CN108694364B - Fingerprint acquisition device and preparation method thereof - Google Patents
Fingerprint acquisition device and preparation method thereof Download PDFInfo
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- CN108694364B CN108694364B CN201710237274.6A CN201710237274A CN108694364B CN 108694364 B CN108694364 B CN 108694364B CN 201710237274 A CN201710237274 A CN 201710237274A CN 108694364 B CN108694364 B CN 108694364B
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
- G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
- G06V40/12—Fingerprints or palmprints
- G06V40/13—Sensors therefor
- G06V40/1306—Sensors therefor non-optical, e.g. ultrasonic or capacitive sensing
Abstract
The embodiment of the invention provides a fingerprint acquisition device and a preparation method thereof, wherein the device comprises: the substrate, the two-dimensional material array layer and the flexible protective layer are sequentially connected from bottom to top; the substrate comprises a substrate layer, a bottom electrode layer and an insulation array layer; the two-dimensional material array layer is formed on the upper surface of the insulation array layer and is connected with the bottom electrode layer through the through holes in the insulation array layer, and the bottom electrode layer and the two-dimensional material array layer are electrically connected with the substrate respectively to form a plurality of detection loops. The method comprises the following steps: forming a bottom electrode layer on the substrate layer, forming an insulation array layer with a plurality of through holes on the bottom electrode layer, forming a connecting electrode layer on one side of each through hole, forming a plurality of two-dimensional material units on the connecting electrode layer and the insulation array layer, wherein two ends of each two-dimensional material unit are respectively connected with the connecting electrode layer and the top electrode layer, and the bottom electrode layer and the top electrode layer are respectively electrically connected with a preset substrate; the surface of the device is covered with a flexible protective layer. The embodiment of the invention improves the accuracy and efficiency of fingerprint identification.
Description
Technical Field
The embodiment of the invention relates to the technical field of image acquisition, in particular to a fingerprint acquisition device and a preparation method thereof.
Background
With the development of electronic information technology and the popularization of electronic products, personal data and information security in some electronic products (especially mobile phones and computers) are receiving more and more attention. At present, common verification means include password verification, graphic verification and the like, namely, a specific character string combination is input, or a specific graphic is input into the electronic products, and if an input value is the same as a preset value, the purpose of verifying the identity of a user is achieved.
In recent years, identity authentication means such as biometric identification has been developed, which is to detect a specific biometric feature on a person, such as a fingerprint, a voiceprint, an iris, etc., to verify the validity of a user's identity. The existing fingerprint identification technology is mainly divided into three types, namely optical detection, capacitance detection and ultrasonic detection. The optical detection obtains the gray level image of the surface texture on the surface of the finger by irradiating light, although the technology is mature and cheap, the equipment volume is large, and the requirement on the cleanliness of hands is high; the capacitance detection obtains the gray level image of the lines through different capacitance differences between the finger lines and the silicon sensor, the technology overcomes the defect of large volume of optical detection equipment, realizes the target of integration in the smart phone, but still has higher requirements on the cleanliness of the fingers, and the reliability of the detection is still not high; ultrasonic detection utilizes ultrasonic waves to generate echoes with different sizes on different material interfaces to detect the positions of fingerprint ridges and valleys, and the technology also has smaller volume, so that the requirement on the cleanness degree of fingers is reduced to a certain extent, but the acquisition time is relatively longer, and the fingerprint identification efficiency is reduced.
Therefore, how to provide a scheme for realizing accuracy and efficiency of fingerprint identification becomes a problem to be solved urgently.
Disclosure of Invention
Aiming at the defects in the prior art, the embodiment of the invention provides a fingerprint acquisition device and a preparation method thereof.
In one aspect, an embodiment of the present invention provides a fingerprint acquisition apparatus, including:
the device comprises: the substrate, the two-dimensional material array layer and the flexible protective layer are sequentially arranged from bottom to top;
the substrate comprises a substrate layer, a bottom electrode layer and an insulation array layer which are sequentially arranged from bottom to top, wherein a plurality of through holes are formed in the insulation array layer;
the two-dimensional material array layer is formed on one surface, far away from the bottom electrode layer, of the insulation array layer and is connected with the bottom electrode layer through the through hole, and the bottom electrode layer and the two-dimensional material array layer are respectively and electrically connected with a substrate outside the device to form a plurality of detection loops;
the detection loop is used for collecting resistance changes corresponding to different deformations of the two-dimensional material array layer due to pressure so as to obtain a gray level image of fingerprint lines.
Further, the two-dimensional material array layer comprises a connecting electrode layer, a top electrode layer and a two-dimensional material layer, the connecting electrode layer is connected with the bottom electrode layer through the through hole, and a gap is reserved between the connecting electrode layer and the side wall of the through hole;
the two-dimensional material layer includes a plurality of two-dimensional material units, and is a plurality of the shaping of two-dimensional material unit is in connect electrode layer with the insulating array layer is kept away from the one side of bottom electrode layer, just two-dimensional material unit one end is connected connect electrode layer, and the other end is connected the top electrode layer, the top electrode layer with the outside base plate electricity of device is connected, the top electrode layer with bottom electrode layer constitutes a plurality ofly detect the return circuit.
Further, the two-dimensional material unit covers over the through hole or the upper surfaces of the connection electrode layer and the insulating array layer.
Further, the bottom electrode layer is formed on the upper surface of the substrate layer in a strip shape, and correspondingly, the through holes in the insulation array layer are formed in positions corresponding to the bottom electrode layer.
Further, the top electrode layer is formed on the upper surface of the insulating array layer in a strip shape, and the top electrode layer and the bottom electrode layer are arranged in a crossed mode; each strip bottom electrode and each strip top electrode are electrically connected with an external substrate, the substrate comprises a control circuit, and the control circuit is used for scanning each strip bottom electrode and each strip top electrode to form a plurality of detection loops.
In another aspect, an embodiment of the present invention provides a method for manufacturing a fingerprint acquisition device, including:
forming a bottom electrode layer on the upper surface of the selected substrate layer;
forming an insulating array layer on the upper surface of the bottom electrode layer, and arranging a plurality of through holes on the upper surface of the insulating array layer;
forming a connection electrode layer on one side of the through hole so that the connection electrode layer is connected with the bottom electrode layer;
forming a plurality of two-dimensional material units on the upper surfaces of the connection electrode layer and the insulation array layer, wherein one end of each two-dimensional material unit is connected with the connection electrode layer, the other end of each two-dimensional material unit is connected with the top electrode layer, and the top electrode layer and the bottom electrode layer are electrically connected with a preset substrate to form a plurality of detection loops;
and covering a flexible protective layer on the upper surfaces of the two-dimensional material unit, the top electrode layer and the insulation array layer.
Further, the forming a bottom electrode layer on the surface of the selected substrate layer includes:
and sputtering a series of strip electrodes as the bottom electrode layer on the substrate layer after patterning by taking a hard mask as a template or utilizing a photoetching technology.
Further, the setting of the through hole on the surface of the insulation array layer includes:
patterning is carried out through photoetching or an array of micron-sized through holes are etched on the surface of the insulating array layer by using a hard mask as a template through dry etching or wet etching, wherein the through holes are positioned on the strip-shaped bottom electrode layer.
Further, the forming a connection electrode layer at one side of the through hole to connect the connection electrode layer with the bottom electrode layer includes:
and patterning through photoetching, exposing one side of the through hole, and stripping the photoresist through sputtering, deposition or evaporation to form the connecting electrode layer on one side of the through hole.
Further, the forming a plurality of two-dimensional material units on the surface of the connection electrode layer and the surface of the insulation array layer includes:
transferring a large piece of two-dimensional material to the upper surfaces of the connection electrode layer and the insulation array layer by a dry method or a wet method;
and patterning by photoetching to protect the two-dimensional material on the through hole or on one side of the through hole and connected with the connecting electrode layer, and etching to remove the unprotected two-dimensional material to form a two-dimensional material layer.
The fingerprint acquisition device and the preparation method thereof provided by the embodiment of the invention can realize the rapid acquisition of the fingerprint image, reduce the influence of pollutants such as moisture, grease and the like attached to the skin on the acquisition of the fingerprint image and the accuracy of fingerprint identification, and improve the accuracy and efficiency of the fingerprint identification.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of a fingerprint acquisition device according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of another fingerprint acquisition device according to an embodiment of the present invention;
FIG. 3 is a schematic plane view of a hole-type fingerprint acquisition device according to an embodiment of the present invention;
FIG. 4 is a schematic plane view of a planar fingerprint acquisition device according to an embodiment of the present invention;
FIG. 5 is a schematic flow chart illustrating a method for manufacturing a fingerprint acquisition device according to an embodiment of the present invention;
FIG. 6 is a schematic flow chart illustrating a method for manufacturing a hole-type fingerprint acquisition device according to an embodiment of the present invention;
fig. 7 is a schematic flow chart of a manufacturing method of the planar fingerprint acquisition device in the embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a schematic structural diagram of a fingerprint acquisition device according to an embodiment of the present invention, and as shown in fig. 1, the fingerprint acquisition device according to the embodiment of the present invention includes:
the substrate 10, the two-dimensional material array layer 20 and the flexible protection layer 30 are connected in sequence from bottom to top;
the substrate 10 comprises a substrate layer 11, a bottom electrode layer 12 and an insulation array layer 13 which are sequentially connected from bottom to top, wherein a plurality of through holes 14 are formed in the insulation array layer 13;
the two-dimensional material array layer 20 is formed on one surface, far away from the bottom electrode layer, of the insulation array layer 13 and is connected with the bottom electrode layer 12 through the through hole 14, and the bottom electrode layer 12 and the two-dimensional material array layer 20 are respectively and electrically connected with a substrate outside the device to form a plurality of detection loops;
the detection loop is used for collecting resistance changes corresponding to different deformations of the two-dimensional material array layer 20 caused by pressure so as to obtain a gray level image of fingerprint lines.
Specifically, as shown in fig. 1, a substrate layer 11, a bottom electrode layer 12, and an insulating array layer 13 connected in sequence from bottom to top form a substrate, and a plurality of through holes 14 are disposed on the insulating array layer 13, where the shape of the through holes 14 may be a cylinder, a square, or another shape, and embodiments of the present invention are not limited in particular. The two-dimensional material array layer 20 is disposed on the upper surface of the insulating array layer 13 and connected to the bottom electrode layer 12 through the via hole 14. The bottom electrode layer 12 and the two-dimensional material array layer 20 are respectively electrically connected with a substrate located outside the fingerprint acquisition device through leads to form a detection loop, wherein the bottom electrode layer 12 and the two-dimensional material array layer 20 can form a plurality of detection loops, resistance changes corresponding to different deformations generated by the two-dimensional material array layer 20 due to different pressures in the plurality of detection loops are obtained, and a grayscale image of fingerprint grains is further obtained. A thin flexible protective layer 30 is provided on the top surface of the two-dimensional material array layer 20 and the substrate 10, i.e. the upper surface of the fingerprint acquisition device. Wherein: the material of the substrate layer 11 can be selected from Si and Si/SiO2、Si/HfO2、Si/Al2O3、Si/MgO、Si/TiO2、Si/SiNxSilicon-based substrates, Mica (Mica ore), diamond, SiC (silicon carbide), sapphire, quartz, glass and the like can also be used as the substrates, and can also be flexible substrates PI (plastic raw material, Chinese commonly known as polyimide), PET (polyethylene terephthalate) (II)Dacron resin), PDMS (polydimethylsiloxane), rubber, etc. The bottom electrode layer 12 may be Au, and the insulating array layer 13 may be SiO2、HfO2、TiO2、Al2O3MgO, which is characterized by an insulating array layer being thin and not easily deformed; the insulating array layer 13 can also be made of parylene, PDMS and other organic insulating layers, and is characterized by being thin and flexible, and can be deformed in the same way when a two-dimensional material is deformed. The two-dimensional material array layer 20 may be made of graphene or other two-dimensional materials with good piezoresistive properties, such as tungsten sulfide, black phosphorus, and the like, and the two-dimensional materials refer to materials in which electrons can move freely (planar motion) only on two dimensions of non-nanoscale (1-100nm), such as a nano-film, a superlattice, and a quantum well. The flexible protection layer 30 may be selected from PDMS, PVA (polyvinyl alcohol), PMMA (polymethyl methacrylate), photoresist, parylene, and the like.
The fingerprint line is divided into ridge and valley, and when the finger pressed flexible protection layer 30, the pressure that two-dimensional material array layer 20 below the flexible protection layer 30 of ridge and valley corresponding position received was different, and the deformation volume of production is also different, can produce different resistance changes promptly. It is even possible that the two-dimensional material array layer 20 at locations corresponding to ridges has a change in resistance while the two-dimensional material array layer 20 at locations corresponding to valleys has no change in resistance. Therefore, the fingerprint acquisition device can be electrically connected with the corresponding substrate through a large-array two-dimensional material piezoresistive device, and the gray level image of fingerprint grains can be detected through the detection circuit so as to perform later characteristic comparison and realize the purpose of fingerprint identification. In addition, the pressure sensing can reduce the influence of pollutants such as moisture, grease and the like attached to the skin on the fingerprint identification accuracy. Because these contaminants are squeezed into the valleys of the fingerprint as the finger is pressed, and because of their fluidity, they do not cause a force to the two-dimensional material pressure sensor at the valley locations that is close in magnitude to the pressure of the fingerprint ridges, thereby reducing the likelihood that the location of the contaminants will be detected as ridges. Meanwhile, since the piezoresistive effect is a transient effect, the response speed may exceed that of the ultrasonic detection means.
The fingerprint acquisition device provided by the embodiment of the invention can realize the rapid acquisition of the fingerprint image, reduces the influence of pollutants such as moisture, grease and the like attached to the skin on the acquisition of the fingerprint image and the accuracy of fingerprint identification, and improves the accuracy and efficiency of the fingerprint identification.
On the basis of the above embodiment, the two-dimensional material array layer includes a connection electrode layer, a top electrode layer and a two-dimensional material layer, the connection electrode layer is connected with the bottom electrode layer through the through hole, and a gap is left between the connection electrode layer and the side wall of the through hole;
the two-dimensional material layer includes a plurality of two-dimensional material units, and is a plurality of the shaping of two-dimensional material unit is in connect electrode layer with the insulating array layer is kept away from the one side of bottom electrode layer, just two-dimensional material unit one end is connected connect electrode layer, and the other end is connected the top electrode layer, the top electrode layer with the outside base plate electricity of device is connected, the top electrode layer with bottom electrode layer constitutes a plurality ofly detect the return circuit.
Specifically, as shown in fig. 1, the two-dimensional material array layer 20 includes a connection electrode layer 21, a top electrode layer 22, and a two-dimensional material layer 23, wherein the connection electrode layer 21 is connected to the bottom electrode layer 12 through the through hole 14, and as shown in fig. 1, a certain gap is left between the connection electrode layer 21 and one sidewall of the through hole 14, that is, the through hole 14 is not filled with the connection electrode layer, and a gap is left between the two-dimensional material layer and the bottom electrode layer, that is, the position of the through hole 14, to provide a space for deformation of the two-dimensional material layer 23. The two-dimensional material layer 23 includes a plurality of two-dimensional material units 231, and as shown in fig. 1, the two-dimensional material units 231 are formed on the top surfaces of the connection electrode layer 21 and the insulation array layer 13, that is, the plurality of two-dimensional material units 231 are arranged in an array on the upper surfaces of the connection electrode layer 21 and the insulation array layer 13. And one end of the two-dimensional material unit 231 is connected with the connecting electrode layer 21, the other end is connected with the top electrode layer 22, the top electrode layer 22 and the bottom electrode layer 12 are respectively and electrically connected with a substrate outside the device to form a plurality of detection loops, so that when the two-dimensional material deforms due to pressure, the change of the resistance value of the two-dimensional material is detected, and the gray level image of the fingerprint is acquired.
On the basis of the above embodiment, the two-dimensional material unit covers the through hole or the upper surfaces of the connection electrode layer and the insulation array layer.
Specifically, as shown in fig. 1, the two-dimensional material unit 231 is completely covered above the through hole 14, but of course, the two-dimensional material unit 231 may be covered on the upper surfaces of the insulating array layer 13 and the connection electrode layer 21 other than the through hole 14 as needed. Fig. 2 is a schematic structural diagram of another fingerprint acquisition device according to an embodiment of the present invention, as shown in fig. 2, the structure of fig. 2 is different from that of the fingerprint acquisition device in fig. 1 in that a two-dimensional material unit 231 covers a position, in which the two-dimensional material unit 231 completely covers a through hole 14 in fig. 1, and in fig. 2, the two-dimensional material unit 231 covers the upper surface of an insulating array layer 13 and a connection electrode layer 21 outside the through hole 14. It should be noted that the material used for the insulating array layer 13 in fig. 1 is a hard material, such as SiO, which is not easily deformed2、HfO2、TiO2、Al2O3Or MgO, and thus, the space required for deformation is provided for the two-dimensional material by the through-hole 14 by covering the two-dimensional material unit 231 on the through-hole 14. The insulating array layer 13 in fig. 2 is made of a flexible and easily deformable material, such as parylene, PDMS, and the like, and the two-dimensional material unit 231 covers the upper surfaces of the insulating array layer 13 and the connection electrode layer 21 outside the through hole 14, so that a space required for deformation is provided for the two-dimensional material by using the flexible material used for the insulating array layer 13.
On the basis of the above embodiment, the bottom electrode layer is formed on the upper surface of the substrate layer in a strip shape, and correspondingly, the through holes on the insulation array layer are arranged at positions corresponding to the bottom electrode layer.
Specifically, the bottom electrode layer 12 is arranged in a stripe shape on the upper surface of the substrate layer 11, that is, the upper surface of the substrate layer 11 is not completely covered with the bottom electrode layer 12, and a plurality of stripe-shaped bottom electrodes are arranged on the upper surface of the substrate layer 11 to form the bottom electrode layer. At this time, the through holes 14 on the insulating array layer 13 are disposed at positions corresponding to the strip-shaped bottom electrode layers 12, so that each strip-shaped bottom electrode has a plurality of corresponding through holes, which facilitates the connection between the bottom electrode layer 12 and the two-dimensional material array layer 20.
On the basis of the above embodiment, the top electrode layer forms the upper surface of the insulating array layer in a strip shape, and the top electrode layer and the bottom electrode layer are arranged in a cross manner;
each strip bottom electrode and each strip top electrode are electrically connected with an external substrate, the substrate comprises a control circuit, and the control circuit is used for scanning each strip bottom electrode and each strip top electrode to form a plurality of detection loops.
Specifically, the top electrode layer 22 is disposed in a stripe shape on the upper surface of the insulating array layer 13, a plurality of stripe-shaped top electrodes are disposed on the upper surface of the insulating array layer 13 to form the top electrode layer 22, and the top electrode layer 22 is disposed to intersect with the bottom electrode layer 12, that is, the top electrode layer 22 and the bottom electrode layer 12 are disposed in different directions to form an electrode scanning array. In practical application, each strip-shaped bottom electrode and each strip-shaped top electrode are connected with the external substrate, and the external substrate is provided with the control circuit, so that each strip-shaped bottom electrode and each strip-shaped top electrode can be scanned to form a plurality of detection loops, and the resistance change in each detection loop is obtained to obtain the gray level image of the fingerprint.
Fig. 3 is a schematic plan structure diagram of a hole-type fingerprint acquisition device in an embodiment of the present invention, fig. 4 is a schematic plan structure diagram of a plane-type fingerprint acquisition device in an embodiment of the present invention, fig. 3 is a schematic plan view of fig. 1, and fig. 4 is a schematic plan view of fig. 2, in which embodiments of the present invention distinguish whether a hole-type fingerprint acquisition device and a plane-type fingerprint acquisition device are covered with a two-dimensional material layer mainly through a through hole, if so, the hole-type fingerprint acquisition device is used, otherwise, the plane-type fingerprint acquisition device is used. As shown in fig. 3, a bottom electrode layer 12 is disposed on the upper surface of the substrate layer 11 in a stripe distribution, an insulating array layer 13 is disposed on the upper surface of the bottom electrode layer 12, a two-dimensional material layer 23 and a top electrode layer 22 are disposed on the upper surface of the insulating array layer 13 in a stripe arrangement, and the through holes 14 in fig. 3 are all covered by the two-dimensional material layer 23. As shown in fig. 4, fig. 4 is different from fig. 3 in that the through hole 14 in fig. 4 is not entirely covered with the two-dimensional material layer 23. As can be seen from fig. 3 and 4, the bottom electrode layer 12 and the top electrode layer 22 in the embodiment of the present invention are vertically arranged, that is, arranged crosswise, and in practical applications, the crossing angle may be set according to needs, and the embodiment of the present invention is not particularly limited.
According to the fingerprint acquisition device provided by the embodiment of the invention, the piezoresistive property of the two-dimensional semiconductor material is applied to a fingerprint identification technology, the structure of the piezoresistive sensor fingerprint acquisition device is reasonably set, the piezoresistive sensor is used as a basic unit of fingerprint identification and is used for acquiring the gray level image of a fingerprint, and then subsequent characteristic comparison is carried out, so that novel fingerprint identification with higher accuracy and higher speed is realized, and the accuracy and efficiency of fingerprint identification are improved.
Fig. 5 is a schematic flow chart of a manufacturing method of a fingerprint acquisition device according to an embodiment of the present invention, and as shown in fig. 5, the manufacturing flow of the fingerprint acquisition device according to the embodiment of the present invention includes:
s1, forming a bottom electrode layer on the upper surface of the selected substrate layer;
s2, forming an insulation array layer on the upper surface of the bottom electrode layer, and arranging a plurality of through holes on the upper surface of the insulation array layer;
s3, forming a connecting electrode layer on one side of the through hole so that the connecting electrode layer is connected with the bottom electrode layer;
s4, forming a plurality of two-dimensional material units on the upper surfaces of the connection electrode layer and the insulation array layer, wherein one end of each two-dimensional material unit is connected with the connection electrode layer, the other end of each two-dimensional material unit is connected with the top electrode layer, and the top electrode layer and the bottom electrode layer are electrically connected with a preset substrate to form a plurality of detection loops;
and S5, covering a flexible protection layer on the upper surfaces of the two-dimensional material unit, the top electrode layer and the insulation array layer.
Specifically, in the method for manufacturing a fingerprint acquisition device according to the embodiment of the present invention, a suitable substrate layer is selected first, and the selection of specific materials is the same as that in the above embodiment, which is not described herein again. After selecting a proper substrate layer, cleaning the substrate layer, and selecting different cleaning modes according to the substrate layers made of different materials, such as Si/SiO2The silicon-based substrate can be made of piranha solution(concentrated sulfuric acid: 30% hydrogen peroxide: 7:3) is soaked, then is washed by deionized water, and is dried by high-purity nitrogen gas, and the organic flexible substrate of PI or PET and the like can be dried by high-purity nitrogen gas after being sequentially subjected to ultrasonic cleaning by organic solvents of acetone, methanol, isopropanol, alcohol and the like. Covering metal on the upper surface of the cleaned substrate layer to form a bottom electrode layer, arranging an insulation array layer on the upper surface of the bottom electrode layer, and arranging a plurality of through holes on the surface of the insulation array layer. And forming a connection electrode layer on one side of the through hole on the surface of the insulating array layer so that the connection electrode layer is connected with the bottom electrode through the through hole. And forming a plurality of two-dimensional material units on the upper surfaces of the connecting electrode layer and the insulating array layer to form a two-dimensional material layer, wherein one end of each two-dimensional material unit is connected with the connecting electrode layer, and the other end of each two-dimensional material unit is connected with the top electrode layer. And electrically connecting the top electrode layer and the bottom electrode layer with a preset substrate to form a plurality of detection loops so as to detect the resistance change of the two-dimensional material layer and further obtain the gray level image of the fingerprint lines. After each structural layer of the fingerprint acquisition device is set, a flexible protective layer is formed on the upper surface of the fingerprint acquisition device so as to protect the fingerprint acquisition device.
According to the preparation method of the fingerprint acquisition device, the implementation process is simple, the prepared fingerprint acquisition device is reliable and high in applicability, the fingerprint acquisition device prepared by the method can realize rapid acquisition of fingerprint images, the influence of pollutants such as moisture, grease and the like attached to the skin on fingerprint image acquisition and fingerprint identification accuracy is reduced, and the accuracy and the efficiency of fingerprint identification are improved.
On the basis of the above embodiment, the forming a bottom electrode layer on the surface of the selected substrate layer includes:
and sputtering a series of strip electrodes as the bottom electrode layer on the substrate layer after patterning by taking a hard mask as a template or utilizing a photoetching technology.
Specifically, a strip-shaped bottom electrode layer is formed on the upper surface of the substrate layer, and specifically, a series of strip-shaped electrodes are sputtered as the bottom electrode layer after patterning is performed by using a hard mask as a template or by using a photolithography technique. The shape of the template and the shape of the pattern formed by the photolithography technique may be selected as desired, and embodiments of the present invention are not particularly limited.
On the basis of the above embodiment, the providing of the through hole on the surface of the insulating array layer includes:
patterning is carried out through photoetching or an array of micron-sized through holes are etched on the surface of the insulating array layer by using a hard mask as a template through dry etching or wet etching, wherein the through holes are positioned on the strip-shaped bottom electrode layer.
Specifically, after the bottom electrode layer is formed, an insulating array layer is deposited on the bottom electrode layer, and the selection of the material of the insulating array layer is the same as that of the above embodiment, which is not described herein again. After the insulating array layer is formed, a plurality of through holes need to be formed in the insulating array layer to connect the two-dimensional material array layer and the bottom electrode layer. The method for arranging the through holes can be as follows: patterning is carried out through photoetching or a hard mask is used as a template, and a plurality of micron-sized through holes are etched on the surface of the insulating array layer in an array mode through dry etching or wet etching (the dry etching or the wet etching is selected according to the material of the insulating array layer), wherein the through holes are located on the strip-shaped bottom electrode layer. The shape of the template and the shape of the pattern formed by the photolithography technique may be selected as desired, and embodiments of the present invention are not particularly limited. Wherein, the etching agent for dry etching is plasma, which is a process for forming volatile substances by utilizing the reaction of the plasma and the surface film or directly bombarding the surface of the film to corrode the film; wet etching is an etching method in which an etched substance is corroded by a chemical reaction between a chemical etching liquid and the etched substance.
On the basis of the above embodiment, the forming a connection electrode layer on one side of the through hole to connect the connection electrode layer with the bottom electrode layer includes:
and patterning through photoetching, exposing one side of the through hole, and stripping the photoresist through sputtering, deposition or evaporation to form the connecting electrode layer on one side of the through hole.
Specifically, after the through holes of the insulating array layer are arranged, patterning is carried out through photoetching, one side of each through hole is exposed, metal is injected into one side of each through hole through sputtering, deposition or evaporation to form an electrode, then photoresist is stripped, and a connecting electrode layer is formed on one side of each through hole. That is, a part of the volume of each through hole is covered as necessary, and an electrode, i.e., a connection electrode layer, is formed on the exposed side of the through hole by a technique such as sputtering, deposition, or evaporation, and the connection electrode layer is connected to the bottom electrode layer. The volume of the exposed through hole may be set as required, and the embodiment of the present invention is not particularly limited. Or, a layer of metal is firstly made on the insulation array layer with the through holes to be used as an electrode, then, photoetching is carried out for patterning, the required part is etched after being protected by photoresist, and then, the photoresist is removed to achieve the same purpose.
On the basis of the above embodiment, the forming a plurality of two-dimensional material units on the surfaces of the connection electrode layer and the insulation array layer includes:
transferring a large piece of two-dimensional material to the upper surfaces of the connection electrode layer and the insulation array layer by a dry method or a wet method;
and patterning by photoetching to protect the two-dimensional material on the through hole or on one side of the through hole and connected with the connecting electrode layer, and etching to remove the unprotected two-dimensional material to form a two-dimensional material layer.
Specifically, after the substrate layer, the bottom electrode layer, the connection electrode layer and the insulation array layer are arranged, a large piece of two-dimensional material such as graphene is transferred to the upper surfaces of the connection electrode layer and the insulation array layer through a dry method or a wet method. Patterning is carried out through photoetching to protect the two-dimensional material which is arranged on the through hole or connected with the connecting electrode layer on one side of the through hole, etching is carried out again to remove the unprotected two-dimensional material, and a two-dimensional material layer is formed. Namely, the two-dimensional material layer covers the through holes or the insulation array layer except the through holes, as shown in fig. 1, the two-dimensional material above the through holes is protected, and other two-dimensional material is removed, so that the through holes are completely covered by the two-dimensional material layer; as shown in fig. 2, the two-dimensional material on the insulating array layer outside the via hole is protected, and the two-dimensional material above the via hole is removed such that the two-dimensional material covers the insulating array layer outside the via hole.
Fig. 6 is a schematic flow chart of a manufacturing method of a hole-type fingerprint acquisition device in an embodiment of the present invention, and as shown in fig. 6, a specific flow of the fingerprint acquisition device in the embodiment of the present invention is as follows:
and 61, selecting a Si wafer with a 300nm thermal oxygen layer as a substrate layer, taking a hard mask as a template, and adopting magnetron sputtering deposition with the thickness of 50nmCr/Au as a buffer layer and a bottom electrode layer to improve the combination between the electrode and the substrate layer, wherein the step is specifically shown as (1) in FIG. 6.
Step 62, depositing 80nm HfO on the surface by ALD (Atomic layer deposition)2As an insulating array layer, and polished flat by CMP (Chemical mechanical polishing/planarization), as shown in (2) of fig. 6.
Step 63, utilizing photoetching and dry etching to etch HfO on the insulation array layer2The through holes of 10 μm by 10 μm are formed, as shown in (3) of fig. 6.
And step 64, aligning one side of the through hole by using the hard mask as a template, and depositing 50nmAu as a connecting electrode layer for connecting the bottom electrode layer by adopting magnetron sputtering, as shown in (4) in fig. 6.
Step 65, transferring a large single-layer graphene sheet onto a silicon wafer by wet transfer, specifically as shown in (5) in fig. 6.
And 66, forming a 15 μm by 15 μm small piece on the graphene by using photolithography and dry etching to cover the through hole, and forming a two-dimensional material layer, which is specifically shown as (6) in fig. 6.
And 67, aligning the side, without the electrode, of the two-dimensional material layer by using the hard mask as a template, and depositing 50nm Cr/Au as a buffer layer and a top electrode layer by adopting magnetron sputtering, as shown in (7) in FIG. 6.
And 68, throwing a layer of PDMS as a flexible protective layer by using a spin coating method, specifically as shown in (8) in FIG. 6, and finally preparing the fingerprint acquisition device.
Fig. 7 is a schematic flow chart of a manufacturing method of a planar fingerprint acquisition device in an embodiment of the present invention, and as shown in fig. 7, a specific flow chart of the fingerprint acquisition device in the embodiment of the present invention is as follows:
step 71, selecting a Si wafer with a 300nm thermal oxygen layer as a substrate layer, taking a hard mask as a template, and adopting magnetron sputtering deposition with the thickness of 50nmCr/Au as a buffer layer and a bottom electrode layer to improve the combination between the electrode and the substrate layer, as shown in (1) in fig. 7.
And 72, throwing a layer of 80nm parylene serving as an insulating layer by adopting a spin coating method, and grinding the insulating layer to be flat, wherein the step is specifically shown as (2) in fig. 7.
Step 73, utilizing photoetching and dry etching to etch HfO on the insulation array layer2The through holes of 10 μm by 10 μm are formed, as shown in (3) of fig. 7.
And step 74, aligning one side of the through hole by using the hard mask as a template, and depositing 50nmAu as a connecting electrode layer for connecting the bottom electrode layer by adopting magnetron sputtering, which is specifically shown as (4) in fig. 7.
Step 75, wet transfer, which is to transfer a large single-layer graphene sheet onto a silicon wafer, specifically as shown in (5) in fig. 7.
And 76, forming a 15 μm by 15 μm small piece on the graphene by photoetching and dry etching to cover the connection electrode layer and the parylene insulating array layer, and forming a two-dimensional material layer, which is specifically shown as (6) in fig. 7.
And 77, aligning the side, without the electrode, of the two-dimensional material layer by using the hard mask as a template, and depositing 50nm Cr/Au as a buffer layer and a top electrode layer by adopting magnetron sputtering, as shown in (7) in FIG. 7.
And 78, finally, throwing a layer of PDMS as a flexible protective layer by using a spin coating method, which is specifically shown as (8) in FIG. 7.
It can be seen that the difference between fig. 6 and 7 is that the insulating array layer is made of different materials, which results in different coverage of the two-dimensional material layer. In fig. 6, the insulating array layer is made of a hard material and is not easy to deform, and the two-dimensional material layer covers the through holes, so that the through holes are used for providing a space required by deformation for the two-dimensional material. In fig. 7, the insulating array layer is made of a flexible and easily deformable material, the two-dimensional material layer covers the upper surfaces of the insulating array layer and the connecting electrode layer outside the through hole, and a space required by deformation is provided for the two-dimensional material layer by using the flexible material used by the insulating array layer. In addition, the width and thickness of the electrode, the thickness of the insulating array layer and the side length of the graphene sheet can be designed according to requirements, so that the size of the fingerprint acquisition device is reduced, and the performance of the fingerprint acquisition device is improved.
It should be noted that graphene is selected as the two-dimensional material in the embodiment of the present invention, because graphene has a characteristic that resistivity changes with stress under the stress action such as pressure, tensile force, and the like. And the suspended graphene can be stretched under the pressing of the needle point, when the stretching amount reaches about 3%, the resistance change is about 5%, and the graphene can bear about 25% of the stretching stress in the plane at most, so that the large stress intensity is enough to generate very large resistance change for circuit detection. Of course, other two-dimensional materials can be selected to prepare the fingerprint acquisition device according to the requirement, such as tungsten sulfide, black phosphorus and the like.
The preparation method of the fingerprint acquisition device provided by the embodiment of the invention has the advantages that the process is simple, the operation is convenient, the prepared fingerprint acquisition device has strong anti-interference performance, the acquisition speed is high, the volume is small, the gray level image of the fingerprint can be acquired quickly and accurately, and the accuracy and the efficiency of fingerprint identification are further improved.
The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
Claims (8)
1. A fingerprint acquisition device, the device comprising:
the substrate, the two-dimensional material array layer and the flexible protective layer are sequentially arranged from bottom to top;
the substrate comprises a substrate layer, a bottom electrode layer and an insulation array layer which are sequentially arranged from bottom to top, a plurality of through holes are formed in the insulation array layer, the bottom electrode layer is formed on the upper surface of the substrate layer in a strip shape, and correspondingly, the through holes in the insulation array layer are formed in positions corresponding to the bottom electrode layer; the insulating array layer is made of a thin hard material which is not easy to deform;
the two-dimensional material array layer is formed on one surface, far away from the bottom electrode layer, of the insulation array layer and is connected with the bottom electrode layer through the through hole, and the bottom electrode layer and the two-dimensional material array layer are respectively and electrically connected with a substrate outside the device;
the two-dimensional material array layer comprises a connecting electrode layer, a top electrode layer and a two-dimensional material layer, the connecting electrode layer is connected with the bottom electrode layer through the through hole, a gap is reserved between the connecting electrode layer and the side wall of the through hole, the top electrode layer is formed on the upper surface of the insulating array layer in a strip shape, and the top electrode layer and the bottom electrode layer are arranged in a crossed mode;
the two-dimensional material layer comprises a plurality of two-dimensional material units, the two-dimensional material units are formed on one surfaces, far away from the bottom electrode layer, of the connecting electrode layer and the insulating array layer, one end of each two-dimensional material unit is connected with the connecting electrode layer, the other end of each two-dimensional material unit is connected with the top electrode layer, the top electrode layer is electrically connected with a substrate outside the device, the top electrode layer and the bottom electrode layer form a plurality of detection loops, the top electrode layer comprises a plurality of strip-shaped top electrodes, the bottom electrode layer comprises a plurality of strip-shaped bottom electrodes, and the strip-shaped top electrodes and the strip-shaped bottom electrodes are arranged in a three-dimensional cross mode according to preset cross angles to form a plurality of detection loops;
the detection circuit is used for acquiring resistance changes corresponding to different deformations of the two-dimensional material array layer due to pressure so as to obtain a gray level image of fingerprint lines;
the two-dimensional material unit is made of two-dimensional materials with piezoresistive properties, and the two-dimensional materials refer to materials with electrons capable of freely moving only on non-nanoscale of two dimensions.
2. The device of claim 1, wherein the two-dimensional material unit covers over the via hole or an upper surface of the connection electrode layer and the insulating array layer.
3. The device of claim 1, wherein each strip bottom electrode and each strip top electrode is electrically connected to an external substrate, the substrate comprising a control circuit for scanning each strip bottom electrode and strip top electrode to form a plurality of said detection loops.
4. A method of making a fingerprint acquisition device, the method comprising:
forming a bottom electrode layer on the upper surface of the selected substrate layer, and forming the bottom electrode layer into a strip shape;
forming an insulating array layer on the upper surface of the bottom electrode layer, and arranging a plurality of through holes on the upper surface of the insulating array layer; the through holes in the insulating array layer are arranged at positions corresponding to the bottom electrode layer; the insulating array layer is made of a thin hard material which is not easy to deform;
forming a connection electrode layer on one side of the through hole so that the connection electrode layer is connected with the bottom electrode layer;
forming a plurality of two-dimensional material units on the upper surfaces of the connection electrode layer and the insulation array layer, wherein one end of each two-dimensional material unit is connected with the connection electrode layer, the other end of each two-dimensional material unit is connected with a top electrode layer, the top electrode layer and the bottom electrode layer are electrically connected with a preset substrate, the top electrode layer and the bottom electrode layer form a plurality of detection loops, the top electrode layer comprises a plurality of strip-shaped top electrodes, the bottom electrode layer comprises a plurality of strip-shaped bottom electrodes, and the strip-shaped top electrodes and the strip-shaped bottom electrodes are arranged in a three-dimensional crossing mode according to preset crossing angles to form a plurality of detection loops; the detection circuit is used for acquiring resistance changes corresponding to different deformations of the two-dimensional material array layer due to pressure so as to obtain a gray level image of fingerprint lines; the two-dimensional material unit is made of a two-dimensional material with piezoresistive properties, and the two-dimensional material refers to a material with electrons capable of freely moving only on the non-nanoscale of two dimensions;
and covering a flexible protective layer on the upper surfaces of the two-dimensional material unit, the top electrode layer and the insulation array layer.
5. The method of claim 4, wherein forming the bottom electrode layer on the selected substrate layer surface comprises:
and sputtering a series of strip electrodes as the bottom electrode layer on the substrate layer after patterning by taking a hard mask as a template or utilizing a photoetching technology.
6. The method of claim 5, wherein the providing the via hole on the surface of the insulation array layer comprises:
patterning is carried out through photoetching or an array of micron-sized through holes are etched on the surface of the insulating array layer by using a hard mask as a template through dry etching or wet etching, wherein the through holes are positioned on the strip-shaped bottom electrode layer.
7. The method according to claim 4, wherein the forming a connection electrode layer at one side of the through hole to connect the connection electrode layer with the bottom electrode layer comprises:
and patterning through photoetching, exposing one side of the through hole, and stripping the photoresist through sputtering, deposition or evaporation to form the connecting electrode layer on one side of the through hole.
8. The method of claim 4, wherein the forming a plurality of two-dimensional material units on the surface of the connection electrode layer and the insulation array layer comprises:
transferring a large piece of two-dimensional material to the upper surfaces of the connection electrode layer and the insulation array layer by a dry method or a wet method;
and patterning by photoetching to protect the two-dimensional material on the through hole or on one side of the through hole and connected with the connecting electrode layer, and etching to remove the unprotected two-dimensional material to form a two-dimensional material layer.
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| KR100798481B1 (en) * | 2006-11-15 | 2008-01-28 | 한국표준과학연구원 | Fingerprint identification device using surface pressure measurement |
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