CN112115758A

CN112115758A - Fingerprint identification module, forming method thereof and electronic equipment

Info

Publication number: CN112115758A
Application number: CN202010266613.5A
Authority: CN
Inventors: 石虎; 刘孟彬; 向阳辉
Original assignee: China Core Integrated Circuit Ningbo Co Ltd
Current assignee: China Core Integrated Circuit Ningbo Co Ltd
Priority date: 2020-04-07
Filing date: 2020-04-07
Publication date: 2020-12-22
Anticipated expiration: 2040-04-07
Also published as: CN112115758B

Abstract

A fingerprint identification module, a forming method thereof and electronic equipment are provided, wherein the forming method comprises the following steps: providing a substrate; forming a plurality of discrete sacrificial layers on a substrate; forming a piezoelectric transducer on the sacrificial layer, wherein the piezoelectric transducer comprises a first electrode, a piezoelectric layer positioned on the first electrode and a second electrode positioned on the piezoelectric layer, and the piezoelectric layer is used for generating vibration according to a signal provided by a signal processing circuit to form ultrasonic waves for fingerprint identification; forming a release hole exposing the top of the sacrificial layer part; and removing the sacrificial layer through the release hole by adopting an ashing process to form a cavity. The embodiment of the invention adopts the ashing process to remove the sacrificial layer, realizes the release of the sacrificial layer under the gas phase condition, is beneficial to reducing the residue of the sacrificial layer, is easy to completely remove the sacrificial layer, and has small influence on the piezoelectric transducer by the process for removing the sacrificial layer; in addition, the embodiment of the invention directly forms the cavity on the substrate without consuming an additional bearing substrate, thereby being beneficial to reducing the process cost and realizing the mass production of the fingerprint identification module.

Description

Fingerprint identification module, forming method thereof and electronic equipment

Technical Field

The invention relates to the field of semiconductor manufacturing, in particular to a fingerprint identification module, a forming method thereof and electronic equipment.

Background

Fingerprint identification technique passes through fingerprint imaging module and gathers human fingerprint image, then compares with fingerprint identification system in have fingerprint imaging information to realize identification. Due to the convenience of use and the uniqueness of human fingerprints, fingerprint identification technology has been widely applied to various fields, such as: the security inspection field such as public security bureau, customs, etc., the entrance guard system of buildings, and the consumer goods field such as personal computer and mobile phone, etc.

At present, the ultrasonic fingerprint identification technology has stronger environmental adaptability because of having the advantages of oil resistance, water resistance, strong penetrability and the like, can be used for more complex environments, and has become one of the main fingerprint identification technologies. The identification unit used by the ultrasonic fingerprint identification technology is a piezoelectric transducer. The piezoelectric transducer mainly comprises a bottom electrode, a top electrode and a piezoelectric layer positioned between the bottom electrode and the top electrode, and by utilizing the inverse piezoelectric effect of the piezoelectric layer, as long as voltages with fixed frequencies are applied to the bottom electrode and the top electrode on the upper surface and the lower surface of the piezoelectric layer, the piezoelectric layer can vibrate, so that ultrasonic waves are generated. Because the ultrasonic waves are absorbed, penetrated and reflected to different degrees when reaching the surfaces of different materials, the positions of the ridges and the valleys of the fingerprint can be identified by utilizing the difference of the skin and air or different skin layers on the impedance of the sound waves. In addition, the ultrasonic fingerprint sensor usually has a cavity corresponding to the piezoelectric transducer, and the cavity is used for providing a vibration space for the piezoelectric transducer.

Disclosure of Invention

The invention provides a fingerprint identification module, a forming method thereof and electronic equipment, and is beneficial to improving the performance of the fingerprint identification module.

In order to solve the above problems, the present invention provides a method for forming a fingerprint identification module, comprising: providing a substrate having signal processing circuitry; forming a plurality of discrete sacrificial layers on the substrate; forming a piezoelectric transducer on the sacrificial layer, wherein the piezoelectric transducer comprises a first electrode, a piezoelectric layer located on the first electrode, and a second electrode located on the piezoelectric layer, and the piezoelectric layer is used for generating vibration according to a signal provided by the signal processing circuit to form ultrasonic waves for fingerprint identification; forming a release hole on the sacrificial layer to expose a portion of the top of the sacrificial layer; and removing the sacrificial layer through the release hole by adopting an ashing process to form a cavity.

Correspondingly, the invention also provides a fingerprint identification module, which comprises: a substrate having a signal processing circuit; a plurality of piezoelectric transducers which are separated on the substrate and comprise piezoelectric transducer side parts which are arranged vertically to the substrate and piezoelectric transducer top parts which are parallel to the substrate and are connected with the top ends of the piezoelectric transducer side parts, the piezoelectric transducer side parts and the piezoelectric transducer top parts and the substrate enclose a cavity, the piezoelectric transducers comprise first electrodes, piezoelectric layers which are arranged on the first electrodes and second electrodes which are arranged on the piezoelectric layers, and the piezoelectric layers are used for generating vibration according to signals provided by the signal processing circuit to form ultrasonic waves for fingerprint identification; and the release hole penetrates through the top of the piezoelectric transducer and is communicated with the cavity.

Correspondingly, the invention also provides an electronic device, comprising: the invention provides a fingerprint identification module.

Compared with the prior art, the technical scheme of the invention has the following advantages:

in the method for forming the fingerprint identification module, provided by the embodiment of the invention, after a plurality of discrete sacrificial layers are formed on the substrate, piezoelectric transducers are formed on the sacrificial layers; then, forming a release hole exposing the top of part of the sacrificial layer on the sacrificial layer, and removing the sacrificial layer through the release hole by adopting an ashing process to form a cavity; the embodiment of the invention selects the material which can be removed by the ashing process as the material of the sacrificial layer, so that the sacrificial layer is removed by the ashing process, the ashing process adopts oxygen for etching, the sacrificial layer is correspondingly released under the gas phase condition, the sacrificial layer residue is favorably reduced, the sacrificial layer is easily and cleanly removed, the etching selection ratio of the ashing process to the sacrificial layer and the piezoelectric transducer material is higher, the two aspects are favorable for reducing the probability of residue or pollution generated by the process for removing the sacrificial layer and the influence of the process for removing the sacrificial layer on the piezoelectric transducer, and the cost of the ashing process is lower; in addition, compared with the scheme of forming the cavity in a bonding mode, the embodiment of the invention directly forms the cavity on the substrate without consuming an additional bearing substrate, thereby being beneficial to reducing the process cost and realizing the mass production of the fingerprint identification module; in addition, in the embodiment of the invention, the signal processing circuit is integrated with the piezoelectric transducer, and the piezoelectric layer directly generates vibration according to the signal provided by the signal processing circuit to form ultrasonic waves, so that signal connecting circuits are reduced, the number of connecting circuits is reduced, the manufacturing process flow is reduced correspondingly, and the electrical property of the device is improved.

Drawings

Fig. 1 to 8 are schematic structural diagrams corresponding to steps of an embodiment of a fingerprint identification module according to the present invention.

Detailed Description

As is known in the art, an ultrasonic fingerprint sensor typically has a cavity corresponding to a piezoelectric transducer.

A method for forming the cavity is to form a sacrificial layer firstly, wherein the sacrificial layer is used for occupying space positions for forming the cavity, and the material of the sacrificial layer comprises silicon oxide or germanium; forming a release hole exposing the sacrificial layer after forming the piezoelectric transducer; and then, removing the sacrificial layer through the release hole by adopting a wet etching process to form a cavity.

The sacrificial layer is removed by adopting a wet etching process in the forming method; the whole fingerprint identification module is required to be placed in a cleaning tank with etching solution in the wet etching process, so that the etching solution is easy to enter the cavity and is difficult to completely remove, and the performance of the piezoelectric transducer and the performance of the cavity are affected; in addition, in the method, silicon oxide or germanium is used as a material of the sacrificial layer, and the etching selection ratio of the process for removing the sacrificial layer to the materials of the sacrificial layer and the piezoelectric transducer is not high enough, which easily increases the probability of occurrence of the residual sacrificial layer.

Another method is to form the cavity by means of bonding. However, forming the cavity by bonding requires consuming a piece of carrier substrate, which easily results in a too high cost for forming the fingerprint recognition module.

In order to solve the technical problem, in the method for forming the fingerprint identification module provided by the embodiment of the invention, the material capable of being removed by the ashing process is selected as the material of the sacrificial layer, so that the sacrificial layer is removed by the ashing process, the ashing process usually adopts oxygen for etching, the sacrificial layer can be correspondingly released under the gas phase condition, the residue of the sacrificial layer can be reduced, the sacrificial layer can be easily and cleanly removed, the etching selectivity of the ashing process on the sacrificial layer and the piezoelectric transducer material is higher, the probability of residue or pollution generated by the process for removing the sacrificial layer can be reduced, the influence of the process for removing the sacrificial layer on the piezoelectric transducer can be reduced, and the cost of the ashing process is lower; in addition, compared with the scheme of forming the cavity in a bonding mode, the embodiment of the invention directly forms the cavity on the substrate without consuming an additional bearing substrate, thereby being beneficial to reducing the process cost and realizing the mass production of the fingerprint identification module; in addition, in the embodiment of the invention, the signal processing circuit is integrated with the piezoelectric transducer, and the piezoelectric layer directly generates vibration according to the signal provided by the signal processing circuit to form ultrasonic waves, so that signal connecting circuits are reduced, the number of connecting circuits is reduced, the manufacturing process flow is reduced correspondingly, and the electrical property of the device is improved.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Fig. 1 to 8 are schematic structural diagrams corresponding to steps in an embodiment of a method for forming a fingerprint identification module according to the present invention.

Referring to fig. 1, a substrate 100 having signal processing circuitry is provided.

The substrate 100 is used for providing a process platform for forming the piezoelectric transducer and the cavity, and the substrate 100 and the piezoelectric transducer form a fingerprint identification module. In this embodiment, the substrate 100 is formed based on a CMOS process.

The substrate 100 has a signal processing circuit formed therein, the signal processing circuit is used for connecting with a subsequent piezoelectric transducer, and the signal processing circuit is used for driving the piezoelectric transducer to generate vibration to form ultrasonic waves and process detection signals generated by the piezoelectric transducer in the working process of the fingerprint identification module.

In this embodiment, the substrate 100 further includes a first connection terminal 101 and a second connection terminal 102 electrically connected to the signal processing circuit. The first connection terminal 101 and the second connection terminal 102 are used to electrically connect the signal processing circuit in the substrate 100 to the piezoelectric transducer or other devices.

In this embodiment, the number of the first connection ends 101 and the number of the second connection ends 102 are both plural.

Specifically, the top surfaces of the first connection terminal 101 and the second connection terminal 102 are exposed to the substrate 100, so as to prepare for the subsequent electrical connection between the first connection terminal 101 and the first electrode, and the electrical connection between the second connection terminal 102 and the second electrode.

In this embodiment, the first connection end 101 and the second connection end 102 are pads (Pad).

Referring to fig. 2, a plurality of discrete sacrificial layers 120 are formed on a substrate 100. The sacrificial layer 120 is used to occupy a spatial location for subsequent formation of a cavity. A cavity is subsequently formed at the location of the sacrificial layer 120.

Therefore, in the present embodiment, the shape, position and size of the sacrificial layer 120 determine the shape, position and size of the subsequent cavity, and accordingly, the sacrificial layer 120 is formed according to the shape, position and size of the desired cavity.

In this embodiment, the material of the sacrificial layer 120 includes amorphous carbon, polyimide, or epoxy. The amorphous carbon, polyimide or epoxy resin can be removed through an ashing process, so that the sacrificial layer 120 can be removed through the ashing process to form a cavity, the ashing process has a high etching selectivity on the sacrificial layer 120 and the piezoelectric transducer, the influence of the process for removing the sacrificial layer 120 on the piezoelectric transducer is reduced, and the ashing process is low in cost and small in side effect.

Specifically, in the present embodiment, the material of the sacrificial layer 120 is amorphous carbon. The cost of the amorphous carbon material is low, the etching selection ratio of the subsequent ashing process to the amorphous carbon and piezoelectric transducer material is high, and the oxygen-containing gas adopted by the ashing process can oxidize the amorphous carbon into carbon dioxide, so that reaction byproducts are directly discharged from the reaction chamber, the risk of generating the residual sacrificial layer 120 is favorably reduced, the probability of the residual reaction byproducts in the cavity is reduced, and the performance of the fingerprint identification module is favorably improved correspondingly. In other embodiments, the material of the sacrificial layer may be other organic materials or inorganic materials capable of being removed by the ashing process.

In this embodiment, in the step of forming the sacrificial layer 120, the sacrificial layer 120 exposes the first connection end 101 and the second connection end 102, so that after the piezoelectric transducer covering the top surface and the side wall of the sacrificial layer 120 is formed subsequently, a first electrode in the piezoelectric transducer can extend to cover the first connection end 101, and a second electrode in the piezoelectric transducer can extend to cover the piezoelectric layer located above the second connection end 102.

In this embodiment, the step of forming the sacrificial layer 120 includes: forming a sacrificial material layer (not shown) covering the substrate 100; the sacrificial material layer is patterned and the remaining sacrificial material layer on the substrate 100 is used as the sacrificial layer 120. In this embodiment, the process of forming the sacrificial material layer includes a chemical vapor deposition process.

In this embodiment, a dry etching process is used to pattern the sacrificial material layer.

In this embodiment, before forming the sacrificial layer 120 on the substrate 100, the method for forming the fingerprint identification module further includes: an etch stop layer 110 is formed on the substrate 100. Accordingly, the sacrificial layer 120 is formed on the etch stop layer 110.

The forming of the sacrificial layer 120 includes a deposition process and an etching process that are sequentially performed, the etching stop layer 110 is used to define an etching stop position in the process of forming the sacrificial layer 120, so as to reduce damage to the substrate 100, and the etching stop layer 110 is also used to protect the substrate 100; furthermore, the material of the etch stop layer 110 is a dielectric material, and the etch stop layer 110 is also used to isolate the first electrode in the subsequent piezoelectric transducer from the substrate 100.

The material of the etch stop layer 110 includes one or more of silicon oxide, silicon nitride, and silicon oxynitride. In this embodiment, the material of the etch stop layer 110 is silicon oxide.

In this embodiment, the etch stop layer 110 is formed by a deposition process. Specifically, the deposition process may be a chemical vapor deposition process or an atomic layer deposition process, or the like.

Referring to fig. 3, a piezoelectric transducer 130 is formed on the sacrificial layer 120, the piezoelectric transducer 130 includes a first electrode 31, a piezoelectric layer 32 on the first electrode 31, and a second electrode 33 on the piezoelectric layer 32, and the piezoelectric layer 32 is configured to generate vibration according to a signal provided by a signal processing circuit to form an ultrasonic wave for fingerprint recognition.

Piezoelectric transducer 130 is the identification element in the fingerprint identification module. When the fingerprint identification module works, the signal processing circuit in the substrate 100 applies alternating voltage to the first electrode 31 and the second electrode 33 of the piezoelectric transducer 130, so that the piezoelectric layer 32 vibrates to generate ultrasonic waves by utilizing the inverse piezoelectric effect of the piezoelectric layer 32; vibration is transmitted upwards, i.e. ultrasonic waves are transmitted upwards, the ultrasonic waves pass through different media layers (screens, glass, etc.) to the valleys or ridges of the fingers, because the ultrasonic waves reach different material surfaces to different degrees of absorption, penetration and reflection, the ultrasonic waves encounter the surface of the ridge and are partially reflected and partially transmitted, and because the acoustic impedance of the air in the valley is much higher than that of the ridge, the ultrasonic waves encounter the valleys and are almost totally reflected, and when the different acoustic wave energies reflected from the valleys and ridges are transmitted to the corresponding piezoelectric transducer 130 surface, according to the piezoelectric effect of the piezoelectric layer 32, the corresponding piezoelectric transducers will generate different electrical signals (amplitude, frequency, phase, etc.) as detection signals, so that the piezoelectric transducers 130 can identify the positions of the ridges and valleys of the fingerprint, and causes the signal processing circuit to identify and process the detection signals generated by the piezoelectric transducer 130.

In this embodiment, the number of the sacrificial layers 120 is multiple, the number of the piezoelectric transducers 130 is also multiple, the piezoelectric transducers 130 are separated from the substrate 100, and the piezoelectric transducers 130 correspond to the sacrificial layers 120 one by one, so that after the cavities are formed at the positions of the sacrificial layers 120, the piezoelectric transducers 130 correspond to the cavities one by one.

In this embodiment, in the step of forming the piezoelectric transducer 130, the piezoelectric transducer 130 covers the top surface and the sidewall of the sacrificial layer 120, that is, before the piezoelectric transducer 130 is formed, a planarization layer does not need to be formed on the substrate 100, so that the process flow is simplified, and the deposition process and the planarization process are generally required to be sequentially performed to form the planarization layer, which is higher in cost.

In this embodiment, the portion of the piezoelectric transducer 130 on the sidewall of the sacrificial layer 120 serves as a piezoelectric transducer side portion, which is disposed perpendicular to the substrate 100; the portion of the piezoelectric transducer 130 on the top surface of the sacrificial layer 120 serves as the piezoelectric transducer top, which is parallel to the substrate 100 and connected to the top of the piezoelectric transducer side, and subsequently after a cavity is formed at the location of the sacrificial layer 120, the cavity is enclosed by the piezoelectric transducer side and the piezoelectric transducer top and the substrate 100.

The first electrode 31 is used as a Bottom electrode (Bottom electrode) of the piezoelectric transducer 130, i.e., an electrode closer to the substrate 100 in the fingerprint recognition module.

The material of the first electrode 31 may be a conductive material such as metal, metal silicide, metal nitride, metal oxide, or conductive carbon, for example, the material of the first electrode 31 may be Mo, Al, Cu, Ag, Au, Ni, Co, TiAl, TiN, TaN, or the like. In this embodiment, the material of the first electrode 31 is Mo.

The piezoelectric layer 32 is used to generate vibrations in accordance with signals provided by the signal processing circuitry to form ultrasonic waves for fingerprint identification. The material of piezoelectric layer 32 may be a piezoelectric crystal, piezoelectric ceramic, or piezoelectric polymer, among others. The piezoelectric crystal can be aluminum nitride, lead zirconate titanate, quartz crystal, lithium gallate, lithium germanate, titanium germanate, lithium iron niobate or lithium tantalate, and the piezoelectric polymer can be polyvinylidene fluoride, vinylidene fluoride-trifluoroethylene copolymer, nylon-11 or vinylidene dicyan-vinyl acetate alternating copolymer. In this embodiment, the piezoelectric layer 32 is made of aluminum nitride.

The second electrode 33 is used as a Top electrode (Top electrode) of the piezoelectric transducer 130, i.e., an electrode farther from the substrate 100 in the fingerprint recognition module. When the fingerprint identification module works, the signal processing circuit applies alternating current signals to the first electrode 31 and the second electrode 33, so that voltage is generated at two ends of the piezoelectric layer 32, and the piezoelectric layer 32 generates vibration to form ultrasonic waves.

In this embodiment, the material of the second electrode 33 may be a conductive material such as metal, metal silicide, metal nitride, metal oxide, or conductive carbon, for example, Mo, Al, Cu, Ag, Au, Ni, Co, TiAl, TiN, or TaN. In this embodiment, the material of the second electrode 33 is Mo.

In this embodiment, in the step of forming the piezoelectric transducer 130, the first electrode 31 further covers the sidewall of the sacrificial layer 120 and extends to cover the first connection end 101, and the second connection end 102 is exposed from the first electrode 31; the piezoelectric layer 32 also covers the first electrode 31 on the first connection 101, and the substrate 100 between the sacrificial layers 120; the second electrode 33 also extends to cover the piezoelectric layer 32 above the second connection end 102 and expose the piezoelectric layer 32 above the first connection end 101.

The first electrode 31 further extends to cover the first connection end 101, so that a first conductive plug which penetrates through the piezoelectric layer 32 and the first electrode 31 and is in contact with the first connection end 101 can be formed subsequently, the first conductive plug can realize the electrical connection between the first electrode 31 and the first connection end 101, the difficulty in forming the first conductive plug is favorably reduced, the first electrode 31 exposes out of the second connection end 102, the second conductive plug formed subsequently is prevented from being in short circuit with the first electrode 31, the influence of the first electrode 31 on the subsequent formation of the second conductive plug is favorably reduced, the subsequent formation of the second conductive plug does not need to etch the first electrode 31, and the process difficulty in forming the second conductive plug is favorably reduced; in addition, compared with the scheme that the second connecting end is not exposed out of the first electrode, after the second conductive through hole is formed subsequently, the step of forming the insulating layer on the side wall of the first electrode to prevent the second conductive plug from being short-circuited with the first electrode does not need to be additionally performed in the embodiment, so that the process flow is correspondingly simplified, and the process difficulty is reduced.

The second electrode 33 further extends to cover the piezoelectric layer 32 above the second connection end 102, so that a second conductive plug which penetrates through the second electrode 33 and the piezoelectric layer 32 and is in contact with the second connection end 102 can be formed subsequently, the second conductive plug can realize the electrical connection between the second electrode 33 and the second connection end 102, and is favorable for reducing the difficulty of forming the second conductive plug, and the second electrode 33 exposes the piezoelectric layer 32 above the first connection end 101, so that the first conductive plug formed subsequently is prevented from being short-circuited with the second electrode 33, the influence of the second electrode 33 on the subsequent formation of the first conductive plug is favorably reduced, and the subsequent formation of the first conductive plug does not need to etch the second electrode 33, and is favorable for reducing the process difficulty of forming the first conductive plug; in addition, compared with the piezoelectric layer of which the second electrode is not exposed above the first connection end, after the first conductive through hole is formed subsequently, the step of preventing the first conductive plug from being short-circuited with the second electrode on the side wall of the second electrode does not need to be additionally performed in the embodiment of the invention, so that the process flow is simplified and the process difficulty is reduced.

Specifically, in this embodiment, the first electrode 31 covers the etching stop layer 110 on the first connection end 101 and exposes the etching stop layer 110 on the second connection end 102; the second electrode 33 covers the piezoelectric layer 32 above the second connection terminal 103 and exposes the piezoelectric layer 32 above the first connection terminal 101.

In this embodiment, the first electrode 31 further has a first opening (not shown) located above the first connection end 101; the piezoelectric layer 32 also fills in the first opening; the second electrode 33 on the piezoelectric layer 32 also has a second opening 20 above the second connection end 102 and exposing the piezoelectric layer 23.

By arranging the first electrode 31 with the first opening above the first connection end 101, the first electrode 31 does not need to be etched in the subsequent process of forming the first conductive through hole which penetrates through the piezoelectric layer 32 and the first electrode 31 and exposes the first connection end 101, which is beneficial to reducing the types of films to be etched for forming the first conductive through hole and further beneficial to reducing the difficulty of the etching process for forming the first conductive through hole; by providing the second electrode 33 with the second opening 20 located above the second connection end 102, the second electrode 33 does not need to be etched in the subsequent process of forming the second conductive through hole penetrating through the second electrode 33 and the piezoelectric layer 32 and exposing the second connection end 102, which is beneficial to reducing the types of films to be etched for forming the second conductive through hole, and is further beneficial to reducing the difficulty of the etching process for forming the second conductive through hole.

In this embodiment, the step of forming the piezoelectric transducer 130 includes: forming a first electrode film (not shown) conformally covering the substrate 100, and the top surface and the sidewalls of the sacrificial layer 120; patterning the first electrode film, leaving the first electrode film on the top surface and the side wall of the sacrifice layer 120 as the first electrode 31; forming a piezoelectric layer 32 on the first electrode 31, the piezoelectric layer 32 further covering the substrate 100 between the sacrificial layers 120; forming a second electrode film (not shown) on the piezoelectric layer 32; the second electrode film is patterned, leaving the second electrode film on the piezoelectric layer 32 covering over the sacrifice layer 120 and over the second connection terminal 102 as the second electrode 33.

In this embodiment, in the process of forming the piezoelectric transducer 130, the first electrode film is patterned to form the first electrode 31 after the first electrode film is formed, and the second electrode film is patterned to form the second electrode 33 after the second electrode film is formed, and compared with the scheme of sequentially forming the first electrode film, the piezoelectric layer, and the second electrode film and then patterning the first electrode film and the second electrode film, in the process of patterning the first electrode film, only the material of the first electrode film needs to be etched, and in the process of patterning the second electrode film, only the material of the second electrode film needs to be etched, which is beneficial to reducing the difficulty of forming the piezoelectric transducer 130.

In this embodiment, in the process of patterning the first electrode film to form the first electrode 31, the first opening is formed, which is beneficial to improving the process integration degree and the process compatibility; in the process of patterning the second electrode film to form the second electrode 33, the second opening 20 is formed, which is advantageous to improve process integration and process compatibility.

In this embodiment, a dry etching process is adopted, for example: and patterning the first electrode film by an anisotropic dry etching process. The anisotropic dry etching process has anisotropic etching characteristics, and is beneficial to improving the sidewall morphology quality and the dimensional accuracy of the first electrode 31.

In this embodiment, the piezoelectric layer 32 further covers the substrate 100 between the sacrificial layers 120, and the piezoelectric layer 32 on the substrate 100 is further used to support the subsequent formation of other film layers.

In this embodiment, the process of forming the first electrode film, the piezoelectric layer 32, and the second electrode film includes a physical vapor deposition process. In particular, the physical vapor deposition process may be an ion sputtering process.

In this embodiment, a dry etching process is adopted, for example: and patterning the second electrode film by an anisotropic dry etching process. The anisotropic dry etching process has anisotropic etching characteristics, and is beneficial to improving the sidewall morphology quality and the dimensional accuracy of the second electrode 33.

A cavity is subsequently formed at the location of the sacrificial layer 120. It should be noted that, when the fingerprint identification module is in operation, the portion of the piezoelectric transducer top having the three-layer laminated structure of the first electrode 31, the piezoelectric layer 32 and the second electrode 33 serves as a functional layer for effective vibration, and accordingly, the area corresponding to the functional layer for effective vibration serves as an active area, and the corresponding pair of areas of the portion of the piezoelectric transducer top not having the three-layer laminated structure of the first electrode 31, the piezoelectric layer 32 and the second electrode 33 serves as an inactive area.

Therefore, the piezoelectric transducer located in the active area may have a three-layer stacked structure of the first electrode 31, the piezoelectric layer 32 and the second electrode 33 on top, and the piezoelectric transducer located in the inactive area may have no three-layer stacked structure of the first electrode 31, the piezoelectric layer 32 and the second electrode 33 on top, and only one or more of the first electrode 31, the piezoelectric layer 32 and the second electrode 33 need to cover the top surface of the sacrificial layer 120.

In this embodiment, the first electrode 31 further covers the sidewall of the sacrificial layer 120 and extends over the first connection end 101 as an example. The invention is not limited to the position relation among the first electrode, the piezoelectric layer, the second electrode and the side wall of the sacrificial layer, and only one or more of the first electrode, the piezoelectric layer and the second electrode is/are required to cover the side wall of the sacrificial layer, so that the sacrificial layer is coated by the first electrode, the piezoelectric layer and the second electrode together with the piezoelectric transducer positioned on the top surface of the sacrificial layer.

Referring to fig. 4, a release hole 200 exposing a portion of the top of the sacrificial layer 120 is formed on the sacrificial layer 120.

The release holes 200 are located on the sacrificial layer 120 and expose the sacrificial layer 120, so that the sacrificial layer 120 can be subsequently removed through the release holes 200.

In this embodiment, the number of the release holes 200 is plural, so as to improve the efficiency of removing the sacrificial layer 120 through the release holes 200.

As an example, in the step of forming the release hole 200, the release hole 200 penetrates the first electrode 31, the piezoelectric layer 32, and the second electrode 33 and exposes a portion of the top of the sacrificial layer 120. In other embodiments, the release hole may further penetrate through one or two of the first electrode, the piezoelectric layer, and the second electrode and expose a part of the top of the sacrificial layer, a part of the piezoelectric transducer top not having the three-layer stacked structure of the first electrode, the piezoelectric layer, and the second electrode is located in the inactive area, that is, the release hole penetrates through the top of the piezoelectric transducer located in the inactive area, and the release hole does not penetrate through the top of the piezoelectric transducer located in the active area, so as to not etch the top of the piezoelectric transducer located in the active area in the process of forming the release hole, thereby facilitating reduction of influence on the top of the piezoelectric transducer located in the active area, thereby facilitating improvement of accuracy of fingerprint identification, and correspondingly improving performance of the fingerprint identification module.

In this embodiment, the step of forming the release hole 200 includes: forming a mask layer (not shown) on the piezoelectric transducer 130, the mask layer having an opening (not shown) formed therein over the sacrificial layer 120; and etching the piezoelectric transducer 130 below the opening by taking the mask layer as a mask to form the release hole 200.

The mask layer is used as an etching mask for forming the release holes 200. In this embodiment, the material of the mask layer includes a photoresist, and the mask layer can be formed by a photolithography process such as coating, exposure, and development.

In this embodiment, a dry etching process is adopted, for example: the piezoelectric transducer 130 on the sacrificial layer 120 is etched by an anisotropic dry etching process to form the release hole 200.

After the release hole 200 is formed, the forming method of the fingerprint identification module further comprises the following steps: and removing the mask layer. The mask layer is removed, exposing the top surface of the piezoelectric transducer 130 in preparation for the formation of subsequent film layers.

Referring to fig. 5, the sacrificial layer 120 is removed through the release holes 200 using an ashing process to form cavities 300.

By removing the sacrificial layer 120, a cavity 300 is formed at the location of the sacrificial layer 120.

In the embodiment of the invention, the material capable of being removed by the ashing process is selected as the material of the sacrificial layer 120, so that the sacrificial layer 120 is removed by the ashing process, the ashing process usually adopts oxygen for etching, accordingly, the sacrificial layer 120 can be released under a gas phase condition, the residue of the sacrificial layer 120 can be reduced, the sacrificial layer 120 can be easily and cleanly removed, the etching selection ratio of the ashing process to the materials of the sacrificial layer 120 and the piezoelectric transducer 130 is higher, the etching is carried out by adopting oxygen, the two aspects are favorable for reducing the probability of residue or pollution generated by the process for removing the sacrificial layer 120 and the influence of the process for removing the sacrificial layer 120 on the piezoelectric transducer 130, and the cost of the ashing process is lower; in addition, compared with the scheme of forming the cavity by bonding, the embodiment directly forms the cavity 300 on the substrate 100 without consuming an additional bearing substrate, which is beneficial to reducing the process cost and realizing the mass production of the fingerprint identification module; in addition, in the embodiment of the present invention, the signal processing circuit is integrated with the piezoelectric transducer 130, and the piezoelectric layer 32 directly generates vibration according to the signal provided by the signal processing circuit to form ultrasonic waves, which is beneficial to reducing signal connection lines, reducing connection lines, correspondingly reducing the manufacturing process flow, and improving the electrical performance of the device.

In particular, the ashing process uses oxygen as the etching gas, which is much less costly than HF or XeF₂The cost of materials; moreover, the oxygen selectivity is higher, and the other functional layers are not damaged by reaction with only the material of the sacrificial layer 120 during the ashing process.

Moreover, in the embodiment, the sacrificial layer 120 is removed by using the ashing process, so that the mask layer can be removed together in the step of removing the sacrificial layer 120 through the release hole 200 by using the ashing process, which is not only beneficial to simplifying the process steps and improving the process integration degree and the process compatibility, but also avoids the removal of the mask layer by using the wet photoresist removal process, and prevents the cavity 300 from being exposed in the wet etching environment, thereby being beneficial to reducing the probability of generating etching residues in the cavity 300 and reducing the influence on the cavity 300, and being correspondingly beneficial to improving the performance of the fingerprint identification module.

The cavity 300 is a functional area in the fingerprint identification module, and in the working process of the fingerprint identification module, an alternating voltage with a fixed frequency is applied to the first electrode 31 and the second electrode 33, the piezoelectric layer 32 vibrates to generate ultrasonic waves, the ultrasonic waves are transmitted upwards to reach valleys or ridges of fingers, the sound waves are partially reflected and partially transmitted after encountering the surfaces of the ridges, and the sound waves are almost totally reflected when encountering the valleys because the acoustic impedance of air in the valleys is far higher than that of the ridges. When different acoustic wave energy reflected from the valleys and the ridges is transmitted to the surfaces of the corresponding piezoelectric transducers 130, the corresponding piezoelectric transducers 130 generate different electrical signals (amplitude, frequency, phase, etc.) corresponding to the piezoelectric effect of the piezoelectric layer 32 as detection signals, so as to collect fingerprint information.

Wherein the cavity 300 provides a vibration space for the piezoelectric layer 32 by forming the cavity 300; moreover, the cavity 300 can also contact the piezoelectric transducer 130 with air, so that the ultrasonic wave is reflected at the interface between the cavity 300 and the piezoelectric transducer 130, thereby being beneficial to reducing the interference signal.

In this embodiment, the cavity 300 is enclosed by the piezoelectric transducer side and the piezoelectric transducer top with the substrate 100. The piezoelectric transducer is provided with a piezoelectric functional area on the top.

In this embodiment, the top of the cavity 300 is a piezoelectric functional area, the cavity 300 is in direct contact with the piezoelectric transducer 130, and compared with a scheme that other films (e.g., dielectric layers) are formed between the cavity and the piezoelectric transducer, the piezoelectric transducer 130 formed in the embodiment of the present invention does not need to vibrate the other films between the cavity and the piezoelectric transducer when vibrating, which is beneficial to accurately controlling the vibration frequency of the piezoelectric transducer 130, and further beneficial to improving the performance of the fingerprint identification module.

In this embodiment, the cavity 300 is located between the piezoelectric transducer 130 and the substrate 100, when the fingerprint identification module operates, the finger is located on a side of the piezoelectric transducer 130 opposite to the substrate 100, that is, the finger is farther away from the substrate 100 than the piezoelectric transducer 130, and the cavity 300 is correspondingly located below the top of the piezoelectric transducer, so that even if impurity particles enter the cavity 300 through the release hole 200 in a subsequent process (for example, a passivation layer is formed on the piezoelectric transducer 130 and the release hole 200 is sealed), because the piezoelectric functional region is located on the top of the cavity 300 when the fingerprint identification module operates, the probability of the impurity particles contacting the piezoelectric functional region is low, which is beneficial to reducing the influence on the operating performance of the piezoelectric transducer 130, and is correspondingly beneficial to improving the reliability and production yield of the fingerprint identification module.

The gas used in the ashing process includes oxygen. In this embodiment, an ashing process is performed using oxygen. The oxygen can react with the amorphous carbon to form carbon dioxide gas, the process cost is low, the side effect is small, and the influence on the piezoelectric transducer 130 is further reduced, and the probability of generating reaction byproduct residues or sacrificial layer 120 residues in the cavity 300 is reduced.

In this embodiment, the sidewalls and the top wall of the cavity 300 expose the first electrode 31.

In this embodiment, after the cavity 300 is formed, the method for forming the fingerprint identification module further includes: a passivation layer 140 is formed on the piezoelectric transducer 130, the passivation layer 140 sealing the release hole 200.

The passivation layer 140 is used for sealing the release hole 200, correspondingly seals the cavity 300, and the passivation layer 140 is also used for protecting the piezoelectric transducer 130, so that the influence of external impurities, ionic charges, water vapor and the like on the piezoelectric transducer 130 is favorably reduced, and the performance and the reliability of the fingerprint identification module are favorably improved.

The passivation layer 140 may be silicon oxide, silicon nitride, silicon carbonitride, silicon oxycarbonitride, silicon oxynitride, boron nitride, boron carbonitride, a low-k dielectric material, or polyimide. In this embodiment, the passivation layer 140 is made of silicon oxide. In this embodiment, a deposition process is used, for example: a chemical vapor deposition process forms the passivation layer 140. In this embodiment, the passivation layer 140 also covers the piezoelectric layer 32 exposed by the second electrode 33.

With reference to fig. 7, after the cavity 300 is formed, the method for forming the fingerprint identification module further includes: a first conductive via 150 penetrating the piezoelectric layer 32 and the first electrode 31 and exposing the first connection terminal 101, and a second conductive via 160 penetrating the second electrode 33 and the piezoelectric layer 32 and exposing the second connection terminal 102 are formed.

The first conductive via 150 is used for providing a spatial position for forming a first conductive plug, and the first conductive via 150 penetrates through the first electrode 31 and exposes the first connection end 101, so that a first conductive plug formed subsequently can be electrically connected with the first electrode 31 and the first connection end 101; the second conductive via 160 is used to provide a spatial location for forming a second conductive plug, and the second conductive via 160 penetrates through the second electrode 33 and exposes the second connection terminal 102, so that a subsequently formed second conductive plug can electrically connect the second electrode 33 and the second connection terminal 102.

In this embodiment, the first conductive via 150 and the second conductive via 160 further penetrate the passivation layer 140 and the etch stop layer 110.

In this embodiment, the step of forming the first conductive via 150 and the second conductive via 160 includes: the piezoelectric layer 32 located above and in the first opening and below the second opening 20 is etched to form a first conductive via 150 penetrating the piezoelectric layer 32 and the first electrode 31 and exposing the first connection terminal 101, and a second conductive via 160 penetrating the second electrode 33 and the piezoelectric layer 32 and exposing the second connection terminal 102, respectively.

In the process of forming the first conductive via 150 and the second conductive via 160, the first electrode 31 and the second electrode 33 do not need to be etched, which is beneficial to reducing the types of film materials to be etched and the process difficulty of forming the first conductive via 150 and the second conductive via 160.

In this embodiment, the first conductive via 150 and the second conductive via 160 are stepped vias, the first conductive via 150 further exposes a portion of the top surface of the first electrode 31, and the second conductive via 160 further exposes a portion of the top surface of the second electrode 33, so that after a first conductive plug located in the first conductive via 150 and a second conductive plug located in the second conductive via 160 are subsequently formed, the first conductive plug can cover a portion of the top surface of the first electrode 31, and the second conductive plug can cover a portion of the top surface of the second electrode 32, compared with the case where the sidewalls of the first conductive via and the second conductive via are steep sidewalls, the first conductive plug has a larger contact area with the first electrode 31 and better contact performance, and the second conductive plug has a larger contact area with the second electrode 33 and better contact performance, thereby facilitating improvement of the performance of the fingerprint identification module.

As an example, in the present embodiment, the step of forming the first conductive via 150 and the second conductive via 160 includes: forming a first sub-via (not labeled) penetrating the passivation layer 140 and respectively located above the first connection terminal 101 and the second connection terminal 102, a sidewall of the first via located above the second connection terminal 102 protruding with respect to a sidewall of the second opening 20; removing the piezoelectric layer 32 in the second opening 20 to expose the sidewall of the second opening 20, so that the second opening 20 is communicated with the first sub-via; forming a second sub through hole (not labeled) which penetrates through the piezoelectric layer 32 and is communicated with the first sub through hole, wherein the side wall of the second sub through hole is retracted relative to the side wall of the first sub through hole, the side wall of the second sub through hole positioned above the first connecting end 101 is protruded relative to the side wall of the first opening, and the side wall of the second sub through hole positioned above the second connecting end 102 is retracted relative to the side wall of the second opening 20; removing the piezoelectric layer 32 in the first opening to expose the sidewall of the first opening and to communicate the first opening with the second sub-via; a third sub-via penetrating through the etching stop layer 110 is formed, the third sub-via located above the first connection end 101 is communicated with the first opening, the sidewall of the third sub-via located above the first connection end 101 is recessed relative to the sidewall of the first opening, the sidewall of the third sub-via located above the second connection end 102 is recessed relative to the sidewall of the second sub-via, and the third sub-via located above the second connection end 102 is communicated with the second sub-via, the first opening, the second sub-via and the third sub-via located above the first connection end 101 are used for forming a first conductive via 150, and the first sub-via, the second opening 20 and the third sub-via located above the second connection end 102 are used for forming a second conductive via 160.

In this embodiment, the first sub-via, the second sub-via, and the third sub-via are formed in different steps, so that the positions and the opening sizes of the first sub-via, the second sub-via, and the third sub-via are precisely controlled, and the first conductive via 150 and the second conductive via 160 are step-like vias.

In this embodiment, the step of forming the first sub-via includes: forming a first pattern layer (not shown) on the passivation layer 140; etching the passivation layer 140 above the first connection end 101 and the second connection end 102 by using the first pattern layer as a mask to form a first sub-through hole; and removing the first graphic layer.

In this embodiment, the step of forming the second sub-via includes: forming a second pattern layer on the passivation layer 140, the second pattern layer also covering a portion of the piezoelectric layer 32 at the bottom of the first sub-via; etching the piezoelectric layer 32 by using the second pattern layer as a mask to form a second sub-via hole; and removing the second graphic layer.

In this embodiment, the step of forming the third sub-via includes: forming a third pattern layer on the passivation layer 140, the third pattern layer exposing the etch stop layer 110 under the second sub-via; etching the etching stop layer 110 by taking the third pattern layer as a mask to form a third sub-through hole; and removing the third graphic layer.

In this embodiment, the material of the first pattern layer, the second pattern layer and the third pattern layer may include a photoresist, and the first pattern layer, the second pattern layer and the third pattern layer may be formed through a photolithography process such as coating, exposure, development and the like. In this embodiment, the etching process for forming the first sub-via, the second sub-via, and the third sub-via includes a dry etching process, for example: anisotropic dry etching process.

The process for removing the first pattern layer, the second pattern layer and the third pattern layer comprises an ashing process.

Referring to fig. 8 in combination, a first conductive plug 170 located in the first conductive via 150 and contacting the first electrode 31 and the first connection terminal 101, and a second conductive plug 180 located in the second conductive via 160 and contacting the second electrode 33 and the second connection terminal 102 are formed.

A first conductive plug 170 for electrically connecting the first electrode 31 and the first connection terminal 101, and a second conductive plug 180 for electrically connecting the second electrode 33 and the second connection terminal 102; thus, the piezoelectric transducer 130 is electrically connected to the signal processing circuitry in the substrate 100 through the first and second

conductive plugs

170 and 180.

The first conductive plug 170 is also used to electrically connect the substrate 100 and the first electrode 31 with an external circuit or other devices; the second conductive plug 180 also serves to electrically connect the substrate 100 and the second electrode 33 with an external circuit or other devices.

In this embodiment, the first conductive plug 170 and the second conductive plug 180 are in a stepped structure, that is, in addition to contacting with the sidewall of the first electrode 31, the first conductive plug 170 also contacts with a portion of the top surface of the first electrode 31, and the contact area between the first conductive plug 170 and the first electrode 31 is larger, and the contact is more stable, so that the contact resistance between the first conductive plug 170 and the first electrode 31 is reduced, and the contact performance between the first conductive plug 170 and the first electrode 31 is improved; besides contacting with the sidewall of the second electrode 33, the second conductive plug 180 also contacts with a portion of the top surface of the second electrode 33, and the second conductive plug 180 also has a larger contact area with the second electrode 33, so that the contact is more stable, which is beneficial to reducing the contact resistance between the second conductive plug 180 and the second electrode 33 and improving the contact performance between the second conductive plug 180 and the second electrode 33.

In the present embodiment, the first conductive plug 170 and the second conductive plug 180 are made of the same material, and include one or more of Cu, Au, Ag, and Al.

In this embodiment, the first electrode 31 is electrically connected to the first connection end 101 through the first conductive plug 170, and the first electrode 31 is electrically connected to an external circuit or other devices through the first conductive plug 170; the second electrode 33 is electrically connected with the second connection end 102 through the second conductive plug 180, and the second electrode 33 is electrically connected with an external circuit or other devices through the second conductive plug 180; compared with the method that the first electrode is electrically connected with the first connecting end or the external circuit through the rewiring structure and the second electrode is electrically connected with the second connecting end or the external circuit through the rewiring structure, the method has the advantages that the size of the device is smaller, and the improvement of the electrical connection performance of the fingerprint identification module is facilitated.

Moreover, in this embodiment, the first electrode 31 is electrically connected to the first connection terminal 101 or the external circuit and other devices by using the first conductive plug 170, and the second electrode 33 is electrically connected to the second connection terminal 102 or the external circuit and other devices by using the second conductive plug 180, which is also beneficial to simplifying the process flow and accordingly reducing the process cost.

In this embodiment, in the step of forming the first conductive plug 170 and the second conductive plug 180, an interconnect structure 190 is further formed on a portion of the passivation layer 140 and connected to the first conductive plug 170 and the second conductive plug 180, respectively. The interconnect structure 190 is prepared for a subsequent packaging process. The interconnect structure 190 is the same material as the first and second

conductive plugs

170 and 180.

In this embodiment, the steps of forming the first conductive plug 170, the second conductive plug 180, and the interconnect structure 190 include: forming a seed layer (not shown) on the bottom surface and the sidewall of the first conductive via 150, the bottom surface and the sidewall of the second conductive via 160, and the passivation layer 140; forming a shielding layer (not shown) on the seed layer and above the passivation layer 140, wherein the shielding layer has a fourth pattern opening located above the first conductive via 150 and exposing a portion of the seed layer on the passivation layer 140 adjacent to the first conductive via 150, and the fourth pattern opening is also located above the second conductive via 160 and exposing a portion of the seed layer on the passivation layer 140 adjacent to the second conductive via 160; filling a conductive layer (not shown) in the first conductive via 150 and the second conductive via 160, wherein the conductive layer further covers the seed layer below the fourth pattern opening; removing the shielding layer; the seed layer exposed by the conductive layer and a part of the thickness of the conductive layer are removed, the conductive layer and the seed layer located in the first conductive via 150 serve as a first conductive plug 170, the conductive layer and the seed layer located in the second conductive via 160 serve as a second conductive plug 180, and the seed layer and the conductive layer located on the passivation layer 140 serve as an interconnection structure 190.

In the present embodiment, an example is given in which the electrical connection between the first connection terminal 101 and the first electrode 31 is realized by forming the first conductive plug 170 penetrating the etch stop layer 110, the first electrode 31, the piezoelectric layer 32, and the passivation layer 140 above the first connection terminal 101. In other embodiments, the first electrode and the first connection end may be electrically connected by other methods, for example: interconnect structures such as rewiring structures.

In the present embodiment, as an example, a second conductive plug 180 is formed to penetrate the etch stop layer 110, the piezoelectric layer 32, the second electrode 33, and the passivation layer 140 above the second connection terminal 102 to achieve electrical connection between the second connection terminal 102 and the second electrode 32. In other embodiments, the second electrode and the second connection terminal may be electrically connected by other methods, such as: interconnect structures such as rewiring structures.

In this embodiment, the first conductive plug 170 and the second conductive plug 180 are formed by a conductive plug (Contact) process, so that the process complexity of the electrical connection process is reduced, the subsequent packaging process is facilitated, and the process compatibility is improved.

Correspondingly, the invention further provides a fingerprint identification module. Continuing to refer to fig. 8, a schematic structural diagram of an embodiment of the fingerprint identification module of the present invention is shown.

Fingerprint identification module includes: a substrate 100 having a signal processing circuit; a plurality of piezoelectric transducers 130 discrete on the substrate 100, including piezoelectric transducer side portions (not labeled) arranged perpendicular to the substrate 100 and piezoelectric transducer top portions (not labeled) parallel to the substrate 100 and connected to top ends of the piezoelectric transducer side portions, the piezoelectric transducer side portions and the piezoelectric transducer top portions enclosing a cavity 300 with the substrate 100, the piezoelectric transducers 130 including a first electrode 31, a piezoelectric layer 32 on the first electrode 31, and a second electrode 33 on the piezoelectric layer 32, the piezoelectric layer 32 for generating vibration according to signals provided by the signal processing circuit to form ultrasonic waves for fingerprint identification; and a release hole 200 penetrating the top of the piezoelectric transducer and communicating with the cavity 300.

The top of the cavity 300 is a piezoelectric functional area, that is, the cavity 300 is in direct contact with the piezoelectric transducer 130, and compared with a scheme that other films (e.g., dielectric layers) are formed between the cavity and the piezoelectric transducer, the embodiment of the present invention does not require that other films between the cavity and the piezoelectric transducer vibrate together when the piezoelectric transducer 130 vibrates, which is beneficial to accurately controlling the vibration frequency of the piezoelectric transducer 130, and is further beneficial to improving the performance of the fingerprint identification module.

Moreover, cavity 300 is located between piezoelectric transducer top and substrate 100, at fingerprint identification module during operation, the finger is located piezoelectric transducer 130 one side of substrate 100 dorsad, that is to say, compare with the piezoelectric transducer top, the finger is farther away from substrate 100, cavity 300 is corresponding to be located the below at piezoelectric transducer top, even there are impurity particle to get into cavity 300 through release hole 200, because at fingerprint identification module during operation, the piezoelectricity functional area is located the top of cavity 300, the probability that impurity particle and piezoelectricity functional area contacted is low, be favorable to reducing the influence to piezoelectric transducer 130's working property, be favorable to improving fingerprint identification module's reliability and production yield correspondingly.

In addition, the cavity 300 is formed by surrounding the side part and the top part of the piezoelectric transducer with the substrate 100, and compared with the scheme of forming the cavity by bonding, the cavity 300 is directly formed on the substrate 100 in the embodiment of the present invention, and an additional supporting base is not required to be consumed, which is beneficial to reducing the process cost and realizing the mass production of the fingerprint identification module.

In addition, in the embodiment of the present invention, the signal processing circuit is integrated with the piezoelectric transducer 130, and the piezoelectric layer 32 directly generates vibration according to the signal provided by the signal processing circuit to form ultrasonic waves, which is beneficial to reducing signal connection lines, correspondingly beneficial to reducing the manufacturing process flow, and improving the electrical performance of the device.

The substrate 100 and the piezoelectric transducer 130 form a fingerprint recognition module. The signal processing circuit is connected with the piezoelectric transducer 130 and used for driving the piezoelectric transducer 130 to generate vibration to form ultrasonic waves and processing detection signals generated by the piezoelectric transducer 130 in the working process of the fingerprint identification module.

In this embodiment, the substrate 100 further includes a first connection terminal 101 and a second connection terminal 102 electrically connected to the signal processing circuit. The first connection terminal 101 and the second connection terminal 102 are used to electrically connect the signal processing circuit in the substrate 100 and the piezoelectric transducer 130 or other devices.

Specifically, top surfaces of the first connection terminal 101 and the second connection terminal 102 are exposed to the substrate 100.

In this embodiment, the fingerprint identification module still includes: etch stop layers 110 between the piezoelectric transducer sides and the substrate 100, and between the cavity 300 and the substrate 100.

The etch stop layer 110 serves to protect the substrate 100. The material of the etch stop layer 110 is a dielectric material, and the etch stop layer 110 is also used to electrically isolate the first electrode 31 of the piezoelectric transducer 130 from the substrate 100.

The material of the etch stop layer 110 includes one or more of silicon oxide, silicon nitride, and silicon oxynitride.

Piezoelectric transducer 130 is the identification element in the fingerprint identification module. When the fingerprint identification module is in operation, the signal processing circuit in the substrate 100 applies an alternating voltage to the first electrode 31 and the second electrode 33 of the piezoelectric transducer 130, so that the piezoelectric layer 32 is vibrated to generate ultrasonic waves by utilizing the inverse piezoelectric effect of the piezoelectric layer 32; vibration is transmitted upwards, i.e. ultrasonic waves are transmitted upwards, the ultrasonic waves pass through different media layers (screens, glass, etc.) to the valleys or ridges of the fingers, because the ultrasonic waves reach different material surfaces to different degrees of absorption, penetration and reflection, the ultrasonic waves encounter the surface of the ridge and are partially reflected and partially transmitted, and because the acoustic impedance of the air in the valley is much higher than that of the ridge, the ultrasonic waves encounter the valleys and are almost totally reflected, and when the different acoustic wave energies reflected from the valleys and ridges are transmitted to the corresponding piezoelectric transducer 130 surface, according to the piezoelectric effect of the piezoelectric layer 32, the corresponding piezoelectric transducers 130 will generate different electrical signals (amplitude, frequency, phase, etc.) as detection signals, so that the piezoelectric transducers 130 can identify the positions of the ridges and valleys of the fingerprint, and causes the signal processing circuit to identify and process the detection signals generated by the piezoelectric transducer 130.

In this embodiment, the piezoelectric transducers 130 correspond to the cavities 300 one to one.

The first electrode 31 serves as the bottom electrode in the piezoelectric transducer 130. In this embodiment, the material of the first electrode 31 is Mo.

The piezoelectric layer 32 is used to generate vibrations in accordance with signals provided by the signal processing circuitry to form ultrasonic waves for fingerprint identification. In this embodiment, the piezoelectric layer 32 is made of aluminum nitride.

The second electrode 33 is used as the top electrode in the piezoelectric transducer 130. When the fingerprint identification module works, an alternating current signal is applied to the first electrode 31 and the second electrode 33 through the signal processing circuit, so that voltage is generated at two ends of the piezoelectric layer 32, and the piezoelectric layer 32 vibrates. In this embodiment, the material of the second electrode 33 is Mo.

The cavity 300 is a functional area in the fingerprint identification module, and in the working process of the fingerprint identification module, an alternating voltage with fixed frequency is applied to the first electrode 31 and the second electrode 33, the piezoelectric layer 32 can vibrate to generate ultrasonic waves, the ultrasonic waves are transmitted upwards to reach valleys or ridges of fingers, the sound waves are partially reflected and partially transmitted after encountering the surfaces of the ridges, and the sound waves are almost totally reflected when encountering the valleys because the acoustic impedance of air in the valleys is far higher than that of the ridges. When the ultrasonic waves reflected from the valleys and the ridges are transmitted to the piezoelectric transducers 130, the corresponding piezoelectric transducers 130 generate different electrical signals (amplitude, frequency, phase, etc.) to be used as detection signals according to the piezoelectric effect of the piezoelectric layer 32, so as to realize the collection of fingerprint information.

Wherein the cavity 300 is used to provide a vibration space for the piezoelectric layer 32; moreover, the cavity 300 can also contact the piezoelectric transducer 130 with air, so that the ultrasonic wave is reflected at the interface between the cavity 300 and the piezoelectric transducer 130, thereby being beneficial to reducing the interference signal.

In this embodiment, the first connection end 101 and the second connection end 102 are located at the periphery of the cavity 300, the first electrode 31 is exposed from the sidewall and the top wall of the cavity 300, the first electrode 31 further extends and covers the first connection end 101, and the second connection end 102 is exposed from the first electrode 31; the piezoelectric layer 32 also covers the substrate 100 between the cavities 300 and the first electrode 31 on the first connection terminal 101; the second electrode 33 also extends to cover the piezoelectric layer 32 above the second connection end 102 and expose the piezoelectric layer 32 above the first connection end 101; fingerprint identification module still includes: a first conductive plug 170 penetrating the piezoelectric layer 32 and the first electrode 31 and contacting the first connection terminal 101; and a second conductive plug 180 penetrating the second electrode 33 and the piezoelectric layer 32 and contacting the second connection terminal 102.

The first electrode 31 further extends and covers the first connection end 101, so as to provide a foundation for forming the first conductive plug 170 electrically connecting the first electrode 31 and the first connection end 101, which is beneficial to reducing the difficulty in forming the first conductive plug 170.

The first electrode 31 also exposes the second connection terminal 102, so as to prevent the first electrode 31 from being shorted with the second conductive plug 180, and reduce the influence of the first electrode 31 on the formation of the second conductive plug 180, and in this embodiment, an insulating layer for electrically isolating the first electrode 31 from the second conductive plug 180 is not required.

In this embodiment, the piezoelectric layer 32 on the substrate 100 between the cavities 300 also serves as a support for forming other film layers.

The second electrode 33 also extends to cover the piezoelectric layer 32 above the second connection end 102, so as to provide a basis for forming a second conductive plug 180 electrically connecting the second electrode 33 and the second connection end 102, which is beneficial to reducing the difficulty in forming the second conductive plug 180. The second electrode 33 also exposes the piezoelectric layer 32 above the first connection end 102, which is beneficial to preventing the second electrode 33 from being shorted with the first conductive plug 170, and is beneficial to reducing the influence of the second electrode 33 on the formation of the first conductive plug 170, and in this embodiment, an insulating layer for electrically isolating the second electrode 33 from the first conductive plug 170 does not need to be provided.

It should be noted that, when the fingerprint identification module is in operation, the portion of the piezoelectric transducer top having the three-layer laminated structure of the first electrode 31, the piezoelectric layer 32 and the second electrode 33 serves as a functional layer for effective vibration, and accordingly, the area corresponding to the functional layer for effective vibration serves as an active area, and the corresponding pair of areas of the portion of the piezoelectric transducer top not having the three-layer laminated structure of the first electrode 31, the piezoelectric layer 32 and the second electrode 33 serves as an inactive area. Therefore, the piezoelectric transducer located in the active area has a three-layer stacked structure of the first electrode 31, the piezoelectric layer 32 and the second electrode 33 on top, and the piezoelectric transducer located in the inactive area may not have a three-layer stacked structure of the first electrode 31, the piezoelectric layer 32 and the second electrode 33 on top, and only one or more of the first electrode 31, the piezoelectric layer 32 and the second electrode 33 need be located on the top surface of the cavity 300.

In this embodiment, the top surface and the sidewall of the cavity 300 are used to expose the first electrode 31, and the first electrode 31 further extends and covers the first connection end 101 as an example. However, the embodiment of the present invention does not limit whether the piezoelectric transducer has a three-layer laminated structure of the first electrode, the piezoelectric layer and the second electrode in the side portion, and the side portion of the piezoelectric transducer only needs to have one or more of the first electrode, the piezoelectric layer and the second electrode, so that the top portion of the piezoelectric transducer, the top portion of the piezoelectric transducer and the substrate enclose a cavity.

conductive plugs

170, 180.

In this embodiment, the first conductive plug 170 and the second conductive plug 180 are in a stepped structure, that is, in addition to contacting with the sidewall of the first electrode 31, the first conductive plug 170 also contacts with a portion of the top surface of the first electrode 31, and the contact area between the first conductive plug 170 and the first electrode 31 is larger, so that the contact resistance between the first conductive plug 170 and the first electrode 31 is reduced, and the contact performance between the first conductive plug 170 and the first electrode 31 is improved; in addition to contacting the sidewall of the second electrode 33, the second conductive plug 180 also contacts a portion of the top surface of the second electrode 33, and the contact area between the second conductive plug 180 and the second electrode 33 is larger, which is beneficial to reducing the contact resistance between the second conductive plug 180 and the second electrode 33 and improving the contact performance between the second conductive plug 180 and the second electrode 33.

In the present embodiment, the material of the first and second

conductive plugs

170 and 180 includes one or more of Cu, Au, Ag, and Al.

The release hole 200 penetrates the top of the piezoelectric transducer and communicates with the cavity 300. The release holes 200 are used to release the sacrificial layer, thereby forming the cavities 300. In this embodiment, the number of the release holes 200 is plural, thereby improving the efficiency of removing the sacrificial layer through the release holes 200 to form the cavity 300.

As an example, the release hole 200 penetrates the first electrode 31, the piezoelectric layer 32, and the second electrode 33 and communicates with the cavity 300. In other embodiments, the release hole may further penetrate through one or two of the first electrode, the piezoelectric layer and the second electrode and be communicated with the cavity, a portion of the piezoelectric transducer top, which does not have the three-layer laminated structure of the first electrode, the piezoelectric layer and the second electrode, is located in the inactive area, that is, the release hole penetrates through the top of the piezoelectric transducer located in the inactive area, the release hole does not penetrate through the top of the piezoelectric transducer located in the active area, thereby etching is not performed on the top of the piezoelectric transducer located in the active area in the process of forming the release hole, which is beneficial to reducing the influence on the top of the piezoelectric transducer located in the active area, thereby being beneficial to improving the accuracy of fingerprint identification, and correspondingly being beneficial to improving the performance of the.

Fingerprint identification module still includes: a passivation layer 140 on the piezoelectric transducer 130, the passivation layer 140 sealing the release hole 200. The passivation layer 140 is used for sealing the release hole 200, correspondingly sealing the cavity 300, and the passivation layer 140 also protects the piezoelectric transducer 130, so that the influence of external impurities, ionic charges, water vapor and the like on the piezoelectric transducer 130 can be reduced, and the fingerprint identification performance and stability can be improved.

In this embodiment, the passivation layer 140 is made of silicon oxide.

In this embodiment, the passivation layer 140 also covers the piezoelectric layer 32 exposed by the second electrode 33.

In this embodiment, the first conductive plug 170 further penetrates through the passivation layer 140 located above the first connection end 101, and the second conductive plug 180 further penetrates through the passivation layer 140 located above the second connection end 102.

Fingerprint identification module still includes: and an interconnection structure 190 on a portion of the passivation layer 140 and connected to the first conductive plug 170 and the second conductive plug 180, respectively. The interconnect structure 190 is prepared for a subsequent packaging process. In this embodiment, the interconnect structure 190 connected to the first conductive plug 170 and the first conductive plug 170 are of an integral type structure, and the interconnect structure 190 connected to the second conductive plug 180 and the second conductive plug 180 are of an integral type structure. The interconnect structure 190 is the same material as the first conductive plug 170.

In the present embodiment, an example is given in which the electrical connection between the first connection terminal 101 and the first electrode 31 is realized by providing the first conductive plug 170 penetrating the etch stop layer 110, the first electrode 31, the piezoelectric layer 32, and the passivation layer 140 above the first connection terminal 101. In other embodiments, the first electrode and the first connection end may be electrically connected by other methods, for example: interconnect structures such as rewiring structures.

In the present embodiment, an example is given in which the electrical connection between the second connection terminal 102 and the second electrode 32 is realized by providing the second conductive plug 180 penetrating the etch stop layer 110, the piezoelectric layer 32, the second electrode 33, and the passivation layer 140 above the second connection terminal 102. In other embodiments, the second electrode and the second connection terminal may be electrically connected by other methods, for example: interconnect structures such as rewiring structures.

The fingerprint identification module can adopt the formation method of aforementioned embodiment fingerprint identification module to form, also can adopt the formation method of other fingerprint identification modules to form. In this embodiment, for the specific description of the fingerprint identification module, reference may be made to the corresponding description in the foregoing embodiments, and this embodiment is not described herein again.

Accordingly, an embodiment of the present invention further provides an electronic device, including: the embodiment of the invention provides a fingerprint identification module.

Through dispose this embodiment in electronic equipment fingerprint identification module to realize fingerprint identification. The electronic device may be a personal computer, a smart phone, a Personal Digital Assistant (PDA), a media player, a navigation device, a game console, a tablet computer, a wearable device, an access control prevention electronic system, an automobile keyless entry electronic system or an automobile keyless start electronic system, etc.

According to the analysis, in the forming process of the fingerprint identification module, the probability that the sacrificial layer is remained in the cavity is low, the influence of the ashing process for removing the sacrificial layer on the piezoelectric transducer is less, and the performance of the fingerprint identification module (for example, the fingerprint identification accuracy of the fingerprint identification module) is improved, so that the use sensitivity of a user is improved. For a specific description of the fingerprint identification module in the electronic device according to this embodiment, reference may be made to the corresponding description in the foregoing embodiments, and details of this embodiment are not repeated herein.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A method for forming a fingerprint identification module is characterized by comprising the following steps:

providing a substrate having signal processing circuitry;

forming a plurality of discrete sacrificial layers on the substrate;

forming a piezoelectric transducer on the sacrificial layer, wherein the piezoelectric transducer comprises a first electrode, a piezoelectric layer located on the first electrode, and a second electrode located on the piezoelectric layer, and the piezoelectric layer is used for generating vibration according to a signal provided by the signal processing circuit to form ultrasonic waves for fingerprint identification;

forming a release hole on the sacrificial layer to expose the top of the sacrificial layer part;

and removing the sacrificial layer through the release hole by adopting an ashing process to form a cavity.

2. The method of claim 1, wherein the step of forming the piezoelectric transducer covers a top surface and sidewalls of the sacrificial layer.

3. The method as claimed in claim 1, wherein the material of the sacrificial layer comprises amorphous carbon, polyimide, or epoxy.

4. The method of claim 1, wherein the step of forming the sacrificial layer comprises: forming a sacrificial material layer overlying the substrate; and patterning the sacrificial material layer, wherein the residual sacrificial material layer on the substrate is used as the sacrificial layer.

5. The method of claim 4, wherein the sacrificial material layer is patterned using a dry etching process.

6. The method of claim 1, wherein the forming the first electrode, the piezoelectric layer, and the second electrode comprises a physical vapor deposition process.

7. The method as claimed in claim 1, wherein the ashing process uses a gas including oxygen.

8. The method of claim 1, wherein the step of forming the release aperture comprises: forming a mask layer on the piezoelectric transducer, wherein an opening positioned above the sacrificial layer is formed in the mask layer; etching the piezoelectric transducer below the opening by taking the mask layer as a mask to form the release hole;

the forming method of the fingerprint identification module further comprises the following steps: and removing the mask layer in the step of removing the sacrificial layer through the release hole by adopting an ashing process.

9. The method as claimed in claim 1, wherein the step of forming the release hole penetrates the first electrode, the piezoelectric layer, and the second electrode and exposes a portion of the top of the sacrificial layer;

alternatively, the release hole penetrates through one or both of the first electrode, the piezoelectric layer, and the second electrode and exposes a portion of the top of the sacrificial layer.

10. The method of claim 1, wherein prior to forming the sacrificial layer on the substrate, the method further comprises: and forming an etching stop layer on the substrate.

11. The method of claim 1, wherein after forming the cavity, the method further comprises: forming a passivation layer on the piezoelectric transducer, the passivation layer sealing the release hole.

12. The method of claim 1, wherein the step of providing a substrate further comprises a first connection terminal and a second connection terminal electrically connected to the signal processing circuit;

in the step of forming the sacrificial layer, the sacrificial layer exposes the first connection end and the second connection end;

in the step of forming the piezoelectric transducer, the first electrode also covers the side wall of the sacrificial layer and extends to cover the first connecting end, and the first electrode exposes the second connecting end; the piezoelectric layer also covers a first electrode positioned on the first connecting end and a substrate positioned between the sacrificial layers; the second electrode also extends to cover the piezoelectric layer above the second connecting end and expose the piezoelectric layer above the first connecting end;

after the cavity is formed, the forming method of the fingerprint identification module further comprises the following steps: forming a first conductive through hole penetrating the piezoelectric layer and the first electrode and exposing the first connection terminal, and forming a second conductive through hole penetrating the second electrode and the piezoelectric layer and exposing the second connection terminal;

and forming a first conductive plug which is positioned in the first conductive through hole and is contacted with the first electrode and the first connecting end, and a second conductive plug which is positioned in the second conductive through hole and is contacted with the second electrode and the second connecting end.

13. The method of claim 12, wherein in the step of forming the piezoelectric transducer, the first electrode further has a first opening over the first connection end; the piezoelectric layer is also filled in the first opening; the second electrode on the piezoelectric layer further has a second opening over the second connection end and exposing the piezoelectric layer;

the step of forming the first and second conductive vias includes: and etching the piezoelectric layer above the first opening, in the first opening and below the second opening to form a first conductive through hole penetrating through the piezoelectric layer and the first electrode and a second conductive through hole penetrating through the second electrode and the piezoelectric layer respectively.

14. The method of forming a fingerprint identification module of claim 13 wherein the step of forming the piezoelectric transducer comprises: forming a first electrode film conformally covering the substrate, and the top surface and the side wall of the sacrifice layer; patterning the first electrode film, and reserving the first electrode film which is positioned on the top surface and the side wall of the sacrificial layer and extends and covers the first connection end as the first electrode; forming the piezoelectric layer on the first electrode, the piezoelectric layer further covering the substrate between the sacrificial layers; forming a second electrode film on the piezoelectric layer; patterning the second electrode film, and keeping the second electrode film of the piezoelectric layer covering the sacrificial layer and the second connecting end as the second electrode;

wherein, in the step of patterning the first electrode film, the first opening is formed; in the step of patterning the second electrode film, the second opening is formed.

15. The utility model provides a fingerprint identification module which characterized in that includes:

a substrate having a signal processing circuit;

the piezoelectric transducers are divided on the substrate and comprise piezoelectric transducer side parts and piezoelectric transducer top parts, the piezoelectric transducer side parts are arranged perpendicular to the substrate, the piezoelectric transducer top parts are parallel to the substrate and are connected with the top ends of the piezoelectric transducer side parts, the piezoelectric transducer side parts and the piezoelectric transducer top parts and the substrate enclose a cavity, the piezoelectric transducers comprise first electrodes, piezoelectric layers located on the first electrodes and second electrodes located on the piezoelectric layers, and the piezoelectric layers are used for generating vibration according to signals provided by the signal processing circuit to form ultrasonic waves for fingerprint identification;

and the release hole penetrates through the top of the piezoelectric transducer and is communicated with the cavity.

16. The fingerprint identification module of claim 15 wherein said substrate further comprises a first connection terminal and a second connection terminal electrically connected to said signal processing circuitry;

the first connecting end and the second connecting end are positioned on the periphery of the cavity;

the top surface and the side wall of the cavity are exposed out of the first electrode, the first electrode further extends to cover the first connecting end, and the first electrode is exposed out of the second connecting end; the piezoelectric layer also covers the substrate between the cavities and the first electrode on the first connection end; the second electrode also extends to cover the piezoelectric layer above the second connecting end and expose the piezoelectric layer above the first connecting end;

fingerprint identification module still includes: a first conductive plug penetrating the piezoelectric layer and the first electrode and contacting the first connection terminal; and the second conductive plug penetrates through the second electrode and the piezoelectric layer and is in contact with the second connecting end.

17. The fingerprint identification module of claim 15, wherein the fingerprint identification module further comprises: and the etching stop layer is positioned between the side part of the piezoelectric transducer and the substrate and between the cavity and the substrate.

18. The fingerprint identification module of claim 15, wherein the release aperture extends through the first electrode, the piezoelectric layer, and the second electrode and is in communication with the cavity; alternatively, the release hole penetrates one or both of the first electrode, the piezoelectric layer, and the second electrode and communicates with the cavity.

19. The fingerprint identification module of claim 15, wherein the fingerprint identification module further comprises: a passivation layer on the piezoelectric transducer, the passivation layer sealing the release hole.

20. An electronic device, comprising: the fingerprint recognition module of any one of claims 15 to 19.