MEMS capacitor device and method of making the same

Abstract

The application provides a MEMS capacitor and a manufacturing method thereof, wherein a first isolation layer, a first electrode plate layer, a second isolation layer and a second electrode plate layer are sequentially formed on the upper surface of a substrate, the substrate has a first through hole, the first isolation layer has a second through hole above the first through hole and larger than the first through hole in radial dimension, the second through hole exposes a sharp corner formed by the side wall of the first through hole and the upper surface of the substrate, the first electrode plate layer is suspended on the second through hole, the second isolation layer exposes the middle area of the first electrode plate layer to form a cavity between the second electrode plate layer and the first electrode plate layer, at least one connecting column connecting the first electrode plate layer and the second electrode plate layer is arranged in the cavity, and the horizontal distance between the connecting column and the sharp corner is within a set range. In this way, when the first electrode plate layer vibrates downward, the connecting column provides an upward pulling force to the first electrode plate layer, and the probability of the first electrode plate layer touching the sharp corner can be reduced without affecting the performance of the MEMS capacitor.

Description

TECHNICAL FIELD

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

[0002] Micro-Electro-Mechanical System (MEMS) refers to a micro system that can integrate mechanical components, driving components, optical systems and electrical control systems into a whole. It uses a manufacturing process that combines microelectronic technology and microprocessing technology (such as silicon body microprocessing, silicon surface microprocessing, wafer bonding, etc.) to manufacture various sensors (such as inertial sensors, pressure sensors, acceleration sensors, etc.), actuators, drivers and micro systems with excellent performance, low price and miniaturization.

[0003] Figure 1 Fig. 1 is a structural schematic diagram of a MEMS capacitor device. As shown in Fig. 1, in the MEMS capacitor device, an upper surface of a substrate 101 is formed with a first isolation layer 102, the substrate 101 and the first isolation layer 102 are respectively formed with a first through hole 112 and a second through hole 113, a sharp corner of an edge of the first through hole 112 is exposed at a bottom of the second through hole 113, a part of a lower surface of a first electrode plate layer 103 is exposed from the first through hole 112, the first electrode plate layer 103 and a second electrode plate layer 108 have a cavity 114 located directly above the second through hole 113, a side wall of the cavity 114 is flush with a side wall of the second through hole 113, an edge of the first electrode plate layer 103 is fixed on the substrate 101, and an upper and lower surface of a middle part of the first electrode plate layer 103 is released by the second through hole 113 and the cavity 114, so as to be able to vibrate up and down. Figure 1 Figure 2 Figure 3 As shown in Figs. 2 and 3, it is found that in the process of vibrating up and down, the first electrode plate layer 103 is easy to touch the sharp corner of the edge of the first through hole 112 of the substrate 101, which causes the first electrode plate layer 103 to crack, thereby reducing the reliability of the MEMS capacitor device.

[0004] Figure 4 Fig. 4 is a structural schematic diagram of another MEMS capacitor device. As shown in Fig. 4, in the MEMS capacitor device, an edge part of the first electrode plate layer 103 is arranged in a spring structure (as shown in Figs. 5 and 6). Figure 4 Figure 4 As shown in Figs. 5 and 6, it is found that in the process of vibrating up and down, the first electrode plate layer 103 is not easy to touch the sharp corner of the edge of the first through hole 112 of the substrate 101, which reduces the possibility of the first electrode plate layer 103 cracking, thereby improving the reliability of the MEMS capacitor device.​​The spring structure is used to absorb deformation stress to avoid the first electrode plate layer 103 touching the sharp corner of the edge of the first through hole 112 when the deformation of the first electrode plate layer 103 is transmitted to the edge during the up-and-down vibration of the first electrode plate layer 103 on the first electrode plate layer 105. However, the MEMS capacitor device has the following defects: first, the rigidity of the position where the first electrode plate layer 103 is provided with the spring structure is weaker than the surrounding, resulting in uneven rigidity of the vibrating part of the first electrode plate layer 103; second, the spring structure is zigzag, and when the first electrode plate layer 103 vibrates up and down and deforms, stress will be concentrated at the zigzag position of the spring structure, which is easy to cause the spring structure to break from the zigzag position, resulting in a decrease in the reliability of the first electrode plate layer 103; and moreover, for the first electrode plate layer 103 with different thickness designs, the width and spacing of the spring structure also need to be adjusted, that is, different product requirements need different designs, which increases the development cost of the MEMS capacitor device.

[0005] In addition, the first isolation layer 102 is thickened to avoid the first electrode plate layer 103 touching the sharp corner of the edge of the first through hole 112, but still has the following defects: first, although the thickened first isolation layer 102 increases the distance between the first electrode plate layer 103 and the sharp corner of the edge of the first through hole 112, avoiding the problem of puncture, it will introduce stress problems, and the wafer is easy to warp during the device preparation process, and the first electrode plate layer 103 in the final device structure will also be affected by the thickened first isolation layer 102, thereby affecting the device performance. Second, the thickened first isolation layer 102 will limit the device performance. Specifically, since the first isolation layer 102 of the device for some applications needs to be prepared with a pattern, if the thickness of the first isolation layer 102 is increased, a higher step will be formed from the upper surface of the first isolation layer 102 to the upper surface of the substrate 101. The step will be conformal after the first electrode plate 103 is deposited and continue to exist, thereby limiting the minimum line width of the pattern on the first electrode plate 103, limiting the performance of the device, and even when the step is too large, the photoresist will produce a defect of poor coverage in the corner, thereby being unable to be compatible with the ordinary process. SUMMARY

[0006] The present application provides a MEMS capacitor device which can reduce the probability of electrode plate layer fracture and improve the reliability of the MEMS capacitor device without affecting the performance of the MEMS capacitor device. The present application also provides a manufacturing method of a MEMS capacitor device.

[0007] In order to achieve the above object, the application provides a MEMS capacitor device. The MEMS capacitor device comprises a substrate, a first isolation layer, a first electrode plate layer, a second isolation layer and a second electrode plate layer. The substrate has a first through hole; the first isolation layer is arranged on the upper surface of the substrate, the first isolation layer has a second through hole above the first through hole and with a radial dimension larger than that of the first through hole, the second through hole exposes the upper surface of the substrate connected with the sidewall of the first through hole, and the sidewall of the first through hole and the upper surface of the substrate exposed by the second through hole form an acute angle; the first electrode plate layer is suspended on the second through hole and has an edge on the first isolation layer; the second isolation layer is arranged on the first electrode plate layer, the second isolation layer exposes the middle area of the first electrode plate layer, and the second isolation layer and the exposed middle area of the first electrode plate layer respectively serve as the sidewall and bottom wall of a cavity above the second through hole; the second electrode plate layer is suspended on the cavity and has an edge on the second isolation layer; and at least one connecting column is arranged in the cavity, the two ends of the connecting column are connected with the second electrode plate layer and the first electrode plate layer respectively, and the lateral distance between the connecting column and the acute angle is within a set range.

[0008] Optionally, the at least one connecting column is a ring-shaped connecting column, and the central axis of the ring-shaped connecting column coincides with the central axis of the first through hole.

[0009] Optionally, the cavity is provided with two or more ring-shaped connecting columns with different radial dimensions.

[0010] Optionally, the cavity is provided with a plurality of connecting columns, and the plurality of connecting columns are dispersedly arranged in different radial directions of the cavity.

[0011] Optionally, the included angle between the connecting column and the first electrode plate layer and the second electrode plate layer is 90 degrees.

[0012] Optionally, the thickness of the connecting column ranges from 0.45 microns to 1.1 microns.

[0013] Optionally, the MEMS capacitor device further comprises a protective layer between the second electrode plate layer and the second isolation layer and covering the lower surface of the second electrode plate layer, and the connecting column is connected with the second electrode plate layer through the protective layer.

[0014] Optionally, the connecting column and the protective layer belong to the same deposition layer.

[0015] The application further provides a manufacturing method of the MEMS capacitor device, and the manufacturing method comprises the following steps.

[0016] A substrate is provided, and a first isolation layer, a first electrode plate layer and a second isolation layer are sequentially formed on a top surface of the substrate;

[0017] A groove is etched in the second isolation layer, and a bottom of the groove exposes a top surface of the first electrode plate layer;

[0018] The groove is filled to form a connecting column;

[0019] A second electrode plate layer is formed, and the second electrode plate layer covers top surfaces of the second isolation layer and the connecting column;

[0020] A first via hole and a second via hole located directly above the first via hole are formed in the substrate and the first isolation layer, respectively, and a cavity located directly above the second via hole is formed between the first electrode plate layer and the second electrode plate layer;

[0021] The second isolation layer exposes a top surface of a middle region of the first electrode plate layer, and the second isolation layer and the exposed top surface of the middle region of the first electrode plate layer serve as a side wall and a bottom wall of the cavity, respectively; the second via hole exposes a top surface of the substrate connected to a side wall of the first via hole, the side wall of the first via hole and the top surface of the substrate exposed by the second via hole form an acute angle, and a lateral distance between the connecting column and the acute angle is within a set range.

[0022] Optionally, the method for forming the first via hole and the second via hole in the substrate and the first isolation layer, respectively, and forming the cavity between the first electrode plate layer and the second electrode plate layer comprises:

[0023] A plurality of third via holes are etched in the second electrode plate layer and the protective layer, and the third via holes expose a top surface of the second isolation layer;

[0024] The first via hole is etched in the substrate to expose the first isolation layer; and

[0025] The first isolation layer is etched by using the first via hole to form the second via hole, and the second via hole exposes a bottom surface of a middle region of the first electrode plate layer; the second isolation layer is etched by using the plurality of third via holes to form the cavity.

[0026] In the MEMS capacitor device and its fabrication method of the present invention, the substrate has a first through hole, and the first insulating layer has a second through hole located directly above the first through hole and having a radial dimension larger than the first through hole. The second through hole exposes the upper surface of the substrate connected to the sidewall of the first through hole. The sidewall of the first through hole and the upper surface of the substrate exposed by the second through hole form a sharp angle. The second insulating layer is disposed on the first electrode layer and exposes the middle region of the first electrode layer. The second insulating layer and the middle region of the exposed first electrode layer respectively serve as the sidewall and bottom wall of a cavity. The second electrode layer is suspended on the cavity, that is, a cavity is formed between the first electrode layer and the second electrode layer. At least one connecting post is disposed in the cavity, and the two ends of the connecting post are respectively connected to the... The first electrode layer and the second electrode layer are connected, and the lateral distance between the connecting post and the sharp corner is within a set range. In this way, the middle area of ​​the first electrode layer released by the second through hole and the cavity can vibrate up and down. During the downward vibration of the first electrode layer, the connecting post provides an upward pulling force to the first electrode layer to limit the amplitude of the downward vibration of the first electrode layer. This reduces the probability of the first electrode layer touching the sharp corner without affecting the performance of the MEMS capacitor, which helps to reduce the probability of the first electrode layer breaking and improve the reliability of the MEMS capacitor. At the same time, it can avoid increasing the thickness of the first isolation layer, thereby avoiding the limitation on the performance of the MEMS capacitor and increasing the process compatibility of the MEMS capacitor. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a MEMS capacitor.

[0028] Figure 2 for Figure 1 A schematic diagram of the first electrode layer of the MEMS capacitor vibrating.

[0029] Figure 3 for Figure 2 A partial schematic diagram of the MEMS capacitor device is shown.

[0030] Figure 4 This is a schematic diagram of another type of MEMS capacitor.

[0031] Figure 5 This is a flowchart illustrating a method for fabricating a MEMS capacitor according to an embodiment of the present invention.

[0032] Figures 6 to 12 This is a cross-sectional schematic diagram of a MEMS capacitor device during the fabrication process according to an embodiment of the present invention.

[0033] Explanation of reference numerals in the attached figures:

[0034] 101 - substrate; 102 - first isolation layer; 103 - first electrode plate layer; 103a - electrode predetermined formation area; 104 - second electrode plate layer; 105 - groove; 106 - protective layer; 107 - connecting column; 108 - second electrode plate layer; 109 - third through hole; 110 - first electrode; 111 - second electrode; 112 - first through hole; 113 - second through hole; 114 - cavity. DETAILED DESCRIPTION

[0035] The MEMS capacitor device and the manufacturing method thereof according to the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present application will be more apparent from the following description. It should be noted that the accompanying drawings are very simplified and use non-precise proportions, which are only used to facilitate and clarify the purpose of assisting the description of the embodiments of the present application.

[0036] It should be understood that the specific embodiments described herein merely serve to explain the present application and do not limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of the present application. In addition, it should be understood that although the efforts made in the development process can be complex and lengthy, some modifications, such as design, manufacture or production, etc. based on the technical content disclosed in the present application, are only routine technical means for those of ordinary skill in the art related to the content disclosed in the present application, and should not be understood as insufficient disclosure of the content disclosed in the present application.

[0037] In the present application, the phrase "embodiment" means that the specific features, structures or characteristics described in conjunction with the embodiment can be included in at least one embodiment of the present application. The appearance of this phrase at various places in the specification does not necessarily mean the same embodiment, nor is it an independent or alternative embodiment to other embodiments. Those of ordinary skill in the art explicitly and implicitly understand that the embodiments described in the present application can be combined with other embodiments without conflict.

[0038] In order to improve the reliability of the MEMS capacitor device without affecting the performance of the MEMS capacitor device, the present embodiment provides a manufacturing method of a MEMS capacitor device. Figure 5 The flowchart of the manufacturing method of the MEMS capacitor device according to an embodiment of the present application is shown in FIG. 1. As shown in FIG. 1, the manufacturing method of the MEMS capacitor device comprises the following steps. Figure 5 The manufacturing method of the MEMS capacitor device comprises the following steps.

[0039] In step S1, a substrate is provided, and a first isolation layer, a first electrode plate layer and a second isolation layer are sequentially formed on the upper surface of the substrate;

[0040] Step S2: Etch the second isolation layer to form a groove, the bottom of the groove exposing the upper surface of the first electrode layer;

[0041] Step S3: Fill the groove to form a connecting column;

[0042] Step S4: Form a second electrode layer, which covers the second isolation layer and the upper surface of the connecting column;

[0043] Step S5: A first through hole and a second through hole located on the first through hole are formed in the substrate and the first isolation layer, respectively; and a cavity located directly above the second through hole is formed between the first electrode layer and the second electrode layer.

[0044] Wherein, the second isolation layer exposes the upper surface of the middle region of the first electrode layer, and the second isolation layer and the upper surface of the exposed middle region of the first electrode layer serve as the sidewall and bottom wall of the cavity, respectively; the second through hole exposes the upper surface of the substrate connected to the sidewall of the first through hole, and the sidewall of the first through hole forms a sharp angle with the upper surface of the substrate exposed by the second through hole, and the lateral distance between the connecting post and the sharp angle is within a set range.

[0045] Figures 6 to 12 This is a cross-sectional schematic diagram of the MEMS capacitor device of the present invention during the fabrication process. The following is in conjunction with... Figures 5 to 12 The fabrication method of the MEMS capacitor device in this embodiment will be described.

[0046] like Figure 6 As shown, a first isolation layer 102, a first electrode layer 103, and a second isolation layer 104 are sequentially stacked on the upper surface of the substrate 101 provided in step S1.

[0047] The substrate 101 may be a silicon substrate. However, it is not limited to this. The substrate 101 may also be a germanium substrate, a silicon-germanium substrate, silicon on insulator (SOI), or germanium on insulator (GOI), etc. The substrate 101 may also be implanted with certain dopants to change the electrical parameters according to design requirements.

[0048] Optionally, the materials of the first isolation layer 102 and the second isolation layer 104 are silicon oxide. The material of the first electrode layer 103 may include doped polycrystalline silicon, germanium silicon, germanium, other suitable metals or semiconductor materials, to ensure that the portion of the first electrode layer 103 subsequently released can vibrate and deform under the action of sound or inertial forces and can also return to its original shape, and to ensure that the first electrode layer 103 has good conductivity.

[0049] like Figure 7 As shown, in step S2, the second isolation layer 104 is etched to form a groove 105, the bottom of which exposes the upper surface of the first electrode layer 103. Specifically, a patterned first photoresist layer can be formed on the upper surface of the second isolation layer 104. Using the patterned first photoresist layer as a mask, the second isolation layer 104 is etched to form the groove 105, and then the first photoresist layer is removed.

[0050] In one embodiment of this application, the groove 105 may be an annular groove. Figure 8 The planar shape of the second isolation layer 104 after a groove 105 is formed is shown. For example... Figure 8 The second isolation layer 104 may form only one annular groove 105, and subsequently only one annular connecting post 107. Figure 9 The planar shape after two grooves 105 are formed in the second isolation layer 104 is shown. In another embodiment, in order to strengthen the connecting column 107 (see reference 105), Figure 10 The reliability of the connection between the first electrode layer 103 and the limiting effect of the reinforcing connecting column 107 on the amplitude of the first electrode layer 103, such as Figure 9 As shown, two annular grooves 105 can be formed in the second isolation layer 104, and two annular connecting posts 107 can be formed subsequently. The two grooves 105 can be concentric rings. However, this is not a limitation; multiple non-annular grooves 105 can be formed in the second isolation layer 104. These multiple non-annular grooves 105 can be distributed along a circumferential direction and all exposed above the upper surface of the first electrode layer 103. The number of grooves 105 formed in the second isolation layer 104 can be set according to the number of connecting posts to be formed, and the number of connecting posts can be specifically set according to the specific circumstances of the MEMS capacitor device.

[0051] It should be noted that, in this embodiment, as Figure 7 As shown, while etching the second isolation layer 104 to form the groove 105, the second isolation layer 104 on the electrode predetermined formation area 103a of the first electrode layer 103 can be removed, which facilitates the subsequent formation of the first electrode on the upper surface of the first electrode layer 103.

[0052] After step S2 is completed, step S3 is executed, as follows: Figure 10 As shown, the groove 105 is filled to form a connecting column 107.

[0053] Specifically, a protection layer 106 is formed on the second isolation layer 104, the protection layer 106 covers the upper surface of the second isolation layer 104 and fills the recess 105, the part of the protection layer 106 in the recess 105 is the connecting column 107, and the bottom surface of the connecting column 107 is connected with the upper surface of the first electrode plate layer 103. In this way, the protection layer 106 can cover the lower surface of the second electrode plate layer formed subsequently, and the connecting column 107 and the protection layer 106 belong to the same deposition layer, which helps to enhance the connection reliability of the connecting column 107 and the second electrode plate layer and improve the reliability of the MEMS capacitor.

[0054] In the embodiment, the material of the protection layer 106 can be silicon nitride. However, the material of the protection layer 106 can also be other materials which are not easy to be etched when the second isolation layer 104 is etched.

[0055] When the width of the recess 105 in the second isolation layer 104 is too large, the recess 105 is not easy to be filled, and when the width of the recess 105 is too small, holes are easy to appear in the recess 105 during the filling process. In order to make the recess 105 easy to be filled and not easy to have holes inside, in the embodiment, the width (for example, the lateral dimension of the recess 105) of the recess 105 can range from 0.45 microns to 1.1 microns. That is, the thickness (i.e. the wall thickness) of the connecting column 107 can range from 0.45 microns to 1.1 microns. Figure 10

[0056] Next, still referring to Figure 10 , step S4 is performed to form a second electrode plate layer 108 on the upper surface of the protection layer 106, and the second electrode plate layer 108 covers the upper surface of the protection layer 106. The material of the second electrode plate layer 108 can be doped polysilicon, germanium silicon or germanium, and can also be other metals such as aluminum or other doped semiconductor materials, or other materials known to those skilled in the art.

[0057] Then, as shown in Figures 10 to 12 , step S5 is performed to form a first through hole 112 in the substrate 101 and a second through hole 113 located directly above the first through hole 112 in the first isolation layer 102, and to form a cavity 114 located directly above the second through hole 113 between the first electrode plate layer 103 and the second electrode plate layer 108.

[0058] Specifically, the step S5 can include the following sub-steps S51-S53.

[0059] Sub-step S51: refer to Figure 10 ​etching the second plate layer 108 and the protection layer 106 to form a plurality of third through holes 109. Part of the third through holes 109 are located at the inner side of the connecting column 107 (the side of the connecting column 107 close to the center of the cavity 114), and part of the third through holes 109 are located at the outer side of the connecting column 107 (the side of the connecting column 107 far away from the center of the cavity 114). In this way, the cavity 114 can be formed by etching the second isolation layer 104 exposed by the third through holes 109.

[0060] Before forming the plurality of third through holes 109, the method for manufacturing the MEMS capacitor device can further include: forming a blocking layer on the substrate 101, the blocking layer covering at least the sidewalls of the first isolation layer 102 and the second isolation layer 104, so as to avoid the sidewalls of the first isolation layer 102 and the second isolation layer 104 from being etched by mistake during the formation of the second through holes 113 and the cavity 114. When the blocking layer covers the upper surface of the second plate layer 108, the plurality of third through holes 109 can penetrate the blocking layer.

[0061] When the plurality of third through holes 109 are etched, the protection layer 106, the second plate layer 108 and the blocking layer located on the electrode predetermined formation area 103a of the first plate layer 103 can be etched and removed, so as to form the first electrode on the upper surface of the first plate layer 103 and expose the upper surface of the second electrode predetermined formation area of the second plate layer 108.

[0062] After the plurality of third through holes 109 are etched, the sub-step S51 can further include: forming a patterned second photoresist layer on the substrate 101, the patterned second photoresist layer covering the plurality of third through holes 109 and exposing the electrode predetermined formation area 103a of the first plate layer 103 and part of the upper surface of the second plate layer 108 (for example, the upper surface of part of the edge area of the second plate layer 108); depositing an electrode material layer on the substrate 101; etching the electrode material layer to form the first electrode 110 on the upper surface of the electrode predetermined formation area 103a of the first plate layer 103 and the second electrode 111 on the upper surface of the second plate layer 108. The material of the electrode material layer can be gold (Au), silver (Ag) or aluminum (Al) or other metals or metal alloys.

[0063] After the first electrode 110 and the second electrode 111 are formed, the sub-step S52 is performed, as shown in Figure 11As shown, the first via hole 112 is formed by etching the substrate 101 to expose the lower surface of the middle region of the first isolation layer 102. Specifically, a patterned third photoresist layer is formed on the lower surface of the substrate 101, and the substrate 101 is etched from the lower surface to the upper surface of the substrate 101 with the patterned third photoresist layer as a mask to form the first via hole 112, and the lower surface of the middle region of the first isolation layer 102 is exposed from the first via hole 112.

[0064] After the first via hole 112 is formed, sub-step S53 is performed, as shown in Figure 12 As shown, the second via hole 113 is formed by etching the first isolation layer 102 exposed by the first via hole 112 with the first via hole 112, and the second via hole 113 exposes the lower surface of the middle region of the first electrode plate layer 103. The second via hole 113 exposes the upper surface of the substrate 101 connected to the sidewall of the first via hole 112, the sidewall of the first via hole 112 and the upper surface of the substrate 101 exposed by the second via hole 113 form an acute angle, and the lateral distance between the connecting column 107 and the acute angle is within a set range.

[0065] Sub-step S53 further includes etching the second isolation layer 104 exposed by the third via hole 109 with the plurality of third via holes 109 to form the cavity 114. The second isolation layer 104 exposes the upper surface of the middle region of the first electrode plate layer 103, and the second isolation layer 104 and the exposed upper surface of the middle region of the first electrode plate layer 103 respectively serve as the sidewall and the bottom wall of the cavity 114. After the second via hole 113 and the cavity 114 are formed, the blocking layer can also be removed. As shown in Figure 12 As shown, the connecting column 107 can be a ring-shaped connecting column, and the connecting column 107 can separate the cavity 114.

[0066] It should be noted that in the present embodiment, the second via hole 113 formed by etching the first isolation layer 102 with the first via hole 112 and the cavity 114 formed by etching the second isolation layer 104 with the plurality of third via holes 109 can be formed in the same process.

[0067] Specifically, the etchant used for etching the first isolation layer 102 and the second isolation layer 104 can include a buffered oxide etchant (BOE), a hydrofluoric acid solution, or vapor HF. The buffered oxide etchant can be formed by mixing HF and NH4F in different proportions. In step S53, the structure formed in step S52 is placed in a predetermined etchant, and the etchant etches the first isolation layer 102 and the second isolation layer 104 through the first via hole 112 and the plurality of third via holes 109 until the lower surface and the upper surface of the first electrode plate layer 103 are exposed.

[0068] It should be noted that, due to the inevitable side etching of the etchant when etching the first isolation layer 102 using the first via hole 112, the radial dimension of the second via hole 113 formed is inevitably larger than the radial dimension of the first via hole 112.

[0069] In this embodiment, the second via hole 113 and the cavity 114 release the lower surface and the upper surface of the middle region of the first electrode plate layer 103, so that the released middle region of the first electrode plate layer 103 can vibrate up and down.

[0070] The sidewall of the cavity 114 can be flush with the sidewall of the second via hole 113, or the lateral width of the cavity 114 can also be greater than the lateral width of the second via hole 113.

[0071] In this embodiment, the lateral distance between the connecting column 107 and the sharp corner can be set as needed, so that the connecting column 107 limits the vibration amplitude (especially the downward vibration amplitude) of the first electrode plate layer 103 during the vibration of the first electrode plate layer 103, so that the first electrode plate layer 103 is not easy to touch the sidewall of the first via hole 112 and the sharp corner formed by the upper surface of the substrate 101, which helps to reduce the risk of breaking of the first electrode plate layer 103 during vibration and improve the reliability of the MEMS capacitor device.

[0072] Specifically, the connecting column 107 is arranged above the region where the sharp corner is located. In other embodiments, the connecting column 107 is arranged above the region where the first via hole 112 is located. In other embodiments, the connecting column 107 is arranged above the region where the second via hole 113 is located. In other embodiments, the connecting column 107 is arranged above the region where the substrate 101 is located.

[0073] Specifically, when only one connecting column 107 is provided, the inner ring sidewall of the connecting column 107 can be flush with the sidewall of the first through hole 112, that is, the radial dimension (for example, the inner diameter) of the inner ring of the connecting column 107 can be equal to the radial dimension of the first through hole 112. However, the radial dimension of the inner ring of the connecting column 107 can also be slightly larger than the radial dimension of the first through hole 112. In other embodiments, the radial dimension of the inner ring of the connecting column 107 can also be smaller than the radial dimension of the first through hole 112.

[0074] Taking a MEMS capacitor device as a MEMS microphone device as an example, the sensitivity of the MEMS microphone device meets the following formula (1):

[0075] ;

[0076] wherein S is the sensitivity of the MEMS microphone device, V b is the voltage difference between the first electrode plate layer 103 and the second electrode plate layer 108, R is the radius of the effective part of the cavity 114 (for example, when an annular connecting column 107 is provided in the cavity 114, R is the radial dimension of the inner ring of the connecting column 107), σ is the intrinsic stress of the first electrode plate layer 103, t is the thickness of the first electrode plate layer 103, d is the distance between the first electrode plate layer 103 and the second electrode plate layer 108, C a is the effective capacitance between the first electrode plate layer 103 and the second electrode plate layer 108, C p is the parasitic capacitance between the first electrode plate layer 103 and the second electrode plate layer 108.

[0077] In order to make the first electrode plate layer 103 have a certain stiffness, the intrinsic stress σ of the first electrode plate layer 103 cannot be too small, and the thickness t of the first electrode plate layer 103 also cannot be too thin. According to the above formula (1), the industry increases the sensitivity of the MEMS microphone device by increasing the radius of the effective part of the cavity 114. In the present embodiment, since the connecting column 107 can provide an upward pulling force to the first electrode plate layer 103, the intrinsic stress σ and the thickness t of the first electrode plate layer 103 can both have a certain pull-down space, that is, the adjustment window of the intrinsic stress σ and the thickness t of the first electrode plate layer 103 can be increased under the premise of ensuring the sensitivity of the MEMS capacitor device. Or, the connecting column 107 provided in the cavity 114 inevitably reduces the radius of the effective part of the cavity 114, but the connecting column 107 can provide an upward pulling force to the first electrode plate layer 103, and the sensitivity of the MEMS capacitor device can be compensated by reducing the intrinsic stress σ and / or the thickness t of the first electrode plate layer 103, so as to ensure that the MEMS capacitor device has a certain sensitivity.

[0078] This embodiment also provides a MEMS capacitor device, which can be fabricated using the above-described fabrication method. However, it is not limited to this, and the MEMS capacitor device can be fabricated using other methods.

[0079] like Figure 12 As shown, in this embodiment, the MEMS capacitor includes a substrate 101 and a first isolation layer 102, a first electrode layer 103, a second isolation layer 104, and a second electrode layer 108 sequentially stacked on the upper surface of the substrate 101. Specifically, the substrate 101 has a first through-hole 112, the first isolation layer 102 is disposed on the upper surface of the substrate 101, and the first isolation layer 102 has a second through-hole 113 located directly above the first through-hole 112 and having a radial dimension larger than the first through-hole 112. The second through-hole 113 exposes the upper surface of the substrate 101 that is connected to the sidewall of the first through-hole 112, and the sidewall of the first through-hole 112 forms a sharp angle with the upper surface of the substrate 101 exposed by the second through-hole 113. The first electrode layer 103 is suspended above the second through-hole 113, and its edge rests on the first isolation layer 102. A second insulating layer 104 is disposed on the edge region of the first electrode layer 103, exposing the middle region of the first electrode layer 103. The second insulating layer 104 and the exposed middle region of the first electrode layer 103 serve as the sidewall and bottom wall of a cavity 114, which is located directly above the second through hole 113. A second electrode layer 108 is suspended on the cavity 114, with its edge resting on the second insulating layer 104. At least one connecting post 107 is disposed within the cavity 114, with both ends of the connecting post 107 connecting the second electrode layer 108 and the first electrode layer 103, respectively. The lateral distance between the connecting post 107 and the sharp corner is within a predetermined range.

[0080] In this embodiment, at least one of the connecting posts 107 can be an annular connecting post, and the central axis of the annular connecting post can coincide with the central axis of the first through hole 112. For example... Figure 12 As shown, the cavity 114 may contain only one annular connecting post 107. In another embodiment, the cavity 114 may contain two or more annular connecting posts with different radial dimensions to enhance the connection reliability between the connecting post 107 and the first electrode layer 103 and to enhance the limiting effect of the connecting post 107 on the amplitude of the first electrode layer 103. However, this is not a limitation, and the number of connecting posts 107 can be adjusted as needed.

[0081] The annular connecting column 107 can separate the cavity 114. For example... Figure 12As shown, the connecting column 107 divides the cavity 114 into a first part inside the connecting column 107 and a second part outside the connecting column 107, wherein the first part inside the connecting column 107 is an effective part of the cavity 114.

[0082] The radial dimension of the inner ring of the connecting column 107 can be greater than or equal to the radial dimension of the first through hole 112, so that the effective part of the cavity 114 can have a larger radial dimension, so that the MEMS capacitor device can have a certain sensitivity. However, the radial dimension of the inner ring of the connecting column 107 can also be slightly smaller than the radial dimension of the first through hole 112.

[0083] In another embodiment of the present application, the connecting column 107 can be a non-ring-shaped connecting column (for example, the connecting column 107 is an arc-shaped plate with an arc less than 360 degrees), and a plurality of non-ring-shaped connecting columns 107 can be arranged in the cavity 114 and dispersed in different radial directions of the cavity 114. For example, the plurality of non-ring-shaped connecting columns 107 are arranged in a circumferential direction and can have a gap between adjacent two connecting columns 107.

[0084] In order to improve the quality and reliability of the connecting column 107, the thickness (i.e. wall thickness) of the connecting column 107 can range from 0.45 microns to 1.1 microns.

[0085] The included angle between the connecting column 107 and the first electrode plate layer 103 and the second electrode plate layer 108 can be 90 degrees. However, the connecting column 107 can not be arranged perpendicularly between the first electrode plate layer 103 and the second electrode plate layer 108.

[0086] In the present embodiment, the MEMS capacitor device can further include a protective layer 106, which can be located between the second electrode plate layer 108 and the second isolation layer 104 and cover the lower surface of the second electrode plate layer 108, and the connecting column 107 can be connected to the second electrode plate layer 108 through the protective layer 106.

[0087] The materials of the protective layer 106 and the connecting column 107 can be silicon nitride, and the materials of the first isolation layer 102 and the second isolation layer 104 can be silicon oxide, so that when the second isolation layer 104 is etched to form the cavity 114, the material constituting the connecting column 107 will not be etched and removed.

[0088] To enhance the connection reliability between the connecting post 107 and the protective layer 106 and the second electrode layer 108, and to improve the reliability of the MEMS capacitor, the connecting post 107 and the protective layer 106 can belong to the same deposition layer. For example, the protective layer 106 covers the lower surface of the second electrode layer 108 and partially fills the groove 105 of the second isolation layer 104 to form the connecting post 107.

[0089] like Figure 12 As shown, the second electrode layer 108 and the protective layer 106 may have multiple third through holes 109 communicating with the cavity 114, so that sound or inertial force can enter the cavity 114 through the third through holes 109, thereby causing the first electrode layer 103 to vibrate up and down. Some of the third through holes 109 may be located on the inner side of the connecting post 107 (the side closer to the center of the cavity 114), and some of the third through holes 109 may be located on the outer side of the connecting post 107 (the side farther from the cavity 114). This facilitates the etching of the second isolation layer 104 using the multiple third through holes 109 to form the cavity 114, and exposes the sidewalls of the connecting post 107 in the cavity 114.

[0090] In this embodiment, the first electrode layer 103 has an electrode pre-forming region 103a, the upper surface of which is exposed from the side of the second isolation layer 104, the protective layer 106, and the second electrode layer 108. A first electrode 110 is formed on the electrode pre-forming region 103a, and the first electrode layer 103 can be connected to an external circuit through the first electrode 110.

[0091] A second electrode 111 is formed on the upper surface of the second electrode layer 108, and the second electrode layer 108 can be connected to an external circuit through the second electrode 111.

[0092] In the MEMS capacitor device of the embodiment, the substrate 101 has a first through hole 112, the first isolation layer 102 has a second through hole 113 located directly above the first through hole 112 and having a radial dimension greater than that of the first through hole 112, the second through hole 113 exposes an upper surface of the substrate 101 connected with the sidewall of the first through hole 112, the sidewall of the first through hole 112 and the upper surface of the substrate 101 exposed by the second through hole 113 form a sharp corner, the second isolation layer 104 is arranged on the first electrode plate layer 103 and exposes the middle region of the first electrode plate layer 103, the second isolation layer 104 and the middle region of the first electrode plate layer 103 exposed by the second isolation layer 104 respectively serve as the sidewall and bottom wall of an air cavity 114, the second electrode plate layer 108 is arranged in suspension on the air cavity 114, that is, the air cavity 114 is arranged between the first electrode plate layer 103 and the second electrode plate layer 108, at least one connecting column 107 is arranged in the air cavity 114, two ends of the connecting column 107 are connected with the first electrode plate layer 103 and the second electrode plate layer 108 respectively, and the lateral distance between the connecting column 107 and the sharp corner is within a set range, thus, the middle region of the first electrode plate layer 103 released by the second through hole 113 and the air cavity 114 can vibrate up and down, in the process of downward vibration of the first electrode plate layer 103, the connecting column 107 provides upward tension to the first electrode plate layer 103 to limit the amplitude of downward vibration of the first electrode plate layer 103, so that the probability of the first electrode plate layer 103 touching the sharp corner can be reduced without affecting the performance of the MEMS capacitor device, which helps to reduce the probability of fracture of the first electrode plate layer 103 and improve the reliability of the MEMS capacitor device, while the thickness of the first isolation layer 102 can be avoided to be increased, so that the limitation on the performance of the MEMS capacitor device can be avoided, and the process compatibility of the MEMS capacitor device can be increased.

[0093] It should be noted that, unless otherwise defined, technical terms or scientific terms used in the present application should be understood as their common meanings to those who have ordinary skills in the art to which the present application pertains. The terms "a", "an", "one", "this" and similar terms used in the present application do not represent quantity limitation, but can represent singular or plural. The terms "include", "contain", "have" and any variations thereof in the present application are intended to cover non-exclusive inclusion. The term "plurality" in the present application means greater than or equal to two. "And / or" describes the association relationship of the associated objects, which means that there can be three relationships, for example, "A and / or B" can represent the following three cases: A exists alone, A and B exist together, and B exists alone. The terms "first", "second" and the like in the present application only distinguish similar objects, and do not represent a specific order of the objects. The terms "connect", "couple" in the present application include direct and indirect connections (couplings) unless otherwise specified. The terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer" and the like in the present application indicate the orientation or position relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and cannot be understood as limiting the present application.

[0094] The above description is only a description of the preferred embodiments of the present application, and is not any limitation on the scope of the present application. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present application without departing from the spirit and scope of the present application by using the disclosed methods and technical contents. Therefore, any simple modification, equivalent change and modification made on the above embodiments according to the technical essence of the present application, without departing from the technical solutions of the present application, are within the protection scope of the present application.

Claims

1. A MEMS capacitor, characterized in that, include: A substrate having a first through-hole; A first isolation layer is disposed on the upper surface of the substrate. The first isolation layer has a second through hole located directly above the first through hole and having a radial dimension larger than the first through hole. The second through hole exposes the upper surface of the substrate connected to the sidewall of the first through hole. The sidewall of the first through hole forms a sharp angle with the upper surface of the substrate exposed by the second through hole. The first electrode layer is suspended above the second through hole, and its edge rests on the first isolation layer; A second isolation layer is disposed on the first electrode plate layer. The second isolation layer exposes the middle region of the first electrode plate layer. The second isolation layer and the exposed middle region of the first electrode plate layer serve as the sidewall and bottom wall of a cavity, respectively. The cavity is located directly above the second through hole. The second electrode layer is suspended in the cavity, and its edge rests on the second isolation layer; The cavity contains at least one connecting column, with its two ends connected to the second electrode layer and the first electrode layer, respectively. There is a gap between the sidewall of the connecting column and the sidewall of the cavity, and the lateral distance between the connecting column and the sharp corner is within a set range.

2. The MEMS capacitor device as described in claim 1, characterized in that, At least one of the connecting columns is an annular connecting column, and the central axis of the annular connecting column coincides with the central axis of the first through hole.

3. The MEMS capacitor device as described in claim 2, characterized in that, The cavity is provided with two or more annular connecting columns with different radial dimensions.

4. The MEMS capacitor device as described in claim 1, characterized in that, The cavity is provided with a plurality of connecting columns, which are distributed in different radial directions within the cavity.

5. The MEMS capacitor device as described in claim 1, characterized in that, The angle between the connecting column and the first electrode layer and the second electrode layer is 90 degrees.

6. The MEMS capacitor device as claimed in claim 1, characterized in that, The thickness of the connecting column ranges from 0.45 micrometers to 1.1 micrometers.

7. The MEMS capacitor device as claimed in claim 1, characterized in that, The MEMS capacitor also includes a protective layer located between the second electrode layer and the second isolation layer and covering the lower surface of the second electrode layer. The connecting post is connected to the second electrode layer through the protective layer.

8. A method for fabricating a MEMS capacitor, characterized in that, include: A substrate is provided, wherein a first isolation layer, a first electrode layer and a second isolation layer are sequentially stacked on the upper surface of the substrate; The second isolation layer is etched to form a groove, the bottom of which exposes the upper surface of the first electrode layer; The groove is filled to form a connecting column; A second electrode layer is formed, which covers the second isolation layer and the upper surface of the connecting column; A first through hole and a second through hole located directly above the first through hole are formed in the substrate and the first isolation layer, respectively, and a cavity located directly above the second through hole is formed between the first electrode layer and the second electrode layer; The second isolation layer exposes the upper surface of the middle region of the first electrode layer. The second isolation layer and the upper surface of the exposed middle region of the first electrode layer serve as the sidewall and bottom wall of the cavity, respectively. The second through hole exposes the upper surface of the substrate connected to the sidewall of the first through hole. The sidewall of the first through hole and the upper surface of the substrate exposed by the second through hole form a sharp angle. The lateral distance between the connecting post and the sharp angle is within a set range. There is a gap between the sidewall of the connecting post and the sidewall of the cavity.

9. The method for fabricating a MEMS capacitor as described in claim 8, characterized in that, The method of filling the groove to form the connecting column includes: A protective layer is formed on the second isolation layer, the protective layer covers the upper surface of the second isolation layer and fills the groove, and the portion of the protective layer located in the groove serves as the connecting column; The second electrode layer covers the upper surface of the protective layer.

10. The method for fabricating a MEMS capacitor as described in claim 9, characterized in that, The method of forming the first through-hole and the second through-hole in the substrate and the first insulating layer, respectively, and forming the cavity between the first electrode layer and the second electrode layer includes: The second electrode layer and the protective layer are etched to form a plurality of third through holes, which expose the upper surface of the second isolation layer; Etching the substrate to form a first via exposing the first isolation layer; and The first isolation layer is etched using the first through-hole to form the second through-hole, which exposes the lower surface of the middle region of the first electrode layer; the second isolation layer is etched using the plurality of third through-holes to form the cavity.

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