JP5176101B2 - Silicon single crystal manufacturing method and apparatus, and silicon single crystal ingot - Google Patents

Description

The present invention relates to a silicon single crystal manufacturing method, a silicon single crystal manufacturing apparatus, and a silicon single crystal ingot manufactured by the apparatus and method, in which the silicon single crystal is pulled up using the CZ method (Czochralski method) or the like. It is.

(Conventional technology)
In the CZ method (Czochralski method), a melt is stored in a crucible in a CZ furnace, a dopant is supplied to the melt, and a silicon single crystal to which the dopant is added is pulled from the melt by a pulling mechanism and grown. It is to let you.

In order to give N-type electrical characteristics to a silicon single crystal, arsenic As, phosphorus P, antimony S
An n-type dopant (impurity) such as b is added to the silicon single crystal. Among these dopants, arsenic As and phosphorus P are sublimable dopants and sublimate from the solid phase to the gas phase at a relatively low temperature. Therefore, the containment chamber containing these sublimable dopants is lowered to a predetermined position above the melt in the CZ furnace, and the dopant is heated and sublimated by the radiant heat radiated from the melt. A method of adding a dopant to a silicon crystal by introducing the dopant into the melt has been conventionally performed.

One of the methods for introducing the gaseous dopant into the melt is to place the open end of the supply pipe above a predetermined position above the melt and use an inert gas such as argon gas as a carrier gas for transport. There is a method in which a dopant transported by a carrier gas is introduced into the melt by blowing a carrier gas from the supply pipe toward the melt. As another method, there is a method in which the introduction tube is immersed in the melt, and the dopant is sublimated from the introduction tube into a gas and charged into the melt.

(Prior art found in Patent Document 1)
In Patent Document 1, the storage container is disposed at a position that does not interfere with the pulling mechanism, the storage container is lowered to a position above the upper surface of the quartz crucible, and the inside of the storage section is radiated from the melt at that position. The dopant is dissolved. Then, the container is further lowered to a position where the container is immersed in the melt, and the dissolved dopant is introduced into the melt from the open surface of the container. In Patent Document 1, a dopant is introduced into the melt in the course of the pulling process to pull up and grow a silicon single crystal ingot having different specific resistance ranges discontinuously in the growth axis direction. The invention of obtaining a product having a dopant concentration according to the above is described.
JP 2005-336020 A

In order to obtain a silicon single crystal ingot with low resistivity and high concentration N ++ type electrical characteristics, a silicon single crystal with a high concentration of an N type dopant such as arsenic As, phosphorus P, antimony Sb, etc. It is necessary to add to.

However, when pulling up such an N ++ type silicon single crystal, if the dopant concentration to be supplied to the melt before pulling is made high, from the shoulder process of the pulling process to the first half of the straight body process In the meantime, it has been clarified by the present inventors that the crystal collapse frequently occurs.

The present invention has been made in view of such circumstances, and stably pulls up a low resistivity N ++ type silicon single crystal doped with a high concentration without causing crystal collapse. The problem to be solved is to make it possible.

Although Patent Document 1 describes that the dopant is introduced into the melt in the course of the pulling process, it is not an invention targeting an N ++ type silicon single crystal as in the present invention, Further, no problem has been pointed out that crystal collapse occurs when pulling up an N ++ type silicon single crystal.

Further, in the process in which the present inventor can make the present invention, when a dipping method is adopted in which the supply pipe is immersed in the melt and sublimated from the supply pipe to form a gas, the dopant is introduced into the melt. It became clear that the single crystal crystallization rate of the silicon single crystal was hindered and it was difficult to grow the silicon single crystal stably.

Therefore, the present invention is capable of stably growing without increasing the single crystallization rate when pulling up a low resistivity N ++ type silicon single crystal doped with a high concentration of dopant. It is a problem to be solved.

The first invention is
A method for producing a silicon single crystal in which a dopant is supplied to a melt stored in a crucible in a furnace, and the silicon single crystal to which the dopant is added is pulled from the melt to grow a silicon single crystal,
When manufacturing a silicon single crystal doped with a dopant at a high concentration,
Until the first half of the straight body of the silicon single crystal was formed, the dopant was added at a low concentration or the dopant was not added, and the first half of the straight body of the silicon single crystal was formed. Thereafter, the dopant is supplied to the melt so that the dopant is added in a desired high concentration.

The second invention is the first invention,
The dopant is a sublimable dopant and is characterized in that the sublimated dopant is supplied to the melt by spraying the sublimated dopant onto the melt.

The third invention is the first invention,
An N ++ type silicon single crystal is produced by adding a dopant at a high concentration.

The fourth invention is the second invention,
An N ++ type silicon single crystal is produced by adding As or P as a dopant at a high concentration.

5th invention manufactures the silicon single crystal which supplies a dopant to the melt stored in the crucible in the furnace, and pulls up the silicon single crystal to which the dopant is added from the melt by a pulling mechanism to grow the silicon single crystal In the device
An apparatus for producing a silicon single crystal doped with a dopant at a high concentration,
A dopant supply device is arranged at a position not interfering with the silicon single crystal and the pulling mechanism,
Until the first half of the straight body of the silicon single crystal is formed, the dopant is added at a low concentration, or the dopant is not added,
After the first half of the straight body of the silicon single crystal is formed, the dopant is supplied to the melt using the dopant supply device so that the dopant is added at a desired high concentration. Features.

A sixth invention is the fifth invention,
The dopant is a sublimable dopant,
The dopant supply device is disposed at a position where the supply pipe is not immersed in the melt, and the dopant sublimated from the supply pipe is blown to the melt to guide the sublimated dopant to the melt. .

A seventh invention is the fifth invention,
An N ++ type silicon single crystal is produced by adding a dopant at a high concentration.

In an eighth aspect based on the sixth aspect,
An N ++ type silicon single crystal is produced by adding As or P as a dopant at a high concentration.

The ninth invention
From the shoulder part to the front half of the straight body part, the dopant is added at a low concentration, or the dopant is not added, and from the front part of the straight body part to the tail part,
The silicon single crystal ingot is characterized in that a dopant is added at a high concentration and an N ++ type electrical characteristic with a low resistivity is obtained.

The tenth invention is
A silicon single crystal ingot to which As or P is added as a dopant,
From the shoulder to the front half of the straight body part, the dopant is added at a low concentration or no dopant is added, and from the front half of the straight body part to the tail part, the dopant is highly concentrated. It is a silicon single crystal ingot which is in a state of being added to and can obtain N ++ type electrical characteristics with a low resistivity.

When dopant 23 is added to silicon single crystal 6 at a high concentration and an N ++ type silicon single crystal having a low resistivity is to be pulled and grown, a large amount of dopant 2 necessary for the high concentration is obtained.
It has been clarified by the present inventors that when the crystal is pulled up after 3 is introduced into the melt 5, the crystal is liable to collapse. In order not to cause crystal collapse, the dopant 23 is added at a low concentration or the dopant 23 is not added until the first half of the straight body portion of the silicon single crystal 6 is formed. After the first half of the straight body of the silicon single crystal 6 is formed,
It has been clarified by the present inventor that the dopant may be supplied to the melt so that the dopant 23 is added at a desired high concentration. This is considered to be because when a large amount of dopant 23 was introduced into the melt 5 before crystal growth, abnormal growth occurred due to local variations in the dopant concentration in the melt 5. In this specification, “low resistivity N
The “++ type silicon single crystal” means an N type silicon single crystal having a specific resistance value smaller than 0.01 Ω · cm.

Therefore, in the present invention, the dopant 23 is added to the melt 5 so that the dopant concentration until the front half of the straight body portion of the silicon single crystal 6 is formed is low or not added.
Supply. Here, the low concentration means that the concentration of the dopant 23 in the silicon single crystal 6 is 1.6E.
The concentration is 19 atoms / cm 3 or less, and the specific resistance value of the silicon single crystal 6 is 4 mΩ-cm or more (high resistance).

After the first half of the straight body portion of the silicon single crystal 6 is formed, the dopant 23 is supplied to the melt 5 so that each portion of the crystal is in a state where the dopant 23 is added at a desired high concentration. .

According to the present invention, the low resistivity N ++ type silicon single crystal 6 to which the dopant 23 is added at a high concentration can be pulled up stably without causing crystal collapse.

In the second invention, the dopant 23 is a sublimable dopant, and the sublimated dopant 23 is supplied to the melt 5 by spraying the sublimated dopant 23 onto the melt 5.

According to the second light, the dopant 23 is introduced into the melt 5 by the spraying method described above. Such a spraying method is less likely to cause crystal collapse than a dipping method and can stably grow a single crystal. This is because when the supply pipe 22 is immersed in the melt 5, liquid vibration occurs in the melt 5, the liquid temperature decreases, or a change in the convection of the melt 5 occurs. This is thought to be because it becomes difficult to inhibit the single crystallization rate of the crystal and to stably grow the single crystal. For this reason, compared with the dipping method, the spraying method tends to cause crystal collapse in the first place.
It is suitable for application when pulling and growing a high concentration, low resistivity N ++ type silicon single crystal 6. According to the present invention, when pulling up the low resistivity N ++ type silicon single crystal 6 to which the dopant 23 is added at a high concentration, the single crystallization rate can be stably grown without being hindered. become able to.

In the third invention, the N ++ type silicon single crystal 6 is manufactured by adding the dopant 23 at a high concentration.

In the fourth invention, N ++ type silicon single crystal 6 is manufactured by adding As or P as dopant 23 at a high concentration.

The fifth invention is an apparatus for producing a silicon single crystal 6 to which a dopant 23 is added at a high concentration. As shown in FIG. 1, the dopant supply apparatus 20 interferes with the silicon single crystal 6 and the pulling mechanism 4. It is placed in a position that does not. This makes it possible to introduce the sublimated dopant 23 to the melt 5 while pulling up the silicon single crystal 6. Similar to the first invention, the dopant 23 is added at a low concentration or the dopant 23 is not added until the first half of the straight body portion of the silicon single crystal 6 is formed. Then, after the first half of the straight body portion of the silicon single crystal 6 is formed, the sublimated dopant 23 is introduced into the melt 5 while pulling up the silicon single crystal 6 using the dopant supply device 20, The dopant 23 is added in a desired high concentration.

  The sixth invention is an apparatus invention corresponding to the method invention of the second invention.

The seventh invention is an apparatus invention corresponding to the method invention of the third invention.

The eighth invention is an apparatus invention corresponding to the method invention of the fourth invention.

The ninth invention is a silicon single crystal 6 manufactured by the apparatus of the third invention or the method of the seventh invention, and is a state in which the dopant 23 is added at a low concentration from the shoulder to the front half of the straight body. , Dopant 23 is not added, and from the first half of the straight body part to the tail part,
The silicon single crystal ingot 6 is characterized in that the dopant 23 is added at a high concentration and an N ++ type electrical characteristic with a low resistivity is obtained.

A tenth invention is a silicon single crystal 6 manufactured by the apparatus of the fourth invention or the method of the eighth invention, and is a silicon single crystal ingot 6 to which As or P is added as a dopant 23, from the shoulder. Up to the first half of the straight body portion, the dopant 23 is added at a low concentration or the dopant 23 is not added, and the dopant 23 is highly concentrated from the first half of the straight body portion to the tail portion. The silicon single crystal ingot 6 is characterized in that it is in a state of being added to and can obtain N ++ type electrical characteristics with low resistivity.

  Hereinafter, an apparatus according to an embodiment will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a side view of the configuration of the apparatus according to the first embodiment.

As shown in FIG. 1, a single crystal pulling apparatus 1 of the first embodiment includes a CZ furnace (chamber) 2 as a single crystal pulling vessel.

In the CZ furnace 2, a crucible 3 for melting a polycrystalline silicon (Si) raw material and storing it as a melt 5 is provided. The crucible 3 is made of quartz, for example. Around the crucible 3,
A heater 9 for heating and melting the raw material in the crucible 3 is provided.

  A heat insulating cylinder 13 is provided between the heater 9 and the inner wall of the CZ furnace 2.

A pulling mechanism 4 is provided above the crucible 3. The pulling mechanism 4 includes a pulling cable 4a and a seed crystal holder 4b at the tip of the pulling cable 4a. The seed crystal is gripped by the seed crystal holder 4b.

The raw material is heated and melted in the crucible 3. When the melting is stabilized, the pulling mechanism 4 operates and the silicon single crystal (silicon single crystal ingot) 6 is pulled from the melt 5 by the CZ method. That is, the pulling cable 4 a is lowered and the seed crystal held by the seed crystal holder 4 b at the tip of the pulling cable 4 a is immersed in the melt 5. After the seed crystal is adjusted to the melt 5, the pulling cable 4a rises. As the seed crystal held by the seed crystal holder 4b rises, the silicon single crystal 6 grows. When pulling up, the crucible 3 is rotated by the rotary shaft 10. The pulling cable 4a of the pulling mechanism 4 rotates in the opposite direction or the same direction as the rotating shaft 10. Further, the rotary shaft 10 can be driven in the vertical direction, and the crucible 3 can be moved up and down to be positioned at an arbitrary upward position.

By shutting off the outside air from the CZ furnace 2, the inside of the furnace 2 is maintained in a vacuum (for example, about several tens of Torr). That is, argon gas 7 as an inert gas is supplied to the CZ furnace 2 and is exhausted from the exhaust port of the CZ furnace 2 by a pump. Thereby, the inside of the furnace 2 is depressurized to a predetermined pressure.

  Various evaporants are generated in the CZ furnace 2 during the single crystal pulling process (one batch).

Therefore, the argon gas 7 is supplied to the CZ furnace 2 and exhausted together with the evaporated substance outside the CZ furnace 2 to remove the evaporated substance from the CZ furnace 2 and clean it. The supply flow rate of the argon gas 7 is set for each process in one batch.

As the silicon single crystal 6 is pulled up, the melt 5 decreases. As the melt 5 decreases, the area of contact between the melt 5 and the crucible 3 changes, and the amount of oxygen dissolved from the crucible 3 changes. This change affects the oxygen concentration distribution in the pulled silicon single crystal 6.

A heat shielding plate 8 (gas rectifying cylinder) is provided above the crucible 3 and around the silicon single crystal 6. The heat shielding plate 8 guides an argon gas 7 as a carrier gas supplied from above into the CZ furnace 2 to the center of the melt surface 5a, and further passes through the melt surface 5a so that the peripheral portion of the melt surface 5a. Lead to. And the argon gas 7 together with the gas evaporated from the melt 5,
It is discharged from an exhaust port provided in the lower part of the CZ furnace 2. For this reason, the gas flow rate on the liquid surface can be stabilized, and the oxygen evaporated from the melt 5 can be maintained in a stable state.

Further, the heat shielding plate 8 is composed of a seed crystal and a silicon single crystal 6 grown by the seed crystal.
Heat insulation and shielding are performed from radiant heat generated in high-temperature parts such as the crucible 3, the melt 5 and the heater 9. Further, the heat shield plate 8 is formed of impurities (for example, silicon oxide) generated in the silicon single crystal 6 in the furnace.
And the like to prevent the single crystal growth from being hindered. The lower end of the heat shielding plate 8 and the melt surface 5a
The distance D can be adjusted by raising and lowering the rotary shaft 10 and changing the vertical position of the crucible 3. Further, the distance D may be adjusted by moving the heat shielding plate 8 in the vertical direction by the lifting device.

Next, the configuration of the dopant supply apparatus of the apparatus of this embodiment will be described.

In this embodiment, arsenic As or phosphorus P is added to the silicon single crystal 6 as an N-type dopant (impurity) in order to give the silicon single crystal 6 N-type electrical characteristics. These dopants arsenic As and phosphorus P are sublimable dopants, and sublimate from the solid phase to the gas phase at a relatively low temperature.

As shown in FIG. 1, the dopant supply apparatus 20 includes a storage chamber 21, a supply pipe 22, a carrier gas introduction pipe 24, and a flow rate adjustment apparatus 25. In the storage chamber 21, a sublimable dopant 23 is stored. The supply pipe 22 communicates with the storage chamber 21, and guides the sublimated dopant 23 to the melt 5 when the dopant 23 in the storage chamber 21 is sublimated. The introduction pipe 24 is
A carrier gas 17 for transporting dopants, which is in communication with the storage chamber 21 and is supplied from a gas supply source (not shown), is introduced into the storage chamber 21. The carrier gas 17 is a sublimated dopant 2
3 is prevented from staying in the storage chamber 21, and the sublimated dopant 23 is efficiently guided to the melt 5 through the supply pipe 22.

The accommodation chamber 21, the supply pipe 22, and the carrier gas introduction pipe 24 of the dopant supply device 20 are made of, for example, quartz.

The flow rate adjusting device 25 passes through the introduction pipe 24 and is introduced into the storage chamber 21, and the supply pipe 22 is connected to the melt 5.
The flow rate (mass flow rate) of the carrier gas 17 heading toward is adjusted. The flow rate is adjusted by adjusting the opening area of the valve. The carrier gas 17 is an inert gas such as argon gas.

FIG. 2 is a cross-sectional view taken along line AA of the storage chamber 21 of the dopant supply apparatus 20 shown in FIG.

The heater 30 as a heating means is formed in an annular shape so as to surround the housing chamber 21, and heats the dopant 23 in the housing chamber 21. As the heater 30, for example, a resistance heating type heater is used.

The storage chamber 21 is provided with a load cell 26 as a scale for detecting the weight of the dopant 23. The sublimation speed of the dopant 23 can be captured as a change in the weight of the dopant 23 in the storage chamber 21 that changes as the dopant 23 evaporates. For this reason, the sublimation speed is measured from the detection result of the load cell 26.

The controller 40 as a control means controls the heating amount by the heater 30 so that the dopant 23 is sublimated at a desired sublimation speed.

While the sublimated dopant 23 is supplied to the melt 5, the controller 40 monitors the weight of the dopant 23 in the storage chamber 21 detected by the load cell 26, and the amount of change in the dopant weight is actually measured for the dopant 23. The sublimation speed of the heater 30 is fed back, and the electric power applied to the heater 30 is adjusted so that the actual sublimation speed fed back matches the target sublimation speed to control the amount of dopant heating by the heater 30, and the flow rate adjustment device 25 The flow rate of the carrier gas 17 is controlled by adjusting the opening area of the valve. Control is performed so that the power applied to the heater 30 is reduced and the flow rate of the carrier gas 17 is reduced as the weight change of the dopant 23 in the storage chamber 21 is increased. The flow rate of the carrier gas 17 may be maintained at a constant value.

As shown in FIG. 1, the dopant supply device 20 includes a silicon single crystal 6 and a pulling mechanism 4.
It is arranged at a position where it does not interfere with. For this reason, it is possible to guide the sublimated dopant 23 to the melt 5 while pulling up the silicon single crystal 6.

The dopant supply device 20 is disposed at a position where the supply pipe 22 is not immersed in the melt 5.

For this reason, the sublimated dopant 23 is sprayed from the supply pipe 22 onto the melt 5.
The sublimated dopant 23 is guided to the melt 5. That is, in this embodiment, the dopant 23 is introduced into the melt 5 by the above-described spraying method.

In the CZ furnace 2, the dopant supply device 20 is configured so that the dopant 23 in the storage chamber 21 is not affected by radiant heat from the melt 5 or the like, and the dopant 23 is blown from the supply pipe 22 to the melt 5. It arrange | positions in the position where the dopant injection | throwing-in efficiency in the melt 5 becomes the maximum. The distance between the open end 22a of the supply pipe 22 and the melt 5 is desirably 10 mm or less.

By the way, when the dopant 23 is added to the silicon single crystal 6 at a high concentration and an N ++ type silicon single crystal having a low resistivity is to be pulled and grown, a large amount of dopant 23 necessary for increasing the concentration is obtained. It has been clarified by the present inventor that when the crystal is pulled up after being introduced into the melt 5, the crystal tends to collapse. In order not to cause crystal collapse, the dopant 23 is added at a low concentration or the dopant 23 is not added until the first half of the straight body portion of the silicon single crystal 6 is formed. After the first half of the straight body portion of the silicon single crystal 6 is formed, the present inventor may supply the dopant to the melt so that the dopant 23 is added in a desired high concentration. It became clear by. This is considered to be because abnormal growth occurred due to local variations in dopant concentration in the melt 5 by introducing a large amount of dopant 23 into the melt 5 before crystal growth.

5, FIG. 6, and FIG. 7 are graphs showing the relationship between the growth position of the silicon single crystal 6 and the frequency of occurrence of crystal breakage.

FIG. 5 is a graph when the dopant concentration in the pulled silicon single crystal 6 becomes 0 atoms / cm 3 without adding the dopant 23 to the melt 5 (non-doping) before crystal growth.

FIG. 5A shows the relationship between the position of the shoulder of the silicon single crystal 6 (shoulder length: unit mm) and the collapse frequency, and FIG. 5B shows the position of the straight body of the silicon single crystal 6. The relationship between (straight trunk length: unit mm) and the collapse frequency is shown. FIG. 5 shows data when the silicon single crystal 6 is pulled up twice.

As can be seen from FIG. 5, no crystal collapse occurred from the shoulder portion of the silicon single crystal 6 to the front half portion of the straight body portion.

FIG. 6 shows that 80 kg of raw material polycrystalline silicon is charged into the crucible 3 and 400 g of As is added as the dopant 23 to the melt 5, and the dopant concentration in the pulled silicon single crystal 6 with a diameter of 200 mm is 1.6E19 atoms. It is a graph when it becomes / cm 3 and the specific resistance value becomes 4 mΩ-cm. FIG. 6A shows the position of the shoulder of the silicon single crystal 6 (shoulder length: unit mm).
FIG. 6B shows the position of the straight body portion of the silicon single crystal 6 (straight body length:
The relationship between the unit mm) and the collapse frequency is shown. FIG. 6 shows data when the silicon single crystal 6 is pulled up 12 times.

As can be seen from FIG. 6, the crystal breakage occurred nine times at the position of 75 mm to 100 mm of the shoulder portion of the silicon single crystal 6, and the crystal breakage occurred twice at the position of 100 mm to 120 mm of the shoulder portion. Crystal breakage occurred once at a position of 0 mm to 25 mm in the straight body portion of No. 6.

FIG. 7 shows that 80 kg of raw material polycrystalline silicon is charged in the crucible 3, 700 g of dopant 23 is charged into the melt 5, and the dopant concentration in the pulled silicon single crystal 6 is 1.
It is a graph when 9E19 atoms / cm3 and the specific resistance value is 3.5 mΩ-cm. 7A shows the relationship between the position of the shoulder of the silicon single crystal 6 (shoulder length: unit mm) and the collapse frequency, and FIG. 7B shows the position of the straight body of the silicon single crystal 6. The relationship between (straight trunk length: unit mm) and the collapse frequency is shown. FIG. 5 shows data when the silicon single crystal 6 is pulled up 26 times.

As can be seen from FIG. 7, the crystal breakage occurred twice at the position of 25 mm to 50 mm of the shoulder portion of the silicon single crystal 6, and the crystal breakage occurred three times at the position of 50 mm to 75 mm of the shoulder portion. Crystal breakage occurred 10 times at a position of 75 mm to 100 mm of 100 mm to 120 m of the same shoulder.
Crystal breakage occurred once at the position of m, and crystal breakage occurred 10 times at a position of 0 mm to 25 mm in the straight body portion of the silicon single crystal 6.

As can be seen from FIGS. 5, 6, and 7, the dopant concentration until the front half of the straight body portion of the silicon single crystal 6 is formed is a low concentration of 1.6E19 atoms / cm 3 or less, that is, the silicon single crystal It can be seen that crystal collapse does not occur in a low concentration state where the specific resistance value of 6 is 4 mΩ-cm or more (high resistance) or in an additive-free (non-doped) state. The dopant concentration until the first half of the straight body of the single crystal 6 is formed is a low concentration of 1.6E19 atoms / cm 3 or less, and the specific resistance value of the silicon single crystal 6 is a low concentration of 4 mΩ-cm or more. Or an additive-free (non-doped) state. And if the dopant 23 is added so that it may become the desired high concentration and low resistance after the first half part of the straight body part where there is no risk of crystal collapse, the silicon single crystal 6 can be pulled up stably without crystal collapse. .

Hereinafter, the control content of the dopant supply amount from the growth start to the growth end of the silicon single crystal 6 will be described.

(Initial doping into melt 5)
Prior to pulling up the silicon single crystal 6, a low-concentration dopant 23 is added to the melt 5 in advance. The addition method of the dopant 23 to the melt 5 performed before the silicon single crystal 6 is pulled may be a conventional addition method that does not use the dopant supply device 20 of the present embodiment, and the dopant supply device of the present embodiment. 20 may be used.

In this way, the melt 5 is doped with the low-concentration dopant 23, and the silicon single crystal 6
Is pulled, the dopant concentration until the first half of the straight body portion of the silicon single crystal 6 is formed becomes low.

(Second half doping to melt 5)
When the first half of the straight body portion of the silicon single crystal 6 is formed, it is melted by using the dopant supply device 20 of this embodiment so that the dopant 23 is added at a desired high concentration thereafter. The dopant 23 sublimated in the liquid 5 is further doped.

The controller 40 starts control of the heater 30 and the flow rate adjusting device 25 from the middle of the pulling so that the dopant 23 is additionally doped into the melt 5 from the middle of the pulling of the silicon single crystal 6.

When a power command is given to the heater 30 from the controller 40, the heater 30 is supplied with power according to the power command and generates heat. When the heater 30 generates heat, the dopant 23 in the storage chamber 21 absorbs heat, and the dopant 23 in the storage chamber 21 is sublimated and evaporated.

When a flow rate command is given from the controller 40 to the flow rate adjusting device 25, the carrier gas 17
Flows from the introduction pipe 24 through the storage chamber 21 through the supply pipe 22 at a flow rate corresponding to the flow rate command, and the supply pipe 2
A carrier gas 17 is sprayed from 2 toward the melt 5.

For this reason, the gaseous dopant 23 sublimated in the storage chamber 21 is conveyed by the carrier gas 17 and sprayed from the supply pipe 22 toward the melt, and the dopant 23 is introduced into the melt 5.

While the dopant 23 is being supplied to the melt 5, the controller 40 loads the load cell 26.
The weight of the dopant 23 detected in step S1 is monitored, the amount of change in the dopant weight is fed back as the actual sublimation speed of the dopant 23, and applied to the heater 30 so that the actual sublimation speed fed back matches the target sublimation speed The flow rate of the carrier gas 17 is controlled by adjusting the electric power to be controlled to control the dopant heating amount by the heater 30 and adjusting the opening area of the valve of the flow rate adjusting device 25.

In this way, the dopant 23 is sublimated at a desired sublimation rate, and a desired concentration of the dopant 23 is further doped into the melt 5. Thereby, each part of the crystal after the first half part of the straight body part of the silicon single crystal 6 is formed is in a state in which the dopant 23 is added at a desired high concentration.

As described above, according to this embodiment, the N ++ type silicon single crystal 6 having a low resistivity to which the dopant 23 is added at a high concentration can be pulled up stably without causing crystal collapse. become able to.

Further, according to the present embodiment, not the radiant heat from the melt 5 or the like, but the heat adjusted by the heater 30 and controlled by the controller 40 is given to the dopant 23 in the storage chamber 21 and the dopant 23 is sublimated. Therefore, in-furnace parts (hot zones) like sublimation by radiant heat
It is not affected by changes over time. This makes it possible to control the sublimation speed very accurately. Therefore, since it becomes possible to apply an optimal amount of heat that is always stable without variation to the dopant 23, the sublimation speed is optimized, the efficiency of introducing the dopant into the melt 5 is maximized, and the dopant concentration of the silicon single crystal 6 is The resistance value can be accurately controlled to a desired high concentration and low resistance value.

When a dopant is added to the silicon single crystal 6 at a high concentration and the N ++ type silicon single crystal 6 having a low resistivity is pulled up and grown, the crystal is liable to break down.
It is possible to accurately control the concentration of the dopant in the silicon single crystal 6 by accurately controlling the sublimation rate of the sublimable dopant 23 such as arsenic As and phosphorus P that gives the silicon single crystal 6 N-type electrical characteristics. Therefore, it can be adjusted accurately so as not to cause crystal collapse.

Further, the dopant supply device 20 is arranged at a position where it does not interfere with the silicon single crystal 6 and the pulling mechanism 4. This makes it possible to guide the sublimated dopant 23 to the melt 5 while pulling up the silicon single crystal 6, and to perform doping during pulling with extremely high accuracy when performing additional doping.

In this embodiment, the dopant supply device 20 is disposed at a position where the supply pipe 22 is not immersed in the melt 5, and the sublimated dopant 23 is sprayed from the supply pipe 22 onto the melt 5, thereby being sublimated. The dopant 23 is guided to the melt 5. Such a spraying method is less likely to cause crystal collapse than a dipping method and can stably grow a single crystal. This is because when the supply pipe 22 is immersed in the melt 5, liquid vibration occurs in the melt 5, the liquid temperature decreases, or a change in the convection of the melt 5 occurs. This is thought to be because it becomes difficult to inhibit the single crystallization rate of the crystal and to stably grow the single crystal. Therefore, the spraying method is suitable for application when pulling and growing a high-concentration, low-resistivity N ++ type silicon single crystal 6 that is prone to crystal collapse in the first place as compared with the dipping method.

(Second embodiment)
In the first embodiment described above, the actual sublimation rate of the dopant 23 (the amount of change in the weight of the dopant 23) is fed back during the supply of the dopant, and the heating amount by the heater 30 so that the actual sublimation rate matches the target sublimation rate. However, this control is only an example, and another control device as shown in FIG. 3 may be used.

Hereinafter, description of the same components as those in the first embodiment will be omitted as appropriate, and different components will be described.

In the control device shown in FIG. 3, the controller 40 adjusts the heating amount in the current batch according to the sublimation speed and the heating amount in the previous batch.

That is, an experiment is performed in advance, and the relationship between the electric power (heating amount) applied to the heater 30 and the sublimation speed is stored in the storage device 41.

The controller 40 reads out the data stored in the storage device 41 and gives a power command to the heater 30 so as to obtain a power corresponding to a desired sublimation speed for one batch, and adjusts the power applied to the heater 30. To do. Note that the flow rate of the carrier gas 17 is maintained at a constant value during one batch. During one batch, the weight of dopant 23 is monitored at load cell 26,
The actual sublimation speed for one batch is stored in the storage device 42, and the actual power (heating amount) applied to the heater 30 is stored in the storage device 42.

In the next batch, the controller 40 reads the actual sublimation speed and the actual power (heating amount) in the previous batch stored in the storage device 42, and these and the sublimation speed and power (heating) stored in the storage device 41. The power applied to the heater 30 is corrected by comparing the corresponding relationship with the amount), and the corrected power is applied to the heater 30. If the actual sublimation speed in the current batch is faster than the actual sublimation speed in the previous batch, the electric power applied to the heater 30 is decreased accordingly. In this way, the dopant 23 is sublimated at a desired sublimation rate, and a desired concentration of the dopant 23 is further doped into the melt 5.

(Third embodiment)
In the second embodiment described above, the actual sublimation speed of the previous batch is fed back to the current batch to control the power applied to the heater 30, but the sublimation speed and the heater power value obtained in advance in the experiment are controlled. May be controlled so that a fixed electric power corresponding to a desired sublimation speed is applied to the heater 30.

Hereinafter, the same components as those in the first embodiment and the second embodiment will not be described as appropriate, and different components will be described. In the control device shown in FIG. 4, the controller 40 obtains the relationship between the sublimation speed and the heating amount (electric power) in advance, and controls the heating amount (electric power) according to the previously obtained relationship.

That is, an experiment is performed in advance, and the relationship between the electric power (heating amount) applied to the heater 30 and the sublimation speed is stored in the storage device 41.

The controller 40 reads out the data stored in the storage device 41 and gives a power command to the heater 30 so as to obtain a power corresponding to a desired sublimation speed for one batch, and adjusts the power applied to the heater 30. To do. Note that the flow rate of the carrier gas 17 is maintained at a constant value during one batch.

In this way, the dopant 23 is sublimated at a desired sublimation rate, and a desired concentration of the dopant 23 is further doped into the melt 5.

By the apparatus of each embodiment or the method of each embodiment as described above, the dopant 23 is added at a low concentration from the shoulder portion to the front half portion of the straight body portion, and the front half portion of the straight body portion. Thereafter, up to the tail portion, dopant 23 is added in a high concentration, and N ++ having a low resistivity is obtained.
A silicon single crystal ingot 6 that can obtain the electrical characteristics of the mold was manufactured.

In each of the above embodiments, the dopant 23 is added at a low concentration from the shoulder portion to the first half portion of the straight body portion, but from the shoulder portion to the first half portion of the straight body portion, the dopant 23 is present. It is good also as an additive-free (non-dope) state. In this case, the dopant 23 is not added from the shoulder to the front half of the straight body by the apparatus of each embodiment or the method of each embodiment. The silicon single crystal ingot 6 in which the dopant 23 is added at a high concentration and an N ++ type electrical characteristic with a low resistivity is obtained is manufactured.

In each of the above-described embodiments, the dopant 23 is supplied to the melt 5 by a spraying method, but the dopant 23 may be supplied to the melt 5 using an immersion method. Even when the dipping method is used, the accommodation chamber 21 needs to be arranged at a position that is not easily affected by the radiant heat from the melt 5.

In the present embodiment, the dopant supply device 20 is arranged at a position where it does not interfere with the silicon single crystal 6 and the pulling mechanism 4, and the sublimated dopant 23 is added while pulling up the silicon single crystal 6 when performing additional doping. Although it guide | induces to the melt 5, you may arrange | position the dopant supply apparatus 20 in the position where the silicon single crystal 6 and the pulling mechanism 4 are arrange | positioned.

For example, before the crystal growth, the dopant supply device 20 is arranged at the place where the pulling mechanism 4 is arranged, and the dopant 23 is introduced into the melt 5 by the dopant supply device 20.
Thereafter, it is possible to remove the dopant supply device 20 and place the pulling mechanism 4 at the place where the dopant supply device 20 is arranged to pull up and grow the silicon single crystal 6.

FIG. 1 is a side view showing the apparatus configuration of the first embodiment. 2 is a cross-sectional view showing a cross section of the dopant supply apparatus shown in FIG. FIG. 3 is a side view showing the apparatus configuration of the second embodiment. FIG. 4 is a side view showing a device configuration of the third embodiment. FIG. 5 is a graph showing the relationship between the breakage position of the silicon single crystal and the frequency of the breakage of the crystal. FIG. 6 is a graph showing the relationship between the location where the silicon single crystal collapses and the frequency at which the crystal collapse occurred. FIG. 7 is a graph showing the relationship between the breakage position of the silicon single crystal and the frequency at which the breakage of the crystal occurred.

Explanation of symbols

1 Single crystal pulling device, 2 CZ furnace, 3 crucible, 5 melt, 20 dopant supply device, 23 dopant, 30 heater, 40 controller

Claims (10)

A method for producing a silicon single crystal in which a dopant is supplied to a melt stored in a crucible in a furnace, and the silicon single crystal to which the dopant is added is pulled from the melt to grow a silicon single crystal,
When manufacturing a silicon single crystal doped with a dopant at a high concentration,
Until the first half of the straight body of the silicon single crystal was formed, the dopant was added at a low concentration or the dopant was not added, and the first half of the straight body of the silicon single crystal was formed. Thereafter, the dopant is supplied to the melt so that the dopant is added in a desired high concentration. A method for producing a silicon single crystal, comprising: 2. The method for producing a silicon single crystal according to claim 1, wherein the dopant is a sublimable dopant, and the sublimated dopant is supplied to the melt by spraying the sublimated dopant onto the melt. The method for producing a silicon single crystal according to claim 1, wherein an N ++ type silicon single crystal is produced by adding a dopant at a high concentration. The method for producing a silicon single crystal according to claim 2, wherein an N ++ type silicon single crystal is produced by adding As or P as a dopant at a high concentration. In a silicon single crystal manufacturing apparatus in which a dopant is supplied to a melt stored in a crucible in a furnace, and a silicon single crystal to which a dopant is added from the melt is pulled by a pulling mechanism to grow a silicon single crystal.
An apparatus for producing a silicon single crystal doped with a dopant at a high concentration,
A dopant supply device is arranged at a position not interfering with the silicon single crystal and the pulling mechanism,
Until the first half of the straight body of the silicon single crystal is formed, the dopant is added at a low concentration, or the dopant is not added,
After the first half of the straight body of the silicon single crystal is formed, using the dopant supply device,
An apparatus for producing a silicon single crystal, wherein the dopant is supplied to the melt so that the dopant is added in a desired high concentration. The dopant is a sublimable dopant,
The dopant supply device is disposed at a position where the supply pipe is not immersed in the melt, and the dopant sublimated from the supply pipe is blown to the melt to guide the sublimated dopant to the melt. 6. The apparatus for producing a silicon single crystal according to claim 5. 6. The apparatus for producing a silicon single crystal according to claim 5, wherein an N ++ type silicon single crystal is produced by adding a dopant at a high concentration. The apparatus for producing a silicon single crystal according to claim 6, wherein an N ++ type silicon single crystal is produced by adding As or P as a dopant at a high concentration. From the shoulder part to the front half of the straight body part, the dopant is added at a low concentration, or the dopant is not added, and from the front part of the straight body part to the tail part,
A silicon single crystal ingot in which a dopant is added at a high concentration and an N ++ type electrical characteristic with a low resistivity is obtained. A silicon single crystal ingot to which As or P is added as a dopant, from the shoulder portion to the front half of the straight body portion, the dopant is added at a low concentration or the dopant is not added. In addition, a silicon single crystal ingot in which a dopant is added in a high concentration from the first half of the straight body part to the tail part, and an N ++ type electrical characteristic with a low resistivity is obtained.

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