TWI839957B - Capacitive micrormachined ultrasonic transducer and fabrication method thereof - Google Patents

Abstract

The present invention discloses a capacitive micromachined ultrasonic transducer, which includes a lower electrode, a eutectic metal, thin film layer and an upper electrode. The lower electrode includes a lower substrate, a metal layer and a first insulation layer. The lower substrate includes a metal layer covering area and a metal layer non-covering area. The metal layer covers the metal layer covering area. The first insulation layer covers the metal cover layer and the metal layer non-covering area, wherein the first insulation layer covering the metal layer forms a first convex and the first insulation layer covering the metal layer non-covering area forms a first concave. The eutectic metal is deposed on the first concave. The thin film layer is stopped by at least part of the first convex and bonded with the eutectic metal, so that a cavity is formed between the thin film layer and an exposed metal layer. The upper electrode covers an area corresponding to the cavity of the thin film layer a position corresponding to the cavity.

Description

Capacitive micromechanical ultrasonic transducer and manufacturing method thereof

The present invention relates to a sensing element manufactured using semiconductor process technology and a manufacturing method thereof, in particular to a capacitive micromechanical ultrasonic transducer and a manufacturing method thereof.

Capacitive micromechanical ultrasonic transducer (CMUT) is a sensing element used to measure distance. Its main structure is formed by an upper electrode, a thin film layer and a lower electrode from top to bottom, and there is a cavity between the thin film layer and the lower electrode.

It is known that there are many methods for manufacturing capacitive micromechanical ultrasonic transducers using semiconductor process technology. The following is an example of a bonding process using SOI wafers. In the bonding process using SOI wafers, two SOI wafers with patterned contact surfaces are generally bonded together to form an upper electrode, a thin film layer, a cavity, and a lower electrode from top to bottom. The bonding process using SOI wafers has two main disadvantages, namely, high flatness requirements and high costs. The high flatness requirement is mainly because the bonding between the two SOI wafers is achieved through bonding force, and the strength of the bonding force depends on the flatness between the two SOI wafers. The higher the flatness between the two SOI wafers, the stronger the bonding strength, thereby improving the structural strength of the capacitive micromechanical ultrasonic transducer; in other words, in order to improve the structural strength of the capacitive micromechanical ultrasonic transducer, there is a high flatness requirement between the two SOI wafers, but the high flatness requirement also increases the difficulty of the process.

In view of this, the present invention provides a capacitive micromechanical ultrasonic transducer and a manufacturing method thereof without high flatness requirements and at low cost, so as to solve the deficiencies of the previous technology.

The first purpose of the present invention is to provide a capacitive micromechanical ultrasonic transducer and a manufacturing method thereof, which achieves the purpose of not requiring high flatness and not requiring the use of high-cost SOI wafers by bonding the eutectic alloy disposed in the first recess of the lower electrode with the thin film layer covering the upper electrode.

To achieve the above purpose or other purposes, the present invention provides a capacitive micromechanical ultrasonic transducer, comprising a lower electrode, a eutectic alloy, a thin film layer and an upper electrode. The lower electrode comprises a lower substrate, a metal layer and a first insulating layer. The lower substrate comprises a metal layer covering region and a non-metal layer covering region. The metal layer covers the metal layer covering region. The first insulating layer covers the metal layer and the non-metal layer covering region, wherein the first insulating layer covering the metal layer forms a first convex portion, and the first insulating layer covering the non-metal layer covering region forms a first concave portion. The eutectic alloy is disposed in the first concave portion. The thin film layer is stopped by at least a portion of the first protrusion and bonded to the eutectic alloy, so that a cavity is formed between the thin film layer and the exposed metal layer. The upper electrode covers the area of the thin film layer corresponding to the cavity.

To achieve the above purpose or other purposes, the present invention provides another capacitive micromechanical ultrasonic transducer, comprising a lower electrode, a eutectic alloy, a thin film layer and an upper electrode. The lower electrode comprises a lower substrate, a metal layer, a first insulating layer and a second insulating layer. The lower substrate comprises a metal layer covering region and a non-metal layer covering region. The metal layer covers the metal layer covering region. The first insulating layer covers the metal layer and the non-metal layer covering region, wherein the first insulating layer covering the metal layer forms a first protrusion, and the first insulating layer covering the non-metal layer covering region forms a first concave portion. The second insulating layer covers the first insulating layer and the exposed metal layer, wherein the second insulating layer covering the first protrusion forms a second protrusion, and the second insulating layer covering the first concave portion forms a second concave portion. The eutectic alloy is disposed in the second concave portion. The thin film layer is stopped by at least a portion of the second protrusion and bonded to the eutectic alloy, so that the thin film layer, the second insulating layer covering the exposed metal layer, and the second insulating layer located on both sides of the aforementioned second insulating layer form a cavity. The upper electrode covers the region of the thin film layer corresponding to the cavity.

To achieve the above-mentioned purpose or other purposes, the present invention provides a method for manufacturing a capacitive micromechanical ultrasonic transducer, comprising the following steps: S11, providing a lower substrate, wherein the lower substrate includes a metal layer covering region and a non-metal layer covering region; S12, defining the metal layer covering region by patterning; S13, covering the metal layer and the non-metal layer covering region with a first insulating layer, and forming a first convex portion, a first concave portion and a first cavity portion by patterning the first insulating layer; S14, providing a eutectic alloy, and Set in the first concave part, and the height of the eutectic alloy is higher than the height of the first convex part; S15, provide an upper substrate whose bottom surface is covered with a thin film layer; S16, apply a force to make the thin film layer of the upper substrate continue to contact the eutectic alloy of the lower substrate until it is stopped by the first convex part, and make the thin film layer and the eutectic alloy bonded, so as to complete the bonding of the upper substrate and the lower substrate, and the thin film layer and the first cavity part form a cavity; S17, remove the upper substrate; and S18, through patterning, make the upper electrode cover the area of the thin film layer corresponding to the cavity.

To achieve the above-mentioned purpose or other purposes, the present invention provides another method for manufacturing a capacitive micromechanical ultrasonic transducer, S21, providing a lower substrate, and the lower substrate will include a metal layer covering area and a non-metal layer covering area; S22, through patterning, the metal layer covers the metal layer covering area; S23, covering the first insulating layer on the metal layer and the non-metal layer covering area, and through patterning, the first insulating layer forms a first convex portion, a first concave portion and a first cavity portion; S24, covering the first convex portion, the first concave portion and the first cavity portion with a second insulating layer, and forming a second convex portion, a first concave portion and a first cavity portion, respectively; , a second concave portion and a second cavity portion; S25, providing a eutectic alloy and setting it in the second concave portion, and the height of the eutectic alloy is higher than the height of the second convex portion; S26, providing an upper substrate whose bottom surface is covered with a thin film layer; S27, applying a force to make the thin film layer of the upper substrate continue to contact the eutectic alloy until it is stopped by the second convex portion, and making the thin film layer bond with the eutectic alloy, thereby completing the bonding of the upper substrate and the lower substrate, and the thin film layer and the second cavity portion form a cavity; S28, removing the upper substrate; and S29, through patterning, making the upper electrode cover the area of the thin film layer corresponding to the cavity.

Compared with the prior art, the present invention provides a capacitive micromechanical ultrasonic transducer and a manufacturing method thereof. By bonding the eutectic alloy disposed in the first recess of the lower electrode with the thin film layer covering the upper electrode, the capacitive micromechanical ultrasonic transducer and the manufacturing method thereof of the present invention have the following advantages: no high flatness requirement to reduce the difficulty of the process, and no high-cost SOI wafer is used to reduce the cost.

1, 2, 3, 4: Capacitive micromechanical ultrasonic transducer

100, 200: lower electrode

110, 210: Lower substrate

111, 211: Metal layer covering area

113, 213: Non-metallic layer covering area

130, 230: Metal layer

150, 250: First insulation layer

151, 251: first convex part

153, 253: first concave part

170: Second insulation layer

300:Eutectic alloy

500: Thin film layer

700: Cavity

900: Upper electrode

S11~S18: Steps

S21~S29: Steps

Figure 1 is a cross-sectional view of the capacitive micromechanical ultrasonic transducer of the first embodiment of the present invention.

Figure 2 is a cross-sectional view of the capacitive micromechanical ultrasonic transducer of the second embodiment of the present invention.

Figure 3 is a cross-sectional view of the capacitive micromechanical ultrasonic transducer of the third embodiment of the present invention.

Figure 4 is a cross-sectional view of the capacitive micromechanical ultrasonic transducer of the fourth embodiment of the present invention.

Figure 5 is a cross-sectional view of the capacitive micromechanical ultrasonic transducer of the fifth embodiment of the present invention.

Figure 6 is a flow chart of the method for manufacturing a capacitive micromechanical ultrasonic transducer according to the first embodiment of the present invention.

Figure 7(a) to Figure 7(h) are schematic diagrams corresponding to the various steps of the capacitive micromechanical ultrasonic transducer manufacturing method in Figure 6.

Figure 8 is a flow chart of the method for manufacturing a capacitive micromechanical ultrasonic transducer according to the fourth embodiment of the present invention.

Figure 9(a) to Figure 9(i) are schematic diagrams corresponding to the various steps of the capacitive micromechanical ultrasonic transducer manufacturing method in Figure 8.

In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail by the following specific embodiments and the attached drawings, as follows: In the present invention, "one" or "an" is used to describe the units, components and assemblies described herein. This is only for the convenience of explanation and to provide a general meaning for the scope of the present invention. Therefore, unless it is obvious that something else is meant, such description should be understood to include one, at least one, and the singular also includes the plural.

As used herein, the terms "include", "including", "have", "contain" or any similar terms are intended to cover non-exclusive inclusions. For example, a component, structure, article or device containing multiple elements is not limited to those listed herein but may include other elements that are not expressly listed but are generally inherent to the component, structure, article or device. In addition, unless expressly stated to the contrary, the term "or" refers to an inclusive "or" rather than an exclusive "or".

Please refer to Figure 1, which is a cross-sectional view of the capacitive micromechanical ultrasonic transducer of the first embodiment of the present invention. The capacitive micromechanical ultrasonic transducer 1 includes a lower electrode 100, a eutectic alloy 300, a thin film layer 500, a cavity 700, and an upper electrode 900.

The lower electrode 100 includes a lower substrate 110, a metal layer 130 and a first insulating layer 150. The lower substrate 110 includes a metal layer covering region 111 and a non-metal layer covering region 113, wherein the metal layer covering region 111 is a region that can be covered by the metal layer 130, and the region range is indicated by a double-direction dotted arrow; the non-metal layer covering region 113 is a region that is not covered by the metal layer 130, and the region range is indicated by a double-direction solid arrow. The metal layer 130 covers the metal layer covering region 111.

The first insulating layer 150 covers part of the metal layer 130 and the non-metal layer covering area 113. For example, in FIG1 , the first insulating layer 150 completely covers the metal layer 130 on the left side of FIG1 , and partially covers the metal layer 130 on the right side of FIG1 , so that the middle of the metal layer 130 on the right side of FIG1 is exposed. Furthermore, the first insulating layer 150 covering the metal layer 130 forms a first convex portion 151, and the first insulating layer 150 covering the non-metal layer covering area 113 forms a first concave portion 153, and the eutectic alloy 300 is disposed in the first concave portion 153.

The thin film layer 500 is stopped by all the first protrusions 151 and bonded to the eutectic alloy 300, so that a cavity 700 is formed between the thin film layer 500, the exposed metal layer 130 (i.e., the metal layer 130 not covered by the first insulating layer 150) and the first insulating layer 150 on both sides of the aforementioned metal layer 130. The upper electrode 900 covers the area of the thin film layer 500 corresponding to the cavity 700. Specifically, as shown in FIG1, the area of the thin film layer 500 corresponding to the cavity 700 refers to the area of the thin film layer 500 above the metal layer 130 on the right side of FIG1.

Please refer to Figures 1 and 2. Figure 2 is a cross-sectional view of the capacitive micromechanical ultrasonic transducer of the second embodiment of the present invention. The structure of the capacitive micromechanical ultrasonic transducer 2 in Figure 2 is roughly the same as that of the capacitive micromechanical ultrasonic transducer 1 in Figure 1. The only difference is whether the first protrusion 151 formed by the first insulating layer 150 corresponding to the complete covering of the metal layer 130 (i.e., the metal layer 130 on the left side of Figure 1 or Figure 2) is covered by the thin film layer 500.

As shown in FIG1 , the capacitive micromechanical ultrasonic transducer 1 has a non-patterned thin film layer 500, so the first protrusion 151 formed by the first insulating layer 150 that completely covers the metal layer 130 is covered by the thin film layer 500. As shown in FIG2 , the capacitive micromechanical ultrasonic transducer 2 has a pre-patterned thin film layer 500, so the first protrusion 151 formed by the first insulating layer 150 that completely covers the metal layer 130 is not covered by the thin film layer 500, that is, the first protrusion 151 is exposed.

In the capacitive micromechanical ultrasonic transducers 1, 2 of FIGS. 1, 2, the thin film layer 500 is non-conductive, so that the upper electrode 900 and the lower electrode 100 are insulated from each other, thereby preventing the upper electrode 900 and the lower electrode 100 from short-circuiting when the capacitive micromechanical ultrasonic transducers 1, 2 are actuated, thereby preventing the capacitive micromechanical ultrasonic transducers 1, 2 from being damaged. It should be noted that the form of the thin film layer 500 is not limited to this, and any form that can insulate the upper electrode 900 and the lower electrode 100 from each other is within the scope of protection of the present invention. For example, in other embodiments, the thin film layer 500 may be non-conductive only at the position corresponding to the exposed metal layer 130, that is, above the exposed metal layer 130; and may be conductive, non-conductive, or partially conductive at other positions of the thin film layer 500.

Please refer to FIG. 1 and FIG. 3 , FIG. 3 is a cross-sectional view of the capacitive micromechanical ultrasonic transducer of the third embodiment of the present invention. The capacitive micromechanical ultrasonic transducer 3 of FIG. 3 has substantially the same structure as the capacitive micromechanical ultrasonic transducer 1 of FIG. 1 , except that the capacitive micromechanical ultrasonic transducer 3 of FIG. 3 further includes a second insulating layer 170 . The second insulating layer 170 covers the exposed metal layer 130 , and the cavity 700 is formed by the thin film layer 500 , the second insulating layer 170 , and the first insulating layer 150 located on both sides of the second insulating layer 170 .

In the capacitive micromechanical ultrasonic transducer 3 of FIG. 3 , since the second insulating layer 170 covers the exposed metal layer 130 , the upper electrode 900 and the lower electrode 100 are insulated from each other; in other words, the upper electrode 900 and the lower electrode 100 are insulated from each other due to the provision of the second insulating layer 170 . Under this premise, the thin film layer 500 can be conductive, non-conductive, or partially conductive.

Please refer to FIG. 4, which is a cross-sectional view of a capacitive micromechanical ultrasonic transducer of the fourth embodiment of the present invention. The capacitive micromechanical ultrasonic transducer 4 includes a lower electrode 200, a eutectic alloy 300, a thin film layer 500, a cavity 700, and an upper electrode 900.

The lower electrode 200 includes a lower substrate 210, a metal layer 230, a first insulating layer 250, and a second insulating layer 270. The lower substrate 210 includes a metal layer covering region 211 and a non-metal layer covering region 213, wherein the metal layer covering region 211 is a region that can be covered by the metal layer 230, and the region range is indicated by a double-direction dotted arrow; the non-metal layer covering region 213 is a region that is not covered by the metal layer 230, and the region range is indicated by a double-direction solid arrow. The metal layer 230 covers the metal layer covering region 211.

The first insulating layer 250 covers part of the metal layer 230 and the non-metal layer covering area 213. For example, in FIG4 , the first insulating layer 250 completely covers the metal layer 230 on the left side of FIG4 , and partially covers the metal layer 230 on the right side of FIG4 , so that the middle of the metal layer 230 on the right side of FIG4 is temporarily exposed. Furthermore, the first insulating layer 250 covering the metal layer 230 forms a first protrusion 251, and the first insulating layer 250 covering the non-metal layer covering area 213 forms a first concave portion 253.

The second insulating layer 270 covers the first insulating layer 250 and the temporarily exposed metal layer 230, wherein the second insulating layer 270 covering the first protrusion 251 forms the second protrusion 252, and the second insulating layer 270 covering the first concave portion 253 forms the second concave portion 254, and the eutectic alloy 300 is disposed in the second concave portion 254.

The thin film layer 500 is stopped by all the second protrusions 252 and bonded to the eutectic alloy 300, so that a cavity 700 is formed between the thin film layer 500, the second insulating layer 270 covering the exposed metal layer 230, and the second insulating layer 270 located on both sides of the second insulating layer 270. The upper electrode 900 covers the area of the thin film layer 500 corresponding to the cavity 700.

In the capacitive micromechanical ultrasonic transducer 4 of FIG. 4 , since the second insulating layer 170 covers the first insulating layer 250 and the temporarily exposed metal layer 230, the upper electrode 900 and the lower electrode 100 are insulated from each other; in other words, the upper electrode 900 and the lower electrode 100 are insulated from each other due to the provision of the second insulating layer 170. Under this premise, the thin film layer 500 can be conductive, non-conductive or partially conductive.

Please refer to Figures 4 and 5. Figure 5 is a cross-sectional view of the capacitive micromechanical ultrasonic transducer of the fifth embodiment of the present invention. The structure of the capacitive micromechanical ultrasonic transducer 5 in Figure 5 is roughly the same as that of the capacitive micromechanical ultrasonic transducer 4 in Figure 4. The only difference is whether the first protrusion 251 formed by the first insulating layer 250 corresponding to the completely covered metal layer 230 (i.e., the metal layer 230 on the left side of Figure 4 or Figure 5) is indirectly covered by the thin film layer 500.

As shown in FIG4 , the capacitive micromechanical ultrasonic transducer 4 has not been patterned yet, so the first protrusion 251 formed by the first insulating layer 250 that completely covers the metal layer 230 is indirectly covered by the thin film layer 500. As shown in FIG5 , the capacitive micromechanical ultrasonic transducer 5 has been pre-patterned, so the first protrusion 251 formed by the first insulating layer 250 that completely covers the metal layer 230 is not indirectly covered by the thin film layer 500, which means that the second protrusion 252 covering the first protrusion 251 is not directly covered by the thin film layer 500, that is, the second protrusion 252 is exposed.

Please refer to Figure 6 and Figure 7(a) to Figure 7(h). Figure 6 is a flow chart of the method for manufacturing a capacitive micromechanical ultrasonic transducer of the first embodiment of the present invention. Figure 7(a) to Figure 7(h) are schematic diagrams corresponding to the steps of the method for manufacturing a capacitive micromechanical ultrasonic transducer of Figure 6, respectively.

As shown in FIG6 , the manufacturing method of the capacitive micromechanical ultrasonic transducer 1 includes steps S11 to S18, wherein steps S11 to S18 correspond to FIG7(a) to FIG7(h) respectively, for example, step S11 corresponds to FIG7(a), step S12 corresponds to FIG7(b), ... and the corresponding relationship between the subsequent steps and the drawings is similar.

In step S11, please refer to FIG. 7(a) at the same time, a lower substrate 110 is provided, and the lower substrate 110 includes a metal layer covering area 111 and a non-metal layer covering area 113.

In step S12, please also refer to FIG. 7(b), the metal layer covering area 111 is defined by patterning, that is, the metal layer 130 covers the metal layer covering area 113.

In step S13, please refer to FIG. 7(c) at the same time, the first insulating layer 150 is covered on a portion of the metal layer 130 and the non-metal layer covering region 113, and the first insulating layer 150 is patterned to form a first protrusion 151, a first recess 153 and a first cavity 155. Specifically, the first insulating layer 150 covering the metal layer 130 forms the first protrusion 151, and the first insulating layer 150 covering the non-metal layer covering region 113 forms the first recess 153. Taking FIG. 7(c) as an example, the first insulating layer 150 completely covers the metal layer 130 on the left side of FIG. 7(c) and partially covers both sides of the metal layer 130 on the right side of FIG. 7(c), so that the middle of the metal layer 130 on the right side of FIG. 7(c) is exposed, thereby forming a first cavity 155. In addition, the lower substrate 110, the metal layer 130 and the first insulating layer 150 are defined as the lower electrode 100.

In step S14, please refer to FIG. 7(d) at the same time, a eutectic alloy 300 is provided and disposed in the first concave portion 153, and the height of the eutectic alloy 300 is higher than the height of the first convex portion 153.

In step S15, please also refer to FIG. 7(e), which provides an upper substrate 300 whose bottom surface is covered with a thin film layer 500.

In step S16, please refer to Figure 7(f) at the same time, a force is applied to make the thin film layer 500 of the upper substrate 300 continue to contact the eutectic alloy 300 of the lower substrate 110 until it is stopped by the first protrusion 151, and the thin film layer 500 is bonded with the eutectic alloy 300, thereby completing the bonding of the upper substrate 300 and the lower substrate 110, and the thin film layer 500 and the first cavity portion 155 form a cavity 700. Specifically, when a force is applied to make the upper substrate 300 approach the lower substrate 110 in the downward arrow direction as shown in FIG. 7( f), since the height of the eutectic alloy 300 of the lower substrate 110 is higher than the height of the first protrusion 153, the thin film layer 500 will first contact the eutectic alloy 300. Since the eutectic alloy 300 has the property of softening and shaping when squeezed within a temperature range (e.g., less than 500° C.), when the thin film layer 500 first contacts the eutectic alloy 300, The eutectic alloy 300 will be squeezed by the thin film layer 500 to soften and shape until the thin film layer 500 is stopped by the first protrusion 151; at this time, since there is a softened and shaped eutectic alloy 300 between the eutectic alloy 300 and the thin film layer 500, and the softened and shaped eutectic alloy 300 has adhesion, the thin film layer 500 will pass through and be bonded with the eutectic alloy 300 after softening and shaping, thereby completing the bonding of the upper substrate 300 and the lower substrate 110.

In step S17, please also refer to Figure 7(g), which is to remove the upper substrate 300.

In step S18, please refer to FIG. 7(h) at the same time, the upper electrode 900 is patterned to cover the area of the thin film layer 500 corresponding to the cavity 700. Specifically, as shown in FIG. 7(h), the area of the thin film layer 500 corresponding to the cavity 700 refers to the area of the thin film layer 500 above the metal layer 130 on the right side of FIG. 7(h).

After step S11 to step S18, the capacitive micromechanical ultrasonic transducer 1 of the first embodiment of the present invention is manufactured, as shown in FIG1 or FIG7(h). In addition, since the structures of the capacitive micromechanical ultrasonic transducer 2 of the second embodiment of the present invention and the capacitive micromechanical ultrasonic transducer 3 of the third embodiment are similar to the structure of the capacitive micromechanical ultrasonic transducer 1 of the first embodiment, the manufacturing method of the capacitive micromechanical ultrasonic transducer 2 of the second embodiment and the capacitive micromechanical ultrasonic transducer 3 of the third embodiment should be inferred by those with ordinary knowledge in the relevant technical field based on the manufacturing method of the capacitive micromechanical ultrasonic transducer 1 of the first embodiment, so it is not further described.

Referring to FIG. 8 and FIG. 9(a) to FIG. 9(i), FIG. 8 is a flow chart of the method for manufacturing a capacitive micromechanical ultrasonic transducer according to the fourth embodiment of the present invention, and FIG. 9(a) to FIG. 9(i) are schematic diagrams corresponding to each step of the method for manufacturing a capacitive micromechanical ultrasonic transducer in FIG. 8 .

As shown in FIG8 , the manufacturing method of the capacitive micromechanical ultrasonic transducer 4 includes steps S21 to S29, wherein steps S21 to S29 correspond to FIG9(a) to FIG9(i) respectively, for example, step S21 corresponds to FIG9(a), step S22 corresponds to FIG9(b), ..., and the corresponding relationship between the subsequent steps and the drawings is similar.

In step S21, please refer to FIG. 9(a) at the same time, a lower substrate 210 is provided, and the lower substrate 210 defines a metal layer covering area 211 and a non-metal layer covering area 213.

In step S22, please refer to FIG. 9(b) at the same time, the metal layer covering area 211 is defined by patterning, that is, the metal layer 230 covers the metal layer covering area 213.

In step S23, please refer to FIG. 9(c) at the same time, the first insulating layer 250 is covered on a portion of the metal layer 230 and the non-metal layer covering region 213, and the first insulating layer 250 is patterned to form a first protrusion 251, a first recess 253 and a first cavity 255. Specifically, the first insulating layer 250 covering the metal layer 230 forms the first protrusion 251, and the first insulating layer 250 covering the non-metal layer covering region 213 forms the first recess 253. Taking FIG. 9(c) as an example, the first insulating layer 250 completely covers the metal layer 230 on the left side of FIG. 9(c), and partially covers both sides of the metal layer 130 on the right side of FIG. 9(c), so that the middle of the metal layer 130 on the right side of FIG. 9(c) is exposed, thereby forming a first cavity 255.

In step S24, please refer to FIG. 9(d) at the same time, the second insulating layer 230 is covered on the first protrusion 251, the first concave portion 253 and the first cavity portion 255, and the second protrusion 252, the second concave portion 254 and the second cavity portion 256 are formed respectively. In addition, the lower substrate 210, the metal layer 230, the first insulating layer 250 and the second insulating layer 270 are defined as the lower electrode 200.

In step S25, please refer to FIG. 9(e) at the same time, a eutectic alloy 300 is provided and disposed in the second concave portion 254, and the height of the eutectic alloy 300 is higher than the height of the second convex portion 252.

In step S26, please also refer to FIG. 9(f), which provides an upper substrate 300 whose bottom surface is covered with a thin film layer 500.

In step S27, please refer to Figure 9(g) at the same time, a force is applied to make the thin film layer 500 of the upper substrate 300 continue to contact the eutectic alloy 300 of the lower substrate 210 until it is stopped by the second protrusion 252, and the thin film layer 500 is bonded with the eutectic alloy 300, thereby completing the bonding of the upper substrate 300 and the lower substrate 210, and the thin film layer 500 and the second cavity portion 256 form a cavity 700. Specifically, when a force is applied to make the upper substrate 300 approach the lower substrate 210 in the downward arrow direction as shown in FIG. 9( g), since the height of the eutectic alloy 300 of the lower substrate 210 is higher than the height of the first protrusion 253, the thin film layer 500 will first contact the eutectic alloy 300. Since the eutectic alloy 300 has the property of softening and shaping when squeezed under a temperature range (e.g., less than 500° C.), when the thin film layer 500 first contacts the eutectic alloy 300, The eutectic alloy 300 will be squeezed by the thin film layer 500 to soften and shape until the thin film layer 500 is stopped by the first protrusion 251; at this time, since there is a softened and shaped eutectic alloy 300 between the eutectic alloy 300 and the thin film layer 500, and the softened and shaped eutectic alloy 300 has adhesion, the thin film layer 500 will pass through and be bonded with the eutectic alloy 300 after softening and shaping, thereby completing the bonding of the upper substrate 300 and the lower substrate 210.

In step S28, please also refer to Figure 9(h), which is to remove the upper substrate 300.

In step S29, please refer to FIG. 9(i) at the same time, the upper electrode 900 is patterned to cover the area of the thin film layer 500 corresponding to the cavity 700. Specifically, as shown in FIG. 9(i), the area of the thin film layer 500 corresponding to the cavity 700 refers to the area of the thin film layer 500 above the metal layer 230 on the right side of FIG. 9(i).

After step S21 to step S19, the capacitive micromechanical ultrasonic transducer 4 of the fourth embodiment of the present invention is manufactured, as shown in FIG4 or FIG9(i). In addition, since the structure of the capacitive micromechanical ultrasonic transducer 5 of the fifth embodiment of the present invention is similar to that of the capacitive micromechanical ultrasonic transducer 4 of the fourth embodiment, the manufacturing method of the capacitive micromechanical ultrasonic transducer 5 of the fifth embodiment should be inferred by a person with ordinary knowledge in the relevant technical field based on the manufacturing method of the capacitive micromechanical ultrasonic transducer 4 of the fourth embodiment, so it will not be described separately.

The manufacturing methods of the capacitive micromechanical ultrasonic transducers 1, 2, 3, and 4 in the aforementioned embodiments all adopt the technology of known semiconductor manufacturing processes, such as physical vapor deposition, chemical vapor deposition, and lithography patterning, etc. Those with ordinary knowledge in the relevant technical fields should be able to understand, so they will not be elaborated separately.

Next, the composition of the eutectic alloy 300, the first insulating layer 150, 250, the second insulating layer 170, and the metal layer 130, 230 of the aforementioned embodiments is described. The composition of the eutectic alloy 300 may be Ti plus Al, TiCuTi plus Al, Ti plus Au, TiW plus Au, or Ta plus Au, etc. The composition of the first insulating layer 150, 250 and the second insulating layer 170 may be SiO2 or SiNx, etc. The composition of the metal layer 130, 230 may be TiO plus Al, TiTiN plus Al, AlCu, AlSi, or AlSiCu plus TiN, etc. It should be noted that the composition of the aforementioned eutectic alloy 300, the first insulating layer 150, 250, the second insulating layer 170 and the metal layer 130, 230 is only an example, but is not limited thereto.

In summary, the capacitive micromechanical ultrasonic transducer and the manufacturing method thereof of the present invention are bonded by the eutectic alloy disposed in the first recess of the lower electrode and the thin film layer covering the upper electrode, so that the capacitive micromechanical ultrasonic transducer and the manufacturing method thereof of the present invention have the following advantages: no high flatness requirement to reduce the difficulty of the process, and no high-cost SOI wafer is used to reduce the cost.

The present invention has been disclosed in the above text with a preferred embodiment, but those familiar with the present technology should understand that the embodiment is only used to describe the present invention and should not be interpreted as limiting the scope of the present invention. It should be noted that all changes and substitutions equivalent to the embodiment should be included in the scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the patent application.

1: Capacitive micromechanical ultrasonic transducer

100: Lower electrode

110: Lower substrate

111: Metal layer covering area

113: Non-metallic layer covering area

130:Metal layer

150: First insulation layer

151: First convex part

153: First concave part

300:Eutectic alloy

500: Thin film layer

700: Cavity

900: Upper electrode

Claims (10)

A capacitive micromechanical ultrasonic transducer comprises: A lower electrode comprising: A lower substrate comprising a metal layer covering region and a non-metal layer covering region; A metal layer covering the metal layer covering region; and A first insulating layer covering the metal layer and the non-metal layer covering region, wherein the first insulating layer covering the metal layer forms a first protrusion, and the first insulating layer covering the non-metal layer covering region forms a first concave; A eutectic alloy disposed in the first concave; A thin film layer, which is stopped by at least a portion of the first protrusion and bonded to the eutectic alloy, so that a cavity is formed between the thin film layer and the exposed metal layer; and An upper electrode covers the area of the film layer corresponding to the cavity position. As described in item 1 of the patent application, the capacitive micromechanical ultrasonic transducer, wherein the cavity is formed by the thin film layer, the metal layer not covered by the first insulating layer, and the first insulating layer located on both sides of the metal layer. The capacitive micromechanical ultrasonic transducer as described in item 2 of the patent application scope, wherein the thin film layer is stopped by all the first protrusions and bonded to the eutectic alloy. As described in item 3 of the patent application scope, the capacitive micromechanical ultrasonic transducer has no thin film layer covering the first protrusion formed by the first insulating layer that completely covers the metal layer. As described in item 1 of the patent application scope, the capacitive micromechanical ultrasonic transducer, wherein the lower electrode further includes a second insulating layer, the second insulating layer covers the exposed metal layer, and the cavity is formed by the thin film layer, the second insulating layer and the first insulating layer located on both sides of the second insulating layer. A capacitive micromechanical ultrasonic transducer comprises: A lower electrode comprising: A lower substrate comprising a metal layer covering region and a non-metal layer covering region; A metal layer covering the metal layer covering region; A first insulating layer covering the metal layer and the non-metal layer covering region, wherein the first insulating layer covering the metal layer forms a first convex portion, and the first insulating layer covering the non-metal layer covering region forms a first concave portion; and A second insulating layer covering the first insulating layer and the exposed metal layer, wherein the second insulating layer covering the first protrusion forms a second protrusion, and the second insulating layer covering the first concave portion forms a second concave portion; A eutectic alloy disposed in the second concave portion; A thin film layer, which is stopped by at least a portion of the second protrusion and bonded to the eutectic alloy, so that the thin film layer, the second insulating layer covering the exposed metal layer, and the second insulating layer located on both sides of the second insulating layer form a cavity; and An upper electrode covering the region of the thin film layer corresponding to the position of the cavity. The capacitive micromechanical ultrasonic transducer as described in claim 6, wherein the thin film layer is stopped by all the second protrusions and bonded to the eutectic alloy. As described in item 6 of the patent application scope, the capacitive micromechanical ultrasonic transducer, wherein the second protrusion formed by the second insulating layer corresponding to the position of the metal layer completely covering the first insulating layer is not covered by the thin film layer. A method for manufacturing a capacitive micromechanical ultrasonic transducer comprises the following steps: S11, providing a lower substrate, wherein the lower substrate comprises a metal layer covering region and a non-metal layer covering region; S12, defining the metal layer covering region by patterning; S13, covering the metal layer and the non-metal layer covering region with a first insulating layer, and forming a first convex portion, a first concave portion and a first cavity portion by patterning the first insulating layer; S14, providing a eutectic alloy, and setting it in the first concave portion, and the height of the eutectic alloy is higher than the height of the first convex portion; S15, providing an upper substrate whose bottom surface is covered with a thin film layer; S16, applying a force to make the thin film layer of the upper substrate continue to contact the eutectic alloy of the lower substrate until it is stopped by the first protrusion, and making the thin film layer bond with the eutectic alloy, thereby completing the bonding of the upper substrate and the lower substrate, and the thin film layer and the first cavity portion form a cavity; S17, removing the upper substrate; and S18, through patterning, making an upper electrode cover the area of the thin film layer corresponding to the cavity position. A method for manufacturing a capacitive micromechanical ultrasonic transducer comprises the following steps: S21, providing a lower substrate, wherein the lower substrate comprises a metal layer covering region and a non-metal layer covering region; S22, defining the metal layer covering region by patterning; S23, covering the metal layer and the non-metal layer covering region with a first insulating layer, and forming a first convex portion, a first concave portion and a first cavity portion of the first insulating layer by patterning; S24, covering the first convex portion, the first concave portion and the first cavity portion with a second insulating layer, and forming a second convex portion, a second concave portion and a second cavity portion respectively; S25, providing a eutectic alloy and setting it in the second concave portion, and the height of the eutectic alloy is higher than the height of the second convex portion; S26, providing an upper substrate whose bottom surface is covered with a thin film layer; S27, applying a force to make the thin film layer of the upper substrate continue to contact the eutectic alloy until it is stopped by the second convex portion, and making the thin film layer bond with the eutectic alloy, thereby completing the bonding of the upper substrate and the lower substrate, and the thin film layer and the second cavity portion form a cavity; S28, removing the upper substrate; and S29, through patterning, making an upper electrode cover the area of the thin film layer corresponding to the cavity position.