JP2009292684A - Silicon single crystal production method and production apparatus therefore - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method and a production apparatus which, even when applied to case where a large-diameter silicon single crystal is pulled up, are capable of stably pulling up a single crystal and capable of ensuring good crystal quality. <P>SOLUTION: Provided is a method for producing a silicon single crystal by using a CZ method comprising melting a crystal raw material by means of a heater 4 and surrounding a single crystal 11 pulled-up under heating from a melt 2 held in a quartz crucible 3 with a heat-shielding body 10 while solidifying the single crystal 11, wherein the following formulas (1) to (3): 1.1×D≤Fd≤1.9×D (1), 1.9×D≤Cd≤3.5×D (2), and 2.3×D≤Hd≤4.2×D (3) are satisfied, (wherein D (mm) is the diameter of the single crystal 11, Fd (mm) is the diameter of the lower end opening of the heat-shielding body 10, Cd (mm) is the inside diameter of the quartz crucible 3, and Hd (mm) is the inside diameter of the heater 4). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a silicon single crystal manufacturing method and a silicon single crystal manufacturing apparatus used in the Czochralski method (hereinafter referred to as “CZ method”), and more specifically, regardless of the diameter of the single crystal to be pulled up. The present invention relates to a silicon single crystal manufacturing method and a manufacturing apparatus used therefor, which are capable of stably pulling a single crystal even when pulling up a silicon single crystal having a diameter and ensuring good crystal quality.

  Currently, a silicon single crystal is used as a main substrate material in semiconductor device manufacturing, and the CZ method is widely adopted as this manufacturing method. When a silicon single crystal is grown by the CZ method, a polycrystalline silicon raw material is put into a quartz crucible and melted therein by the heating action of a heater. After the silicon raw material is completely melted, the seed crystal is immersed in a silicon melt using this as a crystal raw material to pull up the silicon single crystal.

  The pulling speed and quality of a silicon single crystal pulled by the CZ method depend on the crystal temperature during growth. In particular, since the temperature gradient in the growth axis direction of the single crystal affects the generation of grown-in defects in the single crystal, it is desirable that the temperature gradient be uniform over the entire area of the single crystal. On the other hand, the temperature gradient in the growth axis direction is greatly influenced by the radiant heat received from the melt by the single crystal. Therefore, in order to control this, the CZ method manufacturing apparatus usually surrounds the growing single crystal. Thus, a heat shield is arranged.

  For example, in Patent Document 1, cooling is made of a helical cooling water pipe to a cylindrical metal shielding member whose diameter is gradually reduced as it is opened downward and downward, and forcibly cooling the silicon single crystal. By doing so, a single crystal growth apparatus capable of increasing the pulling rate of the silicon single crystal is shown.

  Further, in Patent Document 2, a donut-shaped water cooling chamber is provided between an intermediate chamber and a heating chamber, and a first screen having good thermal conductivity and thermal radiation rate is provided around the single crystal in the water cooling chamber. An apparatus for producing a silicon single crystal that can increase the cooling rate of the single crystal by arranging in the above is shown.

  Therefore, in the apparatus proposed in Patent Documents 1 and 2, the temperature gradient of the growing single crystal can be ensured uniformly over the entire region, and the single crystal pulling rate is increased without reducing the yield of the single crystal. be able to.

  Further, as impurities of the silicon single crystal to be pulled up, the crystal contains dopants such as boron and phosphorus, and oxygen that is eluted and mixed into the melt from the quartz crucible wall during pulling. Impurities contained in these crystals have a great influence on the quality of a wafer cut out from a silicon single crystal and must be appropriately controlled. In particular, in order to make the in-plane impurity distribution of the wafer uniform, it is necessary to make the impurity concentration distribution in the radial direction in the silicon single crystal uniform.

  Usually, the melt contained in the quartz crucible is heated by the heater from the outer periphery of the crucible, so that natural convection that rises in the vicinity of the side wall of the crucible and descends in the center thereof is generated. Therefore, in order to make the impurity concentration distribution uniform, it is necessary to effectively control these convections.

In order to control the convection of the silicon melt, a pair of exciting coils are arranged coaxially with the quartz crucible, and a transverse static magnetic field generated from the pair of exciting coils is applied to the melt in the quartz crucible. (See, for example, Patent Document 3). By applying a transverse magnetic field, the convection of the silicon melt is controlled, the impurity concentration distribution is made uniform, and the shape of the solid-liquid interface between the silicon single crystal and the silicon melt is controlled to stabilize the pulling. be able to.
JP-A 63-256593 Japanese Patent Laid-Open No. 08-08294 JP 2006-69841 A

Latest silicon device and crystal technology, published by Realize Science and Technology Center, pp. 238-256 “7. Next-generation large-diameter wafer crystal growth, processing, and epitaxial”, December 2005

  In response to the recent high integration, low cost, and improved productivity of semiconductor devices, wafers are also required to have a large diameter, with a diameter of 300 mm or more, for example, a large diameter that can accommodate 400 mm to 450 mm wafers. There is an urgent need for the development of silicon single crystal manufacturing technology. As technologies necessary for producing a large-diameter silicon single crystal, increasing the capacity of the quartz crucible and increasing the filling amount of the silicon raw material are major issues.

  In connection with the technology for producing large-diameter silicon single crystals, it is essential to produce large crucibles in order to increase the capacity of quartz crucibles. The ratio of the diameter of the crystal to be grown and the diameter of the quartz crucible is about 1: 3 based on empirical rules. However, considering the economy, Non-Patent Document 1 shows the transition of the relationship between the diameter of the single crystal and the quartz crucible so far. And the expected size that will be adopted in the future.

  According to this, 32 inches (813 mm) for a 300 mm diameter single crystal, 36 inches (914 mm) to 40 (1016 mm) for a 400 mm diameter single crystal, and 46 for a 450 mm diameter single crystal. It is anticipated that quartz crucibles of inches (1168 mm) to 50 (1270 mm) will be used.

  However, when manufacturing a large-diameter silicon single crystal, if a large-sized quartz crucible is introduced, each member such as a heat shield, a heater, and an exciting coil constituting the manufacturing apparatus becomes large and weight increases. become.

  Further, when the diameter of the pulled single crystal is as large as 300 mm or more, the thermal stress generated at the solid-liquid interface of the single crystal increases, and the disturbance factors affecting the crystal growth also increase. For this reason, it is difficult to secure a temperature gradient during the growth, and it is predicted that dislocation of the single crystal is likely to occur, and it is impossible to pull the single crystal stably.

  The present invention has been made in view of such problems, and it is possible to pull a single crystal stably even when pulling a large-diameter silicon single crystal regardless of the diameter of the single crystal to be pulled. Another object of the present invention is to provide a method for producing a silicon single crystal capable of ensuring good crystal quality and a production apparatus used therefor.

  The dimensions of the heater, the excitation coil, etc. constituting the single crystal manufacturing apparatus are designed according to the quartz crucible. For this reason, when each member constituting the manufacturing apparatus is designed from the ratio of the diameter of the crystal to be grown based on the conventional rule of thumb and the diameter of the quartz crucible as the diameter of the single crystal to be pulled is increased, the quality variation in the crystal plane is determined. Becomes larger, the pulling becomes unstable, and the pulling efficiency is remarkably lowered.

  In addition, if the inside of the manufacturing apparatus is contaminated with contaminants such as heavy metal powder and carbon powder generated from the surfaces of the members constituting the apparatus, the surface of the grown silicon single crystal is also contaminated with this contaminant. . A wafer obtained from a contaminated silicon single crystal has quality problems such as a reduction in recombination lifetime (hereinafter referred to as “lifetime”). The influence of contaminants on the silicon single crystal is partly due to the heat shield.

  The present inventor has made various studies so that a stable single crystal can be pulled up regardless of the diameter of the single crystal to be pulled up, and good crystal quality can be secured. It has been found that it is effective to set the size range of each member such as the diameter of the heat shield, the inner diameter of the quartz crucible, and the inner diameter of the heater with respect to the diameter dimension.

The present invention has been made on the basis of such knowledge, and the gist of the following methods (1) to (3) is a silicon single crystal manufacturing method and a manufacturing apparatus used therefor.
(1) Using the CZ method, the crystal raw material is melted with a heater and then heated, and the single crystal pulled from the melt contained in the quartz crucible is surrounded by a heat shield, and the single crystal is solidified while being solidified. A method of manufacturing a single crystal, wherein the diameter of the single crystal is D (mm), the lower end opening diameter of the heat shield is Fd (mm), the inner diameter of the quartz crucible is Cd (mm), and the heater When the inner diameter of Hd is Hd (mm), the following formulas (1) to (3) are satisfied.

1.1 × D ≦ Fd ≦ 1.9 × D (1)
1.9 × D ≦ Cd ≦ 3.5 × D (2)
2.3 × D ≦ Hd ≦ 4.2 × D (3)

(2) Applied to the CZ method, a heater that forms a melt from a crystal raw material and maintains it at a high temperature, a quartz crucible that contains the formed melt, and a single crystal that is pulled from the melt contained in the quartz crucible. An apparatus for manufacturing a silicon single crystal having a surrounding heat shield, wherein the lower end opening diameter Fd (mm) of the heat shield and the quartz crucible with respect to the diameter D (mm) of the single crystal to be pulled up The silicon single crystal manufacturing apparatus is characterized in that the inner diameter Cd (mm) of the heater and the inner diameter Hd (mm) of the heater are respectively configured by the relationships of the above formulas (1) to (3).

(3) In (1) and (2) above, when a magnetic field is applied in the horizontal direction to the melt contained in the quartz crucible, the bore diameter of the excitation coil arranged coaxially is set to Md. And satisfying the following expression (4). Moreover, it is optimal to apply when the diameter of the silicon single crystal to be pulled is a large diameter of 300 mm or more.
4.4 × D ≦ Md ≦ 7.0 × D (4)

  According to the method and apparatus for producing a silicon single crystal of the present invention, it is possible to ensure the thermal efficiency and the pulling speed even when pulling a large-diameter silicon single crystal regardless of the diameter of the single crystal to be pulled. The crystal can be pulled, and at the same time, the crystal quality with good lifetime and in-plane variation can be ensured.

The contents of the present invention will be described based on an embodiment applied to a silicon single crystal manufacturing apparatus.
FIG. 1 is a front sectional view showing an apparatus for producing a silicon single crystal according to the present invention. The silicon single crystal manufacturing apparatus includes a chamber 1, a quartz crucible 3 that is provided in the chamber 1 and contains a melt 2 that is a raw material of the silicon single crystal, a heater 4 that heats the melt 2, and a heat insulating material. 5 and a crucible driving means 6 are provided. Further, an exciting coil 7 can be provided outside the chamber 1 as a magnetic field applying means, and a horizontal magnetic field can be applied to the chamber 1.

  The quartz crucible 3 is composed of a substantially cylindrical barrel portion whose upper portion is open and a bottom portion that blocks the lower portion of the barrel portion, and an outer surface thereof is supported by a graphite susceptor (crucible support) 8. The lower surface of the quartz crucible 3 is fixed to the upper end of the support shaft 9 via a graphite susceptor 8, and the lower portion of the support shaft 9 is connected to the crucible driving means 6.

  A heater 4 is provided around the outside of the quartz crucible 3 via a graphite susceptor 8. The heater 4 is formed in a coaxial and cylindrical shape so as to surround the quartz crucible 3, for example, and heats the quartz crucible 3. A cylindrical heat insulating material 5 surrounding the heater 4 is provided between the heater 4 and the chamber 1.

  Above the quartz crucible 3, an inverted frustoconical heat shield 10 is disposed coaxially, and the lower end of the heat shield 10 is disposed near the upper surface of the melt 2 surface. When the silicon single crystal 11 is pulled up using the manufacturing apparatus shown in FIG. 1, the radiant heat radiated from the quartz crucible 3 heated by the heater 4 is blocked by the heat shield 10, and is predetermined in the growth axis direction of the single crystal 11. The temperature gradient is formed.

  The exciting coil 7 is composed of a horizontal magnetic field magnet in which a magnet coil is three-dimensionally incorporated in a ring-shaped case so as to surround the chamber 1 that forms the outline of the manufacturing apparatus. Such an excitation coil 7 can apply a transverse magnetic field to the melt 2 accommodated in the quartz crucible 3 via the heater 4, the heat insulating material 5, and the chamber 1.

  The crucible driving means 6 includes a rotation motor (not shown) for rotating the quartz crucible 3 and an elevating motor (not shown) for raising and lowering the quartz crucible 3, and the quartz crucible 3 is predetermined by these motors. It can be rotated in the direction and can be moved in the vertical direction. In particular, the elevating motor maintains the liquid level of the silicon melt 2 that decreases as the seed crystal 12 is pulled up at a predetermined position, so that the quartz crucible 3 is raised according to the liquid level position of the silicon melt 2 that decreases. It is configured.

  A cylindrical casing 13 having a smaller diameter than the chamber 1 is provided above the chamber 1. A pulling head 14 is provided at the upper end of the casing 13 so as to be turnable in a horizontal state. A wire cable 15 is stretched coaxially with the rotation center of the quartz crucible 3 from the pulling head 14. A seed crystal 12 is attached to the lower end of the wire cable 15 so as to pull up the silicon single crystal 11 by dipping in the melt 2.

  The manufacturing method of the present invention is applied to the silicon single crystal manufacturing apparatus shown in FIG. 1, and the lower end opening diameter of the heat shield 10, the inner diameter of the quartz crucible 3, and the heater 4 with respect to the diameter of the single crystal to be pulled up. When the magnetic field is further applied, the range of the bore diameter of the exciting coil 7 is set.

  FIG. 2 is a diagram for explaining the dimension range of each member with respect to the diameter dimension of the single crystal defined in the present invention. In the figure, the diameter of the single crystal 11 to be pulled is D (mm), the lower end opening diameter of the heat shield 10 is Fd (mm), the inner diameter of the quartz crucible 3 is Cd (mm), and the inner diameter of the heater 4 is Hd (mm). Further, the bore diameter of the exciting coil 7 is indicated by Md.

  In the manufacturing method of the present invention, the lower end opening diameter Fd of the heat shield needs to be in the range of 1.1 × D to 1.9 × D (1.1 × D ≦ Fd ≦ 1.9 × D). As described above, when the silicon single crystal is contaminated by a contaminant such as heavy metal from the heat shield, the obtained wafer causes a reduction in lifetime. For this reason, when Fd is less than 1.1 × D, there is a strong possibility that the silicon single crystal is contaminated from the heat shield, and a reduction in lifetime is predicted.

  On the other hand, when the silicon single crystal is pulled up, the heat shield shields the radiant heat from the quartz crucible heated by the heater and can secure a temperature gradient in the growth axis direction and improve the pulling speed. If it exceeds 1.9 × D, the effect of shielding the radiant heat by the heat shield cannot be exhibited.

  In the manufacturing method of the present invention, the inner diameter Cd of the quartz crucible needs to be 1.9 × D to 3.5 × D (1.9 × D ≦ Cd ≦ 3.5 × D). When Cd is less than 1.9 × D, it becomes easy to recrystallize from the inner wall of the quartz crucible during crystal growth due to the in-plane temperature gradient distribution at the solid-liquid interface, and crystal growth cannot be performed.

  On the other hand, when Cd exceeds 3.5 × D, the manufacturing cost increases rapidly as the large quartz crucible is manufactured, and at the same time, the weight increases, so that workability and handling are greatly reduced. .

  If the inner diameter Cd of the quartz crucible becomes smaller than the diameter D of the single crystal to be pulled up, the in-plane distribution is likely to fluctuate, which may affect the device characteristics and yield in the device process. In order to avoid these, it is desirable to manage the lower limit of the inner diameter Cd of the quartz crucible beyond 3.0 × D.

  In the manufacturing method of the present invention, it is necessary to design the inner diameter Hd of the heater within a range of 2.3 × D to 4.2 × D (2.3 × D ≦ Hd ≦ 4.2 × D). If Hd is less than 2.3 × D, the heater power fluctuates greatly, and the change of thermal stress and thermal disturbance at the crystal interface become severe, making it difficult to pull the silicon single crystal stably.

  On the other hand, when Hd exceeds 4.2 × D, the distance between the melt in the quartz crucible and the heater relatively increases, so that a time lag is likely to occur in the temperature control of the melt temperature. Become. For this reason, the efficiency in the pulling operation of the single crystal is hindered.

  In the production method of the present invention, a magnetic field can be applied in the horizontal direction to the melt contained in the quartz crucible as necessary. In this case, it is desirable to control the bore diameter Md of the exciting coil in the range of 4.4 × D to 7.0 × D (4.4 × D ≦ Md ≦ 7.0 × D).

  The lower limit of Md is set to 4.4 × D, which is a design limit value by being arranged so as to surround the chamber of the manufacturing apparatus, and the upper limit of Md is set to 7.0. The larger the size, the higher the manufacturing cost. Usually, when a transverse magnetic field is applied, it is desirable that the magnetic field strength be 0.1T to 0.7T.

  In order to confirm the effect of the present invention, pulling of a silicon single crystal having a diameter of 300 mm was divided into Examples 1 and 2 using the manufacturing apparatus shown in FIG. Of the examples, in the invention example, a quartz crucible of 36 inches (914 mm) to 40 inches (1016 mm) was used, and a hot zone corresponding to this was configured. However, in order to confirm the characteristics of the comparative example compared with the examples, the size range of the quartz crucible used was further varied.

Furthermore, the single crystal having a diameter of 300 mm was pulled up by 301 mm to 315 mm in consideration of the outer diameter cutting allowance at the time of actual operation, and the diameter D of the reference single crystal was taken as the diameter at the time of actual operation.
(Example 1)

  In order to confirm the effect of the opening diameter of the lower end of the heat shield on the quality and pulling condition of the single crystal, a silicon single crystal having a diameter of 300 mm was pulled using a 36 inch (914 mm) quartz crucible. At this time, the ratio (Fd / D) of the lower end opening diameter Fd of the heat shield and the diameter D of the single crystal was changed in the range of 1.05 to 2.2, and the pulling condition at this time was observed, Lifetime was measured by the wave PCD method. The evaluation results at this time are shown in Table 1.

As is clear from Table 1, heavy metal and carbon contamination occurred in Comparative Example 1, and the lifetime was significantly deteriorated. In addition, it was easy to dislocation, and single crystallization was difficult. On the other hand, the crystal was deformed and it was difficult to pull it up. On the other hand, in Invention Examples 1 and 2, the crystal was not deformed and the like was in a good pulling state, and the lifetime of the collected sample was also good.
(Example 2)

  In order to confirm the influence of the inner diameter of the quartz crucible and the inner diameter of the heater on the quality and pulling condition of the single crystal, the ratio (Fd / D) of the lower end opening diameter Fd of the heat shield to the single crystal diameter D is 1.7. As a result, a silicon single crystal having a diameter of 300 mm was pulled up. At this time, the ratio (Cd / D) between the inner diameter Cd of the quartz crucible and the diameter D of the single crystal is changed in the range of 1.8 to 3.8, and at the same time, the inner diameter Hd of the heater and the diameter D of the single crystal The ratio (Hd / D) was varied in the range of 2.2 to 4.5.

  Furthermore, a transverse magnetic field was applied to the melt as necessary, and the magnetic field strength at this time was 0.5T. Thereafter, the pulling condition was observed for each pulling condition, and the in-plane distribution of oxygen concentration and dopant concentration was measured. The evaluation results at this time are shown in Table 2.

  In Comparative Example 3, it was easy to recrystallize from the inner wall of the quartz crucible during crystal growth, and stable crystal growth was difficult. In Comparative Example 4, the heater power fluctuated greatly, and the thermal stress and disturbance at the crystal interface became intense, and could not be pulled up stably.

  On the other hand, in Comparative Example 5, the size of the quartz crucible was increased (for example, 45 inches to 46 inches), and workability and handleability were remarkably deteriorated as the weight increased. Further, in Comparative Example 6, it was difficult to control the temperature rise / fall of the melt temperature in the pulling process, the temperature fluctuation of the melt increased, and the efficiency in the pulling work was hindered.

  In contrast to the comparative example described above, Invention Examples 3 to 7 were all capable of stable pulling, and the collected samples had good in-plane distribution of oxygen concentration and resistivity. In particular, in Examples 5 and 7, a transverse magnetic field was applied to the melt, but the situation was even more stable.

  According to the method and apparatus for producing a silicon single crystal of the present invention, it is possible to ensure the thermal efficiency and the pulling speed even when pulling a large-diameter silicon single crystal regardless of the diameter of the single crystal to be pulled. The crystal can be pulled, and at the same time, the crystal quality with good lifetime and in-plane variation can be ensured.

  As a result, even when pulling up a large-diameter silicon single crystal, high production efficiency can be secured, and the quality of the obtained silicon single crystal can be stabilized at the same time. In this case, it can be suitably used.

It is front sectional drawing which shows the manufacturing apparatus of the silicon single crystal of this invention. It is a figure explaining the dimension range of each member with respect to the diameter dimension of the single crystal prescribed | regulated by this invention.

Explanation of symbols

1: chamber, 2: melt 3: quartz crucible, 4: heater 5: heat insulating material, 6: crucible driving means 7: excitation coil, 8: graphite susceptor 9: spindle, 10: heat shield 11: silicon single crystal 12: Seed crystal 13: Casing 14: Pulling head 15: Wire cable

Claims (6)

Using the Czochralski method, the crystal material is melted with a heater and then heated, while the single crystal pulled from the melt contained in the quartz crucible is surrounded by a heat shield, and the single crystal is solidified while solidifying the single crystal. A method for producing a crystal comprising:
When the diameter of the single crystal is D (mm), the lower end opening diameter of the heat shield is Fd (mm), the inner diameter of the quartz crucible is Cd (mm), and the inner diameter of the heater is Hd (mm) And a method for producing a silicon single crystal, which satisfies the following formulas (1) to (3):
1.1 × D ≦ Fd ≦ 1.9 × D (1)
1.9 × D ≦ Cd ≦ 3.5 × D (2)
2.3 × D ≦ Hd ≦ 4.2 × D (3) Further, when a magnetic field is applied in the horizontal direction to the melt contained in the quartz crucible, the bore diameter of the exciting coil arranged coaxially is Md, and the following expression (4) is satisfied. The method for producing a silicon single crystal according to claim 1.
4.4 × D ≦ Md ≦ 7.0 × D (4)   3. The method for producing a silicon single crystal according to claim 1, wherein the silicon single crystal to be pulled has a large diameter of 300 mm or more. Applied to the Czochralski method, encloses a heater that forms a melt from a crystal raw material and keeps it at a high temperature, a quartz crucible that contains the formed melt, and a single crystal that is pulled from the melt contained in the quartz crucible An apparatus for producing a silicon single crystal comprising a heat shield
With respect to the diameter D (mm) of the single crystal to be pulled up, the lower end opening diameter Fd (mm) of the heat shield, the inner diameter Cd (mm) of the quartz crucible, and the inner diameter Hd (mm) of the heater are as follows ( An apparatus for producing a silicon single crystal, characterized in that it is configured according to the relationships of formulas (1) to (3).
1.1 × D ≦ Fd ≦ 1.9 × D (1)
1.9 × D ≦ Cd ≦ 3.5 × D (2)
2.3 × D ≦ Hd ≦ 4.2 × D (3) Further, an exciting coil for applying a magnetic field in the horizontal direction to the melt contained in the quartz crucible is arranged coaxially, and the bore diameter Md of the exciting coil is as follows with respect to the diameter D (mm) of the single crystal to be pulled up. The apparatus for producing a silicon single crystal according to claim 1, wherein the apparatus is configured according to the relationship of the formula (4).
4.4 × D ≦ Md ≦ 7.0 × D (4)   The silicon single crystal manufacturing apparatus according to claim 1 or 2, wherein a silicon single crystal having a large diameter of 300 mm or more is an object to be pulled.

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