JP2735190B2 - Molecular beam epitaxy growth method and growth apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for molecular beam epitaxial growth of III-V compound semiconductors. 2. Description of the Related Art In recent years, the development of high-speed devices, optical devices, and opto-electronic integrated circuits (OEICs) using III-V compound semiconductors has been rapidly developed, and the device manufacturing process has been complicated accordingly. The molecular beam epitaxial growth method (MBE method) is an important growth technique for the above-described device fabrication because the film thickness can be controlled with high accuracy and a high-quality thin film of a III-V compound semiconductor can be obtained. . A conventional molecular beam epitaxial growth apparatus provides a molecular beam source for each element constituting a thin film in an ultra-high vacuum vessel of about 10 ^-10 Torr, and controls the temperature of the molecular beam source to obtain an appropriate beam intensity. The structure is such that molecular beams are obtained, and these are adhered and deposited on a substrate heated to a predetermined temperature to grow a thin film having a desired composition. However, in order to fabricate a device having higher characteristics or a device that requires a more complicated process, the actual situation is that the conventional MBE apparatus and the growth method cannot respond. As recently announced by Asakawa et al., The use of an ECR ion source has enabled etching under high vacuum (Applied Physics, Vol. 54, No. 11, 1985). When this method is used, etching and growth of a crystal surface under high vacuum can be performed by combining an etching apparatus and an MBE apparatus. Therefore, for example, the crystal surface in the course of growth is once exposed to the air, and can be removed again by etching after re-growth with the surface having impurities, thereby obtaining a good interface. [Problems to be Solved by the Invention] However, when a group III-V compound semiconductor is etched in a high vacuum, there is a problem that a group V element is eliminated from the surface. Especially when etching, substrate temperature is 200 ℃
This is remarkable when the above is set. Therefore, even if the impurities on the surface can be removed by etching, a new defect due to the loss of Group V occurs, causing deterioration of the electrical characteristics of the interface. An object of the present invention is to solve these problems and to provide a method and an apparatus for obtaining a good recrystallization interface. [Means for Solving the Problems] The molecular beam epitaxial growth method according to the present invention comprises a III-V
In the method of molecular beam epitaxial growth of a group III compound semiconductor, a step of ionizing a gas obtained by mixing a reactive gas and a hydride gas containing a group V element and etching the substrate surface under a high vacuum; And epitaxially growing step at least once each. Further, the apparatus for molecular beam epitaxial growth of a group III-V compound semiconductor of the present invention comprises a device for ionizing an introduced gas, a line for supplying a reactive gas, and a line for supplying a hydride gas containing a group V element to a vacuum vessel. And characterized in that: [Action] In the present invention, a reactive gas and a compound gas containing group V are introduced into a MBE growth chamber or a connected vessel capable of maintaining the same ultra-high vacuum as the growth chamber to ionize and etch in a group V atmosphere. By performing re-growth and starting the re-growth, even if etching is performed in a high vacuum, the V-group does not escape and a good re-growth interface can be obtained. Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of an apparatus used in an embodiment of the present invention. The apparatus of the present invention includes a growth chamber 1 compatible with an ultra-high vacuum, an exhaust device 2 installed in the growth chamber 1, a substrate holder 3 having a heating mechanism, a nude ion gauge 4, and a III facing the growth chamber 1. Group element source cell 5, Group V element source cell 6, dopant source cell 7, mass flow controller 8 for introducing reactive gas, mass flow controller 9 for introducing group V compound gas, and ECR ion source 10 for ionizing the introduced gas
And is constituted by. In this embodiment, Ga as a group III element, As as a group V element,
An attempt was made to fabricate a gallium arsenide field effect transistor shown in FIG. 3 using Si as an n-type dopant. In the growth chamber 1, n-type high-purity with a carrier concentration of about 2 × 10 ¹⁴ cm ^{-3 is formed} by doping Si on a semi-insulating gallium arsenide substrate 13 at a substrate temperature of 600 ° C. to form an active layer. Layer 14 was grown 1 μm. This once taken out from the growth chamber 1, the upper heat-resistant gate electrode 15 and the SiO ₂ sidewalls 16 made of WSi is formed on the back again to the growth chamber 1, a thickness of 1000 Å, a carrier concentration of 5 × 10 ¹⁸ cm ^-3
The Si-doped n-type high concentration gallium arsenide layer 17 was grown. In this embodiment, before growing the n-type high concentration layer,
1 cc / min of Cl ₂ gas and 1 cc / min of AsH ₃ are passed through the ECR ion source 10 and ionized to dry-etch the crystal surface for 5 minutes. FIG. 4 shows the result of measuring the carrier concentration in the depth direction by the CV method. As is apparent from FIG. 4, according to the present growth method, no change in the carrier concentration is observed at the interface between the n-type high-concentration layer and the high-purity layer, but the conventional method without supplying the group V gas is used. And a portion with a low carrier concentration is formed at the interface,
This causes the resistance to be high. The apparatus used in the above embodiment has a structure in which the ECR ion source 10 is attached to the growth chamber 1, or the vessel is separated into the etching chamber 11 and the growth chamber 1 as shown in FIG.
In both cases, the etching and the growth may be performed in separate chambers by using a structure in which a high vacuum is applied and the gate valve 12 is attached between them. As a device for ionizing the reactive gas, not only the ECR ion source used in the present embodiment but also an ion gun may be used. The reactive gas is not only chlorine (Cl ₂ ) but also hydrochloric acid (H
Cl), carbon chloride (CCl ₄ ), and group V compound gas not only arsine (AsH ₃ ) but also phosphine (PH ₃ ), triethyl arsenic (As (C ₂ H ₅ ) ₃ ), etc. It can be used to the extent that it does not. In addition, the group III-V compound semiconductors to be etched and grown are not only GaAs, but also mixed crystals such as InGaAs, AlGaAs, and InP.
It goes without saying that similar results can be obtained with other group III-V compounds such as [Effects of the Invention] As described above, according to the present invention, a good regrowth interface can be obtained by etching and regrowth in a high vacuum, and the device characteristics can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of one embodiment of the apparatus of the present invention, FIG. 2 is a schematic view of another embodiment, and FIG. 3 is gallium arsenide manufactured in one embodiment of the present invention. FIG. 4 is a cross-sectional view of a field-effect transistor, and FIG. 4 is a diagram showing a depth distribution of the carrier concentration of the GaAs growth layer from the surface toward the substrate. REFERENCE SIGNS LIST 1 Growth chamber 2 Exhaust device 3 Substrate holder 4 Nude ion gauge 5 Group III element source cell 6 Group V element source cell 7 Dopant source cell 8 Reaction Gas mass flow controller 9 ... Group V gas mass flow controller 10 ... ECR ion source 11, Etching chamber 12 ... Gate valve 13 ... Semi-insulating gallium arsenide substrate 14 ... N-type high purity gallium arsenide layer 15 ...... refractory gate electrode, 16 ...... SiO ₂ sidewalls 17 ...... Si-doped high-concentration n-type GaAs layer

Claims (1)

(57) [Claims] In a method of molecular beam epitaxial growth of a group III-V compound semiconductor, a step of ionizing a gas obtained by mixing a reactive gas and a hydride gas containing a group V element to etch a substrate surface under a high vacuum; Performing the step of epitaxially growing the compound semiconductor at least one each.
A molecular beam epitaxial growth method characterized by comprising: 2. The vacuum vessel is provided with a device for ionizing an introduced gas, a line for supplying a reactive gas, and a line for supplying a hydride gas containing a group V element III-.
A molecular beam epitaxial growth apparatus for a group V compound semiconductor.