JP2007070132A - Method for manufacturing single crystal silicon wafer, single crystal silicon wafer, and method for inspecting wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a single crystal silicon wafer by which the single crystal silicon wafer having uniform gettering capability in the wafer surface can be manufactured without lowering productivity. <P>SOLUTION: The method for producing the single crystal silicon wafer has a process for pulling and growing a silicon single crystal by a Czochralski method. When the constant diameter part in a range of at least 30-70% of the whole length in the pulling direction of an ingot is pulled, the temperature during crystal growth is set to be 1,370-1310°C, the ratio Gc/Ge of the temperature gradient values in the crystal growth axis direction (wherein, Gc is an average temperature gradient at the central part of the crystal; and Ge is an average temperature gradient at the outer peripheral part of the crystal) is set to be ≥1.14 and ≤1.28 when the temperature during crystal growth is 1,370-1310°C, nitrogen is added in an amount of ≥0.8×10<SP>14</SP>atoms/cm<SP>3</SP>, and the growing is performed by pulling the ingot at a prescribed pulling rate in response to the nitrogen concentration so that the oxidation-induced stacking faults are generated on the whole wafer surface in the case when a high temperature oxidation heat treatment is carried out. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a single crystal silicon wafer used for manufacturing a semiconductor device, the single crystal silicon wafer, and a wafer inspection method for manufacturing such a wafer.

Silicon semiconductor wafers used for semiconductor devices are mainly manufactured from silicon single crystals that are pulled and grown by the Czochralski method (CZ method). In the CZ method, a seed crystal is immersed in molten silicon in a quartz crucible and pulled to grow a single crystal.
In the CZ method, oxygen melted from a quartz crucible is taken into the crystal. This oxygen is sufficiently dissolved immediately after solidification, but its solid solubility decreases as it cools, so it usually exists in a supersaturated state in the crystal. The supersaturated oxygen is deposited as an oxide during the heat treatment in the device manufacturing process. This oxygen precipitate or a defect induced by the oxygen precipitate is called BMD (Bulk Micro Defect), and if it exists in the device active region, it becomes a factor that degrades the device characteristics. It effectively acts as a gettering source for capturing metal impurities mixed in.

  In order to effectively use this oxygen precipitate, a DZ-IG (Denuded Zone-Intrinsic Gettering) process has been conventionally performed. In this process, first, a high temperature heat treatment is performed on the wafer at about 1150 ° C. for several hours in an atmosphere of nitrogen gas, oxygen gas or a mixed gas thereof. As a result, oxygen on the surface of the wafer is diffused outward, and the concentration of oxygen present on the surface of the wafer is lowered, and a denewed layer (DZ layer) in which oxygen precipitates and defects induced by the oxygen are not present on the surface of the wafer. ) Is formed. Thereafter, heat treatment is further performed at 500 to 900 ° C. for several hours to form oxygen precipitation nuclei inside the wafer. Then, by undergoing heat treatment in the device process, oxygen precipitation nuclei grow as oxygen precipitates, and a gettering layer is formed. By performing such a process, it is possible to form a high-quality wafer in which the device active region on the surface layer of the wafer is defect-free while the wafer has an absorption layer that removes contaminants from the device active region. .

In addition, the silicon single crystal produced by the CZ method has a size called COP (Crystal Originated Particle) formed at the time of crystal growth of about 0.1 μm separately from the heat treatment induced defects such as the oxygen precipitates described above. Grown-in defects are present in the order of 10 ⁵ to 10 ⁶ cm ⁻³ . This defect cannot be removed by the above-described method, and as it is, causes a deterioration in the characteristics of the semiconductor device.
As a method of reducing the density and size of the COP, there is a method of performing a high-temperature heat treatment at about 1200 ° C. in an atmosphere of hydrogen gas or argon gas, which is known as a method that can easily reduce the COP density of the wafer surface layer. . This process also serves as the oxygen out-diffusion process described above, and the silicon wafer obtained by this method becomes a high-quality wafer in which oxygen precipitates and COP are absent on the wafer surface layer, which is a device active region.

In order to efficiently reduce the COP density in the wafer surface layer region by this method, it has been proposed to increase the cooling rate during crystal growth or to add nitrogen during crystal growth (see Patent Document 1). According to this, the holding time of the single crystal during cooling in the temperature range of 1100 ° C. to 850 ° C. during crystal growth is set to less than 80 minutes, or nitrogen is added at least 1 × 10 ¹⁴ atoms / cm ³ . As a result, the density of COP formed during crystal growth increases, but the size of COP can be reduced, and defects can be easily eliminated by heat treatment.

By the way, the advantages and disadvantages of adding nitrogen at the time of crystal growth as described above include formation of oxygen precipitation nuclei that can grow even at high temperature heat treatment, generation of oxidation induced stacking faults (hereinafter referred to as OSF), and the like. Has been reported (see Non-Patent Document 1). Although there is no description about the distribution of oxygen precipitates in the wafer plane, the generation of OSF strongly depends on the nitrogen concentration, and when nitrogen is added at 5 × 10 ¹⁴ atoms / cm ³ to a crystal having a diameter of 200 mm. In contrast, the OSF generation region extends from the outer periphery to the range of about 50 mm, but when nitrogen is added at 3 × 10 ¹⁵ atoms / cm ³ , OSF is generated on almost the entire surface of the wafer, and the nitrogen concentration in the wafer surface increases. It shows that the uniformity is different.

It has been proposed that the OSF nuclei are stable even at high temperatures and used as a means for promoting oxygen precipitation in the epitaxial wafer (see Patent Document 2). It is sufficiently conceivable that stable oxygen precipitation nuclei even after epitaxial growth can exist even if heat treatment at about 1200 ° C. is performed in an atmosphere containing hydrogen gas or argon gas. Therefore, if OSF can be generated on the entire surface of the wafer, stable oxygen precipitates can be formed on the entire surface of the wafer, but the nitrogen concentration at that time needs to be about 3 × 10 ¹⁵ atoms / cm ^3. (See Non-Patent Document 1).

Further, a crystal growth method for generating OSF on the entire surface of the wafer has been proposed (see Patent Document 3). In this method, when the maximum outer diameter of the grown crystal is Dmax and the minimum outer diameter is Dmin, the crystal deformation rate represented by (Dmax−Dmin) / Dmin × 100 [%] is 1.5-2. In this method, the rate of 0% is set as the maximum pulling rate, and the growing is performed at a pulling rate 0.4 to 0.8 times the maximum pulling rate. According to this method, the expansion of the OSF generation region appears when the nitrogen concentration is 1 × 10 ¹² atoms / cm ³ , and it is desirable that the nitrogen concentration is 1 × 10 ¹⁴ atoms / cm ³ or more.
JP-A-10-98047 JP-A-11-189493 JP 2000-272997 A 52nd Annual Meeting of Crystal Growth Society, Bulk Growth Subcommittee, “Nitrogen and Carbon Effect on the Formation of Grown-in Defects and Oxygen Precipitation Behavior”

However, in the crystal growth method for generating the OSF on the entire surface of the wafer, the nitrogen concentration at which the OSF is actually generated on the entire surface of the wafer is not specified, and the nitrogen concentration can be reduced as compared with the normal pulling rate. It is only shown and it is not certain whether the nitrogen concentration has been reduced as compared with the method disclosed in Non-Patent Document 1.
In this method, since the crystal growth rate is intentionally reduced, when crystal growth is performed without adding nitrogen, the OSF ring region appears in the crystal plane, and this OSF ring region is The types of crystal defects are different between the inner and outer regions. This means that the oxygen precipitate formation behavior is different within the wafer plane.

In addition, the above-described method of adding nitrogen does not disclose OSF in-plane uniformity, nitrogen concentration, crystal in-plane temperature distribution, etc. necessary for obtaining sufficient precipitation uniformity.
Therefore, in order to form OSF generation nuclei effective for high-temperature stable BMD formation on the entire surface of the wafer by the method as described above, it is necessary to set the nitrogen concentration to about 3 × 10 ¹⁵ atoms / cm ³ .

In addition, when nitrogen is added from the silicon melt, the nitrogen concentration changes in the length direction of the crystal due to the segregation phenomenon, and the crystal growth cannot be performed at the same nitrogen concentration over the entire crystal region. Further, the solid solution limit of nitrogen in silicon is about 5 × 10 ¹⁵ atoms / cm ³ , and when crystal growth is performed with the nitrogen concentration set to 3 × 10 ¹⁵ atoms / cm ³ at the crystal top, nitrogen is added. Compared with the case where it does not, the crystal length which can be grown becomes extremely short, and productivity falls significantly.

It is also disclosed that by controlling the temperature gradient in the crystal growth axis direction during crystal growth, the entire OSF region can be obtained even without addition of nitrogen, and if this region is used, in-plane homogenization of BMD is easy ( No specific temperature gradient control range or pulling speed range is disclosed, and the nitrogen concentration range is as wide as 1 × 10 ^{10 to} 5 × 10 ¹⁵ atoms / cc, thus reducing productivity. The range in which the entire OSF region can be obtained is not clear. Similarly, although it has been proposed to use a wafer covered with a region where OSF and BMD are mixed (see Patent Document 5), a method for realizing it without reducing productivity is not disclosed.
JP 2001-139396 A JP 2003-59932 A

  The present invention has been made in view of such problems, and its object is to eliminate in-plane non-uniformity of the BMD density distribution without reducing productivity and to obtain a uniform gettering capability in the wafer surface. It is an object of the present invention to provide a method for manufacturing a single crystal silicon wafer, a single crystal silicon wafer, and a wafer inspection method for manufacturing such a wafer.

In order to solve the above problems, the present inventor has conducted various studies on crystal growth conditions. As a result, by controlling the temperature gradient in the crystal growth axis direction during crystal growth, OSF is applied to the entire wafer surface even at a low nitrogen concentration of 1 × 10 ¹⁵ atoms / cm ³ or less without reducing productivity. I found a way to generate it. This OSF nucleus has the same meaning as an oxygen precipitation nucleus that is stable at a high temperature, and can exist stably even after heat treatment in a temperature range of about 1200 ° C. in a hydrogen gas or argon gas atmosphere.

In the crystal growth step, before the silicon raw material is melted, a crystal grown by adding a silicon wafer on which a silicon nitride film is formed as a nitrogen dope changes the nitrogen concentration over the entire length of the crystal due to a segregation phenomenon. The solid solution limit of nitrogen in the silicon crystal is about 5 × 10 ¹⁵ atoms / cm ³ , and at a concentration higher than this, the crystal can no longer be grown as a single crystal.
The nitrogen concentration in the crystal calculated from the segregation coefficient of nitrogen and the OSF density have a positive correlation. When the nitrogen concentration exceeds 1 × 10 ¹⁴ atoms / cm ³ , OSF is generated at a high density from the outer periphery of the wafer. With the increase in the area, the generation region spread into the wafer, and the nitrogen concentration was 2.6 × 10 ¹⁵ atoms / cm ³ and was uniformly generated on the entire surface of the wafer.

The wafer is extracted from these adjacent crystal parts, heat-treated at 1200 ° C. for 1 hour in an argon gas atmosphere, and then subjected to BMD growth heat treatment at 1000 ° C. for 16 hours in a dry oxygen gas atmosphere to perform etching. As a result of revealing the BMD and examining the in-plane density distribution, the BMD density was uniform in the plane only at the site where the nitrogen concentration was 2.6 × 10 ¹⁵ atoms / cm ³ . At other crystal parts, that is, when the nitrogen concentration is 1 × 10 ¹⁵ atoms / cm ³ or less, density decrease or density increase occurs at the outer periphery of the crystal and depends on non-uniform OSF distribution.
Therefore, in a wafer that can generate OSF uniformly over the entire surface of the wafer, even after heat treatment at a high temperature of about 1200 ° C., BMD is uniformly formed in the wafer surface, and uniform gettering ability is achieved in the surface. It has an excellent wafer.

  From this, as a result of further intensive studies, when the temperature gradient value in the crystal growth axis direction between 1370 ° C. and 1310 ° C. during crystal growth is Gc in the center of the crystal and Ge is in the outer periphery of the crystal, Gc / Ge In the case of a crystal growth furnace designed so that = 1.23, it has been found that OSF can be generated on almost the entire surface of the wafer without doping nitrogen. Then, it was found that such optimization of Gc / Ge makes it possible to generate OSF on the entire wafer surface with a slight nitrogen concentration.

  In other words, the method for producing a single crystal silicon wafer according to the present invention is a method for producing a silicon single crystal wafer having a step of pulling and growing a silicon single crystal by the Czochralski method, and inducing oxidation when a high temperature oxidation heat treatment is performed. Ratio Gc / Ge of temperature gradient values in the crystal growth axis direction when the temperature during crystal growth is 1370 ° C. to 1310 ° C. (where Gc is the average temperature gradient in the center of the crystal so that stacking faults occur on the entire wafer surface) , Ge: average temperature gradient of the outer periphery of the crystal) and pulling growth at a pulling rate according to the nitrogen concentration.

Moreover, the method for producing a single crystal silicon wafer according to the present invention is a method for producing a silicon single crystal wafer having a step of pulling and growing a silicon single crystal by the Czochralski method, wherein the straight body portion in the pulling direction of the ingot is When pulling and growing in the range of 30 to 70% of the total length, the temperature during crystal growth is 1370 ° C. to 1310 ° C., and the temperature gradient value ratio Gc / Ge (where Gc: crystal The average temperature gradient at the center, Ge: average temperature gradient at the outer periphery of the crystal) is in the range of 1.14 to 1.28, and nitrogen is 0.8 × 10 ¹⁴ atoms / cm ^{3 to} 5 × 10 ¹⁵ atoms / cm. It is characterized in that it is added in a range of ³ or less and is raised and grown.

Preferably, the pulling growth is performed at a pulling rate according to the nitrogen concentration so that oxidation-induced stacking faults are generated on the entire surface of the wafer when a high temperature oxidation heat treatment is performed.
Preferably, the ratio (maximum value / minimum value) between the maximum value and the minimum value of the density of the oxidation-induced stacking faults is 4 or less.
Preferably, the method includes a step of performing a heat treatment at 1100 ° C. to 1250 ° C. for 30 minutes to 5 hours in an atmosphere containing hydrogen gas or argon gas.

  In addition, the single crystal silicon wafer according to the present invention is a silicon single crystal wafer manufactured by pulling and growing by the Czochralski method, and oxidation-induced stacking faults are generated on the entire surface of the wafer when subjected to high temperature oxidation heat treatment. Thus, the ratio Gc / Ge of temperature gradient values in the crystal growth axis direction when the temperature during crystal growth is 1370 ° C. to 1310 ° C. (where Gc is the average temperature gradient of the crystal center, Ge is the average of the crystal periphery) It is characterized by being raised and grown at a pulling rate according to the temperature gradient) and the nitrogen concentration.

Moreover, the single crystal silicon wafer according to the present invention is a silicon single crystal wafer that is manufactured by being pulled and grown by the Czochralski method, and is in the range of 30 to 70% of the total length of the straight body portion in the pulling direction of the ingot. When pulling growth is performed, the temperature during crystal growth is 1370 ° C. to 1310 ° C., and the temperature gradient value ratio Gc / Ge in the crystal growth axis direction (where Gc is the average temperature gradient at the center of the crystal, Ge: The average temperature gradient at the outer periphery of the crystal is in the range of 1.14 to 1.28, and nitrogen is added in the range of 0.8 × 10 ¹⁴ atoms / cm ^{3 to} 5 × 10 ¹⁵ atoms / cm ³ and pulled up. It is characterized by being nurtured.

Preferably, the average BMD density in the wafer surface formed when the oxygen precipitation evaluation heat treatment is performed is 1 × 10 ⁴ pieces / cm ² or more and 5 × 10 ⁶ pieces / cm ² or less, and the BMD density in the wafer radial direction The ratio of the maximum value / minimum value is 3 or less.
Preferably, the ratio (maximum value / minimum value) of the maximum value and the minimum value of the density in the wafer plane of the oxidation-induced stacking fault is 4 or less.
In addition, it is preferably manufactured by performing a heat treatment at 1100 ° C. to 1250 ° C. for 30 minutes to 5 hours in an atmosphere containing hydrogen gas or argon gas.

  The wafer inspection method according to the present invention is a method for inspecting the quality of the BMD distribution of a silicon single crystal wafer manufactured by pulling up and growing by the Czochralski method and performing a high temperature oxidation heat treatment. The wafer in-plane density distribution is measured, it is determined whether or not the measured OSF distribution belongs to the quality range determined by the relationship between the BMD distribution and the OSF distribution obtained in advance, and the quality is determined as the BMD distribution. It is characterized by estimating whether it is good or bad.

  According to the present invention, the manufacture of a single crystal silicon wafer that manufactures a single crystal silicon wafer having a uniform gettering ability in the wafer surface by eliminating in-plane non-uniformity of the BMD density distribution without reducing productivity. Methods, such single crystal silicon wafers, and wafer inspection methods for manufacturing such wafers can be provided.

An embodiment of the present invention will be described with reference to FIGS.
Here, two comparative examples and three examples of the method according to the present invention will be described with respect to the manufacturing conditions and manufacturing method of a single crystal silicon wafer including pulling growth of a silicon single crystal, and evaluated for OSF density and BMD density. A result is shown and embodiment of the single crystal silicon wafer which concerns on this invention, its manufacturing method, and an inspection method is described.

First, an OSF density and BMD density evaluation method commonly applied to each example will be described.
After the wafer was cut out from the crystal grown according to the conditions of each comparative example and example, an oxygen donor erasing heat treatment was performed at 650 ° C. for 30 minutes in a nitrogen gas atmosphere. In-plane OSF density and BMD density are evaluated.

OSF density evaluation method (1) Heat treatment at 1140 ° C. for 2 hours in a steam atmosphere.
(2) The oxide film formed on the wafer surface is removed with a solution of HF: H2O = 1: 1.
(3) HF: HNO 3: CrO 3: Cu (NO 3) 2: H 2 O: CH 3 COOH = 1200 μm: 600 cc: 250 g: 40 g: 1700 cc: 1200 cc The surface of the wafer was removed by 2 μm (thus making defects obvious).
(4) The OSF density is measured with an optical microscope at a 5 mm or 10 mm pitch in the wafer radial direction.

BMD density evaluation method (1) Heat treatment at 1000 ° C. for 16 hours in a dry oxygen atmosphere.
(2) The oxide film formed on the wafer surface is removed with a solution of HF: H2O = 1: 1.
(3) Cleave the wafer in half.
(4) HF: HNO 3: CrO 3: Cu (NO 3) 2: H 2 O: CH 3 COOH = 1200 μm: 600 cc: 250 g: 40 g: 1700 cc: 1200 cc of the cleaved surface was removed by 2 μm (thus causing defects to manifest).
(5) The etch pit density is measured at a pitch of 5 mm or 10 mm in the wafer radial direction with an optical microscope.

  Hereinafter, the manufacturing method of a single crystal silicon wafer and its evaluation result are shown about the comparative example 1 and the comparative example 2, and Examples 1-3.

Comparative Example 1
As Comparative Example 1, the temperature of the straight body in the range of 30 to 70% of the total length in the pulling direction of the ingot is at a temperature during crystal growth of 1370 ° C to 1310 ° C, and the temperature gradient ratio Gc in the crystal plane Under the crystal growth condition where / Ge is 1.00, an 8-inch p-type, a resistivity of about 10 Ωcm, and an oxygen concentration of about 12 × 10 ¹⁷ atoms / cm ³ were grown. As the nitrogen doping method, a silicon wafer on which a silicon nitride film was formed was charged together with the silicon raw material as a nitrogen doping material before the step of melting the silicon raw material in the crystal growth step. In order to obtain crystals in a wide range of nitrogen concentration, the amount of nitrogen dope was changed. The nitrogen concentration in the crystal is calculated from the segregation coefficient of nitrogen and is 0.01 to 4 × 10 ¹⁵ atoms / cm ³ . In addition, about the nitrogen concentration added in the case of pulling up, the set density | concentration shall be maintained not only about 30-70% of the ingot total length but the whole region of a straight body part.
After crystal growth, the wafer was processed into an oxygen donor erasing heat treatment at 650 ° C. for 30 minutes in a nitrogen gas atmosphere, and the OSF density and BMD density in the wafer surface were evaluated by the method described above.

FIG. 1 shows the OSF density distribution of the sample of Comparative Example 1 before heat treatment in an argon gas atmosphere.
As shown in FIG. 1, in this example, when the nitrogen concentration is 1.2 × 10 ¹³ atoms / cm ³ , OSF is not generated, and when the nitrogen concentration is 1.35 × 10 ¹⁴ atoms / cm ³ , OSF is generated in the peripheral portion. As the nitrogen concentration increases, the OSF is generated with a high density from the outer peripheral portion of the wafer toward the inside, and is uniformly generated over the entire wafer at 2.6 × 10 ¹⁵ atoms / cm ³ or more.

FIG. 2 shows the BMD density distribution of the sample of Comparative Example 1 before and after heat treatment in an argon gas atmosphere.
As shown in FIG. 2, a decrease in BMD density occurs at a position of 10 to 20 mm from the outer periphery of the wafer at a nitrogen concentration of 3.6 to 5.5 × 10 ¹⁴ atoms / cm ^3. There is no difference in the density distribution. Further, the OSF in this nitrogen concentration range is generated at a high density at a position where the BMD density is lowered.
When the nitrogen concentration increases to 7.8 to 9.4 × 10 ¹⁴ atoms / cm ³ , the BMD density does not decrease at the outer peripheral portion of the wafer, but increases. In addition, as in the case of the low nitrogen concentration, there is no difference in the BMD density distribution before and after argon annealing. The OSF in this nitrogen concentration range is generated at a high density up to the vicinity of the wafer center, but its distribution is non-uniform.
When the nitrogen concentration is 2.6 × 10 ¹⁵ atoms / cm ³ , the BMD is uniformly formed in the wafer surface and the OSF is also uniformly generated. In addition, as in the case of the low nitrogen concentration, there is no difference in the BMD density distribution before and after argon annealing.

Table 1 shows the in-plane variation (maximum value / minimum value) of the BMD density after argon annealing for each nitrogen concentration.
As shown in Table 1, the in-plane variation (maximum value / minimum value) of the BMD density after argon annealing is close to 7 times at maximum.

From the evaluation results of Comparative Example 1, OSF is generated from the outer periphery of the crystal depending on the nitrogen concentration, and the OSF generation nuclei are stable even at high temperatures and disappear by argon annealing at 1200 ° C. for about 1 hour. It can be seen that the BMD density distribution does not change significantly before and after argon annealing.
Therefore, in order to form the BMD density uniformly in the surface, it is necessary to control the nitrogen concentration so that the OSF is uniformly generated in the wafer surface. Similarly, 2.6 × 10 ¹⁵ atoms / cm ³ or more is required.

Comparative Example 2
As Comparative Example 2, the temperature of the straight body in the range of 30 to 70% of the total length in the pulling direction of the ingot is at a temperature during crystal growth of 1370 ° C. to 1310 ° C., and the temperature gradient ratio Gc in the crystal plane A nitrogen-doped crystal having a 12-inch p-type, a resistivity of about 10 Ωcm, and an oxygen concentration of about 14 × 10 ¹⁷ atoms / cm ^{3 was} grown under crystal growth conditions with / Ge of 0.97. The nitrogen doping method was performed in the same manner as in Comparative Example 1. The nitrogen concentration added during the pulling is the same as that in Comparative Example 1 in that the concentration set for the entire area of the straight body portion is maintained.
After crystal growth, the wafer was processed into an oxygen donor erasing heat treatment at 650 ° C. for 30 minutes in a nitrogen gas atmosphere, and the OSF density in the wafer surface was evaluated by the method described above.
Moreover, the BMD density in the sample wafer surface which heat-processed at 1200 degreeC for 1 hour in argon gas atmosphere was evaluated by the method as mentioned above.

FIG. 3 shows the OSF density distribution of the sample before heat treatment in an argon gas atmosphere. Although it occurs at a high density from the outer periphery of the wafer toward the inside, the distribution is non-uniform.
FIG. 4 shows the BMD density distribution of the sample before and after heat treatment in an argon gas atmosphere. The in-plane distribution was non-uniform, reflecting the non-uniform OSF density distribution.
Table 2 shows the in-plane variation (maximum value / minimum value) of the BMD density after argon annealing. As shown in Table 2, the in-plane variation (maximum value / minimum value) of the BMD density after argon annealing is 16 times at maximum.

Example 1
As described above as Comparative Example 1, in the case of the crystal growth condition where the temperature gradient ratio Gc / Ge in the crystal plane is 1.00, the nitrogen concentration is 2. in order to make the BMD density distribution in the wafer plane uniform. Although 6 × 10 ¹⁵ atoms / cm ³ or more is necessary, the solid solution limit of nitrogen in the silicon crystal is about 5 × 10 ¹⁵ atoms / cm ³ , and it can no longer grow as a single crystal at a concentration higher than this. Can not.
Therefore, in order to generate OSF on the entire wafer surface even at a low nitrogen concentration, a crystal growth condition in which the temperature gradient distribution in the wafer surface during crystal growth is different from that in the comparative example is used. Specifically, as Example 1 according to the present invention, a crystal was grown under the condition that the ratio Gc / Ge between the temperature gradient Gc at the center of the crystal and the temperature gradient Ge at the outer periphery of the crystal was 1.23.

The grown crystal was subjected to vertical cutting, heat-treated in a dry oxygen atmosphere at 800 ° C. for 4 hours, and then at 1000 ° C. for 16 hours, and then observed with an XRT photograph. As a result, an OSF generation possible region was observed on almost the entire wafer surface.
As a result, depending on the temperature gradient ratio in the crystal plane, it is possible to generate OSF almost over the entire surface of the wafer without doping nitrogen, and a small amount of nitrogen doping is possible to generate OSF over the entire surface of the wafer. Presumed to be.

Example 2
As Example 2, the temperature during the crystal growth is 1370 ° C. to 1310 ° C. and the temperature gradient ratio Gc in the crystal plane is at least 30% to 70% of the total length in the pulling direction of the ingot. A nitrogen-doped crystal having a 12-inch p-type, a resistivity of about 10 Ωcm, and an oxygen concentration of about 14 × 10 ¹⁷ atoms / cm ³ is grown under the crystal conditions of /Ge=1.10, 1.14, 1.25, The OSD density and the BMD density distribution after heat treatment at 1200 ° C. for 1 hour in an argon gas atmosphere were evaluated by the methods described above.

Although not shown, at a temperature gradient ratio Gc / Ge = 1.10, it is almost the same as the comparative example (Gc / Ge = 1.00), and OSF is generated from the outer periphery of the wafer as the nitrogen concentration increases, and about 2 × 10 OSF is generated on the entire surface of the wafer at ¹⁵ atoms / cm ³ .

At Gc / Ge = 1.14, as shown in FIG. 5, OSF was generated on the entire wafer surface when the nitrogen concentration was 0.79 × 10 ¹⁴ atoms / cm ³ or more. That is, when Gc / Ge = 1.14, it is possible to generate OSF uniformly on the entire wafer surface by doping nitrogen with 0.8 × 10 ¹⁴ atoms / cm ³ or more. / Minimum value ratio) is 4 times or less as shown in Table 3.

When Gc / Ge = 1.25, as shown in FIG. 6, any case where the nitrogen concentration in the evaluation range is from 2.46 × 10 ¹⁴ atoms / cm ^{3 to} 8.47 × 10 ¹⁴ atoms / cm ^3. In FIG. 5, OSF was generated on the entire surface of the wafer. Further, the in-plane variation (maximum value / minimum value ratio) is three times or less as shown in Table 3.

The BMD density distribution after argon annealing in each case of Gc / Ge = 1.14 and 1.25 is shown in FIGS. Except for the case where Gc / Ge = 1.14 where the OSF is not generated on the entire wafer surface and the nitrogen concentration is 0.74 × 10 ¹⁴ atoms / cm ³ , in all cases, the wafer outer peripheral portion seen in the comparative example There is no decrease or increase in the BMD density, and the variation in the wafer surface is within 3 times as shown in Table 4.

Example 3
As Example 3, the temperature during the crystal growth is 1370 ° C. to 1310 ° C., and the temperature gradient ratio Gc in the crystal plane is at least 30% to 70% of the total length in the pulling direction of the ingot. A nitrogen-doped crystal having a 12-inch p-type, a resistivity of about 10 Ωcm, and an oxygen concentration of about 14 × 10 ¹⁷ atoms / cm ^{3 was} grown under the crystal growth conditions of /Ge=1.28. Then, the OSF density and the BMD density distribution after heat treatment at 1200 ° C. for 1 hour in an argon gas atmosphere were evaluated.

The OSF density is shown in FIG. As shown in FIG. 9, OSF is generated on the entire surface of the wafer in any case where the evaluated nitrogen concentration is 0.70 to 1.48 × 10 ¹⁴ atoms / cm ³ . Further, the in-plane variation (maximum value / minimum value ratio), as shown in Table 5, is a value close to five times when the nitrogen concentration is 0.70 × 10 ¹⁴ atoms / cm ³ . In other cases, it is 4 times or less.

FIG. 10 shows the BMD density distribution after argon annealing. When the in-plane variation of the OSF density is close to 5 times, when the nitrogen concentration is 0.70 × 10 ¹⁴ atoms / cm ³ , the BMD density is increased at the center of the wafer. There is no decrease or increase in the BMD density at the portion, and the variation in the wafer surface is within 3 times as shown in Table 6.

As described above, at least the straight body portion is lifted in a range of 30 to 70% of the entire length in the pulling direction of the ingot, the temperature during crystal growth is 1370 ° C to 1310 ° C, and 1370 ° C during crystal growth When the temperature gradient value in the crystal growth axis direction between 1310 ° C. is Gc for the center of the crystal and Ge for the outer periphery of the crystal, the ratio Gc / Ge is 1.14 ≦ Gc / Ge ≦ 1.28. Under the growth conditions, even if the nitrogen concentration is 0.8 × 10 ¹⁴ atoms / cm ³ , OSF can be generated on the entire surface of the wafer, and the density can be increased even after the heat treatment at about 1200 ° C. BMD can be formed uniformly in the wafer surface. As a result, uniform gettering capability can be obtained within the wafer surface.

  In addition, this embodiment is described in order to make an understanding of this invention easy, and does not limit this invention at all. Each element disclosed in the present embodiment includes all design changes and equivalents belonging to the technical scope of the present invention, and various suitable modifications can be made.

FIG. 1 is a diagram showing an in-wafer in-plane OSF density distribution in the single crystal silicon manufacturing method as Comparative Example 1. FIG. FIG. 2 is a diagram showing the in-plane BMD density distribution before and after argon annealing in the single crystal silicon manufacturing method as Comparative Example 1. FIG. FIG. 3 is a view showing an in-plane OSF density distribution in the single crystal silicon manufacturing method as Comparative Example 2. FIG. 4 is a diagram showing the in-plane BMD density distribution after argon annealing in the single crystal silicon manufacturing method as Comparative Example 2. FIG. 5 is a diagram showing the OSF density distribution in the wafer plane in the single crystal silicon manufacturing method as Example 2 of the present invention, and is a diagram showing the distribution when Gc / Ge = 1.14. FIG. 6 is a diagram showing the OSF density distribution in the wafer plane in the single crystal silicon manufacturing method as Example 2 of the present invention, and is a diagram showing the distribution when Gc / Ge = 1.25. FIG. 7 is a view showing the in-plane BMD density distribution after argon annealing in the single crystal silicon manufacturing method as Example 2 of the present invention, and showing the distribution when Gc / Ge = 1.14. is there. FIG. 8 is a diagram showing the in-plane BMD density distribution after argon annealing in the single crystal silicon manufacturing method as Example 2 of the present invention, and showing the distribution when Gc / Ge = 1.25. is there. FIG. 9 is a diagram showing the OSF density distribution in the wafer plane in the single crystal silicon manufacturing method as Example 3 of the present invention, and is a diagram showing the distribution when Gc / Ge = 1.28. FIG. 10 is a diagram showing a BMD density distribution in the wafer surface after argon annealing in the single crystal silicon manufacturing method as Example 3 of the present invention, and a distribution when Gc / Ge = 1.28. is there.

Claims (11)

A method for producing a silicon single crystal wafer having a step of pulling and growing a silicon single crystal by the Czochralski method,
A ratio Gc / Ge of temperature gradient values in the crystal growth axis direction when the temperature during crystal growth is 1370 ° C. to 1310 ° C. so that oxidation-induced stacking faults occur on the entire surface of the wafer when high-temperature oxidation heat treatment is performed. , Gc: average temperature gradient at the center of the crystal, Ge: average temperature gradient at the outer periphery of the crystal), and a method for producing a single crystal silicon wafer, characterized by performing pulling growth at a pulling rate according to the nitrogen concentration. A method for producing a silicon single crystal wafer having a step of pulling and growing a silicon single crystal by the Czochralski method,
When pulling and growing in the range of 30 to 70% of the total length of the straight body in the pulling direction of the ingot, the temperature during crystal growth is 1370 ° C to 1310 ° C, and the ratio of temperature gradient values in the crystal growth axis direction Gc / Ge (where Gc: average temperature gradient at the center of the crystal, Ge: average temperature gradient at the outer periphery of the crystal) is in the range of 1.14 to 1.28, and nitrogen is 0.8 × 10 ¹⁴ atoms / cm ^A method for producing a single crystal silicon wafer, characterized by performing pulling growth by adding in a range of ^{3 to} 5 × 10 ¹⁵ atoms / cm ³ .   3. The single crystal silicon wafer according to claim 2, wherein the pulling growth is performed at a pulling rate according to a nitrogen concentration so that oxidation-induced stacking faults are generated on the entire surface of the wafer when a high temperature oxidation heat treatment is performed. Manufacturing method.   4. The method for producing a single crystal silicon wafer according to claim 2, wherein a ratio (maximum value / minimum value) between a maximum value and a minimum value of the density of the oxidation-induced stacking faults is 4 or less.   5. The single crystal silicon wafer according to claim 1, further comprising a step of performing a heat treatment at 1100 ° C. to 1250 ° C. for 30 minutes to 5 hours in an atmosphere containing hydrogen gas or argon gas. Production method.   A silicon single crystal wafer manufactured by pulling up and growing by the Czochralski method, and when the high temperature oxidation heat treatment is performed, the temperature during crystal growth is from 1370 ° C. so that oxidation-induced stacking faults are generated on the entire surface of the wafer. Ratio Gc / Ge of temperature gradient values in the crystal growth axis direction at 1310 ° C. (where Gc: average temperature gradient at the center of the crystal, Ge: average temperature gradient at the outer periphery of the crystal), and pulling up according to the nitrogen concentration A single crystal silicon wafer characterized by being pulled and grown at a speed. A silicon single crystal wafer manufactured by pulling and growing by the Czochralski method, and when performing pulling growth in the range of 30 to 70% of the total length of the straight body in the pulling direction of the ingot, the temperature during crystal growth Is a temperature gradient value ratio Gc / Ge in the crystal growth axis direction (where Gc: average temperature gradient at the center of the crystal, Ge: average temperature gradient at the outer periphery of the crystal) is 1.14. A single crystal silicon wafer characterized by being grown in a range of 1.28 or less and adding nitrogen in a range of 0.8 × 10 ¹⁴ atoms / cm ³ or more and 5 × 10 ¹⁵ atoms / cm ³ or less. . The average BMD density in the wafer surface formed when the oxygen precipitation evaluation heat treatment is performed is 1 × 10 ⁴ pieces / cm ² or more and 5 × 10 ⁶ pieces / cm ² or less, and the maximum value of BMD density in the wafer radial direction / The single crystal silicon wafer according to claim 7, wherein the ratio of the minimum values is 3 or less.   The single crystal silicon wafer according to claim 7 or 8, wherein a ratio (maximum value / minimum value) of a maximum value and a minimum value of the wafer in-plane density of the oxidation-induced stacking fault is 4 or less.   10. The single crystal silicon wafer according to claim 6, wherein heat treatment is performed at 1100 ° C. to 1250 ° C. for 30 minutes to 5 hours in an atmosphere containing hydrogen gas or argon gas. It is a method for inspecting the quality of BMD distribution of a silicon single crystal wafer produced by raising and growing by the Czochralski method and performing heat treatment,
Measure the distribution of density of oxidation-induced stacking faults in the wafer surface, determine whether the measured OSF distribution belongs to the pass / fail range determined by the relationship between the BMD distribution and the OSF distribution obtained in advance, A wafer inspection method, wherein quality is estimated as quality of a BMD distribution.

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