Patent Publication Number: US-2023161150-A1

Title: Micromirror arrangement

Description:
FIELD 
     The present invention relates to a micromirror arrangement. The present invention also relates to a projection apparatus comprising the micromirror arrangement. 
     BACKGROUND INFORMATION 
     U.S. Patent Application Publication No. US 2005/0157376 A1 describes a micromirror arrangement in which spring elements of a mirror project into the area of an adjacent mirror. 
     An object of the present invention is to develop a micromirror arrangement having increased driving force and/or increased deflectability of the micromirrors. 
     SUMMARY 
     According to the present invention, to achieve the object, a micromirror arrangement and a projection apparatus are provided. 
     According to an example embodiment of the present invention, the micromirror arrangement comprises at least a first micromirror, a second micromirror, and a third micromirror. The second micromirror comprises a first and a second component. The first and the second component are in particular functional components of the respective micromirror. A functional component is a component of the respective micromirror that is technically significant for any function of the respective micromirror. An electrostatic comb drive element as a functional component, for example, is configured for driving the respective micromirror. A micromechanical spring element as a functional component is configured for deflecting the respective micromirror. A capacitive electrode arrangement as a functional component is configured for detecting the deflection of the respective micromirror. The first component is disposed such that it overlaps the first micromirror. The first component is in particular disposed such that, in plan view, it overlaps a first mirror surface of the first micromirror. The first component in particular extends underneath the first mirror surface in plan view. The second component is furthermore disposed such that it overlaps the third micromirror. The second component is in particular disposed such that, in plan view, it overlaps a third mirror surface of the third micromirror. The second component in particular extends underneath the third mirror surface in plan view. The available space for the components of the second micromirror can thus be increased, as a result of which the lever arm and/or the torques for deflecting the second micromirror, for example, can be increased as well. 
     According to an example embodiment of the present invention, the at least first, second and third micromirrors are preferably arranged as an array, in particular a micromirror array. The first, second and third micromirrors are hereby in particular disposed side by side, laterally spaced apart from one another. In particular in plan view, the second micromirror is preferably disposed between the first and the third micromirror. Such an array arrangement can have a one-dimensional or two-dimensional configuration and can be used, for example, in image projectors for deflecting light beams. Other important applications include so-called reconfigurable optical add-drop multiplexers (ROADM), in which signals of specific wavelengths or frequencies can be coupled selectively into glass fibers in glass fiber networks via a micromirror array. Micromirror arrays can furthermore also be used in modern projection exposure systems for microlithography in the semiconductor industry. 
     According to an example embodiment of the present invention, the first micromirror preferably additionally comprises at least one third component. This third component is likewise in particular configured as a third functional component. The third component is disposed such that it overlaps the second micromirror. The third component is in particular disposed such that, in plan view, it overlaps a second mirror surface of the second micromirror. The components of the first and second micromirror therefore mutually overlap one another. A first main extension plane, in particular in plan view, of the first component, and a third main extension plane, in particular in plan view, of the third component further preferably extend substantially parallel to one another. The first main extension plane and the third main extension plane in particular extend side by side parallel. There is therefore no overlapping of the first and the third component in plan view. The first and the third component preferably have cross-sections that differ from one another. The cross-section of the third component, in particular in plan view, is in particular narrower than the cross-section of the first component. The components are therefore configured differently from one another. Alternatively, the first and the third component have cross-sections that are the same. The cross-section of the third component, in particular in plan view, is in particular the same as the cross-section of the first component. The components are therefore configured identically. The first micromirror is hereby further preferably configured identically to the second micromirror. The third micromirror is preferably likewise configured identically to the first and the second micromirror. 
     According to an example embodiment of the present invention, the first, second, and third micromirrors are preferably disposed along a common first main extension plane of the micromirrors. The first, second and third micromirrors, in particular a first main extension plane of the first micromirror, a second main extension plane of the second micromirror and a third main extension plane of the third micromirror, hereby preferably extend on the common first main extension plane and thus form a rectilinear, one-dimensional array. Alternatively, the first, second and third micromirrors, in particular the first main extension plane of the first micromirror, the second main extension plane of the second micromirror and the third main extension plane of the third micromirror, are preferably disposed along the common main extension plane, offset from the main extension plane. The main extension planes of the individual micromirrors therefore do not extend on the common main extension plane, but rather offset from said main extension plane. The micromirrors are thus likewise disposed offset from one another along the one-dimensional array. This consequently makes it possible to one-dimensionally arrange identical micromirrors as an array. 
     According to an example embodiment of the present invention, the first, second, and third micromirrors are preferably arranged as at least a part of a two-dimensional array. The first and the second micromirror extend in the y-direction, for example, and the second and the third micromirror extend in the x-direction of the two-dimensional array. 
     According to an example embodiment of the present invention, the at least first, second and third micromirrors preferably have a common carrier substrate. The carrier substrate is preferably made of silicon. 
     According to an example embodiment of the present invention, the components of the micromirrors are preferably made at least in part of silicon. 
     According to an example embodiment of the present invention, the components of the micromirrors preferably represent at least parts of micromechanical spring elements. The first component of the second micromirror is in particular configured as a first subsection of a first micromechanical spring, in particular a first torsion spring, and the second component of the second micromirror is configured as a second subsection of the first micromechanical spring as the second component. The two subsections are in particular configured as partial turns to the right and left of a vertical axis, in particular a vertical mount of the first micromechanical spring. Overlapping the respective subsection with the adjacent micromirror increases the installation space for the micromechanical spring. This reduces the achievable spring stiffness of the micromechanical spring and consequently increases the possible deflectability of the respective micromirror. 
     According to an example embodiment of the present invention, the components of the micromirrors preferably represent at least parts of a comb drive, in particular a vertical comb drive, of a respective micromirror. One component is in particular configured as a movable comb and a connecting web of the movable comb with the underside of the mirror. The vertical comb drive consists of fixed combs and movable combs connected to the underside of the mirror. When an electrical voltage is applied to either the comb drive disposed to the left or the comb drive disposed to the right of a mount, the mirror is tilted about a specific axis of rotation. Overlapping the comb drive with an adjacent micromirror increases the installation space, in particular the achievable lever arm, for the comb drive, and thus increases a possible torque of the respective micromirror. 
     According to an example embodiment of the present invention, the micromirror arrangement preferably comprises at least four micromirrors, in particular at least sixteen micromirrors, arranged in a two-dimensional, in particular 4×4, array. 
     According to an example embodiment of the present invention, the micromirror arrangement preferably has a fill factor of at least 60%. The fill factor is hereby preferably at least 80%, particularly preferably at least 90%, for a one-dimensional array and at least 60%, particularly preferably at least 80%, for a two-dimensional array. Fill factor refers to the ratio of the area of mirror surface to the total surface area of the array. Because the functional elements overlap the respective adjacent mirrors, whereby the functional elements of the respective adjacent mirrors are not in mutual contact with one another, the micromirrors can be pushed into one another as it were, so that the mirror surfaces of the adjacent micromirrors can be close to one another. 
     A further subject matter of the present invention is a projection apparatus comprising at least one of the above-described micromirror arrangement. Such a projection apparatus preferably further comprises an illumination unit and a projection unit, in particular a screen. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  schematically shows a first embodiment of a micromirror arrangement in plan view, according to the present invention. 
         FIG.  1 B  schematically shows a sectional view of the first embodiment of the micromirror arrangement, according to the present invention. 
         FIG.  2    schematically shows a second embodiment of the micromirror arrangement in plan view, according to the present invention. 
         FIG.  3    schematically shows a third embodiment of the micromirror arrangement in plan view, according to the present invention. 
         FIG.  4    schematically shows a fourth embodiment of the micromirror arrangement in plan view, according to the present invention. 
         FIG.  5    schematically shows a fifth embodiment of the micromirror arrangement in plan view, according to the present invention. 
         FIG.  6    schematically shows a sixth embodiment of the micromirror arrangement in plan view, according to the present invention. 
         FIG.  7 A  schematically shows a seventh embodiment of the micromirror arrangement in plan view, according to the present invention. 
         FIG.  7 B  schematically shows a sectional view of the seventh embodiment of the micromirror arrangement, according to the present invention. 
         FIG.  8    schematically shows a projection apparatus, according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
       FIG.  1 A  schematically shows a first embodiment of a micromirror arrangement  8   a  in plan view. The micromirror arrangement  8   a  comprises a first micromirror  2   a,  a second micromirror  1   a , a third micromirror  2   b  and a fourth micromirror  1   b . The second micromirror  2   a  comprises a first component  10   a , in particular a first functional component, and a second component  10   b,  in particular a second functional component. The first component  10   a  is disposed such that, in plan view, it overlaps a first mirror surface  6   a  of the first micromirror  2   a . The second component  10   b  is furthermore disposed such that, in plan view, it overlaps a third mirror surface  6   b  of the third micromirror  2   b.  The second micromirror  1   a  is disposed between the first  2   a  and the third micromirror  2   b.  The first  10   a  and the second component  10   b  are configured identically to one another and therefore have cross-sections that are the same in plan view. 
     In this first embodiment, the first  2   a  and the third micromirror  2   b  are configured identically to one another. The fourth micromirror  1   b  in this first embodiment is likewise configured identically to the second micromirror  1   a  and comprises a seventh component  10   c,  in particular a seventh functional component, and an eighth component  10   d,  in particular an eighth functional component. All components  10   a - 10   d  in this first embodiment are therefore configured identically to one another. The seventh component  10   c  is furthermore disposed such that, in plan view, it overlaps a third mirror surface  6   b  of the third micromirror  2   b.  In this first embodiment, the four micromirrors  1   a ,  1   b ,  2   a  and  2   b  have a common main extension plane  18   a,  on which all of the micromirrors  1   a ,  1   b ,  2   a  and  2   b  extend. 
     The first  2   a,  the second  1   a , the third  2   b  and the fourth micromirror  1   b  are arranged as a one-dimensional, in particular rectilinear, array. 
       FIG.  1 B  schematically shows a sectional view of the first embodiment of the micromirror arrangement  8   a  along the common main extension plane  18   a.  As can be seen there, the first component  10   a  represents a first part, in particular a first subpart, and the second component  10   b  represents a second part, in particular a second subpart, of a first micromechanical spring element  7   a,  which is disposed on a common carrier substrate  16   a  of the micromirror arrangement  8   a  by means of a first mount  4   a.  The first  10   a  and the second component  10   b  extend underneath the first mirror surface  6   a  and underneath the third mirror surface  6   b.  A partial section of the fourth micromirror  1   b  with the seventh  10   c  and the eighth component  10   d  can similarly be seen here as well. The seventh component  10   c  represents a third part, in particular a third subpart, and the eighth component  10   d  represents a fourth part, in particular a fourth subpart, of a second micromechanical spring element  7   b , which is disposed on the common carrier substrate  16   a  of the micromirror arrangement  8   a  by means of a second mount  4   b.    
     The micromechanical spring elements  7   a  and  7   b  are made entirely of silicon. The mounts  4   a  and  4   b  and also the carrier substrate  16   a  are likewise made of silicon. 
       FIG.  2    schematically shows a second embodiment of a micromirror arrangement  8   b.  In contrast to the first embodiment, the first micromirror  20   a  additionally comprises at least a third component  26   b,  in particular a third functional component. The third component  26   b  is disposed such that, in plan view, it overlaps the second mirror surface  5   a  of the second micromirror  1   a . A first main extension plane  15   a  of the first component  10   a  and a third main extension plane  15   c  of the third component  26   b  extend substantially parallel to one another. The first  10   a  and the third component  26   b  are disposed adjacent one another. 
     The first  10   a  and the third component  26   b  have cross-sections that differ from one another in plan view and are therefore configured differently from one another. The third component  26   b  has a cross-section that is narrower than the cross-section of the first component  10   a.    
     The first micromirror  20   a  in this embodiment additionally comprises a further fourth component  25   b,  in particular a functional component. The fourth component  25   b  is configured identically to the third component  26   b.  A fourth main extension plane  15   b  of the fourth component  25   b,  the third main extension plane  15   c  of the third component  26   b  and the first main extension plane  15   a  of the first component  10   a  extend substantially parallel to one another. In plan view, the first component  10   a  is disposed between the third  26   b  and the fourth component  25   b.    
     The first micromirror  20   a  further comprises a fifth component  25   a,  which is disposed on the fourth main extension plane  15   b  and is configured identically to the fourth component  25   b.  The fifth component is disposed on the opposite side of the first micromirror  20   a  with respect to the fourth component  25   b.  The first micromirror  20   a  further comprises a sixth component  26 , which is disposed on the third main extension plane  15   c  and is configured identically to the third component  26   b.  The sixth component is disposed on the opposite side of the first micromirror  20   a  with respect to the third component  26   b.    
     The third micromirror  20   b  is configured identically to the first micromirror  20   a  and comprises a ninth  26   c,  a tenth  25   c,  an eleventh  26   d  and a twelfth component  25   d  which overlap the adjacent mirror surfaces  5   a  and  5   b.    
       FIG.  3    shows a third micromirror arrangement  8   c,  wherein, in contrast to the previous embodiments, the micromirrors  31   a - 31   h  and  32   a - 32   h  are arranged as a two-dimensional 4×4 array, which extends rectilinearly in the x-direction  19   b  and the y-direction  19   a.  The micromirrors  31   a - 31   h  are configured identically to the second micromirror  1   a  and the fourth micromirror  1   b  from the previous embodiments, with the difference that the micromirrors  31   a - 31   h  comprise a respective component on each side of the mirror surface, which is rectangular in shape here, that overlaps the respective adjacent mirrors  32   a - 32   h.  The micromirrors  32   a - 32   h  are configured identically to the first micromirror  20   a  and the third micromirror  20   b  from the previous second embodiment, with the difference that the micromirrors  31   a - 31   h  comprise two respective components on each side of the mirror surface, which is rectangular in shape here, that overlap the respective adjacent mirrors  31   a - 31   h.    
       FIG.  4    schematically shows a fourth embodiment of a micromirror arrangement  8   d.  In contrast to the first embodiment of  FIGS.  1 A and  1 B , a second micromirror  9   b  and a first micromirror  9   a  comprise a first component  14   a,  a second component  14   b  and a third component  13   b,  the cross-sections of which are identical to one another in plan view. Here, too, a first main extension plane  15   f  in plan view of the first component  14   a  and a third main extension plane  15   e  of the third component  15   e  extend substantially parallel to one another. The micromirrors  9   a - 9   f  are configured identically to one another, but are alternately rotated 180° in the micromirror arrangement  8   d.  This prevents the components of adjacent micromirrors overlapping one another. The micromirrors  9   a - 9   f  extend on the common main extension plane  17   a.    
       FIG.  5    schematically shows a fifth embodiment of a micromirror arrangement  8   e.  In contrast to the fourth embodiment, the micromirrors  22   a - 22   f,  which are configured identically to one another, are disposed along the common main extension plane  17   b  offset from the common main extension plane  17   b.  To achieve this, the micromirrors  22   a - 22   f  are alternately disposed above and beneath the common main extension plane  17   b  in plan view. 
       FIG.  6    shows a sixth micromirror arrangement  8   f,  wherein, in contrast to the fifth embodiment, the identical micromirrors  34   a - 34   p  are arranged as a two-dimensional 4×4 array, which extends in the x-direction  19   b  and the y-direction  19   a.  The micromirrors  34   a - 34   p  are configured and disposed relative to one another identically to the micromirrors  22   a - 22   f  of the fifth embodiment, with the difference that the micromirrors  34   a - 34   p  comprise a respective component on each side of the mirror surface, which is rectangular in shape here, that overlaps the respective adjacent mirrors. 
       FIG.  7 A  schematically shows a seventh embodiment of a micromirror arrangement  8   g.  In contrast to the previous embodiments, the second micromirror  41   a  comprises a first component  48   a  and a second component  47   c  which, as functional components, represent parts of a vertical comb drive and overlap the first mirror surface  42   a  and the third mirror surface  42   b  of the adjacent first micromirror  40   a  and third micromirror  40   b.    
     The second micromirror  41   a  further comprises a fourth component  48   b  and a fifth component  47   d  that likewise overlap the first mirror surface  42   a  and the third mirror surface  42   b  of the adjacent first micromirror  40   a  and third micromirror  40   b.  The first micromirror  40   a  in turn comprises a third component  50   a , which is also configured as a part of a vertical comb drive and overlaps the second mirror surface  43   a  of the second micromirror  41   a.  The third micromirror  40   b  is configured identically to the first micromirror  40   a  and the fourth micromirror  41   b,  which is indicated here only in part, is configured identically to the second micromirror  41   a.    
       FIG.  7 B  schematically shows a portion of a sectional view of the seventh embodiment of the micromirror arrangement  8   g  along the sectional plane  24   a.  As shown there using the second micromirror  41   a,  the first component  48   a  is configured as a movable comb of a vertical comb drive, which is connected to the underside of the mirror of the second mirror surface  43   a  via a connecting web. The comb surfaces  52   b  of the movable comb are in engagement with the comb surfaces of a fixed comb  53   b  attached to the carrier substrate  16   b.  The first component  48   a  extends underneath the first mirror surface  42   a  and is disposed such that it overlaps said first mirror surface, in particular in plan view. Similarly, the second component  47   c  is configured as a movable comb on the opposite side of the second micromirror  41   a  and is disposed such that it overlaps the third mirror surface  42   b.  When an electrical voltage is applied to either the comb drive  48   a  disposed to the left or the comb drive  47   c  disposed to the right of a second mount  45   a,  the second micromirror  41   a  is tilted about an axis of rotation that projects into the image plane. The first micromirror is attached to the carrier substrate  16   b  via a first mount  46   a  and the third micromirror via a third mount  46   b.    
     As can be seen from  FIGS.  1 A- 7 B , the mirror surfaces of the adjacent micromirrors can be disposed very close to one another, even though the extent of at least the second micromirror along the main extension plane is greater than the lateral spacing between the midpoints of the mirror surfaces of adjacent mirrors. This makes it possible to realize micromirror arrangements having a particularly high fill factor. For a one-dimensional array, the fill factor is preferably at least 80%, particularly preferably at least 90%, and for a two-dimensional array at least 60%, particularly preferably at least 80%. 
       FIG.  8    schematically shows a projection apparatus  104  comprising a micromirror arrangement  101  according to any one of the previous embodiments. The projection apparatus  104  further comprises an illumination unit  100  and a projection unit  102 , which is in particular configured as a screen. The illumination unit  100 , which is configured as a laser diode, for example, produces at least one light beam  103   a  which is deflected by the micromirror arrangement  101 , in particular in a scanning manner. The at least one deflected light beam  103   b  is thus projected onto the projection unit  102 .