CN111682045A - Ultrasonic fingerprint identification sensor, method for making the same, and display module - Google Patents

Abstract

The invention relates to an ultrasonic fingerprint identification sensor which comprises a hard substrate, a flexible substrate arranged on the hard substrate, a receiving electrode layer, a piezoelectric film layer and a transmitting electrode layer which are sequentially arranged on the flexible substrate, and a first bonding pad arranged between the hard substrate and the flexible substrate, wherein the first bonding pad is used for binding and connecting the receiving electrode layer and an external circuit board to obtain a fingerprint image. The invention also relates to a manufacturing method of the display module and the ultrasonic fingerprint identification sensor.

Description

Ultrasonic fingerprint identification sensor, method for making the same, and display module

technical field

The invention relates to the technical field of display product manufacturing, in particular to an ultrasonic fingerprint identification sensor, a manufacturing method thereof, and a display module.

Background technique

Piezoelectric materials (such as polyvinylidene fluoride, PVDF, piezoelectric ceramics, electrets, etc.), for example, PVDF is an excellent piezoelectric material, which has piezoelectric effect after crystallization and electric field polarization, and is divided into positive pressure There are two types of electrical effect and inverse piezoelectric effect. Using this principle, AC voltage is applied to the transmitting electrode (Tx), and the piezoelectric film layer generates ultrasonic waves under the action of inverse piezoelectricity, and electricity → sound; then the ultrasonic waves are reflected when they meet the fingerprint of the finger. , once again acts on the piezoelectric film layer, converts ultrasonic waves into electrical signals, sound → electricity, due to the difference in reflected signals from the ridges and valleys, the receiving electrodes (Rx) receive different charges to achieve fingerprint recognition.

The piezoelectric film layer must be electrically polarized to produce a good piezoelectric effect. The purpose of polarization is to make the molecular dipole electric moments in the piezoelectric film layer with random orientations oriented in a specific direction (polarization electric field direction) uniformly, improving and Improve the piezoelectricity of the piezoelectric film. Electropolarization utilizes a non-uniform electric field to cause a corona discharge in which the air is partially broken down to generate an ion beam to bombard the dielectric, and to deposit ion charges in the dielectric, so as to achieve a better polarization effect.

The ultrasonic fingerprint identification sensor includes a binding pad, and the electrical signal received by the receiving electrode is processed (eg amplified) by a TFT circuit, and then transmitted to an external circuit board through the binding pad to identify the fingerprint image. If the polarizing electric field is in direct contact with the bonding pad, the electron cloud (Plasma) will flow away along the bonding pad and even break down the TFT circuit. At present, a shielding layer is provided to avoid contact between the bonding pad and the polarized electric field. However, the shielding layer is made of non-metallic materials, which is easy to deform and cannot be large-scaled, and a hollow area needs to be set on the shielding layer to expose the effective display panel. In the display area, the setting of the hollow area is generally realized by mechanical processing, which is prone to misalignment.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned technical problems, the present invention provides an ultrasonic fingerprint identification sensor, a manufacturing method thereof, and a display module, so as to solve the problem that the shielding layer is arranged to avoid contact between the bonding pad and the polarized electric field, which cannot be large-scaled and easily The problem of misalignment occurs.

In order to achieve the above purpose, the technical solution adopted in the embodiment of the present invention is: an ultrasonic fingerprint identification sensor, comprising a rigid substrate, a flexible substrate disposed on the rigid substrate, and receiving sensors sequentially disposed on the flexible substrate The electrode layer, the piezoelectric film layer and the emitter electrode layer also include a first pad disposed between the hard substrate and the flexible substrate, and the first pad is used for connecting the receiving electrode layer with the External circuit board binding connection to obtain fingerprint image.

Optionally, an isolation layer made of organic material is disposed between the first pad and the hard substrate.

Optionally, the receiving electrode layer includes a thin film transistor disposed on the flexible substrate and a receiving electrode connected to the thin film transistor.

Optionally, the thin film transistor includes an active layer, a gate insulating layer, a gate layer, an interlayer insulating layer, a source and drain layer, and a flat layer that are sequentially arranged on the flexible substrate, and also includes a source and drain layer. and a first metal connection line arranged on the same layer, and the first metal connection line is used to connect the first pad with the source and drain layers.

Optionally, a first insulating layer and a buffer layer are disposed between the flexible substrate and the receiving electrode layer along a direction away from the flexible substrate.

Optionally, a second metal connection line is provided on the first insulating layer, the second metal connection line is connected to the first pad through a via hole, and the first metal connection line passes through the second A metal connection line is connected to the first pad.

Optionally, it also includes a second pad disposed on the same layer as the source and drain layers, for connecting the emitter electrode layer with an external circuit board, so as to provide a voltage to the emitter electrode layer.

Optionally, it also includes a polarization line disposed on the same layer as the source and drain layers, so that the receiving electrode is grounded to be at zero potential.

An embodiment of the present invention further provides a display module, including a display panel, and the above-mentioned ultrasonic fingerprint identification sensor disposed on the backlight side of the display panel.

An embodiment of the present invention also provides a method for making an ultrasonic fingerprint identification module, comprising the following steps:

forming an isolation layer on a rigid substrate;

forming a first pad on the isolation layer;

forming a flexible substrate;

forming a thin film transistor and a receiving electrode in sequence on the flexible substrate, and the receiving electrode and the first pad are respectively connected to the thin film transistor;

forming a piezoelectric film layer;

An emitter electrode layer is formed.

Optionally, forming a thin film transistor and a receiving electrode in sequence on the flexible substrate specifically includes the following steps:

forming a polysilicon active layer;

forming a gate insulating layer;

forming a gate layer;

forming an interlayer insulating layer;

forming a source-drain layer and a first metal connection line, the source-drain layer is connected to the active layer through a via hole, and the first metal connection line is connected to the first pad through a via hole;

forming a flat layer;

forming a receiving electrode, which is connected to the source and drain layers through a via hole;

Optionally, it also includes the following steps:

forming a first insulating layer;

A second metal connection line is formed, and the second metal connection line connects the first metal connection line and the first pad.

The beneficial effects of the present invention are: the setting position of the first pad is set between the hard substrate and the flexible substrate, so as to prevent the contact of the first pad with the polarized electric field, and compared with the related ultrasonic fingerprint identification sensor, shielding is omitted Therefore, the problem of the related ultrasonic fingerprint identification sensor being unable to be large-scaled due to the setting of the shielding layer is solved.

Description of drawings

FIG. 1 shows a schematic structural diagram of an ultrasonic fingerprint recognition sensor in the related art;

2 shows a schematic structural diagram of an ultrasonic fingerprint recognition sensor in an embodiment of the present invention;

FIG. 3 is a schematic view of the structure after the first pad is formed in an embodiment of the present invention;

FIG. 4 is a schematic view of the structure after forming a flexible substrate in an embodiment of the present invention;

FIG. 5 shows a schematic structural diagram of forming a second metal connection line in an embodiment of the present invention;

FIG. 6 is a schematic view of the structure after forming the active layer in the embodiment of the present invention;

FIG. 7 is a schematic view of the structure after the gate layer is formed in an embodiment of the present invention;

FIG. 8 is a schematic view of the structure after the source and drain layers are formed in an embodiment of the present invention;

FIG. 9 is a schematic view of the structure after the receiving electrode is formed in the embodiment of the present invention;

FIG. 10 is a schematic view of the structure after the piezoelectric film layer is formed in the embodiment of the present invention;

FIG. 11 is a schematic view of the structure after the piezoelectric thin film layer is formed in the embodiment of the present invention;

FIG. 12 is a schematic view of the structure after forming a metal hard mask layer in an embodiment of the present invention;

FIG. 13 is a schematic view of the structure after the photoresist is formed in the embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation or a specific orientation. construction and operation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first", "second", and "third" are used for descriptive purposes only and should not be construed to indicate or imply relative importance.

The ultrasonic fingerprint recognition sensor includes a piezoelectric film layer 1, a transmitting electrode (not shown in the figure) and a receiving electrode 3 disposed on opposite sides of the piezoelectric film layer 1, and also includes a signal used for transmitting the signal received by the receiving electrode 3 to the outside. The circuit uses the bonding pad 2 for fingerprint identification. As shown in Figure 1, the bonding pad 2 is exposed and is easily in contact with the polarized electric field. If the polarized electric field and the bonding pad 2 are in direct contact, the electron cloud ( Plasma) will flow away along the bond pads and even break down the TFT circuit (the TFT circuit 20 directly connected to the receiving electrode 3, the TFT circuit 20 includes the source-drain 4 and the gate 5). At present, the shielding layer 10 is provided to avoid the contact between the bonding pad 2 and the polarized electric field, but the shielding layer 10 is made of non-metallic materials, which is easy to deform. Under the premise of yield, large size cannot be achieved, and a hollow area (the area directly above the piezoelectric film layer 1) needs to be set on the shielding layer 10 to expose the effective display area of the display panel. The setting of the hollow area is generally It is realized by mechanical processing, which is prone to misalignment.

In view of the above technical problems, the present embodiment provides an ultrasonic fingerprint recognition sensor, referring to FIG. 2 , comprising a rigid substrate 1 , a flexible substrate 2 disposed on the rigid substrate 1 , and a flexible substrate 2 disposed on the flexible substrate 2 in sequence The receiving electrode layer 10, the piezoelectric film layer 12 and the emitter electrode layer 11 further include a first pad 15 disposed between the hard substrate 1 and the flexible substrate 2, the first pad 15 It is used to bind and connect the receiving electrode layer 10 with an external circuit board to obtain a fingerprint image.

In this embodiment, the first pad 15 is made between the hard substrate 1 and the flexible substrate 2 by using the structure of the ultrasonic fingerprint recognition sensor itself, and the ultrasonic fingerprint recognition sensor is applied to When installed on electronic equipment such as display modules, the hard substrate 1 needs to be removed, which is equivalent to arranging the first pad 15 on the back of the ultrasonic fingerprint recognition sensor, and the transmitting electrode layer 11, the receiving electrode The layer 10 and the piezoelectric film layer 12 are located on the front side of the ultrasonic fingerprint recognition sensor, that is, the transmitting electrode layer 11, the receiving electrode layer 10, and the piezoelectric film layer 12 are located on the first side of the flexible substrate 2, and the first A pad 15 is located on the second side of the flexible substrate 2 opposite to the first side, so that the exposed arrangement of the first pad 15 is avoided and the polarization electric field (the emission of the The contact between the electric field generated between the electrode layer 11 and the receiving electrode layer 10) and the first pad 15, compared with the arrangement of the structure of the ultrasonic fingerprint identification sensor in the related art shown in FIG. The setting of the occlusion layer is also avoided, which avoids the problem of inability to large size caused by the occlusion layer.

In this embodiment, an isolation layer 16 made of an organic material is disposed between the first pad 15 and the rigid substrate 1 , see FIGS. 2 and 3 .

When the ultrasonic fingerprint recognition sensor is applied, the hard substrate 1 needs to be removed, and the adhesion between the first pad 15 and the hard substrate 1 is strong, and the hard substrate 1 needs to be removed. When the substrate 1 is removed, the first pads 15 are easily peeled off together. The isolation layer 16 protects the first pads 15 and prevents the first pads 15 from being damaged when the hard substrate 1 is removed. The effect of a pad 15.

In this embodiment, the receiving electrode layer 10 includes a thin film transistor 8 disposed on the flexible substrate 2 and a receiving electrode 9 connected to the thin film transistor 8 , with reference to FIGS. 2 and 7 to 10 .

The ultrasonic wave reflected by the fingerprint is converted into an electrical signal by the piezoelectric film layer 12, the receiving electrode 9 receives the electrical signal, and after processing (eg, amplification) by the thin film transistor 8, the electrical signal passes through the electrical signal. The first pad 15 is transmitted to an external circuit board for fingerprint identification.

In this embodiment, the thin film transistor 8 includes an active layer 81 , a gate insulating layer 5 , a gate layer 83 , an interlayer insulating layer 6 , and a source and drain layer 82 , which are sequentially arranged on the flexible substrate 2 , and are flat. The layer 20 further includes a first metal connection line 14 disposed in the same layer as the source and drain layers 82 , and the first metal connection line 14 is used to connect the first pad 15 with the source and drain layers 82 .

The first metal connection line 14 is connected to the first pad 15 through a via hole, so as to realize signal transmission between the thin film transistor 8 and the first pad 15 .

In this embodiment, a first insulating layer 3 and a buffer layer 4 are disposed between the flexible substrate 2 and the receiving electrode layer 10 along a direction away from the flexible substrate 2 .

The arrangement of the first insulating layer 3 and the buffer layer 4 both play a protective role, and the buffer layer 4 is added to further avoid the invasion of water and oxygen.

In this embodiment, the first insulating layer 3 is provided with a second metal connection line 17, the second metal connection line 17 is connected to the first pad 15 through a via hole, and the first metal connection line 14 is connected to the first pad 15 through the second metal connection line 17 .

The arrangement of the second metal connection line 17 makes the extension direction of the first metal connection line 14 perpendicular to the rigid substrate, which is beneficial to the connection between the first metal connection line 14 and the first pad 15 . The connection between them reduces the difficulty of the process.

In this embodiment, the ultrasonic fingerprint recognition sensor further includes a second pad 7 disposed on the same layer as the source and drain layers 82 for connecting the emitter electrode layer 11 with an external circuit board, so as to connect the emitter electrode layer 11 to the external circuit board. supply voltage.

The setting of the second pad 7 realizes the bonding connection between the emitter electrode layer 11 and the external circuit board, so as to apply a voltage to the emitter electrode layer 11 .

In this embodiment, the ultrasonic fingerprint recognition sensor further includes a polarization line 13 disposed on the same layer as the source and drain layers 82 , so that the receiving electrode 9 is grounded to be at zero potential.

The emitter electrode layer 11 is applied with an alternating voltage, while the receiving electrode 9 is at a fixed potential (eg, 0 potential), so that a potential difference and a strong electric field are formed on the surface of the piezoelectric film layer 12. The piezoelectric film layer The deformation of 12 will generate ultrasonic waves, and the arrangement of the polarization lines 13 ensures that the receiving electrodes 9 are at a fixed potential, thereby ensuring that the piezoelectric film layer 12 generates ultrasonic waves.

In application, the ultrasonic fingerprint identification sensor includes a plurality of fingerprint identification units to correspond to the effective display areas of the multiple display modules, so as to serve as the receiving electrodes 9 in the multiple fingerprint identification units corresponding to the multiple effective display areas. Perform the function of parallel connection to provide 0 potential uniformly.

An embodiment of the present invention further provides a display module, including a display panel, and the above-mentioned ultrasonic fingerprint identification sensor disposed on the backlight side of the display panel.

The above-mentioned ultrasonic fingerprint identification sensor is arranged by disposing the first pad 15 on the side of the flexible substrate 2 away from the piezoelectric film layer 12 to prevent the first pad 15 from contacting the polarized electric field, and Compared with the structure in which the first pads 15 are exposed, the setting of a shielding layer for shielding the first pads 15 is omitted, and the problem of inaccurate alignment due to the installation of the shielding layer that cannot be large-scaled can be avoided. .

An embodiment of the present invention also provides a method for making an ultrasonic fingerprint identification module, comprising the following steps:

forming an isolation layer 16 on the rigid substrate 1;

A first pad 15 is formed on the isolation layer 16, referring to FIG. 3;

Form the flexible substrate 2, refer to FIG. 4;

A thin film transistor 8 and a receiving electrode 9 are sequentially formed on the flexible substrate 2, and the receiving electrode 9 and the first pad 15 are respectively connected to the thin film transistor 8, referring to FIGS. 5-9;

The piezoelectric film layer 12 is formed, referring to FIG. 10 ;

The emitter electrode layer 11 is formed, referring to FIG. 2 .

In this embodiment, the thin film transistor 8 and the receiving electrode 9 are sequentially formed on the flexible substrate 2, which specifically includes the following steps:

The polysilicon active layer 81 is formed. Referring to FIG. 6 , the specific structural forms of the active layer 81 can include P-type, N-type, and P-N-type. The P-type active layer The P-type doped region, the polysilicon region and the P-type doped region are arranged in sequence in the direction, and the N-type active layer 81 includes an N-type doped region and a polysilicon region arranged in sequence along the direction parallel to the hard substrate 1 and an N-type doped region, the P-N-type active layer includes a P-type doped region, a polysilicon region and an N-type doped region sequentially arranged along a direction parallel to the hard substrate 1 .

Form the gate insulating layer 5, refer to FIG. 7;

forming the gate layer 83, referring to FIG. 7;

Form the interlayer insulating layer 6, refer to FIG. 8;

A source-drain layer 82 and a first metal connection line 14 are formed, the source-drain layer 82 is connected to the active layer 81 through a via hole, and the first metal connection line 14 is connected to the first solder connection through a via hole The disk 15 is connected, refer to Figure 8;

A flat layer 20 is formed, referring to FIG. 9;

The receiving electrode 9 is formed, and the receiving electrode 9 is connected to the source-drain layer 82 through the via hole. Please refer to FIG. 9 ;

In this embodiment, the following steps are also included:

Form the first insulating layer 3, refer to FIG. 5;

A second metal connection line 17 is formed, and the second metal connection line 17 connects the first metal connection line 14 and the first pad 15 , referring to FIG. 6 .

In this embodiment, after the first insulating layer 3 is formed, it further includes forming a buffer layer 4 on the first insulating layer 3 , referring to FIG. 7 .

In this embodiment, before forming the piezoelectric film layer 12 , the method further includes forming an isolation insulating layer 21 on the flat layer 20 .

In this embodiment, the formation of the piezoelectric film layer 12 may be formed at one time through a patterning process, and may also include the following steps:

A piezoelectric thin film layer is formed by using a piezoelectric material (eg PVDF). Referring to FIG. 11 , the piezoelectric thin film layer is formed on the entire surface, and the piezoelectric thin film layer includes a reserved area covering the receiving electrode layer 10 , also covering the removal area above the second pad 7;

A metal hard mask layer 18 is formed on the piezoelectric film layer, referring to FIG. 12 ;

A photoresist 19 is formed on the metal hard mask layer 18, and the orthographic projection of the photoresist 19 on the piezoelectric thin film layer is located in the reserved area of the piezoelectric thin film layer, referring to FIG. 13;

Through a photolithography process, the removed area of the piezoelectric thin film layer is removed to form the piezoelectric thin film layer 12 , referring to FIG. 10 .

The material of the metal hard mask layer is preferably an Al-based material, such as MoAlNdMo, MoAlMo.

In this embodiment, the emitter electrode layer 11 is made of metal Ag, but it is not limited to this.

The above are the preferred embodiments of the present invention. It should be noted that, for those of ordinary skill in the art, without departing from the principles of the present invention, several improvements and modifications can be made. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (12)

1. An ultrasonic fingerprint identification sensor, comprising a rigid substrate, a flexible substrate arranged on the rigid substrate, and a receiving electrode layer, a piezoelectric film layer and a transmitting electrode layer arranged on the flexible substrate in turn, which It is characterized in that, it further comprises a first pad disposed between the rigid substrate and the flexible substrate, and the first pad is used to bind and connect the receiving electrode layer with an external circuit board to obtain a Fingerprint image. 2 . The ultrasonic fingerprint identification sensor according to claim 1 , wherein an isolation layer made of organic material is arranged between the first pad and the hard substrate. 3 . 3 . The ultrasonic fingerprint identification sensor according to claim 1 , wherein the receiving electrode layer comprises a thin film transistor disposed on the flexible substrate and a receiving electrode connected to the thin film transistor. 4 . 4. The ultrasonic fingerprint identification sensor according to claim 3, wherein the thin film transistor comprises an active layer, a gate insulating layer, a gate layer, an interlayer insulating layer, an active layer, a gate insulating layer, a gate insulating layer, an interlayer insulating layer, a The source-drain layer, the flat layer, also includes a first metal connection line arranged in the same layer as the source-drain layer, and the first metal connection line is used for connecting the first pad with the source-drain layer. 5 . The ultrasonic fingerprint identification sensor according to claim 4 , wherein a first insulating layer and a buffer layer are arranged between the flexible substrate and the receiving electrode layer along a direction away from the flexible substrate. 6 . . 6 . The ultrasonic fingerprint identification sensor according to claim 5 , wherein a second metal connection wire is provided on the first insulating layer, and the second metal connection wire is connected to the first pad through a via hole. 7 . connected, the first metal connection line is connected to the first pad through the second metal connection line. 7 . The ultrasonic fingerprint identification sensor according to claim 4 , further comprising a second pad disposed on the same layer as the source and drain layers, for connecting the emitter electrode layer with an external circuit board, so as to connect the The emitter electrode layer provides voltage. 8 . The ultrasonic fingerprint identification sensor according to claim 4 , further comprising a polarization line arranged in the same layer as the source and drain layers, so that the receiving electrode is grounded to be at zero potential. 9 . 9 . A display module, comprising a display panel, and the ultrasonic fingerprint identification sensor according to any one of claims 1 to 8 arranged on the backlight side of the display panel. 10 . 10. A method for making an ultrasonic fingerprint identification sensor, comprising the following steps: forming an isolation layer on a rigid substrate; forming a first pad on the isolation layer; forming a flexible substrate; forming a thin film transistor and a receiving electrode in sequence on the flexible substrate, and the receiving electrode and the first pad are respectively connected to the thin film transistor; forming a piezoelectric film layer; An emitter electrode layer is formed. 11. The method for making an ultrasonic fingerprint identification sensor according to claim 10, wherein, Forming a thin film transistor and a receiving electrode in sequence on the flexible substrate specifically includes the following steps: forming a polysilicon active layer; forming a gate insulating layer; forming a gate layer; forming an interlayer insulating layer; forming a source-drain layer and a first metal connection line, the source-drain layer is connected to the active layer through a via hole, and the first metal connection line is connected to the first pad through a via hole; forming a flat layer; A receiving electrode is formed, and the receiving electrode is connected with the source and drain layers through a via hole. 12. The method for making an ultrasonic fingerprint identification sensor according to claim 11 , further comprising the steps of: forming a first insulating layer; A second metal connection line is formed, and the second metal connection line connects the first metal connection line and the first pad.

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