JP2004328122A - Crystal oscillator and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an ultra-thin crystal oscillator having a uniform thickness. <P>SOLUTION: This method of manufacturing a crystal oscillator comprises a first polishing process (steps S202-S204) of polishing only one face of a quartz cut out in a step S201, and a second polishing process (steps S205-S207) of polishing the opposite face relative to the one face after ending the first polishing process (steps S202-S204), thereby obtaining a crystal oscillator having a thickness of approximately 15 μm or less. The crystal oscillator has a uniform thickness over the entire surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thin crystal resonator capable of oscillating a high frequency and a method for manufacturing the crystal resonator.
[0002]
[Prior art]
2. Description of the Related Art In recent years, in the age of advanced information communication centered on the Internet, it has been required to communicate a large amount of data at a higher speed. Accordingly, it is necessary to use a higher clock frequency such as a microprocessor or a modem used for a communication device or the like. As a method of increasing the clock frequency, it is conceivable to use a multiplier circuit for multiplying the fundamental frequency. However, in consideration of miniaturization and power saving of the entire device, the multiplier frequency itself is increased without using the multiplier circuit as much as possible. Is required. Similarly, a high frequency fundamental wave is required in the field of wireless communication including mobile phones.
[0003]
It is known that a high fundamental frequency can be obtained by reducing the thickness of the crystal resonator. Therefore, conventionally, when manufacturing a fundamental wave crystal resonator having a frequency of 60 MHz or more, a crystal element plate obtained by a manufacturing method in which only a central portion called a mesa-rank is thinned by etching or the like is used. .
[0004]
[Problems to be solved by the invention]
However, even in the above-mentioned conventional technology, a fundamental wave crystal oscillator of 100 MHz or more could not be obtained. Further, in the above-described conventional technology, there are the following problems in manufacturing a fundamental frequency crystal resonator of 100 MHz or less. That is, in the manufacturing method according to the related art, flatness is hardly obtained, and thickness unevenness easily occurs. In addition, the flatness of the main part of the vibrator is deteriorated, and the thickness of the vibrator increases. This results in variation of the center frequency in the vibration.
[0005]
Further, in the manufacturing method in the conventional technique, the surface roughness is deteriorated. That is, the etching rate of crystalline quartz changes depending on the plane orientation. Therefore, there is little effect when etching is performed slightly, but when etching is performed deeply like a mesa type, the surface becomes rough and the surface roughness becomes poor. This lowers the Q value which is the figure of merit of the vibrator.
[0006]
In addition, the manufacturing process in the related art requires a complicated manufacturing process. That is, in the mesa type, a photolithography process such as an ordinary semiconductor IC is required in order to selectively etch a crystal surface, and the manufacturing process is accordingly complicated.
[0007]
In order to further reduce the above problems (defects), it is necessary to slow down the etching conditions (speed, liquid concentration, etc.) and perform etching slowly over a long period of time. There was a problem that it would be.
[0008]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a quartz resonator having a thickness of about 15 μm or less, that is, a fundamental frequency of 110 MHz or more, in order to solve the above-mentioned problems of the prior art. It is another object of the present invention to provide a manufacturing method capable of efficiently manufacturing a quartz oscillator having a thickness of about 15 μm or less, that is, a fundamental frequency of 110 MHz or more.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems and achieve the object, a quartz resonator according to claim 1 is characterized in that the thickness is approximately 15 μm or less.
[0010]
Further, a quartz oscillator according to a second aspect is characterized in that, in the invention according to the first aspect, the thickness is substantially uniform over the entire surface.
[0011]
Further, in the crystal resonator according to the third aspect, in the invention according to the first or second aspect, after polishing only one surface of the cut crystal, only the surface opposite to the one surface is polished. Characterized by being obtained by polishing.
[0012]
A method for manufacturing a crystal unit according to a fourth aspect is the method for manufacturing a crystal unit according to any one of the first to third aspects, wherein only one surface of the cut crystal is provided. And a second polishing step of polishing only the surface opposite to the one surface after completion of the first polishing process.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a crystal resonator and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.
[0014]
(Relationship between crystal oscillator thickness and fundamental frequency)
Normally, the thickness t of the crystal unit can be expressed by the following equation.
f (MHz) = 1670 / t (μm) Equation (1)
Therefore, if the crystal resonator has a thickness of 10 μm, the fundamental frequency is 167 MHz. Similarly, if the thickness is 15 μm, the fundamental frequency is 111.33 MHz. If the thickness is 8 μm, the fundamental frequency is 208.75 MHz.
[0015]
(Overview of quartz crystal units)
Next, an outline of the crystal resonator according to the present embodiment will be described. FIG. 1 is a schematic cross-sectional view schematically showing a crystal resonator according to the embodiment of the present invention. In FIG. 1, a crystal unit 100 has one surface 101 to be polished and the other surface 102 which is the opposite surface.
[0016]
The crystal unit 100 manufactured by the applicant was manufactured by a manufacturing method described later, and the obtained frequency was measured by a network analyzer R-3767CG manufactured by ADVANTEST. As a result, the fundamental frequency was 154.234 MHz. Was. Therefore, the thickness of the crystal unit 100 is 10.828 μm from the above equation (1).
[0017]
(Method of manufacturing quartz oscillator)
Next, a method for manufacturing the crystal resonator according to the embodiment of the present invention will be described. FIG. 2 is a flowchart showing a procedure of a method of manufacturing a crystal resonator according to the embodiment of the present invention. In the flowchart of FIG. 1, first, a portion to be a crystal resonator (wafer) 100 is cut out from a crystal lump (step S201). At this time, the thickness of the wafer 100 is about 200 μm to 500 μm.
[0018]
Next, the wafer 100 is placed (set) on a polishing apparatus (not shown) so that one surface 101 of the cut wafer 100 becomes a polishing surface (step S202), and only the one surface 101 is polished. The processing is performed (Step S203). At this time, the surface opposite to the one surface 101 (the other surface 102) is not polished. Then, it is determined whether a predetermined time has elapsed since the start of the polishing process (step S204).
[0019]
Since the thickness to be polished is determined according to the time during which the polishing process is continuously performed, a polishing time to reach a desired thickness is obtained in advance. If the polishing process is performed with that time as a predetermined time, it is possible to easily polish by a desired thickness. Therefore, instead of determining whether or not the predetermined time has elapsed, it may be directly determined whether or not a predetermined (desired) thickness has been reached.
[0020]
In step S204, if the predetermined time has not yet elapsed, or if the predetermined thickness has not been reached (step S204: No), the process returns to step S203, and the polishing process is continuously performed. Then, in step S204, when a predetermined time has elapsed or when a predetermined thickness has been reached (step S204: Yes), the wafer 100 is then turned over, and this time, the other surface 102 becomes the polished surface. The wafer 100 is placed (set) on the polishing apparatus so as to be (Step S205).
[0021]
Then, only the other surface 102 is polished. (Step S206). At this time, the one surface 101 is not polished. Then, it is determined whether a predetermined time has elapsed since the start of the polishing process (step S207). Here, similarly to step S204, when the predetermined time has not yet elapsed or when the predetermined thickness has not been reached (step S207: No), the process returns to step S206, and the polishing process is continuously performed.
[0022]
After that, in step S207, when a predetermined time has elapsed or when a predetermined thickness has been reached (step S207: Yes), the wafer 100 is taken out of the polishing apparatus (step S208). Thus, the polishing process is completed. Thereafter, the wafer 100 is cleaned, a metal such as silver serving as an electrode is deposited, the frequency is adjusted, and the wafer 100 is sealed.
[0023]
Since it is desirable to use the center portion of the cut crystal in the thickness direction as a crystal oscillator, when the thickness of the cut wafer 100 is about 200 μm, both sides are polished by the same thickness. . Therefore, assuming that the desired thickness is 10 μm, one surface 101 may be polished by about 95 μm, and the other surface 102 may be polished by about 95 μm.
[0024]
Since the quartz oscillator is processed by the above steps, a quartz oscillator having a flat shape on the entire surface can be obtained. If it becomes possible to process a flat crystal oscillator, the productivity can be improved and the reduction in manufacturing cost can be reduced.
[0025]
As described above, when the crystal resonator according to the present embodiment is used, a high clock frequency can be obtained with the fundamental wave without using the third and fifth harmonics. Therefore, components such as a multiplying circuit are not required, so that power consumption can be reduced and the electronic circuit can be simplified. Therefore, miniaturization, low power consumption, and high reliability of the electronic circuit can be obtained at the same time. Furthermore, since the amount of heat generated from the electronic circuit can be reduced, the thermal stability of the electronic circuit can be increased. In particular, it is suitable for use in products in the field of wireless communication.
[0026]
【The invention's effect】
As described above, according to the present invention, a first polishing step of polishing only one surface of a cut crystal, and a surface opposite to the one surface after the first polishing step is completed. And a second polishing step of polishing only a single crystal. Therefore, the crystal resonator has a thickness of about 15 μm or less, that is, a fundamental frequency of 110 MHz or more, and has a substantially uniform thickness over the entire surface and stable oscillation. A practicable quartz oscillator can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view schematically showing a cross section of a crystal resonator according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a procedure of a method of manufacturing a crystal resonator according to the embodiment of the present invention.
[Explanation of symbols]
100 crystal oscillator (wafer)
101 One surface 102 (of the crystal unit 100) The other surface (of the crystal unit 100)

Claims (4)

A quartz oscillator having a thickness of about 15 μm or less. 2. The crystal unit according to claim 1, wherein said thickness is substantially uniform over the entire surface. 3. The crystal resonator according to claim 1, wherein the crystal resonator is obtained by polishing only one surface of the cut crystal and then polishing only a surface opposite to the one surface. 4. It is a manufacturing method of the crystal oscillator as described in any one of Claims 1-3, Comprising:
A first polishing step of polishing only one surface of the cut crystal,
After the end of the first polishing step, a second polishing step of polishing only the surface opposite to the one surface,
A method for manufacturing a crystal resonator, comprising:

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