DE102010062555B4 - Micromechanical membrane device and corresponding manufacturing method and membrane assembly - Google Patents

Abstract

A micromechanical membrane device comprising: a substrate (1); a first electrode (E1; E1 ') formed over the substrate (1); a membrane (M) formed over the first electrode (E1; E1') formed of SiC; a second electrode (E2; E2 ') formed over the membrane (M), the membrane (M) being electrically insulated from the first and second electrodes (E1, E2; E1', E2 ') and being located in a deflectable membrane region (MA ) is formed spaced apart from the first and second electrodes (E1, E2, E1 ', E2') by first and second air gaps (S1, S2).

Description

State of the art

The present invention relates to a micromechanical membrane device and a corresponding manufacturing method and a membrane assembly.

Although applicable to any micromechanical devices, the present invention and its underlying background with respect to micromechanical devices in silicon technology will be explained.

From the WO 2009/066290 A2 For example, a speaker device is known which comprises a first conductive layer for forming a first electrode, an overlying first insulation layer, a conductive membrane layer, an overlying second insulation layer and an overlying second conductive layer for forming a second electrode. Such a speaker device can be operated electrostatically and, in principle, can also be used conversely as a microphone device.

The WO 2007/135 680 A1 discloses an apparatus for generating pressure wave by means of an array of moving parts, each constrained to move back and forth along a respective axis in response to an alternating electromagnetic force applied to the array.

Such speaker devices with element arrays can in principle be realized, for example, with silicon as the membrane and electrode material. The membranes of the individual elements are pressed during operation by high voltages to the associated electrodes.

From the US 2010/0301967 A1 For example, a microelectromechanical system is known that forms a MEMS resonator. For this purpose, a planar movable electrode is arranged at a distance parallel to two further electrodes for driving.

From the US 2002/0067663 A1 For example, a miniaturized broadband acoustic transducer is known. Here, it is proposed to use a diagnostic material and covering materials made of a semiconductor material or of a metal, a noble metal or alloys thereof.

From the DE 10 2006 004 287 A1 a micromechanical device is known which comprises a substrate and a first rigid electrode arrangement arranged on or in the substrate, a second second electrode arrangement suspended on the substrate and a gap provided between the first and the second electrode arrangement, the second electrode arrangement being elastic with respect to the first electrode arrangement mounted on the suspension post deflectable such that the capacitance of a capacitor formed by the first Elektrodenanrodnung, the second electrode assembly and the gap is variable.

From the US 5 146 435 A For example, an acoustic tranducer is known which has a perforated capacitor plate and a movable capacitor plate spaced from the perforated capacitor plate.

From the WO 2009/111874 A1 For example, a microelectromechanical system is known that connects electrical and mechanical components, proposing a method of manufacturing such a system.

From the US 2006/0230835 A1 For example, a micromechanical acoustic transducer is known that has perforated components that form capacitor cells that convert an electrical signal into an acoustic signal or vice versa.

Advantages of the invention

The micro-mechanical membrane device defined in claim 1 and the corresponding manufacturing method according to claim 11 and the membrane arrangement according to claim 15 have the advantage that sticking in a MEMS membrane device can be avoided by the use of SiC as material for the membrane.

SiC has a drastically reduced sticking tendency compared to silicon. In addition, SiC has a high mechanical hardness, whereby very robust elements can be implemented. Robustness is of the utmost importance due to the high load requirements (> 10 ¹⁰ cycles). The manufacturing process can be further simplified and reduced by the use of SiC.

A reliable and powerful anti-adhesive layer in the form of SiC also leads to the avoidance of so-called late loss. These are to be understood as membranes which do not immediately detach from the current contact electrode when the voltage is reversed. This results in a better homogeneity in the response of the individual pixels in the array, which significantly contributes to the improvement of the audio quality.

In principle, the invention is based both on membrane arrangements in the form of MEMS Speaker devices as well as in the form of MEMS microphone devices applicable. However, the MEMS microphone devices are usually operated so that the membrane does not abut against the counter electrode. Sticking is therefore of lesser importance in microphone devices than in MEMS loudspeaker devices, but also for certain applications in the high-pressure sound field also advantageous.

The features listed in the dependent claims relate to advantageous developments and improvements of the subject matter of the invention.

list of figures

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

• 1 eine schematische Querschnittsdarstellung zur Erläuterung einer ersten Ausführungsform der erfindungsgemäßen mikromechanischen Membranvorrichtung in Form einer Lautsprechervorrichtung;
• 2 eine schematische Querschnittsdarstellung zur Erläuterung einer zweiten Ausführungsform der erfindungsgemäßen mikromechanischen Membranvorrichtung in Form einer Lautsprechervorrichtung;
• 3 eine schematische Querschnittsdarstellung zur Erläuterung einer dritten Ausführungsform der erfindungsgemäßen mikromechanischen Membranvorrichtung in Form einer Lautsprechervorrichtung;
• 4a-d schematischen Querschnittsdarstellungen zur Erläuterung einer Ausführungsform des erfindungsgemäßen Herstellungsverfahrens für eine mikromechanische Membranvorrichtung gemäß 1.; und
• 5 eine Membrananordnung gemäß einer weiteren Ausführungsform der vorliegenden Erfindung.

Show it:

• 1 a schematic cross-sectional view for explaining a first embodiment of the micromechanical membrane device according to the invention in the form of a speaker device;
• 2 a schematic cross-sectional view for explaining a second embodiment of the micromechanical membrane device according to the invention in the form of a speaker device;
• 3 a schematic cross-sectional view for explaining a third embodiment of the micromechanical membrane device according to the invention in the form of a speaker device;
• 4a-d schematic cross-sectional views for explaining an embodiment of the manufacturing method according to the invention for a micromechanical membrane device according to 1 . and
• 5 a membrane assembly according to another embodiment of the present invention.

Description of exemplary embodiments

In the figures, like reference numerals designate the same or functionally identical elements.

1 is a schematic cross-sectional view for explaining a first embodiment of the micromechanical membrane device according to the invention in the form of a speaker device.

In 1 denotes reference numeral 1 a silicon substrate having a front side V and a back R having. On the front side V of the silicon substrate 1 there is a first insulation layer O1 on which a structured first conductive layer F1 made of polysilicon is applied. In particular, the first conductive layer comprises F1 a first electrode E1 which through separation trenches T from further areas of the first conductive layer F1 is disconnected.

The first electrode E1 points in the region of a cavity provided in the silicon substrate K Holes L, which serve as etch holes in the manufacturing method to be described later and which on the other hand serve as sound passage holes in operation. The structuring through the cavern from the back R her allows an improvement in the membrane mobility, but is not mandatory.

Above the first conductive layer F1 a second insulation layer is provided O2 , On the second insulation layer O2 a structured conductive membrane layer is provided FM which is a membrane M includes, through dividing trenches T of remaining areas of the conductive membrane layer FM is.

The membrane M has an elastically deflectable membrane area MA and a clamped membrane rim area MR on. The clamping of the membrane edge area MR takes place through the second insulation layer O2 and one above the conductive membrane layer FM provided third insulation layer O3 , Above the third insulation layer O3 a second conductive layer is provided F2 which is in a second electrode E2 is structured, which also by separating trenches T is separated from the remaining regions of the second conductive layer.

The first, second and third insulation layers O1 . O2 and O3 which serve as sacrificial layers in the manufacturing method to be described later, are preferably made of silicon oxide. The conductive membrane layer FM consists of SiC (silicon carbide) in the present example, whereas the second conductive layer F2 and with it the electrode E2 as well as the second conductive layer F1 and with it the electrode E1 consist of polysilicon.

Etching holes or sound passage holes L are also in the deflectable membrane area MA and in the second electrode E2 above the deflectable membrane area MA educated. The deflectable membrane area MA the membrane M is through a first air gap S1 from the first electrode E1 and through a second air gap S2 from the second electrode E2 according to the thickness of the layers O2 or. O3 spaced, whereby a corresponding range of movement of the membrane M is defined.

Laterally offset to the membrane M and to the second electrode E2 formed is a contact plug KS1 polysilicon, which from a top O the second conductive layer F2 to the first electrode E1 enough. Laterally offset to the second electrode E2 and to the first contact plug KS1 is a second contact plug KS2 formed, which from the top O the second conductive layer F2 to the membrane M enough.

At the same height at the top of the second conductive layer F2 formed are connection pads P1 . P2 . P3 for electrically contacting the first electrode E1 over the contact plug KS1 the membrane M over the contact plug KS2 or the second electrode 2 , These connection pads P1 . P2 . P3 are structured from an aluminum metallization by a known etching process.

Due to the configuration of the first and second electrodes E1 . E2 made of polysilicon and the membrane of SiC can be a sticking of the membrane M at the first and second electrodes E1 . E2 prevent, as well as the impact resistance of the membrane M increase.

2 is a schematic cross-sectional view for explaining a second embodiment of the micromechanical membrane device according to the invention in the form of a speaker device.

At the in 2 The second embodiment shown is the first conductive layer F1 ' not made of polysilicon, but like the conductive membrane layer FM also made of SiC. The underlying first insulation layer O1 ' In this example, it is not made of oxide, but of undoped SiOC, whereas the overlying SiC is doped to the conductive membrane layer FM to render highly conductive. Such a layer stack can be produced as a thin layer on the silicon substrate by a simplified deposition method 1 realize, whereby the process costs can be further reduced, since a first polysilicon Epitaxieschicht to form the first conductive layer can be avoided. Another advantage of the first insulation layer O1 ' SiOC is that in the manufacturing process to be described later in the step of RF gas phase etching of the second and third insulation layers O2 . O3 not attacked, causing an undercut of the first electrode E1 ' , which in the embodiment according to 1 occurs, prevents.

In addition, in the second embodiment, unlike the first embodiment described above, there are three caverns K1 . K2 . K3 formed, which serve as Ätzkanäle in the manufacturing process. The caverns extend from the back R of the silicon substrate 1 to the first conductive layer F1 ' ,

3 is a schematic cross-sectional view for explaining a third embodiment of the micromechanical membrane device according to the invention in the form of a speaker device.

In the third embodiment according to 3 is the second conductive layer F2 ' formed of SiC, wherein the third insulating layer O3 is formed of oxide.

In principle, it would also be possible to use the third insulation layer O3 to form SiOC analogous to the second embodiment described above and to produce the two layers in the thin-film process.

As a further modification, it would be conceivable only the lower part of the upper electrode E2 ' through a thin SiC layer and the upper part of SiOC to thereby simultaneously provide insulation for later wiring production.

4a-d are schematic cross-sectional views for explaining an embodiment of the manufacturing method according to the invention for a micromechanical membrane device according to 1 ,

In the described embodiment of the manufacturing method according to the invention is according to 4 a First, the provided silicon substrate 1 at its front V with the first insulation layer O1 Provided. This can be done for example by a suitable deposition process or thermal oxidation. In a subsequent first epitaxial step, the first conductive layer F1 deposited from polysilicon. Subsequently, a structuring of the first conductive layer takes place F1 by a conventional lithographic process with a corresponding trench etching step, on the one hand etch holes L and on the other hand, separation trenches T the latter being the lateral extent of the first electrode E1 define and a demarcation to the remaining area of the first conductive layer F1 create. In a subsequent process step, the second insulation layer O2 above the structured first conductive layer F1 deposited. Subsequently, there is a second step, eg CVD for depositing the conductive membrane layer FM from doped SiC.

In a subsequent structuring step, a left dividing trench is created T in the conductive membrane layer FM formed, which is the left-hand extension of the later membrane M Are defined. Also formed are etching holes L in the conductive membrane layer FM , which laterally offset to the Ätzlöchem L the first conductive layer F1 are. This structuring also takes place in a conventional photolithography step associated with a trench etching step. To go to 4a Subsequently, the third insulation layer is reached O3 oxide over the patterned conductive membrane layer FM deposited.

Continue with reference to 4b is above the third insulation layer O3 in a further Epitaxieschritt or CVD step, the second conductive layer F2 formed of polysilicon. Also in this second conductive layer F2 become etching holes L educated.

This is followed by a structuring of the back R of the silicon substrate 1 come to the cavern K in the present case, essentially the lateral extension of the later deflectable membrane region MA Are defined. In this area or above this area or below this area are also all etch holes L.

Continue with reference to 4c Then, an HF gas phase etching step is performed around the first, second and third insulation layers O1 . O2 . O3 in sacrificial layer technique to partially remove, so that the deflectable membrane area MA is formed.

After reaching the process state according to 4c is according to 4d the contact plug KS1 formed for contacting the first electrode. Likewise, in this process step, the right-hand extension of the membrane M through another dividing trench T which is filled with oxide defined. Furthermore, the formation of the second contact plug takes place KS2 which is the membrane M in the membrane edge area MR contacted. Finally, forming the contact pads P1 . P2 . P3 for contacting the first electrode E1 , the membrane M and the second electrode E2 ,

5 shows a membrane assembly according to another embodiment of the present invention.

The membrane arrangement 100 has a variety of membrane devices 111 according to 1 . 2 or 3 on which on a common substrate 1 are integrated. In the present case, a square array of 12 x 12 membrane devices 111 illustrated, however, such an arrangement, depending on the application significantly more membrane devices 111 respectively. Also, the invention is not limited to the square arrangement shown, but applicable to arrangements of any geometry.

When using such a membrane arrangement 100 as a speaker device controls a controller CT the electrodes via a multiplicity of signal lines (not shown) E1 . E2 the respective membrane device 111 individually or in groups to form an analog signal by inverse digitizing. This can be per membrane device 111 each generate either a positive or negative pressure signal, wherein the analog signal is produced by the superposition of all pressure signals.

Although the present invention has been described above with reference to preferred embodiments, it is not limited thereto, but modifiable in many ways.

It is also possible, for example, the contact plugs already in the state of 4a to create and in the state of 4b to finish.

Although the present invention has been described with respect to a speaker device, it is not limited to the speaker device, but is applicable to any micromechanical membrane assemblies, such as micromechanical microphone devices.

The invention is also not limited to the materials mentioned for substrate, electrodes and insulating layers, but also for other micromechanically processable materials executable.

Of course, the invention is applicable to both single MEMS membrane devices and large area arrays of MEMS membrane devices. Process steps for control devices or evaluation devices or packaging steps can also be integrated into the production process.

Claims (16)

A micromechanical membrane device comprising: a substrate (1); a first electrode (E1, E1 ') formed over the substrate (1); a membrane (M) formed over the first electrode (E1; E1 ') formed of SiC; a second electrode (E2, E2 ') formed over the membrane (M); the membrane (M) being electrically insulated from the first and second electrodes (E1, E2, E1 ', E2') and is formed in a deflectable diaphragm region (MA) by first and second air gaps (S1; S2) spaced apart from the first and second electrodes (E1, E2; E1 ', E2'). Micro-mechanical membrane device according to Claim 1 , wherein between the substrate (1) and the first electrode (E1; E1 '), a first insulating layer (O1; O1') is provided. Micro-mechanical membrane device according to Claim 1 or 2 wherein a second insulation layer (O2) is provided between the membrane (M) and the first electrode (E1; E1 '), and a third insulation layer (O3) is provided between the membrane (M) and the second electrode (E2; E2') and wherein the thickness of the second insulating layer (O2) corresponds to the thickness of the first air gap (S1) and the thickness of the third insulating layer (O3) corresponds to the thickness of the second air gap (S2). A micromechanical membrane device according to any one of the preceding claims, wherein the first and second electrodes (E1, E2; E1 ', E2') are formed of polysilicon. Micromechanical membrane device according to one of the preceding claims, wherein the first electrode (E1; E1 ') is electrically contactable from an upper side (O) of the membrane device via a first contact plug (KS1) offset laterally relative to the membrane (M). Micromechanical membrane device according to one of the preceding claims, wherein the membrane (M) via a laterally to the second electrode (E2; E2 ') offset second contact plug (KS2) from an upper side (O) of the membrane device is electrically contacted. Micromechanical membrane device according to one of the preceding claims, wherein the first electrode (E1; E1 ') is formed at least partially from SiC. Micromechanical membrane device according to one of the preceding claims, wherein the second electrode (E2; E2 ') is formed at least partially from SiC. Method for producing a micromechanical membrane device with the steps: Providing a substrate (1); Forming a first electrode (E1, E1 ') over the substrate (1); Forming a membrane (M) over the first electrode (E1; E1 ') of SiC; Forming a second electrode (E2; E2 ') over the membrane (M); wherein the membrane (M) is electrically isolated from the first and second electrodes (E1, E2, E1 ', E2') and in a deflectable membrane region (MA) by first and second air gaps (S1, S2) of the first and second electrodes Electrode (E1, E2, E1 ', E2') is formed spaced. Method according to Claim 9 comprising the steps of: forming a first insulating layer (O1; O1 ') on a front side (V) of the substrate (1); Forming a first conductive layer (F1; F1 ') on the first insulating layer (O1; O1'); Patterning the first conductive layer (F1; F1 ') to form the first electrode (E1; E1') and to form etch holes (L) in the first electrode (E1; E1 '); Forming a second isolation layer (O2) on the patterned first conductive layer (F1; F1 '); Forming a conductive membrane layer (FM) on the second insulating layer (O2); Patterning the conductive membrane layer (FM) to form etch holes (L) in the later deflectable membrane region (MA); Forming a third insulating layer (O3) on the patterned membrane layer (FM); Forming a second conductive layer (F1; F1 ') on the third insulating layer (O3); Patterning the second conductive layer (F2; F2 ') to form etching holes (L); Forming at least one cavern (K; K1, K2, K3) on a back side (R) of the substrate (1) in the region of the etching holes (L) extending to the first insulation layer (O1; O1 '); partially removing the first, second and third insulating layers (O1, O2, O3) in an etching step for forming the deflectable membrane region (MA), wherein a used etching medium propagates through the etching holes (L); Patterning the conductive membrane layer (FM) to form the membrane (M); Patterning the second conductive layer (F2; F2 ') to form the second electrode (E2; E2'). Method according to Claim 10 comprising the step of: forming a first contact plug (KS1) offset laterally of the membrane (M) from the upper side (O) of the second conductive layer (F2; F2 ') to the first electrode (E1; E1'). Method according to Claim 10 or 11 comprising the step of: forming a second contact plug (KS2) offset laterally of the second electrode (E2; E2 ') from the upper side (O) of the second conductive layer (F2; F2') to the diaphragm (M). Method according to one of Claims 9 to 12 , wherein the first electrode (E1; E1 ') and / or the second electrode (E2; E2 ') is at least partially formed from SiC. Method according to one of Claims 11 to 13 in which the first electrode (E1; E1 ') or the second electrode (E2; E2') or the membrane (M) is in each case surrounded by a SIOC or undoped SIC layer. Membrane arrangement with a plurality of membrane devices according to one of Claims 1 to 8th which are provided on a common substrate (1). Use of a membrane arrangement according to Claim 15 as a speaker device or microphone device.

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