JP5552875B2 - Single crystal manufacturing method and semiconductor wafer manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a single crystal such as a silicon single crystal by the Czochralski method (hereinafter, also simply referred to as “CZ method”), and a method for producing a semiconductor wafer from the single crystal. The present invention relates to a method for manufacturing a single crystal that can reduce the occurrence of selenium and a method for manufacturing a semiconductor wafer that can efficiently detect and remove a site where crystal defects have occurred from a single crystal.

  A silicon single crystal is a material of a silicon wafer used for a semiconductor device, and a single crystal manufacturing method by a CZ method is widely adopted for the manufacture. Usually, in a method for producing a silicon single crystal by the CZ method, a silicon raw material filled in a quartz crucible is heated and melted by a heater in a single crystal growth apparatus maintained in an inert gas atmosphere under reduced pressure. When the silicon melt is formed in the quartz crucible, after the seed crystal is lowered and immersed in the silicon melt, the seed crystal is gradually raised while rotating the seed crystal and the quartz crucible in a predetermined direction, A silicon single crystal is grown below the seed crystal.

  The pulled silicon single crystal is cut into blocks of a predetermined length or less so that it can be sliced in a subsequent process, and a plurality of silicon wafers are cut out from the block. When manufacturing defect-free silicon wafers that do not have crystal defects due to the pulling process, in general, samples are taken from both ends of the block to evaluate crystal defects before cutting the silicon wafer from the block. A silicon wafer is cut out only from a block where the sample satisfies the evaluation criteria. If the sampled sample does not meet the evaluation criteria, the block where the crystal defect has occurred is removed by cutting at a position where it is estimated that the crystal defect has not occurred. Will be evaluated.

  In such a semiconductor wafer manufacturing method, when the diameter becomes non-uniform in the process of pulling up the silicon single crystal by the CZ method, a portion larger than the desired outer diameter takes time to polish the outer diameter. Since the smaller part becomes a product defect, the manufacturing yield decreases.

  In addition, in the method for producing a silicon single crystal by the CZ method, the pulling speed V (mm / min) in the pulling process and the average value G (° C./G) of the temperature gradient in the pulling axis direction in the temperature range from the silicon melting point to 1300 ° C. mm), it is known that a silicon single crystal having no crystal defects can be obtained by setting the V / G value within an appropriate range (Patent Document 1).

  Therefore, in the method of manufacturing a silicon single crystal by the CZ method, it is possible to control the diameter of the silicon single crystal during the pulling process and set the pulling speed within a predetermined range and the V / G value to an appropriate range. This is extremely important from the viewpoint of product quality.

  As a method of keeping the pulling speed within a predetermined range while controlling the diameter of the silicon single crystal, the span and heater temperature for limiting the pulling speed operation based on the detected single crystal diameter and the target value of the pulling speed are set. A method of operating the heater temperature to the set value while calculating the set value and operating the pulling speed within the span is widely adopted.

  When manufacturing a defect-free silicon wafer using a method of setting a span for the pulling rate when controlling the diameter of the silicon single crystal, the target value of the pulling rate, the span of the pulling rate, and the heater temperature are set to V / G values. Must be set or calculated to be in an appropriate range. However, the average value G (° C / mm) of the temperature gradient in the crystal in the direction of the pulling axis is the condition in the furnace, such as the internal structure of the pulling furnace, slight deviation of parts due to furnace disassembly and assembly, and the degree of deterioration of parts. Fluctuates under the influence of For this reason, the average value G (° C./mm) of the temperature gradient in the crystal in the pulling axis direction is the same even when the silicon single crystal is pulled with the same pulling rate and the same manufacturing conditions as the pulling rate target value. Each time it becomes a very different value.

  Thus, since the dispersion of the average value G (° C./mm) of the temperature gradient in the crystal in the pulling axis direction is large, the target value of the pulling speed V (mm / min) so that the V / G value falls within an appropriate range. Is difficult to set, and as a result, the span of the lifting speed is set very narrow.

  If the pulling speed span is set narrow, the moving average calculated from the actual pulling speed when pulling up the silicon single crystal (hereinafter simply referred to as “moving average of pulling speed”) may exceed the span range. is there. In this case, the V / G value also exceeds an appropriate range, and crystal defects such as COP (Crystal Originated Particle) and dislocation clusters tend to occur in the pulled silicon single crystal.

  FIG. 1 shows a pulling rate, a pulling speed target value, a pulling speed span, and a moving average of pulling speeds when a silicon single crystal is obtained by using a single crystal manufacturing method in which a span is set to a conventional pulling speed. It is a figure which shows a relationship. This figure shows the relationship between the pulling rate and the moving average of the pulling speed when the silicon single crystal is pulled according to a comparative example described later. Here, the pulling rate (%) is a percentage of the pulling length with respect to the length of the pulled single crystal. The pulling speed in the figure is expressed as a ratio to the reference speed. The reference speed refers to a pulling speed that is determined within a normally used range.

  From this figure, it is confirmed that the moving average of the pulling speed fluctuates beyond the upper limit or lower limit of the span at four locations. As shown in the figure, when the moving average of the pulling rate fluctuates beyond the span, crystal defects are likely to occur at the corresponding portion of the pulled silicon single crystal. For this reason, the pulled silicon single crystal is cut into a block at a position where the moving average of the pulling speed exceeds the span. As a result, the crystal defect is evaluated by the sample at a position where the moving average of the pulling speed at which the crystal defect is likely to occur exceeds the span, so that the site where the crystal defect has occurred is detected and removed from the block. The

  Also, in order to prevent the moving average of the pulling speed from exceeding the span when pulling the single crystal, the parameters of the formula used to calculate the pull speed span and heater temperature setting values were corrected, and then the single crystal was When pulling up, a method of changing the moving average of the pulling speed within the span can be used.

  Various proposals have heretofore been made with respect to a method for producing a single crystal by setting a span for the pulling speed in the pulling process. In this document, the control value of the pulling speed is calculated based on the detected diameter of the silicon single crystal to obtain a pulling speed output in which a span for limiting the fluctuation range is set, and the pulling speed before setting the span. A silicon single crystal manufacturing method has been proposed in which a heater temperature output is calculated by comparing a control value with a pulling speed set value, and the pulling speed and the heater temperature are controlled by the pulling speed output and the heater temperature output.

  In Patent Document 2, since the heater temperature output is calculated by comparing the pulling speed control value before setting the span and the pulling speed setting value, the pulling speed changes dynamically. It is said that crystals can be obtained.

JP-A-8-330316 JP 2001-316199 A

  By controlling the diameter of the conventional silicon single crystal by setting a span for the pulling speed, even if the moving average of the pulling speed is varied within the span, crystal defects are generated in the pulled silicon single crystal. There is a case. In this case, if the crystal defect exists at the cutting position into the block, the occurrence of the crystal defect is detected by evaluating the collected sample. Since it is necessary to cut and remove the part containing the detected crystal defect from the block and evaluate the crystal defect again with the sample, the number of times the block is cut and the number of evaluations with the sample increase. Decreases.

  On the other hand, when a crystal defect exists in the block, it is not detected in the evaluation of the crystal defect by the sample. For this reason, since a crystal defect is detected after a block is cut out to form a silicon wafer, the manufacturing yield is lowered due to the number of steps required until the crystal defect is detected.

  The present invention has been made in view of such circumstances, and a method for producing a single crystal capable of reducing crystal defects generated in a single crystal pulled by the CZ method, and a site where crystal defects are generated from the single crystal are provided. An object of the present invention is to provide a method of manufacturing a semiconductor wafer that can be efficiently detected and removed.

  The inventors investigated the cause of crystal defects in the pulled silicon single crystal even when a span was set for the pulling rate and the pulling rate was controlled within the range.

  From the relationship between the pulling rate when the silicon single crystal is pulled using the conventional single crystal manufacturing method shown in FIG. 1 and the moving average of the pulling rate, the pulling rate is increased even when the moving average of the pulling rate is within the span. It is confirmed that the moving average of fluctuates. The present inventors have found that when a moving average of the pulling speed fluctuates, if a fluctuation with a large fluctuation ratio (slope) occurs, crystal defects are likely to occur in the pulled silicon single crystal.

  Based on this knowledge, various tests were conducted and extensive studies were conducted. As a result, in the process of pulling up the single crystal, the single crystal diameter was controlled, and the moving average fluctuation of the pulling speed was controlled. It was clarified that crystal defects generated in a single crystal can be reduced.

  In addition, by controlling the fluctuation of the moving average of the pulling speed in the process of pulling up the single crystal and cutting the pulled single crystal at the position where the fluctuation has occurred, it is possible to efficiently detect crystal defects and improve the production yield. Revealed.

The present invention has been completed on the basis of the above findings, and the gist of the method is a single crystal manufacturing method (1 ) below and a semiconductor wafer manufacturing method ( 2 ) and ( 3 ) below.

(1) In the process of pulling up the single crystal by the Czochralski method, based on the detected diameter of the single crystal and the target value of the pulling speed, the set values of the span and the heater temperature that limit the pulling speed operation are calculated, In order to control the fluctuation of the moving average calculated from the actual value of the pulling speed when the pulling speed is operated within the span and the heater temperature is controlled to the set value to control the diameter of the single crystal. , Including a first step and a second step, wherein the first step is a step of extracting the fluctuation from an actual value of the pulling rate in the pulled first single crystal, and the second step is In the condition where the fluctuation is extracted in the first step, the span for limiting the operation of the pulling speed and the setting value of the heater temperature are displayed. The parameters of the equation used for subsequently generating the fluctuation in pulling the second single crystal is step be modified to be suppressed, the fluctuation, the moving average, such as to generate crystal defects The fluctuation has a magnitude of a fluctuation ratio, and when extracting the fluctuation, an upper limit and a lower limit of a fluctuation judgment width for judging the fluctuation of the moving average are set in the span, and the moving average is the fluctuation judgment width. The fluctuation length within the fluctuation judgment width until the fluctuation length becomes equal to the lower limit of the fluctuation judgment width, or the moving average becomes equal to the lower limit of the fluctuation judgment width. A method for producing a single crystal, characterized in that the fluctuation is within the determination range and the pulling length until it becomes equal to the upper limit of the fluctuation determination range is equal to or less than a threshold value.

( 2 ) A single crystal pulled up by the Czochralski method is cut into blocks of a predetermined length or less, crystal defects are evaluated for samples taken from both ends of the obtained block, and a block satisfying the evaluation criteria is cut out to obtain a semiconductor. A method for manufacturing a wafer, wherein the single crystal is pulled up by the method for manufacturing a single crystal described in ( 1 ), and the fluctuation of the moving average calculated from the actual value of the pulling speed in the pulling process is managed. A method for manufacturing a semiconductor wafer, comprising: cutting a single crystal into blocks of a predetermined length or less, and cutting the single crystal at a position where the fluctuation occurs in the process of pulling up the single crystal.

( 3 ) When managing the fluctuation, a fluctuation judgment width is determined from a target value of the pulling speed, and after the moving average becomes equal to the upper limit of the fluctuation judgment width, the fluctuation judgment width varies to change the fluctuation. Raised length until it becomes equal to the lower limit of the judgment width, or raising until the moving average becomes equal to the lower limit of the fluctuation judgment width and then fluctuates within the fluctuation judgment width and becomes equal to the upper limit of the fluctuation judgment width The method for producing a semiconductor wafer according to ( 2 ), wherein the length is less than a threshold value.

  The method for producing a single crystal of the present invention can reduce crystal defects generated in the pulled single crystal by controlling the single crystal diameter in the process of pulling the single crystal and controlling the fluctuation of the moving average of the pulling speed. .

  The semiconductor wafer manufacturing method of the present invention manages the fluctuation of the moving average of the pulling rate in the process of pulling up the single crystal, and cutting the pulled single crystal at the position where the fluctuation has occurred, thereby causing crystal defects from the single crystal. The generated site can be efficiently detected and removed.

The figure which shows the relation between the pulling rate, the pulling speed target value, the pulling speed span, and the moving average of the pulling speed when a silicon single crystal is obtained using a single crystal manufacturing method in which the span is set to the conventional pulling speed. It is. It is a schematic diagram explaining the method of determining the fluctuation | variation which generate | occur | produces in the moving average of pulling speed by defining the fluctuation | variation determination width | variety of this invention. It is a figure which shows the relationship between the moving average of a pulling rate and pulling speed, the target value of pulling speed, the span of pulling speed, and the fluctuation | variation judgment width | variety at the time of obtaining a silicon single crystal with the manufacturing method of the conventional single crystal. It is a figure which shows the relationship between the pulling rate and the moving average of pulling speed, the target value of pulling speed, the span of pulling speed, and the fluctuation | variation judgment width | variety at the time of obtaining the silicon single crystal with the manufacturing method of the single crystal of this invention.

  Below, the manufacturing method of the single crystal of this invention and the manufacturing method of a semiconductor wafer are demonstrated in detail.

  The method for producing a single crystal according to the present invention includes a span and a heater temperature for limiting the operation of the pulling speed based on the diameter of the single crystal detected and the target value of the pulling speed in the process of pulling the single crystal by the Czochralski method. Calculates the set value, operates the pulling speed within the span, and controls the fluctuation of the moving average calculated from the actual pulling speed when controlling the heater temperature to the set value and controlling the diameter of the single crystal. It is characterized by doing.

  As described above, if a fluctuation with a large fluctuation rate (slope) of the moving average of the pulling speed occurs, crystal defects are likely to occur. Therefore, a fluctuation that is highly likely to have occurred due to the moving average of the changing pulling speed is high. It is important to judge and extract. As a method for determining the fluctuation, for example, the fluctuation ratio (slope) of the moving average with respect to the reference pull-up length is calculated, and when the absolute value exceeds the threshold value, the fluctuation can be generated.

  As a method of controlling the moving average fluctuation of the pulling speed, after pulling up the single crystal, the occurrence of fluctuation is judged and extracted from the fluctuation of the moving average of the pulling speed, and the setting of the pulling speed span and heater temperature is calculated. By correcting the parameters of the equation used in the above, it is possible to adopt a method of controlling fluctuations of the single crystal that is subsequently pulled. Specifically, fluctuations with a large fluctuation rate (slope) of the moving average of the pulling speed are likely to occur when the heater temperature is greatly changed. Therefore, the amount of operation of the heater temperature under the conditions where the fluctuation has occurred is small. By correcting the parameters so as to decrease, it is possible to control to suppress the occurrence of fluctuation.

  In the method for producing a single crystal of the present invention, when controlling the fluctuation of the moving average of the pulling speed, the upper limit and the lower limit of the fluctuation determination width for determining the fluctuation are set within the span, and the moving average of the pulling speed is the upper limit of the fluctuation determination width. After the movement length within the fluctuation judgment range is equal to the lower limit of the fluctuation judgment width, or the moving average of the lifting speed is equal to the lower limit of the fluctuation judgment width, It is preferable that the fluctuation length is equal to or less than the upper limit of the fluctuation determination width to be a fluctuation when the pulling length is equal to or less than a threshold value.

  FIG. 2 is a schematic diagram for explaining a method for determining fluctuations occurring in the moving average of the pulling speeds by determining the fluctuation determination width of the present invention. This figure shows the pulling speed in the vertical direction and the pulling rate in the horizontal direction. The moving average of the pulling speed with respect to the pulling rate is indicated by a solid line, the target value of the pulling speed is indicated by a broken line, and the span of the pulling speed is indicated by a one-dot chain line. Each width is indicated by a two-dot chain line.

  As shown in the figure, an upper limit and a lower limit of a fluctuation judgment width for judging fluctuation of the moving average of the pulling speed are determined within the span. After the moving average of the pulling speed fluctuates and the moving average of the pulling speed becomes equal to the upper limit of the fluctuation determination width, the pulling length is obtained until it fluctuates within the fluctuation determination width and becomes equal to the lower limit of the fluctuation determination width. The case where the pulling length is equal to or smaller than the threshold value, that is, the case where the fluctuation ratio (slope) is large is regarded as fluctuation. Similarly, when the moving average of the pulling speed becomes equal to the lower limit of the fluctuation determination width and then the pulling length from the fluctuation determination width to the same as the upper limit of the fluctuation determination width is equal to or less than the threshold, the fluctuation is defined.

  By judging fluctuations using the fluctuation judgment width in this way, fluctuations with a large moving average fluctuation rate (gradient) that can easily cause crystal defects in the pulled single crystal are extracted easily and efficiently. can do. In this case, in order to control fluctuation, a method of controlling fluctuation of a single crystal that is subsequently pulled up by determining the occurrence of fluctuation of the moving average when the single crystal is pulled up and correcting the parameters of the arithmetic expression Can be adopted.

  The pull-up length threshold and the fluctuation determination width used for fluctuation determination can be appropriately determined from the manufacturing conditions, the operation results, and the quality required for the single crystal. If the pull-up length threshold is less than or equal to the maximum length of the block from which the semiconductor wafer can be cut out in the slicing process, the portion where the crystal defect has occurred can be efficiently removed without reducing the manufacturing yield in the slicing process. preferable.

The method for producing a semiconductor wafer according to the present invention includes cutting a single crystal pulled by a Czochralski method into blocks of a predetermined length or less, evaluating crystal defects for samples taken from both ends of the obtained block, and evaluation criteria. A method for manufacturing a semiconductor wafer by slicing blocks satisfying the above requirements, wherein the single crystal is pulled up by the method for manufacturing a single crystal according to the present invention (2) and is calculated from the actual value of the pulling speed in the pulling process. The moving average fluctuation is controlled, and when the single crystal is cut into blocks of a predetermined length or less, the single crystal is cut at a position where fluctuation occurs in the process of pulling up the single crystal.

  By managing fluctuations that occur in the moving average of the pulling rate in the process of pulling up the single crystal, it is possible to specify a site where the crystal defect is likely to occur in the pulled single crystal. By setting the cutting position when cutting this single crystal into blocks of a predetermined length or less as the position where fluctuation occurred in the pulling process, the crystal defect can be evaluated by the sample at a position where there is a high possibility that a crystal defect has occurred. The occurrence of crystal defects due to fluctuations can be efficiently detected.

  Conventionally, crystal defects due to fluctuations existing in the block have been detected after being cut into a silicon wafer, but in the method for manufacturing a semiconductor wafer of the present invention, it can be detected and removed before being cut into a silicon wafer. .

  In the semiconductor wafer manufacturing method of the present invention, when managing fluctuations, the fluctuation judgment width is determined from the target value of the pulling speed, and after the moving average becomes equal to the upper limit of the fluctuation judgment width, the fluctuation judgment width fluctuates. The pull-up length until it becomes equal to the lower limit of the fluctuation judgment width, or the raising length until the moving average becomes equal to the lower limit of the fluctuation judgment width and then fluctuates within the fluctuation judgment width and becomes equal to the upper limit of the fluctuation judgment width. It is preferable that the fluctuation is less than the threshold value.

  The possibility of the occurrence of crystal defects in the pulled single crystal by determining and managing the fluctuation generated in the moving average of the pulling speed by the fluctuation judging method using the fluctuation judging width described with reference to FIG. It is possible to easily identify a site having high properties.

  As described above, when manufacturing a defect-free silicon wafer, in a block that does not satisfy the evaluation criteria for crystal defects, cutting at a position where it is estimated that no crystal defects have occurred, and evaluation of crystal defects by a sample, Repeat until the collected sample meets the evaluation criteria. The method for manufacturing a semiconductor wafer of the present invention can accurately estimate a portion where a crystal defect is likely to occur by managing fluctuations in the pulling process, and the number of times a block that does not satisfy the evaluation criteria is cut. It becomes possible to reduce the number of times the sample is evaluated again later. As a result, the semiconductor wafer manufacturing method of the present invention can reduce the number of single crystal and block cuts and the number of crystal defects evaluated by a sample.

  In order to confirm the effects of the method for producing a single crystal and the method for producing a semiconductor wafer of the present invention, the following tests were conducted.

[Test conditions]
As a comparative example, based on the detected diameter of the single crystal and the target value of the pulling speed, the setting values of the span and heater temperature that limit the pulling speed operation are calculated, the pulling speed is operated within the span, and the heater temperature Was adjusted to a set value to control the diameter of the single crystal to pull up the silicon single crystal. At this time, the span of the pulling speed was set to ± 1% of the target value of the pulling speed.

  In the comparative example, the pulled silicon single crystal was cut into blocks with the position where the moving average of the pulling speed exceeded the span as the cutting position. Crystal defects were evaluated for samples collected from both ends of the obtained block, and a block satisfying the evaluation criteria was cut out to obtain a silicon wafer. The block that did not satisfy the evaluation criteria was cut at a position where it was estimated that no crystal defect occurred, and after removing the portion where the crystal defect occurred, a sample was taken again to evaluate the crystal defect.

  In the example of the present invention, the fluctuation was determined using a diagram showing the relationship between the pulling rate in the comparative example shown in FIG. 3 described later, the moving average of the pulling speed, the target value of the pulling speed, the span of the pulling speed, and the fluctuation determination width. Use the same lifting furnace as in the comparative example after correcting the parameters of the calculation formula so that the manipulated value of the heater temperature decreases at the place where the fluctuation occurs and the moving average of the pulling speed exceeds the span The silicon single crystal was pulled up. The determination of fluctuation was performed by the determination method using the fluctuation determination width described with reference to FIG. At this time, the upper limit or lower limit of the fluctuation determination width was set to ± 0.6% of the target value of the pulling speed, and the pulling length threshold was set to 200 mm.

  In the example of the present invention, the pulled silicon single crystal was cut into blocks with the position where the moving average of the pulling speed and the upper limit or lower limit of the fluctuation determination width became equal as the cutting position. In the example of the present invention, the obtained block was evaluated for crystal defects by a sample in the same manner as in the comparative example, and then cut into a silicon wafer.

  In both the inventive example and the comparative example, the number of block cuttings and the number of sample evaluations were counted, and the defect-free area ratio (%) was calculated. The defect-free area ratio (%) is the percentage of the length (mm) at which no crystal defect was detected in the evaluation of the crystal defect performed by taking a sample from the block with respect to the length (mm) of the silicon single crystal body It is.

[Test results]
FIG. 3 is a diagram showing the relationship between the moving average of the pulling rate and the pulling speed, the target value of the pulling speed, the span of the pulling speed, and the fluctuation determination width when a silicon single crystal is obtained by the single crystal manufacturing method of the comparative example. It is. The pulling speed in the figure is expressed as a ratio to the reference speed. In the comparative example, as shown in FIG. 1, the moving average of the lifting speed fluctuated beyond the span at four locations. Further, as shown in FIG. 3, even when the moving average of the pulling speed fluctuated within the span, fluctuations occurred at 12 locations.

  In the comparative example, since the crystal was dislocationized after the pulling rate of 72%, the crystal defect was not evaluated by the sample. Crystal defects were evaluated at two places out of four places where the moving average of the pulling speed exceeded the span, and crystal defects were found at two places. In addition, the crystal defects were evaluated at 9 locations out of 12 locations where fluctuations occurred, and crystal defects were observed at all 9 locations.

  In the comparative example, the number of times of cutting the silicon single crystal and the block was 12, the number of crystal defects evaluated by the sample was 12, and the defect-free area ratio was 57.1%.

  FIG. 4 shows the relationship between the moving average of the pulling rate and the pulling speed, the target value of the pulling speed, the span of the pulling speed, and the fluctuation judgment width when a silicon single crystal is obtained by the single crystal manufacturing method of the present invention example. FIG. The pulling speed in the figure is expressed as a ratio to the reference speed. As shown in the figure, the moving average of the pulling speed did not fluctuate beyond the span, and the moving average of the pulling speed fluctuated only in two places. When the crystal defect was evaluated at the place where the fluctuation occurred, the crystal defect was observed.

  In the comparative example, the crystal defect evaluation by the sample was performed in the range of less than 72% pulling rate. In the present invention example, the number of times of cutting the silicon single crystal and the block was 6, and the number of evaluation of the crystal defect by the sample was 6. It was. In the example of the present invention, the defect-free area ratio was 82.6%.

  From these, if the moving average of the pulling speed fluctuates and fluctuations occur, crystal defects are likely to occur in the pulled silicon single crystal, and by controlling the fluctuations using the single crystal manufacturing method of the present invention, the silicon single crystal is controlled. It has been clarified that crystal defects generated in crystals can be reduced.

  In addition, if the moving average of the pulling speed fluctuates and fluctuations occur, crystal defects are likely to occur. Therefore, the single crystal is cut at the position where fluctuations are generated using the method for manufacturing a semiconductor wafer of the present invention to form a block. As a result, it was revealed that the site where the crystal defect occurred from the single crystal can be efficiently detected and removed.

  The method for producing a single crystal of the present invention can reduce crystal defects generated in the pulled single crystal by controlling the single crystal diameter in the process of pulling the single crystal and controlling the fluctuation of the moving average of the pulling speed. .

  The semiconductor wafer manufacturing method of the present invention manages the fluctuation of the moving average of the pulling rate in the process of pulling up the single crystal, and cutting the pulled single crystal at the position where the fluctuation has occurred, thereby causing crystal defects from the single crystal. The generated site can be efficiently detected and removed.

  Therefore, if the method for producing a single crystal and the method for producing a semiconductor wafer of the present invention are applied to the production of a defect-free silicon wafer, the production yield can be greatly improved.

Claims (3)

In the process of pulling up the single crystal by the Czochralski method, based on the detected diameter of the single crystal and the target value of the pulling speed, the setting values of the span and heater temperature that limit the pulling speed operation are calculated, and the pulling speed is calculated. When operating within the span and controlling the diameter of the single crystal by operating the heater temperature to the set value,
In order to control the fluctuation of the moving average calculated from the actual value of the pulling speed, including a first step and a second step,
The first step is a step of extracting the fluctuation from the actual value of the pulling rate in the pulled first single crystal;
In the condition in which the second step has extracted the fluctuation in the first step, the parameters of the formula used for the calculation of the span and the heater temperature set value for restricting the operation of the pulling speed, and then the second Correcting the generation of the fluctuations when pulling up the single crystal,
The fluctuations are fluctuations having a magnitude of the moving average fluctuation rate so as to generate crystal defects ;
When extracting the fluctuation, an upper limit and a lower limit of a fluctuation determination width for determining the fluctuation of the moving average are set in the span, and the moving average becomes equal to the upper limit of the fluctuation determination width, and then the fluctuation determination width is within the fluctuation determination width. And the moving length becomes equal to the lower limit of the fluctuation determination width after the moving average becomes equal to the lower limit of the fluctuation determination width, and then the upper limit of the fluctuation determination width is changed within the fluctuation determination width. A method for producing a single crystal, characterized in that when the pulling length until it becomes equal to or less than a threshold value, the fluctuation occurs.
A single crystal pulled up by the Czochralski method is cut into blocks of a predetermined length or less, a crystal sample is collected from both ends of the obtained block, crystal defects are evaluated, and a semiconductor wafer is manufactured by cutting out a block that satisfies the evaluation criteria. A way to
As the single crystal, a single crystal produced by the method for producing a single crystal according to claim 1 , and using a moving average fluctuation calculated from the actual value of the pulling speed in the pulling process,
A method for manufacturing a semiconductor wafer, comprising: cutting a single crystal into blocks having a predetermined length or less, wherein the single crystal is cut at a position where the fluctuation occurs in the process of pulling up the single crystal. When managing the fluctuation, the fluctuation determination width is determined from the target value of the pulling speed, and after the moving average becomes equal to the upper limit of the fluctuation determination width, the fluctuation determination width is changed to change the fluctuation determination width. The raising length until it becomes equal to the lower limit, or the raising length until the moving average becomes equal to the lower limit of the fluctuation determination width, and then varies within the fluctuation determination width and becomes equal to the upper limit of the fluctuation determination width. 3. The method of manufacturing a semiconductor wafer according to claim 2 , wherein the fluctuation is not more than a threshold value.

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