JPH07115996B2 - Neodymium gallium garnet single crystal and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a neodymium gallium garnet single crystal and a method for producing the same, particularly a neodymium gallium
The present invention relates to a garnet single crystal and a method for producing the same.

[Conventional technology]

The neodymium / gallium / garnet single crystal is used as a substrate material for magnetic bubbles, an optical substrate material, etc.
The neodymium gallium garnet single crystal used for these applications is required to have high quality, that is, constant and uniform lattice constant and defect-free.

Further, as for the single crystal for the valve memory substrate and the optical substrate, the one having a gradually larger diameter is required, and recently, a considerable part of the demand is shifted from the one having a diameter of 2 inches to the one having a diameter of 3 inches. However, since it is expected that a large one up to 4 inches will be used in the near future, securing a high quality at the time of manufacturing a single crystal, and at the same time, preventing the occurrence of a clutch related to the crystal is an issue. That is, the large diameter of the single crystal causes a large nonuniformity of the composition and characteristic values in the single crystal ingot, and the single crystal ingot is not only processed into a substrate but also manufactured in an epitaxial film growth step, a pattern forming step, etc. There are also disadvantages in the process.

Thus, a method for growing a single crystal from a melt having a stoichiometric composition is usually used for the production of the composite compound single crystal such as the neodymium gallium garnet single crystal. The composition of melt and single crystal does not match because the segregation coefficient of the single crystal is greatly deviated from 1.00, and the single crystal does not grow stably, so long ones cannot be pulled up and dislocation easily occurs. However, this also has a disadvantage in that each device using a wafer cut from the thus obtained single crystal as a substrate has inconsistent characteristic values.

[Structure of Invention]

The present invention relates to a neodymium gallium garnet single crystal and a method for producing the same, in which such disadvantages are solved, which is a neodymium gallium garnet single crystal containing 37.60 to 37.80 mol% of Nd ₂ O ₃ and Nd ₂ O. ₃ to 37.60
～37.80 consisting congruent composition containing mol% Nd ₂
It is characterized in that a neodymium-gallium-garnet single crystal is grown from a mixed melt of O ₃ and Ga ₂ O ₃ .

That is, as a result of various studies on the method for producing a neodymium gallium garnet single crystal without the above disadvantages, the present inventors have found that the melt used in pulling a single crystal by the Czochralski method has a congruent composition. If a Nd ₂ O ₃ is grown at 37.60 to 37.80 mol% and the balance is essentially Ga ₂ O ₃ , a neodymium gallium garnet single crystal is grown from the Nd ₂ O ₃ at 37.60 to 37.60%. It was confirmed that the content was 37.80 mol%, the segregation coefficient was about 1.00, and the composition of the single crystal was constant in each part, so it was easy to manufacture a single crystal wafer with a large diameter such as 4 ″. The present invention has been completed based on the finding that it can be performed at a low temperature, a small crack rate, and a small crystal transition.

The method of the present invention is to grow a neodymium gallium garnet single crystal from a melt having a congruent composition as described above.
It is preferable that ₂ O ₃ and Ga ₂ O ₃ are as pure as possible, and therefore, it is preferable that all of them be 99.99% or more, and the mixing ratio of them is as described above. Is Nd ₂ O ₃ is 37.60 to 37.80
It is necessary to make the balance substantially Ga ₂ O _{3 in} mol%. Each of these is weighed and then stored in a crucible to be melted. This crucible has a melting temperature of 1,600 ° C.
As described above, it may be made of iridium. This may be melted by high-frequency induction according to a conventional method, and for this purpose, for example, a high frequency of 7 KHz and 10 KW may be used to heat these to 1,700 to 1,800 ° C. to melt them.

The target single crystal may be produced by pulling a single crystal from the melt by the Czochralski method,
The atmosphere in this case is 1 to 5% oxygen or 25 to 100 CO ₂ .
% Nitrogen gas or argon gas atmosphere may be used. Further, the seed crystal used for pulling the single crystal may be represented by a formula of the same quality as the target single crystal, for example, the formula Nd ₃ Ga ₅ O ₁₂ , which is a gadnium gallium garnet (GGG) or the like. A single crystal of a garnet-type crystal body such as
It should be 20 mm / hour.

It should be noted that pulling of this single crystal does not cause twisting of the single crystal during pulling unlike SGG, and this pulling can be performed extremely easily. Can be obtained.

Single crystal represented by the formula Nd ₃ Ga ₅ O ₁₂ of the present invention obtained in this manner is characterized in that it contains Nd ₂ O ₃ from 37.60 to 37.80 mol%, the intended crack rate is small The number of transitions is extremely small, and the crystal lattice constant is approximately 12.509Å and the segregation coefficient is approximately 1 as described above. Therefore, it is represented by the formula (BiRe) ₃ (FeM) ₅ O _12. Although it is useful as a garnet substrate single crystal for epitaxially growing a bismuth-substituted magnetic garnet film, it is also useful as a substrate for an optical isolator because it also has excellent light transmittance.

Next, examples of the present invention will be given.

Example 1 Nd ₂ O ₃ 1 was placed in an iridium crucible having an outer diameter of 100 mm and a height of 100 mm.
562.0 g (37.70 mol%) and Ga ₂ O ₃ 1,438.0 g (62.30 mol%) were weighed in and charged, and heated to 1,650 ° C. by high frequency induction in a nitrogen gas atmosphere gas containing 1 to 5% oxygen gas. When melted, a 5 mm square GGG seed crystal was immersed in this melt, and when this was pulled at a speed of 1 to 10 mm / hour under a rotation of 20 rpm to pull a single crystal, 1,500 g of a transparent crystal was obtained. Was given.

Next, when 1 g of each sample was taken from the melt in the lower part of the crystal and in the crucible after pulling the crystal, quantitative analysis for Nd ₂ O ₃ was performed, and the results shown in Table 1 were obtained.
It was confirmed that this had a crystal structure of the formula Nd _3.02 Ga _4.98 O ₁₂ , but the Nd segregation coefficient was calculated to be 1.00 based on the results of this quantitative analysis.

For this crystal, a wafer with a thickness of 1 mm was cut out from the crystal upper part and the crystal lower part, etched with hot phosphoric acid, and then the lattice constant precision measurement device APL2 (trade name of Rigaku Denki Co., Ltd.) was used to bond it. When the lattice constants were measured, they all showed a value of 12.509Å.

In addition, when the crystal was pulled 10 times under the same conditions, no cracks occurred during cooling or during working cutting after pulling, and 1 mm thick wafers cut from the upper and lower parts of the crystal were hot-phosphorized. After etching with acid, dislocations were observed, which were 5 co / cm ² or less.

Comparative Examples 1 to 2 The compounding amounts of Nd ₂ O ₃ and Ga ₂ O ₃ in Example 1 described above were changed to the second amount.
In the same manner as in Example 1 except that the amounts shown in the table were used, transparent single crystals were obtained. Nd ₂ O ₃ (wt%) and segregation coefficient of these were shown in Table 3. The results shown in Table 4 were obtained, and the crack ratio and the number of dislocations were obtained as shown in Table 4.

 ─────────────────────────────────────────────────── --Continued front page (56) References Journal of Crystal Growth, 12 (1972), (US), North-Holland Publishing Co., C. D. BRANDL E, et al, "The Elimination of Defects in Czochralski Grown Rare-Earth Gallium Garnets" P.P. 195-200

Claims (2)

[Claims] 1. Nd ₂ O ₃ is 37.60 to 37.80 mol%, and the balance is Ga ₂ O _3.
Neodymium gallium garnet single crystal characterized by And wherein wherein growing the Nd ₂ O ₃ neodymium gallium garnet single crystals from the melt mixture of Nd ₂ O ₃ and Ga ₂ O ₃ consisting of congruent composition containing 37.60 to 37.80 mol% A method for manufacturing a neodymium gallium garnet single crystal.