DE102018209512A1 - Micromechanical system - Google Patents

Abstract

Micromechanical system (100), comprising: - at least one seismic mass (10) movable in a deflection direction; and- at least one frame-shaped spring element (20) which can be deflected in a direction different from the deflection direction of the seismic mass (10) due to a deflection of the seismic mass (10); and a stop device (30) for striking the spring element (20) in the event of a mechanical overload acting on the micromechanical system (100).

Description

The invention relates to a micromechanical system. The invention further relates to a method for producing a micromechanical system.

State of the art

Micromechanical inertial sensors, for example for the detection of acceleration or rotation rate, as well as micromechanical micromirrors are generally based on spring-mass systems. There are movable structures that are suspended from springs and can deflect within certain areas. In normal operation of the sensors mentioned, these deflections are small enough that mechanical stops do not occur. In the event of mechanical overload, e.g. caused by external linear or rotational accelerations as well as by excessive electrostatic forces, it can happen that parts of the moving structure strike mechanically.

Mechanical striking can take place between two movable structures and between a movable and a fixed structure. If such contact occurs, there is a risk of damage or particle formation.

Another unfavorable case is when there is no movement-restricting structure in the event of an overload, which can result in large deflections which, under certain circumstances, can lead to e.g. Springs break because the mechanical stresses exceed the breaking stress limit of the material used.

In order to avoid these two unfavorable situations, so-called mechanical stops are usually used, which allow a defined braking of the deflecting structures. Ideally, these stops should be designed so that a good compromise between sufficient mobility and early prevention of excessive deflections is achieved.

1 shows such a structure with a seismic mass in a highly simplified manner 10 , in the x -Direction (deflection direction) is movable and a frame-shaped spring element 20 having. A dashed border around the seismic mass 10 indicates the geometric rest position of the seismic mass 10 on. The spring element 20 is also with an immobile connecting element 11 connected.

In 2 is a deflection of the seismic mass 10 indicated from the rest position, whereby due to a movement of the seismic mass 10 in x -Direction of the frame-shaped spring element 20 inside, ie in y Direction works and strikes itself before the seismic mass 10 to the stop elements 31 struck.

In 3 can be seen that the seismic mass 10 to the stop elements 31 is struck, but at this time the frame-like spring element may already be 20 has been damaged or caused particle formation.

The 1 to 3 thus show a schematic representation of a movable structure in the form of a seismic mass 10 which, due to its deflection, also deflects another filigree bar structure. The stop elements 31 form "target stops". It can be seen that the filigree bar structure is aligned with the direction of deflection of the seismic mass 10 deflects different directions, whereby the filigree structure collides with itself before the target stops can act.

• - dass der notwendige Platz für ausreichend stabil dimensionierte Anschläge nicht vorhanden ist
• - dass nicht alle an der Auslenkung beteiligten Teilstrukturen in die gleiche Hauptrichtung auslenken, sondern aufgrund von Schrägbewegungen und/oder Umlenkungseffekten zum Teil schräg, quer oder gar rückwärtig dazu gerichtet sind
• - dass es über Layout-Regeln prozesstechnisch bedingte Vorgaben bezüglich minimal möglicher Anschlagsgaps gibt, und diese in gewissen Situationen nicht wirksam sein können, wenn z.B. Hebelarme auslenkungsverstärkend wirken.

Stops in sensor design are usually placed in such a way that movements in the main direction of movement of the deflecting mass are prevented. However, difficulties that often arise are:

• - That the necessary space for sufficiently sturdy stops is not available
• - That not all of the substructures involved in the deflection deflect in the same main direction, but are directed partly obliquely, transversely or even backwards due to oblique movements and / or deflection effects
• - That there are process-related specifications regarding minimum possible stop gaps, which cannot be effective in certain situations if, for example, lever arms reinforce the deflection.

A coupling structure in the form of a so-called “coupling cross” of a micromechanical inertial sensor has ended US 2012/247206 A known. A basic plan view of such a coupling structure is shown in 4 shown. Two seismic masses can be seen 10 by means of the coupling structure in the form of a frame-shaped spring element 20 to an immovable connection element 11 are connected.

Disclosure of the invention

An object of the present invention is to provide an improved micromechanical system.

• - wenigstens eine in eine Auslenkrichtung bewegliche seismische Masse; und
• - wenigstens ein rahmenförmiges Federelement, das aufgrund einer Auslenkung der seismischen Masse in eine von der Auslenkrichtung der seismischen Masse unterschiedliche Richtung auslenkbar ist; und
• - eine Anschlagseinrichtung zum Anschlagen des Federelements im Falle eines Einwirkens einer mechanischen Überlast auf das mikromechanische System.

According to a first aspect, the task is solved with a micromechanical system, comprising:

• - At least one seismic mass movable in a deflection direction; and
• - At least one frame-shaped spring element which can be deflected in a direction different from the deflection direction of the seismic mass due to a deflection of the seismic mass; and
• - A stop device for striking the spring element in the event of a mechanical overload acting on the micromechanical system.

• - Bereitstellen wenigstens einer in eine Auslenkrichtung beweglichen seismischen Masse;
• - Bereitstellen wenigstens eines rahmenförmigen Federelements, das aufgrund einer Auslenkung der seismischen Masse in eine von der Auslenkrichtung der seismischen Masse unterschiedliche Richtung auslenkbar ist; und
• - Bereitstellen einer Anschlagseinrichtung zum Anschlagen des Federelements im Falle eines Einwirkens einer mechanischen Überlast auf das mikromechanische System.

According to a second aspect, the object is achieved with a method for producing a micromechanical system, comprising the steps:

• - Providing at least one seismic mass movable in a deflection direction;
• Providing at least one frame-shaped spring element which can be deflected in a direction different from the deflection direction of the seismic mass due to a deflection of the seismic mass; and
• - Providing a stop device for striking the spring element in the event of a mechanical overload acting on the micromechanical system.

Preferred developments of the micromechanical system are the subject of dependent claims.

An advantageous development of the micromechanical system is characterized in that the stop device has a stop element arranged on an anchoring element within the frame-shaped spring element. In this way, stop knobs are provided on an anchoring element which prevent the frame-shaped spring element from striking itself when mechanical overload acts on the micromechanical system. The presence of the anchoring element can also advantageously be used to homogenize an etching environment, which is favorable for the production of homogeneous structures in a manufacturing process of the micromechanical system. In particular, this can minimize edge loss.

Another advantageous development of the micromechanical system is characterized in that the stop element is arranged within the frame-like spring element. In this way, an integral design of the stop elements with the frame-shaped spring element can advantageously be realized. A functional interaction of the stop elements takes place through a suitably designed anchoring element in the interior of the frame-shaped spring element.

Another advantageous development of the micromechanical system is characterized in that at least one stop element is arranged outside the frame-shaped spring element. In this way, an alternative embodiment of the stop element is advantageously provided, which advantageously makes it possible to form an electrical conductor track inside the frame-shaped spring element.

Further advantageous developments of the micromechanical system are characterized in that at least two stop elements are arranged orthogonally to the direction of movement of the seismic mass or that at least two stop elements are arranged obliquely to the direction of movement of the seismic mass. This advantageously supports a high degree of design freedom in the design of the stop device.

Another advantageous development of the micromechanical system is characterized in that the anchoring element is designed without a stop element. This variant can be used in particular for homogenizing the etching environment, it being possible to produce more uniform structures with less edge loss.

The invention is described in more detail below with further features and advantages using several figures. The figures are intended in particular to illustrate the principles essential to the invention and are not necessarily carried out to scale. The same or functionally identical elements have the same reference numerals. For the sake of clarity, it can be provided that not all reference numbers are drawn in all the figures.

Revealed device features result analogously from corresponding disclosed process features and vice versa. This means in particular that features, technical advantages and designs relating to the method for producing a micromechanical system result analogously from corresponding designs, features and advantages relating to the micromechanical system and vice versa.

• 1-3 prinzipielle Ansichten eines bekannten mikromechanischen Systems in verschiedenen Bewegungsphasen;
• 4 eine Draufsicht auf eine herkömmliche Koppelstruktur für einen mikromechanischen Inertialsensor;
• 5 eine Draufsicht auf einen Ausschnitt der herkömmlichen Koppelstruktur von 4;
• 6-9 prinzipielle Ansichten von unterschiedlichen Ausführungsformen eines vorgeschlagenen mikromechanischen Systems; und
• 10 einen prinzipiellen Ablauf einer Ausführungsform eines Verfahrens zum Herstellen eines vorgeschlagenen mikromechanischen Systems.

The figures show:

• 1-3 basic views of a known micromechanical system in different movement phases;
• 4 a plan view of a conventional coupling structure for a micromechanical inertial sensor;
• 5 a plan view of a section of the conventional coupling structure of 4 ;
• 6-9 basic views of different embodiments of a proposed micromechanical system; and
• 10 a basic sequence of an embodiment of a method for producing a proposed micromechanical system.

Description of embodiments

A key idea of the invention is in particular to provide an improved micromechanical system which has improved stop properties.

Stops are typically used along the direction corresponding to the main direction of deflection of the deflecting structure. In the proposed micromechanical system, it is also advantageously possible to protect substructures that move or deflect in directions that deviate therefrom.

The use of stop elements at selected locations that do not correspond to the main direction of movement of the deflecting structure protects areas that can be damaged in conventional systems. Among other things, this can lead to particle formation that is the cause of further error patterns, such as Offset shifts, changes in sensor parameters via temperature and / or service life, etc. come. All of this can be avoided by using the specific stop elements of a micromechanical system described below.

The fixed connection of the stop structures can advantageously also be used as a homogenization of the etching environment of sensitive spring structures. This is advantageous with regard to checking the effects of the so-called edge loss on mechanical properties and for the predictability of modal frequencies (natural frequencies) by simulation.

Furthermore, a dimensioning and the perforation of the fixed connection can also influence a degree of filling of the polycrystalline layer structure, which allows a favorable influence on the global edge loss within the wafer. This can be explained in particular by the fact that the etching gases or plasmas can act with less dynamic or etching rate, the more homogeneous the etching environment is.

5 shows a top view of a left upper section ( 2 , Quadrant) of the conventional coupling structure from 4 , the representation of 5 represents a section of the unprotected original structure. It can be seen that the frame-shaped spring element 20 has an obliquely aligned section in the form of a 45 ° support spring, which with the rigid connecting element 11 connected is.

In the 6 to 9 is the top left quarter of the structure of 5 shown, but each supplemented with a proposed stop device.

6 shows a first embodiment of the micromechanical system 100 , In this case, the seismic mass moves 10 in x Direction a possible deflection of the frame-shaped spring element 20 stopped after a very short distance. As a result, kinetic energy can advantageously only build up to a small extent due to interference acceleration. As a result, the risk of particle formation is lower compared to a situation where there is a longer “run-up distance” before a stop. Due to the early movement restrictions, however, vibration can also occur very early (clipping), which can be unfavorable for a clipping performance from an application perspective.

Another possible problem with this type of implementation is that the striking is not accompanied by a frontal movement but rather by a certain sideways movement relative to the fixed stop. This results in a certain risk of jamming or snagging of the structure, i.e. there is a risk that the structure may not come loose after striking.

This is achieved by means of stop elements 31 that inside the frame-shaped spring element 20 on immovable anchoring elements 30 are anchored. Gap between the stop elements 31 and the frame-shaped spring element 20 and deflections of the frame-shaped spring element 20 are sufficiently different in size so that in normal operation of the micromechanical system 100 no striking of the spring element 20 to the stop elements 31 he follows. However, this can also result in the event of an overload on the micromechanical system, for example as a result of a crash in the vehicle or a falling sensor the micromechanical system 100 , etc., so that in this way the micromechanical system 100 is protected.

7 shows a further implementation of a micromechanical system 100 that of the deflecting structure compared to the embodiment of 6 leaves a larger free space, and thus strikes later. For this, the attack process takes place in comparison to the embodiment of 6 head-on instead. Here are the stop element 31 integral to the interior of the frame-shaped spring element 20 trained with grooves of the anchoring elements 30 interact. Both mentioned disadvantages of the embodiment of 6 are circumvented here, in which case more kinetic energy can build up and there may be an increased risk of particle formation.

In the embodiments of the micromechanical systems 100 of the 6 and 7 are also triangular anchoring elements 30 recognizable, in addition to their function as a permanent connection of the stop elements 31 also perform a function of homogenizing the etching environment, and are useful for a positive influence in the form of an increase in the degree of filling.

The 8th and 9 show top views of alternative embodiments of a micromechanical system 100 , where the corresponding stop elements 31 outside the frame-like spring element 20 are arranged. It would also be conceivable, analogous to the embodiments of the 6 and 7 trained stop elements 31 to be provided (not shown).

The variants of the 6 and 7 also with the variants of 8th and 9 can be combined (not shown).

As a result, with the measures explained above, the seismic mass can be struck in a defined manner 10 to the stop elements 31 can be achieved, thereby the entire micromechanical system 100 is effectively protected.

The proposed micromechanical system can be advantageous 100 can be used for an inertial sensor or for a micromechanical micromirror. An impact of a device equipped with the proposed micromechanical system (for example a mobile phone) advantageously has no disadvantageous consequences for a device equipped with the proposed micromechanical system 100 equipped inertial sensor.

It is not shown in figures that the anchoring elements 30 even without any stop elements 31 can be designed so that in this case an increase in the degree of filling can be realized.

10 shows a basic sequence of an embodiment for producing a micromechanical system 100 ,

In one step 200 is a provision of at least one seismic mass movable in a deflection direction 10 carried out.

In one step 210 is a provision of at least one frame-shaped spring element 20 carried out due to a deflection of the seismic mass 10 in one of the direction of deflection of the seismic mass 10 different direction can be deflected.

In one step 220 is a provision of a stop device for striking the spring element 20 in the event of mechanical overload acting on the micromechanical system 100 carried out.

The order of the steps 200 and 220 is also interchangeable in a suitable manner.

In summary, the present invention provides an improved micromechanical system which realizes a defined stop behavior of the seismic mass on stop elements. This is achieved by so-called "deflection stops", which protect the coupling structure from destruction or at least damage due to deflection of the seismic mass.

Although the invention was described above on the basis of a specific exemplary embodiment, it is in no way limited to it. The person skilled in the art will recognize that a large number of modifications of the proposed micromechanical system are possible in accordance with the principle explained.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included 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

• US 2012247206 A [0011]

Claims (8)

Micromechanical system (100), comprising: - At least one seismic mass (10) movable in a deflection direction; and - At least one frame-shaped spring element (20) which can be deflected in a direction different from the deflection direction of the seismic mass (10) due to a deflection of the seismic mass (10); and - A stop device for striking the spring element (20) in the event of a mechanical overload acting on the micromechanical system (100). Micromechanical system (100) according to Claim 1 , characterized in that the stop device has a stop element (31) arranged on an anchoring element within the frame-shaped spring element (20). Micromechanical system (100) according to Claim 1 or 2 , characterized in that the stop element (31) is arranged within the frame-like spring element (20). Micromechanical inertial sensor (100) according to one of the preceding claims, characterized in that at least one stop element (31) is arranged outside the frame-like spring element (20). Micromechanical system (100) according to one of the preceding claims, characterized in that at least two stop elements (31) are arranged orthogonally to the direction of movement of the seismic mass (10). Micromechanical system (100) according to one of the preceding claims, characterized in that at least two stop elements (31) are arranged obliquely to the direction of movement of the seismic mass (10). Micromechanical system (100) according to one of the preceding claims, characterized in that the anchoring element is designed without a stop element (31). Method for producing a micromechanical system (100), comprising the steps: - Providing at least one seismic mass (10) movable in a deflection direction; - Providing at least one frame-shaped spring element (20) which can be deflected in a direction different from the deflection direction of the seismic mass (10) due to a deflection of the seismic mass (10); and - Providing a stop device (30) for striking the spring element (20) in the event of a mechanical overload acting on the micromechanical system (100).

Images