JP2002246874A - High frequency oscillator and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shift a region in which a frequency is excited to a high drive level side under the consideration of the drive level dependency of a frequency by forming a non-contact part at an electrode in a high frequency oscillator. SOLUTION: An inverse mesa structural crystal blank 2 is formed so that a frequency of 80 MHz or more can be ensured, and a surface side electrode 3F and a back side electrode 3R are formed on the surface and back sides. Those electrodes 3F and 3R are constituted of electrode pad parts 3a and 3g which are brought into contact with at least an outer peripheral frame part 2b, and non-contact parts 3d and 3j facing an exciting part 2a connected through connecting parts 3b and 3h and a rising part 3c and a falling part 3i to the electrode pad parts 3a and 3g with a prescribed distance. In this case, the surface side electrode 3F and the back side electrode 3R are formed so that they can cross at a right angle when viewed in the y' axial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a high-frequency vibrator of not less than Hz and a manufacturing method thereof.

[0002]

2. Description of the Related Art As a conventional high-frequency vibrator, for example, as described in Japanese Patent Application Laid-Open No. HEI 12-228618, the continuity of the extraction electrodes of a crystal vibrator having concave portions on both main surfaces is ensured and the workability is improved. In order to improve the quality, a rectangular groove having the X and Y 'axes of the crystal axis (XY'Z') on each side is formed at the center of both main surfaces, and an excitation electrode is provided at the bottom of the groove. AT in which the extraction electrode extends to the upper surface of the outer peripheral frame
In the cut quartz resonator, the extraction electrode is connected to the crystal axis (X
There has been proposed a crystal resonator that extends to the upper surface of the outer peripheral wall frame via a wall surface orthogonal to the X axis or the Z ′ axis of Y′Z ′).

[0003]

Generally, an AT-cut quartz resonator has a drive level of 10 as shown in FIG.
When power of 0 μW or more is applied, the frequency becomes 2 times the applied current.
There is a problem that the oscillation frequency increases in proportion to the power and a stable oscillation frequency cannot be obtained. Further, at a high frequency, the electrode area is often reduced in design in order to suppress the generation of so-called spurious vibrations in which vibrations having different vibration modes are excited. Therefore, the current density increases, and as a result, the current 2 It enters the region where the frequency rises due to the power law. For this reason, there is an unsolved problem that a serious problem such as an increase in frequency fluctuation due to power supply fluctuation occurs.

In order to solve these unresolved problems, measures such as adding a limiting resistor to reduce the power applied to the vibrator in the oscillation circuit may be taken. There is a new problem that the accuracy of the oscillator is reduced because the temperature characteristics of the components to be used also affect the stability of the oscillation frequency. In addition, if the applied power is limited without inserting a limiting resistor in a high-frequency oscillation circuit, there remains a problem that a negative resistance of the oscillation circuit cannot be sufficiently obtained and stable oscillation cannot be obtained.

Further, when the drive level increases, not only main vibrations but also vibrations having different vibration modes called spurious vibrations are excited. In addition, since the drive level dependence of the strength is larger than that of the main vibration, as the drive level becomes higher, the strength of the spurious relative to the main vibration increases, which may cause a frequency jump or the like. For these reasons, it is generally said that the drive level applied to the vibrator is preferably as low as 25 μW or less.

Accordingly, the present invention has been made in view of the above-mentioned unresolved problems of the prior art, and a non-contact portion is formed on an electrode to provide a space between an electrode film and a vibrator substrate. Accordingly, it is an object of the present invention to provide a high-frequency vibrator capable of shifting a region where a frequency rises in a drive level dependence of a frequency to a high drive level side, and a method of manufacturing the same.

[0007]

To achieve the above object, a high frequency vibrator according to claim 1 has a frequency of 80 MHz.
In the high-frequency vibrator corresponding to z or more, at least one of the front and back electrodes formed on the vibrator substrate is in contact with the electrode forming surface other than the excitation portion, and is in contact with the contact portion in a non-contact state with the excitation portion , And a non-contact portion opposed thereto.

According to the first aspect of the invention, by forming a non-contact portion which is in a non-contact state with respect to the excitation portion on one of the front and back electrodes, the electric field applied to the vibrator substrate is not limited to just below the electrode. Since the electrode has a slight spread, the effective current density is smaller than when the electrode is directly mounted on the excitation part as in the conventional example, and the region where the frequency rises in the drive level dependence of the frequency is shifted to the high drive level side. Can be shifted.

According to a second aspect of the present invention, in the high-frequency vibrator having a frequency corresponding to 80 MHz or more, a contact portion in which both front and back electrodes formed on the vibrator substrate are brought into contact with the electrode forming surface other than the excitation portion. And a non-contact portion connected to the contact portion and facing the excitation portion in a non-contact state, and the front and back electrodes are formed in directions crossing each other.

According to the second aspect of the present invention, since both the front and back electrodes of the vibrator substrate are constituted by the contact portion and the non-contact portion, and the front and back electrodes are formed in the direction crossing each other, the frequency depends on the drive level. It is possible to shift the region where the frequency in the characteristic rises to a higher drive level side. Further, the high frequency vibrator according to claim 3 is characterized in that, in the invention according to claim 1 or 2, the vibrator substrate is formed of a thin flat plate type AT-cut quartz blank corresponding to a frequency of 80 MHz or more. And

According to the third aspect of the present invention, since the flat AT-cut quartz blank is used as the vibrator substrate, the thickness of the quartz blank determines the main vibration frequency, and the outer shape (width and length) of the quartz blank is determined. ) Determines the frequency of spurious vibration such as contour vibration depending on the shape. As the side ratio (X dimension or Z dimension / thickness) is smaller, the combination of spurious components due to the coupling of the contours is suppressed, which leads to spurious suppression.

Further, in the high-frequency vibrator according to claim 4, in the invention according to claim 1 or 2, the vibrator substrate is formed by chemically forming a central portion on one of the front and back surfaces of a flat AT-cut quartz substrate. It is characterized by being constituted by a crystal resonator blank having an inverted mesa structure in which etching is performed and the main vibration frequency of the portion to be etched is adjusted to 80 MHz or more.

In the invention according to claim 4, since the quartz crystal blank having the inverted mesa structure is used as the vibrator substrate, the thickness of the portion to be etched determines the main vibration frequency, and the outer shape (width and length) of the portion to be etched. ) Determines the frequency of spurious vibrations such as contour vibrations according to the shape, and the smaller the side ratio (X dimension or Z dimension / thickness), the more spurious compounding due to the coupling of contours is suppressed, leading to suppression of spurious.
Further, the peripheral frame portion hardly contributes to the vibration, but plays an important role in enhancing the mechanical strength of the inverted mesa resonator.

Still further, according to a fifth aspect of the present invention, there is provided a method of manufacturing a high-frequency oscillator corresponding to a frequency of 80 MHz or more, wherein a photo-electrode surface of an oscillator substrate having a frequency of 80 MHz or more is provided on the electrode forming surface. A step of applying a resist, and exposing and developing the applied photoresist to leave a non-contact electrode portion using a photomask, and removing the photoresist other than the non-contact electrode portion, Forming an electrode on the electrode forming surface;
A step of forming an electrode pattern in which a central portion is not in contact with an electrode forming surface by applying a photoresist on a film-formed electrode and then exposing using a photomask so as to leave an electrode pattern, and developing the electrode pattern. And, in this electrode step, one of the contact portions in contact with the electrode forming surface sandwiching the non-contact electrode pattern portion of the electrode pattern is removed by etching, and then the resist under the non-contact electrode pattern portion is removed to remove the non-contact electrode portion. It is characterized by forming.

According to the fifth aspect of the present invention, a contact portion other than the excitation portion is formed on the electrode forming surface, and the non-contact non-contact electrode portion can be easily formed on the excitation portion connected to the contact portion.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. In the figure, reference numeral 1 denotes an inverted-mesa structure quartz oscillator as a high-frequency oscillator,
This quartz crystal resonator 1 is a quartz crystal blank 2 having an inverted mesa structure in which a central portion of a flat AT-cut quartz substrate is chemically etched from both sides to adjust the main vibration frequency of a portion to be etched to 80 MHz or more. A front-side electrode 3F and a rear-side electrode 3R are formed on both front and back surfaces.

The front surface side electrode 3F has an electrode pad portion 3a formed on one end side outer peripheral frame portion 2b in the x direction surrounding a central excitation portion 2a on the surface of the crystal blank 2. This electrode pad portion 3a A connecting portion 3b extending from an inner end of the connecting portion 3a to the outer peripheral side of the exciting portion 2a along the inclined wall surface; a rising portion 3c rising from the end of the connecting portion 3b on the exciting portion 2a side, that is, rising in the y 'direction; A non-contact portion 3d connected to the upper end of the portion 3c and extending above the central portion of the excitation portion 2a and facing the excitation portion 2a in a non-contact state, and a non-contact portion 3d on the opposite side to the rising portion 3c of the non-contact portion 3d. A falling portion 3e that falls from the side end downward, that is, in the y 'direction, and an excitation portion contact portion 3f that extends from the lower end of the falling portion 3e to the right, that is, the x direction in contact with the excitation portion 2a. To have.

The back side electrode 3R has an electrode pad portion 3g formed on the outer peripheral portion on one end side in the z 'direction surrounding the excitation portion 2a of the crystal blank 2, and extends from the inner end of the contact portion 3g to the inclined wall surface. A connecting portion 3h extending along the outer peripheral side of the exciting portion 2a along the lower portion, a falling portion 3i falling downward, that is, in the y 'direction from an end of the connecting portion 3h on the exciting portion 2a side, and a lower end of the falling portion 3i. A non-contact portion 3j that is connected and extends above the central portion of the excitation portion 2a and faces the excitation portion 2a in a non-contact state, and a side end opposite to the falling portion 3i of the non-contact portion 3j. It is composed of a rising portion 3k that rises upward, that is, in the y 'direction, and an excitation portion contact portion 31 that extends from the upper end of the rising portion 3k to contact the excitation portion 2a and extend rearward, that is, in the x direction.

Here, the electrode pad portions 3a and 3g and the connecting portions 3b and 3h form contact portions that come into contact with portions other than the excitation portion. Therefore, the front side electrode 3F and the back side electrode 3
The non-contact portions 3d and 3j of R are arranged so as to intersect at right angles at the excitation portion 2a when viewed from the front side, that is, the y 'direction.

In order to form the AT-cut quartz resonator 1, as shown in FIG. 3, photolithography is used. That is, first, as shown in FIG.
Chemical etching is performed on both sides of the central portion of the flat AT-cut quartz substrate, and the main vibration frequency of the portion to be etched is 80
A quartz crystal blank 11 having an inverted mesa structure adjusted to be equal to or higher than MHz is prepared, and a photoresist 12 is provided on both front and back surfaces of the quartz blank 11 as shown in FIG. It is applied with a thickness corresponding to the distance (for example, 10 μm) from the surface of the excitation portion.

Next, as shown in FIG. 3C, ultraviolet light is exposed using a photomask 13 so as to leave the resist 12 in a region corresponding to the non-contact portions 3d and 3j. By performing development and rinsing as shown in d), a resist pattern leaving only regions corresponding to the non-contact portions 3d and 3j is formed. Next, FIG.
As shown in FIG. 3, electrodes 14 and 15 to be the front side electrode 3F and the back side electrode 3R are formed on the front and back surfaces of the crystal blank 11 by vapor deposition or the like, and then, as shown in FIG.
A resist 16 is applied on the deposited electrodes 14 and 15, and then exposed to ultraviolet light using a photomask 17 having a shape that leaves the shapes of the front-side electrode 3F and the back-side electrode 3R, followed by development and rinsing. By performing this, a resist pattern having a shape corresponding to the front surface side electrode 3F and the back surface side electrode 3R is formed as shown in FIG.

Next, the electrodes 14 and 15 are etched to form an electrode pattern having the shape of the front side electrode 3F and the back side electrode 3R as shown in FIG. 3 (h). As shown in FIG. 3 (i), by removing the resist under the non-contact portions 3d and 3j using a resist removing agent, the intended front-side electrode 3F and back-side electrode 3R are formed.

In the thus-formed inverted-mesa crystal resonator 1, the portions of the front-side electrode 3F and the back-side electrode 3R facing the excitation portion 2a of the crystal blank 2 are non-contact portions 3d and 3j. When electric power is applied to these electrodes 3F and 3R, the electric field formed by these non-contact portions 3d and 3j causes the electric fields formed by the non-contact portions 3d and 3j.
j, not only the excitation portion 2a immediately below, but also the excitation portion 2a slightly wider than the non-contact portions 3d and 3j, with a slight spread, and the effective current density is applied directly to the excitation portion 2a. It becomes smaller than when it is formed.

In the present embodiment, the shape of the inverted-mesa-structured quartz resonator 1 is set as shown in Table 1 below. The results of measuring the frequency response characteristics showing the relationship are shown in FIGS. 4 and 5, respectively.

[0025]

[Table 1]

As is apparent from FIG. 4, the rise of the frequency deviation is shifted to the higher drive level side by about 100 μW as compared with 25 μW of the conventional example having the same configuration shown in FIG. Therefore, frequency stability can be obtained even when a higher voltage is applied. Therefore, when the inverted-mesa-structured crystal resonator 1 is applied to a voltage-controlled oscillator, it is possible to prevent frequency fluctuations due to power supply fluctuations.

By increasing the drive level, it is possible to prevent the spurious vibration from becoming strong. By suppressing the spurious vibration, the temperature characteristics are improved, and further, the phase noise in which the vibrator spurious becomes a gain is obtained. Is also improved. In addition, when an electrode is directly formed as in the conventional example, the frequency decreases due to mass loading of the electrode film. Therefore, the thickness of the quartz blank is set to be higher than the target frequency in consideration of the decrease in the frequency. In this embodiment, the non-contact portions 3d and 3j of the front surface side electrode 3F and the back surface side electrode 3R are required to be thin.
Since the crystal blank 2 is spaced apart from a, the thickness of the quartz blank 2 can be made thicker by the absence of the electrode as compared with the conventional method in which the electrode is directly formed into a film, and processing is easy.

The frequency response characteristic representing the relationship between the frequency and the impedance has a maximum peak near the frequency of 155.5 MHz, as is apparent from FIG.
A characteristic having a secondary peak near 156.25 MHz is obtained, and a resonance characteristic substantially equal to the frequency response characteristic shown in FIG. 6 in the case of the conventional example described above can be obtained. In the first embodiment, the case where the contact portions 3f and 3l are formed on the opposite sides of the non-contact portions 3d and 3j from the electrode pad portions 3a and 3g has been described. However, the present invention is not limited to this. And z 'of the non-contact portions 3d and 3j
It may be formed on the axial end side.

Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the present invention is applied to a flat AT-cut quartz crystal unit instead of the inverted mesa structure quartz crystal unit. That is, in the second embodiment,
As shown in FIG. 7, the front side electrode 3F and the back side electrode 3R are formed on both front and back surfaces of a thin flat AT-cut quartz substrate 21 whose frequency is set to a thickness corresponding to 80 MHz or more to form a flat AT-cut quartz oscillation. A child 20 is configured.

Here, the front side electrode 3F is connected to the central excitation portion 2 on the front side of the flat AT-cut quartz substrate 21.
An electrode pad portion 23a is formed on an outer peripheral portion on one end portion in the x direction surrounding 2a, and a rising portion 23 rising upward, that is, in the y 'direction from an inner end portion of the electrode pad portion 23a.
b, a non-contact portion 23c connected to the upper end of the rising portion 23b and extending above the central portion of the excitation portion 22a and facing the excitation portion 22a in a non-contact state, and a rising portion 23b of the non-contact portion 23c. A falling portion 23d that falls from the opposite side end in the y direction, and a contact portion 23e that extends from the lower end of the falling portion 23d to the right, that is, the x direction in contact with the excitation portion 2a. It is composed of

Here, the electrode pad portions 23a and 23f and the contact portions 23e and 23j constitute contact portions that come into contact with portions other than the excitation portion 22a. The back side electrode 3R is a flat type A
Excitation part 22a on the back side of T-cut quartz substrate 21
An electrode pad portion 2 is provided on the outer peripheral portion on one end side in the z 'direction surrounding
3f is formed, and a falling part 23g which falls from the inner end of the electrode pad part 23f downward, that is, in the y 'direction.
A non-contact portion 23h connected to the lower end of the falling portion 23g and extending above the central portion of the excitation portion 22a and facing the excitation portion 22a in a non-contact state;
3h, a rising portion 23i that rises upward from the side end opposite to the falling portion 23g, that is, in the y 'direction, and a contact portion that extends from the upper end of the rising portion 23i to contact the excitation portion 2a and extend rearward, that is, in the x direction. 23j.

Here, the electrode pad portions 23a and 23f and the contact portions 23e and 23j constitute a contact portion that contacts other than the excitation portion 22a. To manufacture the flat AT-cut quartz resonator 20, in the manufacturing process of FIG. 3 in the above-described embodiment, a flat quartz blank having a desired frequency of 80 MHz or more is prepared in FIG. Except for this, the front-side electrode 3F and the back-side electrode 3R can be formed in the same steps as in FIGS. 3B to 3H.

As described above, also in the flat AT-cut crystal resonator 20, the non-contact portion 2 which faces the excitation portion 22a at a predetermined interval to the front surface electrode 3F and the rear surface electrode 3R.
Since 3c and 23f are formed, it is possible to obtain the same operation and effects as those of the inverted-mesa structure quartz crystal resonator 1 in the above-described embodiment. In the second embodiment, the case where the contact portions 23e and 23j are formed on the opposite sides of the non-contact portions 23c and 23h from the electrode pad portions 23a and 23f has been described, but the present invention is not limited to this. The z 'of the non-contact portions 23c and 23f
You may make it form in an axial direction edge.

In the first and second embodiments, the non-contact portions 3d, 23c and 3c are provided on both the front-side electrode 3F and the back-side electrode 3R on the front and back surfaces of the quartz blank 2.
Although the case where j and 23h are formed has been described, the non-contact portion 3
d, 23c or 3j, 23h, and the other
The contact electrode portion may be configured to be in direct contact with a.

In the first and second embodiments,
Although the case where the present invention is applied to the AT-cut quartz resonator has been described, the present invention is not limited to this, and can be applied to a thickness-slip resonator other than the AT-cut quartz resonator.

[0036]

As described above, according to the first aspect of the present invention, a non-contact portion that is in a non-contact state with respect to the excitation portion is formed on one of the front and back electrodes, so that the vibrator substrate can be formed. Since such an electric field has a slight spread, not just below the electrode, the effective current density is smaller than when the electrode is directly mounted on the excitation portion as in the conventional example, and the drive level dependency of the frequency is dependent on the drive level. Since the region where the frequency rises can be shifted to the high drive level side, the frequency rise due to the application of the high drive level can be suppressed, and when applied to a voltage controlled oscillator, the fluctuation of the frequency due to power supply fluctuation is prevented. The higher the drive level, the higher the spurious vibration can be prevented and the better the temperature characteristics. With wear, the effect is obtained that the phase noise oscillator spurious causes can be improved.

According to the second aspect of the present invention, since both the front and back electrodes of the vibrator substrate are constituted by the contact portion and the non-contact portion, and the front and back electrodes are formed in the directions crossing each other, the drive level of the frequency is increased. The effect that the region where the frequency rises in the dependency can be shifted to the higher drive level side can be obtained. Furthermore, in the invention according to claim 3, since the flat AT-cut quartz blank is used as the vibrator substrate, the thickness of the quartz blank determines the main vibration frequency, and the outer shape (width and length) of the quartz blank is reduced. The frequency of spurious vibrations such as contour vibrations is determined by the shape, and as the side ratio (X dimension or Z dimension / thickness) is smaller, the spurious compounding due to the coupling of the contours is suppressed, and spurious suppression can be performed. Is obtained.

Further, in the invention according to claim 4, since the inverted mesa structure quartz crystal blank is used as the vibrator substrate, the thickness of the portion to be etched determines the main vibration frequency.
The outer shape (width and length) of the portion to be etched determines the frequency of spurious vibration such as contour vibration depending on the shape, and the smaller the side ratio (X dimension or Z dimension / thickness), the more spurious compounding due to coupling between contours. Suppression is suppressed, which leads to spurious suppression. Further, the peripheral frame portion hardly contributes to vibration, but an effect that it can play an important role in enhancing the mechanical strength of the inverted mesa vibrator is obtained.

Still further, according to the fifth aspect of the present invention, a contact portion is formed on the electrode forming surface of the vibrator substrate other than the excitation portion, and a non-contact non-contact electrode portion is formed on the excitation portion connected to the excitation portion. The effect that it can be easily formed is obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example in which the present invention is applied to a quartz crystal unit having an inverted mesa structure.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an explanatory view showing a method for manufacturing an inverted-mesa type crystal resonator.

FIG. 4 is a characteristic diagram showing a relationship between a drive level and a frequency deviation in the embodiment of FIG.

FIG. 5 is a frequency response characteristic diagram showing a relationship between frequency and impedance in the embodiment of FIG. 1;

FIG. 6 is a frequency response characteristic diagram showing a relationship between frequency and impedance in a conventional example.

FIG. 7 is a perspective view showing an embodiment in which the present invention is applied to a flat AT-cut crystal unit.

FIG. 8 is a characteristic diagram showing a relationship between a drive level and a frequency deviation in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inverted mesa structure crystal oscillator 2 Inverted mesa structure crystal blank 2a Excitation part 3F Front side electrode 3R Back side electrode 3a, 3g Electrode pad part 3b, 3h Connecting part 3c Rising part 3d, 3j Non-contact part 3e Falling part 3f, 3l contact portion 3i falling portion 3k rising portion 3l contact portion 20 flat AT cut crystal resonator 21 flat AT cut crystal blank 22a excitation portion 23a, 23f electrode pad portion 23b rising portion 23g falling portion 23c, 23h non-contact portion

Claims (5)

[Claims] In a high-frequency vibrator corresponding to a frequency of 80 MHz or more, at least one of front and back electrodes formed on a vibrator substrate is brought into contact with an electrode forming surface in a portion other than an excitation portion, and is connected to the contact portion to generate an excitation. A high-frequency vibrator characterized by comprising a non-contact portion facing a portion in a non-contact state. 2. A high-frequency vibrator having a frequency of 80 MHz or higher, wherein both a front and back electrode formed on a vibrator substrate are in contact with an electrode forming surface other than an excitation portion, and an excitation portion is connected to the contact portion. A high-frequency vibrator comprising: a non-contact portion opposed to a non-contact state with respect to the first and second electrodes; and front and back electrodes formed in directions intersecting each other. 3. The vibrator substrate has a frequency of 80 MHz.
3. The high-frequency vibrator according to claim 1, wherein the high-frequency vibrator is formed of a thin flat AT-cut quartz blank corresponding to the above. 4. The inverted vibrator substrate in which the center portion of one of the front and back sides of the flat AT-cut quartz substrate is chemically etched, and the main vibration frequency of the portion to be etched is adjusted to be 80 MHz or more. 3. The high-frequency vibrator according to claim 1, wherein the high-frequency vibrator is constituted by a quartz crystal blank having a mesa structure. 5. A method for manufacturing a high-frequency vibrator corresponding to a frequency of 80 MHz or more, a step of applying a photoresist to an electrode forming surface of a vibrator substrate having a frequency of 80 MHz or more, Using a photomask to expose and develop so as to leave the non-contact electrode portion, developing, removing the photoresist other than the non-contact electrode portion, and forming an electrode on the electrode forming surface,
A step of forming an electrode pattern in which a central portion is not in contact with an electrode forming surface by applying a photoresist on a film-formed electrode and then exposing using a photomask so as to leave an electrode pattern, and developing the electrode pattern. And, in this electrode step, one of the contact portions in contact with the electrode forming surface sandwiching the non-contact electrode pattern portion of the electrode pattern is removed by etching, and then the resist under the non-contact electrode pattern portion is removed to remove the non-contact electrode portion. A method for manufacturing a high-frequency vibrator, characterized by being formed.