Cavity structure and forming method thereof
By adding reinforcing ribs at the corners of the cavity structure, the structure at stress concentration points is altered, increasing the strength of the cavity structure and solving the problem of easy breakage of the cavity structure, thus achieving an increase in the strength of the cavity structure.
Patent Information
- Application Number
- CN202511265596.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-05
- Publication Date
- 2025-12-12
AI Technical Summary
In the prior art, the cavity structure of MEMS microphones is prone to performance degradation due to breakage during high reliability verification, while the back cavity structure is prone to breakage during post-processing or mechanical reliability verification.
By adding reinforcing ribs at the corners of the cavity structure, the structure at stress concentration points is altered, increasing the strength of the cavity structure and thus its overall strength.
By adding reinforcing ribs at the corners of the cavity structure, the structure at stress concentration points is altered, increasing the strength of the cavity structure and solving the problem of easy breakage of the cavity structure.
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Figure CN121107350A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of semiconductor, in particular to a cavity structure and a forming method thereof. BACKGROUND
[0002] With the increasing demand for audio performance in consumer electronics, Internet of Things and wearable devices, the design of micro-electro-mechanical system (MEMS) microphones faces the continuous challenge of balancing between high performance and high reliability. Among them, increasing the size of the back cavity has become a key technology path to improve the acoustic performance of the device. Increasing the volume of the back cavity is usually beneficial to improve the acoustic performance such as low frequency response and sensitivity. However, for MEMS microphones with a large back cavity, during post-processing or mechanical reliability verification (such as drop test), or during use, the product is prone to failure due to rupture of the back cavity. SUMMARY
[0003] The purpose of the present application is to provide a cavity structure and a forming method thereof to solve the problem that the cavity of a product with a cavity structure is prone to rupture.
[0004] To solve the above problems, the present application provides a forming method of a cavity structure, comprising:
[0005] providing a substrate;
[0006] forming a sacrificial layer on the substrate;
[0007] etching the sacrificial layer to form a groove structure, the position of the groove structure corresponding to the top profile position of the cavity unit to be formed;
[0008] filling the groove structure with a reinforcing rib material to form a reinforcing rib;
[0009] etching the sacrificial layer to etch out the cavity unit;
[0010] forming a cavity material layer covering the cavity unit and the reinforcing rib; and
[0011] releasing the cavity unit to form a cavity.
[0012] Optionally, in the forming method of the cavity structure, the material of the reinforcing rib is silicon nitride or polycrystalline silicon, and the material of the sacrificial layer is silicon oxide.
[0013] Optionally, the reinforcing rib is made of the same material as the cavity material layer.
[0014] Optionally, in the forming method of the cavity structure, the width of the reinforcing rib is 2-8 μm.
[0015] Optionally, in the method for forming the cavity structure, the thickness of the reinforcing rib is 0.5-1 μm.
[0016] Optionally, in the method for forming the cavity structure, the profile shape of the reinforcing rib is a closed rectangle, a ring or a polygon.
[0017] Optionally, in the method for forming the cavity structure, the reinforcing rib comprises a plurality of reinforcing rib units spaced from each other, and the combined profile shape of all the reinforcing rib units is an open rectangle, a ring or a polygon.
[0018] Optionally, in the method for forming the cavity structure, the longitudinal section of the reinforcing rib is in the shape of a rectangle, a triangle or a zigzag line.
[0019] Optionally, in the method for forming the cavity structure, the right angle of the reinforcing rib is in line with the corner of the cavity material layer.
[0020] The present application also provides a cavity structure formed by the method as described in any one of the preceding embodiments.
[0021] In summary, the method for forming a cavity structure provided by the present application comprises the following steps: providing a substrate; forming a sacrificial layer on the substrate; etching the sacrificial layer to form a groove structure, the position of the groove structure corresponding to the position of the top profile of the cavity unit to be formed; filling the groove structure with a reinforcing rib material to form a reinforcing rib; etching the sacrificial layer to etch out the cavity unit; forming a cavity material layer covering the cavity unit and the reinforcing rib; and releasing the cavity unit to form a cavity. The method provided by the present application changes the structure at the stress concentration position by arranging a reinforcing rib at the corner of the cavity structure, increases the strength at the stress concentration position, and thus increases the strength of the cavity structure. BRIEF DESCRIPTION OF DRAWINGS
[0022] Figure 1 A schematic diagram of the stress concentration position of a cavity structure;
[0023] Figure 2 A flow chart of the method for forming a cavity structure provided by an embodiment of the present application;
[0024] Figures 3-9 A schematic diagram of the structure corresponding to each step in the method for forming a cavity structure provided by the present application; Figure 2 Figure 10 A schematic diagram of the groove structure in an embodiment of the present application, in which the shape of the groove structure is a closed figure; Figure 11 A schematic diagram of the groove structure in an embodiment of the present application, in which the shape of the groove structure is an intermittent figure; Figure 12 A schematic view of a longitudinal section shape of a groove structure in an embodiment of the present application.
[0025] In the various drawings:
[0026] 100 - corner of a cavity structure;
[0027] 11 - substrate; 12 - sacrificial layer; 13 - groove structure; 14 - reinforcing rib; 15 - cavity unit; 16 - cavity material layer; 17 - release hole; 18 - cavity. DETAILED DESCRIPTION
[0028] It has been found through research that the reason why a product with a large cavity structure is prone to breakage of the cavity structure is mainly because, as shown in FIG. 1, the corner 100 of the cavity structure (the intersection of the top wall and the side wall of the cavity) is prone to stress concentration. Figure 1
[0029] In view of this, the present application provides a cavity structure and a forming method thereof, which changes the structure of the stress concentration place by arranging a reinforcing rib at the corner of the cavity structure, increases the strength of the stress concentration place, and thus increases the strength of the cavity structure.
[0030] The cavity structure and the forming method thereof proposed by the present application will be described in further detail below in conjunction with the drawings and specific embodiments. It should be noted that the drawings are all very simplified and use non-precise scales, and are only used to facilitate and clarify the purpose of assisting in the description of the embodiments of the present application. In addition, the structures shown in the drawings are often only a part of the actual structures. In particular, the emphasis of each drawing needs to be different, and sometimes different scales are used. It should be recognized that relative terms such as "above", "below", "top", "bottom" and the like shown in the drawings can be used to describe the relationship between various elements. These relative terms are intended to cover different orientations of the elements in addition to the orientation depicted in the drawings. For example, if the device is inverted with respect to the view in the drawing, an element described as "above" another element would now be below that element.
[0031] As shown in FIG. 2, an embodiment of the present application provides a cavity structure, which comprises a substrate 11, a sacrificial layer 12, a groove structure 13, a reinforcing rib 14, a cavity unit 15, a cavity material layer 16, a release hole 17, and a cavity 18. Figure 2 As shown in FIG. 2, an embodiment of the present application provides a cavity structure, which comprises a substrate 11, a sacrificial layer 12, a groove structure 13, a reinforcing rib 14, a cavity unit 15, a cavity material layer 16, a release hole 17, and a cavity 18.
[0032] S1, providing a substrate and forming a sacrificial layer on the substrate;
[0033] S2, etching the sacrificial layer to form a groove structure, the position of the groove structure corresponding to the position of the top profile of a cavity unit to be formed;
[0034] S3, filling the groove structure with a reinforcing rib material to form a reinforcing rib;
[0035] S4, the sacrificial layer is etched to etch out the cavity unit;
[0036] S5, forming a cavity material layer, the cavity material layer covering the cavity unit and the reinforcing rib;
[0037] S6, release the cavity unit to form a cavity.
[0038] The method provided in this embodiment of the invention increases the strength of the cavity structure by setting reinforcing ribs at the corners of the cavity structure, changing the structure at stress concentration points, and increasing the strength at stress concentration points.
[0039] The following combination Figures 3-9 The method for forming the cavity structure provided in this embodiment will be further described.
[0040] First, such as Figure 3 As shown, step S1 is performed, a substrate 11 is provided, and a sacrificial layer 12 is formed on the substrate 11.
[0041] The sacrificial layer 12 is used to form a cavity structure by subsequent release, which is the cavity described in this embodiment. In addition, the cavity structure also includes a cavity wall, which is the cavity material layer described in this embodiment.
[0042] As an example, in this embodiment, the substrate 11 is a silicon substrate, and the material of the sacrificial layer 12 is silicon oxide.
[0043] Secondly, such as Figure 4 As shown, step S2 is performed to etch the sacrificial layer 12 to form a groove structure 13, the position of which corresponds to the top contour position of the cavity unit to be formed. Combined with... Figure 7 or Figure 8 Understandably, the cavity unit 15 is formed by etching the sacrificial layer 12. The cavity unit 15 defines the formation location of the cavity structure, and the cavity of the cavity structure is obtained after the cavity unit 15 is released.
[0044] Since the shape of a cavity structure can generally be rectangular, annular, or polygonal, therefore, such as Figure 10 As shown, the shape of the groove structure 13 is correspondingly set as a closed rectangle, ring, or polygon, or as... Figure 11 As shown, the groove structure 13 is intermittently arranged and is rectangular, circular or polygonal in shape.
[0045] Optional, such as Figure 12 As shown, the longitudinal section of the groove structure 13 is rectangular, triangular, or polygonal.
[0046] Next, as Figure 6As shown, step S3 is performed to fill the groove structure 13 with the reinforcing rib material to form the reinforcing rib 14.
[0047] Specifically, the method can comprise: Figure 5 As shown, the reinforcing rib material 141 is deposited to fill the groove structure 13 and extend to the surface of the sacrificial layer 12; and Figure 5 As shown, the reinforcing rib material 141 on the surface of the sacrificial layer 12 is removed by a grinding process.
[0048] Preferably, the reinforcing rib is made of the same material as the cavity material layer formed in the subsequent step, so that the reinforcing rib and the surrounding cavity wall are a continuous and complete whole without physical interface, providing optimal mechanical strength and stress transfer, and the stress can be smoothly transferred from the cavity wall to the reinforcing rib without being concentrated at the interface. Alternatively, the material of the reinforcing rib 14 is made of silicon nitride or polysilicon, etc. which has a large etching selectivity with silicon oxide, so that the reinforcing rib 14 can be preserved when the sacrificial layer 12 is etched subsequently.
[0049] In some other embodiments, when the material of the sacrificial layer 12 changes with the material of the substrate 11, the material of the reinforcing rib 14 can also be adjusted, as long as the material of the sacrificial layer 12 has a large etching selectivity with the material of the reinforcing rib 14.
[0050] When the shape of the groove structure 13 is a closed rectangle, a ring or a polygon, the profile shape of the reinforcing rib 14 is correspondingly a closed rectangle, a ring or a polygon; when the groove structure 13 is arranged discontinuously and the overall shape is a rectangle, a ring or a polygon, the reinforcing rib 14 comprises a plurality of reinforcing rib units spaced from each other, and the combined profile shape of all the reinforcing rib units is a non-closed rectangle, a ring or a polygon.
[0051] Alternatively, when the longitudinal section of the groove structure 13 is a rectangle, a triangle or a broken line, the longitudinal section of the reinforcing rib 14 is correspondingly a rectangle, a triangle or a broken line. With such a structure design, the reinforcing rib 14 has a right angle which fits the corner of the cavity material layer, thereby effectively increasing the structural strength at the stress concentration point.
[0052] When the reinforcing rib 14 comprises a plurality of reinforcing rib units spaced from each other, preferably, the gap width between the reinforcing rib units is comparable to or slightly larger than the width of the reinforcing rib units, to ensure that the stress can be effectively dispersed by the reinforcing rib 14, rather than being concentrated again at the end of the reinforcing rib units.
[0053] If the width of the reinforcing rib 14 is too large, it will significantly reduce the effective area or volume of the cavity, affecting performance (such as reducing the acoustic compliance of the MEMS microphone). If the width is too small, it will not provide sufficient reinforcement and may be difficult to achieve in terms of manufacturing process. Since the width of the cavity structure is usually in the range of tens to hundreds of micrometers, in this embodiment, it is preferred that the width of the reinforcing rib 14 is 2μm to 8μm, that is, the groove width of the groove structure 13 is preferably 2μm to 8μm.
[0054] The thickness of the reinforcing rib 14 directly affects its bending stiffness. The greater the thickness, the higher the strength, but it will also increase the stiffness and mass of the overall structure, which may affect the performance of movable parts such as the diaphragm above the cavity. In combination with the usual height setting of the cavity structure, in the embodiment, the thickness of the reinforcing rib 14 is preferably 0.5μm to 1μm, that is, the groove depth of the groove structure 13 is preferably 0.5μm to 1μm.
[0055] In practical applications, the dimensions of the reinforcing rib 14 can be determined through simulation based on the target dimensions of the cavity structure.
[0056] Then, as Figure 7 As shown, step S4 is performed to etch the sacrificial layer 12 to create the cavity unit 15. Through this etching, the remaining sacrificial layer 12 defines the cavity location of the cavity structure. When there are two or more cavity structures, this etching also separates the different cavity structures.
[0057] After that, as Figure 8 As shown, step S5 is performed to form a cavity material layer 16, which covers the cavity unit 15 and the reinforcing rib 14. The cavity material layer 16 constitutes the cavity wall of the cavity structure.
[0058] The cavity material layer 16 is made of the same material as the reinforcing rib 14. When the reinforcing rib 14 is made of silicon nitride or polycrystalline silicon, the cavity material layer 16 is also made of silicon nitride or polycrystalline silicon.
[0059] Finally, as Figure 9 As shown, step S6 is executed to release the cavity unit 15 to form a cavity.
[0060] Specifically, a release hole 17 is formed by etching the cavity material layer 16, and then the cavity unit 15 (i.e. the remaining sacrificial layer 12) is released and removed through the release hole 17. Specifically, the release can be carried out by BOE (buffered oxide etchant) wet process or VHF (vapor phase hydrofluoric acid) process, which will not be elaborated here.
[0061] After the cavity unit 15 is released, the corresponding position thereof constitutes a cavity of the cavity structure, and the cavity material layer 16 remaining constitutes a cavity wall of the cavity structure.
[0062] In addition, the embodiment of the present application further provides a cavity structure formed by the forming method of the cavity structure provided by the embodiment. As an example, the cavity structure can be applied to a back cavity in a MEMS microphone device.
[0063] In summary, the forming method of the cavity structure provided by the embodiment of the present application comprises: providing a substrate; forming a sacrificial layer on the substrate; etching the sacrificial layer to form a groove structure, the position of the groove structure corresponding to the position of the top profile of a cavity unit to be formed; filling the groove structure with a reinforcing rib material to form a reinforcing rib; etching the sacrificial layer to etch out the cavity unit; forming a cavity material layer covering the cavity unit and the reinforcing rib; and releasing the cavity unit to form a cavity. The method provided by the present application changes the structure at the stress concentration by arranging a reinforcing rib at the corner of the cavity structure, increases the strength at the stress concentration, and thus increases the strength of the cavity structure.
[0064] It should be noted that although the present application has been disclosed with the preferred embodiments as above, the above embodiments are not intended to limit the present application. For any skilled person in the art, many possible changes and modifications, or equivalent embodiments of equivalent changes can be made to the technical solutions of the present application by using the disclosed technical contents without departing from the scope of the technical solutions of the present application. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, without departing from the content of the technical solutions of the present application, still belongs to the protection scope of the technical solutions of the present application.
Claims
1. A method for forming a cavity structure, characterized in that, include: Provide substrate; A sacrificial layer is formed on the substrate; The sacrificial layer is etched to form a groove structure, the position of which corresponds to the top contour position of the cavity unit to be formed; The groove structure is filled with reinforcing material to form reinforcing ribs; The sacrificial layer is etched to create the cavity unit; A cavity material layer is formed, which covers the cavity unit and the reinforcing rib; as well as, Release the cavity unit to form a cavity.
2. The method for forming a cavity structure as described in claim 1, characterized in that, The sacrificial layer is made of silicon oxide, and the reinforcing ribs are made of silicon nitride or polycrystalline silicon.
3. The method for forming a cavity structure as described in claim 1 or 2, characterized in that, The reinforcing ribs are made of the same material as the cavity material layer.
4. The method for forming a cavity structure as described in claim 1, characterized in that, The width of the reinforcing rib is 2μm to 8μm.
5. The method for forming a cavity structure as described in claim 1, characterized in that, The thickness of the reinforcing rib is 0.5 μm to 1 μm.
6. The method for forming a cavity structure as described in claim 1, characterized in that, The reinforcing rib has a closed rectangular, ring-shaped, or polygonal outline.
7. The method for forming a cavity structure as described in claim 1, characterized in that, The reinforcing rib comprises multiple spaced-apart reinforcing rib units, and the combined outline shape of all the reinforcing rib units is a non-closed rectangle, ring, or polygon.
8. The method for forming a cavity structure as described in claim 1, characterized in that, The longitudinal section of the reinforcing rib is rectangular, triangular, or polygonal.
9. The method for forming a cavity structure as described in claim 8, characterized in that, The right angle of the reinforcing rib fits into the corner of the cavity material layer.
10. A cavity structure, characterized in that, The cavity structure is formed using the method described in any one of claims 1 to 9.