JPS6289323A - Organo metallic chemical vapor deposition - Google Patents

Abstract

PURPOSE:To enable a hetero junction interface, an impurity doping interface, etc., to be formed steeply by a method wherein multiple gas leading-in ports are separately arranged in the longitudinal direction of a horizontal reactive tube; respective gas leading-in ports lead in specified gas to form regions with different gas compositions; and substrates are shifted by susceptors. CONSTITUTION:A horizontal reactive tube 1 separately arranged in the longitudinal direction of the tube 1 is used to lead in specified organic metallic material, impurity material etc. selecting the leading-in ports, flow rate etc. The returning gas from downstream to upstream is negligible while a region wherein the gas composition is fit for the growth of each specified crystal is formed in the reactive tube 1. Besides, another region for retracting a substrate 11 before and after crystal growing can be formed as necessary. Furthermore susceptors 5 loaded with the substrate 11 for growing crystal can be shifted rapidly in the longitudinal direction anytime in a series of crystal growing processes from the crystal growing in one region to that in another region. Through these procedures, an epitaxial growing and an impurity doping can be started and stopped very rapidly.

Description

[Detailed Description of the Invention] [Summary] The present invention is a metal-organic pyrolysis vapor phase growth method that uses a plurality of gas inlets spaced apart in the length direction of a reaction tube to adjust the composition of the gas. In this method, a plurality of mutually different regions are formed, and a susceptor on which a substrate on which a crystal is to be grown is placed is moved to position the substrate within the region, thereby making the single crystal growth interface steep.

[Industrial application field]

The present invention is a metal organic pyrolysis vapor phase growth method (MOCVD method)
In particular, the present invention relates to improvements that make it possible to form steep interfaces such as heterojunctions and impurity doping.

For example, in compound semiconductor devices, semiconductor substrates are often used in which single crystal layers of various compositions or doped with impurities are epitaxially grown on a single crystal substrate. There is a heterojunction field-effect I transistor that spatially separates a region in which carriers move by a heterojunction interface to increase carrier mobility especially at low temperatures, thereby achieving even higher speeds.

An example of the structure of this heterojunction field effect transistor is shown in FIG. A non-doped i-type GaAs layer 12, an aluminum gallium arsenide (AIxGa+ -
The s-layer 13 usually consists of a non-doped spacer layer 13a and an n-type electron supply layer 13b containing donor impurities at a concentration of, for example, about 2×10Il10l11, and from this layer i-type Ga
The electrons transferred to the As layer 12 form a two-dimensional electron gas 12e near the heterojunction interface.

Source and drain electrodes 1 are placed on this n-type GaAs layer 14.
A gate electrode 16 is provided in contact with the AlGaAs layer 13, and a transistor operation is performed by controlling the surface concentration of the two-dimensional electron gas 12e with the gate electrode 16.

Conventionally, epitaxial growth on molecular beams has been applied as a method for epitaxially growing the semiconductor substrate of this heterojunction field effect transistor, but this method is time-consuming and has been used for the purpose of reducing throughput and preventing surface defects. It is desired to apply the MOCVD method to epitaxial growth.

However, according to the conventional MOCVD method, it is difficult to form steep heterojunction interfaces, impurity doping interfaces, etc., as will be described later, and there is a strong demand for improvement.

[Conventional technology]

The MOCVD method has conventionally been carried out as illustrated in FIG. 5 using the following procedure. However, in the figure, 21 is a horizontally arranged reaction tube made of, for example, quartz glass;
is a gas inlet provided at one end of the reaction tube 21, 23 is a gas outlet, 24 is a flange that closes the opposite end of the reaction tube 21, 25 is a susceptor made of graphite, for example, and 27 is a high frequency coil that heats the susceptor 25. 11 is a single crystal substrate on which a single crystal layer is grown.

The procedure for growing a single crystal layer is, for example: (1) The substrate 11 is placed on the susceptor 25, put into the reaction tube 21, and the flange 24 is closed.

■ After introducing carrier gas from the gas inlet 22 to create a carrier gas atmosphere inside the reaction tube 21, the susceptor 25
The substrate 11 is heated by heating.

(2) When a predetermined temperature is reached, a reaction gas for the first single crystal layer is introduced into the reaction tube 21, and its epitaxial growth is started.

(2) When the time for the first single crystal layer to grow to a predetermined thickness has elapsed, the reaction gas is switched and a second single crystal layer is grown. This procedure is repeated to sequentially grow the required single crystal layers.

(2) When the time for the last single crystal layer to grow to a predetermined thickness has elapsed, the reaction gas is stopped and the growth is completed using only the carrier gas.

(2) Stop heating the substrate 11 and take out the substrate 11 after the temperature is lower than a predetermined temperature.

You can proceed as follows.

For example, in the growth of GaAs/AlGaAs,
For example, hydrogen (H2) is used as the carrier gas, and arsine (85H3) and trimethylgallium ((C) are used as the organic metal materials.
I+3) 5Ga), trimethylaluminum ((CH
3) Using 3A1), the impurity material is monosilane (Si
tL) etc.

[Problem that the invention attempts to solve]

Even if an attempt is made to grow a semiconductor substrate of, for example, a heterojunction field effect transistor using the conventional MOCVD method as described above, when the delivery of the reactive gas is switched, the concentration of the reactive gas at the position of the substrate 11 will gradually decrease. death,
Since the concentration of the new reactant gas rises slowly, the heterojunction interface and the impurity doping interface become dull.

As a result, even if the reaction tube 21 is thin enough to barely accommodate the substrate 11 with a diameter of about 5 cm, for example, two-dimensional electron gas is only generated in a portion of the substrate 11.
It is very difficult to apply the conventional MOCVD method to such a purpose.

[Means for solving the problem] The above problem is solved by arranging a plurality of gas inlet ports spaced apart in the length direction of the horizontal reaction tube, and introducing the required gas through the gas inlet ports. According to the present invention, a plurality of regions having mutually different gas compositions are formed in a horizontal reaction tube, and a susceptor on which a substrate on which a crystal is to be grown is placed is moved to position the substrate within the region, thereby performing crystal growth. Solved by organometallic pyrolysis vapor phase growth method.

[For production]

In the organometallic pyrolysis vapor phase growth method according to the present invention, a horizontal reaction tube in which a plurality of gas inlets are spaced apart in the length direction is used to introduce required organometallic materials, impurity materials, etc. Select the port, flow rate, etc. and install. The movement of gas from the downstream side to the upstream side is negligible, and a region can be created in the horizontal reaction tube where the gas composition is compatible with the growth of each desired crystal.

Note that, if necessary, a region for retreating the substrate on which the crystal will grow is also formed before and after the crystal growth.

According to the present invention, the susceptor on which the substrate on which the crystal is to be grown can be moved in the length direction of the horizontal reaction tube at any time during a series of crystal growth steps, and the Promptly move on to crystal growth in other areas. The same applies to the round trip from the evacuation area at the time of initial growth start, growth completion, etc.

This makes it possible to start and stop epitaxial growth and impurity doping extremely quickly.
A steep interface can be realized.

〔Example〕

The present invention will be specifically explained below with reference to an example schematically shown in FIG.

In the figure, 1 is a horizontally arranged reaction tube made of quartz glass, 2a, 2b, and 2C are gas inlets provided in the reaction tube 1, 3 is a gas outlet, and 4 is the terminal end of the reaction tube 1. a closing flange, 5 a susceptor made of graphite, 6 a drive mechanism for the susceptor 5, 7 a susceptor 5;
11 is a high frequency coil for induction heating, and 11 is a single crystal substrate on which a single crystal layer is grown.

In order to move the susceptor 5 quickly and accurately, its drive mechanism 6 is constructed as illustrated in FIG. 2, for example. In this embodiment, a member 6a that is fixed to the susceptor 5 and has a female thread, a member 6b that has a male thread that fits therein, a rotating shaft 60 that drives this with a motor, etc. are all made of stainless steel. The space between the rotating shaft 6c and the flange 4 is vacuum sealed with electromagnetic fluid. Note that carbon is used for the members 6a and 6b, for example.

Further, the susceptor 5 is made easy to move by, for example, providing a cylindrical recess on its bottom surface and fitting the rollers 5a into the recess.

The growth of each semiconductor layer of the heterojunction field effect transistor is performed, for example, as follows using this metal organic pyrolysis vapor phase growth apparatus.

Gas is introduced, for example, as shown below, and from the upstream side, region A between the inlet ports 2a and 2b is a retreat region where no growth is performed, and a non-doped GaAs layer is grown in the right region B between the inlet ports 2b and 2c. The region C downstream of the inlet 2c is the region where the following three layers are grown.

(al Most upstream inlet 2a: H2 (carrier gas) 20-307!
/m1nAsHs (H2 dilution; 3-18χ)
0.5~I E /m1n (bl Middle inlet 2b
: H21~2 j! /m1n ASH3 (H2 dilution; 3-18χ) 0.5-I
Il/m1n (C1,) 3ca (bubbling with H2) 20-30cc/m1n (C) Most downstream inlet 2c: i) Until growth of non-doped AlGaAs spacer layer: H
z 1~21/win
AS)+3 (H2 dilution; 3-18χ) 0.5
~I Il/m1n(CH3)3Al (bubbling with H2) 2 (1-30cc/m1nii) n-type A
During growth of lGaAs layer: Hz 1-2 j!
/m1nAs)13 (+(2 dilution; 3-1.8χ)
0.5 to I A /m1n(CHs)i (
Buffing with H2) 20-30cc/1IlinSi
H4 (H2 dilution; 20-200ppm) approx. 5
0cc/m1niii) When growing an n-type GaAs layer; fiz 1~2 j!
/m1nAsl! 3 (H2 dilution; 3-18χ)
0.5-1 j2/m1nSiH4 (H2 dilution; 20
~200 ppm) Approximately 50 cc/min The semi-insulating GaAs substrate 11 is placed on the susceptor 5 and placed in the region, and the gas is introduced as described above so that the temperature inside the substrate 11 and the reaction tube becomes, for example, 700'C. Heat to.

After reaching a steady state, the susceptor 5 is moved to the region B, and the non-doped GaAs layer 12 is formed to a thickness of, for example, about 0.5 cm.
Grows to trm.

Next, the susceptor 5 is moved to the region C, and the non-doped A
A spacer layer 13a of 10, 3 Gao, 7 AS is grown to a thickness of, for example, about 5 am.

Once the susceptor 5 is returned to the region and 5il14 is added to the gas introduced from the inlet port 2C to reach the steady state of ii), the susceptor 5 is moved to the region C and the impurity concentration is, for example, about IXl010cm-3. n-type A10.3G
ao, TAS layer 13b is grown to a thickness of, for example, about 40 nm.

The susceptor 5 is returned to the region A, and the gas (C) 13) 3A] introduced from the inlet port 2C is stopped to reach the steady state of the above-mentioned mountain. n-type GaA with a concentration of about I x 1017 cm-'
The thickness of the s layer 14 is, for example, 1. It grows about OOnm.

Through the above procedure, each semiconductor layer is simultaneously grown on three substrates with a diameter of approximately 5 cm. The vibration magnetoresistive effect (Shubnikho-de-Haas effect; conduction electrons move quantumly to the Landau level due to the magnetic field) The generation state of two-dimensional electron gas was detected using the phenomenon in which the electrical resistance changes periodically as the magnetic field changes due to the magnetic field.However, when the magnetic field is perpendicular to the substrate, A periodic change in resistance value as illustrated in FIG. 3 is detected, and 2
Generation of dimensional electron gas was confirmed.

Furthermore, a heterojunction field effect transistor was manufactured using this semiconductor substrate, and characteristics almost equivalent to those of a comparative sample using a semiconductor substrate produced by the molecular beam epitaxy method were obtained.

Although the above description refers to a semiconductor substrate used in a heterojunction field effect transistor, the present invention can be applied to the formation of other equivalent semiconductor substrates to obtain similar effects.

〔Effect of the invention〕

As explained above, according to the present invention, a single crystal layer of a semiconductor device, etc. can be grown at a much steeper interface with better reproducibility than the conventional metal-organic pyrolysis vapor phase growth method, and much more easily than the molecular beam epitaxial growth method. This makes it possible to grow the compound semiconductor, which has a great effect on the practical application of compound semiconductor devices and the like.

In addition, conventionally, the gas flow rate has often been increased in order to shorten the gas switching time, but according to the present invention, there is no need to increase the gas flow rate, and a large economic effect can be obtained for gas resources and their purification equipment. It will be done.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an embodiment of the present invention, Fig. 2 is a schematic diagram showing an example of a susceptor drive mechanism, Fig. 3 is an example of data showing the vibration magnetoresistive effect, and Fig. 4 is a heterojunction electric field effect l.・Schematic diagram of transistor. Figure 5 is a schematic diagram of the conventional method. In the figure, 1 is a horizontal reaction tube, 2a, 2b and 2C are gas inlets, 3 is a gas outlet, 4 is a flange, 5 is a susceptor, 5a is a roller, 6 is a drive mechanism for the susceptor, 6a and 6b are screws The following members include: 6c is a rotating shaft, 7 is a heating high-frequency coil, 11 is a single crystal substrate on which a single crystal layer is grown, such as a semi-insulating GaAs substrate, 12 is a non-doped i-type GaAs layer, 12e is a two-dimensional electron gas, 13 is a 1XGa+-xAs layer, 13a is a non-doped spacer layer 13b is an n-type electron supply layer containing donor impurities, and 14 is an n-type electron supply layer.
15 is a source and drain electrode, and 16 is a gate electrode. The location of the main house, the 70th standard map of the telegraph code No. 1 Map of the town, and the standing arch of the bridge of the ward, A year 2
Flash 5 211 4Of, 11 Power C cry 1 concealment - ψ force / buake C moonshake Oe Shi η No 31 m L imitation T Deni 74 Fu j No. 3 Hetero ladder measurement electric field - woman Lika Transsunu Stock Illustration No. 4
Fig. 3. Conventional method is Hōbō Ebisu Senryo, Fig. 3

Claims (1)

[Scope of Claims] A plurality of gas inlet ports are disposed spaced apart in the length direction of the horizontal reaction tube, and a required gas is introduced from the gas inlet ports so that the compositions of the gases are mutually matched within the horizontal reaction tube. metal-organic pyrolysis vapor phase growth, which is characterized in that a plurality of different regions are formed in the region, and a susceptor on which a substrate on which a crystal is to be grown is placed is moved to position the substrate within the region to perform crystal growth. Method.