JP2749635B2 - Compound semiconductor crystal growth method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method and an apparatus for growing a crystal, and
anic Chemical Vapor Deposition method and gas source MBE
The present invention relates to a crystal growth method and apparatus for growing a crystal containing a group V element using a (Melecular Beam Epitaxy) method. In a crystal growth method using an organic group V, there is no need to use a hydride of the group V. A method of providing a crystal growth method and apparatus capable of obtaining sufficiently favorable crystal characteristics, a step of heating and heating a substrate containing a group V element while supplying a group V element alone; A step of supplying an organic compound of a group V element onto the substrate to grow a compound semiconductor layer containing a group V element on the substrate, and then supplying the group V element alone onto the substrate while supplying the group V element alone to the substrate. And a step of lowering the temperature.

Further, in the above method, a configuration is adopted in which a radical comprising a group V element and a hydrogen element is supplied onto the substrate when the substrate is heated and heated.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal growth method and apparatus, and more particularly, to a crystal growth method and apparatus for growing a crystal containing a group V element by using a MOCVD method or a gas source MBE method.

[Prior Art] In general, MOCV is used as a method for growing compound semiconductor crystals because of its high mass productivity, good crystallinity, and few surface defects.
The D method and the gas source MBE method are used. Using these conventional MOCVD and gas source MBE methods, for example, III
When growing a group V compound semiconductor crystal, an organic metal such as TMG (trimethylgallium) or TEG (triethylgallium) is used as a group III material, and a group V material is
Hydrides such as AsH ₃ (arsine) and PH ₃ (phosphine) are used.

However, hydrides such as AsH ₃ and PH ₃ as Group V raw materials are extremely toxic and are gaseous at room temperature, so that they are filled in pressurized cylinders. The handling is therefore very dangerous and requires great care.

Therefore, instead of AsH ₃ or PH ₃ etc., T
A crystal growth method using an organic group V such as MAs (trimethylarsine), TEAs (triethylarsine), and PhAs (phenylarsine) has been proposed (A. Brauer, O. Kayser, R. Ka).
ll, H. Heinecke, P. Balk and H. Hofmann, “The use of or
ganic As precursors in the low pressure MOCVD of G
aAs ", Journal of Crystal Growth 93 (1988) pp. 7-14.
reference).

By the way, even in the crystal growth method using the organic group V, in order to remove the oxide adhering to the substrate surface, a temperature of 60 ° C.
It is necessary to perform thermal cleaning at 0 to 700 ° C. before growth, but in order to prevent the V group element from being detached from the substrate surface during this thermal cleaning, the V group element is removed from the substrate in any form. Must be supplied to the surface. For the same reason, the supply of the group V element to the substrate surface is required even when the temperature is raised before thermal cleaning and when the temperature is lowered after growth.

However, if the organic V group is used before the growth, there is a problem that carbon adheres to the substrate surface and deteriorates the characteristics of the grown crystal.

In addition, a large amount of organic V group is used during growth, and the organic V
If a group had to be used, the amount of the organic group V required for one growth would be enormous and the cost would be high.

Due to these problems, in the above-described crystal growth method using the organic group V, a hydride of the group V, not the organic group V, is still used as an auxiliary during the temperature increase, the thermal cleaning, and the temperature decrease. . However, this does not eliminate the danger associated with the use of highly toxic Group V hydrides.

[Problems to be Solved by the Invention] As described above, in the above-described conventional crystal growth method using the organic group V, if satisfactory crystal characteristics cannot be obtained or if the crystal characteristics are to be improved, , Highly toxic V
Faced the challenge of having to risk using the hydride of the tribe.

Therefore, the present invention provides a crystal growth method and apparatus capable of obtaining sufficiently good crystal characteristics without using any hydride of group V in a crystal growth method using an organic group V. With the goal.

[Means for Solving the Problems] The above-mentioned problems are achieved by a step of heating and heating a substrate containing a group V element while supplying a simple substance of a group V element, and then adding an organic compound of a group V element to the substrate. Providing a compound semiconductor layer containing a group V element on the substrate by supplying the
Lowering the temperature of the substrate while supplying the elemental group element alone onto the substrate.

The object is also achieved by a method for growing a compound semiconductor crystal according to the above method, wherein a radical comprising a group V element and a hydrogen element is supplied onto the substrate when the substrate is heated and heated.

Further, the object is to provide a reaction furnace, a substrate installation means for installing a substrate containing a group V element in the reaction furnace, a heating means for heating the substrate, and an organic V for supplying an organic group V on the substrate.
Group supply means and V for supplying a group V element alone on the substrate
Means for supplying a group V element alone, wherein an organic group V is supplied by the organic group V supply means during growth to grow a crystal containing a group V element on the substrate.
The present invention is attained by a compound semiconductor crystal growth apparatus characterized in that a single group V element is supplied by a single group element supply means.

The above object is achieved by a compound semiconductor crystal growth apparatus according to the above apparatus, further comprising radical supply means for supplying hydrogen radicals onto the substrate, wherein the substrate surface is cleaned before growth.

[Operation] In other words, the present invention supplies an organic group V element during growth and supplies a group V element alone on a substrate containing a group V element before and after growth to grow a crystal containing a group V element. The use of strong Group V hydrides can be entirely eliminated.

At the time of temperature rise and thermal cleaning before growth, and at the time of temperature decrease after growth, a single group V element is supplied onto the substrate containing the group V element. The group V element can be prevented from being eliminated.

Also, since it is sufficient to supply the organic group V only during growth,
The amount of expensive organic group V can be suppressed.

In addition, since the radicals are supplied to the substrate containing a group V element during thermal cleaning, the surface of the substrate can be cleaned to a level equal to or greater than when a group V hydride is used, and the crystal to be grown can be formed. Characteristics can be improved.

[Examples] Hereinafter, the present invention will be specifically described based on the illustrated examples. In this example, the MOCVD method was used.

FIG. 1 is a schematic view of a crystal growth apparatus used in a crystal growth method according to one embodiment of the present invention.

In the oblique chimney type reactor 2, a susceptor 6 is provided as a substrate installation means for installing, for example, a GgAs substrate 4. As a heating means for heating the GaAs substrate 4, an infrared lamp 8 is mounted outside the oblique chimney type reaction furnace 2.

In addition, a group V element simple substance supply means is attached to the oblique chimney reactor 2 upstream of the susceptor 6 with respect to the flow of the source gas and the carrier gas in the oblique chimney reactor 2. That is, the oblique chimney type reactor 2
And a PBN (Pyrolytic Bro) through an openable shutter
A crucible 12 made of n (Niteide) is mounted. The crucible 12 contains, for example, an As (arsenic) element 14 as a group V element element, and is heated by a heater 16.

Furthermore, as a radical supply means, a CO ₂ laser oscillator 1
8 and a condenser 20 are provided, and the laser light output from the CO ₂ laser oscillator 18 is focused on the GaAs substrate 6 by the condenser 20.

 Next, the gas system will be described.

Pd (palladium) H ₂ (hydrogen) H ₂ gas passed through the purifier 24 with the remain unchanged carrier gas and III
For example, TMG26 as a group raw material is bubbled to become a group III source gas, or tBAs (tertiary butylarsine) 28 as an organic group V raw material is bubbled to become a group V source gas. The carrier gas, the group III source gas and the group V source gas are passed through a sequencer 30 for controlling the switching and flow rate of these gases.
The pipe is provided so as to flow into the oblique chimney type reactor 2. The gas is exhausted from the outlet of the oblique chimney reactor 2.

 Next, the operation will be described.

After the GaAs substrate 4 is placed on the susceptor 6 in the oblique chimney type reactor 2, the temperature is raised by the infrared lamp 8.
At the time of the temperature rise before the growth, up to a temperature of 300 ° C., only H ₂ gas as a carrier gas is flowed. When the temperature exceeds 300 ° C., the shutter 10 of the crucible 12 is opened, and the As simple substance 14 is fed into the oblique chimney type reaction furnace 2 and supplied to the surface of the GaAs substrate 4. At this time, the As simple substance 14 is heated to a temperature of 400 to 600 ° C. by the heater 16.

After the temperature of the GaAs substrate 4 reaches the target growth temperature of 600 to 700 ° C., after the temperature is further stabilized, thermal cleaning is performed to remove the oxide on the surface of the GaAs substrate 4. At the time of this thermal cleaning, H radicals are supplied to the surface of the GaAs substrate 4.

That is, as shown in FIG. 2 (a), the lateral width of the laser beam 32 having a CW output of, for example, 100 W oscillated by the CO ₂ laser oscillator 18 is first passed through the lateral width enlarging lenses 34 and 36, thereby forming the GaAs substrate. 4 to be wider than the diameter. Then, the expanded laser beam 32 is introduced into the chimney type reaction furnace 2 obliquely in a direction parallel to the surface of the GaAs substrate 4. At this time, as shown in FIG. 2 (b), the condenser 20 condenses the laser light 32 only in the vertical direction while maintaining the state where the horizontal width is widened. This occurs discharge at the condensing unit 38 by the focusing, the reaction of H ₂ As and H ₂ gas supplied from As single 14 in the crucible 12 is caused by the discharge.
And consequently, H, AsH, radicals such as AsH ₂ occurs.

By setting this condensing part 38 on the upstream side of the gas flow above the GaAs substrate 4, radicals such as H, AsH, AsH ₂
It is supplied to the aAs substrate 4 surface. The strong reduction of radicals accelerates oxide removal from the surface of the GaAs substrate 4 and cleans the surface.

As shown in FIG. 2 (c), by using a separation type concentrator 40 instead of the concentrator 20, the laser beam 32 is separated into a plurality of laser beams 32 and condensed at a plurality of positions above the GaAs substrate 4. Parts 42,44,
46 can be shifted. This allows Ga
Radicals can be supplied to the entire area of the As substrate 4 surface,
The surface of the GaAs substrate 4 is more effectively cleaned.

FIG. 2 (c) shows the case of three light-collecting portions 42, 44 and 46, but the present invention is not limited to this, and necessary light-collecting portions are required depending on the area of the GaAs substrate 4. What is necessary is just to set the number of copies.

After performing such thermal cleaning for about 10 minutes, crystal growth is started. That is, the shutter 10 of the crucible 12 is closed to stop the supply of the As simple substance 14, and the oscillation of the CO ₂ laser oscillator 18 is also stopped. Then, TMG 26 as a group III source gas and tBAs 28 as a group V source gas are supplied into the oblique chimney reactor 2. Then, such crystal growth is performed, for example, for 30 minutes to 1 hour to grow a GaAs crystal having a required thickness on the GaAs substrate 4.

Next, when the crystal growth is completed, the temperature of the GaAs substrate 4 is lowered. At the end of the crystal growth, TMG26 and tBA
When the supply of s28 is stopped, the shutter 10 of the crucible 12
And supply of the As single substance 14 to the surface of the GaAs substrate 4 is started again. Then, the GaAs substrate 4 is heated from a temperature of 600 to 700 ° C to a temperature of 300 ° C.
It takes about one hour to lower the temperature to ℃, but the supply of As simple substance 14 to the surface of the GaAs substrate 4 is continued until the temperature becomes 300 ℃ or less.

In this way, in the present embodiment, the tBAs28 an organic group V source used after bubbled with H ₂ gas as a group V source gas, the prior grow to the GaAs substrate 4 reaches the growth temperature 600 to 700 ° C. At the time of raising the temperature, performing thermal cleaning for removing oxides on the surface of the GaAs substrate 4, and lowering the temperature of the GaAs substrate 4 to a temperature of 300 ° C. or less after the growth, the As single substance 14 is supplied to the surface of the GaAs substrate 4. During thermal cleaning, radicals such as H, AsH, and AsH ₂ are supplied to the surface of the GaAs substrate 4 using the CO ₂ laser oscillator 18 and the condenser 20.

Therefore, by not using any highly toxic hydrides such as AsH ₃ and PH ₃ , the danger associated with the work can be eliminated, and the growth can be achieved by using the organic V group tBAs only during growth. It is possible to reduce the cost by reducing the required amount of the organic group V required for the above.

In addition, by supplying As simple substance 14, it is possible to prevent As which is a V group element having a high vapor pressure from being released from the surface of the GaAs substrate 4.

Furthermore, by supplying the radicals, the oxide on the surface of the GaAs substrate 4 can be removed and cleaned, and the adhesion of carbon to the interface between the surface of the GaAs substrate 4 and the GaAs crystal to be grown can be prevented.

The present inventors have developed SIMS (Secondary Ion Mass Spectroscop).
Examination of the GaAs crystal grown on the GaAs substrate using y) revealed no carbon contamination at the interface between the GaAs substrate and the GaAs crystal. In addition, the characteristics of the GaAs crystal represented by the carrier mobility show that AsH ₃
As compared with the case of using, the same or better characteristics were exhibited.

Next, another embodiment of the present invention will be described with reference to FIG.

In this embodiment, as a radical supply means, a radical is supplied using a discharger and a radical introduction tube instead of the CO ₂ laser oscillator 18 and the condenser 20 in the embodiment shown in FIG. .

In FIG. 3 (a), a discharger 50 is installed outside the oblique chimney type reactor 2 near the susceptor 6 on which the GaAs substrate 4 is installed, and the tip of a radical introduction tube 52 extending from the discharger 50 is inclined. The gas in the chimney reactor 2 reaches the susceptor 6 upstream. Note that the length from the discharge machine 50 to the tip of the radical introduction tube 52 is desirably 10 to 20 cm or less.

A vacuum pump is provided at the outlet of the oblique chimney type reactor 2.
54 is attached to control the pressure in the oblique chimney type reactor 2.

As shown in FIG. 3 (a), the discharger 50 includes a microwave oscillator 54 and a cavity resonator 56 connected thereto.
The radical introduction tube 52 passes through the cavity resonator 56.

 Next, the operation will be described.

At the time of raising the temperature of the GaAs substrate 4 before growth, the pressure in the oblique chimney type reactor 2 is reduced to 10 Torr or less. When the temperature exceeds 300 ° C., the crucible 1 is heated in the same manner as in the above embodiment.
The second shutter 10 is opened, and As simple substance 14 is fed into the oblique chimney type reaction furnace 2 and supplied to the surface of the GaAs substrate 4.

Next, after the temperature of the GaAs substrate 4 is stabilized at a growth temperature of 600 to 700 ° C., thermal cleaning is performed to remove the oxide on the surface of the GaAs substrate 4. At the time of this thermal cleaning, radicals are supplied to the surface of the GaAs substrate 4.

That is, for example, a microwave of 2.45 GHz oscillated by the microwave oscillator 56 shown in FIG. 3B is introduced into the cavity resonator 58, and the inside of the cavity resonator 56 of the radical introduction pipe 52 through which H ₂ gas flows. A discharge is generated in the part. By this discharge, H radicals are formed in the radical introduction tube 52. The H radicals reach the upstream side above the GaAs substrate 4 through the radical introduction tube 52, where the H radicals in the crucible 12
Reacts with As supplied from the As simple substance 14 to produce H, AsH, AsH ₂
And other radicals.

Thus, in the same manner as in the above embodiment, these H, As
H, AsH _{2 and} other radicals are supplied to the surface of the GaAs
The oxide on the surface of the substrate 4 is removed for cleaning.

After performing such thermal cleaning for about 10 minutes, crystal growth is started. At the start of this crystal growth,
And the oscillation of the microwave oscillator 56 also stops. Then, the flow rate of the H ₂ carrier gas is gradually increased and the vacuum pump 54 is controlled to return the pressure in the oblique chimney type reactor 2 to 50 to 760 Torr suitable for growth.

Subsequent crystal growth and temperature reduction are exactly the same as in the above embodiment.

As described above, in the present embodiment, the discharger 50 and the radical introduction pipe 52 serve as means for supplying radicals to the surface of the GaAs substrate 4.
However, the same effect as the above embodiment can be obtained.

In the above two embodiments, the slanted chimney type reactor 2 was used. However, as shown in FIGS. 4 and 5, a conventionally used horizontal reactor 60 or vertical reactor 62 is used. May be used.

However, in the case of the horizontal reactor 60 or the vertical reactor 62, when the As simple substance 14 is fed into the reactor,
Accumulates on the inner wall of the reactor upstream of the GaAs substrate 4 with respect to the gas flow, where a reaction between As and a group III element occurs to grow a ternary mixed crystal (such as AlGaAs). The composition tends to fluctuate in the plane of the substrate. In this regard, the oblique chimney type reactor 2 used in the above embodiment is
Since the deposition of As simple substance 14 on the inner wall of the reaction furnace can be prevented, a crystal having a stable composition ratio can be grown in the substrate surface.

Further, in the above embodiment, as the organic group V raw material, As
The system tBAs28 was used, but in addition to the already described TMAs, TEAs, PhAs, etc., organic V such as DMAs (dimethylarsine), DEAs (diethylarsine), and nPAs (neopentylarsine).
A tribe may be used.

In addition to these As-based compounds, for example, TMP (trimethylphosphine), TEP (triethylphosphine), tBP
A P (phosphorus) -based organic V group such as (tert-butylphosphine) may be used as a raw material.

Needless to say, the present invention is implemented even when the gas source MBE method is used.

[Effects of the Invention] As described above, according to the present invention, in a crystal growth method and apparatus for growing a crystal containing a group V element on a substrate containing a group V element, an organic group V is supplied as a group V material during growth. By supplying a group V element alone on the substrate containing the group V element before and after the growth, and by supplying radicals together with the group V element alone on the substrate during thermal cleaning to grow a crystal containing the group V element, It is possible to prevent the group V element from desorbing from the substrate surface before and after the growth while suppressing the amount of expensive organic group V used, and to use a group V hydride by enhancing the effect of thermal cleaning. The surface of the substrate can be cleaned as much as or better than it is, and the characteristics of the crystal to be grown can be improved.

This provides a safer growth method and apparatus that does not require the use of highly toxic Group V hydrides,
High quality crystals can be realized at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an apparatus used for a crystal growth method according to one embodiment of the present invention, FIG. 2 is a diagram for explaining a crystal growth method according to one embodiment of the present invention, and FIG. FIG. 4 is a view for explaining a crystal growth method according to another embodiment of the present invention. FIGS. 4 and 5 are views showing modified examples of the apparatus of FIG. In the figure, 2 ... an oblique chimney type reactor, 4 ... a GaAs substrate, 6 ... a susceptor, 8 ... an infrared lamp, 10 ... a shutter, 12 ... a crucible, 14 ... a simple substance, 16 ... a heater, 18 ...... CO ₂ laser oscillator, 20 ...... concentrator, 24 ...... H ₂ purifier, 26 ...... TMG, 28 ...... TBAs, 30 ...... sequencer, 32 ...... laser light, 34, 36 ...... width Magnifying lens, 38,42,44,46… Condenser, 40 …… Separate condenser, 50… Discharger, 52… Radical introduction tube, 54… Vacuum pump, 56… Microwave Oscillator, 58: cavity resonator, 60: horizontal reactor, 62: vertical reactor.

Claims (4)

(57) [Claims] A step of heating and heating the substrate while supplying a simple substance of a group V element on a substrate containing a group V element, and then supplying an organic compound of a group V element onto the substrate and Growing a compound semiconductor layer containing a group V element, and then cooling the substrate while supplying a simple substance of a group V element onto the substrate. 2. The method according to claim 1, wherein a radical comprising a group V element and a hydrogen element is supplied onto the substrate when the substrate is heated and heated. 3. A reaction furnace, substrate installation means for installing a substrate containing a group V element in the reaction furnace, heating means for heating the substrate, and organic group V for supplying an organic group V on the substrate A supply means for supplying a group V element alone on the substrate, and a crystal containing a group V element by supplying an organic group V by the organic group V supply means during growth. Grown on a substrate, and before and after the growth, the V
An apparatus for growing a compound semiconductor crystal, characterized by supplying a simple group element. 4. A compound semiconductor crystal growth apparatus according to claim 3, further comprising radical supply means for supplying hydrogen radicals onto said substrate, wherein said substrate surface is cleaned before growing.