Mask, MEMS acoustic device and preparation method of MEMS acoustic device

Abstract

The invention provides a mask, an MEMS acoustic device and a preparation method of the MEMS acoustic device, 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 light-transmitting, the other one of the photoetching area and the non-photoetching area is light-proof, the photoetching area is alternately divided into wide areas and narrow areas along the length direction of the photoetching area, a transition area is arranged between the wide areas and the narrow areas, and the transition area is arranged between the wide areas and the narrow areas. The minimum width of the wide region is larger than the minimum machining size of etching equipment, the maximum width of the narrow region is smaller than the minimum machining size of the etching equipment, and the total length of the plurality of narrow regions does not exceed 20% of the length of the photoetching region. The width of the photoetching area of the mask plate is changed, and even if a part of area of a vibrating film is not etched through during etching, the vibrating film can be snapped due to tension between the films. Therefore, the mask plate can easily process the slit with the minimum width smaller than the minimum processing size of etching equipment on the vibration film, and can ensure that the vibration film is completely etched through.

Description

Technical Field

[0001] The present application relates to the field of semiconductor processing technologies, and more particularly, to a mask, a MEMS acoustic device, and a preparation method thereof. Background Art

[0002] A piezoelectric MEMS (Micro-Electro-Mechanical System) acoustic sensor is a micro sensor obtained by etching and processing a piezoelectric material. With a vibrating thin film as the core structural element, it can realize functions such as transmitting and receiving various acoustic wave signals. In recent years, in devices such as smart phones, MEMS acoustic devices manufactured using MEMS technology have been increasingly widely used.

[0003] In the actual process of preparing a MEMS acoustic device, it is often required that the front and back parts of the vibrating thin film be separated by a slit. However, the size of such a slit that is completely separated front and back 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 the area where the width of the slit pattern in the mask layer is less than a will not be etched, and even sometimes, the area where the width of the slit pattern is equal to a may not be completely etched through.

[0004] However, in a MEMS acoustic device, it is of great significance that the vibrating thin film is separated by a slit at a very small size front and back, which can effectively reduce the acoustic short-circuit phenomenon at low frequencies. Therefore, when designing the slit pattern, the smaller the width of the slit pattern, the better, but it cannot be less than the minimum processing size of the etching equipment. Otherwise, once the vibrating thin film cannot be etched through, waste wafers will be produced. Moreover, the entire design and process flow need to be corrected again, resulting in huge waste. Summary of the Invention

[0005] An object of the present application is to provide, in view of the above deficiencies in the prior art, a mask, a MEMS acoustic device, and a preparation method thereof, which can process a slit with a minimum width less than the minimum processing size of the etching equipment on the vibrating thin film, ensure complete etching through the vibrating thin film, and have a relatively low process difficulty.

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

[0007] In the first aspect of the embodiment of the present application, a mask is provided, including: at least one lithography area and a non-lithography area surrounding the at least one lithography area, one of the lithography area and the non-lithography area is light-transmitting and the other is light-impermeable. Along the length direction of the lithography area, the lithography area is alternately divided into wide areas and narrow areas, and 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 the etching equipment, the maximum width of the narrow area is less than the minimum processing size of the etching equipment, and the total length of the multiple narrow areas does not exceed 20% of the length of the lithography area.

[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 edge widths where the transition area is connected to the wide area are equal, the edge widths where the transition area is connected to the narrow area are equal, and the sides of the wide area, the transition area, and the narrow area are all smooth sides without sharp corners.

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

[0011] Optionally, the cross-section of the transition area parallel to the length direction of the lithography area is trapezoidal, or the side surface of the transition area is a spline surface, or the side surface of the transition area is arc-connected to the side surface of the wide area, and the side surface of the transition area is arc-connected to the side surface of the narrow area.

[0012] Optionally, at least one through groove is provided on the mask, and the through groove is a lithography area.

[0013] In the second aspect of the embodiment of the present application, a method for manufacturing a MEMS acoustic device is provided. Using the mask as described in any one of the above, the method for manufacturing a MEMS acoustic device includes: disposing the mask above the vibrating film coated with photoresist and aligning it at a preset position so that the lithography area on the mask corresponds to the area on the vibrating film where slits need to be etched; exposing the photoresist on the side of the mask facing away from the vibrating film, and developing the exposed photoresist to obtain a photoresist layer with etching holes; removing the mask, and starting the etching equipment again to etch the vibrating film along the etching holes to etch through the lower surface of the vibrating film; removing the photoresist layer.

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

[0016] In the third aspect of the embodiments of the present application, a MEMS acoustic device is provided, which is prepared by using the preparation method of the MEMS acoustic device according to any one of the above.

[0017] The beneficial effects of the present application include:

[0018] The present application provides a mask plate, including: at least one lithography area and a non-lithography area wrapping at least one lithography area, one of the lithography area and the non-lithography area is light-transmitting and the other is light-impermeable. Along the length direction of the lithography area on the lithography area, a wide area and a narrow area are alternately divided. 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 the etching equipment, the maximum width of the narrow area is less than the minimum processing size of the etching equipment, and the total length of multiple narrow areas does not exceed 20% of the length of the lithography area. The width of the lithography area on this mask plate changes, and there are three areas with widths greater than, equal to, and less than the minimum processing size of the etching equipment, and the area ratio of the area with a width less than the minimum processing size of the etching equipment is relatively small. In this way, when masking and etching the 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, thereby forming slits penetrating the upper and lower surfaces of the vibrating film. Therefore, this mask plate can process slits with a minimum width less than the minimum processing size of the etching equipment on the vibrating film, and can ensure complete etching through the vibrating film, and the process difficulty is relatively low. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation of the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0020] Figure 1 It is one of the structural schematic diagrams of the mask plate provided by the embodiments of the present application;

[0021] Figure 2 It is Figure 1 The partial enlarged schematic diagram at A in

[0022] Figure 3 It is a schematic diagram of etching a vibrating film by using the mask plate provided by this embodiment;

[0023] Figure 4 It is the structural schematic diagram of the MEMS acoustic device provided by the embodiments of the present application;

[0024] Figure 5 The second structural schematic diagram of the photomask provided by the embodiment of the present application;

[0025] Figure 6 The first flowchart of the preparation method of the MEMS acoustic device provided by the embodiment of the present application;

[0026] Figure 7 The second flowchart of the preparation method of the MEMS acoustic device provided by the embodiment of the present application;

[0027] Figure 8 The structural schematic diagram of the existing photomask;

[0028] Figure 9 The schematic diagram of etching the vibrating film using the existing photomask.

[0029] Icons: 10 - existing photomask; 11 - conventional lithography area; 12 - conventional non-lithography area; 20 - photomask; 21 - lithography area; 211 - wide area; 212 - narrow area; 213 - transition area; 22 - non-lithography area; 30 - vibrating film; 31 - groove; 32 - slit; 40 - conventional photoresist layer; 41 - conventional etching hole; 50 - photoresist layer; 51 - etching hole; 60 - MEMS acoustic device. Detailed implementation manners

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

[0031] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but merely represents the selected embodiments of the present application. It should be noted that, without conflict, the various features in the embodiments of the present application can be combined with each other, and the combined embodiments are still within the protection scope of the present application.

[0032] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0033] In the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of this application is usually placed when in use. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation to the present application. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0034] In the description of the present application, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "couple" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0035] In the first aspect of the embodiments of the present application, please refer to Figure 1 and Figure 2 , and a mask 20 is provided, including: at least one lithography area 21 and a non-lithography area 22 that wraps at least one lithography area 21. One of the lithography area 21 and the non-lithography area 22 is light-transmitting and the other is light-impermeable. The lithography area 21 is alternately divided into a wide area 211 and a narrow area 212 along the length direction of the lithography area 21, and a transition area 213 is between the wide area 211 and the narrow area 212. That is to say, there are three types of areas divided on the lithography area 21, namely the wide area 211, the transition area 213, and the narrow area 212, and the numbers of the wide area 211, the transition area 213, and the narrow area 212 are all multiple. Along the length direction of the lithography area 21, the wide area 211, the transition area 213, and the narrow area 212 are periodically distributed, that is, wide area 211 - transition area 213 - narrow area 212 - transition area 213 - wide area 211 - transition area 213 - narrow area 212 - transition area 213...

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

[0037] Please refer to in combination with Figure 3, during 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 lithography area 21 of the mask 20 is aligned with the area on the vibrating film 30 where the slit 32 needs to be etched. The photoresist above the vibrating film 30 is exposed on the side of the mask 20 facing away from the vibrating film 30. After exposure, the photoresist below the lithography area 21 is in a soluble state, and the photoresist below the non-lithography area 22 is in a cured state. After development, the photoresist below the non-lithography area 22 forms a photoresist layer 50 covering the vibrating film 30, and the photoresist below the lithography area 21 is dissolved and removed, forming an etching hole 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 etching hole 51 varies. The width of some areas is greater than the minimum processing size of the etching equipment, the width of some areas is equal to the minimum processing size of the etching equipment, and the width of some areas is less than the minimum processing size of the etching equipment.

[0038] When using an etching equipment to perform mask etching on the vibrating film 30, the vibrating film 30 below the area on the etching hole 51 with a width greater than the minimum processing size of the etching equipment will surely be etched through, and the vibrating film 30 below the area on the etching hole 51 with a width equal to the minimum processing size of the etching equipment may be etched through. Since the total length of multiple narrow areas 212 does not exceed 20% of the length of the lithography area 21, the area ratio of the unetched area on the vibrating film 30 by the etching equipment is relatively small. When the vibrating film 30 has been etched through in a large area, the tension between the films will completely break the unetched area by the etching equipment. That is to say, the vibrating film 30 has actually been completely broken, but geometrically, the width of the slit 32 in the unetched area by the etching equipment can be considered 0. Thus, please refer to Figure 4 , which not only ensures that a slit 32 with a minimum width less than the minimum processing size of the etching equipment can be processed on the vibrating film 30, but also ensures that the vibrating film 30 is completely etched through, and the process difficulty is relatively low and easy to implement.

[0039] The width of the lithography area 21 on the above mask varies, and there are three types of areas with widths greater than, equal to, and less than the minimum processing size of the etching equipment, and the area ratio of the area with a width less than the minimum processing size of the etching equipment is relatively small. Thus, 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 broken due to the tension between the films, thereby forming a slit 32 penetrating the upper and lower surfaces of the vibrating film 30. Therefore, the above mask assembly can process a slit 32 with a minimum width less than the minimum processing size of the etching equipment on the vibrating film 30, and can ensure that the vibrating film 30 is completely etched through, and the process difficulty is relatively low.

[0040] Please refer to Figure 1 and Figure 3 Whether the photolithography area 21 of the mask 20 is light-transmissive or not is related to the properties of the photoresist used during mask etching. If the photoresist used during mask etching is a positive photoresist, the photolithography area 21 is light-transmissive. At this time, as Figure 1 shown, the mask 20 can be an opaque thin plate, the photolithography area 21 is a through groove formed on the mask 20, and the non-photolithography area 22 is the remaining opaque thin plate. If the photoresist used during mask etching is a negative photoresist, the photolithography area 21 is opaque. At this time, please refer to Figure 5 , the photolithography area 21 can be an opaque strip-shaped thin plate, and the non-photolithography area 22 can be a hollowed-out area around the opaque strip-shaped thin plate.

[0041] Optionally, 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 dimension of the etching equipment, and the minimum width of the narrow area 212 is greater than 80% of the minimum processing dimension of the etching equipment.

[0042] The widths of the wide area 211 and the narrow area 212 can both vary, but the minimum width of the wide area 211 needs to be greater than the minimum processing dimension of the etching equipment, and the maximum width needs to be less than 120% of the minimum processing dimension of the etching equipment. The maximum width of the narrow area 212 needs to be less than the minimum processing dimension of the etching equipment, and the minimum width needs to be greater than 80% of the minimum processing dimension of the etching equipment. With such a setting, it is easier to obtain the slit 32 that penetrates the upper and lower surfaces of the vibrating film 30.

[0043] Optionally, the edge widths where the transition area 213 is connected to the wide area 211 are equal, the edge widths where the transition area 213 is connected to the narrow area 212 are equal, and the side surfaces of the wide area 211, the transition area 213, and the narrow area 212 are all smooth side surfaces without sharp corners.

[0044] The width of the edge of the transition area 213 connected to the wide area 211 is equal to the width of the edge of the wide area 211 connected to the transition area 213, and the width of the edge of the transition area 213 connected to the narrow area 212 is equal to the width of the edge of the narrow area 212 connected to the transition area 213. Then, by setting the side surfaces of the wide area 211, the transition area 213, and the narrow area 212 as smooth side surfaces without sharp corners, the width of the photolithography area 21 can be made to show a gradually changing state, ensuring that there is no area with a sudden change in width on the photolithography area 21. In this way, it helps the vibrating film 30 to automatically break under the action of tension.

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

[0046] Figure 2 What is shown is the shape of the cross-section of the photolithography area 21. Figure 4 What is shown is the shape of the longitudinal section of the photolithography area 21. With such a setting, the mask 20 can be more convenient to process, reducing the processing cost of the mask 20.

[0047] Optionally, the cross-section of the transition area 213 parallel to the length direction of the photolithography area 21 is trapezoidal. In this way, the width of the second photolithography area 21 can show a gradual change state, realizing a smooth transition between the wide area 211 and the narrow area 212, and it is also easy to process.

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

[0049] In the second aspect of the embodiments of the present application, please refer to Figure 1 and Figure 6 , and a method for manufacturing a MEMS acoustic device is provided, using the mask 20 as described in any one of the above.

[0050] The method for manufacturing a MEMS acoustic device includes:

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

[0052] Please refer to Figure 3 , and a mask 20 is provided. Among them, at least one photolithography area 21 and a non-photolithography area 22 wrapping at least one photolithography area 21 are defined on the mask 20. One of the photolithography area 21 and the non-photolithography area 22 is light-transmitting and the other is light-impermeable. Along the length direction of the photolithography area 21, a wide area 211 and a narrow area 212 are alternately defined on the photolithography area 21. A transition area 213 is provided between the wide area 211 and the narrow area 212. The minimum width of the wide area 211 is greater than the minimum processing dimension of the etching equipment, and the maximum width of the narrow area 212 is less than the minimum processing dimension of the etching equipment. The total length of multiple narrow areas 212 does not exceed 20% of the length of the photolithography area 21. Place the mask 20 at the preset position. At this time, the photolithography area 21 on the mask 20 corresponds to the area on the vibrating film 30 where slits 32 need to be etched. S200: Expose the photoresist on the side of the mask facing away from the vibrating film, and develop the exposed photoresist to obtain a photoresist layer with etching holes.

[0053] On one side of the photomask 20 away from the vibrating film 30, a light beam is used to irradiate the photoresist. Part of the light beam is blocked by the lithography area 21 or the non-lithography area 22 when passing through the photomask 20, so that the photoresist located below the lithography area 21 becomes soluble, and the photoresist below the non-lithography area 22 becomes solidified. Thus, the exposure operation of the photoresist is completed. Whether the lithography area 21 is light-transmitting or not is related to the properties of the photoresist, and relevant descriptions have been made in the previous text.

[0054] The exposed photoresist is developed to remove the photoresist located below the lithography area 21 and retain the photoresist located below the non-lithography area 22 to form a photoresist layer 50. The photoresist layer 50 has etching holes 51, and the etching holes 51 penetrate the upper and lower surfaces of the photoresist layer 50. The etching holes 51 are obtained by transferring the pattern formed by the lithography area 21 onto the photoresist layer 50.

[0055] S300: Remove the photomask, 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 photomask 20, start the etching equipment to etch the area of the vibrating film 30 exposed by the etching holes 51, so as to etch through the bottom of the vibrating film 30.

[0057] It should be noted that since the minimum width of the wide area 211 on the photomask 20 is greater than the minimum processing dimension of the etching equipment, and the maximum width of the narrow area 212 is less than the minimum processing dimension of the etching equipment, the width of the etching holes 51 varies. The width of some areas is greater than the minimum processing dimension of the etching equipment, the width of some areas is equal to the minimum processing dimension of the etching equipment, and the width of some areas is less than the minimum processing dimension of the etching equipment. When etching the vibrating film 30 using the etching holes 51, the vibrating film 30 below the area of the etching holes 51 with a width greater than the minimum processing dimension of the etching equipment will surely be etched through, and the vibrating film 30 below the area of the etching holes 51 with a width equal to the minimum processing dimension of the etching equipment may be etched through. However, because the total length of the narrow area 212 on the photomask 20 does not exceed 20% of the length of the lithography area 21, most of the area of the vibrating film 30 can be etched through by the etching equipment, and the area ratio of the remaining area not etched through by the etching equipment is relatively small. In the case where the vibrating film 30 has been etched through in a large area, the tension between the films will completely break the area not etched through by the etching equipment, thus forming a slit 32 that penetrates the upper and lower surfaces of the vibrating film 30.

[0058] S400: Remove the photoresist layer.

[0059] Please refer to Figure 4, by removing the photoresist layer 50, the vibrating film 30 with the slit 32 penetrating through the upper and lower surfaces can be obtained, and the minimum width of the slit 32 is less than the minimum processing dimension of the etching equipment.

[0060] The above preparation method of the MEMS acoustic device can process a slit 32 with a minimum width less than the minimum processing dimension of the etching equipment on the vibrating film 30, and can ensure that the vibrating film 30 is completely etched through, with low process difficulty and easy to implement. The minimum width of the slit 32 on the MEMS acoustic device 60 prepared by the above preparation method of the MEMS acoustic device is less than the minimum processing dimension of the etching equipment, having a wider low-frequency response range and less acoustic short-circuit phenomenon at low frequencies.

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

[0062] Please refer to in combination with Figure 7 , setting the mask plate above the vibrating film coated with photoresist and aligning it according to a preset position so that the photolithography area on the mask plate corresponds to the area on the vibrating film where the slit needs to be etched includes:

[0063] S110: Set the mask plate above the vibrating film coated with photoresist and align it according to a preset position so that the photolithography area on the mask plate corresponds to the bottom of the groove.

[0064] That is to say, when etching with the mask plate 20, start etching from the bottom of the groove 31 until the lower surface of the vibrating film 30 is etched through.

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

[0066] Thinning the thickness of the area on the vibrating film 30 where the slit 32 needs to be etched by 30%-70% can effectively reduce the difficulty of etching through the bottom of the vibrating film 30 when using the mask plate 20 for masked 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 9, the groove 31 can be formed by means of mask etching, that is, the existing mask 10 is first used to etch the vibrating film 30 once. Please refer to Figure 3 , and then the mask 20 provided in the embodiment of the present application is used for another etching.

[0068] At least one conventional photolithography area 11 and a conventional non-photolithography area 12 wrapping at least one conventional photolithography area 11 are defined on the existing mask 10. One of the conventional photolithography area 11 and the conventional non-photolithography area 12 is light-transmitting and the other is light-impermeable. The minimum width of the conventional photolithography area 11 is greater than the minimum processing dimension of the etching equipment. Please refer to Figure 2 , compared with the photolithography area 21 on the mask 20 provided in the embodiment of the present application, the width of the conventional photolithography area 11 is significantly larger, and there is no periodic alternation distribution of the wide area 211, the narrow area 212 and the transition area 213.

[0069] When mask etching is performed using the existing mask 10, the existing mask 10 is placed above the vibrating 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 film 30 where the slit 32 needs to be etched. The photoresist above the vibrating film 30 is exposed on the side of the existing mask 10 facing away from the vibrating film 30. After exposure, the photoresist under the conventional photolithography area 11 is in a soluble state, and the photoresist under the conventional non-photolithography area 12 is in a solidified state. After development, the photoresist under the conventional non-photolithography area 12 forms a conventional photoresist layer 40 covering the vibrating film 30, and the photoresist under the conventional photolithography area 11 is dissolved and removed, and conventional etching holes 41 are formed on the conventional photoresist layer 40. Then, the vibrating film 30 is etched using an etching device, and grooves 31 having the same width as the conventional etching holes 41 can be etched on the vibrating 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, optionally, the minimum width of the conventional photolithography area 11 is at least twice the minimum processing dimension 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 in the direction of the arrows, these steps are not necessarily executed sequentially in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, at least some of the steps in the flowchart may include multiple steps or multiple stages. These steps or stages are not necessarily executed 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 executed alternately or in rotation with at least some of the steps or stages in other steps or other steps.

[0072] In the third aspect of the embodiments of the present application, please refer to Figure 4 , a MEMS acoustic device 60 is provided, which is prepared by using the preparation method of the MEMS acoustic device according to any one of the above.

[0073] The minimum width of the slit 32 on the MEMS acoustic device 60 is less than the minimum processing size of the etching equipment, having a wider low-frequency response range and less acoustic short-circuit phenomenon at low frequencies.

[0074] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A mask, characterized in that: include: At least one photolithography area and a non-photolithography area wrapping at least one of the photolithography areas, one of the photolithography area and the non-photolithography area is light-transmissive and the other is opaque, the photolithography area is alternately divided into wide areas and narrow areas along the length direction of the photolithography 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 the etching equipment, the maximum width of the narrow area is less than the minimum processing size of the etching equipment, and the total length of the plurality of narrow areas does not exceed 20% of the length of the photolithography area.

2. The mask according to claim 1, characterized in that: The maximum width of the wide area is less than 120% of the minimum processing dimension of the etching device, and the minimum width of the narrow area is greater than 80% of the minimum processing dimension of the etching device.

3. The mask according to claim 1, wherein: The widths of the edges connecting the transition zone and the wide zone are equal, the widths of the edges connecting the transition zone and the narrow zone are equal, and the sides of the wide zone, the transition zone and the narrow zone are all smooth sides without sharp corners.

4. The mask according to claim 3, characterized in that: The cross sections of the wide area and the narrow area parallel to the length direction of the photolithography area are both rectangular, and the longitudinal sections of the wide area, the narrow area and the transition area perpendicular to the length direction of the photolithography area are rectangular.

5. The mask according to claim 4, characterized in that: The cross section of the transition zone parallel to the length direction of the lithography zone is trapezoidal, or the side of the transition zone is a spline surface, or the side of the transition zone is connected to the side arc of the wide zone, and the side of the transition zone is connected to the side arc of the narrow zone.

6. The mask according to claim 1, characterized in that: The mask plate is provided with at least one through groove, and the through groove is the photolithography area.

7. A method for preparing a MEMS acoustic device, characterized in that: Using the mask according to any one of claims 1 to 6, the method for preparing the MEMS acoustic device comprises: The mask is placed above the vibrating film coated with photoresist and aligned according to a preset position so that the photoetching area on the mask corresponds to the area on the vibrating film where the slit needs to be etched; Exposing the photoresist on the side of the mask away from the vibration film, and developing the exposed photoresist to obtain a photoresist layer with etching holes; Removing the mask, and starting the etching device again to etch the vibration film along the etching hole to etch through the lower surface of the vibration film; The photoresist layer is removed.

8. The method for preparing a MEMS acoustic device according to claim 7, characterized in that: The upper surface of the vibration film is provided with a groove, and the depth of the groove is less than the thickness of the vibration film; The step of placing the mask above the vibrating film coated with photoresist and aligning the mask according to a preset position so that the photoetching area on the mask corresponds to the area on the vibrating film where the slit needs to be etched comprises: The mask is arranged above the vibration film coated with photoresist and aligned according to a preset position so that the photoetching area on the mask corresponds to the bottom of the groove.

9. The method for preparing a MEMS acoustic device according to claim 8, characterized in that: The depth of the groove is 30%-70% of the thickness of the vibration film.

10. A MEMS acoustic device, characterized in that: The MEMS acoustic device is prepared by the method for preparing the MEMS acoustic device as described in any one of claims 7 to 9.

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