JPS62197388A - Method and device for producing semiconductor single crystal - Google Patents

Abstract

PURPOSE:To obtain the title single crystal without any variance and having an excellent stoichiometrical property by controlling the temp. distribution in a single crystal growth chamber and the vapor pressures of specified plural high-vapor pressure components. CONSTITUTION:A grounded closed reaction tube 20 is separated by a vertical partition wall 21 and a horizontal partition wall into a growth chamber 22 and two high-pressure component storage chambers 24 and 25. The growth chamber 22 is independently communicated with the storage chambers 24 and 25 through capillaries 26a and 26b. The reaction tube is inserted into a furnace provided with temp-controllable heaters H1-H5 to form the raw material melt or raw material solid zone T0 or T'0, a crystal growth zone T1, a crystal zone T2, a zone T3 for heating the first high-vapor pressure component A, and a zone T4 for heating the second high-vapor pressure component B. A polycrystal material A.B is charged in a quartz boat 27 in the growth chamber 22, the high-vapor pressure components A and B are respectively stored in the storage chambers 24 and 25, and the reaction tube is inserted into the furnace wherein the temp. in the single crystal melting zone is controlled by the heaters H1-H5 to a temp. higher than the b.p. and moved to grow a single crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for manufacturing compound semiconductor single crystals or mixed crystals. More specifically, by improving the natural solidification method, controlling the vapor pressure with high precision, and strictly controlling the stoichiometric composition, it is possible to produce uniform single crystals or mixed crystals of compound semiconductors with no variation. The present invention relates to a highly productive method of formation and an apparatus therefor.

2. Description of the Related Art Si semiconductor devices, which have been widely used in the past, have become unable to meet recent needs due to limitations in the physical properties of Si. For example, when the dimensions of a diode are fixed, the larger the forbidden band and the greater the mobility, the higher the cutoff frequency can be obtained, but this is a limit with Si, and this point has been overcome by using compound semiconductors. (
For example, ultra-high frequency diodes). In addition, indirect transition type S
Due to the limitations of the band structure of i-semiconductors, it has also been difficult to produce highly efficient light emitting devices. This was also solved by the use of compound semiconductors, which are direct transition types.

In this way, in electronics technology, semiconductor elements with higher performance such as high-speed operation and high-frequency operation,
With the increasing demand for devices, compound semiconductors, which have higher mobility and a wider forbidden band width than Si, are attracting attention.

This compound semiconductor further has a zinc blend lateral crystal structure similar to a diamond-type covalent crystal, making it possible to obtain a functional device that cannot be obtained with a model element semiconductor such as Si. In addition, by combining two types of binary compound semiconductors that share one element in common, a ternary mixed crystal whose lattice constant continuously and monotonically changes depending on the composition can be obtained, resulting in the formation of a semiconductor. A Peter junction that can ensure lattice matching between crystals can be obtained, and the same is true for multi-component mixed crystals of quaternary or higher elements. By changing the composition in this way, it becomes possible to control the physical properties of the semiconductor, including the lattice constant.

By the way, in the manufacturing process of various compound semiconductor devices as described above, first of all, it is essential to form a highly pure single crystal or mixed crystal.

However, since these have various properties different from conventional Si, their crystal growth techniques are also completely different.
The Czochralski method (CZ method), floating zone method (FZ method), etc. are widely used for Sl, etc. However, for example, when using GaAs as an example, strict control of the composition (Ga:As ratio) is required. Furthermore, there are subtle technical problems such as the fact that the critical shear stress at high temperatures is small, and dislocations are likely to occur due to thermal strain.

Crystal growth of compound semiconductors can be broadly divided into bulk crystal growth and epitaxy. A plate-shaped crystal called a wafer is cut from the bulk crystal, and this is either directly sent to the following processing process or used as a substrate for epitaxy. It will be used as. On the other hand, the latter crystal grown by epitaxy is thin and therefore has insufficient mechanical strength, so it cannot be used as is and requires the use of a substrate.

The Bridgman method (vertical Bridgman method, horizontal Bridgman method), pulling method (LEC method), FZ method, etc. have been used for a long time as methods for growing bulk crystals of the above-mentioned compound semiconductors, and the principles thereof are, for example, In the vertical Bridgman method, as shown in Fig. 2, a heating furnace is provided with a predetermined temperature gradient (shown on the left side of Fig. 2) consisting of a high temperature section and a low temperature section set by a heater 1.2. A crystal 5 is grown by moving a quartz container 4 containing a raw material melt 3. In addition, in order to prevent the formation of disordered crystal nuclei, the diameter of the container is narrowed at the start of assimilation of the melt.In this area, fewer nuclei are generated, and within this area, the orientation in which they grow faster than in other areas is avoided. The one with this functions as a seed crystal.

The current mainstream Bridgman method is the horizontal Bridgman method, in which the raw material melt is moved horizontally using a boat.It is used as a mass production method for single crystals such as GaAs, and is called the three-temperature method (three-temperature HB). method), two-temperature method (two-temperature HB method), etc. However, the latter two-temperature method has inherent problems such as insufficient reproducibility of the characteristics of GaAs grown, such as electron density, and a low proportion of solidified GaAs that becomes a single crystal. and
The former three-temperature method was mainly used.

The conventional three-temperature method will be explained in more detail with reference to the attached FIG. 3. As is clear from the figure, this method has three plateau portions in the temperature distribution. Each temperature T, , T2, and T3 is adjusted to a constant value so that the relationship TI > T2 > T3 is established. These temperatures are controlled by a plurality of heaters (not shown) provided on the outer periphery of the reaction tube 10 made of a quartz tube or the like. The reaction tube 10 has a partition wall 1 equipped with a capillary 11 for preventing gas diffusion, for example.
2, and a quartz boat 13 is sealed in the growth chamber on the left side of the reaction tube 10. On the other hand, compartment 1 on the right
2 contains a solid of a high dissociation pressure component (for example, B) of the single crystal forming raw materials (A-B), and by controlling the vapor pressure, the crystal growth raw material melt is dissociated, and the resulting crystal is The stoichiometry of the composition can be controlled. A raw material melt (AB) L is stored in the quartz boat 13, and by moving the boat 13 to the low temperature side (T2), a single crystal (AB) is produced. grows.

In the actual three-temperature HB method, a quartz boat called a shelf boat is used. In this figure, the solid-liquid interface is approximately T,
The melting point (m, p,
) part.

The methods for manufacturing bulk crystals of compound semiconductors as described above are used appropriately depending on the physical properties of the crystal to be grown, its type, etc.

Recently, there has been a need for semiconductor materials with low defects, especially in view of the need to improve device characteristics. Then, the dislocation density is already 100/Cd.
The following high dislocation-free properties have been achieved. On the other hand, II
- Also in group VI compound semiconductors, Zn5e, CdT
The development and research of C
It is known that it is possible to reduce defects in dTe by doping Zn at a high concentration to form a mixed crystal.

However, when a third additive element such as In or Zn is used for the purpose of reducing defects in the bulk crystal as described above, the concentration distribution within the crystal may change, especially for substances whose segregation coefficient deviates by a large amount. known to occur.

In this way, even though dopants were originally used for the purpose of reducing defects, the resulting crystal has a concentration distribution along its growth direction, making it difficult to maintain a predetermined composition and sufficiently control the stoichiometry. It is not possible to obtain a homogeneous product. Furthermore, attempts have been made to grow crystals by providing a high temperature gradient in order to solve the problem of concentration distribution, but this resulted in an increase in defect density.

It seems that the above problem can be solved by the three-temperature HB method as shown in Figure 3, but it is also possible to create a mixed crystal containing two or more components with high dissociation pressure, or to create a mixed crystal containing three or more components with high dissociation pressure. This is ineffective when attempting to add a high concentration of a dopant with a high dissociation pressure to the crystal, and it is impossible to obtain the desired bulk crystal with few defects and sufficient stoichiometry.

Problems to be Solved by the Invention As mentioned above, in the field of semiconductors, there is an increasing demand for higher performance and higher functionality, and the conventional S
It is becoming difficult to meet these requirements using only single-element semiconductors such as i. Therefore, compound semiconductors that can operate at high speeds and operate at high frequencies, have high mobility, saturation drift speed, etc. are attracting attention, and are expected to become even more important in the future.

In order to fabricate various devices using such compound semiconductors, it is necessary to obtain compound semiconductor crystals or mixed crystals with high purity and low defects, but unlike Si, etc., these require special care when growing single crystals. There are some technical issues that require this. Among these, it is especially important to perform strict vapor pressure control to stably obtain bulk single crystals and mixed crystals with stoichiometric composition and uniform characteristics.

In this regard, the conventional method described above is particularly useful when using an element whose segregation coefficient deviates widely from 1, such as when using a third additive element, or when using an element whose segregation coefficient deviates widely from 1, or when using an element that contains two or more components with a high dissociation pressure. This method is completely ineffective for producing mixed crystals, and the development of new bulk crystal manufacturing techniques is strongly desired. Incidentally, in order to overcome the drawbacks particularly related to the segregation coefficient, a growth method in which a high temperature gradient is provided has been proposed, but the only negative result has been that the defect density increases.

Therefore, the purpose of the present invention is to use the natural coagulation method (normalFr).
eezing method) or zone melting method, maintain the concentration of high dissociation pressure components in the growth direction at a predetermined uniform value, and produce bulk single crystals of multi-element compound semiconductors with excellent stoichiometry and uniform properties. The object of the present invention is to provide a manufacturing method.

Another object of the present invention is to provide a bulk single crystal manufacturing apparatus for carrying out the above method.

Means for Centralizing the Problems The present inventor has addressed the above-mentioned current state of the manufacturing method and manufacturing apparatus for bulk single crystals of multi-element compound semiconductors, particularly multi-element compound semiconductors containing elements having high dissociation pressure as components. In view of this, as a result of various studies and research aimed at developing new techniques to solve the drawbacks of the conventional methods described above, it has been found that it is effective to independently control the vapor pressures of at least two high dissociated equilibrium vapor pressure components. The present invention was completed based on this finding.

That is, the present invention first relates to a method for manufacturing a semiconductor single crystal (hereinafter, the term "single crystal" is used to include mixed crystals and dopants), and this method involves controlling raw materials in a reaction tube in a predetermined manner. A method for producing a multi-element compound semiconductor single crystal in which the single crystal is grown by moving the single crystal in a furnace maintained at a temperature gradient of , the temperature of the melting region of the single crystal being maintained at a temperature higher than its melting point. On the other hand, it is characterized in that the total pressure is controlled by controlling the vapor pressure of each high dissociation equilibrium vapor pressure component.

The present invention also relates to an apparatus for carrying out the above method, the apparatus comprising a growth chamber separated by a partition wall perpendicular to the central axis of the growth chamber and parallel to the central axis. A reaction tube equipped with two high vapor pressure component storage chambers divided into two by the vertical partition wall and means for independently communicating each storage chamber with the growth chamber, and a predetermined temperature distribution set. It is characterized by comprising a furnace equipped with heating means for heating.

The method and apparatus for producing multi-element compound semiconductor single crystals of the present invention relate to improvements in natural solidification methods such as zone melting method or horizontal Bridgman method. It can be advantageously applied to those containing a vapor pressure (or dissociation pressure) component, and those whose segregation coefficient deviates widely from 1, but are of course not limited to these.
It can also be applied to elements containing elements or their dopants.

When the method of the present invention is applied as a zone melting method, the temperature of the growth chamber is controlled as follows.

That is, the temperature of the region other than the single crystal growth region (crystal melting zone) is made to be just below the melting point of the crystal. On the other hand, when applied as a horizontal Bridgman method, it can be carried out by setting the temperature of the growth chamber up to the single crystal growth region just above the melting point.

Therefore, the present invention is applicable to, for example, a mixed system of CdTe and ZnTe, a system in which CdTe is doped with Se, a mixed crystal of a ■-■ group compound semiconductor or an IV group compound semiconductor, and a ■-II group compound semiconductor.
It can be advantageously applied to the production of I-VI type compound semiconductors, II-rV-V type compound semiconductor single crystals, etc.

FIG. 1 is a schematic cross-sectional view of the apparatus of the present invention, and the apparatus of the present invention will be explained in more detail below based on this figure. That is, the device of the present invention has T.

(or T', > (raw material melt zone or raw material solid zone), TI (crystal growth zone), T (crystal zone)
, T3 (heating zone to the first high vapor pressure component, e.g.)
and T, (heating zone of the second high vapor pressure component, e.g. B), respectively, in a furnace equipped with heaters (H, ~H5) whose temperature is controlled separately and independently. A sealed reaction tube 20, such as a quartz glass tube, Pyrex,
Vycor pipe etc. are grounded. This reaction tube 20 has a growth chamber 22 separated by a vertical partition 21, two high vapor pressure component storage chambers 24 and 25 further divided into two by a horizontal partition 23, and a growth chamber 22 and each storage chamber. 24.2
For example, Capilla U-26
a and 26b.

By configuring the reaction tube 20 as described above and independently controlling the temperature of each component in the storage chamber, which is independently communicated with the reaction chamber 22 by each capillary, the corresponding high vapor pressure component in the reaction chamber 22 can be controlled. The vapor pressure can be sufficiently adjusted, and a uniform single crystal with a predetermined composition and excellent stoichiometry can be obtained.

Here, the setting and adjustment of the temperature gradient at the raw material melt-crystal interface, raw material-molten zone, and crystal-molten zone is performed by H, -H, and the control of the blade high vapor pressure components A and B, respectively. This is performed by H1 and H5, which are coupled with thermocouples TC and Te2 connected to storage chambers 24 and 25, and highly accurate temperature control can be performed based on information from the thermocouples.

Further, in the apparatus of the present invention, the heating format is not particularly limited, and any conventionally known means may be used, such as resistance heating, induction heating,
Radiant heating (lamp, arc, laser, etc.) can all be used. Furthermore, in cases where direct heating poses a problem, it is also possible to provide heat shielding using a soaking tube, a liner tube, or the like.

The configuration of the apparatus of the present invention can of course be applied to a vertical reaction tube, and in this case, a component holding container is fixed to the side wall of the high vapor pressure component storage chamber.

It is also possible to provide the storage chamber at either the top or the bottom, but especially when it is installed at the bottom, the growth chamber should have a double cylindrical structure with the top open and communicating, and the space between the cylinders at the bottom. It is necessary to devise measures such as providing a capillary for communication between the storage chamber and each storage chamber. Of course, the reaction tube or the furnace can be moved either upwardly or downwardly, and this is accomplished by appropriately changing the control temperature of each heater.

Rule J As mentioned above, when producing multi-element compound semiconductor single crystals or mixed crystals, single crystals containing high concentrations of dopants, etc., in most cases they contain components with a high dissociation equilibrium vapor pressure. In addition, vapor pressure control is insufficient in the conventional horizontal/vertical Bridgman method and zone melting method, making it difficult to obtain high-quality single crystals or mixed crystals with excellent stoichiometry. For example, in the vertical Bridgman method, as shown in FIG. 2, high vapor pressure components are often extracted from the space 6, resulting in a large deviation from the stoichiometric composition. This is the same in the horizontal Brifziman method, and in systems with only one component element storage chamber for vapor pressure control, the limit is two-element compound semiconductors, and three or more element-based or dopant-added semiconductors. This was a problem in some cases. Furthermore, the segregation coefficient is 1
In the above methods, a non-uniform concentration distribution of specific components occurs along the growth direction of the single crystal, making it impossible to obtain a single crystal (or wafer) with uniform properties.

However, according to the method and apparatus of the present invention, the first
The temperature of substance A determined by heater H4 in the figure is independently controlled by thermocouple TC, while the temperature of substance B determined by heater H5 is independently controlled by thermocouple TC2, and the total pressure inside the growth chamber P
By controlling 1, the stoichiometric composition of the produced single crystal can be controlled with sufficient accuracy. In the case of four or more elements, the same effect can be achieved by comparing and considering the dissociation vapor pressures of the constituent elements and using a multi-element alloy as the element whose partial pressure is to be controlled.

As mentioned above, the stoichiometric composition of the grown single crystal is controlled by the total pressure, but it is also possible to change the partial pressure at each growth position in order to control the distribution coefficient to the solid phase. In this case, a preliminary experiment is conducted to determine the optimum temperature profile, and T3 and T can be varied accordingly. Furthermore, it is also possible to combine it with a convenience store, etc. to automatically set such a temperature profile. Such temperature (or partial pressure) control is particularly effective for substances whose segregation coefficient at the solid-liquid interface deviates widely from 1.

In the case of growing a single crystal by the zone melting method using a horizontal reaction tube (or growth furnace) as shown in FIG. On the other hand, high vapor pressure components A and B are respectively stored in the storage chamber, heaters Hl-Hs are activated, and the above-mentioned components are placed in a furnace in which a predetermined temperature distribution is set, for example, as shown in Fig. 1. After the reaction tube 20 is inserted and temperature equilibrium is sufficiently reached, a single crystal is formed by moving the reaction tube or furnace at a predetermined speed to move the melting zone. At this time, the partial pressures of the high vapor pressure components (A, B) are controlled as described above, and there is no concentration gradient of the component elements.
Products with excellent J-characteristics can be advantageously grown.

It should be noted that the same operation can be performed in the case of a vertical type, and similarly excellent results can be expected.

Thus, according to the present invention, high-quality compound semiconductor single crystals, particularly single crystal ingots of multi-element compound semiconductors, can be obtained with good mass production, and the wafers obtained from these can also be produced with uniform characteristics at a high yield. It can be mass-produced and is economically advantageous.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 Using the apparatus of the present invention shown in the attached FIG.
A Zn, Te (x = 0.05) single crystal was produced.

A high-purity quartz boat 27 is coated with carbon by thermal decomposition of benzene, ethanol, etc.
, Zn, and Te were weighed and added in predetermined amounts, while A
Each storage chamber 2 contains Cd as a substance and Zn as a B substance.
4.25 and sealed in a quartz reaction tube 20.

The length of the boat was 20 cm, the width was 2 cm, and heaters H1, H2, and H3 were adjusted so that the width of the melting zone was 10 mm (1050 °C, 1180 °C, and 1030 °C, respectively).
).

On the other hand, when Hl is set to 820°C, Cd partial pressure: 1.8 atm
), H3 is set to 650°C, Zn partial pressure: 0.05 atm
), the total pressure was controlled at 1.85 atm.

Under these conditions, the quartz tube 20 was moved to the low temperature side at a speed of 3 mm 7:00 to gradually move the molten zone in the boat to obtain the desired Cd+-xZnJe single crystal ingot. The spectrum of the thus obtained single crystal was measured by photoluminescence. On the other hand, the above-mentioned spectrum measurement was also performed on the same single crystal grown by the conventional method shown in FIG. The results obtained are shown in FIGS. 4 and 5, respectively.

As is clear from the comparison between Figures 4 and 5, the crystal produced by the conventional method has a broad peak around 1.42 eV and the edge emission (around 1.6 eV) is weak, whereas this It can be seen that the single crystal obtained according to the invention shows high edge emission, while the peak at 1.42 eV is hardly observed.

This result shows that C due to incomplete control of stoichiometric composition.
It is considered that defects such as vacancies at the d5Zn site are greatly reduced.

Furthermore, the half width of the X-ray rocking curve was determined using the two-crystal method for the above two types of crystals, and the results showed that the crystal according to the present invention is extremely sharp at 65 arc sec, whereas that of the conventional method. The thing is about 200 arcs
ec and broad, and it was confirmed that there was a large difference in the completeness of the lattice.

Effects of the Invention As explained in detail above, according to the method and apparatus for producing a single crystal of a multi-element compound semiconductor of the present invention, the vapor pressure of a plurality of high vapor pressure components is independently controlled, and the overall pressure is Since the P process can be controlled, it is possible to advantageously mass-produce single crystal ingots with excellent stoichiometry, such as multi-element single crystals containing multiple high vapor pressure components, mixed crystals, or systems containing dopants. Even for substances whose segregation coefficient deviates widely from 1, a product with a uniform composition without concentration distribution along the crystal growth direction can be obtained.

Therefore, according to the present invention, highly reliable wafers with uniform characteristics can be cut from a grown single crystal ingot with a high yield, which is extremely advantageous in terms of productivity and economy.

[Brief explanation of drawings]

Attached FIG. 1 is a schematic cross-sectional view showing a preferred example of the apparatus for producing a multi-element compound semiconductor single crystal of the present invention, and also shows the temperature distribution of the apparatus. Figure 3 is a schematic cross-sectional view for explaining the conventional vertical and horizontal Bridgman methods, and also shows the temperature distribution. 1 is a graph plotting the results of photoluminescence spectrum measurement of a single crystal obtained by a conventional method. (Main reference numbers) ■, 2... Heater, 3... Raw material melt, 4... Quartz container, 5... Growing crystal, 6... Space, 1
0.20...Quartz tube, 11...Capillary, 12.
・Partition wall, 13..Quartz boat, 21..Vertical partition wall, 22..Growth chamber, 23..Parallel partition wall, 24.25..Storage chamber, 26a, 26b
・Capillary,

Claims (11)

[Claims] (1) A method for producing a multi-element compound semiconductor single crystal in which a single crystal is grown by moving raw materials stored in a reaction tube in a furnace with a predetermined temperature gradient, the method comprising: The total pressure is controlled by controlling the temperature distribution in the growth chamber so that the temperature in the melting region of the single crystal is higher than its melting point, and by controlling the vapor pressure of each high dissociation equilibrium vapor pressure component independently. The method for producing the above multi-element compound semiconductor single crystal, which comprises adjusting the multi-element compound semiconductor single crystal. (2) The method for producing a multi-element compound semiconductor single crystal according to claim 1, wherein the reaction tube is horizontal. (3) The multi-element method according to claim 2, wherein the method is a zone melting method, and the temperature on the raw material solid side of the growth chamber is controlled to be just below the melting point of the single crystal. A method for manufacturing compound semiconductor single crystals. (4) The multi-element method according to claim 2, wherein the method is a horizontal Bridgman method, and the temperature of the raw material melt in the growth chamber is controlled to be just above the single crystal melting point. A method for manufacturing compound semiconductor single crystals. (5) The method for producing a multi-element compound semiconductor single crystal according to claim 1, wherein the reaction tube is of a vertical type. (6) The multi-element method according to claim 5, wherein the method is a zone melting method, and the temperature on the raw material solid side of the growth chamber is controlled to be just below the melting point of the single crystal. A method for manufacturing compound semiconductor single crystals. (7) The multi-element method according to claim 5 is characterized in that the method is a horizontal Bridgman method, and the temperature of the raw material melt in the growth chamber is controlled to be just above the single crystal melting point. A method for manufacturing compound semiconductor single crystals. (8) a growth chamber separated by a partition wall perpendicular to the growth chamber and its central axis, and separated by a partition wall parallel to the central axis;
A reaction tube comprising two separate storage chambers for high vapor pressure component elements, a means provided on the vertical partition wall for independently communicating the storage chambers and the growth chamber, and an axis of the reaction tube. 1. An apparatus for producing a multi-element compound semiconductor single crystal, comprising: a furnace equipped with a heating means for setting a predetermined temperature distribution along the . (9) The apparatus for manufacturing a multi-element compound semiconductor single crystal according to claim 8, wherein the communication means is a capillary. (10) The apparatus for producing a multi-element compound semiconductor single crystal according to claim 8 or 9, characterized in that a high vapor pressure component support container is attached to the side wall of each of the storage chambers. (11) The above-mentioned growth chamber has a double cylindrical structure communicating at the upper part, and is equipped with a capillary at the lower part communicating the gap between the cylinders and each of the above-mentioned storage chambers. 9. The apparatus for producing a multi-element compound semiconductor single crystal according to item 8.