JPH07518B2 - Molecular beam crystal growth equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention relates to a molecular beam crystal growth apparatus, including a substrate holder for supporting a peripheral portion of a substrate for growing a single crystal, and a heater for heating the substrate by heat radiation through a space. And a heat reflection plate formed by laminating two or more metal plates that heat shield the substrate holder from the heater at a predetermined interval, and control the temperature of the substrate holder. The uniformity of the temperature distribution in the inside is improved, and the growing single crystal layer is improved.

[Industrial application field]

The present invention relates to a molecular beam crystal growth apparatus, and more particularly to a molecular beam crystal growth apparatus that improves the temperature distribution of a growing single crystal substrate to improve the uniformity of epitaxial growth.

A substrate obtained by epitaxially growing a required single crystal layer on a single crystal substrate is widely used for semiconductor devices and the like. Although various methods are used for epitaxial growth, the molecular beam crystal growth method (MBE method) can most accurately control the crystal growth rate, the composition ratio of mixed crystals, or the impurity doping amount. Most suitable for precise crystal growth such as superlattice structure.

However, the MBE method has not only a low growth rate as compared with other growth methods, but also uniform growth has heretofore been difficult, and improvement thereof is strongly demanded.

[Conventional technology]

The MBE method is to evaporate the element composing the target single crystal and the impurity element to be doped into this into a molecular beam from a cell in a high vacuum of about 10 ^-10 Torr to form a single crystal layer on a single crystal substrate. This is an epitaxial growth method, and the main part of the apparatus is constructed, for example, as shown in the schematic view of FIG.

In the figure, 1 is a mechanism for supporting and heating a substrate, 2 is a molecular beam source cell, 3 is a liquid nitrogen shroud, 4A is an electron gun for RHEED, and 4B is a fluorescent screen for RHEED. The crystal substrate 10 is attached to the mechanism 1 that supports and heats the substrate, for example, as described below.

The mechanism 1 for supporting and heating this substrate has a structure as illustrated in FIG. That is, 11 is a substrate holder made of, for example, molybdenum (Mo), 12 is a spacer made of, for example, boron nitride (BN), 13 is a soaking plate made of, for example, BN, 14 is a heater, 15 is a rotating mechanism, 10 is a single crystal substrate.

The single crystal substrate 10 is heated on the substrate holder 11 by radiant heat from the heater 14 to a temperature selected as an optimum substrate temperature, for example, gallium arsenide (GaAs) at 600 to 700 ° C. and silicon (S
In i), the substrate temperature is heated to about 700 to 800 ° C., but the substrate temperature has a great influence on the growth rate of the single crystal layer, the crystalline state, the composition of the multi-element compound, the impurity doping concentration, etc. It is necessary to make the temperature distribution within about ° C.

[Problems to be solved by the invention]

In the conventional mechanism for supporting and heating the substrate, the heater 14
Radiant heat from the substrate holder 11 also strongly heats the substrate holder 11, which becomes a higher temperature than the single crystal substrate 10. Due to the heat flow from the substrate holder 11 to the single crystal substrate 10, the peripheral portion has a higher temperature than the central portion, and the temperature is non-uniformly distributed. And the uniformity of the grown single crystal layer is a problem.

[Means for solving problems]

The problem is that the substrate holder is thermally shielded from the heater between the substrate holder that supports the peripheral portion of the substrate on which the single crystal is grown and the heater that heats the substrate by heat radiation through the space. The problem is solved by the molecular beam crystal growth apparatus according to the present invention, which comprises a heat reflection plate formed by laminating one or more metal plates at a predetermined interval.

A heat reflection plate can be used for the heat shield means, for example.

[Work]

According to the present invention, as illustrated in FIG. 1, the temperature of the substrate holder 11 and thus the amount of heat conduction between the substrate holder 11 and the substrate 10 is controlled by thermally shielding the space between the heater 14 and the heater 14, for example. By controlling the amount appropriately, the uniformity of the temperature distribution in the plane of the substrate 10 is improved, and the uniformity of the growing single crystal layer is improved.

[Examples] The present invention will be specifically described below with reference to Examples.

FIG. 2 is a schematic view showing a mechanism part for supporting and heating the substrate in the first embodiment of the present invention, 11 is a substrate holder, 12 is a spacer, 13 is a soaking plate, 14 is a heater, 15 Is a rotating mechanism, 16 is a heat reflecting plate for heat shielding according to the present invention, and 10 is a single crystal substrate for growing a single crystal.

For example, Mo is used for the substrate holder 11 of this embodiment, and six substrates having a substrate mounting surface diameter of about 190 mm and a diameter d _w of about 51 mm can be arranged and mounted in a rotationally symmetrical manner.
The inner diameter d _{0 of} each opening is about 45 mm.

The heat reflection plate 16 is, for example, tantalum (Ta) having a thickness of 0.1 mm.
The board holder 11 has a structure in which four plates are stacked with a pitch of 0.5 mm.
An opening having an inner diameter d ₁ of about 40 mm is provided at a position concentric with each opening.

The distance between the heater 14 and the substrate holder 11 is about 5 mm as in the conventional example, and the heat reflecting plate 16 rotates together with the substrate holder 11 about the central axis of the substrate mounting surface as a rotation axis at a speed of about 20 rpm or less. be able to.

Further, FIG. 3 is a schematic diagram showing a second embodiment of the present invention, in which the same reference numerals as in FIG. In the substrate holder 11 of this embodiment, the number of substrates to be mounted is one as in the conventional example.

As shown in the figure, the heat reflection plate 16 of the present embodiment is formed of a Ta plate whose thickness, number, and pitch are, for example, the same as those of the above-described embodiments, in a coaxial cylindrical shape whose axial direction is perpendicular to the substrate mounting surface of the substrate holder 11. ,
The heater 14 is provided in this cylinder.

In the above embodiments, for example, gallium arsenide (GaAs) MBE is used.
At a temperature suitable for growth of 680 ° C., a temperature distribution within ± 5 ° C. is secured with a margin over the entire surface of the substrate 10.

Further, in the first embodiment, the molecular beam source cell 2 is a Langmuir type with a large opening, and the molecular beam is incident on the entire surface of the substrate holder 11 with good uniformity, and a high electron mobility field effect transistor is formed on the GaAs single crystal substrate. Undoped GaAs layer for
AlGaAs layer selectively doped with Si and Ga doped with Si
The As layer was grown continuously, but the variation of the thickness of each semiconductor layer, the impurity concentration, etc. between substrates and within each substrate was within ± 1%. Was obtained.

〔The invention's effect〕

As described above, according to the present invention, the uniformity of a single crystal layer can be improved by the molecular beam epitaxial growth method, and the structure of the device is simple and easy to implement. For example, in a semiconductor device having a superlattice structure, etc. A remarkable effect can be obtained for development and practical use.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention, FIG. 2 is a schematic diagram of a first embodiment of the present invention, FIG. 3 is a schematic diagram of a second embodiment, and FIG. 4 is a schematic diagram of a molecular beam crystal growth apparatus. Fig. 5 is a schematic view of a conventional example of a substrate supporting and heating mechanism of a molecular beam crystal growth apparatus. In the diagram, 1 is a mechanism for supporting and heating the substrate, 11 is a substrate holder, 12 is a spacer, 13 is soaking. A plate, 14 is a heater, 15 is a rotating mechanism, 16 is a heat reflection plate for heat shielding according to the present invention, 2 is a molecular beam source cell, and 10 is a single crystal substrate for growing a single crystal.

Claims (1)

[Claims] 1. A substrate holder that supports a peripheral portion of a substrate on which a single crystal is grown and a heater that heats the substrate by heat radiation through a space, and shields the substrate holder from the heater. A molecular beam crystal growth apparatus comprising a heat reflection plate (16) formed by laminating at least one metal plate at a predetermined interval.