JP2741859B2 - Molecular beam epitaxy - Google Patents

Description

The present invention relates to line-of-sight epitaxy, and particularly to III-
The present invention relates to a molecular beam epitaxy suitable for producing a group V compound semiconductor thin film crystal. [Prior Art] Conventionally, regarding cracking of group V molecular beam raw materials in molecular beam epitaxy, see "Molecular Beam Epitaxy Technology", edited by Kiyoshi Takahashi, pp. 69-70 (edited by the Industrial Research Institute, 1984).
As discussed in U.S. Pat. No. 5,867,838, a method is used in which evaporating particles from a crucible are further heated to a high temperature by heating with a heater to crack from tetramer to dimer. [Problems to be Solved by the Invention] In the above prior art, since cracking is performed by heating with a heater, degassing (CO, H ₂ O, etc.) from the crucible is induced at the same time as cracking, which adversely affects the film quality. . An object of the present invention is to provide a molecular beam epitaxy using the cracking method which does not have the above-mentioned disadvantages. [Means for Solving the Problems] An object of the present invention is to provide a method for transporting vaporized molecules of a molecular beam raw material by hydrogen gas when the molecular beam raw material is a solid, and forming a mixed gas of hydrogen and vaporized molecules. This can be achieved by exciting the plasma with high frequency. When the molecular beam source is a gas such as AsH _3, it can be achieved by directly exciting this gas with plasma. [Operation] The case where the molecular beam raw material is a solid will be described with reference to the molecular beam source of the embodiment of the present invention shown in FIG. Evaporated molecules (tetramers) generated by heating the raw material 2 by the heater 3 are transported to the cracking cell 6 by H ₂ gas. The transported tetramer in the H ₂ atmosphere becomes plasma due to the high-frequency power induced in the cracking cell 6 and dissociates from the tetramer into a dimer. At this time, since the cracking cell 6 is not heated, the adsorbed gas does not desorb from the inner wall of the cell. That is, since cracking is performed by plasma excitation, cracking can be performed at a low temperature, and the object of the present invention can be achieved. The object of the present invention can be achieved by the same operation when the molecular beam raw material is a gas. JP-A-61-32413 describes plasma excitation of vaporized molecules of a group V solid molecular beam raw material. Further, Japanese Patent Application Laid-Open No. 61-32414 describes plasma excitation of group V gas molecular beam source molecules. However, in both cases, there is no description about transporting vaporized molecules of a solid molecular beam source or molecules of a gaseous molecular beam source with hydrogen gas. EXAMPLES Hereinafter, the present invention will be described with reference to examples. In the embodiment, the case of arsenic will be described.
It is also feasible for group V raw materials such as Sb. Example 1 FIG. 1 is a schematic explanatory view of a molecular beam source and a cracking method according to Example 1 of the present invention. As as raw material for solid molecular beam 2
Is loaded into the crucible 1 of pyrolytic BN (boron nitride). Ultra-high vacuum (<1 × 10 ^-10 Torr) of the above As by heater 3
When heated to 300 ° C in the chamber, the As ₄ molecules evaporate. This As ₄ is introduced into the cracking cell 6 by introducing H ₂ gas. Here, plasma is excited by high frequency (13.56 MHz), and H ₂ and As ₄ are dissociated to form As ₂ molecules and cracking is performed. In addition, H ₂ is converted into H radicals and irradiates the substrate, and thus has an effect of removing surface oxides. As described above, in GaAs fabricated using As ₂ molecules,
The mobility is 7600 cm when the carrier concentration is n-type 1 × 10 ¹⁶ cm ^-3
And improved ² / v · s, highly purified crystals were Hakare compared to 5300cm ² / v · s normal As _4. Second Embodiment FIG. 2 is a schematic explanatory view of a molecular beam source and a cracking method according to a second embodiment of the present invention. The case where the gas source AsH ₃ is used will be described. The gas molecular beam source AsH ₃ is directly introduced into the cracking cell 11 as a carrier gas H ₂ , and is plasma-excited at a high frequency (13.56 MHz). In the plasma 13, As ₁ , As ₁ *, As ₁ +,
H * is generated and irradiates the substrate. In the case where GaAs is formed using the above-described active species by the plasma, the n-type GaAs of Example 1 is used.
Mobility obtained 7000cm ² / v · s under the same conditions as the normal A
It was Hakare significant improvement as compared to the s ₄ source. In the case of a gas molecular beam raw material, similar results can be obtained by plasma-exciting and irradiating not only group V but also group III trimethylgallium, trimethylaluminum and the like. [Effects of the Invention] According to the present invention, a vaporized molecule can be cracked without heating the cell at a high temperature. Therefore, when applied to a molecular beam epitaxy apparatus, a group III-V compound semiconductor having good crystallinity is produced. And has the effect of improving the electron mobility of the semiconductor by 40% or more.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view for explaining an outline of a molecular beam source and a cracking method according to a first embodiment of the present invention, and FIG. 2 is a molecular beam source and a cracking according to a second embodiment of the present invention. It is sectional drawing for demonstrating the outline of a method. 1 ... crucible, 2 ... material, 3 ... heater, 4,13 ... plasma, 5,12 ... high frequency coil, 6,11 ... cracking cell.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Masahiko Kawata               1-280 Higashi Koigabo, Kokubunji-shi, Tokyo                 Central Research Laboratory, Hitachi, Ltd.                (56) References JP-A-61-32413 (JP, A)                 JP-A-61-32414 (JP, A)

Claims (1)

(57) [Claims] A mixed gas of vaporized molecules of the solid molecular beam source or molecules of the gaseous molecular beam source and hydrogen gas transporting the vaporized molecules of the solid molecular beam source or the molecules of the gaseous molecular beam source is plasma-excited, and The process in which the vaporized molecules of the raw material or the molecules of the gas molecular beam raw material cracks and the hydrogen gas is converted into hydrogen radicals, Molecular beam epitaxy having a process of irradiating a substrate. 2. 2. The molecular beam epitaxy according to claim 1, wherein said vaporized molecules of said solid molecular beam raw material comprise a group V element, and said molecules of said gas molecular beam raw material include a group V element. 3. 3. The molecular beam epitaxy according to claim 2, wherein a group III-V compound is produced by said molecular beam epitaxy. 4. 4. The group III element constituting the group III-V compound is gallium or aluminum, and the group V element is one selected from the group consisting of arsenic, P and Sb. Molecular beam epitaxy as described. 5. 5. The molecular beam epitaxy according to claim 4, wherein said group III element is gallium and said group V element is arsenic. 6. Group III element and V constituting the above group III-V compound
Using the above gaseous molecular beam raw material as the raw material for the group II element,
The molecular beam epitaxy according to any one of claims 3 to 5, wherein a mixed gas of a molecule of a group I element gas molecular beam raw material and a hydrogen gas transporting the gas is excited by plasma.