JPH0489399A - Formation of thin film of iii-v compound semiconductor - Google Patents

Abstract

PURPOSE:To form a high-quality thin film of a III-V compd. semiconductor by epitaxial growth at a low temp. by alternately feeding a hydrogen compd. having the direct bond of a group III element and a halogen element as a volatile complex compd. and a group V element to the surface of a substrate. CONSTITUTION:A hydrogen compd. having the direct bond of a group III element and a halogen element as a volatile complex compd., e.g. GaH2Cl and a group V element or a volatile compd. of a group V element e.g. a nitrogen compd. such as trimethyleneamine [N(CH3)3] are alternately fed to the surface of a substrate and a thin film of a III-V compd. semiconductor is formed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for vapor phase growth of ■-■ group compound semiconductors. The present invention relates to an atomic layer epitaxial growth technique that enables the formation of semiconductor thin films.

[Conventional technology]

■-Epitaxially grown layers of group V compound semiconductors are used in optical devices such as light emitting diodes and laser diodes, and in FE.
It is widely applied to high-speed devices such as T. More recently, structures in which several to dozens of thin film semiconductors are stacked are required to improve device performance. As such a structure, for example, a laser diode having a quantum well structure can reduce driving current, improve temperature characteristics, and shorten the oscillation wavelength. Additionally, FETs that use two-dimensional electron gas are expected to be high-speed, low-noise devices, and have already begun to be put into practical use at the individual level.

Conventionally, vapor phase epitaxy (VPE) using gases such as metal organic chemical vapor deposition (MOCVD) and halogen transport are known as thin film epitaxial growth methods. The film thickness was controlled through precise controls such as Furthermore, the molecular beam epitaxial growth method (MBE method), in which growth is performed by irradiating molecular or atomic beams of constituent elements in a high vacuum, is known as a growth method that allows relatively easy thickness control; Precise control of line strength, growth temperature, time, etc. was required.As a result of such precise control, it is now possible to create a superlattice structure by stacking one atomic layer at a time.

However, it has been difficult to integrate such thin film devices and manufacture them uniformly and with good reproducibility on a large-area substrate, even at a single unit level.

A technique that appears to be able to overcome this problem was recently reported by Suntora et al. This method is called the atomic layer epitaxial growth method (ALE method), and is published in the Proceedings of the 16th Envelope Elements and Materials Conference (T,
5untora, Extended Abstract
of the 16th Conference
on 5solid 5tate Device
sand Mat, erials, Kobe, 1984
．． pp. 647-650). In this method, constituent elements of a compound semiconductor or gases containing the elements are alternately supplied and adsorbed or reacted one atomic layer or one molecular layer at a time, thereby growing a compound semiconductor with a desired thickness as a whole. That is, in the case of growth of a ■-V group compound semiconductor, the thickness of the grown film is determined by the number of repetitions of the operation of alternately supplying the group ■ raw material and the group V raw material. Furthermore, by optimally selecting the Group III raw material and optimizing the growth conditions, it is possible to keep the adsorption amount per scum feeding operation constant regardless of the raw material supply partial pressure or growth temperature. It is possible to grow multilayer thin films with steep interfaces at the monoatomic layer level. At the same time, it has the great advantage of being able to form thin films with high uniformity due to its properties.
The aforementioned quantum well laser tie-out and two-dimensional electron gas FE
Atomic layer epitaxy technology plays a major role in the integration of TNTs.

Among the atomic layer epitaxy methods with the above-mentioned features, there is a method that uses group III elements and halogen elements, especially organometallic compounds with bonds with chlorine, such as diethyl gallium chloride (DEGaC1), as group III raw materials. teeth,
Magazine “Applied Physics Letters”
e Physics Letters) Volume 52, No. 1
As explained on pages L27-29 of the issue (January 1988), growth of GaAs monolayer units was obtained over the widest range of growth conditions reported to date, and growth of GaAs monolayer units was achieved. It was considered the most suitable mass production technology, as it was possible to grow on many large-diameter substrates at once because the raw materials were switched and supplied to the reaction vessel using a valve.

[Problem to be solved by invention]

Organometallic compounds that have a bond between a group ■ element and a halogen element, such as DEGaC that has a bond with chlorine, as a group ■ raw material
Let us consider the problems in the above-mentioned conventional atomic layer epitaxy technique in which I is used and V group materials are alternately supplied.

According to the above-mentioned literature, atomic layer epitaxy using DEGaC1 allows growth in monolayer units over a wide growth temperature range of 450 to 600'C. However, at low temperatures, there is a problem that large amounts of carphones are incorporated as impurities. This is thought to be due to the carphone being incorporated into the crystal. Therefore, in order to obtain a highly pure film, it was necessary to perform the growth at a relatively high temperature of 525-600'C.

However, in atomic layer epitaxy using DEGaCl, in order to achieve growth in monolayer units, that is, to obtain a self-stopping function, it is necessary to use very thermally stable GaCl generated by the decomposition of DEGaCl, or to grow the substrate within a wide range of growth conditions. This is thought to be due to monomolecular layer adsorption onto the top.

In other words, even if there is a compound with a Ga-C1 bond, there is no need to use an organic compound that causes carphone uptake; for example, chlorogalane (GaH2CI)
), dichlorocalane (GaHC12), and even GaCl
If an inorganic compound such as No. 3 is used, carbon uptake can be fundamentally prevented.

However, GaH2CI and GaHC12 have major problems such as being extremely unstable at room temperature and having low vapor pressure. On the other hand, GaCl3 is stable and has a reasonable vapor pressure, so it is considered possible to transport it in a gaseous state through piping and supply it to the reaction vessel by switching with a valve.

However, GaCl3 has the problem of being extremely difficult to handle due to its strong deliquescent and corrosive properties, and has never been satisfactory as a raw material for atomic layer epitaxy.

An object of the present invention is to overcome the drawbacks of the prior art and to provide a method for forming a thin film of a high-quality 1-V group compound semiconductor at a lower temperature.

[Means to solve the problem]

According to the present invention, a group ■-■ compound semiconductor thin film is formed by alternately supplying a volatile complex compound consisting of a group II compound and a group V compound, and a group V element or a group V volatile compound onto a substrate. In this method, a method for forming a semiconductor thin film of a group (1)-(2) compound is obtained, characterized in that the group (1) compound constituting the volatile complex compound is a hydrogen compound having a direct bond between a group (1) element and a halogen element. Furthermore, there is obtained a method for forming a semiconductor thin film of a 1-V group compound, characterized in that the V group compound constituting the volatile complex compound is a nitrogen compound.

[Effect]

In general, the group III ring constituting group III compounds has an empty p electron orbital, and therefore these compounds are electron acceptors (Lew).
is acid). On the other hand, since the V group ring constituting the V group compound has a lone pair of electrons, these compounds act as an electron donor (Lewis base). As a result, the Group II compound and the Group V compound undergo a so-called acid-base reaction, in other words, the lone pair of electrons in the Group V ring coordinates with the vacant p-electron orbital of the Group III ring, resulting in a more stable complex. Attempt to form a union.

Hydrogen compounds that have a direct bond between a group element and a halogen element, such as GaH2C1 and GaH that have a Ga-Cl bond
There was a problem that Cl2 and the like were extremely unstable at room temperature. However, in this case as well, if a suitable group V compound is selected and reacted with these hydrogen compounds, a complex that is stable at room temperature and has an appropriate vapor pressure can be formed. Such a complex easily decomposes into (1) hydrogen-hydrogen compound and (2) group compound at the growth temperature. At this time, if the group (I) compound itself is stable and does not decompose, it can be considered that there is substantially no supply of group V elements. Furthermore, unless decomposed, even if a group V organic compound is used, it will not become a source of carbon impurities. On the other hand, (2) Hydrogen compounds such as GaH2Cl are easily decomposed at the growth temperature, so only Ga-Cl can be ultimately supplied to the substrate surface through the above process.

As the V group compound, any of compounds such as arsenic, phosphorus, or nitrogen is considered to be capable of forming a stable complex with the hydrogen-hydrogen compound. However, among them, nitrogen compounds with the lowest atomic number, such as NH3, and organic compounds, especially trimethylamine (TMN: N
(CH3) 3 ) and dimethylamine (DMNH: N
H(CH3)2) etc. are the most thermally stable, and the resulting complex has a high vapor pressure.

From the above, by using a volatile complex compound, such as GaH2C1・TMN, obtained by the reaction of a hydrogen-hydrogen compound having a group-group element-halogen bond and a left-element compound, such as GaH2C1/TMN, as a group-group raw material, high-quality materials can be produced at lower temperatures. Atomic layer epitaxy of ■-■ group compound semiconductors that can form semiconductor thin films can be realized.

〔Example〕

Hereinafter, embodiments in which the present invention is applied to atomic layer epitaxial growth (ALE) based on metal organic chemical vapor deposition (MOCVD) will be described in detail with reference to the drawings.

Using the horizontal reduced pressure MOCVD apparatus shown in Fig. 1, GaAs
GaAs was grown on a (100) substrate.

There is a servo susceptor 2 in the reaction vessel 1, which is supported by a susceptor holder 4. The substrate crystal 3 is placed on the susceptor 2. A high frequency coil 8 is wound around the outside of the reaction vessel 1 to heat the susceptor 2. Further, there are systems 5 to 7 for exhausting gas, where 5 is a filter, 6 is an exhaust device, and 7 is an exhaust pipe. Also, 9 to 14 are gas introduction systems,
9゜10.11 generates raw material gas respectively AsH3
Gas cylinder, DEGaC1 bubbler, GaH2C1・TM
It is an N bubbler, and 12 is H2 gas serving as a carrier. The flow rate of each gas is controlled by a flow control device 13 and a valve 14.

In order to simultaneously examine the presence or absence of selectivity during growth, a 5i02 mask portion was provided on a part of the surface of the GaAs substrate 3. GaAs substrate 3 on carbon susceptor 2 was heated to 200'C to 600°C by high-frequency heating by flowing H2 as a carrier gas at 9J2/win and setting the pressure inside the reaction tube to 100Torr.
It was heated to 0"C. At this time, AsH3 at a partial pressure of ITorr was supplied into the reaction vessel. After heating, AsH3 was heated to 0"C.
Stop, and after 1 second I x 10-3~3 x 10
GaH2C1.TMN at a partial pressure of -2 Torr was supplied for 3 seconds. Thereafter, there was a period of 1 second during which no raw material was supplied, and then AsH3 at a partial pressure of ITorr was supplied for 1 second. The raw material non-supply time of 1 second is sufficient time for the raw material to be removed from the reaction tube in this embodiment. This 6 second operation was repeated 1000 times.

For comparison, an experiment was also conducted using conventional DEGaCl instead of GaO2C1 and TMN.

As a result of changing the GaO2C1 and TMNQ partial pressures at a growth temperature of 500℃, GaAs
The thickness of one molecular layer of GaAs at (100) was in very good agreement with the thickness of 2.83. Figure 2 shows GaO2C] ・TM
It shows the film thickness per cycle when the partial pressure of N is fixed at 2X10-2 Torr and the growth temperature is varied from 200°C to 600'C.
In the 'C range, the thickness of one GaAs monolayer was 2.83 mm regardless of the temperature. Further, in this temperature range, no precipitation of GaAs was observed on the 5i02 mask portion in any case, and selective growth was possible. 300°C
The film thickness increase seen below is caused by the decomposition of the raw material.
This is considered to be because CI becomes unstable at 300° C. or lower, and the disequilibrium reaction of formula (1) occurs, causing unlimited accumulation of Ga.

3GaCI=2Ga(↓)±GaCl 3- (1)
On the other hand, when DEGaC1, which is a conventional raw material, was used, the thickness of the grown film decreased significantly at temperatures below 400'C, as shown in FIG. This is thought to be because the decomposition rate of DEGaCl decreases at low temperatures.

Figure 3 shows GaO2C1-TMN and DEGa for comparison.
These are the results of evaluating the impurity density of a film grown using Cl in a temperature range of 300° C. to 60° C. by Hall measurement. All the films grown using GaO2C1.TMN showed n-type conductivity at a low concentration of 1014 to 1015 cm-3. On the other hand, the film grown using conventional DEGaC1 exhibits p-type conductivity at temperatures below 500° C., and the impurity density increases at low temperatures. This highly concentrated impurity was confirmed to be carbon by SIMS measurement.

As described above, it has been shown that by using GaH2Cl -TMN as a group II raw material, ideal atomic layer epitaxial growth of GaAs can be realized at lower temperatures, there is no incorporation of carphone impurities, and selective growth is also possible. It was done.

Note that GaO2C] and DMNH etc. may be used as the group Ga raw material.The present invention is also applicable to the growth of GaP and GaSb with different types of group V elements, as well as the growth of mixed crystals such as GaAsP. It's coming. Also, similar results are obtained from AIH
2I Growth of AlAs and In using TMN and ASH3
It can also be obtained by the growth of InP using H2C1-TMN and PH3, and the present invention can be applied to the growth of a wide range of 1-V group compound semiconductors, not limited to these examples.

In the above embodiments, similar results can be obtained using a low pressure MOCVD apparatus as the vapor phase growth apparatus, an atmospheric pressure MOCVD apparatus, or conversely a MOMBE apparatus which performs growth in a vacuum.

〔Effect of the invention〕

As described above, according to the present invention, ideal atomic layer epitaxial growth can be achieved at low temperatures and there is no incorporation of carbon impurities, so a vapor phase growth method for forming high quality semiconductor thin films at lower temperatures can be realized. The effect of

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a vapor phase growth apparatus as an example according to an embodiment of the present invention, and FIG.
, Further, for comparison, a diagram showing the relationship between the growth film thickness per cycle and the growth temperature when DEGaCl is used, and FIG. 3 is a diagram showing the relationship between the impurity density of the obtained film and the growth temperature. . 1... Reaction container, 2... Carbon susceptor, 2...
・Substrate crystal, 4... Susceptor holder, 5... Filter, 6... Exhaust device, 7... Exhaust pipe, 8... High frequency induction coil, 9-A s H3 bomb, 1O-DEG
aC1 bubbler, 11・-GaO2C1-7MN bubbler,
12...Carrier H2 gas, 13...Flow rate control device, 14...Valve.

Claims (1)

[Claims] 1. A III-V compound semiconductor obtained by alternately supplying a volatile complex compound consisting of a Group III compound and a Group V compound, and a Group V element or a Group V volatile compound onto a substrate. A method for forming a III-V compound semiconductor thin film, characterized in that the Group III compound constituting the volatile complex compound is a hydrogen compound having a direct bond between a Group III element and a halogen element. 2. The method for forming a III-V compound semiconductor thin film according to claim 1, wherein the group V compound constituting the volatile complex compound is a nitrogen compound. .