JP5536816B2 - K-cell crucible, K-cell, and MBE device - Google Patents

Description

  The present invention relates to a crucible for a K cell, a K cell, and an MBE apparatus, and more particularly to a crucible for a K cell for obtaining a molecular beam of silicon, a K cell, and an MBE apparatus including the crucible.

  A molecular beam epitaxy (MBE) apparatus is used to deposit a layer of a semiconductor material or the like on a substrate with good controllability. In a molecular beam epitaxy apparatus, a material such as gallium or indium is heated by putting a material such as gallium or indium into a Knudsen-Cells (hereinafter referred to as “K cell”) placed in a vacuum chamber, and the molecules are evaporated. A layer of these materials is grown on a substrate, which is a line and is also placed in a vacuum chamber. When silicon is used as a material, since the melting point of silicon is as high as 1414 ° C., there is a problem that when a conventional PBN (Pyrolytic Boron Nitride) crucible is used, the crucible and silicon react at a high temperature. On the other hand, a method of dissolving silicon using an electron beam instead of the K cell has been proposed, but there are problems such as poor controllability of molecular beams and difficulty in miniaturization.

  In contrast, when the crucible for the K cell is formed from a refractory metal such as W, Ta, or Mo, and the silicon melts, the crucible material and silicon react with the inner wall of the crucible to form a metal silicide. There has been proposed a crucible for a K cell that prevents the reaction with the silicon crucible material at a high temperature by protection (see, for example, Patent Document 1).

JP-A-10-214787

In a crucible made of a refractory metal, resistance to silicon is improved by forming silicide on the inner surface, but when used at a high temperature for a long time, the reaction between the crucible and silicon proceeds and the crucible is deformed. For this reason, there was a problem that the life of the crucible was shortened to about 100 hours.
In addition, when the thickness of the crucible is about 1 mm as in a normal PBN crucible, silicon melts the crucible when forming the metal silicide, and a hole is formed. Therefore, the thickness of the crucible needs to be at least about 3 mm. For this reason, the diameter of the opening of the crucible is reduced, the flux strength of the molecular beam is reduced, and in order to increase the flux strength, it is necessary to further increase the temperature, and there is a problem that the life of the crucible is shortened.
Further, the K cell has a problem that impurities are mixed into the growth film because the heater insulating material made of PBN or the like decomposes at a high temperature such as the melting point of silicon.

  Accordingly, an object of the present invention is to provide a crucible for K cells, a K cell, and an MBE apparatus that can stably supply a molecular beam of high-strength silicon without being mixed with impurities and that has a long lifetime.

  The present invention relates to a crucible for a K cell characterized in that the surface of a crucible made of carbon is coated with tantalum carbide, or a surface of a crucible made of tantalum coated with tantalum carbide. Concerning crucible for use.

  Further, the present invention is a cylindrical reflector having a crucible inserted from one end and a base plate provided at the other end, and attached to the base plate inside the reflector so as to heat the inserted crucible. Including a heater, and the heater is a K-cell that is self-supporting in the space inside the reflector, or a cylindrical reflector having a crucible inserted from one end and a base plate provided at the other end. A heater attached to the base plate inside the reflector and a heater support attached to the base plate inside the reflector so that a part of the heater is supported by the heater support so as to heat the crucible The present invention relates to a K cell, which is disposed in a space inside a reflector.

  Moreover, this invention relates to the molecular beam epitaxy apparatus provided with the said K cell.

  As described above, by using the crucible for K cell, the K cell, and the MBE apparatus of the present invention, it is possible to stably supply a molecular beam of silicon having a high flux strength, and to provide a long life for the crucible for K cell and K cell. Can be realized. In addition, a growth film free from impurities can be obtained.

It is the schematic of the MBE apparatus concerning embodiment of this invention. It is sectional drawing of the crucible concerning embodiment of this invention. It is a fragmentary sectional view of K cell concerning an embodiment of the invention. It is the schematic of K cell concerning embodiment of this invention.

  FIG. 1 is a schematic diagram of an MBE apparatus according to an embodiment of the present invention, indicated as a whole by 500. The MBE apparatus 500 includes a chamber 510. The chamber 510 is provided with a holder 520, and a substrate 530 such as silicon is disposed on the holder 520. A plurality of K cells 100 and their shutters 120 are attached to the flange 110, which is attached to the chamber 510.

  The chamber 510 is evacuated by a vacuum pump (not shown) and kept at a high vacuum. A plurality of K cells 100 are arranged so as to face the substrate holder 530. A crucible (see FIG. 2), which will be described later, is inserted into each K cell 100, and a film-forming material such as silicon, germanium, gallium, or arsenic is inserted into the crucible.

  When the material in the crucible using the K cell is heated, the molecular beam 130 is irradiated toward the substrate 530. The molecular beam 130 is supplied to the substrate 530 by opening and closing the shutter 120 between the substrate 530 and the K cell 100.

  FIG. 2 is a cross-sectional view of a crucible for a K cell according to an embodiment of the present invention, the whole being represented by 20. The crucible 20 is a cylindrical cup, and a flange is provided around the opening. The dimensions of the crucible 20 are, for example, a height h of 90 mm, a thickness t of 1 to 2 mm, a flange diameter r of 33 mm, and an opening diameter r ′ of 19 mm.

  The crucible 20 is made of carbon (C), and the surface thereof is coated with tantalum carbide (TaC). The coating is performed using, for example, a CVD method, and the film thickness of the coated tantalum carbide is, for example, 20 μm. The coating is usually performed on the entire crucible 20, but at least the inner wall of the crucible 20 needs to be coated.

  The crucible 20 may be made of tantalum (Ta), and the surface thereof may be coated with tantalum carbide (TaC). The coating is performed using, for example, a carburizing method, and the thickness of the coated tantalum carbide is, for example, 200 μm. The coating is usually performed on the entire crucible 20, but at least the inner wall of the crucible 20 needs to be coated.

  In the crucible 20 according to the embodiment of the present invention, since the surface of the crucible 20 made of carbon or tantalum is coated with tantalum carbide, silicon is put in the crucible 20 and is, for example, 1400 ° C. or higher, preferably 1500 ° C. or higher. Even if silicon is melted at a high temperature, the material of the crucible 20 and silicon do not react. For this reason, it is possible to extend the life of the crucible 20 more than twice as compared with the case of the conventional refractory metal crucible. Further, since the material of the crucible 20 is not melted, a growth film free from impurities can be formed.

  Also, the film thickness t of the crucible 20 can be about 1 to 2 mm, which is equivalent to that of the PBN crucible, and is thinner than 3 mm or more of the high melting point metal crucible. For this reason, the diameter r ′ of the opening is also increased, and the flux intensity of the molecular beam can be increased at the same heating temperature.

  FIG. 3 is a partial cross-sectional view of the K cell according to the embodiment of the present invention, indicated as a whole by 100. XX is a center line in the longitudinal direction of the K cell 100, and FIG. 3 shows a cross section of the left half of the K cell. For ease of understanding, a part of the vertical direction is omitted, and the illustrated dimensions do not correspond to actual dimensions.

  The K cell 100 according to the embodiment of the present invention includes a cylindrical reflector 1. The reflector 1 is made of a refractory metal such as W, Ta, or Mo. One end (upper end) of the reflecting plate 1 has an opening, and a crucible 20 (indicated by a broken line) is inserted therein. The flange portion of the crucible 20 is placed on the upper end of the reflecting plate 1 and is fixed by a claw (not shown) provided at the end portion of the reflecting plate 1. A base plate 2 made of, for example, Mo is fixed to the other end (lower end) of the reflection plate 1. On the base plate 2 is also provided a reflector 3 made of a refractory metal such as W, Ta, or Mo. The temperature of the crucible 20 is measured by a thermocouple (not shown) provided so as to contact the bottom of the crucible 20 from below.

  The lead portions 5 of the heater 6 are fixed to the base plates 2 and 12 using an insulating bush 7 made of alumina, for example, and a fixture 8 made of Mo, for example. A rod 10 is provided below the base plate 12, and the other end of the rod 10 is fixed to a flange (indicated by reference numeral 110 in FIG. 2).

  The heater 6 includes a heat generating portion 4 made of W or Ta and a lead portion 5 made of Ta. The heat generating part 4 is a metal wire having a diameter of 0.2 to 2.0 mm, preferably 0.6 to 1.0 mm, and may be spiral or linear as shown in FIG.

  Further, a heater support 9 made of, for example, W or Ta is fixed to the base portion 2. The heater support 9 extends in a direction parallel to the XX axis, and has a structure in which the heat generating portion 4 is suspended and supported at the upper part. Thereby, the heater 6 is arrange | positioned in the space between the reflecting plate 1 and the crucible 20 without contacting a heater insulating material etc. When the heat generating part 4 of the heater 6 is relatively thick, the heat generating part 4 is in a self-supporting state in the space between the reflector 1 and the crucible 20 without providing the heater support 9, that is, the heater support or the heater insulation. It is held without being supported by the material.

  FIG. 4 is a schematic view when the K cell 100 according to the embodiment of the present invention is viewed from the opening in the XX axis direction. As shown in (a), a plurality of heaters 6 extending in the XX axis direction may be provided between the crucible 20 and the reflector. In this case, the heater 6 is evenly arranged around the crucible 20 so that the crucible 20 is uniformly heated. Moreover, as shown in (b), the heater 6 may surround the periphery of the crucible 20 in a spiral shape.

  As described above, in the K cell according to the embodiment of the present invention, the heater 6 has a structure that is held hollow by the heater support 9 made of W or Ta or a self-supporting structure. It is not in contact with the heater insulation material. Therefore, even if the temperature of the crucible 20 is heated to a temperature equal to or higher than the melting temperature of silicon (1414 ° C.) in order to obtain a molecular beam of silicon, decomposition of PBN or the like does not occur and a growth film free from impurities can be produced.

  The crucible 20 (FIG. 2) is preferably attached to the K cell 100 (FIG. 3), but may be attached to another K cell. Further, a crucible other than the crucible 20 may be inserted into the K cell 100 described above.

DESCRIPTION OF SYMBOLS 1 Reflecting plate 2 Base plate 3 Reflecting plate 4 Heat generating part 5 Lead part 6 Heater 7 Insulating bush 8 Fixing bracket 9 Heater support 10 Rod 12 Base board 20 Crucible 100 K cell 500 MBE apparatus

Claims (8)

  A crucible for K cell, wherein the surface of a crucible made of carbon is coated with tantalum carbide.   A crucible for K-cell, characterized in that the surface of a tantalum crucible is coated with tantalum carbide.   The crucible for a K cell according to claim 1 or 2, wherein the crucible is used for forming a molecular beam of silicon. A K-cell for heating the crucible,
A cylindrical reflector with a crucible inserted from one end and a base plate provided at the other end;
A heater attached to the base plate inside the reflector so as to heat the inserted crucible,
The K-cell is characterized in that the heater is independent from a heater insulating material and is self-supporting in a space inside the reflector. A K-cell for heating the crucible,
A cylindrical reflector with a crucible inserted from one end and a base plate provided at the other end;
A heater attached to the base plate inside the reflector so as to heat the inserted crucible;
A heater support attached to the base plate within the reflector,
A K cell, wherein a part of the heater is supported by the heater support, and the heater is disposed in a space inside the reflector without contacting a heater insulating material .   The K cell according to claim 4 or 5, wherein the heater is disposed between the reflector and the crucible when a crucible is inserted into the K cell.   A molecular beam epitaxy apparatus comprising the K cell according to claim 4.   The molecular beam epitaxy apparatus according to claim 7, wherein the crucible according to claim 1 is inserted into the K cell.

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