KR19980068756A - Silicon Single Crystal Growth Method - Google Patents

Abstract

In the silicon single crystal growth method by the magnetic field applying Czochralski method, the cusp is installed during the crystal growth using a magnetic field applied Czochralski method in which the solenoid coils with opposite directions of current are installed up and down outside the single crystal growth path. By applying magnetic field while controlling the type of magnetic field and the intensity of the magnetic field, two blocks of oxygen concentration and low oxygen concentration are formed in one silicon single crystal rod to meet various oxygen concentration specifications and at the same time Silicon single crystal rods with a uniform distribution can be produced.

Description

Silicon Single Crystal Growth Method

[Industrial use]

The present invention relates to a silicon single crystal growth method by magnetic field applying Czochralski (MCZ) method, and more particularly, by growing the silicon single crystal while controlling the time and the intensity of the magnetic field of the cusp type It is possible to form two blocks having a low oxygen concentration and a middle oxygen concentration in the determination of the silicon single crystal growth method by the magnetic field applied Czochralski method which can save the power cost according to the cusp magnetic field application by improving the magnetic field application efficiency. It is about.

[Prior art]

Silicon wafers that are mainly used as substrates in the manufacture of semiconductor devices are generally manufactured by Czochralski (CZ) crystal growth method or floating-zone (FZ) crystal growth method after fabricating high purity polycrystalline silicon rods. Accordingly, single crystals are grown from polycrystalline silicon to produce single crystal silicon rods, which are thinly cut to produce silicon wafers, mirror-polished on one surface of the wafer, cleaned, and finally manufactured. N-type and p-type silicon wafers are prepared by adding appropriate dopants during single crystal growth.

In the single crystal silicon crystal growth method, Czochralski crystal growth and floating zone crystal growth are used.

The Czochralski crystal growth method is a method of heating a polycrystalline silicon specimen to 1415 ° C., which is the melting point of polycrystalline silicon in a crucible. The crucible used is made of quartz (SiO ₂ ) and the heating method uses high frequency heating or heat resistance method. During crystal growth, the crucible is rotated to keep the temperature constant regardless of the site. Around the crystal puller may be filled with argon (Ar) gas to prevent contamination of the molten silicon. When the temperature of the silicon is stable, the arm to which the silicon specimen is attached is slowly lowered to reach the surface of the molten silicon. This silicon specimen is called a seed crystal and is the starting material for later growth of larger crystals. When the lower part of the seed crystal starts to melt in the molten silicon, the downward movement of the arm or cable supporting the silicon is changed to upward movement. At this time, when the seed crystal is slowly pulled out from the molten silicon, the molten silicon attached to the seed crystal solidifies and has the same crystal structure as the seed crystal. Arms or cables, on the other hand, continue to move upward to grow larger crystals, which continue until a certain amount of silicon remains in the crucible. In this process, if the rotation speed of the crucible and seed crystal and the temperature of the crucible are properly adjusted, single crystals of uniform diameter can be obtained. The concentration of impurities can be controlled by increasing the doping concentration of silicon prior to crystal growth.

In addition, the floating zone crystal growth method uses a polycrystalline silicon rod prepared in advance. A silicon rod having a predetermined diameter is placed in the crystal growth machine so that the upper end of the silicon rod touches the seed crystal fixed at the upper side of the crystal growth machine and the lower end thereof. The induction heating coil is wound around the reaction tube into which the silicon rod is inserted and the atmosphere in the reaction tube is controlled. When the silicon rod starts to melt from the seed crystal part in the longitudinal direction of the rod due to the heat generated by the coil, the coil moves upward while the molten portion moves upward in the longitudinal direction of the silicon rod. On the other hand, the molten portion starts to solidify from where it is in contact with the seed crystal and has the same crystal structure as the seed crystal. In addition, as the molten portion moves in the longitudinal direction of the silicon rod, the polycrystalline silicon rod is also melted to become a single crystal silicon rod after solidification. In the floating zone growth method, the diameter of the silicon rod is controlled by controlling the moving speed of the heating coil, and the impurity concentration can be adjusted by appropriately doping the gas containing the dopant in the melting zone of the polycrystalline silicon rod.

On the other hand, it has been found that the application of a magnetic field around the crucible interferes with the tropical currents occurring in the silicon melt, and on the basis of this, the magnetic field or Czochralski method is currently used. This method demonstrates that Lorentz's law applies to molten silicon that the current is induced when the conductor crosses the magnetic field line and that the induced current is in the opposite direction to the change that causes it, resulting in suppressing tropical flow. It is used. This disruption of the tropical stream causes small temperature fluctuations at the crystal and melt interfaces, resulting in very small fluctuations in the diameter and resistance of the ingots and less oxygen transport from the crucible wall to the solid phase interface, thus introducing less oxygen into the ingot. do. In the magnetic field-applied Czochralski method, 7-12 ppma of oxygen is injected, while in the conventional Czochralski method, oxygen of 13-19 ppma is introduced. Due to the lower oxygen content, very little oxygen thermal donor is formed and it is reported that problems caused by the association of oxygen such as precipitation and stacking are reduced.

In the silicon single crystal growth method by the magnetic field applying Czochralski method, in order to control the oxygen concentration in the crystal rod, convection of the silicon melt in the crucible is suppressed by applying a horizontal magnetic field or cusp field of 1000 to 3000 Gauss. As a result, the oxygen concentration was controlled and the quality was uniform.

Cusp magnetic field is a kind of magnetic field coordination for sealing high temperature plasma. It is a magnetic field coordination obtained by arranging linear conductors in parallel at four points and flowing currents in the opposite direction between neighbors. This is called. Sealing has the drawback that there is a large number of escape of particles (cusp loss) from the cusp because the magnetic field is zero.

When the silicon single crystal is grown by applying such cusp magnetic field, since the magnetic field of the same intensity is applied from the beginning, the difference of oxygen concentration in the direction of crystal growth is large, and the magnetic field of the same intensity is applied until the end. Considering the oxygen concentration in the second half, the range to control the oxygen concentration is extremely limited.

The horizontal magnetic field of the applied magnetic field has a problem that the temperature distribution becomes asymmetrical in the axial direction and thus the in-plane homogeneity of the wafer is inferior.

The present invention has been made to solve the problems of the prior art, an object of the present invention is to form two blocks of low oxygen concentration and middle oxygen concentration in one crystal, silicon single crystal with uniform oxygen concentration distribution on the wafer surface To provide a silicon single crystal growth method using the Cusp magnetic field or Czochralski method with low power consumption.

1 is a cross-sectional view schematically showing a magnetic field applying single crystal growth apparatus according to an embodiment of the present invention.

Figure 2 is a graph showing the magnetic field application conditions applied to one embodiment of the present invention.

FIG. 3 shows the in-plane distribution of oxygen concentration at each site of a silicon single crystal grown by a cusp-type magnetic field-injected single crystal growth method of the present invention, measured by Fourier transform infrared (FT-IR). Graph showing the length of a single crystal.

Figure 4 is a graph showing the in-plane distribution of the oxygen concentration at each site of the silicon single crystal grown by the conventional Czochralski growth method by the length of the single crystal measured by FT-IR.

FIG. 5 is a graph showing the in-plane distribution of oxygen concentration at each site of a silicon single crystal grown by a conventional magnetic field applying Czochralski growth method by FT-IR and plotting the length of the single crystal.

Explanation of symbols on the main parts of the drawings

1a upper coil of cusp magnetic application device

1b Hacoil of cusp magnetic field applying device

2 graphite heating element 3 graphite crucible 4 quartz crucible

5 silicon melt 6 crystal 7 seed crystal

8 Rotating shaft 9 Cable 10 Crystal growth furnace

11 neck 12 thermos 13 shoulder

[Means for solving the problem]

The present invention has the following configuration to achieve the above object of the present invention.

In the present invention, polycrystalline silicon is heated and dissolved to form a silicon melt, and seed crystals are brought into contact with the surface of the silicon melt, and seed crystals are taken out when the lower portion of the seed crystal starts to melt in the silicon melt to grow a silicon single crystal. In the silicon single crystal growth method comprising the step of applying a cusp magnetic field during the silicon single crystal growth process, the cusp magnetic field is applied to increase the strength of the magnetic field at a constant rate to reach the target magnetic field strength and then increase the strength of the magnetic field. It provides a silicon single crystal growth method to reduce the crystallization to a certain ratio to achieve crystal growth while maintaining a constant diameter and to zero the magnetic field strength immediately before crystal growth is completed.

The increase rate of the magnetic field strength is that when the length of the constant diameter portion of the crystal is 20 cm, the current of the phase coil increases at a rate of 21.5 A / cm and the current of the phase coil is 6.1 A / cm at the point where the crystal length is 30 cm. It is desirable to decrease the ratio of.

In addition, in the present invention, when the single crystal has a length of 0 to 25 cm, the oxygen concentration is 7 to 8 × 10 ¹⁷ particles / cm ^3, and the single crystal is 25 to 60 cm in length when the single crystal is produced by the silicon single crystal growth method. A silicon single crystal of 5 to 6 x 10 ¹⁷ particles / cm ³ is provided.

[Action]

In the present invention, the silicon single crystal growth method is applied by a cusp magnetic field or a method in which the strength of the magnetic field is gradually increased to a target magnetic field when the crystal reaches a certain length during growth in the silicon single crystal growth method by the Czochralski growth method. Afterwards, it is a method of gradually decreasing the magnetic field strength to 0 at an arbitrary length in the second half of the crystal growth. To 3~6 × 10 ¹⁷ atoms / cm ³ and a low oxygen concentration of 7~10 × 10 ¹⁷ pieces / second, and improve efficiency of a magnetic field applied so that the blocks formed with a middle small farmers in cm ³ also in a crystal by this method As a result, the power cost of applying the magnetic field can be reduced by 50% or more.

In the present invention, the growth is performed by a general Czochralski method without first applying a magnetic field to form a block having a concentration of oxygen, and then the intensity of the magnetic field is gradually increased at a constant ratio to reach the target magnetic field strength. Then, the strength of the magnetic field is reduced to a certain ratio so that the strength of the magnetic field becomes zero at an arbitrary point.

Among the silicon crystal rods grown by this method, two blocks having characteristics of low oxygen concentration of [Oi] of 3 to 6 × 10 ¹⁷ atoms / cm ³ and heavy oxygen concentration of 7 to 10 × 10 ¹⁷ atoms / cm ³ Is formed. By applying the cusp magnetic field from any point of growth for the first time, the efficiency of the magnet is improved and crystal growth of low oxygen concentration is easy. According to the present invention, the magnetic field is not applied to any point by starting crystal growth from melting, and when the point is reached, the intensity of the magnetic field is gradually increased at a constant rate. When the strength of the magnetic field reaches the target value, it is possible to control the oxygen concentration in the crystal in a wide range by reducing the strength of the magnetic field to a certain ratio again.

The following presents a preferred embodiment to aid the understanding of the present invention. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited to the following examples.

EXAMPLE

Representative Example

The following describes an embodiment of the present invention with reference to the drawings. 1 is a cross-sectional view schematically showing the crystal growth apparatus used in the embodiment of the present invention. The crystal growth apparatus of FIG. 1 includes the upper coil 1a and the lower coil 1b, the graphite heating element 2, the graphite crucible 3, the quartz crucible 4, the silicon melt 5, and the crystal of the cusp magnetic field applying device. (6), seed crystal (7), rotary shaft (8), cable (9), and crystal growth furnace chamber (chamber) (10). Using such a crystal growth apparatus, silicon single crystals are grown by the following single crystal growth method.

Polycrystalline silicon is charged into a quartz crucible 4 in a crystal growth furnace chamber to form a silicon melt 5 by heating melting. After heating dissolution is completed, when the temperature is maintained, the seed crystal 7 is immersed in the silicon melt 5 by lowering the cable 9. The cable 9 is pulled up while maintaining the diameter of the neck 11 at 4-5 mm. When the neck 11 having a constant diameter is formed, a shoulder 12 is formed to reduce the pulling speed of the cable 9 to have a diameter of 207 mm. When the shoulder is formed, the silicon single crystal having a diameter of 207 mm is grown by adjusting the pulling speed of the graphite heating element 2 and the cable 9. At this time, the cable 9 and the crucible rotation shaft 8 rotate in opposite directions to each other.

As shown in FIG. 2, the strength of the magnetic field is gradually increased at a constant rate using a magnetic field applying device at a point where the crystal grows 20 cm. The magnetic field applying device is composed of two solenoid coils, the upper coil 1a and the lower coil 1b, and the direction of the current is reversed. Therefore, the distribution of the magnetic field in the crystal growth furnace has a cusp shape.

At the point where the crystal is grown 30cm in length, the intensity of the magnetic field on the crucible wall is adjusted to 380 Gauss. The strength of the magnetic field is reduced at a constant rate so that the strength of the magnetic field becomes zero immediately before the completion of crystal growth while maintaining a constant diameter. After cooling for a certain time, the crystals were taken out of the growth furnace to obtain a silicon single crystal having a diameter of 207 mm and a length of a constant diameter portion of 64 cm.

Example

Polycrystalline silicon was charged into a quartz crucible 4 in a crystal growth furnace chamber to form a silicon melt 5 by melting. After the heat dissolution was completed, the seed crystal 7 was immersed in the silicon melt 5 by lowering the cable 9 when the constant temperature was maintained. The cable 9 was pulled up while maintaining the diameter of the neck 11 at 4-5 mm. When the neck 11 of a constant diameter was formed, the shoulder 13 was formed to reduce the pulling speed of the cable 9 to have a diameter of 207 mm. When the shoulder was formed, the silicon single crystal having a diameter of 207 mm was grown by controlling the temperature of the graphite heating element 2 and the pulling speed of the cable 9. At this time, the cable 9 and the crucible rotating shaft 8 rotated in opposite directions to each other.

As shown in FIG. 2, the strength of the magnetic field was gradually increased at a constant rate by using a magnetic field applying device at the point where the crystal grew 20 cm. At the point where the crystals were grown to 30 cm in length, the intensity of the magnetic field applied to the crucible wall was adjusted to 380 Gauss. The strength of the magnetic field was reduced at a constant rate such that the strength of the magnetic field became zero immediately before the completion of crystal growth, while maintaining a constant diameter. After cooling for a certain time, the crystals were taken out of the growth furnace to obtain a silicon single crystal having a diameter of 207 mm and a length of a constant diameter portion of 64 cm.

The in-plane distribution of oxygen concentration at each site of the crystal grown under such conditions was measured by FT-IR and shown in FIG. 3.

As shown in FIG. 3, ingots starting at 0 cm and up to 32 cm form a block of lower oxygen concentration as the length of the ingot increases, starting at 40 cm and starting at the maximum value of 32 cm. At 48cm, as the length of the ingot increases, a high oxygen concentration block is formed. However, at 56 cm again, a block with reduced oxygen concentration is formed. This is because the amount of molten silicon decreases immediately before the end of growth, and thus the amount of oxygen dissolved in the quartz crucible is reduced by decreasing the contact area with the quartz crucible, which is the source of oxygen, and the magnetic field effect is relatively increased.

Comparative Example 1

The same procedure as in Example 1 was performed except that the silicon single crystal was grown by using a general Czochralski method in which the magnetic field was not applied.

Comparative Example 2

In Example 1, the same procedure as in Example 1 was carried out except that silicon single crystals were grown by using the magnetic field-applied Czochralski method applied with the same magnetic field strength from the time of temperature stabilization.

As a comparative example, Fig. 4 shows the Czochralski method, and Fig. 5 shows the oxygen concentration distribution of crystals grown by the magnetic field or Czochralski method applying the same magnetic field strength from the time of temperature stabilization. Grown by Czochralski method single crystal that is controlled to less than 7 × 10 ¹⁷ atoms / the other hand, the growth in cm ³ or more of the oxygen concentration if the growth of only the magnetic field applied Czochralski method is approximately 6.3 × 10 ¹⁷ atoms / cm ³ Able to know. On the other hand, the silicon single crystal according to the present invention has two kinds of [Oi] of 7 to 8 × 10 ¹⁷ pieces / cm ^{3 up to} 0 to 25 cm and 5 to 6 × 10 ¹⁷ pieces / cm ^{3 up} to ^{25 to} 60 cm from the result of FIG. It can be seen that a section having an oxygen concentration level is formed. Compared with FIG. 5, when the magnetic field of the same intensity is applied, low oxygen concentration crystals are formed more efficiently in the method according to the present invention, and more uniform oxygen concentration distribution is shown at a length after 90 mm from the center.

According to the present invention, the oxygen concentration can be controlled in an arbitrary range from 3 × 10 ¹⁷ pieces / cm ³ to 1 × 10 ¹⁸ pieces / cm ³ . In addition, it is possible to form blocks having two or more different oxygen concentration specifications in one crystal, which can reduce the power cost required to apply a magnetic field by 50% or more.

Claims (3)

Heat dissolving the polycrystalline silicon to form a silicon melt; Contacting the seed crystals with the surface of the silicon melt; When the lower part of the seed crystal starts to melt in the silicon melt, the seed crystal is taken out to grow a silicon single crystal; Applying a cusp magnetic field during the silicon single crystal growth process; In the silicon single crystal growth method comprising the step, the cusp magnetic field is applied to increase the strength of the magnetic field at a predetermined rate when the crystal having a predetermined diameter reaches a certain length to reach the target magnetic field strength, A method of growing silicon single crystals by reducing the ratio to a certain diameter while maintaining a constant diameter and bringing the magnetic field to zero just before the crystal growth is completed. The rate of increase of the magnetic field strength of the magnetic field strength of claim 1, wherein when the length of the constant diameter portion of the crystal is 20 cm, the current of the phase coil increases at a rate of 21.5 A / cm and the length of the crystal is 30 cm. The silicon single crystal growth method in which the ratio decreases at a ratio of 6.1 A / cm. Prepared by the silicon single crystal growth method according to claim 1, when the length of the single crystal is 0 to 25 cm, the oxygen concentration is 7 to 8 × 10 ¹⁷ particles / cm ³ and the length of the single crystal is 25 to 60 cm. × 10 ¹⁷ pcs / cm ³ silicon single crystal