JPH01296613A - Method of vapor growth of iii-v compound semiconductor - Google Patents

Abstract

PURPOSE:To make it possible to form an ultrathin film on a number of sheets of substrates simultaneously by a method wherein a plurality of reaction parts are provided on an epitaxial growing chamber, and raw gas is fed to each reaction part successively. CONSTITUTION:Four independent reaction containers 1-4 are provided in a quartz container 5, and carbon susceptors 6, on which a plurality of substrate crystals 7 are placed, are provided in the four reaction containers 1-4. Also, there are an AsH3 gas cylinder 9, a DEGaCl bubbler 10, a DMInCl container 11, and H2 gas 12, which becomes a carrier in gas introducing systems 9-20, and the flow rate of each gas is controlled by a flow rate controlling device 13. The DEGaCl gas and the AsH3 gas are supplied from the reaction container 1 by staggering the time and switching to the containers 2-4. As a result, a highly uniform superthin film can be formed simultaneously on a large number of substrates having a large area in a highly efficient manner.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for vapor phase growth of ■-V group compound semiconductors;
More specifically, this article relates to a method for vapor phase growth of ■-V group compound semiconductors that can efficiently form extremely thin films of ■-V group compound semiconductors and their mixed crystals on a large number of large-area substrates at once. It is something.

[Prior art] ■-Epitaxially grown layers of group V compound semiconductors are used in optical devices such as light emitting diodes and laser diodes, and FEs.
It is widely applied to high-speed devices such as T. More recently, structures in which several to tens of thin film semiconductors are stacked are required to improve device performance. For example, a laser diode with a quantum well structure can reduce driving current, improve temperature characteristics, and shorten the emission wavelength. Furthermore, FETs that utilize two-dimensional electron gas are expected to be high-speed, low-noise devices.

Conventionally known methods for thin film epitaxial growth include metal organic chemical vapor deposition (MOCVD) and vapor phase epitaxy (VPE) using gases such as halogen transport methods, which depend on the amount of gas supplied, growth temperature, and growth time. The film thickness was controlled through precise control such as In addition, the molecular beam epitaxial growth method (MBE method), in which growth is performed by ejecting an elemental beam in a high vacuum, is known as a growth method that is relatively easy to control the thickness, but there are still various factors such as molecular beam intensity, growth temperature, time, etc. Precise control was required.

In recent years, this has been improved by Suntra (T).

The atomic layer epitaxial growth method (ALE method) reported by 5untora et al.
abstract of the 16th
Conference on 5solidState
Devices and materials
s, Kobe, 1984. pp. 647-650>, a compound semiconductor (quaternary element, or a gas containing the element is alternately supplied, adsorbed one atomic layer or one molecular layer at a time, and caused to react, This is a method for growing a compound semiconductor with a desired overall thickness.In this method, the thickness of the grown film is determined by the number of repetitions of the operation of alternately supplying M group and II group raw materials, and the thickness of the grown film depends on the partial pressure of the raw materials supplied. This makes it possible to easily grow transposed thin film structures with steep interfaces at the monoatomic layer level.Furthermore, it can be grown uniformly on a large number of substrates, making it a great advantage as a mass production technology.

By the way, the method of alternately switching gases and supplying them onto the substrate is usually carried out by fixing the substrate in a reaction vessel and alternately switching the valves disposed in the respective raw material gas supply lines. As an example of a growth method using a vapor phase growth apparatus that has been conventionally used to perform atomic layer epitaxy cell growth by switching the valves alternately, a metal organic vapor phase growth apparatus using a group II organometallic raw material and a V oxyhydride raw material is used. The vapor phase growth method using (MOCVD apparatus) will be explained below.

FIG. 4 is a schematic diagram showing an example of the MOCVD apparatus. First group organic metal material 41 which is usually liquid at room temperature
0, and the second group (III) organometallic raw material 411, which is solid, is kept at a constant temperature with an appropriate vapor pressure, and is bubbled with a carrier gas controlled by a flow rate controller 413 or bubbled in the vicinity. It is vaporized and transported by passing through it.

For example, by opening the valve 417, the first
Group organometallic raw material 410 can be introduced into reaction vessel 41 and flowed directly to the exhaust system by closing valve 417 and opening valve 418. The same applies to the group V hydrochloride raw material 49, which is introduced into the reaction vessel 41 by opening the valve 415, and is introduced into the reaction vessel 41 by closing the valve 415.
By opening 16, it can flow directly to the exhaust system. In the figure, 46 is a carbon susceptor, 47 is a substrate crystal, and 48 is a high frequency coil.

Conventionally, such a device was used, and by switching the operation such that one raw material was introduced into the reaction vessel while the other raw material was flowed directly to the exhaust system, Group M and Group V raw materials were alternately pumped into the reaction vessel. was introduced to perform atomic layer epitaxy cell growth.

[Problem to be solved by the invention] When performing atomic layer epitaxial growth using the above-mentioned vapor phase growth apparatus, the thickness of the grown film changes depending on the number of repetitions of the operation of alternately supplying the M group and II group raw materials. Since this method does not depend on the supply partial pressure of raw materials, it is possible to grow uniform films on many substrates in one reaction vessel, and it has a great advantage as a mass production technology.

However, on the other hand, unlike the normal continuous growth method, m
Group and V group raw material gas supply times are required separately. Purge time, which takes into account the time required to turn on and off the valve for gas switching operation and the time required for the rise and fall of the pulse that occurs when raw gas flows through the piping in pulses. is required.

The time required to turn the valve on and off is extremely short and does not pose a problem when using a high-pressure air-operated valve.

However, the time required for the "rise" and "fall" of the raw material gas flow depends on the length of the piping from the valve to the reaction vessel, the presence or absence of gas accumulation in the middle, the gas flow rate, the volume of the reaction vessel, etc., but it is short. If the length is from a few tenths of a second to a few seconds, it may take more than a few seconds.

Therefore, when performing atomic layer epitaxial growth, a purge time is usually provided between the operations of alternately supplying the M-group and V-group raw materials, and a total of four steps are made into one cycle, and growth is performed by repeating this cycle.

Therefore, compared to the conventional MOCVD method, where the supply time of the group III raw material corresponds directly to the growth time,
This means that three extra steps will require a longer growth time.

In other words, if the number of substrates that can be processed at one time in one reaction vessel is the same for both MOCVD and ALE, the number of substrates that can be processed per unit time will be the same as the ALE method, which requires a longer growth time. This decreases the processing efficiency. Furthermore, during the three steps other than the step in which one of the raw material gases is introduced into the reaction vessel, the raw material is directly discarded into the exhaust system, so the raw material utilization efficiency is low and there is an extremely large amount of waste.

The object of the present invention is to overcome these drawbacks of the prior art and to -
■-V efficiently and highly uniformly on multiple large-area substrates at the same time
An object of the present invention is to provide a method for vapor phase growth of group (1)-v compound semiconductors, which can form ultrathin films of group compound semiconductors and their mixed crystals.

"Means for Solving the Problems" The present invention provides a method for producing a ■-V group compound semiconductor by alternately introducing a Group III element and a Group V element into an epitaxial growth chamber and supplying them onto a substrate crystal in the growth chamber. In the vapor phase growth method, the epitaxial growth chamber has a plurality of independent reaction sections in which a substrate crystal is held, and each source gas is sequentially supplied to the plurality of reaction sections for a predetermined period of time. This is a method for vapor phase growth of group V compound semiconductors.

[Operation] During the three steps other than the step in which one of the raw material gases is introduced into the reaction vessel, the raw material is directly "discarded" into the exhaust system.
In order to eliminate the waste of raw materials that occur due to storage and increase the number of substrates that can be processed per unit time, it is necessary to prepare multiple reaction vessels instead of one, and to remove the waste of raw materials that were previously disposed of directly into the exhaust system. The raw material gas may also be supplied to another reaction vessel during that time, and growth may be performed there as well. The raw material gas from each raw material supply line is sequentially and repeatedly supplied to the plurality of reaction sections for a predetermined period of time by opening and closing the valves.

First, let us consider the case where a binary compound is grown using one type of raw material each of group (I) and group V. In that case, in order to completely eliminate waste of raw materials, the supply time t (111) of the group II organometallic raw material and the supply time t (Vl of the group V hydride raw material) must be
l = t 1 (equal to (1)), where the length of one cycle is ts and the number of reaction vessels is N, it is necessary that N = tS/j+≧2 (2). Purge time of group m raw material t D flail
and purge time tl of group V raw material) (the sum of Vl is 1D
(nll+jl) (V] = 1:1X (N 2>...
・(3) To. The ratio of t p fl) and t p (Vl can be arbitrarily selected. When iS/11=2, the purge time cannot be taken without wasting raw materials. If t
(If ml and t?Vl are not equal, for example, t t
■If t≧t IVI, t s = t(Illlx
N becomes t (1111-t (Vl time means V group raw material is wasted. Table 1 below summarizes cases where no waste occurs.

(Leaving space below) Table 1 In the above example, if the number of substrates that can be processed in one reaction vessel is the same, the processing capacity per batch will increase as the number of reaction vessels increases, but the time required to grow one batch will increase. becomes proportionally longer.

Therefore, in terms of processing power per unit time, they are all the same.

Furthermore, the greater the number of reaction vessels, the longer the purge time can be taken. Even if a thick film is absolutely required in a short period of time, it is better to have two reaction vessels than one. The time it takes to grow one batch is the same whether there is one or two reaction vessels, but the throughput is twice as long with two reaction vessels, and even if there is some waste, it is possible to set up a purge time. Even in this case, the amount wasted is much smaller when the number of reaction vessels is two.

Next, let us consider the case of growing a mixed crystal.

In this case, when group I raw materials and group V raw materials are mixed together and supplied at a ratio that yields the desired mixed crystal composition, in other words, the composition is controlled in an analog manner as in normal growth. In this case, it can be grown efficiently in exactly the same way as binary compounds.

On the other hand, if you want to digitally control the mixed crystal composition, which is a feature of the atomic layer epitaxial growth method,
In other words, when it is desired to grow a so-called ordered mixed crystal having a superlattice structure at the level of a monomolecular layer, using the same method as for binary compounds, raw materials are wasted during the time when the type of gas is changed. Of course, by extending the concept of binary compounds, it is possible to eliminate waste of raw materials even in the growth of aligned mixed crystals, as shown below, but this requires a complicated apparatus and is not a very practical method.

Now, for example, ll11xI21-xVl, yV 2 as a quaternary mixed crystal consisting of two constituent elements each of group ■ and group V
Think about i-y. Each of these compositions is an integer n.

Using m, h, k, respectively X = n/(n4m)
, 1-X=m/(n4m), V=h/(h+k),
It can be expressed as 1-V=k/(h+k), where n, m
, h, and k, for example, suppose that n is the smallest.

In that case, in order to grow without wasting any raw materials, 10m=h+k
... (4) t fllll= t (V]=
t 1 ...(5) holds, and the number of reaction vessels is N = ((n4m)/n)X (t s/ t 1)
≧((n4m)/n) x 2...(6) It is necessary to prepare n, m, h, k raw material supply lines for raw materials ■1, ■2, Vl, and v2, respectively. . However, when tS/11=2, the purge time cannot be taken without wasting the raw material.

For example, In□, 4 Ga□, 6 As□, 2PO, 8
If you want to grow, n=2, m=3, h=1, k=4
, n++++=h+=5, and h=1 is the minimum rIrl.

2, 3, and 3 Ga, As, and P raw material lines, respectively.
For example, prepare 4 1° and 10 or more reaction vessels.
In(1) −As(1) →In(2) −*P(1
)-Ga(1) →P(2)→Ga(2) →P(3)
→Ga(3) →P(4) It is sufficient to supply the gases sequentially at staggered times.

For the simplest mixed crystals, such as group ■ elements, In□, 5
In cases where the composition ratios are equal, such as Gao and 5 As, n=1, m=1, n+m=2.
2 + O = 2, and it is sufficient to prepare four or more reaction vessels for a total of four raw material lines, two for In and Ga raw material lines and two for As raw material lines. Become. If purge time is 1/2
If tj is to be taken, the number of reaction vessels should be increased by 3/2.

As described above, the growth process has a plurality of independent reaction sections holding substrate crystals, and the group (I) and group V raw material supply lines are already connected to each of the plurality of reaction sections via independent valves. By using a device and supplying raw material gas from each raw material supply line to multiple reaction sections by repeatedly opening and closing valves for a certain period of time, highly uniform ■-V can be produced on many large-area substrates at once. It is possible to realize a method for vapor phase growth of group 1-v compound semiconductors that efficiently forms ultrathin films of group compound semiconductors and their mixed crystals.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. In this example, a case will be explained in which the present invention is applied to an atomic layer epitaxial growth method (ALE method) based on a metal organic chemical vapor deposition method (MOCVD method) using a group I organic metal raw material and a group V hydride raw material. do.

Example 1 Horizontal MOC with four independent reaction vessels as shown in Figure 1
GaAs was grown on a GaAs substrate using a VD apparatus.

There are four independent reaction vessels (reaction parts) 1 to 4 in a quartz vessel (epitaxial growth chamber) 5, and in each of these four reaction vessels, a carbon susceptor 6 on which a plurality of substrate crystals 7 are placed is placed. be.

The carbon susceptor 6 is heated by a high frequency coil 8 wound around the outside of the quartz container 5.

Further, 9 to 20 are gas introduction systems, and 9, 10 and 11 are AsH3 gas cylinders and D, respectively, which generate raw material gas.
EGaCi bubbler and D old nc12 container, 12
is H2 gas which becomes Kyrelia. Each gas flow rate is controlled by a flow rate controller 13. 14 to 20 are valves, and by opening the valve 15a, the group V hydride raw material 9 is introduced into the reaction vessel 1, and 15b, 1 are similarly introduced.
By opening 5C and 15d, they can be introduced into the reaction vessel 2°3.4, respectively. Also, the valves 15a to 1
5d are all closed and can flow directly to the exhaust system by opening valve 16. The same applies to group (3) organic metal raw materials, such as DE Gall and elO, and the valve 17a
into the reaction vessel 1 by opening, and similarly 17b.
, 17c, 17d to open the reaction vessel 2,
3.4, respectively.

Further, by closing all the valves 17a to 17d and opening the valve 18, it is possible to flow directly to the exhaust system.

Using the horizontal MOCVD apparatus configured as described above, GaAs was grown in the following manner.

3 on the carbon susceptor 6 in the four reaction vessels 1 to 4.
A total of 12 3-inch GaAS substrates 7 are placed, and 112 as a carrier gas is placed in each reaction vessel 1-4. /min. The GaAs substrate 7 on the carbon susceptor 6 is heated by high frequency heating by the coil 8.
The IJO was heated to 00°C, and at this time, AsH3 was supplied at a partial pressure of 1 Torr into all reaction vessels.

After that, the supply of A S H3 to the reaction vessel 1 was first stopped, and after 1 second, DEGa (J) with a partial pressure of 5 x 1O-2 Torr was supplied for 1 second. After that, a period of 1 second was taken without supplying the raw material. , then AsH with a partial pressure of 'l ding orr
3 was supplied for 1 second. This 4 second operation was repeated 4000 times. Similarly to 1, for reaction vessels 2 to 4, the supply of DEGa(i for 1 second and the supply of AsH3 for 1 second) were
The process was repeated 4,000 times with a raw material supply period of seconds in between.

At this time, according to the flow sequence shown in FIG.
GaCl and AsH3 are supplied from reaction vessel 1 at different times, switching to 2, 3.4, and then returning to 1 and repeating the same <2.3.4, and so on.
Switched and supplied.

Atomic layer epitaxial growth using DEGal as a raw material (A
In LE>, DEGaCJ decomposition product AlGa(,() is first adsorbed in a single layer on the As surface, and then the supplied As
It is thought that this reacts and a single molecular layer of GaAs layer grows. In the device of this example, the maximum partial pressure is 5 x 1 O-2
It is possible to supply up to TOrr of Gaα, which is 1
The area of the substrate that can sufficiently adsorb a single layer valve by supplying it for seconds,
That is, here, the maximum number of GaAs substrates with a diameter of 3 inches was three. However, as in this example, 4
Two reaction vessels were prepared, and DEGa(, e, and Ash were sequentially mixed from reaction vessel 1 to 2, 3, and 4 times, respectively).
By switching and supplying the 0EGaC1 material, it is possible to use all the 0EGaC1 raw material that would have been wasted in the direct exhaust system when there was only one reaction vessel, and to grow 12 substrates, four times as many, in the same amount of time. It was possible.

Example 2 GaAs was grown on a GaAs substrate using an apparatus having three independent reaction vessels. This is a horizontal MOCVD apparatus with four independent reaction vessels as shown in Figure 1.
Since this corresponds to the case in which only the second reaction vessel is not used, the same apparatus shown in FIG. 1 was used here for growth.

3 on the carbon susceptor 6 in the three reaction vessels 1 to 3.
A total of nine 3-inch GaAs substrates 7 are placed, and 9 L of H2 as a carrier gas is placed in each reaction vessel 1 to 3.
'min' at a time. The GaAs substrate 7 on the carbon susceptor 6 is heated to 500 nm by high-frequency heating using a coil.
At this time, AsH3 was supplied to all reaction vessels at a partial pressure of 1 Torr.

Thereafter, the supply of AsH3 to the reaction vessel 1 was first stopped, and after 0.5 seconds had elapsed, 0EGa group at a partial pressure of 5 x 10-2 Torr was supplied for 1 second. After this, there is a period of 0.5 seconds without raw material supply, and then the As of the partial pressure of 'l TOrr is
t13 was supplied for 1 second. This 3 seconds operation is 4000 times
Repeated several times. Similarly to 1, for reaction vessels 2 and 3, 1
The supply of DEGaα for 1 second and the supply of AsH3 for 1 second,
The process was repeated 4,000 times with a 0.5 second no-supply period in between.

At this time, according to the flow sequence shown in FIG.
GaCi and AsH3 were supplied from reaction vessel 1 at different times, switching to 2 and 3, and then returning to 1 and repeating the same procedure at 2 and 3, and then switching and supplying.

Even when three reaction vessels are used as in this example, DE
By using all the Ga(i) raw materials, it was possible to grow 9 substrates at once, which is 3 times as much as when using only one reaction vessel, in the same amount of time. - The number of substrates that can be processed at a time is 4. This is reduced by 3/4 compared to the case of Example 1 using two reaction vessels, but the purge time is also reduced by half, so the time required to obtain the same film thickness is reduced by 3/4. Can grow quickly.

That’s it for DEGaCJ! , and the growth of GaAs using AsH3 was explained as an example. However, using the apparatus shown in FIG.
InGaAs mixed crystal could be grown in the same manner as above by alternately supplying EGal, I2+ DHlnCl and AsH3.

The group (I) and group V raw materials that can be applied to the method of the present invention basically only need to be able to be supplied as a gas. For example, MAS growth using Kano MC1 and AsH3, D old ncj
The present invention can also be applied to the growth of InP using 2 and P[13. Further, as the group (Ⅰ) organic metal raw material, TIG, TEG, etc., which do not have a bond with chlorine, may be used.

Furthermore, an inorganic raw material such as Ga (13) may be used as the group III raw material, and conversely, a group V hydride raw material may be replaced with a group V organic metal raw material such as TEAs. Although a pressure device was used, a similar effect can be expected with a pressure reduction device.

[Effects of the Invention] As explained above, according to the method of the present invention, by providing a plurality of reaction sections in the epitaxial growth chamber and sequentially supplying raw material gas to each reaction section, a large number of substrates can be grown at one time. In addition to being able to form ultra-thin films of ■-V group compound semiconductors, there is no need to ``dump'' raw material gas into the exhaust system as in the conventional method, which increases raw material utilization efficiency and reduces waste. can.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of an apparatus for implementing the method of the present invention, FIGS. 2 and 3 are diagrams showing gas flow sequences in Example 1 and Example 2, respectively,
FIG. 4 is a block diagram showing an example of an MOCVD apparatus for explaining the prior art. 1 to 4, 41... Reaction container 5... Quartz container 6
．． 46... Carbon susceptor 7, 47... Substrate crystal 8.48... High frequency coil 9... AsH3
Cylinder 1O-DEGaCi Bubbler 1l-D)
fInC1 container 12, 412...112 gas 13.413...flow rate control device

Claims (1)

[Claims] (1) In a method for vapor phase growth of a III-V compound semiconductor in which group III elements and group V elements are alternately introduced into an epitaxial growth chamber and supplied onto a substrate crystal in the growth chamber, the epitaxial growth chamber is 1. A method for vapor phase growth of a III-V compound semiconductor, comprising a plurality of independent reaction sections in which a substrate crystal is held, and each source gas is sequentially supplied to the plurality of reaction sections for a predetermined period of time.