JP4736622B2 - Single crystal growth substrate - Google Patents

Description

  The present invention relates to a single crystal growth substrate, and more particularly to a single crystal growth substrate used when a magnetic garnet single crystal film is grown using a liquid phase epitaxial method.

  Magnetic garnet single crystal films are often used in optical communication systems as Faraday rotators used in optical isolators and the like. The magnetic garnet single crystal film is grown on a single crystal substrate by a liquid phase epitaxial (LPE) method.

  FIG. 5 shows a part of the process of growing the magnetic garnet single crystal film by the LPE method. As shown in FIG. 5, a single crystal substrate 10 for growing a single crystal is held by a substrate fixing jig 2. The substrate fixing jig 2 includes three linear support portions that support the single crystal substrate 10 at three points, and a substrate holding portion that is bent at one end of each linear support portion in order to hold the single crystal substrate 10. And have. The other end side of each linear support part is put together and connected and fixed to a ceramic support rod 7. When growing the single crystal film, the support rod 7 is carried into a noble metal crucible 4 by a predetermined distance, and at least one surface of the single crystal substrate 10 is immersed in the raw material melt 8 in the crucible 4. The When the support bar 7 rotates about its central axis, the single crystal substrate 10 also rotates with the substrate fixing jig 2. Thereby, the magnetic garnet single crystal film 12 is epitaxially grown on one surface of the single crystal substrate 10. The grown magnetic garnet single crystal film 12 is subjected to processing such as polishing and cutting to produce a single crystal piece, and an antireflective film is formed on the surface of the single crystal piece to produce a Faraday rotator.

  In recent years, in order to reduce the cost by increasing the number of Faraday rotators obtained from one single crystal substrate 10, a larger 3 inch single crystal is used instead of the conventional 2 inch single crystal substrate 10. A substrate 10 is used.

  Generally, in order to prevent cracking in the process of processing a single crystal, it is desirable to reduce the stress inherent in the single crystal as much as possible at the room temperature at which the processing is performed. For this purpose, the lattice constants of the entire single crystal including the single crystal substrate and the magnetic garnet single crystal film need only coincide at room temperature. However, since the single crystal substrate and the magnetic garnet single crystal film have different linear expansion coefficients, even if the lattice constants coincide with each other at room temperature, the lattice constants differ from each other at a growth temperature of 700 to 900 ° C. . Therefore, stress is generated in the growing single crystal, and the single crystal may break.

  FIG. 6 shows cracks (cracks) generated in the growing single crystal substrate. In a single crystal substrate having a relatively thick substrate, cleavage cracks as shown by broken lines in FIG. 6A are likely to occur, and conversely, in a single crystal substrate having a relatively thin substrate thickness, shown by broken lines in FIG. 6B. Such concentric cracks are likely to occur. Any cracks are likely to occur on the outer periphery of the single crystal substrate where the generated stress is large. If the single crystal substrate is cracked, the number of single crystal pieces obtained is reduced, resulting in a decrease in yield. Here, the yield is a single crystal piece that can geometrically take the average number of single crystal pieces actually produced through one growth process using one single crystal substrate from the single crystal substrate. The value divided by the number of.

  Furthermore, since the single crystal substrate 10 is supported by the substrate fixing jig 2 at three points on the outer peripheral portion as shown in FIG. It may fall into the inside. In particular, when the substrate size is increased, the stress generated in the outer peripheral portion in the single crystal is increased, so that the frequency at which the single crystal is broken increases. Therefore, even if the size of the single crystal substrate 10 is increased, the yield of the single crystal pieces is lowered, so that the average number of Faraday rotators obtained is not sufficiently increased. For this reason, there is a problem that even if the size of the single crystal substrate 10 is simply increased, the manufacturing cost of the Faraday rotator cannot be sufficiently reduced.

Japanese Patent No. 3197383

  An object of the present invention is to provide a substrate for growing a single crystal that can reduce the manufacturing cost of a Faraday rotator.

  The above object is achieved by a single crystal growth substrate characterized in that the substrate diameter is 2.5 inches or more and 2.7 inches or less.

  The substrate for growing a single crystal according to the present invention is characterized in that the substrate diameter is about 2.6 inches.

  The single crystal growth substrate of the present invention is characterized in that the substrate thickness is not less than 500 μm and not more than 800 μm.

  A substrate for growing a single crystal according to the present invention, which is manufactured using an oxide.

  The substrate for growing a single crystal according to the present invention is characterized in that the crystal structure is a garnet structure.

  The single crystal growth substrate of the present invention is characterized in that it is used for growing a magnetic garnet single crystal film.

  The substrate for growing a single crystal according to the present invention is characterized in that it is used for growing a single crystal film having a thickness of 200 μm or more and 600 μm or less.

  ADVANTAGE OF THE INVENTION According to this invention, the board | substrate for single crystal growth which can reduce the manufacturing cost of a Faraday rotator is realizable.

  A single crystal growth substrate according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing a configuration of a single crystal substrate 20 for growing a single crystal according to the present embodiment. As shown in FIG. 1, the single crystal substrate 20 has a substantially disc shape. The single crystal substrate 20 has a substrate diameter d and a substrate thickness t. The single crystal substrate 20 is manufactured using an oxide single crystal such as a CaMgZr-substituted GGG single crystal, and the crystal structure thereof is a garnet structure. The single crystal substrate 20 is used when growing a magnetic garnet single crystal film having a film thickness of 200 μm or more and 600 μm or less using, for example, the LPE method.

FIG. 2 is a graph showing the relationship between the substrate diameter d of the single crystal substrate 20 and the substrate thickness t. The horizontal axis of the graph represents the substrate diameter d (inch), and the vertical axis represents the substrate thickness t (μm). As a premise of the present embodiment, when a single crystal substrate 20 having a relatively thin substrate thickness t is used when a single crystal film is grown using the LPE method, concentric cracks are likely to occur. It is preferable to use a single crystal substrate 20 that satisfies (μm) (line a in FIG. 2 and above). On the other hand, if a single crystal substrate 20 having a relatively thick substrate thickness t is used, cleavage cracks are likely to occur. It is preferable to use a single crystal substrate 20 that satisfies the relationship (below). In addition to these conditions, the present embodiment uses a single crystal substrate 20 having a substrate diameter d of 2.5 inches (about 63.5 mm) or more and 2.7 inches (about 68.6 mm) or less. The substrate thickness t of the single crystal substrate 20 is desirably 500 μm or more and 800 μm or less. That is, when the relationship between the substrate diameter d of the single crystal substrate 20 and the substrate thickness t is included in the region A in the graph of FIG. 2, the single crystal piece obtained per growth using the single crystal substrate 20 In particular, the number of the Faraday rotators is further reduced and the manufacturing cost of the Faraday rotator is further reduced.
Hereinafter, the substrate for single crystal growth according to the present embodiment will be described more specifically with reference to Examples and Comparative Examples.

Example 1
A CaMgZr substituted GGG single crystal was grown by a pulling method. A single crystal was oriented by X-ray diffraction, and subjected to cylindrical grinding and wire saw cutting to produce a disc-shaped substrate having a (111) plane as a growth surface. The substrate diameter of the disk-shaped substrate was three types of 2.5 inches, 2.6 inches, and 2.7 inches, and the substrate thicknesses were all 500 μm. The side surfaces of these disk-shaped substrates were subjected to end face rounding, and mirror polishing such as final polishing using colloidal silica as abrasive grains was performed on the growth surface. Further, etching with a mixed acid of phosphoric acid and sulfuric acid was performed at about 80 ° C. to remove the work-affected layer, and a single crystal substrate 20 for epitaxial growth having three types of substrate diameters d was produced.

A platinum crucible was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , Ge ₂ O ₃ , B ₂ O ₃ , Bi ₂ O ₃ and PbO. Next, the composition of Bi _1.20 Gd _0.60 Yb _0.58 Pb _0.02 Fe _4.98 Ge _0.01 Pt _0.01 O is obtained by LPE using the single crystal substrate 20 produced in the previous step. ₁₂ was grown to a thickness of about 500 μm. The grown single crystal film was polished and cut to produce a 10 mm square plate-like magnetic garnet single crystal piece. If the single crystal film is not cracked, the number of single crystal pieces corresponds to the number of 10 mm square single crystal pieces that can be geometrically taken from one single crystal substrate 20. The growth was repeated 10 times for each single crystal substrate 20 having three types of substrate diameters d, and the average number of single crystal pieces actually obtained from the grown single crystal film was evaluated. When the single crystal substrate 20 having a substrate diameter d of 2.5 inches, 2.6 inches, and 2.7 inches is used, the geometrically possible number of single crystal pieces A is 21 and 24, respectively. The average number B of actually obtained single crystal pieces was 20.6, 23.0, and 22.6, respectively.

(Comparative Example 1)
A CaMgZr substituted GGG single crystal was grown by a pulling method. A single crystal was oriented by X-ray diffraction, and subjected to cylindrical grinding and wire saw cutting to produce a disc-shaped substrate having a (111) plane as a growth surface. The substrate diameter of the disk-shaped substrate was set to four types of 2.0 inches, 2.4 inches, 2.8 inches, and 3.0 inches, and the substrate thicknesses were all 500 μm. The side surfaces of these disk-shaped substrates were subjected to end face rounding, and mirror polishing such as final polishing using colloidal silica as abrasive grains was performed on the growth surface. Further, etching with a mixed acid of phosphoric acid and sulfuric acid was performed at about 80 ° C. to remove the work-affected layer, and a single crystal substrate 20 for epitaxial growth having four types of substrate diameters d was produced.

A platinum crucible was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , Ge ₂ O ₃ , B ₂ O ₃ , Bi ₂ O ₃ and PbO. Next, the composition of Bi _1.20 Gd _0.60 Yb _0.58 Pb _0.02 Fe _4.98 Ge _0.01 Pt _0.01 O is obtained by LPE using the single crystal substrate 20 produced in the previous step. ₁₂ was grown to a thickness of about 500 μm. The grown single crystal film was polished and cut to produce a 10 mm square plate-like magnetic garnet single crystal piece. The growth was repeated 10 times for each of the four types of single crystal substrates 20, and the average number of single crystal pieces actually obtained from the grown single crystal film was evaluated. When the single crystal substrates 20 having the substrate diameters d of 2.0 inches, 2.4 inches, 2.8 inches, and 3.0 inches are used, the geometrically possible number of single crystal pieces A is 12 respectively. The average number B of actually obtained single crystal pieces is 11.8, 19.6, 19.6, and 19.2, respectively. there were.

  Table 1 collectively shows Example 1 and Comparative Example 1. FIG. 3 is a graph showing the relationship between the substrate diameter d of the single crystal substrate 20 in Example 1 and the comparative example, the average number B of actually obtained single crystal pieces, and the yield. The horizontal axis of the graph represents the substrate diameter d of the single crystal substrate 20, and the vertical axis represents the average number B of single crystal pieces and the yield. As shown in Table 1, the number A of single crystal pieces that can be geometrically taken increases as the substrate diameter d increases. However, as shown in Table 1 and FIG. 3, since the yield (B / A) decreases as the substrate diameter d increases, the average number B of single crystal pieces actually obtained increases monotonously depending on the substrate diameter d. Not to do. The average number B takes a maximum value when the substrate diameter d is about 2.6 inches. Further, compared with the case where the single crystal substrate 20 having the substrate diameter d of 2.0 inches or 3.0 inches is used, the single crystal substrate 20 having the substrate diameter d of 2.5 inches or more and 2.7 inches or less is obtained. By using it, the average number B of single crystal pieces actually obtained is obviously increased.

  Thus, by using the single crystal substrate 20 having a substrate diameter d of 2.5 inches or more and 2.7 inches or less, preferably about 2.6 inches, the number of single crystal pieces obtained per growth is increased. In addition, the manufacturing cost of the Faraday rotator is reduced.

(Example 2)
A CaMgZr substituted GGG single crystal was grown by a pulling method. A single crystal was oriented by X-ray diffraction, and subjected to cylindrical grinding and wire saw cutting to produce a disc-shaped substrate having a (111) plane as a growth surface. At this time, a total of four types of disk-shaped substrates were prepared with two types of substrate diameters of 2.5 inches and 2.7 inches and two types of substrate thicknesses of 500 μm and 750 μm. The side surfaces of these disk-shaped substrates were subjected to end face rounding, and mirror polishing such as final polishing using colloidal silica as abrasive grains was performed on the growth surface. Furthermore, etching with a mixed acid of phosphoric acid and sulfuric acid is performed at about 80 ° C. to remove the work-affected layer, and four types of single crystal substrates for epitaxial growth in which two types of substrate diameters d and two types of substrate thickness t are combined. 20 was produced.

A platinum crucible was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , Ge ₂ O ₃ , B ₂ O ₃ , Bi ₂ O ₃ and PbO. Next, the composition of Bi _1.20 Gd _0.60 Yb _0.58 Pb _0.02 Fe _4.98 Ge _0.01 Pt _0.01 O is obtained by LPE using the single crystal substrate 20 produced in the previous step. ₁₂ was grown to a thickness of about 500 μm. The grown single crystal film was polished and cut to produce a 10 mm square plate-like magnetic garnet single crystal piece. The growth was repeated 10 times for each of the four types of single crystal substrates 20, and the average number of single crystal pieces actually obtained from the grown single crystal film was evaluated. When the single crystal substrate 20 having a substrate diameter d of 2.5 inches is used, the number of single crystal pieces A that can be geometrically taken is 21, whereas the number of single crystal pieces actually obtained is 21. The average number B was 20.6 when the substrate thickness t was 500 μm, and 20.4 when the substrate thickness t was 750 μm. When the single crystal substrate 20 having a substrate diameter d of 2.7 inches is used, the number of single crystal pieces A that can be geometrically taken is 26, whereas the actually obtained single crystal The average number B of the pieces was 22.6 when the substrate thickness t was 500 μm, and 19.8 when the substrate thickness t was 750 μm.

(Comparative Example 2)
A CaMgZr substituted GGG single crystal was grown by a pulling method. A single crystal was oriented by X-ray diffraction, and subjected to cylindrical grinding and wire saw cutting to produce a disc-shaped substrate having a (111) plane as a growth surface. The substrate diameter of the disk-shaped substrate was 2.5 inches and 2.7 inches, and the substrate thickness was 1000 μm. The side surfaces of these disk-shaped substrates were subjected to end face rounding, and mirror polishing such as final polishing using colloidal silica as abrasive grains was performed on the growth surface. Further, etching with a mixed acid of phosphoric acid and sulfuric acid was performed at about 80 ° C. to remove the work-affected layer, and a single crystal substrate 20 for epitaxial growth having two types of substrate diameters d was produced.

A platinum crucible was filled with Gd ₂ O ₃ , Yb ₂ O ₃ , Fe ₂ O ₃ , Ge ₂ O ₃ , B ₂ O ₃ , Bi ₂ O ₃ and PbO. Next, the composition of Bi _1.20 Gd _0.60 Yb _0.58 Pb _0.02 Fe _4.98 Ge _0.01 Pt _0.01 O is obtained by LPE using the single crystal substrate 20 produced in the previous step. ₁₂ was grown to a thickness of about 500 μm. The grown single crystal film was polished and cut to produce a 10 mm square plate-like magnetic garnet single crystal piece. The growth was repeated 10 times for each of the two types of single crystal substrates 20, and the average number of single crystal pieces actually obtained from the single crystal film after the growth was evaluated. When the single crystal substrate 20 having a substrate diameter d of 2.5 inches and 2.7 inches is used, the geometrically possible number of single crystal pieces A is 21 and 26, respectively. The average number B of actually obtained single crystal pieces was 19.0 and 16.8, respectively.

  Table 2 collectively shows Example 2 and Comparative Example 2. FIG. 4 is a graph showing the relationship between the substrate thickness t of the single crystal substrate 20 in Example 2 and Comparative Example 2 and the average number B of actually obtained single crystal pieces. The horizontal axis of the graph represents the substrate thickness t (μm) of the single crystal substrate 20, and the vertical axis represents the average number B of single crystal pieces. As shown in Table 2 and FIG. 4, even when the substrate diameter d is the same, when the substrate thickness t is increased to about 1000 μm, the average number B of actually obtained single crystal pieces tends to decrease. Accordingly, it has been found effective to use the single crystal substrate 20 having a substrate thickness t of 500 μm or more and 800 μm or less in order to reduce the manufacturing cost of the Faraday rotator.

  As described above, according to the present embodiment, by selecting the range of the substrate diameter d and / or the substrate thickness t of the single crystal substrate 20, cracks generated in the growing single crystal are suppressed, and Faraday rotation is performed. Child manufacturing costs are reduced.

It is a perspective view which shows the structure of the board | substrate for single crystal growth by one embodiment of this invention. It is a graph which shows the relationship between the substrate diameter d and the substrate thickness t of a single crystal substrate. It is a graph which shows the relationship between the board | substrate diameter d of a single crystal substrate, the average number B of the single crystal piece actually obtained, and the yield. It is a graph which shows the relationship between the board | substrate thickness t of a single crystal substrate, and the average number B of the single crystal piece actually obtained. It is a figure which shows the process of growing a magnetic garnet single crystal film by LPE method. It is a figure which shows the crack which arises in the single crystal substrate under the growth.

Explanation of symbols

2 substrate fixing jig 4 crucible 7 support rod 8 raw material melt 10, 20 single crystal substrate 12 magnetic garnet single crystal film

Claims (3)

Produced using a CaMgZr-substituted GGG single crystal, the crystal structure is a garnet structure,
A substrate for growing a single crystal used for growing a magnetic garnet single crystal film,
Substrate diameter Ri der less 2.7 inches to 2.5 inches,
A substrate for single crystal growth, wherein the substrate thickness is 500 μm or more and 800 μm or less . The single crystal growth substrate according to claim 1,
The substrate for single crystal growth, wherein the substrate diameter is about 2.6 inches. The single crystal growth substrate according to claim 1 or 2 ,
A single crystal growth substrate characterized by being used for growing a single crystal film having a thickness of 200 μm or more and 600 μm or less.

Images