Method for manufacturing MEMS membranes comprising corrugations

Abstract

A method comprising: providing a substrate (102, 202, 402, 502, 602a / b, 802, 1002); selectively etching the substrate (102, 202, 402, 502, 602a / b, 802, 1002) to form at least one enclosed recess (605a) or one enclosed pillar (605b) on the substrate (102, 202, 402, 502, 602a / b, 802, 1002); depositing a first structural layer (608a / b, 806a / b, 906a / b, 1008) on the substrate (102, 202, 402, 502, 602a / b, 802, 1002), wherein the first structural layer (608a / b, 806a / b, 906a / b, 1008) comprises at least one depression (609a) or one elevation (609b) corresponding to the enclosed depression (605a) or the enclosed column (605b); heating the first structural layer (608a / b, 806a / b, 906a / b, 1008) to a temperature above a glass transition temperature of the first structural layer (608a / b, 806a / b, 906a / b, 1008), thereby refluxing the first structural layer (608a / b, 806a / b, 906a / b, 1008);Applying a membrane layer (410a / b, 510a / b, 610a / b, 810a / b, 910a / b) to the first structural layer (608a / b, 806a / b, 906a / b, 1008) such that the membrane layer (410a / b, 510a / b, 610a / b, 810a / b, 910a / b) comprises at least one downwardly directed corrugation corresponding to the depression (609a) or an upwardly directed corrugation corresponding to the elevation (609b) formed in the first structural layer (608a / b, 806a / b, 906a / b, 1008); andreleasing the membrane layer (410a / b, 510a / b, 610a / b, 810a / b, 910a / b), thereby forming a membrane suspended above the substrate (102, 202, 402, 502, 602a / b, 802, 1002);

Description

Cross-reference to related registrations

[0001] The present application claims priority over US Provisional Application No. 62 / 742,164, filed on October 5, 2018, entitled “METHODS OF FORMING MEMS DIAPHRAGMS INCLUDING CORRUGATIONS”, which is incorporated herein by reference in its entirety. Technical field

[0002] The present disclosure relates generally to systems and methods for improving the compliance of membranes, including acoustic transducers. background

[0003] Microphone arrays are generally used in electronic devices to convert acoustic energy into electrical signals. Microphones typically include diaphragms for converting acoustic signals into electrical signals. Pressure sensors can also incorporate such diaphragms. Advances in micro- and nanofabrication technology have led to the development of increasingly smaller microphone arrays and pressure sensors using microelectromechanical systems (MEMS). Some microphones incorporate tensioned or clamped diaphragms, which can reduce the compliance of such diaphragms. Summary

[0004] The embodiments described here generally relate to methods and processes for manufacturing tensioned or clamped membranes for MEMS acoustic transducers that exhibit increased compliance. In particular, the described methods and processes enable the production of tensioned membranes that have one or more upward and / or downward-pointing corrugations to increase the membrane's compliance, wherein the corrugations have smooth corners to reduce stress concentration and thus increase the membrane's robustness and reduce failure.

[0005] In some embodiments, a method for forming an acoustic transducer comprises providing a substrate and depositing a first structural layer onto the substrate. The first structural layer is selectively etched to form at least one enclosed depression or column on the structural layer. A second structural layer is deposited on top of the first structural layer. The second structural layer comprises a depression or elevation corresponding to the enclosed depression or column. At least the second structural layer is heated to a temperature above its glass transition temperature, causing the second structural layer to reflux.A membrane layer is applied to the second structural layer, such that the membrane layer includes at least one downward-pointing corrugation corresponding to the depression, or one upward-pointing corrugation corresponding to the elevation formed in the second structural layer. The membrane layer is then removed, forming a membrane suspended above the substrate.

[0006] In some embodiments, a method for forming an acoustic transducer comprises providing a substrate and selectively etching the substrate to form at least one enclosed depression or column on the substrate. A first structural layer is deposited on the substrate. The first structural layer comprises at least one depression or elevation corresponding to the enclosed depression or column. The first structural layer is heated to a temperature above its glass transition temperature, causing the first structural layer to reflux. A membrane layer is deposited on the first structural layer such that the membrane layer comprises at least one downward-facing corrugation corresponding to the depression or one upward-facing corrugation corresponding to the elevation formed in the first structural layer.The membrane layer is dissolved, forming a membrane that is suspended above the substrate.

[0007] In some embodiments, an acoustic transducer is formed by the process of providing a substrate and selectively etching the substrate to form at least one enclosed depression or column on the substrate. A first structural layer can be applied to the substrate, the first structural layer comprising at least one depression or elevation corresponding to the enclosed depression or column. The first structural layer can be heated to a temperature above its glass transition temperature, thereby causing the first structural layer to reflux. A membrane layer can be applied over the first structural layer, such that the membrane layer comprises at least one downward-facing corrugation corresponding to the depression or one upward-facing corrugation corresponding to the elevation formed in the first structural layer.The membrane can then be detached, forming a membrane that is suspended above the substrate. List of characters

[0008] The aforementioned and other features of the present disclosure will become more fully apparent from the following description and the attached claims in conjunction with the attached drawings. Since these drawings represent only some embodiments according to the disclosure and are therefore not to be considered as limiting the scope of the disclosure, the disclosure is described with additional specificity and detail using the attached drawings. Fig. Figures 1A-1B are schematic representations of various operations included in a method for shaping the membrane of an acoustic transducer according to one embodiment; Fig. 1C is a top view of the acoustic transducer membrane, which was manufactured using the process of Fig. 1A-1B was formed, whereby Fig. 1 B, Operation 6 a lateral cross-sectional view of Fig. 1C along line XX in Fig. 1C represents. Fig. Figures 2A-2B are schematic representations of various operations comprising a method for manufacturing the membrane of an acoustic transducer with upward-pointing corrugations according to one embodiment; Fig. 2C is a top view of the membrane of the acoustic transducer, which is manufactured using the process of Fig. 2A-2B was manufactured, whereby Fig. 2B, Operation 6 a side cross-sectional view of Fig. 2C along line YY in Fig. 2C represents. Fig. Figure 3 is a schematic flowchart of a method for manufacturing an acoustic transducer having a membrane in which an upward or downward corrugation is defined, according to one embodiment. Fig. Figures 4A-4C are schematic illustrations of various operations that are included in a process for manufacturing an acoustic transducer having upward or downward directed undulations, according to one embodiment. Fig. Figures 5A-5D are schematic representations of various processes included in a process for manufacturing an acoustic transducer with upward or downward directed corrugations according to one embodiment; Fig. 5E is an enlarged view of a section of the acoustic transducer from Fig. 5A-5D, which are represented by arrow A in operation 14a of Fig. 5D display is shown. Fig. Figure 6 is a top view of a section of a backplate layer of the acoustic transducer of Fig. 5A-5D, which shows a plurality of apertures formed therein according to one embodiment. Fig. 7, Batch A is a table summarizing membranes including downward-facing corrugations formed in two wafer batches using different methods, the shape of their edges (or corners) and the associated pressure at which the membranes fail; Fig. 7, Batch BE are scanning electron microscopy (SEM) images of representative samples from the two wafer batches. Fig. Figure 8 is a diagram of the membrane thickness of membranes found in representative samples of the two batches of wafers. Fig. 7A were formed. Fig. Figures 9A-9C are schematic illustrations of various operations included in a process for manufacturing an acoustic transducer according to an embodiment comprising upward or downward directed corrugations. Fig. Figure 10 is a schematic flow diagram of a method for manufacturing an acoustic transducer having a membrane in which an upward or downward corrugation is defined, according to another embodiment. Fig. Figures 11A-11C are schematic illustrations of various operations included in a process for manufacturing an acoustic transducer comprising upward or downward directed corrugations according to one embodiment. Fig. Figures 12A-12D are schematic illustrations of various operations comprising a process for manufacturing an acoustic transducer containing upward or downward directed corrugations, according to one embodiment. Fig. Figures 13A-13E are schematic representations of various operations included in a process for manufacturing an acoustic transducer comprising two corrugated membranes according to one embodiment.

[0009] The following detailed description refers to the accompanying drawings. In the drawings, similar symbols typically denote similar components unless the context specifies otherwise. The illustrative implementations described in the detailed description, the drawings, and the claims are not to be construed as limitations. Other implementations may be used, and other modifications may be made, without departing from the spirit or scope of the subject matter presented here. It is understood that the aspects of the present disclosure, as generally described here and illustrated in the figures, may be arranged, substituted, combined, and designed in a multitude of different configurations, all of which are expressly considered and incorporated into this disclosure. Detailed description of the different designs

[0010] The embodiments described here generally relate to methods and processes for manufacturing tensioned or clamped diaphragms for MEMS transducers that exhibit increased compliance. In particular, the described methods and processes enable the production of tensioned diaphragms that have one or more upward and / or downward-facing corrugations to increase the diaphragm's compliance, wherein the corrugations have smooth corners to reduce stress concentration and thus increase the diaphragm's robustness and reduce failures.

[0011] Many acoustic transducers comprise one or more diaphragms suspended above, below, or with an intermediate backplate. In some acoustic transducers, the diaphragm may be tensioned or forced to achieve high linearity. However, such tensioned diaphragms may lack sufficient compliance, which can result in low sensitivity or diaphragm movement when the acoustic transducer is subjected to sound pressures. To increase compliance, corrugations or ribs, such as upward or downward-pointing corrugations, may be formed in such tensioned diaphragms. Some manufacturing processes can produce corrugations with sharp corners (i.e., a radius of curvature of less than 1 µm).Stress can concentrate at such sharp corners, for example during impacts and high pressure, which leads to membrane failure and reduces robustness.

[0012] In contrast, the methods and processes described here offer advantages that include, for example: (1) enabling the production of membranes incorporating corrugations with smooth or rounded corners (i.e., having a radius of curvature at the corners greater than 1 µm and less than 50 µm), thereby reducing stress concentration and increasing robustness; (2) the use of a simple PSG reflow process to smooth corners in depressions or protrusions formed in the PSG layer, which acts as a template or mold to form the membrane with corrugations with smooth corners; (3) easy integration into current manufacturing processes, thereby reducing manufacturing complexity and costs; and (4) enabling the production of upward-facing corrugations, downward-facing corrugations, or a combination thereof.

[0013] As described here, the terms “downward-facing corrugations” refer to corrugations or ribs that project from the membrane towards a substrate on which the membrane is suspended, and “upward-facing corrugations” refer to corrugations or ribs that project from the membrane away from the substrate.

[0014] Fig. 1A-1B illustrate a process flow 100 for the production of an acoustic transducer 10 , which is a membrane 110 exhibiting downward-pointing waves or ribs 112 According to one embodiment, the acoustic transducer comprises... 10 It may, for example, include a MEMS acoustic transducer for use in a MEMS microphone array or a MEMS pressure sensor, and may be configured to generate electrical signals in response to acoustic signals or atmospheric pressure changes.

[0015] During surgery 1 a substrate 102provided, which includes a first structural layer arranged on it 104 includes the substrate 102 This may include, for example, silicon, glass, Pyrex, quartz, or any other substrate described herein. The first structural layer 104 may include an initial PSG or BPSG layer containing an initial impurity level, for example an initial phosphorus level in a range between 2% and 6%, and may be applied over the substrate 102 deposited using CVD, LPCVD, PECVD, ALD, any other suitable method or a combination thereof.

[0016] In operation 2 one or more enclosed depressions 105 in the first structural layer 104 formed. The enclosed depressions 105They can be formed using wet etching (for example, BHF etching) or dry etching (for example, RIE or DRIE etching). Etching can cause the enclosed depressions to... 105 have sharp corners and edges. In some embodiments, one or more enclosed recesses may be 105 have a circular cross-section, for example define a circular depression that is centered around a longitudinal axis AL of the substrate 102 is etched.

[0017] In operation 3 A second structural layer will be formed 108 on the first structural layer 104 applied so that the second structural layer 108 one or more depressions 109 includes one or more enclosed depressions 105 correspond to those in the first structural layer 104 are defined. The depressions formed in the cavities109 may also have sharp corners and edges, similar to the sharp edges or corners of those in the first structural layer 104 defined enclosed depressions 105 correspond. The second structural layer 108 may include a second PSG layer that has a second impurity content, for example a second phosphorus content.

[0018] The second structural layer 108 may have a second phosphorus content that is higher than the first phosphorus content of the first PSG layer 104 , for example, in a range between 4% and 10%. The higher phosphorus content in the second structural layer 108 causes the second structural layer to 108 has a lower glass transition temperature than the first structural layer 104 In operation 4 The second structural layer 108to a temperature above its glass transition temperature, but below a glass transition temperature of the first structural layer 104 heated, which only exposes the second structural layer 108 is brought back to the surface ("reflow"), which smooths the corners and edges of the depressions. 109 smoothed or rounded.

[0019] In operation 5 a membrane layer 110 on the second structural layer 108 separated, so that the membrane layer 110 one or more downward-pointing waves 112 includes those extending from it towards the substrate. 102 They protrude. Furthermore, the downward-pointing ripples include 112 smooth or rounded corners 113 , which fit the smooth corners of the recesses 109 are equivalent to.

[0020] During surgery 6 at least a section of the substrate will 102 , the first structural layer 104and the second structural layer 108 etched in such a way that a membrane 110 with downward-pointing waves 112 above the substrate 102 suspended, causing the acoustic transducer to remain 10 is formed. In some embodiments, the downward-pointing ripples can 112 for example, circumferential ripples that include circularly enclosed depressions. 105 include those originally located in the first structural layer 104 were formed. Fig. 1C shows a top view of the membrane 110 with the downward-facing wave 112 Although depicted as a pair of waves 112 includes any number of corrugations in the membrane 110 be formed. In various embodiments, the corrugations can be 112have a depth in the range of 0.5 micrometers to 5 micrometers (for example, 0.5, 1, 2, 3, 4 or 5 micrometers including all ranges and values ​​in between).

[0021] Fig. 2A-2B illustrates a process flow 200 for the production of an acoustic transducer 20 , which is a membrane 210 includes upward-pointing waves 212 exhibits, according to one embodiment. The acoustic transducer 20 It may, for example, include a MEMS acoustic transducer for use in a MEMS microphone array or a MEMS pressure sensor, and may be configured to generate electrical signals in response to acoustic signals or atmospheric pressure changes.

[0022] In operation 1 a substrate 202 provided, which is a first structural layer arranged on it 204 includes the substrate 202This can include, for example, glass, silicon, Pyrex, quartz, or any other substrate suitable for the process. 300 , 700 is described. The first structural layer 204 may contain an impurity, for example an initial amount of phosphorus or an initial phosphorus content in a range between 2% and 6%, and may be present on the substrate. 202 deposited using CVD, LPCVD, PECVD, ALD, another suitable method or a combination thereof.

[0023] During surgery 2 one or more enclosed ("enclosed") columns 205 in the first structural layer 204 formed. The enclosed column 205 can be formed by wet etching (e.g., BHF etching) or dry etching (e.g., RIE or DRIE etching) to remove large sections of the first structural layer 204 to remove, whereby the enclosed column 205 on the substrate202 remains standing. The enclosed column 205 can, for example, define an enclosed circular column centered around a longitudinal axis AL of the substrate 202 is formed and extends towards the substrate 202 extends. Etching can cause the enclosed columns to 205 have sharp corners and edges. During surgery 3 A second structural layer will be formed 208 on the substrate and the enclosed column 205 isolated, which are from the first structural layer 204 was formed, so that the second structural layer 208 one or more surveys 209 includes those corresponding to one or more columns. The enclosed column 205 surveys 209 They may also have sharp corners and edges, which correspond to the sharp edges or corners of the first structural layer. 204 formed enclosed column 205are equivalent to.

[0024] The second structural layer 208 may have a second impurity content, for example a second phosphorus content that is greater than the first phosphorus content of the first structural layer 204 , for example in a range between 4% and 10%, and therefore a lower glass transition temperature than the first structural layer 204 In operation 4 The second structural layer 208 to a temperature above its glass transition temperature, but below a glass transition temperature of the first structural layer 204 heated, which only exposes the second structural layer 208 is brought back to the surface ("reflow"), which smooths the corners and edges of the protrusions. 209 smoothed or rounded.

[0025] During surgery 5 a membrane layer 210 on the second structural layer 208deposited in such a way that the membrane layer 210 one or more upward-pointing waves 212 includes those derived from the substrate 202 They protrude away. Furthermore, the upward-pointing ripples include 212 smooth or rounded corners 213 , which form the smooth corners of the elevations 209 correspond. During surgery 6 at least a section of the substrate will 202 and the first structural layer 204 as well as the pillars 205 etched, so that the membrane layer 210 , which is a membrane with upward-pointing ripples 212 exhibits above the substrate 202 suspended, causing the acoustic transducer to remain 20 is formed. In some embodiments, the upward-pointing corrugations include 212enclosed circumferential grooves and can have a height in a range of 0.5 micrometers to 5 micrometers (for example, 0.5, 1, 2, 3, 4 or 5 micrometers including all intermediate ranges and values). Fig. 2C, for example, shows a top view of the membrane. 210 , which is the upward-pointing wave 212 shows, which is formed as an enclosed circular wall or column that extends from the substrate 202 extends away.

[0026] Fig. Figure 3 is a schematic flowchart of an exemplary procedure. 300 for the manufacture of an acoustic transducer (for example, the acoustic transducer) 10 , 20 , 40 , 50 , 80 , 90), comprising a membrane that has upward- or downward-facing corrugations with smooth or rounded corners. The acoustic transducer can, for example, include a MEMS acoustic transducer for use in a MEMS microphone array or a MEMS pressure sensor and can be configured to generate electrical signals in response to acoustic signals or atmospheric pressure changes.

[0027] The process involves providing a substrate at 302. The substrate can be formed from silicon, silicon dioxide, glass, Pyrex, quartz, ceramic, or another suitable material and can be the substrate 102 , 202 , 402 or 502 or 802 include, as detailed herein in relation to the procedures 100 , 200 , 400 , 500 or 800 described. In some embodiments, a back wall layer (for example, the back wall layer) is described. 403 , 503The back wall layer is deposited on the substrate layer at 304. The back wall layer can be formed from a low-stress material, such as low-stress silicon nitride (LSN), low-stress oxide, or another suitable material. The back wall layer can be deposited by physical vapor deposition (PVD), chemical vapor deposition (CVD), low-pressure chemical vapor deposition (LPCVD), plasma-enhanced CVD (PECVD), atomic layer deposition (ALD), any other suitable method, or a combination thereof. The back wall layer can be relatively inflexible compared to a membrane formed on the substrate.

[0028] In some embodiments, a first conductive layer (for example, the first conductive layer) is 416 , 516 , 816 , 916 , which in relation to the procedure 400 , 500 , 800 , 900The first conductive layer (as described) is deposited on the backplate layer at 306. In some embodiments, the first conductive layer can be formed from polysilicon (poly). In other embodiments, the first conductive layer can be formed from metals (e.g., gold, platinum, etc.), doped silicon, or another suitable conductive material. The first conductive layer can be deposited by PVD, thermal evaporation, E-beam evaporation, CVD, PECVD, LPCVD, ALD, or another suitable method, or a combination thereof.

[0029] At 308Apertures can be formed through the backplate layer and the first conductive layer. For example, a wet etching process or a dry etching process (such as reactive ion etching (RIE), deep RIE (DRIE), focused ion beam etching (FIB), etc.) or any other suitable etching process can be used to form appropriate apertures in the backplate and the first conductive layer. The apertures can have any suitable shape, such as square, rectangular, oblong, round, oval, polygonal (such as hexagonal, octagonal, etc.), or any other suitable shape.

[0030] At 310 The first conductive layer can be selectively etched (for example, using a wet or dry etching process) to form an electrical contact on the backplate. For example, the radial or circumferential etchings of the first conductive layer can be selectively etched to form the electrical contact on the backplate.

[0031] At 312 A first structural layer is applied to the substrate. In various embodiments, the first structural layer can comprise a first PSG layer containing an initial phosphorus content. For example, the first PSG layer can 406 , 506 , 806 , 906 applied to the substrate. In other embodiments, the structural layer can comprise a boron phosphosilicate glass layer (BPSG), an oxide, a nitride, or another suitable material.

[0032] At 314The first structural layer is selectively etched to form one or more enclosed depressions or columns within the structural layer. In some embodiments, the first structural layer (for example, a first PSG layer) is selectively etched down to the backplate structural layer using a wet etching process (for example, using buffered hydrofluoric acid (BHF)), such that portions of the structural layer in the areas to be etched are completely removed (for example, as described herein in relation to the process). 100 , 200 , 400 , 800 described). In such embodiments, the backplate layer can serve as an etch stop for the wet etching process. In other embodiments, the structural layer can be selectively etched with a time-controlled dry etching process (for example, a RIE or DRIE process) so that the dry etching does not reach the backplate layer (for example, as described herein with respect to the process).500 , 900 (described). For example, the dry etching process can be carried out for a predetermined time, leaving a portion of the first structural layer above the substrate or, in some embodiments, the backing plate layer. The enclosed depressions or pillars defined in the first structural layer can have sharp corners (for example, with a radius of curvature of less than 1 µm). In some embodiments where the first structural layer includes a first PSG layer, the first PSG layer can be heated above its glass transition temperature, causing the first PSG layer to reflux and rounding its corners (for example, resulting in corners with a radius of curvature greater than 1 µm and less than 50 µm).

[0033] At 316A second structural layer containing impurities, for example a second PSG layer (for example the second PSG layer), is added. 108 , 208 , 408 , 508 , 808 , 908 The impurity, which contains phosphorus, is deposited onto the first structural layer. The second structural layer can be conformally deposited (i.e., uniformly arranged so that it adheres to the contours of the underlying first structural layer) such that the second structural layer comprises one or more depressions or protrusions corresponding to the one or more cavities or columns already formed in the first structural layer. In some embodiments, the impurity may include phosphorus, so that the phosphorus content is greater than 2%.

[0034] At 318The second structural layer is heated above its glass transition temperature, causing it to reflow. Furthermore, the enclosed depressions or columns that form in the structural layer during the operation 314The resulting structures have sharp corners and edges (for example, with a radius of curvature of less than 1 µm). Since the second structure layer is deposited conformally onto the first, it follows the contours of the first, so that the depressions and / or protrusions of the second structure layer also have sharp corners and edges. Heating the second structure layer above its glass transition temperature causes a phase change, allowing it to flow. Through reflow, the corners and edges of the depressions or protrusions formed in the second structure layer are smoothed or rounded, so that the corners and edges of the second structure layer can have a radius of curvature of more than 1 µm and less than 50 µm.

[0035] In some embodiments, the first structural layer is made of PSG with a first phosphorus content, and the second structural layer is made of PSG with a second phosphorus content that differs from the first. In other embodiments, the first phosphorus content can be equal to the second phosphorus content.

[0036] In some embodiments, the first phosphorus content, encompassed in the first structural layer, can range from 2% to 6%, and the second phosphorus content, encompassed in the second structural layer, can range from 4% to 10%. In such embodiments, the second structural layer can have a higher phosphorus content than the first structural layer. The higher amount of phosphorus lowers the glass transition temperature of the second structural layer relative to the glass transition temperature of the first structural layer. Heating can be performed to a temperature higher than the glass transition temperature of the second structural layer but lower than the glass transition temperature of the first structural layer, causing only the second structural layer to flow and rounding its edges without causing the first structural layer to reflow.

[0037] In other embodiments, the first phosphorus content, comprising the first structural layer, is between 4% and 10%, and the second phosphorus content in the second structural layer is between 2% and 6%, so that the second structural layer has a lower phosphorus content and therefore a higher glass transition temperature than the first structural layer. In such embodiments, the first structural layer can be heated to its glass transition temperature before the second structural layer is deposited onto the first. In some embodiments, the second structural layer can be heated to a temperature higher than the glass transition temperature of both the first and second structural layers to induce reflow. This can result in smoother corners and edges in the second structural layer.

[0038] At 322A membrane layer is deposited on the second structural layer such that the membrane layer comprises downward-pointing corrugations corresponding to the one or more depressions, upward-pointing corrugations corresponding to the one or more protrusions formed in the second structural layer, or a combination thereof. For example, a low-stress material, such as LSN or a low-stress ceramic, can be applied to the second structural layer (for example, by a physical or chemical vapor deposition process). In other embodiments, the membrane layer can comprise a dielectric or conductive material (for example, silicon oxide, silicon nitride, silicon carbide, gold, aluminum, platinum, etc.).The second structural layer acts as a mold or template for the membrane layer, ensuring that each downward-facing or upward-facing corrugation defined in the membrane layer has a radius of curvature corresponding to the second radius of curvature, i.e., the radius of curvature after backflow. This reduces the stress concentration at the edges or corners of the corrugations, thereby increasing robustness and shock resistance.

[0039] In some embodiments, a second conductive layer is applied and structured on the second structural layer before a membrane layer is applied to the second structural layer, at 320. The second conductive layer can be formed from poly or another conductive material. At least a portion of the membrane layer can contact the second conductive layer, so that the second conductive layer forms an electrical contact with the membrane layer.

[0040] At 324 The membrane layer is released, forming a membrane that floats on the substrate. Releasing the membrane can, for example, involve etching through the substrate, the first structural layer, and the second structural layer. Furthermore, back-side etching can be performed to etch the substrate in such a way as to define an opening through it, allowing the membrane to be released from the substrate side. In particular embodiments, the substrate can comprise a thin oxide layer (for example, SiO2) arranged on a first surface of the substrate facing the membrane. For example, the oxide layer can be deposited or grown on the substrate before the first structural layer or, alternatively, the backplate structural layer is deposited on it. The oxide layer can serve as an etch stop for back-side etching of the substrate.

[0041] The backside etching can be continued, or a further backside etching can subsequently be performed through the apertures defined in the backplate layer to remove the first and second structural layers and expose the membrane. In other embodiments, the backplate layer can be arranged above the membrane, so that the membrane is positioned between the substrate and the backplate. In such embodiments, the subsequent etching can include an etching of the front side, performed through the apertures defined in the backplate.

[0042] In various embodiments, releasing the membrane also releases the back wall layer, forming a back wall that hangs above or below the membrane over the substrate. In some embodiments, the etching of the first and second structural layers can be performed for a predetermined time, so that a portion of the first structural layer and a portion of the second structural layer near the upward-pointing corrugations or the downward-pointing corrugations of the membrane layer are not removed, in order to form a circumferential (also referred to as "peripheral") support structure (for example, as in Fig. (5E shown). The sections of the first structural layer and / or the second structural layer can facilitate the rounding of the corners and edges of the upward or downward-pointing corrugations formed in the membrane. In some embodiments, an inner radial edge of the section of the second structural layer is positioned closer to the downward-pointing corrugation or the upward-pointing corrugation defined in the membrane layer, relative to an inner radial edge of the section of the first structural layer. In other words, an inner side wall of the sections of the first and second structural layers can taper from a first edge therein near the substrate to a second edge near the membrane layer, such that the second edge is radially closer to the downward-pointing or upward-pointing corrugations relative to the first edge.

[0043] In some embodiments, the membrane, which is produced using the method 300 The membrane, when formed, exhibits a compliance at least twice greater than that of a similar restricted membrane that does not include the corrugations. Furthermore, the membrane can withstand a pressure differential in the range of 50 to 70 psi. Although not shown, the process 300 In some embodiments, this may also include forming a penetration or through-opening through the membrane and optionally the back plate, for example to allow pressure equalization between a front volume and a rear volume of the acoustic transducer, which is connected to the method. 300 was trained.

[0044] Fig. 4A-4C illustrate process flows 400a / b for shaping acoustic transducers 40a and 40b, which have downward or upward directed waves, according to one embodiment. The method 400a / b includes providing a substrate 402a / b (for example, glass, Pyrex, quartz, silicon, silicon oxide or another suitable substrate) during operation 1a / b .

[0045] In operation 2a / b A back layer will be created. 403a / b on the substrate 402a / b isolated and a first leading layer 416a / b is applied to the back layer 403a / b deposited. In some embodiments, the backplate layer can be 403a / b for example, an LSN layer, and the first conductive layer 416a / b It can include a conductive material (for example, polypropylene). In operation 3a / b A variety of apertures will be used. 417a / b in the back wall layer 403a / b and the first management layer 416a / b defined, for example, by a wet or dry etching process. In operation 4a / b The first conductive layer is selectively etched to create an electrical contact on the back wall layer. 403a / b to form.

[0046] In operation 5a / b A first structural layer will be formed 406a / b , for example a first PSG or BPSG layer, onto the backplate layer 403a / b applied. The first structural layer 406a / b can be applied to the backplate layer 403a / b planarized (for example, using CMP). The first structural layer 406a / b It may contain impurities, for example, a primary phosphorus content in the range of 2% to 5%. In operation 6a one or more enclosed depressions will be created. 407a into the first structural layer 406aetched patterns that serve as templates for forming downward-facing corrugations in a membrane. In contrast, the first structural layer 406b etched in such a way that one or more enclosed columns 407b from the first structural layer 406b These are formed as templates for creating upward-pointing corrugations in a membrane. In special embodiments, a wet etching process can be used to create the first structural layer. 406a / b up to the backplate layer located below it 403a / b to etch, whereby the backplate layer 403a / b It serves as an etching stop for wet etching.

[0047] In operation 7a / b A second structural layer will be formed 408a / b , for example, a second PSG or BPSG layer that has a second impurity content, for example, a second phosphorus content, which is greater than the first impurity content, so that it has a lower glass transition temperature than the first structural layer 406a / b exhibits on the first structural layer 406a / b and the open areas of the backplate layer 403a / b isolated. The second structural layer 408a / b becomes conformal on the first structural layer 406a / b isolated, so that they have one or more depressions 409a includes one or more enclosed depressions 407a correspond to those in the first structural layer 406a are trained, or one or more surveys 409b , which enclose one or more columns 407b correspond to those from the first structural layer 406b are formed. The enclosed depressions 407aor the enclosed columns 407b may have sharp corners, as previously described herein.

[0048] During surgery 8a / b The second structural layer 408a / b to a temperature above a glass transition temperature of the second structural layer 408a / b This heats up the second structural layer. 408a / b This caused the backflow ("reflow"), which smoothed the sharp edges and corners of the recesses. 409a and the one in the second structural layer 408a / b surveys 409b smoothed or rounded.

[0049] In operation 9a / b A second conductive layer will be added 418a / b (for example, a polylayer) onto the second structural layer 408a / b applied and structured. In operation 10a / b Both the second structural layer 408a / b as well as the first structural layer 406a / b along the edges of each layer up to the backplate structural layer 403a / b etched to create space for sealing a membrane layer 410a / b with the backplate structural layer 403a / b to accomplish.

[0050] During surgery 11a / b The membrane layer 410a / b (for example, an LSN layer) on the second structural layer 408a / b so separated that the membrane layer 410a one or more downward-pointing waves 412a includes those with one or more depressions 409a correspond to those in the second structural layer 408a are formed, or one or more upward-pointing ripples 412b , which are the one or more surveys 409b correspond to those in the second structural layer 408b are formed. In addition, the membrane layer touches 410a / b the backplate layer 403a / b , to the edges of the acoustic transducer 40a / b to seal during surgery 12a / b A section of the substrate will be removed. 402a / b and a large part of the first structural layer 406a / b and the second structural layer 408a / b etched (for example, by the backplate layer) 403a / b defined apertures 417a / b) , to the membrane layer 410a / b as well as the backplate layer 403a / b to release, thereby releasing a membrane and a backplate of the acoustic transducer 40a / b be formed.

[0051] During the operations of the procedure 400a / b this causes the backplate 416a / b below the membrane 410a / b In other embodiments, a backplate can be arranged above a membrane that includes corrugations (for example, the membrane). 410a / b) In such embodiments, a second structural layer is applied to the membrane layer (for example, the membrane layer). 410a / b) A backplate structural layer is deposited on the second structural layer; and a multitude of apertures are formed (e.g., etched) in the backplate structural layer. The apertures allow an etchant, used to release the membrane layer, to pass through the backplate and etch the second structural layer, so that releasing the membrane also releases the backplate layer, forming a backplate that is deposited on the substrate (e.g., the substrate). 402a / b) hangs above the membrane.

[0052] Fig. 5A-5D illustrate process flows 500a / b for the production of acoustic transducers 50a and 50b , which have downward or upward directed ripples, according to one embodiment. The process 500a / b includes providing a substrate 502a / b (for example, glass, Pyrex, quartz, silicon, silicon oxide or another suitable substrate) during operation 1a / b .

[0053] In operation 2a / b A back wall layer will be created. 503a / b on the substrate 502a / b isolated and a first leading layer 516a / b is applied to the back wall layer 503a / b deposited. In some embodiments, the back layer can be 503a / b for example, an LSN layer, and the first conductive layer 516a / b It can include a conductive material (for example, polypropylene). In operation 3a / b A variety of apertures will be used. 517a / b in the back wall layer 503a / b and the first management layer 516a / b defined, for example, by a wet or dry etching process. The apertures 517a / b They can have any suitable shape, for example square, rectangular, circular, oval, oblong, polygonal, etc. In special embodiments, the apertures can 517a / b have a hexagonal shape with rounded corners. Fig. Figure 6, for example, shows a top view of a section of the back wall layer. 503a / b , the hexagonal aperture 517a / b features which are defined therein. In special embodiments, the hexagonal apertures can 517a / b have a width W between their parallel sides in a range between 10 and 20 micrometers (for example, 10, 12, 14, 16, 18 and 20 micrometers including all ranges and values ​​in between) and a distance of 10-30 micrometers (for example, 10, 15, 25 or 30 micrometers including all ranges and values ​​in between).

[0054] In operation 4a / b will be the first leading layer 516a / b selectively etched to create an electrical contact on the backplate layer 503a / b to form. In operation 5a / b A first structural layer will be formed 506a / b on the substrate 502a / b isolated. The first structural layer 506a / b It may comprise a PSG or BPSG layer containing an initial impurity level, for example, an initial phosphorus level in the range of 4% to 10%. In one embodiment, the first structural layer may 506a / b after application to the backplate layer 503a / b to be planarized (for example, by means of a through hole).

[0055] In operation 6a are in the first structural layer 506a enclosed depressions 507a formed, which serve as templates for the formation of downward-facing undulations in a membrane. In contrast, in surgery 6b the first structural layer 506b etched in such a way that enclosed columns507b from the first structural layer 506b are formed that serve as templates for an upward-pointing corrugation created in a membrane. In particular embodiments, the first structural layer 506a / b etched in a time-limited dry etching process, so that the dry etching removes the backplate layer 503a / b not reached and sections of the first structural layer 506a / b across the entire backplate layer 503a / b remain in order.

[0056] In operation 7a / b will be the first structural layer 506a / b to a temperature above the glass transition temperature of the first structural layer 506a / b heated to form the first structural layer 506a / b to cause backflow ("reflow") and the edges or corners of the enclosed recesses 507a or enclosed columns 507b , which are in the first structural layer 506a or 506bare defined, to smooth. In operation 8a / b A second structural layer will be formed 508a / b , for example a second PSG or BPSG layer, above the first structural layer 506a / b separated, so that the second structural layer 508a / b Depths 509a or surveys 509b includes those in the first structural layer 506a / b defined enclosed depressions 507a or enclosed columns 507b correspond. The second structural layer 508a / b may have a second impurity content, for example a second phosphorus content that is lower than the first impurity content (for example a first phosphorus content) of the first structural layer 506a / b (for example, in a range between 2% and 6%) and therefore a higher glass transition temperature than the first structural layer 506a / b exhibits.

[0057] In operation 9a / b The second structural layer 508a / b heated to a temperature above its glass transition temperature to form the second structural layer 508a / b to cause backflow ("reflow"), thereby clearing the corners of the depressions 509a and surveys 509b to be further refined. In operation 10a / b A second conductive layer will be added 518a / b to the second structural layer 508a / b applied and structured. In operation 11a / b Both the second structural layer 508a / b as well as the first structural layer 506a / b along the edges of each layer up to the backplate structural layer 503a / b etched to create space for sealing a membrane layer 510a / b with the backplate structural layer 503a / b to accomplish.

[0058] During surgery 12a / b a membrane layer 510a / b (for example, an LSN layer) on the second structural layer 508a / b so separated that the membrane layer 510a one or more downward-pointing waves 512a includes those with one or more depressions 509a correspond to those in the second structural layer 508a are formed, or one or more upward-pointing ripples 512b , which are the one or more surveys 509b correspond to those in the second structural layer 508b are formed. In addition, the membrane layer touches 510a / b the backplate layer 503a / b at their radial edges, around the edges of the acoustic transducer 50a / b to seal during surgery 13a / b A section of the substrate will be removed. 502a / b etched, and during surgery 14a / b a large part of the first structural layer 506a / b and the second structural layer 508a / b etched (for example, by the backplate layer) 503a / b defined apertures 517a / b) , to the membrane layer 510a / b as well as the backplate layer 503a / b to expose a membrane and a backplate of the acoustic transducer 50a / b be formed.

[0059] Fig. Figure 5E shows an enlarged view of a section of the acoustic transducer. 50a , which is indicated by arrow A in Fig. 5D Surgery 14a is displayed. As in Fig. 5E shows the first and second structural layers 506a / b and 508a / b etched for a predetermined time, so that a section 522a the first structural layer 506a and a section 522b the second structural layer 508b near the circumferential edge of the membrane layer 510a / b and the downward-pointing waves 512a or the upward-pointing waves 512b the membrane layer 510a or 510b is not removed. The remaining sections 522a and 522bthe first and / or second structural layers 506a / b and 508a / b can the rounding of the corners and edges in the membrane layer 510a / b formed downward or upward pointing waves 512a and 512b facilitated by providing a surrounding support structure 522 to increase the strength and robustness of the membrane 510a / b form. The section 522b the second structural layer 508a contacts the membrane layer 510a Furthermore, there is an inner radial edge. 524b of the section 522b the second structural layer 508a near the membrane layer 510a relative to an inner radial edge 524a of the section 522a the first structural layer 506a near the substrate 502a radially closer to the membrane layer 510a defined, downward-pointing undulation 512aarranged. This can be due, for example, to the fact that the first structural layer 506a and the second structural layer 508a different levels of impurities (for example, different levels of phosphorus), which causes uneven etching, or the proximity of the first structural layer 506a to an isotropic etching front.

[0060] Fig. Table 7, A, summarizes the failure pressure of various representative sample wafers contained in three wafer batches (Batch A, B, and C). These wafers comprise membranes exhibiting corrugations with sharp and more or less smooth edges, produced by wet or dry etching. The membranes contained in each wafer batch were tested by applying pressure to one side of the membrane until failure.

[0061] The representative wafer 24Batch A comprises a membrane with downward-facing corrugations formed by dry etching a cavity hole in a PSG layer. Fig. 7, Plate B is a SEM image of the representative sample wafer. 24 from batch A. Focused ion beam (FIB) etching was used to etch the wafer. 24 to cut so that a cross-section of the membrane containing the wafer 24 It includes, can be depicted. The membranes, the Batch A wafers 24 included, failed at a pressure of about 9 psi.

[0062] A representative wafer 5 The component included in Batch B comprises a membrane with downward-facing corrugations formed by etching a through-hole in a PSG layer using a wet etching process. The corrugations have a depth of approximately 4.00 µm in the center of the membrane and approximately 4.45 µm at the edges, and include rounded corners. Fig. 7, Field C is a SEM image of batch B wafer 5 The membranes, the wafers 5 The components failed at a pressure of approximately 18 psi.

[0063] The representative wafer 15 , which is included in batch B, has corrugations with a depth in the middle of the membrane of about 4.45 µm and at the edges of about 4.83 µm and includes rounded corners. Fig. 7, Field D is a SEM image of the representative sample wafer. 15 The membranes, the batch B wafers 15 included, failed at a pressure of approximately 34 psi.

[0064] The representative wafer 25 Wafers from batch C, produced by dry etching, exhibit corrugations with a depth of approximately 3.66 µm in the center of the membrane and approximately 3.32 µm at the edges, featuring rounded corners. The corrugation depth is the smallest in the group of wafers in Fig. 7, Plate A. During the etching of the corrugations, unetched PSG was intentionally left at the bottom, resulting in the smoothest corners after PSG reflow, as described in the operation. 6a / b and 7 a / b of Fig. 5B described. Fig. 7, Plate E is a SEM image of the representative sample wafer. 25 , Batch C. The membranes that hold the wafer 25 included, failed at a pressure of approximately 60 psi. Fig. Figure 8 is a scatter plot of the membrane failures of various membranes produced using the methods described here, and shows that smoothing the corrugations increases the failure resistance of the membranes.

[0065] Fig. 9A-9C illustrate a process flow 600a / b for the production of acoustic transducers 60a and 60b , which have downward or upward directed waves, according to one embodiment. The method 600a / b includes providing a substrate 602a / b (for example, glass, Pyrex, quartz, silicon, silicon dioxide or another suitable substrate) in operation 1a / b In operation 2a one or more enclosed depressions will be created. 605a etched into the substrate using a wet or dry etching process. In contrast, in operation 2b enclosed columns 605b in the substrate 602b formed (for example, using a wet or dry etching process). The one or more enclosed depressions 605a or columns 605b may have sharp corners and edges, as described previously herein.

[0066] During surgery 3a / b A first structural layer will be formed 608a / b , for example, a first PSG or BPSG layer, which has an initial impurity content, for example, an initial phosphorus content, on the substrate 602a / b isolated. The first structural layer 608a / b can conform to the substrate 602a / b are deposited so that the first structural layer 608a / b Depths 609a and surveys 609b includes the enclosed recesses 605a or the pillars 605b correspond. Furthermore, one or more depressions may be present. 609a and surveys 609b have sharp corners and edges that correspond to the sharp corners and edges of the enclosed recesses 605a or the columns 605b are equivalent to.

[0067] In operation 4a / b will be the first structural layer 608a / b heated to a temperature above its glass transition temperature, thereby forming the first structural layer 608a / b flows back and smooths its corners and edges, as previously described herein. In operation 5a / b a membrane layer 610a / b on the first structural layer 608a / b isolated, and a first leading layer 618a / b (for example, a polylayer) is applied to the membrane layer 610a / b deposited. The membrane layer 610a / b is conformally deposited on the first structural layer, so that the membrane layer 610a downward-pointing waves 612a includes those in the first structural layer 608a formed depressions 609a correspond, and the membrane layer 610b upward-pointing waves 612b includes those in the first structural layer 608b surveys 609b correspond, whereby the upward and downward pointing waves 612a / b Includes smooth or rounded corners and edges.

[0068] In operation 6a / b will be the first leading layer 618a / b selectively etched to create an electrical contact on the membrane layer 610a / b to form. In operation 7a / b A second structural layer will be formed 606a / b (for example, an oxide layer, a second PSG or BPSG layer) on the membrane layer 610a / b and the first management layer 618a / b separated and planarized (for example, in the through-hole (CMP)). The second structural layer 606a / b can serve as a spacer to create a gap between the membrane layer 610a / b and to define a backplate layer.

[0069] In operation 8a / b A second conductive layer will be added 616a / b (for example, a polylayer) on the second structural layer 606a / b deposited and structured to define an electrical contact for a backplate layer. In operation 9a / b The structural layer will 606a / b along their edges up to the membrane layer 610a / b etched to create space for sealing a backplate layer to the membrane layer 610a / b to accomplish.

[0070] In operation 10a / b A back wall layer will be created. 603a / b (for example, an LSN layer) onto the second structural layer 606a / b and the second leading layer 616a / b applied to the back wall layer 603a / b contacts the membrane layer 610a / b at the edges of the acoustic transducer 60a / b , to the acoustic transducer 60a / b to seal. In operation 11 a / b become apertures 617a / b through the back wall layer 603a / b and the second leading layer 616a / b etched. The apertures 617a / b They can have any suitable shape, for example square, rectangular, circular, oblong, oval, hexagonal, polygonal, any other suitable shape or a combination thereof.

[0071] In operation 12a / b will the substrate 602a / b selectively down to the first PSG layer 606a / b etched to define a channel within it. In operation 13a / b will be the first structural layer 608b etched to remove the membrane layer 610a / b to release from a first page. A section of the first structural layer. 608a / b , which is on the remaining section of the substrate 602a / b The arrangement remains unetched and can serve as a support structure for the membrane layer. 610a / b serve. In addition, the second structural layer 606a / b (for example, a second PSG layer) through the apertures 617a / b etched to remove the membrane layer 610a / b to release from a second side opposite the first, thereby enabling the acoustic transducer 60a / b with a membrane 610a / b is formed above an opening in the substrate 602a / b is suspended. By etching the structural layer 606a / b The backplate layer will also be 603a / b Exposed. A section of the structural layer 606a / b near the waves 612a / b The edges of the membrane layer remain unetched and can smooth the surface within the membrane layer. 610a / b formed ripples 612a / b facilitate and / or increase the strength of the membrane layer 610a / b increase.

[0072] Fig. 10 is a schematic flowchart of another procedure 700 to train an acoustic transducer (for example, the acoustic transducer) 60 ), comprising a membrane having upward-pointing corrugations or downward-pointing corrugations with smooth corners and edges formed therein, according to one embodiment. The acoustic transducer may, for example, comprise a MEMS acoustic transducer for use in a MEMS microphone array or a MEMS pressure sensor and may be configured to generate electrical signals in response to acoustic signals or atmospheric pressure changes.

[0073] The procedure 700 includes the provision of a substrate ( 702The substrate can be made of silicon, silicon dioxide, glass, Pyrex, quartz, ceramic, or another suitable material and can be used in relation to the process. 600 substrate described in detail 602 include. 704 The substrate is selectively etched to form at least one of one or more enclosed depressions or columns on the substrate. For example, the substrate can be etched using a wet or dry etching process to define the enclosed depressions or columns on the substrate. 706 A first structural layer (for example, the first PSG layer) is formed. 608The first structural layer, which has a first impurity content, is deposited onto the substrate. In some embodiments, the first structural layer may comprise a PSG or BPSG. Furthermore, the impurity may comprise phosphorus, so that the first phosphorus content of the first structural layer may be greater than 2% (for example, in a range between 2% and 10%). The first structural layer is conformally deposited onto the substrate such that the first structural layer comprises one or more defined depressions or protrusions that correspond to the one or more enclosed depressions or columns formed in the substrate.

[0074] At 708The first structural layer is heated to a temperature above its glass transition temperature, causing it to reflow. As previously described, the cavities or columns formed in the substrate may have sharp corners and edges (for example, with a radius of curvature of less than 1 µm), so the depressions or protrusions formed in the first structural layer may also have correspondingly sharp corners and edges. The reflow of the first structural layer smooths or rounds the corners and edges of these depressions or protrusions, allowing them to have a radius of curvature greater than 1 µm and less than 50 µm.

[0075] At 710 A membrane layer (for example, the membrane layer) is created. 610) deposited on the first structural layer such that the membrane layer comprises at least one of the downward-facing corrugations corresponding to the depressions or the upward-facing corrugations corresponding to the protrusions formed in the first structural layer. For example, a low-stress material, such as LSN or a low-stress ceramic, can be deposited on the first structural layer (for example, by a physical or chemical vapor deposition process). In other embodiments, the membrane layer can comprise a dielectric or conductive material (for example, silicon oxide, silicon nitride, silicon carbide, gold, aluminum, platinum, etc.). Furthermore, the one or more downward-facing corrugations or upward-facing corrugations defined in the membrane layer have corners with a radius of curvature corresponding to the second radius of curvature, i.e.,the radius of curvature after the return flow of the first structural layer. In this way, the stress concentration at the edges or corners of the corrugations is reduced, which increases robustness and impact resistance.

[0076] In some embodiments, the method includes 700 including the application of a first conductive layer (for example, the first conductive layer) 618 ) to the membrane layer at 712. In some embodiments, the first conductive layer may be formed of polysilicon (poly). In other embodiments, the first conductive layer may be formed of metals, doped silicon, or another suitable material. 714 The first conductive layer is structured in such a way that it forms an electrical contact on the membrane layer.

[0077] In some embodiments, the method includes 700also the application of a second structural layer, such as a second PSG or BPSG layer (for example, the second PSG layer) 606 ) on the membrane layer, at 716. The second structural layer may contain a second impurity content, for example, a second phosphorus content in a range between 2% and 10%, which may be the same or different (for example, higher or lower) from the first phosphorus content contained in the first structural layer. In other embodiments, the second structural layer may comprise an oxide, a nitride, or another suitable layer that serves as an intermediate layer or spacer between the membrane layer and a backplate layer. In some embodiments, the second structural layer may be planarized, for example, by a chemical-mechanical planarization (CMP) process.

[0078] In some embodiments, a backplate layer (for example, the backplate layer) may be used. 603 ) at 720 onto the second structural layer. The backplate layer can be formed from a low-stress material, for example, low-stress silicon nitride (LSN), low-stress oxide, or any other suitable material. The backplate layer can be deposited by PVD, LPCVD, PECVD, ALD, another suitable method, or a combination thereof. The backplate layer can be relatively inflexible with respect to a membrane to be formed from the membrane layer. A variety of apertures can be formed in the backplate layer, at 722, as previously described in relation to the method. 300 described.

[0079] In some embodiments, the method can 700 including the application and structuring of a second conductive layer (for example, the second conductive layer) 616) before the application of the backplate layer to the structural layer at 718. In some embodiments, the first conductive layer can be formed from polysilicon (Poly). In other embodiments, the first conductive layer can be formed from metals, doped silicon, or another suitable material. The first conductive layer can be deposited by PVD, thermal evaporation, E-beam evaporation, CVD, LPCVD, PECVD, ALD, or another suitable method, or a combination thereof. In other embodiments, the second conductive layer can be deposited on the backplate layer. The second conductive layer contacts the backplate layer and forms an electrical contact with it. Furthermore, the formation of the plurality of apertures also creates corresponding apertures through the second conductive layer.

[0080] At 724The membrane layer is detached, forming a membrane suspended above the substrate. In some embodiments, the membrane detachment may involve etching through the substrate and the first structural layer to detach the membrane from a first side (for example, a rear side of the acoustic transducer). Additionally, the second structural layer (for example, a second PSG layer) may be etched through the apertures to release the membrane from a second side opposite the first. The etching may also release the back wall layer to form a back wall suspended above the first membrane. In particular embodiments, the etching is performed for a predetermined time, ensuring that a portion of the second structural layer near the upward-facing corrugations or downward-facing corrugations of the membrane layer remains intact.The section of the second structural layer can facilitate the rounding of the corners and edges of the upward or downward pointing corrugations formed in the membrane.

[0081] In some embodiments, the method 700 The formed membrane exhibits a compliance at least twice that of a similar restricted membrane that does not include the corrugations. Furthermore, the membrane can withstand a pressure differential in the range of 50 to 70 psi. Although not shown, the process can 700 In some embodiments, this may also include forming a penetration or passage opening through the membrane and optionally through the back plate, for example to allow pressure equalization between a front volume and a rear volume of the acoustic transducer.

[0082] Fig. 11A-11C illustrate process flows 800a / b for the production of acoustic transducers 80a and 80b , which have downward or upward directed waves, according to one embodiment. The method 800 is the procedure 500 Essentially similar, but with some differences which are highlighted here. The procedure 800a / b includes providing a substrate 802a / b (for example, glass, Pyrex, quartz, silicon, silicon oxide or another suitable substrate) during operation 1a / b .

[0083] In operation 2a / b A back layer will be created. 803a / b on the substrate 802a / b isolated and a first leading layer 816a / b is applied to the back layer 803a / b isolated. In operation 3a / b A variety of apertures will be used. 817a / b in the back wall layer 803a / b and the first management layer 816a / b defined, for example, by a wet or dry etching process. In operation 4a / b The first conductive layer is selectively etched to create an electrical contact on the back wall layer. 803a / b to form.

[0084] In operation 5a / b A first structural layer will be formed 806a / b (for example, a first PSG or BPSG layer) on the backplate layer 803a / b isolated. The first structural layer 806a / b can be applied to the backplate layer 803a / b planarized (for example, using CMP). The first structural layer 806a / b It may contain an initial level of impurities, for example, an initial phosphorus content in the range between 2% and 10%. During operation 6a one or more enclosed depressions will be created. 807a into the first structural layer 806a etched, during surgery 6b will be the first structural layer 806betched to enclose columns 807b from the first structural layer 806b to form, as previously referred to herein in relation to Fig. 4A-4C described. In special embodiments, a wet etching process can be used to create the first structural layer. 806a / b up to the backplate layer located below it 803a / b to etch, whereby the backplate layer 803a / b It serves as an etching stop for wet etching.

[0085] In operation 7a / b A second structural layer will be formed 808a / b , for example a second PSG or BPSG layer, onto the first structural layer 806a / b and the open areas of the backplate layer 803a / b secluded. Unlike the one in Fig. 4A-4C process shown 400 the second structural layer 808a / b the same level of impurities, for example the same phosphorus content as the first structural layer 806a / b (for example, in a range between 2% and 10%). The second structural layer 808a / b becomes conformal on the first structural layer 806a / b isolated, so that they have one or more depressions 809a includes one or more enclosed depressions 807a correspond to those in the first structural layer 806a were formed, or one or more surveys 809b , which enclose one or more columns 807b correspond to those from the first structural layer 806b were formed. The cavities 809a or the pillars 809b may have corners that are rounder than the corners of the cavities 807a or columns 807b the underlying first structural layer 806a / b .

[0086] During surgery 8a / b The second structural layer 808a / b to a temperature above a glass transition temperature of the second structural layer 808a / b and thus also the first structural layer 806a heated, thereby the second structural layer 808a / b and in some embodiments also the first structural layer 806a The backflow will also smooth the sharp edges and corners of the depressions. 809a and the surveys 809b , which are in the second structural layer 808a / b formed, smoothed or rounded.

[0087] In operation 9a / b A second conductive layer will be added 818a / b (for example, a polylayer) onto the second structural layer 808a / b applied and structured. In operation 10a / b Both the second structural layer 808a / b as well as the first structural layer 806a along the edges of each layer up to the backplate structural layer 803a / b etched to create space for sealing a membrane layer 810a / b with the backplate structural layer 803a / b to accomplish.

[0088] During surgery 11a / b The membrane layer 810a / b (for example, an LSN layer) on the second structural layer 808a / b so separated that the membrane layer 810a one or more downward-pointing waves 812a includes one or more in the second structural layer 808a formed depressions 809a correspond to, or one or more upward-pointing ripples 812b , which are one or more in the second structural layer 808b surveys 809b correspond. Furthermore, the membrane layer touches 810a / b the backplate layer 803a / b , to the edges of the acoustic transducer 80a / b to seal during surgery 12a / b A section of the substrate will be removed. 802a / b and a large part of the first structural layer 806a and the second structural layer 808a / b etched (for example, by the backplate layer) 803a / b defined apertures 817a / b) , to the membrane layer 810a / b as well as the backplate layer 803a / b to expose a membrane and a backplate of the acoustic transducer 80a / b be formed.

[0089] A small section of the structural layers 806a and 808a / b is left unetched near a circumference or edge of the membrane layer, as in the operations 12a / b shown to create a surrounding support structure. The use of structural layers. 806a and 808a / b , which have the same level of impurities, can make it possible to perform etching for each of the structural layers 806a and 808a / b proceeds at the same speed, and can form a tapered profile for the remaining section of the structural layers. 806a and 808a / b This results from the etching of the structural layers. 806a and 808a / b of those in the backplate 803a / b defined apertures 817a / b The etching process is isotropic. Therefore, the sections of the structural layers etch. 806a and 808a / b , those furthest from the apertures 817a / b are removed last. The remaining section of the structural layers 806a and 808a / b can detach from the backplate layer 803a / b inwards towards the membrane layer 810a / b tend and can serve to increase the strength of the membrane layer 810a / b to increase and / or round off the waves 812a / b to make it easier.

[0090] Fig. 12A-12D illustrate process flows 900a / b for the production of acoustic transducers 90a and 90b , which have downward or upward directed ripples, according to one embodiment. The process 900a / b is essentially similar to the process 500a / b with some differences, which are highlighted here.

[0091] The process 900a / b includes providing a substrate 902a / b (for example, glass, Pyrex, quartz, silicon, silicon oxide, or another suitable substrate) in operation 1a / b In operation 2a / b A back layer will be created. 903a / b on the substrate 902a / b isolated and a first leading layer 916a / b is applied to the back layer 903a / b isolated. In operation 3a / b A variety of apertures will be used. 917a / b in the back layer 903a / b and the first management layer 916a / b defined, for example by a wet or dry etching process.

[0092] In operation 4a / b will be the first leading layer 916a / b selectively etched to create an electrical contact on the backplate layer 903a / bto form. In operation 5a / b A first structural layer will be formed 906a / b , for example a first PSG or BPSG layer, onto the substrate 902a / b applied. The first PSG layer 906a / b It can have an initial impurity content, for example an initial phosphorus content, in a range between 2% and 10%. In one embodiment, the first structural layer can 906a / b after deposition on the backplate layer 903a / b be planarized (for example via CMP).

[0093] During surgery 6a one or more enclosed depressions will be created. 907a in the first structural layer 906a formed, or the first structural layer 906b is etched in such a way that one or more enclosed columns are formed. 907b are formed. In special embodiments, the first structural layer 906a / b etched using a timed dry etching process, so that the dry etching removes the backplate layer 903a / b not reached and sections of the first structural layer 906a / b across the entire backplate layer 903a / b remain in order.

[0094] In operation 7a / b will be the first structural layer 906a / b heated to a temperature above its glass transition temperature to form the first structural layer 906a / b to cause backflow and the edges or corners of the enclosed depressions 907a or columns 907b , which are in the first structural layer 906a or 906b are defined, to smooth. During operation 8a / b A second structural layer will be formed 908a / b , for example a second PSG or BPSG layer, above the first structural layer 906a / b separated, so that the second structural layer 908a / b Depths 909a or surveys 909bincludes those in the first structural layer 906a / b defined enclosed depressions 907a or columns 907b correspond to the edges or corners of the recesses. 909a or surveys 909b may be smoother or rounder than the corresponding enclosed depressions 907a and columns 907b The process 500a / b differs in that the second structural layer 908a / b It may contain a second impurity, for example a second phosphorus content, which is equal to the first impurity content (for example, in a range between 2% and 10%). For example, the second structural layer may 908a / b comprise the same materials as the first structural layer 906a / b

[0095] During surgery 9a / b The second structural layer 908a / b heated to a temperature above its glass transition temperature to form the second structural layer 908a / b and in some implementations also to cause the first structural layer to flow back, thereby clearing the corners of the depressions 909a and surveys 909b to be further refined. In operation 10a / b A second conductive layer will be added 918a / b to the second structural layer 908a / b applied and structured. Also in operation 10a / b The second structural layer will be formed 908a / b and the first structural layer 906a / b each along the edges up to the backplate structural layer 903a / b etched to create space for sealing a membrane layer 910a / b with the backplate structural layer 903a / b to accomplish.

[0096] During surgery 11a / b The membrane layer 910a / b (for example, an LSN layer) on the second structural layer 908a / b so separated that the membrane layer 910a one or more downward-pointing waves 912aincludes one or more in the second structural layer 908a trained specializations 909a correspond to, or one or more upward-pointing waves 912b , which are one or more in the second structural layer 908b trained surveys 909b correspond. Furthermore, the membrane layer touches 910a / b the backplate layer 903a / b at their radial edges, around the edges of the acoustic transducer 90a / b to seal during surgery 12a / b A section of the substrate will be removed. 902a / b etched, and during surgery 13a / b a large part of the first structural layer 906a / b and the second structural layer 908a / b etched (for example, by the backplate layer) 903a / b defined apertures 917a / b) , to the membrane layer 910a / b as well as the backplate layer 903a / b to expose a membrane and a backplate of the acoustic transducer 90a / b are formed. A small section of the structural layers 906a / b and 908a / b is left unetched near the perimeter or edge of the membrane layer, as in the operations 13a / b shown to form a circumferential support structure. The remaining section of the structural layers 906a / b and 908a / b can detach from the backplate layer 903a / b inwards towards the membrane layer 910a / b rejuvenate and can serve to increase the strength of the membrane layer 910a / b to increase and / or round off the waves 912a / b to make it easier.

[0097] Fig. 13A-13E illustrate a process flow 1000 for the manufacture of an acoustic transducer having downward and upward directed corrugations, according to one embodiment. The process 1000 can be used in particular to create a double-diaphragm acoustic transducer 100 (shown in Fig.13E) to form, which includes downward and upward ripples. The process 1000 includes the provision of a substrate 1002 (for example, glass, Pyrex, quartz, silicon, silicon dioxide or another suitable substrate) in operation 1 In operation 2 one or more enclosed depressions will be created. 1005 etched into the substrate using wet or dry etching. The one or more enclosed depressions 1005 may have sharp corners and edges, as described previously herein.

[0098] In operation 3 A first structural layer will be formed 1008 , for example, a first PSG or BPSG layer, which has an initial impurity content, for example, an initial phosphorus content, onto the substrate 1002 applied. The first structural layer 1008 can conform to the substrate 1002are deposited so that the first structural layer 1008 Depths 1009 includes the enclosed recesses 1005 correspond. Furthermore, one or more depressions may be present. 1009 have sharp corners and edges that correspond to the sharp corners and edges of the enclosed recesses 1005 are equivalent to.

[0099] In operation 4 will be the first structural layer 1008 heated to a temperature above its glass transition temperature, thereby forming the first structural layer 1008 flows back and smooths its corners and edges, as previously described herein. In operation 5 A first membrane layer will be formed 1010 on the first structural layer 1008 isolated, and a first leading layer 1018 (for example, a polylayer) is applied to the first membrane layer 1010 deposited. The first membrane layer 1010is conformally applied to the first structural layer, so that the first membrane layer 1010 downward-pointing waves 1012 includes those in the first structural layer 1008 trained specializations 1009 correspond. The downward-pointing waves 1012 can include smooth or rounded corners and edges.

[0100] In operation 6 will be the first leading layer 1018 selectively etched to create an electrical contact on the first membrane layer 1010 to form. In operation 7 A second structural layer will be formed 1006 (for example, an oxide layer, a second PSG or BPSG layer) on the first membrane layer 1010 and the first management layer 1018 deposited and planarized (for example, by chemical-mechanical polishing (CMP)). The second structural layer 1006can serve as a spacer to create a gap between the membrane layer 1010 and to define a backplate layer.

[0101] In operation 8 The second structural layer 1006 along their edges to the first membrane layer 1010 etched to create space for sealing a backplate layer to the first membrane layer 1010 to create. In operation 9 A backplate layer will be created. 1016 on the second structural layer 1006 separated and structured. The back wall layer 1016 It can comprise one or more layers of poly and silicon nitride. For example, the back wall layer can 1016 comprise a silicon nitride layer between two polymer layers. The backplate layer 1016 It is structured in such a way that it forms apertures through which supports can be passed in a second membrane (discussed further below).

[0102] In operation 10 A third structural layer will be formed 1014 above the backplate structural layer 1016 deposited. In some embodiments, the third structural layer can be 1014 have a similar composition to the first and second structural layers 1008 and 1006 , which were discussed above. In operation 11 will be the third structural layer 1014 structured around columns 1024 to form structures that aid in the formation of undulations in a second membrane, which is described below. In operation 12 A fourth structural layer will be added 1020 applied to support the second membrane, which can form part of a peripheral support structure. In some embodiments, the fourth structural layer can 1020 comprise one or more layers. For example, the fourth structural layer can 1020comprise several layers of PSG or BPSG with different concentration levels. For example, the fourth structural layer can 1020 The system comprises two sublayers of PSG or BPSG, a first with a concentration of 5%–9% and a second with a concentration of 2.5%–6.5%. In some embodiments, the sublayers can be deposited on top of each other with increasing concentrations. In some embodiments, a middle sublayer can be layered between two sublayers having concentrations lower than that of the middle layer. The fourth structural layer 1020 can conform to the third structural layer 1014 formed columns 1024 to be separated, so that columns 1022 They arise from the fourth structural layer. At least a section of the fourth structural layer. 1020 is in contact with the backplate structural layer.

[0103] In operation13 A second conductive layer will be added 1026 above the fourth structural layer 1020 isolated and structured. The second management layer 1026 can be made from a similar material to the first conductive layer 1018 It consists of and can be structured in some sections to form apertures through it. At least some apertures in the second conductive layer. 1026 can be used with baffles in the back wall layer 1016 be aligned. In operation 14 will be the fourth structural layer 1020 and the second structural layer 1006 structured to form the first leading layer 1018 or the first membrane layer 1010 to expose. In particular, the fourth and second structural layers can be exposed. 1020 and 1006 especially in areas that are not above the fourth structural layer 1020 isolated second conducting layer 1026and those above the second structural layer 1006 deposited backplate layer 1016 exhibit and which are above the first conductive layer 1018 lie. The sections of the fourth structural layer 1020 , which the pillars 1022 The fourth structural layer is formed, but remains intact. Etching of the fourth structural layer 1020 and the second structural layer 1006 can one or more cavities 1028 form, which are at least partially formed by the apertures in the backplate layer 1016 and the apertures in the second conductive layer 1026 are defined. As discussed below, the cavities can 1028 to be used to form supports for the second membrane.

[0104] In operation 15 can a spacer layer 1030 following the structuring of the fourth structural layer 1020 and the second structural layer 1006to be separated and structured to create the cavities 1028 to form the spacer layer. 1030 can be formed using silicon oxide and can be conformed via the fourth structural layer 1020 , the second leading layer 1026 , the exposed sections of the first conductive layer 1018 within the cavities 1028 and the pillars 1022 The fourth structural layer is deposited. The spacer layer 1030 can be structured in such a way that it apertures 1032 forms the sections of the underlying second conductive layer 1026 and the first management layer 1018 Expose the spacer layer. 1030 The formation of a gap between sections of supports of the second membrane and the first conductive layer can occur. 1018 the first membrane layer 1008This allows the thickness of the spacer layer to be adjusted according to the desired gap size. In some embodiments where no gap is desired, the spacer layer can be... 1030 cannot be applied.

[0105] During surgery 16 A second membrane layer will be formed 1034 above the spacer layer 1030 or, if the spacer layer 1030 is not used, conforming above the fourth structural layer 1020 , the second leading layer 1026 , the exposed sections of the first conductive layer 1018 within the cavities 1028 and the pillars 1022 deposited in the fourth structural layer. The second membrane layer 1034 can the first membrane layer 1010 be similar. In contrast to the first membrane layer 1010 , the downward-pointing waves 1012 includes the second membrane 1034however, upward-pointing waves 1038 include those above the pillars 1022 are formed in the fourth structural layer. The second membrane 1034 It can also include at least one anchor post. 1040 and at least two supports 1042 form those that extend from the anchor post 1040 are spaced apart. The support 1040 includes a vertex 1044 , which is located at the bottom of the cavity 1028 is trained (operation 15 ) and with the first conductive layer 1018 is in contact with and coupled to it. The sections of the second membrane 1034 between the anchored support 1040 and at least two supports 1042 contact the second conductive layer 1026 and are coupled to it. The second membrane layer 1034 can be structured in such a way that it has a multitude of openings 1036 forms the underlying spacer layer 1030or, in cases where no spacer layer 1030 is used, the underlying fourth structural layer 1020 can uncover.

[0106] During surgery 17 will be a section of the vertex 1044 (the support 1040 ) the second membrane 1034 , a section of the first conductive layer 1018 under the crown 1044 and a section of the first membrane layer 1008 under the crown 1044 structured to allow penetration or a passage opening 1046 to form. The passageway 1046 can enable pressure equalization between a front volume and a rear volume of the acoustic transducer.

[0107] During surgery 18 sections of the second structural layer 1006 (between the first membrane 1010 and the backplate structural layer 1016 ), sections of the fourth structural layer 1020(between the backplate structural layer 1016 and the second membrane 1034 ) and the third structural layer 1014 (for example, columns) 1024 ) removed by an etchant. For example, an isotropic etchant (such as a wet etchant like buffered hydrofluoric acid) can be removed by the etching in the second membrane. 1034 trained openings 1036 They will be allowed to flow. The removal of sections of the fourth structural layer. 1020 and the second structural layer 1006 leads to internal cavities 1048 , which pass through the second membrane 1034 and the first membrane 1010 are defined. However, the process can be controlled in such a way that not the entire second structural layer is affected. 1006 and the fourth structural layer 1020 is removed. Instead, a peripheral support structure is built. 1038 between the edges of the first membrane layer 1010 and the second membrane layer1034 retained. The peripheral support structure 1038 is near the waves 1012 and 1038 arranged and can increase the strength of the first membrane layer 1010 and the second membrane layer 1034 increase.

[0108] In some embodiments, the second structural layer 1006 and the fourth structural layer 1020 They exhibit different concentrations of impurities, such as phosphorus or boron. In some embodiments, for example, the second structural layer may contain different concentrations of impurities. 1006 exhibit a phosphorus concentration between 2% and 6%, and the fourth structural layer 1020 It can have a phosphorus concentration between 4% and 10%. Varying the phosphorus concentration or other impurities can lead to uneven etching of the second structural layer. 1006 with regard to the fourth structural layer 1020enable the formation of a tapered peripheral support structure 1038 This leads to the strength of the first and second membranes. 1010 and 1034 can improve it.

[0109] During surgery 19 A section of the substrate will be removed. 1002 and a large part of the first structural layer 1008 etched to create the first membrane layer 1010 to release and the acoustic transducer 100 to form.

[0110] In some embodiments, a method for forming an acoustic transducer comprises providing a substrate and depositing a first structural layer onto the substrate. The first structural layer is selectively etched to form at least one enclosed depression or column on the structural layer. A second structural layer is deposited onto the first structural layer. The second structural layer comprises a depression or elevation corresponding to the enclosed depression or column formed in the first structural layer. At least the second structural layer is heated to a temperature above its glass transition temperature, causing the second structural layer to reflux.A membrane layer is deposited onto the second structural layer such that the membrane layer includes at least one downward-pointing corrugation corresponding to the depression, or one upward-pointing corrugation corresponding to the elevation formed in the second structural layer. The membrane layer is then released, forming a membrane suspended above the substrate.

[0111] In some embodiments, a method for forming an acoustic transducer comprises providing a substrate and selectively etching the substrate to form at least one enclosed depression or column on the substrate. A first structural layer is deposited on the substrate. The first structural layer comprises at least one depression or elevation corresponding to the enclosed depression or column formed in the substrate. The first structural layer is heated to a temperature above its glass transition temperature, causing the first structural layer to reflux. A membrane layer is deposited on the first structural layer such that the membrane layer comprises at least one downward-facing corrugation corresponding to the depression or one upward-facing corrugation corresponding to the elevation formed in the first structural layer.The membrane layer is released, forming a membrane that is suspended above the substrate.

[0112] In some embodiments, an acoustic transducer is formed by the process of providing a substrate and depositing a first structural layer onto the substrate. The first structural layer is selectively etched to form at least one enclosed depression or column. A second structural layer is deposited onto the first. The second structural layer comprises a depression or elevation corresponding to the enclosed depression or column formed in the first structural layer. At least the second structural layer is heated to a temperature above its glass transition temperature, causing the second structural layer to reflux.A membrane layer is deposited onto the second structural layer such that the membrane layer includes at least one downward-pointing corrugation corresponding to the depression, or one upward-pointing corrugation corresponding to the elevation formed in the second structural layer. The membrane layer is then detached, forming a membrane suspended above the substrate.

[0113] In some embodiments, a method may comprise: providing a substrate; depositing a first structural layer on the substrate; selectively etching the first structural layer to form at least one enclosed depression or enclosed column on the first structural layer; depositing a second structural layer on the first structural layer, wherein the second structural layer comprises at least one depression or elevation corresponding to the at least one enclosed depression or enclosed column formed in the first structural layer; heating at least the second structural layer to a temperature above a glass transition temperature of the second structural layer, thereby causing the second structural layer to reflux;Deposition of a membrane layer onto the second structural layer, such that the membrane layer comprises at least one downward-pointing corrugation corresponding to the depression, or one upward-pointing corrugation corresponding to the elevation formed in the second structural layer; and detachment of the membrane layer, thereby forming a membrane suspended above the substrate.

[0114] In some embodiments, at least one of the first structural layer or the second structural layer contains an impurity. In some embodiments, at least one of the first and second structural layers comprises phosphosilicate glass (PSG) or boron phosphosilicate glass (BPSG), wherein an impurity in at least one of the first or second structural layer comprises phosphorus. In some embodiments, the first structural layer is a first PSG layer containing a first phosphorus content, and the second structural layer is a second PSG layer containing a second phosphorus content that differs from the first phosphorus content. In some embodiments, the first structural layer is a first PSG layer containing a first phosphorus content, and the second structural layer is a second PSG layer containing a second phosphorus content that is equal to the first phosphorus content.In some embodiments, the second phosphorus content is greater than 2%. In some embodiments, the first phosphorus content is between 4% and 10% and the second phosphorus content is between 2% and 6%, with the first phosphorus content being greater than the second. In some embodiments, the first phosphorus content is between 2% and 6%, and the second phosphorus content is between 4% and 10%, with the second phosphorus content being greater than the first.

[0115] In some embodiments, the temperature during heating is higher than the glass transition temperature of the second PSG layer but lower than the glass transition temperature of the first PSG layer. In some embodiments, the temperature during heating is higher than the glass transition temperature of both the first and second PSG layers. In some embodiments, the method further comprises heating the first PSG layer above its glass transition temperature before applying the second PSG layer, in order to cause the first PSG layer to reflux.In some embodiments, the depression or elevation formed in the second structural layer before heating the second structural layer comprises edges with a first radius of curvature of less than 1 mm, and wherein the depression or elevation after heating the structural layer comprises edges with a second radius of curvature of more than 1 µm and less than 50 µm, such that each of the downward-pointing corrugations or the upward-pointing corrugation defined in the membrane layer has a radius of curvature corresponding to the second radius of curvature.In some embodiments, the exposure of the membrane comprises etching through the substrate, the first structural layer and the second structural layer; wherein the etching of the first structural layer and the second structural layer is carried out such that a section of the first structural layer and a section of the second structural layer near a circumferential edge of the membrane layer is not removed.

[0116] In some embodiments, the section of the second structural layer touches the membrane layer, wherein an inner radial edge of the section of the second structural layer near the membrane is positioned radially closer to the downward-pointing corrugation or the upward-pointing corrugation defined in the membrane layer, relative to an inner radial edge of the section of the first structural layer near the substrate.In some embodiments, the method further comprises, prior to the deposition of the first structural layer, the deposition of a backplate layer on the substrate; the deposition of a first conductive layer on the backplate layer; the formation of apertures through the backplate layer and the first conductive layer; and the selective etching of the first conductive layer to form an electrical contact on the backplate layer; wherein the first structural layer is deposited on the first conductive layer and wherein the release of the membrane layer also releases the backplate layer, thereby forming a backplate suspended on the substrate below the membrane.

[0117] In some embodiments, the first structural layer is selectively etched up to the backplate layer. In some embodiments, the first structural layer is selectively etched such that the etching process is stopped before the backplate layer is reached. In some embodiments, the method further comprises: depositing and structuring a second conductive layer on the second structural layer prior to depositing a membrane layer on the second structural layer, wherein at least a portion of the membrane layer contacts the second conductive layer. In some embodiments, the method further comprises planarizing the first structural layer after depositing the first structural layer over the backplate structural layer and prior to selectively etching the first structural layer.In some embodiments, the method further comprises, prior to releasing the membrane layer, depositing a third structural layer on the membrane layer; depositing a backplate layer on the third structural layer; and forming a plurality of apertures in the backplate layer, wherein the release of the membrane also releases the backplate layer, thereby forming a backplate suspended on the substrate above the membrane.

[0118] In some embodiments, an acoustic transducer can be formed by the process of providing a substrate. This process can further include depositing a first structural layer onto the substrate. The process can also include selectively etching the first structural layer to form at least one enclosed depression or column on the first structural layer. The process can further include depositing a second structural layer onto the first structural layer, wherein the second structural layer comprises at least one depression or protrusion corresponding to the at least one enclosed depression or column formed in the first structural layer. The process can also include heating the second structural layer to a temperature above its glass transition temperature, thereby causing the second structural layer to reflux.The process can further include the deposition of a membrane layer onto the second structural layer, such that the membrane layer comprises at least one downward-facing corrugation corresponding to the depression or one upward-facing corrugation corresponding to the elevation formed in the second structural layer. The process can also include the detachment of the membrane layer, thereby forming a membrane suspended above the substrate.

[0119] In some embodiments, at least one of the first structural layer or the second structural layer contains an impurity. In some embodiments, at least one of the first and second structural layers comprises phosphosilicate glass (PSG) or boron phosphosilicate glass (BPSG), wherein the impurity comprises phosphorus. In some embodiments, the first structural layer is a first PSG layer containing a first phosphorus content, and the second structural layer is a second PSG layer containing a second phosphorus content that differs from the first phosphorus content. In some embodiments, the temperature during heating is higher than a glass transition temperature of the second PSG layer but lower than a glass transition temperature of the first PSG layer.In some embodiments, the temperature during heating is higher than the glass transition temperature of both the first and second PSG layers. In some embodiments, the first structural layer is a first PSG layer containing a first phosphorus content, and the second structural layer is a second PSG layer containing a second phosphorus content equal to the first phosphorus content. In some embodiments, the process further includes, prior to the application of the second PSG layer, heating the first PSG layer above its glass transition temperature to induce reflux of the first PSG layer.

[0120] In some embodiments, the depression or protrusion formed in the second structural layer comprises edges with a first radius of curvature of less than 1 mm, wherein the backflow of the second structural layer causes the corners to have a second radius of curvature of more than 1 µm and less than 50 µm, such that each of the downward-facing corrugations or the upward-facing corrugation defined in the membrane layer has a radius of curvature equal to the second radius of curvature. In some embodiments, the process further comprises, prior to the application of the first structural layer, the application of a backplate structural layer to the substrate. The process further comprises the application of a first conductive layer to the backplate layer.The process further includes forming apertures through the backplate layer and the first conductive layer, and selectively etching the first conductive layer to create an electrical contact on the backplate layer. In some embodiments, releasing the membrane layer also releases the backplate layer, forming a backplate suspended on the substrate below the membrane.

[0121] In some embodiments, the process further comprises, prior to the application of a membrane layer to the second structural layer, the application and structuring of a second conductive layer to the second structural layer, wherein at least one section of the membrane layer contacts the second conductive layer and the second conductive layer forms an electrical contact with the membrane layer.

[0122] In some embodiments, a method may comprise: providing a substrate; selectively etching the substrate to form an enclosed trench on the substrate; applying a first structural layer to the substrate, wherein the first structural layer comprises a depression corresponding to the enclosed trench formed on the substrate; applying a first membrane layer to the first structural layer, such that the first membrane layer comprises a downward-facing corrugation corresponding to the depression; applying a second structural layer over the first membrane layer; applying a backplate structural layer over the second structural layer; applying a third structural layer over the backplate, wherein the third structural layer comprises an enclosed column;Applying a second membrane layer over the third structural layer, such that the second membrane layer comprises an upwardly directed corrugation corresponding to the enclosed column in the third structural layer; and separating the first and second membrane layers.

[0123] In some embodiments, the method further comprises applying the backplate structural layer over the second structural layer, wherein the backplate structural layer comprises at least one aperture; selectively etching the third structural layer and the second structural layer to form at least one cavity extending through the at least one aperture; and applying the second membrane layer over the third structural layer, such that the second membrane comprises at least one support corresponding to the at least one cavity, wherein the at least one support is connected to the first membrane layer.

[0124] In some embodiments, the method further comprises forming a through-opening through the second membrane layer and the first membrane layer at a section of the at least one support. In some embodiments, the method further comprises etching at least a section of the first structural layer and the second structural layer to form at least one inner cavity partially defined by the first membrane layer and the second membrane layer. In some embodiments, the method further comprises etching at least a section of the first structural layer and the second structural layer to form a peripheral support structure arranged between the first membrane layer and the second membrane layer, the peripheral support structure being arranged along a circumference of the first membrane layer.

[0125] In some embodiments, at least one of the second and third structural layers contains an impurity. In some embodiments, at least one of the second and third structural layers comprises phosphosilicate glass (PSG) or borophosphosilicate glass (BPSG), wherein the impurity comprises phosphorus. In some embodiments, the second structural layer is a first PSG layer containing a first phosphorus content, and the third structural layer is a second PSG layer containing a second phosphorus content that differs from the first phosphorus content. In some embodiments, the first phosphorus content is between 2% and 6%, and the second phosphorus content is between 4% and 10%, wherein the second phosphorus content is greater than the first phosphorus content.

[0126] In some embodiments, an acoustic transducer can be formed by the following process: providing a substrate; selectively etching the substrate to form an enclosed depression on the substrate; applying a first structural layer to the substrate, wherein the first structural layer comprises a depression corresponding to the enclosed depression formed on the substrate; applying a first membrane layer to the first structural layer, such that the first membrane layer comprises a downward-facing corrugation corresponding to the depression; applying a second structural layer over the first membrane layer; applying a backplate structural layer over the second structural layer; applying a third structural layer over the backplate, wherein the third structural layer comprises an enclosed column;Applying a second membrane layer over the third structural layer, such that the second membrane layer comprises an upward-pointing corrugation corresponding to the enclosed column in the third structural layer; and releasing the first and second membrane layers.

[0127] In some embodiments, the process further comprises applying the backplate structural layer over the second structural layer, wherein the backplate structural layer comprises at least one aperture; selectively etching the third structural layer and the second structural layer to form at least one cavity extending through the at least one aperture; and applying the second membrane layer over the third structural layer, such that the second membrane comprises at least one support corresponding to the at least one cavity, wherein the at least one support is connected to the first membrane layer.

[0128] In some embodiments, the process further comprises forming a through-opening through the second membrane layer and the first membrane layer at a section of the at least one support. In some embodiments, the process further comprises etching at least a section of the first structural layer and the second structural layer to form at least one inner cavity, which is partially defined by the first membrane layer and the second membrane layer. In some embodiments, the process further comprises etching at least a section of the first structural layer and the second structural layer to form a peripheral support structure arranged between the first membrane layer and the second membrane layer, the peripheral support structure being arranged along a circumference of the first membrane layer.In some embodiments, at least one of the second and third structural layers contains an impurity. In some embodiments, at least one of the second and third structural layers comprises phosphosilicate glass (PSG) or borophosphosilicate glass (BPSG), wherein the impurity comprises phosphorus. In some embodiments, the second structural layer is a first PSG layer containing a first phosphorus content, and the third structural layer is a second PSG layer containing a second phosphorus content that differs from the first phosphorus content. In some embodiments, the first phosphorus content is between 2% and 6%, and the second phosphorus content is between 4% and 10%, wherein the second phosphorus content is greater than the first phosphorus content.

[0129] Regarding the use of essentially arbitrary terms in the plural and / or singular herein, persons versed in the technical aspects may translate from plural to singular and / or from singular to plural as is appropriate for the context and / or application. The various singular / plural permutations may be explicitly listed here for clarity.

[0130] It is understood by those who are in the technical field that, in general, terms used herein, and in particular in the attached claims (for example, body of the attached claims), are generally meant to be “open” terms (for example, the term “including” should be interpreted as “including but not limited to”, the term “with” should be interpreted as “with at least”, the term “comprises” should be interpreted as “comprises but is not limited to”, etc.).

[0131] It is further understood by those in the technical field that if a certain number of an introduced claim reference is intended, such intention is explicitly stated in the claim, and in the absence of such a statement, no such intention exists. For example, the following attached claims may, as an aid to understanding, use the introductory phrases "at least one" and "one or more" to introduce claim references.However, the use of such expressions should not be interpreted as meaning that the introduction of a claim by the indefinite articles "a" or "an" limits a particular claim containing such an introduced claim to inventions containing only such a claim, even if the same claim includes the introductory expressions "one or more" or "at least one" and indefinite articles such as "a" or "an" (for example, "a" and / or "an" should typically be interpreted as meaning "at least one" or "one or more"); the same applies to the use of certain articles used to introduce claim formulations.Furthermore, the person skilled in the art will recognize that even if a certain number of introduced claims is explicitly listed, such an enumeration should typically be interpreted as meaning at least the listed number (for example, the mere listing of 'two enumerations' without any other modifiers typically means at least two enumerations or two or more enumerations).

[0132] Furthermore, in cases where a convention is used analogously to "at least one of A, B, and C, etc.", such a construction is generally meant in the sense that a person skilled in the art would understand the convention (for example, "a system comprising at least one of A, B, and C" would include, but is not limited to, systems comprising A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). In cases where a convention is used analogously to "at least one of A, B, or C, etc.", such a construction is generally meant in the sense that a person skilled in the art would understand the convention (for example, "a system comprising at least one of A, B, or C" would include systems comprising A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.).Furthermore, the person skilled in the art understands that practically any disjunctive word and / or disjunctive phrase containing two or more alternative terms, whether in the description, claims, or drawings, is to be understood as including the possibility of including one, one, or both of the terms. For example, the phrase "A or B" is intended to include the possibilities of "A" or "B" or "A and B". Furthermore, unless otherwise stated, the use of the terms "approximately", "about", "circa", "essentially", etc., means plus or minus ten percent.

[0133] The foregoing description of the illustrative embodiments has been presented for illustrative and descriptive purposes. It is not intended to be an exhaustive or limiting disclosure with respect to the exact embodiment, and modifications and variations are possible in light of the above teachings or may be derived from the practice of the disclosed embodiments. It is intended that the scope of the invention be defined by the appended claims and their equivalents. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 62742164

[0001]

Claims

[1] Procedure, encompassing: Providing a substrate; selective etching of the substrate to form at least one enclosed depression or enclosed column on the substrate; Applying a first structural layer to the substrate, wherein the first structural layer comprises at least one depression or elevation corresponding to the enclosed depression or the enclosed column; Heating the first structural layer to a temperature above a glass transition temperature of the first structural layer, thereby causing the first structural layer to reflux; Applying a membrane layer to the first structural layer, such that the membrane layer comprises at least one downward-pointing corrugation corresponding to the depression or one upward-pointing corrugation corresponding to the elevation formed in the first structural layer; and Dissolving of the membrane layer, thereby forming a membrane hanging above the substrate. [2] Method according to claim 1, wherein the first structural layer comprises a phosphosilicate glass (PSG) or boron phosphosilicate glass (BPSG) and comprises a first impurity content. [3] Method according to claim 2, wherein the first impurity content comprises phosphorus and wherein the first structural layer has a first phosphorus content in a range between 2% and 10%. [4] Method according to claim 1, wherein the depression or column formed in the first structural layer before heating the first structural layer has edges with a first radius of curvature of less than 1 µm, and wherein, after heating the first structural layer, the depression or column has edges with a second radius of curvature of more than 1 µm and less than 50 µm, such that the downward-facing corrugation or the upward-facing corrugation defined in the membrane layer has a radius of curvature corresponding to the second radius of curvature. [5] The method of claim 1, further comprising: Applying a first conductive layer to the membrane layer; and Structuring the first conductive layer to form an electrical contact on the membrane layer. [6] The method of claim 1, further comprising: Applying a second structural layer to the membrane layer; Applying a backplate layer to the second structural layer; and Forming a large number of apertures in the backplate layer. [7] Method according to claim 6, wherein the second structural layer comprises a second PSG layer having a second phosphorus content in a range between 2% and 10%. [8] The method of claim 6, further comprising: Before applying the backplate layer, a second conductive layer is applied and structured on the second structural layer. wherein at least one section of the second conductive layer contacts the backplate layer, and the formation of the multitude of apertures also forms corresponding apertures through the second conductive layer. [9] The method of claim 6, wherein releasing the membrane comprises: Etching through both the substrate and the first structural layer to expose the membrane layer from a first side of the membrane layer; and Etching of the second structural layer through the apertures to also expose the membrane layer from a second side of the membrane layer opposite the first side, thereby forming the membrane, with the etching also exposing the backplate layer to form a backplate suspended above the membrane. [10] Method according to claim 9, wherein the etching of the second structural layer is carried out such that a section of the second structural layer is not removed in the vicinity of the upward-facing corrugations or the downward-facing corrugations of the membrane layer. [11] Acoustic transducer formed by the following process: Providing a substrate; selective etching of the substrate to form at least one enclosed depression or enclosed column on the substrate; Applying a first structural layer to the substrate, wherein the first structural layer comprises at least one depression or elevation corresponding to the enclosed depression or the enclosed column; Heating the first structural layer to a temperature above a glass transition temperature of the first structural layer, thereby causing the first structural layer to reflux; Applying a membrane layer to the first structural layer, such that the membrane layer comprises at least one downward-pointing corrugation corresponding to the depression or one upward-pointing corrugation corresponding to the elevation formed in the first structural layer; and Dissolving the membrane layer, thereby forming a membrane that is suspended above the substrate. [12] Acoustic transducer according to claim 11, wherein the first structural layer comprises a phosphosilicate glass (PSG) or boron phosphosilicate glass (BPSG) and comprises a first impurity content. [13] Acoustic transducer according to claim 11, wherein the first impurity content comprises phosphorus and wherein the first structural layer has a first phosphorus content in a range between 2% and 10%. [14] Acoustic transducer according to claim 11, wherein the depression or column formed in the first structural layer before heating the first structural layer has edges with a first radius of curvature of less than 1 µm, and wherein, after heating the first structural layer, the depression or column has edges with a second radius of curvature of more than 1 µm and less than 50 µm, such that the downward-facing corrugation or the upward-facing corrugation defined in the membrane layer has a radius of curvature corresponding to the second radius of curvature. [15] Acoustic transducer according to claim 11, further comprising: Applying a first conductive layer to the membrane layer; and Structuring the first conductive layer to form an electrical contact on the membrane layer. [16] Acoustic transducer according to claim 11, further comprising: Applying a second structural layer to the membrane layer; Applying a backplate structural layer to the second structural layer; and Forming a large number of apertures in the backplate layer. [17] Acoustic transducer according to claim 16, wherein the second structural layer comprises a second PSG layer having a second phosphorus content in a range between 2% and 10%. [18] Acoustic transducer according to claim 16, further comprising: Before applying the backplate layer, a second conductive layer is applied and structured on the second structural layer. wherein at least one section of the second conductive layer contacts the backplate layer, and the formation of the multitude of apertures also forms corresponding apertures through the second conductive layer. [19] Acoustic transducer according to claim 16, wherein releasing the membrane comprises: Etching through both the substrate and the first structural layer to expose the membrane layer from a first side of the membrane layer; and Etching of the second structural layer through the apertures to also expose the membrane layer from a second side of the membrane layer opposite the first side, thereby forming the membrane, with the etching also exposing the backplate layer to form a backplate suspended above the membrane. [20] Acoustic transducer according to claim 19, wherein the etching of the second structural layer is carried out such that a section of the second structural layer is not removed in the vicinity of the upward-pointing corrugations or the downward-pointing corrugations of the membrane layer. [21] Procedures, including: Providing a substrate; Applying a first structural layer to the substrate; Selective etching of the first structural layer to form at least one enclosed depression or enclosed column on the first structural layer; Applying a second structural layer to the first structural layer, wherein the second structural layer comprises at least one depression or elevation corresponding to the enclosed depression and / or enclosed column formed in the first structural layer; Heating at least the second structural layer to a temperature above a glass transition temperature of the second structural layer, thereby causing a reflux of the second structural layer; Applying a membrane layer to the second structural layer, such that the membrane layer comprises at least one downward-pointing corrugation corresponding to the depression or one upward-pointing corrugation corresponding to the elevation formed in the second structural layer; and Dissolving the membrane layer, thereby forming a membrane that is suspended above the substrate. [22] Method according to claim 21, wherein at least one of the first structural layer and the second structural layer comprises phosphosilicate glass (PSG) or boron phosphosilicate glass (BPSG), and wherein an impurity content in at least one of the first structural layer or the second structural layer comprises phosphorus. [23] Method according to claim 22, wherein the first structural layer is a first PSG layer having a first phosphorus content, and the second structural layer is a second PSG layer having a second phosphorus content that differs from the first phosphorus content. [24] Method according to claim 22, wherein the first structural layer is a first PSG layer having a first phosphorus content, and the second structural layer is a second PSG layer having a second phosphorus content equal to the first phosphorus content. [25] Method according to claim 24, wherein the second phosphorus content is greater than 2%. [26] Method according to claim 23, wherein the first phosphorus content is between 4% and 10% and the second phosphorus content is between 2% and 6%, wherein the first phosphorus content is greater than the second phosphorus content. [27] Method according to claim 23, wherein the first phosphorus content is between 2% and 6% and the second phosphorus content is between 4% and 10%, wherein the second phosphorus content is greater than the first phosphorus content. [28] Method according to claim 27, wherein the temperature during heating is greater than a glass transition temperature of the second PSG layer but lower than a glass transition temperature of the first PSG layer. [29] Method according to claim 21, wherein the removal of the membrane comprises etching through the substrate, the first structural layer and the second structural layer; and wherein the etching of the first structural layer and the second structural layer is carried out such that a section of the first structural layer and a section of the second structural layer in the vicinity of a circumferential edge of the membrane layer is not removed. [30] Method according to claim 29, wherein the section of the second structural layer touches the membrane layer, and wherein an inner radial edge of the section of the second structural layer is arranged radially closer to the membrane to the downward-pointing corrugation or the upward-pointing corrugation defined in the membrane layer relative to an inner radial edge of the section of the first structural layer near the substrate.

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