Patent Description:
An electro-thermal micro-electro-mechanical system (Micro Electro mechanical System, MEMS) micromirror draws much attention in the fields such as optical imaging, medical testing, micro display, and optical communication because of advantages such as a large scanning angle, a low drive voltage, low manufacturing costs, and simple control. Especially in the field of optical communication, an electro-thermal MEMS micromirror array chip with a large deflection angle is applicable to assembly of a large-scale optical cross-connect (optical cross-connect, OXC) module.

However, after being integrated into an array, electro-thermal MEMS micromirrors have a problem of heat crosstalk. When one or more micromirrors adjacent to a working micromirror start to be powered on to work, generated heat changes ambient temperature distribution around the working micromirror, causing a drive arm of the working micromirror to heat up and resulting in a change in a deflection angle of the working micromirror. Severity of the heat crosstalk is also related to a raised height of a mirror surface of the micromirror, and the heat crosstalk is particularly severe when the mirror surface is raised out of a mirror frame. This results in extremely complicated control over the micromirror and degraded performance.

US <NUM>/<NUM> A1 discloses a MEMS assembly having a MEMS subassembly sandwiched between and bonded to a cap and a base. The MEMS subassembly includes at least one MEMS device element flexibly connected to the MEMS assembly. The vertical separation between the MEMS device element and an electrode on the base is lithographically defined. Precise control of this critical vertical gap dimension is thereby provided.

An objective of this application is to provide a MEMS chip structure, so as to resolve a problem of heat crosstalk for an electro-thermal MEMS micromirror.

According to a first aspect, a MEMS chip structure is provided, including a substrate, a side wall, a dielectric plate, a MEMS micromirror array, and a grid array, where the side wall is of an annular structure, the substrate covers an opening on one side of the side wall, the dielectric plate covers an opening on the other side of the side wall, and the side wall, the substrate, and the dielectric plate form a hollow structure; the MEMS micromirror array and the grid array are located inside the hollow structure; the MEMS micromirror array is located above the substrate, and the MEMS micromirror array includes a plurality of grooves and a plurality of MEMS micromirrors, where the plurality of MEMS micromirrors are in a one-to-one correspondence with the plurality of grooves, and the plurality of MEMS micromirrors are located in the corresponding grooves or above the corresponding grooves; and the grid array is located above the MEMS micromirror array, and a lower surface of the grid array is connected to upper surfaces of side walls of at least some of the plurality of grooves,.

In the MEMS chip structure provided in this embodiment of this application, the grid array is introduced to restrain heat of adjacent MEMS micromirrors in the MEMS micromirror array from cross-talking through gas above the MEMS micromirror array, thereby ensuring that control of each MEMS micromirror is relatively independent and reducing an impact of the heat crosstalk.

In a possible implementation, an upper surface of the grid array is connected to the dielectric plate. The grid array, the plurality of grooves, and the dielectric plate form a plurality of hollow structures to separate MEMS chips from each other, thereby further reducing the impact of the heat crosstalk.

In a possible implementation, a height of the grid array is not less than <NUM>/<NUM> of a distance from an upper surface of a side wall of any of the plurality of grooves to the dielectric plate. A relatively significant effect of reducing the heat crosstalk is achieved only after this requirement is met. In a possible implementation, a distance from an upper surface of the grid array to the substrate is not less than a farthest distance from any of the plurality of MEMS micromirrors to the substrate. In this embodiment of this application, while an effect of reducing the heat crosstalk is achieved, space required for rotation of the MEMS micromirror can be further ensured without affecting a rotation angle of the MEMS micromirror.

In a possible implementation, the grid array includes a plurality of grid units, and the grid unit is of an annular structure, where the plurality of grid units are in a one-to-one correspondence with the plurality of grooves, and a width of a frame of the grid unit is not greater than a width of a side wall of the corresponding groove. In this embodiment of this application, it is ensured that there is no obstruction above the MEMS micromirror, and an optical path switching function of the MEMS micromirror is not affected.

In a possible implementation, a line connecting a geometric center of the grid unit and a geometric center of the corresponding groove is perpendicular to a bottom surface of the corresponding groove.

The dielectric plate has a light transmission characteristic. The dielectric plate may be further coated with an antireflective film to improve a light transmission property and to reduce a loss of an optical signal while protecting the MEMS micromirror from external dust, where the loss of the optical signal is generated when the optical signal passes through the dielectric plate. In a possible implementation, the MEMS chip structure further includes a solder ball layer, and the solder ball layer is located inside the hollow structure and between the substrate and the MEMS micromirror array to lead out an electrode.

In a possible implementation, the MEMS chip structure further includes a thin film layer, the thin film layer is located inside the hollow structure and between the lower surface of the grid array and upper surfaces of side walls of the plurality of grooves, and a heat conductivity of the thin film layer is greater than a heat conductivity of the grid array. In this embodiment of this application, a larger portion of heat can be conducted by a frame of a grid unit and the thin film layer down to a side wall of a corresponding groove and then to the substrate, thereby further reducing the impact of the heat crosstalk.

In a possible implementation, a material of the grid array includes any one of silicon, glass, resin, and metal, and the grid array is produced by using a semiconductor etching process.

According to a second aspect, an optical switch is provided, including an input port array, an input port micromirror array, an output port micromirror array, and an output port array, where the input port array is configured to receive an optical signal; the input port micromirror array is configured to reflect, to the output port micromirror array, the optical signal output by the input port array; the output port micromirror array is configured to reflect, to the output port array, the optical signal reflected by the input port micromirror array; and the output port array is configured to send the received optical signal; where the input port micromirror array and the output port micromirror array each include the MEMS chip structure according to the first aspect or any possible implementation of the first aspect, and MEMS micromirrors included in the input port micromirror array and the output port micromirror array are deflected to switch, to different output ports of the output port array, an optical signal that is input from an input port in the input port array, to implement optical path switching.

In the MEMS chip structure provided in this embodiment of this application, a grid array is introduced to suppress heat crosstalk between adjacent MEMS micromirrors in a MEMS micromirror array, thereby ensuring that control of each MEMS micromirror is relatively independent and reducing an impact of heat crosstalk.

This application relates to a MEMS chip structure, which is a core component of an optical switch in the field of optical switching. <FIG> is a schematic block diagram of a MEMS optical switch. The MEMS optical switch includes an input port array, an input port micromirror array, an output port micromirror array, and an output port array. The input port array is configured to receive an optical signal; the input port micromirror array reflects the received optical signal to the output port micromirror array; and the output port micromirror array reflects, to the output port array, the optical signal reflected by the input port micromirror array, so as to send the optical signal. Micromirrors included in the input port micromirror array or the output port micromirror array can be deflected in two directions perpendicular to each other, and may switch, to different output ports, an optical signal that is input from an input port, thereby implementing a switching function of the optical switch. In addition, the MEMS optical switch generally further includes an input port collimator array and an output port collimator array. The input port collimator array and the output port collimator array are configured to collimate and expand a received optical signal.

Specifically, an electro-thermal MEMS micromirror chip is applicable to assembly of a large-scale optical switch structure because of a large scanning angle and a low drive voltage. The MEMS chip structure related in this application is an electro-thermal MEMS chip structure, and may be used as the input port micromirror array or the output port micromirror array of the MEMS optical switch shown in <FIG>, to be applied to the field of optical switching. <FIG> is a side view of a MEMS chip structure according to an embodiment of this application. The MEMS chip structure includes a substrate <NUM>, a side wall <NUM>, a dielectric plate <NUM>, a MEMS micromirror array <NUM>, and a grid array <NUM>. The side wall <NUM> is of an annular structure. The substrate <NUM> covers an opening on one side of the side wall <NUM>, the dielectric plate <NUM> covers an opening on the other side of the side wall <NUM>, and the side wall <NUM>, the substrate <NUM>, and the dielectric plate <NUM> form a hollow structure. Specifically, the side wall <NUM> may be of any annular structure such as a square ring or a circular ring. As shown in <FIG>, the side wall <NUM> includes a support ring <NUM> and a sealing ring <NUM>. The support ring <NUM> is located on the substrate <NUM>, and the sealing ring <NUM> is located between the support ring <NUM> and the dielectric plate <NUM> to bond, for example, airtightly bond the support ring <NUM> to the dielectric plate <NUM>.

Optionally, the substrate <NUM> may be made of a printed circuit board (Printed Circuit Board, PCB), ceramic, or the like. The dielectric plate <NUM> has a light transmission characteristic, and may be made of a material such as quartz or sapphire. Further, the dielectric plate <NUM> may be coated with an antireflection film, to improve a light transmission property of the dielectric plate <NUM>. The sealing ring <NUM> may use solder to bond the support ring <NUM> to the dielectric plate <NUM> through welding. The support ring <NUM> may be made of a material such as Kovar alloy, copper, or steel.

The MEMS micromirror array <NUM> and the grid array <NUM> are both located inside the hollow structure. The MEMS micromirror array <NUM> is located above the substrate <NUM>, and the MEMS micromirror array <NUM> includes a plurality of grooves <NUM> and a plurality of MEMS micromirrors <NUM>, where the plurality of MEMS micromirrors <NUM> are in a one-to-one correspondence with the plurality of grooves <NUM>, and the plurality of MEMS micromirrors <NUM> are located in the corresponding grooves <NUM> or above the corresponding grooves <NUM>. The grid array <NUM> is located above the MEMS micromirror array <NUM>, and a lower surface of the grid array <NUM> is connected to upper surfaces of side walls of at least some of the plurality of grooves <NUM>.

Specifically, when the lower surface of the grid array <NUM> is connected to upper surfaces of side walls of all of the plurality of grooves <NUM>, a heat insulation effect is better.

Further, the MEMS micromirror array <NUM> includes drive arms <NUM>. The drive arms <NUM> connect the MEMS micromirror <NUM> to a side wall of the corresponding groove <NUM>, and the drive arm <NUM> can move or deform. A voltage or a current that is loaded on the drive arm <NUM> is changed, so that the drive arm <NUM> moves or deforms and drives the MEMS micromirror <NUM> to rotate. Optionally, the MEMS chip structure further includes a solder ball layer <NUM>. The solder ball layer <NUM> is located inside the hollow structure and between the substrate <NUM> and the MEMS micromirror array <NUM> to lead out an electrode to supply power to the drive arms <NUM> of the MEMS micromirror array <NUM>.

However, after being integrated into an array, electrically driven MEMS micromirrors have a problem of heat crosstalk. When one or more MEMS chip units (a MEMS micromirror, a groove and drive arms in the MEMS micromirror array together constitute a MEMS chip unit, where the groove and the drive arms are corresponding to the MEMS micromirror) adjacent to a MEMS micromirror unit (which is denoted as a MEMS chip unit <NUM>) in a working state start to be powered on to work, generated heat changes ambient temperature distribution around the MEMS chip unit <NUM>, causing a drive arm of the MEMS chip unit <NUM> to heat up and resulting in a change in a deflection angle of a MEMS micromirror of the MEMS chip unit <NUM>. In the MEMS chip structure provided in this embodiment of this application, the grid array is introduced to restrain heat of adjacent MEMS chip units from cross-talking through gas above the MEMS micromirror array, thereby ensuring that control of each MEMS chip unit is relatively independent and reducing an impact of the heat crosstalk.

Optionally, a height of the grid array <NUM> is not less than <NUM>/<NUM> of a distance from the upper surfaces of the side walls of the plurality of grooves <NUM> to the dielectric plate <NUM>. Further, an upper surface of the grid array <NUM> is connected to the dielectric plate <NUM>. MEMS chip units are separated into closed units independent of each other by using the grid array <NUM> and the dielectric plate <NUM>, to minimize the impact of the heat crosstalk. In addition, in some special cases, for example, in a case in which frames of the grooves of the MEMS micromirror array <NUM> are not allowed to be connected to the grid array <NUM>, the grid array <NUM> may alternatively be connected to the dielectric plate <NUM> without contacting the MEMS micromirror array <NUM>, as shown in <FIG>. In this way, heat is introduced by the grid array <NUM> to the dielectric plate <NUM>, so that the heat crosstalk is reduced. Alternatively, the grid array <NUM> may be connected by a support structure <NUM> to the side wall <NUM> without contacting the MEMS micromirror array <NUM>, as shown in <FIG>. In this way, heat is introduced by the grid array <NUM> and the support structure <NUM> to the side wall <NUM>, so that the heat crosstalk can also be suppressed to some extent. It should be noted that, any one or more of the following three characteristics may be met: (<NUM>) The upper surface of the grid array is connected to the dielectric plate; (<NUM>) the grid array is connected to the side wall through the support structure; and (<NUM>) the lower surface of the grid array is connected to upper surfaces of the side wall of the grooves. This is not limited in this embodiment of this application.

Optionally, a distance from an upper surface of the grid array <NUM> to the substrate <NUM> is not less than a farthest distance from any of the plurality of MEMS micromirrors <NUM> to the substrate <NUM>. In a working state, the MEMS micromirror <NUM> is driven by the drive arm <NUM> to rotate by different angles. Therefore, a distance from the MEMS micromirror <NUM> to the substrate <NUM> is variable. A farthest distance from the MEMS micromirror <NUM> to the substrate <NUM> is a distance from the substrate <NUM> to a highest position (namely, a position closest to the dielectric plate <NUM>) to which the MEMS micromirror <NUM> can be moved. A position of the upper surface of the grid array is not lower than the highest position to which the MEMS micromirror <NUM> can be moved, so that the impact of the heat crosstalk can be suppressed more effectively.

<FIG> shows effects of suppressing heat crosstalk by not adding a grid array and by adding grid arrays with different heights (an ordinate indicates a normalized value of a heat crosstalk amount). The grid array herein is made of a silicon material. Optionally, a material of the grid array may be any one of silicon, glass, resin, and metal. Heat conductivities of the silicon, glass, resin, and metal each are higher than a heat conductivity of gas (for example, air, krypton, or argon) filled in the hollow structure. It can be seen from <FIG> that, with introduction of the grid array, the effect of suppressing the heat crosstalk is clearly enhanced. As the height of the grid array increases, the effect of suppressing the heat crosstalk is gradually enhanced. When a ratio of the height of the grid array to a distance from the upper surfaces of the side walls of the grooves to the dielectric plate is close to <NUM>, heat crosstalk is only approximately <NUM>/<NUM> of heat crosstalk generated when the grid array is not added, and the effect is very significant.

Optionally, the MEMS chip structure further includes a thin film layer <NUM>. The thin film layer <NUM> is located inside the hollow structure and between the lower surface of the grid array and the upper surfaces of the side walls of the plurality of grooves <NUM>, as shown in <FIG>. A heat conductivity of the thin film layer <NUM> is greater than a heat conductivity of the grid array <NUM>. The thin film layer <NUM> may be made of a material with a high heat conductivity, such as graphite or graphene. One MEMS chip unit in a working state is used as an example. After the MEMS chip unit is powered on, heat dissipated by drive arms <NUM> may be transferred by the grid array <NUM> and the thin film layer <NUM> to a side wall of a groove <NUM> of the MEMS micromirror array <NUM> and then to the substrate <NUM>, so that heat transferred to an adjacent MEMS chip unit by gas filled in the hollow structure is decreased, and the impact of the heat crosstalk is further reduced.

<FIG> shows three-dimensional structures of a MEMS micromirror array <NUM> and a grid array <NUM>. <FIG> shows a connection relationship between the MEMS micromirror array <NUM> and the grid array <NUM> that are in a MEMS chip structure according to an embodiment of this application. It should be noted that, for ease of understanding the connection relationship between the MEMS micromirror array <NUM> and the grid array <NUM>, the grid array <NUM> in <FIG> has a missing part in a lower left corner. An actual structure of the grid array <NUM> may have no missing part. In <FIG> and <FIG>, the MEMS micromirror array <NUM> includes nine grooves <NUM>, nine MEMS micromirrors <NUM>, and nine groups of drive arms <NUM>. Each MEMS micromirror <NUM> is corresponding to one groove <NUM> and one group of drive arms <NUM>. Each MEMS micromirror <NUM> is located in the corresponding groove <NUM> or above the corresponding groove <NUM>, and is connected by the corresponding drive arms <NUM> to a side wall of the groove <NUM>. The grid array <NUM> in the figure also includes nine grid units <NUM>. Each annular frame is one grid unit <NUM>. It may be understood that, the grid unit may alternatively be in a structure such as a circular ring or a hexagon ring, provided that the grid unit is corresponding to the groove. This is not limited in this embodiment of this application. It can be learned from <FIG> that, the grid units <NUM> are in a one-to-one correspondence with the grooves <NUM>, and a frame of each grid unit <NUM> is connected to an upper surface of a side wall of the corresponding groove <NUM>, so that isolation between two adjacent MEMS micromirrors <NUM> is higher, and heat conduction is more difficult.

Optionally, a width of the frame of the grid unit <NUM> is not greater than a width of the side wall of the groove <NUM>, so that the MEMS micromirror <NUM> is not blocked, and an optical path switching function of the MEMS micromirror <NUM> is not affected. Optionally, a line connecting a geometric center of the grid unit <NUM> and a geometric center of the corresponding groove <NUM> is perpendicular to a bottom surface of the corresponding groove <NUM>.

The grid array disclosed in this embodiment of this application may be produced by using a semiconductor etching process, such as photoetching, development, or corrosion. Due to a limitation of the etching process, a thickness of the grid array cannot be too large. When a distance from the MEMS micromirror array to a dielectric plate is relatively long, a requirement for the thickness of the grid array may be satisfied by superimposing a plurality of grid arrays, so as to implement effective suppression of heat crosstalk. In addition, the grid array may be separately produced, and then the produced grid array is packaged above the MEMS micromirror array. A packaging process is simple and easy.

<FIG> is a side view of still yet another MEMS chip structure according to an embodiment of this application. The MEMS chip structure includes a substrate <NUM>, a MEMS micromirror array <NUM>, a grid array <NUM>, and a dielectric plate <NUM>. The MEMS micromirror array <NUM> is located above the substrate <NUM>, and includes a plurality of grooves <NUM> and a plurality of MEMS micromirrors <NUM>, where the plurality of MEMS micromirrors <NUM> are in a one-to-one correspondence with the plurality of grooves <NUM>, and the plurality of MEMS micromirrors <NUM> are located in the corresponding grooves <NUM> or above the corresponding grooves <NUM>. The grid array <NUM> is located above the MEMS micromirror array <NUM>, and a lower surface of the grid array <NUM> is connected to upper surfaces of side walls of at least some of the plurality of grooves <NUM>. The dielectric plate <NUM> is located above the grid array <NUM>, and is connected to an upper surface of the grid array <NUM>.

Optionally, the substrate <NUM> may be made of a material such as a PCB or ceramic. The dielectric plate <NUM> has a light transmission characteristic, and may be made of a material such as quartz or sapphire. Further, the dielectric plate <NUM> may be coated with an antireflection film, to improve a light transmission property of the dielectric plate <NUM>. A material of the grid array may be any one of silicon, glass, resin, and metal. Heat conductivities of the silicon, glass, resin, and metal each are higher than a heat conductivity of gas (for example, air, krypton, or argon) filled in a hollow structure formed by the dielectric plate <NUM>, the grid array <NUM>, and the grooves <NUM>.

Further, the MEMS micromirror array <NUM> includes drive arms <NUM>. The drive arms <NUM> connect the MEMS micromirror <NUM> to a side wall of the corresponding groove <NUM>, and the drive arm <NUM> can move or deform. A voltage or a current that is loaded on the drive arm <NUM> is changed, so that the drive arm <NUM> moves or deforms and drives the MEMS micromirror <NUM> to rotate. Optionally, the MEMS chip structure further includes a solder ball layer <NUM>. The solder ball layer <NUM> is located between the substrate <NUM> and the MEMS micromirror array <NUM> to lead out an electrode to supply power to the drive arms <NUM> of the MEMS micromirror array <NUM>. A structure of the solder ball <NUM> is shown in <FIG>.

Similarly, after being integrated into an array, electrically driven MEMS micromirrors have a problem of heat crosstalk. A reason for having the problem of the heat crosstalk is described in detail in the foregoing embodiment, and details are not described in this embodiment. In the MEMS chip structure provided in this embodiment of this application, the grid array with a high heat conductivity is introduced to suppress heat crosstalk between adjacent MEMS chip units (a MEMS micromirror, a groove, and drive arms in the MEMS micromirror array together constitute a MEMS chip unit, where the groove and the drive arms are corresponding to the MEMS micromirror), thereby ensuring that control of each MEMS chip unit is relatively independent and reducing an impact of the heat crosstalk. In addition, due to a limitation of an etching process, it is difficult to etch side walls of the grooves in the MEMS micromirror array fairly deep. The grid array is connected to upper surfaces of side walls of the grooves, so that space of the hollow structure formed by the grooves, the grid array, and the dielectric plate can be large enough, thereby ensuring that rotation of the MEMS micromirrors is not affected.

Optionally, the MEMS chip structure further includes a thin film layer, the thin film layer is located between the lower surface of the grid array <NUM> and upper surfaces of side walls of the plurality of grooves <NUM>, and a heat conductivity of the thin film layer is greater than a heat conductivity of the grid array <NUM>. The thin film layer may be made of a material with a high heat conductivity, such as graphite or graphene. The thin film layer with a high heat conductivity is introduced, so that a larger portion of heat dissipated by the drive arms <NUM> can be transferred by the grid array <NUM> and the thin film layer to the side walls of the grooves <NUM> of the MEMS micromirror array <NUM> and then to the substrate <NUM>, and the impact of the heat crosstalk is further reduced.

Optionally, the grid array <NUM> includes a plurality of grid units <NUM>, and the grid unit <NUM> is of an annular structure and may be a square ring, a circular ring, or the like. The plurality of grid units <NUM> are in a one-to-one correspondence with the plurality of grooves <NUM>, and a width of a frame of the grid unit <NUM> is not greater than a width of the side wall of the groove <NUM>, so that the MEMS micromirror is not blocked, and an optical path switching function of the MEMS micromirror is not affected. Optionally, a line connecting a geometric center of the grid unit <NUM> and a geometric center of the corresponding groove <NUM> is perpendicular to a bottom surface of the corresponding groove <NUM>.

Claim 1:
A MEMS chip structure, comprising a substrate (<NUM>), a side wall (<NUM>), a dielectric plate (<NUM>), a MEMS micromirror array (<NUM>), and a grid array (<NUM>), wherein
the side wall is of an annular structure, the substrate (<NUM>) covers an opening on one side of the side wall (<NUM>), the dielectric plate (<NUM>) covers an opening on the other side of the side wall (<NUM>), and the side wall (<NUM>), the substrate (<NUM>), and the dielectric plate (<NUM>) form a hollow structure;
the MEMS micromirror array and the grid array are located inside the hollow structure;
the MEMS micromirror array is located above the substrate (<NUM>), and the MEMS micromirror array comprises a plurality of grooves (<NUM>)
and a plurality of MEMS micromirrors, wherein the plurality of MEMS micromirrors are in a one-to-one correspondence with the plurality of grooves, and the plurality of MEMS micromirrors are located in the corresponding grooves or above the corresponding grooves; and
the grid array is located above the MEMS micromirror array, and a lower surface of the grid array is connected to upper surfaces of side walls of at least some of the plurality of grooves.