JP2825974B2 - Molecular beam source container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a thin film forming method suitably used for forming a laminated structure using a highly controlled thin film, such as various electronic devices and optical devices. Molecular beam epitaxy equipment (MB used in molecular beam epitaxy method)
E device) for the molecular beam source container for containing the solid raw material.

[Prior art] The molecular beam epitaxy is a non-equilibrium film forming method using an ultra-high vacuum, and therefore is a low-temperature process in an extremely clean environment. Because it can form a steeper interface, this technology is widely used from scientific research on thin film crystal growth to application development.

That is, in the molecular beam epitaxy method, a raw material is put into a molecular beam source container usually called a K cell (Knudsen cell), and heated to, for example, 100 to 1200 ° C. by a heater such as tungsten provided around the cell. Heat the cell, 10
^In this method, the raw material is evaporated by applying a high vacuum of about ^-9 to 10 ^-11 Torr, and the raw material molecules or atoms are supplied to the substrate in the form of a molecular beam from a molecular beam source. Since such a molecular beam epitaxy method can form an extremely thin film with good control, it has been frequently used in recent years as a method of forming a thin film.

When a solid raw material is used as a raw material, a crucible (usually made of graphite, boron nitride (PBN) or quartz glass) made of a material having excellent heat and corrosion resistance called a K cell, that is, A raw material is put in a molecular beam source container, and a molecular beam is generated under high vacuum and heating as described above to form a thin film. In the case of a gaseous raw material, it is extracted as a necessary molecular beam by cracking or the like.

Solid raw materials include, for example, elements such as Zn, Cd, and As, and compounds such as CdS and ZnS, and the like.
They also take different forms, such as rods, chunks, powders, etc., depending on the processing. Since metal and the like are relatively easy to process and form, a highly pure metal can be obtained in a shape suitable for the purpose. However, this is not always possible in all cases, and in particular, there are many cases where a raw material having a desired purity cannot be obtained unless a compound or the like is in a powder form.

FIG. 2 is a cross-sectional view of a conventional molecular beam source container containing a solid powder material.

It is a tubular container having an opening 1 of the container at the top and comprising a bottom 2 and side walls 3. A solid powder raw material 4 serving as a molecular beam source is placed inside the container, and a heater (not shown) is provided around the molecular beam container, and the raw material 4 is heated under high vacuum as described above. Then, it is taken out from the opening 1 of the container as a molecular beam.

[Problems to be Solved by the Invention] In the molecular beam epitaxy method, the molecular beam intensity is controlled by the temperature, and when the raw material is a rod or a chunk, the stability is relatively good. During this period, for example, for several hours, a molecular beam having almost constant intensity is obtained once the temperature of the raw material becomes constant. However, when a powdery raw material is used, the effect of the residual amount of the raw material in the container is large. Particularly, when the heating temperature required for obtaining the molecular beam is high and the raw material consumption is large, several hours are required. It is difficult to maintain a uniform molecular beam intensity even if the film is formed to a certain degree.

In film formation by the molecular beam epitaxy method, a stable molecular beam is required for controlling a thin film crystal structure, particularly, a superlattice structure.

An object of the present invention is to provide a molecular beam source container capable of supplying a stable molecular beam in film formation by a molecular beam epitaxy method.

Means for Solving the Problems In order to solve the above problems, the present invention is directed to a tubular container having an opening at the top, in which a solid raw material is placed inside and heated to generate a molecular beam of the raw material. An auxiliary shelf for storing the solid raw material is provided inside the container to be used, the auxiliary shelf has an opening at a substantially central portion thereof, and the opening of the container is provided around the opening of the auxiliary shelf. An object of the present invention is to provide a molecular beam source container having a wall protruding in a direction.

[Operation] The molecular beam source container according to the present invention has an auxiliary shelf for storing a solid raw material having an opening at a substantially central portion and having a wall whose peripheral portion protrudes toward the opening direction of the container. Since the raw material can be put not only in the bottom of the container but also in this auxiliary shelf, by using a container having such an internal structure, the molecular beam obtained can be averaged from the upper and lower parts in the container. Therefore, the residual amount of the raw material, that is, the position of the uppermost part of the raw material is less affected by gradually lowering toward the bottom of the container, and a molecular beam having a stable intensity can be obtained.

Embodiment An embodiment will be described below in detail with reference to the drawings.

FIG. 1 is a conceptual view of a molecular beam source container according to one embodiment of the present invention, and FIG. 1 (a) is a plan view seen from the opening side of the molecular beam source container. FIG. 1 (a) shows b)
FIG. 3 is a cross-sectional view of the molecular beam source container taken along line AA ′ of FIG.

The molecular beam source container according to the embodiment of the present invention has an opening 1
And a tubular container in which the side wall 3 and the bottom 2 are integrally formed. Inside the side wall 3 of the container, there is provided an auxiliary shelf 6 for accommodating the solid raw material, and the auxiliary shelf 6 has an opening 7 at a substantially central portion thereof, and the raw material existing below the shelf is provided. Molecular beam can pass through. The periphery of the opening 7 of the auxiliary shelf 6 for storing solid raw materials is
A raw material storage space 9 which has a wall 8 protruding toward the direction of the opening 1 of the container and is surrounded by a container side wall 3 and a solid raw material storage auxiliary shelf 6 having the wall 8 also has a molecular beam source. Can be stored.

The material constituting the molecular beam source container of the present invention has sufficient heat resistance, and does not react with various raw materials,
Since a material that does not degas is required for use in an ultra-high vacuum, boron nitride (PBN), graphite, quartz glass, or the like is preferably used.

The number of the auxiliary shelves 6 for storing the solid raw material provided in the molecular beam source container is one or more, and it depends on the kind of the raw material, how much thin film is to be formed, the thin film forming time, and the like. However, it is usually preferable to provide about 1 to 5 steps.

Although the size of the opening 7 is not particularly limited, it is usually preferable to set the size to about 5 to 20% of the area of the cross section of the container.

Since the size of the molecular beam source container differs depending on the size of the apparatus used, it is difficult to specify the size, but usually, the diameter of the container is about 10 to 50 mm and the length is about 20 to 200 mm.

Next, based on FIGS. 2 and 3, a comparison of molecular beam intensity between a conventional molecular beam source container (hereinafter abbreviated as a cell) and the cell of the present invention will be described. FIG. 3 is a cross-sectional view of a cell according to an embodiment of the present invention (however, a state in which a solid powder raw material is inserted). FIG. 1B, the same parts are denoted by the same reference numerals as in FIG. 1B, and the description of each part is omitted.

An experiment using CdS as an example of a powder raw material was performed.
Using a conventional molecular beam epitaxy apparatus, the degree of vacuum in the growth chamber was set at about 5 × 10 ⁻¹⁰ Torr. The molecular beam intensity is measured by an ionization vacuum gauge attached to the manipulator. A CdS powder was added as a solid powder raw material 4 to the conventional cell (FIG. 2) and the cell of the present invention (FIG. 3) as shown in the figure, so that the molecular beam intensity became 2 × 10 ⁻⁶ Torr. The time change of the set temperature of the cell heater was measured.

The results are shown in FIG. 4 shows the case where the cell of the embodiment of the present invention shown in FIG. 3 is used, and 11 shows the case where the conventional cell shown in FIG. 2 is used. In the conventional cell as shown in FIG. 11, the set temperature required to keep the molecular beam intensity constant changes with time, whereas in the case of the cell of the present invention, several hours are constant as shown in FIG. Therefore, it can be seen that even when a powdery raw material is used, an extremely stable molecular beam can be obtained during the usual one-time film formation.

[Effects of the Invention] According to the present invention, when a thin film or the like is manufactured by a molecular beam epitaxy method, a molecular beam having a stable intensity can be obtained for a long time, and a feedback system for controlling a complicated temperature is required. It is possible to provide a molecular beam source container capable of achieving a high-precision molecular beam intensity without using the same.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a molecular beam source container according to an embodiment of the present invention, wherein FIG. 1 (a) is a plan view of the molecular beam source container viewed from the opening side, and FIG. 1A is a cross-sectional view of the molecular beam source container taken along line AA 'of FIG. 1A, FIG. 2 is a cross-sectional view of a conventional molecular beam source container in which a solid powder raw material is placed, and FIG. FIG. 4 is a cross-sectional view showing a state in which a solid powder raw material is placed in a molecular beam source container of the example. FIG. . DESCRIPTION OF SYMBOLS 1 ... Opening of container, 2 ... Bottom part, 3 ... Side wall, 4 ... Solid powder raw material, 6 ... Storage shelf of solid raw material, 7 ... Opening, 8 ... Projected wall, 9 ... ... space for storing raw materials, 10
... the present invention, 11 ... conventional examples.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tsuneo Sanro 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-1-305895 (JP, A) JP-A Sho 59-64594 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C30B 1/00-35/00 H01L 21/203

Claims (1)

(57) [Claims] 1. A tubular container having an opening at an upper part thereof,
An auxiliary shelf for storing the solid raw material is provided inside a container used to generate a molecular beam of the raw material by putting the solid raw material therein and heating the auxiliary raw shelf, and the auxiliary shelf has an opening at a substantially central portion thereof. A molecular beam source container having a wall protruding toward the opening direction of the container around the opening of the auxiliary shelf.