JPS60171292A - Method and device for producing single crystal - Google Patents

Abstract

PURPOSE:To obtain a single crystal having uniform quality with decreased crystal defects by controlling temp. superposedly with a specified temp. below the m.p. of the crystal of a raw material melt by a heater which is provided around a crucible and does not generate a static magnetic field. CONSTITUTION:A crucible 2 having internally a raw material melt 1, a susceptor 3 for supporting the crucible 3 and a lower revolving shaft 9 supporting freely rotatably and liftably the crucible 2 and the susceptor 3 are provided in a chamber 7. An upper revolving shaft 8 extends downward from the upper part of the chamber 7. The shaft 8 is rotatable and movable vertically and is attached with a seed crystal 4 at the bottom end thereof. When the shaft 8 is risen under rotation, the single crystal 5 grows successively from the bottom surface of the seed crystal. The pressure in the chamber 7 which is a pressure- resistant hermetic vessel is adequately set with the kind of the single crystal to be pulled up. The chamber inside is maintained in a vacuum or under atm. pressure in the case of silicon but a high pressure is often exerted therein in the case of a compd. semiconductor. A heater 6 is further provided in the chamber 7 so as to enclose the crucible 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (7) Technical Field The present invention relates to a method and apparatus for producing a single crystal using the Czochralski method.

To manufacture semiconductor products such as lasers, LEDs, photodiodes, transistors, and integrated circuits (ICs), semiconductor single crystals such as silicon (Si) or GaAs are used as substrates.

Since the condition of the substrate affects the characteristics of semiconductor products, a homogeneous single crystal semiconductor substrate with few crystal defects is desired.

A substrate for a semiconductor device is obtained by cutting a single crystal ingot into thin pieces. As a result, there is a strong demand for growing a uniform single crystal with a large diameter and few crystal defects.

Semiconductor single crystals can be produced by several manufacturing methods, and the Czochralski method (CZ method) is one of the leading methods.

As shown in Fig. 4, the elements to form the crystal are blended at an appropriate mixing ratio, the melted raw material melt 1 is placed in a crucible 2, supported by a susceptor 3, and seeded with crystals from above. 4 is immersed in the raw material melt, and the single crystal 5 is pulled up while rotating.

Since the seed crystal 4 and the susceptor 3 rotate relative to each other and move up and down relative to each other, the single crystal 5 is gradually pulled up.

A heating device is provided around the crucible 2 and susceptor 3, so that the temperature of the raw material melt 1 can be controlled to an appropriate value.

Furthermore, the entire structure is surrounded by a pressure chamber, and high pressure is applied to the internal space.

In addition to silicon single crystals, it is also suitable as a growth device for compound semiconductor single crystals such as GaAs and GaP. The present invention was developed for the growth of compounds and Si single crystals.

What is shown here is a simple configuration of the pulling method, but in addition, the top of the raw material melt 1 is covered with a B2O3 melt,
A pulling method that prevents evaporation of raw material components with high vapor pressure is also known. This is called the LEC method (liquid-filled Czochralski method).

Single crystal ingots made by the pulling method have a cylindrical shape. This is cut perpendicular to the axial direction to make a substrate (wafer), and since a circular wafer is immediately obtained, there is less loss of parts due to polishing etc., so there is no waste.
There is an advantage. This is different from the single-crystal ingot produced by the boat method (w" shaped like a 0 with a deformed surface).

Furthermore, single crystals made by the pulling method can easily have high resistance. The boat method does not yield a high-resistance single crystal, but is doped with impurities to create a high-resistance substrate.

In this way, the pulling method (C2 method) has advantages, but
On the other hand, it has the disadvantage that it has many dislocations and is poor in uniformity.

(a) Conventional CZ method and its problems Crystal defects in the substrate (wafer) are caused by error pit density (Etc
The yacht can be evaluated by measuring the h Pit Density.

When the wafer is immersed in a suitable etching solution and the surface is etched, small bits corresponding to defects appear on the wafer surface (etch bits), and the number of these bits is measured.

When a single crystal ingot made by the CZ method (pulling method) is cut into wafers and the etch bit density is measured, the following trends are found.

EPD is high at the center and periphery of the wafer and low at the middle. When plotted on a graph, it shows a W-shaped distribution.

Regarding the entire single crystal ingot, the EPD of the head that grows at the beginning of pulling is low, and the EPD of the tail that grows at the end of pulling is high.

Such an EPD distribution is commonly seen in single crystals grown by the CZ method, but such a distribution is not found in single crystals grown by the boat method or the like.

The reason why the number of crystal defects increases is that the temperature gradient at the solid-liquid interface S between the single crystal 5 and the raw material melt 1 in FIG. 4 becomes too steep. At the solid-liquid interface S, the liquid phase transforms into the solid phase, so that a rapid temperature change occurs here. It also causes thermal stress to remain.

Another reason is that the solid-liquid interface S is not flat. It takes on a W-shaped shape, lower at the center and periphery and higher at the middle, as shown in FIG. The solid-liquid interface S is one of the isotemperature curved surfaces, but it is not flat and has four downward facing parts, so thermal distortion tends to occur and non-uniformity remains. It is desirable to avoid the formation of downward facing quarters.

When producing a single crystal by the pulling method, if the diameter of the single crystal to be grown is d and the inner diameter of the crucible is D, then D needs to be twice or more than d.

The depth H8 of the crucible is often approximately equal to the inner diameter.

As the heating device, resistance heating, high frequency heating, etc. are used, and resistance heating is used in most cases. Since the heat from the heating device heats the outside of the raw material melt 1, the raw material melt 1 is hot at the outer periphery and colder at the center.

In order to alleviate such a thermal non-equilibrium state, convection occurs within the raw material melt.

Convection flows upward near the side walls of the crucible, toward the center at the top, and toward the side walls at the bottom.

Corresponding to this convection, it is thought that the solid-liquid interface S at the bottom of the single crystal becomes W-shaped.

(1) Horizontal magnetic field method and its problems If the convection of the raw material melt 1 is suppressed, the flow of the melt at the bottom of the single crystal 5 should be suppressed, and the solid-liquid interface S should become flat.

A method of applying a magnetic field has been proposed to suppress thermal convection of the raw material melt.

FIG. 5 is a sectional view of such a horizontal magnetic field application type pulling furnace.

A heating device 6 is provided around the raw material melt 1, the crucible 2, and the susceptor 3. This is a carbon resistor or a high frequency application coil. 7 is a chamber that can withstand high pressure;
The interior is filled with high-pressure inert gas.

The seed crystal 4 is fixed to the lower end of the upper rotating shaft 8. The susceptor 3 is supported by a lower rotating shaft 9. Both the upper rotating shafts 8 and 9 are shafts that can be rotated and moved up and down.

The above configuration is just the configuration of the normal CZ method.

Two electromagnets 11.1 are used to apply a magnetic field to the raw melt.
1 are installed outside the pressure chamber 1 so as to face each other in the horizontal direction. A large direct current is passed through the two electromagnets, and their opposing surfaces are magnetized to N or S. The magnetic field lines horizontally cross the interior of the chamber 7 from one electromagnet 11 to the other electromagnet 11 .

The high temperature raw material melt has good electrical conductivity even if it is a semiconductor single crystal material. When the raw material melt moves by convection, it is subjected to a Lorentz force by the magnetic field H because it is a flow of charged particles.

In the apparatus of FIG. 5, a horizontal magnetic field is present in the raw material melt. The vertical flow of the raw material melt 1 is orthogonal to the horizontal magnetic field H. Therefore, the second term of the Lorentz force is applied to the charged particles in the melt. This becomes a force that pushes the positively and negatively charged particles toward the sides of the raw material melt. If a particle moves in free space, due to the existence of an electric field E and a magnetic field H perpendicular to it, the particle will not move in the direction of the electric field E, but will move in the direction of an axis perpendicular to both E and H. do. It moves along this axis while drawing a semicircular arc. The period is given by the cyclotron frequency eH/m.

However, in reality, the cyclotron motion of charged particles does not occur completely, and there is a finite relaxation time.

Relaxation time is the time during which charged particles move freely under the action of E and H only. In other words, ° is the time from one particle collision to the next collision.

Since the Lorentz force due to the magnetic field H is proportional to the velocity V, if the relaxation time is short, the velocity V will not be sufficient, so the vH product will be small. However, it is still possible to significantly prevent the movement of the electric field E in the direction.

Here, although the electric field E does not exist, it may be considered that the difference in specific gravity that causes convection corresponds to an effective electric field.

In other words, the upward movement (at the periphery) and downward movement of convection are suppressed by the plowing of the magnetic field. When looking at particle motion collectively, the magnetic field acts to slow the flow, making it appear as if the viscosity has increased.

This horizontal magnetic field suppresses the convection of the raw material melt,
It has been reported that a single crystal with few defects was obtained by growing a single crystal.

However, such a horizontal magnetic field method has the following drawbacks.

(1) The electromagnet is placed outside the chamber, and the distance between the magnetic poles of the electromagnet is large. An extremely large electromagnet is required to apply a magnetic field of the required magnitude to the raw material melt. The power supply will also be larger.

Rather, the electromagnet becomes larger than the CZ furnace body. This is difficult to achieve with a large pulling furnace due to space and weight considerations.

(2) To apply a magnetic field from outside the chamber of the CZ furnace,
The material forming the chamber of the CZ furnace must be non-magnetic. This is because the chamber must not be magnetically shielded. For this reason, materials such as stainless steel are used, but when the pressure inside the furnace is high, the chamber wall must be particularly thick, making it extremely expensive.

(3) If the strength of the magnetic field suddenly changes, the internal heating device 6 will be damaged. The heating device is, for example, a high purity carbon resistor. A fairly large current is passed through this, and the carbon resistor receives the Lorentz force due to the interaction between the magnetic field and the current. When the magnetic field suddenly changes, the Lorentz force also changes suddenly, applying impact force to the heating device and damaging it.

(4) The horizontal magnetic field acts on and suppresses the upward and downward movements of convection. As crystal growth progresses, the raw material melt decreases and the height H1 decreases. The ascent and descent distances are also shorter. Then, the convection suppressing effect due to the magnetic field also decreases. Thus, there is also the drawback that the effects are not constant.

←) Vertical magnetic field method and its problems Horizontal magnetic fields mainly suppress the vertical movement of convection, so they are expected to have a direct effect.

If a magnetic field is applied vertically, it is thought to have a suppressing effect on the flow in the horizontal plane of convection.

However, since convection is an annular flow, it is the same whether the vertical movement is suppressed or the horizontal movement is suppressed. In any case, it should be possible to reduce the force of convection.

Therefore, a vertical magnetic field type CZ furnace as shown in FIG. 6 was invented.

This is a coil 12 wound horizontally around the outer circumference of the C2 furnace.
is installed to generate a vertical magnetic field inside the CZ furnace.

The advantages of the vertical magnetic field method are as follows.

(1) Even if the height Hl of the raw material melt decreases with crystal growth, the cross section of the raw material melt does not change. The vertical magnetic field acts on the centrifugal motion and centrifugal motion on the top surface (near the solid-liquid interface S) and bottom surface of the raw material melt. Liquid level height H
Since the cross-sectional area is constant regardless of l, the convection suppressing effect due to the vertical magnetic field does not vary.

(2) When D>H+, strong electromagnetic force can be obtained.

(3) The apparent viscosity of the liquid surface near the solid-liquid interface S, which is most closely related to crystal growth, can be increased. .

(4) Large-diameter, low-defect crystals can be stably grown.

Such effects were expected. However, the vertical magnetic field type CZ furnace shown in FIG. 6 still has the following drawbacks.

(1) Since the solenoid coil is provided outside the main body of the cz furnace, the coil diameter becomes extremely large.

Applying a predetermined magnetic field to the raw material melt requires an extremely large solenoid coil and an excitation power source.

(2) The strong influence of the magnetic field affects not only the inside of the cz pulling furnace but also the surrounding area.

(3) Since a magnetic field is applied from outside the CZ pulling furnace, the members forming the chamber of the CZ pulling furnace must be made of non-magnetic material that does not provide magnetic shielding.

(4) If the strength of the magnetic field suddenly changes, the internal heating device 6 will be damaged. Due to resistance heating, a large current flows through the heating device 6, and the heating device 6 receives a strong force due to the interaction of this current and a magnetic field. The sudden change in the magnetic field generates a strong impact force on the heating device 6, causing it to break.

These drawbacks are the same as those of the horizontal magnetic field system shown in FIG.

FIG. 7 is a perspective view of a carbon resistor commonly used as the heating device 6. FIG. Although it is a cylindrical carbon, there are deep notches 21 and 21 cut from the top or bottom in the axial direction, so the conductive path meanders in the axial direction (vertical direction). The reason why the conductive path is formed in a meandering manner is to prevent a magnetic field from being generated inside the carbon resistor due to the current flowing through the carbon resistor. The current in the conductive path generates an internal magnetic field according to Biot-Savart's law, but since the direction of the current is opposite in adjacent conductive paths, the magnetic fields cancel each other out. For this reason, the resistance heating body is not coiled but has a meandering conductive path.

(g) Internal coil vertical magnetic field type (copper tube) The drawbacks of the horizontal and vertical magnetic field type CZ furnaces mentioned in the previous sections are ultimately due to the fact that the device that generates the magnetic field is located outside the furnace chamber.

It is sufficient if the coil that generates the magnetic field is located inside the chamber.

Some pull furnaces use high-frequency coils as heating devices. Unlike resistance heating, this method generates a high-frequency magnetic field to generate eddy currents in a metal (platinum, iridium, etc.) crucible, which generates heat.

A high frequency coil is placed just outside the crucible. Since it is located inside the chamber, its dimensions can also be made smaller. High frequency coils are often water-cooled copper tubes.

The immediate question is whether it is possible to construct a DC internal coil using water-cooled steel pipes, like a high-frequency coil. A water-cooled steel pipe is one in which water is constantly allowed to flow inside the steel pipe to cool it.

The inventor believes that if a water-cooled steel pipe is wound into a coil, placed inside a chamber, and a direct current (or pulsating current) is passed through it to generate a vertical static magnetic field, the following drawbacks will occur: think.

(1) In the case of a high-frequency coil, sufficient impedance can be obtained even with a small number of turns, so a sufficient voltage can be applied even if the current is small. Therefore, the current is small. Since the present invention requires generation of a static magnetic field,
A large current must flow.

The inside of the furnace is high temperature and pressure. Cooling water-cooled steel pipes that carry large currents,
Electrical insulation is difficult.

(2) Two things will be installed in the CZ furnace: a carbon resistance heating element and a water-cooled steel pipe coil for the magnetic field.

Steel pipe coils are water-cooled, so their temperature is low.

The carbon resistor is hot because it generates heat.

Since objects with significantly different temperatures exist in close proximity, the inside of the furnace cannot be in a uniform state of thermal equilibrium. As a result, the interior of the crucible also becomes more strongly non-equilibrium, resulting in a decrease in crystal growth yield.

(3) Although the raw material melt in the pulling furnace must be made of high-purity crystal material, there is a risk that impurities may scatter from the solenoid coil material and contaminate the raw material melt.

(4) The inside of the cz furnace is maintained at a high pressure depending on the type of crystal to be pulled. Since water-cooled steel pipes are hollow, they do not have sufficient pressure resistance, and may be distorted or destroyed by pressure.

(5) Heating equipment will be larger and furnaces will be larger.

The above drawbacks are expected when water-cooled steel pipes are used.

Copper has low electrical resistance and bends easily, making it ideal for making into coils. However, it is sensitive to heat, so when using it in a furnace, make sure to run cooling water inside. However, steel pipes have the above-mentioned drawbacks and are not suitable for the purpose of generating a static magnetic field in a CZ furnace.

Trout) Coiled carbon resistor system Carbon resistors can be used in high-temperature, high-pressure CZ furnaces without worrying about contamination.

Conventional carbon resistors have been provided with alternating notches 21 in the axial direction to avoid the generation of a magnetic field inside as much as possible.

The inventor of the present invention, on the contrary, thought that it would be sufficient to generate heat and a magnetic field using a heater resistor. In other words, the heater resistor constitutes a solenoid coil.

FIG. 8 is a perspective view of such a coiled resistor 10. One heater member is machined into a fill shape, and the spiral gap is filled with spacers 22 to fix adjacent coils.

Since the spacer 22 is fixed to a member of the heater and must withstand high temperature and high pressure, an alumina-based spacer, for example, is selected. Other heat-resistant and pressure-resistant ceramic materials may also be used.

The heater part is made of conventionally used high-purity carbon (
C), silicon carbide (SiC), etc. are used.

The reason for filling spacers between coils is as follows.

When current is passed through the solenoid coils, forces are exerted on each other in the direction that the coils approach each other. This attractive force is proportional to the strength of the current. If the current is 0, the attractive force between the coils is also 0. A +1 large current must be passed through the coiled resistor 10, and this current generates a strong attractive force between adjacent coils. Attractive force changes by increasing, decreasing, or interrupting the current. Without the spacer, the coiled resistor is free to flex, but since both ends are fixed, the flexure creates a large stress. Therefore, there is a risk that the coiled resistor may break.

The spacer 22 is provided to prevent such accidents and increase mechanical strength.

FIG. 9 is a sectional view of a CZ pulling furnace having only a coiled resistor inside.

On the outside of the crucible 2 and susceptor 3, there is no resistor cylinder having alternating notches as shown in FIG. 7, but a coiled resistor 10 is provided. A direct current (or pulsating current obtained by rectifying alternating current) current flows through the coiled resistor 10 from a power source 23 .

A CZ furnace using such a single resistor solenoid is expected to have the following advantages.

(1) Because the vertical magnetic field generator also serves as a heater,
There is no need to cool the solenoid coil to a low temperature.

(2) Since the temperature environment inside the furnace does not change, conventional crystal pulling technology can be used as is. Unlike water-cooled steel pipes, a cooling device is not newly inserted into the furnace, and the temperature distribution is uniform as before due to resistance heating.

(3) There is no change in the pollution level.

This is because a heater material that has traditionally been used as a resistance heating element is used. The possibility of contamination is the same as the conventional method.

(4) There is no problem with gas resistance.

This is because the coil is made from a heater material that is chemically stable and resistant to high temperatures and pressures.

(5) There is no need to modify the furnace body to make it larger. A conventional pulling furnace can be used.

It has such great advantages. The CZ method using a single solenoid resistor as shown in FIG.
It is described in 92. This is made by processing the heater material into a solenoid coil shape and arranging it in double or triple layers concentrically. In order to obtain a sufficient magnetic field, the product of the number of turns and the current must be large. In order to effectively increase the number of turns, the coiled resistor is arranged in multiple layers.

This has multiple resistors, but since the heating by the resistors and the magnetic field generation are proportional, there is little freedom in control. Even if there are multiple solenoid resistors, there is no difference in controllability compared to a single solenoid resistor. There is always a proportional relationship between resistance heat generation and magnetic field strength.

In the process of pulling a single crystal, the raw material melt gradually decreases, so the output of the heating device gradually decreases. In other words, the current passing through the resistor is often lowered. This current is also used to generate a magnetic field, so the strength of the magnetic field decreases accordingly. In this case, the convection suppressing effect due to the magnetic field will also vary during the entire process of crystal growth.

Rather, it is considered desirable that the magnetic field viscosity that suppresses convection is always constant.

In the device shown in FIG. 9, the amount of heat generated and the magnitude of the magnetic field cannot be controlled independently.

However, it is not clear whether the optimal conditions for growing a single crystal meet the condition that the amount of heat generated and the viscosity of the magnetic field are proportional, and even if the optimal conditions are found, the amount of heat generated and the magnetic field must be controlled independently. It is necessary to know.

The crystal growth apparatus disclosed in JP-A-57-149894 also has similar drawbacks.

(G) Single crystal manufacturing device of the present invention In order to overcome the drawbacks of these conventional techniques, the single crystal manufacturing device of the present invention includes a conventional heating device shown in FIG. 7 and a conventional heating device shown in FIG. 8 in a CZ pulling furnace. Both of the coiled resistors 10 shown in FIG. 1 are provided so that the amount of heat generated and the strength of the magnetic field can be controlled independently.

FIG. 1 is a sectional view of a pulling furnace according to an embodiment of the present invention.

A chamber 7 is provided with a crucible 2 having a raw material melt 1 therein, a susceptor 3 supporting the crucible 2, and a lower rotating shaft 9 supporting the crucible 2 and the susceptor 3 so as to be rotatable and movable up and down. From above the chamber 7, the upper rotating shaft 8
extends downward.

The upper rotating shaft 8 can be rotated, raised and lowered, and a seed crystal 4 is attached to the lower end of the shaft.
is the installation. When the upper rotating shaft 8 is rotated and raised, the single crystal 5 grows from the lower surface of the seed crystal.

Chamber 7 is a pressure-tight sealed container. The pressure within the chamber is appropriately set depending on the type of single crystal to be pulled.

In the case of silicon, vacuum or normal pressure is applied, but in the case of compound semiconductors, high pressure is often applied. A heating device 6 is further provided in the chamber 7 so as to surround the crucible 2 . The heating device 6 is the same as the conventional one. A carbon or SiC resistor having alternating cutouts 21 as shown in FIG. 7 can be used.

The above configuration is the same as a general CZ pulling furnace. In the present invention, an independent coiled resistor 10 is further provided inside the chamber 7 so as to surround the crucible 2. This is a new point.

Which of the heating device 6 and the coiled resistor 10 is inward,
Either one may be on the outside.

A direct current (or pulsating current obtained by rectifying alternating current) current is applied to the coiled resistor 10 by a power source 23 .

Let Pal be the power consumed by the coiled resistor 10.

Most of this is consumed as Joule heat due to the current flowing through the resistor. A small portion acts on the charged particles of the raw melt by creating a magnetic field and is consumed by particle movement. In either case, it will eventually be converted into heat. After all, the electric power Pa is equal to the amount of heat generated by the coiled resistor 10.

Electric power is supplied to the heating device 6 by a power source 24 .

Since this is a resistor as shown in FIG. 7, it does not generate a magnetic field. Let pb be the power consumed by the heating device 6. This is all energy that turns into heat.

The single crystal manufacturing apparatus of the present invention includes (1) a crucible 2 that holds a raw material melt 1, (2) a lower rotating shaft 9 that supports the crucible 2, and (3) a seed crystal 4 attached to the lower end. (4) an upper rotating shaft 8 that can be rotated up and down to grow a single crystal 5 by dipping the crystal 4 into the raw material melt 1 and pulling it up;
(5) a heating device 6 provided around the crucible that does not generate a static magnetic field; (6) a raw material melt 1, a crucible 2, Upper and lower rotating shafts 8.9,
It consists of a pressure chamber 7 containing a heating device 6 and a coiled resistor 10 therein.

(b) Temperature control method In the present invention, there are a heating device 6 that does not generate a static magnetic field and a heating device that generates a vertical static magnetic field. The power of the former is pb
1. Let Pa be the power of the latter. These are controlled independently using independent power supplies.

The temperature of the raw material melt 1 is determined at each step of single crystal growth.
It must be adjusted to the optimum temperature.

To change the temperature, it is sufficient to vary the sum of Pa and pb (Pa+Pb).

On the other hand, the strength of the magnetic field H for increasing the effective viscosity of the melt is determined only by Pa. Therefore, the temperature T in the melt and the magnetic field H can be controlled independently.

FIG. 2 is a graph showing an example of controlling the temperature of the raw material melt during single crystal growth in the apparatus of the present invention. The horizontal axis represents the time from the beginning to the end of growth, and the vertical axis represents the temperature T of the raw material melt 1.

Broken lines t1 to t5 are temperature T control values. The shaded area below To is a heating device (coiled resistor 1) that generates a static magnetic field.
This is due to heat generation (Pa) caused by 0).

The portion surrounded by To and the broken line is due to heat generation (pb) by the non-static magnetic field heating device 6.

Temperature T and heating device power 6.10 cannot be said to be directly equal because they have different dimensions, but since they have a roughly proportional relationship, what proportion of temperature T should be determined by Pa or by pb? It is possible to predefine whether the information can be maintained or not.

(1) The crystal raw material is heated to tl in the crucible and becomes a stable melt.

(2) After seeding with a seed crystal, the crystal shoulder K is grown. During growth on the shoulder, the temperature is lowered at t2.

(3) When the growth of the shoulder progresses and the desired crystal diameter is reached, the temperature is temporarily kept constant as at t3. Since the temperature is constant, the crystal diameter becomes constant and the straight body portion M begins to grow.

(4) Thereafter, as the straight body portion M grows, the temperature is gradually increased as at t4.

(5) When it reaches the tail of the straight body, it is maintained at a constant temperature t5.

In this manner, temperature program control is performed to vary the temperature from t1 to t5 during the crystal growth process.

Temperature T is the sum of the power of the two heating devices (Pa + Pb)
Determined by

In the example shown in FIG. 2, the electric power Pa applied to the coiled resistor 10 is constant. The temperature T of the resulting melt is set to be equal to or lower than the melting point of the crystal material.

When Pa is constant, the coil current is constant, so the magnitude of the vertical magnetic field formed in the coil is constant. Therefore, the suppressing force against thermal convection of the raw material melt is constant.

Since the suppressing force is constant, the crystal growth model has the advantage of making it easier to stably understand operating conditions. Further, when actually comparing the ingots cut out from the head and tail of the wafer, it can be seen that the difference in EPD distribution is smaller.

Since Pa is constant, the reason for changing the temperature from t1 to t5 is mainly the heating device 6 that does not generate a magnetic field (DC).
This is done by converting the electric power pb into Hfm.

FIG. 3 is also a graph showing an example of temperature control of the raw material melt during single crystal growth. This also follows the temperature program and the power P
The temperature is changed from t1 to t by appropriately controlling a and Pb.

In this example, after the shoulder K(7) starts to grow, the power Pa is gradually decreased. The rate of decrease gradually increases in the shoulder region and remains constant in the straight trunk region.

The reason for doing this is that as the crystal grows, the raw material melt decreases and the liquid level H1 decreases, so that the convection suppressing force decreases in proportion to the depth.

In addition to this, various temperature control programs for Pa and Pb can be considered. Whether it is better to keep Pa constant or gradually decrease Pa depends on the components of the raw material melt.

In the control method described above in which the electric power Pa is proportional to the height Hl of the melt, Pa = pa? + kH, (1). The height H3 of the melt can be determined by calculating the amount of remaining melt from this amount since there is a load cell on the upper rotating shaft for pulling the crystal and constantly measures the weight of the single crystal. .

In reality, the diameter of the single crystal is determined while strictly controlling the temperature, so if the height of the upper rotating shaft is known, the weight of the pulled single crystal can be determined, and the liquid level height Hl can also be determined.

Instead of the linear control in equation (1), Pa
= pa? +hHl(2) may be controlled. It is only necessary to relate the liquid level height H and the electric power Pa of the heater that generates the static magnetic field in a certain way.

i) Example 3 An example of growing a GaAs crystal with a diameter of 3 inches by the CZ method will be described.

Coil pitch l T/1M Raw material melt (GaAs) 6 kg Coil current Approximately 1000 A Melt temperature 1238.4°C or higher Magnetic field 1500 to 2500 Gauss When the single crystal is pulled up by this, the solid-liquid interface as a whole is downward. It protrudes to the top and the recess disappears. The solid-liquid interface S is now shown by the broken line in FIG.

(J) Effects (1) In the present invention, two heating devices that can be controlled independently are used. The magnitude of the vertical static magnetic field and the temperature of the raw material melt can be controlled independently.

The magnitude of the vertical magnetic field should be constant or the liquid level height Hl
We are trying to reduce this by relating it to

Therefore, the convection suppressing force can be kept constant and the single crystal with few crystal defects can be increased in σ[.

(2) Because the magnetic field generating coil also serves as a heater,
No need to cool the coil. The temperature environment inside the furnace does not change. For this reason, conventional crystal pulling techniques can be used.

(3) The degree of contamination is not affected by this.

(4) There is no problem with gas resistance.

(5) There is no need to modify the furnace body.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a single crystal manufacturing apparatus according to an embodiment of the present invention. FIG. 2 is a graph showing a temperature change program of the raw material melt when pulling a single crystal using the single crystal manufacturing apparatus of the present invention. The horizontal axis represents time, and the vertical axis represents the temperature of the raw material melt. Pa is the raw material melt T. This shows the part of the power supplied from the coiled resistor to maintain the voltage. pb indicates the portion of electric power given from the heating device 6 to provide heat corresponding to the temperature fluctuation. t2 is the shoulder forming temperature t4, and t4 is the straight trunk forming temperature. Figure 3 shows how to prepare a single crystal using the single crystal manufacturing apparatus of the present invention.
A graph showing a temperature change program of the raw material melt during heating. The power of the heating device Pa that generates the vertical static magnetic field decreases with growth. FIG. 4 is an enlarged sectional view showing only the crucible and single crystal portion of the crystal pulling furnace. FIG. 5 is a sectional view of a known CZ pulling furnace in which a horizontal magnetic field is applied to the raw material melt. FIG. 6 is a sectional view of a known cz furnace in which a vertical magnetic field is generated by an external coil and applied to the raw material melt. FIG. 7 is a perspective view of a known carbon, SiC resistor. FIG. 8 is a perspective view of a coiled resistor used in the present invention. FIG. 9 is a sectional view showing a known example of a vertical magnetic field type CZ furnace using an internal fill. 1 ・・・・・・・・・ Raw material Melt 2 ・・・・
・ ・ Crucible 3 ...... Susceptor 4 ...... Seed Crystal 5 ...... Single crystal 6 ...... Addition Heat device 7...
...... Chamber 8...
・Upper rotation shaft 9 ・・Lower rotation shaft 10 ・・・・・ Coiled resistor 12 ・・・
... Coil 21 ... Notch 22 ... ... Heater 23 ...
...... Coiled resistor power supply 24 ...
...Power source D for the heating device that does not generate a static magnetic field...
・・・・・・Inner diameter of crucible Ho・・・・・・・・・
Crucible height Hl ・・・・・・・・・ Depth of raw material melt K ・・・
・・・・・・ Shoulder part M of single crystal ・・・・・・ Straight body part S of single crystal ・・・・・・
・・・・・・ Solid-liquid interface Pa ・・・・・・・・・
Electric power Pb of a heating device that generates a static magnetic field ... - Electric power of a heating device that does not generate a static magnetic field Inventor Osamu Shikatani Moto Kazu Kusasaki Masaru Michikawa Kei Patent applicant Sumitomo Electric Industries, Ltd. Nippon Telegraph and Telephone Public corporation Figure 9 Figure 1 Figure 2 (Figure 3) Figure 5 Figure 6 Figure 7 Figure 8, -A0 Procedural amendment (voluntary) February 27, 1985 1, Incident Patent Application No. 59-25680 3. Relationship with the case of the person making the amendment Patent Applicant Residence 5-15 Kitahama, Higashi-ku, Osaka Name (213) Sumitomo Electric Industries Co., Ltd. Representative President Tetsube Kawakami and one other person 4. Agent Cloud 537

Claims (3)

[Claims] (1) In a single crystal manufacturing method in which a seed crystal 4 is immersed in a raw material melt 1 in a crucible 2 heated from the surroundings by a heating device, and a single crystal is grown while pulling up the seed crystal 4, the surroundings of the crucible 2 are heated. The provided coiled resistor 10 provides an environment of a constant temperature To below the crystal melting point and a constant vertical static magnetic field of 1000 Gauss or more, and the constant temperature T is maintained by the heating device 6 provided around the crucible 2 that does not generate a static magnetic field. A single crystal manufacturing method characterized by controlling temperature by superimposing the temperature on the (2) In the single crystal production method in which the seed crystal 4 is immersed in the raw material melt 1 in the crucible 2 heated from the surroundings by a heating device and the single crystal is grown while pulling the seed crystal 4, the surroundings of the crucible 2 are heated. A heating device 6 provided around the crucible 2 that provides a temperature environment and a vertical static magnetic field that change in relation to the depth Hl of the raw material melt 1 in the crucible 2 using the provided coiled resistor 10, and does not generate a static magnetic field provided around the crucible 2. A single crystal manufacturing method characterized in that temperature control is performed superimposed on the temperature environment by: (3) A crucible 2 that holds the raw material melt 1, a lower rotating shaft 9 that supports the crucible 2, and a seed crystal 4 are attached to the lower end, and by dipping the seed crystal 4 into the raw material melt 1 and pulling it up, a single crystal is produced. an upper rotating shaft 8 that can be rotated up and down to grow 5; a heating device 6 that is provided and does not generate a static magnetic field;
A chamber 7 containing therein a raw material melt 1, a crucible 2, upper and lower rotating shafts 8.9, a heating device 6, and a coiled resistor 10.
and a power source 23 that supplies power to the coiled resistor 10.
A single crystal manufacturing apparatus characterized by comprising a power source 24 that supplies power to a heating device 6 (which does not generate a static magnetic field).