JPH02199818A - Molecular beam crystal growth apparatus - Google Patents

Abstract

PURPOSE:To always observe a reflection electron diffraction image during a growth operation by a method wherein a bellows is installed between a growth-chamber upper part in which a manipulator and a reflection high-energy electron diffraction apparatus have been installed and a growth-chamber lower part in which a molecular-beam source has been installed and the growth-chamber upper part and the growth-chamber lower part are constituted so as to be movable independently of each other. CONSTITUTION:A growth-chamber upper part 10 in which a manipulator 1, a reflection high- energy electron diffraction apparatus 3 and a fluorescent screen 4 have been installed is connected, via a bellows 12, to a growth-chamber lower part 11 in which a molecular-beam source 6 has been installed. When the bellows 12 is expanded and contracted, it is possible to change a distance between a semiconductor substrate 2 and the molecular-beam source 6 and their angle. During this process, since both the semiconductor substrate 2 and the reflection high-energy electron diffraction apparatus 3 are installed in the growth-chamber upper part 10, a positional relationship among the semiconductor substrate 2, the reflection high-energy electron diffraction apparatus 3 and the fluorescent screen 4 is not changed even when the semiconductor substrate 2 is moved with reference to the molecular-beam source 6. Thereby, when a graded mixed crystal is grown by changing the angle of the substrate, it is possible to observe a reflection electron diffraction image during this growth operation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a molecular beam crystal growth apparatus for growing thin film crystals of compound semiconductors on semiconductor substrates.

(Prior Art and Problems to be Solved) One of the techniques for epitaxially growing a thin film crystal of a compound semiconductor such as GaAs or JGaAs on a semiconductor substrate such as CaAs is the molecular beam crystal growth method (XBE method).

In this IBE method, a shroud cooled with liquid nitrogen is installed in a growth chamber that can reach an ultra-high vacuum state of 10 to 10 inches, and a semiconductor substrate held by a manipulator is placed in the center of the shroud. Then, facing this semiconductor substrate, a molecular beam source is installed in which a crucible is filled with the constituent elements and dopant source materials of the semiconductor crystal to be epitaxially grown.The molecules are heated by the molecular beam source and turned into molecular beams. A source material is irradiated onto a semiconductor substrate heated to an appropriate temperature to grow epitaxially.

Since such an IBE method has extremely good controllability, it is widely used as an epitaxial growth technique for various semiconductor devices.

Some high-speed devices and light-emitting devices use epitaxial films that have a composition distribution in the film thickness direction.

As a method for growing an epitaxial film having such a structure using the IBH method, there is a method in which the angle between the substrate and each molecular beam source is changed by manipulating the substrate during growth.

When growing a film with a compositional distribution in the film thickness direction, the composition on the growth surface changes over time, so by observing the backscattered electron diffraction image during growth,
It is expected that we will receive detailed information regarding growth.

However, in such devices, while the substrate is movable, the reflection high-speed electron diffraction device is fixed in the growth chamber of the molecular beam crystal growth device, so the substrate cannot be moved during growth. During operation, the substrate and the high-speed reflection electron diffraction device do not move together, resulting in a problem that the reflection electron diffraction image cannot be observed at all times during growth.

(Means for Solving the Problems) The present invention solves the above-mentioned problems and provides a molecular beam crystal growth apparatus that allows reflection electron beam diffraction to be observed at all times during growth. A bellows is provided between the upper part of the growth chamber where the reflection high-speed electron diffraction device is installed and the lower part of the growth chamber where the molecular beam source is installed, so that the upper part of the growth chamber and the lower part of the growth chamber can be moved independently. .

FIG. 1 is a sectional view of a specific example of a growth chamber in the molecular beam crystallization apparatus of the present invention.

As shown in the drawing, a manipulator (1) that heats, rotates, and holds a semiconductor substrate (2) to an appropriate temperature is installed in the center of the upper part (10) of the growth chamber, and a high-speed reflection An electron beam diffraction device t (3) is installed, and a fluorescent screen (4) is installed on the other side opposite to this. Further, in the lower part (11) of the growth chamber, a semiconductor constituent element such as Ga1 is placed at a position facing the manipulator (1).
Crucibles (HA) (8B) (B
A molecular beam source (6) equipped with G) is installed. A bellows (12) is provided between the growth chamber upper part (10) and the growth chamber lower part (11) to connect them. In the drawings, (5) is a liquid nitrogen shroud placed inside the growth chamber.

(Function) The above-described molecular beam crystal growth apparatus of the present invention includes a manipulator (1), a reflection high-speed electron beam diffraction apparatus (3),
The upper part of the growth chamber (10) where the fluorescent screen (4) is installed and the lower flB (11) of the growth chamber where the molecular beam [(8) is installed are connected via the bellows (12). ) can change the distance and angle between the semiconductor substrate (2) and the molecular beam source (8). At this time, between the semiconductor substrate (2) and the reflected high-speed electron diffraction [(3)
are both installed in the upper part of the growth chamber (10), so even if the semiconductor substrate (2) moves relative to the molecular beam source (B), the semiconductor substrate (2) and The positional relationship between the reflection high-speed electron diffraction device (3) and the fluorescent screen (4) does not change, making it possible to always observe the reflection electron diffraction image.

(Example) Experiments were conducted using a growth chamber having the structure shown in FIG. M1
The growth of xGa1-xAg graded mixed crystal will be explained as an example.

As shown in FIG. 2, the upper part of the growth chamber was moved with respect to the molecular beam source without changing the distance, only the angle m was changed.

Growth conditions θ = 06 to 3 G" Distance between crucible and semiconductor substrate: 250 cm As molecular beam intensity: 3 Even though the angle of the semiconductor substrate with respect to the molecular beam source was changed until the growth was completed (θ=15°), the reflection electron beam diffraction image could always be observed.

(Effects of the Invention) As explained above, according to the molecular beam crystal growth apparatus of the present invention, even if the position of the semiconductor substrate with respect to the molecular beam source is changed, the positional relationship of the reflection high-speed electron beam diffraction apparatus with respect to the semiconductor substrate is maintained. It never changes. Therefore, when growing a tilted mixed crystal by changing the substrate angle, reflection electron beam diffraction can be observed at all times during the growth.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a specific example of a growth chamber in the molecular beam crystal growth apparatus of the present invention. FIG. 2 is a detailed explanatory diagram of the present invention. +1...manipulator, 2...semiconductor substrate, 3.
... Reflection high-speed electron diffraction device, 4... Fluorescent screen, 5... Liquid nitrogen shroud, 6... Molecular beam source, 1
0... Upper part of the growth chamber, 11... Lower part of the growth chamber, 12...
・Bellows.

Claims (1)

[Claims] (1) A manipulator that heats, rotates, and holds a semiconductor substrate to an appropriate temperature in an ultra-high vacuum, a reflection high-speed electron diffraction device that observes reflection electron beam diffraction, and a semiconductor substrate that is to be epitaxially grown facing the manipulator. In a growth chamber of a molecular beam crystallization device equipped with a molecular beam source for constituent elements, a bellows is provided between the upper part of the growth chamber where the manipulator and the reflection high-speed electron diffraction device are installed and the lower part of the growth chamber where the molecular beam source is installed. , a molecular beam crystal growth apparatus characterized in that the upper part of the growth chamber and the lower part of the growth chamber are configured to be movable independently.