KR102568647B1 - Piezoelectric sensor and method for manufacturing piezoelectric sensor - Google Patents

Abstract

A piezoelectric sensor and a method of manufacturing the piezoelectric sensor according to an embodiment include a substrate and at least one piezoelectric element disposed on the substrate, wherein the at least one piezoelectric element includes a plurality of piezoelectric elements spaced apart from each other, and a plurality of piezoelectric elements A piezoelectric sensor including first electrodes respectively disposed on upper surfaces and second electrodes respectively disposed on lower surfaces of the plurality of piezoelectric materials, wherein a width of the first electrode is greater than a width of the second electrode.

Description

Piezoelectric sensor and manufacturing method of piezoelectric sensor

An embodiment relates to a piezoelectric sensor and a method for manufacturing the piezoelectric sensor.

A fingerprint recognition sensor is a sensor that detects a person's fingerprint and is widely used in devices such as door locks that have been widely applied in the past, as well as for determining whether to turn on/off the power of electronic devices or release the sleep mode. It is becoming.

The fingerprint recognition sensor may be classified into an ultrasonic method, an infrared method, a capacitive method, and the like according to its operation principle. For example, in the ultrasonic method, when an ultrasonic signal of a certain frequency emitted from a plurality of piezoelectric elements is reflected from valleys and valleys of a fingerprint, the acoustic impedance difference between valleys and valleys is measured. It is a method of detecting a fingerprint by measuring using a plurality of piezoelectric elements, which are sources of ultrasonic waves, and in particular, the advantage of the ultrasonic method is that it goes beyond simple fingerprint recognition and generates ultrasonic waves in a pulse type to reduce the Doppler effect caused by the echo. Since it has a function of grasping the blood flow inside the finger by detecting it, it can have an advantage of determining whether or not a fake fingerprint is present.

Such a fingerprint sensor can recognize a fingerprint by arranging a piezoelectric element on a substrate and placing electrodes on both sides of the piezoelectric element to generate ultrasonic waves. In the process of doing it, there are problems such as filler separation, misalignment, non-formation of filler, or damage to the substrate.

Accordingly, a fingerprint recognition sensor having a new structure capable of solving such problems is required.

Embodiments provide a piezoelectric sensor with improved sensor precision and a manufacturing method of the piezoelectric sensor.

In addition, a piezoelectric sensor and a manufacturing method of the piezoelectric sensor having a reduced defect rate during the manufacturing process are provided.

The problem to be solved in the embodiment is not limited thereto, and it will be said that the solution to the problem described below or the purpose or effect that can be grasped from the embodiment is also included.

A piezoelectric sensor according to an embodiment of the present invention includes a substrate; and at least one piezoelectric element disposed on the substrate; Including, wherein the at least one piezoelectric element is a plurality of mutually spaced piezoelectric elements; first electrodes respectively disposed on upper surfaces of the plurality of piezoelectric materials; and second electrodes respectively disposed on lower surfaces of the plurality of piezoelectric materials. Including, the width of the first electrode is greater than the width of the second electrode.

The width of the second electrode may be 50% or more to less than 100% of the width of the first electrode.

A width of the second electrode may be smaller than a width of the piezoelectric body.

An insulating member disposed between the plurality of piezoelectric materials may be further included.

The insulating member may surround side surfaces of the plurality of piezoelectric materials.

A concave portion may be formed on an upper surface of the insulating member.

The plurality of piezoelectric materials may be disposed spaced apart from each other in a lattice structure.

The first electrode and the piezoelectric body may have the same horizontal width and vertical width.

A side surface of the first electrode may be disposed on the same plane as a side surface of the piezoelectric body.

An upper surface of the piezoelectric body may be disposed on the same plane as an upper surface of the insulating member, and a lower surface of the piezoelectric body may be disposed on the same plane as the lower surface of the insulating member.

A method of manufacturing a piezoelectric sensor according to an embodiment of the present invention includes providing a bulk type piezoelectric body having a first surface on one side and a second surface on the other side; disposing a first electrode on a first surface of the piezoelectric body; forming a lattice groove at a first depth on a first surface of the piezoelectric body through the first electrode; disposing an insulating member in a lattice groove on one side of the piezoelectric body; disposing an adhesive layer and a support substrate on one side of the piezoelectric body; grinding the second surface of the other side of the piezoelectric material to expose the insulating member to form a plurality of piezoelectric elements spaced apart by the insulating member; forming a piezoelectric element by disposing a plurality of second electrodes on each of the second surfaces of the plurality of piezoelectric elements; electrically connecting the piezoelectric element to a substrate; and removing the adhesive layer and the supporting substrate; The forming of the lattice grooves may include: forming a plurality of first grooves in a first direction on a first surface of the piezoelectric body through the first electrode; and forming a plurality of second grooves in a second direction on the first surface of the piezoelectric body through the first electrode; In the step of forming the lattice grooves, the plurality of first grooves have the same distance apart from each other, the plurality of second grooves have the same distance apart from each other, and forming the piezoelectric element. In, the width of the second electrode is smaller than the width of the piezoelectric body, the width of the second electrode is smaller than the width of the first electrode disposed on the first surface of the piezoelectric body, and disposing the insulating member In the step, a concave portion is formed on one side of the insulating member.

According to an embodiment, a fingerprint sensor with improved sensor accuracy may be provided.

In addition, the piezoelectric sensor and the manufacturing method of the piezoelectric sensor may reduce a defect rate during the manufacturing process.

Various advantageous advantages and effects of the present invention are not limited to the above description, and will be more easily understood in the process of describing specific embodiments of the present invention.

1 is a flowchart of a method for manufacturing a piezoelectric sensor according to an embodiment of the present invention;
2 to 6, 8, 10 to 12, 14, and 16 to 18 are perspective views sequentially illustrating a manufacturing process of a piezoelectric sensor,
7 is a cross-sectional view along line A-A' of FIG. 6;
9 is a BB′ line cross-sectional view of FIG. 8;
13 is a cross-sectional view taken along line C-C′ of FIG. 12;
15 is a cross-sectional view along line D-D' of FIG. 14;
19 is a cross-sectional view taken along line E-E' of FIG. 18;

The present embodiments may be modified in other forms or combined with each other, and the scope of the present invention is not limited to each of the embodiments described below.

Even if a matter described in a specific embodiment is not described in another embodiment, it may be understood as a description related to another embodiment, unless there is a description contrary to or contradictory to the matter in another embodiment.

For example, if the characteristics of component A are described in a specific embodiment and the characteristics of component B are described in another embodiment, the opposite or contradictory description even if the embodiment in which components A and B are combined is not explicitly described. Unless there is, it should be understood as belonging to the scope of the present invention.

In the description of the embodiment, in the case where an element is described as being formed “on or under” of another element, on or under (on or under) or under) includes both elements formed by directly contacting each other or by indirectly placing one or more other elements between the two elements. In addition, when expressed as "on or under", it may include the meaning of not only the upward direction but also the downward direction based on one element.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention.

1 is a flowchart of a method for manufacturing a piezoelectric sensor according to an embodiment of the present invention, and FIGS. 2 to 6, 8, 10 to 12, 14, and 16 to 18 sequentially illustrate a manufacturing process of a piezoelectric sensor. , Figure 7 is a cross-sectional view taken along the line AA' of FIG. 6, Figure 9 is a cross-sectional view taken along the line BB' of FIG. 8, Figure 13 is a cross-sectional view taken along the line CC' of FIG. is a cross-sectional view taken along the line D-D' in FIG. 14, and FIG. 19 is a cross-sectional view taken along the line E-E' in FIG.

First, referring to FIG. 1 , a method for manufacturing a piezoelectric sensor according to an embodiment of the present invention includes providing a piezoelectric material (S10), arranging a first electrode (S20), forming a lattice groove (S30), and disposing an insulating member ( S40), arranging the adhesive layer and supporting substrate (S50), grinding (S60), arranging the second electrode (S70), and connecting the substrate (S80).

Next, with reference to FIGS. 2 to 20 , the method of manufacturing the piezoelectric sensor according to FIG. 1 will be sequentially described according to a process sequence.

First, referring to FIG. 2 , the providing of the piezoelectric material (S10) includes a first surface 111 on one side (upper side) and a second surface 112 on the other side (lower side) opposite to one side in the Z-axis direction. A bulk type piezoelectric body 110 is provided.

Here, the piezoelectric body 110 may be made of single crystal ceramics, polycrystalline ceramics, a polymer material, a thin film material, or a composite material in which a polycrystalline material and a polymer material are combined in a bulk form.

Piezoelectric materials of single crystal ceramics include α-AlPO ₄ , α-SiO ₂ , LiTiO ₃ , LiNbO ₃ , SrxBayNb ₂ O ₃ , Pb ₅ -Ge ₃ O ₁₁ , Tb ₂ (MnO ₄ ) ₃ , Li ₂ B ₄ O ₇ , CdS, ZnO, Bi1 ₂ SiO ₂₀ or Bi1 ₂ GeO ₂₀ , and the piezoelectric material of polycrystalline ceramics may include PZT-based, PT-based, PZT-Complex Perovskite-based or BaTiO ₃ .

In addition, the piezoelectric material of the polymer material may include PVDF, P(VDF-TrFe), P(VDFTeFE) or TGS, and the piezoelectric material of the thin film material may include ZnO, CdS or AlN, In addition, the piezoelectric material of the composite material may include PZT-PVDF, PZT-Silicon Rubber, PZT-Epoxy, PZT-foamed polymer or PZT-foamed urethane.

Then, referring to FIG. 3 , in the first electrode arrangement step ( S20 ), the first electrode 120 is disposed on the first surface 111 of the piezoelectric body 110 .

Here, the first electrode 120 may include a transparent conductive material. For example, indium tin oxide, indium zinc oxide, copper oxide, tin oxide, zinc oxide, titanium oxide, etc. May contain metal oxides.

In addition, the first electrode 120 may include nanowires, photosensitive nanowire films, carbon nanotubes (CNTs), graphene, conductive polymers, or mixtures thereof.

In addition, the first electrode 120 may include various metals except for the above-mentioned exceptions. For example, the first electrode 120 may include chromium (Cr), nickel (Ni), copper (Cu), aluminum (Al), silver (Ag), or molybdenum (Mo). It may include at least one metal selected from gold (Au), titanium (Ti), and alloys thereof.

Here, the first electrode 120 may be formed on the entire surface of the first surface 111 of the piezoelectric body 110 by a method such as a vacuum deposition method or a sputtering method.

Then, referring to FIGS. 4 and 5 , in the grid groove forming step ( S30 ), the grid grooves 10 penetrating the first electrode 120 are formed on the first surface 111 of the piezoelectric body 110 .

Here, the lattice grooves 10 may include a plurality of first grooves 11 formed along the Y-axis direction and a plurality of second grooves 12 formed along the X-axis direction.

Here, it is preferable that each of the plurality of first grooves 11 and the plurality of second grooves 12 are spaced apart from each other at equal intervals.

Meanwhile, the number of first electrodes 120 separated into a plurality of pieces in the width of the piezoelectric body 110a and the lattice groove 10 through the separation distance between each of the plurality of first grooves 11 or each of the plurality of second grooves 12 width can be determined.

Here, it is preferable that the plurality of first grooves 11 and the plurality of second grooves 12 perpendicularly cross each other.

However, the intersection angle of the first groove 11 and the second groove 12 may be changed according to piezoelectric characteristics, structural rigidity, and resolution of the ultrasonic sensor.

The plurality of first grooves 11 and the plurality of second grooves 12 are formed to a first depth H1 from the first surface 111 of the piezoelectric body 110 through laser dicing or mechanical or thermal dicing. It can be.

Here, the first depth H1 is a value similar to the height of the piezoelectric body 110a and may be set to approximately 50 μm to 400 μm.

In addition, referring to FIGS. 6 and 7 , in the step of arranging the insulating member (S40), a synthetic resin or the like is coated on one upper part in the Z-axis direction of the piezoelectric body 110 on which the lattice grooves 10 are formed, so that the lattice grooves 10 are formed. let it be filled

Here, the coating process may be performed by a process such as spray coating, spin coating, or thermal spray coating, but the present invention is not limited thereto.

Here, the insulating member 130 is preferably composed of an insulating material that is cured naturally or through a separate process after filling the lattice grooves 10 .

Meanwhile, the insulating member 130 is filled along the lattice grooves 10, and in particular, may be filled inside the lattice grooves 10 through capillarity, and the area reduced by the capillary phenomenon is one part of the insulating member 130. A concave portion 131 in which a predetermined area is depressed is formed on the side surface (upper surface).

Through this, the insulating member 130 can be removed from the side of the first electrode 120, so that reliability of electrical connection through the first electrode 120 can be secured.

Subsequently, referring to FIGS. 8 to 11 , in the step of arranging the adhesive layer and the support substrate ( S50 ), the adhesive layer 140 and the support substrate 150 are attached to an upper portion of one side of the piezoelectric body 110 in the Z-axis direction.

The adhesive layer 140 is for attaching the support substrate 150 to the top of one side of the piezoelectric body 110, and may be composed of metal, metal oxide, organic, inorganic, or organic/inorganic composites, and may be formed by a roller coating method or a flow coating method. can be formed through

Here, the adhesive layer 140 is preferably easily removed by a physical, chemical, optical or thermal process, and may be selected from known examples according to the material of the support substrate 150 .

The support substrate 150 is a temporary support substrate and is attached to a surface opposite to the surface to be ground to grind the second surface 112, which is the other side of the piezoelectric body 110 in the Z-axis direction.

The support substrate 150 is attached to one side of the piezoelectric body 110 in the Z-axis direction through the adhesive layer 140 and provides a portion substantially held by a jig to be held during grinding.

Meanwhile, it is preferable that the outer surface of the support substrate 150 is specially coated so as not to react to a physical, chemical, optical or thermal process applied when the adhesive layer 140 is removed.

Then, referring to FIGS. 12 and 13, in the grinding step (S60), the second surface 112 on the other side in the Z-axis direction of the piezoelectric body 110 is ground by a predetermined thickness to obtain an insulating member disposed in the lattice groove 10 (130) is exposed to the other side.

Here, the grinding method may be performed using, for example, a diamond grinder and equivalents thereof.

Thus, the piezoelectric body 110 is separated into a plurality of piezoelectric bodies 110a spaced apart by the insulating member 130 . As described above, the plurality of piezoelectric elements 110a preferably have a height approximately similar to the first depth H1, which is the depth of the grid grooves 10, and have a first width W1, which is the distance between the grid grooves 10. ) can have.

Here, the first width W1, which is the width of the piezoelectric body 110a, may be set to approximately 100 μm to 500 μm. Of course, these values can be changed according to the piezoelectric characteristics of the piezoelectric body and the resolution of the ultrasonic sensor.

Here, each of the plurality of piezoelectric elements 110a preferably has the same or similar vertical width and horizontal width.

Then, referring to FIGS. 14 and 15 , in the step of arranging the second electrode (S70), the second electrode 160 is disposed on the second surface 112 of the plurality of piezoelectric elements 110a to form the piezoelectric element 200. form

Here, the second electrode 160 may include a transparent conductive material. For example, indium tin oxide, indium zinc oxide, copper oxide, tin oxide, zinc oxide, titanium oxide, etc. May contain metal oxides.

In addition, the second electrode 160 may include a nanowire, a photosensitive nanowire film, carbon nanotube (CNT), graphene, a conductive polymer, or a mixture thereof.

Also, the second electrode 160 may include various metals except for the above-mentioned exceptions. For example, the second electrode 160 may include chromium (Cr), nickel (Ni), copper (Cu), aluminum (Al), silver (Ag), or molybdenum (Mo). It may include at least one metal selected from gold (Au), titanium (Ti), and alloys thereof.

Here, the second electrode 160 may be formed on the second surface 112 of the piezoelectric body 110a by a method such as a vacuum deposition method or a sputtering method.

Meanwhile, since the second electrode 120 is deposited by placing a mask pattern on the second surface 112 of the piezoelectric body 110a, it is preferable to have a smaller width or area than the width W1 or area of the piezoelectric body 110a. do.

In addition, since the first electrode 120 is formed by a dicing process to have the same width or area as the width W1 of the piezoelectric body 110a, the first electrode 120 has the width W1, so that the second electrode 120 ) preferably has a smaller width or area than the width or area of the first electrode 120 .

For example, the width W2 of the second electrode 160 may be 50% or more and less than 100% of the width W1 of the piezoelectric body 110a.

Here, when the width W2 of the second electrode 160 is less than 50% of the width W1 of the piezoelectric body 110a, reliability of electrical connection between the second electrode 160 and the substrate cannot be secured, and the piezoelectric body It is easy to remove the second electrode 160 from the second surface 112 of (110a).

16 to 19, in the substrate connection step (S80), a connection part 2 electrically connected to the wiring pattern is formed on the board 1 on which the wiring pattern is formed, and a second connection part 2 is formed on the connection part 2. The piezoelectric element 200 is attached so that the electrode 160 is connected.

Here, the substrate 1 may be bent while partially having a curved surface. That is, the substrate 1 may be bent while partially having a flat surface and partially having a curved surface. In detail, the end of the substrate 1 may be bent while having a curved surface, or may be bent or bent while having a surface with a random curvature.

In addition, the substrate 1 may be a flexible substrate having flexible characteristics.

Also, the substrate 1 may be a curved or bent substrate. That is, the fingerprint sensor including the substrate 1 may also be formed to have flexible, curved or bended characteristics. Due to this, the fingerprint sensor according to the embodiment is easy to carry or combine, and can be changed into various designs.

Thereafter, the adhesive layer 140 is removed by a physical, chemical, optical or thermal process, and thus the support substrate 150 is separated from the piezoelectric element 200 .

In this way, the piezoelectric sensor shown in FIGS. 18 and 19 is manufactured.

Hereinafter, referring to FIGS. 18 and 19 , a piezoelectric sensor according to an embodiment of the present invention and operation of a fingerprint sensor using the same will be described in detail.

A piezoelectric sensor according to an embodiment of the present invention is disposed on a substrate 1 and includes a piezoelectric element 200 electrically connected to the substrate 1 .

Here, the substrate 1 may be bent while partially having a curved surface. That is, the substrate 1 may be bent while partially having a flat surface and partially having a curved surface. In detail, a flexible substrate, a curved or bent substrate having a curved surface at the end of the substrate 1 or having a surface with a random curvature and capable of being bent or bent can be

The piezoelectric element 200 includes a plurality of piezoelectric materials 110a, an insulating member 130, a first electrode 120, and a second electrode 160.

The plurality of piezoelectric materials 110a may be spaced apart from each other in a lattice structure.

The insulating member 130 is disposed between the plurality of piezoelectric materials 110a and may be formed in an integral grid pattern.

The insulating member 130 may be formed by crossing a first line in the Y-axis direction and a second line in the X-axis direction.

Here, the upper surface of the insulating member 130 is formed with a concave portion 131 recessed in a predetermined area from top to bottom.

The first electrode 120 is disposed on the upper surface of the piezoelectric body 110a and has a width equal to or similar to that of the piezoelectric body 110a.

The second electrode 160 is disposed on the lower surface of the piezoelectric body 110a, and has a width of about 50% or more and less than 100% of the width of the piezoelectric body 110a.

The second electrode 160 is electrically connected to the connection portion 2 electrically connected to the wiring pattern of the substrate 1 .

Hereinafter, driving of a fingerprint sensor including a piezoelectric sensor will be described.

A voltage having a resonant frequency in the ultrasonic band is applied to the first electrode 120 and the second electrode 160 disposed on the upper and lower surfaces of the piezoelectric element 110a from an external controller to generate an ultrasonic signal to the piezoelectric element 200. can cause

When a finger or the like does not touch or approach such an ultrasonic signal, the ultrasonic signal is transmitted from the node region of the piezoelectric element 200 due to a difference in acoustic impedance between the node region of the piezoelectric element 200 where the ultrasonic signal is emitted and the air. Most of the signal returns to the inside of the piezoelectric element 200 without passing through the interface between the sensor and the air.

On the other hand, when a finger touches or approaches, a part of the ultrasonic signal transmitted from the node region of the piezoelectric element 200 penetrates the interface between the skin of the finger and the piezoelectric element 200 and proceeds to the inside of the finger, and is thus reflected. The intensity of the returned signal is lowered, from which a fingerprint pattern can be detected.

Although it is difficult to check with the naked eye, a fingerprint of a finger may have a pattern in which numerous valleys and crests are repeated, and may have a height difference as the valleys and crests are repeated. Accordingly, the piezoelectric element 200 does not directly contact the skin at the valley of the fingerprint, and the piezoelectric element 200 may directly contact the skin at the crest of the fingerprint.

Accordingly, only a very small number of ultrasonic signals transmitted from the node region of the piezoelectric element 200 corresponding to the valley of the fingerprint are emitted to the outside, and most of the ultrasonic signals are reflected to the inside and received back to the node region. A significant amount of the ultrasonic signal emitted from the node region of the piezoelectric element 200 corresponding to the crest of is reflected after passing through the finger interface, and the intensity of the ultrasonic signal received back to the node region is relatively greatly reduced.

Accordingly, a fingerprint pattern of a finger may be detected by measuring the strength or reflection coefficient of a reflection signal received by an ultrasonic signal generated from a difference in acoustic impedance according to valleys and crests of a fingerprint in each node region.

Although the above has been described with reference to the embodiments, this is only an example and does not limit the present invention, and those skilled in the art to which the present invention belongs will not deviate from the essential characteristics of the present embodiment. It will be appreciated that various variations and applications are possible. For example, each component specifically shown in the embodiment can be modified and implemented. And differences related to these modifications and applications should be construed as being included in the scope of the present invention as defined in the appended claims.

Claims (11)

Board; and
at least one piezoelectric element disposed on the substrate; including,
The at least one piezoelectric element is
a plurality of piezoelectric bodies spaced apart from each other;
first electrodes respectively disposed on upper surfaces of the plurality of piezoelectric materials;
second electrodes respectively disposed on lower surfaces of the plurality of piezoelectric materials; and
An insulating member disposed between the plurality of piezoelectric materials,
The insulating member surrounds side surfaces of each of the plurality of piezoelectric bodies, and upper and lower surfaces thereof are positioned on the same plane as the upper and lower surfaces of the piezoelectric body, so that the upper and lower surfaces of the first electrode are higher than the upper surface of the insulating member. It is exposed to the outside at a protruding position, and the lower surface and side surface of the second electrode are exposed to the outside at a lower protruding position than the lower surface of the insulating member,
A concave portion is formed on an upper surface of the insulating member, and the concave portion is configured to be exposed upward from a position lower than the upper surface of the first electrode.
According to claim 1,
The width of the second electrode is
50% or more to less than 100% of the width of the first electrode,
A piezoelectric sensor smaller than the width of the piezoelectric body.
delete According to claim 1,
A width of the first electrode is greater than a width of the second electrode.
delete delete According to claim 1,
The plurality of piezoelectric materials are disposed spaced apart from each other in a lattice structure.
According to claim 1,
The first electrode and the piezoelectric body have the same horizontal width and vertical width,
A side surface of the first electrode is disposed on the same plane as a side surface of the piezoelectric body.
delete delete providing a bulk type piezoelectric body having a first surface on one side and a second surface on the other side;
disposing a first electrode on a first surface of the piezoelectric body;
forming a lattice groove at a first depth on a first surface of the piezoelectric body through the first electrode;
disposing an insulating member in a lattice groove on one side of the piezoelectric body;
disposing an adhesive layer and a support substrate on one side of the piezoelectric body;
grinding the second surface of the other side of the piezoelectric material to expose the insulating member to form a plurality of piezoelectric elements spaced apart by the insulating member;
forming a piezoelectric element by disposing a plurality of second electrodes on each of the second surfaces of the plurality of piezoelectric elements;
electrically connecting the piezoelectric element to a substrate; and
removing the adhesive layer and the support substrate; including,
The step of forming the lattice groove is
forming a plurality of first grooves in a first direction on a first surface of the piezoelectric body through the first electrode; and
forming a plurality of second grooves in a second direction on the first surface of the piezoelectric body by penetrating the first electrode; including,
In the step of forming the lattice groove,
The plurality of first grooves have the same distance apart from each other, and the plurality of second grooves have the same distance apart from each other,
In the step of forming the piezoelectric element,
The width of the second electrode is smaller than the width of the piezoelectric body,
The width of the second electrode is smaller than that of the first electrode disposed on the first surface of the piezoelectric body;
In the step of disposing the insulating member,
A piezoelectric sensor manufacturing method in which a concave portion is formed on one side of the insulating member.

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