JP2011228459A - Silicon wafer and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon wafer containing a plate-like oxygen precipitate capable of preventing occurrence of implantation even if a LSA treatment is performed in a device process.SOLUTION: The silicon wafer of present invention is subjected to a device process including the LSA treatment. At the time of the LSA treatment, T×S≤9×10is satisfied, where a length of a diagonal of the plate-like oxygen precipitate contained in the silicon wafer is S (nm), and the highest temperature that is reached in the LSA treatment is T(°C). In the present invention, by performing the LSA treatment under the above condition, occurrence of implantation, whose starting point is the plate-like oxygen precipitate contained in the silicon wafer, can be prevented.

Description

  The present invention relates to a silicon wafer and a manufacturing method thereof, and more particularly, to a silicon wafer used for a device process including a LSA (Laser Spike Anneal) process and a manufacturing method thereof.

  In a semiconductor device manufacturing process (so-called device process), various heat treatments are performed on a silicon wafer. For example, when forming a source / drain region of a MOS transistor, after ion implantation of a dopant into a silicon wafer, annealing for activating the dopant is performed. As annealing for activating the dopant, a method of heating the entire surface of the wafer using a lamp furnace or the like is generally used.

  However, in recent years, since the channel length of the MOS transistor is designed to be very short, an increase in the subthreshold current due to the short channel effect has been a problem. In order to suppress the short channel effect, it is effective to form a source / drain region by an ultra-shallow junction having a steep impurity profile. As an annealing method for obtaining such an ultra-shallow junction, an LSA (Laser Spike) is used. Anneal) processing is attracting attention.

  Unlike the method of heating the entire surface of the wafer using a lamp furnace or the like, the LSA process is performed by scanning the wafer with a laser beam having a beam diameter of about several millimeters. As a result, the region irradiated with the laser beam reaches a temperature of 1000 ° C. or higher and a melting point (1414 ° C.) or lower in the order of milliseconds or less, so that a steep impurity profile can be obtained. However, in the LSA process, a steep temperature gradient is formed not only in the thickness direction of the wafer but also in the in-plane direction, so that a strong thermal stress is generated inside the wafer. When a strong thermal stress is generated inside the wafer, dislocation may occur starting from oxygen precipitates. When dislocation occurs in the device process, misalignment occurs before and after the occurrence of dislocation, so that a so-called overlay error occurs in the photolithography process.

  As described in Patent Document 1, the occurrence of dislocations starting from oxygen precipitates is more likely to occur when the oxygen precipitates are plate-like than when they are polyhedral. From this point of view, Patent Document 1 discloses a method for preventing the occurrence of dislocations due to thermal stress by making a silicon wafer contain carbon so that the shape of oxygen precipitates is not a plate but a polyhedron. Yes.

Japanese Patent Laid-Open No. 10-150048 JP 2008-205024 A No. 2006-3812

  However, as is apparent from the description of paragraph [0004], Patent Document 1 assumes that heat treatment is performed using a batch furnace or the like, and is strong in the thickness direction and in-plane direction of the wafer as in LSA processing. The case where thermal stress occurs is not assumed. For this reason, it is unclear whether or not the occurrence of dislocation can be prevented when the LSA process is performed on the silicon wafer described in Patent Document 1. Further, since Patent Document 1 is an invention that excludes plate-like oxygen precipitates, under what conditions LSA treatment should be performed on a silicon wafer that actually contains plate-like oxygen precipitates, Patent Document 1 Is unknown.

  On the other hand, Patent Document 2 discloses a method in which light scattering defects are zero in a region having a depth of 25 μm to 100 μm from the surface layer of the silicon wafer, and a large amount of light scattering defects are included in a region having a depth of 100 μm. . Further, Patent Document 3 discloses a method for setting the size and density of oxygen precipitates during heat treatment and the thermal stress applied by the heat treatment within a predetermined range.

  However, since Patent Document 2 assumes a flash lamp annealing apparatus as a rapid heating / cooling heat treatment apparatus, there is almost no temperature gradient in the in-plane direction of the wafer. For this reason, in the invention described in Patent Document 2, it is unclear whether or not it is effective when the LSA process in which a steep temperature gradient occurs in the in-plane direction is performed. Even if it is effective for the LSA process, it is possible to prevent the occurrence of dislocation by setting the LSA process for a silicon wafer containing plate-like oxygen precipitates. Is unknown.

  Patent Document 3 describes conditions for performing flash lamp annealing and spike lamp annealing, but as in Patent Document 2, it is unclear whether it is effective when LSA treatment is performed, Even if it is effective, it is unclear from Patent Document 3 how dislocations can be prevented by setting LSA treatment conditions for a silicon wafer containing plate-like oxygen precipitates.

  On the other hand, among silicon wafers, there is an epitaxial wafer having an epitaxial layer formed on the surface. In order to increase the gettering ability of an epitaxial wafer, it is effective to contain nitrogen or boron in the wafer body at a high concentration.

  However, a wafer doped with nitrogen or boron at a high concentration is very likely to form oxygen precipitates in the device process as compared with a normal wafer. This is because nitrogen and boron have the effect of increasing the stability of the precipitation nuclei. Therefore, when such an epitaxial wafer is put into a device process, a plate-like fine precipitate is easily formed by a low-temperature treatment of about 750 ° C. included in the device process, followed by a heat treatment of about 1000 ° C. Then, fine precipitates grow and become large plate-like oxygen precipitates. When the LSA treatment is performed in a state where the plate-like oxygen precipitates are grown in this way, there is a problem that dislocations are easily generated starting from the oxygen precipitates and reach the epitaxial layer. The reason why dislocations are easily generated during the LSA treatment is that a very strong thermal stress is locally applied in the LSA treatment as compared with other heat treatments. For this reason, it is particularly important to prevent the occurrence of dislocation due to the LSA process in a silicon wafer in which plate-like oxygen precipitates are likely to grow, such as an epitaxial wafer doped with nitrogen or boron at a high concentration.

  In this way, it has been unknown in the past how under what conditions LSA treatment can be performed on silicon wafers containing plate-like oxygen precipitates to prevent the occurrence of dislocations. In addition, it has been unknown in the past how much the concentration of oxygen in an epitaxial wafer doped with nitrogen or boron at a high concentration can prevent the occurrence of dislocations in the LSA process.

  Accordingly, an object of the present invention is a silicon wafer containing plate-like oxygen precipitates and a method for manufacturing the same, and silicon that can prevent the occurrence of dislocation even when LSA treatment is performed in a device process. It is to provide a wafer and a manufacturing method thereof.

  When the LSA process is performed on a silicon wafer containing a plate-like oxygen precipitate, the present inventors have intensively studied what conditions should be met to generate dislocations starting from the oxygen precipitate. As a result, it was found that whether or not dislocations originated from oxygen precipitates strongly depends on the relationship between the maximum temperature reached in the LSA treatment and the size of the plate-like oxygen precipitates. The present invention has been made based on such technical knowledge.

That is, the silicon wafer according to one aspect of the present invention is a silicon wafer that is used in a device process including an LSA (Laser Spike Anneal) process, and the plate-like oxygen precipitates included in the silicon wafer during the LSA process. When the diagonal length is S (nm) and the highest temperature in the LSA treatment is T (° C.),
T × S ² ≦ 9 × 10 ⁶
It is characterized by satisfying.

A method for manufacturing a silicon wafer according to an aspect of the present invention is a method for manufacturing a silicon wafer used in a device process including an LSA (Laser Spike Anneal) process, and is included in the silicon wafer during the LSA process. When the diagonal length of the plate-like oxygen precipitate is S (nm) and the highest temperature in the LSA treatment is T (° C.),
T × S ² ≦ 9 × 10 ⁶
It is characterized by satisfying.

  According to the present invention, it is possible to prevent the occurrence of dislocations starting from plate-like oxygen precipitates by performing the LSA treatment under the above conditions. Here, the diagonal length of the plate oxygen precipitates refers to the average value of the diagonal lengths of a large number of plate oxygen precipitates contained in the silicon wafer.

The silicon wafer according to the present invention includes a wafer body having a nitrogen concentration of 1 × 10 ¹² atoms / cm ³ or more or a specific resistance set to 20 mΩ · cm or less by boron doping, and an epitaxial layer provided on the surface of the wafer body It is preferable to comprise. In addition, the silicon wafer manufacturing method and the semiconductor device manufacturing method according to the present invention are such that the nitrogen concentration is 1 × 10 ¹² atoms / cm ³ or more, or the resistivity of the wafer body is set to 20 mΩ · cm or less by boron doping. Preferably, the method includes a step of forming an epitaxial layer. As described above, a wafer doped with nitrogen or boron at a high concentration is much easier to form oxygen precipitates in the device process than a normal wafer, but the LSA treatment is performed under the above conditions as in the present invention. By doing so, it becomes possible to prevent the occurrence of dislocations starting from the plate-like oxygen precipitates.

A silicon wafer according to another aspect of the present invention is a silicon wafer used in a device process including an LSA process, and has a nitrogen concentration of 1 × 10 ¹² atoms / cm ³ or more or a specific resistance of 20 mΩ by boron doping. A wafer main body set to cm or less and an epitaxial layer provided on the surface of the wafer main body, wherein the initial oxygen concentration of the wafer main body is 14 × 10 ¹⁷ atoms / cm ³ or less. .

Furthermore, a method for manufacturing a silicon wafer according to another aspect of the present invention is a method for manufacturing a silicon wafer used in a device process including an LSA process, wherein the nitrogen concentration is 1 × 10 ¹² atoms / cm 2 by the Czochralski method. cm ³ or more, or, specific resistance by boron dope is set below 20 m [Omega · cm, a step of initial oxygen concentration to cultivate configured silicon single crystal below ^{14 × 10 17 atoms / cm 3} , from the silicon single crystal Forming an epitaxial layer on the surface of the cut wafer main body.

  According to the present invention, even when a plate-like oxygen precipitate grows before the LSA treatment by a general heat treatment performed before the LSA treatment, a general LSA having a maximum reached temperature of about 1250 ° C. It is possible to prevent the occurrence of dislocation due to the treatment. As a general heat treatment performed before the LSA treatment, for example, a heat treatment that is held at a temperature of 750 ° C. or more for 3 hours or more and that is held at a temperature range of 1000 ° C. to 1050 ° C. for 1 hour or more. Including heat treatment.

In the present invention, the initial oxygen concentration of the wafer body is preferably 12 × 10 ¹⁷ atoms / cm ³ or less. According to this, even when the heat treatment is performed for a longer time before the LSA treatment, it is possible to prevent the occurrence of dislocation due to a general LSA treatment with a maximum temperature of about 1250 ° C. . As the heat treatment for a longer time, for example, a heat treatment including a heat treatment for 4 hours or more at a temperature of 750 ° C. or more and a treatment for holding for 2 hours or more in a temperature range of 1000 ° C. to 1050 ° C. can be given.

  Thus, according to the present invention, a silicon wafer containing plate-like oxygen precipitates, which can prevent the occurrence of dislocation even when the LSA treatment is performed in the device process, It becomes possible to provide. It is an epitaxial wafer with a wafer body doped with nitrogen or boron at a high concentration, and it is possible to prevent the occurrence of dislocation even when the LSA treatment is performed after a predetermined heat treatment in the device process. It becomes possible to provide a simple silicon wafer.

  In addition, according to the present invention, there is provided a method for producing a silicon wafer containing plate-like oxygen precipitates, which is capable of preventing the occurrence of dislocation even when LSA treatment is performed in a device process. It is possible to provide a manufacturing method. Also, it is a method for manufacturing an epitaxial wafer having a wafer body doped with nitrogen or boron at a high concentration, and prevents the occurrence of dislocation even when the LSA process is performed in the device process after a predetermined heat treatment. It is possible to provide a method for manufacturing a silicon wafer.

It is a schematic sectional drawing which shows the structure of the silicon wafer by preferable embodiment of this invention. It is a schematic perspective view for demonstrating the structure of a plate-shaped oxygen precipitate. It is a schematic perspective view for demonstrating the structure of a polyhedral oxygen precipitate. It is a flowchart for demonstrating the manufacturing method (wafer process) of a silicon wafer. It is a flowchart which shows a part of device process.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic cross-sectional view showing the structure of a silicon wafer 10 according to a preferred embodiment of the present invention.

  As shown in FIG. 1, the silicon wafer 10 according to the present embodiment includes a wafer body 11 and an epitaxial layer 12 formed on the surface thereof. The wafer main body 11 is single crystal silicon grown by the Czochralski method, and plays a role of ensuring the mechanical strength of the silicon wafer 10 and also serving as a heavy metal gettering source. The thickness of the wafer body 11 is not particularly limited as long as the mechanical strength is ensured, but is about 725 μm, for example.

Although not particularly limited, the wafer body 11 is doped with nitrogen or boron. When the wafer body 11 is doped with nitrogen, the concentration is preferably 1 × 10 ¹² atoms / cm ³ or more. On the other hand, when boron is doped in the wafer body 11, the specific resistance of the wafer body 11 is preferably set to 20 mΩ · cm or less by boron doping. This is because sufficient gettering capability is given to the wafer body 11 if nitrogen or boron is doped at the above concentration. The upper limit of the concentration of nitrogen or boron is not particularly limited, but it is preferable to set nitrogen to 5 × 10 ¹⁴ atoms / cm ³ or less and boron to ³ mΩ · cm or more in terms of specific resistance. This is because if the concentration of nitrogen exceeds 5 × 10 ¹⁴ atoms / cm ³ , dislocations are likely to occur during single crystal growth. Further, if the specific resistance due to boron is less than 3 mΩ · cm, misfit dislocations are likely to occur due to lattice mismatch with the growing epitaxial film.

The initial oxygen concentration of the wafer body 11 is preferably 7 × 10 ¹⁷ atoms / cm ³ or more and 2.4 × 10 ¹⁸ atoms / cm ³ or less. This is because if the oxygen concentration is less than 7 × 10 ¹⁷ atoms / cm ³ , the formation density of oxygen precipitates necessary for gettering heavy metals such as Ni may be insufficient, and the oxygen concentration is 2 This is because it is difficult to form the defect-free epitaxial layer 12 when the thickness exceeds 0.4 × 10 ¹⁸ atoms / cm ³ . However, when nitrogen doping or boron doping is performed, the formation of oxygen precipitates is promoted by nitrogen doping or boron doping, so that the initial oxygen concentration of the wafer body 11 is 7 × 10 as long as the oxygen precipitates are formed by heat treatment. ^It may be less than ¹⁷ atoms / cm ³ . In addition, all the oxygen concentrations described in this specification are measured values by Fourier transform infrared spectrophotometry (FT-IR) standardized by ASTM F-121 (1979).

Further, in the device process, a heat treatment in which precipitation nuclei can grow before the LSA treatment, for example, a heat treatment held at a temperature of 750 ° C. or higher for 3 hours or longer, and a temperature range of 1000 to 1050 ° C. When the heat treatment including the treatment to be held is performed, the initial oxygen concentration of the wafer body 11 needs to be 14 × 10 ¹⁷ atoms / cm ³ or less. In addition, a heat treatment including a treatment for a longer time before the LSA treatment, for example, a heat treatment for 4 hours or more at a temperature of 750 ° C. or more and a temperature range of 1000 ° C. to 1050 ° C. for 2 hours or more is performed. In this case, the initial oxygen concentration of the wafer main body 11 needs to be 12 × 10 ¹⁷ atoms / cm ³ or less. This is because the size of the plate-like oxygen precipitate formed by the heat treatment is determined by the heat treatment conditions (temperature and time) and the initial oxygen concentration of the wafer body 11. Assuming the above general heat treatment, if the initial oxygen concentration of the wafer body 11 is set to 14 × 10 ¹⁷ atoms / cm ³ or less, the size of the plate-like oxygen precipitate immediately before the LSA treatment is set to a predetermined value. The following can be suppressed. In addition, assuming a longer heat treatment as described above, if the initial oxygen concentration of the wafer body 11 is set to 12 × 10 ¹⁷ atoms / cm ³ or less, the size of the plate-like oxygen precipitate immediately before the LSA treatment is set. Can be kept below a predetermined value. The initial oxygen concentration can be adjusted by convection control of the silicon melt at the time of growing a silicon single crystal by the Czochralski method. The relationship between the size of the plate-like oxygen precipitate and the presence or absence of dislocation generation will be described later.

  Thus, when the wafer body 11 is doped with a high concentration of nitrogen or boron, a semiconductor device such as a MOS transistor cannot be directly formed on the wafer body 11. Semiconductor devices such as MOS transistors are formed in the epitaxial layer 12 on the wafer body 11. The specific resistance of the epitaxial layer 12 is normally set higher than the specific resistance of the wafer body 11. The film thickness of the epitaxial layer 12 is not particularly limited, and may be set to about 1 μm or more and 10 μm or less.

  When the silicon wafer 10 having such a structure is subjected to a heat treatment at 750 ° C. for 4 hours and further subjected to a heat treatment at 1000 ° C. for 4 hours, the wafer body 11 has more plate-like oxygen than polyhedral oxygen precipitates. Precipitates grow predominantly. The plate-like oxygen precipitate is an oxygen precipitate mainly having the structure shown in FIG. 2, and its main surface 21 is along the [100] plane, the [010] plane, or the [001] plane. The size of the plate oxygen precipitate is defined by the diagonal length S. On the other hand, the polyhedral oxygen precipitate is an octahedral oxygen precipitate mainly having the structure shown in FIG. 3, and each surface 22 thereof is along the [111] plane. The size of the polyhedral oxygen precipitate is defined by the length S of one side.

  FIG. 4 is a flowchart for explaining the manufacturing method (wafer process) of the silicon wafer 10 according to the present embodiment.

As shown in FIG. 4, first, a wafer body 11 cut out from a silicon single crystal ingot is prepared (step S11), and its surface is mirror-polished (step S12). The silicon single crystal ingot is grown by the Czochralski method, and thereby, the oxygen eluted from the quartz crucible is contained in the wafer body 11 in supersaturation. As described above, the initial oxygen concentration contained in the wafer main body 11 is preferably set to 14 × 10 ¹⁷ atoms / cm ³ or less, and more preferably set to 12 × 10 ¹⁷ atoms / cm ³ or less. Next, the epitaxial layer 12 is formed on the mirror-polished surface of the wafer body 11 (step S13).

  As described above, the silicon wafer 10 according to the present embodiment is completed. The silicon wafer 10 manufactured by such a wafer process is put into a device process for forming a semiconductor device on the epitaxial layer 12.

  FIG. 5 is a flowchart showing a part of the device process.

  The device process includes various steps depending on the type of semiconductor device to be manufactured (logic device, memory device, etc.). As shown in FIG. 5, the temperature is raised to a temperature at which precipitation nuclei can grow. The heat treatment process (step S21) to be performed and the LSA treatment process (step S22) may be included. Examples of the heat treatment step shown in step S21 include an example of performing heat treatment at 850 ° C. for 30 minutes, 900 ° C. for 30 minutes, 1000 ° C. for 100 minutes, and 950 ° C. for 30 minutes in this order. In addition, examples of the heat treatment step in which the precipitation nuclei are more likely to grow include an example in which heat treatment is performed in this order for 45 minutes at 750 ° C., 30 minutes at 900 ° C., 120 minutes at 1050 ° C., and 45 minutes at 950 ° C. In these cases, the precipitation nuclei contained in the wafer main body 11 grow into oxygen precipitates by the heat treatment step shown in step S21. Examples of the oxygen precipitate formed include a plate-like oxygen precipitate and a polyhedral oxygen precipitate. Of these, when compared with the same volume, polyhedral oxygen precipitates have less stress than plate-like oxygen precipitates, so they are unlikely to start dislocations, but are not subjected to special heat treatment (described later). Since the plate-like oxygen precipitates grow predominantly on the wafer, this is the starting point for the occurrence of dislocations.

  After the plate-like oxygen precipitates are formed by such a heat treatment step (step S21), when the LSA process (step S22) is performed, a strong thermal stress is applied to the wafer body 11, so that the dislocation starts from the oxygen precipitates. May occur. The LSA process is performed by scanning the epitaxial layer 12 of the silicon wafer 10 with a laser beam having a beam diameter of about several mm in a state where the silicon wafer 10 is initially heated to a temperature of about 400 ° C. to 600 ° C. As a result, the region irradiated with the laser light reaches a temperature of 1000 ° C. or higher and a melting point or lower in the order of milliseconds or less, so that a steep impurity profile can be obtained.

In the LSA process, when the diagonal length of the plate-like oxygen precipitates included in the depth region of 50 μm or less from the surface layer of the wafer body 11 is S (nm) and the maximum temperature reached is T (° C.),
T × S ² ≦ 9 × 10 ⁶
If the LSA treatment is performed under the conditions satisfying the above conditions, dislocations starting from the plate-like oxygen precipitates hardly occur. The reason why the value (= 9 × 10 ⁶ ) indicated by the above formula is a threshold is not clear, but is supported by many experimental data to be described later.

  In addition, if a special heat treatment is performed in the wafer process, after performing a heat treatment at 750 ° C. for 4 hours and further at a temperature of 1000 ° C. for 4 hours, a plate-like oxygen precipitate is formed on the wafer body 11. Rather than polyhedral oxygen precipitates grow. Specifically, after forming the epitaxial layer 12 (step S13), the temperature is raised at a rate of 5 ° C./min or more in a temperature range of at least 800 ° C. or more, and at a temperature of 1050 ° C. or more and a melting point or less for 5 minutes or more. Hold. As a result, oxygen contained in the wafer body 11 forms precipitation nuclei, but if the temperature at the time of formation of the precipitation nuclei is less than 1050 ° C., the type of precipitation nuclei that grows into plate-like oxygen precipitates is formed predominantly. On the other hand, if precipitation nuclei are formed in the above temperature range, precipitation nuclei of the type that grow into polyhedral oxygen precipitates are formed predominantly. However, which type of precipitation nuclei cannot be determined by current technology unless the precipitation nuclei are actually grown.

  Here, the time for holding at 1050 ° C. or more and the melting point or less is set to 5 minutes or more because if the holding time is less than 5 minutes, precipitation nuclei of the type that grows into polyhedral oxygen precipitates are not sufficiently formed. The holding time is preferably 2 hours or less. This is because even if the heat treatment is performed for more than 2 hours, the effect is not further improved, and if the holding time is more than 2 hours, the manufacturing cost of the wafer is significantly increased.

  The temperature rising rate in the temperature range of 800 ° C. or higher is set to 5 ° C./min or higher. The temperature range in which precipitation nuclei of the type that grows on the plate-like oxygen precipitates are predominantly formed is 800 ° C. or higher and 1050 ° C. This is because it is necessary to shorten the transit time in the lower temperature range. That is, when the temperature rising rate in the temperature region of 800 ° C. or higher is less than 5 ° C./min, a precipitation nucleus of a type that already grows into a plate-like oxygen precipitate when the holding temperature (1050 ° C. or higher and melting point or lower) is reached. Is formed, and even if it is maintained at 1050 ° C. or higher and the melting point or lower, precipitation nuclei of the type that grow into polyhedral oxygen precipitates do not become dominant. The upper limit of the temperature rising rate is not particularly limited, but is preferably 10 ° C./min or less. This is because if the temperature is increased at a rate exceeding 10 ° C./min, the occurrence of slip dislocation may become remarkable due to an increase in thermal stress caused by the in-plane temperature difference of the wafer. The temperature range in which the temperature increase rate is set to 5 ° C./min or higher is not particularly limited as long as it is at least 800 ° C., but it is preferable to set the temperature increase rate to 5 ° C./min or higher in the temperature region of 700 ° C. or higher. According to this, it becomes possible to more effectively prevent the formation of precipitation nuclei of the type that grows into plate-like oxygen precipitates.

  As described above, if the above heat treatment is performed, precipitation nuclei of the type that grows into polyhedral oxygen precipitates are formed predominately. Therefore, after the heat treatment step (step S21) in the device process, the plate-like oxygen is formed on the wafer body 11. Polyhedral oxygen precipitates grow predominantly than precipitates. For this reason, dislocations are less likely to occur even if LSA treatment is performed thereafter.

However, even in this case, the wafer main body 11 may contain plate-like oxygen precipitates. For this reason,
T × S ² ≦ 9 × 10 ⁶
By performing the LSA treatment under the conditions satisfying the above conditions, it is possible to prevent the occurrence of dislocations starting from the plate-like oxygen precipitates.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

  For example, although an example using an epitaxial wafer has been described in the above embodiment, the application target of the present invention is not limited to an epitaxial wafer.

[Example 1]
A plurality of 300 mm diameter polished wafers having an interstitial oxygen concentration of 12.5 × 10 ¹⁷ atoms / cm ³ were prepared. These wafers were subjected to various heat treatments to form oxygen precipitates having different sizes and shapes. The size and form of the precipitates were specified by measuring and observing another sample subjected to the same heat treatment with a transmission electron microscope (TEM). Table 1 shows the size and form of precipitates present in the depth region of 50 μm or less from the surface layer of the wafer.

  Next, LSA treatment was performed on each wafer on which precipitates were formed. Table 1 shows the maximum temperature reached on the wafer surface for each sample. Then, after the LSA treatment, the presence or absence of dislocation generation was examined using an X-ray topography apparatus.

As a result, as shown in Table 1, for Samples 1 to 24 in which the form of oxygen precipitates was plate-like, dislocation did not occur if the value given by T × S ² was 9 × 10 ⁶ or less. However, dislocation occurred in samples ⁶ , 12, 17, 18, 23, and 24 in which the value given by T × S ² exceeded 9 × 10 ⁶ . This
T × S ² ≦ 9 × 10 ⁶
It was demonstrated that the dislocation generation starting from the plate-like oxygen precipitates does not occur when the LSA treatment is performed under the conditions satisfying the above conditions.

On the other hand, in the samples 25 to 33 in which the form of oxygen precipitates is a polyhedron, dislocation did not occur regardless of the value of T × S ² .

[Example 2]
An epitaxial wafer in which an epitaxial film is formed on the surface of the wafer body having a nitrogen concentration of 3 to 6 × 10 ¹³ atoms / cm ³ , and an epitaxial film on the surface of the wafer body in which the specific resistance by boron doping is 6 to 8 mΩ · cm A plurality of formed epitaxial wafers were prepared. The initial oxygen concentration of each wafer is as shown in Table 2.

  Next, a part of these samples was subjected to heat treatment (heat treatment A) at 850 ° C. for 30 minutes, 900 ° C. for 30 minutes, 1000 ° C. for 100 minutes, and 950 ° C. for 30 minutes. Precipitation nuclei were grown. In addition, the remaining sample is subjected to heat treatment (heat treatment B) for 45 minutes at 750 ° C., 30 minutes at 900 ° C., 120 minutes at 1050 ° C., and 45 minutes at 950 ° C. Grown up. These heat treatments A and B imitate the heat treatment applied in the manufacturing process of the advanced logic device.

  Each sample was subjected to LSA treatment under the condition that the maximum temperature T was 1250 ° C. After the LSA treatment, the size of the plate-like oxygen precipitate existing in the depth region of 50 μm or less from the surface layer of the wafer body is observed using a transmission electron microscope (TEM), and the dislocation is performed using an X-ray topography apparatus. The presence or absence of occurrence was examined.

As a result, as shown in Table 2, if the value given by T × S ² is 9 × 10 ⁶ or less, the type of the wafer body (nitrogen-doped or boron-doped) or the type of heat treatment performed in advance (heat treatment A Alternatively, dislocations did not occur regardless of heat treatment B), but dislocations occurred for samples 34, 39, 44 to 46, 51, 56 in which the value given by T × S ² exceeds 9 × 10 ^6. It was.

Further, among the nitrogen-doped epitaxial wafers subjected to the heat treatment A, dislocation did not occur in the sample 38 having an initial oxygen concentration of 13.6 × 10 ¹⁷ atoms / cm ³ , whereas the initial oxygen concentration was 14. Dislocation occurred in Sample 39, which was 5 × 10 ¹⁷ atoms / cm ³ . Further, among the nitrogen-doped epitaxial wafers subjected to the heat treatment B, dislocation did not occur in the sample 43 having an initial oxygen concentration of 11.8 × 10 ¹⁷ atoms / cm ³ , whereas the initial oxygen concentration was 12. Dislocation occurred in Sample 44, which was 5 × 10 ¹⁷ atoms / cm ³ .

In the boron-doped epitaxial wafer subjected to the heat treatment A, dislocation did not occur in the sample 50 having an initial oxygen concentration of 13.0 × 10 ¹⁷ atoms / cm ³ , whereas the initial oxygen concentration was 13.6. Dislocation occurred in the sample 51 of × 10 ¹⁷ atoms / cm ³ . Further, among the boron-doped epitaxial wafers subjected to the heat treatment B, dislocation did not occur in the sample 55 having an initial oxygen concentration of 12.0 × 10 ¹⁷ atoms / cm ³ , whereas the initial oxygen concentration was 12.6. Dislocation occurred in Sample 56, which was × 10 ¹⁷ atoms / cm ³ .

From these results, when the heat treatment equivalent to the heat treatment A is performed before the LSA treatment, whether the initial oxygen concentration is 14 × 10 ¹⁷ atoms / cm ³ or less regardless of whether it is nitrogen-doped or boron-doped. It was confirmed that dislocation did not occur in the LSA treatment with the maximum temperature of 1250 ° C. In addition, when the heat treatment equivalent to the heat treatment B is performed before the LSA treatment, the maximum is achieved if the initial oxygen concentration is 12 × 10 ¹⁷ atoms / cm ³ or less regardless of whether nitrogen doping or boron doping is performed. It was confirmed that no dislocation occurred in the LSA treatment at a temperature of 1250 ° C.

DESCRIPTION OF SYMBOLS 10 Silicon wafer 11 Wafer main body 12 Epitaxial layer 21 Main surface 22 of plate-like oxygen precipitate The surface of polyhedral oxygen precipitate

Claims (10)

A silicon wafer used for device processes including LSA (Laser Spike Anneal) processing,
When the diagonal length of the plate-like oxygen precipitates contained in the silicon wafer during the LSA treatment is S (nm), and the highest temperature reached in the LSA treatment is T (° C.),
T × S ² ≦ 9 × 10 ⁶
A silicon wafer characterized by satisfying A wafer body having a nitrogen concentration of 1 × 10 ¹² atoms / cm ³ or more or a specific resistance of 20 mΩ · cm or less by boron doping, and an epitaxial layer provided on the surface of the wafer body, The silicon wafer according to claim 1. A silicon wafer used for device processes including LSA (Laser Spike Anneal) processing,
A wafer body having a nitrogen concentration of 1 × 10 ¹² atoms / cm ³ or more, or a specific resistance of 20 mΩ · cm or less by boron doping, and an epitaxial layer provided on the surface of the wafer body,
An initial oxygen concentration of the wafer main body is 14 × 10 ¹⁷ atoms / cm ³ or less. The silicon wafer according to claim 3, wherein an initial oxygen concentration of the wafer main body is 12 × 10 ¹⁷ atoms / cm ³ or less.   In the device process, before the LSA treatment, a heat treatment that is held at a temperature of 750 ° C. or more for 4 hours or more and that is held at a temperature range of 1000 ° C. to 1050 ° C. for 2 hours or more is performed. The silicon wafer according to claim 4, wherein A method of manufacturing a silicon wafer used in a device process including LSA (Laser Spike Anneal) processing,
When the diagonal length of the plate-like oxygen precipitates contained in the silicon wafer during the LSA treatment is S (nm), and the highest temperature reached in the LSA treatment is T (° C.),
T × S ² ≦ 9 × 10 ⁶
The manufacturing method of the silicon wafer characterized by satisfy | filling. 7. The method according to claim 6, further comprising the step of forming an epitaxial layer on the surface of the wafer body in which the nitrogen concentration is 1 × 10 ¹² atoms / cm ³ or more or the specific resistance is set to 20 mΩ · cm or less by boron doping. The manufacturing method of the silicon wafer of description. A method of manufacturing a silicon wafer used in a device process including LSA (Laser Spike Anneal) processing,
By the Czochralski method, the nitrogen concentration is set to 1 × 10 ¹² atoms / cm ³ or more, or the resistivity is set to 20 mΩ · cm or less by boron doping, and the initial oxygen concentration is set to 14 × 10 ¹⁷ atoms / cm ³ or less. Growing a single crystal of silicon,
And a step of forming an epitaxial layer on the surface of the wafer body cut out from the silicon single crystal. 9. The method for producing a silicon wafer according to claim 8, wherein in the step of growing the silicon single crystal, an initial oxygen concentration is set to 12 × 10 ¹⁷ atoms / cm ³ or less.   In the device process, before the LSA treatment, a heat treatment that is held at a temperature of 750 ° C. or more for 4 hours or more and that is held at a temperature range of 1000 ° C. to 1050 ° C. for 2 hours or more is performed. The method for producing a silicon wafer according to claim 9, wherein:

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