JPH04224192A - Shutter for molecular-beam epitaxy device - Google Patents

Abstract

PURPOSE:To eliminate the defective opening and closing of a sutter and to stably operate the device for a long period by providing a reservoir at the lower side of the surface of the shutter where the molecular beam comes flying and storing the vapor-deposited molten material in the reservoir to prevent the splashing of the molten material. CONSTITUTION:In this molecular-beam epitaxy device, a shutter 1 provided with a holding rod 5 is arranged on the front surface of an effusion cell (not shown in the figure) set in a liq. nitrogen shroud to block a molecular beam 2, and the growth of an epitaxial crystal is controlled. A reservoir 4 for storing the vapor-deposited molten material 3 as the block of the molecular beam 2 deposited on the shutter 1 surface is arranged at the lower side of the surface of the shutter where the molecular beam 2 comes flying. Consequently, the molten material 3 is not splashed or deposited on the liq. nitrogen shroud, etc., hence the defective opening and closing of the shutter 1 are obviated, and the working rate of the device is improved.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to molecular beam epitaxy (M
BE) relates to improvements in the molecular beam source shutter in the device.

[0002] In recent years, MBE crystal growth technology has made great progress, and high-quality heterostructures and superlattice structures can now be obtained with good reproducibility. One of the representative devices developed using this growth method is the high electron mobility transistor (
HEMT) has already been commercialized and mass produced.

However, the MBE growth apparatus based on ultra-high vacuum is not fully compatible with such mass production, and there is a desire for further improvements to make it more reliable.

0004

2. Description of the Related Art FIG. 3 is an explanatory diagram of a conventional example. In the figure, 16 is a vacuum chamber, 17 is a shutter, 18 is a fusion cell, 19 is a molecular beam, 20 is a liquid nitrogen shroud, 21 is a substrate, 22 is a molecular beam source, 23 is a vapor deposition melt, 24 is a heater, and 25 is a thermostat. They are a couple.

As shown in FIG. 3(a), conventionally, MBE
The shutter 17 of the device is installed in front of the fusion cell 18 (between the fusion cell 18 and the substrate 21) for the purpose of blocking the molecular beam 19 generated in the fusion cell 18.
It is located in

Further, the fusion cell 18 and the shutter 17 are separated by a liquid nitrogen shroud 20 to prevent contamination due to mutual mixing of the molecular beams 19. Normally, in order to maintain a highly uniform film thickness of the epitaxial crystal, each fusion cell 18 and shutter 17 (usually six or seven sets) are arranged at rotationally symmetrical positions with respect to the normal to the substrate 21.

Therefore, the spatial space between the liquid nitrogen shroud 20, the fusion cell 18, and the shutter 17 is very narrow.

[0008]

[Problem to be solved by the invention] Therefore, Fig. 3(b)
As shown in the enlarged view of the vicinity of one fusion cell 18, when the shutter 17 is closed, the molecular beams 19 attached to the shutter 17 are scattered onto the walls of the liquid nitrogen shroud 20 when the shutter 17 is opened and closed. There is a problem in that the shutter 17 bites into the vapor deposition melt 23, which is a mass of the molecular beams 19 that have been deposited and deposited, and the opening and closing operations of the shutter 17 are hindered, and in extreme cases, the shutter 17 may not open or close. , which was a major problem in operating the MBE equipment stably for a long period of time.

The present invention suppresses the scattering of the molecular beam 19 attached to the shutter 17 and allows the opening/closing operation of the shutter 17 to be performed even when the spatial space between the liquid nitrogen shroud 20, the fusion cell 18, and the shutter 17 is very narrow. This is provided for the purpose of keeping the MBE system running smoothly and stably over a long period of time.

0010

[Means for Solving the Problems] Fig. 1 shows a shutter with a reservoir according to the present invention. In the figure, 1 is a shutter, 2 is a molecular beam, 3 is a deposited melt, 4 is a reservoir, and 5 is a shutter holding rod.

By observing in detail the scattering situation of the molecular beam 2 attached to the shutter 1, it was found that: (1) With the shutter closed, the temperature of the shutter becomes higher than the melting point of the molecular beam source due to radiation from the fusion cell; (Specifically, indium (I)
It has been empirically determined that this phenomenon occurs with aluminum (Al), which has a high melting point, and does not occur with aluminum (Al), which has a high melting point.

[0012] It has been found that the attached molecular beams gather downward due to gravity, become a deposited melt, and after reaching a certain size, scatter. From these facts, it has been found that the above-mentioned problems can be solved by providing a reservoir 4 at the bottom of the shutter 1 with a shape that can store the deposited melt 3 and prevent it from scattering.

That is, the object of the present invention is to provide, as shown in FIG. 1, a reservoir 4 below the surface of the shutter 1 from which the molecular beam 2 flies, for storing the evaporated melt 3 adhering to the surface of the shutter 1. This is achieved by

[0014]

[Operation] According to the present invention, the molecular beams that have melted and become vapor-deposited melt accumulate in the reservoir provided below the shutter, so that when the shutter is closed, the molecular beams that have adhered to it are transferred to liquid nitrogen when the shutter is opened and closed. This eliminates the problem of the shutter plate becoming stuck in the mass of molecular beams that scatter and adhere to the shroud wall, etc., and prevent the shutter from opening or closing.

[0015]

[Example] Fig. 1 shows a shutter with a reservoir of the present invention, Fig. 2
1 is a schematic cross-sectional view of a HEMT in which each semiconductor layer is grown using an MBE apparatus using a shutter with a reservoir according to the present invention.

In the figure, 1 is a shutter, 2 is a molecular beam,
3 is a vapor deposited melt, 4 is a reservoir, 5 is a shutter holding rod,
6 is n-InGaAs, 7 is n-In0.52AlO.
48As, 8 is two-dimensional electron gas, 9 is i-In0.5
3GaO. 47As, 10 is i-In0.52AlO
．． 48As, 11 is i-In0.53GaO. 47A
s, 12 is a semi-insulating InP substrate, 13 is a gate,
14 is a source, and 15 is a drain.

As shown in FIG. 1 described above, by providing the reservoir 4 below the shutter 1, even if In and Ga are evaporated from the fusion cell of the MBE apparatus shown in FIG. The molecular beams adhere to the shutter surface as evaporated melt and accumulate in a reservoir provided below the shutter, so when the shutter is closed, the molecular beams that adhere to the shutter are scattered onto the liquid nitrogen shroud wall etc. when the shutter is opened and closed. This eliminates the problem of the shutter plate not being able to open or close due to the stuck and deposited mass of molecular beams getting stuck in the shutter plate.

By using the MBE device using the shutter of the present invention, a HEMT with an InGaAs/n-AlInAs structure can be
An example in which a film was formed will be described. In, G
a, Al, arsenic (As), silicon (Si) 5
A variety of substances are placed as a molecular beam source 22 into the five fusion cells 18 shown in FIG. They are sequentially laminated to a desired thickness on the semi-insulating InP substrate 12. S
i is an n-type dopant and is doped into the semiconductor layer at a concentration of 5×10 17 /cm 3 .

The temperature of the molecular beam source 22 is 750°C for In.
Ga: 950 ℃, Al: 1,080 ℃, As
is 320 °C, Si is 1,250 °C, the degree of vacuum during growth is 5 x 10-8 Torr, and the growth rate of the film is 1.2.
Film formation was performed under conditions of μm/h.

After that, recesses are formed in the substrate 12 on which each semiconductor layer is laminated, and the gate 13, source 14,
Each electrode of the drain 15 is formed to complete the device. In forming the semiconductor layer of this HEMT, by providing the reservoir 4 below the shutter 1 as shown in FIG. The molecular beams that collide with the shutter 1 adhere to the surface of the shutter 1 as vapor deposited melt 3 and accumulate in the reservoir 4 provided below the shutter 1, so that when the shutter 1 is closed, the attached molecular beams 2
However, when the shutter 1 is opened and closed, the molecular beams 2 are scattered and deposited on the walls of the liquid nitrogen shroud, and the shutter 1 is no longer stuck in the mass of the deposited molecular beams 2 and becomes unable to open or close.

[0021]

[Effect of the invention] As explained above, according to the present invention,
By applying the above solution, the shutter opening/closing failure of the MBE apparatus, which had been a problem in the past, could be eliminated, and a significant improvement was seen in terms of stable operation of the MBE apparatus over a long period of time.

[0022] As a result, the present invention greatly contributes to stabilizing the MBE apparatus and, in turn, greatly contributes to improving the operating rate of the semiconductor manufacturing apparatus.

[Brief explanation of the drawing]

[Figure 1] Shutter with reservoir of the present invention

[Figure 2]
A schematic cross-sectional view of a HEMT in which each semiconductor layer is grown using an MBE apparatus using a shutter with a reservoir of the present invention.

[Figure 3]
Explanatory diagram of conventional example

[Explanation of symbols]

1 Shutter 2 Molecular beam 3 Vapor deposition melt 4 Reservoir 5 Shutter holding rod 6 n-InGaAs, 7 n-In0.52AlO. 48As8 Two-dimensional electron gas 9 i-In0.53GaO. 47As10 i-
In0.52AlO. 48As, 11 i-In0
．． 53GaO. 47As12 Semi-insulating InP 13 Gate 14 Source 15 Drain

Claims (1)

[Claims] Claim 1: A reservoir (4) is provided below the surface of the shutter (1) from which the molecular beam (2) comes, for storing the evaporated melt (3) adhering to the surface of the shutter (1). Shutter for molecular beam epitaxy equipment.