JP3669133B2 - Single crystal diameter control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention immerses a seed crystal in a melt stored in a crucible, and pulls up the seed crystal to increase the diameter of the crystal on the melt surface when growing the single crystal with the seed crystal as a nucleus. The present invention relates to a method for controlling the diameter of a single crystal that detects and controls the diameter of a crystal based on the detected data.
[0002]
[Prior art]
Conventionally, a CZ (Czochralski) method is known as one of methods for growing a semiconductor single crystal such as silicon (Si) or gallium arsenide (GaAs). This CZ method is a method used for growth of various semiconductor crystals because it has characteristics such as that a large-diameter, high-purity single crystal can be easily obtained without dislocations or having very few lattice defects.
The outline of the CZ method will be described. As shown in FIG. 4, a polycrystalline silicon lump (or granular polycrystalline silicon) is filled in a quartz crucible (not shown) and melted to obtain a silicon melt 6. A dislocation-free seed crystal 9 suspended from a lower end of a pulling wire (upper shaft) 7 via a seed crystal holder 8 is immersed in the silicon melt 6 and the tip itself of the seed crystal 9 is melted to be pulled up. Start. The crystal diameter is gradually increased by continuing the pulling, and the constant diameter portion (main body) 5 is pulled through the steps of forming the neck 2, the cone 3 and the shoulder 4. In this way, the silicon single crystal 1 having a predetermined length is obtained.
[0003]
[Problems to be solved by the invention]
By the way, in the above-described single crystal pulling operation, it is an indispensable operation for the production of a single crystal to pull the seed crystal thin and long to remove dislocations generated in the crystal and to make it dislocation free. For this reason, conventionally, the diameter of the crystal on the melt surface is detected by a line image sensor or the like to control the diameter of the seed crystal based on this detection data. The accuracy was not always good. And since the accuracy of diameter control is poor, if the diameter of the seed crystal is large, dislocations cannot be removed easily, and dislocation-free crystallization cannot be realized, resulting in a longer pulling time (increased loss time). The problem that the length of a neck part also becomes long (increase in a dead stroke) arises. On the other hand, if the diameter of the seed crystal is too small than the target diameter, this portion could not withstand the crystal weight and the crystal might fall.
Therefore, as a result of intensive studies by the present inventors on the above problem, the following has been found. That is, as shown in FIG. 2, a thick portion called the crystal habit line 10 appears periodically in the crystal during pulling growth. The crystal habit line 10 appears due to the crystal axis, and three crystal habit lines appear in the <111> axis crystal and four (see FIG. 2) in the <100> axis crystal. This crystal habit line appears remarkably when the diameter of the crystal tends to increase (for example, in FIG. 2, the diameter D2 of the crystal habit line portion is about 6 mm, and the diameter D1 of the other portion is about 5 mm, The difference reaches about 1 mm). If the diameter data of the crystal collected for diameter control includes data of the portion where the crystal habit line appears, the diameter control of the crystal performed based on this detection data is adversely affected. It was found that the accuracy deteriorated.
The present invention has been made in view of the above-described knowledge, can perform accurate diameter control, maintain the seed crystal at a desired diameter, and realize dislocation-free crystallization in a short time. Therefore, the single crystal can be pulled up and grown smoothly, the single crystal can be prevented from falling completely, and the high quality single crystal can be obtained reliably. It aims to provide a method.
[0004]
[Means for Solving the Problems]
In order to achieve the above object , the present invention employs the following means.
In the method for controlling the diameter of a single crystal of the present invention, a seed crystal is immersed in a melt stored in a crucible, and the seed crystal is pulled up to grow the single crystal using the seed crystal as a nucleus. The diameter of the crystal on the melt surface is detected in the neck formation step in which the dislocations generated in the crystal are removed by removing the dislocations generated by thin and long, and the diameter of the neck is controlled based on the detected data. In the crystal diameter control method, the sampling period for diameter detection is at least different from the habit line appearance period T = 60 / RN seconds (where R is the number of seed crystal rotations per minute and N is the crystal axis factor). After setting the value and processing the detection data collected at each sampling period, the crystal diameter is controlled based on the processed data, and the processing of the detection data, The difference between one detection data and the next detection data is taken, and when the difference value is larger than a preset threshold value, either the detection data that is larger than the two detection data is excluded, or the detection As the data processing, the above-mentioned problems were solved by adding the detection data collected sequentially and taking the average.
In the method for controlling the diameter of a single crystal according to the present invention, a seed crystal is immersed in a melt stored in a crucible, and the seed crystal is pulled up to grow a single crystal using the seed crystal as a nucleus. In the diameter control method of the single crystal, which detects the diameter of the crystal on the melt surface in the process of forming the cone, shoulder and fixed part, and controls the diameter of the crystal based on the detection data,
The sampling cycle for diameter detection is set to a value different from at least the habit line appearance cycle T = 60 / RN seconds (where R is the seed crystal rotation number per minute and N is the crystal axis factor), and the sampling After processing the detection data collected every period, the diameter of the crystal is controlled based on the processed data, and one detection data and the next detection data are processed as the processing of the detection data. When the difference value is larger than a preset threshold value, the means for excluding the large detection data from the two detection data or the processing of the detection data sequentially It is possible to employ a means for adding the collected detection data and taking the average.
This onset Ming, immersing the seed crystal melt stored in the crucible, by pulling the seed crystal, when a single crystal is grown with the seed crystal as a nucleus, the diameter of the crystal on the melt surface In the single crystal diameter control method for controlling the diameter of the crystal based on the detected data, the sampling period of the diameter detection is at least a habit line appearance period T = 60 / RN seconds (where R is The number of seed crystal rotations per minute (N is the crystal axis factor) is set to a different value, and the detection data collected at each sampling period is processed, and then the crystal is generated based on the processed data. is the Umo line diameter control. In the present invention , by collecting the diameter detection data at least at a different period from the crystal line appearance cycle, it is possible to prevent all of the collected diameter detection data from becoming the data at the time of the crystal line appearance. Furthermore, the diameter detection data is processed to reduce the influence of the data when the crystal habit line appears on the diameter control as much as possible. The present onset Ming, as processing of the detected data, calculates a difference between one of the detected data and the next detection data, if the difference value is larger than the preset threshold, the both detection also the in is to exclude a large detection data among the data. In this invention , when two consecutively collected detection data are compared and the difference value is larger than a preset threshold value, the larger detection data of both detection data is crystallized. Judging from the detection data when the shoreline appears, it is not used as diameter control data. Furthermore, the onset Ming, as processing of the detected data, by adding the detection data are sequentially taken is the even Ru preparative average. In this invention , even if the detection data at the time of the appearance of the crystal habit line is included in the collected detection data by taking the average of a plurality of detection data collected continuously, Reduce the effect and make it smaller.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an example of a silicon single crystal pulling apparatus. In FIG. 1, the same parts as those shown in FIG.
As shown in FIG. 1, a quartz crucible 21 supported by a graphite susceptor 22 is accommodated in a chamber (airtight container) 20 of a single crystal pulling apparatus, and this quartz crucible 21 is made of silicon melt (semiconductor melt). (Liquid) 6 is stored. A substantially columnar graphite heater 23 is provided around the quartz crucible 21, and a heat shield plate 24 is provided on the outside thereof. The optical system 25 measures the diameter of the liquid surface portion of the silicon melt 6 of the silicon single crystal (semiconductor single crystal) 1 during crystal growth, and controls the pulling speed of the pulling wire 7 based on the measured value. ing.
[0006]
Next, the case where the diameter control method of the single crystal which is one embodiment of the present invention is carried out using the above-described silicon single crystal pulling apparatus will be described.
First, a polycrystalline silicon lump is filled in a quartz crucible 21 and melted by heating with an heater 23 in an inert gas (Ar) to obtain a silicon melt 6. If granular polycrystalline silicon is used instead of the polycrystalline silicon lump, filling and melting can be performed in a shorter time.
Next, the seed crystal 9 is lowered and immersed in the silicon melt 6. Then, after melting the tip of the seed crystal 9 itself, the temperature of the silicon melt 6 is controlled to a temperature suitable for pulling the single crystal, and the pulling is started.
That is, while the quartz crucible 21 is rotated in one direction and the seed crystal 9 is pulled in the opposite direction, the silicon single crystal 1 is pulled and grown. At this time, the diameter of the silicon single crystal 1 (seed crystal 9) on the melt surface is measured by the optical system 25 such as a line image sensor, and pulling up control is performed based on the measurement data. Among these, the control at the time of pulling growth of the seed crystal 9 according to the present invention will be described with reference to FIGS. Here, in FIG. 3, a) shows a diameter detection signal, b) shows a sampling command signal, and c) shows the collected diameter detection data.
[0007]
When the seed crystal 9 is pulled, for example, the upper shaft 7 rotates at a rotation speed R = 10 rpm, and as shown in FIG. 2, in the case of a <100> axis crystal, the crystal axis factor N = 4. (In the case of <111> axis crystal, N = 3),
T = 60 / RN = 60 / (10 × 4) = crystal habit lines appear at a cycle of 1.5 seconds (see FIG. 3a). Therefore, this crystal habit line appearance cycle T = 1.5 seconds and a sampling cycle different from that in FIG. 3, T / 6 = 1.5 seconds / 6 = 0.25 seconds (see FIG. 3b), The diameter data detected by the system 25 is collected (see FIG. 3c).
Next, based on the collected diameter detection data (see FIG. 3c), these diameter detection data groups are processed.
[0008]
That is, the difference between one detection data and the next detection data is taken, the difference value is compared with a preset threshold value, and if the difference value is larger than the threshold value, the larger detection data Is detected as the detection data when the crystal habit line appears, and this detection data is excluded. For example, in FIG. 3c, the detection data d1 and d2 are compared, and if the difference is larger than the threshold value, the detection data d2 is excluded. Then, the diameter control of the seed crystal 9 is performed based on the detection data obtained by the processing. In this diameter control, the pulling speed of the upper shaft 7 is controlled based on a preset target value of the diameter. If the deviation from the target value is large only by controlling the pulling speed, the melt is controlled. 6 is used together. In this way, the diameter control of the seed crystal 9 is performed by excluding the detection data that seems to be the detection data at the time of the appearance of the crystal habit line from the collected diameter detection data by the above processing, so the accuracy of diameter control is The seed crystal 9 having a desired diameter is pulled up and grown significantly, and dislocation-free crystallization is realized in a short time.
[0009]
Further, instead of processing the collected diameter detection data, the diameter detection data continuously collected may be averaged, and the diameter control of the seed crystal may be performed based on the average value. In this case, for example, in the case of taking the average of the six diameter detection data in the diameter detection data groups d1, d2, d3,... In FIG. Although the average of the detection data d7 to d12 may be taken, if the average of the diameter detection data d2 to d7 is taken, the control response is improved accordingly. In this way, by taking the average of the collected diameter detection data group, the influence when the crystal habit line appears is reduced and made small.
[0010]
【The invention's effect】
As described above, according to this onset bright, at least, by taking diameter detection data in a cycle different from that of the crystal habit lines revealing period, all harvested diameter detection data during the crystal habit lines revealing Data is prevented from being processed, and the diameter detection data is processed to reduce the influence of the data when the crystal habit line appears on the diameter control as much as possible. As a result, more accurate diameter control can be performed, the seed crystal can be maintained at a desired diameter, and dislocation-free crystallization can be realized in a short time. It can be pulled and grown, and the single crystal can be completely prevented from falling, and a high-quality single crystal can be obtained with certainty. Further, according to this onset bright, by comparing the diameter detection data taken two consecutive, if the difference value is larger than the preset threshold, greater of the two diameters detection data The diameter detection data is determined as the detection data when the crystal habit line appears, and is not used as diameter control data. As a result, the diameter detection data when the crystal habit line appears can be prevented from adversely affecting the diameter control, and accurate diameter control can be realized. Further, according to this onset bright, by taking the average of a plurality of detection data taken in succession, for example, contain a detection data during crystal habit line emerges into the collected detection data has been But diminish the effect and make it smaller. As a result, the diameter can be controlled smoothly, and dislocation-free crystallization can be realized with certainty.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an example of a single crystal pulling apparatus.
FIG. 2 is a cross-sectional view of a seed crystal portion explaining a crystal habit line.
FIG. 3 is an explanatory diagram for explaining the collection timing of diameter detection data.
FIG. 4 is an explanatory diagram of a silicon single crystal being pulled.
[Explanation of symbols]
1 Silicon single crystal (semiconductor single crystal)
2 Neck 3 Cone 4 Shoulder 5 Constant diameter part (main body)
6 Silicon melt (semiconductor melt)
7 Pull-up wire (upper shaft)
8 Seed crystal holder (chuck)
9 Seed crystal 10 Crystal habit line 20 Chamber (airtight container)
21 Quartz crucible 22 Graphite susceptor 23 Graphite heater 24 Heat shield plate 25 Optical system D1, D2 Diameter d1, d2, d3, d4, d5, d6, d7 Diameter detection data

Claims (4)

By immersing the seed crystal in the melt stored in the crucible and pulling up the seed crystal, when the single crystal is grown using the seed crystal as a nucleus, the seed crystal is pulled thin and long, and the dislocations generated in the crystal are removed. In the diameter control method of the single crystal that detects the diameter of the crystal on the melt surface in the step of forming the neck to be dislocation-free by removing, and controls the diameter of the neck based on this detection data,
The sampling cycle for diameter detection is set to a value different from at least the habit line appearance cycle T = 60 / RN seconds (where R is the seed crystal rotation number per minute and N is the crystal axis factor), and the sampling After processing the detection data collected for each cycle, and performing the crystal diameter control based on the processed data ,
As the processing of the detection data, the difference between one detection data and the next detection data is taken, and when the difference value is larger than a preset threshold value, the larger detection data among the two detection data The diameter control method of the single crystal characterized by excluding By immersing the seed crystal in the melt stored in the crucible and pulling up the seed crystal, when the single crystal is grown using the seed crystal as a nucleus, the seed crystal is pulled thin and long, and the dislocations generated in the crystal are removed. In the diameter control method of the single crystal that detects the diameter of the crystal on the melt surface in the step of forming the neck to be dislocation-free by removing, and controls the diameter of the neck based on this detection data,
The sampling cycle for diameter detection is set to a value different from at least the habit line appearance cycle T = 60 / RN seconds (where R is the seed crystal rotation number per minute and N is the crystal axis factor), and the sampling After processing the detection data collected for each cycle, and performing the crystal diameter control based on the processed data ,
A method for controlling the diameter of a single crystal, characterized in that, as processing of the detection data, detection data collected sequentially are added and the average is taken . By immersing the seed crystal in the melt stored in the crucible and pulling up the seed crystal, when the single crystal is grown with the seed crystal as a nucleus, the melt surface in the process of forming the cone, shoulder and fixed part In the diameter control method of a single crystal that detects the diameter of the upper crystal and controls the diameter of the crystal based on the detected data,
The sampling cycle for diameter detection is set to a value different from at least the habit line appearance cycle T = 60 / RN seconds (where R is the seed crystal rotation number per minute and N is the crystal axis factor), and the sampling After processing the detection data collected for each cycle, and performing the crystal diameter control based on the processed data ,
As the processing of the detection data, the difference between one detection data and the next detection data is taken, and when the difference value is larger than a preset threshold value, the larger detection data among the two detection data The method for controlling the diameter of a single crystal according to claim 1 or 2, wherein: By immersing the seed crystal in the melt stored in the crucible and pulling up the seed crystal, when the single crystal is grown with the seed crystal as a nucleus, the melt surface in the process of forming the cone, shoulder and fixed part In the diameter control method of a single crystal that detects the diameter of the upper crystal and controls the diameter of the crystal based on the detected data,
The sampling cycle for diameter detection is set to a value different from at least the habit line appearance cycle T = 60 / RN seconds (where R is the seed crystal rotation number per minute and N is the crystal axis factor), and the sampling After processing the detection data collected for each cycle, and performing the crystal diameter control based on the processed data ,
The method for controlling the diameter of a single crystal according to claim 1 or 2, wherein as the processing of the detection data, the detection data collected sequentially are added and the average is taken .

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