Low resistance fingerprint sensor and method of manufacturing the same

A fingerprint sensor includes a substrate, and a plurality of first electrodes disposed on the substrate, and including a plurality of first pattern parts and a plurality of first connectors. The plurality of first electrodes is repeatedly arranged in a second direction intersecting a first direction, and the plurality of first connectors connects the plurality of first pattern parts in the first direction. The fingerprint sensor further includes an insulating layer disposed on the plurality of first electrodes, and a plurality of second electrodes disposed on the insulating layer, and including a plurality of second pattern parts and a plurality of second connectors. The plurality of second electrodes is repeatedly arranged in the first direction, and the plurality of second connectors connects the plurality of second pattern parts in the second direction. The plurality of first connectors and/or the plurality of second connectors include a metal material.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No. 10-2018-0095732, filed on Aug. 16, 2018, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

Apparatuses and methods consistent with embodiments relate to a fingerprint sensor and a method of manufacturing the fingerprint sensor.

2. Description of the Related Art

There is an increasing need for personal authentication using a unique characteristic of a person, the characteristic including fingerprints, a voice, a face, hands, or irises. A personal authentication function is mainly used in financial equipment, access controllers, mobile devices, notebooks, or the like, and due to the wide spread of mobile devices such as smartphones, a fingerprint recognition device for personal authentication is used to protect lots of information stored in a smartphone.

A touchscreen device is mounted in a display of a smartphone and provides an intuitive input interface to a user, and in general, a fingerprint recognition device is arranged separately from the touchscreen device and is enabled to recognize a fingerprint only when a preset position is touched.

When a fingerprint recognition device is embodied on a display panel, an electrode of the fingerprint recognition device may be arranged as a transparent electrode to allow clear view of an image of the display panel. However, when the electrode includes such transparent electrode material, resistance of the electrode may be increased. Furthermore, to increase the resolution of the image of the display panel and sensitivity of the fingerprint recognition device, the size of the electrode has to be reduced, and accordingly, the resistance of the electrode including the transparent electrode material may be further increased.

SUMMARY

According to embodiments, a fingerprint sensor includes a substrate, and a plurality of first electrodes disposed on the substrate, and including a plurality of first pattern parts and a plurality of first connectors. The plurality of first electrodes is repeatedly arranged in a second direction intersecting a first direction, and the plurality of first connectors connects the plurality of first pattern parts in the first direction. The fingerprint sensor further includes an insulating layer disposed on the plurality of first electrodes, and a plurality of second electrodes disposed on the insulating layer, and including a plurality of second pattern parts and a plurality of second connectors. The plurality of second electrodes is repeatedly arranged in the first direction, and the plurality of second connectors connects the plurality of second pattern parts in the second direction. Either one or both of the plurality of first connectors and the plurality of second connectors include a metal material.

The metal material may include any one or any combination of platinum (Pt), ruthenium (Ru), gold (Au), silver (Ag), molybdenum (Mo), aluminum (Al), tungsten (W), palladium (Pd), magnesium (Mg), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), titanium (Ti), or copper (Cu), and a metal alloy.

A remaining one of the plurality of first connectors and the plurality of second connectors may not include the metal material, and may include a first material same as a second material included in the plurality of first pattern parts and the plurality of second pattern parts.

The plurality of first connectors and the plurality of second connectors may include the metal material.

The plurality of first pattern parts and the plurality of second pattern parts may include a transparent conductive material.

The transparent conductive material may include either one or both of indium tin oxide (ITO) and a first material having an oxide-metal-oxide (OMO) structure.

Each of the plurality of first pattern parts and the plurality of second pattern parts may have a rhombus shape.

The first direction may be perpendicular to the second direction.

According to embodiments, a method of manufacturing a fingerprint sensor, includes forming, on a substrate, a plurality of first electrodes that includes a plurality of first pattern parts and a plurality of first connectors and is repeatedly arranged in a second direction intersecting a first direction. The plurality of first connectors connects the plurality of first pattern parts in the first direction. The method further includes forming an insulating layer on the plurality of first electrodes, and forming, on the insulating layer, a plurality of second electrodes that includes a plurality of second pattern parts and a plurality of second connectors and is repeatedly arranged in the first direction. The plurality of second connectors connects the plurality of second pattern parts in the second direction, and either one or both of the plurality of first connectors and the plurality of second connectors include a metal material

The forming of the plurality of first electrodes may include forming the plurality of first pattern parts on the substrate, and forming the plurality of first connectors connecting the plurality of first pattern parts in the first direction, respectively in spaces among the plurality of first pattern parts.

The forming of the plurality of first electrodes may include forming the plurality of first connectors on the substrate, and forming the plurality of first pattern parts respectively in spaces among the plurality of first connectors, such that the plurality of first connectors connect the plurality of first pattern parts in the first direction.

The forming of the plurality of second electrodes may include forming the plurality of second pattern parts on the insulating layer, and forming the plurality of second connectors connecting the plurality of second pattern parts in the second direction, respectively in spaces among the plurality of second pattern parts.

The forming of the plurality of second electrodes may include forming the plurality of second connectors on the insulating layer, and forming the plurality of second pattern parts respectively in spaces among the plurality of second connectors, such that the plurality of second connectors connect the plurality of second pattern parts in the second direction.

A remaining one of the plurality of first connectors and the plurality of second connectors may not include the metal material, and may include a first material same as a second material included in the plurality of first pattern parts and the plurality of second pattern parts.

The plurality of first connectors and the plurality of second connectors may include the metal material.

DETAILED DESCRIPTION

Hereinafter, a low resistance fingerprint sensor and a method of manufacturing the low resistance fingerprint sensor will now be described with reference to the accompanying drawings. In the drawings, like reference numerals in the drawings denote like elements, and the size or thickness of each component may be exaggerated for clarity.

While terms “first” and “second” are used to describe various components, it is obvious that the components are not limited to the terms “first” and “second.” The terms “first” and “second” are used only to distinguish between each of components. The low resistance fingerprint sensor and the method of manufacturing the low resistance fingerprint sensor may be embodied in many different forms and may not be construed as being limited to the embodiments set forth herein.

Throughout the specification, when a part “includes” or “comprises” an element, unless there is a particular description contrary thereto, the part can further include other elements, not excluding the other elements.

FIG. 1is a plan view illustrating a fingerprint sensor1000according to embodiments.FIG. 2is a cross-sectional view of the fingerprint sensor1000ofFIG. 1, taken along a line A-A′.FIG. 3is a cross-sectional view of the fingerprint sensor1000ofFIG. 1, taken along a line B-B′.

Referring toFIG. 1, the fingerprint sensor1000may include a plurality of first electrodes Tx1and Tx2and a plurality of second electrodes Rx1and Rx2arranged on the plurality of first electrodes Tx1and Tx2, wherein the first electrodes Tx1and Tx2are arranged in parallel to a first direction (a y-axis direction) and are repeatedly arranged in a second direction (an x-axis direction) crossing the first direction (the y-axis direction) and the second electrodes Rx1and Rx2are arranged in parallel to the second direction (the x-axis direction) and are repeatedly arranged in the first direction (the y-axis direction). The first direction (the y-axis direction) and the second direction (the x-axis direction) may be perpendicular to each other.

A voltage may be externally applied to one of the first electrodes Tx1and Tx2and the second electrodes Rx1and Rx2. When the voltage is applied to one of the first electrodes Tx1and Tx2and the second electrodes Rx1and Rx2, mutual capacitance may be generated between the first electrodes Tx1and Tx2and the second electrodes Rx1and Rx2. When a user touches one of the first electrodes Tx1and Tx2and the second electrodes Rx1and Rx2by using a finger, variation may occur in mutual capacitance generated between a touched region of the touched electrode and an untouched electrode. The variation in the mutual capacitance may vary in an electrode adjacent to ridges of a fingerprint of a surface of the finger of the user and in an electrode adjacent to valleys of the fingerprint. By allowing a distance between electrodes to be narrower than a distance between ridges or valleys of the fingerprint, variation in mutual capacitance due to the finger may be detected for each position, such that a fingerprint image may be calculated.

The first electrodes Tx1and Tx2may be driving electrodes to which a voltage is applied from an external source, and in this case, the second electrodes Rx1and Rx2may be sensing electrodes to which a measurer to sense variation in capacitance is connected. On the other hand, the second electrodes Rx1and Rx2may be driving electrodes to which a voltage is applied from an external source, and in this case, the first electrodes Tx1and Tx2may be sensing electrodes to which a measurer to sense variation in capacitance is connected. The sensing electrode may be an electrode to be touched by the finger of the user.

Referring toFIG. 2, a plurality of first pattern parts110may be arranged and spaced apart from each other on a substrate S. A plurality of first connectors120may be arranged in a plurality of spaces formed among the plurality of first pattern parts110. In this case, the plurality of first connectors120may connect the plurality of first pattern parts110in the first direction (the y-axis direction). In this manner, the plurality of first pattern parts110are connected in the first direction (the y-axis direction) by the plurality of first connectors120, such that the first electrodes Tx1and Tx2may be formed. The first electrodes Tx1and Tx2may be repeatedly arranged in the second direction (the x-axis direction). An insulating layer300may be formed on the first electrodes Tx1and Tx2. The second electrodes Rx1and Rx2including a second pattern part210and a second connector220may be formed on the insulating layer300. The insulating layer300may cover the first pattern part110and the first connector120, thereby spacing the first electrodes Tx1and Tx2from the second electrodes Rx1and Rx2. In the cross-section of the portion A-A′, the second connector220of the second electrode Rx1and Rx2may be illustrated.

Referring toFIG. 3, a plurality of the second pattern parts210may be spaced apart from each other on the insulating layer300. A plurality of the second connectors220may be arranged in a plurality of spaces formed among the plurality of second pattern parts210. In this case, the plurality of second connectors220may connect the plurality of second pattern parts210in the second direction (the x-axis direction). In this manner, the plurality of second pattern parts210are connected in the second direction (the x-axis direction) by the plurality of second connectors220on the insulating layer300, such that second electrodes Rx1and Rx2may be formed. The second electrodes Rx1and Rx2may be repeatedly arranged in the first direction (the y-axis direction).

The plurality of first electrodes Tx1and Tx2are arranged on the substrate S, and may include the plurality of first connectors120that connect the plurality of first pattern parts110in the first direction (the y-axis direction).FIG. 1illustrates that each of first electrodes Tx1and Tx2includes three first pattern parts110and two first connectors120, but the number of first pattern parts110and the number of first connectors120are not limited thereto and may be more than the illustration. The first electrodes Tx1and Tx2may be repeatedly arranged in parallel to the second direction (the x-axis direction). The insulating layer300may be arranged on the plurality of first electrodes Tx1and Tx2.

The plurality of second electrodes Rx1and Rx2are arranged on the insulating layer300, and may include the plurality of second pattern parts210and the plurality of second connectors220that connect the plurality of second pattern parts210in the second direction (the x-axis direction) crossing the first direction (the y-axis direction).FIG. 1illustrates that each of second electrodes Rx1and Rx2includes three second pattern parts210and two second connectors220, but the number of second pattern parts210and the number of second connectors220are not limited thereto and may be more than the illustration. The second electrode Rx1and Rx2may be repeatedly arranged in parallel to the first direction (the y-axis direction).

Each of the plurality of first pattern parts110and each of the plurality of second pattern parts210may include a transparent conductive material. The transparent conductive material may include either one or both of indium tin oxide (ITO) and a material having an oxide-metal-oxide (OMO) structure. A sheet resistance of the transparent conductive material may be between about 1Ω and about 20Ω. Also, light transmittance of the transparent conductive material may be between about 70% and about 95%.

Each of the plurality of first pattern parts110and each of the plurality of second pattern parts210may have a rhombus shape. However, a pattern shape of the plurality of first pattern parts110and the plurality of second pattern parts210is not limited to the rhombus shape and may have one of various shapes including a polygonal shape, a round shape, or the like.

The fingerprint sensor1000ofFIG. 1includes two first electrodes Tx1and Tx2and two second electrodes Rx1and Rx2, but the disclosure is not limited thereto and the fingerprint sensor1000may include at least three first electrodes Tx1and Tx2and at least three second electrodes Rx1and Rx2.

Either one or both of the first connector120and the second connector220may include a metal material. The metal material may include a conductive metal material including platinum (Pt), ruthenium (Ru), gold (Au), silver (Ag), molybdenum (Mo), aluminum (Al), tungsten (W), palladium (Pd), magnesium (Mg), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), titanium (Ti), or copper (Cu) or a metal alloy. A thickness and length of each of the first connector120and the second connector220may be appropriately set so that a value of sheet resistance of each of the first connector120and the second connector220is between about 0.01Ω and about 1Ω.

Because the plurality of first pattern parts110and the plurality of second pattern parts210are connected by the plurality of first connectors120and the plurality of second connectors220, each of the plurality of first connectors120and each of the plurality of second connectors220including the metal material, sheet resistance of each of the first electrode Tx1and Tx2and the second electrode Rx1and Rx2may be decreased compared to a case in which each of the plurality of first connectors120and each of the plurality of second connectors220do not include the metal material.

FIG. 4is a graph of a comparison between resistance values of an electrode of the fingerprint sensor1000according to types and shapes of a connector included in the fingerprint sensor1000ofFIG. 1.

Referring toFIG. 4, a resistance value of the electrode of the fingerprint sensor1000when the first connector120or the second connector220includes a transparent conductive material, e.g., ITO, may be different from a resistance value of the electrode of the fingerprint sensor1000when the first connector120or the second connector220includes a metal material.

First, in a case in which the first connector120or the second connector220includes ITO that is the transparent conductive material, a line width of the first connector120or the second connector220is 7 μm, and a thickness of the first connector120or the second connector220in a z-axis direction ofFIGS. 1 to 3is 0.2 μm, a resistance value of the electrode may be about 27Ω.

When the first connector120or the second connector220includes the metal material, three cases of a resistance value of the electrode are illustrated. First, in the case in which the line width of the first connector120or the second connector220is 3 μm, and the thickness of the first connector120or the second connector220in the z-axis direction is 0.2 μm, a resistance value of the electrode may be about 10.4Ω. Next, in the case in which the line width of the first connector120or the second connector220is 1 μm, and the thickness of the first connector120or the second connector220in the z-axis direction is 0.2 μm, a resistance value of the electrode may be about 11.2Ω. Lastly, in the case in which the line width of the first connector120or the second connector220is 3 μm, and the thickness of the first connector120or the second connector220in the z-axis direction is 0.2 μm, a resistance value of the electrode may be about 12.4Ω.

In this manner, a resistance value of the electrode of the case in which the first connector120or the second connector220includes the metal material may be decreased to about ⅓ to about ½ of a resistance value of the electrode of the case in which the first connector120or the second connector220includes the transparent conductive material.

FIG. 5illustrates sequential operations of a method of manufacturing a fingerprint sensor1001according to embodiments.FIG. 6illustrates sequential operations of a method of manufacturing a fingerprint sensor1002according to other embodiments.

Referring toFIG. 5, in first operation S101, a plurality of first pattern parts111may be formed separately from each other on a substrate S. The plurality of first pattern parts111may each be formed via etching. Alternatively, well-known techniques may be used to form the plurality of first pattern parts111.

In second operation S102, a plurality of first connectors121may be arranged in a plurality of spaces formed among the plurality of first pattern parts111. In this case, the plurality of first connectors121may connect the plurality of first pattern parts111in a first direction (a y-axis direction). In this manner, a first electrode Tx including the plurality of first connectors121and the plurality of first pattern parts111may be formed.

In third operation S103, an insulating layer301may be formed on the first electrode Tx. The insulating layer301may include various insulating materials that are not conductive. The insulating layer301may insulate the first electrode Tx from a second electrode Rx to be arranged on the insulating layer301as will be described below.

In fourth operation S104, the second electrode Rx including a second pattern part and a second connector221may be formed on the insulating layer301. A process of forming the second electrode Rx may be equal to a process of forming the first electrode Tx described with reference toFIG. 5.FIG. 5illustrates only the second connector221of the second electrode Rx and does not illustrate the second pattern part, because the first electrode Tx and the second electrode Rx are arranged in an intersecting direction.

Referring toFIG. 6, in first operation S201, a plurality of first connectors122may be formed on a substrate S. The plurality of first connectors122may connect a plurality of first pattern parts112to be formed in a first direction (a y-axis direction).

In second operation S202, the first pattern part112may be formed at both sides of the first connector122in the first direction (the y-axis direction). By doing so, the plurality of first pattern parts112may be connected by the plurality of first connectors122in the first direction (the y-axis direction). In this manner, a first electrode Tx including the plurality of first connectors122and the plurality of first pattern parts112may be formed.

In third operation S203, an insulating layer302may be formed on the first electrode Tx including the plurality of first pattern parts112and the plurality of first connectors122. The insulating layer302may include various insulating materials that are not conductive. The insulating layer302may insulate the first electrode Tx from a second electrode Rx to be arranged on the insulating layer302as will be described below.

In fourth operation S204, the second electrode Rx including a second pattern part and a second connector222may be formed on the insulating layer302. A process of forming the second electrode Rx may be equal to a process of forming the first electrode Tx described with reference toFIG. 6.FIG. 6illustrates only the second connector222of the second electrode Rx and does not illustrate the second pattern part, because the first electrode Tx and the second electrode Rx are arranged in an intersecting direction.

As described above with reference toFIG. 5, when the first electrode Tx is formed, the first pattern part111may be first formed and then the first connector121may be formed. Alternatively, as described above with reference toFIG. 6, when the first electrode Tx is formed, the first connector122may be first formed and then the first pattern part112may be formed. The manufacturing order of the first electrode Tx may be selected according to etching selectivity by a manufacturer, the etching selectivity being with respect to a transparent conductive material that may be included in the first pattern part111or112and a metal material that may be included in the first connector121or122. The manufacturing order of the second electrode Rx may also be selected according to etching selectivity by a manufacturer.

FIG. 7is a plan view illustrating a fingerprint sensor2000according to other embodiments. Descriptions ofFIG. 7that are redundant with descriptions ofFIG. 1are not provided.

Referring toFIG. 7, a plurality of first connectors123included in a plurality of first electrodes Tx1and Tx2may include a transparent conductive material, the plurality of first electrodes Tx1and Tx2being in parallel to a first direction (a y-axis direction) and repeatedly arranged in a second direction (an x-axis direction).

A plurality of second connectors223included in a plurality of second electrodes Rx1and Rx2may include a metal material, the plurality of second electrodes Rx1and Rx2being in parallel to the second direction (the x-axis direction) and repeatedly arranged in the first direction (the y-axis direction).

By doing so, the fingerprint sensor2000in which only the second connector223among the first connector123and the second connector223includes the metal material may be manufactured.

FIG. 8is a plan view illustrating a fingerprint sensor3000according to other embodiments. Descriptions ofFIG. 8that are redundant with descriptions ofFIG. 1are not provided.

Referring toFIG. 8, a plurality of first connectors124included in a plurality of first electrodes Tx1and Tx2may each include a metal material, the plurality of first electrodes Tx1and Tx2being in parallel to a first direction (a y-axis direction) and repeatedly arranged in a second direction (an x-axis direction).

A plurality of second connectors224included in a plurality of second electrodes Rx1and Rx2may each include a transparent metal material, the plurality of second electrodes Rx1and Rx2being in parallel to the second direction (the x-axis direction) and repeatedly arranged in the first direction (the y-axis direction).

By doing so, the fingerprint sensor3000in which only the first connector124among the first connector124and the second connector224includes the metal material may be manufactured.

Various embodiments of the disclosure may provide a fingerprint sensor whose resistance value is decreased by including a plurality of connectors including a metal.