Patent Publication Number: US-2021165211-A1

Title: Micromechanical component and manufacturing method for a micromechanical component

Description:
CROSS REFERENCE 
     The present application claims the benefit under 35 U.S.C. § 119 of German Patent Application No. DE 102019218468.5 filed on Nov. 28, 2019, which is expressly incorporated herein by reference in its entirety. 
     FIELD 
     The present invention relates to a micromechanical component. The present invention also relates to a manufacturing method for a micromechanical component. 
     BACKGROUND INFORMATION 
     An adjustable micromirror is described in Japan Patent Application No. JP 2009-223165 A, which is to be adjustable with the aid of two meander-shaped springs having sections that are each covered by at least one piezoelectric material, in relation to a mount of the adjustable micromirror. In particular, alternately a bending stress or a tensile stress is to be able to be formed on the sections of the two meander-shaped springs by applying at least one voltage to the at least one piezoelectric material in such a way that the adjustable micromirror is adjusted in relation to its mount with the aid of an effectuated mirror-symmetrical deformation of the two meander-shaped springs. 
     An object of the present invention is to provide a simplified micromechanical component. 
     SUMMARY 
     In accordance with an example embodiment of the present invention, a micromechanical component including a mount, an adjustable part, and a meander-shaped spring is provided. The meander-shaped spring is attached in this case at an outer end of the meander-shaped spring directly or indirectly to the mount and at an inner end of the meander-shaped spring directly or indirectly to the adjustable part. An actuator device is formed on an outer surface of the meander-shaped spring and/or in the meander-shaped spring in such a way that periodic deformations of the meander-shaped spring are excitable with the aid of the actuator device, by which the adjustable part is adjustable in relation to the mount around a rotational axis of the adjustable part. In addition, the mechanical component includes a torsion spring. This torsion spring is situated on a side opposite to the meander-shaped spring with respect to a plane which is situated perpendicularly to the rotational axis of the adjustable part. The rotational axis is thus essentially orthogonal to this plane. This plane corresponds in particular to a plane of symmetry of the adjustable part, in particular a micromirror. The torsion spring extends at least in sections along the rotational axis and is attached at an outer end of the torsion spring directly or indirectly to the mount and at an inner end of the torsion spring directly or indirectly to the adjustable part. The meander-shaped spring which is located on the other side of the plane is situated in sections on the rotational axis. 
     The drive of the adjustable part is thus provided by only one single meandering drive. A passive torsion spring, which is used for suspending the adjustable part at the mount, is situated opposite to the meandering drive. The deflection of the adjustable part may be determined easily by this torsion spring, since in a torsion spring without drive, the deflection angle is proportional to the load measured at the torsion spring. A further advantage of this mechanical component is that the torsion spring requires less space than a second meandering drive. Space may thus be saved. 
     The meander-shaped spring preferably extends in sections along the rotational axis. A relatively symmetrical suspension of the adjustable part at the mount thus results. 
     An extension of the meander-shaped spring in the direction of an axis essentially perpendicular to the rotational axis preferably corresponds to at least 50% of an extension of the adjustable part in the direction of the axis essentially perpendicular to the rotational axis. The axis essentially perpendicular to the rotational axis is in particular a transverse axis of the adjustable part, in particular a micromirror. Since the micromechanical component only has one single meandering drive on one side of the adjustable part, this meandering drive may be designed to be wider and a greater deflection angle of the adjustable part may thus be achieved upon deflection. The extension of the meander-shaped spring in the direction of the axis essentially perpendicular to the rotational axis preferably corresponds to the extension of the adjustable part in the direction of the axis essentially perpendicular to the rotational axis. The meandering drive thus uses the full width of the micromirror. The greatest possible deflection angle of the adjustable part may thus be achieved by only one single meandering drive. 
     The meander-shaped spring is preferably attached centrally in the rotational axis of the adjustable part directly or indirectly at the adjustable part. A symmetrical suspension of the adjustable part at the mount thus results. 
     The adjustable part is preferably designed as a micromirror. The mirror surface of the micromirror is in particular formed rectangular or circular here. The micromirror or its mirror surface thus has two planes of symmetry situated perpendicularly to one another. 
     The torsion spring preferably has a height and a width, the height of the torsion spring being designed to be greater than the width of the torsion spring. In particular, a dimension of the height in relation to a dimension of the width of the torsion spring corresponds at least to a ratio of 1.2:1. A comparatively tall and narrow torsion spring thus results, which is designed to be comparatively soft with respect to the torsion deformation. The meandering drive thus does not have to exert a large force to deflect the torsion spring. A large deflection angle of the adjustable part may thus in turn be maintained. However, a torsion spring designed in this way is designed to be comparatively rigid in the z direction. The z mode, also called the stroke mode, is shifted toward higher frequencies by this torsion spring which is rigid in the z direction, which is accompanied by advantages for the control of the adjustable part, in particular the micromirror. 
     The torsion spring is preferably designed as a meandering torsion spring. This saves space in relation to a linear torsion spring and the micromechanical component may thus be designed to be smaller as a whole. 
     The micromechanical component preferably includes at least one sensor device, which is designed to output or provide at least one sensor signal corresponding to a deflection of the adjustable part from its idle position in relation to the mount. The sensor device is connected via at least one signal line formed on an outer surface of the torsion spring and/or in the torsion spring to evaluation electronics formed on the mount or an evaluation electronics connection contact formed on the outer surface of the mount. For electrical contacting of the sensor device, a signal line formed on the outer surface and/or in the at least two meander-shaped springs according to the related art may thus be omitted. The electrical contacting of the sensor device is thus not linked to any secondary effects with regard to a desired good flexibility of the meander-shaped springs. Alternatively, the sensor device is preferably situated at the outer end of the torsion spring and is connected via at least one signal line formed on an outer surface of the mount and/or in the mount to evaluation electronics formed on the mount or an evaluation electronics connection contact formed on the outer surface of the mount. Leading the signal line via the torsion spring may thus also be omitted. 
     The actuator device preferably includes at least one piezoelectric actuator layer made of at least one piezoelectric material, which is formed on the outer surface and/or in multiple sections of the associated meander-shaped spring. The actuator device additionally includes at least one electrical line, which is formed on the outer surface and/or in the meander-shaped spring in such a way that at least one voltage signal is applicable to the piezoelectric actuator layer of the meander-shaped spring in such a way that the periodic deformations of the meander-shaped spring may be effectuated. In this way, the sections of the meander-shaped spring formed having the piezoelectric actuator layer may be bent so that the adjustable part is adjusted by a relatively high adjustment angle out of its idle position in relation to the mount around the rotational axis. 
     The above-described advantages are also provided when a corresponding manufacturing method is carried out for such a micromechanical component. It is to be expressly noted that the manufacturing method may be refined in such a way that all above-explained micromechanical components may be manufactured thereby. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 a    shows a first specific embodiment of a micromechanical component in accordance with the present invention. 
         FIG. 1 b    shows a second specific embodiment of a micromechanical component in accordance with the present invention. 
         FIG. 1 c    shows a third specific embodiment of a micromechanical component in accordance with the present invention. 
         FIG. 2  shows a sequence of a manufacturing method for a micromechanical component in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
       FIG. 1 a    shows a schematic overall representation of a first specific embodiment of micromechanical component  1   a . Micromechanical component  1   a  includes a mount  10   a , an adjustable part  2   a , and a meander-shaped spring  3   a . Meander-shaped spring  3   a  is attached here at an outer end  23   a  of meander-shaped spring  3   a  directly to mount  10   a  and at an inner end  23   b  of meander-shaped spring  3   a  directly to adjustable part  2   a . In this first exemplary embodiment, meander-shaped spring  3   a  is attached at inner end  23   b  of meander-shaped spring  3   a  centrally in rotational axis  30   b  of adjustable part  2   a  directly to adjustable part  2   a . An actuator device  20   a  and  20   b  in the form of a piezoelectric layer is formed in meander-shaped spring  3   a  in such a way that periodic deformations of meander-shaped spring  3   a  are excitable with the aid of actuator device  20   a  and  20   b , by which adjustable part  2   a  is adjustable in relation to mount  10   a  around a rotational axis  30   b  of adjustable part  2   a . In addition, mechanical component  1   a  includes a torsion spring  6   a . This torsion spring  6   a  is formed here as a linear torsion spring. The torsion spring is situated on a side opposite to meander-shaped spring  3   a  with respect to a plane  9   a , which is situated essentially perpendicularly to rotational axis  30   b  of adjustable part  2   a . Rotational axis  30   b  is thus essentially orthogonal to this plane. Adjustable part  2   a  is designed here by way of example as a micromirror having a rectangular mirror surface. Adjustable part  2   a  thus has two planes of symmetry situated perpendicularly to one another in this specific embodiment. Plane  9   a  situated perpendicularly to rotational axis  30   b  of adjustable part  2   a  corresponds in this context to a first plane of symmetry of adjustable part  2   a . Rotational axis  30   b  extends in the direction of second plane of symmetry  8   a  of adjustable part  2   a.    
     Torsion spring  6   a  extends in this exemplary embodiment in section  7   a  completely along rotational axis  30   b  and is attached at an outer end  26   b  directly to mount  10   a . At an inner end of torsion spring  6   a , torsion spring  6   a  is directly attached to adjustable part  2   a . On the one hand, torsion spring  6   a  contributes to stabilizing the desired rotational movement of adjustable part  2   a  around rotational axis  30   b . In particular, torsion spring  6   a  increases a rigidity of micromechanical component  1   a  in relation to an undesired adjustment movement of adjustable part  2   a  in an axis  30   a  aligned perpendicularly to rotational axis  30   b . On the other hand, the deflection of the adjustable part may also be determined easily via torsion spring  6   a , since in a torsion spring without drive, the deflection angle is proportional to the load measured at the torsion spring. 
     In contrast, meander-shaped spring  3   a , which is located on the other side of plane  9   a , is only situated in sections  4   a ,  23   a , and  23   b  on rotational axis  30   b . While meander-shaped spring  3   a  only intersects rotational axis  30   b  in sections  4   a , meander-shaped spring  3   a  extends in sections  23   a  and  23   b  along rotational axis  30   b.    
     Due to the meandering shape, meander-shaped spring  3   a  may be made comparatively long without the individual length of meander-shaped spring  3   a  contributing to a significant enlargement of micromechanical component  1   a . An individual length of meander-shaped spring  3   a  may be, for example, greater than or equal to 200 μm, in particular greater than or equal to 500 μm, especially greater than or equal to 1 mm (millimeter). 
     In the example of  FIG. 1 , actuator device  20   a  and  20   b  includes in each case at least one piezoelectric actuator layer (not shown here) made of at least one piezoelectric material. The piezoelectric material may be, for example, PZT. The piezoelectric actuator layer may have, for example, a layer thickness between 0.5 μm (micrometer) and 2 μm (micrometer). For the interaction with the piezoelectric actuator layer, actuator device  20   a  and  20   b  also has at least one electrical line (not shown), which is formed at an outer surface and/or in meander-shaped spring  3   a . Therefore, at least one voltage signal may be applied to the piezoelectric actuator layer in such a way that at least the periodic deformations of meander-shaped spring  3   a  may be effectuated/are effectuated. Such a design of actuator device  20   a  and  20   b  as a piezoelectric actuator device is distinguished by high adjustment forces, but only low positioning distances. An adjustment of adjustable part  2   a  around rotational axis  30   b  with the aid of piezoelectric actuator devices  20   a  and  20   b  described here preferably does not take place in a resonant manner. If voltage is not applied to the piezoelectric actuator layer, adjustable part  2   a  is thus provided in its so-called idle position in relation to mount  10   a.    
     As an advantageous refinement of the present invention, the micromechanical component may also include at least one sensor device  15   a , which is designed to output or provide at least one sensor signal corresponding to a deflection of adjustable part  2   a  out of its idle position in relation to mount  10   a . Sensor device  15   a  may be, for example, a piezoelectric or piezoresistive sensor device  15   a . In this exemplary embodiment, sensor device  15   a  is formed on an “anchoring area” of torsion spring  6   a  at mount  10   a . The formation of sensor device  15   a  at the outer end of torsion spring  6   a  enables an unambiguous detection/recognition of a deflection of adjustable part  2   a  out of its idle position around rotational axis  30   b  in relation to mount  10   a . In particular, such a design of sensor device  15   a  is more advantageous than the conventional positioning of a sensor at one of meander-shaped springs  3   a , which often does not permit reliable correlation to the deflection of adjustable part  2   a  and furthermore results in the disadvantage that interference modes of micromechanical component  1   a  are incorrectly indicated as the desired deflection of adjustable part  2   a  out of its idle position around rotational axis  30   b.    
     Sensor device  15   a  is advantageously additionally connected via at least one signal line (not shown) formed at the outer surface of mount  10   a  to evaluation electronics formed on mount  10   a  or an evaluation electronics connection contact formed on mount  10   a . Forming the at least one signal line at the outer surface and/or in meander-shaped spring  3   a  may thus be omitted without problems. A bending rigidity of meander-shaped spring  3   a  is thus not negatively affected by the signal line guided via torsion spring  6   a . Furthermore, the signal line is not influenced by the convex/concave bending of meander-shaped spring  3   a  nor do the electrical signals interfere with the actuator and sensor signal line. 
     In this first specific embodiment of the present invention, meander-shaped spring  3   a  has an extension  14   a  in the direction of an axis  30   a  essentially perpendicular to rotational axis  30   b , which is at least 50% of an extension  12   a  of adjustable part  2   a  in the direction of axis  30   a  essentially perpendicular to rotational axis  30   b . The extension of meander-shaped spring  3   a  is in this case a length of the bent spring sections in the corresponding direction. The extension of adjustable part  2   a  is in this context a width of adjustable part  2   a.    
     Torsion spring  6   a  has in this case a height (not shown in this illustration) and a width  17   a . The height of the torsion spring is greater than width  17   a  of torsion spring  6   a.    
       FIG. 1 b    shows a schematic overall illustration of a second specific embodiment of micromechanical component  1   b , in accordance with the present invention. 
     In this case, in contrast to the first specific embodiment, extension  14   b  of meander-shaped spring  3   b  in the direction of axis  30   a  essentially perpendicular to rotational axis  30   b  corresponds to extension  12   a  of adjustable part  2   a  in the direction of axis  30   a  essentially perpendicular to rotational axis  30   b . The maximum deflection angle of adjustable part  2   a  is thus achieved. 
       FIG. 1 c    shows a schematic overall illustration of a third specific embodiment of micromechanical component  1   c , in accordance with the present invention. 
     In contrast to the second specific embodiment, torsion spring  6   c  is formed as a meandering torsion spring in this case. Meandering torsion spring  6   c  extends on sections  7   c  on rotational axis  30   b  and is attached at an outer end  26   d  of torsion spring  6   c  directly to mount  2   a  and at an inner end  26   c  of torsion spring  6   c  directly to adjustable part  2   a.    
       FIG. 2  shows a flowchart to explain one specific embodiment of the manufacturing method, in accordance with the present invention. 
     All above-described micromechanical components may be manufactured with the aid of the manufacturing method described hereinafter. However, a feasibility of the manufacturing method is not restricted to the manufacturing of the above-described micromechanical components. 
     Attaching an adjustable part to a mount via at least one meander-shaped spring, which is situated sectionally on a rotational axis of the adjustable part, an outer end of the meander-shaped spring being attached directly or indirectly to the mount and an inner end of the meander-shaped spring being attached directly or indirectly to the adjustable part; and forming an actuator device at an outer surface of the meander-shaped spring and/or in the meander-shaped spring in such a way that during operation of the later micromechanical component with the aid of the actuator device, periodic deformations of the meander-shaped spring are excited, by which the adjustable part is adjusted in relation to the mount around the rotational axis of the adjustable part; 
     characterized by the step: 
     forming a torsion spring, which extends at least sectionally along the rotational axis of the adjustable part, where an outer end of the torsion spring is attached directly or indirectly to the mount and an inner end of the torsion spring is attached directly or indirectly to the adjustable part in such a way that the adjustable part is adjusted with the aid of at least the periodic deformations of the meander-shaped spring in relation to the mount around the rotational axis. 
     In a method step  50 , an adjustable part is attached to a mount via at least one meander-shaped spring. The meander-shaped spring is situated for this purpose in sections on a rotational axis of the adjustable part. An outer end of the meander-shaped spring is attached directly or indirectly to the mount and an inner end of the meander-shaped spring is attached directly or indirectly to the adjustable part. In a following method step  51 , an actuator device is formed at an outer surface of the meander-shaped spring and/or in the meander-shaped spring in such a way that during operation of the later micromechanical component with the aid of the actuator device, periodic deformations of the meander-shaped spring are excited. The adjustable part is adjusted in relation to the mount by these excited periodic deformations. 
     In a following method step  52 , a torsion spring is formed, which extends at least in sections along the rotational axis of the adjustable part. An outer end of the torsion spring is attached directly or indirectly to the mount and an inner end of the torsion spring is attached directly or indirectly to the adjustable part. This has the effect that the adjustable part is adjusted with the aid of at least the periodic deformations of the meander-shaped spring in relation to the mount around the rotational axis. The manufacturing method described here thus also effectuates the above-described advantages. To carry out method steps  50  and  52 , the particular components may be structured, for example, out of monocrystalline, polycrystalline, or epi-polycrystalline silicon, especially out of a silicon layer of an SOI substrate (silicon-on-insulator substrate). 
     As an optional refinement, the manufacturing method may also include method steps  53  and  54 . In method step  53 , a sensor device is formed for providing or outputting at least one sensor signal corresponding to a deflection of the adjustable part out of its idle position in relation to the mount. In method step  54 , the sensor device is connected via at least one signal line formed at an outer surface of the torsion spring and/or in the torsion spring to evaluation electronics formed on the mount or an evaluation electronics connection contact formed on the mount. Alternatively to this step, the sensor device is connected via at least one signal line formed on an outer surface of the mount and/or in the mount to evaluation electronics formed at the mount or an evaluation electronics connection contact formed on the mount. Further components of the above-described micromechanical components may also be formed with the aid of corresponding method steps. The above-described micromechanical components are technologically implementable in a simple manner. 
     Method steps  50  through  54  may be carried out in any sequence, overlapping in time, or simultaneously.