Epitaxial silicon wafer, method for manufacturing the same, and method for manufacturing semiconductor device

Abstract

The method for manufacturing an epitaxial silicon wafer (100) of the present invention is characterized by comprising: irradiating a surface (10A) of a silicon wafer (10) with a molten silicon nitride (SiH) x (x is one or more integers selected from 1 to 3) ions and C2H y The present invention relates to a process for forming a modified layer (14) in which a constituent element of the cluster ion beam is solid-dissolved on the surface of the silicon wafer by using a beam of cluster ions (12) of ions (y is one or more integers selected from 2 to 5); and a process for forming a silicon epitaxial layer (16) on the modified layer (14) of the silicon wafer, wherein the SiH x The ion dose was set to 1.5×10 14 ions / cm 2 above.

Description

Technical Field

[0001] The present invention relates to an epitaxial silicon wafer and a manufacturing method thereof, as well as a manufacturing method of a semiconductor device. Background Art

[0002] Epitaxial silicon wafers, which have an epitaxial layer of single-crystal silicon formed on a silicon wafer, are used as device substrates for manufacturing various semiconductor devices such as MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), DRAM (Dynamic Random Access Memory), power transistors, and BSI (Back Side Illumination) type CIS (CMOS Image Sensor).

[0003] Here, if the epitaxial layer is contaminated by heavy metals, it will become a major factor in increasing the dark current of the CIS and causing defects known as white damage defects, which will degrade the characteristics of the semiconductor device. Therefore, in order to suppress this heavy metal contamination, there is a technology that forms a gettering site in the silicon wafer to capture heavy metals. As one of the methods, there is a method known to implant ions into the silicon wafer and then form the epitaxial layer. In this method, the ion implanted area acts as a gettering site.

[0004] Patent Documents 1 and 2 describe a method for manufacturing an epitaxial silicon wafer, which includes: irradiating the surface of a silicon wafer with cluster ions (cluster ion) containing carbon and hydrogen as constituent elements such as C3H5, thereby forming a modified layer in which the constituent elements of the cluster ions are solid dissolved in the surface portion of the silicon wafer; and forming a silicon epitaxial layer on the modified layer of the silicon wafer.

[0005] Patent Document 1 discloses that a modified layer formed by irradiation with cluster ions containing carbon and hydrogen as constituent elements exhibits higher gettering ability than an ion-implanted region obtained by implanting carbon simple ions.

[0006] Patent Document 2 describes, as an improvement to the technique described in Patent Document 1, a technique for enhancing the heavy metal gettering ability by irradiating a modified layer with cluster ions containing carbon and hydrogen at a high dose, thereby rendering a portion of the modified layer in the thickness direction amorphous. Furthermore, Patent Document 2 describes that, when irradiating the modified layer with high doses of cluster ions as described above, tiny black dot-like defects caused by carbon implantation, etc., were observed in cross-sectional TEM images of the epitaxially grown modified layer. The authors investigated whether these black dot-like defects contribute to the improvement of the gettering ability.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: International Publication No. 2012 / 157162

[0010] Patent Document 2: International Publication No. 2015 / 104965 Summary of the Invention

[0011] Technical problem to be solved by the invention

[0012] In the irradiation technology of cluster ions containing carbon and hydrogen such as Patent Documents 1 and 2, in order to further improve the gettering ability based on the modified layer, it is effective to increase the carbon dose obtained by the cluster ions. However, according to the research of the inventors of the present invention, with respect to epitaxial silicon wafers produced with a high carbon dose, it has been found that, in particular, when the thickness of the epitaxial layer is as thin as 4 μm or less, such as in the application of BSI type CIS, there is a situation where the electrical characteristics deteriorate. It is speculated that the reason is that: in the case of a high carbon dose, during epitaxial growth and device formation process, the high concentration of carbon present in the modified layer diffuses into the silicon epitaxial layer, forming point defects caused by carbon on the silicon epitaxial layer. In particular, when the epitaxial layer is thin, point defects caused by carbon are present in the device formation region of the epitaxial layer.

[0013] However, if the carbon dose from cluster ions is reduced to suppress the formation of point defects caused by carbon, the gettering ability of heavy metals cannot be fully achieved. In other words, the previous irradiation technology using cluster ions containing carbon and hydrogen cannot achieve both high gettering ability and the suppression of carbon diffusion into the epitaxial layer during epitaxial growth and device formation processes.

[0014] In view of the above technical problems, an object of the present invention is to provide a method for manufacturing an epitaxial silicon wafer that can ensure gettering capability and suppress carbon diffusion into the epitaxial layer during epitaxial growth and device formation processes.

[0015] Furthermore, another object of the present invention is to provide an epitaxial silicon wafer that ensures gettering capability and suppresses carbon diffusion into the epitaxial layer during epitaxial growth and device formation processes.

[0016] Solutions for solving technical problems

[0017] To address the above-mentioned technical problems, the inventors of the present invention conducted intensive research and reached the following conclusion: While irradiating with cluster ions containing carbon and hydrogen at a low carbon dose can suppress carbon diffusion into the epitaxial layer, the gettering capacity is insufficient. Therefore, the inventors of the present invention devised a method to compensate for the reduced gettering capacity caused by the low carbon dose by irradiating with cluster ions containing carbon and hydrogen in addition to cluster ions containing a constituent element other than carbon.

[0018] Furthermore, it was found that by irradiating the surface of the silicon wafer with C2H y (y is one or more integers selected from 2 to 5) ions and a predetermined dose or more of SiH x (x is one or more integers selected from 1 to 3) ions, even if the dosage of carbon is reduced, sufficient gettering ability can be obtained.

[0019] Here, the SiH implanted into the surface of the silicon wafer x Ionic Si is difficult to distinguish from Si that constitutes the silicon wafer. However, the inventors of the present invention have been able to indirectly grasp the desired effects of Si implantation through analysis using secondary ion mass spectrometry (SIMS) or observation using a transmission electron microscope (TEM).

[0020] First, in the epitaxial silicon wafer produced in the above manner, the amount of carbon distributed in the silicon epitaxial layer and the modified layer is small due to the low carbon dose. However, in the cross-sectional TEM image of the modified layer, EOR defects with a maximum width of 50 to 250 nm were observed. It is speculated that these are different from the black dot defects caused by carbon implantation and are caused by SiH x Defects caused by ion implantation.

[0021] Moreover, it can be seen that: in the epitaxial silicon wafer produced in the above manner, even with a low carbon dose, a steep peak appears in the carbon concentration distribution of STMS in the depth direction of the modified layer near the interface between the modified layer and the epitaxial layer, and a peak also appears in the hydrogen concentration distribution of SIMS in the depth direction of the modified layer.

[0022] The gist of the present invention, which was accomplished based on the above findings, is as follows.

[0023] [1] A method for manufacturing an epitaxial silicon wafer, characterized by comprising:

[0024] The surface of the silicon wafer is irradiated with SiH x (x is one or more integers selected from 1 to 3) ions and C2H y a step of forming a modified layer in which constituent elements of the cluster ion beam are solid-dissolved on a surface portion of the silicon wafer by using a cluster ion beam of ions (y is one or more integers selected from 2 to 5); and

[0025] forming a silicon epitaxial layer on the modified layer of the silicon wafer;

[0026] The SiH x The ion dose was set to 1.5×10 14 ions / cm 2 above.

[0027] [2] The method for manufacturing an epitaxial silicon wafer according to [1] above, wherein:

[0028] The C2H y The ion dose was set to 1.0×10 14 ions / cm 2 the following.

[0029] [3] The method for manufacturing an epitaxial silicon wafer according to [1] or [2] above, wherein:

[0030] The raw material gas of the cluster ion beam is diethylsilane.

[0031] [4] The method for producing an epitaxial silicon wafer according to any one of [1] to [3] above, wherein:

[0032] In the cluster ion beam, x is 1, 2, and 3, and y is 5.

[0033] [5] The method for producing an epitaxial silicon wafer according to any one of [1] to [4] above, wherein:

[0034] The thickness of the silicon epitaxial layer is less than 4 μm.

[0035] [6] An epitaxial silicon wafer characterized by having:

[0036] silicon wafers;

[0037] a modified layer formed on a surface portion of the silicon wafer and containing a solid solution of at least one of carbon and hydrogen; and

[0038] a silicon epitaxial layer formed on the modified layer,

[0039] In the defect evaluation based on the cross-sectional TEM image of the modified layer, EOR defects with a maximum width of 50 to 250 nm were observed in the modified layer at a rate of 5.0×10 7 pieces / cm2 Defective areas with a density above

[0040] The amount of carbon distributed in the silicon epitaxial layer and the modified layer is 2.0×10 14 atoms / cm 2 the following,

[0041] In the hydrogen concentration distribution of SIMS in the depth direction of the modified layer, the peak concentration was 1.0×10 16 atoms / cm 3 above.

[0042] [7] A method for manufacturing a semiconductor device, comprising:

[0043] The method for manufacturing an epitaxial silicon wafer according to any one of [1] to [5] above; and

[0044] The process of forming a semiconductor device on the silicon epitaxial layer of the epitaxial silicon wafer.

[0045] [8] A method for manufacturing a semiconductor device, comprising the step of forming a semiconductor device on the silicon epitaxial layer of the epitaxial silicon wafer described in [6] above.

[0046] Effects of the Invention

[0047] According to the method for manufacturing an epitaxial silicon wafer of the present invention, it is possible to manufacture an epitaxial silicon wafer that ensures gettering capability and suppresses diffusion of carbon into the epitaxial layer during epitaxial growth and device formation processes.

[0048] The epitaxial silicon wafer of the present invention ensures gettering capability and suppresses carbon diffusion into the epitaxial layer during epitaxial growth and device formation processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 Schematic cross-sectional views illustrating a method for manufacturing an epitaxial silicon wafer 100 according to one embodiment of the present invention.

[0050] Figure 2 It represents the diethylsilane (SiC4H 12 ) Mass fragmentation chart (mass spectrum) of various cluster ions obtained.

[0051] Figure 3 This is a graph showing the carbon and hydrogen concentration distributions based on SIMS after ion implantation and before epitaxial layer formation in Inventive Example 6.

[0052] Figure 4 This is a graph showing the relationship between the total dose and the implanted carbon amount obtained from Inventive Examples 1 to 6 and Comparative Examples 1 and 2.

[0053] Figure 5 This is a graph showing carbon concentration distributions based on SIMS after the epitaxial layer formation in Inventive Example 6 and Comparative Examples 1, 2, and 4.

[0054] Figure 6 This is a graph showing hydrogen concentration distributions based on SIMS after the epitaxial layer formation in Inventive Example 6 and Comparative Examples 1 and 2.

[0055] Figure 7 These are cross-sectional TEM images of the modified layers in Inventive Example 6 and Comparative Examples 1 and 2 (magnification: 200,000 times).

[0056] Figure 8 This is a cross-sectional TEM image of the modified layer in Inventive Example 6 (magnification: 1,000,000 times). DETAILED DESCRIPTION

[0057] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Figure 1 In FIG. 1 , for convenience of explanation, the thicknesses of the modified layer 14 and the silicon epitaxial layer 16 are exaggerated relative to the silicon wafer 10 , unlike the ratio of the actual thickness.

[0058] (Method for Manufacturing Epitaxial Silicon Wafer)

[0059] like Figure 1 As shown, the method for manufacturing an epitaxial silicon wafer 100 according to one embodiment of the present invention comprises: a first step ( Figure 1 In step A and step B), the surface 10A of the silicon wafer 10 is irradiated with ions 12A containing SiHx (x is one or more integers selected from 1 to 3) and C2H y (y is one or more integers selected from 2 to 5) a cluster ion beam 12 of ions 12B, thereby forming a modified layer 14 in which the constituent elements of the cluster ion beam are solid-dissolved on the surface of the silicon wafer 10; and a second step ( Figure 1 In step C), a silicon epitaxial layer 16 is formed on the modified layer 14 of the silicon wafer 10. The silicon epitaxial layer 16 becomes a device layer for manufacturing semiconductor elements such as BSI type CIS.

[0060] [Step 1]

[0061] Examples of the silicon wafer 10 include bulk single crystal silicon wafers without an epitaxial layer on their surfaces. Furthermore, carbon and / or nitrogen may be added to the silicon wafer to achieve higher gettering capability. Furthermore, any dopant may be added to the silicon wafer at a predetermined concentration to create a so-called n+ type, p+ type, n- type, or p- type substrate.

[0062] Alternatively, an epitaxial silicon wafer having a silicon epitaxial layer formed on the surface of a bulk single crystal silicon wafer may be used as the silicon wafer 10. The silicon epitaxial layer can be formed by CVD under conventional conditions. The thickness of the epitaxial layer is preferably within the range of 0.1 to 10 μm, more preferably within the range of 0.2 to 5 μm.

[0063] In the first step, the surface 10A of the silicon wafer 10 is irradiated with SiH x (x is one or more integers selected from 1 to 3) ions 12A and C2H y (y is one or more integers selected from 2 to 5) a beam of cluster ions 12 of ions 12B. The "cluster ions" in this specification are obtained by using an electron collision method to cause electrons to collide with gaseous molecules to dissociate the bonds of the gaseous molecules, thereby producing atomic aggregates of various atomic numbers, and generating fragments to ionize the atomic aggregates, and performing mass separation on the ionized atomic aggregates of various atomic numbers to extract ionized atomic aggregates of a specific mass number. That is, the "cluster ions" in this specification are clusters of multiple atoms that are aggregated into a mass and are given a positive or negative charge and ionized, and can be clearly distinguished from monoatomic ions such as carbon ions, or monomolecular ions such as carbon monoxide ions. The number of atoms constituting a cluster ion is generally about 5 to 100. As a cluster ion implantation device using this principle, for example, CLARIS (registered trademark) manufactured by Nissin Ion Instruments Co., Ltd. can be used.

[0064] When the silicon wafer 10 is irradiated with SiH x Ions 12A and C2H y When a beam of cluster ions 12B is irradiated, the silicon on the surface of the silicon wafer 10 is instantly heated to a high temperature of about 1350°C to 1400°C due to its irradiation energy and melted. Thereafter, the silicon is rapidly cooled, and the carbon, hydrogen, and silicon of the source cluster ions 12 are dissolved in the surface of the silicon wafer. That is, the so-called "modified layer" in this specification refers to a layer formed by dissolving at least one of the carbon, hydrogen, and silicon that are the constituent elements of the irradiated cluster ions in the intercrystalline position or substitution position of the crystal on the surface of the silicon wafer. Among them, the SiH x The Si of ions is difficult to distinguish from the Si that constitutes the silicon wafer. Therefore, in this specification, the "modified layer" is specifically defined as the following area: an area where the concentration of any element is detected to be higher than the background in the SIMS concentration distribution of carbon and hydrogen in the depth direction of the silicon wafer. In the stage after the injection of cluster ions and before the formation of the epitaxial layer, the surface portion approximately 500nm below the surface of the silicon wafer becomes the modified layer. In the stage after the epitaxial layer is formed, since carbon diffuses from the surface of the silicon wafer to the inside, the surface portion of about 2 to 4μm from the surface of the silicon wafer (the interface between the epitaxial layer and the silicon wafer) becomes the modified layer.

[0065] The details are described in the examples based on the experimental results. However, in this embodiment, it is important to use a x Ions 12A and C2H y Cluster ion 12 of ion 12B. x is one or more integers selected from 1 to 3, that is, SiH x Ions 12A include one or more of SiH ions, SiH2 ions, and SiH3 ions. y is one or more integers selected from 2 to 5, that is, C2H y Ions 12B include one or more of C2H2, C2H3, C2H4, and C2H5 ions. This ensures gettering capability in the subsequently obtained epitaxial silicon wafer 100 and suppresses carbon diffusion into the epitaxial layer during epitaxial growth and device formation processes. Consequently, the formation of carbon-induced point defects in the device formation region of epitaxial layer 16 can be suppressed.

[0066] Although not limiting the present invention, the inventors of the present invention consider the mechanism by which this effect can be obtained as follows. Since the mass number of silicon atoms is greater than that of carbon atoms, by irradiating SiH x ions, and introduces large damage (implantation defects) into the surface of the silicon wafer, which is believed to contribute to high gettering ability. x The ion implantation forms a relatively large implantation defect in the modified layer 14. y The implanted carbon ions gather at the implanted defects and further capture hydrogen there, thereby forming a defect region (EOR defect) capable of exhibiting a high gettering ability.

[0067] If the gaseous molecules that become the raw materials of cluster ions can simultaneously generate the above-mentioned SiH x (x is one or more integers selected from 1 to 3) ions and C2H y (y is one or more integers selected from 2 to 5) ions are not particularly limited, and examples thereof include diethylsilane (SiC4H 12 ), butylsilane (SiC4H 12 ), methylpropylsilane (SiC4H 12 ), pentylsilane (SiC5H 14 ), methylbutylsilane (SiC5H 14 ), ethylpropylsilane (SiC5H 14 ) etc. Among them, cluster ions of various sizes can be generated from these raw material gases. For example, Figure 2 As shown in Table 1, from diethylsilane (SiC4H 12) generates C2H2 ions, C2H3 ions, C2H4 ions and C2H5 ions as C2H in the range of mass number 26 to mass number 31. y ions, and generate SiH ions, SiH2 ions and SiH3 ions as SiH x ions. Therefore, as the raw material gas used in this embodiment, diethylsilane is most preferred. By extracting cluster ions (fragments) in the desired mass number range, a cluster ion beam of the desired ion species can be generated. For example, if fragments with mass numbers of 29 to 31 are extracted, a cluster ion beam containing SiH3 ions, SiH2 ions, and SiH ions as SiH can be generated. x ions and contains C2H5 ions as C2H y Cluster ion beam of ions.

[0068] The total dose of cluster ions can be adjusted by controlling the ion irradiation time as a device setting value. In this embodiment, the total dose is preferably set to SiH x Ion dosage and C2H y The dose of ions satisfies the following range.

[0069] It is important to put SiH x The ion dose was set to 1.5×10 14 ions / cm 2 The reason is that: at this dose less than 1.5×10 14 ions / cm 2 In the case of failure to obtain sufficient x Furthermore, from the viewpoint of more fully obtaining the effects of the present invention, the dose is preferably set to 3.0×10 14 ions / cm 2 On the other hand, if the dose is too high, the damage to the silicon wafer due to ion implantation becomes excessive, and defects are generated in the epitaxial layer after the epitaxial layer is formed. Therefore, the dose is preferably set to 1.0×10 15 ions / cm 2 the following.

[0070] C2H y The ion dose is preferably set to 1.0×10 14 ions / cm 2 As a result, the amount of carbon implanted can be reduced, and the diffusion of carbon into the epitaxial layer can be suppressed during epitaxial growth and device formation processes. From this point of view, the dose is more preferably set to 5.0×10 13 ions / cm 2 On the other hand, from the viewpoint of ensuring sufficient gettering ability, the dose is preferably set to 1.0×1013 ions / cm 2 above.

[0071] In addition, the total dose can be controlled as a device setting value. y Ion dose and SiH x The ion dose cannot be determined individually, so it is determined as follows. Specifically, the carbon concentration distribution in the depth direction from the surface of the silicon wafer after cluster ion irradiation is measured by SIMS measurement, and the amount of carbon implanted into the modified layer is determined based on this carbon concentration distribution. y The number of carbon atoms in the ion is 2, so the value obtained by dividing the implanted carbon amount obtained above by 2 can be regarded as "C2H y ion dose". And, "SiH x The “dose of ions” can be calculated by subtracting the C2H y ion dose. y Ion dose and SiH x The ratio of the ion dose to the total dose can be controlled in the ion implantation device by the resolution of the mass separation device for sorting ions, the mass number setting value of the implanted ions, the amount of the raw gas introduced, the energy of the electrons irradiated during ionization, and other conditions. As long as these conditions are not changed, the same ratio of cluster ions can be generated (refer to Figure 4 Comparative Example 2 and Invention Examples 1 to 3, Invention Example 5).

[0072] The acceleration voltage of the cluster ions affects the peak position of the concentration distribution in the depth direction of the constituent elements in the modified layer together with the ion species. In the present embodiment, the acceleration voltage of the cluster ions can be set to more than 0keV / ion and less than 200keV / ion, preferably set to less than 100keV / ion, and further preferably set to less than 80keV / ion. In addition, regarding the adjustment of the acceleration voltage, the two methods of (1) electrostatic acceleration and (2) high-frequency acceleration are generally used. As the former method, there is a method of arranging a plurality of electrodes at equal intervals, applying equal voltages between these electrodes, and making an equal accelerating electric field in the axial direction. As the latter method, there is a linear linear accelerator method in which ions are accelerated using high frequency while traveling in a straight line.

[0073] The cluster ion beam current value is not particularly limited and can be appropriately determined within the range of, for example, 50 to 5000 μA. The cluster ion beam current value can be adjusted by, for example, changing the decomposition conditions of the raw material gas in the ion source.

[0074] [Step 2]

[0075] The silicon epitaxial layer 16 can be formed under normal conditions. For example, hydrogen is used as a carrier gas, and source gases such as dichlorosilane and trichlorosilane are introduced into the chamber. The growth temperature also varies depending on the source gas used, but it can be epitaxially grown on the modified layer 14 of the silicon wafer 10 by the CVD method at a temperature in the range of approximately 1000°C to 1200°C. The silicon epitaxial layer 16 preferably has a thickness in the range of 1 to 15 μm. The reason is that when the thickness is less than 1 μm, there is a possibility that the resistivity of the silicon epitaxial layer 16 will change due to the diffusion of dopants from the silicon wafer 10, and when it exceeds 15 μm, there is a possibility that the spectral sensitivity characteristics of the CIS will be affected. Among them, in this embodiment, it is preferred that the thickness of the silicon epitaxial layer 16 is set to 4 μm or less. In this case, the effect of the present invention can be advantageously exerted.

[0076] The manufacturing method of the present embodiment described above makes it possible to manufacture an epitaxial silicon wafer that ensures gettering capability and suppresses carbon diffusion into the epitaxial layer during epitaxial growth and device formation processes.

[0077] Furthermore, after the first step and before the second step, the silicon wafer 10 may be subjected to a recovery heat treatment to restore its crystallinity. This recovery heat treatment may be performed by, for example, maintaining the silicon wafer 10 at a temperature of 900°C to 1100°C for a period of 10 minutes to 60 minutes in an atmosphere of nitrogen or argon. Furthermore, the recovery heat treatment may be performed using a rapid temperature ramp heat treatment apparatus other than the epitaxial apparatus, such as RTA (Rapid Thermal Annealing) or RTO (Rapid Thermal Oxidation).

[0078] (Epitaxial silicon wafer)

[0079] refer to Figure 1 An epitaxial silicon wafer 100 according to an embodiment of the present invention can be obtained by the above-mentioned manufacturing method, and comprises: a silicon wafer 10; a modified layer 14 formed on the surface of the silicon wafer 10 and containing at least one of carbon and hydrogen as a solid solution; and a silicon epitaxial layer 16 formed on the modified layer 14.

[0080] [SIMS distribution]

[0081] It is important that the amount of carbon distributed in the silicon epitaxial layer 16 and the modified layer 14 of the epitaxial silicon wafer 100 is 2.0×10 14 atoms / cm 2 As a result, the amount of carbon implanted can be reduced, and the diffusion of carbon into the epitaxial layer can be suppressed during epitaxial growth and device formation processes. From this point of view, the amount of carbon is more preferably set to 1.0×10 14atoms / cm 2 On the other hand, from the viewpoint of ensuring sufficient gettering ability, the carbon amount is preferably set to 2.0×10 13 atoms / cm 2 In addition, in the present invention, the "carbon content" can be obtained by measuring the carbon concentration distribution ( Figure 5 ), and integrate the range of the carbon concentration higher than the background from the surface of the epitaxial layer to the end of the modified layer (the position where the carbon concentration distribution becomes flat in the silicon wafer).

[0082] In this embodiment, for example, Figure 5 As shown in Example 6 of the invention, the carbon concentration profile of the silicon epitaxial layer and the modified layer in the depth direction of the SIMS has a gentle first peak that exists throughout the silicon epitaxial layer and the modified layer, and a steep second peak that protrudes from the first peak and exists near the interface between the modified layer and the epitaxial layer. In this embodiment, although the amount of carbon implanted is small, the carbon concentration profile having such a steep second peak is included. This allows for sufficient gettering capability. The peak concentration of the steep second peak in the carbon concentration profile is preferably 2.0×10 17 atoms / cm 3 More than 3.0×10 17 atoms / cm 3 above, preferably 1.0×10 18 atoms / cm 3 the following.

[0083] In this embodiment, for example, Figure 6 As shown in Example 6 of the present invention, in the SIMS hydrogen concentration distribution in the depth direction of the modified layer, there is a peak concentration of 1.0×10 16 atoms / cm 3 As described above, the hydrogen remaining in the modified layer diffuses into the epitaxial layer due to the heat treatment during the device formation process of forming a semiconductor device on the epitaxial layer, and it is expected that the defects in the epitaxial layer will be passivated. In this embodiment, the peak concentration of hydrogen is approximately 1.0×10 17 atoms / cm 3 the following.

[0084] [Cross-sectional TEM image]

[0085] In the defect evaluation of the modified layer based on the cross-sectional TEM image of the epitaxial silicon wafer 100, EOR defects with a maximum width of 50 to 250 nm were observed at a rate of 5.0×10 7 pieces / cm 2The defect area with a density above 1000 is speculated to be caused by SiH x Defects caused by ion implantation. That is, by having this feature, it is possible to exert sufficient doping ability despite a small amount of carbon implanted. In addition, in the present invention, "EOR (End of Range) defects" are a general term for defects in the form of {111} stacking faults, dislocation loops, {311} defects, etc. formed by atoms (in this description, silicon atoms in a silicon wafer) squeezed out of the crystal lattice by ion implanted elements and condensed at a position deeper than the implantation range (the peak position of the carbon concentration distribution based on SIMS) through heat treatment. Figure 8 As shown in FIG, the "maximum width" of the EOR defect refers to the maximum width of each EOR defect in the TEM image. In addition, when the carbon dose is high, the black dot-shaped defects caused by the carbon injection are formed at a position shallower than the injection range. As a result, in the present invention, since the amount of carbon injected is small, the black dot-shaped defects caused by the carbon injection are not visually observed in the cross-sectional TEM image. In addition, in this embodiment, the density of the EOR defects is approximately 1.0×10 15 pieces / cm 2 Below. In addition, in this specification, the so-called "cross-sectional TEM image" refers to an image obtained by cleaving the epitaxial silicon wafer 100 in the thickness direction and observing the cleaved cross section of the modified layer using TEM. And, in the present invention, the "EOR defect density" is calculated as follows. Figure 7 The TEM image of Invention Example 6 clearly shows that in the present invention, EOR defects are basically densely generated at the same depth position (specifically, a position slightly deeper than the carbon concentration peak position detected by SIMS measurement). Therefore, a TEM evaluation sample was cut out from the depth position of the carbon concentration peak observed during SIMS measurement so as to include the area where EOR defects occurred, and TEM observation was performed on the evaluation sample. Then, as shown in FIG. Figure 7 As shown in FIG, the density calculation region (i.e., defect region) is set to 300 nm in length (depth) so as to include EOR defects. The number of defects with a maximum width of 50 to 250 nm observed in this region is counted, and the number of defects is divided by the area of the region to obtain the EOR defect density (number / cm 2 ). In addition, Figure 7 In the example of FIG, the density calculation region is set to a region of 300 nm in length and 3 μm in width, but the width is not particularly limited.

[0086] (Method for Manufacturing Semiconductor Device)

[0087] A method for manufacturing a semiconductor device according to one embodiment of the present invention includes the steps of the method for manufacturing the epitaxial silicon wafer 100 described above, and a step of forming a semiconductor device on the silicon epitaxial layer 16. Furthermore, a method for manufacturing a semiconductor device according to another embodiment of the present invention includes a step of forming a semiconductor device on the silicon epitaxial layer 16 of the epitaxial silicon wafer 100 described above. These manufacturing methods can ensure gettering capability and suppress the formation of point defects caused by carbon in the device formation region of the epitaxial layer.

[0088] The semiconductor device formed on the silicon epitaxial layer 16 is not particularly limited, and examples thereof include MOSFET, DRAM, power transistor, and back-illuminated solid-state imaging device.

[0089] Example

[0090] [Preparation of silicon wafer]

[0091] An n-type silicon wafer (diameter: 300 mm, thickness: 775 μm, dopant type: phosphorus, resistivity: 10 Ω·cm) obtained from a CZ single crystal silicon ingot was prepared.

[0092] [Cluster ion irradiation]

[0093] As shown in Table 2, eight experiments (Inventive Examples 1 to 6 and Comparative Examples 1 to 4) were conducted under different cluster ion irradiation conditions.

[0094] (Inventive Examples 1 to 6 and Comparative Examples 1 and 2)

[0095] In Inventive Examples 1 to 6 and Comparative Examples 1 and 2, diethylsilane (SiC4H 12 ) as the raw material gas. The mass spectrum of diethylsilane is shown in Figure 2 And, will be with Figure 2 The ion species corresponding to mass numbers 26 to 31 in the mass spectrum shown are shown in Table 1. The peak of mass number 31 corresponds to SiH3 ions. The low peak of mass number 30 corresponds to SiH2 ions. The peak of mass number 29 corresponds to SiH ions and C2H5 ions. The peaks of mass number 28, mass number 27 and mass number 26 correspond to C2H4 ions, C2H3 ions and C2H2 ions, respectively. In this embodiment, a cluster ion generator (manufactured by Nissin Ion Instruments Co., Ltd., CLARIS (registered trademark)) was used. Figure 2 Among the various ion species corresponding to the mass spectrum shown, ion species in the range of mass number 29 to mass number 31 were extracted to obtain a cluster ion beam, and the surface of the silicon wafer was irradiated with this cluster ion beam at an acceleration voltage of 80 keV / ion. xions, mainly including SiH3 ions, further including trace amounts of SiH2 ions and SiH ions, further as C2H y ions, including C2H5 ions. In the cluster ion generating apparatus, the total dose of all ion species can be set, so in Inventive Examples 1 to 6 and Comparative Examples 1 and 2, the total dose shown in Table 2 is set as the apparatus setting value.

[0096] [Table 1]

[0097] Mass number <![CDATA[SiH x ]]> <![CDATA[C2H y ]]> 31 <![CDATA[SiH3]]> - 30 <![CDATA[SiH2]]> - 29 SiH <![CDATA[C2H5]]> 28 - <![CDATA[C2H4]]> 27 - <![CDATA[C2H3]]> 26 - <![CDATA[C2H2]]>

[0098] In Inventive Examples 1 to 6 and Comparative Examples 1 and 2, the dose of C2H5 ions and SiH x First, the concentration distribution of carbon and hydrogen in the depth direction from the surface of the silicon wafer was measured by SIMS measurement on the silicon wafer after cluster ion irradiation (before epitaxial growth). As a representative example, the concentration distribution of Example 6 is shown in FIG. Figure 3 In. Figure 3 In the , the hydrogen concentration is higher than the background within a range of approximately 150 nm from the surface of the silicon wafer, and the carbon concentration is higher than the background within a range of approximately 300 nm from the surface of the silicon wafer. Therefore, in Inventive Example 6, approximately 300 nm of the surface of the silicon wafer is designated as the modified layer. The amount of carbon injected into the modified layer is calculated by integrating the horizontal axis of this carbon concentration distribution from 30 nm to 300 nm. The amount of carbon injected into the modified layer is similarly calculated for Inventive Examples 1 to 5 and Comparative Examples 1 and 2. The results are shown in Table 2.

[0099] C2H y The number of carbon atoms in the ion is 2, so the value obtained by dividing the implanted carbon amount calculated above by 2 is taken as "C2H y The dose of C2H2O2 is shown in Table 2. And, the C2H2O2 dose is subtracted from the total dose. y The "SiH x The relationship between the total dose and the amount of carbon implanted obtained from Inventive Examples 1 to 6 and Comparative Examples 1 and 2 is shown in Table 2. Figure 4 In. Figure 4 As shown, it can be seen that: in Comparative Example 1 and Inventive Example 6, the amount of injected carbon is 10% of the total dose, in Comparative Example 2 and Inventive Examples 1 to 3, and Inventive Example 5, the amount of injected carbon is 7% of the total dose, and in Inventive Example 4, the amount of injected carbon is 4% of the total dose.

[0100] (Comparative Example 3, Comparative Example 4)

[0101] In Comparative Examples 3 and 4, cyclohexane was used as a raw material gas to generate and extract C3H5 cluster ions, and the surface of the silicon wafer was irradiated with an acceleration voltage of 80 keV / ion. The dose of C3H5 cluster ions is shown in the "Total Dose" column of Table 2. In Comparative Example 3, the dose was set so that the amount of carbon injected was the same as that of Inventive Example 6, and in Comparative Example 4, the dose was set so that the amount of carbon injected was 10 times that of Inventive Example 6. In Comparative Examples 3 and 4, the carbon injection amount was calculated based on the carbon concentration distribution after cluster ion irradiation in the same manner as Inventive Examples 1 to 6 and Comparative Examples 1 and 2, and is shown in Table 2.

[0102] [Epitaxial Growth]

[0103] Next, the cluster ion irradiated silicon wafer was transported to a single-wafer epitaxial growth apparatus (manufactured by Applied Materials, Inc.), and after a hydrogen bake treatment was performed at a temperature of 1120°C for 30 seconds in the apparatus, a silicon epitaxial layer (thickness: 5 μm, dopant type: phosphorus, resistivity: 10 Ω·cm) was epitaxially grown on the surface of the side of the silicon wafer on which the modified layer was formed by a CVD method at 1120°C using hydrogen as a carrier gas and trichlorosilane as a source gas, thereby obtaining an epitaxial silicon wafer.

[0104] [SIMS analysis]

[0105] The carbon and hydrogen concentration distributions in the depth direction from the surface of the silicon epitaxial layer were measured by SIMS measurement for the epitaxial silicon wafers of Inventive Examples 1 to Inventive Examples 6 and Comparative Examples 1 to Comparative Examples 4. The carbon concentration distributions of Inventive Example 6 and Comparative Examples 1, 2, and 4 are shown in FIG. Figure 5 The hydrogen concentration distributions of Inventive Example 4 and Comparative Examples 1 and 2 are shown in FIG. Figure 6 middle.

[0106] refer to Figure 5 In Inventive Example 6, the carbon concentration is higher than the background within a range of about 2.5 μm from the surface of the silicon wafer (i.e., about 2.5 μm from the interface between the silicon epitaxial layer and the silicon wafer). Figure 6 In Example 6 of the invention, the hydrogen concentration is higher than the background in a very small range of about 0.3 μm on the surface of the silicon wafer. Therefore, in Example 6 of the invention, about 2.5 μm on the surface of the silicon wafer is specifically designated as the modified layer. In addition, it is believed that the reason why the range of carbon concentration higher than the background becomes larger than that before epitaxial growth is that the injected carbon diffuses from the surface of the silicon wafer to the depth direction as the epitaxial growth progresses. And, from Figure 5 It is read that carbon also diffuses into the epitaxial layer as the epitaxial growth occurs. In addition, the amount of carbon distributed in the silicon epitaxial layer and the modified layer is taken as the range in which the carbon concentration is higher than the background under each condition (in the case of Inventive Example 6, Figure 5 The carbon amount was calculated by integrating the obtained carbon amount (from 3.0 μm to 7.5 μm on the horizontal axis) and shown in the "Carbon amount after epitaxy" column in Table 2.

[0107] Depend on Figure 5 It is clear that in any one of Inventive Example 6 and Comparative Examples 1, 2, and 4, a gentle first peak exists throughout the silicon epitaxial layer and the modified layer in the carbon concentration distribution. Moreover, in Inventive Example 6 and Comparative Example 4, a steep second peak appears near the interface between the modified layer and the epitaxial layer, protruding from the gentle first peak. Table 2 shows the presence or absence of the second peak of carbon and its peak concentration. It is believed that in Comparative Example 4, such a steep peak appears due to the large amount of carbon injected. Among them, in Inventive Example 6, such a steep peak appears despite a small amount of carbon injected. It is believed that the appearance of such a steep peak in Inventive Example 6 is caused by the injection of SiH x The impact of ions.

[0108] Depend on Figure 6 It is clear that in Inventive Example 6, the hydrogen concentration distribution has a peak concentration of 1.0×10 16 atoms / cm 3 Above the peak. Figure 6 It is not shown in the figure, but the same is true for Comparative Example 4. On the other hand, such a peak does not appear in Comparative Examples 1 and 2. It is believed that in Comparative Example 4, since the amount of carbon injected is large, carbon is locally present at that location, and hydrogen is also captured there. In Inventive Example 6, such a peak appears despite the small amount of carbon injected. It is believed that the appearance of such a peak in the Inventive Example is due to the injection of SiH x The impact of ions.

[0109] Inventive Examples 1 to 5 also have the same carbon concentration distribution and hydrogen concentration distribution as Inventive Example 6, and the peak concentration of the second peak, the carbon amount after epitaxy, and the presence or absence of a hydrogen peak are shown in Table 2. Comparative Example 3 also shows the peak concentration of the second peak, the carbon amount after epitaxy, and the presence or absence of a hydrogen peak in Table 2.

[0110] [Cross-sectional TEM observation]

[0111] TEM observation was performed on the cross-section of the modified layer (near the interface with the epitaxial layer) of the epitaxial wafers of Inventive Examples 1 to Inventive Examples 6 and Comparative Examples 1 to Comparative Examples 4. The TEM images obtained in Inventive Example 6 and Comparative Examples 1 and 2 are shown as representative. Figure 7 In the invention example 6, Figure 7 TEM images of different fields of view are shown in Figure 8In Invention Example 6, EOR defects with a maximum width of 50 to 250 nm were observed. The same was true for Invention Examples 1 to 5. It is speculated that this is due to SiH x Defects caused by ion implantation. Furthermore, in the TEM image of Comparative Example 4 (not shown), black dot-like defects with a diameter of approximately 5 nm were observed at a location shallower than the implantation range. Since a large amount of carbon was implanted in Comparative Example 4, these defects are believed to be caused by carbon implantation. Table 2 shows the presence or absence of black dot-like defects and the density of EOR defects for Inventive Examples 1 to 6 and Comparative Examples 1 to 4.

[0112] [Investigation based on SIMS distribution and cross-sectional TEM observation]

[0113] When SIMS distribution and cross-sectional TEM observation are considered together, it is speculated that the following phenomena occurred in Invention Examples 1 to 6. x The ion implantation forms relatively large implantation defects near the interface between the modified layer and the epitaxial layer. It is speculated that the implanted carbon originating from the C2H5 ions gathers at these implantation defects and further captures hydrogen there, thereby forming EOR defect regions that can exert high gettering ability.

[0114] [Evaluation of Carbon Diffusion Amount after Epitaxial Growth]

[0115] In Inventive Examples 1 to 6 and Comparative Examples 1 to 4, Figure 5 The carbon concentration profile shown was integrated from 4.0 μm to 4.9 μm to determine the amount of carbon diffusion from the modified layer into the epitaxial layer during epitaxial growth. The results are shown in Table 2. As is clear from Table 2, in Inventive Examples 1 to 6, the carbon implantation amount was reduced compared to Comparative Example 4, resulting in a reduced carbon diffusion amount compared to Comparative Example 4.

[0116] [Evaluation of Carbon Diffusion Amount after Simulated Heat Treatment of Devices]

[0117] Inventive Examples 1 to 6 and Comparative Examples 1 to 4, heat treatment was performed under device-simulating heat treatment conditions (1050°C, 2.5 hours, nitrogen atmosphere). The carbon concentration profile was then integrated from 0.2 μm to 4.9 μm to determine the amount of carbon diffusion from the modified layer into the epitaxial layer during the device-simulating heat treatment. The results are shown in Table 2. As is clear from Table 2, in Inventive Examples 1 to 6, the carbon implantation amount was reduced compared to Comparative Example 4, resulting in a reduced carbon diffusion amount.

[0118] [Evaluation of impurity gettering ability]

[0119] In Inventive Examples 1 to 6 and Comparative Examples 1 to 4, a Ni contamination liquid was used and the surface of the epitaxial layer of the epitaxial silicon wafer was forcibly contaminated by a spin coating contamination method. Subsequently, a heat treatment was performed at 900°C in a nitrogen environment for 60 minutes. Thereafter, SIMS measurement was performed on each epitaxial wafer, and the Ni concentration distribution in the depth direction of the wafer was measured to obtain the peak area. The larger the peak area, the more Ni can be captured, so it can be evaluated as having a high impurity absorption capacity. Therefore, the peak area is shown in Table 2 as the Ni capture amount. In addition, the same experiment was performed using a Cu contamination liquid, and the Cu capture amount was similarly obtained and shown in Table 2.

[0120] As is clear from Table 2, Inventive Example 6 exhibits a high gettering capability comparable to that of Comparative Example 4, in which the carbon implantation amount is 10 times that of the Inventive Example. Inventive Examples 1 to 5 also exhibit high gettering capabilities.

[0121] [Table 2]

[0122]

[0123] Industrial applicability

[0124] According to the method for manufacturing an epitaxial silicon wafer of the present invention, it is possible to manufacture an epitaxial silicon wafer that ensures gettering capability and suppresses diffusion of carbon into the epitaxial layer during epitaxial growth and device formation processes.

[0125] Description of Reference Numerals

[0126] 100-epitaxial silicon wafer, 10-silicon wafer, 10A-silicon wafer surface, 12-cluster ions, 12A-SiH x ion, 12B-C2H y ions, 14-modified layer, 16-silicon epitaxial layer.

Claims

1. A method for manufacturing an epitaxial silicon wafer, characterized in that include: In the modified layer forming step, the surface of the silicon wafer is irradiated with SiH x ions and C2H y ions, thereby forming a modified layer in which the constituent elements of the cluster ion beam are solid-dissolved on the surface layer of the silicon wafer, wherein x is one or more integers selected from 1 to 3, and y is one or more integers selected from 2 to 5; and forming a silicon epitaxial layer on the modified layer of the silicon wafer; The SiH x The ion dose was set to 1.5×10 14 ions / cm 2 above.

2. The method for manufacturing an epitaxial silicon wafer according to claim 1, wherein: The C2H y The ion dose was set to 1.0×10 14 ions / cm 2 the following.

3. The method for producing an epitaxial silicon wafer according to claim 1 or 2, wherein: The raw material gas of the cluster ion beam is diethylsilane.

4. The method for producing an epitaxial silicon wafer according to claim 1 or 2, wherein: In the cluster ion beam, x is 1, 2, and 3, and y is 5.

5. The method for producing an epitaxial silicon wafer according to claim 1 or 2, wherein: The thickness of the silicon epitaxial layer is less than 4 μm.

6. An epitaxial silicon wafer, characterized in that have: silicon wafers; a modified layer formed on a surface portion of the silicon wafer and containing a solid solution of at least one of carbon and hydrogen; and a silicon epitaxial layer formed on the modified layer, In the defect evaluation based on the cross-sectional TEM image of the modified layer, EOR defects with a maximum width of 50 to 250 nm were observed in the modified layer at a rate of 5.0×10 7 pieces / cm 2 Defective areas with a density above The amount of carbon distributed in the silicon epitaxial layer and the modified layer is 2.0×10 14 atoms / cm 2 the following, In the hydrogen concentration distribution of SIMS in the depth direction of the modified layer, the peak concentration was 1.0×10 16 atoms / cm 3 above.

7. A method for manufacturing a semiconductor device, comprising: The method for manufacturing an epitaxial silicon wafer according to any one of claims 1 to 5; and The process of forming a semiconductor device on the silicon epitaxial layer of the epitaxial silicon wafer. 8 . A method for manufacturing a semiconductor device, comprising the step of forming a semiconductor device on the silicon epitaxial layer of the epitaxial silicon wafer according to claim 6 .

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