CN112115758B

CN112115758B - Fingerprint identification module, forming method thereof and electronic equipment

Info

Publication number: CN112115758B
Application number: CN202010266613.5A
Authority: CN
Inventors: 石虎; 刘孟彬; 向阳辉
Original assignee: Ningbo Semiconductor International Corp
Current assignee: Ningbo Semiconductor International Corp
Priority date: 2020-04-07
Filing date: 2020-04-07
Publication date: 2024-03-29
Anticipated expiration: 2040-04-07
Also published as: CN112115758A

Abstract

A fingerprint identification module, a forming method thereof and electronic equipment, 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 signals provided by a signal processing circuit to form ultrasonic waves for fingerprint identification; forming a release hole exposing the top of the sacrificial layer portion; and removing the sacrificial layer through the release hole by adopting an ashing process to form a cavity. According to the embodiment of the invention, the ashing process is adopted to remove the sacrificial layer, release of the sacrificial layer is realized under the gas phase condition, the residue of the sacrificial layer is reduced, the sacrificial layer is easy to remove cleanly, and the influence of the process for removing the sacrificial layer on the piezoelectric transducer is small; in addition, the embodiment of the invention directly forms the cavity on the substrate without additionally consuming a 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 present invention relates to the field of semiconductor manufacturing, and in particular, to a fingerprint identification module, a method for forming the fingerprint identification module, and an electronic device.

Background

The fingerprint identification technology collects fingerprint images of human bodies through the fingerprint imaging module, and then compares the fingerprint images with existing fingerprint imaging information in the fingerprint identification system so as to realize identity identification. Due to the convenience of use and the uniqueness of human fingerprints, fingerprint recognition technology has been largely applied to various fields, such as: security inspection fields such as public security bureau and customs, access control systems for buildings, consumer product fields such as personal computers and mobile phones, and the like.

At present, the ultrasonic fingerprint identification technology has the advantages of oil resistance, water resistance, strong penetrability and the like, has stronger environment adaptability, can be used for more complex environments, and becomes one of the main fingerprint identification technologies. The identification unit used in the ultrasonic fingerprint identification technology is a piezoelectric transducer. The piezoelectric transducer is mainly composed of a bottom electrode, a top electrode and a piezoelectric layer positioned between the bottom electrode and the top electrode, and the piezoelectric layer can vibrate by utilizing the inverse piezoelectric effect of the piezoelectric layer as long as a voltage with fixed frequency is applied to the bottom electrode and the top electrode on the upper surface and the lower surface of the piezoelectric layer, so that ultrasonic waves are generated. Because the ultrasonic wave reaches the different material surfaces and is absorbed, penetrated and reflected to different degrees, the difference of the skin and air or different skin layers on the acoustic wave impedance can be utilized to identify the positions of the ridges and the valleys of the fingerprint. In addition, the ultrasonic fingerprint sensor generally further comprises a cavity corresponding to the piezoelectric transducer, wherein the cavity is used for providing a vibration space for the piezoelectric transducer.

Disclosure of Invention

The invention solves the problem of providing a fingerprint identification module, a forming method thereof and electronic equipment, which are 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, including: providing a substrate with a signal processing circuit; 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 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 the signal processing circuit to form ultrasonic waves for fingerprint identification; forming a release hole exposing a part of the top 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.

Correspondingly, the invention also provides a fingerprint identification module, which comprises: a substrate having a signal processing circuit; the piezoelectric transducers are separated from the substrate and comprise piezoelectric transducer side parts which are perpendicular to the substrate and piezoelectric transducer tops which are parallel to the substrate and connected with the top ends of the piezoelectric transducer side parts, the piezoelectric transducer side parts and the piezoelectric transducer tops enclose a cavity with the substrate, each 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 signals provided by the signal processing circuit to form ultrasonic waves for fingerprint identification; and a release hole penetrates through the top of the piezoelectric transducer and is communicated with the cavity.

Correspondingly, the invention also provides electronic equipment, which comprises: 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, a piezoelectric transducer is formed on the sacrificial layers; then forming a release hole exposing part of the top 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; according to the embodiment of the invention, the material which can be 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 oxygen is adopted for etching by the ashing process, the release of the sacrificial layer is correspondingly realized under the gas phase condition, the residue of the sacrificial layer is reduced, the sacrificial layer is easy to remove cleanly, the etching selection of the material of the sacrificial layer and the piezoelectric transducer by the ashing process is higher, the probability of residue or pollution generated by the process for removing the sacrificial layer is reduced, the influence of the process for removing the sacrificial layer on the piezoelectric transducer is reduced, and the cost of the ashing process is lower; in addition, compared with the scheme of forming the cavity by bonding, the embodiment of the invention directly forms the cavity on the substrate without additionally consuming a 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 lines are reduced, the number of the connecting lines is reduced, the manufacturing process flow is correspondingly reduced, and the electrical performance of the device is improved.

Drawings

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

Detailed Description

As known from the background art, an ultrasonic fingerprint recognition sensor generally further has a cavity corresponding to the piezoelectric transducer.

A method for forming a cavity comprises forming a sacrificial layer, wherein the sacrificial layer is used for occupying space position 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.

In the forming method, a wet etching process is adopted to remove the sacrificial layer; the wet etching process needs to place the whole fingerprint identification module into a cleaning tank with etching solution, which easily causes the etching solution to enter into the cavity and is difficult to be completely removed, thereby influencing the performance of the piezoelectric transducer and the cavity; furthermore, in the above method, silicon oxide or germanium is used as the material of the sacrificial layer, and the etching selectivity of the process for removing the sacrificial layer to the material of the sacrificial layer and the piezoelectric transducer is not high enough, which easily increases the probability of occurrence of sacrificial layer residue.

Another method is to form the cavity by bonding. However, forming the cavity by bonding requires the consumption of a single carrier substrate, which tends to result in excessive costs for forming the fingerprint recognition module.

In order to solve the technical problems, in the method for forming the fingerprint identification module provided by the embodiment of the invention, the material which can be 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 is usually performed by etching with oxygen, the release of the sacrificial layer can be realized correspondingly under the gas phase condition, the residue of the sacrificial layer is reduced, the sacrificial layer is easy to be removed cleanly, the etching selection of the sacrificial layer and the piezoelectric transducer material by the ashing process is higher, the probability of residue or pollution generated by the process for removing the sacrificial layer is reduced, the influence of the process for removing the sacrificial layer on the piezoelectric transducer is reduced, and the cost of the ashing process is lower; in addition, compared with the scheme of forming the cavity by bonding, the embodiment of the invention directly forms the cavity on the substrate without additionally consuming a 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 lines are reduced, the number of the connecting lines is reduced, the manufacturing process flow is correspondingly reduced, and the electrical performance of the device is improved.

In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.

Fig. 1 to 8 are schematic structural diagrams corresponding to each step 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 to provide a process platform for forming the piezoelectric transducer and the cavity, and the substrate 100 also forms a fingerprint recognition module with the piezoelectric transducer. In this embodiment, the substrate 100 is formed based on a CMOS process.

The substrate 100 is formed with a signal processing circuit, which is used for being connected 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 processing 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 make electrical connection between the signal processing circuitry in the substrate 100 and the piezoelectric transducer or other device.

In this embodiment, the number of the first connection terminals 101 and the second connection terminals 102 is plural.

Specifically, the top surfaces of the first connection terminal 101 and the second connection terminal 102 are exposed from the substrate 100, so as to provide 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 terminal 101 and the second connection terminal 102 are pads (pads).

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 cavity formation. A cavity is subsequently formed at the location of the sacrificial layer 120, respectively.

Accordingly, 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. Amorphous carbon, polyimide or epoxy resin can be removed through an ashing process, so that the sacrificial layer 120 can be removed by the ashing process to form a cavity, the material of the sacrificial layer 120 and the piezoelectric transducer is etched by the ashing process in a relatively high selectivity, 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 amorphous carbon material has low cost, and the subsequent ashing process has higher etching selection on the amorphous carbon and the material of the piezoelectric transducer, 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 residues of the sacrificial layer 120 is reduced, the probability of the residues of the reaction byproducts in the cavity is reduced, and the performance of the fingerprint identification module is correspondingly improved. In other embodiments, the material of the sacrificial layer may also be other organic or inorganic materials that can be removed by an ashing process.

In the step of forming the sacrificial layer 120, the sacrificial layer 120 exposes the first connection terminal 101 and the second connection terminal 102, so that after the piezoelectric transducer covering the top surface and the side wall of the sacrificial layer 120 is formed, the first electrode in the piezoelectric transducer can be extended to cover the first connection terminal 101, and the second electrode in the piezoelectric transducer can be extended to cover the piezoelectric layer above the second connection terminal 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 serves 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 the sacrificial layer 120 is formed on the substrate 100, the method for forming the fingerprint recognition 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.

Forming the sacrificial layer 120 includes a deposition process and an etching process performed sequentially, the etching stop layer 110 is used to define a stop position of etching in the process of forming the sacrificial layer 120, thereby reducing damage to the substrate 100, and the etching stop layer 110 is also used to protect the substrate 100; moreover, the material of the etching stop layer 110 is a dielectric material, and the etching 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 etching stop layer 110 is silicon oxide.

In this embodiment, the etch stop layer 110 is formed using 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 a sacrificial layer 120, the piezoelectric transducer 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 being configured to vibrate according to a signal provided from a signal processing circuit to form an ultrasonic wave for fingerprint recognition.

The piezoelectric transducer 130 is an identification unit in the fingerprint identification module. When the fingerprint identification module works, alternating voltage is applied to the first electrode 31 and the second electrode 33 of the piezoelectric transducer 130 through the signal processing circuit in the substrate 100, so that the piezoelectric layer 32 is vibrated to generate ultrasonic waves by utilizing the inverse piezoelectric effect of the piezoelectric layer 32; the vibration is transmitted upwards, that is, the ultrasonic wave is transmitted upwards, the ultrasonic wave passes through different dielectric layers (screen, glass, etc.) to reach the valley or the ridge of the finger, the ultrasonic wave encounters the surface of the ridge due to different absorption, penetration and reflection degrees when reaching the surface of different materials, partial reflection and partial transmission occur, and because the acoustic impedance of the air in the valley is far higher than that of the ridge, the ultrasonic wave almost totally reflects when encountering the valley, and when the different acoustic energy reflected from the valley and the ridge is transmitted to the surface of the corresponding piezoelectric transducer 130, the corresponding piezoelectric transducer can generate different electrical signals (amplitude, frequency, phase, etc.) correspondingly as detection signals according to the piezoelectric effect of the piezoelectric layer 32, so that the piezoelectric transducer 130 recognizes the positions of the ridge and the valley of the fingerprint, and the signal processing circuit recognizes and processes the detection signals generated by the piezoelectric transducer 130.

In this embodiment, the number of the sacrificial layers 120 is plural, the number of the piezoelectric transducers 130 is plural, the piezoelectric transducers 130 are separated on the substrate 100, and the piezoelectric transducers 130 are in one-to-one correspondence with the sacrificial layers 120, so that after cavities are formed at the positions of the sacrificial layers 120, the piezoelectric transducers 130 are in one-to-one correspondence with the cavities.

In the step of forming the piezoelectric transducer 130, the piezoelectric transducer 130 covers the top surface and the side wall of the sacrificial layer 120, that is, before forming the piezoelectric transducer 130, a planarization layer is not required to be formed on the substrate 100, which is advantageous for simplifying the process flow, and the planarization layer is usually required to be sequentially deposited and planarized, so that the planarization process has higher cost, and the planarization process is not required to be formed, which is advantageous for saving the cost, and further is advantageous for realizing the mass production of the fingerprint identification module.

In this embodiment, the portion of the piezoelectric transducer 130 located on the sidewall of the sacrificial layer 120 is used as a piezoelectric transducer side portion, and the piezoelectric transducer side portion 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 a piezoelectric transducer top parallel to the substrate 100 and connected to the top end of the piezoelectric transducer side, and after a cavity is subsequently formed at the location of the sacrificial layer 120, the cavity is surrounded by the piezoelectric transducer side and the piezoelectric transducer top with the substrate 100.

The first electrode 31 is used as a Bottom electrode (Bottom electrode) in 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 a metal, a metal silicide, a metal nitride, a metal oxide, or conductive carbon, and 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 for generating vibration according to a signal provided by the signal processing circuit to form ultrasonic waves for fingerprint recognition. The material of the piezoelectric layer 32 may be a piezoelectric crystal, a piezoelectric ceramic, a piezoelectric polymer, or the like. The piezoelectric crystal can be aluminum nitride, lead zirconate titanate, quartz crystal, lithium gallate, lithium germanate, titanium germanate, iron transistor lithium niobate or lithium tantalate, and the piezoelectric polymer can be polyvinylidene fluoride, vinylidene fluoride-trifluoroethylene copolymer, nylon-11 or vinylidene dicyano-vinyl acetate alternating copolymer, and the like. In this embodiment, the material of the piezoelectric layer 32 is aluminum nitride.

The second electrode 33 is used as a Top electrode (Top electrode) in the piezoelectric transducer 130, i.e., an electrode farther from the substrate 100 in the fingerprint recognition module. When the fingerprint recognition 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 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 the step of forming the piezoelectric transducer 130, the first electrode 31 also covers the sidewall of the sacrificial layer 120 and extends to cover the first connection end 101, and the first electrode 31 exposes the second connection end 102; the piezoelectric layer 32 also covers the first electrode 31 located on the first connection terminal 101, and the substrate 100 located between the sacrificial layers 120; the second electrode 33 also extends over the piezoelectric layer 32 over the second connection terminal 102, and exposes the piezoelectric layer 32 over the first connection terminal 101.

The first electrode 31 is further extended to cover the first connection end 101, so that a first conductive plug penetrating through the piezoelectric layer 32 and the first electrode 31 and contacting the first connection end 101 can be formed subsequently, the first conductive plug can realize electrical connection between the first electrode 31 and the first connection end 101, difficulty in forming the first conductive plug is reduced, the first electrode 31 is exposed out of the second connection end 102, a second conductive plug formed subsequently is prevented from being short-circuited with the first electrode 31, influence of the first electrode 31 on the second conductive plug formed subsequently is reduced, etching of the first electrode 31 is not needed for forming the second conductive plug subsequently, and process difficulty in forming the second conductive plug is reduced; compared with the scheme that the first electrode does not expose the second connecting end, 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 shorted with the first electrode is not needed, so that the process flow is simplified correspondingly, and the process difficulty is reduced.

The second electrode 33 is further extended to cover the piezoelectric layer 32 above the second connection end 102, so that a second conductive plug penetrating through the second electrode 33 and the piezoelectric layer 32 and contacting the second connection end 102 can be formed subsequently, the second conductive plug can realize electric connection between the second electrode 33 and the second connection end 102, difficulty in forming the second conductive plug is reduced, the second electrode 33 is exposed out of the piezoelectric layer 32 above the first connection end 101, short circuit between the subsequently formed first conductive plug and the second electrode 33 is prevented, influence of the second electrode 33 on the subsequently formed first conductive plug is reduced, the subsequently formed first conductive plug does not need to etch the second electrode 33, and process difficulty in forming the first conductive plug is reduced; compared with the piezoelectric layer, the second electrode of which is not exposed above the first connecting end, after the first conductive through hole is formed subsequently, the embodiment of the invention does not need to additionally carry out the step of preventing the first conductive plug from being shorted with the second electrode on the side wall of the second electrode, and is correspondingly beneficial to simplifying the process flow and reducing the process difficulty.

Specifically, in the present embodiment, the first electrode 31 covers the etching stop layer 110 on the first connection terminal 101 and exposes the etching stop layer 110 on the second connection terminal 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) above the first connection terminal 101; the piezoelectric layer 32 is also filled 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 exposing the piezoelectric layer 23.

The first electrode 31 is further provided with the first opening above the first connection end 101, so that in the process of subsequently forming the first conductive through hole penetrating through the piezoelectric layer 32 and the first electrode 31 and exposing the first connection end 101, the first electrode 31 is not required to be etched any more, the type of a film layer required to be etched for forming the first conductive through hole is reduced, and the difficulty of an etching process for forming the first conductive through hole is reduced; by providing the second electrode 33 with the second opening 20 above the second connection end 102, in the subsequent process of forming the second conductive via hole penetrating the second electrode 33 and the piezoelectric layer 32 and exposing the second connection end 102, etching of the second electrode 33 is not required, which is beneficial to reducing the types of film layers to be etched for forming the second conductive via hole, and further is beneficial to reducing the difficulty of the etching process for forming the second conductive via hole.

In this embodiment, the step of forming the piezoelectric transducer 130 includes: forming a first electrode film (not shown) conformally covering the top surface and sidewalls of the substrate 100 and the sacrificial layer 120; patterning the first electrode film, leaving the first electrode film on the top surface and the sidewalls of the sacrificial layer 120 as the first electrode 31; forming a piezoelectric layer 32 on the first electrode 31, the piezoelectric layer 32 also 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 as the second electrode 33, which covers the piezoelectric layer 32 above the sacrificial layer 120 and above the second connection terminal 102.

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

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 for improving process integration and process compatibility.

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

In this embodiment, the piezoelectric layer 32 also covers the substrate 100 between the sacrificial layers 120, and the piezoelectric layer 32 on the substrate 100 also serves 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. Specifically, the physical vapor deposition process may be an ion sputtering process.

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

A cavity is subsequently formed at the location of the sacrificial layer 120. When the fingerprint recognition module is in operation, a portion of the piezoelectric transducer having the three-layer laminated structure of the first electrode 31, the piezoelectric layer 32, and the second electrode 33 on top is used as the functional layer for effective vibration, and accordingly, a region corresponding to the functional layer for effective vibration is used as the effective region, and a region of the piezoelectric transducer having no corresponding pair of the three-layer laminated structure of the first electrode 31, the piezoelectric layer 32, and the second electrode 33 on top is used as the ineffective region.

Therefore, the piezoelectric transducer top in the active region has a three-layer laminated structure of the first electrode 31, the piezoelectric layer 32, and the second electrode 33, and the piezoelectric transducer top in the inactive region may not have a three-layer laminated structure of the first electrode 31, the piezoelectric layer 32, and the second electrode 33, 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 also covers the sidewall of the sacrificial layer 120 and extends to cover the first connection terminal 101 as an example. The invention is not limited to the position relation between the first electrode, the piezoelectric layer, the second electrode and the side wall of the sacrificial layer, and only one or more layers of the first electrode, the piezoelectric layer and the second electrode cover the side wall of the sacrificial layer, so that the piezoelectric transducer and the piezoelectric transducer positioned on the top surface of the sacrificial layer can jointly cover 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 hole 200 is located on the sacrificial layer 120 and exposes the sacrificial layer 120, so that the sacrificial layer 120 can be removed through the release hole 200 later.

In this embodiment, the number of the release holes 200 is plural, thereby improving the efficiency of removing the sacrificial layer 120 through the release holes 200 later.

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 also penetrate one or two of the first electrode, the piezoelectric layer and the second electrode and expose a portion of the top of the sacrificial layer, where a portion of the top of the piezoelectric transducer that 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 the top of the piezoelectric transducer that is located in the inactive area, and the release hole does not penetrate the top of the piezoelectric transducer that is located in the active area, so that the top of the piezoelectric transducer that is located in the active area is not etched in the process of forming the release hole, which is beneficial to reducing the influence on the top of the piezoelectric transducer that is located in the active area, thereby being beneficial to improving the accuracy of fingerprint identification, and correspondingly improving the 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; the piezoelectric transducer 130 below the opening is etched using the mask layer as a mask to form a release hole 200.

The mask layer is used as an etch mask for forming the release holes 200. In this embodiment, the material of the mask layer includes 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 used, for example: an anisotropic dry etching process etches the piezoelectric transducer 130 on the sacrificial layer 120 to form the release holes 200.

After forming the release hole 200, the method for forming the fingerprint identification module further includes: and removing the mask layer. The mask layer is removed to expose the top surface of the piezoelectric transducer 130 in preparation for the subsequent formation of the membrane layer.

Referring to fig. 5, the sacrificial layer 120 is removed through the release hole 200 using an ashing process, forming a cavity 300.

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

According to the embodiment of the invention, the material which can be 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 is usually etched by oxygen, the release of the sacrificial layer 120 can be realized under the gas phase condition correspondingly, the residue of the sacrificial layer 120 is reduced, the sacrificial layer 120 is easy to be removed cleanly, the material of the sacrificial layer 120 and the piezoelectric transducer 130 is etched by the ashing process with higher selection, and the oxygen is adopted for etching, so that the probability of residue or pollution generated by the process for removing the sacrificial layer 120 is reduced, the influence of the process for removing the sacrificial layer 120 on the piezoelectric transducer 130 is reduced, 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 a piece of 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 130, and the piezoelectric layer 32 directly generates vibration according to the signal provided by the signal processing circuit to form ultrasonic waves, so that signal connection lines are reduced, the number of the connection lines is reduced, the manufacturing process flow is reduced correspondingly, and the electrical performance of the device is improved.

In particular, the ashing process uses oxygen as the etching gas, which is much less costly than HF or XeF ₂ Cost of the materials; moreover, the oxygen is selected to be higher, and the material of the sacrificial layer 120 is only reacted during the ashing process, so that other functional layers are not damaged.

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

The cavity 300 is a functional area in the fingerprint recognition module, during the operation of the fingerprint recognition module, an ac voltage with a fixed frequency is applied to the first electrode 31 and the second electrode 33, the piezoelectric layer 32 vibrates to generate an ultrasonic wave, the ultrasonic wave is transmitted upwards to reach the valley or the ridge of the finger, the ultrasonic wave is reflected and transmitted partially after encountering the surface of the ridge, and the acoustic impedance of air in the valley is far higher than that of the ridge, so that the acoustic wave is almost totally reflected when encountering the valley. When different acoustic energy reflected from the valleys and the ridges is transferred to the surface of the corresponding piezoelectric transducer 130, the corresponding piezoelectric transducer 130 generates different electrical signals (amplitude, frequency, phase, etc.) as detection signals according to the piezoelectric effect of the piezoelectric layer 32, so as to collect fingerprint information.

Wherein, by forming the cavity 300, the cavity 300 provides a vibration space for the piezoelectric layer 32; furthermore, the cavity 300 also enables the piezoelectric transducer 130 to be in contact with the air, such that ultrasonic waves are reflected at the interface of the cavity 300 and the piezoelectric transducer 130, thereby facilitating the reduction of interference signals.

In this embodiment, the cavity 300 is defined by the piezoelectric transducer sides and piezoelectric transducer top and the substrate 100. The top of the piezoelectric transducer is a piezoelectric functional area.

In this embodiment, the top of the cavity 300 is a piezoelectric functional area, and the cavity 300 is in direct contact with the piezoelectric transducer 130, and compared with the scheme that other film layers (for example, dielectric layers) are formed between the cavity and the piezoelectric transducer, the piezoelectric transducer 130 formed in the embodiment of the invention does not need to vibrate together with other film layers located 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 is 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 recognition module works, the finger is located on the side of the piezoelectric transducer 130 facing away from 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, even if impurity particles enter the cavity 300 through the release hole 200 in the subsequent process (for example, a passivation layer is formed on the piezoelectric transducer 130, and the release hole 200 is sealed), since the piezoelectric functional area is located at the top of the cavity 300 when the fingerprint recognition module works, the probability that the impurity particles contact with the piezoelectric functional area is low, which is beneficial to reducing the influence on the working performance of the piezoelectric transducer 130, and is correspondingly beneficial to improving the reliability and the production yield of the fingerprint recognition module.

The gas employed 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, which has low process cost and little side effect, and is beneficial to further reducing the influence on the piezoelectric transducer 130 and reducing the probability of generating reaction by-product residues or sacrificial layer 120 residues in the cavity 300.

In this embodiment, the side walls and 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 and correspondingly sealing 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 reduced, and the performance and the reliability of the fingerprint identification module are improved.

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

Referring to fig. 7 in combination, after forming the cavity 300, the method for forming the fingerprint recognition module further includes: a first conductive via 150 is formed through the piezoelectric layer 32 and the first electrode 31 and exposes the first connection terminal 101, and a second conductive via 160 is formed through the second electrode 33 and the piezoelectric layer 32 and exposes the second connection terminal 102.

The first conductive via 150 is configured to provide a space for forming a first conductive plug, and the first conductive via 150 penetrates the first electrode 31 and exposes the first connection terminal 101, so that the subsequently formed first conductive plug can electrically connect the first electrode 31 and the first connection terminal 101; the second conductive via 160 is used to provide a space for forming a second conductive plug, and the second conductive via 160 penetrates the second electrode 33 and exposes the second connection terminal 102, so that the second conductive plug formed later 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 also penetrate the passivation layer 140 and the etching 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 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 reducing the difficulty of the process 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 the first conductive plug located in the first conductive via 150 and the second conductive plug located in the second conductive via 160 are formed subsequently, the first conductive plug can cover a portion of the top surface of the first electrode 31, the second conductive plug can cover a portion of the top surface of the second electrode 32, and compared with the steep side walls of the first conductive via and the second conductive via, the contact area between the first conductive plug and the first electrode 31 is larger, the contact performance is better, and the contact area between the second conductive plug and the second electrode 33 is larger, the contact performance is better, thereby being beneficial to improving the performance of the fingerprint recognition 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 shown) penetrating the passivation layer 140 and respectively located above the first connection terminal 101 and the second connection terminal 102, wherein a sidewall of the first via located above the second connection terminal 102 protrudes with respect to a sidewall of the second opening 20; removing the piezoelectric layer 32 located 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-through hole; forming a second sub-via (not shown) penetrating the piezoelectric layer 32 and communicating with the first sub-via, the sidewall of the second sub-via being recessed with respect to the sidewall of the first sub-via, the sidewall of the second sub-via above the first connection terminal 101 protruding with respect to the sidewall of the first opening, and the sidewall of the second sub-via above the second connection terminal 102 being recessed with respect to the sidewall of the second opening 20; removing the piezoelectric layer 32 in the first opening, exposing the side wall of the first opening and enabling the first opening to be communicated with the second sub-through hole; a third sub-via penetrating the etch stop layer 110 is formed, the third sub-via above the first connection terminal 101 is communicated with the first opening, a sidewall of the third sub-via above the first connection terminal 101 is retracted relative to a sidewall of the first opening, a sidewall of the third sub-via above the second connection terminal 102 is retracted relative to a sidewall of the second sub-via, and the third sub-via above the second connection terminal 102 is communicated with the second sub-via, the first opening, the second sub-via, and the third sub-via above the first connection terminal 101 are used to form the first conductive via 150, and the first sub-via, the second opening 20, and the third sub-via above the second connection terminal 102 are used to form the second conductive via 160.

In this embodiment, the first sub-via hole, the second sub-via hole and the third sub-via hole are formed in different steps, so that the positions and the opening sizes of the first sub-via hole, the second sub-via hole and the third sub-via hole can be controlled accurately, and the first conductive via hole 150 and the second conductive via hole 160 can be formed in a stepped manner.

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 terminal 101 and above the second connection terminal 102 by using the first pattern layer as a mask to form a first sub-via; the first pattern layer is removed.

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 further covering a portion of the piezoelectric layer 32 at the bottom of the first sub-via; etching the piezoelectric layer 32 with the second pattern layer as a mask to form a second sub-via; and removing the second graph 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 using the third pattern layer as a mask to form a third sub-via; and removing the third pattern layer.

In this embodiment, the materials of the first, second and third pattern layers may include photoresist, and the first, second and third pattern layers may be formed by photolithography processes 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: an anisotropic dry etching process.

The process of removing the first, second and third pattern layers includes an ashing process.

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

The first conductive plug 170 is used to make an electrical connection between the first electrode 31 and the first connection terminal 101, and the second conductive plug 180 is used to make an electrical connection between 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 conductive patch 170 and the second conductive patch 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 device; the second conductive plug 180 also serves to electrically connect the substrate 100 and the second electrode 33 with an external circuit or other device.

In this embodiment, the first conductive plug 170 and the second conductive plug 180 are in a step structure, that is, in addition to contacting with the sidewall of the first electrode 31, the first conductive plug 170 contacts with a portion of the top surface of the first electrode 31, so that the contact area between the first conductive plug 170 and the first electrode 31 is larger and the contact is more stable, thereby being beneficial to reducing the contact resistance between the first conductive plug 170 and the first electrode 31 and improving the contact performance between the first conductive plug 170 and the first electrode 31; in addition to contacting the sidewall of the second electrode 33, the second conductive plug 180 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, so that the contact is more stable, thereby being 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 this embodiment, the first conductive plug 170 and the second conductive plug 180 are made of the same material, including one or more of Cu, au, ag, and Al.

In this embodiment, the first electrode 31 is electrically connected to the first connection terminal 101 through the first conductive plug 170, and the first electrode 31 is also 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 electric connection between the first electrode and the first connecting end or the external circuit through the rewiring structure and the electric connection between the second electrode and the second connecting end or the external circuit through the rewiring structure, the device in the embodiment is smaller in size, and the electric connection performance of the fingerprint identification module is improved.

Moreover, in the present embodiment, the electrical connection between the first electrode 31 and the first connection terminal 101 or the external circuit, and other devices is achieved by using the first conductive plug 170, and the electrical connection between the second electrode 33 and the second connection terminal 102 or the external circuit, and other devices is achieved 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 plugs 170 and the second conductive plugs 180, an interconnection structure 190 is further formed on a portion of the passivation layer 140 and connected to the first conductive plugs 170 and the second conductive plugs 180, respectively. Interconnect structure 190 provides for a subsequent packaging process. The interconnect structure 190 is the same material as the first conductive plug 170 and the second conductive plug 180.

In this embodiment, the steps of forming the first conductive plugs 170, the second conductive plugs 180, and the interconnect structure 190 include: forming a seed layer (not shown) on the bottom and sidewall of the first conductive via 150, the bottom and sidewall of the second conductive via 160, and the passivation layer 140; forming a shielding layer (not shown) over the passivation layer 140 on the seed layer, the shielding layer having a fourth pattern opening over the first conductive via 150 exposing a portion of the seed layer on the passivation layer 140 adjacent to the first conductive via 150, the fourth pattern opening also being over the second conductive via 160 exposing a portion of the seed layer on the passivation layer 140 adjacent to the second conductive via 160; filling the first and second conductive vias 150 and 160 with a conductive layer (not shown) that also covers the seed layer under the fourth pattern opening; removing the shielding layer; the exposed seed layer and a portion of the thickness of the conductive layer are removed, the conductive layer and seed layer in the first conductive via 150 serve as a first conductive plug 170, the conductive layer and seed layer in the second conductive via 160 serve as a second conductive plug 180, and the seed layer and conductive layer on the passivation layer 140 serve as an interconnect structure 190.

In the present embodiment, the electrical connection between the first connection terminal 101 and the first electrode 31 is taken as an example 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 over the first connection terminal 101. In other embodiments, the first electrode and the first connection end may be electrically connected by other manners, for example: interconnect structures such as rewiring structures.

In the present embodiment, the second conductive plug 180 penetrating the etching stop layer 110, the piezoelectric layer 32, the second electrode 33 and the passivation layer 140 above the second connection terminal 102 is formed to achieve electrical connection between the second connection terminal 102 and the second electrode 32 as an example. In other embodiments, the second electrode and the second connection end may be electrically connected by other manners, for example: 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, which reduces the process complexity of the electrical connection process, facilitates the subsequent packaging process, and is beneficial to improving the process compatibility.

Correspondingly, the invention further provides a fingerprint identification module. With continued reference to fig. 8, a schematic diagram of a fingerprint recognition module according to an embodiment of the present invention is shown.

The fingerprint identification module includes: a substrate 100 having a signal processing circuit; a plurality of piezoelectric transducers 130 separated from the substrate 100, including a piezoelectric transducer side portion (not shown) disposed perpendicular to the substrate 100, and a piezoelectric transducer top portion (not shown) parallel to the substrate 100 and connected to a top end of the piezoelectric transducer side portion, the piezoelectric transducer side portion and the piezoelectric transducer top portion enclosing a cavity 300 with the substrate 100, the piezoelectric transducer 130 including a first electrode 31, a piezoelectric layer 32 disposed on the first electrode 31, and a second electrode 33 disposed on the piezoelectric layer 32, the piezoelectric layer 32 being configured to vibrate according to a signal provided by the signal processing circuit to form an ultrasonic wave for fingerprint recognition; a release hole 200 extends through the top of the piezoelectric transducer and communicates 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 the scheme that other film layers (for example, dielectric layers) are formed between the cavity and the piezoelectric transducer, the piezoelectric transducer 130 in the embodiment of the invention does not need to vibrate together with other film layers 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 improving the performance of the fingerprint identification module.

In addition, the cavity 300 is located between the top of the piezoelectric transducer and the substrate 100, when the fingerprint recognition module works, the finger is located on one side of the piezoelectric transducer 130 facing away from the substrate 100, that is, the finger is farther away from the substrate 100 than the top of the piezoelectric transducer, the cavity 300 is correspondingly located below the top of the piezoelectric transducer, even if impurity particles enter the cavity 300 through the release hole 200, because the piezoelectric functional area is located at the top of the cavity 300 when the fingerprint recognition module works, the probability that the impurity particles are contacted with the piezoelectric functional area is low, thereby being beneficial to reducing the influence on the working performance of the piezoelectric transducer 130 and correspondingly improving the reliability and the production yield of the fingerprint recognition module.

In addition, the cavity 300 is formed by enclosing the side part of the piezoelectric transducer 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, and a piece of bearing substrate is not required to be additionally consumed, so that the process cost is reduced, and the mass production of the fingerprint identification module is realized.

In addition, in the embodiment of the 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, so that signal connection lines are reduced, the manufacturing process flow is correspondingly reduced, and the electrical performance of the device is improved.

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 is used for driving the piezoelectric transducer 130 to vibrate 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 make electrical connection between the signal processing circuitry in the substrate 100 and the piezoelectric transducer 130 or other device.

Specifically, the 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 further includes: an etch stop layer 110 is located between the piezoelectric transducer side 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 further used to electrically isolate the first electrode 31 in 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.

The piezoelectric transducer 130 is an identification unit 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 by utilizing the inverse piezoelectric effect of the piezoelectric layer 32 to generate ultrasonic waves; the vibration is transmitted upwards, that is, the ultrasonic wave is transmitted upwards, the ultrasonic wave passes through different dielectric layers (screen, glass, etc.) to reach the valley or the ridge of the finger, the ultrasonic wave encounters the surface of the ridge due to different absorption, penetration and reflection degrees when reaching the surface of different materials, partial reflection and partial transmission occur, and because the acoustic impedance of the air in the valley is far higher than that of the ridge, the ultrasonic wave almost totally reflects when encountering the valley, and when the different acoustic energy reflected from the valley and the ridge is transmitted to the surface of the corresponding piezoelectric transducer 130, the corresponding piezoelectric transducer 130 generates different electrical signals (amplitude, frequency, phase, etc.) correspondingly as detection signals according to the piezoelectric effect of the piezoelectric layer 32, so that the piezoelectric transducer 130 recognizes the positions of the ridge and the valley of the fingerprint, and the signal processing circuit recognizes and processes the detection signals generated by the piezoelectric transducer 130.

In this embodiment, the piezoelectric transducers 130 are in one-to-one correspondence with the cavities 300.

The first electrode 31 serves as a 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 for generating vibration according to a signal provided by the signal processing circuit to form ultrasonic waves for fingerprint recognition. In this embodiment, the material of the piezoelectric layer 32 is aluminum nitride.

The second electrode 33 is used as a top electrode in the piezoelectric transducer 130. When the fingerprint recognition 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 recognition module, during the operation of the fingerprint recognition module, an ac voltage with a fixed frequency is applied to the first electrode 31 and the second electrode 33, the piezoelectric layer 32 vibrates to generate an ultrasonic wave, the ultrasonic wave is transmitted upwards to reach the valley or the ridge of the finger, the ultrasonic wave is reflected and transmitted partially after encountering the surface of the ridge, and the acoustic impedance of air in the valley is far higher than that of the ridge, so that the acoustic wave is almost totally reflected when encountering the valley. 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.) as detection signals according to the piezoelectric effect of the piezoelectric layer 32, so as to collect fingerprint information.

Wherein the cavity 300 is used to provide a vibration space for the piezoelectric layer 32; furthermore, the cavity 300 also enables the piezoelectric transducer 130 to be in contact with the air, such that ultrasonic waves are reflected at the interface of the cavity 300 and the piezoelectric transducer 130, thereby facilitating the reduction of interference signals.

In this embodiment, the first connection end 101 and the second connection end 102 are located at the periphery of the cavity 300, the side wall and the top wall of the cavity 300 expose the first electrode 31, and the first electrode 31 extends to cover the first connection end 101, and the first electrode 31 exposes the second connection end 102; the piezoelectric layer 32 also covers the substrate 100 between the cavities 300 and the first electrode 31 on the first connection end 101; the second electrode 33 also extends to cover the piezoelectric layer 32 above the second connection terminal 102 and exposes the piezoelectric layer 32 above the first connection terminal 101; the 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; the second conductive plug 180 penetrates the second electrode 33 and the piezoelectric layer 32 and contacts the second connection terminal 102.

The first electrode 31 further extends to cover 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 end 102, so as to prevent the first electrode 31 from shorting with the second conductive plug 180, reduce the influence of the first electrode 31 on forming the second conductive plug 180, and eliminate the need for providing an insulating layer for electrically isolating the first electrode 31 from the second conductive plug 180.

In this embodiment, the piezoelectric layer 32 on the substrate 100 between the cavities 300 also serves to support the formation of other layers.

The second electrode 33 further extends to cover the piezoelectric layer 32 above the second connection terminal 102, thereby providing a basis for forming the second conductive plug 180 electrically connecting the second electrode 33 and the second connection terminal 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, so that shorting of the second electrode 33 to the first conductive plug 170 is advantageously prevented, the influence of the second electrode 33 on forming the first conductive plug 170 is advantageously reduced, and an insulating layer for electrically isolating the second electrode 33 from the first conductive plug 170 is not required in the present embodiment.

When the fingerprint recognition module is in operation, a portion of the piezoelectric transducer having the three-layer laminated structure of the first electrode 31, the piezoelectric layer 32, and the second electrode 33 on top is used as the functional layer for effective vibration, and accordingly, a region corresponding to the functional layer for effective vibration is used as the effective region, and a region of the piezoelectric transducer having no corresponding pair of the three-layer laminated structure of the first electrode 31, the piezoelectric layer 32, and the second electrode 33 on top is used as the ineffective region. Therefore, the piezoelectric transducer top in the active region has a three-layer laminated structure of the first electrode 31, the piezoelectric layer 32, and the second electrode 33, and the piezoelectric transducer top in the inactive region may not have a three-layer laminated structure of the first electrode 31, the piezoelectric layer 32, and the second electrode 33, only one or more of the first electrode 31, the piezoelectric layer 32, and the second electrode 33 may be located on the top surface of the cavity 300.

In the present embodiment, the top surface and the side wall of the cavity 300 are used to expose the first electrode 31, and the first electrode 31 also extends to cover the first connection end 101 as an example. However, the embodiment of the invention does not limit the three-layer laminated structure of whether the side part of the piezoelectric transducer is provided with the first electrode, the piezoelectric layer and the second electrode, and the side part of the piezoelectric transducer only needs to be provided with one or more of the first electrode, the piezoelectric layer and the second electrode, so that the top part of the piezoelectric transducer, the top part of the piezoelectric transducer and the substrate can form a cavity.

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

In this embodiment, the materials of the first conductive plugs 170 and the second conductive plugs 180 include one or more of Cu, au, ag, and Al.

The release hole 200 extends through 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 cavity 300. In the present 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 also penetrate one or two of the first electrode, the piezoelectric layer and the second electrode and be in communication with the cavity, where a portion of the piezoelectric transducer top that 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 the piezoelectric transducer top located in the inactive area, and the release hole does not penetrate the piezoelectric transducer top located in the active area, so that the piezoelectric transducer top located in the active area is not etched in the process of forming the release hole, which is beneficial to reducing the influence on the piezoelectric transducer top 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.

The fingerprint identification module still includes: and 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, so that the cavity 300 is correspondingly sealed, the passivation layer 140 also plays a role in protecting the piezoelectric transducer 130, and is beneficial to reducing the influence of external impurities, ionic charges, water vapor and the like on the piezoelectric transducer 130, so that the performance and stability of fingerprint identification are 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 the passivation layer 140 above the first connection terminal 101, and the second conductive plug 180 further penetrates the passivation layer 140 above the second connection terminal 102.

The fingerprint identification module still includes: an interconnect structure 190 is located on a portion of passivation layer 140 and is connected to first conductive plugs 170 and to second conductive plugs 180, respectively. Interconnect structure 190 provides for a subsequent packaging process. In this embodiment, the interconnection structure 190 connected to the first conductive plug 170 and the first conductive plug 170 are formed as a single piece, and the interconnection structure 190 connected to the second conductive plug 180 and the second conductive plug 180 are formed as a single piece. The interconnect structure 190 is the same material as the first conductive plug 170.

In the present embodiment, the electrical connection between the first connection terminal 101 and the first electrode 31 is taken as an example 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 manners, for example: interconnect structures such as rewiring structures.

In the present embodiment, the electrical connection between the second connection terminal 102 and the second electrode 32 is taken as an example by disposing 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 end may be electrically connected by other manners, for example: interconnect structures such as rewiring structures.

The fingerprint recognition module can be formed by adopting the forming method of the fingerprint recognition module in the previous embodiment, and can also be formed by adopting other forming methods of the fingerprint recognition module. In this embodiment, for a specific description of the fingerprint identification module, reference may be made to the corresponding description in the foregoing embodiment, which is not repeated herein.

Correspondingly, the embodiment of the invention also provides electronic equipment, which comprises: the embodiment of the invention provides a fingerprint identification module.

The fingerprint identification module set described in the embodiment is configured in the electronic device, so as 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 electronic system, an automobile keyless entry electronic system, an automobile keyless start electronic system, or the like.

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

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.

Claims

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

providing a substrate with a signal processing circuit;

forming a plurality of discrete sacrificial layers on the substrate, wherein the sacrificial layers are formed by adopting a dry etching process; 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, the piezoelectric layer is used for generating vibration according to signals provided by the signal processing circuit, ultrasonic waves for fingerprint identification are formed, and in the step of forming the piezoelectric transducer, the piezoelectric transducer covers the top surface and the side wall of the sacrificial layer;

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

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 sacrificial layer comprises amorphous carbon, polyimide, or epoxy.

3. The method of claim 1, wherein the step of forming the sacrificial layer comprises: forming a sacrificial material layer covering the substrate; patterning the sacrificial material layer, and using the remaining sacrificial material layer on the substrate as the sacrificial layer.

4. A method of forming a fingerprint recognition module according to claim 3, wherein the sacrificial material layer is patterned using a dry etching process.

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

6. The method of claim 1, wherein the gas used in the ashing process comprises oxygen.

7. The method of forming a fingerprint recognition module according to claim 1, wherein the step of forming the release hole includes: forming a mask layer on the piezoelectric transducer, wherein an opening 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 method for forming 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.

8. The method of claim 1, wherein in the step of forming the release hole, 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 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.

9. The method of forming a fingerprint recognition module according to claim 1, wherein before forming a sacrificial layer on the substrate, the method of forming a fingerprint recognition module further comprises: an etch stop layer is formed on the substrate.

10. The method of forming a fingerprint recognition module according to claim 1, wherein after forming the cavity, the method further comprises: a passivation layer is formed on the piezoelectric transducer, the passivation layer sealing the release hole.

11. The method of claim 1, wherein in the step of providing a substrate, the 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 located on the first connection end, and a substrate located between the sacrificial layers; the second electrode also extends to cover the piezoelectric layer above the second connecting end and exposes the piezoelectric layer above the first connecting end;

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

a first conductive plug is formed in the first conductive via and in contact with the first electrode and the first connection terminal, and a second conductive plug is formed in the second conductive via and in contact with the second electrode and the second connection terminal.

12. The method of claim 11, 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 is also provided with a second opening which is positioned above the second connecting end and exposes 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 the first conductive through hole penetrating through the piezoelectric layer and the first electrode and the second conductive through hole penetrating through the second electrode and the piezoelectric layer respectively.

13. The method of claim 12, wherein the step of forming the piezoelectric transducer comprises: forming a first electrode film conformally covering the substrate, the top surface and the side walls of the sacrificial 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 to cover the first connection end as the first electrode; forming the piezoelectric layer on the first electrode, the piezoelectric layer also covering the substrate between the sacrificial layers; forming a second electrode film on the piezoelectric layer; patterning the second electrode film, and reserving the second electrode film of the piezoelectric layer which is covered on 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.

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

a substrate having a signal processing circuit;

the piezoelectric transducers are separated from the substrate and comprise piezoelectric transducer side parts which are perpendicular to the substrate and piezoelectric transducer tops which are parallel to the substrate and connected with the top ends of the piezoelectric transducer side parts, the piezoelectric transducer side parts and the piezoelectric transducer tops enclose a cavity with the substrate, each 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 signals provided by the signal processing circuit to form ultrasonic waves for fingerprint identification;

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

15. The fingerprint recognition module of claim 14, wherein the substrate further comprises a first connection terminal and a second connection terminal electrically connected to the signal processing circuit;

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

the top surface and the side wall of the cavity expose the first electrode, the first electrode also extends to cover the first connecting end, and the first electrode exposes 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 exposes the piezoelectric layer above the first connecting end;

the 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 contacted with the second connecting end.

16. The fingerprint recognition module of claim 14, wherein the fingerprint recognition module further comprises: an etch stop layer is positioned between the piezoelectric transducer side and the substrate, and between the cavity and the substrate.

17. The fingerprint recognition module of claim 14, wherein the release hole extends through the first electrode, the piezoelectric layer, and the second electrode and is in communication with the cavity; alternatively, the release hole extends through one or both of the first electrode, the piezoelectric layer, and the second electrode and is in communication with the cavity.

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

19. An electronic device, comprising: a fingerprint recognition module according to any one of claims 14 to 18.