KR100847700B1 - Device for preparing silicon single crystal and method for preparing silicon single crystal using the same - Google Patents

Abstract

The present invention provides an apparatus for producing a silicon single crystal, which is easy to handle and has high versatility, while improving the pulling speed by appropriately and efficiently cooling the single crystal pulled out from the silicon melt.

The apparatus for producing a silicon single crystal 50 includes a crystal cooling cylinder 13 and a crystal cooling cylinder arranged in the growth furnace main body 1 so as to surround the silicon single crystal 3 pulled up from the silicon melt 4. Along the inner circumferential surface of the lower end portion 13, the inner circumferential insulation material 15 made of graphite is provided to protrude toward the outer circumferential surface of the silicon single crystal 3 pulled out from the silicon melt 4. The inner circumferential insulation material 15 is disposed in a section in which the central temperature of the silicon single crystal 3 becomes 1000 ° C or more and 1250 ° C or less in the axial direction of the silicon single crystal 3.

Silicon, single crystal, growing furnace, Czochralski method, inner heat insulating material, crystal cooling tube, pyrolytic carbon, silicon carbide

Description

DEVICE FOR PREPARING SILICON SINGLE CRYSTAL AND METHOD FOR PREPARING SILICON SINGLE CRYSTAL USING THE SAME

BRIEF DESCRIPTION OF THE DRAWINGS It is an overall schematic diagram which shows an example of the manufacturing apparatus of the silicon single crystal of this invention.

FIG. 2 is an overall schematic diagram showing a modification of the manufacturing apparatus of FIG. 1. FIG.

3 is an explanatory view of the operation of the inner circumferential insulation.

4 is a diagram conceptually explaining the effect of the inner circumferential insulation material on the defect formation.

5 is an enlarged cross-sectional view showing a first and second modified examples of the inner circumferential insulation.

6 is an enlarged cross-sectional view showing a third modification likewise.

Fig. 7 is a schematic diagram showing some examples of the attachment structure of the inner circumferential insulation material to the crystal cooling cylinder.

FIG. 8 is a diagram showing a pulling rate profile and a defect distribution measurement result of the silicon single crystal obtained in Experiment 1 of Example 1. FIG.

9 is a diagram visualizing and showing a difference between the proper pulling speeds of the invention example and the comparative example in Experiment 2 of Example 1. FIG.

Field of technology

TECHNICAL FIELD This invention relates to the manufacturing apparatus of the silicon single crystal by the Czochralski method (henceforth a CZ method), and the manufacturing method of the silicon single crystal using the same.

Prior art

BACKGROUND ART In recent years, electronic circuits constituting semiconductor devices are becoming more miniaturized due to the higher integration and size of semiconductor devices. For this reason, the demand for higher quality of the silicon wafer serving as the substrate for semiconductor element formation only increases, and various measures have also been investigated in the growth of silicon single crystal to satisfy this requirement. In particular, the most widely used material for silicon wafers is silicon single crystals produced by the CZ method, and the crystal defects formed inside the crystals when growing the crystals greatly affect the characteristics of the elements formed in the wafer surface layer. There is a demand for a pulling method in which crystal defects formed in a crystal at low density are suppressed at the time of single crystal growth.

For example, Japanese Unexamined Patent Application Publication No. 11-79889 discloses a technique for growing a silicon single crystal having a very low density even when there is no defect incorporated in the crystal when the silicon single crystal is grown. In the growth of silicon single crystals by the CZ method, crystal defects due to thermal history at the time of crystal growth called grain-in defects mixed into the crystals due to pulling speed, crystal cooling conditions, and the like. I noticed a difference.

In the case where single crystals are grown in a state of rapid quenching of silicon single crystals, the shortage of silicon atoms occurs inside the crystals during single crystal growth, and a portion is formed at the silicon lattice point. This cavity agglomerates during cooling of the single crystal and appears in the form of recesses or holes on the wafer surface when the single crystal is processed into wafers, and is a silicon single crystal predominantly grown-in defects caused by voids (voids and holes). do. Such cavity-type point defects are called vacancy (hereinafter abbreviated as V), and the area inside the silicon single crystal in which the point defects caused by aggregation of vacancy predominates is called the V region. Growing-in defects attributable to bacon include flow patterning defects (FPD), crystal originated particle (COP), laser scattering tomography defects (LSTD), and the like. It is observed as point defects of an octahedral void shape on the back side.

On the other hand, when the pulling speed of the silicon single crystal is extremely suppressed and the growing crystal is pulled while cooling slowly, this time, silicon atoms that are present in excess between the lattice of the silicon single crystal, that is, interstitial silicon (hereinafter referred to as interstitial-Si) or less, A silicon single crystal having predominantly point defects, referred to as I), is obtained. The inside of such a silicon single crystal has a low density of interstitial silicon defects called L / D (large dislocation: abbreviation for inter-lattice dislocation loops, and generic term for crystal defects such as LSPD and LFPD), which are thought to be caused by dislocation loops. When a single crystal is processed on a wafer substrate and a semiconductor element is formed on the surface layer, these defects may cause serious defects such as current leakage. The region inside the crystal where this interstitial silicon predominates is called the I region.

When the silicon single crystal is pulled up under the growing conditions such that the V region where the vacancy prevails or the intermediate region other than the I region where the interstitial silicon prevails, there is no shortage of atoms or extra atoms present between the silicon atoms. Alternatively, the silicon single crystal can be grown in a state of neutral neutrality (hereinafter sometimes abbreviated as N) even if present. The region inside the crystal in this neutral state is called N region.

In addition, between the N region formed inside the silicon single crystal and the above-described V region, there is a defect due to oxygen called OSF (oxidation induced stress stacking defect) or a region where the nucleus is present at a high density. When the single crystal is processed into the wafer substrate, the region is observed as a ring shape, and therefore, the region where the OSF or the nucleus serving as the OSF exists is called the OSF ring or the OSF ring region.

In Japanese Unexamined Patent Application Publication No. 11-79889, in order to obtain a high quality silicon single crystal by keeping the grown-in defects inside the crystal at an extremely low density, the OSF ring generated inside the silicon single crystal is adjusted by adjusting the temperature atmosphere of the single crystal. The silicon single crystal is grown under the condition that the entire crystal becomes the N region, which is finished at the crystal center. However, in the method of crystal growth in which the entire single crystal or most of the single crystal is formed in the N region, as disclosed in Japanese Patent Laid-Open No. 11-79889, in order to form a desired crystal growth atmosphere, the upper side of the silicon melt surface It is necessary to arrange complex structures in the structure or to keep the growth rate of single crystal at an extremely low speed of about 0.5 mm / min or less. Therefore, there is an advantage in that a single crystal of high quality with few crystal defects can be obtained, but there are many problems in terms of production efficiency, such as complicated device structure, lack of versatility, and low crystal productivity.

In order to raise the crystallization to the N area in a conventional manufacturing apparatus, the crystal atmosphere is adjusted so that the cooling atmosphere of the raised crystal is a desired value, and crystal growth is performed by maintaining the pulling speed of the crystal at a low speed of about 0.4 mm / min. . This is a manufacturing method which is remarkably inferior in productivity considering that the general silicon single crystal pulling speed is about 1.0 mm / min. As a method for increasing the pulling speed, a method of producing a crystal by arranging a structure having enhanced thermal insulation at the top of the manufacturing apparatus and adjusting to a temperature atmosphere suitable for obtaining a single crystal having low crystal defects is also studied. However, in such a method, the upper structure in the build-up furnace becomes complicated, and when the maintenance and general use of the apparatus are taken into consideration, problems such as lowering work efficiency, lowering productivity, and high value of apparatus cost remain. In addition, in order to speed up the growth of crystals and to produce high-quality crystals with little or no crystal defects, it is necessary to maintain a large cooling effect of single crystals at a portion closer to the crystal growth interface. It was.

In particular, in large crystals having a diameter exceeding 200 mm Ø, the heat capacity also increases, and therefore, the problem is to simplify the apparatus and to appropriately cool the growing crystals. In this case, the amount of crystal defects influencing the characteristics of the silicon single crystal obtained is very closely related to which temperature range of the grown crystal is actively promoted. However, the technical examination which put both the problem solving in this viewpoint and the simplification of an apparatus structure into the visual field has not been made conventionally.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and in the development of high quality silicon single crystals having no crystal defects or very few, the single crystals drawn from the silicon melt are appropriately and efficiently cooled to improve the pulling speed. At the same time, it is an object of the present invention to provide a single crystal manufacturing apparatus which is simple in structure of a manufacturing apparatus, is easy to handle and has high versatility, and a silicon single crystal manufacturing method using the same.

In the silicon single crystal production apparatus of the present invention, in the silicon single crystal production apparatus in which the silicon single crystal is pulled from the silicon melt contained in the crucible in the growth furnace of the silicon single crystal by the Czochralski method,

The raising furnace body which a crucible is arranged inside,

In this growth passage main body, a crystal cooling passage arranged to surround the silicon single crystal pulled up from the silicon melt,

A carbon inner circumferential insulating material is provided along the inner circumferential surface of the lower end of the crystal cooling cylinder and protrudes toward the outer circumferential surface of the silicon single crystal drawn from the silicon melt.                     

The inner circumferential insulation material is disposed so that the whole of the inner circumferential insulation material is located in a section in which the central temperature of the silicon single crystal is 1000 ° C or more and 1250 ° C or less.

Moreover, the manufacturing method of the silicon single crystal of this invention raises and manufactures a silicon single crystal by the Czochralski method from the silicon melt accommodated in the crucible using the manufacturing apparatus of said silicon single crystal.

In order to increase the growth rate of the crystal when growing the single crystal from the silicon melt, it is necessary to shield radiant heat from the heating heater or the silicon melt to the single crystal as much as possible, and efficiently cool the grown crystal. For this reason, in a silicon single crystal manufacturing apparatus, a crystal cooling cylinder is arranged immediately above the silicon melt so as to surround the grown crystal, and removes radiant heat from the crystal, and radiant heat from the heating heater or the silicon melt does not touch the crystal. It is valid to devise to avoid. However, near the crystal growth interface near the surface of the silicon melt, it is difficult to efficiently shield radiant heat from the silicon melt, and in particular, in the growth of high quality crystals in which defects are suppressed, it is necessary to maintain the crystal cooling rate at a desired value with high accuracy. Because of this, it was difficult to speed up the growth of the crystals.

On the other hand, in the apparatus of the present invention, a carbon inner circumferential insulation material having a high heat resistance temperature and excellent thermal insulation properties is disposed along the inner circumferential surface of the lower end of the crystal cooling cylinder and protruded toward the outer circumferential surface of the silicon single crystal pulled from the silicon melt. In addition, the radiant heat caused by the heating heater and the silicon melt surface can be shielded to increase the cooling efficiency of the crystal high temperature part. In addition, since the gap between the cooling cylinder and the grown single crystal at this position is kept narrow by arranging the inner circumferential insulating material at such a position, heat transfer due to radiation or convection through the gap from the silicon melt side can be suppressed. It is also possible to enhance the cooling effect of the crystal at a position spaced upward from the melt surface.

In order to increase the cooling efficiency and to ensure heat resistance and mechanical structural strength, the crystal cooling cylinder is preferably made of at least a lower end portion on which the inner circumferential insulation material is to be made of graphite. In this case, it is preferable that the inner circumferential insulation material is made of a carbon material having a higher porosity than the lower end of the crystal cooling cylinder made of graphite, in terms of enhancing the heat insulation effect.

In the present invention, the inner circumferential insulating material is further disposed in the entire axial direction of the silicon single crystal in a section in which the center temperature of the silicon single crystal is from 1000 ° C to 1250 ° C. Specifically, as shown in FIG. 3, the lower edge (lower end surface) of the inner circumferential insulation material 15 has a first temperature T1 lower than 1250 ° C., which is estimated to start defect growth by coagulation of a silicon single crystal. The upper edge (upper end surface) of the inner circumferential insulation material 15 is positioned at the second temperature T2 higher than 1000 ° C. in which the defect growth becomes relatively inactive. In addition, when the lower end part 13a of the crystal cooling cylinder 13 is arrange | positioned returning to the lower end side of the inner peripheral heat insulating material 15, it is considered that this lower end part 13a does not belong to the inner peripheral heat insulating material 15. As shown in FIG. Moreover, when the upper end side of the inner circumferential insulation material 15 is covered with the coating material of the same material as the crystal cooling cylinder 13 (FIG. 5 (a), etc.), it is considered that the coating material does not belong to the inner circumferential insulation material 15.                     

As a result, it is possible to increase the growth rate while reliably suppressing defect formation that adversely affects the electrical characteristics of the silicon single crystal. This reason is as follows. In the growth of silicon single crystals by the CZ method, empirically, when the crystal temperature is generally lowered to about 1250 ° C, aggregation of the lattice point and the lattice silicon atoms to become a grown-in defect nucleus is initiated. It is estimated that defect growth is settled around 1050 degreeC. As shown to Fig.4 (a), in this temperature range of 1000 degreeC-1250 degreeC, there exists a temperature range (tau) in which growth of a defect is considered to be remarkable. In order to obtain a high quality silicon single crystal, the cooling rate at the time of passing through the temperature section τ is appropriately increased so that the silicon single crystal does not stay in the temperature section τ for a long time, thereby suppressing defect growth in the crystal. It is important to do.

For example, as shown by the broken line B in FIG. 4A, when the cooling rate in the temperature section τ is small, as shown in (c), the temperature of the system is high. Cavities rapidly agglomerate to individual defect nuclei and grow large, and have defects that adversely affect the electrical properties of silicon single crystals (hereinafter, referred to as "bad defects" and, in this specification, only "defects") The number of defects) increases. However, by arranging the inner circumferential insulation material at a position corresponding to a temperature section of 1000 DEG C to 1250 DEG C, the cooling rate in the temperature section τ can be increased as shown by the solid line A in Fig. 4A. have. In this case, as shown in (b), the number of generation of defect nuclei N increases because the degree of supercooling increases, but since the temperature of the system decreases, aggregation of cavities into individual defect nuclei is suppressed, and The growth rate is small. Therefore, it is thought that the above-mentioned bad defect number decreases and a high quality silicon single crystal is obtained. In addition, by cooling such crystals, the cooling in the crystal high temperature portion is accelerated and the crystal growth rate can be increased.

In addition, when the upper edge position of the inner circumferential insulation material extends upward to the section where the center temperature of the silicon single crystal becomes 1000 ° C or less, the movement of the inner circumferential insulation material as the heat insulating material becomes remarkable in the extension section, and therefore, 1000 ° C to 1050 degrees. The temperature gradient in the temperature zone near which the growth of defects is settled near the temperature is moderate. As a result, in the temperature range in which defects are actively formed, the silicon single crystal is slowly cooled, coagulation of the cavity to the defects is continued, and the defect size is coarsened. It is connected to what brings about. On the other hand, when the lower edge position of the inner circumferential insulation material extends downward to the section where the center temperature of the silicon single crystal becomes 1250 ° C or more, the temperature distribution in the radial direction of the single crystal becomes uneven due to the cooling effect of the inner circumferential insulation material. It is easy to produce the lattice defect which is considered to be a dislocation loop origin inside. In any case, this is disadvantageous in terms of obtaining a high quality crystal in which the entire surface is N-regioned on the axial cross section of the single crystal.

In addition, in order to enhance the effect, the upper edge position of the inner circumferential insulation material is located in a section in which the center temperature of the silicon single crystal is from 1000 ° C to 1050 ° C. It is preferable to be located in the section which becomes. The axial dimension of the inner circumferential insulation material is so short that, for example, the upper edge position is located in a section where the center temperature of the silicon single crystal is higher than 1050 ° C, or the lower edge position is in a section where the center temperature of the silicon single crystal is lower than 1150 ° C. When located, it becomes impossible to cool the entire temperature section τ at which defect formation becomes remarkable at a sufficient cooling rate, and it is difficult to achieve the above-described effects of the present invention.

Embodiment of the invention

EMBODIMENT OF THE INVENTION Below, embodiment of this invention is given and demonstrated the example of the growth of a silicon single crystal using the CZ method, referring an accompanying drawing, but this invention is not limited only to these. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows one Embodiment of the silicon single crystal manufacturing apparatus for implementing the manufacturing method of the silicon single crystal of this invention. The silicon single crystal manufacturing apparatus 50 shown in FIG. 1 is comprised by the growth furnace main body 1 and the upper growth furnace 2. As shown in FIG. In order to hold and protect the quartz crucible 5 containing the silicon melt 4 and the quartz crucible 5 inside the growth furnace main body 1, the graphite crucible 6 is a quartz crucible. It is arrange | positioned outside of (5).

On the outer circumference of the graphite crucible 6, a graphite heating heater 7 for heating the polycrystalline silicon, which is a raw material contained in the quartz crucible 5, to melt it to form the silicon melt 4 is placed. During the growth of the silicon single crystal, power is supplied from the electrode to the heating heater to generate heat, and after the polycrystalline silicon is melted, the temperature of the silicon melt 4 is maintained at a desired value to promote the growth of the silicon single crystal 3. will be.

Between the heating heater 7 and the furnace wall of the growth furnace main body 1, a carbon inner furnace heat insulating material 8 is placed to protect the metal furnace wall and to effectively insulate the interior of the growth furnace main body 1. Furthermore, the growth furnace main body 1 has a furnace wall as a dual structure in order to prevent the furnace wall from being heated to a high temperature more than necessary during the growth of the silicon single crystal by radiant heat from the heating heater 7. It is a structure in which silicon single crystal is grown while forced cooling is performed by flowing cooling water through the gap.

On the other hand, the graphite crucible 6 arranged in the substantially center of the growth furnace main body 1 is supported by the crucible support shaft 19 made of graphite, and is not shown in the lower end of the crucible support shaft 19. By the crucible shaft drive mechanism, the vertical movement and the rotational movement are free. As a result, the liquid surface of the silicon melt 4 can be held at a predetermined position during single crystal growth, or the crucibles 5 and 6 can be rotated at a desired direction or speed during single crystal growth.

The carbon member used in the apparatus includes a crucible 6, a heating heater 7, a crucible support shaft 19, or a crystal cooling tube 13, which are described later. On the other hand, the member which requires heat insulation, such as said furnace heat insulating material 8 and the inner circumferential heat insulating material 15, is a carbon material with a higher porosity than this graphite structural member (henceforth a heat insulating carbon material). It consists of. Specifically, a porous carbon material such as a carbon sintered body, or a fibrous carbon material, for example, a product in which carbon fibers are molded into a prepreg or nonwoven fabric can be employed.

Next, in the growth of the silicon single crystal 3, in order to prevent oxides such as SiO (silicon monoxide) evaporating from the silicon melt 4 from adhering to the furnace walls such as the furnace walls of the growth furnace and the furnace thermal insulation material, It is necessary to perform crystal growth while circulating an inert gas such as argon gas in a growth furnace. For this reason, the bottom part of the growth furnace main body 1 is equipped with the exhaust gas pipe 9 for exhausting inert gas out of a furnace, and the pressure control device not shown in figure for adjusting the pressure inside a growth furnace, and a silicon single crystal is provided. At the time of growth, the pressure in the furnace is adjusted to a desired value by this pressure control device.

On the other hand, the top growth path 2 for accommodating and taking out the silicon single crystal 3 pulled out from the silicon melt 4 is provided in the ceiling part of the growth path main body 1 in communication. During the single crystal growth, if the crystal temperature decreases until the silicon single crystal 3 is cooled in the upper growth furnace 2 and reaches a temperature at which it can be taken out, the upper growth furnace 2 opens a door (not shown) to open the silicon single crystal. Let (3) move out of the development furnace.

From the ceiling of the growth furnace main body 2, the crystal cooling cylinder 13 is disposed toward the silicon melt surface so as to surround the single crystal 3 pulled up from the silicon melt 4, and on the outer circumferential surface of the tip portion thereof, A graphite heat insulating ring 14 is provided to efficiently reflect the radiant heat of the melt 4 and the heating heater 7 and to keep the silicon melt surface warm (this heat insulating ring 14 may be omitted). In the growth of the silicon single crystal 3, the crystal cooling cylinder 13 can efficiently absorb radiant heat from the silicon single crystal 3, thereby increasing the crystal growth rate. In addition, the crystal cooling cylinder 13 also has a rectifying action of an inert gas downstream from the upper growth path 2 through the inside of the cooling cylinder to the silicon melt surface, and allows impurities discharged from the melt surface to be discharged out of the furnace without stagnation. It also plays a role. In addition, as shown in FIG. 2, on the upper side of the crystal cooling cylinder 13, a forced cooling cylinder 11 for forcibly discharging radiant heat from the crystal out of the furnace by circulation of a cooling medium is provided. It is also possible to further increase. In order to improve heat transfer property, the crystal cooling cylinder 13 is made of graphite at least in the lower end part, and in the present embodiment (however, the upper end part which forms the connection part with the forced cooling cylinder 11 etc. may be made of metal). ). In addition. The denser than the heat insulating carbon material which forms the inner peripheral heat insulating material 15 etc. which are mentioned later are used.

Returning to FIG. 1, the upper growth path 2 is provided with a gas introduction pipe 10 for introducing an inert gas into the interior of the growth path, and grows from the gas introduction pipe 10 in accordance with the process of crystal growth operation. Inert gas is introduced into the furnace. In the growth of the silicon single crystal 3, the inert gas introduced from the upper growth path 2 is located in the bottom of the growth path body 1 through the silicon melt surface downstream of the inside of the crystal cooling cylinder 13. It is discharged out of the furnace from the exhaust gas pipe 9. As a result, evaporates such as SiO, which evaporate from the silicon melt, are removed out of the furnace.

In addition, a wire winding mechanism (not shown) is provided above the upper growth path 2 to wind up or wind up the wire 18 for pulling up the silicon single crystal 3 from the silicon melt 4. A seed crystal holder 18a is attached to the tip end portion of the pulling wire 18 wound from the wire winding mechanism. The seed crystal holder 18a is hanged on the seed crystal holder 18a, and the tip thereof is attached to the silicon melt 4. The silicon single crystal 3 is grown below this seed crystal 17 by bringing it into contact with the surface of the surface.

Next, the silicon single crystal manufacturing apparatus 50 shown in FIG. 1 or 2 protrudes toward the outer circumferential surface of the silicon single crystal 3 pulled out of the silicon melt along the inner circumferential surface of the lower end of the crystal cooling cylinder 13. It has the carbon inner peripheral heat insulating material 15 provided. The inner circumferential insulation material 15 is comprised with the above-mentioned heat insulating carbon material. As described above with reference to FIG. 3, the inner circumferential insulation material 15 has a section in which the center temperature of the silicon single crystal 3 becomes 1000 ° C or more and 1250 ° C or less in the direction of the axis O of the silicon single crystal 3. It is arranged inside. The effects and effects of this have already been explained.

As shown in FIG. 1, the crystal cooling cylinder 13 not only obtains the cooling effect of the crystal, but also inert gas flowing in the cooling cylinder 13 along the crystal from above the grown single crystal 3. There is also a rectifying action. Preferably, as shown in Fig. 5 (a), the upper end surface 15a of the inner circumferential insulation material 15 is preferably an inclined surface in which the inner circumferential edge side is lowered so as not to disturb the rectifying action (here Is covered by the graphite material 13b described later, but this is regarded as not belonging to the inner circumferential insulation material 15). By providing such inclination in the inner circumferential insulation material, it is possible to smoothly flow from the upper side toward the silicon melt surface without disturbing inert gas such as argon (Ar) gas flowing through the inside of the cooling cylinder 13. Thereby, the evaporate, such as SiO, which evaporates from the surface of the silicon melt is discharged to the outside of the furnace by the inert gas without stagnation, and the oxides which may bring potential to the crystals are attached to the furnace walls or the members arranged in the furnace. It becomes possible to prevent that. In addition, although the inner wall surface 15c of the upright form is formed in FIG. 5 (a) in the form which continues to the upper end surface 15a of the inner peripheral heat insulating material 15, as shown to (b), the inner peripheral heat insulating material 15 is shown. It can be set as a triangular cross section, and the upper end surface 15a can be made into the inclined surface which reaches the lower end part of the inner peripheral heat insulating material 15. As shown in FIG.                     

It is very suitable for the upper surface 15a to form an angle (hereinafter, referred to as an inclination angle) θ to the horizontal plane in a range of 30 ° to 70 °. When the inclination angle θ is 30 ° or less, the inert gas downstream from the upper side of the crystal cooling cylinder 13 may contact the upper end surface 15a of the inner circumferential insulating material 15, and the flow may be disturbed. When the inclination of more than or equal to °, the inner circumferential insulation material 15 extends above the cooling cylinder, it becomes difficult to form an appropriate crystal cooling atmosphere, or the inner circumferential insulation material is enlarged, the handling becomes inconvenient. In addition, the upper end surface 15a can also be formed in a curved surface as shown in FIG. In this case, the inclination angle θ is defined as an angle formed between a horizontal line and a straight line connecting the upper and lower edges of the curved upper end surface 15a in the cross section including the axis of the inner circumferential insulation material 15.

In FIG. 5, the inner circumferential insulating material 15 has a distance d between its inner wall surface 15c and the outer peripheral surface 3c of the regular diameter portion of the silicon single crystal 3 that is pulled up is 20 mm or more. It is preferable to arrange | position so that it may become 50 mm or less. When the distance d exceeds 50 mm, the thickness of the inner circumferential insulation material 15 becomes so small that the heat insulation effect is weakened, and radiant heat from the silicon melt surface is separated from the gap between the inner circumferential insulation material 15 and the silicon single crystal 3. Direct contact with the crystal high temperature portion makes it impossible to cool the crystal effectively. On the other hand, when the distance d is 20 mm or less, the shielding effect of radiant heat is increased, but the flow path of the inert gas flowing through the interior of the cooling tube is narrowed, so that the flux of the inert gas near the crystal growth interface is increased and the crystal growth is increased. There is also the potential for inhibition. In addition, the maximum thickness in the radial direction of the inner circumferential insulating material 15 is appropriately, for example, so that the inner circumferential insulating material 15 can sufficiently secure the cooling capacity for the silicon single crystal 3 to which the inner circumferential insulating material 15 is further heated. For example, it is desirable to ensure 40 mm or more. Moreover, the upper limit of this thickness is suitably determined in the range which can ensure 20 mm or more of distances d with the outer peripheral surface 3c of the diameter part of the silicon single crystal 3.

Next, although the inner circumferential insulation material 15 which consists of a heat insulation carbon material has a high heat shielding effect, it is fragile and unstable, it is difficult to process it to a desired shape, Furthermore, since it is fibrous, from the silicon melt There is also a problem such that the evaporate is easy to adhere to the surface. As a method of replenishing this, as shown in Fig. 5 (a), it is preferable to coat the surface of the inner heat insulating material 15 exposed inside the crystal cooling cylinder with the graphite material 13b (which is denser than the inner heat insulating material). It is advantageous. As a result, the handling of the inner circumferential insulation material 15 can be facilitated and the workability can be improved, and the evaporated material from the silicon melt such as SiO can be prevented from adhering to the fibrous body portion of the inner circumferential insulation material 15. can do. In addition, since the main body portion collapses and does not fall into the silicon melt, it is possible to suppress the growth of the crystal or to affect the quality such as bringing slip dislocations.

And more preferably, it is good to further coat the surface of the graphite material 13b with pyrolytic carbon or silicon carbide. By using the graphite material 13b coated with pyrolytic carbon or silicon carbide, the silicon evaporated from the silicon melt can penetrate to the vicinity of the graphite material 13b surface layer, and the formation of silicon carbide can be suppressed. Thereby, durability improvement of the graphite material 13b can be aimed at. Moreover, it also has the effect of preventing the falling of the graphite into the raw material melt caused by the occurrence of cracking or cracking of the graphite material 13b accompanying silicon carbide production. As a result, stable crystal growth can be achieved. . In addition, by forming the film so that the iron (Fe) concentration in the film formed of pyrolytic carbon or silicon carbide is 0.05 ppm or less, the growth single crystal is grown from the inner circumferential surface of the inner circumferential insulation material 15 or the crystal cooling tube 13 close to the crystal. Iron (Fe) contamination caused by can be reliably prevented. As a result, when the grown silicon single crystal is processed into a silicon wafer, a decrease in carrier life caused by contamination of heavy metals, particularly iron (Fe), is suppressed. In addition, the iron (Fe) concentration of the film is measured by ICP (inductively coupled coupled plasma) emission spectrometry. In the case where the crystal cooling cylinder 13 is made of graphite, it is more preferable to coat the inner circumferential surface 13 'on which the inner circumferential insulation material is not formed with pyrolytic carbon or silicon carbide.

In addition, in order to attach the inner circumferential insulation material 15 to the front end of the crystal cooling cylinder 13, as shown in FIG. 7 (a), the wall portions of the inner circumferential insulation material 15 and the crystal cooling cylinder 13 which overlap each other are overlapped. And a fastening member 30, such as a bolt (of course, made of a material having heat resistance, such as graphite), can be exemplified. In addition, as shown in (b), the inner circumferential insulation material 15 may be provided only on the lower end portion 13a integrated in the L-shape in the main body portion of the crystal cooling cylinder 13. In addition, as shown in Fig. 7C, the male screw portion 15m formed on the inner circumferential insulation material 15 (the graphite material covering the side) is attached to the female screw portion 13f formed on the lower end portion of the inner circumferential surface of the crystal cooling cylinder 13. It is also possible to fix by screwing.

Hereinafter, the manufacturing process of the silicon single crystal using the apparatus 50 is demonstrated according to FIG. First, a quartz crucible 6 placed inside the growth furnace main body 1 is filled with polycrystalline silicon ingots, and the furnace is replaced with an inert gas such as argon gas to fill the furnace. The heating heater 7 is heated to heat the polycrystalline silicon at a melting point of silicon of 1420 ° C. or higher to form the silicon melt 4. At this time, the inside of the growth furnace maintains a low pressure of about 500 hPa or less while always flowing an inert gas so that evaporates, such as SiO, which evaporate from the silicon melt do not adhere to the low-temperature furnace structures, and discharge the outside of the evaporates from the furnace. It promotes melting of polycrystalline silicon while urging. This continues even when the transition to the growth of the silicon single crystal 3 is continued. During the growth of the single crystal, operation is performed while maintaining an inert gas at a low pressure while flowing the inert gas into the growth furnace.

When all of the polycrystalline silicon contained in the quartz crucible 5 is dissolved, the temperature of the silicon melt 4 is adjusted to a temperature suitable for single crystal growth, the wire 18 is wound around the tip of the seed crystal 17 to the melt surface. It is complexed. Then, the amount of inert gas downstream from the upper growth furnace 2 and the in-house pressure are adjusted to the growth conditions, and the graphite crucible 6 and the seed crystal 17 are rotated in opposite directions. By slowly winding the wire 18 at a desired speed, the silicon single crystal 3 is grown below the seed crystal 17.

In order to form the silicon single crystal 3 having a predetermined diameter below the seed crystal 17, first, in order to remove the slip dislocation caused by thermal shock when the seed crystal 17 is brought into contact with the silicon melt 4, First, the slip dislocation is removed by making the narrower portion by narrowing the crystal diameter. After the narrowing portion is formed, the diameter is expanded until it reaches a predetermined diameter, the diameter expansion is stopped at the desired diameter, and the silicon single crystal 3 is grown to the desired constant diameter.

When the diameter portion having a constant diameter is pulled up to a desired length, the diameter of the crystal is gradually reduced to form a reduced diameter portion so that the slip dislocation is not caused by the temperature change generated when the silicon single crystal 3 is separated from the silicon melt 4. Thereafter, the silicon single crystal 3 is separated from the melt, and the silicon single crystal 3 is silently rolled up to the upper growth path 2 and cooled to near normal temperature to finish the growth.

Hereinafter, in order to confirm the effect of this invention, the following experiment was done.

Example 1 Experiment 1

When growing a silicon single crystal using the apparatus of the present invention, in order to raise the single crystal so that the OSF ring region ends and becomes the N region, the apparatus shown in FIG. 50) was used to grow silicon single crystals with varying pulling speeds.

First, 100 kg of polycrystalline silicon was put in a 60 cm quartz crucible and heated and melted, and a seed crystal having a crystal axis direction of <100> was allowed to land in a silicon melt to grow a single crystal having a diameter of 200 mm. At this time, the center temperature of the silicon single crystal to be pulled is 50 mm at the lower end position of the crystal cooling tube 13 at a position of about 10 cm upward from the lower portion of the crystal cooling tube 13 with a gap of 50 mm between the inner circumferential insulation material, that is, the cooling tube and the silicon melt surface. The inner circumferential insulation material 15 was arrange | positioned so that it might become (degree. All by simulation), and crystal growth was carried out. At this time, the thickness of the inner circumferential insulation material 15 was adjusted and arrange | positioned so that the space | interval of a crystal | crystallization and the inner circumference insulation material 15 may be about 30 mm.                     

The pulling conditions of the silicon single crystal were gradually decreased so that the pulling speed was set to 0.7 mm / min throughout the regular diameter portion of the crystal, and gradually decreased to near 0.3mm / min near the tail of the latter half of the regular diameter portion. In addition, the growth conditions such as the crucible rotation speed and the amount of inert gas flowing in the furnace were grown while adjusting the oxygen concentration in the silicon single crystal to be 19-20 ppma (ASTM (1979): F-121 measurement value).

After the growth, the single crystal was removed every 10 cm from the tip of the diameter portion after removing the enlarged diameter portion and the reduced diameter portion, and the pulling speed at which the OSF ring region disappeared and reached the N region was examined while vertically dividing from the crystal center. In addition, the defect was identified as follows. First, the single crystal regular diameter part was cut | disconnected at about 10 cm space | interval, the wafer-shaped measurement sample which divided | segmented longitudinally from the center of the impression axis | shaft, and made the rectangle of about 2 mm in thickness was created. After further subjecting the measurement sample to 600 ° C × 2hr + 800 ° C × 4hr in a nitrogen atmosphere and 1000 ° C × 16hr in an oxygen atmosphere, the oxide film on the surface of the measurement sample was removed with a chemical solution, and the surface was subjected to X-ray topography. The defects were measured. The result is as showing in FIG. According to this, it turned out that OSF ring area | region disappeared in the site | part where the pulling speed fell to 0.51 mm / min, and became N area | region to the place where pulling speed became 0.48 mm / min.

Example 1 Experiment 2

In the same manner as in Experiment 1, 100 kg of a polycrystalline raw material was put into a quartz crucible and melted, thereby growing a silicon single crystal having the same diameter and the same orientation. The operating conditions for obtaining the single crystal at this time were the same operation conditions as those in Test 1, except that the pulling speed was adjusted to fall within the range of 0.48 to 0.51 mm / min in the diameter section after 10 cm of the single crystal diameter section. Crystal growth was performed while adjusting the resistivity to be approximately equal. The evaluation sample on the silicon wafer was produced from the site | part except 10 cm from the tip part of the diameter part of the obtained single crystal, and defect evaluation was performed as follows. In order to evaluate the crystal defect in the V region, the oxide withstand voltage measurement in the C mode was performed (invention example). In addition, the measurement conditions of C mode oxide withstand voltage are as follows.

1) Oxide film thickness: 25 nm 2) Measuring electrode: phosphorus-doped polysilicon

3) Electrode area: 8 mm ² 4) Judgment current: 1 mA / cm ²

5) Defective good judgment: Determination of good quality showing a breakdown pressure of 8 MV / cm or more.

As a result, it turned out that the yield of about 100% can be obtained. Next, in order to evaluate the crystal defect L / D observed in the region I, the evaluation sample was etched with a mixture of hydrofluoric acid and nitric acid to remove surface deformation, and then Ｋ ₂ Cr ₂ 0 ₇ and hydrofluoric acid. After the Secco etching was performed again with a mixture of water and water, the bits attributable to L / D on the surface of the evaluation sample were observed. However, no defect due to L / D was observed. From the result of the said defect evaluation in V and I area | region, it was confirmed that the single crystal | crystallization of N area | region with very few defects was grown over the crystal whole.

On the other hand, for comparison, except that the inner circumferential insulation material 15 at the tip of the cooling cylinder of the silicon single crystal manufacturing apparatus was removed, the same apparatus as the manufacturing apparatus shown in FIG. 1 was used, and the pulling speed was adjusted under the same conditions as the invention example. A silicon single crystal having a diameter of 200 mm was grown, and the C-mode oxide film internal pressure was measured in the same manner (Comparative Example A). Furthermore, the apparatus in which the inner circumferential insulation material 15 extended from the upper edge position to the low temperature portion so that the center temperature of the silicon single crystal became about 800 ° C (Comparative Example B), conversely, the center temperature of the silicon single crystal at the lower edge position was about 1350 ° C. Crystal growth was also performed in the apparatus (comparative example C) extended to the high temperature part so as to be. As a result, in the C mode oxide film breakdown voltage measurement, in Comparative Examples A and B, the yield ratio remained at a value of about 50 to 70%, and in Comparative Example C, the value was close to 100%. However, in the single crystal obtained from Comparative Example C, as a result of evaluation of crystal defects (L / D) observed in region I, bits due to low density L / D were observed on the wafer surface.

In addition, by the apparatus used in Comparative Example A, what kind of manufacturing conditions should be used to produce a single crystal having the same quality as that of the Example, i.e., a single crystal in which the entire region is in the N region, the same pulling speed as in Experiment 1 It was confirmed by the diminishing experiment of. As a result, it turned out that the pulling speed | rate area | region used as N area | region has become considerably small by 0.44-0.46 mm / min. 9, the difference of the appropriate pulling speed of an invention example (solid line) and a comparative example (broken line) is visualized and shown.

Example 2 Experiment 1

Using a silicon single crystal manufacturing apparatus having a cooling cylinder with a forced cooling mechanism shown in Fig. 2, 100 kg of polycrystalline silicon was put in a quartz crucible in the same manner as in Experiment 1 of Example 1 to produce a silicon single crystal having a diameter of 200 mm, and OSF. In order to pull up a single crystal in the area | region which a ring area disappears and becomes a low defect area | region N, the confirmation experiment of the pulling conditions was done. At this time, the center temperature of the silicon single crystal to be pulled up with a gap of 50 mm between the inner circumferential insulation material, that is, the cooling tube and the silicon melt surface, was about 1250 ° C. at the lower end position of the crystal cooling tube 13, and about 1000 cm at the position therefrom. The inner circumferential insulation material 15 was arrange | positioned so that it might become (degree. All by simulation), and crystal growth was carried out. At this time, the thickness of the inner circumferential insulation material 15 was adjusted and arrange | positioned so that the space | interval of the crystal and the inner circumference insulation material 15 might be about 30 mm. In addition, the crystal quality such as the oxygen concentration is adjusted to the operating conditions so as to be substantially the same as in Example 1, and a single crystal is grown.

This silicon single crystal was confirmed in the same manner as in Experiment 1 of Example 1, and the site of the OSF ring region and the N region was confirmed. In the manufacturing apparatus of FIG. 2, the single crystal was used so that the pulling speed was in the range of 0.57 to 0.54 mm / min. When it grew, it turned out that the silicon wafer excellent in the oxide-pressure-resistant characteristic with low defect density can be obtained.

Example 2 Experiment 2

And the silicon single crystal of diameter 200mm was produced by the manufacturing apparatus of FIG. 2, adjusting so that the pulling speed might be in the range of 0.54-0.57 mm / min at the position of about 10 cm from the tip part of the diameter part of the silicon single crystal to pull up (invention example). ). A silicon wafer was fabricated in the same manner as in Experiment 2 of Example 1 from the portion except about 10 cm of the tip of the diameter section, and the C mode oxide film withstand pressure was measured under the same conditions, and the yield was almost 100%. . Moreover, as a result of evaluation of the crystal defect L / D observed in the region I, it was confirmed that a bit due to L / D was not confirmed, and a high quality crystal in which defects throughout the crystal region were suppressed was obtained.                     

On the other hand, for comparison, a diameter of 200 mm was adjusted while adjusting the pulling speed under the same conditions as those of the invention example, except that the inner heat-resistant material at the tip of the cooling cylinder of the silicon single crystal production apparatus was removed. A silicon single crystal was grown and the C-mode oxide film breakdown voltage was measured in the same manner (Comparative Example D). Moreover, the apparatus in which the inner circumferential insulation material 15 extended from the upper edge position to the low temperature portion so that the center temperature of the silicon single crystal became about 800 ° C (Comparative Example E), conversely, the center temperature of the silicon single crystal at the lower edge position was about 1350 ° C. Crystal growth was also performed in the apparatus (Comparative Example F) extended to the high temperature portion as As a result, in Comparative Examples D and E, the yield was lower than about 50 to 70%, compared to the C mode oxide film breakdown voltage measurement, and in Comparative Example F, the value was approximately 100%. However, in the silicon single crystal produced in Comparative Example F, as a result of evaluating crystal defects (L / D) observed in region I, bits due to low density L / D were observed on the wafer surface.

In addition, by using the apparatus used in Comparative Example C, what kind of manufacturing condition is preferable for producing a single crystal having the same quality as that of the Example product, was confirmed by a diminishing experiment at the same pulling speed as in Experiment 1 It was found that the pulling speed region serving as the in-N area was reduced to 0.49 to 0.52 mm / min.

In addition, this invention is not limited to embodiment mentioned above. The above-mentioned embodiment is a mere illustration, Any thing which has a structure substantially the same as the technical idea described in the claim of this invention, and has the same effect is a thing included in the technical scope of this invention. For example, although the CZ method of pulling up the silicon single crystal from the silicon melt without applying a magnetic field to the silicon melt has been described as an example of the method for producing the silicon single crystal of the present invention, a magnet is placed outside the growth path of the single crystal manufacturing apparatus. It goes without saying that the same effect can be obtained also in the production of the silicon single crystal by the MCZ method for arranging the silicon single crystal to grow while applying a magnetic field to the silicon melt.

Moreover, in the said embodiment, although the case where the silicon single crystal of 200 mm in diameter was raised was demonstrated for example, this invention is not limited to this, The diameter of the silicon single crystal which has a diameter of 200-400 mm or more is demonstrated. It is applicable to growth and can work more effectively.

By using the silicon single crystal production apparatus of the present invention, it is possible to grow a high quality silicon single crystal free of crystal defects or very few, and to improve the pulling speed by appropriately and efficiently cooling the single crystal pulled up from the silicon melt. Moreover, this manufacturing apparatus is simple in structure, easy to handle, and has high versatility.

Claims (22)

In an apparatus for producing a silicon single crystal in which a silicon single crystal is pulled up by a Czochralski method from a silicon melt contained in a crucible in a growth furnace of a silicon single crystal, A growth furnace body in which the crucible is disposed, In this growth furnace body, a crystal cooling passage arranged to surround the silicon single crystal pulled up from the silicon melt, It has a carbon inner circumferential insulation material installed along the inner circumferential surface of the lower end of the crystal cooling cylinder, protruding toward the outer circumferential surface of the silicon single crystal pulled from the silicon melt, The inner circumferential insulation material is disposed so that the whole thereof is located in the axial direction of the silicon single crystal so as to be located within a section where the center temperature of the silicon single crystal is 1000 ° C or more and 1250 ° C or less. 2. The apparatus for producing a silicon single crystal according to claim 1, wherein at least the lower end of the crystal cooling cylinder is made of graphite, and the inner circumferential insulation material is made of a carbon material having a higher porosity than the lower end of the crystal cooling cylinder of the graphite. . 2. The apparatus for producing a silicon single crystal according to claim 1, wherein an upper end surface of the inner circumferential insulating material is an inclined surface at which the inner circumferential edge side is lowered. 4. The apparatus for producing a silicon single crystal according to claim 3, wherein an angle between the inclined surface and the horizontal surface is in the range of 30 to 70 degrees. 2. The apparatus for producing a silicon single crystal according to claim 1, wherein the inner circumferential insulation material is arranged such that a distance between its inner wall surface and the outer circumferential surface of the regular diameter portion of the pulled silicon single crystal is 20 mm or more and 50 mm or less. 4. The apparatus for producing a silicon single crystal according to claim 3, wherein the inner circumferential insulation material is arranged so that a distance between its inner wall surface and the outer circumferential surface of the regular diameter portion of the pulled silicon single crystal is 20 mm or more and 50 mm or less. 5. The apparatus for producing a silicon single crystal according to claim 4, wherein the inner circumferential insulation material is arranged so that a distance between its inner wall surface and the outer circumferential surface of the regular diameter portion of the pulled silicon single crystal is 20 mm or more and 50 mm or less. 8. The apparatus for producing a silicon single crystal according to any one of claims 1 to 7, wherein a surface exposed to the inside of the crystal cooling cylinder of the inner circumferential insulating material is coated with a graphite material. 9. The apparatus for producing a silicon single crystal according to claim 8, wherein the surface of the graphite material is further coated with pyrolytic carbon or silicon carbide. 2. The apparatus for producing a silicon single crystal according to claim 1, wherein the crystal cooling cylinder is made of graphite, and an inner circumferential surface on which the inner circumferential insulating material is not formed is coated with pyrolytic carbon or silicon carbide. 10. The apparatus for producing a silicon single crystal according to claim 9, wherein the crystal cooling cylinder is made of graphite, and an inner circumferential surface on which the inner circumferential insulating material is not formed is coated with pyrolytic carbon or silicon carbide. 10. The apparatus for producing a silicon single crystal according to claim 9, wherein the iron (Fe) concentration in the film formed of the pyrolytic carbon or the silicon carbide is more than 0 ppm and 0.05 ppm or less. 11. The apparatus for producing a silicon single crystal according to claim 10, wherein the iron (Fe) concentration in the film formed of the pyrolytic carbon or the silicon carbide is more than 0 ppm and 0.05 ppm or less. 12. The apparatus for producing a silicon single crystal according to claim 11, wherein the iron (Fe) concentration in the film formed of the pyrolytic carbon or the silicon carbide is more than 0 ppm and 0.05 ppm or less. Using the apparatus for producing a silicon single crystal according to any one of claims 1 to 7, the silicon single crystal is pulled up by the Czochralski method and manufactured from the silicon melt contained in the crucible. Manufacturing method. A method for producing a silicon single crystal, characterized in that the silicon single crystal is pulled up by the Czochralski method from the silicon melt contained in the crucible using the apparatus for producing a silicon single crystal according to claim 8. A method for producing a silicon single crystal, wherein the silicon single crystal is pulled up by the Czochralski method from the silicon melt contained in the crucible using the apparatus for producing a silicon single crystal according to claim 9. A method for producing a silicon single crystal, comprising using the apparatus for producing a silicon single crystal according to claim 10, by pulling up the silicon single crystal from the silicon melt contained in the crucible by the Czochralski method. A method for producing a silicon single crystal, comprising using the apparatus for producing a silicon single crystal according to claim 11, by pulling up a silicon single crystal from the silicon melt contained in the crucible by the Czochralski method. A silicon single crystal is produced by pulling up a silicon single crystal by the Czochralski method from the silicon melt contained in the crucible using the apparatus for producing a silicon single crystal according to claim 12. A method for producing a silicon single crystal, comprising using the apparatus for producing a silicon single crystal according to claim 13, by pulling up a silicon single crystal from the silicon melt contained in the crucible by the Czochralski method. A silicon single crystal is produced by pulling up a silicon single crystal from the silicon melt contained in the crucible by the Czochralski method using the apparatus for producing a silicon single crystal according to claim 14.

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