Manufacturing method of electrostatic flat plate driving micromirror

Abstract

The invention discloses a manufacturing method of an electrostatic flat plate driving micromirror, and relates to the technical field of driving micromirrors, and the method comprises the steps: 1, manufacturing a substrate with a bottom driving electrode on one surface; manufacturing a wafer of which one surface is provided with a cavity structure; step 2, bonding the surface, with the cavity structure, of the wafer with the surface, with the bottom driving electrode, of the substrate; 3, manufacturing a mirror reflection layer and a ground electrode bonding pad on the surface, far away from the substrate, of the wafer; 4, the wafer is etched, residual materials form a mirror plate, an outer frame assembly, a torsion beam and a heat conduction beam, the mirror plate is located in the outer frame assembly, and the mirror plate and the outer frame assembly are connected through the torsion beam and the heat conduction beam; and step 5, removing the heat conduction beam. According to the manufacturing method of the electrostatic flat plate driving micromirror, when a large amount of wafer materials are etched, heat on the mirror plate and the movable frame can be transferred out through the reserved heat conduction beams, then normal operation of the etching process is guaranteed, and the yield can be remarkably increased.

Description

Technical Field

[0001] The invention relates to the technical field of driving micromirrors, and in particular to a method for manufacturing an electrostatic flat-plate driven micromirror. Background Art

[0002] MEMS (Microelectromechanical System) micromirrors are manufactured using micro-nano technology, integrating mirror plates and actuators. They have the advantages of small size, fast response, high scanning frequency and large scanning angle, and are widely used in medical endoscopic imaging, barcode recognition, fingerprint recognition, optical attenuators, lidar, micro-projection and space optical communications. According to the driving mode, MEMS micromirrors can be divided into electrostatic, electromagnetic, piezoelectric and electrothermal micromirrors, and different driving modes are suitable for different application scenarios. Among them, the electrostatic flat-plate driven micromirror does not require complex electrical isolation, has a simple structure, and the driving electrode is located at the bottom of the mirror plate, with high space utilization and a high duty cycle.

[0003] At present, the main processing technologies of electrostatic flat-plate driven micromirrors include sacrificial layer process, microassembly process and bonding process. The bonding process bonds the wafer with cavity to the bottom electrode substrate, and then etches the micromirror structure. It has the advantages of high alignment accuracy and easy mass production. However, since the bottom of the etched area is a cavity, its thermal conductivity is poor, which can easily cause the torsion beam to break during the etching process. Therefore, in order to realize the bonding process of electrostatic flat-plate micromirrors, it is necessary to solve the problem of thermal conductivity of the micromirror structure during the etching process. Summary of the invention

[0004] The purpose of the present invention is to provide a method for manufacturing an electrostatic flat-plate driven micromirror to solve the problems existing in the above-mentioned prior art and improve the yield rate.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides a method for manufacturing an electrostatic flat-plate driven micromirror, comprising:

[0007] Step 1: fabricate a substrate with a bottom driving electrode on one side; fabricate a wafer with a cavity structure on one side;

[0008] Step 2: bonding the side of the wafer with the cavity structure to the side of the substrate with the bottom driving electrode;

[0009] Step 3: manufacturing a mirror reflection layer and a ground electrode pad on the surface of the wafer away from the substrate;

[0010] Step 4, etching the wafer and making the remaining material constitute a mirror plate, an outer frame assembly, a torsion beam and a thermal beam, wherein the mirror plate is located in the outer frame assembly, and the mirror plate and the outer frame assembly are connected through the torsion beam and the thermal beam;

[0011] Step 5: removing the thermal beam.

[0012] Preferably, in step four, the outer frame assembly includes a movable frame and a fixed frame, the movable frame is arranged in the fixed frame, the mirror plate is arranged in the movable frame, the movable frame and the fixed frame are connected through the torsion beam and the thermally conductive beam, and the mirror plate and the movable frame are connected through the torsion beam and the thermally conductive beam.

[0013] Preferably, the movable frame and the fixed frame are connected via two outer torsion beams and a plurality of the heat-conducting beams, and the mirror plate and the movable frame are connected via two inner torsion beams and a plurality of the heat-conducting beams; the two outer torsion beams both extend along a first straight line, the two inner torsion beams both extend along a second straight line, and the first straight line and the second straight line intersect perpendicularly.

[0014] Preferably, the wafer is a silicon wafer or a SOI wafer.

[0015] Preferably, a plurality of the heat-conducting beams are arranged between any two adjacent torsion beams.

[0016] Preferably, the thermally conductive beam is a rectangular structure or a structure with large ends and a small middle.

[0017] Preferably, a width w1 of the heat-conducting beam between the movable frame and the fixed frame is smaller than a width w2 of the heat-conducting beam between the mirror plate and the movable frame, and the ratio w1:w2 is between 4:5 and 1:2.

[0018] Preferably, the mirror plate, the movable frame and the fixed frame are nested in sequence from the inside to the outside, and grooves are provided on the outer annular surface of the mirror plate, the inner annular surface of the fixed frame, and the inner and outer annular surfaces of the movable frame, and both ends of the thermal conductive beam are respectively embedded in two of the grooves, the distance between the mirror plate and the movable frame and the distance between the movable frame and the fixed frame are m, the height of the groove is n, and m:n is between 1:4 and 2:3.

[0019] Preferably, in the step 1, metal is deposited on the glass substrate and then peeled off to form a bottom driving electrode.

[0020] Preferably, in step five, the thermally conductive beam is removed by isotropic etching.

[0021] Compared with the prior art, the present invention has achieved the following technical effects:

[0022] The manufacturing method of the electrostatic flat-plate driven micromirror provided by the present invention can transfer the heat on the mirror plate and the movable frame through the reserved heat-conducting beam when etching a large amount of wafer materials, thereby ensuring the normal operation of the etching process and significantly improving the yield rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A top view of a semi-finished product obtained in step 4 of the method for manufacturing an electrostatic flat-plate driven micromirror provided in an embodiment of the present invention;

[0025] Figure 2 It is a schematic diagram of the structure of three settings of the torsion beam;

[0026] Figure 3 When the wafer is a silicon wafer, a flow chart of manufacturing an electrostatic flat-plate driven micromirror by using the manufacturing method of the electrostatic flat-plate driven micromirror provided by an embodiment of the present invention;

[0027] Figure 4 When the wafer is an SOI wafer, a flow chart of manufacturing an electrostatic flat-plate driven micromirror by using the manufacturing method of the electrostatic flat-plate driven micromirror provided by an embodiment of the present invention;

[0028] In the figure: 101-fixed frame; 102-movable frame; 103-mirror plate; 104-external torsion beam; 105-internal torsion beam; 106-torsion beam; 107-thermal beam; 108-external thermal beam; 109-internal thermal beam; 201-groove; 301-silicon wafer; 302-substrate; 303-driving electrode; 304-electrode pad; 305-photoresist; 307-micromirror structure; 308-device layer; 309-buried oxide layer; 310-substrate layer. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] The present invention provides a method for manufacturing an electrostatic flat-plate driven micromirror, such as Figure 1 , Figure 3 and Figure 4 As shown, including:

[0032] Step 1: Prepare a substrate 302 with a bottom driving electrode 303 on one side, preferably depositing metal on a glass substrate 302 and peeling off to form the bottom driving electrode 303; prepare a wafer with a cavity structure on one side;

[0033] Step 2: Bonding the side of the wafer with the cavity structure to the side of the substrate 302 with the bottom driving electrode 303;

[0034] Step 3: manufacturing a mirror reflection layer and a ground electrode pad 304 on the surface of the wafer away from the substrate 302;

[0035] Step 4: Etch the wafer and make the remaining material form the mirror plate 103, the outer frame assembly, the torsion beam 106 and the thermal beam 107, the mirror plate 103 is located in the outer frame assembly, and the mirror plate 103 and the outer frame assembly are connected by the torsion beam 106 and the thermal beam 107;

[0036] Step 5: Remove the thermal beam 107. Specifically, the thermal beam 107 may be removed by isotropic etching and the photoresist 305 on the wafer may be removed by dry etching.

[0037] The electrostatic flat-plate driven micromirror manufacturing method provided by the present invention can transfer the heat on the mirror plate 103 and the movable frame 102 through the reserved heat-conducting beam 107 when etching a large amount of wafer material (in step four), thereby ensuring the normal operation of the etching process and significantly improving the yield rate.

[0038] Note that the wafer can be a polygon such as a circle or a square.

[0039] In some embodiments, in step four, the outer frame assembly includes a movable frame 102 and a fixed frame 101, the movable frame 102 is arranged in the fixed frame 101, the mirror plate 103 is arranged in the movable frame 102, the movable frame 102 and the fixed frame 101 are connected by an inner torsion beam 105 and an internal heat-conducting beam 109, and the mirror plate 103 and the movable frame 102 are connected by an outer torsion beam 104 and an external heat-conducting beam 108.

[0040] In some embodiments, the width w1 of the outer heat-conducting beam 108 is smaller than the width w2 of the inner heat-conducting beam 109, and the ratio w1:w2 is between 4:5 and 1:2. This is to prevent the inner heat-conducting beam 109 from breaking before the outer heat-conducting beam 108 during the heat-conducting beam release process, so that the heat on the mirror plate 103 cannot be transferred away, causing chip failure.

[0041] In the solution provided in this embodiment, the obtained product includes a movable frame 102 and a fixed frame 101. The movable frame 102 and the fixed frame 101 in the final product are connected only by an external torsion beam 104, and the movable frame 102 and the mirror plate 103 are also connected only by an internal torsion beam 105, so that the mirror plate 103 can rotate in the X-axis and Y-axis directions.

[0042] It is understandable that in other embodiments, the movable frame 102 may not be provided, and the mirror plate 103 may be directly connected to the fixed frame 101 through the torsion beam 106, or multiple movable frames 102 may be nested in sequence, which is not limited in the present invention.

[0043] like Figure 3 and Figure 4 The micro-mirror structure 307 shown in the figure may be a single mirror plate 103 , may include one movable frame 102 and mirror plate 103 , or may include multiple movable frames 102 and mirror plates 103 .

[0044] In some embodiments, the movable frame 102 and the fixed frame 101 are connected by two outer torsion beams 104 and a plurality of outer heat-conducting beams 108, and the mirror plate 103 and the movable frame 102 are connected by two inner torsion beams 105 and a plurality of inner heat-conducting beams 109; the two outer torsion beams 104 both extend along a first straight line, the two inner torsion beams 105 both extend along a second straight line, and the first straight line and the second straight line intersect vertically.

[0045] In some embodiments, the wafer is a silicon wafer 301 or a SOI wafer.

[0046] The SOI wafer in this embodiment includes a device layer 308, a buried oxide layer 309 and a substrate layer 310, wherein the substrate layer 310 is made of low-resistance silicon with a resistivity lower than 0.1Ω·cm. In step 4, the SOI wafer substrate layer 310 is etched to the cavity to form a fixed frame 101, a movable frame 102, a mirror plate 103, a torsion beam 106 and a heat-conducting beam 107.

[0047] In some embodiments, a plurality of heat-conducting beams 107 are disposed between any two adjacent torsion beams 106 .

[0048] The plurality of heat-conducting beams 107 in this embodiment are preferably evenly arranged, so that the heat on the mirror plate 103 and / or the movable frame 102 can be evenly dissipated.

[0049] In some embodiments, such as Figure 2 As shown, the heat conducting beam 107 is a rectangular parallelepiped structure or a structure with large ends and a small middle.

[0050] In some embodiments, Figure 2 As shown, the mirror plate 103, the movable frame 102 and the fixed frame 101 are nested from the inside to the outside, and grooves 201 are provided on the outer annular surface of the mirror plate 103, the inner annular surface of the fixed frame 101, and the inner and outer annular surfaces of the movable frame 102. The two ends of the heat-conducting beam 107 are respectively embedded in the two grooves 201. The distance between the mirror plate 103 and the movable frame 102 and the distance between the movable frame 102 and the fixed frame 101 are m, and the height of the groove 201 is n, and m:n is between 1:4 and 2:3. In order to facilitate the rapid removal of the heat-conducting beam in the subsequent release process.

[0051] In order to further illustrate the scheme of the present application, the following examples are provided.

[0052] Embodiment 1, as Figure 3 shown.

[0053] Step (a): preparing a silicon wafer 301;

[0054] Step (b): etching the back side of the silicon wafer 301 to form a cavity structure;

[0055] Step (c): bonding the side of the silicon wafer 301 with the cavity structure to the side of the glass substrate 302 with the driving electrode 303 to form a bonding sheet;

[0056] Step (d): depositing metal on one side of the silicon wafer 301 of the bonding sheet and peeling off to form a mirror reflection layer and a ground electrode pad 304;

[0057] Step (e): Spin-coating a photoresist 305 on one side of the silicon wafer 301 of the bonding sheet and patterning it;

[0058] Step (f): etching one side of the silicon wafer 301 of the bonding sheet to the cavity to form a heat-conducting beam 107 and a micromirror structure 307, wherein the micromirror structure includes a fixed frame 101, a movable frame 102, a mirror plate 103, and a torsion beam 106;

[0059] Step (g): removing the thermal beam 107 by isotropic etching;

[0060] Step (h): removing the photoresist on the surface of the bonding wafer by dry etching to complete chip processing.

[0061] Embodiment 2, as Figure 4 shown.

[0062] Step (a): preparing a SOI wafer consisting of a device layer 308, a buried oxide layer 309 and a substrate layer 310, wherein the substrate layer 310 is made of low-resistance silicon with a resistivity lower than 0.1Ω·cm;

[0063] Step (b): etching the SOI wafer device layer 308 to form a cavity structure, and removing the exposed buried oxide layer 309 by using a BOE solution;

[0064] Step (c): bonding the SOI wafer device layer 308 to the side of the glass substrate 302 having the driving electrode 303 to form a bonding wafer;

[0065] Step (d): depositing metal on the SOI wafer substrate layer 310 and peeling off to form a mirror reflection layer and a ground electrode pad 304;

[0066] Step (e): Spin-coating photoresist 305 on the SOI wafer substrate layer 310 and patterning it;

[0067] Step (f): etching the SOI wafer substrate layer 310 to the cavity to form a heat-conducting beam 107 and a micromirror structure 307 , wherein the micromirror structure includes a fixed frame 101 , a movable frame 102 , a mirror plate 103 , and a torsion beam 106 ;

[0068] Step (g): removing the thermal beam 107 by isotropic etching;

[0069] Step (h): removing the photoresist on the surface of the SOI wafer substrate layer 310 by dry etching to complete chip processing.

[0070] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for manufacturing an electrostatic plate-driven micromirror, characterized in that: include: Step 1: fabricate a substrate with a bottom driving electrode on one side; fabricate a wafer with a cavity structure on one side; Step 2: bonding the side of the wafer with the cavity structure to the side of the substrate with the bottom driving electrode; Step 3: manufacturing a mirror reflection layer and a ground electrode pad on the surface of the wafer away from the substrate; Step 4, etching the wafer and making the remaining material constitute a mirror plate, an outer frame assembly, a torsion beam and a thermal beam, wherein the mirror plate is located in the outer frame assembly, and the mirror plate and the outer frame assembly are connected through the torsion beam and the thermal beam; Step 5: removing the thermal beam.

2. The method for manufacturing an electrostatic plate driven micromirror according to claim 1, characterized in that: In the step four, the outer frame assembly includes a movable frame and a fixed frame, the movable frame is arranged in the fixed frame, the mirror plate is arranged in the movable frame, the movable frame and the fixed frame are connected through the torsion beam and the thermally conductive beam, and the mirror plate and the movable frame are connected through the torsion beam and the thermally conductive beam.

3. The method for manufacturing an electrostatic plate driven micromirror according to claim 2, characterized in that: The movable frame and the fixed frame are connected by two outer torsion beams and a plurality of the heat-conducting beams, and the mirror plate and the movable frame are connected by two inner torsion beams and a plurality of the heat-conducting beams; the two outer torsion beams both extend along a first straight line, and the two inner torsion beams both extend along a second straight line, and the first straight line and the second straight line intersect vertically.

4. The method for manufacturing an electrostatic plate driven micromirror according to claim 1, characterized in that: The wafer is a silicon wafer or a SOI wafer.

5. The method for manufacturing an electrostatic plate driven micromirror according to claim 3, characterized in that: A plurality of the heat-conducting beams are arranged between any two adjacent torsion beams.

6. The method for manufacturing an electrostatic plate driven micromirror according to claim 1, characterized in that: The heat-conducting beam is a rectangular parallelepiped structure or a structure with large ends and a small middle.

7. The method for manufacturing an electrostatic plate driven micromirror according to claim 2, characterized in that: The mirror plate, the movable frame and the fixed frame are nested in sequence from the inside to the outside, and grooves are provided on the outer annular surface of the mirror plate, the inner annular surface of the fixed frame, and the inner and outer annular surfaces of the movable frame. Both ends of the thermal conductive beam are respectively embedded in two of the grooves. The distance between the mirror plate and the movable frame and the distance between the movable frame and the fixed frame are m, the height of the groove is n, and m:n is between 1:4 and 2:

3.

8. The method for manufacturing an electrostatic plate driven micromirror according to claim 7, characterized in that: The thickness w1 of the heat-conducting beam between the fixed frame and the movable frame is smaller than the thickness w2 of the heat-conducting beam between the mirror plate and the movable frame, and the ratio of w1:w2 is between 4:5 and 1:

2.

9. The method for manufacturing an electrostatic plate driven micromirror according to claim 1, characterized in that: In the step 1, metal is deposited on a glass substrate and then peeled off to form a bottom driving electrode.

10. The method for manufacturing an electrostatic plate driven micromirror according to claim 1, characterized in that: In the step five, the thermal beam is removed by isotropic etching.

Images