JPH04300278A - Production of crystal and apparatus for producing the same crystal - Google Patents

Abstract

PURPOSE:To reduce dislocation and defects occurring in a single crystal by maintaining the ratio of exothermic power of a main heating unit to that of an auxiliary heating unit constant, controlling the temperature of the main heating unit and performing seeding operation. CONSTITUTION:A crucible 5 is vertically installed in a susceptor 6 provided in an airtight vessel 11 having a heat insulating material 10 and a seed crystal 1 is contained in the bottom of the crucible 5. A raw material 3 and a liquid encapsulating agent 4 are filled in a place above the seed crystal 1. A current is then passed through a main heating unit 19 and auxiliary heating units (20a) and (20b) to maintain the ratio of the exothermic power of the main heating unit 19 to that of the auxiliary heating units (20a) and (20b) at 0.5-0.7. Thereby, the raw material 3 and the liquid encapsulating agent 4 are melted to bring the seed crystal 1 into contact with the raw material melt 3 and seeding operation is performed. The exothermic power of the main heating unit 19 is then slowly increased to control the temperature of the main heating unit 19. As a result, crystal growth is completed.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method and apparatus for producing a single crystal, and in particular to a vertical Bridgman method in which a melt is solidified as it is in a vertically arranged crucible, a molten raw material and a seed crystal are brought into contact with each other. The present invention relates to a method for manufacturing a single crystal and an apparatus therefor, which make it possible to reliably perform a single crystal manufacturing operation and precisely control changes in the position of a growth interface.

0002

[Prior Art] Single crystals of inorganic compound semiconductors (hereinafter referred to as "III-V compound semiconductors") consisting of elements of group IIIb and group Vb of the periodic table, especially gallium arsenide (Ga
Single crystals of gallium phosphide (GaP) are widely used in the manufacture of various semiconductor devices such as field effect transistors (FETs), Schottky barrier diodes, and integrated circuits (ICs).

III used for the substrate of these semiconductor devices
A crystal growth method from a melt is mainly used as a method for producing a single crystal of a -V group compound semiconductor, particularly GaAs.

The pulling method, which is one of the methods for growing crystals from melt, is suitable for increasing the diameter of crystals and has the advantage that circular (100) wafers can be obtained. On the other hand, since crystal growth is performed under a large temperature gradient, there is a problem in that the dislocation density of the produced crystal becomes high.

Another promising method for growing crystals from a melt is the vertical boat method, in which a single crystal is obtained by directly solidifying the melt in a crucible. The vertical boat growth method includes the vertical Bridgman method (VB method) and the vertical temperature gradient solidification method (VGF method). According to the VB method or VGF method, crystal growth can be performed under a low temperature gradient, so a single crystal with good crystallinity can be obtained. Furthermore, these methods have the advantage of being suitable for manufacturing circular (100) wafers.

By the way, it is necessary for the single crystal that becomes the product to have a desired crystallographic orientation, and for this purpose, the raw material melt is brought into contact with a seed crystal at the beginning of crystal growth (hereinafter referred to as "seeding"). A predetermined crystal orientation must be determined. However, in these vertical boat methods, in which a crucible is arranged vertically and raw materials are filled above it, the seed crystal is not movable, making it impossible to precisely control the seeding position, crystal growth rate, etc.

FIG. 6 is a schematic cross-sectional view for explaining GaAs single crystal growth by the conventional liquid-sealed vertical Bridgman method.

In FIG. 6, 1 is a seed crystal, 2 is a grown GaAs crystal, 3 is a GaAs melt, 4 is a liquid sealant, and 5 is a grown GaAs crystal.
6 is a crucible holder, 7 is a crucible shaft that supports this holder 6, 8 is a crucible drive mechanism for rotating and moving the crucible 5 via this shaft 7, and 9 is a heating element. , 10 is a heat insulating material, 11 is an airtight container,
Reference numeral 21 denotes a control device for changing the heating power of the heating element 9 and the rotation and position of the crucible 5. (21 is not shown)

In such an apparatus configuration, the conventional technology first places a seed crystal 1 and a raw material GaA in a crucible 5.
s A polycrystalline, solid liquid sealant 4 is filled, and the inside of the furnace is heated to a high temperature by a heating element 9 to melt the liquid sealant 4 and GaAs.
After melting the polycrystal, seeding was performed while monitoring the temperature using a thermocouple installed nearby to start crystal growth, and crystal growth was performed as shown in FIG.

However, in the conventional method described above, the seed crystal is not movable and observation from the outside is difficult, so the "seeding" operation is extremely difficult. Furthermore, in the conventional method, the growth rate of the crystal, that is, the movement speed of the growth interface 12 cannot be detected, and therefore the growth rate and the interface shape cannot be accurately controlled.

[0011]

[Problems to be Solved by the Invention] Currently, the liquid encapsulation drawing method (LEC method) or the horizontal Bridgman method (HB method) is in practical use as a manufacturing method for compound semiconductor crystals such as GaAs single crystals. In the case of crystal growth, a viewing window is installed in the airtight container or furnace body to observe the growth situation and control the crystal growth conditions inside the furnace.

On the other hand, in the case of a crystal growth method such as the vertical Bridgman method according to the present invention, the crystal growth conditions such as the growth interface position, growth rate, and interface shape are not controlled.

By the way, since the crystal growth rate has a significant effect on the quality of the crystal that becomes a product, precisely controlling this is one of the basic techniques for crystal growth. Furthermore, in crystal growth from a melt, it is essential to precisely control the crystal growth surface over the entire length of the growing crystal from the time of seeding in order to obtain uniform, high-quality crystals.

However, it has been difficult to solve the above problems with conventional methods. An object of the present invention is to provide a single crystal manufacturing method and apparatus for manufacturing a uniform and high quality single crystal.

[0015]

[Means for Solving the Problems] According to the present invention, the above problem is achieved by storing a seed crystal at the bottom of a vertically arranged crucible, filling a raw material above the seed crystal, and heating and melting the raw material. In a crystal manufacturing method using the vertical Bridgman method, in which a melt is formed by heating and the melt is solidified to obtain a single crystal, the raw material is heated and melted using a main heating element and an auxiliary heating element, and the main heating element is The seeding operation is performed by keeping the ratio of the heating power of the heating element and the heating power of the auxiliary heating element constant, controlling the temperature of the main heating element, and bringing the seed crystal into contact with the melt. The problem is solved by a crystal manufacturing method.

Furthermore, in the present invention, in order to ensure a temperature gradient so that the seeding operation can be performed reliably, the value of the ratio of the heating power of the main heating element to the heating power of the auxiliary heating element is 0.
．． It is preferable that it is 5-0.7.

Furthermore, according to the present invention, the above-mentioned problem is solved by accommodating a seed crystal at the bottom of a vertically arranged crucible, filling a raw material above it, heating and melting the raw material to form a melt, and In a crystal manufacturing method using the vertical Bridgman method to solidify a melt and obtain a single crystal, the raw material is heated and melted using a main heating element and an auxiliary heating element, and the heating power of the main heating element and the auxiliary heating element are The problem is solved by a crystal manufacturing method characterized in that the ratio of the heating power of the heating element to the heating power is gradually increased after a seeding operation in which the seed crystal and the melt are brought into contact, and the temperature of the main heating element is controlled to terminate crystal growth. be done.

According to the present invention, in order to ensure a temperature gradient and perform the seeding operation reliably, and to reduce the temperature gradient and the dislocation density, the heating power of the main heating element and the heating power of the auxiliary heating element are adjusted. It is preferable that the value of the ratio to the exothermic power is 0.5 to 0.7 at the time of the seeding operation, and 1.0 to 1.2 at the end of the crystal growth.

According to the present invention, the above-mentioned problem is further solved by accommodating a seed crystal at the bottom of a vertically arranged crucible, filling a raw material above the seed crystal, and distributing the raw material into a crucible arranged around the crucible. In a crystal manufacturing apparatus using a vertical Bridgman method in which a heating element is used to heat and melt a melt to form a melt, and the melt is solidified to obtain a single crystal, the heating element is composed of a main heating element and an auxiliary heating element. The problem is solved by a crystal manufacturing apparatus characterized in that the power ratio of the main heating element and the auxiliary heating element can be changed to a predetermined condition.

[0020]

[Function] According to the present invention, in addition to the main heating element that melts the raw material, at least one auxiliary heating element is provided, and the main heating element and the auxiliary heating element are kept at a constant ratio of heating power. By varying the body temperature, the temperature gradient within the furnace can be precisely controlled. Therefore, the seeding operation is facilitated, and the crystal growth surface shape and crystal growth rate can be precisely controlled over the entire length of the growing crystal.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a single crystal manufacturing apparatus according to the present invention. In the figure, 19 indicates a main heating element, and 20a and 20b indicate auxiliary heating elements according to the present invention. 1
3 is a thermocouple for measuring the temperature at the lower end of the crucible.

As shown in FIG. 1, the single crystal production apparatus of the present invention has a susceptor 6 made of isotropic graphite provided in an airtight container 11 having a heat insulating material 10 such as graphite felt. Height 150mm рB
A crucible 5 made of N is installed, and a susceptor 6 is attached by a support shaft 7.
Hold crucible 5. The heating element is made of isotropic graphite, and the height of the main heating element (main heater) 19 is 20 cm, and the height of auxiliary heating elements (sub heaters) 20a and 20b is 10 cm.
m was used.

A typical example of the temperature distribution on the central axis of the hot zone is shown in FIG. Insert the thermocouple from the top of the airtight container,
Measurement was performed by heating the heater and changing the position of the thermocouple when the inside of the airtight container reached a steady state. Note that the inside of the airtight container was filled with an argon atmosphere controlled at 7 atmospheres.

FIG. 3 shows that the temperature gradient at the center of the furnace is determined by the ratio of the heating power of the main heating element and the auxiliary heating element (heating power of the auxiliary heating element/
This is a graph showing how it changes depending on the heating power of the main heating element. It can be seen from FIG. 3 that the temperature gradient in the hot zone is determined by the ratio of the heating power of the main heating element and the auxiliary heating element.

The temperature gradient at the center of the furnace can be derived from the following equation. (Temperature gradient in the center of the furnace) = -17 x (calorific value of auxiliary heating element / calorific value of main heating element) + 24.5 Also, a thermocouple is installed at the lower end of the crucible (= seed crystal end). Since the temperature at the lower end of the crucible can be measured, the temperature distribution inside the furnace can be accurately determined from this temperature and the temperature gradient inside the furnace, which is determined by the ratio of the heating power of the main heating element and the auxiliary heating element. . As a result, growth rate and interface shape can be precisely controlled.

Crystal growth was performed using the hot zone described above. The raw material is 1.5 kg of high-purity GaAs polycrystal, B2
300g of O3 was used.

The seed crystal has a cross section perpendicular to the growth direction with a side of 5
A piece with a square size of mm and a length of 5 cm was used.

After melting the raw materials, a crystal with a diameter of 3 inches could be grown at a growth rate of 3 mm/h in an argon atmosphere of 7 atm.

At the start of crystal growth, a seeding operation must be performed, but in order to perform seeding, it is sufficient that one point in the region where the seed crystal is placed reaches the melting point.

FIG. 4 shows a graph of the temperature at the lower end of the crucible that enables seeding and the ratio of the calorific value of the main heating element to the auxiliary heating element. The shaded area in the figure is the condition that allows seeding. After seeding was performed under the conditions indicated by the points (x marks) shown in FIG. 4, the temperature distribution inside the crucible and the position of the growth interface were controlled, and as a result, the crystal growth rate and crystal shape were controlled.

COMPARATIVE EXAMPLE Hereinafter, data for comparison with the above-mentioned example will be shown, using as a comparative example a case in which there is no auxiliary heating element in the above-mentioned example of the present invention.

(1) Comparative example of reproducibility of seeding: 10 runs were performed and there was no reproducibility. That is, the seeding position changed by ±5 mm. Three of the 10 runs failed in seeding. This example: 10 runs were performed and there was good reproducibility. That is, the seeding position changed by only ±1.5 mm. There was no seeding failure in the 10 runs.

[Table 1]

(2) Crystal dislocation density (EPD, unit: pieces/cm2) Next, as a comparative example, in the case where the power ratio (power consumption ratio) of the auxiliary heating element/main heating element deviates from the present invention (power ratio) be.

[Table 2]

It can be seen that the dislocation density is smaller in the case of the present invention. Figure 5 shows an example of the change in the power ratio of the auxiliary heating element/main heating element from seeding to the end of crystal growth. This is an example where the increase is 1.2. The result is that the dislocation density is 1 x 104 pieces/cm over the entire length.
2 or less, which was good.

[0035]

As described above, according to the present invention, it is possible to accurately control the seeding operation and the position of the growth interface, which were difficult in the past. Thereby, the growth rate and growth interface shape can be controlled, and the single crystallization rate can be significantly improved. Furthermore, it becomes possible to control the temperature distribution inside the crystal during and after crystal growth, and it is also possible to reduce dislocations and defects generated in the crystal.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal cross-sectional view of a single crystal manufacturing apparatus of the present invention.

FIG. 2 is a temperature distribution diagram inside the single crystal manufacturing apparatus of the present invention.

FIG. 3 is a diagram showing how the temperature gradient inside the single crystal manufacturing apparatus of the present invention changes depending on the ratio of the calorific value of the main heating element and the auxiliary heating element.

FIG. 4 is a diagram showing the temperature at the lower end of the crucible that enables seeding and the ratio of heat generation power between the main heating element and the auxiliary heating element.

[Figure 5] From seeding to crystal growth (nurturing)
It is a figure which shows the power ratio change of the main heating element and an auxiliary heating element until the end.

FIG. 6 is a schematic vertical cross-sectional view of a conventional single crystal manufacturing apparatus.

[Explanation of symbols]

1... Seed crystal 2...Growed GaAs crystal 3...GaAs melt 4...Liquid sealant 5... Crucible 6... Crucible holder 9...Heating element 10...Heat insulation material 19...Main heating element 20a, 20b...Auxiliary heating element

Claims (5)

[Claims] Claim 1: A seed crystal is housed in the bottom of a vertically arranged crucible, a raw material is filled above the seed crystal, the raw material is heated and melted to form a melt, and the melt is solidified. In a crystal manufacturing method using the vertical Bridgman method to obtain a single crystal, the raw material is heated and melted using a main heating element and an auxiliary heating element, and the heating power of the main heating element and the heating power of the auxiliary heating element are 1. A method for producing a crystal, characterized in that a seeding operation is carried out by maintaining a constant ratio to power, controlling the temperature of the main heating element, and bringing the seed crystal into contact with the melt. 2. The method according to claim 1, wherein the ratio of the heating power of the main heating element to the heating power of the auxiliary heating element is 0.5 to 0.7. 3. A seed crystal is housed at the bottom of a vertically arranged crucible, a raw material is filled above it, and the raw material is heated and heated.
In a crystal manufacturing method using the vertical Bridgman method, which melts to form a melt and solidifies the melt to obtain a single crystal,
A seeding operation in which the raw material is heated and melted using a main heating element and an auxiliary heating element, and the ratio of the heating power of the main heating element and the heating power of the auxiliary heating element is adjusted by bringing the seed crystal into contact with the melt. A crystal manufacturing method characterized in that the temperature of the main heating element is then gradually increased and the temperature of the main heating element is controlled to terminate crystal growth. 4. The value of the ratio of the heating power of the main heating element to the heating power of the auxiliary heating element is 0 during the seeding operation.
5 to 0.7, and 1.0 to 1.2 at the end of the crystal growth.
The method according to claim 3, characterized in that: 5. A seed crystal is housed in the bottom of a vertically arranged crucible, a raw material is filled above the seed crystal, and the raw material is heated and melted by a heating element disposed around the crucible. In a crystal manufacturing apparatus using the vertical Bridgman method in which a melt is formed by heating and the melt is solidified to obtain a single crystal, the heating element is composed of a main heating element and an auxiliary heating element, and the heating element and the main heating element are A crystal manufacturing apparatus characterized in that the power ratio of the auxiliary heating element can be changed to predetermined conditions.