JPH09309792A - Molecular beam epitaxial growth equipment - Google Patents

Abstract

(57) Abstract: A molecular beam epitaxial growth apparatus capable of reducing the consumption of raw materials and growing an epitaxial crystal having uniform properties with good reproducibility. A solid source cell (7, 8) and a gas source cell (9) are provided, a molecular beam generated from the solid source cell (7, 8) and the gas source cell (9) is supplied to a substrate (3), and an epitaxial film is formed on the substrate (3). In the molecular beam epitaxial growth apparatus for growing crystals, the distance between the gas source cell 9 and the substrate 3 is set shorter than the distance between the solid source cells 7 and 8 and the substrate 3, and the liquid nitrogen shroud is extended to the tip 9a of the gas source cell 9. Surround with 11e and 11f.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molecular beam epitaxial growth apparatus used for epitaxially growing a compound semiconductor.

[0002]

2. Description of the Related Art Molecular beam epitaxial growth (Molecular
A beam epitaxy (MBE) apparatus is used for epitaxial growth of a compound semiconductor. For example, when a Group 3-5 compound semiconductor is epitaxially grown using an MBE apparatus, metals such as Ga, In, and Al may be used as Group 3 materials, and As may be used as Group 5 materials. These raw materials are independently used as metal sources in Knudsen cells (K-cells) installed in an ultra-high vacuum apparatus, and heated to obtain a molecular beam to obtain GaAs.
An epitaxial layer such as GaAs or AlGaAs is grown on a substrate such as. Further, in the metalorganic molecular beam epitaxial growth (MOMBE) apparatus for supplying the raw material by gas, trimethylgallium (TMG),
An organometallic gas such as trimethylaluminum (TMA) is used, and arsine (AsH ₃ ) and phosphine (PH ₃ ) are used as Group 5 raw materials. Then, an epitaxial layer of GaAs, AlGaAs or the like is grown on a substrate of GaAs or the like using these organic metal gases as a gas source.

[0003]

However, in the conventional MBE device, the P-based material (InP, InGaAsP) is used.
Etc.) was difficult to grow with good reproducibility. In addition, in the conventional M0MBE device, Al
When a system material (AlAs, AlGaAs, etc.) is grown, carbon C, which is a methyl group of TMA, is mixed, and it is difficult to grow a high-purity crystal. Recently, therefore, an Al-based solid metal material was put into a solid source cell by using an apparatus using both a solid source and a gas source, and P
By introducing a metal-organic gas material of the system to the gas source cell, an attempt is made to avoid problems when a P-based material is used in the conventional MBE apparatus and problems when an Al-based material is used in the M0MBE apparatus. However, no suitable design tool for this type of equipment has yet been established.

[0004]

The present invention has been made to solve the above problems, and the invention according to claim 1 comprises a solid source cell and a gas source cell, and the solid source cell and the gas are provided. In a molecular beam epitaxial growth apparatus for supplying a molecular beam generated from a source cell to a substrate and growing an epitaxial crystal on the substrate, the distance between the gas source cell and the substrate is shorter than the distance between the solid source cell and the substrate. It is characterized by. The invention according to claim 3 is characterized in that, in the invention according to claim 1, the gas source cell is surrounded by a liquid nitrogen shroud up to its tip.

By the way, from the solid source cell, 3
Epitaxial crystals of high purity, although group atoms are supplied
In order to grow the
10 ^-7It is introduced to the grown crystal after raising it to about Torr.
It is necessary to reduce the impurities generated. Meanwhile, gas source
The group 5 atoms are mainly supplied from the cell.
Pressure in the chamber is 10^-Five-10^-FourIt is about Torr. Ma
In addition, the gas consumption is suppressed and the supply ratio of group 5/3 is large.
For this reason, the gas source cell must be installed close to the substrate.
It is desirable to be placed. Therefore, in the growth chamber
Solid with body and gas source cells
The degree of vacuum near the source cell is higher than that near the gas source cell.
Combustion and gas source cells are located close to the substrate
Need to be Therefore, as described above, the gas source cell
Distance from the substrate of the solid source cell than the distance from the substrate
Shorter, solid source cell than near the gas source cell
The vacuum degree in the vicinity can be increased and the gas source
It is possible to suppress gas consumption from the cell.

In addition, from the gas source cell, arsine (As
H ₃ ), phosphine (PH ₃ ) and the like are supplied with hydrogen compounds, these hydrogen compounds have a thermal decomposition temperature of 100.
Since the temperature is high at about 0 ° C., it is necessary to raise the temperature of the gas source cell. Then, the temperature of the substrate rises, and As or P may re-evaporate from the grown crystal. Therefore,
If the tip of the gas source cell located closer to the substrate than the solid source cell is surrounded by a liquid nitrogen shroud, re-evaporation of As and P from the substrate can be prevented and a crystal can be grown with good reproducibility.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a conceptual explanatory view of an embodiment of a molecular beam epitaxial growth apparatus according to the present invention. In the figure, 1 is an ultra-high vacuum chamber, 2 is a substrate holder, 3 is a substrate, 4 is a heater for heating the substrate 3, 5 is a shutter provided in front of the substrate 3, 6 is a vacuum pump,
Reference numerals 7 and 8 are solid source cells, 9 is a gas source cell, 10 is a shutter provided in front of the solid source cells 7, 8 and the gas source cell 9, and 11a to f are liquid nitrogen shrouds. Here, the tip portion 9a of the gas source cell 9 is located closer to the substrate 3 than the tip portions 7a and 8a of the solid source cells 7 and 8. Further, the liquid nitrogen shrouds 11e and 11f surrounding the gas source cell 9 surround the gas source cell 9 up to its tip 9a.

The arrangement of the solid source cells 7 and 8 and the gas source cell 9 will be specifically described below. First, G
Regarding the solid source cells 7 for Group 3 such as a and In (provided with two pieces), the opening diameter of the crucible is 35 mm, the opening angle is 2 °, the incident angle is 35 °, and the substrate 3 from the tip 7a of the solid source cell 7 The distance to the surface was 240 mm. Next, A
Since the solid source cell 8 for 1 consumes a relatively large amount, it is brought closer to the substrate 3 than the solid source cell 7, and the distance from the tip portion 8a of the solid source cell 8 to the surface of the substrate 3 is set to 180 mm. The opening diameter, the opening angle, and the incident angle of the crucible are the same as those of the solid source cell 7. Next, regarding the solid-state source cell (not shown) for the dopant,
The opening diameter of the crucible is 23.5 mm, the opening angle is 2 °, the incident angle is 35 °, and the distance from the tip to the surface of the substrate 3 is 240 m.
m. Further, in the gas source cells 9 (two provided) for arsine (AsH ₃ ) and phosphine (PH ₃ ), the distance from the tip 9a to the surface of the substrate 3 was set to 150 mm in order to suppress gas consumption.

With the arrangement of the solid source cells 7 and 8 and the gas source cell 9 as described above, an epitaxial crystal of a group 3-5 compound semiconductor containing Al and P was grown on the rotating substrate 3 having a diameter of 2 inches. . Then, if the inside of the ultra-high vacuum chamber 1 is evacuated by the vacuum pump 6, the vicinity of the tips 7a and 8a of the solid source cells 7 and 8 at the time of crystal growth is 10 ⁻⁷ T.
The tip portion 9a of the gas source cell 9 has a vacuum degree of about orr.
The vicinity could be maintained at a vacuum degree of about 10 ^-5 Torr. Also, the grown epitaxial crystal has good reproducibility and the thickness is +/- within the range of about 40 mmφ on the substrate 3 surface.
It had a uniformity of 1% and good electrical characteristics.

The present invention is not limited to the above embodiment, and the solid source cell and the gas source cell may be installed such that the distance from the substrate is variable by using, for example, a bellows type flange. Good. Then, it is possible to realize the optimal arrangement of the solid source cell and the gas source cell according to the crystal growth conditions. In addition, if a thermocouple is provided in the part surrounding the tip of the gas source cell of the liquid nitrogen shroud that covers the gas source cell and the flow rate of liquid nitrogen flowing therethrough is controlled to enable temperature control of that part, crystal growth will occur. Reproducibility can be further improved.

[0011]

As described above, according to the invention of claim 1, the distance from the substrate of the gas source cell is made shorter than the distance from the substrate of the solid source cell. There is an excellent effect that an epitaxial crystal having a uniform property can be grown. Further, according to the invention described in claim 3, since the gas source cell is surrounded by the liquid nitrogen shroud up to its tip, there is an excellent effect that crystals can be grown with good reproducibility.

[Brief description of drawings]

FIG. 1 is a conceptual explanatory view of an embodiment of a molecular beam epitaxial growth apparatus according to the present invention.

[Explanation of symbols]

 1 Ultra High Vacuum Chamber 2 Substrate Holder 3 Substrate 4 Heater 5, 10 Shutter 6 Vacuum Pump 7, 8 Solid Source Cell 7a, 8a, 9a Tip 9 Gas Source Cell 11a-11f Liquid Nitrogen Shroud

Claims (4)

[Claims] 1. A molecular beam epitaxial growth apparatus comprising a solid source cell and a gas source cell, supplying a molecular beam generated from the solid source cell and the gas source cell to a substrate to grow an epitaxial crystal on the substrate. A molecular beam epitaxial growth apparatus, wherein the distance between the gas source cell and the substrate is shorter than the distance between the solid source cell and the substrate. 2. A molecular beam epitaxial growth apparatus comprising a solid source cell and a gas source cell, supplying a molecular beam generated from the solid source cell and the gas source cell to a substrate to grow an epitaxial crystal on the substrate. The molecular beam epitaxial growth apparatus, wherein the solid source cell and the gas source cell are installed so that the distance to the substrate is variable. 3. The gas source cell is surrounded by a liquid nitrogen shroud up to its tip.
Alternatively, the molecular beam epitaxial growth apparatus according to item 2. 4. The molecular beam epitaxial growth apparatus according to claim 3, wherein the liquid nitrogen shroud covering the gas source cell has a temperature controllable portion at the portion surrounding the tip of the gas source cell.