JP2013070351A - Crystal oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystal oscillator having a high Q-value by centralizing energy in a center section, which causes high productivity and a good yield; and especially to provide a crystal oscillator whose productivity can be heightened by a few etching processes.SOLUTION: Duty is made to be higher from a periphery of a crystal blank toward its center, by: forming a salient having a specific height on base material of the crystal blank; forming many ditches having a specific depth on the salient; and making widths of the ditches reduce gradually from the periphery of the crystal blank toward its center.

Description

  The present invention relates to a crystal resonator, and is particularly suitable for an AT cut crystal resonator. Specifically, when the electrical axis of the crystal of the crystal is the X-axis, the mechanical axis is the Y-axis, and the optical axis is the Z-axis, the vibrator cut out at an angle of 35 degrees and 15 minutes from the Z-axis is AT-cut vibration Call it a child. The frequency of the crystal resonator varies depending on the temperature, but the AT-cut crystal resonator has a lower temperature dependency than that of the BT-cut resonator and is used in many fields.

  The natural vibration of such a crystal resonator is determined by the thickness. In the crystal resonator, vibration energy is concentrated on a portion where the mass of the crystal is large. That is, when an electrode is formed on the crystal of a crystal resonator, the mass of the electrode portion is large, and energy concentrates on this portion. Furthermore, it is known that the resonance frequency of the thickness shear vibration is inversely proportional to the thickness of the crystal. For example, in the case of an AT cut crystal resonator, a value obtained by dividing a constant having a value of about 1670 by the crystal thickness is the resonance frequency.

  In other words, there is a means for preventing energy waste by concentrating energy in the central portion by forming an electrode in the central portion of the crystal resonator. As a result, a crystal resonator having a high Q value can be obtained.

  Alternatively, there is a means for more actively increasing the thickness of the central portion of the crystal resonator and further concentrating energy on the central portion. However, in order to adopt such means, polishing processing using a dedicated abrasive and jig to make the crystal resonator like a convex lens, or dry etching processing using a resist processed into a convex lens shape, etc. In order to use the processing method by, it has problems such as processing accuracy and yield.

  Therefore, as disclosed in Patent Document 1, means for increasing the thickness of the electrode toward the center of the crystal resonator has been developed. By doing in this way, manufacture became easy rather than changing the thickness of a crystal oscillator.

JP-A-10-308645

  However, in the conventional crystal resonator disclosed in Patent Document 1 as described above, it is necessary to increase the thickness of the electrode from the outer peripheral portion toward the central portion. For this reason, as described in paragraph 0007 of Patent Document 1, a plurality of electrode layers (aluminum or the like) having different areas are sequentially used on both front and back surfaces of a base material (large wafer) of a quartz base plate by using masks having different opening diameters. ) Are sequentially laminated to form a vapor deposition.

  In this case, it is necessary to repeat the vapor deposition step a plurality of times. Vapor deposition is performed by putting a processed product in a vacuum chamber and is a batch process. Therefore, when such a process is performed a plurality of times, productivity is lowered.

  The present invention pays attention to the above points, and aims to provide a crystal resonator having a high Q value by concentrating energy in a central portion with high productivity and good yield.

  A convex part with a specific height is formed on the base material of the quartz base plate, and a groove with a specific depth is formed on the convex part. Depending on the width of the groove, the duty is increased from the outer periphery to the center of the quartz base plate. I tried to get bigger.

  Since the crystal unit of the present invention is configured as described above, the thickness of the crystal base plate can be constant in a specific portion, and energy can be concentrated toward the center of the crystal unit, and thus has a high Q value. A crystal resonator can be obtained.

  And since the thickness of a quartz base plate is constant in a specific part as mentioned above, processing is easy and productivity can be made high.

  Furthermore, since the groove is formed in a specific part of the quartz base plate and the duty is increased toward the center, it can be manufactured by performing the etching process only once, resulting in high productivity and high yield. .

  In particular, by appropriately devising an etching pattern, it is possible to obtain desired characteristics as a crystal resonator.

  Further, the technology of the present invention can not only increase the duty two-dimensionally from the outer periphery to the center of the crystal resonator, but also increase the duty one-dimensionally from the outer periphery to the center of the crystal resonator. .

  It is sectional drawing which shows Example 1 of the crystal oscillator of this invention.   It is sectional drawing which shows the principle of the crystal oscillator of this invention.   It is a top view which shows Example 2 of the crystal oscillator of this invention.   It is a top view which shows Example 3 of the crystal oscillator of this invention.   FIG. 9 is a top view showing a fourth embodiment of the crystal unit of the present invention.   It is a graph which shows the characteristic of the crystal oscillator of this invention.

  In the invention according to claim 1 of the present invention, a convex portion having a specific height is formed on the base material of the quartz base plate, and a groove having a specific depth is formed on the convex portion. Since the duty increases from the outer periphery of the quartz base plate toward the center, the energy increases toward the center of the quartz base plate and the Q value increases.

  Hereinafter, embodiments of the crystal resonator according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a crystal resonator according to the present invention. A convex portion 2 having a certain height is formed on the surface of the quartz base plate 1, and a groove 3 having a depth equal to the thickness of the convex portion 2 is formed in the convex portion 2. Thereby, a plurality of protrusions having a predetermined height are formed.

  Formation of the convex part 2 and the groove | channel 3 is realizable with dry etching apparatuses, such as reactive ion etching. That is, the convex portion 2 and the groove 3 can be formed by one etching. By projecting a metal mask made of gold, chromium, nickel, or the like on the quartz surface by photolithography, and then performing dry etching, a convex shape having an arbitrary height can be formed. The height of the convex portion 2 is the same as the height of the convex to be simulated, and generally about 5% of the crystal thickness is considered good. Since it can be processed by dry etching, a large number of crystal resonators arranged in a crystal wafer can be processed uniformly at the same time, which is advantageous for mass production. In order to use it as a crystal resonator, it is necessary to pattern an electrode with respect to the convex part 2. For electrode patterning on the projections 2, it is desirable to apply a photoresist using a spray coater or the like, but it can also be solved by spin coating a thick photoresist that is thicker than the projections 2.

  That is, all the protrusions have the same height and a predetermined width and pitch. In Example 1, all the protrusions have the same width and the same pitch. In the first embodiment, the duty of the central portion is large with respect to both ends of the quartz base plate 1. Even if the pitch of the convex portion 2 is fixed and only the duty ratio is changed in the entire range from 0% to 100%, similarly, it vibrates at a resonance frequency corresponding to the average height between one pitch.

  FIG. 2 is a cross-sectional view of a crystal resonator according to a second embodiment of the present invention. FIG. 2 also shows a quartz resonator formed by smoothly inflating the center into a conventional convex lens shape and a quartz resonator having a thickness gradually increased toward the center.

  A second embodiment of the present invention is shown at the bottom of FIG. In Example 2, the pitches of the convex portions 2 are the same, and the width of the convex portions 2 increases toward the center. In other words, due to this configuration, the duty of the central portion is large with respect to both ends of the quartz base plate 1.

  The plano-convex crystal resonator has a convex lens-like protrusion at the center of the crystal piece. In order to simulate this, first, the convex part is divided into regions with a certain pitch. Next, find the average height of each area. Deforms into a staircase. Finally, the convex part 2 having a duty ratio corresponding to the average height of each region is designed. By the above simple operation, a shape simulating a plano-convex shape in terms of vibration can be obtained.

  FIG. 3 shows a plan view of the third embodiment of the present invention. In Example 3, the duty increases one-dimensionally from both ends of the quartz base plate 1 toward the center. That is, the quartz base plate 1 has a rectangular shape, and a plurality of convex portions 2 are formed on the upper surface thereof at an equal pitch. Each convex part 2 is linear. In addition, the width of each convex portion 2 gradually increases toward the center of the quartz base plate 1.

  In the crystal resonator according to the third embodiment of the present invention having the above-described configuration, the width of the convex portion 2 increases from both ends of the crystal base plate 1 toward the center. growing.

  FIG. 4 shows a plan view of Embodiment 4 of the present invention. In the fourth embodiment, as in the third embodiment, the duty increases one-dimensionally from both ends of the quartz base plate 1 toward the center. That is, the quartz base plate 1 has a rectangular shape, and a plurality of convex portions 2 are formed on the upper surface thereof at an equal pitch. Each convex part 2 is linear. In addition, the width of each convex portion 2 gradually increases toward the center of the quartz base plate 1.

  In the fourth embodiment, each convex portion 2 is inclined with respect to the center line of the crystal base plate 1 as compared with the third embodiment. By tilting in this way, the change in the duty from the both ends of the quartz base plate 1 toward the center becomes gradual, and the required level of processing accuracy becomes lenient.

  FIG. 5 shows a plan view of the fifth embodiment. In the fifth embodiment, the quartz base plate 1 has a disk shape, and the convex portions 2 and the grooves 3 are formed concentrically on the surface thereof. The finer the pitch of the convex portions 2, the more accurately the shape that simulates the plano-convex shape in terms of vibration.

  However, in actual manufacturing, the width of the minimum convex portion 2 is limited to several microns due to the resolution of the exposure apparatus and the patterning accuracy of the metal mask. Further, from the viewpoint of the reproducibility of the plano-convex shape, the width of the convex portion 2 is desirably at least 10 patterns. From this situation, the pitch becomes several tens of microns.

  The fifth embodiment solves the above problem. These problems can be solved by forming a wide portion and a narrow portion on the convex portion 2 as shown in FIG. 5 and arranging patterns in which the phases of the portions having different widths are slightly shifted. Although it is divided into about 10 groups in FIG. 5, a shape closer to a plano-convex shape can be obtained by dividing as many as possible.

  Since the quartz crystal resonator of the present invention can reproduce a convex without depending on a polishing apparatus or a convex lens-like resist shape, a curved surface shape can be arbitrarily selected. Therefore, a crystal resonator with high mass productivity, low cost, and good yield can be obtained.

1 Crystal base plate 2 Convex part 3 Groove

Claims (5)

A convex portion having a specific height is formed on the base material of the crystal base plate, and a groove having a specific depth is formed on the convex portion. Depending on the width of the groove, the duty is increased from the outer periphery to the center of the crystal base plate. A crystal unit that is designed to be large. 2. The crystal resonator according to claim 1, wherein the thickness is increased stepwise toward the center of the crystal base plate. 2. The crystal resonator according to claim 1, wherein a plurality of grooves are formed in parallel one-dimensionally from both ends of the quartz base plate toward the center, and the duty is increased by the width of the grooves. 4. The crystal resonator according to claim 3, wherein each groove is formed obliquely with respect to the center line of the crystal base plate. The crystal base plate is disk-shaped, and a plurality of concentric protrusions and grooves are formed on the surface thereof. Wide portions and narrow portions are formed on the protrusions, and the phases of the portions having different widths are shifted. 2. The crystal resonator according to claim 1, wherein the crystal resonator has a shape approximate to a plano-convex shape by arranging patterns.

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