JP2012250866A - Semiconductor single crystal pulling process and pulling apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor single crystal pulling process which manufactures a high quality semiconductor single crystal by decreasing the diameter variation of the semiconductor single crystal, controlling the variation of the pulling rate that is the manipulated variable of the diameter control and pulling the semiconductor single crystal as set.SOLUTION: The semiconductor single crystal pulling process comprises the steps of retaining a semiconductor melt 14 in a crucible 13 by melting a semiconductor raw material with a heater 18, and pulling the semiconductor single crystal 11 while controlling the heater 18 based on the temperature profile as set in advance. The pulling data for the past semiconductor single crystal 11 which contributes to the setting of the temperature profile of the heater 18 is accumulated in the data base and the temperature profile of the heater 18 for the semiconductor single crystal 11 that is pulled next from the pulling data for the past semiconductor single crystal 11 is evaluated based on a particular evaluation function. Then, the temperature profile of the heater 18 for the semiconductor single crystal 11 to be pulled next based on the particular evaluation function is amended before the pulling and the semiconductor single crystal 11 is pulled while controlling the heater 18 based on the amended temperature profile.

Description

  The present invention relates to a method for pulling a semiconductor single crystal such as a silicon single crystal and an apparatus for pulling the semiconductor single crystal.

  Conventionally, as a method for pulling up this type of semiconductor single crystal, when the silicon single crystal is produced by pulling up the seed crystal from the silicon melt melted by the heater by the Czochralski method, the diameter of the silicon single crystal is detected, A method for producing a silicon single crystal is disclosed in which the detected diameter is fed back to the pulling speed and the temperature of the heater to pull the silicon single crystal while controlling its diameter (see, for example, Patent Document 1). In this silicon single crystal manufacturing method, the control value of the pulling speed is calculated by comparing the detected diameter of the silicon single crystal with the set diameter, and the pulling speed span is limited to the pulling speed control value so that the fluctuation range is Calculate the temperature correction amount of the heater by obtaining the output of the limited pulling speed and comparing the pulling speed control value with the set pulling speed before limiting the span to the calculated pulling speed control value. The temperature setting output of the heater is obtained, and the diameter of the silicon single crystal is controlled by controlling the pulling speed and the heater temperature by the pulling speed output and the heater temperature setting output.

  In the method of manufacturing a silicon single crystal configured in this way, the calculated temperature correction amount changes dynamically even though the pulling speed of the silicon single crystal is limited. Make up for things you can't control. As a result, the diameter controllability is improved, and a good single crystal with little diameter fluctuation can be obtained.

  On the other hand, when a single crystal is grown by the Czochralski method by setting a heating temperature pattern in advance, the response characteristic that the heating temperature of the heating means for heating the raw material melt affects the diameter of the single crystal, By subdividing the changing heating temperature at regular time intervals, specifying the amount of diameter change corresponding to each step change amount, comparing the diameter of the single crystal that can be overlapped with these diameter change amounts and the target diameter, By adjusting so as to eliminate these errors, the time-dependent change of the diameter of the single crystal with respect to the heating temperature pattern is predicted at least for each single crystal growth device or for each history of parts constituting the single crystal growth device. The raw material melt is heated on the basis of a heating temperature pattern determined by adjusting the predicted diameter value and the pulling length or pulling time so as to match the preset diameter target value. Method for growing single crystals is disclosed (for example, see Patent Document 2.). In this single crystal growth method, the heating temperature pattern subdivides the heating temperature that changes during the growth process of the single crystal at regular intervals to identify the diameter change amount corresponding to each step change amount, and It is determined by comparing the diameter of the single crystal formed by superimposing the diameter variation and the target diameter, and adjusting so as to eliminate these errors.

  In the method of growing a single crystal thus configured, the raw material melt is heated based on a predetermined heating temperature pattern, so that even a single crystal having a large diameter can be grown while accurately controlling its diameter. it can. In particular, it is suitable for shape control of the shoulder part up to the straight body part which becomes the target diameter of the single crystal. Further, it is possible to absorb the influence on the diameter of the heating temperature pattern, which is different for each single crystal growing apparatus or for each history of parts constituting the single crystal growing apparatus. That is, the heating temperature is subdivided, and the temperature (step change) changed in each part changes the diameter of the single crystal, and fine adjustment is possible by measuring the change in the diameter of the single crystal finely. Become. As a result, the best heating temperature pattern can be obtained by finely adjusting the diameter of the single crystal formed by superimposing the diameter variation in each part, that is, by finely adjusting so as to eliminate the error from the target diameter. It can be created.

JP 2001-316199 A (Claim 1, paragraph [0015]) Japanese Patent No. 4039055 (Claims 1 and 2, paragraphs [0011] and [0013])

  However, in the conventional method for producing a silicon single crystal disclosed in Patent Document 1, in order to control the diameter of the silicon single crystal, it is necessary to greatly increase the pulling speed of the silicon single crystal. The ratio V / G between the pulling speed V and the temperature gradient G in the pulling direction of the silicon single crystal fluctuates, resulting in a variation in the quality of the silicon single crystal. Further, the conventional single crystal growth method disclosed in Patent Document 2 does not predict the disturbance during the pulling of the single crystal to be pulled next, and therefore heats the disturbance expected during the pulling of the single crystal. When the single crystal growth method of Patent Document 2 is applied to the control for pulling up the diameter of the straight body of the single crystal to be constant because the temperature pattern is not taken into account, the diameter variation of the single crystal increases. was there.

  The object of the present invention is to reduce the fluctuation in the diameter of the semiconductor single crystal, to suppress the fluctuation in the pulling speed, which is the operation amount for controlling the diameter of the semiconductor single crystal, and to realize the pulling of the semiconductor single crystal as set. Thus, it is an object of the present invention to provide a semiconductor single crystal pulling method and a pulling apparatus for manufacturing a high quality semiconductor single crystal.

  According to a first aspect of the present invention, a semiconductor raw material supplied to a crucible of a semiconductor single crystal pulling apparatus is melted by a heater, a semiconductor melt is stored in the crucible, and a temperature profile preset in the pulling apparatus is used. In a method for pulling a semiconductor single crystal that pulls the semiconductor single crystal from the semiconductor melt in the crucible while controlling the heater, a step of accumulating in the database past pulling data of the semiconductor single crystal that contributes to setting of the temperature profile of the heater; The process of evaluating the temperature profile of the next semiconductor single crystal heater to be pulled up from the past semiconductor single crystal pull-up data stored in the database based on the specific evaluation function, and then based on this specific evaluation function The process of modifying the temperature profile of the semiconductor single crystal heater to be raised before pulling, and this modified temperature profile. Characterized in that it comprises a step of pulling up the semiconductor single crystal from the semiconductor melt in the crucible while controlling the heater based on Le.

  A second aspect of the present invention is an invention based on the first aspect, wherein the specific evaluation function is further fed back to the temperature profile of the next semiconductor single crystal heater to be pulled up. The reliability determined from the proximity of the set value and actual value of the heater temperature profile, the set pulling condition of the next semiconductor single crystal to be pulled up, and the temperature profile of the next semiconductor single crystal heater to be pulled up The weighting factor determined from the set pulling condition and the proximity of the actual pulling condition when comparing with the actual pulling condition of the pulling data of the past semiconductor single crystal to be fed back, Based on the reliability and the weighting factor, the temperature profile of the next semiconductor single crystal heater is corrected.

  A third aspect of the present invention is an invention based on the first or second aspect, and further includes a semiconductor single crystal to be pulled next so that the temperature profile of the heater of the next semiconductor single crystal to be pulled is kept continuous. The heater has a leveling function for correcting the temperature profile of the heater.

  A fourth aspect of the present invention is an invention based on the first or second aspect, and is further fed back to the next semiconductor single crystal pulling data and the next semiconductor single crystal heater temperature profile. The semiconductor single crystal to which the difference between one or both of the component used for pulling the semiconductor single crystal and the pulling condition of the semiconductor single crystal is compared with the pulling data of the past semiconductor single crystal This is characterized in that the temperature profile of the heater of the semiconductor single crystal to be pulled up next is corrected in terms of the temperature setting value of the heater.

  According to a fifth aspect of the present invention, the semiconductor raw material supplied to the crucible is melted by the heater, the semiconductor melt is stored in the crucible, and the controller controls the heater based on a preset temperature profile. In a semiconductor single crystal pulling apparatus configured to pull a semiconductor single crystal from a semiconductor melt, the controller accumulates past pulling data of the semiconductor single crystal contributing to setting of the temperature profile of the heater in the database, and the database The semiconductor single crystal heater temperature profile to be pulled up next is evaluated based on a specific evaluation function based on the previous semiconductor single crystal pull-up data stored in Modify the temperature profile of the crystal heater before pulling up, and based on this modified temperature profile Characterized in that it consists of a semiconductor melt in the crucible so as to pull the semiconductor single crystal while controlling the over data.

  A sixth aspect of the present invention is an invention based on the fifth aspect, wherein the specific evaluation function is further fed back to the temperature profile of the next semiconductor single crystal heater to be pulled up. It is fed back to the reliability determined from the proximity of the set value and actual value of the temperature profile of the heater, the set pulling condition of the next semiconductor single crystal to be pulled up, and the temperature profile of the heater of the next single semiconductor crystal to be pulled up A weighting factor determined from the set pulling condition and the proximity of the actual pulling condition when compared with the actual pulling condition of the pulling data of the past semiconductor single crystal, and the controller has the reliability and weighting coefficient Based on the above, the temperature profile of the next semiconductor single crystal heater to be pulled up is modified.

  A seventh aspect of the present invention is the invention based on the fifth or sixth aspect, and the controller further increases the temperature profile of the next semiconductor single crystal heater so that the temperature profile of the heater is increased continuously. It has a leveling function for correcting the temperature profile of a semiconductor single crystal heater.

  An eighth aspect of the present invention is an invention based on the fifth or sixth aspect, wherein the controller further includes pulling data of the next semiconductor single crystal to be pulled up and a temperature profile of the next semiconductor single crystal heater to be pulled up. In comparison with the pulling data of the past semiconductor single crystal fed back to the semiconductor single crystal, the difference between either or both of the constituent member used for pulling up the semiconductor single crystal and the pulling conditions of the semiconductor single crystal is determined. The temperature profile of the heater of the semiconductor single crystal, which is converted to the temperature set value of the heater of the crystal and then pulled up, is corrected.

  In the pulling method according to the first aspect and the pulling apparatus according to the fifth aspect of the present invention, the pulling data of the past semiconductor single crystal contributing to the setting of the temperature profile of the heater is accumulated in a database, and the past semiconductor single crystal The temperature profile of the next semiconductor single crystal heater to be pulled up from the pull-up data is evaluated based on a specific evaluation function, and the temperature profile of the next semiconductor single crystal heater to be pulled up based on this specific evaluation function is Further, the semiconductor single crystal is pulled up while controlling the heater based on the corrected temperature profile, so that the fluctuation in the diameter of the semiconductor single crystal is reduced, and the pulling speed, which is the operation amount of the diameter control of the semiconductor single crystal, is reduced. Variations can be suppressed. As a result, it is possible to manufacture a high-quality semiconductor single crystal by realizing the pulling of the semiconductor single crystal as set. Compared with the conventional method for producing a silicon single crystal, which requires a large operation of the pulling speed of the silicon single crystal in order to control the diameter of the silicon single crystal, in the present invention, the operation of the pulling speed of the semiconductor single crystal is controlled. Since it can be suppressed to the necessary minimum, fluctuations in the ratio V / G between the pulling rate V of the semiconductor single crystal and the temperature gradient G in the pulling direction of the semiconductor single crystal are suppressed, and variations in the quality of the semiconductor single crystal can be reduced. . That is, in the present invention, the variation in the ratio V / G is suppressed by suppressing the variation in diameter. Furthermore, the disturbance during pulling of the next single crystal to be pulled up is not predicted, and therefore the expected disturbance is not taken into account in the heating temperature pattern. Compared with the conventional method for growing a single crystal, in which the crystal diameter fluctuation may be large, the present invention determines the temperature profile of the next semiconductor single crystal heater from the pulling data of the past semiconductor single crystal. By evaluating the temperature profile of the next semiconductor single crystal heater to be evaluated based on this specific evaluation function and modifying the temperature profile of the next semiconductor single crystal heater based on this specific evaluation function, it is expected during the next semiconductor single crystal pulling. Therefore, even if the straight body portion of the semiconductor single crystal is pulled up, fluctuations in the diameter can be suppressed and the target diameter can be maintained.

  In the pulling method according to the second aspect and the pulling apparatus according to the sixth aspect of the present invention, the temperature profile of the next semiconductor single crystal heater to be pulled is corrected before pulling based on the reliability and weighting factor of the specific evaluation function. Therefore, similarly to the above, by realizing the pulling of the semiconductor single crystal as set, it is possible to manufacture a high-quality semiconductor single crystal and to achieve high accuracy of the temperature profile of the heater.

  In the pulling method according to the third aspect and the pulling apparatus according to the seventh aspect of the present invention, the temperature profile is corrected so that the temperature profile of the next semiconductor single crystal heater is maintained by the smoothing function. Therefore, when the slope of the temperature profile of the heater becomes uneven in a certain section during the pulling of the semiconductor single crystal, the unevenness is relaxed to approach the average value of the slope of the temperature profile in that section. As a result, large irregularities generated in the temperature profile of the heater can be reduced.

  In the pulling method according to the fourth aspect and the pulling apparatus according to the eighth aspect of the present invention, the difference between one or both of the constituent member used for pulling the semiconductor single crystal and the pulling condition of the semiconductor single crystal is next pulled. By converting to the temperature setting value of the semiconductor single crystal heater to be raised, the disturbance expected during the pulling is predicted with high accuracy and the temperature profile of the semiconductor single crystal heater to be raised next is corrected. The disturbance expected during the pulling of the semiconductor single crystal is further added to the heating temperature pattern, and the temperature profile of the heater can be further improved.

It is a longitudinal cross-sectional block diagram of the pulling apparatus of the silicon single crystal of embodiment of this invention. It is a figure which shows the change of the temperature gradient deviation (difference between the setting value of a heater temperature gradient, and a track record value) with respect to the change of the pulling length of the past silicon single crystal. It is a figure which shows the change of the acceptance rate (acceptance rate with respect to the threshold value set to the temperature inclination deviation of a heater) with respect to the change of the pulling length of the past silicon single crystal. It is a figure which shows the state before and behind equalizing a heater temperature inclination by the factor 0.8. It is a figure which shows the state before and after leveling a heater temperature inclination by the leveling coefficient of 0.2. It is a flowchart figure which shows the procedure which corrects and determines a heater temperature profile before pulling up the silicon single crystal. It is a figure which shows the change of the diameter standardization value [(diameter data-diameter average value) / standard deviation] of the silicon single crystal with respect to the change of the pulling rate of the silicon single crystal of Example 1. It is a figure which shows the change of the diameter standardization value [(diameter data-diameter average value) / standard deviation] of the silicon single crystal with respect to the change of the pulling rate of the silicon single crystal of Comparative Example 1.

  Next, an embodiment for carrying out the present invention will be described with reference to the drawings. As shown in FIG. 1, the pulling device for the silicon single crystal 11 includes a main chamber 12 configured to be vacuumable inside, and a crucible 13 provided in the center of the chamber 12. The main chamber 12 is a cylindrical vacuum container. The crucible 13 includes a bottomed cylindrical inner layer container 13a formed of quartz and storing the silicon melt 14, and a bottomed cylindrical outer layer container 13b formed of graphite and fitted to the outside of the inner layer container 13a. It consists of. The upper end of the shaft 16 is connected to the bottom of the outer layer container 13b, and a crucible driving means 17 for rotating and raising / lowering the crucible 13 via the shaft 16 is provided at the lower end of the shaft 16. Further, the outer peripheral surface of the crucible 13 is surrounded by a cylindrical heater 18 at a predetermined interval from the outer peripheral surface of the crucible 13, and the outer peripheral surface of the heater 18 is predetermined from the outer peripheral surface of the heater 18 by a cylindrical heat retaining cylinder 19. Surrounded at intervals.

  On the other hand, a cylindrical pull chamber 21 having a smaller diameter than the main chamber 12 is connected to the upper end of the main chamber 12 so as to communicate with the inside. A pulling rotation means 22 is provided at the upper end of the pull chamber 21. The pulling rotation means 22 is configured to move up and down a pulling shaft 24 with a seed chuck 23 attached to the lower end, and to rotate the pulling shaft 24 about its axis. A seed crystal 26 is detachably attached to the seed chuck 23. After immersing the lower end of the seed crystal 26 in the silicon melt 14, the seed crystal 26 is rotated and pulled up by the pulling and rotating means 22, and the crucible 13 is rotated and raised by the crucible driving means 17, thereby The silicon single crystal 11 is pulled up and pulled up from the lower end of the crystal 26.

  An inert gas such as argon gas is circulated in the main chamber 12. One end of a gas supply pipe 27 is connected to the side wall of the pull chamber 21, and the other end of the gas supply pipe 27 is connected to a tank (not shown) for storing an inert gas. One end of a gas discharge pipe 28 is connected to the lower wall of the main chamber 12, and the other end of the gas discharge pipe 28 is connected to the suction port of the vacuum pump 29. The inert gas in the tank is introduced into the pull chamber 21 through the gas supply pipe 27, passes through the main chamber 12, and is then discharged from the main chamber 12 through the gas discharge pipe 28. . The gas supply pipe 27 and the gas discharge pipe 28 are respectively provided with first and second flow rate adjusting valves 31 and 32 for adjusting the flow rate of the inert gas flowing through these pipes.

  In the main chamber 12, a heat shield 33 is provided for blocking the irradiation of the radiant heat of the heater 18 to the outer peripheral surface of the silicon single crystal 11 and rectifying the inert gas. The heat shield 33 has a truncated cone-like cylindrical body that gradually decreases in diameter as it goes downward and surrounds the outer peripheral surface of the silicon single crystal 11 pulled up from the silicon melt 14 at a predetermined interval from the outer peripheral surface. 33a and a flange portion 33b that is connected to the upper edge of the cylindrical body 33a and projects outward in a substantially horizontal direction. In the heat shield 33, the flange 33b is placed on the heat retaining cylinder 19 via the ring plate 33c, so that the lower edge of the cylinder 33a is positioned above the surface of the silicon melt 14 with a predetermined gap. In this way, it is fixed in the main chamber 12.

  On the other hand, a viewing window 12 a is formed on the shoulder of the main chamber 12. The viewing window 12 a includes a boundary portion between the silicon melt 14 and the seed crystal 26, a boundary portion between the silicon melt 14 and the neck portion 11 a of the silicon single crystal 11, and a shoulder portion between the silicon melt 14 and the silicon single crystal 11. The CCD camera 36 is installed so as to face the solid-liquid interface 34 that is the boundary between the silicon melt 14 and the straight body 11 c of the silicon single crystal 11. The CCD camera 36 is configured to photograph the silicon single crystal 11 being pulled up. Here, the CCD camera 36 accumulates signal charges generated by light in a capacitor formed by arranging metal film electrodes on a silicon substrate with an oxide film interposed therebetween, and the CCD camera 36 receives a drive pulse from the image processing means 37 and applies it. This is a camera that sequentially transfers in the direction and obtains an image signal that is an electrical signal. An image captured by the CCD camera 36 is processed by an image processing means 37. The detection output of the CCD camera 36 is connected to the camera control input of the image processing means 37, and the camera control output of the image processing means 37 is connected to the control input of the CCD camera 36. Further, the control input / output of the image processing means 37 is connected to the control input / output of the controller 38, and the control output of the controller 38 is connected to the crucible driving means 17, the heater 18 and the pulling rotation means 22. The control input / output of the controller 38 is connected to the control input / output of the image processing means 37 of all pulling devices that pull up the silicon single crystal 11 having the same diameter regardless of the type. These are connected to the crucible driving means 17, the heater 18 and the pulling rotation means 22 of all pulling devices that pull the silicon single crystal 11 having the same diameter regardless of the type.

  A storage medium 39 is connected to the controller 38. A database is stored in the storage medium 39, and the past pulling data of the silicon single crystal 11 contributing to the setting of the temperature profile of the heater 18 is accumulated in this database. The pulling data of the silicon single crystal 11 in the past includes the date when the silicon single crystal 11 is pulled, the amount of the silicon melt 14 charged into the crucible 13, the diameter of the silicon single crystal 11 taken by the CCD camera 36 at the time of pulling. Change, type of pulling device, number of pulling silicon single crystals 11 by the pulling device, next whether or not the pulling device is the same as the pulling device for pulling up the silicon single crystal 11, and parts such as the heater 18 of the pulling device were replaced. For example, the date of the withdrawal data. Examples of the storage medium 39 include an external storage medium through a network in addition to the memory.

  Further, the controller 38 is configured to evaluate the temperature profile of the heater 18 of the silicon single crystal 11 to be pulled next from the previous pulling data of the silicon single crystal 11 stored in the database based on a specific evaluation function. This specific evaluation function is determined based on the proximity of the set value and the actual value of the temperature profile of the heater 18 of the silicon single crystal 11 in the past that is fed back to the temperature profile of the heater 18 of the silicon single crystal 11 to be pulled next. Reliability, the set pulling condition of the silicon single crystal 11 to be pulled next, and the actual pulling condition of the pulling data of the past silicon single crystal 11 fed back to the temperature profile of the heater 18 of the silicon single crystal 11 to be pulled next And a weighting factor determined from the proximity of the set pulling condition and the actual pulling condition.

  The reliability is calculated by calculating the temperature gradient deviation of the heater 18 which is the difference between the set value of the temperature gradient in the minimum unit and the actual value in the temperature profile of the heater 18 of the silicon single crystal 11 pulled up in the past. After a threshold value is set for the temperature gradient deviation and the pass / fail is determined by comparing the temperature gradient deviation of the heater 18 with the threshold value, the temperature gradient deviation of the heater 18 over the entire length of the straight body portion 11c of the silicon single crystal 11 is determined. The acceptance rate is calculated, and the temperature profile of the heater 18 of the silicon single crystal 11 pulled in the past from the acceptance rate is evaluated. Specifically, as shown in FIGS. 2 and 3, the temperature gradient deviation of the heater 18 for each pulling length of 5 mm (minimum unit) is calculated as an average value, and the temperature gradient deviation of the heater 18 is a plurality of threshold values. (First threshold value: ± 0.002 ° C./5 mm, second threshold value: ± 0.003 ° C./5 mm), it is evaluated as good when smaller, and it is evaluated as defective when larger, When the ratio evaluated to be good is 80% or more, the pass rate for passing is calculated for every pulling length of 100 mm, and finally the pass rate is calculated over the entire length of the straight body portion 11c of the silicon single crystal 11. .

  In the portion surrounded by the one-dot chain line in FIG. 3, since the pass rate of the temperature gradient deviation of the heater 18 with respect to the first and second threshold values is low, it is evaluated that the setting is poor, and is surrounded by the two-dot chain line in FIG. In the portion, since the passing rate of the temperature gradient deviation of the heater 18 with respect to the first and second threshold values is high, it is evaluated that the setting is good. In this way, in the silicon single crystal 11 pulled in the past, it is possible to grasp in which range of the pulling length the pass rate of the temperature profile of the heater 18 was good or bad. When the temperature profile of the heater 18 of the silicon single crystal 11 pulled up in the past is fed back to the temperature profile of the heater 18, the feedback amount approaches 100% if the pass rate is high, and the feedback amount is set if the pass rate is low. Reliability is determined to be low. That is, the reliability for the pass rate is stored as a map in the storage medium 39, and the controller 38 is configured to determine the reliability from the pass rate. In this embodiment, it is assumed that the temperature gradient deviation of the heater for every pulling length of 5 mm is calculated as an average value, the pass rate is calculated for every pulling length of 100 mm, and the rate evaluated as good is 80. Although it was determined to be acceptable when the value was greater than or equal to%, it is not limited to these values. In this embodiment, two threshold values are set, but one or three or more threshold values may be set.

  On the other hand, the weighting factor is a function that is determined based on the proximity between the set pulling condition of the silicon single crystal 11 to be pulled next and the actual pulling condition of the silicon single crystal 11 pulled in the past. For example, when the pulling device used for the silicon single crystal 11 to be pulled next is the same as the pulling device used for the silicon single crystal 11 pulled in the past, or when the silicon single crystal 11 to be pulled next is pulled up When the pulling date / time of the silicon single crystal 11 pulled in the past is close, the weighting factor is set high. Further, even if the pulling device used for the silicon single crystal 11 to be pulled next is the same as the pulling device used for the silicon single crystal 11 pulled in the past, parts such as the heater 18 are exchanged, or Next, when the pulling date / time of the silicon single crystal 11 to be pulled is far from the pulling date / time of the silicon single crystal 11 pulled in the past, the weighting factor is set low. That is, when the temperature profile of the heater 18 of the silicon single crystal 11 that was pulled up in the past is fed back to the temperature profile of the heater 18 of the silicon single crystal 11 that is pulled up next, the feedback amount is set to 100% if the weighting factor is high. If the weight coefficient is low, the feedback amount is determined to be low. A weighting factor for the set pulling condition and the actual pulling condition is stored as a map in the storage medium 39, and the controller 38 is configured to determine the weighting factor from the set pulling condition and the actual pulling condition. As described above, the controller 38 is configured to correct the temperature profile of the heater 18 of the silicon single crystal 11 to be pulled next before pulling based on the reliability and weighting factor of the specific evaluation function.

  On the other hand, the controller 38 compares the pulling data of the silicon single crystal 11 to be pulled next with the pulling data of the silicon single crystal 11 to be fed back to the temperature profile of the heater 18 of the silicon single crystal 11 to be pulled next. The difference between one or both of the constituent members used for pulling up the silicon single crystal 11 and the pulling conditions of the silicon single crystal 11 is converted into the temperature setting value of the heater 18 of the silicon single crystal 11 to be pulled up next. It is comprised so that the temperature profile of the heater 18 of the silicon single crystal 11 pulled up may be corrected.

Further, the controller 38 has a leveling function of correcting the temperature profile of the next silicon single crystal 11 heater 18 so that the temperature profile of the next silicon single crystal 11 heater 18 is kept continuous. When the leveling value when correcting the temperature profile of the heater 18 using the leveling function is N, N = [K + (K ₀ −K) × R]. In this formula, interval K has irregularities of the temperature profile of the heater 18 which is set (hereinafter, referred to as uneven intervals) and heater temperature gradient of the minimum unit in, K ₀ is the mean value of the heater temperature gradient in the irregular section R is a ratio (hereinafter referred to as a smoothing coefficient) that approaches the average value K ₀ of the heater temperature gradient. This leveling coefficient is set as a constant in the range of 0-1. When the leveling coefficient is “0”, it indicates that the leveling is not performed, and when the leveling coefficient is “1”, it indicates that the leveling is performed up to the average value of the heater temperature gradient. The uneven section where the above leveling is executed is a section in which the minimum unit heater temperature gradient changes from diagonally upward to diagonally downward and changes diagonally upward again, or the minimum unit heater temperature gradient changes from diagonally downward to diagonally upward again. This is a section that changes diagonally downward. Further, when the neck portion 11a and the shoulder portion 11b of the silicon single crystal 11 are pulled up, the temperature profile of the heater 18 is unstable or changes greatly, so that the leveling is not performed and the straight body portion 11c of the silicon single crystal 11 is pulled up. It is set to run in at times. Furthermore, the above-mentioned leveling is preferably performed in such a manner that the unevenness of the heater temperature gradient is not completely eliminated but the ratio of the unevenness of the heater temperature gradient is reduced. For example, if the leveling coefficient is set to about 0.8, the unevenness of the temperature gradient is excessively relaxed (FIG. 4). If the leveling coefficient is set to about 0.2, the silicon single crystal 11 is pulled manually. It has been found by trial operation that it substantially matches the setting of the setter when raising (FIG. 5).

  A procedure for pulling up the silicon single crystal 11 using the pulling apparatus configured as described above will be described with reference to the flowchart of FIG. First, the controller 38 selects a pulling device to be set for the temperature profile of the heater 18 of the silicon single crystal 11 to be pulled next. Next, the controller 38 selects past pulling data to be used as reference for setting from the database in the storage medium 39 based on the pulling condition of the pulling device to be set. Then, the controller 38 calculates the weighting factor and the reliability from the pulling conditions of the past pulling data used as reference for setting. At this time, when there are a plurality of pull-up data, the controller 38 calculates the average value of these data. Next, the controller 38 calculates the temperature profile of the heater 18 to be set from the pulling data used as a reference for the weighting factor, reliability, and setting, and then uses the pulling of the silicon single crystal 11 to be set. A correction amount of the temperature profile of the heater 18 is calculated based on one or both of the member and the pulling condition, and this correction amount is added to or subtracted from the temperature profile of the heater 18 to be set. Furthermore, the controller 38 applies a smoothing function to the temperature profile of the heater 18 of the silicon single crystal 11 to be set as necessary to determine the final temperature profile of the heater 18.

  In the pulling apparatus for the silicon single crystal 11 configured as described above, past pulling data of the silicon single crystal 11 contributing to the setting of the temperature profile of the heater 18 of the silicon single crystal 11 to be pulled next is accumulated in the database. The temperature profile of the silicon single crystal 11 to be pulled next is evaluated based on the specific evaluation function from the pulling data of the silicon single crystal 11 in the past, and then based on the reliability and weighting coefficient of the specific evaluation function. The temperature profile of the heater 18 of the silicon single crystal 11 to be pulled up is corrected before pulling up, and the silicon single crystal 11 is pulled up while controlling the heater 18 based on the corrected temperature profile. Thereby, the diameter fluctuation | variation of the silicon single crystal 11 reduces, and the fluctuation | variation of the pulling speed which is the operation amount of the diameter control of the silicon single crystal 11 can be suppressed. As a result, by pulling up the silicon single crystal 11 as set, a high-quality silicon single crystal 11 can be manufactured, and the temperature profile of the heater 18 can be increased in accuracy. Further, since it is not necessary to control the pulling speed of the silicon single crystal 11, the ratio V / G between the pulling speed V of the silicon single crystal 11 and the temperature gradient G in the pulling direction of the silicon single crystal 11 does not vary, and the silicon single crystal 11 The quality of 11 does not vary. That is, since the diameter fluctuation can be reduced, the fluctuation of the ratio V / G can be suppressed. Further, the temperature profile of the heater 18 of the silicon single crystal 11 to be pulled up next is evaluated based on a specific evaluation function based on the pulling data of the silicon single crystal 11 in the past, and the silicon single to be pulled up next on the basis of this specific evaluation function. By correcting the temperature profile of the heater 18 of the crystal 11 before pulling, the disturbance expected during the pulling of the silicon single crystal 11 to be pulled next is added to the heating temperature pattern. Even if the trunk portion 11c is pulled up, the diameter does not change.

  On the other hand, the difference between either or both of the constituent members used for pulling up the silicon single crystal 11 and the pulling conditions of the silicon single crystal 11 is converted into the temperature setting value of the heater 18 of the silicon single crystal 11 to be pulled up next. Next, since the temperature profile of the heater 18 of the silicon single crystal 11 to be pulled up is corrected, a disturbance expected during the pulling of the silicon single crystal 11 to be pulled up next is further added to the heating temperature pattern. It is possible to further improve the accuracy of the temperature profile. Further, the temperature profile is corrected so that the temperature profile of the heater 18 of the silicon single crystal 11 to be pulled next is kept continuity by the leveling function, so that the heater 18 is heated in a certain section during the pulling of the silicon single crystal 11. When the inclination of the temperature profile becomes uneven, the unevenness is relaxed and brought closer to the average value of the inclination of the temperature profile in that section. As a result, large unevenness generated in the temperature profile of the heater 18 can be reduced. In the above embodiment, a silicon single crystal is used as the silicon single crystal. However, a GaAs single crystal, an InP single crystal, a ZnS single crystal, a ZnSe single crystal, or the like may be used.

Next, examples of the present invention will be described in detail together with comparative examples.
<Example 1>
Twenty pulling apparatuses shown in FIG. 1 were prepared, and these pulling apparatuses were designated as first to twentieth pulling apparatuses, and using these pulling apparatuses, a silicon single crystal 11 for manufacturing a silicon wafer having a diameter of 300 mm was pulled. . Specifically, the crucible 13 was filled with a polycrystalline silicon raw material and melted by the heater 18, and the silicon single crystals 11 for manufacturing a silicon wafer having a diameter of 300 mm were pulled up from the silicon melt 14 five times each. These pull-up data were stored in the database of the storage medium 39. Then, before pulling up the next silicon single crystal 11 using the seventh pulling device, the controller 38 determines whether the heater 18 of the silicon single crystal 11 to be pulled up next is based on the reliability and weighting factor of the specific evaluation function. The temperature profile was corrected before pulling up. Here, the controller 38 determined the reliability as follows. The temperature gradient deviation of the heater 18 for every pulling length of 5 mm is calculated as an average value, and the temperature gradient deviation of the heater 18 is calculated using two threshold values (first threshold value: ± 0.002 ° C./5 mm, second threshold value). Value: ± 0.003 ° C./5 mm), and a pass rate that is acceptable when the rate evaluated as good is 80% or more is calculated for every 100 mm of pull length, and the silicon single crystal 11 After calculating the pass rate over the entire length of the body portion 11c, the reliability was determined based on the relationship of the reliability with respect to the pass rate stored as a map in the storage medium 39.

  Further, the controller 38 compares the pulling data of the silicon single crystal 11 to be pulled next with the pulling data of the silicon single crystal 11 to be fed back to the temperature profile of the heater 18 of the silicon single crystal 11 to be pulled next. The difference between either or both of the constituent members used for pulling up the single crystal 11 and the pulling conditions of the silicon single crystal 11 is converted into the temperature setting value of the heater 18 of the silicon single crystal 11 to be pulled up next, and then pulled. The temperature profile of the heater 18 of the silicon single crystal 11 to be raised was corrected. Further, the controller 38 modified the temperature profile of the next silicon single crystal 11 heater 18 to be pulled up so that the temperature profile of the next silicon single crystal 11 heater 18 was kept continuous. Here, the leveling coefficient was set to 0.2. Further, the controller pulled the silicon single crystal 11 from the silicon melt 14 in the crucible 13 while controlling the heater 18 based on the heater temperature profile corrected and corrected as described above. This silicon single crystal was designated as Example 1.

<Comparative Example 1>
A silicon wafer having a diameter of 300 mm was formed using a tenth pulling device of the same type as the seventh pulling device of Example 1 except that the reliability and weighting factor of the specific evaluation function were not used and the smoothing function was not used. Pulled up silicon single crystal for fabrication. This silicon single crystal was designated as Comparative Example 1.

<Comparative test 1 and evaluation>
The diameter standardization value for the pulling rate of 20 to 80% of the straight body portion of the silicon single crystal of Example 1 and Comparative Example 1 was determined. The results are shown in FIGS. Here, when the pulling rate when the silicon melt stored in the crucible is all pulled up as a silicon single crystal is 100%, the straight body portion of the silicon single crystal is pulled up within the range of the pulling rate of 20 to 80%. It becomes a range. Further, the diameter standardized value Z _i of the silicon single crystal is expressed as Z _i = x _i / A, where x _i is an actual measurement value of the diameter of the silicon single crystal and A is an average value of the diameter of the silicon single crystal. . The reason for using the diameter standardized value is to facilitate comparison.

  As is apparent from FIGS. 7 and 8, the silicon single crystal of Comparative Example 1 has a large variation in diameter over the entire length, whereas the silicon single crystal of Example 1 has a small variation in diameter over the entire length. I found out. As a result, in Example 1, the variation in the pulling speed operated for the diameter control was reduced, the fluctuation of the ratio V / G was suppressed, and the quality variation was also reduced. Further, in Comparative Example 1, crystal defects were generated, whereas in Example 1, the generation of crystal defects was suppressed. As a result, in Example 1, the defect rate was halved.

11 Silicon single crystal (semiconductor single crystal)
13 Crucible 14 Silicon melt (semiconductor melt)
18 Heater

Claims (8)

The semiconductor raw material supplied to the crucible of the semiconductor single crystal pulling device is melted by a heater, the semiconductor melt is stored in the crucible, and the heater is controlled based on a temperature profile set in advance in the pulling device. In the method for pulling up a semiconductor single crystal that pulls up the semiconductor single crystal from a semiconductor melt in a crucible,
Accumulating in the database the pulling data of past semiconductor single crystals that contribute to the setting of the temperature profile of the heater;
Evaluating a temperature profile of a silicon single crystal heater to be next pulled from the pulling data of the past semiconductor single crystal accumulated in the database based on a specific evaluation function;
Correcting the temperature profile of the next semiconductor single crystal heater to be raised based on the specific evaluation function before pulling;
And pulling the semiconductor single crystal from the semiconductor melt in the crucible while controlling the heater based on the corrected temperature profile. The specific evaluation function is a reliability determined from the proximity of the set value and the actual value of the temperature profile of the past semiconductor single crystal heater that is fed back to the temperature profile of the next semiconductor single crystal heater to be pulled up. And the set pulling condition of the next semiconductor single crystal to be pulled up and the actual pulling condition of the pulling data of the past semiconductor single crystal fed back to the temperature profile of the heater of the next single semiconductor to be pulled up A weighting factor determined from the proximity of the set pulling condition and the actual pulling condition when
2. The method for pulling up a semiconductor single crystal according to claim 1, wherein a temperature profile of a heater of the semiconductor single crystal to be pulled up next is corrected based on the reliability and the weighting factor.   3. The semiconductor according to claim 1, wherein the semiconductor has a leveling function of correcting a temperature profile of the next semiconductor single crystal heater to be maintained so that a temperature profile of the next semiconductor single crystal heater is maintained continuously. A method of pulling a single crystal.   When comparing the pulling data of the next semiconductor single crystal with the pulling data of the previous semiconductor single crystal fed back to the temperature profile of the heater of the next semiconductor single crystal to be pulled up, The semiconductor single crystal to be pulled up next is converted into a temperature setting value of the heater of the semiconductor single crystal to be pulled up next, with respect to the difference between one or both of the constituent member used for pulling up or the pulling condition of the semiconductor single crystal The method for pulling a semiconductor single crystal according to claim 1, wherein the temperature profile of the heater is corrected. The semiconductor raw material supplied to the crucible is melted by the heater, the semiconductor melt is stored in the crucible, and the controller controls the heater based on a preset temperature profile while the semiconductor melt is stored in the crucible. In a semiconductor single crystal pulling apparatus configured to pull a crystal,
The controller is
Accumulating past semiconductor single crystal pulling data that contributes to the setting of the temperature profile of the heater in a database;
Evaluating the temperature profile of the next semiconductor single crystal heater to be pulled up from the past semiconductor single crystal pull-up data stored in the database based on a specific evaluation function,
Based on this specific evaluation function, the temperature profile of the next semiconductor single crystal heater will be modified before pulling,
A semiconductor single crystal pulling apparatus configured to pull up a semiconductor single crystal from a semiconductor melt in the crucible while controlling the heater based on the corrected temperature profile. The specific evaluation function is a reliability determined from the proximity of the set value and the actual value of the temperature profile of the past semiconductor single crystal heater that is fed back to the temperature profile of the next semiconductor single crystal heater to be pulled up. And the set pulling condition of the next semiconductor single crystal to be pulled up and the actual pulling condition of the pulling data of the past semiconductor single crystal fed back to the temperature profile of the heater of the next single semiconductor to be pulled up A weighting factor determined from the proximity of the set pulling condition and the actual pulling condition when
6. The semiconductor single crystal pulling apparatus according to claim 5, wherein the controller is configured to correct a temperature profile of the next semiconductor single crystal heater to be pulled up based on the reliability and the weighting factor.   The controller has a leveling function of correcting the temperature profile of the next semiconductor single crystal heater to be continued so that the temperature profile of the next semiconductor single crystal heater is kept continuous. 6. The semiconductor single crystal pulling apparatus according to 6.   The controller compares the pulling data of the next semiconductor single crystal to be pulled up with the previous pulling data of the semiconductor single crystal fed back to the temperature profile of the heater of the next semiconductor single crystal to be pulled up. The difference between either or both of the constituent member used for pulling up the crystal and the pulling condition of the semiconductor single crystal is converted into the temperature setting value of the heater of the semiconductor single crystal to be pulled up next, and the semiconductor to be pulled up next 7. The semiconductor single crystal pulling device according to claim 5, wherein the single crystal heater is configured to correct a temperature profile of the single crystal heater.

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