JP2004217503A - Graphite heater for producing single crystal, single crystal production device, and single crystal production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a graphite heater for producing single crystals by which, at the time when silicon single crystals are pulled up in a prescribed non-defective region or a prescribed defective region, the silicon single crystals can be produced at high productive efficiency. <P>SOLUTION: The graphite heater used for producing single crystals by the Czochralski method is at least provided with a terminal part fed with electric current and a cylindrical heat generation part by resistance heating, and is arranged so as to surround a crucible housing a raw material melt. In the heat generation part, a heat generation slit part is formed in such a manner that upper slits elongating downward from the upper ends thereof and lower slits elongating upward from the lower ends thereof are alternatively provided. Also, the upper slits consist of long and short two kinds. The width of the lower end of each long upper slit is wider than the width of the upper end, and/or the width of the lower end of each lower slit is wider than the width of the upper end, and the heat generation distribution in the heat generation part is changed. <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 production apparatus using the same, and a single crystal production method, and in particular, to precisely control a crystal defect of a single crystal. The present invention relates to a graphite heater for producing a single crystal which is suitable for producing the single crystal with high production efficiency, a single crystal producing apparatus and a single crystal producing method using the same.

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

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

  In the main chamber 11, a quartz crucible 16 for accommodating the melted raw material melt 15 and a graphite crucible 17 for supporting the quartz crucible 16 are provided, and these crucibles 16 and 17 are rotated by a driving mechanism (not shown). It is supported by a shaft 18 so as to be able to move up and down. The drive mechanism of the crucibles 16 and 17 raises the crucibles 16 and 17 by an amount corresponding to the lowering of the liquid level in order to compensate for the lowering of the liquid level of the raw material melt 15 due to the pulling of the single crystal 13.

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

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

  FIG. 7 shows a commonly used graphite heater 19. The shape of this graphite heater is cylindrical, and is mainly made of isotropic graphite. In the current mainstream DC system, two terminal portions 27 are arranged, and the terminal portion 27 supports the graphite heater 19. The heating portion 28 of the graphite heater 19 has two types of slits 29, an upper slit 29 extending downward from the upper end of the heating portion 28 and a lower slit 30 extending upward from the lower end of the heating portion 28, so as to generate heat more efficiently. , 30 are carved from several places to tens of places. Such a graphite heater 19 mainly generates heat mainly from the respective heat generating slit portions 31 which are portions between the lower end of the upper slit 29 and the upper end of the lower slit 30 among the heat generating portions 28.

  The raw material mass is accommodated in the quartz crucible 16 arranged in the single crystal manufacturing apparatus shown in FIG. 6 as described above, and this crucible 16 is heated by the graphite heater 19 as described above. Melt the mass. The seed crystal 22 fixed by the seed holder 21 connected to the lower end of the wire 14 is immersed in the raw material melt 15 obtained by melting the raw material lump as described above, and then the seed crystal 22 is rotated. The single crystal 13 having a desired diameter and quality is grown below the seed crystal 22 by pulling. At this time, after the seed crystal 22 is immersed in the raw material melt 15, so-called seed drawing (necking) is performed, in which the diameter is once reduced to about 3 mm to form a drawn portion, and then the diameter is increased until a desired diameter is obtained. To pull up dislocation-free crystals.

  A single crystal manufactured by such a CZ method, for example, a silicon single crystal is mainly used for manufacturing a semiconductor device. 2. Description of the Related Art In recent years, semiconductor devices have been highly integrated, and elements have been miniaturized. With the progress of miniaturization of devices, the problem of grown-in crystal defects introduced during crystal growth has become more important.

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

  In recent years, it has been discovered that a region where neither FPDs or the like due to holes nor LEPs or the like due to interstitial silicon exists outside the OSF ring between the V region and the I region. This region is called an N (Neutral) region. Further, it has been discovered that there is a region outside the OSF region where a defect detected by Cu deposition processing exists in a part of the N region.

  It is believed that the amount of these grown-in defects is determined by the parameter V / G, which is the ratio of the pulling rate (V) to the temperature gradient (G) near the solid-liquid interface of the single crystal. (For example, Non-Patent Document 1.) That is, if the pulling speed and the temperature gradient are adjusted so that V / G becomes constant, the single crystal can be pulled in a desired defect region or a desired defect-free region. However, for example, when a single crystal is pulled by controlling the pulling speed to a predetermined defect-free region such as an N region, the single crystal grows at a low speed, and a rise in manufacturing cost due to a drastic decrease in productivity was unavoidable. Therefore, in order to reduce the manufacturing cost of this single crystal, it is desired to grow the single crystal at a higher speed to increase the productivity, but this is theoretically the temperature near the solid-liquid interface of the single crystal. This can be achieved by increasing the gradient (G).

  Conventionally, by using a chamber and a hot zone structure equipped with an effective cooling body, and further efficiently cutting off the radiant heat from the heater, the single crystal being pulled is cooled and the vicinity of 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 accommodated in the crucible.

In addition, by arranging the heat conducting radiating member below the graphite crucible and radiating heat from the graphite heater to transmit the heat by heat conduction and radiating the radiant heat toward the crucible, it is possible to efficiently consume the graphite heater surrounding the graphite crucible. A method has also been proposed in which the power is reduced, the amount of heat is reduced, the radiant heat to the silicon single crystal being pulled is reduced, the temperature gradient (G) near the solid-liquid interface is increased, and high-speed growth is achieved. (For example, Patent Document 2).
However, it is difficult to say that high-speed single crystal growth was sufficiently achieved by these methods alone, and there is still room for improvement.

WO 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 withstand voltage and excellent electric characteristics that exists outside the OSF region and has no defect region detected by Cu deposition processing. When pulling a silicon single crystal in a predetermined defect-free region or a predetermined defect region such as an N region, a temperature distribution is controlled with high precision to obtain a crystal of desired quality, and the silicon single crystal is manufactured with high production efficiency. It is an object of the present invention to provide a graphite heater for manufacturing a single crystal, a single crystal manufacturing apparatus using the same, and a single crystal manufacturing method using the same.

  The present invention has been made in order to solve the above-mentioned problems, and at least a terminal portion to which a current is supplied and a cylindrical heating portion formed by resistance heating are provided so as to surround a crucible accommodating a raw material melt. A graphite heater used for producing a single crystal by the Czochralski method, wherein the heating portion has an upper slit extending downward from an upper end thereof and a lower slit extending upward from a lower end thereof alternately. And the length of the upper slit is made of two types, the width of the lower end of the longer upper slit is wider than the width of the upper end thereof. And / or wherein the width of the lower end of the lower slit is wider than the width of the upper end and the heat generation distribution of the heat generating portion is changed, and a graphite heater for producing a single crystal is provided. That (claim 1).

  In this way, the length of the upper slit is made of two types, long and short, and the width of the lower end of the longer upper slit is wider than the width of the upper end thereof, and / or the lower end of the lower slit. By changing the heat generation distribution of the heat generating portion as the width is larger than the width of the upper end, the convection in the vertical direction from the bottom of the crucible to the surface of the raw material melt due to the heat generation distribution of the heater itself. Can be caused. Due to the convection in the vertical direction, the temperature gradient (G) near the solid-liquid interface of the silicon single crystal being pulled is increased, so that the crystal growth interface is easily changed to an upwardly convex shape. Speedup can be achieved. Further, by adjusting the convection by the heat generation distribution of the heater, the oxygen concentration in the single crystal to be produced 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, the width of the lower end of the longer upper slit is wider than the width of the upper end by 1.5 times or more and 2.5 times or less, and the width of the lower end of the lower slit is set to the upper end. It is preferable that the width is 1.5 times or more and 2.5 times or less than the width (claim 2).

  Thus, the width of the lower end of the longer upper slit is wider than the width of the upper end in a range of 1.5 times or more and 2.5 times or less, and the lower end width of the lower slit is Since the width of the heating slit is 1.5 to 2.5 times the width of the upper end, the center of heat generation of the heat generating slit portion is below the center line that divides the heat generating portion vertically into two in the height direction. , The effect of concentrated heating on the crucible bottom or the crucible R portion reliably promotes vertical convection from the crucible bottom to the surface of the raw material melt in the raw material melt. be able to. Further, since the convection is appropriate within this range, the temperature gradient (G) near the solid-liquid interface in the crystal can be made substantially uniform in the radial direction. Therefore, the manufacturing margin of the predetermined defect-free region such as the N region can be expanded, and a single crystal of the predetermined defect-free region can be manufactured stably and at high speed.

  In this case, it is preferable that the shorter upper slit has a length shorter than 50% of the length from the upper end to the lower end of the heat generating portion (Claim 3). It is preferable that the length is 70% or more of the length from the upper end to the lower end of the heat generating portion (claim 4).

As described above, the shorter upper slit has a length shorter than 50% of the length from the upper end to the lower end of the heat generating portion, and the longer upper slit has the length of the heat generating portion. By having a length of 70% or more of the length from the upper end to the lower end, the heat generating centers of the heat generating slits can be distributed above and below the center line that vertically divides the heat generating portion into two in the height direction. it can.
The shorter upper slit has a heating efficiency of about 10% or more of the length from the upper end to the lower end of the heat-generating portion. The strength of the heater body can be maintained by setting the length of the longer upper slit to about 90% or less of the length from the upper end to the lower end of the heat generating portion.

  In this case, it is preferable that the two types of upper slits are formed periodically in the circumferential direction, and the heat generation distribution of the heat generating portion is such that high-temperature portions and low-temperature portions are periodically distributed in the circumferential direction. (Claim 5) For example, it is preferable that one cycle of the heat generation distribution is 180 ° (Claim 6).

  In this manner, the two types of upper slits are formed periodically 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. In addition, convection in the raw material melt can be promoted not only in the vertical direction but also in the circumferential direction.

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

  If a single crystal is manufactured by the CZ method using such a crystal manufacturing apparatus provided with 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 having a high withstand voltage and excellent electrical characteristics, which is present outside the OSF region and has no defect region detected by the Cu deposition process. When a silicon single crystal is pulled in a defect-free region or a predetermined defect region, the silicon single crystal can be supplied with high production efficiency.

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

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

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

  As means for promoting this vertical convection, a method of installing a bottom heater for heating the raw material melt in the crucible from the bottom of the crucible in addition to the usual graphite heater, or A method of installing two-stage graphite heaters for heating from above and below can be considered. However, these methods cannot be expected to have an economic merit because the equipment in the furnace becomes complicated and the power consumption increases. Then, the present inventors promoted convection in the vertical direction from the bottom of the crucible toward the surface of the raw material melt with a single graphite heater disposed so as to surround the crucible, and further reduced the convection by a helical flow. The present inventors have completed the present invention by conceiving that a single crystal having a target quality can be manufactured with good productivity and at low cost if it can be promoted in the direction.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.
The graphite heater of the present invention does not uniformly distribute the heat distribution of the heat generating portion in the circumferential direction as in the prior art, but one graphite heater generates heat even at the top of the crucible, at the bottom of the crucible, or at the crucible R portion. It is designed to have an uneven temperature distribution so as to have a distribution peak.

  1 and 2 show 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 slit 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. The 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, three 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, were provided as the upper slits, and a lower slit C was provided as the lower slit.

  Further, the width of the lower end of the upper slit B is wider than the width of the upper end thereof (see FIG. 2A), and / or the width of the lower end of the lower slit C is wider than the width of the upper end thereof (FIG. 2). (See (b)). At this time, the width of the lower end of the upper slit B is wider than the width of the upper end by 1.5 times or more and 2.5 times or less, and the width of the lower end of the lower slit C is 1.times. It is preferable to design so as to be wider in the range of 5 times to 2.5 times. When 1.5 times or more, the concentrated heating effect on the crucible bottom or crucible R portion effectively promotes the vertical convection from the crucible bottom to the surface of the raw material melt in the raw material melt. And the effect of increasing the temperature gradient (G) near the solid-liquid interface of the single crystal being pulled can be obtained. On the other hand, if the ratio is 2.5 times or less, the interval between adjacent slits is sufficient, so that the calorific value of the graphite heater is moderate, and therefore, the graphite material of the heater is prevented from being deteriorated by its own heat generation. Can prolong the life of the graphite heater. Further, since the convection is appropriate within this range, the temperature gradient (G) near the solid-liquid interface in the crystal can be made substantially uniform in the radial direction. Therefore, the manufacturing margin of the predetermined defect-free region such as the N region can be expanded, and a single crystal of the predetermined defect-free region can be manufactured stably and at high speed.

  At this time, the upper slit A is preferably designed to have a length shorter than 50% of the length from the upper end to the lower end of the cylindrical heating portion of the graphite heater. It is preferable to design so that the length is 70% or more of the length from the upper end to the lower end of the heat generating portion. Thereby, the heat generating slit portion 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 vertically into two in the height direction. In order to make the center of heat generation of the heating slit formed by the lower slit C and the lower slit C corresponding thereto smaller than the width of the lower side of the heating slit in comparison with the upper side, the heat generating part is moved up and down in the height direction by two. It can be located below the dividing center line.

  Furthermore, each slit is formed periodically in the circumferential direction, and the heat generation distribution of the heat generating part is such that the high temperature part and the low temperature part are periodically distributed in the circumferential direction, and one cycle thereof is 180 °. I have to. Further, the heat generation distribution of the heat generating portion of the graphite heater is shifted by 90 ° between the upper side and the lower side of the center line which vertically divides the heat generating portion into two.

  FIG. 3 shows the temperature distribution of the raw material melt contained in the crucible when heated by such a graphite heater. As shown in FIG. 3A, the heating 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 is a portion of the raw material melt. It plays the role of heating near the surface. On the other hand, as shown in FIG. 3B, the heat generation center of the heat generation slit formed by the upper slit B and the lower slit C corresponds to the second quadrant and the fourth quadrant, and is located at the crucible bottom or the crucible R. Plays the role of heating. Therefore, the raw material melt in the crucible has a temperature distribution as shown in FIG. 3C as a whole.

  As a result, the temperature distribution in the raw material melt promotes the convection in the raw material melt from the crucible bottom to the raw material melt surface in a vertical direction and further in a helical direction. This promotes convection immediately below the single crystal solid-liquid interface, which is generated secondarily, and increases the temperature gradient (G) near the single crystal solid-liquid interface. Therefore, the shape of the single crystal solid-liquid interface is more likely to change to an upward convex shape, and the OSF disappears in the higher growth rate region. For example, the crystal in the N region can be pulled up at a high speed.

  Further, in the conventional graphite heater, since the heat generating portion has a uniform heat generation distribution in the circumferential direction, the control of the oxygen concentration in the single crystal by changing the convection of the raw material melt is performed by using a crucible and graphite. I could only change the relative positional relationship in the height direction of the heater. 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.

  Further, the present invention provides a crystal manufacturing apparatus equipped with the above-described graphite manufacturing graphite heater, and also provides a method for manufacturing a single crystal by the Czochralski method using the crystal manufacturing apparatus. In the present invention, a heater having the above-described characteristics is simply set in a single crystal manufacturing apparatus having a conventional in-furnace structure, and a single crystal in a desired defect-free region such as an N region or a single crystal in a desired defect region is pulled up at a high speed. And increase productivity. Further, since there is no need to change the design of the existing device, the configuration can be made very simply 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 of <100> was pulled. When the single crystal was pulled, the growth rate was controlled so as to gradually decrease from the head to the tail in the range of 0.7 mm / min to 0.3 mm / min. In addition, a silicon single crystal was manufactured such that the oxygen concentration was 22 to 23 ppma (ASTM '79).

  At this time, the graphite heater shown in FIG. 1 was used. That is, this graphite heater has a heating section with a total length of 500 mm, and is provided with six upper slits A, four upper slits B, and twelve lower slits C. The upper slit A has a length of 200 mm, and the upper slit B and the lower slit C each have a length of 400 mm. Further, the upper slit A and the upper slit B were designed so that the width was uniform from the upper end to the lower end. On the other hand, as shown in FIG. 2B, the lower slit C is designed such that the width of the lower end is wider than the width of the upper end. The width of the lower end of the first and second (six in total) lower slits C from the terminal side is designed to be 1.7 times wider than the width of the upper end, and the remaining (four in total) lower slits The width of the lower end of the slit C is designed to be 2.0 times wider than the width of the upper end.

Then, 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 is 10 cm or more), a wafer is cut at a length of every 10 cm in the crystal axis direction, and then surface grinding and polishing are performed. Investigation was conducted as follows.

(A) FPD (V region) and LEP (I region) investigation:
After seco etching (without stirring) for 30 minutes, the in-plane density of the sample was measured.
(B) OSF area survey:
After heat treatment at 1100 ° C. for 100 minutes in a Wet-O ₂ atmosphere, the in-plane density of the sample was measured.
(C) Inspection of defects by Cu deposition processing:
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 area was as shown in FIG. That is, the growth rate at the boundary of each region was as follows.
Growth rate at the boundary between the V region and the OSF region = 0.63 mm / min.
The growth rate at the boundary between the OSF region and the N region where a defect was detected by the Cu deposition process = 0.62 mm / min.
The growth rate at 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 = 0.61 mm / min.
The growth rate at the boundary between the N region and the I region where no defect was detected by the Cu deposition process = 0.59 mm / min.

Next, based on the above results, the growth rate was controlled from 0.60 to 0.59 mm / min from the straight body 10 cm to the straight body tail so as to aim at the N region where no defect was detected by the Cu deposition process. Then, the silicon single crystal was pulled up (see FIGS. 5A and 5B). The mirror-finished wafer was processed from the pulled silicon single crystal, and the oxide film breakdown voltage characteristics were evaluated. The C mode measurement conditions are as follows.
1) Oxide film: 25 nm 2) Measurement electrode: phosphorus-doped polysilicon 3) Electrode area: 8 mm ² 4) Judgment 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. 7 was used. This graphite heater has a heating section with a total length of 500 mm, and is provided with 10 upper slits and 12 lower slits. The upper slits were all 400 mm long and designed to have a uniform width from the upper end to the lower end. The lower slits were all 400 mm long, and were designed to have a uniform width from the upper end to the lower end. A silicon single crystal was manufactured under the same conditions as in Example 1 except that this graphite heater was used. Then, as in Example 1, the OSF, FPD, LEP, and Cu deposition were investigated.

As a result, the distribution state of each area was as shown in FIG. That is, the growth rate at the boundary of each region was as follows.
Growth rate at the boundary between the V region and the OSF region = 0.50 mm / min.
The growth rate at the boundary between the OSF region and the N region where a defect was detected by the Cu deposition process = 0.48 mm / min.
The growth rate at 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 = 0.47 mm / min.
The 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 was 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 was detected by the Cu deposition process could be aimed. Then, the silicon single crystal was pulled up (see FIGS. 5A and 5B). The mirror-finished wafer was processed from the pulled silicon single crystal, 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. 4 shows the distribution of various defects with respect to the growth rate in Example 1 and Comparative Example 1. According to this, when growing a single crystal in the N region where no defect was detected by the Cu deposition process, in Comparative Example 1, it was 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 can be performed at a very high speed with the growth rate being 0.60 to 0.59 mm / min (see FIG. 5). Therefore, when the graphite heater of the present invention is used, the productivity can be improved, and the manufacturing cost can be reduced.

  Note that the present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present invention, and any device having the same operation and effect can be realized by the present invention. It is included in the technical scope of the invention.

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

It is the schematic which shows an example of the graphite heater of this invention. (A) Development view, (b) Side view. It is an enlarged view of the slit of the graphite heater of the present invention. (A) The width of the lower end of the upper slit B is wider than its upper end, and (b) the width of the lower end of the lower slit C is wider than its upper end. FIG. 2 is a conceptual diagram showing a temperature distribution of a raw material melt in the crucible when the crucible is heated by the graphite heater of FIG. 1. (A) Temperature distribution on the surface side of the raw material melt, (b) Temperature distribution on the crucible bottom side of the raw material melt, (c) Temperature distribution of the entire raw material melt. FIG. 3 is an explanatory diagram showing a growth rate and a crystal defect distribution of a single crystal. (a) Example 1, (b) Comparative Example 1. Investigation of the relationship between the growth rate of single crystals and the distribution of crystal defects revealed that the growth of single crystals when silicon single crystals were grown by controlling the growth rate of N regions where no defects were detected by Cu deposition processing. It is the comparison figure which compared the speed between 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) Development view, (b) Side view.

Explanation of reference numerals

10: Single crystal manufacturing apparatus, 11: Main chamber, 12: Pulling chamber,
13: single crystal, 14: wire, 15: raw material melt, 16: quartz crucible,
17: graphite crucible, 18: shaft, 19: graphite heater, 20: heat insulating member,
21: seed holder, 22: seed crystal, 23: cooling cylinder, 24: graphite cylinder,
25: inner heat insulating cylinder, 26: outer heat insulating material,
27 terminal part, 28 heating part, 29 upper slit, 30 lower slit,
31: Heat generation slit part.

Claims (8)

  When a single crystal is manufactured by the Czochralski method, at least a terminal portion to which a current is supplied and a cylindrical heating portion by resistance heating are provided and arranged so as to surround a crucible containing a raw material melt. In the graphite heater used in the heating unit, the heating unit, the upper slit extending downward from the upper end, the lower slit extending upward from the lower end is provided alternately to form a heating slit portion, and the The length of the upper slit is made of two types, long and short, and the width of the lower end of the longer upper slit is wider than the width of its upper end, and / or the width of the lower end of the lower slit is its upper end. A graphite heater for producing a single crystal, characterized in that the heat generation distribution of the heat generating portion is changed as a width wider than the width of the graphite heater.   The width of the lower end of the longer upper slit is wider than the width of the upper end by 1.5 times or more and 2.5 times or less, and the width of the lower end of the lower slit is larger than the width of the upper end. 2. The graphite heater for producing a single crystal according to claim 1, wherein the width is also 1.5 times or more and 2.5 times or less.   The graphite heater for producing a single crystal according to claim 1, wherein the shorter upper slit has a length shorter than 50% of a length from an upper end to a lower end of the heat generating portion. 4. .   4. The unit according to claim 1, wherein the longer upper slit has a length of 70% or more of a length from an upper end to a lower end of the heat generating unit. 5. Graphite heater for crystal production.   The two types of upper slits are formed periodically in a circumferential direction, and a heat generation distribution of the heat generating portion is a high temperature portion and a low temperature portion periodically distributed in a circumferential direction. The graphite heater for producing a single crystal according to any one of claims 1 to 4.   The graphite heater according to claim 5, wherein one cycle of the heat generation distribution is 180 °.   A single crystal production apparatus 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 apparatus for producing a single crystal according to claim 7.

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