TWI727410B - Method for producing single crystal silicon ingot and apparatus for pulling silicon single crystal - Google Patents

Abstract

Provided is a method for producing a single crystal silicon ingot, which method is capable of producing a single crystal silicon ingot in which the concentration of carbon is low at a high yield rate. A method for producing a single crystal silicon ingot in the present invention, is characterized in that in a raw material melting step and a crystal growing step, by gathering the gas from the chamber, intermittently measuring the CO gas concentration in the gathered gas, and multiplying the measured CO gas concentration by the flow of the inert gas supplied to a chamber, calculate the CO gas generating rate and monitor the calculated CO gas generating rate.

Description

Manufacturing method of single crystal silicon ingot and silicon single crystal pulling device

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

The silicon wafer used as the substrate of the semiconductor element is manufactured through a thin-cut silicon single crystal ingot, through a lapping step, an etching step, and a mirror polishing step, and finally it is cleaned and manufactured. then. Large-diameter silicon single crystals over 300mm are generally manufactured by the Czochralski (CZ) method.

Figure 4 shows a conventional silicon single crystal pulling device 400 for manufacturing a single crystal silicon ingot by the CZ method. The silicon single crystal pulling device 400 has a closed chamber 10 at its periphery and a crucible 16 at its center. The crucible 16 has a two-layer structure, composed of a quartz crucible 16A on the inner side and a black lead crucible 16B on the outer side, and is fixed to the upper end of a transmission shaft 18 that can be rotated and raised by a shaft drive mechanism 20.

On the outside of the crucible 16, a resistance heating type cylindrical heater 24 is arranged around the crucible 16, and a heat-insulating body 26 is arranged along the inner surface of the chamber 10 on the outside thereof. Also, above the crucible 16, the pull lead 30 of the seed chuck 28 holding the seed crystal S is arranged coaxially with the drive shaft 18 at the lower end, and while rotating at a predetermined speed in the opposite direction or the same direction as the drive shaft 18, Lifting line lifting mechanism 32.

In the closed chamber 10, a cylindrical heat shield 22 is arranged above the crucible 16 around the growing single crystal silicon ingot I. This heat shield 22 adjusts the amount of high-temperature radiation heat incident from the silicon melt M in the crucible 16, the heater 24, and the side wall of the crucible 16 to the growing ingot I, and controls the center and outer periphery of the single crystal silicon ingot I The task of pulling the temperature gradient in the X direction of the axis.

The upper part of the closed chamber 10 is provided with a gas inlet 12 for introducing an inert gas such as Ar (argon) gas into the closed chamber 10. In addition, the bottom of the closed chamber 10 is provided with a gas discharge port 14 that is driven by a vacuum pump (not shown) to suck and discharge the gas in the closed chamber 10. The inert gas introduced into the closed chamber 10 from the gas inlet 12 descends from the growing single crystal silicon ingot I and the heat shield 22, and flows through the gap between the lower end of the heat shield 22 and the liquid surface of the silicon melt M , Flows to the outside of the heat shield 22 and further to the outside of the crucible 16, then descends from the outside of the crucible 16, and is discharged from the gas discharge port 14.

Using this silicon single crystal pulling device 400, the inside of the chamber 10 is maintained in the Ar gas atmosphere under reduced pressure, and the silicon material such as polysilicon filled in the crucible 16 is melted by the heating of the heater 24 to form a silicon melt M. Secondly, the wire lifting mechanism 32 is used to lower and pull the lead 30 to make the seed crystal S contact the silicon melt M, rotate the crucible 16 and the lead 30 in a predetermined direction, and pull the lead 30 upward to grow an ingot below the seed crystal S I. In addition, as the ingot I grows, although the amount of the silicon melt M decreases, the crucible 16 is raised to maintain the level of the melt surface.

A CCD camera 36 is installed in the opening 34 at the upper part of the secret room 10. The CCD camera 36 photographs the vicinity of the boundary between the single crystal silicon ingot I and the molten liquid M. The meniscus (meniscus) formed at the boundary between the crystal and the molten liquid is photographed with a higher brightness than the crystal and the molten liquid. The meniscus in the image shows a ring-shaped high-brightness zone (hereinafter referred to as the "melt ring"). (fusion ring)”). The interval of the fusion ring is recognized as the crystal diameter, and the crystal pulling speed and the temperature of the melt are controlled to make the crystal diameter a desired constant value.

In the manufacture of a single crystal silicon ingot using such a silicon single crystal pulling device, it is well known that CO gas is generated in a closed chamber. One of the reasons for this is, for example, the reaction of SiO gas generated from the silicon melt with the black lead material (for example, a cylindrical heater) present in the closed chamber to generate CO gas. Patent Document 1 has a technique for measuring the concentration of CO gas in this closed chamber.

Patent Document 1 describes a method for manufacturing a single crystal in which a single crystal is pulled from a raw material melt by heating and melting the raw material by the Czochralski (CZ) method, which is characterized in that the raw material is stored in a quartz crucible while one side The raw material contained in the quartz crucible is heated and melted, while measuring the concentration of carbon monoxide contained in the exhaust gas discharged from the raw material melt, and based on the measured carbon monoxide concentration in the exhaust gas contained in the measured raw material melt, it is determined that the melting of the raw material is complete. Pull single crystals from the above-mentioned raw material melt (the 6th item in the scope of patent application)". [Advanced Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 2017-114709

[The problem to be solved by the invention]

The inventors of the present invention focused on the single crystal silicon ingot manufactured by the conventional silicon single crystal pulling device, in which carbon was mixed during the growth process. As a result, the carbon concentration of the silicon wafer produced by the above ingot unexpectedly changed. High subject. When the carbon concentration in the silicon wafer becomes higher, defects caused by electroactive carbon called killing defects are generated in the heat treatment step of the device, which causes the problem of reducing the life cycle of the wafer. In addition, because the high concentration of carbon promotes the formation of oxygen precipitates, if the oxygen precipitates are present on the surface of the device, leak failure occurs, which is a cause of low yield. In this way, the carbon contamination in the single crystal silicon ingot has a bad influence on the manufacturing steps of the semiconductor element. Therefore, the carbon concentration in the single crystal silicon ingot is strictly limited by the specifications according to the type of the device.

The reason for the increase in the carbon concentration in the crystal is believed to be the CO gas generated in the closed chamber taken into the silicon melt. In Patent Document 1, the concentration of CO gas in the gas in the sealed chamber becomes the maximum when all the raw materials are melted in the raw material melting step, the CO gas concentration is measured, and the end of the raw material melting step (the end of melting) is determined based on the measured value. However, Patent Document 1 focuses too much on shortening the processing time and preventing the deformation of the quartz crucible based on the accurate detection of the end of the melting, and does not pay attention to the incorporation of CO gas in the silicon melt or the increase in the carbon concentration in the crystal caused by this. .

In view of the above-mentioned problems, an object of the present invention is to provide a single crystal silicon ingot manufacturing method and a silicon single crystal pulling device that can manufacture a single crystal silicon ingot with a low carbon concentration in a high yield. [Means to solve the problem]

The inventors of the present invention who should solve the above-mentioned problems have conceived of monitoring the CO gas generation rate (CO gas generation amount per unit time) instead of monitoring the CO gas concentration in the air in the secret chamber. That is, it is considered that the amount of CO gas taken in the silicon melt is positively correlated with the amount of CO gas generated per unit time. On the other hand, the CO gas concentration, even if the CO gas production amount per unit time is the same, becomes smaller when the flow rate of the inert gas in the secret chamber is large, and becomes larger when the flow rate of the inert gas in the secret chamber is small. In fact, the flow rate of the inert gas in the raw material melting step and the crystal growth step are different, and the flow rate of the inert gas in the crystal growth step fluctuates. Therefore, the CO gas concentration is not suitable for monitoring as an indicator for evaluating the amount of CO gas taken in the silicon melt. The inventors found that by measuring the CO gas concentration in the secret chamber, multiplying the measured value by the internal inert gas flow rate in the secret chamber, calculating the CO gas generation rate, and monitoring the CO gas generation rate, it is possible to properly evaluate not only the silicon melt The amount of CO gas taken in the liquid or even the carbon concentration in the crystal.

The present invention has been completed based on the above findings, and its gist is structured as follows. (1) The manufacturing method of a single crystal silicon ingot is carried out by using a silicon single crystal pulling device. The above silicon single crystal pulling device includes: Closed chamber, the upper part has a gas inlet for introducing inert gas, and the bottom has a gas outlet for discharging the gas in the furnace containing the above-mentioned inert gas; The crucible is located in the aforementioned chamber; and A cylindrical heater located in the above-mentioned closed chamber and surrounding the above-mentioned crucible; The above manufacturing method includes: In the raw material melting step, while maintaining the enclosed chamber in the inert gas air under reduced pressure, the heater is used to heat and melt the silicon raw material put into the crucible to form a silicon melt in the crucible; and The crystal growth step, then, while maintaining the enclosed chamber in the inert gas air under reduced pressure, heating and maintaining the silicon melt with the heater, and then pulling the single crystal silicon ingot from the silicon melt; Wherein, in the above-mentioned raw material melting step and the above-mentioned crystal growth step, Collect the above-mentioned furnace gas; Intermittently measure the CO (carbon monoxide) gas concentration in the collected gas with a gas analysis device; The measured CO gas concentration is multiplied by the inert gas flow rate supplied to the aforementioned chamber to calculate the CO gas generation rate; Monitor the calculated CO gas generation rate.

(2) The method for producing a single crystal silicon ingot as described in (1) above, wherein the maximum value of the CO gas generation rate in the raw material melting step is A (mol/h (mol/h)), and the crystal grows The maximum value of the CO gas generation rate in the direct drying step in the steps is B (mol/h), and the above-mentioned raw material melting step and the above-mentioned crystal growth step are performed under the condition that A/B≦10.

(3) The method for producing a single crystal silicon ingot as described in (1) or (2), wherein the gas in the furnace is collected via an exhaust pipe extending from the gas discharge port.

(4) The method for producing a single crystal silicon ingot according to any one of (1) to (3), wherein the gas in the furnace is heated from a cylindrical heat set above the crucible and surrounding the single crystal silicon ingot The space between the shielding body and the crucible is collected.

(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 four-layer pole type mass analyzer.

(6) Silicon single crystal pulling device, characterized by including: Closed chamber, the upper part has a gas inlet for introducing inert gas, and the bottom has a gas outlet for discharging the gas in the furnace containing the above-mentioned inert gas; The crucible is located in the above-mentioned closed chamber and contains the silicon melt; and A cylindrical heat shield is set above the crucible and surrounds the single crystal silicon ingot pulled from the silicon melt; A cylindrical heater, located in the above-mentioned closed chamber, surrounding the above-mentioned crucible, and heating the above-mentioned silicon melt; Exhaust piping extending from the above-mentioned gas discharge port; The main pump is connected to the exhaust piping, and while depressurizing the secret chamber, it sucks the gas in the furnace to the exhaust piping; The main valve is set in the exhaust pipe, and opens when the pressure is reduced in the closed chamber; The collection port is provided at one or both of the upstream portion of the main valve of the exhaust piping and the space between the heat shield and the crucible; The secondary piping extends from the gas collection port and is connected to the downstream portion of the main valve of the exhaust piping; The secondary pump is installed in the secondary piping to suck the gas in the furnace to the secondary piping; A gas analysis device is installed upstream of the secondary pump of the secondary piping, and intermittently measures the CO gas concentration in the gas sucked into the secondary piping; A flow adjustment valve, which is arranged upstream of the gas analysis device of the secondary piping, and adjusts the gas flow rate supplied to the gas analysis device; A filter is installed upstream of the flow control valve of the secondary piping, and removes SiO powder in the gas sucked into the secondary piping; and The intake valve is set near the gas collection port of the secondary piping, and opens when the gas in the furnace is sucked into the secondary piping; It also includes: An arithmetic unit, multiplying the CO gas concentration measured by the gas analysis device by the inert gas flow rate supplied to the secret chamber, thereby calculating the CO gas generation rate; and The output device outputs the calculated CO gas generation rate.

(7) The silicon single crystal pulling device described in (6) above, wherein the gas collection port is provided at an upstream portion of the main valve of the exhaust pipe.

(8) The silicon single crystal pulling device described in (6) or (7), wherein the gas collection port is located in a space between the heat shield and the crucible.

(9) The silicon single crystal pulling device described in any one of (6) to (8) above, wherein the gas analysis device is a quadrupole type mass analysis device. [Effects of the invention]

According to the method for manufacturing a single crystal silicon ingot and the silicon single crystal pulling device of the present invention, a single crystal silicon ingot with a low carbon concentration can be manufactured at a high yield.

(Si single crystal pulling device)

With reference to Figs. 1 to 3, the basic structure common to the silicon single crystal pulling apparatus 100, 200, and 300 according to the embodiment of the present invention will be described. Also, regarding these common basic structures, the same symbols are attached in Figures to 3rd.

The silicon single crystal pulling device 100, 200, 300 has a closed chamber 10, a crucible 16, a transmission shaft 18, a shaft drive mechanism 20, a cylindrical heat shield 22, a heater 24, a cylindrical heat insulator 26, and a seed crystal chuck 28. The lead wire 30, the wire lifting mechanism 32, the CCD camera 36, the exhaust pipe 40, and the main pump 42.

The upper part of the secret chamber 10 is provided with a gas inlet 12 for introducing inert gas such as Ar gas into the secret chamber 10. In addition, at the bottom of the secret chamber 10, a gas discharge port 14 is provided for sucking and discharging the gas (hereinafter referred to as "furnace gas") in the secret chamber 10 by the driving of the main pump 42 (vacuum pump).

The crucible 16 is arranged in the center of the chamber 10 and contains the silicon melt M. As shown in FIG. The crucible 16 has a two-layer structure of a quartz crucible 16A and a black lead crucible 16B. The quartz crucible 16A directly supports the silicon melt M on the inner surface. The black lead 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 black lead crucible 16B, that is, the upper end of the quartz crucible 16A protrudes from the upper end of the black lead crucible 16B.

The drive shaft 18 penetrates the bottom of the chamber 10 in the vertical direction, and supports the crucible 16 at the upper end. Then, the shaft drive mechanism 20 raises and lowers the crucible 16 while rotating the crucible 16 via the transmission shaft 18.

The heat shield 22 is arranged above the crucible 16 to surround the single crystal silicon ingot I pulled up from the silicon melt M. Specifically, the heat shielding body 22 has an inverted truncated cone-shaped shielding body 22A, an inner flange portion 22B extending horizontally from the lower end of the shielding body 22A to the side of the drawing axis X (inside), and the shielding body 22A The outer flange portion 22C extends horizontally from the upper end of the upper end to the chamber side (outer side), and the outer flange portion 22C is fixed to the heat insulator 26. The function of the heat shield 22 is the same as that described in the previous technical column.

The cylindrical heater 24 is located in the closed chamber 10 and surrounds the crucible 16. The heater 24 is a resistance heating heater made of carbon, which melts the silicon material put into the crucible 16 to form a silicon melt M, and also heats it to maintain the formed silicon melt M.

The cylindrical heat insulator 26 is provided below the upper end of the heat shield 22 along the inner surface of the closed chamber 10. In this embodiment, the heat insulating body is further arranged at the bottom of the secret chamber. The thermal insulation material constituting these thermal insulation bodies is not particularly limited, but examples thereof include carbon, aluminum oxide (alumina), and zirconia (zirconia). The heat insulator 26 particularly gives a heat preservation effect to the area below the heat shield 22 in the closed chamber 10, and has the function of easily maintaining the silicon melt M in the crucible 16. The thickness of the insulator 26 is not particularly limited, and it can be formed into a general thickness equal to the conventional one. The pulling device for growing crystals with a diameter of 300mm (millimeters) can form a pulling device for crystals with a diameter of about 30 to 90mm and a diameter of 450mm. It can be formed in about 45~100mm.

Above the crucible 16, the pull lead 30 of the seed crystal chuck 28 holding the seed crystal S at the lower end is arranged coaxially with the drive shaft 18, and the wire lifting mechanism 32 moves to the opposite direction or the same direction of the drive shaft 18 at a predetermined speed The lead 30 is pulled up and down while the lead 30 is rotated and pulled.

A CCD camera 36 is installed in the opening 34 at the upper part of the secret room 10. The CCD camera 36 photographs the vicinity of the boundary between the single crystal silicon ingot I and the silicon melt M. Taking the interval of the fusion ring in the obtained image as the crystal diameter, the crystal pulling speed and the temperature of the melt are controlled so that the crystal diameter becomes a desired constant value.

The exhaust piping 40 extends from the gas discharge port 14. The main pump 42 may be a vacuum pump such as a dry pump, and is connected to the exhaust piping 40 to reduce the pressure in the closed chamber 10 to about 5-100 Torr (torr) while achieving the suction furnace The role of the gas to the exhaust piping 40. The main valve 44 is provided in the exhaust piping 40, and has the effect of converting the pressure in the closed chamber 10 to normal pressure and reducing pressure. That is, when the inside of the secret chamber 10 is opened to the atmosphere, when the structure in the secret chamber 10 is installed or exchanged, etc., when the pressure in the secret chamber 10 becomes normal, the main valve 44 is closed. On the other hand, when the inside of the closed chamber 10 including the raw material melting step and the crystal growth step is reduced in pressure, the main valve 44 is opened.

又，作為副生長物生長的SiC在加熱器24的表面上析出。Here, in the raw material melting step and the crystal growth step, CO gas is generated in the closed chamber 10. The first reason is the same as below. That is, since the silicon melt M reacts with the inner surface of the quartz crucible 16A, SiO gas is generated from the silicon melt M in the crucible 16. The SiO gas reaches the heater 24 along with the flow of the inert gas. As shown in the following reaction formula, CO gas is generated by reacting with the carbon of the heater material.

In addition, SiC grown as a by-growth is deposited on the surface of the heater 24.

又，作為副生長物生長的SiC，在石英坩堝16A的外周面與黑鉛坩堝16B的內周面之間析出。The second reason is as follows. That is, the quartz crucible 16A and the black lead crucible 16B that are in contact with each other react to generate CO gas.

In addition, SiC grown as a by-growth is deposited between the outer peripheral surface of the quartz crucible 16A and the inner peripheral surface of the black lead crucible 16B.

In each embodiment of the present invention, as described above, regarding the CO gas generated in the closed chamber 10, the generation amount per unit time (that is, the CO gas generation rate) is monitored. Hereinafter, the device configuration used for this will be described.

[First Embodiment] Referring to FIG. 1, in this embodiment, there is a secondary pipe 52 which branches from the upstream portion of the main valve 44 of the exhaust pipe 40 and is connected to the downstream portion of the main valve 44. That is, the gas collection port 46 is provided at an upstream portion of the main valve 44 of the exhaust pipe 40. In the secondary piping 52, an intake valve 54, a filter 58, a flow adjustment valve 60, a gas analysis device 62, and a secondary pump 64 are installed in this order from the upstream thereof. In addition, in this specification, the "upstream" and "downstream" of the exhaust pipe 40 and the sub-pipe 52 refer to the flow of gas passing through each pipe.

The secondary pump 64 is installed in the secondary piping 52 and sucks in the furnace gas (strictly speaking, the gas sucked to the exhaust piping) to the secondary piping 52 through the gas collection port 46. The secondary pump 64 can be configured by, for example, a vacuum pump device that combines a rotary pump and a turbine molecular pump. As mentioned above, the inside of the closed chamber 10 contains about 5-100 Torr (torr) of decompressed air. In order to draw gas from the decompressed air to the secondary piping 52, the secondary piping 52 must produce lower decompression air. From this point of view, due to the driving of the secondary pump 64, it is desirable that the pressure in the secondary pipe 52 (upstream of the filter 58) is 1 Torr or less.

The gas analyzer 62 is installed upstream of the secondary pump 64 of the secondary piping 52, and intermittently measures the CO gas concentration in the gas sucked into the secondary piping. Examples of the gas analysis device 62 include a four-layer polar mass analysis device and a gas chromatography (gas chromatography) device. If it is a four-layer polar mass analyzer, the measurement interval of CO gas concentration is about 1 second, which is very short. On the other hand, in the case of a currently commercially available gas chromatography device, the shortest measurement interval of the CO gas concentration is about 15 minutes. Therefore, in this embodiment, it is desirable to use a four-layer polar mass spectrometer.

The flow rate adjustment valve 60 is installed upstream of the gas analysis device 62 of the secondary pipe 52, and adjusts the opening and closing degree to achieve the function of adjusting the gas flow rate supplied to the gas analysis device 62. Thereby, it is possible to supply the furnace gas at an appropriate flow rate to the gas analysis device 62. The gas flow rate supplied to the gas analyzer 62 is ideally 4×10 ^{-1 to} 4×10 ^-4 Pa. L/min.

The filter 58 is provided upstream of the flow control valve 60 of the secondary pipe 52 and serves to remove SiO powder in the gas sucked into the secondary pipe 52. Among the above gases, the cooling SiO gas generated from the silicon melt M includes SiO powder formed by solidification. Figure 6 shows a graph of the particle size distribution of SiO powder in the gas collected from a general chamber. As shown in Figure 6, the general average particle size of SiO powder is about 13 μm, and the general minimum particle size is 1 μm. Therefore, in this embodiment, it is desirable to use a gas filter having a nano-scale mesh size that can remove 99% by mass or more of particles with a particle size of 1 μm or more. Examples of such a gas filter include wafer card IISF in-line gas filter (coaxial gas filter) manufactured by Entegris Co., Ltd., and small flow filter for NAS Clean Process gas line of Nippon Seisen Co., Ltd.. By installing the filter 58 upstream of the flow control valve 60, the opening and closing failure of the flow control valve 60 caused by the SiO powder is avoided, and the mixing of the SiO powder into the gas analysis device 62 is avoided.

The intake valve 54 is provided near the gas collection port 46 of the secondary piping 52, and is opened when the furnace gas is sucked to the secondary piping 52. In this embodiment, since the measurement of the CO gas concentration and the monitoring of the CO gas generation rate are often performed in the raw material melting step and the crystal growth step, the intake valve 54 is always opened. Therefore, a part of the gas sucked into the exhaust pipe is taken into the secondary pipe 52.

The calculation unit 66 calculates the CO gas generation rate by multiplying the CO gas concentration measured by the gas analysis device 62 by the flow rate of the inert gas supplied into the secret chamber 10. The arithmetic unit 66 may be constituted by a general central arithmetic processing unit (CPU) or a micro processing unit (MPU). In addition, as the flow rate of the inert gas supplied into the chamber 10, the gas flow rate setting value may be used.

The output device 68 outputs the CO gas generation rate calculated by the calculation unit 66. The output device 68 may be composed of a general display, a projector, a printer, a speaker, and the like.

In this embodiment, according to the above configuration, instead of the CO gas concentration of the furnace gas, the CO gas generation rate of the furnace gas can be monitored in real time. In this way, by monitoring the CO gas generation rate in-situ, it is possible to appropriately evaluate not only the amount of CO gas taken in the silicon melt but also the carbon concentration in the crystal.

[Second Embodiment]

Referring to FIG. 2, in this embodiment, the gas collection port 48 is located in the space between the heat shield 22 and the crucible 16. That is, the sampling tube 50 is suspended from the upper part of the closed chamber 10 so that the gas collection port 48 at the tip is located in the space between the heat shield 22 and the crucible 16. The sampling pipe 50 is connected to the secondary pipe 52 outside the secret chamber 10. The intake valve 56 is provided near the upstream end of the secondary pipe 52.

In the first embodiment, with regard to collecting the gas in the furnace through the secondary pipe 52, the gas in the furnace is collected from the space between the heat shield 22 and the crucible 16 in this embodiment. The filter 58, the flow control valve 60, the gas analysis device 62, and the secondary pump 64, and the calculation unit 66 and the output device 68 provided in the secondary piping 52 are the same as those in the first embodiment, so the description will be omitted.

In this embodiment, the furnace gas is directly collected from the upper edge of the quartz crucible. Therefore, it is possible to directly collect CO gas generated by the reaction with the quartz crucible and the black lead crucible. As a result, the CO gas generation rate can be monitored with higher accuracy.

[Third Embodiment]

Referring to Fig. 3, this embodiment combines the configuration of the first embodiment and the configuration of the second embodiment. That is, the gas in the furnace is collected via the secondary pipe 52 and also from the space between the heat shield 22 and the crucible 16.

In the present embodiment, the secondary piping 52 is composed of a first piping 52B, a second piping 52C, and a third piping 52D. The first piping 52B branches from the upstream portion of the main valve 44 of the exhaust piping 40. The second piping 52C is connected to the upper end of the sampling pipe 50 and extends from the upper part of the closed chamber. The third piping 52D is formed by joining the first piping 52B and the second piping 52C. The sampling pipe 50 and the intake valve are the same as in the second embodiment. The filter 58, the flow control valve 60, the gas analysis device 62, the sub pump 64, the calculation unit 66, and the output device 68 provided in the secondary piping 52C are the same as those in the first embodiment. The description is omitted.

In this embodiment, the intake valve 54 and the intake valve 56 are switched at an appropriate timing, and by measuring the CO gas concentration, it is possible to confirm the positional dependence of the CO gas generation. Specifically, since the CO concentration difference measured at each position is obtained, the CO gas concentration generated by the reaction between the quartz crucible and the black lead crucible and the CO gas concentration generated by the reaction between the SiO gas and the black lead can be cut.

(Manufacturing method of single crystal silicon ingot) The method of manufacturing a single crystal silicon ingot according to an embodiment of the present invention can be suitably implemented using the silicon single crystal pulling devices 100, 200, and 300 described above. Then, referring to Figs. 1 to 3, a method of manufacturing a single crystal silicon ingot according to an embodiment of the present invention will be described. First, the crucible 16 is filled with silicon raw materials such as polycrystalline silicon ingots, and the main pump 42 is driven with the main valve 44 opened to maintain the inside of the chamber 10 in the inert gas atmosphere such as Ar gas under reduced pressure. At this time, the crucible 16 is located below the inside of the closed chamber 10 so that the silicon material does not contact the heat shield 22. After that, the silicon raw material in the crucible 16 is heated by the heater 24 to form a silicon melt M. After that, the crucible 16 is raised to the pulling start position. In this specification, the "raw material melting step" is defined as the period from the time when the heating of the heater 24 is started to the time when the crucible rising ends. In the raw material melting step, the flow rate of the inert gas is preferably 10~400L (liter)/min.

Next, the wire lifting mechanism 32 lowers and pulls the lead wire 30 so that the seed crystal S contacts the silicon melt M. After that, while rotating the crucible 16 and the lead wire 30 in a predetermined direction, the lead wire 30 is pulled upward to grow the ingot I under the seed crystal S. In addition, as the ingot I grows, although the amount of the silicon melt M decreases, the crucible 16 rises to maintain the level of the melt surface. In this specification, the “crystal growth step” is defined as the period from the time when the pull-down lead 30 starts to the time when the growth of the ingot I (the rise of the pull-lead 30) ends.

Crystal growth step, firstly because of the dislocation-free single crystal, a Dash (plunging) seeding reduction method (necking), forming a neck I _n. Secondly, in order to obtain an ingot of the necessary diameter, the shoulder portion I _{s is grown, and the straight stem portion I b} is grown with a certain diameter even if the silicon single crystal becomes the desired diameter. After the straight stem I _{b is} grown to a predetermined length, in order to cut the single crystal from the silicon melt M without dislocation, the tail is reduced (the formation of the tail). In this specification, _{the growth period of the straight stem portion I b} is referred to as the "straight stem step".

In the crystal growth step, the flow rate of the inert gas is preferably 50~300L/min. In addition, in the crystal growth step, the flow rate of the inert gas increases or decreases (varies) with time within the above-mentioned range.

This embodiment is characterized in that the following steps are performed in the raw material melting step and the crystal growth step. First collect the gas in the furnace. This step is performed by sucking the gas in the furnace to the secondary pipe 52 from one or both of the gas collection port 46 and the gas collection port 48 as shown in FIGS. 1 to 3.

Next, the gas analyzer 62 intermittently measures the CO gas concentration in the collected gas. 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 secret chamber 10. Then, the output device 68 outputs the calculated CO gas generation rate. In this embodiment, instead of the CO gas concentration of the furnace gas, the CO gas generation rate of the furnace gas can be monitored in real time. In this way, since the CO gas generation rate is monitored in-situ, it is possible to appropriately evaluate not only the amount of CO gas taken in the silicon melt but also the carbon concentration in the crystal. Also, as mentioned earlier, the flow rate of the inert gas supplied into the chamber 10 differs between the raw material melting step and the crystal growth step, and even if the crystal growth step changes, the gas flow rate setting value at the time of monitoring may be used.

In this embodiment, the maximum CO gas generation rate in the raw material melting step is A (mol/h), the maximum CO gas generation rate in the direct drying step of the crystal growth step is B (mol/h), the raw material melting step and crystal growth The step is ideally performed under the condition that A/B≦10 is satisfied. Under the condition of A/B≦10, it is possible to produce _{single crystal silicon ingots with a solidification rate of less than 0.75 and a carbon concentration (C s} ) of 2×10 ¹⁵ atom/cm ³ (atoms/cubic centimeter) or less in all positions. . That is, a single crystal silicon ingot with a low carbon concentration can be manufactured at a high yield. In addition, the crystal solidification rate (%) is defined by the crystal mass during pulling/the added mass percentage of the raw material. Also, during the first 10 hours of the raw material melting step, the CO gas generation rate was unstable due to the gas detached from the element in the closed chamber. Therefore, in this specification, the maximum value during the initial 10-hour period of removal in the raw material melting step is taken as A.

The A/B value can be adjusted mainly by controlling the electric energy of the heater 24 in the raw material melting step. Generally, in the crystal growth step, the electric energy of the heater 24 required to maintain the silicon melt M is determined by itself and a predetermined range value, and the heater 24 is driven to maintain the silicon melt M with the above-mentioned specific electric energy. Therefore, the CO gas generation rate in the crystal growth step is relatively low and stable (without major fluctuations). On the other hand, in the raw material melting step, in order to melt the silicon raw material, it is necessary to drive the heater 24 with large electric energy, and the CO gas generation rate is relatively high and unstable (large fluctuation). In particular, at the end of the raw material melting step (at the end of melting), the CO gas generation rate tends to increase. Therefore, by controlling the electric energy of the heater 24 in the raw material melting step, and by suppressing the maximum value A of the CO gas generation rate, A/B≦10 can be achieved. However, the values of A and B are not exclusively determined by the electric energy of the heater 24, but also depend on the thermal insulation properties in the chamber 10 (that is, the structure of the chamber, the amount and arrangement of the thermal insulation body).

A/B is preferably 1 or more. This is because when A/B is less than 1, the silicon melt solidifies and crystal growth may not be established. [Example]

(Experimental example 1) Using the silicon single crystal pulling device configured as shown in Fig. 1, single crystal silicon ingots were manufactured at the four levels shown in Table 1. For each level, the loading capacity of silicon raw material is 320Kg (kg), the diameter of the ingot is 300mm (mm), the straight stem length is 1800mm, and the growth rate is 1.0mm/min. The flow rate of Ar gas supplied to the chamber during the raw material melting step is 100L/min. . Use a gas filter with a nano-level mesh size that can remove 99% by mass or more of particles with a particle size of 1 μm or more. The heater electric energy in the raw material melting step and the crystal growth step is the value shown in Table 1.

A four-layer polar mass analyzer is used as a gas analyzer, and the CO gas generation rate is monitored during the entire process of the raw material melting step and the crystal growth step. Table 1 shows the maximum value A of the CO gas generation rate in the raw material melting step and the maximum value B of the CO gas generation rate in the direct drying step. In addition, the display in Figure 5 represents the full level, and level No. 1 shows the transition of the monitored CO gas generation rate.

For each level, the "low-carbon crystal yield" shown in Table 1 was obtained according to the following procedure. First, cut out the straight stems of single crystal silicon ingots manufactured at various levels, and process and manufacture multiple silicon wafers. At one point in the center of each wafer, the FT-IR device was used to measure the carbon concentration (Cs) substituted in the silicon crystal position. Regarding the growth of the crystal length as the denominator, the crystal length satisfying Cs≦2×10 ¹⁵ atoms/cm ³ or less is the numerator, and the crystal yield is determined to be the "low carbon crystal yield". The results are shown in Table 1.

As shown in Table 1, it is clear that the implementation level No. 1 to 4 under the condition of A/B≦10 is the level No. 5 implemented under the condition of A/B=11 for low-carbon crystal yields of 75% or more and high. The yield rate of medium and low-carbon crystals dropped significantly by 25%.

(Experimental example 2)

Depending on the performance and presence of the gas filter, the measurement of the time during which the secondary piping (specifically, the flow adjustment valve, the flow adjustment valve, and the gas analysis device) is not clogged and the CO gas generation rate can be continuously monitored. The manufacturing method of the single crystal silicon ingot was the same as in Experimental Example 1 except for the filter.

Level 1, the same as Experimental Example 1, using a gas filter with a nano-level mesh size that can remove 99% by mass or more of particles with a particle size of 1 μm or more. In this level 1, the CO gas generation rate can be monitored continuously for more than 100 hours.

Level 2, using a gas filter with a mesh size that can remove 99% by mass or more of particles with a particle size of 10 μm or more. In this level 2, even if the CO gas generation rate is monitored continuously for more than 70 hours, the secondary piping is clogged and cannot be monitored.

Level 3, no gas filter is used. In this level 2, even if the CO gas generation rate is monitored continuously for more than 20 hours, the secondary piping is clogged and cannot be monitored. [Industrial Utilization Possibility]

According to the method for manufacturing a single crystal silicon ingot and the silicon single crystal pulling device of the present invention, a single crystal silicon ingot with a low carbon concentration can be manufactured at a high yield.

10: Secret Chamber 12: Gas inlet 14: Gas outlet 16: Crucible 16A: Quartz crucible 16B: Black lead crucible 18: drive shaft 20: Shaft drive mechanism 22: Heat shielding body 22A: Cover the body 22B: Inside flange 22C: Outer flange 24: heater 26: Insulating body 28: Seed chuck 30: Pull the lead 32: Line lifting mechanism 34: Opening 36: CCD camera 40: Exhaust pipe 42: main pump 44: main valve 46: Gas collection port (exhaust piping) 48: Gas collection port (secret room) 50: Sampling tube (closed room) 52: Secondary piping 52A: Secondary piping terminal 54: Take-in valve 56: Take-in valve 58: filter 60: Flow adjustment valve 62: Gas analysis device 64: Secondary pump 66: calculation department 68: output device 100, 200, 300, 400: silicon single crystal pulling device I: Single crystal silicon ingot In: neck Is: Shoulder Ib: Straight Officer M: Silicon melt S: seed crystal X: pull shaft

[Figure 1] is a cross-sectional view along the pulling axis X schematically showing the structure of the silicon single crystal pulling device 100 according to the first embodiment of the present invention; [Figure 2] is a cross-sectional view along the pulling axis X schematically showing the structure of the silicon single crystal pulling device 200 according to the second embodiment of the present invention; [Figure 3] is a cross-sectional view along the pulling axis X schematically showing the structure of the silicon single crystal pulling device 300 according to the third embodiment of the present invention; [Figure 4] is a cross-sectional view along the pulling axis X schematically showing the structure of the conventional silicon single crystal pulling device 400; [Figure 5] is a graph showing the transition of the CO gas generation rate in the No. 1 (No. 1) raw material melting step and the crystal growth step; and [Figure 6] is a graph of the particle size distribution of SiO powder in the gas collected from the chamber.

10: Secret Chamber

12: Gas inlet

14: Gas outlet

16: Crucible

16A: Quartz crucible

16B: Black lead crucible

18: drive shaft

20: Shaft drive mechanism

22: Heat shielding body

22A: Cover the body

22B: Inside flange

22C: Outer flange

24: heater

26: Insulating body

28: Seed chuck

30: Pull the lead

32: Line lifting mechanism

34: Opening

36: CCD camera

40: Exhaust pipe

42: main pump

44: main valve

46: Gas collection port (exhaust piping)

52: Secondary piping

52A: Secondary piping terminal

58: filter

60: Flow adjustment valve

62: Gas analysis device

64: Secondary pump

66: calculation department

68: output device

100: Silicon single crystal pulling device

I: Single crystal silicon ingot

In: neck

Is: Shoulder

Ib: Straight Officer

M: Silicon melt

S: seed crystal

X: pull shaft

Claims (11)

A method for manufacturing a single crystal silicon ingot, using a silicon single crystal pulling device, the silicon single crystal pulling device includes: Closed chamber, the upper part has a gas inlet for introducing inert gas, and the bottom has a gas outlet for discharging the gas in the furnace containing the above-mentioned inert gas; The crucible is located in the aforementioned chamber; and A cylindrical heater, located in the above-mentioned closed chamber and surrounding the above-mentioned crucible; Its characteristics are: The above manufacturing method includes: In the raw material melting step, while maintaining the enclosed chamber in the inert gas air under reduced pressure, the heater is used to heat and melt the silicon raw material put into the crucible to form a silicon melt in the crucible; and The crystal growth step, then, while maintaining the enclosed chamber in the inert gas air under reduced pressure, the heater is used to heat and maintain the silicon melt, and then the single crystal silicon ingot is pulled from the silicon melt; Wherein, in the above-mentioned raw material melting step and the above-mentioned crystal growth step, Collect the above-mentioned furnace gas; Intermittently measure the CO (carbon monoxide) gas concentration in the collected gas with a gas analysis device; The measured CO gas concentration is multiplied by the inert gas flow rate supplied to the aforementioned chamber to calculate the CO gas generation rate; Monitor the calculated CO gas generation rate. The method for manufacturing a single crystal silicon ingot as described in the first item of the patent application, wherein the maximum value of the CO gas generation rate in the raw material melting step is A (mol/h), and the direct drying step in the crystal growth step The maximum value of the CO gas generation rate is B (mol/h), and the above-mentioned raw material melting step and the above-mentioned crystal growth step are performed under the condition that A/B≦10. The method for manufacturing a single crystal silicon ingot as described in item 1 or 2 of the scope of patent application, wherein: The gas in the furnace is collected via an exhaust pipe extending from the gas discharge port. The method for manufacturing a single crystal silicon ingot as described in item 1 or 2 of the scope of patent application, wherein: The gas in the furnace is collected from the space between the cylindrical heat shielding body arranged above the crucible and surrounding the single crystal silicon ingot and the crucible. The method for manufacturing a single crystal silicon ingot as described in item 3 of the scope of patent application, wherein: The gas in the furnace is collected from the space between the cylindrical heat shielding body arranged above the crucible and surrounding the single crystal silicon ingot and the crucible. The method for manufacturing a single crystal silicon ingot as described in item 1 or 2 of the scope of patent application, wherein: The above-mentioned gas analysis device is a four-layer pole type mass analysis device. The method for manufacturing a single crystal silicon ingot as described in item 3 of the scope of patent application, wherein: The above-mentioned gas analysis device is a four-layer pole type mass analysis device. A silicon single crystal pulling device, which is characterized in that it comprises: Closed chamber, the upper part has a gas inlet for introducing inert gas, and the bottom has a gas outlet for discharging the gas in the furnace containing the above-mentioned inert gas; The crucible is located in the above-mentioned closed chamber and contains the silicon melt; A cylindrical heat shield is set above the crucible and surrounds the single crystal silicon ingot pulled from the silicon melt; A cylindrical heater, located in the above-mentioned closed chamber, surrounding the above-mentioned crucible, and heating the above-mentioned silicon melt; Exhaust piping extending from the above-mentioned gas discharge port; The main pump is connected to the exhaust piping, and while depressurizing the secret chamber, it sucks the gas in the furnace to the exhaust piping; The main valve is set in the exhaust pipe, and opens when the pressure is reduced in the closed chamber; A gas collection port is provided at one or both of the upstream portion of the main valve of the exhaust pipe and the space between the heat shield and the crucible; The secondary piping extends from the gas collection port and is connected to the downstream portion of the main valve of the exhaust piping; The secondary pump is installed in the secondary piping to suck the gas in the furnace to the secondary piping; A gas analysis device is installed upstream of the secondary pump of the secondary piping, and intermittently measures the CO gas concentration in the gas sucked into the secondary piping; A flow adjustment valve, which is arranged upstream of the gas analysis device of the secondary piping, and adjusts the gas flow rate supplied to the gas analysis device; A filter is installed upstream of the flow control valve of the secondary piping, and removes SiO powder in the gas sucked into the secondary piping; and The intake valve is set near the gas collection port of the secondary piping, and opens when the gas in the furnace is sucked into the secondary piping; It also includes: An arithmetic unit, multiplying the CO gas concentration measured by the gas analysis device by the inert gas flow rate supplied to the secret chamber, thereby calculating the CO gas generation rate; and The output device outputs the calculated CO gas generation rate. Such as the silicon single crystal pulling device described in item 8 of the scope of patent application, wherein: The gas collection port is provided at an upstream portion of the main valve of the exhaust pipe. Such as the silicon single crystal pulling device described in item 8 of the scope of patent application, wherein: The gas collection port is located in the space between the heat shield and the crucible. The silicon single crystal pulling device described in any one of items 8 to 10 in the scope of patent application, wherein: The above-mentioned gas analysis device is a four-layer pole type mass analysis device.

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