CN112850637B - Capacitive transducer and method for manufacturing the same - Google Patents

Abstract

A capacitive transducer comprises a substrate, a lower electrode, an oscillating element, an upper electrode and a plurality of hole sealing structures. The bottom electrode is disposed on the substrate. The oscillating element comprises an oscillating part, a connecting part and a plurality of perforations. The oscillating portion is connected to the lower electrode by a connecting portion to form a cavity. The upper electrode is disposed in the oscillating portion, and the oscillating portion is located between the upper electrode and the lower electrode. The plurality of hole sealing structures are arranged on the oscillating element. The plurality of hole sealing structures respectively extend through the plurality of perforations along the first direction. The first direction is perpendicular to the extending direction of the substrate, and the second direction is perpendicular to the first direction. Wherein, the sum of the heights of a part of the substrate and the lower electrode, which are overlapped with the plurality of through holes in the second direction, in the first direction is smaller than the sum of the heights of another part of the substrate and the lower electrode, which are not overlapped with the plurality of through holes in the second direction, in the first direction.

Description

Capacitive transducer and manufacturing method thereof

technical field

The present invention relates to a transducer device and its manufacturing method, and in particular to a capacitive transducer device and its manufacturing method.

Background technique

In the current development of ultrasonic transducers, they can be divided into bulk piezoelectric ceramic transducers (Bulk Piezoelectric Ceramics Transducer), capacitive micromachined ultrasonic transducers (Capacitive Micromachined Ultrasonic Transducer, CMUT) and piezoelectric micromachined ultrasonic transducers. (Piezoelectric Micromachined Ultrasonic Transducer, PMUT), among which bulk piezoelectric ceramic transducers are the most widely used. However, in the future trend, since the micromechanical ultrasonic transducer is prepared by the microelectromechanical system (Microelectromechanical Systems, MEMS) process, it has greater process compatibility with the integrated circuit, thus becoming the best realization of the miniaturized ultrasonic system. . Therefore, large-scale preparation and packaging can be further realized, and it can be applied in fields such as non-destructive testing, medical imaging, ultrasonic microscopy, fingerprint identification or the Internet of Things.

However, in the production of the current capacitive micro-mechanical transducer, vacuum coating technology and multiple etching processes are required to complete it. Therefore, the manufacturing cost of the capacitive micromachined ultrasonic transducer is relatively high, and the equipment is expensive. In addition, the current manufacturing method will also easily cause the substrate to bend, and there will be problems of poor uniformity after etching.

Contents of the invention

The invention provides a capacitive energy transducing device and a manufacturing method thereof, which can simplify the manufacturing process and reduce the manufacturing cost, and can avoid warpage of the board surface to obtain good measurement quality.

The invention provides a capacitive energy transducing device, which includes a substrate, a lower electrode, an oscillation element, an upper electrode and a plurality of sealing structures. The lower electrode is configured on the substrate. The oscillating element includes an oscillating part, a connecting part and a plurality of through holes. The oscillating part is connected to the lower electrode through the connecting part to form a cavity. The upper electrode is arranged on the oscillating part, and the oscillating part is located between the upper electrode and the lower electrode. A plurality of sealing structures are configured on the vibration element. The multiple sealing structures respectively extend through the multiple through holes along the first direction. The first direction is perpendicular to the extending direction of the substrate, and the second direction is perpendicular to the first direction. Wherein, the sum of heights in the first direction of a part of the substrate and the lower electrode overlapping the plurality of through holes in the second direction is smaller than that of the other part of the substrate and the lower electrode that does not overlap the plurality of through holes in the second direction in the first direction. sum of heights.

The present invention also provides a method for manufacturing a capacitive transducer, comprising the following steps: sequentially providing a substrate, a lower electrode, and a sacrificial layer; sequentially arranging an oscillating element and an upper electrode to a lower electrode and covering the sacrificial layer; forming a plurality of through holes and removing the sacrificial layer to form a cavity; removing a portion of the lower electrode overlapping the plurality of through holes in a first direction, wherein the first direction is perpendicular to the extending direction of the substrate, and the second direction is perpendicular to the first direction and providing a liquid material to a plurality of through holes to form a plurality of sealing structures, wherein the plurality of sealing structures respectively extend through the plurality of through holes along the first direction, and the substrate and the lower electrode overlap the plurality of through holes in the second direction The sum of the heights of a portion in the first direction is smaller than the sum of the heights of the other portion of the substrate and the lower electrode not overlapping the plurality of through holes in the second direction.

Based on the above, in the capacitive transducing device of the present invention, the oscillating element is used as an oscillating part, and the sum of the heights of a part of the substrate and the lower electrode overlapping the through hole in the horizontal direction is less than that of the substrate and the lower electrode not overlapping in the horizontal direction. The sum of the heights of the other part of the piercing. Therefore, the sealing structure disposed in the through hole can be made of liquid material. In this way, vacuum coating and etching processes are not required for the sealing structure, thereby simplifying the overall manufacturing process and reducing manufacturing costs. At the same time, it can avoid the warping of the board surface caused by the coating to obtain good measurement quality.

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments, but not as a limitation of the present invention.

Description of drawings

FIG. 1 is a schematic cross-sectional view of a capacitive transducer according to an embodiment of the present invention.

2A to 2F are schematic cross-sectional views of the manufacturing process of the capacitive transducer device of FIG. 1 in sequence.

FIG. 3 is a schematic cross-sectional view of a capacitive transducer according to another embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of a capacitive transducer according to another embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view of a capacitive transducer according to another embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view of a capacitive transducer according to another embodiment of the present invention.

FIG. 7 is a flowchart of a manufacturing method of a capacitive transducer according to an embodiment of the present invention.

reference sign

10: sacrificial layer

100, 100A, 100B, 100C, 100D: capacitive transducer

110, 110A: Substrate

120, 120A, 120B: lower electrodes

130:Oscillating element

132: Oscillating Department

134: connection part

140: Upper electrode

150: Sealing structure

C: Cavity

D: Aperture

D1: the first direction

D2: Second direction

G: Hollow out

H1, H2: sum of heights

H3: height

S1, S2, S3: top surface

S200, S201, S202, S203, S204: steps

V1, V2: Groove

Detailed ways

Below in conjunction with accompanying drawing, structural principle and working principle of the present invention are specifically described:

FIG. 1 is a schematic cross-sectional view of a capacitive transducer according to an embodiment of the present invention. Please refer to Figure 1. The capacitive transducer device 100 of this embodiment is, for example, a capacitive micromachined ultrasonic transducer, which can be applied in fields such as nondestructive testing, medical imaging, ultrasonic microscopy, fingerprint recognition, or the Internet of Things, and the present invention is not limited thereto. In this embodiment, the capacitive transducer device 100 includes a substrate 110 , a lower electrode 120 , an oscillation element 130 , an upper electrode 140 and a plurality of sealing structures 150 .

2A to 2F are schematic cross-sectional views of the manufacturing process of the capacitive transducer device of FIG. 1 in sequence. Please refer to FIG. 1 and FIG. 2A at the same time. The lower electrode 120 is disposed on the substrate 110 . In detail, in the steps of manufacturing the capacitive transducer device 100 , the lower electrode 120 is formed on the surface of the substrate 110 by, for example, a photoengraving process (Photo Engraving Process, PEP). The substrate 110 is, for example, a silicon substrate, and the material of the bottom electrode 120 is, for example, titanium or aluminum, but the invention is not limited thereto.

Please refer to FIG. 1 and FIG. 2B at the same time. Next, after the above steps, the sacrificial layer 10 to the lower electrode 120 are arranged. The sacrificial layer 10 is used to be etched to form a cavity in a subsequent step. In this embodiment, the heights of the sacrificial layers 10 in the first direction D1 (ie, the direction perpendicular to the extending direction of the substrate 110 ) are the same. The sacrificial layer 10 is, for example, formed on the surface of the substrate 110 by a photolithography process, and the sacrificial layer 10 is, for example, copper, but the invention is not limited thereto.

Please refer to FIG. 1 and FIG. 2C at the same time. Next, after the above steps, the oscillation element 130 is arranged to the lower electrode 120 and covers the sacrificial layer 10 . A part of the oscillating element 130 is used as an oscillating film in the capacitive transducer device 100 . For example, in this embodiment, the oscillating element 130 is, for example, silicon nitride (SiNx), and its heights in the first direction D1 are all the same, for example, 4500 angstroms, but the present invention is not limited to this. The oscillation element 130 is formed on the surface of the sacrificial layer 10 and the bottom electrode 120 by, for example, a photolithography process, and the invention is not limited thereto.

Please refer to FIG. 1 and FIG. 2D at the same time. Next, after the above steps, the upper electrode 140 is arranged to the oscillation element 130 . The upper electrode 140 and the sacrificial layer 10 are arranged in the center, and occupy an area slightly smaller than the sacrificial layer 10 on a plane parallel to the horizontal plane. The oscillation part 130 is located between the upper electrode 140 and the lower electrode 120 . The upper electrode 140 is formed on the surface of the oscillation element 130 by, for example, a photolithography process, and the material of the upper electrode 140 is the same as that of the lower electrode, such as titanium or aluminum, but the invention is not limited thereto.

Please refer to FIG. 1 and FIG. 2E at the same time. Next, after the above steps, a plurality of through holes H are formed on the oscillation element 130 and the sacrificial layer 10 is removed to form a cavity C. Referring to FIG. Specifically, in this step, an etching process (etching) is performed on the oscillating element 130 to form a through hole H at the edge of the sacrificial layer 10 (see FIG. 2D ), for subsequent etching process on the sacrificial layer 10 . The oscillation part 132 is connected to the lower electrode 120 through the connection part 134 . Then, the inner sacrificial layer 10 is etched to form the cavity C, so as to form the oscillation part 132 and the connection part 134 . The heights of the cavities C in the first direction D1 are all the same, for example, 2000 angstroms, but the invention is not limited thereto.

It is worth mentioning that in this step, the lower electrode 120 is etched while the sacrificial layer 10 is etched to form a groove V1 in the lower electrode 120 . In other words, in this embodiment, the lower electrode 120 has a plurality of grooves V1, and the grooves V1 of the lower electrode 120 overlap the corresponding through holes in the second direction D2 (ie, the perpendicular direction to the first direction D1). H. In other words, the sum of the heights H1 of the part of the substrate 110 and the lower electrode 120 that overlap the through hole H in the second direction D2 in the first direction D1 is smaller than the height H1 of the substrate 110 and the lower electrode 120 that do not overlap the through hole in the second direction D2. The sum H2 of the heights of the other part of H in the first direction D1. That is, the thickness of the lower electrode 120 at the position overlapping the through hole H in the first direction D1 is smaller than the thickness of the lower electrode 120 at the position not overlapping the through hole H in the first direction D1, and is parallel to the bottom of the cavity C and not The plane overlapping the through hole H is not coplanar with the top surface S1 of the bottom electrode 120 overlapping the through hole H in the second direction D2.

Please refer to FIG. 1 and FIG. 2F at the same time. Next, after the above steps, a plurality of sealing structures 150 are arranged on the oscillating element 130 . The sealing structures 150 respectively extend through the corresponding plurality of through holes H along the first direction D1. The material of the sealing structure 150 is a liquid organic material, such as SU-8 photoresist, but the invention is not limited thereto. The top surface S2 of the sealing structure 150 is a convex surface, but the invention is not limited thereto. In detail, since the lower electrode 120 has a groove V1 at the position overlapping the through hole H in the first direction D1, when the liquid material is supplied to the through hole H, the liquid material will not contact the surface of the lower electrode 120, thereby avoiding The liquid material penetrates into the cavity C between the oscillation part 132 and the lower electrode 120 due to the tension change. Therefore, the liquid material suspended and filled in the through hole H can be dried to form the sealing structure 150 , and then the capacitive transducer device 100 can be completed. In this way, compared with the prior art, the capacitive transducing device 100 of this embodiment does not need to perform vacuum coating and etching processes on the sealing structure 150, thereby simplifying the overall manufacturing process and reducing the manufacturing cost. At the same time, since the vacuum coating and etching processes are saved, the warping of the board surface can be avoided to obtain good measurement quality.

In detail, in this embodiment, the ratio of the diameter D of the etching hole to the height H3 is less than 7, wherein the height H3 of the etching hole is the sum of the thickness of the oscillation part 132, the height of the cavity C and the depth of the groove V1 . For example, in this embodiment, the diameter D of the etched hole is 6 microns, and the height H3 of the etched hole is 9800 angstroms, so the ratio of the diameter D of the etched hole to the height H3 is about 6.1, and no liquid is generated. Case of infiltration into cavity C. In another embodiment, the aperture D of the etched hole can be designed to be 6 microns, and the height H3 of the etched hole is 1.13 microns, so the ratio of the aperture D of the etched hole to the height H3 is about 5.3, without liquid infiltration The case of cavity C. Therefore, when the ratio of the diameter D of the etching hole to the height H3 is less than 7, the liquid material used to form the sealing structure 150 can be effectively prevented from penetrating into the cavity C.

In another embodiment, an insulating layer may be additionally disposed above the lower electrode 120 to protect the lower electrode 120 . Among them, the method of forming the groove V1 in the lower electrode 120 can also be applied to the insulating layer, so that the upper surface of the insulating layer is formed with a groove, so that the ratio of the aperture to the height of the etching hole can be within the required range, so it can effectively avoid The liquid material used to form the sealing structure penetrates into the cavity, but the invention is not limited thereto.

FIG. 3 is a schematic cross-sectional view of a capacitive transducer according to another embodiment of the present invention. Please refer to Figure 3. The capacitive transducing device 100A of this embodiment is similar to the capacitive transducing device 100 shown in FIG. 1 . The difference between the two is that, in this embodiment, the capacitive transducing device 100A further includes a protective layer 152 configured to cover the upper electrode 140 , wherein the protective layer 152 is made of the same material as the plurality of sealing structures 150 . Specifically, in this embodiment, during the step of disposing the plurality of sealing structures 150 on the oscillating element 130 , a liquid material can be further provided to cover the upper electrode 140 to form the protective layer 152 . Furthermore, in this embodiment, a liquid material may be provided to cover the integral oscillating element 130 . In this embodiment, the protective layer 152 can be made of the same material as the sealing structure 150, so it can be completed in only one process. In this way, the difficulty of configuring the sealing structure 150 can be simplified. In the present embodiment, the protective layer 152 covers the oscillating element 130 , and the top surface S3 of the protective layer 152 is a plane. In this way, the top surface of the capacitive transducer device 100A can be further planarized to facilitate subsequent processing, but the invention is not limited thereto.

FIG. 4 is a schematic cross-sectional view of a capacitive transducer according to another embodiment of the present invention. Please refer to Figure 4. The capacitive transducing device 100B of this embodiment is similar to the capacitive transducing device 100 shown in FIG. 1 . The difference between the two is that in this embodiment, the thickness of the lower electrode 120A can be further designed to be larger. In this way, the depth of the groove V1 of the lower electrode 120A can be further increased, thereby reducing the ratio of the aperture to the height of the etching hole, so as to prevent the liquid material from penetrating into the cavity C when forming the sealing structure 150 . In addition, the thickness of the substrate 110 can be further thinned.

FIG. 5 is a schematic cross-sectional view of a capacitive transducer according to another embodiment of the present invention. Please refer to Figure 5. The capacitive transducing device 100C of this embodiment is similar to the capacitive transducing device 100 shown in FIG. 1 . The difference between the two is that, in this embodiment, the lower electrode 120B has a plurality of hollows G, and the substrate 110 is exposed to these hollows G, and the multiple hollows G overlap in the second direction D2. Multiple perforations H. In this way, the depth of the etching hole can be further increased, thereby reducing the ratio of the aperture to the height of the etching hole, so as to prevent the liquid material from penetrating into the cavity C when the sealing structure 150 is manufactured.

FIG. 6 is a schematic cross-sectional view of a capacitive transducer according to another embodiment of the present invention. Please refer to Figure 6. The capacitive transducing device 100D of this embodiment is similar to the capacitive transducing device 100C shown in FIG. 5 . The difference between the two is that, in this embodiment, the substrate 110A has a plurality of grooves V2, and the grooves V2 of the substrate 110A overlap the plurality of hollows G in the second direction D2. The manner of forming the groove V2 of the substrate 110A in this embodiment may refer to the manner of forming the groove of the lower electrode, and will not be repeated here. In this way, the depth of the etching hole can be further increased, thereby reducing the ratio of the aperture to the height of the etching hole, so as to prevent the liquid material from penetrating into the cavity C when the sealing structure 150 is manufactured. In addition, the thickness of the lower electrode 120B can be further thinned.

FIG. 7 is a flowchart of a manufacturing method of a capacitive transducer according to an embodiment of the present invention. Please refer to FIG. 2A to FIG. 2F and FIG. 7 at the same time. In this embodiment, first, step S200 is performed to provide the substrate 110 , the lower electrode 120 and the sacrificial layer 10 in sequence. Next, after the above steps, step S201 is executed to sequentially arrange the oscillation element 130 and the upper electrode 140 to the lower electrode 120 to cover the sacrificial layer 10 . Next, after the above steps, step S202 is performed to form a plurality of through holes H on the oscillation element 130 and remove the sacrificial layer 10 to form a cavity C. Next, after the above steps, step S203 is performed to remove a portion of the lower electrode 120 overlapping the plurality of through holes H in the first direction D1, wherein the first direction D1 is perpendicular to the extending direction of the substrate 110, and the second direction D2 is perpendicular to The first direction D1. Finally, after the above steps, step S204 is performed to provide liquid material to the plurality of through holes H to form a plurality of sealing structures 150, wherein the plurality of sealing structures 150 respectively extend through the plurality of through holes H along the first direction D1, and the substrate 110 and the lower electrode 120 overlap the plurality of through holes H in the second direction D2. The total height H1 in the first direction D1 is smaller than that of the substrate 110 and the lower electrode 120 that do not overlap the plurality of through holes H2 in the second direction D2. The sum H2 of the heights of the other part in the first direction D1. In this way, it is not necessary to perform vacuum coating and etching processes on the sealing structure 150, thereby simplifying the overall manufacturing process and reducing the manufacturing cost. At the same time, it can avoid the warping of the board surface caused by the coating to obtain good measurement quality.

To sum up, in the capacitive transducing device of the present invention, the oscillating element is used as the oscillating part, and the sum of the heights of the part of the substrate and the lower electrode overlapping the through hole in the horizontal direction is less than that of the substrate and the lower electrode in the horizontal direction. The sum of the heights of the other part that overlaps the perforation. Therefore, the sealing structure disposed in the through hole can be made of liquid material. In this way, vacuum coating and etching processes are not required for the sealing structure, thereby simplifying the overall manufacturing process and reducing manufacturing costs. At the same time, it can avoid the warping of the board surface caused by the coating to obtain good measurement quality.

Certainly, the present invention also can have other multiple embodiments, without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding Changes and deformations should belong to the scope of protection of the appended claims of the present invention.

Claims (13)

1. A capacitive transducer, characterized in that it comprises: a substrate; The lower electrodes are arranged on the substrate; An oscillating element, including an oscillating part, a connecting part and a plurality of through holes, the oscillating part is connected to the lower electrode through the connecting part to form a cavity; an upper electrode disposed on the oscillating part, and the oscillating part is located between the upper electrode and the lower electrode; and a plurality of sealing structures configured on the oscillating element, the plurality of sealing structures respectively extending through the plurality of through holes along a first direction, the first direction being perpendicular to the extending direction of the substrate, and A second direction is perpendicular to the first direction, wherein the sum of the heights of a part of the substrate and the lower electrode overlapping the plurality of through holes in the first direction in the second direction is smaller than the The sum of the heights of another part of the substrate and the lower electrode in the second direction that does not overlap the plurality of through holes in the first direction. 2. The capacitive transducer device according to claim 1, wherein the lower electrode has a plurality of grooves, and the plurality of grooves of the lower electrode overlap in the second direction in the plurality of perforations. 3. The capacitive transducer device according to claim 1, wherein the lower electrode has a plurality of hollows, the substrate is exposed to the plurality of hollows, and the plurality of hollows The void overlaps the plurality of through holes in the second direction. 4. The capacitive transducer device according to claim 3, wherein the substrate has a plurality of grooves, and the plurality of grooves of the substrate overlaps the grooves in the second direction The multiple hollows mentioned above. 5. The capacitive transducing device according to claim 1, wherein the plane parallel to the bottom of the cavity and not overlapping with the plurality of through-holes is overlapped with the plane in the second direction The top surface of the bottom electrode or the substrate of the plurality of through holes is not coplanar. 6. The capacitive transducer device according to claim 1, wherein the ratio of the diameter of the etched hole to the height is less than 7, wherein the height of the etched hole is the thickness of the oscillation part, the cavity The sum of the height of the groove and the depth of the groove. 7. The capacitive transducer device according to claim 1, wherein the material of the plurality of sealing structures is a liquid organic material. 8. The capacitive transducer device according to claim 1, wherein the top surfaces of the plurality of sealing structures are convex. 9. The capacitive transducer according to claim 1, further comprising: A protection layer configured to cover the upper electrode, wherein the material of the protection layer is the same as that of the plurality of sealing structures. 10 . The capacitive transducer device according to claim 9 , wherein the protection layer covers the oscillating element, and the top surface of the protection layer is a plane. 11 . 11. A method for manufacturing a capacitive transducer, comprising: sequentially providing a substrate, a lower electrode and a sacrificial layer; sequentially disposing an oscillating element and an upper electrode to the lower electrode, and covering the sacrificial layer; forming a plurality of through holes on the oscillating element and removing the sacrificial layer to form a cavity; removing a portion of the lower electrode overlapping the plurality of through holes in a first direction, wherein the first direction is perpendicular to the extending direction of the substrate, and a second direction is perpendicular to the first direction; and providing a liquid material to the plurality of through holes to form a plurality of sealing structures, wherein the plurality of sealing structures respectively extend through the plurality of through holes along the first direction, and the substrate and the lower electrode The sum of heights in the first direction of a portion overlapping the plurality of through holes in the second direction is smaller than that of the substrate and the lower electrode not overlapping the plurality of through holes in the second direction The sum of the heights of the other part in the first direction. 12. The method for manufacturing a capacitive transducer according to claim 11, further comprising: The liquid material is provided and covers the upper electrode to form a protection layer. 13. The method for manufacturing a capacitive transducer according to claim 12, further comprising: The liquid material is provided to cover the oscillatory element.

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