JP6504082B2 - Semiconductor epitaxial wafer, method of manufacturing the same, and method of manufacturing solid-state imaging device - Google Patents

Description

  The present invention relates to a semiconductor epitaxial wafer, a method of manufacturing the same, and a method of manufacturing a solid-state imaging device.

  A semiconductor epitaxial wafer in which an epitaxial layer is formed on a semiconductor wafer includes various types such as MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), DRAM (Dynamic Random Access Memory) memory, power transistor, and backside illuminated solid-state imaging device. It is used as a device substrate for producing semiconductor devices.

  Here, metal contamination is mentioned as a factor which degrades the characteristic of a semiconductor device. For example, in the backside illuminated solid-state imaging device, the metal mixed in the semiconductor epitaxial wafer as the substrate of this device causes the dark current of the solid-state imaging device to increase and causes a defect called a white flaw defect. The back-illuminated solid-state imaging device can receive external light directly into the sensor and can capture clearer images and moving images even in a dark place by arranging the wiring layer and the like in the lower layer than the sensor unit. In recent years, it is widely used in mobile phones such as digital video cameras and smartphones. Therefore, it is desirable to reduce white flaw defects as much as possible.

  The metal contamination of the wafer mainly occurs in the manufacturing process of the semiconductor epitaxial wafer and the manufacturing process (device manufacturing process) of the solid-state imaging device. The metal contamination in the former semiconductor epitaxial wafer manufacturing process is caused by heavy metal particles from the components of the epitaxial growth furnace or the pipe material corrodes metal because chlorine-based gas is used as the furnace gas at the time of epitaxial growth. The thing by the heavy metal particle which generate | occur | produces etc. is considered. In recent years, these metal contaminations have been improved to some extent, for example, by replacing the constituent material of the epitaxial growth furnace with a material having excellent corrosion resistance, but this is not sufficient. On the other hand, in the process of manufacturing the latter solid-state imaging device, heavy metal contamination of the semiconductor substrate may be concerned during the processes such as ion implantation, diffusion, and oxidation heat treatment.

  In order to suppress such heavy metal contamination, there is a technique of forming gettering sites for capturing heavy metals in a semiconductor wafer. As one of the methods, a method is known in which ions are implanted into a semiconductor wafer and then an epitaxial layer is formed. In this method, the ion implantation region functions as a gettering site.

  In Patent Document 1, the applicant of the present application irradiates cluster ions on the surface of a semiconductor wafer to form a modified layer in which component elements of the cluster ions are solid-solved on the surface of the semiconductor wafer; And a second step of forming an epitaxial layer on the modified layer of the semiconductor wafer.

International Publication No. 2012/157162

  Patent Document 1 shows that a modified layer formed by irradiating cluster ions can obtain higher gettering capability than an ion-implanted region obtained by implanting monomer ions (single ions). Here, in order to further increase the gettering ability of the modified layer in Patent Document 1, for example, it is effective to increase the dose amount of cluster ions. However, if the dose amount is too high, a large number of epitaxial defects will occur in the epitaxial layer to be formed later in the modified layer. Thus, there is a limit to the improvement of the gettering ability by the increase of the dose.

  Then, in view of the above-mentioned subject, an object of the present invention is to provide a manufacturing method of a semiconductor epitaxial wafer which has more superior gettering ability, and can control generating of an epitaxial fault.

  The present inventors diligently studied to solve the above problems. By the way, when manufacturing a semiconductor epitaxial wafer, especially an epitaxial silicon wafer, oxygen contained in a silicon wafer to be a base substrate is diffused into the epitaxial layer by heat treatment at the time of forming the epitaxial layer. The epitaxial layer having a relatively high concentration of oxygen may have adverse effects on the semiconductor device quality depending on the application. Therefore, in the prior art, it was considered that oxygen ion implantation into the base substrate was not preferable when producing a semiconductor epitaxial wafer. In addition, when a high concentration layer of oxygen is formed on the base substrate by oxygen ion implantation, oxygen precipitates which are crystal defects inside the silicon wafer due to heat treatment at the time of epitaxial layer formation (common name of silicon oxide precipitates) BMD: also referred to as “Bulk Micro Defect” may be formed, and in turn, there may be an occurrence of an epitaxial defect due to BMD on the surface of the epitaxial layer.

  Here, when the semiconductor wafer is irradiated with oxygen together with carbon and hydrogen in the form of cluster ions, a reformed layer in which carbon is solid-solved locally can be formed. According to the study of the present inventor, this modified layer can also trap oxygen, so it was considered that the influence on the epitaxial layer may be small. In addition, since oxygen atoms have a mass number larger than carbon atoms and an atomic radius also, it is considered that irradiation damage can be increased even if the carbon dose is small, and gettering ability can be increased. Furthermore, since the atomic weights of carbon and oxygen are relatively close, the implantation range of carbon when both are irradiated in the form of cluster ions becomes shallower than the implantation range of oxygen, and oxygen diffusion to the epitaxial layer can be suppressed. I also thought it was not. Therefore, the inventors have conceived of the irradiation of cluster ions containing carbon, hydrogen and oxygen as constituent elements, and higher gettering ability can be obtained even if conventional cluster ion irradiation and the dose amount of carbon are comparable. And, it has been found that the occurrence of epitaxial defects can be suppressed, and the present invention has been completed. That is, the gist configuration of the present invention is as follows.

(1) Irradiating cluster ions containing carbon, hydrogen and oxygen as constituent elements on the surface of the semiconductor wafer to form a modified layer in which the constituent elements of the cluster ions form a solid solution on the surface of the semiconductor wafer The first step;
A second step of forming an epitaxial layer on the modified layer of the semiconductor wafer after the first step, and a method of manufacturing a semiconductor epitaxial wafer.

(2) The method for producing a semiconductor epitaxial wafer according to (1), wherein the number of carbon atoms of the cluster ion is 16 or less, and the number of oxygen atom of the cluster ion is 16 or less.

(3) The above-mentioned (1) or (2), wherein the dose amount of carbon by the irradiation of the cluster ion is 1.0 × 10 ¹³ atoms / cm ² or more and 1.0 × 10 ¹⁷ atoms / cm ² or less Method of manufacturing semiconductor epitaxial wafer.

(4) The manufacturing method of the semiconductor epitaxial wafer in any one of said (1)-(3) whose said semiconductor wafer is a silicon wafer.

(5) A semiconductor wafer, a reformed layer formed on the surface portion of the semiconductor wafer, in which carbon, hydrogen and oxygen are solid-solved in the semiconductor wafer, and an epitaxial layer on the reformed layer ,
The carbon peak concentration of the carbon concentration profile in the depth direction of carbon in the modified layer is 1.0 × 10 ¹⁵ atoms / cm ³ or more and 1.0 × 10 ²⁰ atoms / cm ³ or less,
The hydrogen peak concentration of the hydrogen concentration profile in the depth direction of the hydrogen in the reforming layer is 1.0 × 10 ¹⁷ atoms / cm ³ or more,
A semiconductor epitaxial wafer characterized in that an oxygen peak concentration of the oxygen concentration profile in the depth direction of the oxygen in the modified layer is 5.0 × 10 ¹⁸ atoms / cm ³ or more.

(6) The semiconductor epitaxial wafer according to (5), wherein the oxygen peak concentration is 1.0 × 10 ¹⁹ atoms / cm ³ or more.

(7) The semiconductor epitaxial wafer according to (5) or (6), wherein at least one of the carbon concentration profile, the hydrogen concentration profile, and the oxygen concentration profile is a bimodal concentration profile.

(8) A first layer including a first black dot defect and a second layer including a second black dot defect are present in the modified layer,
The semiconductor epitaxial wafer according to (5) to (7), wherein the first layer is located closer to the epitaxial layer than the second layer in the depth direction.

(9) The density of the first black dot defect is 1.0 × 10 ¹⁶ / cm ³ or more and 1.0 × 10 ¹⁸ / cm ³ or less,
The semiconductor epitaxial wafer according to (8), wherein the density of the second black dot defect is 1.0 × 10 ¹⁴ pieces / cm ³ or more and 1.0 × 10 ¹⁶ pieces / cm ³ or less.

(10) In the modified layer, the first black dot-like defect is present at a depth of 30 nm or more and 150 nm or less in a depth direction from an interface between the semiconductor wafer and the epitaxial layer.
The semiconductor epitaxial wafer according to (8) or (9), wherein the second black dot-like defect is present at a depth of 60 nm or more and 150 nm or less in the depth direction from the interface.

(11) The semiconductor epitaxial wafer according to any one of (5) to (10), wherein the semiconductor wafer is a silicon wafer.

(12) The epitaxial of the semiconductor epitaxial wafer manufactured by the manufacturing method according to any one of (1) to (4) or the semiconductor epitaxial wafer according to any of (5) to (11) A method of manufacturing a solid-state imaging device, comprising forming a solid-state imaging device in a layer.

  According to the present invention, it is possible to provide a method of manufacturing a semiconductor epitaxial wafer having more excellent gettering capability and capable of suppressing the occurrence of epitaxial defects.

FIG. 7 is a schematic cross-sectional view illustrating the method of manufacturing the semiconductor epitaxial wafer 100 according to the embodiment of the present invention. FIG. 6 is a schematic cross-sectional view illustrating the method of manufacturing the semiconductor epitaxial wafer 100 according to the preferred embodiment of the present invention. In the reference experiment example 1, it is a graph which shows the concentration profile of carbon of the silicon wafer after irradiating cluster ion, hydrogen, and oxygen. It is a TEM cross-section photograph of the silicon wafer after irradiating cluster ion in reference experiment example 1, (A) It is a TEM cross-section photograph of reference example 1, (B) is a TEM cross-section photograph of reference example 2, C) is a TEM cross-sectional photograph of Reference Example 3. FIG. It is a graph which shows the concentration profile of carbon, hydrogen, and oxygen of the epitaxial silicon wafer concerning the example 1 of an invention. It is a graph which shows the concentration profile of oxygen of the epitaxial silicon wafer concerning the example 1 of an invention, and the comparative example 1. It is a LPD map which shows the epitaxial defect of the epitaxial wafer in Experimental example 1, (A) is a LPD map of the invention example 1, (B) is a LPD map of the comparative example 1. FIG. It is a TEM cross-section photograph of the epitaxial silicon wafer in Experimental example 1, (A) is a TEM cross-section photograph of the invention example 1, (B) is a TEM cross-section photograph of the comparative example 2. It is a TEM cross-sectional photograph of the invention example 1 acquired on conditions different from FIG. 7 (A).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In FIGS. 1 and 2, for convenience of explanation, the thicknesses of the modified layer 14, the amorphous layer 16, and the epitaxial layer 18 are exaggerated for the semiconductor wafer 10, unlike the ratio of the actual thickness.

(Method of manufacturing semiconductor epitaxial wafer)
In the method of manufacturing a semiconductor epitaxial wafer 100 according to an embodiment of the present invention, as shown in FIG. 1, the surface 10A of the semiconductor wafer 10 is irradiated with cluster ions 12 containing carbon, hydrogen and oxygen as constituent elements A first step (FIGS. 1A and 1B) of forming a modified layer 14 in which the constituent elements of the cluster ions 12 form a solid solution on the surface portion of the wafer 10 and the semiconductor wafer after the first step And a second step (FIG. 1C) of forming an epitaxial layer 18 on the ten modified layers 14. FIG. 1C is a schematic cross-sectional view of a semiconductor epitaxial wafer 100 obtained as a result of this manufacturing method. In addition, the epitaxial layer 18 is a device layer for manufacturing a semiconductor element such as a backside illuminated solid-state imaging element.

  The semiconductor wafer 10 may be, for example, a bulk single crystal wafer made of silicon, compound semiconductors (GaAs, GaN, SiC) and having no epitaxial layer on the surface. In the case of manufacturing a back-illuminated solid-state imaging device, a bulk single crystal silicon wafer is generally used. The semiconductor wafer 10 may be a single crystal silicon ingot grown by the Czochralski method (CZ method) or the floating zone melting method (FZ method) and sliced by a wire saw or the like. In addition, carbon and / or nitrogen may be added to the semiconductor wafer 10 in order to obtain higher gettering ability. Furthermore, a predetermined concentration of an arbitrary dopant may be added to the semiconductor wafer 10 to form a so-called n + -type or p + -type or n--type or p--type substrate.

  Further, as the semiconductor wafer 10, an epitaxial semiconductor wafer in which a semiconductor epitaxial layer is formed on the surface of a bulk semiconductor wafer may be used. For example, it is an epitaxial silicon wafer in which a silicon epitaxial layer is formed on the surface of a bulk single crystal silicon wafer. This silicon epitaxial layer can be formed by CVD under general conditions. The thickness of the epitaxial layer is preferably in the range of 0.1 to 20 μm, and more preferably in the range of 0.2 to 10 μm.

  Here, one of the characteristic steps of this embodiment is the first step shown in FIG. As used herein, “cluster ion” refers to an ion or ion that imparts a positive charge or a negative charge to a cluster formed by aggregating a plurality of atoms or molecules. A cluster is a massive group in which a plurality of (usually about 2 to 2000) atoms or molecules are bonded to one another.

  When cluster ions are irradiated to a silicon wafer which is a kind of semiconductor wafer, the cluster ions 12 instantaneously become high temperature of about 1350 to 1400 ° C. by the energy when the silicon ions are irradiated to the silicon wafer, and the silicon melts. Thereafter, the silicon is rapidly cooled, and the constituent elements of the cluster ions 12 form a solid solution near the surface in the silicon wafer. That is, the "reformed layer" in the present specification means a layer in which the constituent element of the ion to be irradiated is solid-solved at the interstitial position or substitution position of the crystal of the surface portion of the semiconductor wafer. The concentration profile of carbon in the depth direction of the silicon wafer by secondary ion mass spectrometry (SIMS) depends on the acceleration voltage and cluster size of cluster ions, but is sharper than that of monomer ions. The thickness of the locally present region (i.e., the modified layer) of the irradiated element is approximately 500 nm or less (e.g., about 50 to 400 nm). In addition, "the concentration profile of the depth direction of each element of carbon, hydrogen, and oxygen in this specification" means concentration distribution of hydrogen of the depth direction measured by SIMS.

  The elements irradiated in the form of cluster ions differ in behavior depending on the element species, but some thermal diffusion occurs in the process of forming the epitaxial layer 18 described later. When carbon is contained in the constituent element of the cluster ion, the concentration profile of carbon after the formation of the epitaxial layer 18 forms a broad diffusion region on both sides of the peak where the carbon element is present locally. However, the thickness of the modified layer (ie, the width of the peak) does not change significantly. As a result, the deposition region of carbon can be locally and highly concentrated. And this local precipitation area of carbon becomes a powerful gettering site. This is because a carbon atom at a lattice position has a smaller covalent bond radius compared to a silicon single crystal, so that a contraction field of the silicon crystal lattice is formed to attract impurities between the lattices. Further, since the modified layer 14 is formed in the vicinity of the surface of the silicon wafer, that is, immediately below the epitaxial layer 18, proximity gettering becomes possible. As described above, it is considered that high gettering ability can be obtained by solid solution of carbon in the modified layer.

  Cluster ions exist in various clusters depending on the binding mode, and can be generated by known methods, for example, as described in the following documents. As a method of generating a gas cluster beam, (1) JP-A-9-41138, (2) JP-A-4-354865, as a method of generating an ion beam, (1) Charged particle beam engineering: Junkawa Ishikawa: ISBN 978 -4-339-00734-3: Corona, (2) Electron and ion beam engineering: Institute of Electrical Engineers of Japan: ISBN 4-88686-217-9: Ohm, (3) Cluster Ion Beam Basics and Applications: ISBN 4-526-05765 -7: Nikkan Kogyo Shimbun. In general, a Nielsen type ion source or a Kauffmann type ion source is used to generate positive charge cluster ions, and a large current negative ion source using volume generation method is used to generate negative charge cluster ions. Be

  Here, constituent elements of the cluster ions 12 to be irradiated in the present embodiment are carbon, hydrogen and oxygen as described above. In the present embodiment, technical significance of using hydrogen and oxygen as constituent elements of the cluster ion 12 in addition to carbon will be described below.

The details of the experimental conditions in Reference Experimental Example 1 will be described later, but a TEM cross-sectional view of Reference Example 1 (dose of carbon: 1.0 × 10 ¹⁵ atoms / cm ² ) in which cluster ions are irradiated onto silicon wafers as CH ₃ O In (FIG. 4A), it can be confirmed that an amorphous region is formed. On the other hand, TEM cross-sectional view of Reference Example 2 (dose of carbon: 1.0 × 10 ¹⁵ atoms / cm ² ) in which cluster ion irradiation was performed in the same manner as Reference Example 1 except that the cluster ion was changed to C ₂ H ₃ . In FIG. 4B, it can be confirmed that the amorphous region is not formed. Light-colored portions surrounded by broken lines in FIGS. 4A and 4B are amorphous regions. When the amorphous region is formed, the gettering ability is enhanced as compared to the case where the amorphous region is not formed.

As experimentally shown by the above-described reference examples 1 and 2, it is experimentally found that the amorphous region is more easily formed when cluster ions contain oxygen as a constituent element even if the dose of carbon is the same. It became clear. When C ₂ H ₃ similar to Reference Example 2 is used as a cluster ion, Reference Example 3 (a dose of carbon: 1.5 × 10 ¹⁵ atoms / cm ² ) described in detail later to form an amorphous region. It is necessary to increase the dose of carbon, as shown in the TEM cross-sectional view (FIG. 4C). As described above, if the dose of carbon is increased too much, although high gettering capability can be obtained, there is a possibility that epitaxial defects will occur.

  The details of the experimental conditions will be described later in Experimental Example 1. In the epitaxial silicon wafer according to Inventive Example 1 in which the cluster layer containing carbon, hydrogen and oxygen as constituent elements is irradiated and then the epitaxial layer is formed, It has been confirmed that even if oxygen is locally dissolved in the silicon wafer, there is almost no influence on the surface of the epitaxial layer, or even if the influence is limited, it is limited.

  As can be understood from these experimental results, by irradiating cluster ions 12 containing carbon, hydrogen and oxygen as constituent elements, an amorphous region is easily formed in the modified layer 14 (that is, the irradiation damage becomes large) Finally, the gettering capability of the semiconductor epitaxial wafer 100 can be enhanced. And the bad influence by oxygen injection will also be limited if it is a form of cluster ion irradiation.

Although the invention according to the present embodiment is not bound by theory, the present inventors currently consider the reason why such an effect can be obtained as follows. That is, since the atomic radius of the oxygen atom is larger than that of the carbon atom, the irradiation damage by cluster ions can be increased. And since oxygen has a larger atomic weight than carbon, when implanted in the form of cluster ions, the injection range of oxygen becomes slightly larger than the injection range of carbon, and the oxygen concentration at the deeper side The peak will be located. Therefore, it is conceivable that the gettering capability is increased by the increase in the width of the formed modified layer 14. In addition, the irradiated oxygen and oxygen existing before irradiation in the silicon wafer substrate are diffused by the heat treatment at the time of forming the epitaxial layer, but are trapped in the local precipitation region of carbon, and the oxygen diffusion to the epitaxial layer is limited. It is On the other hand, hydrogen which is simultaneously implanted diffuses to a considerable extent at the time of formation of the epitaxial layer to form vacancies. At this time, it is also considered that the vacancy bonding of oxygen results in the formation of a new gettering sink which did not exist conventionally. Indeed, carbon, by performing cluster ion irradiation comprising the constituent elements of hydrogen and oxygen, gettering capability increases dramatically compared to the case of performing the morphism cluster ion Intel free oxygen constituent elements. The formation of such a non-conventional gettering sink can be inferred also from two types of black-spot-like defects of different sizes present in the TEM cross-sectional photographs of FIG. 7A and FIG. . Small size black point defects near the interface with the epitaxial layer are due to carbon, and large size black spots near the interface with the epitaxial layer are interstitial silicon due to implantation of the three elements including oxygen. It is presumed to be the cause. The reason why such a black dot-like defect is observed is not because the recrystallized region takes the form of a complex clustered defect when the amorphous region formed by the cluster ion irradiation is recrystallized at the time of forming the epitaxial layer. It is thought that. Furthermore, due to the simultaneous irradiation of carbon and oxygen, carbon is injected shallower because the distribution of acceleration energy is smaller than that of oxygen under irradiation conditions with the same acceleration voltage, which is also advantageous in terms of proximity gettering. it is conceivable that. The inventor thinks that the synergetic effect of simultaneous irradiation of the three elements of carbon, hydrogen and oxygen in the form of cluster ions as described above has resulted in a clear increase in gettering ability. There is.

The compound to be ionized is not particularly limited, but examples of compounds that can be ionized include diethyl ether (C ₄ H ₁₀ O), ethanol (C ₂ H ₆ O), diethyl ketone (C ₅ H ₁₀ O), etc. It can be used. In particular, clusters C _n H _m O _l (l, m, n are independent of one another, and formed from diethyl ether, ethanol, etc., and 1 ≦ n ≦ 16, 1 ≦ m ≦ 16, 1 ≦ l ≦ 16) are used Is preferred. In particular, the number of carbon atoms of the cluster ion is preferably 16 or less, and the number of oxygen atom of the cluster ion is preferably 16 or less. This is because it is easy to control a small size cluster ion beam.

  In addition, as long as the three elements of carbon, hydrogen and oxygen described above are contained, other constituent elements may be contained in the cluster ion 12. Examples of constituent elements of the cluster ions 12 other than these three elements include dopant elements such as boron, phosphorus, and arsenic. That is, in addition to carbon, hydrogen and oxygen, it is also preferable to irradiate with one or more dopant elements selected from the group consisting of boron, phosphorus, arsenic and antimony in the form of cluster ions. Because the types of impurity metals that can be gettered efficiently differ depending on the type of element to be solid-solved, it is possible to cope with a wider range of metal contamination by solid-dissolving a plurality of elements. For example, in the case of carbon, nickel (Ni) can be gettered efficiently, and in the case of boron, copper (Cu) and iron (Fe) can be gettered efficiently. In the present specification, a dopant element refers to an element which is substituted at a lattice position of a silicon crystal and can change the electrical conductivity of the silicon crystal. Specifically, examples of the p-type dopant include boron, and examples of the n-type dopant include phosphorus, arsenic, and antimony.

  The cluster size can be appropriately set to 2 to 100, preferably 60 or less, more preferably 50 or less. The cluster size can be adjusted by adjusting the gas pressure of the gas ejected from the nozzle, the pressure of the vacuum vessel, the voltage applied to the filament at the time of ionization, and the like. The cluster size can be determined by obtaining a cluster number distribution by mass spectrometry or time-of-flight mass spectrometry using a quadrupole high frequency electric field, and taking an average value of the number of clusters.

  The acceleration voltage of the cluster ions affects the peak position of the concentration profile in the depth direction of the constituent elements of the cluster ions as well as the cluster size. In the present embodiment, the acceleration voltage of cluster ions can be more than 0 keV / Cluster but less than 200 keV / Cluster, preferably 100 keV / Cluster or less, and more preferably 80 keV / Cluster or less. In addition, two methods of (1) electrostatic acceleration and (2) high frequency acceleration are generally used for adjustment of acceleration voltage. As the former method, there is a method of arranging a plurality of electrodes at equal intervals and applying an equal voltage between them to create an equal acceleration electric field in the axial direction. As the latter method, there is a linear linac method in which ions are accelerated by using high frequency while traveling linearly.

Also, the dose amount of cluster ions can be adjusted by controlling the ion irradiation time. The dose of each element of carbon, hydrogen and oxygen is determined by the cluster ion species and the dose (Cluster / cm ² ) of cluster ions. In this embodiment, the dose amount of carbon can be 1 × 10 ¹³ to 1 × 10 ¹⁷ atoms / cm ² , preferably 5 × 10 ¹³ atoms / cm ² or more and 5 × 10 ¹⁶ atoms / cm ² or less. Do. When the dose of carbon is less than 1 × 10 ¹³ atoms / cm ² , sufficient gettering ability may not be obtained, and when the dose of carbon is more than 1 × 10 ¹⁶ atoms / cm ² , the epitaxial layer 18 is It is because there is a possibility of giving a great damage to the surface of.

  Now, in the present embodiment, after the above-described first step, the second step of forming the epitaxial layer 18 on the modified layer 14 of the semiconductor wafer 10 is performed (FIG. 1C). The epitaxial layer 18 may be, for example, a silicon epitaxial layer, which can be formed under general conditions. In this case, for example, hydrogen is used as a carrier gas, and a source gas such as dichlorosilane or trichlorosilane is introduced into the chamber, and the growth temperature varies depending on the source gas used, but CVD is generally performed at a temperature in the range of 1000 to 1200 ° C. The epitaxial growth can be performed on the semiconductor wafer 10 by the method. The epitaxial layer 18 preferably has a thickness in the range of 1 to 15 μm. If it is less than 1 μm, the outward diffusion of the dopant from the semiconductor wafer 10 may change the resistivity of the epitaxial layer 18, and if it exceeds 15 μm, the spectral sensitivity characteristic of the solid-state imaging device is affected. It is because there is a fear.

  As described above, according to the present embodiment, it is possible to provide a method of manufacturing the semiconductor epitaxial wafer 100 which has more excellent gettering capability and can suppress the occurrence of epitaxial defects.

  Note that, after the first step, prior to the second step, the semiconductor wafer 10 may be subjected to a recovery heat treatment for crystalline recovery. As the recovery heat treatment in this case, for example, the semiconductor wafer 10 may be held in the epitaxial apparatus at a temperature of 900 ° C. to 1100 ° C. for 10 minutes to 60 minutes in an atmosphere such as nitrogen gas or argon gas. . Alternatively, the recovery heat treatment can also be performed using a rapid thermal processing apparatus or the like that is separate from an epitaxial apparatus such as RTA (Rapid Thermal Annealing) or RTO (Rapid Thermal Oxidation).

  However, the above-described recovery heat treatment may not be performed in the present embodiment. Monomer ions are generally implanted at an acceleration voltage of about 150 to 2000 keV, and each ion collides with silicon atoms with its energy, so that the crystallinity of the silicon wafer surface portion into which the monomer ions are implanted is disturbed, and then the wafer surface Disrupt the crystallinity of the epitaxial layer grown on it. On the other hand, cluster ions are generally irradiated at an accelerating voltage of about 10 to 100 keV / cluster, but since clusters are an assembly of a plurality of atoms or molecules, the energy per one atom or molecule should be reduced. Damage to the crystal of the semiconductor wafer is small. Therefore, in the present embodiment, after the first step, the semiconductor wafer can be transported to the epitaxial growth apparatus to perform the second step without performing heat treatment for recovering the crystallinity of the semiconductor wafer. The semiconductor epitaxial wafer 100 having high gettering ability can be efficiently manufactured.

  The reason is that the crystallinity of the semiconductor wafer 10 can be sufficiently recovered by the hydrogen baking process performed prior to the epitaxial growth in the epitaxial device for forming the epitaxial layer 18 described above. The general conditions of the hydrogen baking treatment are that the inside of the epitaxial growth apparatus is a hydrogen atmosphere, the semiconductor wafer 10 is introduced into the furnace at a furnace temperature of 600 ° C. to 900 ° C., and 1 ° C./s to 15 ° C./s The temperature is raised to a temperature range of 1100 ° C. or more and 1200 ° C. or less at a temperature rising rate, and the temperature is maintained for 30 seconds or more and 1 minute or less. Although this hydrogen baking treatment is originally for removing the natural oxide film formed on the wafer surface by the cleaning treatment before the epitaxial layer growth, the crystallinity of the semiconductor wafer 10 is sufficiently recovered by the hydrogen baking of the above conditions It can be done.

Next, a preferred embodiment according to the present invention will be described using FIGS. 2 (A) to 2 (C). About the content which overlaps with embodiment as stated above using FIG. 1, the description which overlaps with reference to the same code | symbol is abbreviate | omitted. In this preferred embodiment, in the first step (FIG. 2A) of irradiating cluster ions 12, the dose of carbon which is a constituent element of cluster ions 12 is set to 1.0 × 10 ¹⁵ atoms / cm ³ or more. Is preferred. After formation of the epitaxial layer 18, it is possible to form a first layer comprising a first black dot defect S ₁ the reforming layer 14, and a second layer comprising a second black dot defect S ₂ It is. The modified layer 14 under these conditions will be described in more detail below.

  As shown in FIG. 2B, by performing cluster ion irradiation under the above-described conditions, a part in the depth direction in the modified layer 14 becomes the amorphous layer 16. When the amorphous layer 16 is present in the modified layer 14, the gettering ability by the above-mentioned modified layer 14 can be more reliably obtained. When the average depth D of the surface 16A of the amorphous region 16 is 20 nm or more from the semiconductor wafer surface 10A, generation of epitaxial defects in the epitaxial layer 18 to be formed later can be sufficiently suppressed.

  The average depth of the surface 16A of the amorphous region 16 is preferably 20 nm or more and 200 nm or less from the surface 10A of the semiconductor wafer from the viewpoint of sufficiently suppressing the occurrence of epitaxial defects.

  The average thickness of the amorphous region 16 is preferably 100 nm or less, and more preferably 60 nm or less. If it exceeds 100 nm, it may be difficult to select cluster irradiation conditions for making the average depth of the surface 16A 20 nm or more from the semiconductor wafer surface 10A.

  As shown in FIG. 2B and FIG. 4A which will be described in detail later, the surface 16A of the amorphous region 16 varies in depth depending on the position in the lateral direction. The “average depth of the surface on the wafer surface side” is defined by observing the cross section of the amorphous layer with a transmission electron microscope (TEM), and defining the average depth of the surface in the obtained TEM image. The “average depth” is an intermediate depth between the shallowest position and the deep position of the boundary between the amorphous region and the crystalline region. The "average thickness of the amorphous region" is also defined by the average thickness of the amorphous layer in the TEM image, ie the difference in the average depth of the two surfaces of the amorphous layer. The magnification of the TEM image should be such that the amorphous layer can be clearly observed. In the reference example 1 shown in FIG.

Further, as shown in FIG. 2C, when the amorphous region 16 is formed as described above and then the epitaxial layer 18 is formed, the first black spot in the modified layer 14 is formed after the epitaxial layer 18 is formed. a first layer comprising Jo defect S _1, it is possible to form a second layer comprising a second black dot defect S ₂ larger than the size of the first black dot defect. Black dot defect S ₁ and black spot defect S ₂ may be dispersed in a predetermined thickness in the depth direction. In FIG. 2 (C), the is a schematic view showing that the black dot defect S ₁ is dispersed in a predetermined thickness. The first layer is located closer to the epitaxial layer 18 than the second layer in the depth direction of the semiconductor epitaxial wafer 100. Incidentally, black dot defect S ₁ and when dispersed at a predetermined thickness in one or both the depth direction of the black dot defect S ₂ is the average depth of each layer in the depth direction as described above The positional relationship between the first layer and the second layer is determined based on the position. When the distance to the average depth position of the black spot defects S ₁ and S ₂ is represented as D ₁ and D ₂ respectively as shown in FIG. 2C, if D ₁ <D ₂ , the first layer is It will be located closer to the epitaxial layer 18 than the second layer. The second layer may be included in the range of the thickness direction of the first layer.

In the present specification, “black-spot-like defect” means a defect observed as a black spot in the modified layer 14 when the cleavage cross section of the semiconductor epitaxial wafer 100 is observed in a bright mode by TEM. According to the study of the present inventors, the black spot defects are generated in the modified layer 14 after the formation of the epitaxial layer 18 only when the amorphous layer 16 is formed in the modified layer 14 after the irradiation of the cluster ions 12. It is If no amorphous layer is formed in the modified layer, it is considered that neither of the black spot defects S ₁ and S ₂ occurs in the modified layer after the formation of the epitaxial layer. Also, depending on the type of cluster ion, for example, when the dose amount of carbon is less than 1.0 × 10 ¹⁵ atoms / cm ³ and the dose amount of cluster ions 12 is low, the black spot defect S ₂ is not formed, only black dot defect S ₁ is formed.

According to the studies of the present inventors, the semiconductor epitaxial wafer 100 first black dot defect S ₁ and the second black dot defect S ₂ is present, it was confirmed that a higher gettering capability can be obtained. Such semiconductor epitaxial wafer 100, as compared to the case where only the black dot defect S ₁ is formed, a higher gettering capability can be obtained.

(Semiconductor epitaxial wafer)
Next, a semiconductor epitaxial wafer 100 obtained by the above manufacturing method will be described. As shown in FIG. 1C, the semiconductor epitaxial wafer 100 includes a semiconductor wafer 10, and a modified layer 14 formed on the surface of the semiconductor wafer 10, in which a predetermined element is solid-solved in the semiconductor wafer 10. And an epitaxial layer 18 on the modified layer 14.

Then, in the present embodiment, the carbon peak concentration of the carbon concentration profile in the depth direction of carbon in the modified layer 14 is 1.0 × 10 ¹⁵ atoms / cm ³ or more and 1.0 × 10 ²⁰ atoms / cm ³ or less The hydrogen peak concentration of the hydrogen concentration profile in the depth direction of hydrogen in the reforming layer 14 is 1.0 × 10 ¹⁷ atoms / cm ³ or more, and the oxygen concentration in the depth direction of the oxygen in the reforming layer 14 The peak oxygen concentration of the profile is 5.0 × 10 ¹⁸ atoms / cm ³ or more. Such a semiconductor epitaxial wafer 100 has more excellent gettering capability, and the occurrence of epitaxial defects is suppressed. In order to further enhance the gettering ability, the oxygen peak concentration is more preferably 1.0 × 10 ¹⁹ atoms / cm ³ or more.

  Here, it is more preferable that at least one of the carbon concentration profile, the hydrogen concentration profile, and the oxygen concentration profile is a bimodal concentration profile. As clarified by the later-described FIG. 5A, according to the study of the present inventor, when the dose amount of cluster ions at the time of forming the modified layer 14 is large, such a bimodal concentration profile is obtained Was found to be easily formed. That is, when the bimodal concentration profile is formed in the semiconductor epitaxial wafer, the gettering capability is further enhanced. On the other hand, when the dose amount of cluster ions at the time of forming the modified layer 14 is small, it is difficult to form a bimodal concentration profile.

  In the present specification, when a bimodal concentration profile is formed on the semiconductor epitaxial wafer 100, for example, when the carbon concentration profile is bimodal as shown in FIG. 5A, the larger one of the two peaks is used. The concentration (ie the maximum value of the concentration) is taken as the peak concentration. The same applies to the hydrogen concentration profile and the oxygen concentration profile.

  Moreover, in order to surely obtain the effect of the present invention, it is preferable that the carbon peak concentration is larger than the oxygen peak concentration, and the carbon peak concentration is 1.0 times to 5.0 times the oxygen peak concentration. More preferable. Furthermore, in the modified layer 18, it is preferable that the carbon concentration profile includes an oxygen concentration profile.

Then, as shown in FIG. 2 (C), a first layer comprising a first black dot defect S ₁ to the reforming layer 18, the second black dot is larger than the first size of the black dot defect S ₁ there is a second layer containing a defective S _2, it is preferable that the first layer located on the epitaxial layer 18 side than the second layer. Such a semiconductor epitaxial wafer 100 has more excellent gettering capability, and the occurrence of epitaxial defects is suppressed. The second black dot defect S ₂ is not easy to be formed or the present inventors when bimodal concentration profile described above are formed is considered.

At this time, the first density of the black dot defect S ₁ is 1.0 × 10 ¹⁶ atoms / cm ³ or more 1.0 × 10 ¹⁸ atoms / cm ³ or less, and, the second black dot defect S ₂ The density is preferably 1.0 × 10 ¹⁴ pieces / cm ³ or more and 1.0 × 10 ¹⁶ pieces / cm ³ or less. The presence of these two types of black dot defects increases the gettering ability.

Furthermore, in the modified layer 18, the first black spot-like defect S ₁ is present at a depth of 30 nm to 150 nm in the depth direction from the interface between the semiconductor wafer 10 and the epitaxial layer 18. defect _{S 2} is preferably present at a depth position of 60nm or 150nm or less in the depth direction from the interface. This is to suppress the occurrence of epitaxial defects. The first size of the black dot defect _{S 1} is is a 1nm or 10nm or less, and is preferably a second size black dot defect _{S 2} is 15nm or more 100nm or less. Here, “the first and second black spot defects” are observed in the form of black spots in a TEM image obtained by observing the cross section of the cluster irradiation area after epitaxial growth with a transmission electron microscope (TEM: Transmission Electron Microscope) Defined as a visible defect. The "size of the black dot-like defect" is the diameter of the defect in the TEM image. In addition, “density of black dot-like defect” is defined by the number of defects per predetermined area in a region where black dot defects exist in the TEM image by the final thickness of the sample used for the TEM observation at that time. When the black dot defects S ₁ and S ₂ are not circular or have a shape that can not be regarded as a circle, the diameter is determined by approximating to a circle using a circumscribed circle of the smallest diameter including the black dot defects.

  The semiconductor wafer is preferably made of a silicon wafer.

  Furthermore, it is preferable that peaks of carbon, hydrogen and oxygen concentration profiles exist in a range from the surface 10A of the semiconductor wafer 10 to a depth of 150 nm in the depth direction. The above range can be defined as the surface portion of the semiconductor wafer in the present specification. And it is preferable that the peak of the concentration profile of each element exists in the range from the surface 10A of the semiconductor wafer 10 to the depth 100 nm in the depth direction. The peak position of the concentration profile of each element can not physically exist on the outermost surface of the semiconductor wafer (0 nm deep from the surface 10A of the semiconductor wafer 10) irradiated with the cluster ions 12, so at least 5 nm or more It will be in the depth position of

  Moreover, it is also preferable that the half value width (FWHM) of the peak of the carbon concentration profile in the depth direction of the semiconductor wafer 10 in the modified layer 18 is 100 nm or less. Such a modified layer 18 is a region where carbon is solid-dissolved and locally exists at interstitial positions or substitution positions of crystals of the surface portion of the semiconductor wafer, and can function as a strong gettering site. Further, from the viewpoint of obtaining high gettering ability, the half width is more preferably 85 nm or less, and the lower limit can be set to 10 nm. The half width (FWHM) of the peak of the concentration profile of oxygen and hydrogen is also preferably 100 nm or less, and more preferably 85 nm or less. When a bimodal concentration profile in which two different peaks appear is formed as in the carbon concentration profile shown in FIG. 5A described later, Gaussian fitting is performed to obtain a half value width (FWHM) from the distribution after fitting. ) Shall be determined.

  The thickness of the modified layer 18 is defined as a region where the concentration profile of the constituent element of the cluster ion 12 is locally detected in the concentration profile, and can be, for example, in the range of 30 to 400 nm.

(Method of manufacturing solid-state imaging device)
In the method of manufacturing a solid-state imaging device according to an embodiment of the present invention, a solid-state imaging device is formed on the semiconductor epitaxial wafer manufactured by the above-described method of manufacturing a semiconductor epitaxial wafer, ie, the epitaxial layer 18 located on the surface of the semiconductor epitaxial wafer 100 It is characterized by The solid-state imaging device obtained by this manufacturing method can sufficiently suppress the occurrence of the white defect as compared with the prior art.

  Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to the following examples.

(Reference Experiment Example 1)
Reference Example 1
An n-type silicon wafer (diameter: 300 mm, thickness: 775 μm, dopant type: phosphorus, resistivity: 20 Ω · cm) obtained from a CZ single crystal was prepared. Next, cluster ions of CH ₃ O obtained by cluster ionizing diethyl ether (C ₄ H ₁₀ O) using a cluster ion generator (manufactured by Nisshin Ion Instruments Co., Ltd., model number: CLARIS) are accelerated at an accelerating voltage of 80 keV / Cluster (hydrogen accelerating voltage 2.58keV / atom per atom, an accelerating voltage 30.1keV / atom, an acceleration voltage 41.3keV / atom per oxygen 1 atom per one carbon atom, range distance of hydrogen 60 nm, carbon The silicon wafer according to the reference example 1 was obtained by irradiating the surface of the silicon wafer under the irradiation conditions of the range of 120 nm and the range of oxygen of 125 nm. In addition, the dose amount of carbon at the time of cluster ion irradiation was 1.0 * 10 < ¹⁵ > cluster / cm < ² >. In terms of the number of hydrogen atoms is ^{3.0 × 10 15 atoms / cm 2} , in terms of number of carbon atoms is ^{1.0 × 10 15 atoms / cm 2} , in terms of the number of oxygen atoms 1.0 × 10 ¹⁵ atoms / cm ² The beam current value of cluster ions was 550 μA.

Reference Example 2
Instead of CH ₃ O obtained by cluster ionizing diethyl ether in Reference Example 1, C ₂ H ₃ obtained by cluster ionizing cyclohexane is irradiated, and the dose per carbon atom is the same as in Reference Example 1 (that is, the carbon dose amount is 1. The cluster ion irradiation was performed under the same conditions as in Reference Example 1 except that the concentration was changed to 0 × 10 ¹⁵ atoms / cm ² ), to prepare a silicon wafer according to Reference Example 2. In this case, the acceleration voltage per hydrogen atom is 2.96 keV / atom, the acceleration voltage per carbon atom is 35.6 keV / atom, the range distance of hydrogen is 60 nm, and the range distance of carbon is 120 nm.

Reference Example 3
A cluster was produced under the same conditions as in Reference Example 2 except that the carbon dose was changed to 1.5 × 10 ¹⁵ atoms / cm ² instead of 1.0 × 10 ¹⁵ atoms / cm ² in Reference Example 2. Ion irradiation was performed to produce a silicon wafer according to Reference Example 3.

<Reference evaluation 1: Evaluation of concentration profile of silicon wafer by quadrupole SIMS>
As a representative example, with respect to a silicon wafer according to Reference Example 1, carbon in the depth direction is obtained by quadrupole SIMS (resolution in the depth direction: 2 nm, lower limit of detection of hydrogen: 4.0 × 10 ¹⁷ atoms / cm ³ ) The concentration profiles of hydrogen and oxygen were measured. The concentration profile of Reference Example 1 is shown in FIG. From FIG. 3, peaks of concentration profiles of hydrogen, carbon and oxygen are observed in the depth direction from the surface side of the silicon wafer.

<Reference evaluation 2: Observation by TEM cross section photograph>
About each of the silicon wafer which concerns on the reference examples 1-3, the cross section around the modification layer after cluster ion irradiation was observed by TEM (Transmission Electron Microscope: transmission electron microscope). A TEM cross-sectional view of Reference Example 1 is shown in FIG. 4 (A), a TEM cross-sectional view of Reference Example 2 is shown in FIG. 4 (B), and a TEM cross-sectional view of Reference Example 3 is shown in FIG. 4 (C). In the TEM cross-sectional photograph, the light (white) visible portion is the amorphized region. While the formation of the amorphous region can be confirmed in FIGS. 4A and 4C, the formation of the amorphous region can not be confirmed in FIG. 4B.

  Therefore, it was confirmed that when the dose amount of carbon is the same, the damage given to the irradiation area is larger when the cluster ion contains oxygen as a constituent element. Furthermore, when the constituent elements of the cluster ions of Reference Example 1 and Reference Example 2 are compared, since the atomic weight of the oxygen element is larger than that of the carbon element, the cluster ion of Reference Example 1 is more than Reference Examples 2 and 3. It is scrutinized. Then, the position of the formed modified layer is closer to the surface of the silicon wafer, and the thickness of the modified layer is increased.

(Experimental example 1)
Invention Example 1
Under the same conditions as in Reference Example 1, silicon wafers were irradiated with CH ₃ O cluster ions. Next, the silicon wafer is transferred into a single wafer type epitaxial growth apparatus (manufactured by Applied Materials) and subjected to a hydrogen baking treatment for 30 seconds at a temperature of 1120 ° C. in the apparatus, and then hydrogen is used as a carrier gas and trichlorosilane as a source. A silicon epitaxial layer (thickness: 9 μm, dopant type: phosphorus, resistivity: 10 Ω · cm) is epitaxially grown on the surface of the silicon wafer on which the modified layer is formed by CVD method at 1120 ° C. An epitaxial silicon wafer according to invention example 1 was produced.

<Invention Example 2>
Clusters under the same conditions as in Inventive Example 1 except that the carbon dose was 5.0 × 10 ¹⁴ atoms / cm ² instead of 1.0 × 10 ¹⁵ atoms / cm ² in Inventive Example 1 Ion irradiation was performed to produce an epitaxial silicon wafer according to Inventive Example 2.

Comparative Example 1
In Comparative Example 1, instead of CH ₃ O obtained by cluster ionizing diethyl ether, C ₃ H ₅ cluster ions obtained by cluster ionizing cyclohexane (C ₆ H ₁₂ ) are irradiated, and the dose per carbon atom is changed to Inventive Example 1 Cluster ion irradiation was performed under the same conditions as in Inventive Example 1 except that it was the same (that is, the carbon dose was 1.0 × 10 ¹⁵ atoms / cm ² ), and an epitaxial silicon wafer according to Comparative Example 1 was produced.

Comparative Example 2
Clusters under the same conditions as Comparative Example 1 except that in Comparative Example 1, the carbon dose was changed to 1.0 × 10 ¹⁵ atoms / cm ² and the carbon dose was changed to 5.0 × 10 ¹⁴ atoms / cm ^2. Ion irradiation was performed to fabricate an epitaxial silicon wafer according to Comparative Example 2.

<Evaluation 1: Evaluation of concentration profile of epitaxial wafer by magnetic field SIMS>
Magnetic field SIMS measurement (resolution in the depth direction: 30 nm, lower limit of detection of hydrogen: 4.0 × 10 ¹⁶ atoms / cm ³ ) is performed on epitaxial silicon wafers according to Inventive Example 1 and Comparative Example 1, and the wafer depth direction The respective concentration profiles of hydrogen, carbon and oxygen at. The concentration profile of Inventive Example 1 is shown in FIG. 5A. Moreover, the graph which piled up the oxygen concentration profile of the invention example 1 and the comparative example 1 is shown to FIG. 5B. Here, the depth of the horizontal axis in FIG. 5A and FIG. 5B makes the surface of the epitaxial layer of the epitaxial silicon wafer zero. A depth of up to 9 μm corresponds to the epitaxial layer, and a depth of 9 μm or more corresponds to the silicon wafer. Since an unavoidable measurement error of about ± 0.1 μm occurs in the thickness of the epitaxial layer when the epitaxial wafer is measured by SIMS, the boundary between the epitaxial layer and the silicon wafer in the strict meaning of 9 μm in the figure. It does not become a value.

First, it can be confirmed from FIG. 5A that in the invention example 1, the carbon concentration profile and the hydrogen concentration profile are bimodal. Next, from FIG. 5B, while the oxygen peak concentration of Inventive Example 1 is about 6.5 × 10 ¹⁹ atoms / cm ³ , the oxygen peak concentration of Comparative Example 1 is about 3.7 × 10 ¹⁸ atoms / cm ^3. It was cm ³ . That is, the oxygen peak concentration of Inventive Example 1 is about 18 times the oxygen peak concentration of Comparative Example 1. As described above, when the modified layer is formed by cluster ion irradiation and then the epitaxial layer is formed, it can be confirmed that oxygen is trapped in the modified layer in both Inventive Example 1 and Comparative Example 1. And in the example 1 of the invention, since oxygen is contained in the component element of cluster ion, it was confirmed that the oxygen peak concentration of the produced epitaxial silicon wafer turns into very high concentration which is not before.

<Evaluation 2: Evaluation of gettering ability>
The surface of the epitaxial layer of each epitaxial wafer of Inventive Examples 1 and 2 and Comparative Examples 1 and 2 is forcibly contaminated by a spin coat contamination method using Ni contamination liquid (2.0 × 10 ¹³ atoms / cm ² ). Then, heat treatment was performed at 900 ° C. for 30 minutes in a nitrogen atmosphere. Thereafter, SIMS measurement was performed on each epitaxial wafer to measure profiles of carbon concentration and Ni concentration in the depth direction of the wafer. The ratio of the capture amount to the intentional contamination concentration of 2.0 × 10 ¹³ atoms / cm ² of Ni of each epitaxial wafer is shown together in Table 1.

<Evaluation 3: Evaluation of epitaxial defects>
Further, separately from the gettering ability evaluation, each epitaxial wafer was measured in Normal mode with Surfscan SP1 (manufactured by KLA-Tencor), and the number counted as LPD-N was confirmed. As representative examples, the measurement results of the LPD maps of the epitaxial wafers of Inventive Example 1 and Comparative Example 1 are shown in FIGS. 6A and 6B, respectively. The evaluation results of the epitaxial defects observed by Surfscan SP1 are also shown in Table 1. Evaluation criteria are as follows.
○: The density of epitaxial defects is 0.002 pieces / cm ² or less.
X: The density of epitaxial defects is more than 0.002 pieces / cm ² .
In any of Inventive Examples 1 to 3, no stacking defect caused by BMD was observed in the surface defect inspection.

  According to the above evaluations 1 to 3, the epitaxial silicon wafer manufactured according to the conditions of the present invention has a better gettering ability than an epitaxial silicon wafer irradiated with cluster ions not containing oxygen as a constituent element. confirmed. Moreover, it was confirmed that the incidence rate of epitaxial defects is approximately the same even when comparing Inventive Examples 1 and 2 and Comparative Examples 1 and 2.

<Evaluation 4: Observation by TEM cross-sectional photograph>
As a representative example, for each of the epitaxial silicon wafers according to Inventive Example 1 and Comparative Example 1, a cross section around the modified layer after cluster ion irradiation was observed with a TEM (Transmission Electron Microscope: transmission electron microscope). A TEM cross-sectional view of Invention Example 1 is shown in FIG. 7 (A), and a TEM cross-sectional view of Comparative Example 1 is shown in FIG. 7 (B). Furthermore, FIG. 8 shows a TEM cross-sectional view of Inventive Example 1 in which the cross section of the epitaxial wafer subjected to the same process as that of FIG. 7A was obtained under different TEM observation conditions.

  From FIGS. 7A and 7B, in the invention example 1 in which the constituent elements of the cluster ion are carbon, hydrogen and oxygen, the first layer including the first black dot-like defect in the modified layer, and the second layer It was confirmed that the second layer including the black spot defects was formed. Moreover, it was confirmed from FIG. 8 that the second layer is formed in the first layer, and that the second black dot defect may include the first black dot defect. And, as is clear from Table 1, it was confirmed that Inventive Example 1 is superior to Comparative Example 1 in gettering ability.

  According to the present invention, it is possible to provide a method of manufacturing a semiconductor epitaxial wafer having more excellent gettering capability and capable of suppressing the occurrence of epitaxial defects.

100 Semiconductor Epitaxial Wafer 10 Semiconductor Wafer 10A Semiconductor Wafer Surface 12 Cluster Ions 14 Modified Layer 16 Amorphous Region 16A Amorphous Region Surface of Semiconductor Wafer Surface Side 18 Epitaxial Layer S ₁ First Black Spot Defect S ₂ Second Black Point Shape defect

Claims (11)

The first step of irradiating the surface of a semiconductor wafer with cluster ions containing carbon, hydrogen and oxygen as constituent elements to form a modified layer in which the constituent elements of the cluster ions form a solid solution on the surface of the semiconductor wafer When,
A second step of forming an epitaxial layer on the modified layer of the semiconductor wafer after the first step, and a method of manufacturing a semiconductor epitaxial wafer.   The method for producing a semiconductor epitaxial wafer according to claim 1, wherein the number of carbon atoms of the cluster ion is 16 or less and the number of oxygen atom of the cluster ion is 16 or less. The method for producing a semiconductor epitaxial wafer according to claim 1 or 2, wherein the dose amount of carbon by the irradiation of the cluster ions is 1.0 × 10 ¹³ atoms / cm ² or more and 1.0 × 10 ¹⁷ atoms / cm ² or less. .   The method for manufacturing a semiconductor epitaxial wafer according to any one of claims 1 to 3, wherein the semiconductor wafer is a silicon wafer. A semiconductor wafer, a reformed layer formed on the surface of the semiconductor wafer, in which carbon, hydrogen and oxygen are solid-solved in the semiconductor wafer, and an epitaxial layer on the reformed layer,
The carbon peak concentration of the carbon concentration profile in the depth direction of carbon in the modified layer is 1.0 × 10 ¹⁵ atoms / cm ³ or more and 1.0 × 10 ²⁰ atoms / cm ³ or less,
The hydrogen peak concentration of the hydrogen concentration profile in the depth direction of the hydrogen in the reforming layer is 1.0 × 10 ¹⁷ atoms / cm ³ or more,
A semiconductor epitaxial wafer characterized in that an oxygen peak concentration of the oxygen concentration profile in the depth direction of the oxygen in the modified layer is 5.0 × 10 ¹⁸ atoms / cm ³ or more. The semiconductor epitaxial wafer according to claim 5, wherein the peak oxygen concentration is 1.0 × 10 ¹⁹ atoms / cm ³ or more.   The semiconductor epitaxial wafer according to claim 5 or 6, wherein at least one of the carbon concentration profile, the hydrogen concentration profile, and the oxygen concentration profile is a bimodal concentration profile. The modified layer includes a first layer including a first black dot-like defect and a second layer including a second black dot-like defect larger than the size of the first black dot-like defect.
The semiconductor epitaxial wafer according to any one of claims 5 to 7, wherein the first layer is located closer to the epitaxial layer than the second layer in the depth direction. The density of the first black dot defect is 1.0 × 10 ¹⁶ / cm ³ or more and 1.0 × 10 ¹⁸ / cm ³ or less,
9. The semiconductor epitaxial wafer according to claim 8, wherein the density of the second black dot defect is 1.0 × 10 ¹⁴ pieces / cm ³ or more and 1.0 × 10 ¹⁶ pieces / cm ³ or less. In the modified layer, the first black spot-like defect is present at a depth of 30 nm or more and 150 nm or less in a depth direction from an interface between the semiconductor wafer and the epitaxial layer.
The semiconductor epitaxial wafer according to claim 8, wherein the second black dot-like defect is present at a depth of 60 nm or more and 150 nm or less in the depth direction from the interface.   The semiconductor epitaxial wafer according to any one of claims 5 to 10, wherein the semiconductor wafer comprises a silicon wafer.