Ultrasonic fingerprint sensing chip, electronic device, and manufacturing method

Abstract

The present invention relates to an ultrasonic fingerprint sensing chip and an electronic device with a fingerprint recognition function and a manufacturing method. In the manufacturing method, an excitation structure of a fingerprint sensing unit is formed on a first substrate, and a corresponding cavity is formed on the excitation structure or on another substrate, and then the two substrates are buckled to form a closed cavity of the fingerprint sensing unit. After removing the first substrate, an electrical connection structure is formed to lead the first electrode and the second electrode in the excitation structure to the surface. The formed ultrasonic fingerprint sensing chip includes a plurality of fingerprint sensing units obtained by the method for fingerprint recognition, and each fingerprint sensing unit has a compact structure, which helps to improve the design density of the fingerprint sensing unit and the fingerprint recognition performance.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to an ultrasonic fingerprint sensing chip and a manufacturing method thereof, and an electronic device with a fingerprint recognition function. Background Art

[0002] At present, fingerprint recognition technology has become one of the hot spots in the field of biometrics, and is widely used in various applications involving user information verification, such as consumer electronics, access control systems, and information collection. Taking fingerprint recognition technology applied to mobile terminals as an example, capacitive fingerprint recognition technology currently dominates the mainstream. However, with the industry's demand for full-screen mobile phones, fingerprint recognition requires the ability to penetrate dielectric layers with a thickness of more than 1mm (such as glass, metal, plastic, or display and glass). This requirement is a difficult problem for capacitive fingerprint recognition technology. The optional solution is to dig a hole in the glass screen below the recognition area, but this will destroy the integrity of the screen on the one hand, and it is also easy to reduce the yield of display production and increase costs on the other hand.

[0003] In principle, both optical fingerprint recognition technology and ultrasonic fingerprint recognition technology have stronger dielectric layer penetration capabilities and can penetrate glass media greater than 1mm, which can maximize the integrity of the display screen. However, optical fingerprint recognition technology mainly collects the epidermal texture of the finger, which has poor anti-counterfeiting properties. Moreover, both optical fingerprint recognition technology and capacitive fingerprint recognition technology have poor recognition effects for wet fingers. In comparison, ultrasonic fingerprint recognition technology can collect not only the epidermal texture of the finger, but also the dermal texture, which has higher security. Moreover, ultrasonic fingerprint recognition technology can better identify wet fingers based on the difference in acoustic impedance between water and skin. Therefore, ultrasonic fingerprint recognition technology has now become one of the important development directions of fingerprint recognition.

[0004] The fingerprint recognition device using ultrasonic fingerprint recognition technology adopts the principle of piezoelectric transduction. Usually, multiple piezoelectric transducer units are set within the fingerprint recognition range. Each piezoelectric transducer unit has a cavity, and the top of the cavity is covered by an excitation layer. After the ultrasonic wave of a specific frequency emitted by the excitation layer encounters the valley or ridge of the finger, the excitation ultrasonic wave and the reflected ultrasonic wave can penetrate materials such as glass or metal with a thickness greater than 1mm. The reflected ultrasonic wave can form a corresponding electrical signal through the excitation layer. The electrical signal is transmitted to the controller after processing, and the fingerprint image is formed after further processing.

[0005] In order to improve the quality of fingerprint recognition, the cavity of the piezoelectric transducer unit should be set larger. At the same time, in order to improve the sensitivity of fingerprint recognition, it is preferred to set more piezoelectric transducers in the fingerprint recognition range, that is, the range between adjacent cavities should be set smaller. This puts higher requirements on the design and production of fingerprint recognition devices. Summary of the invention

[0006] In order to optimize the structure of an ultrasonic fingerprint sensing chip and improve the quality of fingerprint recognition, the present invention provides a method for manufacturing an ultrasonic fingerprint sensing chip, and also provides an ultrasonic fingerprint sensing chip and an electronic device with a fingerprint recognition function.

[0007] In one aspect, the present invention provides a method for manufacturing an ultrasonic fingerprint sensing chip, wherein the ultrasonic fingerprint sensing chip comprises a substrate and a plurality of fingerprint sensing units disposed on the substrate, wherein the fingerprint sensing units comprise an excitation structure and a closed cavity disposed between the substrate and the excitation structure; the manufacturing method comprises:

[0008] Step S1: using a first substrate, forming a plurality of excitation structures of the fingerprint sensing unit on the first substrate, wherein the excitation structures include an elastic layer, a first electrode, a piezoelectric layer, and a second electrode sequentially formed on the first substrate;

[0009] Step S2: forming a cavity dielectric layer on the excitation structure or the substrate, and forming cavities corresponding to the fingerprint sensing units in the cavity dielectric layer;

[0010] Step S3: snapping the surface of the first substrate having the excitation structure formed thereon with the substrate to form a closed cavity of the fingerprint sensing unit;

[0011] Step S4: removing the first substrate;

[0012] Step S5: forming an electrical connection structure of the fingerprint sensing unit, wherein the electrical connection structure respectively leads the first electrode and the second electrode in the excitation structure to the surface of the fingerprint sensing unit.

[0013] Optionally, in step S2, before forming the cavity dielectric layer on the excitation structure, a support layer located in the cavity region is first formed, and the cavity dielectric layer covers the support layer.

[0014] Optionally, step S2 includes:

[0015] forming a cavity in the cavity dielectric layer and exposing the support layer; and removing the support layer.

[0016] Optionally, in step S2, before forming the cavity dielectric layer on the excitation structure or the substrate, a cavity defining layer is formed on the excitation structure, wherein the cavity defining layer defines the range of the cavity.

[0017] Optionally, a CMOS control circuit is formed on the substrate, and the CMOS control circuit has a first contact pad and a second contact pad corresponding to each of the fingerprint sensing units; the electrical connection structure electrically connects the first electrode and the second electrode in the excitation structure to the first contact pad and the second contact pad respectively.

[0018] In one aspect, the present invention provides an ultrasonic fingerprint sensing chip, the ultrasonic fingerprint sensing chip comprising a substrate and a plurality of fingerprint sensing units disposed on the substrate, the fingerprint sensing units comprising:

[0019] A cavity dielectric layer, disposed on the substrate, wherein cavities corresponding to the fingerprint sensing units are formed in the cavity dielectric layer;

[0020] an excitation structure, arranged on the cavity dielectric layer, the excitation structure covers the cavity to form a closed cavity, the excitation structure comprises a second electrode, a piezoelectric layer, a first electrode and an elastic layer arranged in sequence on the closed cavity;

[0021] An electrical connection structure, wherein the electrical connection structure respectively leads the first electrode and the second electrode in the excitation structure to the surface of the fingerprint sensing unit.

[0022] In one aspect, the present invention provides an ultrasonic fingerprint sensing chip, the ultrasonic fingerprint sensing chip comprising a CMOS control circuit and a fingerprint sensing unit disposed on the CMOS control circuit, the CMOS control circuit comprising a plurality of first contact pads and a plurality of second contact pads arranged in an array, the fingerprint sensing unit comprising:

[0023] A cavity dielectric layer, disposed on the CMOS control circuit, wherein cavities corresponding to the fingerprint sensing units are formed in the cavity dielectric layer;

[0024] an excitation structure, arranged on the cavity dielectric layer, the excitation structure sealing the cavity to form a closed cavity, the excitation structure comprising a second electrode, a piezoelectric layer, a first electrode and an elastic layer arranged in sequence on the closed cavity;

[0025] an electrical connection structure, wherein the electrical connection structure electrically connects a first electrode in the excitation structure with a first contact pad in the CMOS control circuit corresponding to the first electrode, and electrically connects a second electrode in the excitation structure with a second contact pad in the CMOS control circuit corresponding to the second electrode;

[0026] The CMOS control circuit provides power control for excitation and / or reception to the corresponding fingerprint sensing unit through the first contact pad and the second contact pad.

[0027] Optionally, the fingerprint sensing unit further includes a cavity defining layer, wherein the cavity defining layer is embedded in the cavity medium layer on the side of the enclosed cavity and faces the enclosed cavity.

[0028] On the one hand, the present invention provides an electronic device with a fingerprint recognition function, characterized in that the electronic device has an ultrasonic fingerprint sensing area, and the ultrasonic fingerprint sensing area is provided with the above-mentioned ultrasonic fingerprint sensing chip.

[0029] By using the method for manufacturing an ultrasonic fingerprint sensing chip provided by the present invention, an excitation structure of a fingerprint sensing unit is formed on a first substrate, and a corresponding cavity is formed on the excitation structure or on another substrate (the substrate retained by the final chip), and then the two substrates are buckled together to form a closed cavity of the fingerprint sensing unit. After removing the first substrate, an electrical connection structure is formed to lead the first electrode and the second electrode in the excitation structure to the surface. The ultrasonic fingerprint sensing chip formed includes a plurality of fingerprint sensing units obtained by the method for fingerprint recognition, and each fingerprint sensing unit has a compact structure, which helps to improve the design density of the fingerprint sensing unit and the fingerprint recognition performance. The ultrasonic fingerprint sensing chip and the electronic device with fingerprint recognition function provided by the present invention have similar advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart of a method for manufacturing an ultrasonic fingerprint sensing chip according to an embodiment of the present invention.

[0031] FIG. 2A to FIG. 2N It is a schematic cross-sectional structure diagram of a method for manufacturing an ultrasonic fingerprint sensing chip according to Embodiment 1 of the present invention during the manufacturing process.

[0032] FIG. 3A to FIG. 3D It is a schematic cross-sectional structure diagram of a method for manufacturing an ultrasonic fingerprint sensing chip according to a second embodiment of the present invention during the manufacturing process.

[0033] FIG. 4A to FIG. 4E It is a schematic diagram of the cross-sectional structure of the manufacturing method of the ultrasonic fingerprint sensing chip in the manufacturing process of the third embodiment of the present invention.

[0034] FIG. 5A to FIG. 5C It is a schematic diagram of the cross-sectional structure of the manufacturing method of the ultrasonic fingerprint sensing chip in the manufacturing process of the fourth embodiment of the present invention.

[0035] 6A to 6H It is a schematic diagram of the cross-sectional structure of the manufacturing method of the ultrasonic fingerprint sensing chip in the manufacturing process of the fifth embodiment of the present invention.

[0036] Figure 7 FIG. 4 is a plan view of an ultrasonic fingerprint sensing chip according to an embodiment of the present invention.

[0037] Description of reference numerals:

[0038] 100-first substrate; 110-elastic layer; 120-first electrode; 121-first electrode body; 122-first electrode rib; 130-piezoelectric layer; 140-second electrode; 141-second electrode body; 142-second electrode rib; 10-excitation structure; 101-seed layer; 102-first electrode material layer; 103-second electrode material layer; 104-first protective layer; 105-cavity dielectric layer; 106-support layer; 107-cavity limiting layer;

[0039] 200 - second substrate; 210 - first contact pad; 220 - second contact pad; 230 - third contact pad; 201 - second protective layer; 31 - first connecting electrode; 32 - second connecting electrode; 33 - third connecting electrode; 202 - third protective layer;

[0040] 210a, 220a - first etched holes; 210b, 220b - second etched holes; 210c - first connecting hole; 220c - second connecting hole; 230c - third connecting hole; 105a - cavity; 103a - first hollow hole; 103b - second hollow hole; 20 - closed cavity. DETAILED DESCRIPTION

[0041] The ultrasonic fingerprint sensing chip of the present invention, its manufacturing method, and electronic device are further described in detail below in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be understood that the drawings in the specification are all in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. For the sake of clarity, in all the drawings used to assist in explaining the embodiments of the present invention, the same components are marked with the same reference numerals in principle, and repeated descriptions thereof are omitted. For the sake of clarity, some of the drawings do not repeat the markings for structures that have been marked in other drawings. In the case where the method described herein includes a series of steps, the order of the steps presented herein is not the only order in which the steps can be performed, and some of the steps described may be omitted and / or some other steps not described herein may be added to the method.

[0042] When making an ultrasonic fingerprint sensing chip that uses ultrasonic fingerprint recognition technology, it is necessary to make a MEMS cavity and an excitation structure located on the MEMS cavity. By using the inverse piezoelectric effect of piezoelectric materials, a voltage of a certain frequency is applied to the bottom electrode and the top electrode located on the upper and lower surfaces of the piezoelectric film in the excitation structure, and the piezoelectric film will vibrate and generate ultrasonic waves. The ultrasonic wave propagates in the medium and encounters the finger to be identified. Because the acoustic impedance of the valley and ridge of the finger is different, at least one of the amplitude, phase and frequency of the reflected sound wave signal is different, which is manifested in that the reflected sound wave signal will cause vibrations with different vibration characteristics when it is transmitted to the surface of the piezoelectric film, and accordingly different electrical signals can be collected. Fingerprint information can be collected by analyzing the electrical signals.

[0043] Figure 1 FIG. 1 is a flow chart of a method for manufacturing an ultrasonic fingerprint sensing chip according to an embodiment of the present invention. Figure 1 In one embodiment, the ultrasonic fingerprint sensing chip to be manufactured includes a substrate and a plurality of fingerprint sensing units disposed on the substrate, wherein the fingerprint sensing units include an excitation structure and a closed cavity disposed between the substrate and the excitation structure. The substrate is represented by a second substrate 200 in the following text and the accompanying drawings.

[0044] The method for manufacturing the ultrasonic fingerprint sensing chip comprises the following steps:

[0045] Step S1, using a first substrate, forming a plurality of excitation structures of the fingerprint sensing unit on the first substrate, wherein the excitation structures include an elastic layer, a first electrode, a piezoelectric layer, and a second electrode sequentially formed on the first substrate;

[0046] Step S2, forming a cavity dielectric layer on the excitation structure or the substrate, and forming cavities corresponding to the fingerprint sensing units in the cavity dielectric layer;

[0047] Step S3, fastening the surface of the first substrate on which the excitation structure is formed with the substrate to form a closed cavity of the fingerprint sensing unit;

[0048] Step S4, removing the first substrate;

[0049] Step S5, forming an electrical connection structure of the fingerprint sensing unit, wherein the electrical connection structure respectively leads the first electrode and the second electrode in the excitation structure to the surface of the fingerprint sensing unit.

[0050] In the above-mentioned manufacturing method, the excitation structure of the fingerprint sensing unit is manufactured using the first substrate, and the cavity dielectric layer is used to form a cavity on the excitation structure or the substrate on which the fingerprint sensing unit is finally set, and then the side of the first substrate formed with the excitation structure is buckled with the substrate to form a closed cavity of the fingerprint sensing unit. After removing the first substrate, an electrical connection structure is manufactured to lead the first electrode and the second electrode in the excitation structure to the surface of the fingerprint sensing unit, so as to facilitate the provision of excitation to the fingerprint sensing unit or receive fingerprint sensing signals to achieve the purpose of fingerprint identification. The ultrasonic fingerprint sensing chip formed by this manufacturing method avoids the problem of causing a relatively large stress effect on the CMOS control circuit when each fingerprint sensing unit is directly formed on the CMOS control circuit; at the same time, it can avoid the problem that when the cavity is made, if the sacrificial layer material is used to fill the cavity, and then a release hole is made to release the sacrificial layer material to form the fingerprint sensing unit cavity, it is easy to have residual sacrificial layer material in the final formed cavities of several fingerprint sensing units, resulting in the performance or yield of the ultrasonic fingerprint sensing chip being affected.

[0051] The ultrasonic fingerprint sensing chip of the present invention, its manufacturing method, and electronic device are further described in detail below in conjunction with the accompanying drawings and multiple specific embodiments. It should be understood that each embodiment is only an exemplary specific implementation method for manufacturing and applying the embodiments, and does not constitute a scope limitation when manufacturing and applying the present invention. In addition, the description of multiple embodiments is only to more clearly explain the connotation of the present invention, but the technical features in each embodiment are not unique to the embodiment. In the absence of conflict, all the features of each embodiment can also be used as the features of a general embodiment. In some embodiments, the technical features in the following multiple embodiments can also be interrelated and inspired to form new embodiments.

[0052] Embodiment 1

[0053] FIG. 2A to FIG. 2N FIG. 1 is a schematic diagram of a cross-sectional structure of a method for manufacturing an ultrasonic fingerprint sensing chip according to Embodiment 1 of the present invention during the manufacturing process. Figure 1 and FIG. 2A to FIG. 2N , a method for manufacturing an ultrasonic fingerprint sensing chip according to the first embodiment of the present invention is described.

[0054] See also Figure 2D The manufacturing method of the ultrasonic fingerprint sensing chip of this embodiment includes step S1, providing a first substrate 100, forming an excitation structure 10 of a plurality of fingerprint sensing units on the first substrate 100, and the excitation structure 10 includes an elastic layer 110, a first electrode 120, a piezoelectric layer 130 and a second electrode 140 formed in sequence on the first substrate 100.

[0055] The material of the first substrate 100 can be any suitable substrate known to those skilled in the art, for example, it can be at least one of the following materials: silicon (Si), germanium (Ge), silicon germanium (SiGe), carbon silicon (SiC), carbon germanium silicon (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP) or other III, V group compound semiconductors, and can also include a multilayer structure composed of these semiconductor materials, etc. The first substrate 100 can be silicon on insulator (SOI), stacked silicon on insulator (SSOI), stacked silicon germanium on insulator (S-SiGeOI), silicon germanium on insulator (SiGeOI) and germanium on insulator (GeOI), or can also be double-sided polished silicon wafers (Double Side Polished Wafers, DSP), or can also be a ceramic substrate made of alumina, quartz or glass substrate, etc. In this embodiment, the first substrate 100 is, for example, a single crystal silicon wafer.

[0056] The surface of the first substrate 100 may be provided with an ultrasonic fingerprint sensing area for providing a plurality of fingerprint sensing units (or fingerprint recognition pixels). The size and shape of the ultrasonic fingerprint sensing area may be determined according to the design of the ultrasonic fingerprint sensing chip to be manufactured. Figures 2A to 2G Only a part of the first substrate 100 is shown). In this embodiment, a plurality of fingerprint sensing units distributed in an array are to be arranged within the range of the ultrasonic fingerprint sensing area, so the ultrasonic fingerprint sensing area includes a plurality of unit areas for setting fingerprint sensing units distributed in an array. As an example, the ultrasonic fingerprint sensing area includes a total of 6400 unit areas arranged in 80 rows and 80 columns, or the ultrasonic fingerprint sensing area includes a total of 10000 unit areas arranged in 100 rows and 100 columns. Each unit area includes a cavity area and an isolation area outside the cavity area. The size of each unit area is about 60μm×60μm.

[0057] It should be noted that, although the formation of the ultrasonic fingerprint sensing chip is mainly described below with reference to the ultrasonic fingerprint sensing area, in the area outside the ultrasonic fingerprint sensing area of ​​the first substrate 100, a corresponding structure can be manufactured according to the design of the peripheral area of ​​the ultrasonic fingerprint sensing chip. In the manufacturing process described below, the processes of the ultrasonic fingerprint sensing area and the peripheral area can be carried out simultaneously, and some of the following material layers can continuously cover the ultrasonic fingerprint sensing area and the peripheral area.

[0058] The method of forming the excitation structure of the fingerprint sensing unit in step S1 is described in detail below.

[0059] First, see Figure 2A, an elastic layer 110 and a first electrode material layer 102 are sequentially stacked on the upper surface of the first substrate. The elastic layer 110 has a stress regulating effect during the transmission of ultrasound. The elastic layer 110 may include silicon, silicon dioxide, silicon nitride, etc. In this embodiment, the elastic layer 110 is, for example, a layer of silicon dioxide with a thickness of about 500nm to 10μm. More specifically, the elastic layer 110 is about 1.5μm to 4μm. Optionally, before depositing the first electrode material layer, a seed layer 101 may be deposited on the elastic layer 110. The seed layer 101 is used to improve the adhesion of the piezoelectric layer subsequently formed thereon. In this embodiment, the seed layer 101 and the subsequent piezoelectric layer above are both aluminum nitride (AlN). In another embodiment, the seed layer and the piezoelectric layer may also be made of other materials.

[0060] The first electrode material layer 102 is deposited on the seed layer 101, and its material may include platinum (Pt), gold (Au), molybdenum (Mo), aluminum (Al), copper (Cu), tungsten (W), tantalum (Ta), platinum (Pt), ruthenium (Ru), rhodium (Rh), iridium (Ir), chromium (Cr), titanium (Ti), silver (Ag), osmium (Os), rhenium (Re), palladium (Pd), tin (Sn) and other metals or their alloys. In this embodiment, the first electrode material layer 102 is, for example, molybdenum. The thickness of the first electrode material layer 102 is about 50nm to 1μm, more specifically, about 100nm to 300nm. The first electrode material layer 102 is used to form an electrode of the excitation structure.

[0061] See also Figure 2B Then, the first electrode material layer 102 is etched to form a first electrode 120. The first electrode 120 includes a cavity region ( Figure 2B The first electrode body 121 is a first electrode body 121 in the cavity and a first electrode rib 122 extending from the cavity to the outside of the cavity. The first electrode body 121 is subsequently suspended in the cavity in the fingerprint sensing unit and vibrates with the vibration of the piezoelectric layer. The first electrode rib 122 is electrically connected to the first electrode body 121, and an electrical signal can be transmitted through the first electrode rib 122. When etching the first electrode material layer 102, the seed layer 101 below is also etched, so that part of the elastic layer 110 is exposed.

[0062] See also Figure 2C, then, a piezoelectric layer 130 and a second electrode material layer 103 are sequentially stacked on the first electrode material layer 102. The piezoelectric layer 130 covers the first electrode 120 and the elastic layer 110 (directly covering the exposed part of the elastic layer of the patterned first electrode material layer 102 and indirectly covering the elastic layer part under the first electrode 120). The piezoelectric layer 130 may include at least one of piezoelectric materials such as aluminum nitride (AlN), scandium-doped aluminum nitride (Sc x Al 1-x N, 0 < x < 1), quartz, zinc oxide (ZnO), lead zirconate titanate (PZT) and doped PZT (such as PLZT, PNZT, PMN-PT), lithium niobate oxide (LiNbO3), lithium tantalate oxide (LiTaO3), KNN, and polyvinylidene fluoride (PVDF). The material of the second electrode material layer 103 may include at least one of metals such as platinum (Pt), gold (Au), molybdenum (Mo), molybdenum (Mo), aluminum (Al), copper (Cu), tungsten (W), tantalum (Ta), platinum (Pt), ruthenium (Ru), rhodium (Rh), iridium (Ir), chromium (Cr), titanium (Ti), silver (Ag), osmium (Os), rhenium (Re), palladium (Pd), tin (Sn), or their alloys. In this embodiment, for example, it is molybdenum. The second electrode material layer 103 is used to form another electrode of the excitation structure, and its thickness is about 50 nm to 1 μm, more specifically, about 100 nm to 300 nm.

[0063] Optionally, after depositing the second electrode material layer 103 and before patterning it, a protective material, denoted as the first protective layer 104, may be deposited on the second electrode material layer 103 to protect the second electrode material layer 103 and the overall excitation structure. The material of the first protective layer 104 may include one or a combination of aluminum nitride, undoped silicon, silicon dioxide, silicon nitride, and silicon oxynitride. The thickness of the first protective layer 104 is about 10 nm to 1 μm, more specifically, about 50 nm to 300 nm.

[0064] Refer to Figure 2D , then, the second electrode material layer 103 is etched to form a second electrode 140, and the second electrode 140 includes a portion located within the cavity range ( Figure 2DIn the present embodiment, the first protective layer 104 can be first etched using the same mask pattern, and then the second electrode material layer 103 can be etched downward to form the second electrode 140. The second electrode body 141 located in the cavity range is subsequently suspended on the cavity in the fingerprint sensing unit and vibrates with the vibration of the piezoelectric layer 130. The second electrode rib 142 is electrically connected to the second electrode body 141, and electrical signals can be transmitted through the second electrode rib 142.

[0065] After the above steps, the excitation structures 10 of several fingerprint sensing units are formed on the first substrate 100. The excitation structure 10 is used in the ultrasonic fingerprint sensing chip to emit ultrasonic waves and detect the ultrasonic waves reflected by the finger to form an electrical signal. The excitation structure 10 includes an elastic layer 110, a first electrode 120, a piezoelectric layer 130 and a second electrode 140 formed in sequence on the first substrate 100. The elastic layer 110 covers the upper surface of the first substrate 100, the first electrode 120 is located on the elastic layer 110 and the elastic layer 110 is exposed, the piezoelectric layer 130 covers the first electrode 120 and the elastic layer 110, and the second electrode 140 is located on the piezoelectric layer 130 and the piezoelectric layer 130 is exposed. In this embodiment, for each unit area of ​​the ultrasonic fingerprint sensing area used to set the fingerprint sensing unit, at least one excitation structure 10 can be formed, and the specific number and position of the excitation structure 10 correspond to the number and position of the cavity to be formed in the same unit area.

[0066] The sizes of the first electrode 120 and the second electrode 140 can be determined according to the design of the excitation structure in the fingerprint sensing unit. In this embodiment, the first electrode body 121 and the second electrode body 141 overlap each other in the cavity range, and the extension directions of the first electrode rib 122 and the second electrode rib 142 form an angle. Figure 7 The small figure in FIG. 1 illustrates the planar shape of the excitation structure in one embodiment of the present invention. Figure 7In one embodiment, the first electrode body 121 and the second electrode body 141 are located within the cavity range, and are both designed to be circular (the cavity range is also circular), and the first electrode rib 122 and the second electrode rib 142 extend from the cavity range to outside the cavity range in different directions. The present invention is not limited to this. In one embodiment, in the ultrasonic fingerprint sensing area, the shape of the cavity set corresponding to each unit area (the cross section parallel to the upper surface of the first substrate) can be a circle, an ellipse, a polygon, or a closed shape surrounded by an arc and a straight line. The size of the first electrode body and the second electrode body set within the cavity range is smaller than the size of the cavity, and the shape of the first electrode body and the second electrode body can be the same as or different from the shape of the cavity. In one embodiment, for a square unit area, the cavity inside it can be circular. At this time, the first electrode rib 122 and the second electrode rib 142 can extend toward the two corners of the unit area respectively to obtain a larger processing area of ​​the electrical connection structure.

[0067] Furthermore, in this embodiment, in the ultrasonic fingerprint sensing chip to be manufactured, a CMOS control circuit is formed on a substrate on which a plurality of fingerprint sensing units are arranged, and the CMOS control circuit has a group of contact pads corresponding to each of the fingerprint sensing units, wherein the first electrode 120 is subsequently electrically connected to a corresponding contact pad on the substrate through the first electrode rib 122, and the second electrode 140 is subsequently electrically connected to another contact pad on the substrate through the second electrode rib 142, and the two contact pads are used to provide excitation and / or receive power control for the corresponding fingerprint sensing unit. Therefore, the first electrode rib 122 can be designed to extend from the first electrode body 121 to a region corresponding to the first contact pad, and the second electrode rib 142 can be designed to extend from the second electrode body 141 to a region corresponding to the second contact pad.

[0068] After forming the above-mentioned excitation structure 10, the step S2 of the method for manufacturing the ultrasonic fingerprint sensing chip is then performed. Figure 2E and Figure 2F In step S2 , in this embodiment, a cavity dielectric layer 105 is formed on the excitation structure 10 located on the first substrate 100 , and cavities 105 a corresponding to the fingerprint sensing units are formed in the cavity dielectric layer 105 .

[0069] Specifically, the cavity dielectric layer 105 covers the second electrode 140 and the piezoelectric layer 130. When forming the cavity 105a, the cavity dielectric layer 105 is etched corresponding to the range of the cavity to form an opening penetrating therein along the thickness direction, and the opening serves as the cavity 105a corresponding to the fingerprint sensing unit one by one.

[0070] The material of the cavity dielectric layer 105 may include inorganic materials such as undoped silicon, silicon dioxide, silicon nitride, etc., and may also include organic materials such as polyimide, epoxy resin, polyurethane, vinyl ester, phenolic resin, acrylic resin, etc. The upper surface of the cavity dielectric layer 105 is used to snap together with the substrate on which the fingerprint sensing unit is subsequently arranged, and therefore is preferably flat. In addition, a suitable etching process can be selected according to the material of the cavity dielectric layer 105 to form an opening passing through it, and the cavity shape that meets the design requirements can be obtained by adjusting the process parameters. In the preferred embodiment, the longitudinal section of the opening formed in the cavity dielectric layer 105 is as follows: Figure 2F The trapezoid shown, that is, the angle between the side surface of the cavity dielectric layer 105 in the opening and the upper surface of the first substrate 100 is less than 90°, and its technical effect is that when the first substrate 100 is inverted onto another substrate and the cavity 105a is closed, the cavity 105a is transformed into an inverted trapezoid, and the pressure resistance is better.

[0071] After the excitation structure 10 and the cavity 105a are formed on the first substrate 100, step S3 of the method for manufacturing the ultrasonic fingerprint sensor chip is then performed. Figure 2G In step S3, the first substrate 100 having the excitation structure 10 formed thereon is buckled with the substrate on which the fingerprint sensing unit is subsequently disposed to form a sealed cavity 20 of the fingerprint sensing unit. For simplicity, the substrate on which the fingerprint sensing unit is subsequently disposed in the chip is referred to as the second substrate 200.

[0072] For details, see Figure 2G The second substrate 200 is used to bond with the first substrate 100. The second substrate 200 has an ultrasonic fingerprint sensing area that matches the ultrasonic fingerprint sensing area on the first substrate 100. Optionally, the second substrate 200 has a CMOS control circuit that matches the unit area design on the first substrate 100 formed in the ultrasonic fingerprint sensing area thereon. The CMOS control circuit is electrically connected to the first electrode 120 and the second electrode 140 in the above-mentioned excitation structure 10, and the transducer feedback signal transmitted by the excitation structure 10 can be received during fingerprint recognition. In this embodiment, the second substrate 200 has an internal circuit and a first contact pad 210 and a second contact pad 220 connected to the internal circuit formed in each unit area of ​​the ultrasonic fingerprint sensing area. The first contact pad 210 and the second contact pad 220 correspond to the above-mentioned several excitation structures 10 one by one. The material of the first contact pad 210 and the second contact pad 220 is, for example, aluminum or copper. In addition, a protective material can be formed on the second substrate 200, which is recorded as a second protective layer 201. The second protective layer 201 is, for example, silicon oxide.

[0073] When the first substrate 100 and the second substrate 200 are buckled together, a bonding process can be used to fix them. Figure 2GThe first substrate 100 and the second substrate 200 can be bonded by fusing bonding, vacuum bonding or bonding. For example, the first substrate 100 and the second substrate 200 can be bonded by die attach film (DAF) or dry film. When buckling, the first substrate 100 and the second substrate 200 are first aligned, specifically aligning the ultrasonic fingerprint sensing area on the first substrate 100 with the ultrasonic fingerprint sensing area on the second substrate 200, wherein the excitation structure 10 formed in each unit area on the first substrate 100 is opposite to the unit area having a group of first contact pads 210 and second contact pads 220 on the second substrate 200. After buckling, the cavity 105a formed on the first substrate 100 is sealed to form a closed cavity 20.

[0074] See also Figure 2H After the first substrate 100 and the second substrate 200 are buckled together, the step S4 of the method for manufacturing the ultrasonic fingerprint sensing chip is then performed to remove the first substrate 100. Specifically, the first substrate 100 can be removed by various public thinning processes (such as etching and chemical mechanical polishing). During the removal process, the thickness of the elastic layer 110 may be reduced. As an example, the thickness of the elastic layer 110 is retained to be about 1 μm to 6 μm.

[0075] After removing the first substrate 100, step S5 of the method for manufacturing the ultrasonic fingerprint sensing chip is then performed to form an electrical connection structure of the fingerprint sensing unit, which respectively leads the first electrode 120 and the second electrode 140 in the excitation structure 10 to the surface of the fingerprint sensing unit (here, the surface obtained after removing the first substrate 100).

[0076] Furthermore, in this embodiment, a CMOS control circuit is disposed on the second substrate 200, and the CMOS control circuit has a first contact pad 210 and a second contact pad 220 corresponding to each of the fingerprint sensing units. The electrical connection structure manufactured in step S5 electrically connects the first electrode 120 and the second electrode 140 in the excitation structure 10 with the first contact pad 210 and the second contact pad 220, respectively.

[0077] Specifically, the electrical connection structure includes a first connection electrode and a second connection electrode, the first connection electrode electrically connects the first electrode 120 and the first contact pad 210, and the second connection electrode electrically connects the second electrode 140 and the second contact pad 220. The method of forming the electrical connection structure is described in detail below.

[0078] See also Figure 2DIn this embodiment, in the process of etching the first electrode material layer 102 to form the first electrode 120, step S1 allows the first electrode material layer 102 to retain a portion that is opposite to the second contact pad 220 when it is subsequently buckled with the second substrate 200, and in the process of etching the second electrode material layer 103 to form the second electrode 140, allows the second electrode material layer 103 to retain a portion that is opposite to the first contact pad 210 when it is subsequently buckled with the second substrate 200. The purpose is that when etching is simultaneously performed in the excitation structure 10 corresponding to the first contact pad 210 and the second contact pad 220 to facilitate the formation of a via hole (or a connecting electrode), the materials to be etched in the two etching areas in the same unit area are close, so the etching difficulty is close, which is conducive to forming a via hole (or a connecting electrode) with the same size. Specifically, the production of the electrical connection structure may include the following process:

[0079] First, see Fig.2I , with the second substrate 200 as support, a first hole etching process is performed to remove the elastic layer 110 and the seed layer 101 in the corresponding area, and a first etching hole (such as Fig.2I A first etching hole 210a on the left and a first etching hole 220a on the right), wherein the first etching hole exposes the first electrode material layer 102 (the first electrode material layer 102 may be used as an etching stop layer);

[0080] Next, see Figure 2J , perform a second hole etching process, etch downward from the first etching hole, remove the first electrode material layer 102 and the piezoelectric layer 130 in the corresponding area, and obtain a second etching hole (such as Figure 2J The second etching hole 210b on the left and the second etching hole 220b on the right), the second etching hole 200b extends downward from the elastic layer 130 and exposes the second electrode material layer 103 (the second electrode material layer 103 can be used as an etching stop layer);

[0081] Next, see Figure 2K , performing a third hole etching process, etching downward from the second etching hole 200b, removing the second electrode material layer 103, the first protection layer 104, the connecting layer 300 and the second protection layer 201 in the corresponding area, and obtaining a first connecting hole 210c and a second connecting hole 220c corresponding to the first contact pad 210 and the second contact pad 220, respectively, wherein the first connecting hole 210c and the second connecting hole 220c extend downward from the elastic layer 130 and expose the first contact pad 210 and the second contact pad 220, respectively;

[0082] Then, see Figure 2LConductive material is deposited in the first connecting hole 210c and the second connecting hole 220c to obtain a first connecting electrode 31 electrically connecting the first contact pad 210 and the first electrode rib 122 and a second connecting electrode 32 electrically connecting the second contact pad 220 and the second electrode rib 142 respectively.

[0083] The above-mentioned first hole etching process, second hole etching process and third hole etching process are all carried out outside the cavity range. These three drilling processes can be carried out directly above the first contact pad 210 and the second contact pad 220, so that the area ratio of the unit area occupied by the first connection electrode 31 and the second connection electrode 32 is as small as possible, that is, the cavity range can be designed to be larger, which helps to improve the fingerprint sensing performance. Specifically, in the first hole etching process, a portion of the first electrode rib 122 located above the first contact pad 210 (for example, the end of the first electrode rib 122 away from the first electrode body 121) is exposed, and a portion of the first electrode material layer 102 retained above the second contact pad 220 when the fingerprint sensing unit 10 is formed is exposed; in the second hole etching process, a portion of the second electrode material layer 103 retained above the first contact pad 210 when the fingerprint sensing unit 10 is formed is exposed, and a portion of the second electrode rib 142 located above the second contact pad 220 (for example, the end of the second electrode rib 142 away from the second electrode body 141); in the third hole etching process, the second electrode material layer 103, the first protective layer 104, the connecting layer 300 and the second protective layer 201 located above the first contact pad 210 and the second contact pad 220 are removed, so that the first contact pad 210 and the second contact pad 220 are exposed. Here, "exposed" also includes the situation where a portion of the thickness is reduced due to etching.

[0084] In a preferred embodiment, the opening range of the second hole etching process is smaller than that of the first hole etching process. Thus, after etching downward from the first etching hole to form the second etching hole, part of the upper surface of the first conductive material layer 102 exposed by the first etching hole is still retained in the second etching hole. Preferably, the etching conditions can be set (such as adjusting the opening size on the mask) so that the opening range of the third hole etching process is smaller than that of the second hole etching process. Thus, after etching downward from the second etching hole to obtain the first connecting hole 210c and the second connecting hole 220c, part of the upper surface of the first conductive material layer 102 exposed by the first hole etching process and part of the upper surface of the second conductive material layer 103 exposed by the second hole etching process are still retained.

[0085] Furthermore, since a portion of the upper surface of the first electrode 120 (specifically, a portion of the upper surface of the first electrode rib 122) is exposed in the first connecting hole 210c, and a portion of the upper surface of the second electrode 140 (specifically, a portion of the upper surface of the second electrode rib 142) is exposed in the second connecting hole 220c, when the conductive material is deposited on the inner surfaces of the first connecting hole 210c and the second connecting hole 220c, the conductive material not only covers the inner surfaces of the first connecting hole 210c and the second connecting hole 220c, but also covers a portion of the upper surface of the first electrode rib 122 and a portion of the upper surface of the second electrode rib 142. In this way, the contact area between the conductive material and the first electrode rib 122 and the second electrode rib 142 can be increased, thereby avoiding excessive impedance of the first connecting electrode 31 and the second connecting electrode 32 and connection failure.

[0086] The conductive material deposited in the first connecting hole 210c and the second connecting hole 220c may include one or more metals of metal materials such as copper, nickel, zinc, tin, silver, gold, tungsten and magnesium, or an alloy including elements such as copper, nickel, zinc, tin, silver, gold, tungsten and magnesium. The conductive material may be deposited by a process such as physical vapor deposition. Since the electroplating and chemical plating processes have a good hole filling effect, the conductive material may also be deposited by an electroplating process or a chemical plating process. In this embodiment, the material of the first connecting electrode 31 and the second connecting electrode 32 is, for example, aluminum. In the process of depositing the conductive material, the conductive material may also cover the outside of the first connecting hole 210c and the second connecting hole 220c. The conductive material covering the outside of the first connecting hole 210c and the second connecting hole 220c may be patterned by etching or chemical mechanical polishing to prevent the first contact pad 210 and the second contact pad 220 from being connected through the conductive material outside the connecting hole, and also to prevent adjacent fingerprint sensing units from being connected through the conductive material outside the connecting hole.

[0087] The electrical connection structure of this embodiment includes the first connection electrode 31 and the second connection electrode 32. After forming the electrical connection structure, this embodiment may further include a step of forming a protective layer. For details, see Figure 2M , a third protective layer 202 is formed on the second substrate 200 , and the third protective layer 202 covers the first connecting electrode 31 , the second connecting electrode 32 and the surface of the elastic layer 110 .

[0088] In addition, on the second substrate 200 in the embodiment of the present invention, in addition to the ultrasonic fingerprint sensing area for fingerprint identification, a pin area and a signal processing area located outside the ultrasonic fingerprint sensing area can also be formed, the pin area is used to set the pins connected to the external circuit for signal input / output, and the signal processing area is used to set the signal processing circuit, the signal processing circuit is connected to the internal circuit of the ultrasonic fingerprint sensing area, and can be used to pre-process the signal to be input into the internal circuit, and to perform subsequent processing on the feedback electrical signal received by the internal circuit. The first substrate 100 can also have a peripheral area corresponding to the pin area and signal processing area of ​​the second substrate 200. Therefore, after the first substrate 100 and the second substrate 200 are buckled together, the signal processing area and the pin area on the second substrate 200 can also be covered with the elastic layer 110, the seed layer 101, the first electrode material layer 102, the piezoelectric layer 130, the second electrode material layer 103, the first protective layer 104 and the third protective layer 202 stacked in sequence.

[0089] See also Figure 2N In this embodiment, the second substrate 200 is formed with a third contact pad 230 connected to the internal circuit in the above-mentioned pin area. In addition, in the method for manufacturing the ultrasonic fingerprint sensing chip of this embodiment, a third connecting hole 230c (which can be formed simultaneously with the above-mentioned first connecting hole 210c and the second connecting hole 220c) exposing the third contact pad 230, and a third connecting electrode 33 (which can be formed simultaneously with the first connecting electrode 31 and the second connecting electrode 32) covering the inner surface of the third connecting hole 230c can also be formed on the second substrate 200, the third connecting electrode 33 is electrically connected to the third contact pad 230, and an opening is formed in the third protective layer 202 exposing the third connecting electrode 33, and the size of the opening is set as required, such as Figure 2N As shown, in one embodiment, the third protection layer 202 in the pin area may also be completely removed.

[0090] Embodiment 2

[0091] This embodiment relates to a method for manufacturing an ultrasonic fingerprint sensing chip. The main difference between this embodiment and the first embodiment is the method for forming the cavity.

[0092] This embodiment Figure 2D The method for manufacturing the ultrasonic fingerprint sensing chip is further described based on the process after forming the second electrode shown in FIG. 1 . This embodiment may include the following steps: FIG. 2A to FIG. 2D The production process shown. FIG. 3A to FIG. 3D FIG. 1 is a schematic diagram of the cross-sectional structure of the manufacturing method of the ultrasonic fingerprint sensing chip according to the second embodiment of the present invention during the manufacturing process. FIG. 3A to FIG. 3DThe manufacturing method of the ultrasonic fingerprint sensing chip of this embodiment is described.

[0093] See also Figure 3A First, corresponding to the cavity area CA where the cavity is to be made, a support layer 106 is formed on the first substrate 100. The support layer 106 will be removed after the cavity is formed, so the support layer 106 can be made of a material with a large etching selectivity ratio with the cavity dielectric layer. For example, in one embodiment, the support layer 106 is silicon dioxide or silicon carbide.

[0094] Next, see Figure 3B , a cavity dielectric layer 105 is formed on the first substrate 100, and the cavity dielectric layer 105 covers the second electrode 120, the support layer 106 and the piezoelectric layer 130. The features of the cavity dielectric layer 105 can be found in the introduction of the first embodiment. In this embodiment, the thickness of the cavity dielectric layer 105 is greater than the thickness of the support layer 106. The upper surface of the cavity dielectric layer 105 can be processed by a planarization process (such as chemical mechanical polishing) to obtain a flat upper surface. Then, the cavity dielectric layer 105 is etched to form a cavity 105a in the cavity dielectric layer 105, and the cavity 105a exposes the support layer 106.

[0095] Next, see Figure 3C Since the support layer 106 is exposed by the cavity 105a, the cavity 105a can be used to apply an etching process to remove the support layer 106. Optionally, in the process of removing the support layer 106, the etching selectivity ratio of the support layer 106 to the cavity dielectric layer 105 is greater than 10. The high etching selectivity ratio can avoid the influence on the cavity dielectric layer when removing the support layer 106. After removing the support layer 106, the cavity 105a is enlarged.

[0096] See also Figure 3D , the side of the first substrate 100 formed with the cavity 105a is buckled with the second substrate 200. Similar to the first embodiment, the second substrate 200 may have a CMOS control circuit, and the CMOS control circuit has a first contact pad 210 and a second contact pad 220 corresponding to each fingerprint sensing unit. When buckled, the first contact pad 210 and the second contact pad 220 are opposite to the excitation structure 10 of the corresponding fingerprint sensing unit, and the cavity 105a is sealed to form a closed cavity 20. For the buckling step and the subsequent steps of removing the first substrate 100 and forming an electrical connection structure, please refer to the description of the first embodiment.

[0097] In this embodiment, a support layer 106 is provided in the cavity area, and then a cavity dielectric layer 105 and a cavity 105a are formed. The purpose is to use the support layer 106 to determine the size of the cavity (especially the portion adjacent to the excitation structure 10). On the one hand, compared with the cavity obtained by directly etching the cavity dielectric layer 105, the size has better consistency. In addition, since the area adjacent to the cavity and the excitation structure 10 is limited by the support layer 106, the influence of the alignment deviation that may be generated during the buckling on the cavity range can be reduced, which helps to improve the performance of the manufactured ultrasonic fingerprint sensing chip.

[0098] Embodiment 3

[0099] This embodiment relates to a method for manufacturing an ultrasonic fingerprint sensing chip. The main difference between this embodiment and the first and second embodiments is the method for forming the cavity.

[0100] This embodiment Figure 2D The method for manufacturing the ultrasonic fingerprint sensing chip is further described based on the process after forming the second electrode shown in FIG. FIG. 2A to FIG. 2D The production process shown. FIG. 4A to FIG. 4E FIG. 1 is a schematic diagram of the cross-sectional structure of the manufacturing method of the ultrasonic fingerprint sensing chip of the third embodiment of the present invention during the manufacturing process. FIG. 4A to FIG. 4E The manufacturing method of the ultrasonic fingerprint sensing chip of this embodiment is described.

[0101] First, see Figure 4A A cavity defining layer 107 is formed on the excitation structure 10 on the first substrate 100. The cavity defining layer 107 is arranged along the periphery of the cavity to be made, that is, the cavity defining layer 107 defines the range of the cavity. The cavity defining layer 107 can be made of a material similar to the cavity dielectric layer 105 or a material with a higher hardness than the cavity dielectric layer 105.

[0102] Next, optionally, see Figure 4B A support layer 106 is formed in the area surrounded by the cavity defining layer 107, and the upper surface of the support layer 106 is flush with the upper surface of the cavity defining layer 107. The support layer 106 may have the same or similar features as those in the second embodiment.

[0103] Next, see Figure 4C , a cavity dielectric layer 105 is formed on the first substrate 100, and the cavity dielectric layer 105 covers the second electrode 120, the cavity defining layer 107, the support layer 106, and the piezoelectric layer 130. Then, the cavity dielectric layer 105 is etched to form a cavity 105a penetrating the cavity dielectric layer 105. At this time, the bottom area of ​​the cavity 105a can be smaller than the upper surface area of ​​the support layer 106.

[0104] Next, see Figure 4D , since it is exposed by the cavity 105a, the support layer 106 can be removed by etching process using the cavity 105a, the cavity defining layer 107 is retained, and the range of the cavity 105a is further expanded. After removing the support layer 106, the remaining cavity defining layer 107 and the cavity dielectric layer 105 define the range of the cavity 105a parallel to the upper surface of the first substrate 100. Since the support layer 106 is used to fill part of the cavity depth in advance, the time for etching the cavity dielectric layer 105 in this embodiment is relatively short, which is conducive to the control of the cavity morphology.

[0105] Next, see Figure 4E , align and buckle the side of the first substrate 100 formed with the excitation structure 10 with the second substrate 200 to form a closed cavity 20 in the manufactured fingerprint sensing unit. For the buckling step and the subsequent steps of removing the first substrate 100 and forming an electrical connection structure, refer to the description of the first embodiment. The cavity defining layer 107 can be made of a material with a higher hardness, which can further improve the compressive strength of the cavity dielectric layer 105.

[0106] See also Figure 4E In this embodiment, the cavity defining layer 107 is used to define the range of the cavity to be made, so as to control the morphology of the subsequent closed cavity. During the buckling process, the cavity defining layer 107 is located on the cavity dielectric layer close to the excitation structure 10, which helps to improve the anti-deformation ability and avoid the collapse of the cavity dielectric layer 105 located at the edge of the cavity. In addition, by forming a support layer 106 in the cavity area, the influence of the alignment offset that may occur during bonding on the cavity range can be reduced, thereby helping to improve the performance of the ultrasonic fingerprint sensing chip manufactured.

[0107] Embodiment 4

[0108] This embodiment relates to a method for manufacturing an ultrasonic fingerprint sensing chip. The main difference between this embodiment and the first, second and third embodiments is the method for forming the cavity.

[0109] In this embodiment, Figure 2D The method for manufacturing the ultrasonic fingerprint sensing chip is further described based on the process after forming the second electrode shown in FIG. FIG. 2A to FIG. 2D The production process shown. FIG. 5A to FIG. 5C FIG. 1 is a schematic diagram of the cross-sectional structure of the ultrasonic fingerprint sensing chip during the manufacturing process using the manufacturing method of the fourth embodiment of the present invention. FIG. 5A to FIG. 5C The manufacturing method of the ultrasonic fingerprint sensing chip of this embodiment is described.

[0110] First, see Figure 5A A cavity defining layer 107 is formed on the first substrate 100, and the cavity defining layer 107 is arranged along the periphery of the cavity to be made. The cavity defining layer 107 defines the boundary of the cavity.

[0111] Next, see Figure 5B A second substrate 200 is provided, on which a first contact pad 210 and a second contact pad 220 are formed, and the first contact pad 210 and the second contact pad 220 may be covered with a second protective layer 201. Then, a cavity dielectric layer 105 is formed on the second substrate 200, and a cavity 105a is formed in the cavity dielectric layer 105 to penetrate therein, and the longitudinal section of the cavity 105a may be an inverted trapezoid, which is specifically determined according to the etching process. The cavity dielectric layer 105 covers the first contact pad 210 and the second contact pad 220.

[0112] Then, see Figure 5C , align and buckle the surface of the first substrate 100 formed with the cavity defining layer 107 and the surface of the second substrate 200 formed with the cavity dielectric layer 105. During the buckling process, the cavity defining layer 107 is located at the opening of the cavity 105a in the cavity dielectric layer 105, and the size of the closed cavity 20 obtained after the closed cavity 105a is defined by the cavity defining layer 107 is close to the excitation structure 10. After the first substrate 100 and the second substrate 200 are buckled, the subsequent steps of removing the first substrate 100 and forming the electrical connection structure can refer to the description of the first embodiment.

[0113] In this embodiment, a cavity defining layer 107 and a cavity dielectric layer 105 are formed on the first substrate 100 and the second substrate 200, respectively. During bonding, the cavity defining layer 107 is used to define the range of the closed cavity 20. The obtained closed cavity has good consistency, which helps to improve production efficiency.

[0114] Embodiment 5

[0115] This embodiment relates to a method for manufacturing an ultrasonic fingerprint sensing chip. The main difference between this embodiment and embodiments 1 to 4 is the method for manufacturing an electrical connection structure, and in order to provide a different manufacturing process for the electrical connection structure, different settings are used before the first substrate 100 and the second substrate 200 are fastened together. The specific description is as follows.

[0116] In this embodiment, Figure 2C The method for manufacturing the ultrasonic fingerprint sensing chip is further described based on the process after forming the second electrode material layer shown in FIG. 1 . This embodiment may also include the following steps: FIG. 2A to FIG. 2C The production process shown. 6A to 6HFIG. 1 is a schematic diagram of the cross-sectional structure of the manufacturing method of the ultrasonic fingerprint sensing chip according to the fifth embodiment of the present invention during the manufacturing process. 6A to 6H The manufacturing method of the ultrasonic fingerprint sensing chip of this embodiment is described.

[0117] First, see Fig. 6A After forming the second electrode material layer 103, the second electrode material layer 103 is etched to form the second electrode 140, and the second electrode 140 includes a second electrode body 141 and a second electrode rib 142. For the features of the second electrode body 141 and the second electrode rib 142, refer to the description of the first embodiment.

[0118] In this embodiment, during the process of forming the second electrode 140, a first hollow hole 103a and a second hollow hole 103b are respectively formed in the second electrode material layer 103 corresponding to the areas that are subsequently opposite to the first contact pad 210 and the second contact pad 220 on the second substrate 200. The excitation structure 10 formed on the first substrate 100 includes the second electrode material layer 103 having the first hollow hole 103a and the second hollow hole 103b formed therein.

[0119] Next, the cavity dielectric layer can be formed by the method described in any one of the first to fourth embodiments and the first substrate 100 and the second substrate 200 can be buckled together. Fig. 6A After the incentive structure 10 shown, see Figure 6B , a cavity dielectric layer 105 is formed on the first substrate 100 , and the cavity dielectric layer 105 covers the second electrode material layer and the exposed piezoelectric layer 130 .

[0120] Next, see Figure 6C , the cavity dielectric layer 105 is etched corresponding to the cavity area to form a cavity 105a penetrating therein along the thickness direction, and, corresponding to the positions of the hollow holes (including the first hollow holes 103a and the second hollow holes 103b) in the second electrode material layer 103, holes connecting the hollow holes are formed in the cavity dielectric layer 105, serving as the first hollow holes 103a and the second hollow holes 103b with increased depth.

[0121] Then, see Fig.6D The side of the first substrate 100 formed with the excitation structure 10 is aligned with the second substrate 200 and buckled to form a fingerprint sensing unit including the excitation structure 10 and the closed cavity 20. After buckling, the first hollow hole 103a and the second hollow hole 103b are closed.

[0122] Next, see Fig. 6E , remove the first substrate 100.

[0123] Next, make the electrical connection structure, see Fig. 6F , with the second substrate 200 as support, a first hole etching process is performed to remove the elastic layer 110 and the seed layer 101 in the corresponding area, and a first etching hole (such as Fig. 6F A first etching hole 210 a on the left and a first etching hole 220 a on the right), wherein the first etching holes expose the first electrode material layer 102 .

[0124] Next, see Figure 6G , performing a second hole etching process, penetrating the excitation structure 10 from the bottom surface of the first etching hole (if a second passivation layer 201 is provided on the second substrate, it will also be selectively removed to expose the first contact pad 210 and the second contact pad 220), so that the first etching hole is connected with the closed first hollow hole 103a and the second hollow hole 103b, thereby, corresponding to the first contact pad 210 and the second contact pad 220, respectively, the first connecting hole 210c and the second connecting hole 220c are obtained, and the first connecting hole 210c and the second connecting hole 220c extend downward from the elastic layer 110, and the first contact pad 210 and the second contact pad 220 are exposed.

[0125] Then, see Figure 6H , a conductive material is deposited on the inner surfaces of the first connecting hole 210c and the second connecting hole 220c to obtain a first connecting electrode 31 electrically connecting the first contact pad 210 and the first electrode 120 and a second connecting electrode 32 electrically connecting the second contact pad 220 and the second electrode 140, respectively. The process of obtaining the first connecting electrode 31 and the second connecting electrode 32 can refer to the description of the first embodiment. In addition, after the first connecting electrode 31 and the second connecting electrode 32 are formed, a third protective layer can be further formed on the top, and the details can refer to the description of the first embodiment.

[0126] In the present embodiment, before the first substrate 100 and the second substrate 200 are buckled together, hollow holes are formed in the second electrode material layer 103 and the cavity dielectric layer 105 in the areas corresponding to the first contact pad 210 and the second contact pad 220. After the first substrate 100 and the second substrate 200 are buckled together, only the first hole etching process and the second hole etching process need to be performed to expose the first contact pad 210 and the second contact pad 220, which can save process and help improve production efficiency.

[0127] Embodiment 6

[0128] This embodiment relates to an ultrasonic fingerprint sensing chip, which can be obtained by using the manufacturing methods described in Embodiments 1 to 6.

[0129] Figure 7 FIG. 4 is a plan view of an ultrasonic fingerprint sensing chip according to an embodiment of the present invention. 2A to 6H Can be seen as along Figure 7 Schematic diagram of the cross-sectional structure in the XY direction in the enlarged figure.

[0130] See also Figure 7 The ultrasonic fingerprint sensing chip has an ultrasonic fingerprint sensing area (or fingerprint sensing area), and a plurality of fingerprint sensing units (or fingerprint recognition pixels) arranged in an array are arranged in the ultrasonic fingerprint sensing area. Each fingerprint sensing unit has an excitation structure, a cavity dielectric layer, an electrical connection structure, and protection, etc. obtained by the method described in Embodiments 1 to 5. In addition to the ultrasonic fingerprint sensing area, the ultrasonic fingerprint sensing chip may also be provided with a pin area and a signal processing area. The pin area is used to set pins connected to an external circuit for signal input / output. The signal processing area is used to set a signal processing circuit. The signal processing circuit is connected to the internal circuit (such as a CMOS signal circuit) at each fingerprint sensing unit position, and can pre-process the signal to be input into the fingerprint sensing unit, and perform subsequent processing on the feedback electrical signal received by the fingerprint sensing unit.

[0131] Combination Figure 7 as well as 2A to 6H The ultrasonic fingerprint sensing chip in this embodiment includes a substrate ( 2A to 6H The second substrate 200 is represented by a second substrate 200 and a plurality of fingerprint sensing units disposed on the substrate, wherein the fingerprint sensing units include:

[0132] A cavity dielectric layer 105 is disposed on the substrate, and cavities 105a corresponding to the fingerprint sensing units are formed in the cavity dielectric layer 105;

[0133] The excitation structure 10 is disposed on the cavity dielectric layer 105, the excitation structure 10 covers the cavity to form a closed cavity 20, and the excitation structure 10 includes a second electrode 140, a piezoelectric layer 130, a first electrode 120 and an elastic layer 110 sequentially disposed on the closed cavity 20;

[0134] An electrical connection structure, wherein the electrical connection structure respectively leads the first electrode 120 and the second electrode 140 in the excitation structure 10 to the surface of the fingerprint sensing unit.

[0135] In addition, refer to Figure 4E and Figure 5CWhen the ultrasonic fingerprint sensing chip is manufactured by the method described in the third and fourth embodiments, the obtained fingerprint sensing unit further includes a cavity defining layer 107, and the cavity defining layer 107 is embedded in the cavity dielectric layer 105 on the side of the enclosed cavity 20 and faces the enclosed cavity 20.

[0136] Combination Figure 7 As shown in the enlarged view of the fingerprint sensing unit in FIG. 2 , the first electrode 120 may include a first electrode body 121 located within the enclosed cavity 20 and a first electrode rib 122 extending from the enclosed cavity to the outside. The second electrode 140 includes a second electrode body 141 located within the enclosed cavity 20 and a second electrode rib 142 extending from the enclosed cavity to the outside. In this embodiment, the first electrode body 121 and the second electrode body 141 overlap each other within the enclosed cavity, and the extension directions of the first electrode rib 122 and the second electrode rib 142 form an angle. The shape of the enclosed cavity 20 (a cross section parallel to the upper surface of the first substrate) may be a circle, an ellipse, a polygon, or a closed shape surrounded by an arc and a line segment.

[0137] In one embodiment, a CMOS control circuit may be formed on a substrate on which a fingerprint sensing unit is provided, and the CMOS control circuit is electrically connected to a first contact pad and a second contact pad provided on the substrate. The CMOS control circuit may be electrically connected to the fingerprint sensing unit through a group of first contact pads and second contact pads corresponding to each of the fingerprint sensing units, thereby providing power control for excitation and / or reception to each of the fingerprint sensing units.

[0138] Specifically, refer to Figure 2M and Figure 6H (Not limited to the chip structure shown in the figure), an ultrasonic fingerprint sensing chip of an embodiment includes a CMOS control circuit and a fingerprint sensing unit arranged on the CMOS control circuit, the CMOS control circuit includes a plurality of first contact pads 210 and a plurality of second contact pads 220 arranged in an array, and the fingerprint sensing unit includes:

[0139] A cavity dielectric layer 105 is disposed on the CMOS control circuit, and cavities corresponding to the fingerprint sensing units are formed in the cavity dielectric layer 105;

[0140] The excitation structure 10 is disposed on the cavity dielectric layer 105. The excitation structure 10 seals the cavity to form a closed cavity 20. The excitation structure 10 includes a second electrode 140, a piezoelectric layer 130, a first electrode 120 and an elastic layer 110 which are sequentially disposed on the closed cavity 20.

[0141] An electrical connection structure, wherein the electrical connection structure electrically connects the first electrode 120 in the excitation structure 10 and the first contact pad 210 in the CMOS control circuit corresponding to the first electrode 120, and electrically connects the second electrode 140 in the excitation structure 10 and the second contact pad 220 in the CMOS control circuit corresponding to the second electrode 140, and the CMOS control circuit provides power control for excitation and / or reception for the corresponding fingerprint sensing unit through the first contact pad 210 and the second contact pad 220.

[0142] Reference Figure 2M The ultrasonic fingerprint sensing chip may further include a third protective layer 202 , and the third protective layer 202 covers the first connecting electrode 31 , the second connecting electrode 32 and the surface of the elastic layer 110 .

[0143] In addition, see Figure 2N In the ultrasonic fingerprint sensing chip, the substrate may be provided with a third contact pad 230 in the pin region, a third connecting hole 230c and a third connecting electrode 33 covering the inner surface of the third connecting hole 230c may be formed on the third contact pad 230, and the third connecting electrode 33 is electrically connected to the third contact pad 230. In order to connect with an external circuit, an opening exposing the third connecting electrode 33 may be formed in the third protective layer 202.

[0144] The manufacture of the ultrasonic fingerprint sensing chip of the embodiment of the present invention can be implemented through standard semiconductor processes, wherein a plurality of fingerprint sensing units are arranged in the ultrasonic fingerprint sensing area for fingerprint recognition, each fingerprint sensing unit has a compact structure, and the area of ​​the isolation area between adjacent cavities is small, which is convenient for increasing the area ratio of the cavity range, helps to improve the design density of the fingerprint sensing unit, and thus helps to improve the sensitivity of fingerprint recognition.

[0145] Embodiment 7

[0146] The present invention relates to an electronic device with a fingerprint recognition function, wherein the electronic device has an ultrasonic fingerprint sensing area, the ultrasonic fingerprint sensing area is provided with the ultrasonic fingerprint sensing chip described in embodiment 6, and can be formed by the manufacturing methods described in embodiments 1 to 5.

[0147] The ultrasonic fingerprint sensing chip can be configured in any suitable electronic device with fingerprint recognition function. Such electronic devices are usually provided with an ultrasonic fingerprint sensing area for a finger to contact the ultrasonic fingerprint sensing area. Under this ultrasonic fingerprint sensing area, the ultrasonic fingerprint sensing chip described above is usually provided.

[0148] Taking a smart phone as an example, the ultrasonic fingerprint sensing chip is arranged under the display screen of the smart phone, or between the glass cover plate and the display screen on the front of the mobile phone, or on the back or side of the mobile phone, which can be selected according to the design requirements. For an electronic device equipped with the ultrasonic fingerprint sensing chip, when the user's finger touches the ultrasonic fingerprint sensing area above the ultrasonic fingerprint sensing chip, the ultrasonic wave emitted by the ultrasonic fingerprint sensing chip will be reflected after encountering the finger. Since the fingerprint has raised ridges and sunken ridges, the reflected ultrasonic wave will carry the fingerprint information of the finger; and the reflected ultrasonic wave will in turn act on the excitation structure in the ultrasonic fingerprint sensing chip, so that it generates corresponding electrical signals carrying fingerprint information. These electrical signals carrying fingerprint information are transmitted to the processing device in the smart phone (the processing device can be specific processing software, hardware or a combination of software and hardware). After obtaining the collected fingerprint information, the processing device compares and matches it with the specific fingerprint information pre-stored in the smart phone. If the collected fingerprint information is consistent with the specific fingerprint information, the identity is recognized.

[0149] When the ultrasonic fingerprint sensing chip of this embodiment is used, since the ultrasonic fingerprint sensing chip has good penetration, it is not necessary to dig holes or grooves in the display screen, which ensures the integrity of the screen and can be used with a full screen. In addition to collecting the skin texture of the finger, the ultrasonic fingerprint sensing chip can also collect the dermis texture, which has high recognition security. Compared with traditional optical fingerprint recognition chips and capacitive fingerprint recognition chips, this type of ultrasonic fingerprint sensing chip has strong resistance to external environmental influences. For example, this type of ultrasonic fingerprint sensing chip is not easily affected by humid environments and does not require an excitation light source, and has no requirements for the brightness of ambient light.

[0150] In some exemplary embodiments of the present application, the electronic device may also be a personal computer, a laptop computer, a personal digital assistant (PDA), a phone watch, a media player, a navigation device, a game console, a tablet computer, a wearable device, an anti-access electronic system, a car keyless entry electronic system or a car keyless start electronic system, etc.

[0151] Each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the method embodiment.

[0152] The above description is only a description of the preferred embodiment of the present invention, and is not any limitation on the scope of rights of the present invention. Any technical personnel in this field can make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for manufacturing an ultrasonic fingerprint sensing chip, characterized in that: The ultrasonic fingerprint sensing chip comprises a substrate and a plurality of fingerprint sensing units arranged on the substrate, wherein the fingerprint sensing unit comprises an excitation structure and a closed cavity arranged between the substrate and the excitation structure; the manufacturing method comprises: Step S1: using a first substrate, forming a plurality of excitation structures of the fingerprint sensing unit on the first substrate, wherein the excitation structures include an elastic layer, a first electrode, a piezoelectric layer, and a second electrode sequentially formed on the first substrate; Step S2: forming a cavity dielectric layer on the excitation structure or the substrate, and forming cavities corresponding to the fingerprint sensing units in the cavity dielectric layer; Step S3: snapping the surface of the first substrate having the excitation structure formed thereon with the substrate to form a closed cavity of the fingerprint sensing unit; Step S4: removing the first substrate; Step S5: forming an electrical connection structure of the fingerprint sensing unit, wherein the electrical connection structure respectively leads the first electrode and the second electrode in the excitation structure to the surface of the fingerprint sensing unit, wherein a first contact pad and a second contact pad are formed in the substrate, and the electrical connection structure comprises a first connection electrode corresponding to the first contact pad and passing through the excitation structure to connect the first electrode and the first contact pad, and further comprises a second connection electrode corresponding to the second contact pad and passing through the excitation structure to connect the second electrode and the second contact pad; In step S1, the first electrode and the retained portion of the first electrode material outside the cavity are formed by etching the first electrode material layer located on the elastic layer, and the second electrode and the retained portion of the second electrode material outside the cavity are formed by etching the second electrode material layer located on the piezoelectric layer; in step S3, after buckling, the retained portion of the first electrode material is opposite to the second contact pad, and the retained portion of the second electrode material is opposite to the first contact pad; in step S5, the first connecting electrode is connected to the first contact pad through the retained portion of the second electrode material, and the second connecting electrode is connected to the second contact pad through the retained portion of the first electrode material.

2. The method according to claim 1, characterized in that: In step S2, before forming the cavity dielectric layer on the excitation structure, a support layer located in the cavity region is first formed, and the cavity dielectric layer covers the support layer.

3. The method according to claim 2, characterized in that: Step S2 includes: forming a cavity in the cavity dielectric layer and exposing the support layer; The support layer is removed.

4. The method according to claim 1, characterized in that: In step S2, before forming the cavity dielectric layer on the excitation structure or the substrate, a cavity defining layer is formed on the excitation structure, wherein the cavity defining layer defines the range of the cavity.

5. The method according to claim 1, characterized in that: A CMOS control circuit is formed on the substrate, and the CMOS control circuit has the first contact pad and the second contact pad corresponding to each of the fingerprint sensing units; the electrical connection structure electrically connects the first electrode and the second electrode in the excitation structure to the first contact pad and the second contact pad respectively.

6. An ultrasonic fingerprint sensing chip, characterized in that: The ultrasonic fingerprint sensing chip includes a substrate and a plurality of fingerprint sensing units arranged on the substrate, wherein the fingerprint sensing units include: A cavity dielectric layer, disposed on the substrate, wherein cavities corresponding to the fingerprint sensing units are formed in the cavity dielectric layer; an excitation structure, arranged on the cavity dielectric layer, the excitation structure covers the cavity to form a closed cavity, the excitation structure comprises a second electrode, a piezoelectric layer, a first electrode and an elastic layer arranged in sequence on the closed cavity; an electrical connection structure, wherein the electrical connection structure respectively leads the first electrode and the second electrode in the excitation structure to the surface of the fingerprint sensing unit, wherein the substrate is formed with a first contact pad and a second contact pad, and the electrical connection structure includes a first connection electrode corresponding to the first contact pad and passing through the excitation structure to connect the first electrode and the first contact pad, and also includes a second connection electrode corresponding to the second contact pad and passing through the excitation structure to connect the second electrode and the second contact pad; A first electrode material retaining portion is located outside the cavity and in the plane of the first electrode and opposite to the second contact pad, and the second connecting electrode passes through the first electrode material retaining portion and is connected to the second contact pad; The second electrode material retaining portion is located outside the cavity, on the plane of the second electrode and opposite to the first contact pad, and the first connecting electrode is connected to the first contact pad through the second electrode material retaining portion.

7. An ultrasonic fingerprint sensing chip, characterized in that: The ultrasonic fingerprint sensing chip includes a CMOS control circuit and a fingerprint sensing unit arranged on the CMOS control circuit, the CMOS control circuit includes a plurality of first contact pads and a plurality of second contact pads arranged in an array, and the fingerprint sensing unit includes: A cavity dielectric layer, disposed on the CMOS control circuit, wherein cavities corresponding to the fingerprint sensing units are formed in the cavity dielectric layer; an excitation structure, arranged on the cavity dielectric layer, the excitation structure sealing the cavity to form a closed cavity, the excitation structure comprising a second electrode, a piezoelectric layer, a first electrode and an elastic layer arranged in sequence on the closed cavity; an electrical connection structure, wherein the electrical connection structure electrically connects a first electrode in the excitation structure with a first contact pad corresponding to the first electrode in the CMOS control circuit, and electrically connects a second electrode in the excitation structure with a second contact pad corresponding to the second electrode in the CMOS control circuit, wherein the electrical connection structure comprises a first connection electrode corresponding to the first contact pad and passing through the excitation structure to connect the first electrode and the first contact pad, and further comprises a second connection electrode corresponding to the second contact pad and passing through the excitation structure to connect the second electrode and the second contact pad; A first electrode material retaining portion is located outside the cavity and in the plane of the first electrode and opposite to the second contact pad, and the second connecting electrode passes through the first electrode material retaining portion and is connected to the second contact pad; A second electrode material retaining portion, located outside the cavity and on a plane of the second electrode and opposite to the first contact pad, wherein the first connecting electrode passes through the second electrode material retaining portion and is connected to the first contact pad; The CMOS control circuit provides power control for excitation and / or reception to the corresponding fingerprint sensing unit through the first contact pad and the second contact pad.

8. The ultrasonic fingerprint sensing chip according to claim 6 or 7, characterized in that: The fingerprint sensing unit further includes a cavity defining layer, which is embedded in the cavity medium layer on the side of the enclosed cavity and faces the enclosed cavity.

9. An electronic device with a fingerprint recognition function, characterized in that: The electronic device has an ultrasonic fingerprint sensing area, and the ultrasonic fingerprint sensing area is provided with an ultrasonic fingerprint sensing chip as claimed in any one of claims 6 to 8.

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