MICROMECHANICAL COMPONENT FOR A SOUND TRANSDUCER AND CORRESPONDING PRODUCTION METHOD
20220080461 · 2022-03-17
Inventors
- Jochen Reinmuth (Reutlingen, DE)
- Daniel Monteiro Diniz Reis (Esslingen Am Neckar, DE)
- Martin Rambach (Pliezhausen, DE)
Cpc classification
International classification
Abstract
A micromechanical component for a sound transducer device. The component includes a diaphragm element which includes a first diaphragm surface and a second diaphragm surface which points away from the first diaphragm surface, and at least one piezoelectric element situated on and/or at the first diaphragm surface. The micromechanical component includes a substrate having at least one control and/or evaluation circuit developed thereon and/or therein, the first diaphragm surface pointing toward the substrate, and the substrate is attached to the diaphragm element at least via at least one an electrically conductive bond connection structure which is developed on and/or at the first diaphragm surface, from which the second diaphragm surface is pointing away, and the at least one piezoelectric element is electrically connected to the at least one control and/or evaluation circuit at least via the at least one electrically conductive bond connection structure.
Claims
1. A micromechanical component for a sound transducer, comprising: a diaphragm element having a first diaphragm surface and a second diaphragm surface that points away from the first diaphragm surface; at least one piezoelectric element situated on and/or at the first diaphragm surface, from which the second diaphragm surface points away; a substrate having at least one control and/or evaluation circuit developed thereon and/or therein, the first diaphragm surface pointing toward the substrate and the second diaphragm surface pointing away from the substrate, the substrate being attached to the diaphragm element at least via at least one an electrically conductive bond connection structure which is developed on and/or at the first diaphragm surface and from which the second diaphragm surface points away; wherein the at least one piezoelectric element is electrically connected to the at least one control and/or evaluation circuit at least via the at least one electrically conductive bond connection structure.
2. The micromechanical component as recited in claim 1, wherein the at least one electrically conductive bond connection structure is an aluminum-germanium bond connection structure.
3. The micromechanical component as recited in claim 1, wherein a reinforcement and/or gel-restriction and/or protection structure, which surrounds or spans at least a subregion of the second diaphragm surface, is attached on and/or at the second diaphragm surface of the diaphragm element.
4. The micromechanical component as recited in claim 1, wherein the substrate has at least one through-contact, which extends from an inner surface of the substrate pointing toward the diaphragm element to a countersurface of the substrate pointing away from the inner surface.
5. The micromechanical component as recited in claim 4, wherein the countersurface of the substrate may be soldered to a circuit board.
6. The micromechanical component as recited in claim 1, wherein a maximum distance between the at least one control and/or evaluation circuit and the inner surface of the substrate pointing toward the diaphragm element is smaller than a minimum distance between the at least one control and/or evaluation circuit and the countersurface of the substrate pointing away from the inner surface.
7. A production method for a micromechanical component for a sound transducer, the method comprising the following steps: positioning at least one piezoelectric element on and/or at a first diaphragm surface of a diaphragm element of the produced micromechanical component in such a way that a second diaphragm surface pointing away from the first diaphragm surface points away from the at least one piezoelectric element; attaching a substrate of the produced micromechanical component having at least one control and/or evaluation circuit developed thereon and/or therein to the diaphragm element in such a way that the first diaphragm surface points toward the substrate and the second diaphragm surface points away from the substrate in that the substrate is attached to the diaphragm element at least via at least one electrically conductive bond connection structure which is developed on and/or at the first diaphragm surface and from which the second diaphragm surface points away, in such a way that the at least one piezoelectric element is electrically connected to the at least one control and/or evaluation circuit at least via the at least one electrically conductive bond connection structure.
8. The production method as recited in claim 7, wherein the at least one electrically conductive bond connection structure is formed using a eutectic bonding method.
9. The production method as recited in claim 8, wherein, to carry out the eutectic bonding method, germanium is deposited on and/or at the first diaphragm surface prior to positioning the at least one piezoelectric element on and/or at the first diaphragm surface, and only after germanium has been deposited on and/or at the first diaphragm surface, the at least one piezoelectric element is positioned on and/or at the first diaphragm surface at a temperature that is greater than or equal to 400° C., and, to carry out the eutectic bonding method, aluminum is additionally deposited on and/or at an inner surface of the substrate that later points toward the diaphragm element and then the at least one electrically conductive bond connection structure is formed out of the germanium deposited on and/or at the first diaphragm surface and the aluminum deposited on and/or at the inner surface of the substrate.
10. The production method as recited in claim 7, wherein the at least one piezoelectric element is positioned on and/or at the first diaphragm surface of a diaphragm element that is attached to a carrier substrate and abuts an etch-stop layer of the carrier substrate, and after the substrate is attached to the diaphragm element, the carrier substrate is at least partially etched off using an etching method that is carried out up to the etch-stop layer.
11. The production method as recited in claim 10, wherein a reinforcement and/or gel-restriction and/or protection structure, which is fixed in place on and/or at the second diaphragm surface of the diaphragm element and surrounds or spans at least a subregion of the second diaphragm surface, is structured out of the carrier substrate when the carrier substrate is etched.
12. The production method as recited in claim 11, wherein the diaphragm element with the attached substrate is introduced into a receiving opening of a housing in such a way that a sealing ring which is at least partially situated in a groove developed at the receiving opening makes contact with the reinforcement and/or gel-restriction and/or protection structure.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Additional features and advantages of the present invention will be described below with the aid of the figures.
[0019]
[0020]
[0021]
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0022]
[0023] When the production method described in the following text is carried out, at least one piezoelectric element (not shown in
[0024] Preferably, a layer thickness of the diaphragm element aligned perpendicular to first diaphragm surface 10a and/or perpendicular to second diaphragm surface 10b may be smaller than or equal to 20 μm. However, in order to still ensure excellent stability of the diaphragm element in the course of the production method, the at least one piezoelectric element in the embodiment described here is positioned on and/or at first diaphragm surface 10a of a diaphragm element that is attached on a carrier substrate 12 and abuts an etch-stop layer 14 of carrier substrate 12. In this case, first diaphragm surface 10a of diaphragm element 10 denotes a boundary surface of diaphragm element 10 pointing away from carrier substrate 12, while second diaphragm surface 10b of diaphragm element 10 abuts etch-stop layer 14. Carrier substrate 12, for instance, may be a semiconductor substrate, in particular a silicon substrate. Carrier substrate 12 preferably has a thickness of at least 250 μm. Etch-stop layer 14 can be a silicon dioxide layer 14, for instance. Thus, a SOI substrate (silicon on insulator substrate) is also able to be used as a starting material for a layer stack, which includes carrier substrate 12, etch-stop layer 14 and diaphragm element 10.
[0025] Optionally, first diaphragm surface 10a is at least partially covered by an insulation layer 16 such as a silicon dioxide layer 16. Then, at least one circuit trace 18, preferably of doped polysilicon, is able to be formed on a side of insulation layer 16 that points away from diaphragm element 10. A layer thickness d of the at least one circuit trace 18 aligned perpendicular to first diaphragm surface 10a may be smaller than or equal to 5 μm.
[0026] In addition, in the production method described here, a substrate of the later micromechanical component, which has at least one control and/or evaluation circuit formed thereon and/or therein, is attached to diaphragm element 10 in a method step to be described at a later point. The attachment of the substrate to diaphragm element 10 is accomplished by way of at least one electrically conductive bond connection structure, which is preferably developed using a eutectic bonding method. In the embodiment described here, the eutectic bonding method is carried out in a plurality of partial steps, of which a first partial step is schematically illustrated in
[0027] The at least one bonding material region 20a and 20b of germanium thus forms a first bond interface for the later completed eutectic bonding method. The at least one bonding material region 20a and 20b of germanium preferably covers at least one circuit trace 18 at least partially. Optionally, it is also possible to introduce at least one further layer between the at least one circuit trace 18 and the respective covering bonding material region 20a and 20b. A height h.sub.20 of the at least one bonding material region 20a and 20b of germanium aligned perpendicular to first diaphragm surface 10a is furthermore able to be selected relatively freely.
[0028] It is expressly pointed out that in the embodiment of the production method described here the at least one bonding material region 20a and 20b of germanium is deposited prior to positioning/developing the at least one piezoelectric element 22 on and/or at first diaphragm surface 10a. For this reason, the positioning/development of the at least one piezoelectric element 22 on and/or at first diaphragm surface 10a is schematically first illustrated in
[0029] In the embodiment of the production method described here, (after germanium has been deposited on and/or at first diaphragm surface 10a), the at least one piezoelectric element 22 is furthermore positioned/developed on and/or at first diaphragm surface 10a at a temperature that is greater than or equal to 400° C. This is possible because both the at least one circuit trace 18 of doped polysilicon and the at least one bonding material region 20a and 20b of germanium are not damaged or destroyed at such a high temperature. As a result, it is possible to produce the at least one piezoelectric element 22 at a temperature that is so high that a very high piezo coefficient of the at least one piezoelectric element 22 is able to be induced.
[0030] For example, a piezo layer stack 22 as the at least one piezoelectric element 22 may be deposited on insulation layer 16 and structured. Such a piezo layer stack 22 can have a first electrode 22a and a second electrode 22b in each case and at least one piezoelectric material 22c which is inserted between its first electrode 22a and its second electrode 22b. Lead-zirconate titanate (PZT) or potassium-sodium-niobate (KNN or (K,Na)NbO.sub.3) is preferably used as the at least one piezoelectric material 22c. Optionally, a still further layer such as a lanthanum-nickel oxide layer (LaNiO.sub.3) is additionally able to be formed between first electrode 22a and piezoelectric material 22c in order to facilitate the formation/deposition of the at least one piezoelectric material 22c.
[0031] If desired, in order to protect the at least one piezoelectric element 22 from environmental influences, the at least one piezoelectric element 22 is also able to be encapsulated in a protective layer 25 such as a tantalum-nitride layer, a silicon nitride layer and/or an aluminum-oxide layer. However, it is pointed out that protective layer 25 can usually be dispensed with when the described production method is executed because the at least one piezoelectric element 22 is already well protected from environmental influences by the circumferential bond frame described further below.
[0032] In addition, a height h.sub.22 of the at least one piezoelectric element 22 aligned perpendicular to first diaphragm surface 10a is able to be selected relatively freely. As the following explanations will reveal, the circumferential bond frame 36 described below already reliably protects the at least one piezoelectric element 22 from environmental influences even at a relatively great height h.sub.22 of the at least one piezoelectric element 22.
[0033] Optionally, at least one further circuit trace 24 by which the at least one piezoelectric element 22 is electrically connected to the at least one circuit trace 18 is subsequently able to be formed. The at least one further circuit trace 24 can easily be made of aluminum because once the at least one piezoelectric element 22 has been produced, the rest of the production method described in the further text is able to be carried out at a relatively low temperature.
[0034]
[0035] The at least one bonding material region 26a and 26b of aluminum serves as a second bond interface of the eutectic bonding method concluded later. The at least one bonding material region 26a and 26b of aluminum is able to be deposited and structured on inner surface 28a of substrate 28 using a standard process of semiconductor technology. In addition, a height h.sub.26 of the at least one bonding material region 26a and 26b of aluminum aligned perpendicular to inner surface 28a of substrate 28 is easily specifiable in such a way that a sum of layer thickness d of the at least one circuit trace 18, height h.sub.20 of the at least one bonding material region 20a and 20b of germanium, and height h.sub.26 of the at least one bonding material region 26a and 26b of aluminum is greater than height h.sub.22 of the at least one piezoelectric element 22. In this way, framing of relatively high piezoelectric elements 22 with the aid of the circumferential bonding frame is therefore possible as well.
[0036] As may be gathered from
[0037]
[0038] As may be gathered from
[0039] As can also be gathered from the intermediate product of
[0040] After substrate 28 has been attached to diaphragm element 10, substrate 28 is optionally able to be thinned starting from a countersurface 28b that points away from its inner surface 28a. The intermediate product is shown in
[0041] If desired, at least one through-contact 38 through substrate 28 may then be formed, which extends from inner surface 28a of substrate 28 pointing toward diaphragm element 10 to countersurface 28b of substrate 28 pointing away from inner surface 28a. Optionally, the at least one through-contact 38 may also extend through an insulation layer 40 deposited on countersurface 28b. Countersurface 28b of substrate 28 is able to be soldered to a circuit board (not shown). To this end, at least one solder ball 42, for example, may be attached to the at least one through-contact 38 on the side of substrate 28 pointing away from diaphragm element 10. The side of substrate 28 pointing away from diaphragm element 10 may thus be embodied as a rewiring plane, which allows for a more flexible positioning of substrate 28 together with attached diaphragm element 10 on the circuit board, and for positioning substrate 28 with the aid of a flip-chip process, in particular.
[0042] As a last, optional, method step of the production method,
[0043]
[0044] The micromechanical component schematically illustrated in
[0045] In addition, the micromechanical component includes a substrate 28 having at least one control and evaluation circuit 30 formed thereon and/or therein. While first diaphragm surface 10a is pointing toward substrate 28, second diaphragm surface 10b is pointing away from substrate 28. At the same time, substrate 28 is attached to diaphragm element 10 at least via at least one electrically conductive bond connection structure 34 which is developed on and/or at first diaphragm surface 10a and from which second diaphragm surface 10b points away. Furthermore, the at least one piezoelectric element 22 is electrically connected to the at least one control and evaluation circuit 30 at least via the at least one conductive bond connection structure 34.
[0046] In the micromechanical component of
[0047] In addition, a maximum distance between the at least one control and/or evaluation circuit 30 and inner surface 28a of substrate in the micromechanical component of
[0048] As has become clear from the preceding description, the micromechanical component of
[0049] As an optional refinement, substrate 28 of the micromechanical component of
[0050] With regard to further properties and features of the micromechanical component of
[0051]
[0052] As a supplementation, the micromechanical component of
[0053] With regard to further features and advantages of the micromechanical component of
[0054] The afore-described micromechanical components, for example, may advantageously be used as (at least part of) a sound transducer such as an ultrasonic transducer, in particular. More specifically, the micromechanical components are able to be used in a variety of ways as MEMS ultrasonic transducers and/or as PMUT (piezoelectric micromachines ultrasonic transducers). In the same way, the afore-described micromechanical components are also able to be used as (at least part of) a spatially resolved material detector or detectors. The afore-described micromechanical components are also suitable for (at least part of an) optical device such as an optical mirror device or an interferometer, in particular.
[0055] Second diaphragm surface 10b of diaphragm element 10 used as an actuator and/or sensor surface of diaphragm element 10 may also be referred to as an ultrasonic head of the respective micromechanical component. It is expressly pointed out that an extension of the afore-described micromechanical components aligned in parallel with second diaphragm surface 10b of diaphragm element 10 may be relatively small despite a relatively high number of electrical connections between piezoelectrical elements 22 and control and/or evaluation circuits 30. This is also known as a miniaturization of an ultrasonic head of the micromechanical component. For that reason, the afore-described micromechanical components may be used for a variety of purposes, in particular also in the field of medical technology.
[0056] All previously described micromechanical components are also able to be combined very flexibly with virtually any application-specific integrated circuit (ASIC).