JPH02166723A - Growth of compound semiconductor - Google Patents

Abstract

PURPOSE:To make it possible to control the composition and the growth rate at specified values by supplying the raw material of an element A in the same group on a substrate, adsorbing the element at a specified covering rate, then supplying the raw material of an element B, adsorbing the element in a region where the element A is not adsorbed, preventing the adsorption of the raw material of the element B which is supplied later, supplying an element in another group, and adsorbing the element on the elements A and B. CONSTITUTION:The concentration and the supplying time length of the raw material A of an element A are controlled. Thus the A atoms are adsorbed on substrate crystals at a specified covering rate. The raw material B of an element B is adsorbed on vacant sites which are not occupied by the A atoms. When a single atom layer wherein the A atoms and the B atoms are mixed is formed, growing is stopped. A specified composition AxB1-x is obtained only by performing precise control for concentration supplying time of the raw material A. When an R layer is grown at the same time, the single molecule layer of AxB1-XR can be grown readily at the accurate composition. In the case of AxB1-xCyD1-y, C and A are the same type for the part of CyD1-y, and D and B are the same type. Therefore, when the concentration of the raw material C and the supply time length are precisely controlled, the accurate composition CyD1-y is obtained, and the growing can be performed at the accurate composition.

Description

[Detailed Description of the Invention] [Summary] The purpose of this invention is to provide a method for growing compound semiconductors that can control the composition and growth rate to desired values. A method for growing a compound semiconductor crystal consisting of a mixed crystal with one of the plurality of homologous elements on a substrate.
a step of supplying a raw material of a first element that is one of the plurality of homologous elements and adsorbing the first element onto the substrate at a predetermined coverage rate; a step of supplying a raw material to cause the second element to be adsorbed to a region on the substrate where the first element is not adsorbed, and then blocking the adsorption of the raw material for the second element supplied thereafter; and a step of supplying a raw ore of the target group element and adsorbing the target group element onto the first and second elements.

[Industrial application field] The present invention relates to a method for growing compound semiconductors.

The development of semiconductor devices has been remarkable in recent years, and recently Al
GaAs, InGaAs, InGaP, InGaAs
Ternary or quaternary mixed semiconductor crystals such as P, InGaAlAs, etc. are becoming increasingly important. This is a high-speed functional device that utilizes the resonant tunneling phenomenon,
This is because the above-mentioned materials are indispensable when producing devices such as quantum well lasers that actively utilize quantum size effects.

In order to provide these devices with excellent characteristics and to manufacture them with good reproducibility, it is necessary to develop excellent crystal growth techniques. Specifically, it is necessary to develop a crystal growth method that allows the composition of the crystal to be freely controlled and the unevenness of the heterointerface to be controlled on the order of one atomic layer.

[Prior Art] Conventionally, as a crystal growth method for a mixed crystal compound semiconductor containing two or more types of homologous elements, a substance that will become a top layer is made into a molecular beam state on a substrate placed in an ultra-high vacuum. MBE method (Ho 1ecu far Beara E) in which growth is performed by irradiating
pitaxy (molecular beam epitaxy), MO, CVD method (Me
tal Organic Chemical Vap
or Deposition: organometallic chemical vapor phase growth method).

FIGS. 2A and 2B show apparatuses implementing these conventional techniques.

FIG. 2(A) shows a conceptual diagram of the MBE device.

The vacuum vessel 31 is evacuated by an evacuation system 32 and equipped with a liquid nitrogen shroud 33 on the inner wall, an electron gun 34 for reflected high energy electron diffraction (RHEED), a RHEED monitor system 35, a peephole 36 for internal observation, and a vacuum gauge 3.
9, a monitor such as a mass spectrometer 40 is provided. Substrate 10
can be sequentially supplied and exchanged from the substrate exchange chamber 37 evacuated by the exhaust system 38.

Crystal growth raw materials are contained in molecular beam cells 41, 43, 45, 47. Each molecular beam cell is provided with an independently controllable shutter and shutter.

The substrate 10 is also heated by the substrate heater.

A process control computer 49 receives monitor signals from a monitor device and controls the shutter temperature, shutter, substrate shutter, etc. of each molecular beam cell according to a setting program.For example, when growing an InGaAs layer,
The shutters of the In, Ga, and S cells are opened to irradiate In, Ga, and As molecules or atoms onto the substrate.

Figure 2 (B)! i, MOCVD equipment
l The quartz reaction tube 51 shown in the drawing is a water-cooled jacket 5.
2, and a high-frequency heating coil 53 is wound around the outside thereof. The substrates 10 can be sequentially supplied and exchanged from a substrate exchange room 37 equipped with an exhaust system 38. A thermocouple is installed inside the susceptor on which the substrate 1° is placed to monitor the substrate temperature.9 The reaction gas is introduced from above and is discharged through the filter 55, pressure regulating valve 56, exhaust system 57, and waste gas treatment device 58. be done.

The raw material for the reaction gas can be supplied in the gas phase or in the liquid phase by bubbling.
・Limethylindium (TMIn) 61, triethylgallium (TEGa) 62, phosphine (PH3>63, arsine (^5H3) 64 as gas phase supply source 11 are shown).Hydrogen 65 is passed through a purification device 67 to become a carrier. It is introduced as a gas.By bubbling hydrogen into the raw materials 161 and 62, the gas phase raw material in the pond is mixed with hydrogen, and the raw material is supplied.Mass flow meters 68a, 68b
, 68c, and 68d respectively adjust hydrogen for bubbling, hydrogen for dilution, hydrogen for gas-phase raw material-second dilution, and hydrogen for secondary dilution of gas-phase raw material.

In this way, each raw material is diluted at a predetermined ratio, mixed, and then sent to the raw material supply port of the reaction tube 51.

[Problems to be Solved by the Invention] When growing a mixed crystal compound semiconductor using the above-mentioned MBE or MOCVD method, raw materials are simultaneously supplied for growth. For example, when growing InGaAs, In, Ga,
^S is supplied at the same time.

At this time, the growth rate and composition of the crystal are greatly influenced by the molecular beam intensity or concentration of each raw material. In other words, growth rate and composition are related to each other, so it is difficult to control them independently4.For example, in the case of InGaAs mentioned above,
In order to grow a crystal with a high ratio of , it is necessary to increase the ratio of raw material In, but when the amount of In supplied increases, the growth rate becomes extremely fast. In this way, the growth rate is the rate of supply, and it has not been possible to grow a mixed crystal compound semiconductor crystal of a desired composition at a desired rate.

An object of the present invention is to provide a method for growing a compound semiconductor in which the composition and growth rate can be controlled to desired values.

In addition, according to the prior art, it was often difficult to control the composition itself.For example, in the case of InGaAs containing Ga and In as group Ⅰ elements, the amount of trimethylindium (TMIn) introduced into the gas as a raw material for In I in solid
The relationship with n composition is as shown in FIG.

That is, compared to Ga, In does not easily enter the solid, and when the amount of TMIn introduced is increased, it enters rapidly. Therefore, it has not been easy to control the In composition when the In composition is higher than a certain level.

Another object of the present invention is to provide a method for growing a compound semiconductor whose composition can be easily controlled.

[Means for Solving the Problems] According to the present invention, when growing a crystal of an AxBl-xR type mixed crystal compound semiconductor, atoms of component A and atoms of B are sequentially and independently supplied and adsorbed, and further B atoms are A material that has a self-limiting effect is used as the raw material. A and R may be a single element, a group of elements, or a combination of elements at a predetermined ratio.

FIGS. 1A and 1B are diagrams explaining the principle of the present invention.

FIG. 1(A) schematically shows the growth of an AxB, , R monolayer, where A is a single atom. First, a raw material [A] of element A is supplied onto the base crystal. Here, the concentration of raw material [A], C
1 and the supply time t1 is controlled to adsorb A atoms at a predetermined coverage rate that achieves composition X.

Next, as the raw material [B] for element B, a material that has a self-limiting effect, that is, an iR side that automatically stops depending on the thickness of the grown film, is used, and if the supply amount is sufficient, it is supplied at a combination of a degree and time length. do.

Furthermore, an R layer is grown. For example, if R is a single atom,
Grow R monoatomic layer.

In this way, grow an AB R monolayer ×1-X Ru.

Figure 1 (B) shows AB CD single molecule x 1
-x y 1-y This schematically shows the growth of a layer, A and C are single atoms.

First, a raw material [A] of element A is supplied onto the base crystal. Here, the concentration of raw material [A], C1, and supply time t1 are controlled to adsorb A atoms at a predetermined coverage rate that achieves composition X.

Next, element B having a self-limiting effect, that is, an automatic stopping mechanism depending on the thickness of the grown film, is used as the source tl[B] of element B, and is supplied at a combination of concentration and time that provides a sufficient supply amount.

Subsequently, raw material [C] of element C is supplied. Raw material [C]
C atoms are adsorbed at a predetermined coverage rate that achieves the composition y by controlling the concentration C2 and supply time t2.

On top of this, an element f='l [D] is supplied. [
For D], a material having a self-limiting effect is used. Supply at a concentration and supply time that will provide a sufficient supply amount.

In this way, an Ax B1-x Cv Dl-y monolayer is grown.

Although the growth of a monomolecular layer has been described above, the required film thickness can be obtained by stacking and growing multiple layers.

[Operation] By controlling the concentration and supply time length of the raw material [A] of element A, it is easy to adsorb A atoms onto the base crystal at a predetermined coverage rate.

Since the raw material [B] of element B has a self-limiting effect, it adsorbs to empty sites not occupied by A atoms,
Growth is stopped when a monoatomic layer containing a mixture of A and B atoms is formed.

In this way, the desired composition A3B1-x can be obtained by precisely controlling only the concentration supply time of the raw material [A].

By growing the R layer together, an AxBl-xR monolayer can be easily grown with a precise composition.

In the case of AxB,,C,Dl-, the part Ax''1-x is the same as above.For the part C, Dl, C and A are types, and D and B are types. be.

Therefore, if the concentration of raw material [C] and supply time length are precisely controlled, accurate compositions C, D1. is obtained. In this way, AxBl-xCyDl-7 can be easily grown with a precise composition.

[Example] FIG. 4 schematically shows an example of the m-m-v type warm-crystalline compound semiconductor crystal growth method.

In the growth of ■-V group compounds, in general, group ■ metal elements are easy to stack in multiple layers, and group V elements have a high vapor pressure and are difficult to adsorb onto group V elements. Therefore, ■-m-v type crystals It has not been easy to grow compound semiconductors with high precision and high quality.6 In FIG. 4, the 2N-type materials are not supplied simultaneously but in a time-divided manner. As the second group material to be supplied, a material having a self-limiting effect in atomic layer epitaxy is selected. After that, the V group raw material is supplied and 1
Crystals corresponding to molecular layers grow. The growth environment may be an ultra-high vacuum such as MBE, or a normal pressure or reduced pressure atmosphere such as MOCVD.

Group ■ raw materials supplied first are I [11th and 21st materials are ■
First, 1 is sent at a certain density M for a certain time m seconds. As a result, 1 of the coverage ratio θ(M, m), which depends on M and m, is adsorbed onto the crystal surface. Continuing ■2
When a sufficient amount of 2 is supplied, since 2 has a self-limiting effect, it adsorbs on the crystal surface where 1 was not adsorbed, and the total coverage of 1 and 2 becomes 1. At this time, ■2 does not adsorb on either ■1 or ■2 itself. After that, by supplying the V group raw material, the crystal becomes 1.
Only molecular layers grow. The composition of the crystal is controlled by the concentration M of 1.
This can be freely done by selecting the supply time m'@- and changing the coverage rate θ. Controlling the growth film thickness is possible because ■2 fills in all the areas that were not filled by ■1, so regardless of the coverage rate of ■1,
One molecular layer per cycle. In other words, the crystal composition can be changed freely while maintaining the growth rate of one molecular layer per cycle. Moreover, only the concentration and supply time of ■1 need to be strictly controlled, and ■2
Even if the introduction conditions of Group V raw materials are changed, the composition and growth rate are not affected.

Above, we have explained the case of the m-■-v type hybrid compound semiconductor crystal length, and also in the case of the growth of ff[-V-V type warm crystal compound semiconductor crystal, the above-mentioned ■ and V group should be exchanged. You can do the same thing. Furthermore, the growth of m-m-v-v type quaternary mixed crystal compound semiconductor crystals can be carried out by performing coverage control and self-limiting growth for each of the (I) and V groups.

Next, we will use InGa as an nr-m-v type warm crystal compound semiconductor.
A specific example of growing As will be described.

Here, trimethylindium was used as a raw material for In, trimethylgallium was used as a raw material for Ga, and arsine was used as a raw material for As. As for group (2) raw materials, trimethylindium was first supplied, and then trimethylgallium was supplied. Trimethyl gallium has a self-limiting effect. In FIG. 5, the composition ratio of indium and the growth rate when 500'Cf InGaAs was grown are plotted against the supply time of trimethylindium. Hydrogen is used as a carrier gas, and trimethylindium is used at a mole fraction of 1.2X10-4.
So, 11 methyl gallium was treated at a mole fraction of 2.1X10-3 for 5 seconds, arsine was treated at a mole fraction of 4.8X10-2 for 20 seconds,
It was introduced under a reduced pressure atmosphere of about 15 torr. As the supply time of trimethylindium increases, the composition ratio of indium increases almost linearly. In other words, the composition ratio can be controlled extremely easily. On the other hand, the film thickness grown per cycle takes a constant value of one molecular layer.

Therefore, the growth rate (growth rate) can also be easily controlled.

A growth model of InGaAs is shown in FIGS. 6(A), (B), and (C).

FIG. 6(A) shows a state in which trimethylindium is supplied onto a substrate while controlling concentration and time. On the surface of the substrate 1, sites 2 to which group Ⅰ elements can be adsorbed are distributed. In site 3 occupies x/1 of site 2 .

FIG. 6(B) shows a state in which a sufficient amount of trimethyl gallium has been supplied. In terms of concentration and time, a sufficient amount of 1-trimethylgallium is supplied, and all unoccupied groups are filled with G.
A atom 5 is adsorbed. Trimethylgallium has a self-limiting effect and does not adsorb onto group III atoms, so the reaction is complete when a monoatomic layer of group III atoms (In, Ga) is completed.6 Figure 6 (C) indicates a state in which arsine is supplied.

A sufficient amount of arsine is supplied, and a monoatomic layer of 7 As atoms is grown on the preformable monoatomic layer.

Arsine has a self-limiting effect, and the reaction stops when a monoatomic layer grows.

In addition, in the above embodiment, ■
Trimethylgallium [Ga(CH3)31
In addition, gallium chloride [GaCl]
, diethylgallium chloride [Ga(C2H5) 2
CI] may be used as a raw material having a self-removal effect.

In addition, when growing a 1-v-v group mixed crystal compound semiconductor containing multiple group V elements, hydrogen compounds such as arsine [AS] (3), phosphine [PH31] and trimethyl arsenic [AS
Organic metals such as (CH3)3] can be used as raw materials having a self-limiting effect. By using such raw materials, 1-v-v mixed crystal compound semiconductor crystals such as GaAsP and GaAsSb can be grown with high precision.

In addition, m-m-v of rnGaAsP, GaAIAsP, etc. can be produced by using both the Group I element raw material having a self-limiting effect and the V Group element raw material having a self-limiting effect.
-V mixed crystal compound semiconductor crystal can be grown with high precision.

Although the above description has been made by exemplifying III-V compound semiconductors, the present invention is not limited to III-V compound semiconductors, but also applies to group III-V compound semiconductors.
It can also be applied to crystal growth of Vl group compound semiconductors.

[Effects of the Invention] As explained above, according to the present invention, it is possible to independently control the composition and the growth rate in the growth of a mixed crystal compound semiconductor, and to Simplifying the Growth of Physical Semiconductors 6 Furthermore, composition control itself is facilitated.

[Brief explanation of the drawing]

111ffi (A) and (B) are diagrams explaining the principle of the present invention, (A) is a graph showing the growth process of A, B 1-8R monolayer, (B) is A x B 1-x C
, D Graph showing the growth of a 1-1 monolayer, FIG. 2<A), (B) show the conventional technology, (A)
(B) is a conceptual diagram of the MOCVD equipment. Figure 3 is a graph showing the relationship between the amount of trimethylindium introduced and the In composition in the solid according to the prior art. Figure 4 is II
[1-I [[2- A graph showing the growth process of a group V compound semiconductor. FIG. Figures (A), (B), and (C) show models of InGaAs crystal growth, where (A) is the process of supplying trimethylindium, (B) is the process of supplying trimethylgallium, and (B) is the process of supplying trimethylindium.
In Figure 6, which is a model diagram explaining the crystal growth mechanism in the arsine supply process, A, C, R D [A] [B] [Cl [D co[R colc3] and 1. t3 Component element Principle 1 of raw material element B of component A Principle 4 of raw material element R of component C Supply time length of raw material concentration of component R Substrate (underlying crystal) Site In atom Ga atom As atom (A) MBE apparatus conceptual diagram (B ) MOCVD system f iE concept 2 Conventional technology Fig. 2 shoulder (A) Growth of 1-SiR star molecular layer from A (B) A, -E C, D + -, growth of monomolecular layer M of the present invention Figure 1: Amount of trimethylindium introduced

Claims (1)

[Claims] (1), multiple homologous elements (A, B) and other group elements (R
, C, D), the method comprises: growing a compound semiconductor crystal consisting of a mixed crystal with a first element (
A) A step of supplying the raw material to adsorb the first element onto the substrate at a predetermined coverage rate, and then adsorbing the second element (
B) Supplying the raw material to cause the second element to be adsorbed in a region on the substrate where the first element is not adsorbed, and preventing the adsorption of the second element raw material that is subsequently supplied. and then, a step of supplying a raw material for the element (R, C, D) of the other group to adsorb the element of the other group onto the first and second elements. A method for growing compound semiconductors.