JP5040846B2 - Silicon single crystal growth method and temperature estimation method - Google Patents

Description

  The present invention relates to a silicon single crystal growth method and a temperature estimation method.

When a silicon single crystal is grown by the Czochralski method, the thermal environment, that is, the temperature conditions of various parts greatly affects the product quality. However, there are sites where temperature measurement is impossible, such as the internal temperature distribution of the silicon melt and the internal temperature distribution of the silicon ingot being pulled up. For this reason, it has been proposed to estimate the temperature of various parts including a part that cannot be measured using a comprehensive heat transfer analysis program and to feed it back to the growth conditions (Patent Document 1).

In addition, as a comprehensive heat transfer analysis program, a comprehensive heat transfer analysis program FEMAG (Reference: Int. J. Heat Mass Transfer, Vol. 33 (1990) 1849) developed by UCL (University of Catholic Louvain), ITCM (Reference: Int. J. Numerical Methods in Engineering, Vol. 30 (1990) 133) developed by MIT (Massachusetts Institute of Technology) is known.

JP 2001-302385 A

However, the conventional temperature measurement method has a problem that the estimated temperature is inaccurate because the simulation is executed by substituting values disclosed in the literature as parameters of various members constituting the pulling device.

The problem to be solved by the present invention is to provide a temperature estimation method capable of accurately detecting the temperature of a site to be estimated and a silicon single crystal growth method capable of growing based on the accurate estimated temperature.

  In the method for growing a silicon single crystal according to the first invention, silicon is stored in a crucible housed in a chamber, the silicon is heated to form a silicon melt, and a seed crystal is immersed in the silicon melt and rotated. The silicon single crystal is pulled up and grown from the seed crystal while pulling up, and the optimum value of the thermal conductivity of the heat insulating material of the rectifier and the optimum value of the emissivity of the inner wall of the chamber are being grown. It was obtained by measuring the actual temperature of the silicon single crystal, and the optimum value was substituted into the overall heat transfer analysis program, and the overall heat transfer analysis program was executed to estimate the temperature of the growing silicon crystal. The cooling condition of the growing silicon single crystal is controlled based on the silicon crystal temperature.

  In the temperature estimation method for a silicon single crystal according to the second invention, silicon is stored in a crucible housed in a chamber, the silicon is heated to form a silicon melt, and the seed crystal is immersed in the silicon melt and rotated. The temperature of the silicon single crystal is estimated in the silicon single crystal growth step in which the silicon single crystal is pulled up and grown from the seed crystal, and the thermal conductivity of the heat insulating material of the rectifier is optimized. Value and the optimum value of the emissivity of the inner wall of the chamber are obtained by measuring the actual temperature of the growing silicon single crystal, and the optimum value is substituted into a comprehensive heat transfer analysis program. It is characterized by estimating the temperature of the silicon crystal during growth.

  According to the above invention, two parameters having a large influence on the estimated temperature of the silicon single crystal among the plurality of parameters of the comprehensive heat transfer analysis program, namely, the thermal conductivity of the heat insulating material of the rectifier and the emissivity of the inner wall of the chamber, respectively. The optimum value is obtained by measuring the actual temperature of the growing silicon single crystal, and this optimum value is substituted into the program, so that the temperature at the site to be estimated can be detected accurately, and accurate estimation is possible. A silicon single crystal can be grown based on the temperature.

  Hereinafter, embodiments of the invention will be described with reference to the drawings.

<Basic method>
FIG. 1 is a longitudinal sectional view showing an example of a pulling apparatus 1 used in the silicon single crystal growth method and the silicon single crystal temperature estimation method according to this embodiment. As shown in the figure, the pulling apparatus 1 of this example is provided with a quartz crucible 12 in a main chamber 11, and this quartz crucible 12 is attached to a rotatable lower shaft 14 via a graphite susceptor 13. ing.

  A cylindrical heater 15 for controlling the temperature of the silicon melt 20 in the quartz crucible 12 is disposed around the quartz crucible 12, and a cylindrical heater is interposed between the heater 15 and the main chamber 11. A heat insulating cylinder 16 is provided.

  The heat insulation cylinder 16 includes a heat insulation cylinder 16a disposed around the quartz crucible 12 (hot zone) and a heat insulation cylinder 16b disposed below the quartz crucible 12 (lower part of the hot zone). The surface of is coated with graphite.

  An annular support member 17 is attached to the upper surface of the heat insulating cylinder 16, and the rectifying body 18 is fixed in the chamber 11 by placing a locking portion 18 a of the rectifying body 18 on the support member 17. The rectifier 18 has a heat insulating material coated with graphite.

  Reference numeral 19 denotes a pull chamber for cooling the growing single crystal, reference numeral 20 denotes a silicon melt, reference numeral 21 denotes a growing silicon single crystal, reference numeral 22 denotes a seed crystal, and reference numeral 23 denotes a pulling shaft. The pulling shaft 23 is provided so as to be rotatable and movable up and down with respect to the main chamber 11 through the pull chamber 19, and after immersing the seed crystal 22 attached to the lower end of the pulling shaft 23 in the silicon melt 20, the seed crystal 22 and the quartz product are made. By rotating and raising the crucible 12 in a predetermined direction, the silicon single crystal 21 is pulled up from the lower end of the seed crystal 22.

  An inert gas such as argon gas circulates in the main chamber 11, and this inert gas is introduced into the pull chamber 19 from the gas supply pipe 24 connected to the side wall of the pull chamber 19 and connected to the lower wall of the main chamber 11. The gas exhaust pipe 25 is discharged out of the main chamber 11. At this time, the rectifier 18 provided on the outer periphery of the silicon single crystal 21 in the main chamber 11 blocks the irradiation of the radiant heat of the heater 15 and rectifies the inert gas described above.

The silicon single crystal 21 may be pulled up while applying a magnetic field to the silicon melt 20.

  When a silicon single crystal is pulled and grown using the pulling apparatus 1 configured as described above, the silicon single crystal is grown using the UCL comprehensive heat transfer analysis program FEMAG or the MIT comprehensive heat transfer analysis program ITCM. Estimate the temperature of the crystal and feed it back to the pulling condition.

  Here, the literature values of the thermal properties of the pulling device 1 conventionally used as tuning parameters of the comprehensive heat transfer analysis program are as shown in Tables 1 and 2.

これらの熱伝導率と輻射率の文献値を総合伝熱解析プログラムに代入し、育成中のシリコン単結晶の中心軸上の温度勾配等の変化率を演算した。

The literature values of these thermal conductivity and emissivity were substituted into the comprehensive heat transfer analysis program, and the rate of change such as temperature gradient on the central axis of the growing silicon single crystal was calculated.

  FIG. 2 maintains the radiation rate of each physical property shown in Table 2 at a constant value in the range from the lower limit value to the upper limit value, and changes one of the thermal conductivities of each physical property shown in Table 1 from the lower limit value to the upper limit value. The temperature gradient (1423K) on the central axis of the growing silicon single crystal when the crystal temperature is around 1100 ° C. when the thermal conductivity of the remaining physical properties is maintained at a constant value in the range from the lower limit value to the upper limit value. It is the result of calculating the change rate of ˜1323K).

  For example, a value of thermal conductivity other than the thermal conductivity of silicon (solid) is substituted with a constant value within the range of the literature values shown in Table 1, and similarly, the value of emissivity is the range of the literature values shown in Table 2. Substitute a constant value. And the program is executed by substituting the value of the thermal conductivity of silicon (solid) from the lower limit value of 18.99 W / mK to the upper limit value of 27.2 W / mK at predetermined intervals, Estimate the temperature on the central axis of the growing silicon single crystal in the vicinity. One point of the obtained estimated value is used as a reference value for calculating the rate of change, and the rate of change of the remaining estimated value is obtained.

  According to the result of FIG. 2 obtained in this way, the value of the thermal conductivity of the heat insulating material of the rectifier 18 is strong against the estimated value of the temperature on the central axis of the growing silicon single crystal in the vicinity of 1100 ° C. In turn, the value of the thermal conductivity of the silicon (solid) 21 affects. Even if the thermal conductivity values of the other silicon (liquid) 20, the quartz crucible 12, the graphite susceptor 13, and the heat insulating cylinders 16a and 16b vary from the lower limit value to the upper limit value, the silicon being grown It can be seen that the estimated value of the temperature on the central axis of the single crystal has no significant effect.

  Similarly, FIG. 3 shows that the thermal conductivity of each physical property shown in Table 1 is maintained at a constant value in the range from the lower limit value to the upper limit value, and one of the emissivity of each physical property shown in Table 2 is changed from the lower limit value. The temperature gradient on the central axis of the growing silicon single crystal when the crystal temperature is around 1100 ° C. when the emissivity of the remaining physical properties is changed to the upper limit value and maintained at a constant value in the range of the lower limit value to the upper limit value It is the result of calculating the change rate of (1423K to 1323K).

  According to the result shown in FIG. 3, the value of the emissivity of the inner wall of the chamber 11 has the most influence on the estimated value of the temperature on the central axis of the growing silicon single crystal at 1100 ° C., and subsequently the silicon (solid) 21 The value of emissivity is affected. The emissivities of the other silicon (liquid) 20, quartz crucible 12, graphite susceptor 13, heat insulation cylinders 16 a and 16 b and rectifier 18 are estimated from the temperature on the central axis of the growing silicon single crystal. It can be seen that the value is not greatly affected.

  FIG. 4 is a result of calculating the influence of the thermal conductivity in the example of FIG. 2 in the vicinity of 900 ° C. and the lower temperature region, that is, the change rate of the temperature gradient of the crystal (1223K to 1123K). Even in the low temperature region where the crystal temperature is 900 ° C., similarly to the vicinity of 1100 ° C., the thermal conductivity value of the heat insulating material of the rectifier 18 strongly affects the estimated value of the temperature on the central axis of the growing silicon single crystal. Subsequently, it can be seen that the value of the thermal conductivity of the silicon (solid) 21 is affected.

  FIG. 5 is a result of calculating the influence of the radiation rate in the vicinity of 900 ° C. and lower temperature in the example of FIG. 3, that is, the change rate of the temperature gradient (1223K to 1123K) of the crystal. Even in the low temperature region where the crystal temperature is 900 ° C., similarly to the vicinity of 1100 ° C., the value of the emissivity of the inner wall of the chamber 11 strongly affects the estimated value of the temperature on the central axis of the growing silicon single crystal. It can be seen that the emissivity value of the silicon (solid) 21 is affected.

  FIG. 6 shows the result of calculating the influence of the thermal conductivity in the vicinity of the solid-liquid interface in the example of FIG. 2, that is, the rate of change of the temperature gradient of the crystal (silicon melting point: 1685K to 1650K), on the central axis of the silicon crystal. It is the result of calculating the influence.

  According to the results of FIG. 6, in the vicinity of the solid-liquid interface and on the crystal central axis, the value of the thermal conductivity of silicon (solid) 21 has the most influence on the estimated value of the temperature on the central axis of the growing silicon single crystal. Subsequently, the value of the thermal conductivity of the heat insulating material of the rectifier 18 is affected. Even if the thermal conductivity values of the other silicon (liquid) 20, the quartz crucible 12, the graphite susceptor 13, and the heat insulating cylinders 16a and 16b vary from the lower limit value to the upper limit value, the silicon being grown It can be seen that the estimated value of the temperature on the central axis of the single crystal has no significant effect.

  FIG. 7 is a result of calculating the influence of the emissivity in the vicinity of the solid-liquid interface in the example of FIG. 3, that is, the change rate of the temperature gradient of the crystal (silicon melting point 1685K to 1650K), and the influence on the central axis of the silicon crystal. Is the result of computing.

  According to the result shown in FIG. 7, the value of the emissivity of the inner wall of the chamber 11 affects the estimated value of the temperature on the central axis of the growing silicon single crystal, but other silicon (solid) 21, silicon (liquid 20) The respective emissivities of the quartz crucible 12, the graphite susceptor 13, the heat insulating cylinders 16a and 16b, and the heat insulating material of the rectifier 18 greatly affect the estimated value of the temperature on the central axis of the growing silicon single crystal. I understand that I don't.

  FIG. 8 shows the influence of the thermal conductivity in the vicinity of the solid-liquid interface in the example of FIG. 6, and is the result of calculating the change rate of the temperature gradient of the crystal (silicon melting point: 1685K to 1650K) at the side of the silicon crystal.

  According to the result of FIG. 8, in the vicinity of the solid-liquid interface and the crystal side, the thermal conductivity value of the heat insulating material of the rectifier 18 has the most influence on the estimated temperature of the side of the growing silicon single crystal. Subsequently, the thermal conductivity values of the heat insulating cylinders 16a and 16b are affected. The thermal conductivity values of other silicon (solid) 21, silicon (liquid) 20, quartz crucible 12, and graphite susceptor 13 vary from the lower limit value to the upper limit value. It can be seen that there is no significant effect on the estimated side temperature.

  FIG. 9 shows the influence of the emissivity in the vicinity of the solid-liquid interface in the example of FIG. 3, and is the result of calculating the change rate of the temperature gradient (silicon melting point 1685K to 1650K) of the side of the silicon crystal.

  According to the results shown in FIG. 9, the value of the emissivity of the inner wall of the chamber 11, the value of the emissivity of silicon (solid) 21 and the value of the emissivity of silicon (liquid) 20 are as follows. The radiation rate of the heat insulating material of the other quartz crucible 12, graphite susceptor 13, thermal insulation cylinders 16a and 16b and rectifier 18 is the side of the growing silicon single crystal. It can be seen that there is no significant effect on the estimated temperature of the part.

  From the above results, the following matters were found.

  As is apparent from the results of FIGS. 2 to 5, in the cooling region where the temperature of the growing silicon single crystal is 1100 ° C. to 900 ° C., the rate of change of the temperature gradient on the central axis of the silicon single crystal is The heat conductivity value of the heat insulating material 18 and the emissivity value of the inner wall of the chamber 11 are strongly influenced, and then the heat conductivity value of the silicon (solid) 21 and the emissivity value of the silicon (solid) 21 are significant. Influences. Conversely, the thermal conductivity and emissivity of other members have little influence on the estimated temperature value even if the general literature values shown in Tables 1 and 2 are substituted.

  Therefore, when the silicon single crystal is pulled and grown, the thermal conductivity value of the heat insulating material of the rectifier 18 and the emissivity of the inner wall of the chamber 11 are used to estimate the crystal temperature during cooling by the comprehensive heat transfer analysis program. It is important to determine the optimum value of, and conversely, general literature values can be used for other parameters.

  Then, the temperature of the growing silicon single crystal is estimated using the optimum value of the thermal conductivity of the heat insulating material of the rectifier 18 and the optimum value of the emissivity of the inner wall of the chamber 11, and silicon based on the estimated value. If the cooling condition of the single crystal is controlled, it can be grown with a target ideal temperature history.

  6 to 9, the temperature of the silicon single crystal in the vicinity of the solid-liquid interface (on the crystal central axis or on the side portion) is the value of the thermal conductivity of the heat insulating material of the rectifier 18 described above. In addition to the emissivity value of the inner wall of the chamber 11, the thermal conductivity value of the silicon (solid) 21, the emissivity value of the silicon (solid) 21, and the emissivity value of the silicon (liquid) 20 are significant. Affects. Conversely, the thermal conductivity and emissivity of other members have little influence on the estimated temperature value even if the general literature values shown in Tables 1 and 2 are substituted.

  Therefore, when the silicon single crystal is pulled up and grown, in estimating the crystal temperature in the vicinity of the solid-liquid interface with the comprehensive heat transfer analysis program, the value of the thermal conductivity of the heat insulating material of the rectifier 18, the inner wall of the chamber 11 It is important to determine the optimum values for the emissivity value, the thermal conductivity value of silicon (solid) 21, the emissivity value of silicon (solid) 21, and the emissivity value of silicon (liquid) 20. On the other hand, for other parameters, general literature values can be used.

  Then, the temperature in the vicinity of the solid-liquid interface of the silicon single crystal being grown is set to the optimum value of the thermal conductivity of the heat insulating material of the rectifier 18, the optimum value of the emissivity of the inner wall of the chamber 11, and the silicon (solid) 21 The optimum value of the thermal conductivity, the optimum value of the emissivity of the silicon (solid) 21 and the optimum value of the emissivity of the silicon (liquid) 20 are estimated, and the silicon single crystal is pulled up based on the estimated value. By controlling the speed condition, it is possible to grow with a target ideal temperature history.

  By the way, the thermal conductivity of the heat insulating material of the rectifier 18, the emissivity of the inner wall of the chamber 11, the thermal conductivity of silicon (solid) 21, the emissivity of silicon (solid) 21, silicon ( The actual value of the emissivity of the liquid 20 is difficult to measure. However, it is possible to obtain these optimum values from the actual temperature of the growing silicon single crystal.

  That is, a specific pulling apparatus was prepared, and a silicon single crystal having a crystal diameter of 200 mm was pulled and grown under three kinds of conditions A, B, and C having different thermal environmental conditions in the hot zone. The initial charge amount of the silicon raw material was 80 kg. Pulling condition A is pulling speed 1.0 mm / min, crystal rotation speed 3 rpm, crucible rotation speed 10 rpm, pulling condition B is pulling speed 0.3 mm / min, crystal rotation speed 8 rpm, crucible rotation speed 6 rpm, pulling condition C is The pulling speed was 0.45 mm / min, the crystal rotation speed was 5 rpm, and the crucible rotation speed was 15 rpm.

  Before starting the pulling of each condition A, B, and C, a temperature sensor (thermocouple) was set so that the actual temperature of the growing silicon single crystal could be measured, and the actual temperature of the silicon single crystal being pulled was measured. . Then, from the actual temperatures of the silicon single crystals under the three conditions A, B, and C, the thermal conductivity of the heat insulating material of the rectifier 18 of the pulling device, the emissivity of the inner wall of the chamber 11, and the heat of the silicon (solid) 21 The optimum values of the conductivity and the emissivities of silicon (solid) 21 and silicon (liquid) 20 were determined. In obtaining the optimum value, known optimization software can be used.

  As an example, the obtained thermal conductivity of the heat insulating material of the rectifier 18, the emissivity of the inner wall of the chamber 11, the thermal conductivity of silicon (solid) 21, and the emissivities of silicon (solid) 21 and silicon (liquid) 20 Each optimum value of was substituted into a comprehensive heat transfer analysis program to estimate the crystal temperature during growth.

  Further, as a comparative example, the thermal conductivity of the heat insulating material of the rectifier 18, the emissivity of the inner wall of the chamber 11, the thermal conductivity of silicon (solid) 21, and the emissivities of silicon (solid) 21 and silicon (liquid) 20 As in the past, appropriate values of literature values described in Table 1 and Table 2 were substituted into the same comprehensive heat transfer analysis program as before, and the crystal temperature during growth was similarly estimated.

  These results are shown in FIG. 10A, FIG. 10B, and FIG. 10C together with the actually measured value of the crystal temperature by the thermocouple. As shown in the figure, all of the present examples match the measured values compared to the comparative example.

  Further, the thermal conductivity of the heat insulating material of the rectifier 18 obtained as described above, the emissivity of the inner wall of the chamber 11, the thermal conductivity of the silicon (solid) 21, the silicon (solid) 21 and the silicon (liquid) ) Substituting the respective optimal values of the emissivity of 20 into the comprehensive heat transfer analysis program, thermal environment conditions D (pulling speed 0.7 mm / min, crystal rotation speed 5 rpm, different from the above conditions A, B, C) The crystal temperature during growth at a crucible rotation speed of 10 rpm was estimated. As a comparative example, the same literature values as in the comparative example were substituted into the comprehensive heat transfer analysis program, and the crystal temperature during growth was similarly estimated. In addition, a silicon single crystal was actually grown under the condition D, and the crystal temperature was measured by a thermocouple set to the crystal being grown at that time. These results are shown in FIG. 10D.

  As shown in the figure, it can be seen that the estimated value of the temperature according to the present example also matches the actually measured value in comparison with the comparative example even in the thermal environmental conditions other than the conditions A, B, and C.

《Application example》
The temperature estimation method and silicon single crystal growth method of the present embodiment described above can be applied to, for example, the following specific silicon single crystal growth method.

  The silicon single crystal described below is a silicon single crystal grown by the Czochralski method (CZ method). The silicon single crystal does not rupture during the growth, and has a particularly large diameter of about 450 mm. This is a method for growing a silicon single crystal having a straight body part capable of producing a silicon wafer having no defect.

  First, the necessity and usefulness of this type of silicon wafer will be explained. As a method for producing a rod-shaped silicon single crystal that is a material of a semiconductor silicon wafer, a method of growing a silicon single crystal by the CZ method is widely adopted. ing.

  Further, in recent years, a silicon single crystal free from glow-in defects such as crystal-origin particles (hereinafter also referred to as COP) and dislocation clusters observed on the surface of a silicon wafer obtained by slicing a silicon single crystal. In order to grow efficiently, a heat shield (rectifier) surrounding the periphery of the growing silicon single crystal is provided above the surface of the silicon melt with a predetermined gap, and the heat shield A pulling device having a water-cooled body that surrounds the periphery of the single crystal is also proposed.

By the way, when a silicon single crystal is pulled and grown, point defects (atomic vacancies, interstitial silicon) are taken into the silicon single crystal at the solid-liquid interface between the silicon single crystal and the silicon melt, and the single crystal Various glow-in defects are formed during the cooling process. The size and density of defects generated in the silicon single crystal are determined by the time that the silicon single crystal stays while being pulled from the silicon melt. In the same silicon single crystal pulling device, when the pulling speed V of the silicon single crystal is decreased, the concentration of point defects is changed, and from the region where the vacancies are excessive, the vacancy and the lattice It is known that the silicon concentration changes to a balanced region, and further, the interstitial silicon changes to an excessive region (see, for example, paragraph 0062 and FIG. 4 of Japanese Patent Laid-Open No. 2000-327486).

  On the other hand, interstitial oxygen (Oi) present in the silicon single crystal forms oxygen precipitates through oxygen precipitation nuclei by heat treatment, and these oxygen precipitates capture metal impurities that may be contaminated in the semiconductor device manufacturing process. Become a gettering site. When metal impurities are present in the operating region of a semiconductor device, the electrical characteristics of the semiconductor device are deteriorated. Therefore, the gettering site for capturing the metal impurities is useful. In recent years, an increase in the diameter of a silicon single crystal has been promoted, a silicon single crystal for a silicon wafer having a diameter of 300 mm has already been manufactured, and a silicon single crystal for a silicon wafer having a diameter of 450 mm is being manufactured (for example, “ Current Status of Wafer Technology Required by LSI ”Latest Silicon Device and Crystal Technology, Publisher: Realize Science Center / Realize AT Corporation, Author: Super Silicon Laboratory Nobuyuki Hayashi, Issue Date: December 29, 2005, Chapter 3“ Crystal technology ”, 1.5“ Crystal technology subject assuming 450 mm diameter ”(pages 243 and 244)).

  As described above, if the diameter of the straight body to be pulled up is increased, as in the case of a silicon single crystal for a silicon wafer having a diameter of 450 mm, not only the silicon single crystal but also the silicon single crystal pulling device is enlarged and the heat capacity is increased. Thus, the temperature gradient (G) in the silicon single crystal is reduced, and the silicon single crystal is gradually cooled. Then, the time for staying in the temperature region where the glow-in defect occurs while the silicon single crystal is pulled up becomes longer, and the size of the defect [COP, OSF (Oxidation Induced Stacking Fault) nucleus, oxygen precipitate, etc.) is coarse. Happens. When these defects become coarse, large indentations due to COP have an adverse effect on polished wafers, and even if silicon wafers or heat-treated wafers are used to grow epitaxial layers, the COP indentations and defects present on the surface of OSF nuclei disappear. This makes it difficult to form dents and stacking faults on the wafer surface.

  In order to prevent this, it is conceivable to increase the pulling rate of the silicon single crystal. However, there is a problem that the latent heat of solidification of silicon increases as the pulling rate increases. As described above, since the temperature gradient (G) in the silicon single crystal is small, the dissipation of the generated latent heat does not progress, and the solid state of the silicon single crystal and the silicon melt is secured in order to ensure the balance of the heat balance. The liquid interface becomes a shape that is largely convex upward. As a result, a large thermal stress is generated in the silicon single crystal being pulled, which exceeds the limit strength at the temperature during the pulling of the silicon single crystal, and the silicon single crystal being pulled may be broken.

  Therefore, in order to prevent slow cooling of the silicon single crystal, it is conceivable to change the thermal environment of the silicon single crystal being pulled up to a configuration that rapidly cools. For this purpose, it is necessary to reduce the height of the crucible for storing the silicon raw material.

  When verifying the temperature distribution of the silicon single crystal when the height of the crucible was changed, the temperature distribution during the pulling of the silicon single crystal for a 450 mm diameter silicon wafer was reduced by reducing the height of the crucible. Although the temperature distribution during the pulling of the silicon single crystal can be made substantially equal, in this case, the amount of silicon melt that can be stored in the crucible is limited.

  On the other hand, as the diameter of the straight body portion of the silicon single crystal to be pulled up increases, the dimensions and weights of the shoulder portion and tail portion also increase. Therefore, the yield when pulling up the silicon single crystal from the same amount of silicon melt obtained using the crucible of the same shape decreases as the diameter of the straight body portion increases.

  For example, when obtaining 0.6 as the yield (arbitrary unit) of the single crystal, the initial raw material amount of the silicon single crystal for the 450 mm diameter silicon wafer with respect to the initial raw material amount of the silicon single crystal for the 300 mm diameter silicon wafer. Is more than three times that. Also, when pulling up a silicon single crystal for a 450 mm diameter silicon wafer, the ratio of the crucible height to the crucible diameter required to obtain a temperature distribution substantially equivalent to that of a silicon single crystal for a 300 mm diameter silicon wafer is 0. In order to satisfy the condition of 5 or less, the diameter of the crucible becomes extremely large, which is not realistic.

  In addition, a silicon single crystal for a silicon wafer having a diameter of 450 mm has a diameter larger than that of a silicon single crystal for a silicon wafer having a diameter of 300 mm, and a temperature difference in the radial direction becomes large. It becomes large and crystal cracks and dislocations are likely to occur. For this reason, it is difficult to cool the silicon single crystal excessively, so that the temperature gradient in the axial direction of the silicon single crystal is reduced, and the time for passing through each temperature region of the single crystal is increased, so that it is generated in the single crystal. There is a problem in that the size of crystal defects increases.

  Therefore, when a silicon single crystal is pulled in a normal vacancy dominant region where the pulling rate is high, COP is generated first, but its COP (Void) size becomes too large, and a hole due to COP on the wafer surface is formed. It becomes larger and causes problems when manufacturing semiconductor devices. On the other hand, when dislocation clusters are generated at a lower pulling rate, the semiconductor device is adversely affected.

  Therefore, in this embodiment, a silicon melt is stored in a crucible housed in a chamber, and a seed crystal is immersed in the silicon melt and pulled up while being rotated, so that a dislocation-free silicon single crystal is obtained from the seed crystal. Raise and train.

  The feature is that the silicon single crystal is a silicon single crystal for a 450 mm diameter silicon wafer, and Gc is an axial temperature gradient from the melting point to 1350 ° C. at the center of the growing silicon single crystal, and the outer periphery of the growing silicon single crystal When the axial temperature gradient from the melting point to 1350 ° C. is Ge, the outer peripheral portion of the growing silicon single crystal is cooled so that the ratio Gc / Ge is 1.2 to 1.3. The gap between the lower end of the heat shield (rectifier) surrounding the outer peripheral surface of the silicon single crystal and the surface of the silicon melt is set to 40 to 100 mm, and the interstitial silicon type point defects in the silicon single crystal are set. The region where the agglomerates are present is [I], the region where the agglomerates of vacancy-type point defects are present [V], and there are agglomerates of interstitial silicon-type point defects and agglomerates of vacancy-type point defects. Do not perfect When the first region is [P], the ratio V / Gc is controlled to be constant so that the silicon single crystal consists of the perfect region [P], thereby preventing COP and dislocation clusters from being generated in the silicon single crystal. By controlling the pulling rate of the silicon single crystal, the thermal stress at the center of the silicon single crystal on the solid-liquid interface between the silicon single crystal and the silicon melt is 50 MPa or less.

  According to this method, it is possible to obtain a high-quality silicon single crystal for a 450 mm diameter silicon wafer having no dislocation and no glow-in defect, without the silicon single crystal being ruptured during growth. Further, by adjusting V / Gc, which is the ratio of the pulling speed V and the axial temperature gradient Gc, a region where infrared scattering defects (COP) and OSF rings are generated due to excessive vacancies, and dislocation clusters due to excessive interstitial silicon When a silicon single crystal for a silicon wafer having a diameter of 450 mm is pulled under conditions for growing a defect-free region located in the middle of the region that generates GaN, an epitaxial layer is grown on the surface of the silicon wafer made from this silicon single crystal. Since the introduction of defects into the epitaxial layer can be suppressed, an epitaxial wafer with a low defect density can be obtained.

  An alternative feature is that the silicon single crystal is a silicon single crystal for a 450 mm diameter silicon wafer, and Gc is the temperature gradient in the axial direction from the melting point to 1350 ° C. at the center of the growing silicon single crystal. When the axial temperature gradient from the melting point to 1350 ° C. in the outer periphery of the single crystal is Ge, the outer periphery of the growing silicon single crystal is cooled so that the ratio Gc / Ge is 1.2 to 1.3. The gap between the lower end of the heat shield (rectifier) surrounding the outer peripheral surface of the growing silicon single crystal and the surface of the silicon melt is set to 40 to 100 mm, and the interstitial silicon type in the silicon single crystal The region where the point defect agglomerates exist is [I], and the region where the vacancy point defect agglomerates exist is [V]. There are no aggregates If the perfect region is [P], the ratio V / Gc is controlled to be constant so that the silicon single crystal is composed of the perfect region [P], so that COP and dislocation clusters are not generated in the silicon single crystal. By controlling the pulling rate of the silicon single crystal, the thermal stress at the temperature of 1000 ° C. in the outer periphery of the growing silicon single crystal is 37 MPa or less.

  According to this method, a silicon single crystal for a relatively high quality 450 mm diameter silicon wafer having no glow-in defect without causing cracks in the silicon single crystal even if it is a dislocation silicon single crystal during the growth. Can be obtained. Similarly to the above method, V / Gc, which is the ratio between the pulling speed V and the axial temperature gradient Gc, is adjusted to generate an infrared scattering defect (COP) or OSF ring due to excess vacancies, A silicon single crystal for a silicon wafer having a diameter of 450 mm is pulled under the condition of growing a defect-free region located in the middle of the region where dislocation clusters are generated due to excess silicon, and an epitaxial layer is formed on the surface of the silicon wafer produced from this silicon single crystal. Since the introduction of defects into the epitaxial layer can be suppressed, an epitaxial wafer with a low defect density can be obtained.

  A silicon single crystal having such a defect-free region can be manufactured by a pulling apparatus shown in FIG.

  However, although detailed conditions are omitted in the above embodiment, it is preferable to apply a transverse magnetic field to the silicon melt 20 under the following conditions. The transverse magnetic field is arranged so that the first and second coils having the same coil diameter are opposed to each other around the crucible 12 on the outer side at a predetermined interval in the horizontal direction from the outer peripheral surface of the crucible 12. These currents are generated by flowing currents in the same direction through these coils. The magnetic field strength of this transverse magnetic field is measured at the intersection of the surface of the silicon melt 20 and the central axis of the crucible 12, and the magnetic field strength is 0.25 to 0.45 Tesla, preferably 0.30 to 0.40. The current flowing through the first and second coils is controlled so as to be Tesla. The reason why the magnetic field intensity is limited to the range of 0.25 to 0.40 Tesla is that if it is less than 0.25 Tesla, the effect of suppressing the melt flow is weakened and the controllability of the diameter of the single crystal may be disturbed. It becomes difficult to control the crystal quality such as the concentration within a certain range, and if it exceeds 0.45 Tesla, the magnetic field strength is strong, so the leakage magnetic field becomes large, which has a negative effect on the single crystal pulling device and the environment, or the magnetic field applying device This is because the cost of the equipment becomes high.

  Next, a method for growing the silicon single crystal of this example will be described.

  The diameter of the silicon single crystal 21 grown by the above apparatus is set to 458 mm, for example.

  The gap G between the silicon single crystal 21 and the surface of the silicon melt 20 is set to 40 to 100 mm, preferably 60 to 90 mm. Here, the gap G is limited to the range of 40 to 100 mm because, if it is less than 40 mm, the value of Gc described later increases and the pulling speed can be increased, but the ratio Gc / Ge described later is higher than the predetermined range. This is because a region where the defect-free region is reduced and the entire surface of the wafer is not obtained is obtained, and dislocation clusters are generated from the outer periphery before the OSF ring contracts and disappears. On the other hand, when G exceeds 100 mm, the value of Gc decreases and the pulling speed decreases, and the ratio Gc / Ge is larger than a predetermined range, and a region where the defect-free region spreads over the entire wafer surface cannot be obtained. This is because dislocation clusters are generated from the center before the ring contracts and disappears.

  Further, an axial temperature gradient from the melting point to 1350 ° C. at the center of the growing silicon single crystal 21 is Gc, and an axial temperature gradient from the melting point to 1350 ° C. at the outer periphery of the growing silicon single crystal 21 is Ge. At this time, the outer peripheral portion of the growing silicon single crystal 21 is cooled so that the ratio Gc / Ge is 1.2 to 1.3, preferably 1.21 to 1.29. Here, the ratio Gc / Ge is limited to the range of 1.2 to 1.3. When the ratio Gc / Ge is less than 1.2, the area where the defect-free area spreads over the entire wafer surface is the same as when the gap G is small. Before the OSF ring contracts and disappears, dislocation clusters are generated from the outer periphery, and when 1.3 is exceeded, the defect-free region spreads over the entire wafer surface as in the case where the gap G is larger. This is because a region is not obtained, and dislocation clusters are generated from the center before the OSF ring contracts and disappears.

  Also, the region where the interstitial silicon type point defect aggregates exist in the silicon single crystal 21 is [I], the region where the hole type point defect aggregates exist is [V], and the lattice silicon type point The ratio V / Gc is controlled to be constant so that the silicon single crystal 21 is composed of the perfect region [P], where [P] is a perfect region where no defect aggregates and no vacancy-type point defect aggregates exist. Thus, COP and dislocation clusters are prevented from being generated in the silicon single crystal 21.

  Furthermore, by controlling the pulling rate V of the silicon single crystal 21, the thermal stress at the center of the silicon single crystal 21 on the solid-liquid interface between the silicon single crystal 21 and the silicon melt 20 is preferably 50 MPa or less, preferably 48 MPa or less. Here, the thermal stress at the central portion of the silicon single crystal 21 on the solid-liquid interface is limited to 50 MPa or less. When the thermal stress exceeds 50 MPa, the dislocation-free silicon single crystal 21 for a silicon wafer having a diameter of 450 mm is thermally stressed. This is because there is a risk of bursting during pulling. For this reason, the pulling speed of the dislocation-free silicon single crystal 21 for a silicon wafer having a diameter of 450 mm is set to 0.77 mm / min or less, preferably 0.75 mm / min or less.

  In the case of a silicon single crystal for a 450 mm diameter silicon wafer in which the silicon single crystal is dislocated during pulling, the thermal stress at the temperature of 1000 ° C. is 37 MPa on the outer periphery of the growing silicon single crystal 21. Hereinafter, it is preferably 36 MPa or less. Here, the reason why the thermal stress at the outer peripheral portion of the growing silicon single crystal 21 at a temperature of 1000 ° C. is limited to 37 MPa or less is that the silicon crystal for a 450 mm diameter silicon wafer having a dislocation when exceeding 37 MPa is used. This is because cracks may occur. For this reason, the pulling rate of the silicon single crystal 21 for the 450 mm diameter silicon wafer having a dislocation is 0.75 mm / min or less, preferably 0.74 mm / min or less when the crucible 12 having an outer diameter of 36 inches is used. When the crucible 12 having an outer diameter of 40 inches is used, it is set to 0.52 mm / min or less, preferably 0.51 mm / min or less.

  Note that whether or not the silicon single crystal has undergone dislocation can be determined by whether or not the crystal habit line has disappeared. That is, although the crystal habit line appears every 90 degrees in the pulling direction on the outer peripheral surface of the (100) plane silicon single crystal that is dislocation-free during pulling, when the silicon single crystal becomes dislocation, Since this disappears, it can be determined that the part where the crystal habit line of the silicon single crystal disappeared is dislocation.

  In the method for growing the silicon single crystal 21 configured as described above, the silicon single crystal 21 for a high-quality 450 mm diameter silicon wafer having no dislocation and no grow-in defect is generated without the silicon single crystal 21 being ruptured during the growth. Can be obtained. Further, by adjusting V / Gc, which is the ratio between the pulling rate V of the silicon single crystal 21 and the axial temperature gradient Gc from the melting point to 1350 ° C. at the center of the silicon single crystal 21, infrared scattering defects ( COP) or OSF ring region (region [V] where agglomerates of vacancy-type point defects exist in the silicon single crystal 21) and a region where dislocation clusters are generated due to excessive interstitial silicon (silicon single crystal) The silicon single crystal 21 for a silicon wafer having a diameter of 450 mm is pulled under the condition of growing a defect-free region [P] located in the middle of the region [I]) in which an aggregate of interstitial silicon type point defects exists in the region 21. increase. In addition, when an epitaxial layer is grown on the surface of a silicon wafer produced from the silicon single crystal 21, introduction of defects into the epitaxial layer can be suppressed, so that an epitaxial wafer with a low defect density can be obtained.

It is sectional drawing which shows the pulling apparatus which concerns on embodiment of invention. It is a graph which shows the temperature estimation result by a comprehensive heat-transfer analysis program. It is a graph which shows the temperature estimation result by a comprehensive heat-transfer analysis program. It is a graph which shows the temperature estimation result by a comprehensive heat-transfer analysis program. It is a graph which shows the temperature estimation result by a comprehensive heat-transfer analysis program. It is a graph which shows the temperature estimation result by a comprehensive heat-transfer analysis program. It is a graph which shows the temperature estimation result by a comprehensive heat-transfer analysis program. It is a graph which shows the temperature estimation result by a comprehensive heat-transfer analysis program. It is a graph which shows the temperature estimation result by a comprehensive heat-transfer analysis program. It is a graph which shows the verification result of the temperature estimation method which concerns on embodiment. It is a graph which shows the verification result of the temperature estimation method which concerns on embodiment. It is a graph which shows the verification result of the temperature estimation method which concerns on embodiment. It is a graph which shows the verification result of the temperature estimation method which concerns on embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pull-up apparatus 11 ... Main chamber 12 ... Crucible 13 ... Susceptor 15 ... Heater 16 ... Insulation cylinder 18 ... Rectifier (heat shield)
19 ... Pull chamber 20 ... Silicon melt 21 ... Silicon crystal 22 ... Seed crystal G ... Gap

Claims (15)

Silicon is stored in a crucible housed in a chamber, and the silicon is heated to form a silicon melt. The silicon single crystal is pulled up from the seed crystal by pulling up the seed crystal by immersing and rotating it in the silicon melt. A method of nurturing
Measure the actual temperature of the growing silicon single crystal using the optimum value of the thermal conductivity of the heat insulating material of the rectifier disposed around the growing silicon single crystal and the optimum value of the emissivity of the inner wall of the chamber To find
Substituting the optimum value into the comprehensive heat transfer analysis program,
Run the comprehensive heat transfer analysis program to estimate the silicon crystal temperature during growth,
A method for growing a silicon single crystal, comprising controlling a cooling condition of the silicon single crystal being grown based on an estimated silicon crystal temperature. The method for growing a silicon single crystal according to claim 1,
The thermal conductivity of the heat insulating material of the rectifier has a temperature-dependent characteristic,
A method for growing a silicon single crystal, wherein an optimum value of thermal conductivity based on the temperature-dependent characteristic is substituted into the comprehensive heat transfer analysis program. The method for growing a silicon single crystal according to claim 2,
The method for growing a silicon single crystal, wherein the thermal conductivity of the heat insulating material of the rectifier has a temperature-dependent characteristic of 1.2 to 0.1 (W / mK) in a temperature range of 1500 ° C. to 600 ° C. . The method for growing a silicon single crystal according to claim 1,
The optimum value of the thermal conductivity of the heat insulating material of the heat insulating cylinder provided in the chamber is determined by measuring the actual temperature of the growing silicon single crystal,
Substituting the optimum value into the comprehensive heat transfer analysis program,
A method for growing a silicon single crystal, comprising: executing the comprehensive heat transfer analysis program to estimate a heating capability of the silicon. The method for growing a silicon single crystal according to claim 1,
The optimum value of the thermal conductivity of silicon and the optimum value of the emissivity of silicon are determined by measuring the actual temperature of the growing silicon single crystal,
Substituting the optimum value into the comprehensive heat transfer analysis program,
Run the comprehensive heat transfer analysis program to estimate the temperature distribution of the silicon in the solid-liquid interface region,
A method for growing a silicon single crystal, wherein the pulling rate of the silicon single crystal being grown is controlled based on the estimated temperature distribution. The method for growing a silicon single crystal according to claim 5,
The total heat transfer analysis is performed using the axial temperature gradient Gc from the melting point to 1350 ° C. at the center of the growing silicon single crystal and the axial temperature gradient Ge from the melting point to 1350 ° C. at the outer periphery of the growing silicon single crystal. Estimated by the program,
Growing a silicon single crystal characterized by cooling the outer periphery of the silicon single crystal being grown so that the estimated temperature gradient Gc / Ge ratio Gc / Ge is 1.2 to 1.3 Method. The method for growing a silicon single crystal according to claim 6,
The thermal stress at the center of the silicon single crystal on the solid-liquid interface between the silicon single crystal and the silicon melt is estimated by the comprehensive heat transfer analysis program,
A method for growing a silicon single crystal, wherein the pulling rate of the silicon single crystal is controlled so that the estimated thermal stress is 50 MPa or less. The method for growing a silicon single crystal according to claim 6,
Estimating the thermal stress at a temperature of 1000 ° C. at the outer peripheral portion of the silicon single crystal being grown by the comprehensive heat transfer analysis program,
A method for growing a silicon single crystal, wherein the pulling rate of the silicon single crystal is controlled so that the estimated thermal stress is 37 MPa or less. Silicon is stored in a crucible housed in a chamber, and the silicon is heated to form a silicon melt. The silicon single crystal is pulled up from the seed crystal by pulling up the seed crystal by immersing and rotating it in the silicon melt. A method for estimating the temperature of the silicon single crystal in the step of growing the silicon single crystal,
Measure the actual temperature of the growing silicon single crystal using the optimum value of the thermal conductivity of the heat insulating material of the rectifier disposed around the growing silicon single crystal and the optimum value of the emissivity of the inner wall of the chamber To find
Substituting the optimum value into the comprehensive heat transfer analysis program,
A method for estimating a temperature of a silicon single crystal, wherein the comprehensive heat transfer analysis program is executed to estimate a silicon crystal temperature during growth. The temperature estimation method for a silicon single crystal according to claim 9,
The thermal conductivity of the heat insulating material of the rectifier has a temperature-dependent characteristic,
A method for estimating a temperature of a silicon single crystal, wherein an optimum value of thermal conductivity based on the temperature-dependent characteristic is substituted into the comprehensive heat transfer analysis program. In the temperature estimation method of the silicon single crystal according to claim 10,
The method for estimating a temperature of a silicon single crystal, wherein the thermal conductivity of the heat insulating material of the rectifier has a temperature-dependent characteristic of 1.2 to 0.4 in a temperature range of 1500 to 600 ° C. The temperature estimation method for a silicon single crystal according to claim 9,
The optimum value of the thermal conductivity of silicon and the optimum value of the emissivity of silicon are determined by measuring the actual temperature of the growing silicon single crystal,
Substituting the optimum value into the comprehensive heat transfer analysis program,
A temperature estimation method for a silicon single crystal, wherein the silicon heat distribution analysis program is executed to estimate a temperature distribution of the silicon in a solid-liquid interface region. In the temperature estimation method of the silicon single crystal according to claim 12,
A method for estimating a temperature of a silicon single crystal, comprising: estimating an axial temperature gradient Gc at a center portion of the growing silicon single crystal and an axial temperature gradient Ge at an outer peripheral portion of the growing silicon single crystal. The temperature estimation method for a silicon single crystal according to claim 13,
A method for estimating a temperature of a silicon single crystal, comprising: estimating a thermal stress at a central portion of the silicon single crystal on a solid-liquid interface between the silicon single crystal and the silicon melt. The temperature estimation method for a silicon single crystal according to claim 13,
A method for estimating a temperature of a silicon single crystal, wherein thermal stress is estimated at a predetermined temperature position on the outer periphery of the growing silicon single crystal.

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