JPH05304098A - Quantum dot crystal growth device and manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To realize an ultraflat crystal surface and to enable a crystal growth nucleus to grow uniformly as a quantum dot by a method wherein material gas is supplied at ten times the conventional flow rate. CONSTITUTION:A semiconductor crystal substrate 1 is held by a graphite susceptor 2, a lid 3 of the same crystal with the crystal substrate 1 is made to cover the susceptor 2 confronting the semiconductor crystal substrate 1, and the lid 3 is covered with a graphite presser 4. A material gas introducing guide pipe 7 is inserted into an opening 5 formed of the susceptor 2 and the presser 4. Material gas is fed at a flow rate of 50L/min, whereby a crystal growth speed at a kink becomes 5 times or so as high as crystal nucleus generation speed, and consequently an ultraflat crystal surface can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quantum dot crystal growth apparatus for manufacturing a quantum dot structure for dramatically improving the characteristics of a semiconductor device and a method for manufacturing the semiconductor device.

[0002]

2. Description of the Related Art While quantum dots confine carriers three-dimensionally, as a conventional example of a quantum well crystal growth device for producing a quantum well structure in which carriers are confined one-dimensionally, a MOVPE crystal growth device is shown in FIG. Shown in. this is,
Reactor 31 and semiconductor single crystal substrate (GaAs, InP
Etc.) 32, a graphite susceptor 33, an RF coil 34 for heating the graphite susceptor, and a gas line 35 for flowing a raw material gas into the reaction tube [Esaki et al .: Superlattice heterostructure device, Industrial Research Committee (1988) 253]. ..

In the conventional MOVPE crystal growth apparatus of FIG. 3, a semiconductor single crystal substrate 32 is installed in a reactor 31, and crystal growth is performed by flowing a source gas into the reactor 31 heated by a graphite susceptor 33. is there.

FIG. 4 shows a first conventional example of a crystal growth method for quantum dots. GaA by conventional MOVPE method or MBE method
An AlGaAs layer 41 is grown on the s substrate 40, and Ga is
An As / AlGaAs ultrathin film crystal and an AlGaAs cap layer 43 are grown (FIG. 4a). Next, when the quantum box 44 is formed by etching (FIG. 4b) and the buried layer 45 is grown (FIG. 4c), or as shown in FIG.
Step 50 of AlGaAs layer 51 grown on substrate 52
There is a case where the GaAs quantum box 53 (FIG. 5b) is produced by alternately supplying two kinds of gases having different compositions by using (FIG. 5a), and the buried layer 55 is grown (FIG. 5c). Esaki et al .: Superlattice heterostructure device, Industrial Research Committee (1988) 464].

[0005]

However, in the MOVPE device having the above-mentioned structure, although the thin film quantum well structure can be grown, the cross-sectional area of the reactor tube is large and the flow velocity of the source gas cannot be increased, so that a perfectly flat crystal is obtained. It is not possible.
As a result, the crystal growth nuclei cannot be generated uniformly, and the growth of the quantum dot structure is impossible. I will explain it in detail. An enlarged view of FIG. 3 is shown in FIG. In the crystal growth on the substrate as shown in FIG. 6A, the temperature of the reactor is raised and the reaction gas is allowed to flow into the reactor 31, but if the flow velocity of this gas is low, the step shown in FIG. Not only that, the crystal grows on the crystal terrace 61. Therefore, when the gas flow rate is increased, the crystal grows flat as shown in FIG.

That is, in the conventional MOVPE crystal growth apparatus, the reactor has a large cross-sectional area and the flow velocity of the reaction gas cannot be increased, so that a flat crystal as shown in FIG. 6C cannot be obtained. Therefore, there is a drawback that it is not possible to grow quantum dots on a flat crystal surface.

In view of the above problems, the present invention provides a quantum dot crystal growth apparatus for uniformly generating crystal growth nuclei on the entire surface of a crystal to form quantum dots.

Further, in the quantum dot crystal growth method as described above, firstly, the shape of the quantum dots depends on the etching processing technique. At present, processing of about 0.1 μm is the limit, and processing of about 10 nm square actually required as a quantum dot is impossible. At the same time, a good regrowth interface cannot be formed due to damage due to processing, and good device characteristics cannot be exhibited. Further, in the method of growing a quantum dot structure by utilizing a crystal step, it is possible to obtain steps with uniform intervals to some extent by growing the crystal after polishing the crystal step obliquely. It is necessary to form regular steps in the initial state,
Quantum dots are not formed if the growth time of the crystal is slightly deviated. There was a problem that the uniformity and crystallinity of the quantum dot structure deteriorated in the process of continuing the crystal growth.

In view of the above problems, it is an object of the present invention to provide a method of manufacturing a semiconductor device capable of uniformly generating crystal growth nuclei on an ultra-flat surface to manufacture a quantum dot structure.

[0010]

In order to achieve this object, a quantum dot crystal growth apparatus of the present invention is a semiconductor single crystal substrate and a semiconductor single crystal substrate, which holds the semiconductor substrate, forms a flow path for a source gas, and is heated. The reaction tube is composed of an outer tube including the reaction tube for sealing the source gas, and the cross-sectional area of the flow path of the reaction tube is reduced to increase the flow rate of the source gas on the semiconductor substrate.

Further, in a method of manufacturing a semiconductor device for solving the above problems, a semiconductor crystal substrate is kept at a temperature higher than an optimum crystal growth temperature and a source gas is supplied to grow a crystal on a terrace. Crystal growth process, a quantum dot formation process in which the gas of the quantum dot forming component is supplied for a short time on a hyperplane crystal maintained at a temperature lower than the optimum crystal growth temperature, and a crystal different from the quantum dot crystal at the optimum crystal growth temperature And a step of growing a buried crystal for burying the quantum dots.

[0012]

The susceptor is arranged so as to surround the crystal substrate, and the distance between the crystal growth substrate and the top plate is set to about 1 mm. The cross section perpendicular to the flow of the gas flow was 10 mm * 1 mm, the total gas flow rate was 40 L (liter) / min, and the growth pressure was 17 to.
A flow velocity of 300 m / sec was obtained by setting rr.

Further, in order to increase the utilization efficiency of the raw material due to the low growth pressure, the top plate is made of graphite to improve the gas decomposition efficiency. On the other hand, when the mixing of impurities becomes a problem, it is possible to prevent contamination from the susceptor by placing a single crystal substrate similar to the crystal substrate under the top plate.

When crystal-growing quantum dots, it is necessary to obtain an ultra-flat surface. To obtain this ultra-flat surface, the crystal surface is flattened at the atomic level by the quantum dot crystal growth apparatus described above. This is because by increasing the flow velocity of the gas, the capture rate of atoms on the crystal surface decreases with respect to the position of the kink or step, the generation of crystal nuclei is suppressed, and the steps move to the periphery of the crystal substrate one after another. (Fig. 6
An ultra-flat surface can be obtained in (c)). However, in order to increase the migration rate of atoms on the crystal surface, the growth temperature needs to be higher than the optimum condition for crystal growth by about 100 degrees. Further, as the crystal substrate, it is necessary to use a dislocation-free substrate having no screw dislocation or the like.

Next, it is necessary to uniformly form quantum dots on this flat surface. In order to reduce migration of raw material atoms of the quantum dots and increase the nucleation rate on the flat surface to be higher than the nucleus growth rate, the growth is performed at a temperature of about 150 ° C. lower than the optimum condition for crystal growth. Here, quantum dots can be uniformly formed by growing the quantum well for about 1/5 of the thickness of one atomic layer.

Further, a crystal having a different band gap from that of the quantum dots is grown at a growth temperature equal to that of the quantum dots, which has a different composition.
Quantum dots can be built into crystals.

[0017]

【Example】

(Embodiment 1) FIG. 1 shows an embodiment of the quantum dot crystal growth apparatus of the present invention.

As shown in FIG. 1, the InP semiconductor crystal substrate 1 is held by a graphite susceptor 2, the same crystal as the semiconductor crystal substrate 1 is used as a lid 3, and the susceptor 2 is covered with the lid 3 facing the substrate 1. Then, the crystal substrate 1 is protected by holding the graphite substrate 4 with the graphite substrate 4. A guide pipe 7 for inflowing the raw material gas 6 is provided in an opening 5 formed by the susceptor 2 and the presser foot 4.
Is inserted. In order to prevent leakage of the raw material gas 6, the susceptor 2 and the guide pipe 7 are shielded from the outside air by an outer pipe 8. The opening 5 has a height of 1 mm and a width of 10 mm, and the semiconductor crystal substrate 1 of 10 mm × 20 mm can be loaded therein.

Next, the operation of the structure of this quantum dot crystal growth apparatus will be described. First, the temperature of the graphite susceptor 2 is raised by high frequency heating. And increase the flow velocity of gas,
The gas basin area was set to 10 mm ^{2 in} order to grow a crystal whose substrate 1 surface was extremely flat at the atomic level. The substrate 1 was installed in the susceptor 2 to supply the raw material gas 6 in order to suppress the decrease in the yield of the raw material gas 6 due to the increased flow velocity. That is, the gas flow region was surrounded by the susceptor 2, and all the gases contributed to the growth, and the raw material gas 6 was heated from four directions to improve the gas pyrolysis efficiency and further improve the yield of the raw material gas 6.

In this apparatus, the cross-sectional area through which the raw material gas passes can be made considerably smaller than that in the conventional crystal growth apparatus. Further, in this apparatus, the gas flow path should be as short as possible in order to prevent the growth pressure from rising due to the small cross-sectional area of the gas flow path. This time, the distance from the gas mixing section to the crystal substrate was set to about 50 cm.

Further, in order to prevent a sudden decrease in the growth pressure on the crystal, a susceptor is provided extending from the crystal growth part to the gas downstream part. The guide tube covers the susceptor to prevent leakage of the source gas from the opening. A pressure sensor is installed in the gas supply pipe to control the growth pressure, and the butterfly valve is used to adjust the suction force of the pump to perform depressurized growth. The susceptor temperature can be raised up to 1000 degrees.

(Embodiment 2) A method of manufacturing a semiconductor device according to the present invention will be described with reference to FIG. Here, as a semiconductor device, a method for manufacturing a semiconductor laser using quantum dots will be described.

As shown in FIG. 2, the (001) InP substrate 21 was set in the quantum dot crystal growth apparatus described in Example 1, and 50 L / min of hydrogen gas 6 containing 200 ccm of PH3 (40%) was added. Supply (Fig. 2a). The growth pressure is 17 torr.

After the temperature of the susceptor 2 was raised and kept at 740 ° C. for 10 minutes, PH3 as a source gas was 200 ccm and TM.
I (trimethylindium 1%) was supplied at 20 ccm and the InP crystal 22 was grown for about 10 nm for 5 minutes (FIG. 2).
b).

Here, by increasing the flow velocity of the gas, as shown in FIG. 6C, the capture rate of atoms on the crystal surface decreases with respect to the position of the kink or step, and the generation of crystal nuclei occurs. Is suppressed and the steps move to the periphery of the crystal substrate one after another, so that an ultra-flat surface is obtained.

Next, only the supply of TMI is stopped and the susceptor temperature is lowered to 390 degrees. InGaAsP (λg =
1.4 μm) Quantum dots are prepared. In this case, TMI
Is 5.0 ccm, TEG (1.8%) is 2.2 ccm,
PH3 20ccm, AsH3 (10%) 3.0sc
The mixed gas added in cm is added to the hydrogen gas for 0.8 seconds at intervals of 0.5 seconds. Total gas flow is 5
It is set to 0 L / min. Then, InGa with one side of 3 nm
AsP quantum dots 23 are formed with a pitch of approximately 20 nm (FIG. 2c). Here, the InP crystal 22 has InGaAs
The P quantum dots 23 grow on the flat InP crystal 2
This is because the optimum condition for nucleation of the quantum dots 23 is selected above 2. The optimum condition is a low temperature of about 150 ° C. At that temperature, the raw material atoms of the quantum dots have a small migration and the nucleation rate is higher than the nucleus growth rate, so that the quantum dots 23 are formed on the InP crystal 22. it can.

Further, while keeping the susceptor at 390 ° C., PH3 of 200 ccm and TMI of 20 are used as source gases.
After adding ccm, the InP crystal 24 was grown to about 10 nm for 5 minutes and embedded with quantum dots (FIG. 2d). The quantum dot manufacturing process and the quantum dot embedding process are repeated 10 times.

Finally, the susceptor is heated to 640 ° C. and PH3 is 200 ccm and TMI is 200 cc as a source gas.
InP crystal 25 is grown to a thickness of about 100 nm at a growth pressure of 100 torr for 5 minutes (FIG. 2e). PH3 2
The growth is completed by cooling the susceptor while adding 00 ccm.

As a result of measuring the photoluminescence of the obtained crystal, the energy shift amount was about 120 meV, and the quantum dot effect was confirmed.

Although the crystal substrate is placed on the susceptor, the quantum dots are formed even in the crystal used as the lid. Further, although the growing crystal is InP-based, it may be GaAs-based or ZnSe-based. In addition, the guide tube may have a structure that covers the susceptor in order to prevent the gas from leaking from the joint between the guide tube and the susceptor.

[0031]

As described above, since the quantum dot crystal growth apparatus of the present invention can reduce the cross-sectional area of the portion through which the source gas flows, the gas flow rate supplied to the crystal can be made 10 times higher than the conventional one. Thus, an extremely flat crystal surface without kinks can be produced. By continuously supplying a small amount of quantum dot component gas, it is possible to grow a quantum dot crystal that dramatically improves the characteristics of a semiconductor device.

Further, by using the quantum dot crystal growth apparatus, the quantum dot crystal can be grown and the characteristics of the semiconductor device can be remarkably improved.

[Brief description of drawings]

FIG. 1 is a structural diagram of a quantum dot crystal growth apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of a quantum dot structure according to a second embodiment of the present invention.

FIG. 3 is a diagram showing the structure of a MOVPE device.

FIG. 4 is a manufacturing process sectional view showing a manufacturing process of a quantum dot structure by etching.

FIG. 5 is a manufacturing process cross-sectional view showing a manufacturing process of a quantum dot structure using a crystal step.

FIG. 6 is a diagram for explaining a difference in crystal growth in steps of a substrate depending on a flow rate of a source gas.

[Explanation of symbols]

 1 Semiconductor Crystal Substrate 2 Susceptor 3 Lid 4 Presser 5 Opening 6 Raw Material Gas 7 Guide Tube 8 Outer Tube 21 InP Substrate 22 InP Crystal 23 InGaAsP Quantum Dot 24 InP Crystal 25 InP Crystal

Claims (2)

[Claims] 1. A semiconductor single crystal substrate, and a reaction tube which holds the semiconductor substrate, forms a flow path of a raw material gas, and is heated,
An outer tube including the reaction tube for sealing the raw material gas, and reducing the cross-sectional area of the flow path of the reaction tube to increase the flow rate of the raw material gas on the semiconductor substrate. Quantum dot crystal growth device. 2. A hyperplane crystal growth step of maintaining a semiconductor crystal substrate at a temperature higher than an optimum crystal growth temperature and supplying a source gas to grow crystals on a terrace, and a gas of a component forming a quantum dot is crystallized. Includes a quantum dot forming step of supplying for a short time on a hyperplane crystal maintained at a temperature lower than the optimum growth temperature, and a buried crystal growth step of growing a crystal different from the quantum dot crystal at the optimum crystal growth temperature and embedding the quantum dot A method of manufacturing a semiconductor device, comprising: