A MEMS micromirror and preparation method thereof

Abstract

The present application discloses a MEMS micromirror and a preparation method, including a stacked substrate layer, a fixed comb-tooth layer and a movable comb-tooth layer, a reflector is arranged on the movable comb-tooth layer; a plurality of through holes, which vertically penetrate the substrate layer and the fixed comb-tooth layer, and a dielectric layer is arranged between the substrate layer, the fixed comb-tooth layer and the through holes; a plurality of metal interconnect structures, which are filled in the through holes, part of the metal interconnect structures are electrically connected to the fixed comb-tooth layer, and the other part is electrically connected to the movable comb-tooth layer; a first pad layer, which is connected to one end of the metal interconnect structure exposed to the substrate layer; a second pad layer, which is electrically connected to one end of the metal interconnect structure exposed to the surface of the fixed comb-tooth layer. The present application adopts a metal interconnect structure to realize the electrical connection between the first pad layer at the bottom of the MEMS micromirror and the second pad layer on the front side, without the need to wire on one side of the reflector, thereby reducing the complexity of array packaging and the risk of cross-interference, reducing power consumption and parasitic capacitance, and improving the reliability and long-term performance of the MEMS micromirror.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a MEMS micromirror and a preparation method thereof. Background Art

[0002] MEMS micromirrors are usually electrically connected by wire bonding, but the wire bonding process on the front side increases the length of the wiring, making the array packaging extremely complicated. In addition, the wires formed on the front side of the micromirror will occupy a certain angle. During the process of the MEMS micromirror reflecting light, the wires themselves will interfere with the optical path, increasing the possibility of cross-interference, thereby affecting the efficiency and quality of signal transmission, which is not conducive to the reliability and long-term performance of the MEMS micromirror. Summary of the invention

[0003] In view of the problems existing in the above-mentioned prior art, the present application provides a MEMS micromirror and a preparation method, which can effectively reduce the wiring complexity, reduce the cross-interference, power consumption and parasitic capacitance of the MEMS micromirror, improve the signal transmission efficiency and quality, and have good reliability and excellent long-term performance. The technical solution is as follows:

[0004] On the one hand, the present application provides a MEMS micromirror, comprising:

[0005] The functional layer comprises a stacked substrate layer, a fixed comb-tooth layer and a movable comb-tooth layer, wherein a reflector is arranged on the movable comb-tooth layer;

[0006] A plurality of through holes vertically penetrate the substrate layer and the fixed comb-tooth layer, and a dielectric layer is disposed between the substrate layer, the fixed comb-tooth layer and the through holes;

[0007] A plurality of metal interconnect structures are filled in the through holes, and one end of the metal interconnect structures is exposed to the surface of the substrate layer, and the other end is exposed to the surface of the fixed comb-tooth layer; some of the metal interconnect structures are electrically connected to the fixed comb-tooth layer, and another part of the metal interconnect structures is electrically connected to the movable comb-tooth layer;

[0008] A first pad layer, comprising a plurality of first pads, wherein the first pads are electrically connected to one end of the metal interconnect structure exposed to the substrate layer;

[0009] The second pad layer includes a plurality of second pads, and the second pads are electrically connected to one end of the metal interconnect structure exposed on the surface of the fixed comb-tooth layer.

[0010] Furthermore, it also includes a bonding metal layer located between the fixed comb tooth layer and the movable comb tooth layer, the bonding metal layer has a preset pattern, and the through hole is located within a projection area of ​​the preset pattern in the longitudinal direction.

[0011] Furthermore, the material of the bonding metal layer includes at least one of titanium and gold.

[0012] Further, the bonding metal layer includes a mutually isolated structural bonding area, a plurality of first metal electrical interconnection areas and a plurality of second metal electrical interconnection areas, and the first metal electrical interconnection areas and the second metal electrical interconnection areas are located between the movable comb layer and the metal interconnection structure;

[0013] The first metal electrical interconnection region is electrically connected to the movable comb tooth region in the movable comb tooth layer;

[0014] The second metal electrical interconnection region is electrically connected to the fixed comb-tooth layer and isolated from the movable comb-tooth region in the movable comb-tooth layer.

[0015] Furthermore, at least a portion of the dielectric layer is located on the surface of the fixed comb-tooth layer, a connection window penetrating the dielectric layer is opened on the surface of the fixed comb-tooth layer, and the fixed comb-tooth layer is electrically connected to the metal interconnection structure through the connection window.

[0016] Further, the movable comb-tooth layer includes a movable comb-tooth area, a first electrical interconnection area, and a second electrical interconnection area, wherein the first electrical interconnection area and the second electrical interconnection area are respectively located between the second pad and the metal interconnection structure;

[0017] The movable comb teeth area is connected to the first electrical interconnection area;

[0018] The second electrical interconnection region is isolated from the first electrical interconnection region, and the second electrical interconnection region is electrically connected to the fixed comb-tooth layer.

[0019] Furthermore, at least a portion of the dielectric layer is located on the surface of the substrate layer and the surface of the fixed comb-tooth layer, and the dielectric layer is provided between each of the substrate layer, the fixed comb-tooth layer and the through hole.

[0020] On the other hand, the present application also provides a method for preparing a MEMS micromirror, comprising:

[0021] Providing an SOI substrate, the SOI substrate comprising a substrate layer and an initial fixed tooth layer, wherein a dielectric layer is formed between the substrate layer and the initial fixed tooth layer;

[0022] Forming a plurality of through holes in the SOI substrate, wherein the through holes vertically penetrate the substrate layer and the initial fixed tooth layer;

[0023] A metal interconnection structure is formed in the through hole; one end of the metal interconnection structure is exposed to the surface of the substrate layer, and the other end is exposed to the surface of the initial fixed tooth layer; some of the metal interconnection structures among the plurality of metal interconnection structures are electrically connected to the initial fixed tooth layer, and another part of the metal interconnection structures are used to be electrically connected to the movable comb tooth layer;

[0024] A first pad layer is formed on a surface of the substrate layer facing away from the initial fixed tooth layer; the first pad layer includes a plurality of first pads, and the first pads are electrically connected to one end of the metal interconnect structure exposed to the substrate layer;

[0025] Etching the initial fixed tooth layer to form a fixed comb tooth layer;

[0026] Bonding a second substrate to a side of the fixed comb-tooth layer facing away from the substrate layer to obtain a bonding structure;

[0027] A reflector and a second pad layer are formed on a surface of the second substrate facing away from the substrate layer; the second pad layer includes a plurality of second pads, and the second pads are electrically connected to one end of the metal interconnect structure exposed on the surface of the initial fixed tooth layer;

[0028] The second substrate is etched to form a movable comb-tooth layer to obtain the MEMS micromirror.

[0029] Further, after forming the first pad layer on the surface of the substrate layer on the side away from the initial fixed tooth layer, and before etching the initial fixed tooth layer to form a fixed comb tooth layer, the method further includes:

[0030] A bonding metal layer is formed on a surface of the initial fixed tooth layer which is away from the substrate layer; the bonding metal layer has a preset pattern, and the through hole is located within a projection area of ​​the preset pattern in the longitudinal direction;

[0031] Bonding the second substrate to a side of the fixed comb-tooth layer facing away from the substrate layer to obtain a bonding structure comprises:

[0032] The second substrate is bonded to the bonding metal layer on the surface of the fixed comb-tooth layer to obtain the bonding structure.

[0033] Further, forming a metal interconnection structure in the through hole includes:

[0034] forming a seed layer in the through hole and filling it with metal material to form an initial metal interconnection structure;

[0035] The initial metal interconnection structure is planarized and subjected to vacuum heat treatment at 350° C. to 500° C. to form the metal interconnection structure.

[0036] Implementing this application has the following beneficial effects:

[0037] 1. The present application introduces TSV technology into the MEMS micromirror, and adopts a metal interconnection structure to realize the electrical connection between the first pad layer at the bottom of the MEMS micromirror and the second pad layer on the front. On the one hand, the length of the interconnection path is reduced, which is beneficial to improving the signal transmission efficiency, thereby reducing power consumption and parasitic capacitance; on the other hand, after being led out from the first pad layer at the bottom of the MEMS micromirror and connected to the power supply current, there is no need to wire on the surface of the side close to the reflector, thus avoiding messy wire bonding, which is beneficial to reducing the complexity of the array packaging, and also effectively avoiding the interference of traditional leads on the optical path, reducing the possibility of cross interference, which is beneficial to improving the signal transmission efficiency and quality, reducing power consumption and parasitic capacitance, reducing signal delay, and improving the reliability and long-term performance of the MEMS micromirror.

[0038] 2. The present application adopts a bonding metal layer with a preset pattern, that is, the structural interconnection and electrical interconnection between the upper and lower layers are realized through the same layer of metal, which gives way to each other and does not interfere with each other. The preset pattern of the bonding metal layer occupies a relatively small area, which is beneficial to reduce the accumulation of thermal stress at the interface between different layers during the bonding process due to the different thermal expansion coefficients of their respective materials, that is, it reduces the stress distribution introduced by the TSV process, reduces the preparation cost, and improves the bonding strength between adjacent layers, which is beneficial to improve the structural reliability and long-term performance of the metal interconnection structure and the MEMS micromirror as a whole.

[0039] 3. The preparation method of the present application performs heat treatment during the process of forming the metal interconnect structure, which can further reduce the stress of the metal interconnect structure; and in the subsequent step, a movable comb tooth layer is formed by etching the second substrate, so that only one seed layer and one electroplating are needed in the early stage to achieve the final electrical interconnection and structural bonding, which simplifies the preparation process and further reduces the stress accumulation in the preparation process, which is conducive to further improving the reliability and long-term performance of the MEMS micromirror. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the embodiments, wherein the same components are represented by the same reference numerals. Obviously, the drawings described below are only some embodiments of the present application, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 A schematic diagram of the structure of a MEMS micromirror provided in an embodiment of the present application;

[0042] Figure 2A schematic structural diagram of a MEMS micromirror prepared by a method for preparing a MEMS micromirror provided in an embodiment of the present application;

[0043] Figure 3 A top view of the structure of a bonding metal layer provided in an embodiment of the present application;

[0044] Figure 4 A schematic structural diagram of a substrate structure having a plurality of through holes provided in an embodiment of the present application;

[0045] Figure 5 A schematic diagram of the distribution position of a dielectric layer provided in an embodiment of the present application;

[0046] Figure 6 A structural schematic diagram of a connection window provided in an embodiment of the present application;

[0047] Figure 7 A schematic structural diagram of a substrate structure having a metal interconnect structure provided in an embodiment of the present application;

[0048] Figure 8 A schematic structural diagram of a substrate structure having a first pad layer provided in an embodiment of the present application;

[0049] Fig. 9 A schematic structural diagram of a substrate structure having a bonding metal layer provided in an embodiment of the present application;

[0050] Fig.10 A schematic structural diagram of a substrate structure for forming a limiting groove provided in an embodiment of the present application;

[0051] Fig.11 A schematic structural diagram of a substrate structure having a fixed comb-tooth layer provided in an embodiment of the present application;

[0052] Fig.12 A schematic structural diagram of a bonding structure provided in an embodiment of the present application;

[0053] Fig.13 A schematic structural diagram of a bonding structure provided in an embodiment of the present application, which is provided with a reflector and a second pad layer.

[0054] Wherein, the accompanying drawings are marked as follows:

[0055] 100-substrate layer, 200-fixed comb tooth layer, 201-fixed comb tooth area, 2010-fixed comb teeth, 2011-first spacing groove, 202-limiting structure, 203-second isolation groove, 210-initial fixed tooth layer, 300-movable comb tooth layer, 301-movable comb tooth area, 3010-movable comb teeth, 3011-second spacing groove, 3012-supporting area, 302-first electrical interconnection area, 303-second electrical interconnection area, 304-first isolation groove, 310-second substrate, 400-reflector, 500-through hole, 501-metal interconnection structure, 5010-fixed tooth metal interconnection connecting structure, 5011-moving tooth metal interconnection structure, 600-first pad layer, 601-first pad, 6010-first fixed tooth pad, 6011-first moving tooth pad, 700-second pad layer, 701-second pad, 7010-second fixed tooth pad, 7011-second moving tooth pad, 800-bonding metal layer, 801-structural bonding area, 802-first metal electrical interconnection area, 803-second metal electrical interconnection area, 804-metal spacing groove, 805-slicing road area, 900-dielectric layer, 901-connection window, 902-limiting groove, 1000-SOI substrate. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments, and therefore cannot be understood as limiting the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0057] It should be noted that in the description of the present application, for the following defined terms, unless a different definition is given in the claims or elsewhere in this specification, these definitions should be applied. All numerical values, whether or not explicitly indicated, are defined herein as being modified by the term "about". The term "about" generally refers to a numerical range that a person of ordinary skill in the art would consider to be equivalent to the stated value to produce substantially the same properties, functions, results, etc. A numerical range indicated by a low value and a high value is defined to include all numerical values ​​included in the numerical range and all subranges included in the numerical range.

[0058] It should be noted that the terms "first", "second", etc. in the specification, claims and drawings of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the objects used in this way can be interchanged where appropriate, so that the embodiments of the present application can be implemented in a sequence other than the following diagrams or the following descriptions. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, the process, method, system, product comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, or products.

[0059] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that the depth direction of an element or layer is the direction perpendicular to the surface of the element or layer, and the direction of the cross section of an element or layer is the direction parallel to the surface of the element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. When discussing a second element, component, region, layer or section, it does not necessarily mean that the first element, component, region, layer or section must be present.

[0060] The existing MEMS micromirror usually uses wire bonding to make electrical connections on the front of the device. The wire arrangement is complicated and easily interferes with the optical path, resulting in cross interference and affecting signal transmission. In order to solve the above technical problems, the embodiment of the present application provides a MEMS micromirror and a preparation method thereof. The MEMS micromirror includes a functional layer, which includes a stacked substrate layer, a fixed comb layer and a movable comb layer, and a reflector is provided on the movable comb layer; a plurality of through holes vertically penetrate the substrate layer and the fixed comb layer, and the substrate layer, the fixed comb layer and the through holes are provided with each other. a dielectric layer is disposed; a plurality of metal interconnect structures are filled in the through holes, and one end of the metal interconnect structures is exposed to the surface of the substrate layer, and the other end is exposed to the surface of the fixed comb tooth layer; some of the metal interconnect structures in the plurality of metal interconnect structures are electrically connected to the fixed comb tooth layer, and another part of the metal interconnect structures is electrically connected to the movable comb tooth layer; a first pad layer includes a plurality of first pads, and the first pads are electrically connected to one end of the metal interconnect structure exposed to the substrate layer; a second pad layer includes a plurality of second pads, and the second pads are electrically connected to one end of the metal interconnect structure exposed to the surface of the fixed comb tooth layer. The MEMS micromirror introduces a through hole and a metal interconnection structure, and electrically connects a second pad layer located on one side of the reflector to a first pad layer located on the side of the substrate layer away from the reflector through the metal interconnection structure, and then connects to the power supply current through the first pad layer. There is no need to bond wires on one side of the reflector, which effectively reduces the wiring complexity in the MEMS micromirror, simplifies the array packaging, shortens the length of the signal transmission path, avoids interference of the front wiring on the optical path, reduces the possibility of cross interference, and greatly improves the signal transmission efficiency and quality. The metal interconnection structure can greatly reduce the power consumption and parasitic capacitance of the MEMS micromirror, reduce signal delay, and is conducive to improving the reliability and long-term performance of the MEMS micromirror.

[0061] The preparation method of the MEMS micromirror is used to prepare the MEMS micromirror. First, an SOI substrate is provided. The SOI substrate includes a substrate layer and an initial fixed tooth layer. A dielectric layer is formed between the substrate layer and the initial fixed tooth layer. Then, a plurality of through holes are formed in the SOI substrate. The through holes vertically penetrate the substrate layer and the initial fixed tooth layer. A metal interconnection structure is formed in the through hole. One end of the metal interconnection structure is exposed to the surface of the substrate layer, and the other end is exposed to the surface of the initial fixed tooth layer, so that in the subsequent process, part of the metal interconnection structures in the plurality of metal interconnection structures are electrically connected to the initial fixed tooth layer, and the other part of the metal interconnection structure is used to be electrically connected to the movable comb tooth layer. Then, in the substrate layer A first pad layer is formed on the surface of one side away from the initial fixed tooth layer, the first pad layer includes a plurality of first pads, and the first pads are electrically connected to one end of the metal interconnection structure exposed to the substrate layer; then, the initial fixed tooth layer is etched to form a fixed comb layer; then, a second substrate is bonded to the side of the fixed comb layer away from the substrate layer to obtain a bonding structure; then, a reflector and a second pad layer are formed on the surface of the second substrate away from the substrate layer, the second pad layer includes a plurality of second pads, and the second pads are electrically connected to one end of the metal interconnection structure exposed to the surface of the initial fixed tooth layer; finally, the second substrate is etched to form a movable comb layer to obtain a MEMS micromirror. The preparation method can not only improve the insulation effectiveness of the MEMS micromirror in the X and Y directions, improve the functional effectiveness and functional reliability of the MEMS micromirror, but also effectively reduce the stress accumulation introduced by the through hole and the metal interconnection structure during the preparation process, greatly improve the reliability, yield and long-term performance of the MEMS micromirror, and the process is simple, which is conducive to reducing the preparation cost.

[0062] The following combination Figure 1-3 The semiconductor structure of the embodiment of the present application is described in detail.

[0063] like Figure 1 As shown, a MEMS micromirror provided in an embodiment of the present application includes a functional layer, a plurality of through holes 500, a plurality of metal interconnect structures 501, a first pad layer 600 and a second pad layer 700; wherein the functional layer includes a stacked substrate layer 100, a fixed comb tooth layer 200 and a movable comb tooth layer 300, and a reflector 400 is provided on the movable comb tooth layer 300, and the reflector 400 is connected to the movable comb tooth layer 300, and can rotate with the vibration of the movable comb tooth layer 300.

[0064] Specifically, the substrate layer 100 and the fixed comb-tooth layer 200 are formed based on an SOI (silicon on insulator) substrate. The silicon material used to form the substrate layer 100 in the SOI substrate is thicker, and the silicon material used to form the fixed comb-tooth layer 200 is thinner, that is, the thickness of the silicon material used to form the substrate layer 100 is greater than the thickness of the silicon material of the fixed comb-tooth layer 200, and a dielectric layer pre-exists in the SOI substrate. The dielectric layer is located between the silicon material of the substrate layer 100 and the silicon material of the fixed comb-tooth layer 200, which can form good isolation, improve isolation effectiveness and isolation reliability, and is conducive to improving the device performance of the MEMS micromirror; at the same time, the use of the SOI substrate can simplify the preparation process during the preparation process, SO The SOI substrate has a dielectric layer. During the process of forming the fixed comb-tooth layer 200 by etching, the dielectric layer cannot be etched, that is, the longitudinal dimension of the fixed comb-tooth layer 200 has been determined, so there is no need to perform additional control on the etching process of the fixed comb-tooth layer 200, thereby avoiding the need to accurately control the etching conditions (such as etching time and etching depth) in a conventional process without a dielectric layer, thereby avoiding defects such as over-etching or insufficient etching depth of the fixed comb-tooth layer 200. During the process of forming the fixed comb-tooth layer 200 on the SOI substrate, the etching endpoint must stop at the surface of the dielectric layer, which greatly simplifies the etching difficulty, improves the longitudinal dimension accuracy of the substrate layer 100 and the fixed comb-tooth layer 200, and is also beneficial to improving the performance of the MEMS micromirror.

[0065] Specifically, the fixed comb tooth layer 200 includes a fixed comb tooth area 201, in which a plurality of fixed comb teeth 2010 are provided, and the plurality of fixed comb teeth 2010 are separated from each other by first spacing grooves 2011; the movable comb tooth layer 300 includes a movable comb tooth area 301, in which a plurality of movable comb teeth 3010 are provided, and the plurality of movable comb teeth 3010 are separated from each other by second spacing grooves 3011; wherein, the movable comb teeth 3010 are staggered with the fixed comb teeth 2010, and the lateral dimension of the movable comb teeth 3010 is smaller than the lateral dimension of the first spacing grooves 2011, so that when a voltage is applied to the MEMS micromirror, the movable comb teeth 3010 vibrate longitudinally under the action of electrostatic attraction, and can be inserted into each first spacing groove 2011 between the fixed comb teeth 2010, thereby realizing the function of the MEMS micromirror.

[0066] Specifically, Figure 2As shown, the fixed comb tooth layer 200 includes a limiting structure 202, which is located in the projection area of ​​the reflector 400 in the fixed comb tooth layer 200 and is used to limit the maximum rotation angle of the reflector 400; wherein the longitudinal dimension of the limiting structure 202 is less than or equal to the longitudinal dimension of the fixed comb tooth area 201 in the fixed comb tooth layer 200; in some preferred embodiments, the longitudinal dimension of the limiting structure 202 is smaller than the longitudinal dimension of the fixed comb tooth area 201, which, on the one hand, can reserve sufficient space for the rotation of the reflector 400 to avoid excessive obstruction of the rotation of the reflector 400, and on the other hand, can abut against the edge bottom surface of the reflector 400 during the rotation of the reflector 400, thereby limiting the rotation stroke of the reflector 400, that is, limiting the maximum rotation angle of the reflector 400, so that the reflector 400 can only rotate within a preset rotation angle, thereby improving the performance stability of the MEMS micromirror.

[0067] In some exemplary embodiments, the movable comb tooth area 301 also includes a supporting area 3012, which is located at the inner periphery of the plurality of movable comb teeth 3010, that is, the movable comb teeth 3010 are located on the outer side of the supporting area 3012 in the lateral direction, and the reflector 400 is located on the supporting area 3012; accordingly, the limiting structure 202 is located at the inner periphery of the plurality of fixed comb teeth 2010, that is, the fixed comb teeth 2010 are located on the outer side of the limiting structure 202 in the lateral direction, so that the limiting structure 202 is located below the supporting area 3012, and when the reflector 400 rotates with the overall vibration of the movable comb tooth area 301 having the supporting area 3012, the limiting structure 202 can well limit the maximum rotation angle of the reflector 400, thereby maintaining the operating stability and reliability of the MEMS micromirror.

[0068] A plurality of through holes 500 vertically penetrate the substrate layer 100 and the fixed comb tooth layer 200, and a dielectric layer 900 is arranged between the substrate layer 100, the fixed comb tooth layer 200 and the through holes 500, so that the substrate layer 100, the fixed comb tooth layer 200 and the through holes 500 are isolated from each other; a plurality of metal interconnection structures are filled in the through holes 500, and one end is exposed to the surface of the substrate layer 100, and the other end is exposed to the surface of the fixed comb tooth layer 200; some of the metal interconnection structures in the plurality of metal interconnection structures are electrically connected to the fixed comb tooth layer 200 to independently control the conduction of the fixed comb tooth layer 200, and another part of the metal interconnection structures are electrically connected to the movable comb tooth layer 300 to independently control the conduction of the movable comb tooth layer 300, with good isolation reliability and avoiding cross interference.

[0069] Specifically, Figure 1As shown, the first pad layer 600 includes a plurality of first pads 601, the plurality of first pads 601 are isolated from each other, and the first pad 601 is electrically connected to one end of the metal interconnection structure 501 exposed to the substrate layer 100, that is, the first pad 601 is located on the bottom surface of the side away from the reflector 400 in the MEMS micromirror, and the first pad layer 600 is connected to the power supply current on the back side of the MEMS micromirror device; the second pad layer 700 includes a plurality of second pads 701, the plurality of second pads 701 are isolated from each other, and the second pad 701 is electrically connected to one end of the metal interconnection structure 501 exposed to the surface of the fixed comb layer 200, and the second pad 701 is located on the side close to the reflector 400, so that the front side can be connected to the MEMS micromirror through the metal interconnection structure 501. The second pad 701 is electrically connected to the first pad 601 on the back side, and is connected to the power supply current on the back side through the first pad 601, so as to realize the conduction of the MEMS micromirror. There is no need to wire the second pad 701 on the side close to the reflector 400, thus avoiding the interference of the front lead on the optical path on the reflector 400, effectively reducing cross interference, and helping to improve the signal transmission quality; at the same time, it reduces the wiring length, especially greatly simplifies the array packaging; and compared with the traditional wire bonding method, the length of the signal transmission path between the first pad layer 600 and the second pad layer 700 is shortened through the metal interconnect structure 501, which is beneficial to improving the signal transmission efficiency and quality, reducing power consumption and parasitic capacitance, and also helping to reduce signal delay.

[0070] like Figure 1 As shown, in some exemplary embodiments, multiple metal interconnect structures 501 include a fixed tooth metal interconnect structure 5010 and a movable tooth metal interconnect structure 5011, multiple first pads 601 include a first fixed tooth pad 6010 and a first movable tooth pad 6011, and multiple second pads 701 include a second fixed tooth pad 7010 and a second movable tooth pad 7011; wherein, the fixed tooth metal interconnect structure 5010 is electrically connected to the fixed comb tooth area 201 of the fixed comb tooth layer 200, the first fixed tooth pad 6010 is located above the fixed tooth metal interconnect structure 5010, and the second fixed tooth pad 7010 is located below the fixed tooth metal interconnect structure 5010, so that the electrical connection between the first fixed tooth pad 6010, the fixed comb tooth area 201 and the second fixed tooth pad 7010 is achieved through the fixed tooth metal interconnect structure 5010.

[0071] Correspondingly, the movable tooth metal interconnection structure 5011 is electrically connected to the movable comb tooth area 301 of the movable comb tooth layer 300, the first movable tooth pad 6011 is located above the movable tooth metal interconnection structure 5011, and the second movable tooth pad 7011 is located below the movable tooth metal interconnection structure 5011, so that the electrical connection between the first movable tooth pad 6011, the fixed comb tooth area 201 and the second movable tooth pad 7011 is achieved through the movable tooth metal interconnection structure 5011.

[0072] Specifically, Figure 1 As shown, in some exemplary embodiments, at least a portion of the dielectric layer 900 is located on the surface of the fixed comb tooth layer 200, including but not limited to the surface of the fixed comb tooth layer 200 on one side facing away from the substrate layer 100 and the outer side surface of the fixed comb tooth layer 200; wherein, the portion of the dielectric layer 900 located on the surface of the fixed comb tooth layer 200 on the side facing away from the substrate layer 100 can isolate the fixed comb tooth layer 200 and the movable comb tooth layer 300 from each other in the longitudinal direction to avoid mutual interference between the two and affecting the functional effectiveness and functional reliability of the MEMS micromirror as a whole, and one end of the metal interconnection structure 501 is exposed to the dielectric layer 900 on the surface, so that the metal interconnection structure 501 can cross the dielectric layer 900 to be electrically connected to the second pad layer 700, thereby improving the stability of the electrical connection.

[0073] like Figure 1 As shown, in some exemplary embodiments, at least a portion of the dielectric layer 900 is located on the surface of the substrate layer 100, including but not limited to the side surface of the substrate layer 100 away from the fixed comb tooth layer 200 and the outer side surface of the substrate layer 100, wherein the portion of the dielectric layer 900 located on the side surface of the substrate layer 100 away from the fixed comb tooth layer 200 can isolate the substrate layer 100 and the first pad layer 600 from each other in the vertical direction, avoid cross interference caused by unexpected breakdown, and improve the reliability of the MEMS micromirror. At the same time, one end of the metal interconnect structure 501 is exposed to the surface of the dielectric layer 900, so that the metal interconnect structure 501 can be electrically connected to the first pad layer 600 without being blocked by the dielectric layer 900, thereby improving the reliability of the electrical connection.

[0074] like Figure 1 As shown, in some exemplary embodiments, a dielectric layer 900 is provided between each of the substrate layer 100, the fixed comb-tooth layer 200 and the through hole 500, that is, at least a portion of the dielectric layer 900 is located between the substrate layer 100 and the fixed comb-tooth layer 200, and the portion of the dielectric layer 900 is a dielectric layer structure of the SOI substrate itself, so as to effectively isolate the substrate layer 100 and the fixed comb-tooth layer 200; another portion of the dielectric layer 900 is located between the substrate layer 100 and the through hole 500, so that the substrate layer 100 and the metal interconnection structure 501 filled in the through hole 500 are isolated from each other in the lateral direction; another portion of the dielectric layer 900 is located between the fixed comb-tooth layer 200 and the through hole 500, so that the fixed comb-tooth layer 200 and the metal interconnection structure 501 are isolated from each other in the lateral direction, thereby improving the isolation reliability, preventing unexpected breakdown from occurring and causing interference, and thus helping to improve the reliability of the MEMS micromirror.

[0075] Specifically, in some preferred embodiments, Figure 1As shown, the MEMS micromirror further includes a bonding metal layer 800 located between the fixed comb-tooth layer 200 and the movable comb-tooth layer 300. Figure 3 As shown, the bonding metal layer 800 has a preset pattern, and the through hole 500 is located within the projection area of ​​the preset pattern in the longitudinal direction. The preset pattern is the bonding area, which is bonded to the fixed comb tooth layer 200 on one side and to the movable comb tooth layer 300 on the other side. On the one hand, the bonding area provides a certain bonding area to improve the bonding strength. The same layer of bonding metal layer 800 can be used to achieve structural bonding and electrical interconnection through different areas in the bonding area. Different areas avoid each other and do not interfere with each other, which is conducive to reducing the difficulty of preparation and saving preparation costs. On the other hand, compared with the entire bonding surface in the traditional bonding process, the patterned bonding area reduces the area of ​​the bonding interface, which is conducive to reducing the thermal stress distribution and thermal stress accumulation introduced at the bonding interface during the temperature change process due to the different thermal expansion coefficients of different materials during the preparation process, thereby improving the overall structural reliability and preparation yield of the MEMS device and improving its long-term performance.

[0076] Specifically, the material of the bonding metal layer 800 includes at least one of titanium and gold; exemplarily, the material of the bonding metal layer 800 includes titanium; exemplarily, the material of the bonding metal layer 800 includes gold; exemplarily, the material of the bonding metal layer 800 includes titanium and gold.

[0077] Among them, the gold layer has high conductivity, can improve the effectiveness of current transmission, reduce resistance, improve the performance and efficiency of the MEMS micromirror, and has high stability, which is beneficial to the long-term performance of the MEMS micromirror; and the gold layer has good wettability and adhesion, which can greatly improve the bonding strength between the bonding metal layer 800 and the dielectric layer 900 (and the metal interconnect structure 501) on the surface of the fixed comb tooth layer 200, and can also greatly improve the bonding strength between the bonding metal layer 800 and the movable comb tooth layer 300, thereby improving the overall bonding strength and structural reliability of the MEMS micromirror, which is beneficial to improving the long-term performance of the MEMS micromirror.

[0078] The titanium layer can improve the stability of the semiconductor material, which is beneficial to improving the molding accuracy of the gold layer in the bonding metal layer 800, and is also beneficial to improving the conductivity and corrosion resistance of the bonding metal layer 800, thereby improving the long-term performance of the MEMS micromirror; in addition, the titanium layer can prevent the metal material (for example, copper) of the metal interconnect structure 501 from diffusing into structures such as the substrate layer 100 and the movable comb layer 300 to a certain extent, thereby improving the performance of the MEMS micromirror.

[0079] Specifically, in some exemplary embodiments, the thickness of the bonding metal layer 800 is 470nm to 650nm; it can be understood that the thickness of the bonding metal layer 800 can be any point value between 470nm and 650nm; exemplarily, the thickness of the bonding metal layer 800 can be 470nm, 500nm, 530nm, 560nm, 600nm, 625nm, 650nm, etc.; in this way, it can provide good bonding strength and avoid adverse effects on the performance of the MEMS micromirror.

[0080] In some exemplary embodiments, the bonding metal layer 800 includes a titanium layer and a gold layer, and the titanium layer is located between the gold layer and the metal interconnection structure 501; wherein the thickness of the titanium layer is 20nm to 50nm, and the thickness of the gold layer is 450nm to 600nm; it can be understood that the thickness of the titanium layer can be any point value between 20nm and 50nm, and the thickness of the gold layer can be any point value between 450nm and 600nm; exemplarily, the thickness of the titanium layer can be 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, etc., and the thickness of the gold layer can be 450nm, 480nm, 500nm, 520nm, 550nm, 580nm, 600nm, etc.

[0081] Specifically, Figure 3 As shown, the bonding metal layer 800 includes a mutually isolated structural bonding area 801, a plurality of first metal electrical interconnection areas 802 and a plurality of second metal electrical interconnection areas 803, wherein the structural bonding area 801 can be an integral structure, or can include a plurality of structural bonding sub-areas, and adjacent structural bonding sub-areas are isolated by spacing areas to respectively enhance the bonding strength of different areas, and in the longitudinal direction, the structural bonding area 801 is located between the fixed comb tooth layer 200 and the movable comb tooth layer 300 to enhance the bonding strength between the two layers of the structure, thereby facilitating the overall structural reliability and long-term performance of the MEMS micromirror.

[0082] And, if Figure 1 As shown, in the longitudinal direction, the first metal electrical interconnection area 802 and the second metal electrical interconnection area 803 are located between the movable comb tooth layer 300 and the metal interconnection structure 501, and the surface of the first metal electrical interconnection area 802 (and the second metal electrical interconnection area 803) close to the substrate layer 100 is directly in contact with the metal interconnection structure 501, while the surface close to the reflector 400 is electrically connected to the second pad 701 with the structure of the movable comb tooth layer 300 as a transition, so as to realize the electrical interconnection between the first pad layer 600 and the second pad layer 700 in the longitudinal direction.

[0083] It should be noted that the first metal electrical interconnection area 802 is electrically connected to the movable comb tooth area 301 in the movable comb tooth layer 300, so that the movable comb tooth area 301 can be effectively driven after the power supply current is connected; and the second metal electrical interconnection area 803 is electrically connected to the fixed comb tooth layer 200, and is isolated from the movable comb tooth area 301 in the movable comb tooth layer 300, so as to improve the reliability of the electrical connection with the fixed comb tooth layer 200, and avoid cross interference with the movable comb tooth area 301, thereby improving the reliability of the MEMS micromirror.

[0084] Specifically, Figure 3 As shown, in some exemplary embodiments, a plurality of metal spacing grooves 804 are provided in the bonding metal layer 800, and the metal spacing grooves 804 penetrate the bonding metal layer 800 in the vertical direction; wherein part of the metal spacing grooves 804 are located between the structural bonding area 801 and the first metal electrical interconnection area 802, that is, part of the metal spacing grooves 804 are arranged around the first metal electrical interconnection area 802, so that the first metal electrical interconnection area 802 is completely isolated from the structural bonding area 801, and the first metal electrical interconnection area 802 is relatively independently arranged in the horizontal direction, which can effectively prevent cross interference; at the same time, another part of the metal spacing grooves 804 are located between the structural bonding area 801 and the second metal electrical interconnection area 803, that is, part of the metal spacing grooves 804 are arranged around the second metal electrical interconnection area 803, so that the second metal electrical interconnection area 803 is effectively isolated from the structural bonding area 801, and the second metal electrical interconnection area 803 is also relatively independently arranged in the horizontal direction, avoiding the possibility of cross interference, which is conducive to improving the reliability and stability of the MEMS micromirror.

[0085] In this way, vertical electrical interconnection and structural interconnection can be achieved simultaneously through the same bonding metal layer 800. Multiple areas with different functions in the patterned bonding metal layer 800 give way to each other and do not interfere with each other, which is beneficial to reducing stress accumulation in the preparation process, saving preparation costs, and enhancing the bonding strength between the vertical layer structures, which is beneficial to improving the reliability and long-term performance of the MEMS micromirror.

[0086] Specifically, Figure 3 As shown, in some exemplary embodiments, the bonding metal layer 800 also includes a scribe line area 805, which is located on the peripheral side of the structural bonding area 801, and can reserve a certain cutting space. During the preparation process, the array-packaged wafer is used to be cut as a whole into multiple MEMS micromirrors, thereby avoiding damage to the functional layers and other structures in the MEMS micromirrors in subsequent processes, which is beneficial to improving the preparation yield and structural reliability of the MEMS micromirrors.

[0087] Specifically, Figure 1As shown, in a portion of the dielectric layer 900 located on the surface of the fixed comb-tooth layer 200, a connection window 901 penetrating the dielectric layer 900 is opened on the surface of the fixed comb-tooth layer 200, and the connection window 901 is located on both sides of the metal interconnection structure 501 for electrically connecting to the fixed comb-tooth layer 200, so that the fixed comb-tooth layer 200 can be connected to the second electrical interconnection area 303 in the movable comb-tooth layer 300 through the connection window 901, and the second electrical interconnection area 303 is electrically connected to the metal interconnection structure 501, thereby realizing the electrical connection between the fixed comb-tooth layer 200 and the metal interconnection structure 501 through the connection window 901; or In some preferred embodiments, during the preparation process, the material of the metal interconnection structure 501 can be filled in the connection window 901, and the fixed comb tooth layer 200 can be connected to the second metal electrical interconnection area 803 through the material of the metal interconnection structure 501 partially filled in the connection window 901, and the second metal electrical interconnection area 803 is connected to the metal interconnection structure 501, thereby realizing the electrical connection between the fixed comb tooth layer 200 and the metal interconnection structure 501 through the connection window 901; the formation process of the connection window 901 is simple, and can effectively improve the effectiveness and reliability of the electrical connection of the fixed comb tooth layer 200.

[0088] Specifically, Figure 1 As shown, the movable comb tooth layer 300 includes a movable comb tooth area 301, a first electrical interconnection area 302 and a second electrical interconnection area 303, wherein the first electrical interconnection area 302 and the second electrical interconnection area 303 are respectively located on the outer peripheral side of the movable comb tooth area 301, and the movable comb tooth area 301 is a functional area of ​​the movable comb tooth layer 300, and the movable comb tooth area 301 is suspended above the fixed comb tooth layer 200 to enhance the effectiveness and reliability of electrical isolation between the movable comb tooth layer 300 and the fixed comb tooth layer 200 in the longitudinal direction; the first electrical interconnection area 302 is connected to the movable comb tooth area 301, and in the longitudinal direction, the first electrical interconnection area 302 is located between the second pad 701 and the metal interconnection structure 501, so that the movable comb tooth area 301 The first electrical interconnection area 302 can be connected to the second pad 701, the metal interconnection structure 501, the first pad 601 and the electrical connection structure of the power supply current, so as to realize the electrical connection between the power supply current and the movable comb tooth area 301, prevent cross interference, and improve the electrical connection reliability and stability of the movable comb tooth area 301; further, in some preferred embodiments, in the longitudinal direction, the first electrical interconnection area 302 is located between the second pad 701 and the first metal electrical interconnection area 802, so that the movable comb tooth area 301 is connected to the second pad 701, the first metal electrical interconnection area 802, the metal interconnection structure 501, the first pad 601 and the electrical connection structure of the power supply current through the first metal electrical interconnection area 802.

[0089] Specifically, the second electrical interconnection area 303 is electrically connected to the fixed comb-tooth layer 200 through the connection window 901. In the longitudinal direction, the second electrical interconnection area 303 is located between the second pad 701 and the metal interconnection structure 501, so that the fixed comb-tooth layer 200 is connected to the metal interconnection structure 501 through the second electrical interconnection area 303, thereby realizing the electrical connection between the power supply current and the fixed comb-tooth layer 200, and improving the reliability and stability of the electrical connection of the fixed comb-tooth layer 200; further, in some preferred embodiments, the second electrical interconnection area 303 is located between the second pad 701 and the metal interconnection structure 501. 03 is located between the second pad 701 and the second metal electrical interconnection area 803, so that the fixed comb tooth layer 200 is connected to the metal interconnection structure 501 through the second metal electrical interconnection area 803, thereby realizing the electrical connection between the power supply current and the fixed comb tooth layer 200; and the second electrical interconnection area 303 and the first electrical interconnection area 302 are isolated from each other, so that the fixed comb tooth layer 200 and the movable comb tooth area 301 are effectively isolated, cross interference is prevented, and the signal transmission quality is improved, which is beneficial to improving the reliability and long-term performance of the MEMS micromirror.

[0090] Specifically, Figure 2 As shown, in some preferred embodiments, a first isolation groove 304 is provided on the periphery of the second electrical interconnection zone 303, that is, the first isolation groove 304 surrounds the second electrical interconnection zone 303, and the first isolation groove 304 penetrates the material of the movable comb tooth layer 300 in the longitudinal direction, so that the second electrical interconnection zone 303 is independent of the first electrical interconnection zone 302 and the movable comb tooth zone 301, so as to achieve effective isolation of the second electrical interconnection zone 303 and prevent a short circuit between the second electrical interconnection zone 303 and the movable comb tooth zone 301.

[0091] Specifically, Figure 2 As shown, in some exemplary embodiments, the fixed comb tooth layer 200 also includes an electrical area, wherein the electrical area is located at the periphery of the fixed comb tooth area 201. In this embodiment, the first electrical interconnection area 302, the second electrical interconnection area 303, the interconnection structure 501, the first solder pad 601 and the second solder pad 701 are all arranged within the projection area of ​​the electrical area to facilitate electrical interconnection in the longitudinal direction while avoiding the introduction of additional leads.

[0092] It should be noted that if Figure 2As shown, the fixed comb tooth layer 200 also includes a second isolation groove 203, which is located in the electrical area. The second isolation groove 203 is located on the side of the metal interconnection structure 501 electrically connected to the movable comb tooth layer 300, that is, the second isolation groove 203 is located on the side of the movable tooth metal interconnection structure 5011, so that the silicon material located at the movable tooth interconnection structure in the electrical area is isolated from the silicon material of the fixed comb tooth layer 200, especially isolated from the silicon material in the fixed comb tooth area 201, thereby further improving the isolation reliability between the fixed comb tooth layer 200 and the movable comb tooth layer 300 and avoiding short circuit.

[0093] So, Figure 1 As a reference, in the MEMS micromirror, in the projection direction of the first electrical interconnection area 302, the second pad 701 is connected to one end surface of the first electrical interconnection area 302, so that the second pad 701 is electrically connected to the movable comb tooth area 301 of the movable comb tooth layer 300, and then the other end surface of the first electrical interconnection area 302 is connected to the first metal electrical interconnection area 802, the lower surface of the first metal electrical interconnection area 802 is in contact with the metal interconnection structure 501 to achieve electrical connection, and then electrically connected to the first pad 601 at the bottom through the metal interconnection structure 501, and finally the first pad 601 is connected to the power supply current on the back of the device to achieve conduction and drive of the movable comb tooth area 301; and in the projection direction of the second electrical interconnection area 303, The second pad 701 is connected to the surface of one end of the second electrical interconnection area 303, but the second electrical interconnection area 303 and the movable comb tooth area 301 are isolated from each other, so that the second pad 701 can be isolated from the movable comb tooth area 301. Then, the other end surface of the second electrical interconnection area 303 is connected to the second metal electrical interconnection area 803, and the second metal electrical interconnection area 803 is also electrically connected to the fixed comb tooth layer 200 through the connection window 901. Then, the lower surface of the second metal electrical interconnection area 803 contacts the metal interconnection structure 501, and can be electrically connected to the first pad 601 at the bottom through the metal interconnection structure 501. Finally, the first pad 601 is connected to the power supply current on the back of the device, thereby realizing the electrical connection between the fixed comb tooth layer 200 and the power supply current.

[0094] The following combination Figure 4-13 The preparation method of the MEMS micromirror according to the embodiment of the present application is described in detail.

[0095] First, see Figure 4 , providing an SOI substrate.

[0096] The SOI substrate 1000 includes a substrate layer 100 and an initial toothing layer 210, and a dielectric layer 900 is formed between the substrate layer 100 and the initial toothing layer 210; in the SOI substrate 1000, the materials of the substrate layer 100 and the initial toothing layer 210 are both silicon, and correspondingly, the material of the dielectric layer 900 is silicon oxide, which has good electrical properties and low power consumption, can significantly reduce parasitic capacitance, reduce signal transmission delay, and improve signal transmission efficiency. In addition, there is a partial dielectric layer 900 in the SOI substrate 1000, which can isolate the substrate layer 100 and the initial toothing layer 210, improve the internal isolation effect, and reduce the undesired current from the subsequently formed functional layer to the substrate layer 100, which is beneficial to improving the overall performance of the MEMS micromirror such as reliability.

[0097] It should be noted that the silicon layer serving as the initial tooth-fixing layer 210 in the SOI substrate is relatively thin, and the thickness has been determined. There is a dielectric layer 900 between the initial tooth-fixing layer 210 and the underlying substrate layer 100. In the subsequent etching process of the initial tooth-fixing layer 210, the dielectric layer 900 will not be etched, and only the silicon material of the initial tooth-fixing layer 210 will be etched and stop on the surface of the dielectric layer 900. Compared with traditional silicon substrates, in the subsequent etching process, there is no need to precisely control the etching conditions, such as etching time and etching depth, so as to effectively control the thickness of the fixed tooth layer 200 and avoid damage to the substrate layer 100, which greatly simplifies the preparation process, avoids the problems of insufficient etching depth and over-etching, and is beneficial to improving the preparation accuracy and yield of MEMS micromirrors.

[0098] Next, see Figure 4 , forming a plurality of through holes in the SOI substrate.

[0099] The through hole 500 vertically penetrates the substrate layer 100 and the initial fixed tooth layer 210, and is opened in the area corresponding to the electrical area in the initial fixed tooth layer 210, and is used to fill the metal interconnection structure 501 in the subsequent steps. A part of the through hole 500 is used to electrically connect the fixed comb tooth layer 200, and another part of the through hole 500 is used to electrically connect the movable comb tooth layer 300, and the two ends of the metal interconnection structure 501 are exposed to the substrate layer 100 and the initial fixed tooth layer 210, respectively, to improve the effectiveness and reliability of the vertical electrical connection; in some exemplary embodiments, the photoresist can be patterned on the SOI substrate 1000, and at least one of deep silicon etching and reactive ion etching is used to pattern the photoresist on the SOI substrate 1000. The through hole 500 is etched in the I substrate 1000. This step pre-etches the through hole 500 for electrically connecting the fixed comb tooth layer 200 and the movable comb tooth layer 300, so that only one seed layer preparation and one electroplating are required to solve the problems of interconnection and bonding, which greatly simplifies the overall preparation process, is beneficial to reducing thermal stress accumulation, improving preparation yield and reducing preparation cost, and thus is beneficial to improving the reliability and long-term performance of the through hole 500 and the MEMS micromirror as a whole; in some preferred embodiments, deep silicon etching, reactive ion etching and deep silicon etching are used alternately for etching, the process is simple, and the through hole 500 has high forming accuracy, which is beneficial to improving preparation accuracy and preparation yield.

[0100] Next, see Figure 5 After forming a plurality of through holes, a dielectric layer is formed on the SOI substrate having the through holes.

[0101] In some exemplary embodiments, the SOI substrate 1000 may be thermally oxidized so that each exposed surface in the SOI substrate 1000 having the through hole 500 is thermally oxidized to form a thermal oxidation layer; in other exemplary embodiments, a dielectric deposition layer is covered on the SOI substrate 1000 having the through hole 500 by deposition, and the deposition method may optionally include at least one of physical vapor deposition (PVD), chemical vapor deposition (CVD) and plasma chemical vapor deposition (PECVD), preferably PECVD; the partial dielectric layer 900 (thermal oxidation layer or dielectric deposition layer) formed in this step and the original partial dielectric layer 900 in the SOI substrate 1000 together constitute an overall dielectric layer 900 to achieve a good isolation effect.

[0102] Next, see Figure 6 , forming a connection window on the dielectric layer on the surface of the initial fixed tooth layer.

[0103] The connection window 901 is used to electrically connect the fixed comb tooth layer 200 formed by the initial fixed tooth layer 210 and the metal interconnection structure 501 (and the first pad 601) filled in the through hole 500 in the subsequent preparation steps, so as to improve the effectiveness, reliability and stability of the electrical connection of the fixed comb tooth layer 200, thereby helping to improve the reliability of the MEMS micromirror; in some exemplary embodiments, the connection window 901 can be formed on both sides or the surrounding side of a portion of the through hole 500 by etching, and can be set to a point shape, a ring shape, etc., and the etching depth and width are controllable, which is conducive to improving the reliability of the electrical connection. The metal interconnection structure 501 filled in the portion of the through hole 500 is electrically connected to the fixed comb tooth layer 200 in the subsequent steps, and is kept isolated from the movable comb tooth area 301 in the movable comb tooth layer 300, so as to improve the reliability of the MEMS micromirror.

[0104] Next, see Figure 7 , forming a metal interconnect structure in the through hole.

[0105] One end of the metal interconnect structure 501 is exposed to the surface of the substrate layer 100, and the other end is exposed to the surface of the initial fixed tooth layer 210; some of the multiple metal interconnect structures are electrically connected to the initial fixed tooth layer 210, and the other part of the metal interconnect structure is used to electrically connect to the movable comb tooth layer 300.

[0106] Specifically, forming a metal interconnection structure in the through hole includes:

[0107] forming a seed layer in the through hole and filling it with metal material to form an initial metal interconnection structure;

[0108] The initial metal interconnection structure is planarized and subjected to vacuum heat treatment at 350° C. to 500° C. to form the metal interconnection structure.

[0109] In this step, a double-sided magnetron sputtering seed layer is used, and electroplating is performed to fill the metal material. The seed layer includes a titanium / copper seed layer, and the metal material of the metal interconnect structure 501 includes copper metal. Among them, the chemical properties of titanium metal are stable and can effectively protect the inner wall of the through hole 500, and titanium metal has good adhesion and conductivity, which can improve the quality and stability of the seed layer and the metal interconnect structure 501. The copper seed layer can provide conductivity, which is conducive to the subsequent electroplating of metal materials. The process is carried out stably and effectively. Afterwards, the initial metal interconnect structure is formed to protrude from the surface of the initial fixed tooth layer 210 (or the dielectric layer 900). The chemical mechanical polishing (CMP) process can be used for planarization to grind the surface of the initial metal interconnect structure until it is flush with the dielectric layer 900 on the surface of the initial fixed tooth layer 210, which is conducive to improving the flatness of each layer structure formed subsequently and improving the morphological accuracy and structural reliability of the overall MEMS structure.

[0110] In the process of filling the metal material, part of the metal material is filled in the connection window 901, and along with the planarization process, it is also ground to be flush with the surface of the dielectric layer 900 to improve the surface flatness and precision of the overall structure.

[0111] It can be understood that the temperature of the vacuum heat treatment can be any point value between 350°C and 500°C; illustratively, the temperature can be 350°C, 375°C, 400°C, 425°C, 450°C, 475°C, 500°C, etc.; in this way, the vacuum heat treatment can effectively reduce the stress of the metal material (i.e., copper), improve the reliability of the metal interconnect structure 501 and the long-term performance of the MEMS micromirror.

[0112] Next, see Figure 8 A first pad layer is formed on a surface of the substrate layer facing away from the initial fixed tooth layer.

[0113] This step adopts a metal stripping process, in which a photoresist is coated on the surface of the side of the substrate layer 100 away from the initial fixed tooth layer 210, and after exposure and development, the photoresist film layer with the target pattern is used as a mask to evaporate the metal material of the first pad layer 600 with glue, and then the metal on the mask is stripped and removed together with the photoresist, leaving the metal of the target pattern on the surface of the substrate layer 100, that is, the first pad layer 600 is formed, and the first pad layer 600 includes a plurality of mutually isolated first pads 601, and the pattern formed by the plurality of first pads 601 is the same as the target pattern, and each first pad 601 is aligned and connected to a metal interconnection structure 501, so as to realize the electrical connection between the first pad 601 and the corresponding metal interconnection structure 501.

[0114] In some exemplary embodiments, the first pad layer 600 includes a BGA pad layer, the first pad 601 includes a BGA pad, and the first pad layer 600 includes multiple metal layers, the multiple metal layers include at least one of a titanium layer, an aluminum layer, a nickel layer and a gold layer; in some preferred embodiments, the multiple metal layers include a stacked titanium layer, an aluminum layer, a nickel layer and a gold layer.

[0115] In some exemplary embodiments, the thickness of the first pad layer 600 is 420nm to 620nm; it can be understood that the thickness of the first pad layer 600 can be any point value between 450nm and 600nm; exemplarily, the thickness of the first pad layer 600 can be 450nm, 480nm, 500nm, 525nm, 550nm, 575nm, 600nm, etc.

[0116] In some exemplary embodiments, the thickness of the titanium layer is 40 nm to 60 nm, the thickness of the aluminum layer is 170 nm to 250 nm, the thickness of the nickel layer is 40 nm to 60 nm, and the thickness of the gold layer is 170 nm to 250 nm.

[0117] The first pad layer 600 utilizes the space on the back of the MEMS micromirror, and can also achieve a higher pin density, and has a lower thermal resistance and a larger heat dissipation area. It can also reduce the stress caused by differences in thermal expansion coefficients and reduce the risk of cracking, which is beneficial to improving the stability, reliability and long-term performance of the MEMS micromirror; in addition, it can also reduce lead inductance and capacitance, which is also beneficial to reducing signal transmission delay.

[0118] Next, in some exemplary embodiments, see Fig. 9 After forming the first pad layer and before etching the initial fixed tooth layer to form the fixed comb tooth layer, a bonding metal layer is formed on the surface of the initial fixed tooth layer facing away from the substrate layer.

[0119] The bonding metal layer 800 has a preset pattern and a certain thickness. The second metal electrical interconnection area 803 of the bonding metal layer 800 can cover the connection window 901 and the metal interconnection structure 501, so that the metal interconnection structure 501 material filled in the connection window 901 can contact the initial fixed tooth layer 210 (or the fixed comb tooth layer 200) on one side and contact the second metal electrical interconnection area 803 on the other side, thereby realizing the final electrical interconnection between the fixed comb tooth layer 200 and the second metal electrical interconnection area 803 and the metal interconnection structure 501, and the electrical connection reliability is good.

[0120] In the process of forming the bonding metal layer 800 having a preset pattern, within the projection area corresponding to the electrical area, on the metal interconnection structure 501 for electrically connecting to the movable comb tooth area 301, that is, on the movable tooth metal interconnection structure 5011, part of the bonding metal forms a first metal electrical interconnection area 802, so that the first metal electrical interconnection area 802, the movable tooth metal interconnection structure 5011 and the corresponding first movable tooth pad 6011 are electrically connected; on the metal interconnection structure 501 for electrically connecting to the fixed comb tooth area 201, that is, on the fixed tooth metal interconnection structure 5011, part of the bonding metal forms a first metal electrical interconnection area 802, so that the first metal electrical interconnection area 802, the movable tooth metal interconnection structure 5011 and the corresponding first movable tooth pad 6011 are electrically connected; On the connecting structure 5010, part of the bonding metal forms a second metal electrical interconnection area 803, so that the second metal electrical interconnection area 803, the fixed tooth metal interconnection structure and the corresponding second movable tooth pad 7011 are electrically connected; and no bonding metal is deposited on the periphery of the first metal electrical interconnection area 802 and the periphery of the second metal electrical interconnection area 803, thereby forming a metal spacing groove 804, thereby realizing electrical isolation between the first metal electrical interconnection area 802, the second metal electrical interconnection area 803 and the structural bonding area 801 deposited in other areas, thereby effectively avoiding short circuits.

[0121] Next, see Fig.10 In some exemplary embodiments, a limiting groove is formed on the dielectric layer on the surface of the initial fixed tooth layer.

[0122] The limiting groove 902 is used to form a limiting structure 202 in a subsequent step, and the limiting structure 202 is used to limit the rotation angle of the reflector 400. In addition, during the preparation process, the limiting groove 902 is formed before the reflector 400. The limiting groove 902 can also locate the position of the reflector 400 formed in the subsequent step to improve the structural accuracy of the reflector 400 and the MEMS micromirror, which is beneficial to improving the preparation yield and performance of the MEMS micromirror; illustratively, the limiting groove 902 passes through the dielectric layer 900 on the surface of the initial fixed tooth layer 210. On the one hand, it can improve the positioning accuracy of the reflector 400. On the other hand, in the process of subsequently forming the fixed comb tooth layer 200, the silicon material in the area corresponding to the limiting groove can be etched to a certain extent, thereby increasing the spacing distance between the fixed comb tooth layer 200 and the movable comb tooth layer 300 formed subsequently, further reducing the possibility of cross interference, which is beneficial to improving the reliability and stability of the MEMS micromirror.

[0123] Next, see Fig.11 , the initial fixed tooth layer is etched to form a fixed comb tooth layer.

[0124] In this step, the initial fixed tooth layer 210 can be etched by at least one of dry etching and wet etching; in some preferred embodiments, deep silicon etching (i.e., deep reactive ion etching, DRIE) can be used to form a high aspect ratio structure with simple process and high precision, which can improve the preparation efficiency and improve the morphology accuracy of the fixed comb tooth layer 200.

[0125] It should be noted that during the etching process of the initial fixed tooth layer 210, the silicon material at the position corresponding to the limiting groove 902 is only partially etched, thereby forming a limiting structure 202. The longitudinal dimension of the limiting structure 202 is smaller than the longitudinal dimension of the initial fixed tooth layer 210, but still has a certain thickness. While reserving rotation space for the subsequent rotation of the reflector 400, it can also limit the rotation angle of the reflector 400 to a certain extent, thereby preventing the reflector 400 from rotating too much and affecting the performance of the MEMS micromirror.

[0126] In the process of forming the fixed comb tooth layer, in the area corresponding to the fixed comb tooth area 201, part of the silicon material is etched to form a plurality of fixed comb teeth 2010 and a first spacing groove 2011 between each fixed comb tooth 2010, but the silicon material at the first spacing groove 2011 is not completely etched through, so that the fixed comb tooth layer 200 as a whole can be electrically connected; in the electrical area outside the fixed comb tooth area 201, part of the silicon material is also etched, so that a second isolation groove 203 is formed on the side of the metal interconnection structure 501 used for electrical connection with the movable comb tooth layer 300, effectively improving the reliability of electrical isolation between the fixed comb tooth area 201 and the movable comb tooth area 301; and, in this step, isolation is first achieved, and then the second substrate is bonded, so that after bonding, there will be no short circuit with materials in other areas, which greatly improves the performance stability of the MEMS micromirror.

[0127] Next, see Fig.12 , bonding the second substrate to the side of the fixed comb-tooth layer facing away from the substrate layer to obtain a bonding structure.

[0128] The second substrate 310 is used to form a movable comb tooth layer 300 in subsequent steps. After the second substrate 310 is bonded to the fixed comb tooth layer 200, the surface of the second substrate 310 facing away from the substrate layer 100 is ground and polished to a target thickness to improve the molding accuracy of the subsequent movable comb tooth layer 300.

[0129] In some preferred embodiments, this step specifically involves bonding the second substrate 310 to the bonding metal layer 800 on the surface of the fixed comb tooth layer 200 to obtain a bonding structure, wherein a gold-silicon bonding surface is formed between the silicon material of the fixed comb tooth layer 200 and the gold material of the bonding metal layer 800, and the bonding strength is high and the bonding reliability is good, which is beneficial to improving the preparation yield of the MEMS micromirror and its long-term performance.

[0130] Next, see Fig.13 A reflector and a second pad layer are formed on a surface of the second substrate facing away from the substrate layer.

[0131] Among them, the reflector 400 and the second pad layer 700 can be respectively located in different areas of the same layer, so as to reduce the overall thickness of the MEMS micromirror, which is beneficial to improving its photoelectric performance; the reflector 400 is formed with the limiting groove 902 as the positioning reference to improve the accuracy of the molding position of the reflector 400, which is beneficial to improving the overall accuracy and reliability of the MEMS micromirror; the second pad layer 700 includes a plurality of mutually isolated second pads 701, wherein some of the second pads 701 are located above the first metal electrical interconnection area 802 to achieve electrical connection with the movable comb tooth layer 300, and some of the second pads 701 are located above the second metal electrical interconnection area 803 to achieve electrical connection with the fixed comb tooth layer 200.

[0132] In addition, the surface of the reflector and the second pad layer is covered with a metal layer. The material of the metal layer includes gold. The metal layer can be formed in the same process step. On the one hand, it can form a metal film reflector, which is beneficial for light to be incident at any angle, and can also improve the reflectivity of the reflector surface, thereby helping to improve the performance of the MEMS micromirror; on the other hand, the metal layer on the surface of the second pad layer can play an anti-oxidation role and is also convenient for thickness control, which is beneficial to improving the stability and durability of the MEMS micromirror.

[0133] Next, the second substrate is etched to form a movable comb-tooth layer to obtain a MEMS micromirror.

[0134] The etching process used in this step can be the same as the etching process used to etch the initial fixed tooth layer 210, such as a deep silicon etching process, to reduce the manufacturing complexity and improve the manufacturing efficiency; wherein, in the step of Fig.13 The structure shown is formed Figure 2 In the process of forming the structure shown in the figure, the silicon material at the position corresponding to the limiting groove 902 in the fixed comb tooth layer 200 may have a certain height of residue in the early process of forming the fixed comb tooth layer 200. In the process of etching the second substrate 310 in this step, it can be further etched and removed without affecting the functional area of ​​the fixed comb tooth layer 200, thereby reducing the risk of accidental interference caused by the short longitudinal spacing between this part of the silicon material and the movable comb tooth layer 300, which is beneficial to improving the reliability of the MEMS micromirror.

[0135] Among them, in the area corresponding to the movable comb tooth area 301, part of the silicon material is etched to form a plurality of movable comb teeth 3010 and a second spacing groove 3011 between each movable comb tooth 3010, so that the movable comb teeth 3010 can effectively vibrate when subjected to electrostatic attraction, and the movable comb teeth 3010 are connected to each other through the silicon material in the edge area, so that the movable comb tooth layer 300 as a whole can be electrically connected; in the area outside the movable comb tooth area 301, part of the silicon material is also etched to form a first isolation groove 304, so that after the silicon material in the area is isolated, the silicon material on the metal interconnection structure 501 electrically connected to the movable comb tooth layer 300 forms a first electrical interconnection area 302, and the silicon material on the metal interconnection structure 501 electrically connected to the fixed comb tooth layer 200 forms a second electrical interconnection area 303, thereby realizing precise electrical isolation and electrical connection in the MEMS micromirror and improving the performance stability of the MEMS micromirror.

[0136] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0137] What is described above are only some embodiments of the present application and are not intended to limit the present application. Those skilled in the art should understand that the present application may undergo various changes and improvements, and any modifications, equivalent substitutions and improvements made in accordance with the present application shall fall within the scope of protection required by the present application.

Claims

1. A MEMS micromirror, characterized in that: include: The functional layer comprises a stacked substrate layer, a fixed comb-tooth layer and a movable comb-tooth layer, wherein a reflector is arranged on the movable comb-tooth layer; A plurality of through holes vertically penetrate the substrate layer and the fixed comb-tooth layer, and a dielectric layer is disposed between the substrate layer, the fixed comb-tooth layer and the through holes; A plurality of metal interconnect structures are filled in the through holes, and one end of the metal interconnect structures is exposed to the surface of the substrate layer, and the other end is exposed to the surface of the fixed comb-tooth layer; some of the metal interconnect structures are electrically connected to the fixed comb-tooth layer, and another part of the metal interconnect structures is electrically connected to the movable comb-tooth layer; a bonding metal layer, located between the fixed comb-tooth layer and the movable comb-tooth layer, the bonding metal layer having a preset pattern, the through hole being located within the projection area of ​​the preset pattern in the longitudinal direction; the bonding metal layer comprising mutually isolated structural bonding areas, a plurality of first metal electrical interconnection areas and a plurality of second metal electrical interconnection areas, the first metal electrical interconnection areas and the second metal electrical interconnection areas being located between the movable comb-tooth layer and the metal interconnection structure; the first metal electrical interconnection areas are electrically connected to the movable comb-tooth areas in the movable comb-tooth layer; the second metal electrical interconnection areas are electrically connected to the fixed comb-tooth layer, and are mutually isolated from the movable comb-tooth areas in the movable comb-tooth layer; A first pad layer, comprising a plurality of first pads, wherein the first pads are electrically connected to one end of the metal interconnect structure exposed to the substrate layer; The second pad layer includes a plurality of second pads, and the second pads are electrically connected to one end of the metal interconnect structure exposed on the surface of the fixed comb-tooth layer.

2. The MEMS micromirror according to claim 1, characterized in that: The substrate layer and the fixed comb-teeth layer are formed based on an SOI substrate.

3. The MEMS micromirror according to claim 1, characterized in that: The fixed comb-tooth layer comprises a limiting structure, and the limiting structure is located in the projection area of ​​the reflector on the fixed comb-tooth layer, and is used to limit the maximum rotation angle of the reflector.

4. The MEMS micromirror according to claim 1, characterized in that: The material of the bonding metal layer includes at least one of titanium and gold.

5. The MEMS micromirror according to claim 1, characterized in that: The thickness of the bonding metal layer is 470nm-650nm.

6. The MEMS micromirror according to claim 1, characterized in that: A plurality of metal spacing grooves are provided in the bonding metal layer, at least some of the metal spacing grooves are located between the structural bonding area and the first metal electrical interconnection area, and another portion of the metal spacing grooves are located between the structural bonding area and the second metal electrical interconnection area.

7. The MEMS micromirror according to any one of claims 1 to 5, characterized in that: At least a portion of the dielectric layer is located on the surface of the fixed comb-tooth layer. A connection window penetrating the dielectric layer is opened on the surface of the fixed comb-tooth layer. The fixed comb-tooth layer is electrically connected to the metal interconnection structure through the connection window.

8. The MEMS micromirror according to any one of claims 1 to 5, characterized in that: The movable comb-tooth layer comprises a movable comb-tooth region, a first electrical interconnection region and a second electrical interconnection region, wherein the first electrical interconnection region and the second electrical interconnection region are respectively located between the second pad and the metal interconnection structure; The movable comb teeth area is connected to the first electrical interconnection area; The second electrical interconnection region is isolated from the first electrical interconnection region, and the second electrical interconnection region is electrically connected to the fixed comb-tooth layer.

9. The MEMS micromirror according to claim 8, characterized in that: A first isolation groove is provided on the periphery of the second electrical interconnection area, for isolating the second electrical interconnection area from the movable comb tooth area.

10. The MEMS micromirror according to any one of claims 1 to 5, characterized in that: The fixed comb-tooth layer includes a second isolation groove, and the second isolation groove is used to isolate the material of the fixed comb-tooth layer from the metal interconnection structure electrically connected to the movable comb-tooth layer.

11. The MEMS micromirror according to any one of claims 1 to 5, characterized in that: At least part of the dielectric layer is located on the surface of the substrate layer and the surface of the fixed comb-tooth layer, and the dielectric layer is arranged between each of the substrate layer, the fixed comb-tooth layer and the through hole.

12. A method for preparing a MEMS micromirror, characterized in that: For preparing the MEMS micromirror according to any one of claims 1 to 11, comprising: Providing an SOI substrate, the SOI substrate comprising a substrate layer and an initial toothing layer, wherein a dielectric layer is formed between the substrate layer and the initial toothing layer; Forming a plurality of through holes in the SOI substrate, wherein the through holes vertically penetrate the substrate layer and the initial fixed tooth layer; A metal interconnection structure is formed in the through hole; one end of the metal interconnection structure is exposed to the surface of the substrate layer, and the other end is exposed to the surface of the initial fixed tooth layer; some of the metal interconnection structures among the plurality of metal interconnection structures are electrically connected to the initial fixed tooth layer, and another part of the metal interconnection structures are used to be electrically connected to the movable comb tooth layer; A first pad layer is formed on a surface of the substrate layer facing away from the initial fixed tooth layer; the first pad layer includes a plurality of first pads, and the first pads are electrically connected to one end of the metal interconnect structure exposed to the substrate layer; A bonding metal layer is formed on a surface of the initial fixed tooth layer which is away from the substrate layer; the bonding metal layer has a preset pattern, and the through hole is located within a projection area of ​​the preset pattern in the longitudinal direction; Etching the initial fixed tooth layer to form a fixed comb tooth layer; Bonding a second substrate to the bonding metal layer on the surface of the fixed comb-tooth layer to obtain a bonding structure; A reflector and a second pad layer are formed on a surface of the second substrate facing away from the substrate layer; the second pad layer includes a plurality of second pads, and the second pads are electrically connected to one end of the metal interconnect structure exposed on the surface of the initial fixed tooth layer; The second substrate is etched to form a movable comb tooth layer to obtain the MEMS micromirror; the bonding metal layer includes a mutually isolated structural bonding area, a plurality of first metal electrical interconnection areas and a plurality of second metal electrical interconnection areas, the first metal electrical interconnection area and the second metal electrical interconnection area are located between the movable comb tooth layer and the metal interconnection structure; the first metal electrical interconnection area is electrically connected to the movable comb tooth area in the movable comb tooth layer; the second metal electrical interconnection area is electrically connected to the fixed comb tooth layer, and is mutually isolated from the movable comb tooth area in the movable comb tooth layer.

13. The method for preparing a MEMS micromirror according to claim 12, characterized in that: The forming of a metal interconnection structure in the through hole comprises: forming a seed layer in the through hole and filling it with metal material to form an initial metal interconnection structure; The initial metal interconnection structure is planarized and subjected to vacuum heat treatment at 350° C. to 500° C. to form the metal interconnection structure.

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