Patent Application
20170332176
The present application claims the benefit under 35 U.S.C. ยง119 of German Patent Application No. DE 102016208325.2 filed on May 13, 2016, which is expressly incorporated herein by reference in its entirety.
The present invention relates to a micromechanical component and to a microphone. In addition, the present invention relates to a method for packaging a substrate having a micro-electromechanical microphone structure including at least one piezoelectric layer.
A piezoelectric microphone, which has a multitude of bending beams, is described in U.S. Patent Appl. Pub. No. 2014/0339657 A1. Each bending beam is made up of a first electrode, which is made from molybdenum and is anchored on a substrate; a first piezoelectric layer of aluminum nitride which at least partially covers the first electrode; a second electrode of molybdenum, which covers the first piezoelectric layer; a second piezoelectric layer of aluminum nitride covering the second electrode; and a third electrode of molybdenum covering the second piezoelectric layer.
The present invention provides a micromechanical component, a microphone, and a method for packaging a substrate having a micro-electromechanical microphone structure, which includes at least one piezoelectric layer.
Example embodiment of the present invention provide more advantageous and cost-effective options for packaging a substrate having a micro-electromechanical microphone structure that includes at least one piezoelectric layer. In this context, the improved robustness of such a micro-electromechanical microphone structure (in particular in comparison with a capacitive micro-electromechanical microphone structure) with regard to mechanical stress that occurs in the at least one polymer mass, is utilized by the present invention for the realization of smaller and less expensive packages.
While relatively resource-intensive packaging is conventionally used for substrates having at least one micro-electromechanical microphone structure, e.g., a cover that freely arches over the respective substrate and is mounted on a carrier fitted with the substrate, the present invention provides packaging that is able to be produced more easily and cheaply with the aid of the at least one polymer mass. The conventional cover, which is typically made of metal, has to have a significant clearance from the substrate over which it arches (due to process tolerances when bonding the cover to the carrier) and will typically be attached to the carrier in a separate process. As a result, it is hardly possible to minimize the conventional cover and the carrier that interacts with the cover. As described in greater detail in the following text, the packaging of the substrate fitted with the micro-electromechanical microphone structure that is realizable with the aid of the present invention is able to be produced in a rapid manner and by an easily executable method step. This not only makes it possible to utilize the advantageous robustness of the micro-electromechanical microphone structure with regard to particles and fluids, but also to use its low stress sensitivity for minimizing the micromechanical component and for lowering its production costs.
When referring to the at least one piezoelectric layer, a material layer is described, which has a charge/voltage at its oppositely oriented surfaces when subjected to a mechanical force or to mechanical stress. Examples of a piezoelectric material of the at least one piezoelectric layer particularly are aluminum nitride (AlN), zinc oxide (ZnO), and lead zirconate titanate (PZT). However, it is pointed out that the ability to develop the at least one piezoelectric layer is not restricted to the use of the materials described here.
For example, the at least one polymer mass may be, or may include, a gel, a molding mass, an underfill material and/or a glob top material. Thus, it is possible to use more cost-effective and more easily processable materials for the present invention.
In particular, the micro-electromechanical microphone structure may include at least one bending-beam substructure, which encompasses the respective at least one piezoelectric layer. Such a bending-beam substructure is less sensitive to stress than a diaphragm, and is therefore better suited for the packaging according to the present invention with the aid of the at least one polymer mass.
In an advantageous specific embodiment of the micromechanical component, the micro-electromechanical microphone structure includes a first outer electrode, a second outer electrode, an intermediate electrode situated between the first outer electrode and the second outer electrode, and a first piezoelectric layer and a second piezoelectric layer as the at least one piezoelectric layer. A first intermediate volume between the first outer electrode and the intermediate electrode is at least partially filled with the first piezoelectric layer, and a second intermediate volume between the intermediate electrode and the second outer electrode is at least partially filled with the second piezoelectric layer. As a result, the micro-electromechanical microphone structure may have a relatively simple design and is therefore easily able to be developed on the substrate. In addition, such a micro-electromechanical microphone structure has an advantageous robustness with regard to mechanical stress and may therefore be packaged to good effect using the at least one polymer mass, which contacts at least the partial outer surface of the substrate fitted with the micro-electromechanical microphone structure.
Preferably, at least an edge region of the micro-electromechanical microphone structure is anchored on the substrate while at least one self-supporting area of the micro-electromechanical microphone structure at least partially spans a cavity or recess developed in the substrate. The micro-electromechanical microphone structure is thus well suited for executing a microphone function.
In another advantageous specific embodiment of the micromechanical component, the substrate fitted with the micro-electromechanical microphone structure is attached, either directly or indirectly, to a carrier side of a carrier, and the at least one polymer mass covers the carrier side of the carrier over at least part of its surface. The substrate fitted with the micro-electromechanical microphone structure may also be attached to the carrier side of the carrier via an interposer or an intermediate substrate. Attaching the conventional cover to the carrier with the aid of an individual process or a batch process from the related art is therefore not necessary in order to cover the carrier side fitted with the substrate.
A first depression may possibly be developed adjacent to the micro-electromechanical microphone structure in the carrier side of the carrier. In the same way, a second depression or an uninterrupted recess may be developed adjacent to the micro-electromechanical microphone structure in the interposer or in the intermediate substrate. It is therefore still possible to provide a sufficient volume (back volume) for excellent acoustics of the micro-electromechanical microphone structure even if the entire micromechanical component has a relatively small design. (A back volume that is too small may acoustically act like a spring and may thus reduce the deflection.)
For example, a maximum height of the at least one polymer mass perpendicular to the carrier side of the carrier may at least be greater than a distance of the substrate from the carrier side of the carrier. In particular, the maximum height of the at least one polymer mass perpendicular to the carrier side of the carrier may be greater than or equal to a sum of a height of the substrate perpendicular to the carrier side of the carrier and the distance of the substrate from the carrier side of the carrier. The substrate fitted with the micro-electromechanical microphone structure may thus be easily embedded into the at least one polymer mass to such a depth that only an active side of the micro-electromechanical microphone structure is freely exposed.
In an advantageous further refinement of the micromechanical component, a depression framing the substrate fitted with the micro-electromechanical microphone structure is developed in a surface that is pointing away from the carrier side of the carrier and is formed by the at least one polymer mass. The depression is able to be used for the reliable insertion of a sealing ring so that the part of the packaging developed from the at least one polymer mass is able to form a fluid-tight and/or air-tight, and especially an acoustically tight, package together with other package components.
The advantages described above may be likewise provided in a microphone having such a micromechanical component.
In addition, the execution of a corresponding method for packaging a substrate having a micro-electromechanical microphone structure that includes at least one piezoelectric layer also provides the afore-described advantages. It is expressly pointed out that the method according to the afore-described specific embodiments of the micromechanical component is able to be further refined.
Additional features and advantages of the present invention will be described in the following text on the basis of the figures.
The micromechanical component schematically shown in
The micromechanical component of
In the specific embodiment of
In addition to substrate 10 fitted/developed with micro-electromechanical microphone structure 12, at least one further semiconductor device 28 such as an application-specific integrated circuit (ASIC) may optionally be attached to carrier side 24 of carrier 26 (e.g., via at least one flip chip connection and/or bond connection). Moreover, further semiconductor device 28 may be electrically linked to carrier 26 by way of at least one electrical connection 30 such as via at least one wire connection 30, for example, in particular to at least one through-connection 31 developed in carrier 26. The at least one electrical connection/wire connection 30 may be surrounded by a respective dielectric sheath in order to improve an electrical insulation of the at least one electrical connection/wire connection 30, so as to prevent parasitic effects or to avoid ageing processes.
The at least one polymer mass 18 covers carrier side 24 of carrier 26 over at least parts of its surface. The at least one polymer mass 18 may thereby be utilized for protecting the at least one flip chip connection 22 and/or bond connection between substrate 10 and carrier side 24; the at least one flip chip connection and/or bond connection between additional semiconductor device 28 and carrier side 24; and/or the at least one electrical connection 30. In particular, a maximum height h of the at least one polymer mass 18 perpendicular to carrier side 24 of carrier 26 may be greater than or equal to a sum of a height/length | of substrate 10 (perpendicular to carrier side 24 of carrier 26) and a distance a of substrate 10 from carrier side 24 or carrier 26. All components attached to/developed on carrier side 24 of carrier 26 may therefore be embedded in the at least one polymer mass 18 to such a depth that (nearly) only active side 14 of micro-electromechanical microphone structure 12 remains exposed.
Optionally, a depression 32 may also be developed adjacent to micro-electromechanical microphone structure 12 in carrier side 24 of carrier 26. Depression 32 ensures a volume of sufficient size (back volume) for excellent acoustics of micro-electromechanical microphone structure 12.
As a further refinement to that of
The micromechanical component of
Carrier 26 is attached (e.g., via at least one flip chip connection 38 and/or bond connection and/or soldered connection) to a carrier board 40 (such as a circuit board). In addition, a cover 42 such as the housing of a mobile telephone, spans a surface 44 which is pointing away from carrier side 24 of carrier 26 and is formed by the at least one polymer mass 18. Preferably, cover 42 has a sound opening 46, which lies adjacent to active side 16 of micro-electromechanical microphone structure 12. Preferably, sound opening 46 terminates in a volume framed by a sealing ring 48, sealing ring 48 being inserted/mounted between surface 44, formed by the at least one polymer mass 18, and an inner side of cover 42.
In contrast to the previously described specific embodiment, in the micromechanical component of
The micromechanical component of
In the specific embodiment of
The micromechanical component from
In the specific embodiment of
In a variation of the previously described specific embodiment, in the micromechanical component of
In the specific embodiment of
In the specific embodiment of
All specific embodiments described above may be developed with a small overall volume. In particular, the micro-electromechanical microphone structure in each of the afore-described specific embodiments may include a first outer electrode, a second outer electrode, an intermediate electrode situated between the first outer electrode and the second outer electrode, and a first piezoelectric layer and a second piezoelectric layer as the at least one piezoelectric layer. A first intermediate volume between the first outer electrode and the intermediate electrode is at least partially filled with the first piezoelectric layer, and a second intermediate volume between the intermediate electrode and the second outer electrode is at least partially filled with the second piezoelectric layer. In the same way, the micro-electromechanical microphone structure may have at least one bending-beam substructure which in each case includes at least the first outer electrode, the first piezoelectric layer, the intermediate electrode, the second piezoelectric layer and the second outer electrode. Preferably, at least one edge region of the micro-electromechanical microphone structure is anchored on the substrate while at least one self-supporting area of the micro-electromechanical microphone structure at least partially spans a cavity or recess developed in the substrate.
In the afore-described specific embodiments, the at least one polymer mass 18 may be, or may include, a gel, a molding mass, an underfill material and/or a glob top material. However, it is pointed out that a producibility of the micromechanical components is not restricted to the use of a specific polymer material.
The present method includes at least one method step S1 in which at least a portion of a packaging of the substrate fitted with the micro-electromechanical microphone structure is developed from at least one polymer mass. To do so, the at least one polymer mass is applied directly onto at least a partial outer surface of the substrate fitted with the micro-electromechanical microphone structure. An active side (sound-receiving side), on which sound waves may impinge during an operation of the later micro-electromechanical microphone structure, remains uncovered by the at least one polymer mass or will be exposed from the at least one polymer mass following method step S1. The active side may be protected, especially while the at least one polymer mass is deposited, with the aid of a (flexible) stamp, a foil or an (easily removable) polymer material such as with the aid of a thermally decomposable polymer material.
The at least one polymer mass is able to be applied via an injection process (injection molding), for example, or via a dispensing process. In particular, the at least one polymer mass may be/include a gel, a molding mass, an underfill material, and/or a glob top material. It is pointed out that an executability of the method described here is not restricted to the use of a specific polymer material.
In an optional method step S2, which is able to be carried out prior to developing the packaging (i.e. prior to method step S1), the substrate fitted with the micro-electromechanical microphone structure is attached directly or indirectly to a carrier side of a carrier. The substrate fitted/developed with the micro-electromechanical microphone structure, for example, is able to be attached/bonded to the carrier or to an intermediate component such as especially an interposer, via a flip chip assembly/a flip chip process, for instance. At least one flip chip connection (bump connection, stud-bump connection, solder connection), for example, and/or at least one bonding connection (wafer bonding connection) is/are formed between the substrate and the carrier/intermediate component. At least one electrical connection, in particular a wire connection, is also able to be developed between the substrate/a further semiconductor device and the carrier/intermediate component. Subsequently, the carrier side of the carrier is able to be covered across at least part of the surface with the at least one polymer mass in method step S1. Preferably, the at least one polymer mass is deposited up to a maximum height (perpendicular to the carrier side of the carrier) of at least a distance of the substrate fitted with the micro-electromechanical microphone structure from the carrier side of the carrier.
For example, the at least one polymer mass is able to be deposited up to a maximum height (perpendicular to the carrier side of the carrier) that is greater than or equal to a sum of a height/length of the substrate (perpendicular to the carrier side of the carrier) and the distance of the substrate fitted with the micro-electromechanical microphone structure from the carrier side of the carrier. In an optional method step S3, a depression, which frames the substrate (fitted with the micro-electromechanical microphone structure), is subsequently able to be developed in a surface that is pointing away from the carrier side of the carrier and that is developed from the at least one polymer mass, the depression later ensuring a reliable hold for a sealing ring introduced therein.
In a further optional method step S4, which is likewise able to be carried out prior to developing the packaging (i.e. prior to method step S1), the at least one electrical connection, in particular the at least one wire connection, is surrounded by a dielectric sheath (prior to applying the at least one polymer mass) in order to improve an electrical insulation of the at least one electrical connection/wire connection, to restrict parasitic effects, or to prevent ageing processes. The at least one dielectric sheath, for example, is able to be applied with the aid of an atomic layer deposition (ALD).
| Number | Date | Country | Kind |
|---|---|---|---|
| 102016208325.2 | May 2016 | DE | national |
