JP5510256B2 - Silicon wafer manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a silicon wafer, and more particularly to a method for manufacturing a silicon wafer that maintains a high resistance even after heat treatment in a device manufacturing process.

  The demand for high-frequency circuits is increasing due to the spread or miniaturization of high-frequency devices such as for mobile communication and short-range wireless LAN and the increase in signal amount. The substrate of the high-frequency circuit is required to have a high resistivity, and conventionally, an expensive compound semiconductor such as gallium arsenide (GaAs) has been used.

  In such applications, for example, in a CMOS (Complementary Metal Oxide Semiconductor) using a substrate manufactured from a silicon ingot by a normal Czochralski method (CZ method), power consumption is large and generation of substrate noise increases. Has been considered inappropriate. Recently, however, improvements in miniaturization technology and design have been promoted, and these problems can be overcome using a silicon wafer having a high resistivity.

Here, the resistivity of the high-purity silicon is about 2.3 × 10 ⁵ Ω · cm, and the electrical resistance is too large as it is. Therefore, a small amount of dopant such as boron (B) or phosphorus (P) is added to obtain a desired value. Is adjusted to the resistivity.

This silicon ingot by the CZ method is manufactured by melting a raw material using a quartz crucible and growing it directly from the melt, so that oxygen dissolved from the crucible is usually 20 ppma (1 × 10 ¹⁸ atoms / cm 2). ³ ) About contained.

  However, oxygen in the silicon wafer obtained by the CZ method forms an electrically active oxygen donor such as a thermal donor or a new donor in a heat treatment at about 350 to 500 ° C. in the device manufacturing process. There was a problem that the resistivity of the wafer fluctuated before and after the heat treatment, and the desired resistivity could not be obtained.

  When the resistivity is small like a normal silicon wafer, the influence of the oxygen donor generated by the heat treatment in the device manufacturing process on the resistivity of the wafer is negligible. However, in a high resistance p-type silicon wafer, when oxygen donors are generated by the heat treatment, the resistivity increases, and when the oxygen concentration before heat treatment is high and the amount of oxygen donors generated further increases, the oxygen donor becomes p-type. A significant variation in resistivity occurs, in which the conductivity is reversed from p-type to n-type by canceling out the impurities and the resistivity is reduced.

As a method for suppressing such a variation in resistivity, a method of manufacturing a CZ crystal having a low oxygen concentration by a magnetic field application CZ method (MCZ method) has been proposed. For example, Patent Document 1 proposes a method of manufacturing a silicon wafer having a resistance value of 10000 Ω · cm or more by using a high-purity synthetic quartz glass crucible in the MCZ method.
In Patent Document 2, a low-oxygen silicon ingot having a resistivity of 100 Ω · cm or more and an oxygen concentration of 5 to 10 ppma is grown by the CZ method, and rapid heating and rapid cooling are performed on the obtained silicon wafer. A method of manufacturing a silicon wafer having a high gettering effect by preventing the decrease in resistivity due to the generation of oxygen donors by injecting atomic vacancies into the silicon wafer by performing heat treatment has been proposed.

Japanese Patent Laid-Open No. 5-58788 JP 2003-68744 A

However, although the methods described in Patent Documents 1 and 2 achieve high resistance of a silicon wafer by using a high-purity crucible and reducing the oxygen concentration when manufacturing a silicon ingot, the required resistance Regardless of the rate, the oxygen concentration is controlled to a very low range. Therefore, the oxygen concentration at the time of ingot growth may be excessively reduced, and as a result of the occurrence of slip in the wafer in the device manufacturing process, there is a problem that mechanical strength is lowered and causes a device defect.
Further, since the oxygen concentration is extremely low, oxygen precipitates are hardly formed, and the gettering ability of heavy metal impurities in the device manufacturing process is insufficient.
Accordingly, an object of the present invention is to provide a method for manufacturing a high-resistance silicon wafer having high mechanical strength and high gettering capability, which maintains high resistance even after heat treatment in a device manufacturing process.

  As a result of intensive investigations on how to solve the above problems, the inventors have found that for each set resistivity of the silicon wafer, the correlation between the post-heat treatment resistivity in the device manufacturing process and the oxygen concentration of the silicon ingot from which the silicon wafer was cut out Based on this correlation, it is found that it is effective to perform the growth of the silicon ingot under the condition that the high resistance can be maintained without being influenced by the oxygen donor, The present invention has been completed.

That is, in the method for producing a silicon wafer of the present invention, a silicon ingot is grown by adding a dopant according to the set resistivity by the Czochralski method, and the silicon wafer having the set resistivity is obtained by slicing the silicon ingot. In manufacturing, for each set resistivity, the correlation between the heat-treated resistivity of the silicon wafer after the heat treatment in the device manufacturing process for providing the silicon wafer and the oxygen concentration of the silicon ingot from which the silicon wafer was cut is obtained in advance. The oxygen concentration at which the conductivity type is reversed is grasped, and the growth of the silicon ingot is equal to or higher than the oxygen concentration corresponding to the post-heat treatment resistivity twice the set resistivity in the correlation with the set resistivity of the ingot , Perform under the condition that the measured conductivity type is less than the reversing oxygen concentration It is an feature.

  Further, in the method for producing a silicon wafer of the present invention, the oxygen concentration at the time of producing the silicon ingot is equal to or higher than the oxygen concentration corresponding to the post-heat treatment resistivity twice the set resistivity in the correlation. It is preferable that the oxygen concentration be equal to or less than the resistivity after the heat treatment of 4 times.

In the method for producing a silicon wafer according to the present invention, the carbon concentration in the silicon wafer is 1 × 10 ¹⁶ atoms / cm ³ (ASTM F123-1981) or more.

In the method for producing a silicon wafer of the present invention, the nitrogen concentration in the silicon wafer is 1 × 10 ¹³ atoms / cm ³ or more.

  Further, the surface of the silicon wafer obtained by the method for producing a silicon wafer according to the present invention is irradiated with a transparent laser to form a gettering sink at a predetermined depth from the surface of the silicon wafer. It is.

  Further, a gettering sink is formed at a predetermined depth position from the surface of the silicon wafer by carbon ion implantation with respect to the silicon wafer obtained by the method for producing a silicon wafer of the present invention. Manufacturing method.

  Further, the present invention is characterized in that a silicon wafer obtained by the silicon wafer manufacturing method of the present invention is used as a base wafer, and an SOI structure is formed on the base wafer.

  Moreover, the silicon wafer obtained by the silicon wafer manufacturing method of the present invention is used as a base wafer, and an epitaxial structure is formed on the base wafer.

  According to the present invention, a high resistance silicon wafer having a high mechanical strength and a high gettering capability is provided for setting a range of an initial oxygen concentration that can maintain a high resistance without being influenced by an oxygen donor for each set resistivity. It can be manufactured with good yield.

It is a figure which shows the relationship between the resistivity of the wafer after the heat processing in the device manufacturing process for every set resistivity, and the oxygen concentration before heat processing. It is a figure which shows the setting range and suitable range of initial stage oxygen concentration by this invention. It is a figure which shows formation of the gettering sink in the silicon wafer inside by transmission laser irradiation. It is a figure which shows formation of the gettering sink in the silicon wafer inside by carbon ion implantation.

Embodiments of the present invention will be described below with reference to the drawings.
First, the experimental results that led to the present invention will be described in detail. For the p-type silicon wafer manufactured according to the set resistivity, the inventors have determined, for each set resistivity, the resistivity of the silicon wafer after the heat treatment in the device manufacturing process and the oxygen concentration of the silicon ingot, that is, in the device manufacturing process. The relationship with the oxygen concentration (hereinafter referred to as “initial oxygen concentration”) of the silicon wafer before the heat treatment was examined in detail. Here, as the heat treatment in the device manufacturing process, a heat treatment was adopted at 400 ° C. for 60 minutes, and then the temperature was lowered to 350 ° C. for 40 minutes. The obtained results are shown in FIG.
In the present invention, the oxygen concentration and the carbon concentration in the silicon wafer are obtained using conversion factors of ASTM F121-1979 and ASTM F123-1981, respectively.

From FIG. 1, it can be seen that the resistivity after heat treatment varies greatly with the variation of the initial oxygen concentration at any resistivity. In the extremely low region where the initial oxygen concentration is 4 × 10 ¹⁷ atoms / cm ³ or less, the variation in resistivity is small even after the heat treatment, and the set resistivity is maintained. However, when the initial oxygen concentration is increased, oxygen donors are formed and the resistivity is increased as described above, and when the peak is exceeded, the conductivity type is reversed from p-type to n-type. As the initial oxygen concentration further increases, the resistivity is gradually reduced to become smaller than the set resistivity.
For example, when the set resistivity is 3000 Ω · cm, the resistivity is maintained at 3000 Ω · cm until the initial oxygen concentration is about 5 × 10 ¹⁷ atoms / cm ^3, but the resistivity increases as the initial oxygen concentration increases. Then, the conductivity type is reversed from the p-type to the n-type with a boundary value of about 8 × 10 ¹⁷ atoms / cm ³ . As described above, the resistivity peak position (boundary value of the initial oxygen concentration) at which the conductivity type is reversed from the p-type to the n-type varies depending on the set resistivity value, and becomes smaller as the resistivity value increases. Therefore, in order to manufacture a silicon wafer with high mechanical strength and gettering capability, an appropriate initial oxygen concentration is set according to the set resistance value, that is, the growth of the silicon ingot is set to an appropriate oxygen concentration. It is important to do this.

Here, since the conventional high-resistance silicon wafer manufacturing technology does not adjust the oxygen concentration, for example, 5 × 10 ¹⁷ atoms / cm ³ or less regardless of the value of the set resistivity, the set resistivity is, for example, In the case of 750 Ω · cm, the oxygen concentration is excessively reduced, thereby reducing the mechanical strength and gettering ability of the wafer.
On the other hand, for each set resistivity, a correlation between the post-heat treatment resistivity of the silicon wafer after the heat treatment in the device manufacturing process for providing the silicon wafer and the oxygen concentration of the silicon ingot from which the silicon wafer was cut out is obtained in advance. The mechanical strength of the wafer due to excessive reduction of oxygen concentration by performing ingot growth under the condition that the conductivity type is less than the oxygen concentration that reverses from p-type to n-type in the correlation with the set resistivity of the ingot. In addition, it is possible to prevent a decrease in gettering ability.
Here, the resistivity of the silicon wafer is not particularly limited, but in order to improve the inductor characteristics of the transmission / reception circuit, 500 Ω · cm or more, and in consideration of the variation of the metal contamination level in the wafer manufacturing apparatus, In practice, it is preferably less than 10,000 Ω · cm.
From the viewpoint of wafer strength, the initial oxygen concentration is preferably 2 × 10 ¹⁷ atoms / cm ³ or more in order to suppress the occurrence of slip in the device manufacturing process.

  Thus, in order to appropriately set the oxygen concentration range in which high resistance can be maintained without being affected by oxygen donors for each resistivity to be set, a silicon wafer having high mechanical strength and gettering ability can be manufactured. it can.

In addition, when the oxygen concentration of the ingot is set to a value in the vicinity of the peak position of the resistivity, it is conceivable that the conductivity type is reversed due to variations among ingots and pulling devices. In consideration of such variation and ingot yield, the oxygen concentration corresponds to a post-heat treatment resistivity that is twice the set resistivity in the correlation between the silicon wafer heat treatment resistivity and the initial oxygen concentration obtained in advance. It is preferable that the oxygen concentration be equal to or higher than the oxygen concentration corresponding to the resistivity after heat treatment that is four times the set resistivity. For example, when a wafer having a set resistivity of 3000 Ω · cm is taken as an example, the preferred range is 6.0 × 10 ^{17 to} 7.0 × 10 ¹⁷ atoms / cm ³ as shown in FIG. Even if the variation is taken into consideration, a silicon wafer whose conductivity type does not reverse from p-type to n-type can be manufactured with high yield.

  In growing the silicon ingot in the present invention described above, the pulling conditions other than the oxygen concentration are not particularly limited, and are appropriately set according to the application and purpose. For example, when growing an ingot, crystallinity may deteriorate depending on pulling conditions, and a COP (Crystal Originated Particle) may be formed. As a result of intensive studies on the pulling conditions of the ingot where the COP is not formed, the inventors succeeded in pulling up the p-type silicon ingot having a resistivity of 3000 Ω · cm and no COP. Hereinafter, specific pulling conditions will be described as an example only, but the present invention is not limited to these conditions.

  First, the horizontal magnetic field strength is set to 2000 to 4000 gauss to suppress the flow of the silicon melt in the vicinity of the crucible wall. The reason for limiting the horizontal magnetic field strength is that when the flow rate is less than 2000 gauss, the flow of the silicon melt is not sufficiently suppressed, and the reason why the upper limit is 4000 gauss is 4000 gauss or less. This is because the flow can be sufficiently controlled.

Further, the rotational speed of the ingot is set to 10 rpm or less, and the rotational speed of the crucible is set to 1.0 rpm or less to suppress oxygen taken into the silicon ingot. The reason for limiting the rotational speeds of the ingot and the crucible is that if the value is larger than those values, a large amount of oxygen is taken in.
Further, the pulling speed of the silicon ingot is 0.65 mm / min. Thereby, crystal defects such as COP taken into the silicon ingot can be suppressed.
Further, the flow rate of argon (Ar) gas is set to 40 to 60 torr to suppress the incorporation of impurities such as SiO, CO, and CO ₂ into the silicon ingot. The reason for limiting the Ar gas flow rate is that when the gas flow rate is less than 40 torr, the gas flow rate is insufficient and the impurity suppression is insufficient, and when it exceeds 60 torr, the flow of the melt at the melt interface is affected. It is.

By growing a silicon ingot under the above pulling conditions, a high-resistance silicon wafer without COP can be produced, which is particularly effective when the oxygen concentration is extremely low, 4.0 × 10 ¹⁷ atoms / cm ³ or less. It is.

By appropriately setting the carbon concentration and the nitrogen concentration in the silicon wafer produced by the method of the present invention, the effect of precipitating oxygen contained in the wafer can be enhanced and the gettering ability can be improved. Therefore, the carbon concentration in the silicon wafer is preferably 1 × 10 ^{16 to} 3 × 10 ¹⁷ atoms / cm ³ . Here, the reason for limiting the carbon concentration is that when it is less than 1 × 10 ¹⁶ atoms / cm ³ , precipitates cannot be sufficiently formed, and when the concentration is larger than 3 × 10 ¹⁷ atoms / cm ^3. This is because dislocations are formed.

Moreover, adding nitrogen to the silicon substrate has the effect of increasing the size of oxygen precipitates. Therefore, the nitrogen concentration in the silicon wafer is preferably 1 × 10 ^{13 to} 3 × 10 ¹³ atoms / cm ³ . Here, the reason for limiting the nitrogen concentration is that if it is less than 1 × 10 ¹³ atoms / cm ³ , the effect of increasing the precipitate size cannot be obtained, and if it is greater than 3 × 10 ¹³ atoms / cm ³ , This is because the decrease in substrate resistivity becomes obvious due to the influence of nitrogen donors.

By irradiating the silicon wafer manufactured by the above-described method of the present invention with a transmission laser, a gettering sink for heavy metal impurities can be formed at a predetermined depth from the surface, and the gettering capability can be further enhanced.
FIG. 3 is an enlarged cross-sectional view for explaining the vicinity of the focal position of the laser beam immediately after the irradiation of the laser beam on the silicon wafer is started. The laser beam 10 is irradiated from either one of the both surfaces of the silicon wafer 20 by using the condensing lens 11 so that the focal position of the laser beam 10 is aligned with a predetermined depth position 21 of the silicon wafer 20. By focusing the laser beam 10 at a predetermined depth position 21, a multiphoton absorption process is caused to form the modified portion 22. Although the modified portion 22 is considered to be in an amorphous state, the modified portion 22 is used as a gettering sink.

  The predetermined depth position 21 is set such that the thickness d from the surface of the silicon wafer 20 to the predetermined depth position 21 is the thickness of the chip finally obtained. The adjustment of the depth position 21 is performed by condensing the laser beam 10 using the condensing lens 11 having excellent transparency in the near infrared region, and moving the silicon wafer 20 up and down to focus on the predetermined depth position 21. Can be controlled by imaging.

Here, it is preferable to use a low-power laser as the laser source, and it is more preferable to use an ultrashort pulse laser such as a femtosecond laser. An ultrashort pulse laser can make a laser wavelength into a suitable range by exciting a titanium sapphire crystal (solid laser crystal) using a semiconductor laser or the like. The ultrashort pulse laser can reduce the pulse width of the excitation laser beam to 1.0 × 10 ⁻¹⁵ (femto) seconds or less, and therefore can suppress the diffusion of thermal energy generated by excitation compared to other lasers. The light energy can be collected only in the vicinity of the focal point.

  When irradiating the laser, it is important that the surface layer 23 through which the laser beam 10 passes does not modify the surface layer and the laser is irradiated under conditions that allow the laser beam 10 to pass through reliably. This laser irradiation condition is determined from 1.1 eV which is the energy band gap of silicon, and the incident wavelength is preferably 1000 nm or more from the viewpoint of transparency. When the wavelength exceeds 1200 nm, the photon energy (laser beam energy) is low because it is a long wavelength region, and even if the laser beam is collected by a lens, sufficient photon energy for reforming the inside of the semiconductor is obtained. Since there exists a possibility that it cannot obtain, it is preferable to set it as 1200 nm or less.

  Thus, by irradiating the silicon wafer manufactured by the method of the present invention with a transmission laser, a gettering sink is formed at a predetermined depth position from the wafer surface, and in the device manufacturing process, the gettering ability for heavy metal impurities is obtained. It can be further increased.

Also, instead of the above-described transmission laser irradiation, a gettering sink can be formed at a predetermined depth from the surface of the silicon wafer manufactured by the method of the present invention by implanting carbon ions.
FIG. 4 is a diagram showing formation of a gettering sink inside a silicon wafer by carbon ion implantation. As shown in this figure, first, carbon ions are implanted into the silicon wafer 30 by ion implantation. The ion implantation conditions at that time are acceleration energy: 1 M to 5 MeV, and dose: 2 × 10 ^{13 to} 5 × 10 ¹⁵ ions / cm ² . At that time, the peak concentration of carbon ions is 5 × 10 ^{15 to} 3 × 10 ¹⁷ ions / cm ³ .

Next, heat treatment is performed at 1000 ° C. or higher for 1 minute or less in a nitrogen atmosphere. Thereby, carbon implanted by ion implantation and interstitial oxygen are combined to produce a compound, and a carbon implanted region 32 having a peak concentration at a predetermined depth position 31 is formed. This carbon ion implantation region 32 functions as a gettering sink. The predetermined depth position 31 is set such that the thickness d from the surface of the silicon wafer 30 to the predetermined depth position 31 is the thickness of the chip finally obtained.
Thus, by implanting carbon ions into the silicon wafer manufactured by the method of the present invention, a gettering sink is formed at a predetermined depth position from the surface of the wafer. In the device manufacturing process, the gettering ability for heavy metal impurities is obtained. It can be further increased.

By using the silicon wafer obtained by the method of the present invention as a base wafer, an SOI wafer having a high resistivity can be manufactured. At that time, except for using the silicon wafer obtained by the present invention as a base wafer, a conventional method for manufacturing an SOI wafer may be used, and there is no particular limitation. For example, by a bonding method, a bond wafer as a device forming layer and a silicon wafer of the present invention as a base wafer are brought into close contact with each other through an oxide film, and heat treatment is performed to firmly bond both. By making the film thinner, an SOI wafer having a high resistivity can be manufactured.
The SOI wafer manufactured in this way can be used as a high-frequency device because the high resistivity of the base wafer is maintained even after the device manufacturing heat treatment.

  Further, by using the silicon wafer obtained by the above method as a base wafer and growing an epitaxial film on the base wafer, an epitaxial wafer having high surface flatness and high resistivity can be manufactured. . In this case as well, a conventional epitaxial wafer manufacturing method may be used except that the silicon wafer obtained by the present invention is used as a base wafer, and there is no particular limitation.

(Invention Examples 1 to 5)
Examples of the present invention will be described below.
For p-type silicon wafers with a diameter of 200 mm having respective resistivity of 750 Ω · cm, 1000 Ω · cm, 1200 Ω · cm, 3000 Ω · cm, and 5000 Ω · cm, the oxygen concentration of the ingot and after the heat treatment in the device manufacturing process The relationship with resistivity was investigated. Here, as the heat treatment in the device manufacturing process, a heat treatment at 400 ° C. for 60 minutes + 350 ° C. for 40 minutes was adopted. As a result, the boundary values of the initial oxygen concentration when the conductivity type is reversed from the p-type to the n-type are 12 × 10 ¹⁷ atoms / cm ³ (750Ω · cm) and 11 × 10 ¹⁷ atoms / cm ³ (1000Ω · cm, respectively). cm), 10 × 10 ¹⁷ atoms / cm ³ (1200 Ω · cm), 8 × 10 ¹⁷ atoms / cm ³ (3000 Ω · cm), and 7 × 10 ¹⁷ atoms / cm ³ (5000 Ω · cm). It was.
Therefore, 12 × 10 ¹⁷ atoms / cm ³ (750Ω · cm), 11 × 10 ¹⁷ atoms / cm ³ (1000Ω · cm), 10 × 10 ¹⁷ atoms / cm ³ (1200Ω · cm), and 8 × 10 ¹⁷ atoms, respectively. / Cm ³ (3000 Ω · cm) and 7 × 10 ¹⁷ atoms / cm ³ (5000 Ω · cm) oxygen ingots were grown and processed, and 750 Ω · cm (Invention Example 1), 1000 Ω · cm (Invention Example 1) Invention Example 2) A p-type silicon wafer having a diameter of 200 mm having a resistivity of 1200 Ω · cm (Invention Example 3), 3000 Ω · cm (Invention Example 4) and 5000 Ω · cm (Invention Example 5) was obtained. The ingot growth conditions other than the oxygen concentration were as follows: horizontal magnetic field strength: 3500 gauss, ingot rotation speed: 5 rpm, crucible rotation speed: 0.1 rpm, ingot pulling speed: 0.65 mm / min, Ar gas flow rate : 50 torr, all the same.

(Comparative Examples 1-5)
A silicon ingot was grown under the same conditions as Invention Examples 1 to 5 except that the initial oxygen concentration was kept constant at 1 × 10 ¹⁷ atoms / cm ³ regardless of the resistivity, and 750 Ω · cm (Comparative Example 1) A p-type silicon wafer having a diameter of 200 mm having a resistivity of 1000 Ω · cm (Comparative Example 2), 1200 Ω · cm (Comparative Example 3), 3000 Ω · cm (Comparative Example 4), and 5000 Ω · cm (Comparative Example 5). Obtained.

(Evaluation of mechanical strength)
First, the mechanical strength of each silicon wafer having the above-described resistivity (Invention Examples 1 to 5 and Comparative Examples 1 to 5) was verified by measuring the slip length generated from the wafer fixing pins after the RTA heat treatment. The results obtained are summarized in Table 1. As is apparent from this table, it can be seen that the strength of the silicon wafer obtained by the method of the present invention is high.

(Evaluation of gettering ability)
Next, the gettering ability of each obtained silicon wafer was verified. For this purpose, first, the surface of each wafer was cleaned (DHF cleaning → SC-1 cleaning → SC-2 cleaning), and the entire wafer surface was contaminated with copper (1 × 10 ¹¹ atoms / cm ² ). Copper is one of the heavy metal elements that cause the leakage failure in the device process and the most need to reduce pollution. After contamination with copper, heat treatment was performed at 900 ° C. for 30 minutes in order to capture copper at the gettering site in the diffusion layer.

  In order to evaluate the gettering ability of the diffusion layer, the copper concentration on the epitaxial wafer surface was measured using a high frequency inductively coupled plasma mass spectrometer (ICP-MS). The obtained results are shown in Table 2. Copper was not detected from the surface for all of the five silicon wafers (Invention Examples 1 to 5) manufactured by the method of the present invention and having different resistivity. On the other hand, about the wafer of Comparative Examples 1-5, copper was detected from the surface. Thus, it was found that the silicon wafer manufactured by the method of the present invention has sufficient gettering capability.

(Invention Example 6)
A p-type silicon wafer having a resistivity of 3000 Ω · cm and having a resistivity of 3000 Ω · cm manufactured under the same conditions as in Invention Example 4 is irradiated with a transmission laser to form a gettering sink at a depth of 30 μm from the surface. (Invention Example 6). At that time, a semiconductor-excited solid YAG laser was used as the laser source, and the wavelength of the laser beam was set to 1064 nm.

(Evaluation of gettering ability improvement by transmission laser irradiation)
Except that the amount of copper contamination was 1 × 10 ¹² atoms / cm ² , the copper concentration on the wafer surface according to Invention Example 6 and Invention Example 4 was examined under the same conditions as in [Example 1]. As a result, for the wafer of Invention Example 6, copper was not detected from the surface. On the other hand, for the wafer of Invention Example 4, copper of 5 × 10 ¹¹ atoms / cm ² was detected from the surface. Thus, it was confirmed that the gettering ability of heavy metal impurities is improved by forming a gettering sink inside the wafer by irradiating with a transmissive laser.

(Invention Example 7)
A p-type silicon wafer having a resistivity of 3000 Ω · cm and having a resistivity of 3000 Ω · cm manufactured under the same conditions as in Invention Example 4 is implanted with carbon ions from the surface, and a gettering sink at a depth of 30 μm from the surface. Was formed (Invention Example 7). At that time, as a specific procedure of carbon ion implantation, a SiO ₂ film is formed on the wafer surface, and then carbon ion implantation is performed from the wafer surface at an acceleration energy of 2 MeV and a dose of 5 × 10 ¹⁴ atoms / cm ^3. The SiO ₂ film on the wafer surface was removed.

(Evaluation of gettering ability improvement by carbon ion implantation)
Except for the slightly contaminated amount of copper being 2 × 10 ¹² atoms / cm ² , the copper concentration on the wafer surface according to Invention Example 7 and Invention Example 4 was examined under the same conditions as in Example 1. As a result, for the wafer of Invention Example 7, copper was not detected from the surface. On the other hand, with respect to the wafer of Invention Example 4, 3 × 10 ¹¹ atoms / cm ² of copper was detected from the surface. Thus, it was confirmed that the gettering ability of heavy metal impurities is improved by implanting carbon ions into a silicon wafer manufactured by the method of the present invention to form a gettering sink inside the wafer.

DESCRIPTION OF SYMBOLS 10 Laser beam 11 Condensing lens 20, 30 Silicon wafer 21, 31 Predetermined depth position 22 Modified part 23, 33 Surface layer 24 Modified part width 32 Carbon ion implantation area 34 Width of carbon ion implantation area

Claims (8)

In manufacturing a silicon wafer having the set resistivity by slicing the silicon ingot by adding a dopant according to the set resistivity by the Czochralski method and growing the silicon ingot,
For each of the set resistivity values, the conductivity type is determined in advance by calculating the correlation between the post-heat treatment resistivity of the silicon wafer after the heat treatment in the device manufacturing process for providing the silicon wafer and the oxygen concentration of the silicon ingot from which the silicon wafer is cut out. Know the oxygen concentration to reverse,
The condition that the growth of the silicon ingot is equal to or higher than the oxygen concentration corresponding to the post-heat treatment resistivity twice the set resistivity in the correlation with the set resistivity of the ingot and less than the oxygen concentration at which the grasped conductivity type is reversed. A process for producing a silicon wafer, characterized in that   The oxygen concentration at the time of manufacturing the silicon ingot is equal to or higher than the oxygen concentration corresponding to the post-heat treatment resistivity twice the set resistivity in the correlation and the oxygen corresponding to the post-heat treatment resistivity four times the set resistivity. The method for producing a silicon wafer according to claim 1, wherein the concentration is not more than the concentration. ^{3. The} method for producing a silicon wafer according to claim 1, wherein the carbon concentration in the silicon wafer is 1 × 10 ¹⁶ atoms / cm ³ (ASTM F123-1981) or more. The method for producing a silicon wafer according to claim 1, wherein a nitrogen concentration in the silicon wafer is 1 × 10 ¹³ atoms / cm ³ or more.   The surface of the silicon wafer obtained by the manufacturing method according to claim 1 is irradiated with a transmissive laser to form a gettering sink at a predetermined depth from the surface of the silicon wafer. A method for manufacturing a silicon wafer.   A gettering sink is formed at a predetermined depth position from the surface of the silicon wafer by carbon ion implantation with respect to the silicon wafer obtained by the manufacturing method according to any one of claims 1 to 4. A method for manufacturing a silicon wafer.   A method for producing a silicon wafer, wherein the silicon wafer obtained by the production method according to claim 1 is used as a base wafer, and an SOI structure is formed on the base wafer.   A method for producing a silicon wafer, wherein the silicon wafer obtained by the production method according to claim 1 is used as a base wafer, and an epitaxial structure is formed on the base wafer.

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