JP2006112848A - Capacitance detection device and smart card - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitance detection device capable of highly accurately detecting electrostatic capacitance. <P>SOLUTION: The capacitance detection device 10 is provided with a reference capacitor C<SB>R</SB>having a constant capacitance value; a sensor electrode SE forming capacitance C<SB>F</SB>in-between with an object surface HB; a signal amplification element Tr1 for modulating a drain current on the basis of a gate potential determined by a capacitance ratio between the reference capacitor C<SB>R</SB>and the capacitance C<SB>F</SB>; and a reset element Tr2 for resetting the gate potential of the signal amplification element Tr1 at a ground potential. By resetting the gate potential of the signal amplification element Tr1 belonging to a nonselected row at the ground potential when the shape of the object surface is to be read, highly accurate detection accuracy is secured. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a capacitance detection device that reads a surface shape of an object having fine irregularities such as fingerprints by detecting a capacitance that changes according to the distance from the surface of the object.

FIG. 13 illustrates the operating principle of a conventional electrostatic capacity detection device. The electrostatic capacitance C _F is a variable capacitance in which one electrode is a sensor electrode SE and the other electrode is a human body (for example, a fingertip fingerprint) HB. Here, the potential of the human body HB is the ground potential. The electrostatic capacitance C _F changes according to the unevenness of the fingerprint in contact with the surface of the dielectric film IL. On the other hand, the semiconductor substrate formed in advance a reference capacitor having a fixed capacitance value C _R, a predetermined voltage is applied to these two capacitors connected in series. By doing so, a charge Q corresponding to the unevenness of the fingerprint is generated between the two capacitors. The surface shape of the object is read by detecting this charge Q using a normal semiconductor technology. For example, JP-A-11-118415, JP-A-2000-346608, JP-A-2001-56204, or JP-A-2001-133213 is known as a conventional technique related to a fingerprint sensor.
JP 11-118415 A JP 2000-346608 A JP 2001-56204 A JP 2001-133213 A

  However, since these conventional capacitance detection devices are formed on a single crystal silicon substrate, there is a problem that when the device is used as a fingerprint sensor, the device breaks when the finger is strongly pressed. It was.

  Furthermore, the fingerprint sensor is inevitably required to have a size of about 20 mm × 20 mm depending on its use, and most of the capacitance detection device area is occupied by the sensor electrode. Although the sensor electrode is made on a single crystal silicon substrate, most of the single crystal silicon substrate manufactured by spending enormous energy and labor (lower part of the sensor electrode) serves only as a support. That is, the conventional capacitance detection device is not only expensive, but has a problem that it is formed on a great deal of waste and waste.

  In addition, in recent years, it is strongly pointed out that a personal authentication function should be provided on a card such as a credit card or a cash card to enhance the safety of the card. However, since the conventional capacitance detection device made on a single crystal silicon substrate lacks flexibility, there is a problem that the device cannot be manufactured on a plastic substrate.

  From such a background, it is considered preferable to provide a thin film semiconductor directly on a substrate such as a plastic substrate. However, a thin film semiconductor device formed on a substrate is not as good as a semiconductor device formed on a single crystal silicon substrate, so that a very small change in electric charge that needs to be detected by a fingerprint sensor is observed. There was a problem that it could not be read accurately.

  In view of the above-described circumstances, an object of the present invention is to provide a capacitance detection device capable of detecting a capacitance with high accuracy. That is, it is an object of the present invention to provide an excellent electrostatic capacity detection device that operates stably, can reduce unnecessary energy and labor during manufacture, and can be manufactured other than a single crystal silicon substrate. More specifically, it is an object of the present invention to provide a capacitance detection device that operates favorably using a thin film semiconductor device.

  In order to solve the above problems, the capacitance detection device of the present invention reads the surface shape of the object by detecting the capacitance that changes according to the distance to the object. Output from the capacitance detection elements arranged in M rows and N columns, power supply lines for supplying power to the capacitance detection elements, and capacitance detection elements arranged in the respective columns. N output lines for transmitting signals and M reset lines for resetting the capacitance detection elements arranged in a specific row, each of the capacitance detection elements a) A signal detection element for accumulating electric charge according to capacitance; b) a signal amplification element for amplifying a signal corresponding to the electric charge accumulated by the signal detection element; and c) the signal detection element by a signal from the reset line. Reset element that resets the charge stored in The signal detection element includes a sensor electrode for forming a capacitance with the object, and the signal amplification element includes a source electrode, a drain electrode, and a gate electrode. The reset element is composed of a semiconductor device having a source electrode, a drain electrode, and a gate electrode, and the gate electrode of the signal amplification element, the sensor electrode, and the drain electrode of the reset element are connected, The source electrode of the signal amplification element is connected to the power supply line, the drain electrode of the signal amplification element is connected to the output line, the gate electrode of the reset semiconductor device is connected to the reset line, The source electrode is connected to the power line. By forcibly turning off the signal amplifying elements of the capacitance detection elements arranged in the non-selected rows, the electrostatic capacitance arranged in the selected rows without degrading the detection accuracy of the capacitance detection device. A capacitance detection element can be uniquely selected.

  In addition to the above-described configuration, the capacitance detection device of the present invention further includes a reference capacitor, and the reference capacitor includes a reference capacitor first electrode, a reference capacitor dielectric film, and a reference capacitor first. The capacitance detection device includes a row line for controlling the potential of the reference capacitor first electrode, the reference capacitor first electrode is connected to the row line, and the reference capacitor second electrode May be connected to the gate electrode of the signal amplification semiconductor device, the sensor electrode, and the drain electrode of the reset semiconductor device. By further providing a reference capacitor, the detection accuracy can be stabilized.

  The capacitance detection device of the present invention may be configured such that a ground potential is supplied to the power supply line. When the surface potential of the object is set to the ground potential, supplying the ground potential to the power supply line eliminates the voltage applied to the variable capacitor formed between the sensor electrode in the non-selected row and the object, and is unnecessary. In addition, the charge flow to the sensor electrode can be suppressed even when the capacitance of the variable capacitor changes due to the movement of the object.

  The capacitance detection device of the present invention may further include a guard electrode for making the surface potential of the object and the potential of the sensor electrode substantially the same in addition to the above-described configuration. By further providing the guard electrode, the potential of the object surface and the potential of the sensor electrode (ground potential) can be matched. As a result, the potential difference between the surface of the object and the sensor electrode of the non-selected row becomes zero, and even if the electrostatic capacity changes due to movement of the surface of the object, a large current does not flow through the power supply line.

  The smart card of the present invention includes the capacitance detection device of the present invention. Thereby, a smart card with high fingerprint detection accuracy can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. Each example is for facilitating the understanding of the present invention, and is not intended to limit the present invention. The present invention can be modified and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

  In this embodiment, a thin film semiconductor device made of a metal-insulating film-semiconductor film is used as a capacitance detecting device that reads the surface shape of these objects by detecting the capacitance that changes according to the distance to the object. Manufactured by. A thin-film semiconductor device is usually manufactured on a glass substrate, so that it is known as a technique for manufacturing a semiconductor integrated circuit requiring a large area at a low cost. Specifically, it has recently been applied to a liquid crystal display device or the like. Therefore, when a capacitance detection device adapted for a fingerprint sensor or the like is manufactured by a thin film semiconductor device, it is not necessary to use an expensive substrate made by consuming a great amount of energy such as a single crystal silicon substrate. The device can be manufactured at a low cost without wasting valuable earth resources. In addition, a thin film semiconductor device uses a transfer technique called SUFTLA (see Japanese Patent Application Laid-Open No. 11-312811 or S. Utsunomiya et. Al. Society for Information Display p. 916 (2000)) to make a semiconductor integrated circuit a plastic. Since it can be manufactured on a substrate, the capacitance detection device can also be released from the single crystal silicon substrate and formed on a plastic substrate.

  Now, it is very difficult to manufacture the capacitance detecting device shown in FIG. 13 using a thin film semiconductor device with the current technology of the thin film semiconductor device. Since the charge Q induced between two series-connected capacitors is very small, the charge Q can be accurately read using single crystal silicon LSI technology that enables high-precision sensing. However, the charge Q cannot be read accurately because it is not as good as the single crystal silicon LSI technology and the characteristic deviation between thin film semiconductor devices is large.

FIG. 5 shows a basic operation principle diagram of this embodiment. In the figure, C _F is a capacitance (variable capacitance) formed between the sensor electrode SE and the human body (fingerprint, etc.) HB via the dielectric film IL, and C _R is a reference with a constant capacitance value. capacitance of the capacitor, C _T is the transistor capacitance of the signal amplifying element (semiconductor device) Tr1. Here, a fingerprint is illustrated as an object for reading the surface shape, but the object is not limited to this, and any minute uneven shape can be read. When the human body HB such as a fingertip is brought close to the sensor electrode SE, the capacitance C _F slightly changes according to the uneven shape of the fingerprint (surface shape of the object). When a predetermined voltage is applied to the electrode of the reference capacitor that is not connected to the signal amplifying element, the combined capacitance C _R + C _T + _CF and the variable capacitance are applied to the gate terminal (G in the drawing) of the signal amplifying element Tr1. potential V _G according to the capacitance ratio between C _R is induced, changing the gate potential. In this state, when a predetermined voltage is applied to the drain region (D in the figure) of the signal amplifying element Tr1, the drain current I _ds flowing between the source and drain of the signal amplifying element Tr1 in accordance with the induced gate potential V _G is Significantly modulated. Although the gate electrodes and the like are charge Q is generated in accordance with the potential V _G, since these charges are stored without flowing anywhere, current I _ds is substantially constant. Therefore, the current I _ds can be easily measured by increasing the drain voltage of the signal amplifying element Tr1 or increasing the measurement time, and the surface shape of the object can be measured sufficiently accurately. A signal (current signal or voltage signal) obtained by amplifying the capacitance information of the object is read through the output line.

In order to measure the capacitance of the object, the current I _ds amplified by the signal amplifying element Tr1 may be measured, or the voltage V corresponding to the current I _ds may be measured. The case without the reference capacitor C _R, the reference capacitor C _R to zero, by applying a predetermined voltage source electrode of the signal amplifying element (figure S) or the drain electrode (figure D), the object The same principle works by using the capacitance C _F and the transistor capacitance C _T that change according to the surface shape of the transistor. Hereinafter, will be explained using an example configuration in which the reference capacitor C _R in the present embodiment, without providing the reference capacitor C _R, as described later, the reference capacitor C _R in the transistor capacitance C _T of the signal amplifier element Tr1 It is also effective when used in combination.

FIG. 1 is a circuit configuration diagram of a capacitance detection device 10 according to the present embodiment. The electrostatic capacitance detection device 10, by detecting the electrostatic capacitance C _F, which changes according to the distance to the object, a device for reading surface contours of a target object. The capacitance detection device 10 includes a capacitance detection element 20 arranged in M rows and N columns, a power line PL that supplies power to each capacitance detection element 20, and a capacitance arranged in each column. N output lines OL _j (1 ≦ j ≦ N) for transmitting a signal output from the capacitance detection element 20 and M reset lines RESET for resetting the capacitance detection elements 20 arranged in a specific row. _i (1 ≦ i ≦ M). Each capacitance detection element 20 includes a signal detection element C _F that accumulates charges according to the capacitance C _F , and a signal amplification element Tr1 that amplifies a signal corresponding to the charges accumulated by the signal detection element C _F. comprises a reset device Tr2 for resetting charges accumulated in the signal detecting element C _F by a signal outputted from the reset line rESET _i. The signal detection element _CF includes a sensor electrode SE and a dielectric film IL for forming a capacitance between the signal detection element CF and an object. The signal amplifying element Tr1 includes a semiconductor device including a source electrode, a drain electrode, and a gate electrode. The reset element Tr2 includes a reset semiconductor device including a source electrode, a drain electrode, and a gate electrode. The gate electrode of the signal amplifying element Tr1, the sensor electrode SE, and the drain electrode of the reset element Tr2 are connected. The source electrode of the signal amplifying element Tr1 is connected to the power supply line PL, the drain electrode of the signal amplifying element Tr1 is connected to the output line OL _j, the gate electrode of the reset element Tr2 is connected to a reset line RESET _i, the reset element The source electrode of Tr2 is connected to the power supply line PL. The reference capacitor _CR is composed of a reference capacitor first electrode E1, a reference capacitor dielectric film EI, and a reference capacitor second electrode E2. The reference capacitor first electrode E1 is connected to the row line RL _i (1 ≦ i ≦ M), and the reference capacitor second electrode E2 is a gate electrode of the signal amplification element Tr1, a sensor electrode SE, and a drain electrode of the reset element Tr2. And connected to.

When a predetermined potential is applied to the row line RL _i while an object such as a fingerprint is in contact with or close to the dielectric film IL, the sensor electrode SE is applied to the sensor electrode SE according to the capacitance C _F with the object. A potential V _G is generated. In this embodiment, the potential V _G amplified by the signal amplifier element Tr1 provided in each of the electrostatic capacitance detection elements 20 and converts the current signal or voltage signal. By detecting this current signal or voltage signal, the surface shape of the object can be read.

  Note that in this specification, a source electrode and a drain electrode of a semiconductor device (transistor) are not distinguished for convenience of explanation. One electrode is referred to as a source electrode, and the other electrode is referred to as a drain electrode. Strictly speaking, a relatively low potential is defined as a source electrode in an N-type transistor, and a relatively high potential is defined as a source electrode in a P-type transistor. However, which electrode has a higher potential varies depending on the operating state. Therefore, strictly speaking, the source electrode and the drain electrode can always be interchanged in one transistor. In the present specification, for the purpose of clarifying the description, such strictness is eliminated, and for convenience, one electrode is referred to as a source electrode and the other electrode is referred to as a drain electrode.

In this embodiment, when reading the surface shape of the object, signals are detected from a plurality of capacitance detection elements 20 arranged in a specific row, and all the capacitance detection elements 20 arranged in other rows are reset. To do. Here, the reset means that the signal amplification element Tr1 is forcibly turned off by applying a predetermined voltage to the gate electrode of the signal amplification element Tr1. Since the gate electrode and the sensor electrode of the signal amplification element is connected, a predetermined voltage is applied to the sensor electrode by a reset, excess charge from the capacitance C _F is removed. In the case of the conventional example without the reset element Tr2, the potential of the gate electrode of the signal amplifying element Tr1 is not determined when signals are read from the plurality of capacitance detection elements 20 arranged in a specific row. Thus, the electrostatic capacitance element 20 is not completely turned off, and currents flowing from a plurality of current paths are superimposed on the output line OL _j , and accurate signal detection is difficult. In addition, since a plurality of signal amplifying elements are connected to the output line, the drain capacity of the signal amplifying element in the non-selected row becomes a parasitic capacity at the time of reading, but the drain capacity (drain. (Parasitic capacitance between the gates) becomes very large, which has been a factor in reducing detection sensitivity. On the other hand, according to the present embodiment, the above inconvenience can be solved by resetting all the capacitance detection elements 20 other than the signal reading target. Further, when reading the surface shape of the object, by applying a predetermined voltage to the capacitance C _F , unnecessary accumulated charges can be removed and detection accuracy can be improved.

In order to select the capacitance detection elements 20 arranged in each row, a reset signal is supplied to the reset line RESET _i . The reset signal is a signal for turning on the reset element Tr2. If the reset element Tr2 is an N-type transistor, the reset signal is an H level signal. If the reset element Tr2 is a P-type transistor, the reset signal is an L level signal. When the reset element Tr2 is turned on, the gate electrode and the source electrode of the signal amplifying element Tr1 have the same potential, so that no drain current flows through the signal amplifying element. When the potential of the power supply line PL is set to the ground potential, the potential of the sensor electrode SE arranged in the non-selected column becomes equal to the ground potential. Since the human body HB is at ground potential, no charge is accumulated in the capacitance C _F. Therefore, also vary such as to rapidly capacitance C _F moves the human body HB, a large current is no possibility that flows through the power line PL.

When signals are detected from the plurality of capacitance detection elements 20 arranged in a specific row and the surface shape of the object is read, the reset element Tr2 is turned off and the potential of the row line RL _i is changed. Then, by applying a voltage between the power supply line PL and the output line OL _j, read by amplified by the signal amplifying element Tr1 potential V _G generated to the gate terminal of the signal amplifier element Tr1.

FIG. 3 shows signal waveforms output to the row line RL _i and the reset line RESET _i when the surface shape of the object is read. Now, it is assumed that each capacitance detection element 20 arranged in the i row is selected and each capacitance detection element 20 arranged in the (i + 1) row is in a non-selected state. An i-level reset line RESET _i outputs an H level signal during the reset period, and the reset element Tr2 is turned on. In this state, since the gate potential of the signal amplification element Tr1 is equal to the ground potential, the signal amplification element Tr1 is turned off. On the other hand, an L level signal is output during the reset-off period, and the reset element Tr2 is turned off. An H level signal is output to the row line RL _i in the reading period. Then, a potential V _G determined by the capacitance ratio of the electrostatic capacitance C _F , the reference capacitor C _R, and the transistor capacitance C _T of the signal amplification device is induced at the gate terminal of the signal amplification device Tr1. The signal amplifying element Tr1 modulates the drain current based on the potential V _G, and outputs the electrostatic capacitance information (or unevenness information) amplified signal of the object (current signal or voltage signal) to the output line OL _j. The start of the read period is set slightly later than the start of the reset off period, and the end of the read period is set slightly earlier than the end of the reset off period. That is, a certain degree of margin is provided so that the potential change of the row line RL _i during the read period is completed within the reset-off period.

In the case where the signal is read from the signal detection element 20 for each row, the signal timing output to the row line RL _i and the reset line RESET _i of each row is set so that the readout period of each row does not overlap in time. It has been adjusted.

FIG. 2 is a circuit configuration diagram for generating the signal waveform shown in FIG. Each output stage SROUT _i (1 ≦ i ≦ M) of the shift register 30 is connected to an AND gate AE _i (1 ≦ i ≦ M) and a NOR gate NE _i (1) via delay elements DE _i (1 ≦ i ≦ M). 1 ≦ i ≦ M) are connected. The output stage of the AND gate AE _i is connected to the row line RL _i, the output stage of the NOR gate NE _i is connected to a reset line RESET _i. As shown in FIG. 4, the shift register 30 outputs a pulse signal SROUT _i having a time width ΔT. Then, a pulse signal (time width ΔT−ΔD) whose rising edge is delayed by ΔD is output to the row line RL _i . Further, a falling edge of the pulse signal SROUT _i is delayed by ΔD and a logically inverted signal (time width ΔT + ΔD) is output to the reset line RESET _i . With such a configuration, the signal waveforms shown in FIG. 3 are output to the row line RL _i and the reset line RESET _i of each row.

According to the present embodiment, when the surface shape of the object is read, the signal amplifying element Tr1 included in the capacitance detection element 20 that is not to be read can be forcibly turned off by the reset element Tr2. Thus, conventionally, turned on unexpectedly signal amplifier element Tr1 included in the reading object outside the capacitance detection element 20, the current flowing from a plurality of current paths are superimposed on the output line OL _j The detection error due to can be suppressed.

FIG. 6 is a circuit configuration diagram of the capacitance detection device 11 of the present embodiment. Elements having the same reference numerals as those shown in FIG. 1 are designated as the same elements, and detailed description thereof is omitted. The electrostatic capacitance detection device 11 has a structure omitting the reference capacitor C _R and the row line RL _i from the configuration of the electrostatic capacitance detection device 10 described above. To stabilize the reading accuracy of the electrostatic capacitance detection device 11, it is desirable and a reference capacitor C _R, by applying a predetermined voltage to the drain electrode of the signal amplifying element Tr1 during signal reading, the signal amplification to the same function and the reference capacitor C _R (parasitic capacitance between the drain and gate) drain capacitance of the device Tr1, it is omitted reference capacitor C _R can read the surface shape of the object.

7 is a plan view of the fingerprint sensor 61, and FIG. 8 is a sectional view taken along the line 8-8 in FIG. The fingerprint sensor 61 includes any one of the capacitance detection devices 10 and 11 described above, and is configured to be able to read the unevenness information of the fingerprint. In the matrix array 62, sensor electrodes SE are arranged in a matrix. A guard electrode GE is formed on the dielectric film IL so as to partition each sensor electrode SE. The guard electrode GE is a line-like electrode extending along the row direction and the column direction. By providing the guard electrode GE, the potential of the object surface and the potential (ground potential) of the sensor electrode SE can be matched. Thus, the potential difference between the sensor electrode SE of the unselected row and the object surface becomes zero, even if the change in the electrostatic capacitance C _F and the like moving the target object surface, that large current flows to the power supply line PL The power source of the fingerprint sensor 61 is stabilized.

9 is a plan view of the fingerprint sensor 63, and FIG. 10 is a cross-sectional view taken along the line 10-10 in FIG. The fingerprint sensor 63 includes any one of the capacitance detection devices 10 and 11 described above, and is configured to be able to read the unevenness information of the fingerprint. In the matrix array 64, sensor electrodes SE are arranged in a matrix. A guard electrode GE is formed on the outer periphery of the matrix array 64. By providing the guard electrode GE, the potential of the object surface and the potential (ground potential) of the sensor electrode SE can be matched. Thus, the potential difference between the sensor electrode SE of the unselected row and the object surface becomes zero, even if the change in the electrostatic capacitance C _F and the like moving the target object surface, that large current flows to the power supply line PL The power source of the fingerprint sensor 61 is stabilized.

  FIG. 11 is an exploded perspective view of an IC card (smart card) 70. The IC card 70 includes a substrate 73 formed by bonding two plastic base materials 71 and 72, an IC chip (integrated circuit) 80 sandwiched between the two base materials 71 and 72, and And a fingerprint sensor 61. In addition, as an interface for exchanging information with an external device (not shown) such as a card terminal, a contact IC terminal 81 that is in direct contact with the external device, and a non-contact type that receives and transmits radio waves of a constant frequency with the external device. IC antenna 82 is provided. Further, an opening 83 is formed on the upper surface 71a of the base material 71 in order to expose the matrix array 62 of the fingerprint sensor 61 on the upper surface of the substrate. Furthermore, a static elimination electrode 90 that discharges static electricity charged on the human body is provided on the upper surface 71a of the base material 71. By forming the static elimination electrode 90 as described above, it is possible to measure the capacitance between the finger and the static electricity charged on the human body, and to avoid discharge breakdown due to the static electricity charged on the human body. Is possible.

  The contact IC terminal 81 is formed so as to be exposed to the upper surface 71 a of the substrate 71 while being in contact with the upper surface of the IC chip 80. On the other hand, the non-contact type IC antenna 82 is formed in a coil shape between the two base materials 71 and 72. In this embodiment, a combination card (dual interface) including a contact IC terminal and a non-contact IC antenna is illustrated. In the case where only the antenna is provided (see ISO 14443, etc.), or a hybrid card including a contact IC chip and a non-contact IC chip may be used.

  FIG. 12 is a configuration diagram of the IC chip 80. The IC chip 80 includes a data processing unit 84 that extracts features of a fingerprint pattern captured by the fingerprint sensor 61, a memory 85 that stores various types of information such as feature amounts of a specific fingerprint pattern, and features extracted by the data processing unit 84. A comparison unit 86 that compares the amount and the feature amount stored in the memory 85, and a control unit 87 that controls the operation of the IC card 70. A contact IC terminal 81 and a non-contact IC antenna 82 are connected to the comparison unit 86.

  IC card 70 equipped with IC chip 80 has higher information capacity, improved security (prevents counterfeiting and unauthorized use), supports multiple applications, and reduces host load (offline processing is possible) compared to magnetic stripe cards Etc. Therefore, the IC card 70 can be used for entrance / exit management of credit cards, cash cards, electronic money, electronic commerce, transportation fields such as railways and buses, medical insurance fields, and buildings.

1 is a circuit configuration diagram of a capacitance detection device of Example 1. FIG. It is a circuit block diagram of a driver. It is signal waveform diagrams, such as a reset signal. It is a signal waveform diagram output from a driver circuit. FIG. 3 is an operation principle diagram of the first embodiment. It is a circuit block diagram of the electrostatic capacitance detection apparatus of Example 2. 6 is a plan view of a fingerprint sensor according to Embodiment 3. FIG. It is sectional drawing of the fingerprint sensor of Example 3. 6 is a plan view of a fingerprint sensor according to Embodiment 4. FIG. It is sectional drawing of the fingerprint sensor of Example 4. FIG. 10 is an exploded perspective view of an IC card according to a fifth embodiment. It is a block diagram of an IC chip. It is an operation principle diagram of a conventional fingerprint sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 11, 12 ... Capacitance detection apparatus 20 ... Capacitance detection element Tr1 ... Signal amplification element Tr2 ... Reset element Tr3 ... Row selection element Tr4 ... Column selection element SE ... Sensor electrode

Claims (5)

A capacitance detection device that reads a surface shape of the object by detecting a capacitance that changes according to a distance to the object,
Capacitance detection elements arranged in M rows and N columns, power supply lines for supplying power to each of the capacitance detection elements, and signals output from the capacitance detection elements arranged in the respective columns are transmitted. N output lines to be reset, and M reset lines for resetting the capacitance detection elements arranged in a specific row,
Each of the capacitance detection elements is
a) a signal detection element for accumulating charges according to the capacitance;
b) a signal amplifying element for amplifying a signal corresponding to the charge accumulated in the signal detecting element;
c) a reset element that resets the electric charge accumulated in the signal detection element by a signal from the reset line,
The signal detection element includes a sensor electrode for forming a capacitance with the object,
The signal amplification element includes a semiconductor device including a source electrode, a drain electrode, and a gate electrode,
The reset element includes a semiconductor device including a source electrode, a drain electrode, and a gate electrode,
The gate electrode of the signal amplification element, the sensor electrode, and the drain electrode of the reset element are connected,
A source electrode of the signal amplification element is connected to the power line;
The drain electrode of the signal amplification element is connected to the output line,
A gate electrode of the reset element is connected to the reset line;
A capacitance detection device, wherein a source electrode of the reset element is connected to the power supply line. The capacitance detection device according to claim 1,
The signal detection element comprises a reference capacitor;
The reference capacitor comprises a reference capacitor first electrode, a reference capacitor dielectric film, and a reference capacitor second electrode,
The capacitance detection device includes a row line for controlling a potential of the reference capacitor first electrode,
The reference capacitor first electrode is connected to the row line,
The capacitance detecting device, wherein the reference capacitor second electrode is connected to a gate electrode of the signal amplifying element, the sensor electrode, and a drain electrode of the reset element. The capacitance detection device according to claim 1 or 2,
A capacitance detection device in which a ground potential is supplied to the power line. The capacitance detection device according to any one of claims 1 to 3,
A capacitance detection device further comprising a guard electrode for making the surface potential of the object substantially the same as the potential of the sensor electrode. A smart card comprising the capacitance detection device according to any one of claims 1 to 4.

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