WO2002027077A1

WO2002027077A1 - Method of manufacturing silicon monocrystal and device for manufacturing semiconductor monocrystal

Info

Publication number: WO2002027077A1
Application number: PCT/JP2001/008408
Authority: WO
Inventors: Makoto Iida; Hiromi Watanabe
Original assignee: Shin-Etsu Handotai Co.,Ltd.
Priority date: 2000-09-26
Filing date: 2001-09-26
Publication date: 2002-04-04
Also published as: JP2002097098A; TWI289614B; JP3838013B2

Abstract

A method of manufacturing a silicon monocrystal and a device for manufacturing a semiconductor monocrystal containing silicon monocrystal; the method of manufacturing the silicon monocrystal, comprising the steps of, inside a cultivating furnace (2), disposing a crucible (12) having molten silicon liquid (14) stored therein, disposing upper in-furnace structures (5, 30) so as to surround a cultivated monocrystal (23), and adjusting the flow velocity of the inert gas allowed to flow out of the tip opening part of the upper in-furnace structure (5) when the inert gas passes through a space surrounded by the inner wall of the crucible (12) and the outer wall of the upper in-furnace structures (5, 30) to 6.5 cm/sec. or higher when the inert gas is discharged to the outside of the cultivating furnace (2) through the space surrounded by the inner and outer walls while the silicon monocrystal (23) is cultivated by the Czochralski method while the inert gas is allowed to flow down from the upper side to a molten silicon liquid level (14a) in the crucible (12) in the upper in-furnace structure (5).

Description

Description: Manufacturing method of silicon single crystal and manufacturing apparatus of semiconductor single crystal

The present invention relates to a method for manufacturing a silicon single crystal and an apparatus for manufacturing a semiconductor single crystal including the silicon single crystal. Background art

As a method for producing a semiconductor single crystal, a so-called Czochralski method is used.

Method, hereinafter referred to as CZ method). In this method, a raw material mass is accommodated in a crucible disposed in a growth furnace of a single crystal manufacturing apparatus, and a raw material in the crucible is melted by heating a heater disposed around the crucible to a high temperature. When the temperature of the melt is stabilized, the seed crystal is immersed on the surface of the raw material melt. Thereafter, the seed crystal is gently pulled up to form a semiconductor single crystal having a desired diameter and quality below the seed crystal. Cultivate.

Recent semiconductor single crystal manufacturing equipment using the CZ method has been developed with the advancement of automation and the development of optical equipment, and an imaging device for observing the inside of the growth furnace outside the growth furnace and a crystal pulled from the melt. Devices equipped with an optical detection device such as an optical diameter detection device for detecting the diameter of a laser or a radiation thermometer for measuring the temperature of a melt have been used. For example, when an imaging device is used, the main body of the device is mounted outside the growth furnace, and through the furnace observation window provided on the growth furnace wall and the upper furnace internal structure disposed inside the growth furnace. The raw material melt surface and the single crystal growing part inside the growing furnace are photographed. The image data obtained by the photographing is used as growth control information for the semiconductor single crystal. Such an observation window inside the furnace may separate the inside and outside of the growth furnace and impair the function of the upper furnace internal structure. In general, transparent glass is inserted so that the inside of the growth furnace can be observed and measured without the need to check the growth status of the single crystal through this glass, and to collect information inside the growth furnace. Processing and performing various controls necessary for single crystal growth. On the other hand, in the recent production of single crystals, in order to suppress defects during single crystal growth as much as possible, or by increasing the cooling rate of the grown single crystal, the pulling rate of the single crystal, and thus the productivity, Various methods have been sought for improvement. As a method for efficiently cooling the single crystal pulled from the raw material melt, the upper furnace internal structure is placed just above the raw material melt surface so as to surround the single crystal, and the heater and the raw material melt surface A common method is to rapidly cool the crystal by shielding radiant heat. In this case, the upper furnace internal structure to be used includes a cylindrical gas rectifying cylinder disposed so as to hang down from the upper growth furnace, a heat shielding screen having an inverted conical appearance, and an inner structure of the growth furnace. Various shapes are being studied according to the environment and crystal quality.

It also shields radiant heat from around the crystal for the purpose of suppressing the crystal defects introduced during crystal growth to a low density, and improving the productivity by increasing the crystal growth rate at high speed. In addition, studies were also conducted on upper furnace internal structures, which were designed to improve the thermal conductivity of the upper internal structures and to improve the heat insulation structure, thereby taking measures to actively increase the cooling efficiency of crystals. Is being transformed.

By the way, from the raw material melt heated to a temperature as high as 140 ° C. or more by the heater, evaporates such as SiO 2 (—silicon oxide) are constantly emitted toward the growth furnace. When the evaporant hits a relatively low temperature part in the growth furnace, the evaporate solidifies and precipitates in the low temperature part, adheres to the structure of the furnace wall of the growth furnace and the structure in the furnace, and gradually accumulates. To go. If the amount of such deposits becomes too large, the deposits may come off during the operation, fall into the raw material melt, or adhere to the growing part of the single crystal, causing crystals such as dislocations. This may cause defects and may hinder normal single crystal growth. In addition, there is another problem that the members are eroded by the deposits and the life is shortened. Also, if the evaporation from the raw material melt adheres to the above-mentioned observation window inside the furnace, the glass will become cloudy, and the operator will not be able to observe the single crystal growth part, and the measured values of the optical measuring equipment attached outside the growth furnace May be unstable, or in the worst case, it may be impossible to continue the single crystal growing operation itself.

In a conventional single crystal manufacturing apparatus using the CZ method, as a means for avoiding the above-mentioned problems, when growing a single crystal, an inert gas such as Ar (argon) gas having low reactivity is supplied to the inside of the growth furnace. It is circulated at a sufficient flow rate, and evaporates from the raw material melt are discharged out of the growth furnace together with the inert gas. In particular, large-diameter long single crystals, which require time to grow single crystals, and the so-called Multiple Czochralski Method (single crystal growth), without solidifying the crucible material melt after growing the single crystals. A method of growing multiple semiconductor single crystals from one crucible by refilling the raw material mass into the crucible again). In the production of single crystals using a single crucible, the evaporation from the raw material melt is efficiently removed from the growth furnace. It is an important requirement to keep the growth furnace clean for a long time from the start to the end of the operation, and to maintain a stable operation.

However, if the crystal cooling function of the upper furnace internal structure is enhanced as described above in order to lower the density of crystal defects incorporated in the single crystal and improve productivity, the upper furnace internal structure The temperature of the gas itself has also dropped significantly, resulting in the accelerated adhesion of evaporants. Also, the attachment of evaporants to the upper furnace internals tends to be further promoted as the size of single crystal manufacturing equipment increases. Specifically, single crystal manufacturing equipment for growing large single crystals uses large-diameter crucibles to hold a large amount of molten material, or it is necessary to hold large-diameter crucibles. As a result, the growth furnace itself also had a large volume, and relatively low-temperature parts were more likely to be formed in places away from the heat source.

An object of the present invention is to grow and deposit silicon vapor from a silicon melt on an upper furnace structure located immediately above a silicon melt in growing a silicon single crystal using the CZ method. To provide a method for producing a silicon single crystal that can effectively suppress the occurrence of a single crystal, for example, can continue operation for a long time without obstructing in-reactor observation necessary for growing a single crystal and controlling equipment. In order to realize the method rationally, it is possible to appropriately recirculate the inert gas flowing into the growth furnace during the growth of the single crystal. It is an object of the present invention to provide an apparatus for manufacturing a semiconductor single crystal having a function of uniformly or promptly discharging the growth out of the growth furnace while preventing or suppressing the stagnation. Disclosure of the invention

In order to solve the above-mentioned problems, a method for producing a silicon single crystal according to the present invention comprises: disposing a crucible containing a silicon melt inside a growing furnace; and forming an upper furnace so as to surround the grown single crystal. An internal structure is provided, and a silicon single crystal is grown by the Czochralski method while flowing an inert gas downstream from above in the upper furnace internal structure toward the silicon melt surface in the rutupo. During the growth of the silicon single crystal, the inert gas flowing out of the opening at the tip of the upper furnace internal structure is transferred to the outside of the growth furnace via a space surrounded by the inner wall of the crucible and the outer wall of the upper furnace internal structure. When discharging, the flow rate of the inert gas when passing through the space is adjusted to be 6.5 cm / sec or more.

According to the method of the present invention, the flow rate of the inert gas flowing into the growth furnace from the space between the outer wall of the upper furnace structure and the inner wall of the crucible along the melt surface is adjusted to be 6.5 cm / sec or more. By doing so, the amount of inert gas convection up to the upper part of the growth furnace can be increased, and the evaporant is reduced in the lower temperature part above the furnace, especially in the upper furnace structure where the cooling effect is enhanced and the temperature is lowered. Can be effectively suppressed from being deposited and becoming a deposit. In this specification, the flow rate of the inert gas is represented by the value at the position where the radial distance between the inner wall of the crucible and the outer wall of the upper furnace internal structure with respect to the single crystal pulling axis in the radial direction is minimum. Shall be.

In the above method of the present invention, from the outside of the growth furnace, through the furnace observation window made of a transparent material (for example, heat-resistant glass such as quartz glass) formed on the growth furnace and the upper furnace internal structure, respectively. It is possible to grow a silicon single crystal while optically detecting or observing the state inside the upper furnace internal structure. By adopting the present invention, even in a situation where the temperature of the upper furnace internal structure in which the furnace observation window is provided is relatively low, the furnace observation window may be fogged by the deposits. It becomes difficult. This makes it possible to continue photographing and observing a single crystal during growth by a photographing means such as a force camera or the like and measurement by an optical system detector such as a crystal diameter detecting device without any problem for a long time. In particular, in the production of semiconductor single crystals in which the diameter of the grown crystal is controlled by detecting the illuminated ring (fusion ring) formed at the boundary between the melt surface and the crystal, it is caused when evaporates adhere to the observation window in the furnace. Since the measurement error is reduced over a long period of time, it is possible to control the diameter with high accuracy, and it is possible to improve the productivity and yield of the single crystal. Further, since it is possible to continue pulling a crystal having a desired diameter with a small error, it is possible to grow a single crystal in which the quality is stable over the entire length of the crystal and the dispersion of impurities such as oxygen is suppressed.

The effects of the present invention are particularly remarkable in the production of large-diameter crystals, which require time for crystal growth, and in pulling long crystals. In particular, the space in the ceiling of the growth furnace main body is relatively large, the diameter exceeds 50 cm, and a large single crystal capable of accommodating a large-diameter rutupo capable of melting 100 kg or more of polycrystalline silicon material. The effect can also be fully exhibited in manufacturing equipment. Also, after pulling the single crystal, the same crucible is refilled with the polycrystalline raw material without solidifying the raw material melt, and a single pulling method using a multiple pulling method to grow a plurality of single crystals from one quartz crucible is used. Satisfactory effects can be obtained in crystal production.

Next, in the present invention, the above-mentioned effect is sufficiently achieved by controlling the flow rate of the inert gas. The lower limit is set at 6.5 cm / sec, but increasing the flow rate more than necessary wastes inert gas, which is not desirable in view of manufacturing costs. Absent. In view of this situation, the space (gap) between the outer wall of the upper furnace internal structure and the inner wall of the crucible Force (flow rate) It is desirable that the flow rate of the inert gas flowing out does not exceed 20 cm / sec at the maximum. The flow rate is more desirably set in the range of 6.5 to 8.5 cmZ sec.

Next, the upper furnace internal structure is arranged so as to surround the grown single crystal so as to function as a means for adjusting the thermal history of the grown single crystal, and is placed immediately above the melt surface. The upper furnace internal structure serves to prevent radiant heat from the heater, raw material melt, etc. from directly hitting the crystal. In this case, the crystal growth part where the melt surface of the raw material and the grown single crystal are in contact is the shadow of the upper furnace internal structure placed just above these melts, and can be directly observed from outside the growth furnace. Therefore, it is particularly effective to provide the in-furnace observation window, and the effect of the present invention is more remarkably exhibited from the viewpoint of preventing fogging and the like. The upper furnace internal structure can be made of a material having good thermal conductivity such as metal or graphite, and the structure is designed so as to exhibit its effect immediately after the single crystal is pulled. In some cases, the lower end is placed with a slight gap of about 5 to 5 Omm from the surface of the raw material melt.

For the upper furnace internal structure, the cooling temperature atmosphere of the single crystal part surrounded by the upper furnace internal structure can be adjusted by devising the thermal conductivity and the heat insulation structure. In particular, in the case of an upper furnace internal structure such as a heat shield screen with a truncated cone inverted, the inert 1 "raw gas blown up from the melt surface easily hits the surface of the upper furnace internal structure. On the other hand, even in the case of an upper furnace structure having a substantially cylindrical shape such as a gas flow control cylinder, the outer wall of the upper furnace internal structure can be effectively suppressed. the flow rate of inert I ¹ product gas flowing out from between the the Rutsupo inner wall 6. by adjusting such that the 5 cm / sec or more, is possible to effectively suppress the adhesion of vaporized substances evaporated from the raw material melt Possible It is.

In addition, a gas rectifying cylinder is provided at the lower end facing the surface of the raw material melt so that the surface of the raw material melt is kept warm to suppress temperature fluctuations of the melt near the crystal growth interface and grow the single crystal smoothly. A heat shield ring integrally formed on the side can be used. Although it can be said that such an upper furnace internal structure tends to have a lower temperature and a lower temperature, the use of the method of the present invention can effectively suppress the adhesion of evaporants. In this case, the flow velocity of the inert gas flowing from the space between the outer peripheral surface of the heat shield ring and the inner wall of the crucible into the growth furnace main body is adjusted to be 6.5 cm / sec or more.

In addition, in the production of single crystals using the CZ method, single crystals are grown by arranging upper furnace structures of complicated and various shapes directly above the raw material melt. In this case, the effect can be obtained by adjusting the flow rate of the inert gas flowing between the upper furnace internal structure and the crucible inner wall containing the raw material melt to 6.5 cm / sec or more and flowing it into the growth furnace. Can be obtained.

Next, in the method of the present invention, it is desirable to grow a silicon single crystal while keeping the inside of the growth furnace at a reduced pressure of 200 hPa or less. As a result, the operation at a relatively low pressure is performed, so that the evaporation of the evaporation from the raw material melt on the furnace wall of the growth furnace and the surface of the upper internal structure can be further reduced. In addition, (1) the amount of inactive I "raw gas flowing into the breeding furnace is small and it is economical. The pressure inside the breeding furnace during operation should be kept at a lower limit of at least 50 hPa. This is because the required flow rate of the inert gas can be easily obtained, and separately from the following reasons: that is, the amount of Si in the evaporating from the melt surface Oxygen is supplied by the elution of oxygen from the wall of the quartz crucible containing the raw material melt, so that if the pressure inside the growth furnace holding the raw material melt becomes lower than necessary, the melting will occur. In some cases, the amount of SiO 2 evaporating from the liquid surface increases, and as a result, the quartz crucible wall containing the raw material melt deteriorates quickly and it becomes difficult to continue the operation for a long time. Lower the pressure of the breeding furnace to avoid Even in this case, it is preferable to grow the single crystal while keeping the pressure at about 50 hPa.

In addition, over a long period of operation, evaporates from the sulfuric acid solution often accumulate on the bottom of the growth furnace where the heat insulator, heater, heater electrode, etc. are located. Therefore, in order to suppress such deposition, it is preferable to provide an exhaust gas port at the bottom of the growth furnace of the manufacturing apparatus. For example, when using a growth furnace in which a recovery space forming part for forming a semiconductor single crystal recovery space is integrated in the upper part of the growth furnace main body, the gas rectification cylinder is placed in the growth furnace from the lower end side of the recovery space. An inert gas is provided so as to extend inside the main body, and the inert gas is introduced into the above-mentioned recovery space, and is discharged out of the growth furnace through an exhaust gas pipe connected to the bottom of the growth furnace main body. The adoption of such a method enables a smooth gas flow in the growth furnace main body and is effective in increasing the flow rate of the inert gas to 6.5 cm / sec or more.

In a single-crystal manufacturing device equipped with an exhaust gas port at the bottom of the growth furnace main body and an upper furnace internal structure, the inert gas introduced from the upper part of the growth furnace main body passes through, for example, a gas flow straightening tube to melt the raw material. After passing partly from the outer periphery of the crucible to the ceiling of the breeding furnace body, partly from the outer periphery of the crucible to the ceiling of the breeding furnace body, it flows downstream to the lower part of the breeding furnace and out of the furnace through the exhaust gas port. Is discharged. In this case, if there is only one gas outlet, the flow of the gas returning to the breeding furnace tends to be uneven, and the flow rate of the inert gas is slow, and the inert gas is sufficiently recirculated. In places where evaporation does not occur, there is a possibility that evaporates may easily adhere.

In order to prevent such a problem, it is effective to discharge an inert gas from gas outlets provided at a plurality of locations around the single crystal pulling shaft on the bottom of the growth furnace main body. Further, in the apparatus for producing a semiconductor single crystal of the present invention, a crucible containing a raw material melt is arranged inside a growth furnace, and an upper furnace internal structure is arranged so as to surround the grown single crystal. In order to grow a silicon single crystal by the Kralski method, an inert gas is flowed down from the upper part of the growth furnace toward the raw material melt surface in the rutupo in the upper furnace internal structure. In addition, a plurality of exhaust ports for exhausting inert gas are formed at substantially equal angular intervals on a circumferential path centered on the single crystal pulling shaft on the bottom surface of the growth furnace. It is characterized by the following.

That is, according to the semiconductor single crystal manufacturing apparatus of the present invention, the inert gas flowing in the growth furnace can be refluxed and discharged out of the growth furnace without stagnation. The obtained effect can be made more reliable. In addition, since the inert gas flowing through the growth furnace can be smoothly discharged outside the growth furnace without stagnation in the growth furnace, oxides such as SiO 2 evaporated from the raw material melt can be removed from the growth furnace. Precipitation in the low-temperature portion of the furnace is suppressed, and the inside of the growth furnace can be kept clean for a long time. This makes it difficult for precipitates to accumulate in the upper part of the furnace, causing precipitates to fall into the raw material melt during operation and attaching to the growing single crystal, causing slip dislocation in the crystal. As a result, it is possible to reduce the factors that hinder the crystal growth itself, and to achieve operations.

In this case, considering the quality of the crystal and the continuation of stable operation for a long time, it is desirable to recirculate the inert gas into the growth furnace as uniformly as possible about the crystal pulling axis. Preferably, a plurality of gas outlets are formed at substantially equal angular intervals on a circumferential path centered on the single crystal pulling axis on the bottom portion of the growth furnace main body. Also, in order to make the inactive 14 gas recirculate more evenly inside the breeding furnace body, two or more exhaust gas slots should be provided at the bottom of the furnace so that each has the same gas exhaust capacity. It is desirable to configure manufacturing equipment. In particular, a single crystal growing apparatus having a large volume inside the growing furnace works more effectively, and by adopting such a structure of the single crystal manufacturing apparatus, the structure in the upper furnace and the material melt can be improved. The inert gas flowing out from between the crucible inner walls accommodating the gas can be kept uniform throughout the gap. As a result, the inert gas flowing above the melt in the growth furnace body is uniformly recirculated without stagnation, so that it is possible to prevent evaporation substances from adhering to the furnace wall of the growth furnace and the upper furnace internal structure. . BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram showing an example of a single crystal manufacturing apparatus of the present invention in a longitudinal section.

FIG. 2 is a schematic diagram showing a modified example of the single crystal manufacturing apparatus of FIG. 1, in which a heat shield ring at the lower end of the gas flow straightening tube is replaced with a heat reflecting plate.

FIG. 3 is a schematic view showing a modification in which an inverted conical heat shielding screen is provided instead of the gas flow tube.

Fig. 4 is a cross-sectional view of Fig. 1 near the bottom of the growth furnace main body.

FIG. 5 is a schematic diagram showing the exhaust protrusion together with various modifications thereof.

FIG. 6 is a schematic view showing a modified example in which three sets of exhaust gas ports and exhaust gas pipes are formed at equal intervals in a cross section and a partial vertical section.

FIG. 7 is a cross-sectional view showing a modification of the exhaust gas port shape.

FIG. 8 is a cross-sectional view showing still another modified example. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, taking as an example the growth of a silicon single conductor single crystal manufactured by the CZ method. FIG. 1 is a schematic cross-sectional view showing one embodiment of a semiconductor single crystal manufacturing apparatus according to the CZ method of the present invention. The semiconductor single crystal manufacturing apparatus (hereinafter simply referred to as “single crystal manufacturing apparatus”) 1 accommodates a rutupo 12 filled with a silicon melt 14 as a raw material melt, and a growing furnace for the silicon single crystal 2 3 And a recovery space forming part 4 integrally formed above the growth furnace main body 2 and containing and holding the silicon single crystal 23 pulled up from the silicon melt 14. A crucible 12 having a quartz crucible 12a on the inside and a graphite crucible 12b on the outside is placed at approximately the center of the inside of the growth furnace body 2 via a crucible support shaft 13. The crucible 12 is driven by a crucible drive mechanism 19 attached to the lower end of the crucible support shaft 13. In other words, it is freely rotatable and vertically operable in accordance with the growth conditions and work process of the silicon single crystal 23.

Above the silicon melt 14 housed in the crucible 12, a gas rectifying cylinder 5 as an upper furnace internal structure is positioned, with its lower end surface located immediately above and immediately adjacent to the silicon melt 14, and pulled up It is arranged so as to surround the silicon single crystal 23 to be formed. In the present embodiment, a heat shield ring 30 is attached to the lower end of the gas flow straightening tube 5 so as to face the melt surface 14a. The heat shield ring 30 is made of a heat insulating layer made of a porous or fibrous heat insulating material, and more effectively shields the radiant heat from the silicon melt 14 to enhance the heat retaining effect of the melt. The temperature fluctuation of 14 can be further reduced. In particular, if the heat insulating layer is made of a material having a high heat insulating effect such as a fibrous heat insulating material made of carbon fiber, a larger heat retaining effect can be obtained, and more stable crystal growth can be performed. The periphery of the heat insulating layer can be covered with a coating layer made of graphite or the like for the purpose of, for example, reducing the influence of carbon contamination derived from the heat insulating layer on the melt.

Next, the in-furnace observation windows 44 and 8 made of quartz glass are formed in the growth furnace main body 2 and the gas flow straightening tube 5 as the upper furnace internal structure, respectively. These furnace observation windows 4

The silicon single crystal is grown while the state inside the gas rectifying cylinder 5 is not detected or observed by the photographing means such as the camera 6 after passing through steps 4 and 8.

Here, as shown in FIG. 2, instead of the heat shielding ring 30, a plate-like heat reflecting ring 130 (for example, made of isotropic graphite) having an outer diameter on an inverted truncated cone is provided. You may. FIG. 3 shows an example in which a graphite heat shielding screen 55 having a truncated conical outer shape with a narrowed lower end is provided as an upper furnace internal structure. In this case, a flange-shaped heat reflection plate 55a (here, substantially parallel to the melt surface) can be provided at the lower end so as to protrude inward. 2 and 3, the same reference numerals are given to the same elements as those in FIG. 1, and the detailed description will be omitted.

Returning to Fig. 1, the outside of the crucible 12 melts the polycrystalline raw material put in the crucible 12 A heater 15 for maintaining the silicon melt 14 at a desired temperature is provided upright on the bottom surface of the growth furnace main body 2 with a heater electrode (not shown) as a support. When growing a single crystal, the heater 15 is heated by supplying electric power from the heater electrode to the heater 15 so that the silicon melt 14 is kept at a high temperature.

Next, the recovery space forming section 4 has a gas inlet 9a for introducing an inert gas such as Ar gas into the breeding furnace. In operation, the gas inlet 9a is connected to the gas inlet 9a. After the flow rate of the inactive raw gas is adjusted by the gas flow rate control device 122 on the inert gas pipe 9 via the active gas pipe 9, the gas is introduced into the growth furnace.

On the other hand, a heat insulating material 16 and a lower heat insulating material 3 are provided inside the growth furnace main body 2 in order to efficiently keep the inside of the growth furnace main body 2 warm and to protect the furnace wall. In addition, a gas outlet 11 for exhausting the inert gas introduced into the breeding furnace is provided at the bottom of the breeding furnace main body 2. From the breeding furnace through the exhaust gas pipe 7. The exhaust gas pipe 7 is collected in a collecting pipe 17, and a conductance valve 18 is installed in the middle of the pipe 17, and further ahead is a diagram for assisting the exhaust of inert gas from the growth furnace. A vacuum pump is provided to keep the inside of the growth furnace under reduced pressure. The pressure inside the growth furnace is maintained at a furnace pressure suitable for crystal growth (for example, 50 to 200 hPa) by adjusting the conductance pulp 18 provided in the exhaust gas pipe. Each exhaust gas pipe 7 has substantially the same axial cross-sectional area and length, and is commonly sucked by the above-described vacuum pump via the collective pipe 17. As a result, the inert gas is exhausted from each exhaust gas port 11 at the same flow rate.

In the present embodiment, in order to efficiently and uniformly discharge the inert gas in the growth furnace main body 2 from the growth furnace, as shown in FIG. At the bottom of the growth furnace main body 2, two points are provided at the center of the growth furnace, that is, at positions symmetrical with respect to the single crystal pulling axis (that is, the formation angle interval around the single crystal pulling axis is approximately 1). 80 ° C). As shown in FIG. 6, three or more exhaust gas ports 11 (and corresponding exhaust gas pipes 7) may be formed at substantially equal angular intervals with respect to the single crystal pulling shaft. As a result, more uniform inert gas reflux is possible.

In this embodiment, as shown in FIG. 1, when the silicon melt 14 leaks out of the root 12 for some reason and reaches the lower part of the growth furnace main body 2, the high-temperature silicon melt 14 is discharged. The following measures have been taken to prevent the gas from flowing out of the growth furnace directly from the exhaust gas port 11. That is, on the bottom surface of the growth furnace body (growth furnace) 2, an exhaust protrusion 7a is formed to project from the bottom surface in a form corresponding to the communication position of the exhaust gas pipe 7, and the exhaust gas port 11 The opening lower edge position is formed to be separated from the bottom surface by a predetermined height H with respect to the portion 7a. In addition, as shown in FIG. 5 (b), an exhaust port 61 may be provided in the exhaust projection 7a so as to open to the upper end surface, but in this embodiment, the exhaust projection 7a is provided. Has a distal end closing portion 7c for closing the distal end portion, and has a shape in which the exhaust gas slot 11 is opened on the side surface of the exhaust projecting portion 7a. This can effectively prevent splashes of the melt 14 falling from above from directly entering the exhaust gas pipe 7. As shown in FIG. 5 (a), here, a plurality of the exhaust gas ports 11 are formed at predetermined intervals in the circumferential direction of the outer peripheral surface of the exhaust protrusion 7a.

In the present embodiment, the exhaust projection 7a is formed by projecting the upper end of the exhaust gas pipe 7 through the bottom of the growth furnace main body 2 and projecting a predetermined length H from the bottom. As a result, the exhaust protrusion 7a can be formed at the same time by the pipe member forming the exhaust gas pipe 7, thereby reducing the number of parts. However, as shown in FIG. 5 (c), a configuration in which a cylindrical exhaust protrusion 67 is separately formed outside the exhaust gas pipe 7 may be adopted. In FIG. 5 (c), the upper surface side of the exhaust projection 67 is open to form an exhaust gas port 69, and a shielding plate 68 which forms a front end blocking portion at a predetermined interval is located above the exhaust port 69. It is provided. The shielding plate 68 is connected to the annular upper end surface of the exhaust protrusion 67 via a plurality of columns 69 arranged at predetermined intervals in the circumferential direction. In any case, the exhaust gas port 11 is filled with the silicon melt from the exhaust gas port 11 even if all of the silicon melt 14 that can be stored in the crucible 12 flows out into the growth furnace. If it is formed at a position where it does not flow, a more reliable device can be obtained. Specifically, for example, in FIG. 1, the height to the lower edge of the exhaust gas port 11 is H, and the volume of the liquid that can fill the growth furnace up to the height H is V (H) crucible 1. It is better to determine H so that V (H) ≥ VC, where VC is the internal volume of 2.

Next, a wire 22 is wound above the recovery space forming part 4 to pull up the silicon single crystal 23 from the silicon melt 14 or to rotate the crystal during the growth of the single crystal. (Not shown) is provided. A seed holder 120 is attached to the tip of the wire 22 unwound from the wire winding and unwinding mechanism, and the seed crystal 21 is locked to the seed holder 20.

Hereinafter, an example of a method for manufacturing a silicon single crystal using the single crystal manufacturing apparatus 1 will be described. First, a polycrystalline silicon material is filled in a quartz crucible 12 b provided in the single crystal manufacturing apparatus 1, and the material is melted by heating the heater 15 to obtain a silicon melt 14. . Then, when the melt 14 is stabilized at the desired temperature, the wire 22 is unwound by operating the wire winding and unwinding mechanism, and the seed crystal 21 locked on the seed holder 20 is operated. The tip is gently brought into contact with the surface of the silicon melt 14. Thereafter, the wire 22 is wound up while rotating the rutupo 12 and the seed crystal 21 in directions opposite to each other, and the silicon single crystal 23 can be grown below the seed crystal 21 by pulling up. .

During the growth of the silicon single crystal 23, the inert gas flowing into the recovery space forming part 4 from the gas inlet 9a flows from inside the recovery space forming part 4 as a subsequent upper furnace internal structure. It flows down into the gas straightening tube 5 and is blown out onto the raw material melt surface 14a. Then, along the raw material melt surface 14 a, it goes around upward through the lower edge of the gas flow straightening tube 5, and is heat shielded. After flowing through the gap between the ring 30 and the inner wall of the root 12, it flows into the breeding furnace main body 2. Specifically, by controlling the amount of the inert gas flowing in the growth furnace main body 2 and the furnace pressure, the heat shield ring 30 disposed directly above the silicon melt 14 and the inside of the rupture 12 are controlled. The flow rate of the inert gas flowing through the gap D with the wall is adjusted so that it is 6.5 cm / sec or more. Is almost constant at). In addition, some inert gas directly travels around the gas flow straightening tube 5 and reaches near the ceiling of the growth furnace body 2. After that, the gas flows downward from the upper part of the breeding furnace body 2 toward the exhaust gas port 11, while refluxing the inside of the breeding furnace body 2, and substantially uniformly from the respective exhaust gas ports 11 provided on the bottom surface of the breeding furnace body 2. The gas is exhausted to the outside of the growth furnace through the exhaust gas pipe 7 and the collecting pipe 17.

Thereby, it is possible to effectively suppress the evaporation of the SiO 2 and the like from the silicon melt 14 from adhering to the ceiling wall of the recovery space forming section 4, the outer surface of the gas rectifying tube 5, and the like. In particular, by preventing evaporation substances from adhering to the in-furnace observation window glass 8 of the gas flow straightening tube 5, the in-furnace observation window glass 8 becomes cloudy and a problem that a single crystal growing portion cannot be observed can be avoided. You.

In the single crystal production apparatus 1, the opening shape or axial cross-sectional shape (exhaust gas shape) of the exhaust gas pipe 7 communicating with the exhaust gas outlet at the bottom of the growth furnace is a circle centered on the single crystal pulling shaft. The shape may be elongated along the circumferential path. As an example, as shown in FIG. 7, the shape of the exhaust gas port can be an arc shape along a circumferential path. By adopting such a shape, the inert gas can be recirculated into the growth furnace more uniformly without unevenness.

Further, a plurality of exhaust gas ports may be formed along the plurality of circumferential paths set at different positions in the radial direction with the single crystal pulling axis as a center on the bottom portion of the growth furnace. . FIG. 8 shows an example in which the exhaust gas pipe 7 having the shape of the exhaust gas port shown in FIG. 7 is formed in two rows along two concentric circular paths. This As a result, the inert gas can be more uniformly refluxed.

The present invention is not limited only to the growth of the silicon single crystal as described above. For example, the method for producing a silicon single crystal and the apparatus for producing a semiconductor single crystal according to the present invention are applied to a method and apparatus for producing a silicon single crystal using the MCZ method in which a single crystal is grown while a magnetic field is applied to the melt. The present invention is naturally possible, and the present invention can be applied to the case where another semiconductor single crystal such as a compound semiconductor is grown by the CZ method.

(Example)

Hereinafter, the present invention will be described more specifically with reference to experimental examples, but the present invention is not construed as being limited thereto.

(Example 1)

Except that only one set of the exhaust gas pipe 7 and the exhaust gas port 11 on the bottom of the growth furnace was used, the silicon single crystal Training was conducted. The diameter of the heat shielding ring 30 was 40 O mm. Then, using a quartz crucible 12b with a diameter of 44 mm, 60 kg of polycrystalline silicon material was filled, and after filling the inside of the growth furnace with Ar gas, the heater 15 was heated. As a result, a silicon melt 14 as a raw material melt was obtained. After that, wait for the temperature of silicon melt 14 to stabilize to a temperature suitable for single crystal growth, then immerse seed crystal 21 on the surface of silicon melt 14 and rotate in the opposite direction to crucible 12 A single crystal with a diameter of 150 mm was grown below the seed crystal by gently pulling the melt upward. The Ar gas of 100 liters Zmin was refluxed in order to discharge the evaporated matter from the silicon melt 14 to the outside of the growth furnace. The distance D between the outer periphery of the heat shield ring 30 and the inner wall of the crucible was 20 mm, and the flow rate of the inert gas flowing through the gap D was estimated to be about 6.5 cm / sec. The pressure in the furnace was 100 hPa.

At this time, when the inside of the growth furnace was observed from outside, the observation window 8 There was no dirt or fogging, and the diameter of the pulled silicon single crystal 23 had an error of about 1 mm from the target value, so the polycrystalline silicon material was crucible without solidifying the silicon melt 14. The single crystal was grown again. The amount of the raw material melt at this time was 60 kg, and a silicon single crystal 23 having the same diameter of 150 mm was grown from the silicon melt 14.

This operation was repeated, and when the growth of the third single crystal was completed, the inside of the growth furnace was confirmed.Haze appeared in the observation window 8 in the furnace, and adhesion of silicon oxide under the gas rectification cylinder 5 was observed. Therefore, it was judged that it was difficult to continue the production of the single crystal any more, so the power of the heater 15 was turned off, the temperature in the growth furnace was lowered, and the work was completed. At this time, the growth of the third single crystal was completed after a lapse of 80 hours from the start of operation. When the diameter of the finally grown silicon single crystal 23 was confirmed, the error became large from the point where the observation window 8 in the furnace became cloudy, and in the latter half of the silicon single crystal 23, ± A diameter variation of 2 mm was observed. After the temperature dropped to near normal temperature, the state of adhesion of oxidized substances inside the growth furnace was confirmed. At the top of the outer surface of No. 5, some deposits such as SiO 2 were observed. On the other side, farther from the exhaust gas port 11, more deposits were found in the upper part of the gas flow straightening tube 5 and near the ceiling of the growth furnace main body 2.

(Example 2)

Next, using a single crystal manufacturing apparatus shown in FIG. 1 in which a set of exhaust gas pipe 7 and exhaust gas port 11 was provided at two locations, the other conditions were the same as those of Example 1 and silicon single crystal was used. Training was conducted. As a result, as in Example 1, when three silicon single crystals were pulled, clouding occurred in the observation window 8 in the furnace, making it difficult to continue the operation, and the pulling of the single crystal was terminated. After the temperature was sufficiently lowered, the inside of the furnace was observed in the same manner as in Example 1, and it was found that the amount of deposits on the ceiling of the growth furnace main body 2 and the upper part of the outer surface of the gas flow straightening tube 5 was relatively small. The adhesion was relatively uniform with little deviation. This is an inert gas Is returned to the furnace without stagnation, and evaporates from the raw material melt can be smoothly discharged to the outside of the furnace.

(Example 3)

Using the single crystal manufacturing apparatus 1 shown in FIG. 1, a silicon single crystal was grown. The same conditions as in Example 2 were adopted except that the diameter of the heat shield ring 30 disposed at the lower end of the flow straightening tube 5 was set to be slightly larger, 410 mm. At this time, the distance D between the outer circumference of the heat shield ring 30 and the inner wall of the ruppo was 15 mm, and the flow velocity of the inert gas flowing through the gap D was estimated to be approximately 8 cm / sec. The pressure in the furnace was 100 hPa. Then, even after the growth of the fourth single crystal was completed, no fogging or the like was observed in the observation window portion 8 in the furnace, and the surface of the gas rectifying cylinder 5 was not so much stained by deposits. On the other hand, since the operation time exceeded 100 hours at this point, it was judged that the durability of the crucible 12 was approaching its limit, and the work of growing the single crystal was completed. When the diameter of the fourth single crystal was confirmed, there was no large variation in the crystal diameter, and there was only a diameter error of about 1 mm in soil from the target value, and the operating time was 100 hours. It was found that the measurement function of the detector was sufficiently ensured even after the above.

(Comparative example)

Using the single crystal manufacturing apparatus 1 shown in FIG. 1, a silicon single crystal was grown. Note that the same conditions as in Example 2 were adopted except that the diameter of the heat shielding ring 30 disposed at the lower end of the rectifying tube 5 was set to 39 O mm, which was smaller than that in Example 1 or 2. At this time, the distance between the outer periphery of the heat shielding ring 30 and the inner wall of the crucible was 25 mm, and the flow velocity of the inert gas flowing through the gap was estimated to be approximately 5 cmZsec. The pressure inside the furnace was 100 hPa.

When the single crystal was pulled up and the inside of the growth furnace was observed, there was no dirt or fogging in the observation window 8 inside the furnace, and the diameter of the pulled crystal had an error of about 1 mm soil from the target value. Therefore, the polycrystalline silicon raw material can be And the silicon single crystal was pulled again. Even when pulling up the second and subsequent single crystals, the amount of the raw material melt is returned to 60 kg as in the first crystal, and a single crystal with the same diameter of 15 O mm as the first crystal is grown from this raw material melt. did.

However, when the growth of the second single crystal was completed and the melting of the polycrystalline silicon material for growing the third single crystal was completed, clouding of the observation window 8 in the furnace began to be observed, and the seed crystal was started. At the stage where 21 is immersed in the silicon melt 14, the fogging became intense, making it difficult to confirm the illuminated ring seen at the boundary between the grown silicon single crystal 23 and the silicon melt 14. The operation was stopped at this point. At this time, 50 hours had passed since the start of operation. After that, when the inside of the growth furnace was observed, a large amount of deposits such as oxides were deposited on the upper surface of the gas flow straightener 5 and above the growth furnace body 2, and the outer surface of the gas flow straightener 5 was substantially removed. The whole was covered by the deposit. In addition, the adhesion of the oxidized substance was remarkably observed also in a part of the observation window portion 8 in the furnace.

Claims

The scope of the claims

1. A crucible containing the silicon melt is placed inside the growth furnace, and an upper furnace structure is arranged so as to surround the grown single crystal. A silicon single crystal is grown by the Czochralski method while an inert gas is downstream from above toward the silicon melt surface in the crucible, and during the growth of the silicon single crystal, When discharging the inert gas flowing out of the tip opening through the space surrounded by the inner wall of the rutupo and the outer wall of the upper furnace internal structure, the inert gas removes the space from the growth furnace. A method for producing a silicon single crystal, characterized in that a flow velocity at the time of passing is adjusted to be 6.5 cm / sec or more.

2. From outside the breeding furnace, optically change the state inside the upper furnace structure through the furnace observation windows made of a transparent material formed on the growth furnace and the upper furnace structure, respectively. 2. The method for producing a silicon single crystal according to claim 1, wherein said silicon single crystal is grown while detecting or observing.

3. The method for producing a silicon single crystal according to claim 1, wherein the internal structure of the upper furnace is a gas straightening cylinder.

4. The gas rectifying cylinder according to any one of claims 1 to 3, wherein a heat shielding ring is integrated with a lower end side facing the silicon melt surface. The method for producing a silicon single crystal according to the above.

5. The method according to any one of claims 1 to 4, wherein the silicon single crystal is grown while keeping the inside of the growth furnace at a reduced pressure of 200 hPa or less. A method for producing a silicon single crystal.

6. In the growth furnace, a recovery space forming portion that forms a recovery space for the silicon single crystal is integrated with an upper portion of a growth furnace main body, and the gas rectifying cylinder is provided from a lower end side of the recovery space. It is provided in a form extending inside the growth furnace main body, and The gas according to any one of claims 1 to 5, wherein the reactive gas is introduced into the recovery space, and is discharged out of the growth furnace through an exhaust gas pipe connected to a bottom portion of the growth furnace body. A method for producing a silicon single crystal according to any one of the above.

7. The inert gas is discharged from gas outlets provided at a plurality of places around the single crystal pulling shaft in a bottom portion of the growth furnace main body. Production method of silicon single crystal.

8. The method according to claim 7, wherein the plurality of gas outlets are formed at substantially equal angular intervals on a circumferential path centered on the single crystal pulling axis on a bottom surface of the growth furnace main body. A method for producing a silicon single crystal.

9. A crucible containing the raw material melt is placed inside the growth furnace, and an upper furnace structure is arranged so as to surround the grown single crystal. Silicon single crystal growth by the Chiyoklarski method For this reason, an inert gas is caused to flow downstream from the upper part of the growth furnace toward the surface of the raw material melt in the crucible in the upper furnace internal structure, and furthermore, an exhaust gas for exhausting the inert gas. A plurality of openings formed at substantially equal angular intervals on a circumferential path centered on the single crystal pulling axis in a bottom portion of the growth furnace;

10. The apparatus for producing a semiconductor single crystal according to claim 9, wherein said inert gas is exhausted from each of said plurality of exhaust gas ports at an equal flow rate.

1 1. Opening or axial cross-sectional shape (hereinafter referred to as “exhaust gas port shape”) of the exhaust gas pipe communicating with the exhaust gas port at the bottom surface of the growth furnace, along a circumferential path centered on the single crystal pulling shaft. 12. The apparatus for producing a semiconductor single crystal according to claim 10, wherein the apparatus has an elongated shape.

12. The apparatus for manufacturing a semiconductor single crystal according to claim 11, wherein the exhaust gas port shape has an arc shape along the circumferential path.

1 3. The exhaust gas port is centered on the single crystal pulling axis at the bottom of the growing furnace. 13. The semiconductor single unit according to claim 11 or 12, wherein a plurality of the plurality of circumferential paths set at different positions in the radial direction are formed along each of the plurality of circumferential paths.

14. An exhaust protrusion is formed on the bottom surface of the growth furnace so as to correspond to the communication position of the exhaust gas pipe from the bottom surface, and the exhaust gas port has an opening lower edge position with respect to the exhaust protrusion. The apparatus for producing a semiconductor single crystal according to any one of claims 9 to 13, wherein the apparatus is formed so as to be separated from the bottom surface by a predetermined height.

15. An exhaust projection formed by projecting a predetermined length from the bottom surface through the bottom of the growth furnace at an upper end portion of the exhaust gas pipe. Item 5. An apparatus for producing a semiconductor single crystal according to item 4.

16. The exhaust port according to claim 14, wherein the exhaust protrusion has a distal end closing portion that closes a distal end portion, and the exhaust gas port is opened on a side surface of the exhaust protrusion. Or the apparatus for producing a semiconductor single crystal according to Item 15.