US-12628566-B2 - Micromechanical component, sound transducer device, and method for producing a micromechanical component

US12628566B2US 12628566 B2US12628566 B2US 12628566B2US-12628566-B2

Abstract

A micromechanical component for a sound transducer device. The micromechanical component includes a substrate, a diaphragm, at least one piezoelectric element, and at least one electrical contact connection. The diaphragm can vibrate and is connected to the substrate. The at least one piezoelectric element is disposed between the diaphragm and the substrate and is connected to the diaphragm. The at least one piezoelectric element is designed to produce and/or detect vibrations of the diaphragm in the ultrasonic range. The at least one electrical contact connection is electrically connected to the at least one piezoelectric element. The micromechanical component can be connected, using flip chip technology, to a control circuit such that the at least one piezoelectric element can be electrically connected to the control circuit by means of the at least one electrical contact connection.

Inventors

Florian Herzog
Jochen Reinmuth

Assignees

ROBERT BOSCH GMBH

Dates

Publication Date: 20260512
Application Date: 20210818
Priority Date: 20200915

Claims (13)

1 . A micromechanical component for a sound transducer device, comprising: a substrate; a vibrating diaphragm connected to the substrate; at least one piezoelectric element arranged between the diaphragm and the substrate and connected to the diaphragm, wherein the at least one piezoelectric element is configured to produce and/or detect vibrations of the diaphragm in an ultrasonic range; and at least one electrical contact connection electrically connected to the at least one piezoelectric element, wherein the micromechanical component is configured to be connected, using flip chip technology, to a control circuit such that the at least one piezoelectric element can be electrically connected to the control circuit using the at least one electrical contact connection; wherein the substrate is connected to the diaphragm and/or the at least one piezoelectric element using a bonded connection, wherein a circumferential insulation trench is formed in the substrate around at least one bonded connection.
2 . The micromechanical component according to claim 1 , wherein the bonded connection includes at least one of aluminum and germanium.
3 . The micromechanical component according to claim 1 , wherein an electrically insulating material is formed on a surface of the substrate in a region of the insulation trench.
4 . The micromechanical component according to claim 1 , wherein the at least one electrical contact connection includes at least one of at least one solder ball and a first conductive path on a side of the substrate facing away from the diaphragm.
5 . The micromechanical component according to claim 1 , wherein at least one of the at least one piezoelectric element is electrically connected to at least one bonded connection using a second conductive path, wherein a material of the second conductive path includes aluminum.
6 . The micromechanical component according to claim 1 , wherein the at least one piezoelectric element is surrounded by a completely circumferential bond frame, wherein the bond frame connects the substrate to the diaphragm.
7 . A sound transducer device, comprising: a micromechanical component, including: a substrate, a vibrating diaphragm connected to the substrate, at least one piezoelectric element arranged between the diaphragm and the substrate and connected to the diaphragm, wherein the at least one piezoelectric element is configured to produce and/or detect vibrations of the diaphragm in an ultrasonic range, and at least one electrical contact connection electrically connected to the at least one piezoelectric element, wherein the substrate is connected to the diaphragm and/or the at least one piezoelectric element using a bonded connection, wherein a circumferential insulation trench is formed in the substrate around at least one bonded connection; and a control circuit, wherein the micromechanical component is connected, using flip chip technology, to the control circuit, and wherein the at least one piezoelectric element of the micromechanical component is electrically connected to the control circuit using the at least one electrical contact connection.
8 . A method for producing a micromechanical component, comprising the following steps: providing a substrate; forming a vibrating diaphragm connected to the substrate; providing at least one piezoelectric element arranged between the diaphragm and the substrate and connected to the diaphragm, wherein the at least one piezoelectric element is configured to produce and/or detect vibrations of the diaphragm in an ultrasonic range; and forming at least one electrical contact connection electrically connected to the at least one piezoelectric element, wherein the micromechanical component is configured to be connected, using flip chip technology, to a control circuit such that the at least one piezoelectric element can be electrically connected to the control circuit using the at least one electrical contact connection; wherein the substrate is connected to the diaphragm and/or the at least one piezoelectric element using a bonded connection, wherein a circumferential insulation trench is formed in the substrate around the bonded connection.
9 . The method according to claim 8 , wherein the forming of the vibrating diaphragm connected to the substrate includes the following steps: forming an etch stop layer on a surface of a carrier substrate; forming a diaphragm layer on the etch stop layer; and at least partially removing the carrier substrate, at least in part using etching methods.
10 . The method according to claim 9 , wherein the carrier substrate and the etch stop layer are removed only partially and are structured at least in an edge region.
11 . The method according to claim 8 , wherein the diaphragm is connected to the substrate using the bonded connection.
12 . The method according to claim 11 , wherein for bonding, a layer including aluminum is used on the diaphragm side, and a layer including germanium is used on the substrate side.
13 . The method according to claim 12 , wherein an electrically insulating material is formed on a surface of the substrate in a region of the insulation trench.

Description

FIELD The present invention relates to a micromechanical component for a sound transducer device, to a sound transducer device and to a method for producing a micromechanical component for a sound transducer device. The micromechanical component may also be designed for use as a spatially resolved material detector, as an optical mirror, or as an interferometer. BACKGROUND INFORMATION Ultrasonic transducers may be designed as micro-electromechanical systems (MEMS). Such devices that emit and detect ultrasonic waves by means of the piezoelectric effect are referred to as piezoelectric micromachined ultrasonic transducers (PMUTs). An exemplary PMUT with low stress sensitivity is described in International Patent Application No. WO 2016/106153 A1. PMUTs are characterized by a compact structure and a high resolution. Piezoelectric elements produce vibrations of diaphragms and surrounding liquids, whereby ultrasonic waves are emitted. Reflected ultrasonic waves are detected by means of the piezoelectric elements. Due to the semiconductor production processes, many individual PMUTs can be combined into an array on one chip particularly easily and inexpensively. By using an array of such PMUTs, the environment can thereby be mapped. MEMS PMUTs are therefore particularly suitable for imaging methods, for example in medical technology. An exemplary structure of an ultrasonic head 7 is illustrated in FIG. 1, wherein an array comprising a plurality of PMUT cells 3 is formed. By means of a piezoelectric layer 2, a thin diaphragm 1 is excited to vibrations, which are transferred to a gel 8. Each individual PMUT cell 3 is supplied with an electrical signal, which is delivered by a control chip or application-specific integrated circuit (ASIC) chip 5. In a traditional approach, two chips 4, 5 are typically combined. On a first MEMS chip 4, the array with the PMUT cells 3 is provided. A second ASIC chip 5 is placed next to the MEMS chip 4 on a common substrate. The many electrical connections between the MEMS chip 4 and the ASIC chip 5 are produced by bonding wires 6, which are each placed at the edges of the two chips 4, 5. In this arrangement, in an array, the electrical connections by means of bonding wires 6 can take place only at the edge of the MEMS chip 4. The length of the edge of the MEMS chip 4 scales with the diameter of the MEMS chip 4, while the number of possible PMUTs 3 on the MEMS chip 4 scales with the surface area thereof, i.e., the square of the diameter. This makes contacting the MEMS chip 4 difficult, especially for large arrays. Furthermore, for the traditional wire bonding technique, the ASIC chip 5 must be arranged next to the MEMS chip 4 if possible. Due to the parallel arrangement of the two chips 4, 5, the ultrasonic head 7 becomes larger than would be necessary for technical reasons. In addition, the bonding wires 6 must be protected while the ultrasonic signal of the PMUTs 3 should be transmitted as undisturbed as possible. This requires a complex structure. A defined gelling process, wherein a gel 8 is applied to the diaphragm 1, is difficult with such an arrangement. In an alternative approach illustrated in FIG. 2, MEMS PMUTs 3 are produced by means of additional steps on a finished ASIC wafer above the ASIC chip. By means of suitable measures, a direct electrical connection is produced between the ASIC chip and the PMUTs 3. Thus, very large PMUT arrays can be produced on the one hand and more favorable, smaller design concepts can be achieved on the other hand. This concept results in limitations in the production process of the PMUT cells 3 if the latter are to be arranged on an ASIC chip. For example, typical ASIC wafers may not be heated above 400° C. for an extended period. This makes it difficult to produce inexpensive and performant PMUTs. In particular, piezoelectric layers with high piezo coefficients are difficult to produce. Furthermore, the ASIC production process must be adjusted if electrical contacts are to be produced between the PMUTs and the ASICs. This reduces the flexibility of the system. If a new ASIC process that provides advantages comes onto the market, the process must first be adjusted before the process can be used. Furthermore, the ASIC chip and the MEMS chip must be the same size. If one of the chips is larger by default, the size of the smaller type must be adjusted accordingly, whereby additional costs are incurred. SUMMARY The present invention provides a micromechanical component for a sound transducer device, a sound transducer device, and a method for producing a micromechanical component for a sound transducer device. Preferred embodiments of the present invention are disclosed herein. According to a first aspect, the present invention accordingly relates to a micromechanical component for a sound transducer device. According to an example embodiment of the present invention, the micromechanical component comprises a substrate, a diaphragm, at least one p