MEMS device and manufacturing method thereof
By forming trenches and multi-layer mask layers on the substrate, the interlaced MEMS comb tooth structure is solved, and the cost reduction, process simplification and structural stability are achieved.
Patent Information
- Application Number
- CN202411954231.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-27
- Publication Date
- 2025-03-28
AI Technical Summary
The manufacturing method of existing MEMS devices uses SOI wafers, which leads to high costs, complex processes and complex stress control of thin film structures, making it easy to introduce large cavity and weak structures, affecting the device yield.
By forming a plurality of trenches arranged at intervals on the substrate and forming a multi-layer mask layer thereon, patterning and etching, the interlaced first and second comb teeth are formed, the dependence on the SOI wafer is reduced, the cost is reduced, and the stress regulation of the film structure is simplified.
It has achieved reduced manufacturing cost, process simplification and structural stability of MEMS devices, and improved the yield and performance of the device.
Smart Images
Figure CN119706739A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of semiconductor technology, and in particular to a MEMS device and a method for manufacturing the same. Background Art
[0002] Some micro-electro-mechanical system (MEMS) devices, such as MEM mirror driver devices, usually require the preparation of upper and lower comb teeth that are staggered up and down. MEM mirror driver devices can deflect, modulate, open and close, and phase-control the light beam under the driving action. MEM mirror driver devices are light in weight, small in size, easy to mass produce, low in production cost, and excellent in optical, mechanical properties and power consumption. Therefore, they are widely used in projection, display, optical communication, lidar and other scenarios.
[0003] In the related art, one or two SOI wafers are usually used to prepare devices, which is costly, and the stress control of the thin film structure is complicated, the process is complex, and large cavities are often introduced, with many weak structures.
[0004] Therefore, it is necessary to propose a new MEMS device and a manufacturing method thereof to at least partially solve the above problems. Summary of the invention
[0005] A series of simplified concepts are introduced in the Summary of the Invention section, which will be further described in detail in the Detailed Description of the Invention section. The Summary of the Invention section of this application does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the scope of protection of the claimed technical solution.
[0006] In view of the existing problems, the present application provides a method for manufacturing a MEMS device, comprising the following steps:
[0007] Providing a substrate, and forming a plurality of grooves spaced apart from each other in the substrate;
[0008] forming a first mask layer to cover the sidewalls of the trench, the surface of the substrate and seal the opening of the trench;
[0009] Patterning the first mask layer to expose a portion of the surface of the substrate and define the position and size of the first comb teeth to be formed;
[0010] forming an epitaxial layer on the surface of the substrate and the first mask layer;
[0011] Forming a patterned second mask layer on the epitaxial layer, wherein the second mask layer defines the positions and sizes of second comb teeth to be formed, and each of the second comb teeth is located on a corresponding groove;
[0012] Using the second mask layer and the first mask layer as masks, etching the epitaxial layer and the substrate to form the second comb teeth and the first comb teeth, wherein the first comb teeth and the second comb teeth are staggered;
[0013] At least the first mask layer located below the second comb teeth is removed.
[0014] In one example, a filling cavity is further formed in the first mask layer located in the trench, wherein a top of the filling cavity is located below the surface of the substrate.
[0015] In one example, the forming of a first mask layer to cover the sidewalls of the trench, the surface of the substrate and seal the opening of the trench includes:
[0016] forming a first mask material layer on the sidewall of the trench and the surface of the substrate, wherein the thickness of the first mask material layer on the top sidewall of the trench is greater than that of the first mask material layer on the bottom sidewall of the trench;
[0017] Etching and removing a portion of the first mask material layer so that the minimum opening of the trench is located below the surface of the substrate;
[0018] forming a second mask material layer on the first mask material layer, wherein the second mask material layer seals the opening of the trench;
[0019] A third mask material layer is formed on the second mask material layer, and planarization is performed to form the first mask layer, wherein the third mask material layer has higher density than the second mask material layer.
[0020] In one example, the etching removes a portion of the first mask material layer so that a minimum opening of the trench is located below the surface of the substrate, including:
[0021] A portion of the first mask material layer is removed by etching through a full etching process.
[0022] In one example, the etching and removing a portion of the first mask material layer by a full etching process includes:
[0023] The first mask material layer is bombarded with plasma to remove a portion of the first mask material layer.
[0024] In one example, the material of the first mask material layer includes plasma enhanced oxide, the material of the second mask material layer includes oxide formed by sub-atmospheric pressure chemical vapor deposition using oxygen source and tetraethyl orthosilicate as raw materials, and the material of the third mask material layer includes PE TEOS oxide.
[0025] In one example, after forming the first comb teeth and the second comb teeth and before removing the first mask layer, the manufacturing method further includes:
[0026] Wet cleaning is performed to remove etching residues caused by the etching, wherein during the cleaning process, the first mask layer supports the second comb teeth.
[0027] In one example, the method further includes:
[0028] The second mask layer is removed while a portion of the first mask layer is removed.
[0029] In one example, the thickness of the first mask layer on the surface of the substrate is less than 1.5 μm; and / or
[0030] The aspect ratio of the groove is greater than or equal to 3 and less than or equal to 60.
[0031] The present application also provides a MEMS device, which is manufactured according to any of the above-mentioned methods for manufacturing a MEMS device.
[0032] According to the MEMS device and its manufacturing method provided by the present application, an 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 technology of traditional use of SOI wafers, the present application reduces the use of SOI wafers, so its cost is lower, and the stress of the thin film layer structure can be regulated during the formation of the epitaxial layer, and the regulation method is simpler. The position of each of the second comb teeth of the present application corresponds to a groove, and the groove is filled with the first mask layer. Then, after the first comb teeth and the second comb teeth are formed, the first mask under the second comb teeth can be used to support them, thereby improving the stability of the structure and making the subsequent process more stable. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The following drawings of the present application are used as a part of the present application for understanding the present application. The drawings show the embodiments of the present application and their descriptions, which are used to explain the principle of the present application.
[0034] In the attached figure:
[0035] Figure 1A to Figure 1B A cross-sectional schematic diagram of a device obtained by sequentially implementing a manufacturing method of a MEMS device in a related art is shown;
[0036] FIG. 2A to FIG. 2B A cross-sectional schematic diagram of a device obtained by sequentially implementing a manufacturing method of a MEMS device in another related art is shown;
[0037] FIG. 3A to FIG. 3C A cross-sectional schematic diagram of a device obtained by sequentially implementing a method for manufacturing a MEMS device in another related art is shown;
[0038] Figure 4 A schematic flow chart showing a method for manufacturing a MEMS device in one embodiment of the present application is shown;
[0039] FIG. 5A to FIG. 5K A cross-sectional schematic diagram of a device obtained by sequentially implementing a method for manufacturing a MEMS device according to an embodiment of the present application is shown. DETAILED DESCRIPTION
[0040] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present application. However, it is apparent to those skilled in the art that the present application can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present application, some technical features well known in the art are not described.
[0041] It should be understood that the present application can be implemented in different forms and should not be construed as being limited to the embodiments presented herein. On the contrary, providing these embodiments will make the disclosure thorough and complete and fully convey the scope of the present application to those skilled in the art. In the accompanying drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. The same reference numerals throughout represent the same elements.
[0042] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer or part discussed below can be represented as a second element, component, region, layer or part.
[0043] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," and the like, may be used herein for convenience of description to describe the relationship of one element or feature shown in the figures to other elements or features. It should be understood that the spatially relative terms are intended to include different orientations of the galvanometer in use and operation in addition to the orientations shown in the figures. For example, if the galvanometer in the accompanying drawings is flipped, then the elements or features described as "under the other elements" or "under it" or "under it" will be oriented as "over" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. The galvanometer may be otherwise oriented (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.
[0044] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present application. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.
[0045] Currently, there are three related technologies for preparing the comb-tooth structure of MEMS devices.
[0046] In the first related art, first, as Figure 1A As shown, the SOI wafer 100 is etched to form a bottom comb structure 110, and then, as shown in Figure 1B As shown, the side of the SOI wafer 100 formed with the bottom comb-tooth structure 110 is bonded to the top Si film layer through a bonding process such as silicon-oxygen or silicon-silicon bonding, and then the top Si film layer is etched to obtain the top comb-tooth structure 120.
[0047] In the second related technology, first, as Figure 2A As shown, the top silicon layer of the SOI wafer 100 is etched to form a top comb structure 120, and then, as shown in FIG. Figure 2B As shown, the SOI wafer 100 is turned over, and the bottom silicon of the SOI wafer 100 is etched to form a bottom comb-tooth structure 110 .
[0048] In the third related art, first, as Figure 3A As shown, the SOI wafer 100 is etched to form a bottom comb structure 110, and then, as shown in Figure 3BAs shown, a bonding process such as silicon-oxygen or silicon-silicon bonding is used to bond the side of the SOI wafer 100 with the bottom comb structure 110 to the top Si film layer, and an oxide hard mask layer and a photoresist mask layer are formed on the top Si film layer. After patterning, a top comb structure and an auxiliary structure are defined, and the auxiliary structure corresponds to the bottom comb structure. Then, etching is performed to form the top comb structure 120 and the auxiliary structure, and the auxiliary structure plays a role of self-alignment. Then, as shown in FIG. Figure 3C As shown, the photoresist mask layer is removed, and the top comb-tooth structure 120 is retained with an oxide hard mask while the redundant auxiliary structure is removed, thereby completing the preparation of the comb-tooth structure.
[0049] However, the above-mentioned related technologies generally use one or two SOI wafers, which are relatively expensive and have complex processes. In addition, the stress control of the thin film structure is complex, and the process is complex. Large cavities are often introduced, and there are many weak structures, which are prone to structural cracks and affect the device yield.
[0050] In order to solve the problems existing in the related art, the present application proposes a method for manufacturing a MEMS device. Figure 4 and FIG. 5A to FIG. 5K A method for manufacturing a MEMS device according to the present application is described, wherein: Figure 4 A schematic flow chart showing a method for manufacturing a MEMS device in one embodiment of the present application is shown; FIG. 5A to FIG. 5K A cross-sectional schematic diagram of a device obtained by sequentially implementing a method for manufacturing a MEMS device according to an embodiment of the present application is shown.
[0051] In one embodiment, Figure 4 As shown, the manufacturing method 400 of the MEMS device provided in the present application includes the following steps S410 to S470:
[0052] First, in step S410, Figure 5A As shown, a substrate 500 is provided, and a plurality of trenches 510 arranged at intervals are formed in the substrate 500 .
[0053] In one example, the substrate 500 may 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.
[0054] Any suitable method may be used to form the grooves 510 in the substrate 500. In one embodiment, a mask layer may be first formed on the surface of the substrate 500, and then the mask layer may be patterned to expose the area where the grooves are to be formed, and then the substrate 500 may be etched by, for example, dry etching or wet etching to form a plurality of grooves 510, wherein the number of the grooves 510 may be consistent with the number of the second comb-tooth structures to be formed. Preferably, dry etching is used for etching.
[0055] Optionally, the trench 510 may have an aspect ratio greater than or equal to 3 and less than or equal to 60, which may be reasonably set according to actual needs. By making the trench 510 have a higher aspect ratio, it may be beneficial to form a filling cavity in the trench 510 when the first mask layer 520 is subsequently formed. Optionally, the depth of the trench 510 may range from 5 μm to 60 μm, and the width of the trench 510 may range from 1 μm to 5 μm micrometers. This may be reasonably set according to actual needs.
[0056] Next, in step S420, FIG. 5B to FIG. 5F As shown, a first mask layer 520 is formed to cover the sidewalls of the trench 510 , the surface of the substrate 500 , and seal the opening of the trench 510 .
[0057] It is worth mentioning that, for the convenience of presentation, FIG. 5B to FIG. 5F Only the local structure of the device is shown, for example Figure 5A A local schematic diagram of the area in the dashed box.
[0058] Exemplarily, the first mask layer 520 may fill the trench 510 completely, or, in other examples, a filling hole 511 is formed in the first mask layer 520 in the trench 510, wherein the top of the filling hole 511 is located below the surface of the substrate 500. By forming the filling hole 511 in the trench 510, the filling amount of the first mask layer 520 in the trench 510 can be reduced, so that the first mask layer 520 can be quickly removed in a short time. The top of the filling hole 511 is located below the surface of the substrate 500, which can ensure that the sealing of the opening of the trench 510 can be maintained during the subsequent process.
[0059] Optionally, the material of the first mask layer 520 may be silicon oxide, silicon nitride, silicon oxynitride or any other suitable insulating material, and may be composed of multiple material layers or a single film layer, which may be reasonably selected according to process requirements.
[0060] In a specific embodiment, the first mask layer 520 may be formed by the following method, including the following steps S421 to S424:
[0061] In step S421, if Figure 5B As shown, a first mask material layer 521 is formed on the sidewalls of the groove 510 and the surface of the substrate 500, wherein the thickness of the first mask material layer 520 located on the top sidewall of the groove 510 is greater than the first mask material layer 521 located on the bottom sidewall of the groove, that is, the first mask material layer 521 located at the opening of the groove 510 protrudes further toward the center of the groove 510 than the first mask material layer 521 located on the bottom sidewall of the groove, thereby reducing the size of the opening of the groove 510 to facilitate subsequent sealing.
[0062] The material of the first mask material layer 521 may include silicon oxide, silicon nitride, silicon oxynitride or other suitable materials, wherein preferably, the material of the first mask material layer 521 includes plasma enhanced oxide (PEOX), that is, silicon oxide formed by a silicon dioxide precursor (such as a silicon source such as silane, and oxygen such as molecular oxygen and ozone) using a plasma enhanced chemical vapor deposition (PECVD) process. Due to the inherent characteristics of the plasma enhanced oxide, when the trench 510 is filled, the thickness of the first mask layer 520 located on the top sidewall of the trench 510 is greater than that of the first mask material layer 521 located on the bottom sidewall of the trench, so that the trench 510 can be partially sealed first, so that the opening of the trench 510 is significantly reduced.
[0063] In step S422, if Figure 5C As shown, a portion of the first mask material layer 521 is etched away so that the minimum opening of the groove 510 is located below the surface of the substrate 500, thereby ensuring that the sealing of the opening of the groove 510 can be maintained during subsequent processes; optionally, the first mask material layer 521 can be etched by any suitable etching method, for example, a portion of the first mask material layer 521 is etched away by a blanket etching process, and the etching can be isotropic etching. Optionally, a blanket etching process can be performed by plasma etching, for example, the first mask material layer 521 is bombarded with plasma to achieve the purpose of removing a portion of the first mask material layer 521, and the plasma can be formed by ionizing a rare gas such as argon or helium. Optionally, a comprehensive etching process can be used to form a basically truncated cone-shaped inner groove that is narrow at the bottom and wide at the top above the opening of the groove 510, and the bottom of the inner groove is also the minimum opening of the groove 510, which is located below the surface of the substrate 500. In this way, it is convenient to seal the opening of the groove 510 later.
[0064] In step S423, if Figure 5D 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 .
[0065] The second mask material layer 522 may be deposited by any suitable deposition method, such as physical vapor deposition, chemical vapor deposition or 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 pressure chemical vapor deposition (SACVD) using an oxygen source and tetraethyl orthosilicate (TEOS) as raw materials, that is, SACVD TEOS oxide. Usually, the density of the oxide is relatively low, so 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 trench 510 can also be better sealed.
[0066] The trench 510 is only partially filled by the first mask material layer 521 and the second mask material layer 522, so that the trench 510 can form a filling cavity 511. Optionally, the filling cavity 511 is located below the surface of the substrate 500, for example, at least 0.5 μm below the surface of the substrate 500.
[0067] Optionally, the thickness of the first mask layer 520 on the surface of the substrate 500 is less than 1.5 μm, or may be any other suitable thickness, and the first mask layer 520 on the surface of the substrate 500 is used as a mask for subsequently etching the substrate 500 to form first comb teeth.
[0068] In step S424, if Figure 5E and Fig. 5F As shown, a third mask material layer 523 is formed on the second mask material layer 522 , and planarization is performed to form the first mask layer 520 , wherein the third mask material layer 523 has a higher density than the second mask material layer 522 .
[0069] The second mask material layer 522 can be formed by depositing by 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, TEOS and O2 can be used as raw material gases to deposit a PETEOS oxide layer by PECVD, and its component is usually SiO2.
[0070] Optionally, the third mask material layer 523 has a higher density than 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.
[0071] like Fig. 5FAs shown, in order to obtain the first mask layer 520 with a flat surface, the third mask material layer 523 can be flattened, for example, a portion of the third mask material layer 523 can be removed by etching or chemical mechanical polishing. Since the bottom of the third mask material layer 523 at the groove 510 is lower than the top surface of the second mask material layer 522, the flattening can be stopped at the third mask material layer 523, and the third mask material layer 523 is retained at the groove 510. Finally, 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.
[0072] It is worth mentioning that for grooves 510 of different sizes, the first mask layer 520 can be formed through different process steps. For example, for a groove 510 of a larger size, 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 groove 510.
[0073] Next, in step S430, Figure 5G As shown, the first mask layer 520 is patterned to expose a portion of the surface of the substrate 500 and define the position and size of the first comb teeth 550 to be formed.
[0074] The first mask layer 520 may be patterned by any suitable method, for example, a photoresist layer may be formed on the first mask layer 520, and then the photoresist layer may 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 may be etched using the patterned photoresist layer as a mask to achieve patterning of the first mask layer 520, and then the photoresist layer may 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 channel between adjacent first comb teeth 550. Moreover, at the position of the groove 510, the first mask layer 520 still keeps the opening of the capping groove 510.
[0075] Part of the substrate 500 outside the groove 510 can be used to make the first comb teeth 550. Specifically, the number of grooves 510 can be reasonably set according to the number of first comb teeth 550 to be made and the number of second comb teeth 560 to be made subsequently.
[0076] It should be noted that, for the convenience of illustration, Figure 5GAfterwards, the first mask layer 520 is shown with the same filling pattern, but this is intended to limit the number of layers of the first mask layer 520 , and the filling cavity 511 is also shown with a blank rectangle, but this is not intended to limit the shape of the filling cavity 511 .
[0077] Next, in step S440, Figure 5H As shown, an epitaxial layer 530 is formed on the surface of the substrate 500 and the first mask layer 520 .
[0078] The material of the epitaxial layer 530 is a semiconductor material, which can be Si, SiB, SiGe, SiC, SiP, SiGeB, SiCP, AsGa or other III-V binary or ternary compounds. In this embodiment, the material of the epitaxial layer 530 is Si.
[0079] The epitaxial layer 530 may be formed using 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).
[0080] Optionally, the epitaxial layer 530 can be used to subsequently fabricate the second comb teeth, ie, the top comb tooth structure, and its thickness can depend on the size of the second comb teeth to be fabricated, which is not specifically limited here. Exemplarily, the thickness of the epitaxial layer 530 can range from 20 μm to 30 μm.
[0081] By forming an epitaxial layer 530 on the surface of the substrate 500 and the first mask layer 520, the epitaxial layer 530 is used to prepare the second comb teeth. Compared with the related technology of traditional use of SOI wafers, the present application reduces the use of SOI wafers, so its cost is lower, and the stress of the thin film layer structure can be regulated during the formation of the epitaxial layer 530, and the regulation method is simpler.
[0082] Next, in step S450, Fig.5I As shown, a patterned second mask layer 540 is formed on the epitaxial layer 530 , and the second mask layer 540 defines the positions and sizes of the second comb teeth to be formed, and the position of each second comb tooth corresponds to a groove 510 .
[0083] The material of the second mask layer 540 can be 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 multi-layer film structure.
[0084] The second mask layer 540 may be formed by deposition using any suitable deposition process such as chemical vapor deposition, physical vapor deposition or atomic layer deposition. The thickness of the second mask layer 540 may be reasonably set according to actual needs and is not specifically limited herein.
[0085] The second mask layer 540 can be patterned by 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 a photolithography process to define the position and size of the predetermined second comb teeth 560, and then the second mask layer 540 is etched with the patterned photoresist layer as a mask, and stops in the epitaxial layer 530 to achieve the patterning of the second mask layer 540, and then the photoresist layer is removed. In addition to the defined position, the second mask layer 540 also defines the position and size of the channel between adjacent second comb teeth. Among them, the patterned second mask layer 540 corresponds to the position of the groove 510, that is, the position of each second comb tooth is respectively located on a groove 510. Through such an arrangement, after the second comb teeth are formed, the bottom of each second comb tooth can be connected to a part of the first mask layer (the part of the first mask layer constitutes a supporting structure), and the part of the first mask layer can play a supporting role for the second comb teeth.
[0086] Next, in step S460, Figure 5J As shown, the second mask layer 540 and the first mask layer 520 are used as masks to etch the epitaxial layer 530 and the substrate 500 to form the second comb teeth 560 and the first comb teeth 550 , wherein the first comb teeth 550 and the second comb teeth 560 are staggered.
[0087] For example, the second mask layer 540 may be used as a mask to firstly etch the epitaxial layer 530 to form the second comb teeth 560, exposing the first mask layer 520 outside the second comb teeth 560, and then the first mask layer 520 may be used as a mask to etch the substrate 500 to form the first comb teeth 550. The number of the first comb teeth 550 and the number of the second comb teeth 560 may both be multiple, and the specific number may be reasonably set according to actual needs.
[0088] The second comb teeth 560 are also the top comb teeth structure, which are movable comb teeth, and the first comb teeth 550 are also the bottom comb teeth structure, which are fixed comb teeth.
[0089] The epitaxial layer 530 and the substrate 500 may be etched by dry etching, wet etching or any other suitable etching method, for example, the epitaxial layer 530 and the substrate 500 may be etched by deep reactive ion etching (DRIE).
[0090] Deep reactive ion etching is a process that uses high-energy ions and free radicals generated by plasma to etch silicon. It can achieve the requirements of 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 includes 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 sidewalls and bottom of the etched area to prevent the sidewalls from being etched. In the etching step, a sulfur-containing gas (such as SF6) is used to etch silicon, and the protective film at the bottom is removed at the same time, so that the etched area extends downward. In this way, through repeated deposition and etching cycles, etching of deeper openings or grooves or channels between comb teeth can be achieved.
[0091] After etching, the bottom ends of the second comb teeth 560 are respectively connected to part of the first mask layer 520, and the first mask layer 520 can support the second comb teeth 560, thereby making the structure of the device more stable, so as to facilitate subsequent process steps, such as wet cleaning.
[0092] Since etching residues, such as polymer residues, are easily generated during the etching process of the epitaxial layer 530 and the substrate 500, if not removed, the polymer residues may exist on the surface of the comb teeth and affect the device performance. Therefore, in some embodiments, the manufacturing method of the present application also includes: after forming the first comb teeth 550 and the second comb teeth 560, before removing the second mask layer 540 and the first mask layer 520, wet cleaning is performed to remove the etching residues, wherein during the cleaning process, the first mask layer 520 supports the second comb teeth 560, and the supporting effect of the first mask layer 520 under the second comb teeth 560 can make the second comb teeth 560 more stable during wet cleaning, which is beneficial to effectively remove the etching residues through wet cleaning, thereby improving the device yield and performance.
[0093] It is worth mentioning that a 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 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 also be larger than the size of the groove 510 in the first direction, so 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 also be smaller than the size of the groove 510 in the first direction, so after etching, in the first direction, the size of the first mask layer 520 under each second comb tooth 560 is larger than the size of the corresponding second comb tooth 560. In either case, it can play a supporting role for the second comb teeth 560.
[0094] Next, in step S470, Figure 5K As shown, at least the first mask layer 520 located under the second comb teeth 560 is removed.
[0095] The first mask layer 520 under the second comb teeth 560 is removed to release the second comb teeth 560 to make them movable comb teeth.
[0096] In some examples, continue to refer to Figure 5K , 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 simultaneously.
[0097] The first mask layer 520 and the second mask layer 540 may be removed by a suitable method selected according to their materials. For example, the first mask layer 520 and the second mask layer 540 may be removed by using a buffered oxide etchant or gaseous hydrogen fluoride (VHF).
[0098] 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: 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. Hexafluorosilicic acid reacts with 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 exhausted from the reaction chamber to achieve etching removal of the first mask layer 520 and the second mask layer 540.
[0099] It is worth mentioning that the MEME device in the present application can be any MEMS device that needs to form an interlaced comb-tooth structure. The above method of the present application is only used as an example and is not strictly limited in sequence. Under the premise of no contradiction, it can be performed alternately or in reverse order.
[0100] The description of some steps of the method of the present application has been completed so far. Other steps may be included to form a complete device, which will not be repeated here.
[0101] The manufacturing method of the MEMS device provided in the present application has the following beneficial effects: by forming an epitaxial layer on the surface of the substrate and the first mask layer, the epitaxial layer is used to prepare the second comb teeth. Compared with the related technology of traditional use of SOI wafers, the present application reduces the use of SOI wafers, so its cost is lower, and the stress of the thin film layer structure can be regulated during the formation of the epitaxial layer, and the regulation method is simpler. The position of each second comb tooth of the present application corresponds to a groove, and the groove is filled with the first mask layer. Then, after the first comb teeth and the second comb teeth are formed, the first mask under the second comb teeth can be used to support them, thereby improving the stability of the structure, so as to carry out subsequent process steps and make the process more stable.
[0102] The present application also provides a MEMS device, which can be manufactured by the above-mentioned method for manufacturing a MEMS device. The MEMS device can be an optoelectronic device such as a MEM mirror drive device (also called a MEMS galvanometer), a pressure sensor, an acceleration sensor or an inertial sensor.
[0103] The MEMS device of the present application is prepared by the aforementioned method, and therefore has substantially the same advantages as the aforementioned method.
[0104] The present application has been described through the above-mentioned embodiments, but it should be understood that the above-mentioned 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. In addition, it can be understood by those skilled in the art that the present application is not limited to the above-mentioned embodiments, and more variations and modifications can be made according to the teachings of the present application, and these variations and modifications all fall within the scope of protection claimed by the present application. The scope of protection of the present application is defined by the attached claims and their equivalents.
Claims
1. A method for manufacturing a MEMS device, characterized in that: The following steps are involved: Providing a substrate, and forming a plurality of grooves spaced apart from each other in the substrate; forming a first mask layer to cover the sidewalls of the trench, the surface of the substrate and seal the opening of the trench; Patterning the first mask layer to expose a portion of the surface of the substrate and define the position and size of the first comb teeth to be formed; forming an epitaxial layer on the surface of the substrate and the first mask layer; Forming a patterned second mask layer on the epitaxial layer, wherein the second mask layer defines the positions and sizes of second comb teeth to be formed, and each of the second comb teeth is located on a corresponding groove; Using the second mask layer and the first mask layer as masks, etching the epitaxial layer and the substrate to form the second comb teeth and the first comb teeth, wherein the first comb teeth and the second comb teeth are staggered; At least the first mask layer located below the second comb teeth is removed.
2. The manufacturing method according to claim 1, characterized in that A filling cavity is also formed in the first mask layer located in the trench, wherein the top of the filling cavity is located below the surface of the substrate.
3. The manufacturing method according to claim 2, characterized in that: The forming of a first mask layer to cover the sidewalls of the trench, the surface of the substrate and seal the opening of the trench comprises: forming a first mask material layer on the sidewall of the trench and the surface of the substrate, wherein the thickness of the first mask material layer on the top sidewall of the trench is greater than that of the first mask material layer on the bottom sidewall of the trench; Etching and removing a portion of the first mask material layer so that the minimum opening of the trench is located below the surface of the substrate; forming a second mask material layer on the first mask material layer, wherein the second mask material layer seals the opening of the trench; A third mask material layer is formed on the second mask material layer, and planarization is performed to form the first mask layer, wherein the third mask material layer has higher density than the second mask material layer.
4. The manufacturing method according to claim 3, characterized in that: The etching removes part of the first mask material layer so that the minimum opening of the trench is located below the surface of the substrate, including: A portion of the first mask material layer is removed by etching through a full etching process.
5. The manufacturing method according to claim 4, characterized in that: The etching and removing part of the first mask material layer by a full etching process includes: The first mask material layer is bombarded with plasma to remove a portion of the first mask material layer.
6. The manufacturing method according to claim 3, characterized in that: The material of the first mask material layer includes plasma enhanced oxide, the material of the second mask material layer includes oxide formed by sub-atmospheric pressure chemical vapor deposition using oxygen source and tetraethyl orthosilicate as raw materials, and the material of the third mask material layer includes PE TEOS oxide.
7. The manufacturing method according to claim 1, characterized in that: After forming the first comb teeth and the second comb teeth and before removing the first mask layer, the manufacturing method further includes: Wet cleaning is performed to remove etching residues caused by the etching, wherein during the cleaning process, the first mask layer supports the second comb teeth.
8. The manufacturing method according to claim 1, characterized in that: The method further comprises: The second mask layer is removed while a portion of the first mask layer is removed.
9. The manufacturing method according to claim 1, characterized in that: 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 groove is greater than or equal to 3 and less than or equal to 60.
10. A MEMS device, characterized in that: The MEMS device is manufactured by the manufacturing method according to any one of claims 1 to 9.