JP5459352B2 - Vibrating piece - Google Patents

Description

The present invention relates to a resonator element, to mesa resonator element greater in particular than the peripheral portion of the thickness of the vibrating section.

2. Description of the Related Art In recent piezoelectric vibrating pieces that are becoming smaller and thinner, it is known to adopt a mesa structure for the purpose of confining vibration energy and reducing CI (crystal impedance) value.
Here, the mesa structure exhibits effects such as confinement of vibration energy and reduction of the CI value as described above when its characteristics act appropriately, and it is possible to reduce superposition of unnecessary modes. However, if the digging amount of the substrate for obtaining the mesa structure exceeds the appropriate range, the unnecessary mode overlaps (bonds) again, and holes such as etching erosion are formed on the substrate surface. Further, the outer shape may vary due to over-etching or the like, and the vibration characteristics will be adversely affected. Accordingly, it has been proposed to provide a piezoelectric vibrating piece in which an optimum value of the amount of substrate digging for obtaining a mesa structure is determined. For example, this is the technique disclosed in Patent Document 1.

  Patent Document 1 describes that the long side dimension of a quartz substrate is 20 times or more the thickness dimension of the substrate, and the amount of digging of the substrate for obtaining a mesa structure is about 10% to 30% of the thickness dimension. Yes.

JP 2006-340023 A

  By determining the mesa digging amount and the side ratio (long side dimension / thickness dimension of the quartz substrate) as described above, it is possible to surely reduce the CI value and suppress the unwanted mode coupling. However, the effects of reducing the CI value and suppressing the coupling of unnecessary modes cannot be achieved uniformly if the above requirements are met, and it is known that variations occur due to the relationship between the edge ratio and the amount of mesa digging. It has been.

  Therefore, an object of the present invention is to provide a piezoelectric vibrating piece having a mesa digging amount for achieving a particularly significant effect on reducing CI value and suppressing coupling of unnecessary modes. Another object of the present invention is to provide a piezoelectric vibrating piece having a configuration for obtaining further superiority in connection with suppression of unwanted mode coupling in addition to the above configuration.

の関係を満足するように定められることを特徴とする。このような構成とすることにより、堀量の割合をＣＩ値の特性変化がフラットとなる最小の値に設定することができる。このため、エッチング時間を必要最低限の時間とすることができ、エッチング喰われによる圧電振動片の形状のバラツキを抑えることができる。また、堀量を少なく抑えることができ、不要振動との結合が少ないため、振動特性の悪化を招くこと無くＣＩ値を低下させることができる。すなわち、設計余裕度の高い圧電振動片を提供することが可能となる。 In order to achieve the above object, a resonator element according to an embodiment of the present invention includes a vibrating portion that vibrates by thickness-shear vibration, and a thickness that is thinner than the vibrating portion. Including a base plate including a peripheral portion provided integrally and an excitation electrode provided on a main surface of the vibration portion, wherein a dimension of the base plate along a vibration direction of the thickness-shear vibration is x The thickness dimension of the vibration part is t, the dimension of the vibration part along the vibration direction is Mx, the dimension of the excitation electrode along the vibration direction is Ex, and the element along the vibration direction is When the wavelength of the bending vibration generated in the plate is λ,
Mx = 2 × (n / 2 + 1/4) × λ, where n is a positive integer,
(Mx−Ex) / 2 = λ / 2
Satisfied,
When the difference between the thickness of the t and the peripheral portion is divided by the t, and the value expressed as a percentage is y,
y = −0.89 × (x / t) + 34 ± 3 (%)
16.2 ≦ x / t ≦ 26.3, except for the range of x / t ≧ 20,
It is characterized by satisfying .
A vibrating piece according to another embodiment of the present invention is characterized in that the base plate is made of an AT cut crystal.
In a resonator element according to another embodiment of the present invention, a dimension from one end portion of the base plate crossing the vibration direction to the stepped portion is dx, and the base plate and the mounting substrate are fixed. When the dimension along the vibration direction of the adhesive is Sx,
0.1 ≦ Sx <dx−0.05 (mm)
It is characterized by satisfying.
[Application Example 1] The mesa-type piezoelectric vibrating piece according to Application Example 1 is a mesa-type piezoelectric vibration in which a vibration part having a thickness dimension larger than that of a peripheral part is formed on a plate surface of a piezoelectric substrate having thickness shear vibration as a main vibration. The height y of the stepped portion is the length of the piezoelectric substrate x, and the thickness of the piezoelectric substrate in the vibrating portion is t.

It is determined to satisfy the relationship. With such a configuration, the ratio of the moat amount can be set to the minimum value at which the change in the characteristic of the CI value becomes flat. For this reason, the etching time can be set to the minimum necessary time, and variations in the shape of the piezoelectric vibrating piece due to the etching biting can be suppressed. Further, since the amount of moat can be reduced and the coupling with unnecessary vibration is small, the CI value can be reduced without causing deterioration of vibration characteristics. That is, it is possible to provide a piezoelectric vibrating piece with a high design margin.

Application Example 2 In the mesa-type piezoelectric vibrating piece according to Application Example 2, it is preferable that the side ratio x / t is 30 or less. When the side ratio is higher than 30, the calculated value of the moat amount is remarkably reduced. Therefore, the effect of forming the vibration part is not matched with the time and the number of steps for forming the vibration part. Therefore, by obtaining y for a piezoelectric substrate having a side ratio x / t of 30 or less, determining the amount of moat, and forming the vibration part, an effect commensurate with time and the number of steps can be obtained.

の範囲で定めたものであっても良い。このような範囲で接合範囲Ｓｘを定めることによれば、不要モードの結合を抑制しつつＣＩ値の低下も促すことが可能となる。
また、上記構成は、上述した特徴を有するメサ型圧電振動片に適用することもできる。
[Application Example 3] The mesa-type piezoelectric vibrating piece according to Application Example 3 is a mesa-type piezoelectric vibration in which a vibration part having a thickness dimension larger than that of the peripheral part is formed on a plate surface of a piezoelectric substrate whose thickness vibration is a main vibration. Long side in the application range of the conductive adhesive applied when the piezoelectric vibrating reed is mounted on a mounting board, where dx is a dimension from one end part in the long side direction to the step part. The direction dimension Sx is

It may be determined within the range. By determining the joining range Sx within such a range, it is possible to promote a decrease in the CI value while suppressing coupling of unnecessary modes.
The above configuration can also be applied to a mesa-type piezoelectric vibrating piece having the above-described characteristics.

It is a figure which shows the shape of the mesa type | mold piezoelectric vibrating piece which concerns on this invention. It is a figure which shows the suppression effect of the bending mode by formation of a vibration part. It is a graph which shows the relationship between the moat amount and CI value in a mesa type piezoelectric vibrating piece with a certain side ratio. It is a graph which shows the relationship between the moat amount and CI value in the mesa type piezoelectric vibrating piece having a plurality of side ratios. It is a graph which shows the relationship between CI value and temperature when side ratio and mesa moat amount are the same and width dimensions are changed. It is a graph which shows the minimum value of the moat amount in which the characteristic change of CI value becomes flat in the mesa type piezoelectric vibrating piece having different side ratios. It is a figure which shows the 1st application form in the mesa type piezoelectric vibrating piece which concerns on this invention. It is a figure which shows the 2nd application form in the mesa type piezoelectric vibrating piece which concerns on this invention. It is a graph which shows the relationship between CI value and temperature at the time of changing the dimension of the fixed range of a support part.

Hereinafter, embodiments of the mesa-type piezoelectric vibrating piece of the present invention will be described in detail with reference to the drawings. Note that the embodiments described below are only some of the embodiments of the present invention.
FIG. 1 is a diagram showing a form of a mesa-type piezoelectric vibrating piece (hereinafter simply referred to as a piezoelectric vibrating piece) 10 according to the present invention. 1A is a diagram illustrating a planar shape of the piezoelectric vibrating piece, and FIG. 1B is a diagram illustrating a cross-section taken along the line AA in FIG. The piezoelectric vibrating piece 10 according to the present embodiment is a mesa type in which a vibrating portion 14 having a thicker thickness than the peripheral portion 16 is formed on a plate surface of a piezoelectric substrate whose main vibration is thickness shear vibration. Specifically, the piezoelectric substrate 12 constituting the piezoelectric vibrating piece 10 according to the present embodiment is a crystal piece cut out at a cut angle called AT cut, and the outer shape and the shape of the vibrating portion 14 are rectangular. Is formed. Further, each side of the vibrating portion 14 is formed in parallel with each side of the piezoelectric substrate 12 constituting the outer shape, the plate thickness t'the plate thickness t and the peripheral portion 16 of the vibrating portion 14 The mesa excavation amount Md, which is a value representing the difference as a percentage of the plate thickness dimension t, is generally 30% or less .

Here, the vibration part 14 is preferably formed so that a stepped part that forms a boundary with the peripheral part 16 is located at an antinode of the amplitude of the unnecessary mode (for example, bending mode) propagating to the peripheral part 16. This is because the unnecessary mode can be suppressed and the vibration characteristics can be kept good by using such a configuration (see FIG. 2). Specifically, it can be shown in a known range as shown in Formula 1. In Equation 1, λ represents the bending mode period, and Mx represents the long side dimension of the vibrating portion.

  An excitation electrode 18 is formed on the vibration portion 14 of the piezoelectric substrate 12 having such a shape, and a support portion 20 is formed at one end of the peripheral portion 16. A connection electrode 19 is routed between the excitation electrode 18 and the support portion 20. It is also known that when the relationship between the long side dimension Mx of the vibrating portion 14 and the long side dimension Ex of the excitation electrode 18 satisfies the relationship expressed by Formula 2, an effect of suppressing bending vibration, which is an unnecessary mode, is obtained. (See FIG. 2).

With respect to the piezoelectric vibrating piece 10 having such a configuration, as a result of performing experiments and simulations on the relationship between the mesa moat amount Md and the CI value of the piezoelectric substrate 12 when forming the vibrating portion 14, the tendency as shown in FIG. I was able to derive. According to the tendency shown in FIG. 3, the CI value of the piezoelectric vibrating piece 10 tends to decrease as the proportion of the mesa moat amount Md increases, but the mesa moat amount Md has a certain value (about 15 in FIG. 3). %) After that, even if the proportion of the mesa excavation amount Md is increased, there is almost no change in the characteristic of the CI value, and it can be read that it becomes a substantially flat state. The relationship between the mesa excavation amount Md and the CI value shown in FIG. 3 is that the side ratio x / t with respect to the long side dimension x of the piezoelectric substrate 12 is 21.3, that is, the long side dimension with respect to the plate thickness dimension t of the vibrating portion 14. This relates to a piezoelectric vibrating piece having an x ratio of 21.3.

The inventors of the present application have found that the relationship between the mesa excavation amount Md and the CI value has a tendency as shown in FIG. FIG. 4 shows the relationship between the mesa excavation amount Md and the CI value when the mesa excavation amount Md is variously changed with respect to the piezoelectric vibrating piece with the side ratio x / t varied from 16.2 to 26.3. FIG. As can be read from FIG. 4, edge ratio x / t affects the relationship between the mesa etching depth Md and the CI value, the mesa characteristic change of the CI value higher fineness ratio x / t is less it becomes flat etching depth It can be read that the ratio of Md increases.

  In the case of forming a so-called mesa-type piezoelectric vibrating piece 10 as shown in FIG. 1, first, a protective film such as a resist film is formed on the main surface of a wafer (not shown), and exposure and development are performed. A mask in which the individual regions are formed is formed. By etching the wafer using this mask, the outer shape of a plurality of piezoelectric substrates is formed on the wafer. The mesa portion (vibration portion 14) can be formed by performing a mask formation process and an etching process step by step. After forming the outer shape of the piezoelectric substrate in units of individual pieces, a metal film (for example, gold with chromium as a base) is formed on the main surface of the wafer by using a technique such as vapor deposition or sputtering. Thereafter, a protective film is formed on the metal film, and etching is performed in the same manner as the outer shape to obtain a desired electrode pattern. The piezoelectric substrates thus batch-processed are separated into pieces by being separated from the wafer.

Here, when the etching time for obtaining the mesa excavation amount Md in the process of forming the outer shape is increased because the surface of the piezoelectric substrate 12 has different etching rates such as defects due to crystal abnormality, Through-holes may be formed on the plate surface of the peripheral portion 16 due to the progress of crystal defects (etching erosion), or the outer shape of the piezoelectric substrate 12 may be destroyed due to deterioration of the protective film. Crystal defects and collapse of the outer shape are different for each substrate. For this reason, when the etching time is extended, the influence of etching erosion and the like is increased, and the variation in characteristics of the formed piezoelectric vibrating reed 10 is increased.

Further, by providing the mesa etching depth Md, the main mode (thickness shear vibration) can be concentrated in the oscillating portion 14, while it is possible to inhibit the binding of unwanted modes (e.g. flexural vibration), Mesa When the ratio of the moat amount Md exceeds a certain range, the vibration unit 14 itself is regarded as an isolated vibration piece, and an unnecessary mode is generated in the vibration unit 14 itself, and the coupling ratio of the unnecessary mode is increased. It is in.

For this reason, if the minimum value at which the change in the CI value characteristic becomes flat can be selected as the mesa moat amount Md , the influence of etching erosion and unwanted mode coupling can be suppressed, and the vibration characteristics are excellent. It is considered that the piezoelectric vibrating piece 10 can be obtained.

  As inferred from the above-described tendency, when the edge ratio is high (for example, the edge ratio is 26.3 in FIG. 4), even if the mesa moat amount Md is about 5%, the effect of reducing the CI value is sufficient. Can be expected. However, the inventors of the present application change the width dimension (short side dimension) Z ′ of the piezoelectric substrate 12 when the amount of excavation is not sufficient even if the mesa excavation amount is within a range in which the CI value can be reduced. It has been found that there is a possibility that coupling of unnecessary modes increases.

  For example, the example shown in FIG. 5 is a simulation when a piezoelectric substrate having a side ratio of 28 is used, and FIG. 5A shows the relationship between the CI value and the temperature when the mesa excavation amount Md is 5%. FIG. 5B is a diagram showing the relationship between the CI value and the temperature when the mesa excavation amount Md is 10%. 5A and 5B, the relationship when the width dimension of the piezoelectric substrate is increased from the graph arranged on the left side (graph a) to the graph arranged on the right side (graph d) in FIG. Is shown.

  In particular, according to FIG. 5, when the mesa excavation amount Md is not sufficient, it is not necessary when the width dimension is reduced (FIG. 5A) and when the width dimension is increased (FIG. 5Ad). It can be seen that the coupling of modes appears remarkably. In addition, compared with FIG. 5A, in FIG. 5B, in any width dimension from a to d, the change in the CI value due to the temperature change is small, and the temperature change is accompanied. It can also be read that the increase in CI value is reduced. That is, it is necessary to select a necessary and sufficient mesa excavation amount Md in order to achieve a reduction in CI value and suppression of coupling of unnecessary modes in a wide range.

Therefore, the inventors of the present application have further conducted intensive research and found the relationship shown in FIG. FIG. 6 is a graph showing the minimum value Md_min of the mesa excavation amount Md when the change in the CI value is investigated by changing the mesa excavation amount Md for each side ratio x / t and the change in the CI value characteristic is flat. is there. It can be said that the relationship between the side ratio x / t and the minimum value Md_min of the mesa excavation amount Md at which the characteristic change of the CI value becomes flat is substantially proportional as can be seen from FIG. When the minimum value Md_min of the moat amount is expressed by y in the mathematical formula, the minimum value y of the moat amount is based on the plate thickness dimension t .

と表すことができる。すなわち、板厚寸法ｔのｙ％の厚みがメサ堀量Ｍｄの最小値ということである。したがって、本実施形態に係るメサ型の圧電振動片１０は、メサ堀量Ｍｄの割合として、数式１の関係を満たす圧電振動片である。

It can be expressed as. That is, the thickness of the plate thickness dimension t of y% is the minimum value of the mesa excavation amount Md . Therefore, the mesa-type piezoelectric vibrating piece 10 according to the present embodiment is a piezoelectric vibrating piece that satisfies the relationship of Equation 1 as a proportion of the mesa moat amount Md .

  The graph shown in FIG.

とした場合の例を示すグラフである。

It is a graph which shows the example in the case of becoming.

As described above, the CI value of the piezoelectric vibrating piece can be reduced by determining the mesa excavation amount Md based on Equation 1. Further, since the minimum value Md_min of the moat amount calculated by Equation 1 is the minimum value of the moat amount in which the change in the CI value characteristic is flat, the shape due to the deterioration of the vibration characteristics accompanying the increase of the moat amount or the etching bite Can be reduced. Further, since the minimum value Md_min is the minimum value of the moat amount at which the characteristic change of the CI value becomes flat, by determining the moat amount based on this, the processing time by etching can be shortened and the productivity is increased. be able to. Furthermore, it is possible to average good and bad products that tend to be bipolar as the amount of moat increases, which contributes to improved yield. Further, since the minimum value Md_min is the minimum value of the moat that makes the change in the CI value characteristic flat, it is possible to provide a piezoelectric vibrating piece that has few couplings of unnecessary modes and a high design margin.

Further, as can be seen from FIG. 6, when the side ratio x / t exceeds 30, the value of the minimum value Md_min tends to be remarkably small, so that it is not necessary to form the piezoelectric substrate in a mesa shape. For this reason, when manufacturing the piezoelectric vibrating piece as described above, it is preferable to use a piezoelectric substrate having a side ratio x / t of 30 or less. As a result, the piezoelectric vibrating reed as a product can have an effect commensurate with the time and the number of steps spent on manufacturing, and an excessive increase in size of the piezoelectric vibrating reed can be prevented.

  In recent years, where the piezoelectric vibrator itself mounted with the piezoelectric vibrating piece is required to be downsized, the piezoelectric vibrating pieces 10a and 10b configured as shown in FIGS. 7 and 8 corresponding to the CSP (chip size package) are used. On the other hand, the same effect can be obtained by applying the requirements according to the present invention.

  That is, even if the peripheral portion 16 and the vibrating portion 14 of the piezoelectric vibrating reeds 10a and 10b are supported by the frame portion 22 having a thickness dimension larger than that of the peripheral portion 16, the piezoelectric vibrating reed according to the present embodiment is used. Can do it. 7 and 8, a portion indicated by a broken line is a sealing plate in the case where a CSP structure piezoelectric vibrator is configured. In FIGS. 7 and 8, the description of the support portion and the connection electrode is omitted. Further, dx may be set based on the end of the peripheral portion 16.

  Next, the case where the mesa-type piezoelectric vibrating piece of the present invention is designed to reduce the CI value and suppress the unnecessary mode from other aspects will be described. In the process of studying and simulating the reduction of the CI value and the suppression of the unnecessary mode for the mesa-type piezoelectric vibrating piece, the inventors of the present application have the effects of reducing the CI value and suppressing the unnecessary mode. It has been found that this also varies depending on the form of fixing to the mounting substrate or the like. That is, when the piezoelectric vibrating piece 10 is fixed to the mounting board or the like in a weak state, the CI value tends to decrease, but the unnecessary mode tends to be used. In this tendency, the inventors of the present application have the effect of suppressing the unnecessary mode while obtaining the effect of lowering the CI value in the use range (room temperature) when the fixed state is set within a predetermined range. The range that can be obtained was found (see FIG. 9).

Therefore, in this embodiment, an appropriate value of the fixed dimension Sx (see FIG. 1) in the long side direction of the piezoelectric vibrating piece with respect to the mounting substrate or the like is determined. In the present embodiment, the long side direction dimension from the end portion on the side having the support portion to the vibrating portion 14 (stepped portion) is dx.

FIG. 9A is a diagram showing a relationship between a certain CI value and temperature when the fixed dimension Sx is less than 0.1. As can be seen from FIG. 9A, the CI value can be kept very low, but coupling of unnecessary modes is conspicuous in the temperature range of the use range.

On the other hand, FIG. 9B is a diagram showing a relationship between a certain CI value and temperature when the fixed dimension Sx is larger than dx−0.05. From FIG. 9B, the coupling of the unnecessary mode is considerably suppressed as compared with FIG. 9A, but it is strongly influenced by the fixed state of the piezoelectric vibrating piece with respect to the mounting substrate and the CI value in the low temperature region. The rise of is conspicuous. As described above, when the value of the fixed dimension Sx is set to an extreme range such as less than 0.1 or greater than dx−0.05, undesirable characteristics such as coupling of unnecessary modes and an increase in CI value occur. There is a case. On the other hand, in the case of a figure * (particularly figure * (B)) in which a certain value in the range of 0.1 ≦ Sx <dx−0.05 is a fixed dimension Sx, an increase in CI value with a change in temperature region, It can be read that the unnecessary mode coupling is suppressed.

Therefore, the fixed dimension Sx in the support portion is

の範囲で定めることが望ましい。このような範囲で固定寸法Ｓｘを定めることによれば、不要モードの結合を抑制しつつＣＩ値の低下も促すことが可能となるからである。

It is desirable to set within the range. This is because, by setting the fixed dimension Sx in such a range, it is possible to promote a decrease in the CI value while suppressing coupling of unnecessary modes.

In the above-described embodiment, the effects of setting appropriate values for the mesa moat amount Md and the fixed dimension Sx are individually verified and described. However, since Md and Sx interact with the CI value and the unnecessary mode, respectively, by determining both of them, it is possible to obtain a higher effect for reducing the CI value and suppressing the unnecessary mode. It becomes possible. That is, in creating the piezoelectric vibrating piece, the fixed dimension Sx of the support portion is determined based on Formula 5, and the mesa excavation amount Md is determined based on Formula 3.

According to the piezoelectric vibrating piece of such a form, it is possible to achieve the respective advantageous effects in the setting range of the mesa moat amount Md and the setting range of the fixed dimension Sx. Here, since the energy confinement effect for each frequency, that is, the relationship between the size of the piezoelectric substrate 12 and the CI value is determined by the mesa moat amount Md regardless of the substrate size, the setting range of the fixed dimension Sx depends on the substrate size. There is no big change.

  In the above embodiment, the piezoelectric vibrating piece has a rectangular shape. However, it is considered that the same effect can be obtained even when the piezoelectric vibrating piece has a non-rectangular shape such as a trapezoid or an ellipse. As shown in FIG. 1, even when the width Z ′ of the piezoelectric substrate is changed, a similar tendency can be obtained for the reduction of the CI value.

  DESCRIPTION OF SYMBOLS 10 ...... Piezoelectric vibrating piece, 12 ...... Piezoelectric substrate, 14 ...... Vibrating part, 16 ...... Peripheral part, 18 ...... Excitation electrode, 19 ...... Connection electrode, 20 ...... Supporting part.

Claims (3)

A vibrating plate that vibrates by thickness shear vibration, and a base plate that includes a peripheral portion that is thinner than the vibrating portion and is provided integrally with the vibrating portion along an outer edge of the vibrating portion;
An excitation electrode provided on the main surface of the vibrating part;
Including
The dimension of the base plate along the vibration direction of the thickness shear vibration is x,
The thickness dimension of the vibrating part is t,
The dimension of the vibration part along the vibration direction is Mx,
Ex is the dimension of the excitation electrode along the vibration direction,
When the wavelength of the bending vibration generated in the base plate along the vibration direction is λ,
Mx = 2 × (n / 2 + 1/4) × λ, where n is a positive integer,
(Mx−Ex) / 2 = λ / 2
Satisfied,
When the difference between the thickness of the t and the peripheral portion is divided by the t, and the value expressed as a percentage is y,
y = −0.89 × (x / t) + 34 ± 3 (%)
16.2 ≦ x / t ≦ 26.3, except for the range of x / t ≧ 20,
A vibrating piece characterized by satisfying In claim 1,
The resonator element, wherein the base plate is made of an AT cut crystal. In claim 1 or 2,
The dimension from one end of the base plate intersecting the vibration direction to the stepped portion is dx, and the dimension along the vibration direction of the adhesive fixing the base plate and the mounting substrate is Sx. When
0.1 ≦ Sx <dx−0.05 (mm)
A vibrating piece characterized by satisfying

Images