MEMS device and method of manufacturing the same

Abstract

The application provides a MEMS device and a manufacturing method thereof, comprising the following steps: providing a substrate, the substrate comprising a mirror area and a comb area outside the mirror area; etching the substrate to form a plurality of grooves arranged at intervals in the mirror area and the comb area; forming a first mask layer to cover the sidewalls of the grooves, the surface of the substrate and seal the openings of the grooves; etching the first mask layer to expose part of the surface of the substrate and cover each area of the substrate for forming a first comb and the mirror area; forming an epitaxial layer on the surface of the substrate and the first mask layer; forming a mirror structure on the epitaxial layer; etching the epitaxial layer to form a support structure for supporting the mirror structure and a plurality of second combs outside the mirror structure; etching the substrate to form a plurality of first combs with the first mask layer as a mask, the plurality of first combs and the plurality of second combs being arranged alternately; and removing at least the first mask layer under the second combs and the support structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a MEMS device and a manufacturing method thereof. BACKGROUND

[0002] Some micro-electro-mechanical system (MEMS) devices, such as MEM mirror driving devices (for example, MEMS galvanometer), generally need to prepare upper and lower interleaved upper and lower combs. The MEM mirror driving device can deflect, modulate, open and close, and phase control the light beam under the driving action. The MEM mirror driving device has the characteristics of light weight, small size, easy mass production, low production cost, excellent optical, mechanical performance and power consumption, and is widely used in projection, display, optical communication, laser radar and other scenes.

[0003] In the related art, two SOI wafers are generally used to prepare the device, which has a high cost, and the stress regulation of the thin film structure is complex, the process is complex, the bonding process is used multiple times, the bonding cavity affects the yield, increases the probability of abnormality in the process, and a large cavity is often introduced, and there are many weak structures.

[0004] Therefore, it is necessary to provide a new MEMS device and a manufacturing method thereof to at least partially solve the above problems. SUMMARY

[0005] A series of simplified concepts are introduced in the summary section, which will be further described in detail in the detailed description section. The summary section of the present application does not mean to attempt to limit the key features and necessary technical features of the claimed technical solution, nor to determine the protection scope of the claimed technical solution.

[0006] In view of the existing problems, the present application provides a manufacturing method of a MEMS device, comprising the following steps:

[0007] A substrate is provided, which includes a mirror area and a comb area located outside the mirror area;

[0008] The substrate is etched to form a plurality of grooves arranged at intervals in the mirror area and the comb area;

[0009] A first mask layer is formed to cover the sidewalls of the grooves, the surface of the substrate and seal the openings of the grooves;

[0010] The first mask layer is etched to expose part of the surface of the substrate and cover each area of the substrate for forming the first comb and the mirror area;

[0011] An epitaxial layer is formed on the surface of the substrate and the first mask layer;

[0012] forming a mirror structure on the epitaxial layer, the mirror structure corresponding to the mirror region;

[0013] etching the epitaxial layer to form a support structure for supporting the mirror structure and a plurality of second combs outside the mirror structure, wherein each of the second combs corresponds to one of the trenches in the comb region, and the plurality of second combs are outside the support structure;

[0014] using the first mask layer as a mask, etching the substrate to form a plurality of first combs, the plurality of first combs and the plurality of second combs being arranged alternately;

[0015] removing at least the first mask layer under the second combs and the support structure.

[0016] In one example, the first mask layer in the trench further forms a filling cavity, wherein the top of the filling cavity is below the surface of the substrate.

[0017] In one example, the first mask layer is formed to cover the sidewalls of the trenches, the surface of the substrate, and seal the openings of the trenches, comprising:

[0018] forming a first mask material layer on the sidewalls of the trenches and the surface of the substrate, wherein the thickness of the first mask layer on the top sidewalls of the trenches is greater than the thickness of the first mask material layer on the bottom sidewalls of the trenches;

[0019] etching to remove part of the first mask material layer, so that the smallest opening of the trench is below the surface of the substrate;

[0020] forming a second mask material layer on the first mask material layer, and the second mask material layer seals the openings of the trenches;

[0021] forming a third mask material layer on the second mask material layer, and performing planarization to form the first mask layer, wherein the compactness of the third mask material layer is higher than that of the second mask material layer.

[0022] In one example, before etching the epitaxial layer to form the plurality of second combs outside the mirror structure, after forming the epitaxial layer, the manufacturing method further comprises:

[0023] thinning the side of the substrate away from the epitaxial layer.

[0024] In one example, after forming the first combs and the second combs, before removing the first mask layer, the manufacturing method further comprises:

[0025] wet cleaning to remove etching residues formed during etching the epitaxial layer and etching the substrate, wherein during the cleaning process, the first mask layer supports the second combs, and the first mask layer of the mirror region supports the support structure.

[0026] In one example, the method of forming a substrate includes: providing a substrate, forming an insulating layer on the surface of the substrate, and epitaxially growing a device layer on the insulating layer, the device layer being used to form the first comb teeth.

[0027] In one example, the manufacturing method further includes, prior to forming the trench:

[0028] At least two spaced isolation trenches are formed in the device layer;

[0029] The substrate is etched to form multiple trenches spaced apart in the mirror region and the comb region, including:

[0030] The device layer is etched to form a plurality of spaced trenches in the mirror area and the comb area, while the isolation trenches are etched so that the bottom of the isolation trenches extends to the insulating layer.

[0031] In one example, the thickness of the first mask layer on the surface of the substrate is less than 1.5 μm; and / or

[0032] The trench has a depth-to-width ratio greater than or equal to 3 and less than or equal to 60.

[0033] This application also provides a MEMS device, the MEMS device comprising:

[0034] The substrate includes a mirror region and a comb region located outside the mirror region;

[0035] Multiple first comb teeth are spaced apart in the comb tooth area;

[0036] Multiple grooves are spaced apart in the mirror area;

[0037] An epitaxial layer is disposed on a substrate. The epitaxial layer includes a plurality of spaced second comb teeth and a support structure. The plurality of second comb teeth are located outside the support structure, and the plurality of second comb teeth and the plurality of first comb teeth are staggered.

[0038] A mirror structure is set on the supporting structure, with the mirror structure and the mirror area facing each other.

[0039] In one example, the substrate includes a base layer, a device layer, and an insulating layer disposed between the base layer and the device layer. At least two spaced-apart isolation trenches are formed in the substrate, and a plurality of first comb teeth are disposed between adjacent isolation trenches. The isolation trenches extend through the device layer into the insulating layer.

[0040] According to the MEMS device and the manufacturing method thereof provided in the present application, the epitaxial layer is formed on the surface of the substrate and the first mask layer, and the epitaxial layer is used to prepare the second comb teeth. Compared with the related art using the SOI wafer, the present application reduces the use of the SOI wafer, and thus has lower cost, reduces the difficulty of stress regulation, and shortens the adjustment period. The position of each second comb tooth corresponds to a groove, and the groove is filled with the first mask layer. After the first comb teeth and the second comb teeth are formed, the first mask layer under the second comb teeth can be used to support the second comb teeth, and the first hard mask layer under the support structure also supports the support structure, so that the stability of the structure is improved, and the stability of the subsequent process is higher. BRIEF DESCRIPTION OF DRAWINGS

[0041] The following drawings for the present application are hereby incorporated as a part of the present application for the purpose of understanding the present application. The embodiments of the present application and the description thereof shown in the drawings are used to explain the principles of the present application.

[0042] In the drawings:

[0043] Figures 1A-1J A cross-sectional schematic diagram of a device obtained by sequentially implementing a manufacturing method of a MEMS device in the related art is shown;

[0044] Figure 2 A schematic flowchart of a manufacturing method of a MEMS device in an embodiment of the present application is shown;

[0045] Figures 3A-3K A cross-sectional schematic diagram of a device obtained by sequentially implementing a manufacturing method of a MEMS device according to an embodiment of the present application is shown;

[0046] Figures 4A-4E A partial cross-sectional schematic diagram of a device obtained by sequentially implementing a manufacturing method of a first mask layer according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0047] In the following description, a large number of specific details are given to provide a more thorough understanding of the present application. However, it is obvious to those skilled in the art that the present application can be implemented without one or more of these details. In other examples, some technical features known in the art are not described in order not to obscure the present application.

[0048] It is to be understood that the application can assume various alternative embodiments, and that no limitation of the scope of the present application is intended by the description or illustration of the embodiments. Further, each of the embodiments can be used alone or in combination with one another. Regardless of the particular combination of embodiments, the application is intended to cover and embrace all suitable processes, systems, compositions, and articles of manufacture. In the drawings, the size and relative sizes of layers and regions can be exaggerated for clarity. Like reference numerals can represent like elements throughout the drawings.

[0049] It will be understood that when an element or layer is referred to as being "on" or "connected to" another element or layer, it can be directly on or connected to the other element or layer or intervening elements or layers can be present. In contrast, when an element is referred to as being "directly on" or "directly connected to" another element, there are no intervening elements or layers present. It will also be understood that, when a term is used in the singular, it can be intended to mean the singular or plural, unless the context clearly dictates otherwise.

[0050] Spatially relative terms, such as "beneath", "below", "lower", "under", "above", "upper" and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" or "over" the other elements or features. Thus, the exemplary term "below" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0051] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. When used herein, the singular forms “a,” “an,” and “ / the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “compose” and / or “comprising,” when used in this specification, identify the presence of features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0052] like Figures 1A-1J As shown, in related technologies, MEMS optoelectronic devices are fabricated using the following methods. First, as... Figure 1A As shown, an SOI wafer 100 is provided for forming the bottom comb structure;

[0053] Next, as Figure 1B As shown, a marker pattern 110 is formed in an SOI wafer 100 by photolithography and etching processes. Then, an oxide mask layer 120 is deposited to cover the surface of the SOI wafer 100 and fill the marker pattern 110. The oxide mask layer 120 is then etched to form a comb mask layer that defines the size and position of the first comb tooth.

[0054] Next, as Figure 1C As shown, a photoresist mask layer 140 is formed to cover the comb mask layer and the surface of the SOI wafer 100. Photolithography is performed on the photoresist mask layer 140 to define the position and size of the predetermined isolation trench, that is, to form an opening in the photoresist mask layer 140. The opening exposes the area of ​​the SOI wafer 100 to be etched to form the isolation trench. The SOI wafer 100 is etched to form the isolation trench 130.

[0055] Next, as Figure 1D As shown, the photoresist mask layer is removed, and the SOI wafer 100 is etched using the comb mask layer as a mask to form multiple bottom comb structures 150. The isolation trench 130 is then etched to connect with the buried oxide layer of the SOI wafer 100.

[0056] Next, as Figure 1E and Figure 1F As shown, the cap wafer 201 is etched to form a groove opposite to the bottom comb teeth, and a support layer located in the groove. The support layer covers the area of ​​the cap wafer 201 used to form the top comb teeth. The side of the cap wafer 201 with the support layer is bonded to the side of the SOI wafer 100 with the bottom comb tooth structure 150. The cap wafer 201 is also an SOI wafer.

[0057] Next, as Figure 1FAs shown, the side of the cap wafer 201 opposite to the bottom comb structure 150 is trimmed, mechanically polished, and fully etched to expose the buried oxide layer of the cap wafer 201, and the buried oxide layer is removed to expose the underlying silicon of the cap wafer 201.

[0058] Next, as Figure 1G As shown, a hard mask layer 202, such as a silicon oxide hard mask layer, is deposited on the cap wafer 201. The hard mask layer 202 is then etched to define the position and size of the predetermined top comb structure and expose the area of ​​the bottom silicon of the cap wafer 201 used to set the mirror structure. Aluminum pads are then formed on the bottom silicon.

[0059] Next, as Figure 1H and Figure 1I As shown, a mirror structure 203 (e.g., a mirror pattern formed of metal material) is formed on the cap wafer 201. The top comb structure and the bottom comb structure are located outside the mirror structure. The side of the SOI wafer 100 away from the bottom comb structure 150 is back-grinded (i.e., back-side thinning) to thin the SOI wafer 100. However, since the size of the mirror structure is relatively large, about 1000 μm, and the area of ​​the SOI wafer corresponding to the mirror structure is a large cavity structure, the support structure (e.g., silicon film structure) used to support the mirror structure is easily broken during back-side thinning, resulting in silicon explosion problem.

[0060] Finally, continue as follows Figure 1I As shown, the cap wafer 201 is etched using deep reactive ion etching (DRIE) with a hard mask layer as a mask to form multiple top comb structures 204 and support structures 205 for supporting the mirror structure 203.

[0061] After that, as Figure 1J As shown, the support layer and hard mask layer are released, making the top comb structure 204 movable.

[0062] The aforementioned technologies have the following drawbacks:

[0063] 1. Using two SOI wafers results in higher costs and more complex processes;

[0064] 2. The Si film layer obtained through SOI wafers requires the adjustment of the top silicon of the SOI wafer to adjust the stress, which is complex. The thinning process during SOI wafer fabrication can easily introduce a polishing damage layer.

[0065] 3. Bonding two SOI wafers is achieved through bonding technology. However, bonding voids are prone to exist at the bonding interface, which affects the yield and may increase the probability of abnormalities in the process.

[0066] 4. When the back is thinned, it is easy to break the support structure (such as a silicon film structure) for supporting the mirror structure, and a problem of exploding silicon occurs.

[0067] 5. After the structure layer is released, the side wall polymer and photoresist residues of the comb teeth can only rely on a dry cleaning process, and cannot be cleaned by a wet cleaning process, so that the residues cannot be effectively cleaned.

[0068] To solve the problems in the related art, the present application provides a manufacturing method of a MEMS device, and the following Figure 2 、 Figures 3A-3K and Figures 4A-4E describes the manufacturing method of the MEMS device provided by the present application, wherein Figure 2 a schematic flow chart of the manufacturing method of the MEMS device in one embodiment of the present application is shown; Figures 3A-3K a cross-sectional schematic diagram of the device obtained by sequentially implementing the manufacturing method of the MEMS device according to an embodiment of the present application is shown; Figures 4A-4E a partial cross-sectional schematic diagram of the device obtained by sequentially implementing the manufacturing method of the first mask layer according to an embodiment of the present application is shown.

[0069] In one embodiment, as shown in Figure 2 the manufacturing method 200 of the MEMS device provided by the present application includes the following steps S210 to S290:

[0070] First, in step S210, as shown in Figure 3A a substrate 500 is provided, and the substrate 500 includes a mirror area and a comb tooth area located outside the mirror area.

[0071] In one example, the substrate 500 can include at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs or other III / V compound semiconductors. Although several examples of materials that can form the substrate 500 are described herein, any material that can be used as the substrate 500 falls within the spirit and scope of the present application.

[0072] Without considering the cost, the substrate 500 can also be an SOI substrate or other suitable substrate.

[0073] In some embodiments, to reduce cost, the substrate 500 can be formed by the following method, for example, first, providing a base 501, forming an insulating layer 502 on the surface of the base 501, and epitaxially growing a device layer 503 on the insulating layer 502. The insulating layer 502 can be grown by a method such as thermal oxidation, i.e. an oxygen embedding layer. The device layer 503, for example a silicon layer, can be formed on the insulating layer 502 by an epitaxial growth method, and the thickness of the device layer 503 can range from 10 μm to 30 μm, or other suitable thickness. The device layer 503 is used to subsequently form the first comb teeth and the plurality of grooves in the mirror region.

[0074] The mirror region of the substrate 500 corresponds to the subsequently formed mirror structure, and the comb region is used to form the first comb teeth.

[0075] In some examples, as shown in Figure 3B The mark pattern can also be formed in the substrate by a lithography and etching process, which is an inner groove and located in the edge region of the substrate 500, outside the comb region.

[0076] Next, in step S220, as shown in Figures 3B-3D The substrate 500 is etched to form a plurality of grooves 510 in the mirror region and the comb region.

[0077] Any suitable method can be used to form the grooves 510 in the substrate 500. In one embodiment, a hard mask layer 505 can be first formed on the surface of the substrate 500, and then the hard mask layer 505 is patterned to expose the region where the grooves 510 are to be formed, and then the substrate 500 is etched by a method such as dry etching or wet etching to form a plurality of grooves 510. The number of grooves 510 can be reasonably determined according to actual needs, and the material of the hard mask layer 505 can be any suitable material for a hard mask in the art, including but not limited to SiO2, SiCN, SiN, SiC or SiON, etc. Any suitable deposition method can be used to form the hard mask layer 505, for example, chemical vapor deposition, physical vapor deposition or atomic layer deposition, etc. Preferably, dry etching is used for etching. Specifically, the device layer 503 of the substrate can be etched to form a plurality of grooves 510 in the mirror region and the comb region. Alternatively, the thickness of the hard mask layer 505 can be 1000-5500 angstroms, for example, 2000 angstroms, 3000 angstroms or 5000 angstroms, etc.

[0078] Optionally, the trench 510 can have a depth-to-width ratio greater than or equal to 3 and less than or equal to 60, which can be set according to actual needs. By having a higher depth-to-width ratio, the trench 510 can be filled with a filling hole in subsequent formation of the first mask layer 520. Optionally, the depth of the trench 510 can range from 5 μm to 60 μm, and the width of the trench 510 can range from 1 μm to 5 μm, or further, the width can range from 2 μm to 3 μm. The depth and width can be set according to actual needs.

[0079] The trench 510 formed in the comb tooth region is opposite to the subsequently formed second comb tooth 560, and the trench 510 formed in the mirror region is opposite to the subsequently formed mirror structure 509.

[0080] In some embodiments, before etching the trench, at least two isolation grooves 507 can be formed in the substrate 500, as shown in Figure 3C and Figure 3D For example, a photoresist layer 506 is formed to cover the patterned hard mask layer 505, and then the photoresist layer 506 is patterned by a photolithography process to expose the area of the substrate 500 where the isolation groove 507 is to be etched. The isolation groove 507 is etched in the substrate 500 with the photoresist layer 506 as a mask, and the isolation groove 507 is formed in the device layer 503 and spaced from the insulating layer 502. Then, the photoresist layer 506 is removed, and the trench 510 and the isolation groove 507 are etched simultaneously to extend the bottom of the isolation groove 507 to the insulating layer 502, as shown in Figure 3D Optionally, the depth of the trench can be less than the depth of the isolation groove. Optionally, the hard mask layer can also be removed after the trench is formed.

[0081] Then, in step S230, a first mask layer 520 is formed to cover the sidewall of the trench 510, the surface of the substrate 500, and seal the opening of the trench 510, as shown in Figure 3E and Figures 4A-4E

[0082] It is worth mentioning that, for convenience of presentation, Figures 4A-4E only a partial structure of the device is shown, for example, a partial schematic view corresponding to the area in the dashed box in Figure 3E

[0083] ​​For example, the first mask layer 520 may completely fill the trench 510. Alternatively, in other examples, the first mask layer 520 located within the trench 510 may also have filling voids 511 formed therein, wherein the top of the filling voids 511 is below the surface of the substrate 500. By forming filling voids 511 in the trench 510, the amount of the first mask layer 520 filling the trench 510 can be reduced, thereby facilitating the rapid removal of this portion of the first mask layer 520 in a shorter time. Furthermore, ensuring that the top of the filling voids 511 is below the surface of the substrate 500 guarantees that the opening of the trench 510 remains sealed during subsequent processes.

[0084] Optionally, the material of the first mask layer 520 can be, for example, silicon oxide, silicon nitride, silicon oxynitride, or any other suitable insulating material. It can consist of multiple material layers or it can be a single-layer film, which can be reasonably selected according to process requirements.

[0085] In one specific embodiment, the first mask layer 520 can be formed by the following method, including the steps S231 to S234:

[0086] In step S231, as Figure 4A As shown, a first mask material layer 521 is formed on the sidewall of the trench 510 and the surface of the substrate 500. The thickness of the first mask material layer 520 on the top sidewall of the trench 510 is greater than that of the first mask material layer 521 on the bottom sidewall of the trench. That is, the first mask material layer 521 at the opening of the trench 510 protrudes further towards the center of the trench 510 than the first mask material layer 521 on the bottom sidewall of the trench, thereby reducing the size of the opening of the trench 510 to facilitate subsequent sealing.

[0087] The material of the first mask material layer 521 may include silicon oxide, silicon nitride, silicon oxynitride, or other suitable materials. Preferably, the material of the first mask material layer 521 includes plasma-enhanced oxide (PEOX), which is silicon oxide formed using a plasma-enhanced chemical vapor deposition (PECVD) process via a silicon dioxide precursor (e.g., a silicon source such as silane, and oxygen such as molecular oxygen and ozone). Due to the inherent characteristics of plasma-enhanced oxide, when filling the trench 510, the thickness of the first mask layer 520 on the top sidewall of the trench 510 is greater than that of the first mask material layer 521 on the bottom sidewall of the trench. Therefore, the trench 510 can be partially sealed first, significantly reducing the opening of the trench 510.

[0088] In step S232, as Figure 4BAs shown, the first mask material layer 521 is etched to make the minimum opening of the trench 510 below the surface of the substrate 500, so that the opening of the trench 510 can be kept sealed when subsequent processes are performed. Optionally, the first mask material layer 521 can be etched by any suitable etching method, for example, by a blanket etch process to etch and remove part of the first mask material layer 521, which can be an isotropic etching. Optionally, the blanket etch process can be performed by plasma etching, for example, by bombarding the first mask material layer 521 with plasma formed by ionizing a rare gas such as argon or helium. Optionally, the blanket etch process can form a concave groove with a bottom that is a substantially circular truncated cone type and is below the surface of the substrate 500 at the minimum opening of the trench 510, which facilitates subsequent sealing of the opening of the trench 510.

[0089] In step S233, as shown, a second mask material layer 522 is formed on the first mask material layer 521, and the second mask material layer 522 seals the opening of the trench 510. Figure 4C

[0090] The second mask material layer 522 can be formed by any suitable deposition method, for example, physical vapor deposition, chemical vapor deposition, atomic layer deposition, etc. In one example, in order to further seal the opening of the trench 510, the material of the second mask material layer 522 includes an oxide formed by sub-atmospheric chemical vapor deposition (SACVD) using oxygen source and tetraethyl orthosilicate (TEOS) as raw materials, i.e., SACVD TEOS oxide. Generally, the oxide has relatively low density, so that the second mask material layer 522 can be formed on the first mask material layer 521 in the trench 510 by the SACVD TEOS oxide, and the sealing of the trench 510 can be better performed.

[0091] The first mask material layer 521 and the second mask material layer 522 partially fill the trench 510 as described above, so that the trench 510 forms a filling void 511. Optionally, the filling void 511 is below the surface of the substrate 500, for example, at least 0.5 μm below the surface of the substrate 500.

[0092] Optionally, the thickness of the first mask layer 520 on the surface of the substrate 500 is less than 1.5 μm, or can be any other suitable thickness, which is used as a mask for etching the substrate 500 to form the first comb teeth. ​

[0093] In step S234, as Figure 4D and Figure 4E As shown, a third mask material layer 523 is formed on the second mask material layer 522, and planarization is performed to form a first mask layer 520, wherein the density of the third mask material layer 523 is higher than that of the second mask material layer 522.

[0094] The second mask material layer 522 can be deposited using any suitable deposition method, such as physical vapor deposition, chemical vapor deposition, or atomic layer deposition. In one example, the material of the third mask material layer 523 includes PE TEOS oxide, that is, TEOS oxide deposited by PECVD. For example, a PECVD layer of PETEOS oxide can be deposited using TEOS and O2 as raw material gases, and its composition is usually SiO2.

[0095] Optionally, the density of the third mask material layer 523 is higher than that of the second mask material layer 522. By using a material with higher density for the third mask material layer 523, the density of the first mask layer 520 can be improved, and the sealing of the trench 510 can be made more secure.

[0096] like Figure 4E As shown, to obtain a first mask layer 520 with a flat surface, the third mask material layer 523 can be planarized, for example, by removing part of the third mask material layer 523 through etching or chemical mechanical polishing. Since the bottom of the third mask material layer 523 at the trench 510 is lower than the top surface of the second mask material layer 522, planarization can stop at the third mask material layer 523, leaving the third mask material layer 523 at the trench 510. Ultimately, the first mask material layer 521, the second mask material layer 522, and the third mask material layer 523 constitute the first mask layer 520. The planarization process allows the first mask layer to have a flatter surface, thereby facilitating the subsequent deposition of epitaxial layers.

[0097] It is worth mentioning that different processes can be used to form the first mask layer 520 for trenches 510 of different sizes. For example, for larger trenches 510, a blanket etching process can be performed after the second mask material layer 522 is formed for the first time, and then the second mask material layer 522 can be formed for the second time. That is, the blanket etching process and the second mask material layer 522 can be repeated at least once to better seal the trench 510.

[0098] Next, in step S240, as Figure 3FAs shown, the first mask layer 520 is etched to expose part of the surface of the substrate and cover each region of the substrate for forming the first comb teeth and the mirror region.

[0099] The first mask layer 520 can be etched to be patterned by any suitable method. For example, a photoresist layer can be formed on the first mask layer 520, and the photoresist layer can be patterned by a photolithography process to define the position and size of the first comb teeth 550 to be formed, and then the first mask layer 520 can be etched using the patterned photoresist layer as a mask to achieve the patterning of the first mask layer 520, and then the photoresist layer can be removed. In addition to defining the position of the first comb teeth 550, the first mask layer 520 also defines the position and size of the channels between adjacent first comb teeth 550 (i.e., the first mask layer exposes the region of the substrate for forming the channels between adjacent first comb teeth 550 for subsequent etching). Moreover, the first mask layer 520 still covers the openings of the trenches 510 at the positions of the trenches 510. The covering of the mirror region by the first mask layer can avoid etching of the mirror region in subsequent formation of the first comb teeth.

[0100] The part of the substrate 500 outside the trenches 510 can be used to fabricate the first comb teeth 550. Specifically, the number of trenches 510 can be reasonably set according to the number of first comb teeth 550 to be fabricated and the number of second comb teeth 560 to be fabricated subsequently.

[0101] It should be noted that, for the convenience of illustration, Figure 3E Then, the first mask layer 520 is shown using the same filling pattern, but this is intended to limit the number of layers of the first mask layer 520, and the filling void 511 is also shown as a blank rectangle, but this is not intended to limit the shape of the filling void 511.

[0102] It should also be noted that, Figures 3F-3H , and Figure 3J and Figure 3K (b) of FIG. is a partial enlarged view of the region in the rectangular dashed box in (a).

[0103] Next, in step S250, as shown in Figure 3G , an epitaxial layer 530 is formed on the surface of the substrate 500 and the first mask layer 520.

[0104] The material of the epitaxial layer 530 is a semiconductor material, which can be Si, SiB, SiGe, SiC, SiP, SiGeB, SiCP, AsGa, or other binary or ternary compounds of group III-V. In the present embodiment, the material of the epitaxial layer 530 is Si.

[0105] The epitaxial layer 530 can be formed by one of low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD), ultra-high vacuum chemical vapor deposition (UHVCVD), rapid thermal chemical vapor deposition (RTCVD) and molecular beam epitaxy (MBE).

[0106] Optionally, the epitaxial layer 530 can be used for subsequent manufacturing of the second comb teeth 560, i.e. the top comb structure, and the thickness thereof can depend on the size of the second comb teeth to be manufactured, which is not specifically limited herein. Exemplarily, the thickness of the epitaxial layer 530 can range from 20 μm to 30 μm.

[0107] By forming the epitaxial layer 530 on the surface of the substrate 500 and the first mask layer 520, and using the epitaxial layer 530 to manufacture the second comb teeth 560, compared with the related art using SOI wafers, the use of SOI wafers is reduced, and thus the cost is lower. Moreover, the stress of the thin film layer structure can be adjusted during the formation of the epitaxial layer 530, and the adjustment method is simpler, and the difficulty of stress adjustment and the adjustment period are reduced. Furthermore, by the method of depositing to form the epitaxial layer, the use of the bonding process can be avoided, and thus the influence of the voids at the bonding interface on the yield of the device is avoided, and the yield of the product is improved.

[0108] In some embodiments, the method of the present application further comprises the step of forming the pads 508 on the surface of the epitaxial layer 530. Specifically, a metal layer can be first deposited on the surface of the epitaxial layer 530, and then the metal layer is etched by using a photolithography and etching process to form the pads 508, such as aluminum pads.

[0109] Optionally, the device layer 503 and the epitaxial layer 530 described above can both be formed by a thick epitaxial (EPI) growth process, and the thickness thereof can range from 20 μm to 30 μm, so as to reduce the use of SOI wafers, reduce the cost and simplify the process.

[0110] Next, as shown in FIG. 5B, in step S260, a mirror structure 509 is formed on the epitaxial layer 530. Figure 3H and Figure 3I The mirror structure 509 corresponds to the mirror region.

[0111] Before forming the mirror structure 509, the following process steps can also be performed, for example, as shown in FIG. 5C. Figure 3HAs shown, the second mask layer 540 can be formed on the surface of the epitaxial layer 530 first, and the second mask layer 540 is patterned to form the first openings defining the channels between the second combs 560 and the second openings defining the mirror structures 509, and the second mask layer 540 also defines the positions and sizes of the second combs 560 to be formed (i.e. the position areas covered by the second mask layer 540), and the positions of each second comb 560 correspond to one groove 510 respectively.

[0112] The material of the second mask layer 540 can be selected from any suitable material, for example, the material of the second mask layer 540 can include silicon oxide, silicon nitride or silicon oxynitride, etc. It can be a single layer or a multi-layer film structure.

[0113] The second mask layer 540 can be deposited by using any suitable deposition process, such as chemical vapor deposition, physical vapor deposition or atomic layer deposition, etc. The thickness of the second mask layer 540 can be reasonably set according to actual needs, which is not specifically limited here.

[0114] The second mask layer 540 can be patterned by using any suitable method, for example, a photoresist layer can be formed on the second mask layer 540, and then the photoresist layer is patterned by using a photolithography process to define the positions and sizes of the second combs 560 to be formed and the positions and sizes of the mirror structures 509, and then the second mask layer 540 is etched with the patterned photoresist layer as a mask to stop in the epitaxial layer 530 to achieve the patterning of the second mask layer 540, and then the photoresist layer is removed. The second mask layer 540 defines the positions and sizes of the channels between the adjacent second combs 560 in addition to the defined positions. The patterned second mask layer 540 corresponds to the positions of the grooves 510, i.e. the positions of each second comb 560 correspond to one groove 510 respectively. By such arrangement, after the second combs 560 are formed, the bottoms of each second comb 560 are connected to part of the first mask layer 520 (which constitutes the support structure 531) respectively, and the part of the first mask layer 520 can support the second comb 560. The mirror structures 509 correspond to multiple grooves 510, and the support structure 531 below the mirror structures 509 has multiple grooves 510 and the first mask layer 520 filling the grooves, and the substrate area between the first mask layer 520 and the multiple grooves 510 can support the support structure 531 and the mirror structures 509 to facilitate subsequent steps such as back thinning, wet cleaning, etc., to avoid the problem of breakage of the support structure.

[0115] The mirror structure 509 can be a reflective mirror formed by a metal, such as one or more of gold, silver, or aluminum, or other metal materials. In one embodiment, the mirror structure 509 can be formed by any suitable method, such as depositing a mirror material layer covering the epitaxial layer 530 and the second mask layer 540, and performing a planarization process, such as a chemical mechanical polishing process or an etching process that stops at the second mask layer 540, on the mirror material layer to form the mirror structure 509. If the pad 508 is not formed in the foregoing step, the pad 508 opening can also be formed in the second mask layer 540 at the same time, so that the pad 508 can be formed at the same time as the mirror structure 509.

[0116] In some embodiments, the mirror structure 509 can also be formed by a lift-off process, such as forming a photoresist layer on the surface of the epitaxial layer 530 and the surface of the second mask layer 540 and the surface of the pad 508, and then using a photolithography process to remove part of the photoresist layer to form a mirror pattern opening in the photoresist layer, which exposes part of the surface of the epitaxial layer 530, and then depositing a mirror material layer covering the photoresist layer and filling the mirror pattern opening, and then using a solvent to dissolve the photoresist layer to lift off the mirror material layer covering the photoresist layer, and only the mirror material layer deposited on the epitaxial layer is left, thereby forming the mirror structure 509.

[0117] In some embodiments, the method of the present application further includes thinning the substrate 500 away from the epitaxial layer 530, such as to achieve a total thickness of about 400 μm between the thinned substrate 500 and the epitaxial layer 530, or other suitable thickness. The thinning can remove part of the base 501 of the substrate 500, and any suitable method can be used to thin the substrate 500, such as one or more of a chemical mechanical polishing process or an etching process.

[0118] Since the mirror structure 509 corresponds to the plurality of grooves 510, and since the support structure 531 is below the plurality of grooves 510 and the first mask layer 520 filling the grooves, the support structure 531 and the mirror structure 509 can be supported by the substrate area between the first mask layer 520 and the plurality of grooves 510, making the support structure more stable, that is, compared to related art, the present application has no large cavity structure, so that the risk of exposure caused by the breakage of the support structure 531 during thinning can be avoided.

[0119] Next, in step S270, as shown in FIG. 7B, the substrate 500 is thinned to a thickness of about 400 μm, or other suitable thickness, away from the epitaxial layer 530. Figure 3JAs shown, the epitaxial layer 530 is etched to form a plurality of second comb teeth 560 structures outside the mirror structure 509 and a support structure 531 for supporting the mirror structure 509, wherein each second comb tooth 560 structure corresponds to one groove 510 in the comb region, and the plurality of second comb teeth 560 structures are outside the support structure 531.

[0120] For example, the epitaxial layer 530 can be etched to form the second comb teeth 560 and the support structure 531 separated from the second comb teeth 560 by using the second mask layer 540 as a mask, and the first mask layer 520 outside the second comb teeth 560 is exposed, i.e., the channels outside the second comb teeth are exposed to the first mask layer 520.

[0121] The epitaxial layer 530 can be etched by dry etching or wet etching or any other suitable etching method, for example, the epitaxial layer 530 can be etched by using a deep reactive ion etching (DRIE) method.

[0122] Deep reactive ion etching is a process that uses high-energy ions and free radicals generated by plasma to etch silicon, which can achieve high aspect ratio, high etching rate and high mask selectivity. The DRIE etching process can be a Bosch process, which is a cyclic etching process, each cycle including two steps: deposition and etching. In the deposition step, a fluorine-containing gas (such as C4F8) is used to deposit a protective film on the sidewall and bottom of the etching area to prevent the sidewall from being etched. In the etching step, a sulfur-containing gas (such as SF6) is used to etch silicon, while the protective film on the bottom is removed, so that the etching area extends downward. In this way, by repeatedly depositing and etching cycles, etching of deep openings or grooves or channels between comb teeth can be achieved.

[0123] The second comb teeth 560 are top comb tooth structures, which are movable comb teeth, and the first comb teeth 550 are bottom comb tooth structures, which are fixed comb teeth.

[0124] In some embodiments, a protective layer can be formed to cover the mirror structure 509 and the pad 508 before etching to avoid corrosion of the mirror structure 509 and the pad 508 caused by subsequent etching, which affects the performance of the device. The protective layer can be a photoresist layer or any other suitable material that can be used as a protective layer.

[0125] After the etching, the bottom ends of the second combs 560 are respectively connected to the partial first mask layer 520 (i.e. the support formed by the first mask layer 520 filled in the grooves 510), and the second combs 560 can be supported by the first mask layer 520, so that the structure of the device is more stable, so as to facilitate the subsequent process steps, such as wet cleaning, etc. At the same time, the bottom of the support structure 531 is connected to the partial first mask layer 520, and the partial first mask layer 520 fills the grooves 510 and covers part of the surface of the substrate 500, so as to better support the support structure 531, and also make the structure of the device more stable, so as to facilitate the subsequent process steps, such as wet cleaning, etc.

[0126] Next, in step S280, continuing to refer to Figure 3J With the first mask layer 520 as a mask, the substrate 500 is etched to form a plurality of first combs 550, and the plurality of first combs 550 and the plurality of second combs 560 are arranged alternately.

[0127] That is, the first mask layer 520 exposed by the channels outside the second combs 560 is used as a mask to etch the substrate 500 to form the first combs 550. The number of the first combs 550 and the second combs 560 can be multiple, and the specific number can be reasonably set according to actual needs. The plurality of first combs 550 and the plurality of second combs 560 are arranged alternately.

[0128] Dry etching or wet etching or any other suitable etching method can be used to etch the substrate 500, for example, using a deep reactive ion etching (DRIE) method to etch the substrate 500.

[0129] As it is easy to generate etching residues, such as polymer residues and photoresist residues, in the etching process of the epitaxial layer 530 and the substrate 500 (for example, in the etching process of forming the second comb teeth 560 and the support structure 531 from the epitaxial layer, and in the etching process of forming the first comb teeth 550 from the substrate 500), if the polymer residues and the photoresist residues are not removed, they can exist on the surface of the comb teeth and affect the performance of the device, therefore, in some embodiments, the manufacturing method of the present application further comprises: after forming the first comb teeth 550 and the second comb teeth 560, and before removing the second mask layer 540 and the first mask layer 520, performing a wet cleaning process to remove the etching residues, wherein, in the cleaning process, the first mask layer 520 supports the second comb teeth 560, and the bottom of the support structure 531 is connected to the part of the first mask layer 520, and the part of the first mask layer 520 fills the plurality of grooves 510 and covers part of the surface of the substrate 500, thereby providing better support to the support structure 531, making the second comb teeth 560 and the support structure 531 more stable during the wet cleaning process, and facilitating the effective removal of etching residues by the wet cleaning process, thereby improving the yield and performance of the device.

[0130] It is worth mentioning that the plurality of second comb teeth 560 are arranged in the first direction and at intervals, and the size of the second comb teeth 560 in the first direction can be equal to the size of the groove 510 in the first direction, so that after etching, in the first direction, the size of the first mask layer 520 under each second comb tooth 560 is substantially the same as the size of the corresponding second comb tooth 560, or can be greater than the size of the groove 510 in the first direction, so that after etching, in the first direction, the size of the first mask layer 520 under each second comb tooth 560 is smaller than the size of the corresponding second comb tooth 560, or can be smaller than the size of the groove 510 in the first direction, so that after etching, in the first direction, the size of the first mask layer 520 under each second comb tooth 560 is greater than the size of the corresponding second comb tooth 560. Regardless of the case, it can support the second comb teeth 560.

[0131] Next, in step S290, as shown in FIG. 2B, at least the first mask layer 520 located under the second comb teeth 560 and the support structure 531 is removed. Figure 3K

[0132] By removing the first mask layer 520 under the second comb teeth 560, the second comb teeth 560 are released and become movable comb teeth. At the same time, the first mask layer 520 under the mirror structure 509 can also be removed, so that the support structure 531 and the substrate 500 thereunder have a spacing space, thereby facilitating the movement of the support structure 531 and the mirror structure 509 in the spacing space.

[0133] ​The second comb teeth 560 are connected to the support structure 531, and the second comb teeth 560 can rotate along the axis of the arrangement direction thereof, so as to drive the support structure 531 and the mirror structure 509 to twist.

[0134] In some examples, continuing to refer to Figure 3K The second mask layer 540 on the second comb teeth 560 and the first mask layer 520 on the first comb teeth 550 can also be removed at the same time.

[0135] The first mask layer 520 and the second mask layer 540 can be removed according to the material selection of the first mask layer 520 and the second mask layer 540, for example, the first mask layer 520 and the second mask layer 540 can be removed by using a buffer oxide etchant or by using gaseous hydrogen fluoride (VHF).

[0136] Taking the removal of the first mask layer 520 and the second mask layer 540 by using gaseous hydrogen fluoride (VHF) as an example, the basic principle of the process is that gaseous hydrogen fluoride (VHF) reacts with the first mask layer 520 and the second mask layer 540 such as silicon dioxide to generate water and hexafluorosilicic acid. The hexafluorosilicic acid reacts with the silicon on the surface of the substrate 500 and the surface of the epitaxial layer 530 to generate water and silicon tetrafluoride. Silicon tetrafluoride is a volatile gas that can be discharged from the reaction chamber, achieving etching and removal of the first mask layer 520 and the second mask layer 540.

[0137] When the isolation groove is exposed and connected to the insulating layer 502, the VHF can also remove the part of the insulating layer 502 exposed by the isolation groove.

[0138] The release of the first mask layer 520 and the second mask layer 540 by gaseous hydrogen fluoride has a larger process window and can reduce side etching. In addition, since the first mask layer 520 filled in the trench 510 has a filling hole 511, it can be more easily removed and the process time can be shortened.

[0139] It is worth mentioning that the MEME device in the present application can be a MEMS mirror, and the above-mentioned method of the present application is only an example and does not have a strict sequence limitation. The steps can also be alternately performed or the order can be changed without contradiction.

[0140] The description of some steps of the method of the present application is completed, and other steps can also be included for forming a complete device, which will not be described here.

[0141] The MEMS device manufacturing method provided in this application has the following advantages: By forming an epitaxial layer on the surface of the substrate and on the first mask layer, and using the epitaxial layer to fabricate the second comb teeth, compared with the traditional related technologies using SOI wafers, this application reduces the use of SOI wafers, thus lowering the cost, reducing the difficulty of stress control, and shortening the adjustment cycle. Each second comb tooth in this application is located on a trench, which is filled with the first mask layer. After the first and second comb teeth are formed, the first mask below the second comb tooth can be used to support it, and the first hard mask layer below the support structure also provides support, thereby improving the structural stability and making subsequent processes more stable.

[0142] This application also provides a MEMS device, which can be manufactured by the aforementioned MEMS device manufacturing method. Details of this MEMS device can be found in the preceding description and will not be repeated here. This MEMS device can be an optoelectronic device, such as a MEMS mirror actuator (also known as a MEMS galvanometer).

[0143] In one example, such as Figure 3K As shown, the MEMS device of this application includes a substrate 500, which includes a mirror region and a comb region located outside the mirror region. A plurality of first comb teeth 550 are spaced apart in the comb region. A plurality of trenches 510 are spaced apart in the mirror region. An epitaxial layer 530 is disposed on the substrate 500, and the epitaxial layer 530 includes a plurality of spaced second comb tooth structures 560 and a support structure 531. The plurality of second comb tooth structures 560 are located outside the support structure 531, and the plurality of second comb teeth 560 and the plurality of first comb teeth 550 are staggered. A mirror structure 509 is disposed on the support structure 531, and the mirror structure 509 is opposite to the mirror region. Each second comb tooth 560 has a channel penetrating the epitaxial layer 530 on its outer side.

[0144] For example, the substrate 500 includes a base layer 501, a device layer 503, and an insulating layer 502 disposed between the base layer 501 and the device layer 503. At least two spaced-apart isolation trenches 507 are formed in the substrate 500, and a plurality of first comb teeth 550 are disposed between adjacent isolation trenches 507. The isolation trenches 507 extend through the device layer 503 into the insulating layer 502.

[0145] The MEMS device of this application is prepared by the aforementioned method, and therefore has the same advantages as the aforementioned method.

[0146] The present application has been described by the above embodiments, but it should be understood that the above embodiments are only for the purpose of example and illustration, and are not intended to limit the present application to the scope of the described embodiments. Furthermore, those skilled in the art can understand that the present application is not limited to the above embodiments, and more various modifications and changes can be made according to the teachings of the present application, and these modifications and changes all fall within the scope of the present application claimed. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method of manufacturing a MEMS device, characterized by, The method comprises the following steps: providing a substrate comprising a mirror area and a comb area outside the mirror area; etching the substrate to form a plurality of trenches arranged at intervals in the mirror area and the comb area; forming a first mask layer to cover the sidewalls of the trenches, the surface of the substrate and seal the openings of the trenches; etching the first mask layer to expose part of the surface of the substrate and cover each area of the substrate for forming the first comb and the mirror area; forming an epitaxial layer on the surface of the substrate and the first mask layer; forming a mirror structure on the epitaxial layer, the mirror structure corresponding to the mirror area; etching the epitaxial layer to form a support structure for supporting the mirror structure and a plurality of second combs outside the mirror structure, wherein each of the second combs corresponds to one of the trenches in the comb area, and a plurality of the second combs are arranged outside the support structure, and the first mask layer supports the second combs and the support structure; using the first mask layer as a mask, etching the substrate to form a plurality of the first combs, and the plurality of the first combs and the plurality of the second combs are arranged alternately; removing at least the first mask layer under the second combs and the support structure.

2. The production method according to claim 1, wherein The first mask layer in the trench also forms a filling cavity, wherein the top of the filling cavity is below the surface of the substrate.

3. The production method according to claim 2, wherein The forming of the first mask layer to cover the sidewalls of the trenches, the surface of the substrate and seal the openings of the trenches comprises: forming a first mask material layer on the sidewalls of the trenches and the surface of the substrate, wherein the thickness of the first mask layer on the top sidewall of the trench is greater than that on the bottom sidewall of the trench; etching to remove part of the first mask material layer, so that the smallest opening of the trench is below the surface of the substrate; forming a second mask material layer on the first mask material layer, and the second mask material layer seals the opening of the trench; forming a third mask material layer on the second mask material layer, and performing planarization to form the first mask layer, wherein the compactness of the third mask material layer is higher than that of the second mask material layer.

4. The production method according to claim 1, wherein Before etching the epitaxial layer to form a plurality of second combs outside the mirror structure, after forming the epitaxial layer, the manufacturing method further comprises: thinning the side of the substrate away from the epitaxial layer.

5. The production method according to claim 1, wherein After forming the first combs and the second combs, before removing the first mask layer, the manufacturing method further comprises: performing wet cleaning to remove etching residues formed during etching the epitaxial layer and etching the substrate, wherein during the cleaning process, the first mask layer supports the second combs, and the first mask layer of the mirror area supports the support structure.

6. The production method according to claim 1, wherein The method for forming the substrate comprises: providing a substrate, forming an insulating layer on the surface of the substrate, and epitaxially growing a device layer on the insulating layer, wherein the device layer is used to form the first comb.

7. The production method according to claim 6, wherein Before forming the trenches, the manufacturing method further comprises: forming at least two isolation grooves in the device layer; the etching the substrate to form the plurality of trenches in the mirror area and the comb area comprises: etching the device layer to form the plurality of trenches in the mirror area and the comb area, and etching the isolation grooves at the same time, so that the bottom of the isolation grooves extends to the insulating layer.

8. The production method according to claim 1, wherein the thickness of the first mask layer on the surface of the substrate is less than 1.5 μm; and / or the aspect ratio of the trenches is greater than or equal to 3 and less than or equal to 60.

9. A MEMS device, characterized by The MEMS device is prepared by the manufacturing method according to any one of claims 1-8, and the MEMS device comprises: a substrate comprising a mirror area and a comb area outside the mirror area; a plurality of first combs arranged in the comb area; a plurality of trenches arranged in the mirror area; an epitaxial layer arranged on the substrate, the epitaxial layer comprising a plurality of second combs and a support structure, the plurality of second combs being outside the support structure, and the plurality of second combs and the plurality of first combs being arranged alternately; a mirror structure arranged on the support structure, the mirror structure being opposite to the mirror area.

10. The MEMS device of claim 9, wherein, The substrate comprises a base layer, a device layer, and an insulating layer arranged between the base layer and the device layer, at least two isolation grooves are formed in the substrate, and a plurality of first combs are arranged between adjacent isolation grooves, wherein the isolation grooves extend through the device layer into the insulating layer.

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