Vibration piece

Abstract

To provide a vibration piece having high oscillation stability.SOLUTION: The vibrator element includes a base portion, three vibrating arms extending from the base portion in a first direction and arranged side by side in a second direction, and a weight portion disposed at a distal end portion of each of the vibrating arms, and when a mass of the weight portion of the vibrating arm located at a center of the arrangement is defined as M1 and a mass of the weight portion of each of the vibrating arms located at both ends of the arrangement is defined as M2, a weight mass ratio A represented by M1 / M2 is represented on a horizontal axis, (A, B) = (2.39,2,), (0.01,2,), (0.23,1.6,), (1.65,1,), where a vertical axis represents an arm width ratio B represented by W1 / W2, where W1 is a length along the second direction of the vibrating arm located at the center of the array, and W2 is a length along the second direction of each of the vibrating arms located at both ends of the array. It is located within a region surrounded by a polygon formed by connecting six points of (7.15,1) and (4.02,1.6) with straight lines.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a vibrating element. [Background technology]

[0002] The vibrating element described in Patent Document 1 has a base and three vibrating arms extending from the base in the Y-axis direction. The three vibrating arms are arranged in the X-axis direction, which is perpendicular to the Y-axis direction, and have piezoelectric elements on their upper surfaces. When a drive voltage is applied, the piezoelectric elements expand and contract, causing each vibrating arm to vibrate in the Z-axis direction, which is perpendicular to the X-axis and Y-axis. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-164130 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, the vibrating arm deforms linearly in response to the force applied by the expansion and contraction of the piezoelectric element. In other words, the greater the expansion and contraction of the piezoelectric element, the greater the amplitude of the vibrating arm. However, when a force greater than a certain level is applied, the spring rigidity of the vibrating arm appears to increase, making it difficult for the vibrating arm to deform. In other words, the linear relationship between the force applied to the vibrating arm and the deformation of the vibrating arm is lost. This phenomenon is also known as spring nonlinearity. When nonlinearity appears, the vibration frequency of the vibrating arm fluctuates depending on the magnitude of the drive voltage, affecting oscillation stability. Patent Document 1 does not take this nonlinearity into consideration, so there is a risk of reduced oscillation stability. [Means for solving the problem]

[0005] The vibrating element according to the present invention includes a base and Three vibrating arms extending in a first direction from the base and arranged side by side in a second direction perpendicular to the first direction; a weight portion disposed at the tip end of each of the vibrating arms, When the mass of the weight portion arranged on the vibrating arm located at the center of the array is M1 and the mass of the weight portion arranged on each of the vibrating arms located at both ends of the array is M2, the horizontal axis represents a weight mass ratio A expressed as M1 / M2, and when the width which is the length along the second direction of the vibrating arm located at the center of the array is W1 and the width which is the length in the second direction of each of the vibrating arms located at both ends of the array is W2, the vertical axis represents an arm width ratio B expressed as W1 / W2, (A,B) is located within the area enclosed by a polygon formed by connecting the six points (A,B)=(2.39,2), (A,B)=(0.01,2), (A,B)=(0.23,1.6), (A,B)=(1.65,1), (A,B)=(7.15,1) and (A,B)=(4.02,1.6) with straight lines. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a plan view of a MEMS element according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 2 is a plan view of a vibrating element included in the MEMS element. [Figure 4] FIG. 2 is a cross-sectional view of a vibrating arm of the vibrator element. [Figure 5] 10 is a graph showing the relationship between weight mass ratio A and arm width ratio B. [Figure 6] 10 is a graph showing the relationship between arm width ratio B and Q value. [Figure 7] 10 is a graph showing the relationship between the weight mass ratio A and the frequency difference Δf. [Figure 8] FIG. 2 is a plan view showing the configuration of the weight portion. [Figure 9] FIG. 4 is a cross-sectional view showing the configuration of the weight portion. [Figure 10] FIG. 2 is a plan view showing the configuration of the weight portion. [Figure 11] FIG. 10 is a plan view showing a vibrator element according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The resonator element of the present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.

[0008] First Embodiment FIG. 1 is a plan view of a MEMS element according to a first embodiment. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. FIG. 3 is a plan view of a vibrating element included in the MEMS element. FIG. 4 is a cross-sectional view of a vibrating arm included in the vibrating element. FIG. 5 is a graph showing the relationship between the weight mass ratio A and the arm width ratio B. FIG. 6 is a graph showing the relationship between the arm width ratio B and the Q value. FIG. 7 is a graph showing the relationship between the weight mass ratio A and the frequency difference Δf. FIG. 8 is a plan view showing the configuration of the weight section. FIG. 9 is a cross-sectional view showing the configuration of the weight section. FIG. 10 is a plan view showing the configuration of the weight section.

[0009] For ease of explanation, each figure except for Figures 5 to 7 illustrates an X-axis, a Y-axis, and a Z-axis that are perpendicular to one another. The direction along the X-axis is also referred to as the X-axis direction, the direction along the Y-axis as the Y-axis direction, and the direction along the Z-axis as the Z-axis direction. The X-axis direction corresponds to the "second direction," the Y-axis direction as the "first direction," and the Z-axis direction as the "third direction." The arrowed side of each axis is also referred to as the "plus side," and the opposite side as the "minus side." The plus side of the Z-axis is also referred to as the "upper," and the minus side as the "lower."

[0010] As shown in FIGS. 1 and 2, the MEMS element 1 includes an SOI (Silicon on Insulator) substrate 10 on which a resonator element 20 is formed, and a lid 5 that hermetically seals the resonator element 20 between the SOI substrate 10. The lid 5 is made of single crystal silicon or the like and has a recess that opens to its bottom surface. The bottom surface of the lid 5 is bonded to the top surface of the SOI substrate 10. As shown in FIG. 2, the SOI substrate 10 is a multilayer substrate in which a silicon layer 11 serving as a handle layer, a BOX (Buried Oxide) layer 12, and a surface silicon layer 13 serving as a device layer are stacked in this order from the bottom. For example, the silicon layer 11 and the surface silicon layer 13 are each made of single crystal silicon, and the BOX layer 12 is made of a silicon oxide (SiO2) layer.

[0011] 1, the surface silicon layer 13 is formed with a vibrating substrate 21 provided on the vibrating element 20 and a frame-shaped frame portion 131 surrounding the periphery of the vibrating substrate 21. A pair of electrode pads PAD1 and PAD2 are disposed on the upper surface of the frame portion 131. As shown in FIG. 2, through electrodes 14 and 15 that penetrate the SOI substrate 10 in the thickness direction are formed at positions overlapping with the electrode pads PAD1 and PAD2. The through electrode 14 is electrically connected to the electrode pad PAD1, and the through electrode 15 is electrically connected to the electrode pad PAD2. This allows the electrode pads PAD1 and PAD2 to be drawn out from the lower surface of the MEMS element 1. This facilitates electrical connection with an external device such as an oscillator circuit.

[0012] Furthermore, the vibrating element 20 has a vibrating substrate 21 formed on the surface silicon layer 13. That is, the vibrating substrate 21 is formed from a silicon substrate. By forming the vibrating substrate 21 from a silicon substrate, the vibrating substrate 21 can be formed using a silicon wafer process, which makes it easy to process the vibrating substrate 21 and allows the vibrating substrate 21 to be formed with high processing accuracy.

[0013] The vibration substrate 21 is plate-shaped and has an upper surface and a lower surface that are opposite surfaces. As shown in FIG. 3, the vibration substrate 21 has a base 210 and three vibrating arms 22A, 22B, and 22C extending from the base 210. As shown in FIG. 4, the base 210 is supported by the silicon layer 11 and the BOX layer 12 located below, whereas the vibrating arms 22A, 22B, and 22C are separated from the BOX layer 12. Therefore, the vibrating arms 22A, 22B, and 22C are cantilever beams that are cantilevered at their base ends on the base 210. The entire vibration substrate 21 is formed to have the same thickness as the surface silicon layer 13.

[0014] As shown in FIG. 3, the vibrating arms 22A, 22B, and 22C each extend from the base 210 toward the positive side in the Y-axis direction and are arranged side by side at equal intervals in the X-axis direction. Specifically, the vibrating arm 22A is located in the center of the arrangement, the vibrating arm 22B is located on the positive side of the vibrating arm 22A in the X-axis direction, and the vibrating arm 22C is located on the negative side in the X-axis direction. In other words, the vibrating arm 22A is located between the vibrating arms 22B and 22C. Each of the vibrating arms 22A, 22B, and 22C has an arm portion 221 extending from the base 210 toward the positive side in the Y-axis direction and a wide portion 222 that is located at the tip side of the arm portion 221 and is wider than the arm portion 221. Note that, hereinafter, for convenience of explanation, the length of each of the vibrating arms 22A, 22B, and 22C along the Y-axis direction will be referred to as the "length," and the length along the X-axis direction will be referred to as the "width."

[0015] Each arm 221 is straight and has a constant width along the Y-axis direction. The width of the wide portion 222 is greater than the width of the arm 221. Each wide portion 222 is straight and has a constant width along the Y-axis direction. With this configuration, the mass of the tip of each of the vibrating arms 22A, 22B, and 22C increases due to the mass effect of the wide portion 222. Therefore, if the resonant frequency of the vibrating arm 20 is the same, the overall length of each of the vibrating arms 22A, 22B, and 22C can be shortened compared to when the wide portion 222 is not present, thereby enabling the miniaturization of the vibrating arm 20. Alternatively, if the overall length of each of the vibrating arms 22A, 22B, and 22C is the same, the resonant frequency of the vibrating arm 20 can be lower compared to when the wide portion 222 is not present. However, the wide portion 222 may be omitted from each of the vibrating arms 22A, 22B, and 22C.

[0016] The vibrating element 20 also includes a thin-film weight M disposed at the tip of each of the vibrating arms 22A, 22B, and 22C, specifically on the upper surface of the wide portion 222 in this embodiment. The weight M further increases the mass of the wide portion 222, making the aforementioned mass effect more pronounced. While the material for the weight M is not particularly limited, it preferably includes at least one of aluminum (Al), titanium (Ti), chromium (Cr), gold (Au), silver (Ag), copper (Cu), and polysilicon (Si). The term "aluminum (Al)" includes aluminum compounds such as aluminum oxide and aluminum nitride, in addition to aluminum. The same applies to the other materials mentioned above. Although not shown, the weight M in this embodiment is configured by laminating a gold (Au) surface layer on a titanium (Ti) base layer. Using these materials allows for easy formation of a high-specific-gravity weight M. However, the weight M may be omitted.

[0017] 2 and 3, the vibrating element 20 has a temperature characteristic adjusting section 24 that adjusts the frequency temperature characteristic of the resonant frequency. The temperature characteristic adjusting section 24 has a temperature characteristic adjusting film 24A arranged on the upper surface of the vibrating arm 22A, a temperature characteristic adjusting film 24B arranged on the upper surface of the vibrating arm 22B, and a temperature characteristic adjusting film 24C arranged on the upper surface of the vibrating arm 22C.

[0018] As shown in FIG. 4, the temperature characteristic adjustment films 24A, 24B, and 24C are disposed across the base 210 and the arm 221. In other words, the temperature characteristic adjustment films 24A, 24B, and 24C are disposed so as to overlap the boundary between the base 210 and the arm 221. The temperature characteristic adjustment films 24A, 24B, and 24C are configured as a laminate of a first layer 241, which is a silicon oxide (SiO2) layer, and a second layer 242, which is a zirconium oxide (ZrO2) layer, and this laminate is further covered with a polysilicon layer 243 as a coating layer. Silicon, which is the constituent material of the vibration substrate 21, has a frequency-temperature characteristic in which the resonant frequency decreases as the temperature increases. On the other hand, silicon oxide (SiO2) and zirconium oxide (ZrO2) have a frequency-temperature characteristic in which the resonant frequency increases as the temperature increases. Therefore, these frequency-temperature characteristics are canceled out, and the frequency-temperature characteristics of the resonant frequency of the composite formed by the vibrating arms 22A, 22B, and 22C and the temperature characteristic adjusting films 24A, 24B, and 24C can be made closer to flat. For example, the variation in the resonant frequency of the vibrating substrate 21, which is approximately ±3,000 ppm in the temperature range from -25°C to +75°C, can be flattened to approximately ±200 ppm to ±500 ppm by arranging the temperature characteristic adjusting portion 24.

[0019] The configuration of the temperature characteristic adjustment films 24A, 24B, and 24C is not particularly limited, and they may be configured with only either the first layer 241 or the second layer 242. They may also include another layer in addition to the first and second layers 241 and 242. The temperature characteristic adjustment portion 24 may also be omitted.

[0020] As shown in FIG. 3, the vibrating element 20 includes a driving unit 23 that causes the vibrating arms 22A, 22B, and 22C to vibrate in a bending manner in the Z-axis direction. The driving unit 23 includes a piezoelectric element 23A that is overlaid on a temperature characteristic adjustment film 24A and disposed on the upper surface of the vibrating arm 22A, a piezoelectric element 23B that is overlaid on a temperature characteristic adjustment film 24B and disposed on the upper surface of the vibrating arm 22B, and a piezoelectric element 23C that is overlaid on a temperature characteristic adjustment film 24C and disposed on the upper surface of the vibrating arm 22C. The piezoelectric elements 23A, 23B, and 23C are shorter than the arm portion 221 and are disposed in approximately half of the base end of the vibrating arms 22A, 22B, and 22C. The piezoelectric elements 23A, 23B, and 23C are disposed across the base portion 210 and the arm portion 221. The piezoelectric elements 23A, 23B, and 23C each expand and contract in the Y-axis direction when a driving voltage is applied. By expanding and contracting the piezoelectric elements 23A, 23B, and 23C in the Y-axis direction, the vibrating arms 22A, 22B, and 22C flexurally vibrate in the Z-axis direction. To balance the vibration, in the vibrating element 20, at least the vibrating arms 22B and 22C located at both ends of the arrangement have the same configuration (shape, size), and the central vibrating arm 22A has a different configuration (shape, size) from the vibrating arms 22B and 22C as necessary. This will be described in detail later.

[0021] 4, each of the piezoelectric elements 23A, 23B, and 23C has a lower electrode 231, a piezoelectric layer 232 disposed on the upper surface of the lower electrode 231, and an upper electrode 233 disposed on the upper surface of the piezoelectric layer 232. The materials constituting each of the piezoelectric elements 23A, 23B, and 23C are not particularly limited, but for example, the piezoelectric layer 232 is made of aluminum nitride (AlN) or the like, and the lower electrode 231 and the upper electrode 233 are made of titanium nitride (TiN) or the like. However, the configuration of the piezoelectric elements 23A, 23B, and 23C is not particularly limited, and another layer may be interposed between each layer.

[0022] 3, the piezoelectric elements 23A, 23B, and 23C are wired so that adjacent vibrating arms 22A, 22B, and 22C flex and vibrate in opposite phases. That is, the piezoelectric elements 23A, 23B, and 23C are wired so that a first state in which the vibrating arms 22B and 22C flex and deform upward and the vibrating arm 22A flexes and deforms downward, and a second state in which the vibrating arms 22B and 22C flex and deform downward and the vibrating arm 22A flexes and deforms upward are alternately repeated. Specifically, the lower electrodes 231 of the piezoelectric elements 23B and 23C and the upper electrode 233 of the piezoelectric element 23A are electrically connected to the electrode pad PAD1 via wiring (not shown), and the upper electrodes 233 of the piezoelectric elements 23B and 23C and the lower electrode 231 of the piezoelectric element 23A are electrically connected to the electrode pad PAD2 via wiring (not shown).

[0023] In this way, by causing adjacent vibrating arms 22A, 22B, and 22C to flexurally vibrate in opposite phases to each other, at least a portion of the vibrations of vibrating arms 22A, 22B, and 22C are canceled, effectively suppressing vibration leakage from vibrating element 20. The flexural vibration of vibrating arms 22A, 22B, and 22C is greatly excited at the resonant frequency, minimizing impedance. As a result, by connecting this MEMS element 1 to an oscillation circuit, an oscillator that oscillates at an oscillation frequency determined by the resonant frequency is obtained.

[0024] The overall configuration of the vibrating element 20 has been described above. Next, the dimensions of the vibrating element 20 will be described in detail. Fig. 5 shows a graph in which the horizontal axis represents the weight mass ratio A expressed as M1 / M2 when the mass of the weight M arranged on the vibrating arm 22A located at the center of the arrangement among the three vibrating arms 22A, 22B, and 22C is M1 and the mass of the weight M arranged on each of the vibrating arms 22B and 22C located at both ends of the arrangement is M2, and the vertical axis represents the arm width ratio B expressed as W1 / W2 when the width of the arm portion 221 of the vibrating arm 22A is W1 and the width of the arm portion 221 of each of the vibrating arms 22B and 22C is W2.

[0025] And, in the graph, when a region Q surrounded by a polygon formed by connecting six points, namely point P1(A, B) = (2.39, 2), point P2(A, B) = (0.01, 2), point P3(A, B) = (0.23, 1.6), point P4(A, B) = (1.65, 1), point P5(A, B) = (7.15, 1), and point P6(A, B) = (4.02, 1.6) with straight lines, is set, the mass ratio A of the weight and the arm width ratio B of the vibrating piece 20 are set such that (A, B) is located within the region Q. According to such a configuration, it becomes difficult for the non-linearity of the spring to appear, and the frequency change of the vibrating piece 20 due to the driving voltage applied to the piezoelectric elements 23A, 23B, and 23C can be reduced. Preferably, the frequency difference Δf between the frequency f1 when the driving voltage is 10 mV and the frequency f2 when the driving voltage is 100 mV can be suppressed to 30 ppm or less. Furthermore, the Q value of the vibrating piece 20 can be made 10,000 or more. Therefore, the vibrating piece 20 has high oscillation stability and frequency characteristics.

[0026] Hereinafter, the reason for obtaining the above effects will be described. In the vibrating piece 20, the central vibrating arm 22A and the vibrating arms 22B and 22C at both ends vibrate in opposite phases. And when there is a difference between the total mass Mb (the mass of the vibrating arm 22B + the mass of the vibrating arm 22C) of the vibrating arms 22B and 22C that vibrate in the same phase and the mass Ma of the vibrating arm 22A that vibrates in the opposite phase to them, the lighter vibrating arm vibrates more greatly with respect to the heavier vibrating arm. For example, if Ma < Mb, the vibrating arm 22A vibrates more greatly than the vibrating arms 22B and 22C. Thus, when only some of the vibrating arms 22A, 22B, and 22C vibrate greatly, since the some vibrating arms reach the non-linear region earlier than the other vibrating arms, the non-linearity described above appears earlier. That is, the non-linearity appears at a lower driving voltage. From this, in order to make it difficult for the non-linearity to appear, for example, it is preferable to make the width W1 of the vibrating arm 22A larger than the width W2 of each of the vibrating arms 22B and 22C to sufficiently reduce the difference between the mass Ma and the total mass Mb, and to make the amplitudes of the vibrating arms 22A, 22B, and 22C approximately the same. From this perspective, it is preferable that it is about 1 ≦ W1 / W2 ≦ 3.

[0027] However, as shown in FIG. 6, as W1 / W2, which is the ratio of widths W1 and W2, increases, the Q value of vibrating element 20 decreases. In other words, if W1 / W2 is made too large to make nonlinearity less likely to occur, the Q value of vibrating element 20 decreases, and the oscillation stability of vibrating element 20 decreases. Therefore, in vibrating element 20, 1≦W1 / W2≦2 is set. With this configuration, it is possible to make nonlinearity less likely to occur while maintaining a sufficiently high Q value. In this way, the optimal value of arm width ratio B is determined.

[0028] Next, within the range of 1≦W1 / W2≦2, we calculated the relationship between the mass ratio A and the frequency difference Δf for three configurations: W1 / W2=1, which is the lower limit; W1 / W2=2, which is the upper limit; and W1 / W2=1.6, which is near the median. The results are shown in the graph in Figure 7. In this graph, when W1 / W2=1, the mass ratios A at which the frequency difference Δf=30 ppm are 1.65 and 7.15; when W1 / W2=1.6, the mass ratios A at which the frequency difference Δf=30 ppm are 0.23 and 4.02; and when W1 / W2=2, the mass ratios A at which the frequency difference Δf=30 ppm are 0.01 and 2.39.

[0029] Based on the above results, as shown in Figure 5, six points were plotted on a graph with the arm width ratio B on the vertical axis and the weight mass ratio A on the horizontal axis: point P1(A,B) = (2.39,2), point P2(A,B) = (0.01,2), point P3(A,B) = (0.23,1.6), point P4(A,B) = (1.65,1), point P5(A,B) = (7.15,1), and point P6(A,B) = (4.02,1.6). Furthermore, a polygonal area Q was defined by connecting these six points with straight lines. Therefore, if (A,B) is located within area Q, the frequency difference Δf can be kept below 30 ppm and the Q value can be maintained above 10,000. As described above, by designing the weight mass ratio A and the arm width ratio B so that (A, B) is located within the region Q, the vibrating element 20 has high oscillation stability and frequency characteristics.

[0030] Furthermore, in the graph shown in Fig. 7, the weight mass ratios A when the frequency difference Δf = 20 ppm at W1 / W2 = 1 are 2.17 and 6.63, the weight mass ratios A when the frequency difference Δf = 20 ppm at W1 / W2 = 1.6 are 0.6 and 3.66, and the weight mass ratios A when the frequency difference Δf = 20 ppm at W1 / W2 = 2 are 0.24 and 2.17. Therefore, as shown in Fig. 5, six points of point P11(A,B) = (2.17,2), point P12(A,B) = (0.24,2), point P13(A,B) = (0.6,1.6), point P14(A,B) = (2.17,1), point P15(A,B) = (6.63,1) and point P16(A,B) = (3.66,1.6) are plotted, and furthermore, a region Q1 surrounded by a polygon connecting these six points with straight lines is set. Therefore, if (A,B) is located within the region Q1, the frequency difference Δf can be suppressed to 20 ppm or less and the Q value can be maintained at 10,000 or more. Therefore, it is further preferable to design the weight mass ratio A and the arm width ratio B so that (A,B) is located within the region Q1. Thereby, the vibrating piece 20 having higher oscillation stability and frequency characteristics is obtained.

[0031] In addition, within the region Q, it is further preferable that the weight mass ratio A > 1 or the weight mass ratio A < 1. That is, it is preferable that the weight mass ratio A ≠ 1. According to such a configuration, the difference ΔM between the total mass Mb of the vibrating arms 22B and 22C generated at the determined arm width ratio B and the mass Ma of the vibrating arm 22A can be further reduced using the weight mass ratio A. That is, if Ma < Mb when the arm width ratio B is determined, the difference ΔM can be further reduced by setting the weight mass ratio A > 1. Conversely, if Ma > Mb when the arm width ratio B is determined, the difference ΔM can be further reduced by setting the weight mass ratio A < 1. On the other hand, when the weight mass ratio A = 1, such an effect does not occur. Therefore, by setting the weight mass ratio A > 1 or the weight mass ratio A < 1, the difference in the amplitudes of the vibrating arms 22A, 22B, and 22C can be suppressed to be smaller, and the non-linearity can be made more difficult to appear. Therefore, a larger drive voltage can be set.

[0032] Next, a method for realizing the determined mass ratio A will be described. In this embodiment, as shown in FIG. 8, the determined mass ratio A may be realized by making at least one of the length Lm of the mass M, i.e., the length along the Y-axis direction, and the width Wm of the mass M, i.e., the length along the X-axis direction, different between the vibrating arm 22A located at the center of the array and the vibrating arms 22B and 22C located at both ends of the array. In other words, the determined mass ratio A may be realized by making the area of ​​the mass M in a plan view from the Z-axis direction different between the vibrating arm 22A and the vibrating arms 22B and 22C. Note that in the illustrated example, both the length Lm and the width Wm are made different. According to this method, the determined mass ratio A can be realized with a simple configuration.

[0033] However, without being limited to this, for example, the determined weight mass ratio A can be realized by making the thickness H of the weight portion M, that is, the length along the Z-axis direction, different between the resonating arm 22A located at the center of the array and the resonating arms 22B and 22C located at both ends of the array, as shown in Fig. 9. Even by such a method, the determined weight mass ratio A can be realized with a simple configuration.

[0034] Furthermore, for example, in the case of the vibrating element 20, a process is performed in which a laser is irradiated onto the weight M to remove a portion of the weight M in order to adjust the resonance frequency of the vibrating element 20. When performing such a process, as shown in FIG. 10, the determined weight mass ratio A may be realized by making the total area of ​​the laser processing marks D for frequency adjustment formed on the weight M different between the vibrating arm 22A located at the center of the array and the vibrating arms 22B and 22C located at both ends of the array. This method also makes it possible to realize the determined weight mass ratio A with a simple configuration. Naturally, the above three methods can be combined as appropriate.

[0035] The above has described the MEMS element 1. As described above, the vibrating element 20 included in such a MEMS element 1 has the base 210, the three vibrating arms 22A, 22B, and 22C that extend from the base 210 in the Y-axis direction, which is a first direction, and are arranged side by side in the X-axis direction, which is a second direction orthogonal to the Y-axis direction, and the weights M that are arranged at the tip ends of the respective vibrating arms 22A, 22B, and 22C. When the mass of the weight M arranged on the vibrating arm 22A located at the center of the array is M1 and the mass of the weight M arranged on each of the vibrating arms 22B and 22C located at both ends of the array is M2, the horizontal axis represents the weight mass ratio A expressed as M1 / M2, and when the width that is the length along the X-axis direction of the vibrating arm 22A located at the center of the array is W1 and the width that is the length along the X-axis direction of each of the vibrating arms 22B and 22C located at both ends of the array is W2, the vertical axis represents the arm width ratio B expressed as W1 / W2, (A,B) is located within an area Q surrounded by a polygon formed by connecting six points, (A,B) = (2.39,2), (A,B) = (0.01,2), (A,B) = (0.23,1.6), (A,B) = (1.65,1), (A,B) = (7.15,1), and (A,B) = (4.02,1.6), with straight lines. With this configuration, the vibrator element 20 has high oscillation stability and frequency characteristics.

[0036] As described above, (A, B) is located within the area Q1 surrounded by a polygon formed by connecting the six points (A, B) = (2.17, 2), (A, B) = (0.24, 2), (A, B) = (0.6, 1.6), (A, B) = (2.17, 1), (A, B) = (6.63, 1), and (A, B) = (3.66, 1.6) with straight lines. This configuration results in a vibrating element 20 with higher oscillation stability and frequency characteristics.

[0037] As mentioned above, the weight ratio A is greater than 1. This configuration makes it possible to further reduce the difference in amplitude between the vibrating arms 22A, 22B, and 22C, making it more difficult for nonlinearity to appear. As a result, the drive voltage can be set higher.

[0038] As mentioned above, the mass ratio A is less than 1. This configuration makes it possible to further reduce the difference in amplitude between the vibrating arms 22A, 22B, and 22C, making it more difficult for nonlinearity to appear. As a result, the drive voltage can be set higher.

[0039] As described above, the thickness H, which is the length along the Z-axis direction, of the weight M disposed on the resonating arm 22A located at the center of the array is different from the thickness H of the weight M disposed on each of the resonating arms 22B and 22C located at both ends of the array. With this configuration, the determined weight mass ratio A can be achieved by a simple method.

[0040] As described above, in the vibrating element 20, the weight M disposed on the vibrating arm 22A located at the center of the array is different from the weight M disposed on each of the vibrating arms 22B, 22C located at both ends of the array in at least one of the length Lm along the Y-axis direction and the width Wm, which is the length along the X-axis direction. With this configuration, the determined weight mass ratio A can be achieved by a simple method.

[0041] As described above, the total area of ​​the laser processing marks D formed for frequency adjustment is different between the weight M disposed on the vibrating arm 22A located at the center of the array and the weight M disposed on each of the vibrating arms 22B and 22C located at both ends of the array in the vibrating element 20. With this configuration, the determined weight mass ratio A can be achieved by a simple method.

[0042] As described above, each of the three vibrating arms 22A, 22B, and 22C has an arm portion 221 extending from the base portion 210 and a wide portion 222 located at the tip of the arm portion 221 and wider than the arm portion 221, with the weight portion M disposed on the wide portion 222. With this configuration, the mass of the tip portions of the vibrating arms 22A, 22B, and 22C increases due to the mass effect of the wide portion 222. Therefore, if the resonant frequency of the vibrating arm 20 is the same, the overall length of the vibrating arms 22A, 22B, and 22C can be shortened compared to a case in which the wide portion 222 is not provided, thereby enabling the miniaturization of the vibrating arm 20. Alternatively, if the overall length of the vibrating arms 22A, 22B, and 22C is the same, the resonant frequency of the vibrating arm 20 can be lower compared to a case in which the wide portion 222 is not provided.

[0043] As described above, the vibrating element 20 has the temperature characteristic adjusting portion 24 arranged on each of the vibrating arms 22A, 22B, and 22C, which adjusts the frequency-temperature characteristic. With this configuration, the frequency-temperature characteristic of the vibrating substrate 21 can be improved.

[0044] Second Embodiment FIG. 11 is a plan view showing a vibrator element according to the second embodiment.

[0045] The MEMS element 1 according to this embodiment is similar to the MEMS element 1 of the first embodiment described above, except that the configuration of the vibrating arm 22A is different. Therefore, in the following description, the differences between the MEMS element 1 of this embodiment and the first embodiment described above will be mainly described, and a description of similar points will be omitted. Furthermore, in each drawing of this embodiment, the same reference numerals are used to designate similar components to those of the above-described embodiment.

[0046] As shown in FIG. 11 , in the vibrating element 20 of this embodiment, the width W1 of the vibrating arm 22A is equal to the width W2 of the vibrating arms 22B and 22C. That is, W1=W2, and the arm width ratio B=1. Furthermore, when comparing the vibrating arm 22A with the vibrating arms 22B and 22C, the arm portions 221 have the same length, but the wide portions 222 of the vibrating arm 22A are longer than those of the vibrating arms 22B and 22C. Thus, the length Lh1 of the wide portions 222 of the vibrating arm 22A is greater than the length Lh2 of the wide portions 222 of the vibrating arms 22B and 22C. With this configuration, the mass of the vibrating arm 22A is greater than that of the vibrating arms 22B and 22C. By adjusting the length Lh1 of the wide portions 222 of the vibrating arm 22A, the difference ΔM between the total mass Mb of the vibrating arms 22B and 22C and the mass Ma of the vibrating arm 22A can be kept small. Therefore, the difference in amplitude between the vibrating arms 22A, 22B, and 22C can be kept small, making it more difficult for nonlinearity to appear.

[0047] In particular, in this embodiment, the tip of the weight M of the vibrating arm 22A protrudes on both sides in the X-axis direction. This makes it possible to increase the mass of the weight M without excessively increasing the length Lh1 of the weight M of the vibrating arm 22A. However, the configuration of the weight M is not particularly limited.

[0048] The second embodiment as described above can also achieve the same effects as the first embodiment.

[0049] While the vibrating element of the present invention has been described above based on the illustrated embodiment, the present invention is not limited thereto. The configuration of each part can be replaced with any configuration having a similar function. Furthermore, any other configuration may be added to the present invention. For example, in the above-described embodiment, the vibrating substrate 21 is made of silicon, but this is not limited thereto. For example, the vibrating substrate 21 may be made of quartz crystal or a piezoelectric material other than quartz crystal. [Explanation of symbols]

[0050] 1...MEMS element, 10...SOI substrate, 11...silicon layer, 12...BOX layer, 13...surface silicon layer, 131...frame portion, 14...through electrode, 15...through electrode, 20...vibration element, 21...vibration substrate, 210...base portion, 22A...vibration arm, 22B...vibration arm, 22C...vibration arm, 221...arm portion, 222...wide portion, 23...drive portion, 23A...piezoelectric element, 23B...piezoelectric element, 23C...piezoelectric element, 231...lower electrode, 232...piezoelectric layer, 233...upper electrode Pole, 24...Temperature characteristic adjustment part, 24A...Temperature characteristic adjustment film, 24B...Temperature characteristic adjustment film, 24C...Temperature characteristic adjustment film, 241...First layer, 242...Second layer, 243...Polysilicon layer, 5...Cover part, A...Sink mass ratio, B...Arm width ratio, D...Laser processing mark, H...Thickness, M...Sink part, Lh1...Length, Lh2...Length, Lm...Length, PAD1...Electrode pad, PAD2...Electrode pad, Q...Area, Q1...Area, W1...Width, W2...Width, Wm...Width, Δf...Frequency difference

Claims

1. A base and Three vibrating arms extending in a first direction from the base and arranged side by side in a second direction perpendicular to the first direction; a weight portion disposed at the tip end of each of the vibrating arms, When the mass of the weight portion arranged on the vibrating arm located at the center of the array is M1 and the mass of the weight portion arranged on each of the vibrating arms located at both ends of the array is M2, the horizontal axis represents a weight mass ratio A expressed as M1 / M2, and when the width which is the length along the second direction of the vibrating arm located at the center of the array is W1 and the width which is the length in the second direction of each of the vibrating arms located at both ends of the array is W2, the vertical axis represents an arm width ratio B expressed as W1 / W2, A vibrating element characterized in that (A, B) is located within a region surrounded by a polygon formed by connecting six points, (A, B) = (2.39, 2), (A, B) = (0.01, 2), (A, B) = (0.23, 1.6), (A, B) = (1.65, 1), (A, B) = (7.15, 1), and (A, B) = (4.02, 1.6), with straight lines.

2. 2. The resonator element of claim 1, wherein (A, B) is located within a polygonal area formed by connecting six points, (A, B) = (2.17, 2), (A, B) = (0.24, 2), (A, B) = (0.6, 1.6), (A, B) = (2.17, 1), (A, B) = (6.63, 1), and (A, B) = (3.66, 1.6), with straight lines.

3. The vibrator element according to claim 1 , wherein A>1.

4. The vibrator element according to claim 1 , wherein A<1.

5. When a direction perpendicular to the first direction and the second direction is defined as a third direction, The vibrating element according to claim 1, wherein the weight portion arranged on the vibrating arm located at the center of the array and the weight portions arranged on each vibrating arm located at both ends of the array have different lengths along the third direction.

6. The vibrating element of claim 1, wherein at least one of the lengths along the first direction and the lengths along the second direction is different between the weight portion arranged on the vibrating arm located at the center of the array and the weight portions arranged on each of the vibrating arms located at both ends of the array.

7. The vibrating piece of claim 1, wherein the total area of ​​the laser processing marks formed for frequency adjustment is different between the weight portion located on the vibrating arm located at the center of the array and the weight portion located on each vibrating arm located at both ends of the array.

8. Each of the three vibrating arms has an arm portion extending from the base portion and a wide portion located at a tip end side of the arm portion and wider than the arm portion, The vibrator element according to claim 1 , wherein the weight portion is disposed on the wide portion.

9. The vibrator element according to claim 1 , further comprising a temperature characteristic adjusting portion arranged on each of the vibrating arms to adjust a frequency-temperature characteristic.

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