JPS6090897A - Method and apparatus for manufacturing compound semiconductor single crystal - Google Patents

Abstract

PURPOSE:To manufacture a long-sized compound semiconductor single crystal without dislocation by forming a single crystal in the shape of an umbrella extending to the inner diameter of a crucible with a seed crystal in the long-sized crucible, and growing the crystal while specifying the product of a temp. gradient and a growing speed. CONSTITUTION:A specified amt. of the mother materials Ga and As is charged into a crucible 1, and a liquid sealing material B2O3 3 is added thereon. The crucible is heated by an upper heater 6a and a lower heater 6b, and the GaAs melt 2 is covered with the sealing material 3. Then a seed crystal 4 is brought into contact with the melt 2, and the vertical temp. gradient in the vicinity of the interface between the seed crystal 4 and the melt 2 is regulated by the upper heater 6a and a temp. gradient controlling heater 8. An umbrella-shaped thin plate single crystal is grown by controlling the output of the lower heater 6b. Then the umbrella-shaped single crystal is further grown while regulating the product of the temp. gradient and the growing temp. to <=1 deg.C/h, and the single crystal 5 having the diameter almost the same as the inner diameter of the crucible 1 is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field of the invention] The present invention relates to a Bl-v film such as GaAg, InP, etc.
This article relates to methods and apparatus for producing single crystals of group compound semiconductors and other compound semiconductors.

[Prior art]

This kind of compound semiconductor, recently used in electronic applications,
For example, a single crystal of an m-V group compound semiconductor represented by GaAs or InP is required to have a high resistance of 10 7 Ωα and semi-insulating properties at room temperature.

Traditionally, this type of ■-V group compound semiconductor single crystal was manufactured using the horizontal Bridgman method CHB method, in which a melt of the target compound is placed in a quartz boat and the electric furnace or boat is moved horizontally to produce a single crystal. , boat method) or the Czochralski method (C2 method, LEC method) in which seed crystals of the same type as the target compound are brought into contact with a melt and pulled up.

LEC (Liquid Encap) has been attracting attention recently.
GaAs single crystals produced by the Czochralskis aluminized liquid confinement (Liquid-confined pulling) method yield a semi-insulating (100) circular single crystal with few residual impurities. 1
00~b, the density of dislocations caused by crystal defects is 10'10++27)
A et al. 5 x 105/cm2, which is high and (100) Ueno, has the disadvantage of large non-uniformity of electrical properties due to non-uniform distribution within the plane, and low dislocation/no dislocation is desired. ing. Note that Fig. 1(a) shows the lifting device, and Fig. 1(b)
) shows the temperature distribution, 1 is the crucible, 2 is the melt, 3#
'i liquid sealing material, 4 is a seed crystal, 5 is a single crystal, 6 is a heater, and 7 is a crucible susceptor.

On the other hand, in crystal growth by the HB method, the dislocation density is essentially lower because it is grown under a lower temperature gradient (e.g. 5°C/(7)) than in the LEC method, for example 4 x 103 to 8 x 10
”/1yn2, and is uniformly distributed. In the boat growth method, to grow a single crystal along the (111) axis, it is necessary to obtain a (100) plane wafer, which is advantageous for devices. ) It is necessary to cut the wafer at an angle of 54.7 degrees from the ingot, so a circular wafer cannot be obtained.Furthermore, since the (100) plane wafer is inclined at 54.7 degrees from the growth direction, The drawback is that the distribution of residual impurities becomes non-uniform.In any case, it is difficult to obtain large single crystals free of dislocations using conventional methods.

[Object and structure of the invention]

The present invention has been made in view of these circumstances, and its purpose is to provide dislocation-free compound semiconductor single crystals, particularly (100)
It is an object of the present invention to provide a method and apparatus for manufacturing a dislocation-free compound semiconductor single crystal, which enables the production of circular wafers.

In order to achieve all of these objectives, the method for manufacturing a semiconductor single crystal of the present invention involves bringing a seed crystal into contact with the melt in a long crucible, and forming a single crystal that initially spreads into an umbrella shape almost to the inner diameter of the long crucible. After growing a crystal, a single crystal is grown below it under conditions of an extremely low temperature gradient and a low growth rate, that is, the product of the temperature gradient and the growth rate is 1° C./h or less.

A single crystal is grown within the elongated crucible. Further, in order to prevent the volatile components in the compound from dissipating, the single crystal is covered with a liquid sealing material or grown in an atmosphere of the volatile components.

Furthermore, the uniformity of the crystal can be further improved by holding the grown single crystal in that state for several hours or more without immediately removing it to room temperature after separating it from the melt.

In addition, in order to carry out such a method, the compound semiconductor single crystal production apparatus according to the present invention provides at least two independent crucibles, upper and lower, disposed around the outer periphery of an elongated crucible with a circular cross section over the length of the ruriho. That is, it may be equipped with a heater whose temperature can be controlled independently, and a mechanism for raising the elongated crucible and the seed crystal at a predetermined speed relative to the heater. An extremely low temperature gradient is achieved over the entire growth process of the single crystal in the elongated crucible by means of the heater arranged over the length of the elongated crucible.

Hereinafter, the present invention will be explained in detail using Examples.

〔Example〕

FIG. 2(a) is a sectional view of a manufacturing apparatus showing an embodiment of the present invention, in which 1 is a long crucible, 2 is a GaAs melt, 3 is a liquid sealant, 4 is a seed crystal, and 5 is a seed crystal. GaA grown from
s single crystal, 6a an upper heater, 6b a lower heater, 7 a crucible rotating susceptor, 8 a temperature gradient control heater, and 9 a crystal pulling support shaft. Also, Figure 2 (b
) shows a typical axial temperature distribution. However, although the high-pressure vessel is not marked in the figure, each part shown in this figure is housed in a high-pressure vessel that can withstand approximately 100 atmospheres.

Next, a manufacturing method showing an embodiment of the present invention will be described.
This will be explained in detail using FIG.

First, Ga and As as base materials are weighed to a stoichiometric composition, placed in a pyrolytic BN (pBN) crucible 1, and B2O3 is added thereon as a liquid sealant, and then placed in a pressure vessel. to about 60 atmospheres using nitrogen gas. Next, a liquid sealing material 3 made of B2O3 is formed using the upper heater 6a. That is, by heating the upper heater 6a to approximately 400°C and melting B2O3, the inserted Ga and As are converted into B2O3.
J) This can minimize the dissociation of As. Next, the melting point of GaAs is raised to 1328° C. or higher using the lower heater 6b to form a GaAs melt.

At this time, the output of the upper heater 6a is also increased at the same time as the output of the lower heater 6b, and is set to a temperature slightly lower than the melting point of GaAs. Here, the long crucible 1 used had an inner diameter of 5
5 mm-, length 10 saws, GaAs is about 1.5
Added kf. Here, the pressure in the pressure vessel was lowered to 3 atmospheres.

This means that the vapor pressure of A6 alone, which is made up of volatile components, is 60~
As mentioned above, it is desirable to increase the pressure to around 60 atm in order to obtain a pressure of 70 atm.
This is because in the state of a compound, the pressure is 1 to 3 atm, and on the other hand, a lower pressure is desirable in order to suppress convection of the melt and achieve a low temperature gradient.

Next, the seed crystal 4 with the GaAg ClOO〉 axis
The seed crystal 4 and the GaAs are brought into contact with the As melt 2 by the upper heater 6a and the temperature gradient control heater 8.
The longitudinal temperature gradient near the interface of the melt was adjusted to 5° C./F as shown in FIG. 2(b) (FIG. 3, 6)).

At this time, the rotary susceptor 1 is rotated at 5 revolutions per hour.

Next, the output of the lower heater 6b is controlled to gradually lower the temperature and gradually spread the GaAs crystal from the seed crystal 4. At this time, the lower heater 6 is turned on so that the lateral growth rate of the growing GaAa crystal is 10 man/hour.
Adjust the output of b. In this way, after about 2.5 hours, a GaAs thin plate crystal 5' covering the GaAs melt 2 was formed from the seed crystal 4 (FIGS. 3(b) and 3(c)). The formation of this thin plate crystal 5' is one of the features of the present invention, and its effect is to completely cover the surface of the GaAs melt 2 (for example, 99%).
) 8) In particular, the evaporation of As from the GaAs melt is suppressed, the stoichiometric composition ratio of the crystal remains unchanged, and the contamination of impurities from the surrounding heaters is suppressed.

In the process of growing this thin plate crystal 5', the seed crystal 4 was raised via the support rod 9 at a very slow speed of 0.1 mm/hour to suppress the generation of parts.

Next, the crucible 1 was raised via the susceptor 7e at a rate of 2 mm/hour, and the seed crystal 4 was raised at a rate of 2 mm/hour by the support rod 9, so that the entire crucible was raised in the upper and lower heaters. As a result, as a result of the extremely low temperature gradient (the initial setting is 5°C/F) formed by the upper and lower heaters, the temperature of the lower heater 6b Th decreases by 2 to 3 in the process of forming the thin plate crystal 5'. The crystals slowly grow under the thin plate crystal 5' under a very low temperature gradient of 50°C. As mentioned above, by controlling the temperature during the formation of the thin plate crystal 5', the crystal diameter was approximately the same as the inner diameter of 1. Figures (d), (e)).

Here, since the grown single crystal is grown at an extremely low temperature gradient and the grown crystal is present in the upper heater 6a at a constant temperature, the generation of dislocations is suppressed. The number of transitions in the obtained crystals was 100 or less. No dislocation is achieved by
This can be achieved by controlling the way the thin plate crystal 5' spreads, that is, the rate of rise of the seed crystal 4 and the way the temperature of the lower heater 6b is lowered.

Note that the synchronous rising speed t? of the crucible 1 and the seed crystal 4? 2
When the speed exceeds mrn'fc, it is difficult and rare to obtain a single crystal. In this case, there is a certain correlation between the temperature gradient and the rate of increase, that is, the growth rate, and the product of the two is 1°C.
/h or less, good results were obtained. When the temperature gradient is small, the growth rate can be increased somewhat, and conversely, when the growth rate is decreased, the temperature gradient can be made slightly larger.

Now, at the end of the crystal, the rising of the susceptor T is stopped, the rising speed of the support rod 9 is set to 20 mm per hour, and the output of the temperature gradient control heater 8 is increased to heat the grown GaAs.
At the same time as the crystal 5 and the melt 2 were separated, the lifting of the support rod 9 was stopped. By doing so, the liquid sealing material 3 does not enclose the crystal, but has the effect of suppressing the dissociation of As from the surface of the Ga'As crystal (FIG. 3(f)). Thereafter, the heater temperature was gradually lowered, and before the B2O3 solidified, the crystals were pulled upward and taken out from the pressure vessel. (100) wafers were cut from the approximately 1 kf ingot obtained in this manner, and as a result of detecting dislocations by KOH etching, less than 100 dislocations were detected except at the periphery of the wafer.

In this embodiment, the total pulling speed of the seed crystal was set to 0.1 mm/hour during the growth process of the thin plate crystal 5', but the formation of the thin plate crystal 5' depends on the pulling speed and the lower heater 6b as described above. The generation of dislocations can be suppressed by combining the temperature reduction rate, and the method for forming the thin plate crystal 5' is not limited to the above-mentioned example. In short, from the seed crystal to a dislocation-free thin plate crystal 5
′ by forming GaAs in the shortest possible time.
It is important to suppress the dispersion of As from the melt as much as possible, and the gist of the present invention is to form this umbrella-shaped thin plate crystal 5' and then grow it at an extremely low temperature gradient and at a low growth rate to form a dislocation-free single crystal. In manufacturing.

In addition, in the above-mentioned slower single crystal growth of 9, the temperature stability due to thermal convection in the GaAs melt and the uniformity of impurity mixing are not necessarily good, but the melt 2
This convection can be suppressed by applying a strong magnetic field vertically or horizontally to the liquid surface. Fourth
The figure is a sectional view showing such a creation device. here 4
, the support rod 9, susceptor 7 and high pressure vessel shown in FIG. 2 are omitted. Also, since the left and right sides are symmetrical, only the right hand is shown. In this case, the magnetic field generating magnet 11
) As a result of applying a magnetic field of 500 to 2000 oersted to the GaAs melt 2, the temperature change # in the melt was ±± under no magnetic field.
What was 5°C was suppressed to ±1°C by applying 500 oersteds, and further suppressed to below ±1°C by applying a magnetic field. 10
Applying a magnetic field of 00 oersted, Cr (chromium) k O,
A 2-inch diameter single crystal (about 10 cm in length) was similarly obtained by adding 1 wt ppm, and the Cr# degree from the top to the bottom of the ingot was analyzed. Compared to the Cr distribution within the grown ingot ((a) in the same figure), it was confirmed that there is a region where the Cr concentration distribution is uniform in the ingot grown under a magnetic field ((b) in the same figure). . This is because convection within the melt is suppressed by applying a magnetic field, resulting in psychostatic stability II, which is different from normal solidification in the absence of a magnetic field.
! This shows that it is possible to obtain an ingot that is hard and has a uniform impurity concentration. Furthermore, when a high magnetic field greater than 1000 oersteds is applied, ideally the region with a constant Cr concentration in the ingot occupies ~80 oers or more, as shown by the dashed line (c) in Figure 5. Become.

In the above example, crystal growth in a long crucible was performed by fixing the upper and lower heaters and raising the crucible and seed crystal synchronously under the low temperature gradient formed by the upper and lower heaters. In this case, since the relative positional relationship between the solid-liquid interface between the crystal 5 and the melt 2 and the low temperature gradient region is the key, the entire upper and lower heaters 6a and 6b are lowered without moving the crucible, the crucible, and the seed crystal. Single crystal growth can be achieved in exactly the same way. In short, it is achieved by raising the melting point and the seed crystal relative to the heater.

Next, another embodiment of the present invention will be described using FIG. 6. In FIG. 6, the same symbols as in FIG. 2 indicate corresponding parts, but the long melt consists of an arsenic reservoir 13 above 1 into which metal arsenic 12 can be inserted, and B2O3 around the crystal pulling support shaft 9. A flange cover 15 having a structure to bring the sealing material 14 into contact with the metal arsenic 12t and a heater 16 for controlling the arsenic pressure are installed. It goes without saying that this entire figure is installed inside a high-pressure vessel. Further, the crucible cover 15 and the long glass 1 can be inserted and removed by sliding them together.

In order to produce a crystal with this configuration, it is slightly different from the above-mentioned embodiment.
Only s is inserted into the stoichiometric ratio, and the liquid sealant 3 is not used. Specifically, after putting the base materials Ga and As and the entire length inside, the metal arsenic 12 is put into the arsenic reservoir 13, and the encapsulant 14-karat gold is put in. The cover 15'ft is lowered together with the crystal pulling support shaft 9, and the long glass plate 1 and the crucible cover 15 are brought together. Next, the pressure inside the high-pressure container is increased. Next, the arsenic pressure control heater 16 is
Metal arsenic (12t) is heated to 00 DEG C. and sublimated, and an arsenic vapor atmosphere is created by passing through the gap between the arsenic reservoir 13 and the shaft 9 into the space 17 constituted by the ruribo cover 15 and the elongated ruribo 1. At this time, the pressure inside the high-pressure container is made higher than the arsenic vapor pressure to prevent arsenic from escaping from the space 17.

On the other hand, due to the preheating of the arsenic pressure control heater, the B2O3 of the sealing material 15 melts and comes into contact with the shaft 9, and the gap of approximately 1 mm between the shaft 9 and the arsenic reservoir 14 is filled with highly viscous B2O3.
The arsenic vapor cannot escape from the space 17 because it is blocked by 2O3. After this twisting, the lower heater 6b first melts the mother alloy Ga, and then the upper heater 6b gradually melts the mother alloy Ga.
a and the lower heater 6b to heat the GaAs melt 2.
Synthesize.

After this, as shown in the above example, after contacting the seed crystal 4, the temperature distribution and growth rate are controlled and the seed crystal is placed in the crucible.
P crystal was grown. During this whole process, the metal arsenic 12 is heated, and therefore the arsenic pressure in the space 17 is controlled, so that dissociation of arsenic during the synthesis and crystal growth of the QaAs melt can be prevented. Further, the degree of dissociation can be controlled by adjusting the output of the arsenic pressure control heater 16.

The surface of the crystal thus obtained was very smooth and had a metallic luster because it was not in contact with the liquid sealant 3 and was grown under arsenic pressure.

(100) When a wafer is cut out and dislocation pits are detected,
The occurrence of dislocations from the crystal surface was extremely rare, with an average of 100 or less dislocations per wafer.

In this example, a device capable of applying a magnetic field of 500 microns or more to the entire structure was installed, and when the magnetic field was applied, an even more homogeneous single crystal could be obtained.
In the case of the above-mentioned embodiment and Mr. r#J. Furthermore, the structure of the cover 15 itself is not limited to the form shown in FIG. It is sufficient if the dissipation of arsenic can be prevented by growing in an atmosphere.

In each of the embodiments described above, the grown single crystal 5 is placed in the melt 2.
After separating it from the crystal (at this time, the liquid sealing material 3
Or covered with arsenic vapor.

(see Figure 3(f)), and after being maintained in this state for 5 hours,
By lowering the temperature to room temperature and taking it out, the uniformity of the crystals could be further improved. This is because, for example, when we observed the cathode luminescence intensity distribution of a crystal taken out after performing this kind of holding, we found that the distribution was more uniform and had a lower resistance than that of a crystal taken out immediately to room temperature without such holding. This can also be confirmed from the fact that the strength of the background has also increased. Note that the above holding time varies depending on the holding temperature at that time 9. For example, if the holding time is as low as 800 to 900°C, holding for 10 hours or more is required;
At a temperature higher than before and after, the effect of improving uniformity can be obtained even for a time shorter than 5 hours.

The above temperature varies depending on the target compound.

As mentioned above, [GaAs, which is a representative side of the 1-V group compound semiconductor]
has been described as an example, but the present invention is not limited thereto, and other compounds containing volatile components, such as InP,
■-V group like InAg, GaP, and fcZnS
, Zn5e, ZnTe and CdS.

■-■ group compounds such as CdSe, and even Pb5n
It is easy to understand that this method can also be applied to the growth of uniform single crystals of ternary compounds such as Te and Pb5eTe.

〔Effect of the invention〕

As explained above, according to the present invention, crystal growth can be achieved under extremely low temperature gradients and low growth rates, which are realized by, for example, two independent heaters arranged over the length of a long crucible, and By covering almost the entire surface of the melt with a single crystal, it is possible to extremely reduce the number of dislocations caused by crystal defects, and the growth rate is slow, and by being kept in the upper heater for a long time, strain within the crystal can be reduced. It will be resolved. Furthermore, by forming an umbrella crystal from the seed crystal to near the inner diameter of the crucible, it is possible to avoid dispersion of volatile components from the surface of the melt and furthermore to avoid contamination of impurities into the melt from heater materials and surrounding containers.

Furthermore, when growing in a volatile component vapor atmosphere, there is no need to use a liquid encapsulant, so the surface is extremely smooth and has a metallic luster, resulting in high quality with very few defects introduced from the crystal surface. Crystals are obtained, and whether the process is carried out using a liquid encapsulant or in a volatile component vapor atmosphere, if the grown single crystal is separated and held for several hours before being taken out to room temperature, The uniformity can be further improved.

In addition, the method according to the present invention does not involve pulling up the seed crystal to the rutsutsuho, but rather allows the entire crystal to grow within the rutsutsutsu. However, unlike the so-called boat method, the seed crystal is Since the crystals are not in direct contact with the crucible during cooling, no strain is introduced from the interface between the material and the crystals, which also makes it possible to achieve low dislocations.

[Brief explanation of the drawing]

Figure 1 (a) is a cross-sectional view showing an example of the configuration of a conventional single crystal pulling apparatus, Figure 1 (b) is a diagram showing its temperature distribution, and Figure 2 (
a) is a cross-sectional view showing an embodiment of the present invention, FIGS. 3(a) to 3(f) are views showing the temperature distribution, FIG. Figure 5 is a diagram showing the relationship between the distribution of Cr in the crystal in the direction of the growth axis and the applied magnetic field; Figure 6 is a cross-sectional view of yet another embodiment of the present invention. Ruru. 1... Crucible, 2... Temperature L 3. Jar... Liquid sealing material (B203), 4... Seed crystal, 5... Single crystal, 5'... Umbrella shaped thin plate crystal, 611L-fist...upper heater, 6b...lower heater,
T: Susceptor, 8: Temperature gradient control heater, 9: Crystal pulling support shaft, 11:
・Magnetic field generating magnet, 12... Metal arsenic, 13.
e... Arsenic reservoir, 14... Sealing material, 15... Crucible cover, 16... Heater for cumulative pressure control, 11...
・φRutsu is the inner space. Patent Applicant Nippon Telegraph and Telephone Public Corporation Sumitomo Electric Industries Co., Ltd. Agent Masaki Yamakawa No. 1 (0) (b) j&&

Claims (5)

[Claims] (1) After melting the target compound semiconductor base material and liquid encapsulant in a long melt, a seed crystal of the same type as the compound semiconductor is brought into contact with the compound semiconductor melt through the liquid encapsulant. a step of gradually lowering the temperature of the melt to gradually grow a single crystal from the seed crystal and expanding it into an umbrella shape almost up to the inner diameter of the long melt; 1. A method for manufacturing a compound semiconductor single crystal, comprising the step of continuously growing the single crystal under conditions where the product of temperature gradient and growth rate is 1° C./h or less. (2) After melting the target compound semiconductor base material and liquid encapsulant in a long crucible, seed crystals of the same type as the compound semiconductor are brought into contact with the metal semiconductor melt through the liquid encapsulant. a step of gradually lowering the temperature of the melt to gradually grow a single crystal from the seed crystal and expanding it into an umbrella shape almost to the inner diameter of the elongated melt; A process of continuously growing a single crystal downward under conditions where the product of temperature gradient and growth rate is 1°C/h or less, and after cutting the grown single crystal from the melt, it is brought to room temperature. 1. A method for producing a compound semiconductor single crystal, comprising the step of holding it in that state for several hours or more before releasing it. (3) The process of bringing into contact the compound semiconductor melt with a maple tree in which the target compound semiconductor base material is melted in a long melt, and a seed crystal of the same type as the compound semiconductor, and gradually increasing the temperature of the melt. a step of gradually growing a single crystal from the seed crystal and expanding it into an umbrella shape almost to the inner diameter of the elongated crystal;
Continuously growing the single crystal under the umbrella-shaped single crystal under conditions where the product of temperature gradient and growth rate is 1° C./h or less, and each of these steps has the above purpose. A method for manufacturing compound semiconductor single crystals that is specially designed to be carried out in a vapor atmosphere of volatile components in compound semiconductors. (4) After melting the target compound semiconductor base material gold in a long crucible, a step of bringing a seed crystal of the same type as the compound semiconductor into contact with the compound semiconductor melt, and gradually lowering the temperature of the melt. Gradually growing a single crystal from the seed crystal and expanding it into an umbrella shape almost up to the inner diameter of the long rutsuho;
A process of continuously growing a single crystal under the umbrella-shaped single crystal under conditions where the product of temperature gradient and growth rate is 1°C/h or less, and removing the grown single crystal from the melt with a cutting blade. and holding it in that state for several hours or more before taking it out to room temperature, and each of these steps is carried out in an atmosphere of vapor of volatile components in the compound semiconductor for the above-mentioned purpose. A method for manufacturing semiconductor single crystals. (5) An elongated crucible with a circular cross section for melting the target compound semiconductor base material, and at least two upper and lower crucibles arranged around the outer periphery of the elongated crucible over the length of the elongated crucible.
two or more independent heaters, a mechanism for synchronously raising the elongated crucible and the seed crystal supported in the crucible at a predetermined speed relative to the heater; 1. A compound semiconductor single crystal manufacturing apparatus, comprising: a pressure vessel housing a heater.