MANUFACTURING METHOD AND MANUFACTURING SYSTEM FOR SILICON SINGLE CRYSTAL

Abstract

Spatial coordinates of multiple points on an inner surface of a vitreous silica crucible are measured prior to filling raw material in the vitreous silica crucible, and a three-dimensional shape of the inner surface of the vitreous silica crucible using a combination of polygons having vertex coordinates constituted by the respective measured points is specified (S11); a predictive value of an initial liquid surface level of the silicon melt in the vitreous silica crucible is preset (S12); a volume of the silicon melt satisfying the predictive value of the initial liquid surface level is obtained based on the three-dimensional shape of the inner surface of the vitreous silica crucible (S13); a weight of the silicon melt having the volume is obtained (S14); raw material having the weight is filled in the vitreous silica crucible (S15); a dipping control of the seed crystal is performed based on the predictive value of the initial liquid surface level (S17).

Claims

1. A manufacturing method of a silicon single crystal by the Czochralski method in which a silicon melt is formed by heating a raw material filled in a vitreous silica crucible and a seed crystal dipped in the silicon melt is pulled up, thereby growing a silicon single crystal, the manufacturing method being characterized by: measuring spatial coordinates of a number of points on an inner surface of a vitreous silica crucible prior to filling raw material in the vitreous silica crucible, and specifying a three-dimensional shape of the inner surface of the vitreous silica crucible using a combination of polygons having vertex coordinates constituted by the respective measured points; presetting a predictive value of an initial liquid surface level of a silicon melt in the vitreous silica crucible; obtaining a volume of the silicon melt which satisfies the predictive value of the initial liquid surface level based on the three-dimensional shape of the inner surface of the vitreous silica crucible; obtaining a weight of the silicon melt having the volume; filling the raw material having the weight in the vitreous silica crucible; and performing a dipping control of a seed crystal based on the predictive value of the initial liquid surface level.

2. The manufacturing method of the silicon single crystal according to claim 1, wherein the three-dimensional shape of the inner surface of the vitreous silica crucible is measured by scanning the inner surface of the vitreous silica crucible with a distance measuring device provided at a tip of an arm of an arm robot.

3. The manufacturing method of the silicon single crystal according to claim 2, wherein a measurement item different from the three-dimensional shape is simultaneously measured with the three-dimensional shape.

4. The manufacturing method of the silicon single crystal according to claim 2, wherein the arm robot is positionally controlled by using a spatial coordinate (x,θ.sub.0,z) of an arbitrary point on the inner surface of the vitreous silica crucible which is obtained by using a function formula of a design model of the vitreous silica crucible, wherein when D is a vitreous silica crucible diameter, H is a vitreous silica crucible height, R is a curvature radius of a bottom portion of the vitreous silica crucible, and r is a curvature radius of a curved portion of the vitreous silica crucible, the function formula representing an x coordinate and a z coordinate of an arbitrary point on the inner surface of a sidewall portion of the vitreous silica crucible is:
x=D/2
z=(H−R+α.sup.1/2)t+R−α.sup.1/2, the function formula representing an x coordinate and a z coordinate of an arbitrary point on the inner surface of a curved portion of the vitreous silica crucible is:
x=r cos {−(π/2−θ)t}+D/2−r
z=r sin {−(π/2−θ)t}+R−α.sup.1/2, the function formula representing an x coordinate and a z coordinate of an arbitrary point on the inner surface of a bottom portion of the vitreous silica crucible is:
x=R cos(θt−π/2)
z=R sin(θt−π/2)+R, parameters α, θ, and t contained in the function formula are
α=(R−2r+D/2)(R−D/2)
θ=arctan {(D/2−r)/α.sup.1/2}
t=0 to 1, wherein the θ is an intersection point angle of a curvature radius R of the bottom portion of the vitreous silica crucible intersecting with the curved portion of the vitreous silica crucible.

5. The manufacturing method of the silicon single crystal according to claim 1, further comprising a multi-pulling process in which a subsequent pulling of a silicon single crystal is performed by adding raw material in the vitreous silica crucible after the previous pulling of the silicon single crystal is completed, wherein a residual amount of the silicon melt remaining in the vitreous silica crucible is obtained from a weight of the silicon single crystal which is pulled previously, and an additional filling amount of the raw material which satisfies the predictive value of the initial liquid surface level of the silicon melt used in the subsequent pulling of the silicon single crystal is obtained based on the three-dimensional shape of the inner surface of the vitreous silica crucible and the residual amount of the silicon melt.

6. The manufacturing method of the silicon single crystal according to claim 5, wherein the additional filling amount of the raw material is adjusted so that the initial liquid surface level at the time of the subsequent pulling of the silicon single crystal is lower than the initial liquid surface level at the time of the previous pulling of the silicon single crystal.

7. A manufacturing method of a silicon single crystal by the Czochralski method in which a silicon melt is formed by heating a raw material filled in a vitreous silica crucible and a seed crystal dipped in the silicon melt is pulled up, thereby growing a silicon single crystal, the manufacturing method being characterized by: measuring spatial coordinates of a number of points on an inner surface of the vitreous silica crucible prior to filling raw material in the vitreous silica crucible, and specifying a three-dimensional shape of the inner surface of the vitreous silica crucible using a combination of polygons having vertex coordinates constituted by the respective measured points; obtaining a weight of the raw material to be filled in the vitreous silica crucible; obtaining a volume of a silicon melt to be formed by melting the raw material having the weight; obtaining a predictive value of an initial liquid surface level of the silicon melt to be formed by melting the raw material in the vitreous silica crucible, based on the three-dimensional shape of the inner surface of the vitreous silica crucible and the volume of the silicon melt; and performing a dipping control of the seed crystal based on the predictive value of the initial liquid surface level.

8. The manufacturing method of the silicon single crystal according to claim 7, wherein the three-dimensional shape of the inner surface of the vitreous silica crucible is measured by scanning the inner surface of the vitreous silica crucible with a distance measuring device provided at a tip of an arm of an arm robot.

9. The manufacturing method of the silicon single crystal according to claim 8, wherein a measurement item different from the three-dimensional shape is simultaneously measured with the three-dimensional shape.

10. A manufacturing system of a silicon single crystal by the Czochralski method in which a silicon melt is formed by heating raw material filled in a vitreous silica crucible and a seed crystal dipped in the silicon melt is pulled up, thereby growing a silicon single crystal, the manufacturing system being characterized by comprising: a measuring system for measuring spatial coordinates of a number of points on an inner surface of a vitreous silica crucible prior to filling a raw material in the vitreous silica crucible, and specifying a three-dimensional shape of the inner surface of the vitreous silica crucible using a combination of polygons having vertex coordinates constituted by the respective measured points; a silicon raw material measuring section for obtaining a weight of the raw material to be filled in the vitreous silica crucible; a silicon single crystal pulling furnace; and a pulling furnace control section for controlling a pulling condition of the silicon single crystal pulling furnace, wherein an analysis/calculation unit is provided in the measuring system, in which a predictive value of an initial liquid surface level of the silicon melt in the vitreous silica crucible is preset, a volume of the silicon melt satisfying the predictive value of the initial liquid surface level is obtained based on the three-dimensional shape of the inner surface of the vitreous silica crucible, and a weight of the raw material to be filled in the vitreous silica crucible is obtained based on the volume of the silicon melt, and the pulling furnace control section performs a dipping control of the seed crystal based on the predictive value of the initial liquid surface level.

11. The manufacturing method of the silicon single crystal according to claim 3, wherein the arm robot is positionally controlled by using a spatial coordinate (x,θ.sub.0,z) of an arbitrary point on the inner surface of the vitreous silica crucible which is obtained by using a function formula of a design model of the vitreous silica crucible, wherein when D is a vitreous silica crucible diameter, H is a vitreous silica crucible height, R is a curvature radius of a bottom portion of the vitreous silica crucible, and r is a curvature radius of a curved portion of the vitreous silica crucible, the function formula representing an x coordinate and a z coordinate of an arbitrary point on the inner surface of a sidewall portion of the vitreous silica crucible is:
x=D/2
z=(H−R+α.sup.1/2)t+R−α.sup.1/2, the function formula representing an x coordinate and a z coordinate of an arbitrary point on the inner surface of a curved portion of the vitreous silica crucible is:
x=r cos {−(π/2−θ)t}+D/2−r
z=r sin {−(π/2−θ)t}+R−α.sup.1/2, the function formula representing an x coordinate and a z coordinate of an arbitrary point on the inner surface of a bottom portion of the vitreous silica crucible is:
x=R cos(θt−π/2)
z=R sin(θt−π/2)+R, parameters α, θ, and t contained in the function formula are
α=(R−2r+D/2)(R−D/2)
θ=arctan {(D/2−r)/α.sup.1/2}
t=0 to 1, wherein the θ is an intersection point angle of a curvature radius R of the bottom portion of the vitreous silica crucible intersecting with the curved portion of the vitreous silica crucible.

12. The manufacturing method of the silicon single crystal according to claim 2, further comprising a multi-pulling process in which a subsequent pulling of a silicon single crystal is performed by adding raw material in the vitreous silica crucible after the previous pulling of the silicon single crystal is completed, wherein a residual amount of the silicon melt remaining in the vitreous silica crucible is obtained from a weight of the silicon single crystal which is pulled previously, and an additional filling amount of the raw material which satisfies the predictive value of the initial liquid surface level of the silicon melt used in the subsequent pulling of the silicon single crystal is obtained based on the three-dimensional shape of the inner surface of the vitreous silica crucible and the residual amount of the silicon melt.

13. The manufacturing method of the silicon single crystal according to claim 3, further comprising a multi-pulling process in which a subsequent pulling of a silicon single crystal is performed by adding raw material in the vitreous silica crucible after the previous pulling of the silicon single crystal is completed, wherein a residual amount of the silicon melt remaining in the vitreous silica crucible is obtained from a weight of the silicon single crystal which is pulled previously, and an additional filling amount of the raw material which satisfies the predictive value of the initial liquid surface level of the silicon melt used in the subsequent pulling of the silicon single crystal is obtained based on the three-dimensional shape of the inner surface of the vitreous silica crucible and the residual amount of the silicon melt.

14. The manufacturing method of the silicon single crystal according to claim 4, further comprising a multi-pulling process in which a subsequent pulling of a silicon single crystal is performed by adding raw material in the vitreous silica crucible after the previous pulling of the silicon single crystal is completed, wherein a residual amount of the silicon melt remaining in the vitreous silica crucible is obtained from a weight of the silicon single crystal which is pulled previously, and an additional filling amount of the raw material which satisfies the predictive value of the initial liquid surface level of the silicon melt used in the subsequent pulling of the silicon single crystal is obtained based on the three-dimensional shape of the inner surface of the vitreous silica crucible and the residual amount of the silicon melt.

15. The manufacturing method of the silicon single crystal according to claim 11, further comprising a multi-pulling process in which a subsequent pulling of a silicon single crystal is performed by adding raw material in the vitreous silica crucible after the previous pulling of the silicon single crystal is completed, wherein a residual amount of the silicon melt remaining in the vitreous silica crucible is obtained from a weight of the silicon single crystal which is pulled previously, and an additional filling amount of the raw material which satisfies the predictive value of the initial liquid surface level of the silicon melt used in the subsequent pulling of the silicon single crystal is obtained based on the three-dimensional shape of the inner surface of the vitreous silica crucible and the residual amount of the silicon melt.

Description

DESCRIPTION OF DRAWINGS

[0039] FIG. 1 is a flowchart for explaining the manufacturing method of a silicon single crystal according to the first embodiment of the present disclosure.

[0040] FIG. 2 is a schematic view for explaining the manufacturing method of the silicon single crystal.

[0041] FIG. 3 is a graph showing the change in the in-furnace temperature from the melting of the raw material to the pulling.

[0042] FIG. 4 is a photograph showing the corrosion occurred on the circumference of the inner surface of the vitreous silica crucible which is generated in the necking process from the dipping at the time of the first pulling of the silicon single crystal.

[0043] FIG. 5 is a schematic view showing one example of the manufacturing system of the silicon single crystal according to the present disclosure.

[0044] FIG. 6 is a schematic view showing one example of the measuring system for measuring the three-dimensional shape of the inner surface of the vitreous silica crucible 1.

[0045] FIG. 7 is an approximately perspective view showing the three-dimensional shape of the inner surface of the vitreous silica crucible which is specified by the measured value.

[0046] FIG. 8 is a schematic view showing another example of the measuring system for measuring the three-dimensional shape of the inner surface of the vitreous silica crucible 1.

[0047] FIG. 9 is a flowchart showing the manufacturing method of a silicon single crystal according to the second embodiment of the present disclosure.

DETAILED DESCRIPTION

[0048] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0049] FIG. 1 is a flowchart for explaining the manufacturing method of the silicon single crystal according to the first embodiment of the present disclosure. In addition, FIG. 2 is a schematic view for explaining the manufacturing method of the silicon single crystal.

[0050] As shown in FIG. 1 and FIG. 2, in the manufacture of the silicon single crystal according to the present embodiment, first, a vitreous silica crucible 1 is prepared, and the three-dimensional shape of the inner surface thereof is measured (step S11). Here, the three-dimensional shape of the inner surface of the vitreous silica crucible 1 is specified by obtaining the spatial coordinates of a number of points on the inner surface of the vitreous silica crucible 1. The vitreous silica crucible 1 is a container made of vitreous silica supporting the silicon melt in the CZ method, including a curved bottom portion, a cylindrical sidewall portion, and a bottom portion having a larger curvature than the bottom portion and connecting the bottom portion and the sidewall portion. Details of the measuring method of the three-dimensional shape of the inner surface of the vitreous silica crucible 1 will be described later.

[0051] Although the size of the vitreous silica crucible 1 is not particularly limited, since a larger-sized crucible has a larger capacity in proportion to its size, a large amount of raw material can be filled. For example, the inner capacity of a 32-inch crucible is 211470 cm.sup.3, and it is possible to hold about 529 kg of silicon raw material. The inner capacity of a 36-inch crucible is 268065 cm.sup.3, and it is possible to hold about 670 kg of silicon raw material. The inner capacity of a 40-inch crucible is 375352 cm.sup.3, and it is possible to hold about 938 kg of silicon raw material. Such a large capacity crucible has a greater influence of variation of the initial liquid surface level, and the effect of the present disclosure is also greater. Therefore, the present disclosure is suitable for a manufacturing method of a silicon single crystal using a vitreous silica crucible which has an opening diameter of 32 inches (800 mm) or more.

[0052] Next, a predictive value of the initial liquid surface level H.sub.1 of the liquid surface 3a of the silicon melt 3 is set (step S12), and the capacity V in the crucible up to the predictive value of the initial liquid surface level H.sub.1 is obtained based on the obtained data of the three-dimensional shape and the residual amount of the silicon melt in the crucible (step S13). This capacity V corresponds to the volume of the silicon melt required to satisfy the predictive value of the initial liquid surface level H.sub.1. At this time, when there is no silicon single crystal pulled previously, since there is no silicon melt in the vitreous silica crucible, there is also no residual amount. When the height of the vitreous silica crucible is H.sub.0 (see FIG. 2), the predictive value of the initial liquid surface level H.sub.1 is preferably 0.7 H.sub.0 or more and 0.9 H.sub.0 or less.

[0053] Next, the weight M of the silicon melt satisfying the obtained capacity V is obtained (step S14). The specific gravity in the vicinity of the melting point (about 1413 □) of the silicon melt is 2.6×10.sup.6 (g/m.sup.3), the relational expression between the volume V (m.sup.3) and the weight M(g) of the silicon raw material is M=2.6×10.sup.6×V. The specific gravity of silicon at normal temperature is 2.3×10.sup.6 (g/m.sup.3). If the same weight of silicon is used, the volume of the silicon melt is smaller than the volume of the silicon at normal temperature.

[0054] Next, the silicon raw material having the obtained weight M is measured and filled in the vitreous silica crucible 1 (step S15), and manufacture of the silicon single crystal is started. The method for measuring the weight is not particularly limited as long as it can ensure certain measurement accuracy. In the manufacture of the silicon single crystal, first, the raw material 2 in the vitreous silica crucible 1 is heated in a furnace to generate a silicon melt 3 (step S16). As shown in FIG. 3, for example, the silicon melt 3 is generated by maintaining 1580□ for about 25 hours after heating by a heater while controlling the inside of the furnace and raising the temperature from normal temperature to 1580□ over about 5 hours. Next, after lowering the temperature in the furnace to 1500□, a dipping process is performed to clip the seed crystal in the silicon melt while controlling the descending speed of the seed crystal and the up-and-down movement of the vitreous silica crucible (step S17). Thereafter, while controlling the pulling speed and the up-and-down movement of the vitreous silica crucible over about 100 hours, the clipped seed crystal is slowly pulled while controlling the descending speed of the silicon melt, so that a pulling process of the silicon single crystal is performed (step S18).

[0055] When the pulling of the silicon single crystal is completed, the silicon single crystal is taken out from the pulling furnace (CZ furnace) (step S19). At this time, whether or not a subsequent pulling of a silicon single crystal is performed by the multi-pulling method is determined (step S20), and in the case where the pulling is performed, the weight of the taken out silicon single crystal is measured (step S21). Then, the residual amount of the melt in the vitreous silica crucible is calculated from the weight of the taken out silicon single crystal (step S22), the initial liquid surface level H.sub.2 for pulling the subsequent silicon single crystal is set (step S23), and the initial liquid surface level H.sub.2 is set as the predictive value of the next initial liquid surface level H.sub.1 (return to step 12). At that time, it is important to set it lower than the initial liquid surface level H.sub.1 for the previous pulling of the silicon single crystal.

[0056] As described above, in the method of manufacturing a silicon single crystal according to the present embodiment, the volume of the silicon melt satisfying the predetermined initial liquid surface level is obtained from the three-dimensional shape of the vitreous silica crucible, the weight of the silicon melt having the volume is obtained, and the raw material of this weight is filled in the vitreous silica crucible, so it is possible to accurately match the actual initial liquid surface level with the predictive value. Therefore, the dipping control can be performed very easily. That is, the seed crystal can be reliably dipped, and also the seed crystal will not descend too much below the initial liquid surface level to be melted. Particularly, since the seed crystal can be descended at a high speed to a level very close to the liquid surface, the time it takes to clip the seed crystal can be shortened. In addition, even in the second and subsequent pulling in the multi-pulling method, it is possible to accurately adjust the actual initial liquid surface level to match the predictive value as in the first time.

[0057] FIG. 4 is a photograph showing the corrosion occurred on the circumference of the inner surface of the vitreous silica crucible which is generated in the necking process from the clipping at the time of the first pulling of the silicon single crystal.

[0058] As shown in FIG. 4, on the inner surface of the vitreous silica crucible after the first pulling of the silicon single crystal, a band-shaped groove recessed with respect to the wall direction is formed on the circumference. At the initial liquid surface level at the start of the pulling of the silicon single crystal, the operation at the same liquid surface level is carried out for several hours for the necking process from the dipping of the seed crystal. On the inner surface of the vitreous silica crucible at the initial liquid surface level at this time, three phases of the silicon melt, the vitreous silica, and the atmospheric gas in the pulling furnace are in contact with the inner surface of the vitreous silica crucible. In this portion, the reaction between the vitreous silica and the silicon melt is quick, the inner surface of the vitreous silica crucible is corroded and a groove is formed, and fine silica crystals are deposited on the inner surface of the vitreous silica crucible.

[0059] In the multi-pulling, the first pulling of the silicon single crystal is completed, and the vitreous silica crucible used for the first pulling the silicon single crystal is filled again with polycrystalline silicon and the polycrystalline silicon is melted, without replacing the vitreous silica crucible. The second and the subsequent pulling of the silicon single crystal are performed in the same vitreous silica crucible. At this time, when the liquid surface of the silicon melt passes through the band-shaped groove portion where the silica crystals are deposited at the time of pulling the first one, since the silica crystals attached to the groove portion of the vitreous silica crucible are peeled off and enter the silicon melt, crystal defects are caused. Further, since the vitreous silica crucible is provided with a high-purity region on the inner surface, the high-purity region is lost when the groove becomes deeper, and the metal impurities are eluted from the region where the purity of the vitreous silica crucible is low and adversely affect the purity of the silicon single crystal.

[0060] Therefore, in the second and subsequent CZ pulling, it is necessary to avoid the corrosion position of several millimeters of recesses in the wall direction generated on the circumference of the inner surface of the vitreous silica crucible at the first pulling. When the corrosion of the inner surface of the vitreous silica crucible is large, the transparent vitreous silica portion on the innermost surface disappears and the necking process (eliminating of the seed dislocation) does not go well. Accordingly, it is possible to determine the filling amount of the silicon raw material to be charged additionally as to form the liquid surface level avoiding the corrosion position on the circumference of the inner surface of the vitreous silica crucible generated at the first CZ pulling. The liquid surface level at the second CZ pulling falls in the depth direction of the vitreous silica crucible by about 10 mm below the first liquid surface level. Thereafter, the same operation as above can be performed even in the third time and the fourth time.

[0061] FIG. 5 is a schematic view showing one example of the entire configuration of the silicon single crystal manufacturing system of the present embodiment. This silicon single crystal manufacturing system 1000 includes: a pulling furnace 20 for pulling a silicon single crystal; a pulling furnace control section 30 for controlling the pulling condition of the pulling furnace 20; a silicon raw material measuring section 40 for measuring the weight of the silicon raw material filled in a vitreous silica crucible provided in the pulling furnace 20; and a measuring system section 100 for measuring the three-dimensional shape of the inner surface of the vitreous silica crucible provided in the pulling furnace and obtaining the predictive value of the initial liquid surface level. In addition, each unit is connected by a communication network for exchanging the obtained information.

[0062] The pulling furnace 20 is a general CZ method pulling furnace, or a multi-pulling furnace equipped with a re-charging mechanism. And in addition to a carbon susceptor for disposing the vitreous silica crucible whose three-dimensional shape has been measured, a single crystal weight measuring mechanism for measuring the weight of the silicon single crystal, a crucible lifting mechanism for moving the vitreous silica crucible up and down, and a heater for heating the silicon raw material and the silicon melt are provided. Further, in the case of the multi-pulling furnace, a charging mechanism for adding silicon raw material to the silicon melt is also provided.

[0063] In the pulling furnace control section 30, a pulling speed control unit 301 for controlling the up-and-down moving speed of the seed crystal and the pulling speed of the silicon single crystal, a crucible up-and-down moving speed setting unit 302 for controlling the up-and-down position and the up-and-down moving speed of the vitreous silica crucible, a heating temperature setting unit 303 for controlling the temperature of the silicon melt with a heater, a single crystal weight calculating unit 304 for calculating the weight of the pulled silicon single crystal and the like are provided.

[0064] In the measuring system section 100, a measuring unit 101 for measuring the three-dimensional shape of the inner surface of the vitreous silica crucible 1, and an analysis/calculation unit 102 performing the analysis for obtaining the measured data and the predictive value of the initial liquid surface level are provided. The analysis/calculation unit 102 includes an image processing unit 106. Further, the analysis/calculation unit 102 is provided with a database engine 103 for storing the measured data, and a CAE system 104 and a CAD system 105 for calculating the volume V and the initial liquid surface level H.sub.1, H.sub.2. The measuring system section 100 will be described later.

[0065] FIG. 6 is a schematic view showing one example of the measuring system section 100 for measuring the three-dimensional shape of the inner surface of the vitreous silica crucible 1.

[0066] As shown in FIG. 6, there is a measuring unit 101 in this measuring system section 100. The measuring unit 101 includes a cylindrical rotating base 11 for supporting the vitreous silica crucible 1 with its opening facing downward; an arm robot 12 that is provided inside the rotating base 11 and inside the vitreous silica crucible 1; and a distance measuring device 13 provided at the tip of the arm 12a of the arm robot 12. The arm robot 12 is provided inside the cylindrical rotating base 11, and fixedly disposed without rotating together with the rotating base 11.

[0067] The arm robot 12 can make the distance measuring device 13 move along the inner surface of the vitreous silica crucible 1. In particular, the arm 12a does not move in the circumferential direction of vitreous silica crucible 1, but moves only in the radial direction and the height direction of the vitreous silica crucible 1, so that the distance measuring device 13 moves from the rim of the vitreous silica crucible 1 toward the center of the bottom portion in the arrow A direction. Further, the movement of the distance measuring device 13 in the circumferential direction (arrow B direction) of the vitreous silica crucible is performed by rotating the rotating base 11, not the arm robot 12, but the movement may also be performed by the arm robot 12.

[0068] The distance measuring device 13 optically measures the distance from a reference point to one point on the inner surface of the vitreous silica crucible 1, sets the center of the bottom portion of the vitreous silica crucible 1 as the origin of the cylindrical coordinates system, and adds the distance from this origin to the reference point of the distance measuring device 13, so as to calculate the spatial coordinate of one point on the inner surface of the vitreous silica crucible 1. This measurement is performed with respect to the entire inner surface of the vitreous silica crucible. Since the measuring system section 100 measures a very large number of points of at least 10,000 points or more, preferably 30,000 points or more, it is possible to measure the three-dimensional shape of the inner surface of the vitreous silica crucible 1 with high accuracy.

[0069] The spatial coordinate (x, θ.sub.0, z) of an arbitrary point on the inner surface of the vitreous silica crucible necessary for the position control of the arm robot 12 can be obtained by using a function formula of a design model of the vitreous silica crucible. By using the function formula, even when changing the measuring pitch arbitrarily, the coordinate position of the arm robot 12 can be accurately calculated and determined. When θ.sub.0 is a fixed value, the coordinate (x, z) of an arbitrary point on the inner surface of the vitreous silica crucible can be expressed as follows by using the vitreous silica crucible diameter D, the vitreous silica crucible height H, the curvature radius R of the bottom portion of the vitreous silica crucible, the curvature radius r of the curved portion (R portion) of the vitreous silica crucible, and the parameters α, θ, t.

TABLE-US-00001 <Sidewall Portion of Vitreous Silica Crucible>  x=D/2  z= (H−R+α.sup.1/2) t+R−α.sup.1/2 <Curved Portion of Vitreous Silica Crucible>  x=rcos {−(π/2−θ) t} +D/2−r  z=rsin {−(π/2−θ) t} +R−α.sup.1/2 <Bottom Portion of Vitreous Silica Crucible>  x=Rcos (θt−π/2)  z=Rsin (θt−π/2) +R

[0070] Incidentally, θ is an intersection point angle of the curvature radius R of the bottom portion of the vitreous silica crucible intersecting with the curved portion of the vitreous silica crucible. The parameters α, θ, and t are represented by the following formula.

α=(R−2r+D/2)(R−D/2)

θ=arctan {(D/2−r)/α.sup.1/2}

t=0 to 1

[0071] By defining the coordinate (x, z) of an arbitrary point on the inner surface of the vitreous silica crucible in this manner, the three-dimensional shape of the inner surface of the vitreous silica crucible can be represented as a continuous function, and an accurate measurement can be performed efficiently.

[0072] Further, not only in the sidewall portion of the vitreous silica crucible which is a region where the inner diameter of the vitreous silica crucible is substantially constant, but also in the curved portion of the vitreous silica crucible and in the bottom portion of the vitreous silica crucible which are regions where the inner diameter of the vitreous silica crucible is changed, an accurate measurement can be performed. Based on the measured three-dimensional shape, it is possible to predict the initial liquid surface level of the silicon melt, and the moving speed (descending speed) of the liquid surface position at the time of pulling the silicon single crystal.

[0073] FIG. 7 is an approximately perspective view showing the three-dimensional shape of the inner surface of the vitreous silica crucible which is specified by the measured value.

[0074] As shown in FIG. 7, the three-dimensional shape of the inner surface of the vitreous silica crucible 1 is specified by a collection of a large number of measurement points (spatial coordinates). Here, the measurement point is an intersection point of the vertical line and the horizontal line, and the three-dimensional shape of the inner surface of the vitreous silica crucible can be represented by a combination of polygons having each of a large number of measurement points as a vertex coordinate. By reducing the mesh size of the polygon, the measurement accuracy of the three-dimensional shape of the vitreous silica crucible can be increased, and the capacity of the vitreous silica crucible is possible to be accurately obtained.

[0075] The spatial coordinate data of the inner surface of the vitreous silica crucible 1 measured in this manner together with the weight data of the silicon raw material and the weight data of the silicon single crystal are put in the CAE (Computer Aided Engineering) system 104 or the control CAD system 105 of the computer 15 provided in the analysis/calculation unit 102, and the volume V and the initial liquid surface level H are calculated.

[0076] FIG. 8 is a schematic view showing another example of the measuring system for measuring the three-dimensional shape of the inner surface of the vitreous silica crucible 1.

[0077] As shown in FIG. 8, the measurement of the three-dimensional shape of the inner surface of the vitreous silica crucible 1 may be performed simultaneously with the photographing of the inner surface using a CCD camera 14. In this case, the CCD camera 14 and the distance measuring device 13 are mounted together at the tip of the arm 12a of the arm robot 12, and the coordinates of each point on the inner surface are also measured by the distance measuring device 13, while the inner surface is scanned by the CCD camera 14. As one of the quality inspection of the vitreous silica crucible 1, there are observation inspections for the presence or absence of scratches or deformations on the inner surface of the vitreous silica crucible, bubbles at the outermost surface layer, adhesion of dust and the like. By performing the measurement of the three-dimensional shape of the inner surface of the vitreous silica crucible 1 while performing this observation inspection automatically by image processing on the image photographed by the CCD camera 14, it is possible to omit the process of measuring the three-dimensional shape independently. Therefore, it is possible to improve the efficiency of the inspection/measurement process using the arm robot 12.

[0078] FIG. 9 is a flowchart showing the manufacturing method of a silicon single crystal according to the second embodiment of the present disclosure.

[0079] As shown in FIG. 9, in the manufacture of the silicon single crystal according to the present embodiment, first, a vitreous silica crucible is prepared, and the three-dimensional shape of the inner surface of the vitreous silica crucible is measured (step S31). The measuring method of the three-dimensional shape of the inner surface of the vitreous silica crucible is as described above.

[0080] Next, a predetermined amount of silicon raw material 2 to be filled in the vitreous silica crucible 1 is prepared, and the weight M (g) of this raw material 2 is measured (step S32). The raw material 2 is a polycrystalline silicon block, and an appropriate amount may be prepared according to the size of the vitreous silica crucible to be used. The method for measuring the weight is not particularly limited as long as it can ensure certain measurement accuracy.

[0081] Next, the volume V (m.sup.3) of the silicon melt 3 when the raw material 2 having the weight M has been melted is obtained (step S33), and the predictive value of the initial liquid surface level H.sub.1 (m) of the silicon melt 3 filled in the vitreous silica crucible 1 is obtained from the volume V of the silicon melt 3 and the three-dimensional shape of the inner surface of the vitreous silica crucible 1 (step S34). Next, it is determined whether the predictive value of the initial liquid surface level H.sub.1 is appropriate (step S35). Here, it is determined whether the predictive value of the initial liquid surface level is lower than the height H.sub.0 of the vitreous silica crucible. Or in the case of the second and subsequent pulling of the multi-pulling, it is determined whether the predictive value of the initial liquid surface level is a range lower than the previous initial liquid surface level. When the predictive value of the initial liquid surface level is not appropriate, the measurement of the raw material is performed again (return to step S32). Incidentally, the calculation of the predictive value of the initial liquid surface level H.sub.1 can be performed at any time, as long as the weight M of the raw material 2 to be filled in the vitreous silica crucible 1 has been determined and before the dipping process of the seed crystal is performed. The specific gravity of the silicon melt is 2.6×10.sup.6 (g/m.sup.3), the relational expression between the volume V (m.sup.3) and the weight M (g) of the silicon raw material is V=M/2.6×10.sup.6.

[0082] Thereafter, the prepared raw material 2 is filled in the vitreous silica crucible 1 (step S36), and the manufacture of the silicon single crystal is started. In the manufacture of the silicon single crystal, first, the raw material 2 in the vitreous silica crucible 1 is heated in a furnace to generate a silicon melt 3 (step S37). As shown in FIG. 3, for example, the silicon melt 3 is generated by maintaining 1580□ for about 25 hours after heating the inside of the furnace and raising the temperature from normal temperature to 1580□ over about 5 hours. Next, after lowering the temperature in the furnace to 1500□, a dipping process is performed to clip the seed crystal in the silicon melt 3 (step S38). Thereafter, a pulling process of the silicon single crystal is performed to slowly pull the dipped seed crystal over about 100 hours or longer (step S39). The pulling process of the silicon single crystal from the dipping process of the seed crystal is the same as in the embodiment 1.

[0083] When the pulling of the silicon single crystal is completed, the silicon single crystal is taken out from the CZ furnace (step S40). Therefore, whether or not the pulling of the subsequent silicon single crystal is performed by the multi-pulling method is determined (step S41), and in the case where the pulling is performed, the weight of the taken out silicon single crystal is measured (step S42). Then, the residual amount of the melt in the vitreous silica crucible is calculated from the weight of the taken out silicon single crystal (step SS43), and the range of the initial liquid surface level H.sub.2 for the subsequent pulling of the silicon single crystal is set. At that time, a range lower than the initial liquid surface level H.sub.1 for the previous pulling of the silicon single crystal is set (step S44). Thereafter, for the subsequent pulling of the silicon single crystal, a predetermined amount of silicon raw material 2 to be filled in the vitreous silica crucible 1 is prepared, and the weight M (g) of this raw material 2 is measured (return to step S32).

[0084] As described above, in the manufacturing method of the silicon single crystal according to the present embodiment, since the predictive value of the initial liquid surface level is accurately obtained before starting the dipping process of the seed crystal, the clipping control can be very easily performed. That is, the seed crystal can be reliably dipped, and also the seed crystal will not descend too much below the initial liquid surface level to be melted. Particularly, since the seed crystal can be descended at a high speed to a level very close to the liquid surface, the time it takes to dip the seed crystal can be shortened. A multi-pulling is also possible.

[0085] It is obvious that the present disclosure is not limited to the above embodiments and that various modifications can be made without departing from the spirit of the present disclosure and these modifications are also included in the present disclosure.

[0086] For example, in the above embodiments, a manufacturing method of the silicon single crystal using the vitreous silica crucible has been mentioned, but the present disclosure is not limited thereto, and other manufacturing methods of the single crystal may be used. The crucible used in the manufacture of the single crystal is not limited to the vitreous silica crucible. However, since the very large-sized crucible with large capacity is used in the manufacture of the silicon single crystal, the effect of the present disclosure is remarkable.

[0087] Further, in the above-mentioned embodiment, the case where the measurement performed simultaneously with the measurement of the three-dimensional shape of the inner surface of the vitreous silica crucible 1 is the photographing of the inner surface by the CCD camera, but the present disclosure is not limited to such a case and any measurement item may be used as long as it is an item different from the three-dimensional shape, such as FT-IR measurement.

EXPLANATION OF REFERENCE SYMBOLS

[0088] 1 vitreous silica crucible [0089] 2 silicon raw material [0090] 3 silicon melt [0091] 10 measuring system [0092] 11 rotating base [0093] 12 arm robot [0094] 12a arm [0095] 13 distance measuring device [0096] 14 camera [0097] 15 computer [0098] 20 pulling furnace [0099] 30 pulling furnace control section [0100] 40 silicon raw material measuring section [0101] 100 measuring system section [0102] 101 measuring unit [0103] 102 analysis/calculation unit [0104] 103 database engine [0105] 104 CAE system [0106] 105 CAD system [0107] 106 image processing unit [0108] 301 speed control unit [0109] 302 crucible up-and-down moving speed setting unit [0110] 303 heating temperature setting unit [0111] 304 single crystal weight calculating unit [0112] 1000 silicon single crystal manufacturing system