TWI486493B - Inspection method and fabricating method for silicon single crystal - Google Patents

Description

Method and method for inspecting single crystal

The present invention relates to a method for inspecting a single crystal of silicon grown by the Czochralski method. In detail, the present invention relates to a method for inspecting a single crystal of the following, the inspection of the single crystal of the single crystal The method can detect the L/D region and the B-band region in the single crystal of low oxygen concentration cultivated by the Chai method with high sensitivity.

Further, the present invention relates to a method for producing a ruthenium single crystal which is obtained by using the inspection result of the above-described inspection method, thereby providing a single crystal which does not include an L/D region and a B-band region. .

The Chai method (hereinafter also referred to as "CZ method") is widely used as a method for cultivating a single crystal for semiconductor wafer manufacturing, which is a single crystal from a raw material melt. The crystal is grown on one side.

Regarding the CZ method described above, it is known that the type and distribution of defects introduced into the crystal during the single crystal growth depends on the pulling speed V of the crystal and the temperature gradient G of the solid-liquid interface. Fig. 6 is a view showing a general relationship between V/G and the type and distribution of defects. As shown in Fig. 6, when V/G reaches a certain value or more, the vacancies are excessive, and a void originated (COP), which is a void defect formed by atomic vacancy, is generated. On the other hand, in the case where V/G is small, the germanium atoms between the crystal lattices are excessive, so that the aggregates of germanium between the crystal lattices are called large dislocations (L/D). Dislocation cluster.

Further, between the region where the COP is generated and the region where the L/D is generated (L/D region), a plurality of regions having different behaviors at the time of heat treatment are included. As shown in FIG. 6, between the region where the COP is generated and the region where the L/D is generated, the OSF region, the Pv region, and the Pi region exist in the order of V/G from large to small. The OSF region refers to a region containing a plate-like oxygen precipitate in an as-grown state (a state in which no heat treatment is performed after crystal growth) (Oxidation Induced Stacking Fault (OSF)) Nuclear), when thermally oxidized by high temperature (generally about 1000 ° C to 1200 ° C), OSF is produced. The Pv region is a region which contains an oxygen deposition nucleus in an as-grown state, and is likely to generate oxygen evolution when subjected to heat treatment at a low temperature and a high temperature (for example, at about 800 ° C and about 1000 ° C). Things. The Pi region refers to a region which hardly contains an oxygen deposition nucleus in an as-grown state, and it is difficult to generate oxygen precipitates even when heat treatment is performed. Further, when V/G is gradually lowered, a B-band region is formed adjacent to the L/D region, and the B-band region is a region which is a part of the Pi region and is likely to generate oxygen precipitates.

When an integrated circuit is formed on the surface layer portion of the single crystal wafer, the COP and L/D have a large influence on the device characteristics. Therefore, it is preferable to cultivate the single crystal without causing the above defects. Therefore, it is important to examine the cultivated single crystals, correctly grasp the distribution of each region, and make the feedback required for crystal growth. For example, when the OSF region is generated, the cultivation condition is corrected so that the pulling speed V is lowered, and when the B-band is generated, the cultivation condition is corrected so that the pulling speed V is increased. Thus, it is possible to produce a simple crystal having no crystal defects with good yield and stability.

At present, a Cu decoration method is widely used as a method for discriminating each region in a single crystal (see, for example, Patent Document 1 and Non-Patent Document 1). The Cu decoration method is a method in which the Cu attached to the surface of the sample is diffused into the inside of the sample by heat treatment, and the defects of the crystal surface are made apparent by rapid cooling, and selective etching is performed as needed. Fine defects are detected.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2001-81000

[Non-patent literature]

[Non-Patent Document 1] Luciano Muller Stein, "Technology Depicting Defects", Solid State Phenomena, No. 82-84 (2002), pp. 753-758 (Luciano Mule'Stagno, "A Technique For Delineating Defects in Silicon.” Solid State Phenomena Vols. 82-84 (2002) pp753-758)

However, there has been a strong need to provide a wafer having a high oxygen precipitate density and excellent gettering ability. However, the oxygen precipitate is a type of so-called crystal defect, and if an oxygen precipitate is present in the surface layer portion of the wafer in which the element is formed, the element is defective. In recent years, components have been gradually cleaned, and the risk of impurity contamination has been greatly reduced. Therefore, it is predicted that the following wafers will be required as next-generation wafers, which need to have the required quality as wafers. The adsorption capacity not only reduces COP, L/D, but also infinitely reduces oxygen precipitates as a crystal defect.

In general, the oxygen precipitates in the wafer can be reduced by lowering the oxygen concentration in the crystal. However, according to the study by the present inventors, it is known that it is difficult to identify the L/D region and the B-band region by the previous Cu decoration method for a single crystal sample having a low oxygen concentration.

Accordingly, an object of the present invention is to provide a method for detecting an L/D region and a B-band region in a single crystal of a low oxygen concentration with high sensitivity.

In order to achieve the above object, the inventors have conducted intensive studies repeatedly, and as a result, the following new findings have been obtained.

(1) Cu decoration is performed at a low temperature at which oxygen precipitates are not generated in the B-band region, thereby preventing generation of oxygen precipitates in the B-band region and not allowing Cu to be fast from diffusion rate. The D region diffuses outwardly, and the cooling is rapidly performed, whereby L/D can be selectively made only apparent, whereby the L/D in the single crystal of low oxygen concentration can be highly sensitive. The area is tested.

(2) A predetermined pre-treatment (heat treatment) is performed before the Cu decoration of the above (1), whereby the B-band region and the L/D region can be made apparent by Cu decoration, and it has become In the obvious region, the L/D region detected in the above (1) is removed, whereby the B-band region in the single crystal of the low oxygen concentration which was previously difficult to detect can be detected.

The present invention is an invention completed based on the above findings.

That is, the above object is achieved by the following method.

[1] A method for inspecting a single crystal, comprising the steps of: contaminating a surface of a sample cut from a single crystal ingot using copper, the above-mentioned single crystal ingot being cultivated by the Chai method The oxygen concentration between the crystal lattices (American Society for Testing and Materials (ASTM)) is less than 12E17 atoms/cm ³ ; the sample after the above contamination is subjected to a heat-cooling treatment, which is 700 After heating for more than 5 minutes in a temperature region of not less than °C and less than 800 ° C, rapid cooling is performed from the temperature zone at a temperature decreasing rate exceeding 2.5 ° C / min; the surface of the sample after the above heating and cooling treatment is performed The etching is selected; and the L/D region is determined based on the local presence state of the pit of the sample surface after the selective etching described above.

[2] A method for inspecting a single crystal, comprising the steps of: pretreating one of two samples having substantially the same crystal region distribution cut from a single crystal ingot, the above-mentioned crucible The oxygen concentration (old ASTM) between the crystal lattices of the single crystal ingot grown by the Chai method is less than 12E17 atoms/cm ³ , and the above pretreatment is heated at a temperature of 750 ° C to 900 ° C, and then 1000 ° C. Heating at a temperature of 1150 ° C; contaminating the surface of the two samples with copper; and heating and cooling the sample after the contamination, the heating and cooling treatment is performed at a temperature of 700 ° C or more and less than 800 ° C. After the minute or more, rapid cooling is performed at a temperature decreasing rate exceeding 2.5 ° C / min from the temperature zone; selective etching is performed on the surface of the sample after the above heating and cooling treatment; and based on the sample subjected to the pretreatment described above and before being implemented The B-band region is determined by comparing the local presence state of the pits on the sample surface after the above-described selective etching of the processed sample.

[3] The method for inspecting a single crystal according to [1] or [2], wherein the selective etching is performed by Wright etching.

[4] The method for inspecting a single crystal according to any one of [1] to [3] wherein the sample is immersed in a copper-containing solution having a copper concentration of 3E20 atoms/cm ³ or more, thereby Conduct the above copper contamination.

[5] A method for producing a single crystal, comprising the steps of: cultivating a single crystal for inspection by a Chai method; using the method according to any one of [1] to [4], Checking the single crystal for the above inspection; determining the pulling condition of the single crystal based on the result of the inspection; and cultivating the single crystal by the Chai method under the determined pulling condition, thereby obtaining no A single crystal comprising an L/D region and a B-band region.

According to the present invention, the L/D region and the B-band region in the low oxygen concentration 矽 single crystal grown by the CZ method can be detected with high sensitivity. The obtained results are fed back to the crystallization conditions in the CZ method, whereby high-quality cerium single crystals can be stably mass-produced.

The present invention relates to an inspection method for ruthenium single crystal.

The following method for inspecting a single crystal (hereinafter referred to as "method 1") is characterized by comprising the step of contaminating the surface of a sample cut from a single crystal ingot with copper, the above-mentioned single crystal ingot from firewood The oxygen concentration (old ASTM) between the crystal lattices cultivated by the method is less than 12E17 atoms/cm ³ ; the sample after the contamination is subjected to a heat-cooling treatment, which is a temperature region of 700 ° C or more and less than 800 ° C. After heating for more than 5 minutes, rapid cooling is performed at a temperature decreasing rate exceeding 2.5 ° C / min from the temperature zone; selective etching is performed on the surface of the sample after the above heating and cooling treatment; and concave of the surface of the sample after the selective etching is performed based on the above The local presence state of the pit determines the L/D region.

The following inspection method for single crystals (hereinafter referred to as "method 2") is characterized by comprising the steps of: one of two samples having substantially the same crystal region distribution cut from a single crystal ingot. Before the pretreatment, the oxygen concentration (old ASTM) between the crystal lattices of the above-mentioned single crystal ingot grown by the Chai method is less than 12E17 atoms/cm ³ , and the pretreatment is performed by heating in a temperature range of 750 ° C to 900 ° C. Thereafter, the heating is performed in a temperature range of 1000 ° C to 1150 ° C; the surface of the two samples is contaminated with copper; and the sample after the contamination is subjected to a heating and cooling treatment, which is 700 ° C or more and less than 800 ° C. After the temperature zone is heated for more than 5 minutes, rapid cooling is performed at a temperature decreasing rate exceeding 2.5 ° C / min from the temperature zone; selective etching is performed on the surface of the sample after the above heating and cooling treatment; and based on the above pretreatment The B-band region is determined by comparing the sample with the local presence state of the pit on the sample surface after the above-described selective etching of the sample that has not been subjected to the pre-treatment.

In the method for inspecting the single crystal of the present invention, the single crystal to be inspected is an oxygen concentration (old ASTM) between the crystal lattices cultivated by the Chai method (CZ method) of less than 12E17 atoms/cm ³ . Single crystal. Thus, the problem of a single crystal having a low oxygen concentration is that it is difficult to identify the L/D region and the B-band region by the previous Cu decoration method, thereby causing the detected L/D region to be small or difficult to be B. - Band area detection.

On the other hand, according to the present invention, the L/D area can be detected with high sensitivity by the method 1, and the L/D area and the B-band area can be detected with high sensitivity by the method 2. The reason is that Cu decoration can be selectively performed on the L/D region by Cu decoration containing heating and rapid cooling at a lower temperature; and two stages of heat treatment including low temperature and high temperature are performed before Cu decoration as The pre-processing can also perform Cu decoration on the L/D region and the adjacent B-band region.

Hereinafter, the method for inspecting the single crystal of the present invention will be described in more detail.

The sample for performing Cu decoration may be a longitudinally cut sample or a wafer sample, and the longitudinal cut sample is a sample obtained by cutting a single crystal ingot grown by a CZ method perpendicular to the axial direction, the wafer sample. The sample obtained by slicing in the lateral direction is performed using a wire saw or the like. As described above, the oxygen concentration between the crystal lattices of the above samples was less than 12E17 atoms/cm ³ in accordance with the old ASTM. When the oxygen concentration between the crystal lattices is 12E17 atoms/cm ³ or more, in the Cu decorative process of the present invention to be described later, in addition to Cu decoration in the L/D region, regions where oxygen precipitates are likely to occur are also generated. Since the Cu decoration is performed, the L/D area cannot be detected with high sensitivity. That is, the inspection method of the present invention is directed to a single crystal of ruthenium having a low oxygen concentration. When the lower limit of the oxygen concentration (old ASTM) between the crystal lattices of the single crystal to be inspected is, for example, about 10E17 atoms/cm ³ , the L/D region and the adjacent region can be clearly distinguished. Preferably.

In Method 2, two samples having approximately the same distribution of crystalline regions were used. The reason is that, as described below, in order to compare the determined L/D region in one sample with the pitted region in another sample, thereby determining the B-band region, the samples must have substantially the same Crystalline region distribution. The two samples having substantially the same distribution of crystal regions, for example, one sample and the other sample obtained by longitudinally cutting the ingot by means of a central axis, or by means of a geometric center, Each sample obtained by dividing the wafer sample in two or four equal divisions.

The method 2 includes the steps in common with the method 1. Therefore, the method 2 will be described below mainly after the method 1 is described.

As described above, the method 1 includes "Cu contamination", "heating and cooling treatment", "selection etching", and "determination of the L/D region". Hereinafter, each step will be described in order.

Cu contamination can be performed in the same manner as a general Cu decoration. Specifically, for example, after immersing the sample in a solution containing copper, the sample is taken out from the solution, and the sample is dried for a predetermined period of time by natural drying or the like. A copper nitrate aqueous solution, a mixed solution of copper nitrate and hydrofluoric acid (HF), or the like can be used as the copper-containing solution. From the viewpoint of uniformly decorating the L/D region (the L/D region + the B-band region in the method 2), the copper concentration in the solution is preferably 3E20 atoms/cm ³ or more. From the viewpoint of achieving a uniform decoration, the copper concentration of the solution containing copper is preferably as high as possible. For example, a solution containing copper up to the upper limit of solubility may be used. Further, the solubility of copper depends on the temperature. For example, at 0 ° C, the solubility of copper is about 44E20 atoms/cm ³ .

Next, the sample after the contamination is subjected to a heat and cooling treatment. Heating and cooling treatment can be performed using various heat treatment furnaces such as a desktop electric furnace or a horizontal oxidation furnace which are generally used for heat treatment of a tantalum wafer. Further, in the present invention, the temperature and speed disclosed in connection with the heat treatment of the sample refer to the temperature and speed associated with the environment in which the sample is exposed (for example, the furnace environment of the heat treatment furnace) unless otherwise specified. Further, in the present invention, the environment in which the sample is exposed is not particularly limited as long as it is not particularly described, and the environment may be any environment such as air.

The Cu can be thermally diffused into the sample by the heat treatment after the Cu contamination described above. In the present invention, the heating temperature of the sample after the contamination is set to 700 ° C or more and less than 800 ° C. When the heating temperature is 800 ° C or higher, oxygen precipitates are generated in the B-band region due to heating. Therefore, it is difficult to selectively decorate the L/D region with Cu, and if the heating temperature is less than 700 ° C, The Cu decoration in the L/D area may be insufficient. When the heat treatment time at the above heating temperature is less than 5 minutes, it is difficult to clearly distinguish the boundary of the L/D region. Therefore, the heat treatment time is set to 5 minutes or longer. When the heat treatment time is 5 minutes or longer, the effect does not vary greatly even if the heat treatment time is increased. Therefore, the upper limit of the heat treatment time is not particularly limited. For example, heat treatment may be performed for about 10 minutes. However, in order to perform inspection in a short time, it is preferable to set the heat treatment time to 5 minutes. In the heating process, it is not necessary to maintain the temperature constant, and the temperature may be changed as long as it is in the range of 700 ° C or more and less than 800 ° C. Further, the heating furnace may be heated to the heating temperature before the introduction of the sample, or the heating furnace may be heated to the heating temperature after the introduction of the sample. When the temperature is raised after the introduction of the sample, it is preferable to set the temperature increase rate to about 2 ° C / min to 7 ° C / min from the viewpoint of depositing the Cu compound during rapid cooling after the temperature rise.

In the present invention, the sample is rapidly cooled after the above heating, whereby the Cu compound can be precipitated to L/D (dislocation cluster). In the usual Cu decoration, for example, as described in the above-mentioned Patent Document 1, the sample is taken out from the heating furnace and placed, thereby cooling the sample to room temperature. On the other hand, in the present invention, the cooling rate is controlled so that the cooling rate at the time of cooling exceeds 2.5 ° C / min. It is preferable that the temperature drop rate when the temperature is lowered to a temperature lower by 50 ° C to 100 ° C than the heating temperature zone (700 ° C or more and less than 800 ° C) exceeds 2.5 ° C / min. The reason is that if the cooling rate at the time of cooling from the heating temperature zone is 2.5 ° C / min or less, Cu having a high diffusion speed spreads outward from the L/D region, and the Cu decoration in the L/D region is insufficient. As a result, the boundary with the adjacent area is unclear, making it difficult to identify the L/D area. The cooling rate can be controlled according to the setting of the heat treatment furnace.

In order to suppress the diffusion of Cu, the above-described temperature drop rate is preferably as fast as possible. For example, the temperature drop rate may be 100 ° C / min or more, and may be 200 ° C / min or more, and particularly 300 ° C / min or more. In view of the performance of the general heat treatment furnace, the upper limit of 500 ° C / min or less may be the upper limit. However, as described above, in order to suppress the diffusion of Cu, the above-described temperature drop rate is faster, and therefore the upper limit is not particularly limited. The sample which has been cooled to the predetermined temperature can be taken out from the heat treatment furnace and then left at room temperature.

After selective etching of the surface of the sample subjected to the Cu contamination and the heating and cooling treatment described above, the Cu compound precipitated to L/D by Cu decoration is removed from the surface of the sample. Thereby, the L/D can be detected as a pit. Therefore, in the present invention, the L/D region is determined based on the local existence state of the pit of the sample surface after the selective etching. For example, when the surface of the sample after selective etching is observed under a spotlight, a region in which pits are locally present may be determined as an L/D region. Further, in the region determination process of the present invention, the life map (recombination lifetime distribution) may be used in combination. The life map measurement can identify the region in the crystal, and the method is well known (for example, refer to Japanese Patent No. 4200845). The above method has the advantage of clearly expressing the boundary of the region, and on the other hand, since the relative determination is performed based on the magnitude of the lifetime value, it is difficult to reliably determine the L/D region or B using only the lifetime measurement. - Band area. On the other hand, in the present invention, as described above, the L/D region and the B-band region in the low oxygen concentration 矽 single crystal grown by the previously difficult CZ method can be detected with high sensitivity, and the combination is used. The life map is determined, and therefore, the boundary between the L/D region or the B-band region and other regions can be more clearly determined.

The above selective etching can be performed by Secco liquid (Secco etching: for example, HF=100 cc, K ₂ Cr ₂ O ₇ = 50 g (0.15 mol/liter)), The above selective etching can be performed by Wright liquid (Wright etching: for example, composition of HF=60 cc, HNO ₃ =30 cc, Cr ₂ O ₃ =30 cc (5 mol/liter) Cu(NO ₃ ) ₂ = 2.2 g, H ₂ O = 60 cc, CH ₃ COOH = 60 cc)). From the viewpoint of the stability of the etching liquid, it is preferred to perform Wright etching. The pits can be observed by visual observation, and the pits can also be observed under a microscope.

In general, the size of the L/D is small in the vicinity of the boundary between the L/D region and the B-band region of the outer peripheral portion. Therefore, if the etching amount is increased, the L/D recess originating from the outer peripheral portion may be generated. The pit will be removed, resulting in a small L/D area being determined. Therefore, in order to improve the detection sensitivity of the L/D region, it is preferable to set the etching amount to 5 μm or less.

The method 1 described above determines the L/D region based on the local presence state of the pit of the sample surface after the selective etching. The method 1 includes a mode in which it is determined that the L/D region is not included in the sample when no pit is locally observed.

Method 2 performed different treatments on the two samples cut from the same single crystal ingot. The processing performed on one sample is the same as the processing in the above method 1. Thereby, the L/D region in the sample can be determined. Before the other sample is subjected to the same processing as the sample for determining the L/D region, pre-processing is performed to make the L/D region and the B-band region become apparent by Cu decoration. Heating the sample before Cu contamination (hereinafter referred to as "low temperature heating") in a temperature range of 750 ° C to 900 ° C, and then heating in a temperature range of 1000 ° C to 1150 ° C (hereinafter referred to as "high temperature heating") In order to perform the above pre-processing. The two-stage heating is performed in the above temperature range, whereby oxygen precipitates can be generated in the B-band region, and therefore, L/D and L/D can be obtained by the subsequent Cu contamination and heating and cooling treatment. The oxygen precipitates are decorated with Cu. As a result, the Cu compound precipitated to the L/D and the Cu compound precipitated to the oxygen precipitate in the B-band region are also removed by selective etching, and therefore, the pit is locally present in the "L/D region + B-band". In the area. If the sample surface that makes the "L/D region + B-band region" becomes apparent is compared with another sample that only makes the L/D region become apparent, the local region other than the L/D region can be partially The area where the pit is present is determined as the B-band area. Thereby, the L/D region and the B-band region in the single crystal of the low oxygen concentration which was previously difficult to recognize can be detected with high sensitivity. On the other hand, when heating is performed in one stage or by heating at a temperature deviating from the temperature range, oxygen precipitates cannot be generated in the B-band region, and it is difficult to determine the B-band region. Further, when the B-band region is determined, as described above, the life map can be used in combination, and by using the life map in combination, the boundary of the region can be more clearly determined.

It is preferred to carry out the low-temperature heating in the pretreatment described above for a time sufficient to grow a precipitated core having a critical size, preferably about 3 hours. Of course, the above-described low-temperature heating may be performed for 3 hours or more. However, since the density of the precipitated nuclei does not change much, it is sufficient for about 3 hours. On the other hand, it is preferred to carry out high-temperature heating for a period of time sufficient to cause the precipitated nuclei formed by heating at a low temperature to grow into precipitates, and it is preferably about 16 hours. Of course, it is also possible to carry out the above-described high-temperature heating for 16 hours or more, but since the density of the precipitates does not change so much, it is sufficient for about 16 hours. The temperature increase rate at the time of transition from low-temperature heating to high-temperature heating can be, for example, about 1 ° C / min to 10 ° C / min. Further, from the viewpoint of allowing the precipitate to grow well, it is preferred to carry out pretreatment in an environment containing oxygen (oxidizing atmosphere). The oxygen concentration in the oxidizing atmosphere is, for example, 10% by volume to 100% by volume. Further, in order to grow the precipitate well, it is preferred to carry out the above pretreatment by dry oxidation.

When transitioning from the above pretreatment to the Cu decoration, the sample may be taken out from the heat treatment furnace immediately after the pretreatment, but in order to prevent slip or the like caused by rapid cooling, it is preferred to carry out the temperature drop rate. control. According to the above viewpoint, after the high-temperature heating, the sample is taken out from the heat treatment furnace in the heat treatment furnace, for example, after cooling to 900 ° C to 950 ° C at a temperature decreasing rate of about 1 ° C / min to 10 ° C / min. Then it was placed at room temperature.

Method 2 makes the "L/D region + B-band region" in one of the two samples having substantially the same crystal region distribution become apparent, and only makes the L/D region in the other sample become apparent Thereby, the L/D area and the B-band area can be detected together, and the method 2 also includes the following aspects.

(1) When only a region in which a pit exists locally is present in the sample subjected to the pre-processing, and no local pit exists in the other sample, it is determined that the region in which the pit is locally present is B- Band region, and there is no L/D region in the above sample.

(2) When it is opposite to the above (1), it is determined that the L/D region exists in the above sample, but the B-band region does not exist.

(3) When no local pit exists in any of the two samples, it is determined that the sample does not include the L/D region or the B-band region.

As described above, the method 2 can also determine whether or not there is an L/D area and a B-band area.

Pretreatment such as mirror etching using mixed acid (HF, HNO ₃ system), cleaning with pure water, HF cleaning, and SC-1 cleaning may be performed arbitrarily before or after the above-described steps. Or post processing. For example, a cleaning treatment or an etching treatment for removing the natural oxide film may be performed on the sample before the heat treatment, and a cleaning treatment or an etching treatment for removing the Cu remaining on the surface may be performed on the sample before the selective etching.

The pulling condition at the time of cultivating the quinone single crystal by the CZ method can be optimized by the inspection result of the inspection method of the present invention. If neither the L/D region nor the B-band region is detected, the above-mentioned pulling condition (specifically, V/G) can be determined to be most suitable for cultivating a single crystal which does not include the above region. conditions of. On the other hand, when the L/D region and/or the B-band region has been detected, for example, the lifting condition is adjusted to increase the V/G by increasing the pulling speed, thereby cultivating A single crystal containing neither the L/D region nor the B-band region is included.

That is, according to the present invention, there is also provided a method for producing a single crystal, which comprises the steps of: cultivating a single crystal for inspection by the Chai method; using the inspection method of the present invention Checking the single crystal for the above inspection; determining the pulling condition of the single crystal based on the result of the inspection; and cultivating the single crystal according to the Chai method under the determined pulling condition, thereby obtaining no inclusion Single crystals in the L/D region and the B-band region. In the method for producing a simple crystal of the present invention, as described above, when the pulling condition in the Chai method is removed, the simple crystal can be produced by a well-known manufacturing process using the Chai method. Furthermore, in the present invention, the well-known inspection methods may be combined to determine the pulling conditions, and the well-known inspection method can detect the COP region, the OSF region, the Pv region, and the Pi region. Thereby, it is possible to provide a high-quality single crystal having no crystal defects or generating no oxygen precipitates with higher reliability.

[Example]

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

Example 1: Detection of L/D and B-band regions in wafer samples

(1) Cultivating single crystal by the Chai method

Using a single crystal pulling device shown in Fig. 1, a single crystal ingot having an oxygen concentration of 11.8E17 atoms/cm ³ (old ASTM) between crystal lattices was developed (single crystal diameter: 300 mm, crystal orientation) : <100>, polarity: p-type (doped with boron), single crystal straight body length: 2000 mm). Hereinafter, details of the single crystal pulling device shown in Fig. 1 will be described.

The single crystal pulling device 10 shown in Fig. 1 comprises: a chamber 11; a rotating shaft 12 is supported, the center of the bottom of the chamber 11 is penetrated, and is arranged along the vertical direction; the graphite heat sink (graphite) a susceptor 13 fixed to the upper end portion of the supporting rotating shaft 12; a quartz crucible 14 housed in the graphite heat receiver 13; a heater 15 disposed around the graphite heat receiver 13; and a support shaft driving mechanism 16, a seed chuck for holding the rotating shaft 12; a seed chuck holding the crystal; a pulling wire 18 for holding the seed chuck 17; and a wire for winding the wire 18. a winding mechanism 19; a heat insulating member 22 for preventing radiant heat from the heater 15 and the quartz crucible 14 from heating the single crystal ingot 20, and suppressing temperature fluctuation of the crucible melt 21; and the control device 23 Partial control.

A gas introduction port 24 for introducing Ar gas into the chamber 11 is provided at an upper portion of the chamber 11. The Ar gas is introduced into the chamber 11 through the gas pipe 25 from the gas introduction port 24, and the introduction amount of the Ar gas is controlled by a conductance valve 26.

A gas discharge port 27 for discharging the Ar gas in the chamber 11 is provided at the bottom of the chamber 11. The Ar gas in the sealed chamber 11 is discharged outward from the gas discharge port 27 via the exhaust pipe 28. A flow guide valve 29 and a vacuum pump 30 are provided in the middle of the exhaust pipe 28, and the Ar gas is sucked into the chamber 11 by the vacuum pump 30, and the flow rate of the Ar gas is measured by the flow guiding valve 29. Control is performed to maintain the reduced pressure state in the chamber 11.

Further, a magnetic field supply device 31 for applying a magnetic field to the crucible melt 21 is provided outside the chamber 11. The magnetic field supplied by the magnetic field supply device 31 may be a horizontal magnetic field or a cusped magnetic field.

(2) Production of inspection samples

The tantalum single crystal ingot grown in the above (1) was cut in the lateral direction using a wire saw to obtain a wafer sample. The obtained sample is divided into fan-shaped four-part sample pieces, one sample piece is used for the process of the following (3), and the other sample piece is used for the process of the following (4).

(3) Heating and Cooling Process for Detecting the L/D Area The following process is performed on one sample (hereinafter referred to as "sample 1") prepared in the above (2).

(i) Ultrasonic cleaning of the sample with pure water, followed by mirror etching for 5 minutes using an etching solution of HNO ₃ : HF = 5:1 (volume ratio), followed by a 10 minute rinse (rinse) .

(ii) preparing a copper nitrate aqueous solution as a copper-containing solution for Cu decoration, wherein the copper nitrate aqueous solution dissolves 30 g of copper nitrate trihydrate (Cu(NO ₃ ) ₂ ‧3H ₂ O) in 5 liters of water. An aqueous solution. After the sample subjected to the above treatment (i) was immersed in the prepared aqueous solution of copper nitrate for 5 minutes, the sample was pulled up and the sample was naturally dried.

(iii) Loading the sample subjected to the above treatment (ii) to a table type electric furnace (the furnace temperature is 660 ° C, the furnace environment: air), and heating up at a temperature increase rate of 5 ° C / minute, and then Hold at 750 ° C for 5 minutes. Then, after cooling to 660 ° C at a cooling rate of 5 ° C / min, the sample was unloaded from the table type electric furnace.

(iv) The surface of the sample subjected to the above treatment (iii) was etched for 5 minutes using an etching solution of HNO ₃ : HF = 5:1 (volume ratio), followed by washing with water for 10 minutes to precipitate Cu on the surface. The matter is removed.

(4) Pre-processing and heating and cooling processing for detecting the L/D region + B-band region

The following processing is performed on one sample (hereinafter referred to as "sample 2") prepared in the above (2).

(i) Ultrasonic cleaning of the sample with pure water was carried out, and mirror etching was performed for 5 minutes using an etching solution of HNO ₃ : HF = 5:1 (volume ratio), followed by washing with water for 10 minutes.

(ii) The sample subjected to the above treatment (i) was loaded into a heat treatment furnace, and maintained at an oxidizing atmosphere (dry O ₂ (= dry oxygen 100%)) at 780 ° C for 3 hours, at 5 ° C / min. The temperature increase rate was raised to 1000 ° C and maintained at this temperature for 16 hours. Then, the temperature was lowered to 950 ° C at a cooling rate of 2 ° C /min, and the sample was unloaded from the heat treatment furnace, and the sample was cooled to room temperature.

(iii) The sample subjected to the above treatment (ii) was etched for 3 minutes using an etching solution of H ₂ O: HF = 1:1 (volume ratio) to remove the oxide film on the surface.

(iv) The sample subjected to the above treatment (iii) was subjected to mirror etching for 5 minutes using an etching solution of HNO ₃ : HF = 5:1 (volume ratio), followed by washing with water for 10 minutes. Then, the processes of (ii) to (iv) of the above (3) are carried out.

(5) forming pits by selective etching

The surface of the wafer after the above treatments (3) and (4) was selectively etched by a Wright solution at an etching amount of 5 μm. Fig. 2 shows a photograph obtained by observing the surface after etching under a spotlight. The left diagram of Fig. 2 is an observation result of the wafer surface on which the above-described (3) processing is performed, and the right diagram of Fig. 2 is an observation result of the wafer surface on which the above-described (4) processing is performed.

As shown in FIG. 2, it has been confirmed that pits are locally present in the L/D region in the wafer surface on which the above-described (3) processing is performed, and it has been confirmed in the wafer surface on which the above-described (4) processing is performed. There are local pits in the "L/D region + B-band region". In the region where the pit is partially present on the surface of the wafer on which the processing of the above (4) is performed, the region where the pit is partially present on the surface of the wafer subjected to the above-described (3) processing is removed. The B-band region can be determined.

The above results indicate that the L/D region and the B-band region in the single crystal of the low oxygen concentration can be determined by the present invention.

Furthermore, in the right diagram of Fig. 2, it has been confirmed that pits are also present in the Pv region. The reason is that the oxygen precipitates generated in the Pv region by the pretreatment are decorated with Cu, but it is known that the position and shape of the Pv region are different from the positions and shapes of the L/D region and the B-band region, and therefore, it is easy to Regional points. Further, in the right diagram of FIG. 2, the region which is confirmed to have no pit between the B-band region and the Pv region is a Pi region which is a deposition suppression region. As described above, according to the present invention, it is also possible to detect the L/D area, the B-band area, and the Pv area and the Pi area.

Example 2: Determination and detection of L/D and B-band regions in wafer samples

The same treatment as in Example 1 was carried out, except that a sample obtained from a single crystal ingot in which a single crystal ingot was grown under a different incubation condition from that of Example 1 was used. The surface of the wafer after the treatment was selectively etched by a Wright solution at an etching amount of 5 μm. Fig. 3 shows a photograph obtained by observing the surface after etching under a spotlight. The left diagram of Fig. 3 is an observation result of the wafer surface on which the above-described (3) processing (heat-cooling processing for detecting the L/D region) is performed, and the right diagram of Fig. 3 is the same as (4) above. The observation result of the wafer surface (pretreatment for detecting the L/D region + B-band region and heating and cooling treatment).

As shown in the left diagram of FIG. 3, in the surface of the wafer on which the above-described (3) processing was performed, no pit was locally observed, and therefore it was determined that the L/D region was not included in the evaluated sample. On the other hand, according to the local existence state of the pit of the right drawing of FIG. 3, it can be confirmed that the B-band region and the Pv region exist in the evaluated sample. Further, according to the right diagram of FIG. 3, an area which is confirmed to have no pit between the B-band area and the Pv area can be determined as the Pi area.

Life chart measurement

Using the life measuring device WT-2000 manufactured by SEMILAB Co., Ltd., in Example 2, the above-described (4) processing (pre-processing and heating and cooling processing for detecting the L/D region + B-band region) and The sample of the above (5) (selective etching) was subjected to recombination lifetime measurement to obtain a lifetime map. The results are shown in the left diagram of FIG. Further, a life chart was obtained in the same manner as the sample below, and the above samples were subjected to the heat treatment at 1000 ° C for 10 hours instead of the pretreatment in the above (4) (ii), and the above (4) and (5) were carried out. The same processing. The results are shown in the right diagram of FIG.

In the right diagram of FIG. 4, the B-band region is not detected. On the other hand, in the left diagram of FIG. 4, the same region distribution as that of the right diagram of FIG. 3 is confirmed including the B-band region. In this way, in combination with the results of the life map measurement, the boundaries of the respective regions can be more clearly identified.

Example 3: Detection of L/D and B-band regions in longitudinally cut samples

The single crystal ingots grown in the same manner as in Example 1 were cut along the axial direction in a manner including the central axis of the ingot to obtain a longitudinally cut sample. The obtained sample is halved using the ingot central axis, the processing of (3) of Example 1 is performed on one sample, and the (4) processing of Example 1 is performed on the other sample, and (5) of Example 1 is performed. The choice of etching. Fig. 5 shows a photograph obtained by observing the surface after selective etching under a spotlight and taking a photograph. In Fig. 5, "CE" means the direction of the central axis of the ingot, and "ED" means the direction of the outer peripheral surface of the ingot.

The upper left diagram of Fig. 5 is the observation result of the sample surface on which the above-described (3) treatment is performed, and the upper right diagram of Fig. 5 is the observation result of the sample surface on which the above-described (4) treatment is performed. The lower diagram of Fig. 5 is a result of superimposing the result of the area determination in the upper left diagram and the upper right diagram. The overlap is performed in the above manner, whereby the B-band region can be determined as shown in the lower diagram of FIG.

The present invention is useful in the field of manufacturing single crystal wafers.

10. . .矽Single crystal pulling device

11. . . Chamber

12. . . Support rotary axis

13. . . Graphite heat exchanger

14. . . Quartz crucible

15. . . Heater

16. . . Support shaft drive mechanism

17. . . Seed chuck

18. . . Lifting wire/line

19. . . Wire winding mechanism

20. . . Single crystal ingot

twenty one. . .矽 melt

twenty two. . . Insulation member

twenty three. . . Control device

twenty four. . . Gas inlet

25. . . Gas tube

26, 29. . . Flow guiding valve

27. . . Gas discharge

28. . . exhaust pipe

30. . . Vacuum pump

31. . . Magnetic field supply device

B-band, COP, L/D, OSF, Pi, Pv. . . region

CE. . . Ingot central axis direction

ED. . . Ingot peripheral direction

Fig. 1 is an explanatory view showing the configuration of a single crystal pulling apparatus used in an example.

Fig. 2 shows an observation result of the local existence state of the pit in Example 1.

Fig. 3 shows the observation results of the local existence state of the pits in Example 2.

Fig. 4 shows the life measurement results (left image) in Example 2 and the life measurement results (right image) of samples having different pretreatments.

Fig. 5 shows the observation results of the local existence state of the pits in Example 3.

Fig. 6 is an explanatory view showing the relationship between the crystal growth conditions in the CZ method and the type and distribution of the regions generated in the single crystal ingot.

B-band, L/D, Pi, Pv. . . region

Claims (7)

A method for inspecting single crystals, comprising the steps of: contaminating a surface of a sample cut from a single crystal ingot by using copper, wherein the single crystal ingot is ingot between the crystal lattices cultivated by the Chai method The oxygen concentration (old ASTM) is less than 12E17 atoms/cm ³ ; the sample after the contamination is subjected to a heating and cooling treatment, and the heating and cooling treatment is performed by heating in a temperature range of 700 ° C or more and less than 800 ° C for 5 minutes or more, from the above temperature. Starting from the zone, rapid cooling is performed at a cooling rate exceeding 2.5 ° C / min; selective etching is performed on the surface of the sample after the above heating and cooling treatment; and a local existence state of the pit based on the surface of the sample after the selective etching is selected Determine the L/D area. The method for inspecting a single crystal according to the first aspect of the patent application, wherein the selective etching is performed by Wright etching. The method for inspecting a single crystal according to the first or second aspect of the patent application, wherein the sample is immersed in a copper-containing solution having a copper concentration of 3E20 atoms/cm ³ or more, thereby performing the copper contamination. . A method for inspecting a single crystal, comprising the steps of: pretreating one of two samples having substantially the same crystal region distribution cut from a single crystal ingot, the above single crystal casting The oxygen concentration (old ASTM) between the crystal lattices ingots grown by the Chai method is less than 12E17 atoms/cm ³ , and the above pretreatment is performed at a temperature of 750 ° C to 900 ° C, and then at 1000 ° C to 1150 ° C. The temperature zone is heated; the surface of the two samples is contaminated with copper; and the sample after the contamination is subjected to a heating and cooling treatment, and the heating and cooling treatment is performed after heating for more than 5 minutes in a temperature range of 700 ° C or more and less than 800 ° C. Rapid cooling from a temperature lower than 2.5 ° C / min from the temperature zone; selective etching of the surface of the sample after the heating and cooling treatment; and the above-mentioned sample based on the pre-treatment described above The B-band region is determined by the comparison result of the local existence state of the pits of the surface of the sample after the above-described selective etching of the processed sample. The method for inspecting a single crystal as described in claim 4, wherein the selective etching is performed by Wright etching. The method for inspecting a single crystal according to the fourth or fifth aspect of the patent application, wherein the sample is immersed in a copper-containing solution having a copper concentration of 3E20 atoms/cm ³ or more, thereby performing the copper contamination. . A method for producing a single crystal, comprising the steps of: cultivating a single crystal for inspection by a Chai method; and using the sheet according to any one of claims 1 to 6 a method for inspecting crystallization, inspecting the single crystal for the inspection; determining the pulling condition of the single crystal based on the result of the inspection; and cultivating the crucible by the above-described Czochralski method under the determined pulling condition Single crystals, whereby the above-mentioned monocrystals which do not contain the L/D region and the B-band region are obtained.