JPS62115820A - Molecular beam crystal growth device - Google Patents

Abstract

PURPOSE:To allow growth of high quality impurity-free crystal and obtain a high performance semiconductor material by providing a shutter for capturing impurity comprising a control shutter and impurity accommodating part in front of the molecular beam source cell of molecular beam crystal growth device. CONSTITUTION:A movable shutter 21 for capturing vaporized substance is arranged in parallel with a opening and closing controllable control shutter 22 at the rear position of said shutter arranged in front of the molecular beam source cells of MBE device. Namely, the control shutter 22 is moved in the direction of arrow mark A in front of the opening 9 of molecular beam source cell, the shutter 21 for capturing impurity moves, in place of it, in the direction of arrow mark C and it is then arranged in front of the aperture 9 of molecular beam source cell. Under this condition, impurity, gas or vaporized substance from the molecular beam source material are adhered to the impurity shielding shutter surface and impurity is not adhered at all to the control shutter. Therefore, since vaporized substance of impurity adhered to the surface of foreign matter capturing shutter drops to and is accommodated in the impurity accommodating part of foreign matter capturing shutter, the peeled impurity drops into the impurity accommodation part and does not enter the molecular beam source cell even when the molecular beam growth device vibrates.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a structure of a shutter of a molecular beam source cell in a molecular beam crystal growth apparatus (hereinafter abbreviated as MBE apparatus), which comprises a molecular beam source charged in the molecular beam source cell. In order to remove gases and impurities contained in the material, the molecular beam source material is heated for a long period of time in an ultra-high vacuum, but at that time the molecular beam source material also evaporates in the ultra-high vacuum and its The evaporated material attaches to the low temperature molecular beam control shutter.

As a result, the deposits on the control shutter are peeled off during photographing when the control shutter is opened and closed and mixed into the molecular beam source cell, becoming a source of contamination of the molecular beam source.

The present invention provides an apparatus that performs high-quality epitaxial growth without contamination by foreign matter by newly providing a shutter for trapping foreign matter.

[Industrial Field of Application] The present invention relates to a molecular beam crystal growth apparatus, and particularly to the structure of a shutter disposed in front of a molecular beam source cell.

Recently, by using the molecular beam crystal growth method, it has become possible to create thin films with superlattice structures and multilayer heterojunction structures. Furthermore, since thin film formation conditions can be controlled with high precision, its use is rapidly increasing.

In particular, gallium arsenide (G) is used in new laser devices, including high electron mobility transistors (HEMTs).
aAs), aluminum, gallium arsenide (AIGaAs)
) The MBE method, which has good controllability, high quality, and excellent reproducibility, is used for forming thin films.

In general, in order to obtain high-quality epitaxial crystals, molecular beam sources used in MBE equipment charge the molecular beam source material and remove gases and impurities contained in the molecular beam source material prior to crystal growth. Must. As a method for removing impurities from the molecular beam source material, the impurities are removed by evaporation from the molecular beam source material by heating the material in an ultra-high vacuum for a long time.

At this time, in addition to gases and impurities contained in the molecular beam source material, a considerable amount of the molecular beam source material itself is evaporated due to heating.

However, in conventional MBE equipment, gases and impurities are removed while a low-temperature control shaft is placed in front of the molecular beam source, so all of the evaporated molecular beam source material and impurities are Adhere to the temperature control shutter. As a result, this deposit peels off due to vibrations caused by opening and closing of the control shaft, etc.
Since there is a problem that it mixes into the molecular beam source cell and becomes a source of contamination, there is a desire to improve this problem.

[Prior Art] As a conventional example, GaA used in HEMT etc.
s compound, aluminum gallium arsenide (AIGaAs)
Among the compounds, a case where a GaAs compound is grown using an MBE apparatus will be described.

FIG. 2 is a schematic cross-sectional view of essential parts showing the arrangement inside a conventional molecular beam crystal growth apparatus.

There is an ultra-high vacuum chamber 1 of a molecular beam crystal growth apparatus, and the degree of vacuum is normally maintained at an ultra-high vacuum of 1Q-Torr or less. is heated to a temperature of 600°C to 700°C.

Each molecular beam source cell is charged with a predetermined raw material, and arsenic 7 and gallium 8 are passed through the molecular source cell 5 filled with arsenic and the molecular source cell 6 filled with gallium, respectively. Only filled.

The material used for the molecular beam source cell is usually pyrolytically deposited boron nitride (PBN), which has high purity and does not easily chemically react with gallium or arsenic. The shape of the molecular beam source cell is usually a cylindrical or conical crucible with an opening 9 of a perfect circle.

When crystal growth is performed in an MBEW device, the entire vacuum container is heated at approximately 250'C for a long period of time in order to remove gas and moisture adhering to the inner wall of the vacuum container of the MBE device. Perform degassing. Subsequently, heating is performed to remove gas and impurities from the molecular beam source material filled in each molecular source cell. In this case, a control shutter 11 is disposed in front of the molecular beam source cell to prevent evaporated matter from being deposited around the substrate support. As a result, the molecular source material and the impurities contained therein evaporate and adhere to the surface of each control shutter.

Next, when growing a crystal of a gallium arsenide compound, the control shutter 11 is moved in the direction of arrow A, the molecular beam source cell 5 filled with arsenic 7 is heated to about 300°C, and the molecular beam source cell 5 filled with arsenic 7 is heated to about 300°C. The molecular beam source material is evaporated by heating the molecular beam source cell 6 to about 1000°C.

The evaporated arsenic and gallium molecules evaporate from each molecular beam source cell 5.6 toward the substrate support and grow on the substrate. At a growth rate of about 1 μm/hr,
High quality gallium arsenide compounds are grown.

However, the film of impurities attached to the control shutter is 1. Due to vibrations, shocks during opening and closing, etc., these impurities enter the molecular source cell and cause contamination of the molecular beam material. Particularly in the case of gallium, the gallium that adheres to the control shutter is in the form of a viscous melt, so it adheres quite thickly. The extent to which gallium falling from the attached portion contaminates the molecular beam source increases. Further, the gallium that has adhered to the control shutter flows out and adheres to the movable parts of the shutter, resulting in problems such as inhibiting the function of the shutter.

In the case of arsenic, if arsenic adheres to a certain thickness on the control shutter, it will peel off and scatter, causing the same drawbacks as in the case of gallium.

[Problems to be Solved by the Invention] The conventional control shank placed in front of the molecular beam source cell of the MBEvi device has the problem that impurities and the molecular beam source material are deposited during heating of the molecular beam source material. The problem is that the deposits may peel off and fall due to vibrations or the like, enter the molecular source cell, and reduce the purity of the molecular beam source material.

c. Means for solving the problems The present invention provides an MBE apparatus for solving the above problems. The problem is solved by arranging a movable stem capture shutter parallel to the control shutter in a rear position of the control shutter.

[Function] The present invention prevents evaporated matter from adhering to the control shutter disposed on the i:1 side of the molecular beam source cell when heating the molecular beam source cell of the MBE apparatus to purify the molecular beam material. This is to prevent the evaporated matter from entering the molecular source cell and reducing the purity of the molecular beam source material. When heating the molecular beam source material for purification, the control shutter is moved from the front of the molecular beam source cell. Instead, a movable foreign matter trapping shutter is placed in front of the molecular beam source cell. Impurities are attached to the surface of the shutter for trapping foreign matter, and after the impurities are sufficiently removed from the molecular beam source material, the shutter for trapping foreign matter hti is removed. Then, the control shutter is moved to the front of the molecular beam source cell again. As described above, when impurities are removed from the molecular beam material, the vapor deposits are removed by appropriately opening and closing both the shutters and the valve, thereby preventing re-contamination. This makes it possible to grow epitaxial crystals of high quality and uniformity.

[Example 1] Figures 1(a) to 1(bl are schematic cross-sectional views of essential parts for explaining the operation of the molecular beam crystal growth apparatus according to the present invention.

FIG. 1(a) shows a state in which the molecular beam source material is heated to purify impurities.

The substrate 2, substrate holder 3, molecular beam source cell 5.6, and molecular beam source material 7.8 in the vacuum container 20 are the same as those shown in FIG.

In front of the opening 9 of the molecular beam source cell, a control shutter 2 is installed.
2 is moved in the six directions of the arrow, and the moving impurity trapping shutter 21 is moved in the direction of the arrow C to be placed in front of the opening 9 of the molecular beam source cell.

In this state, impurities, gases, or evaporated substances from the molecular beam source material adhere to the impurity shielding shutter surface, whereas no impurities adhere to the control shutter surface.

FIG. 1(bl) shows the operation of the control shutter and the impurity trapping shutter during epitaxial growth performed after In purification of the molecular beam source cell shown in FIG. 1(a).

In this state, the impurity trapping shutter 21 to which impurities and evaporated substances have adhered moves in the direction D shown by the arrow from the front of the opening 9 of the molecular beam source cell, and the control shutter 22 replaces the molecular beam source cell. The molecular beam crystallization sphere is controlled by moving in the direction of arrow B in front of the opening and opening and closing as appropriate.

Therefore, the evaporated substances of impurities attached to the surface of the shutter for trapping foreign matter fall and are stored in the impurity storage section 23 provided at the bottom of the shutter for trapping foreign matter, so even if there is vibration etc. in the molecular beam crystal growth apparatus. The peeled impurities fall into the impurity storage section and do not mix into the molecular beam source cell.

[Effects of the Invention] As explained above in detail, by providing a control shutter and an impurity trapping shutter including an impurity storage section on the front side of the molecular beam source cell of the molecular beam crystal growth apparatus according to the present invention, This has the great effect of allowing the growth of high-quality crystals free of impurities and providing high-performance semiconductor materials.

[Brief explanation of drawings]

1(a) to 1(b) are schematic cross-sectional views of main parts showing the function of the shutter of the molecular beam source cell of the present invention, and FIG. 2 shows the function of the shutter of the conventional molecular beam source cell. 2 is a substrate, 3 is a substrate holder, 5.6 is a molecular beam source cell, 7.8 is a molecular beam source material, 9 is an opening, 21 is an impurity trapping shutter, 22 23 indicates a control shank, and 23 indicates an impurity storage section. Representative of Printing Construction and Repairs Irika Sat 1jII Figure 2

Claims (1)

[Claims] A substrate holder that holds a substrate, a molecular beam source cell that accommodates a molecular beam source material, and an openable and closable control shutter disposed in front of an opening (9) of the molecular beam source cell. (22), and an impurity trapping shutter (21) provided closer to the substrate holder than the control shutter (22), and the impurity trapping shutter (21) traps evaporated matter from the molecular beam source cell. and a storage part that stores the captured substance, and is movable so as to cover the opening when heating of the molecular beam source material with a heater starts and to be removed during crystal growth. A molecular beam crystal growth apparatus characterized by the following.