Transducer and method of manufacturing the same

Abstract

A transducer and its manufacturing method are disclosed. The transducer includes a substrate, a lower electrode, an insulating layer, an oscillating film, and an upper electrode. The substrate has a recess and island-shaped protrusions defining the recess. The lower electrode is disposed on the recess and island-shaped protrusions of the substrate. The insulating layer is disposed on the lower electrode. The oscillating film includes a contact portion and an oscillating portion. The contact portion contacts the insulating layer and is located between the oscillating portion and the insulating layer. A cavity is located between the oscillating portion and the recess of the substrate. The upper electrode is disposed on the oscillating film.

Description

Technical Field

[0001] This invention relates to a transducer and its manufacturing method. Background Technology

[0002] Ultrasonic transducers include bulk piezoelectric ceramic transducers, capacitive micromechanical ultrasonic transducers, and piezoelectric micromechanical ultrasonic transducers. In recent years, many manufacturers and research institutions have invested in the development of capacitive micromechanical ultrasonic transducers. This technology utilizes semiconductor processes, enabling the miniaturization of ultrasonic transducers and making them easier to integrate into various products compared to traditional bulk piezoelectric materials.

[0003] A capacitive micromechanical ultrasonic transducer includes a lower electrode, an oscillating diaphragm located above the lower electrode, and an upper electrode located on the oscillating diaphragm, wherein there is a cavity between the lower electrode and the oscillating diaphragm. The electric field between the lower electrode and the upper electrode causes the oscillating diaphragm to oscillate within the cavity, thereby emitting ultrasonic waves.

[0004] Capacitive micromechanical ultrasonic transducers can operate in either a normal mode or a breakdown mode. In normal mode, they offer stable control (linear operation) and low mechanical coupling efficiency (low sound pressure level and bandwidth), but with a narrow adjustable frequency range. In breakdown mode, they exhibit high coupling efficiency (high sound pressure level / bandwidth / sensitivity) and flexible design (wide frequency range / frequency conversion). However, the drawback is that breakdown mode consumes excessive power. Summary of the Invention

[0005] This invention provides a transducer with the advantage of low energy consumption.

[0006] The transducer of the present invention includes a substrate, a lower electrode, an insulating layer, an oscillating diaphragm, and an upper electrode. The substrate has a recess and island-shaped protrusions defining the recess. The lower electrode is disposed on the recess and island-shaped protrusions of the substrate. The insulating layer is disposed on the lower electrode. The oscillating diaphragm includes a contact portion and an oscillating portion. The contact portion contacts the insulating layer and is located between the oscillating portion and the insulating layer. A cavity is located between the oscillating portion and the recess of the substrate. The upper electrode is disposed on the oscillating diaphragm.

[0007] The method for manufacturing the transducer of the present invention includes the following steps: forming a first conductive layer on a substrate, wherein the substrate has a recess and island-shaped protrusions defining the recess, the first conductive layer including a lower electrode disposed on the recess and island-shaped protrusions of the substrate; forming an insulating layer on the first conductive layer; forming a sacrificial material layer on the insulating layer, wherein the sacrificial material layer includes a sacrificial region disposed above the lower electrode, the sacrificial region having through holes, the through holes of the sacrificial region overlapping the island-shaped protrusions of the substrate; forming an oscillating material film to cover the sacrificial material layer, wherein a portion of the oscillating material film fills the through holes of the sacrificial region and contacts the insulating layer; forming a second conductive layer on the oscillating material film, wherein the second conductive layer includes an upper electrode; forming a plurality of through holes in the oscillating material film to form an oscillating film, wherein the plurality of through holes of the oscillating film respectively exposes a plurality of locations of the sacrificial region; allowing an etching solution to enter the plurality of through holes of the oscillating film to remove the sacrificial region; forming an encapsulation layer on the oscillating film, wherein the encapsulation layer includes a plurality of sealing portions, the plurality of sealing portions being disposed in the plurality of through holes of the oscillating film and extending to the insulating layer. Attached Figure Description

[0008] Figures 1A to 1I This is a cross-sectional schematic diagram of the manufacturing process of a transducer according to an embodiment of the present invention.

[0009] Figures 2A to 2I This is a top view and perspective schematic diagram of the manufacturing process of a transducer according to an embodiment of the present invention.

[0010] Figure 3 This is a top view schematic diagram of a transducer according to an embodiment of the present invention.

[0011] Explanation of reference numerals in the attached figures:

[0012] 10: Transducer

[0013] 110: Substrate

[0014] 112: Depression

[0015] 114: Island-shaped boss

[0016] 120: First conductive layer

[0017] 122: Lower electrode

[0018] 130: Insulation layer

[0019] 132, 152': Partial

[0020] 140: Sacrificial Material Layer

[0021] 142: Sacrifice Zone

[0022] 142a, 150a: Through-hole

[0023] 150': Oscillating material film

[0024] 150: Oscillating membrane

[0025] 152: Contact Department

[0026] 154: Oscillation section

[0027] 160: Second conductive layer

[0028] 162: Upper electrode

[0029] 170: Encapsulation layer

[0030] 172: Seal Department

[0031] C: Cavity

[0032] EL: Etching solution

[0033] U: Transducer structure

[0034] I-I': section line Detailed Implementation

[0035] Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same element references are used in the drawings and description to denote the same or similar parts.

[0036] It should be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "connected" to another element, it may be directly on or connected to the other element, or an intermediate element may also be present. Conversely, when an element is referred to as being "directly on" or "directly connected" to another element, no intermediate element is present. As used herein, "connection" can refer to physical and / or electrical connection. Furthermore, "electrical connection" or "coupling" may involve the presence of other elements between the two elements.

[0037] As used herein, “about,” “approximately,” or “substantially” includes the value and the average value within an acceptable range of deviations from a particular value as determined by one of ordinary skill in the art, taking into account the measurement under discussion and a particular number of errors associated with the measurement (i.e., limitations of the measurement system). For example, “about” may mean within one or more standard deviations of the value, or within ±30%, ±20%, ±10%, ±5%. Furthermore, the use of “about,” “approximately,” or “substantially” herein may be chosen based on the optical, etched, or other properties to select a more acceptable range of deviations or standard deviations, and may not require a single standard deviation to apply to all properties.

[0038] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant technology and this invention, and will not be interpreted as having idealized or overly formal meanings unless expressly defined herein.

[0039] Figures 1A to 1I This is a cross-sectional schematic diagram of the manufacturing process of a transducer according to an embodiment of the present invention.

[0040] Figures 2A to 2I This is a top view and perspective schematic diagram of the manufacturing process of a transducer according to an embodiment of the present invention.

[0041] Figures 1A to 1I correspond Figures 2A to 2I Section I-I' Figures 1A to 1I and Figures 2A to 2I The manufacturing process of a transducer structure U of transducer 10 is shown as an example.

[0042] Please refer to Figure 1A and Figure 2A First, a substrate 110 is provided. The substrate 110 has a recess 112 and an island-shaped protrusion 114 defining the recess 112. In one embodiment, the recess 112 may be closed annular and surround the island-shaped protrusion 114. In one embodiment, the substrate 110 is made of, for example, glass. However, the invention is not limited thereto; in other embodiments, the substrate 110 may be made of quartz, an organic polymer, or other suitable materials.

[0043] Please refer to Figure 1B and Figure 2B Next, a first conductive layer 120 is formed on the substrate 110, wherein the first conductive layer 120 includes a lower electrode 122. In this embodiment, the first conductive layer 120 may selectively and completely cover the substrate 110, and the lower electrode 122 may be a region of the first conductive layer 120, but the present invention is not limited thereto. In one embodiment, the first conductive layer 120 includes, for example, a stacked layer of titanium / aluminum / titanium (Ti / Al / Ti). However, the present invention is not limited thereto, and in other embodiments, the first conductive layer 120 may also include other types of conductive materials. Furthermore, the present invention does not limit the first conductive layer 120 to necessarily including a stacked layer of multiple conductive materials; in other embodiments, the first conductive layer 120 may also include a single conductive material.

[0044] Please refer to Figure 1C and Figure 2CNext, an insulating layer 130 is formed on the first conductive layer 120. In this embodiment, the insulating layer 130 may selectively and completely cover the first conductive layer 120, but the present invention is not limited thereto. In one embodiment, the material of the insulating layer 130 may be an inorganic material (e.g., silicon nitride, silicon oxide, silicon oxynitride, or a stack of at least two of the above materials), an organic material, or a combination thereof.

[0045] Please refer to Figure 1D and Figure 2D Next, a sacrificial material layer 140 is formed on the insulating layer 130, wherein the sacrificial material layer 140 includes a sacrificial region 142 disposed above the lower electrode 122. Specifically, the sacrificial region 142 has a through-hole 142a, which overlaps with an island-shaped boss 114 on the substrate 110. In one embodiment, the island-shaped boss 114 may fall within the vertical projection of the through-hole 142a of the sacrificial region 142 onto the substrate 110, but this is not a limitation of the invention. For example, in one embodiment, the material of the sacrificial material layer 140 may be molybdenum (Mo). However, this is not a limitation of the invention, and in other embodiments, the material of the sacrificial material layer 140 may be other types of materials.

[0046] Please refer to Figure 1E and Figure 2E Next, an oscillating material film 150' is formed to cover the sacrificial material layer 140, wherein a portion 152' of the oscillating material film 150' fills the through-holes 142a of the sacrificial region 142 and contacts the insulating layer 130. In one embodiment, the material of the oscillating material film 150' may be an inorganic material (e.g., silicon nitride, silicon oxide, silicon oxynitride, or a stack of at least two of the above materials), an organic material, or a combination thereof.

[0047] Please refer to Figure 1F and Figure 2F Next, a second conductive layer 160 is formed on the oscillating material film 150', wherein the second conductive layer 160 includes an upper electrode 162. The upper electrode 162 is located above the sacrificial region 142. For example, in one embodiment, the second conductive layer 160 includes a molybdenum / aluminum / molybdenum (Mo / Al / Mo) stack. However, the invention is not limited to this, and in other embodiments, the second conductive layer 160 may also include other types of conductive materials. Furthermore, the invention does not limit the second conductive layer 160 to necessarily including a stack of multiple conductive materials; in other embodiments, the second conductive layer 160 may also include a single conductive material.

[0048] Please refer to Figure 1F , Figure 1G , Figure 2F and Figure 2GNext, a plurality of through holes 150a are formed in the oscillating material film 150' to form an oscillating film 150, wherein the plurality of through holes 150a of the oscillating film 150 exposes multiple locations of the sacrificial region 142. A portion 152' of the oscillating material film 150' that fills the through holes 142a of the sacrificial region 142 and contacts the insulating layer 130 forms a contact portion 152 of the oscillating film 150. The contact portion 152 of the oscillating film 150 contacts the insulating layer 130.

[0049] Please refer to Figure 1G , Figure 1H , Figure 2G and Figure 2H Next, the etching solution EL is introduced into the multiple through holes 150a of the oscillating film 150 to remove the sacrificial region 142.

[0050] Please refer to Figure 1I and Figure 2I Next, an encapsulation layer 170 is formed on the oscillating membrane 150, wherein the encapsulation layer 170 includes a plurality of sealing portions 172, which are respectively disposed in a plurality of through holes 150a of the oscillating membrane 150 and extend to the insulating layer 130. Thus, the transducer 10 of this embodiment is completed. In this embodiment, the material of the encapsulation layer 170 may be an inorganic material (e.g., silicon nitride, silicon oxide, silicon oxynitride, or a stack of at least two of the above materials), an organic material, or a combination thereof.

[0051] Figure 3 This is a top view schematic diagram of a transducer according to an embodiment of the present invention. Please refer to... Figure 1I , Figure 2I and Figure 3 The transducer 10 includes multiple transducer structures U. Multiple lower electrodes 122 of the multiple transducer structures U of the transducer 10 are electrically connected to each other. Multiple upper electrodes 162 of the multiple transducer structures U of the transducer 10 are electrically connected to each other.

[0052] Please refer to Figure 1I and Figure 2IEach transducer structure U includes a substrate 110, a lower electrode 122, an insulating layer 130, an oscillating diaphragm 150, and an upper electrode 162. The substrate 110 has a recess 112 and island-shaped protrusions 114 defining the recess 112. The lower electrode 122 is disposed on the recess 112 and island-shaped protrusions 114 of the substrate 110. The insulating layer 130 is disposed on the lower electrode 122. In one embodiment, the lower electrode 122 is conformally disposed on the recess 112 and island-shaped protrusions 114 of the substrate 110, and the insulating layer 130 is conformally disposed on the lower electrode 122. The oscillating diaphragm 150 includes a contact portion 152 and an oscillating portion 154. The contact portion 152 contacts the insulating layer 130 and is located between the oscillating portion 154 and the insulating layer 130. A cavity C is located between the oscillating portion 154 and the recess 112 of the substrate 110. The upper electrode 162 is disposed on the oscillating diaphragm 150. Each transducer structure U also includes an encapsulation layer 170. The encapsulation layer 170 includes a plurality of sealing portions 172. The plurality of sealing portions 172 are respectively disposed in a plurality of through holes 150a of the oscillating diaphragm 150 and extend to the insulating layer 130.

[0053] In one embodiment, the contact portion 152 of the oscillating diaphragm 150 overlaps the island-shaped protrusion 114 of the substrate 110. In one embodiment, the insulating layer 130 has a portion 132 disposed on the island-shaped protrusion 114 of the substrate 110, and the contact portion 152 of the oscillating diaphragm 150 is fixed to the portion 132 of the insulating layer 130. In one embodiment, the upper electrode 162 overlaps at least a portion of the island-shaped protrusion 114 and the recess 112 of the substrate 110. In one embodiment, in a top view, at least a portion of the island-shaped protrusion 114 and the recess 112 of the substrate 110 are located between a plurality of through holes 150a of the oscillating diaphragm 150.

[0054] Please refer to Figure 1I , Figure 2I and Figure 3 Regardless of whether the lower electrode 122 and upper electrode 162 of the transducer 10 are turned on by an applied electrical signal, the contact portion 152 of the oscillating diaphragm 150 is in contact with the insulating layer 130. The transducer 10 is suitable for operation in a single breakdown mode. That is, the electrical signal applied to the lower electrode 122 and upper electrode 162 of the transducer 10 can contain an AC component but does not need to contain a DC component. Therefore, in addition to possessing the advantages of high coupling efficiency (high sound pressure level / bandwidth / sensitivity) and flexible design (wide frequency range / frequency conversion) of conventional breakdown mode transducers, the transducer 10 also has the advantage of low power consumption.

Claims

1. A method for manufacturing a transducer, comprising: A first conductive layer is formed on a substrate, wherein the substrate has a recess and an island-shaped protrusion defining the recess, and the first conductive layer includes a lower electrode disposed on the recess and the island-shaped protrusion of the substrate. An insulating layer is formed on the first conductive layer; A sacrificial material layer is formed on the insulating layer, wherein the sacrificial material layer includes a sacrificial region disposed above the lower electrode, the sacrificial region having a through hole, and the through hole of the sacrificial region overlapping the island-shaped protrusion of the substrate; An oscillating material film is formed to cover the sacrificial material layer, wherein a portion of the oscillating material film fills the through-hole in the sacrificial region and contacts the insulating layer; A second conductive layer is formed on the oscillating material film, wherein the second conductive layer includes an upper electrode; Multiple through holes are formed in the oscillating material film to form an oscillating film, wherein the through holes of the oscillating film expose multiple locations of the sacrificial region; An etching solution is introduced into the vias of the oscillating film to remove the sacrificial region; and An encapsulation layer is formed on the oscillating membrane, wherein the encapsulation layer includes a plurality of sealing portions, which are respectively disposed in the through holes of the oscillating membrane and extend to the insulating layer.

2. The method for manufacturing a transducer as claimed in claim 1, wherein the oscillating diaphragm includes a contact portion and an oscillating portion, wherein the contact portion contacts the insulating layer and is located between the oscillating portion and the insulating layer, and a cavity of the transducer is located between the oscillating portion and the recess of the substrate.

3. The method of manufacturing a transducer as claimed in claim 2, wherein the contact portion of the oscillating diaphragm overlaps the island-shaped protrusion of the substrate.

4. The method of manufacturing a transducer as claimed in claim 2, wherein the insulating layer has a portion disposed on the island-shaped protrusion, and the contact portion of the oscillating diaphragm is fixed to the portion of the insulating layer.

5. The method of manufacturing a transducer as claimed in claim 1, wherein the upper electrode overlaps at least a portion of the island-shaped boss and the recess.

6. The method of manufacturing a transducer as claimed in claim 1, wherein, in a top view of the transducer, at least a portion of the island-shaped boss and the recess are located between the through holes of the oscillating diaphragm.

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