Mask, MEMS acoustic device and method for manufacturing the same

Abstract

The application provides a mask, a MEMS acoustic device and a preparation method thereof, and relates to the technical field of semiconductor processing. The mask comprises at least one photoetching area and a non-photoetching area wrapping the at least one photoetching area, one of the photoetching area and the non-photoetching area is transparent, and the other is not transparent, the photoetching area is alternately divided into a wide area and a narrow area along the length direction of the photoetching area, a transition area is between the wide area and the narrow area, the minimum width of the wide area is greater than the minimum processing size of an etching device, the maximum width of the narrow area is less than the minimum processing size of the etching device, and the total length of the multiple narrow areas is less than 20% of the length of the photoetching area. The width of the photoetching area of the mask changes, and even if the partial area of the vibrating diaphragm is not etched through, the vibrating diaphragm will be pulled off due to the tension between the diaphragms during etching. Therefore, the mask can more easily process a slit with a minimum width less than the minimum processing size of the etching device on the vibrating diaphragm, and can ensure that the vibrating diaphragm is etched through completely.

Description

Technical Field

[0001] This application relates to the field of semiconductor processing technology, and more specifically, to a photomask, a MEMS acoustic device, and a method for fabricating the same. Background Technology

[0002] Piezoelectric MEMS (Micro-Electro-Mechanical System) acoustic sensors are miniature sensors obtained by etching piezoelectric materials. Using a vibrating thin film as the core structural element, they can transmit and receive various acoustic signals. In recent years, MEMS acoustic devices manufactured using MEMS technology have been increasingly widely used in devices such as smartphones.

[0003] In the actual fabrication of MEMS acoustic devices, it is often required that the front and back portions of the vibrating thin film be slit apart. However, the size of this slit, which completely separates the front and back portions, depends entirely on the minimum processing size of the etching equipment. For example, if the minimum processing size of the etching equipment is 'a', then areas in the mask layer with a slit pattern width less than 'a' will not be etched. Sometimes, even areas with a slit pattern width equal to 'a' may not be completely etched apart.

[0004] However, in MEMS acoustic devices, the diaphragm being slit open at both ends within a very small size is crucial, as it effectively reduces acoustic short circuits at low frequencies. Therefore, when designing the slit pattern, designers should aim for a smaller slit width, but it cannot be smaller than the minimum processing size of the etching equipment; otherwise, if the diaphragm cannot be etched through, scrap will result. Furthermore, the entire design and process flow will need to be revised, leading to significant waste. Summary of the Invention

[0005] The purpose of this application is to address the shortcomings of the prior art by providing a mask, a MEMS acoustic device, and a method for fabricating the same, which can process slits with a minimum width smaller than the minimum processing size of the etching equipment on the vibrating thin film, and can ensure complete etching through the vibrating thin film, with relatively low process difficulty.

[0006] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows:

[0007] A first aspect of this application provides a photomask, comprising: at least one photolithographic region and a non-photolithographic region surrounding the at least one photolithographic region, wherein one of the photolithographic region and the non-photolithographic region is light-transmitting and the other is opaque, the photolithographic region is alternately divided into wide regions and narrow regions along the length direction of the photolithographic region, and there is a transition region between the wide regions and the narrow regions, wherein the minimum width of the wide region is greater than the minimum processing size of the etching equipment, the maximum width of the narrow region is less than the minimum processing size of the etching equipment, and the total length of the multiple narrow regions does not exceed 20% of the length of the photolithographic region.

[0008] Optionally, the maximum width of the wide area is less than 120% of the minimum processing size of the etching equipment, and the minimum width of the narrow area is greater than 80% of the minimum processing size of the etching equipment.

[0009] Optionally, the edges connecting the transition zone and the wide zone are of equal width, the edges connecting the transition zone and the narrow zone are of equal width, and the sides of the wide zone, the transition zone, and the narrow zone are all smooth sides without sharp corners.

[0010] Optionally, the cross-sections of the wide and narrow regions parallel to the length direction of the photolithography area are rectangular, and the longitudinal cross-sections of the wide, narrow, and transition regions perpendicular to the length direction of the photolithography area are rectangular.

[0011] Optionally, the cross-section of the transition region parallel to the length direction of the photolithography region is trapezoidal, or the side of the transition region is a spline surface, or the side of the transition region is connected to the side of the wide region by an arc, or the side of the transition region is connected to the side of the narrow region by an arc.

[0012] Optionally, the photomask has at least one through slot, which is a photolithography area.

[0013] A second aspect of this application provides a method for fabricating a MEMS acoustic device, using a photomask as described in any of the above claims. The method includes: placing the photomask above a vibrating thin film coated with photoresist and aligning it according to a preset position so that the photolithographic area on the photomask corresponds to the area on the vibrating thin film where slits need to be etched; exposing the photoresist on the side of the photomask away from the vibrating thin film and developing the exposed photoresist to obtain a photoresist layer with etch holes; removing the photomask and restarting the etching equipment to etch the vibrating thin film along the etch holes to etch through the lower surface of the vibrating thin film; and removing the photoresist layer.

[0014] Optionally, the upper surface of the vibrating film is provided with a groove, the depth of which is less than the thickness of the vibrating film; placing the mask above the vibrating film coated with photoresist and aligning it according to a preset position so that the photolithographic area on the mask corresponds to the area on the vibrating film where the slits need to be etched includes: placing the mask above the vibrating film coated with photoresist and aligning it according to a preset position so that the photolithographic area on the mask corresponds to the bottom of the groove.

[0015] Optionally, the depth of the groove is 30%-70% of the thickness of the vibrating diaphragm.

[0016] A third aspect of the embodiments of this application provides a MEMS acoustic device, which is prepared by the fabrication method of any of the above-mentioned MEMS acoustic devices.

[0017] The beneficial effects of this application include:

[0018] This application provides a photomask, comprising: at least one photolithographic region and a non-photolithographic region surrounding the at least one photolithographic region. One of the photolithographic region and the non-photolithographic region is transparent, while the other is opaque. The photolithographic region is alternately divided into wide and narrow regions along its length, with transition regions between the wide and narrow regions. The minimum width of the wide region is greater than the minimum processing size of the etching equipment, and the maximum width of the narrow region is less than the minimum processing size of the etching equipment. The total length of the multiple narrow regions does not exceed 20% of the length of the photolithographic region. The width of the photolithographic region on this photomask varies, and there are three regions with widths greater than, equal to, and less than the minimum processing size of the etching equipment. The area of ​​the region with a width less than the minimum processing size of the etching equipment is relatively small. Thus, during mask etching of a vibrating film, even if some areas of the vibrating film are not etched through, they will be broken due to the tension between the films, forming a slit penetrating the upper and lower surfaces of the vibrating film. Therefore, this photomask can process slits with a minimum width less than the minimum processing size of the etching equipment on the vibrating film, ensuring complete etching through the vibrating film, and with relatively low process difficulty. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is one of the structural schematic diagrams of the mask provided in the embodiments of this application;

[0021] Figure 2 for Figure 1 A magnified view of a portion of point A in the middle;

[0022] Figure 3 This is a schematic diagram of etching a vibrating thin film using the mask provided in this embodiment;

[0023] Figure 4 This is a schematic diagram of the structure of the MEMS acoustic device provided in the embodiments of this application;

[0024] Figure 5 This is the second schematic diagram of the structure of the mask provided in the embodiments of this application;

[0025] Figure 6 This is one of the flowcharts for a method of fabricating a MEMS acoustic device provided in an embodiment of this application;

[0026] Figure 7 A second flowchart illustrating the fabrication method of the MEMS acoustic device provided in the embodiments of this application;

[0027] Figure 8 This is a schematic diagram of the structure of an existing photomask;

[0028] Figure 9 This is a schematic diagram of etching a vibrating thin film using an existing photomask.

[0029] Icons: 10 - Existing photomask; 11 - Conventional photolithography area; 12 - Conventional non-photolithography area; 20 - Photomask; 21 - Photolithography area; 211 - Wide area; 212 - Narrow area; 213 - Transition area; 22 - Non-photolithography area; 30 - Vibrating film; 31 - Groove; 32 - Slit; 40 - Conventional photoresist layer; 41 - Conventional etched hole; 50 - Photoresist layer; 51 - Etched hole; 60 - MEMS acoustic device. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0031] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. It should be noted that, unless otherwise specified, the various features in the embodiments of this application can be combined with each other, and the combined embodiments are still within the protection scope of this application.

[0032] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0033] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0034] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0035] The first aspect of the embodiments of this application is referred to. Figure 1 and Figure 2 A photomask 20 is provided, comprising: at least one photolithographic region 21 and a non-photolithographic region 22 surrounding the at least one photolithographic region 21. One of the photolithographic region 21 and the non-photolithographic region 22 is transparent to light, while the other is opaque. Wide regions 211 and narrow regions 212 are alternately divided along the length of the photolithographic region 21, with a transition region 213 between the wide regions 211 and the narrow regions 212. That is, the photolithographic region 21 is divided into three types of regions: wide regions 211, transition regions 213, and narrow regions 212, with multiple wide regions 211, transition regions 213, and narrow regions 212. Along the length of the photolithographic region 21, the wide regions 211, transition regions 213, and narrow regions 212 are periodically distributed, i.e., wide region 211-transition region 213-narrow region 212-transition region 213-wide region 211-transition region 213-narrow region 212-transition region 213…

[0036] The lithography region 21 is a lithography region with varying width. The minimum width of the wide region 211 is greater than the minimum processing size of the etching equipment, and the maximum width of the narrow region 212 is less than the minimum processing size of the etching equipment. The total length of the multiple narrow regions 212 does not exceed 20% of the length of the lithography region 21. It can be understood that there must be a point in the transition region 213 whose width is exactly equal to the minimum processing size of the etching equipment.

[0037] Please refer to the reference. Figure 3During mask etching, the mask 20 is placed above the vibrating film 30 coated with photoresist and aligned according to a preset position, so that the photolithographic area 21 of the mask 20 is aligned with the area on the vibrating film 30 where the slits 32 need to be etched. The photoresist above the vibrating film 30 is exposed on the side of the mask 20 away from the vibrating film 30. After exposure, the photoresist below the photolithographic area 21 is in a soluble state, while the photoresist below the non-photolithographic area 22 is in a solidified state. After development, the photoresist below the non-photolithographic area 22 forms a photoresist layer 50 covering the vibrating film 30, and the photoresist below the photolithographic area 21 is dissolved and removed, forming etching holes 51 on the photoresist layer 50. Since the minimum width of the wide area 211 is greater than the minimum processing size of the etching equipment, and the maximum width of the narrow area 212 is less than the minimum processing size of the etching equipment, the width of the etched hole 51 varies. Some areas have a width greater than the minimum processing size of the etching equipment, some areas have a width equal to the minimum processing size of the etching equipment, and some areas have a width less than the minimum processing size of the etching equipment.

[0038] When the vibrating film 30 is etched using an etching device, the vibrating film 30 located below the area on the etching hole 51 whose width is greater than the minimum processing size of the etching device will definitely be etched through, and the vibrating film 30 located below the area on the etching hole 51 whose width is equal to the minimum processing size of the etching device may be etched through. Since the total length of the multiple narrow regions 212 does not exceed 20% of the length of the photolithography region 21, the area of ​​the vibrating film 30 not etched by the etching device is relatively small. When the vibrating film 30 has been etched through a large area, the tension between the films will completely break the area not etched by the etching device. That is to say, the vibrating film 30 is actually completely broken, but geometrically speaking, the width of the slit 32 in the area not etched by the etching device can be considered 0. Therefore, please refer to the reference... Figure 4 This ensures that a slit 32 with a minimum width smaller than the minimum processing size of the etching equipment can be processed on the vibrating film 30, while also ensuring that the vibrating film 30 is completely etched through. Moreover, the process is relatively simple and easy to implement.

[0039] The width of the photolithographic region 21 on the aforementioned mask varies, encompassing three regions: those with widths greater than, equal to, and less than the minimum processing size of the etching equipment. The area of ​​the region with a width less than the minimum processing size of the etching equipment is relatively small. Therefore, during the secondary mask etching of the vibrating film 30, even if some areas of the vibrating film 30 are not etched through, they will be pulled apart due to the tension between the films, thus forming a slit 32 penetrating the upper and lower surfaces of the vibrating film 30. Therefore, the aforementioned mask assembly can process slits 32 with a minimum width less than the minimum processing size of the etching equipment on the vibrating film 30, while ensuring complete etching through the vibrating film 30, and the process difficulty is relatively low.

[0040] Please refer to Figure 1 and Figure 3 Whether the photolithographic area 21 of the mask 20 is transparent or opaque depends on the properties of the photoresist used during mask etching. If the photoresist used during mask etching is a positive photoresist, then the photolithographic area 21 is transparent. In this case, if... Figure 1 As shown, the photomask 20 can be an opaque thin plate, the photolithographic area 21 is a through-groove formed on the photomask 20, and the non-photolithographic area 22 is the remaining opaque thin plate. If the photoresist used during photomask etching is a negative photoresist, then the photolithographic area 21 is opaque. In this case, please refer to... Figure 5 The photolithography area 21 can be an opaque elongated thin plate, and the non-photolithography area 22 can be a hollowed-out area around the opaque elongated thin plate.

[0041] Alternatively, please refer to Figure 1 and Figure 2 The maximum width of the wide area 211 on the mask 20 is less than 120% of the minimum processing size of the etching equipment, and the minimum width of the narrow area 212 is greater than 80% of the minimum processing size of the etching equipment.

[0042] The widths of both the wide region 211 and the narrow region 212 can vary, but the minimum width of the wide region 211 must be greater than the minimum processing size of the etching equipment, and the maximum width must be less than 120% of the minimum processing size of the etching equipment. The maximum width of the narrow region 212 must be less than the minimum processing size of the etching equipment, and the minimum width must be greater than 80% of the minimum processing size of the etching equipment. This configuration makes it easier to obtain the slit 32 that penetrates the upper and lower surfaces of the vibrating film 30.

[0043] Optionally, the edges connecting the transition area 213 and the wide area 211 are of equal width, the edges connecting the transition area 213 and the narrow area 212 are of equal width, and the sides of the wide area 211, the transition area 213, and the narrow area 212 are all smooth sides without sharp corners.

[0044] The width of the edge connecting the transition region 213 to the wide region 211 is equal to the width of the edge connecting the wide region 211 to the transition region 213, and the width of the edge connecting the transition region 213 to the narrow region 212 is equal to the width of the edge connecting the narrow region 212 to the transition region 213. Furthermore, by setting the sides of the wide region 211, the transition region 213, and the narrow region 212 to smooth sides without sharp corners, the width of the photolithography region 21 can be made to gradually change, ensuring that there are no areas with abrupt width changes on the photolithography region 21. This facilitates the automatic breakage of the vibrating thin film 30 under tension.

[0045] Optionally, the cross-sections of the wide region 211 and the narrow region 212 parallel to the length direction of the photolithography region 21 are both rectangular, and the longitudinal cross-sections of the wide region 211, the narrow region 212 and the transition region 213 perpendicular to the length direction of the photolithography region 21 are rectangular.

[0046] Figure 2 The image shows the shape of the cross-section of the photolithographic region 21. Figure 4 The image shows the shape of the longitudinal section of the photolithography area 21. This design makes the photomask 20 easier to process and reduces its processing cost.

[0047] Optionally, the cross-section of the transition region 213 parallel to the length direction of the photolithography region 21 is trapezoidal. This allows the width of the second photolithography region 21 to gradually change, achieving a smooth transition between the wide region 211 and the narrow region 212, while also facilitating processing.

[0048] Optionally, the side of the transition region 213 is a spline surface, or the side of the transition region 213 is connected to the side of the wide region 211 by an arc, and the side of the transition region 213 is connected to the side of the narrow region by an arc. In this way, a smooth transition between the wide region 211 and the narrow region 212 can also be achieved.

[0049] The second aspect of the embodiments of this application is referred to. Figure 1 and Figure 6 A method for fabricating a MEMS acoustic device is provided, using the mask 20 as described above.

[0050] Methods for fabricating MEMS acoustic devices include:

[0051] S100: Place the photomask above the vibrating film coated with photoresist and align it according to the preset position so that the photolithographic area on the photomask corresponds to the area on the vibrating film where the slits need to be etched.

[0052] Please refer to the reference. Figure 3 A photomask 20 is provided, wherein the photomask 20 is divided into at least one photolithographic region 21 and a non-photolithographic region 22 surrounding the at least one photolithographic region 21. One of the photolithographic region 21 and the non-photolithographic region 22 is transparent and the other is opaque. The photolithographic region 21 is alternately divided into wide regions 211 and narrow regions 212 along the length direction of the photolithographic region 21. There is a transition region 213 between the wide regions 211 and the narrow regions 212. The minimum width of the wide region 211 is greater than the minimum processing size of the etching equipment, and the maximum width of the narrow region 212 is less than the minimum processing size of the etching equipment. The total length of the multiple narrow regions 212 does not exceed 20% of the length of the photolithographic region 21. The photomask 20 is placed in a preset position, at which time the photolithographic region 21 on the photomask 20 corresponds to the area on the vibrating film 30 where the slits 32 need to be etched. S200: The photoresist is exposed on the side of the photomask away from the vibrating film, and the exposed photoresist is developed to obtain a photoresist layer with etched holes.

[0053] A light beam is used to irradiate the photoresist on the side of the photomask 20 opposite to the vibrating film 30. Part of the beam is blocked by the photolithographic area 21 or the non-photolithographic area 22 as it passes through the photomask 20, thus making the photoresist below the photolithographic area 21 soluble and the photoresist below the non-photolithographic area 22 solidified. This completes the photoresist exposure process. Whether the photolithographic area 21 is transparent or opaque depends on the properties of the photoresist, as described earlier.

[0054] The exposed photoresist is developed to remove the photoresist located below the photolithographic region 21, while retaining the photoresist located below the non-photolithographic region 22, thus forming a photoresist layer 50. The photoresist layer 50 has etched holes 51 that penetrate both the upper and lower surfaces of the photoresist layer 50. The etched holes 51 are obtained by transferring the pattern formed in the photolithographic region 21 onto the photoresist layer 50.

[0055] S300: Remove the mask and restart the etching equipment to etch the vibrating film along the etching holes to etch through the lower surface of the vibrating film.

[0056] After removing the mask 20, the etching equipment is started to etch the area exposed by the etching hole 51 on the vibrating film 30, thereby etching through the bottom of the vibrating film 30.

[0057] It should be noted that, because the minimum width of the wide area 211 on the mask 20 is greater than the minimum processing size of the etching equipment, and the maximum width of the narrow area 212 is less than the minimum processing size of the etching equipment, the width of the etching hole 51 varies. Some areas have a width greater than the minimum processing size of the etching equipment, some areas have a width equal to the minimum processing size of the etching equipment, and some areas have a width less than the minimum processing size of the etching equipment. When etching the vibrating film 30 using the etching hole 51, the vibrating film 30 located below the area on the etching hole 51 whose width is greater than the minimum processing size of the etching equipment will definitely be etched through, while the vibrating film 30 located below the area on the etching hole 51 whose width is equal to the minimum processing size of the etching equipment may be etched through. However, since the total length of the narrow area 212 on the mask 20 does not exceed 20% of the length of the photolithography area 21, most of the area of ​​the vibrating film 30 can be etched through by the etching equipment. The remaining area that is not etched through by the etching equipment is relatively small. When the vibrating film 30 has been etched through a large area, the tension between the films will completely break the area that has not been etched through by the etching equipment, thus forming a slit 32 that runs through the upper and lower surfaces of the vibrating film 30.

[0058] S400: Removes the photoresist layer.

[0059] Please refer to the reference. Figure 4By removing the photoresist layer 50, a vibrating thin film 30 is obtained that is penetrated by the slit 32 on the upper and lower surfaces, and the minimum width of the slit 32 is less than the minimum processing size of the etching equipment.

[0060] The aforementioned method for fabricating MEMS acoustic devices can create slits 32 on the vibrating film 30 with a minimum width smaller than the minimum processing size of the etching equipment, while ensuring complete etching through the vibrating film 30. Furthermore, the process is simple and easy to implement. The MEMS acoustic device 60 fabricated using this method has a slit 32 with a minimum width smaller than the minimum processing size of the etching equipment, resulting in a wider low-frequency response range and fewer acoustic short circuits at low frequencies.

[0061] Please refer to Figure 3 When the vibrating film 30 is relatively thick, in order to reduce the difficulty of etching and ensure that the etched slit 32 can penetrate the vibrating film 30, optionally, a groove 31 is provided on the upper surface of the vibrating film 30, the depth of the groove 31 being less than the thickness of the vibrating film 30. The position of the groove 31 corresponds to the position of the area on the vibrating film 30 where the slit 32 needs to be etched. The function of the groove 31 is to first thin the area on the vibrating film 30 where the slit 32 needs to be etched to a certain extent, thereby reducing the difficulty of etching through the vibrating film 30 when using the mask 20 for mask etching.

[0062] Please refer to the reference. Figure 7 The photomask is placed above the vibrating film coated with photoresist and aligned according to a preset position, so that the photolithographic area on the photomask corresponds to the area on the vibrating film where the slits need to be etched, including:

[0063] S110: Place the photomask above the vibrating film coated with photoresist and align it according to the preset position so that the photolithographic area on the photomask corresponds to the bottom of the groove.

[0064] In other words, when etching with mask 20, etching starts from the bottom of groove 31 and continues until the lower surface of vibrating film 30 is etched through.

[0065] Optionally, the depth of the groove 31 is 30%-70% of the thickness of the vibrating diaphragm 30.

[0066] Reducing the thickness of the area on the vibrating film 30 where the slits 32 need to be etched by 30%-70% can effectively reduce the difficulty of etching through the bottom of the vibrating film 30 when using mask 20 for etching. Generally speaking, the depth of the groove 31 is 50% of the thickness of the vibrating film 30.

[0067] Please refer to Figure 8 and Figure 9The groove 31 can be formed by mask etching, that is, by first etching the vibrating film 30 using the existing mask 10. Please refer to the reference. Figure 3 Then, the mask 20 provided in this embodiment is used for another etching.

[0068] The existing photomask 10 is divided into at least one conventional photolithography area 11 and a conventional non-photolithography area 12 surrounding the at least one conventional photolithography area 11. One of the conventional photolithography area 11 and the conventional non-photolithography area 12 is transparent, while the other is opaque. The minimum width of the conventional photolithography area 11 is greater than the minimum processing size of the etching equipment. Please refer to the reference. Figure 2 Compared to the photolithography area 21 on the mask 20 provided in this application embodiment, the conventional photolithography area 11 is significantly wider and does not have the periodic alternating distribution of wide area 211, narrow area 212 and transition area 213.

[0069] When performing mask etching using the existing mask 10, the existing mask 10 is placed above the vibrating thin film 30 coated with photoresist and aligned according to a preset position, so that the conventional photolithography area 11 of the existing mask 10 is aligned with the area on the vibrating thin film 30 where the slits 32 need to be etched. The photoresist above the vibrating thin film 30 is exposed on the side of the existing mask 10 away from the vibrating thin film 30. After exposure, the photoresist below the conventional photolithography area 11 is in a soluble state, while the photoresist below the conventional non-photolithography area 12 is in a solidified state. After development, the photoresist below the conventional non-photolithography area 12 forms a conventional photoresist layer 40 covering the vibrating thin film 30, and the photoresist below the conventional photolithography area 11 is dissolved and removed, forming conventional etched holes 41 on the conventional photoresist layer 40. Then, the vibrating thin film 30 is etched using an etching device to etch grooves 31 with the same width as the conventional etched holes 41 on the vibrating thin film 30.

[0070] Since the width of the slit 32 on the vibrating film 30 is determined by the size of the photolithography area 21, and the conventional photolithography area 11 is mainly used to thin the vibrating film 30, the minimum width of the conventional photolithography area 11 can optionally be at least twice the minimum processing size of the etching equipment. Setting the minimum width of the conventional photolithography area 11 to be larger can reduce the processing difficulty and achieve uniform etching of the vibrating film 30.

[0071] It should be understood that although the steps in the flowchart are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowchart may include multiple steps or stages, which are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps.

[0072] For a third aspect of the embodiments of this application, please refer to Figure 4 A MEMS acoustic device 60 is provided, which is prepared by any of the above methods for preparing MEMS acoustic devices.

[0073] The minimum width of the slit 32 on the MEMS acoustic device 60 is smaller than the minimum processing size of the etching equipment, resulting in a wider low-frequency response range and fewer acoustic short circuits at low frequencies.

[0074] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A mask, characterized in that, The mask plate comprises: at least one photoetching area and a non-photoetching area surrounding the at least one photoetching area, one of the photoetching area and the non-photoetching area is light-transmissive and the other is not light-transmissive, the photoetching area is alternately divided into wide areas and narrow areas along the length direction of the photoetching area, the wide areas and the narrow areas are separated by transition areas, the minimum width of the wide areas is greater than the minimum processing size of the etching equipment, the maximum width of the narrow areas is less than the minimum processing size of the etching equipment, and the total length of the narrow areas is less than 20% of the length of the photoetching area.

2. The mask of claim 1, wherein, The maximum width of the wide areas is less than 120% of the minimum processing size of the etching equipment, and the minimum width of the narrow areas is greater than 80% of the minimum processing size of the etching equipment.

3. The mask of claim 1, wherein, The edge width of the transition areas and the wide areas is equal, and the edge width of the transition areas and the narrow areas is equal, and the side surface of the wide areas, the transition areas and the narrow areas is a smooth side surface without sharp corners.

4. The mask of claim 3, wherein, The cross section of the wide areas and the narrow areas parallel to the length direction of the photoetching area is rectangular, and the longitudinal section of the wide areas, the transition areas and the narrow areas perpendicular to the length direction of the photoetching area is rectangular.

5. The mask of claim 4, wherein, The cross section of the transition areas parallel to the length direction of the photoetching area is trapezoidal, or the side surface of the transition areas is a spline surface, or the side surface of the transition areas is connected with the side surface of the wide areas in a circular arc, or the side surface of the transition areas is connected with the side surface of the narrow areas in a circular arc.

6. The mask of claim 1, wherein, The mask plate is provided with at least one through slot, and the through slot is the photoetching area.

7. A method for fabricating a MEMS acoustic device, characterized in that, The method for preparing the MEMS acoustic device by using the mask plate of any one of claims 1 to 6 comprises: placing the mask plate above the vibrating diaphragm coated with photoresist and aligning according to the preset position, so that the photoetching area on the mask plate corresponds to the area on the vibrating diaphragm where the slit needs to be etched; exposing the photoresist on the side of the mask plate away from the vibrating diaphragm, and developing the exposed photoresist to obtain a photoresist layer with etching holes; removing the mask plate, and starting the etching equipment again to etch the vibrating diaphragm along the etching holes to etch through the lower surface of the vibrating diaphragm; removing the photoresist layer.

8. The method of claim 7, wherein the MEMS acoustic device is a microphone. The upper surface of the vibrating diaphragm is provided with a groove, and the depth of the groove is less than the thickness of the vibrating diaphragm. The method for placing the mask plate above the vibrating diaphragm coated with photoresist and aligning according to the preset position, so that the photoetching area on the mask plate corresponds to the area on the vibrating diaphragm where the slit needs to be etched comprises: placing the mask plate above the vibrating diaphragm coated with photoresist and aligning according to the preset position, so that the photoetching area on the mask plate corresponds to the bottom of the groove.

9. The method of claim 8, wherein the MEMS acoustic device is a microphone. The depth of the groove is 30%-70% of the thickness of the vibrating diaphragm.

10. A MEMS acoustic device, characterized by, The MEMS acoustic device is prepared by using the method for preparing the MEMS acoustic device of any one of claims 7 to 9.

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