JP4146829B2 - Crystal manufacturing equipment - Google Patents

Description

  The present invention relates to a crystal manufacturing apparatus, and more particularly to a crystal manufacturing apparatus for improving the crystal quality at the center of a wafer manufactured from crystals in the vertical Bridgman method and the vertical temperature gradient solidification method.

  Conventionally, the oxide crystal material is produced by a horizontal Bridgman method in which the melt in the growth vessel is gradually solidified from the seed crystal, and the growth vessel is placed vertically to give a temperature gradient and moved to the lower temperature side. A vertical Bridgman method for solidifying crystals and a vertical temperature gradient solidification method for solidifying crystals by changing the temperature gradient by fixing the growth vessel vertically are known (for example, see Patent Document 1).

  With reference to FIG. 1, a method for producing a crystal material by a conventional vertical Bridgman method will be described. A seed crystal 4 and a raw material 2 are placed in a crucible 1. The raw material 2 is heated and dissolved by the heating element 6 to obtain the raw material solution 2. The heating amount of the heating element 6 is adjusted to keep the inside of the crystal production furnace at a constant temperature gradient curve 5. When the raw material solution 2 is cooled by moving the crucible 1 to the low temperature side at a constant speed, the crystal 3 that has reached the crystal growth temperature grows into a crystal having the same crystal orientation as the seed crystal 4, and the enlarged portion The grown crystal 3 is obtained through the growth process and the constant diameter portion growth process.

  At this time, since the growth crystal 3 grows sequentially with the seed crystal 4 as a nucleus, it can inherit the crystal orientation of the seed crystal 4 and grow as the growth crystal 3 having the same crystal orientation as the crystal orientation of the seed crystal 4. . In the vertical Bridgman method, the crucible 1 is moved to a lower temperature side at a constant speed. In the vertical temperature gradient solidification method, the heating element 6 is moved from the lower side to the upper side to grow a crystal in the same manner as the above-described manufacturing method. Can be made.

For example, defects _{KTaO 3, K (Ta, Nb} ) crystals, such as O _3, when grown by pulling method, the defects present in the seed crystal is propagated to the growing crystal, propagates particularly along the seed crystal in the growth direction It is known that it is difficult to prevent. In the conventional vertical Bridgman method and vertical temperature gradient solidification method, defects existing in the seed crystal 4 may propagate to the growth crystal 3.

JP 59-107996 A

  As shown in FIG. 1, in the conventional method, the seed crystal 4 is arranged so as to coincide with the central axis of the crucible 1. If it is assumed that there is a defect in the seed crystal 4 at this time, the grown crystal has a defect 7 at the center as shown in FIG. 2, similarly to the crystal grown by the pulling method. The element or part formed in the defective part of the wafer cut out from the grown crystal cannot obtain desired characteristics, and the element or part manufactured from the center of the wafer has a high defect rate. was there.

  On the other hand, in the manufacturing process of an element or a component, for example, there is a tendency that homogeneity is good near the center of the wafer, such as resist coating and film formation with wafer rotation. That is, in the manufacturing process, the non-defective rate is higher at the wafer center. Therefore, it can be said that the presence of defects in crystal growth in the vicinity of the wafer center, which is advantageous in the device or component manufacturing process, is a significant disadvantage from the viewpoint of product yield.

  The present invention has been made in view of such problems. The object of the present invention is to limit the defects generated in the grown crystal to the outer periphery of the crystal and to improve the crystal quality at the center of the wafer made from the crystal. An object of the present invention is to provide a crystal manufacturing apparatus that improves the above.

In order to achieve such an object, the invention according to claim 1 is characterized in that seed crystals are arranged in a crucible held in a furnace, and a raw material solution filled in the crucible is heated and dissolved. In the crystal manufacturing apparatus for crystal growth by gradually cooling the raw material solution from the lower side to the upper side of the crucible, the seed crystal is propagated through the outer periphery of the crystal where the seed crystal defect grows. Is arranged at a position away from the central axis of the crucible.

  As described above, according to the present invention, by arranging the seed crystal away from the central axis of the crucible, defects generated in the grown crystal can be limited to the outer periphery of the crystal. Since a wafer in which defects are concentrated on the outer peripheral portion of the wafer can be obtained, the vicinity of the central portion of the wafer with high homogeneity can be effectively used in the element or component manufacturing process. Therefore, it becomes possible to manufacture a high-yield element or component.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In a top-seeded solution-growing (TSSG) method in which a seed crystal is soaked in a molten solution and grown while being pulled, the axial symmetry of the temperature distribution in the grown crystal must be maintained. If the axial symmetry is not maintained, the crystal grows preferentially in one direction, and the thermal stress applied in the crystal is concentrated on a part of the crystal, resulting in cracks and the like.

  On the other hand, in the crystal growth method using the vertical Bridgman method or the vertical temperature gradient solidification method, the seed crystal 4 and the shape of the crucible, that is, the growth crystal 3 are used in order to maintain the axial symmetry of the temperature distribution in the growth crystal. Is kept axisymmetric. As shown in FIG. 1, the crystal grows from the upper end of the seed crystal 4, and a growth crystal 3 conforming to the shape of the crucible 1 is formed. At this time, it is necessary to maintain the axial symmetry with respect to the heating element 6 and the crucible 1 from the viewpoint of thermal stress applied to the crystal, but the seed crystal 4 is not necessarily located at the center of the crucible.

  FIG. 2 shows a configuration of a crystal manufacturing apparatus using the vertical Bridgman method according to an embodiment of the present invention. The seed crystal 14 is arranged at a position away from the center of the crucible 11. Since the growth crystal 13 grows sequentially with the seed crystal 14 as a nucleus, similarly to the conventional method, the crystal orientation of the seed crystal 14 is inherited, and the growth crystal 13 having the same crystal orientation as the crystal orientation of the seed crystal 14 is grown. Can be made.

  The role of the seed crystal is to determine the crystal structure and crystal orientation of crystallization. In the case of the vertical Bridgman method and the vertical temperature gradient solidification method, the shape and size of the growth crystal are determined by the crucible shape regardless of the crystallization start position. It doesn't matter. Since the propagation of defects existing in the seed crystal proceeds from the seed crystal edge along the growth direction regardless of the position of the seed crystal, the defects of the grown crystal are localized in the outer periphery of the grown crystal as shown in FIG. .

  By using a wafer produced by cutting and polishing from a crystal grown by this method, it is possible to effectively use the vicinity of the wafer center with high homogeneity in the element or component manufacturing process. Elements or components can be manufactured. As shown in FIGS. 2 and 4, the shape of the crucible has been described in the case of using a cylindrical shape. However, even if a crucible having a polygonal column shape such as a quadrangular column is used, the same effect can be obtained. it can.

  Examples of the present invention will be specifically described below. In addition, this Example is an illustration and it cannot be overemphasized that a various change or improvement can be performed in the range which does not deviate from the mind of this invention.

FIG. 5 shows a configuration of a crystal manufacturing apparatus according to the vertical Bridgman method according to the first embodiment. A case where a KTa _x Nb _1-x O ₃ (0 ≦ x ≦ 1) crystal material is manufactured will be described. A {100} -oriented K (Ta, Nb) O ₃ seed crystal 24 is placed at a position 20 mm away from the central axis of the 2-inch diameter crucible 21. However, when the composition of the K (Ta, Nb) O ₃ seed crystal 24 is KTa _{x ′} Nb _{1-x ′} O ₃ , x ′ is equal to _{x of} KTa _x Nb _1-x O ₃ to be grown. Choose a composition that is larger or larger and has an equal or higher melting temperature. As raw materials for KTa _x Nb _1-x O ₃ , K ₂ CO ₃ , Ta ₂ O _5, and Nb ₂ O ₅ , which are raw materials, are weighed to achieve a desired composition ratio, and a total of 1 kg is charged in a crucible 21.

The crucible 21 filled with the K (Ta, Nb) O ₃ seed crystal 24 and the raw material 22 is heated by a heating element, and the raw material 22 is heated and dissolved to obtain a K (Ta, Nb) O ₃ raw material solution 22. Next, the heat generation amount of the heating element is adjusted to realize the furnace temperature distribution 25 shown in FIG. Thereafter, the 2-inch diameter crucible 21 is lowered at a speed of 2 mm / day. Thus, the K (Ta, Nb) O ₃ raw material solution 22 is gradually crystallized from the lower part of the crucible 21 having a low temperature, starting from the K (Ta, Nb) O ₃ seed crystal 24, and K (Ta, Nb) The O ₃ crystal 23 grows. After crystal growth is completed, the temperature is gradually cooled to room temperature by adjusting the heating value of the heating element.

When the produced K (Ta, Nb) O ₃ crystal is taken out, a {100} facet plane that is four-fold symmetric appears on the crystal surface in the same manner as in the conventional method in which a seed crystal is arranged at the center. Cracks and abnormal shapes cannot be confirmed on the appearance of the grown crystal. Observing the etch pits of the wafer cut from the crystal in a plane perpendicular to the growth direction, the defect is limited to the upper extension of the seed crystal on the outer periphery of the wafer, and a high-quality crystal having no defect in the center is grown. be able to. Also, when a KTaO ₃ seed crystal is used as a seed crystal, a high-quality crystal can be obtained with a high yield.

FIG. 6 shows a configuration of a crystal manufacturing apparatus according to the vertical Bridgman method according to the second embodiment. A case where a KTaO ₃ crystal material is manufactured will be described. 3 position away 30mm from the center of inch diameter crucible 31, to place the KTaO ₃ seed crystal 34 of the {100} orientation. The raw materials of KTaO ₃ are weighed such that the raw materials K ₂ CO ₃ and Ta ₂ O ₅ have a desired composition ratio, and a total of 3 kg is filled in the crucible 31.

The temperature of the crucible 31 filled with the KTaO ₃ seed crystal 34 and the raw material 32 is raised, and the raw material is heated and dissolved to obtain a KTaO ₃ raw material solution 32. Next, the amount of heat generated by the heating element is adjusted to realize the furnace temperature distribution 35 shown in FIG. Thereafter, the 3-inch diameter crucible 31 is lowered at a speed of 2 mm / day. As a result, the KTaO ₃ solution 32 is gradually crystallized from the lower part of the crucible 31 having a low temperature, starting from the KTaO ₃ seed crystal 34, and the KTaO ₃ crystal 33 grows. After crystal growth is completed, the temperature is gradually cooled to room temperature by adjusting the heating value of the heating element.

When the produced KTaO ₃ crystal is taken out, a {100} plane facet plane that is four-fold symmetric appears on the crystal surface as in the conventional method in which the seed crystal is arranged at the center. Cracks and abnormal shapes cannot be confirmed on the appearance of the grown crystal. Observing the etch pits of the wafer cut from the crystal in a plane perpendicular to the growth direction, the defect is limited to the upper extension of the seed crystal on the outer periphery of the wafer, and a high-quality crystal having no defect in the center is grown. be able to. Also, when a KTaO ₃ seed crystal is used as a seed crystal, a high-quality crystal can be obtained with a high yield.

  5 and 6 show an embodiment in which the present invention is applied to the vertical Bridgman method. However, the present invention can also be applied to the vertical temperature gradient solidification method, and the basic growth process is as follows. The same effects can be obtained.

It is a figure for demonstrating the preparation methods of the crystal material by the conventional perpendicular Bridgman method. It is a figure which shows a mode that a defect exists in the center part of the grown crystal. It is a figure which shows the structure of the crystal manufacturing apparatus by the vertical Bridgman method concerning one Embodiment of this invention. It is a figure which shows a mode that a defect exists in the crystal grown by the method of this embodiment. 1 is a diagram illustrating a configuration of a crystal manufacturing apparatus using a vertical Bridgman method according to Example 1. FIG. It is a figure which shows the structure of the crystal manufacturing apparatus by the vertical Bridgman method concerning Example 2. FIG.

Explanation of symbols

1,11,21,31 Crucible 2,12,22,32 Raw material, raw material solution 3,13,23,33 Crystal, grown crystal 4,14,24,34 Seed crystal 5,15,25,35 Temperature distribution in furnace 6 Heating element 7, 17 Defect

Claims (1)

Crystal growth is achieved by placing seed crystals in a crucible held in a furnace, heating and melting the raw material solution filled in the crucible, and gradually cooling the raw material solution upward from below the crucible. In the crystal manufacturing apparatus
The crystal manufacturing apparatus , wherein the seed crystal is arranged at a position distant from a central axis of the crucible so that a defect of the seed crystal propagates in an outer peripheral portion of the growing crystal .

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