielectric layer is set larger than a relative dielectric constant of the first dielectric layer. A detection region defined by a distance between adjacent wirings in the row wiring and the column wiring is provided,
In the detection region, a detection row wiring connected to the row wiring and a detection column wiring connected to the column wiring are provided, and the detection row wiring and the detection column wiring are mutually viewed in plan view. 2. The capacitance sensor according to claim 1, wherein the capacitance sensor is formed in a comb-tooth shape so as to fill the gap. The capacitance sensor according to claim 1, wherein the detection row wiring and the detection column wiring are formed in an L shape so as to fill a gap therebetween in a plan view. 2. The capacitance sensor according to claim 1, wherein the detection row wiring and the detection column wiring are formed in a spiral shape so as to fill a gap therebetween in a plan view. The capacitance sensor according to claim 1, wherein the detection row wiring and the detection column wiring are formed in a quadrant shape so as to fill a gap therebetween in a plan view. The ratio of the dielectric constant ε1 of the first dielectric layer to the dielectric constant ε2 of the second dielectric layer is:
3 ≦ ε2 / ε1 ≦ 3500
The capacitance sensor according to any one of claims 1 to 5, wherein the capacitance sensor is configured as follows. The first dielectric layer is made of at least one selected from SiO ₂ , Si ₃ N ₄ , MgO, Al ₂ O ₃ , acrylic resin, polyimide, and epoxy resin,
The second dielectric layer is made of at least one selected from Ta ₂ O ₅ , ZrO ₂ , HfO ₂ , La ₂ O ₃ , Pr ₂ O ₃ , TiO ₂ , CaTiO ₃ , SrTiO ₃ , and BaTiO _3. The capacitance sensor according to claim 1, wherein

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