JP2008311418A - Epitaxial wafer, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epitaxial wafer having strong gettering capability in the vicinity of a lower part of an epitaxial layer without forming an epitaxial defect in the epitaxial layer, in an epitaxial wafer; and its manufacturing method. <P>SOLUTION: This epitaxial wafer is composed by forming the epitaxial layer on a silicon single-crystal substrate. The epitaxial wafer is characterized in that the silicon single-crystal substrate is formed by doping carbon therein in growing a silicone single crystal, and has a carbon ion injected layer formed thereon by injecting carbon ions therein from a surface thereof, and the epitaxial layer is formed on the surface of the silicon single-crystal substrate with the carbon ion injected layer formed thereon. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an epitaxial wafer in which an epitaxial layer is formed on a silicon single crystal substrate and a manufacturing method thereof.

  Usually, as a silicon substrate for manufacturing a semiconductor device, a silicon substrate in which a substrate is cut out from a silicon single crystal rod grown by the Czochralski method (CZ method) and the surface is polished into a mirror surface is used. However, in many cases, a silicon single crystal grown by the CZ method has octahedral void defects called COP formed by gathering silicon atomic vacancies in the crystal, and this is the main cause of oxide film breakdown voltage degradation of the silicon substrate. Cause.

  Further, a silicon substrate manufactured by the CZ method contains supersaturated interstitial oxygen and a large number of oxygen precipitation nuclei formed during cooling after pulling up the crystal. When a semiconductor device is manufactured using this supersaturated interstitial oxygen and a silicon substrate containing a large number of oxygen precipitation nuclei, interstitial oxygen precipitates in the oxygen precipitation nuclei during the heat treatment in the device manufacturing process, and the silicon substrate interior In addition, a large number of oxygen precipitates and minute defects resulting from this occur. When such oxygen precipitates and minute defects resulting from such oxygen precipitates are present in the bulk portion of the substrate, they become gettering sites (usually called the IG (Internal Gettering) effect) and are suitable for device manufacturing. However, it is known that when it exists in a device manufacturing region near the substrate surface, the operation of the semiconductor device is hindered.

  In recent years, as a countermeasure against the above COP defects, in order to make a device fabrication region near the surface of a silicon substrate defect-free, a CZ silicon mirror substrate was used as a base silicon substrate, and a silicon single crystal was epitaxially grown thereon by a CVD method. The demand for epitaxial wafers is increasing.

  However, the epitaxial wafer has a problem that its IG capability is low as compared with the silicon mirror substrate. That is, in the epitaxial wafer, the growth process of the epitaxial layer is at a high temperature of about 1050 ° C. to 1150 ° C., and the rate of temperature increase is large at this time. Decrease or disappear, and vacancy due to Si implantation during the growth process of the epitaxial layer disappears, so that it becomes difficult to form precipitates in the underlying silicon substrate even by the subsequent heat treatment, compared with a normal mirror substrate IG ability is reduced.

  Conventionally, as a manufacturing method for solving this problem and realizing an epitaxial wafer with high IG capability, an oxygen precipitation nucleus is grown by annealing a silicon wafer as a base at 700 ° C. to 1000 ° C. before the epitaxial layer growth step. A method of adding nitrogen to the underlying CZ silicon crystal (see, for example, Patent Document 2), a method of adding carbon to the underlying CZ silicon crystal (see, for example, Patent Document 3), A method of adding nitrogen and carbon to the CZ silicon crystal (see, for example, Patent Document 4), a method of combining nitrogen addition and pre-annealing (for example, see Patent Document 5), a method of combining carbon addition and pre-annealing (see, for example, Patent Document 6) ) Add nitrogen or carbon or both to the underlying CZ silicon and then boron ion implantation Such as the Hare method (for example, see Patent Document 7) has been devised.

  However, in the epitaxial wafer manufactured by the manufacturing method described above, the proximity gettering in the vicinity of the epitaxial layer is weak, the desired gettering ability cannot be obtained, or the added nitrogen causes a plate-like defect and the epitaxial layer There was a problem that epi defects occurred.

JP 11-354525 A JP-A-11-189493 Japanese Patent Laid-Open No. 10-50715 Japanese Patent Laid-Open No. 2000-272995 JP 2000-44389 A Japanese Patent Laid-Open No. 11-204534 Japanese Patent Laid-Open No. 2003-100760

  An object of the present invention is to provide an epitaxial wafer in which no epitaxial defects are formed in the epitaxial layer and which has a strong gettering capability in the vicinity of the lower portion of the epitaxial layer, and a method for manufacturing the same.

  In order to solve the above problems, in the present invention, an epitaxial wafer in which an epitaxial layer is formed on a silicon single crystal substrate, wherein the silicon single crystal substrate is doped with carbon during silicon single crystal growth, and Carbon ions are implanted from the surface to form a carbon ion implanted layer, and the epitaxial layer is formed on the surface of the silicon single crystal substrate on which the carbon ion implanted layer is formed. An epitaxial wafer is provided (claim 1).

  Thus, in the epitaxial wafer of the present invention, a complex is formed in the carbon ion implanted layer by implanting carbon ions into the substrate doped with carbon during single crystal growth, and the complex is being grown during epi growth. The interstitial silicon to be implanted can be captured and the interstitial silicon and the oxygen precipitation nuclei can be prevented from being combined. For this reason, oxygen precipitation nuclei existing in the bulk can be secured even after the epitaxial layer is formed, whereby the oxygen precipitation inherent in the substrate occurs during the heat treatment, and BMD can be easily formed. It is possible to obtain an epitaxial wafer having a high gettering ability in which no epitaxial defects are formed in the epitaxial layer.

Moreover, it is preferable that the carbon concentration doped at the time of single crystal growth of the silicon single crystal substrate is 0.1 ppma or more.
By setting the carbon concentration of the silicon single crystal substrate to 0.1 ppma or more, oxygen precipitation in the substrate is more likely to occur during the heat treatment, so that an epitaxial wafer with high gettering ability can be obtained.

The oxygen concentration of the silicon single crystal substrate is preferably 14 ppma (JEIDA) or more.
By setting the oxygen concentration of the silicon single crystal substrate to 14 ppma (JEIDA) or higher, the oxygen to be precipitated is sufficiently contained in the bulk substrate in advance, so that sufficient oxygen precipitation can be generated during the heat treatment. The gettering ability can be made stronger.

The silicon single crystal substrate preferably has a dose of implanted carbon ions of 1 × 10 ¹¹ to 1 × 10 ¹⁵ ions / cm ² (Claim 4).
When the dose amount is in the range of 1 × 10 ¹¹ to 1 × 10 ¹⁵ ions / cm ² , the proximity gettering ability is high and there is no epi defect, and the ion dose time is shortened. be able to.

Moreover, it is preferable that the BMD density in the region from the lower part of the carbon ion implanted layer to 5 μm is 1 × 10 ⁸ pieces / cm ³ or more.
As described above, if the BMD density formed in the wafer when the oxygen precipitation heat treatment is performed is 1 × 10 ⁸ pieces / cm ³ or more, the gettering ability with respect to the impurity metal is surely high near the epitaxial layer. It becomes an epitaxial wafer provided with a ring site.

Further, it is preferable that the carbon ion implanted layer is formed with a carbon composite (claim 6).
As described above, since the carbon composite (hereinafter sometimes abbreviated as C composite) is formed in the carbon ion implanted layer, the interstitial silicon to be implanted is captured in the composite when the epitaxial layer is formed. Therefore, the oxygen precipitation nuclei existing in the bulk wafer do not disappear due to bonding with interstitial silicon, and the epitaxial wafer having a high gettering ability is maintained by maintaining the BMD formation degree in the bulk at the original level of the substrate. It can be.

  Further, in the present invention, in the epitaxial wafer manufacturing method, carbon is doped by Czochralski method to grow a silicon single crystal rod, the silicon single crystal rod is sliced and processed into a silicon single crystal substrate, Provided is a method for manufacturing an epitaxial wafer, wherein carbon ions are implanted from the surface of a silicon single crystal substrate to form a carbon ion implanted layer, and then an epitaxial layer is formed on the surface subjected to the carbon ion implantation. (Claim 7).

  As described above, carbon ions are implanted into a silicon single crystal substrate doped with carbon during the growth of the single crystal to form a carbon ion implanted layer, and an epitaxial layer is formed on the surface of the ion implanted substrate. It is possible to form a gettering site in the vicinity of the lower portion of the epitaxial layer, and thus an epitaxial wafer having a strong gettering ability can be manufactured.

Moreover, it is preferable that the carbon concentration doped into the silicon single crystal at the time of growth is set to 0.1 ppma or more by the Czochralski method.
By growing the single crystal so that the carbon concentration in the silicon single crystal substrate is in the above range, the amount of oxygen precipitated during the heat treatment can be increased, thereby enhancing the gettering ability of metal impurities. Can do.

In addition, it is preferable that the oxygen concentration be 14 ppma (JEIDA) or higher when a silicon single crystal is grown by the Czochralski method.
By growing the single crystal so that the oxygen concentration in the silicon single crystal substrate is within the above range, the oxygen to be precipitated is sufficiently contained in the substrate in advance, so that oxygen precipitation is more likely to occur during the heat treatment. And the gettering ability can be made stronger.

Moreover, it is preferable that the dose amount of carbon ions at the time of carbon ion implantation be 1 × 10 ¹¹ to 1 × 10 ¹⁵ ions / cm ² .
By making the dose amount of carbon ions within the above range, it is possible to suppress the occurrence of epi defects in the epitaxial layer and to shorten the ion dose time, thereby increasing productivity.

When the dose of carbon ions is 1 × 10 ¹³ ions / cm ² or more, it is preferable to perform a crystallinity recovery heat treatment with a rapid heating / rapid cooling device or a resistance heating furnace after ion implantation. .
When the dose amount of carbon ions is 1 × 10 ¹³ ions / cm ² or more, by performing the crystallinity recovery heat treatment, the surface has crystallinity on the surface on which the epitaxial layer is formed in addition to having a strong gettering ability. Since it is recovered, an epitaxial wafer in which no epitaxial defect is formed in the epitaxial layer can be produced.

When the dose of carbon ions is less than 1 × 10 ¹³ ions / cm ^2, it is preferable not to perform the crystallinity recovery heat treatment after the ion implantation.
When the dose of carbon ions is less than 1 × 10 ¹³ ions / cm ² , the disorder of crystallinity is sufficiently small, so that an epitaxial wafer is produced in which no epitaxial defects are formed in the epitaxial layer without performing a recovery heat treatment. be able to.

Further, the BMD size, BMD density and DZ width formed under the carbon ion implantation layer in the epitaxial wafer depend on the carbon doping amount at the time of growing the single crystal, the carbon ion dose amount, and the crystallinity recovery heat treatment conditions. It is preferable to control (claim 13).
By controlling the BMD size, BMD density, and DZ width of the epitaxial wafer after the oxygen precipitation heat treatment according to the carbon doping amount, carbon ion dose amount, and crystallinity recovery heat treatment conditions during single crystal growth, the lower part of the carbon ion implanted layer The gettering ability of the gettering site formed in the step can be changed as appropriate, and the degree of freedom in designing the epitaxial wafer can be increased.

Moreover, when performing carbon ion implantation, it is preferable to form a carbon composite in the carbon ion implanted layer.
Thus, by forming a C complex in the carbon ion implanted layer during carbon ion implantation, interstitial silicon implanted in forming the epitaxial layer can be captured by the complex, and the bulk wafer It is possible to prevent the oxygen precipitation nuclei existing therein from bonding and disappearing with interstitial silicon, so that it is possible to produce an epitaxial wafer with high gettering ability by maintaining the BMD formation in the bulk in its original state. it can.

Moreover, it is preferable to form a solid-state image sensor in the epitaxial layer of the epitaxial wafer of the present invention.
As described above, since the epitaxial wafer of the present invention has high gettering capability and almost no epitaxial defects are formed in the epitaxial layer, a good solid-state imaging device is manufactured with a high yield when a solid-state imaging element is formed. be able to.

  As described above, the epitaxial wafer of the present invention has an epitaxial layer formed on the surface subjected to carbon ion implantation using a substrate doped with carbon during single crystal growth and further implanted with carbon ions. Is. As a result, a C complex is formed in the carbon ion implanted layer, and the interstitial silicon implanted during the epi growth is easily captured by the complex, thereby preventing the interstitial silicon from entering the bulk. Can do. For this reason, oxygen precipitation nuclei existing in the bulk can be secured even after the epitaxial layer is formed. As a result, oxygen precipitation inherent in the substrate occurs during heat treatment, and BMD can be easily formed. An epitaxial wafer having high gettering capability and no epitaxial defects formed in the epitaxial layer can be obtained.

Hereinafter, the present invention will be described more specifically.
As described above, the development of an epitaxial wafer and a method for manufacturing the same that have no epitaxial defects in the epitaxial layer and have strong gettering ability near the lower portion of the epitaxial layer has been awaited.

  Therefore, the present inventors added a single crystal with an element that does not form a crystal defect on the substrate surface even when doped into a silicon single crystal substrate, and forms a strong gettering layer by ion implantation. In addition, intensive studies were conducted to determine whether defects could occur on the substrate surface.

  As a result, the inventors focused on carbon, implanted carbon ions into a silicon single crystal substrate doped with carbon during the growth of the single crystal to form a carbon ion implanted layer, and epitaxially formed the surface on which the ions were implanted. By forming the layer, it was found that an epitaxial wafer having a gettering ability in the vicinity of the epitaxial layer and having no epitaxial defect was obtained, and the present invention was completed.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.
In the epitaxial wafer of the present invention, a carbon ion implantation layer is formed by implanting carbon ions into a silicon single crystal substrate doped with carbon during the growth of the silicon single crystal, and the epitaxial layer is formed on the surface where the ion implantation layer is performed. Is formed.

  FIG. 1 shows an example of the epitaxial wafer of the present invention. For comparison, an epitaxial wafer in the prior art is also shown in FIG. The epitaxial wafer of the present invention will be described in detail with reference to FIG.

Conventionally, as shown in FIG. 5A, when an epitaxial layer 23 is formed on a silicon single crystal substrate 21 doped with carbon (C _s ) during single crystal growth, it is implanted during epitaxial layer growth. Since the interstitial silicon (Si _I ) is bonded to the small-sized oxygen precipitation nuclei (V) existing in the substrate bulk, the oxygen precipitation nuclei disappear, and BMD is hardly formed during the heat treatment inside the substrate. As a result, the wafer gettering ability is weakened. As shown in FIG. 5B, this is an epitaxial wafer in which an epitaxial layer 23 is formed on a surface where carbon ions (C _i ) are implanted into a silicon single crystal substrate 24 to form a carbon ion implanted layer 22. The same can be said about.

In contrast, the epitaxial wafer of the present invention is formed by implanting carbon ions (C _i ) into a silicon single crystal substrate 11 doped with carbon (C _s ) during single crystal growth. A composite made of (C _i ), (C _s ), (O _i ), (Si _I ) or the like is formed on the layer 12. When the epitaxial layer 13 is formed, the composite described above is formed. Interstitial silicon (Si _I ) implanted during epi-growth is easily trapped and can prevent interstitial silicon from penetrating into the bulk of the substrate and bonding with oxygen precipitation nuclei. Is. Therefore, the oxygen precipitation nuclei (V) existing in the bulk can be secured even after the epitaxial layer is formed, whereby the oxygen precipitation inherent in the substrate occurs during the heat treatment and the BMD can be easily formed. An epitaxial wafer having high gettering ability in the vicinity of the layer can be obtained.

Here, C _i (Si _I ) _n , C _i C _s (Si _I ) _n , C _i O _i (Si _I ) can be cited as C composites formed in the carbon ion implanted layer by carbon ion implantation. _n, it is a _C i _{C s} and the like. In addition to the C complex, related complexes formed simultaneously include H-Va-N, H-O-Si, which are structures involving hydrogen (H), nitrogen (N), and vacancies (Va). , Va-N and the like.

Here, the carbon concentration doped during the single crystal growth of the silicon single crystal substrate can be 0.1 ppma or more.
When the carbon concentration in the silicon substrate is within the above range, oxygen precipitation in the substrate can be more easily caused during the heat treatment in the device manufacturing process. Therefore, the BMD density can be increased and an epitaxial wafer with high gettering ability can be obtained.
Here, the upper limit of the carbon concentration is not particularly provided, but it is desirable to set the upper limit of 5 ppma so as not to prevent the single crystallization of the silicon single crystal.

The oxygen concentration in the silicon single crystal substrate can be 14 ppma (JEIDA) or more.
By preliminarily containing 14 ppma or more of oxygen to be precipitated in the bulk substrate, oxygen precipitation can easily occur during the heat treatment in the device manufacturing process, and the gettering ability can be further enhanced.
Here, the upper limit of the oxygen concentration is not particularly provided, but is preferably 20 ppma or less.

Further, the dose amount of carbon ions implanted into the silicon single crystal substrate can be set to 1 × 10 ¹¹ to 1 × 10 ¹⁵ ions / cm ² .
By setting the dose amount of carbon ions within the range of the low dose amount as described above, it is possible to suppress the deterioration of crystallinity and to suppress the occurrence of epi defects in the epitaxial layer. In addition, since the ion dose time can be shortened, productivity can be improved and the manufacturing process can be simplified. Therefore, the manufacturing cost of the epitaxial wafer can be reduced.
In the present invention, even with such a low dose, sufficient carbon doping and oxygen concentration are ensured in the wafer as described above, and the disappearance of precipitation nuclei in the bulk portion in the epitaxial process is also suppressed. So it has a strong gettering ability.

In the present invention, the BMD density in the region from the bottom of the carbon ion implantation layer to 5 μm can be 1 × 10 ⁸ pieces / cm ³ or more.
If the BMD density formed in the wafer during the heat treatment (oxygen precipitation heat treatment) in the device process is 1 × 10 ⁸ pieces / cm ³ or more, the gettering ability for the impurity metal is high near the epitaxial layer. The epitaxial wafer has ring sites.

  The epitaxial wafer of the present invention can be produced by the following steps, and an example thereof is shown below, but the method for producing the epitaxial wafer of the present invention is not limited to the following.

  In the present invention, a silicon single crystal rod doped with carbon is grown by the Czochralski method. In order to dope carbon into the single crystal rod, a general method may be used. When the seed crystal was brought into contact with the melt of the polycrystalline silicon raw material contained in the quartz crucible, and the silicon single crystal rod having a desired diameter was grown by rotating it slowly, the atmosphere gas contained carbon. A high-purity carbon powder can be added to the raw material melt as a dopant, and a carbon lump (block-like carbon) can be previously placed in a quartz crucible. Furthermore, carbon fibers and / or silicon carbide fibers can be used as the dopant.

At this time, the amount of carbon dope in the single crystal rod can be controlled by adjusting the carbon gas concentration or introduction time, and the amount of added carbon powder.
The carbon concentration doped during the growth of the single crystal rod can be set to 0.1 ppma or more. This makes it possible to sufficiently increase the density of oxygen precipitates that precipitate during the heat treatment during the device manufacturing process.

Further, the oxygen concentration in the single crystal rod can be made 14 ppma (JEIDA) or more.
A general method can also be used as a method for controlling the oxygen concentration. For example, when pulling up the single crystal rod, the rotational speed of the crucible holding the raw material melt can be changed, or a magnetic field can be applied to the raw material melt. By preliminarily containing oxygen in the above range in the silicon single crystal substrate, oxygen precipitation is more likely to occur during the heat treatment in the device manufacturing process, so that the silicon single crystal substrate can have high gettering ability. Therefore, an epitaxial wafer having a high gettering ability can be manufactured.

  Next, after the grown silicon single crystal rod is sliced by a cutting device such as an inner peripheral slicer or a wire saw, a silicon single crystal substrate is manufactured through processes such as chamfering, lapping, etching, and polishing.

Thereafter, carbon ion implantation is performed on one main surface of the silicon single crystal substrate using a high current ion implanter to form a carbon ion implanted layer on the silicon single crystal substrate. The dose of carbon ions is not particularly limited, but can be 1 × 10 ¹¹ to 1 × 10 ¹⁵ atoms / cm ² which is a relatively low dose.
By setting the dose in the above range, by performing heat treatment to recover the crystallinity of the silicon single crystal substrate disturbed by the carbon ion implantation, while suppressing the crystallinity to a sufficient range, Gettering capability can be added to the substrate. Therefore, the occurrence of epi defects can be reliably suppressed in the subsequent epitaxial process.
Further, if the dose is in the above range, the ion dose time can be shortened, so that productivity can be improved.

When the carbon ion implantation amount is 1 × 10 ¹³ ions / cm ² or more, heat treatment is performed to recover the crystallinity of the silicon wafer disturbed by the carbon ion implantation. The heat treatment can be performed using a rapid heating / rapid cooling (RTA) apparatus. As heat treatment conditions, the atmosphere is preferably an argon atmosphere. The processing temperature can be 1100 ° C. to the silicon melting point temperature. The processing time can be 10 to 60 seconds. Although the number of heat treatments is sufficient, there is no particular limitation on the number of heat treatments. When emphasizing recovery of crystallinity, it can be repeated 2 to 3 times.
When the carbon ion implantation amount is a low dose amount of less than 1 × 10 ¹³ ions / cm ² , disorder of crystallinity of the substrate on the carbon ion implantation surface is such that epi defects are generated when the epitaxial layer is formed. Therefore, it is not necessary to perform the crystallinity recovery heat treatment. In this case, it becomes possible to simplify a further process, and an inexpensive and high quality epitaxial wafer can be obtained.

Thereafter, an epitaxial layer is formed on the surface implanted with carbon ions. General conditions can be used to form the epitaxial layer.
For example, a source gas such as SiHCl ₃ is introduced into the chamber using H ₂ as a carrier gas, and the carbon-doped and carbon ion implanted layer disposed on the susceptor is provided at 1050 to 1250 ° C. on the RTA-treated wafer. It can be epitaxially grown by the CVD method.

Here, the BMD size and BMD density formed under the carbon ion implantation layer in the epitaxial wafer by adjusting the carbon doping amount during carbon single crystal growth, the carbon ion dose amount, or the crystalline recovery heat treatment conditions. And the DZ width can be controlled. For example, when the crystalline recovery heat treatment is performed by a rapid heating / cooling apparatus, the BMD size decreases and the BMD density increases as the carbon dose increases. Further, when the amount of carbon dope and the amount of carbon ion at the time of growth are the same, if the recovery heat treatment is performed in a resistance heating furnace, the BMD size can be reduced as compared with the case where the heat treatment is performed with a rapid heating / rapid cooling device.
Thus, if it is possible to control the formation of BMD, the gettering capability of the gettering site formed under the carbon ion implantation layer can be changed as appropriate according to the purpose. The degree of freedom in design can be increased.

  Moreover, a solid-state image sensor can be formed on the epitaxial layer of the epitaxial wafer of the present invention. As described above, since the epitaxial wafer of the present invention has high gettering capability and almost no epitaxial defects are formed in the epitaxial layer, a good solid-state imaging device is manufactured with high yield when a solid-state imaging element is formed. be able to.

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
First, an N-type silicon single crystal rod having a diameter of 200 mm was grown by the Czochralski method. At this time, carbon was doped into the single crystal by previously putting carbon powder in a quartz crucible. The carbon concentration was controlled so that the carbon doping amount was 1.0 ppma. Moreover, the single crystal rod was grown so that the oxygen concentration was 16.8 ppma. The grown silicon single crystal rod was 0.5 Ωcm.
Thereafter, the silicon single crystal rod was sliced to produce a silicon single crystal substrate.
Carbon was ion-implanted into the produced silicon single crystal substrate using a high-current ion implanter under the condition of a dose amount of 1 × 10 ¹² atoms / cm ² to form a carbon ion implanted layer.
Thereafter, an epitaxial layer was formed on the wafer surface on which the carbon injection layer was formed under the processing conditions of 1130 ° C., and an epitaxial wafer was produced. The thickness of the formed epitaxial layer is about 6 μm.

The characteristics of the produced epitaxial wafer were evaluated as follows.
Epi defects on the surface of the epitaxial wafer were observed using a particle counter.
Moreover, oxygen precipitation heat processing was performed and BMD size and BMD density were evaluated. Oxygen precipitation heat treatment conditions were 800 ° C. · 4 hours and 1000 ° C. · 16 hours. Thereafter, the oxygen precipitation amount of the wafer before and after the oxygen precipitation heat treatment was evaluated by FTIR. The result is shown in FIG. Furthermore, Angle Polish evaluation was performed on the surface of the epitaxial wafer after the oxygen precipitation heat treatment, and the cross sections of the epitaxial layer, the carbon implanted layer, and the lower portion of the carbon implanted layer were observed to evaluate the BMD size and the BMD density. FIG. 3 shows a comparison of BMD sizes in each example and comparative example. Moreover, the BMD density in each Example and a comparative example is shown in FIG.

(Comparative Example 1)
In Example 1, an epitaxial wafer was produced under the same conditions as in Example 1 except that carbon was not doped when the single crystal was grown. The produced wafer was evaluated in the same manner as in Example 1.

(Comparative Example 2)
In Example 1, an epitaxial wafer was produced under the same conditions as in Example 1 except that carbon ion implantation was not performed on the silicon single crystal substrate. And evaluation similar to Example 1 was performed.

The epitaxial wafer of Example 1 has an oxygen precipitation amount (ΔOi) of about 5 times that of the wafers of Comparative Examples 1 and 2, the BMD size is large, and the BMD density can sufficiently secure the gettering ability. Was observed to form. On the other hand, the epitaxial wafers of Comparative Examples 1 and 2 have a small oxygen precipitation amount, a small BMD, a small size, and a low density, and their gettering ability is not satisfactory compared to the wafer of Example 1. I understood.
In the epitaxial wafers of Example 1 and Comparative Example 2, no epitaxial defects were formed in the epitaxial layer, but it was confirmed that the epitaxial wafers of Comparative Example 1 were formed with epitaxial defects.

(Examples 2 and 3)
In Example 1, the epitaxial wafer was grown under the same conditions as in Example 1 except that the carbon concentration doped into the single crystal substrate during growth was 1.5 ppma and 2.0 ppma (Examples 2 and 3 respectively). Produced. And evaluation similar to Example 1 was performed.

  As a result, it was found that the epitaxial wafer of Example 2 had a slightly larger amount of oxygen precipitation, a smaller BMD size, and a higher density than the wafer of Example 1. Compared with Example 2, the wafer of Example 3 had a slightly larger amount of precipitated oxygen and a smaller BMD size, but was found to have a higher density. No epitaxial defects were formed in the epitaxial layers of the epitaxial wafers of Examples 2 and 3.

Example 4
In Example 1, an epitaxial wafer was produced under the same conditions as in Example 1 except that the carbon ion dose to be implanted into the silicon single crystal substrate was 1 × 10 ¹³ ions / cm ² . And evaluation similar to Example 1 was performed.

  As a result, the epitaxial wafer of Example 4 had a smaller BMD size and a slightly higher density than the wafer of Example 1, but the amount of precipitated oxygen was almost the same. It was also found that no epi defects were formed on the wafer of Example 4.

(Examples 5 and 6)
In Example 1, after performing the dose amount of carbon ions at 1 × 10 ¹⁴ ions / cm ² , the crystalline heat recovery treatment was performed using a rapid heating / rapid cooling device, the temperature was 1175 ° C., and the treatment time was 30 Second, an epitaxial wafer was produced under the same conditions as in Example 1 except that an Ar atmosphere containing 1% NH ₃ was added (Example 5), and then an epitaxial layer was formed. Further, the crystallinity recovery heat treatment was performed using a resistance heating apparatus under conditions of a temperature of 1100 ° C., a treatment time of 10 min, and an atmosphere of a mixed gas of oxygen + nitrogen (Example 6). And evaluation similar to Example 1 was performed.

  As a result, the epitaxial wafer of Example 5 was almost the same in size as the wafer of Example 1, and the density was about twice as high, but the amount of precipitated oxygen was slightly higher. It was. Compared with the wafer of Example 5, the epitaxial wafer of Example 6 had a smaller BMD size and a density of about twice that of the wafer, but the amount of precipitated oxygen was almost the same. It was also found that no epitaxial defects were formed on the wafers of Examples 5 and 6. From this, it was found that the BMD size and BMD density can be changed by changing the conditions of the crystalline recovery heat treatment.

(Example 7)
In Example 5, an epitaxial wafer was produced under the same conditions as in Example 5 except that the dose of carbon ions was 1 × 10 ¹⁵ ions / cm ² . And evaluation similar to Example 1 was performed.

  As a result, the epitaxial wafer of Example 7 had a slightly larger amount of oxygen precipitation and a smaller BMD size than the wafer of Example 5. Although the density was about twice as high, the amount of precipitated oxygen was almost the same. The wafer of Example 7 was also found to have no epitaxial defects formed in the epitaxial layer, as in the other examples.

Here, the results of Examples 1 to 7 are summarized.
In Examples 1, 2, and 3, an epitaxial wafer was produced under the same conditions except that the carbon doping amount during silicon single crystal growth was changed, but as the carbon doping amount increased, the oxygen precipitation amount increased, The BMD density also increased, but the BMD size decreased.
In Examples 1, 4, 5, and 7, epitaxial wafers were produced under the same conditions except that the carbon ion dose was changed. However, as the carbon ion dose increased, the oxygen precipitation amount increased, and the size of the BMD increased. It became clear that the BMD density was getting higher.
In Examples 5 and 6, epitaxial wafers were produced under the same conditions except that the crystallinity recovery heat treatment conditions after carbon ion implantation were changed, but the amount of precipitated oxygen was almost the same, but the size and density of BMD were It was different.
From the above results, the BMD size and BMD density formed under the carbon ion implanted layer in the epitaxial wafer of the present invention depend on the carbon doping amount, carbon ion dose amount, and crystallinity recovery heat treatment conditions during single crystal growth. It turns out that it can be controlled. And since BMD size and density were controllable, it turned out that DZ width | variety can also be controlled.

  As described above, the epitaxial wafer of the present invention is doped with carbon at the time of single crystal growth, processed into a silicon single crystal substrate, then carbon ion implantation is performed, and an epitaxial wafer is formed on the surface of the ion-implanted surface. As a result, an epitaxial wafer having a strong gettering capability in the vicinity of the epitaxial layer and having no epitaxial defects can be obtained.

  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 sectional drawing which shows an example of the epitaxial wafer of this invention. It is the figure which compared the amount of oxygen precipitation in each Example and a comparative example. It is a figure of the comparison of the BMD size of the wafer bulk part after the oxygen precipitation heat processing in each Example. It is a figure of the BMD density of the wafer bulk part after the oxygen precipitation heat processing in each Example. It is sectional drawing which shows an example of the epitaxial wafer of a prior art.

Explanation of symbols

  11, 21... Silicon single crystal substrate doped with carbon during single crystal growth, 12, 22... Carbon ion implanted layer, 13, 23... Epitaxial layer, 24.

Claims (15)

  An epitaxial wafer in which an epitaxial layer is formed on a silicon single crystal substrate, wherein the silicon single crystal substrate is doped with carbon during the growth of the silicon single crystal, and carbon ions are implanted from the surface thereof. An epitaxial wafer in which a layer is formed and the epitaxial layer is formed on a surface of the silicon single crystal substrate on which the carbon ion implantation layer is formed.   2. The epitaxial wafer according to claim 1, wherein a concentration of carbon doped at the time of growing a single crystal of the silicon single crystal substrate is 0.1 ppma or more.   The epitaxial wafer according to claim 1, wherein the silicon single crystal substrate has an oxygen concentration of 14 ppma (JEIDA) or more. 4. The silicon single crystal substrate according to claim 1, wherein a dose amount of the implanted carbon ions is 1 * 10 < ¹¹ > to 1 * 10 < ¹⁵ > ions / cm < ² >. The epitaxial wafer described. 5. The epitaxial wafer according to claim 1, wherein a BMD density in a region from a lower portion of the carbon ion implantation layer to 5 μm is 1 × 10 ⁸ pieces / cm ³ or more. 6. .   The epitaxial wafer according to any one of claims 1 to 5, wherein the carbon ion implantation layer is formed with a carbon composite.   In the epitaxial wafer manufacturing method, carbon is doped by the Czochralski method to grow a silicon single crystal rod, and after the silicon single crystal rod is sliced and processed into a silicon single crystal substrate, the surface of the silicon single crystal substrate A method for producing an epitaxial wafer, comprising: forming a carbon ion implanted layer by implanting carbon ions from the substrate, and then forming an epitaxial layer on the surface subjected to the carbon ion implantation.   8. The method for producing an epitaxial wafer according to claim 7, wherein the carbon concentration doped into the silicon single crystal at the time of growth is 0.1 ppma or more by the Czochralski method.   9. The method for producing an epitaxial wafer according to claim 7, wherein an oxygen concentration is set to 14 ppma (JEIDA) or more when a silicon single crystal is grown by the Czochralski method. 10. 10. The dose according to claim 7, wherein a dose amount of carbon ions at the time of performing the carbon ion implantation is 1 × 10 ¹¹ to 1 × 10 ¹⁵ ions / cm ² . Epitaxial wafer manufacturing method. The crystallinity recovery heat treatment is performed by a rapid heating / rapid cooling apparatus or a resistance heating furnace after ion implantation when the dose amount of the carbon ions is set to 1 × 10 ¹³ ions / cm ² or more. The manufacturing method of the epitaxial wafer of description. 11. The method of manufacturing an epitaxial wafer according to claim 10, wherein when the dose amount of the carbon ions is less than 1 × 10 ¹³ ions / cm ² , the crystalline recovery heat treatment is not performed after the ion implantation.   The BMD size, BMD density and DZ width formed under the carbon ion implantation layer in the epitaxial wafer are controlled by the carbon doping amount, the carbon ion dose amount, and the crystallinity recovery heat treatment conditions during the single crystal growth. The method for producing an epitaxial wafer according to any one of claims 7 to 12, wherein:   The method for producing an epitaxial wafer according to any one of claims 7 to 13, wherein a carbon composite is formed in the carbon ion implanted layer when the carbon ion implantation is performed.   A method for manufacturing a solid-state imaging device, wherein a solid-state imaging device is formed on the epitaxial layer of the epitaxial wafer described in any one of claims 1 to 6.

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