Molecular beam epitaxy apparatus

[Detailed Description of the Invention]

Field of the Invention The present invention relates to a molecular beam epitaxy system. PRIOR ART Molecular beam epitaxy is the method of performing epitaxy crystal growth, making the molecular beam which evaporated crystal material in the ultrahigh vacuum by heating etc. vapor-deposit slowly on a crystal base board. By this method, it has the features which are not in other crystal growth methods -- control by the ultra-thin film of a monoatomic layer is possible, and simultaneous observation is possible in crystal growth. In molecular beam epitaxy, the most important point is a degree of vacuum. When a degree of vacuum is bad, the impurities molecule which remains in a vacuum is taken in during a crystal, and worsens crystal quality. Generally, a degree of vacuum is 6x10 in order to obtain a quality crystal. To be the following is demanded. The molecule (H2O) of the water which is a remains impurities molecule, or carbon dioxide (Co2) is removed as much as possible. Thus, in order to maintain the inside of a device at an ultrahigh vacuum, it is reducing the number of times of exposing the inside of the most effective method device to the atmosphere. Once it will expose the inside of a device to the atmosphere, it will add to needing to be vacuum exhausted for several days, in order to acquire the state of the ultrahigh vacuum of a basis, and will take in again the impurities molecule which has a bad influence on crystal quality out of the atmosphere. In the molecular beam epitaxy system by conventional technology, the number of times of exposing the inside of a device to the atmosphere has increased for the reason of two points as follows. In the case of failure [ a device ], the 1st point could not but expose the inside of a device to the atmosphere for repair of failure. The 2nd point needed to be exposed to the atmosphere, in order to fill up materials with the case of drain of materials periodically. In the molecular beam epitaxy system by conventional technology, failure of these devices and the problem of drain of materials have the method of improving the homogeneity of growth film thickness, and deep relation directly. In conventional technology, in order to acquire high homogeneity, the method of rotating a crystal base board, and the method of shifting the plane direction of a crystal base board remarkably to the radial direction of the molecular beam of materials are used together. In the method of rotating a crystal base board, the homogeneity of growth film thickness can be improved from K as if it is equalized by rotation even if the amount of molecular beams in the crystal base board surface is uneven. However, since it is necessary to also take into consideration simultaneously the temperature controllability of a crystal base board, and the homogeneity of temperature when rotating a crystal base board, a rotating machine style is complicated. Since it is used in an ultrahigh vacuum in spite of such a complicated mechanism and any lubricating oil cannot be used for moving parts, the life of moving parts has been contracted remarkably. Therefore, most failures which occur inside a device are based on this rotating machine style. The method of shifting the plane direction of a crystal base board to the radial direction of the molecular beam of materials can improve the homogeneity of film thickness by taking the small solid angle which looked at the crystal base board from the source of a molecular beam. However, by this method, it evaporates from the source of a molecular beam, and most of all the molecular beams are not deposited on a crystal base board, but several percent of all the molecular beams is effectively used on a crystal base board. Since this cannot perform effective use of materials, it brings drain of materials forward remarkably, and it is making the number of times of supply of materials increase. The problem which an invention tends to solve Problems which the present invention tends to solve are reducing failure of a crystal base board rotating machine style in conventional technology, and raising utilization efficiency of materials. The object of the present invention is to raise a working ratio of a device at the same time it reduces the number of times of removing these problems and exposing an inside of a molecular beam epitaxy system to the atmosphere and makes quality of a growth crystal improve. A useless means to solve a problem The means for solving the problem by the present invention is that the radiation axis used as the maximum of the molecular beam radiant quantities of the source of a molecular beam makes the source of a molecular beam movable so that the main surface top of a crystal base board may be scanned. OPERATION By the present invention, since the amount of molecular beams emitted from the source of a molecular beam is scanned in a substrate face, it becomes uniform on the average, and it can obtain the uniform epitaxial growth layer of film thickness. For this reason, the complicated substrate rotation mechanism explained previously becomes unnecessary, and can remove many causes of fault accompanying a substrate rotation mechanism. Since the radiation axis used as the maximum of molecular beam radiant quantities is scanned on the crystal base board surface and a molecular beam can be effectively used for epitaxial growth, drain of the materials of the source of a molecular beam is delayed, and To give up is made. It becomes possible to raise the efficiency of crystal growth and to obtain a quality crystal to stability for this reason of two points, since the number of times of exposing the inside of a molecular beam epitaxy system to the atmosphere decreases sharply. EXAMPLE The example by the present invention explains molecular beam epitaxy growth of a gallium arsenide (henceforth, GaAs) semiconductor crystal to an example, and shows the example in a figure. 1 is a molybdenum substrate maintenance stand and, as for 2, Ah Si and 3 are heaters which heat a G a A s single crystal board via molybdenum substrate maintenance stand 1 in a G a A s single crystal board. 4 is metal Ga of high purity from the materials of the source of a gallium (henceforth, Ga) molecular beam. 5 is a container which comprises boron nitride and 6 is a heater for heating the source of a molecular beam. Although 7 is a vacuum vessel which covers the source of a molecular beam and 8 is a vacuum vessel similarly, it is a bellows type vacuum vessel so that the molecular beam radial direction of the source of a molecular beam can be changed freely. G In the molecular beam epitaxial growth of a A s, although two sorts of molecular beams, the molecular beam of Ga and the molecular beam of As+, are required, the growth rate of the grown-up G a A a growth layer is determined by the amount of molecular beams of Ga. Therefore, since the homogeneity of Ga molecular beam is required to consider the homogeneity of film thickness, the source of a molecular beam of As is not shown in Drawing 1, but is an example only about the source of a molecular beam of Ga. As shown in a figure, 9 is the maximum radial direction of Ga molecular beam, but the maximum radial direction has G a A s crystal base board 2 top scanned on deflection square theta. Therefore, the average of the amount of Ga molecular beams which reaches on G a A s crystal base board 2 obtains the uniform growth layer of a fixed quantity and the Si film thickness. Therefore, G a A g crystal base board 2 does not need any rotating machine style. Failure of the substrate maintenance stand became that there is nothing. Since effective use of the source of Ga molecular beam was completed, the time to drain of metal Ga which is materials of Ga molecular beam became long 4~6 times as compared with the case where it is based on conventional technology. EFFECT OF THE INVENTION Since it could decrease sharply and failure of effective use of the source of a molecular beam in a device was moreover completed by using the molecular beam epitaxy system by the present invention, the effect of the present invention was also able to reduce the number of times of a supplement of materials. 0 which could stabilize [ grow the crystal of the good-quality item epitaxially since the number of times that a big effect exposed the inside of a device to the atmosphere for a supplement of failure and materials decreased sharply

[Brief Description of the Drawings]

A figure is a schematic diagram of the molecular beam epitaxy system of one example by the present invention. 1 ...... substrate maintenance stand, 2 ...... crystal base board, 4 ...... source of a molecular beam, 9 ...... the molecular beam radial direction where the amount of molecular beams serves as the maximum, and theta ...... Deflection angle of a molecular beam radial direction.