Method and means for insulating element for sensor array

The present invention generally relates to sensor arrays (eg, light, heat, pressure, ultrasound). Specifically, the present invention relates to an ultrafine processed ultrasonic transducer (MUT). One particular application of MUT is in medical diagnostic ultrasound imaging systems. Another particular example is in non-destructive evaluation (NDE) of materials such as casting, forging, or pipelines.

A typical ultrasonic imaging transducer uses a polarized piezoelectric ceramic material to convert electrical energy into acoustic energy, generating acoustic energy by a piezoelectric effect. The acoustic energy transmitted forward, which is the direction of the patient to be scanned, is coupled to the patient through one or more acoustic matching layers. However, the acoustic energy transmitted away from the patient being scanned is typically absorbed and / or scattered by an acoustic backing material located on the back of the transducer array. This prevents the acoustic energy from being reflected off the structure or interface on the back of the transducer and returning to the piezoelectric material, degrading the quality of the acoustic image obtained from the reflections within the patient. Many compositions of acoustic backing materials are known. For example, the acoustic backing material can consist of a composite of metal particles (eg tungsten) of a damped soft material such as rubber, epoxy, or plastic. Also, other acoustic backing compositions may be used.

Ultrasonic transducers used for medical diagnostic imaging have a wide band width and are highly sensitive to low-level ultrasonic signals, and these characteristics enable high-quality generation. Piezoelectric materials that meet this criterion and are conventionally used in the manufacture of ultrasonic transducers include lead zirconate titanate (PZT) ceramics and polyvinylidene fluoride resin. However, PZT transducers require a ceramic manufacturing process that differs from the process techniques used to manufacture other components of ultrasonic systems, such as semiconductor components. Ultrasonic transducers are preferably manufactured using the same process used to manufacture semiconductor components.

Recently, ultrasonic transducers of a type known as ultrafine processed ultrasonic transducers (MUT), which can be capacitive type (cMUT) or piezoelectric type (pMUT), have been manufactured by using a semiconductor process. The cMUT is a microdiaphragm-like device equipped with electrodes that convert the acoustic vibration of the received ultrasonic signal into modulated capacitance. For transmission, sound waves are transmitted by modulating the capacitive charge and vibrating the diaphragm of the device. pMUT is similar except that the diaphragm consists of a piezoelectric material and an inert material such as silicon nitride or silicon and is bimorph.

One advantage of MUTs is that they can be manufactured using semiconductor manufacturing processes such as ultra-fine manufacturing processes, which are classified as "microfabrication". Ultrafine processing is US Pat. No. 6,359, It is explained in No. 367 as follows. "Microfabrication includes (A) pattern forming tools (generally etching such as projection aligners or wafer steppers) and (B) PVD (physical vapor deposition), CVD (chemical vapor deposition), LPCVD (low pressure chemical vapor deposition). ), PECVD (Plasma Chemical Vapor Deposition) and other evaporation tools combined with (C) wet chemical etching, plasma etching, ion milling, sputter etching, or laser etching and other etching tools, or some of these. Microstructure formation. Micromachining is usually performed on substrates or wafers made of silicon, glass, sapphire, or ceramic. Such substrates or wafers are generally very flat and smooth, laterally. It has a size of a few inches. These are usually processed as groups in a cassette, moving from process tool to process. Each substrate advantageously (but not always) many copies of the product. It can be incorporated. There are two common types of microfabrication: 1) bulk micromachining with a thick portion where the wafer or substrate is formed, and 2) shaping is generally on the surface, especially on the surface. Surface microfabrication limited to deposited thin films. The definition of microfabrication used herein is silicon, sapphire, all types of glass materials, polymers (such as polyimide), polysilicon, silicon nitrides. Includes silicon oxide nitrides, thin metal such as aluminum and copper alloys and tungsten, spin-on glass (SOG), implantable or diffusible additives, and growth films such as silicon oxide and nitrides. Includes the use of conventional or known micromachinable materials. Similar definitions of ultrafine machining are adopted herein. The system obtained by such an ultrafine processing process is usually called an "ultrafine processing electromechanical system" (MEMS).

The acoustic energy generated by using the capacitive ultrafine processing ultrasonic transducer device does not depend on the piezoelectric material to generate the ultrasonic energy. Rather, the basic structure of the cMUT cell is that of a conductive membrane or diaphragm suspended above the conductive electrode by a small gap. When a voltage is applied between the membrane and the electrodes, Coulomb forces attract the membrane to the electrodes. As the applied voltage changes over time, the position of the membrane also changes, generating acoustic energy radiated from the surface of the device as the membrane moves. Acoustic energy is generated primarily forward, i.e. towards the patient, but some of the acoustic energy is propagated within the cMUT support structure. This structure is generally a high concentration doped silicone wafer, i.e. a semiconductor wafer.

cMUT devices are typically constructed with multiple membranes per transducer element. Complete transducer probes used in medical imaging, non-destructive evaluation, or other imaging devices include multiple transducer elements arranged in one or more rows to form an array, each of which is electrical. It is composed of a plurality of cMUT cells having electrodes connected to each other. Each element of the array needs to operate independently of the adjacent element. Since the array of transducer elements is constructed on a common substrate, there is a problem that both electrical and mechanical obstacles (that is, crosstalk) exist between adjacent elements.<patcit num="1"><text>U.S. Pat. No. 6,359,367</text></patcit>

<p> There is a need to form insulation between the transducer elements of MUT (cMUT and pMUT) devices.</p>

<p> The present invention relates to an apparatus including an array of sensors constructed on or within a substrate, and means for insulating each sensor element from its adjacent element. In the case of a semiconductor wafer, the semiconductor surface is usually one surface of the semiconductor wafer, but it may also be a thin film of semiconductor on an insulating substrate. The present invention also relates to a method of manufacturing such an apparatus. According to some disclosed embodiments, acoustic insulation is formed between adjacent sensor elements to reduce acoustic crosstalk. According to another disclosed embodiment, electrical insulation is formed between adjacent sensor elements to reduce electrical crosstalk. These types of insulation can be used alone or in combination with the sensor device. The sensor can be a light, heat, or pressure sensor, or an ultrasonic transducer.</p><p> One embodiment of the present invention is arranged in front of the substrate, each in contact with the material of the substrate, and within the material of the substrate so as to reduce the coupling in energy form between any of the sensor elements. A sensor device that is arranged and each has a plurality of barriers that impede the propagation of the energy forms incident therein.</p><p> Another aspect of the present invention is a method of manufacturing a sensor device, in (a) a step of ultra-fine processing an array of sensor elements in or on a substrate, and (b) in an energy form between arbitrary sensor elements. It involves forming a plurality of barriers in the material of the substrate that impede the propagation of the energy forms, each of which collides with it, so as to reduce coupling.</p><p> Yet another aspect of the invention is an ultrasonic transducer device, each group of ultrasonic transducer cells arranged in front of a substrate, each of which is electrically co-connected and acoustically coupled to the substrate. It comprises a plurality of ultrasonic transducer elements, including, and a plurality of trenches in the material of the substrate, which are arranged in a region between the transducer elements and hinder the propagation of sonic energy through the transducer elements.</p><p> Yet another aspect of the invention is of a substrate that is arranged on the front surface of the substrate and is located in a region between the plurality of sensor elements, each of which contacts the material of the substrate, and impedes the flow of current through the sensor elements. It is a sensor device including a plurality of bands for injecting a dopant into a material.</p><p> Yet another aspect of the present invention is a method of manufacturing a sensor device, wherein (a) a step of ultrafinely processing a sensor array on one surface of a substrate and (b) one surface or the other surface of the substrate. It includes a step of attaching to the first support structure and a step of (c) forming a plurality of trenches arranged in the region between the sensor elements in the material on the surface of the substrate not attached to the support structure.</p><p> Other aspects of the invention are disclosed and claimed below.</p>

Here, reference is made to a drawing in which the same element of a different drawing is assigned the same reference number.

For illustration purposes, various embodiments of the present invention belonging to the category of capacitive ultrafine processed ultrasonic transducers (cMUTs) will be described. However, each aspect of the invention disclosed herein is not limited to the structure or manufacture of cMUTs, but may also apply to the structure or manufacture of other types of sensor arrays on a substrate. I want to be understood. The present invention is not limited to substrates made of semiconductor materials.

Referring to FIG. 1, a cross section of a typical cMUT transducer cell 2 is shown. Arrays of such cMUT transducer cells are typically made on substrate 4, such as highly doped silicon (and thus semiconducting) wafers. In each cMUT transducer cell, a thin film or diaphragm 8 made of silicon or silicon nitride is suspended on the substrate 4. The film 8 is supported at its periphery by an insulating support 6, which can be made of silicon oxide, silicon nitride, or substrate material. The cavity 16 between the membrane 8 and the substrate 4 may be filled with air or gas, or may be completely or partially evacuated. A film or layer of a conductive material, such as an aluminum alloy or other suitable conductive material, forms an electrode 12 on the film 8, and another film or layer made of the conductive material is an electrode on a substrate 4. Form 10. Alternatively, the bottom electrode can be formed with suitable doping of the substrate. As shown in FIG. 1, the electrode 12 is at the top of the membrane, but can also be embedded in the membrane or placed on the bottom of the membrane.

The two electrodes 10 and 12 are separated by a cavity 16 to form a capacitance. When an incident acoustic signal vibrates the membrane 8, changes in capacitance can be detected using the associated electronic circuit configuration (not shown in FIG. 1), thereby converting the acoustic signal into an electrical signal. Can be done. Conversely, the AC signal applied to one of the electrodes modulates the charge on the electrodes, causing a modulation in the capacitive force between the electrodes, which moves the diaphragm to send out an acoustic signal.

Since typical cMUTs are micron-sized, a large number of cMUT cells are usually manufactured in close proximity to form a single transducer element. Each cell can have a circular, rectangular, hexagonal, or other peripheral shape. Of the simple shapes that achieve close pack, the hexagon is the closest to a circle and therefore has the simplest resonance mode. The hexagonal cMUT cell is shown in Figure 2. The hexagon provides a dense mounting of the cMUT cell of the transducer element. The cMUT cell can have different dimensions so that the transducer element has the combined properties of different cell sizes and gives the transducer more wideband properties. The "spokes" 14 shown in FIG. 2, which electrically connect the cells to each other, are the parts of the patterned electrodes referenced in item 12 of FIG. The electrodes 12 can be patterned for optimum acoustic performance and can be placed at the bottom of the membrane 8.

The cMUT device further includes a layer of acoustic damping material, referred to herein as "acoustic backing," which is acoustically coupled to the back of the substrate. The acoustic backing layer is rigid enough to provide structural support for a very thin substrate. Such an acoustic backing layer can be directly bonded to the back surface of the substrate using, for example, an epoxy layer thin enough to be substantially acoustically transparent, or can be laminated to the substrate using an intervening layer. Alternatively, the acoustic backing can be a cast or moldable composition with sufficient acoustic impedance. In one embodiment, the intervening layer is made of an acoustic impedance matching material that has an acoustic impedance between the acoustic impedance of the silicon substrate and the acoustic impedance of the acoustic damping material. In another embodiment, the intervening layer is a flexible printed circuit board (flex circuit) with conductive pads that connect to conductive vias within the substrate. The acoustic backing preferably has an damping performance such that the wave propagating in the lateral direction in the substrate is absorbed to the extent that the crosstalk between the transducer elements is reduced.

FIG. 3 shows a side view of the cMUT device 20 connected via electrical connections (eg, flex circuits) 22 and 24 to a suitable electronic circuit configuration (not shown). (The term "cMUT device" as used herein means a structure comprising a substrate and a plurality of cMUT cells supported by the substrate.) In the illustrated embodiment, the cMUT device 20 is an acoustic backing material 18. It is placed in a well formed in the body of the. The top of the board is located approximately flush with the top of the acoustic backing section that extends beyond the area occupied by the board, and the distal ends of the flexible electrical connections 22 and 24 are with each end of the board. Overlapping, the adjacent portions of the flexible electrical connections 22 and 24 are overlapped and joined to their respective portions of the acoustic backing layer. As can be seen in FIG. 3, the acoustic backing layer 18 supports the cMUT device 20 as well as the flexible electrical connections 22 and 24. The acoustic backing 18 can be stacked directly on the cMUT device 20, or, as described above, the acoustic impedance matching intervening layer can be included in the stack.

The ultrafinely machined ultrasonic transducer array can be built on the surface of the substrate or can be etched by removing material from the substrate. The array can include one or more rows of transducer elements, or the transducer elements are in a mosaic pattern of cMUT cells or elements on a substrate, as disclosed in US Patent Application No. 10 / 383,990. It can be organized in a two-dimensional array that does not have rows, such as a so-called "mosaic array".

Each transducer element of a typical cMUT device is constructed with multiple cMUT cells. For illustration, Figure 4 shows a "daisy" transducer element made from seven hexagonal cMUT cells 2, in which the center cell is surrounded by a ring of six cells, and each cell in the ring is the center cell. It touches each side of the ring and the adjacent cell of the ring. The top electrodes 12 of each cell 2 are electrically connected to each other (this connection cannot be switched and disconnected). For a hexagonal array, the six conductors 14 (shown in both FIGS. 2 and 4) radiate outward from the top electrode 12 and are connected to the top electrodes of adjacent cMUT cells (with six). (Except for peripheral cells that are connected to three other cells). Similarly, the bottom electrodes 10 of each cell 2 are electrically connected to each other to form a 7x larger capacitive transducer element 39.

The array of cells seen in FIG. 4 can extend in one direction to form an overall rectangular long transducer element 40. These rectangular transducer elements can be arranged in one row to form a linear array. Such a cMUT device 20 is shown in FIG. 5 as a whole, and each rectangular transducer element 40 is drawn to have a single column of cMUT cells for simplification of the drawing, but in practice each element. It should be understood that will contain multiple columns of cMUT cells.

Each transducer element in the array must operate independently of its adjacent elements. As shown in FIG. 5, since the array is built on a common substrate 4, there is a problem that both electrical and mechanical obstacles (ie, crosstalk) can exist between adjacent elements. .. The present invention forms the required insulation between the elements.

According to the first embodiment of the present invention, insulation is formed by removing all or part of the substrate material between adjacent transducer elements. This can be achieved using wafer dicing saws, lasers, wet etching methods, reactive ion etching (RIE), or deep RIE.

One way to create an insulated trench is to first attach the substrate supporting the cMUT cell or element to the backing material, as seen in FIG. FIG. 6 shows a substrate 4 laminated on a backing layer 18 made of an acoustic damping material. A wafer dicing saw (not shown) is used to cut through substrate 4 and separate the backing material 18 to create multiple isolated, parallel insulating trenches or channels, such as the insulating trench 26 seen in FIG. Form. Depending on the operating frequency of the cMUT device, it may not be necessary to completely cut the substrate 4. Instead, an insulating trench or channel 28 with a depth shallower than the total thickness of the substrate 4 can be formed as well, as shown in FIG. For brevity, it should be understood that trenches of different depths are shown in the same drawing, and that the insulating trenches of a particular cMUT wafer are usually the same depth.

The backing material provides mechanical support for each transducer element as the insulating trench penetrates the entire thickness of the substrate 4 and into the backing layer 18. Since the backing material attenuates acoustic energy, the crosstalk through the backing layer 18 is significantly less than the crosstalk through the substrate 4.

Regardless of the depth of the insulating trench, the insulating trench is arranged with a space between adjacent transducer elements. FIG. 6 shows one row of transducer elements, each transducer element containing multiple cMUT cells 2. In the case of a linear array with one row of elements, insulating trenches parallel to each other are arranged with space between adjacent elements. If the array contains two or more rows, the insulated trenches are also spaced apart from each other and intersect the trenches within each row to form an interconnected network of insulated trenches. In this case, the insulating trenches between the rows are parallel to each other and perpendicular to the insulating trenches within each row. If the elements in each row are aligned to form a column, the intersecting insulating trenches will form a grid or grid.

When the transducer elements are acoustically insulated, the insulating trenches between the transducer elements can be filled with a sound absorbing material such as silicone rubber. If the lens is glued to the surface of the cMUT device, the lens is glued to the cMUT device by filling an insulating trench with a lens adhesive for either focusing sound waves and / or protecting the surface of the device. Is improved. Filling the trench between the elements also adds mechanical support to the element.

It can also be determined that the structure of the trench should have the optimum shape. Referring to FIG. 7, the insulating trench does not have to have a right-angled bottom profile (see trench 30), instead the profile is of the "V" (see trench 32) or "U" (not shown) shape. It can be shaped. Trench 34 and 36 in FIG. 6 show other profiles. The profile of trench 34 has a parallel side wall and a nearly parabolic bottom profile, and trench 36 has a parallel side wall and a V-shaped bottom profile. All of the insulating trenches formed on substrate 4 usually have the same profile, and the different shapes shown in FIG. 6 are grouped together in one substrate to minimize the number of drawings required. Please understand that.

The use of a dicing saw is an effective way to remove the substrate material placed between the transducer elements as long as the resulting cut or trench has a linear geometry. If the material needs to be removed along non-straight lines, other methods such as laser cutting, wet etching, or RIE are more appropriate. This example would be a device constructed in a circular shape (eg, an annular array). This circular transducer array has elements that form a concentric annular ring and therefore require a circular insulation pattern. This geometry allows for point focusing of acoustic energy.

It is within the scope of the present invention to perform any of the acoustic insulation methods described above on one side of the substrate. When material is removed from the back of the device opposite the cMUT cell shown in FIG. 8, a larger active region can be obtained unless the insulating trench 38 extends through the full thickness of substrate 4. In this case, the trench can be formed to occupy the area directly below the cMUT cell or device.

The cMUT device needs to be supported on the front side (ie, on the cMUT cell side) to form back insulation. However, dicing tape cannot be used because the cMUT device can be easily damaged. The tape attached to the suspended membrane can be peeled off. According to one embodiment of the invention, while forming acoustic insulation on the back surface, the cMUT device is supported by a cold mounting wax applied to the front surface of the device in contact with a fragile cMUT film. Once the insulation is complete and the debris generated by the dicing operation is removed from the cMUT device, the cMUT requires a support before removing the mounting wax. This support can be the acoustic damping backing material described above. When the cMUT device is attached to the support, the attachment wax is heated and melted. The wax will be removed from the cMUT device using a solvent suitable for the mounting wax. Another support method is to support the cMUT outside the active region and avoid direct adhesion to the membrane.

Any of the methods described above for forming the insulation of the cMUT element can result in damage such as microcracks, which can spread into the active cMUT cell. As a result, the conductive liquid may slightly permeate and short-circuit the signal and the ground electrode. Another aspect of the invention provides precautionary measures by applying a conformal coating such as sputtered or vapor-deposited silica, silicon nitride, alumina, or other insulating inorganic material to cover and seal such defects. The thin film deposition process is capable of forming pinhole-free coatings with excellent consistency and thickness uniformity and is performed under vacuum.

The coating process is carried out as follows. After removing the material from between the cMUT elements to form an insulating trench, the cMUT cell is cleaned to remove any residue left on it. The cMUT device is then dried in vacuum at high temperature. After drying, the cMUT device is placed in a sputtering or vapor coating machine and coated with a few microns of selected material. Even if such a coating is extremely conformal, if it is small enough, the microcracks will be sealed and the cMUT cell will be evacuated. Many insulating inorganic materials have a high dielectric strength, which helps to insulate the cMUT cell from the external environment.

Yet another aspect of the present invention is the manufacture of cMUT devices in which transducer elements are electrically isolated from each other. According to one embodiment of the invention, electrical insulation can be achieved by selective ion implantation. Since the electrical coupling is dominated by the flow of electromagnetic energy, mainly the flow of electrons, the coupling can be minimized by changing the conductivity of the substrate. More precisely, specific regions of the substrate between the transducer elements can be doped with ions that alter the semiconductor properties of the substrate. By selectively injecting the dopant into the region between the elements, it is possible to form a junction such as a back-to-back pn junction diode, that is, a region close to insulation that suppresses electrical crosstalk. This technique does not remove the material, but changes the electrical properties in the selected region. This process can be performed before, during, or after the formation of the cMUT cell. If the ion implantation conditions indicate a temperature higher than the predominant temperature during micromachining of the cMUT cell, you can choose to perform ion implantation prior to micromachining.

Alternatively, non-conductive substrates can be used primarily for cMUT production, where the bottom electrode is either a metal deposited under the cMUT or a selectively doped region. In this case, it may be desirable to ground the regions between the elements by selectively doping these regions and electrically grounding them. Another method of grounding the area between elements separated by an insulating trench (as described above) is to coat the surface of the trench (eg, a wall) with a conductive material such as aluminum or an aluminum-silicon alloy, and then this metal. Is grounded to electrically insulate between adjacent elements. By either method, the stray charge can be conducted to the ground instead of the adjacent element.

A pn junction diode contains two volumes of doped semiconductor material that are adjacent along a surface, the surface of which constitutes the junction. The material in one area is an n-type semiconductor material and the material in the other area is a p-type material. That is, the semiconductor material is doped differently on one side of the junction. The pn junction diode conducts in one direction and does not conduct in the other direction. By arranging the two pn junction diodes back to back, the device can be formed so that it does not conduct in either direction. By extending the length of such a pair of back-to-back pn junction diodes, a long barrier to current flow can be formed. 9 and 10 show two examples of such electrically insulating devices, where the substrate 4 is doped to form an npn-type back-to-back diode. In either case, the back-to-back diode is made by injecting the doping agent to the required depth of the substrate material.

In the embodiment shown in FIG. 9, the transducer elements (each element containing a plurality of cMUT cells 2) are constructed on regions 44 and 48 made of n-type semiconductor material, and the p-dopant is between the transducer elements. Ion implantation into region 46. Each region made of n-type semiconductor material functions as the bottom electrode of the transducer element built on it. In each p-type region, each n-type region is located on both sides to form the respective np junctions 50 and 52. Alternatively, the transducer element can be constructed on a p-type material, and the p-type region is interleaved into an ion-implanted n-type region between the transducer elements.

In the embodiment shown in FIG. 10, the transducer elements are constructed on and adjacent to each region made of a semiconductor that is neither p-type nor n-type, that is, a non-conductive material (such as non-doped polysilicon). In each region located between the transducer elements, the n-dopant is ion-implanted into regions 44 and 48, and the p-dopant is ion-implanted into region 46 between regions 44 and 48. Again, in each p-type region, each n-type region is located on both sides to form the respective np junctions 50 and 52. Alternatively, instead of the npn junction, a pnp junction can be injected into the region between the transducer elements.

Therefore, adjacent transducer elements can be electrically isolated from each other by placing a barrier of the type shown in FIG. 9 or 10 in an unoccupied space between adjacent transducer elements.

FIG. 11 shows a cross-sectional view of two transducer elements sharing a common wall 46 made of p-type material according to another embodiment of the present invention. For brevity, no additional transducer elements are shown, but it should be understood that each pair of adjacent transducer elements shares a common wall made of p-type material. The bottom electrode of each element consists of regions 44 and 46 of n-type material, respectively. The area between adjacent regions of the n-type material is occupied by the p-type material, and this p-type material projects upward to form a common wall. A wall of p-shaped material supports membrane 8, which is suspended above the respective cavities 10 of the individual cMUT cells that form the transducer element. The cMUT cell of a particular transducer element preferably shares a common bottom electrode made of n-type material.

In embodiments where the acoustic backing layer is located on the back of the substrate, the acoustic backing material should have a composition that is acoustically compatible with the cMUT substrate, preventing reflections of acoustic energy from returning to the device. When the substrate 4 is made of silicon, one example of a suitable backing material is as disclosed in US Patent Application No. 10 / 248,022 of the name "Backing Material for Micromachined Ultrasonic Transducer Devices" ( It consists of a mixture of 96.3% tungsten (85% by weight) with a particle size of 10 microns and 15% with a particle size of 1 micron and 3.67% polyvinyl chloride (PVC) powder. Tungsten-vinyl composites are also found in the research paper "Acoustic Properties of Tungsten-Vinyl Composites" by Lees, Gilmore and Kranz, IEEE Transactions on Sonics and Ultrasonics, SU-20, No. 1, pp.1-2, January, 1972. It will be appreciated by those skilled in the art that the composition of the acoustic backing material can be modified from the examples given above.

Further, the embodiment shown in FIG. 3 comprises placing a flexible interconnect circuit on top of the cMUT array. Another possible means of interconnecting the arrays is to form a connection through the backing material via a wire or trace embedded in the backing material. These connections can then be formed on the surface of the cMUT device by wafer penetration vias or wraparound connections. In another variation, the flex circuit can be placed under the substrate and then signaled to the top of the cMUT device using a wafer penetration via or wraparound connection. In another form of variation, the cMUT substrate can be connected to a second substrate that provides electrical functions separated or associated with ultrasonic transformations such as impedance matching, multiplexing, switching, and transmission and reception of beam formation. it can. The acoustic backing layer can be placed between these substrates. In this embodiment, the electrical connection from the cMUT cell electrode to the electronic circuit configuration of the second substrate can pass through the vias formed by the substrate and the acoustic backing layer.

Although the present invention has been described with reference to preferred embodiments, it will be appreciated by those skilled in the art that various modifications can be made without departing from the scope of the invention and equivalents can be replaced with its elements. Will be. In addition, many modifications can be made to adapt a particular situation to the teachings of the invention without departing from the essential scope of the invention. Accordingly, the invention is not limited to the particular embodiments disclosed as the best possible mode in carrying out the invention, and the invention includes all embodiments included within the appended claims. Is intended.

The term "ultrasonic transducer" as used in the claims includes capacitive and piezoelectric ultrasonic transducers. The phrase "microfabrication of a substrate" as used in the claims should be construed to include microfabrication of both the surface and / or bulk. Further, the reference numerals in the claims corresponding to the reference numerals in the drawings are used merely for facilitating the understanding of the invention of the present application, and are not used for the purpose of narrowing the scope of the invention of the present application. Absent. Then, the matters described in the claims of the present application are incorporated in the specification and become a part of the matters described in the specification.

<figref num="1">Sectional view of a typical cMUT cell.</figref><figref num="2">Isometric view of the cMUT cell shown in Figure 1.</figref><figref num="3">Side view of the cMUT device and the associated electrical connection supported by a layer of acoustic backing material.</figref><figref num="4">Isometric view of a group of cMUT cells electrically connected together on a substrate and acoustic backing material.</figref><figref num="5">Isometric view of a substrate forming one ultra-finely machined, spaced, row of transducer elements, each element containing multiple electrically connected cMUT cells.</figref><figref num="6">FIG. 5 shows two different types of acoustically insulated trenches that can be formed on the ultrafinely machined substrate of FIG. 1 according to each embodiment of the invention.</figref><figref num="7">FIG. 5 shows four different types of acoustically insulated trenches that can be formed within the ultrafine processed substrate of FIG. 1 according to each embodiment of the present invention.</figref><figref num="8">FIG. 5 shows the formation of an acoustically insulated trench on the back surface of an ultrafinely machined substrate according to yet another embodiment of the present invention.</figref><figref num="9">FIG. 5 shows each cMUT element constructed on a semiconductor substrate doped to provide electrical insulation between the transducer elements according to another embodiment of the present invention.</figref><figref num="10">FIG. 5 shows each cMUT element constructed on a semiconductor substrate doped to provide electrical insulation between the transducer elements according to another embodiment of the present invention.</figref><figref num="11">FIG. 5 shows a pair of cMUT cells built on an n-type semiconductor substrate, the wall supporting the film according to another embodiment of the invention, made of a p-type semiconductor material that provides electrical insulation.</figref>

Code description

2 cMUT Transducer Cell 4 Board 18 Backing Layers 26, 28 Insulated Trench