JP4134800B2 - Graphite heater for single crystal production, single crystal production apparatus and single crystal production method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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.
[0002]
[Prior art]
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).
[0003]
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.
[0004]
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.
[0005]
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.
[0006]
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.
[0007]
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.
[0008]
A raw material lump is accommodated in the quartz crucible 16 arranged in the single crystal manufacturing apparatus shown in FIG. 6 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.
[0009]
Such a silicon single crystal manufactured by the CZ method is mainly used for manufacturing semiconductor devices. 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.
[0010]
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, exist at a low density, and a region where these defects exist 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.
[0011]
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.
[0012]
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).
[0013]
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.
[0014]
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 the radiation heat from the graphite heater and transmitting the heat by heat conduction to release 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.
[0015]
[Patent Document 1]
International Publication No. 97/21853 Pamphlet
[Patent Document 2]
JP-A-12-53486
[Non-Patent Document 1]
V. V. Voronkov, Journal of Crystal Growth, 59 (1982), 625-643.
[0016]
[Problems to be solved by the invention]
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. The temperature distribution is highly accurate not only when pulling up a silicon single crystal in a predetermined defect-free region such as the N region or in a predetermined defect region, but also when pulling up a silicon single crystal with improved oxygen concentration uniformity in the crystal diameter direction. Provided is a graphite heater for manufacturing a single crystal that can be controlled to obtain a crystal of a desired quality and that the silicon single crystal can be manufactured with high production efficiency, and a single crystal manufacturing apparatus and a single crystal manufacturing method using the graphite heater. The purpose is to do.
[0017]
[Means for Solving the Problems]
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. The upper slit and the lower slit are each composed of two types of long and short, and the number of the shorter upper slits is lower than the shorter one. There is provided a graphite heater for producing a single crystal, characterized in that the number of slits is larger than that of the slit and the heat generation distribution of the heat generating portion is changed.
[0018]
Thus, the lengths of the upper slit and the lower slit are each composed of two types of long and short, and it is assumed that the number of the shorter upper slits is larger than the number of the shorter lower slits. The heater having the changed heat generation distribution can cause vertical convection in the raw material melt from the crucible bottom to the raw material melt surface by the heat generation distribution of the heater itself. This vertical convection increases the temperature gradient (G) in the vicinity of the solid-liquid interface of the silicon single crystal that is being pulled up, so that the crystal growth interface easily changes to an upwardly convex shape. For example, the growth of a silicon single crystal in the N region High speed 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. Furthermore, the oxygen concentration of the single crystal to be manufactured can be made substantially uniform in the crystal diameter direction.
[0019]
In this case, it is preferable that the number of the shorter upper slits is in a range of 1.5 to 5 times the number of the shorter lower slits.
[0020]
Thus, when the number of the shorter upper slits is in the range of 1.5 to 5 times the number of the shorter lower slits, the oxygen concentration of the single crystal to be manufactured can be adjusted in the crystal diameter direction. It can be made more uniform. In addition, the convection in the longitudinal direction from the bottom of the crucible to the surface of the raw material melt can be appropriately promoted in the raw material melt, and the temperature gradient (G) in the vicinity of the solid-liquid interface in the crystal can be increased in the radial direction. It can also be made almost uniform. 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.
[0021]
In this case, the two types of upper slits and lower slits are periodically formed in the circumferential direction, and the heat generation distribution of the heat generating part is a periodic distribution of the high temperature part and the low temperature part in the circumferential direction. (Claim 3), for example, it is preferable that one period of the heat generation distribution is 180 ° (Claim 4).
[0022]
As described above, the two types of upper and lower 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 periodically distributed in the circumferential direction. By doing so, convection in the raw material melt can be promoted not only in the vertical direction but also in the circumferential direction.
[0023]
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.
[0024]
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.
[0025]
In this case, it is preferable that the shorter upper slit and the lower slit have a length shorter than 50% of the length from the upper end to the lower end of the heat generating portion (Claim 6). It is preferable that the lower slit has a length of 70% or more of the length from the upper end to the lower end of the heat generating portion.
[0026]
Thus, the shorter upper slit and lower slit have 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 and lower slit. Is a length of 70% or more of the length from the upper end to the lower end of the heat generating portion, and the heat generating slit portions are provided above and below the center line that bisects the heat generating portion in the vertical direction. Easy to distribute.
[0027]
Furthermore, the present invention provides a single crystal production apparatus comprising at least the graphite heater for producing a single crystal (Claim 8), and a single crystal for producing crystals by the Czochralski method using the single crystal production apparatus. A crystal production method is provided (claim 9).
[0028]
If a single crystal is produced by the CZ method using such a crystal production apparatus equipped with the heater for producing a single crystal of the present invention, there is no crystal defect, and the oxygen concentration is highly uniform in the crystal diameter direction. Can be produced with high productivity.
[0029]
In the case of manufacturing 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 and STHAMAS-3D was performed on the relationship with the temperature gradient (G).
[0030]
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)).
[0031]
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.
[0032]
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.
[0033]
On the other hand, the vertical temperature distribution of the raw material melt may affect the quality of the produced single crystal. In particular, oxygen that is eluted from the quartz crucible into the raw material melt during production of the single crystal and taken into the crystal forms oxygen precipitates in the wafer bulk in the heat treatment step when producing the wafer from the single crystal. Because it can be a gettering site for heavy metal elements that diffuse inward during the process, it also plays a very important role in the quality of the manufactured wafer. Accordingly, in recent years, the demand for having a uniform distribution of oxygen concentration as a source for forming oxygen precipitates in the crystal diameter direction is becoming stricter as the performance of devices increases.
[0034]
Therefore, the present inventors further designed the oxygen concentration distribution in the crystal diameter direction to be even more uniform if the upper peak of the two exothermic peaks is designed such that the calorific value of the upper peak is larger than the calorific value of the lower peak. I found out that
[0035]
From the above, the present inventors promoted the convection in the vertical direction from the bottom of the crucible toward the surface of the raw material melt with the graphite heater alone arranged so as to surround the crucible. If the amount of heat generated at the top of the heater is greater than the amount of heat generated at the bottom of the crucible or the crucible R part, the target quality can be achieved with high productivity and low cost. The present invention has been completed by conceiving that it is possible to produce a single crystal having the following.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
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 non-uniform temperature distribution with a distribution peak, and is designed so that the amount of heat generated at the top of the crucible is higher than the amount of heat generated at the bottom of the crucible or the crucible R portion. Is.
[0037]
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.
[0038]
Furthermore, the number of upper slits A was designed to be larger than the number of lower slits D. The number of upper slits A is preferably designed to be in the range of 1.5 to 5 times the number of lower slits D. If it is 1.5 times or more, the oxygen concentration in the crystal diameter direction of the single crystal to be manufactured can be made more uniform, so that the wafer manufactured from this single crystal has excellent gettering ability in the plane. It can have. Further, the upper part of the crucible is sufficiently heated, and the temperature gradient (G) in the vicinity of the solid-liquid interface in the crystal can be made substantially uniform in the radial direction. On the other hand, if it is 5 times or less, the lower part of the crucible is sufficiently heated, and the longitudinal convection from the bottom of the crucible to the surface of the raw material melt can be effectively promoted. The effect of increasing the temperature gradient (G) in the vicinity of the solid-liquid interface can be sufficiently obtained.
[0039]
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. The lower slit C is preferably designed to be 70% or more 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 into two in the height direction, and the lower slit D And the heat generating slit portion formed by the corresponding upper slit B can be positioned below the center line that divides the heat generating portion into two in the vertical direction.
The upper slit A is more preferably designed to have a length in the range of 20% to 40% of the length from the upper end to the lower end of the cylindrical heating portion of the graphite heater. Thereby, the uniformity of the oxygen concentration in the crystal diameter direction can be further enhanced.
[0040]
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. Also, for example, the heat generation distribution between the upper side and the lower side of the center line that divides the period based on the upper slit and the period based on the lower slit by 105 ° in the circumferential direction and divides the heat generating part into two in the vertical direction. Is shifted by 105 °.
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.
[0041]
FIG. 2 shows the temperature distribution of the raw material melt stored in the crucible when heated by such a graphite heater. As shown in FIG. 2A, the heat generating slit formed by the upper slit A and the lower slit C corresponds to the first quadrant to the second quadrant and the third quadrant to the fourth quadrant when the crucible is viewed from directly above. It plays the role of heating a part of the portion and the vicinity of the surface of the raw material melt. On the other hand, as shown in FIG. 2 (b), the heating slit portion formed by the upper slit B and the lower slit D is a part of the portion corresponding to the first quadrant to the fourth quadrant and the second quadrant to the third quadrant, In addition, it plays the role of heating the crucible bottom or the crucible R portion. Therefore, the raw material melt in the crucible has a non-uniform temperature distribution as shown in FIG. 2C as a whole, and the amount of heat generated at the upper part of the crucible is larger than the amount of heat generated at the lower part of the crucible. Yes.
[0042]
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.
[0043]
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.
Further, the single crystal to be manufactured can have high oxygen concentration in the crystal diameter direction, and the wafer manufactured from the single crystal has excellent in-plane uniformity of gettering ability.
[0044]
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. In addition, a single crystal having an oxygen concentration that is substantially uniform in the crystal diameter direction can be pulled at a 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.
[0045]
【Example】
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 with a diameter of 24 inches (600 mm) is charged with 150 kg of raw material polycrystalline silicon, and a silicon single crystal with a diameter of 8 inches (200 mm) and orientation <100> is applied while applying a 4000 G transverse magnetic field at the center of the crystal. Raised. 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. A silicon single crystal was manufactured so that the oxygen concentration was 22 to 23 ppma (ASTM'79).
[0046]
At this time, the graphite heater shown in FIG. 1 was used. That is, in this graphite heater, the total length of the heat generating portion is 500 mm, and six upper slits A, four upper slits B, eight lower slits C, and four lower slits D are provided (upper slits). Number of A / number of lower slits D = 1.5). The upper slit A and the lower slit D are each 200 mm in length, and the upper slit B and the lower slit C are each 400 mm in length.
[0047]
The silicon single crystal thus manufactured was examined for OSF, FPD, LEP, and Cu deposition.
That is, the following investigation was conducted when the crystal solidification rate was about 10% or more (in the case of the conditions of this example, the crystal straight body portion was 10 cm or more).
[0048]
(A) Investigation of FPD (V region) and LEP (I region):
A slab sample having a length of every 10 cm in the direction of the crystal axis and a thickness of about 2 mm was taken, and after surface grinding, after 30 minutes of seco etching (no stirring), the in-plane density of the sample was measured.
(B) OSF field survey:
A slab sample having a length of about 2 mm and a length of every 10 cm in the crystal axis direction is collected, and Wet-O₂After heat treatment at 1100 ° C. for 100 minutes in the 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
[0049]
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 = 0.54 mm / min.
Growth rate at the boundary between the OSF region and the N region where defects were detected by the Cu deposition process = 0.53 mm / min.
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 = 0.52 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 = 0.50 mm / min.
[0050]
Next, based on the above result, the growth rate was controlled from 0.52 to 0.50 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. 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: 8mm²    4) Judgment current: 1 mA / cm²
As a result, the oxide film breakdown voltage level was 100% non-defective.
[0051]
Next, evaluation of oxygen concentration distribution in the surface inner diameter direction was performed using a wafer manufactured by the same method as that used in the evaluation of the oxide film breakdown voltage characteristics. Specifically, FT-IR (Fourier Transform Infrared Spectroscopy) is used as a method for measuring the oxygen concentration, and a total of 21 points are connected on a straight line connecting 5 mm points from both ends of the wafer and passing through the center of the wafer surface. As a measurement point, the oxygen concentration was measured. The result is shown in FIG.
FIG. 5 shows that when the heater of the present invention is used, the oxygen concentration of the single crystal to be produced can be made substantially uniform in the surface inner diameter direction.
[0052]
(Comparative Example 1)
As the graphite heater, the one shown in FIG. 7 was used. In this graphite heater, the total length of the heat generating part is 500 mm, and 10 upper slits and 12 lower slits are provided. The upper slits are all 400 mm long, and the lower slits are all 400 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.
[0053]
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 = 0.49 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 = 0.48 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 = 0.46 mm / min.
[0054]
Next, based on the above results, the growth rate is controlled from 0.48 to 0.46 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.
[0055]
Next, evaluation of oxygen concentration distribution in the surface inner diameter direction was performed in the same manner as in Example 1 using a wafer manufactured by the same method as used in the evaluation of the oxide film breakdown voltage characteristics. The result is shown in FIG.
From FIG. 5, it can be seen that when the conventional heater is used, the oxygen concentration of the single crystal to be produced is greatly changed and distributed in the surface inner diameter direction as compared with Example 1.
[0056]
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 0.48 to 0.46 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 0.52 to 0.50 mm / min (see FIG. 3).
Therefore, when the graphite heater of the present invention is used, the oxygen concentration of the single crystal to be produced can be made substantially uniform in the crystal diameter direction, productivity can be improved, and production cost can be reduced.
[0057]
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.
[0058]
For example, in the above embodiment, the MCZ method in which a 4000 G transverse magnetic field is applied at the center of the crystal when pulling up the silicon single crystal has been described as an example. Applicable to law.
Further, in the above-described embodiment, the case where the diameter of the silicon single crystal to be manufactured is 8 inches (200 mm) has been described as an example. However, the present invention is not limited to this and is a case of manufacturing a crystal having any diameter. It can be applied regardless of the size of the single crystal production apparatus.
[0059]
【The invention's effect】
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, and the oxygen concentration of the manufactured silicon single crystal can be made substantially uniform in the crystal diameter direction. can do.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a graphite heater of the present invention.
(A) Development view, (b) Side view.
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.
(A) Temperature distribution on the raw material melt surface layer side,
(B) Temperature distribution on the crucible bottom side of the raw material melt,
(C) Overall temperature distribution of the raw material melt.
FIG. 3 is an explanatory diagram showing the growth rate and crystal defect distribution of a single crystal.
(a) Example 1, (b) Comparative Example 1.
FIG. 4 shows the relationship between the growth rate of a single crystal and the distribution of crystal defects, which was found when a silicon single crystal was grown by controlling the growth rate of an N region in which no defects were detected by Cu deposition treatment. It is the comparison figure which compared the growth rate of the single crystal in Example 1 and Comparative Example 1 ((a), (b)).
FIG. 5 is a graph showing the distribution of oxygen concentration in the surface inner diameter direction.
FIG. 6 is a schematic view of a single crystal manufacturing apparatus.
FIG. 7 is a schematic view showing an example of a conventional graphite heater.
(A) Exploded view, (b) Side view.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 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 ... Insulating member, 21 ... Seed holder, 22 ... Seed crystal, 23 ... Cooling cylinder, 24 ... Graphite cylinder, 25 ... Inner insulating cylinder, 26 ... Outer insulating material, 27 ... Terminal part, 28 ... Heat generating part, 29 ... Upper slit, 30 ... lower slit, 31 ... heating slit part.

Claims (9)

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 lengths of the upper slit and the lower slit are each made up of two types of short and long, and the heat distribution of the heat generating part is changed so that the number of the short upper slits is larger than the number of the short lower slits. A graphite heater for producing a single crystal, characterized by comprising: 2. The graphite heater for producing a single crystal according to claim 1, wherein the number of the shorter upper slits is in a range of 1.5 to 5 times the number of the shorter lower slits. The two types of upper slits and lower slits are periodically formed in the circumferential direction, and the heat generation distribution of the heat generating portion is a distribution in which a high temperature portion and a low temperature portion are periodically distributed in the circumferential direction. The graphite heater for producing a single crystal according to claim 1 or 2. 4. The graphite heater for producing a single crystal according to claim 3, wherein one cycle of the heat generation 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 producing a single crystal as described in 1. 6. The shorter one of the upper and lower slits has a length shorter than 50% of the length from the upper end to the lower end of the heat generating portion. A graphite heater for producing a single crystal as described. The long upper slit and the lower slit have a length of 70% or more of the length from the upper end to the lower end of the heat generating portion, according to any one of claims 1 to 6. Graphite heater for single crystal production. 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 7. 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 8.

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