Method for manufacturing a vibration element

Abstract

To provide a method for manufacturing a vibration element that can prevent the occurrence of unnecessary vibration and damage to the vibration element.SOLUTION: A method for manufacturing a vibration element 1 includes: a first dry etching step S3 of performing dry etching on a crystal substrate 20 having a first surface 2A and a second surface 2B from the first surface 2A side to form the contours of first grooves 221, 231 and a first vibration arm 22 and a second vibration arm 23; a second dry etching step S5 of performing dry etching on the crystal substrate 20 from the second surface 2B side to form the contours of second grooves 222, 232 and the first vibration arm 22 and the second vibration arm 23; and a wet etching step S6 of subsequently performing wet etching on side faces 101, 103 of the first vibration arm 22 and the second vibration arm 23.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[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, by making the width of the groove narrower than the width between the pair of vibrating arms, the etching depth of the groove is made shallower than the etching depth between the pair of vibrating arms using the microloading effect, and the groove and the outer shape of the vibration element are formed together.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the method for manufacturing a vibration element in Patent Document 1, since dry etching is performed from both the front and back surfaces of the substrate, due to the misalignment between the resist film formed on the front surface of the substrate and the resist film formed on the back surface of the substrate, there is a risk that a step is formed on the side surface of the vibrating arm. When a step is formed on the side surface of the vibrating arm, there are problems such as the generation of unnecessary vibrations and breakage such as cracks and chips starting from the step during impact.

Means for Solving the Problems

[0005] The manufacturing method of the vibration element of the present invention includes a first vibration arm and a second vibration arm that extend along a first direction and are arranged side by side along a second direction intersecting the first direction. The first vibration arm and the second vibration arm are arranged side by side in a third direction intersecting the first direction and the second direction, and have a first surface and a second surface in a front-back relationship, a bottomed first groove opening on the first surface, a bottomed second groove opening on the second surface, and a side surface connecting the first surface and the second surface. The manufacturing method of the vibration element includes: a step of preparing a quartz substrate having the first surface and the second surface; a first dry etching step of dry etching the quartz substrate from the first surface side to form the first groove and the outer shapes of the first vibration arm and the second vibration arm; a second dry etching step of dry etching the quartz substrate from the second surface side to form the second groove and the outer shapes of the first vibration arm and the second vibration arm; and then, a wet etching step of wet etching the side surfaces of the first vibration arm and the second vibration arm.

Brief Description of the Drawings

[0006]

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Mode for Carrying Out the Invention

[0007] 1. Embodiment 1 The manufacturing method of the vibration element 1 according to Embodiment 1 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. 3 to 16.

[0008] For the sake of convenience in explanation, FIGS. 1, 2, and 14 to 17 show three mutually orthogonal axes, the X-axis, the Y-axis, and the Z-axis. Also, the direction along the X-axis is also referred to as the X-direction (second direction), the direction along the Y-axis is also referred to as the Y-direction (first direction), and the direction along the Z-axis is also referred to as the Z-direction (third direction). Also, the arrow side of each axis is also referred to as the plus side, and the opposite side is also referred to as the minus side. Also, the plus side in the Z-direction is also referred to as "up", and the minus side is also referred to as "down". Also, the plan view from the Z-direction is simply referred to as the "plan view". Also, the X-axis, the Y-axis, and the Z-axis correspond to the crystal axes of the crystal, 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 crystal substrate (Z-cut crystal plate) into a desired shape, has an extent in the X-Y plane defined by the X-axis and the Y-axis, which are the crystal axes of the crystal, and has 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 has a plate shape and has a first surface 2A and a second surface 2B that are in a front-back relationship with each other and are arranged side by side in the Z-direction. Also, the vibration substrate 2 includes a base portion 21, and a first vibration arm 22 and a second vibration arm 23 that extend from the base portion 21 along the Y-direction and are arranged side by side in the X-direction.

[0012] The first vibrating arm 22 has a bottomed first groove 221 that opens to the first surface 2A, a bottomed second groove 222 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 bottomed first groove 231 that opens to the first surface 2A, a bottomed second groove 232 that opens to the second surface 2B, and a side surface 103 that connects the first surface 2A and the second surface 2B. Each of these grooves 221, 222, 231, 232 extends along the Y direction. Therefore, the first vibrating arm 22 and the second vibrating arm 23 each have a substantially H-shaped cross-sectional shape. As a result, the thermoelastic loss is reduced, and the vibrating element 1 has excellent vibration characteristics.

[0013] The electrode 3 has a signal electrode 31 and a ground electrode 32. The signal electrode 31 is disposed on the first surface 2A and the second surface 2B of the first vibrating arm 22 and the side surface 103 of the second vibrating arm 23. On the other hand, the ground electrode 32 is disposed on the side surface 101 of the first vibrating arm 22 and 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, as indicated by the arrow in FIG. 1, the first vibrating arm 22 and the second vibrating arm 23 bend and vibrate in the X direction so as to repeatedly approach and separate.

[0014] The vibrating element 1 has been briefly described above. Next, a method for manufacturing the vibrating element 1 will be described. As shown in FIG. 3, the method for manufacturing the vibrating element 1 includes a preparation step S1 of preparing a quartz substrate 20 that is a base material of the vibrating substrate 2, a first protective film forming 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 forming 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 wet etching step S6 of wet etching the quartz substrate 20, and an electrode forming step S7 of forming the electrode 3 on the surface of the vibrating substrate 2 obtained by the above steps. Hereinafter, each of these steps will be described in order.

[0015] <<Preparation Step S1>> As shown in FIG. 4, a quartz substrate 20, which is a base material of the vibrating substrate 2, is prepared. The quartz substrate 20 is adjusted to a desired thickness by CMP (Chemical Mechanical Polishing) or the like, and has a sufficiently smooth first surface 2A and second surface 2B. A plurality of vibrating elements 1 are integrally formed from the quartz substrate 20.

[0016] <<First Protective Film Formation Step S2>> As shown in FIG. 5, metal films M1 and M2 are formed on the first surface 2A and the second surface 2B of the quartz substrate 20. 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 opening of the first resist film R1, and then the first resist film R1 is removed. As a result, it becomes as 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 portions of the quartz substrate 20 to be removed. Among these, the opening 51 overlaps with the first groove formation region Q1 where the first grooves 221 and 231 are formed. The opening 52 overlaps with the arm gap region Q4 located between the first vibrating arm formation region Q2 where the first vibrating arm 22 is formed and the second vibrating arm formation region Q3 where the second vibrating arm 23 is formed. The opening 53 overlaps with the element gap region Q5 located between adjacent vibrating substrates 2. That is, the first protective film 5 is formed except for the first groove formation region Q1, the arm gap region Q4, and the element gap region Q5.

[0018] <<First Dry Etching Step S3>> As shown in FIG. 7, the quartz substrate 20 is dry-etched from the first surface 2A side through the first protective film 5 to simultaneously form the first grooves 221 and 231 and the outer shape of the vibrating substrate 2 on the first surface 2A. Note that "simultaneously forming" means forming both in one step. More specifically, this step is reactive ion etching and is performed using an RIE (Reactive Ion Etching) apparatus. The reaction gas introduced into the RIE apparatus is not particularly limited, and for example, SF6, CF4, C2F4, C2F6, C3F6, C4F8, etc. can be used.

[0019] This step ends when the first grooves 221 and 231 reach the desired depth. Here, in dry etching, there is a known "microloading effect" in which the etching rate decreases as the pattern density of the first protective film 5 increases. In the present embodiment, when comparing the width W in the X direction of the first grooves 221 and 231 with the width A in the X direction of the inter-arm region Q4, W < A. Also, when comparing the width W with the width B in the X direction of the inter-element region Q5, 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 inter-arm region Q4 and the inter-element region Q5. Therefore, at the end of this step, 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 quartz substrate 20. That is, if the thickness of the quartz substrate 20 is Ta, then Aa ≥ 0.5Ta, Ba ≥ 0.5Ta. Note that the depth Wa, the depth Aa, and the depth Ba are each defined as the deepest depth in the regions of the width W, the width A, and the width B, respectively.

[0020] After the end of this step, the first protective film 5 and the metal film M1 are removed, and the process proceeds to the processing of the back surface of the quartz 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, 63 in portions of the quartz substrate 20 to be removed. Among these, the opening 61 overlaps with the second groove formation region Q6 where the second grooves 222, 232 are formed. The opening 62 overlaps with the inter-arm region Q4. The opening 63 overlaps with the inter-element region Q5.

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

[0023] This step ends when the second grooves 222, 232 reach a desired depth. In the present embodiment, when the width W in the X direction of the second grooves 222, 232 is compared with the width A in the X direction of the inter-arm region Q4, W < A. Also, when the width W is compared with the width B in the X direction of the inter-element region Q5, W < B. Therefore, due to the microloading effect, the etching rate of the second groove formation region Q6 becomes lower than the etching rates of the inter-arm region Q4 and the inter-element region Q5. For this reason, the depth Wa of the second grooves 222, 232 is shallower than the depths Aa, 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, Ba are each at least half of the thickness of the quartz substrate 20. That is, Aa ≥ 0.5Ta, Ba ≥ 0.5Ta. Therefore, the inter-arm region Q4 and the inter-element region Q5 are each penetrated. By the inter-arm region Q4 and the inter-element region Q5 being each penetrated, the first vibrating arm 22 and the second vibrating arm 23 are formed.

[0024] As shown in FIG. 10, after this step is completed, the second protective film 6 and the metal film M2 are removed.

[0025] As described above, in the first dry etching step S3, the crystal substrate 20 is dry-etched from the first surface 2A side, and in the second dry etching step S5, the crystal substrate 20 is dry-etched from the second surface 2B side, thereby forming the outer shape of the vibrating substrate 2. Therefore, 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 region 105 where both the dry etching in the first dry etching step S3 and the dry etching in the second dry etching step S5 overlap, steps 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] As shown in FIGS. 11 and 12, for example, when the position of the second protective film 6 is displaced to the minus side in the X direction with respect to the first protective film 5, the outer shape of the vibrating substrate 2 formed in the second dry etching step S5 is displaced to the minus side in the X direction with respect to the outer shape of the vibrating substrate 2 formed in the first dry etching step S3, so that a stepped portion 107 is formed on the side surface 101 of the first vibrating arm 22. Further, for example, when the position of the second protective film 6 is displaced to the plus side in the X direction with respect to the first protective film 5, the stepped portion 107 is also formed. Although the first vibrating arm 22 has been illustrated and described, when the position of the second protective film 6 is displaced with respect to the first protective film 5, the stepped portion 107 is similarly formed on the side surface 103 of the second vibrating arm 23.

[0027] ≪Wet etching step S6≫ The wet etching step S6 is a step of wet etching the crystal substrate 20 by immersing the crystal substrate 20 in an etching solution. As the etching solution, hydrofluoric acid and ammonium fluoride can be used.

[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 step S3 and the second dry etching step S5. That is, this step is a step of wet etching the first vibrating arm 22 and the second vibrating arm 23. In this step, by wet etching the side surfaces 101 and 103 of the first vibrating arm 22 and the second vibrating arm 23, the step portions 107 formed on the side surfaces 101 and 103 can be reduced. By reducing the step portions 107, the generation of unnecessary vibrations when the vibrating element 1 vibrates and the breakage of the vibrating element 1 when an impact is applied to the vibrating element 1 can be suppressed.

[0029] In this step, the etching amount of the side surfaces 101 and 103 is preferably 0.01 μm or more. Thereby, the step portions 107 are reduced, and the generation of unnecessary vibrations when the vibrating element 1 vibrates and the breakage of the vibrating element 1 when an impact is applied to the vibrating element 1 can be suppressed. Note that the etching amount of the side surfaces 101 and 103 is the displacement amount of the side surfaces 101 and 103 in the X direction, which is the direction orthogonal to the side surfaces 101 and 103 before and after the wet etching step S6.

[0030] Also, in this step, the etching amount of the side surfaces 101 and 103 is preferably 1 μm or less. When the etching amount of the side surfaces 101 and 103 exceeds 1 μm, each part of the vibrating substrate 2 other than the step portions 107, for example, the first surface 2A, the second surface 2B, the first grooves 221 and 231, the second grooves 222 and 232, etc. are wet etched, so that the outer dimensions of the vibrating element 1 become different from the desired outer dimensions. Therefore, there is a risk that the vibrating element 1 vibrates at a frequency greatly deviated from the desired frequency. By setting the etching amount of the side surfaces 101 and 103 to 1 μm or less, the deviation from the desired frequency can be suppressed.

[0031] Also, in this step, the etching amount of the side surfaces 101 and 103 is preferably 0.5 μm or less. When the etching amount on the side surfaces 101 and 103 exceeds 0.5 μm, for example, the corners of the vibrating arms 22 and 23 where the first surface 2A and the second surface 2B are connected to the side surfaces 101 and 103 are wet-etched, resulting in a complex shape of the vibration element 1 that is different from the desired shape. Therefore, unnecessary vibrations may occur when the vibration element 1 is vibrated, and the vibration characteristics such as the Q value may deteriorate. By setting the etching amount of the side surfaces 101 and 103 to 0.5 μm or less, the generation of unnecessary vibrations can be suppressed.

[0032] Through the above steps S1 to S6, as shown in FIG. 13, a plurality of vibration substrates 2 are integrally formed from the crystal substrate 20.

[0033] ≪Electrode formation step 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.

[0034] Thus, the vibration element 1 is obtained. As described above, according to dry etching, processing can be performed without being affected by the crystal plane of the crystal, so excellent dimensional accuracy can be achieved. In addition, by integrally forming the first grooves 221 and 231 and the second grooves 222 and 232 with the outer shape of the vibration substrate 2, the manufacturing process of the vibration element 1 can be reduced, and the cost of the vibration element 1 can be reduced. Also, the displacement of the first grooves 221 and 231 and the second grooves 222 and 232 with respect to the outer shape is prevented, and the formation accuracy of the vibration substrate 2 is improved.

[0035] Also, when the crystal substrate 20 is dry-etched from both the first surface 2A side and the second surface 2B side, the step portions 107 formed on the side surfaces 101 and 103 of the first vibrating arm 22 and the second vibrating arm 23 can be reduced by wet etching. Therefore, the generation of unnecessary vibrations when the vibration element 1 is vibrated and the breakage of the vibration element 1 when an impact is applied to the vibration element 1 can be suppressed.

[0036] The manufacturing method of the vibration element 1 has been described above. Next, conditions for more surely realizing the microloading effect will be described with reference to FIGS. 14 and 15. FIG. 14 shows the relationship between W / A and Wa / Aa when the etching time is varied. As can be seen from the figure, it can be understood that the microloading effect is significantly manifested in the region where W / A ≤ 40% or less for each time.

[0037] Also, the microloading effect varies depending on the reaction gas species used in dry etching. FIG. 15 shows the relationship between W / A and Wa / Aa when three different general reaction gases are used.

[0038] For example, when a fluorine-based gas containing a large amount of carbon such as C2F4, C2F6, C3F6, or C4F8 is used as the reaction gas, a thick sidewall protective film can be obtained, and the inclination becomes small like gas species G3. Therefore, it becomes easy to increase Wa / Aa in a shape where A is smaller than W, and the vibration element 1 can be miniaturized. For example, when designing the frequency and the CI value, a depth Wa close to a certain width W and a depth Aa may be required. In that case, it is necessary to reduce the width A to miniaturize the vibration element 1. In such a case, at least one of C2F4, C2F6, C3F6, and C4F8 is particularly effective.

[0039] On the other hand, when a fluorine-based gas containing little or no carbon such as SF6 or CF4 is used alone or in combination with a fluorine-based gas containing a large amount of carbon, the sidewall protective film becomes thin, and the inclination becomes large like gas species G1. Therefore, while keeping Wa larger than Aa, A can be increased with respect to W. For example, when it is desired to increase the depth Wa while narrowing the widths 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.

[0040] When W / A = x and Wa / Aa = y, gas species G1 is represented by the following formula (1), gas species G2 is represented by the following formula (2), and gas species G3 is represented by the following formula (3).

[0041]

Number

[0042]

Number

[0043]

Number

[0044] As shown in FIG. 15, 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 exhibited using a general reaction gas. Therefore, the manufacturing of the vibration element 1 becomes easy and its manufacturing cost can be reduced.

[0045]

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[0046]

Number

[0047] In addition, when y does not satisfy formula (4), the change in depth Wa with respect to the change in width W becomes large, and there is a possibility that the depth Wa varies. By making y satisfy formula (4), this can be suppressed. Also, when y does not satisfy formula (5), it becomes difficult to increase y in the region where x is large, and the depth Wa becomes shallow. Or, in order to increase the depth Wa, it is necessary to approach W = A, and shape constraints are likely to occur. By making y satisfy formula (5), this can be suppressed.

[0048] Here, for example, when the width W and the depth Wa are constant, if the gas species G2 is selected, the width A can be made smaller than that of the gas species G1, and the size reduction of the vibrating element 1 can be achieved. When the gas species G3 is selected, the width A can be made even smaller than that of the gas species G2, and further size reduction of the vibrating element 1 can be achieved. Thus, from the viewpoint of size reduction, among the regions P, it is more preferable that y is in the region PP between the formula (2) and the formula (3). That is, it is preferable that y satisfies the following formula (6) and the above formula (5).

[0049]

Equation

[0050] Next, the improvement effect of the CI value of the vibrating element 1 when the first grooves 221 and 231 and the second grooves 222 and 232 are formed will be described with reference to FIG. 16. As shown in FIG. 16, it is preferable that Wa / Aa≧0.2. In this embodiment, since the microloading effect is utilized, Wa / Aa<1. Thereby, the CI value can be reduced to 30% or less compared to the case where the first grooves 221 and 231 and the second grooves 222 and 232 are not formed. Therefore, a vibrating element 1 having excellent vibration characteristics can be manufactured. Further, it is preferable that Wa / Aa≧0.4, whereby the CI value can be reduced to 10% or less compared to the case where the first grooves 221 and 231 and the second grooves 222 and 232 are not formed.

[0051] The conditions for more surely exhibiting the microloading effect in the manufacturing method of the vibrating element 1 have been described above. As described above, the manufacturing method of the vibration element 1 includes a first vibration arm 22 and a second vibration arm 23 that extend along the Y direction, which is the first direction, and are arranged side by side along the X direction, which is the second direction intersecting the Y direction. The first vibration arm 22 and the second vibration arm 23 are arranged side by side in the Z direction, which is the third direction intersecting the Y direction and the X direction, and have a first surface 2A and a second surface 2B in a front-back relationship, bottomed first grooves 221, 231 opening on the first surface 2A, bottomed second grooves 222, 232 opening on the second surface 2B, and side surfaces 101, 103 connecting the first surface 2A and the second surface 2B. The manufacturing method of the vibration element 1 includes a step S1 of preparing a quartz substrate 20 having the first surface 2A and the second surface 2B, a first dry etching step S3 of dry etching the quartz substrate 20 from the first surface 2A side to form the first grooves 221, 231 and the outer shapes of the first vibration arm 22 and the second vibration arm 23, a second dry etching step S5 of dry etching the quartz substrate 20 from the second surface 2B side to form the second grooves 222, 232 and the outer shapes of the first vibration arm 22 and the second vibration arm 23, and then a wet etching step S6 of wet etching the side surfaces 101, 103 of the first vibration arm 22 and the second vibration arm 23. According to this manufacturing method, the step portions 107 formed on the side surfaces 101, 103 of the first vibration arm 22 and the second vibration arm 23 can be reduced. Thereby, the generation of unnecessary vibration when the vibration element 1 is vibrated and the breakage of the vibration element 1 when an impact is applied to the vibration element 1 can be suppressed.

[0052] Also, as described above, in the manufacturing method of the vibration element 1, the etching amount of the side surfaces 101, 103 in the wet etching step S6 is preferably 0.01 μm or more. Thereby, the step portion 107 becomes smaller, and the generation of unnecessary vibration when the vibration element 1 is vibrated and the breakage of the vibration element 1 when an impact is applied to the vibration element 1 can be suppressed.

[0053] Also, as described above, in the manufacturing method of 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. Thereby, the deviation from the desired frequency when the vibration element 1 is vibrated can be suppressed.

[0054] Also, as described above, in the manufacturing method of the vibration element 1, it is preferable that the etching amount of the side surfaces 101 and 103 in the wet etching step S6 is 0.5 μm or less. Thereby, the generation of unnecessary vibration when the vibration element 1 is vibrated can be suppressed.

[0055] Also, as described above, in the manufacturing method of the vibration element 1, the depths of the first grooves 221 and 231 formed in the first dry etching step S3 and the depths of the second grooves 222 and 232 formed in the second dry etching step S5 are each set to Wa, and the outer shape depths of the first vibration arms 22 and 23 formed in the first dry etching step S3 and the outer shape depths of the first vibration arms 22 and 23 formed in the second dry etching step S5 are each set to Aa. In at least one of the first dry etching step S3 and the second dry etching step S5, it is preferable to satisfy Wa / Aa < 1. Thereby, the first grooves 221 and 231 and the second grooves 222 and 232 and the outer shape of the vibration substrate 2 can be formed collectively. Therefore, the manufacturing process of the vibration element 1 can be reduced and the cost of the vibration element 1 can be reduced. Also, the displacement of the first grooves 221 and 231 and the second grooves 222 and 232 with respect to the outer shape is prevented, and the formation accuracy of the vibration substrate 2 is improved.

[0056] Also, as described above, in the manufacturing method of the vibration element 1, it is preferable to satisfy Wa / Aa ≥ 0.2. Thereby, the CI value can be reduced to 30% or less compared to the case where the first grooves 221 and 231 and the second grooves 222 and 232 are not formed. Therefore, a vibration element 1 having excellent vibration characteristics can be manufactured.

[0057] 2. Embodiment 2 The manufacturing method of the vibration element 1 according to Embodiment 2 will be described with reference to FIGS. 17 to 19. Note that the same components as those in Embodiment 1 are denoted by the same reference numerals, and redundant descriptions are omitted. Embodiment 2 has a third protective film forming step S10 between the second dry etching step S5 and the wet etching step S6. In the third protective film forming step S10, a third protective film 109 is formed on the first surface 2A and the second surface 2B of the quartz substrate 20. Except that in the wet etching step S6, the first surface 2A and the second surface 2B of the quartz substrate 20 are masked by the third protective film 109, it is the same as Embodiment 1.

[0058] As shown in FIG. 17, the method for manufacturing the vibration element 1 according to Embodiment 2 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 forming 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 forming 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 forming 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 forming step S7 of forming an electrode 3 on the surface of the vibration substrate 2 obtained by the above steps.

[0059] Since the steps from the preparation step S1 to the second dry etching step S5 are the same as those in Embodiment 1, the description thereof is omitted, and the description will start from the third protective film forming step S10. Similar to Embodiment 1, after the completion of the second dry etching step S5, the second protective film 6 and the metal film M2 are removed from the quartz substrate 20.

[0060] ≪Third Protective Film Forming Step S10≫ As shown in FIG. 18, 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 sequentially depositing chromium and gold 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 patterning this metal film using photolithography techniques and etching techniques.

[0061] ≪Wet etching step S6≫ In this step, the quartz substrate 20 is wet-etched by immersing the quartz substrate 20 in an etching solution. In Embodiment 2, 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 the 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. Thereby, it is possible to suppress the dimensions and shapes of the vibrating element 1 from becoming different from the desired dimensions and shapes. Therefore, it is possible to suppress the deviation from the desired frequency and the generation of unnecessary vibrations in the vibrating element 1.

[0062] 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 smaller as in Embodiment 1.

[0063] As shown in FIG. 19, after this step is completed, the third protective film 109 is removed. As described above, a plurality of vibrating substrates 2 are integrally formed from the quartz substrate 20.

[0064] ≪Electrode forming step S7≫ This process is carried out in the same manner as in Embodiment 1. A metal film is formed on the surface of the vibrating substrate 2, and the electrode 3 is formed by patterning this metal film.

[0065] Thus, the vibration element 1 is obtained.

[0066] According to this embodiment, in addition to the effects in Embodiment 1, the following effects can be obtained. In the wet etching step S6, since the first surface 2A and the second surface 2B of the quartz substrate 20 are masked by the third protective film 109, it is possible to suppress the dimensions and shape of the vibration element 1 from becoming dimensions and shapes different from the desired dimensions and shapes. Thereby, it is possible to suppress the deviation from the desired frequency and the generation of unnecessary vibration in the vibration element 1.

[0067] As described above, the method for manufacturing the vibration element of the present invention has been described based on Embodiment 1 and Embodiment 2. However, the present invention is not limited thereto, and the configuration of each part can be replaced with any configuration having the same function. Also, any other arbitrary components may be added to the present invention. Further, the respective embodiments may be appropriately combined.

[0068] 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 it is not limited thereto, and it is sufficient that at least one of them satisfies Wa / Aa < 1.

[0069] Further, the vibration element manufactured by the method for manufacturing a vibration element of the present invention is not particularly limited, and for example, it may be a vibration element 1A as shown in FIGS. 20 and 21. In the vibration 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 vibration 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 vibration arm 23, and a pair of second grooves 232 are formed side by side in the X direction on the second surface 2B. In such a configuration, since a plurality of 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 reaction gas in the first dry etching step S3 and the second dry etching step S5. Thereby, each groove can be formed deeply and the CI value can be lowered.

[0070] Further, the vibration element may be a double tuning fork type vibration element 7 as shown in FIGS. 22 and 23. In FIGS. 22 and 23, illustration of the electrodes is omitted. The double tuning fork type vibration element 7 includes a pair of bases 711 and 712, and a first vibration arm 72 and a second vibration arm 73 that connect the bases 711 and 712. Further, the first vibration arm 72 and the second vibration arm 73 each have bottomed first grooves 721 and 731 that open on the first surface 7A, and bottomed second grooves 722 and 732 that open on the second surface 7B.

[0071] Alternatively, for example, the vibration element may be the gyro vibration element 8 as shown in FIGS. 24 to 26. Note that in FIGS. 24 to 26, the illustration of the electrodes is omitted. The gyro vibration element 8 includes a base portion 81, a pair of detection vibration arms 82 and 83 extending from both sides of the base portion 81 in the Y direction, a pair of connection arms 84 and 85 extending from both sides of the base portion 81 in the X direction, drive vibration arms 86 and 87 extending from the tip of the connection arm 84 to both sides in the Y direction, and drive vibration arms 88 and 89 extending from the tip of the connection arm 85 to both sides in the Y direction. In such a gyro vibration element 8, when an angular velocity ωz about the Z axis acts in a state where the drive vibration arms 86, 87, 88, and 89 are bent and vibrated in the direction of arrow SD in FIG. 24, the Coriolis force newly excites the detection vibration arms 82 and 83 to bend and vibrate in the direction of 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 bending vibration.

[0072] Further, the detection vibration arms 82 and 83 have bottomed first grooves 821 and 831 opening on the first surface 8A and bottomed second grooves 822 and 832 opening on the second surface 8B. Further, the drive vibration arms 86, 87, 88, and 89 have bottomed first grooves 861, 871, 881, and 891 opening on the first surface 8A and bottomed second grooves 862, 872, 882, and 892 opening on the second surface 8B. In such a gyro vibration element 8, for example, a pair of vibration arms adjacent to each other in the X direction, 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, and the detection vibration arm 83 and the drive vibration arm 89, can be defined as a first vibration arm and a second vibration arm.

[0073] Note that in the case of the gyro vibration element 8, it is necessary to increase the inter-arm region Q4 structurally. In such a case, in the region between the above formulas (2) and (3), the depth Wa becomes shallow, which may cause a decrease in sensitivity. Therefore, it is preferable to use the region between the above formulas (1) and (2).

[0074] Further, for example, the vibration element may be the gyro vibration element 9 as shown in FIGS. 27 to 29. The gyro vibration element 9 includes a base portion 91, a pair of drive vibration arms 92 and 93 that extend from the base portion 91 to the +Y direction side and are arranged in the X direction, and a pair of detection vibration arms 94 and 95 that extend from the base portion 91 to the -Y direction side and are arranged in the X direction. In such a gyro vibration element 9, when an angular velocity ωy about the Y axis acts in a state where the drive vibration arms 92 and 93 are bent and vibrated in the direction of arrow SD in FIG. 27, due to the Coriolis force, the detection vibration arms 94 and 95 are newly excited to bend and vibrate in the direction of arrow SS, and the angular velocity ωy is detected based on the charge output from the detection vibration arms 94 and 95 due to the bending vibration.

[0075] Further, the drive vibration arms 92 and 93 include bottomed first grooves 921 and 931 that open to the first surface 9A, and bottomed second grooves 922 and 932 that open to the second surface 9B. The detection vibration arms 94 and 95 include bottomed first grooves 941 and 951 that open to the first surface 9A, and bottomed second grooves 942 and 952 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 serve as the first vibration arm and the second vibration arm.

Description of Reference Numerals

[0076] 1... Vibration element, 2... Vibration substrate, 2A... First surface, 2B... Second surface, 101, 103... Side surfaces, 20... Quartz substrate, 21... Base portion, 22... First vibration arm, 23... Second vibration arm, 221, 231... First groove, 222, 232... Second groove, 3... Electrode, 31... Signal electrode, 32... Ground electrode, 5... First protective film, 51, 52, 53... Openings, 6... Second protective film, 61, 62, 63... Openings, 107... Step portion, 109... Third protective film, A... Width, Aa... Depth, B... Width, Ba... Depth, M1... Metal film, M2... Metal film, Q1... First groove formation region, Q2... First vibration arm formation region, Q3... Second vibration arm formation region, Q4... Region between arms, Q5... Region between elements, Q6... Second groove formation region, R1... First resist film, S1... Preparation process, S2... First protective film formation process, S3... First dry etching process, S4... Second protective film formation process, S5... Second dry etching process, S6... Wet etching process, S7... Electrode formation process, S10... Third protective film formation process, Ta... Thickness, W... Width, Wa... Depth.

Claims

1. A first vibrating arm extending along a first direction and aligned along a second direction intersecting the first direction, and a second vibrating arm, comprising: The first vibrating arm and the second vibrating arm are respectively arranged side by side in a third direction intersecting the first direction and the second direction, and a first surface and a second surface having a front-back relationship, a bottomed first groove opening on the first surface, a bottomed second groove opening on the second surface, and a side surface connecting the first surface and the second surface, a method for manufacturing a vibrating element, comprising: preparing a quartz substrate having the first surface and the second surface; a first dry etching step of dry etching the quartz substrate from the first surface side to form the first groove and the outer shapes of the first vibrating arm and the second vibrating arm; a second dry etching step of dry etching the quartz substrate from the second surface side to form the second groove and the outer shapes of the first vibrating arm and the second vibrating arm; and then, a wet etching step of wet etching the side surfaces of the first vibrating arm and the second vibrating arm, wherein, in the wet etching step, the first surface and the second surface are masked, and the etching amount of the side surface in the wet etching step is 0.01 μm or more and 1 μm or less. A method for manufacturing a vibrating element.

2. The etching amount of the side surface in the wet etching step is 0.5 μm or less, and a method for manufacturing a vibrating element according to claim 1.

3. The depth of the first groove formed in the first dry etching step and the depth of the second dry etching Let the depths of the second grooves formed in the etching process be Wa, respectively, When the depth of the outer shape formed in the first dry etching process and the depth of the outer shape formed in the second dry etching process are Aa, respectively, In at least one of the first dry etching process and the second dry etching process Wa / Aa < 1 is satisfied, The method for manufacturing a vibration element according to claim 1 or claim 2.

4. Wa / Aa ≥ 0.2 is satisfied, The method for manufacturing a vibration element according to claim 3.

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