Multilayer movable optical chip

Abstract

The invention discloses a multilayer movable optical chip, which belongs to the technical field of semiconductors and comprises a bottom light transmission conductive layer, a middle low-loss dielectric waveguide layer and a top movable layer. Wherein the low-loss dielectric waveguide layer serves as a core optical dielectric layer and cooperates with the upper layer and the lower layer to construct a high-performance optical control element, the dependence of a traditional optical device on a thin silicon layer optical control mode is broken through, and function reconstruction is creatively achieved; meanwhile, the core function of a traditional thin silicon structure is converted into conductive light transmission; according to the MEMS silicon optical chip, the problem of optical loss in the MEMS silicon optical technology is effectively solved, and the system performance is remarkably improved by strengthening the electrical driving and transmission functions of the bottom thin silicon layer, so that the MEMS silicon optical chip can fully meet the performance requirements of an MEMS-silicon optical chip signal processing unit and an optical network system.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, specifically to a multi-layer movable optical chip structure, and more particularly to an optical chip process and system structure that integrates optical and electrical signal transmission functions and low-loss on-chip optical signal manipulation. Background Art

[0002] Traditional silicon photonic chips manipulate optical signals by changing the phase of light through carrier injection or thermal regulation. This has achieved some success in optical modules for optical modulation and demodulation. However, with the advent of the era of high computing power and big data, the demand for optical interconnection and optical computing has emerged. This has necessitated the expansion of optical manipulation chips from single units to large-scale or even ultra-large-scale arrays. Traditionally, carrier injection or thermal regulation, because they rely on current control, generate significant heat, posing significant challenges for large-scale optical device chips.

[0003] From the existing solutions, an effective way to solve the problem of current heating is to change the current drive to voltage drive, thereby suppressing the current. Common technologies include electro-optical lithium niobate, phase change materials, MEMS technology, etc. Lithium niobate devices cause zero-point drift due to the release effect, which poses great challenges in static phase adjustment; phase change materials are difficult to batch process due to their complex materials and are still in the exploratory stage; MEMS technology and silicon photonics technology are relatively mature in themselves, and the combination of the two has a certain industrial and technical foundation, but the current common solutions still have practical problems, mainly due to the loss, process and control difficulties.

[0004] In particular, in MEMS silicon photonic hybrid technology, there are two common technologies: horizontal coupling and top-bottom coupling: One is horizontal coupling. Horizontal coupling can achieve better position control, but because the mode field needs to be leaked laterally during coupling, the optical waveguide needs to be narrow. However, the roughness of the waveguide sidewall is the main source of waveguide loss, so horizontal coupling loss is often large. The other is vertical coupling. On the one hand, the transmission of vertical coupling technology is still silicon, so the loss is still on the order of dB / cm. Although some people use three-layer silicon technology to avoid cross-waveguide loss, the coupler and the two highly coupled devices cause the loss to increase. On the other hand, due to the pull-in effect of MEMS, vertical coupling cannot make precise control of the position.

[0005] Currently, the industry has silicon nitride or silicon oxynitride waveguides to solve the problem of waveguide loss. However, the current silicon photonics-MEMS hybrid solution requires the waveguide to be charged to complete the corresponding driving action. Dielectric waveguides such as silicon nitride and silicon oxynitride are themselves dielectric materials and cannot achieve MEMS optical control like controlling silicon. Summary of the Invention

[0006] The purpose of this application is to solve the problem of high loss of MEMS silicon photonic chips in the existing technology, while improving the accuracy of MEMS optical devices in controlling light fields.

[0007] To achieve the above objectives, the present application adopts the following technical solution: a multi-layer movable optical chip, characterized by being divided into a movable region and a fixed region in the horizontal direction; and comprising three layers of optical waveguide structures in the vertical direction, namely, a bottom light-transmitting conductive layer, a middle low-loss waveguide layer, and a top movable layer, from bottom to top; the movable region is located in the middle of the optical chip and contains the MEMS movable structure through a release process; the fixed region is mainly located at the edge of the optical chip, is not protected by the release process, and therefore does not contain the MEMS movable structure; Specifically, the bottom light-transmitting conductive layer is a thin silicon structure, whose main functions are light transmission and electrical connection after doping, as well as providing a support anchor base for the thin silicon movable layer; The low-loss waveguide layer has an upper portion exposed to the air in the movable area and a bottom portion connected to the silicon oxide base; in the fixed area, the entire low-loss waveguide layer is covered by a covering layer; The top movable layer is a thin silicon structure, which is mainly distributed in the movable area. The main part has no upper and lower covers. The top movable layer is connected to the bottom light-transmitting conductive layer through anchor points to form mechanical fixation and electrical connection.

[0008] Specifically, the light-transmitting conductive layer is located below the low-loss waveguide layer, with a spacing of 0.05um to 1um between the light-transmitting conductive layer and the light-transmitting conductive layer, allowing an optical coupling effect to occur between the two layers. The top movable layer is located above the low-loss waveguide layer, with a spacing of 0.1um to 2um between the two layers. The bottom light-transmitting conductive layer can be made of thin single-crystal silicon with a thickness of less than 0.5um. The middle low-loss waveguide layer can transmit optical signals and can be made of dielectric materials such as silicon nitride, silicon oxynitride, lithium niobate, and doped silicon oxide, with a refractive index parameter between 1.45 and 2.9. The top movable structure can be made of thin single-crystal silicon or polycrystalline silicon with a thickness of 0.1um to 0.8um. Specifically, the top of the fixed area and the movable area are protected by a passivation material to define whether the area during the release process is a fixed area or a movable area: when the passivation layer height is higher than the movable layer height, the defined area is a fixed area; when the passivation layer height is lower than the movable layer height, the defined area is a movable area; More specifically, the top passivation material can be a dense dielectric material such as aluminum oxide or silicon nitride; In particular, the top movable layer includes a movable structure, which can be horizontally driven or rotated by the same layer structure, or vertically driven or rotated by the bottom light-transmitting conductive layer structure, thereby causing phase perturbation, energy transfer and other effects on the optical signal of the intermediate low-loss waveguide layer.

[0009] Furthermore, in the present application, the fixed area in the multi-layer movable optical chip includes a metal pad, a light detector, a light source, and a cover bonding area.

[0010] The cover bonding area includes a bonding ring and a cover. The cover can protect the movable device and facilitate subsequent complex optical and electrical packaging. At the same time, the inside of the cover can also be filled with vacuum or inert gas to enhance the life of the device.

[0011] The photodetector is used to monitor the light intensity in the low-loss waveguide layer, and specifically includes a bottom light-transmitting conductive layer close to the corresponding low-loss waveguide. Partial or complete energy transfer can occur between the bottom light-transmitting conductive layer waveguide and the low-loss waveguide. The end or the entire area of ​​the bottom light-transmitting conductive layer waveguide in the light transmission direction is heavily doped. When an optical signal is transmitted in the low-loss waveguide, the optical signal is first transmitted to the bottom light-transmitting conductive layer waveguide, and is absorbed in the heavily doped area to generate photoelectrons, thereby acting as a photodetector.

[0012] Furthermore, in the present application, the manner in which the movable structure layer manipulates the optical signal of the low-loss waveguide layer may include horizontal movement, vertical movement, or rotation of the movable structure, thereby affecting the phase of the optical signal by influencing the evanescent field of the low-loss waveguide layer; the energy transfer of the movable layer to the low-loss layer may be achieved by controlling all or part of the energy transfer through horizontal movement or vertical movement.

[0013] Specifically, the bottom light-transmitting conductive layer structure can form a wire through doping. When a flat plate is set directly below the movable layer, a flat plate driver can be formed to control the up and down movement or rotation of the top thin silicon movable layer; the top movable layer is controlled to achieve horizontal movement through the action of horizontal comb teeth or horizontal electrostatic adsorption.

[0014] Furthermore, in the present application, the top movable structure, the middle low-loss waveguide structure, and the bottom light-transmitting conductive layer can constitute a digital optical switching device, specifically: The middle low-loss structure is a cross-waveguide structure, and the top movable structure is a horizontally curved structure, wherein one end of the top movable structure is parallel to the first port of the cross-waveguide, and the other end is parallel to the second port adjacent to the cross-waveguide; The bottom light-transmitting conductive layer structure is heavily doped to form a driving electrode; above the bottom light-transmitting conductive layer is a medium, the thickness of which is less than about 2 / 3 of the distance between the top movable layer and the bottom light-transmitting conductive layer; in particular, the 2 / 3 here may vary due to differences in the fringe field of the structure, the dielectric constant of the material, etc.

[0015] The specific control method of the digital optical switching device is as follows: when the bottom driving electrode is not powered, the optical switching device is in a first state, and the optical signal directly passes from the first port of the low-loss cross waveguide to the third port of the cross waveguide, thereby realizing a direct optical path; when the bottom driving electrode is powered, the optical switching device is in a second state, and the optical signal is coupled from the first port of the low-loss cross waveguide into the movable bending structure, and then coupled into the second port of the low-loss cross waveguide, thereby realizing optical path switching; Furthermore, the movable digital optical switching device can be arrayed by a plurality of devices, i.e., a cross-waveguide unit in each row and column, wherein the third port is connected to the first port of the switching device, and the fourth port is connected to the second port of the adjacent switching device, thereby realizing a grid array; Furthermore, the movable digital optical switching device can be composed of two or more groups of bending structures and bottom driving electrodes to form multi-channel and multi-directional switching.

[0016] Furthermore, in the present application, the top movable structure, the middle low-loss structure, and the bottom light-transmitting conductive layer structure can constitute an analog optical phase perturbation device, specifically: The dielectric material is placed above the bottom light-transmitting conductive layer, and its thickness limits the maximum displacement of the movable structure to less than about 2 / 3 of the distance between the top waveguide layer and the bottom light-transmitting conductive layer. On the one hand, the height of the middle low-loss waveguide layer is raised to make it closer to the top movable structure, making the phase more easily disturbed. On the other hand, the pull-in effect is avoided, making the control more precise. More specifically, the upper dielectric material may be a single material or a combination of aluminum oxide, silicon oxide, or the same material as the low-loss waveguide layer.

[0017] The low-loss dielectric layer is located between the top waveguide layer and the bottom thin silicon layer. When the movable structure moves up and down, the optical signal in the low-loss waveguide layer is disturbed by the top movable structure through the action of the evanescent field, thereby achieving the effect of phase adjustment. Furthermore, the analog optical phase perturbation device can be arrayed by multiple devices and multiple straight-through low-loss waveguides to realize the network structure of the optical phase matrix, and the grid unit is configured by the phase perturbation device at each position; The beneficial effects of this application are: 1. This application realizes optical manipulation by setting up a movable silicon waveguide layer at the top, a low-loss waveguide layer in the middle, and a light-transmitting conductive layer at the bottom. The coupling effect of the first two layers is used to achieve optical manipulation. This application breaks through the traditional method of using thin silicon waveguides and converts its function into a light-transmitting conductive layer. On the one hand, this layer is still used for light transmission or light jump layer in some areas. On the other hand, it is heavily doped to realize the function of electrical devices such as wires. Unlike the traditional MEMS-silicon photonic hybrid architecture, it mainly relies on the low-loss waveguide in the middle to transmit light signals rather than the traditional thin silicon layer. It not only retains the availability of the rich optical device library of traditional silicon photonic technology, but also provides the feasibility of optoelectronic devices. At the same time, it avoids the excessive dependence of traditional optical devices on the manipulation of light in traditional thin silicon layers, thus solving the loss problem in traditional silicon photonic technology and traditional MEMS silicon photonic technology.

[0018] 2. This application introduces a low-loss dielectric waveguide layer and creatively adjusts the function of the bottom thin silicon layer to weaken its optical waveguide properties. The optical transmission function is more carried by the bottom low-loss waveguide layer. Therefore, the driving electrode area constructed by the bottom thin silicon layer can be greatly increased, and the driving voltage for up and down movement can be significantly reduced.

[0019] 3. In an embodiment of the present application, the conventional light-transmitting conductive layer structure can transfer all or part of the energy of the optical signal in the middle low-loss waveguide through coupling. When the end of the waveguide is highly doped through ion implantation or diffusion process to form an N-type or P-type waveguide, the function of light detection can be realized.

[0020] 4. The thickness of the silicon oxide layer on top of this layer is adjustable. Therefore, when the thickness of the dielectric material (such as the silicon oxide layer) on the top is greater than approximately 2 / 3 of the top waveguide spacing, on the one hand, the height of the intermediate low-loss waveguide is raised, making its phase more susceptible to interference from the top. On the other hand, the pull-in effect can be avoided, allowing precise control of the device position and achieving analog drive. When the thickness of the dielectric material (such as the silicon oxide layer) on the top is less than or equal to approximately 2 / 3 of the top waveguide spacing, the pull-in effect can be utilized to achieve digital drive.

[0021] 5. The bonding ring and bonding cover at the top of this structure can protect the movable device, facilitate the subsequent complex optical and electrical packaging, and have strong operability. It can also effectively control overflow. At the same time, the inside of the cover can also be filled with vacuum or inert gas to enhance the life of the device.

[0022] 6. The unit structure of the present application can be easily implemented in an array structure. Combined with a digital optical switching mode, it can realize a multi-port optical switching function. Combined with an analog optical control mode, it can realize a large-scale optical computing architecture. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1This is a schematic diagram of a multi-layer movable chip according to an embodiment of the present application.

[0024] Figure 2 Schematic diagram of a multi-layer low-loss dielectric waveguide chip according to an embodiment of the present application Figure 3 This is a schematic diagram of the unit structure of a digital optical switching device according to an embodiment of the present application.

[0025] Figure 4 This is a schematic diagram of the array structure of digital optical switching device units according to an embodiment of the present application.

[0026] Figure 5 This is a schematic diagram of an upload-download digital optical switching device according to an embodiment of the present application.

[0027] Figure 6 Schematic diagram of the analog phase shifter unit structure according to an embodiment of the present application.

[0028] Figure 7 Schematic diagram of the calculation matrix structure composed of analog phase shifter units in the embodiment of the present application Figure 8 Schematic diagram of the method and process for manufacturing a multi-layer movable chip according to an embodiment of the present application 1. Light-transmitting conductive layer, 2. Middle low-loss waveguide layer, 3. Top movable layer, 4. Anchor base, 5. Pad, 6. Cladding layer, 7. Drive electrode, 8. Side coupler, 9. Cladding layer, 10. Cover, 11. First passivation layer, 12. Second passivation layer. DETAILED DESCRIPTION

[0029] In order to make the purpose and technical solution of this application clearly and completely described, and the advantages more clearly understood, the embodiments of this application are further described in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are part of the embodiments of this application, rather than all the embodiments, and are only used to explain the embodiments of this application, and are not used to limit the embodiments of this application. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0030] In the description of this application, it should be noted that the terms "center", "middle", "upper", "lower", "left", "right", "inner", "outer", "top", "bottom", "side", "vertical", "horizontal", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they should not be understood as limiting this application. In addition, the terms "one", "first", "second", "third", "fourth", "fifth", and "sixth" are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0031] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0032] For the purposes of simplicity and illustration, the principles of the embodiments are primarily described with reference to examples. In the following description, numerous specific details are provided to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that these embodiments may not be limited to these specific details in practice. In some instances, well-known mechanical seal methods and structures used between the submarine center shaft and the hull are not described in detail to avoid unnecessarily obscuring the understanding of these embodiments. Furthermore, all embodiments may be used in combination with one another. Example

[0033] It should be noted that the drawings in the specification are the contents of the specification. The structural shapes, connection relationships, coordination relationships, and positional relationships that can be obtained without any doubt in the drawings in the specification should be understood as the contents of the specification.

[0034] A multi-layer movable optical chip, such as Figure 1 As shown, the horizontal direction is divided into a movable area and a fixed area; the vertical direction includes three layers of optical waveguide structure, which are the bottom light-transmitting conductive layer 1, the middle low-loss waveguide layer 2, and the top movable layer 3 from bottom to top; the movable area is located in the middle of the optical chip and contains the MEMS movable structure through the release process; the fixed area is mainly located at the edge of the optical chip and is not protected during the release process, so it does not contain the MEMS movable structure.

[0035] More specifically, the bottom light-transmitting conductive layer is a thin silicon structure with a classic thickness of 0.22um. Its main functions are light transmission and electrical connection after doping, as well as providing a support anchor base 4 for the thin silicon movable layer.

[0036] In particular, the low-loss waveguide layer 2 in the movable area is made of silicon nitride and has a thickness of 0.4 μm. Its upper portion is exposed to air and has a loss of less than 0.5 dB / cm. Its bottom is connected to the silicon oxide base. The low-loss waveguide layer is entirely covered by a cladding layer 6 made of silicon oxide with a refractive index generally around 1.45.

[0037] The top movable layer is a thin silicon structure with a thickness of 0.4um. It is mainly distributed in the movable area. The main part has no upper and lower covers. The top movable layer is connected to the bottom light-transmitting conductive layer through the anchor point 4 to form a mechanical fixation and electrical connection.

[0038] The advantage of this application lies in that, by installing a movable silicon waveguide layer at the top, a low-loss waveguide layer in the middle, and a light-transmitting conductive layer at the bottom, the coupling effect of the two different waveguide materials, the movable waveguide layer and the low-loss waveguide layer, is used to achieve optical manipulation. This breaks through the traditional use of thin silicon waveguides, converting the function of the traditional thin silicon structure into the light-transmitting conductive layer, switching the main optical transmission to the low-loss waveguide layer, and the thin silicon layer only plays a supporting role. For most scenarios, the main optical signal is still transmitted in the low-loss waveguide layer, thus avoiding the over-reliance of traditional optical devices on the traditional thin silicon layer to manipulate light, and solving the loss problem of traditional silicon photonics technology and traditional MEMS silicon photonics technology.

[0039] Another advantage of the present application is that the thin silicon structure at the bottom, i.e. the light-transmitting conductive layer, is still used for light transmission or light jumping layer in some areas on the one hand, and on the other hand, it is heavily doped to realize the function of electrical devices such as wires, which not only retains the availability of the rich optical device library of traditional silicon photonics technology, but also provides a channel for light detection for the architecture of the present application.

[0040] Another advantage of the present application is that in the core functional device, the middle low-loss dielectric waveguide layer carries most of the light transmission functions, so the bottom thin silicon layer is freed up to construct a larger driver electrode area, so that the up and down movement driving voltage can be greatly reduced.

[0041] Another advantage of the present application is that the bonding ring at the top of the structure combined with the bonding cover can protect the movable device, facilitate the subsequent complex optical and electrical packaging, and have strong operability. It can also effectively control overflow. At the same time, the inside of the cover can also be filled with vacuum or inert gas to enhance the life of the device.

[0042] Compared with the existing technology, this application has achieved significant improvements. By introducing a low-loss dielectric waveguide layer and creatively adjusting the functions of the bottom thin silicon layer, its optical waveguide properties are weakened, its mechanical support, electrical connection, photoelectric effect and other functions are strengthened, and the overall system loss is effectively reduced. At the same time, more functions are added, achieving an exponential upgrade in technical effects.

[0043] Specifically, such as Figure 1 As shown, the fixed area and the movable area are protected by the first passivation layer 11 and the second passivation layer 12, which are specifically used to block the corrosion effect of VHF during the process, so as to define the area during the release process as a fixed area or a movable area. More specifically, the height of the first passivation layer 11 is lower than the height of the movable layer 3; the height of the second passivation layer 12 is higher than the height of the movable layer 3. The second passivation layer has a higher priority than the first passivation layer, that is, when there is no second passivation layer protection above the first passivation layer, the first passivation layer plays a major role, and the area is defined as a movable area; when there is a second passivation layer, the second passivation layer plays a major role, and the area is defined as a fixed area. Optionally, the passivation layer material can be a dense dielectric material such as silicon nitride, aluminum oxide, or aluminum nitride.

[0044] Specifically, the specific position and parameter relationship of the three-layer structure are as follows: below the low-loss waveguide layer is a thin silicon light-transmitting conductive layer with a thickness of 0.22um, and the spacing between it is 0.3um, which can ensure effective optical coupling effect between the two layers; above the low-loss waveguide layer is a top movable layer of thin silicon with a thickness of 0.4um, and the spacing between the two layers is 1um. This distance can ensure that the top movable structure can effectively control the light of the middle low-loss waveguide layer, while ensuring that the driving voltage of the bottom driving electrode is within the easily accessible 100V; the middle low-loss waveguide layer can propagate optical signals, and the wavelength of the optical signal is specifically around 1.3um or 1.55um, and its material is silicon nitride.

[0045] The top movable layer includes a movable structure, under which a driving electrode 7 is arranged. Specifically, when the spacing is around 1um and the eigenfrequency of the up and down movement of the movable structure is around 1MHz, a voltage of around 50V can effectively drive the position of the movable structure, thereby controlling the optical signal in the low-loss waveguide layer.

[0046] Next, in this application, the fixed area in the multi-layer movable optical chip, such as Figure 1 As shown, it includes a metal pad 5, a photodetector 1, a cover 10, and an edge coupler 8.

[0047] The cover bonding area includes a bonding ring 9 and a cover 10. The cover can protect the movable device and facilitate subsequent complex optical and electrical packaging. At the same time, the inside of the cover can also be filled with vacuum or inert gas to enhance the life of the device.

[0048] The photodetector 1 specifically includes a bottom light-transmitting conductive layer close to the corresponding low-loss waveguide. Partial energy transfer occurs between the bottom light-transmitting conductive layer waveguide and the low-loss waveguide. By controlling the length of the overlapping area to be approximately 20um, the energy transfer ratio is made to be 5%, or about 0.2dB; finally, the end area of ​​the bottom silicon wave is heavily doped. In this way, when an optical signal is transmitted in the low-loss waveguide, the optical signal is first transmitted to the bottom light-transmitting conductive layer waveguide, and is absorbed in the heavily doped area to generate photoelectrons, thereby acting as a photodetector for monitoring the light intensity in the low-loss waveguide layer. Example

[0049] A multi-layer movable optical chip, which differs from Example 1 in that it has a low-loss dielectric waveguide in the middle and has a two-layer structure. The remaining features and technical effects of this embodiment are the same as those of Example 1, specifically: The intermediate low-loss dielectric waveguide, such as Figure 2 As shown, the structure consists of two layers, namely an upper low-loss dielectric waveguide layer 801 and a lower low-loss dielectric waveguide layer 802; the specific material is a silicon nitride structure, and the distance between the two layers is 300nm to ensure the optical coupling efficiency between the two waveguide layers; The advantage of this embodiment is that more electrical properties are transmitted to the bottom light-transmitting conductive layer, and the core functions are electrical transmission, driving electrodes, and PD functions; the phase and delay of the optical signal in the double-layer low-loss dielectric waveguide are more matched. Example

[0050] A multi-layer movable optical chip differs from Example 1 in that the top movable structure, the middle low-loss structure, and the bottom light-transmitting conductive layer can form a digital optical switching device, which can be constructed into an array to achieve optical switching functions. The remaining features and technical effects of this embodiment are the same as those of Example 1, specifically: The digital optical switching device, such as Figure 1 As shown, the dielectric layer is located above the light-transmitting conductive layer, and its thickness is less than about 2 / 3 of the distance between the top waveguide layer and the bottom light-transmitting conductive layer; Figure 3 As shown, the central low-loss structure is specifically a cross-waveguide structure 201, the top movable structure is a horizontal curved structure 301, and the two ends of the curved structure are each provided with two sharp corners for reducing coupling loss. The bottom light-transmitting conductive layer structure is heavily doped to form a driving electrode 7; wherein one end of the top movable structure is parallel to the cross-waveguide port 1, and the other end is parallel to the port 2 adjacent to the cross-waveguide.

[0051] More specifically, the low-loss transmission waveguide layer is a silicon nitride structure, which has lower transmission loss than the silicon waveguide in the traditional silicon photonic MEMS structure.

[0052] Optionally, the low-loss cross waveguide may be a ridge waveguide structure to further reduce transmission loss.

[0053] Optional, such as Figure 1 As shown, the first passivation layer 11 in this embodiment of the present application can be made of silicon nitride, the same material as the low-loss transmission layer. This has the advantages of reducing the complexity of using additional materials for the first passivation layer and preventing the impact of other passivation materials on the optical mode field within the optical waveguide. Furthermore, due to the thickness of the silicon nitride in the low-loss waveguide layer, its passivation protection is even more effective.

[0054] The specific control method of the digital optical switching device is as follows: Figure 3 As shown, when the bottom driving electrode is not powered, the optical switching device is in the first state, the top movable structure is away from the low-loss waveguide, and the optical signal goes directly from port 1 of the low-loss cross waveguide to port 3 of the cross waveguide, realizing direct optical path; when the bottom driving electrode is powered, the optical switching device is in the second state, the top movable structure is close to the low-loss waveguide, and the optical signal is coupled from port 1 of the low-loss cross waveguide into the movable bending structures 302 and 301, and then coupled into port 2 of the low-loss cross waveguide, realizing optical path switching.

[0055] Furthermore, if Figure 4 As shown, the movable digital optical switching device can be composed of an array of multiple devices, namely, cross waveguide units in each row and column, with port 3 connected to port 1 of the switching device; port 4 is connected to port 2 of the adjacent switching device, thereby realizing a grid array, controlling the device states at the cross nodes respectively, and controlling the transmission direction of the light path therein, thereby realizing the function of an optical switch.

[0056] In particular, such as Figure 4 As shown, when switch A is in the second state and the other switches are in the first state, the optical signal reaches the b' exit from the b entrance; at the next moment, when switch A is switched to the first state, when switch B is switched to the second state, and the other switches remain in their original states, the optical signal reaches the c' exit from the b entrance, thereby achieving state switching.

[0057] The advantage of the embodiments of the present application is that, compared with the traditional MEMS-silicon photonic hybrid optical switch, in the switch matrix area, the bottom thin silicon layer is mainly used for conducting and driving electrodes, so the driving electrode area can be greatly increased and the up and down movement driving voltage can be greatly reduced.

[0058] Another advantage of the embodiment of the present application is that, within the switch matrix area, the main body of optical signal transmission is the low-loss waveguide layer, and the transmission loss can be greatly reduced. Example

[0059] A multi-layer movable optical chip differs from Example 3 in that the unit structure can include two or more sets of bending structures and bottom drive electrodes, forming multi-channel and multi-directional switching, as well as upload and download functions. The remaining features and technical effects of this embodiment are the same as those of Example 3, specifically: The digital optical switching device, such as Figure 5 As shown, the unit structure can include two sets of driving structures, 304 located in the second quadrant of the cross waveguide and 305 located in the fourth quadrant of the cross waveguide; and includes four ports: Port 1, Port 2, Port 3, and Port 4. Similarly, the unit elements can be connected end to end to form an array structure.

[0060] The specific control methods are: When the optical switch is not driven, the optical signal passes directly from Port 1 to Port 3, which is the series connection state; When the second quadrant switch is driven, the optical signal passes directly from Port 1 to Port 4, which is the download state; When the fourth quadrant switch is driven, the optical signal passes directly from Port2 to Port3, which is the uplink state; Example

[0061] A multi-layer movable optical chip differs from Example 3 in that: the dielectric above the electrode has a thickness greater than approximately 2 / 3 of the distance between the top waveguide layer and the bottom light-transmitting conductive layer; precise analog control of the upper and lower positions of the device is achieved, realizing an analog phase shifter. The remaining features and technical effects of this embodiment are the same as those of Example 2, specifically: The analog phase shifter, such as Figure 1 As shown, above the light-transmitting conductive layer is a dielectric, the thickness of which is greater than approximately 2 / 3 of the distance between the top waveguide layer and the bottom light-transmitting conductive layer; more specifically, the upper dielectric material can be a single material or a combination including aluminum oxide, silicon oxide, or the same material as the low-loss waveguide layer.

[0062] The analog phase shifter, such as Figure 6 As shown, the middle low-loss structure is specifically a strip waveguide structure 202, and the top movable structure 304 is a conical movable structure with a specific structural length of about 50um. This length can not only ensure the fast driving speed of the device, but also obtain relatively strong phase disturbance; the bottom is the driving electrode 7. Since the middle low-loss waveguide 202 carries the function of all light transmission, the electrical effect of the bottom light-transmitting conductive layer is released, and a larger driving electrode 7 can be configured to reduce the driving voltage.

[0063] The specific control method of the digital optical switching device is as follows: Figure 1As shown, when a driving voltage is applied to driving electrode 7, the movable structure pulls downward due to electrostatic attraction, affecting the phase of the optical signal in low-loss waveguide 202. The greater the driving voltage, the stronger the downward pull of the movable structure, and the greater the phase change. Precise control of the driving voltage can achieve precise phase control. As the movable structure moves up and down, the optical signal in the low-loss waveguide layer is disturbed by the top movable structure through the evanescent field, thus achieving phase adjustment.

[0064] The advantage of the embodiment of the present application is that, since the optical and electrical functions of the middle low-loss waveguide and the bottom light-transmitting conductive layer are separated, by increasing the thickness of the dielectric layer between the low-loss waveguide 202 and the electrode 7, on the one hand, the height of the middle low-loss waveguide is raised, making it closer to the top movable structure, and the phase is more easily disturbed; on the other hand, the movement amplitude of the movable structure is limited to be less than the pull-in distance, the control stability is enhanced, and analog precision control becomes possible.

[0065] Furthermore, if Figure 7 The analog phase shifter can be composed of an array of multiple devices and multiple straight-through low-loss waveguides to realize the calculation matrix structure of the optical phase matrix, and configure the grid unit through the phase perturbation device at each position. Example

[0066] A method for preparing a multi-layer movable optical chip, based on the multi-layer movable optical chips of Examples 1 to 5 above, is as follows: like Figure 8 As shown, SOI wafer is selected as the chip substrate; Using ultraviolet lithography or electron beam lithography technology, the top silicon material is etched one or more times to form a light-conducting layer pattern, and some areas are doped; during the doping process, heavy doping and super-heavy doping doses are applied according to the device function to ensure device performance, such as Figure 8 b; Next, a dielectric material is deposited on top of the light-transmitting conductive layer and chemically mechanically polished, with different thicknesses being matched for different types of devices and applications. An upper low-loss waveguide layer is then prepared, and the waveguide layer material can be silicon oxynitride or silicon nitride. A first passivation layer can then be optionally covered and patterned on top, and the first passivation layer material can be aluminum oxide, such as Figure 8 c; Next, a dielectric material is deposited on the low-loss waveguide layer and chemically mechanically polished. Then, a movable structural layer is prepared. The movable structural layer is made of polysilicon. After the polysilicon film is formed, one or more etchings are performed to form the movable geometric structure above, such as Figure 8 d; Next, dielectric materials are deposited to prepare metal vias, wires, pads, and bonding rings; a second passivation layer is deposited and patterned to define the movable and fixed areas, such as Figure 8 e; Next, define and etch the pad area, mechanical structure release, e.g. Figure 8 f; Finally, wafer-level cap bonding, such as Figure 8 g; Finally, the final structure is formed by thinning the top cover, such as Figure 8 h.

[0067] Although the above describes the illustrative specific implementation methods of the present application so that those skilled in the art can understand the present application, the present application is not limited to the scope of the specific implementation methods. For those skilled in the art in the present art, as long as various changes are within the spirit and scope of the present application as defined and determined by the attached claims, all inventions and creations conceived using the present application are protected.

Claims

1. A multi-layer movable optical chip, characterized in that: The horizontal direction is divided into a movable area and a fixed area; the vertical direction includes a three-layer optical waveguide structure, which is composed of a bottom light-transmitting conductive layer, a middle low-loss waveguide layer, and a top movable layer from bottom to top. The movable area is located in the middle of the optical chip and includes a MEMS movable structure through a release process; The fixed area is mainly located at the edge of the optical chip and is not protected during the release process, so it does not include the MEMS movable structure; The bottom light-transmitting conductive layer is a thin silicon structure, whose main functions are light transmission and electrical connection after doping, as well as providing a support anchor base for the thin silicon movable layer; The low-loss waveguide layer has an upper portion exposed to the air in the movable area, and a bottom portion connected to the cladding material; In the fixed area, the whole is covered by the cladding layer; The top movable layer is a thin silicon structure, which is mainly distributed in the movable area. The main part has no upper and lower covers. The top movable layer structure is connected to the bottom light-transmitting conductive layer through anchor points to form mechanical fixation and electrical connection.

2. The low-loss waveguide layer according to claim 1 is provided with a thin silicon waveguide layer below, with a spacing of 0.05 μm to 1 μm between the thin silicon waveguide layer and the top movable layer above the low-loss waveguide layer, with a spacing of 0.1 μm to 2 μm between the thin silicon waveguide layer and the top movable layer.

3. According to claim 1, the low-loss waveguide layer can propagate optical signals, and its material can be a dielectric material such as silicon nitride, silicon oxynitride, lithium niobate, doped silicon oxide, etc., and its refractive index parameter is between 1.45 and 2.

9.

4. The low-loss waveguide layer according to claim 1 may specifically include two or more sub-layers, and the distance between each sub-layer is between 0.1 and 0.5 μm.

5. The top movable layer according to claim 1 comprises a movable structure, thereby optically manipulating the light signal of the middle low-loss waveguide layer.

6. The top movable structure according to claim 5 may have a movement mode including horizontal movement, up and down movement, or in-plane or out-of-plane rotation.

7. The optical manipulation according to claim 5 mainly involves manipulating the phase or energy of the optical signal by influencing the evanescent field of the low-loss layer through a movable structure, wherein the energy manipulation includes partial or complete energy transfer.

8. According to the top movable structure of claim 5, when it rotates up and down or out of the plane, its driving electrode is specifically composed of a flat electrode formed by doping the light-transmitting conductive layer.

9. According to the top movable structure of claim 5, when it rotates horizontally or in-plane, its driving structure is specifically the horizontal comb teeth or horizontal capacitors of the top movable layer.

10. According to claim 1, the top of the fixed area and the top of the movable area are passivation layers, the height of the passivation layer in the fixed area is higher than the height of the movable layer; the height of the passivation layer in the movable area is lower than the height of the movable layer.

11. The top passivation material according to claim 10 can be a dense dielectric material such as aluminum oxide, silicon nitride, etc.

12. The fixing area according to claim 1, comprising a metal pad, a photodetector, a light source, and a capping bonding structure; The sealing cap bonding structure includes a bonding ring and a sealing cap, and the interior of the sealing cap may also be filled with vacuum or inert gas.

13. The photodetector comprises a low-loss waveguide and a bottom light-transmitting conductive waveguide, wherein the end or the entire region of the bottom light-transmitting conductive layer waveguide in the light transmission direction is heavily doped, and the bottom light-transmitting conductive layer waveguide and the low-loss waveguide are coupled to achieve partial or complete energy transfer; When an optical signal is transmitted in a low-loss waveguide, the optical signal is first transmitted to the bottom light-transmitting conductive layer waveguide, where it is absorbed in the heavily doped area to generate photoelectrons for optical detection.

14. The multi-layer movable optical chip according to claim 1 can be specifically a digital optical switching device, wherein: The middle low-loss structure is a cross-waveguide structure; The top movable structure is a horizontally curved structure, one end of which is parallel to the first port of the cross waveguide, and the other end of which is parallel to the second port adjacent to the cross waveguide; The bottom light-transmitting conductive layer structure is heavily doped to form a driving electrode, above which is a dielectric layer having a thickness less than 2 / 3 of the distance between the top movable layer and the bottom light-transmitting conductive layer; When the bottom driving electrode is not powered, the optical switching device is in the first state, and the optical signal passes directly from the first port of the low-loss cross waveguide to the third port of the cross waveguide, thereby achieving a direct optical path. When the bottom driving electrode is powered on, the optical switching device is in the second state, and the optical signal is coupled from the first port of the low-loss cross waveguide into the movable bending structure, and then coupled into the second port of the low-loss cross waveguide to achieve optical path switching.

15. The digital optical switching device according to claim 13 can be expanded into an array structure, that is, the cross waveguide units in each row and column, the third port is connected to the first port of the switching device, and the fourth port is connected to the second port of the adjacent switching device, thereby realizing a grid array.

16. The digital optical switching device according to claim 13, wherein the unit structure may include two or more groups of curved structures and bottom driving electrodes to form multi-channel and multi-directional switching.

17. The multi-layer movable optical chip according to claim 1 can be specifically an analog optical phase perturbation device, wherein: The bottom light-transmitting conductive layer is a dielectric material for limiting the displacement of the movable structure, and its thickness is greater than about 2 / 3 of the distance between the top waveguide layer and the bottom light-transmitting conductive layer; The intermediate low-loss waveguide layer is located between the top movable structure and the bottom light-transmitting conductive layer. The optical signal in the low-loss waveguide layer is disturbed by the top movable structure through the action of the evanescent field, thereby achieving the effect of phase adjustment.

18. The analog optical phase perturbation device according to claim 16 can be arrayed by multiple devices and multiple straight-through low-loss waveguides to realize the network structure of the optical phase matrix, and the grid unit is configured by the phase perturbation device at each position.

19. The dielectric material above the bottom light-transmitting conductive layer according to claim 14 is a single material or a combination of aluminum oxide, silicon oxide, or similar materials for the low-loss waveguide layer.

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