JP2017014080A - Inspection method and production method for silicon single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide new means capable of performing a DSOD quality decision of a low oxygen concentration silicon single crystal having neither COP nor a dislocation cluster.SOLUTION: A silicon single crystal inspecting method comprises: performing a Cu contamination and either a treatment 1 containing a predetermined thermal cooling treatment or selective etching, or a treatment 2 performing the treatment 1 after a predetermined previous treatment, on a sample cut out of a silicon single-crystal ingot grown by the Czochralski process, and a DSOD propriety decision on the basis of a criterion, in which it is decided that the DSOD is the more as the area, in which pits are locally in the sample surface after the treatment 1 or a treatment 2 is wider. Said sample does not contain the COP and dislocation cluster, and an interstitial oxygen concentration (old ASTM) of the sample to be subjected to the treatment 1 is 7.5E17atoms/cmor less, but the interstitial oxygen concentration (old ASTM) of the sample to be subjected to the treatment 2 is 5.0E17atoms/cmor more and 10.0E17atoms/cmor less.SELECTED DRAWING: None

Description

  The present invention relates to a method for inspecting and manufacturing a silicon single crystal grown by the Czochralski method.

  As a method for growing a silicon single crystal ingot for manufacturing a semiconductor wafer, the Czochralski method (hereinafter also referred to as “CZ method”) in which a silicon single crystal is grown from a raw material melt is widely used.

  As for the CZ method, it is known that the type and distribution of defects introduced into the crystal during the growth of the silicon single crystal depend on the crystal pulling speed V and the temperature gradient G at the solid-liquid interface. FIG. 7 is a diagram showing a general relationship between V / G and the type and distribution of defects. As shown in FIG. 7, when V / G exceeds a certain value, the vacancies become excessive, and microvoids (generally called COP (Crystal Originated Particle)) that are aggregates of vacancies are generated. On the other hand, when V / G is small, interstitial silicon atoms become excessive, and dislocation clusters, which are aggregates of interstitial silicon, are generated.

  Since COP and dislocation clusters greatly affect device characteristics when an integrated circuit is formed on the surface layer portion of a silicon single crystal wafer, it is desirable to grow a silicon single crystal under conditions that do not cause these defects. For this purpose, it is important to inspect the grown silicon single crystal to accurately grasp the distribution of each region and to give necessary feedback to the crystal growth conditions. In the crystal growth conditions, the temperature gradient G is not easily changed because it is determined by the structure of the high temperature portion (hot zone) in the furnace of the single crystal pulling apparatus. Therefore, the control of V / G is mainly performed by strictly controlling the pulling speed V within a very narrow range. For example, if COP has occurred, the growth condition is corrected so as to decrease the pulling speed V, and if a dislocation cluster is generated, the growth condition is corrected so as to increase the pulling speed V. It becomes possible to stably produce a silicon single crystal having no COP and dislocation clusters with a high yield.

  By the way, conventionally, it has been strongly demanded to provide a wafer excellent in gettering capability in which the density of oxygen precipitates is high. However, oxygen precipitates are a kind of so-called crystal defects, and if oxygen precipitates are present on the surface layer of a wafer where devices are formed, they cause a device failure. In recent years, the device has become cleaner and the risk of impurity contamination has been greatly reduced. Therefore, the gettering ability is unquestioned as a quality required for wafers, and is not limited to COP and dislocation clusters. It is expected that wafers with even fewer objects will be required in the future as next-generation wafers. Generally, oxygen precipitates in a wafer can be reduced by reducing the oxygen concentration in the crystal.

  Under such circumstances, attention has been focused on a silicon single crystal having a low oxygen concentration in recent years. For example, Patent Document 1 discloses a method for evaluating a crystal defect of a silicon single crystal having a low oxygen concentration by using copper decoration. Note that the copper (Cu) decoration is a method in which Cu adhering to the sample surface is diffused into the sample by heat treatment and then defects on the crystal surface are revealed by rapid cooling. Further, if necessary, selective etching may be performed after the Cu decoration to detect fine defects. On the other hand, Patent Document 2 includes adjusting the growth conditions based on the determination in the evaluation step including the ramping temperature rising heat treatment for forming the nucleus of the oxygen precipitate and the oxygen precipitate growth heat treatment for growing the oxygen precipitate. A method for growing a silicon single crystal having a low oxygen concentration is disclosed.

JP 2001-081000 A JP 2010-132509 A

  In recent years, in silicon single crystals grown under pulling conditions in which COP and dislocation clusters do not occur, a minute crystal defect called DSOD (Direct Surface Oxide Defect) can occur, and the cause of DSOD degrading the electrical characteristics of the device Turned out to be. If this DSOD generation tendency can be determined in a low oxygen concentration silicon single crystal that does not contain COP and dislocation clusters, by determining the pulling conditions so as to suppress the generation of DSOD based on the determination result, COP and It is possible to provide a silicon single crystal that does not contain dislocation clusters, has a low oxygen concentration, and has a reduced DSOD that causes deterioration of electrical characteristics of the device.

  However, since the DSOD is extremely small in size, it cannot be detected by a particle counter used for normal crystal inspection. Further, neither Patent Document 1 nor Patent Document 2 describes a DSOD evaluation in a silicon single crystal having a low oxygen concentration.

  On the other hand, with respect to DSOD, a method for evaluating DSOD by a copper (Cu) deposition method has been proposed as described in JP-A 2006-208314, paragraphs 0005 to 0007. Specifically, the evaluation of DSOD by the Cu deposition method is performed as follows. An oxide insulating film (hereinafter also simply referred to as an oxide film) having a predetermined thickness is formed on the surface of the silicon single crystal wafer, and the oxide film on the defect site formed on the wafer surface layer is destroyed. Then, Cu is deposited (deposited) on the broken oxide film portion. More specifically, when a voltage is applied to an oxide film formed on the wafer surface in a solution containing Cu ions, a current flows through a portion where the oxide film is degraded, and Cu ions are deposited as Cu. Thus, by determining the portion where Cu is deposited as a DSOD existing portion, the distribution and density of DSOD are evaluated.

  However, DSOD evaluation by the Cu deposition method usually requires about 2 to 3 weeks to complete the evaluation. Therefore, a situation may occur in which defective lots containing a large amount of DSOD continue to be produced before the necessary feedback for crystal growth is applied based on the evaluation results.

  Accordingly, an object of the present invention is to provide a new means for enabling a DSOD quality determination of a low oxygen concentration silicon single crystal that does not contain COPs and dislocation clusters.

As a result of intensive investigations to achieve the above object, the present inventors have described a low oxygen concentration silicon single crystal, specifically, interstitial oxygen concentration (former ASTM) (hereinafter simply referred to as “oxygen concentration”). ) Is 10.0E17 atoms / cm ³ or less of a silicon single crystal,
(1) For a silicon single crystal having an oxygen concentration on the low oxygen concentration side within the above range, a region where pits are localized is obtained by performing predetermined copper decoration and selective etching (specifically, treatment 1 described later). There is a tendency for DSOD to occur more easily,
(2) For a single crystal having an oxygen concentration on the high oxygen concentration side within the above range, a region where pits are localized by performing treatment 1 after performing a predetermined heat treatment (specifically, treatment 2 described later) The wider the value, the more likely DSOD will occur.
It came to obtain the new knowledge which was not known conventionally. The present inventors consider this reason as follows. However, the following description is a guess by the present inventors and does not limit the present invention.
As shown in FIG. 7, there are three regions, an OSF region, a Pv region, and a Pi region, in descending order of V / G between the region where COP occurs and the region where dislocation clusters occur. The area is included. These regions have different behavior when heat treated. The OSF region includes plate-like oxygen precipitates (OSF (Oxidation Induced Stacking Fault) nuclei) in an as-grown state (a state in which no heat treatment is performed after crystal growth), and has a high temperature (generally 1000 ° C. to 1200 ° C.). This is a region where OSF is generated when thermal oxidation is performed at a temperature of about 0.degree. However, the OSF region is not normally revealed in a silicon single crystal having an oxygen concentration of 10.0E17 atoms / cm ³ or less.
On the other hand, the Pv region contains oxygen precipitation nuclei in an as-grown state, and oxygen precipitates are generated when two-stage heat treatment is performed at low and high temperatures (for example, about 800 ° C. and about 1000 ° C.). This is an easy area. The Pi region is a region that hardly contains oxygen precipitation nuclei in an as-grown state and hardly generates oxygen precipitates even when heat treatment is performed.
The inventors of the present invention tend to generate more DSOD for a silicon single crystal having an oxygen concentration of 10.0E17 atoms / cm ³ or less as the silicon single crystal has a wider Pv region. It is assumed that the Pv region is selectively exposed as a region where pits are localized by processing 1 described later for a silicon single crystal having a low concentration and by processing 2 described later for a silicon single crystal having a higher oxygen concentration. Yes. Therefore, after the process 1 for the former silicon single crystal and after the process 2 for the latter silicon single crystal, if the DSOD quality is determined based on the determination criterion that the larger the region where pits are localized, the greater the DSOD is. For example, it is possible to distinguish between a silicon single crystal containing a large amount of DSOD and a silicon single crystal containing a small amount of DSOD without performing a DSOD evaluation by a Cu deposition method requiring a long time as described above.
The present invention has been completed based on the above findings.

One embodiment of the present invention relates to the following silicon single crystal inspection method (hereinafter also referred to as “inspection method A”).
Subjecting one of two samples cut from the same silicon single crystal ingot grown by the Czochralski method to the following treatment 1 and the other to the following treatment 2;
The sample surface after the following treatment 1 is compared with the sample surface after the following treatment 2, and a sample in which the localized state of the pits is more clearly confirmed is determined as an evaluation sample, and
Performing a DSOD pass / fail determination based on a determination criterion that determines that the larger the region where the pits are localized in the determined sample surface for evaluation, the greater the DSOD,
Including
The method for inspecting a silicon single crystal, wherein the two samples are silicon single crystals having an interstitial oxygen concentration not including COP and dislocation clusters (former ASTM) of 10.0E17 atoms / cm ³ or less.
(Process 1)
Contaminating the surface of the sample with copper,
Subjecting the contaminated sample to a heating and cooling treatment in which the sample is heated at a temperature range of 700 ° C. or higher and lower than 800 ° C. for 5 minutes or more and then rapidly cooled at a temperature-decreasing rate exceeding 2.5 ° C./min.
Selectively etching the sample surface after the heating and cooling treatment;
Processing including
(Process 2)
Subjecting the sample to heating at a temperature range of 750 to 900 ° C. and then pre-heating at a temperature range of 1000 to 1150 ° C .;
Contaminating the surface of the pretreated sample with copper;
Subjecting the contaminated sample to a heating and cooling treatment in which the sample is heated at a temperature range of 700 ° C. or higher and lower than 800 ° C. for 5 minutes or more and then rapidly cooled at a temperature-decreasing rate exceeding 2.5 ° C./min from the temperature range;
Selectively etching the sample surface after the heating and cooling treatment;
Processing including

Another embodiment of the present invention relates to the following silicon single crystal inspection method (hereinafter also referred to as “inspection method B”).
Subjecting a sample cut from a silicon single crystal ingot grown by the Czochralski method to the treatment 1;
Performing a DSOD pass / fail determination based on a determination criterion that determines that the larger the region where the pits are localized on the sample surface after the processing 1, the greater the DSOD,
Including
The method for inspecting a silicon single crystal, wherein the sample is a silicon single crystal having an interstitial oxygen concentration not including COP and dislocation clusters (former ASTM) of 7.5E17 atoms / cm ³ or less.

Another embodiment of the present invention relates to the following silicon single crystal inspection method (hereinafter also referred to as “inspection method C”).
Subjecting the sample cut from the silicon single crystal ingot grown by the Czochralski method to the above treatment 2;
Performing a DSOD pass / fail determination based on a determination criterion that determines that the larger the region where the pits are localized on the sample surface after the processing 2 is, the greater the DSOD is;
Including
The method for inspecting a silicon single crystal, wherein the sample is a silicon single crystal having an interstitial oxygen concentration (former ASTM) not including COP and dislocation clusters of 5.0E17 atoms / cm ³ or more and 10.0E17 atoms / cm ³ or less.

As described above, a silicon single crystal having an oxygen concentration of 10.0E17 atoms / cm ³ or less should be treated 1 for a lower oxygen concentration and treated 2 for a higher oxygen concentration. . A silicon single crystal having a lower oxygen concentration has a tendency that the localized state of pits is more clearly confirmed when the treatment 1 is performed than when the treatment 2 is performed. When the process 2 is performed, the localized state of the pits tends to be clearly confirmed than when the process 1 is performed. Therefore, although it has been found that the oxygen concentration is 10.0E17 atoms / cm ³ or less, the silicon single crystal whose specific oxygen concentration is unknown is divided into two samples cut from the same silicon single crystal ingot. Processing 1 or processing 2 is performed, respectively, and the DSOD quality determination may be performed using a sample in which the pit localization state is more clearly confirmed. The inspection method for performing the DSOD quality determination is the inspection method A.
On the other hand, the inspection method B is a method in which a silicon single crystal having a lower oxygen concentration within the range of the oxygen concentration of 10.0E17 atoms / cm ³ or less is to be inspected, and includes the treatment 1. On the other hand, the inspection method C is for inspecting a silicon single crystal having a higher oxygen concentration within an oxygen concentration range of 10.0E17 atoms / cm ³ or less, and includes performing treatment 2. Details of processing 1 and processing 2 will be described later.

  The following description shall be applied to any of inspection methods A, B, and C unless otherwise specified. In the following, inspection methods A, B, and C are collectively referred to as the inspection method of the present invention.

  In the present invention, “DSOD pass / fail judgment” means that a silicon single crystal containing a large amount of DSOD (or presumed to contain a large amount) is judged as a defective product, and a silicon single crystal having a low DSOD (or presumed to be low) is judged as a good product To do.

Moreover, it can be confirmed, for example, by the following method that a sample cut from a silicon single crystal ingot grown by the CZ method or a silicon single crystal ingot grown by the CZ method does not contain COP and dislocation clusters. . Hereinafter, a silicon single crystal ingot grown by the Czochralski method (CZ method) is also simply referred to as “silicon single crystal ingot” or “ingot”.
A sample cut from a silicon single crystal ingot was immersed in an etching solution (mixing ratio was HF: K ₂ Cr ₂ O ₇ (0.15 mol) = 2: 1 by volume) for 30 minutes, and then the surface of the sample was optically processed. Observe with a microscope (magnification 100 to 400 times). As a result of the observation, it can be confirmed that COP and dislocation clusters are not included when no etch pit is observed.

  In one aspect, the sample for which the DSOD quality determination is performed can be a wafer shape sample. In another embodiment, the sample may be a sample obtained by cutting a silicon single crystal ingot in the ingot pulling-up axis direction (crystal growth axis direction).

In one aspect, the sample for determining whether or not the DSOD is good is a wafer shape sample, and the size of the region where the pits are localized is determined based on the following S1 and S2.
S1: Distance from the center of the sample to the inner peripheral edge of the outermost ring-shaped region where the pits are localized from the adjacent region, but in the sample where the outermost ring-shaped region does not exist, S1 = the sample The radius of
S2: The distance from the center of the sample to the outer peripheral edge of the central disk-shaped region where the pits are localized from the adjacent region, provided that S2 = 0 in the sample where the central disk-shaped region does not exist.

In one aspect, the wafer shape sample is a slag sample cut from the end of the silicon single crystal ingot. A slag sample is cut out from the end of the silicon single crystal ingot in the ingot pulling-up axis direction (crystal growth axis direction), and is obtained through wafer processing (including a wafer slicing step and a wafer polishing step). Absent.
The DSOD evaluation by the Cu deposition method described above is performed on a silicon single crystal wafer that has been subjected to mirror polishing as described in paragraph 0007 of Japanese Patent Laid-Open No. 2006-208314. Therefore, normally, the DSOD evaluation by the Cu deposition method is performed by extracting an evaluation wafer from a lot in which mirror polishing, which is the final process of wafer processing, is performed. However, as a result of evaluation at this stage, it is determined that a wafer in the same lot cannot be shipped as a product because it contains a lot of DSOD. This means that the waste of performing wafer processing (consuming labor and cost) as in the case of the lot to be shipped is generated. On the other hand, the silicon single crystal inspection method of the present invention can also be implemented using a slag sample. This makes it possible to inspect the silicon single crystal without causing the above waste.

A further aspect of the invention provides:
Growing an inspecting silicon single crystal ingot having an interstitial oxygen concentration not including COP and dislocation clusters (former ASTM) of 10.0E17 atoms / cm ³ or less by the Czochralski method,
Performing an inspection by the inspection method A, B or C on a sample cut from the inspection silicon single crystal ingot;
Determining a pulling condition of the silicon single crystal ingot based on the result of the inspection; and
Growing a silicon single crystal ingot having an interstitial oxygen concentration not including COP and dislocation clusters (former ASTM) of 10.0E17 atoms / cm ³ or less by the Czochralski method under the determined pulling conditions;
A method for producing a silicon single crystal containing
About.

  According to the present invention, it is possible to determine whether or not DSOD is good in a low oxygen concentration silicon single crystal that does not contain COP and dislocation clusters. Furthermore, by determining the pulling conditions based on the determination result, it is possible to stably supply a low oxygen concentration silicon single crystal that does not contain COPs and dislocation clusters and has a reduced DSOD.

It is a schematic diagram which shows the specific aspect of the pit location state in the surface of the wafer shape sample after the process 1 or the process 2. FIG. It is a schematic diagram which shows the specific aspect of the pit location state in the surface of the wafer shape sample after the process 1 or the process 2. FIG. It is a schematic diagram which shows the specific aspect of the pit location state in the surface of the wafer shape sample after the process 1 or the process 2. FIG. It is explanatory drawing which shows the structure of the silicon single crystal pulling apparatus used in the Example. The DS1 quality evaluation result by S1, oxygen concentration, and Cu deposition method measured about the sample group 1 mentioned later in an Example is shown. The DS2 quality evaluation result by S2, oxygen concentration, and Cu deposition method measured about the sample group 2 mentioned later in an Example is shown. It is explanatory drawing which shows the relationship between the crystal growth conditions in CZ method, and the kind and distribution of the area | region which generate | occur | produce in a silicon single crystal ingot.

[Inspection method of silicon single crystal]
In any of the inspection methods A, B and C described above, DSOD pass / fail judgment of a silicon single crystal sample having an oxygen concentration of 10.0E17 atoms / cm ³ or less that does not include COP and dislocation clusters is performed, including copper decoration and selective etching. This is performed based on the localized state of pits on the sample surface after (Process 1 or Process 2).

A silicon single crystal having an oxygen concentration of 10.0E17 atoms / cm ³ or less is a silicon single crystal having a low oxygen concentration that has been attracting attention in recent years. As described above, the present inventors within the above oxygen concentration range,
-A silicon single crystal having a lower oxygen concentration has a tendency that DSOD is more likely to occur as the region where pits are localized by treatment 1 is larger;
-A silicon single crystal with a higher oxygen concentration has a tendency that DSOD is more likely to occur as the region where pits are localized by treatment 2 is larger.
New knowledge that was previously unknown was obtained. As described above, the present inventors have determined that the region where the pits are localized is the Pv region, and the silicon single crystal having a lower oxygen concentration is processed 1 and the silicon single crystal having a higher oxygen concentration is processed 2. It is presumed that the Pv region can be selectively revealed as a region where pits are localized.
Therefore, in the present invention, the inspection method B including the treatment 1 is performed on a silicon single crystal having a lower oxygen concentration, specifically, a silicon single crystal having an oxygen concentration of 7.5E17 atoms / cm ³ or less. Further, the inspection method C including the treatment 2 is performed on a silicon single crystal having a higher oxygen concentration, specifically, a silicon single crystal having an oxygen concentration of 5.0E17 atoms / cm ³ or more and 10.0E17 atoms / cm ³ or less.
Note that, in the above, the oxygen concentration of the sample for performing the inspection method B and the oxygen concentration of the sample for performing the inspection method C partially overlap, but the sample in the range where the oxygen concentration is overlapped is the inspection method B. In any of the inspection methods C, it is possible to determine whether or not the DSOD is good based on the localized state of the pits on the sample surface after the process including the copper decoration and the selective etching (process 1 or process 2).

On the other hand, if it is known from the manufacturing conditions that the oxygen concentration of the silicon single crystal is 10.0E17 atoms / cm ³ or less, but the oxygen concentration is not known in detail, the inspection method A is performed. . In the inspection method A, one of two samples cut out from the same ingot is subjected to treatment 1 and the other is subjected to treatment 2, and the sample surface after treatment 1 is compared with the sample surface after treatment 2. If the localized state of the pits is more clearly confirmed in the former, it can be estimated that the silicon single crystal ingot has an oxygen concentration on the low oxygen concentration side within a range of 10.0E17 atoms / cm ³ or less. . On the other hand, if the localized state of pits is more clearly observed in the latter, the silicon single crystal ingot is assumed to have an oxygen concentration on the high oxygen concentration side within a range of 10.0E17 atoms / cm ³ or less. Can do. As described above, the Pv region can be selectively revealed as a region where pits are localized by treatment 1 for a silicon single crystal having a lower oxygen concentration and by treatment 2 for a silicon single crystal having a higher oxygen concentration. It is because it is considered.
In the inspection method A, a sample in which the localized state of the pits is more clearly confirmed is determined as an evaluation sample among the sample subjected to the processing 1 and the sample subjected to the processing 2, and the surface of the evaluation sample is The DSOD quality determination is performed based on a determination criterion for determining that the DSOD is larger as the area where the pits are localized is wider.

As described above, according to the present invention, the DSOD determination of various silicon single crystals having an oxygen concentration of 10.0 E17 atoms / cm ³ or less can be performed by the inspection methods A, B, or C.

  Hereinafter, the inspection method of the present invention will be described in more detail.

<Inspection target>
In the inspection method of the present invention, the sample on which the DSOD quality determination is performed is a sample cut out from a silicon single crystal ingot grown by the CZ method. For example, a silicon single crystal ingot can be sliced laterally using a wire saw or the like to obtain a wafer-shaped sample. Alternatively, the sample can be cut by cutting a silicon single crystal ingot in the crystal growth axis direction. For the aforementioned reasons, the sample is preferably a slag sample. However, the inspection method of the present invention may be performed on a sample that has undergone wafer processing.

The sample is a silicon single crystal that does not contain COP and dislocation clusters and has an oxygen concentration of 10.0E17 atoms / cm ³ or less. The oxygen concentration of the sample for which the inspection methods B and C are performed is as described above. Note that the oxygen concentration of the sample for performing the inspection methods A and B is, for example, 4.0E17 atoms / cm ³ or more, but is not limited thereto.

  Next, processing (processing 1 and processing 2) performed on the sample will be described.

<Process 1 and Process 2>
Processing 1 performed in the inspection methods A and B is as follows:
Contaminating the surface of the sample with copper (Cu) (hereinafter also referred to as “Cu contamination”);
Subjecting the contaminated sample to a heating and cooling treatment in which the sample is heated at a temperature range of 700 ° C. or higher and lower than 800 ° C. for 5 minutes or more and then rapidly cooled at a temperature-decreasing rate exceeding 2.5 ° C./min.
Selectively etching the sample surface after the heating and cooling treatment;
Is a process including
Processing 2 performed in the inspection methods A and C is as follows:
Subjecting the sample to heating at a temperature range of 750 to 900 ° C. and then pre-heating at a temperature range of 1000 to 1150 ° C .;
Contaminating the surface of the pretreated sample with copper;
Subjecting the contaminated sample to a heating and cooling treatment in which the sample is heated at a temperature range of 700 ° C. or higher and lower than 800 ° C. for 5 minutes or more and then rapidly cooled at a temperature-decreasing rate exceeding 2.5 ° C./min from the temperature range;
Selectively etching the sample surface after the heating and cooling treatment;
Is a process including

As described above, the process 1 includes “Cu contamination”, “heating / cooling process”, and “selective etching”. Process 2 performs the pre-processing prior to process 1.
As described above, the present inventors presume that a silicon single crystal having a wider Pv region tends to generate more DSOD. A sample having an oxygen concentration on the low oxygen concentration side within a range of 10.0E17 atoms / cm ³ or less can selectively decorate the Pv region by Cu contamination and heating / cooling treatment in treatment 1 (Pv The present inventors consider that the Pv region can be exposed as a region where the pits are localized by removing the Cu compound by selective etching and forming pits by selective etching. .
On the other hand, a sample in which the oxygen concentration is on the high oxygen concentration side within a range of 10.0E17 atoms / cm ³ or less can selectively Cu decorate the Pv region by Cu contamination and heating / cooling treatment performed after the pretreatment. If the Cu compound is removed by selective etching and pits are formed by the selective etching, the Pv region can be manifested as a region where the pits are localized. I guess.

  Since the process 2 includes steps common to the process 1, the process 2 will be described below mainly after the process 1 is mainly described.

Cu contamination can be performed in the same manner as Cu contamination in general Cu decoration. Specifically, Cu contamination can be performed as follows, for example. After the sample is immersed in the copper-containing solution, the sample is taken out from the solution and dried by natural drying or the like for a predetermined time. As the copper-containing solution, an aqueous copper nitrate solution, a mixed solution of copper nitrate and hydrofluoric acid (HF), or the like can be used. The copper concentration of the copper-containing solution is preferably 3E20 atoms / cm ³ or more from the viewpoint of improving the reliability of the DSOD quality determination. The higher the copper concentration of the copper-containing solution, the better from the viewpoint of improving the reliability of the DSOD quality determination. For example, a solution containing copper up to the upper limit of solubility can also be used. Note that the solubility of copper depends on the temperature, and is, for example, about 44E20 atoms / cm ^{3 at} 0 ° C.

  Next, a heat-cooling process is performed in which the sample after Cu contamination is heat-treated and then rapidly cooled. The heat treatment can be performed using various heat treatment furnaces such as a desktop electric furnace and a horizontal oxidation furnace that are usually used for heat treatment of silicon wafers. In the present invention, the temperature and speed described for the heat treatment of the sample refer to the temperature and speed for the atmosphere to which the sample is exposed (for example, the atmosphere in the furnace of the heat treatment furnace) unless otherwise specified. In the present invention, the atmosphere to which the sample is exposed is not particularly limited unless otherwise specified, and can be any atmosphere such as in the air.

  Cu can be thermally diffused in the sample by heat treatment after Cu contamination. In the treatment 1, the heating temperature of the sample after Cu contamination is 700 ° C. or more and less than 800 ° C., and the heating time in this temperature range is 5 minutes or more. If it is 5 minutes or more, Cu can be sufficiently thermally diffused, and even if it is made longer, there is no significant difference, so the upper limit of the heating time is not particularly limited. For example, it can be performed for about 10 minutes, but in order to perform the inspection in a short time, it is most preferable that the heating time is about 5 minutes. It is not essential to keep the temperature constant during heating, and the temperature may be changed as long as it is in the range of 700 ° C. or higher and lower than 800 ° C. In addition, the heat treatment furnace before introducing the sample may be heated to the above heating temperature, or may be heated to the above heating temperature after introducing the sample. When the temperature is raised after sample introduction, the rate of temperature rise is preferably about 2 to 7 ° C./minute from the viewpoint of precipitation of the Cu compound during subsequent quenching.

  In the treatment 1, the present inventors infer that the Cu compound can be precipitated in the Pv region by rapidly cooling the sample after the heat treatment. In normal Cu decoration, for example, as described in Patent Document 1 described above, the sample is removed from the heat treatment furnace and left to cool to room temperature. On the other hand, in the process 1, the cooling rate is controlled so that the cooling rate during cooling exceeds 2.5 ° C / min. Preferably, the temperature lowering rate when the temperature is lowered from the heating temperature range (700 ° C. or higher and lower than 800 ° C.) to a temperature lower by 50 to 100 ° C. is set to exceed 2.5 ° C./min. Since Cu is an element having a high diffusion rate among various elements, Cu is diffused outward from the Pv region when the cooling rate from the heating temperature range is 2.5 ° C. or less, and Cu decoration in the Pv region is caused. The present inventors believe that there is a tendency to become insufficient. The temperature drop rate can be controlled by setting the heat treatment furnace.

  The temperature lowering rate is preferably as fast as possible to suppress the outward diffusion of Cu. For example, it can be set to 100 ° C./min or more, further 200 ° C./min or more, particularly 300 ° C./min or more. Considering the performance of a general heat treatment furnace, the upper limit may be about 500 ° C./min or less. However, as described above, the upper limit is not particularly limited because it is preferably as fast as possible to suppress the outward diffusion of Cu. The sample cooled to a predetermined temperature may be removed from the heat treatment furnace and allowed to stand at room temperature, for example. In addition, the room temperature in this invention shall mean the temperature of about 15-25 degreeC.

  When the sample surface subjected to the Cu contamination and the heating and cooling treatment is selectively etched, the Cu compound deposited by Cu decoration can be removed from the sample surface. Thereby, it is possible to detect a portion where the Cu compound is deposited as a pit.

The selective etching may be performed using a seco solution (Secco etching (eg, HF = 100 cm ^3, K ₂ Cr ₂ O ₇ = 50 g (0.15 mol / liter) composition)) or by a light solution (Light etching (for example, HF = 60 cm ³ , HNO ₃ = 30 cm ³ , Cr ₂ O ₃ = 30 cm ³ (5 mol / liter), Cu (NO ₃ ) ₂ = 2.2 g, H ₂ O = 60 cm ³ , CH ₃ COOH = 60 cm ³ composition)). It is preferable to perform light etching from the viewpoint of the stability of the etching solution. The etching amount may be an etching amount capable of confirming the pit from which the Cu compound has been removed.

In the treatment 2, the pretreatment performed before the Cu contamination is performed by heating the sample before the Cu contamination in a temperature range of 750 to 900 ° C. (hereinafter referred to as “low temperature heating”), and a temperature of 1000 to 1150 ° C. It is performed by heating in a temperature range (hereinafter referred to as “high temperature heating”). By performing treatment 1 (the above-mentioned Cu contamination, heating / cooling treatment and selective etching) after performing two-step heating in the above temperature range, the oxygen concentration is within the range of 10.0E17 atoms / cm ³ or less, and the oxygen concentration side is high. The present inventors infer that the Pv region can be revealed as the region where the pits are localized in the sample in FIG.

  The low-temperature heating in the pretreatment can be performed for about 1 to 3 hours, for example, but can be performed for longer than 3 hours. On the other hand, high-temperature heating can be performed for about 5 to 16 hours, but can be performed for longer than 16 hours. The rate of temperature rise when shifting from low temperature heating to high temperature heating can be set to about 1 to 10 ° C./min, for example. The pretreatment is preferably performed in an oxygen-containing atmosphere (oxidizing atmosphere). The oxygen concentration in the oxidizing atmosphere is, for example, 10 to 100% by volume. In addition, it is preferable to perform the pretreatment by dry oxidation in order to promote the growth of precipitates.

  When shifting from the pretreatment to Cu contamination, the sample may be taken out from the heat treatment furnace immediately after the pretreatment, but in order to prevent the occurrence of slip or the like due to rapid cooling, it is preferable to control the temperature drop rate. From this point, it is preferable to cool the sample to 900 to 950 ° C. at a temperature drop rate of about 1 to 10 ° C./min after heating at a high temperature, and then remove the sample from the heat treatment furnace and leave it at room temperature.

<DSOD pass / fail judgment>
In the inspection methods A, B, and C, the pit localization state on the sample surface after the processing 1 or the processing 2 described above is observed, and a criterion for determining that the larger the region where the pit is localized is, the greater the DSOD is. Based on this, the DSOD quality determination is performed. As described above, it is presumed that the Pv region can be selectively exposed as a region where pits are localized by the processing 1 or the processing 2, and the DSOD is generated as the region thus exposed becomes wider. This is because it tends to be easy. The pits may be observed visually or under a microscope. In the inspection method A, as described above, one of the two samples is subjected to the treatment 1 and the other is subjected to the treatment 2, and the two sample surfaces are compared, and the sample in which the localized state of the pits is more clearly confirmed. Are determined as samples for evaluation. For example, among the two samples, a sample with clearer contrast (shading) in a photograph or image obtained by photographing the sample surface can be determined as an evaluation sample.

  FIGS. 1 to 3 are schematic views showing a specific mode of a pit locality state on the surface of a wafer-shaped sample after the process 1 or the process 2. FIG. In the figure, the area shown in gray is the area where the pits are localized. As described above, the region where the pits are localized is assumed to be a Pv region.

In the wafer shape sample, since the region where the pits are localized usually appears concentrically as shown in FIGS. 1 to 3, the area of the pits is increased by the following distances S1 and S2 from the center of the sample. Can be evaluated.
S1: Distance from the center of the sample to the inner peripheral edge of the outermost peripheral ring-shaped region where pits are localized from the adjacent region, but in the sample where the outermost peripheral ring-shaped region does not exist as shown in FIG. , S1 = the radius of the sample.
S2: Distance from the center of the sample to the outer peripheral edge of the central disk-shaped area where the pits are localized from the adjacent area, but in the sample where the central disk-shaped area does not exist as shown in FIG. 3, S2 = 0.
That is, the smaller S1, the wider the outermost ring-shaped region, and the larger S2, the wider the central disc-like region. Therefore, it can be determined that the smaller the S1 and the larger S2, the more DSOD. For example, in one aspect, threshold values can be set for S1 and S2, or S1 + S2, and in the determination of DSOD quality, it can be determined that the measured value is equal to or less than the threshold value, and can be determined to be defective if the measured value exceeds the threshold value. . The measurement of S1 and S2 can be performed on, for example, a photograph or image obtained by photographing the sample surface.

As described above, according to the inspection methods A, B, and C, it is possible to perform the DSOD quality determination based on the localized state of the pits on the sample surface after the processing 1 or the processing 2.
In one aspect, the occurrence rate of DSOD defects can be reduced by setting a pulling condition based on the inspection result. This point will be further described below.
In one embodiment, if a sample (for example, a slag sample) is inspected by the inspection method of the present invention and is determined to be a non-defective product as a result of the DSOD quality determination, a silicon single crystal wafer manufactured from the same ingot as this sample Can be shipped as a product wafer. This makes it possible to stably supply product wafers that do not contain DSOD (or have low DSOD) to the market.

[Method for producing silicon single crystal]
A further aspect of the invention provides:
Growing an inspecting silicon single crystal ingot having an interstitial oxygen concentration not including COP and dislocation clusters (former ASTM) of 10.0E17 atoms / cm ³ or less by the Czochralski method,
Inspecting the sample cut out from the inspection silicon single crystal ingot by any of the inspection methods A, B, and C described above,
Determining a pulling condition of the silicon single crystal ingot based on the result of the inspection (hereinafter, also simply referred to as “pulling condition”); and
Growing a silicon single crystal ingot having an interstitial oxygen concentration not including COP and dislocation clusters (former ASTM) of 10.0E17 atoms / cm ³ or less by the Czochralski method under the determined pulling conditions;
A method for producing a silicon single crystal containing
About. According to the inspection methods A, B, and C, since it is possible to determine the quality of the DSOD in a shorter time compared to the Cu deposition method described above, feedback to the pulling conditions can be performed quickly. As a result, it is possible to prevent the continuous production of a silicon single crystal ingot containing a DSOD defect. Further, as described above, since the inspection methods A, B, and C can be performed on a sample that has not undergone wafer processing, the advantages detailed above can also be obtained. Furthermore, by applying feedback to the pulling conditions based on the result of the inspection by such an inspection method, the DSOD failure occurrence rate (DSOD failure rate) can be reduced. If the DSOD defect rate can be reduced, the necessity of storing a large amount of stock in preparation for a delay in product shipment due to the occurrence of defective products is reduced, and the number of stocks can be reduced.

The silicon wafer manufacturing process, including the growth of silicon single crystals by the CZ method,
(1) Lifting condition setting step;
(2) A step of growing a silicon single crystal ingot by the CZ method under the set pulling conditions;
(3) Cutting process of the grown ingot;
(4) Wafer processing process (including wafer slicing process and wafer polishing process);
Is usually included. For example, the inspection methods A, B, and C can be performed using the slag sample obtained in the ingot cutting process as described above. By setting the pulling condition in the pulling condition setting step based on the result of the inspection performed using such a sample, the DSOD defect rate can be lowered. For example, when the DSOD defect rate exceeds a preset threshold value, the DSOD non-defective rate (ratio of the number of non-defective products to the total number of manufactured products) can be increased by decreasing the pulling speed V. In the silicon single crystal manufacturing method of the present invention, the silicon single crystal manufacturing and the silicon wafer manufacturing are performed except that the pulling condition is fed back based on the inspection result of any of the inspection methods A, B, and C. The publicly known technique can be applied without any limitation.

  Hereinafter, the present invention will be further described based on examples. However, the present invention is not limited to the embodiment shown in the examples.

1. Silicon Single Crystal Growth by CZ Method Using a silicon single crystal pulling apparatus shown in FIG. 4, silicon single crystal ingots having various oxygen concentrations not containing COP and dislocation clusters were grown. Details of the silicon single crystal pulling apparatus shown in FIG. 4 will be described below.
A silicon single crystal pulling apparatus 10 shown in FIG. 4 includes a chamber 11, a support rotating shaft 12 that passes through the center of the bottom of the chamber 11 and is provided in the vertical direction, and a graphite susceptor fixed to the upper end of the supporting rotating shaft 12. 13, a quartz crucible 14 accommodated in the graphite susceptor 13, a heater 15 provided around the graphite susceptor 13, a support shaft driving mechanism 16 for moving the support rotating shaft 12 up and down, and a seed crystal Heating of the silicon single crystal ingot 20 by radiant heat from the seed chuck 17 to be held, the pulling wire 18 for suspending the seed chuck 17, the wire winding mechanism 19 for winding the wire 18, and the heater 15 and the quartz crucible 14. In order to prevent temperature fluctuation of the silicon melt 21 A member 22, and a control unit 23 that controls each unit.
A gas inlet 24 for introducing Ar gas into the chamber 11 is provided in the upper part of the chamber 11. Ar gas is introduced into the chamber 11 from the gas introduction port 24 through the gas pipe 25, and the introduction amount is controlled by the conductance valve 26.
A gas discharge port 27 for exhausting Ar gas in the chamber 11 is provided at the bottom of the chamber 11. Ar gas in the sealed chamber 11 is discharged from the gas outlet 27 through the exhaust pipe 28 to the outside. A conductance valve 29 and a vacuum pump 30 are installed in the middle of the exhaust gas pipe 28, and the pressure inside the chamber 11 is reduced by controlling the flow rate with the conductance valve 29 while sucking Ar gas in the chamber 11 with the vacuum pump 30. The state is maintained.
Further, a magnetic field supply device 31 for applying a magnetic field to the silicon melt 21 is provided outside the chamber 11. The magnetic field supplied from the magnetic field supply device 31 may be a horizontal magnetic field or a cusp magnetic field.

2. Preparation of inspection sample The silicon single crystal ingot grown in step 1 was cut, and a slag sample (wafer shape sample, radius 150 mm) was cut out from the end of the ingot. The slag sample obtained from an ingot having an oxygen concentration of 7.0E17 atoms / cm ³ or less is subjected to the following treatment 1, and the slag sample obtained from an ingot having an oxygen concentration of more than 7.0E17 atoms / cm ^{3 is} 10.0E17 atoms / cm ³ or less. Treatment 2 was performed.

3. Process 1
(I) The sample was ultrasonically washed with pure water, then mirror-etched with an etching solution of HNO ₃ : HF = 5: 1 (volume ratio) for 5 minutes, and then rinsed with water for 10 minutes.
(Ii) As a copper-containing solution for Cu decoration, an aqueous copper nitrate solution in which 30 g of copper nitrate trihydrate (Cu (NO ₃ ) ₂ .3H ₂ O) was dissolved in 5 liters of water was prepared. The sample treated with the above (i) was immersed in the prepared aqueous copper nitrate solution for 5 minutes, and then pulled up and allowed to dry naturally.
(Iii) The sample subjected to the above treatment (ii) was loaded into a desktop electric furnace (furnace temperature 660 ° C., furnace atmosphere: air), heated at 5 ° C./min, and held at 750 ° C. for 5 min. . Then, after cooling to 660 degreeC with the temperature-fall rate of 5 degree-C / min, it unloaded from the desktop electric furnace.
(Iv) The sample surface subjected to the treatment (iii) is etched with an etching solution of HNO ₃ : HF = 5: 1 (volume ratio) for 5 minutes, rinsed with water for 10 minutes, and further etched with a light solution at an etching amount of 5 μm. Selective etching was performed.

4). Process 2
(I) The sample was ultrasonically washed with pure water, then mirror-etched with an etching solution of HNO ₃ : HF = 5: 1 (volume ratio) for 5 minutes, and then rinsed with water for 10 minutes.
(Ii) The sample subjected to the above treatment (i) was loaded into a heat treatment furnace, maintained in an oxidizing atmosphere (dry O ₂ (= dry oxygen 100%)) at 780 ° C. for 3 hours, and then 1000 ° C. at 5 ° C./min. The temperature was raised to and kept at the same temperature for 16 hours. Thereafter, the temperature was lowered to 950 ° C. at 2 ° C./min, unloaded from the heat treatment furnace, and cooled to room temperature.
(Iii) The sample subjected to the treatment (ii) was etched with an etching solution of H ₂ O: HF = 1: 1 (volume ratio) for 3 minutes to remove the oxide film on the surface.
(Iv) The sample subjected to the treatment (iii) was mirror-etched with an etching solution of HNO ₃ : HF = 5: 1 (volume ratio) for 5 minutes, and then rinsed with water for 10 minutes. Thereafter, the above 3. (Ii) to (iv) were applied.

5. Evaluation of S1 and S2 The surface of the sample after the selective etching in the above processing 1 and processing 2 was observed under a condenser lamp, and a photograph was taken. The sample was classified into the following sample group 1 and sample group 2 using the photograph taken. S1 for sample group 1 and S2 for sample group 2 were measured.
(Sample group 1)
A sample group in which the outermost peripheral ring-shaped region in which pits are localized is confirmed from the adjacent region, and the central disk-shaped region in which pits are localized is not confirmed from the adjacent region. Therefore, S2 = 0.
(Sample group 2)
A sample group in which a central disk-shaped region in which pits are localized is confirmed from an adjacent region, and an outermost ring-shaped region in which pits are localized is not confirmed from an adjacent region. Therefore, S1 is the sample radius.

6). DSOD pass / fail evaluation by Cu deposition method After wafer processing was performed on a wafer sample cut out from the same ingot as the slag samples subjected to the above processing 1 and processing 2, DSOD pass / fail evaluation by Cu deposition method was performed, and a predetermined threshold value was obtained. Based on the above, good products and defective products were classified. This evaluation took about two weeks.

7). Evaluation Results FIG. 5 shows DSOD quality evaluation results for sample group 1 by S1, oxygen concentration, and Cu deposition method. For sample group 1, FIG. 5 shows the oxygen concentration at a position 10 mm inside from the outermost peripheral edge of the sample.
For sample group 2, DSOD quality evaluation results by S2, oxygen concentration, Cu deposition method are shown in FIG. For sample group 2, the oxygen concentration at the center of the sample is shown in FIG.
The oxygen concentration is a value measured by an infrared absorption method.
The broken line shown in FIG. 5 is a straight line of the linear function y = −4.3 × x + 136. From the results shown in FIG. 5, with respect to the sample group 1 (S2 = 0 as described above), “S1> −4.3Oi + 136” is used as a criterion for determining the DSOD quality for the interstitial oxygen concentration Oi. By using it, it can be confirmed that a sample determined as a non-defective product in the DSOD quality evaluation by the Cu deposition method can be specified based on S1.
On the other hand, the broken line shown in FIG. 6 is a straight line with y = 65. From the results shown in FIG. 6, for sample group 2 (as described above, S1 is the sample radius), “S2 <65 mm” is used as a criterion for determining the DSOD quality, thereby determining the DSOD quality by the Cu deposition method. It can be confirmed that the sample determined to be non-defective in the evaluation can be specified based on S2.

8). DSOD pass / fail judgment based on S1 and S2 Ingots with various oxygen concentrations are nurtured in the same manner as in 2. above. Similarly, a slag sample was obtained. The slag sample obtained from an ingot having an oxygen concentration of 7.0E17 atoms / cm ³ or less is 3. The slag sample obtained from the ingot having the oxygen concentration of 7.0E17 atoms / cm ^{3 and} 10.0E17 atoms / cm ³ or less was applied to the above 4. Treatment 2 was performed.
The sample surface after the selective etching in treatment 1 and treatment 2 was observed under a condenser lamp, and a photograph was taken. Samples were classified into Sample Group 1 and Sample Group 2 described above using the photographed photographs. S1 for sample group 1 and S2 for sample group 2 were measured. For sample group 1, “S1> -4.3Oi + 136” and for sample group 2, “S2 <65 mm” was used as a determination criterion for determining DSOD quality, and a DSOD quality determination based on S1 and S2 was performed.
After wafer processing was performed on a wafer sample cut out from the same ingot as each slag sample subjected to processing 1 and processing 2, DSOD quality evaluation was performed by the Cu deposition method. Based on the same threshold value, non-defective products and defective products were classified.
As for the sample group 1, as for the 30 non-defective samples satisfying “S1> −4.3Oi + 136”, as a result of the DSOD pass / fail evaluation of the wafer samples cut out from the same ingot by the Cu deposition method, 29 non-defective samples were found. On the other hand, as a result of DSOD quality evaluation by the Cu deposition method of wafer samples cut out from the same ingot for 30 defective samples that do not satisfy “S1> −4.3Oi + 136”, there were only 3 good samples. It was.
As for sample group 2, as a result of DSOD quality evaluation of the wafer samples cut out from the same ingot with respect to 30 good samples satisfying “S2 <65 mm”, the number of good samples was 28. On the other hand, as for the 30 defective samples not satisfying “S2 <65 mm”, as a result of DSOD quality evaluation of the wafer samples cut out from the same ingot by the Cu deposition method, there were only 5 good samples.
From the above results, it can be confirmed that the quality determination of DSOD can be performed with high reliability by the inspection method of the present invention.

9. Setting of Pulling Conditions Based on DSOD Pass / Fail Judgment Results Based on S1 and S2 Two types of apparatuses shown in FIG. 4 (apparatus 1 and apparatus 2) were prepared, and ingots were grown under various pulling conditions in each apparatus. About the obtained ingot, the DSOD pass / fail judgment based on S1 and S2 is performed by the above-described method, and for the sample classified into the sample group 1, the ingot growing condition in which a sample not satisfying “S1> −4.3Oi + 136” is cut out Is changed (lowering the pulling speed), and for the samples classified into the sample group 2, the growing condition of the ingot in which the sample not satisfying “S2 <65 mm” is changed (lowering the pulling speed) is changed. Ingots were nurtured under conditions.
Before and after the change of the growth conditions (feedback) and after the feedback, the wafer sample cut out from the obtained ingot is subjected to wafer processing, and then the DSOD quality evaluation is performed by the Cu deposition method. Based on the same threshold value, non-defective products and defective products were classified. The results are shown in Table 1 below.

  From the results shown in Table 1, it can be confirmed that the DSOD non-defective product rate can be improved by changing the pulling conditions based on the inspection result by the inspection method of the present invention.

10. Study on Oxygen Concentration For wafer-shaped slag samples cut from silicon single crystal ingots of various oxygen concentrations not containing COP and dislocation clusters, the above 3. Process 1 or 4 above. After performing the treatment 2, the sample surface after each treatment was observed under a condenser lamp, and the following tendency was confirmed.
(1) For the sample having an oxygen concentration of 7.5E17 atoms / cm ³ or less, the localized state of the pits was clearly confirmed on the sample surface after the treatment 1. When the oxygen concentration exceeded 7.5E17 atoms / cm ³ (particularly when the oxygen concentration was 8.0E17 atoms / cm ³ or more), it was difficult to confirm the region where the pits were localized on the sample surface after treatment 1.
(2) For samples having an oxygen concentration of 5.0E17 atoms / cm ³ or more and 10.0E17 atoms / cm ³ or less, the localized state of pits was clearly confirmed on the surface of the sample after treatment 2. When the oxygen concentration is 6.0E17 atoms / cm ³ or less, compared to the case where the oxygen concentration is more than 6.0E17 atoms / cm ³ , there is a tendency that the contrast (shading) of the photograph and the image of the sample surface after the processing 2 becomes lighter. When the oxygen concentration was less than 5.0E17 atoms / cm ³ , it was difficult to confirm the region where the pits were localized on the sample surface after the treatment 2.

  The present invention is useful in the field of manufacturing silicon single crystals.

Claims (6)

Subjecting one of two samples cut from the same silicon single crystal ingot grown by the Czochralski method to the following treatment 1 and the other to the following treatment 2;
The sample surface after the following treatment 1 is compared with the sample surface after the following treatment 2, and a sample in which the localized state of the pits is more clearly confirmed is determined as an evaluation sample, and
Performing a DSOD pass / fail determination based on a determination criterion that determines that the larger the region where the pits are localized in the determined sample surface for evaluation, the greater the DSOD,
Including
The method for inspecting a silicon single crystal, wherein the two samples are silicon single crystals having an interstitial oxygen concentration not including COP and dislocation clusters (former ASTM) of 10.0E17 atoms / cm ³ or less.
(Process 1)
Contaminating the surface of the sample with copper,
Subjecting the contaminated sample to a heating and cooling treatment in which the sample is heated at a temperature range of 700 ° C. or higher and lower than 800 ° C. for 5 minutes or more and then rapidly cooled at a temperature-decreasing rate exceeding 2.5 ° C./min from the temperature range;
Selectively etching the sample surface after the heating and cooling treatment;
Processing including
(Process 2)
Subjecting the sample to heating at a temperature range of 750 to 900 ° C. and then pre-heating at a temperature range of 1000 to 1150 ° C .;
Contaminating the surface of the pretreated sample with copper;
Subjecting the contaminated sample to a heating and cooling treatment in which the sample is heated at a temperature range of 700 ° C. or higher and lower than 800 ° C. for 5 minutes or more and then rapidly cooled at a temperature-decreasing rate exceeding 2.5 ° C./min from the temperature range;
Selectively etching the sample surface after the heating and cooling treatment;
Processing including Subjecting a sample cut from a silicon single crystal ingot grown by the Czochralski method to the following treatment 1;
Performing a DSOD pass / fail determination based on a determination criterion that determines that the greater the region where pits are localized on the sample surface after the following treatment 1, the greater the DSOD,
Including
The method for inspecting a silicon single crystal, wherein the sample is a silicon single crystal having an interstitial oxygen concentration not including COP and dislocation clusters (former ASTM) of 7.5E17 atoms / cm ³ or less.
(Process 1)
Contaminating the surface of the sample with copper,
Subjecting the contaminated sample to a heating and cooling treatment in which the sample is heated at a temperature range of 700 ° C. or higher and lower than 800 ° C. for 5 minutes or more and then rapidly cooled at a temperature-decreasing rate exceeding 2.5 ° C./min from the temperature range;
Selectively etching the sample surface after the heating and cooling treatment;
Processing including Subjecting a sample cut from a silicon single crystal ingot grown by the Czochralski method to the following treatment 2;
Performing a DSOD pass / fail judgment based on a judgment criterion for determining that the larger the region where the pits are localized on the sample surface after the treatment 2 below, the greater the DSOD,
Including
The method for inspecting a silicon single crystal, wherein the sample is a silicon single crystal having an interstitial oxygen concentration (former ASTM) not including COP and dislocation clusters of 5.0E17 atoms / cm ³ or more and 10.0E17 atoms / cm ³ or less.
(Process 2)
Subjecting the sample to heating at a temperature range of 750 to 900 ° C. and then pre-heating at a temperature range of 1000 to 1150 ° C .;
Contaminating the surface of the pretreated sample with copper;
Subjecting the contaminated sample to a heating and cooling treatment in which the sample is heated at a temperature range of 700 ° C. or higher and lower than 800 ° C. for 5 minutes or more and then rapidly cooled at a temperature-decreasing rate exceeding 2.5 ° C./min from the temperature range;
Selectively etching the sample surface after the heating and cooling treatment;
Processing including The sample is a wafer shape sample,
The method for inspecting a silicon single crystal according to any one of claims 1 to 3, wherein the area of the region where the pits are localized is determined based on S1 and S2 below.
S1: Distance from the center of the sample to the inner peripheral edge of the outermost ring-shaped region where the pits are localized from the adjacent region, but in the sample where the outermost ring-shaped region does not exist, S1 = the sample The radius of
S2: The distance from the center of the sample to the outer peripheral edge of the central disk-shaped region where the pits are localized from the adjacent region, provided that S2 = 0 in the sample where the central disk-shaped region does not exist. 5. The method for inspecting a silicon single crystal according to claim 4, wherein the wafer shape sample is a slag sample cut out from an end portion of the silicon single crystal ingot. Growing an inspecting silicon single crystal ingot having an interstitial oxygen concentration not including COP and dislocation clusters (former ASTM) of 10.0E17 atoms / cm ³ or less by the Czochralski method,
Performing the inspection by the method according to any one of claims 1 to 5 for a sample cut from the silicon single crystal ingot for inspection,
Determining a pulling condition of the silicon single crystal ingot based on the result of the inspection; and
Growing a silicon single crystal ingot having an interstitial oxygen concentration not including COP and dislocation clusters (former ASTM) of 10.0E17 atoms / cm ³ or less by the Czochralski method under the determined pulling conditions;
A method for producing a silicon single crystal comprising: