CN109308470B - Fingerprint sensing device and manufacturing method thereof - Google Patents
Fingerprint sensing device and manufacturing method thereof Download PDFInfo
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- CN109308470B CN109308470B CN201811135390.8A CN201811135390A CN109308470B CN 109308470 B CN109308470 B CN 109308470B CN 201811135390 A CN201811135390 A CN 201811135390A CN 109308470 B CN109308470 B CN 109308470B
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 25
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims abstract description 102
- 229920005591 polysilicon Polymers 0.000 claims abstract description 90
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 65
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 65
- 238000000034 method Methods 0.000 claims abstract description 28
- 239000000758 substrate Substances 0.000 claims abstract description 18
- 229910052751 metal Inorganic materials 0.000 claims abstract description 15
- 239000002184 metal Substances 0.000 claims abstract description 15
- 239000010409 thin film Substances 0.000 claims description 26
- 239000010408 film Substances 0.000 claims description 13
- 238000000059 patterning Methods 0.000 claims description 13
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 claims description 10
- 238000000151 deposition Methods 0.000 claims description 9
- JAONJTDQXUSBGG-UHFFFAOYSA-N dialuminum;dizinc;oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Al+3].[Al+3].[Zn+2].[Zn+2] JAONJTDQXUSBGG-UHFFFAOYSA-N 0.000 claims description 8
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 7
- AMGQUBHHOARCQH-UHFFFAOYSA-N indium;oxotin Chemical compound [In].[Sn]=O AMGQUBHHOARCQH-UHFFFAOYSA-N 0.000 claims description 6
- BEQNOZDXPONEMR-UHFFFAOYSA-N cadmium;oxotin Chemical compound [Cd].[Sn]=O BEQNOZDXPONEMR-UHFFFAOYSA-N 0.000 claims description 5
- 230000008859 change Effects 0.000 claims description 5
- SKRWFPLZQAAQSU-UHFFFAOYSA-N stibanylidynetin;hydrate Chemical compound O.[Sn].[Sb] SKRWFPLZQAAQSU-UHFFFAOYSA-N 0.000 claims description 5
- YVTHLONGBIQYBO-UHFFFAOYSA-N zinc indium(3+) oxygen(2-) Chemical compound [O--].[Zn++].[In+3] YVTHLONGBIQYBO-UHFFFAOYSA-N 0.000 claims description 5
- 239000011787 zinc oxide Substances 0.000 claims 2
- 230000008569 process Effects 0.000 abstract description 11
- 230000009286 beneficial effect Effects 0.000 abstract description 5
- 238000005516 engineering process Methods 0.000 abstract description 5
- 238000001259 photo etching Methods 0.000 abstract description 3
- 229910021417 amorphous silicon Inorganic materials 0.000 description 19
- 238000010586 diagram Methods 0.000 description 6
- 238000005229 chemical vapour deposition Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 230000003287 optical effect Effects 0.000 description 4
- 238000000206 photolithography Methods 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- 230000007547 defect Effects 0.000 description 3
- 238000004518 low pressure chemical vapour deposition Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000005240 physical vapour deposition Methods 0.000 description 2
- 238000000137 annealing Methods 0.000 description 1
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- 230000015572 biosynthetic process Effects 0.000 description 1
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- 238000001289 rapid thermal chemical vapour deposition Methods 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
Images
Classifications
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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
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V10/00—Arrangements for image or video recognition or understanding
- G06V10/94—Hardware or software architectures specially adapted for image or video understanding
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/142—Energy conversion devices
- H01L27/1421—Energy conversion devices comprising bypass diodes integrated or directly associated with the device, e.g. bypass diode integrated or formed in or on the same substrate as the solar cell
Abstract
A panel identification technology, in particular to a fingerprint sensing device and a manufacturing method thereof are provided, wherein the device comprises: a pixel substrate having a plurality of sensing pixel units formed thereon, each sensing pixel unit having an identification region and a readout region, each sensing pixel unit comprising: a patterned light shielding layer arranged in the identification region and the reading region; a polysilicon layer disposed on the patterned light-shielding layer; a gate layer disposed on the polysilicon layer in the read region; a patterned dielectric layer disposed on the gate layer in the read region; a metal oxide layer disposed on the polysilicon layer in the identification region; and the source drain metal film layer is arranged on the metal oxide layer in the identification area and the patterned dielectric layer in the reading area, so that the beneficial effects of no need of complex film forming and photoetching processes and higher resolution are achieved. A method of manufacturing the fingerprint sensing device is also provided.
Description
Technical Field
The present disclosure relates to the field of panel identification technologies, and more particularly, to a fingerprint sensing device and a method for manufacturing the same.
Background
Fingerprint identification has recently attracted wide attention as a biometric identification method, and has a wide prospect particularly in mobile payment. The existing fingerprint identification method also comprises various modes such as optical, capacitance, microwave, temperature, ultrasonic and the like. However, the conventional optical sensor method cannot be made thin and light, and especially under the requirement of high resolution, the conventional device is bulky and cannot be portable, so that it is difficult to integrate into a device such as a mobile phone. Other methods solve the problem of light weight and thinness, but cannot realize large-area arrays or combine other functions, and have complex process and high cost.
A medical amorphous silicon flat panel detector in the prior art is a conventional optical sensor, and includes an amorphous silicon photodiode and a thin film transistor, fig. 1 shows a schematic cross-sectional view of a pixel unit of an amorphous silicon flat panel detector in the prior art, a plurality of flat panel detector pixel units are formed on a transparent substrate 1, and each flat panel detector pixel unit includes: the thin film transistor 3 and the amorphous silicon photodiode are sequentially formed on the surface of the transparent substrate 1, the amorphous silicon photodiode comprises a first shading layer 2, a first insulating layer 4, a drain electrode layer 5, an N-type layer 6, an intermediate layer 7, a P-type layer 8 and a contact electrode 9, the thin film transistor 3 and the amorphous silicon photodiode are insulated by the dielectric layer 10, a second shading layer 12 is formed on the thin film transistor 3 and the surface of the dielectric layer 10 of a part of region which does not need to be irradiated with light, a connecting electrode 11 is formed on the contact electrode 9, and a passivation layer 13 is formed above the second shading layer 12 and the connecting electrode 11. As can be seen from fig. 1, the main part of the amorphous silicon photodiode is a stacked structure of a P-type layer 8, an intermediate layer 7 and an N-type layer 6, so that the thickness of the amorphous silicon flat panel detector is about the thickness of the drain of the thin film transistor 3, which is also stacked by the thickness of the amorphous silicon photodiode, and the thickness of the intermediate layer 7 in the amorphous silicon photodiode is about 1 micron, so that the thickness of the amorphous silicon flat panel detector is larger, the optical path of incident light in a pixel unit of the flat panel detector is longer, and the incident light may enter an adjacent pixel unit to generate interference. And the pixel unit of the flat panel detector comprises a discrete thin film transistor 3 and an amorphous silicon photodiode, wherein the thin film transistor 3 and the amorphous silicon photodiode are separately arranged, namely, a certain distance is reserved between the thin film transistor 3 and the amorphous silicon photodiode, so that the pixel unit of the flat panel detector occupies a larger area, and the resolution is lower. In addition, the amorphous silicon photodiode needs to be manufactured separately after the thin film transistor 3 is formed, and a plurality of steps of film formation and photolithography processes are required, so that the production cost is high. If the amorphous silicon flat panel detector is used in the fields of fingerprint identification and the like, the defects of high production cost and low resolution ratio exist, and the application of the amorphous silicon flat panel detector to portable equipment such as mobile phones and the like is limited.
Therefore, it is necessary to provide a fingerprint sensing device and a method for manufacturing the same, which solve the problems of high production cost and low resolution in the prior art.
Disclosure of Invention
In order to solve the above technical problems, the present disclosure provides a low temperature polysilicon fingerprint sensing device with low production cost and high resolution and a method for manufacturing the same, in which a thin film transistor is manufactured by using a low temperature polysilicon technology, a heterojunction photodiode is formed by an N-type metal oxide layer and a P-type polysilicon layer, and the polysilicon thin film transistor and the heterojunction photodiode are integrated into an integral structure, so as to overcome the above drawbacks.
To achieve the above objects, the present disclosure provides a fingerprint sensing device and a method of manufacturing the same, the device including: a pixel substrate, a plurality of sensing pixel units formed on the pixel substrate, each sensing pixel unit having an identification region and a reading region, each sensing pixel unit comprising: a patterned light shielding layer disposed in the identification region and the reading region; a polysilicon layer disposed on the patterned light-shielding layer; a gate layer disposed on the polysilicon layer in the read region; a patterned dielectric layer disposed on the gate layer in the read region; a metal oxide layer disposed on the polysilicon layer in the identification region; and a source drain metal film layer arranged on the metal oxide layer in the identification region and the patterned dielectric layer in the reading region.
According to an embodiment of the fingerprint sensing device described herein, the polysilicon layer is a P-type polysilicon layer.
According to an embodiment of the fingerprint sensing device described herein, the metal oxide layer is an N-type metal oxide layer.
According to an embodiment of the fingerprint sensing device described herein, the N-type metal oxide layer comprises a material selected from Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), Aluminum Zinc Oxide (AZO), cadmium tin oxide, antimony tin oxide, zinc oxide (ZnO), and tin dioxide (SnO)2) One or more of the group consisting of.
According to an embodiment of the fingerprint sensing device described herein, an interface of the polysilicon layer and the metal oxide layer has an uneven structure.
In order to achieve the above object, the present disclosure further provides a method for manufacturing a fingerprint sensing device, including: providing a pixel substrate; forming a plurality of sensing pixel units on the pixel substrate, wherein each sensing pixel unit is provided with an identification area and a reading area; forming a light shielding layer on the identification area and the reading area on the pixel substrate, and patterning the light shielding layer to form a patterned light shielding layer; forming a polysilicon layer on the identification region and the patterned light-shielding layer of the reading region; forming a gate layer on the polysilicon layer of the read region; depositing a dielectric layer on the polysilicon layer of the identification region and the read region; patterning the dielectric layer to form a patterned dielectric layer so that the patterned dielectric layer is formed only on the polysilicon layer of the read region; depositing and patterning a metal oxide layer on the polysilicon layer without the patterned dielectric layer; and depositing a source drain metal film layer on the metal oxide layer of the identification area and the patterned dielectric layer of the reading area to form a source drain wiring.
According to an embodiment of the method of manufacturing a fingerprint sensing device described herein, the polysilicon layer is a P-type polysilicon layer.
According to an embodiment of the method of manufacturing a fingerprint sensing device described herein, the metal oxide layer is an N-type metal oxide layer.
According to an embodiment of the method of manufacturing a fingerprint sensing device described herein, the N-type metal oxide layer comprises a material selected from Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), Aluminum Zinc Oxide (AZO), cadmium tin oxide, antimony tin oxide, zinc oxide (ZnO), and tin dioxide (SnO)2) One or more of the group consisting of.
According to an embodiment of the method for manufacturing a fingerprint sensing device described herein, an interface of the polysilicon layer and the metal oxide layer has an uneven structure.
The fingerprint sensing device and the manufacturing method provided by the disclosure are characterized in that a thin film transistor is prepared by a low-temperature polycrystalline silicon technology, a heterojunction photodiode is formed by an N-type metal oxide layer and a P-type polycrystalline silicon layer, a signal light beam reflected from a finger is identified by the photodiode, namely, the light intensity weak change of the fingerprint reflected signal light beam can be identified by the photodiode and converted into photocurrent, and the thin film transistor reads and identifies the photocurrent generated by the photodiode, so that the fingerprint identification function is realized. Because the interface between the N-type metal oxide layer and the P-type polycrystalline silicon layer presents a rough/concave-convex interface, a heterojunction contact area with a larger area is formed between the N-type metal oxide layer and the P-type polycrystalline silicon layer, which is beneficial to absorbing fingerprint reflected light and increasing the separation capability of electron hole pairs in the P-type polycrystalline silicon layer. Meanwhile, the thin film transistor and the heterojunction photodiode are realized in an integrated structure, and complex film forming and photoetching processes are not needed. In order to make the aforementioned and other features and advantages of the disclosure more comprehensible, embodiments accompanied with figures are described in detail below.
Drawings
In order to illustrate the embodiments or the technical solutions in the prior art more clearly, the drawings needed to be 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 only some embodiments of the invention, and it is obvious for a person skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic diagram of a pixel unit structure of a conventional flat panel sensor.
Fig. 2 is a schematic diagram of a sensing pixel unit structure of the fingerprint sensing device according to the present invention.
FIGS. 3A-3E are schematic flow charts illustrating a method for manufacturing a fingerprint sensing device according to the present disclosure.
FIG. 4 is a schematic diagram illustrating a manufacturing method of a fingerprint sensing device according to the present invention.
Detailed Description
The following description of the various embodiments refers to the accompanying drawings, which illustrate specific embodiments in which the disclosure may be practiced. Directional phrases used in this disclosure, such as [ upper ], [ lower ], [ front ], [ back ], [ left ], [ right ], [ inner ], [ outer ], [ side ], etc., refer only to the directions of the attached drawings. Accordingly, the directional terms used are used for the purpose of illustration and understanding of the present disclosure, and are not used to limit the present disclosure. In the drawings, elements having similar structures are denoted by the same reference numerals.
The following describes the implementation of the embodiments of the present disclosure in detail with reference to the accompanying drawings.
Referring to fig. 2, which is a schematic structural diagram of a sensing pixel unit of a fingerprint sensing device according to the present disclosure, in an embodiment of the present disclosure, a fingerprint sensing device for detecting a finger 300 includes: a pixel substrate 101, wherein a plurality of sensing pixel units 102 (one sensing pixel unit 102 is shown in the figure) are formed on the pixel substrate 101, each sensing pixel unit 102 has an identification area a and a reading area R, and a photodiode structure is disposed on the identification area a to identify the intensity change of a signal light beam L2 reflected by the finger 300 and convert the signal light beam into a photoelectric current form; the reading region R is provided with a Thin Film Transistor (TFT) structure for reading and identifying the photocurrent generated by the photodiode.
Each of the sensing pixel units 102 includes: a patterned light-shielding layer 103 disposed in the identification region a and the reading region R, and more specifically, the patterned light-shielding layer 103 disposed in the identification region a and the patterned light-shielding layer 103 disposed in the reading region R are discontinuous; a polysilicon layer 104 disposed on the patterned light-shielding layer 103 corresponding to the identification region a and the reading region R; a gate layer 105 disposed on the polysilicon layer 104 in the read region R; a patterned dielectric layer (i.e., a third dielectric layer 106) disposed on the gate layer 105 in the read region R; a metal oxide layer 107 disposed on the polysilicon layer 104 in the identification region a; and a source/drain metal film layer 108 disposed on the metal oxide layer 107 in the identification region a and on the patterned dielectric layer (i.e., the third dielectric layer 106) in the reading region R.
A light emitting unit (not shown) for emitting a sensing light beam L1 to the finger 300, the finger 300 reflects the sensing light beam L1 as a signal light beam L2. The signal beam L2 is not limited to the reflected beam from the surface of the finger 300 shown in fig. 1, but also includes the beam reflected by the tissue in the finger 300 after penetrating the surface of the finger 300, and fig. 1 is only an exemplary illustration of one of the beams, which is not intended to limit the disclosure.
In the present embodiment, all the sensing pixel units 102 of the fingerprint sensing device form a photosensitive array. For clarity of illustration of the arrangement of the above components, fig. 1 is a schematic diagram of one of the sensing pixel units 102.
The sensing pixel unit 102 includes a photodiode on the identification area a and a thin film transistor on the reading area R. The photodiode includes a polysilicon layer 104 and a metal oxide layer 107, which are stacked, in more detail, the polysilicon layer 104 is a P-type polysilicon layer, the metal oxide layer 107 is an N-type metal oxide layer, and the N-type metal oxide layer is stacked on the P-type polysilicon layer. A first dielectric layer 111 is disposed between the patterned light-shielding layer 103 and the polysilicon layer 104, the P-type polysilicon layer is disposed on the first dielectric layer 111 corresponding to the identification region a and the reading region R, and the first dielectric layer 111 can be formed by a Chemical Vapor Deposition (CVD) method, such as a Low Temperature Chemical Vapor Deposition (LTCVD) method, a Low Pressure Chemical Vapor Deposition (LPCVD) method, a rapid thermal chemical vapor deposition (LTCVD), a plasma chemical vapor deposition (PECVD), or a Physical Vapor Deposition (PVD) method or a sputtering method.
A gate metal layer (not shown) is formed on the P-type polysilicon layer corresponding to the read region R, and the gate metal layer is patterned to form the gate layer 105 at a predetermined position on the polysilicon layer 104 in the read region R. A second dielectric layer 112 is disposed between the gate layer 105 and the polysilicon layer 104, and corresponds to the gate layer 105 after the patterning.
In one embodiment, the patterned dielectric layer is a third dielectric layer 106 disposed on the polysilicon layer 104 in the reading region R and disposed on two sides of the metal oxide layer 107 in the identification region a, but not covering the metal oxide layer 107. The thickness of the third dielectric layer 106 is greater than the thickness of the metal oxide layer 107. The third dielectric layer 106 is formed on the gate layer 105, source/drain contact holes 151 are formed on the third dielectric layer 106 corresponding to two sides of the gate layer 105, and source/drain electrodes formed by the source/drain metal film layer 108 are electrically connected to the polysilicon layer 104 through the source/drain contact holes 151.
In addition, the metal Oxide layer 107 includes a material selected from Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), Aluminum Zinc Oxide (AZO), cadmium tin Oxide, antimony tin Oxide, Zinc Oxide (ZnO), and tin dioxide (SnO)2) The formed group. In the present embodiment, the material of the metal Oxide layer 107 is Indium Tin Oxide (ITO). The metal oxide layer 107 is disposed only on the polysilicon layer 104 in the identification area a, i.e., the identification area a corresponding to the photodiode.
As shown in the enlarged view of fig. 2, an uneven structure 200 is formed at the interface between the polysilicon layer 104 and the metal oxide layer 107, and the uneven structure 200 is a rough type, a concave-convex type, a mutual embedding type, etc., but not limited thereto. Due to the uneven structure 200, the interface between the polysilicon layer 104 and the metal oxide layer 107 has a larger contact area, i.e. a larger area of heterojunction contact region is formed between the N-type metal oxide layer and the P-type polysilicon layer, which is beneficial to absorbing the signal light beam L2 reflected by a finger and increasing the separation capability of electron-hole pairs in the P-type polysilicon layer.
It should be noted that the polysilicon layer 104 is disposed on the first dielectric layer 111 of the identification region a and the reading region R, that is, the polysilicon layer 104 is formed on the same horizontal level structure of the photodiode of the identification region a and the thin film transistor of the reading region R, the gate layer 105 is disposed above the patterned light-shielding layer 103, and an intermediate layer is not required to be disposed between the metal oxide layer 107 and the polysilicon layer 104, thereby avoiding the defect caused by the large thickness of the intermediate layer in the amorphous silicon photodiode in the prior art, and eliminating the need for complicated film-forming and photolithography processes in the manufacturing process.
Please refer to fig. 3A-3E to fig. 4 in conjunction with fig. 2, which are schematic diagrams illustrating steps and a flow chart of a manufacturing method of a fingerprint sensing device according to the present disclosure. The manufacturing method of the fingerprint sensing device comprises the following steps: step S01: providing a pixel substrate 101; step S02: forming a plurality of sensing pixel units 102 on the pixel substrate 101, each sensing pixel unit having an identification region a and a reading region R; step S03: forming a light-shielding layer on the identification region a and the reading region R on the pixel substrate 101, and patterning the light-shielding layer to form a patterned light-shielding layer 103; step S04: forming a polysilicon layer 104 on the patterned light-shielding layer 103 of the identification region a and the reading region R; step S05: forming a gate layer 105 on the polysilicon layer 104 of the read region R; step S06: depositing a dielectric layer on the polysilicon layer 104 of the identification region a and the reading region R; step S07: patterning the dielectric layer to form a patterned dielectric layer (i.e., the third dielectric layer 106) such that the patterned dielectric layer (i.e., the third dielectric layer 106) is formed on the polysilicon layer 104 in the reading region R and on both sides of the metal oxide layer 107 in the identification region a, but not covering the metal oxide layer 107; step S08: depositing and patterning a metal oxide layer 107 on the polysilicon layer 104 without the patterned dielectric layer (i.e., the third dielectric layer 106); and step S09: depositing a source/drain metal film layer 108 on the metal oxide layer 107 of the identification region a and the patterned dielectric layer of the reading region R to form a source/drain trace.
In more detail, step S03 further includes forming a light-shielding layer on the identification area a and the reading area R of the pixel substrate by a film-forming process, and patterning the light-shielding layer by a photolithography process to form a patterned light-shielding layer 103, as shown in fig. 3A.
In step S04, the polysilicon layer 104 is formed on the patterned light-shielding layer 103 by using a chemical vapor deposition process, and it should be noted that before forming the polysilicon layer 104, a first dielectric layer 111 is deposited on the patterned light-shielding layer 103, as shown in fig. 3B, and then the polysilicon material forming the polysilicon layer 104 is subjected to laser low temperature annealing to form the polysilicon layer 104 on the first dielectric layer 111 of the identification region a and the reading region R, wherein the polysilicon layer 104 is a P-type polysilicon layer and the polysilicon layer 104 is patterned.
In step S05, a gate metal layer (not shown) is formed on the polysilicon layer 104 in the reading region R, and the gate metal layer is patterned to form the gate layer 105 at a predetermined position on the polysilicon layer 104 in the reading region R, wherein, as shown in fig. 3C, a second dielectric layer 112 is disposed between the gate layer 105 and the polysilicon layer 104, and the patterned second dielectric layer corresponds to the gate layer 105. And performing source-drain doping on the polysilicon layer 104 by using the gate layer 105 and the second dielectric layer 112 as masks. The regions of the polysilicon layer 104 corresponding to the gate layer 105 and the second dielectric layer 112 are not doped with ions.
In step S07, the patterned dielectric layer is a third dielectric layer 106, and the step of patterning the third dielectric layer 106 includes forming a source/drain contact hole 151 corresponding to the gate layer 105 in the third dielectric layer 106, as shown in fig. 3D, and subsequently, a source/drain (not shown) formed by the source/drain metal film layer 108 is electrically connected to the polysilicon layer 104 through the source/drain contact hole 151. And the third dielectric layer 106 insulates the photodiode of the identification area a from the thin film transistor of the reading area R.
In step S08, the metal oxide layer 107 is deposited on the remaining portion of the polysilicon layer 104, i.e., in the above step, the polysilicon layer 104 corresponding to the reading region R to form the third dielectric layer 106, and thus the metal oxide layer 107 is deposited on the polysilicon layer 104 where the third dielectric layer 106 is not disposed, i.e., the metal oxide layer 107 is formed on the polysilicon layer 104 corresponding to the identification region a. And thus a larger area of heterojunction contact region is formed between the metal oxide layer 107 and the polysilicon layer 104. In more detail, a portion of the identification area constitutes a photodiode, and a portion of the reading area constitutes a thin film transistor. The photodiode comprises a polysilicon layer 104 and a metal oxide layer 107 which are laminated, wherein the polysilicon layer 104 is a P-type polysilicon layer, and the metal oxide layer 107 is an N-type metal oxide layer.
In step S09, a source/drain metal film 108 is deposited on the third dielectric layer 106, and a source/drain formed by patterning the source/drain metal film 108 is electrically connected to the polysilicon layer 104 through the source/drain contact hole 151, as shown in fig. 3E. Specifically, the source/drain is used for assisting the movement of electron holes mechanically emitted in the metal oxide layer 107 and the polysilicon layer 104 and transmitting the photocurrent formed by the electron holes.
In addition, the interface between the polysilicon layer 104 and the metal oxide layer 107 is an uneven structure 200, and the uneven structure 200 is a rough type, a concave-convex type, a mutual embedding type, and the like, but not limited thereto. Due to the uneven structure, the interface between the polysilicon layer 104 and the metal oxide layer 107 has a larger contact area, i.e. a larger area of heterojunction contact region is formed between the N-type metal oxide layer and the P-type polysilicon layer, which is beneficial to absorbing the reflected light of the fingerprint and increasing the separation capability of electron-hole pairs in the P-type polysilicon layer.
As can be seen from the above, the P-type polysilicon layer is formed on the same horizontal level structure of the photodiode in the identification region a and the thin film transistor in the reading region R, the photodiode and the thin film transistor are simultaneously fabricated, the gate layer 105 is disposed above the patterned light-shielding layer 103, and an intermediate layer is not required to be disposed between the metal oxide layer 107 and the polysilicon layer 104, thereby avoiding the defect caused by the large thickness of the intermediate layer in the amorphous silicon photodiode in the prior art, and the process does not require complicated film-forming and photolithography processes.
The fingerprint sensing device and the manufacturing method provided by the disclosure are characterized in that a thin film transistor is prepared by a low-temperature polycrystalline silicon technology, a heterojunction photodiode is formed by an N-type metal oxide layer and a P-type polycrystalline silicon layer, a signal light beam reflected from a finger is identified by the photodiode, namely, the light intensity weak change of the fingerprint reflected signal light beam can be identified by the photodiode and converted into photocurrent, and the thin film transistor reads and identifies the photocurrent generated by the photodiode, so that the fingerprint identification function is realized. Because the interface between the N-type metal oxide layer and the P-type polycrystalline silicon layer presents a rough/concave-convex interface, a heterojunction contact area with a larger area is formed between the N-type metal oxide layer and the P-type polycrystalline silicon layer, which is beneficial to absorbing fingerprint reflected light and increasing the separation capability of electron hole pairs in the P-type polycrystalline silicon layer. Meanwhile, the thin film transistor and the heterojunction photodiode are realized in an integrated structure, and complex film forming and photoetching processes are not needed. In order to make the aforementioned and other features and advantages of the disclosure more comprehensible, embodiments accompanied with figures are described in detail below.
While the foregoing is directed to the preferred embodiment of the present disclosure, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the principles of the disclosure, and it is intended that such changes and modifications be covered by the appended claims.
Claims (8)
1. A fingerprint sensing device, comprising: the pixel substrate is provided with a plurality of sensing pixel units, each sensing pixel unit is provided with an identification area and a reading area, and a photodiode is arranged on the identification area and used for identifying the intensity change of a signal light beam reflected by a finger and converting the signal light beam into a photoelectric current form; the reading area is provided with a thin film transistor for reading and identifying the photocurrent generated by the photodiode, and each sensing pixel unit comprises:
a patterned light-shielding layer disposed in the identification region and the reading region of the sensing pixel unit;
a polysilicon layer disposed on the patterned light-shielding layer;
a gate layer disposed on the polysilicon layer in the read region;
a patterned dielectric layer disposed on the gate layer in the read region;
a metal oxide layer disposed on the polysilicon layer in the identification region; and
the source drain metal film layer is arranged on the metal oxide layer in the identification area and the patterned dielectric layer in the reading area;
wherein the junction of the polysilicon layer and the metal oxide layer is in an uneven structure.
2. The fingerprint sensing device of claim 1, wherein the polysilicon layer is a P-type polysilicon layer.
3. The fingerprint sensing device of claim 1, wherein the metal oxide layer is an N-type metal oxide layer.
4. The fingerprint sensing device of claim 3, wherein the N-type metal oxide layer comprises one or more selected from the group consisting of indium tin oxide, indium zinc oxide, aluminum zinc oxide, cadmium tin oxide, antimony tin oxide, zinc oxide, and tin dioxide.
5. A method of manufacturing a fingerprint sensing device, comprising:
providing a pixel substrate;
forming a plurality of sensing pixel units on the pixel substrate, wherein each sensing pixel unit is provided with an identification area and a reading area, and a photodiode is arranged on the identification area and used for identifying the intensity change of a signal beam reflected by a finger and converting the signal beam into a photoelectric current form; the reading area is provided with a thin film transistor used for reading and identifying photocurrent generated by the photodiode;
forming a light shielding layer on the identification area and the reading area on the pixel substrate, and patterning the light shielding layer to form a patterned light shielding layer;
forming a polysilicon layer on the identification region and the patterned light-shielding layer of the reading region;
forming a gate layer on the polysilicon layer of the read region;
depositing a dielectric layer on the polysilicon layer of the identification region and the read region;
patterning the dielectric layer to form a patterned dielectric layer so that the patterned dielectric layer is formed only on the polysilicon layer of the read region;
depositing and patterning a metal oxide layer on the polycrystalline silicon layer without the patterned dielectric layer, wherein the junction of the polycrystalline silicon layer and the metal oxide layer is in an uneven structure; and
and depositing a source drain metal film layer on the metal oxide layer of the identification area and the patterned dielectric layer of the reading area to form a source drain wiring.
6. The method of claim 5, wherein the polysilicon layer is a P-type polysilicon layer.
7. The method of claim 5, wherein the metal oxide layer is an N-type metal oxide layer.
8. The method of claim 7, wherein the N-type metal oxide layer comprises one or more selected from the group consisting of indium tin oxide, indium zinc oxide, aluminum zinc oxide, cadmium tin oxide, antimony tin oxide, zinc oxide, and tin dioxide.
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