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    • 专利摘要:
    18 SAM MANDRAG: Uppfinningen avser en prekursorstruktur (26) för ett ventileringshål i en mel-lanprodukt till en halvledaranordning med ömtåliga strukturer (27, 28). Dennamellanprodukt har en kavitet (21) med ett tryck som skiljer sig från omgivning-ens och mellanprodukten innefattar en första skiva (20) som har en fördjupning(21) formad däri. Denna första skiva år bondad till en andra skiva (22) innefat-tande ett komponentlager (23) ur vilket strukturerna (27, 28) skall etsas fram.Det finns också ett hål eller ett spår (26) som har ett fördefinierat djup och somstråcker sig nedåt in i komponentlagret, så att kaviteten (21) vid etsning öppnasupp innan etsninngsprocessen bryter igenom komponentlagret (23) till bildande av strukturerna (27, 28). Uppfinningen avser åven en metod för att tillverka en halvledaranordning med utnyttjande av nåmnda prekursorstruktur.
    公开号:SE1051391A1
    申请号:SE1051391
    申请日:2008-12-23
    公开日:2010-12-30
    发明作者:Thorbjoern Ebefors；Edvard Kaelvesten；Niklas Svedin
    申请人:Silex Microsystems Ab；
    IPC主号:
    专利说明:

    15 20 25 30 many different ways and have many different constructions. For example, a via may be a metal plug surrounded by an insulating material or it may be a doped or non-doped semiconductor plug surrounded by an insulating material. The via plugs can have different cross-sections, i.e. circular, rectangular, square or organ bound, although in most cases circular cross-sections are preferred.
    Routing by means of vials Fig. 1 thus schematically (not to scale) shows a first aspect of the invention, namely a mirror structure in a mirror array, which has routing elements according to the invention.
    The mirrors 1 and 2 are mounted on a support pillar 3 via hinge structures 4 and 5, respectively, manufactured by means of MEMS techniques in a substrate plate SW. Under each mirror there are actuating electrodes 6, 7 which will cause the mirrors 1 and 2 to bend when the electrode 6,7 is activated with energy.
    In devices according to the prior art, the electrodes are routed "away" from the array by means of electrical wires 8, 9 arranged on the substrate surface (indicated by a dashed line contour in Figure 1). As will be appreciated, the wire 8 from the electrode 6 for actuating the mirror 1 must pass under the mirror 2, and when it is activated with energy it will also affect the mirror 2 to some extent which causes functional errors l in accordance with the invention are arranged via 10, 1 l through the disk SW and connected to routing wires 12, 13 on the back of the disk SW. The routing leads 12, 13 are of course arranged next to each other, suitably parallel to the periphery of the disc where wire bonding 14 can be provided if desired. Alternatively, a double layer of metal could be provided on the back with an insulating layer between the conductive layers. In this way, it would be possible to avoid intersecting conductors and thereby increase the ibil flexibility in the routing structures. By plating (or any other suitable method known to those skilled in the art) contact bumps can be provided. Preferably so-called Under Bump Metallization (UBM), which enables flip-chip mounting of the mirror component. Control circuits, e.g. ASICs can then be mounted directly on the back of the mirror component. For larger mirror arrays, e.g. > 12 x 12, such a solution is more cost effective than conventional prior art wire bonding. Flip-chip mounting is not possible without the via technology.
    Method of manufacturing micro mirrors In a process for manufacturing deflectable micro mirrors and / or arrays of such mirrors, two sheets are bonded together in one step in such a process before the actual mirror structure is manufactured (a first sheet and a second sheet), in a controlled atmosphere. for example vacuum. One of the discs (first disc) then has a recess formed therein to provide a necessary space in the final structure for the deflectable mirrors to be able to move freely during deflection. The second disc (preferably an SOI disc) provides a "lid" over the recess.
    Thus, after the disks are bonded together, the recess in the first disk will be sealed by the second disk and thus a cavity with a controlled atmosphere (eg vacuum) is created. In subsequent steps in the process, machining of the second disk is performed to fabricate the final mirror structures. The mirror structures comprise an actual mirror part which is relatively thick and rigid and a hinge part.
    However, the mirror can have different thicknesses to provide different resonant frequencies - thick mirror means large mass and low frequency; thin mirror means small mass and high frequency. The frequency requirements may be opposite to the flatness requirements. Thinner mirrors can be bent more easily due to mechanical impact.
    It is possible to manufacture a mirror with a rigid frame part and remaining areas thinned to provide low mass and higher rigidity. The hinges can also be thinned to varying degrees. The hinge will be substantially thinner than the mirror in some embodiments, to provide the required flexibility of the hinge to function as desired. In particular, the hinge can be arranged as a so-called gimbal structure.
    In other cases, e.g. however, when a torsional effect is desired, the hinge may have the same thickness as the mirror, but it will then have a lateral extent (i.e. in the transverse direction of the hinge) which is relatively small.
    Manufacture of these structures is carried out by means of mandatory masking and etching of the second board. However, the process steps for manufacturing the mirror structures are performed in an atmosphere having a different pressure (normal pressure) than the pressure prevailing inside the cavity. Thus, since there will be a pressure difference across the "lid" when the etching process "breaks through" the SOI board to provide the free-hanging threaded mirrors, a sudden pressure equalization will occur. This pressure equalization produces strong forces so that the fragile hinge structures on the mirrors very easily break and the mirrors fall out of the devices, with extremely low yields as a result.
    According to the invention, controlled ventilation of the structure is provided so that the pressure equalization will be very soft and no strong forces will be exerted on the delicate hinges.
    The solution according to an embodiment of the invention is shown schematically in Figures 2a-d.
    Fig. 2a shows a first disk 20 (substrate disk) having a recess 21 formed therein, bonded to an SOI disk 22 comprising a component layer 23, an oxide layer 24 and a support layer 25. In the component layer 23 of the second disk, suitably a thinned portion 23 'is made to define the thickness of a hinge 28 (see Fig. 2c) which is to connect the mirror to the load-bearing structures of the final product. The carrier layer 25 is removed and after appropriate masking MV, a first etching is performed to provide a vent hole precursor structure 26 in the rest of the component layer 23. This precursor structure is essentially a hole or groove having a predefined depth, i.e. extending downward into the component bearing.
    Thereafter, suitable masking MMH is provided to define the mirror 27 and its hinge structures 28 and a second etching is performed. This is schematically illustrated in Fig. 2c. Thereby, the vent hole precursor structure 26 will open up the cavity 2 l with a controlled atmosphere (eg vacuum) before the etching has removed so much material from the component layer that the hinge structure has become so thin that it could break due to the forces exerted when the pressure is equalized through the vent hole.
    The etching is continued until the mirror 27 is free-etched and the hinges 28 are made. The mirrors can be free-etched in the same process step as the hinges are manufactured by dimensioning the surfaces on which the etching acts to control the etching speed. Thus, the etching will be broken through in the grooves that define the mirror before the etching has penetrated too deep into the grooves that define the hinges.
    In an alternative embodiment, the whole process can be performed in one step. This is possible by dimensioning the vent hole precursor structure 26 so that it is large enough for the etching to cut material therein at a faster speed than in the groove defining the mirror, which in turn will be etched faster than the hinges, as in the previous embodiment. This is shown schematically in Fig. 2d, which shows a larger ventilation hole 26 than in Fig. 2c.
    Electrical connection to desired layers in a structure comprising alternating insulating and conductive layers 10 15 20 25 30 This invention relates to MEMS devices in which it is desirable to provide electrical potential including ground potential at desired locations in a layered structure.
    Referring to Fig. 3a, there is schematically shown a layered structure comprising three (first, second and third) layers 30, 31 and 32 of, for example, silicon or other semiconductive or conductive material, and between these layers a first insulating layer 33 and a second insulating layer 34. This layered structure is suitably made of two SOI disks which have been bonded together, the first conductive layer 30 constituting the carrier layer and the second conductive layer 31 constituting the component layer of a first SOI disk.
    The third conductive layer is the component layer in a second SO1 disk. Thus, as will be appreciated, the structure shown in Fig. 3a can be accomplished by bonding the two SOI disks and removing the carrier layer from the second SOI disk.
    There is also provided a vias structure 35 extending as through the first conductive layer 30. The vias structure may comprise heavily doped Si surrounded by an insulating enclosure 36 so as to provide electrical insulation from the surrounding conductive first layer 30. Other materials such as metal may also used for vian.
    For MEMS applications in which this type of layered structure is frequently used, it is often desirable to apply electrical potential to selected layers, and sometimes at selected points or areas in such layers.
    According to the invention, a flexible method is provided for tailoring such applications of electrical potential to the need which exists.
    Thus, the invention provides a method of manufacturing an electrical connection into desired layers in a layer structure and at the same time preventing electrical connection to adjacent layers. Referring to Fig. 3b, there is shown how in a first step a hole 37 is etched through the third and second conductive layers 32 and 31, and thus also through the insulating layer 34, as well as through the insulating layer. 33, and a short distance into the via plug 35. The hole 37 is filled with polysilicon to provide conductivity. The invention does not limit the choice of material to polysilicon, although this is preferred. Any metal or conductive material could be used. Poly-silicon is preferred due to that it has very similar thermal expansion properties to silicon. Excessive differences in expansion properties could lead to mechanical stress that could "dent" the mirror. As shown in Fig. 3b, if a potential is applied to the vane 35, this potential will be transferred to both the second 31 and the third 32 layers.
    However, in a first embodiment of the invention, illustrated in Fig. 3c, electrical potential is provided through the vane 35 and into the third conductive layer 32 only. To accomplish this, the first SOI disk has been processed before being bonded to the second SOI disk. Namely, there must be an insulating enclosure 38 surrounding the part of the disc where the polysilicon plug will extend through the second layer 31 in the layered structure.
    This is accomplished by etching a trench 38 in a closed loop in the component layer of the first SOI wafer down to the buried oxide layer, and filling the trench at least partially with oxide. On the other hand, the trenches could be left as they are, filled with air, if they are wide enough so that no "ash-over" can occur. Once the two SOI disks have been bonded together and the carrier layer in the second SGI disk has been removed, the procedure discussed with reference to Fig. 3b is performed, a polysilicon plug 37 is provided by the layered structure, and the result shown in Figs. 3c will be obtained. If an electric potential is applied to the wire in this structure, the potential will be transferred to the third layer 32 without affecting the second layer. 10 15 20 25 30 To eliminate the risk of damaging the mirror surface while filling the holes with polysilicon, which requires removal of polysilicon from the mirrors, most of the carrier layer can be mechanically sanded away, leaving only a thin layer. The holes are then made by lithography and etching and filled with polysilicon. This structure, i.e. from bottom to top: mirror - carrier layer residue - polysilicon, then subjected to etching until the mirror is exposed. The poly-silicon "plugs" can be manufactured so that they exhibit low resistivity by suitable doping, with processes well known to those skilled in the art.
    On the other hand, if it is desired to provide a potential selectively to the second layer 31, again a trench 38 is made by etching, but in this case it will be done after the SGI disks have been bonded together and the carrier layer has been removed from the second SOI disk. . Thus, the trench 38 is made in the third layer 32, and again, as in the embodiment of Fig. 3c, is at least partially filled with insulating material. Even in this case, it is possible to leave the trenches unfilled. Then, a hole 37 is etched through the layered structure, as described with reference to Fig. 3b, and the resulting structure is shown in Fig. Sd. Here, an applied potential will be transferred to only the second layer 31 and leave the third layer unaffected.
    In the embodiments shown, it has been shown how the applied potential is transferred to entire layers. However, the principle can also be used to route signals or electrical potential locally within layers. For example, if the applied potential is to be used for actuation purposes at a specific location within a layer, insulating trenches could be provided which form routing "channels" within the layer in question, so that the wire can be located at any desired point on the disk and signals routed to another point. This is exemplified in Fig. 3c, where such a routing "channel" is shown schematically at 39.
    Of course, the principle according to the method is equally applicable if there are only two layers in the structure.
    Actuation of deflectable structures In devices comprising deflectable structures, such as micromirrors in projectors, fiber optic switches, optical amplifiers, etc., one of the desired features is to make it possible to control deflection of the structures.
    Below, reference will be made to mirrors even if the principles are applicable to any deflectable structures, such as speaker elements, etc.
    There are a number of different ways available to achieve the desired controlled deflection. First of all, there must be some type of "hinge" structure to which the mirrors are connected. Such a structure is illustrated above with reference to Fig. 1, and thus the mirror is mounted on a support structure via a leg or an arm which has a substantially smaller dimension in cross section so as to provide e.g. a torsional deflection.
    Another type of hinge structure is a so-called gimbal structure. A gimbal is a rotatably suspended support structure that allows rotation of an object about a single axis. A set of two gimbals, one mounted on the other with the pivot axes perpendicular, can be used to allow an object mounted on the innermost gimbal to remain vertical regardless of how its support structure moves. In the present context, a gimbal-type structure is used to enable deflection of a mirror in substantially all X-Y directions (i.e., 2D actuation) by electrostatic actuation.
    The electrostatic actuation can be achieved in a couple of different ways.
    The first that should be mentioned using what is referred to as "plate capacitor actuation". For a mirror that is suspended in e.g. a torsion arm, one or more electrodes are thus arranged below the mirror at points such that when a potential is applied to the electrode, an electric field will arise between the mirror and the electrode, causing an attraction towards the electrode, whereby the mirror will be deflected. The mirror can itself act as an electrode or electrode elements can be arranged on the mirrors. According to the present invention, in a first aspect, the actuation potential is applied to the electrodes by arranging via structures extending through the substrate from its back. Thereby, there will be no need to provide routing structures in the same plane as the electrodes, which has the disadvantage that it takes up space, and can also be rather complicated from a manufacturing point of view.
    In a second aspect, the actuation can be accomplished by the "cam electrode structure". An example of a design of such cam electrodes is shown in Fig. 4, applied to a deflectable micromirror.
    As shown in fi g. 4, there are mating cam structures on the mirror and on the support structure, respectively. The cam electrodes on the support structure (actuating electrodes) are connected to via structures below the structure and extend through the support structure from its back, as in the example discussed above. Furthermore, these combs are arranged at different levels, i.e. they are manufactured in different component layers in the SOI disks used for the manufacture.
    Thus, when a potential is applied to the actuating electrodes, the cam structure of the mirror will be pulled downwards, but in view of the fact that the "fingers" of the cams fit together in an alternating, interleaved manner, the deflection can be achieved more smoothly than in the case of electrodes the mirror. For example, it will be possible to manufacture more compact structures using the cam electrodes.
    Fig. 4 schematically illustrates a gimbal hinge structure comprising both plate capacitor actuation and cam electrode actuation.
    Thus, a mirror 50 is supported by torsion elements 52 in a frame 54, which in turn is supported by torsion elements 56 mounted on a surrounding support structure 58. Below the mirror 50, two electrode pairs 59a and 59b, respectively, are shown in shadow lines.
    These electrodes are provided with vias which extend through the disc and which expose a breathing surface. When the electrodes 59a are activated, they will cause a deflection of the mirror in an inward direction (at the left part seen in the figure) relative to the plane of the drawing. Corresponding activation of the electrodes 59b will cause an inward deflection at the right part. Obviously, the opposite part will be deflected outwards.
    For deflection in the other direction, two cam electrode structures öOa and 60b are provided. The fingers attached to the support structure will form actuating electrodes. Thus, when the actuating electrodes are activated, the gimbal frame 54 will deflect around its torsional hinges 56 and cause the mirror to deflect correspondingly.
    In another embodiment, the hinges are "hidden" under the mirrors, which has the advantage that the mirrors can be placed very tightly, i.e. one can obtain a very compact design. For certain light wavelengths, the mirrors may also often need to be coated with a suitable material. Such a reflective coating usually only needs to be present on the mirror surface itself, and not on the hinges and / or gimbal structures. With the concept of hidden hinges, the entire board can be coated. If the hinges are not hidden, a selective coating of the reflective material must be performed, e.g. using "lift-off", shadow mask, stencil shadow mask and other techniques that are much more complicated and do not give as good yields.
    To manufacture such hidden hinges, the process sequence will differ from that described above. Reference is made to fi g. 5.
    The same basic process involving two SGI boards can be used, but the hinges are made in the component layer DL1 in the first SGI board, and the mirror and a pillar supporting the mirror are made in the component layer in the second SOI board. Once the SOI sheets have been bonded together after the required structures have been fabricated in each sheet, a back-defined opening is made from the back of the carrier layer in the first SOI sheet to provide a free space in which the hinges can move during deflection.
    Alternatively, an additional SOI disk is bonded to the structure. In this case, its component bearing is used to provide a spacer element to enable the mirror to move (deflect) as desired. The component bearing DLO is etched in this case to provide a recess which, when the disc is bonded, provides the space for movement.
    The processes described above are also applicable to the provision of cam electrode structures, arranged in double axis mirror designs containing gimbal structures, even if they are not hidden structures.
    For cam electrodes, a further method is available, see Fig. 7. Namely, in order to accomplish this, one must perform a miracle under the hinge structures after the plates have been bonded together. In this case, the hinge structure is protected by an oxide layer and a silicon is made, whereby material is also removed from under the hinge in order to thus provide a free space for deflection. The carrier part of this further disc is removed by etching when the other disc (s) has been bonded.
    权利要求:
    Claims (7)
    [1]
    Ventilation hole precursor structure (26) in an intermediate to a semiconductor device with fragile structures (27, 28), which intermediate has a cavity (21) with a pressure different from that of the environment, wherein the intermediate comprises a first wafer (20) having a recess (21) formed therein, said first disc being bonded to a second disc (22) comprising a component layer (23) from which the structures (27, 28) are to be etched forward; and a hole or groove (26) having a predefined depth and extending downwardly into the component layer so that the etching cavity (21) opens up before the etching process breaks through the component layer (2 3) to form the structures (27, 28). ).
    [2]
    A structure according to claim 1, wherein the hole or groove (26) is a separately arranged hole or groove (29) which is visible as a hole or groove also when the etching is performed.
    [3]
    A structure according to claim 1 or 2, wherein the fragile structures are mirror and threaded structures (27, 28).
    [4]
    A semiconductor device comprising a first wafer (20) having a recess (21) formed therein, said first wafer being bonded to a second wafer (22) comprising a component layer (23), a portion (23) of the component layer (23) of the second wafer 23) forming a framed structure (27, 28); and a vent hole or groove (26) in the material of the second disc (22), disposed above the cavity.
    [5]
    A semiconductor device according to claim 4, wherein said portion (23 ') of the component layer (23) of the second disk constitutes a hinge (28) and a mirror (27) suspended in the hinge (28).
    [6]
    A method of manufacturing a semiconductor device having fragile mirror and hinge structures (27, 28) and having a cavity (21), comprising providing a first wafer (20) having a recess (21) formed therein. , providing a second disc comprising at least one component layer (23); masking the component layer to define the mirror (27) and its hinge structures 28 and performing a second etching; bonding the first and second disks together to form the cavity (21); mesh the second disk to define a vent hole precursor structure (26) and etch through the mask to a predefined depth; etching through the mask whereby the vent hole precursor structure (26) will be opened towards the cavity before the mirror and hinge structures (27, 28) are finished, whereby a controlled ventilation of the structure is provided so that the pressure equalization will be very soft and no strong forces will be exerted on the fragile the parts.
    [7]
    A method according to claim 6, wherein the steps of etching ventilation holes and frying the hinge structures take place in the same step, wherein the ventilation heel is dimensioned so that the etching takes place faster through them than the frying of the hinges.
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    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    SE1051391A|SE536769C2|2008-12-23|2008-12-23|Device comprising a deflectable structure|SE1051391A| SE536769C2|2008-12-23|2008-12-23|Device comprising a deflectable structure|
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