WO2021203732A1 - 指纹识别模组及其形成方法 - Google Patents

指纹识别模组及其形成方法 Download PDF

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Publication number
WO2021203732A1
WO2021203732A1 PCT/CN2020/137214 CN2020137214W WO2021203732A1 WO 2021203732 A1 WO2021203732 A1 WO 2021203732A1 CN 2020137214 W CN2020137214 W CN 2020137214W WO 2021203732 A1 WO2021203732 A1 WO 2021203732A1
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Prior art keywords
layer
electrode
forming
piezoelectric
substrate
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PCT/CN2020/137214
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English (en)
French (fr)
Inventor
石虎
刘孟彬
向阳辉
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中芯集成电路（宁波）有限公司
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Publication of WO2021203732A1 publication Critical patent/WO2021203732A1/zh

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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
    • G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
    • G06V40/12—Fingerprints or palmprints
    • G06V40/13—Sensors therefor
    • G06V40/1306—Sensors therefor non-optical, e.g. ultrasonic or capacitive sensing

Definitions

  • the invention relates to the field of semiconductors, in particular to a fingerprint identification module and a method for forming the same.
  • Biometric recognition is a technology used to distinguish different biological characteristics, including fingerprint, palmprint, face, DNA, voice and other recognition technologies. Fingerprints refer to the uneven lines on the front skin of the end of a human finger. The lines are arranged regularly to form different patterns. Fingerprint recognition refers to identification by comparing the minutiae feature points of different fingerprints. Because of its lifetime immutability, uniqueness and convenience, the application of fingerprint recognition is becoming more and more widespread.
  • fingerprint sensors In fingerprint recognition, a sensor is used to obtain fingerprint image information.
  • fingerprint sensors can be divided into optical, capacitive, pressure, and ultrasonic sensors.
  • the optical sensor is large in size, relatively expensive, and sensitive to the dry or wet state of fingerprints, and belongs to the first generation of fingerprint recognition technology.
  • Capacitive fingerprint sensor technology uses capacitor arrays to detect fingerprint lines, and belongs to the second generation of fingerprint sensors.
  • a third-generation fingerprint sensor has been developed in which the inverse piezoelectric effect of piezoelectric materials is used to generate ultrasonic waves. When the ultrasonic wave touches the fingerprint, it exhibits different reflectivity and transmittance in the ridges and ridges of the fingerprint.
  • the fingerprint information can be read by scanning the ultrasonic beam signal in a certain area.
  • Ultrasonic waves generated by the ultrasonic fingerprint sensor may be able to penetrate the mobile phone housing made of glass, aluminum, stainless steel, sapphire or plastic for scanning, so that the ultrasonic fingerprint sensor is arranged in the mobile phone housing.
  • This advantage provides flexibility for customers to design a new generation of elegant, innovative and differentiated mobile terminals.
  • the user experience has also been improved. Scanning fingerprints will not be affected by possible contamination on the fingers, such as sweat, hand cream, etc., thereby improving the stability and accuracy of the fingerprint sensor.
  • the ultrasonic fingerprint sensor usually has a cavity corresponding to the piezoelectric transducer, and the cavity is used to provide a vibration space for the piezoelectric transducer.
  • the problem solved by the present invention is to provide a fingerprint identification module and a forming method thereof to improve the performance of the fingerprint identification module.
  • the present invention provides a method for forming a fingerprint recognition module, which includes: providing a substrate with a signal processing circuit; forming a discrete sacrificial layer on the substrate; forming a flat layer, the flat layer covering The sacrificial layer and the substrate exposed by the sacrificial layer; a piezoelectric transducer is formed on the flat layer, the piezoelectric transducer includes a first electrode, and a pressure on the first electrode Electrical layer, and a second electrode located on the piezoelectric layer, the first electrode, the piezoelectric layer, and the second electrode have overlapping areas on the sacrificial layer, and the piezoelectric layer is used to The signal provided by the signal processing circuit generates vibration; after the piezoelectric transducer is formed, a release hole that penetrates the flat layer and exposes the top of the sacrificial layer is formed; an ashing process is used to remove all the components through the release hole.
  • the sacrificial layer forms a
  • the present invention also provides a fingerprint identification module, including: a substrate with a signal processing circuit; a flat layer on the substrate; a plurality of cavities on the bottom of the flat layer; piezoelectric The transducer is located on the flat layer, the piezoelectric transducer includes a first electrode, a piezoelectric layer located on the first electrode, and a second electrode located on the piezoelectric layer, the The first electrode, the piezoelectric layer, and the second electrode have an overlapping area on the cavity, and the piezoelectric layer is used to generate vibration according to the signal provided by the signal processing circuit; a release hole penetrates the flat layer Communicate with the cavity.
  • the technical solution of the present invention has the following advantages: in the method for forming a fingerprint recognition module provided by the embodiment of the present invention, after the sacrificial layer is formed on the substrate, a pressure covering the sacrificial layer is formed.
  • an electric transducer then a release hole is formed through the piezoelectric transducer and exposes the top of the sacrificial layer, and an ashing process is adopted to remove the sacrificial layer through the release hole; the embodiment of the present invention can be selected
  • the material removed by the ashing process is used as the material of the sacrificial layer, so that the sacrificial layer is removed by the ashing process, and the sacrificial layer can be released under the gas phase condition, which is beneficial to reduce the residue of the sacrificial layer and easy to remove the sacrificial layer cleanly ,
  • the process of removing the sacrificial layer has little effect on the piezoelectric transducer; moreover, compared with the solution of forming a cavity by bonding, the embodiment of the present invention does not need to consume an additional carrier substrate, which is beneficial to reduce the process cost , Realize the mass production of fingerprint recognition module.
  • a flat layer covering the sacrificial layer and the substrate is formed.
  • the material of the flat layer is a dielectric material
  • the step of forming the piezoelectric transducer is formed on the flat layer, so that the piezoelectric transducer has a higher flatness, so that the formation quality of the piezoelectric transducer is higher, and the piezoelectric transducer is subsequently removed.
  • the sacrificial layer forms a cavity.
  • the sidewalls and top of the cavity are made of dielectric materials.
  • the structure of the cavity is more stable, so that the cavity can better support the piezoelectric transducer, making the fingerprint recognition model
  • the group has better device life and quality.
  • the signal processing circuit is integrated with the piezoelectric transducer, and the piezoelectric layer directly vibrates to form ultrasonic waves according to the signal provided by the signal processing circuit, so that the signal connection line is short, the connection line is few, the production process flow is reduced, and the electrical performance of the device is improved .
  • 1 to 9 are schematic diagrams of the structure corresponding to each step in an embodiment of the method for forming a fingerprint identification module of the present invention.
  • the ultrasonic fingerprint recognition sensor usually also has a cavity corresponding to the piezoelectric transducer.
  • a method of forming a cavity is to first form a sacrificial layer to occupy a space for forming the cavity.
  • the material of the sacrificial layer includes silicon oxide or germanium; after forming the piezoelectric transducer, form a release hole exposing the sacrificial layer; Then, a wet etching process is used to remove the sacrificial layer through the release hole to form a cavity.
  • a wet etching process is used to remove the sacrificial layer; the wet etching process requires the entire fingerprint recognition module to be placed in a cleaning tank with an etching solution, which easily causes the etching solution to enter the cavity
  • it is difficult to be completely removed which easily affects the performance of the piezoelectric transducer and the cavity
  • silicon oxide or germanium is used as the material of the sacrificial layer in the above method, and the process of removing the sacrificial layer affects the sacrificial layer and pressure.
  • the etching selection ratio of the material of the electrical transducer is not high enough, which easily increases the probability of the residual sacrificial layer, resulting in poor cavity formation quality.
  • Another method is to form a cavity by bonding.
  • forming the cavity by bonding usually requires a piece of carrier substrate, which leads to the high cost of forming the fingerprint recognition module.
  • the present invention provides a method for forming a fingerprint recognition module. After a sacrificial layer is formed on the substrate, a piezoelectric transducer covering the sacrificial layer is formed; The electrical transducer exposes the release hole on the top of the sacrificial layer, and uses an ashing process to remove the sacrificial layer through the release hole; the embodiment of the present invention selects a material that can be removed by the ashing process as the sacrificial layer Therefore, the ashing process is used to remove the sacrificial layer, and the release of the sacrificial layer can be achieved under gas phase conditions, which is conducive to reducing the residue of the sacrificial layer, easy to remove the sacrificial layer, and the process of removing the sacrificial layer is effective for piezoelectric exchange
  • the impact of the energy device is small; moreover, compared with the solution of forming the cavity by bonding, the embodiment of the present invention does not need to
  • a flat layer covering the sacrificial layer and the substrate is formed.
  • the material of the flat layer is a dielectric material
  • the step of forming the piezoelectric transducer the piezoelectric transducer is formed on the flat layer, so that the piezoelectric transducer has a higher flatness, so that the formation quality of the piezoelectric transducer is higher, and the piezoelectric transducer is subsequently removed.
  • the sacrificial layer forms a cavity. The sidewalls and top of the cavity are made of dielectric material.
  • the structure of the cavity is more stable, so that the cavity can better support the piezoelectric transducer, making the fingerprint recognition model
  • the group has better device life and quality.
  • the signal processing circuit is integrated with the piezoelectric transducer, and the piezoelectric layer directly vibrates to form ultrasonic waves according to the signal provided by the signal processing circuit, so that the signal connection line is short, the connection line is few, the production process flow is reduced, and the electrical performance of the device is improved .
  • 1 to 9 are schematic diagrams of the structure corresponding to each step in the first embodiment of the method for forming a fingerprint identification module of the present invention.
  • a substrate 100 having a signal processing circuit 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.
  • the substrate 100 is formed based on a CMOS process.
  • the signal processing circuit is connected to the subsequent piezoelectric transducer for driving the piezoelectric transducer and processing the piezoelectric transducer during the working process of the fingerprint recognition module. Heartbeat.
  • the substrate 100 further includes a first connection terminal 101 and a second connection terminal 102 that are electrically connected to the signal processing circuit.
  • the first connection terminal 101 and the second connection terminal 102 are used to realize electrical connection between the signal processing circuit in the substrate 100 and other devices or piezoelectric transducers.
  • the number of the first connection terminal 101 and the number of the second connection terminal 102 are both multiple.
  • the substrate 100 exposes the first connection terminal 101 and the second connection terminal 102.
  • the first connection terminal 101 and the second connection terminal 102 are pads (Pad).
  • a discrete sacrificial layer 120 is formed on the substrate 100.
  • the sacrificial layer 120 is used to occupy a space for the subsequent formation of the cavity.
  • the shape, position, and size of the sacrificial layer 120 determine the shape, position, and size of the subsequent cavity. Accordingly, the sacrificial layer 120 is formed according to the shape, position, and size of the required cavity.
  • the material of the sacrificial layer 120 includes amorphous carbon, polyimide or epoxy.
  • Amorphous carbon, polyimide or epoxy resin can be removed by an ashing process to form a cavity.
  • the ashing process has relatively high etching options for the material of the sacrificial layer 120 and the piezoelectric transducer, which is beneficial to reduce the removal
  • the process of the sacrificial layer 120 has an impact on the piezoelectric transducer, and the ashing process has low cost and small side effects.
  • the material of the sacrificial layer 120 is amorphous carbon.
  • the cost of amorphous carbon is low, and the subsequent ashing process has relatively high etching options for amorphous carbon and piezoelectric transducer materials.
  • the oxygen-containing gas used in the ashing process can oxidize the amorphous carbon to carbon dioxide, thereby directly Excluding the reaction chamber is beneficial to reduce the risk of residual sacrificial layer 120 and the probability of residual reaction by-products in the cavity, which is correspondingly beneficial to improve the performance of the fingerprint recognition module.
  • the step of forming the sacrificial layer 120 includes: forming a sacrificial material layer (not shown) covering the substrate 100; patterning the sacrificial material layer, and the remaining sacrificial material layer on the substrate 100 serves as the sacrificial layer 120.
  • the process of forming the sacrificial material layer includes a chemical vapor deposition (Chemical Vapor Deposition, CVD) process.
  • CVD Chemical Vapor Deposition
  • a dry etching process is used to pattern the sacrificial material layer.
  • the dry etching process has anisotropic etching characteristics and better control of the etching profile, which is beneficial to make the shape of the sacrificial layer 120 meet the process requirements.
  • the sacrificial layer 120 is located around the first connection terminal 101 and the second connection terminal 102.
  • the sacrificial layer 120 is located on the substrate 100 between the first connection terminal 101 and the second connection terminal 102, or on the substrate 100 on the same side of the first connection terminal 101 and the second connection terminal 102, as shown in FIG.
  • the layer 120 is located on the substrate 100 between the first connection terminal 101 and the second connection terminal 102 as an example, so that the cavity formed subsequently is located on the substrate 100 between the first connection terminal 101 and the second connection terminal 102.
  • the cavity can reflect ultrasonic waves, which is not easy Affected by the first conductive plug and the second conductive plug, the working performance of the fingerprint identification module is improved.
  • the method for forming the fingerprint recognition module further includes: before forming the sacrificial layer 120 on the substrate 100, forming an etch stop layer 110 on the substrate 100, the etch stop layer 110 covering the signal processing circuit, the first connection terminal 101, and the second ⁇ 102 ⁇ Two connection terminal 102.
  • the material of the etch stop layer 110 includes one or more of silicon oxide, silicon nitride, and silicon oxynitride. In this embodiment, the material of the etch stop layer 110 is silicon oxide.
  • the etch stop layer 110 is formed by a deposition process.
  • the deposition process may be a chemical vapor deposition process or an atomic layer deposition process (Atomic layer deposition, ALD) etc.
  • the sacrificial layer 120 is formed on the etch stop layer 110.
  • the formation of the sacrificial layer 120 includes sequential deposition and etching processes.
  • the etching stop layer 110 is used to define the etching stop position during the formation of the sacrificial layer 120, thereby reducing damage to the substrate 100.
  • the etch stop layer 110 is also used to protect the substrate 100.
  • a planarization layer 130 is formed, and the planarization layer 130 covers the sacrificial layer 120 and the substrate 100 exposed by the sacrificial layer 120.
  • a flat layer 130 covering the sacrificial layer 120 and the substrate 100 is formed.
  • the material of the flat layer 130 is a dielectric material.
  • the piezoelectric transducer is formed on the flat layer. 130, so that the piezoelectric transducer has a higher flatness, so that the formation quality of the piezoelectric transducer is higher.
  • the sacrificial layer 120 is subsequently removed to form a cavity.
  • the sidewalls and top of the cavity are made of dielectric materials. As a result, the cavity provides better support for the piezoelectric transducer, and the structure of the cavity is more stable, so that the fingerprint recognition module has better device life and quality.
  • the material of the planarization layer 130 includes one or two of silicon oxide and silicon nitride.
  • the material of the planarization layer 130 includes silicon oxide.
  • Silicon oxide is a low-cost dielectric material commonly used in processes, and has high process compatibility, which is beneficial to reduce the process difficulty and process cost of forming the flat layer 130; in addition, the dielectric constant of silicon oxide is small, and It is beneficial to improve the subsequent electrical isolation of adjacent devices.
  • the step of forming the flat layer 130 covering the sacrificial layer 120 and the substrate 100 includes: forming a flat material layer (not shown in the figure) on the sacrificial layer 120 and the substrate 100 exposed by the sacrificial layer 120; and flattening the flat material layer After processing, a flat layer 130 is formed.
  • a chemical vapor deposition process is used to form a flat material layer covering the sacrificial layer 120 and the substrate 100.
  • a flow chemical vapor deposition process (Flowable Chemical Vapor Deposition, FCVD) to form a flat material layer.
  • FCVD Flowable Chemical Vapor Deposition
  • the flow-type chemical vapor deposition process has a good filling ability, which is beneficial to reduce the probability of defects such as voids in the flat material layer, and is correspondingly beneficial to improve the film formation quality of the flat layer 130.
  • the flat material layer is flattened to form a flat layer 130.
  • the flattening process makes the top surface of the flat layer 130 have a higher flatness, and prepares for the subsequent formation of a flatter piezoelectric transducer.
  • CMP chemical mechanical planarization
  • the chemical mechanical planarization process is a global surface planarization technology, which can accurately and uniformly grind the flat material layer to the required thickness and flatness.
  • the distance from the top surface of the flat layer 130 to the top surface of the sacrificial layer 120 should not be too large or too small. If the distance is too large, the final fingerprint identification module will be too large, resulting in poor sensitivity of the fingerprint identification module and affecting the frequency performance of the device. If the distance is too small, the sacrificial layer 120 is easily damaged during the process of forming the flat layer 130 by the planarization process, and accordingly, the quality of the subsequently formed cavity is poor. If the distance is too small, the sacrificial layer 120 will be removed afterwards.
  • the thickness of the flat layer 130 on the top surface of the formed cavity is relatively thin, which cannot provide a good support for the piezoelectric transducer, resulting in poor structural stability of the cavity, which tends to reduce the device life of the fingerprint recognition module And quality.
  • the distance from the top surface of the flat layer 130 to the top surface of the sacrificial layer 120 is greater than 500 ⁇ and less than 5000 ⁇ .
  • a piezoelectric transducer 140 is formed on the flat layer 130.
  • the piezoelectric transducer 140 includes a first electrode 141, a piezoelectric layer 142 on the first electrode 141, and a second electrode on the piezoelectric layer 142.
  • the two electrodes 143, the first electrode 141, the piezoelectric layer 142, and the second electrode 146 have overlapping areas on the sacrificial layer 120, and the piezoelectric layer 142 is used to generate vibration according to the signal provided by the signal processing circuit.
  • the piezoelectric transducer 140 is an identification unit in a fingerprint identification module.
  • the signal processing circuit in the substrate 100 applies electrical signals to the first electrode 141 and the second electrode 143 of the piezoelectric transducer 140, thereby using the inverse piezoelectric effect of the piezoelectric layer 142 to make
  • the piezoelectric layer 142 vibrates to generate ultrasonic waves; because the ultrasonic waves are absorbed, penetrated, and reflected to different levels when they reach the surface of different materials, the difference in acoustic impedance between the skin and air or different skin layers can be used to make the reflected ultrasonic waves.
  • the piezoelectric layer 142 in the piezoelectric transducer 140 vibrates and deforms, and the piezoelectric effect of the piezoelectric layer 142 is used to generate a detection signal, so that the piezoelectric transducer 140 can identify the location of the ridges and valleys of the fingerprint. And make the signal processing circuit recognize and process the detection signal generated by the piezoelectric transducer 140.
  • the piezoelectric transducer 140 is formed on the sacrificial layer 120, the number of the sacrificial layer 120 is multiple, and the number of the piezoelectric transducer 140 is also multiple, and the multiple piezoelectric transducers 140 is separated on the substrate 100, and the piezoelectric transducer 140 corresponds to the sacrificial layer 120 one-to-one, so that after a cavity is subsequently formed at the position of the sacrificial layer 120, the piezoelectric transducer 140 corresponds to the cavity one-to-one.
  • the first electrode 141 is used as a bottom electrode in the piezoelectric transducer 140, that is, an electrode closer to the substrate 100 in the fingerprint recognition module.
  • the material of the first electrode 141 may be a conductive material such as metal, metal silicide, metal nitride, metal oxide, or conductive carbon.
  • the material of the first electrode 141 may be Mo, Al, Cu, Ag, Au, Ni, Co, TiAl, TiN or TaN, etc. In this embodiment, the material of the first electrode 141 is Mo.
  • the inverse piezoelectric effect of the piezoelectric layer 142 is used to generate ultrasonic waves; at the same time, the positive piezoelectric effect of the piezoelectric layer 142 is also used after the ultrasonic waves hit the ridges or valleys of the fingers and reflect back. , To generate the detection signal, and then the signal processing circuit to process and identify the detection signal.
  • the material of the piezoelectric layer 142 may be piezoelectric crystal, piezoelectric ceramic, or piezoelectric polymer.
  • the piezoelectric crystal can be aluminum nitride, lead zirconium titanate, quartz crystal, lithium gallate, lithium germanate, titanium germanate, iron transistor lithium niobate or lithium tantalate, etc.
  • the piezoelectric polymer can be polypolarized Vinyl fluoride, vinylidene fluoride-trifluoroethylene copolymer, nylon-11 or vinylidene dicyanide-vinyl acetate alternating copolymer, etc.
  • the material of the piezoelectric layer 142 is aluminum nitride.
  • the second electrode 143 is used as a top electrode in the piezoelectric transducer 140, that is, an electrode farther away from the substrate 100 in the fingerprint recognition module.
  • the first electrode 141 and the second electrode 143 are energized, so that a voltage is generated at both ends of the piezoelectric layer 142, so that the piezoelectric layer 142 is deformed.
  • the material of the second electrode 143 may be conductive materials such as metal, metal silicide, metal nitride, metal oxide, or conductive carbon.
  • the material of the second electrode 143 may be Mo, Al, Cu, Ag. , Au, Ni, Co, TiAl, TiN or TaN, etc. In this embodiment, the material of the second electrode 143 is Mo.
  • the steps of forming the piezoelectric transducer 140 include: forming a first electrode film (not shown in the figure) on the substrate 100; patterning the first electrode film, and the remaining first electrode film is used as the first electrode 141; A piezoelectric layer 142 is formed on the substrate 100 where one electrode 141 and the first electrode 141 are exposed; a second electrode film (not shown in the figure) is formed on the piezoelectric layer 142; the second electrode film is patterned, and the remaining second The electrode film serves as the second electrode 143.
  • the piezoelectric transducer 140 is formed on the flat layer 130.
  • the first electrode 141 is formed directly above the first connecting terminal 101 and the second connecting terminal 102 is exposed. Subsequently, a first conductive through hole that penetrates the piezoelectric layer 142 and the first electrode 141 and exposes the first connection terminal 101 is formed, and a first conductive through hole that contacts the first electrode 141 and the first connection terminal 101 is formed in the first conductive through hole. For conductive plugs, the first electrode 141 is formed directly above the first connecting terminal 101 and the second connecting terminal 102 is exposed, so that the first conductive plug to be formed later is only electrically connected to the first connecting terminal 101.
  • the second electrode 143 is formed directly above the second connecting terminal 102 and the first connecting terminal 101 is exposed. Subsequently, a second conductive through hole that penetrates the second electrode 143 and the piezoelectric layer 142 and exposes the second connection terminal 102 is formed, and a second conductive through hole that contacts the second electrode 143 and the second connection terminal 102 is formed in the second conductive through hole. Conductive plugs, the second electrode 143 is formed directly above the second connection terminal 102 and exposes the first connection terminal 101, so that the second conductive plug formed subsequently is only electrically connected to the second connection terminal 102.
  • the process of forming the first electrode film includes a physical vapor deposition (PVD) process.
  • the physical vapor deposition process may be an ion sputtering process.
  • the first electrode film is formed on the flat layer 130.
  • a dry etching process such as an anisotropic dry etching process, is used to pattern the first electrode film to form the first electrode 141.
  • the anisotropic dry etching process has anisotropic etching characteristics, which is beneficial to improve the sidewall topography quality and dimensional accuracy of the first electrode 141.
  • the process of forming the piezoelectric layer 142 includes a physical vapor deposition process.
  • the physical vapor deposition process may be an ion sputtering process.
  • the process of forming the second electrode film includes a physical vapor deposition process.
  • the physical vapor deposition process may be an ion sputtering process.
  • a dry etching process such as an anisotropic dry etching process, is used to pattern the second electrode film to form the second electrode 143.
  • the anisotropic dry etching process has anisotropic etching characteristics, which is beneficial to improve the sidewall topography quality and dimensional accuracy of the second electrode 143.
  • the flat layer 130 is flattened, and the surface of the flat layer 130 is relatively flat, so that the piezoelectric transducer 140 has a high flatness, and the formation quality of the piezoelectric transducer 140 is good.
  • the sacrificial layer 120 is subsequently removed.
  • a cavity is formed.
  • the side walls and top of the cavity are made of dielectric materials, so that the cavity can better support the piezoelectric transducer 140, and the structure of the cavity is more stable, making the fingerprint recognition module better The life and quality of the device.
  • the first electrode 141, the piezoelectric layer 142, and the second electrode 146 have overlapping areas on the sacrificial layer 120. Accordingly, after the sacrificial layer 120 is subsequently removed, a cavity 300 is formed in the flat layer 130, that is, In other words, the first electrode 141, the piezoelectric layer 142, and the second electrode 146 have overlapping areas on the cavity 300.
  • the cavity 300 is a functional area in the fingerprint recognition module.
  • the first An electrode 141 and a second electrode 143 apply an alternating voltage. Under the action of the inverse piezoelectric effect, the piezoelectric layer 142 will vibrate, thereby generating ultrasonic waves.
  • the cavity 300 provides a technological basis for the vibration of the piezoelectric layer 142.
  • the 300 interface can also reflect the generated ultrasonic waves to avoid interference signals.
  • a release hole 200 that penetrates the flat layer and exposes the top portion of the sacrificial layer 120 is formed.
  • the release hole 200 exposes a part of the top of the sacrificial layer 120 so that the sacrificial layer 120 can be removed later through the release hole 200.
  • the number of the release holes 200 is multiple, so as to improve the subsequent removal efficiency of the sacrificial layer 120 through the release holes 200.
  • a dry etching process such as an anisotropic dry etching process, is used to etch the piezoelectric transducer 140 on the sacrificial layer 120 to form the release hole 200.
  • a release mask layer (not shown in the figure) is usually formed on the piezoelectric transducer 140.
  • the release mask layer includes photoresist.
  • the release mask layer is used as a mask and a dry etching process is adopted. , Forming a release hole 200 penetrating the flat layer 130 and exposing a part of the top of the sacrificial layer 120.
  • the release hole 200 in the step of forming the release hole 200 that penetrates the planarization layer 130 and exposes the top portion of the sacrificial layer 120, the release hole 200 also penetrates the first electrode 141, the piezoelectric layer 142 and the second electrode 143. In other embodiments, the release hole also penetrates the first electrode and the piezoelectric layer, or the release hole also penetrates the piezoelectric layer and the second electrode, or the release hole also penetrates the piezoelectric layer.
  • the sacrificial layer 120 is removed through the release hole 200 to form a cavity 300.
  • a cavity 300 is formed at the position of the sacrificial layer 120.
  • the piezoelectric transducer 140 covering the sacrificial layer 120 is formed; then the penetrating piezoelectric transducer 140 is formed and exposed
  • the release hole 200 on the top of the sacrificial layer 120 uses an ashing process to remove the sacrificial layer 120 through the release hole 200; the embodiment of the present invention adopts an ashing process by selecting a material that can be removed by the ashing process as the material of the sacrificial layer 120
  • the removal of the sacrificial layer 120 can correspondingly realize the release of the sacrificial layer 120 under the gas phase condition, which is beneficial to reduce the residue of the sacrificial layer 120, easy to remove the sacrificial layer 120, and the process of removing the sacrificial layer 120 affects the piezoelectric transducer.
  • the embodiment of the present invention has a small impact; moreover, compared with the solution of forming a cavity by bonding, the embodiment of the present invention does not need to consume an additional piece of carrier substrate, which is beneficial to reduce the process cost and realize the mass production of the fingerprint identification module.
  • a flat layer 130 covering the sacrificial layer 120 and the substrate 100 is formed.
  • the material of the flat layer 130 is a dielectric material.
  • the piezoelectric The transducer 140 is formed on the flat layer 130, so that the piezoelectric transducer 140 has a high flatness, so that the formation quality of the piezoelectric transducer 140 is high.
  • the sacrificial layer 120 is subsequently removed to form a cavity 300.
  • the side walls and top of the cavity 300 are made of dielectric materials, and the structure of the cavity 300 is more stable, so that the cavity 300 can better support the piezoelectric transducer 140, so that the fingerprint recognition module has a better device life and quality.
  • the signal processing circuit is integrated with the piezoelectric transducer 140, and the piezoelectric layer 142 directly vibrates to form ultrasonic waves according to the signal provided by the signal processing circuit. In this way, the signal connection line is short, the connection line is few, the production process is reduced, and the device is improved. Electrical performance.
  • the cavity 300 is a functional area in the fingerprint recognition module. During the operation of the fingerprint recognition module, an alternating voltage is applied to the first electrode 141 and the second electrode 143. Under the action of the inverse piezoelectric effect, the piezoelectric layer 142 will vibrate and generate ultrasonic waves. The cavity 300 provides a technological basis for the vibration of the piezoelectric layer 142. The interface of the cavity 300 can also reflect the generated ultrasonic waves to avoid generating interference signals. The ultrasonic waves are transmitted upwards to the valley or ridge of the finger. When the sound wave encounters the surface of the ridge, it is partially reflected and partially transmitted.
  • the piezoelectric transducer 140 is deformed, and voltages of different amplitudes, phases or frequencies will be generated at both ends of the piezoelectric layer 142, thereby realizing fingerprint information. Collection.
  • the sacrificial layer 120 is removed to form a cavity 300.
  • the cavity 300 is surrounded by a flat layer 130 and an etch stop layer 110.
  • the sidewalls and top of the cavity 300 are made of dielectric material, so that the cavity 300 is effective for the piezoelectric transducer 140 plays a better support, and the structure of the cavity 300 is more stable, so that the fingerprint recognition module has better device life and quality.
  • the piezoelectric transducer 140 is located on the top surface of the cavity 300, and the corresponding piezoelectric functional area is located on the top surface of the cavity 300.
  • the cavity 300 is located between the piezoelectric transducer 140 and the substrate 100.
  • the finger is located on the side of the piezoelectric transducer 140 facing away from the substrate 100, that is to say Compared with the piezoelectric transducer 140, the finger is farther away from the substrate 100, and the cavity 300 is correspondingly located below the top of the piezoelectric transducer, even in subsequent processes (for example: forming on the piezoelectric transducer 140
  • the passivation layer seals the release hole 200). Impurity particles enter the cavity 300 through the release hole 200.
  • the piezoelectric functional area is located on the top surface of the cavity 300 when the fingerprint recognition module is working, the impurity particles and the piezoelectric functional area The low probability of contact is beneficial to reducing the impact on the working performance of the piezoelectric transducer 140, and correspondingly beneficial to improving the reliability and production yield of the fingerprint identification module.
  • the gas used in the ashing process may include oxygen.
  • oxygen is used for the ashing process.
  • Oxygen can react with amorphous carbon to form carbon dioxide gas. The process cost is low and the side effects are small, which is beneficial to further reduce the impact on the piezoelectric transducer 140 and reduce the residual reaction by-products or the sacrificial layer 120 in the cavity 300 Probability of residual.
  • the ashing process is used to remove the sacrificial layer 120 through the release hole 200 to form the cavity 300.
  • the ashing process also removes the release mask layer and correspondingly removes the photoresist.
  • the glue removal process is not required, which simplifies the formation process of the fingerprint identification module and reduces the cost.
  • the method of forming the fingerprint recognition module further includes: forming a passivation layer 150 on the piezoelectric transducer 140 after the cavity 300 is formed, and the passivation layer 150 seals the release hole 200.
  • the passivation layer 150 is used to seal the release hole 200 so as to seal the cavity 300.
  • the passivation layer 150 is also used to protect the piezoelectric transducer 140, thereby helping to reduce external impurities, ion charges, water vapor, etc.
  • the influence on the piezoelectric transducer 140 is beneficial to improve the performance and stability of fingerprint recognition.
  • the material of the passivation layer 150 may be silicon oxide, silicon nitride, silicon carbon nitride, silicon carbon oxynitride, silicon oxynitride, boron nitride, boron carbon nitride, low-k dielectric material, or polyimide.
  • the material of the passivation layer 150 is silicon oxide.
  • the step of forming the passivation layer 150 includes: forming a passivation material layer (not shown in the figure) covering the second electrode 143 and the piezoelectric layer 142 exposed by the second electrode 143; and a patterned passivation material layer , The remaining passivation material layer serves as the passivation layer 150.
  • a deposition process such as a chemical vapor deposition process, is used to form the passivation material layer.
  • the method for forming the fingerprint recognition module further includes: forming a first conductive via 160 penetrating the piezoelectric layer 142 and the first electrode 141 and exposing the first connection terminal 101, and forming a penetrating first conductive via 160 The two electrodes 143 and the piezoelectric layer 142 expose the second conductive via 170 of the second connection terminal 102.
  • the first conductive via 160 is used to provide a space for forming the first conductive plug.
  • the first conductive via 160 penetrates the first electrode 141 and exposes the first connection terminal 101, so that the subsequently formed first conductive plug can be electrically connected
  • the first electrode 141 and the first connection terminal 101 have better electrical connection performance, and because the first conductive via 160 does not expose other conductive film layers, it is avoided that other conductive films are formed in the first conductive via 160 to cover other conductive films.
  • the insulating layer of the layer is beneficial to simplify the formation process of the fingerprint recognition module and reduce the cost;
  • the second conductive via 170 is used to provide a space for forming the second conductive plug, and the second conductive via 170 penetrates the second electrode 143 and The second connecting terminal 102 is exposed, so that the subsequently formed second conductive plug can electrically connect the second electrode 143 and the second connecting terminal 102, and the electrical connection performance is more excellent, and because the second conductive via 170 does not expose other conductive
  • the film layer avoids forming an insulating layer covering other conductive film layers in the second conductive via 170, which is beneficial to simplify the formation process of the fingerprint recognition module and reduce the cost.
  • the first conductive via 160 and the second conductive via 170 further penetrate the passivation layer 150, the planarization layer 130, and the etch stop layer 110.
  • the first conductive via 160 and the second conductive via 170 are stepped vias, that is, the first conductive via 160 also exposes part of the top surface of the first electrode 141, and the second conductive via 170 also exposes part of the top surface of the second electrode 143.
  • the first conductive plug located in the first conductive via 160 and the second conductive plug located in the second conductive via 170 are subsequently formed, the first conductive plug The plug can cover part of the top surface of the first electrode 141, the second conductive plug can cover part of the top surface of the second electrode 143, and the sidewalls of the first conductive via and the second conductive via are steep sidewalls.
  • the contact area between the first conductive plug and the first electrode 141 is larger, and the contact performance is better, and the contact area between the second conductive plug and the second electrode 143 is larger, and the contact performance is better, thereby helping to improve fingerprint recognition.
  • the performance of the module reduces energy consumption.
  • a dry etching process such as an anisotropic dry etching process, is used to form the first conductive via 160 and the second conductive via 170.
  • the step of forming the first conductive via 160 includes: forming a first mask layer; etching the passivation layer 150 using the first mask layer as a mask to form the first sub-via 161; After sub-via 161, remove the first mask layer; form a second mask layer; etch the piezoelectric layer 142 using the second mask layer as a mask to form a second sub-via 162; form a second sub-via After 162, remove the second mask layer; form a third mask layer; use the third mask layer as a mask to etch the first electrode 141 and the flat layer 130 to form a third sub-via exposing the first connection terminal 101 163, the first sub-via 161, the second sub-via 162, and the third sub-via 163 serve as the first conductive via 160.
  • the step of forming the second conductive via 170 includes: forming a fourth mask layer; etching the passivation layer 150 using the fourth mask layer as a mask to form the fourth sub via 171; after forming the fourth sub via 171 , Remove the fourth mask layer; form a fifth mask layer; use the fifth mask layer as a mask to etch the second electrode 143 and the piezoelectric layer 142 to form a fifth sub-via 172; form a fifth sub-via After 172, the fifth mask layer is removed; the sixth mask layer is formed; the flat layer 130 is etched using the sixth mask layer as a mask to form the sixth sub-via 173 exposing the second connection terminal 102, and the fourth sub-via
  • the via 171, the fifth sub via 172 and the sixth sub via 173 serve as the second conductive via 170.
  • etching stop layer 110 is also etched through the process of forming the third sub-via 163 and the sixth sub-via 173.
  • the first conductive plug 180 is used to realize the electrical connection between the first electrode 141 and the first connection terminal 101
  • the second conductive plug 190 is used to realize the electrical connection between the second electrode 143 and the second connection terminal 102; Therefore, through the first conductive plug 180 and the second conductive plug 190, the piezoelectric transducer 130 is directly electrically connected to the signal processing circuit in the substrate 100, which is beneficial to make the first conductive plug 180 and the second conductive plug
  • the plug 190 has a smaller size, better electrical connection performance, simple process flow, and low cost.
  • the first connection terminal can be connected to the first electrode
  • the second connection terminal can be connected to the second electrode in other ways.
  • the first conductive plug 180 is also used to connect the substrate 100 and the first electrode 141 to an external circuit or other devices; the second conductive plug 190 is also used to connect the substrate 100 and the second electrode 143 to an external circuit or Other devices are electrically connected.
  • the first conductive plug 180 and the second conductive plug 190 have a stepped structure, that is to say, in addition to contacting the sidewall of the first electrode 141, the first conductive plug 180 is also in contact with the A part of the top surface of an electrode 141 is in contact with each other, and the contact area between the first conductive plug 180 and the first electrode 141 is larger, which is beneficial to reduce the contact resistance between the first conductive plug 180 and the first electrode 141 and improve the first conductive plug.
  • a conductive plug 180 has a larger contact area with the second electrode 143, which is beneficial to reduce the contact resistance between the second conductive plug 190 and the second electrode 143, and increase the contact resistance between the second conductive plug 170 and the second electrode 143. Between the contact performance.
  • the materials of the first conductive plug 180 and the second conductive plug 190 are the same, and the material of the first conductive plug 180 and the second conductive plug 190 includes one of Cu, Au, Ag, and Al. Many kinds.
  • the formation is also formed on the partial passivation layer 150 and connected to the first conductive plug 180 and the second conductive plug 190 respectively. Connected interconnect structure 191.
  • the interconnect structure 191 prepares for the subsequent packaging process.
  • the interconnect structure 191 is made of the same material as the first conductive plug 180 and the second conductive plug 190. Moreover, in the step of forming the first conductive plug 180 and the second conductive plug 190, the interconnect structure 191 is formed, which is beneficial to simplify the formation process of the fingerprint recognition module and reduce the cost.
  • the step of forming the first conductive plug 180, the second conductive plug 190, and the interconnect structure 191 includes: on the bottom surface and sidewalls of the first conductive via 160 and the bottom surface of the second conductive via 170
  • a seed layer (not shown) is formed on the sidewalls and the passivation layer 150;
  • a shielding layer (not shown) is formed above the passivation layer 150 on the seed layer, and a pattern opening is formed in the shielding layer, and the pattern opening is located Above the first conductive via 160 and exposing a part of the seed layer on the passivation layer 150 adjacent to the first conductive via 160, the pattern opening is also located above the second conductive via 170 and exposing the second conductive via 170.
  • the exposed seed layer and the conductive layer of a part of the thickness of the layer, the conductive layer and the seed layer located in the first conductive via 160 are retained as the first conductive plug 180, and the conductive layer and the seed layer located in the second conductive via 170 are retained As the second conductive plug 190, the seed layer and the conductive layer on the passivation layer 150 remain as the interconnect structure 191.
  • the present invention also provides a fingerprint identification module.
  • a fingerprint identification module Continuing to refer to FIG. 9, there is shown a schematic structural diagram of an embodiment of the fingerprint identification module of the present invention.
  • the fingerprint recognition module includes: a substrate 100 with a signal processing circuit; a flat layer 130 on the substrate 100; a plurality of cavities 300 on the bottom of the flat layer 130; a piezoelectric transducer 140 on the flat layer 130
  • the piezoelectric transducer 140 includes a first electrode 141, a piezoelectric layer 142 on the first electrode 141, and a second electrode 143 on the piezoelectric layer 142, the first electrode 141, the piezoelectric layer 142, and the second electrode 143.
  • the two electrodes 143 have an overlapping area on the cavity 300.
  • the piezoelectric layer 142 is used to generate vibration according to the signal provided by the signal processing circuit; the release hole 200 penetrates the flat layer 130 and communicates with the cavity 300.
  • the surface of the flat layer 130 has high flatness, and the piezoelectric transducer 140 is formed on the flat layer 130, so that the piezoelectric transducer 140 has high flatness.
  • the formation quality of the cavity 300 is better, and the cavity 300 is located at the bottom of the flat layer 130.
  • the sidewalls and the top of the cavity 300 are made of dielectric materials.
  • the structure of the cavity 300 is more stable, so that the cavity 300 is effective for the piezoelectric transducer 140 plays a better support, so that the fingerprint recognition module has better device life and quality.
  • the signal processing circuit is integrated with the piezoelectric transducer 140, and the piezoelectric layer 142 directly vibrates to form ultrasonic waves according to the signal provided by the signal processing circuit. In this way, the signal connection line is short, the connection line is few, the production process is reduced, and the device is improved. Electrical performance.
  • the first electrode 141, the piezoelectric layer 142, and the second electrode 143 have overlapping areas on the cavity 300.
  • the cavity 300 is a functional area in the fingerprint recognition module.
  • the piezoelectric layer 142 will vibrate under the action of the inverse piezoelectric effect, thereby generating ultrasonic waves.
  • the cavity 300 provides a technological basis for the vibration of the piezoelectric layer 142.
  • the interface of the cavity 300 can also reflect the generated ultrasonic waves to avoid generating interference signals.
  • the cavity 300 is located between the piezoelectric transducer 140 and the substrate 100.
  • the finger is located on the side of the piezoelectric transducer 140 facing away from the substrate 100, that is to say Compared with the piezoelectric transducer 140, the finger is farther away from the substrate 100, the cavity 300 is correspondingly located below the top of the piezoelectric transducer, and the piezoelectric functional area is located on the top surface of the cavity 300. It works in the fingerprint recognition module. When the finger is in contact with the piezoelectric functional area, it is beneficial to improve the reliability and production yield of the fingerprint recognition module.
  • 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.
  • the substrate 100 is formed based on a CMOS process.
  • the substrate 100 has a signal processing circuit, which is connected to the subsequent piezoelectric transducer, and is used to drive the piezoelectric transducer and process the piezoelectric transducer during the working process of the fingerprint identification module.
  • the heartbeat is used to drive the piezoelectric transducer and process the piezoelectric transducer during the working process of the fingerprint identification module.
  • the substrate 100 further includes a first connection terminal 101 and a second connection terminal 102 that are electrically connected to the signal processing circuit.
  • the first connection terminal 101 and the second connection terminal 102 are used to realize electrical connection between the signal processing circuit in the substrate 100 and other devices or piezoelectric transducers.
  • the number of the first connection terminal 101 and the number of the second connection terminal 102 are both multiple.
  • the substrate 100 exposes the first connection terminal 101 and the second connection terminal 102.
  • the first connection terminal 101 and the second connection terminal 102 are pads (Pad).
  • the fingerprint recognition module further includes an etching stop layer 110 located between the substrate 100 and the cavity 300 and between the substrate 100 and the flat layer 130.
  • the material of the etch stop layer 110 includes one or more of silicon oxide, silicon nitride, and silicon oxynitride. In this embodiment, the material of the etch stop layer 110 is silicon oxide.
  • the cavity 300 is surrounded by the flat layer 130 and the etch stop layer 110, and the sidewalls and top of the cavity 300 are made of dielectric material, so that the cavity 300 provides a better support for the piezoelectric transducer 140 , And the structure of the cavity 300 is more stable, so that the fingerprint recognition module has better device life and quality.
  • the material of the flat layer 130 includes one or two of silicon oxide and silicon nitride.
  • the material of the planarization layer 130 includes silicon oxide.
  • Silicon oxide is a low-cost dielectric material commonly used in processes, and has high process compatibility, which is beneficial to reduce the process difficulty and process cost of forming the flat layer 130; in addition, the dielectric constant of silicon oxide is small, and It is beneficial to improve the subsequent electrical isolation of adjacent devices.
  • the cavity 300 is located in the flat layer 130 around the first connecting end 101 and the second connecting end 102.
  • the cavity 300 is located in the flat layer 130 between the first connecting end 101 and the second connecting end 102, or in the flat layer 130 on the same side of the first connecting end 101 and the second connecting end 102, as shown in FIG. 9
  • the cavity 300 is located in the flat layer 130 between the first connection terminal 101 and the second connection terminal 102 as an example.
  • the first connection terminal 101 is connected to the first conductive plug 180
  • the second connection terminal 102 is connected to the second conductive plug.
  • the 190 connection enables the cavity to reflect ultrasonic waves when the fingerprint recognition module is working, and is not easily affected by the first conductive plug 180 and the second conductive plug 190, and improves the working performance of the fingerprint recognition module.
  • the distance from the top surface of the flat layer 130 to the top surface of the cavity 300 should not be too large or too small. If the distance is too large, the volume of the fingerprint identification module will be too large, resulting in poor sensitivity of the fingerprint identification module and affecting the frequency performance of the device. If the distance is too small, the thickness of the flat layer 130 on the top surface of the cavity is thin, and it is difficult to support the piezoelectric transducer 140 well, and the structural stability of the cavity 300 is poor, which is easy to reduce the fingerprint recognition module. The life and quality of the device. In this embodiment, the distance from the top surface of the flat layer 130 to the top surface of the cavity 300 is greater than 500 ⁇ and less than 5000 ⁇ .
  • the piezoelectric transducer 140 is an identification unit in a fingerprint identification module.
  • the signal processing circuit in the substrate 100 applies electrical signals to the first electrode 141 and the second electrode 143 of the piezoelectric transducer 140, thereby using the inverse piezoelectric effect of the piezoelectric layer 142 to make
  • the piezoelectric layer 142 vibrates to generate ultrasonic waves; because the ultrasonic waves are absorbed, penetrated, and reflected to different levels when they reach the surface of different materials, the difference in acoustic impedance between the skin and air or different skin layers can be used to make the reflected ultrasonic waves.
  • the piezoelectric layer 142 in the piezoelectric transducer 140 vibrates and deforms, and the piezoelectric effect of the piezoelectric layer 142 is used to generate a detection signal, so that the piezoelectric transducer 140 can identify the location of the ridges and valleys of the fingerprint. And make the signal processing circuit recognize and process the detection signal generated by the piezoelectric transducer 140.
  • the first electrode 141 is used as a bottom electrode in the piezoelectric transducer 140, that is, an electrode closer to the substrate 100 in the fingerprint recognition module.
  • the material of the first electrode 141 may be a conductive material such as metal, metal silicide, metal nitride, metal oxide, or conductive carbon.
  • the material of the first electrode 141 may be Mo, Al, Cu, Ag, Au, Ni, Co, TiAl, TiN or TaN, etc. In this embodiment, the material of the first electrode 141 is Mo.
  • the first electrode 141 is located directly above the first connection terminal 101 and exposes the second connection terminal 102.
  • the fingerprint recognition module further includes: a first conductive plug 180 penetrates the piezoelectric layer 142 and the first electrode 141 and is in contact with the first connection terminal 101, and the first conductive plug 180 connects the first connection terminal 101 with the first electrode 141 Electric connection.
  • the first connection terminal can be connected to the first electrode in other ways.
  • the inverse piezoelectric effect of the piezoelectric layer 142 is used to generate ultrasonic waves; at the same time, the positive piezoelectric effect of the piezoelectric layer 142 is also used after the ultrasonic waves hit the ridges or valleys of the fingers and reflect back. , To generate the detection signal, and then the signal processing circuit to process and identify the detection signal.
  • the material of the piezoelectric layer 142 may be piezoelectric crystal, piezoelectric ceramic, or piezoelectric polymer.
  • the piezoelectric crystal can be aluminum nitride, lead zirconium titanate, quartz crystal, lithium gallate, lithium germanate, titanium germanate, iron transistor lithium niobate or lithium tantalate, etc.
  • the piezoelectric polymer can be polypolarized Vinyl fluoride, vinylidene fluoride-trifluoroethylene copolymer, nylon-11 or vinylidene dicyanide-vinyl acetate alternating copolymer, etc.
  • the material of the piezoelectric layer 142 is aluminum nitride.
  • the second electrode 143 is used as a top electrode in the piezoelectric transducer 140, that is, an electrode farther away from the substrate 100 in the fingerprint recognition module.
  • the first electrode 141 and the second electrode 143 are energized, so that a voltage is generated at both ends of the piezoelectric layer 142, so that the piezoelectric layer 142 is deformed.
  • the material of the second electrode 143 may be conductive materials such as metal, metal silicide, metal nitride, metal oxide, or conductive carbon.
  • the material of the second electrode 143 may be Mo, Al, Cu, Ag. , Au, Ni, Co, TiAl, TiN or TaN, etc. In this embodiment, the material of the second electrode 143 is Mo.
  • piezoelectric transducer 140 is located on the flat layer 130.
  • the second electrode 143 is located directly above the second connection terminal 102 and exposes the first connection terminal 101.
  • the fingerprint recognition module further includes: a second conductive plug 190 that penetrates the second electrode 143 and the piezoelectric layer 142 and is in contact with the second connecting terminal 102.
  • the second conductive plug 190 connects the second connecting terminal 102 with the second electrode.
  • 143 is directly electrically connected, so that the second connecting terminal 102 and the second electrode 143 have excellent electrical connection performance, and the structure of the fingerprint recognition module is simple, which is beneficial to make the first conductive plug 180 and the second conductive plug 190 have Smaller size, low cost.
  • the second connection terminal can be connected to the second electrode in other ways.
  • the release hole 200 is a process hole for forming the cavity 300.
  • the release hole 200 further penetrates the first electrode 141, the piezoelectric layer 142 and the second electrode 143.
  • the release hole also penetrates the first electrode and the piezoelectric layer; or, the release hole also penetrates the piezoelectric layer and the second electrode; or, the release hole also penetrates the piezoelectric layer.
  • the release hole 200 penetrates the first electrode 141, the piezoelectric layer 142, and the second electrode 143 at the same time.
  • the release hole may only penetrate the first electrode and the piezoelectric layer to expose the cavity, or only penetrate the piezoelectric layer and the second electrode to expose the cavity, or only penetrate the piezoelectric layer to expose the cavity.
  • the fingerprint recognition module further includes a passivation layer 150 on the piezoelectric transducer 140, and the passivation layer 150 seals the release hole.
  • the passivation layer 150 is used to seal the release hole 200 so as to seal the cavity 300.
  • the passivation layer 150 is also used to protect the piezoelectric transducer 140, thereby helping to reduce external impurities, ion charges, water vapor, etc.
  • the influence on the piezoelectric transducer 140 is beneficial to improve the performance and stability of fingerprint recognition.
  • the material of the passivation layer 150 may be silicon oxide, silicon nitride, silicon carbon nitride, silicon carbon oxynitride, silicon oxynitride, boron nitride, boron carbon nitride, low-k dielectric material, or polyimide.
  • the material of the passivation layer 150 is silicon oxide.
  • the first conductive plug 180 and the second conductive plug 190 have a stepped structure, that is to say, in addition to being in contact with the sidewall of the first electrode 141, the first conductive plug 180 is also connected to a portion of the first electrode 141.
  • the contact area between the first conductive plug 180 and the first electrode 141 is larger, which is beneficial to reduce the contact resistance between the first conductive plug 180 and the first electrode 141, and increase the contact resistance between the first conductive plug 180 and the first electrode 141.
  • the contact area with the second electrode 143 is large, which is beneficial to reduce the contact resistance between the second conductive plug 190 and the second electrode 143 and improve the contact performance between the second conductive plug 170 and the second electrode 143.
  • the materials of the first conductive plug 180 and the second conductive plug 190 are the same, and the material of the first conductive plug 180 and the second conductive plug 190 includes one of Cu, Au, Ag, and Al. Many kinds.
  • the fingerprint recognition module further includes: an interconnection structure 191 located on part of the passivation layer 150 and connected to the first conductive plug 180 and the second conductive plug 190 respectively.
  • the interconnection structure is the same material as the first conductive plug 180 and the second conductive plug 190.
  • etching stop layer 110 is also penetrated during the process of the first conductive plug 180 and the second conductive plug 190.
  • an embodiment of the present invention also provides an electronic device, including: the fingerprint identification module provided by the embodiment of the present invention.
  • the fingerprint identification module described in this embodiment is configured in the electronic device 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 anti-access control electronic system, an automobile keyless entry electronic system Or car keyless start electronic system, etc.
  • PDA personal digital assistant
  • the probability of the sacrificial layer remaining in the cavity is low, and the removal of the sacrificial layer in the ashing process has less impact on the piezoelectric transducer, which is beneficial to Improve the performance of the fingerprint recognition module (for example: fingerprint recognition accuracy of the fingerprint recognition module), thereby improving the user experience.
  • the fingerprint recognition module for example: fingerprint recognition accuracy of the fingerprint recognition module
  • the fingerprint identification module may be formed by the method for forming the fingerprint identification module described in the foregoing embodiment, or may be formed by other methods for forming the fingerprint identification module. In this embodiment, for the specific description of the fingerprint identification module, reference may be made to the corresponding description in the foregoing embodiment, and this embodiment will not be repeated here.

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Abstract

一种指纹识别模组及其形成方法，指纹识别模组的形成方法包括：提供具有信号处理电路的衬底（100）；在衬底（100）上形成分立的牺牲层（120）；形成平坦层（130），平坦层（130）覆盖牺牲层（120）以及牺牲层（120）露出的衬底（100）；在平坦层（130）上形成压电换能器（140），压电换能器（140）包括第一电极（141）、位于第一电极（141）上的压电层（142）、以及位于压电层（142）上的第二电极（143）；形成贯穿平坦层（130）且露出牺牲层（120）部分顶部的释放孔（200）；采用灰化工艺，通过释放孔（200）去除牺牲层（120），形成空腔（300）。采用灰化工艺去除牺牲层（120），相应能够在气相条件下实现对牺牲层（120）的释放，有利于减小牺牲层（120）的残留、易于将牺牲层（120）去除干净，且去除牺牲层（120）的工艺对压电换能器（140）的影响小，有利于降低工艺成本、实现指纹识别模组的量产化。

Description

指纹识别模组及其形成方法 技术领域
本发明涉及半导体领域，尤其涉及一种指纹识别模组及其形成方法。
 背景技术
生物特征识别是用于区分不同生物特征的技术，包括指纹、掌纹、脸部、DNA、声音等识别技术。指纹是指人的手指末端正面皮肤上凹凸不平的纹路，纹路有规律的排列形成不同的纹型。指纹识别指通过比较不同指纹的细节特征点来进行身份鉴定。由于具有终身不变性、唯一性和方便性，指纹识别的应用越来越广泛。
在指纹识别中，采用传感器获取指纹图像信息。根据工作原理的不同，指纹传感器可以分为光学、电容、压力、超声传感器。光学传感器体积较大，价格相对高，并且对于指纹的干燥或者潮湿状态敏感，属于第一代指纹识别技术。电容指纹传感器技术采用电容器阵列检测指纹的纹路，属于第二代指纹传感器。作为进一步的改进，已经开发出第三代指纹传感器，其中利用压电材料的逆压电效应产生超声波。该超声波在接触到指纹时，在指纹的嵴、峪中表现出不同的反射率和透射率。通过扫描一定面积内的超声波束信号即可读取指纹信息。超声波指纹传感器产生的超声波可以能够穿透由玻璃、铝、不锈钢、蓝宝石或者塑料制成的手机外壳进行扫描，从而将超声波指纹传感器设置在手机外壳内。该优点为客户设计新一代优雅、创新、差异化的移动终端提供灵活性。此外，用户的体验也得到提升，扫描指纹能够不受手指上可能存在沾污的影响，例如汗水、护手霜等，从而提高了指纹传感器的稳定性和精确度。
此外，超声波指纹传感器中通常还具有压电换能器相对应的空腔，空腔用于为压电换能器提供振动空间。
 技术问题
本发明解决的问题是提供一种指纹识别模组及其形成方法，提升指纹识别模组的性能。
 技术解决方案
为解决上述问题，本发明提供一种指纹识别模组的形成方法，包括：提供具有信号处理电路的衬底；在所述衬底上形成分立的牺牲层；形成平坦层，所述平坦层覆盖所述牺牲层以及所述牺牲层露出的所述衬底；在所述平坦层上形成压电换能器，所述压电换能器包括第一电极、位于所述第一电极上的压电层、以及位于所述压电层上的第二电极，所述第一电极、所述压电层和所述第二电极在牺牲层上有重叠区域，所述压电层用于根据所述信号处理电路提供的信号产生振动；形成所述压电换能器后，形成贯穿所述平坦层且露出所述牺牲层部分顶部的释放孔；采用灰化工艺，通过所述释放孔去除所述牺牲层，形成空腔。
相应的，本发明还提供一种指纹识别模组，包括：具有信号处理电路的衬底；平坦层，位于所述衬底上；多个空腔，位于所述平坦层中的底部；压电换能器，位于所述平坦层上，所述压电换能器包括第一电极、位于所述第一电极上的压电层、以及位于所述压电层上的第二电极，所述第一电极、所述压电层和所述第二电极在空腔上有重叠区域，所述压电层用于根据所述信号处理电路提供的信号产生振动；释放孔，贯穿所述平坦层与所述空腔相连通。
 有益效果
与现有技术相比，本发明的技术方案具有以下优点：本发明实施例提供的指纹识别模组的形成方法中，在所述衬底上形成牺牲层后，形成覆盖所述牺牲层的压电换能器；随后形成贯穿所述压电换能器且露出所述牺牲层顶部的释放孔，并采用灰化工艺，通过所述释放孔去除所述牺牲层；本发明实施例通过选用能够被灰化工艺去除的材料作为牺牲层的材料，从而采用灰化工艺去除牺牲层，相应能够在气相条件下实现对牺牲层的释放，有利于减小牺牲层的残留、易于将牺牲层去除干净，且去除牺牲层的工艺对压电换能器的影响小；而且，与通过键合的方式形成空腔的方案相比，本发明实施例不需额外消耗一片承载基底，有利于降低工艺成本、实现指纹识别模组的量产化。且本发明实施例，形成所述牺牲层后，形成覆盖所述牺牲层以及所述衬底的平坦层，通常所述平坦层的材料为介电材料，形成所述压电换能器的步骤中，所述压电换能器形成在所述平坦层上，从而所述压电换能器具有较高的平整度，使得所述压电换能器的形成质量较高，后续去除所述牺牲层，形成空腔，所述空腔的侧壁和顶部为介电材料，所述空腔的结构更稳固，从而空腔对压电换能器起到较好的支撑，使得指纹识别模组具有更佳的器件寿命以及品质。信号处理电路与压电换能器集成，压电层直接根据信号处理电路提供的信号产生振动形成超声波，这样信号连接线路短，连接线路少，减少制作的工艺流程，并提升了器件的电性能。
 附图说明
图1至图9是本发明指纹识别模组的形成方法一实施例中各步骤对应的结构示意图。
 本发明的实施方式
由背景技术可知，超声波指纹识别传感器中通常还具有与压电换能器对应的空腔。
一种形成空腔的方法是先形成牺牲层，用于为形成空腔占据空间位置，牺牲层的材料包括氧化硅或锗；在形成压电换能器后，形成露出牺牲层的释放孔；之后再采用湿法刻蚀工艺，通过释放孔去除所述牺牲层，形成空腔。
上述形成方法中采用湿法刻蚀工艺，去除牺牲层；湿法刻蚀工艺需要将整个指纹识别模组放置到具有刻蚀溶液的清洗槽中，这容易导致有刻蚀溶液进入到空腔中而难以被完全去除，从而容易对压电换能器和空腔的性能产生影响；而且，上述方法中采用氧化硅或锗作为牺牲层的材料，去除所述牺牲层的工艺对牺牲层和压电换能器的材料的刻蚀选择比不够高，这容易增加产生牺牲层残留的概率，导致空腔的形成质量较差。
另一种方法是通过键合的方式形成空腔。但是，通过键合的方式形成空腔通常需要消耗一片承载基底，这导致形成指纹识别模组的成本过高。
为了解决所述技术问题，本发明提供一种指纹识别模组的形成方法，在所述衬底上形成牺牲层后，形成覆盖所述牺牲层的压电换能器；随后形成贯穿所述压电换能器且露出所述牺牲层顶部的释放孔，并采用灰化工艺，通过所述释放孔去除所述牺牲层；本发明实施例通过选用能够被灰化工艺去除的材料作为牺牲层的材料，从而采用灰化工艺去除牺牲层，相应能够在气相条件下实现对牺牲层的释放，有利于减小牺牲层的残留、易于将牺牲层去除干净，且去除牺牲层的工艺对压电换能器的影响小；而且，与通过键合的方式形成空腔的方案相比，本发明实施例不需额外消耗一片承载基底，有利于降低工艺成本、实现指纹识别模组的量产化。且本发明实施例，形成所述牺牲层后，形成覆盖所述牺牲层以及所述衬底的平坦层，通常所述平坦层的材料为介电材料，形成所述压电换能器的步骤中，所述压电换能器形成在所述平坦层上，从而所述压电换能器具有较高的平整度，使得所述压电换能器的形成质量较高，后续去除所述牺牲层，形成空腔，所述空腔的侧壁和顶部为介电材料，所述空腔的结构更稳固，从而空腔对压电换能器起到较好的支撑，使得指纹识别模组具有更佳的器件寿命以及品质。信号处理电路与压电换能器集成，压电层直接根据信号处理电路提供的信号产生振动形成超声波，这样信号连接线路短，连接线路少，减少制作的工艺流程，并提升了器件的电性能。
为使本发明的上述目的、特征和优点能够更为明显易懂，下面结合附图对本发明的具体实施例做详细的说明。
图1至图9是本发明指纹识别模组的形成方法第一实施例中各步骤对应的结构示意图。
参考图1，提供具有信号处理电路的衬底100。
衬底100用于为形成压电换能器和空腔提供工艺平台，衬底100还与压电换能器形成指纹识别模组。
本实施例中，衬底100基于CMOS工艺形成。
提供衬底100的步骤中，信号处理电路与后续的压电换能器相连接，用于在指纹识别模组的工作过程中，驱动压电换能器、以及处理压电换能器产生的检测信号。
本实施例中，衬底100还包括与信号处理电路电连接的第一连接端101和第二连接端102。
第一连接端101和第二连接端102用于实现衬底100中的信号处理电路与其他器件或压电换能器之间的电连接。
本实施例中，第一连接端101和第二连接端102的数量均为多个。
本实施例中，衬底100露出第一连接端101和第二连接端102。具体地，第一连接端101和第二连接端102为焊垫（Pad）。
参考图2，在衬底100上形成分立的牺牲层120。牺牲层120用于为后续形成空腔占据空间位置。
因此，本实施例中，牺牲层120的形状、位置和尺寸决定了后续空腔的形状、位置和尺寸，相应的，根据所需空腔的形状、位置和尺寸来形成牺牲层120。
本实施例中，牺牲层120的材料包括无定形碳、聚酰亚胺或环氧树脂。无定形碳、聚酰亚胺或环氧树脂均可以通过灰化工艺去除，形成空腔，灰化工艺对牺牲层120和压电换能器的材料的刻蚀选择比较高，有利于降低去除牺牲层120的工艺对压电换能器的影响，且灰化工艺的成本低、副作用小。
具体地，本实施例中，牺牲层120的材料为无定形碳。无定形碳的成本低，且后续灰化工艺对无定形碳与压电换能器的材料的刻蚀选择比较高，灰化工艺采用的含氧气体能够将无定形碳氧化为二氧化碳，从而直接排除反应腔室，有利于减小牺牲层120残留的风险、降低在空腔中残留反应副产物的概率，相应有利于提升指纹识别模组的性能。
本实施例中，形成牺牲层120的步骤包括：形成覆盖衬底100的牺牲材料层（图未示）；图形化牺牲材料层，位于衬底100上剩余的牺牲材料层作为牺牲层120。
本实施例中，形成牺牲材料层的工艺包括化学气相沉积工艺（Chemical Vapor Deposition，CVD）。
本实施例中，采用干法刻蚀工艺，图形化牺牲材料层。干法刻蚀工艺具有各向异性刻蚀特性，具有较好的刻蚀剖面控制性，有利于使牺牲层120的形貌满足工艺需求。
本实施例中，形成牺牲层120的步骤中，牺牲层120位于第一连接端101和第二连接端102的周边。例如：牺牲层120位于第一连接端101和第二连接端102之间的衬底100上，或者位于第一连接端101和第二连接端102同一侧的衬底100上，图2以牺牲层120位于第一连接端101和第二连接端102之间的衬底100上为例，从而后续形成的空腔位于第一连接端101和第二连接端102之间的衬底100上。后续形成与第一连接端101连接的第一导电插塞，形成与第二连接端102连接的第二导电插塞连接，在指纹识别模组工作时，使得空腔能够对超声波进行反射，不易受到第一导电插塞和第二导电插塞的影响，提高指纹识别模组的工作性能。
指纹识别模组的形成方法还包括：在衬底100上形成牺牲层120之前，在衬底100上形成刻蚀停止层110，刻蚀停止层110覆盖信号处理电路、第一连接端101以及第二连接端102。
刻蚀停止层110的材料包括氧化硅、氮化硅和氮氧化硅中的一种或多种。本实施例中，刻蚀停止层110的材料为氧化硅。
本实施例中，采用沉积工艺形成刻蚀停止层110。具体地，沉积工艺可以为化学气相沉积工艺或原子层沉积工艺（Atomic layer deposition，ALD）等。
相应地，牺牲层120形成在刻蚀停止层110上。
形成牺牲层120包括依次进行的沉积工艺和刻蚀工艺，刻蚀停止层110用于在形成牺牲层120的过程中起到定义刻蚀停止位置的作用，从而减小对衬底100的损伤，刻蚀停止层110还用于保护衬底100。
参考图3，形成平坦层130，平坦层130覆盖牺牲层120以及牺牲层120露出的衬底100。
形成牺牲层120后，形成覆盖牺牲层120以及衬底100的平坦层130，通常平坦层130的材料为介电材料，形成压电换能器的步骤中，压电换能器形成在平坦层130上，从而压电换能器具有较高的平整度，使得压电换能器的形成质量较高，后续去除牺牲层120，形成空腔，空腔的侧壁和顶部为介电材料，从而空腔对压电换能器起到较好的支撑，且空腔的结构更稳固，使得指纹识别模组具有更佳的器件寿命以及品质。
具体的，平坦层130的材料包括氧化硅和氮化硅中的一种或两种。本实施例中，平坦层130的材料包括氧化硅。氧化硅是工艺常用、成本较低的介电材料，且具有较高的工艺兼容性，有利于降低形成平坦层130的工艺难度和工艺成本；此外，氧化硅的介电常数较小，还有利于提高后续电隔离相邻器件的作用。
形成覆盖牺牲层120以及衬底100的平坦层130的步骤包括：在牺牲层120以及牺牲层120露出的衬底100上形成平坦材料层（图中未示出）；对平坦材料层进行平坦化处理，形成平坦层130。
本实施例中，采用化学气相沉积工艺形成覆盖牺牲层120以及衬底100的平坦材料层。具体的，采用流动式化学气相沉积工艺（Flowable Chemical Vapor Deposition，FCVD）形成平坦材料层。流动式化学气相沉积工艺具有良好的填充能力，有利于降低平坦材料层内形成空洞等缺陷的概率，相应有利于提高平坦层130的成膜质量。
对平坦材料层进行平坦化处理，形成平坦层130。平坦化处理使得平坦层130顶面的平坦度较高，为后续形成较为平整的压电换能器做准备。
具体的，采用化学机械平坦化工艺（chemical mechanical planarization，CMP）对平坦材料层进行平坦化处理，形成平坦层130。化学机械平坦化工艺是一种全局表面平坦化技术，可精确并均匀地把平坦材料层研磨为需要的厚度和平坦度。
需要说明的是，形成平坦层130的步骤中，平坦层130的顶面至牺牲层120的顶面的距离不宜过大也不宜过小。若距离过大，会导致最终形成的指纹识别模组的体积过大，导致指纹识别模组的灵敏度较差，影响器件频率性能。若距离过小，采用平坦化工艺形成平坦层130的过程中，易对牺牲层120造成损伤，相应的导致后续形成的空腔的质量较差，且若距离过小，后续去除牺牲层120后，形成的空腔的顶面的平坦层130的厚度较薄，不能对压电换能器起到较好的支撑，导致空腔的结构稳固性较差，易降低指纹识别模组的器件寿命以及品质。本实施例中，形成平坦层130的步骤中，平坦层130的顶面至牺牲层120的顶面的距离大于500Å且小于5000Å。
参考图4，在平坦层130上形成压电换能器140，压电换能器140包括第一电极141、位于第一电极141上的压电层142、以及位于压电层142上的第二电极143，第一电极141、压电层142和第二电极146在牺牲层120上有重叠区域，压电层142用于根据信号处理电路提供的信号产生振动。
压电换能器140为指纹识别模组中的识别单元。在指纹识别模组工作时，衬底100中的信号处理电路对压电换能器140的第一电极141和第二电极143施加电信号，从而利用压电层142的逆压电效应，使压电层142发生振动，进而产生超声波；由于超声波到达不同材质表面时被吸收、穿透和反射的程度不同，因而可以利用皮肤和空气或不同皮肤层对于声波阻抗的差异，反射回来的超声波使压电换能器140中的压电层142发生振动和变形，利用压电层142的压电效应，产生检测信号，使压电换能器140对指纹的脊与谷所在的位置进行识别，且使信号处理电路对压电换能器140产生的检测信号进行识别和处理。
本实施例中，具体的，压电换能器140形成在牺牲层120上，牺牲层120的数量为多个，压电换能器140的数量也为多个，多个压电换能器140分立于衬底100上，压电换能器140与牺牲层120一一对应，从而后续在牺牲层120的位置处形成空腔后，压电换能器140与空腔一一对应。
第一电极141用于作为压电换能器140中的底电极（Bottom electrode），即指纹识别模组中更靠近衬底100的电极。
第一电极141的材料可以为金属、金属硅化物、金属氮化物、金属氧化物或导电碳等导电材料，例如，第一电极141的材料可以为Mo、Al、Cu、Ag、Au、Ni、Co、TiAl、TiN或TaN等。本实施例中，第一电极141的材料为Mo。
在指纹识别模组的工作过程中，利用压电层142的逆压电效应，产生超声波；同时，在超声波碰到手指的脊或谷反射回来后，还利用压电层142的正压电效应，产生检测信号，进而使信号处理电路对检测信号进行处理和识别。
压电层142的材料可以为压电晶体、压电陶瓷或压电聚合物等。其中，压电晶体可以为氮化铝、锆钛酸铅、石英晶体、镓酸锂、锗酸锂、锗酸钛、铁晶体管铌酸锂或钽酸锂等，压电聚合物可以为聚偏氟乙烯、偏氟乙烯-三氟乙烯共聚物、尼龙-11或亚乙烯基二氰-醋酸乙烯交替共聚物等。本实施例中，压电层142的材料为氮化铝。
第二电极143用于作为压电换能器140中的顶电极（Top electrode），即指纹识别模组中更远离衬底100的电极。在指纹识别模组工作时，对第一电极141和第二电极143通电，使压电层142的两端产生电压，从而使压电层142发生形变。
本实施例中，第二电极143的材料可以为金属、金属硅化物、金属氮化物、金属氧化物或导电碳等导电材料，例如，第二电极143的材料可以为Mo、Al、Cu、Ag、Au、Ni、Co、TiAl、TiN或TaN等。本实施例中，第二电极143的材料为Mo。
形成压电换能器140的步骤包括：在衬底100上形成第一电极膜（图中未示出）；图形化第一电极膜，剩余的第一电极膜作为第一电极141；在第一电极141以及第一电极141露出的衬底100上形成压电层142；在压电层142上形成第二电极膜（图中未示出）；图形化第二电极膜，剩余的第二电极膜作为第二电极143。
需要说明的是，形成压电换能器140的步骤中，压电换能器140形成在平坦层130上。
在形成压电换能器140的步骤中，第一电极141形成在第一连接端101的正上方且露出第二连接端102。后续形成贯穿压电层142和第一电极141且露出第一连接端101的第一导电通孔，在第一导电通孔中形成与第一电极141和第一连接端101相接触的第一导电插塞，第一电极141形成在第一连接端101的正上方且露出第二连接端102，使得后续形成的第一导电插塞只与第一连接端101电连接。
在形成压电换能器140的步骤中，第二电极143形成在第二连接端102正上方且露出第一连接端101。后续形成贯穿第二电极143和压电层142且露出第二连接端102的第二导电通孔，在第二导电通孔中形成与第二电极143和第二连接端102相接触的第二导电插塞，第二电极143形成在第二连接端102正上方且露出第一连接端101，使得后续形成的第二导电插塞只与第二连接端102电连接。
本实施例中，形成第一电极膜的工艺包括物理气相沉积工艺(Physical Vapor Deposition，PVD)。具体地，物理气相沉积工艺可以为离子溅射工艺。
相应的，第一电极膜形成在平坦层130上。
本实施例中，采用干法刻蚀工艺，例如：各向异性的干法刻蚀工艺，图形化第一电极膜，形成第一电极141。各向异性的干法刻蚀工艺具有各向异性的刻蚀特性，有利于提高第一电极141的侧壁形貌质量和尺寸精度。
本实施例中，形成压电层142的工艺包括物理气相沉积工艺。具体地，物理气相沉积工艺可以为离子溅射工艺。
本实施例中，形成第二电极膜的工艺包括物理气相沉积工艺。具体地，物理气相沉积工艺可以为离子溅射工艺。
本实施例中，采用干法刻蚀工艺，例如：各向异性的干法刻蚀工艺，图形化第二电极膜，形成第二电极143。各向异性的干法刻蚀工艺具有各向异性的刻蚀特性，有利于提高第二电极143的侧壁形貌质量和尺寸精度。
具体的，平坦层130经过平坦化处理，平坦层130的表面较为平整，从而压电换能器140具有较高的平整度，压电换能器140的形成质量较好，后续去除牺牲层120，形成空腔，空腔的侧壁和顶部为介电材料，从而空腔对压电换能器140起到较好的支撑，且空腔的结构更稳固，使得指纹识别模组具有更佳的器件寿命以及品质。
需要说明的是，第一电极141、压电层142和第二电极146在牺牲层120上有重叠区域，相应的，后续去除牺牲层120后，在平坦层130中形成空腔300，也就是说，第一电极141、压电层142和第二电极146在空腔300上有重叠区域，空腔300为指纹识别模组中的功能区域，在指纹识别模组的工作过程中，在第一电极141和第二电极143施加交流的电压，在逆压电效应的作用下，压电层142会发生振动，进而产生超声波，空腔300为压电层142的震动提供工艺基础，空腔300界面还能够对产生的超声波进行反射，避免产生干扰信号。
参考图5，形成压电换能器后，形成贯穿平坦层且露出牺牲层120部分顶部的释放孔200。
释放孔200露出牺牲层120的部分顶部，从而后续能够通过释放孔200去除牺牲层120。
本实施例中，释放孔200的数量为多个，从而提高后续通过释放孔200去除牺牲层120的效率。
本实施例中，采用干法刻蚀工艺，例如：各向异性的干法刻蚀工艺，刻蚀位于牺牲层120上的压电换能器140，形成释放孔200。
本实施例中，通常在压电换能器140上形成释放掩膜层（图中未示出），释放掩膜层包括光刻胶，以释放掩膜层为掩膜采用干法刻蚀工艺，形成贯穿平坦层130且露出牺牲层120部分顶部的释放孔200。
需要说明的是，形成贯穿平坦层130且露出牺牲层120部分顶部的释放孔200的步骤中，释放孔200还贯穿第一电极141、压电层142以及第二电极143。其他实施例中，释放孔还贯穿第一电极和压电层，或者释放孔还贯穿压电层和第二电极，或者释放孔还贯穿压电层。
参考图6，采用灰化工艺，通过释放孔200去除牺牲层120，形成空腔300。
通过去除牺牲层120，从而在牺牲层120的位置处形成空腔300。
本发明实施例提供的指纹识别模组的形成方法中，在衬底100上形成牺牲层120后，形成覆盖牺牲层120的压电换能器140；随后形成贯穿压电换能器140且露出牺牲层120顶部的释放孔200，并采用灰化工艺，通过释放孔200去除牺牲层120；本发明实施例通过选用能够被灰化工艺去除的材料作为牺牲层120的材料，从而采用灰化工艺去除牺牲层120，相应能够在气相条件下实现对牺牲层120的释放，有利于减小牺牲层120的残留、易于将牺牲层120去除干净，且去除牺牲层120的工艺对压电换能器140的影响小；而且，与通过键合的方式形成空腔的方案相比，本发明实施例不需额外消耗一片承载基底，有利于降低工艺成本、实现指纹识别模组的量产化。且本发明实施例，形成牺牲层120后，形成覆盖牺牲层120以及衬底100的平坦层130，通常平坦层130的材料为介电材料，形成压电换能器140的步骤中，压电换能器140形成在平坦层130上，从而压电换能器140具有较高的平整度，使得压电换能器140的形成质量较高，后续去除牺牲层120，形成空腔300，空腔300的侧壁和顶部为介电材料，空腔300的结构更稳固，从而空腔300对压电换能器140起到较好的支撑，使得指纹识别模组具有更佳的器件寿命以及品质。信号处理电路与压电换能器140集成，压电层142直接根据信号处理电路提供的信号产生振动形成超声波，这样信号连接线路短，连接线路少，减少制作的工艺流程，并提升了器件的电性能。
空腔300为指纹识别模组中的功能区域，在指纹识别模组的工作过程中，在第一电极141和第二电极143施加交流的电压，在逆压电效应的作用下，压电层142会发生振动，进而产生超声波，空腔300为压电层142的震动提供工艺基础，空腔300界面还能够对产生的超声波进行反射，避免产生干扰信号，超声波向上传输到达手指的谷或者脊，声波遇到脊的表面后部分反射、部分透射，而因为谷中空气的声阻抗远高于脊，所以声波遇到谷时几乎为全反射。从谷和脊反射回来的超声波传到压电换能器140时，压电换能器140产生形变，压电层142两端就会产生不同幅值、相位或频率的电压，从而实现指纹信息的采集。
去除牺牲层120，形成空腔300，空腔300由平坦层130和与刻蚀停止层110围成，空腔300的侧壁和顶部为介电材料，从而空腔300对压电换能器140起到较好的支撑，且空腔300的结构更稳固，使得指纹识别模组具有更佳的器件寿命以及品质。
本实施例中，压电换能器140位于空腔300的顶面，相应的压电功能区域位于空腔300的顶面。
本实施例中，空腔300位于压电换能器140与衬底100之间，在指纹识别模组工作时，手指位于压电换能器140背向衬底100的一侧，也就是说，与压电换能器140相比，手指更远离衬底100，空腔300相应位于压电换能器顶部的下方，即使在后续的工艺中（例如：在压电换能器140上形成钝化层，密封释放孔200）有杂质颗粒通过释放孔200进入空腔300中，由于在指纹识别模组工作时，压电功能区域位于空腔300的顶面，杂质颗粒与压电功能区相接触的概率低，有利于降低对压电换能器140的工作性能的影响，相应有利于提高指纹识别模组的可靠性和生产良率。
灰化工艺采用的气体可以包括氧气。本实施例中，采用氧气进行灰化工艺。氧气能够与无定形碳发生反应形成二氧化碳气体，工艺成本低、且副作用小，有利于进一步降低对压电换能器140的影响、以及减小空腔300中产生反应副产物残留或牺牲层120残留的概率。
需要说明的是，采用灰化工艺，通过释放孔200去除牺牲层120，形成空腔300的步骤中，灰化工艺还去除了释放掩膜层，相应的也就去除了光刻胶，后续过程中，不需要进行去胶工艺，简化了指纹识别模组的形成工艺，降低成本。
参考图7，指纹识别模组的形成方法还包括：形成空腔300后，在压电换能器140上形成钝化层150，钝化层150密封释放孔200。
钝化层150用于密封释放孔200，从而使空腔300密封，钝化层150还用于对压电换能器140起到保护作用，从而有利于减小外界杂质、离子电荷和水汽等对压电换能器140产生的影响，有利于提高指纹识别的性能和稳定性。
钝化层150的材料可以为氧化硅、氮化硅、碳氮化硅、碳氮氧化硅、氮氧化硅、氮化硼、碳氮化硼、低k介质材料或聚酰亚胺。本实施例中，钝化层150的材料为氧化硅。
本实施例中，钝化层150的形成步骤包括：形成覆盖第二电极143以及第二电极143露出的压电层142的钝化材料层（图中未示出）；图形化钝化材料层，剩余的钝化材料层作为钝化层150。
本实施例中，采用沉积工艺，例如：化学气相沉积工艺，形成钝化材料层。
参考图8，形成空腔300后，指纹识别模组的形成方法还包括：形成贯穿压电层142和第一电极141且露出第一连接端101的第一导电通孔160、以及形成贯穿第二电极143和压电层142且露出第二连接端102的第二导电通孔170。
第一导电通孔160用于为形成第一导电插塞提供空间位置，第一导电通孔160贯穿第一电极141且露出第一连接端101，从而后续形成的第一导电插塞能够电连接第一电极141和第一连接端101，电连接性能更为优异，且因为第一导电通孔160未露出其他的导电膜层，避免了在第一导电通孔160中形成覆盖其他的导电膜层的绝缘层，有利于简化指纹识别模组的形成工艺，降低成本；第二导电通孔170用于为形成第二导电插塞提供空间位置，第二导电通孔170贯穿第二电极143且露出第二连接端102，从而后续形成的第二导电插塞能够电连接第二电极143和第二连接端102，电连接性能更为优异，且因为第二导电通孔170未露出其他的导电膜层，避免了在第二导电通孔170中形成覆盖其他的导电膜层的绝缘层，有利于简化指纹识别模组的形成工艺，降低成本。
本实施例中，第一导电通孔160和第二导电通孔170还贯穿钝化层150、平坦层130以及刻蚀停止层110。
本实施例中，第一导电通孔160和第二导电通孔170为阶梯状通孔，也就是说，第一导电通孔160还露出第一电极141的部分顶面，第二导电通孔170还露出第二电极143的部分顶面，后续形成位于第一导电通孔160中的第一导电插塞、以及位于第二导电通孔170中的第二导电插塞后，第一导电插塞能够覆盖第一电极141的部分顶面，第二导电插塞能够覆盖第二电极143的部分顶面，与第一导电通孔和第二导电通孔的侧壁为陡直的侧壁相比，第一导电插塞与第一电极141的接触面积更大、接触性能更好，第二导电插塞与第二电极143的接触面积更大、接触性能更好，从而有利于提高指纹识别模组的性能，降低能量损耗。
本实施例中，采用干法刻蚀工艺，例如：各向异性的干法刻蚀工艺，形成第一导电通孔160和第二导电通孔170。
本实施例中，形成第一导电通孔160的步骤包括：形成第一掩膜层；以第一掩膜层为掩膜刻蚀钝化层150，形成第一子通孔161；形成第一子通孔161后，去除第一掩膜层；形成第二掩膜层；以第二掩膜层为掩膜刻蚀压电层142，形成第二子通孔162；形成第二子通孔162后，去除第二掩膜层；形成第三掩膜层；以第三掩膜层为掩膜刻蚀第一电极141和平坦层130，形成露出第一连接端101的第三子通孔163，第一子通孔161、第二子通孔162以及第三子通孔163作为第一导电通孔160。
形成第二导电通孔170的步骤包括：形成第四掩膜层；以第四掩膜层为掩膜刻蚀钝化层150，形成第四子通孔171；形成第四子通孔171后，去除第四掩膜层；形成第五掩膜层；以第五掩膜层为掩膜刻蚀第二电极143和压电层142，形成第五子通孔172；形成第五子通孔172后，去除第五掩膜层；形成第六掩膜层；以第六掩膜层为掩膜刻蚀平坦层130，形成露出第二连接端102的第六子通孔173，第四子通孔171、第五子通孔172以及第六子通孔173作为第二导电通孔170。
需要说明的是，形成第三子通孔163以及第六子通孔173的过程中还刻穿刻蚀停止层110。
结合参考图9，通过填充工艺，形成位于第一导电通孔160中且与第一电极141和第一连接端101相接触的第一导电插塞180、以及位于第二导电通孔170中且与第二电极143和第二连接端102相接触的第二导电插塞190。
第一导电插塞180用于实现第一电极141和第一连接端101之间的电连接，第二导电插塞190用于实现第二电极143和第二连接端102之间的电连接；因此，通过第一导电插塞180和第二导电插塞190，使压电换能器130与衬底100中的信号处理电路直接电连接，有利于使得第一导电插塞180和第二导电插塞190具有较小的尺寸，具有更优的电连接性能，且工艺流程简便，成本低。其他实施例中，可以通过其他方式将第一连接端与第一电极连接，将第二连接端与第二电极连接。
第一导电插塞180还用于使衬底100和第一电极141与外部电路或其他器件实现电连接；第二导电插塞190还用于使衬底100和第二电极143与外部电路或其他器件实现电连接。
本实施例中，第一导电插塞180和第二导电插塞190为阶梯状结构，也就是说，除了与第一电极141的侧壁相接触之外，第一导电插塞180还与第一电极141的部分顶面相接触，第一导电插塞180和第一电极141的接触面积较大，从而有利于降低第一导电插塞180与第一电极141的接触电阻、提高第一导电插塞180与第一电极141的接触性能；第二导电插塞190除了与第二电极143的侧壁相接触之外，第二导电插塞190还与第二电极143的部分顶面相接触，第一导电插塞180与第二电极143的接触面积较大，从而有利于降低第二导电插塞190与第二电极143之间的接触电阻、提高第二导电插塞170与第二电极143之间的接触性能。
本实施例中，第一导电插塞180和第二导电插塞190的材料相同，第一导电插塞180和第二导电插塞190的材料包括Cu、Au、Ag和Al中的一种或多种。
本实施例中，形成第一导电插塞180和第二导电插塞190的步骤中，还形成位于部分钝化层150上且分别与第一导电插塞180相连、与第二导电插塞190相连的互连结构191。
互连结构191为后续的封装工艺做准备。互连结构191与第一导电插塞180和第二导电插塞190的材料相同。且在形成第一导电插塞180和第二导电插塞190的步骤中，形成互连结构191，有利于简化指纹识别模组的形成工艺，降低成本。
本实施例中，形成第一导电插塞180、第二导电插塞190、以及互连结构191的步骤包括：在第一导电通孔160的底面和侧壁、第二导电通孔170的底面和侧壁、以及钝化层150上形成种子层（图未示）；在种子层上形成位于钝化层150上方的遮挡层（图未示），遮挡层中形成有图形开口，图形开口位于第一导电通孔160上方、且露出与第一导电通孔160相邻的钝化层150上的部分种子层，图形开口还位于第二导电通孔170上方、且露出与第二导电通孔170相邻的钝化层150上的部分种子层；在第一导电通孔160和第二导电通孔170中填充导电层，导电层还覆盖图形开口下方的种子层；去除遮挡层；去除导电层露出的种子层以及部分厚度的导电层，保留位于第一导电通孔160中的导电层和种子层作为第一导电插塞180，保留位于第二导电通孔170中的导电层和种子层作为第二导电插塞190，保留位于钝化层150上的种子层和导电层作为互连结构191。
相应的，本发明还提供一种指纹识别模组。继续参考图9，示出了本发明指纹识别模组一实施例的结构示意图。
指纹识别模组包括：具有信号处理电路的衬底100；平坦层130，位于衬底100上；多个空腔300，位于平坦层130中的底部；压电换能器140，位于平坦层130上，压电换能器140包括第一电极141、位于第一电极141上的压电层142、以及位于压电层142上的第二电极143，第一电极141、压电层142和第二电极143在空腔300上有重叠区域，压电层142用于根据信号处理电路提供的信号产生振动；释放孔200，贯穿平坦层130与空腔300相连通。
指纹识别模组中，平坦层130表面具有较高的平整度，压电换能器140形成在平坦层130上，从而压电换能器140具有较高的平整度，压电换能器140的形成质量较好，且空腔300，位于平坦层130中的底部，空腔300的侧壁和顶部为介电材料，空腔300的结构更稳固，从而空腔300对压电换能器140起到较好的支撑，使得指纹识别模组具有更佳的器件寿命以及品质。信号处理电路与压电换能器140集成，压电层142直接根据信号处理电路提供的信号产生振动形成超声波，这样信号连接线路短，连接线路少，减少制作的工艺流程，并提升了器件的电性能。
本实施例中，第一电极141、压电层142和第二电极143在空腔300上有重叠区域，空腔300为指纹识别模组中的功能区域，在指纹识别模组的工作过程中，在第一电极141和第二电极143施加交流电压，在逆压电效应的作用下，压电层142会发生振动，进而产生超声波，空腔300为压电层142的震动提供工艺基础，空腔300界面还能够对产生的超声波进行反射，避免产生干扰信号。
本实施例中，空腔300位于压电换能器140与衬底100之间，在指纹识别模组工作时，手指位于压电换能器140背向衬底100的一侧，也就是说，与压电换能器140相比，手指更远离衬底100，空腔300相应位于压电换能器顶部的下方，压电功能区域位于空腔300的顶面，在指纹识别模组工作时，手指与压电功能区相接触，有利于提高指纹识别模组的可靠性和生产良率。
衬底100用于为形成压电换能器和空腔提供工艺平台，衬底100还与压电换能器形成指纹识别模组。
本实施例中，衬底100基于CMOS工艺形成。
衬底100中具有信号处理电路，信号处理电路与后续的压电换能器相连接，用于在指纹识别模组的工作过程中，驱动压电换能器、以及处理压电换能器产生的检测信号。
本实施例中，衬底100还包括与信号处理电路电连接的第一连接端101和第二连接端102。
第一连接端101和第二连接端102用于实现衬底100中的信号处理电路与其他器件或压电换能器之间的电连接。
本实施例中，第一连接端101和第二连接端102的数量均为多个。
本实施例中，衬底100露出第一连接端101和第二连接端102。具体地，第一连接端101和第二连接端102为焊垫（Pad）。
指纹识别模组还包括：刻蚀停止层110，位于衬底100和空腔300之间，以及衬底100和平坦层130之间。
刻蚀停止层110的材料包括氧化硅、氮化硅和氮氧化硅中的一种或多种。本实施例中，刻蚀停止层110的材料为氧化硅。
相应的，空腔300由平坦层130和与刻蚀停止层110围成，空腔300的侧壁和顶部为介电材料，从而空腔300对压电换能器140起到较好的支撑，且空腔300的结构更稳固，使得指纹识别模组具有更佳的器件寿命以及品质。
平坦层130的材料包括氧化硅和氮化硅中的一种或两种。本实施例中，平坦层130的材料包括氧化硅。氧化硅是工艺常用、成本较低的介电材料，且具有较高的工艺兼容性，有利于降低形成平坦层130的工艺难度和工艺成本；此外，氧化硅的介电常数较小，还有利于提高后续电隔离相邻器件的作用。
本实施例中，空腔300位于第一连接端101和第二连接端102周边的述平坦层130中。例如：空腔300位于第一连接端101和第二连接端102之间的平坦层130中，或者位于第一连接端101和第二连接端102同一侧的平坦层130中，图9中以空腔300位于第一连接端101和第二连接端102之间的平坦层130中为例，第一连接端101与第一导电插塞180连接，第二连接端102与第二导电插塞190连接，在指纹识别模组工作时，使得空腔能够对超声波进行反射，不易受到第一导电插塞180和第二导电插塞190的影响，提高指纹识别模组的工作性能。
需要说明的是，平坦层130的顶面至空腔300的顶面的距离不宜过大也不宜过小。若距离过大，会导致指纹识别模组的体积过大，导致指纹识别模组的灵敏度较差，影响器件频率性能。若距离过小，空腔的顶面的平坦层130的厚度较薄，难以对压电换能器140起到较好的支撑，空腔300的结构稳固性较差，易降低指纹识别模组的器件寿命以及品质。本实施例中，平坦层130的顶面至空腔300的顶面的距离大于500Å且小于5000Å。
压电换能器140为指纹识别模组中的识别单元。在指纹识别模组工作时，衬底100中的信号处理电路对压电换能器140的第一电极141和第二电极143施加电信号，从而利用压电层142的逆压电效应，使压电层142发生振动，进而产生超声波；由于超声波到达不同材质表面时被吸收、穿透和反射的程度不同，因而可以利用皮肤和空气或不同皮肤层对于声波阻抗的差异，反射回来的超声波使压电换能器140中的压电层142发生振动和变形，利用压电层142的压电效应，产生检测信号，使压电换能器140对指纹的脊与谷所在的位置进行识别，且使信号处理电路对压电换能器140产生的检测信号进行识别和处理。
第一电极141用于作为压电换能器140中的底电极（Bottom electrode），即指纹识别模组中更靠近衬底100的电极。
第一电极141的材料可以为金属、金属硅化物、金属氮化物、金属氧化物或导电碳等导电材料，例如，第一电极141的材料可以为Mo、Al、Cu、Ag、Au、Ni、Co、TiAl、TiN或TaN等。本实施例中，第一电极141的材料为Mo。
本实施例中，第一电极141位于第一连接端101的正上方且露出第二连接端102。
指纹识别模组还包括：第一导电插塞180贯穿压电层142和第一电极141且与第一连接端101相接触，第一导电插塞180将第一连接端101与第一电极141电连接。其他实施例中，可以通过其他方式将第一连接端与第一电极连接。
在指纹识别模组的工作过程中，利用压电层142的逆压电效应，产生超声波；同时，在超声波碰到手指的脊或谷反射回来后，还利用压电层142的正压电效应，产生检测信号，进而使信号处理电路对检测信号进行处理和识别。
压电层142的材料可以为压电晶体、压电陶瓷或压电聚合物等。其中，压电晶体可以为氮化铝、锆钛酸铅、石英晶体、镓酸锂、锗酸锂、锗酸钛、铁晶体管铌酸锂或钽酸锂等，压电聚合物可以为聚偏氟乙烯、偏氟乙烯-三氟乙烯共聚物、尼龙-11或亚乙烯基二氰-醋酸乙烯交替共聚物等。本实施例中，压电层142的材料为氮化铝。
第二电极143用于作为压电换能器140中的顶电极（Top electrode），即指纹识别模组中更远离衬底100的电极。在指纹识别模组工作时，对第一电极141和第二电极143通电，使压电层142的两端产生电压，从而使压电层142发生形变。
本实施例中，第二电极143的材料可以为金属、金属硅化物、金属氮化物、金属氧化物或导电碳等导电材料，例如，第二电极143的材料可以为Mo、Al、Cu、Ag、Au、Ni、Co、TiAl、TiN或TaN等。本实施例中，第二电极143的材料为Mo。
需要说明的是，压电换能器140位于平坦层130上。
本实施例中，第二电极143位于第二连接端102的正上方且露出第一连接端101。
指纹识别模组还包括：第二导电插塞190，贯穿第二电极143和压电层142且与第二连接端102相接触，第二导电插塞190将第二连接端102与第二电极143直接电连接，使得第二连接端102和第二电极143具有优异的电连接性能，且使得指纹识别模组的结构简单，有利于使得第一导电插塞180和第二导电插塞190具有较小的尺寸，成本低。其他实施例中，可以通过其他方式将第二连接端与第二电极连接。
释放孔200为形成空腔300的工艺孔。
需要说明的是，本实施例中，释放孔200还贯穿第一电极141、压电层142以及第二电极143。其他实施例中，释放孔还贯穿第一电极和压电层；或者，释放孔还贯穿压电层和第二电极；或者，释放孔还贯穿压电层。
需要说明的是，本实施例中，释放孔200同时贯穿第一电极141、压电层142以及第二电极143。其他实施例中，释放孔还可以仅贯穿第一电极和压电层露出空腔，或者仅贯穿压电层和第二电极露出空腔，或者仅贯穿压电层露出空腔。
指纹识别模组还包括：位于压电换能器140上的钝化层150，钝化层150密封释放孔。
钝化层150用于密封释放孔200，从而使空腔300密封，钝化层150还用于对压电换能器140起到保护作用，从而有利于减小外界杂质、离子电荷和水汽等对压电换能器140产生的影响，有利于提高指纹识别的性能和稳定性。
钝化层150的材料可以为氧化硅、氮化硅、碳氮化硅、碳氮氧化硅、氮氧化硅、氮化硼、碳氮化硼、低k介质材料或聚酰亚胺。本实施例中，钝化层150的材料为氧化硅。
第一导电插塞180和第二导电插塞190为阶梯状结构，也就是说，除了与第一电极141的侧壁相接触之外，第一导电插塞180还与第一电极141的部分顶面相接触，第一导电插塞180和第一电极141的接触面积较大，从而有利于降低第一导电插塞180与第一电极141的接触电阻、提高第一导电插塞180与第一电极141的接触性能；第二导电插塞190除了与第二电极143的侧壁相接触之外，第二导电插塞190还与第二电极143的部分顶面相接触，第一导电插塞180与第二电极143的接触面积较大，从而有利于降低第二导电插塞190与第二电极143之间的接触电阻、提高第二导电插塞170与第二电极143之间的接触性能。
本实施例中，第一导电插塞180和第二导电插塞190的材料相同，第一导电插塞180和第二导电插塞190的材料包括Cu、Au、Ag和Al中的一种或多种。
指纹识别模组还包括：互连结构191，位于部分钝化层150上且分别与第一导电插塞180和第二导电插塞190相连。
互连结构与第一导电插塞180和第二导电插塞190的材料相同。
需要说明的是，第一导电插塞180和第二导电插塞190的过程中还贯穿刻蚀停止层110。
相应地，本发明实施例还提供一种电子设备，包括：本发明实施例提供的指纹识别模组。
通过在电子设备中配置本实施例所述的指纹识别模组，以实现指纹识别。其中，所述电子设备可以为个人计算机、智能手机、个人数字助理(PDA)、媒体播放器、导航设备、游戏控制台、平板计算机、可穿戴设备、防门禁电子系统、汽车无钥进入电子系统或汽车无钥启动电子系统等。
由前述分析可知，在指纹识别模组的形成过程中，所述空腔中残留有牺牲层的概率较低，且在灰化工艺去除牺牲层对压电换能器的影响较少，有利于提高指纹识别模组的性能（例如：指纹识别模组的指纹识别精准度），从而提高了用户的使用感受度。对本实施例所述电子设备中的指纹识别模组的具体描述，可参考前述实施例中的相应描述，本实施例在此不再赘述。
所述指纹识别模组可以采用前述实施例所述指纹识别模组的形成方法所形成，也可以采用其他指纹识别模组的形成方法所形成。本实施例中，对所述指纹识别模组的具体描述，可参考前述实施例中的相应描述，本实施例在此不再赘述。
虽然本发明披露如上，但本发明并非限定于此。任何本领域技术人员，在不脱离本发明的精神和范围内，均可作各种更动与修改，因此本发明的保护范围应当以权利要求所限定的范围为准。

Claims (20)

  1. 一种指纹识别模组的形成方法，其特征在于，包括：
    提供具有信号处理电路的衬底；
    在所述衬底上形成分立的牺牲层；
    形成平坦层，所述平坦层覆盖所述牺牲层以及所述牺牲层露出的所述衬底；
    在所述平坦层上形成压电换能器，所述压电换能器包括第一电极、位于所述第一电极上的压电层、以及位于所述压电层上的第二电极，所述第一电极、所述压电层和所述第二电极在牺牲层上有重叠区域，所述压电层用于根据所述信号处理电路提供的信号产生振动；
    形成所述压电换能器后，形成贯穿所述平坦层且露出所述牺牲层部分顶部的释放孔；
    采用灰化工艺，通过所述释放孔去除所述牺牲层，形成空腔。
  2. 如权利要求1所述的指纹识别模组的形成方法，其特征在于，形成所述平坦层的步骤中，所述平坦层的顶面至所述牺牲层的顶面的距离大于500Å且小于5000Å。
  3. 如权利要求1所述的指纹识别模组的形成方法，其特征在于，所述平坦层的材料包括氧化硅和氮化硅中的一种或两种。
  4. 如权利要求1所述的指纹识别模组的形成方法，其特征在于，形成覆盖所述牺牲层以及所述衬底的平坦层的步骤包括：在所述牺牲层以及所述牺牲层露出的所述衬底上形成平坦材料层；对所述平坦材料层进行平坦化处理，形成所述平坦层。
  5. 如权利要求4所述的指纹识别模组的形成方法，其特征在于，采用化学机械平坦化工艺对所述平坦材料层进行平坦化处理，形成平坦层。
  6. 如权利要求4所述的指纹识别模组的形成方法，其特征在于，采用化学气相沉积工艺形成覆盖所述牺牲层以及所述衬底的平坦材料层。
  7. 如权利要求1所述的指纹识别模组的形成方法，其特征在于，所述牺牲层的材料包括无定形碳、聚酰亚胺或环氧树脂。
  8. 如权利要求1所述的指纹识别模组的形成方法，其特征在于，形成所述牺牲层的步骤包括：形成覆盖所述衬底的牺牲材料层；图形化所述牺牲材料层，位于所述衬底上剩余的所述牺牲材料层作为所述牺牲层。
  9. 如权利要求8所述的指纹识别模组的形成方法，其特征在于，采用干法刻蚀工艺，图形化所述牺牲材料层。
  10. 如权利要求1所述的指纹识别模组的形成方法，其特征在于，形成所述压电换能器的步骤包括：
    在所述衬底上形成第一电极膜；图形化所述第一电极膜，剩余的所述第一电极膜作为所述第一电极；在所述第一电极以及所述第一电极露出的所述衬底上形成所述压电层；在所述压电层上形成第二电极膜；图形化所述第二电极膜，剩余的所述第二电极膜作为所述第二电极。
  11. 如权利要求1所述的指纹识别模组的形成方法，其特征在于，所述灰化工艺采用的气体包括氧气。
  12. 如权利要求1所述的指纹识别模组的形成方法，其特征在于，所述指纹识别模组的形成方法还包括：形成所述空腔后，在所述压电换能器上形成钝化层，所述钝化层密封所述释放孔。
  13. 如权利要求1所述的指纹识别模组的形成方法，其特征在于，形成贯穿所述平坦层且露出所述牺牲层部分顶部的释放孔的步骤中，所述释放孔还贯穿所述第一电极、压电层以及所述第二电极；
    或者，所述释放孔还贯穿所述第一电极和压电层；
    或者，所述释放孔还贯穿所述压电层和第二电极；
    或者，所述释放孔还贯穿所述压电层。
  14. 如权利要求1所述的指纹识别模组的形成方法，其特征在于，所述提供衬底的步骤中，所述衬底中还包括与所述信号处理电路电连接的第一连接端和第二连接端；
    形成所述牺牲层的步骤中，所述牺牲层位于所述第一连接端和第二连接端的周边；
    形成所述压电换能器的步骤中，所述第一电极形成在所述第一连接端的正上方且露出所述第二连接端；所述第二电极形成在所述第二连接端正上方且露出所述第一连接端；
    形成所述空腔后，所述指纹识别模组的形成方法还包括：形成贯穿所述压电层和第一电极且露出所述第一连接端的第一导电通孔、以及形成贯穿所述第二电极和压电层且露出所述第二连接端的第二导电通孔；
    通过填充工艺，形成位于所述第一导电通孔中且与所述第一电极和第一连接端相接触的第一导电插塞、以及位于第二导电通孔中且与所述第二电极和第二连接端相接触的第二导电插塞。
  15. 一种指纹识别模组，其特征在于，包括：
    具有信号处理电路的衬底；
    平坦层，位于所述衬底上；
    多个空腔，位于所述平坦层中的底部；
    压电换能器，位于所述平坦层上，所述压电换能器包括第一电极、位于所述第一电极上的压电层、以及位于所述压电层上的第二电极，所述第一电极、所述压电层和所述第二电极在空腔上有重叠区域，所述压电层用于根据所述信号处理电路提供的信号产生振动；
    释放孔，贯穿所述平坦层与所述空腔相连通。
  16. 如权利要求15所述的指纹识别模组，其特征在于，所述衬底还包括与所述信号处理电路电连接的第一连接端和第二连接端；
    所述空腔位于所述第一连接端和第二连接端周边的述平坦层中；
    所述第一电极位于所述第一连接端的正上方且露出所述第二连接端；所述第二电极位于所述第二连接端正上方且露出所述第一连接端；
    所述指纹识别模组还包括：第一导电插塞，贯穿所述压电层和第一电极且与所述第一连接端相接触；第二导电插塞，贯穿所述第二电极和压电层且与所述第二连接端相接触。
  17. 如权利要求15或16所述的指纹识别模组，其特征在于，所述平坦层的顶面至所述空腔的顶面的距离大于500Å且小于5000Å。
  18. 如权利要求15或16所述的指纹识别模组，其特征在于，所述平坦层的材料包括氧化硅和氮化硅中的一种或两种。
  19. 如权利要求15或16所述的指纹识别模组，其特征在于，所述指纹识别模组还包括：位于所述压电换能器上的钝化层，所述钝化层密封所述释放孔。
  20. 如权利要求15或16所述的指纹识别模组，其特征在于，所述释放孔还贯穿所述第一电极、压电层以及所述第二电极；
    或者，所述释放孔还贯穿所述第一电极和压电层；
    或者，所述释放孔还贯穿所述压电层和第二电极；
    或者，所述释放孔还贯穿所述压电层。
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