TW201732097A - Single crystal manufacturing method and device - Google Patents

Abstract

The invention can measure a crystal diameter precisely in a single crystal pulling-up step without being influenced by intensity unevenness of light irradiated from the heater. The single crystal manufacturing method of the invention includes: capturing an image of an interface between the crystal and the surface of the molten liquid in the single crystal pulling-up step adopted with Czochralski process, setting a value at least lower than the maximum value in the maximum brightness distribution 101 along the circumference direction of a fusion ring appearing on the interface as a threshold value H, and specifying an area whose maximum brightness of the maximum brightness distribution 101 is equal to or lower than the threshold value H as a diameter measurement area and performing a diameter measurement.

Description

Single crystal manufacturing method and manufacturing device

The present invention relates to a method and a device for producing a single crystal, and particularly relates to measuring a crystal diameter in a pulling step of a single crystal crucible using a Tchaikovsky method (hereinafter referred to as "CZ" method). A method and a single crystal manufacturing apparatus using the method.

The single crystal germanium which is a substrate material of a semiconductor device is often produced by a CZ method. In the CZ method, the seed crystal is immersed in a crucible melt contained in a quartz crucible, and the seed crystal is gradually pulled while rotating the seed crystal and the crucible, thereby growing a large-diameter single crystal at the lower end of the seed crystal.

In order to reliably obtain a germanium wafer having a predetermined diameter from a single crystal germanium, it is important to suppress the diameter variation of the single crystal germanium. In order to control the diameter of the single crystal crucible to a certain value, it is necessary to measure the diameter of the single crystal in the pulling up, and to control the pulling condition according to the measurement result to maintain the crystal diameter constant. Patent Document 1 discloses a method of photographing a diameter of a single crystal pulled up by a two-dimensional camera from a distance between two luminance peaks on a scanning line intersecting a melting ring generated at an interface between a single crystal and a molten metal surface, Find the diameter. Further, it is described that the image data is processed by the two-dimensional measurement method for the neck, and the image data is processed by the one-dimensional measurement method for the body, thereby controlling the diameter with high precision throughout the entire step of single crystal growth.

A heater is placed around the quartz crucible, and the crucible melt in the quartz crucible is heated by the radiant heat from the heater to maintain its molten state. The heater has a cylindrical appearance. More specifically, for example, in the case of the patent documents 2 and 3, a member having an elongated strip shape travels in the circumferential direction while being meandering up and down to form a cylindrical appearance.

Fig. 12 is a structural view showing a heater, (a) is a perspective view, and (b) is a schematic view of the side.

As shown in Fig. 12(a), the slits 15a from the upper end toward the lower side and the slits 15b from the lower end toward the upper side are alternately arranged in the circumferential direction of the cylindrical heater 15. Therefore, the cylindrical heater 15 has a single current path extending in the circumferential direction while being meandered in the vertical direction, and a U-shaped corner that is folded back is provided at the upper end or the lower end of the heater 15. When the heater 15 has such a shape, as shown in Fig. 12(b), the current concentrates on the upper end corner and the lower end corner to increase the heat generation of the portion, and the radiation light becomes strong. On the other hand, since there are slits on both sides, this portion does not generate radiant light, so there is a strong light intensity in the circumferential direction.

On the other hand, the melting ring referred to when measuring the diameter of the single crystal is an annular high-luminance field formed by the interface between the single crystal and the molten surface, because it is formed at the interface between the single crystal and the molten surface. When the light reflected by the molten metal surface (half moon surface) is incident on the meniscus from the heater 15, the circumferential direction of the molten ring is also strong and weak. That is, since the molten ring generated by the radiant light from the heater 15 has a high-luminance portion which is affected by the strong radiant light and a low-luminance portion which is affected by the weak radiant light, the circumferential luminance distribution of the fused ring may not be generated. All.

Advanced technical literature

Patent Document 1: Japanese Laid-Open Patent Publication No. 2004-149368

Patent Document 2: Japanese Laid-Open Patent Publication No. Hei 11-139895

Patent Document 3: Japanese Patent Publication No. 2005-179099

However, the conventional method for measuring the diameter of the single crystal crucible does not take into consideration the fact that the thickness distribution of the melting ring is affected by the structure of the heater 15, and the diameter measurement is performed. Therefore, the diameter measurement error may increase. That is to say, in the case where the crystal diameter is determined by the high-luminance portion of the molten ring which is affected by the intense radiation from the heater 15, a larger diameter is measured than the original crystal diameter, according to this amount. In the case where the diameter is measured for diameter control, the diameter of the actually grown single crystal is smaller than the diameter of the target.

Accordingly, it is an object of the present invention to provide a method for producing a single crystal and a manufacturing apparatus thereof capable of accurately measuring the diameter of a single crystal in a pulling-up step without being affected by the intensity of the radiation from the heater. The crystal diameter was measured.

In order to solve the above problems, the single crystal manufacturing method of the present invention includes: capturing an image of an interface portion between the single crystal and the molten metal surface by a camera in a single crystal pulling step using a Tchaikovsky method; In the highest luminance distribution in the circumferential direction of the melting ring of the interface portion, at least a value smaller than the maximum value is set as a threshold value; and a region in which the highest luminance among the highest luminance distributions is below the threshold value is designated as a diameter measurement field; The pulled single crystal is subjected to diameter measurement processing. According to the present invention, when the diameter is measured in the pulling-up step of the single crystal, it can be received without heating The intensity of the radiant light of the device is used to accurately measure the crystal diameter.

Further, the single crystal manufacturing apparatus of the present invention includes: a crucible, a support melt; a heater to heat the melt; a pull-up shaft to pull up the single crystal from the melt; and a lift mechanism to control the up-and-down direction of the crucible a camera that captures an image of the interface between the single crystal and the melt; an image processing unit that processes the image captured by the camera; and a control unit that controls the heater, the pull-up shaft, and the pick-up mechanism, the image The processing unit appears in the highest luminance distribution in the circumferential direction of the melting ring of the interface portion, and at least a value smaller than the maximum value is set as a threshold value; and a region in which the highest luminance among the highest luminance distributions is below the threshold value is designated as the diameter amount The field of measurement; and the diameter measurement of the pulled single crystal.

In the present invention, it is preferable that the captured image of the camera is a two-dimensional image in which the direction perpendicular to the pulling axis direction of the single crystal is the row direction and the direction parallel to the pulling axis direction is the column direction. The diameter measuring process includes: setting a measurement line intersecting the molten ring and extending at least one of the row directions in the diameter measurement field; determining the single crystal from a position of an intersection of the fusion ring and the measurement line diameter of. According to this method, the diameter of the single crystal can be accurately and easily obtained from the melting ring in the captured image.

In the present invention, it is preferable that the measurement line has a line having the highest brightness of the threshold or less among the highest brightness of each line of the captured image. According to this method, the range of the diameter measurement field can be expanded, and the degree of freedom in setting the measurement line can be improved. Further, it is also possible to set two or more measurement lines.

In the present invention, it is preferable that the measurement line is set to have a minimum value of the highest luminance among the highest luminances of the respective lines of the captured image. According to this method, the field that is least affected by the strong radiation from the heater is referred to Designed as a field of diameter measurement, it is able to reduce the diameter measurement error to a very small size.

In the present invention, it is preferable that the captured image is divided in the column direction, and in each of the plurality of divided regions, a row having a minimum value of the highest luminance among the highest luminances of the respective rows in the divided region is selected. The measurement line is set to at least one of a plurality of lines selected from each of the plural divided fields. According to this method, it is possible to suppress the influence of the abnormality of the luminance distribution and improve the reliability of the setting of the measurement line. Further, it is also possible to set two or more measurement lines.

In the present invention, it is preferable that the captured image is divided in the column direction, and in each of the plurality of divided fields, a segmentation region in which the average value is the smallest among the average values of the highest luminances of the respective rows in the divided region is selected. The measurement line is set within the selected segmentation field. In this way, when the divided area in which the measurement line is to be set is selected from the divided areas of the plurality of divided images in the column direction, the average value of the highest brightness of each line in each divided area is used, whereby the abnormality of the luminance distribution can be suppressed. The effect of increasing the reliability of the measurement line setting.

In the present invention, it is preferable that the dividing line is set to a line having a maximum value of the highest brightness of the respective lines, and the captured image is divided. According to this method, when a plurality of measurement lines are set, the minimum value of the highest brightness of two points that crosses the peak of the highest luminance distribution and is far apart can be obtained, and the interval between the two measurement lines can be opened.

In the present invention, it is preferable to set the first and second measurement lines at positions of the first and second distances of the origin which are set on the extension line of the pull-up axis of the single crystal, and calculate the first measurement. The first interval between the line and the intersection of the two melting points, the second interval between the second measurement line and the two intersections of the melting ring is calculated, and the first and second intervals and the first and the second 2 distance, calculate the bit The center position of the melting ring on the extension line of the pull-up shaft. In this way, the center position can be obtained from a part of the melting ring, and the crystal diameter can be accurately obtained using the center position.

According to the present invention, it is possible to provide a method for producing a single crystal and a manufacturing apparatus thereof, which can accurately measure the crystal diameter in the pulling-up step of the single crystal without being affected by the intensity of the radiation from the heater.

1‧‧‧Single crystal manufacturing equipment

2‧‧‧矽 melt

3‧‧‧ Single crystal 矽 (stick)

3a‧‧‧Neck

3b‧‧‧Shoulder

3c‧‧‧ Body

3d‧‧‧ tail

4‧‧‧melting ring

Part of the 4L, 4R‧‧‧ melting ring

5‧‧‧ Pulling up the extension of the shaft

10‧‧‧Water-cooled chamber

10a‧‧‧ main chamber

10b‧‧‧ traction chamber

10c‧‧‧ gas inlet

10d‧‧‧ gas discharge

10e‧‧‧ observation window

11‧‧‧Quartz

12‧‧‧Graphite

13‧‧‧Rotary axis

14‧‧‧Rotary shaft drive mechanism

15‧‧‧heater

15a, 15b‧‧‧ heater slit

16‧‧‧Insulation

17‧‧‧Hot shield

17a‧‧‧ openings for thermal shields

18‧‧‧ line

19‧‧‧winding mechanism

20‧‧‧CCD camera

21‧‧‧Image Processing Department

22‧‧‧Control Department

100‧‧‧Photographing

101‧‧‧ Distribution of the highest brightness in the column direction

H‧‧‧ threshold

L ₁ , L ₂ , L ₃ , La, Lb‧‧‧ measuring lines

Pm‧‧‧highest brightness

Pi‧‧‧ brightness

P ₁ , P ₂ , P ₃ ‧‧‧ Minimum brightness minimum

Fig. 1 is a side cross-sectional view schematically showing the structure of a single crystal production apparatus according to an embodiment of the present invention.

Fig. 2 is a flow chart showing a manufacturing procedure of a single crystal germanium according to an embodiment of the present invention.

Figure 3 is a schematic cross-sectional view showing the shape of a single crystal crucible rod.

Fig. 4 is a perspective view schematically showing an image of an interface portion between the single crystal 3 and the melt 2 taken by the CCD camera 20.

Fig. 5 is a schematic view for explaining a method of calculating the diameter R of the molten ring 4.

Fig. 6 is a view for explaining the luminance distribution of the molten ring, (a) is a captured image, (b) shows a luminance distribution in the Y-axis direction (column direction), and (c) shows a luminance distribution in the X-axis direction (row direction).

Fig. 7 is a view showing a first example of a method of setting a measurement line.

Fig. 8 is a view showing a second example of the method of setting the measurement line.

Fig. 9 is a third example for explaining a method of setting a measurement line.

Fig. 10 is a fourth example for explaining a method of setting a measurement line.

Fig. 11 is a graph showing changes in the diameter of a single crystal of Examples and Comparative Examples.

Fig. 12 is a view showing the structure of the heater, (a) is a schematic sectional view, and (b) is a schematic view of the side surface.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

Fig. 1 is a side cross-sectional view showing the structure of a single crystal production apparatus according to an embodiment of the present invention.

As shown in Fig. 1, the single crystal manufacturing apparatus 1 includes a water-cooled chamber 10, a quartz crucible 11 holding the crucible 2 in the chamber 10, a graphite crucible 12 holding the quartz crucible 11, and a rotation supporting the graphite crucible 12. a shaft 13 , a rotating shaft drive mechanism 14 that drives the rotating shaft 13 to rotate and lift, a heater 15 disposed around the graphite crucible 12 , a heat insulating material 16 disposed outside the heater 15 and along the inner surface of the chamber 10 , The heat shielding body 17 disposed above the quartz crucible 11 , the wire 18 for pulling up the single crystal disposed above the quartz crucible 11 and coaxial with the rotating shaft 13 , and the winding mechanism 19 disposed above the chamber 10 .

The chamber 10 is composed of a main chamber 10a and an elongated cylindrical drawing chamber 10b that connects the upper opening of the main chamber 10a. The quartz crucible 11, the graphite crucible 12, the heater 15 and the heat shielding body 17 are disposed in the main chamber. Inside the chamber 10a. The traction chamber 10b is provided with a gas introduction port 10c for introducing an inert gas (flush gas) such as argon gas or a doping gas into the chamber 10, and a gas discharge port 10d for discharging the atmospheric gas is provided at a lower portion of the main chamber 10a. . Further, an observation window 10e is provided on the upper portion of the main chamber 10a, and the growth state of the single crystal crucible 3 can be observed through the observation 10e.

The quartz crucible 11 is a quartz container having a cylindrical side wall portion and a curved bottom portion. In order to maintain the shape of the heat-softened quartz crucible 11, the black lead crucible 12 is supported by enclosing the quartz crucible 11 against the outer surface of the quartz crucible 11. The quartz crucible 11 and the graphite crucible 12 constitute a double structure of crucible in the chamber 10 to support the crucible.

The quartz crucible 12 is fixed to the upper end portion of the rotary shaft 13, and the lower end portion of the rotary shaft 13 penetrates the bottom of the chamber 10 to be connected to the rotary shaft drive mechanism 14 provided outside the chamber 10. The graphite crucible 12, the rotating shaft 13, and the rotating shaft drive mechanism 14 constitute a rotating mechanism and a lifting mechanism of the quartz crucible 11.

The heater 15 is used to melt the crucible material filled in the quartz crucible 11 to generate a crucible night 2, and maintain the molten state of the crucible 2. The heater 15 is a carbon-made impedance heating heater and is provided to surround the quartz crucible 11 in the graphite crucible 12. Further, a heat insulating material 16 surrounding the heater 15 is provided outside the heater 15, thereby improving the heat retaining property in the chamber 10.

As shown in Fig. 12, the heater 15 has an elongated and strip-shaped member that advances in the circumferential direction while being meandered in a meandering manner to form a cylindrical appearance. Therefore, the intensity of the radiant light from the heater 15 is strong in the circumferential direction. When such light from the heater is incident on the meniscus, the luminance distribution in the circumferential direction of the molten ring is also uneven. That is, the melting ring will have a high-luminance portion that is affected by the intense radiation from the heater, and a low-luminance portion that is affected by the weak radiation from the heater. This unevenness in the brightness distribution becomes a diameter measurement error. s reason.

The heat shielding body 17 is provided to suppress the temperature fluctuation of the ruthenium solution 2, and an appropriate hot zone is formed in the vicinity of the crystal growth interface to prevent the radiant heat from the heater 15 and the quartz crucible 11 from heating the single crystal crucible 3. Heat shield 17 It is a member made of graphite and covers an upper region of the crucible melt 2 other than the pulling path of the single crystal crucible 3, and has, for example, a truncated cone shape having a larger opening size from the lower end toward the upper end.

The diameter of the opening 17a at the lower end of the heat shield 17 is larger than the diameter of the single crystal crucible 3, thereby securing the pulling path of the single crystal crucible 3. The diameter of the opening 17a of the heat shield 17 is smaller than the diameter of the quartz crucible 11, and the lower end portion of the heat shield 17 is located inside the quartz crucible 11, so that the upper end of the edge of the quartz crucible 11 is raised above the lower end of the thermal shield 17 The heat shield 17 does not interfere with the quartz crucible 11.

As the growth of the single crystal germanium 3 increases, the amount of the solution in the quartz crucible 11 decreases. However, by increasing the interval ΔG between the melt surface and the end of the heat shield 17 by raising the quartz crucible 11, it is possible to suppress the crucible melt. The temperature of 2 changes, and the flow rate of the gas flowing in the vicinity of the molten metal surface can be made constant, and the amount of evaporation of the doping from the crucible melt 2 is controlled. Therefore, the stability of the crystal defect distribution, the oxygen concentration distribution, the impedance ratio distribution, and the like in the axial direction of the single crystal crucible 3 can be improved.

Above the quartz crucible 11, a wire 18 as a drawing shaft of the single crystal crucible 3 and a winding mechanism 19 for winding up the wire 18 are provided. The winding mechanism 19 has a function of rotating the single crystal crucible 3 together with the wire 18. The winding mechanism 19 is disposed above the traction chamber 10b, and the wire 18 extends from the winding mechanism 19 through the traction chamber 10b to the lower side, and the front end portion of the wire 18 reaches the internal space of the main chamber 10a. Fig. 1 shows a state in which the single crystal crucible 3 in the middle of the growth is suspended on the line 18. When the single crystal crucible 3 is pulled up, the quartz crucible 11 and the single crystal crucible 3 are each rotated, and the wire 18 is gradually pulled up to grow the single crystal crucible 3.

The upper portion of the main chamber 10a is provided with an observation window for observing the interior. 10e, the CCD camera 20 is disposed outside the observation window 10e. The captured image of the CCD camera 20 may be a grayscale image or a color image. In the single crystal pulling step, the CCD camera photographs the interface portion between the single crystal crucible 3 and the crucible melt 2 seen from the observation window 10e through the opening 17a of the heat shielding body 17 from obliquely above. The image captured by the CCD camera 20 is processed by the image processing unit 21, and the processing result is used in the control unit 22 for the control of the pull-up condition.

Fig. 2 is a flow chart showing the manufacturing steps of the single crystal germanium of the present embodiment. Further, Fig. 3 is a schematic cross-sectional view showing the shape of a single crystal crucible rod.

As shown in Fig. 2, in the production of the single crystal crucible of the present embodiment, the crucible raw material in the quartz crucible 11 is heated by the heater 15 to generate the crucible melt 2 (step S11). Next, the seed crystal of the tip end portion of the mounting wire 18 is lowered to contact the tantalum melt 2 (step S12). After that, the single crystal pulling step is performed, and the seed crystal is gradually pulled up while maintaining the contact state with the tantalum melt 2, and a single crystal is grown (steps S13 to S16).

In the pulling-up step of the single crystal, the necking step is performed in order to form the neck portion 3a having a reduced crystal diameter in order to be free from misalignment (step S13); and the shoulder-growing step to form a shoulder portion in which the crystal diameter is gradually increased. 3b (step S14); a body growth step of forming a body portion 3c having a crystal diameter maintained at a predetermined diameter (for example, 300 mm) (step S15); and a tail portion growing step to form a tail portion 3d having a gradually decreasing crystal diameter (step S16), and finally The single crystal is separated from the melt surface. By the above steps, a single crystal pry bar having the neck portion 3a, the shoulder portion 3b, the body portion 3c, and the tail portion 3d as shown in Fig. 3 is completed.

In order to control the diameter of the single crystal crucible 3, the image of the melt surface and the interface portion of the single crystal 3 is captured by the CCD camera 20, and is generated from the interface portion. The center position of the melting ring and the distance between the two brightness peaks of the melting ring were used to determine the diameter of the single crystal crucible 3. Further, in order to control the liquid level position of the crucible melt 2, the liquid level position is obtained from the center position of the melting ring. The control unit 22 controls the pulling-up conditions such as the pulling speed of the wire 18, the power of the heater 15, and the rotational speed of the quartz crucible 11, so that the diameter of the single crystal crucible 3 becomes the target diameter. Moreover, the control unit 22 controls the vertical direction of the quartz crucible 11, and maintains the interval between the molten metal surface and the lower end of the thermal shield 17 constant.

Fig. 4 is a perspective view schematically showing an image of an interface portion between the single crystal germanium 3 and the melt 2 taken by the CCD camera 20.

As shown in Fig. 4, the image processing unit 21 obtains the coordinate position of the center Co of the molten ring 4 and the coordinate position of an arbitrary point on the melting ring 4 which are generated at the interface portion between the single crystal germanium 3 and the germanium melt 2; The radius r of the molten ring 4 and the diameter R = 2r. That is, the image processing unit 21 calculates the diameter R of the single crystal 3 on the solid-liquid interface. The position of the center Co of the molten ring 4 is the intersection of the extension line 5 of the pull-up axis of the single crystal 3 and the molten metal surface.

Since the CCD camera 20 photographs the interface portion between the single crystal crucible 3 and the molten metal surface obliquely upward, the molten ring 4 cannot be captured in a true circular shape. However, if the CCD camera 20 is correctly set at a predetermined angle at a predetermined position, it is possible to correct the slightly elliptical molten ring 4 into a true circular shape according to the viewing angle with respect to the molten metal surface, and then from the The diameter of the modified molten ring 4 is calculated geometrically.

The molten ring 4 is an annular high-luminance field formed by light reflected by the meniscus, and is generated in the entire circumference of the single crystal germanium 3, but the molten ring on the back side of the single crystal germanium 3 cannot be seen from the observation window 10e. 4. Further, when the molten ring 4 is seen from the gap between the opening 17a of the heat shield 17 and the single crystal germanium 3, the straight line of the single crystal germanium 3 When the diameter is relatively large, a part of the melting ring 4 located on the observer side (lower side in FIG. 4) in the observation direction is also hidden on the back side of the heat shielding body 17 and cannot be seen. Therefore, the portion of the molten ring 4 that can be observed only has a portion 4L on the left side of the observer and a portion 4R on the right side of the observer as seen from the observation direction. In the present invention, even when only a part of the molten ring 4 can be observed, the diameter can be calculated from a part thereof.

Fig. 5 is a schematic view for explaining a method of calculating the diameter R of the molten ring 4.

As shown in FIG. 5, the calculated diameter R 4 of the molten ring, setting a measurement line L ₁ in the two-dimensional image captured by CCD camera 20 in. The measurement line L ₁ is a straight line that intersects the molten ring 4 twice and is perpendicular to the extension line 5 of the pull-up axis. The measurement line L _{1 is} set on the lower side of the center Co of the molten ring 4. Further, the Y-axis of the captured image is set to be parallel to the extension line 5 of the pull-up shaft, and the X-axis is set to be perpendicular to the direction of the extension line 5 of the pull-up shaft. Further, the molten ring 4 shown in Fig. 5 is assumed to have an ideal shape that coincides with the outer circumference of the single crystal.

Assuming that the coordinate of the center Co of the molten ring 4 with respect to the origin O(0, 0) of the XY coordinates of the captured image is (x ₀ , y ₀ ), the distance from the center Co to the measurement line L ₁ is Y=(y ₁ -yo).

Next, two intersections D ₁ and D ₁ ' of the measurement line L ₁ and the molten ring 4 are detected. The coordinate of one intersection D ₁ of the melting ring 4 and the first measurement line L ₁ is assumed to be (x ₁ , y ₁ ), and the coordinate of the intersection D ₁ ' of the other point is assumed to be (y ₁ ', y ₁ ). The approximate position of the intersection D ₁ and D ₁ ' of the molten ring 4 and the measurement line L _{1 is} the position of the luminance peak on the measurement line L ₁ . The detailed position of the intersections D ₁ and D ₁ ' of the molten ring 4 and the measurement line L ₁ will be described later.

Then, assuming that the distance X of the two intersections D ₁ and D ₁ ' on the measurement line L ₁ is X=(x ₁ '-x ₁ ), assuming that the diameter of the molten ring 4 is R and the radius is r=R/2, Obtain (1).

r ² =(R/2) ² =(X/2) ² +Y ² (1)

Therefore, the diameter R of the molten ring 4 can be obtained from the formula (1) as in the formula (2).

R={X ² +4Y ² } ^1/2 ...(2)

Melt ring is a high-brightness field having a constant width of the strip, and therefore in order to correctly determine the measured coordinates of the intersection line L _1, must be made of a molten ring 4 line pattern. Thus, detection of the intersection of the molten ring 4 and the measurement line of L _1, a luminance reference value, detect the edge of the molten ring pattern 4 from the captured image, the edge of intersection of the line pattern as measured melt ring 4 The intersection. The edge pattern of the molten ring 4 is a pattern composed of pixels having a luminance in accordance with the luminance reference value. The reference value used to define the brightness of the edge pattern can be the value of the highest brightness in the captured image multiplied by a predetermined coefficient (eg, 0.8).

The set position of the measurement line L ₁ is not limited as long as it can intersect the molten ring 4, and actually there is an appropriate position where the diameter can be more accurately measured. This is because although the radiant light of the heater 15 is incident on the meniscus formed at the interface portion between the single crystal and the molten metal surface, the intensity distribution in the circumferential direction of the radiant light of the heater 15 is uneven. In the case where the strong light from the heater 15 is incident, the peak value of the melting ring becomes very large due to the influence thereof, and the measurement error is caused when referring to such a strong luminance peak in the diameter measurement. Big.

Figure 6 is used to illustrate the brightness distribution of the melting ring, (a) is a shot The photographic image, (b) shows the luminance distribution in the Y-axis direction (column direction), and (c) shows the luminance distribution in the X-axis direction (row direction).

As shown in Fig. 6(a), the molten ring 4L appearing on the left side of the single crystal crucible 3 is a linear high-luminance field which is curved from the lower right side toward the upper left side of the captured image. As shown in Fig. 6(b), the distribution of the highest luminance Pm of the molten ring 4L in the Y-axis direction fluctuates within the range of 195 to 235, and has two peaks having the highest luminance Pm being extremely large. As described above, since the intensity distribution in the circumferential direction of the radiation light of the heater 15 is uneven, the melting ring generated by the radiation from the heater 15 into the meniscus becomes a position at which the intense radiation light is incident to form high luminance, weak radiation. The position at which light is incident forms a low brightness. On the other hand, the brightness of the solid-liquid interface portion is almost constant near 190. Therefore, in the vicinity of the maximum value of the highest luminance Pm of the molten ring 4, the difference from the luminance Pi of the solid-liquid interface portion becomes extremely large, and the difference from the luminance Pi of the solid-liquid interface portion is extremely small in the vicinity of the minimum value.

As shown in Fig. 6(c), the maximum luminance Pm is extremely large by the luminance distribution on the measurement line La near the maximum value of the highest luminance Pm of the molten ring, and the maximum luminance Pm is higher than the luminance Pi of the solid-liquid interface portion. The position is located on the left side of the position of the luminance Pi of the solid-liquid interface portion (the melt side viewed from the single crystal). Therefore, when the position slightly lower than the highest brightness Pm of the melting ring 4 is obtained as the position of the brightness Pi of the solid-liquid interface portion, the position of the brightness Pi of the solid-liquid interface portion cannot be accurately obtained, and the diameter is measured. When the vicinity of the occurrence position of the highest luminance Pm of the molten ring is referred to, the error of the diameter measurement becomes large.

However, the luminance distribution on the measurement line Lb near the minimum value of the highest luminance Pm of the molten ring is almost the same as the luminance Pi of the highest luminance Pm at the solid-liquid interface portion, and thus will be slightly lower than the highest luminance Pm of the molten ring. When the luminance position is obtained as the position of the luminance Pi of the solid-liquid interface portion, the position of the luminance Pi of the solid-liquid interface portion can be accurately obtained, and the diameter measurement error can be reduced.

For the above reasons, the present invention measures the diameter by setting the measurement line on a line where the highest brightness of the molten ring is as low as possible. Hereinafter, a method of setting the measurement line will be described.

Fig. 7 is a view showing a first example of a method of setting a measurement line.

As shown in Fig. 7, in this setting method, first, the highest luminance of each line of the captured image 100 including the melting ring is extracted, and the distribution 101 of the column direction (Y direction) of the highest luminance is obtained. The pixel having the highest brightness in the captured image 100 is a constituent pixel of the molten ring 4. The molten ring 4 is affected by the intensity of the radiant light of the heater 15, and has the highest intensity in the column direction of the captured image 100. Then, from the distribution 101 of the column direction of the highest luminance, the line from the measurement line L ₁ to the minimum value P ₁ having the highest luminance is set. Specifically, the luminance of a pixel having a certain brightness or more in a certain range is regarded as the luminance Pi of the solid-liquid interface portion, and the luminance Pi of the solid-liquid interface portion is compared with the highest luminance Pm in the same pixel column. The pixel sequence in the X-axis direction when the luminance difference between the luminance Pi of the solid-liquid interface portion and the highest luminance Pm is the smallest is taken as the diameter measurement target region. In this way, it is possible to avoid a part of the melting ring 4 which is affected by the strong radiation light of the heater 15 from being a diameter measurement target, whereby the measurement accuracy of the crystal diameter can be improved.

Fig. 8 is a view showing a second example of the method of setting the measurement line.

As shown in Fig. 8, in this setting method, the measurement line L _{1 is} set in the row 101 having the highest luminance of the threshold H or less from the distribution 101 of the column direction of the highest luminance. Specifically, the luminance of a pixel having a certain brightness or more in a certain range is regarded as the luminance Pi of the solid-liquid interface portion, and the luminance Pi of the solid-liquid interface portion is compared with the highest luminance Pm in the same pixel column. The pixel sequence in the X-axis direction when the luminance difference between the luminance Pi of the solid-liquid interface portion and the highest luminance Pm is equal to or less than the threshold value H is used as the diameter measurement target region. As shown in FIG. 8, is set at the minimum value measurement lines having the highest brightness row P _1, the measuring line can be set only in the line, thus limiting the image processing large, and can not be set plural measurement line . However, if it can be set at any position under the threshold H, the set range of the measurement line can be made to have some flexible space, and the degree of freedom of the set position of the measurement line can be improved. Further, it is also possible to set two or more measurement lines in the captured image.

The threshold H must be smaller than the maximum value of the highest luminance distribution in the column direction, and preferably less than 50% of the difference between the maximum value and the minimum value of the highest luminance distribution in the column direction (central value) plus the minimum value. The value below 20% plus the minimum value is better. The closer the threshold H of the difference between the threshold H and the minimum value of the highest luminance distribution in the column direction is to the minimum value, the more the influence of the strong radiation light from the heater 15 can be suppressed, and the diameter measurement accuracy can be improved, but the measurement line can be set freely. The degree will become lower. In addition, when the threshold value H is set to the minimum value of the highest luminance distribution in the column direction, it is the same as the first example shown in FIG. In this manner, the field in which the highest luminance distribution in the circumferential direction of the molten ring is relatively low is designated as the diameter measurement field, and the measurement lines L ₁ and L _{2 are set} , whereby the strong radiation from the heater 15 can be received. The diameter is measured for influence.

Fig. 9 is a third example for explaining a method of setting a measurement line.

As shown in Fig. 9, in this setting method, the captured image 100 is divided in the column direction, and the average value of the highest luminance of each row in the divided fields A ₁ to A ₁₂ is obtained (indicated by square dots). Set the measurement line to the segmentation field where the average value is the smallest. Here, the measurement line L ₁ is set in the divided area A ₆ in which the average value is the smallest. In this way, it is possible to suppress the influence of the abnormality of the luminance distribution and improve the reliability of the setting of the measurement line.

Fig. 10 is a fourth example for explaining a method of setting a measurement line.

As shown in Fig. 10, in this setting method, the captured image 100 is divided at the position of the maximum value of the distribution 101 of the column direction of the highest luminance, and the minimum having the highest luminance is selected in each of the plurality of divided regions A ₁ to A ₃ . The line of values. Therefore, for example, the first measurement line L _{1 is} set to the line having the highest luminance P ₁ in the first divided area A1, and the second measurement line L _{2 is} set to the minimum having the highest brightness in the second divided area A2. In the row of the value P ₂ , the third measurement line L _{3 is} set to the row having the lowest luminance P ₃ of the highest luminance in the third division domain A3.

The distribution of the highest brightness of the molten ring 4 alternates between high brightness and low brightness in the circumferential direction, and thus is divided at the position of the maximum value of the distribution of the highest brightness, and when the measurement line is set for each divided area, the crossing can be obtained. The minimum value of the highest brightness (for example, P ₁ and P ₂ ) of the 2 points at which the peak of the highest luminance distribution is far away is opened, and the interval between the two measurement lines (for example, L ₁ , L ₂ ) is opened.

As described above, in the method for producing a single crystal germanium according to the present embodiment, in the highest luminance distribution in the circumferential direction of the molten ring which occurs at the interface between the single crystal germanium and the molten metal surface, the diameter is determined by specifying a region having a relatively high maximum luminance. Since the measurement process is performed, it is possible to accurately measure the crystal diameter without being affected by the intensity of the radiation light from the heater.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and does not depart from the gist of the present invention. Various changes can be made, and these changes are of course included in the scope of the present invention.

For example, although the above embodiment has been described as an example of producing a single crystal germanium, the present invention is not limited thereto, and can be applied to the production of various single crystals grown by the CZ method.

[Examples]

Using the single crystal manufacturing apparatus 1 shown in Fig. 1, a single crystal crucible rod for a wafer having a diameter of 300 mm was produced by a CZ method. At this time, the imaging image control pull-up condition is processed while the interface portion between the single crystal cymbal and the molten metal surface is taken by the camera.

In the single crystal pulling step of the embodiment, the crystal diameter is measured from the distance between the peaks of the luminances on the measurement line at the position where the highest luminance in the circumferential direction of the melting ring in the image capturing image is almost the smallest, and the measurement result is returned based on the measurement result. The pull-up condition is controlled so that the actual crystal diameter is close to the target diameter.

In the single crystal pulling step of the comparative example, the crystal diameter is measured from the distance between the peaks of the luminances on the measurement line at the position where the highest luminance in the circumferential direction of the molten ring in the image is substantially maximal, and the measurement result is returned based on the measurement result. The pull-up condition is controlled such that the actual crystal diameter is close to the above target diameter.

Fig. 11 is a graph showing the measurement results of the diameters of the single crystals of the examples and the comparative examples, wherein the horizontal axis shows the position in the crystal growth direction from the top end of the single crystal crucible rod, and the vertical axis shows the crystal diameter with respect to the target diameter. Deviation (specification value of crystal diameter). Further, Fig. A shows the measured diameter of the molten ring at a position of low luminance (Example), and Fig. B shows the measured diameter of the molten ring at a position of high luminance (Comparative Example), and the diamond dot indicates the actual measurement by the vernier caliper Crystalline diameter.

As can be seen from Fig. 11, the graph A showing the highest brightness of the molten ring at a relatively low position is almost the same as the actual crystal diameter. However, the graph B showing the measured diameter of the highest brightness of the molten ring at a relatively high position is always larger than the actual crystal diameter. That is, the diameter measurement error can be reduced by suppressing the influence of the unevenness of the highest brightness of the molten ring.

100‧‧‧Photographing

101‧‧‧ Distribution of the highest brightness in the column direction

H‧‧‧ threshold

L ₁ ‧‧‧ measuring line

Claims (8)

A single crystal manufacturing method comprising: capturing an image of an interface portion between the single crystal and a molten metal surface by a camera in a single crystal pulling step using a Tchaikovsky method; and forming a melting ring of the interface portion Among the highest luminance distributions in the circumferential direction, at least a value smaller than the maximum value is set as a threshold value; an area in which the highest luminance among the highest luminance distributions is below the threshold is designated as a diameter measurement field; and a diameter of the pulled single crystal is made Measurement processing. The single crystal manufacturing method according to claim 1, wherein: the captured image of the camera is in a direction perpendicular to a direction of a pulling axis of the single crystal, in a direction parallel to the pulling axis direction. a two-dimensional image in the column direction, the diameter measurement process comprising: setting a measurement line intersecting the molten ring and extending at least one of the row directions in the diameter measurement field; from the melting ring and the measurement line The position of the intersection is determined by the diameter of the single crystal. The single crystal manufacturing method according to claim 2, wherein the measurement line is set to have a line of the highest brightness of the threshold or less among the highest brightness of each line of the captured image. The single crystal manufacturing method according to claim 2, wherein the measurement line is set to have a minimum value of the highest brightness among the highest brightness of each line of the captured image. The method for manufacturing a single crystal according to claim 4, wherein the column is in the column Dividing the captured image in the direction, selecting, in each of the plurality of divided regions, a row having the lowest value of the highest luminance among the highest luminances of the respective rows in the divided region, and setting the measurement line in the divided region from each of the plural numbers At least one of the selected plural lines. The single crystal manufacturing method according to claim 4, wherein the captured image is divided in the column direction, and in each of the plurality of divided regions, the average value of the highest brightness of each row in the divided region is selected. The segmentation field with the smallest average value sets the measurement line within the selected segmentation domain. The single crystal manufacturing method according to claim 5, wherein the dividing line is set to a line having a maximum value of the highest brightness of the respective lines, and the captured image is divided. A single crystal manufacturing apparatus comprising: a crucible, a support melt; a heater to heat the melt; a pull-up shaft to pull a single crystal from the melt; and a lifting mechanism to control a position of the crucible in a vertical direction; Shooting an image of the interface between the single crystal and the melt; the image processing unit processes the image captured by the camera; and the control unit controls the heater, the pull-up shaft, and the pick-up mechanism, and the image processing unit outputs In the highest luminance distribution in the circumferential direction of the melting ring of the interface portion, at least a value smaller than the maximum value is set as a threshold value; and a region in which the highest luminance among the highest luminance distributions is below the threshold value is designated as a diameter measurement field; Diameter measurement is performed on the pulled single crystal.