MEMS element
The MEMS element addresses sensitivity and AOP/SNR issues by structuring the vibrating membrane into sections and dividing the fixed electrode, achieving improved performance in capacitive MEMS devices.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- NISSHINBO MICRO DEVICES INC
- Filing Date
- 2022-07-22
- Publication Date
- 2026-07-01
Smart Images
Figure 0007883585000004 
Figure 0007883585000005 
Figure 0007883585000006
Abstract
Description
Technical Field
[0001] The present disclosure relates to a capacitive MEMS device used as a microphone, various sensors, etc.
Background Art
[0002] As a MEMS (Micro Electro Mechanical Systems) device using a semiconductor process, a capacitive MEMS device is known in which a backplate including a fixed electrode having a plurality of acoustic holes and a diaphragm including a movable electrode are disposed on a substrate with an insulating film serving as a spacer interposed therebetween.
[0003] The capacitive MEMS device is configured to detect a displacement of the movable electrode caused by vibration of the diaphragm as a capacitance change between the movable electrode and the fixed electrode and output a detection signal. This type of MEMS device is described in, for example, Patent Document 1.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
[0006] Figure 14 is a schematic plan view illustrating the arrangement of the fixed electrode 35 with respect to the vibrating membrane 33 in the MEMS element 300 shown in Figure 13. In Figure 14, the joint between the vibrating membrane 33 and the spacer 34 (or the outer circumference of the back chamber 39) is indicated by a dashed line A. If the part corresponding to the back chamber 39 is circular, then dashed line A is a circle (note that the slit 40 is not shown). The vibrating membrane 33, which includes a conductive movable electrode, is connected to the movable electrode output terminal 41 formed on the surface of the MEMS element 300 via a through electrode formed in the spacer 34. The fixed electrode 35 is connected to the fixed electrode output terminal 42 via wiring 43. When the vibrating membrane 33 vibrates due to sound pressure or the like while a predetermined bias voltage is applied to the vibrating membrane 33 (movable electrode) and the fixed electrode 35 from the movable electrode output terminal 41 and the fixed electrode output terminal 42, a voltage change corresponding to the magnitude of the vibration of the vibrating membrane 33 occurs, and a detection signal can be obtained. This detection signal is output from the fixed electrode output terminal 42 to an integrated circuit device that has a signal processing circuit formed thereon to perform desired signal processing.
[0007] Figure 15 illustrates the vibration characteristics of the vibrating membrane 33 in the MEMS element 300 shown in Figure 13. The vertical axis of Figure 15 represents the amplitude, expressed as a relative value with the largest amplitude set to 1.00. The horizontal axis of Figure 15 represents the radial distance from the center of the vibrating membrane 33, with the center of the vibrating membrane 33 set to 0.00 and the part corresponding to the outer circumference of the back chamber of the vibrating membrane 33 in Figure 14 set to 1.00. As shown in Figure 15, the central part of the vibrating membrane 33 vibrates greatly, while the amplitude is small at the periphery. Therefore, the fixed electrode 35 is positioned in a region opposite the central part of the vibrating membrane 33, which vibrates greatly, as shown in Figures 13 and 14. Generally, the fixed electrode is formed at a distance from the center of the vibrating membrane in the range of 0.40 to 0.70 on the horizontal axis of Figure 15. This is because if the fixed electrode is placed in a region with a small vibration amplitude, the change in capacitance due to the vibration of the vibrating membrane is small, resulting in parasitic capacitance and a decrease in sensitivity.
[0008] Furthermore, as the displacement of the vibrating membrane 33 increases, a difference in amplitude occurs between the central part of the vibrating membrane 33 where the displacement is large and the peripheral part where the displacement is small. This reduces the area of the vibrating membrane 33 that is displaced parallel to the fixed electrode 35, within the region of the vibrating membrane 33 that is relative to the fixed electrode 35. As a result, the detection signal becomes nonlinear, and the AOP (Acoustic Overload Point) deteriorates.
[0009] However, when using capacitive MEMS elements as microphones, it is necessary to improve the AOP (Audio-Oriented Prototype) while minimizing the decrease in sensitivity, and naturally, an improvement in the SNR (Signal-Noise Ratio) is also required.
[0010] Therefore, the object of this disclosure is to provide a MEMS element having good sensitivity and improved AOP and SNR characteristics. [Means for solving the problem]
[0011] One embodiment of the MEMS element of the present disclosure comprises a substrate having a back chamber, a vibrating membrane including a movable electrode bonded to the substrate, and a back plate including a fixed electrode positioned opposite the movable electrode, wherein the vibrating membrane has a column in its central part connecting the back plate and the vibrating membrane, and has a plurality of vibrating parts in the region between the joint between the column and the vibrating membrane and the peripheral edge of the vibrating membrane, each of the plurality of vibrating parts being formed from a region enclosed by a column-side slit where a first slit portion and a second slit portion are joined, extending in mutually different directions from the joint side of the column and the vibrating membrane toward the peripheral edge, and a peripheral-side slit positioned on the peripheral edge between an extension line from the first slit portion toward the peripheral edge and an extension line from the second slit portion toward the peripheral edge, and the fixed electrode has a plurality of fixed electrode portions each positioned in a region opposite to each of the plurality of vibrating parts. [Effects of the Invention]
[0012] According to the MEMS element of this disclosure, the central part of the vibrating membrane is joined to the backplate by a column, thereby suppressing the amplitude of the central part of the vibrating membrane. Furthermore, by providing slits in the vibrating membrane, it is possible to form a vibrating section with little difference in amplitude between the central and peripheral parts of the vibrating membrane. Multiple such vibrating sections are formed on the vibrating membrane, and fixed electrode sections are placed in the region opposite each of the multiple vibrating sections, thereby obtaining a large detection signal overall. In addition, by dividing the system into multiple vibrating sections with a small area, the force applied to each vibrating section when a bias voltage is applied between the fixed electrode section and the movable electrode is reduced, thereby reducing distortion of the detection signal. Furthermore, by dividing the fixed electrode into multiple fixed electrode sections and thereby connecting multiple variable capacitance elements in parallel, a detection signal with low noise can be obtained. Thus, according to this disclosure, it is possible to provide a MEMS element that can improve AOP without reducing sensitivity and also improve SNR characteristics. As a result, a high-performance MEMS element for microphones can be obtained. [Brief explanation of the drawing]
[0013] [Figure 1] Cross-sectional schematic view of a MEMS device (Embodiment 1) which is an embodiment of the present disclosure. [Figure 2] Planar schematic view explaining the diaphragm portion in Embodiment 1. [Figure 3] Planar schematic view explaining the arrangement of the diaphragm portion and the fixed electrode portion in Embodiment 1. [Figure 4] Diagram explaining the vibration characteristics of the vibrating portion in Embodiment 1. [Figure 5] Diagram explaining the vibration characteristics of the vibrating portion in Embodiment 1. [Figure 6] Diagram explaining the vibration characteristics of the vibrating portion in Embodiment 1. [Figure 7] Diagram explaining the vibration characteristics of the vibrating portion in Embodiment 1. [Figure 8] Planar schematic view explaining the arrangement of the diaphragm portion and the fixed electrode portion in a MEMS device (Embodiment 2) which is another embodiment of the present disclosure. [Figure 9] Cross-sectional schematic view of a MEMS device (Embodiment 3) which is yet another embodiment of the present disclosure. [Figure 10] Planar schematic view explaining the arrangement of the diaphragm portion and the fixed electrode portion in Embodiment 3. [Figure 11] Diagram explaining a MEMS device using the MEMS device of the present disclosure. [Figure 12] Diagram explaining another MEMS device using the MEMS device of the present disclosure. [Figure 13] Cross-sectional schematic view of a conventional MEMS device. [Figure 14] Planar schematic view explaining the arrangement of the diaphragm portion and the fixed electrode portion of a conventional MEMS device. [Figure 15] Diagram explaining the vibration characteristics of the diaphragm of a conventional MEMS device.
Best Mode for Carrying Out the Invention
[0014] Next, embodiments of the MEMS elements of this disclosure will be described with reference to the drawings. However, this disclosure is not limited to these embodiments, and the components, materials, etc. described below can be modified in various ways within the scope of the spirit of this disclosure. In addition, the same reference numerals in the drawings indicate equivalent or identical components, and the sizes and positional relationships between each component are for convenience only and do not reflect the actual situation.
[0015] (Embodiment 1) Figure 1 is a schematic cross-sectional view illustrating Embodiment 1 of the MEMS element of the present disclosure. As shown in Figure 1, in one embodiment of the MEMS element 100 of the present disclosure, an insulating film 2 made of, for example, a thermal oxide film is formed on a substrate 1 made of, for example, a silicon substrate as a support substrate, and a vibrating membrane 3 including a conductive movable electrode made of, for example, polysilicon is formed on this insulating film 2. Furthermore, an insulating spacer 4 made of, for example, a USG (Undoped Silicate Glass) film, a conductive fixed electrode 5 made of, for example, polysilicon, and a back plate 7 including an insulating film 6 made of, for example, silicon nitride are laminated together. 8 is an acoustic hole, and 9 is a back chamber formed on the substrate 1.
[0016] In the MEMS element 100 of this embodiment, the insulating film 6 constituting the vibrating membrane 3 and the back plate 7 are joined and connected to the column 10, and the vibrating membrane 3 is provided with a column-side slit 11 and a peripheral-side slit 12.
[0017] Figure 2 is a schematic plan view illustrating the diaphragm portion of the MEMS element 100 shown in Figure 1, illustrating the arrangement of the column 10, the column-side slit 11, and the peripheral-side slit 12A. In Figure 1, the back chamber 9 formed on the substrate 1 is circular, and the outer circumference of Figure 2 corresponds to the outer circumference of the back chamber 9 on the substrate 1. The schematic cross-sectional view shown in Figure 1 is a cross-sectional view passing through the center of the column 10 and the two column-side slits 11 that are opposite each other with respect to the column 10 in Figure 2.
[0018] As shown in Figure 2, when the portion of the vibrating membrane 3 corresponding to the back chamber 9 is circular, the column 10 is positioned on the vibrating membrane 3 such that the center of the vibrating membrane 3 coincides with the center of the circular column 10, and the column-side slit 11 and the peripheral-side slit 12A are evenly distributed around the column 10. In the vibrating membrane 3 configured in this way, four vibrating sections 13 are formed in the region between the joint with the column 10 and the peripheral section.
[0019] Let us take one vibrating section 13 as an example and explain in detail. In the upper right region of the column 10 of the vibrating membrane 3 shown in Figure 2, a column-side slit 11 is formed by a first slit 11a that extends from the column 10 side parallel to the radial direction of the vibrating membrane 3 and in the direction upward in the drawing, and a second slit 11b that extends from the column 10 side parallel to the radial direction of the vibrating membrane 3 and in the direction to the right in the drawing, and is joined to the first slit 11a at a joining angle of 90 degrees.
[0020] By forming the column-side slit 11, a portion of the vibrating membrane 3 on the column 10 side, which is normally limited by the column 10, becomes more susceptible to vibration.
[0021] Furthermore, the periphery slit 12A is formed on the periphery of the vibrating membrane 3 where it is joined to the substrate 1, insulating film 2, and spacer 4. This makes the periphery of the vibrating membrane 3, which is normally restricted by its connection to the substrate 1, more susceptible to vibration. This periphery slit 12A has a similar effect to the slit 40 formed on a typical MEMS element 300 as described in Figure 13. In particular, the periphery slit 12A in this embodiment is formed so that the region enclosed by the extension lines in the extension direction of the first slit portion 11a and the extension line in the extension direction of the second slit portion 11b, respectively, shown by dashed lines in Figure 2, constitutes a single vibrating portion 13. Therefore, both ends of the slit are formed to open up to or near the position where they intersect with these extension lines.
[0022] In this way, the region enclosed by the column-side slit 11 and the peripheral-side slit 12A becomes one vibrating section 13. Multiple vibrating sections 13 are evenly arranged around the center of the column 10 (the center of the vibrating membrane 3), resulting in four vibrating sections 13 with matching characteristics.
[0023] Figure 3 is a schematic plan view illustrating the arrangement of the vibrating membrane portion and the fixed electrode portion of the MEMS element 100 shown in Figure 1. It is a schematic plan view illustrating the arrangement of the vibrating membrane 3, which has a column 10, a column-side slit 11, and a peripheral-side slit 12A, and the fixed electrode portion 14. The fixed electrode 5 shown in Figure 1 consists of multiple fixed electrode portions 14 arranged in regions facing each of the multiple vibrating portions 13 described in Figure 2. In the MEMS element 100 of this embodiment shown in Figure 3, four fixed electrode portions 14 are formed. As described above, the region enclosed by the column-side slit 11 formed from the first slit portion 11a and the second slit portion 11b, and the peripheral-side slit 12A, constitutes one vibrating portion 13 (not shown in Figure 3). Therefore, the fixed electrode portion 14 is positioned in a region opposite to the region enclosed by the column-side slit 11 formed by the first slit portion 11a and the second slit portion 11b, and the peripheral-side slit 12A, and each of the multiple fixed electrode portions 14 is positioned opposite each of the multiple vibrating portions 13. Note that the acoustic holes formed in the fixed electrode portions 14 are not shown in Figure 3. Also, the wiring connecting each fixed electrode portion 14 to the fixed electrode output terminal is not shown. The connection between each fixed electrode portion 14 and the fixed electrode output terminal will be described later.
[0024] Next, the vibration characteristics of the vibrating part will be explained using the vibration characteristics of one vibrating part 13 as an example. The vibration characteristics of the vibrating part 13 vary depending on the material, thickness, and size of the vibrating membrane 3. Furthermore, it is possible to change the vibration characteristics by changing the shape of the column-side slit 11 and the peripheral-side slit 12A.
[0025] Figures 4-7 illustrate the vibration characteristics of the vibrating section 13 of the MEMS element 100 in this embodiment. The vertical axis in Figure 4 represents the amplitude, expressed as a relative quantity with the largest amplitude set to 1.00. The horizontal axis in Figure 4 represents the distance from the center of the vibrating membrane 3, and its direction is the radial direction of the vibrating membrane 3, passing through the joint between the first slit portion 11a and the second slit portion 11b of the column-side slit 11 from the center of the column 10. The distance is expressed as a relative distance with the center of the column 10 set to 0.00 and the outer circumference shown in Figure 2 set to 1.00. In Figure 4, the amplitude of the vibrating section 13 is compared when the extension length of the column-side slit 11 is changed to 19% (vibrating membrane A), 38% (vibrating membrane B), and 56% (vibrating membrane C). Here, the extension length of the column-side slit 11 is expressed as a ratio with the length from the center of the column 10 to the outer circumference shown in Figure 2 set to 100. All other conditions are kept the same.
[0026] As shown in Figure 4, it can be seen that vibration occurs between the column-side slit 11 and the peripheral-side slit 12A in both cases. Furthermore, it can be seen that the longer the length of the column-side slit 11 (slit length: vibrating membrane A < vibrating membrane B < vibrating membrane C), the larger the amplitude near the column-side slit 11 (amplitude: vibrating membrane A < vibrating membrane B < vibrating membrane C). It can also be seen that the amplitude near the peripheral-side slit 12A changes accordingly.
[0027] In particular, in the case of vibrating membrane B, it can be seen that vibrations with a nearly uniform amplitude occur throughout the entire vibrating section 13 between the column-side slit 11 and the peripheral-side slit 12A. This indicates that the movable electrode (vibrating membrane 3) of the vibrating section 13 is displaced nearly parallel to the opposing fixed electrode section 14. Therefore, in this embodiment, from the standpoint of improving AOP, it is preferable to use vibrating membrane B as the slit length of the column-side slit 11 among vibrating membranes A to C.
[0028] The adjustment of the vibration characteristics of the vibrating section 13 is not limited to the adjustment by the length of the column-side slit 11 as explained in Figure 4. The vibration characteristics of the vibrating section 13 can also be adjusted by changing the arrangement of the column-side slit 11. Figure 5 compares the amplitude of the vibrating section 13 when the vibrating membrane B shown in Figure 4 and the vibrating membrane D are made by moving the column-side slit 11 in the peripheral direction by a few percent, with the position corresponding to the outer circumference shown in Figure 2 from the column 10 being 100, while keeping the conditions such as slit length the same. As shown in Figure 5, when the column-side slit 11 is moved towards the peripheral side, it can be seen that the column-side end of the vibration region moves from the center of the vibrating membrane towards the peripheral side. Therefore, the shape of the vibrating section 13 changes and the vibration characteristics change. In this case, the area of the vibrating section 13 becomes smaller and the relative amplitude becomes smaller. Therefore, it is preferable to determine the arrangement of the column-side slit 11 in order to obtain the desired vibration characteristics. Naturally, moving the column-side slit 11 towards the center of the vibrating membrane 3 also changes the shape of the vibrating section 13 and changes the vibration characteristics. Furthermore, changing the arrangement of the peripheral slits 12A also changes the shape of the vibrating section 13, thus altering the vibration characteristics. Therefore, the shape and arrangement are modified to achieve the desired vibration characteristics. The following describes the case of the vibrating membrane B.
[0029] Figure 6 illustrates the vibration characteristics of the vibrating portion 13 of the MEMS element 100 of this embodiment, which includes a vibrating membrane B, in comparison with the vibration characteristics of the vibrating membrane 33 of the conventional MEMS element 300 described in Figure 15. In Figure 6, each amplitude is expressed as a relative quantity with the largest amplitude set to 1.00. The distance from the center of the vibrating membrane is expressed as a relative distance with the center of the vibrating membrane set to 0.00 and the position corresponding to the outer circumference shown in Figure 2 set to 1.00.
[0030] As shown in Figure 6, in the conventional example of a typical MEMS element 300, the amplitude is largest at the center of the vibrating membrane 33, and decreases towards the periphery. In other words, the region that can be described as a vibrating area is limited to a certain distance from the center, and the area around the periphery does not function as a vibrating area. In contrast, in the MEMS element 100 of this embodiment, it can be seen that the entire vibrating membrane in the region between the column-side slit 11 and the peripheral-side slit 12A vibrates relatively uniformly and functions as a vibrating area.
[0031] In this embodiment, as shown in Figure 2, four vibrating sections 13 each act as movable electrodes, and as shown in Figure 3, the fixed electrode is composed of four fixed electrode sections 14. Therefore, the signals output from each vibrating section 13 and fixed electrode section 14 become small. However, with multiple vibrating sections 13, the area over which each vibrating section 13 is displaced in the radial direction of the vibrating membrane 3, almost parallel to the fixed electrode section 14, increases, as shown in Figure 6. On the other hand, the area of the region where the fixed electrode section 14 is not formed is reduced by the division of the fixed electrode. However, for example, in the example of this embodiment shown in Figure 3, the diameter of the part of the vibrating membrane 3 corresponding to the back chamber 9 is 1800 μm, while the dimension between the fixed electrode sections 14 where the fixed electrode section 14 is not formed is about 20 μm, so the reduction in the area of the fixed electrode section 14 is very small. Also, the region where the fixed electrode section 14 is not formed is also the region where the vibrating section 13 is not formed. Therefore, in the MEMS element 100 of this embodiment, which comprises multiple vibrating parts 13 and multiple fixed electrode parts 14, and includes vibrating parts 13 that are displaced parallel to the fixed electrode parts 14 in the radial direction of the vibrating membrane 3, it is possible to obtain a sufficiently large sensitivity.
[0032] Figure 7 shows the change in amplitude when a sound pressure of 130 dB is applied to the vibrating membrane 3 (vibrating membrane B) of the MEMS element 100 of this embodiment and the vibrating membrane 33 of the conventional MEMS element 300. There is no significant difference in the amplitude between the vibrating membrane B of this embodiment and the vibrating membrane of the conventional example. However, comparing the changes in amplitude, it can be seen that the amplitude of this embodiment is more symmetrical. Thus, in the MEMS element 100 of this embodiment, in which the vibrating part 13 of the vibrating membrane 3 including the movable electrode is displaced almost parallel to the fixed electrode part 14, the AOP is improved. Furthermore, if the vibrating membrane 3 is constructed from a material that vibrates easily with a small spring constant, the force applied to each vibrating part 13 becomes smaller when a bias voltage is applied between the fixed electrode part 14 and the movable electrode, reducing the distortion of the detection signal and improving the AOP. In this embodiment, by providing the column 10, even if the vibrating membrane 3 has a small spring constant, problems such as the vibrating membrane 3 vibrating too much do not occur.
[0033] Furthermore, the MEMS element 100 of this embodiment can improve noise characteristics by forming the fixed electrode 5 with a plurality of fixed electrode sections 14, and connecting a plurality of variable capacitance elements, each consisting of one vibrating section 13 and one fixed electrode section 14, in parallel. The noise N of the n variable capacitance elements when the fixed electrode 5 is divided into n variable capacitance elements (fixed electrode sections 14) tot This can be expressed by the following equation (1). TIFF0007883585000001.tif1687 Here N o This represents the noise of the variable capacitance element when the fixed electrodes are not divided.
[0034] From equation (1), The result is TIFF0007883585000002.tif1487, and the noise is reduced according to the number of divisions.
[0035] By configuring the fixed electrode 5 with multiple fixed electrode sections 14 in this way, the output voltage does not decrease and noise can be reduced. When the fixed electrode 5 is divided into n fixed electrode sections 14, the noise can be expressed by equation (2), thus reducing the signal-to-noise ratio (SNR). tot teeth, This will result in TIFF0007883585000003.tif1587. o This is the detection signal of the MEMS element 100 in this embodiment. As described above, the decrease in the voltage of the detection signal due to dividing the fixed electrode 5 into n parts is negligibly small, and it can be seen that the SNR is improved by dividing the fixed electrode 5 into n parts. For example, when the fixed electrode 5 is divided into 4 parts (n=4), the SNR of the MEMS element 100 with the fixed electrode 5 divided is twice that of the MEMS element without the fixed electrode divided, which is a characteristic improvement of 6 dB.
[0036] (Embodiment 2) Next, Embodiment 2 of the MEMS element of the present disclosure will be described. Figure 8 corresponds to Figure 3 in Embodiment 1 described above, and is a schematic plan view illustrating the arrangement of the vibrating membrane portion and the fixed electrode portion of the MEMS element of this embodiment. It illustrates the arrangement of the vibrating membrane 3, on which the column 10, column-side slit 11, and peripheral-side slit 12B are arranged, and the fixed electrode portion 14. In this embodiment as well, the back chamber 9 formed on the substrate 1 is circular, and the outer circumference of Figure 8 corresponds to the outer circumference of the back chamber 9 of the substrate 1. In the MEMS element of this embodiment shown in Figure 8, the only difference from the MEMS element 100 described in Embodiment 1 shown in Figure 3 is the shape of the peripheral-side slit 12B. Therefore, the cross-sectional shape of the MEMS element of this embodiment can be represented as shown in the schematic cross-sectional view in Figure 1.
[0037] Let us explain in detail using one vibrating section 13 as an example. In the upper right region of the column 10 of the vibrating membrane 3 shown in Figure 8, a column-side slit 11 is formed, consisting of a first slit section 11a and a second slit section 11b. In addition, a peripheral-side slit 12B is formed, consisting of a third slit section 12a and a fourth slit section 12b. The third slit section 12a corresponds to the peripheral-side slit 12A shown in Figures 2 and 3. In this embodiment, the fourth slit section 12b is placed on the column 10 side of the third slit section 12a, and the third slit section 12a and the fourth slit section 12b constitute the peripheral-side slit 12B.
[0038] The peripheral slit 12B, composed of the third slit portion 12a and the fourth slit portion 12b, is formed so that the region enclosed by the extension lines in the extension direction of the first slit portion 11a and the extension line in the extension direction of the second slit portion 11b, respectively shown by dashed lines in Figure 8, becomes a single vibrating portion 13. In this way, both ends of the third slit portion 12a and one end of the fourth slit portion 12b are formed to open up to a position where they intersect with the aforementioned extension lines, or to the vicinity thereof. By adding this fourth slit portion 12b, the peripheral portion of the vibrating membrane 3 becomes more susceptible to vibration compared to the case where only the third slit portion 12a is provided.
[0039] In this way, the region enclosed by the column-side slit 11 and the peripheral-side slit 12B becomes one vibrating section 13. As shown in Figure 8, when the portion of the vibrating membrane 3 corresponding to the back chamber 9 is circular, the column 10 is positioned on the vibrating membrane 3 such that the center of the vibrating membrane 3 coincides with the center of the circular column 10, and the column-side slit 11 and the peripheral-side slit 12B are evenly distributed around the column 10. In the vibrating membrane 3 configured in this way, four vibrating sections 13 are formed in the region between the joint with the column 10 and the peripheral section.
[0040] In this embodiment as well, the material, thickness, and size of the vibrating membrane 3, as well as the shape and arrangement of the column-side slits 11 and peripheral-side slits 12B, can be appropriately set so that the vibrating section 13 has the desired vibration characteristics.
[0041] The fixed electrode sections 14, which are positioned opposite the four vibrating sections 13, are located in the region opposite to the area enclosed by the column-side slit 11 formed by the first slit section 11a and the second slit section 11b, and the peripheral-side slit 12B. Each of the multiple fixed electrode sections 14 is positioned to face each of the multiple vibrating sections 13 (not shown in Figure 8). Note that the acoustic holes formed in the fixed electrode sections 14 and the wiring connecting each fixed electrode section 14 to the fixed electrode output terminals are not shown in Figure 8.
[0042] In this embodiment as well, since each of the four vibrating parts 13 acts as a movable electrode and the fixed electrode is composed of four fixed electrode parts 14, the signals output from each vibrating part 13 and fixed electrode part 14 become small. However, even in the MEMS element of this embodiment, which is equipped with multiple vibrating parts 13 and multiple fixed electrode parts 14, and which is equipped with vibrating parts 13 that are displaced parallel to the fixed electrode parts 14 in the radial direction of the vibrating membrane 3, it is possible to obtain sufficiently large sensitivity, as in Embodiment 1 above.
[0043] Furthermore, since the vibrating part 13 is displaced almost parallel to the fixed electrode part 14, the AOP is also improved. Moreover, by forming the fixed electrode with multiple fixed electrode parts 14 and connecting multiple variable capacitance elements, each consisting of one vibrating part 13 and one fixed electrode part 14, in parallel, the noise characteristics are also improved.
[0044] (Embodiment 3) Next, Embodiment 3 of the MEMS element of the present disclosure will be described. In Embodiments 1 and 2 described above, the peripheral slits 12A and 12B are composed of through holes formed in the vibrating membrane 3. In contrast, this embodiment differs in that the peripheral slit 12C is an opening formed between the open end of the vibrating membrane 3 and the surface opposite to this open end, as shown in Figure 9. Figure 9 is a schematic cross-sectional view illustrating Embodiment 3 of the MEMS element of the present disclosure. Figure 10 is a schematic plan view illustrating the arrangement of the vibrating membrane portion and the fixed electrode portion of the MEMS element shown in Figure 9, illustrating the arrangement of the vibrating membrane 3 on which the column 10 and column-side slit 11 are arranged, the peripheral slit 12C formed between the open end of the vibrating membrane 3 and the surface opposite to this open end, and the fixed electrode portion 14. Compared with the MEMS element 100 described in Embodiments 1 and 2 described above, the MEMS element 200 according to this embodiment differs in the support structure of the vibrating membrane 3 including the movable electrode, and a part of the end of the vibrating membrane 3 is an open end.
[0045] In the MEMS element 200 of this embodiment, a portion of the end of the vibrating membrane 3 facing the substrate 1, insulating film 2, or spacer 4 is an open end, and a portion of the vibrating membrane 3 that is not an open end forms a support portion 15. The schematic cross-sectional view shown in Figure 9 is a cross-sectional view passing through the center of the column 10 in Figure 10 and two column-side slits 11 that are opposite each other with respect to the column 10. Therefore, the support portion 15 of the vibrating membrane 3 is not shown in Figure 9, and in the region not shown, the support portion 15 of the vibrating membrane 3 is laminated on the insulating film 2, and the spacer 4 is laminated on this support portion 15.
[0046] In the MEMS element 200 of this embodiment, the end of the vibrating membrane 3 is an open end, and the gap between this open end and the surface opposite it, specifically the spacer 4, becomes the peripheral slit 12C.
[0047] This peripheral slit 12C corresponds to the peripheral slit 12A described in Embodiment 1 above. Therefore, as shown in Figure 10, when the portion of the vibrating membrane 3 corresponding to the back chamber 9 is circular, the column 10 is positioned on the vibrating membrane 3 such that the center of the vibrating membrane 3 coincides with the center of the circular column 10, and the column-side slit 11 and peripheral slit 12C are evenly distributed around the column 10. In the vibrating membrane 3 configured in this way, four vibrating portions 13 are formed in the region between the joint with the column 10 and the open end.
[0048] Let us take one vibrating section 13 as an example and explain in detail. In the upper right region of the column 10 of the vibrating membrane 3 shown in Figure 10, a column-side slit 11 is formed by a first slit 11a that extends from the column 10 side parallel to the radial direction of the vibrating membrane 3 and in the direction upward in the drawing, and a second slit 11b that extends from the column 10 side parallel to the radial direction of the vibrating membrane 3 and in the direction to the right in the drawing, and is joined to the first slit 11a at a joining angle of 90 degrees.
[0049] By forming the column-side slit 11, a portion of the vibrating membrane 3 on the column 10 side, which is normally limited by the column 10, becomes more susceptible to vibration.
[0050] The peripheral slits 12C formed by the open end of the vibrating membrane 3 are formed so that the region enclosed by the extension lines in the extension direction of the first slit portion 11a and the extension line in the extension direction of the second slit portion 11b, respectively shown by dashed lines in Figure 10, constitutes a single vibrating portion 13. In this way, both ends of the slits 12C are formed to open up to a position where they intersect with the aforementioned extension lines, or to the vicinity thereof.
[0051] In this way, the region enclosed by the column-side slit 11 and the peripheral-side slit 12C becomes one vibrating section 13. As shown in Figure 10, when the portion of the vibrating membrane 3 corresponding to the back chamber 9 is circular, the column 10 is positioned on the vibrating membrane 3 such that the center of the vibrating membrane 3 coincides with the center of the circular column 10, and the column-side slit 11 and the peripheral-side slit 12C are evenly distributed around the column 10. In the vibrating membrane 3 configured in this way, four vibrating sections 13 are formed in the region between the joint with the column 10 and the peripheral section.
[0052] In this embodiment as well, the material, thickness, and size of the vibrating membrane 3, and the shape and arrangement of the column-side slits 11 can be appropriately set so that the vibrating section 13 has the desired vibration characteristics.
[0053] The fixed electrode portions 14, which are positioned opposite the four vibrating portions 13, are located in a region opposite to the area between the column-side slit 11 formed by the first slit portion 11a and the second slit portion 11b and the end of the vibrating membrane 3 that forms the peripheral-side slit 12C. Each of the multiple fixed electrode portions 14 is positioned to face each of the multiple vibrating portions 13. Note that the acoustic holes formed in the fixed electrode portions 14 and the wiring connecting each fixed electrode portion 14 to the fixed electrode output terminal are not shown in Figure 10.
[0054] In this embodiment as well, since each of the four vibrating parts 13 acts as a movable electrode and the fixed electrode 5 is composed of four fixed electrode parts 14, the signals output from each vibrating part 13 and fixed electrode part 14 become small. However, even in the MEMS element 200 of this embodiment, which is equipped with multiple vibrating parts 13 and multiple fixed electrode parts 14, and which is equipped with vibrating parts 13 that are displaced parallel to the fixed electrode parts 14 in the radial direction of the vibrating membrane 3, it is possible to obtain sufficiently large sensitivity, as in embodiments 1 and 2 described above.
[0055] In particular, the vibrating membrane 3 of this embodiment has a small contact area with the substrate 1, making it less susceptible to the effects of deformation of the substrate 1, and the area of the vibrating portion 13 that can be displaced in the radial direction of the vibrating membrane 3 almost parallel to the fixed electrode portion 14 is increased, making it possible to obtain sufficiently high sensitivity.
[0056] Furthermore, since the vibrating part 13 is displaced almost parallel to the fixed electrode part 14, the AOP (Attention Opposition) is improved. Moreover, by forming the fixed electrode with multiple fixed electrode parts 14 and connecting multiple variable capacitance elements, each consisting of one vibrating part 13 and one fixed electrode part 14, in parallel, the noise characteristics are also improved.
[0057] (Embodiment 4) Next, Embodiment 4 of the MEMS element of the present disclosure will be described. Embodiments 1 to 3 described above described how the fixed electrode 5 is divided into a plurality of fixed electrode sections 14. When a plurality of fixed electrode sections 14 are provided in this way, it is possible to configure a MEMS device using the MEMS element of the present disclosure by changing the connection between each fixed electrode section 14 and the fixed electrode output terminal (not shown). For example, each of the plurality of fixed electrode sections 14 can be connected to a different fixed electrode output terminal, or two or more of the plurality of fixed electrode sections 14 can be connected to a common fixed electrode output terminal.
[0058] For example, let us take the MEMS element 100 according to Embodiment 1 as an example. As shown in Figure 3, the MEMS element 100 according to Embodiment 1 has four fixed electrode sections 14. When connecting these four fixed electrode sections 14 to fixed electrode output terminals, the connection method can be changed according to the number of fixed electrode output terminals.
[0059] If there is only one fixed electrode output terminal, all four fixed electrode units 14 are connected to this single fixed electrode output terminal.
[0060] If there are two fixed electrode output terminals, one fixed electrode section 14 is connected to one fixed electrode output terminal, and the remaining three fixed electrode sections 14 are all connected to the other fixed electrode output terminal. Alternatively, two fixed electrode sections 14 are connected to one fixed electrode output terminal, and the remaining two fixed electrode sections 14 are connected to the other fixed electrode output terminal.
[0061] If there are three fixed electrode output terminals, one fixed electrode section 14 is connected to one fixed electrode output terminal, another fixed electrode section 14 is connected to another fixed electrode output terminal, and the remaining two fixed electrode sections 14 are connected to yet another fixed electrode output terminal.
[0062] If there are four fixed electrode output terminals, each fixed electrode unit 14 is connected to one fixed electrode output terminal.
[0063] In this way, by setting the number of fixed electrode units 14 connected to a single fixed electrode output terminal to one or two or more, the level of the detection signal can be changed by selecting the detection signal output from the MEMS element 100, except when all fixed electrode units 14 are connected to a single fixed electrode output terminal.
[0064] For example, let's consider the case where one of the four fixed electrode output terminals is connected to each of the four fixed electrode sections 14. The capacitive MEMS element detects the displacement of the movable electrode caused by the vibration of the vibrating membrane 3 as a change in capacitance between the movable electrode and the fixed electrode. In other words, in the MEMS element 100 according to Embodiment 1, the change in capacitance between the vibrating section 13 and the fixed electrode section 14 becomes the detection signal. Therefore, when different fixed electrode output terminals are connected to each of the fixed electrode sections 14, detection signals are output independently from the four variable capacitance elements composed of the vibrating section 13 and the fixed electrode sections 14.
[0065] Figure 11 is a diagram illustrating a MEMS device using the MEMS element of the present disclosure. As shown in Figure 11, with respect to the MEMS element 100 described in Embodiment 1, if four vibrating sections 13 are connected to one movable electrode output terminal 101 and four fixed electrode sections 14 are each connected to separate fixed electrode output terminals 102, the variable capacitance elements C1 to C4, each composed of a vibrating section 13 and a fixed electrode section 14, are connected in parallel. A bias power supply circuit 400 is connected to the movable electrode output terminal 101 connected to the vibrating section 13 in order to apply a predetermined bias voltage to the variable capacitance elements C1 to C4. On the other hand, the four fixed electrode output terminals 102, each connected to one of the four fixed electrode sections 14, are each connected to an integrated circuit input terminal 501 of an integrated circuit device 500, which has a signal processing circuit formed therein that performs desired signal processing on the output detection signal. The integrated circuit device 500 shown in Figure 11 includes an amplifier 502 that selects signals input from the integrated circuit input terminal 501 by opening and closing switches SW1 to SW3, adds and amplifies the selected signals, and outputs them from the output terminal out.
[0066] When sound pressure or other signals are applied to the MEMS element 100, the vibrating part 13 vibrates, and detection signals are output from the variable capacitance elements C1 to C4. The detection signals output from each of the variable capacitance elements C1 to C4 are equal in value.
[0067] Generally, an integrated circuit device 500 has a set maximum input voltage. For example, this maximum input voltage is determined by the power supply voltage of the integrated circuit device 500. If the voltage range of the detection signal output from the MEMS element 100 is less than or equal to the maximum input voltage of the integrated circuit device 500, no problems arise. However, in battery-powered electronic devices, the maximum input voltage of the integrated circuit device 500 may not be set high enough, and the voltage range of the detection signal output from the MEMS element 100 may exceed the maximum input voltage of the integrated circuit device 500.
[0068] If the input detection signal exceeds the maximum input voltage of the integrated circuit device 500, the signal that is processed and output from the integrated circuit device 500 will be distorted.
[0069] Therefore, it is possible to set the signal level of the input detection signal within the integrated circuit device 500. In the example shown in Figure 11, when all switches SW1 to SW3 are closed and the detection signals output from the variable capacitance elements C1 to C4 of the MEMS element 100 are all added together and amplified by the amplifier 502, if it is determined that the detection signal exceeds a predetermined maximum input voltage, switch SW3 is opened to reduce the signal level of the detection signal input to the integrated circuit device 500. In this case, the signal level can be reduced to 3 / 4 of the detection signal output from all variable capacitance elements C1 to C4. Furthermore, by sequentially opening switch SW2 and then switch SW1, the signal level of the input detection signal can be sequentially reduced to 1 / 2 and 1 / 4. The opening and closing control of switches SW1 to SW3 can be performed by well-known methods, such as comparing the signal level output from the amplifier 502 with a preset reference voltage level.
[0070] By setting the signal level of the detection signal to be processed by the integrated circuit device 500 according to the signal level of the detection signal input from the MEMS element 100, distortion-free signal processing becomes possible even for the integrated circuit device 500, which cannot set a large maximum input voltage. In other words, it becomes possible to expand the dynamic range of sound pressure and other signals input to the MEMS element 100 without degrading the AOP.
[0071] (Embodiment 5) Next, Embodiment 5 of the MEMS element of the present disclosure will be described. Figure 12 is a diagram illustrating another MEMS device using the MEMS element of the present disclosure. In Embodiment 4 described above, an example was described in which one of the four fixed electrode output terminals is connected to each of the four fixed electrode sections 14, but in this embodiment, the number of fixed electrode output terminals is set to three.
[0072] As shown in Figure 12, in the MEMS element 100 described in Embodiment 1, four vibrating sections 13 are connected to one movable electrode output terminal 101, two fixed electrode sections 14 are each connected to independent fixed electrode output terminals 102, and two other fixed electrode sections 14 are connected to another fixed electrode output terminal 102, resulting in a configuration where variable capacitance elements C1 to C4, each composed of a vibrating section 13 and a fixed electrode section 14, are connected in parallel. A bias power supply circuit 400 is connected to the movable electrode output terminal 101 connected to the vibrating section 13 in order to apply a predetermined bias voltage to the variable capacitance elements C1 to C4. On the other hand, the three fixed electrode output terminals 102, each connected to one of the four fixed electrode sections 14, are connected to input terminals 501 of an integrated circuit device 500, which has a signal processing circuit formed therein that performs desired signal processing on the output detection signal. The integrated circuit device 500 shown in Figure 12 includes an amplifier 502 that selects the signal input from the input terminal 501 by opening and closing switches SW1 and SW2, and adds and amplifies the selected signal.
[0073] In the example shown in Figure 12, when switches SW1 and SW2 are closed and the detection signals output from the variable capacitance elements C1 to C4 of the MEMS element 100 are all added together and amplified by the amplifier 502, if it is determined that the detection signal exceeds a predetermined maximum input voltage, switch SW1 is opened to reduce the signal level of the detection signal input to the integrated circuit device 500. In this case, the signal level can be reduced to 3 / 4 of the detection signal output from all variable capacitance elements C1 to C4. Furthermore, if switch SW1 is closed and switch SW2 is open, the signal level of the input detection signal can be reduced to 1 / 2. Also, if switches SW1 and SW2 are open, the signal level of the input detection signal can be reduced to 1 / 4. The opening and closing control of switches SW1 and SW2 can be performed by known methods, such as comparing the signal level output from the amplifier 502 with a preset reference voltage level.
[0074] By setting the signal level of the detection signal to be processed by the integrated circuit device 500 according to the signal level of the detection signal input from the MEMS element 100, it becomes possible to reduce the number of switches and, similar to Embodiment 4 above, enable distortion-free signal processing even in an integrated circuit device 500 that cannot set a large maximum input voltage. In other words, it becomes possible to expand the dynamic range of sound pressure and other signals input to the MEMS element 100 without degrading the AOP.
[0075] Furthermore, in order to enable similar signal processing, the fixed electrode output terminals 102 connected to the fixed electrode portion 14 of the MEMS element 100 may be set to two. In this case, in the MEMS device shown in Figure 12, the MEMS element 100 will have two fixed electrode output terminals 102: one connected to the variable capacitance element C1 and another connected to the variable capacitance elements C2 to C4. The integrated circuit device 500 will be configured to have switches SW1 and SW2 at the integrated circuit input terminals 501 connected to each of the two fixed electrode output terminals 102. With this configuration, by controlling the open and closed states of the two switches SW1 and SW2, the signal level of the detection signal input to the integrated circuit device 500 can be controlled to 1x, 3 / 4x, and 1 / 4x of the detection signal output from all the variable capacitance elements C1 to C4. Similarly, by connecting two variable capacitance elements C1 to C4 to each of the two fixed electrode output terminals 102, the signal level of the detection signal input to the integrated circuit device 500 can be controlled to be 1x or 1 / 2x the detection signal output from all variable capacitance elements C1 to C4.
[0076] In the above embodiments 4 and 5, the case using the MEMS element 100 according to embodiment 1 or 2 was described, but the detection signal level can be controlled similarly when the MEMS element 200 according to embodiment 3 is used instead of the MEMS element 100. Furthermore, the MEMS element is not limited to having four vibrating parts 13 and fixed electrode parts 14, but may have multiple vibrating parts 13 and multiple fixed electrode parts 14, for example, a MEMS element having six vibrating parts 13 and fixed electrode parts 14 may be used. In that case, by appropriately setting the number of fixed electrode output terminals 102 connected to the fixed electrode parts 14 according to the number of fixed electrode parts 14, the signal level of the output signal by the integrated circuit device that processes the detection signal can be appropriately controlled.
[0077] (summary) (1) One embodiment of the MEMS element of the present disclosure comprises a substrate having a back chamber, a vibrating membrane including a movable electrode bonded to the substrate, and a back plate including a fixed electrode disposed opposite to the movable electrode, wherein the vibrating membrane has a column in its central part connecting the back plate and the vibrating membrane, and has a plurality of vibrating parts in the region between the joint between the column and the vibrating membrane and the peripheral edge of the vibrating membrane, each of the plurality of vibrating parts is formed from a region enclosed by a column-side slit where a first slit portion and a second slit portion are joined, extending in mutually different directions from the joint side of the column and the vibrating membrane toward the peripheral edge, and a peripheral-side slit disposed on the peripheral edge between the extension line from the first slit portion toward the peripheral edge and the extension line from the second slit portion toward the peripheral edge, and the fixed electrode has a plurality of fixed electrode portions each disposed in a region opposite to each of the plurality of vibrating parts.
[0078] According to the MEMS element of this embodiment, by placing a column that connects to the backplate in the center of the vibrating membrane, the amplitude in the center of the vibrating membrane is suppressed. Furthermore, by providing slits on the column side and slits on the peripheral side of the vibrating membrane, a vibrating section with a small difference in amplitude between the central and peripheral parts of the vibrating membrane can be formed. Multiple such vibrating sections are formed, and a large detection signal can be obtained overall. Moreover, by dividing the device into multiple vibrating sections and multiple fixed electrode sections, the force applied to each vibrating section when a bias voltage is applied between the fixed electrode and the movable electrode can be reduced, thereby reducing the distortion of the detection signal and obtaining a detection signal with low noise.
[0079] (2) Each of the above-mentioned fixed electrode sections is connected to a different fixed electrode output terminal. This makes it possible to easily change the level of the detection signal by selecting various detection signals output from the MEMS element when configuring a MEMS device using this MEMS element.
[0080] (3) Two or more of the above-mentioned fixed electrode units are connected to a common fixed electrode output terminal. In this case, except when all fixed electrode units are connected to one fixed electrode output terminal, the other fixed electrode units may each be connected to a different fixed electrode output terminal, or two or more fixed electrode units may be connected to another common fixed electrode output terminal. This allows for efficient switching of the desired detection signal level.
[0081] (4) The column-side slit is an opening that penetrates the vibrating membrane, and the peripheral-side slit is an opening that penetrates the vibrating membrane or an opening between the open end of the vibrating membrane and the surface opposite the open end.
[0082] (5) The peripheral slits include a third slit portion formed along the inner side of the peripheral edge of the vibrating membrane, and a fourth slit portion formed along the third slit portion on the column side of the third slit portion. [Explanation of Symbols]
[0083] 100, 200, 300 MEMS elements 400 bias power supply circuit 500 Integrated Circuit Devices 1 circuit board 2 insulating film 3. Vibrating membrane 4 Spacers 5 Fixed electrode 6. Insulating film 7 Backplate 8 Acoustic Halls 9 Back Chamber 10 pillars 11 Column-side slits 11a First slit section 11b Second slit section 12, 12A~12C Peripheral side slits 12a Third slit section 12b Fourth slit section 13. Vibration section 14 Fixed electrode section 15 Support Department
Claims
1. A circuit board equipped with a back chamber, A vibrating membrane including a movable electrode bonded to the substrate, A back plate including a fixed electrode positioned opposite the movable electrode and Equipped with, The vibrating membrane is It has a column in its center that connects the back plate and the vibrating membrane, The region between the joint between the column and the vibrating membrane and the peripheral edge of the vibrating membrane has a plurality of vibrating parts, Each of the aforementioned multiple vibrating parts is The region is formed from a column-side slit where a first slit portion and a second slit portion are joined, extending in mutually different directions from the joint side of the column and the vibrating membrane toward the peripheral edge, and a peripheral-side slit located on the peripheral edge between the extension line from the first slit portion toward the peripheral edge and the extension line from the second slit portion toward the peripheral edge. The aforementioned fixed electrode is It has a plurality of fixed electrode portions, each of which is arranged in a region facing each of the plurality of vibrating portions. MEMS element.
2. Each of the aforementioned multiple fixed electrode sections is connected to a different fixed electrode output terminal. The MEMS element according to claim 1.
3. Two or more of the aforementioned multiple fixed electrode sections are connected to a common fixed electrode output terminal. The MEMS element according to claim 1.
4. The column-side slit is an opening that penetrates the vibrating membrane, and the peripheral-side slit is an opening that penetrates the vibrating membrane or an opening between the open end of the vibrating membrane and the surface opposite the open end. A MEMS element according to any one of claims 1 to 3.
5. The peripheral slit includes a third slit portion formed along the inner side of the peripheral edge of the vibrating membrane, and a fourth slit portion formed along the third slit portion on the column side of the third slit portion. A MEMS element according to any one of claims 1 to 3.