JP6973366B2 - Manufacturing method of single crystal silicon ingot and silicon single crystal pulling device - Google Patents

Description

The present invention relates to a method for manufacturing a single crystal silicon ingot and a silicon single crystal pulling device.

A silicon wafer used as a substrate for a semiconductor device is manufactured by thinly slicing an ingot of a silicon single crystal and finally cleaning it through a surface grinding (wrapping) step, an etching step, and a mirror polishing (polishing) step. A silicon single crystal having a large diameter of 300 mm or more is generally manufactured by the Czochralski (CZ) method.

FIG. 4 shows a conventional silicon single crystal pulling device 400 that manufactures a single crystal silicon ingot by the CZ method. The outer shell of the silicon single crystal pulling device 400 is composed of a chamber 10, and a crucible 16 is arranged at the center thereof. The crucible 16 has a double structure, is composed of an inner quartz crucible 16A and an outer graphite crucible 16B, and is fixed to the upper end of a shaft 18 that can be rotated and moved up and down by a shaft drive mechanism 20.

A resistance heating type tubular heater 24 is disposed on the outside of the crucible 16 so as to surround the crucible 16, and a heat insulating body 26 is disposed on the outside thereof along the inner surface of the chamber 10. Further, above the rutsubo 16, a pull-up wire 30 for holding the seed chuck 28 holding the seed crystal S at the lower end is arranged coaxially with the shaft 18, and the wire elevating mechanism 32 reverses the pull-up wire 30 to the shaft 18. It moves up and down while rotating at a predetermined speed in the same direction or in the same direction.

In the chamber 10, a tubular heat shield 22 is arranged so as to surround the single crystal silicon ingot I being grown above the crucible 16. The heat shield 22 adjusts the incident amount of high-temperature radiant heat from the silicon melt M in the rutsubo 16, the heater 24, and the side wall of the rutsubo 16 with respect to the growing ingot I, and adjusts the incident amount of high-temperature radiant heat to the heat in the vicinity of the crystal growth interface. It adjusts the amount of diffusion and plays a role of controlling the temperature gradient in the pull-up axis X direction of the central portion and the outer peripheral portion of the single crystal silicon ingot I.

A gas introduction port 12 for introducing an inert gas such as Ar gas into the chamber 10 is provided in the upper part of the chamber 10. Further, a gas discharge port 14 is provided at the bottom of the chamber 10 to suck and discharge the gas in the chamber 10 by driving a vacuum pump (not shown). The inert gas introduced into the chamber 10 from the gas introduction port 12 descends between the growing single crystal silicon ingot I and the heat shield 22, and the lower end of the heat shield 22 and the liquid of the silicon melt M. After flowing through the gap with the surface, it flows toward the outside of the heat shield 22 and further toward the outside of the rutsubo 16, and then descends outside the rutsubo 16 and is discharged from the gas discharge port 14.

Using this silicon single crystal pulling device 400, a silicon raw material such as polycrystalline silicon filled in the crucible 16 is melted by heating the heater 24 while the inside of the chamber 10 is maintained in an Ar gas atmosphere under reduced pressure, and the silicon is silicon. Form the melt M. Next, the pulling wire 30 is lowered by the wire elevating mechanism 32, the seed crystal S is landed on the silicon melt M, and the pulling wire 30 is pulled upward while rotating the rutsubo 16 and the pulling wire 30 in a predetermined direction. , Ingot I is grown below the seed crystal S. As the growth of the ingot I progresses, the amount of the silicon melt M decreases, but the crucible 16 is increased to maintain the level of the melt surface.

A CCD camera 36 is provided in the opening 34 at the top of the chamber 10. The CCD camera 36 images the vicinity of the boundary between the crystal I and the melt M. Since the meniscus formed at the boundary between the crystal and the melt is imaged with higher brightness than the crystal and the melt, the meniscus in the image is referred to as a ring-shaped high-intensity band (hereinafter referred to as "fusion ring"). .) Will manifest itself. The interval between the fusion rings is recognized as the crystal diameter, and the crystal pulling speed and the melt temperature are controlled so that the crystal diameter becomes a desired constant value.

It is known that CO gas is generated in a chamber in the production of a single crystal silicon ingot using such a silicon single crystal pulling device. One of the causes is that CO gas is generated by the reaction between the SiO gas generated from the silicon melt and the graphite material (for example, a tubular heater) existing in the chamber. Patent Document 1 is a technique for measuring the concentration of CO gas in the chamber.

Patent Document 1 describes, "A method for producing a single crystal in which a single crystal is pulled up from a raw material melt obtained by heating and melting a raw material by the Chokralsky method, and the raw material is housed in a quartz rut and housed in the quartz rut. While heating and melting the raw material, the carbon monoxide concentration contained in the exhaust gas discharged during the melting of the raw material is measured, and the melting of the raw material is completed based on the measurement result of the carbon monoxide concentration contained in the exhaust gas during the measured melting of the raw material. A method for producing a single crystal (claim 6), which comprises pulling up a single crystal from the raw material melt after determining that the single crystal has been produced is described.

Japanese Unexamined Patent Publication No. 2017-114709

The present inventors inject carbon into the single crystal silicon ingot manufactured by the conventional silicon single crystal pulling device in the growing process, and as a result, the carbon concentration of the silicon wafer manufactured from the ingot is intended. We focused on the problem of becoming expensive. When the carbon concentration in the silicon wafer is high, defects caused by electrically active carbon called killer defects occur during the device heat treatment process, which causes a problem of shortening the lifetime of the wafer. Further, since high-concentration carbon promotes the formation of oxygen precipitates, if oxygen precipitates are present on the surface of the device, leak defects occur, which causes a decrease in yield. As described above, the contamination of carbon into the single crystal silicon ingot has an adverse effect in the manufacturing process of the semiconductor device. Therefore, the carbon concentration in the single crystal silicon ingot is severely limited by the standard according to the type of device.

It is considered that the reason why the carbon concentration in the crystal increases is that the CO gas generated in the chamber is taken into the silicon melt. In Patent Document 1, the CO gas concentration is measured in the raw material melting step, focusing on the fact that the CO gas concentration in the gas in the chamber becomes maximum when all the raw materials are melted, and the raw material melting step is based on this measured value. The end of (melt completion) is judged. However, Patent Document 1 merely focuses on shortening the process time and preventing the deformation of the quartz crucible by accurately detecting the completion of the melt, and incorporates CO gas into the silicon melt. No attention is paid to the increase in carbon concentration in the crystal caused by this.

In view of the above problems, it is an object of the present invention to provide a method for producing a single crystal silicon ingot and a silicon single crystal pulling device capable of producing a single crystal silicon ingot having a low carbon concentration with a high yield.

In order to solve the above problems, the present inventors have conceived to monitor the CO gas generation rate (CO gas generation amount per unit time) instead of monitoring the CO gas concentration in the gas in the chamber. That is, it is considered that the amount of CO gas taken into the silicon melt has a positive correlation with the amount of CO gas generated per unit time. On the other hand, the CO gas concentration becomes smaller when the flow rate of the inert gas in the chamber is large and the flow rate of the inert gas in the chamber is small even if the amount of CO gas generated per unit time is the same. Will grow in size. In fact, the flow rate of the inert gas differs between the raw material melting step and the crystal growing step, and the flow rate of the inert gas also fluctuates during the crystal growing step. Therefore, the CO gas concentration is not suitable for monitoring as an index for evaluating the amount of CO gas taken into the silicon melt. The present inventors measure the CO gas concentration in the chamber, calculate the CO gas generation rate by multiplying this measured value by the flow rate of the inert gas in the chamber, and monitor this CO gas generation rate. It has been found that the amount of CO gas taken into the silicon melt and the carbon concentration in the crystal can be appropriately evaluated.

The present invention has been completed based on the above findings, and its gist structure is as follows.
(1) A chamber having a gas introduction port for introducing the inert gas at the top and a gas discharge port at the bottom for discharging the gas in the furnace containing the inert gas.
The crucible located in the chamber and
A cylindrical heater located in the chamber so as to surround the crucible,
It is a manufacturing method of a single crystal silicon ingot performed by using a silicon single crystal pulling device having the above.
A raw material melting step of heating and melting the silicon raw material charged into the crucible with the heater to form a silicon melt in the crucible while maintaining the atmosphere of the inert gas in the chamber under reduced pressure.
Subsequently, a crystal growing step of heating and maintaining the silicon melt with the heater to pull up the single crystal silicon ingot from the silicon melt while maintaining the atmosphere of the inert gas under reduced pressure in the chamber.
In the raw material melting step and the crystal growing step
The gas in the furnace was collected and
The CO gas concentration in the collected gas was intermittently measured by a gas analyzer.
The CO gas generation rate is calculated by multiplying the measured CO gas concentration by the flow rate of the inert gas supplied into the chamber.
A method for manufacturing a single crystal silicon ingot, which comprises monitoring the calculated CO gas generation rate.

(2) The maximum value of the CO gas generation rate in the raw material melting step is A (mol / h), and the maximum value of the CO gas generation rate in the straight body step during the crystal growth step is B (mol / h). The method for producing a single crystal silicon ingot according to (1) above, wherein the raw material melting step and the crystal growing step are performed under the condition that A / B ≦ 10 is satisfied.

(3) The method for manufacturing a single crystal silicon ingot according to (1) or (2) above, wherein the collection of the gas in the furnace is performed via an exhaust pipe extending from the gas discharge port.

(4) The gas in the furnace is collected from the space between the cylindrical heat shield provided above the crucible so as to surround the single crystal silicon ingot and the crucible. The method for producing a single crystal silicon ingot according to any one of (3).

(5) The method for producing a single crystal silicon ingot according to any one of (1) to (4) above, wherein the gas analyzer is a quadrupole mass spectrometer.

(6) A chamber having a gas inlet for introducing the inert gas at the top and a gas outlet at the bottom for discharging the gas in the furnace containing the inert gas.
A crucible located in the chamber and accommodating the silicon melt,
Above the crucible, a tubular heat shield provided so as to surround the single crystal silicon ingot pulled up from the silicon melt,
A cylindrical heater located in the chamber so as to surround the crucible and heats the silicon melt.
The exhaust pipe extending from the gas outlet and
A main pump connected to the exhaust pipe, depressurizing the inside of the chamber, and sucking the gas in the furnace into the exhaust pipe.
A main valve provided in the exhaust pipe and opened when depressurizing the inside of the chamber,
A gas sampling port provided in one or both of a portion of the exhaust pipe upstream of the main valve and a space between the heat shield and the rutsubo.
A sub-pipe that extends from the gas sampling port and is connected to a portion of the exhaust pipe downstream of the main valve.
A sub-pump provided in the sub-pipe to suck the gas in the furnace into the sub-pipe,
A gas analyzer provided upstream of the sub-pump of the sub-pipe and intermittently measuring the CO gas concentration in the gas sucked into the sub-pipe.
A flow rate adjusting valve provided upstream of the gas analyzer in the sub-pipe to adjust the flow rate of the gas supplied to the gas analyzer.
A filter provided upstream of the flow rate adjusting valve of the sub-pipe to remove SiO powder in the gas sucked into the sub-pipe.
An intake valve provided in the vicinity of the gas sampling port of the sub-pipe and opened when the gas in the furnace is sucked into the sub-pipe.
And, in addition
A calculation unit that calculates the CO gas generation rate by multiplying the CO gas concentration measured by the gas analyzer by the flow rate of the inert gas supplied into the chamber.
An output device that outputs the calculated CO gas generation rate, and
A silicon single crystal pulling device characterized by having.

(7) The silicon single crystal pulling device according to (6) above, wherein the gas sampling port is provided at a portion upstream of the main valve of the exhaust pipe.

(8) The silicon single crystal pulling device according to (6) or (7) above, wherein the gas sampling port is located in the space between the heat shield and the crucible.

(9) The silicon single crystal pulling device according to any one of (6) to (8) above, wherein the gas analyzer is a quadrupole mass spectrometer.

According to the method for producing a single crystal silicon ingot and the silicon single crystal pulling device of the present invention, it is possible to produce a single crystal silicon ingot having a low carbon concentration with a high yield.

It is sectional drawing along the pulling axis X which shows typically the structure of the silicon single crystal pulling apparatus 100 by 1st Embodiment of this invention. It is sectional drawing along the pulling axis X which shows typically the structure of the silicon single crystal pulling apparatus 200 by 2nd Embodiment of this invention. It is sectional drawing along the pulling axis X which shows typically the structure of the silicon single crystal pulling apparatus 300 by the 3rd Embodiment of this invention. It is sectional drawing along the pulling axis X which shows typically the structure of the conventional silicon single crystal pulling apparatus 400. No. It is a graph which shows the transition of the CO gas generation rate in the raw material melting process and the crystal growth process in 1. It is a graph which shows the particle size distribution of the SiO powder in the gas collected from the inside of a chamber.

(Silicon single crystal pulling device)
With reference to FIGS. 1 to 3, a basic configuration common to the silicon single crystal pulling devices 100, 200, and 300 according to the embodiment of the present invention will be described. Note that these common basic configurations are designated by the same reference numerals in FIGS. 1 to 3.

The silicon single crystal pulling devices 100, 200, and 300 include a chamber 10, a crucible 16, a shaft 18, a shaft drive mechanism 20, a tubular heat shield 22, a tubular heater 24, a tubular heat insulating body 26, and a seed chuck 28. It has a pull-up wire 30, a wire elevating mechanism 32, a CCD camera 36, an exhaust pipe 40, and a main pump 42.

A gas introduction port 12 for introducing an inert gas such as Ar gas into the chamber 10 is provided in the upper part of the chamber 10. Further, a gas discharge port 14 is provided at the bottom of the chamber 10 to suck and discharge the gas in the chamber 10 (hereinafter, referred to as “in-furnace gas”) by driving the main pump 42 (vacuum pump).

The crucible 16 is located in the center of the chamber 10 and houses the silicone melt M. The crucible 16 has a double structure of a quartz crucible 16A and a graphite crucible 16B. The quartz crucible 16A directly supports the silicon melt M on the inner surface. The graphite crucible 16B supports the quartz crucible 16A on the outside of the quartz crucible 16A. As shown in FIGS. 1 to 3, the upper end of the quartz crucible 16A is higher than the upper end of the graphite crucible 16B, that is, the upper end of the quartz crucible 16A protrudes from the upper end of the graphite crucible 16B.

The shaft 18 vertically penetrates the bottom of the chamber 10 and supports the crucible 16 at the upper end. Then, the shaft drive mechanism 20 moves the crucible 16 up and down while rotating the crucible 16 via the shaft 18.

The heat shield 22 is provided above the crucible 16 so as to surround the single crystal silicon ingot I pulled up from the silicon melt M. Specifically, the heat shield 22 includes a shield main body 22A having an inverted truncated cone shape and an inner flange portion 22B extending horizontally from the lower end portion of the shield main body 22A toward the pull-up shaft X side (inside). And an outer flange portion 22C extending horizontally from the upper end portion of the shield main body 22A toward the chamber side (outside), and the outer flange portion 22C is fixed to the heat insulating body 26. The function of the heat shield 22 is as described in the background art section.

The tubular heater 24 is located in the chamber 10 so as to surround the crucible 16. The heater 24 is a resistance heating type heater made of carbon, and is for melting the silicon raw material charged in the crucible 16 to form a silicon melt M and further maintaining the formed silicon melt M. Perform heating.

The tubular heat insulating body 26 is provided below the upper end of the heat shielding body 22 along the inner surface of the chamber 10. In this embodiment, a heat insulating body is further arranged at the bottom of the chamber. The heat insulating material constituting these heat insulating bodies is not particularly limited, and examples thereof include carbon, alumina, and zirconia. The heat insulating body 26 has a function of imparting a heat retaining effect to a region in the chamber 10 particularly below the heat shielding body 22 and facilitating the maintenance of the silicon melt M in the crucible 16. The thickness of the heat insulating body 26 is not particularly limited and can be a general thickness equivalent to that of the conventional one. In a pulling device for growing a crystal having a diameter of 300 mm, a crystal having a diameter of about 30 to 90 mm and a diameter of 450 mm is grown. In the pulling device, it can be about 45 to 100 mm.

Above the rutsubo 16, a pull-up wire 30 that holds the seed chuck 28 that holds the seed crystal S at the lower end is arranged coaxially with the shaft 18, and the wire elevating mechanism 32 moves the pull-up wire 30 in the opposite direction to the shaft 18 or. It moves up and down while rotating at a predetermined speed in the same direction.

A CCD camera 36 is provided in the opening 34 at the top of the chamber 10. The CCD camera 36 images the vicinity of the boundary between the crystal I and the melt M. The crystal pulling speed and the melt temperature are controlled so that the crystal diameter becomes a desired constant value, with the interval between the fusion rings in the obtained image as the crystal diameter.

The exhaust pipe 40 extends from the gas discharge port 14. The main pump 42 can be a vacuum pump such as a dry pump, and is connected to the exhaust pipe 40 to reduce the pressure in the chamber 10 to about 5 to 100 Torr and to suck the gas in the furnace into the exhaust pipe 40. Fulfill. The main valve 44 is provided in the exhaust pipe 40 and serves to switch the pressure in the chamber 10 between normal pressure and reduced pressure. That is, the main valve 44 is closed when the inside of the chamber 10 becomes normal pressure, such as when the inside of the chamber 10 is opened to the atmosphere or when the structure inside the chamber 10 is installed or replaced. On the other hand, when the pressure in the chamber 10 including the raw material melting step and the crystal growing step is reduced, the main valve 44 is opened.

Here, in the raw material melting step and the crystal growing step, CO gas is generated in the chamber 10. The first cause is as follows. That is, from the silicon melt M in the crucible 16, SiO gas is generated by the reaction of the silicon melt M with the inner surface of the quartz crucible 16A. The SiO gas reaches the heater 24 on the flow of the inert gas, and as shown in the following reaction formula, CO gas is generated by the reaction with carbon, which is the material of the heater.
SiO (g) + 2C (s) → CO (g) + SiC (s)
The SiC produced as a by-product is deposited on the surface of the heater 24.

The second cause is as follows. That is, CO gas is generated by the reaction between the quartz crucible 16A and the graphite crucible 16B that are in contact with each other.
SiO ₂ (s) + 3C (s) → 2CO (g) + SiC (s)
The SiC produced as a by-product is deposited between the outer peripheral surface of the quartz crucible 16A and the inner peripheral surface of the graphite crucible 16B.

Each embodiment of the present invention monitors the amount of CO gas generated in the chamber 10 per unit time (that is, the CO gas generation rate) as described above. Hereinafter, the device configuration for that purpose will be described.

[First Embodiment]
With reference to FIG. 1, the present embodiment has a sub-pipe 52 that branches from a portion upstream of the main valve 44 of the exhaust pipe 40 and is connected to a portion downstream of the main valve 44. That is, the gas sampling port 46 is provided at a portion upstream of the main valve 44 of the exhaust pipe 40. The intake valve 54, the filter 58, the flow rate adjusting valve 60, the gas analyzer 62, and the sub pump 64 are attached to the sub-pipe 52 in this order from the upstream. In the present specification, the "upstream" and "downstream" of the exhaust pipe 40 and the sub pipe 52 are related to the flow of gas passing through each pipe.

The sub pump 64 is provided in the sub pipe 52, and sucks the gas in the furnace (strictly speaking, the gas sucked into the exhaust pipe) into the sub pipe 52 through the gas sampling port 46. The sub pump 64 can be configured by, for example, a vacuum pump device that combines a rotary pump and a turbo molecular pump. As described above, the inside of the chamber 10 has a decompression atmosphere of about 5 to 100 Torr, and in order to suck gas from this decompression atmosphere to the sub-pipe 52, it is necessary to create a lower decompression atmosphere in the sub-pipe 52. From this point of view, it is preferable that the pressure in the sub pipe 52 (the part upstream of the filter 58) is set to 1 Torr or less by driving the sub pump 64.

The gas analyzer 62 is provided upstream of the sub pump 64 of the sub pipe 52, and intermittently measures the CO gas concentration in the gas sucked into the sub pipe. Examples of the gas analyzer 62 include a quadrupole mass spectrometer and a gas chromatograph. In the case of a quadrupole mass spectrometer, the measurement interval of CO gas concentration is as short as about 1 second. On the other hand, in the case of a gas chromatography apparatus currently on the market, the measurement interval of the CO gas concentration is at least about 15 minutes. Therefore, in this embodiment, it is preferable to use a quadrupole mass spectrometer.

The flow rate adjusting valve 60 is provided upstream from the gas analyzer 62 of the sub-pipe 52, and plays a role of adjusting the flow rate of the gas supplied to the gas analyzer 62 by adjusting the opening / closing degree. As a result, the gas in the furnace at an appropriate flow rate can be supplied to the gas analyzer 62. The flow rate of the gas supplied to the gas analyzer 62 ^{is preferably 4 × 10 -1} to 4 × 10 ^-4 Pa · L / min.

The filter 58 is provided upstream from the flow rate adjusting valve 60 of the sub-pipe 52 and serves to remove SiO powder in the gas sucked into the sub-pipe 52. The gas contains SiO powder formed by cooling and solidifying the SiO gas generated from the silicon melt M. FIG. 6 shows a graph showing the particle size distribution of SiO powder in a gas collected from a general chamber. As shown in FIG. 6, the general average particle size of the SiO powder is about 13 μm, and the general minimum particle size is 1 μm. Therefore, in the present embodiment, it is preferable to use a gas filter having a mesh size on the order of nanometers, which can remove 99% by mass or more of particles having a particle size of 1 μm or more. Examples of such a gas filter include a wafer guard IISF in-line gas filter manufactured by Nippon Seisen Co., Ltd., a small flow rate filter for a NAS Clean process gas line manufactured by Nippon Seisen Co., Ltd., and the like. By providing the filter 58 upstream of the flow rate adjusting valve 60, the opening / closing failure of the flow rate adjusting valve 60 due to the SiO powder is avoided, and the SiO powder is also prevented from being mixed into the gas analyzer 62.

The intake valve 54 is provided in the vicinity of the gas sampling port 46 of the sub-pipe 52, and is opened when the gas in the furnace is sucked into the sub-pipe 52. In the present embodiment, the CO gas concentration is constantly measured and the CO gas generation rate is monitored during the raw material melting step and the crystal growing step, so that the intake valve 54 is always open. As a result, a part of the gas sucked into the exhaust pipe is taken into the sub pipe 52.

The calculation unit 66 calculates the CO gas generation rate by multiplying the CO gas concentration measured by the gas analyzer 62 by the flow rate of the inert gas supplied into the chamber 10. The arithmetic unit 66 can be configured by a general central processing unit (CPU) or microprocessing unit (MPU). As the flow rate of the inert gas supplied into the chamber 10, the gas flow rate set value may be used.

The output device 68 outputs the CO gas generation rate calculated by the calculation unit 66. The output device 68 can be configured by a general display, a projector, a printer, a speaker, or the like.

In the present embodiment, with the above configuration, the CO gas generation rate of the furnace gas can be monitored in real time instead of the CO gas concentration of the furnace gas. In this way, by monitoring the CO gas generation rate on the spot (in-situ), the amount of CO gas taken into the silicon melt and the carbon concentration in the crystal can be appropriately evaluated.

[Second Embodiment]
With reference to FIG. 2, in the present embodiment, the gas sampling port 48 is located in the space between the heat shield 22 and the crucible 16. That is, the sampling tube 50 is hung from the upper part of the chamber 10, and the gas sampling port 48 at the tip thereof is positioned in the space between the heat shield 22 and the crucible 16. The sampling tube 50 is connected to the sub-pipe 52 outside the chamber 10. The intake valve 56 is provided in the vicinity of the upstream tip of the sub-pipe 52.

In the first embodiment, the gas in the furnace is collected through the exhaust pipe 52, whereas in the present embodiment, the gas in the furnace is collected from the space between the heat shield 22 and the rutsubo 16. be. The filter 58, the flow rate adjusting valve 60, the gas analyzer 62, the sub pump 64, the calculation unit 66, and the output device 68 installed in the sub pipe 52 are the same as those in the first embodiment, and thus the description thereof will be omitted. ..

In this embodiment, the gas in the furnace is collected directly from the upper edge of the quartz crucible. Therefore, the CO gas generated by the reaction between the quartz crucible and the carbon crucible can be directly collected. As a result, the CO gas generation rate can be monitored with higher accuracy.

[Third Embodiment]
With reference to FIG. 3, the present embodiment is a combination of the configuration of the first embodiment and the configuration of the second embodiment. That is, the gas in the furnace is collected through the exhaust pipe 52 and also from the space between the heat shield 22 and the crucible 16.

In the present embodiment, the sub-pipe 52 includes a first sub-pipe 52B, a second sub-pipe 52C, and a third sub-pipe 52D. The first sub-pipe 52B branches from a portion upstream of the main valve 44 of the exhaust pipe 40. The second sub-pipe 52C is connected to the upper end of the sampling tube 50 and extends from the upper part of the chamber. The third sub-pipe 52D is formed by merging the first sub-pipe 52B and the second sub-pipe 52C. The sampling tube 50 and the intake valve are the same as those in the second embodiment. The filter 58, the flow rate adjusting valve 60, the gas analyzer 62, the sub pump 64, the calculation unit 66, and the output device 68 installed in the sub pipe 52C are the same as those in the first embodiment, and thus the description thereof will be omitted. ..

In the present embodiment, the position dependence of CO gas generation can be confirmed by switching the intake valve 54 and the intake valve 56 at an appropriate timing and measuring the CO gas concentration. Specifically, by taking the difference in CO concentration measured at each position, the CO gas concentration generated by the reaction between the quartz crucible and the graphite crucible and the CO gas concentration generated by the reaction between the SiO gas and graphite can be obtained. Can be carved out.

(Manufacturing method of single crystal silicon ingot)
The method for producing a single crystal silicon ingot according to the embodiment of the present invention can be suitably carried out by using the silicon single crystal pulling devices 100, 200, 300 described above. Therefore, a method for manufacturing a single crystal silicon ingot according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. First, a silicon raw material such as a polycrystalline silicon nugget is filled in the rutsubo 16, and the main pump 42 is driven with the main valve 44 open to maintain the inside of the chamber 10 in an inert gas atmosphere such as Ar gas under reduced pressure. do. At this time, the crucible 16 is located below in the chamber 10 so that the silicon raw material does not come into contact with the heat shield 22. After that, the silicon raw material in the crucible 16 is heated by the heater 24 and melted to form the silicon melt M. After that, the crucible 16 is raised to the pulling start position. In the present specification, the "raw material melting step" is defined as the period from the time when the heating by the heater 24 is started to the time when the ascending of the crucible is completed. In the raw material melting step, the flow rate of the inert gas is preferably 10 to 400 L / min.

Next, the pull-up wire 30 is lowered by the wire elevating mechanism 32 to land the seed crystal S on the silicon melt M. Then, while rotating the crucible 16 and the pulling wire 30 in a predetermined direction, the pulling wire 30 is pulled upward to grow the ingot I below the seed crystal S. As the growth of the ingot I progresses, the amount of the silicon melt M decreases, but the crucible 16 is increased to maintain the level of the melt surface. In the present specification, the "crystal growing step" is defined as a period from the time when the pulling wire 30 starts to descend to the time when the growing of the ingot I (the pulling wire 30 rises) is completed.

The crystal growth step, performed aperture seed (necking) First by Dash method for dislocation-free single crystal to form a neck portion I _n. Next, foster shoulder portion I _s to obtain an ingot of the required diameter, the silicon single crystal to grow a cylindrical body portion I _b and a constant diameter upon reaching the desired diameter. After growing the straight body portion _Ib to a predetermined length, a tail drawing (formation of the tail portion) is performed in order to separate the single crystal from the silicon melt M in a dislocation-free state. In the present specification, the growing period of the straight body portion I _b is referred to as a “straight body step”.

In the crystal growth step, the flow rate of the inert gas is preferably 50 to 300 L / min. In the crystal growth step, the flow rate of the non-volatile gas is increased / decreased (variated) with time within the above range.

The present embodiment is characterized in that the following steps are performed in the raw material melting step and the crystal growing step. First, the gas in the furnace is collected. As shown in FIGS. 1 to 3, this step is performed by sucking the gas in the furnace into the sub-pipe 52 from one or both of the gas sampling port 46 and the gas sampling port 48.

Next, the CO gas concentration in the collected gas is intermittently measured by the gas analyzer 62. Then, the calculation unit 66 calculates the CO gas generation rate by multiplying the measured CO gas concentration by the flow rate of the inert gas supplied into the chamber 10. Then, the output device 68 outputs the calculated CO gas generation rate. In the present embodiment, the CO gas generation rate of the furnace gas can be monitored in real time instead of the CO gas concentration of the furnace gas. In this way, by monitoring the CO gas generation rate on the spot (in-situ), the amount of CO gas taken into the silicon melt and the carbon concentration in the crystal can be appropriately evaluated. As described above, the flow rate of the inert gas supplied into the chamber 10 differs between the raw material melting step and the crystal growing step, and also varies during the crystal growing step, but the gas flow rate set value at the time of monitoring. Should be used.

In the present embodiment, the maximum value of the CO gas generation rate in the raw material melting step is A (mol / h), and the maximum value of the CO gas generation rate in the straight body step during the crystal growth step is B (mol / h). The melting step and the crystal growing step are preferably performed under the condition that A / B ≦ 10 is satisfied. Under the condition that A / B ≦ 10 is satisfied, a single crystal silicon ingot having a ^{carbon concentration (Cs) of 2 × 10 15} atoms / cm ³ or less can be produced at all sites having a crystal solidification rate of 0.75 or less. .. That is, a single crystal silicon ingot having a low carbon concentration can be produced with a high yield. The crystal solidification rate (%) is defined as a percentage of the mass of the crystal being pulled up / the mass of the raw material charged. In the first 10 hours of the raw material melting process, the CO gas generation rate is not stable due to degassing from the parts in the chamber. Therefore, in the present specification, the maximum value of the period excluding the initial 10 hours in the raw material melting process is adopted as A.

The value of A / B can be adjusted mainly by controlling the amount of electric power of the heater 24 in the raw material melting step. Generally, in the crystal growth step, the electric power of the heater 24 required to maintain the silicon melt M is naturally determined to be a value within a predetermined range, and the heater is driven by the specific electric power to drive the silicon melt. Maintain M. Therefore, the CO gas generation rate in the crystal growth step is relatively low and stable (there is no large fluctuation). On the other hand, in the raw material melting step, it is necessary to drive the heater 24 with a large amount of electric power in order to melt the silicon raw material, and the CO gas generation rate is relatively high and unstable (largely fluctuates). In particular, the CO gas generation rate tends to increase at the end of the raw material melting process (when the melting is completed). Therefore, A / B ≦ 10 can be realized by controlling the electric power amount of the heater 24 in the raw material melting step to suppress the maximum value A of the CO gas generation rate. However, the values of A and B are not uniquely determined by the amount of electric power of the heater 24, but also depend on the heat insulating property in the chamber 10 (that is, the structure of the chamber, the amount and arrangement of the heat insulating body). ..

The A / B is preferably 1 or more. This is because if the A / B is less than 1, the silicon melt may solidify and crystal growth may not be established.

(Experimental Example 1)
Using the silicon single crystal pulling device having the configuration shown in FIG. 1, a single crystal silicon ingot was manufactured at the four levels shown in Table 1. At each level, the charge amount of the silicon raw material is 320 kg, the diameter of the ingot is 300 mm, the straight body length is 1800 mm, the growth rate is 1.0 mm / min, and the flow rate of Ar gas supplied into the chamber in the raw material melting process is 100 L / min. And said. A gas filter having a mesh size on the order of nanometers capable of removing 99% by mass or more of particles having a particle size of 1 μm or more was used. The amount of heater power in the raw material melting step and the crystal growing step was the value shown in Table 1.

A quadrupole mass spectrometer was used as the gas analyzer, and the CO gas generation rate was monitored in all the raw material melting steps and the crystal growing steps. Table 1 shows the maximum value A of the CO gas generation rate in the raw material melting process and the maximum value B of the CO gas generation rate in the straight body process. In addition, on behalf of all levels, level No. The transition of the CO gas generation rate monitored in 1 is shown in FIG.

At each level, the "low carbon crystal yield" shown in Table 1 was determined by the following procedure. First, a large number of silicon wafers were manufactured by cutting out from the straight body of a single crystal silicon ingot manufactured at each level and processing it. At one central point of each wafer, the concentration of carbon substituted at the crystal position of silicon (Cs concentration) was measured using an FT-IR device. The crystal yield was determined by using the grown crystal length as the denominator and the ^{crystal length satisfying Cs ≦ 2 × 10 15} atoms / cm ³ or less as the numerator, and set it as “low carbon crystal yield”. The results are shown in Table 1.

As is clear from Table 1, the level No. 1 performed under the condition that A / B ≦ 10 was satisfied. In 1 to 4, the low carbon crystal yield was as high as 75% or more, whereas the level No. 1 performed under the condition of A / B = 11. In No. 5, the low carbon crystal yield was significantly reduced to 25%.

(Experimental Example 2)
Depending on the performance and presence of the gas filter, it is possible to continuously monitor the CO gas generation rate without clogging the sub piping (specifically, the flow rate adjustment valve or between the flow rate adjustment valve and the gas analyzer). Time was measured. The manufacturing conditions for the single crystal silicon ingot were the same as in Experimental Example 1 except for the filter.

As Level 1, a gas filter having a mesh size on the order of nanometers, which can remove 99% by mass or more of particles having a particle size of 1 μm or more, was used as in Experimental Example 1. At this level 1, it was possible to continuously monitor the CO gas generation rate for 100 hours or more.

As level 2, a gas filter having a mesh size capable of removing 99% by mass or more of particles having a particle size of 10 μm or more was used. At this level 2, when the CO gas generation rate was continuously monitored for 70 hours, the sub-pipe was clogged and monitoring became impossible.

As level 3, no gas filter was used. At this level 2, when the CO gas generation rate was continuously monitored for 20 hours, the sub-pipe was clogged and monitoring became impossible.

According to the method for producing a single crystal silicon ingot and the silicon single crystal pulling device of the present invention, it is possible to produce a single crystal silicon ingot having a low carbon concentration with a high yield.

100,200,300 Silicon single crystal pulling device 10 Chamber 12 Gas inlet 14 Gas outlet 16 Rutsubo 16A Quartz Rutsubo 16B Graphite Rutsubo 18 Shaft 20 Shaft drive mechanism 22 Thermal shield 22A Shield body 22B Inner flange 22C Outer flange 24 Heater 26 Insulation 28 Seed chuck 30 Pull-up wire 32 Wire elevating mechanism 34 Opening 36 CCD camera 40 Exhaust piping 42 Main pump 44 Main valve 46 Gas sampling port (exhaust piping)
48 Gas sampling port (inside the chamber)
50 Sampling tube (inside the chamber)
52 sub pipe 52A sub pipe end 54 captures valve 56 capture valve 58 filter 60 flow regulating valve 62 gas analyzer 64 subsidiary pump 66 operation unit 68 output apparatus S seed crystal M silicon melt I monocrystalline silicon ingot I _n the neck I _s shoulder Part I _b Straight body part X Pull-up shaft

Claims (9)

A chamber having a gas inlet for introducing the inert gas at the top and a gas outlet at the bottom for discharging the gas in the furnace containing the inert gas.
The crucible located in the chamber and
A cylindrical heater located in the chamber so as to surround the crucible,
It is a manufacturing method of a single crystal silicon ingot performed by using a silicon single crystal pulling device having the above.
A raw material melting step of heating and melting the silicon raw material charged into the crucible with the heater to form a silicon melt in the crucible while maintaining the atmosphere of the inert gas in the chamber under reduced pressure.
Subsequently, a crystal growing step of heating and maintaining the silicon melt with the heater to pull up the single crystal silicon ingot from the silicon melt while maintaining the atmosphere of the inert gas under reduced pressure in the chamber.
In the raw material melting step and the crystal growing step
The gas in the furnace was collected and
The CO gas concentration in the collected gas was intermittently measured by a gas analyzer.
The CO gas generation rate is calculated by multiplying the measured CO gas concentration by the flow rate of the inert gas supplied into the chamber.
A method for manufacturing a single crystal silicon ingot, which comprises monitoring the calculated CO gas generation rate. The raw material melting step is defined as A (mol / h) as the maximum value of the CO gas generation rate in the raw material melting step and B (mol / h) as the maximum value of the CO gas generation rate in the straight body step during the crystal growth step. The method for producing a single crystal silicon ingot according to claim 1, wherein the crystal growth step is performed under conditions that satisfy A / B ≦ 10. The method for manufacturing a single crystal silicon ingot according to claim 1 or 2, wherein the collection of the gas in the furnace is performed via an exhaust pipe extending from the gas discharge port. The gas in the furnace is collected from the space between the cylindrical heat shield provided above the crucible so as to surround the single crystal silicon ingot and the crucible, according to any one of claims 1 to 3. The method for manufacturing a single crystal silicon ingot according to item 1. The method for manufacturing a single crystal silicon ingot according to any one of claims 1 to 4, wherein the gas analyzer is a quadrupole mass spectrometer. A chamber having a gas inlet for introducing the inert gas at the top and a gas outlet at the bottom for discharging the gas in the furnace containing the inert gas.
A crucible located in the chamber and accommodating the silicon melt,
Above the crucible, a tubular heat shield provided so as to surround the single crystal silicon ingot pulled up from the silicon melt,
A cylindrical heater located in the chamber so as to surround the crucible and heats the silicon melt.
The exhaust pipe extending from the gas outlet and
A main pump connected to the exhaust pipe, depressurizing the inside of the chamber, and sucking the gas in the furnace into the exhaust pipe.
A main valve provided in the exhaust pipe and opened when depressurizing the inside of the chamber,
A gas sampling port provided in one or both of a portion of the exhaust pipe upstream of the main valve and a space between the heat shield and the rutsubo.
A sub-pipe that extends from the gas sampling port and is connected to a portion of the exhaust pipe downstream of the main valve.
A sub-pump provided in the sub-pipe to suck the gas in the furnace into the sub-pipe,
A gas analyzer provided upstream of the sub-pump of the sub-pipe and intermittently measuring the CO gas concentration in the gas sucked into the sub-pipe.
A flow rate adjusting valve provided upstream of the gas analyzer in the sub-pipe to adjust the flow rate of the gas supplied to the gas analyzer.
A filter provided upstream of the flow rate adjusting valve of the sub-pipe to remove SiO powder in the gas sucked into the sub-pipe.
An intake valve provided in the vicinity of the gas sampling port of the sub-pipe and opened when the gas in the furnace is sucked into the sub-pipe.
And, in addition
A calculation unit that calculates the CO gas generation rate by multiplying the CO gas concentration measured by the gas analyzer by the flow rate of the inert gas supplied into the chamber.
An output device that outputs the calculated CO gas generation rate, and
A silicon single crystal pulling device characterized by having. The silicon single crystal pulling device according to claim 6, wherein the gas sampling port is provided at a portion upstream of the main valve of the exhaust pipe. The silicon single crystal pulling device according to claim 6 or 7, wherein the gas sampling port is located in a space between the heat shield and the crucible. The silicon single crystal pulling device according to any one of claims 6 to 8, wherein the gas analyzer is a quadrupole mass spectrometer.

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