JP2007149799A - Annealed wafer and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for inexpensively manufacturing an annealed wafer having a thick non-defect layer in a wafer surface, and having strong gettering capability. <P>SOLUTION: In the manufacturing method of the annealed wafer, carbon ions 14 are injected to a silicon single crystal wafer 11 to which nitrogen is doped so that a peak of carbon ion concentration is given to depth of not less than 1.5 μm from a surface of the wafer. Heat treatment is performed on the wafer 11 to which the ions are injected for not less than one second at a temperature from 1,000°C to a melting point of silicon under non-oxidizing atmosphere. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides an annealed wafer having strong gettering capability (capability of capturing heavy metal contaminants in a device process) in the vicinity of the surface layer of a silicon single crystal wafer, in particular, an annealed wafer useful for forming a solid-state imaging device. The present invention relates to a method and an annealed wafer.

  As a silicon single crystal wafer for forming a semiconductor element, a silicon single crystal wafer grown by a CZ (Czochralski) method or an MCZ (Magnetic field CZ) method, or an epitaxial layer was formed on the surface of these silicon single crystal wafers An epitaxial wafer, an annealed wafer obtained by subjecting a silicon single crystal wafer to heat treatment, and the like have been conventionally used.

  On the other hand, the semiconductor element formation process is performed in an ultra clean room of class 100 or less, but contamination of the silicon single crystal wafer due to impurities from gas, water, semiconductor manufacturing equipment, etc. cannot be completely avoided. If these impurities are present in the element active region of the silicon single crystal wafer, the quality and characteristics of the semiconductor element are significantly deteriorated. Therefore, intrinsic gettering (IG) and extrinsic gettering (EG) are conventionally performed in order to getter these impurities and remove them from the element active region. Further, an epitaxial layer may be formed on the surface of the wafer subjected to these treatments.

  In particular, from the viewpoint of manufacturing a semiconductor element, an epitaxial wafer can form an electrically active layer having a resistivity different from that of a substrate wafer, so that the degree of freedom in designing a semiconductor element is great. Since there are many advantages such as the ability to form a single crystal thin film of high purity with a low concentration of oxygen or carbon that causes crystal defects to an arbitrary thickness, a high voltage semiconductor element, a bipolar integrated circuit element, a solid-state imaging element (CCD ( (Charge-Coupled Device) imaging device) and the like.

As a practical method for forming an epitaxial layer, a CVD method (Chemical Vapor Deposition method) is used, and the following four main source gases are used.
In the hydrogen reduction method, SiCl ₄ and SiHCl ₃ are used as source gases.
SiCl ₄ + 2H ₂ → Si + 4HCl
SiHCl ₃ + H ₂ → Si + 3HCl
In the thermal decomposition method, SiH ₂ Cl ₂ and SiH ₄ are used as source gases.
SiH ₂ Cl ₂ → Si + 2HCl
SiH ₄ → Si + 2H ₂
Among these, as the solid-state imaging device, SiHCl ₃ is mainly used because it is inexpensive, has a high growth rate, and is suitable for epitaxial growth of thick films.

  However, in an epitaxial wafer in which an epitaxial layer is formed using any source gas, many impurities, particularly metal impurities, are mixed during the formation of the epitaxial layer. When such metal impurities are applied to a solid-state imaging device, white scratch defects due to dark current cannot be sufficiently reduced, causing deterioration in characteristics and yield.

Possible sources of heavy metal impurities are those from SUS-based members in bell jars of epitaxial growth apparatuses and those from source gas piping. If the source gas contains chlorine, it is decomposed during epitaxial growth to produce HCl gas. It is considered that the HCl gas corrodes the SUS-based member in the bell jar and is taken into the source gas as a metal chloride, and this metal chloride is taken into the epitaxial layer.
In addition, HCl gas may be intentionally introduced to lightly etch off the surface of the silicon single crystal wafer before forming the epitaxial layer, which also contributes to corrosion.

  Therefore, when a solid-state imaging device is formed using an epitaxial wafer, carbon ions are implanted from one surface of a silicon wafer as a gettering technique for gettering and removing the metal impurities, and a carbon ion implantation region is obtained. There is a method of manufacturing a carbon gettering epitaxial wafer in which a silicon epitaxial layer is formed on the surface (see Patent Document 1). In order to further improve the gettering ability, carbon ions and nitrogen ions are implanted into one surface of a silicon wafer to form an epitaxial layer on the surface (see Patent Document 2), or on one surface of a silicon wafer containing nitrogen. A method of implanting carbon ions and forming a silicon epitaxial layer on the surface has been proposed (see Patent Document 3).

However, when the device process is a low-temperature process, it is difficult for oxygen to precipitate, so that there is a problem that the gettering ability is weak even if carbon ions are implanted.
In addition, the higher the dose of implanted carbon ions, the more difficult the recovery process before the epitaxial process becomes and the silicon epitaxial layer cannot be grown. Even when the silicon epitaxial layer can be grown, epi defects occur. There was a problem that it was easy to do.

JP-A-6-338507 JP-A-11-251322 JP 2002-134511 A

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to reduce the cost of an annealed wafer having a thick defect-free layer on the wafer surface layer portion and having a strong gettering capability. It is to provide a method of manufacturing and the annealed wafer.

  In order to achieve the above-described object, according to the present invention, at least a nitrogen ion-doped silicon single crystal wafer has a carbon ion concentration peak at a depth of 1.5 μm or more from the wafer surface. After the ion implantation, an annealed wafer manufacturing method is provided in which the ion-implanted wafer is heat-treated in a non-oxidizing atmosphere at a temperature of 1000 ° C. or higher and lower than the melting point of silicon for 1 second or longer ( Claim 1).

  Thus, after carbon ions are ion-implanted to have a carbon ion concentration peak at a depth of 1.5 μm or more from the surface of the nitrogen-doped silicon single crystal wafer, the wafer is 1000 ° C. or higher in a non-oxidizing atmosphere. By performing heat treatment for 1 second or more at a temperature lower than the melting point of silicon, a thick defect-free layer having a sufficient thickness necessary for an element active region of a state-of-the-art semiconductor element of 1.5 μm or more from the surface of the wafer is formed, For high-integrated devices having a strong gettering capability having a sufficiently high density of internal microdefects (BMD) in the bulk portion, particularly the carbon ion implantation region immediately below the defect-free layer An annealed wafer that is extremely useful as a wafer can be manufactured at low cost without epitaxial growth. .

At this time, the ion implantation of the carbon ions is preferably performed at a dose of 1 × 10 ¹³ atoms / cm ² or more and less than 5 × 10 ¹³ atoms / cm ² (Claim 2), and the ion implantation of the carbon ions is performed. It is preferable to carry out with acceleration energy of 1 MeV or more.
Thus, carbon ions are implanted at a low dose of 1 × 10 ¹³ atoms / cm ² or more and less than 5 × 10 ¹³ atoms / cm ² and / or with a high acceleration energy of 1 MeV or more. Since the projected range of ions can be increased, the carbon ions can be ion-implanted so that the peak of the carbon ion concentration is at a deep position of 1.5 μm or more from the wafer surface.

Furthermore, by performing ion implantation of carbon ions at a low dose and high acceleration energy in this way, the ion implantation of carbon ions is performed at a depth of 2.5 to 4.0 μm from the wafer surface. It can also carry out so that it may have a peak of carbon ion concentration.
In this way, a thicker defect-free layer is formed on the wafer surface layer by performing ion implantation of carbon ions so as to have a carbon ion concentration peak at a depth of 2.5 to 4.0 μm from the surface of the wafer. Thus, the entire 1.5 μm from the surface of the wafer, which is the element active region of the most advanced semiconductor element, can be reliably formed as a defect-free layer.

The silicon single crystal wafer may be one having a nitrogen concentration of 1 × 10 ^{13 to} 5 × 10 ¹⁴ atoms / cm ³ and an oxygen concentration of 1.0 to 1.3 × 10 ¹⁸ atoms / cm ^3. Preferred (claim 5).
As described above, a silicon single crystal wafer having a nitrogen concentration of 1 × 10 ^{13 to} 5 × 10 ¹⁴ atoms / cm ³ and an oxygen concentration of 1.0 to 1.3 × 10 ¹⁸ atoms / cm ³ is used. Thus, an annealed wafer having a sufficiently high density BMD can be manufactured very easily by accelerating oxygen precipitation in the bulk portion, particularly in the carbon ion implantation region immediately below the defect-free layer.

Furthermore, according to the present invention, an annealed wafer manufactured by the above-described annealed wafer manufacturing method is provided.
Thus, the annealed wafer produced by the above-described annealed wafer production method has a thick defect-free layer formed in the wafer surface layer portion, and has a high density in the carbon ion implantation region immediately below the bulk portion, particularly the defect-free layer. It has a powerful gettering capability with BMD and is an extremely useful and low-cost annealed wafer as a wafer for highly integrated devices.

Further, according to the present invention, an annealed wafer obtained by performing a heat treatment on a nitrogen-doped silicon single crystal wafer into which carbon ions have been ion-implanted, wherein the ion-implanted carbon ions are introduced from the surface of the ion-implanted wafer. It has a peak of carbon ion concentration of 1 × 10 ¹⁵ atoms / cm ³ or more at a depth of 1.5 μm or more, and a defect-free layer is formed on the surface into which the carbon ions are implanted. An annealed wafer is provided (claim 7).

Thus, the ion-implanted carbon ions have a peak of carbon ion concentration of 1 × 10 ¹⁵ atoms / cm ³ or more at a depth of 1.5 μm or more from the surface of the ion-implanted wafer. If the annealed wafer is formed with a defect-free layer on the surface implanted with the defect-free layer, the defect-free layer formed on the surface of the wafer serving as an element active region is thick, and the bulk portion, particularly the defect-free layer is directly under the defect-free layer. Annealed wafer that is extremely useful as a wafer for highly integrated devices with a strong gettering capability with a sufficiently high density BMD in a carbon ion implantation region having a high concentration peak of 1 × 10 ¹⁵ atoms / cm ³ or more It becomes. Further, since it is not necessary to grow an epitaxial layer, the manufacturing cost is low.

Furthermore, it is preferable that the ion-implanted carbon ions have a concentration peak at a depth of 2.5 to 4.0 μm from the surface of the ion-implanted wafer.
As described above, if the ion-implanted carbon ions have a concentration peak at a depth of 2.5 to 4.0 μm from the surface of the ion-implanted wafer, a thicker defect-free layer is formed on the surface layer of the wafer. A layer can be formed, and the entire 1.5 μm from the surface of the wafer which is an element active region of the most advanced semiconductor element can be surely made a defect-free layer.

The peak of the carbon ion concentration is preferably 5 × 10 ¹⁶ atoms / cm ³ or more (Claim 9).
Thus, if the peak of the carbon ion concentration has a higher concentration peak of 5 × 10 ¹⁶ atoms / cm ³ or more, the carbon ion concentration is stronger than the sufficiently strong BMD in the carbon ion implantation region. An annealed wafer having gettering capability is obtained.

Further, the silicon single crystal wafer has a nitrogen concentration of 1 × 10 ^{13 to} 5 × 10 ¹⁴ atoms / cm ³ and an oxygen concentration of 1.0 to 1.3 × 10 ¹⁸ atoms / cm ^3. Preferred (claim 10).
Thus, the silicon single crystal wafer is assumed to have a nitrogen concentration of 1 × 10 ^{13 to} 5 × 10 ¹⁴ atoms / cm ³ and an oxygen concentration of 1.0 to 1.3 × 10 ¹⁸ atoms / cm ^3. The oxygen deposition is accelerated in the bulk portion, particularly in the carbon ion implantation region immediately below the defect-free layer, so that an extremely high quality and low cost annealed wafer having a sufficiently high density BMD can be obtained.

The defect-free layer preferably has a thickness of 2.5 μm or more.
As described above, if the defect-free layer has a thickness of 2.5 μm or more, the entire wafer surface layer serving as an element active region can be more reliably formed as a defect-free layer.

As described above, according to the present invention, it is not necessary to perform epitaxial growth, and an annealed wafer having a thick defect-free layer on the wafer surface layer portion and having a strong gettering capability can be manufactured at low cost.
In particular, the annealed wafer of the present invention makes it possible to manufacture a cutting-edge semiconductor element having excellent quality characteristics and a high yield, particularly a solid-state imaging element, at a low cost.

Conventionally, there is a method of manufacturing a wafer having high gettering ability by forming an oxygen precipitate layer by carbon ion implantation, but the carbon ion implantation depth is usually 0.5 μm or less, and at most 1.3 μm. For this reason, after ion implantation, epitaxial growth must be performed in order to form a defect-free layer having a predetermined thickness necessary for device formation on the wafer surface layer.
Further, when a normal substrate is used, the dose amount of ion implantation is required to be at least 5 × 10 ¹⁴ atoms / cm ² in order to promote oxygen precipitation. In order to recover the crystallinity in the vicinity, a long-time recovery heat treatment is required, resulting in a problem that the manufacturing cost increases.

  Therefore, the present inventors diligently studied a method of forming a defect-free layer having a predetermined depth on the wafer surface without epitaxial growth after carbon ion implantation and forming a high-density oxygen precipitate layer therebelow. As a result, at least after nitrogen ions are implanted into a silicon single crystal wafer doped with nitrogen at a low dose so as to have a carbon ion concentration peak at a depth of 1.5 μm or more from the surface of the wafer, the ions The implanted wafer is heat-treated at a temperature of 1000 ° C. or higher and lower than the melting point of silicon in a non-oxidizing atmosphere for 1 second or longer, so that epitaxial growth is not performed, and a thick defect-free layer is formed on the wafer surface layer. The inventors have conceived that an annealed wafer having a gettering capability can be manufactured at low cost, and completed the present invention.

  Specifically, if a silicon single crystal wafer having a high oxygen concentration and nitrogen doping is used, and carbon ions of high energy and low dose are implanted into the surface layer of these wafers, 1.5 μm or more from the wafer surface. After that, a defect-free layer with a predetermined thickness can be formed on the surface layer just by performing heat treatment in an argon atmosphere without epitaxial growth. High density oxygen precipitates can be formed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.
FIG. 1 is a flowchart showing an example of a method for manufacturing an annealed wafer according to the present invention. FIG. 2 is a diagram showing a BMD density distribution in the thickness direction of the annealed wafer of the present invention.

  In the present invention, after carbon ions 14 are ion-implanted into a silicon single crystal wafer 11 doped with nitrogen at least at a depth of 1.5 μm or more from the surface of the wafer, This is a method for manufacturing an annealed wafer, in which an implanted wafer 11 is heat-treated for 1 second or longer at a temperature of 1000 ° C. or higher and lower than the melting point of silicon in a non-oxidizing atmosphere (FIG. 1).

  As a result, a thick defect-free layer 16 having a sufficient thickness necessary for creating an active region of a state-of-the-art semiconductor device of 1.5 μm or more from the surface of the wafer is formed. As shown in FIG. For high-integrated devices having a strong gettering capability having a sufficiently high density of internal micro defects (hereinafter abbreviated as BMD) in the carbon ion implantation region 15 directly below the defect-free layer. An annealed wafer extremely useful as the wafer 11 can be manufactured at low cost without performing epitaxial growth.

  Note that BMD is a process of manufacturing a semiconductor device and a thermal history until interstitial oxygen contained as impurities in a silicon single crystal grown by the CZ method or the like is solidified during the crystal growth process and then cooled to room temperature. This is an internal micro defect formed by silicon oxide precipitates (oxygen precipitates) because it is supersaturated in the heat treatment process in and effective as a gettering site for capturing heavy metal impurities mixed in the device process Can improve device characteristics and yield. Therefore, a wafer having a higher BMD has a stronger gettering capability.

Hereinafter, the method of the present invention will be described in the order of steps.
For example, as shown in FIG. 1A, first, a silicon single crystal wafer 11 sliced from a silicon single crystal ingot grown by the CZ method and mirror-polished is prepared.
Here, the silicon single crystal wafer 11 has a nitrogen concentration of 1 × 10 ^{13 to} 5 × 10 ¹⁴ atoms / cm ³ and an oxygen concentration of 1.0 to 1.3 × 10 ¹⁸ atoms / cm ^3. It is preferable to use a material obtained by slicing and slicing this, so that oxygen precipitation can be accelerated in the carbon ion implantation region 15 even when the bulk portion, particularly carbon, has a low dose. An annealed wafer having a high density BMD can be manufactured very easily.
It is preferable that the silicon single crystal wafer 11 is first washed with an NH ₄ OH / H ₂ O ₂ aqueous solution and further washed with an HCl / H ₂ O ₂ aqueous solution.

Next, dry oxidation is performed at a temperature of 950 ° C. for 150 minutes to form a SiO ₂ film 13 having a thickness of about 30 nm on the mirror surface 12 of the silicon single crystal wafer 11 as shown in FIG. preferable. Thereby, mixing of impurities at the time of ion implantation can be prevented.

Then, ion implantation of carbon ions 14 is performed with a low dose amount of, for example, 1 × 10 ¹³ atoms / cm ² or more and less than 5 × 10 ¹³ atoms / cm ² through the SiO ₂ film 13 by a high energy ion implantation apparatus, and By performing with high acceleration energy of 1 MeV or higher, the projected range distance (the peak depth 22 of the carbon ion concentration) of the carbon ions 14 can be increased.

The peak concentration of the carbon ions 14 in the carbon ion implantation region 15 may be 1 × 10 ¹⁵ atoms / cm ³ , but more preferably 5 × 10 ¹⁶ atoms / cm ³ or more. This is because if the density is 5 × 10 ¹⁶ atoms / cm ³ or more, a sufficiently high-density BMD can be formed.

  The ion implantation of the carbon ions 14 may be 1.5 μm or more from the wafer surface, but by performing so that the carbon ion concentration has a peak at a depth of 2.5 to 4.0 μm from the wafer surface, A thicker defect-free layer 16 can be formed on the surface layer portion, and the entire 1.5 μm from the surface of the wafer 11 which is the element active region of the most advanced semiconductor element can be more reliably made a defect-free layer. .

Here, in general, the depth of ion implantation is controlled by acceleration energy, and the implantation amount (dose amount) of ion particles (impurities) is controlled by the product of the beam current and the implantation time.
An ion implantation apparatus with a high acceleration energy exceeding 1 MeV cannot inject a high dose because the beam current is low, but if it is a low dose of 1 to 5 × 10 ¹³ atoms / cm ^2. It has been found that the projection range distance can be increased as described above.

As a result, as shown in FIG. 1C, a carbon ion implantation region 15 having a peak concentration is formed at a position deeper than the mirror surface 12 of the silicon single crystal wafer 11 by 1.5 μm or more.
Conventionally, the dose amount of carbon was considered to be required to be at least 5 × 10 ¹³ atoms / cm ² in order to promote precipitation, so the implantation depth was 1 μm or less, particularly 0.5 μm at most. The invention makes it possible to inject carbon to a depth of 1.5 μm or more by using a low dose and high acceleration energy.

Thereafter, as shown in FIG. 1D, the SiO ₂ film 13 is removed with an HF / NH ₄ F aqueous solution or HF.
And as shown in FIG.1 (e), it heat-processes for 1 second or more by the temperature below 1000 degreeC or more and the melting | fusing point of silicon | silicone in non-oxidizing atmosphere. As a result, the crystallinity of the mirror surface 12 made amorphous by ion implantation is recovered, and a thick defect-free layer 16 is formed in a region near the wafer surface, which is an element active region. As shown in FIG. An annealed wafer in which high-density oxygen precipitates are formed in the carbon ion region 15 immediately below can be completed.
In particular, heat treatment is preferably performed at 1200 ° C. for 1 hour in an argon atmosphere. Thereby, the annealed wafer in which the thick defect-free layer 16 is more reliably formed and sufficiently dense oxygen precipitates are formed can be manufactured at low cost.
The heat treatment furnace used here is not particularly limited. For example, the heat treatment furnace may be a heat treatment for 1 second to 10 minutes in a rapid heating furnace and a heat treatment furnace (batch furnace) for 1 minute to 120 minutes.

  In the annealed wafer of the present invention thus produced, a thick defect-free layer is formed in the wafer surface layer portion, and the high-density BMD has a high density in the carbon ion implantation region 15 immediately below the bulk portion, particularly the defect-free layer. It is a low-cost annealed wafer that has excellent gettering capability, is extremely useful as a wafer for highly integrated devices, and is manufactured without epitaxial growth.

Specifically, the annealed wafer of the present invention is an annealed wafer obtained by performing a heat treatment on a nitrogen-doped silicon single crystal wafer into which carbon ions have been ion-implanted, and the ion-implanted carbon ions have been ion-implanted. It has a peak of carbon ion concentration of 1 × 10 ¹⁵ atoms / cm ³ or more, more preferably 5 × 10 ¹⁶ atoms / cm ³ or more at a depth of 1.5 μm or more from the surface of the wafer, and the carbon ions are implanted. This is an annealed wafer having a defect-free layer 16 formed on the surface. This annealed wafer is a strong getter having a sufficiently high density BMD in a carbon ion implantation region having a high concentration peak of 1 × 10 ¹⁵ atoms / cm ³ or more directly below a bulk portion, particularly a defect-free layer. It becomes a low cost annealed wafer having a ring capability and high in usefulness.
In particular, the defect-free layer 16 preferably has a thickness of 2.5 μm or more. Thereby, the whole wafer surface layer used as an element active region can be made into the defect-free layer 16 more reliably.

  If a state-of-the-art semiconductor device, particularly a solid-state imaging device, which requires high gettering capability is formed on the defect-free layer of the annealed wafer of the present invention as described above, it has excellent quality characteristics, high yield and low cost. A simple device can be manufactured.

As described above, according to the present invention, it is not necessary to perform epitaxial growth, and an annealed wafer having a thick defect-free layer on the wafer surface layer portion and having a strong gettering capability can be manufactured at low cost.
In particular, the annealed wafer of the present invention makes it possible to manufacture a cutting-edge semiconductor element having excellent quality characteristics and a high yield, particularly a solid-state imaging element, at a low cost.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
Example 1
According to the process of FIG. 1, the single crystal growth rate is 0.82 mm / min, the oxygen concentration is 1.12 × 10 ¹⁸ atoms / cm ³ , the nitrogen concentration is 3 × 10 ¹³ atoms / cm ³ , the diameter is 200 mm, and the P-type 8-12Ω. -Ten silicon single crystal wafers of cm were prepared, and carbon ions were implanted with an acceleration energy of 1.2 MeV and a dose of 3 × 10 ¹³ atoms / cm ² .

Then, after the oxide film on the wafer surface was removed by etching, heat treatment was performed at 1200 ° C. for 1 hour in an Ar atmosphere using a batch furnace. For the five wafers, the projected range distance (carbon ion concentration peak depth 22) (calculated value), carbon ion peak concentration (measuring instrument: SIMS), defect-free layer thickness (post-polish particle counter ( Measured by SP1)), and a BMD density of 5 μm (measuring device: MO601, manufactured by Mitsui Mining & Smelting Co., Ltd.) was evaluated from the surface layer.
As a result, the average value of the evaluated wafers was a projected range distance of 3.5 μm, a carbon ion peak concentration of 5.0 × 10 ¹⁶ atoms / cm ³ , a defect-free layer thickness of 2.8 μm, and a BMD density of 1. It was 12 × 10 ⁹ / cm ³ . The remaining five sheets were observed for a defect distribution on the wafer surface of 35 μm or more with a laser microscope (MAGICS, manufactured by Lasertec Corporation). As a result, in the observation of the defect distribution on the wafer surface, defects of 100 to 150/200 mmφ wafer were observed.

(Example 2)
Five silicon single crystal wafers as in Example 1 were prepared, and carbon ions were implanted with an acceleration energy of 1.0 MeV and a dose of 3 × 10 ¹³ atoms / cm ² . Then, after the oxide film on the wafer surface was removed by etching, heat treatment was performed at 1200 ° C. for 1 hr in an Ar atmosphere. The projected range distance (calculated value), carbon ion peak concentration (SIMS), defect-free layer thickness (SP1 after polishing), and BMD density (MO601) of 5 μm from the surface layer were evaluated.
As a result, the average value of the evaluated wafers was a projected range distance of 3.0 μm, a carbon ion peak concentration of 8.0 × 10 ¹⁶ atoms / cm ³ , a defect-free layer thickness of 2.5 μm, and a BMD density of 1 It was 0.0 × 10 ⁹ / cm ³ .

(Comparative Example 1)
Five silicon single crystal wafers as in Example 1 were prepared, and carbon ions were implanted with an acceleration energy of 800 keV and a dose of 3 × 10 ¹³ atoms / cm ² . Then, after the oxide film on the wafer surface was removed by etching, heat treatment was performed at 1200 ° C. for 1 hr in an Ar atmosphere. The projected range distance (calculated value), carbon ion peak concentration (SIMS), defect-free layer thickness (SP1 after polishing), and BMD density (MO601) of 5 μm from the surface layer were evaluated.
As a result, the average value of the evaluated wafers was a projection range distance of 1.3 μm, a carbon ion peak concentration of 3.0 × 10 ¹⁷ atoms / cm ³ , a defect-free layer thickness of 0.5 μm, and a BMD density of 3. It was 5 × 10 ⁷ / cm ³ .

(Comparative Example 2)
Ten silicon single crystal wafers as in Example 1 were prepared, and carbon ions were implanted with an acceleration energy of 600 keV and a dose of 5 × 10 ¹⁴ atoms / cm ² . Then, after the oxide film on the wafer surface was removed by etching, heat treatment was performed at 1200 ° C. for 1 hr in an Ar atmosphere. Five of them were evaluated for projected range distance (calculated value), carbon ion peak concentration (SIMS), defect-free layer thickness (SP1 after polishing), and BMD density (MO601) of 5 μm from the surface layer.
As a result, the average value of the evaluated wafers was a projection range distance of 0.8 μm, a carbon ion peak concentration of 5.0 × 10 ¹⁶ atoms / cm ³ , a defect-free layer thickness of 0.1 μm, and a BMD density of <2 It was 0.0 × 10 ⁷ / cm ³ (detection limit value).

For the remaining five wafers, after heat treatment, an epitaxial layer of 3 μm was grown on the wafer surface, and the defect distribution on the wafer surface of 35 nm or more was observed with a laser microscope (MAGICS, manufactured by Lasertec Corporation).
As a result, in the observation of the defect distribution on the wafer surface, defects of 600 to 1200/200 mmφ wafer were confirmed. This is presumably because the crystallinity is not sufficiently recovered even when a recovery heat treatment is performed at 1200 ° C. for 1 hour, so that defects existing on the wafer surface are transferred to the epitaxial layer and an epi defect is generated.

  Table 1 summarizes the conditions and results of Examples 1 and 2 and Comparative Examples 1 and 2.

  By carrying out with high acceleration energy of 1 MeV or more as in Examples 1 and 2, the projected range of carbon ions can be increased to 2.5 to 4.0 μm, and 2.5 to 4 from the wafer surface. A carbon ion implantation region 15 having a carbon ion concentration peak at a deep position of 0.0 μm is formed.

  As a result, a thick defect-free layer having a thickness of 2.5 μm or more can be formed by heat treatment, and it has a strong gettering capability possessed by a high-density BMD in the bulk portion, particularly in the carbon ion implantation region. Therefore, it was confirmed that a low-cost annealed wafer can be manufactured because it is extremely useful as a wafer for a highly integrated device, in particular, a solid imaging element and does not require epitaxial growth.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

It is a flowchart which shows an example of the manufacturing method of the annealed wafer which concerns on this invention. It is a figure which shows BMD density distribution with respect to the thickness direction of the annealed wafer of this invention.

Explanation of symbols

11 ... silicon single crystal wafer, 12 ... mirror surface, 13 ... SiO ₂ film,
14 ... carbon ions, 15 ... carbon ion implantation region, 16 ... defect-free layer,
21: thickness of defect-free layer, 22: depth of peak of carbon ion concentration.

Claims (11)

  At least, after carbon ions are ion-implanted into a silicon single crystal wafer doped with nitrogen so as to have a carbon ion concentration peak at a depth of 1.5 μm or more from the surface of the wafer, non-implantation is performed on the ion-implanted wafer. A method for producing an annealed wafer, comprising performing a heat treatment for 1 second or more at a temperature of 1000 ° C. or higher and lower than a melting point of silicon in an oxidizing atmosphere. ^{2. The} method of manufacturing an annealed wafer according to claim 1, wherein the ion implantation of the carbon ions is performed at a dose of 1 × 10 ¹³ atoms / cm ² or more and less than 5 × 10 ¹³ atoms / cm ² .   The method for producing an annealed wafer according to claim 1 or 2, wherein the ion implantation of the carbon ions is performed with an acceleration energy of 1 MeV or more.   4. The carbon ion ion implantation is performed so as to have a carbon ion concentration peak at a depth of 2.5 to 4.0 [mu] m from the surface of the wafer. The manufacturing method of the annealed wafer as described in claim | item. A silicon single crystal wafer having a nitrogen concentration of 1 × 10 ^{13 to} 5 × 10 ¹⁴ atoms / cm ³ and an oxygen concentration of 1.0 to 1.3 × 10 ¹⁸ atoms / cm ³ is used. The manufacturing method of the annealed wafer as described in any one of Claim 1 thru | or 4.   An annealed wafer manufactured by the method for manufacturing an annealed wafer according to any one of claims 1 to 5. An annealed wafer obtained by performing a heat treatment on a nitrogen-doped silicon single crystal wafer into which carbon ions have been ion-implanted, wherein the ion-implanted carbon ions have a depth of 1.5 μm or more from the surface of the ion-implanted wafer. An annealed wafer having a peak of a carbon ion concentration of 1 × 10 ¹⁵ atoms / cm ³ or more and having a defect-free layer formed on the surface into which the carbon ions are implanted.   The annealed wafer according to claim 7, wherein the ion-implanted carbon ions have a concentration peak at a depth of 2.5 to 4.0 µm from the surface of the ion-implanted wafer. . 9. The annealed wafer according to claim 7, wherein the peak of the carbon ion concentration is 5 × 10 ¹⁶ atoms / cm ³ or more. The silicon single crystal wafer has a nitrogen concentration of 1 × 10 ^{13 to} 5 × 10 ¹⁴ atoms / cm ³ and an oxygen concentration of 1.0 to 1.3 × 10 ¹⁸ atoms / cm ^3. The annealed wafer according to any one of claims 7 to 9.   The annealed wafer according to any one of claims 7 to 10, wherein the defect-free layer has a thickness of 2.5 µm or more.

Images