JP2020059116A - Sensor device and method for manufacturing sensor device - Google Patents

Abstract

To provide a sensor device which is prone to emit heat generated in a sensor region during an operation.SOLUTION: A sensor device 1 includes: a substrate 2 and the substrate 2 which has a top face 2a and a cavity 3 in the substrate 2 formed from the top face 2a in the substrate 2; a carrier 4 which is arranged on the top face 2a of the substrate 2 and contains a filling material MT for at least partially covering the cavity 3; a sensitive layer 5 which is constructed on the carrier 4 above the cavity 3 on a side in which the sensitive layer is not directed to the substrate 2 and the sensitive layer 5 in which spreading in a lateral direction of the cavity 3 is centered in at least one direction with respect to the sensitive layer 5; and a passivation 6 which covers the sensitive layer 5 and the carrier 4 on a side in which the passivation is not directed to the substrate 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sensor device and a method for manufacturing a sensor device.

  Membrane-based sensors, in particular micromechanical sensors, are exposed to heating of the sensor area (thermal principle) during operation and usually require that the heat generated in the sensor area can be released. Air mass sensors are often based on the thermal principle, and usually the thermosensitive element (temperature sensor, functional structure) is arranged as thermally separated as possible from the body of the sensor chip. In film sensors, the film on the front side of the sensor is typically created by an etching process by exposing a cavity from the backside of the film, ie, the wafer on which the film can be made. In addition, KOH etching is often used.

  DE-A-102016203239 describes a micromechanical sensor device comprising a sensor substrate having a backside cavity, the front side of which is provided with a membrane region arranged above the backside cavity. Has been.

Published German patent application No. 102016203239

  The present invention provides a sensor device according to claim 1 and a method of manufacturing a sensor device according to claim 8.

  Preferred embodiments are the subject of the dependent claims.

Advantages of the invention The idea underlying the invention is a sensor device and a method of manufacturing a sensor device, wherein a cavity below the sensor membrane can be used to improve heat dissipation, in particular the cavity and the edge of the sensor. It is an object of the present invention to provide a sensor device and a method for manufacturing the sensor device, which are capable of directing and releasing heat in a defined manner, for example symmetrically. The etching process, which can be done from the front side of the sensor membrane, can shorten the etching process and improve the stability of the cavity by the edges and the carrier. Due to the etching of the front side, the cavities above the sensing elements (air sensitive layer, temperature sensor, etc.) are advantageously centered automatically during the fabrication process (etching).

  According to the invention, the sensor device is a substrate, the substrate having a top surface and a cavity in the substrate formed from the top surface, and the sensor device is arranged on the top surface of the substrate, the cavity being at least partially A carrier comprising a filling material covering the carrier and a sensitive layer built into the carrier above the cavity on the side facing away from the substrate, the lateral dimension of the cavity being centered in at least one direction relative to the sensitive layer. And a passivation covering the sensitive layer and the carrier on the side facing away from the substrate.

  According to a preferred embodiment of the sensor device, the filling material at least partially covers the edges of the cavity.

  According to the invention, the sensor device comprises a substrate having a top surface and a cavity in the substrate formed in the substrate from the top surface. Furthermore, the sensor device is a carrier containing a filling material, which is arranged on the upper surface of the substrate and at least partly covers the edge of the cavity, at least partly covering the cavity and the side not facing the substrate. A sensitive layer built into the carrier above the cavity at which the lateral extent of the cavity is centered in at least one direction with respect to the sensitive layer, and at the side not facing the substrate. Passivation over the layers and carrier.

  According to a preferred embodiment of the sensor device, the passivation and filling material each comprises a vent.

  The sensor device can advantageously be configured as a membrane sensor, for example as a micromechanical element (MEMS).

  The symmetrical heat dissipation makes it possible to radiate the heat flow through the edges of the cavities respectively, preferably at least in the lateral extent. Preferably, the cavities have a further symmetry in the lateral direction, especially in plan view, so that they can evenly dissipate heat in the other lateral directions. Centralization of the detection layer above the cavity (in plan view) reduces or prevents different temperature conditions (so-called "bridge offset") at the edge of the cavity and on the side of the sensor device. You can

  The upper surface of the substrate advantageously faces or forms the front surface of the sensor device. The etching step for forming the cavities is advantageously carried out from the front side of the carrier on which the film for the sensor area can be formed. The etching can be done through the etching holes so that the complete etching of the carrier in the entire area of the cavity can be omitted. In this way, the processing time required (for etching, to deposit the film above the cavity) can advantageously be reduced.

  The carrier preferably forms a film and extends at least partially at the edge of the cavity, which may advantageously form with the carrier material at least the upper part of the cavity the inner wall of the cavity. . This provides an advantage in particular for the stability of the membrane, since the inner wall which at least partly covers the cavity and the carrier (strip or overall cover) consist of the same material.

  The carrier may completely cover the cavity or may include only strips. A cavity below the region of the sensitive layer makes it possible to achieve thermal isolation of the carrier from the substrate in the region of the cavity and the sensitive layer.

  According to a preferred embodiment of the sensor device, the passivation and carrier include in the region of the cavity a plurality of through-etch holes which extend into the cavity.

  According to a preferred embodiment of the sensor device, the sensor device comprises a heat carrier sensor and the sensitive layer comprises a heat sensitive layer.

  The media sensor can include, for example, an air mass sensor.

  The sensor device may advantageously be a gas sensor or a pressure sensor.

  According to a preferred embodiment of the sensor device, the sensor device comprises a first adhesive layer arranged between the sensitive layer and the carrier at least in the region of the sensitive layer.

  According to a preferred embodiment of the sensor device, the sensor device comprises at least a second adhesive layer arranged on the sensitive layer in the region of the sensitive layer, between the sensitive layer and the passivation.

  The passivation can be arranged by deposition and can protect the sensitive layer and / or the second adhesive layer from environmental influences.

  According to a preferred embodiment of the sensor device, the sensor device comprises an additional passivation arranged in the passivation.

  In this case, this additional passivation can be arranged on the first passivation.

  According to a preferred embodiment of the sensor device, the lateral extent of the cavity is centered in at least one direction with respect to the sensitive layer, so that heat can be dissipated symmetrically via the edges.

  According to a preferred embodiment of the sensor device, the cavity has a center in plan view and the constructed sensitive layer is arranged symmetrically around this center in at least one direction.

  In a typical embodiment of OMM membranes (surface micromechanics), the etching is usually isotropic with respect to the sides without a defined edge of the cavities, which results in a laterally wider membrane. And an inconvenient film shift may occur. This may reduce the stability of the membrane and increase the bridge offset. Alternate embodiments of the backside release cavity may require significantly longer etch times as the wafer often needs to be fully etched. Film shifts can be well controlled using KOH, but in most cases only rectangular films can be produced. In the case of backside trenches, processing time can be quite long and lateral shifts (film shifts and bridge offsets) can occur across the wafer.

  Symmetrical alignment can reduce or eliminate the displacement of the membrane, ie the displacement of the edge position with respect to the sensitive layer, in at least one dimension.

  According to the present invention, in a method for manufacturing a sensor device, a step of preparing a substrate, a step of applying a filling material on the upper surface of the substrate, thereby forming a carrier on the upper surface of the substrate, Arranging the sensitive layer, and at least laterally, constructing the sensitive layer such that the lateral extent of the region between the edge for the cavity is centered with respect to the sensitive layer; Providing a plurality of etching holes in the carrier that extend through to the substrate and forming cavities in the edge within the substrate by an etching process through the etching holes.

  According to a preferred embodiment of this method, a trench structure is formed from the top surface of the substrate as an edge for a cavity in the substrate, and the trench structure is filled with a filling material so that the filling material at least partially forms the edge. To introduce.

  According to the invention, in a method of manufacturing a sensor device, the steps of preparing a substrate, forming a trench structure from the top surface of the substrate as an edge for a cavity in the substrate, and filling material into the trench structure. Introducing and applying a fill material to the top surface of the substrate and applying a fill material to the top surface of the substrate such that a carrier is formed on the top surface of the substrate and at least partially on the edges, and placing a sensitive layer on the carrier. And constructing the sensitive layer such that the lateral extent of the region between the edges is centered at least laterally with respect to the sensitive layer, and a plurality of etching holes extending through the carrier to the substrate. In the carrier and forming a cavity in the edge in the substrate by an etching process through the etching holes , Comprising a.

  This method is also advantageous by virtue of the features already mentioned in connection with the sensor device and the advantages of these features, and vice versa.

  According to a preferred embodiment of this method, the passivation is arranged on the side of the carrier and the sensitive layer facing away from the substrate and a plurality of etching holes extending through the passivation and the carrier to the substrate are provided in the passivation and carrier. To be installed.

  The method can also be used to advantage for producing other products with surface membranes, for example in pressure sensors, air mass sensors or gas sensors.

  The at least one trench structure can be formed, for example, by a masking and etching process.

  The edges can advantageously define the contour of the cavity.

  The formation of the carrier at the edge is preferably done from the inside of the cavity and thus advantageously so as to cover the inner wall of the cavity. This allows the cavity to be etched deeper, at the same depth, or shallower than the edge (trench) is formed in subsequent etching. The farther the bottom of the cavity is from the carrier and the sensitive layer, the lower the thermal effect of the bottom on the sensitive layer (during heat dissipation) may be.

  The area between the edges, in which the cavity is laterally centered, advantageously represents the total width of the cavity in this respective dimension (direction).

  The edges can have a straight or curved shape, which is advantageous for stability and prevention of contamination. In this way, the edge boundary of the cavity can advantageously be preset and the etching method can comprise an omni-directional etching method, since advantageously no contouring is required by etching. .

  The cavity may advantageously be formed in the edge such that a region of the cavity may be formed between the edges, this part forming the contour of the cavity in plan view. It can be provided between the possible edges. The lateral direction is preferably to be understood as always parallel to the planar dimension of the upper surface of the substrate.

According to a preferred embodiment of this method, stoichiometric or silicon-rich nitrides or SiO ₂ (silicon oxide) are used as filling material.

  Silicon nitride or silicon oxide is advantageously well suited as a filler with respect to stability and thermal conductivity.

  According to a preferred embodiment of this method, a first adhesive layer is placed on the carrier in the region of the sensitive layer, before the step of placing the sensitive layer.

  According to a preferred embodiment of this method, the step of building the sensitive layer is performed by a lithographic method and an etching method, the etching holes and the sensitive layer are produced by lithography and etching from the front side, and the trench structure is formed from the same front side. To do.

  The etching method may be ion beam etching.

  Alternatively, the construction of the sensitive layer can also be carried out by providing a preliminary structure in the carrier and filling this preliminary structure, for example a trench for the sensitive layer, with the sensitive layer. The sensitive layer can be deposited in the trench (prestructure) and then ground flat by a grinding process to be substantially planar with the top surface of the carrier. Grinding can be done, for example, by chemical mechanical polishing (CMP) or other methods (Cu damascene process).

  According to a preferred embodiment of this method, the cavities are formed using an etching method which comprises at least one isotropic etching step which laterally undercuts at least half the spacing of the etching holes.

  According to a preferred embodiment of this method, a gas or vacuum is enclosed within the cavity.

  The vacuum can advantageously increase the sensitivity of the sensor and can further promote thermal insulation. Conventional methods of manufacturing sensor devices with backside trenches typically do not contain a stable vacuum.

  According to a preferred embodiment of this method, additional passivation is placed on the passivation.

  Further features and advantages of the embodiments of the present invention will become apparent from the following description with reference to the accompanying drawings.

The invention will be described in more detail with reference to exemplary embodiments shown in the schematic drawings.

1 is a schematic side view showing a sensor device according to an embodiment of the present invention. 1 is a schematic plan view showing a sensor device according to an exemplary embodiment of the present invention. FIG. 6 is a schematic flow chart illustrating a method for manufacturing the sensor device according to the embodiment of the present invention.

  In the drawings, like reference numbers indicate identical or functionally identical elements.

  FIG. 1 shows a schematic side view of a sensor device according to an embodiment of the invention.

  The sensor device 1 includes a substrate 2, and the substrate 2 has an upper surface 2a and a cavity 3 in the substrate 2, and the cavity 3 is molded in the substrate 2 from the upper surface 2a. Furthermore, the sensor device 1 comprises a carrier 4 containing a filling material MT, which is arranged on the upper surface 2a of the substrate 2 and at least partially covers the edge 3a of the cavity 3 and at least partially covers the cavity 3. Covered. The sensor device 1 comprises a sensitive layer 5, which is structured and is arranged on the side of the carrier 4 facing away from the substrate 2 and above the cavity 3, the lateral extent of the cavity 3 being , And is centered in at least one direction with respect to the sensitive layer 5, so that heat can be radiated symmetrically via the edge 3a. The sensor device 1 comprises a sensitive layer 5 and a passivation 6 covering the carrier 4 on the side not facing the substrate 2.

  The sensitive layer 5 may include a single layer or multiple layers. Depending on the manufacturing process, for example by coating on the carrier 4, the cross section of the sensitive layer 5 may be rectangular or trapezoidal, for example. The second adhesive layer H2 can then be placed (deposited) on the upper surface of the sensitive layer 5 and a direct contact can be formed by adhesion with the passivation 6.

  The etching holes 7 are preferably provided in the passivation 6 and in the carrier 4 at a distance g from each other. The spacing g between the etching holes may advantageously be the same. For clarity, only a pair of sensitive layers 5 that are part of one loop are shown in the figure. However, it is also possible to arrange a plurality of loops on the carrier 4 with the sensitive layers 5 (layer 5 pairs). It is also possible to place one or more temperature sensors (on the carrier 4) laterally between or next to the loops. By choosing the distance g, the depth of the cavity 3 can be advantageously determined. If the spacing chosen is too large, it is only after a long time that continuous cavities can be formed through the etching holes, which also makes the cavities deeper. However, the depth can also be controlled by the etching time even when the gap g is small.

  The sensor device 1 can include an additional passivation 8 which can at least partially cover the carrier 4, the sensitive layer 5 and the passivation 6. This additional passivation 8 can also advantageously cover the etching holes further and close them. A gas or vacuum having a different pressure than its surroundings may thus be confined within the cavity. The trapped gas or vacuum can advantageously improve the thermal insulation of the membrane (to the substrate or structure below the sensor), ie the carrier 4.

  The substrate 2 can also be provided as a wafer containing Si, for example.

  The depth of the cavity 3 may advantageously be formed differently depending on the application. If a high heat flow is expected, the cavity 3 can be formed deeper so that the bottom of the cavity 3 gives less or no interference with the sensitive layer 5 during heat dissipation. The cavity 3 can have a depth of, for example, about 25-100 μm. The choice of the respective depth of the cavities 3 is preferably made with the intent that the cavities are centered below the sensitive layer 5 and that the width of the cavities can advantageously be additionally determined. be able to.

  The placement and construction of the sensitive layer 5 is advantageously performed before the formation of the cavities 3 in the substrate 2 (prior to releasing the carrier 4 in the region of the cavities 3), which advantageously (for construction Can provide the flat topography of the carrier (film) required for lithography.

  When manufacturing the carrier 4, a trench structure can be formed in the substrate, and the filling material MT of the carrier 4 can be introduced later into the substrate. Since this introduction can completely fill the entire width of the created trench only if the trench is not formed too wide, the trench structure and the resulting edge 3a are correspondingly thin. Alternatively, multiple trench structures can be provided in the substrate parallel to each other (not shown). These trenches can then be filled with the filling material MT. After etching the cavity 3, the substrate material between the filled trenches can also be removed if the trenches do not extend to the bottom of the cavity. The vertical supports which are parallel to one another can then be left as edges 3a, which can have a distance d from each other, for example. This distance d may advantageously be the same or different for all edges 3a.

  The first adhesive layer H1 may be a diffusion barrier for the material of the sensitive layer 5 to the carrier 4. The second adhesive layer H2 may likewise be a diffusion barrier for the sensitive layer. The second adhesive layer H2 can be deposited on the sensitive layer 5.

The cavity can be provided in the substrate 2 in an isotropic manner, for example, using XeF ₂ (xenon difluoride). In addition to or instead of etching with XeF ₂ , the etching process can also be carried out with SF ₆ (sulfur hexafluoride), which can then be depth oriented. Otherwise, it is also possible to advantageously use a non-directional etching method.

  The additional passivation 8 may advantageously be formed as a protection against environmental influences (moisture, dust) and may comprise suitable materials.

  Etching can also be done with KOH.

  FIG. 2 shows a schematic plan view of a sensor device according to an embodiment of the present invention.

  As shown in the plan view of the sensor device 1, the cavity 3 comprises an exemplary oval (elliptical) shape with an edge 3 a, which edge can surround the cavity 3 entirely. The sensitive layer 5 is preferably arranged symmetrically with respect to the center M at least along the transverse direction k. Therefore, the sensitive layers 5 can be arranged at the same distance along the direction k (from the center to both sides), so that the temperature flux to the edge portion 3a intersecting the lateral direction k is symmetrical on both sides. be able to.

  The sensitive layer 5 can advantageously also be connected to an electrical circuit, or the sensitive layer 5 itself can form a circuit with measuring elements, which may advantageously depend on the parameter to be measured. It is also possible to measure the electrical resistance of the layer. This loop can advantageously be a Wheatstone bridge.

  The advantageous optional shape of the edge 3a advantageously makes it possible to realize any design of the edge boundary in plan view, and thus of the cavity 3, which in turn favors the stability and contamination properties of the cavity 3. Can affect. The etching holes 7 are preferably provided between the sensitive layers 5 and are preferably evenly spaced from one another. The top view illustratively shows three loops of the sensitive layer 5.

  The carrier with the substrate and the cavity may be arranged on the chip or may be formed as a chip.

  FIG. 3 shows a schematic flow chart of a method for manufacturing a sensor device according to an embodiment of the present invention.

  In the method for manufacturing the sensor device, step S1 of preparing a substrate, step S2 of forming a trench structure from the top surface of the substrate as an edge of a cavity in the substrate, and step S3a of introducing a filling material into the trench structure, Applying S3b to the top surface of the substrate, whereby a carrier is formed on the top surface of the substrate and at least partially on its edge region. Further, a step S4 of arranging the sensitive layer on the carrier and a step S5 of constructing the sensitive layer are performed so that at least the lateral extension of the region between the edge and the edge is centered on the sensitive layer. Advantageously, the step S6 of placing the passivation on the carrier and the sensitive layer is carried out on the side of the sensitive layer which is not facing the substrate. Furthermore, the edge boundary is advantageously provided by a step S7 of providing in the passivation and carrier a plurality of etching holes that can extend through the carrier to the substrate, preferably by means of an etching process through the etching holes. Step S8 of forming a cavity in the substrate inside is performed. The above method steps S3a and S3b can be performed simultaneously in sequence.

  The trench structure can be introduced by a trench process.

  Although the present invention has been completely described above based on the preferred embodiments, the present invention is not limited thereto and can be modified in various ways.

1 Sensor Device 2 Substrate 2a Upper Surface 3 Cavity 3a Edge 4 Carrier 5 Sensitive Layer 6 Passivation 7 Etching Hole 8 Passivation d Interval M Center MT Filling Material RB Trench Structure S1 to S8 Steps

Claims (18)

A sensor device (1),
A substrate (2) having an upper surface (2a) and a cavity (3) in the substrate (2) formed from the upper surface (2a) in the substrate (2);
A carrier (4) arranged on the upper surface (2a) of the substrate (2) and comprising a filling material (MT) at least partially covering the cavity (3);
A sensitive layer (5) constructed on the carrier (4) above the cavity (3) on the side facing away from the substrate (2), the lateral extent of the cavity (3) being the sensitive layer (5). 5) a sensitive layer (5) centered in at least one direction, and a passivation (6) covering the sensitive layer (5) and the carrier (4) on the side not facing the substrate (2). ,
A sensor device (1) including. The sensor device (1) according to claim 1,
Sensor device (1), wherein the filling material (MT) at least partially covers the edge (3a) of the cavity (3). A sensor device (1),
A substrate (2) having an upper surface (2a) and a cavity (3) in the substrate (2) formed from the upper surface (2a) in the substrate (2);
A carrier (4) comprising a filling material (MT), which is arranged on the upper surface (2a) of the substrate (2) and at least partially covers the edge (3a) of the cavity (3) and covers the cavity (3). A carrier (4) at least partially covering,
A sensitive layer (5) built into the carrier (4) above the cavity (3) on the side facing away from the substrate (2), the lateral extension of the cavity (3) being the sensitive layer (5). ), Which is centered in at least one direction with respect to), and a passivation (6) covering the sensitive layer (5) and the carrier (4) on the side facing away from the substrate (2),
A sensor device (1) including. The sensor device (1) according to claim 3,
Sensor device (1), wherein the passivation (6) and the filling material (MT) each comprise a vent. The sensor device (1) according to claim 3 or 4,
Sensor device (1), wherein the passivation (6) and the carrier (4) comprise a plurality of through etching holes (7) in the region (3) of the cavity extending into the cavity (3). The sensor device (1) according to any one of claims 3 to 5,
Sensor device (1), wherein the sensor device (1) comprises a heat carrier sensor and the sensitive layer (5) comprises a heat sensitive layer. The sensor device (1) according to any one of claims 3 to 6,
Sensor device (1), wherein the sensor device (1) comprises a first adhesive layer (H1) arranged at least in the region of the sensitive layer (5) between the sensitive layer (5) and the carrier (4). . The sensor device (1) according to any one of claims 3 to 7,
The sensor device (1) comprises a second adhesive layer (H2) arranged between the sensitive layer (5) and the passivation (6) at least in the region of the sensitive layer (5), which is arranged on the sensitive layer (5). , Sensor device (1). The sensor device (1) according to any one of claims 3 to 8,
Sensor device (1) centered in at least one direction with respect to the sensitive layer (5) such that the lateral extent of the cavity (3) can dissipate heat symmetrically via the edge (3a). ). The sensor device (1) according to any one of claims 3 to 9,
A sensor arrangement (1) in which the cavity (3) has a center (M) in plan view and the constructed sensitive layer (5) is symmetrically arranged around this center (M) in at least one direction. ). A method of manufacturing a sensor device (1), comprising:
A step (S1) of preparing the substrate (2),
Applying a filling material to the upper surface (2a) of the substrate (2) (S3b), thereby forming a carrier (4) on the upper surface (2a) of the substrate (S3b);
Positioning (S4) the sensitive layer (5) on the carrier (4), and at least laterally, the lateral extent of the area between the edge (3a) for the cavity (3) is sensitive layer. Constructing a sensitive layer (5) so as to be centered with respect to (5) (S5),
The step (S7) of providing in the carrier (4) a plurality of etching holes (7) extending through the carrier (4) to the substrate (2), and an etching process through the etching holes (7), thereby forming the substrate (2). ), Forming a cavity (3) in the edge (3a) (S8),
Including the method. The method of claim 11, wherein
Forming a trench structure (RB) from the top surface (2a) of the substrate (2) as an edge (3a) for the cavity (3) in the substrate (2) (S3), and a filling material (MT) ) Introducing a filling material (MT) into the trench structure (RB) so that at least partially forms the edge (3a), (S3a),
Including the method. A method of manufacturing a sensor device (1), comprising:
A step (S1) of preparing the substrate (2),
Forming a trench structure (RB) from the upper surface (2a) of the substrate (2) as an edge (3a) for the cavity (3) in the substrate (2) (S2),
Introducing the filling material (MT) into the trench structure (RB) (S3a) and applying the filling material (MT) to the upper surface (2a) of the substrate (2) (S3b), whereby the substrate Forming a carrier (4) on the upper surface (2a) of (2) and at least partially on the edge (3a) (S3b);
The step (S4) of placing the sensitive layer (5) on the carrier (4) and the lateral extent of the area between it and the edge (3a) is centered with respect to the sensitive layer (5) at least laterally. So as to construct the sensitive layer (5) (S5),
The step (S7) of providing in the carrier (4) a plurality of etching holes (7) extending through the carrier (4) to the substrate (2), and an etching process through the etching holes (7), thereby forming the substrate (2). ), Forming a cavity (3) in the edge (3a) (S8),
A method of manufacturing a sensor device (1) comprising: The method according to claim 13, wherein
Through the step (S6) of placing the passivation (6) on the side of the carrier (4) and the sensitive layer (5) facing away from the substrate (2), and through the passivation (6) and the carrier (4) Providing a plurality of etching holes (7) in the passivation (6) and carrier (4) extending to the substrate (2) (S7),
Including the method. The method according to claim 13 or 14, wherein
Method using stoichiometric or silicon rich nitride or SiO ₂ as fill material (MT). The method according to any one of claims 13 to 15,
A method of arranging a first adhesive layer (H1) on the carrier (4) in the region of the sensitive layer (5) before the step (S4) of disposing the sensitive layer (5). The method according to any one of claims 13 to 16,
Method (S5) of building a sensitive layer (5) by a lithographic method and an etching method, producing etching holes and a sensitive layer by lithography and etching from the front side and forming a trench structure (RB) from the same front side. . A method according to any one of claims 13 to 17,
A method (S8) of forming a cavity (3) using an etching method comprising at least one isotropic etching step of laterally undercutting at least half of the spacing of the etching holes.

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