JPS632313A - Gas source molecular beam crystal growth apparatus - Google Patents

Abstract

PURPOSE:To obtain a gas source molecular beam crystal growing apparatus which accurately controls molecular beam intensity without necessity of a large- sized exhaust pump by providing a mass flowrate controller having a flow rate control valve at a material vessel side and a flowrate measuring sensor at a molecular beam cell side in an organic metal gas supply passage. CONSTITUTION:A flowrate control valve 18b is coupled with the vicinity of a gas inlet side 18a, a flowrate measuring sensor 18e having a sensor tube 18d therein is coupled with the vicinity of a gas outlet side 18c, organic metal gases TEGa, TMIn contained in organic metal gas cylinders 9a, 9b are supplied through a mass flowrate controller (MFC) 18 to corresponding molecular beam cells 11a, 11b to be emitted to a growing substrate 8. In this case, the outlet side 18c of the MFC 18 is in high vacuum state, and the pressure of the inlet side 18a is substantially equal to the vapor pressure of the organic metal gas. However, since the MFC 18 becomes high vacuum in the sensor 18e, it can measure a fine flow rate to accurately control a fine gas flow rate, the molecular beam intensity of the organic metal can be accurately controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gas source molecular beam crystal growth apparatus that grows crystals by irradiating the surface of a growth substrate with a gas containing an organometallic gas.

[Conventional technology]

In recent years, in the field of 11-V group compound semiconductors, a gas source MBE method has been developed that solves various disadvantages of the conventional molecular beam crystal growth method (hereinafter abbreviated as MBE method) using a solid material as a raw material (for example, Y., Kawaguchi et.
al, Jan, J, Appl, Phys, (
Journal of the Japanese Society of Applied Physics), 23, L737 (1984)
). The MBE method has the following features.

That is, (1) since the raw materials can be replenished or replaced while the growth chamber is kept in a vacuum, there is almost no deterioration in the quality of the grown crystal due to replenishment or replacement of the raw materials. That is, crystal growth can be performed with stable quality over a long period of time.

(2) Highly pure crystals, which are difficult to obtain using conventional MBE methods, can be grown relatively easily. For example, in an InP crystal, the carrier concentration is 9.9% at liquid nitrogen temperature. I X 10' 3cm=3+ Electron mobility is 1
There is a report that it was possible to grow ultrapure crystals of 0.05000 an/VS (Y, Kawagu
chiet, al, In5t, Phys-Conf, S
cr, (Physical Society Conference Series) Bear 9.79 (1
985)).

(3), SixNy, 5ixty-r)e.

selective growth is possible. In the conventional MBE method,
Polycrystalline precipitation occurred over the entire surface of the dielectric film, but no precipitation or only granular precipitates were observed in the gas source MBE method.

(4) Multi-component liquid crystal containing two or more types of group V elements, which was difficult to grow using conventional MBE methods, can be grown with good controllability.

(5) Since an organic metal can be used as a raw material for aluminum, the problem of short life of the aluminum molecular beam cell, which has been a problem in the conventional MBE method, is eliminated.

Methods for controlling the molecular beam intensity in gas source MBE apparatuses reported to date include methods using a high-precision leak valve (varia pull leak valve) or a mass flow controller.

Figure i4 shows the barrier pull/leak φ valve (hereinafter referred to as V
This figure shows a configuration diagram of a gas source MBg apparatus using a gas source MBg (abbreviated as LV) for molecular beam intensity control, and this figure is a diagram of the apparatus for growing InP:crystal. In the figure, a growth chamber 1 is evacuated by an exhaust pump 3 via a gate valve 2. It's a trench, this growth room 1 has V.
Examples of organic compound gases containing group elements include phosphine (
The raw material tank 4 containing PH3) is connected to the gas supply pipe 5.
VLV6 connected to this pipe 5 via
The amount of diphosphine introduced is adjusted, and the diphosphine is ejected onto the heated growth substrate 8 through a thermal decomposition cell heated to about 800°C. Furthermore, in the growth chamber 1, an organometallic gas containing group Ⅰ elements, such as triethyl indium (TEIn), is also used.
) is connected to the gas supply pipe 5 via a valve, and VLVlo, which is connected to the pipe 5, is ejected onto the growth substrate 8 through the molecular beam cell 11. In addition, 12
is liquid nitrogen shract. In this case, phosphine,
The molecular beam intensity of triethyl indium is adjusted individually by the reading of the ion gauge 13, but the precision and reproducibility were very good, at about 5%. -On the other hand, in order to grow InxGa1- However, the molecular beam intensity of each organic metal must be controlled with good reproducibility with an accuracy of at least about 1% error or less.Therefore, in a growth system where the molecular beam intensity is adjusted by VLv6°10, It is difficult to grow crystals that require strict compositional control.

In addition, a gas source M that controls the molecular beam intensity by the aforementioned mass flow controller (hereinafter abbreviated as MFC)
The BE device is (W, T, Tsang-J, App
l, Phy, (Applied Physics Society Letter), 58, 14
15 (1985)). A block diagram of the device is shown in FIG. 5, and the same or corresponding parts as in the previous figures are given the same reference numerals.

In the figure, a group 1 element 14a containing a group 1 element.

14b as organic gold Ii (T E I n + '
T M I n r T E G a rTMGa)
A group V source 15a containing a group V element.

Organic compounds (TEP, TMAs) are used as 15b. The group V sources 15a and 15b are directly introduced into the growth chamber 1 through the MF016 at varying flow rates for growth, but the group V sources 15a and 15b are grown by
As for 4a and 14b, H2'! Or Ar is used as a transport gas and introduced into the growth chamber 1 through the MFC 16 at varying flow rates to perform growth.

Note that 17 is a stop valve for stopping the apparatus.

In such a configuration, VLV6 explained in FIG.
．． 10 is different from the case where υ is used, the molecular beam intensity has an error of about 1
It is possible to adjust the fl# degree within %, and it becomes possible to grow crystals that require strict compositional control.

[Problem that the invention seeks to solve]

However, in the gas source molecular beam crystal growth apparatus configured in this manner, the organic metals such as the group III sources 14a and 14b generally have a low vapor pressure, and a large amount of transport is required to obtain the desired gas flow rate. Requires gas for use. for example,
In the above-mentioned report on the growth of InxGax-z Afi, Group II source 14a.

14b as TEGa + Hz (35°C), TMI
The flow rate of n+H* (37℃) is 17.58CCM each.
l 8.48 CCM. That is, the flow rate of the organic metal contained therein is approximately 0.25 SCCM, 0.
13 sccM, most of the remaining 25.511CC
M is the flow rate of H2. In this case, for example, 1000t
Even if an evacuation pump of /sec is used, the pressure inside the growth chamber 1 will be approximately 3X due to only the Group II bases t4a and 14b.
10"" Torr, and ■family source 1
If a large amount of 5a or 15b is added, there is a large possibility that the pressure conditions will deviate from the molecular beam region, and there is a problem that the evacuation pump will become large in order to evacuate a large amount of transport gas. Ta. Furthermore, since the MFC 16 controls the flow rate of the mixed gas of the organic metal and the transport gas, fluctuations in the vapor pressure of the organic metal and temperature fluctuations in the cylinder 9 that accommodates the organic metal affect the composition of the growing crystal. There was a problem.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a gas source molecular beam crystal that can control the molecular beam intensity of organic metals with high precision and does not require a large exhaust pump. Our goal is to provide growth equipment.

[Means for solving problems]

In the gas source molecular beam crystal growth apparatus according to the present invention, an organometallic gas supply path connected between a molecular beam cell that irradiates a growth substrate with an organometallic molecular beam and an organometallic gas source container is provided with a A mass flow control device having a flow rate control valve and a flow rate measurement sensor on the molecular beam cell side is installed.

[Effect]

In the present invention, since the mass flow rate controller is coupled to the organometallic gas supply path, highly accurate control of minute gas flow rates is possible. Furthermore, since the flow rate of the organic metal itself is controlled, there is no need to control the temperature of the container containing the organic metal with high precision.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a gas source molecular beam crystal growth apparatus according to the present invention.
This is a diagram of an apparatus for epitaxially growing l-x As, and parts that are the same as or corresponding to those in the previous figure are given the same reference numerals. In the figure, for example, 100%' arsine (AtH3) is stored as an organic compound gas containing a group II element in an organic compound gas raw material tank 4, and a group II element is stored in two organometallic gas cylinders 9a and 9b, respectively. For example, TEGa and TMIn are stored as organometallic gases containing elements. The gas supply vibe 5 that connects the organic compound gas raw material tank 4 and the pyrolysis self is connected with a stop valve 17 on the pyrolysis sulfur side and an MFC 16 on the organic compound gas raw material tank 4 side. . Further, in the gas supply pipe 5 that connects the organometallic gas cylinders 9a, 9b and the corresponding molecular beam cells 11a, 11b, a stop valve 17 is provided on the side of the molecular beam cells 11a, 11b.
A mass flow controller (hereinafter abbreviated as MFC) 1 is installed on the 9b side.
8 are connected to each other. As shown in FIG. 2, this MFC 18 has a flow rate measuring sensor 1 which is connected to a flow rate yA regulating valve 18b near the gas inlet side 18a and has a sensor tube 18d inside near the gas outlet side 18c.
．． 8e is combined with the conventional MFC16.
These arrangements are reversed.

In the gas source molecular beam crystal growth apparatus configured as described above, the organometallic gases TEGa and TMIn stored in the organometallic gas cylinders 9a and 9b are transferred to the corresponding molecular beam cells 11a and 11b via MF'018. The light is supplied and irradiated onto the growth substrate 8. In this case, the outlet side 18c of the MFC 18 is in a high vacuum state, and the pressure on the inlet side 18a is approximately equal to the vapor pressure of the organometallic gas. Usually, M
The flow rate measurement sensor 18e in the FC18 is 100 to 150
℃, so if the flow rate measurement sensor 18e is present near the inlet side 18a as in the conventional MFC 16, the time for which the organometallic gas, which is easily thermally decomposed, is exposed to heat becomes longer, for example, C2H,... The molecular beam intensity of the organic metal itself fluctuates due to accumulation of decomposition products such as CH4 upstream of the MFC 16, and the sensor tube 18d is clogged with metal formed by decomposition. This makes it difficult to operate stably. However, in MPClB shown in Fig. 2, a high vacuum wave is generated inside the flow rate measuring sensor 18e, which makes it possible to measure minute flow rates, and the time the organometallic gas receives heat is short, reducing the effects of thermal decomposition. Since there is almost no interference, stable operation can be achieved over a long period of time. Note that any type of MPClB can be used as the MPClB to be combined with the organic compound gas raw material tank 4. Figure 3 shows the TEG gases respectively supplied to the two organometallic gas cylinders 9a and 9b mentioned above.
The graph shows the relationship between the ratio of the TMIn flow rate to the sum of the flow rates of a and TMI n and the composition
In order to epitaxially grow cGal-xAs (X = 0.53), it is necessary to control the molecular beam intensity of the organometallic gas containing group III elements within about 1%, which is shown in Figure 3. MF of TEGa and TMIn as
By adjusting the flow rate controlled by C18), it became possible to easily obtain crystals with a composition ratio of x:o of 53 with good reproducibility.

Further, according to such a configuration, the organometallic gas TIEG
Since no transport gas such as H2 or Ar is used to transport a and TMI n in the pipe 5, the pumping speed is approximately 5.
Even if a relatively small exhaust pump with a capacity of about 00 A/sea was used, the pressure in the growth shell was about 1 x 10-4 Torr, and the thermal decomposition product of the functional compound arsine was the main one.

In addition, in the above-mentioned embodiment, InX and Ga1-X
A! Although gas source MBE growth with l is described, the present invention is not limited thereto, and may be applied to other crystals,
It is impossible to say that this method can be applied to the growth of amorphous materials.

〔Effect of the invention〕

As explained above, according to the present invention, the organometallic gas supply path that connects the molecular beam cell that irradiates the crystal growth substrate with an M-machine metal molecular beam and the organometallic gas raw material container is provided. By combining a quality flow control device with a flow rate control valve on the side and a flow rate measurement sensor on the molecular beam cell side, minute gas flow rates can be controlled with high precision, making it possible to control organic metal molecular beams. In addition to being able to precisely control the strength, there is no need for a transport gas to transport the organometallic gas raw material, so it is possible to use a small exhaust pump to perform crystal growth that violates compositional control. Extremely excellent effects can be obtained.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the gas source molecular beam crystal growth apparatus according to the present invention, Fig. 2 is a block diagram showing the mass flow rate control device of Fig. 1, and Fig. 3 shows the aX ratio (TM
InxG for In/(TMIn+ TFJGa))
A diagram showing the relationship with the composition X of the a1-xAa crystal, FIG.
FIG. 5 is a configuration diagram showing a conventional gas source molecular beam crystal growth apparatus. 11I...Growth chamber, 2...Φ, gate valve, 3@@
Exhaust pump, 4...organic compound, gas raw material tank, 5...gas supply pipe, T...-pyrolysis cell, 8...-growth substrate, 9a, 9b・・・
・・Aerated metal gas raw material tank, 11a, llb ・・
... Molecular beam cell, 12 ... Liquid nitrogen shroud, 14a, -14b @ ...
15b ・* * 'V group 7-s, 16----・MF
C, 17・Stop valve, 18・Mass flow controller (MFC), 18a・・Inlet side, 1
3b...Flow rate adjustment valve, 18c...-One outlet side, 18d--Working/sensor pipe, 18e...
・Senna for flow rate measurement.

Claims (1)

[Claims] In a gas source molecular beam crystal growth apparatus comprising a growth substrate and a molecular beam cell for irradiating the surface of the growth substrate with a molecular beam of an organometallic gas in an evacuated growth chamber, the molecular beam cell and the organometallic gas A gas characterized in that a mass flow rate control device having a flow rate control valve on the organometallic gas raw material container side and a flow rate measurement sensor on the molecular beam cell side is provided in the organometallic gas supply path that connects the organometallic gas raw material container. Source molecular beam crystal growth equipment.