Increased MUT coupling efficiency and bandwidth through end grooves, virtual pivots, and unconstrained boundaries.

Abstract

To improve the electromechanical coupling coefficient and bandwidth of micromachine ultrasonic transducers (MUTs). [Solution] In the piezoelectric micromachine ultrasonic transducer (pMUT), the circular diaphragm (101) and central anchor (105) are located on a handle substrate (103). In this case, the piezoelectric layer deposition area (bottom electrode (200), piezoelectric film (201), and upper electrode (202)) is located on the dielectric film (102) on the diaphragm (101).

Description

[Technical Field]

[0001] cross reference This patent application claims the interests of U.S. Provisional Patent Application No. 62 / 899,602, filed on 12 September 2019, which is incorporated herein by reference in its entirety. [Background technology]

[0002] Micromachine ultrasonic transducers (MUTs) are devices that convert energy between the electrical and acoustic domains. They generally come in two types: capacitive MUTs (cMUTs) and piezoelectric MUTs (pMUTs). cMUTs utilize capacitance between two plates for electromechanical conversion, while pMUTs utilize the piezoelectric properties of a piezoelectric film to perform the conversion. [Overview of the project]

[0003] Examples of conventional circular diaphragm pMUTs and cMUTs are shown in Figures 1a-1b and 2a-2d, respectively. The diaphragm (101) is formed from a substrate (100). In the case of a pMUT, the piezoelectric layer deposition area consisting of a bottom electrode (200), the piezoelectric layer (201), and the top electrode (202) are located on or near the diaphragm (101) above the dielectric layer (102). In the case of a cMUT, the substrate is attached to the dielectric layer (102) above the handle substrate (103). The diaphragm (101) is assumed to be conductive, and the second bottom electrode (200) is located below the diaphragm to form a capacitor between (101) and (200).

[0004] While MUT is described by many metrics, two of the most important is the effective electromechanical coupling of the MUT. eff 2 , and its electrical and mechanical quality factors, Q, respectively. e and Q m , that is. k of the device eff 2determines how efficiently it converts electrical energy into acoustic energy. As a result, k eff 2 is an important factor in the power specifications of the product using that MUT. k eff 2 generally varies between 0 and 1, with 1 being preferred. The mechanical and electrical quality factors drive the transducer's bandwidth, which is the frequency at which the transducer functions most effectively. For most applications, especially those related to imaging, a larger bandwidth is better, which means a lower quality factor is better.

[0005] Advantageously, the electromechanical coupling and the quality factor are related:

[0006]

Number

[0007] This means both that maximizing k eff 2 maximizes the conversion efficiency and, along with it, minimizes the quality factor of the system.

[0008] k eff 2 There are multiple ways to affect k [[ID=३४]]For a circular p

[0009]

Number

[0010] In the formula, k 31 2 is the coupling coefficient (material coefficient) of the material, λ 0n is the natural frequency parameter of the nth mode (highly dependent on the end clamping conditions), J0 is the Bessel function of the first kind of order 0, and Cn is a constant that depends on a specific pMUT design (electrode coupling constant, bending stiffness, and ratio of electrode area to diaphragm area; for the complete equation, see [2]). For a given k 31 2 coupling coefficient and C of the design constants n for, k eff,n 2 can be maximized by approaching λ 0n to zero.

[0011] The natural frequency parameter depends strongly on the boundary conditions of interest, as shown in the comparative bar graph of Figure 3. Conventional MUT designs utilize clamped ends. The “unconstrained end” in Figure 3 is equivalent to an ideal piston motion and represents the optimal coupling. Between these two extremes, multiple end conditions are of interest for improving electromechanical coupling and bandwidth.

[0012] While multiple factors affect k eff 2 an increase in the coupling coefficient can intuitively be inversely related to the normalized volume displacement. For example, the comparative graph in Figure 4 shows the normalized displacement curves for three standard circular diaphragm MUTs: namely, those with clamped ends (similar to Figures 1a - 1b and 2a - 2d), simply supported ends (i.e., ends that permit rotation but not displacement), and unconstrained ends - clamped center. Integrating the displacement over the surface area allows calculation of the displacement volume for each MUT relative to an ideal piston:

[0013] Clamped ends = 31% of the piston displacement volume.

[0014] Simply supported end MUT = 45% of the piston displacement volume.

[0015] Unconstrained ends - clamped center MUT = 54% of the piston displacement volume.

[0016] Higher displacement volumes indicate better coupling.

[0017] In one embodiment, a micromachine ultrasonic transducer (MUT) is disclosed herein, the MUT comprising: a diaphragm having substantially unconstrained ends; one or more electrodes; and one or more anchors clamping the diaphragm to a substrate within the outer edge of the diaphragm, along the outer edge of the diaphragm, or both within and along the outer edge of the diaphragm. The diaphragm may have one or more electrodes and one or more anchors of any shape. In some embodiments, the ends are unconstrained, and the anchors are entirely within the diaphragm. In some embodiments, the MUT is a pMUT comprising a piezoelectric film. In further embodiments, one or more electrodes are electrically coupled to the piezoelectric film. In further embodiments, the piezoelectric film is located on the opposite side of one or more anchors. In other embodiments, the piezoelectric film is located on the same side as one or more anchors. In some embodiments, the piezoelectric film is between one or more anchors and the diaphragm. In some embodiments, the diaphragm includes a groove. In some embodiments, the MUT comprises a plurality of anchors, where a subset of the plurality of anchors comprises one or more It is mounted on a vertical cantilever shell. In some embodiments, the MUT includes a plurality of anchors, where a subset of the plurality of anchors is mounted on one or more vertical cantilever shells, and the diaphragm includes grooves. In some embodiments, the MUT is a cMUT. In further embodiments, one or more electrodes are electrically coupled to the diaphragm in the gap. In further embodiments, the diaphragm includes grooves. In yet another embodiment, the MUT includes a plurality of anchors, where a subset of the plurality of anchors is mounted on one or more vertical cantilever shells. In yet another embodiment, the MUT includes a plurality of anchors, where a subset of the plurality of anchors is mounted on one or more vertical cantilever shells, and the diaphragm includes grooves.

[0018] In another embodiment, a micromachine ultrasonic transducer (MUT) is disclosed herein, comprising a clamped diaphragm including a vertical cantilever shell, the vertical cantilever shell being attached to the end of the diaphragm. The diaphragm can have any shape. In some embodiments, the vertical cantilever shell forms a virtual pivot that substantially prevents planar motion but allows rotation of the diaphragm end while applying a reverse torque. In various embodiments, the vertical cantilever shell has a thickness of 0.1 μm to 50 μm, and here the vertical cantilever shell has a height 1 to 100 times greater than its thickness. In yet another embodiment, the vertical cantilever shell has an area that is not continuous with respect to the diaphragm end but where no virtual pivot exists. In yet another embodiment, the MUT is multimodal.

[0019] In another embodiment, a micromachine ultrasonic transducer (MUT) comprising a clamped diaphragm including a groove is disclosed herein. The clamped diaphragm can have any shape. In some embodiments, the MUT is a pMUT. In various embodiments, the groove lies within a diaphragm thickness of 20 of the diaphragm boundary, and therein the groove has a width of up to 10 of the diaphragm thickness, and therein the groove has a depth of 1% to 100% of the diaphragm thickness. In some embodiments, the groove has a constant width. In other embodiments, the groove has a variable width. In some embodiments, the groove is split at one or more positions to allow electrical routing. In some embodiments, the MUT is multimodal. In some embodiments, the MUT is a cMUT. In various embodiments, the groove lies within a diaphragm thickness of 20 of the diaphragm boundary, where the groove has a width of up to 10 of the diaphragm thickness, and where the groove has a depth of 1% to 100% of the diaphragm thickness. In some embodiments, the groove has a constant width. In other embodiments, the groove has a variable width. In some embodiments, the groove is split at one or more positions to allow electrical routing. In some embodiments, the MUT is multimodal.

[0020] In yet another embodiment, a MUT array configured for ultrasonic imaging is disclosed herein, wherein the array comprises a plurality of MUTs as described herein. In some embodiments, each MUT in the plurality of MUTs is a pMUT. In other embodiments, each MUT in the plurality of MUTs is a cMUT. In some embodiments, each MUT in the plurality of MUTs comprises a vertical cantilever shell formed by a plurality of etchings.

[0021] In yet another embodiment, a method for manufacturing the MUT and MUT array described herein is disclosed herein.

[0022] In one embodiment, a micromachine ultrasonic transducer (MUT) is disclosed herein, the MUT comprising: a substrate, an insulating layer, an upper electrode, a piezoelectric layer, and a bottom electrode, a piezoelectric layer deposition section. Here, the piezoelectric layer deposition portion has an end portion and a central portion, and here the piezoelectric layer deposition portion has one or more grooves that pass through at least the upper electrode, the piezoelectric layer, the bottom electrode, and the insulating layer and extend into at least a part of the substrate, and here the one or more grooves are disposed between the end portion and the central portion of the piezoelectric layer deposition portion, the piezoelectric layer deposition portion, the base, and one or more anchors that connect the central portion of the piezoelectric layer deposition portion to the base and keep the end portion of the piezoelectric layer deposition portion in an unrestrained state, and the central portion of the piezoelectric layer deposition portion is clamped to the base The invention provides one or more anchors that provide an electrical connection between the base and the piezoelectric layer deposition, and a plurality of conductors, the plurality of conductors including (i) a first conductor that electrically connects the upper electrode of the piezoelectric layer deposition to the base through a first via passing through the thickness of the piezoelectric layer deposition, and (ii) a second conductor that electrically connects the bottom electrode of the piezoelectric layer deposition to the base through a second via passing through the thickness of the piezoelectric layer deposition, wherein the first via and the second via are a plurality of conductors positioned between the end portion and the central portion of the piezoelectric layer deposition. [Brief explanation of the drawing]

[0023] A better understanding of the features and advantages of this subject matter can be obtained by referring to the following detailed description and accompanying drawings illustrating exemplary embodiments. [Figure 1a] A conventional circular diaphragm pMUT is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 1b] A conventional circular diaphragm pMUT is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 2a] A conventional circular diaphragm cMUT is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 2b]A conventional circular diaphragm cMUT is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 2c] A conventional circular diaphragm cMUT, which has a conductive portion on the top of the handle substrate instead of the bottom electrode as shown in the cMUTs of Figures 2a and 2b, is shown in (c) layout and (d) cross-sectional view, respectively. [Figure 2d] A conventional circular diaphragm cMUT, which has a conductive portion on the top of the handle substrate instead of the bottom electrode as shown in the cMUTs of Figures 2a and 2b, is shown in (c) layout and (d) cross-sectional view, respectively. [Figure 3] This is a bar graph showing the natural frequency parameters of the fundamental mode, λ01, as a function of boundary conditions. Interpreted from [1] by [2]. Blue represents the most common MUT end conditions, i.e., the clamped state. Red represents boundary conditions assuming that [2] is "physically feasible". [Figure 4] The graphs of normalized displacement curves for different end conditions for a circular diaphragm of radius a are shown. [Figure 5a] An exemplary circular diaphragm pMUT with an upper surface groove is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 5b] An exemplary circular diaphragm pMUT with an upper surface groove is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 5c] An exemplary circular diaphragm pMUT having an upper surface groove, using silicon on an insulating (SOI) wafer, and including an oxide layer embedded between the device layer and the handle layer, is shown in (c) layout and (d) cross-sectional view, respectively. [Figure 5d] An exemplary circular diaphragm pMUT having an upper surface groove, using silicon on an insulating (SOI) wafer, and including an oxide layer embedded between the device layer and the handle layer, is shown in (c) layout and (d) cross-sectional view, respectively. [Figure 6a]An exemplary circular diaphragm cMUT having an upper surface groove is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 6b] An exemplary circular diaphragm cMUT having an upper surface groove is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 6c] An exemplary circular diaphragm cMUT having an upper surface groove and a conductive portion on the upper part of the handle substrate instead of a bottom electrode as in the cMUT of Figures 6a and 6b is shown in (c) layout and (d) cross-sectional view, respectively. [Figure 6d] An exemplary circular diaphragm cMUT having an upper surface groove and a conductive portion on the upper part of the handle substrate instead of a bottom electrode as in the cMUT of Figures 6a and 6b is shown in (c) layout and (d) cross-sectional view, respectively. [Figure 7a] An exemplary circular diaphragm pMUT with upper surface virtual pivot etching is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 7b] An exemplary circular diaphragm pMUT with upper surface virtual pivot etching is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 7c] An exemplary circular diaphragm pMUT, having a top surface virtual pivot etching, using silicon on an insulating (SOI) wafer, and including an oxide layer embedded between the device layer and the handle layer, is shown in (c) layout and (d) cross-sectional view, respectively. [Figure 7d] An exemplary circular diaphragm pMUT, having a top surface virtual pivot etching, using silicon on an insulating (SOI) wafer, and including an oxide layer embedded between the device layer and the handle layer, is shown in (c) layout and (d) cross-sectional view, respectively. [Figure 8a] An exemplary circular diaphragm cMUT with upper surface virtual pivot etching is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 8b]An exemplary circular diaphragm cMUT with upper surface virtual pivot etching is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 8c] An exemplary circular diaphragm cMUT having a top surface virtual pivot etching and a conductive portion on the top of the handle substrate instead of the bottom electrode as in the cMUT in Figures 8a and 8b is shown in (c) layout and (d) cross-sectional view, respectively. [Figure 8d] An exemplary circular diaphragm cMUT having a top surface virtual pivot etching and a conductive portion on the top of the handle substrate instead of the bottom electrode as in the cMUT in Figures 8a and 8b is shown in (c) layout and (d) cross-sectional view, respectively. [Figure 9a] Exemplary variations of end grooves are shown: (a) any diaphragm shape, (b) multiple grooves, (c) grooves with variable width, and (d) a grooveless selection area. For simplification, only diaphragm ends (dotted lines) and grooves (solid lines) are shown. [Figure 9b] Exemplary variations of end grooves are shown: (a) any diaphragm shape, (b) multiple grooves, (c) grooves with variable width, and (d) a grooveless selection area. For simplification, only diaphragm ends (dotted lines) and grooves (solid lines) are shown. [Figure 9c] Exemplary variations of end grooves are shown: (a) any diaphragm shape, (b) multiple grooves, (c) grooves with variable width, and (d) a grooveless selection area. For simplification, only diaphragm ends (dotted lines) and grooves (solid lines) are shown. [Figure 9d] Exemplary variations of end grooves are shown: (a) any diaphragm shape, (b) multiple grooves, (c) grooves with variable width, and (d) a grooveless selection area. For simplification, only diaphragm ends (dotted lines) and grooves (solid lines) are shown. [Figure 10a]Exemplary variations of the virtual pivot are shown: (a) an arbitrary diaphragm shape, (b) multiple virtual pivot trenches, (c) a virtual pivot trench with variable width, and (d) a selected area without virtual pivot trenches. For simplification, only the diaphragm ends (dotted lines) and the first and second virtual pivot etchings (solid lines, black and gray, respectively) are shown. [Figure 10b] Exemplary variations of the virtual pivot are shown: (a) an arbitrary diaphragm shape, (b) multiple virtual pivot trenches, (c) a virtual pivot trench with variable width, and (d) a selected area without virtual pivot trenches. For simplification, only the diaphragm ends (dotted lines) and the first and second virtual pivot etchings (solid lines, black and gray, respectively) are shown. [Figure 10c] Exemplary variations of the virtual pivot are shown: (a) an arbitrary diaphragm shape, (b) multiple virtual pivot trenches, (c) a virtual pivot trench with variable width, and (d) a selected area without virtual pivot trenches. For simplification, only the diaphragm ends (dotted lines) and the first and second virtual pivot etchings (solid lines, black and gray, respectively) are shown. [Figure 10d] Exemplary variations of the virtual pivot are shown: (a) an arbitrary diaphragm shape, (b) multiple virtual pivot trenches, (c) a virtual pivot trench with variable width, and (d) a selected area without virtual pivot trenches. For simplification, only the diaphragm ends (dotted lines) and the first and second virtual pivot etchings (solid lines, black and gray, respectively) are shown. [Figure 11a] An exemplary pMUT having unrestrained ends, a clamped center, and a piezoelectric layer deposition area on the opposite side of the anchor is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 11b] An exemplary pMUT having unrestrained ends, a clamped center, and a piezoelectric layer deposition area on the opposite side of the anchor is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 12a] An exemplary pMUT having an unrestrained end, a clamped center, and a piezoelectric layer deposition area on the same side as the anchor is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 12b] An exemplary pMUT having an unrestrained end, a clamped center, and a piezoelectric layer deposition area on the same side as the anchor is shown in (a) layout and (b) cross-sectional view, respectively. [Figure 13a] An exemplary cMUT, having unrestrained ends and a clamped center, and a counter electrode located between the substrate and a diaphragm (assumed to be conductive in this exemplary embodiment), is shown (a) in layout form and (b) in cross-sectional view, respectively. [Figure 13b] An exemplary cMUT, having unrestrained ends and a clamped center, and a counter electrode located between the substrate and a diaphragm (assumed to be conductive in this exemplary embodiment), is shown (a) in layout form and (b) in cross-sectional view, respectively. [Figure 14a] Exemplary variations of an unconstrained end having a fixed internal area and / or a fixed end area are shown: (a) any diaphragm shape, (b) multiple anchor areas, (c) multiple anchor areas of any shape, and (d) a selected area having a fixed end where the anchors overlap the end. For simplification, only the diaphragm (101) and anchors are shown (dotted lines indicate dark gray interiors). [Figure 14b] Exemplary variations of an unconstrained end having a fixed internal area and / or a fixed end area are shown: (a) any diaphragm shape, (b) multiple anchor areas, (c) multiple anchor areas of any shape, and (d) a selected area having a fixed end where the anchors overlap the end. For simplification, only the diaphragm (101) and anchors are shown (dotted lines indicate dark gray interiors). [Figure 14c]Exemplary variations of an unconstrained end having a fixed internal area and / or a fixed end area are shown: (a) any diaphragm shape, (b) multiple anchor areas, (c) multiple anchor areas of any shape, and (d) a selected area having a fixed end where the anchors overlap the end. For simplification, only the diaphragm (101) and anchors are shown (dotted lines indicate dark gray interiors). [Figure 14d] Exemplary variations of an unconstrained end having a fixed internal area and / or a fixed end area are shown: (a) any diaphragm shape, (b) multiple anchor areas, (c) multiple anchor areas of any shape, and (d) a selected area having a fixed end where the anchors overlap the end. For simplification, only the diaphragm (101) and anchors are shown (dotted lines indicate dark gray interiors). [Figure 15a] An exemplary circular diaphragm pMUT having both end groove etching and virtual pivot etching is shown in (a) layout form and (b) cross-sectional view, respectively. [Figure 15b] An exemplary circular diaphragm pMUT having both end groove etching and virtual pivot etching is shown in (a) layout form and (b) cross-sectional view, respectively. [Figure 15c] An exemplary circular diaphragm pMUT, which has both edge groove etching and virtual pivot etching, uses silicon on an insulating (SOI) wafer, and includes an oxide layer embedded between the device layer and the handle layer, is shown in (c) layout and (d) cross-sectional view, respectively. [Figure 15d] An exemplary circular diaphragm pMUT, which has both edge groove etching and virtual pivot etching, uses silicon on an insulating (SOI) wafer, and includes an oxide layer embedded between the device layer and the handle layer, is shown in (c) layout and (d) cross-sectional view, respectively. [Figure 16a]An exemplary circular diaphragm cMUT having both end groove etching and virtual pivot etching is shown (a) in layout form and (b) in cross-sectional view (end groove (300) in beige and virtual pivot etching (301b) in gray), respectively. [Figure 16b] An exemplary circular diaphragm cMUT having both end groove etching and virtual pivot etching is shown (a) in layout form and (b) in cross-sectional view (end groove (300) in beige and virtual pivot etching (301b) in gray), respectively. [Figure 16c] An exemplary circular diaphragm cMUT having both end groove etching and virtual pivot etching, and having a conductive portion on the top of the handle substrate instead of the bottom electrode as in the cMUT in Figures 16a and 16b, is shown in (c) layout form and (d) cross-sectional view (end groove (300) in beige and virtual pivot etching (301b) in gray, respectively. [Figure 16d] An exemplary circular diaphragm cMUT having both end groove etching and virtual pivot etching, and having a conductive portion on the top of the handle substrate instead of the bottom electrode as in the cMUT in Figures 16a and 16b, is shown in (c) layout form and (d) cross-sectional view (end groove (300) in beige and virtual pivot etching (301b) in gray, respectively. [Figure 16e] An exemplary circular diaphragm cMUT having both end groove etching and virtual pivot etching, and having a gap defining the diaphragm formed in the handle portion, is shown in (e) layout form and (f) cross-sectional view (end groove (300) in beige and virtual pivot etching (301b) in gray). [Figure 16f] An exemplary circular diaphragm cMUT having both end groove etching and virtual pivot etching, and having a gap defining the diaphragm formed in the handle portion, is shown in (e) layout form and (f) cross-sectional view (end groove (300) in beige and virtual pivot etching (301b) in gray). [Figure 16g] An exemplary circular diaphragm cMUT having both end groove etching and virtual pivot etching, and having a gap defining the diaphragm formed in the handle portion, is shown in (g) layout and (h) cross-sectional view (end groove (300) in beige and virtual pivot etching (301b) in gray, respectively. [Figure 16h] An exemplary circular diaphragm cMUT having both end groove etching and virtual pivot etching, and having a gap defining the diaphragm formed in the handle portion, is shown in (g) layout and (h) cross-sectional view (end groove (300) in beige and virtual pivot etching (301b) in gray, respectively. [Figure 17a] An exemplary pMUT having unrestrained ends, a clamped center, and piezoelectric layer deposits on the opposite side of the anchor is shown (a) in layout form and (b) in cross-sectional view, respectively (for clarity, virtual pivot etching (301b) is not shown in layout form). [Figure 17b] An exemplary pMUT having unrestrained ends, a clamped center, and piezoelectric layer deposits on the opposite side of the anchor is shown (a) in layout form and (b) in cross-sectional view, respectively (for clarity, virtual pivot etching (301b) is not shown in layout form). [Figure 18a] An exemplary pMUT having an unrestrained end and a clamped center, and a piezoelectric layer deposition area on the same side as the anchor, is shown (a) in layout form and (b) in cross-sectional view, respectively (for clarity, a virtual pivot etching (301b) is not shown in layout form). [Figure 18b] An exemplary pMUT having an unrestrained end and a clamped center, and a piezoelectric layer deposition area on the same side as the anchor, is shown (a) in layout form and (b) in cross-sectional view, respectively (for clarity, a virtual pivot etching (301b) is not shown in layout form). [Figure 19a]An exemplary cMUT, having unconstrained ends and a clamped center, and a counter electrode located between the substrate and a diaphragm (assumed to be conductive in this exemplary embodiment), is shown (a) in layout form and (b) in cross-sectional view, respectively (for clarity, a virtual pivot etching (301b) is not shown in layout form). [Figure 19b] An exemplary cMUT, having unconstrained ends and a clamped center, and a counter electrode located between the substrate and a diaphragm (assumed to be conductive in this exemplary embodiment), is shown (a) in layout form and (b) in cross-sectional view, respectively (for clarity, a virtual pivot etching (301b) is not shown in layout form). [Figure 20a] An exemplary pMUT having unconstrained ends and a clamped center, two parallel independent electrodes, and a redistribution layer in contact with the upper and bottom electrodes of the piezoelectric layer deposition area is shown (a) in layout form and (b) in cross-sectional view. [Figure 20b] An exemplary pMUT having unconstrained ends and a clamped center, two parallel independent electrodes, and a redistribution layer in contact with the upper and bottom electrodes of the piezoelectric layer deposition area is shown (a) in layout form and (b) in cross-sectional view. [Modes for carrying out the invention]

[0024] In some embodiments, a micromachine ultrasonic transducer (MUT) is disclosed herein, the MUT comprising: a diaphragm having substantially unconstrained ends; one or more electrodes; and one or more anchors clamping the diaphragm to a substrate within the diaphragm, along the outer edge of the diaphragm, or both within and along the outer edge of the diaphragm. The diaphragm may have one or more electrodes and one or more anchors of any shape. In some embodiments, the ends are unconstrained, and the anchors are entirely within the diaphragm. In some embodiments, the MUT is a pMUT comprising a piezoelectric film. In further embodiments, one or more electrodes are electrically coupled to the piezoelectric film. In further embodiments, the piezoelectric film is located on the opposite side of one or more anchors. In other embodiments, the piezoelectric film is located on the same side as one or more anchors. In some embodiments, the piezoelectric film is located between one or more anchors and the diaphragm. In some embodiments, the diaphragm includes a groove. In some embodiments, the MUT comprises a plurality of anchors, wherein a subset of the plurality of anchors is attached to one or more vertical cantilever shells. In some embodiments, the MUT includes a plurality of anchors, where a subset of the plurality of anchors is attached to one or more vertical cantilever shells, and where the diaphragm includes a groove. In some embodiments, the MUT is a cMUT. In further embodiments, one or more electrodes are electrically coupled to the diaphragm in a gap. In further embodiments, the diaphragm includes grooves. In yet another embodiment, the MUT includes a plurality of anchors, wherein a subset of the plurality of anchors is attached to one or more vertical cantilever shells. In yet another embodiment, the MUT includes a plurality of anchors, wherein a subset of the plurality of anchors is attached to one or more vertical cantilever shells, and the diaphragm includes grooves.

[0025] In some embodiments, a micromachine ultrasonic transducer (MUT) is disclosed herein, comprising a clamped diaphragm including a vertical cantilever shell, the vertical cantilever shell being attached to the end of the diaphragm. The diaphragm can have any shape. In some embodiments, the vertical cantilever shell forms a virtual pivot that substantially prevents planar motion but allows rotation of the diaphragm end while applying a reverse torque. In various embodiments, the vertical cantilever shell has a thickness of 0.1 μm to 50 μm, and here the vertical cantilever shell has a height 1 to 100 times greater than its thickness. In further embodiments, the vertical cantilever shell has an area that is not continuous with respect to the diaphragm end but where no virtual pivot exists. In further embodiments, the MUT is multimodal.

[0026] In some embodiments, micromachine ultrasonic transducers (MUTs) comprising a clamped diaphragm including a groove are disclosed herein. The clamped diaphragm can have any shape. In some embodiments, the MUT is a pMUT. In various embodiments, the groove lies within a diaphragm thickness of 20 of the diaphragm boundary, where the groove has a width of up to 10 of the diaphragm thickness, and where the groove has a depth of 1% to 100% of the diaphragm thickness. In some embodiments, the groove has a constant width. In other embodiments, the groove has a variable width. In some embodiments, the groove is split at one or more positions to allow electrical routing. In some embodiments, the MUT is multimodal. In some embodiments, the MUT is a cMUT. In various embodiments, the groove lies within a diaphragm thickness of 20 of the diaphragm boundary, where the groove has a width of up to 10 of the diaphragm thickness, and where the groove has a depth of 1% to 100% of the diaphragm thickness. In some embodiments, the groove has a constant width. In other embodiments, the groove has a variable width. In some embodiments, the groove is split at one or more positions to allow electrical routing. In some embodiments, the MUT is multimodal.

[0027] In various embodiments, MUT arrays configured for ultrasonic imaging are disclosed herein, wherein the array comprises a plurality of MUTs as described herein. In some embodiments, each MUT in the plurality of MUTs is a pMUT. In other embodiments, each MUT in the plurality of MUTs is a cMUT. In some embodiments, each MUT in the plurality of MUTs comprises a vertical cantilever shell formed by a plurality of etchings.

[0028] In various embodiments, methods for manufacturing the MUT and MUT array described herein are disclosed herein.

[0029] In certain embodiments, a micromachine transducer (MUT) is disclosed herein, the MUT comprising: a substrate, an insulating layer, an upper electrode, a piezoelectric layer, and a bottom electrode, wherein the piezoelectric layer deposition comprises an end portion and a central portion, wherein the piezoelectric layer deposition comprises at least the upper electrode, the piezoelectric layer, the bottom electrode, and the insulating layer, and at least the substrate A piezoelectric layer deposition portion having one or more grooves extending in part thereof, wherein the one or more grooves are located between the end portion and the central portion of the piezoelectric layer deposition portion, a base, one or more anchors connecting the central portion of the piezoelectric layer deposition portion to the base and keeping the end portion of the piezoelectric layer deposition portion unrestrained, wherein the central portion of the piezoelectric layer deposition portion is clamped to the base, and the one or more anchors provide an electrical coupling between the base and the piezoelectric layer deposition portion, and a plurality of conductors, the plurality of conductors including (i) a first conductor electrically coupling the upper electrode of the piezoelectric layer deposition portion to the base through a first via passing through the thickness of the piezoelectric layer deposition portion, and (ii) a second conductor electrically coupling the bottom electrode of the piezoelectric layer deposition portion to the base through a second via passing through the thickness of the piezoelectric layer deposition portion, wherein the first via and the second via include a plurality of conductors located between the end portion and the central portion of the piezoelectric layer deposition portion.

[0030] Specific definition Unless otherwise defined, all technical terms used herein have the same meaning as those generally understood by those skilled in the art to which the present invention pertains. When used herein and in the appended claims, the singular forms “a,” “an,” and “the” also include plural references unless explicitly indicated by the context. Any reference to “or” herein is intended to include “and / or” unless otherwise specified.

[0031] An overview of methodology Three methods are presented to improve the electromechanical coupling coefficient and bandwidth of micromachine ultrasonic transducers, or MUTs:

[0032] 1) Forming a groove along the end of the clamped diaphragm to locally increase the diaphragm's adaptability at that end.

[0033] 2) A virtual pivot is formed via a vertical cantilever shell, thereby constraining planar motion but allowing reverse rotation due to reverse torque, thus creating boundary conditions similar to those of a simply supported end, which are restrained by a torsion spring, and,

[0034] 3) To form a diaphragm having ends that are mostly unrestrained and that are clamped at one or more positions within the diaphragm or on its outer edge.

[0035] Diaphragm with end grooves This specification discloses a method for reducing the stiffness of a diaphragm near a diaphragm end by etching a groove near the diaphragm end. This results in a diaphragm having a boundary that acts between a clamped end and a simply supported end by a torsion spring. This “end groove” promotes piston-like motion, better coupling, and a wider bandwidth.

[0036] As shown in Figures 5a-5b and 6a-6b, this end groove (300) can be applied to both pMUT and cMUT embodiments. For it to be effective, the diaphragm end (101a) should be within approximately 5 of the diaphragm thickness. The width of the groove affects the stiffness; a wider groove promotes the simple support action, while simultaneously reducing the planar bending stiffness, resulting in a greater frequency shift.

[0037] Virtual pivot-assisted diaphragm Similarly, a methodology for forming a "virtual pivot" acting on a simply supported end, which is similarly restrained by a torsion spring, is further disclosed. This is accomplished by forming a vertical cantilever shell at the diaphragm end. This cantilever shell is opposed to vertical displacement. It is extremely rigid and effectively prevents displacement in the z-direction. The cantilever shell is relatively adaptable to torsion of the diaphragm end, allowing rotation but imparting a counter-moment based on the dimensions of the shell. The cantilever shell is also highly sensitive to lateral displacement in the x and y directions via external lateral forces. In the absence of such lateral forces, the cantilever shell thus prevents displacement of the diaphragm end, while allowing rotation and imparting a counter-moment.

[0038] The formation of the cantilever shell can be carried out in several ways. One example for a pMUT is shown in Figures 7a and 7b, where a virtual pivot trench (301a) is etched outside the diaphragm end (101a) and deeper than the diaphragm thickness. The cantilever shell is formed by the remaining material between the virtual pivot etching (301a) and the cavity (100) that forms the diaphragm (101). The properties of the virtual pivot (e.g., torsion spring stiffness, resistance to lateral forces) depend on the dimensions of the cantilever shell. The longer and thinner the shell, the greater the adaptability of the virtual pivot.

[0039] As shown in Figures 8a and 8b, a similar approach can also be used for cMUTs. The virtual pivot trench (301a) is etched around the outer edge of the diaphragm. For the most common cMUT construction, the cavity formed between the diaphragm (101) and the bottom electrode is very narrow. By placing a single virtual pivot trench (301a), the resulting cantilever shell (10b) is short and wide, resulting in a very rigid torsion spring. To create a more adaptable cantilever shell (101b), a second virtual pivot trench (301b) can be etched inside the first trench (301a), and both trenches extend through the dielectric layer (102) into the handle substrate (103). This results in a more adaptable virtual pivot.

[0040] Diaphragm of any shape having end grooves In light of the disclosure herein, it will be apparent to those skilled in the art that the basic design features of the end grooves can be applied to any diaphragm shape, as shown in Figure 9a. Furthermore, the number and position of the grooves (Figure 9b) and the width of the grooves (Figure 9c) can also be varied. In fact, the end grooves do not need to be of a constant width to provide a beneficial effect. For practical purposes such as routing electrical signals, it may be necessary to cut the grooves in a selected area without compromising the overall usefulness of the grooves (Figure 9d).

[0041] A diaphragm of any shape with a virtual pivot. Similarly, in light of the disclosure herein, it will be apparent to those skilled in the art that the basic design features of the virtual pivot can be applied to any diaphragm shape, as shown in Figure 10a. It is also possible to vary the number and location of the virtual pivot etchings (Figure 10b) and the width of the etchings (Figure 10c). Even more so than with grooves, virtual pivot etchings do not require a constant width to perform their intended function. Similar to grooves, virtual pivot trenches can be cut in selected areas to enable tasks such as electrical routing (Figure 10d).

[0042] Diaphragm having an unrestrained end and a clamped central area To further increase the electromechanical coupling coefficient and broaden the bandwidth, a design methodology is disclosed in which the diaphragm has mostly unconstrained ends and is arbitrarily clamped at the center by one or more anchors. This design has similar advantages to the unconstrained end-center clamp design referred to in Figure 3.

[0043] Figures 11a and 11b show typical embodiments of the pMUT configuration, where a circular diaphragm (101) and a central anchor (105) are located on a handle substrate (103). In this case, the piezoelectric layer deposition area (bottom electrode (200), piezoelectric film (201), and upper electrode (202)) is located on the dielectric film (102) on the diaphragm (101). Figures 12a and 12b show another pMUT configuration, where the piezoelectric layer deposition area is located between the diaphragm (101) and the anchor (105).

[0044] Figures 13a and 13b show a cMUT with a similar configuration, where electrodes (200) and (202) are located on a dielectric film (102) on a handle substrate (103). An anchor (105) attaches electrode (202) to the diaphragm (101). Many configurations are possible to create a diaphragm with unconstrained ends, fixed by one or more anchors, thereby forming a capacitor of two electrodes spaced apart from each other.

[0045] A diaphragm of any shape having an unrestrained end clamped in one or more arbitrary areas inside, or having an electrode of any shape attached to an unrestrained end. In light of the disclosure herein, it will be apparent to those skilled in the art that the concept of a MUT with an unconstrained end can be applied to a diaphragm of any shape having one or more clamping areas of any shape and upper and lower electrodes of any shape. Figures 14a–14c provide some examples of such variations. Importantly, as illustrated in Figure 14d, it is possible to manufacture a diaphragm with variable unconstrained and clamped boundaries by superimposing anchors on the ends of the diaphragm.

[0046] Combining end grooves and virtual pivots In light of the disclosure herein, it will be apparent to those skilled in the art that combining the concepts of end grooves and virtual pivots makes it possible to create more adaptable end conditions than by applying either concept alone. Examples of pMUTs and cMUTs constructed according to both inventions are shown in Figures 15a-15d and 16a-16d, respectively.

[0047] Combining an unconstrained end, end groove, and virtual pivot. In light of the disclosure herein, it will also be apparent to those skilled in the art that the concepts of end grooves and virtual pivots can be applied together or separately to an unconstrained end MUT invention. Figures 17a-17b, 18a-18b, and 19a-19b illustrate this concept for a pMUT having a piezoelectric layer deposition on a diaphragm (101), a pMUT where the piezoelectric layer deposition is located between the diaphragm (101) and an anchor (105), and a cMUT, respectively.

[0048] Manufacturing method for pMUT with grooves and virtual pivots Exemplary methods for manufacturing pMUTs having grooves and virtual pivots, such as the pMUTs shown in Figures 15a-15b and 15c-15d, are described here.

[0049] (a) Firstly, a single-crystal silicon substrate is generally provided.

[0050] (b) The insulating layer (102) can then be deposited on the substrate. The insulating layer (102) is generally some form of SiO2 and has a thickness of about 0.1 μm to 3 μm. It is generally deposited by thermal oxidation, PECVD deposition, or other techniques.

[0051] (c) Subsequently, a first metal layer (200) (also referred to as M1 or metal 1) may be deposited. Generally, this adheres to the substrate to prevent the diffusion of the piezoelectric element and the structure of the piezoelectric element. This is a combination of conductive films that aid in the deposition / growth of a fabricated film. SRO (SrRuO3) may be used for the growth of the structured film, with Ti as the adhesive layer, acting as a diffusion barrier, and Pt on top for conductivity (Pt on SiO2). Typically, these layers are thin, less than 200 nm, and films of 10-40 nm also exist. Due to issues related to load, production surface, and cost, this deposited layer will usually be limited to less than 1 μm. The conductor (Pt) is generally thicker than the structural layer (SRO) and the adhesive layer (Ti). Other common structural layers are, rather than SRO, (La, to give a few examples) 0.5 Sr 0.5 )CoO3, (La 0.5 Sr 0.5 This includes MnO3, LaNiO3, RuO2, IrO2, and BaPbO3. Pt can be replaced with other conductive materials such as Cu, Cr, Ni, Ag, Al, Mo, W, and NiCr. These other materials typically have disadvantages such as weak diffusion barriers, brittleness, or poor adhesion, and Pt is the most commonly used conductor. The adhesive layer, i.e., Ti, can be replaced with any common adhesive layer such as TiW, TiN, Cr, Ni, Cr, etc.

[0052] (d) A piezoelectric material (201) can then be deposited. Some common examples of suitable piezoelectric materials include PZT, KNN, PZT-N, PMN-Pt, AlN, Sc-AlN, ZnO, PVDF, and LiNiO3. The thickness of the piezoelectric layer may vary from 100 nm to 5 μm or more.

[0053] (e) A second metal layer (202), also referred to as M2 or metal 2, may be deposited thereafter. This second metal layer (202) may be similar to the first metal layer (200) and may serve a similar purpose. For M2, the same deposition area as M1 may be used in reverse, with adhesive Ti placed on top of the Pt to prevent diffusion on top of the SRO for structuring.

[0054] (f) The second metal layer or M2(202) may then be patterned and etched to stop at the piezoelectric layer. Etching may be performed by many of the methods described herein, including, for example, via RIE (reactive ion etching), ion milling, wet chemical etching, isotropic gas etching, etc. After patterning and etching, the photoresist used to pattern M2 may be removed via wet and / or dry etching. In many embodiments for manufacturing cMUTs and pMUTs described herein, any number of etching methods may be used, and the photoresist is generally removed after the patterning and etching processes are substantially completed.

[0055] (g) The piezoelectric layer may then be similarly patterned and etched and stopped at the first metal layer or M1(200). Generally, wet etching, RIE, and / or ion milling etching are used.

[0056] (h) The first metal layer or M1(100) may then be similarly patterned and etched and stopped at the dielectric (102).

[0057] (i) Where desired, one or both of the following methods may be added: (1) H2 barrier. Diffusion of H2 into the piezoelectric layer can limit its lifespan. To prevent this, an H2 barrier can be used. To accomplish this, 40 nm ALD (atomic layer deposition) aluminum oxide (Al2O3) may be used. Other suitable materials may include SiC, diamond-like carbon, etc. (2) Redistribution layer (RDL). This layer can provide connectivity between M1 and M2, and other connections (e.g., wire bonding, bump bonding, etc.). The RDL is initially made by adding a dielectric such as an oxide. The vias are formed by etching them with a dielectric, depositing a conductor (generally Al), and finally patterning the conductor. Additionally, a protective layer (generally oxide + nitride) may be added to prevent physical scratches, accidental short circuits, and / or moisture ingress.

[0058] (j) The grooves (300) may then be patterned. The dielectric layer (102) may be etched via RIE or wet etching. The substrate (100) may also be etched, and since the substrate (100) is generally silicon, the etching is generally DRIE (deep reactive ion etching). These grooves (300) can have a lateral dimension of 100 nm to 1000 μm, but are generally 2 μm to 10 μm. The grooves (300) can have any depth between 0.1% and 100% of the thickness of the device (100), but are generally 25% to 75% of the thickness of the device (100).

[0059] (k) The virtual pivot (301a) may be patterned and etched. The dielectric layer (102) may be etched via RIE or wet etching. The substrate (100) is generally silicon and may generally be etched via DRIE (deep reactive ion etching). These virtual pivots (301a) can have a lateral dimension of 100 nm to 1000 μm, but are generally 2 μm to 10 μm. The virtual pivot can have any depth between 0.1% and 99.9% of the thickness of the handle (103), but generally extends to 10% to 50% of the thickness of the handle (103) (approximately 10 μm to 100 μm).

[0060] (l) As shown in Figures 15c-15d, SOI substrates are frequently used. In this case, an embedded insulating layer or BOX layer (104) is present directly beneath the diaphragm (101). As a result, the diaphragm consists of a “device” layer (100) (a layer above the BOX) and a “handle” layer (103) below the BOX layer. The cavity of (100) may stop at the BOX and be etched outwards from the handle layer (103). In this case, the etching of (301a) may include two additional steps: (1) etching the BOX after the device layer has been etched via DRIE (generally via dry etching, or possibly via wet etching); and (2) etching the handle layer to a desired depth via DRIE. Most SOI wafers are silicon, meaning the device layer and handle layer are generally single-crystal silicon. In this case, the insulating BOX is generally thermally grown silicon dioxide, which is called "buried oxide" and is the origin of the term "BOX". Silicon SOI wafers with single-crystal silicon handles and device layers with oxide BOXes may be commonly used. The device layer may be 5 μm thick, but generally varies from 100 nm to 100 μm, while the handle layer thickness generally varies from 100 μm to 1000 μm. The BOX is generally 100 nm to 5 μm thick, but 1 μm may be used in many cases.

[0061] (m) If desired, the back surface of the wafer or handle may be thinned by grinding, and optionally polished at this point. In many embodiments, the handle layer is thinned to a thickness of 500 μm to 300 μm. Typical thicknesses usually vary from 50 μm to 1000 μm.

[0062] (n) Cavities may be patterned on the back of the wafer or handle, and cavities may be etched. Generally, the wafer / handle is made of silicon, and etching is performed by DRIE. Etching may be performed timely, as in Figures 15a-15b. Etching is performed in a BOX, as in Figures 15c-15d. The process may be selectively stopped. Cavities can be etched via other techniques such as KOH, TMAH, HNA, and RIE. The wafer can be considered in perfect condition after photoresist removal.

[0063] Manufacturing method for pMUT with grooves Exemplary methods for manufacturing pMUTs having grooves, such as the pMUTs shown in Figures 5a-5d, are further provided. These methods may be similar to the above methods for manufacturing pMUTs having grooves and virtual pivots, except that step (k), namely patterning and etching of virtual pivots, is generally omitted (Figures 15a-15b and 15c-15d).

[0064] Manufacturing method for pMUT with virtual pivot Exemplary methods for manufacturing pMUTs having a cantilever shell, such as the pMUT shown in Figures 7a-7d, are further provided. This method may be similar to the above method for manufacturing pMUTs having grooves and virtual pivots, except that step (j), namely groove patterning and etching, is generally omitted (Figures 15a-15b and 15c-15d).

[0065] Manufacturing method for cMUT with grooves and virtual pivots Exemplary methods for manufacturing cMUTs having grooves and virtual pivots, such as the cMUTs shown in Figures 16e and 16f, are described here.

[0066] (a) The method generally begins with a substrate that will serve as the handle (103). Generally, this substrate is single-crystal silicon.

[0067] (b) Shallow cavities may then be patterned and etched. These cavities are generally 10 nm to 5 μm in size, with the most common being 100 nm to 1 μm. For typical single-crystal silicon substrates, these cavities are removed by time etching using DRIE, RIE, HNA, or oxidation.

[0068] (c) An insulating layer (102) may then be deposited. Generally, this insulating layer is some form of SiO2 and is about 0.1 μm to 3 μm thick. It is generally deposited by thermal oxidation and, in some cases, by PECVD deposition or LPCVD deposition or some other technique.

[0069] (d) A metal layer or conductor (200) may be deposited thereafter, and examples of such conductors include Al, Au, Cr, Cu, Pt, etc. This conductor may be located on top of an adhesive layer and / or diffusion barrier layer such as Ti, TiW, TiN, Cr, etc.

[0070] (e) The conductor (and adhesive layer and / or diffusion barrier layer) may be patterned and etched and then stopped with an insulator.

[0071] (f) The virtual pivot (301b) and the bottom (301a) of the virtual pivot may be patterned and etched. First, the insulator (102) may be etched via RIE, wet etching, or another technique. Next, the handle (103) may be etched. Generally, the handle (103) is silicon, and this etching is done via DRIE and is time-dependent. Referring to Figures 15a-15b and 15c-15d, the virtual pivot can be to a depth of 1 μm to 1000 μm, but generally it is 10 μm to 100 μm, or about 10% to 50% of the handle (103).

[0072] (g) The device (100) layer may be bonded to the insulator (102) on the handle (103). This can be carried out through many techniques, examples of which include, but are not limited to, melting, Al-Ge, Au-Si, anode, SLID (solid-liquid interdiffusion), adhesives, Au-Au, Au-Sn, Cu-Cu, Cu-Sn, etc. The choice of bonding method may be determined according to the acceptable thermal budget and available process and integration requirements. The bonding shown in Figures 16e and 16f is melt bonding of oxide (102) to silicon (100).

[0073] (h) The end grooves (300) may be patterned and etched onto the device (100). This is generally carried out by timed DRIE. For the processes in Figures 15a-15b and 15c-15d, these grooves can have lateral dimensions of 100 nm to 1000 μm, but are generally 2 μm to 10 μm. The grooves can have any depth between 0.1% and 100% of the device (100) thickness, but are generally 25% to 75% of the device (100) thickness.

[0074] (j) The top of the virtual pivot (301a) may be patterned and etched. This is generally done by timed DRIE. The lateral dimensions of the top of (301a) are generally smaller or larger along the sides than the bottom of (301a), thereby overcoming alignment problems.

[0075] This method may be modified in many ways. In some embodiments, steps (d) and (e) may be omitted to manufacture the cMUT shown in Figures 16g and 16h. In some embodiments, step (b) may be performed instead at the bottom of the device to manufacture the cMUT shown in Figures 16a and 16b. In some embodiments, steps (d) and (e) may be omitted to manufacture the cMUT shown in Figures 16c and 16d, and step (b) may be performed instead at the bottom of the device.

[0076] Design and manufacturing method of nominally unconstrained ends The design of a nominally unconstrained end for a pMUT generally requires contact points to two independent substrates. This is because pMUTs generally require a voltage difference across their piezoelectric material, and therefore require at least two voltages. Many methods exist for applying at least two voltages. Figures 20a and 20b show an exemplary design of an unconstrained end for a pMUT, and the process or method for its manufacture is described below.

[0077] (a) The method may be started on an SOI wafer. Generally, this is a single-crystal silicon device layer on top of a BOX (oxide) on top of a handle layer. This device layer on this wafer is shown upside down in Figures 20a and 20b.

[0078] (b) An insulating layer (102) may then be deposited. Generally, this deposition is some form of SiO2 and is about 0.1 μm to 3 μm thick. It is generally deposited by thermal oxidation, PECVD deposition, or other techniques.

[0079] (c) A first metal layer or M1(metal 1)(200) may be deposited. Generally, this deposition is a combination of conductive films that adhere to the substrate, prevent the diffusion of the piezoelectric element, and aid in the structured deposition / growth of the piezoelectric element. SRO(SrRuO3) may be used for the growth of the structured film with Ti as an adhesive layer, a diffusion barrier on top, and Pt on top for conductivity (Pt on SiO2). Typically, these layers are They are thin, less than 200 nm, and films of 10-40 nm also exist. Due to issues related to load, production, and cost, this deposited layer will usually be limited to less than 1 μm. The conductor (Pt) is generally thicker than the structural layer (SRO) and the adhesive layer (Ti). Other common structural layers are, rather than SRO, (La, to give a few examples) 0.5 Sr0.5 )CoO3, (La 0.5 Sr 0.5 This includes MnO3, LaNiO3, RuO2, IrO2, and BaPbO3. Pt can be replaced with other conductive materials such as Cu, Cr, Ni, Ag, Al, Mo, W, and NiCr. These other materials typically have disadvantages such as weak diffusion barriers, brittleness, or poor adhesion, and Pt is the most commonly used conductor. The adhesive layer, i.e., Ti, can be replaced with any common adhesive layer such as TiW, TiN, Cr, Ni, Cr, etc.

[0080] (d) A piezoelectric material (201) may then be deposited. Common examples of piezoelectric materials include PZT, KNN, PZTN, PMN-Pt, AlN, Sc-AlN, ZnO, PVDF, and LiNiO3. The thickness of the piezoelectric material may vary from 100 nm to 5 μm (possibly more).

[0081] (e) A second metal layer or M2(metal 2)(202) may be deposited. M2 may be the same as M1(200) and may serve the same purpose. For M2, the same deposited layer as M1 may be used in reverse, with adhesive Ti placed on top of the Pt to prevent diffusion on top of the SRO for structuring.

[0082] (f) M2(202) may be patterned and etched and then stopped with a piezoelectric element. Etching may be done by many of the methods described herein, including, for example, via RIE (reactive ion etching), ion milling, wet chemical etching, isotropic gas etching, etc. After patterning and etching, the photoresist used to pattern M2 may be removed, which may be wet and / or dry. In many embodiments for manufacturing cMUTs and pMUTs described herein, any number of etching methods may be used, and the photoresist is generally removed after the patterning and etching processes are largely complete.

[0083] (g) The piezoelectric layer may then be similarly patterned and etched and stopped at the first metal layer or M1(200). Generally, wet etching, RIE, and / or ion milling etching are used.

[0084] (h) The first metal layer or M1(100) may then be similarly patterned and etched and stopped at the dielectric (102).

[0085] (i) If desired, an H2 barrier may be added. Diffusion of H2 into the piezoelectric layer can limit its lifetime. To prevent this, an H2 barrier can be used. To accomplish this, 40 nm ALD (atomic layer deposited) aluminum oxide (Al2O3) may be used. Other suitable materials may include SiC, diamond-like carbon, etc.

[0086] (j) A dielectric layer (106) may be deposited. This layer is generally an oxide and / or nitride layer (generally PECVD) and is typically 100 nm to 2 μm thick.

[0087] (k) Vias (or holes) (108) may be patterned and etched in the dielectric layer (106). This is generally done via RIE etching or some form of wet etching. Etching may be stopped at M1 or M2.

[0088] (l) The redistributed conductor (107) may be deposited, patterned, and etched. Typical conductors are metals (Al, Cu, Au, Ti, Cr, etc.) and / or semiconductors such as poly-Si, poly-Ge, or poly-SiGe. This layer is generally relatively thick, 100 nm to 5 μm, but usually 0.5 μm to 2 μm, in order to overcome topography and low resistance. In one example, 1 μm of Au is used on top of 100 nm of Ti on top of 1.6 μm of Al. The Au is for integration bonding in the process described further below.

[0089] (m) The grooves (300) may then be patterned. The dielectric layer (102) may be etched via RIE or wet etching. The substrate (100) may also be etched, and since the substrate (100) is generally silicon, the etching is generally DRIE (deep reactive ion etching). These grooves (300) can have a lateral dimension of 100 nm to 1000 μm, but are generally 2 μm to 10 μm. The grooves (300) can have any depth between 0.1% and 99% of the thickness of the device (100), but are generally 25% to 75% of the thickness of the device (100).

[0090] (n) The device layer (101) may be patterned and etched. The dielectric layer (106) may be etched via RIE or wet etching. The substrate (100) may be etched, which is generally silicon, and therefore the etching is generally DRIE (deep reactive ion etching). This etching may pass through the entire device layer (100) until it stops in the BOX. These etchings can have lateral dimensions of 100 nm to several cm, but are generally 5 μm to 1000 μm.

[0091] (o) Optionally, a protective layer may be deposited, patterned, and etched to prevent physical scratches, accidental short circuits, and / or moisture ingress. This protection is generally an oxide and / or nitride and typically extends to a thickness of 300 nm to 2 μm.

[0092] (p) If desired, the back surface of the wafer or handle may be thinned by grinding, and optionally polished at this point. In many embodiments, the handle layer is thinned to a thickness of 500 μm to 300 μm. Typical thicknesses usually vary from 50 μm to 1000 μm.

[0093] (q) The MEMS wafers (101-102, 106-9, 200-202, 300, 101a, and handle layer) are then cut into dies in preparation for bonding.

[0094] (r) The conductive adhesive material (110) may be deposited, patterned, and etched onto the base substrate (111). For example, the base substrate (111) may be a planarized ASIC wafer. The conductive adhesive material may be 1 μm thick Au to enable bonding in step (s).

[0095] (s) The MEMS dies (101-102, 106-9, 200-202, 300, 101a, and handle layer) are aligned and bonded to the base substrate (111), and a conductive bond (109) may be formed between the redistribution conductor (107) and the conductive adhesive material (110). Optionally, only good MEMS dies are selected. To maintain yield, the MEMS dies may be bonded only to verified good ASIC dies. Poor ASIC dies are bonded to dummy MEMS dies for etching loading (process ( t) The bonding can be any conductive adhesive, including Au-Au thermal compression, SLID, Al-Ge, Au-Sn, Cu-Cu, etc. For example, Au-Au thermal compression may be used.

[0096] (t) A MEMS die can be mounted on the base substrate (111). The back of the MEMS die can be etched with a DRIE tool to remove the silicon (not shown) of the handle and then stopped in the BOX.

[0097] (u) The back of the MEMS die may be etched with RIE oxide to remove the BOX, stopping at the device layer (101). Once completed, the layout and cross-sections in Figures 20a and 20b can be considered achieved.

[0098] Notes for pMUT in Figures 20a and 20b:

[0099] (a) The conductive adhesive (109) may allow electrical signals from the base substrate (111) to be transmitted to the MEMS die through the conductive adhesive material (110) to the redistribution conductor (107).

[0100] (b) There may be at least two independent signals, one connected to the M1 layer (202) via via (108) and the other connected to the M2 layer (200) via similar via (108). This allows the designer to apply a known voltage difference to the piezoelectric layer (201) and enable the pMUT to be driven.

[0101] (c) End groove (300) is reinforced k eff 2 We can provide this.

[0102] (d) Optionally, form a virtual pivot, k eff 2 It is possible to increase this. If the conductive adhesive material (110) has a height much greater than its lateral dimensions, the bond can form a cantilever shell.

[0103] (e) The above process can produce pMUT with unconstrained ends, grooves, and cantilever shells, and to enhance yield, only known good dies can be combined.

[0104] (f) Those skilled in the art may use this manufacturing method in combination with design concepts of grooves, unconstrained ends, and virtual pivots to create a wide range of novel pMUTs.

[0105] Various methods for manufacturing pMUTs and cMUTs have been described above according to many embodiments, but those skilled in the art will recognize many variations based on the teachings provided herein. The steps may be completed in different orders. Steps may be added or removed. Some steps may include sub-steps. Production techniques known in the art may be applied to one or more of the steps. Many of the steps may be repeated as long as it is beneficial.

[0106] References [1] RD Blevins. Formulas for natural frequency and mode shape. Kreiger, 1979.

[0107] [2] KM Smyth. Piezoelectric Micro-machined Ultrasonic Transducers for Medical Imaging. Massachusetts Institute of Technology, 2017.

[0108] While preferred embodiments of the present invention have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided only as examples. Many modifications, variations, and substitutions will be conceivable without departing from the present invention. It should be understood that various alternatives to the embodiments of the present invention described herein may be used in carrying out the invention.

Claims

1. A micromachine ultrasonic transducer (MUT), wherein the MUT is: a) A diaphragm having substantially unrestrained ends, b) One or more electrodes, c) A MUT comprising one or more anchors for clamping the diaphragm to a substrate within and / or along the outer edge of the diaphragm.

2. The MUT according to claim 1, wherein the end is in an unrestrained state and the anchor is completely inside the diaphragm.

3. The MUT according to claim 2, wherein the MUT is a pMUT including a piezoelectric film.

4. The MUT according to claim 3, wherein the one or more electrodes are electrically coupled to the piezoelectric film.

5. The MUT according to claim 3, wherein the piezoelectric film is located on the opposite side of the one or more anchors.

6. The MUT according to claim 3, wherein the piezoelectric film is located on the same side as the one or more anchors.

7. The piezoelectric film is located between the one or more anchors and the diaphragm, as described in claim 3.

8. The diaphragm includes a groove, as described in any one of claims 4-7.

9. The MUT according to any one of claims 4-7, comprising a plurality of anchors, wherein a subset of the plurality of anchors is attached to one or more vertical cantilever shells.

10. The MUT according to any one of claims 4-7, comprising a plurality of anchors, wherein a subset of the plurality of anchors is attached to one or more vertical cantilever shells, and wherein the diaphragm comprises a groove.

11. The MUT according to claim 2, wherein the MUT is a cMUT.

12. The MUT according to claim 11, wherein the one or more electrodes are electrically coupled to the diaphragm in the gap between them.

13. The diaphragm includes a groove, as described in claim 11.

14. The MUT according to claim 11, comprising a plurality of anchors, wherein a subset of the plurality of anchors is attached to one or more vertical cantilever shells.

15. The MUT according to claim 11, comprising a plurality of anchors, wherein a subset of the plurality of anchors is attached to one or more vertical cantilever shells, and the diaphragm comprises a groove.

16. A micromachine ultrasonic transducer (MUT) comprising a clamped diaphragm including a vertical cantilever shell, wherein the vertical cantilever shell is the die MUT, attached to the end of the Aphram.

17. The MUT according to claim 16, wherein the vertical cantilever shell substantially prevents planar motion but forms a virtual pivot that allows rotation of the diaphragm end while applying a reverse torque.

18. The MUT according to claim 17, wherein the vertical cantilever shell has a thickness of 0.1 μm to 50 μm, and the vertical cantilever shell has a height that is 1 to 100 times greater than its thickness.

19. The MUT according to claim 18, wherein the vertical cantilever shell has an area that is not continuous with respect to the diaphragm end but is free of virtual pivots.

20. The MUT according to claim 19, wherein the MUT is multimodal.

21. A MUT array configured for ultrasonic imaging, wherein the MUT array comprises a plurality of MUTs according to claim 20.

22. The MUT array according to claim 21, wherein each of the plurality of MUTs is a pMUT.

23. The MUT array according to claim 21, wherein each of the plurality of MUTs is a cMUT.

24. The MUT array according to claim 23, wherein each MUT includes a vertical cantilever shell formed by multiple etchings.

25. A micromachine ultrasonic transducer (MUT) including a clamped diaphragm with grooves.

26. The MUT according to claim 25, wherein the MUT is a pMUT.

27. The MUT according to claim 26, wherein the groove is located within a diaphragm thickness of 20 at the diaphragm boundary, the groove has a width of up to 10 diaphragm thickness, and the groove has a depth of 1% to 100% of the diaphragm thickness.

28. The groove has a certain width, as described in claim 27.

29. The groove has a variable width, as described in claim 27.

30. The MUT according to claim 27, wherein the groove is divided at one or more positions to allow electrical routing.

31. The MUT according to claim 30, wherein the MUT is multimodal.

32. A MUT array configured for ultrasonic imaging, wherein the MUT array includes a plurality of MUTs according to claim 31.

33. The MUT according to claim 25, wherein the MUT is a cMUT.

34. The groove is located within the diaphragm thickness of 20 at the diaphragm boundary, and the groove has a width of up to 10 diaphragm thickness, and the groove is within the diaphragm thickness The MUT according to claim 33, having a depth of 1% to 100%.

35. The groove has a certain width, as described in claim 34.

36. The groove has a variable width, as described in claim 34.

37. The MUT according to claim 34, wherein the groove is divided at one or more positions to allow electrical routing.

38. The MUT according to claim 37, wherein the MUT is multimodal.

39. A MUT array configured for ultrasonic imaging, wherein the MUT array comprises a plurality of MUTs according to claim 38.

40. A micromachine ultrasonic transducer (MUT), wherein the MUT is: a) A piezoelectric layer deposition portion including a substrate, an insulating layer, an upper electrode, a piezoelectric layer, and a bottom electrode, Here, the piezoelectric layer deposition portion has an end portion and a central portion, Here, the piezoelectric layer deposition portion has one or more grooves that pass through at least the upper electrode, the piezoelectric layer, the bottom electrode, and the insulating layer, and extend into at least a part of the substrate, and Here, the one or more grooves are arranged between the end portion and the central portion of the piezoelectric layer deposition portion, a) Bass and, b) One or more anchors that connect the central portion of the piezoelectric layer deposition to the base and maintain the end portion of the piezoelectric layer deposition in an unrestrained state, wherein the central portion of the piezoelectric layer deposition is clamped to the base, and the one or more anchors provide an electrical connection between the base and the piezoelectric layer deposition, c) A plurality of conductors, the plurality of conductors including (i) a first conductor that electrically connects the upper electrode of the piezoelectric layer deposition to the base through a first via passing through the thickness of the piezoelectric layer deposition, and (ii) a second conductor that electrically connects the bottom electrode of the piezoelectric layer deposition to the base through a second via passing through the thickness of the piezoelectric layer deposition, Here, the first via and the second via are MUTs that include a plurality of conductors arranged between the end portion and the central portion of the piezoelectric layer deposition area.

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