JP4432576B2 - Silicon single crystal pulling apparatus and single crystal silicon wafer - Google Patents

Description

  The present invention relates to a silicon single crystal pulling apparatus for forming a silicon single crystal and a single crystal silicon wafer sliced from a silicon single crystal ingot grown by the silicon single crystal pulling apparatus.

  A single crystal silicon wafer used as a substrate for a semiconductor device or the like is manufactured by slicing a silicon single crystal ingot and performing mirror surface processing or the like. Examples of a method for producing such a silicon single crystal ingot include the Czochralski method (CZ method) and the floating zone method (FZ method). Among them, the CZ method occupies most of the production of a silicon single crystal ingot because it is easy to obtain a large-diameter single crystal ingot and the defect control is relatively easy.

  In a silicon single crystal grown by the Czochralski method, defects called COPs or dislocation clusters may exist. COP (Crystal-Originated-Particle) is, for example, manifested as a pit when cleaned with SC-1 cleaning solution, which is a mixed solution of ammonia water and hydrogen peroxide, or found in a particle counter, or by AFM (Atomic force Micriscopy) It is a minute void defect that is directly observed, and was discovered by the applicant of the present application. Such a defect is also called a grow-in defect, and is formed as the crystal grows.

  It is known that COPs among grow-in defects are detected inside the oxidation-induced stacking fault ring (R-OSF) region, and dislocation cluster defects are detected outside the R-OSF region. A defect-free region exists outside the R-OSF. Such an R-OSF generation region depends on the growth rate of the single crystal, and when the crystal pulling speed is increased, the R-OSF generation region moves from the inside to the outside of the crystal. Go.

  OSF is an interstitial dislocation loop generated during the oxidation heat treatment, and when it is present on the wafer surface, which is an active region of the device, causes a leakage current and becomes a defect that degrades device characteristics. For this reason, many single crystals grown at a relatively high pulling speed have been manufactured so that the generation positions of R-OSF are distributed in the outermost peripheral portion of the crystal when growing the single crystal.

  In a silicon single crystal in which the positions of these R-OSFs are distributed on the outermost periphery of the crystal, the silicon wafer can be manufactured by controlling the size and density of the COP inside the R-OSF. This type of wafer is characterized by its low cost and is therefore used by many memory manufacturers.

  In addition, since it is easier to manufacture a chip if the properties in the wafer plane are uniform, silicon wafers in which the R-OSF positions are distributed on the outermost periphery of the crystal have become the mainstream of semiconductor device substrates. ing. Accordingly, various methods for distributing the position of the R-OSF in the outer portion of the silicon single crystal have been proposed.

  For example, in Patent Document 1, in order to control the generation position of R-OSF, the ratio of the pulling speed (V) during single crystal growth to the temperature gradient (G) in the crystal in the pulling axis direction, V / G value It is described that the radius of the R-OSF can be determined almost uniquely by appropriately controlling the R-OSF, and the generation region of the R-OSF can be adjusted.

Further, Patent Document 2 describes a single crystal pulling apparatus including a plurality of heaters provided in the vertical direction around the crucible and supplying a power that is adjusted according to the pulling progress of the single crystal. ing.
JP-A-11-15795 JP 62-153191 A

  However, when the single crystal is grown by controlling the V / G value aiming at the defect-free region close to the R-OSF as in the single crystal pulling apparatus described in Patent Document 1 described above, There is a concern that the speed is likely to be slow and the manufacturing cost of the silicon wafer is high, and there is a problem that the pulling speed can be increased if R-OSF is distributed on the outermost periphery of the single crystal.

  Further, in the single crystal pulling apparatus described in Patent Document 2, it is difficult to appropriately control the COP even though the oxygen concentration can be controlled.

  The present invention has been made in view of the above circumstances, and includes a silicon single crystal pulling apparatus capable of manufacturing a silicon single crystal in which R-OSF is distributed on the outermost periphery of the single crystal and COP is reduced at a low cost. An object is to provide a single crystal silicon wafer.

In order to achieve the above-mentioned object, according to the present invention, a crucible comprising a substantially cylindrical body portion opened upward and a bottom portion closing the lower portion of the body portion, and an outer side of the body portion are surrounded. A silicon single crystal that has a side heater that heats the crucible from the body and a bottom heater that is disposed below the bottom and heats the crucible from the bottom, and pulls up the silicon single crystal by the Czochralski method A lifting device,
Set the distance between the inner peripheral surface of the crucible and the inner peripheral surface of the side heater below 3 times the thickness of the side heater, wherein the distance between the inner bottom surface of the deepest portion of the upper surface and the crucible of the bottom heater Set within 2/3 of the height of the crucible, set the output ratio of the side heater and the bottom heater to 3 to 3.2 to 2, the thickness of the side heater in the range of 16 to 30 mm, A silicon single crystal pulling apparatus is provided in which the thickness of the bottom heater is set in a range of 8 to 30 mm .
The distance between the inner peripheral surface of the side heater and the inner peripheral surface of the crucible is set in a range of 30 to 56 mm, and the distance between the upper surface of the bottom heater and the deepest portion of the inner bottom surface of the crucible is set to 350 mm or less. preferable.

  According to the silicon single crystal pulling apparatus of the present invention, when the thickness value of the side heater is A, the distance between the inner peripheral surface of the side heater and the inner peripheral surface of the crucible is three times the thickness A of the side heater. By setting the distance between the upper surface of the bottom heater and the deepest part of the inner bottom surface of the crucible within two-thirds of the height of the crucible, the R-OSF is distributed on the outermost periphery of the single crystal. , It becomes possible to obtain a single crystal silicon wafer with COP appropriately controlled at low cost.

  According to the silicon single crystal pulling apparatus of the present invention, by setting the output ratio of the side heater and the bottom heater to 3 to 3.2: 2 (side heater: bottom heater), the number of COPs more than a certain size. Can be reduced. When the output ratio of the side heater is made larger than the above range, the number of COPs is not reduced, which is not preferable. When the output ratio of the side heater is made smaller than the above range, the convection in the crucible is not preferable. Is not preferred because it may become too large.

Thus, the oxygen concentration is 1.45 × 10 ¹⁸ atms / cm ³ or less, the average number of oxidation-induced stacking faults in the wafer surface is 3 / cm ³ or less, and the COP generation region is a silicon single crystal ingot. More than 90% of the diameter and the oxidation-induced stacking fault ring is distributed in the outermost peripheral portion of the silicon single crystal ingot, and the number of COPs of 0.106 μm or more is 140 or less in the plane of the single crystal silicon wafer. A COP of 120 μm or more makes it possible to obtain 70 or less single crystal silicon wafers in the plane of the single crystal silicon wafer.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partially broken perspective view schematically showing a silicon single crystal pulling apparatus according to the present invention. The silicon single crystal pulling apparatus 10 includes a substantially cylindrical outer shell 11 and accommodates a quartz crucible 12 for melting and storing silicon therein. For example, the outer shell 11 may have a double-wall structure in which a constant gap is formed inside. By flowing the cooling water 13 through the gap, the outer shell 11 is heated when the quartz crucible 12 is heated. To prevent.

  The outer shell 11 is provided with an air supply / exhaust pipe 21, and an inert gas such as argon is introduced into the silicon single crystal pulling apparatus 10 when pulling the silicon single crystal. A pulling drive device 14 is provided on the top of the outer shell 11. The pulling drive device 14 pulls the seed crystal 6 that is a growth nucleus of the silicon single crystal ingot 5 and the silicon single crystal ingot 5 that is grown therefrom while pulling upward.

  A heat insulating cylinder 15 is provided inside the outer shell 11. The heat insulating cylinder 15 may be made of graphite, for example, and serves to reduce the temperature drop during heating of the quartz crucible 12 and to suppress the temperature rise of the outer shell 11.

  A substantially cylindrical side heater 16 is provided inside the heat insulating cylinder 15. The side heater 16 heats the cylindrical body 12 a of the quartz crucible 12. A quartz crucible 12 and a crucible support (graphite crucible) 17 are accommodated inside the side heater 16. The quartz crucible 12 is formed of quartz as a whole and is composed of a substantially cylindrical body 12a having an open surface 12c on the upper side and a mortar-shaped bottom 12b closing the lower side of the body 12a.

  The quartz crucible 12 stores a silicon melt 7 obtained by melting solid silicon. The crucible support 17 is made of, for example, graphite as a whole, and supports the crucible 12 so as to wrap the quartz crucible 12. The crucible support 17 maintains the shape of the quartz crucible 12 softened when silicon is melted and plays a role of supporting the quartz crucible 12.

  A bottom heater 18 is provided below the quartz crucible 12. The bottom heater 18 heats the bottom 12 b of the quartz crucible 12 via the crucible support 17. The quartz crucible 12 is heated from the side surface and the bottom surface to, for example, 1420 ° C. by the side surface heater 16 and the bottom surface heater 18.

  A crucible support device 19 is provided below the crucible support 17. The crucible support device 19 supports the crucible support 17 and the quartz crucible 12 from below, and moves up and down to adjust the position of the quartz crucible 12 corresponding to the liquid surface position of the silicon melt 7 that changes with growth. It has a mechanism.

  Next, with reference to FIG. 2, the optimal arrangement | positioning and dimension of each part of the silicon | silicone single crystal pulling apparatus of this invention are illustrated. The silicon single crystal pulling apparatus 10 has an inner peripheral surface 16 a of the side heater 16 and an inner side (inner periphery of the quartz crucible 12) when the thickness value of the side heater 16 that heats the quartz crucible 12 is A. The distance B to the surface) is set to 3 times or less the thickness A of the side heater 16. At the same time, the distance C between the upper surface 18 a of the bottom heater 18 and the deepest portion inside (inner bottom surface) of the bottom 12 b of the quartz crucible 12 is set within two thirds of the height H of the quartz crucible 12.

  For example, the thickness A of the side heater 16 is 16 to 30 mm, the thickness D of the bottom heater 18 is 8 to 30 mm, and the distance between the inner peripheral surface 16 a of the side heater 16 and the inner side (inner peripheral surface) of the body 12 a of the quartz crucible 12. B is preferably set to 30 to 56 mm, and the distance C between the upper surface 18a of the bottom heater 18 and the deepest portion on the inner side (inner bottom surface) of the bottom 12b of the quartz crucible 12 is set to 350 mm or less.

  Here, the thickness dimension of the body 12a of the quartz crucible 12 can be 5 mm to 20 mm, and the diameter of the quartz crucible 12 is 40 to 82 cm (16 ″, 18 ″, 22 ″, 24 ″, 26 ″, 28 ″, 30 ″, 32) and the like.

  Then, the quartz crucible 12 is heated by setting the output ratio of the side heater 16 and the bottom heater 18 to 3 to 3.2 to 2, and the silicon single crystal ingot 5 is grown. As described above, the size of the heater and crucible of the silicon single crystal pulling apparatus and the output ratio of the heater are set so that the R-OSF is distributed on the outermost periphery of the single crystal and the COP is appropriately controlled. Can be obtained at low cost.

For example, the oxygen concentration is 1.45 × 10 ¹⁸ atms / cm ³ or less, the average number of oxidation-induced stacking faults in the wafer surface is 3 / cm ³ or less, and the COP generation region is the diameter of the silicon single crystal ingot. And the oxidation-induced stacking fault ring is distributed in the outermost peripheral portion of the silicon single crystal ingot, and the COP of 0.106 μm or more is 140 or less in the plane of the single crystal silicon wafer and 0.120 μm. It becomes possible to obtain a single crystal silicon wafer having 70 or less COPs in the plane of the single crystal silicon wafer.

  The present applicant verified the characteristics of a single crystal silicon wafer obtained by using the silicon single crystal pulling apparatus of the present invention as described above. In the verification, using the silicon single crystal pulling apparatus shown in FIG. 1, the COP generation region is set to a range of 90% or more of the diameter of the grown silicon single crystal ingot, and the oxidation-induced stacking fault ring (R-OSF) is silicon. Set the pulling speed to be distributed on the re-periphery of the single crystal ingot, grow the silicon single crystal ingot under the conditions of using the bottom heater and not using it, and processing the mirror surface wafer. The COP numbers were compared by size.

  The frequency distribution of the number of COPs having a size of 0.106 μm or more in a single crystal silicon wafer produced from a silicon single crystal ingot grown by heating a quartz crucible with only a side heater without using a bottom heater is shown in FIG. The frequency distribution of the number of COPs having a size of 120 μm or more is shown in FIG.

  In contrast, the frequency distribution of the number of COPs having a size of 0.106 μm or more in a single crystal silicon wafer produced from a silicon single crystal ingot grown by heating a quartz crucible using both a bottom heater and a side heater is shown. FIG. 6 shows the frequency distribution of the number of COPs having a size of 0.120 μm or more.

  According to the verification results shown in FIGS. 3 to 6, the quartz crucible is heated by using both the bottom heater and the side heater, so that it is 0.106 μm or more compared with the case where the quartz crucible is heated only by the side heater. The average number of COPs decreased from 158 to 107 on average. The number of COPs having a size of 0.120 μm or more was reduced from 89 to 55 on average. Thereby, the effect of the bottom heater was confirmed.

  Next, using the silicon single crystal pulling apparatus shown in FIG. 1, the COP generation region is set to a range of 90% or more of the diameter of the grown silicon single crystal ingot, and an oxidation-induced stacking fault ring (R-OSF) is formed in silicon. Set the pulling speed to be distributed on the outer periphery of the single crystal ingot, change the output ratio of the side heater and bottom heater, grow each silicon single crystal ingot, process the mirror wafer, then size the number of COPs on the surface Compared separately.

  0.106 μm in a single crystal silicon wafer produced from a silicon single crystal ingot grown by heating a quartz crucible with the output ratio of the side heater and bottom heater set to 3 to 3.2: 2 (side heater: bottom heater) FIG. 7 shows the frequency distribution of the COP number having the above size, and FIG. 8 shows the frequency distribution of the COP number having the size of 0.120 μm or more.

  On the other hand, the output ratio of the side heater and the bottom heater is set to 3.2 to 3.4: 2 (side heater: bottom heater), and a single crystal ingot produced from a silicon single crystal ingot grown by heating a quartz crucible. FIG. 9 shows a frequency distribution of COP numbers having a size of 0.106 μm or more in a crystalline silicon wafer, and FIG. 10 shows a frequency distribution of COP numbers having a size of 0.120 μm or more.

  According to the verification results shown in FIGS. 7 to 10, it was confirmed that the COP number greatly changes by growing the silicon single crystal ingot by changing the output ratio of the side heater and the bottom heater. By setting the output ratio of the side heater and the bottom heater to 3 to 3.2: 2 (side heater: bottom heater), the average number of COPs with a size of 0.106 μm or more becomes 70, that is, 0.120 μm or more. The number of COPs of the size could be 34 on average.

  Further, using the silicon single crystal pulling apparatus shown in FIG. 1, the oxidation-induced stacking fault ring (R-OSF) is formed on the silicon single crystal by setting the COP generation region to a range of 90% or more of the diameter of the grown silicon single crystal ingot. The pulling speed distributed to the re-periphery of the crystal ingot is set, the output of the bottom heater is made constant, and the distance between the top surface of the bottom heater and the deepest portion of the inner bottom surface of the quartz crucible (distance C in FIG. 2) ) Were grown and each single-crystal silicon ingot was grown and mirror-finished wafers were processed. Then, the number of COPs on the surface was compared by size.

  FIG. 11 shows the relationship between the number of COPs by size on the wafer surface and the distance between the upper surface of the bottom heater and the deepest portion of the inner bottom surface of the quartz crucible. From the above verification results, the average number of COP sizes of 0.106 μm or more of single crystal silicon wafers made from silicon single crystal ingots grown under optimum pulling conditions (see FIG. 12) The average number of COP sizes of 0.120 μm or more was 32 (see FIG. 13).

FIG. 1 is a partially broken perspective view schematically showing a silicon single crystal pulling apparatus according to the present invention. FIG. 2 is a cross-sectional view of an essential part of the silicon single crystal pulling apparatus shown in FIG. FIG. 3 is a graph showing the verification results of the present invention. FIG. 4 is a graph showing the verification results of the present invention. FIG. 5 is a graph showing the verification results of the present invention. FIG. 6 is a graph showing the verification results of the present invention. FIG. 7 is a graph showing the verification results of the present invention. FIG. 8 is a graph showing the verification results of the present invention. FIG. 9 is a graph showing the verification results of the present invention. FIG. 10 is a graph showing the verification results of the present invention. FIG. 11 is a graph showing the verification results of the present invention. FIG. 12 is a graph showing the verification results of the present invention. FIG. 13 is a graph showing the verification results of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Silicon single crystal pulling apparatus 12 Quartz crucible 12a Trunk part 12b Bottom part 12c Open surface 16 Side heater 16a Inner peripheral surface 18 Bottom heater

Claims (2)

A crucible composed of a substantially cylindrical body having an open top and a bottom that closes the bottom of the body, a side heater that surrounds the outside of the body and heats the crucible from the body, and the bottom A silicon single crystal pulling apparatus that has a bottom surface heater that heats the crucible from the bottom portion and that pulls up the silicon single crystal by the Czochralski method,
The distance between the inner peripheral surface of the side heater and the inner peripheral surface of the crucible is set to be not more than three times the thickness of the side heater ;
The distance between the upper surface of the bottom heater and the deepest part of the inner bottom surface of the crucible is set within two thirds of the height of the crucible ;
The output ratio of the side heater and the bottom heater is set to 3 to 3.2 to 2,
A silicon single crystal pulling apparatus , wherein the thickness of the side heater is set in a range of 16 to 30 mm, and the thickness of the bottom heater is set in a range of 8 to 30 mm . The distance between the inner peripheral surface of the side heater and the inner peripheral surface of the crucible is set in a range of 30 to 56 mm, and the distance between the upper surface of the bottom heater and the deepest portion of the inner bottom surface of the crucible is set to 350 mm or less. 2. The silicon single crystal pulling apparatus according to claim 1, wherein

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