KR102095597B1 - Manufacturing method of silicon single crystal - Google Patents

Abstract

[Problem] In the method for producing a silicon single crystal by the Czochralski method, occurrence of an epi defect when used as a substrate material for an epitaxial silicon wafer while preventing a decrease in crystallization rate due to crystal warpage or cutting separation from a melt To suppress.
[Solutions] A body part cultivation process for cultivating a body part 3c having a constant crystal diameter and a tail part cultivation process for cultivating a tail part 3d whose crystal diameter is gradually reduced, and a quartz crucible ( Silicon single crystal (3) pulled from the silicon melt (2) using the water cooling body (18) disposed inside the heat shield (17) above the lower end (17b) of the heat shield (17) disposed above 11) ). In the tail portion growing step, the silicon single crystal 3 is pulled at the same pulling speed as the pulling speed at the end of the body portion growing from the start of the tail portion 3d to the end.

Description

Manufacturing method of silicon single crystal

The present invention relates to a method for producing a silicon single crystal by the choralki method (hereinafter referred to as a CZ method), and more particularly, to a method for growing a tail portion of a silicon single crystal ingot.

As a substrate material for semiconductor devices, epitaxial silicon wafers are widely used. An epitaxial silicon wafer is an epitaxial layer formed on the surface of a bulk silicon substrate, and since the crystal integrity is high, it is possible to manufacture a high quality and highly reliable semiconductor device.

Most of the silicon single crystals used as the substrate material for the epitaxial silicon wafer are produced by the CZ method. In the CZ method, a raw material such as polycrystalline silicon is filled in a quartz crucible, and the silicon raw material is heated and melted in a chamber. Next, the seed crystal attached to the lower end of the pulling shaft descends from the upper side of the quartz crucible to contact with the silicon melt, and gradually raises the seed crystal while rotating the seed crystal and the quartz crucible, A large crystal single crystal is grown below the seed crystal.

As a method for manufacturing an epitaxial silicon wafer, for example, in Patent Document 1, when pulling a silicon single crystal ingot, a temperature range of 1030 to 920 ° C during the pulling is continuously cooled at a rate of 1.0 ° C / min or higher, and subsequently 920 to 720 It has been described that a silicon single crystal grown in a temperature range of ° C at a cooling rate of 0.5 ° C / min or less is grown, and then an epitaxial layer is formed on the surface of the wafer cut out from the single crystal. The OSF (Oxygen induced stacking fault) nucleus rapidly passes through a temperature region (1030 to 920 ° C) where the nuclei are easy to grow, so that the OSF nucleus size is very small, and thus epitaxial defects caused by OSF (hereinafter referred to as epi defects) It is possible to suppress the occurrence of).

In the single crystal pulling process, a necking process in which the crystal diameter is narrowly contracted by a dash neck method to dislocate the single crystal, and a shoulder portion gradually increasing the crystal diameter (shoulder portion) A growth process, a body portion growth process that progresses crystal growth while maintaining a constant crystal diameter, and a tail portion growth process that gradually shrinks the crystal diameter to form a conical tail portion are sequentially performed. Among these, in the tail growth process, while the thermal balance between the melt and the single crystal existing at the crystal growth interface is broken, rapid thermal shock is applied to the crystal, and quality abnormalities such as slip dislocation and oxygen precipitation abnormality are prevented from occurring. This is a process required to cut and separate a single crystal from a melt.

Regarding the tail portion cultivation process, for example, in Patent Document 2, the pulling speed of the terminal cone portion (tail portion) of the ingot is set at a relatively constant speed equal to the pulling speed of the second half of the body portion (body portion) of the ingot. It is described to produce a single crystal silicon ingot having a uniform heat history by maintaining and further increasing the power (heat amount) supplied to the heater, or by reducing the crystal rotation speed or the crucible rotation speed, if necessary. have.

(Patent Document 1) Japanese Patent Publication 2010-30856 (Patent Document 2) Japanese Patent Publication No. Hei 10-95698

In Patent Document 1, a single crystal pulling apparatus with a water cooling body is used, and the pulling rate during single crystal growth and the temperature gradient in the pulling axis direction of the single crystal immediately after crystallization are controlled. However, the portion used as the substrate material of the epitaxial silicon wafer is a body portion (directly moving portion) whose crystal diameter is kept constant, and the tail portion is a portion not used as a wafer product. Therefore, in Patent Document 1, the cooling conditions of the body portion are described, but specific pulling conditions such as the pulling speed in the tail portion, the heater power, and the rotational speed of the single crystal are not described.

In the growth of the tail portion, it is common practice to increase the pulling speed of a single crystal and gradually shrink the crystal diameter. This is because tail shrinkage can be easily performed by increasing the pulling rate of a single crystal, and further, the production period is reduced by shortening the tail growing period. Also, as described above, the tail portion is a portion that does not become a wafer product, and it is not a problem even if the crystal quality of the tail portion itself decreases by increasing the pulling speed. For this reason, it is considered that in the conventional general tail portion cultivation process, control to speed up the pulling rate of a single crystal is performed, and in Patent Literature 1, conditions that are easy to tail tapering are also adopted.

However, when the pulling rate of a single crystal is increased in the tail portion growth process, there is a risk that the single crystal is dielectrically distorted due to crystal bending (bending) or sudden separation of the single crystal from the silicon melt.

Patent Document 2 describes that the pulling speed of the tail portion is maintained at a relatively constant speed equal to the pulling speed of the latter half of the body portion. In this way, the control to make the tail portion pulling rate constant is considered to have a relatively constant cooling rate and residence time throughout the entire body portion of the single crystal.

However, when the pulling rate of the tail portion is set to the same speed as the body portion, since the pulling rate of the single crystal is slower than the conventional tail portion growing process, the silicon single crystal pulled from the silicon melt stays in the OSF nucleation temperature region. The time is actually long, and there is a fear that the epi defect is increased.

In addition, in the tail portion growing process, as the crystal diameter gradually decreases, as shown in FIG. 8, the gap D between the heat shield 17 and the silicon single crystal 3 increases, and heat from the silicon melt 2 or the like increases. As indicated by the white arrow, it diffuses upward and the periphery of the silicon single crystal 3 immediately after crystallization becomes high temperature. When the tail portion 3d of the silicon single crystal 3 is slowly pulled up at the same pulling speed as the body portion 3c under such an environment, the influence of the high temperature around the silicon single crystal 3 increases. That is, the time for the silicon single crystal 3 pulled from the silicon melt 2 to stay in the OSF nucleation temperature region becomes longer, so that the epi defect increases.

Furthermore, unlike the case where the body portion 3c is pulled up, the tail portion 3d is prone to dielectric dislocation because the crystal diameter decreases and the state in which the crystal is pulled changes from time to time. In addition, in the tail portion cultivation process, since the amount of melt in the crucible is small and the melt is retained at the bottom of the crucible, the state of the melt in the crucible also changes from time to time as the tail portion 3d is pulled up, resulting in genetic displacement easy. Therefore, when the tail portion 3d is pulled at the same speed as the body portion 3c, the time required to complete the pulling of the tail portion 3d becomes very long, and the risk of dielectric misalignment in the tail portion 3d is reduced. There is a problem of increasing.

Accordingly, an object of the present invention is to produce a silicon single crystal capable of suppressing the occurrence of epidefects when used as a substrate material for an epitaxial silicon wafer while preventing deterioration of a single crystallization rate due to crystal warpage or cutting separation from a melt. In providing a way.

In order to solve the above problems, the method of manufacturing a silicon single crystal according to the present invention is a method of manufacturing a silicon single crystal by a Czochralski method of pulling silicon single crystal from a silicon melt in a quartz crucible, the body having a constant crystal diameter And a body part cultivation process for cultivating a part, and a tail part cultivation process for cultivating a tail part whose crystal diameter is gradually reduced, and water cooling disposed inside the heat shield as an upper side of a bottom of the heat shield disposed above the quartz crucible. A silicon sieve is used to cool the silicon single crystal pulled from the silicon melt, and in the tail part growing step, the pulling rate is the same as the pulling rate at the end of the body part growth from the start to the end of the tail part growth. It is characterized by pulling a silicon single crystal.

In the tail growth process, as the crystal diameter gradually decreases, the lateral gap between the heat shield and the single crystal gradually widens, and the heat blocked by the heat shield diffuses upward, so that the silicon single crystal does not cool well. . Further, in the step of cultivating the tail portion, when stopping the rise of the quartz crucible in order to avoid contact between the heat shield and the crucible, the gap between the heat shield and the melt surface gradually widens due to the lowering of the melt surface, and thus from the quartz crucible. The radiant heat of is more likely to spread upward. Therefore, the crystal quality of the body portion near the tail portion is different from that of the top side under the influence of heat. That is, the residence time in the temperature range of 1020 to 980 ° C is prolonged to be in a slow cooling state, and the crystals include large OSF nuclei prone to occurrence of epidefect.

However, according to the present invention, since the water cooling body is provided around the pulling path above the heat shield, it is possible to shorten the pulling speed of the single crystal and shorten the period during which the silicon single crystal immediately after crystallization stays in the OSF nucleation temperature region. have. Therefore, it is possible to manufacture a silicon single crystal capable of preventing deterioration of a single crystallization rate due to bending of the crystal or cutting and separation of the crystal from the melt, and suppressing occurrence of epidefects when forming an epitaxial layer.

In the tail portion growing step, it is preferable to pass the temperature range from 1020 ° C to 980 ° C of the body portion of the silicon single crystal within 15 minutes. In this way, the silicon single crystal pulled from the silicon melt passes quickly through the OSF nucleation temperature range, whereby the size of the OSF nucleus in the silicon single crystal can be reduced. Therefore, when the epitaxial layer is formed on the surface of the silicon wafer cut out from the single crystal ingot, the occurrence of epi defects caused by OSF can be suppressed.

The method for manufacturing a silicon single crystal according to the present invention gradually increases the power of a heater that heats the silicon melt from the start of the tail portion to the end, and also at the end of the tail portion. It is preferable to set the power to 1.1 times or more and 1.5 times or less of the power of the heater at the start of the growth of the tail portion. According to this, tail shrinkage can be implemented while preventing crystal warpage or cutting separation of a single crystal from a silicon melt.

In the tail portion growing process, it is preferable to raise the quartz crucible so that the gap between the heat shield and the silicon melt is constant. By raising the quartz crucible up to the end of the tail portion cultivation process and keeping the height position of the melt surface constant, the influence of radiant heat from the quartz crucible can be suppressed, and expansion of the OSF nucleation temperature region can be suppressed.

In the tail portion growing step, it is preferable to maintain a constant rotational speed of the quartz crucible or the silicon single crystal, and it is also preferable to apply a magnetic field to the silicon melt. In the tail portion cultivation step, because the amount of melt in the quartz crucible is small and the melt is held at the bottom of the crucible, the effect of the change in the rotational speed of the quartz crucible is easily received by the melt, and the state of the melt is unstable. By keeping the speed constant, stabilization of the melt state can be achieved, and the risk of dielectric dislocation of the silicon single crystal can be reduced. Similarly, by stabilizing the rotational speed of the silicon single crystal or by applying a magnetic field to the silicon melt, stabilization of the melt state in the tail portion growing process can be achieved, and the risk of dielectric dislocation of the silicon single crystal can be reduced. In addition, the rotational speed of the quartz crucible and the silicon single crystal need only be substantially constant, and the fluctuation within ± 2 rpm is an allowable range.

According to the present invention, there is provided a method for manufacturing a silicon single crystal capable of suppressing the occurrence of epidefects when used as a substrate material for an epitaxial silicon wafer while preventing a decrease in the single crystallization rate due to crystal warping or cutting separation from a melt. can do.

1 is a side cross-sectional view schematically showing a configuration of a single crystal manufacturing apparatus according to a first embodiment of the present invention.
2 is a flowchart illustrating a method of manufacturing a silicon single crystal according to an embodiment of the present invention.
3 is a schematic cross-sectional view showing the shape of a silicon single crystal ingot.
4 is a schematic cross-sectional view showing a single crystal pulling state during the tail portion growing process.
5 is a sequence diagram showing a change in the pulling speed and heater power of a single crystal.
6 is a side cross-sectional view schematically showing the configuration of a single crystal manufacturing apparatus according to a second embodiment of the present invention.
7 is a graph showing the relationship between the pulling position of a single crystal and the passage time of the OSF nucleation temperature region (1020 to 980 ° C) of the single crystal.
8 is a schematic view for explaining a conventional problem in the tail portion cultivation process.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a side cross-sectional view schematically showing a configuration of a single crystal manufacturing apparatus according to a first embodiment of the present invention.

As shown in Fig. 1, the single crystal manufacturing apparatus 1A includes a chamber 10, a quartz crucible 11 for holding the silicon melt 2 in the chamber 10, and a quartz crucible 11 Susceptor 12 made of graphite to be retained, a rotating shaft 13 supporting the susceptor 12, a shaft driving mechanism 14 for rotating and elevating driving of the rotating shaft 13, and a susceptor ( A heater 15 disposed around the 12, a heat insulating material 16 disposed along the inner surface of the chamber 10 as the outside of the heater 15, and a heat shield 17 disposed above the quartz crucible 11 ), And a single crystal impression arranged coaxially with the rotating shaft 13 as the upper side of the quartz crucible 11 and the water cooling body 18 provided above the lower end of the thermal barrier 17 as the inside of the heat shield 17 The wire 19 is provided, and the wire winding mechanism 20 disposed above the chamber 10 is provided.

Further, the single crystal manufacturing apparatus 1A includes a magnetic field generator 21 disposed outside the chamber 10, a CCD camera 22 photographing the inside of the chamber 10, and an image photographed by the CCD camera 22. An image processing unit 23 to be processed and a control unit 24 for controlling the shaft driving mechanism 14, the heater 15, and the wire winding mechanism 20 based on the output of the image processing unit 23 are provided.

The chamber 10 is composed of a main chamber 10a, an elongated cylindrical full chamber 10b connected to an upper opening of the main chamber 10a, a quartz crucible 11, a susceptor 12, and a heater 15 and the heat shield 17 are provided in the main chamber 10a. The full chamber 10b is provided with a gas inlet 10c for introducing an inert gas (purge gas) such as argon gas into the chamber 10, and a gas for discharging the inert gas below the main chamber 10a. The outlet 10d is provided. In addition, an observation window 10e is provided on the upper portion of the main chamber 10a, so that the growth condition (solid-liquid interface) of the silicon single crystal 3 can be observed from the observation window 10e.

The quartz crucible 11 is a container made of quartz glass having a cylindrical side wall portion and a curved bottom portion. In order to maintain the shape of the quartz crucible 11 softened by heating, the susceptor 12 is held in close contact with the outer surface of the quartz crucible 11 to surround the quartz crucible 11. The quartz crucible 11 and the susceptor 12 constitute a double-structured crucible for supporting a silicon melt in the chamber 10.

The susceptor 12 is fixed to the upper end portion of the rotating shaft 13 extending in the vertical direction. In addition, the lower end of the rotating shaft 13 passes through the center of the bottom of the chamber 10 and is connected to the shaft driving mechanism 14 provided outside the chamber 10. The susceptor 12, the rotating shaft 13, and the shaft drive mechanism 14 constitute a rotating mechanism and a lifting mechanism of the quartz crucible 11.

The heater 15 is used to melt the silicon raw material filled in the quartz crucible 11 to produce the silicon melt 2. The heater 15 is a resistance heating heater made of carbon, and is provided to surround the quartz crucible 11 in the susceptor 12. Furthermore, the outer side of the heater 15 is surrounded by the heat insulating material 16, thereby increasing the heat retention in the chamber 10.

The heat shield 17 suppresses temperature fluctuations of the silicon melt 2 to form an appropriate hot zone near the solid-liquid interface, and according to radiant heat from the heater 15 and the quartz crucible 11. It is provided to prevent the heating of the silicon single crystal 3. The heat shield 17 is a graphite member that covers the region above the silicon melt 2 excluding the pulling path of the silicon single crystal 3 and has an inverted truncated cone shape whose diameter is reduced from above to below.

A circular opening 17a larger than the diameter of the silicon single crystal 3 is formed in the center of the lower end of the heat shield 17 to secure the pulling path of the silicon single crystal 3. As shown, the silicon single crystal 3 passes through the opening 17a and is pulled upward. Since the diameter of the opening 17a of the heat shield 17 is smaller than the diameter of the quartz crucible 11, and the lower end of the heat shield 17 is located inside the quartz crucible 11, the rim of the quartz crucible 11 is Even if the upper end of the rim) is raised above the lower end of the heat shield 17, the heat shield 17 does not interfere with the quartz crucible 11.

With the growth of the silicon single crystal 3, the amount of melt in the quartz crucible 11 decreases, by raising the quartz crucible 11 so that the gap (gap ΔG) between the melt surface and the heat shield 17 is constant, In addition to suppressing the temperature fluctuation of the silicon melt 2, it is possible to control the evaporation amount of the dopant from the silicon melt 2 by keeping the velocity of the gas flowing near the melt surface (a purge gas induction furnace) constant. Therefore, stability such as crystal defect distribution in the direction of the pulling axis of the single crystal, oxygen concentration distribution, and resistivity distribution can be improved.

A water cooling body 18 is disposed inside the heat shield 17 as an upper side of the lower end 17b of the heat shield 17. Like the heat shield 17 or the like, the water cooling body 18 is provided to surround the pulling path of the silicon single crystal 3. The water cooling body 18 is made of a metal having good thermal conductivity, such as copper, iron, stainless steel (SUS), and molybdenum, and it is preferable to pass the cooling water therein to maintain the surface temperature from room temperature to about 200 ° C. Do. Although it will be described later in detail, the presence of this water cooling body 18 can promote cooling of the silicon single crystal 3 immediately after crystallization.

Above the quartz crucible 11, a wire 19, which is an impression axis of the silicon single crystal 3, and a wire winding mechanism 20 for winding the wire 19 are provided. The wire winding mechanism 20 has a function of rotating a single crystal together with the wire 19. The wire winding mechanism 20 is disposed above the pull chamber 10b, and the wire 19 extends downward from inside the pull chamber 10b from the wire winding mechanism 20 and extends downward. Reaches the inner space of the main chamber 10a. In FIG. 1, a state in which the silicon single crystal 3 during growth is suspended from the wire 19 is shown. When pulling up the single crystal, the single crystal is grown by immersing the seed crystal in the silicon melt 2 and gradually pulling the wire 19 while rotating the quartz crucible 11 and the seed crystal, respectively.

A gas inlet 10c for introducing an inert gas into the chamber 10 is provided at an upper portion of the full chamber 10b, and a gas for exhausting an inert gas in the chamber 10 is provided at the bottom of the main chamber 10a. The outlet 10d is provided. The inert gas is introduced into the chamber 10 from the gas introduction port 10c, and the introduction amount is controlled by a valve. In addition, since the inert gas in the closed chamber 10 is exhausted from the gas outlet 10d to the outside of the chamber 10, the inside of the chamber 10 is cleaned by recovering SiO gas or CO gas generated in the chamber 10. It becomes possible to maintain. Although not shown, a vacuum pump is connected to the gas outlet 10d through a pipe, and the flow rate is controlled by a valve while suctioning an inert gas in the chamber 10 with a vacuum pump to maintain a constant pressure-reduced state in the chamber 10. Is becoming.

The magnetic field generating device 21 applies a horizontal magnetic field or a vertical magnetic field to the silicon melt 2. By applying a magnetic field to the silicon melt 2, it is possible to suppress melt convection in a direction orthogonal to the magnetic force line. Therefore, the elution of oxygen from the quartz crucible 11 can be suppressed, and the oxygen concentration in the silicon single crystal can be reduced.

An observation window 10e for observing the inside is provided on the upper portion of the main chamber 10a, and the CCD camera 22 is installed outside the observation window 10e. During the single crystal pulling process, the CCD camera 22 photographs the image of the boundary between the silicon single crystal 3 and the silicon melt 2 seen through the opening 17a of the heat shield 17 from the observation window 10e. The CCD camera 22 is connected to the image processing unit 23, and the photographed image is processed by the image processing unit 23, and the processing result is used by the control unit 24 to control the pulling condition.

2 is a flowchart illustrating a method of manufacturing a silicon single crystal according to an embodiment of the present invention. 3 is a schematic cross-sectional view showing the shape of a silicon single crystal ingot.

2 and 3, in the production of the silicon single crystal 3, the silicon raw material in the quartz crucible 11 is heated to produce a silicon melt 2 (step S11). Thereafter, the seed crystal attached to the tip end of the wire 19 is lowered to be deposited on the silicon melt 2 (step S12).

Next, a single crystal pulling process is performed in which the seed crystal is gradually pulled up while maintaining the contact state with the silicon melt 2 to grow the single crystal. In the single crystal pulling process, a necking process (step S13) for forming a neck portion 3a having a narrow shrinkage (reduction) of the crystal diameter for non-potentialization, and a shoulder portion 3b whose crystal diameter gradually increases to obtain a prescribed diameter. ) Forming the shoulder portion forming step (step S14), and the body portion forming step (step S15) forming the body portion 3c having a constant crystal diameter, and the tail portion 3d in which the crystal diameter is gradually reduced. The tail part formation process (step S16) to be formed is sequentially performed, and the tail part formation process is terminated by finally cutting and separating the single crystal from the melt surface. As described above, a silicon single crystal ingot 3 having a neck portion 3a, a shoulder portion 3b, a body portion 3c, and a tail portion 3d in order from the upper end (top) of the single crystal to the lower end (bottom). This is completed.

During the single crystal pulling process, in order to control the diameter of the silicon single crystal 3 and the liquid level position of the silicon melt 2, an image of the boundary between the silicon single crystal 3 and the silicon melt 2 is imaged with a CCD camera 22. From the photographed image, the diameter of the single crystal at the solid-liquid interface and the gap (gap ΔG) between the melt surface and the heat shield 17 are calculated. The control unit 24 controls pulling conditions such as the pulling speed of the wire 19 and the power of the heater 15 so that the diameter of the silicon single crystal 3 becomes the target diameter. In addition, the control unit 24 controls the height position of the quartz crucible 11 so that the gap between the melt surface and the heat shield 17 is constant.

4 is a schematic cross-sectional view showing a single crystal pulling state during the tail portion growing process.

As shown in Fig. 4, since the silicon single crystal 3 is cut and separated from the silicon melt 2 in a potential-free state, in the tail portion cultivation process, the crystal diameter gradually decreases with the progress of the pulling, so that the heat shield is blocked. The distance D between (17) and the silicon single crystal 3 gradually widens. Therefore, the width of the heat dissipation path toward the upper side from the silicon melt 2 is widened, and heat is more easily diffused upward than the lower end 17b of the heat shield 17, so the lower end 17b of the heat shield 17 ), The temperature of the space above is higher. Thereby, the upper part of the heat shield 17 is heated, and the heat shield 17 itself becomes a heat source, and the silicon single crystal 3 immediately after crystallization is heated. In this state, the silicon single crystal 3 cannot quickly pass through a temperature region (OSF nucleation temperature region) of 1020 to 980 ° C., in which OSF nuclei are easily formed in a single crystal, and slows down the pulling rate of the silicon single crystal 3 In case it becomes more difficult.

However, in the present embodiment, since the water cooling body 18 is provided on the inner side 17i of the heat shield 17 above the lower end 17b of the heat shield 17, the lower end 17b of the heat shield 17 is provided. ), The temperature of the high temperature region after passing through the opening can be lowered, and the width of the crystal growth direction in the temperature region of 1020 to 980 ° C can be narrowed. Therefore, even when the pulling speed of the silicon single crystal 3 is slower than before, the time for the silicon single crystal 3 to stay in the temperature range of 1020 to 980 ° C can be shortened, and the OSF nucleation temperature region can be quickly passed to pass the single crystal The OSF core size in the middle can be made very small.

5 is a sequence diagram showing changes in the pulling speed of the silicon single crystal 3 and the power of the heater 15.

As shown in Fig. 5, the pulling speed of the silicon single crystal 3 is constantly controlled from the body portion 3c to the tail portion 3d. In addition, the constant pulling speed in the tail part growing process means that the variation rate with respect to the pulling speed at the start of the tail part growing process is within ± 3%.

In the conventional general tail portion growing step, the crystal diameter is shrunk thinly by making the pulling speed faster than the body portion growing step and by increasing the power of the heater 15 auxiliaryly. However, in this embodiment, tail contraction is implemented by changing only the power of the heater 15 without changing the pulling speed. Thus, by keeping the pulling rate constant from the start of the tail portion 3d to the end of the growth, it is possible to prevent the occurrence of dielectric deterioration of the single crystal due to crystal warpage or cutting separation from the melt.

When the pulling speed of the tail part 3d is set at the same speed as the pulling speed of the body part 3c, it is difficult to control the tail shrinkage, but it is difficult to solidify the silicon melt 2 by making the power of the heater 15 stronger. By creating a situation, the tail can be easily contracted. When the power of the heater 15 is hardened, the influence of radiant heat becomes stronger, and without the water cooling body 18, the OSF nucleation temperature range of 1020 to 980 ° C is wider as described above. However, by providing the water cooling body 18 as described above, the OSF nucleation temperature region can be narrowed, and the passage time (retention time) of the OSF nucleation temperature region of the silicon single crystal 3 can be shortened.

As described above, the power of the heater 15 during the tail portion cultivation process is greater than the power of the heater 15 at the end of the body portion cultivation process. In particular, it is preferable that the power of the heater 15 gradually increases from the start of the tail portion cultivation, and the power of the heater 15 at the end of the tail portion cultivation is 1.1 to 1.5 times the start of the tail portion cultivation. In this way, by gradually increasing the power of the heater 15 in the tail portion cultivation step, and by allowing the power of the heater 15 at the end of the tail portion cultivation to fall within the range of 1.1 to 1.5 times when starting the cultivation. , Even when the pulling speed of the tail portion 3d is equal to the body portion 3c, tail shrinkage can be realized, and furthermore, crystal warpage or dielectric deterioration can be prevented.

Even in the tail portion cultivation step, it is preferable to gradually raise the quartz crucible 11 to maintain the liquid melt position of the silicon melt 2 constant. Conventionally, since the remaining amount of the silicon melt 2 in the quartz crucible 11 is reduced as much as possible in order to increase the single crystallization rate, the process of the tail portion growth is carried out, so that the quartz crucible 11 is at a sufficiently high position when the tail portion is started. When the quartz crucible 11 is further raised, the quartz crucible 11 interferes with the heat shield 17 and becomes a situation. Therefore, the rise of the quartz crucible 11 must be stopped at the beginning or the beginning of the tail portion cultivation process, and the gap between the melt surface and the heat shield 17 widens due to the lowering of the melt surface, and the silicon single crystal 3 There is a problem that the heat from the quartz crucible 11 is easily affected and the OSF nucleation temperature region is expanded.

However, in the present embodiment, before the silicon melt 2 is sufficiently consumed, the tail portion growing process is started, and the quartz crucible 11 is raised to the end of the tail portion growing process to maintain the height position of the melt surface constant. , The influence of radiant heat from the quartz crucible 11 can be suppressed, and the expansion of the OSF nucleation temperature region can be suppressed.

During the growth of the tail portion, since the crystal diameter gradually decreases and the crystal pulling state changes from time to time, the silicon single crystal 3 is likely to be dielectrically displaced. In addition, when the pulling speed during tail growth is slower than in the prior art, the tail growth time is increased, and the risk of genetic misalignment increases. In order to reduce the risk of dielectric dislocation under these conditions, it is preferable to keep the rotational speeds of the silicon single crystal 3 and the quartz crucible 11 constant in the tail portion growth process. The rotational speed of these may be the same as or different from the rotational speed in the body part growth process. Accordingly, the convection of the silicon melt 2 in the quartz crucible 11 can be stabilized to stabilize the melt temperature.

It is preferable to apply a horizontal magnetic field or a vertical magnetic field to the silicon melt 2 by operating the magnetic field generating device 21 also in the tail growth process. By doing in this way, convection of the silicon melt 2 in the quartz crucible 11 can be further stabilized. The tail portion 3d of the silicon single crystal 3 is a portion that is not used as a product, and since the productization region is the body portion 3c, an oxygen concentration level or its surface is applied by applying a magnetic field in the tail portion growth process (S16). It is not necessary to control the crystal quality such as distribution. In the tail portion growth step (S16), it is important to cut and separate from the silicon melt 2 quickly so as not to deteriorate the quality of the body portion 3c of the silicon single crystal 3 that has been grown so far. However, when a magnetic field is applied during the growth of the tail portion, the convection of the silicon melt 2 in the quartz crucible 11 can be stabilized to stabilize the melt temperature, thereby preventing crystal warpage or dielectric deterioration. .

6 is a side cross-sectional view schematically showing the configuration of a single crystal manufacturing apparatus according to a second embodiment of the present invention.

As shown in Fig. 6, the feature of the single crystal production apparatus 1B is that the water cooling body 18 is made of a cylindrical member that is sufficiently long compared to that of the first embodiment, and the upper end of the main chamber (lower end of the full chamber) It extends downward from the position of and reaches to the inner side 17i of the heat shield 17 surrounded by a dashed line in the figure. That is, the water cooling body 18 is provided so as to cover the pulling path of the silicon single crystal 3 as long as possible.

Also in this embodiment, since the water cooling body 18 exists in the inside 17i of the heat shield 17 as above the lower end 17b of the heat shield 17, the bottom 17b of the heat shield 17 The temperature of the high temperature region after passing through the opening can be lowered, and the width of the crystal growth direction in the temperature region of 1020 to 980 ° C can be narrowed. Therefore, even when the pulling speed of the silicon single crystal 3 is slower than before, the time for the silicon single crystal 3 to stay in the temperature range of 1020 to 980 ° C can be shortened, and the OSF nucleation temperature region can be quickly passed to pass the single crystal The OSF core size in the middle can be made very small.

As described above, in the manufacturing method of the silicon single crystal according to the present embodiment, the water cooling body 18 is disposed inside the heat shield 17 as above the lower end 17b of the heat shield 17, and the tail portion is grown. In the process, the silicon single crystal 3 immediately after crystallization is cooled with a water-cooled body 18, and the tail portion 3d is pulled at a constant speed with the body portion 3c, so it is determined in the tail portion growth step (S16). High-quality silicon single crystals with very few OSF nuclei, which cause epi-defects, can be produced while preventing warpage or cutting separation from the melt.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention, and they are also included within the scope of the present invention. Needless to say.

Example

The single crystallization rate and the occurrence of epi defects were evaluated according to the difference between the pulling rate of the single crystal and the presence or absence of the water cooling body 18 in the tail growth process. In this evaluation test, samples 1 to 6 of a silicon single crystal ingot having a diameter of 300 mm were pulled using the single crystal production apparatus 1A shown in FIG. 1. At that time, the pulling speed of the body portion was set to 1.0 mm / min, and the single crystal was lifted while raising the quartz crucible so that the gap between the melt surface and the bottom of the heat shield was constant during the growth of the body portion as well as during the growth of the tail portion. .

In samples 1 and 2, the pulling speed of the tail portion 3d was set at a higher speed (1.1 times) than the body portion 3c. In addition, in samples 3 and 4, the pulling speed of the tail portion 3d is equal to the body portion 3c, and in samples 5 and 6, the pulling speed of the tail portion 3d is slower (0.9 times) than the body portion 3c. Was made. In addition, in Samples 1, 3, and 5, the impression was performed using a single crystal manufacturing apparatus 1A with the water cooling body 18 removed, and in Samples 2, 4, and 6, the single crystal manufacturing apparatus in which the water cooling body 18 was grounded. Impression was performed using (1A).

Next, samples 1 to 6 of the silicon single crystal ingot thus obtained were processed to prepare a silicon wafer (polyseed wafer) with a thickness of 775 μm, and an epitaxial layer with a thickness of 4 μm was formed on the surface of the silicon wafer to samples 1 to 6. A corresponding epitaxial silicon wafer was produced. Then, the number of epi defects in each epitaxial silicon wafer was measured with a particle counter.

Table 1 is a table showing the results of the evaluation test of the single crystallization rate and epidefect defects of samples 1-6.

Sample Impression speed Presence or absence of coolant Monocrystalline rate Epi defect
The occurrence situation One high speed none × - 2 high speed has exist × - 3 Uniform velocity none 75% or more 5 ~ 10 pieces / wf 4 Uniform velocity has exist 75% or more 5 / wf  under 5 sleaze none 75% or more More than 10 / wf 6 sleaze has exist 75% or more More than 10 / wf

As shown in Table 1, in Sample 1 prepared without using the water cooling body 18 and pulling the tail portion 3d at a higher speed than the body portion 3c, the tail portion 3d is cut from the silicon melt. Separation occurred and the monocrystallization rate deteriorated. In addition, in the sample 2 manufactured by using the water cooling body 18 and making the pulling speed of the tail part 3d higher than that of the body part 3c, cutting and separation from the silicon melt of the tail part 3d occurred, and single crystal The rate has deteriorated. Therefore, it was not possible to evaluate the occurrence of epi defects in these samples 1 and 2. In Sample 3, in which the pulling rate of the tail portion 3d was equal to the body portion 3c without using the water cooling body 18, the single crystallization rate was 75% or more, and the number of epi defects was 5-10. / wf. In the sample 4 in which the speed of pulling the tail portion 3d was equal to the body portion 3c while using the water cooling body 18, the single crystallization rate was 75% or more, and the number of epi defects was 5 / wf. Less than that, it was confirmed that the quality standards of epidefects were satisfied.

In samples 5 and 6 manufactured by lowering the pulling speed of the tail portion 3d to a lower speed than the body portion 3c, a single crystallization rate of 75% or higher was obtained regardless of the use of the water cooling body 18, but the epidefect was defective. There were more than 10 / wf.

From the above results, it was confirmed that in the sample 4 in which the speed of pulling the tail portion 3d was equal to the body portion 3c while using the water cooling body 18, both the single crystallinity rate and the quality of the epidefect could be satisfied. I could confirm.

Next, under the condition of Sample 4, a simulation was performed on how the gap between the melt surface and the heat shield 17 affects the temperature gradient in the crystal growth direction of the single crystal.

7 is a graph showing the relationship between the pulling position of the single crystal and the passage time of the OSF nucleation temperature region (the region of 1020 to 980 ° C) of the single crystal. The horizontal axis of the graph of FIG. 7 represents the distance from the bottom of the single crystal (the lower end of the tail portion 3d), and the vertical axis represents the passage time of the OSF nucleation temperature region, respectively.

As shown in FIG. 7, the condition where the gap (gap (ΔG)) between the melt surface and the heat shield 17 is enlarged, that is, the quartz crucible 11 is raised against a decrease in the melt surface, thereby increasing the melt surface and the heat shield ( It can be seen that in the case where the control to make the interval with 17) not constant is performed, the passage time of the single crystal OSF nucleation temperature region increases as the pulling position approaches the bottom. Since the pulling speed of the tail portion 3d is constant, the longer the passage time of the OSF nucleation temperature region means, the closer the impression position is to the bottom, the OSF nucleation temperature region expands in the direction of the impression axis.

On the other hand, under the condition that the gap between the melt surface and the heat shield 17 is constant, it is understood that the passage time of the single crystal OSF nucleation temperature region does not become long even when the pulling position is close to the lower end of the tail portion 3d. You can. From the above results, it was confirmed that the expansion of the OSF nucleation temperature region can be suppressed by keeping the gap between the melt surface and the heat shield 17 constant even in the tail portion growth step.

Next, the effect of the difference in the output of the heater 15 during the tail portion growth process on the quality of the single crystal was evaluated. When the power of the heater 15 at the start and end of the tail portion growth is CkW and DkW, respectively, in the evaluation test, the heater power ratio D / C was changed within the range from 0.9 to 1.8. Other impression conditions were the same conditions as those of the evaluation test for the single crystallization rate and epi defect described above.

Table 2 is a table showing the results of the evaluation test of the crystal growth situation according to the difference in the heater power ratio.

As shown in Table 2, when the heater power ratio D / C was less than 1.1, tail shrinkage could not be achieved. Further, when the heater power ratio D / C exceeds 1.5, crystal warpage (bending) occurs, and the tail portion 3d cannot be trimmed into a clean cone shape. On the other hand, when the heater power ratio D / C ranges from 1.1 to 1.5, tail contraction can be performed, and the tail portion 3d can be fostered.

From the above results, the heater power ratio D / C at the end of the tail portion growth to the start of the tail portion growth satisfies 1.1 to 1.5, and the heater power during the tail portion growth is greater than that at the start of the tail portion growth. When the single crystal was grown, a tail portion having a neat shape could be grown, and crystal warping or cutting and separation of the single crystal from the silicon melt did not occur.

1A, 1B: Single crystal manufacturing device
2: Silicone melt
3: Silicon single crystal (ingot)
3a: Neck part
3b: Shoulder part
3c: Body part
3d: Tail part
10: chamber
10a: main chamber
10b: full chamber
10c: gas inlet
10d: gas outlet
10e: Observation window
11: quartz crucible
12: Susceptor
13: rotating shaft
14: shaft drive mechanism
15: heater
16: Insulation
17: heat shield
17a: opening of the heat shield
17b: bottom of heat shield
17i: inside of heat shield
18: water cooling body
19: wire
20: wire winding mechanism
21: magnetic field generating device
22: CCD camera
23: image processing unit
24: control unit

Claims (20)

A method for producing a silicon single crystal by a Czochralski method for pulling a silicon single crystal from a silicon melt in a quartz crucible,
A body part cultivation process for cultivating a body part whose crystal diameter is kept constant;
And a tail portion cultivation step of cultivating a tail portion whose crystal diameter is gradually reduced.
Cooling the silicon single crystal pulled from the silicon melt by using a water cooling body disposed inside the heat shield as an upper side than a lower end of the heat shield disposed above the quartz crucible,
In the tail portion cultivation step, the silicon single crystal is pulled at the same pulling rate as the pulling rate at the end of the body portion cultivation from the start to the end of the tail portion cultivation, and the body portion of the silicon single crystal is 1020 ° C. Method for producing a silicon single crystal, characterized in that the temperature range from 980 ℃ to within 15 minutes to pass. The method according to claim 1,
The power of the heater for heating the silicon melt is gradually increased from the start of the tail portion to the end, and the power of the heater at the end of the tail portion is started at the start of the tail portion. Method of manufacturing a silicon single crystal to be set to 1.1 times or more and 1.5 times or less of the power of the heater. The method according to claim 1 or 2,
In the tail portion cultivation process, a method of manufacturing a silicon single crystal for raising the quartz crucible so that the gap between the heat shield and the silicon melt becomes constant. The method according to claim 1 or 2,
In the tail portion cultivation step, a method of manufacturing a silicon single crystal maintaining a constant rotational speed of the quartz crucible. The method according to claim 1 or 2,
In the tail portion cultivation step, a method for manufacturing a silicon single crystal that maintains a constant rotational speed of the silicon single crystal. The method according to claim 1 or 2,
In the tail portion growing step, a method of manufacturing a silicon single crystal to apply a magnetic field to the silicon melt.
A method for producing a silicon single crystal by a Czochralski method for pulling a silicon single crystal from a silicon melt in a quartz crucible,
A body part cultivation process for cultivating a body part whose crystal diameter is kept constant;
And a tail portion cultivation step of cultivating a tail portion whose crystal diameter is gradually reduced.
Cooling the silicon single crystal pulled from the silicon melt by using a water cooling body disposed inside the heat shield as an upper side than a lower end of the heat shield disposed above the quartz crucible,
In the tail portion cultivation step, the silicon single crystal is pulled at the same pulling rate as the pulling rate at the end of the body portion cultivation from the start to the end of the cultivation of the tail portion, and the heat shield and the silicon melt. A method of manufacturing a silicon single crystal, characterized in that the quartz crucible is raised so that the interval becomes constant. The method according to claim 7,
The power of the heater for heating the silicon melt is gradually increased from the start of the tail portion to the end, and the power of the heater at the end of the tail portion is started at the start of the tail portion. Method of manufacturing a silicon single crystal to be set to 1.1 times or more and 1.5 times or less of the power of the heater. The method according to claim 7 or 8,
In the tail portion cultivation step, a method of manufacturing a silicon single crystal maintaining a constant rotational speed of the quartz crucible. The method according to claim 7 or 8,
In the tail portion cultivation step, a method for manufacturing a silicon single crystal that maintains a constant rotational speed of the silicon single crystal. The method according to claim 7 or 8,
In the tail portion growing step, a method of manufacturing a silicon single crystal to apply a magnetic field to the silicon melt.
A method for producing a silicon single crystal by a Czochralski method for pulling a silicon single crystal from a silicon melt in a quartz crucible,
A body part cultivation process for cultivating a body part whose crystal diameter is kept constant;
And a tail portion cultivation step of cultivating a tail portion whose crystal diameter is gradually reduced.
Cooling the silicon single crystal pulled from the silicon melt by using a water cooling body disposed inside the heat shield as an upper side than a lower end of the heat shield disposed above the quartz crucible,
In the tail portion growing step, the silicon single crystal is pulled at the same pulling speed as the pulling speed at the end of the body portion growing from the start of the tail portion to the end, and the rotational speed of the quartz crucible is constant. A method for producing a silicon single crystal, characterized in that it is maintained. The method according to claim 12,
The power of the heater for heating the silicon melt is gradually increased from the start of the tail portion to the end, and the power of the heater at the end of the tail portion is started at the start of the tail portion. Method of manufacturing a silicon single crystal to be set to 1.1 times or more and 1.5 times or less of the power of the heater. The method according to claim 12 or 13,
In the tail portion cultivation step, a method for manufacturing a silicon single crystal that maintains a constant rotational speed of the silicon single crystal. The method according to claim 12 or 13,
In the tail portion growing step, a method of manufacturing a silicon single crystal to apply a magnetic field to the silicon melt.
A method for producing a silicon single crystal by a Czochralski method for pulling a silicon single crystal from a silicon melt in a quartz crucible,
A body part cultivation process for cultivating a body part whose crystal diameter is kept constant;
And a tail portion cultivation step of cultivating a tail portion whose crystal diameter is gradually reduced.
Cooling the silicon single crystal pulled from the silicon melt by using a water cooling body disposed inside the heat shield as an upper side than a lower end of the heat shield disposed above the quartz crucible,
In the tail portion cultivation step, the silicon single crystal is pulled at the same pulling speed as the pulling speed at the end of the body portion cultivation from the start to the end of the tail portion cultivation, and the rotational speed of the silicon single crystal is constant. A method for producing a silicon single crystal, characterized in that it is maintained. The method according to claim 16,
The power of the heater for heating the silicon melt is gradually increased from the start of the tail portion to the end, and the power of the heater at the end of the tail portion is started at the start of the tail portion. Method of manufacturing a silicon single crystal to be set to 1.1 times or more and 1.5 times or less of the power of the heater. The method according to claim 16 or 17,
In the tail portion growing step, a method of manufacturing a silicon single crystal to apply a magnetic field to the silicon melt.
A method for producing a silicon single crystal by a Czochralski method for pulling a silicon single crystal from a silicon melt in a quartz crucible,
A body part cultivation process for cultivating a body part whose crystal diameter is kept constant;
And a tail portion cultivation step of cultivating a tail portion whose crystal diameter is gradually reduced.
Cooling the silicon single crystal pulled from the silicon melt by using a water cooling body disposed inside the heat shield as an upper side than a lower end of the heat shield disposed above the quartz crucible,
In the tail portion cultivation step, the pulling of the silicon single crystal at the same pulling rate as the pulling rate at the end of the body portion cultivation from the beginning to the end of the cultivation of the tail portion and applying a magnetic field to the silicon melt. A method for producing a silicon single crystal characterized by the above-mentioned. The method according to claim 19,
The power of the heater for heating the silicon melt is gradually increased from the start of the tail portion to the end, and the power of the heater at the end of the tail portion is started at the start of the tail portion. Method of manufacturing a silicon single crystal to be set to 1.1 times or more and 1.5 times or less of the power of the heater.

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