JPS63156094A - Method for growing single crystal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] The invention relates to atomic layer epitaxy of a single crystal of a compound, and a compound containing an alkyl group and a chlorine group of at least one element constituting the single crystal of the compound. By using this element and alternately supplying other elements constituting the single crystal of the compound, the remarkable self-limiting effect makes it possible to accurately grow the required number of atomic layers. It is something to do.

[Industrial application field]

The present invention relates to a method for growing a single crystal, and in particular to an improvement in the method for growing a single crystal that enables good atomic layer epitaxy.

Single crystal growth is being developed on an atomic layer basis for the purpose of miniaturizing electronic devices to improve their performance, and to develop electronic devices with new functions by realizing physical properties not found in conventional bulk materials. There is a strong demand for control.

[Conventional technology]

Molecular beam epitaxy (MBE) and metal-organic vapor phase epitaxy (MO
-CVD method).

In the MO-CVD method, gallium (Ga), aluminum (
The alkyl compound is mainly used to transport single-crystal constituent elements of group Ⅰ such as AI).
(CH3) 3), triethylgallium (Ga (C2
H5) 3), trimethylaluminum (A t (C
H3) 3), triethylaluminum (AI (Cz
For group ■ elements such as Hs) 3), arsine (AS
H3) etc.

The reaction formula in this MO-CVD method is gallium arsenide (
Taking GaAs) as an example, Ga (CH3) :l + As113-GaAs
+3CH4. The reactions that actually occur near the growth surface are not as simple as this, and the elementary processes have not yet been fully understood, but it is a well-established theory that the rate of growth is determined by the diffusion of reactants. .

There is still no established theory as to what the specific diffusion species is, but a typical theory is that Ga(Ct(3)i is completely thermally decomposed in the boundary layer above the heated susceptor). Near the growth surface, AsH3 decomposes and As4 is generated.

In this case, Ga atoms move through the boundary layer due to diffusion and reach the substrate surface, and GaAs is precipitated by the reaction Ga + 'A As4-GaAs. Therefore, the growth rate is determined by the diffusion of Ga atoms, which is consistent with the experimental fact that when the concentration of As 113 is sufficiently large, the growth rate increases in proportion to the amount of Ga(CH:+)z supplied.

this? The 10-CVD method has better controllability than previous vapor phase growth methods that use single metals as raw materials, reducing the growth rate to several seconds/atomic layer and speeding up the switching of raw material gases. It has already been reported that it forms an extremely thin film.

In addition, while the normal vapor phase growth method uses raw material gas containing each structural element to flow simultaneously and takes advantage of the fact that reactions occur on or near the substrate, newer atomic layer epitaxial growth technology uses raw material gases that are alternately supplied. The flowing method is the growth of zinc sulfide (ZnS) using zinc chloride (ZnC1□) and the growth of tantalum oxide (ZnS) using tantalum chloride (TaC1s).
The growth of TazOs) has been reported.

A method of alternately flowing the raw material gases was introduced into the MO-CVD method, and the results of attempting atomic layer epitaxial growth of GaAs are illustrated by broken lines in FIG. In this conventional example, the growth temperature is set to, for example, 400°C, the flow 1x of Ni a (CzHs) 3 is changed as shown on the horizontal axis in the figure, and one cycle of growth is repeated as shown below. The ratio of the growth thickness per period to the thickness of one atomic layer is calculated.

Rest Ga (CzHs) 3 Rest AsH.

Flow rate (SCC gate)
480 hours (seconds) 3 10 3
10 According to the data shown in the same figure, when the flow rate X of Ga(Czlls)3 is about 805 CCH, the growth thickness per period is 1 atomic layer, and when the flow rate X is less than this value, it does not reach 1 atomic layer per period. , if this value is exceeded, it exceeds 1 atomic layer per period, and the correlation between the flow rate X and the growth thickness becomes a continuous monotonically increasing curve.

This result not only shows that in this method it is necessary to control the flow rate X to a constant value in order to control the growth thickness per cycle to one atomic layer, but also shows that The thickness is an average value and does not actually mean that the growth of the next atomic layer starts after the growth of one atomic layer is completed, indicating that there may be partial slowdowns in the progress of epitaxial growth. .

Atomic layer epitaxy using the MBE method is being developed in parallel, but MO, which has a very similar growth mechanism,
-Aiming for a growth method that combines the advantages of CVD and MBE methods, a method of growing crystals in a vacuum of around 10-'Torr using a gas source as a raw material has recently been attracting attention.
-MBE method, vacuum MO-CVD method, etc.

[Problem that the invention seeks to solve]

The above-mentioned conventional example shows that the self-limiting effect in which the growth reaction ends for each atomic layer cannot be expected much even if the raw material gases are alternately flowed, and the growth method that enhances the self-limiting effect is atomic layer epitaxy. There is a strong demand for this to be realized.

[Means for solving problems]

The above problem can be solved by using a compound containing an alkyl group and a chlorine group of at least one of the elements constituting the compound single crystal, and alternately using the element and other elements constituting the compound single crystal. This problem is solved by the single crystal growth method according to the present invention.

In addition, according to the present invention, the elements whose raw materials are compounds containing an alkyl group and a chlorine group are mainly group (1) elements and group (2) elements.

[For production]

According to the present invention, for example, GaAs single crystal can be
When growing using a VD method apparatus, as described below as an example, a compound containing an alkyl group and a chlorine group, such as Ga(CJs)zcl, is used as the Ga raw material, and this and As raw material ASH3 are alternately used. supply to.

This epitaxial growth can be considered as follows. In other words, Ga(CJs)zcl thermally decomposes C, H, and groups in the boundary layer of the heated upper layer of the susceptor, but CI groups with strong bonding strength are not decomposed and Ga-Cl becomes a diffusion species. and reach the substrate surface. If this Ga atom enters the position of the Ga atom on the growth surface, the bonded CI will prevent further stacking on top of it, the Ga atoms will be arranged in a monoatomic layer, and the G
a(Czl(s)) Even if the supply of zcl continues, no further progress is made.

AsH after stopping and exhausting Ga(czos)zct
When 3 is supplied, this is thermally decomposed near the growth surface, As atoms enter the vacant lattice positions between Ga atoms arranged in a monoatomic layer, and the CI is discharged as HCI. In addition, AsH.

Even if more than the equivalent amount is supplied, crystal growth is not affected.

In this way, a remarkable self-limiting effect is achieved as will be described later as an example, but a similar effect can also be obtained in the so-called MO-MBE method, which has a very similar growth mechanism.

〔Example〕

゛゛　゛　The present invention will be specifically explained below with reference to Examples.

In this example, atomic layer epitaxial growth of GaAs on a GaAs substrate was carried out using a vapor phase growth apparatus conventionally used in the MO-CVD method as described below. I have obtained results as shown in the example below.

In this example, the growth temperature was set to 400°C, which is the same as that of the conventional example, and hydrogen (H2) was added to the bubbler at a temperature of 47°C.
The carrier is aerated and the flow rate The ratio of the growth thickness per period to the thickness of one atomic layer is determined.

Rest Ga (CtHs) zcl Rest AsH.

Flow rate (SCCM)
480 hours (seconds) 3 10 3
10 From the data of this example, Ga(CJs)zcl
Flow rate X or time of Ga(Czlls) of the conventional example
:I need to increase more than i, but if the flow rate reaches the limit value at which a monoatomic layer can be deposited, which is approximately 2003 CCH in this example, the flow rate of Ga (CzHs) and Cl must be increased more than this.
Even if X is increased, the growth thickness does not increase, and the growth thickness per period is maintained at one atomic layer, thereby achieving a reliable self-limiting effect.

Although the above examples refer to the growth of single crystals of m-v group compounds, single crystals of ■-■ group compounds can also be grown by epitaxial growth using, for example, zinc sulfide (ZnS) as raw materials with Zn(CJs)C1 and lhs. Similar effects can be obtained by applying the present invention.

Further, although the above-described embodiments are based on the conventional MO-CVD method, similar effects can be obtained by using a method based on the MO-MBE method.

〔Effect of the invention〕

As explained above, according to the present invention, during the epitaxial growth of compound single crystals, the self-limiting effect in which the growth reaction ends for each atomic layer is extremely noticeable, and the growth of the required number of atomic layers can be achieved accurately. This makes it possible to greatly contribute to improving the performance of electronic devices through miniaturization, as well as to the development of electronic devices with new functions that cannot be obtained with conventional bulk materials.

[Brief explanation of the drawing]

FIG. 1 is a diagram comparing the growth thickness per cycle between an embodiment of the present invention and a conventional example. i2 Rin Susagopet Miyakotoge Town

Claims (1)

[Claims] 1) A compound containing an alkyl group and a chlorine group of the element is used as a raw material for at least one of the elements constituting the compound single crystal, and the element and other elements constituting the compound single crystal are combined. A single crystal growth method characterized by alternately supplying. 2) The single crystal growth method according to claim 1, wherein the element used in the compound is a group III element. 3) The single crystal growth method according to claim 1, wherein the element used in the compound is a Group II element.