JP4844127B2 - Single crystal manufacturing apparatus and manufacturing method - Google Patents

Description

  The present invention is capable of controlling the temperature distribution on the surface of a silicon melt when growing a silicon single crystal, and reducing the variation in diameter caused by the temperature of the surface of the silicon melt. The present invention also relates to a silicon single crystal manufacturing method using the single crystal manufacturing apparatus.

  A silicon single crystal is grown by heating a polycrystalline silicon raw material contained in a crucible with a heater to form a silicon melt, and pulling it up from the silicon melt by the Czochralski method (hereinafter abbreviated as “CZ method”). It is manufactured by. In a silicon single crystal grown by the CZ method, a defect called a Grown-in defect is formed during crystal growth, and is detected when a silicon single crystal obtained after crystal growth is evaluated.

It is known that R-OSF (Ring-Oxidation induced Stacking Fault) appears in the longitudinal section of a silicon single crystal grown while gradually reducing the pulling rate. The region where R-OSF appears shrinks from the outer peripheral side of the crystal to the inside as the pulling rate is reduced. The grown-in defects observed after crystal growth are different between the inside (crystal region pulled at a high speed) and the outside (crystal region pulled at a low speed) from the R-OSF. In the crystal region pulled at a high speed, a void defect (a void type defect) called COP (crystal originated particle) or FPD (flow pattern defect) is detected. In addition, in the crystal region pulled at a low speed, interstitial Si aggregates accompanied by dislocations are generated, and interstitial Si defects (dislocation cluster defects) are detected.
In addition, there is a defect-free region in which no Grown-in defect is detected between the R-OSF and the interstitial Si defect region. The void defect in the silicon single crystal is a deterioration factor of the initial oxide film breakdown voltage characteristic of the wafer. In addition, interstitial Si defects in the silicon single crystal also degrade device characteristics. Therefore, crystal growth in a defect-free region is desired because of the quality characteristics of the silicon single crystal.

These Grown-in defects are the ratio of the pulling rate V (mm / min) when growing a silicon single crystal to the crystal temperature gradient G (° C./mm) in the pulling axis direction near the solid-liquid interface. The amount of introduction is considered to be determined by the G (mm ² / ° C./min) value.
That is, it is possible to manufacture a silicon single crystal having a desired defect state or a desired defect-free region by growing the silicon single crystal while keeping the V / G value constant at a predetermined value.

  However, in the conventional method for producing a silicon single crystal, the pulling rate is also used as one of parameters for controlling the diameter of the silicon single crystal to be grown. For this reason, when a silicon single crystal having a desired defect region or a desired defect-free region is grown, the V / G value must be controlled at the same time as the V / G value is controlled by adjusting the pulling rate. Therefore, when the V / G value control and the diameter control are performed during the growth of the silicon single crystal, only one of the controls can be performed when it is desired to change the pulling speeds different from each other. As a result, the diameter of the silicon single crystal greatly fluctuates during the pulling of the silicon single crystal, or in order to prevent this, the V / G value deviates from the desired range. A single crystal having a desired crystal state (defect state) could not be obtained, resulting in a significant decrease in yield.

As an example in which controllability of the temperature gradient is difficult, for example, a technique described in Patent Document 1 is disclosed. In the technology described in this publication, the distance between the crystal surface temperature gradient Gc at the center of the crystal and the crystal temperature gradient Ge at the periphery of the crystal is changed between the melt surface of the raw material melt and the heat shielding member disposed opposite to the raw material melt surface. The difference ΔG = | (Gc−Ge) | between the temperature gradient Gc at the center of the crystal and the temperature gradient Ge at the periphery of the crystal is controlled to be 0.5 ° C./mm or less. A method of manufacturing a single crystal has been proposed in which the ratio V / Gc (mm ² / ° C./min) between the speed V and the temperature gradient Gc at the center of the crystal is controlled so that a single crystal having a desired defect region can be grown.
JP 2005-15313 A

However, in the above-described conventional technology, since the melt surface temperature cannot be controlled without the idea of controlling the temperature of the silicon melt surface, the temperature distribution on the silicon melt surface during the growth of a silicon single crystal is not possible. There is a possibility that the fluctuation of the diameter due to this may become large. In such a case, the pulling speed has to be changed for the diameter control. When the pulling speed is varied for the diameter control, the V / G value may be out of the desired range, and there is a problem that a desired single crystal having a low defect cannot be grown.

  In particular, when the temperature in the vicinity of the surface of the silicon melt has dropped below the melting point of silicon, solidification starts from that portion, and single crystallization itself may be hindered.

  The present invention has been made in view of the above circumstances, can control the temperature distribution on the surface of the silicon melt when growing a silicon single crystal, and has a diameter caused by the temperature of the surface of the silicon melt. It is an object of the present invention to realize a single crystal manufacturing apparatus capable of reducing fluctuations and a silicon single crystal manufacturing method using the single crystal manufacturing apparatus.

  In order to solve the above-mentioned problems, the present inventor has intensively studied and analyzed the cause of the variation in the diameter of the silicon single crystal as shown below.

  FIG. 7 is a schematic cross-sectional view showing a conventional single crystal manufacturing apparatus. In FIG. 7, reference numeral 20 denotes a single crystal manufacturing apparatus. In the main chamber 1 of the single crystal manufacturing apparatus 20, a quartz crucible 5 that contains the silicon melt 4 and a graphite crucible 6 that protects the quartz crucible 5 are supported by a holding shaft 13 so as to be rotatable and movable up and down by a crucible drive mechanism 21. Has been. Further, a gas rectifying cylinder 11 is provided inside the main chamber 1, and a heat shield member 12 is installed at the lower part of the gas rectifying cylinder 11 so as to face the silicon melt 4. The radiation from the silicon melt 4 is prevented from reaching the upper part of the silicon single crystal 3 by preventing the radiation from the surface of the silicon.

    When the single crystal pulling apparatus 20 is used to grow the silicon single crystal 3 by the CZ method under the silicon single crystal pulling conditions as described below, the state of the silicon melt in the crucible is In order to analyze whether or not, the flow velocity, streamline, and isotherm in the longitudinal section of the silicon melt were obtained by simulation analysis. Here, the pulling conditions set in these simulations were the conditions for pulling up a defect-free crystal that is a crystal region in which the Grown-in defect does not extend over the entire length of the straight body portion.

The results are shown in FIGS. FIG. 8 shows the flow velocity vector of the silicon melt, and FIG. 9 shows the flow lines of the silicon melt. In FIG. 9, the shading is given for convenience, and the light-colored center and the dark-colored center indicate the centers of convection formed in the crucible.
FIG. 10 is a diagram showing an isotherm of the silicon melt. In FIG. 10, the interval between the isotherms is 2K, and the light color indicates a low temperature and the dark color indicates a high temperature. From the light and dark in FIG. 10, outside the crucible provided with a heater as a heating source. It can be seen that the right side of the figure is hotter. In addition, although there is a lightest color portion at the uppermost left portion in FIG. 10, this corresponds to a partial region 26 below the silicon melting point, that is, a portion that becomes the solidified silicon single crystal 3. 8 to 10, only the one side portion obtained by cutting the longitudinal section of the silicon melt in the quartz crucible at the central axis 15 of the quartz crucible is shown for easy understanding of the drawings.

In the single crystal pulling apparatus 20 shown in FIG. 7, the surface temperature of the silicon melt 4 is not maintained or insufficient, so that the surface temperature of the silicon melt 4 is immediately outside the solid-liquid interface as shown in FIG. At this position, the temperature gradually decreases from the meniscus M toward the radially outer side of the silicon single crystal 3, and a low temperature region 25 is formed. The low temperature region 25 is in a temperature state equivalent to the partial region 26 that becomes the solidified silicon single crystal described above, that is, a portion that is in a state of being below the silicon melting point or likely to be below the silicon melting point.
The low temperature region 25 is distributed in an annular shape near the surface of the silicon melt 4, and the size thereof is 1.1 of the radius R of the silicon single crystal 3 from the central axis 15 of the quartz crucible toward the quartz crucible 5. It is formed at a position of ~ 1.5 times.
In the region that extends outward in the radial direction of the silicon single crystal 3 from the low temperature region 25, the surface temperature of the silicon melt 4 rises, and a stable temperature gradient in the rising direction is obtained.

In the single crystal pulling apparatus 20 shown in FIG. 7, when the temperature of the low temperature region 25 becomes equal to or lower than the melting point during the growth of the silicon single crystal 3, the diameter of the silicon single crystal 3 being grown tends to increase. For this reason, it is necessary to induce the silicon single crystal 3 being grown to have a small diameter by increasing the pulling speed. However, if the pulling speed is varied to control the diameter of the silicon single crystal 3, the V / G value may deviate from the desired range, and the silicon single crystal 3 having a desired defect region may not be grown. It was.
In particular, when the silicon single crystal 3 having a defect-free region is grown, the temperature gradient G in the crystal axis direction at the single crystal center near the solid-liquid interface is high, and the single crystal center near the solid-liquid interface is When the distribution difference ΔG of the temperature gradient in the crystal axis direction is small and the solid-liquid interface is pulled up under pulling conditions that tend to be upwardly convex, the low temperature region 25 on the surface of the silicon melt 4 is likely to be lowered in temperature. However, when growing the silicon single crystal 3 having a defect-free region, the control range of the pulling rate is very narrow, and it is very difficult to vary the pulling rate in order to perform diameter control. For this reason, it was difficult to grow the silicon single crystal 3 having a defect-free region with a high yield.

  As shown in FIG. 10, the present inventor has conducted extensive research, and as shown in FIG. 10, by maintaining the temperature immediately outside the solid-liquid interface, which is the low-temperature region 25, on the surface of the silicon melt, Phenomenon that causes a low temperature region 25 generated just outside the interface, that is, local low temperature in the vicinity of the surface of the silicon melt, and the silicon melt surface when growing a silicon single crystal It has been found that by controlling the temperature gradient in the radial direction of the silicon crystal, fluctuations in the diameter of the silicon single crystal can be reduced while pulling up the silicon single crystal having a desired crystal state such as a defect-free crystal.

That is, in the single crystal manufacturing apparatus of the present invention, in the single crystal manufacturing apparatus for growing while pulling up the silicon single crystal from the silicon melt contained in the crucible in the chamber,
A gas rectifying cylinder for blocking radiation from the silicon melt to the silicon single crystal and rectifying the gas in the chamber;
A heat shield member installed at the lower part of the gas rectifying cylinder so as to face the entire surface of the silicon melt and cuts radiation from the surface of the silicon melt and keeps the surface of the silicon melt warm;
A heat retaining body that is disposed above the melt surface in the vicinity of the solid-liquid interface, and that keeps the silicon melt in a low-temperature region in which the temperature may drop below the melting point in the vicinity of the solid-liquid interface;
Is provided,
The heat retaining body has an annular shape in plan view so as to retain the annular melt surface surrounding the silicon single crystal, and the outer diameter when viewed in plan is 1.2 of the diameter of the silicon single crystal. -3.0 times, and the inner diameter is 1.0-1.5 times the diameter of the silicon single crystal ,
The heat retaining body is any one of an annular surface, a parabolic ring surface, a spherical ring surface, and an elliptic ring surface whose cross-sectional shape is an arc, and a position where radiation from the heat retaining body is concentrated is in the low temperature region. by the most set from low temperature of the crucible is a significant position central axis so that the silicon melt of 1.2 to 1.3 times the position of the radius R of the silicon single crystal toward the crucible outer Rukoto Solved the above problem .
In the present invention, the position where the radiation from the heat retaining body concentrates may be a position of 0 to 100 mm in the depth direction along the central axis from the surface of the silicon melt.
In the present invention, the distance between the heat retaining body and the silicon melt may be 0.1 to 100 mm.
In the present invention, the thermal conductivity of the heat retaining body is 5.0 W / mK or less and the thickness of the heat retaining body is 0.1 to 100 mm, or the heat retaining body has an emissivity of 0.01 to It is 0.3 and the apparatus with which the thickness of a heat retention body shall be 0.01-100 mm is employable.
The heat retaining body may be supported integrally with the heat shield member.
It is preferable that the height of the heat retaining body and the silicon melt can be set independently of the height of the silicon melt and the heat shield member.
It is preferable that the present invention includes a position adjustment unit that supports the distance between the heat retaining body, the silicon melt, and the heat shield member so as to be adjustable.
In the method for producing a single crystal according to the present invention, in the method for producing a silicon single crystal, the silicon single crystal is grown while being pulled up from the silicon melt contained in the crucible by the single crystal production apparatus according to any one of the above.
A heat insulator placed above the melt surface in the vicinity of the solid-liquid interface covers the portion of the solid-liquid interface where the temperature of the silicon melt may be lowered and keeps the temperature on the surface of the silicon melt. However, the above problem was solved by pulling up the silicon single crystal.
In the present invention, it is preferable to set the distance between the heat retaining body and the silicon melt to be 0.1 to 100 mm.
In the present invention, the solid-liquid interface can be pulled up in a convex state.
The present invention may pull up a grown-in defect-free single crystal.
The present invention can Rukoto concentrate the radiation from the heat retaining body in the coldest of significant positions of the low temperature region.

  In the single crystal manufacturing apparatus of the present invention, in the single crystal manufacturing apparatus for growing while pulling up the silicon single crystal from the silicon melt stored in the crucible, the solid liquid is disposed above the melt surface in the vicinity of the solid-liquid interface. By providing a heat insulator that retains the portion of the silicon melt at a temperature lower than the melting point in the vicinity of the interface, the region immediately outside the solid-liquid interface on the surface of the silicon melt can be kept warm. In particular, the phenomenon of causing the low temperature region 25 generated just outside the solid-liquid interface, which has a significant effect on crystal growth, is mitigated by retaining at least the temperature of the portion where the low temperature region 25 shown in FIG. 10 is generated. , Prevent local low temperature in the vicinity of the surface of the silicon melt, and increase the temperature gradient in the radial direction of the surface of the silicon melt when growing a silicon single crystal. It can be constant. This makes it possible to reduce the variation in the diameter of the silicon single crystal while pulling up the silicon single crystal having a desired crystal state such as a defect-free crystal.

  Further, as described above, the low temperature region 25 in FIG. 10 is distributed in an annular shape near the surface of the silicon melt 4, and the size thereof extends from the central axis 15 of the quartz crucible in FIG. 7 to the quartz crucible 5. Since the silicon single crystal 3 is formed in the vicinity of a position 1.1 to 1.5 times the radius R of the silicon single crystal 3, in order to keep only this portion warm, the present invention provides a silicon single body to be pulled up. The temperature of the annular melt surrounding the periphery of the crystal is kept warm, and the heat retaining body has an annular shape in plan view, and the diameter of the silicon single crystal whose outer diameter is raised in plan view is 1 .2 to 3.0 times, and the silicon melt portion where the low temperature is generated by setting the inner diameter to be 1.0 to 1.5 times the diameter of the silicon single crystal to be pulled up To keep this part warm , It is possible to prevent the low temperature of the above occurs. Thereby, by preventing local lowering of the silicon melt, it is possible to stabilize the silicon melt convection and to suppress the vibration of the flow in the melt convection and to stabilize the pulling speed. . As shown in FIG. 6, the region where the low temperature occurs is generated at a position 1.2 to 1.5 times that of the silicon crystal. Therefore, it is preferable that a heat insulator is provided to cover this position. is there.

  As the shape of the heat insulating body, it is only necessary to cover the portion that becomes the low temperature region and prevent the temperature from being lowered, and when viewed from above, it has a circular plate shape having a width so as to overlap the low temperature region, that is, when viewed from above, the Of the vertical cross section passing through the crystal axis at the ring surface, the cross section on one side from the center of the crucible is preferably a linear shape (rectangular shape) whose lower side is parallel to the silicon melt surface. It only has to be a surface. Specifically, a conical annular surface inclined so as to rise outward from the crucible center side, that is, a linear shape in which a cross section on one side from the center of the crucible rises toward the crucible outer side in a vertical cross section passing through the crystal axis. (Rectangular) shape, or a parabolic annulus that is inclined so as to rise outward from the crucible center, that is, a shape in which the parabola is rotated around the crystal axis (crucible central axis) Or a circular ring surface inclined so as to rise outward from the crucible center side, that is, a shape obtained by rotating an arc around the crystal axis (crucible center axis), or a crucible An elliptical ring shape inclined so as to rise from the center side toward the outside, that is, a shape in which a partial line of the ellipse is rotated around the crystal axis (crucible center axis) can be formed.

  Here, in the case of a parabolic ring surface, a spherical ring surface, and an elliptical ring surface, the radiation (reflection) from the heat insulator is concentrated in the low temperature region where the temperature is most significantly reduced or in the vicinity thereof. Further, by setting the focal point, center, etc. of these parabolas, arcs, ellipses, etc., it becomes possible to further prevent the temperature from being lowered. Specifically, the position where the radiation from the heat insulator is concentrated is a position about 1.2 to 1.3 times the radius R of the silicon single crystal 3 from the central axis 15 of the quartz crucible 5 toward the outside of the quartz crucible 5. Near the surface of the silicon melt. In this case, the position where the radiation from the heat retaining body concentrates may be in the vicinity of the silicon melt surface as long as the horizontal position is as described above. The shape of the heat retaining body on the side not facing the silicon melt surface may be a shape along the surface facing the silicon melt surface, or may not be a shape along the surface facing the silicon melt surface. Well, not particularly limited.

In the present invention, since the distance between the heat retaining body and the silicon melt surface is about 0.1 to 100 mm, more preferably about 1 to 50 mm, the heat retaining body comes into contact with the silicon melt and is simply It does not adversely affect the crystal pulling, and the radiation from the silicon melt is not reflected by the heat retaining body, and is not radiated to the outside from between the heat retaining body and the silicon melt. Therefore, it is possible to stabilize the silicon melt convection and to prevent the flow vibration in the silicon melt convection from occurring and to stabilize the pulling speed.
Note that the distance between the heat retaining body and the silicon melt surface is the distance between the heat retaining body lower surface and the silicon melt surface when the heat retaining body is annular, and has other irregularities. In the case of the heat retaining body, the distance between the lower end of the heat retaining body and the silicon melt surface is set in the above range.

In the present invention, the heat retaining body is made of carbon or the like, the thermal conductivity thereof is 5.0 W / mK or less, more preferably 1.0 W / mK or less, and the thickness of the heat retaining body is about 0.1 to 100 mm. Preferably, the means is about 1 to 50 mm, or the heat insulator is made of a material having a low emissivity such as Mo, and the emissivity is about 0.01 to 0.3, more preferably about 0.3 or less. In addition, by adopting means in which the thickness of the heat retaining body is about 0.01 to 100 mm, preferably about 0.1 to 10 mm, the silicon melt is effectively kept warm, Generation | occurrence | production of the low temperature in a liquid can be prevented.

  Since the heat retaining body is integrally supported by a heat shield member disposed at a position facing the liquid surface of the silicon melt, the height position of the silicon melt changes with respect to the crucible during pulling up. The height position can be changed integrally with the heat shield member that controls the position of the silicon melt and the lower end portion, so that the height of the silicon melt and the lower end portion of the heat shield member can be set by raising the height. The distance between the heat retaining body and the silicon melt surface can be continuously set within the above range following the change in the height position of the silicon melt at, and a preferable heat retaining state can be maintained. Further, since the distance between the lower end of the heat shield member and the silicon melt surface can be set regardless of the heat insulation state of the silicon melt, the distance between the lower end of the heat shield member and the silicon melt liquid surface Even when it is desired to maintain a sufficient gas flow rate, it is possible to simultaneously realize maintaining a suitable chamber state and preventing local low temperature generation by keeping the silicon melt surface warm.

  The present invention includes a position adjusting means that supports the distance between the heat retaining body and the silicon melt so as to be adjustable, so that, for example, the gas flow rate and the like are controlled, the silicon melt and the heat shielding member are controlled. Even when it is necessary to change the height setting state with the lower end, the height of the heat insulator in the chamber can be independently set to a desired state without following these. The distance between the heat retaining body and the silicon melt surface can be maintained within the above range. As a result, it is possible to simultaneously maintain a preferable state in the chamber and prevent occurrence of local low temperature by maintaining the temperature of the silicon melt surface. In addition, the amount of silicon melt changes as it is pulled up, resulting in a change in the convection state in the melt, and when the heat insulation state must follow such a convection change, the heat shield member position is considered. Without this, the distance between the heat retaining body and the silicon melt can be adjusted. Therefore, it is possible to further control the pulled crystal state.

  In the method for producing a single crystal according to the present invention, the temperature of the silicon melt may be lowered in the vicinity of the solid-liquid interface by the above-described production apparatus, due to the heat insulator disposed above the melt surface near the solid-liquid interface. By pulling up the silicon single crystal while keeping the surface of the silicon melt over a certain portion, it is possible to prevent a local low temperature of the silicon melt, thereby preventing the silicon melt convection. In addition to stabilization, it is possible to stabilize the pulling speed by suppressing the vibration of the flow in the melt convection, and to stably pull up the single crystal without the grown-in defect over the entire length of the straight body portion. .

  In the present invention, by setting the distance between the heat retaining body and the silicon melt to be 0.1 to 100 mm, it is possible to prevent the local melt from being lowered in temperature.

In the present invention, as a condition for pulling up a single crystal without a Grown-in defect, the solid-liquid interface can be pulled up in a convex state, whereby the Grown-in over the entire length of the straight body portion. It becomes possible to pull the defect-free silicon single crystal stably.
The silicon single crystal or the silicon wafer of the present invention can be manufactured by any of the above-described single crystal manufacturing apparatuses or any of the above-described single crystal manufacturing methods.

The single crystal manufacturing apparatus of the present invention is a single crystal manufacturing apparatus that grows while pulling up a silicon single crystal from a silicon melt accommodated in a crucible. The single crystal manufacturing apparatus is disposed near a meniscus and keeps the silicon melt near the meniscus warm. A heat insulating body is provided.
In such a single crystal manufacturing apparatus, a heat insulating body is provided in the vicinity of the meniscus and keeps the silicon melt in the vicinity of the meniscus, so that a region where a low temperature region is formed on the surface of the silicon melt is kept warm. Thus, the lowering of the low temperature region can be mitigated. For this reason, the temperature gradient in the radial direction of the silicon melt surface when the silicon single crystal is grown can be stabilized, and the variation in the diameter of the silicon single crystal when the silicon single crystal is grown can be reduced. The pulling speed can be easily controlled, and the V / G value can be easily controlled. Furthermore, according to such a single crystal manufacturing apparatus, since the convection of the silicon melt can be stabilized by providing the heat insulator, the control of the V / G value can be facilitated.
The above-described effects are particularly prominent when growing a silicon single crystal having a defect-free region in which the low-temperature region 25 is easily lowered and the pulling rate control range is very narrow.

In the single crystal manufacturing apparatus, the heat retaining body may be integrated with a heat shield member disposed to face the liquid surface of the silicon melt.
By setting it as such a single crystal manufacturing apparatus, a heat retaining body can be easily arrange | positioned in a predetermined position.

Moreover, in said single crystal manufacturing apparatus, the shape of the said heat retention body shall be an annular | circular shape surrounding the circumference | surroundings of the silicon single crystal pulled up.
By using such a single crystal manufacturing apparatus, the region where the low temperature region is formed on the surface of the silicon melt is effectively kept warm, and the surface of the silicon melt surface when the silicon single crystal is grown is grown. The temperature gradient in the radial direction is further stabilized, and fluctuations in the diameter of the silicon single crystal when the silicon single crystal is grown can be more effectively suppressed.

In the single crystal manufacturing apparatus, the annular heat retaining body is 1.2 to 3.0 times the diameter of the silicon single crystal whose outer diameter is increased, and the silicon single crystal whose inner diameter is increased. It can be 1.0 to 1.5 times the diameter.
By setting it as such a single-crystal manufacturing apparatus, the area | region in which the low temperature area | region in the surface of a silicon melt is formed can be kept warm effectively.

The single crystal manufacturing apparatus may include a position adjusting unit that adjusts a distance between the heat retaining body and the silicon melt during the pulling of the silicon single crystal.
By using such a single crystal manufacturing apparatus, the distance between the heat retaining body and the silicon melt can be set to a predetermined distance even if the amount of the silicon melt changes during the pulling of the silicon single crystal. Thus, the temperature reduction in the low temperature region can be mitigated during the entire crystal growth process.

Moreover, in said single-crystal manufacturing apparatus, the distance of the said heat retention body and the said silicon melt shall be 0.1-100 mm.
By using such a single crystal manufacturing apparatus, a region where a low-temperature region is formed on the surface of the silicon melt can be effectively formed without hindering the flow of gas such as an inert gas introduced into the chamber. It can be kept warm.
If the distance between the heat retaining body and the silicon melt is less than 0.1 mm, the flow of gas such as an inert gas introduced into the chamber may be hindered. If the distance between the heat retaining body and the silicon melt exceeds 100 mm, the heat retaining effect by the heat retaining body cannot be sufficiently obtained.

Moreover, in said single-crystal manufacturing apparatus, the heat conductivity of the said heat insulating body shall be 5.0 W / mK or less, and the thickness of a heat insulating body shall be 0.1-100 mm.
Moreover, in said single-crystal manufacturing apparatus, the emissivity of the said heat insulating body shall be 0.3 or less, and the thickness of a heat insulating body shall be 0.01-100 mm.
By setting it as such a single-crystal manufacturing apparatus, it becomes what was equipped with the heat insulating body which has sufficient heat retention effect, without using the material of a heat insulating body excessively.

The silicon single crystal manufacturing method of the present invention is a silicon single crystal manufacturing method in which a silicon single crystal is grown while being pulled up from a silicon melt contained in a crucible. The silicon single crystal is pulled up while keeping the temperature on the surface of the melt.
In such a method for producing a silicon single crystal, the silicon single crystal can be pulled up while keeping a region where a low temperature region is formed on the surface of the silicon melt, so that the low temperature region can be reduced in temperature. .

In the method for producing a silicon single crystal, the distance between the heat retaining body and the silicon melt can be adjusted by a position adjusting unit during the pulling of the silicon single crystal.
By adopting such a silicon single crystal manufacturing method, even if the amount of the silicon melt changes during the pulling of the silicon single crystal, the distance between the heat insulator and the silicon melt can be set to a predetermined distance. In the whole crystal growth process, the lowering of the low temperature region can be mitigated.

Moreover, in the manufacturing method of said silicon single crystal, it can be set as the manufacturing method which makes the distance of the said heat retention body and the said silicon melt be 0.1-100 mm.
By adopting such a method for producing a silicon single crystal, a region where a low temperature region is formed on the surface of the silicon melt can be effectively obtained without hindering the flow of gas such as an inert gas introduced into the chamber. The silicon single crystal can be pulled up while keeping the temperature constant.

  According to the single crystal manufacturing apparatus and the silicon single crystal manufacturing method of the present invention, the surface of the silicon melt in which the low temperature region is formed on the surface of the silicon melt and the silicon single crystal is grown is maintained. Since the temperature distribution is controlled, the variation in diameter caused by the temperature of the silicon melt surface can be reduced.

  Hereinafter, a single crystal manufacturing apparatus and a silicon single crystal manufacturing method according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a single crystal manufacturing apparatus according to a first embodiment of the present invention. FIG. 2A is an enlarged view showing a part of the single crystal manufacturing apparatus shown in FIG. 1, and FIG. 2B illustrates a heat insulator provided in the single crystal manufacturing apparatus shown in FIG. It is a figure for doing. In the single crystal manufacturing apparatus shown in FIGS. 1 and 2, the same reference numerals as those of the single crystal manufacturing apparatus shown in FIG.

  In FIG. 1, the code | symbol 30 has shown the single crystal manufacturing apparatus. In the main chamber 1 of the single crystal manufacturing apparatus 30, a quartz crucible 5 that stores the silicon melt 4 and a graphite crucible 6 that protects the quartz crucible 5 are supported by a holding shaft 13 so as to be rotatable and movable up and down by a crucible drive mechanism 21. Has been. Further, the heater 7 and the heat insulating material 8 are arranged so as to surround the quartz crucible 5 and the graphite crucible 6. A pulling chamber 2 for accommodating and taking out the grown silicon single crystal 3 is connected to the upper portion of the main chamber 1, and the silicon single crystal 3 is rotated by a wire 14 at the upper portion of the pulling chamber 2. A pulling mechanism (not shown) for pulling up is provided.

In addition, a gas rectifying cylinder 11 is provided inside the main chamber 1 to block radiation from the silicon melt 4 to the silicon single crystal 3 and rectify the gas in the main chamber 1. A heat shield member 12 is installed at the lower part of the cylinder 11 so as to face the entire surface of the silicon melt 4 so as to cut off radiation from the surface of the silicon melt 4 and to keep the surface of the silicon melt 4 warm. Yes.
In the longitudinal section of the silicon melt in the quartz crucible, and in the vicinity of the meniscus M of the single crystal manufacturing apparatus 30, a heat retaining body 40 that keeps a portion of the silicon melt 3 in the vicinity of the meniscus M where low temperature is likely to occur is arranged. Yes. As shown in FIG. 2B, the heat retaining body 40 has an annular shape surrounding the periphery of the silicon single crystal 3 to be pulled up. As shown in FIG. 2 (b), the heat retaining body 40 can be formed in an annular shape, but may be, for example, a conical ring surface, a parabolic ring surface, a spherical ring surface, or an elliptic spherical ring surface shape.

FIG. 12 is a view for explaining another example of the heat retaining body, and is a view showing a cross-sectional view of the heat retaining body together with an isothermal line of a longitudinal section of the silicon melt in the quartz crucible. In FIG. 12, the interval between the isotherms is 2K, the light color indicates the low temperature, and the dark color indicates the high temperature. In FIG. 12, only one side portion obtained by cutting the longitudinal section of the silicon melt in the quartz crucible with the central axis 15 of the quartz crucible is shown for easy viewing of the drawing.
The heat retaining body 41 shown in FIG. 12 has an annular surface shape whose cross-sectional shape is an arc. As shown in FIG. 12, the central axis 42 passing through the center of the arc constituting the heat retaining body 41 is 1.2 to the radius R of the silicon single crystal 3 from the central axis 15 of the quartz crucible 5 toward the outside of the quartz crucible 5. It is the surface of the silicon melt at a position about 1.3 times, and is considered to be the portion where the temperature reduction is most remarkable in the low temperature region 25. The focal point 43 of the heat retaining body 41 is set to a position of 0 to 100 mm, more preferably 10 to 30 mm in the depth direction along the central axis 42 from the silicon melt surface.
In the heat retaining body 41 shown in FIG. 12, radiation (reflection) from the heat retaining body 41 can be concentrated in the portion of the low temperature region 25 where the temperature is most drastically reduced and the vicinity thereof, thereby further preventing the temperature from being lowered. It becomes possible.

As shown in FIG. 2B, the outer diameter D of the heat retaining body 40 is set to 1.2 to 3.0 times the diameter D ₀ of the silicon single crystal 3 to be pulled up, and is 1.5 to 2.5 times. It is desirable that The inner diameter d of the heat insulator 40 is 1.0 to 1.5 times the diameter _{D 0} of the silicon single crystal to be pulled up, it is desirable that 1.0 to 1.2 times.
When the thermal conductivity is 5.0 W / mK or less, the thickness t of the heat retaining body 40 is preferably 0.1 to 100 mm, and more preferably 1 to 50 mm. Further, the thickness t of the heat retaining body 40 is preferably set to 0.01 to 100 mm when the emissivity is a low emissivity of 0.3 or less, and is preferably 0.1 to 10 mm. Is more desirable.
As the heat insulating body 40 having a thermal conductivity of 5.0 W / mK or less, for example, a double carbon structure in which at least two carbon plates are stacked in the direction toward the silicon melt 4 to cover the heat insulating material 40. Things can be mentioned. Further, examples of the heat retaining body 40 having a low emissivity of 0.3 or less include those made of molybdenum (Mo). Since both carbon and molybdenum have been conventionally employed as materials for the chamber internal structure, they are preferable because they can easily affect the cleanliness in the chamber and the like.

  As shown in FIG. 2B, the heat retaining body 40 is located in the middle of the outer diameter D and the inner diameter d at two positions 35 and 35 symmetric with respect to the center of the heat retaining body 40. It is integrated with the heat shield member 12 by being fixed to the tip of the wire 31 penetrating the wire. The heat retaining body 40 is provided with a wire 31, rotation support jigs 34 a, 34 b, 34 c that support the wire 31, and a motor that is provided outside the main chamber 1 and that rotationally drives a gear 33 around which the wire 31 is wound. 32 is supported so as to be movable in the vertical direction.

In the present embodiment, the single crystal pulling apparatus 30 includes two position adjusting means. However, the number of position adjusting means is not particularly limited, and may be three or more. When the number of position adjusting means is three or more, it is preferable that the heat retaining body 40 can be stably supported, but an increase in the number of position adjusting means is not preferable because a factor that contaminates the inside of the chamber increases. For this reason, it is desirable that the number of position adjusting means is two or three. Furthermore, although the heat retaining body 40 is supported by the wire 31, the heat retaining member 40 can also be supported by a rod-shaped member having a rectangular cross section extending in the vertical direction. In this case, the heat retaining body 40 and the rod-shaped member are arranged at one location. The position adjustment means 1 can be moved up and down in a state in which a through hole having a rectangular cross section is provided in the heat shield member 12 instead of the rotation support jig and the rotation about the rod-like member is restricted. It can also be.
The distance H between the heat retaining body 40 and the silicon melt 4 is 0.1 to 100 mm, preferably 1 to 50 mm, and the amount of the silicon melt 4 is increased during the pulling of the silicon single crystal 3 by the position adjusting means. The distance H between the heat retaining body 40 and the silicon melt 4 can be adjusted to a predetermined distance H in accordance with the change.

    An inert gas such as argon gas can be introduced from the gas inlet 10 provided at the upper portion of the pulling chamber 2, and after passing between the silicon single crystal 3 being pulled and the gas rectifying cylinder 11, the gas is blocked. It can be passed between the heat member 12 and the melt surface of the silicon melt 4 and discharged from the gas outlet 9.

In order to grow a silicon single crystal by the CZ method using such a single crystal pulling apparatus 30, first, the seed crystal 16 fixed to the wire 14 is immersed in the silicon melt 4 in the quartz crucible 5, and thereafter The silicon single crystal 3 having a substantially cylindrical straight body is grown by gently pulling up while rotating to form a seed diaphragm and then expanding to a desired diameter.
In the present embodiment, the silicon single crystal 3 is pulled up while the surface of the silicon melt 4 is kept warm by the heat retaining body 40 disposed in the vicinity of the meniscus M to prevent local lowering of the melt temperature. During the pulling of the silicon single crystal 3, the distance H between the heat retaining body 40 and the silicon melt 4 is adjusted to the above range by the position adjusting means. The adjustment by the position adjusting means is performed by operating the motor 32 and rotationally driving the gear 33 in the forward direction or the opposite direction.

  The position adjusting means can be controlled by, for example, the following method by connecting the position adjusting means to position control means (not shown) for controlling the crucible drive mechanism 21. For example, information such as the position of the quartz crucible 5, the position of the heat retaining body 40, the position of the melt surface of the silicon melt 4 measured by a CCD camera, the pulling length of the single crystal, the silicon melt 4 liquid surface and the quartz Information such as the height position of the crucible 5, the temperature in the chamber, the surface temperature of the silicon melt 4, and the gas flow rate is fed back to the position control means, so that the quartz crucible 5 The vertical position and / or the vertical position of the heat retaining body 40 are moved using the crucible drive mechanism 21 and / or the position adjusting means, and the distance H from the lower end of the heat retaining body 40 to the liquid surface of the silicon melt 4 is increased. Control.

Using such a single crystal pulling apparatus 30, the flow velocity, streamline, and isotherm in the longitudinal section of the silicon melt when the silicon single crystal 3 is grown by the CZ method under the pulling conditions of the silicon single crystal shown below. Was obtained by simulation analysis. The pulling condition of the silicon single crystal here is a condition for growing a silicon single crystal having a defect-free region.
Solid-liquid interface shape ΔS-L / ΔS-L (prior art) = 1.100
Crystal center temperature gradient near solid-liquid interface G / G (prior art) = 1.180
Crystal center temperature gradient distribution difference ΔG / ΔG (prior art) = 0.3
It set so that it might become.
Here, as shown in FIG. 1, the solid-liquid interface shape ΔS-L is a distance Zc from the bottom surface in the main chamber 1 to the center of the solid-liquid interface in the crystal axis direction, and the bottom surface in the main chamber 1. It is the difference (Zc−Ze) from the distance Ze to the periphery of the solid-liquid interface, the crystal center temperature gradient G in the vicinity of the solid-liquid interface is the above-described temperature gradient G, and the crystal center temperature gradient distribution difference ΔG is The rate at which the temperature gradient changes during the pulling is shown. The above values are raised by the conventional manufacturing apparatus shown in FIG. 7 in the state shown in FIGS. The ratio with each value at the time of occurrence is shown.

The results are shown in FIGS. FIG. 3 corresponds to FIG. 8 and shows the flow velocity vector of the silicon melt, and FIG. 4 corresponds to FIG. 9 and shows the flow lines of the silicon melt. In FIG. 4, as in FIG. 9, the shades are given for convenience, and the light color center and the dark color center indicate the centers of convection formed in the crucible.
FIG. 5 corresponds to FIG. 10 and shows the isotherm of the silicon melt. In FIG. 5, the interval between the isotherms is 2K, the light color indicates a low temperature and the dark color indicates a high temperature. 3 to 5, only the one side portion obtained by cutting the longitudinal section of the silicon melt in the quartz crucible with the central axis 15 of the quartz crucible is shown for easy viewing of the drawings. FIG. 6 is a graph showing the relationship between the surface temperature of the silicon melt and the radial position of the silicon melt. In addition, the position in the radial direction in FIG. 6 indicates the position of the silicon single crystal 3 to be pulled up having a diameter D ₀ of 1, and the distance from the position of the diameter D ₀ toward the outside in the radial direction is shown as a ratio to the diameter D ₀ .

In the single crystal pulling apparatus 30 shown in FIG. 1, the surface temperature of the silicon melt 4 slightly decreases as it goes from the meniscus M to the radially outer side of the silicon single crystal 3 as shown in FIGS. Although the region 25 is formed, it does not fall below the temperature of the melting point of silicon of 1865 K, and the temperature generally increases in the region from the position of the diameter D ₀ of the silicon single crystal 3 toward the radially outer side of the silicon single crystal 3. is doing. Therefore, it can be seen from this drawing that in this embodiment, silicon melt solidification does not occur in the vicinity of the surface of the silicon melt except in the single crystal growth portion.

  Here, the effects of the present invention were evaluated by comparing the results of the embodiment of the present invention shown in FIGS. 3 to 6 with the conventional results shown in FIGS. 8 to 10 and FIG. 6. The results are shown in Table 1 and below.

When the results of the embodiment of the present invention shown in FIGS. 5 and 6 are compared with the conventional results shown in FIGS. 10 and 6, the lowering of the low temperature region 25 on the surface of the silicon melt 4 is obviously alleviated, and silicon The temperature gradient in the radial direction of the surface of the silicon melt 4 when the single crystal 3 is grown is stable.
Moreover, when the result by embodiment of this invention shown in FIG.3 and FIG.4 is compared with the conventional result shown in FIG.8 and FIG.9, it turns out that the convection of the silicon melt 4 is stable.

  Further, from the embodiment of the present invention shown in FIG. 6 and the conventional results, the average temperature gradient in the range from the position 1 to 1.5 in the radial direction of the surface of the silicon melt 4 was obtained. As shown in Table 1, the result is a temperature gradient in the downward direction in the prior art, but in the present invention, the temperature gradient is in the upward direction.

  Moreover, the simulation analysis of the past and this invention when the growth rate fluctuation rate was controlled by the ADC control system under the above-described pulling conditions was performed, and the growth rate fluctuation rate was obtained. As a result, in the present invention, the pulling rate fluctuation rate was reduced as compared with the prior art. The ADC control system monitors the crystal diameter during pulling, and when the crystal diameter increases, the pulling speed is increased to induce a decrease in the crystal diameter. Conversely, when the crystal diameter decreases, the pulling speed is increased. It is a control system that induces the crystal diameter to increase by lowering. That is, when the crystal diameter direction control is automated, the pulling rate can be stabilized by providing the heat retaining body 40 as in the present embodiment.

Moreover, the simulation analysis of the conventional and this invention was performed on the above pulling conditions, and the defect-free (pure) wafer yield was calculated | required. As a result, the defect-free wafer (pure) yield was higher in the present invention than in the prior art.
The defect-free wafer yield was determined by the method shown below.

Below, the definition and measurement method of a defect-free area | region in a wafer are shown below.
First, an oxide film having a film thickness of 50 nm or 5 nm is formed on the surface of the wafer to be observed, and an average oxide film thickness (an estimated value of the average film thickness using a film thickness monitor is acceptable) is obtained.
5 (MV / cm) ・ Average oxide film thickness (nm) / 10
In addition, a predetermined voltage is applied so that Cu decoration is performed using a Cu elution methanol solution in which the MeOH resistance before elution of Cu is set to 5,3 ± 1 kΩ (φ300 mm).

On the inspection surface of the wafer, a measurement area is set in a ring shape as shown in FIG. 11, and whether each area has a defect is observed with a microscope.
Next, the results are summarized for each region as shown in FIG. Here, reference numeral 59 in FIG. 13 is a defect, and FIG. 13 shows a state in which defects existing in each region are collected on the X axis.

The total area of the regions where such defects exist is excluded from the total area of the wafer, and the remaining area is defined as a pure area (defect-free area).
Next, the defect-free wafer yield is obtained from the following equation.
Pure (defect-free area) yield = number of wafers corresponding to defect-free area / total number of wafers of crystals to be dispensed

FIG. 1 is a schematic cross-sectional view of a single crystal manufacturing apparatus according to a first embodiment of the present invention. FIG. 2A is an enlarged view showing a part of the single crystal manufacturing apparatus shown in FIG. 1, and FIG. 2B illustrates a heat insulator provided in the single crystal manufacturing apparatus shown in FIG. It is a figure for doing. FIG. 3 is a diagram showing the flow rate of the silicon melt. FIG. 4 is a view showing streamlines of the silicon melt. FIG. 5 is a diagram showing an isotherm of the silicon melt. FIG. 6 is a graph showing the relationship between the surface temperature of the silicon melt and the radial position of the silicon melt. FIG. 7 is a schematic cross-sectional view showing a conventional single crystal manufacturing apparatus. FIG. 8 shows the flow rate of the silicon melt. FIG. 9 is a diagram showing streamlines of the silicon melt. FIG. 10 is a diagram showing an isotherm of the silicon melt. FIG. 11 is a diagram showing a defect measurement region. FIG. 12 is a diagram showing an isotherm of the silicon melt. FIG. 13 is a diagram for explaining a defect measurement result.

Explanation of symbols

1: main chamber, 3: silicon single crystal, 4: silicon melt, 5: quartz crucible, 6: graphite crucible, 11: gas rectifier, 12: heat shield member, 13: holding shaft, 15: central shaft, 20 , 30: single crystal manufacturing apparatus, 21: crucible drive mechanism, 25: low temperature region, 31: wire, 32: motor, 33: gear, 40, 41: heat insulator, M: meniscus

Claims (13)

In a single crystal manufacturing apparatus for growing while pulling up a silicon single crystal from a silicon melt contained in a crucible in a chamber,
A gas rectifying cylinder for blocking radiation from the silicon melt to the silicon single crystal and rectifying the gas in the chamber;
A heat shield member installed at the lower part of the gas rectifying cylinder so as to face the entire surface of the silicon melt and cuts radiation from the surface of the silicon melt and keeps the surface of the silicon melt warm;
A heat retaining body that is disposed above the melt surface in the vicinity of the solid-liquid interface, and that keeps the silicon melt in a low-temperature region in which the temperature may drop below the melting point in the vicinity of the solid-liquid interface;
Is provided,
The heat retaining body has an annular shape in plan view so as to retain the annular melt surface surrounding the silicon single crystal, and the outer diameter when viewed in plan is 1.2 of the diameter of the silicon single crystal. -3.0 times, and the inner diameter is 1.0-1.5 times the diameter of the silicon single crystal ,
The heat retaining body is any one of an annular surface, a parabolic ring surface, a spherical ring surface, and an elliptic ring surface whose cross-sectional shape is an arc, and a position where radiation from the heat retaining body is concentrated is in the low temperature region. the the most set from the low temperature is a significant position the crucible center axis such that the silicon melt of 1.2 to 1.3 times the position of the radius R of the silicon single crystal toward the crucible outer Rukoto A single crystal manufacturing apparatus characterized. 2. The single crystal manufacturing apparatus according to claim 1 , wherein a position where radiation from the heat retaining body concentrates is a position of 0 to 100 mm in a depth direction along the central axis from the silicon melt surface. The distance heat retaining body and said silicon melt, a single crystal manufacturing apparatus according to claim 1 or 2, characterized in that there is a 0.1 to 100 mm. The single crystal manufacturing apparatus according to any one of claims 1 to 3 , wherein the heat insulator has a thermal conductivity of 5.0 W / mK or less and a thickness of the heat insulator is 0.1 to 100 mm. . The emissivity of the heat insulator is 0.01 to 0.3, producing a single crystal according to any one of claims 1-3 in which the thickness of the heat insulator is characterized in that there is a 0.01~100mm apparatus. The single crystal manufacturing apparatus according to any one of claims 1 to 5 , wherein the heat retaining body is integrally supported by the heat shield member. Height between the silicon melt and the heat retaining body, to claim 1, wherein the 5 to be formed by the settable the silicon melt and the heat insulating member and the height and independently of the The single crystal manufacturing apparatus described. The single crystal manufacturing apparatus according to claim 7 , further comprising a position adjusting unit that supports the heat retaining body, the silicon melt, and the heat shield member so as to be adjustable. In the manufacturing method of the silicon single crystal which grows while pulling up the silicon single crystal from the silicon melt accommodated in the crucible by the single crystal manufacturing apparatus according to any one of claims 1 to 8 ,
A heat insulator placed above the melt surface in the vicinity of the solid-liquid interface covers the portion of the solid-liquid interface where the temperature of the silicon melt may be lowered and keeps the temperature on the surface of the silicon melt. However, the method for producing a single crystal is characterized by pulling up the silicon single crystal. The method for producing a single crystal according to claim 9 , wherein a distance between the heat retaining body and the silicon melt is set to be 0.1 to 100 mm. The solid-liquid interface, the method for producing a single crystal according to claim 9 or 1 0, characterized in that pulling in the state of protruding upward is performed. Grown- method for producing a single crystal according to claim 9 1 1, characterized in that to increase the in-defect-free single crystal. The method for producing a single crystal according to claim 9 1 2, characterized in Rukoto to concentrate on the most low temperature is significant position of the low temperature region of the radiation from the heat insulator.

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