Deep-trench isolation method for reducing acoustic crosstalk of ultrasonic transducer, and ultrasonic transducer

Abstract

The present disclosure relates to the field of interference blocking. Disclosed are a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, and an ultrasonic transducer. The ultrasonic transducer comprises a CMOS unit, wherein at least one PMUT unit is arranged on the CMOS unit, all the PMUT units share a PMUT substrate, and each PMUT unit is provided with a cavity. The deep-trench isolation method comprises the steps of when the size and area of a PMUT unit are both less than corresponding preset values thereof and the area of a cavity is greater than a preset value thereof, first etching a deep trench from a mechanical layer towards a PMUT substrate and around the cavity, and then depositing a piezoelectric laminated layer on the mechanical layer within the area, which is isolated by the deep trench, otherwise, first depositing the piezoelectric laminated layer on the mechanical layer, then etching a contact hole from the surface of the piezoelectric laminated layer towards the surface of the mechanical layer and around the cavity, and etching, towards the PMUT substrate, at least one deep trench from the surface of the mechanical layer in the contact hole. In the present disclosure, a deep trench is provided between PMUT units to hinder transverse propagation of ultrasonic waves, such that acoustic crosstalk of an ultrasonic transducer can be effectively reduced.

Description

FIELD OF THE INVENTION

[0001] The present disclosure relates to the field of interference blocking technology, specifically to a deep-trench isolation method for reducing acoustic crosstalk of ultrasonic transducer, and ultrasonic transducer.BACKGROUND OF THE INVENTION

[0002] The development of medical ultrasound scanning requires higher and higher image resolution, and in-vivo ultrasound examination requires the continuous miniaturization of ultrasonic probes. The miniaturization and high-density of ultrasonic probes will encounter many challenges, one of which is the acoustic crosstalk between transducer units, which is defined as the voltage, or acoustic amplitude, generated on the component under test (which is not itself excited) due to the acoustic vibration of adjacent components; Ultrasonic Transducer array, there are many Piezoelectric Micromachined Ultrasonic Transducer (PMUT) units arranged in rows and columns to form an array, that is, the PMUT unit will have multiple adjacent units; When the adjacent unit has an exciting signal, the PMUT film deforms up and down in the Z direction and generates vibration. In solid elastic materials, the vibration in the Z direction will also propagate along the X and Y directions of the horizontal plane perpendicular to the Z direction. In other words, when a PMUT unit vibrates, the adjacent unit are interfered with and disturbed by vibrations, and there will be a low amplitude vibration, which affects the normal use; They will interfere with each other.

[0003] The deep trench used in the high-voltage or image sensor process of ordinary Complementary Metal Oxide Semiconductor (CMOS) is for the purpose of better electrical or optical isolation. The requirements for acoustic isolation are very different, and the process of making deep trenches to reduce acoustic crosstalk is mainly to cut off the channels for mechanical wave propagation, reduce coupling and increase damping.

[0004] Creating deep trenches to reduce sound crosstalk in a three-dimensional architecture composed of Capacitive Micromechanical Ultrasonic Transducer (CMUT) and CMOS (specifically formed by placing CMUT on top of the CMOS chip), the process is relatively simple and direct, generally after bonding and thinning, the back of the second wafer is the silicon substrate and silicon oxide thin layer, which can directly perform the process steps related to the deep trench. At the same time, regardless of the relative size of the cavity and the unit area, it is easier to do the layout of the deep trench, as well as photolithography, etching, deep trench filling, Chemical Mechanical Polishing (CMP) and other subsequent processes; And if specific acoustic crosstalk specifications can be met, even as long as shallower deep trench etching is carried out on the silicon substrate, without the need for etching to penetrate the entire silicon mechanical layer, and the above-mentioned three-dimensional architecture composed of CMUT and CMOS can also be more easily isolated by double deep trench to further improve the isolation effect.

[0005] For the three-dimensional architecture composed of PMUT and CMOS (specifically formed by placing CMUT on top of the CMOS chip), the complexity of making deep trenches is relatively high, mainly because there are piezoelectric materials and their upper and bottom metals above the silicon mechanical layer. The thickness of the piezoelectric material layer plus its upper / lower metal layer generally reaches 1.5-3.5 microns ( µ m), and the process is relatively difficult to form deep trenches with a high Aspect Ratio (Aspect Ratio) through this layer of material. At the same time, the photolithographic etching of PZT (Lead Zirconium Titanate Piezoelectric ceramics, Pb(ZrTi)O 3 ) materials to form very small-sized patterns is also not easy, which further increases the difficulty of the deep trench process, so it is urgent to propose a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, and an ultrasonic transducer.SUMMARY OF THE INVENTION

[0006] In view of the deficiencies of the prior art, the present disclosure provides a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, and an ultrasonic transducer, wherein the deep-trench isolation method solves the problem that the current process of doing the deep-trench isolation method is relatively difficult for thinner materials.

[0007] In order to achieve the above purposes, the present disclosure provides the following technical solutions: A deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, at least one PMUT unit is arranged on the CMOS unit, all the PMUT units share a PMUT substrate, and the PMUT substrate is provided with at least one cavity; covering the cavity, a mechanical layer and a piezoelectric laminated layer are sequentially arranged on the PMUT substrate; wherein the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S2, when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, performing a process in which the deep trench is pre-designed: First etching around the cavity and from the mechanical layer to the inside of the PMUT substrate to form the deep trench.

[0008] Then depositing on the mechanical layer in the area isolated by the deep trench to form the piezoelectric laminated layer.

[0009] S3, when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, performing a process in which the deep trench is post-designed: First depositing on the mechanical layer to form the piezoelectric laminated layer.

[0010] Then etching around the cavity and from the surface of the piezoelectric laminated layer to the surface of the mechanical layer to form a contact hole, and etching from the surface of the mechanical layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench.

[0011] As a further embodiment of the present disclosure, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0012] In the step S2, the process in which the deep trench is pre-designed specifically comprises the following steps: S201, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside of the PMUT substrate; through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness. S202, after deposition, forming a mask oxide layer on the mechanical layer. S203, under the mask, photolithography and corrosion are sequentially carried out around the cavity and from the mask oxide layer to the inside of the PMUT substrate to form the deep trench. S204, after removing the mask oxide layer, depositing damping material so that the deep trench is filled with damping material and a damping layer is formed on a surface of the PMUT substrate. S205, after polishing treatment, the damping layer is removed. S206, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer. S207, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form a contact hole on the deep trench.

[0013] In the step S3, the process in which the deep trench is post-designed specifically comprises the following steps: S301, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside of the PMUT substrate, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness. S302, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer. S303, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form a contact hole. S304, after deposition, covering the mechanical layer and the piezoelectric laminated layer to form a mask oxide layer. S305, under the mask, photolithography and corrosion are sequentially carried out around the cavity and from the surface of the mask oxide layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench. S306, after removing the mask oxide layer, coating or depositing damping material, covering the bottom and side walls of the deep trench, the mechanical layer and the piezoelectric laminated layer, forming a damping layer. S307, after polishing treatment, removing excess damping layer, and retaining the damping layer in the deep trench.

[0014] Further, the preset thickness is 2-5 µm.

[0015] On the basis of the preceding scheme, both the step S207 and the step S307 are followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connection hole and a lower metal layer connection hole. S411, by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer.

[0016] Further, the damping material is a porous oxide or a porous plastic.

[0017] On the basis of the preceding scheme, in the step S204, a plasma chemical vapor deposition damping material is used to form a closed vacuum hole in the deep trench after the damping material is filled in the deep trench.

[0018] Further, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, specifically comprising: through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and the back of the mechanical layer is oxidized simultaneously to form an oxide layer between the mechanical layer and the PMUT substrate.

[0019] On the basis of the preceding scheme, the cross-section of the deep trench is a circular ring or a polygonal ring.

[0020] The present disclosure also proposes an ultrasonic transducer, comprising a CMOS unit, at least one PMUT unit is arranged on the CMOS unit, all the PMUT units share a PMUT substrate, at least one cavity is arranged concave from the surface of the PMUT substrate to the inside of the PMUT substrate; covering the cavity, a mechanical layer and a piezoelectric laminated layer are sequentially arranged on the PMUT substrate; When the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, a deep trench is arranged around the cavity and concave from the surface of the mechanical layer to the inside of the PMUT substrate, and the deep trench is filled with damping material; When the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, one or more deep trenches are arranged around the cavity and concave from the surface of the mechanical layer to the inside of the PMUT substrate, and a damping layer is formed at the bottom and side walls of the deep trench.

[0021] The present disclosure provides deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer and an ultrasonic transducer; the deep-trench isolation method has the following beneficial effects as compared to the prior art: 1. In the present disclosure, in view of the different sizes of PMUT units, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good, and the deep trenches are arranged between the PMUT units on the CMOS unit in the ultrasonic transducer for isolation, effectively reducing the acoustic crosstalk of the ultrasonic transducer. 2. In the present disclosure, after the re-deposition, the chemical mechanical polishing treatment is adopted to remove the filling medium on the silicon surface, so that the lower metal electrode material of the piezoelectric material can be deposited. After the formation of a deep trench, the damping material is filled, and outside the wider deep trench is the air, and the Si / damping material / air interface can significantly attenuate the mechanical wave; and the chemical mechanical polishing treatment is adopted after the re-deposition is carried out to remove the filling medium on the silicon surface, so that the lower metal electrode material of the piezoelectric material can be deposited. 3. In the present disclosure, through the plasma chemical vapor phase depositing damping material at low temperature, this deposition method has a fast deposition speed at the top of the deep trench, can quickly seal, and leaves a vacuum hole in the middle or bottom of the deep trench, and this technology cleverly forms the Si / damping material / air / damping material / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench. 4. In the present disclosure, another layer of medium is coated after filling with a high-damping medium, and only the deep trench filling medium and the coating medium are retained in the deep trench area through photolithography, which is reasonably designed and can further reduce acoustic crosstalk. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Fig. 1 shows a schematic diagram of the deep trench pre-design process of the deep-trench isolation method for reducing ultrasonic transducer acoustic crosstalk provided in the present disclosure. Fig. 2 shows a schematic diagram of the deep trench post-design process of a deep trench isolation method for reducing acoustic crosstalk of an ultrasonic transducers provided in the present disclosure. Fig. 3 shows a schematic diagram of the structure of the PMUT unit with deep-trench isolation of an ultrasonic transducer provided in the present disclosure. Fig. 4 shows a schematic diagram of the structure of three PMUT units with deep-trench isolation of an ultrasonic transducer provided in the present disclosure. Fig. 5 shows a schematic diagram of the top view structure of a deep-trench isolated 3×3 PMUT unit array with the small unit size of an ultrasonic transducer provided in the present disclosure. Fig. 6 shows a schematic diagram of the top view structure of a deep-trench isolated 3×3 PMUT unit array with the large unit size of an ultrasonic transducer provided in the present disclosure. FIG. 7 shows a schematic diagram of the top view structure of a deep-trench isolated 3×3 PMUT unit of different shapes with the large unit size of an ultrasonic transducer provided in the present disclosure. Fig. 8 shows a schematic diagram of the top view structure of the double-deep-trenches isolation of an ultrasonic transducer provided in the present disclosure. Fig. 9 shows a schematic diagram of the longitudinal cross-section structure of a deep trench after the plasma chemical vapor deposition damping material provided in the present disclosure.

[0023] The drawings are marked as follows: 1. a PMUT substrate; 2. a cavity; 3. a deep trench; 31. a damping material; 32. a vacuum hole; 4. a mechanical layer; 5. a piezoelectric laminated layer; 51. a top layer of piezoelectric laminated layer.DETAILED DESCRIPTION OF THE INVENTIONEmbodiment 1

[0024] Referring to Fig. 1 and Fig. 3, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, a PMUT unit is arranged on the CMOS unit, the PMUT unit comprises a PMUT substrate 1, a cavity 2 is arranged in the PMUT substrate 1; covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S2, when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, performing a process in which the deep trench is pre-designed: First etching around the cavity and from the mechanical layer to the inside of the PMUT substrate to form a deep trench.

[0025] Then depositing on the mechanical layer in the area isolated by the deep trench to form the piezoelectric laminated layer.

[0026] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0027] In the step S2, the process in which the deep trench is pre-designed specifically comprises the following steps: S201, providing a PMUT substrate, providing a cavity concave from the surface of the PMUT substrate to the inside of the PMUT substrate, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 1. S202, after deposition, forming a mask oxide layer on the mechanical layer; i.e., the "deposition" step shown in Fig. 1. S203, under the mask, photolithography and corrosion successively around the cavity and from the mask oxide layer to the inside of the PMUT substrate to form the deep trench; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 1. S204, after removing the mask oxide layer, depositing damping material so that the deep trench is filled with damping material and a damping layer is formed on a surface of the PMUT substrate; i.e., the "re-deposition" step shown in Fig. 1. S205, after polishing treatment, the damping layer is removed; i.e., the "polishing" step shown in Fig. 1. S206, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "laying material" step shown in Fig. 1. For example, the material of the piezoelectric layer can be PZT or aluminum nitride (AlN). S207, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer, forming a contact hole on the deep trench. i.e., the "piezoelectric photolithography" step shown in Fig. 1. Exemplarily, the preset thickness can be 4 µm.

[0028] In some embodiments, the step S207 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 1. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connecting hole and a lower metal layer connecting hole. S411. by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 1. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0029] Referring to Fig. 9, in some embodiments, the damping material 31 is porous plastic; at the time of deposition, the very edge of the deep trench is porous plastic, and a vacuum hole is arranged in the middle of the trench. The deposition method in the step S204 is the plasma chemical vapor deposition porous plastic at low temperature, and this deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench; and this technology cleverly forms the Si / damping material / air / damping material / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench. In the step S204, a plasma chemical vapor deposition damping material 31 is used, so that after the deep trench 3 is filled with damping material 31, a closed vacuum hole 32 is formed in the deep trench 3. Preferably, the temperature of the plasma chemical vapor deposition damping material 31 is 250-350 °C.

[0030] In other embodiments, the damping material 31 is a porous oxide (such as SiO 2 ), and the very edge of the deep trench is a porous oxide during deposition, and a vacuum hole 32 is arranged in the middle of the trench. For example, the deposition method in step S204 is the plasma chemical vapor deposition of SiO 2 at low temperature; and the deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench, and this technology cleverly forms a Si / SiO 2 / air / SiO 2 / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench. In the step S204, a plasma chemical vapor deposition damping material 31 is used, so that after the deep trench is filled with damping material, a closed vacuum hole is formed in the deep trench; For example, by plasma chemical vapor deposition of SiO 2 at low temperature, this deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench; and this technology cleverly forms a Si / SiO 2 / air / SiO 2 / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench.

[0031] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, a PMUT unit is arranged on the CMOS unit, the PMUT unit comprises a PMUT substrate 1, a cavity 2 is arranged concave from the surface of the PMUT substrate 1 to the inside of the PMUT substrate 1; covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and when the area of the cavity is greater than the second preset area, a deep trench 3 is arranged around the cavity and concave from the surface of the mechanical layer to the inside of the PMUT substrate 1, and the deep trench 3 is filled with damping material.Embodiment 2

[0032] Referring to Fig. 2 and Fig. 3, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, a PMUT unit is arranged on the CMOS unit, the PMUT unit comprises a PMUT substrate 1, a cavity 2 is arranged in the PMUT substrate 1 (i.e., a cavity 2 correspondingly is arranged in a PMUT unit); covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S3, when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, performing a process in which the deep trench is post-designed: First depositing on the mechanical layer to form the piezoelectric laminated layer.

[0033] Then etching around the cavity and from the surface of the piezoelectric laminated layer to the surface of the mechanical layer to form a contact hole, and etching from the surface of the mechanical layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench.

[0034] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0035] In the step S3, the process in which the deep trench is post-designed specifically comprises the following steps: S301, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside the PMUT substrate, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 2. S302, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "piezoelectric layer deposition" step shown in Fig. 2. S303, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form a contact hole; i.e., the "piezoelectric layer photolithography" step shown in Fig. 2. S304, after deposition, covering the mechanical layer and the piezoelectric laminated layer to form a mask oxide layer; i.e., the "deep-trench deposition" step shown in Fig. 2. S305, under the mask, photolithography and corrosion are sequentially carried out around the cavity and from the surface of the mask oxide layer in the contact hole to the inside of the PMUT substrate to form a deep trench; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 2. S306, after removing the mask oxide layer, coating or depositing damping material, covering the bottom and side walls of the deep trench, the mechanical layer and the piezoelectric laminated layer to form a damping layer; i.e., the "deep-trench media deposition" step shown in Fig. 2. S307, after polishing treatment, removing excess damping layer, and retaining the damping layer in the deep trench. i.e., the "polishing" step shown in Fig. 2.

[0036] For example, the preset thickness can be 3 µm.

[0037] In some embodiments, the step S307 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 2. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connection hole and a lower metal layer connection hole. S411, by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 2. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0038] In some embodiments, in step S306, after coating or depositing damping material, through photolithography, only the deep trench filling medium / coating medium is retained in the deep trench area, and the acoustic crosstalk can be further reduced through reasonable design.

[0039] Further, in an embodiment, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, specifically comprising: through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and the back of the mechanical layer is oxidized simultaneously to form an oxide layer between the mechanical layer and the PMUT substrate.

[0040] Further, in one embodiment, the cross-section of the deep trench is in a circular ring.

[0041] Further, in one embodiment, the cross-section of the deep trench is in a polygonal ring; For example, the polygonal ring can be square rings, hexagonal rings, octagonal rings, and so on.

[0042] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, a PMUT unit is arranged on the CMOS unit, the PMUT unit comprises a PMUT substrate 1, a cavity 2 is arranged concave from the surface of the PMUT substrate 1 to the inside of the PMUT substrate 1; covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit greater than or equal to the first preset area, and when the area of the cavity is less than or equal to the second preset area, a deep trench 3 is arranged around the cavity 2 and concave from the surface of the mechanical layer 4 to the inside of the PMUT substrate 1, and a damping layer is formed on the bottom and sidewalls of the deep trench 3.Embodiment 3

[0043] Referring to Fig. 1 and Fig. 4, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, three PMUT units are arranged on the CMOS unit, the three PMUT units are connected, the three PMUT units share a PMUT substrate 1, three cavities 2 are arranged in the PMUT substrate 1 (i.e., a cavity 2 is correspondingly arranged in a PMUT unit); covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S2, when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, performing a process in which the deep trench is pre-designed.

[0044] First etching around the cavity and from the mechanical layer to the inside of the PMUT substrate to form deep trenches.

[0045] Then depositing on the mechanical layer in the area isolated by the deep trenches to form the piezoelectric laminated layer.

[0046] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0047] In the step S2, the process in which the deep trench is pre-designed specifically comprises the following steps: S201, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside of the PMUT substrate, through fusion bonding, covering the cavities to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 1. S202, after deposition, forming a mask oxide layer on the mechanical layer; i.e., the "deposition" step shown in Fig. 1. S203, under the mask, photolithography and corrosion are sequentially carried out around the cavities and from the mask oxide layer to the inside of the PMUT substrate to form deep trenches; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 1. S204, after removing the mask oxide layer, depositing damping material so that the deep trenches are filled with damping material and a damping layer is formed on a surface of the PMUT substrate; i.e., the "re-deposition" step shown in Fig. 1. S205, after polishing treatment, the damping layer is removed; i.e., the "polishing" step shown in Fig. 1. S206, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "laying material" step shown in Fig. 1. S207, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer, forming a contact hole on the deep trench. i.e., the "piezoelectric photolithography" step shown in Fig. 1. Exemplarily, the preset thickness can be 4 µm.

[0048] In some embodiments, the step S207 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 1. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connecting hole and a lower metal layer connecting hole. S411. by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 1. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0049] Referring to Fig. 9, in some embodiments, the damping material 31 is porous plastic; at the time of deposition, the very edge of the deep trench is porous plastic, and a vacuum hole 32 is arranged in the middle of the trench. For example, the deposition method in the step S204 is the plasma chemical vapor deposition porous plastic, and this deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench; and this technology cleverly forms the Si / damping material / air / damping material / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench. In the step S204, a plasma chemical vapor deposition damping material is used, so that after the deep trench is filled with damping material, a closed vacuum hole is formed in the deep trench. Preferably, the temperature of the plasma chemical vapor deposition damping material 31 is 250-350 °C.

[0050] In other embodiments, the damping material 31 is a porous oxide (such as SiO 2 ), and the very edge of the deep trench is a porous oxide during deposition, and a vacuum hole is arranged in the middle of the trench. For example, the deposition method in step S204 is the plasma chemical vapor deposition SiO 2 ; and the deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench, and this technology cleverly forms a Si / SiO 2 / air / SiO 2 / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench. In the step S204, a plasma chemical vapor deposition damping material is used, so that after the deep trench is filled with damping material, a closed vacuum hole is formed in the deep trench; For example, by plasma chemical vapor deposition SiO 2 , this deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench; and this technology cleverly forms a Si / SiO 2 / air / SiO 2 / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench.

[0051] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, three PMUT units are arranged on the CMOS unit, the three PMUT units shares a PMUT substrate 1, three cavities 2 are arranged concave from the surface of the PMUT substrate 1 to the inside of the PMUT substrate 1 (i.e., a cavity 2 is correspondingly arranged in a PMUT unit); covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and when the area of the cavity is greater than the second preset area, deep trenches 3 are arranged around the cavities and concave from the surface of the mechanical layer to the inside of the PMUT substrate 1, and the three deep trenches 3 are filled with damping material, the three PMUT units are adjacent and a deep trench 3 is shared between adjacent PMUT units.Embodiment 4

[0052] Referring to Fig. 2 and Fig. 4, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, three PMUT units are arranged on the CMOS unit, the three PMUT units are connected, the three PMUT units share a PMUT substrate 1, three cavities 2 are arranged in the PMUT substrate 1 (i.e., a cavity 2 is correspondingly arranged in a PMUT unit); covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S3, when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, performing a process in which the deep trench is post-designed: First depositing on the mechanical layer to form the piezoelectric laminated layer.

[0053] Then etching around the cavities and from the surface of the piezoelectric laminated layer to the surface of the mechanical layer to form contact holes, and etching from the surface of the mechanical layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench.

[0054] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0055] In the step S3, the process in which the deep trench is post-designed specifically comprises the following steps: S301, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside the PMUT substrate, through fusion bonding, covering the cavities to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 2. S302, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "piezoelectric layer deposition" step shown in Fig. 2. S303, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form contact holes; i.e., the "piezoelectric layer photolithography" step shown in Fig. 2. S304, after deposition, covering the mechanical layer and the piezoelectric laminated layer to form a mask oxide layer; i.e., the "deep-trench deposition" step shown in Fig. 2. S305, under the mask, photolithography and corrosion are sequentially carried out around the cavities and from the surface of the mask oxide layer in the contact holes to the inside of the PMUT substrate to form three deep trenches; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 2. S306, after removing the mask oxide layer, coating or depositing damping material, covering the bottom and side walls of the deep trench, the mechanical layer and the piezoelectric laminated layer to form a damping layer; i.e., the "deep-trench media deposition" step shown in Fig. 2. S307, after polishing treatment, removing excess damping layer, and retaining the damping layer in the deep trench. i.e., the "polishing" step shown in Fig. 2.

[0056] For example, the preset thickness can be 3 µm.

[0057] In some embodiments, the step S307 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 2. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connection hole and a lower metal layer connection hole. S411, by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 2. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0058] In some embodiments, in step S306, after coating or depositing damping material, through photolithography, only the deep trench filling medium / coating medium is retained in the deep trench area, and the acoustic crosstalk can be further reduced through reasonable design.

[0059] Further, in an embodiment, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, specifically comprising: through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and the back of the mechanical layer is oxidized simultaneously to form an oxide layer between the mechanical layer and the PMUT substrate.

[0060] Further, in one embodiment, the cross-section of the deep trench is in a circular ring.

[0061] Further, in one embodiment, the cross-section of the deep trench is in a polygonal ring; For example, the polygonal ring can be square rings, hexagonal rings, octagonal rings, and so on.

[0062] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, at least one PMUT unit (such as 9 PMUT units) is arranged on the CMOS unit, all the PMUT units share PMUT substrate 1, at least one cavity 2 is arranged concave from the surface of the PMUT substrate 1 to the inside of the PMUT substrate 1 (i.e., a cavity 2 is correspondingly arranged in a PMUT unit); covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit greater than or equal to the first preset area, and when the area of the cavity 2 is less than or equal to the second preset area, a deep trench 3 is arranged around the cavity 2 and concave from the surface of the mechanical layer 4 to the inside of the PMUT substrate 1, and a damping layer is formed on the bottom and sidewalls of the deep trench 3, the three PMUT units are adjacent and a deep trench 3 is shared between adjacent PMUT units.Embodiment 5

[0063] Referring to Fig. 1 and Fig. 5, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, nine PMUT units are arranged on the CMOS unit, and the nine PMUT units are distributed in a 3 × 3 array, all the PMUT units share a PMUT substrate 1, the grid-like pattern is a deep trench 3 structure, the black circle is a cavity 2, and the white circle is the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer of the PMUT unit; In this design, the deep trench 3 grid completely surrounds the cavity 2 and the PMUT unit, and realizes complete isolation with the adjacent PMUT unit; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S2, when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, performing a process in which the deep trench is pre-designed: First etching around the cavity and from the mechanical layer to the inside of the PMUT substrate to form deep trenches.

[0064] Then depositing on the mechanical layer in the area isolated by the deep trenches to form the piezoelectric laminated layer.

[0065] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0066] In the step S2, the process in which the deep trench is pre-designed specifically comprises the following steps: S201, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside of the PMUT substrate, through fusion bonding, covering the cavities to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 1. S202, after deposition, forming a mask oxide layer on the mechanical layer; i.e., the "deposition" step shown in Fig. 1. S203, under the mask, photolithography and corrosion are sequentially carried out around the cavities and from the mask oxide layer to the inside of the PMUT substrate to form deep trenches; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 1. S204, after removing the mask oxide layer, depositing damping material so that the deep trenches are filled with damping material and a damping layer is formed on a surface of the PMUT substrate; i.e., the "re-deposition" step shown in Fig. 1. S205, after polishing treatment, the damping layer is removed; i.e., the "polishing" step shown in Fig. 1. S206, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "laying material" step shown in Fig. 1. S207, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer, forming a contact hole on the deep trench. i.e., the "piezoelectric photolithography" step shown in Fig. 1. Exemplarily, the preset thickness can be 4 µm.

[0067] In some embodiments, the step S207 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 1. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connecting hole and a lower metal layer connecting hole. S411. by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 1. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0068] Referring to Fig. 9, in some embodiments, the damping material 31 is porous plastic; at the time of deposition, the very edge of the deep trench is porous plastic, and a vacuum hole is arranged in the middle of the trench. The deposition method in the step S204 is the plasma chemical vapor deposition porous plastic, and this deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench; and this technology cleverly forms the Si / damping material / air / damping material / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench. In the step S204, a plasma chemical vapor deposition damping material 31 is used, so that after the deep trench 3 is filled with damping material 31, a closed vacuum hole 32 is formed in the deep trench 3. Preferably, the temperature of the plasma chemical vapor deposition damping material 31 is 250-350 °C.

[0069] In other embodiments, the damping material 31 is a porous oxide (such as SiO 2 ), and the very edge of the deep trench is a porous oxide during deposition, and a vacuum hole is arranged in the middle of the trench. For example, the deposition method in step S204 is the plasma chemical vapor deposition SiO 2 at a low temperature; and the deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench, and this technology cleverly forms a Si / SiO 2 / air / SiO 2 / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench. In the step S204, a plasma chemical vapor deposition damping material is used, so that after the deep trench is filled with damping material, a closed vacuum hole is formed in the deep trench; For example, by plasma chemical vapor deposition of SiO 2 at a low temperature, this deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench; and this technology cleverly forms a Si / SiO 2 / air / SiO 2 / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench.

[0070] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, nine PMUT units are arranged on the CMOS unit, and the nine PMUT units are distributed in a 3 × 3 array, all the PMUT units share a PMUT substrate 1, the grid-like pattern is a deep trench 3 structure, the black circle is a cavity 2, and the white circle is the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer of the PMUT unit. In this design, the deep trench 3 grid completely surrounds the cavity 2 and the PMUT unit, and realizes complete isolation with the adjacent PMUT unit.Embodiment 6

[0071] Referring to Fig. 2 and Fig. 6, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, nine PMUT units are arranged on the CMOS unit, and the nine PMUT units are distributed in a 3 × 3 array, all the PMUT units share a PMUT substrate 1, the top of the PMUT unit is provided with a piezoelectric laminated layer 5, a cavity 2 is arranged around the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer from an overhead perspective; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S3, when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, performing a process in which the deep trench is post-designed: First depositing on the mechanical layer to form the piezoelectric laminated layer;

[0072] Then etching around the cavities and from the surface of the piezoelectric laminated layer to the surface of the mechanical layer to form contact holes, and etching from the surface of the mechanical layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench.

[0073] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0074] In the step S3, the process in which the deep trench is post-designed specifically comprises the following steps: S301, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside the PMUT substrate, through fusion bonding, covering the cavities to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 2. S302, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "piezoelectric layer deposition" step shown in Fig. 2. S303, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form contact holes; i.e., the "piezoelectric layer photolithography" step shown in Fig. 2. S304, after deposition, covering the mechanical layer and the piezoelectric laminated layer to form a mask oxide layer; i.e., the "deep-trench deposition" step shown in Fig. 2. S305, under the mask, photolithography and corrosion are sequentially carried out around the cavities and from the surface of the mask oxide layer in the contact holes to the inside of the PMUT substrate to form three deep trenches; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 2. S306, after removing the mask oxide layer, coating or depositing damping material, covering the bottom and side walls of the deep trench, the mechanical layer and the piezoelectric laminated layer to form a damping layer; i.e., the "deep-trench media deposition" step shown in Fig. 2. S307, after polishing treatment, removing excess damping layer, and retaining the damping layer in the deep trench. i.e., the "polishing" step shown in Fig. 2.

[0075] For example, the preset thickness can be 3 µm.

[0076] In some embodiments, the step S307 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 2. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connection hole and a lower metal layer connection hole. S411, by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 2. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0077] In some embodiments, in step S306, after coating or depositing damping material, through photolithography, only the deep trench filling medium / coating medium is retained in the deep trench area, and the acoustic crosstalk can be further reduced through reasonable design.

[0078] Further, in an embodiment, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, specifically comprising: through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and the back of the mechanical layer is oxidized simultaneously to form an oxide layer between the mechanical layer and the PMUT substrate.

[0079] Further, in one embodiment, the cross-section of the deep trench is in a circular ring.

[0080] Further, in one embodiment, the cross-section of the deep trench is in a polygonal ring; For example, the polygonal ring can be square rings, hexagonal rings, octagonal rings, and so on.

[0081] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, all the PMUT units share a PMUT substrate 1, the top of the PMUT unit is provided with a piezoelectric laminated layer 5, a cavity 2 is arranged around the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer from an overhead perspective; when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit greater than or equal to the first preset area, and when the area of the cavity 2 is less than or equal to the second preset area, a deep trench 3 is arranged around the cavity 2 and from the surface of the piezoelectric laminated layer, at the immediate vicinity of the cavity 2, an independent closed deep trench 3 is formed, and the deep trench 3 only isolates the cavity 2 and the vibrating device structure above it.Embodiment 6

[0082] Referring to Fig. 2 and Fig. 7, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, nine PMUT units are arranged on the CMOS unit, and the nine PMUT units are distributed in a 3 × 3 array, all the PMUT units share a PMUT substrate 1, the top of the PMUT unit is provided with a piezoelectric laminated layer 5, a cavity 2 is arranged around the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer from an overhead perspective; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S3, when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, performing a process in which the deep trench is post-designed: First depositing on the mechanical layer to form the piezoelectric laminated layer.

[0083] Then etching around the cavities and from the surface of the piezoelectric laminated layer to the surface of the mechanical layer to form contact holes, and etching from the surface of the mechanical layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench.

[0084] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0085] In the step S3, the process in which the deep trench is post-designed specifically comprises the following steps: S301, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside the PMUT substrate, through fusion bonding, covering the cavities to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 2. S302, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "piezoelectric layer deposition" step shown in Fig. 2. S303, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form contact holes; i.e., the "piezoelectric layer photolithography" step shown in Fig. 2. S304, after deposition, covering the mechanical layer and the piezoelectric laminated layer to form a mask oxide layer; i.e., the "deep-trench deposition" step shown in Fig. 2. S305, under the mask, photolithography and corrosion are sequentially carried out around the cavities and from the surface of the mask oxide layer in the contact holes to the inside of the PMUT substrate to form three deep trenches; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 2. S306, after removing the mask oxide layer, coating or depositing damping material, covering the bottom and side walls of the deep trench, the mechanical layer and the piezoelectric laminated layer to form a damping layer; i.e., the "deep-trench media deposition" step shown in Fig. 2. S307, after polishing treatment, removing excess damping layer, and retaining the damping layer in the deep trench. i.e., the "polishing" step shown in Fig. 2.

[0086] For example, the preset thickness can be 3 µm.

[0087] In some embodiments, the step S307 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 2. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connection hole and a lower metal layer connection hole. S411, by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 2. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0088] In some embodiments, in step S306, after coating or depositing damping material, through photolithography, only the deep trench filling medium / coating medium is retained in the deep trench area, and the acoustic crosstalk can be further reduced through reasonable design.

[0089] Further, in an embodiment, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, specifically comprising: through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and the back of the mechanical layer is oxidized simultaneously to form an oxide layer between the mechanical layer and the PMUT substrate.

[0090] Further, in one embodiment, the cross-section of the deep trench is in a circular ring.

[0091] Further, in one embodiment, the cross-section of the deep trench is in a polygonal ring; For example, the polygonal ring can be square rings, hexagonal rings, octagonal rings, and so on.

[0092] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, nine PMUT units are arranged on the CMOS unit, all the PMUT units share a PMUT substrate 1, the top of the PMUT unit is provided with a piezoelectric laminated layer 5, a cavity 2 is arranged around the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer from an overhead perspective; when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit greater than or equal to the first preset area, and when the area of the cavity 2 is less than or equal to the second preset area, around the cavity 2, a deep trench 3 is surrounded by the surface of the piezoelectric laminated layer 5, at the immediate vicinity of the cavity 2, an independent closed deep trench 3 is formed, and the deep trench 3 only isolates the cavity 2 and the vibrating device structure above it; The shape of deep trench 3 can be quadrilateral ring, hexagonal ring or octagonal ring, and so on.Embodiment 7

[0093] Referring to Fig. 2, Fig. 7 and Fig. 8, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, nine PMUT units are arranged on the CMOS unit, and the nine PMUT units are distributed in a 3 × 3 array, all the PMUT units share a PMUT substrate 1, the top of the PMUT unit is provided with a piezoelectric laminated layer 5, a cavity 2 is arranged around the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer from an overhead perspective; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S3, when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, performing a process in which the deep trench is post-designed: First depositing on the mechanical layer to form the piezoelectric laminated layer;

[0094] Then etching around the cavities and from the surface of the piezoelectric laminated layer to the surface of the mechanical layer to form contact holes, and etching from the surface of the mechanical layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench.

[0095] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0096] In the step S3, the process in which the deep trench is post-designed specifically comprises the following steps: S301, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside the PMUT substrate, through fusion bonding, covering the cavities to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 2. S302, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "piezoelectric layer deposition" step shown in Fig. 2. S303, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form contact holes; i.e., the "piezoelectric layer photolithography" step shown in Fig. 2. S304, after deposition, covering the mechanical layer and the piezoelectric laminated layer to form a mask oxide layer; i.e., the "deep-trench deposition" step shown in Fig. 2. S305, under the mask, photolithography and corrosion are sequentially carried out around the cavities and from the surface of the mask oxide layer in the contact holes to the inside of the PMUT substrate to form three deep trenches; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 2. S306, after removing the mask oxide layer, coating or depositing damping material, covering the bottom and side walls of the deep trench, the mechanical layer and the piezoelectric laminated layer to form a damping layer; i.e., the "deep-trench media deposition" step shown in Fig. 2. S307, after polishing treatment, removing excess damping layer, and retaining the damping layer in the deep trench. i.e., the "polishing" step shown in Fig. 2.

[0097] For example, the preset thickness can be 3 µm.

[0098] In some embodiments, the step S307 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 2. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connection hole and a lower metal layer connection hole. S411, by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 2. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0099] In some embodiments, in step S306, after coating or depositing damping material, through photolithography, only the deep trench filling medium / coating medium is retained in the deep trench area, and the acoustic crosstalk can be further reduced through reasonable design.

[0100] Further, in an embodiment, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, specifically comprising: through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and the back of the mechanical layer is oxidized simultaneously to form an oxide layer between the mechanical layer and the PMUT substrate.

[0101] Further, in one embodiment, the cross-section of the deep trench is in a circular ring.

[0102] Further, in one embodiment, the cross-section of the deep trench is in a polygonal ring; For example, the polygonal ring can be square rings, hexagonal rings, octagonal rings, and so on.

[0103] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, nine PMUT units are arranged on the CMOS unit, all the PMUT units share a PMUT substrate 1, the top of the PMUT unit is provided with a piezoelectric laminated layer 5, a cavity 2 is arranged around the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer from an overhead perspective; when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit greater than or equal to the first preset area, and when the area of the cavity 2 is less than or equal to the second preset area, around the cavity 2, a deep trench 3 is surrounded by the surface of the piezoelectric laminated layer 5, at the immediate vicinity of the cavity 2, an independent closed deep trench 3 is formed, and the deep trench 3 only isolates the cavity 2 and the vibrating device structure above it; The shape of deep trench 3 can be quadrilateral ring, hexagonal ring or octagonal ring, and so on.

[0104] Anti-interference design is not limited to a single deep trench, if the unit area allows, it can also be done double-trench, or even multi- trench design; As an example of the discontinuous double-trench isolation schematic diagram shown in Fig. 8, in the unit layout, the area A, B, C, D already has related element structures, such as the vertical connection of the three-dimensional architecture, or metal wiring, etc.; The double-trench isolation can be a single trench to stagger these areas, and the other deep trench can be staggered and complementary, to ensure that at least one deep trench in the lateral path of the mechanical wave, which plays a role in reducing interference and disturbance. It should be understood that the preset size refers to the minimum transverse size of the PMUT unit when the double-deep-trench isolation process can be used; the first preset area refers to the minimum area of the PMUT unit when the double-deep-trench isolation process can be used; The second preset area refers to the maximum area of the cavity in the PMUT unit when the double-deep-trench isolation process can be used.

[0105] Anti-interference design is not limited to a single deep trench, if the unit area allows, it can also be done double-trench, or even multi- trench design; As an example of the discontinuous double-trench isolation schematic diagram shown in Fig. 8, in the unit layout, the area A, B, C, D already has related element structures, such as the vertical connection of the three-dimensional architecture, or metal wiring, etc.; The double-trench isolation can be a single trench to stagger these areas, and the other deep trench can be staggered and complementary, to ensure that at least one deep trench in the lateral path of the mechanical wave, which plays a role in reducing interference and disturbance. It should be understood that the preset size refers to the minimum transverse size of the PMUT unit when the double-deep-trench isolation process can be used; the first preset area refers to the minimum area of the PMUT unit when the double-deep-trench isolation process can be used; The second preset area refers to the maximum area of the cavity in the PMUT unit when the double-deep-trench isolation process can be used.

[0106] In the description in the present disclosure, it is important to note that: relational terms such as first and second, etc., are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or sequence between those entities or operations. Further, the term "including", "containing" or any other variation thereof is intended to cover non-exclusive inclusion so that a process, process, article or apparatus that includes a series of elements includes not only those elements, but also other elements that are not expressly listed, or that are inherent to such process, method, article or apparatus.

[0107] Although embodiments of the present disclosure have been shown and described, it is understandable to those of ordinary skill in the art that various variations, modifications, substitutions and variants can be made to these embodiments without departing from the principle and spirit of the present disclosure, and the scope of the present disclosure is limited by the attached claims and their equivalents.

Examples

embodiment 1

[0024]Referring to Fig. 1 and Fig. 3, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, a PMUT unit is arranged on the CMOS unit, the PMUT unit comprises a PMUT substrate 1, a cavity 2 is arranged in the PMUT substrate 1; covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; And the deep-trench isolation method comprises the following steps:

S1, obtaining the size and area of the PMUT unit and the area of the cavity. S2, when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, performing a process in which the deep trench is pre-designed: First etching around the cavity and from the mechanical layer to the inside of the PMUT substrate to form a deep trench.

[0025]Then depositing on the ...

embodiment 2

[0032]Referring to Fig. 2 and Fig. 3, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, a PMUT unit is arranged on the CMOS unit, the PMUT unit comprises a PMUT substrate 1, a cavity 2 is arranged in the PMUT substrate 1 (i.e., a cavity 2 correspondingly is arranged in a PMUT unit); covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; And the deep-trench isolation method comprises the following steps:

S1, obtaining the size and area of the PMUT unit and the area of the cavity. S3, when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, performing a process in which the deep trench is post-designed: First depositing on the mechanical layer to form...

embodiment 3

[0043]Referring to Fig. 1 and Fig. 4, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, three PMUT units are arranged on the CMOS unit, the three PMUT units are connected, the three PMUT units share a PMUT substrate 1, three cavities 2 are arranged in the PMUT substrate 1 (i.e., a cavity 2 is correspondingly arranged in a PMUT unit); covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; And the deep-trench isolation method comprises the following steps:

S1, obtaining the size and area of the PMUT unit and the area of the cavity. S2, when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, performing a process in which the deep trench is pre-designed.

[0044]First etching around the cavit...

FIELD OF THE INVENTION

[0001] The present disclosure relates to the field of interference blocking technology, specifically to a deep-trench isolation method for reducing acoustic crosstalk of ultrasonic transducer, and ultrasonic transducer.BACKGROUND OF THE INVENTION

[0002] The development of medical ultrasound scanning requires higher and higher image resolution, and in-vivo ultrasound examination requires the continuous miniaturization of ultrasonic probes. The miniaturization and high-density of ultrasonic probes will encounter many challenges, one of which is the acoustic crosstalk between transducer units, which is defined as the voltage, or acoustic amplitude, generated on the component under test (which is not itself excited) due to the acoustic vibration of adjacent components; Ultrasonic Transducer array, there are many Piezoelectric Micromachined Ultrasonic Transducer (PMUT) units arranged in rows and columns to form an array, that is, the PMUT unit will have multiple adjacent units; When the adjacent unit has an exciting signal, the PMUT film deforms up and down in the Z direction and generates vibration. In solid elastic materials, the vibration in the Z direction will also propagate along the X and Y directions of the horizontal plane perpendicular to the Z direction. In other words, when a PMUT unit vibrates, the adjacent unit are interfered with and disturbed by vibrations, and there will be a low amplitude vibration, which affects the normal use; They will interfere with each other.

[0003] The deep trench used in the high-voltage or image sensor process of ordinary Complementary Metal Oxide Semiconductor (CMOS) is for the purpose of better electrical or optical isolation. The requirements for acoustic isolation are very different, and the process of making deep trenches to reduce acoustic crosstalk is mainly to cut off the channels for mechanical wave propagation, reduce coupling and increase damping.

[0004] Creating deep trenches to reduce sound crosstalk in a three-dimensional architecture composed of Capacitive Micromechanical Ultrasonic Transducer (CMUT) and CMOS (specifically formed by placing CMUT on top of the CMOS chip), the process is relatively simple and direct, generally after bonding and thinning, the back of the second wafer is the silicon substrate and silicon oxide thin layer, which can directly perform the process steps related to the deep trench. At the same time, regardless of the relative size of the cavity and the unit area, it is easier to do the layout of the deep trench, as well as photolithography, etching, deep trench filling, Chemical Mechanical Polishing (CMP) and other subsequent processes; And if specific acoustic crosstalk specifications can be met, even as long as shallower deep trench etching is carried out on the silicon substrate, without the need for etching to penetrate the entire silicon mechanical layer, and the above-mentioned three-dimensional architecture composed of CMUT and CMOS can also be more easily isolated by double deep trench to further improve the isolation effect.

[0005] For the three-dimensional architecture composed of PMUT and CMOS (specifically formed by placing CMUT on top of the CMOS chip), the complexity of making deep trenches is relatively high, mainly because there are piezoelectric materials and their upper and bottom metals above the silicon mechanical layer. The thickness of the piezoelectric material layer plus its upper / lower metal layer generally reaches 1.5-3.5 microns ( µ m), and the process is relatively difficult to form deep trenches with a high Aspect Ratio (Aspect Ratio) through this layer of material. At the same time, the photolithographic etching of PZT (Lead Zirconium Titanate Piezoelectric ceramics, Pb(ZrTi)O 3 ) materials to form very small-sized patterns is also not easy, which further increases the difficulty of the deep trench process, so it is urgent to propose a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, and an ultrasonic transducer.SUMMARY OF THE INVENTION

[0006] In view of the deficiencies of the prior art, the present disclosure provides a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, and an ultrasonic transducer, wherein the deep-trench isolation method solves the problem that the current process of doing the deep-trench isolation method is relatively difficult for thinner materials.

[0007] In order to achieve the above purposes, the present disclosure provides the following technical solutions: A deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, at least one PMUT unit is arranged on the CMOS unit, all the PMUT units share a PMUT substrate, and the PMUT substrate is provided with at least one cavity; covering the cavity, a mechanical layer and a piezoelectric laminated layer are sequentially arranged on the PMUT substrate; wherein the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S2, when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, performing a process in which the deep trench is pre-designed: First etching around the cavity and from the mechanical layer to the inside of the PMUT substrate to form the deep trench.

[0008] Then depositing on the mechanical layer in the area isolated by the deep trench to form the piezoelectric laminated layer.

[0009] S3, when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, performing a process in which the deep trench is post-designed: First depositing on the mechanical layer to form the piezoelectric laminated layer.

[0010] Then etching around the cavity and from the surface of the piezoelectric laminated layer to the surface of the mechanical layer to form a contact hole, and etching from the surface of the mechanical layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench.

[0011] As a further embodiment of the present disclosure, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0012] In the step S2, the process in which the deep trench is pre-designed specifically comprises the following steps: S201, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside of the PMUT substrate; through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness. S202, after deposition, forming a mask oxide layer on the mechanical layer. S203, under the mask, photolithography and corrosion are sequentially carried out around the cavity and from the mask oxide layer to the inside of the PMUT substrate to form the deep trench. S204, after removing the mask oxide layer, depositing damping material so that the deep trench is filled with damping material and a damping layer is formed on a surface of the PMUT substrate. S205, after polishing treatment, the damping layer is removed. S206, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer. S207, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form a contact hole on the deep trench.

[0013] In the step S3, the process in which the deep trench is post-designed specifically comprises the following steps: S301, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside of the PMUT substrate, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness. S302, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer. S303, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form a contact hole. S304, after deposition, covering the mechanical layer and the piezoelectric laminated layer to form a mask oxide layer. S305, under the mask, photolithography and corrosion are sequentially carried out around the cavity and from the surface of the mask oxide layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench. S306, after removing the mask oxide layer, coating or depositing damping material, covering the bottom and side walls of the deep trench, the mechanical layer and the piezoelectric laminated layer, forming a damping layer. S307, after polishing treatment, removing excess damping layer, and retaining the damping layer in the deep trench.

[0014] Further, the preset thickness is 2-5 µm.

[0015] On the basis of the preceding scheme, both the step S207 and the step S307 are followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connection hole and a lower metal layer connection hole. S411, by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer.

[0016] Further, the damping material is a porous oxide or a porous plastic.

[0017] On the basis of the preceding scheme, in the step S204, a plasma chemical vapor deposition damping material is used to form a closed vacuum hole in the deep trench after the damping material is filled in the deep trench.

[0018] Further, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, specifically comprising: through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and the back of the mechanical layer is oxidized simultaneously to form an oxide layer between the mechanical layer and the PMUT substrate.

[0019] On the basis of the preceding scheme, the cross-section of the deep trench is a circular ring or a polygonal ring.

[0020] The present disclosure also proposes an ultrasonic transducer, comprising a CMOS unit, at least one PMUT unit is arranged on the CMOS unit, all the PMUT units share a PMUT substrate, at least one cavity is arranged concave from the surface of the PMUT substrate to the inside of the PMUT substrate; covering the cavity, a mechanical layer and a piezoelectric laminated layer are sequentially arranged on the PMUT substrate; When the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, a deep trench is arranged around the cavity and concave from the surface of the mechanical layer to the inside of the PMUT substrate, and the deep trench is filled with damping material; When the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, one or more deep trenches are arranged around the cavity and concave from the surface of the mechanical layer to the inside of the PMUT substrate, and a damping layer is formed at the bottom and side walls of the deep trench.

[0021] The present disclosure provides deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer and an ultrasonic transducer; the deep-trench isolation method has the following beneficial effects as compared to the prior art: 1. In the present disclosure, in view of the different sizes of PMUT units, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good, and the deep trenches are arranged between the PMUT units on the CMOS unit in the ultrasonic transducer for isolation, effectively reducing the acoustic crosstalk of the ultrasonic transducer. 2. In the present disclosure, after the re-deposition, the chemical mechanical polishing treatment is adopted to remove the filling medium on the silicon surface, so that the lower metal electrode material of the piezoelectric material can be deposited. After the formation of a deep trench, the damping material is filled, and outside the wider deep trench is the air, and the Si / damping material / air interface can significantly attenuate the mechanical wave; and the chemical mechanical polishing treatment is adopted after the re-deposition is carried out to remove the filling medium on the silicon surface, so that the lower metal electrode material of the piezoelectric material can be deposited. 3. In the present disclosure, through the plasma chemical vapor phase depositing damping material at low temperature, this deposition method has a fast deposition speed at the top of the deep trench, can quickly seal, and leaves a vacuum hole in the middle or bottom of the deep trench, and this technology cleverly forms the Si / damping material / air / damping material / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench. 4. In the present disclosure, another layer of medium is coated after filling with a high-damping medium, and only the deep trench filling medium and the coating medium are retained in the deep trench area through photolithography, which is reasonably designed and can further reduce acoustic crosstalk. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Fig. 1 shows a schematic diagram of the deep trench pre-design process of the deep-trench isolation method for reducing ultrasonic transducer acoustic crosstalk provided in the present disclosure. Fig. 2 shows a schematic diagram of the deep trench post-design process of a deep trench isolation method for reducing acoustic crosstalk of an ultrasonic transducers provided in the present disclosure. Fig. 3 shows a schematic diagram of the structure of the PMUT unit with deep-trench isolation of an ultrasonic transducer provided in the present disclosure. Fig. 4 shows a schematic diagram of the structure of three PMUT units with deep-trench isolation of an ultrasonic transducer provided in the present disclosure. Fig. 5 shows a schematic diagram of the top view structure of a deep-trench isolated 3×3 PMUT unit array with the small unit size of an ultrasonic transducer provided in the present disclosure. Fig. 6 shows a schematic diagram of the top view structure of a deep-trench isolated 3×3 PMUT unit array with the large unit size of an ultrasonic transducer provided in the present disclosure. FIG. 7 shows a schematic diagram of the top view structure of a deep-trench isolated 3×3 PMUT unit of different shapes with the large unit size of an ultrasonic transducer provided in the present disclosure. Fig. 8 shows a schematic diagram of the top view structure of the double-deep-trenches isolation of an ultrasonic transducer provided in the present disclosure. Fig. 9 shows a schematic diagram of the longitudinal cross-section structure of a deep trench after the plasma chemical vapor deposition damping material provided in the present disclosure.

[0023] The drawings are marked as follows: 1. a PMUT substrate; 2. a cavity; 3. a deep trench; 31. a damping material; 32. a vacuum hole; 4. a mechanical layer; 5. a piezoelectric laminated layer; 51. a top layer of piezoelectric laminated layer.DETAILED DESCRIPTION OF THE INVENTIONEmbodiment 1

[0024] Referring to Fig. 1 and Fig. 3, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, a PMUT unit is arranged on the CMOS unit, the PMUT unit comprises a PMUT substrate 1, a cavity 2 is arranged in the PMUT substrate 1; covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S2, when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, performing a process in which the deep trench is pre-designed: First etching around the cavity and from the mechanical layer to the inside of the PMUT substrate to form a deep trench.

[0025] Then depositing on the mechanical layer in the area isolated by the deep trench to form the piezoelectric laminated layer.

[0026] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0027] In the step S2, the process in which the deep trench is pre-designed specifically comprises the following steps: S201, providing a PMUT substrate, providing a cavity concave from the surface of the PMUT substrate to the inside of the PMUT substrate, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 1. S202, after deposition, forming a mask oxide layer on the mechanical layer; i.e., the "deposition" step shown in Fig. 1. S203, under the mask, photolithography and corrosion successively around the cavity and from the mask oxide layer to the inside of the PMUT substrate to form the deep trench; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 1. S204, after removing the mask oxide layer, depositing damping material so that the deep trench is filled with damping material and a damping layer is formed on a surface of the PMUT substrate; i.e., the "re-deposition" step shown in Fig. 1. S205, after polishing treatment, the damping layer is removed; i.e., the "polishing" step shown in Fig. 1. S206, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "laying material" step shown in Fig. 1. For example, the material of the piezoelectric layer can be PZT or aluminum nitride (AlN). S207, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer, forming a contact hole on the deep trench. i.e., the "piezoelectric photolithography" step shown in Fig. 1. Exemplarily, the preset thickness can be 4 µm.

[0028] In some embodiments, the step S207 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 1. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connecting hole and a lower metal layer connecting hole. S411. by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 1. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0029] Referring to Fig. 9, in some embodiments, the damping material 31 is porous plastic; at the time of deposition, the very edge of the deep trench is porous plastic, and a vacuum hole is arranged in the middle of the trench. The deposition method in the step S204 is the plasma chemical vapor deposition porous plastic at low temperature, and this deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench; and this technology cleverly forms the Si / damping material / air / damping material / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench. In the step S204, a plasma chemical vapor deposition damping material 31 is used, so that after the deep trench 3 is filled with damping material 31, a closed vacuum hole 32 is formed in the deep trench 3. Preferably, the temperature of the plasma chemical vapor deposition damping material 31 is 250-350 °C.

[0030] In other embodiments, the damping material 31 is a porous oxide (such as SiO 2 ), and the very edge of the deep trench is a porous oxide during deposition, and a vacuum hole 32 is arranged in the middle of the trench. For example, the deposition method in step S204 is the plasma chemical vapor deposition of SiO 2 at low temperature; and the deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench, and this technology cleverly forms a Si / SiO 2 / air / SiO 2 / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench. In the step S204, a plasma chemical vapor deposition damping material 31 is used, so that after the deep trench is filled with damping material, a closed vacuum hole is formed in the deep trench; For example, by plasma chemical vapor deposition of SiO 2 at low temperature, this deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench; and this technology cleverly forms a Si / SiO 2 / air / SiO 2 / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench.

[0031] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, a PMUT unit is arranged on the CMOS unit, the PMUT unit comprises a PMUT substrate 1, a cavity 2 is arranged concave from the surface of the PMUT substrate 1 to the inside of the PMUT substrate 1; covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and when the area of the cavity is greater than the second preset area, a deep trench 3 is arranged around the cavity and concave from the surface of the mechanical layer to the inside of the PMUT substrate 1, and the deep trench 3 is filled with damping material.Embodiment 2

[0032] Referring to Fig. 2 and Fig. 3, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, a PMUT unit is arranged on the CMOS unit, the PMUT unit comprises a PMUT substrate 1, a cavity 2 is arranged in the PMUT substrate 1 (i.e., a cavity 2 correspondingly is arranged in a PMUT unit); covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S3, when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, performing a process in which the deep trench is post-designed: First depositing on the mechanical layer to form the piezoelectric laminated layer.

[0033] Then etching around the cavity and from the surface of the piezoelectric laminated layer to the surface of the mechanical layer to form a contact hole, and etching from the surface of the mechanical layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench.

[0034] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0035] In the step S3, the process in which the deep trench is post-designed specifically comprises the following steps: S301, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside the PMUT substrate, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 2. S302, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "piezoelectric layer deposition" step shown in Fig. 2. S303, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form a contact hole; i.e., the "piezoelectric layer photolithography" step shown in Fig. 2. S304, after deposition, covering the mechanical layer and the piezoelectric laminated layer to form a mask oxide layer; i.e., the "deep-trench deposition" step shown in Fig. 2. S305, under the mask, photolithography and corrosion are sequentially carried out around the cavity and from the surface of the mask oxide layer in the contact hole to the inside of the PMUT substrate to form a deep trench; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 2. S306, after removing the mask oxide layer, coating or depositing damping material, covering the bottom and side walls of the deep trench, the mechanical layer and the piezoelectric laminated layer to form a damping layer; i.e., the "deep-trench media deposition" step shown in Fig. 2. S307, after polishing treatment, removing excess damping layer, and retaining the damping layer in the deep trench. i.e., the "polishing" step shown in Fig. 2.

[0036] For example, the preset thickness can be 3 µm.

[0037] In some embodiments, the step S307 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 2. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connection hole and a lower metal layer connection hole. S411, by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 2. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0038] In some embodiments, in step S306, after coating or depositing damping material, through photolithography, only the deep trench filling medium / coating medium is retained in the deep trench area, and the acoustic crosstalk can be further reduced through reasonable design.

[0039] Further, in an embodiment, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, specifically comprising: through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and the back of the mechanical layer is oxidized simultaneously to form an oxide layer between the mechanical layer and the PMUT substrate.

[0040] Further, in one embodiment, the cross-section of the deep trench is in a circular ring.

[0041] Further, in one embodiment, the cross-section of the deep trench is in a polygonal ring; For example, the polygonal ring can be square rings, hexagonal rings, octagonal rings, and so on.

[0042] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, a PMUT unit is arranged on the CMOS unit, the PMUT unit comprises a PMUT substrate 1, a cavity 2 is arranged concave from the surface of the PMUT substrate 1 to the inside of the PMUT substrate 1; covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit greater than or equal to the first preset area, and when the area of the cavity is less than or equal to the second preset area, a deep trench 3 is arranged around the cavity 2 and concave from the surface of the mechanical layer 4 to the inside of the PMUT substrate 1, and a damping layer is formed on the bottom and sidewalls of the deep trench 3.Embodiment 3

[0043] Referring to Fig. 1 and Fig. 4, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, three PMUT units are arranged on the CMOS unit, the three PMUT units are connected, the three PMUT units share a PMUT substrate 1, three cavities 2 are arranged in the PMUT substrate 1 (i.e., a cavity 2 is correspondingly arranged in a PMUT unit); covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S2, when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, performing a process in which the deep trench is pre-designed.

[0044] First etching around the cavity and from the mechanical layer to the inside of the PMUT substrate to form deep trenches.

[0045] Then depositing on the mechanical layer in the area isolated by the deep trenches to form the piezoelectric laminated layer.

[0046] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0047] In the step S2, the process in which the deep trench is pre-designed specifically comprises the following steps: S201, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside of the PMUT substrate, through fusion bonding, covering the cavities to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 1. S202, after deposition, forming a mask oxide layer on the mechanical layer; i.e., the "deposition" step shown in Fig. 1. S203, under the mask, photolithography and corrosion are sequentially carried out around the cavities and from the mask oxide layer to the inside of the PMUT substrate to form deep trenches; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 1. S204, after removing the mask oxide layer, depositing damping material so that the deep trenches are filled with damping material and a damping layer is formed on a surface of the PMUT substrate; i.e., the "re-deposition" step shown in Fig. 1. S205, after polishing treatment, the damping layer is removed; i.e., the "polishing" step shown in Fig. 1. S206, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "laying material" step shown in Fig. 1. S207, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer, forming a contact hole on the deep trench. i.e., the "piezoelectric photolithography" step shown in Fig. 1. Exemplarily, the preset thickness can be 4 µm.

[0048] In some embodiments, the step S207 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 1. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connecting hole and a lower metal layer connecting hole. S411. by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 1. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0049] Referring to Fig. 9, in some embodiments, the damping material 31 is porous plastic; at the time of deposition, the very edge of the deep trench is porous plastic, and a vacuum hole 32 is arranged in the middle of the trench. For example, the deposition method in the step S204 is the plasma chemical vapor deposition porous plastic, and this deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench; and this technology cleverly forms the Si / damping material / air / damping material / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench. In the step S204, a plasma chemical vapor deposition damping material is used, so that after the deep trench is filled with damping material, a closed vacuum hole is formed in the deep trench. Preferably, the temperature of the plasma chemical vapor deposition damping material 31 is 250-350 °C.

[0050] In other embodiments, the damping material 31 is a porous oxide (such as SiO 2 ), and the very edge of the deep trench is a porous oxide during deposition, and a vacuum hole is arranged in the middle of the trench. For example, the deposition method in step S204 is the plasma chemical vapor deposition SiO 2 ; and the deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench, and this technology cleverly forms a Si / SiO 2 / air / SiO 2 / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench. In the step S204, a plasma chemical vapor deposition damping material is used, so that after the deep trench is filled with damping material, a closed vacuum hole is formed in the deep trench; For example, by plasma chemical vapor deposition SiO 2 , this deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench; and this technology cleverly forms a Si / SiO 2 / air / SiO 2 / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench.

[0051] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, three PMUT units are arranged on the CMOS unit, the three PMUT units shares a PMUT substrate 1, three cavities 2 are arranged concave from the surface of the PMUT substrate 1 to the inside of the PMUT substrate 1 (i.e., a cavity 2 is correspondingly arranged in a PMUT unit); covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and when the area of the cavity is greater than the second preset area, deep trenches 3 are arranged around the cavities and concave from the surface of the mechanical layer to the inside of the PMUT substrate 1, and the three deep trenches 3 are filled with damping material, the three PMUT units are adjacent and a deep trench 3 is shared between adjacent PMUT units.Embodiment 4

[0052] Referring to Fig. 2 and Fig. 4, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, three PMUT units are arranged on the CMOS unit, the three PMUT units are connected, the three PMUT units share a PMUT substrate 1, three cavities 2 are arranged in the PMUT substrate 1 (i.e., a cavity 2 is correspondingly arranged in a PMUT unit); covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S3, when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, performing a process in which the deep trench is post-designed: First depositing on the mechanical layer to form the piezoelectric laminated layer.

[0053] Then etching around the cavities and from the surface of the piezoelectric laminated layer to the surface of the mechanical layer to form contact holes, and etching from the surface of the mechanical layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench.

[0054] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0055] In the step S3, the process in which the deep trench is post-designed specifically comprises the following steps: S301, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside the PMUT substrate, through fusion bonding, covering the cavities to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 2. S302, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "piezoelectric layer deposition" step shown in Fig. 2. S303, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form contact holes; i.e., the "piezoelectric layer photolithography" step shown in Fig. 2. S304, after deposition, covering the mechanical layer and the piezoelectric laminated layer to form a mask oxide layer; i.e., the "deep-trench deposition" step shown in Fig. 2. S305, under the mask, photolithography and corrosion are sequentially carried out around the cavities and from the surface of the mask oxide layer in the contact holes to the inside of the PMUT substrate to form three deep trenches; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 2. S306, after removing the mask oxide layer, coating or depositing damping material, covering the bottom and side walls of the deep trench, the mechanical layer and the piezoelectric laminated layer to form a damping layer; i.e., the "deep-trench media deposition" step shown in Fig. 2. S307, after polishing treatment, removing excess damping layer, and retaining the damping layer in the deep trench. i.e., the "polishing" step shown in Fig. 2.

[0056] For example, the preset thickness can be 3 µm.

[0057] In some embodiments, the step S307 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 2. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connection hole and a lower metal layer connection hole. S411, by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 2. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0058] In some embodiments, in step S306, after coating or depositing damping material, through photolithography, only the deep trench filling medium / coating medium is retained in the deep trench area, and the acoustic crosstalk can be further reduced through reasonable design.

[0059] Further, in an embodiment, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, specifically comprising: through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and the back of the mechanical layer is oxidized simultaneously to form an oxide layer between the mechanical layer and the PMUT substrate.

[0060] Further, in one embodiment, the cross-section of the deep trench is in a circular ring.

[0061] Further, in one embodiment, the cross-section of the deep trench is in a polygonal ring; For example, the polygonal ring can be square rings, hexagonal rings, octagonal rings, and so on.

[0062] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, at least one PMUT unit (such as 9 PMUT units) is arranged on the CMOS unit, all the PMUT units share PMUT substrate 1, at least one cavity 2 is arranged concave from the surface of the PMUT substrate 1 to the inside of the PMUT substrate 1 (i.e., a cavity 2 is correspondingly arranged in a PMUT unit); covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit greater than or equal to the first preset area, and when the area of the cavity 2 is less than or equal to the second preset area, a deep trench 3 is arranged around the cavity 2 and concave from the surface of the mechanical layer 4 to the inside of the PMUT substrate 1, and a damping layer is formed on the bottom and sidewalls of the deep trench 3, the three PMUT units are adjacent and a deep trench 3 is shared between adjacent PMUT units.Embodiment 5

[0063] Referring to Fig. 1 and Fig. 5, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, nine PMUT units are arranged on the CMOS unit, and the nine PMUT units are distributed in a 3 × 3 array, all the PMUT units share a PMUT substrate 1, the grid-like pattern is a deep trench 3 structure, the black circle is a cavity 2, and the white circle is the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer of the PMUT unit; In this design, the deep trench 3 grid completely surrounds the cavity 2 and the PMUT unit, and realizes complete isolation with the adjacent PMUT unit; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S2, when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, performing a process in which the deep trench is pre-designed: First etching around the cavity and from the mechanical layer to the inside of the PMUT substrate to form deep trenches.

[0064] Then depositing on the mechanical layer in the area isolated by the deep trenches to form the piezoelectric laminated layer.

[0065] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0066] In the step S2, the process in which the deep trench is pre-designed specifically comprises the following steps: S201, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside of the PMUT substrate, through fusion bonding, covering the cavities to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 1. S202, after deposition, forming a mask oxide layer on the mechanical layer; i.e., the "deposition" step shown in Fig. 1. S203, under the mask, photolithography and corrosion are sequentially carried out around the cavities and from the mask oxide layer to the inside of the PMUT substrate to form deep trenches; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 1. S204, after removing the mask oxide layer, depositing damping material so that the deep trenches are filled with damping material and a damping layer is formed on a surface of the PMUT substrate; i.e., the "re-deposition" step shown in Fig. 1. S205, after polishing treatment, the damping layer is removed; i.e., the "polishing" step shown in Fig. 1. S206, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "laying material" step shown in Fig. 1. S207, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer, forming a contact hole on the deep trench. i.e., the "piezoelectric photolithography" step shown in Fig. 1. Exemplarily, the preset thickness can be 4 µm.

[0067] In some embodiments, the step S207 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 1. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connecting hole and a lower metal layer connecting hole. S411. by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 1. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0068] Referring to Fig. 9, in some embodiments, the damping material 31 is porous plastic; at the time of deposition, the very edge of the deep trench is porous plastic, and a vacuum hole is arranged in the middle of the trench. The deposition method in the step S204 is the plasma chemical vapor deposition porous plastic, and this deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench; and this technology cleverly forms the Si / damping material / air / damping material / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench. In the step S204, a plasma chemical vapor deposition damping material 31 is used, so that after the deep trench 3 is filled with damping material 31, a closed vacuum hole 32 is formed in the deep trench 3. Preferably, the temperature of the plasma chemical vapor deposition damping material 31 is 250-350 °C.

[0069] In other embodiments, the damping material 31 is a porous oxide (such as SiO 2 ), and the very edge of the deep trench is a porous oxide during deposition, and a vacuum hole is arranged in the middle of the trench. For example, the deposition method in step S204 is the plasma chemical vapor deposition SiO 2 at a low temperature; and the deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench, and this technology cleverly forms a Si / SiO 2 / air / SiO 2 / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench. In the step S204, a plasma chemical vapor deposition damping material is used, so that after the deep trench is filled with damping material, a closed vacuum hole is formed in the deep trench; For example, by plasma chemical vapor deposition of SiO 2 at a low temperature, this deposition method has a fast deposition speed at the top of the deep trench, which can quickly seal and leave a vacuum hole in the middle or bottom of the deep trench; and this technology cleverly forms a Si / SiO 2 / air / SiO 2 / Si interface structure, which can significantly reduce the propagation of ultrasonic waves in the deep trench.

[0070] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, nine PMUT units are arranged on the CMOS unit, and the nine PMUT units are distributed in a 3 × 3 array, all the PMUT units share a PMUT substrate 1, the grid-like pattern is a deep trench 3 structure, the black circle is a cavity 2, and the white circle is the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer of the PMUT unit. In this design, the deep trench 3 grid completely surrounds the cavity 2 and the PMUT unit, and realizes complete isolation with the adjacent PMUT unit.Embodiment 6

[0071] Referring to Fig. 2 and Fig. 6, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, nine PMUT units are arranged on the CMOS unit, and the nine PMUT units are distributed in a 3 × 3 array, all the PMUT units share a PMUT substrate 1, the top of the PMUT unit is provided with a piezoelectric laminated layer 5, a cavity 2 is arranged around the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer from an overhead perspective; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S3, when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, performing a process in which the deep trench is post-designed: First depositing on the mechanical layer to form the piezoelectric laminated layer;

[0072] Then etching around the cavities and from the surface of the piezoelectric laminated layer to the surface of the mechanical layer to form contact holes, and etching from the surface of the mechanical layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench.

[0073] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0074] In the step S3, the process in which the deep trench is post-designed specifically comprises the following steps: S301, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside the PMUT substrate, through fusion bonding, covering the cavities to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 2. S302, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "piezoelectric layer deposition" step shown in Fig. 2. S303, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form contact holes; i.e., the "piezoelectric layer photolithography" step shown in Fig. 2. S304, after deposition, covering the mechanical layer and the piezoelectric laminated layer to form a mask oxide layer; i.e., the "deep-trench deposition" step shown in Fig. 2. S305, under the mask, photolithography and corrosion are sequentially carried out around the cavities and from the surface of the mask oxide layer in the contact holes to the inside of the PMUT substrate to form three deep trenches; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 2. S306, after removing the mask oxide layer, coating or depositing damping material, covering the bottom and side walls of the deep trench, the mechanical layer and the piezoelectric laminated layer to form a damping layer; i.e., the "deep-trench media deposition" step shown in Fig. 2. S307, after polishing treatment, removing excess damping layer, and retaining the damping layer in the deep trench. i.e., the "polishing" step shown in Fig. 2.

[0075] For example, the preset thickness can be 3 µm.

[0076] In some embodiments, the step S307 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 2. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connection hole and a lower metal layer connection hole. S411, by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 2. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0077] In some embodiments, in step S306, after coating or depositing damping material, through photolithography, only the deep trench filling medium / coating medium is retained in the deep trench area, and the acoustic crosstalk can be further reduced through reasonable design.

[0078] Further, in an embodiment, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, specifically comprising: through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and the back of the mechanical layer is oxidized simultaneously to form an oxide layer between the mechanical layer and the PMUT substrate.

[0079] Further, in one embodiment, the cross-section of the deep trench is in a circular ring.

[0080] Further, in one embodiment, the cross-section of the deep trench is in a polygonal ring; For example, the polygonal ring can be square rings, hexagonal rings, octagonal rings, and so on.

[0081] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, all the PMUT units share a PMUT substrate 1, the top of the PMUT unit is provided with a piezoelectric laminated layer 5, a cavity 2 is arranged around the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer from an overhead perspective; when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit greater than or equal to the first preset area, and when the area of the cavity 2 is less than or equal to the second preset area, a deep trench 3 is arranged around the cavity 2 and from the surface of the piezoelectric laminated layer, at the immediate vicinity of the cavity 2, an independent closed deep trench 3 is formed, and the deep trench 3 only isolates the cavity 2 and the vibrating device structure above it.Embodiment 6

[0082] Referring to Fig. 2 and Fig. 7, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, nine PMUT units are arranged on the CMOS unit, and the nine PMUT units are distributed in a 3 × 3 array, all the PMUT units share a PMUT substrate 1, the top of the PMUT unit is provided with a piezoelectric laminated layer 5, a cavity 2 is arranged around the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer from an overhead perspective; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S3, when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, performing a process in which the deep trench is post-designed: First depositing on the mechanical layer to form the piezoelectric laminated layer.

[0083] Then etching around the cavities and from the surface of the piezoelectric laminated layer to the surface of the mechanical layer to form contact holes, and etching from the surface of the mechanical layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench.

[0084] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0085] In the step S3, the process in which the deep trench is post-designed specifically comprises the following steps: S301, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside the PMUT substrate, through fusion bonding, covering the cavities to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 2. S302, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "piezoelectric layer deposition" step shown in Fig. 2. S303, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form contact holes; i.e., the "piezoelectric layer photolithography" step shown in Fig. 2. S304, after deposition, covering the mechanical layer and the piezoelectric laminated layer to form a mask oxide layer; i.e., the "deep-trench deposition" step shown in Fig. 2. S305, under the mask, photolithography and corrosion are sequentially carried out around the cavities and from the surface of the mask oxide layer in the contact holes to the inside of the PMUT substrate to form three deep trenches; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 2. S306, after removing the mask oxide layer, coating or depositing damping material, covering the bottom and side walls of the deep trench, the mechanical layer and the piezoelectric laminated layer to form a damping layer; i.e., the "deep-trench media deposition" step shown in Fig. 2. S307, after polishing treatment, removing excess damping layer, and retaining the damping layer in the deep trench. i.e., the "polishing" step shown in Fig. 2.

[0086] For example, the preset thickness can be 3 µm.

[0087] In some embodiments, the step S307 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 2. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connection hole and a lower metal layer connection hole. S411, by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 2. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0088] In some embodiments, in step S306, after coating or depositing damping material, through photolithography, only the deep trench filling medium / coating medium is retained in the deep trench area, and the acoustic crosstalk can be further reduced through reasonable design.

[0089] Further, in an embodiment, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, specifically comprising: through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and the back of the mechanical layer is oxidized simultaneously to form an oxide layer between the mechanical layer and the PMUT substrate.

[0090] Further, in one embodiment, the cross-section of the deep trench is in a circular ring.

[0091] Further, in one embodiment, the cross-section of the deep trench is in a polygonal ring; For example, the polygonal ring can be square rings, hexagonal rings, octagonal rings, and so on.

[0092] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, nine PMUT units are arranged on the CMOS unit, all the PMUT units share a PMUT substrate 1, the top of the PMUT unit is provided with a piezoelectric laminated layer 5, a cavity 2 is arranged around the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer from an overhead perspective; when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit greater than or equal to the first preset area, and when the area of the cavity 2 is less than or equal to the second preset area, around the cavity 2, a deep trench 3 is surrounded by the surface of the piezoelectric laminated layer 5, at the immediate vicinity of the cavity 2, an independent closed deep trench 3 is formed, and the deep trench 3 only isolates the cavity 2 and the vibrating device structure above it; The shape of deep trench 3 can be quadrilateral ring, hexagonal ring or octagonal ring, and so on.Embodiment 7

[0093] Referring to Fig. 2, Fig. 7 and Fig. 8, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, nine PMUT units are arranged on the CMOS unit, and the nine PMUT units are distributed in a 3 × 3 array, all the PMUT units share a PMUT substrate 1, the top of the PMUT unit is provided with a piezoelectric laminated layer 5, a cavity 2 is arranged around the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer from an overhead perspective; And the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity. S3, when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, performing a process in which the deep trench is post-designed: First depositing on the mechanical layer to form the piezoelectric laminated layer;

[0094] Then etching around the cavities and from the surface of the piezoelectric laminated layer to the surface of the mechanical layer to form contact holes, and etching from the surface of the mechanical layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench.

[0095] In some embodiments, the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer.

[0096] In the step S3, the process in which the deep trench is post-designed specifically comprises the following steps: S301, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside the PMUT substrate, through fusion bonding, covering the cavities to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; i.e., the "bonding and thinning" step shown in Fig. 2. S302, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; i.e., the "piezoelectric layer deposition" step shown in Fig. 2. S303, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form contact holes; i.e., the "piezoelectric layer photolithography" step shown in Fig. 2. S304, after deposition, covering the mechanical layer and the piezoelectric laminated layer to form a mask oxide layer; i.e., the "deep-trench deposition" step shown in Fig. 2. S305, under the mask, photolithography and corrosion are sequentially carried out around the cavities and from the surface of the mask oxide layer in the contact holes to the inside of the PMUT substrate to form three deep trenches; i.e., the "deep-trench photolithography, deep-trench corrosion" step shown in Fig. 2. S306, after removing the mask oxide layer, coating or depositing damping material, covering the bottom and side walls of the deep trench, the mechanical layer and the piezoelectric laminated layer to form a damping layer; i.e., the "deep-trench media deposition" step shown in Fig. 2. S307, after polishing treatment, removing excess damping layer, and retaining the damping layer in the deep trench. i.e., the "polishing" step shown in Fig. 2.

[0097] For example, the preset thickness can be 3 µm.

[0098] In some embodiments, the step S307 is followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; i.e., the "metal interconnect" step shown in Fig. 2. S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate. S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connection hole and a lower metal layer connection hole. S411, by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer; i.e., the "passivation layer" step shown in Fig. 2. According to different situations, the deep-trench process is done by using different methods, which solves the problem that it is difficult to make deep trenches for thinner materials under different circumstances, and the method is simple, the effect is good.

[0099] In some embodiments, in step S306, after coating or depositing damping material, through photolithography, only the deep trench filling medium / coating medium is retained in the deep trench area, and the acoustic crosstalk can be further reduced through reasonable design.

[0100] Further, in an embodiment, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, specifically comprising: through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and the back of the mechanical layer is oxidized simultaneously to form an oxide layer between the mechanical layer and the PMUT substrate.

[0101] Further, in one embodiment, the cross-section of the deep trench is in a circular ring.

[0102] Further, in one embodiment, the cross-section of the deep trench is in a polygonal ring; For example, the polygonal ring can be square rings, hexagonal rings, octagonal rings, and so on.

[0103] The present disclosure further provides an ultrasonic transducer, comprising a CMOS unit, nine PMUT units are arranged on the CMOS unit, all the PMUT units share a PMUT substrate 1, the top of the PMUT unit is provided with a piezoelectric laminated layer 5, a cavity 2 is arranged around the top layer 51 (such as the upper metal layer) of the piezoelectric laminated layer from an overhead perspective; when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit greater than or equal to the first preset area, and when the area of the cavity 2 is less than or equal to the second preset area, around the cavity 2, a deep trench 3 is surrounded by the surface of the piezoelectric laminated layer 5, at the immediate vicinity of the cavity 2, an independent closed deep trench 3 is formed, and the deep trench 3 only isolates the cavity 2 and the vibrating device structure above it; The shape of deep trench 3 can be quadrilateral ring, hexagonal ring or octagonal ring, and so on.

[0104] Anti-interference design is not limited to a single deep trench, if the unit area allows, it can also be done double-trench, or even multi- trench design; As an example of the discontinuous double-trench isolation schematic diagram shown in Fig. 8, in the unit layout, the area A, B, C, D already has related element structures, such as the vertical connection of the three-dimensional architecture, or metal wiring, etc.; The double-trench isolation can be a single trench to stagger these areas, and the other deep trench can be staggered and complementary, to ensure that at least one deep trench in the lateral path of the mechanical wave, which plays a role in reducing interference and disturbance. It should be understood that the preset size refers to the minimum transverse size of the PMUT unit when the double-deep-trench isolation process can be used; the first preset area refers to the minimum area of the PMUT unit when the double-deep-trench isolation process can be used; The second preset area refers to the maximum area of the cavity in the PMUT unit when the double-deep-trench isolation process can be used.

[0105] Anti-interference design is not limited to a single deep trench, if the unit area allows, it can also be done double-trench, or even multi- trench design; As an example of the discontinuous double-trench isolation schematic diagram shown in Fig. 8, in the unit layout, the area A, B, C, D already has related element structures, such as the vertical connection of the three-dimensional architecture, or metal wiring, etc.; The double-trench isolation can be a single trench to stagger these areas, and the other deep trench can be staggered and complementary, to ensure that at least one deep trench in the lateral path of the mechanical wave, which plays a role in reducing interference and disturbance. It should be understood that the preset size refers to the minimum transverse size of the PMUT unit when the double-deep-trench isolation process can be used; the first preset area refers to the minimum area of the PMUT unit when the double-deep-trench isolation process can be used; The second preset area refers to the maximum area of the cavity in the PMUT unit when the double-deep-trench isolation process can be used.

[0106] In the description in the present disclosure, it is important to note that: relational terms such as first and second, etc., are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or sequence between those entities or operations. Further, the term "including", "containing" or any other variation thereof is intended to cover non-exclusive inclusion so that a process, process, article or apparatus that includes a series of elements includes not only those elements, but also other elements that are not expressly listed, or that are inherent to such process, method, article or apparatus.

[0107] Although embodiments of the present disclosure have been shown and described, it is understandable to those of ordinary skill in the art that various variations, modifications, substitutions and variants can be made to these embodiments without departing from the principle and spirit of the present disclosure, and the scope of the present disclosure is limited by the attached claims and their equivalents.

Examples

embodiment 1

[0024]Referring to Fig. 1 and Fig. 3, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, a PMUT unit is arranged on the CMOS unit, the PMUT unit comprises a PMUT substrate 1, a cavity 2 is arranged in the PMUT substrate 1; covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; And the deep-trench isolation method comprises the following steps:

S1, obtaining the size and area of the PMUT unit and the area of the cavity. S2, when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, performing a process in which the deep trench is pre-designed: First etching around the cavity and from the mechanical layer to the inside of the PMUT substrate to form a deep trench.

[0025]Then depositing on the ...

embodiment 2

[0032]Referring to Fig. 2 and Fig. 3, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, a PMUT unit is arranged on the CMOS unit, the PMUT unit comprises a PMUT substrate 1, a cavity 2 is arranged in the PMUT substrate 1 (i.e., a cavity 2 correspondingly is arranged in a PMUT unit); covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; And the deep-trench isolation method comprises the following steps:

S1, obtaining the size and area of the PMUT unit and the area of the cavity. S3, when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, performing a process in which the deep trench is post-designed: First depositing on the mechanical layer to form...

embodiment 3

[0043]Referring to Fig. 1 and Fig. 4, a deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, three PMUT units are arranged on the CMOS unit, the three PMUT units are connected, the three PMUT units share a PMUT substrate 1, three cavities 2 are arranged in the PMUT substrate 1 (i.e., a cavity 2 is correspondingly arranged in a PMUT unit); covering the cavity, a mechanical layer 4 and a piezoelectric laminated layer 5 are sequentially arranged on the PMUT substrate 1; And the deep-trench isolation method comprises the following steps:

S1, obtaining the size and area of the PMUT unit and the area of the cavity. S2, when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, performing a process in which the deep trench is pre-designed.

[0044]First etching around the cavit...

Claims

1. A deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer, the ultrasonic transducer comprises a CMOS unit, at least one PMUT unit is arranged on the CMOS unit, all the PMUT units share a PMUT substrate, and each PMUT unit is provided with a cavity; covering the cavity, a mechanical layer and a piezoelectric laminated layer are sequentially arranged on the PMUT substrate; wherein the deep-trench isolation method comprises the following steps: S1, obtaining the size and area of the PMUT unit and the area of the cavity; S2, when the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, performing a process in which the deep trench is pre-designed: first etching around the cavity and from the mechanical layer to the inside of the PMUT substrate to form the deep trench; then depositing on the mechanical layer in the area isolated by the deep trench to form the piezoelectric laminated layer; S3, when the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, performing a process in which the deep trench is post-designed: first depositing on the mechanical layer to form the piezoelectric laminated layer; then etching around the cavity and from the surface of the piezoelectric laminated layer to the surface of the mechanical layer to form a contact hole, and etching from the surface of the mechanical layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench.

2. The deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer as claimed in claim 1, wherein the piezoelectric laminated layer comprises a lower metal layer, a piezoelectric layer and an upper metal layer; In the step S2, the process in which the deep trench is pre-designed specifically comprises the following steps: S201, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside of the PMUT substrate; through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; S202, after deposition, forming a mask oxide layer on the mechanical layer; S203, under the mask, photolithography and corrosion are sequentially carried out around the cavity and from the mask oxide layer to the inside of the PMUT substrate to form the deep trench; S204, after removing the mask oxide layer, depositing damping material so that the deep trench is filled with damping material and a damping layer is formed on a surface of the PMUT substrate; S205, after polishing treatment, the damping layer is removed; S206, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; S207, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form a contact hole on the deep trench; In the step S3, the process in which the deep trench is post-designed specifically comprises the following steps: S301, providing a PMUT substrate, providing at least one cavity concave from the surface of the PMUT substrate to the inside of the PMUT substrate, through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and thinning the mechanical layer to a preset thickness; S302, after deposition, a lower metal layer, a piezoelectric layer and an upper metal layer are successively formed on the mechanical layer; S303, under the mask, etching from the surface of the upper metal layer to the surface of the mechanical layer to form a contact hole; S304, after deposition, covering the mechanical layer and the piezoelectric laminated layer to form a mask oxide layer; S305, under the mask, photolithography and corrosion are sequentially carried out around the cavity and from the surface of the mask oxide layer in the contact hole to the inside of the PMUT substrate to form at least one deep trench; S306, after removing the mask oxide layer, coating or depositing damping material, covering the bottom and side walls of the deep trench, the mechanical layer and the piezoelectric laminated layer, forming a damping layer; S307, after polishing treatment, removing excess damping layer, and retaining the damping layer in the deep trench.

3. The deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer as claimed in claim 2, wherein the preset thickness is 2-5 µ m.

4. The deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer as claimed in claim 2, wherein the step S207 and the step S307 are followed by steps: S408, forming a metal interconnect layer on the back of the PMUT substrate; S409, forming a metal wiring layer along a first direction within the PMUT substrate, and forming a metal lead hole from the metal wiring layer perpendicular to the first direction, so that the metal wiring layer is connected with the metal interconnect layer, the first direction is the length direction of the PMUT substrate; S410, penetrating through the piezoelectric layer, the lower metal layer and the mechanical layer and extending to the surface of the metal wiring layer, forming an upper metal layer connection hole and a lower metal layer connection hole; S411, by deposition, covering the piezoelectric laminated layer, the mechanical layer and the bottom and side wall of the contact hole to form a passivation layer.

5. The deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer as claimed in claim 2, wherein the damping material is a porous oxide or a porous plastic.

6. The deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer as claimed in claim 2, wherein in the step S204, a plasma chemical vapor deposition damping material is used to form a closed vacuum hole in the deep trench after the damping material is filled in the deep trench.

7. The deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer as claimed in claim 2, wherein through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, specifically comprising: through fusion bonding, covering the cavity to form a mechanical layer on the PMUT substrate, and the back of the mechanical layer is oxidized simultaneously to form an oxide layer between the mechanical layer and the PMUT substrate.

8. The deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer as claimed in any one of claims 1-7, wherein the cross-section of the deep trench is a circular ring or a polygonal ring.

9. The deep-trench isolation method for reducing acoustic crosstalk of an ultrasonic transducer as claimed in claim 8, wherein the polygonal ring is a quadrilateral ring, a hexagonal ring or an octagonal ring.

10. An ultrasonic transducer, wherein comprising a CMOS unit, at least one PMUT unit is arranged on the CMOS unit, all the PMUT units share a PMUT substrate (1), at least one cavity (2) is arranged concave from the surface of the PMUT substrate to the inside of the PMUT substrate; covering the cavity, a mechanical layer (4) and a piezoelectric laminated layer (5) are sequentially arranged on the PMUT substrate (1); When the size of the PMUT unit is less than the preset size, the area of the PMUT unit is less than the first preset area, and the area of the cavity is greater than the second preset area, a deep trench (3) is arranged around the cavity and concave from the surface of the mechanical layer (4) to the inside of the PMUT substrate, and the deep trench (3) is filled with damping material; When the size of the PMUT unit is greater than or equal to the preset size, the area of the PMUT unit is greater than or equal to the first preset area, and the area of the cavity is less than or equal to the second preset area, one or more deep trenches (3) are arranged around the cavity (2) and concave from the surface of the mechanical layer (4) to the inside of the PMUT substrate, and a damping layer is formed at the bottom and side walls of the deep trench (3).

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