JP2003172602A - Surface-shape detecting element and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-shape detecting element and device having excellent scratch resistance and stain resistance with improving productivity and lowering a formation temperature. <P>SOLUTION: The surface-shape detecting device 1 is provided with an active matrix substrate 3 arranging a detection electrode 3b and an active element T connected to the detection electrode 3b in matrix, and an insulation layer 4 formed on the active matrix substrate 3. In the surface-shape detecting device 1 of a capacitance type detecting three-dimensional shape by outputting a signal corresponding to the electrostatic capacity between a finger F placed on the insulation layer 4 and the detection electrode 3b from each active element T, the insulation layer 4 is formed with a resin material of a fluorine resin mixing an organic material such as Ta<SB>2</SB>O<SB>5</SB>or the gel film of a silicon alkoxide mixing an inorganic material. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface shape detecting element and a surface shape detecting device capable of detecting the surface shape of an inspection object such as a fingerprint.

[0002]

2. Description of the Related Art With the progress of IT industry in recent years, electronic commerce using the Internet is rapidly spreading.
For this reason, interest in security technology for authenticating an individual is increasing, and there is an increasing demand for mounting a fingerprint authentication function on a mobile information terminal, a mobile phone, and the like.

Further, in public institutions such as police and financial institutions, which often handle highly confidential information, personal computers having a fingerprint authentication function are being used. As a surface shape detection device used in such a fingerprint authentication device, detection methods such as "optical method", "pressure method", and "electrostatic capacity method" are known.

The "optical method" is a method in which a difference in brightness of light due to unevenness of a fingerprint is converted into charge information by a photodiode or a phototransistor and detected. Therefore, the problem that it is difficult to make the detector thin because a light source is required,
It is necessary to create a photo diode in the detection element,
There is a problem that the device structure becomes complicated.

The "pressure method" is to electrically detect a pressure difference due to unevenness of a fingerprint. In this case, since it is necessary to use a pressure-sensitive sheet that deforms according to the unevenness of the fingerprint, it is not possible to increase the hardness of the element surface, and there is a problem that the scratch resistance against scratching by a nail is low.

On the other hand, the "capacitance method" electrically detects the capacitance generated between the unevenness of the fingerprint and the detector. Therefore, it does not require a light source and can be made thin easily, and the passivation layer (surface protection layer)
The scratch resistance can be improved by properly selecting. Therefore, many "capacitance type" surface shape detecting devices are adopted.

Details of the "capacitance type" surface shape detecting device are described in, for example, Japanese Patent No. 3007714 (corresponding US Patent
5,325,442). According to this, a passivation layer is formed on an active matrix substrate in which a plurality of electrodes and active elements are arranged in a matrix to form a surface shape detection device.

When an object to be inspected, such as a finger, comes into contact with the passivation layer, a capacitance is formed between the object to be inspected and the electrode via the passivation layer. By electrically reading out the two-dimensional distribution of the capacitance value, it is possible to detect a fine pattern of surface irregularities of the inspection object.

A MOS transistor formed on a semiconductor substrate, a thin film transistor (TFT) formed on an insulating substrate, or the like is used as an active element. Further, a Si ₃ N ₄ (silicon nitride) film is widely used as a passivation layer, and is generally used for CVD (Chemical Vapor Depositio).
n) method.

[0010]

However, according to the above-mentioned "capacitance type" surface shape detecting device, Si ₃
The passivation layer made of N ₄ needs to have a film thickness of 1 μm or more in order to sufficiently secure scratch resistance and barrier resistance against contaminants. Therefore, when the Si ₃ N ₄ film having a film thickness of 1 μm or more is formed by the CVD method, there is a problem that it takes much time and productivity is deteriorated.

Further, when the Si ₃ N ₄ film is formed by the CVD method, the film forming temperature rises to about 300 ° C. Therefore, it is necessary to make the heat resistance of the active matrix substrate higher than 300 ° C. Therefore, there is also a problem that materials such as a resin material having a heat resistant temperature of about 200 ° C. cannot be used, which limits the materials.

Further, since fingerprints are likely to adhere to the inorganic film such as Si ₃ N ₄ film, when dirt such as fingerprints adheres strongly to the passivation layer, there is a problem that the surface shape detection performance is deteriorated. is there. Further, when an organic material is used instead of the inorganic film such as the Si ₃ N ₄ film, there is a problem that the scratch resistance is lowered.

It is an object of the present invention to provide a surface shape detecting element and a surface shape detecting device which are excellent in scratch resistance and stain resistance while improving productivity and lowering a forming temperature.

[0014]

In order to achieve the above object, a surface shape detecting element of the present invention comprises an active matrix substrate in which electrodes and active elements connected to the electrodes are arranged in a matrix, and the active matrix. An insulating layer formed on a substrate, and of a capacitance type that outputs a signal corresponding to the capacitance between the object to be inspected arranged on the insulating layer and the electrode from each active element. The surface shape detecting element is characterized in that the insulating layer is made of a resin mixed with an inorganic material.

Further, the present invention is characterized in that, in the surface shape detecting element having the above structure, the insulating layer has water repellency.

The surface shape detection element of the present invention comprises an active matrix substrate in which electrodes and active elements connected to the electrodes are arranged in a matrix, and an insulating layer formed on the active matrix substrate, In a capacitance type surface shape detection element that outputs a signal according to the capacitance between an object to be inspected arranged on the insulating layer and the electrode from the active elements, the insulating layer is an inorganic material. It is characterized in that it consists of a gel mixed with.

The present invention also provides a surface shape detection element having the above structure.
In the child, the inorganic material is SiO ₂, Si₃N_Four, Ti
O₂, Ta₂O_Five, Al₂O_Five, At least one of SiC
It is characterized by including one.

Further, the present invention is characterized in that, in the surface shape detecting element having the above-mentioned structure, an intermediate layer having an insulating property mainly containing an inorganic material is provided between the active substrate and the insulating layer.

Further, the surface shape detecting apparatus of the present invention comprises the surface shape detecting element having each of the above-mentioned constitutions, and a calculating section for calculating the three-dimensional shape of the inspection object based on the output of the surface shape detecting element. Is characterized by.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the surface shape detection device of the first embodiment. Further, FIG. 2 is a schematic sectional view showing the surface shape detection device. Surface shape detector 1 is CP
The control unit 8 is composed of U, and the control unit 8 is connected to a storage unit 9 for storing data, a display unit 10 for displaying data, and a surface shape detection element 2. The control unit 8 has a storage unit 9,
A drive signal can be transmitted to the display unit 10 and the surface shape detection element 2 to control the drive, and an output signal from the surface shape detection element 2 can be calculated.

The surface shape detecting element 2 has a passivation layer (insulating layer) 4 on an active matrix substrate 3 in which active elements composed of detecting electrodes 3b (see FIG. 2) and thin film transistors T are arranged in a matrix on a substrate 3a.
Are formed. The substrate 3a is made of an insulating material such as glass or quartz. You may form the active element which consists of MOS transistors on the board | substrate which consists of semiconductors. The detection electrode 3b is made of Ti, Al or the like.

The detection electrodes 3b and the thin film transistors T are provided at the intersections of the scanning lines 11 and the signal lines 13 arranged in a matrix, and constitute a large number of arranged pixels.
When the surface shape detection element 2 is used as a fingerprint sensor, the pixel density is 200 ppi to 600 ppi (Pixels
Per Inch), and the active area 3c in which pixels are arranged is 10 mm × 10 mm to 30 mm × 30 mm
It is good to design it.

The gate G of the thin film transistor T is the scanning line 1
1 is connected to the Y driver 7, and the source S is connected to the X driver 6 via the signal line 13. The drain D has a capacitance Cxy (xy) between the detection electrode 3b and the finger F which are opposed to each other via the passivation layer 4 (see FIG. 2).
, 11, ..., And the other end of the electrostatic capacitance Cxy is grounded by the finger F. An output signal is output to the X driver 6 via the signal line 13. Here, the X driver 6 is composed of a charge detection amplifier or the like.

When the gate G becomes high level, the source S
And the drain D are conducted to turn on the thin film transistor T. When the gate G becomes low level, the thin film transistor T is turned off. Accordingly, the thin film transistor T functions as an active element, and when the thin film transistor T is turned on, the voltage from the signal line 13 is applied to the electrostatic capacitance Cxy.

The passivation layer 4 is composed of an insulating film in which inorganic fine particles are contained in a binder made of a resin material. As the resin material, fluorine resin or silicon resin can be used. As a result, the passivation layer 4 can be rendered water repellent.

Further, as inorganic fine particles, SiO ₂ (oxygen oxide), Si ₃ N ₄ (silicon nitride), TiO ₂ (titanium oxide), Ta ₂ O ₅ (tantalum oxide), Al ₂ O ₅ (aluminum oxide) are used. , SiC (silicon carbide) can be used. For example, in fluorine-based resin,
Using a material in which fine particles of Ta ₂ O _{5 having} a particle diameter of 100 nm or less are dispersed and mixed in a ratio of 20 to 80% by weight, the thickness is 1
An insulating film having a thickness of up to 3 μm can be formed.

The passivation layer 4 can be easily formed by applying the above resin material on the active matrix substrate 3. Alternatively, it can be easily formed by coating an insulating film made of a resin material with a predetermined thickness on a supporting substrate such as a PET film and then transferring the insulating film onto the surface of the active matrix substrate 3. At this time, since it is difficult for the fluorine-based resin to obtain adhesiveness to the active matrix substrate 3, it is advisable to fix them to each other via an adhesive layer or an adhesive layer, if necessary.

In the surface shape detecting device 1 having the above structure,
When a high level signal is given from the Y driver 7 to one scanning line 11 under the control of the control unit 8, the scanning line 1
The thin film transistor T of each pixel connected to 1 is selected. When a signal voltage is applied to the signal line 13 by the X driver 6, the voltage is applied to the detection electrodes 3b of these pixels.

As a result, each point P ₁₁ , P ₂₁ , P of the finger F is
Capacitances C ₁₁ , C ₂₁ , C ₃₁ , ... vary depending on the distance between ₃₁ , ... and the detection electrode 3b facing these points. Along with this, the electrostatic capacitances C ₁₁ , C ₂₁ , C ₃₁ , ...
The amount of electric charge charged to the electric charge changes, and the electric charge is output to the control unit 8 via the X driver 6.

Then, a high-level signal is sequentially applied to the adjacent scanning lines 11 by the Y driver 7, and a signal voltage is applied by the X driver 6 to electrostatic capacitance (eg, C ₁₂ , C ₂₂ , ...) is a current corresponding to X
It is output to the driver 6. As a result, a signal corresponding to the size of the unevenness of the finger F at each two-dimensional point is output to the control unit 8.
Entered in.

In the control section 8, the points P ₁₁ , P ₂₁ , P ₃₁ , ... Of the finger F are received on the basis of the input signal from the X driver 6.
And the detection electrode 3b are calculated, and a three-dimensional shape corresponding to the unevenness of the finger F is calculated. The obtained three-dimensional shape data is stored in the storage unit 9 and displayed on the display unit 10.

According to this embodiment, since the passivation layer 4 is made of a resin material, it can be easily formed by coating or transfer. Therefore, it is simpler than the conventional method of forming a passivation layer by the CVD method, and a thickness of 1 μm or more can be formed with good productivity. Therefore, as will be described later, the surface shape detection element having high scratch resistance can be easily formed by mixing the inorganic fine particles.

Further, by making the surface of the passivation layer 4 water-repellent by using a fluorine resin or a silicon resin as a binder, dirt such as sweat is unlikely to adhere even if the passivation layer is directly touched with a finger. Even if it gets dirty, it can be easily wiped off with water or alcohol. In addition, when the water repellency may be weak or the water repellency may not be necessary, a polyimide resin, an acrylic resin, an epoxy resin, a polyurethane resin, a polyester may be used instead of the fluorine resin or the silicon resin. Various resins such as a system resin may be used.

Further, since the inorganic fine particles are mixed in the passivation layer 4, the hardness is improved and the scratch resistance is remarkably improved as compared with a film made of a resin alone. For example, in the case of an insulating film in which fine particles of Ta ₂ O _{5 having} a particle diameter of 100 nm or less are dispersed and mixed in the fluorine resin at a ratio of 20 to 80% by weight, a film having a pencil hardness of 4H or more can be obtained. it can. As inorganic fine particles, SiO ₂ , Si ₃ N ₄ , TiO ₂ , Al
It is used ₂ 0 _5, SiC and the like can obtain the same hardness.

Further, with a single resin such as a fluorine resin, the relative dielectric constant of the film is low (about 3.5), and the electrostatic capacitance between the detection electrode and the inspection object (finger in the case of a fingerprint sensor) is small. Therefore, the detection sensitivity deteriorates. However, according to this embodiment, since the insulating film in which the inorganic fine particles are mixed in the resin is used, the passivation layer 4 is selected by selecting the inorganic fine particles.
It is possible to increase the relative dielectric constant of. The effective relative permittivity of the insulating film can be arbitrarily adjusted by selecting the binder resin material and the inorganic fine particle material, the mixing ratio of the two, the film thickness, etc. as parameters, and depending on the selection, high sensitivity can also be achieved. is there.

[0036] In particular, Ta ₂ O ₅ has a high relative dielectric constant of about 25, the effective dielectric constant of the insulating film obtained by mixing fine particles of Ta ₂ 0 ₅ in the fluororesin 3.5 and 25 Most desirable because it is in the middle Accordingly, by appropriately selecting the mixing ratio of the Ta ₂ O ₅ fine particles, it is possible to realize an insulating film having a sensitivity equal to or higher than that of the conventional passivation layer made of a Si ₃ N ₄ film.

Further, since the passivation layer 4 can be transferred onto the active matrix substrate 3 at about 150 ° C. after once forming an insulating film on another supporting substrate, the heat resistance of the active matrix substrate 3 is restricted. Can be relaxed. Therefore, a material having low heat resistance can be used as a constituent member in the active matrix substrate 3. For example, the heat resistant temperature of the interlayer insulating film is about 2
It is possible to use an acrylic resin of 00 ° C. or use a plastic material as the substrate 3a of the active matrix substrate 3.

Next, a second embodiment will be described. The structure of this embodiment is the same as that of the first embodiment shown in FIGS. 1 and 2 described above, but the passivation layer 4 formed on the active matrix substrate 3 is made of an insulating film containing inorganic fine particles in the gel film. Is different.

As the sol for forming the gel film, a coating liquid composed of an alkoxide containing a metal such as titanium or silicon, and a solvent such as an alcohol compound or a ketone compound can be used. As the inorganic fine particles, as in the first embodiment, SiO ₂ , Si ₃ N ₄ , TiO ₂ , Ta are used.
_{2 0 5, Al 2 0 5} , SiC at least one of - one can be used.

It is also possible to improve the coating performance by adding a complexing agent such as acetylacetone to the coating solution composed of sol to suppress the gelation of the coating solution during the coating step. Also,
It is also possible to add an organic compound to the gel material and use an organic-inorganic high-frid gel material.

After the inorganic fine particles are dispersed in the coating liquid containing the sol, the dispersion liquid is coated on the active matrix substrate 3 and dried / baked to form a passivation film composed of a gel film in which the inorganic fine particles are dispersed. The layer 4 can be easily formed. For example, in the gel film of a silicon-based, particle size 100nm following Ta ₂ 0 ₅ particulate 20-8
An insulating film containing 0% by weight and having a thickness of 0.5 to 2 μm can be formed.

When a coating solution containing silicon alkoxide is used, the film can be cured at about 100 to 150 ° C. When the active matrix substrate 3 has heat resistance, it may be heated to several hundreds of degrees Celsius in order to obtain a dense film. Regarding the method of forming a film by the sol-gel method and the method of mixing fine particles into the gel film, "Application of the sol-gel method" (publisher: Agne Jofusha (issued in 1997), author: Sakuhana Mitsuo) etc.

According to this embodiment, since the passivation layer 4 is made of a gel film, it can be formed by coating. Therefore, it is simpler than the conventional method of forming a passivation layer by a CVD method, a thickness of 1 μm or more can be formed with high productivity, and a surface shape detection element 2 having high scratch resistance can be easily formed. You can In addition, since the inorganic fine particles are mixed in the gel film, the hardness is improved and the scratch resistance is dramatically improved as compared with the gel film alone.

On the other hand, since the gel film is generally a porous film, the density of the film is reduced and the effective dielectric constant is reduced. Therefore, the detection electrode and the object to be inspected (finger in case of fingerprint sensor)
Since the capacitance value between the two becomes small, the detection sensitivity deteriorates. However, according to this embodiment, since the inorganic fine particles are contained in the gel film, the dielectric constant of the passivation layer 4 can be increased by selecting the inorganic fine particles. The effective relative permittivity of the insulating film can be arbitrarily adjusted by selecting the gel material and the inorganic fine particle material, the mixing ratio of the two, the film thickness, etc. as parameters, and depending on the selection, high sensitivity can also be achieved. .

[0045] In particular, Ta ₂ O ₅ has a high relative dielectric constant of about 25, most desirable because it can increase the effective dielectric constant of the insulating film obtained by mixing fine particles of Ta ₂ 0 ₅ in the gel material. Accordingly, by appropriately selecting the mixing ratio of the Ta ₂ O ₅ fine particles, it is possible to realize an insulating film having a sensitivity equal to or higher than that of the conventional passivation layer made of a Si ₃ N ₄ film.

Next, FIG. 3 is a cross-sectional view showing a surface shape detecting element according to the surface shape detecting apparatus of the third embodiment. For convenience of explanation, the same parts as those of the first and second embodiments shown in FIGS. 1 and 2 described above are designated by the same reference numerals. The difference from the first embodiment is that an intermediate layer 5 made of an insulating film is provided between the passivation layer 4 and the active matrix substrate 3. Other points are the same as those in the first and second embodiments.

The intermediate layer 5 is a Si film formed by the CVD method.
Made of ₃ N ₄ . On the other hand, the upper passivation layer 4 is made of an insulating film similar to that of the first or second embodiment.

Surface shape detecting apparatus 1 of the first and second embodiments
Then, as the passivation layer 4, an insulating film containing inorganic fine particles in a binder made of a resin material or an insulating film containing inorganic fine particles in a gel film is used. However, these insulating films may deteriorate the active matrix substrate 3 due to easy penetration of moisture, alkali ions, etc. from the outside.

In this embodiment, the Si ₃ N ₄ film having excellent barrier performance against moisture and alkali ions is provided as the intermediate layer 5 to prevent the deterioration of the active matrix substrate 3 due to moisture and alkali ions penetrating from the outside. can do.

The Si ₃ N ₄ film serving as the intermediate layer 5 is formed by CVD.
Since it has to be formed by the method, the productivity is lower than that in the first and second embodiments. However, as in the conventional example, Si
Unlike touching the ₃ N ₄ film itself directly with the fingers, the intermediate layer 5
Need only have a barrier property against moisture and alkali ions.

That is, since the passivation layer 4 has scratch resistance and stain resistance, the intermediate layer 5 is not required to have these characteristics. For this reason, the intermediate layer 5 has a conventional structure of 1
It is not necessary to form the thickness of more than μm, and the thickness of 500 nm or less is sufficient. Therefore, although it is necessary to form the film by the CVD method, the productivity can be improved as compared with the conventional method.

In the first to third embodiments, the case where the surface shape detecting device 1 is used for detecting a fingerprint has been described, but it is also possible to detect a three-dimensional shape of an object other than the fingerprint. .

[0053]

According to the present invention, since the insulating layer (passivation layer) formed on the active substrate is made of a resin material or a gel film, it can be easily formed by coating or transfer. Therefore, it is simpler than the conventional method of forming the passivation layer by the CVD method,
A thickness of 1 μm or more can be formed with good productivity, and a surface shape detection element with high scratch resistance can be easily formed.

Further, since the formation temperature of the insulating layer can be lowered, the restriction of heat resistance of the active matrix substrate can be relaxed. Therefore, it is possible to use a material having low heat resistance as a constituent member in the active matrix substrate.

Moreover, SiO ₂ , Si ₃ N ₄ , and Ti are used as the insulating layer.
Inorganic materials such as O ₂ , Ta ₂ O ₅ , Al ₂ O ₅ , and SiC are mixed in, so the hardness is improved compared to a resin-only film and high scratch resistance equivalent to or better than conventional ones is maintained. You can Furthermore, by selecting the inorganic fine particles, it is possible to increase the relative dielectric constant of the insulating layer, and it is possible to prevent the detection performance from deteriorating.

Further, according to the present invention, since the insulating layer made of the resin material has water repellency, dirt such as sweat is hard to adhere, and even if dirt is adhered, it can be easily wiped off with water, alcohol or the like. .

Further, according to the present invention, since the intermediate layer made of an inorganic material is provided between the active substrate and the insulating layer, the permeation of water and acrylic ions from the outside is prevented, and the deterioration of the active substrate is prevented. As well as
It is possible to shorten the film formation time by CVD and improve the productivity as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a surface shape detection device according to first and second embodiments of the present invention.

FIG. 2 is a schematic cross-sectional view showing a surface shape detection element according to first and second embodiments of the present invention.

FIG. 3 is a schematic sectional view showing a surface shape detection element according to a third embodiment of the present invention.

[Explanation of symbols]

1 Surface shape detector 2 Surface shape detector 3 Active matrix substrate 3b Detection electrode 4 insulating layers 5 Middle class 6 X driver 7 Y driver 8 control unit 9 memory 10 Display T thin film transistor F fingers

Continued front page    F term (reference) 2F063 AA43 BA29 BD05 CA30 CA31                       CA34 DA02 DA05 DB05 DD07                       HA10 HA18 NA06                 4C038 FF01 FG00                 5B047 AA25 AB02 BA02 BB04 BC01                       BC14 CB22 DC09

Claims (6)

[Claims] 1. An active matrix substrate in which electrodes and active elements connected to the electrodes are arranged in a matrix, and an insulating layer formed on the active matrix substrate are provided, and the active matrix substrate is disposed on the insulating layer. In a capacitance type surface shape detection element for outputting a signal according to a capacitance between an object to be inspected and the electrode from each of the active elements, the insulating layer is made of a resin mixed with an inorganic material. Characteristic surface shape detection element. 2. The surface shape detecting element according to claim 1, wherein the insulating layer has water repellency. 3. An active matrix substrate in which electrodes and active elements connected to the electrodes are arranged in a matrix, and an insulating layer formed on the active matrix substrate, the insulating layer being disposed on the insulating layer. In a capacitance type surface shape detecting element for outputting a signal according to a capacitance between an object to be inspected and the electrode from each of the active elements, the insulating layer is made of a gel mixed with an inorganic material. Characteristic surface shape detection element. 4. The inorganic material is SiO₂, Si₃N_Four, T
iO₂, Ta₂O_Five, Al ₂O_Five, At least of SiC
Any one of claims 1 to 3 including one
The surface shape detection element described therein. 5. The surface according to any one of claims 1 to 4, wherein an intermediate layer having an insulating property and containing an inorganic material as a main component is provided between the active substrate and the insulating layer. Shape detection element. 6. A surface shape detecting element according to claim 1, and a calculation section for calculating a three-dimensional shape of an object to be inspected based on an output of the surface shape detecting element. A surface shape detection device characterized by the above.