Method for manufacturing artificial crystal, apparatus for manufacturing artificial crystal, and artificial crystal

Abstract

The present invention improves the quality of an artificial crystal. Lasca (fragments of crystal) (11), a plurality of seed crystals (13), and a solution (14) are housed in a pressure vessel (2) of an apparatus (1) for manufacturing an artificial crystal, and an artificial crystal is grown on each of the plurality of seed crystals (13). The plurality of seed crystals (13) in the pressure vessel (2) comprise a first group that is composed of a plurality of seed crystals (13a), and a second group that is positioned below the first group and is composed of a plurality of seed crystals (13b). Each of the plurality of seed crystals (13a) is disposed in the pressure vessel (2) so as to be perpendicular to the axial direction of the pressure vessel (2). Each of the plurality of seed crystals (13b) is disposed in the pressure vessel (2) so as to be parallel to the axial direction of the pressure vessel (2).

Description

Artificial quartz crystal manufacturing method, artificial quartz crystal manufacturing device, and artificial quartz crystal

[0001] The present invention relates to a method for manufacturing artificial quartz crystal, an apparatus for manufacturing artificial quartz crystal, and artificial quartz crystal.

[0002] For example, Japanese Patent Laid-Open No. 2013-47158 (Patent Document 1) and Japanese Patent Laid-Open No. 2016-13935 (Patent Document 2) describe techniques for manufacturing artificial quartz crystal.

[0003] JP 2013-47158 A JP 2016-13935 A

[0004] When manufacturing artificial quartz crystal, there is a concern that inclusions may occur in the artificial quartz crystal. If inclusions occur in the artificial quartz crystal, the quality of the artificial quartz crystal may deteriorate, and the characteristics of products manufactured using the artificial quartz crystal may be reduced. For this reason, it is desirable to prevent inclusions from occurring in the artificial quartz crystal.

[0005] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

[0006] According to one embodiment, a pressure vessel contains quartz crystal raw material, multiple seed quartz crystals, and a solution, and an artificial quartz crystal is grown on each of the multiple seed quartz crystals. The multiple seed quartz crystals in the pressure vessel consist of a first group consisting of multiple first seed quartz crystals and a second group located below the first group and consisting of multiple second seed quartz crystals. Each of the multiple first seed quartz crystals is placed in the pressure vessel so that it is perpendicular to the axial direction of the pressure vessel. Each of the multiple second seed quartz crystals is placed in the pressure vessel so that it is parallel to the axial direction of the pressure vessel.

[0007] According to one embodiment, the quality of the synthetic quartz crystal can be improved.

[0008] FIG. 1 is a schematic diagram showing the general configuration of an artificial quartz crystal manufacturing apparatus according to one embodiment. FIG. 2 is a schematic diagram showing the general configuration of an artificial quartz crystal manufacturing apparatus according to one embodiment. FIG. 3 is an explanatory diagram showing a plurality of seed quartz crystals housed within the pressure vessel of the artificial quartz crystal manufacturing apparatus shown in FIG. 2. FIG. 4 is a cross-sectional view of the pressure vessel of the artificial quartz crystal manufacturing apparatus shown in FIG. 2. FIG. 5 is a cross-sectional view of the pressure vessel of the artificial quartz crystal manufacturing apparatus shown in FIG. 2. FIG. 6 is an explanatory diagram showing a jig that holds a plurality of seed quartz crystals. FIG. 7 is an explanatory diagram showing a jig that holds a plurality of seed quartz crystals. FIG. 8 is a cross-sectional view of a seed quartz crystal that has been grown into artificial quartz crystals. FIG. 9 is a cross-sectional view of a seed quartz crystal that has been grown into artificial quartz crystals. FIG. 10 is a schematic diagram showing the general configuration of an artificial quartz crystal manufacturing apparatus according to a first method. FIG. 11 is a schematic diagram showing the general configuration of an artificial quartz crystal manufacturing apparatus according to a second method. FIG. 12 is an explanatory diagram showing a jig that holds a plurality of seed quartz crystals.

[0009] Hereinafter, embodiments will be described in detail with reference to the drawings. In all drawings for explaining the embodiments, components having the same functions are designated by the same reference numerals, and repeated explanations thereof will be omitted. In the following embodiments, explanations of the same or similar parts will not be repeated unless particularly necessary.

[0010] (Embodiment 1) <Configuration of the Artificial Quartz Manufacturing Apparatus> The overall configuration of the artificial quartz manufacturing apparatus 1 in this embodiment will be described with reference to FIGS. 1 to 3. FIGS. 1 and 2 are schematic diagrams (longitudinal cross-sectional views) showing the general configuration of the artificial quartz manufacturing apparatus 1 in this embodiment. FIG. 1 shows the artificial quartz manufacturing apparatus 1 without the Lascar 11, seed quartz 13, or solution 14 contained within the pressure vessel 2, while FIG. 2 shows the artificial quartz manufacturing apparatus 1 with the Lascar 11, multiple seed quartz 13, and solution 14 contained within the pressure vessel 2. FIG. 3 is an explanatory diagram (cross-sectional view) showing multiple seed quartz 13 contained within the pressure vessel 2. Each figure shows directions A1, A2, and A3, with direction A1 being perpendicular to directions A2 and A3, and direction A2 being perpendicular to direction A3. FIGS. 1 to 3 show cross-sectional views parallel to directions A1 and A2 and perpendicular to direction A3.

[0011] The artificial quartz crystal manufacturing apparatus 1 shown in Figures 1 and 2 is an apparatus for manufacturing artificial quartz crystal by hydrothermal synthesis. As shown in Figures 1 and 2, the artificial quartz crystal manufacturing apparatus 1 comprises a pressure vessel (autoclave, chamber) 2, a baffle plate (convection control plate) 3 placed inside the pressure vessel 2, a heater (heating mechanism) 4 placed around the pressure vessel 2, and a control unit 5.

[0012] The pressure vessel 2 has a cylindrical side (side wall) 2a, a bottom 2b, and a lid 2c. The bottom 2b seals the lower opening of the cylindrical side 2a. The lid 2c seals the upper opening of the cylindrical side 2a. The lid 2c can be opened and closed relative to the side 2a. A space (sealed space) 6 surrounded by the side 2a, bottom 2b, and lid 2c is formed inside the pressure vessel 2. The pressure vessel 2 is made of a metal material such as stainless steel. The space 6 can be considered a processing chamber for producing artificial quartz crystal by hydrothermal synthesis.

[0013] The direction A1 is the axial direction (extension direction) of the pressure vessel 2 and is also a direction parallel to the vertical direction (direction of gravity). Therefore, the direction A1 is the height direction or up-down direction, and the directions A2 and A3 are horizontal directions.

[0014] The baffle plate 3 is disposed in the pressure vessel 2 so as to divide the space 6 into a space (processing chamber) 6a and a space (processing chamber) 6b. The baffle plate 3 divides the space 6 in the pressure vessel 2 into a space 6b below the baffle plate 3 and a space 6a above the baffle plate 3. Therefore, the space 6 in the pressure vessel 2 has a space 6b and a space 6a, and the space 6b is located below the space 6a.

[0015] As shown in FIG. 2 , a lascar (quartz crystal raw material) 11 is placed in space 6b of pressure vessel 2. Therefore, space 6b can be considered a processing chamber that houses the lascar 11. A plurality of seed quartz crystals (seed quartz crystals) 13 are placed in space 6a of pressure vessel 2. Therefore, space 6a can be considered a processing chamber that houses a plurality of seed quartz crystals 13. No seed quartz crystals 13 are placed in space 6b of pressure vessel 2, and no lascars 11 are placed in space 6a of pressure vessel 2. In space 6a of pressure vessel 2, the plurality of seed quartz crystals 13 are held by a jig or the like. In addition, a solution 14 is poured (contained) in space 6 (6a, 6b) of pressure vessel 2.

[0016] It should be noted that the space 6 of the pressure vessel 2 does not have to be completely filled with the solution 14; for example, approximately 70 to 95% of the space 6 of the pressure vessel 2 is filled with the solution 14. Therefore, the entire space 6b and the lower part of the space 6a of the pressure vessel 2 are filled with the solution 14. As shown in Figure 2, within the space 6 of the pressure vessel 2, the Lasca 11 and the multiple seed crystals 13 are submerged in the solution 14.

[0017] Lasca 11 is a raw material for artificial quartz, and is made up of, for example, multiple pieces of natural quartz. Lasca 11 can be made up of pieces of artificial quartz, or it can be made up of a mixture of pieces of natural quartz and pieces of artificial quartz.

[0018] The seed quartz crystal 13 is a quartz crystal used as a seed for growing an artificial quartz crystal, and has a plate-like shape. The seed quartz crystal 13 can be prepared, for example, by cutting an artificial quartz crystal into a plate-like shape.

[0019] The solution 14 functions as a transport medium for supplying the silicon oxide dissolved from the Lasca 11 to the seed crystal 13 within the pressure vessel 2. A solution in which silicon oxide is highly soluble is preferably used as the solution 14. For example, an alkaline solution such as an aqueous solution of sodium hydroxide or an aqueous solution of sodium carbonate can be used as the solution 14.

[0020] The baffle plate 3 is, for example, a plate-like (disk-like) member having a plurality of through holes. The solution 14 can move from the space 6b to the space 6a and from the space 6a to the space 6b through the plurality of through holes in the baffle plate 3. By appropriately setting the number and size of the through holes in the baffle plate 3, the amount of convection of the solution 14 between the space 6b and the space 6a can be controlled.

[0021] 1, the baffle plate 3 is disposed within the pressure vessel 2 in order to clearly show the space 6a and the space 6b partitioned by the baffle plate 3. However, in reality, if the pressure vessel 2 of the artificial quartz crystal manufacturing apparatus 1 does not contain the Lasca 11, seed quartz crystal 13, and solution 14, the baffle plate 3 does not need to be disposed within the pressure vessel 2.

[0022] The artificial quartz crystal manufacturing apparatus 1 further includes a pressure gauge (not shown) for measuring the pressure inside the pressure vessel 2, and a thermometer (not shown) for measuring the temperature of the pressure vessel 2 or the heater 4. A thermocouple, for example, can be used as the thermometer.

[0023] The heater 4 is a heating mechanism that heats the pressure vessel 2 and has the function of regulating the temperature inside the pressure vessel 2. The heater 4 has a heater section 4a located around the space 6a and a heater section 4b located around the space 6b. The heater section 4a and the heater section 4b can be independently controlled by the control section 5. The control section 5 controls the heater section 4b to control the temperature of the solution 14 in the space 6b. The control section 5 controls the heater section 4a to control the temperature of the solution 14 in the space 6a.

[0024] <Regarding the arrangement of multiple seed crystals 13 within the pressure vessel 2> Next, the arrangement of multiple seed crystals 13 within the pressure vessel 2 will be described with reference to Figures 2 to 5. Figures 4 and 5 are cross-sectional views of the pressure vessel 2 taken approximately perpendicular to the direction A1. The cross-sectional view of the pressure vessel 2 taken along line B1-B1 in Figure 2 corresponds to Figure 4, and the cross-sectional view of the pressure vessel 2 taken along line B2-B2 in Figure 2 corresponds to Figure 5.

[0025] 2 to 5, the multiple seed crystals 13 placed within the space 6a of the pressure vessel 2 of the artificial quartz crystal manufacturing apparatus 1 are configured into a group G1 consisting of multiple seed crystals 13a and a group G2 consisting of multiple seed crystals 13b placed below group G1. Within the space 6 of the pressure vessel 2, the laska 11 is located below group G2.

[0026] Here, seed quartz crystal 13a corresponds to seed quartz crystal 13 having a main surface substantially perpendicular to direction A1, and seed quartz crystal 13b corresponds to seed quartz crystal 13 having a main surface substantially parallel to direction A1.

[0027] The seed crystal 13 has a plate-like planar shape, and has a main surface 21 and a main surface 22 located opposite each other, and a side surface connecting the main surface 21 and the main surface 22. The main surfaces 21 and 22 of the seed crystal 13 are substantially parallel. The main surface 21 of the seed crystal 13a is referred to as the main surface 21a, the main surface 22 of the seed crystal 13a is referred to as the main surface 22a, the main surface 21 of the seed crystal 13b is referred to as the main surface 21b, and the main surface 22 of the seed crystal 13b is referred to as the main surface 22b.

[0028] Each of the multiple seed crystals 13a is arranged in the space 6a of the pressure vessel 2 so that its major surfaces 21a, 22a are approximately perpendicular to direction A1. The major surface 21a of each of the multiple seed crystals 13a faces upward, and the major surface 22a of each of the multiple seed crystals 13a faces downward. Therefore, the major surface 21a is the upper surface, and the major surface 22a is the lower surface. In group G1, the multiple seed crystals 13a are lined up in direction A1. That is, group G1 is composed of multiple seed crystals 13a lined up in direction A1. The major surfaces 21a, 22a are approximately parallel to direction A2 and approximately parallel to direction A3.

[0029] Each of the plurality of seed crystals 13b is disposed in the space 6a of the pressure vessel 2 so that the principal surfaces 21b and 22b are substantially parallel to the direction A1.

[0030] Group G2 consists of multiple subgroups (groups) G2a, G2b, and G2c (see FIG. 3). Subgroups G2a, G2b, and G2c are located at different heights. Specifically, within the space 6a of the pressure vessel 2, subgroup G2a is located below group G1, subgroup G2b is located below subgroup G2a, and subgroup G2c is located below subgroup G2b. Subgroup G2a consists of multiple seed crystals 13b located at the same height. Subgroup G2b consists of multiple seed crystals 13b located at the same height. Subgroup G2c consists of multiple seed crystals 13b located at the same height. The height positions correspond to the positions in direction A1. Within the space 6 of the pressure vessel 2, no seed crystals 13a are located below group G1, and no seed crystals 13b are located above subgroup G2a.

[0031] Fig. 5 shows an example of the arrangement of multiple seed crystals 13b belonging to subgroup G2a. Ten seed crystals 13b with principal surfaces 21b, 22b substantially parallel to directions A1 and A3 are shown in Fig. 5. While the number of seed crystals 13b belonging to subgroup G2a is ten in Fig. 5, the number of seed crystals 13b belonging to subgroup G2a is not limited to ten.

[0032] However, by increasing the number of seed crystals 13b belonging to subgroup G2a, it is possible to increase the number of artificial crystals that can be manufactured in a single manufacturing process using artificial crystal manufacturing apparatus 1. For this reason, it is desirable to efficiently arrange as many seed crystals 13b as possible at the same height position in subgroup G2a. The same applies to subgroups G2b and G2c.

[0033] Also, Figures 2 and 3 show a case where group G2 is made up of three subgroups G2a, G2b, and G2c that are at different height positions, but the number of subgroups that make up group G2 is not limited to three.

[0034] <Operation of the Artificial Quartz Crystal Manufacturing Apparatus> The operation of the artificial quartz crystal manufacturing apparatus 1 shown in FIGS. 1 and 2 will now be outlined.

[0035] The lascar 11 is placed inside the pressure vessel 2. The lid 2c can be opened and closed relative to the cylindrical side portion 2a. With the lid 2c open, the lascar 11 is placed inside the space 6 of the pressure vessel 2.

[0036] Next, the baffle plate 3 is placed inside the pressure vessel 2. Of the spaces 6a and 6b partitioned by the baffle plate 3, the Lasker 11 is placed in the space 6b below the baffle plate 3.

[0037] Next, a plurality of seed crystals 13 are placed inside the pressure vessel 2. Of the spaces 6a and 6b partitioned by the baffle plate 3, a plurality of seed crystals 13 are placed in the space 6a above the baffle plate 3.

[0038] Fig. 6 is an explanatory diagram (cross-sectional view) showing an example of a jig (holding jig, frame) 12a that holds multiple seed crystals 13a. Fig. 7 is an explanatory diagram (cross-sectional view) showing an example of a jig (holding jig, frame) 12b that holds multiple seed crystals 13b.

[0039] For example, multiple seed crystals 13 are held in jigs 12 (12a, 12b) by hanging them thereon, and then the jigs 12 holding the multiple seed crystals 13 are placed (housed) in the space 6a of the pressure vessel 2. This allows the multiple seed crystals 13 held by the jigs 12 to be placed in the space 6a of the pressure vessel 2.

[0040] As shown in Fig. 6, seed crystal 13a is suspended from jig 12a using wire 16 or the like so that the principal surfaces 21a, 22a of seed crystal 13a are approximately perpendicular to direction A1. As shown in Fig. 7, seed crystal 13b is suspended from jig 12b using wire 17 or the like so that the principal surfaces 21b, 22b of seed crystal 13b are approximately parallel to direction A1.

[0041] Next, the solution 14 is poured into the pressure vessel 2. By pouring the solution 14 into the space 6 (6a, 6b) of the pressure vessel 2, the Lasca 11 and the plurality of seed crystals 13 in the space 6 of the pressure vessel 2 become submerged in the solution 14.

[0042] Next, the lid 2c is closed to seal the space 6 of the pressure vessel 2, and then the pressure inside the pressure vessel 2 is pressurized and heated by the heater 4. As a result, the temperature inside the pressure vessel 2 becomes, for example, about 310 to 410°C, and the pressure inside the pressure vessel 2 becomes, for example, about 130 to 147 MPa.

[0043] The control unit 5 controls the heater unit 4b and the heater unit 4a so that the temperature of the solution 14 in the space 6b becomes higher than the temperature of the solution 14 in the space 6a. This causes natural convection in the solution 14 in the space 6. That is, a flow (upward flow) in which the solution 14 in the space 6b rises, moves to the space 6a through the multiple through-holes in the baffle plate 3, and further rises in the space 6a, and a flow (downward flow) in which the solution 14 in the space 6a descends, moves to the space 6b through the multiple through-holes in the baffle plate 3, and further descends in the space 6b, is generated.

[0044] As the Lasca 11 dissolves in the solution 14, silicon oxide dissolves from the Lasca 11 into the solution 14. The silicon oxide dissolved from the Lasca 11 into the solution 14 is transported by the natural convection of the solution 14, and precipitates on the seed quartz crystal 13, where it recrystallizes. This causes quartz crystal (artificial quartz crystal) to grow on the seed quartz crystal 13.

[0045] 8 and 9 are cross-sectional views showing a seed quartz crystal 13 on which an artificial quartz crystal 23 has been grown. Fig. 8 shows seed quartz crystal 13a as the seed quartz crystal 13, and Fig. 9 shows seed quartz crystal 13b as the seed quartz crystal 13. As shown in Figs. 8 and 9, an artificial quartz crystal (artificial quartz crystal region) 23 grows on a main surface 21 and a main surface 22 of the seed quartz crystal 13.

[0046] After a suitable time has elapsed to grow the artificial quartz crystal 23 to the required thickness on the seed quartz crystal 13, heating by the heater 4 is stopped, and the seed quartz crystal 13 on which the artificial quartz crystal 23 has been grown is removed from the pressure vessel 2.

[0047] In this way, synthetic quartz crystal can be produced.

[0048] <Background of the Study> FIG. 10 is a schematic diagram showing an artificial quartz crystal manufacturing apparatus 101 according to the first method, and corresponds to FIG. 2 above.

[0049] In the artificial quartz crystal manufacturing apparatus 101 of the first method shown in FIG. 10, a lascar 11 is placed in the space 6b of the pressure vessel 2, a plurality of seed quartz crystals 113 are placed in the space 6a of the pressure vessel 2, and a solution 14 is poured into the spaces 6a and 6b of the pressure vessel 2.

[0050] The artificial quartz crystal manufacturing apparatus 101 according to the first method shown in FIG. 10 differs from the artificial quartz crystal manufacturing apparatus 1 according to the present embodiment shown in FIG. 2 in the following respects.

[0051] That is, in the case of the artificial quartz crystal manufacturing apparatus 101 of the first method shown in FIG. 10, all of the seed quartz crystals 113 are arranged within the space 6a of the pressure vessel 2 so that the principal surfaces of the seed quartz crystals 113 are parallel to the direction A1.

[0052] The present inventors have found that when artificial quartz crystal is manufactured using the artificial quartz crystal manufacturing apparatus 101 according to the first method shown in FIG. 10, the following problems arise.

[0053] 10, silicon oxide dissolved in the solution 14 from the Lasca 11 is transported by natural convection in the solution 14, and precipitates and recrystallizes on the seed quartz crystal 113. This causes quartz crystal (artificial quartz crystal) to grow on the seed quartz crystal 113.

[0054] In the production of artificial quartz crystal, there is a concern that inclusions may occur in the artificial quartz crystal. Inclusions are impurities made up of metal compounds. The metal elements that make up inclusions include those that originate from metal elements contained in the LASCA 11 and those that originate from metal elements contained in the artificial quartz crystal manufacturing apparatus 101 itself. For example, lithium (Li) elements contained in the LASCA 11 and iron (Fe) elements contained in the artificial quartz crystal manufacturing apparatus 101 itself may become mixed into the solution 14 as impurities and adhere to the surface of the artificial quartz crystal growing on the seed quartz crystal 113. Impurities that adhere to the surface of the artificial quartz crystal are incorporated into the artificial quartz crystal as it continues to grow, causing inclusions in the artificial quartz crystal.

[0055] If inclusions occur in artificial quartz, the quality of the artificial quartz may deteriorate, and the characteristics of products manufactured using the artificial quartz may be reduced. For example, this could lead to a deterioration in the characteristics of resonators and SAW (Surface Acoustic Wave) devices manufactured using the artificial quartz. For this reason, it is desirable to prevent inclusions from occurring in artificial quartz.

[0056] According to the present inventors, it has been found that when artificial quartz crystal is manufactured using the artificial quartz crystal manufacturing apparatus 101 according to the first method shown in FIG. 10, inclusions are likely to occur in the artificial quartz crystal.

[0057] <Main Features and Effects> One of the main features of this embodiment is that the multiple seed crystals 13 arranged in the pressure vessel 2 are divided into a group G1 consisting of multiple seed crystals 13a and a group G2 located below group G1 and consisting of multiple seed crystals 13b. The seed crystals 13a and 13b are oriented in different directions. Specifically, within the pressure vessel 2 (space 6a), each of the multiple seed crystals 13a in group G1 is arranged so that the primary surface 21a or primary surface 22a of the seed crystals 13a is perpendicular to direction A1. Within the pressure vessel 2 (space 6a), each of the multiple seed crystals 13b in group G2 is arranged so that the primary surface 21b or primary surface 21b of the seed crystals 13b is parallel to direction A1. Direction A1 is the axial direction of the pressure vessel 2 and also the vertical direction (direction of gravity).

[0058] This makes it possible to suppress or prevent inclusions from occurring in the synthetic quartz crystal 23 grown on the seed quartz crystal 13. The reason for this will be explained below.

[0059] Impurities (metallic impurities) that cause inclusions are mixed into the solution 14 in the pressure vessel 2 and rise in the solution 14 to the top of the space 6 due to convection in the solution 14. However, because the specific gravity of the impurities is greater than the specific gravity of the solution 14, the impurities that have risen to the top of the space 6 settle due to gravity in the solution 14. As the impurities settle in the solution 14, they are taken up into the artificial quartz crystal growing on the seed quartz crystal 13, causing inclusions.

[0060] In this embodiment, the seed crystals 13a of group G1 are arranged perpendicular to direction A1, so impurities settling in the solution 14 tend to adhere to the surface of the artificial crystal growing on the main surface 21a, which is the upper surface of the seed crystals 13a. Impurities are particularly likely to adhere to the surface of the artificial crystal growing on the main surface 21a of the seed crystal 13a located at the top of the multiple seed crystals 13a in group G1. This acts to reduce the possibility of impurities adhering to the surface of the artificial crystal growing on the multiple seed crystals 13b in group G2. This is because the impurities adhering to the surface of the artificial crystal growing on the main surface 21a of the seed crystals 13a in group G1 reduces the amount of impurities that pass through group G1 and settle around the multiple seed crystals 13b in group G2. This makes it possible to suppress or prevent impurities from adhering to the surface of the artificial crystal growing on each of the multiple seed crystals 13b in group G2. As a result, in each of the multiple seed crystals 13b in group G2, it is possible to suppress or prevent the occurrence of inclusions in the synthetic crystals grown on the main surfaces 21b and 22b of the seed crystals 13b.

[0061] Furthermore, in group G1, impurities are likely to adhere to the surface of the artificial quartz crystal growing on the primary surface 21a (upper surface) of the seed quartz crystal 13a, but impurities are unlikely to adhere to the surface of the artificial quartz crystal growing on the primary surface 22a (lower surface) of the seed quartz crystal 13a. This is because impurities that settle in the solution 14 are likely to adhere to the upper surface of the seed quartz crystal 13a, but are unlikely to adhere to the lower surface of the seed quartz crystal 13a. For this reason, in group G1, inclusions are likely to occur in the artificial quartz crystal growing on the primary surface 21a of the seed quartz crystal 13a, but inclusions are unlikely to occur in the artificial quartz crystal growing on the primary surface 22a of the seed quartz crystal 13a.

[0062] For this reason, in this embodiment, inclusions are likely to occur in the artificial quartz crystals grown on the main surfaces 21a of the seed quartz crystals 13a of group G1. On the other hand, inclusions can be suppressed or prevented from occurring in the artificial quartz crystals grown on the main surfaces 22a of the seed quartz crystals 13a of group G1, in the artificial quartz crystals grown on the main surfaces 21b of the seed quartz crystals 13b of group G2, and in the artificial quartz crystals grown on the main surfaces 22b of the seed quartz crystals 13b of group G2. This makes it possible to improve the quality of the manufactured artificial quartz crystals.

[0063] The artificial quartz crystals grown on the primary surfaces 21b of the seed quartz crystals 13b of group G2 and the artificial quartz crystals grown on the primary surfaces 22b of the seed quartz crystals 13b of group G2 can be used to manufacture products. For example, resonators or SAW devices can be manufactured as products. As a result, the characteristics of products manufactured using the artificial quartz crystals can be improved.

[0064] Furthermore, the artificial quartz crystal grown on the primary surface 22a of the seed quartz crystal 13a of group G1 can be used to manufacture products. For example, optical products, resonators, SAW devices, and the like can be manufactured as products. As a result, the characteristics of products manufactured using the artificial quartz crystal can be improved.

[0065] On the other hand, inclusions are likely to occur in the artificial quartz crystals grown on the major surfaces 21a of the seed quartz crystals 13a of group G1. For this reason, it is desirable not to use the artificial quartz crystals grown on the major surfaces 21a of the seed quartz crystals 13a of group G1 in the manufacture of products.

[0066] In the case of the artificial quartz crystal manufacturing apparatus 101 using the first technique shown in Figure 10, all of the seed quartz crystals 113 inside the pressure vessel 2 are positioned so that the principal surfaces of the seed quartz crystals 113 are parallel to direction A1. In other words, the artificial quartz crystal manufacturing apparatus 101 using the first technique shown in Figure 10 corresponds to a case in which the group G1 does not exist, and only the group G2 exists.

[0067] 10, impurities settling in solution 14 settle around seed quartz crystal 113 and may adhere to the surface of the artificial quartz crystal growing on seed quartz crystal 113. When comparing the first technique shown in Figure 10 with the present embodiment shown in Figures 2 and 3, the likelihood of impurities settling in solution 14 adhering to the surface of the artificial quartz crystal growing on the seed quartz crystal is as follows:

[0068] In the artificial quartz-crystal manufacturing apparatus 1 of this embodiment, the likelihood that impurities settling in the solution 14 will adhere to the surface of the artificial quartz-crystal growing on the main faces 21b, 22b of the seed quartz-crystal 13b is lower than the likelihood that impurities settling in the solution 14 will adhere to the surface of the artificial quartz-crystal growing on the main face of the seed quartz-crystal 113 in the artificial quartz-crystal manufacturing apparatus 101 of the first technique. This is because, in the case of the artificial quartz-crystal manufacturing apparatus 101 of the first technique, no seed quartz-crystal corresponding to the seed quartz-crystal 13a of group G1 is present in the pressure vessel 2, whereas in the case of the artificial quartz-crystal manufacturing apparatus 1 of this embodiment, the seed quartz-crystal 13a of group G1 is present in the pressure vessel 2. Reflecting the fact that impurities settling in solution 14 adhere to the surface of the artificial quartz crystal growing on the main surface 21a of the seed quartz crystals 13a of group G1, the amount of impurities that pass through group G1 and settle around the multiple seed quartz crystals 13b of group G2 in the case of artificial quartz crystal manufacturing apparatus 1 of this embodiment is less than the amount of impurities that settle around seed quartz crystal 113 in the case of artificial quartz crystal manufacturing apparatus 101 of the first technique. As a result, in the case of artificial quartz crystal manufacturing apparatus 1 of this embodiment, the possibility that impurities settling in solution 14 will adhere to the surface of the artificial quartz crystal growing on the main surface 21b, 22b of the seed quartz crystal is lower than the possibility that impurities settling in solution 14 will adhere to the surface of the artificial quartz crystal growing on the main surface of seed quartz crystal 113 in the case of artificial quartz crystal manufacturing apparatus 101 of the first technique. The likelihood that impurities settling in solution 14 will adhere to the surface of the artificial quartz crystal growing on primary surface 21b of seed quartz crystal 13b is roughly the same as the likelihood that impurities settling in solution 14 will adhere to the surface of the artificial quartz crystal growing on primary surface 22b of seed quartz crystal 13b.

[0069] Furthermore, in the artificial quartz-crystal manufacturing apparatus 1 of this embodiment, the likelihood of impurities settling in solution 14 adhering to the surface of the artificial quartz-crystal growing on primary surface 22a (bottom surface) of seed quartz-crystal 13a is lower than the likelihood of impurities settling in solution 14 adhering to the surface of the artificial quartz-crystal growing on primary surfaces 21b, 22b of seed quartz-crystal 13b in the artificial quartz-crystal manufacturing apparatus 1 of this embodiment. This is because impurities settling in solution 14 have difficulty getting around to the vicinity of primary surface 22a (bottom surface) of seed quartz-crystal 13a, and therefore are less likely to adhere to the surface of the artificial quartz-crystal growing on primary surface 22a (bottom surface) of seed quartz-crystal 13a.

[0070] The higher the likelihood that impurities settling in the solution 14 will adhere to the surface of the artificial quartz crystal growing on the seed quartz crystal, the higher the likelihood that inclusions will occur in the artificial quartz crystal growing on the seed quartz crystal. Therefore, in this embodiment, the likelihood of inclusions occurring in the artificial quartz crystal growing on the main surface 22a (lower surface) of the seed quartz crystal 13a is lower than the likelihood of inclusions occurring in the artificial quartz crystal growing on the main surfaces 21b, 22b of the seed quartz crystal 13b. Also, in this embodiment, the likelihood of inclusions occurring in the artificial quartz crystal growing on the main surfaces 21b, 22b of the seed quartz crystal 13b is lower than the likelihood of inclusions occurring in the artificial quartz crystal growing on the main surface of the seed quartz crystal 113 in the first technique shown in Figure 10. The likelihood of inclusions occurring in the artificial quartz crystal growing on the main surface 21b of the seed quartz crystal 13b is approximately the same as the likelihood of inclusions occurring in the artificial quartz crystal growing on the main surface 22b of the seed quartz crystal 13b.

[0071] As a result, when the artificial quartz crystal manufacturing apparatus 1 of this embodiment is used, the occurrence of inclusions in the manufactured artificial quartz crystal can be suppressed, and high-quality artificial quartz crystal can be manufactured, compared to when the artificial quartz crystal manufacturing apparatus 101 of the first method shown in Figure 10 is used.It was confirmed that when the artificial quartz crystal manufacturing apparatus 1 of this embodiment is used, the proportion of high-quality grade (grades Ia and Ib) artificial quartz crystals manufactured as a percentage of the total number of artificial quartz crystals manufactured increases, compared to when the artificial quartz crystal manufacturing apparatus 101 of the first method shown in Figure 10 is used.Specifically, by using the artificial quartz crystal manufacturing apparatus 1 of this embodiment, it was possible to ensure that the inclusions in all of the manufactured artificial quartz crystals were of JIS grade Ib or higher, excluding the artificial quartz crystal grown on the main surface 21a of the seed quartz crystal 13a.

[0072] FIG. 11 is a schematic diagram showing an artificial quartz crystal manufacturing apparatus 201 according to the second method, and corresponds to the above-mentioned FIGS. 2 and 10.

[0073] In the artificial quartz crystal manufacturing apparatus 201 of the second method shown in FIG. 11, a lascar 11 is placed in the space 6b of the pressure vessel 2, a plurality of seed quartz crystals 213 are placed in the space 6a of the pressure vessel 2, and a solution 14 is poured into the spaces 6a and 6b of the pressure vessel 2.

[0074] The artificial quartz crystal manufacturing apparatus 201 according to the second method shown in FIG. 11 differs from the artificial quartz crystal manufacturing apparatus 1 according to the present embodiment shown in FIG. 2 in the following respects.

[0075] 11, all of the seed quartz crystals 213 are arranged so that their principal surfaces are perpendicular to direction A1 within the space 6a of the pressure vessel 2. In other words, the artificial quartz crystal manufacturing apparatus 201 of the second method shown in FIG. 11 corresponds to a case in which the group G2 does not exist, and only the group G1 exists.

[0076] When artificial quartz crystal is manufactured using the artificial quartz crystal manufacturing apparatus 201 of the second technique shown in Figure 11, impurities that settle in the solution 14 tend to adhere to the surface of the artificial quartz crystal that grows on the upper surface of the seed quartz crystal 213, but are less likely to adhere to the surface of the artificial quartz crystal that grows on the lower surface of the seed quartz crystal 213. As a result, while inclusions are likely to occur in the artificial quartz crystal that grows on the upper surface of the seed quartz crystal 213, the occurrence of inclusions can be suppressed in the artificial quartz crystal that grows on the lower surface of the seed quartz crystal 213. As a result, by manufacturing products using artificial quartz crystal that has grown on the lower surface of the seed quartz crystal 213, the characteristics of the products can be improved.

[0077] However, in the case of the artificial quartz crystal manufacturing apparatus 201 of the second technique shown in Figure 11, only a small number of seed quartz crystals 213 can be placed inside the pressure vessel 2. This is because, compared to when the seed quartz crystals are placed parallel to direction A1, when the seed quartz crystals are placed perpendicular to direction A1, fewer seed quartz crystals can be placed inside the space 6a of the pressure vessel 2. For this reason, when the artificial quartz crystal manufacturing apparatus 201 of the second technique shown in Figure 11 is used, only a small number of artificial quartz crystals can be produced at one time, resulting in lower productivity of artificial quartz crystals.

[0078] In contrast, in this embodiment, a group G1 consisting of a plurality of seed quartz crystals 13a arranged so that their main faces 21a or 22a are perpendicular to direction A1, and a group G2 consisting of a plurality of seed quartz crystals 13b arranged so that their main faces 21b or 22b are parallel to direction A1 are arranged within the space 6a of the pressure vessel 2. For this reason, compared to the artificial quartz crystal manufacturing apparatus 201 of the second technique shown in Figure 11, the artificial quartz crystal manufacturing apparatus 1 of this embodiment can accommodate a greater number of seed quartz crystals within the space 6a of the pressure vessel 2. For this reason, compared to the artificial quartz crystal manufacturing apparatus 201 of the second technique shown in Figure 11, the artificial quartz crystal manufacturing apparatus 1 of this embodiment can manufacture a greater number of artificial quartz crystals at one time, thereby improving the productivity of artificial quartz crystal.

[0079] Also, assume that group G1 is placed below group G2, rather than below group G1, within space 6a of pressure vessel 2. In this case, impurities settling in solution 14 may adhere to the surface of the artificial quartz crystal growing on seed quartz crystal 13b of group G2 before adhering to the surface of the artificial quartz crystal growing on the top surface of seed quartz crystal 13a of group G1. For this reason, the effect of suppressing the occurrence of inclusions in the artificial quartz crystal growing on seed quartz crystal 13b cannot be obtained.

[0080] In contrast, in this embodiment, group G2 is placed below group G1 within space 6a of pressure vessel 2. In this case, impurities that settle in solution 14 may adhere to the surface of the artificial quartz crystal growing on main surface 21a of seed quartz crystal 13a of group G1, which is located above group G2. Therefore, the presence of group G1 makes it possible to suppress the adhesion of impurities to the surface of the artificial quartz crystal growing on seed quartz crystal 13b of group G2. As a result, it is possible to obtain the effect of suppressing the occurrence of inclusions in the artificial quartz crystal growing on main surfaces 21b, 22b of seed quartz crystal 13b.

[0081] The seed crystal 13a of group G1 can be either an X-plate or a Z-plate. Here, an X-plate corresponds to a plate crystal cut so that the X-plane of the crystal is the main surface (cut surface), and a Z-plate corresponds to a plate crystal cut so that the Z-plane of the crystal is the main surface (cut surface).

[0082] When an X-plate is used as the seed crystal 13a of group G1, it is preferable to position the seed crystal 13a so that the +X region of the artificial crystal grows on the main surface 22a (bottom surface) of the seed crystal 13a and the -X region of the artificial crystal grows on the main surface 21a (top surface) of the seed crystal 13a. This is because the +X region is more preferable to the -X region for use in manufacturing products. By manufacturing products using the +X region grown on the main surface 22a (bottom surface) of the seed crystal 13a, the product characteristics can be further improved. On the other hand, it is preferable not to use the -X region grown on the main surface 21a (top surface) of the seed crystal 13a for manufacturing products.

[0083] The seed crystal 13b of group G2 can be an X-cut or Z-cut crystal.

[0084] Second Embodiment FIG. 12 is an explanatory diagram (cross-sectional view) showing a jig (holding jig, frame) 12c that holds a plurality of seed crystals 13a, and corresponds to FIG. 6 above.

[0085] 6, in Fig. 12, the seed crystal 13a is suspended from a jig 12c using wires 16 or the like so that the principal surfaces 21a, 22a of the seed crystal 13a are approximately perpendicular to the direction A1. The jig 12c holding the multiple seed crystals 13a is placed within the space 6a of the pressure vessel 2.

[0086] 12, in the space 6a of the pressure vessel 2, the main surfaces 21a (top surfaces) of the multiple seed crystals 13a of the group G1 are covered by the jig 12c. That is, in a plan view, the entire main surfaces 21a (top surfaces) of the seed crystals 13a are covered (shielded) by the jig 12c. Note that the plan view here corresponds to the view from the position of the lid 2c of the pressure vessel 2, on a plane approximately parallel to the main surfaces 21a of the seed crystals 13a.

[0087] 12, in the second embodiment, the main surface 21a (top surface) of the seed crystal 13a is covered by the jig 12c, so that impurities that settle in the solution 14 tend to adhere not to the main surface 21a of the seed crystal 13a, but to the surface of the jig 12c that covers the main surface 21a of the seed crystal 13a. In particular, impurities are most likely to adhere to the top surface 31 of the jig 12c that covers the main surface 21a of the uppermost seed crystal 13a among the multiple seed crystals 13a in group G1.

[0088] The adhesion of impurities to the surface of jig 12c covering main surface 21a of seed crystal 13a acts to reduce the possibility of impurities adhering to the surface of the artificial crystals grown on the multiple seed crystals 13b in group G2. This is because the adhesion of impurities to the surface of jig 12 covering main surface 21a of seed crystal 13a reduces the amount of impurities that pass through group G1 and settle around the multiple seed crystals 13b in group G2. This makes it possible to suppress or prevent impurities from adhering to the surface of the artificial crystals grown on the main surfaces 21b, 22b of each of the multiple seed crystals 13b in group G2. As a result, it is possible to suppress or prevent inclusions from occurring in the artificial crystals grown on the main surfaces 21b and 22b of each of the multiple seed crystals 13b in group G2.

[0089] 12, the main surface 21a (top surface) of the seed quartz crystal 13a is covered by the jig 12, so that although the artificial quartz crystal grows on the main surface 22a (bottom surface) of the seed quartz crystal 13a, the growth of the artificial quartz crystal on the main surface 21a (top surface) of the seed quartz crystal 13a is suppressed or prevented. In the second embodiment, the growth of the artificial quartz crystal on the main surface 21a (top surface) of the seed quartz crystal 13a is suppressed or prevented, so the spacing in direction A1 between the seed quartz crystals 13a in group G1 can be made smaller than in the first embodiment. As a result, in the second embodiment, the number of artificial quartz crystals that can be manufactured at one time can be increased compared to the first embodiment, and the productivity of artificial quartz crystals can be improved.

[0090] On the other hand, in the case of the above-mentioned embodiment 1, as shown in FIG. 6, in a plan view, part of the outer periphery of the principal surface 21 a (top surface) of the seed quartz crystal 13 a is covered by the jig 12 a, but almost the entire surface other than the outer periphery is not covered by the jig 12 a and is exposed from the jig 12 a.

[0091] In the first embodiment, as shown in FIG. 6 , the main surface 21 a (top surface) of the seed quartz crystal 13 a is not covered by the jig 12 except for the outer periphery, so impurities that settle in the solution 14 are likely to adhere to the surface of the artificial quartz crystal growing on the main surface 21 a of the seed quartz crystal 13 a. In particular, impurities are most likely to adhere to the surface of the artificial quartz crystal growing on the main surface 21 a of the seed quartz crystal 13 a that is located highest among the multiple seed quartz crystals 13 a in group G1. Impurities that adhere to the surface of the artificial quartz crystal are incorporated into the growing artificial quartz crystal, causing inclusions, so there is no concern that they will peel off from the artificial quartz crystal and settle again in the solution 14. On the other hand, if impurities that settle in the solution 14 adhere to the surface of the jig 12 c, there is a concern that the impurities that have adhered to the jig 12 c will peel off from the jig 12 c and settle again in the solution 14. Therefore, the effect of reducing the possibility of impurities adhering to the synthetic quartz crystal growing on the seed quartz crystals 13b of group G2 is greater in the first embodiment than in the second embodiment.

[0092] The invention made by the inventor has been specifically described above based on the embodiments thereof, but it goes without saying that the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the invention.

[0093] 1, 101, 201 Artificial quartz crystal manufacturing apparatus 2 Pressure vessel 2a Side 2b Bottom 2c Lid 3 Baffle plate 4 Heater 4a, 4b Heater section 5 Control section 6, 6a, 6b Space 11 Lasker 12, 12a, 12b, 12c Jig 13, 13a, 13b, 113, 213 Seed crystal 14 Solution 16, 17 Wire 21, 21a, 21b, 22, 22a, 22b Main surface A1, A2, A3 Direction G1, G2 Group G2a, G2b, G2c Subgroup

Claims

1. A method for manufacturing artificial quartz crystals, comprising the following steps: (a) placing quartz crystal raw material and a plurality of plate-shaped seed quartz crystals in a pressure vessel and injecting a solution into the pressure vessel; and (b) growing artificial quartz crystals on each of the plurality of seed quartz crystals in the pressure vessel, wherein the plurality of seed quartz crystals placed in the pressure vessel consist of a first group consisting of a plurality of first seed quartz crystals and a second group located below the first group and consisting of a plurality of second seed quartz crystals, the quartz crystal raw material is located below the second group in the pressure vessel, each of the plurality of first seed quartz crystals has a first main surface and a second main surface opposite the first main surface, and each of the plurality of second seed quartz crystals has a third main surface and a fourth main surface opposite the third main surface, and in step (a), each of the plurality of first seed quartz crystals is placed in the pressure vessel so that the first main surface is perpendicular to the axial direction of the pressure vessel, In the step (a), each of the plurality of second seed crystals is placed in the pressure vessel so that the third principal surface is parallel to the axial direction of the pressure vessel.

2. A method for manufacturing an artificial quartz crystal according to claim 1, wherein in step (a), the plurality of first seed quartz crystals are arranged so as to be aligned in the axial direction.

3. A method for manufacturing artificial quartz crystal according to claim 2, wherein each of the plurality of first seed quartz crystals is arranged in the pressure vessel with the first principal surface facing downward.

4. A method for producing artificial quartz crystal according to claim 3, wherein in step (b), artificial quartz crystal is grown on the first main surface and the second main surface of each of the plurality of first seed quartz crystals.

5. A method for producing artificial quartz crystal according to claim 4, wherein the first principal surface is an X-plane, and in step (b), a +X region of the artificial quartz crystal grows on the first principal surface of each of the plurality of first seed quartz crystals, and a -X region of the artificial quartz crystal grows on the second principal surface of each of the plurality of first seed quartz crystals.

6. A method for manufacturing artificial quartz crystal according to claim 3, wherein, within the pressure vessel, the second main surface of each of the plurality of first seed quartz crystals is covered by a jig that holds the plurality of first seed quartz crystals.

7. A method for manufacturing artificial quartz crystals as defined in claim 2, wherein the second group includes a third group consisting of a portion of the plurality of second seed quartz crystals and a fourth group consisting of another portion of the plurality of second seed quartz crystals, the fourth group being located below the third group, the second seed quartz crystals in the third group being arranged at the same height as one another, and the second seed quartz crystals in the fourth group being arranged at the same height as one another.

8. An artificial quartz crystal produced by the method of claim 1.

9. An artificial quartz crystal manufacturing apparatus, comprising: a pressure vessel containing quartz crystal raw material, a plurality of plate-shaped seed quartz crystals, and a solution; and a heating mechanism for heating the pressure vessel, wherein the plurality of seed quartz crystals placed within the pressure vessel consist of a first group consisting of a plurality of first seed quartz crystals, and a second group consisting of a plurality of second seed quartz crystals placed below the first group, each of the plurality of first seed quartz crystals having a first main surface and a second main surface opposite the first main surface, each of the plurality of second seed quartz crystals having a third main surface and a fourth main surface opposite the third main surface, each of the plurality of first seed quartz crystals being placed within the pressure vessel so that the first main surface is perpendicular to the axial direction of the pressure vessel, and each of the plurality of second seed quartz crystals being placed within the pressure vessel so that the third main surface is parallel to the axial direction of the pressure vessel.

10. An artificial quartz crystal manufacturing apparatus according to claim 9, wherein the plurality of first seed quartz crystals are arranged in the pressure vessel so as to be aligned in the axial direction.

11. An artificial quartz crystal manufacturing apparatus according to claim 10, wherein each of the plurality of first seed quartz crystals is arranged in the pressure vessel with the first principal surface facing downward.

12. An artificial quartz crystal manufacturing apparatus according to claim 11, wherein artificial quartz crystal is grown on the first and second main surfaces of each of the plurality of first seed quartz crystals within the pressure vessel.

13. An artificial quartz crystal manufacturing apparatus as defined in claim 12, wherein the first principal surface is an X-plane, and within the pressure vessel, a +X region of the artificial quartz crystal grows on the first principal surface of each of the plurality of first seed quartz crystals, and a -X region of the artificial quartz crystal grows on the second principal surface of each of the plurality of first seed quartz crystals.

14. An artificial quartz crystal manufacturing apparatus according to claim 11, wherein, within the pressure vessel, the second main surface of each of the plurality of first seed quartz crystals is covered by a jig that holds the plurality of first seed quartz crystals.

15. An artificial quartz crystal manufacturing apparatus as defined in claim 9, wherein the second group includes a third group consisting of a portion of the plurality of second seed crystals and a fourth group consisting of another portion of the plurality of second seed crystals, the fourth group is positioned below the third group within the pressure vessel, the second seed crystals in the third group are positioned at the same height as each other within the pressure vessel, and the second seed crystals in the fourth group are positioned at the same height as each other within the pressure vessel.

16. Artificial quartz crystal manufactured using the artificial quartz crystal manufacturing apparatus according to claim 9.

17. An artificial quartz crystal, comprising: a seed crystal; and an artificial quartz crystal region formed on the seed crystal, wherein, when a plurality of seed crystals are placed in a pressure vessel of an artificial quartz crystal manufacturing apparatus to form the artificial quartz crystal region, the plurality of seed crystals in the pressure vessel consist of a first group consisting of a plurality of first seed crystals and a second group located below the first group and consisting of a plurality of second seed crystals, each of the plurality of first seed crystals having a first main surface and a second main surface opposite the first main surface, and each of the plurality of second seed crystals having a third main surface and a fourth main surface opposite the third main surface, each of the plurality of first seed crystals being positioned in the pressure vessel such that the first main surface is perpendicular to the axial direction of the pressure vessel, and each of the plurality of second seed crystals being positioned in the pressure vessel such that the third main surface is parallel to the axial direction of the pressure vessel.

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