JP2950000B2 - How to grow artificial quartz - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing artificial quartz, and more particularly, to a method for growing artificial quartz for obtaining a surface acoustic wave (SAW) element substrate.

[0002]

2. Description of the Related Art Artificial quartz used for cutting a quartz plate is, for example, a rod-shaped (Y-bar) or plate-shaped (Z-plate) as shown in an example of an artificial quartz shape shown in JIS-C-6704 (1981). Usually, the crystals are grown as seed crystals in the Z-axis and X-axis directions by a hydrothermal synthesis method.

FIG. 3A is a front view of an artificial quartz crystal using a Y bar as a seed crystal, FIG. 3B is a side view thereof, and FIG.
FIG. FIG. 4A is a front view of an artificial quartz using a Z plate as a seed crystal, FIG.
(C) is the sectional view on the line AA. In these figures, reference numeral 11 denotes a seed crystal.

At present, ATs widely used for vibrator pieces
The shape, dimensions and processing method used for the cut crystal blank are, for example, 10 [mm] × 10 [mm] or 8 [mm] ×
8 [mm], or 10 [φ] or 8 [φ], 5
It is mainly formed into a strip shape such as [φ] or a disk shape, and further subjected to contour processing such as bevel or convex on the outer peripheral portion thereof. As shown by a dashed line in the figure, the crystal was cut out from a plane including the Z 'axis obtained by rotating the Z axis about the X axis by about 35 ° and the X axis (AT cut method). ) The AT-cut quartz plate is further subdivided and cut into the above-mentioned dimensions, and is molded to obtain an AT-cut quartz piece.

[0005]

In the case of vibrator pieces other than SAW, since individual quartz pieces are cut out and then subjected to shape processing, electrode deposition, etc., the artificial quartz need not be so large, and can be obtained by a conventional growing method. There was no problem with AT-cutting the artificial quartz.

However, in the case of a SAW element, the manufacturing process is completely different from the case of a conventional vibrator piece such as an AT-cut.

That is, similarly to a silicon substrate used in a semiconductor etching method, an extremely large number of device electrodes and the like are simultaneously formed on a large-area ST-cut quartz plate (corresponding to a wafer) by a photoresist method. And then individual S
Cut into AW elements. Also, the cut ST-cut quartz pieces do not require any particular contour processing.

Therefore, in order to increase the productivity of the SAW element, it is desirable to grow an artificial quartz as large as possible and to collect a ST cut quartz plate having a large diameter, and at least 3 inches (about 76 [mm]). Need to be of diameter.

[0009] However, the S
When a T-cut quartz plate is cut out from a conventional artificial quartz, the value of the rotation angle θ about the X axis of the Z ′ axis in FIG. 3 or 4 with respect to the Z axis is generally about 35 ° to 45 °,
As shown by the dashed line, the ST-cut quartz plate is cut out. Therefore, in the conventional method of growing artificial quartz using a Y-bar or a Z-plate as a seed crystal, the growth rate in the Z-axis direction is about 0.45 [mm / day]. Takes days.

For example, FIG. 5 (a) is a ST cut cross-sectional perspective view of an artificial quartz for a SAW substrate grown by using a Z plate as a seed crystal by a conventional method, and it takes about 150 days to grow to such a size. It also takes. Moreover, in this case, the seed crystal 11 is included in the center of the ST-cut quartz plate 10 from which the most SAW elements can be obtained, so that this portion cannot be used and productivity is significantly reduced, and the material density of the quartz plate is low. There is a problem of uniformity.

As shown in FIG. 5 (b), when artificial quartz is grown using a Z plate as a seed crystal until two ST-cut quartz plates 10 can be collected, seeds are placed in each ST-cut quartz plate 10. Although it is possible not to include the crystal 11, it takes about 300 days to grow to such a size, so that the operation rate of an autoclave used for growing artificial quartz becomes poor, and the cost becomes extremely high. is there.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of growing an artificial crystal for obtaining a large ST-cut crystal plate having a uniform crystal density in a short time. It is in.

[0013]

In order to achieve the above object, the present invention provides a method of growing an artificial crystal by growing a seed crystal by a hydrothermal synthesis method. The Z ′ axis rotated about 35 to 45 ° and the X
ST obtained by cutting out the single crystal quartz on the plane including the axis
A plate was used as the seed crystal.

[0014]

The growth rate in the growth of artificial quartz using the ST plate as a seed crystal by hydrothermal synthesis is about 0.26 [mm / day].
Although it is slower than the case where the Z plate or the like is used as a seed crystal, the ST plate grows as it is mainly expanded in the thickness direction. ST
Since it can be cut out parallel to the board, the area is large,
In addition, an ST cut plate containing no seed crystal can be sampled.

[0015]

An embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, in the conventional hydrothermal synthesis method using a Y-bar or a Z-plate as a seed crystal, instead of the Y-bar or the Z-plate,
The ST plate is used as a seed crystal.

This ST plate is obtained by cutting the single crystal quartz on a plane including the Z 'axis obtained by rotating the Z axis about 35 ° to 45 ° around the X axis of the single crystal quartz and the X axis. In this embodiment, the length in the X-axis direction is an integral multiple of the length in the Z′-axis direction.

For example, FIG. 1A shows that the ratio of the length of the ST plate 1 in the X-axis direction to the length of the Z-axis direction is, for example, about 76 m.
m (3 inches) x 76 mm, about 102 mm (4 inches)
× 102mm, ... about 152mm (6 inches) × 15
This is an example of the case where the length is equal to 2 mm, and is suitable for a so-called one-piece artificial quartz seed crystal. FIG. 1 (b)
(C) is an example in which the above-mentioned ratios are 2 and 3, respectively, and are suitable for seed crystals of artificial quartz for collecting two pieces and three pieces, respectively.
Note that this ratio may be further increased.

FIG. 2 shows, for example, an ST plate for collecting two sheets (FIG. 1).
It is an external view of the synthetic quartz crystal obtained by growing (b)) as a seed crystal, (a) is the front view, (b) is the AA sectional view.

As shown in FIGS. 2 (a) and 2 (b), according to the present embodiment, it can be seen that the ST plate 1, which is a seed crystal, grows as it is mainly in the thickness direction.

Therefore, the precipitation of crystals according to the present embodiment
The growth rate is about 0.26 [mm / day], which is slower than the conventional method using a Z plate or the like as a seed crystal.
The cutting of the T-cut quartz plate 2 can be performed in parallel with the Z ′ axis direction, that is, in parallel with the ST plate 1 of the seed crystal.
The ST of the seed crystal used, even for short-term growth
Depending on the size of the plate 1 in the X-axis and Z'-axis directions, a large number of ST cut quartz plates 2 having a large diameter of 3 to 5 inches or more can be easily and efficiently collected. Moreover, since the ST-cut quartz plate 2 is cut out in parallel with the seed crystal, the ST-cut quartz plate 2 does not include the seed crystal and has a uniform material such as crystal density.

For example, from an artificial quartz grown for 60 days using the ST plate 1 shown in FIG.
About 12 practically usable ST-cut quartz plates 2 of [mm] were obtained.

As shown in FIGS. 1B and 1C, when the length of the seed crystal ST plate 1 in the X-axis direction is an integral multiple of the length in the Z′-axis direction, the ST crystal can be more efficiently used. Not only can a cut quartz plate 2 be obtained, but also an ST plate 1 having the shape shown in FIG.
Can be obtained with a more uniform crystal distribution than when a plurality of are used. This is because the growth zone is made uniform by lengthening the X-axis direction, and the distribution of crystals precipitated and grown from the seed crystal becomes uniform.

The ST plate 1 serving as the seed crystal has a value θ substantially equal to the rotation angle θ of the Z ′ axis of the ST plate used for the actual SAW element with respect to the Z axis. The use of an ST plate is preferable for efficiently cutting out a large number of SAW element ST plates from the grown artificial quartz.

[0025]

As described above, in the present invention, since the ST plate is used as the seed crystal in the hydrothermal synthesis method, the following excellent effects are obtained.

(1) It is possible to grow artificial quartz from which a large ST-cut quartz plate for a SAW element substrate containing no seed crystal can be obtained.

(2) Since the ST-cut quartz plate is cut in parallel with the seed crystal plate, that is, in parallel with the Z ′ axis, the growing period of the artificial quartz can be adjusted as necessary. Even in a very short time, a high-quality large-sized ST-cut quartz plate can be obtained.

(3) By increasing the number of seed crystals in accordance with the number of days of growth, etc., artificial crystals can be grown in the entire autoclave. In other words, if the autoclave is for growing 2 tons, 2 tons of artificial quartz can be obtained, and the equipment operation rate of the autoclave can be increased.

(4) By setting the length of the ST plate as a seed crystal in the X-axis direction to be an integral multiple of the length in the Z′-axis direction, an artificial quartz having an integral multiple of the volume can be obtained even if the growth period is the same. . In addition, by increasing the ratio of these lengths, it is possible to obtain an artificial quartz having a more efficient and more uniform crystal density in terms of material.

[Brief description of the drawings]

FIG. 1 is a view showing a dimensional ratio of a seed crystal of an artificial quartz used in one embodiment of the present invention.

FIG. 2A is a front view of an artificial quartz crystal grown according to the present embodiment, and FIG. 2B is a cross-sectional view taken along line AA.

3A is a front view of an artificial quartz obtained by using a Y bar as a seed crystal, FIG. 3B is a side view thereof, and FIG. 3C is a sectional view taken along line AA.

4A is a front view of an artificial quartz obtained by using a Z plate as a seed crystal, FIG. 4B is a side view thereof, and FIG. 4C is a sectional view taken along line AA.

FIG. 5 is an ST cut cross-sectional view of an artificial quartz grown by a conventional hydrothermal synthesis method, (a) is for collecting one sheet, (b)
Shows an example for collecting two sheets.

[Explanation of symbols]

 1 ... ST crystal ST plate, 2,10 ... ST cut quartz plate, 11 ... Seed crystal.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-197394 (JP, A) JP-A-1-126300 (JP, A) JP-A-50-114399 (JP, A) JP-A-55-1979 51795 (JP, A) JP 34-8309 (JP, B1) JP 34-3057 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) C30B 1/00-35 / 00 CA (STN) JICST file (JOIS)

Claims (2)

(57) [Claims] 1. A method of growing an artificial crystal by growing a seed crystal by a hydrothermal synthesis method, wherein Z is formed around the X axis of the crystal.
An artificial quartz growing method, characterized in that an ST plate obtained by cutting the quartz at a plane including the Z 'axis whose axis is rotated and the X axis is used as the seed crystal. 2. The artificial quartz growing method according to claim 1, wherein the length of the ST plate in the X-axis direction is an integral multiple of the length in the Z′-axis direction.