JP4166316B2 - Single crystal manufacturing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for producing a single crystal by the CZ method.
[0002]
[Prior art]
Single crystal silicon is generally manufactured using the CZ method. In the single crystal manufacturing apparatus using the CZ method, as shown in FIG. 6, a crucible 5 is installed at the center of a chamber 31 so as to be movable up and down and rotatable. The crucible 5 contains a quartz crucible 5b in a graphite crucible 5a. The quartz crucible 5b is filled with massive polycrystalline silicon, and the raw material is supplied by a cylindrical heater 6 provided so as to surround the crucible 5. A melt 3 is obtained by heating and dissolving. Then, the seed crystal attached to the seed holder 32 is immersed in the melt 3, and the seed holder 32 is pulled up while rotating the seed holder 32 and the crucible 5 in the same direction or in the opposite direction, so that the single crystal 2 has a predetermined diameter and length. Let it grow.
[0003]
An annular rim 8 is attached to the upper end of the heat insulating cylinder 7 surrounding the heater 6, and a heat shielding plate 33 is hooked on the inner edge of the annular rim 8. The heat shielding plate 33 is an inverted frustoconical cylinder surrounding the single crystal 2 being pulled up, and incorporates a heat insulating material 34 made of carbon fiber or the like. A heat insulating material 9 is attached to the outer edge of the annular rim 8. The heat shielding plate 33 has a function of blocking direct radiant heat from the melt 3, the crucible 5, and the heater 6 with respect to the single crystal 2, and particularly the radial and axial temperatures of the single crystal 2 near the solid-liquid interface. By increasing the gradient and promoting the cooling of the single crystal 2, the pulling speed is improved. Further, the heat shielding plate 33 guides an inert gas introduced from above the chamber 31 to the periphery of the single crystal 2, and vaporizes from the melt 3, SiO ₂ , Si, metal vapor generated from the crucible 5, etc. It has a function of effectively discharging various gases that inhibit single crystallization to improve the dislocation-free crystallization rate.
[0004]
[Problems to be solved by the invention]
However, in the conventional heat shielding plate shown in FIG. 6, the cooling effect of the single crystal 2 is reduced by the radiant heat radiated from the melt 3 or the radiant heat radiated from the main body surface of the heat shielding plate 33 at a high temperature. Therefore, the pulling speed is restricted. As a countermeasure, in the prior art, as shown in FIG. 7, the inner side facing the single crystal 2 being pulled is formed into an inverted truncated cone shape whose diameter is reduced from the upper end side toward the lower end side. A heat shield plate 41 having a cylindrical shape is proposed. The heat shielding plate 41 increases in thickness as it approaches the lower end side, and the inner space is filled with felt having excellent heat insulating properties as the heat insulating material 42, so that the radiant heat from the heater, the crucible, the melt, etc. is effective. Thus, the single crystal 2 can be given an appropriate temperature gradient in the pulling direction, the pulling speed of the single crystal 2 can be increased, and the production efficiency can be improved.
[0005]
However, since the heat shielding plate 41 shown in FIG. 7 acts as a cooling effect on the entire temperature region of the single crystal, the pulling speed is increased, but the temperature in the vicinity of the grown-in defect formation temperature region (1150 to 1000 ° C.). The gradient will also increase. Therefore, the grown-in defect density is higher than that of the single crystal pulled up by the manufacturing apparatus shown in FIG. 6, and as a result, the breakdown voltage characteristics of the oxide film are deteriorated and the yield is lowered after the device process.
[0006]
The present invention has been made by paying attention to the above-mentioned conventional problems. The temperature gradient of the single crystal in the vicinity of the solid-liquid interface can be increased so that the single crystal can be pulled at a higher speed than the conventional one. An object of the present invention is to provide a single crystal manufacturing apparatus in which the in defect density can be suppressed to the same level as in the past.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a first single crystal manufacturing apparatus according to the present invention is a heat shielding plate surrounding a single crystal being pulled, and an inner surface facing the single crystal has a temperature within the single crystal. Is a cylindrical portion arranged parallel to a portion near 1150 to 1000 ° C. which is a grown-in defect formation temperature, and a tapered portion which is connected to the lower portion of the cylindrical portion and is reduced in diameter as it approaches the melt surface. The outer surface side includes a cylindrical portion that hangs down from the inner edge of the annular rim toward the melt surface, and a heat shielding plate filled with a heat insulating material is provided in the inner space sandwiched between the inner surface side and the outer surface side. It is characterized by that.
A second aspect of the single crystal manufacturing apparatus according to the present invention is a heat shielding plate surrounding the single crystal being pulled, and the inner surface facing the single crystal has a grown-in defect formation temperature on the inner surface side of the single crystal. A cylindrical portion arranged so as to be parallel to a portion near 1150 to 1000 ° C., and a tapered portion connected to the lower portion of the cylindrical portion and having a diameter reduced toward the melt surface. A cylindrical portion that hangs down from the inner edge of the annular rim toward the melt surface, and a heat shielding plate filled with a heat insulating material is provided in an internal space sandwiched between the tapered portion on the inner surface side and the outer surface side. Features.
A third aspect of the apparatus for producing a single crystal according to the present invention is a heat shield plate surrounding the single crystal being pulled, and the inner surface facing the single crystal has a grown-in defect formation temperature on the inner side of the single crystal. A cylindrical portion arranged so as to be parallel to a portion near 1150 to 1000 ° C., and a tapered portion connected to the lower portion of the cylindrical portion and having a diameter reduced toward the melt surface. A cylindrical portion that hangs down from the inner edge of the annular rim toward the melt surface and is parallel to the cylindrical portion on the inner surface side, and is connected to the lower side of the cylindrical portion, and has a diameter larger than the diameter of the cylindrical portion on the outer peripheral surface side. And a heat shielding plate filled with a heat insulating material is provided in an internal space sandwiched between the tapered portion on the inner surface side and the lower end portion on the outer surface side.
The most important factor when pulling a single crystal at high speed is the axial temperature gradient of the single crystal in the vicinity of the solid-liquid interface, and the temperature gradient is greatly affected by radiant heat from the heater, crucible, melt, etc. know. There is a positive correlation between the axial temperature gradient and the pulling speed, and the pulling speed can be increased by increasing the axial temperature gradient. According to the above configuration, since the thickness of the lower end of the heat shielding plate is maximized, the heat insulation of the radiant heat is improved, the single crystal being pulled is rapidly cooled, and the crystal temperature gradient in the vicinity of the solid-liquid interface is increased. The crystal shape is likely to be stable. Thereby, the pulling-up speed can be kept equal to that of the conventional example shown in FIG. On the other hand, since the upper part of the heat shielding plate is cylindrical on both the inner surface side and the outer surface side and is thin, the temperature gradient of the single crystal is reduced.
[0008]
Further , according to the above configuration, the inner surface side and the outer surface side of the heat shield plate are both cylindrical with respect to the portion where the single crystal being pulled becomes a grown-in defect formation temperature region, and the thickness of the heat shield plate is smaller than that of the lower portion. Because it is extremely thin, the radiant heat from the hot zone is difficult to block. This radiant heat is radiated to the single crystal through the heat shielding plate. Therefore, the grown-in defect formation temperature region is surrounded by the thin cylindrical portion, and heat dissipation from the single crystal is suppressed, thereby reducing the defect density.
[0009]
In a fourth aspect of the single crystal manufacturing apparatus according to the present invention, the upper end position of the heater provided in the single crystal manufacturing apparatus according to the first to third aspects of the present invention is between 200 mm above the melt surface and 50 mm below the melt surface. It is characterized by being set to. If the upper end position of the heater is higher than the melt surface by 200 mm or more, the axial temperature gradient of the single crystal becomes too small due to the influence of the radiant heat of the heater, and the pulling speed cannot be increased. On the other hand, when the upper end position of the heater is 50 mm or more lower than the melt surface, the temperature gradient in the lateral direction becomes too small, causing a problem that crystals protrude from the quartz crucible. According to the above configuration, since the upper end position of the heater is set so as to fall within the numerical value, it is possible to avoid these problems and increase the crystal pulling speed.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the single crystal manufacturing apparatus according to the present invention will be described with reference to the drawings. Note that the same components as those described in the prior art are denoted by the same reference numerals and description thereof is omitted.
[0011]
FIG. 1 shows a lower structure of the single crystal manufacturing apparatus according to the first embodiment. The inner surface side of the heat shielding plate 1 is connected to a cylindrical portion 1a parallel to the single crystal 2 being pulled up, and a tapered portion that is connected to the lower end of the cylindrical portion 1a through a step and is reduced in diameter as it approaches the melt surface 3a. 1b. The inner surface side is set so that the cylindrical portion 1a faces a region where the single crystal 2 being pulled is at a growth-in defect formation temperature, that is, around 1150 to 1000 ° C. On the other hand, the outer surface side of the heat shielding plate 1 consists only of a cylindrical portion 1c parallel to the single crystal 2 being pulled up, and a space surrounded by the inner surface, outer surface and bottom surface is filled with a heat insulating material 4 made of carbon fiber or the like. Has been. The upper end of the heat shielding plate 1 is hooked on the inner edge of an annular rim 8 provided above the crucible 5, the heater 6 and the heat retaining cylinder 7. If the distance between the lower end of the heat shielding plate 1 and the melt surface 3a is reduced, the radiant heat from the melt 3 to the single crystal 2 can be reduced and the axial temperature gradient of the single crystal 2 increases. In order not to disturb the flow of the inert gas that is thought to affect the crystallization rate, it is desirable that the interval be at least about 10 to 30 mm.
[0012]
The upper end of the heater 6 is set to be located between 200 mm above the melt surface 3a and 50 mm below the melt surface 3a. When the melt surface 3a becomes lower than the upper end position of the heater 6, the axial temperature gradient of the single crystal 2 gradually decreases. On the contrary, when the melt surface 3a increases, the axial temperature gradient of the single crystal 2 becomes Gradually grows. When the upper end of the heater 6 is at a position higher than the melt surface 3a by 200 mm or more, the temperature gradient in the axial direction of the single crystal 2 becomes too small due to the radiant heat radiated from the heater 6, making it difficult to pull up at high speed. In addition, when the upper end of the heater 6 is lower than the melt surface 3a by 50 mm or more, the lateral temperature gradient becomes too small, causing a problem that crystals protrude from the quartz crucible. Therefore, it is desirable to set the upper end position of the heater 6 within the range of the numerical values.
[0013]
In the heat shielding plate 1 installed in the single crystal manufacturing apparatus of the first embodiment, the temperature gradient G1 near the solid-liquid interface (melting point to 1300 ° C.) is the same as that of the single crystal manufacturing apparatus of the second conventional example shown in FIG. Since it can be increased to the same level, the crystal pulling rate can be increased to the same level as before. Further, in the crystal defect formation temperature region (around 1150 to 1080 ° C.), the heat dissipation of the single crystal is suppressed, so that the temperature gradient G2 in the temperature region becomes smaller than that when the single crystal manufacturing apparatus of the second conventional example is used. Density is reduced.
[0014]
Comparison results of the temperature gradient of the single crystal when the single crystal is pulled up using the single crystal manufacturing apparatus of the first embodiment and the temperature gradient when using the conventional single crystal manufacturing apparatus shown in FIGS. Is shown in FIG. In the first conventional example shown in FIG. 6, since the heat shielding effect by the heat shielding plate is uniformly low, the axial temperature gradient of the single crystal is generally small. In particular, since the temperature gradient G1 in the vicinity of the solid-liquid interface is small, it can be seen that high-speed pulling is difficult. However, since the temperature gradient G2 in the crystal defect formation temperature region is small, the crystal defect density can be kept low. Further, in the second conventional example shown in FIG. 7, since the thermal shielding effect becomes higher as it approaches the lower part of the thermal shielding plate, the temperature gradient G1 is particularly large, and the temperature gradient G2 is also correspondingly increased, resulting in a high-density crystal. Defects occur. On the other hand, when the single crystal manufacturing apparatus of the first embodiment shown in FIG. 1 is used, the temperature gradient G1 near the solid-liquid interface can be increased to the same extent as when the heat shield plate shown in FIG. 7 is used. The crystal pulling speed can be increased to the same level as in the second conventional example of FIG. Further, the temperature gradient G2 becomes smaller than that of the first conventional example of FIG. 6, and the crystal defect formation temperature region is not rapidly cooled. In summary, when the heat shield plate installed in the single crystal manufacturing apparatus of the present invention is used, the temperature gradient G1 is increased as in the second conventional example, and the temperature gradient G2 is decreased as compared with the first conventional example. Is possible.
[0015]
Comparison result of defect density of single crystal manufactured using single crystal manufacturing apparatus of first embodiment and single crystal manufactured using conventional single crystal manufacturing apparatus shown in FIGS. Is shown in FIG. However, in FIG. 3, the first embodiment (FIG. 1) and the second conventional example (FIG. 7) are data when the average pulling rate of the single crystal is increased by about 20% compared to the first conventional example (FIG. 6). is there. As is apparent from this figure, in the second conventional example of FIG. 7, the crystal defect formation temperature region is rapidly cooled, so that the LSTD density exceeds 3 × 10 ⁶ / cm ^3. Can be reduced to less than 2 × 10 ⁶ / cm ³ . In addition, when the average pulling rate is maintained equal to that of the first conventional example using the single crystal manufacturing apparatus of the first example, the LSTD density is further lowered.
[0016]
FIG. 4 shows a heat shielding plate installed in the single crystal manufacturing apparatus of the second embodiment. The heat shield plate 11 has the same shape as the heat shield plate 1 shown in FIG. 1, but the cylindrical portion 11a constituting the upper portion is a common layer on the inner surface side and the outer surface side. That is, the inner surface side includes a cylindrical portion 11a that is parallel to the single crystal 2 being pulled up, and a tapered portion 11b that is connected to the lower end of the cylindrical portion 11a through a step and is reduced in diameter as it approaches the melt surface 3a. Provided, and the outer surface side consists only of the cylindrical portion 11a. The heat insulating material 12 is filled in a portion sandwiched between the tapered portion 11b and the outer cylindrical portion 11a.
[0017]
When the heat shield plate 11 is used, the temperature gradient G1 in the vicinity of the solid-liquid interface becomes almost the same as that of the heat shield plate 1 of the first embodiment, so that the crystal pulling speed can be increased to the same level. In addition, since the heat shielding plate 11 has a single layer in the crystal defect formation temperature region, the heat insulation performance is small, and the amount of heat radiated from the heater to the single crystal 2 is large. Therefore, the temperature gradient G2 becomes smaller than that of the heat shield plate of the first embodiment, and the crystal defect density is further reduced.
[0018]
FIG. 5 shows a heat shielding plate installed in the single crystal manufacturing apparatus of the third embodiment. The inner surface side of the heat shielding plate 21 includes a cylindrical portion 21a parallel to the single crystal 2 being pulled up, and a tapered portion 21b that is connected to the lower end of the cylindrical portion 21a and is reduced in diameter as it approaches the melt surface 3a. ing. The inner surface side is set so that the cylindrical portion 21a faces a region where the single crystal 2 being pulled is at a grown-in defect formation temperature, that is, near 1150 to 1000 ° C. On the other hand, the outer surface side of the heat shielding plate 21 is connected to the cylindrical portion 21c parallel to the single crystal 2 being pulled up, the tapered portion 21d connected to the lower end thereof, and diameter-expanding as it approaches the melt surface 3a, and the following. And a cylindrical portion 21e. The bottom width of the heat shield plate 21 is the same as that of the heat shield plate 1 shown in FIG. 1 and the heat shield plate 11 shown in FIG. 4, and a step is provided at the connection portion between the cylindrical portion 21a and the tapered portion 21b on the inner surface side. Therefore, the cylindrical portion 21a is installed at a position closer to the single crystal 2 than the heat shielding plate shown in FIGS. In addition, a heat insulating material 22 made of carbon fiber or the like is filled in the internal space of the heat shielding plate 21.
[0019]
When the heat shielding plate 21 is used, the temperature gradient G1 in the vicinity of the solid-liquid interface becomes almost the same as that in the first embodiment, and the crystal pulling speed can be increased to the same level. Further, in the crystal defect formation temperature region, the distance between the single crystal 2 and the heat shielding plate 21 is narrowed, so that the heat radiation from the single crystal 2 is suppressed, and the temperature gradient G2 is further reduced as compared with the first embodiment. The crystal defect density is further reduced. Similarly to the second embodiment, if the portion of the heat shield plate corresponding to the crystal defect formation temperature region has a single-layer structure, the temperature gradient G2 is further reduced, so that the defect density is reduced as compared with the second embodiment.
[0020]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
(1) In the vicinity of the solid-liquid interface, the radiant heat from the heater, crucible, melt, etc. can be effectively blocked, and the temperature gradient in the axial direction of the single crystal can be increased. ) And can be maintained at a level equal to or higher than that of (1), which contributes to the improvement of single crystal productivity.
(2) On the other hand, in the crystal defect formation temperature range, the radiation heat from the heater, crucible, melt, etc. is received at the same level or higher as that of the prior art (first conventional example), and the heat radiation from the single crystal is suppressed. Even when high-speed pulling is performed, the grown-in defect density is reduced to the same level as in the conventional technique (first conventional example), and the crystal quality can be maintained.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view showing a lower structure of a single crystal manufacturing apparatus according to a first embodiment.
FIG. 2 is a diagram showing a temperature gradient of a single crystal.
FIG. 3 is a diagram showing an axial distribution of defect density of a single crystal.
FIG. 4 is a schematic longitudinal sectional view showing a heat shielding plate of a single crystal manufacturing apparatus according to a second embodiment.
FIG. 5 is a schematic longitudinal sectional view showing a heat shielding plate of a single crystal manufacturing apparatus according to a third embodiment.
FIG. 6 is a schematic longitudinal sectional view showing a lower structure of a single crystal manufacturing apparatus according to a first conventional example.
FIG. 7 is a schematic longitudinal sectional view showing a heat shielding plate of a single crystal manufacturing apparatus of a second conventional example.
[Explanation of symbols]
1,11,21,33,41 Heat shield plates 1a, 1c, 11a, 21a, 21c, 21e Cylindrical portions 1b, 11b, 21b, 21d Tapered portion 2 Single crystal 3a Melt surface 4, 9, 12, 22, 34 , 42 Insulation material 5 Crucible 6 Heater 8 Annular rim

Claims (4)

A heat shield surrounding the single crystal being pulled,
The inner surface facing the single crystal has a cylindrical portion disposed so as to be parallel to a portion of the single crystal whose temperature is around 1150 to 1000 ° C. which is a growth-in defect formation temperature, and a lower portion of the cylindrical portion. And a tapered portion that is reduced in diameter as it approaches the melt surface,
The outer surface side includes a cylindrical portion depending from the inner edge of the annular rim toward the melt surface,
A single crystal manufacturing apparatus, wherein a heat shielding plate filled with a heat insulating material is provided in an internal space sandwiched between the inner surface side and the outer surface side.   A heat shield surrounding the single crystal being pulled,
  The inner surface facing the single crystal has a cylindrical portion disposed so as to be parallel to a portion of the single crystal whose temperature is around 1150 to 1000 ° C. which is a growth-in defect formation temperature, and a lower portion of the cylindrical portion. And a tapered portion that is reduced in diameter as it approaches the melt surface,
  The outer surface side includes a cylindrical portion depending from the inner edge of the annular rim toward the melt surface,
  A heat shielding plate filled with a heat insulating material was provided in an internal space sandwiched between the tapered portion on the inner surface side and the outer surface side.
  A single crystal manufacturing apparatus characterized by the above.   A heat shield surrounding the single crystal being pulled,
  The inner surface facing the single crystal has a cylindrical portion disposed so as to be parallel to a portion of the single crystal whose temperature is around 1150 to 1000 ° C. which is a growth-in defect formation temperature, and a lower portion of the cylindrical portion. And a tapered portion that is reduced in diameter as it approaches the melt surface,
  The outer surface side hangs from the inner edge of the annular rim toward the melt surface and is connected to a cylindrical portion parallel to the cylindrical portion on the inner surface side, and below the cylindrical portion. An enlarged lower end,
  A heat shielding plate filled with a heat insulating material was provided in an internal space sandwiched between the tapered portion on the inner surface side and the lower end portion on the outer surface side.
  A single crystal manufacturing apparatus characterized by the above. The single crystal manufacturing apparatus according to any one of claims 1 to 3, wherein the upper end position of the heater is set between 200 mm above the melt surface and 50 mm below the melt surface.

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