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

Abstract

Provided is a method for producing an epitaxial silicon wafer having a high hydrogen-based passivation effect. This method for producing an epitaxial silicon wafer (100) is characterized by comprising: a first step for irradiating the surface of a silicon wafer (10) with a beam containing cluster ions of SiHx (x is an integer of 1-3) ions (12A) and C2Hy (y is an integer of 2-5) ions (12B), and forming a modified layer (14) on the surface layer portion of the silicon wafer (10); and a second step in which a silicon epitaxial layer (16) is formed on the modified layer (14), the total dose of the silicon epitaxial layer (16) being 6.00 * 1013-1.00 * 1015 ions / cm2 inclusive, the dose of C2Hy ions (12B) exceeding 1.00 * 1014 ions / cm2 inclusive and 3.00 * 1014 ions / cm2 inclusive, and the ratio of the number of implanted Si atoms to the number of implanted C atoms [Si / C] being 0.3-1.6 inclusive.

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 gettering sites in the silicon wafer to capture heavy metals. As one of these 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 functions 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 such as C3H5, whose constituent elements are carbon and hydrogen, thereby forming a modified layer in which the constituent elements of the cluster ions are solid-dissolved on the surface 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 whose constituent elements are carbon and hydrogen exhibits higher gettering ability than an ion-implanted region obtained by implanting simple carbon 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 composed of 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, under such high-dose cluster ion irradiation, 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] On the other hand, if the carbon dose is increased, the high concentration of carbon injected into the surface layer (modified layer) of the silicon wafer diffuses into the silicon epitaxial layer during epitaxial growth and device formation, forming point defects caused by carbon in the silicon epitaxial layer (i.e., the device formation region), which may affect the device characteristics. Therefore, Patent Document 3 describes a method for manufacturing an epitaxial silicon wafer, which irradiates the surface of the silicon wafer with a molten-carbon ion containing 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) to form a modified layer, and a silicon epitaxial layer is formed on the modified layer. y ion dose, reducing the carbon concentration in the modified layer, and by implanting SiH x ions, which can ensure the gettering ability.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: International Publication No. 2012 / 157162

[0011] Patent Document 2: International Publication No. 2015 / 104965

[0012] Patent Document 3: International Publication No. 2022 / 044562 Summary of the Invention

[0013] Technical problem to be solved by the invention

[0014] The hydrogen injected into the surface layer (modified layer) of the silicon wafer diffuses into the epitaxial layer through heat treatment during the device formation process of forming semiconductor devices on the epitaxial layer, passivating (inertizing) the interface state defects within the epitaxial layer, thereby contributing to improvements in device characteristics such as reduced leakage current. However, Patent Documents 1 to 3 only focus on the gettering ability of epitaxial silicon wafers and study the irradiation conditions of cluster ions, without studying the passivation effect based on hydrogen injected into the epitaxial silicon wafer. Therefore, the results of the present inventors' research have determined that there is room for improvement in the passivation effect based on hydrogen in epitaxial silicon wafers.

[0015] In view of the above problems, an object of the present invention is to provide an epitaxial silicon wafer having a high passivation effect by hydrogen and a method for producing the same.

[0016] Solutions for solving technical problems

[0017] In order to solve the above technical problems, the present inventors conducted in-depth research and obtained the following insights. First, when irradiating only cluster ions composed of carbon and hydrogen as in Patent Documents 1 and 2, if the carbon dose is reduced in order to suppress the formation of point defects caused by carbon in the silicon epitaxial layer, not only will the gettering ability not be ensured, but the amount of hydrogen remaining after the epitaxial layer is formed after being injected into the modified layer will also be reduced, and the passivation effect based on hydrogen will not be obtained. Therefore, at least as in Patent Document 3, irradiating with SiH x ions and C2H y Cluster ions of ions. However, even in this case, as described in Patent Document 3, if the carbon dose is excessively reduced, the amount of hydrogen remaining in the modified layer will decrease, and the passivation effect based on hydrogen cannot be fully obtained. Therefore, in order to obtain the passivation effect based on hydrogen, it is necessary to ensure a certain amount of carbon dose. Moreover, by adjusting the ratio of the number of irradiated Si atoms to the number of C atoms within a specified range, the passivation effect based on hydrogen can be fully obtained. Through this manufacturing method, an epitaxial silicon wafer having tiny defects composed of carbon aggregates and EOR (End of Range) defects caused by Si injection in the surface layer (modified layer) of the silicon wafer and a high passivation effect based on hydrogen is obtained.

[0018] That is, the gist of the present invention is as follows.

[0019] [1] A method for manufacturing an epitaxial silicon wafer, characterized by:

[0020] In the first step, the surface of the silicon wafer is irradiated with SiH x ions and C2H yA modified layer in which the constituent elements of the cluster ions are solid-dissolved is formed on the surface 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

[0021] The second step is to form a silicon epitaxial layer on the modified layer of the silicon wafer.

[0022] The total dose of the cluster ions irradiated in the first step is 6.00×10 13 ions / cm 2 Above and 1.00×10 15 ions / cm 2 the following,

[0023] The C2H irradiated in the first step y The ion dose exceeds 1.00×10 14 ions / cm 2 and 3.00×10 14 ions / cm 2 the following,

[0024] In the first step, the ratio of the number of Si atoms to the number of C atoms, that is, Si / C, is 0.3 or more and 1.6 or less.

[0025] [2] The method for manufacturing an epitaxial silicon wafer according to [1] above, wherein:

[0026] The C2H irradiated in the first step y The ion dose was 1.25×10 14 ions / cm 2 above.

[0027] [3] An epitaxial silicon wafer, characterized by having:

[0028] silicon wafers;

[0029] a modified layer formed on a surface portion of the silicon wafer and containing at least one of carbon and hydrogen as a solid solution; and

[0030] a silicon epitaxial layer formed on the modified layer,

[0031] In the defect evaluation based on the cross-sectional TEM image of the modified layer, micro defects consisting of carbon aggregates with a size of 3 nm or more and 10 nm or less were observed in the modified layer at a rate of 1.00×10 16 pieces / cm 2 Above and 8.00×10 16 pieces / cm 2The first defect region existed at a density of less than 2.00×10 7 pieces / cm 2 More than and less than 5.00×10 7 pieces / cm 2 The density of the second defect area exists,

[0032] The amount of carbon distributed in the silicon epitaxial layer and the modified layer exceeds 2.00×10 14 atoms / cm 2 and 6.00×10 14 atoms / cm 2 the following,

[0033] In the hydrogen concentration distribution of SIMS in the depth direction of the modified layer, the peak concentration was 5.00×10 16 atoms / cm 3 Above and 1.00×10 18 atoms / cm 3 the following.

[0034] [4] The epitaxial silicon wafer according to [3] above, wherein:

[0035] In the defect evaluation based on the cross-sectional TEM image of the modified layer, the EOR defect in the second defect region was 2.50×10 7 pieces / cm 2 Above and 4.50×10 7 pieces / cm 2 The following densities exist.

[0036] [5] The epitaxial silicon wafer according to [3] or [4] above, wherein:

[0037] The amount of carbon distributed in the silicon epitaxial layer and the modified layer is 2.50×10 14 atoms / cm 2 above.

[0038] [6] A method for manufacturing a semiconductor device, comprising:

[0039] The method for manufacturing an epitaxial silicon wafer as described in [1] or [2] above; and

[0040] The process of forming a semiconductor device on the silicon epitaxial layer of the epitaxial silicon wafer.

[0041] [7] A method for manufacturing a semiconductor device, comprising forming a semiconductor device on the silicon epitaxial layer of the epitaxial silicon wafer described in [3] or [4] above.

[0042] [8] A method for manufacturing a semiconductor device, comprising forming a semiconductor device on the silicon epitaxial layer of the epitaxial silicon wafer described in [5].

[0043] Effects of the Invention

[0044] According to the method for producing an epitaxial silicon wafer of the present invention, an epitaxial silicon wafer having a high passivation effect by hydrogen can be produced. Furthermore, the epitaxial silicon wafer of the present invention has a high passivation effect by hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic cross-sectional views illustrating a method for manufacturing an epitaxial silicon wafer 100 according to one embodiment of the present invention.

[0046] Figure 2 It represents the diethylsilane (SiC4H 12 ) Mass fragmentation chart (mass spectrum) of various cluster ions obtained.

[0047] Figure 3 These are graphs showing (a) carbon concentration distribution and (b) hydrogen concentration distribution based on SIMS after the epitaxial layer is formed in an example of the present invention.

[0048] Figure 4 These are cross-sectional TEM images (magnification: 200,000 times) of the modified layers of (a) Comparative Example No. 9, (b) Inventive Example No. 6, and (c) Inventive Example No. 4 in Examples of the present invention.

[0049] Figure 5 Equivalent circuit diagrams of the MOS structure during (a) low-frequency CV measurement and (b) high-frequency CV measurement using the QSCV (Quasi-Static Capacitance-Voltage) method.

[0050] Figure 6 is the interface state density D in the embodiment of the present invention. it A chart of the calculation results. DETAILED DESCRIPTION

[0051] 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.

[0052] (Method for Manufacturing Epitaxial Silicon Wafer)

[0053] like Figure 1As 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 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, thereby forming a modified layer 14 in which the constituent elements of the cluster ions 12 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.

[0054] [Step 1]

[0055] 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.

[0056] 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.

[0057] 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.

[0058] When the silicon wafer 10 is irradiated with SiH x Ions 12A and C2H y When a beam of cluster ions 12 of 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 derived from the 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.

[0059] The details are described in the examples based on the experimental results, but 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 xThe ions 12A include one or more selected from the group consisting of SiH ions, SiH2 ions, and SiH3 ions. y is one or more selected from integers of 2 to 5, i.e., C2H y The ions 12B include one or more ions selected from the group consisting of C 2 H 2 ions, C 2 H 3 ions, C 2 H 4 ions, and C 2 H 5 ions.

[0060] Although the present invention is limited, the present inventors believe that the use of a x Ions 12A and C2H y The effect of cluster ion 12 of ion 12B is as follows. First, by irradiating C2H y Ions 12B form micro defects composed of carbon aggregates in the modified layer. These micro defects become hydrogen capture sites. As a result, hydrogen remains in the modified layer at a high concentration even after the epitaxial layer is formed, achieving a hydrogen-based passivation effect. x The mass number of silicon atoms in ions 12A is greater than that of carbon atoms, so they introduce large damage (injection defects) into the surface layer of the silicon wafer and form relatively large injection defects (EOR defects) in the modified layer 14. It is also speculated that the C2H y The implanted carbon of the ions 12B gathers at the implantation defect and further captures hydrogen in the implantation defect, thereby forming a defect region capable of exerting a high passivation effect.

[0061] The gaseous molecules that become the raw materials of cluster ions can generate the above-mentioned SiH x ions and C2H y 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 ) in the mass number range of 26 to 31, as C2H y Ions generate C2H2 ions, C2H3 ions, C2H4 ions and C2H5 ions as SiH xThe ions generate SiH ions, SiH2 ions and SiH3 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, cluster ions of the desired ion species can be generated. For example, if fragments with mass numbers of 29 to 31 are extracted, SiH x ions include SiH3 ions, SiH2 ions and SiH ions and as C2H y ions and cluster ions containing C2H5 ions.

[0062] [Table 1]

[0063] 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]]>

[0064] The total dose of cluster ions can be adjusted by controlling the ion irradiation time as a device setting value. In this embodiment, if the total dose of cluster ions irradiated in the first step is less than 6.00×10 13 ions / cm 2 , no implantation defects that become hydrogen capture sites and heavy metal gettering sinks are formed, and therefore no hydrogen passivation effect and gettering ability are achieved. Therefore, the total dose of cluster ions irradiated in the first step is set to 6.00×10 13 ions / cm 2 Above, preferably 8.00×10 13 ions / cm 2 On the other hand, if the total dose of cluster ions irradiated in the first step exceeds 1.00×10 15 ions / cm 2 Therefore, the total dose of cluster ions irradiated in the first step is set to 1.00×10 15 ions / cm 2 Below, preferably 8.00×10 14 ions / cm 2 the following.

[0065] If the C2H y The ion dose is 1.00×10 14 ions / cm 2 Below, the passivation effect based on hydrogen cannot be fully obtained. Therefore, the CH2H y The ion dose was set to more than 1.00×10 14 ions / cm 2 , preferably 1.25×10 14 ions / cm 2On the other hand, if the C2H irradiated in the first step y The ion dose is 3.00×10 14 ions / cm 2 The following can suppress the diffusion of carbon into the epitaxial layer during epitaxial growth and device formation process. y The ion dose is 3.00×10 14 ions / cm 2 Below, preferably 2.50×10 14 ions / cm 2 the following.

[0066] Regarding SiH irradiation in the first step x ion dose, relative to C2H y That is, if the ratio of the number of Si atoms implanted to the number of C atoms [Si / C] is less than 0.3, the SiH-based x Therefore, [Si / C] is set to be 0.3 or more, preferably 0.5 or more. In order to meet the above conditions, the SiH irradiated in the first step x The ion dose is preferably 2.50×10 14 ions / cm 2 On the other hand, if [Si / C] exceeds 1.6, the passivation effect based on hydrogen is insufficient. Therefore, [Si / C] is set to be 1.6 or less, preferably 1.5 or less. In order to meet the above conditions, the SiH x The ion dose is preferably 4.00×10 14 ions / cm 2 the following.

[0067] 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 of the implanted carbon amount calculated above divided 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 SiHx The ratio of the ion dose to the total dose can be controlled in the ion implantation device based on the resolution of the mass separation device for sorting ions, the mass number setting value of the injected ions, the amount of raw gas introduced, the energy of the electrons irradiated during ionization, etc.

[0068] 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.

[0069] 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.

[0070] [Step 2]

[0071] 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 the thickness exceeds 15 μm, there is a possibility that the spectral sensitivity characteristics of the CIS will be affected.

[0072] The manufacturing method of the present embodiment described above can manufacture an epitaxial silicon wafer that secures gettering capability, suppresses carbon diffusion into the epitaxial layer during epitaxial growth and device formation processes, and has a high passivation effect by hydrogen.

[0073] 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).

[0074] (Epitaxial silicon wafer)

[0075] 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.

[0076] [Defect evaluation based on cross-sectional TEM images]

[0077] In the defect evaluation based on the cross-sectional TEM image of the modified layer in the epitaxial silicon wafer 100, micro defects consisting of carbon aggregates with a size (diameter) of 3 nm or more and 10 nm or less were observed in the modified layer. 16 pieces / cm 2 Above and 8.00×10 16 pieces / cm 2 The first defect region exists at a density below 2.00×10 7 pieces / cm 2 More than and less than 5.00×10 7 pieces / cm 2 In this specification, the term "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 a TEM.

[0078] A first defect region consisting of micro defects (diameters) of carbon aggregates with a size of 3 nm to 10 nm was observed in the modified layer of the epitaxial silicon wafer 100. This is because the micro defects in the form of black dots are formed by the carbon injection. If the density of micro defects is less than 1.00 × 10 16 pieces / cm 2Therefore, the density of micro defects composed of carbon aggregates is set to 1.00×10 16 pieces / cm 2 above, preferably 1.50×10 16 pieces / cm 2 On the other hand, if the density of micro defects exceeds 8.00×10 16 If the density of micro defects composed of carbon aggregates is 8.00×10 16 pieces / cm 2 Below, preferably 7.60×10 16 pieces / cm 2 the following.

[0079] Furthermore, a second defect region of EOR defects with a maximum width of 50 nm to 250 nm was observed in the modified layer of the epitaxial silicon wafer 100. It is speculated that the EOR defects are caused by SiH x Defects caused by ion implantation. That is, by having a second defect region, sufficient gettering ability can be exerted even with a small amount of carbon implanted. In addition, in the present invention, "EOR defects" are a general term for defects in the form of (111} stacking faults, dislocation loops, {311} defects, etc., which are formed by atoms (in this description, silicon atoms in a silicon wafer) squeezed out of the crystal lattice by the ion implanted element and condensed at a position deeper than the implantation range (the peak position of the carbon concentration distribution based on SIMS) due to heat treatment. The "maximum width" of the EOR defect refers to the maximum width of each EOR defect in the TEM image.

[0080] If the density of EOR defects is less than 2.00×10 7 pieces / cm 2 , the passivation effect based on hydrogen cannot be fully obtained. Therefore, the density of EOR defects is set to 2.00×10 7 pieces / cm 2 above, preferably 2.50×10 7 pieces / cm 2 On the other hand, if the density of EOR defects is 5.00×10 7 pieces / cm 2 The above will cause epitaxial defects during epitaxial growth and make it impossible to maintain the crystal integrity of the epitaxial layer. Therefore, the density of EOR defects is set to less than 5.00×10 7 pieces / cm 2 , preferably 4.50×10 7 pieces / cm 2 the following.

[0081] In the present invention, the "micro defect density" and "EOR defect density" are determined as follows. First, micro defects composed of carbon aggregates are confirmed at the same position as the carbon concentration peak position detected by SIMS measurement. Figure 4 As is clear from (b) and (c), EOR defects were observed at a slightly deeper position than the position where micro defects were densely generated. Therefore, a sample for TEM evaluation was cut out from the depth position around the carbon concentration peak observed during SIMS measurement so as to include the region where micro defects and EOR defects were generated, and TEM observation was performed on this evaluation sample. Figure 4 As shown in (b) and (c), the density calculation region (i.e., defect region) is set to 300 nm in length (depth) so as to include micro defects and EOR defects. The number of micro defects observed in this region is counted and the number of defects is divided by the area of ​​the region to obtain the micro defect density ( / cm 2 ). The EOR defect density ( / cm) was obtained by counting the number of EOR defects with a maximum width of 50 to 250 nm observed in the region and dividing the number of defects by the area of ​​the region. 2 ). In addition, Figure 4 In the examples (a) to (c), the density calculation region is set to a region of 300 nm in length and 200 nm in width, but the length in width is not particularly limited.

[0082] [SIMS distribution]

[0083] In the epitaxial silicon wafer 100, if the amount of carbon distributed in the silicon epitaxial layer 16 and the modified layer 14 is 2.00×10 14 atoms / cm 2 Therefore, the amount of carbon distributed in the silicon epitaxial layer 16 and the modified layer 14 is set to be greater than 2.00×10 14 atoms / cm 2 , preferably 2.50×10 14 atoms / cm 2 On the other hand, if the amount of carbon distributed in the silicon epitaxial layer 16 and the modified layer 14 exceeds 6.00×10 14 atoms / cm 2 , carbon diffuses into the epitaxial layer during epitaxial growth and device formation. Therefore, the amount of carbon distributed in the silicon epitaxial layer 16 and the modified layer 14 is set to 6.00×10 14 atoms / cm 2 Below, it is preferably set to 5.50×10 14 atoms / cm 2In the present invention, the "amount of carbon" can be determined as follows: With respect to an epitaxial silicon wafer, the carbon concentration distribution is measured from the surface of the silicon epitaxial layer toward the depth direction by SIMS measurement, and the distribution is integrated from the epitaxial layer surface to the end of the modified layer (the position where the carbon concentration distribution becomes flat in the silicon wafer).

[0084] In this embodiment, for example, Figure 3 As in the invention example shown in (a), the carbon concentration distribution of SIMS in the depth direction of the silicon epitaxial layer and the modified layer has a gentle first peak that exists throughout the silicon epitaxial layer and the modified layer, and a steep second peak that branches 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 distribution including such a steep second peak is included. As a result, sufficient gettering ability can be exerted. The peak concentration of the steep second peak in the carbon concentration distribution is preferably 5.00×10 17 atoms / cm 3 More than, preferably 2.00×10 19 atoms / cm 3 the following.

[0085] In this embodiment, for example, Figure 3 As in the invention example shown in (b), in the SIMS hydrogen concentration distribution in the depth direction of the modified layer, there is a peak concentration of 5.00×10 16 atoms / cm 3 In this peak, if the peak concentration of hydrogen is 5.00×10 16 atoms / cm 3 As a result, during the heat treatment of the device formation process of forming a semiconductor device on the epitaxial layer, the hydrogen remaining in the modified layer can fully diffuse into the epitaxial layer and passivate the defects in the epitaxial layer. Therefore, the peak concentration of hydrogen is set to 5.00×10 16 atoms / cm 3 Above, preferably 8.00×10 16 atoms / cm 3 On the other hand, in this embodiment, the peak concentration of hydrogen is approximately 1.00×10 18 atoms / cm 3 the following.

[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 ensure gettering capability while suppressing the formation of point defects caused by carbon in the device formation region of the epitaxial layer, thereby achieving a sufficient passivation effect due to hydrogen.

[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 element.

[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] Nine experiments (No. 1 to 9) were conducted under different cluster ion irradiation conditions as shown in Table 2. Furthermore, as a comparative example, an epitaxial silicon wafer (No. 10) was produced in which epitaxial growth was performed without cluster ion implantation.

[0094]

[0095] In No. 1 to 8, diethylsilane (SiC4H 12 ). 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 the highest 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 From the various ion species corresponding to the mass spectrum shown, ion species in the mass number range of 29 to 31 were extracted to obtain cluster ions, and the surface of the silicon wafer was irradiated with a beam of the cluster ions at an acceleration voltage of 80 keV / ion and a beam current of 800 μA. xions, mainly including SiH3 ions, further including trace amounts of SiH2 ions and SiH ions, and further, as C2H y ions, including C2H5 ions. In the cluster ion generating device, the total dose of all ion species can be set, so as shown in Table 2, the total dose of different levels in each example is set as the device setting value.

[0096] In No. 9, as shown in Table 2, only cyclohexane (C6H 12 ) extracted C2H3 cluster ions.

[0097] For each case after cluster ion irradiation, the amount of implanted carbon, C2H y Ion dose, SiH x Table 2 shows the cluster ion irradiation conditions for each example.

[0098] [Epitaxial Growth]

[0099] 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.

[0100] [SIMS analysis]

[0101] For No. 1 to 9, the carbon and hydrogen concentration distributions in the depth direction from the surface of the silicon epitaxial layer were measured by SIMS. As a representative example, the carbon concentration distribution in No. 5 is shown in FIG. Figure 3 (a), the hydrogen concentration distribution is shown in Figure 3 (b) In Figure 3 In (a), the carbon concentration distribution is higher than the background in the range of about 3.5 to 7.0 μm from the surface of the silicon epitaxial layer. Figure 3 In (b), the hydrogen concentration is higher than the background within a range of approximately 4.7 to 4.9 μm from the surface of the silicon epitaxial layer. Therefore, in No. 5, the thickness of the epitaxial layer formed on the silicon wafer is approximately 4.7 μm, and the depth of approximately 4.7 to 7.0 μm from the surface of the silicon epitaxial layer is determined to be the modified layer formed on the surface of the silicon wafer.

[0102] The amount of carbon after epitaxial growth of each example was determined by integrating the carbon concentration distribution from the surface of the epitaxial layer to the end of the modified layer (the position where the carbon concentration distribution becomes flat) and is shown in Table 2. Figure 3 As clearly shown in (a), the carbon concentration profile of No. 5 shows a gentle first peak throughout the silicon epitaxial layer and the modified layer. Furthermore, this gentle first peak branches off to form a steep second peak near the interface between the modified layer and the epitaxial layer. This second peak is also observed in Nos. 3 to 9.

[0103] And, from Figure 3 (b) It is clear that in the hydrogen concentration distribution of No. 5, a peak concentration of 1.0×10 16 atoms / cm 3 The above peaks are also confirmed in Nos. 3 to 9. The peak concentrations of these peaks are shown in Table 2 as "hydrogen peak concentrations."

[0104] [Cross-sectional TEM observation]

[0105] TEM observation was performed on the cross section of the modified layer (near the interface with the epitaxial layer) of the epitaxial silicon wafer of each example. Figure 4 The following are TEM images (magnification: 200,000 times) obtained in (a) No. 9, (b) No. 6, and (c) No. 4. In the TEM image of No. 9, tiny defects in the form of black dots with a diameter of about 5 nm were observed. This is known to be an aggregate of carbon and is composed of CH y On the other hand, in addition to micro defects, stacking faults (EOR defects) with a maximum width of 50 to 250 nm were observed in No. 4 and 6. This is presumably caused by SiH x Defects caused by ion implantation. In each case, the micro defect density and EOR defect density were determined by the method described above. Table 2 shows the micro defect density and EOR defect density for each case.

[0106] [Evaluation of passivation effect]

[0107] To evaluate the hydrogen passivation effect, samples were prepared by forming an oxide film (25 nm) on epitaxial silicon wafers of each example at 800°C for 4 hours and then subjected to a post-heat treatment at 700°C for 30 minutes. The samples after the post-heat treatment were measured by the QSCV method, and the interface state density D was calculated based on the obtained capacity values. it o

[0108] The following describes a method for calculating the interface state density based on the QSCV method. Figure 5The equivalent circuits of the MOS structure during (a) low-frequency CV measurement and (b) high-frequency CV measurement are shown in FIG. ox Indicates the gate oxide film capacity, C it represents the capacity of the interface state, C s represents the capacitance on the silicon substrate side and represents the sum of the depletion layer capacitance and the inversion layer capacitance. Based on this equivalent circuit, the minimum capacitance C of the MOS capacitor during low-frequency CV measurement is LF It is represented by the following formula (1). it It is represented by the following formula (2).

[0109] [Number 1]

[0110]

[0111] [Number 2]

[0112]

[0113] In addition, C in formula (2) ox C LF / (C ox -C LF ) is the substrate side capacitance obtained by measurement. The substrate side capacitance C of the ideal MOS structure s There are two methods to obtain the value based on theoretical formula and high-frequency CV measurement. In this experiment, C s Calculations were performed using the results of high-frequency CV measurements.

[0114] Figure 6 The D of No.3, 4, and 6 is shown in it Calculation results. According to D it The calculation results show that the D in the Midgap (mid-band gap) of each case is obtained. it Table 2 shows the D in the Midgap (band gap middle) of each example. it If the D in the Midgap (band gap) is it By comparing the examples, it can be seen that the D it It is lower than the comparative example. x ions and C2H y Cluster ions have a higher passivation effect than conventional hydrogen molecule ion implantation into epitaxial wafers.

[0115] [Investigation based on evaluation results]

[0116] Based on the evaluation results, it is speculated that the following phenomena occurred in the invention examples. y The implantation of ions creates tiny defects, which in turn cause SiH xThe EOR defects are formed by the injection of ions. As the amount of carbon injection decreases, the density of micro defects also decreases. Therefore, it is believed that by limiting the amount of carbon injection, the concentration of hydrogen captured by micro defects is also reduced. However, it is believed that the hydrogen capture capacity (adsorption reaction) of micro defects composed of carbon aggregates is also high. Therefore, it is believed that in the adsorption and desorption reaction of hydrogen, the density of micro defects is low and the amount of hydrogen recaptured is reduced. Moreover, by simultaneously injecting SiH x The ions increase the density of silicon point defects in the pores and interstitial spaces in the mixed molecular ion implantation area, which increases the diffusion rate of hydrogen. Therefore, it is believed that the reduction in the hydrogen recapture rate and the increase in the hydrogen diffusion rate increase the amount of hydrogen reaching the SiO2 / Si interface, thereby enhancing the hydrogen-based passivation effect.

[0117] Industrial applicability

[0118] According to the present invention, an epitaxial silicon wafer having a high passivation effect by hydrogen and a method for manufacturing the same can be provided.

[0119] Description of Reference Numerals

[0120] 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: have: In the first step, the surface of the silicon wafer is irradiated with SiH x ions and C2H y A modified layer in which the constituent elements of the cluster ions are solid-dissolved is formed on the surface 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 The second step is to form a silicon epitaxial layer on the modified layer of the silicon wafer. The total dose of the cluster ions irradiated in the first step is 6.00×10 13 ions / cm 2 Above and 1.00×10 15 ions / cm 2 the following, The C2H irradiated in the first step y The ion dose exceeds 1.00×10 14 ions / cm 2 and 3.00×10 14 ions / cm 2 the following, In the first step, the ratio of the number of Si atoms to the number of C atoms, that is, Si / C, is 0.3 or more and 1.6 or less.

2. The method for manufacturing an epitaxial silicon wafer according to claim 1, wherein: The C2H irradiated in the first step y The ion dose was 1.25×10 14 ions / cm 2 above.

3. An epitaxial silicon wafer, characterized in that have: silicon wafers; a modified layer formed on a surface portion of the silicon wafer and containing at least one of carbon and hydrogen as a solid solution; 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, micro defects consisting of carbon aggregates with a size of 3 nm or more and 10 nm or less were observed in the modified layer at a rate of 1.00×10 16 pieces / cm 2 Above and 8.00×10 16 pieces / cm 2 The first defect region existed at a density of less than 2.00×10 7 pieces / cm 2 More than and less than 5.00×10 7 pieces / cm 2 The density of the second defect area exists, The amount of carbon distributed in the silicon epitaxial layer and the modified layer exceeds 2.00×10 14 atoms / cm 2 and 6.00×10 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 5.00×10 16 atoms / cm 3 Above and 1.00×10 18 atoms / cm 3 the following.

4. The epitaxial silicon wafer according to claim 3, wherein In the defect evaluation based on the cross-sectional TEM image of the modified layer, the EOR defect in the second defect region was 2.50×10 7 pieces / cm 2 Above and 4.50×10 7 pieces / cm 2 The following densities exist.

5. The epitaxial silicon wafer according to claim 3 or 4, wherein The amount of carbon distributed in the silicon epitaxial layer and the modified layer is 2.50×10 14 atoms / cm 2 above.

6. A method for manufacturing a semiconductor device, comprising: The method for manufacturing an epitaxial silicon wafer according to claim 1 or 2; and The process of forming a semiconductor device on the silicon epitaxial layer of the epitaxial silicon wafer. 7 . A method for manufacturing a semiconductor device, comprising forming a semiconductor device on the silicon epitaxial layer of the epitaxial silicon wafer according to claim 3 . 8 . A method for manufacturing a semiconductor device, comprising forming a semiconductor device on the silicon epitaxial layer of the epitaxial silicon wafer according to claim 5 .

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