Large-size MEMS film reflector

Abstract

The invention discloses a large-size MEMS (Micro-Electro-Mechanical System) film reflector, particularly relates to the technical field of MEMS reflectors, and aims to solve the problems that a film reflector in the prior art is easy to deform and the like. The large-size MEMS film reflector comprises a substrate, a brake area is arranged on the substrate, one side of the brake area extends to the outside to be connected with the film reflector, and the other side of the brake area is connected with the MEMS reflector. A silicon-based micropore frame is arranged below the thin film reflector and used for preventing the thin film reflector from bending or deforming, and metal lead points are arranged at the two ends of the braking area and connected with an external power source through metal leads. The problem of film deformation can be solved, and meanwhile the requirement that the size of the reflector reaches the centimeter magnitude can be met.

Description

Technical Field

[0001] The invention relates to a large-size MEMS thin film reflector, belonging to the technical field of MEMS reflectors. Background Art

[0002] MEMS mirrors have a variety of application scenarios, such as microscopy, infrared spectrometers, optical switches, projection and structured lighting, and all of the above applications require large-sized flat mirrors to achieve efficient light coupling and high spatial resolution.

[0003] Large-size mirrors often use thicker reflective films to overcome film deformation and maintain high flatness during movement. However, due to the non-negligible mass of the thick film, the amount of braking displacement is significantly limited without sufficiently high drive power, which hinders MEMS actuators with larger mirrors. In addition, for large-angle and large-range braking, the use of thin-film mirrors is usually necessary.

[0004] MEMS thin film mirrors have the advantages of low cost, low voltage, and high compatibility for large-area configurations due to their light weight. At the same time, they can have the advantages of fast heat dissipation and large driving range when combined with an electrothermal structure based on a thermal bimorph material. However, as the membrane area increases further, the freely moving film is extremely susceptible to various film deformations, such as cracks and buckling. Film deformation occurs when the released film tends to shrink or expand due to its residual tensile or compressive stress. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a large-size MEMS thin film reflector that can solve the problem of thin film deformation while meeting the requirement that the reflector size reaches the centimeter level.

[0006] To achieve the above object, the present invention is implemented by adopting the following technical solutions: The present invention provides a large-size MEMS thin film reflector, comprising a substrate, a braking area is provided on the substrate, one side of the braking area extends to the outside and is connected to the thin film reflector, a silicon-based microporous frame is provided below the thin film reflector, the silicon-based microporous frame is used to prevent the thin film reflector from bending or deformation, metal lead points are provided at both ends of the braking area, and the metal lead points are connected to an external power supply through metal leads.

[0007] Furthermore, the braking zone includes, from bottom to top, a high expansion layer, a heating resistor layer and a low expansion layer, the high expansion layer is used to provide expansion braking stress and enhance the mechanical strength of the braking zone, the low expansion layer is used to provide expansion braking stress matching the high expansion layer, and the heating resistor layer is used to generate heat through resistance under the action of an external voltage to heat the high expansion layer and the low expansion layer, so that the high expansion layer and the low expansion layer expand and produce longitudinal displacement.

[0008] Furthermore, it also includes two isolation layers, the material of which is SiO2 or Si3N4, and the isolation layers are respectively arranged between the substrate and the high expansion layer, and between the high expansion layer and the heating resistor layer. The isolation layer located between the substrate and the high expansion layer is used to isolate the braking area from the substrate and match the stress of the braking area. The isolation layer located between the high expansion layer and the heating resistor layer is used to isolate the high expansion layer and the heating resistor layer to prevent leakage.

[0009] Furthermore, the material of the high expansion layer is a material with a high thermal expansion coefficient, and the material of the low expansion layer is SiO2.

[0010] Furthermore, a resistance pattern is provided in the heating resistance layer, and the resistance pattern is formed by etching.

[0011] Furthermore, windows are provided at both ends of the low expansion layer, lead ends are provided below the windows corresponding to the heating resistor layer, metal lead points are formed in the windows on the lead ends by depositing metal, and the metal lead points are used for bonding metal leads.

[0012] Furthermore, the thin film reflector includes a reflector base film layer and a reflective layer from bottom to top, the reflector base film layer is made of SiO2 or Si3N4, and the reflective layer is formed on the thin film reflector by metal deposition, and its material is aluminum or gold.

[0013] Furthermore, the thickness of the reflector base film layer is 1-5 micrometers, and the thickness of the reflective layer is 50-100 nanometers.

[0014] Furthermore, the silicon-based microporous frame surrounds the edge of the lower surface of the thin film reflector, and a microporous array is arranged inside the frame, wherein the microporous array is composed of a plurality of microporous arrays of the same size and shape.

[0015] Furthermore, the silicon-based microporous frame and the substrate have the same thickness, and the thickness ranges from 350 to 500 microns.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The size of the MEMS thin film reflector provided by the present invention reaches the centimeter level, and the volume is small. A silicon-based microporous frame is provided under the thin film reflector, which can ensure that the thickness of the thin film reflector is several microns while ensuring that the reflector will not undergo deformation such as curling, thereby improving the reliability and stability of the MEMS thin film reflector. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the structure of a large-size MEMS thin film reflector in an embodiment of the present invention; Figure 2 A schematic structural diagram of a substrate and a braking area of ​​a large-size MEMS thin film reflector in an embodiment of the present invention; Figure 3 A schematic structural diagram of a thin film reflector and a silicon-based microporous frame of a large-size MEMS thin film reflector in an embodiment of the present invention; Figure 4 A schematic diagram of the structure of a micro-hole array of a large-size MEMS thin film reflector in an embodiment of the present invention; Figure 5 A schematic diagram of the structure of a micro-hole array of a large-size MEMS thin film reflector in an embodiment of the present invention; In the figure, 1-substrate, 2-metal lead point, 3-braking area, 4-thin film reflector, 5-silicon-based microporous frame, 301 high expansion layer, 302 heating resistor layer, 303 low expansion layer, 305 isolation layer, 401 reflector base film layer, 402 reflective layer, 501 microporous array. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention. Example 1

[0019] like Figure 1 As shown, an embodiment of the present invention provides a large-size MEMS thin film reflector, including a substrate 1. In this embodiment, the material of the substrate 1 is silicon. A brake area 3 is provided on the substrate 1. The brake area 3 is an electrothermal structure based on a thermal double-layer material, which is composed of multiple structural layers. Specifically: like Figure 2As shown, the brake zone 3 includes a high expansion layer 301, a heating resistor layer 302 and a low expansion layer 303 from bottom to top. The high expansion layer 301 is made of a material with a high thermal expansion coefficient, usually metal aluminum, which is used to provide expansion braking stress and improve the strength of the brake zone. The heating resistor layer 302 is usually made of a material with a relatively high resistivity, such as metal platinum, polysilicon, etc. The heating resistor layer 302 is etched to form a preset resistance pattern, and windows are opened at both ends of the low expansion layer 303. A lead-out terminal is provided at the corresponding heating resistor layer 302 below the window. Metal is deposited on the lead-out terminal to form a metal lead point 2 in the window, that is, a lead-out terminal PAD point. The metal lead point 2 is connected to a metal lead by bonding. The other end of the metal lead is connected to an external power supply. A voltage is input through the external power supply, so that the brake zone 3 vibrates.

[0020] In some embodiments, when the heating resistor layer 302 is made of a bondable material, the metal lead point 2 can be formed together with the heating resistor layer 302 .

[0021] The low expansion layer 303 is used together with the high expansion layer 301 to form displacement. A thick SiO2 layer can be selected for this layer. In addition to producing a braking effect, the low expansion layer 303 is also used as a surface passivation layer to isolate the external environment from the heating resistor layer 302 and prevent the heating resistor layer 302 from oxidation or other contamination.

[0022] Each layer is deposited and etched in sequence from bottom to top, thereby forming a braking area 3. One side of the braking area 3 extends to the outside and connects to the thin film reflector 4. The thin film reflector 4 includes two film layers, such as Figure 3 As shown, located at the bottom is the reflector base film layer 401, whose material is usually Si3N4 or SiO2, and the film thickness is several microns. Located at the top is the reflective layer 402, which is formed by immersing high-reflectivity metal on the reflector base film layer 401, and its material is usually aluminum or gold, and the thickness is tens of nanometers.

[0023] A silicon-based microporous frame 5 is provided below the thin film reflector 4 to prevent the thin film reflector from bending or deforming. Figure 4 As shown, the silicon-based microporous frame 5 surrounds the edge of the lower surface of the thin film reflector 4, and a microporous array 501 is arranged inside it. The purpose of setting the microporous array 501 is to minimize the side effects caused by gravity without affecting the stability of the frame structure, thereby improving the working performance of the thin film reflector 4.

[0024] The micropore array 501 is composed of a plurality of micropores of the same size and shape. Figure 4 , Figure 5 As shown, it can be a circular hole or an elliptical hole, but it is not limited thereto. Other shapes that can further increase the empty slot area in the silicon-based microporous frame 5 and reduce the weight of the frame structure should be acceptable. Example 2

[0025] On the basis of Example 1, the braking area also includes two isolation layers 305, which are made of SiO2 or Si3N4. The isolation layers 305 are respectively arranged between the substrate 1 and the high expansion layer 301, and between the high expansion layer 301 and the heating resistor layer 302. Among them, the isolation layer 305 located between the substrate 1 and the high expansion layer 301 is used to isolate the braking area 3 from the substrate 1 and match the braking area stress, and the isolation layer 305 located between the high expansion layer 301 and the heating resistor layer 302 is used to isolate the high expansion layer 301 and the heating resistor layer 302 to prevent leakage.

[0026] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A large-size MEMS thin film reflector, characterized in that: It includes a substrate, a braking area is provided on the substrate, one side of the braking area extends to the outside and is connected to a thin film reflector, a silicon-based microporous frame is provided under the thin film reflector, the silicon-based microporous frame is used to prevent the thin film reflector from bending or deformation, and metal lead points are provided at both ends of the braking area, and the metal lead points are connected to an external power supply through metal leads.

2. The large-size MEMS thin film reflector according to claim 1, characterized in that: The braking zone includes a high expansion layer, a heating resistor layer and a low expansion layer from bottom to top. The high expansion layer is used to provide expansion braking stress and improve the mechanical strength of the braking zone. The low expansion layer is used to provide expansion braking stress matching the high expansion layer. The heating resistor layer is used to generate heat through resistance under the action of an external voltage to heat the high expansion layer and the low expansion layer, so that the high expansion layer and the low expansion layer expand and produce longitudinal displacement.

3. The large-size MEMS thin film reflector according to claim 2, characterized in that: It also includes two isolation layers, the material of which is SiO2 or Si3N4. The isolation layers are respectively arranged between the substrate and the high expansion layer, and between the high expansion layer and the heating resistor layer. The isolation layer located between the substrate and the high expansion layer is used to isolate the braking area from the substrate and match the stress of the braking area. The isolation layer located between the high expansion layer and the heating resistor layer is used to isolate the high expansion layer and the heating resistor layer to prevent leakage.

4. The large-size MEMS thin film reflector according to claim 2, characterized in that: The material of the high expansion layer is a material with a high thermal expansion coefficient, and the material of the low expansion layer is SiO2.

5. The large-size MEMS thin film reflector according to claim 2, characterized in that: A resistance pattern is provided in the heating resistance layer, and the resistance pattern is formed by etching.

6. The large-size MEMS thin film reflector according to claim 2, characterized in that: Windows are provided at both ends of the low expansion layer, and lead-out terminals are provided below the windows corresponding to the heating resistor layer. Metal lead points are formed in the windows on the lead-out terminals by depositing metal, and the metal lead points are used for bonding metal leads.

7. The large-size MEMS thin film reflector according to claim 1, characterized in that: The thin film reflector includes a reflector base film layer and a reflective layer from bottom to top. The reflector base film layer is made of SiO2 or Si3N4. The reflective layer is formed on the thin film reflector by metal deposition, and its material is aluminum or gold.

8. The large-size MEMS thin film reflector according to claim 7, characterized in that: The thickness of the reflector base film layer is 1-5 micrometers, and the thickness of the reflective layer is 50-100 nanometers.

9. The large-size MEMS thin film reflector according to claim 1, characterized in that: The silicon-based micropore frame surrounds the edge of the lower surface of the thin film reflector, and a micropore array is arranged inside the silicon-based micropore frame. The micropore array consists of a plurality of micropores of the same size and shape.

10. The large-size MEMS thin film reflector according to claim 1, characterized in that: The silicon-based microporous frame and the substrate have the same thickness, and the thickness ranges from 350 to 450 microns.

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