JP4305947B2 - Vibrating gyroscope - Google Patents

Description

【００３８】
【表２】

【００３９】
【表３】

【００４０】
【表４】

【００４１】
以上の結果から分かるように、金膜の厚さを４５ｎｍ以下とすることによって、ゼロ点温度ドリフトは著しく低減された。また、金属下地膜の膜厚は６０ｎｍ以下とすることが特に好ましいことも判明した。
【００４２】
【発明の効果】
以上述べたように、本発明によれば、振動子のゼロ点温度ドリフトを一層低減し、特に振動子を小型化してもゼロ点温度ドリフトの増大を抑制できる。
【図面の簡単な説明】
【図１】本発明で使用可能な振動子１Ａ（駆動モード）を概略的に示す平面図である。
【図２】本発明で使用可能な振動子１Ａ（検出モード）を概略的に示す平面図である。
【図３】（ａ）は、駆動振動片１４Ａ（１４Ｂ、１４Ｃ、１４Ｄ）上の電極１９の構成例を示す正面図であり、（ｂ）は、検出振動片１３Ａ（１３Ｂ）上の電極２０の構成例を示す正面図である。
【符号の説明】
１Ａ 振動子 ２ 基部 １０ 金属下地膜 １１ 金膜 １３Ａ、１３Ｂ 検出振動片 １４Ａ、１４Ｂ、１４Ｃ、１４Ｄ 駆動振動片 １９ 駆動電極 ２０ 検出電極 ２２ 金属下地膜 ２３ 金膜 Ａ 駆動モードの振動 Ｂ、Ｃ 検出モードの振動[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vibratory gyroscope .
[0002]
[Prior art]
The present applicant disclosed in Patent Document 1 that the zero point temperature drift is suppressed by providing tapered portions at the bases of both side surfaces of the bending vibration piece.
[Patent Document 1]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2001-12952
Patent Document 2 describes that an electrode having a two-layer structure of a chromium underlayer and a gold surface layer is provided on the surface of a crystal resonator.
[Patent Document 2]
Japanese Patent Laid-Open No. 2003-46365
[Problems to be solved by the invention]
However, it was found that the zero point temperature drift increases when the vibrator is further downsized and the widths of the drive vibration piece and the detection vibration piece are reduced. For example, when the width of the drive vibration piece and the detection vibration piece is about 1 mm, even if the design is such that there is almost no zero point temperature drift, if the width of the drive vibration piece and the detection vibration piece becomes as thin as 100 μm or less, for example, There was a tendency for the point temperature drift to increase.
[0005]
An object of the present invention is to further reduce the zero point temperature drift of the vibrator, and in particular, to suppress an increase in the zero point temperature drift even if the vibrator is downsized.
[0006]
[Means for Solving the Problems]
The present invention
substrate,
A base, a support projecting from the base, a driving vibration piece projecting from the support with a width of 0.15 mm or less, and a detection vibration piece projecting from the base with a width of 0.15 mm or less, are extended in parallel to a predetermined plane. Vibrator,
A drive electrode provided on the drive vibration piece, for exciting drive vibration in the vibrator ;
A detection electrode for detecting a detection vibration excited by the vibrator according to a rotational angular velocity applied to the vibrator; and
A vibrating gyroscope that is bonded to a base and includes a bonding wire that supports the vibrator on a substrate ,
In the drive vibration, the drive vibration piece bends and vibrates parallel to a predetermined plane with the root to the support portion as the center, and in the detection vibration, the detection vibration piece vibrates and vibrates parallel to the predetermined plane with the root to the base portion as the center
A drive electrode and a detection electrode are a gold film having a thickness of 5 nm or more and 45 nm or less, and a base film made of chromium or a chromium alloy having a thickness of 10 nm or more and 70 nm or less provided between the gold film and the vibrator. It is characterized by having.
[0007]
The inventor examined the reason why an increase in the zero point temperature drift is observed when the vibrator is downsized. For example, when the width of the resonator element is 1 mm, the Q value of the vibration of the resonator element substantially depends on the material constituting the resonator. The Q value is a variable indicating energy loss in the vibration state of the vibration type gyroscope.
[0008]
However, when the width of the vibration piece becomes very small, for example, 90 μm, the influence of the electrode film on the vibration piece appears remarkably, and it seems that the zero point temperature drift is increased. This inventor examined this mechanism and obtained the following knowledge. That is, in the vibration type gyroscope, a self-excited circuit is used so that the frequency of vibration detected by the vibrator is optimized by the self-oscillation of the vibrator. When the vibrator is miniaturized, the Q value of the vibration is likely to change in temperature due to the influence of the electrode film. Even when the Q value changes in temperature, in order to make the sensitivity constant, the current value for generating the drive vibration is controlled to be constant, and thereby the amplitude of the drive vibration is controlled to be constant. ing. Thus, the constant drive current value means that the drive voltage needs to be changed. As a result, the leakage signal of the electrostatic coupling component between the drive electrode and the detection electrode varies, and the zero point temperature drift increases.
[0009]
The following mechanism is also conceivable. That is, in order to form the outer contour of the resonator element, for example, a wafer made of a piezoelectric single crystal is etched. At the stage of the etching process, for example, a photoresist is applied to both the front surface side and the back surface side of the wafer, a photomask is placed thereon, and the front side photomask and the back side photomask are aligned. Then, the photoresist is exposed and cured, the photomask is removed, and the photoresist is patterned. Then, the wafer is etched, and a contour corresponding to the photoresist pattern is formed on the wafer.
[0010]
Here, when a photomask is installed on both the front surface side and the back surface side of the wafer for alignment, a slight positional deviation may occur between both masks. In this case, an unnecessary vibration component in the Z direction is generated, and a parasitic vibration with a phase delay with respect to the detected vibration is generated in the detected vibration piece.
[0011]
Such parasitic vibrations are different in mode shape from drive vibrations. For this reason, when the temperature changes, the influence of the driving vibration mode of the electrode on the Q value is different from the influence of the parasitic vibration on the Q value. As a result, the phase of the leakage vibration component based on the parasitic vibration varies according to the temperature change, and the zero point temperature drift increases.
[0012]
Furthermore, noise may be increased by the following mechanism due to a decrease in the Q value of the vibrator. That is, when the Q value of the driving vibration is lowered, the impedance of the driving vibration is increased, and a larger driving voltage is required to pass a constant current. As a result, the leakage signal due to electrostatic coupling increases. Therefore, it is necessary to reduce the AC amplification before detection so that the phase detection circuit is not saturated, but this reduces the sensitivity of the sensor. Therefore, in order to maintain the sensitivity of the sensor above a certain level, it is necessary to increase the DC amplification after detection, but as a result, noise also increases.
[0013]
The present inventor has found that the influence of the electrode film is large with respect to the temperature change of the Q value. Then, it has been found that the zero point temperature drift can be remarkably reduced by making the electrode into a two-layer structure, the thickness of the underlayer of chromium or chromium alloy being 70 nm or less, and the thickness of the gold film being 45 nm or less. Reached.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a plan view schematically showing a vibrator 1A according to an embodiment of the present invention (showing a drive vibration mode). FIG. 2 is a plan view showing vibration in the detection vibration mode of the vibrator 1A.
[0015]
The vibrator 1 </ b> A of this example is provided at the base 2, a pair of detection vibrating pieces 13 </ b> A and 13 </ b> B that protrude from the base 2, a pair of support portions 5 that protrude from the base 2, and the tips of the support portions 5. Each drive vibration piece 14A, 14B, 14C, 14D is provided.
[0016]
Elongated grooves are formed on the main surfaces of the drive vibration pieces 14A to 14D, respectively, and the cross-sectional shapes of the drive vibration pieces 14A to 14D are substantially H-shaped. A drive electrode 19 is formed in the groove. Wide portions or weight portions 15A, 15B, 15C, and 15D are provided at the tips of the drive vibration pieces 14A to 14D, and through holes 17 are formed in the wide portions. Each main surface of each detection vibrating piece 13A, 13B is formed with an elongated groove, and the cross-sectional shape of each detection vibration piece 13A, 13B is substantially H-shaped. A detection electrode 20 is formed in the groove. Wide ends or weight portions 16A and 16B are provided at the respective tips of the detection vibrating pieces 13A and 13B, and through holes 18 are formed in the wide portions.
[0017]
FIG. 1 shows drive mode vibration. At the time of driving, each of the drive vibrating pieces 14 </ b> A to 14 </ b> D bend and vibrate as indicated by an arrow A around the root 21 to the support portion 5. In this state, the vibrator 1A is rotated around a rotation axis Z extending substantially perpendicular to the vibrator 1A. Then, as shown in FIG. 2, the support portion 5 bends and vibrates as indicated by an arrow B around the root 5 a to the fixed portion 2. Each of the detection vibrating pieces 13A and 13B is flexibly vibrated as indicated by an arrow C around the root to the fixed portion 2 by the reaction. Based on the electrical signal generated in each of the detection vibrating pieces 13A and 13B, the rotational angular velocity about the Z axis is calculated.
[0018]
Here, the present invention is applied to at least the drive electrode 19 and the detection electrode 20.
[0019]
FIG. 3A shows one form of the electrode 19 on the drive vibrating piece 14A (14B, 14C, 14D). The electrode 19 in this example is composed of a metal base film 10 and a gold film 11. Here, in the present invention, the metal base film 10 may be a single layer or may be divided into a plurality of layers.
[0020]
FIG. 3B shows one form of the electrode 20 on the detection vibrating piece 13A (13B). The electrode 20 of this example includes a metal base film 22 and a gold film 23. Here, in the present invention, the metal base film 22 may be a single layer or may be divided into a plurality of layers.
[0021]
In the present invention, the thickness of the gold film is 45 nm or less, but from the viewpoint of further reducing the zero point temperature drift, it is preferably 40 nm or less, preferably 30 nm or less, and more preferably 20 nm or less. Further, from the viewpoint of reducing the zero point temperature drift, the thickness of the gold film is 5nm or more. Impurities may be contained in the gold film.
[0022]
From the viewpoint of reducing the zero point temperature drift, the thickness of the metal base film is set to 70 nm or less, more preferably 60 nm or less, and even more preferably 40 nm or less. Further, from the viewpoint of adhesion of the gold film to the vibrating piece, the thickness of the metal base film is 10 nm or more.
[0023]
Metal constituting the base film of chromium, a chromium alloy.
[0024]
Each metal film constituting the electrode system can be produced by a known method such as a vacuum deposition method, a sputtering method, an electrolytic plating method, or an electroless plating method.
[0025]
In the present invention , the vibrator includes a drive vibration piece provided with a drive electrode, a detection vibration piece provided with a detection electrode, and a base provided between the drive vibration piece and the detection vibration piece.
[0026]
In the present invention , the vibrator extends parallel to the predetermined plane. This includes the case where the vibrator is formed within a thickness of 1 mm or less. At this time, the drive vibration and the detection vibration of the vibrator are preferably generated in parallel to the predetermined plane.
[0027]
The material of the vibrator is not limited. However, the present invention is most effective when the vibrator is made of a piezoelectric single crystal. Examples of the piezoelectric single crystal include crystal, lithium niobate single crystal, lithium tantalate single crystal, lithium niobate-lithium tantalate solid solution single crystal, lithium borate single crystal, and langasite single crystal. The present invention is particularly suitable when the piezoelectric single crystal is quartz.
[0028]
The dimensions of the vibrator are not limited, but from the viewpoint of the present invention, the width of the vibrator is preferably 10 mm or less, and more preferably 5 mm or less. From the same viewpoint, the weight of the vibrator is preferably 5 mg or less, and more preferably 1 mg or less. Further, the thickness of the vibrator is preferably 0.3 mm or less, more preferably 0.2 mm or less.
[0029]
The present invention is particularly suitable when the width of the drive vibration piece and the width of the detection vibration piece are 150 μm or less, and further 100 μm or less.
[0030]
In the vibratory gyroscope of the present invention, when a vibration is excited in the vibrator and the vibration state of the vibrator changes due to the influence of the rotational angular velocity on the vibrator during the drive vibration, the change is detected from the change in the vibration state. The rotational angular velocity is detected through a circuit.
[0031]
【Example】
Hereinafter, more specific experimental results will be described.
The vibrator 1A shown in FIGS. 1 and 2 was manufactured.
First, a 2 inch square × 0.1 mmt quartz substrate was etched and washed with dilute hydrofluoric acid, and then dried with a spin dryer to produce a clean quartz substrate. Next, using a sputtering apparatus, a 10 nm thick Cr film was formed on both the front and back surfaces of the quartz substrate as an underlayer, and then a 200 nm thick Au film was formed.
Next, a photoresist was applied onto the Au film formation surface by a spin coater to form a resist film. Using an exposure apparatus capable of high-precision alignment of the front and back surfaces and a photomask on which a crystal outer shape etching pattern was drawn, resist patterns for outer shape etching processing of the crystal resonator were formed on both the front and back surfaces of the crystal substrate by photolithography. Using this resist pattern as a mask, the Au and Cr films formed on the quartz substrate were etched away with a mixed solution of cerium ammonium nitrate, hydrochloric acid and perchloric acid, and an etching mask pattern for external processing of the quartz oscillator was formed. Formed. This substrate was immersed in a 40% ammonium hydrogen fluoride solution heated to 70 ° C. for 10 hours, and crystal was etched to obtain a vibrator shape.
[0032]
Next, using a sputtering apparatus, Cr was formed as a base layer on the front and back surfaces and side surfaces of a vibrator formed on a quartz substrate by etching, and an electrode film was formed using Au as a surface layer. The film thicknesses of Cr and Au were changed as shown in Tables 1, 2, 3, and 4.
[0033]
Next, a photoresist was applied to the front and back surfaces and side surfaces of the vibrator formed on the quartz substrate using a spray resist coater. A resist pattern of desired electrode wiring was formed on the front and back surfaces and side surfaces of the crystal resonator by photolithography using an exposure apparatus capable of high-precision alignment of the front and back surfaces and a photomask on which electrode wiring patterns were drawn.
[0034]
Next, in order to remove the electrode metals Au and Cr by etching, they were immersed in a mixed solution of ceric ammonium nitrate, hydrochloric acid and perchloric acid to obtain a crystal resonator on which a desired electrode pattern was formed.
The entire width of the vibrator is 2 mm and the weight is 0.3 mg. The width of the drive vibration piece is 90 μm, and the width of the detection vibration piece is 70 μm.
[0035]
Next, the vibrator 1A of each example was mounted on a package. However, the substrate was made of alumina ceramics, the contact pads were made of gold, and the frame was made of SUS. The bonding wire was manufactured by plating a copper film wire with gold. The thickness of the copper film wire was about 20 μm, the width was about 100 μm, and the thickness of the gold plating was about 1 μm. The base 2 of the vibrator 1A was bonded to the bonding wire by ultrasonic bonding and fixed on the substrate.
[0036]
The obtained vibratory gyroscope was measured for the output voltage from the vibrator when the package was stationary. A calibration curve was prepared in advance by measuring the gyro sensitivity with respect to the rotational angular velocity. And the output voltage was converted into a rotation angular velocity using the gyro sensitivity measured beforehand, and the temperature drift in -40 degreeC-+85 degreeC was measured. The results are shown in Tables 1, 2, 3, and 4.
[0037]
[Table 1]

[0038]
[Table 2]

[0039]
[Table 3]

[0040]
[Table 4]

[0041]
As can be seen from the above results, the zero point temperature drift was remarkably reduced by setting the thickness of the gold film to 45 nm or less. It has also been found that the thickness of the metal base film is particularly preferably 60 nm or less.
[0042]
【The invention's effect】
As described above, according to the present invention, the zero point temperature drift of the vibrator can be further reduced, and in particular, the increase in the zero point temperature drift can be suppressed even if the vibrator is downsized.
[Brief description of the drawings]
FIG. 1 is a plan view schematically showing a vibrator 1A (driving mode) that can be used in the present invention.
FIG. 2 is a plan view schematically showing a vibrator 1A (detection mode) that can be used in the present invention.
3A is a front view showing a configuration example of an electrode 19 on the drive vibrating piece 14A (14B, 14C, 14D), and FIG. 3B is an electrode 20 on the detection vibrating piece 13A (13B). It is a front view which shows the example of a structure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1A Vibrator 2 Base 10 Metal base film 11 Gold film 13A, 13B Detection vibration piece 14A, 14B, 14C, 14D Drive vibration piece 19 Drive electrode 20 Detection electrode 22 Metal base film 23 Gold film A Drive mode vibration B, C detection Mode vibration

Claims (2)

substrate,
A base, a support projecting from the base, a driving vibration piece projecting from the support section with a width of 0.15 mm or less, and a detection vibration piece projecting from the base with a width of 0.15 mm or less are provided, and are parallel to a predetermined plane. A vibrator extending to
A drive electrode provided on the drive vibration piece, for exciting drive vibration in the vibrator ;
A detection electrode for detecting a detection vibration excited by the vibrator according to a rotational angular velocity applied to the vibrator; and
A vibration type gyroscope that is bonded to the base and includes a bonding wire that supports the vibrator on the substrate ,
In the driving vibration, the driving vibration piece is bent and vibrated in parallel to the predetermined plane with the root to the support portion as the center, and in the detection vibration, the detection vibrating piece is parallel to the predetermined plane with the root to the base portion as the center. Bend and vibrate
The drive electrode and the detection electrode are made of a gold film having a thickness of 5 nm or more and 45 nm or less, and chromium or a chromium alloy having a thickness of 10 nm or more and 70 nm or less provided between the gold film and the vibrator. A vibratory gyroscope characterized by comprising a base film. The vibratory gyroscope according to claim 1, wherein the drive electrode and the detection electrode are provided on a front surface, a back surface, and a side surface of the vibrator by a sputtering method, respectively.

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