Vibration element manufacturing method

Abstract

To provide a manufacturing method for a vibration element, in which the occurrence of unnecessary vibration and the damage of a vibration element are suppressed.SOLUTION: A manufacturing method for a vibration element including a vibration substrate 2 and an electrode formed on a surface of the vibration substrate includes a first dry-etching step of dry-etching a crystal substrate from a first surface 2A side to form first grooves 221 and 231 and an outer shape of a first vibration arm 22 and a second vibration arm 23, a second dry-etching step of dry-etching the crystal substrate from a second surface 2B side to form second grooves 222 and 232 and an outer shape of the vibration arm, and a wet-etching step of wet-etching side surfaces 101 and 103 of the first vibration arm 22 and the second vibration arm 23, the first groove, and the second grove, thereby forming inclined surfaces 114 and 115 for connecting a bottom surface 111 and in-groove side surfaces 112 and 113. When the depth of the first grooves 221 and 231 and the second grooves 222 and 232 is D and the value obtained by subtracting the length of the inclined surface 114 in a Z direction from the depth D is D1, D1 / D≥0.80 is satisfied.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a vibration element. [Background technology]

[0002] Patent Document 1 describes a method for manufacturing a vibration element in which a vibration element having a pair of vibrating arms with grooves formed therein is formed by dry etching. In this manufacturing method, when dry etching a substrate made of a piezoelectric material, the width of the groove is narrowed relative to the width between the pair of vibrating arms, and by using a microloading effect, the etching depth of the groove is made shallower relative to the etching depth between the pair of vibrating arms, and the groove and outer shape of the vibration element are formed simultaneously. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-013382 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the method for manufacturing a vibration element in Patent Document 1, dry etching is performed on both the front and back sides of the substrate, so there is a risk of steps being formed on the side of the vibrating arm due to misalignment between the resist film formed on the front side of the substrate and the resist film formed on the back side of the substrate. If steps are formed on the side of the vibrating arm, there are problems such as the generation of unwanted vibrations and damage such as cracks and chips that start from the steps when an impact is applied. [Means for solving the problem]

[0005] A method for manufacturing a vibration element includes a first vibrating arm and a second vibrating arm extending along a first direction and aligned along a second direction intersecting the first direction, the first vibrating arm and the second vibrating arm being aligned in a third direction intersecting the first direction and the second direction, the first vibrating arm and the second vibrating arm being aligned in a third direction intersecting the first direction and the second direction, the first vibrating arm and the second vibrating arm being aligned in a front-back relationship, a first groove with a bottom opening in the first surface, a second groove with a bottom opening in the second surface, and a side surface connecting the first surface and the second surface, the method comprising the steps of: preparing a quartz substrate having the first surface and the second surface; and dry-etching the quartz substrate from the first surface side to form the first groove and the first vibrating arm and the second vibrating arm. the first dry etching process for forming the second groove and the outer shape of the first vibrating arm and the second vibrating arm; the second dry etching process for dry etching the quartz substrate from the second surface side to form the second groove and the outer shape of the first vibrating arm and the second vibrating arm; and the wet etching process for wet-etching the side surfaces of the first vibrating arm and the second vibrating arm, the first groove, and the second groove to form inclined surfaces in the first groove and the second groove that connect the bottom surfaces to the inner side surfaces of the grooves, wherein the first groove and the second groove satisfy D1 / D≧0.80, where D is a depth and D1 is a value obtained by subtracting the length of the inclined surface in the third direction from the depth. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a plan view showing a vibration element according to a first embodiment. [Figure 2] A cross-sectional view taken along line A1-A1 in Figure 1. [Figure 3] 3A to 3C are diagrams showing a manufacturing process of the vibration element according to the first embodiment. [Figure 4] 5A to 5C are cross-sectional views illustrating a method for manufacturing the vibration element. [Figure 5] 5A to 5C are cross-sectional views illustrating a method for manufacturing the vibration element. [Figure 6] 5A to 5C are cross-sectional views illustrating a method for manufacturing the vibration element. [Figure 7] 5A to 5C are cross-sectional views illustrating a method for manufacturing the vibration element. [Figure 8] 5A to 5C are cross-sectional views illustrating a method for manufacturing the vibration element. [Figure 9] 5A to 5C are cross-sectional views illustrating a method for manufacturing the vibration element. [Figure 10] 5A to 5C are cross-sectional views illustrating a method for manufacturing the vibration element. [Figure 11] FIG. 11 is a cross-sectional view corresponding to the position of part E1 in FIG. [Figure 12] FIG. 11 is a cross-sectional view corresponding to the position of part E2 in FIG. [Figure 13] 5A to 5C are cross-sectional views illustrating a method for manufacturing the vibration element. [Figure 14] Graph showing the relationship between dry ratio and Q value ratio. [Figure 15] Graph showing the relationship between the dry ratio and the Q value ratio when the aspect ratio is changed. [Figure 16] 10 is a graph showing the relationship between W / A and Wa / Aa when etching times are varied. [Figure 17] 10 is a graph showing the relationship between W / A and Wa / Aa when different reaction gases are used. [Figure 18] Graph showing the relationship between Wa / Aa and CI ratio. [Figure 19] 5A to 5C are diagrams showing a manufacturing process of the vibration element according to the second embodiment. [Figure 20] 5A to 5C are cross-sectional views illustrating a method for manufacturing the vibration element. [Figure 21] 5A to 5C are cross-sectional views illustrating a method for manufacturing the vibration element. [Figure 22] FIG. 10 is a plan view showing a modified example of the vibration element. [Figure 23] A cross-sectional view taken along line A2-A2 in Figure 22. [Figure 24] FIG. 10 is a plan view showing a modified example of the vibration element. [Figure 25] Cross-sectional view taken along line A3-A3 in Figure 24. [Figure 26] FIG. 10 is a plan view showing a modified example of the vibration element. [Figure 27] Cross-sectional view taken along line A4-A4 in Figure 26. [Figure 28] Cross-sectional view taken along line A5-A5 in Figure 26. [Figure 29] FIG. 10 is a plan view showing a modified example of the vibration element. [Figure 30]Cross-sectional view taken along line A6-A6 in Figure 29. [Figure 31] A cross-sectional view taken along line A7-A7 in Figure 29. DETAILED DESCRIPTION OF THE INVENTION

[0007] 1. Embodiment 1 A method for manufacturing the vibration element according to the first embodiment will be described. First, the configuration of the vibration element 1 will be described with reference to FIGS. 1 and 2, and then the manufacturing method of the vibration element 1 will be described with reference to FIGS.

[0008] For ease of explanation, each figure (except for some figures) shows three mutually intersecting axes: the X-axis, the Y-axis, and the Z-axis. In this embodiment, these three axes are perpendicular to each other. The direction along the X-axis is also referred to as the X-direction, the direction along the Y-axis is also referred to as the Y-direction, and the direction along the Z-axis is also referred to as the Z-direction. The Y-direction corresponds to the first direction, the X-direction corresponds to the second direction, and the Z-direction corresponds to the third direction. The arrow side of each axis is also referred to as the positive side, and the opposite side is also referred to as the negative side. The positive side of the Z-direction is also referred to as the "upper" side, and the negative side is also referred to as the "lower" side. The planar view from the Z-direction is also simply referred to as the "planar view." The X-axis, Y-axis, and Z-axis correspond to the crystal axes of quartz, as will be described later.

[0009] As shown in FIGS. 1 and 2, the vibration element 1 is a tuning fork type vibration element, and includes a vibration substrate 2 and an electrode 3 formed on the surface of the vibration substrate 2.

[0010] The vibration substrate 2 is formed by patterning a Z-cut quartz substrate (Z-cut quartz plate) into a desired shape, and has an extent in the XY plane defined by the X-axis and Y-axis, which are the crystal axes of the quartz, and a thickness in the Z direction. The X-axis is also called the electrical axis, the Y-axis is also called the mechanical axis, and the Z-axis is also called the optical axis.

[0011] The vibration substrate 2 is plate-shaped and has a first surface 2A and a second surface 2B that are arranged side by side in the Z direction and are opposite each other. The vibration substrate 2 also has a base 21, and a first vibrating arm 22 and a second vibrating arm 23 that extend from the base 21 along the Y direction and are arranged side by side in the X direction.

[0012] The first vibrating arm 22 has a first groove 221 with a bottom that opens to the first surface 2A, a second groove 222 with a bottom that opens to the second surface 2B, and a side surface 101 that connects the first surface 2A and the second surface 2B. Similarly, the second vibrating arm 23 has a first groove 231 with a bottom that opens to the first surface 2A, a second groove 232 with a bottom that opens to the second surface 2B, and a side surface 103 that connects the first surface 2A and the second surface 2B. These first grooves 221, 231 and second grooves 222, 232 each extend along the Y direction, and on their inner surfaces, a bottom surface 111, groove inner side surfaces 112, 113, and inclined surfaces 114, 115 are formed. The groove inner side surfaces 112 and 113 face each other. The groove inner side surface 112 on the negative X-direction side is connected to the bottom surface 111 by an inclined surface 114, and the groove inner side surface 113 on the positive X-direction side is connected to the bottom surface 111 by an inclined surface 115. In this manner, the first vibrating arm 22 and the second vibrating arm 23 each have a substantially H-shaped cross section. This reduces thermoelastic loss, resulting in a vibrating element 1 with excellent vibration characteristics. Note that the bottom surface 111 is the deepest portion in the Z direction from the first surface 2A or the second surface 2B, and does not necessarily have to be a plane parallel to the XY plane. For example, the first grooves 221 and 231 and the second grooves 222 and 232 may have a shape in which the inclined surface 114 and the inclined surface 115 intersect. In this case, the ridge connecting the inclined surface 114 and the inclined surface 115 corresponds to the bottom surface 111.

[0013] The electrode 3 has a signal electrode 31 and a ground electrode 32. The signal electrode 31 is arranged on the first surface 2A and the second surface 2B of the first vibrating arm 22 and on the side surface 103 of the second vibrating arm 23. On the other hand, the ground electrode 32 is arranged on the side surface 101 of the first vibrating arm 22 and on the first surface 2A and the second surface 2B of the second vibrating arm 23. When a drive signal is applied to the signal electrode 31 with the ground electrode 32 grounded, the first vibrating arm 22 and the second vibrating arm 23 flexurally vibrate in the X direction, repeatedly approaching and separating from each other, as shown by the arrows in FIG. 1 .

[0014] The vibration element 1 has been briefly described above. Next, we will explain the manufacturing method of the vibration element 1. As shown in Fig. 3, the manufacturing method of the vibration element 1 includes a preparation step S1 of preparing a quartz substrate 20, which is a base material of the vibration substrate 2, a first protective film formation step S2 of forming a first protective film 5 on a first surface 2A of the quartz substrate 20, a first dry etching step S3 of dry etching the quartz substrate 20 from the first surface 2A side via the first protective film 5, a second protective film formation step S4 of forming a second protective film 6 on a second surface 2B of the quartz substrate 20, a second dry etching step S5 of dry etching the quartz substrate 20 from the second surface 2B side via the second protective film 6, a wet etching step S6 of wet etching the quartz substrate 20, and an electrode formation step S7 of forming electrodes 3 on the surface of the vibration substrate 2 obtained by the above steps. Each of these steps will be explained in turn below.

[0015] ≪Preparation process S1≫ As shown in Fig. 4, a quartz crystal substrate 20 is prepared as the base material of the vibration substrate 2. The quartz crystal substrate 20 is adjusted to a desired thickness by CMP (chemical mechanical polishing) or the like, and has a first surface 2A and a second surface 2B that are sufficiently smooth. A plurality of vibration elements 1 are formed collectively from the quartz crystal substrate 20.

[0016] ≪First protective film formation step S2≫ As shown in FIG. 5, a metal film M1 is formed on the first surface 2A of the quartz substrate 20, and a metal film M2 is formed on the second surface 2B. Next, a first resist film R1 is formed on the metal film M1, and the formed first resist film R1 is patterned. Next, a first protective film 5 is formed in the openings of the first resist film R1, and then the first resist film R1 is removed. This results in the pattern shown in FIG. 6. The first protective film 5 is not particularly limited as long as it has etching resistance, but various metal masks such as a nickel mask can be used.

[0017] The first protective film 5 has openings 51, 52, and 53 in the portion of the quartz crystal substrate 20 to be removed. Of these, the opening 51 overlaps with the first groove forming region Q1 in which the first grooves 221 and 231 are formed. The opening 52 overlaps with the inter-arm region Q4 located between the first vibrating arm forming region Q2 in which the first vibrating arm 22 is formed and the second vibrating arm forming region Q3 in which the second vibrating arm 23 is formed. The opening 53 overlaps with the inter-element region Q5 located between adjacent vibrating substrates 2. In other words, the first protective film 5 is formed excluding the first groove forming region Q1, the inter-arm region Q4, and the inter-element region Q5.

[0018] <First dry etching process S3> As shown in FIG. 7, the quartz crystal substrate 20 is dry-etched from the first surface 2A side via the first protective film 5, and the first grooves 221, 231 and the outer shape of the vibration substrate 2, i.e., the outer shapes of the first vibrating arm 22 and the second vibrating arm 23, are simultaneously formed on the first surface 2A. Note that "simultaneously formed" refers to forming both together in one process. More specifically, this process is reactive ion etching, and is performed using an RIE (reactive ion etching) apparatus. The reactive gas introduced into the RIE apparatus is not particularly limited, and examples thereof include SF6, CF4, C2F4, C2F6, C3F6, and C4F8.

[0019] This process ends when the first grooves 221 and 231 reach the desired depth. Here, in dry etching, it is known that the "microloading effect" causes the etching rate to decrease as the pattern density of the first protective film 5 increases. In this embodiment, when comparing the width W of the first grooves 221 and 231 in the X direction with the width A of the region Q4 between the arms in the X direction, W < A. Also, when comparing the width W with the width B of the region Q5 between the elements in the X direction, W < B. Therefore, due to the microloading effect, the etching rate of the first groove formation region Q1 becomes lower than the etching rates of the region Q4 between the arms and the region Q5 between the elements. As a result, at the end of this process, the depth Wa of the first grooves 221 and 231 is shallower than the depths Aa and Ba of the outer shape of the vibrating substrate 2. That is, Wa < Aa (Wa / Aa < 1), Wa < Ba (Wa / Ba < 1). Also, the depths Aa and Ba are each at least half of the thickness of the crystal substrate 20. That is, if the thickness of the crystal substrate 20 is Ta, then Aa ≥ 0.5Ta and Ba ≥ 0.5Ta.

[0020] After the end of this process, the first protective film 5 and the metal film M1 are removed, and the process moves on to the processing of the back surface of the crystal substrate 20.

[0021] ≪Second protective film formation step S4≫ As shown in FIG. 8, a second protective film 6 is formed on the metal film M2. The method of forming the second protective film 6 is the same as the method of forming the first protective film 5 described above. The second protective film 6 has openings 61, 62, and 63 in the portions of the crystal substrate 20 to be removed. Among these, the opening 61 overlaps with the second groove formation region Q6 where the second grooves 222 and 232 are formed. The opening 62 overlaps with the region Q4 between the arms. The opening 63 overlaps with the region Q5 between the elements. <00,00153>

[0022] ≪Second dry etching step S5≫ As shown in FIG. 9, the crystal substrate 20 is dry-etched from the second surface 2B side through the second protective film 6 to simultaneously form the second grooves 222 and 232 and the outer shape of the vibrating substrate 2, that is, the outer shapes of the first vibrating arm 22 and the second vibrating arm 23, on the second surface 2B. This process is performed in the same manner as the first dry etching step S3.

[0023] This process ends when the second grooves 222 and 232 reach the desired depth. In this embodiment, when comparing the width W of the second grooves 222 and 232 in the X direction with the width A of the inter-arm region Q4 in the X direction, W < A. Also, when comparing the width W with the width B of the inter-element region Q5 in the X direction, W < B. Therefore, due to the microloading effect, the etching rate of the second groove formation region Q6 is lower than the etching rates of the inter-arm region Q4 and the inter-element region Q5. Thus, at the end of this process, the depth Wa of the second grooves 222 and 232 is shallower than the depths Aa and Ba of the outer shape of the vibrating substrate 2. That is, Wa < Aa (Wa / Aa < 1), Wa < Ba (Wa / Ba < 1). Also, the depths Aa and Ba are each at least half of the thickness of the crystal substrate 20. That is, Aa ≥ 0.5Ta, Ba ≥ 0.5Ta. Therefore, the inter-arm region Q4 and the inter-element region Q5 penetrate respectively. By the inter-arm region Q4 and the inter-element region Q5 penetrating respectively, the first vibrating arm 22 and the second vibrating arm 23 are formed.

[0024] As shown in FIG. 10, after the end of this process, the second protective film 6 and the metal film M2 are removed.

[0025] As described above, in the first dry etching process S3, the crystal substrate 20 is dry-etched from the first surface 2A side, and in the second dry etching process S5, the crystal substrate 20 is dry-etched from the second surface 2B side to form the outer shape of the vibrating substrate 2. For this reason, for example, when the positions of the first protective film 5 and the second protective film 6 are displaced due to manufacturing variations or the like in a plan view from the Z direction, in the overlapping region 105 of the dry etching in the first dry etching process S3 and the dry etching in the second dry etching process S5, a step may be formed on the side surface 101 of the first vibrating arm 22 and the side surface 103 of the second vibrating arm 23.

[0026] 11 and 12, for example, when the position of the second protective film 6 is deviated in the negative X-direction with respect to the first protective film 5, the contour of the vibration substrate 2 formed in the second dry etching process S5 is deviated in the negative X-direction with respect to the contour of the vibration substrate 2 formed in the first dry etching process S3, and thus a step portion 107 is formed on the side surface 101 of the first vibrating arm 22. Also, for example, when the position of the second protective film 6 is deviated in the positive X-direction with respect to the first protective film 5, a step portion 107 is also formed. Furthermore, although the first vibrating arm 22 has been described as an example, when the position of the second protective film 6 is deviated in the positive X-direction with respect to the first protective film 5, a step portion 107 is similarly formed on the side surface 103 of the second vibrating arm 23.

[0027] <Wet etching process S6> The wet etching step S6 is a step of wet-etching the quartz substrate 20 by immersing the quartz substrate 20 in an etching solution. The etching solution may be hydrofluoric acid or ammonium fluoride.

[0028] As described above, the first vibrating arm 22 and the second vibrating arm 23 are formed on the quartz substrate 20 by the first dry etching process S3 and the second dry etching process S5. That is, this process is a process of wet-etching the first vibrating arm 22 and the second vibrating arm 23. Specifically, this process wet-etches the side surfaces 101 and 103 of the first vibrating arm 22 and the second vibrating arm 23, and the first grooves 221 and 231 and the second grooves 222 and 232. In this process, wet-etching the side surfaces 101 and 103 of the first vibrating arm 22 and the second vibrating arm 23 makes it possible to reduce the size of the step portions 107 formed on the side surfaces 101 and 103. Reducing the size of the step portions 107 makes it possible to suppress the generation of unwanted vibrations when the vibration element 1 is vibrated and to suppress damage to the vibration element 1 when an impact is applied to the vibration element 1.

[0029] In this step, the first grooves 221, 231 and the second grooves 222, 232 are wet-etched, so that inclined surfaces 114, 115 and bottom surfaces 111 are formed on the inner surfaces of the first grooves 221, 231 and the second grooves 222, 232, as shown in FIG.

[0030] Let D1 be the depth of the grooves formed in the first dry etching step S3 and the second dry etching step S5, and D2 be the depth of the grooves formed in the wet etching step S6. The final groove depth D after the wet etching step S6, i.e., the distance in the Z direction from the first surface 2A or the second surface 2B to the bottom surface 111, is D1 + D2. Note that depth D1 is equal to the depth Wa described above. Depth D1 can be considered to be the distance in the Z direction between the boundary between the groove inner side surface 112 and the inclined surface 114 and the boundary between the groove inner side surface 113 and the inclined surface 115, whichever is farther from the bottom surface 111, and the first surface 2A or the second surface 2B. Depth D2 can be considered to be the distance in the Z direction from the boundary farther from the bottom surface 111 described above to the bottom surface 111. In this embodiment, the distance in the Z direction between the boundary between the groove inner side surface 112 and the inclined surface 114 and the first surface 2A or the second surface 2B is depth D1, and the distance in the Z direction from the boundary to the bottom surface 111 is depth D2. In other words, depth D2 is the length of inclined surface 114 in the Z direction, and depth D1 is the value obtained by subtracting depth D2 from depth D.

[0031] FIG. 14 is a graph showing the results of a simulation of the relationship between the dry ratio D1 / D and the Q-value ratio. Here, the dry ratio D1 / D is the ratio of the groove depth D1 formed by dry etching to the final groove depth D. The Q-value ratio is a ratio of the Q-value of the vibration element 1 normalized to the Q-value when the dry ratio D1 / D is 0, i.e., the Q-value when the first grooves 221, 231 and the second grooves 222, 232 are formed by wet etching alone, set to 100%. As shown in FIG. 14, the Q-value of the vibration element 1 also changes with changes in the dry ratio D1 / D. Specifically, the Q-value increases as the dry ratio D1 / D increases, and the Q-value becomes almost constant when the dry ratio D1 / D is in the range of D1 / D≧0.80. The Q-value at this time is equivalent to the Q-value when the dry ratio D1 / D is 1.00, i.e., the Q-value when the first vibrating arm 22 and the second vibrating arm 23 are formed by dry etching alone to have ideal shapes without the step portion 107. In this way, by forming the first grooves 221, 231 and the second grooves 222, 232 so that the dry ratio D1 / D satisfies D1 / D≧0.80, the Q value can be significantly improved compared to when they are formed by wet etching alone.

[0032] 15 is a graph showing the results of a simulation of the relationship between the dry ratio D1 / D and the Q value ratio when the aspect ratio D / W, which is the ratio of the groove depth D to the groove width W, is changed. As shown in FIG. 15, even when the aspect ratio D / W changes, the Q value can be significantly improved by setting the dry ratio D1 / D to D1 / D≧0.80. Furthermore, if the first grooves 221, 231 and the second grooves 222, 232 are formed so that the dry ratio D1 / D satisfies D1 / D≧0.85, an even better Q value can be obtained.

[0033] In the wet etching step S6, the etching amount of the side surfaces 101, 103 is preferably 0.01 μm or more. This reduces the step portion 107, thereby suppressing the generation of unwanted vibrations when the vibration element 1 is vibrated and the damage to the vibration element 1 when an impact is applied to the vibration element 1. The etching amount of the side surfaces 101, 103 refers to the amount of displacement of the side surfaces 101, 103 in the X direction, which is the direction perpendicular to the side surfaces 101, 103, before and after the wet etching step S6.

[0034] Furthermore, in this process, the etching amount of the side surfaces 101 and 103 is preferably 1 μm or less. If the etching amount of the side surfaces 101 and 103 exceeds 1 μm, each portion of the vibration substrate 2 other than the step portion 107, such as the first surface 2A, the second surface 2B, the first grooves 221 and 231, and the second grooves 222 and 232, will be wet-etched, resulting in the outer dimensions of the vibration element 1 differing from the desired outer dimensions. As a result, there is a risk that the vibration element 1 will vibrate at a frequency that is significantly different from the desired frequency. By setting the etching amount of the side surfaces 101 and 103 to 1 μm or less, deviation from the desired frequency can be suppressed.

[0035] Furthermore, in this process, the etching amount of the side surfaces 101, 103 is preferably 0.5 μm or less. If the etching amount of the side surfaces 101, 103 exceeds 0.5 μm, for example, the corners of the vibrating arms 22, 23 where the first surface 2A or the second surface 2B connects to the side surfaces 101, 103 are wet-etched, resulting in a complex shape of the vibrating element 1 that differs from the desired shape. Therefore, when the vibrating element 1 is vibrated, unwanted vibrations may occur, and vibration characteristics such as the Q value may deteriorate. By setting the etching amount of the side surfaces 101, 103 to 0.5 μm or less, the generation of unwanted vibrations can be suppressed.

[0036] By the above steps S1 to S6, a plurality of vibration substrates 2 are formed from the quartz crystal substrate 20 at once.

[0037] ≪Electrode formation process S7≫ A metal film is formed on the surface of the vibration substrate 2, and the electrode 3 is formed by patterning this metal film.

[0038] In this way, the vibration element 1 is obtained. As described above, dry etching allows processing without being affected by the crystal planes of quartz, thereby achieving excellent dimensional accuracy. Furthermore, by simultaneously forming the first grooves 221, 231 and the second grooves 222, 232 and the outer shape of the vibration substrate 2, it is possible to reduce the number of manufacturing steps for the vibration element 1 and reduce the cost of the vibration element 1. Furthermore, misalignment of the first grooves 221, 231 and the second grooves 222, 232 with respect to the outer shape is prevented, thereby improving the formation accuracy of the vibration substrate 2.

[0039] Furthermore, wet etching can reduce the size of the step portions 107 formed on the side surfaces 101, 103 of the first vibrating arm 22 and the second vibrating arm 23 when the quartz crystal substrate 20 is dry-etched from both the first surface 2A side and the second surface 2B side. This makes it possible to suppress the generation of unwanted vibrations when the vibrating element 1 is vibrated and damage to the vibrating element 1 when an impact is applied to the vibrating element 1.

[0040] The method for manufacturing the vibration element 1 has been described above. Next, conditions for more reliably achieving the microloading effect will be described with reference to FIGS. The relationship between W / A and Wa / Aa when the etching time is varied is shown in Figure 16. As can be seen from the figure, the microloading effect is evident in the region where W / A is 40% or less for each etching time.

[0041] The microloading effect also varies depending on the type of reactive gas used in dry etching. Figure 17 shows the relationship between W / A and Wa / Aa when three different types of common reactive gases are used.

[0042] For example, using a fluorine-based gas containing a large amount of carbon, such as C2F4, C2F6, C3F6, or C4F8, as the reactive gas results in a thick sidewall protective film and a small slope, as with gas type G3. Therefore, by reducing the width A relative to the width W, it becomes easier to increase Wa / Aa, allowing for the miniaturization of the vibration element 1. For example, when designing the frequency and CI value, a width W greater than a certain value and a depth Wa close to the depth Aa may be required. In this case, the width A must be reduced to miniaturize the vibration element 1, and in such cases, at least one of C2F4, C2F6, C3F6, and C4F8 is particularly effective.

[0043] On the other hand, when a fluorine-based gas with little or no carbon, such as SF6 or CF4, is used alone or in combination with a fluorine-based gas with a lot of carbon, the sidewall protective film becomes thinner and the slope becomes larger, as with gas type G1. Therefore, it is possible to increase the width A relative to the width W while maintaining the depth Wa large relative to the depth Aa. For example, when it is desired to increase the depth Wa while narrowing the width of the first vibrating arm 22 and the second vibrating arm 23 and increasing the width A, at least one of SF6 and CF4 is particularly effective.

[0044] When W / A=x and Wa / Aa=y, gas species G1 is expressed by the following formula (1), gas species G2 is expressed by the following formula (2), and gas species G3 is expressed by the following formula (3).

[0045]

number

[0046]

number

[0047]

number

[0048] 17, if y is in the region P between formula (1) and formula (3), that is, if y satisfies the following formulas (4) and (5), the microloading effect can be more reliably achieved using a general reactive gas. This makes it easier to manufacture the vibration element 1, and reduces the manufacturing cost.

[0049]

number

[0050]

number

[0051] If y does not satisfy equation (4), the change in depth Wa relative to the change in width W will be large, which may result in variation in depth Wa. This can be suppressed by making y satisfy equation (4). Furthermore, if y does not satisfy equation (5), it will be difficult to increase y in areas where x is large, resulting in a shallow depth Wa. Alternatively, in order to deepen depth Wa, it will be necessary to approach W=A, which will likely result in shape constraints. This can be suppressed by making y satisfy equation (5).

[0052] Here, for example, when the width W and depth Wa are constant, if gas type G2 is selected, the width A can be made smaller than that of gas type G1, thereby enabling the vibration element 1 to be made more compact. If gas type G3 is selected, the width A can be made even smaller than that of gas type G2, enabling the vibration element 1 to be made even more compact. Thus, from the perspective of miniaturization, it is preferable that, within region P, y be in region PP between formulas (2) and (3). In other words, it is preferable that y satisfy the following formula (6) and the above formula (5).

[0053]

number

[0054] Next, the effect of improving the CI value of the vibration element 1 when the first grooves 221, 231 and the second grooves 222, 232 are formed will be described with reference to FIG. FIG. 18 shows the relationship between Wa / Aa and the CI ratio. Here, the CI ratio is the ratio of the CI value normalized to 1.0 when the first grooves 221, 231 and the second grooves 222, 232 are not formed. As shown in FIG. 18, it is preferable to set Wa / Aa≧0.2. In this embodiment, Wa / Aa<1 is satisfied to utilize the microloading effect. This allows the CI value to be reduced to 30% or less compared to when the first grooves 221, 231 and the second grooves 222, 232 are not formed. Therefore, it is possible to manufacture a vibration element 1 with excellent vibration characteristics. Furthermore, it is preferable to set Wa / Aa≧0.4, which allows the CI value to be reduced to 10% or less compared to when the first grooves 221, 231 and the second grooves 222, 232 are not formed.

[0055] The conditions for more reliably achieving the microloading effect in the method for manufacturing the vibration element 1 have been described above. As described above, the manufacturing method of the vibration element 1 includes the first vibrating arm 22 and the second vibrating arm 23 that extend along the Y direction, which is a first direction, and are aligned along the X direction, which is a second direction intersecting the Y direction, and the first vibrating arm 22 and the second vibrating arm 23 are respectively aligned in the Z direction, which is a third direction intersecting the Y direction and the X direction, and the vibration element has first surfaces 2A and second surfaces 2B that are reverse to each other, first grooves 221 and 231 with bottoms that open on the first surface 2A, second grooves 222 and 232 with bottoms that open on the second surface 2B, and side surfaces 101 and 103 that connect the first surface 2A and the second surface 2B, and includes a preparation step S1 of preparing a quartz substrate 20 that has the first surface 2A and the second surface 2B, and a step of dry-etching the quartz substrate 20 from the first surface 2A side to remove the first grooves 221 and 231 and the first vibrating arms 22 and a first dry etching process S3 in which the second grooves 222 and 232 and the outer shapes of the first vibrating arm 22 and the second vibrating arm 23 are formed; a second dry etching process S5 in which the quartz substrate 20 is dry etched from the second surface 2B side to form the second grooves 222 and 232 and the outer shapes of the first vibrating arm 22 and the second vibrating arm 23; and and a wet etching process S6 in which wet etching is performed to form inclined surfaces 114, 115 that connect the bottom surfaces 111 of the first grooves 221, 231 and the second grooves 222, 232 to the groove inner side surfaces 112, 113, wherein the first grooves 221, 231 and the second grooves 222, 232 satisfy D1 / D≧0.80, where D is the depth and D1 is the value obtained by subtracting the length of the inclined surfaces 114 in the Z direction from the depth. This manufacturing method can reduce the size of the step portions 107 formed on the side surfaces 101, 103 of the first vibrating arm 22 and the second vibrating arm 23. This can suppress the generation of unwanted vibrations when the vibrating element 1 is vibrated and the damage to the vibrating element 1 when an impact is applied to the vibrating element 1. Furthermore, as described above, the dry ratio D1 / D satisfies D1 / D≧0.80, and therefore the Q value can be improved.

[0056] Furthermore, as described above, in the method for manufacturing the vibration element 1, it is preferable that the dry ratio D1 / D of the first grooves 221, 231 and the second grooves 222, 232 satisfy D1 / D≧0.85, thereby further improving the Q value.

[0057] Furthermore, as described above, in the manufacturing method of the vibration element 1, it is preferable that the etching amount of the side surfaces 101, 103 in the wet etching step S6 is 0.01 μm or more, which reduces the step portion 107 and makes it possible to suppress the generation of unwanted vibrations when the vibration element 1 is vibrated and damage to the vibration element 1 when an impact is applied to the vibration element 1.

[0058] As described above, in the method for manufacturing the vibration element 1, the etching amount of the side surfaces 101, 103 in the wet etching step S6 is preferably 1 μm or less, which can suppress deviation from the desired frequency when the vibration element 1 is vibrated.

[0059] As described above, in the method for manufacturing the vibration element 1, the etching amount of the side surfaces 101, 103 in the wet etching step S6 is preferably 0.5 μm or less, which can suppress the generation of unwanted vibrations when the vibration element 1 is vibrated.

[0060] Furthermore, as described above, in the manufacturing method of the vibration element 1, when the depths of the first grooves 221, 231 formed in the first dry etching step S3 and the depths of the second grooves 222, 232 formed in the second dry etching step S5 are each defined as Wa, and the depths of the outer shapes of the first vibrating arms 22 and the second vibrating arms 23 formed in the first dry etching step S3 and the depths of the outer shapes of the first vibrating arms 22 and the second vibrating arms 23 formed in the second dry etching step S5 are each defined as Aa, it is preferable that Wa / Aa<1 be satisfied in at least one of the first dry etching step S3 and the second dry etching step S5. This makes it possible to simultaneously form the first grooves 221, 231 and the second grooves 222, 232 and the outer shape of the vibration substrate 2. This allows for a reduction in the number of manufacturing steps of the vibration element 1 and a reduction in the cost of the vibration element 1. Furthermore, the first grooves 221, 231 and the second grooves 222, 232 are prevented from being misaligned with respect to the outer shape, and the precision with which the vibration substrate 2 is formed is improved.

[0061] 2. Embodiment 2 A method for manufacturing the vibration element 1 according to the second embodiment will be described with reference to Fig. 19 to Fig. 21. Note that the same components as those in the first embodiment are given the same reference numerals, and redundant description will be omitted. Embodiment 2 is similar to embodiment 1 except that it includes a third protective film formation step S10 between the second dry etching step S5 and the wet etching step S6, and that a third protective film 109 is formed on the first surface 2A and the second surface 2B of the quartz substrate 20 in the third protective film formation step S10, and that the first surface 2A and the second surface 2B of the quartz substrate 20 are masked by the third protective film 109 in the wet etching step S6.

[0062] As shown in Figure 19, the manufacturing method of the vibration element 1 of embodiment 2 includes a preparation step S1 of preparing a quartz substrate 20, which is the base material of the vibration substrate 2; a first protective film formation step S2 of forming a first protective film 5 on the first surface 2A of the quartz substrate 20; a first dry etching step S3 of dry etching the quartz substrate 20 from the first surface 2A side through the first protective film 5; a second protective film formation step S4 of forming a second protective film 6 on the second surface 2B of the quartz substrate 20; a second dry etching step S5 of dry etching the quartz substrate 20 from the second surface 2B side through the second protective film 6; a third protective film formation step S10 of forming a third protective film 109 on the first surface 2A and the second surface 2B of the quartz substrate 20; a wet etching step S6 of wet-etching the quartz substrate 20; and an electrode formation step S7 of forming an electrode 3 on the surface of the vibration substrate 2 obtained by the above steps.

[0063] Since the steps from preparation step S1 to second dry etching step S5 are the same as those in embodiment 1, their explanation will be omitted and the explanation will start from third protective film forming step S10. Note that, similar to embodiment 1, after the second dry etching step S5 is completed, the second protective film 6 and metal film M2 are removed from the quartz crystal substrate 20.

[0064] ≪Third protective film formation step S10≫ 20, a third protective film 109 is formed on the first surface 2A and the second surface 2B of the quartz substrate 20. The third protective film 109 is, for example, a metal film formed by depositing chromium and gold in this order from the quartz substrate 20 side. The third protective film 109 can be formed by depositing a metal film on the surface of the quartz substrate 20 using, for example, a sputtering method or a CVD (Chemical Vapor Deposition) method, and then patterning this metal film using photolithography and etching techniques.

[0065] <Wet etching process S6> In this step, the quartz substrate 20 is wet-etched by immersing the quartz substrate 20 in an etching solution. In the second embodiment, prior to this step, a third protective film 109 is formed on the first surface 2A and the second surface 2B of the quartz substrate 20 in a third protective film forming step S10. Therefore, in this step, the first surface 2A and the second surface 2B of the quartz substrate 20 are masked by the third protective film 109. In other words, the first surface 2A and the second surface 2B of the first vibrating arm 22 and the second vibrating arm 23 are masked by the third protective film 109. That is, in this step, the first surface 2A and the second surface 2B of the first vibrating arm 22 and the second vibrating arm 23 are not wet-etched. This makes it possible to prevent the dimensions and shape of the vibration element 1 from differing from the desired dimensions and shape. Therefore, it is possible to prevent deviation from the desired frequency and the generation of unwanted vibrations in the vibration element 1.

[0066] Since the third protective film 109 is not formed on the side surfaces 101, 103 of the first vibrating arm 22 and the second vibrating arm 23, the step portions 107 formed on the side surfaces 101, 103 can be made small, similar to the first embodiment.

[0067] 21, after this step is completed, the third protective film 109 is removed. In this manner, a plurality of vibration substrates 2 are formed collectively from the quartz crystal substrate 20.

[0068] ≪Electrode formation process S7≫ This step is carried out in the same manner as in embodiment 1. A metal film is formed on the surface of the vibration substrate 2, and the electrode 3 is formed by patterning this metal film.

[0069] In this way, the vibration element 1 is obtained.

[0070] According to this embodiment, in addition to the effects of the first embodiment, the following effects can be obtained. In the wet etching step S6, the first surface 2A and the second surface 2B of the quartz crystal substrate 20 are masked with the third protective film 109, which prevents the vibration element 1 from having dimensions and a shape different from the desired dimensions and a shape. This prevents deviation from the desired frequency in the vibration element 1 and the generation of unwanted vibrations.

[0071] The method for manufacturing a vibration element according to the present invention has been described above based on the first and second embodiments. However, the present invention is not limited to this, and the configuration of each part can be replaced with any configuration having a similar function. Also, other arbitrary components may be added to the present invention. Furthermore, each embodiment may be combined as appropriate.

[0072] For example, in the above-described embodiment, Wa / Aa<1 is satisfied in each of the first dry etching step S3 and the second dry etching step S5, but this is not limited thereto, and it is sufficient that Wa / Aa<1 is satisfied in at least one of these steps.

[0073] Furthermore, the vibrating element manufactured by the vibrating element manufacturing method of the present invention is not particularly limited and may be, for example, a vibrating element 1A as shown in FIGS. 22 and 23. In the vibrating element 1A, a pair of first grooves 221 are formed side by side in the X direction on the first surface 2A of the first vibrating arm 22, and a pair of second grooves 222 are formed side by side in the X direction on the second surface 2B. Similarly, a pair of first grooves 231 are formed side by side in the X direction on the first surface 2A of the second vibrating arm 23, and a pair of second grooves 232 are formed side by side in the X direction on the second surface 2B. Note that in this configuration, since multiple grooves are arranged side by side, the width W of each groove tends to be narrow. Therefore, it is preferable to use at least one of SF6 and CF4 as the reactive gas in the first dry etching step S3 and the second dry etching step S5. This allows each groove to be formed deep, thereby reducing the CI value.

[0074] The vibration element may also be a double-ended tuning fork vibration element 7 as shown in Figures 24 and 25. Electrodes are not shown in Figures 24 and 25. The double-ended tuning fork vibration element 7 has a pair of bases 711, 712, and a first vibrating arm 72 and a second vibrating arm 73 connecting the bases 711, 712. The first vibrating arm 72 and the second vibrating arm 73 have first grooves 721, 731 with bottoms that open to the first surface 7A, and second grooves 722, 732 with bottoms that open to the second surface 7B, respectively.

[0075] Also, for example, the vibration element may be a gyro vibration element 8 as shown in Figures 26 to 28. Note that electrodes are not shown in Figures 26 to 28. The gyro vibration element 8 has a base 81, a pair of detection vibration arms 82 and 83 extending from the base 81 on both sides in the Y direction, a pair of connecting arms 84 and 85 extending from the base 81 on both sides in the X direction, drive vibration arms 86 and 87 extending from the tip of the connecting arm 84 on both sides in the Y direction, and drive vibration arms 88 and 89 extending from the tip of the connecting arm 85 on both sides in the Y direction. In such a gyro vibration element 8, when an angular velocity ωz about the Z axis acts while the drive vibration arms 86, 87, 88, and 89 are flexurally vibrating in the direction of the arrow SD in Figure 26, the Coriolis force excites new flexural vibration in the detection vibration arms 82 and 83 in the direction of the arrow SS, and the angular velocity ωz is detected based on the charge output from the detection vibration arms 82 and 83 due to the flexural vibration.

[0076] The detection vibration arms 82 and 83 have first grooves 821 and 831 with a bottom that open to the first surface 8A and second grooves 822 and 832 with a bottom that open to the second surface 8B. The drive vibration arms 86, 87, 88, and 89 have first grooves 861, 871, 881, and 891 with a bottom that open to the first surface 8A and second grooves 862, 872, 882, and 892 with a bottom that open to the second surface 8B. In such a gyro vibration element 8, a pair of vibration arms adjacent in the X direction can be defined as a first vibrating arm and a second vibrating arm, such as the detection vibration arm 82 and the drive vibration arm 86, the detection vibration arm 82 and the drive vibration arm 88, the detection vibration arm 83 and the drive vibration arm 87, or the detection vibration arm 83 and the drive vibration arm 89.

[0077] In the case of the gyro vibration element 8, the inter-arm region Q4 needs to be enlarged due to its structure. In such a case, the depth Wa becomes shallow in the region between the above formula (2) and formula (3), which may result in a decrease in sensitivity. Therefore, it is preferable to use the region between the above formula (1) and formula (2).

[0078] 29 to 31. The gyro vibration element 9 has a base 91, a pair of drive vibration arms 92, 93 extending from the base 91 in the positive Y direction and aligned in the X direction, and a pair of detection vibration arms 94, 95 extending from the base 91 in the negative Y direction and aligned in the X direction. In such a gyro vibration element 9, when an angular velocity ωy about the Y axis acts while the drive vibration arms 92, 93 are flexurally vibrating in the direction of arrow SD in Fig. 29, a new flexural vibration in the direction of arrow SS is excited in the detection vibration arms 94, 95 by the Coriolis force, and the angular velocity ωy is detected based on the charge output from the detection vibration arms 94, 95 due to the flexural vibration.

[0079] The drive vibration arms 92 and 93 have first grooves 921 and 931 with a bottom that open to the first surface 9A and second grooves 922 and 932 with a bottom that open to the second surface 9B. The detection vibration arms 94 and 95 have first grooves 941 and 951 with a bottom that open to the first surface 9A and second grooves 942 and 952 with a bottom that open to the second surface 9B. In such a gyro vibration element 9, the drive vibration arms 92 and 93 or the detection vibration arms 94 and 95 become the first vibrating arms and the second vibrating arms. [Explanation of symbols]

[0080] 1…Vibrating element, 2…Vibrating substrate, 2A…First surface, 2B…Second surface, 101, 103…Side surface, 20…Crystal substrate, 21…Base, 22…First vibrating arm, 23…Second vibrating arm, 221, 231…First groove, 222, 232…Second groove, 3…Electrode, 31…Signal electrode, 32…Ground electrode, 5…First protective film, 51, 52, 53…Opening, 6…Second protective film, 61, 62, 63…Opening, 107…Step section, 109…Third protective film, 111…Bottom surface, 112, 113…Inner side surface of groove, 114, 115…Inclined surface, A…Width, Aa…Depth, B…Width, Ba…Depthさ、D,D1,D2…deepさ、M1…metal film、M2…metal film、Q1…first groove forming area、Q2…first vibrating wrist forming area、Q3…second vibrating wrist forming area、Q4…inter-wrist area、Q5…inter-substrate area、Q6…second groove forming area、R1…first relief film、S1…preparation process、S2…first protective film forming process、S3…first electrode forming process、S4…second protective film forming process、S5…second electrode forming process、S6…wave electrode forming process、S7…electrode forming process、S10…third protective film forming process、Ta…thicknessさ、W…width、Wa…deepさ。

Claims

1. First vibrating arms and a second vibrating arm extending along a first direction and aligned along a second direction intersecting the first direction and a second vibrating arm, The first vibrating arm and the second vibrating arm are in the first direction and the second direction, respectively. a first surface and a second surface that are arranged side by side in a third direction that intersects with the first surface and are in a front-back relationship; a first groove having a bottom that opens to a surface, a second groove having a bottom that opens to the second surface, and a groove between the first surface and the a side surface connecting to the second surface, a preparation step of preparing a quartz crystal substrate having the first surface and the second surface; The quartz crystal substrate is dry-etched from the first surface side to remove the first groove, the first vibrating arm, and the and a first dry etching process for forming the outer shape of the second vibrating arm; The quartz crystal substrate is dry-etched from the second surface side to form the second groove. , penetrates the region between the first vibrating arm and the second vibrating arm, a second dry etching process for forming the outer shape of the second vibrating arm; Thereafter, the side surfaces of the first vibrating arm and the second vibrating arm, the first groove, and the second The grooves are wet-etched to bond the bottom surfaces and the inner side surfaces of the first and second grooves. and a wet etching step for forming a sloped surface connecting the The first groove and the second groove have a depth D, and the depth D is the depth of the inclined surface in the third direction. When the value obtained by subtracting the length in the direction from the length in the direction is defined as D1, D1 / D≧0.80 is satisfied. A method for manufacturing a vibration element.

2. the first groove and the second groove satisfy D1 / D≧0.85; The method for manufacturing the vibration element according to claim 1 .

3. The etching amount of the side surface in the wet etching step is 0.01 μm or more. be, The method for manufacturing the vibration element according to claim 1 or 2.

4. The etching amount of the side surface in the wet etching step is 1 μm or less. A method for manufacturing the vibration element according to claim 1 .

5. The amount of etching of the side surface in the wet etching step is 0.5 μm or less. Ru, A method for manufacturing the vibration element according to claim 1 .

6. In the wet etching step, the first surface and the second surface are masked. Ru, A method for manufacturing the vibration element according to claim 1 .

7. The depth of the first groove formed in the first dry etching step and the depth of the second dry etching step are The depth of the second groove formed in the etching step is Wa, The depth of the contour formed in the first dry etching step and the second dry etching step When the depth of the outer shape formed in the chipping step is Aa, At least one of the first dry etching step and the second dry etching step In this case, Wa / Aa<1 is satisfied. A method for manufacturing the vibration element according to claim 1 .

Images