DE202023102447U1 - Micromechanical ultrasonic transducer - Google Patents

Abstract

Micromechanical ultrasonic transducer, characterized in that the micromechanical ultrasonic transducer has a plurality of base cells which are arranged at least partially in a grid-like manner and are contacted with one another and have at least one electrode and at least one electromechanical transducer, a large number of base cells being arranged on a substrate and forming a chip, the base cells being at substrate level are not connected to one another and that the micromechanical ultrasonic transducer is delimited at the edge by at least one separation line.

Description

The invention relates to a micromechanical ultrasonic transducer according to the first claim.

Micromachined ultrasonic transducers (MUTs) consist of mechanical and electrical elements as well as electromechanical transducers. The natural frequencies of the converter are determined by the geometry of the mechanical components (e.g. a membrane). Electromechanical converters transform electrical energy into mechanical energy and vice versa, for example using electrostatics, piezoelectrics or other conversion methods. The electrical components are electrical conductors. In prior art MUTs, these basic components are laid out in a layout.

The chip size and the electrical wiring of MUTs is defined in the lithography levels. After production using microtechnology at the wafer level, the chips are separated, for example by sawing. The chip size for a MUT layout cannot be changed and the electrical wiring of the individual converter elements on the chip cannot be adapted.

The pamphlet U.S. 7,531,371 B2 describes a method and relates to multi-area arrays that differ in terms of their spatial arrangement, wherein micro-components are provided on one or more wafers. The individual chips are then separated and positioned on a substrate. The connections between the individual chips are then established. The disadvantage is that the electronic configuration is fixed in the layout and can no longer be adjusted later.

In the pamphlet EP 3 684 081 B1 describes a manufacturing process for multiple MEMS transducers. A large number of MEMS sound transducers are arranged on a wafer. These are connected to each other by piezo elements that are fixed in a casting compound. Depending on the requirements of the specific application, the required piezo elements are released so that they become active. This release is done by etching or laser treatment. The disadvantage is that the converters have to be encapsulated with a molding compound. The sawn chips are "made manageable" by the molding compound and subsequently arranged to form a larger chip (sound transducer).

The related prior art solutions define the interconnection of individual transducer elements on the substrate by an electrical connection by means of a thin film metal that is photolithographically defined and not adaptable. Due to the specified electrical contacts and the positions of the transducer elements, the chip size is fixed in the design. The wafer is sawn according to the dimensions of the chip. The sawing dimension is defined in the design and cannot be adapted.

The disadvantage of the prior art is that customer-specific requests for their own chip geometries and connection types of the transducer elements, such as the number of independently operating electrical channels or the shape of a channel as a line, rectangular area, circular area, ring, etc., can only be met by a new design and a new fabrication can be solved. The basic costs (setup costs) are very high and the production time for this is long. Economical systems cannot be offered for small and medium quantities. The technology design according to the state of the art defines the type of connection and the chip size in the lithography levels during production using microtechnology. The basic repeating elements of the MUTs correspond to the image of a chip. According to the state of the art, the electrical conductor tracks of the individual channels are specified in the design at the wafer level and cannot be changed later. Due to the lithographic structuring of the elements, the mechanically movable membranes with the electrodes per channel are also not modular, cannot be adapted or subsequently changed. The chip cannot be separated at any position, otherwise the functionality will be destroyed. There are new setup costs for each custom design.

The object of the invention is to develop a micromechanical ultrasonic transducer that allows micromechanical ultrasonic transducers to be modularly adapted at the substrate level in terms of chip size and channel shape and number, and to be made available as "off the shelf" components with one-off setup costs.

This problem is solved with the features of the first claim for protection.

Advantageous refinements result from the dependent claims.

In a method for producing a micromechanical ultrasonic transducer, the micromechanical ultrasonic transducer is formed from a plurality of modular basic cells, a plurality of basic cells being arranged in a grid on a substrate and each basic cell having at least one electrode and at least one electromechanical has niche converter. A multiplicity of basic cells form a chip, the chip being separated individually from the substrate by separating it along at least one separation line, depending on the requirements. According to the method, in a first variant of the invention, the base cells are not contacted with one another until after the microtechnological production. In a second variant, the basic cells are electrically connected to one another at the level of the thin-film electrodes and their electrical connection is individually separated after micro-technological processing.

The micromechanical ultrasonic transducers are manufactured as semi-finished products with an identical layout and are subsequently separated according to the individual requirements, so that a large number of basic cells are available depending on the requirements and contacting of the basic cells takes place or is canceled according to the requirements.

The basic cells are advantageously produced on the substrate in the form of a wafer using thin-film deposition and a lithographic process.

The separating and separating is particularly preferably carried out by sawing along a sawing line or by breaking edges. The distance between several saw lines or break edges is not necessarily a multiple of the dimensions of the basic cells.

The separation results in an actively usable chip area, with the actively used chip area corresponding to a multiple of a basic cell and being connected to one another or separated from one another. Depending on the isolation process, a passive chip area can also be created. The passive chip area is in the area of the at least one singulation line and cannot be used for the acoustic function of the chip.

The micromechanical ultrasonic transducer according to the invention has a plurality of basic cells which are arranged at least partially in a grid-like manner and are contacted with one another and have at least one electrode and an electromechanical transducer, a multiplicity of basic cells being arranged on a substrate and forming a chip and the micromechanical ultrasonic transducer being delimited at the edge by at least one separation line. This is possible because the basic cells are not connected to each other at the substrate level. After singulation, every basic cell that is not in the area of the singulation line (fracture edge, saw line, etc.) is functionally present on the chip. Depending on the design, the basic cells are either electrically connected to one another or separated from one another at the substrate level. The electrical functionalities, such as electrical connections, are assigned to one another after wafer processing by separating the connections or by contacting the base cells with one another.

The separating line is preferably in the form of a straight line, a free form or a radius/circular shape.

In a preferred embodiment, the electrical level is completely present for each basic cell.

In one configuration of the ultrasonic transducer, the chip has a passive chip area and an actively usable chip area, the actively used chip area corresponding to a multiple of a basic cell and the passive chip area being in the region of the at least one singulation line. It is also possible to configure a chip without a passive chip area.

The basic cells are arranged in a grid and, in one possible configuration, extend next to one another along a first direction and an orthogonal second direction. However, other arrangements are also possible, for example a free form or a radially symmetrical arrangement.

Depending on how the basic cells are contacted with one another, the ultrasonic transducer can have a number of channels. The contact is made depending on the requirements of the ultrasonic transducer.

The ultrasonic transducer preferably has at least one electrical channel, one channel being in contact with a further ultrasonic transducer or some other electrical functionality.

Compared to the state of the art, the invention provides basic cells which in turn can only be electrically assigned later at chip or wafer level and the chip areas can be defined after production at substrate level. The presence of the micromechanical ultrasonic transducers in the form of modular base cells allows the basic costs for MUT production to be paid once at substrate level and a larger number of MUT base cells with modularly adaptable chip surfaces and electrical connections, for example the number of channels, to be produced on substrates. Customer-specific MUTs can be processed downstream of the micro-technological production with isolation and electr. interconnection of the substrate are produced. The substrates are available as "off the shelf" components. The production of MUTs for small and medium-sized quantities becomes economical and the delivery times of customer-specific components decrease significantly. SMEs thus gain access to MUT components that were previously only worthwhile for large companies, and new fields of application can be opened up.

The invention is explained in more detail below using an exemplary embodiment and associated drawings.

• 1 eine Basiszelle eines elektromechanischen Ultraschallwandlers,
• 2 einen dreikanaligen Ultraschallwandler,
• 3 einen zweikanaligen Ultraschallwandler,
• 4 einen einkanaligen Ultraschallwandler,
• 5 Gruppe von Basiszellen, die während der mikrotechnologischen Produktion auf Ebene der Dünnschichtelektroden elektrisch miteinander verbunden sind und in einzelne elektrische Kanäle getrennt werden können,
• 6 Individuelle Vereinzelung der Chip aus dem Waferverbund durch Auftrennen,
• 7 Individuelle Vereinzelung der Chip aus dem Waferverbund durch Auftrennen mit funktionsfähig dargestellten Basiszellen,
• 8 eine alternative Trennung aus dem Waferverbund,
• 9 eine weitere alternative Auftrennung der Basiszellen.

Show it:

• 1 a basic cell of an electromechanical ultrasonic transducer,
• 2 a three-channel ultrasonic transducer,
• 3 a two-channel ultrasonic transducer,
• 4 a single-channel ultrasonic transducer,
• 5 Group of basic cells that are electrically connected to each other during the microtechnological production at the level of the thin-film electrodes and can be separated into individual electrical channels,
• 6 Individual isolation of the chip from the wafer assembly by separating,
• 7 Individual isolation of the chip from the wafer assembly by separating with basic cells shown functional,
• 8th an alternative separation from the wafer composite,
• 9 another alternative separation of the basic cells.

In the 1 a basic cell 1 of an electromechanical ultrasonic transducer is shown, the basic cell having a substrate 2 and one or more electrodes 3 arranged thereon, an individual or a group of electromechanical transducers 4 and optionally further electrical contacts 5 as thin layers, which are produced by thin layer deposition and photolithographic processes Substrate level were produced.

The 2 , 3 and 4 show an arrangement of nine basic cells 1 in a 3×3 arrangement of the basic cells, which can be individually electrically connected via contacts 6 after the micro-technological processing. In 2 a three-channel ultrasonic transducer is shown with three basic cells per channel. In the 3 is a two-channel ultrasonic transducer with three or six basic cells 1 per channel. 4 shows a single-channel ultrasonic transducer with nine basic cells 1 per channel.

An alternative embodiment of the base cells is in the 5 shown.
The basic cells 1 are designed in such a way that they are electrically connected to one another via a contact area 7 during the microtechnological production at the level of the thin-film electrodes. Only after their micro-technological processing is the electrical connection separated individually.

In the 6 and 7 shows the individual singulation of the chip from the substrate/wafer composite 2 by separating, for example sawing, along a singulation line 8, whereby an actively usable chip area 9, a sawn and unused chip area 10 and a passive chip area 11 arise. The actively used chip area 9 corresponds to the multiple of a basic cell 1. 7 shows the actively usable chip area 9, which lies within the singulation line 8.

8th shows an alternative individual singulation of the chip and its basic cells 1 from the substrate/wafer composite 2 by cutting along the singulation line 8. The singulation line 8 is circular. The separation results in a passive chip area 11 and an actively usable chip area 9. The actively used chip area 9 here also corresponds to the multiple of a basic cell 1. The basic cells 1 are connected to one another by electrical contacts 6. The ultrasonic transducer has two channels, each of the channels having an electrical contact from the chip to a further electrical functionality such as electronics or a printed circuit board.

9 shows the individual separation of the basic cells 1 from the substrate/wafer assembly 2 by separating, for example sawing, along a straight separation line 8 in the form of a sawing line, no passive chip surface being produced as a result of optimal division. The actively used chip area 9 corresponds to the multiple of a basic cell 1. The basic cells 1 can be connected to one another by electrical contacts (not shown).

Reference List

1

base cell

2

substrate/wafer composite

3

electrode

4

electromechanical converter

5

optional contact

6

electrical contact/contacting

7

contact area

8th

singulation line

9

actively used chip area

10

unused sawn chip area

11

passive chip area

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US7531371B2 [0004]
• EP 3684081 B1 [0005]

Claims (7)

Micromechanical ultrasonic transducer, characterized in that the micromechanical ultrasonic transducer has a plurality of base cells which are arranged at least partially in a grid-like manner and are contacted with one another and have at least one electrode and at least one electromechanical transducer, a large number of base cells being arranged on a substrate and forming a chip, the base cells being at substrate level are not connected to one another and that the micromechanical ultrasonic transducer is delimited at the edge by at least one separation line. Micromechanical ultrasonic transducer claim 1 , characterized in that at least one separating line is designed in the form of a straight line, free form or a radius/circular. Micromechanical ultrasonic transducer according to one of Claims 1 or 2 , characterized in that the electrical level is complete for each basic cell. Micromechanical ultrasonic transducer according to one of Claims 1 until 3 , characterized in that the chip has a passive chip area and an actively usable chip area, the actively used chip area corresponding to a multiple of a basic cell and the passive chip area being in the region of the at least one singulation line. Micromechanical ultrasonic transducer according to one of Claims 1 until 4 , characterized in that the basic cells are arranged in a grid and extend juxtaposed along a first direction and/or along an orthogonal second direction. Micromechanical ultrasonic transducer according to one of Claims 1 until 5 , characterized in that the ultrasonic transducer has a plurality of channels depending on the contacting of the base cells with one another. Micromechanical ultrasonic transducer according to one of Claims 1 until 6 , characterized in that the ultrasonic transducer has at least one electrical channel and one channel is contacted with a further ultrasonic transducer or some other electrical functionality.