JPH09227294A - Production of artificial quartz crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently and inexpensively obtain an artificial quartz crystal of less linear defect density by controlling the convection in autoclave and varying the growth rates by the positions of the Z growth face within the same crystal at the time of producing the artificial quartz crystal by a water heat method. SOLUTION: The autoclave 6 filled with an aq. alkaline soln. is internally provided with a high-temp. section and a low-temp. section to generate the convection of the aq. alkaline soln. A quartz crystal raw material is melted in the high-temp. section and is made into a supersaturated soln. in the low-temp. section to precipitate and grow the crystal 9 of the quartz crystal on a seed crystal 7 of the quartz crystal previously hung in the low-temp. section. At this time, baffle plates 8 are arranged above and below the seed crystal 7 hung in the autoclave 6 or iron plates 10 are inclined along side the seed crystal 7 to vary the flow velocity of the convection of the alkaline soln. near the seed crystal 7 by the positions in the Y-axis direction of the seed crystal 7. As a result, the growth speeds of the Z growth face are varied by the positions in the Y-axis direction even within the same crystal and this Z growth face is grown to incline with the Z face, by which the artificial quartz crystal 9 is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic quartz produced by a hydrothermal method, and more particularly to a synthetic quartz production method in which linear defects are reduced by varying the growth rate depending on the position of the Z growth surface.

[0002]

2. Description of the Related Art With the demand for miniaturization of quartz devices, the number of quartz devices manufactured by microfabrication methods using photolithography technology has also increased as a method of processing artificial quartz. On the other hand, when a quartz substrate cut out from a crystal of quartz at a predetermined cutting angle is processed by etching, an etch channel (etch pipe,
It is known that needle-shaped pores called an etch tube or an etch tunnel) are formed. It is known that the etch channel is a defect caused by selectively etching linear defects existing inside by etching quartz, and has a great influence on the characteristics and yield of the final product.

Synthetic quartz is grown in a pressure vessel called an autoclave filled with an alkaline aqueous solution under a high temperature and high pressure condition by a method generally called a hydrothermal growth method. The feature of this method is that by providing a high temperature part and a low temperature part in the pressure vessel to make a temperature difference, the crystal raw material is melted in the high temperature part and becomes a supersaturated solution in the low temperature part, and the crystal is hung in the low temperature part in advance. This is a method of precipitating a crystal on the seed crystal of the above and growing the crystal. In such a current state of the art artificial quartz growth technology, when a linear defect is present in the seed crystal, the crystalline crystal precipitated in the seed crystal also grows to include the linear defect, so that the linear defect density is lower than that of the seed crystal. It was considered impossible to grow artificial crystals. FIG. 7 shows a diagram comparing the etch channel density (pieces / cm ² ) of the crystal growth region by the conventional artificial crystal growth method with that of the seed crystal. As a result of measuring the etch channel densities (pieces / cm ² ) of the seed crystal and the growth region for the three samples A, B and C, the etch channel density of the growth region is 12.1% than the density of the seed crystal, and 2. 9%
And 2.2%.

Even in the case of synthetic quartz having linear defects as described above, in a crystal vibrating device using a conventional quartz substrate that has been mechanically processed, for example, lapping or polishing (polishing), the linear defects have a predetermined density. If the following, the characteristics of the crystal vibrating device, for example, the electrical equivalent constant (Q value,
Motional inductance, capacitance, C
I) and aging were hardly affected. However, over the past few years, the number of vibrating devices that use photolithography and etching as the processing method for quartz substrates has increased,
Conventional linear defect densities have become unusable. For example, when finishing an AT-cut ultra-thin oscillator substrate by an etching method, linear defects are selectively etched to open minute holes, the electrodes provided on the front and back of the substrate are short-circuited, and the Q value of the oscillator is It has been found that the yield of the final product is remarkably deteriorated, such as an extreme decrease. For this reason, we have been working on the improvement aiming at artificial quartz with few linear defects.

[0005]

However, as described above, there is a problem that the current artificial quartz growing method cannot efficiently grow artificial quartz with few linear defects. The present invention has been made to solve the above problems, and an object of the present invention is to provide a large amount of artificial quartz having a low linear defect density and at a low cost.

[0006]

Means for Solving the Problems Baffle plates are arranged above and below a seed crystal suspended in an autoclave, or an iron plate or the like is tilted over the seed crystal, and the flow velocity on the side of the seed crystal is set in the Y-axis direction of the seed crystal. By making them different depending on the position, the growth rate of the Z growth surface can be changed to Y even within the same crystal.
This is a method for producing an artificial quartz in which the Z-grown surface is tilted with respect to the Z-plane and is grown by varying the axial position.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. In order to help understanding of the present invention, the artificial quartz is briefly described. The growth of the artificial quartz is controlled by the anisotropy of the crystal, and the growth region is divided into five different regions as shown in FIG. Note that FIG. 5 is a cross section of an artificial quartz, which is commonly called “Y rod quartz” long in the Y-axis direction, cut along a plane perpendicular to the crystal axis Y, and the upper side in the figure is the + X axis. The right side is the + Z axis (also called the C axis or the optical axis). That is, seed crystal 1 and four growth areas,
That is, it is composed of a + X region 2, an S region 3, a Z region 4, and a -X region 5. The boundary of each region is clearly observed by an X-ray topography or the like. It is known that when used in a crystal application product, the optical or electrical characteristics of the crystal are deteriorated especially when twin crystals, striae, and other defects that are concentrated at the above-mentioned boundaries are present. Therefore, when artificial quartz is used for optical products, crystal oscillators, etc., the seed 1, + X and -X regions (2 and 5), which deteriorate in optical and electrical quality, and the S region 3 are usually removed. Generally, it is general to select and use the Z region 4 of FIG. 5 which has particularly good quality. The Y-bar crystal uses seeds that are long in the Y-axis direction and has a small proportion of good-quality Z regions.

Here, in place of the Y rod crystal, Z plate crystal containing a large amount of good Z region has been manufactured and used in large quantities. 6A and 6B show a Z-plate crystal, FIG. 6A is a view seen from the X-axis direction, and FIG. 6B is a view seen from the Z-axis direction. As shown in FIG. 6 (a), the conventional Z plate has been grown so that it grows substantially parallel to a plane perpendicular to the Z axis, the so-called Z plane. When grown in this manner, an artificial quartz crystal with the highest Z region yield is obtained.
When the linear defects in the artificial quartz thus grown are observed by the above X-ray topography, it is known that the linear defects are conically distributed within the range of about 15 ° from the Z axis in the Z region. . From this, it was inferred that the linear defects could extend into the growing region only within the range of about 15 ° from the Z axis.

That is, in FIG. 1 (a), the seed surface, Z plane and Z
The figure showing the relationship of a growth surface is shown. Generally, seeds are Z-cut (the main surface is perpendicular to the Z axis), so the Z surface is parallel to the seed surface. As described above, the conventional Z plate crystal is grown so as to grow parallel to the Z surface. Was there. The synthetic quartz crystal of the present invention is characterized by growing by inclining the Z growth surface by θ ° from the Z surface, and it is inferred that the growth direction (φ ° from the Z axis) is within 15 ° from the Z axis (φ <15 °). It is considered that dislocation growth is possible, and if this angle is exceeded (φ> 15 °), dislocation growth is considered impossible. Where dislocation
Is a kind of lattice defect, which is a displacement of a series of atoms connected linearly due to a shift in the crystal, and dislocations are formed parallel to the growth direction. Further, it is considered that the Z surface of the artificial quartz has a Z surface grown by adhesion growth. That is, since the Z growth surface is grown substantially parallel to the Z surface of the seed crystal, when an artificial quartz crystal is grown with the Z growth surface tilted at about 15 ° from the Z surface, linear defects in the seed crystal are observed in the Z growth area. Various experiments according to the present invention were carried out on the assumption that they would no longer be handed over.

As described above, by providing the high temperature part in the lower part of the autoclave and the low temperature part in the upper part of the autoclave, a temperature difference is generated in the upper and lower parts of the autoclave, which causes complicated convection of the alkaline solution. It is known that artificial quartz grown in a state where the flow rate of the solution is fast grows in a wedge shape slightly with respect to the direction of convection. Since the flow velocity near the baffle plate that controls the convection of the alkaline solution is high in the autoclave, it can be expected that the Z growth surface will be greatly inclined. Therefore, when the seed crystal was hung right above the baffle opening, the Z growth surface angle of the artificial crystal was tilted by 4.6 ° with respect to the Z surface. Furthermore, this experiment was developed and the experiment was conducted by disposing seeds and baffle plates as shown in FIG. 1 (b). FIG. 1 (b) is a diagram schematically showing the inside of the autoclave, in which baffle plates 8 are arranged above and below the seed crystal 7 suspended in the autoclave 6 to control convection and grow the crystal 9. When baffle plates were arranged above and below the seed crystal and the artificial quartz crystal was grown by changing the flow velocity flowing on the side of the seed crystal depending on the position of the seed crystal in the Y-axis direction, the Z growth surface was grown with a larger inclination than the Z surface. I found out. In another experiment, as shown in FIG. 1 (c), one surface of the seed crystal 7 was attached to the iron plate 10 and the iron plate 10 was tilted over the other surface, and the flow rate was changed depending on the position of the seed crystal in the Y-axis direction as described above. When I grew up with artificial quartz 9, it changed as expected Z
The growing surface was inclined with respect to the Z surface.

The inclination of the Z growth surface of the artificial quartz crystal according to the present invention is formed by the difference in the growth rate depending on the flow velocity at each position in the Y axis direction on the same quartz crystal as described above. Further, the water contained in the artificial quartz has a characteristic that its content increases as the growth rate increases. On the other hand, since water in the crystal absorbs at a specific wavelength in the infrared region, it is possible to calculate the growth rate from the infrared absorption value. FIG. 4 (a) is an artificial crystal grown right above a baffle plate, and the point a (35.9 mm), point b (74.8 mm), and point c (74.8 mm) from the left end face in the figure of the sample shown in FIG. The growth rate in the Z-axis direction at each point (105.4 mm) is shown in FIG. On the contrary, when calculated from the growth rate in this figure, it is apparent that the sample is an artificial quartz grown on the Z growth surface inclined by about 4.6 ° from the Z axis.

Since most of the linear defects generated in the growing region of the artificial quartz are due to the succession of the linear defects existing in the seed crystal, the linear defect density in the growing region is higher than that in the seed crystal. Generally higher. Here, Z according to the present invention
FIG. 3 shows the etch channel densities of A, B, and C3 artificial quartz grown with the growth surface inclined from the Z plane in comparison with the density of the seed crystal. As is clear from this figure, in all three cases, the etch channel density in the growth region is 56.7%, 59.5%, and 5 respectively as compared with the density in the seed crystal.
It can be seen that it has decreased to 8.9%.

FIG. 4 shows a shape diagram of a Z-plate crystal grown by using the present invention. FIG. 4A is a view seen from the X-axis direction, Z
It can be seen that the growth plane is tilted from the Z plane. That is, since the growth direction is tilted by φ ° from the Z-axis direction, the conventional Z
Although the Z dimension of the plate quartz is the same at any position, the Z dimension of the Z plate quartz of the present invention is different in the Z dimension at the left end and the Z dimension at the right end in the figure. FIG. 4B is a view of the Z-plate crystal of the present invention viewed from the Z-axis direction. Although the seed crystal is sandwiched between the iron plates in order to change the flow velocity of convection, the iron plate need not necessarily be used to change the flow velocity.

[0014]

Since the present invention is configured as described above, it is possible to grow an artificial quartz crystal having a linear defect density in the growth region much lower than that of a seed crystal, and a quartz plate is used by an etching method. During processing, defects due to the etch channel of the crystal vibrating device are reduced and the yield is significantly improved. For example, a contour-based oscillator such as GT cut or A
This leads to downsizing of T-cut ultra-thin plate vibrators, multimode filters, etc., ultra-high frequencies, high yields, and significant cost reduction. Furthermore, the yield of the material is significantly improved when it is used in an optical system.

[Brief description of drawings]

FIG. 1A is a diagram showing a relationship between a seed surface, a Z-axis, a Z-plane, a growth direction and a growth surface, and FIG. 1B is a schematic diagram showing an arrangement of a baffle plate for changing the flow velocity of convection according to the present invention. , (C)
FIG. 4 is a diagram showing how the flow velocity is changed using an iron plate.

FIG. 2 is a diagram showing a distance from an end face of a sample of artificial quartz and a growth rate in the portion.

FIG. 3 is a diagram comparing the reduction rates of the etch channel densities in the seed crystal and in the growth region using three sample samples A, B, and C.

FIG. 4A is a view seen from the X-axis direction of a Z-plate crystal which is an example of the present invention, and FIG. 4B is a view seen from the Z-axis direction.

FIG. 5 is a cross-sectional view of artificial quartz, which illustrates a growth region, that is, a seed, + X region, S region, Z region, and −X region.

FIG. 6A is a view of a conventional Z-plate crystal viewed from the X-axis direction, and FIG. 6B is a view viewed from the Z-axis direction.

FIG. 7 is a diagram showing a comparison diagram of the etch channel densities of a seed crystal and a crystal growth region by a conventional artificial quartz growth method.

[Explanation of symbols]

φ: Inclination angle between Z-axis and growth direction θ: Inclination angle between Z-plane and growth surface a, b, c: Point indicating the position along the Y-axis direction from the end face of Z-plate crystal 6 ... Auto Inner wall of crave 7 …… Seed crystal 8 …… Baffle plate 9 …… Growth crystal 10 …… Steel plate

Claims (1)

[Claims] 1. A baffle plate is arranged above and below a seed crystal suspended in an autoclave, or an iron plate or the like is tilted over the seed crystal, and the flow velocity near the seed crystal is varied depending on the position of the seed crystal in the Y-axis direction. Thus, the method for producing artificial quartz, wherein the growth rate of the Z growth surface is made different depending on the position in the Y-axis direction even within the same crystal, and the Z growth surface is inclined with respect to the Z plane.