JP2006524349A - Microelectromechanical system two-dimensional mirror with articulated suspension structure for high fill factor arrays - Google Patents

Abstract

The present invention provides a microelectromechanical system (MEMS) mirror device. The device has a mirror, the mirror has a two-dimensional rotationally articulated hinge at a first end, and a one-dimensional rotationally articulated hinge at a second end opposite the first end. Have. A movable cantilever is provided, and the movable cantilever is connected to the mirror via the one-dimensional rotation articulated hinge. A support structure is included, the support structure being connected to the mirror via the two-dimensional rotationally articulated hinge and connected to the movable cantilever. Thereby, the movement of the movable cantilever causes the mirror to rotate about the first axis of rotation, and the mirror can rotate about a second torsion axis of rotation perpendicular to the first axis of rotation. But there is.

Description

The present invention relates to a microelectromechanical system two-dimensional mirror having an articulated suspension structure for high fill factor arrays.

BACKGROUND OF THE INVENTION MEMS (Micro-Electro-Mechanical-System) devices have electrical circuits that are processed together with the devices by a variety of microfabrication processes (mostly derived from integrated circuit manufacturing methods). A micro-sized mechanical structure. Developments in the field of microelectromechanical systems (MEMS) enable mass production of microelectromechanical mirrors and mirror arrays that can be used in all-optical cross-connect switches, 1 × N, N × N optical switches, attenuators, etc. . Many microelectromechanical mirror arrays have already been made using MEMS manufacturing processes and techniques. These arrays have designs that fall into three design categories, which are roughly described below.

a) Conventional 2D Gimbal Mirror with Mirrors Surrounded by Frames Conventional 2D gimbal mirrors are one of the most common types of MEMS 2D micromirrors. An example is shown in FIG. This consists of a central mirror 10 which is connected to the outer frame 12 by a torsional hinge 14 as shown in FIG. The outer frame 12 is then connected to the support structure 16 by another set of torsional hinges 18. Below the central mirror 10 are four electrodes that can be actuated to produce a 2D tilt of the mirror frame assembly. One such device is disclosed in U.S. Patent Application Publication No. US2002 / 0071169A1 (publication date, June 13, 2002). One drawback of this design is that it achieves a high fill factor in the mirror array (this is the spacing between two consecutive mirrors, or the ratio of the active area to the total area in the array). It is impossible.

b) 2D / 3D mirrors with hidden hinge structures Due to significant progress made in spatial light modulators, many 2D micromirror devices with various types of hidden hinge structures have been designed. Examples of these are disclosed in US Pat. No. 5,535,047, US Pat. No. 5,661,591, and US Pat. No. 6,480,320B2.

  A schematic diagram of an example of such a device is shown in FIG. While this device structure can result in a high fill factor array, the manufacturing process is very complex. For further discussion of spatial light modulators and digital mirror devices with hidden hinge structures, reference is made to: US Pat. No. 5,061,049, US Pat. No. 5,079,545, US Pat. No. 5,105, 369, US Patent No. 5,278,652, US Patent No. 4,662,746, US Patent No. 4,710,732, US Patent No. 4,956,619, US Patent No. 5,172,262, and US Patent Number 5,083,857.

c) 2D mirror attached to a single movable flexible post An example of a MEMS tilt platform is supported by a flexible post 30 as shown in FIG. The post 30 extends into the moat 32, or groove, formed in the substrate or support material. The post 30 is made sufficiently long and flexible to operate as a unidirectional hinge and can be bent to allow the mirror 36 to be positioned in two degrees of freedom.

  Some disadvantages of this design are process complexity, post flexibility, wiring, and tilt eccentricity. Some such devices are disclosed in US Pat. No. 5,469,302, US Patent Application Publication No. US2002 / 0075554A1.

  Furthermore, the control of these devices is complex and occupies a significant portion of the device cost.

SUMMARY OF THE INVENTION Some advantages realized in some, but not necessarily all, embodiments include the following.
High fill factor linear array. A high fill factor as high as 99% can be achieved.
An almost negligible coupling between the two tilt axes.
Inexpensive and easy control. Even open loop / look up table controls are possible.
Devices can be manufactured using a simple manufacturing process.
The cantilever portion of the device can also be used for mirror position capacitance detection or light detection.

  According to one broad aspect, the present invention provides a microelectromechanical system (MEMS) mirror device having a mirror that has a two-dimensional rotationally articulated hinge at a first end. And having a one-dimensional rotary articulated hinge at the second end opposite the first end; the device has a movable cantilever, the movable cantilever being connected via the one-dimensional rotary articulated hinge The device has a support structure, the support structure is connected to the mirror via the two-dimensional rotational articulated hinge, and connected to the movable cantilever Whereby the movement of the movable cantilever causes rotation of the mirror about the first rotation axis, and the mirror is a second torsion rotation axis perpendicular to the first rotation axis. Rotate around It is also a function.

  In one embodiment, the two-dimensional rotationally articulated hinge has a first one-dimensional rotationally articulated hinge, and the first one-dimensional rotationally articulated hinge has a first attachment point at a first end. And a second end portion; the two-dimensional rotationally articulated hinge has a second one-dimensional rotationally articulated hinge, and the second one-dimensional rotationally articulated hinge has a second end at the first end portion. Having a mounting point and having a second end, the second end of the first one-dimensional rotary articulating hinge being connected to the second end of the second one-dimensional rotary articulating hinge; A two-dimensional rotary articulated hinge has a third one-dimensional rotary articulated hinge, the third one-dimensional rotary articulated hinge being the first of the first and second articulated one-dimensional rotary hinges; Connected to the two ends; thereby, the first one-dimensional rotary articulated hinge and the second one-dimensional rotary articulated hinge Defines a first axis of rotation between the first attachment point and the second attachment point, and is one-dimensional at the second end of the third one-dimensional articulated hinge and mirror. A rotary articulated hinge defines a second torsional rotational axis that is perpendicular to the first rotational axis.

  In one embodiment, each one-dimensional rotational articulated hinge has a respective articulated beam, the beam having a large aspect ratio with respect to width.

  In some embodiments, the beam is formed as a unitary structure.

  In one embodiment, the silicon beam, mirror, and movable cantilever are formed in a unitary structure.

  In some embodiments, the articulating hinge may be made of a coated material, such as polysilicon, silicon nitride, or any other coatable material, with the mirror and movable cantilever being formed in a unitary structure.

  Preferably, the mirror has a range of motion angles of at least 0.5 degrees in each axis. However, other ranges of motion are not excluded.

  In certain embodiments, the device further comprises an electrode for applying an electrostatic force to the mirror to move the mirror in first and second rotational axes.

  In one embodiment, the electrode has two electrodes for applying an electrostatic force to the mirror to move the mirror about the second axis of rotation, and the electrostatic force is movable to move the mirror about the second axis of rotation. Having at least one electrode for application to the cantilever.

  In one embodiment, the mirror is made of silicon plated with metal.

  In some embodiments, the metal has a gold, aluminum, or copper layer.

  In one embodiment, multiple N devices are arranged side by side to form a 1 × N MEMs array, where N ≧ 2.

  In one embodiment, multiple N × M devices are arranged to be N columns of M devices, thereby forming an N × M MEMs array, where N ≧ 2 and M ≧ 2.

  In some embodiments, the mirror is used for optical switching, and the movable cantilever is used for capacitive sensing or optical sensing of the mirror position.

  According to another broad aspect, the present invention provides an optical switch, the switch comprising a plurality of optical ports, comprising a plurality of devices according to claim 1, each device comprising a respective one of the optical ports. Is adapted to switch light between a pair of.

  According to one broad aspect, the present invention provides a two-dimensional rotationally articulated hinge for connection with a support structure and with a device to be rotated, the hinge comprising a first one-dimensional rotationally articulated hinge. The first one-dimensional rotational articulated hinge has a first attachment point at a first end and a second end; the hinge has a second one-dimensional rotation An articulated hinge, the second one-dimensional rotational articulated hinge has a second attachment point at a first end and a second end, the first one-dimensional rotational articulated A second end of the hinge is connected to a second end of the second one-dimensional rotationally articulated hinge; the hinge has a third one-dimensional rotationally articulated hinge; A two-dimensional rotary articulating hinge is connected to the second end of the first and second articulating one-dimensional rotary hinge; The first one-dimensional rotary articulating hinge and the second one-dimensional rotary articulating hinge define a first rotational axis between the first attachment point and the second attachment point. And the third one-dimensional rotationally articulated hinge defines a second torsional rotational axis perpendicular to the first rotational axis.

  In one embodiment, each one-dimensional rotational articulated hinge has a articulated beam of silicon, which has a high thickness to width aspect ratio.

  In one embodiment, the silicon beam is formed as a unitary structure.

  In some embodiments, the articulating hinge can be formed of a coated material, such as polysilicon, silicon nitride, etc., having a low thickness to width ratio.

  In some embodiments, each articulated hinge may be a unitary single beam of coated single or multiple materials.

  Preferred embodiments of the present invention will now be described with reference to the accompanying drawings.

Detailed Description of the Preferred Embodiment A known 1D MEMS torsional mirror supported by articulated suspension springs / hinges is shown in FIGS. 1A and 1B. The apparatus comprises a support structure 30 in which a mirror 34 connected to the support structure 30 via two articulated hinges 36 is attached. Typically, the entire mirror and articulated hinge device is made of a single piece of silicon. The articulating hinge 36 is made of a silicon beam having a high aspect ratio with respect to the width, thereby enabling torsional rotation. By using articulation, a long silicon beam can be provided in a very narrow space. A set of address electrodes 38 and 40 are also shown. They are connected to a control system that can apply a voltage to the electrodes. Usually, the mirror device is grounded. The mirror 34 can be rotated about its rotation axis (θx) 32 by applying an electrostatic force to either side of the mirror using the electrodes 38 and 40. This is shown in FIG. What is generally indicated at 50 is a mirror in a first configuration (where the mirror is rotating counterclockwise with respect to the axis of rotation 32), and generally indicated at 52 is that the mirror is at axis of rotation 32. Figure 2 shows the same device rotating clockwise.

  To facilitate 2D rotation of the mirror (ie, rotation in both (θx) and (θz), θz is orthogonal to the main torsional tilt (θx)), embodiments of the present invention are 2D A rotatable articulated hinge is provided. A top view of the new articulated hinge is shown in FIG. 3A. The 2D rotatable articulated hinge includes a first series articulated hinge portion 60 and a set of second articulated hinges 62, 63. Each of the second articulated hinges 62, 63 is connectable to a support structure generally indicated at 64 and is also connected to a first series of articulated hinges 60. Each of the three articulated hinges 60, 62, 63 is similar to the conventional articulated hinge 36 of FIG. 1A. That is, each articulated hinge consists of a silicon beam having a high aspect ratio thickness to width. The entire device consisting of three articulated hinges 60, 62, 63 is preferably made from a single integral piece of silicon. In another embodiment, the device is made of a coated material such as polysilicon, silicon nitride, silicon dioxide, and metal coatable material. Other materials may be used. The structure is preferably unitary in that no assembly is required. However, the beam may be made of a plurality of materials, for example a layered structure. The first series hinge 60 allows rotation along the first torsion axis (θx), while the second and third articulated hinges allow rotation about the second axis (θz).

Any suitable dimension can be used for the articulated hinge. Different numbers of articulations can be used. The more articulations included in a given articulated hinge, the less force is required to produce rotation about each axis. In the example implementation, the dimensions of the various hinges are as follows:
Hinges 62 and 63: {75um (L), 1.5um (W), 15um (T), 5um (gap) and 3 (joint)}
Hinges 60 and 74: {75um (L), 1.5um (W), 15um (T), 5um (gap) and 11 (joint)}

  Next, referring to FIG. 3B, a first example of use of the articulated hinge of FIG. 3A will be described. Here, the articulated hinge is shown generally at 70 and is connected to the mirror 72 at the end opposite the end where another 1D articulated hinge 74 is located. The entire device of FIG. 3B is preferably made of a single piece of silicon. The device as shown in FIG. 3 allows the mirror 72 to rotate about a main rotation axis (θx) and an additional rotation axis (θz), which is orthogonal to the main rotation axis. It becomes.

  In a preferred embodiment of the present invention, the apparatus of FIG. 3B is used in the instrument illustrated in FIG. 4A as an example. Here, it is shown again that the 2D rotary articulated hinge 70 is connected to the mirror 72 and the 1D rotational articulated hinge 74. The support structure is indicated generally at 76. The 2D rotary articulating hinge 70 is connected to the support structure at two locations 78, 80. The 1D rotation articulating hinge 74 is connected to the support structure 76 via the cantilever 80. Preferably, the cantilever is simply another piece of silicon that is connected at 82 to the support structure 76 in a manner that does not substantially rotate the cantilever about the main axis of rotation (θx). . However, the cantilever 80 has some flexibility, and in particular, the end 87 of the cantilever 80 furthest from the connection 82 to the support structure is capable of some vertical movement. To obtain additional flexibility of the cantilever 80, the parts may be removed. In the illustrated embodiment, the cantilever 80 includes a gap 89 near the attachment point 82 to the support structure 76. This reduces the amount of force required to cause the point 87 to move up and down.

  In order to control the rotation in the torsion axis (θx), electrodes 84 and 85 are provided, which operate in the same manner as the electrodes 38 and 40 in FIG. 1A. This makes it possible to control the rotation of the mirror 72 with respect to the main torsion axis. In addition, an electrode 86 is shown below the cantilever structure 80 and controls the up and down movement of the end 87 of the cantilever 80 furthest from the connection 82 to the support structure 76. This vertical movement of the point 87 causes the mirror 72 to rotate about an additional axis of rotation (θz). The resulting cantilever deflection rotates the mirror about the second axis (formed by the T-bar), thus tilting the mirror simultaneously or independently in both axes.

  In order to provide the most flexible control over rotation about the additional axis of rotation, an additional support structure with additional electrodes must be provided on top of the cantilever 80, thereby applying force. Thus, the end 87 of the cantilever 80 can be moved upward. However, depending on the application, this additional degree of freedom may not be required. This embodiment is shown in FIG. 4B. FIG. 4B is substantially the same as FIG. 4A, except that an additional support structure 91 and an additional electrode 93 (which allows an electrostatic force to be applied to the cantilever structure to move it both up and down). It is.

  The embodiment of FIG. 4A employs the use of electrodes, whereby an electrostatic force can be applied to control rotation on the two rotational axes. More generally, any other type of force can also be utilized on one or both of these rotational axes. For example, thermal power, magnetic force, thermal bimorph force or piezoelectric power can be utilized to achieve the required rotation and control.

  This combination of a 2D rotating articulated hinge, articulated torsion mirror, and movable cantilever provides a fully functional 2-D MEMS mirror. The cantilever can be deflected in either direction up or down depending on the electrode arrangement or force application, thereby rotating the torsion mirror in either direction about the second axis θz. it can. For most static applications, the cantilever can be deflected only downward, reducing the number of I / Os and controlling the complexity.

  A linear mirror array can be created by arranging a large number of mirrors side by side and minimizing the distance between the two mirrors. This embodiment is shown in FIG. FIG. 5 shows a linear array of four 2D torsional mirrors 90, 92, 94, 96 having 2D rotationally articulated hinges and cantilevers. Such arrays can include any number. Another embodiment provides a two-dimensional array of N × M such mirror devices.

  One of the main advantages of the structure of FIG. 4 is that the coupling between the two tilt axes is minimal. This device structure can be used for any application. This can be used as a single mirror for any suitable application in a single or multiple array configuration. This device achieves a high fill factor for mirror arrays (which is the spacing between two consecutive mirrors in the array) and is very simple to manufacture. The spacing between the two mirrors can be as small as a few microns or can be limited by a microfabrication process.

  The device can be manufactured using current MEMS manufacturing processes. Some suitable processes that are commercially available are optical IMEMS® from Analog Devices Inc (Thor Juneau et al., 2003, “Single-Chip 1x84 MEMS Mirror Array For Optical Telecommunication Applications”, Proceeding of SPIE, MOEMS and Miniaturized Systems III, 27-29 January 2003, Vol. 4983, pp. 53-64), SOI MUMPS from Cronos (a subsidiary of MEMScAP) (http://www.memsrus.com/figs/soimumps .pdf). Devices can also be manufactured using conventional processes.

  It should be understood that in the application of the system, a control system is provided to control the rotation of the mirror at two free angles. This is controlled by the appropriate application of force by the various electrodes. Preferably, the control system is an open loop system with a voltage look-up table for various tilt positions, or a closed loop system with capacitive or light sensing.

  The mirror in the embodiment adopted above should have a reflective coating. For example, a coating in one or more layers of gold, aluminum or copper. The mirror is used for main switching of the light beam. However, it should be understood that the cantilever portion may also have a reflective coating. Cantilever and / or mirror components can be used for capacitive sensing or light sensing. For example, a mirror component may be used for switching, while a cantilever component can be used to sense the generated signal and provide feedback control over mirror orientation.

1A and 1B provide two views of a conventional one-dimensional MEMS mirror having an articulated suspension structure. 1A and 1B provide two views of a conventional one-dimensional MEMS mirror having an articulated suspension structure. FIG. 2 shows the device of FIG. 1 in two rotational states. FIG. 2 shows the device of FIG. 1 in two rotational states. FIG. 3A is a plan view of a two-dimensional articulated rotating hinge provided by an embodiment of the present invention. FIG. 3B represents a MEMS mirror featuring the two-dimensional rotational articulated hinge of FIG. 3A. FIG. 4A is an illustration of a mirror with a two-dimensional rotationally articulated hinge and movable cantilever mounting system provided by an embodiment of the present invention. FIG. 4B provides a cut-away view and a side cross-sectional view of a mirror with a two-dimensional rotationally articulated hinge and movable cantilever mounting system provided by another embodiment of the present invention. FIG. 6 provides a cut-away view and a side cross-sectional view of a mirror having a two-dimensional rotationally articulated hinge and movable cantilever mounting system provided by another embodiment of the present invention. FIG. 5 is a one-dimensional MEMS array of devices similar to the device of FIG. 4A. FIG. 6 is a view of a conventional two-dimensional gimbal mirror having a support frame. FIG. 7 is a typical schematic diagram of a MEMS mirror having a hidden hinge structure. FIG. 8 is an exemplary schematic of a 2D mirror mounted on a single movable flexible post.

Claims (20)

A micro electro mechanical system (MEMS) mirror device comprising:
A mirror having a two-dimensional rotationally articulated hinge at a first end and a one-dimensional rotationally articulated hinge at a second end opposite the first end;
A movable cantilever, the movable cantilever being connected to the mirror via the one-dimensional rotational articulated hinge;
Having a support structure, the support structure being connected to the mirror via the two-dimensional rotationally articulated hinge, and connected to the movable cantilever;
Thereby, the movement of the movable cantilever causes rotation of the mirror about the first rotation axis, and the mirror moves around a second torsion rotation axis perpendicular to the first rotation axis. It is also rotatable,
Said device. Two-dimensional rotary articulated hinge
A first one-dimensional rotational articulated hinge, the first one-dimensional rotational articulated hinge having a first attachment point at a first end and a second end;
A second one-dimensional rotationally articulated hinge, the second one-dimensional rotationally articulated hinge having a second attachment point at a first end and a second end; A second end of the one-dimensional rotary articulating hinge is connected to a second end of the second one-dimensional rotary articulating hinge;
A third one-dimensional rotary articulated hinge, the third one-dimensional rotary articulated hinge connected to the second end of the first and second articulated one-dimensional rotary hinge;
As a result, the first one-dimensional rotationally articulated hinge and the second one-dimensional rotationally articulated hinge define a first rotational axis between the first attachment point and the second attachment point. A second torsional rotation perpendicular to the first axis of rotation of the third one-dimensional articulating hinge and the one-dimensional articulating hinge at the second end of the mirror. Set the axis,
The device of claim 1.   The device of claim 2, wherein each one-dimensional rotating articulated hinge has a respective articulated beam, the beam having a large aspect ratio with respect to width.   Each one-dimensional rotating articulated hinge has its own articulated beam, which has a large aspect ratio of thickness to width, and the beam comprises silicon, polysilicon, silicon nitride, silicon dioxide, and metal The device of claim 2, wherein the device is formed of one or more materials selected from the group consisting of coatable materials.   The device of claim 3, wherein the beam is formed in a unitary structure.   The device of claim 3, wherein the beam, mirror, and movable cantilever are formed in a unitary structure.   The device of claim 1, wherein the mirror has a range of motion angles of at least 0.5 degrees in each axis.   The device of claim 1, further comprising an electrode for applying an electrostatic force to the mirror to move the mirror about the first and second axes of rotation.   An electrode has two electrodes for applying an electrostatic force to the mirror to move the mirror about the second rotational axis, and for applying an electrostatic force to the movable cantilever to move the mirror about the second rotational axis. 9. The device of claim 8, having at least one electrode.   The electrode has two electrodes for applying an electrostatic force to the mirror to move the mirror about the second axis of rotation, and applies an electrostatic force to the movable cantilever to move the mirror in both directions about the second axis of rotation. 9. A device according to claim 8, comprising two electrodes for.   The device of claim 1, wherein the mirror is made of silicon plated with metal.   The device of claim 11, wherein the metal comprises a gold, aluminum, or copper layer.   The device of claim 1, wherein the devices are arranged side by side to form a plurality of N, 1 × N MEMs arrays, where N ≧ 2.   The device of claim 1 is arranged to be a plurality of N × M, N columns of M devices, thereby forming an N × M MEMs array, where N ≧ 2 and M ≧ 2. ,device.   The device according to claim 1, wherein the mirror is used for optical switching and the movable cantilever is used for capacitive sensing or optical sensing of the mirror position. An optical switch,
Has multiple optical ports,
A plurality of devices according to claim 1, wherein each device is adapted to switch light between a respective pair of the optical ports.
The optical switch. A two-dimensional rotationally articulated hinge for connection to a support structure and to a device to be rotated, the hinge comprising:
A first one-dimensional rotationally articulated hinge, the first one-dimensional rotationally articulated hinge having a first attachment point at a first end and a second end;
A second one-dimensional rotationally articulated hinge, the second one-dimensional rotationally articulated hinge having a second attachment point at a first end and a second end; A second end of the one-dimensional rotary articulated hinge is connected to a second end of the second one-dimensional rotary articulated hinge;
A third one-dimensional rotary articulated hinge, the third one-dimensional rotary articulated hinge connected to the second end of the first and second articulated one-dimensional rotary hinge;
As a result, the first one-dimensional rotationally articulated hinge and the second one-dimensional rotationally articulated hinge define a first rotational axis between the first attachment point and the second attachment point. A second torsional rotation perpendicular to the first axis of rotation of the third one-dimensional articulating hinge and the one-dimensional articulating hinge at the second end of the mirror. Set the axis,
Said hinge.   The two-dimensional articulated hinge of claim 17, wherein each one-dimensional rotational articulated hinge has a respective articulated beam, the beam having a high aspect ratio of thickness to width.   The two-dimensional articulated hinge according to claim 18, wherein the beam is formed as a unitary structure.   The two-dimensional articulated hinge of claim 18, wherein the beam is formed of one or more materials selected from the group consisting of silicon, polysilicon, silicon nitride, silicon dioxide, and metal coatable materials.

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