JP2004217504A - Graphite heater, apparatus and method for producing single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a graphite heater for producing a single crystal where a silicon single crystal can be produced with high production efficiency when the silicon single crystal is pulled up at a specified defect-free area or a specified defective area. <P>SOLUTION: The graphite heater is used for producing the single crystal by a Czochralski method, is equipped with a terminal part where electric current is supplied and a cylindrical heating part by resistance heating and is set so as to surround a crucible containing a raw material molten liquid. A heating slit part is formed to space an upper slit extending from the upper edge of the heating part to downward and a lower slit extending from the lower edge of the heating part to upward alternately. The heat distribution at the heating part is changed so that the length of at least one slit among the upper slits is different from other upper slits and/or the length of at least one slit among the lower slits is different from other lower slits. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a graphite heater for producing a single crystal used when producing a single crystal by the Czochralski method, a single crystal producing apparatus using the same, and a method for producing a single crystal, and particularly to control crystal defects of a single crystal with high accuracy. In addition, the present invention relates to a single crystal manufacturing graphite heater suitable for manufacturing the single crystal with high production efficiency, a single crystal manufacturing apparatus using the graphite heater, and a single crystal manufacturing method.

  A single crystal used as a substrate of a semiconductor device is, for example, a silicon single crystal, and is mainly manufactured by a Czochralski method (hereinafter abbreviated as CZ method).

  When a single crystal is manufactured by the CZ method, for example, it is manufactured using a single crystal manufacturing apparatus 10 as shown in FIG. The single crystal manufacturing apparatus 10 includes a member for containing and melting a raw material polycrystal such as silicon, a heat insulating member for shutting off heat, and the like. Contained. A pulling chamber 12 extending upward from the ceiling of the main chamber 11 is connected, and a mechanism (not shown) for pulling the single crystal 13 with a wire 14 is provided on the upper portion.

  A quartz crucible 16 for containing the melted raw material melt 15 and a graphite crucible 17 for supporting the quartz crucible 16 are provided in the main chamber 11, and these crucibles 16 and 17 are rotated by a driving mechanism (not shown). The shaft 18 is supported so as to be movable up and down. The driving mechanism of the crucibles 16 and 17 is configured to raise the crucibles 16 and 17 by the amount corresponding to the liquid level drop in order to compensate for the liquid level drop of the raw material melt 15 accompanying the pulling of the single crystal 13.

  A graphite heater 19 for melting the raw material is disposed so as to surround the crucibles 16 and 17. In order to prevent heat from the graphite heater 19 from being directly radiated to the main chamber 11, a heat insulating member 20 is provided outside the graphite heater 19 so as to surround the periphery thereof.

  Further, a cooling cylinder 23 for cooling the pulled single crystal and a graphite cylinder 24 are provided at the lower part thereof, and the single crystal pulled up by cooling gas downstream from the upper part can be cooled. Further, an inner heat insulating tube 25 is provided at the inner lower end of the graphite tube 24 so as to face the raw material melt 15 to cut radiation from the melt surface and to release the radiant heat from the crystal upward. An outer heat insulating material 26 is provided at the lower end of the outer surface so as to face the raw material melt 15 to cut radiation from the melt surface and to keep the raw material melt surface warm.

  A commonly used graphite heater 19 is shown in FIG. The shape of this graphite heater is cylindrical, and is mainly made of isotropic graphite. In the direct current system, which is currently mainstream, two terminal portions 27 are arranged, and the graphite heater 19 is supported by the terminal portions 27. The heat generating part 28 of the graphite heater 19 has two types of slits 29, an upper slit 29 extending downward from the upper end of the heat generating part 28 and a lower slit 30 extending upward from the lower end of the heat generating part 28 so that heat can be generated more efficiently. , 30 are carved from several to several tens of places. Such a graphite heater 19 generates heat mainly from each heat generating slit portion 31 which is a portion between the lower end of the upper slit 29 and the upper end of the lower slit 30 in the heat generating portion 28.

  The raw material lump is accommodated in the quartz crucible 16 arranged in the single crystal manufacturing apparatus shown in FIG. 5 as described above, and the crucible 16 is heated by the graphite heater 19 as described above, so that the raw material in the quartz crucible 16 is obtained. Melt the mass. In this way, the seed crystal 22 fixed by the seed holder 21 connected to the lower end of the wire 14 is deposited on the raw material melt 15 which is the melted raw material lump, and then the seed crystal 22 is rotated. By pulling up, the single crystal 13 having a desired diameter and quality is grown below the seed crystal 22. At this time, after the seed crystal 22 is deposited on the raw material melt 15, so-called seed drawing (necking) is performed in which the diameter is once narrowed to about 3 mm to form a drawn portion, and then the thickening is performed until a desired diameter is obtained. The dislocation-free crystals are pulled up.

  A single crystal manufactured by such a CZ method, for example, a silicon single crystal is mainly used for manufacturing a semiconductor device. In recent years, semiconductor devices have been highly integrated and elements have been miniaturized. As device miniaturization advances, the problem of Grown-in crystal defects introduced during crystal growth becomes more important.

Here, the Grown-in crystal defect will be described.
In a silicon single crystal, when the crystal growth rate is relatively high, grown-in defects such as FPD (Flow Pattern Defect), which are attributed to voids in which vacancy-type point defects are gathered, are present in the entire crystal diameter direction. A region that exists at high density and has these defects is called a V (vacancy) region. When the growth rate is lowered, an OSF (Oxidation Induced Stacking Fault) region is generated in a ring shape from the periphery of the crystal as the growth rate is lowered, and interstitial silicon is gathered outside the ring. Defects such as LEP (Large Etch Pit), which are considered to be caused by dislocation loops, are present at a low density, and a region where these defects are present is called an I (Interstitial) region. Further, when the growth rate is lowered, the OSF ring shrinks to the center of the wafer and disappears, and the entire surface becomes the I region.

  In recent years, it has been discovered that there is an area outside the OSF ring between the V region and the I region, where neither FPD due to vacancies nor LEP due to interstitial silicon exists. This region is called an N (neutral) region. Further, it has been discovered that there is a region where defects detected by the Cu deposition process exist in a part of the N region outside the OSF region.

  These Grown-in defects are considered to be introduced by the parameter V / G, which is the ratio of the pulling rate (V) and the temperature gradient (G) near the solid-liquid interface of the single crystal. (For example, Non-Patent Document 1). That is, the single crystal can be pulled in a desired defect region or a desired defect-free region by adjusting the pulling rate and the temperature gradient so that V / G is constant. However, for example, when a single crystal is pulled up by controlling the pulling speed to a predetermined defect-free region such as the N region, the single crystal grows at a low speed, and thus an increase in manufacturing cost due to a significant decrease in productivity is inevitable. Therefore, in order to reduce the production cost of this single crystal, it is desired to increase the productivity by growing the single crystal at a higher speed. This is theoretically the temperature near the solid-liquid interface of the single crystal. This can be achieved by increasing the gradient (G).

  Conventionally, using a chamber with an effective cooling body and a hot zone structure, and further effectively blocking the radiant heat from the heater, the single crystal being pulled is cooled to near the solid-liquid interface of the single crystal A method has been proposed in which the temperature gradient (G) is increased to achieve high-speed growth (for example, Patent Document 1). These are mainly performed by changing the structure inside the furnace above the surface of the raw material melt contained in the crucible.

In addition, the heat conduction radiation member is placed under the graphite crucible, and the heat consumption of the graphite heater that surrounds the graphite crucible is efficiently obtained by receiving heat radiated from the graphite heater, transferring heat by heat conduction, and releasing the radiation heat toward the crucible. A method has been proposed to achieve high-speed growth by lowering the power and reducing the overall heat quantity, thereby reducing the radiant heat to the silicon single crystal being pulled and increasing the temperature gradient (G) near the solid-liquid interface. (For example, Patent Document 2).
However, it is difficult to say that these methods alone have sufficiently achieved high-speed growth of single crystals, and there is still room for improvement.

International Publication No. 97/21853 Pamphlet JP-A-12-53486 V. V. Voronkov, Journal of Crystal Growth, 59 (1982), 625-643.

  The present invention has been made in view of such a problem. For example, the present invention has a high breakdown voltage and excellent electrical characteristics that exist outside the OSF region and do not have a defect region detected by the Cu deposition process. When a silicon single crystal is pulled up in a predetermined defect-free region such as an N region or in a predetermined defect region, a temperature distribution is controlled with high accuracy to obtain a crystal of a desired quality, and the silicon single crystal is manufactured with high production efficiency. An object of the present invention is to provide a graphite heater for producing a single crystal, a single crystal production apparatus using the same, and a method for producing a single crystal.

  The present invention has been made to solve the above-described problem, and includes at least a terminal portion to which an electric current is supplied and a cylindrical heat generating portion by resistance heating so as to surround a crucible containing a raw material melt. A graphite heater used in the case of producing a single crystal by the Czochralski method, wherein the heat generating portion has an upper slit extending downward from its upper end and a lower slit extending upward from its lower end. And the length of at least one of the upper slits is different from that of the other upper slits and / or the length of at least one of the lower slits. A graphite heater for producing a single crystal, characterized in that the heat generation distribution of the heat generating portion is changed as being different from other lower slits. 1).

  As described above, the length of at least one of the upper slits is different from that of the other upper slit, and / or the length of at least one of the lower slits is different from that of the other lower slit. By changing the heat generation distribution of the heat generating portion, a desired convection can be caused in the raw material melt. By adjusting the convection to increase the temperature gradient (G) in the vicinity of the solid-liquid interface of the silicon single crystal that is being pulled up and causing the crystal growth interface to easily change to an upwardly convex shape, for example, N region High speed growth of silicon single crystal can be achieved. Further, by adjusting the convection by the heat generation distribution of the heater, the oxygen concentration in the produced single crystal can be adjusted to a wide range from low oxygen to high oxygen, and a single crystal having a desired oxygen concentration can be produced with high accuracy.

  In this case, upper slits and / or lower slits having different lengths from the other slits are periodically formed in the circumferential direction, and the heat generation distribution of the heat generating part is cyclic between the high temperature part and the low temperature part in the circumferential direction. (Claim 2), for example, it is preferable that one period of the heat generation distribution is 180 ° (Claim 3).

  As described above, the upper slit and / or the lower slit having different lengths from the other slits are periodically formed in the circumferential direction, and the heat generation distribution of the heat generating portion is such that the high temperature portion and the low temperature portion are in the circumferential direction. By making it periodically distributed, convection in the raw material melt can be promoted not only in the vertical direction but also in the circumferential direction.

  In this case, it is preferable that the period of the heat generation distribution is such that the period based on the upper slit and the period based on the lower slit are shifted in the range of 45 ° to 135 ° in the circumferential direction.

  As described above, the period of the heat generation distribution is such that the period based on the upper slit and the period based on the lower slit are shifted in the range of 45 ° to 135 ° in the circumferential direction, so that the melting of the raw material from the crucible bottom. Longitudinal convection toward the surface of the liquid can be further promoted in a helical direction.

  In this case, it is preferable to have two or more types of upper slits having different lengths from the other slits and / or to have two or more types of lower slits having different lengths from the other slits ( Claim 5).

  Thus, by having two or more types of upper slits and / or two or more types of lower slits, the heat generation distribution of the heat generating portion can be adjusted easily and with high accuracy.

  In this case, the upper slit and / or the lower slit having a length different from that of the other slits are preferably shorter than 50% of the length from the upper end to the lower end of the cylindrical heating portion (claims). 6).

As described above, the upper slit and / or the lower slit having a length different from that of the other slits is shorter than 50% of the length from the upper end to the lower end of the cylindrical heating portion, and thus the heat generation. The heating slits can be easily distributed on the upper side and / or the lower side of the center line that bisects the part in the height direction.
The upper slit and / or the lower slit having a different length from the other slits have a length of about 10% or more of the length from the upper end to the lower end of the cylindrical heat generating portion, thereby maintaining the heat generation efficiency. can do. Further, the strength of the heater body can be maintained by making the upper slit and / or the lower slit have a length of about 90% or less of the length from the upper end to the lower end of the heat generating portion.

  Furthermore, the present invention provides a single crystal production apparatus comprising at least the graphite heater for producing a single crystal (Claim 7), and a single crystal for producing crystals by the Czochralski method using the single crystal production apparatus. A crystal production method is provided (claim 8).

  If a single crystal is manufactured by the CZ method using such a crystal manufacturing apparatus having the single crystal manufacturing heater of the present invention, a high-quality single crystal can be manufactured with high productivity.

  Furthermore, according to the present invention, at least a terminal portion to which current is supplied and a cylindrical heat generating portion by resistance heating are provided, and the Czochralski is disposed so as to surround the crucible containing the raw material melt. A graphite heater used in the case of producing a single crystal by a method, wherein the heat generation distribution of the heat generating part is a periodic distribution of a high temperature part and a low temperature part in a circumferential direction, and the heat generation part is A graphite heater for producing a single crystal is provided in which the period of the heat generation distribution is shifted between an upper side and a lower side of a center line that is vertically divided into two in the height direction (Claim 9). .

  As described above, the heat generation distribution of the heat generating portion is a distribution in which the high temperature portion and the low temperature portion are periodically distributed in the circumferential direction, and above the center line that bisects the heat generating portion vertically in the height direction. Since the period of the heat generation distribution is shifted between the lower side and the lower side, longitudinal convection from the bottom of the crucible to the surface direction of the raw material melt can be further promoted in a helical direction. As a result, the temperature gradient (G) in the vicinity of the solid-liquid interface of the silicon single crystal being pulled increases, and the crystal growth interface easily changes to an upwardly convex shape. For example, a silicon single crystal having a desired quality such as an N region can be obtained. High speed crystal growth can be achieved.

  In this case, the cyclical heat generation distribution in the circumferential direction of the heat generating portion may be any one of the thickness of the heat generating slit portion, the width of the heat generating slit portion, the length of the slit, and the material of the heat generating slit portion. It is preferable that the distribution has a distribution (claim 10).

  As described above, the periodic heat generation distribution in the circumferential direction of the heat generating part may be any one or more of the thickness of the heat generating part slit part, the width of the heat generating slit part, the length of the slit, and the material of the heat generating slit part. Can be easily adjusted by changing in the circumferential direction.

  In this case, it is preferable that one cycle of the heat generation distribution is 180 °.

  Thus, the period of the heat generation distribution is such that one period is 180 °, so that convection can be more reliably promoted in the circumferential direction in the raw material melt.

  In this case, it is preferable that the shift of the period of the heat generation distribution above and below the center line is in a range of 45 ° to 135 °.

  Thus, the period of the heat generation distribution is such that the period between the upper side and the lower side is shifted in the range of 45 ° to 135 ° in the circumferential direction, so that the surface direction of the raw material melt from the crucible bottom Longitudinal convection can be further promoted in a helical direction.

  Furthermore, the present invention provides a single crystal production apparatus comprising the above-mentioned heater for producing a single crystal (Claim 13), and producing a single crystal by the Czochralski method using the single crystal production apparatus. A method is provided (claim 14).

  If a single crystal is manufactured by the CZ method using such a crystal manufacturing apparatus having the single crystal manufacturing heater of the present invention, a high-quality single crystal can be manufactured with high productivity.

  As described above, according to the present invention, for example, a predetermined region such as an N region that exists outside the OSF region and does not have a defect region detected by the Cu deposition process and has a high breakdown voltage and excellent electrical characteristics. When a silicon single crystal is pulled up in a defect-free region or a predetermined defect region, the silicon single crystal can be supplied with high production efficiency.

The present invention will be described below.
In the case of producing a silicon single crystal by the CZ method, the present inventors have found that the convection caused by the temperature distribution of the raw material melt generated when the graphite heater heats the quartz crucible, and the vicinity of the solid-liquid interface of the silicon single crystal being pulled up The simulation analysis by software such as FEMAG or STHAMAS-3D was performed on the relationship with the temperature gradient (G).

  Here, FEMAG is described in the literature (F. Dupret, P. Nicodeme, Y. Ryckmans, P. Waterers, and M. J. Crochet, Int. J. Heat Mass Transfer, 33, 1849 (1990)) and STHAMAS. -3D is comprehensive heat transfer analysis software disclosed in literature (D. Vizman, O. Graebner, G. Mueller, Journal of Crystal Growth, 233, 687-698 (2001)).

  As a result of this simulation analysis, the present inventors have promoted longitudinal convection from the bottom of the graphite crucible toward the surface of the raw material melt, and further promoted this convection in a helical direction with a temperature gradient ( G) was found to be effective in increasing.

  As a means for promoting this longitudinal convection, in addition to a normal graphite heater, a method of installing a bottom heater for heating the raw material melt in the crucible from the bottom of the crucible, or a raw material melt in the crucible A method of installing a two-stage upper and lower graphite heater for heating from above and below is conceivable. However, these methods cannot be expected to provide an economic advantage because the in-furnace facilities become complicated and the power consumption increases. Therefore, the present inventors have promoted the convection in the vertical direction from the bottom of the crucible toward the surface of the raw material melt with a graphite heater alone arranged so as to surround the crucible. It was conceived that if it can be promoted in the direction, a single crystal having the target quality can be produced with good productivity and at low cost, and the present invention has been completed.

Hereinafter, although embodiment of this invention is described, this invention is not limited to these.
In the graphite heater of the present invention, the heat generation distribution of the heat generating portion is not uniformly distributed in the circumferential direction as in the prior art, and one graphite heater generates heat at the top of the crucible or the bottom of the crucible or the crucible R portion. It is designed to have a distribution peak.

  FIG. 1 shows an example of the graphite heater of the present invention. The graphite heater has an upper slit extending downward from the upper end of the heat generating portion 28 and a lower extending upward from the lower end of the heat generating portion so that the current path of the current from the terminal portion 27 has a zigzag shape in the vertical direction at the heat generating portion 28. Slits are provided alternately. The size and arrangement of these slits are changed to change the heat generation distribution of the heat generating portion. For this purpose, four types of slits are provided here. That is, two types of slits, an upper slit A and an upper slit B longer than the upper slit A, are provided as upper slits, and a lower slit C and a lower slit D shorter than the lower slit C are provided as lower slits. Two types of slits were provided.

  At this time, the upper slit A and the lower slit D are preferably designed to be shorter than 50% of the length from the upper end to the lower end of the cylindrical heating portion of the graphite heater. As a result, the heat generating slit formed by the upper slit A and the corresponding lower slit C can be positioned above the center line that divides the heat generating portion in the vertical direction, and the lower slit D The heating slit portion formed by the corresponding upper slit B can be positioned below the center line that divides the heating portion in the vertical direction.

Furthermore, each slit is periodically formed in the circumferential direction, and the heat generation distribution of the heat generating portion is such that the high temperature portion and the low temperature portion are periodically distributed in the circumferential direction, and one cycle is 180 °. I have to. Further, the period based on the upper slit and the period based on the lower slit are shifted by 90 ° in the circumferential direction, and the heat generation distribution is 90 on the upper side and the lower side of the center line that bisects the heat generating part in the vertical direction. It is designed to deviate.
It should be noted that the period based on the upper slit and the period based on the lower slit are preferably shifted in the range of 45 ° or more and 135 ° or less in the circumferential direction. Longitudinal convection in the liquid surface direction can be surely promoted in a helical direction.

  FIG. 2 shows the temperature distribution of the raw material melt accommodated in the crucible when heated by such a graphite heater. As shown in FIG. 2 (a), the heat generating slit formed by the upper slit A and the lower slit C is a portion corresponding to the first quadrant and the third quadrant when the crucible is viewed from directly above, and the raw material melt It plays the role of heating near the surface. On the other hand, as shown in FIG. 2B, the heat generating slit portion formed by the upper slit B and the lower slit D is a portion corresponding to the second quadrant and the fourth quadrant, and serves to heat the crucible bottom or the crucible R portion. Plays. Therefore, the raw material melt in the crucible has a temperature distribution as shown in FIG.

  Such a temperature distribution in the raw material melt eventually promotes convection in the raw material melt from the crucible bottom to the raw material melt surface in the longitudinal direction and further in the helical direction. As a result, secondary convection immediately below the single crystal solid-liquid interface is promoted, and the temperature gradient (G) near the single crystal solid-liquid interface is increased. Therefore, the shape of the single crystal solid-liquid interface is likely to change to an upward convex shape, and the OSF disappears in a higher growth rate region, and for example, the crystal in the N region can be pulled up at a higher speed.

  In addition, since the conventional graphite heater has a uniform heat generation distribution in the circumferential direction, the oxygen concentration in the single crystal can be controlled by changing the convection of the raw material melt. I could only change the relative position of the heater in the height direction. However, in the present invention, since the heat generation distribution itself of the heat generating portion of the graphite heater can be changed according to various purposes, the convection of the raw material melt can be freely changed, and the oxygen concentration in the single crystal can be freely controlled.

  In addition, the circumferential distribution of the heat generating portion in the circumferential direction is not only provided by changing the slit length as described above, but also the thickness of the heat generating slit portion, the width of the heat generating slit portion, and the slit. The distribution can also be provided by changing any one or more of the length and the material of the heating slit portion.

  Further, it is preferable that the shift of the period of the heat generation distribution on the upper side and the lower side of the center line that divides the heat generation part vertically in the vertical direction is in the range of 45 ° to 135 °. Within this range, heating the crucible bottom or the crucible R part is effective in promoting the convection generated in the vertical direction from the crucible bottom to the raw material melt surface in the raw material melt in a helical direction. is there.

  Furthermore, the present invention provides a crystal production apparatus comprising the above graphite heater for producing crystals, and also provides a method for producing a single crystal by the Czochralski method using the crystal production apparatus. In the present invention, a single crystal of a desired defect-free region such as an N region or a desired defect region can be obtained by simply setting a heater having the above-described characteristics in a single-crystal manufacturing apparatus having a conventional in-furnace structure. Can be raised at high speed to increase productivity. Further, since it is not necessary to change the design of an existing device, it can be configured very easily and inexpensively.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
Example 1
A silicon single crystal was manufactured using the single crystal manufacturing apparatus shown in FIG. A quartz crucible having a diameter of 24 inches (600 mm) was charged with 150 kg of raw material polycrystalline silicon, and a silicon single crystal having a diameter of 8 inches (200 mm) and an orientation <100> was pulled up. When pulling up the single crystal, the growth rate was controlled to gradually decrease from the crystal head to the tail in the range of 0.7 mm / min to 0.3 mm / min. Moreover, the silicon single crystal was manufactured so that the oxygen concentration was 22 to 23 ppma (ASTM'79).

  At this time, the graphite heater shown in FIG. 1 was used. In other words, this graphite heater has a total length of 600 mm, and is provided with four upper slits A, six upper slits B, eight lower slits C, and four lower slits D. The upper slit A and the lower slit D are each 250 mm in length, and the upper slit B and the lower slit C are each 500 mm in length.

The silicon single crystal thus manufactured was examined for OSF, FPD, LEP, and Cu deposition.
That is, at a crystal solidification rate of about 10% or more (in the case of the conditions of the present embodiment, the crystal straight body portion is 10 cm or more), after cutting the wafer at a length of every 10 cm in the crystal axis direction, surface grinding and polishing are performed. I went and investigated as follows.

(A) Investigation of FPD (V region) and LEP (I region):
After 30 minutes of seco-etching (no stirring), the in-plane density of the sample was measured.
(B) OSF field survey:
After heat treatment at 1100 ° C. for 100 minutes in a Wet-O ₂ atmosphere, the sample in-plane density was measured.
(C) Investigation of defects by Cu deposition process:
The processing method is as follows.
1) Oxide film: 25 nm 2) Electric field strength: 6 MV / cm
3) Energizing time: 5 minutes

As a result, the distribution state of each region became the distribution shown in FIG. That is, the growth rate at the boundary of each region was as follows.
Growth rate of boundary between V region and OSF region = 0.56 mm / min.
Growth rate at the boundary between the OSF region and the N region where defects were detected by the Cu deposition process = 0.55 mm / min.
The growth rate of the boundary between the N region where a defect was detected by the Cu deposition process and the N region where no defect was detected by the Cu deposition process = 0.54 mm / min.
Growth rate of the boundary between the N region and the I region where no defect was detected by the Cu deposition process = 0.52 mm / min.

Next, based on the above results, the growth rate was controlled from 0.5 cm to 0.52 mm / min from the straight cylinder 10 cm to the straight tail so that the N region where no defect was detected by the Cu deposition process could be aimed. The silicon single crystal was pulled up (see FIGS. 4A and 4B). The pulled silicon single crystal was processed into a mirror-finished wafer to evaluate the oxide film pressure resistance. The C-mode measurement conditions are as follows.
1) Oxide film: 25 nm 2) Measuring electrode: phosphorus-doped polysilicon 3) Electrode area: 8 mm ² 4) Determination current: 1 mA / cm ²
As a result, the oxide film breakdown voltage level was 100% non-defective.

(Comparative Example 1)
The graphite heater shown in FIG. 6 was used. In this graphite heater, the total length of the heat generating portion is 600 mm, and 10 upper slits and 12 lower slits are provided. The upper slits are all 500 mm long, and the lower slits are all 500 mm long. A silicon single crystal was produced under the same conditions as in Example 1 except that this graphite heater was used. In the same manner as in Example 1, OSF, FPD, LEP, and Cu deposition were investigated.

As a result, the distribution state of each region became the distribution shown in FIG. That is, the growth rate at the boundary of each region was as follows.
Growth rate of boundary between V region and OSF region = 0.50 mm / min.
Growth rate at the boundary between the OSF region and the N region where defects were detected by the Cu deposition process = 0.48 mm / min.
The growth rate of the boundary between the N region in which the defect is detected by the Cu deposition process and the N region in which the defect is not detected by the Cu deposition process = 0.47 mm / min.
Growth rate at the boundary between the N region and the I region where no defect was detected by the Cu deposition process = 0.45 mm / min.

Next, based on the above results, the growth rate is controlled from 0.46 to 0.45 mm / min from the straight body 10 cm to the straight body tail so that the N region where no defect is detected by the Cu deposition process can be aimed. The silicon single crystal was pulled up (see FIGS. 4A and 4B). The pulled silicon single crystal was processed into a mirror-finished wafer, and the oxide film breakdown voltage characteristics were evaluated in the same manner as in Example 1.
As a result, the oxide film breakdown voltage level was 100% non-defective.

  FIG. 3 shows the distribution of various defects with respect to the growth rate in Example 1 and Comparative Example 1. According to this, when growing an N region single crystal in which no defect was detected by the Cu deposition process, in Comparative Example 1, it is necessary to grow at a low speed with a growth rate of 0.46 to 0.45 mm / min. On the other hand, in Example 1, it can be seen that the growth rate can be very high at a growth rate of 0.53 to 0.52 mm / min (see FIG. 4). Therefore, when the graphite heater of the present invention is used, productivity can be improved and manufacturing cost can be reduced.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  For example, in the embodiments of the present invention, the normal CZ method in which a magnetic field is not applied when pulling up a silicon single crystal has been described as an example. However, the present invention is not limited to this and is also applicable to an MCZ method in which a magnetic field is applied. it can.

It is the schematic which shows one example of the graphite heater of this invention. (A) Exploded view, (b) Side view. It is the conceptual diagram which showed the temperature distribution of the raw material melt in a crucible when a crucible is heated with the graphite heater of FIG. (A) Temperature distribution on the raw material melt surface layer side, (b) Temperature distribution on the crucible bottom side of the raw material melt, and (c) Overall temperature distribution of the raw material melt. It is explanatory drawing which shows the growth rate and crystal defect distribution of a single crystal. (a) Example 1, (b) Comparative Example 1. Single crystal growth when growing a silicon single crystal by controlling the growth rate of the N region in which no defect was detected by Cu deposition treatment, which was found by investigating the relationship between the single crystal growth rate and crystal defect distribution It is the comparison figure which compared the speed in Example 1 and Comparative Example 1 ((a), (b)). It is the schematic of a single crystal manufacturing apparatus. It is the schematic which shows an example of the conventional graphite heater. (A) Exploded view, (b) Side view.

Explanation of symbols

10 ... Single crystal manufacturing apparatus, 11 ... Main chamber, 12 ... Lifting chamber,
13 ... single crystal, 14 ... wire, 15 ... raw material melt, 16 ... quartz crucible,
17 ... graphite crucible, 18 ... shaft, 19 ... graphite heater, 20 ... heat insulation member,
21 ... Seed holder, 22 ... Seed crystal, 23 ... Cooling tube, 24 ... Graphite tube,
25 ... Inner insulation tube, 26 ... Outer insulation material,
27 ... Terminal part, 28 ... Heat generating part, 29 ... Upper slit, 30 ... Lower slit,
31 ... heating slit part.

Claims (14)

  In the case of producing a single crystal by the Czochralski method, which is provided with at least a terminal portion to which current is supplied and a cylindrical heat generating portion by resistance heating and is arranged so as to surround a crucible containing a raw material melt. A graphite heater used in the above, wherein the heat generating portion is formed by alternately providing an upper slit extending downward from the upper end thereof and a lower slit extending upward from the lower end thereof, and forming the heat generating slit portion, and The heat generation distribution of the heat generating part is assumed that the length of at least one of the upper slits is different from the other upper slits and / or the length of at least one of the lower slits is different from the other lower slits. A graphite heater for producing a single crystal, characterized in that   Upper slits and / or lower slits having different lengths from the other slits are periodically formed in the circumferential direction, and the heat generation distribution of the heat generating portion is periodically distributed between the high temperature portion and the low temperature portion in the circumferential direction. The graphite heater for producing a single crystal according to claim 1, wherein   3. The graphite heater for crystal production according to claim 2, wherein one cycle of the exothermic distribution is 180 °.   The period of the heat generation distribution is such that the period based on the upper slit and the period based on the lower slit are shifted in a range of 45 ° to 135 ° in the circumferential direction. A graphite heater for crystal production as described in 1.   It has two or more types of upper slits having different lengths from the other slits, and / or has two or more types of lower slits having different lengths from the other slits. The graphite heater for producing a single crystal according to any one of claims 1 to 4.   The upper slit and / or the lower slit having a different length from the other slits are shorter than 50% of the length from the upper end to the lower end of the cylindrical heat generating portion. The graphite heater for producing a single crystal according to claim 5.   An apparatus for producing a single crystal comprising at least the graphite heater for producing a single crystal according to any one of claims 1 to 6.   A method for producing a single crystal, comprising producing a crystal by the Czochralski method using the single crystal production apparatus according to claim 7.   In the case of producing a single crystal by the Czochralski method, which is provided with at least a terminal portion to which current is supplied and a cylindrical heat generating portion by resistance heating and is arranged so as to surround a crucible containing a raw material melt. The heat generation distribution of the heat generating part is a periodic distribution of a high temperature part and a low temperature part in the circumferential direction, and the heat generation part is vertically divided in the height direction for 2 minutes. A graphite heater for producing a single crystal, wherein the period of the heat generation distribution is shifted between the upper side and the lower side of the center line.   The circumferential heat generation distribution of the heat generating part is obtained by changing at least one of the thickness of the heat generating slit part, the width of the heat generating slit part, the length of the slit, and the material of the heat generating slit part. The graphite heater for producing a single crystal according to claim 9, wherein the graphite heater has a distribution.   11. The graphite heater for producing a single crystal according to claim 9, wherein one cycle of the heat generation distribution is 180 °.   The single crystal production according to any one of claims 9 to 11, wherein a shift in the period of the heat distribution above and below the center line is in a range of 45 ° to 135 °. Graphite heater.   A single crystal manufacturing apparatus comprising at least the graphite heater for manufacturing a single crystal according to any one of claims 9 to 12.   A method for producing a single crystal, comprising producing a crystal by the Czochralski method using the apparatus for producing a single crystal according to claim 13.

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