Unequal height vertical comb teeth device and preparation method thereof

Abstract

The unequal height vertical comb tooth device of the present invention comprises an outer frame, a first torsion structure, a second torsion structure and a comb tooth structure, wherein the second torsion structure is arranged between the first torsion structure and the comb tooth structure, the first torsion structure and the second torsion structure are movably arranged on the outer frame, one side of the first torsion structure is fixedly connected to the outer frame, and the other side is connected to the second torsion structure through a limiting structure, and one side of the second torsion structure is provided with a comb tooth portion corresponding to the comb tooth structure, and there is a height difference between the comb tooth portion and the comb tooth structure. The unequal height vertical comb tooth device realizes an unequal height vertical comb tooth structure through a special comb tooth structure, a stop pin structure and a torsion structure under the action of an external force, and has the characteristics of simple and stable structure, and its preparation method does not require complex processes such as high-precision alignment of upper and lower comb teeth and high-precision double-sided alignment lithography, and has low requirements on processes and equipment, low preparation cost, high process stability and easy production and manufacturing.

Description

Technical Field

[0001] The invention relates to a unequal height vertical comb tooth device and a preparation method thereof, belonging to the field of micro-electromechanical devices. Background Art

[0002] In the MEMS unequal height vertical comb teeth structure, the unequal height vertical comb teeth have the advantages of low driving voltage, large driving displacement, off-plane displacement, fast response speed and high frequency. They are often used in MEMS devices such as MEMS electrostatic micro-scanning mirrors, MEMS electrostatic micro-actuators, and MEMS capacitive inertial sensors, especially MEMS micro-scanning mirrors.

[0003] However, there are many types of existing manufacturing methods, but they are all relatively complex. They usually require one or several MEMS process technologies such as polysilicon thin film deposition, high-precision double-sided alignment, silicon-silicon bonding, spraying, composite mask etching or composite thin film, which makes its products difficult to process and has low process maturity.

[0004] In 2010, Hoang Manh Chu et al. reported a method for manufacturing a micro-scanning mirror with unequal vertical comb teeth in the paper “Compact Low-Voltage Operation Micromirror Based on High-Vacuum Seal Technology Using Metal Can”. Using SOI wafers, the top silicon is etched by front lithography to form the top vertical comb teeth connected to the torsion structure, and the bottom silicon is etched by double-sided alignment lithography to form the back cavity and the lower comb teeth structure. Finally, the middle oxide layer is released to form a micro-scanning mirror with unequal vertical comb teeth. This method realizes the upper and lower comb teeth through double-sided lithography and etching processes. The precise relative position between the upper and lower comb teeth requires very high precision of the double-sided alignment lithography machine. The etching of the lower comb tooth structure also has stringent requirements on the process capability of the deep silicon etching machine. It is difficult to achieve in terms of process technology, which also limits the manufacturing of higher performance high aspect ratio comb tooth structures.

[0005] Chinese patent CN103086316B "Method for making a MEMS vertical comb-tooth micro-mirror driver" discloses a method for making a vertical comb-tooth structure of unequal heights by a double-layer mask and silicon-silicon bonding process. It includes: providing an SOI silicon structure with a double-layer silicon device layer; making a first scribe pattern on the surface of the first substrate layer; removing the second substrate layer; making a double-layer mask on the second buried oxide layer; using the double-layer mask to make a high comb-tooth structure, a low comb-tooth structure and a micro-mirror structure; silicon-silicon bonding the double-polished silicon wafer to the SOI silicon structure; making a second scribe pattern on the surface of the double-polished silicon wafer; removing the first substrate layer and exposing the first buried oxide layer; using the first buried oxide layer as a mask, etching the first silicon device layer to release the movable comb-tooth structure, the movable micro-mirror structure and the fixed comb-tooth structure; removing the first buried oxide layer; forming a thin film metal layer in the micro-mirror area and the lead area. This method solves the problem of high-precision alignment of the upper and lower comb teeth through the double-layer mask technology, but introduces silicon-silicon bonding and thinning processes. The process is relatively complex, difficult to implement and costly.

[0006] Chinese patent CN104370272B discloses "a MEMS self-aligned high and low comb teeth and its manufacturing method", which introduces a special lifting mechanism and a comb tooth pair formed in sequence on the mechanical structure layer; the special lifting structure uses the stress between different materials to lift the folded cantilever beam, thereby generating a height difference between the comb tooth pairs. This method uses the stress between different materials on the cantilever beam to lift the cantilever beam, thereby driving the lifting of the comb tooth structure connected to the cantilever beam to form upper and lower comb tooth pairs of unequal heights. The process flow is relatively simple, and it also avoids the problem of high-precision alignment between comb teeth of unequal heights, but the stress between different materials of the cantilever beam is not easy to control, and the structure is unstable, and will change with environmental changes such as temperature and humidity.

[0007] Based on the above situation, the present invention is proposed. Summary of the invention

[0008] The purpose of the present invention is to provide a device with unequal height vertical comb teeth and a method for preparing the same. The unequal height vertical comb teeth device has the characteristics of simple and stable structure, and the preparation method has low requirements on process and equipment, low preparation cost, high process stability and easy production and manufacturing.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solutions: a vertical comb tooth device of unequal heights, comprising an outer frame, a first torsion structure, a second torsion structure and a comb tooth structure, wherein the second torsion structure is arranged between the first torsion structure and the comb tooth structure, the first torsion structure and the second torsion structure are movably arranged on the outer frame, one side of the first torsion structure is fixedly connected to the outer frame, and the other side is connected to the second torsion structure through a limiting structure, one side of the second torsion structure is provided with a comb tooth portion corresponding to the comb tooth structure, and there is a height difference between the comb tooth portion and the comb tooth structure.

[0010] Furthermore, the unequal height vertical comb teeth device further includes a first torsion beam and a second torsion beam, wherein the first torsion beam connects the first torsion structure and the outer frame, and the second torsion beam connects the second torsion structure and the outer frame.

[0011] Further, the limiting structure is a stop pin structure, which includes a first stop pin structure arranged on the first torsion structure and a second stop pin structure arranged on the second torsion structure, the first stop pin structure includes a first gear pin and a first plug pin, and the second stop pin structure includes a second gear pin corresponding to the first gear pin and a second gear pin corresponding to the first plug pin.

[0012] Furthermore, the first torsion structure includes a first pressing plate, the first pressing plate is arranged in the middle of the first torsion structure, and the first stop pin structure is arranged on both sides of the first pressing plate.

[0013] Furthermore, the second torsion structure includes a second pressing plate, the second pressing plate is arranged in the middle of the second torsion structure, and the second stop pin structure is arranged on both sides of the second pressing plate.

[0014] Furthermore, the second torsion beam is arranged between the second stop pin structure and the comb teeth portion to facilitate the torsion of the device.

[0015] Furthermore, the comb tooth structure includes first comb teeth and a comb tooth frame, the first comb teeth are arranged on the comb tooth frame, the comb tooth portion includes second comb teeth, and there is a height difference between the first comb teeth and the second comb teeth.

[0016] In order to achieve the above object, the present invention also provides a method for preparing the unequal height vertical comb teeth device, comprising the following steps:

[0017] S1, cleaning and pre-treating the SOI silicon wafer;

[0018] S2, applying photoresist on the top silicon layer of the SOI silicon wafer and performing photolithography to obtain a comb-tooth structure layer by etching;

[0019] S3, coating the base layer of the SOI silicon wafer with photoresist and performing photolithography to etch out a back cavity, and finally corroding the oxide layer and releasing the top silicon layer to prepare a vertical comb-tooth device;

[0020] S4, applying an external force to the pressing plate on the vertical comb-tooth device to obtain the vertical comb-tooth device with unequal heights.

[0021] Furthermore, in step S3, during the photolithography process, etching is performed to the oxide layer so that the back cavity exposes the oxide layer, thereby facilitating subsequent removal of the oxide layer.

[0022] The beneficial effect of the present invention is that the unequal height vertical comb teeth device of the present invention realizes the unequal height vertical comb teeth structure under the action of external force through the special comb teeth structure, the stop pin structure and the torsion structure. Therefore, the unequal height vertical comb teeth device has the characteristics of simple structure and stability, and its preparation method does not require the alignment process of the upper and lower comb teeth, the high-precision double-sided alignment lithography process, the silicon-silicon bonding process, and the thinning process. At the same time, the deposition of the stress film is avoided. Therefore, the preparation method of the present invention has low requirements on the process and equipment, low preparation cost, high process stability, and easy production and manufacturing.

[0023] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic structural diagram of a vertical comb-tooth device of unequal heights shown in one embodiment of the present invention;

[0025] Figure 2 for Figure 1 A schematic diagram of a stop pin structure of a vertical comb-tooth device of unequal height is shown;

[0026] Figure 3 for Figure 1 The schematic diagram of the structure of the unequal height vertical comb teeth device when the unequal height vertical comb teeth are not formed;

[0027] Figure 4 A flowchart of a method for preparing a vertical comb-tooth device with unequal heights shown in the present invention;

[0028] Figure 5a to Figure 5d for Figure 4 Schematic diagram of the preparation method shown. DETAILED DESCRIPTION

[0029] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0030] See also Figures 1 to 3 The unequal height vertical comb-tooth device shown in an embodiment of the present invention comprises an outer frame 1, a first torsion structure 2, a second torsion structure 3 and a comb-tooth structure 4. The second torsion structure 3 is arranged between the first torsion structure 2 and the comb-tooth structure 4, and the first torsion structure 2 and the second torsion structure 3 are respectively movably arranged on the outer frame 1 through a first torsion beam 11 and a second torsion beam 12, and the comb-tooth structure 4 is connected to the movable structure of the second torsion structure 3. One side of the first torsion structure 2 is fixedly connected to the outer frame 1, and the other side is connected to the second torsion structure 3 through a limiting structure 5. One side of the second torsion structure 3 is provided with a comb-tooth portion 31 corresponding to the comb-tooth structure 4, and there is a height difference between the comb-tooth portion 31 and the comb-tooth structure 4.

[0031] In this embodiment, the limiting structure 5 is a stop pin structure. Of course, in other embodiments, the limiting structure 5 may also be other structures. The stop pin structure 5 includes a first stop pin structure 51 disposed on the first torsion structure 2 and a second stop pin structure 52 disposed on the second torsion structure 3. The first stop pin structure 51 includes a first stop pin 511 and a first latch pin 512. The second stop pin structure 52 includes a second latch pin 521 corresponding to the first stop pin 511 and a second stop pin 522 corresponding to the first latch pin 512. The second torsion beam 12 is disposed between the second stop pin structure 52 and the comb tooth portion 31 to facilitate the torsion of the device.

[0032] In this embodiment, the first torsion structure 2 includes a first pressing plate 21, which is disposed in the middle of the first torsion structure 2, and the first stop pin structures 51 are disposed on both sides of the first pressing plate 21. The second torsion structure 3 includes a second pressing plate 32, which is disposed in the middle of the second torsion structure 3, and the second stop pin structures 52 are disposed on both sides of the second pressing plate 32.

[0033] In this embodiment, the comb tooth structure 4 includes a first comb tooth 41 and a comb tooth frame 42, the first comb tooth 41 is arranged on the comb tooth frame 42, the comb tooth portion 31 includes a second comb tooth 311, and there is a height difference between the first comb tooth 41 and the second comb tooth 311. The two will make relative displacement under voltage drive, thereby causing the movable structure connected to the comb tooth structure 4 to produce torsion or off-plane displacement.

[0034] The structure shown in the present invention is planar before the comb teeth with height difference are formed. External force acts on the adjacent ends of the first pressing plate 21 and the second pressing plate 32 at the same time, so that both of them move in the direction of the force at the same time. When the first pressing plate 21 and the second pressing plate 32 move to a certain distance, the first gear pin 511 or the second gear pin 522 disengages from the second latch 521 or the first latch 512, and then the force is removed. At this time, the first torsion beam 11 and the second torsion beam 12 provide a restoring force, so that the first latch 512 or the second latch 521 stops on the second gear pin 522 or the first gear pin 511, causing the comb tooth portion 31 to tilt around the second torsion beam 12, thereby forming a height difference between the second comb tooth 311 and the first comb tooth 41.

[0035] See also Figure 4 and Figure 5a to Figure 5d The preparation of the unequal height vertical comb teeth device shown in the present invention comprises the following steps:

[0036] S1, cleaning and pre-treating the SOI silicon wafer;

[0037] S2, applying photoresist on the top silicon layer of the SOI silicon wafer and performing photolithography to obtain a comb-tooth structure layer by etching;

[0038] S3, applying photoresist to the base layer of the SOI silicon wafer and performing photolithography, etching to the oxide layer to form a back cavity, and finally etching the oxide layer to release the top silicon layer to prepare a vertical comb device;

[0039] S4, applying an external force to the pressing plate on the vertical comb-tooth device to obtain the vertical comb-tooth device with unequal heights.

[0040] In summary: the unequal height vertical comb teeth device of the present invention realizes the unequal height vertical comb teeth structure under the action of external force through the special comb teeth structure, stop pin structure and torsion structure. Therefore, the unequal height vertical comb teeth device does not need to meet multiple materials in structure, and has the characteristics of simplicity and stability. The preparation method thereof does not require the alignment process of the upper and lower comb teeth, the high-precision double-sided alignment lithography process, the silicon-silicon bonding process, and the thinning process. At the same time, the deposition of stress film is avoided. Therefore, the preparation method of the present invention does not have high requirements on the process and equipment, the preparation cost is low, and the process is mature, the stability is high, and it is easy to produce.

[0041] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0042] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A vertical comb tooth device with unequal heights, characterized in that: The invention comprises an outer frame, a first torsion structure, a second torsion structure and a comb-tooth structure, wherein the second torsion structure is arranged between the first torsion structure and the comb-tooth structure, the first torsion structure and the second torsion structure are movably arranged on the outer frame, one side of the first torsion structure is fixedly connected to the outer frame, and the other side is connected to the second torsion structure through a limiting structure, one side of the second torsion structure is provided with a comb-tooth portion corresponding to the comb-tooth structure, and there is a height difference between the comb-tooth portion and the comb-tooth structure; The unequal height vertical comb device further comprises a first torsion beam and a second torsion beam, wherein the first torsion beam connects the first torsion structure and the outer frame, and the second torsion beam connects the second torsion structure and the outer frame; The limiting structure is a stop pin structure, the stop pin structure includes a first stop pin structure arranged on the first torsion structure and a second stop pin structure arranged on the second torsion structure, the first stop pin structure includes a first gear pin and a first latch pin, the second stop pin structure includes a second latch pin corresponding to the first gear pin and a second gear pin corresponding to the first latch pin; The second torsion beam is disposed between the second stop pin structure and the comb teeth portion.

2. The unequal height vertical comb teeth device according to claim 1, characterized in that: The first torsion structure includes a first pressing plate, the first pressing plate is arranged in the middle of the first torsion structure, and the first stop pin structure is arranged on both sides of the first pressing plate.

3. The unequal height vertical comb teeth device according to claim 2, characterized in that: The second torsion structure includes a second pressing plate, the second pressing plate is arranged in the middle of the second torsion structure, and the second stop pin structure is arranged on both sides of the second pressing plate.

4. The unequal height vertical comb teeth device according to claim 1, characterized in that: The comb tooth structure includes first comb teeth and a comb tooth frame, the first comb teeth are arranged on the comb tooth frame, the comb tooth portion includes second comb teeth, and there is a height difference between the first comb teeth and the second comb teeth.

5. A method for preparing a vertical comb-tooth device of unequal height as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: S1, cleaning and pre-treating the SOI silicon wafer; S2, applying photoresist on the top silicon layer of the SOI silicon wafer and performing photolithography to obtain a comb-tooth structure layer by etching; S3, coating the base layer of the SOI silicon wafer with photoresist and performing photolithography to etch out a back cavity, and finally corroding the oxide layer and releasing the top silicon layer to prepare a vertical comb-tooth device; S4, applying an external force to the pressing plate on the vertical comb-tooth device to obtain the vertical comb-tooth device with unequal heights.

6. The preparation method according to claim 5, characterized in that: In step S3, during the photolithography process, etching is performed to the oxide layer so that the back cavity exposes the oxide layer.

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