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

Abstract

Provided is a method for producing an epitaxial silicon wafer that has a high passivation effect due to hydrogen. This method for producing an epitaxial silicon wafer 100 is characterized by including: a first step of forming a modification layer 14 on a surface layer portion of a silicon wafer 10 by irradiating the surface of the silicon wafer 10 with a beam of cluster ions including ions 12A of SiHx (where x is an integer from 1 to 3) and ions 12B of C2Hy (where y is an integer from 2 to 5); and a second step of forming a silicon epitaxial layer 16 on the modification layer 14. A total dose amount is from 6.00×1013ions / cm2 to 1.00×1015ions / cm2; a dose amount of the C2Hy ions 12B is greater than 1.00×1014ions / cm2 and less than or equal to 3.00×1014ions / cm2; and a ratio [Si / C] of a number of Si atoms to a number of C atoms injected is from 0.3 to 1.6.

Description

[Technical Field]

[0001] The present invention relates to an epitaxial silicon wafer, a method for manufacturing the same, and a method for manufacturing a semiconductor device. [Background technology]

[0002] Epitaxial silicon wafers, which have a single-crystal silicon epitaxial layer formed on a silicon wafer, are used as device substrates for fabricating various semiconductor devices, such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), DRAMs (Dynamic Random Access Memories), power transistors, and BSI (Back Side Illumination) CISs (CMOS Image Sensors).

[0003] Contamination of the epitaxial layer with heavy metals increases the dark current of the CIS and causes defects known as white defects, degrading the characteristics of the semiconductor device. To prevent this heavy metal contamination, a technique is available for forming gettering sites in the silicon wafer to capture heavy metals. One known method involves implanting ions into the silicon wafer and then forming the epitaxial layer. In this method, the ion-implanted region functions as the gettering site.

[0004] Patent Documents 1 and 2 describe methods for producing epitaxial silicon wafers, which include the steps of irradiating the surface of a silicon wafer with cluster ions, such as C3H5, whose constituent elements are carbon and hydrogen, to form a modified layer in the surface layer of the silicon wafer, in which the constituent elements of the cluster ions are dissolved, and forming a silicon epitaxial layer on the modified layer of the silicon wafer.

[0005] Patent Document 1 shows that a modified layer formed by irradiating cluster ions whose constituent elements are carbon and hydrogen exhibits higher gettering ability than an ion-implanted region obtained by implanting carbon monomer ions.

[0006] Patent Document 2 describes, as an improved technique of the technique described in Patent Document 1, that the gettering ability of heavy metals can be improved by irradiating a modified layer with a high dose of cluster ions whose constituent elements are carbon and hydrogen so that a part of the modified layer in the thickness direction becomes an amorphous layer. Patent Document 2 also describes that when irradiating with cluster ions with such a high dose, minute black dot-like defects caused by implanted carbon or the like are visible in a cross-sectional TEM image of the modified layer after epitaxial growth, and that these black dot-like defects may contribute to improving the gettering ability.

[0007] On the other hand, if the carbon dose is increased, the high concentration of carbon implanted in the surface layer (modified layer) of the silicon wafer will diffuse into the silicon epitaxial layer during epitaxial growth and the device formation process, and carbon-induced point defects will be formed in the silicon epitaxial layer (i.e., the device formation region), which may affect the device characteristics. Therefore, Patent Document 3 describes the use of SiH x (x is one or more integers selected from 1 to 3) ion and CH y (y is one or more selected from integers of 2 to 5) to form a modified layer, and then a silicon epitaxial layer is formed on the modified layer. y By lowering the ion dose, the carbon concentration in the modified layer can be reduced while the SiH x It is described that the gettering ability can be ensured by ion implantation. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2012 / 157162 [Patent Document 2] International Publication No. 2015 / 104965 [Patent Document 3] International Publication No. 2022 / 044562 Summary of the Invention [Problem to be solved by the invention]

[0009] Hydrogen implanted into the surface layer (modified layer) of a silicon wafer diffuses into the epitaxial layer through heat treatment during the device formation process of forming a semiconductor device on the epitaxial layer, passivating (inactivating) interface state defects in the epitaxial layer and contributing to improved device characteristics such as reduced leakage current. However, Patent Documents 1 to 3 all focus only on the gettering ability of epitaxial silicon wafers and examine the irradiation conditions of cluster ions, but do not consider the passivation effect of hydrogen implanted into epitaxial silicon wafers. Therefore, the present inventors conducted research and found that there is room for improvement in the passivation effect of hydrogen in epitaxial silicon wafers.

[0010] 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 manufacturing the same. [Means for solving the problem]

[0011] In order to solve the above problems, the present inventors have conducted extensive research and have obtained the following findings. First, when irradiating only cluster ions whose constituent elements are carbon and hydrogen as in Patent Document 1 and Patent Document 2, if the carbon dose is reduced to suppress the formation of point defects caused by carbon in the silicon epitaxial layer, not only is it not possible to ensure gettering ability, but the amount of hydrogen that is implanted into the modified layer and remains after the formation of the epitaxial layer also decreases, making it impossible to obtain the passivation effect of hydrogen. Therefore, at least as in Patent Document 3, it is possible to irradiate SiH x ions and CH y The method involves irradiating the silicon wafer with cluster ions containing carbon ions. However, even in this case, if the carbon dose is reduced too much, as in Patent Document 3, the amount of hydrogen remaining in the modified layer decreases, and the passivation effect by hydrogen is not sufficiently achieved. Therefore, in order to obtain the passivation effect by hydrogen, it is necessary to ensure a certain carbon dose. Furthermore, by adjusting the ratio of the number of Si atoms to the number of C atoms irradiated within a predetermined range, the passivation effect by hydrogen can be sufficiently obtained. This manufacturing method has resulted in the production of epitaxial silicon wafers having microdefects consisting of carbon aggregates and EOR (End of Range) defects caused by Si implantation in the surface layer (modified layer) of the silicon wafer, and having a high passivation effect by hydrogen.

[0012] That is, the gist and configuration of the present invention are as follows.

[0013] [1] SiH x (x is one or more integers selected from 1 to 3) ion and CH y (y is one or more integers selected from 2 to 5) to form a modified layer in a surface layer portion of the silicon wafer, in which constituent elements of the cluster ions are dissolved; a second step of forming a silicon epitaxial layer on the modified layer of the silicon wafer; and The total dose of the cluster ions irradiated in the first step is 6.00×10 13 ions / cm 2 Over 1.00 x 10 15 ions / cm 2 is as follows: The C2H irradiated in the first step y The ion dose is 1.00×10 14 ions / cm 2 Over 3.00 x 10 14 ions / cm 2 is as follows: A method for producing an epitaxial silicon wafer, wherein the ratio of the number of Si atoms to the number of C atoms implanted in the first step [Si / C] is 0.3 or more and 1.6 or less.

[0014] [2] The C2H irradiated in the first step y The ion dose is 1.25×10 14 ions / cm 2 The above is the method for producing an epitaxial silicon wafer according to [1] above.

[0015] [3] a silicon wafer; a modified layer formed on a surface layer portion of the silicon wafer, the modified layer containing a solid solution of at least one of carbon and hydrogen; a silicon epitaxial layer formed on the modified layer; and In defect evaluation of the modified layer using a cross-sectional TEM image, the modified layer contained 1.00×10 microdefects consisting of carbon aggregates with a size of 3 nm or more and 10 nm or less. 16 pieces / cm 2 Over 8.00 x 10 16 pieces / cm 2 and the number of EOR defects having a maximum width of 50 nm or more and 250 nm or less is 2.00 × 10 7 pieces / cm 2 Over 5.00 x 10 7 pieces / cm 2 A second defect region is observed, which exists at a density of less than The amount of carbon distributed in the silicon epitaxial layer and the modified layer is 2.00×10 14 atoms / cm 2 Over 6.00 x 10 14 atoms / cm 2 is as follows: In the SIMS hydrogen concentration profile in the depth direction of the modified layer, the peak concentration is 5.00 × 10 16 atoms / cm 3 Over 1.00 x 10 18 atoms / cm 3 An epitaxial silicon wafer characterized by:

[0016] [4] In the defect evaluation of the modified layer using a cross-sectional TEM image, the EOR defects are 2.50 × 10 7 pieces / cm 2 Over 4.50 x 10 7 pieces / cm 2 The epitaxial silicon wafer according to [3] above, wherein the epitaxial silicon wafer is present at the following density:

[0017] [5] The amount of carbon distributed in the silicon epitaxial layer and the modified layer is 2.50 × 10 14 atoms / cm 2 The epitaxial silicon wafer according to the above [3] or [4].

[0018] [6] The method for producing an epitaxial silicon wafer according to [1] or [2] above; forming a semiconductor device in the silicon epitaxial layer of the epitaxial silicon wafer; A method for manufacturing a semiconductor device comprising:

[0019] [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 [3] or [4] above.

[0020] [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 [5] above. [Effects of the Invention]

[0021] According to the method for producing an epitaxial silicon wafer of the present invention, it is possible to produce an epitaxial silicon wafer having a high passivation effect by hydrogen. Furthermore, the epitaxial silicon wafer of the present invention has a high passivation effect by hydrogen. [Brief explanation of the drawings]

[0022] [Figure 1] 1A to 1C are schematic cross-sectional views illustrating a method for manufacturing an epitaxial silicon wafer 100 according to an embodiment of the present invention. [Figure 2] 1 is a graph (mass spectrum) showing mass fragments of various cluster ions obtained from diethylsilane (SiC4H12) as a source gas. [Figure 3] 4 is a graph showing (a) a carbon concentration profile and (b) a hydrogen concentration profile by SIMS after forming an epitaxial layer in an example of the present invention. [Figure 4] 1 shows cross-sectional TEM images (magnification: 200,000 times) of modified layers of (a) Comparative Example No. 9, (b) Inventive Example No. 6, and (c) Inventive Example No. 4 in the examples of the present invention. [Figure 5] This shows equivalent circuit diagrams of MOS structures during (a) low-frequency CV measurement and (b) high-frequency CV measurement in the QSCV (Quasi-Static Capacitance-Voltage) method. [Figure 6] 10 is a graph showing the calculation results of the interface state density Dit in an example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that, 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 in Fig. 1, which is different from the actual thickness ratio.

[0024] (Method for manufacturing epitaxial silicon wafers) In a method for producing an epitaxial silicon wafer 100 according to an embodiment of the present invention, as shown in FIG. 1, a silicon wafer 10 is formed on a surface 10A thereof by depositing SiH x (x is one or more integers selected from 1 to 3) y (y is one or more integers selected from 2 to 5) to form a modified layer 14 in the surface layer portion of the silicon wafer 10, in which the constituent elements of the cluster ions 12 are dissolved in a solid solution (steps A and B in FIG. 1), and a second step (step C in FIG. 1) to form a silicon epitaxial layer 16 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.

[0025] [1st step] The silicon wafer 10 may be, for example, a bulk single-crystal silicon wafer having no epitaxial layer on its surface. Carbon and / or nitrogen may be added to the silicon wafer to obtain higher gettering capability. Furthermore, any dopant may be added to the silicon wafer at a predetermined concentration to form a so-called n+ type or p+ type, or n- type or p- type substrate.

[0026] Alternatively, the silicon wafer 10 may be an epitaxial silicon wafer in which a silicon epitaxial layer is formed on the surface of a bulk single crystal silicon wafer. The silicon epitaxial layer can be formed by a CVD method under typical conditions. The thickness of the epitaxial layer is preferably in the range of 0.1 to 10 μm, and more preferably in the range of 0.2 to 5 μm.

[0027] In the first step, SiH x (x is one or more integers selected from 1 to 3) y The target is irradiated with a beam of cluster ions 12 containing ions 12B (where y is one or more integers selected from 2 to 5). The term "cluster ions" as used herein refers to a method of electron bombardment, in which electrons collide with gaseous molecules to dissociate the bonds of the gaseous molecules, thereby forming atomic aggregates of various atomic numbers, fragmenting the atomic aggregates to ionize them, and then subjecting the ionized atomic aggregates of various atomic numbers to mass separation to extract ionized atomic aggregates of specific mass numbers. In other words, the term "cluster ions" as used herein refers to clusters of atoms formed by aggregating multiple atoms, which are ionized by imparting a positive or negative charge. These cluster ions are clearly distinguished from monoatomic ions such as carbon ions and monomolecular ions such as carbon monoxide ions. The number of atoms constituting a cluster ion is typically about 5 to 100. An example of a cluster ion implantation device using this principle is CLARIS (registered trademark) manufactured by Nissin Ion Equipment Co., Ltd.

[0028] On the silicon wafer 10, SiH x Ion 12A and C2H y When a beam of cluster ions 12 containing ions 12B is irradiated onto the silicon wafer 10, the irradiation energy instantaneously raises the temperature of the silicon in the surface layer of the silicon wafer 10 to a high temperature of about 1350 to 1400°C, causing it to melt. The silicon is then rapidly cooled, and carbon, hydrogen, and silicon derived from the cluster ions 12 are solid-dissolved in the surface layer of the silicon wafer. In other words, the "modified layer" in this specification means a layer in which at least one of carbon, hydrogen, and silicon, which are constituent elements of the irradiated cluster ions, is solid-dissolved in the interstitial or substitutional positions of the crystals in the surface layer of the silicon wafer. However, SiH implanted in the surface layer of the silicon wafer xIt is difficult to distinguish ion-derived Si from the Si that constitutes the silicon wafer. Therefore, in this specification, the "modified layer" is specified as a region in the SIMS concentration profile of carbon and hydrogen in the depth direction of the silicon wafer, where the concentration of either element is detected to be higher than the background. After the implantation of cluster ions and before the formation of the epitaxial layer, the modified layer generally extends to a surface layer of 500 nm or less from the surface of the silicon wafer. After the formation of the epitaxial layer, carbon diffuses from the surface to the interior of the silicon wafer, so the modified layer extends to a surface layer of approximately 2 to 4 μm from the surface of the silicon wafer (the interface between the epitaxial layer and the silicon wafer).

[0029] Details will be explained based on experimental results in the examples, but in this embodiment, SiH x Ion 12A and C2H y It is important to use cluster ions 12 containing ions 12B. x is one or more selected from integers of 1 to 3, i.e., SiH x The ions 12A include one or more selected from the group consisting of SiH ions, SiH2 ions, and SiH3 ions, and y is one or more selected from integers of 2 to 5, i.e., C2H y The ions 12B include one or more selected from the group consisting of C2H2 ions, C2H3 ions, C2H4 ions, and C2H5 ions.

[0030] Without limiting the present invention, the present inventors have x Ion 12A and C2H y The effect of using cluster ions 12 containing ions 12B is considered as follows. y By irradiating the 12B ions, micro defects consisting of carbon aggregates are formed in the modified layer, and these micro defects become hydrogen trapping sites, so that a high concentration of hydrogen remains in the modified layer even after the epitaxial layer is formed, and a passivation effect by hydrogen is obtained. Furthermore, SiH xBy simultaneously irradiating the silicon wafer with the ions 12A, large damage (implantation defects) is introduced into the surface layer of the silicon wafer because silicon atoms have a larger mass number than carbon atoms, and relatively large implantation defects (EOR defects) are formed in the modified layer 14. Then, C2H y It is presumed that the implanted carbon originating from the 12B ions aggregates, and hydrogen is also captured in these implanted defects, forming defect regions that can exert a high passivation effect.

[0031] The gaseous molecules that serve as the source of cluster ions are the SiH x ions and CH y There is no particular limitation as long as it can simultaneously generate ions, but for example, diethylsilane (SiC4H 12 ), butylsilane (SiC4H 12 ), methylpropylsilane (SiC4H 12 ), pentylsilane (SiC5H 14 ), methylbutylsilane (SiC5H 14 ), ethylpropylsilane (SiC5H 14 However, cluster ions of various sizes can be generated from each of these source gases. For example, as shown in Figure 2 and Table 1, diethylsilane (SiC4H 12 ) in the mass range of 26 to 31, y C2H2, C2H3, C2H4, and C2H5 ions are generated, and SiH x The ions generated are SiH ions, SiH2 ions, and SiH3 ions. Therefore, diethylsilane is the most suitable source gas for use in this embodiment. By extracting cluster ions (fragments) within a desired mass number range from diethylsilane, cluster ions of a desired ion species can be generated. For example, by extracting fragments with a mass number of 29 to 31, SiH x Ions include SiH3 ions, SiH2 ions, and SiH ions, and C2H y Cluster ions containing C2H5 ions can be generated.

[0032] [Table 1]

[0033] 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 of cluster ions irradiated in the first step is 6.00×10 13 ions / cm 2 If the total dose of cluster ions irradiated in the first step is less than 6.00×10, implantation defects that serve as hydrogen trapping sites and gettering sinks for heavy metals are not formed, and therefore the hydrogen passivation effect and gettering ability are not obtained. 13 ions / cm 2 Above 8.00 x 10 13 ions / cm 2 On the other hand, the total dose of the cluster ions irradiated in the first step is preferably 1.00×10 15 ions / cm 2 If the dose exceeds 1.00×10, defects will occur in the epitaxial layer. Therefore, the total dose of cluster ions irradiated in the first step is set to 1.00×10 15 ions / cm 2 The following is true: 8.00 x 10 14 ions / cm 2 It is preferable that:

[0034] C2H irradiated in the first step y The ion dose is 1.00×10 14 ions / cm 2 If the concentration is less than this, the passivation effect of hydrogen cannot be obtained sufficiently. y The ion dose is 1.00 x 10 14 ions / cm 2 Over 1.25 x 10 14 ions / cm 2 On the other hand, the C2H irradiated in the first step yThe ion dose is 3.00 x 10 14 ions / cm 2 If the concentration is less than or equal to 100 ppm, the diffusion of carbon into the epitaxial layer during epitaxial growth and device formation processes can be suppressed. y The ion dose is 3.00 x 10 14 ions / cm 2 The following is true: 2.50 x 10 14 ions / cm 2 It is preferable that:

[0035] SiH irradiated in the first step x Regarding the ion dose, C2H y The ratio of the number of Si atoms to the number of C atoms to be implanted [Si / C] is set to a predetermined range. x Therefore, the [Si / C] is set to 0.3 or more, and preferably 0.5 or more. In order to satisfy the above, the SiH irradiated in the first step is x The ion dose is 2.50 × 10 14 ions / cm 2 On the other hand, if the [Si / C] is more than 1.6, the passivation effect of hydrogen becomes insufficient. Therefore, the [Si / C] is set to 1.6 or less, and preferably 1.5 or less. In order to satisfy the above, the SiH irradiated in the first step x The ion dose is 4.00 x 10 14 ions / cm 2 It is preferable that:

[0036] The total dose can be determined as the device setting value. y Ion dose and SiH xThe ion dose cannot be determined individually, so it is calculated as follows. That is, for the silicon wafer after irradiation with cluster ions, the carbon concentration profile in the depth direction from the surface of the silicon wafer is measured by SIMS, and the amount of carbon implanted into the modified layer is calculated from the carbon concentration profile. C2H y Since the number of carbon atoms in the ions is 2, the amount of implanted carbon calculated above divided by 2 is called "C2H y It can be considered as the "dose of SiH ions." x The "ion dose" is calculated by subtracting the total dose from the CH y The amount of CH ions in the total dose can be calculated by subtracting the amount of CH ions. y Ion dose and SiH x The ion dose ratio can be controlled in the ion implantation device by the resolution of the mass separator that selects ions, the mass number setting value of the ions to be implanted, the amount of raw material gas introduced, the energy of electrons irradiated during ionization, and the like.

[0037] The acceleration voltage of the cluster ions, together with the ion species, affects the peak position of the concentration profile of the constituent elements in the depth direction in the modified layer. In this embodiment, the acceleration voltage of the cluster ions can be set to more than 0 keV / ion and less than 200 keV / ion, preferably 100 keV / ion or less, and more preferably 80 keV / ion or less. Two methods are commonly used to adjust the acceleration voltage: (1) electrostatic acceleration and (2) radio-frequency acceleration. The former method involves arranging multiple electrodes at equal intervals and applying equal voltages between them to create a uniform axial acceleration field. The latter method involves the linear linac method, in which ions are accelerated using radio frequency while traveling in a straight line.

[0038] The beam current value of the cluster ions is not particularly limited, but can be appropriately determined, for example, within the range of 50 to 5000 μA. The beam current value of the cluster ions can be adjusted, for example, by changing the decomposition conditions of the raw material gas in the ion source.

[0039] [Second process] The silicon epitaxial layer 16 can be formed under typical conditions. For example, hydrogen is used as a carrier gas, and a source gas such as dichlorosilane or trichlorosilane is introduced into a chamber. The growth temperature varies depending on the source gas used, but epitaxial growth can be performed on the modified layer 14 of the silicon wafer 10 by CVD at a temperature generally in the range of 1000 to 1200°C. The silicon epitaxial layer 16 preferably has a thickness in the range of 1 to 15 μm. A thickness of less than 1 μm may change the resistivity of the silicon epitaxial layer 16 due to out-diffusion of dopants from the silicon wafer 10, while a thickness of more than 15 μm may affect the spectral sensitivity characteristics of the CIS.

[0040] By the manufacturing method of the present embodiment described above, it is possible to manufacture an epitaxial silicon wafer that has a high passivation effect by hydrogen, while ensuring gettering capability and suppressing the diffusion of carbon into the epitaxial layer during epitaxial growth and the device formation process.

[0041] After the first step and before the second step, the silicon wafer 10 may be subjected to a recovery heat treatment for recovering crystallinity. In this case, the recovery heat treatment may be performed by holding the silicon wafer 10 in an atmosphere of, for example, nitrogen gas or argon gas at a temperature of 900°C or higher and 1100°C or lower for 10 minutes or longer and 60 minutes or shorter. Alternatively, the recovery heat treatment may be performed using a rapid temperature increase / decrease heat treatment device, such as RTA (Rapid Thermal Annealing) or RTO (Rapid Thermal Oxidation), which is separate from the epitaxial device.

[0042] (epitaxial silicon wafer) Referring to FIG. 1 , an epitaxial silicon wafer 100 according to one embodiment of the present invention is obtained by the above-described manufacturing method, and comprises a silicon wafer 10, a modified layer 14 formed in a surface layer portion of the silicon wafer 10 and containing a solid solution of at least one of carbon and hydrogen, and a silicon epitaxial layer 16 formed on the modified layer 14.

[0043] [Defect evaluation using cross-sectional TEM images] In the epitaxial silicon wafer 100, defect evaluation using a cross-sectional TEM image of the modified layer revealed that the modified layer contained 1.00×10 micro-defects consisting of carbon aggregates with a size (diameter) of 3 nm or more and 10 nm or less. 16 pieces / cm 2 Over 8.00 x 10 16 pieces / cm 2 and the number of EOR defects having a maximum width of 50 nm or more and 250 nm or less is 2.00 × 10 7 pieces / cm 2 Over 5.00 x 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 cleavage cross section of the modified layer using a TEM.

[0044] In the modified layer of the epitaxial silicon wafer 100, a first defect region is observed, in which micro-defects consisting of carbon aggregates with a size (diameter) of 3 nm to 10 nm are present. This is because the implanted carbon forms black dot-like micro-defects. The density of the micro-defects is 1.00×10 16 pieces / cm 2 If the density is less than 1.00×10, the passivation effect of hydrogen is not sufficient. 16 pieces / cm 2 or more, 1.50 x 10 16 pieces / cm 2 On the other hand, the density of micro defects is preferably 8.00×1016 If the density of micro defects exceeds 8.00 × 10, the density of carbon atoms diffused from the defects increases during heat treatment of the device, affecting the electrical characteristics of the device. 16 pieces / cm 2 The following is true: 7.60 x 10 16 pieces / cm 2 It is preferable that:

[0045] Furthermore, a second defect region in which EOR defects with a maximum width of 50 nm or more and 250 nm or less exist is observed in the modified layer of the epitaxial silicon wafer 100. The EOR defects are formed by the SiH x These defects are presumed to be defects resulting from ion implantation. That is, by having the second defect region, sufficient gettering ability can be exhibited despite the small amount of implanted carbon. In the present invention, "EOR defects" is a general term for defects in the form of stacking faults in the {111} direction, dislocation loops, {311} defects, etc., which are formed when atoms (in this invention, silicon atoms in a silicon wafer) pushed out of the crystal lattice by ion-implanted elements aggregate at a position deeper than the implantation range (the peak position of the carbon concentration profile measured by SIMS) due to heat treatment. The "maximum width" of an EOR defect refers to the maximum width of each EOR defect in a TEM image.

[0046] The density of EOR defects is 2.00×10 7 pieces / cm 2 If the hydrogen concentration is less than 2.00×10, the passivation effect by hydrogen is not sufficient. Therefore, the density of EOR defects is 2.00×10 7 pieces / cm 2 or more, 2.50 x 10 7 pieces / cm 2 On the other hand, the density of EOR defects is preferably 5.00×10 7 pieces / cm 2 If the density is more than 5.00×10, it will cause epitaxial defects during epitaxial growth, and the crystalline perfection of the epitaxial layer will not be maintained. Therefore, the density of EOR defects is 5.00×10 7pieces / cm 2 Less than 4.50 x 10 7 pieces / cm 2 It is preferable that:

[0047] In the present invention, the "microdefect density" and "EOR defect density" are determined as follows. First, microdefects consisting of carbon aggregates are confirmed at the same position as the carbon concentration peak position detected by SIMS measurement. Furthermore, as is clear from FIGS. 4(b) and (c), EOR defects are confirmed at a position slightly deeper than the position where microdefects occur densely. Therefore, a sample for TEM evaluation is cut out from around the depth position of the carbon concentration peak observed in SIMS measurement so as to include the region where microdefects and EOR defects occur, and this evaluation sample is observed by TEM. Then, as shown in FIGS. 4(b) and (c), a density calculation area (i.e., defect area) is set to a vertical length (depth) of 300 nm so as to include the microdefects and EOR defects. The number of microdefects observed in that area is counted, and the number of defects is divided by the area of ​​that area to calculate the microdefect density ( / cm 2 Furthermore, the number of EOR defects with a maximum width of 50 to 250 nm observed in the area is counted, and the number of defects is divided by the area of ​​the area to determine the EOR defect density ( / cm 2 4(a) to 4(c), the density calculation area is set to a region of 300 nm length×200 nm width, but the width is not particularly limited.

[0048] [SIMS profile] In the epitaxial silicon wafer 100, the amount of carbon distributed in the silicon epitaxial layer 16 and the modified layer 14 is 2.00 × 10 14 atoms / cm 2 If the amount of carbon in the silicon epitaxial layer 16 and the modified layer 14 is less than 2.00×10, the passivation effect of hydrogen is not sufficiently obtained. 14 atoms / cm 2 Over 2.50 x 10 14 atoms / cm 2On the other hand, it is preferable that the amount of carbon distributed in the silicon epitaxial layer 16 and the modified layer 14 is 6.00×10 or more. 14 atoms / cm 2 If the concentration is greater than 6.00×10, carbon diffuses into the epitaxial layer during epitaxial growth and device formation processes. Therefore, the amount of carbon distributed in the silicon epitaxial layer 16 and the modified layer 14 is 6.00×10 14 atoms / cm 2 The following is true: 5.50 x 10 14 atoms / cm 2 In the present invention, the "amount of carbon" can be determined by measuring the carbon concentration profile of an epitaxial silicon wafer from the surface of the silicon epitaxial layer in the depth direction by SIMS measurement, and integrating the profile from the surface of the epitaxial layer to the end of the modified layer (the position in the silicon wafer where the carbon concentration profile becomes flat).

[0049] In this embodiment, as in the example of the invention shown in Figure 3(a), the carbon concentration profile of SIMS in the depth direction of the silicon epitaxial layer and the modified layer has a gentle first peak that exists across the silicon epitaxial layer and the modified layer, and a steep second peak that branches off from this first peak and exists at a position near the interface between the modified layer and the epitaxial layer. In this embodiment, even though the amount of injected carbon is small, the carbon concentration profile has such a steep second peak. This makes it possible to demonstrate sufficient gettering ability. The peak concentration of the steep second peak in the carbon concentration profile is 5.00 x 10 17 atoms / cm 3 It is preferable that the value is equal to or greater than 2.00×10 19 atoms / cm 3 It is preferable that:

[0050] In this embodiment, as shown in FIG. 3B, for example, in the hydrogen concentration profile of the modified layer in the depth direction by SIMS, the peak concentration is 5.00×10 in the modified layer (at a position near the interface with the epitaxial layer). 16 atoms / cm 3 In this peak, the hydrogen peak concentration is 5.00 × 10 16 atoms / cm 3 If this is the case, the hydrogen remaining in the modified layer will be sufficiently diffused into the epitaxial layer during the heat treatment in the device formation process for forming a semiconductor device on the epitaxial layer, and defects in the epitaxial layer will be passivated. Therefore, the peak concentration of hydrogen will be 5.00 × 10 16 atoms / cm 3 Above 8.00 x 10 16 atoms / cm 3 On the other hand, in this embodiment, the peak concentration of hydrogen is preferably about 1.00×10 18 atoms / cm 3 The following is the result.

[0051] (Method of manufacturing semiconductor devices) 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 in 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 in the silicon epitaxial layer 16 of the epitaxial silicon wafer 100. These manufacturing methods can suppress the formation of point defects caused by carbon in the device formation region of the epitaxial layer while ensuring gettering capability, and can obtain a sufficient passivation effect by hydrogen.

[0052] The semiconductor device formed on the silicon epitaxial layer 16 is not particularly limited, and examples thereof include MOSFETs, DRAMs, power transistors, and backside illuminated solid-state imaging devices. [Example]

[0053] [Silicon wafer preparation] 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.

[0054] [Cluster ion irradiation] Nine experiments (Nos. 1 to 9) were carried out under different conditions for cluster ion irradiation, as shown in Table 2. Furthermore, as a comparative example, an epitaxial silicon wafer (No. 10) was produced by epitaxial growth without implanting cluster ions.

[0055] [Table 2]

[0056] In Nos. 1 to 8, diethylsilane (SiC4H 12 ) was used. Figure 2 shows the mass spectrum of diethylsilane. Table 1 shows the ion species corresponding to mass numbers 26 to 31 in the mass spectrum shown in Figure 2. The peak at mass number 31 corresponds to SiH3 ions. The lower peak at mass number 30 corresponds to SiH2 ions. The highest peak at mass number 29 corresponds to SiH ions and C2H5 ions. The peaks at mass numbers 28, 27, and 26 correspond to C2H4 ions, C2H3 ions, and C2H2 ions, respectively. In this example, a cluster ion generator (manufactured by Nissin Ion Equipment Co., Ltd., CLARIS (registered trademark)) was used to extract ion species in the range of mass numbers 29 to 31 from the various ion species corresponding to the mass spectrum shown in Figure 2, to obtain cluster ions, and a beam of these cluster ions was irradiated onto the surface of a silicon wafer at an acceleration voltage of 80 keV / ion and a beam current value of 800 μA. The cluster ions were SiH x The ions mainly contain SiH3 ions, with trace amounts of SiH2 ions and SiH ions, and also C2H yThe ions include C2H5 ions. In the cluster ion generator, the total dose of all ion species can be set, so different levels of total dose were set as the device setting values ​​in each example, as shown in Table 2.

[0057] In No. 9, cyclohexane (CH) was used as the raw material gas as shown in Table 2. 12 Only C2H3 cluster ions extracted from the ion beam were injected.

[0058] For each example after irradiation with cluster ions, the amount of implanted carbon, C2H y Ion dose, SiH x The ion dose was calculated. Table 2 shows the cluster ion irradiation conditions for each example.

[0059] [Epitaxial growth] Next, the silicon wafer after cluster ion irradiation was transferred into a single-wafer epitaxial growth system (manufactured by Applied Materials, Inc.) and subjected to a hydrogen bake treatment at 1120°C for 30 seconds. After that, a silicon epitaxial layer (thickness: 5 μm, dopant type: phosphorus, resistivity: 10 Ω·cm) was epitaxially grown on the surface of the silicon wafer on which the modified layer had been formed by CVD at 1120°C using hydrogen as the carrier gas and trichlorosilane as the source gas, thereby obtaining an epitaxial silicon wafer.

[0060] [SIMS analysis] For Nos. 1 to 9, the carbon and hydrogen concentration profiles in the depth direction from the surface of the silicon epitaxial layer were measured by SIMS. As a representative example, the carbon concentration profile for No. 5 is shown in Figure 3(a) and the hydrogen concentration profile in Figure 3(b). In Figure 3(a), the carbon concentration profile was higher than the background in the range of approximately 3.5 to 7.0 μm from the surface of the silicon epitaxial layer. On the other hand, in Figure 3(b), the hydrogen concentration profile was higher than the background in the range of approximately 4.7 to 4.9 μm from the surface of the silicon epitaxial layer. Therefore, for No. 5, the thickness of the epitaxial layer formed on the silicon wafer was approximately 4.7 μm, and the range of approximately 4.7 to 7.0 μm in depth from the surface of the silicon epitaxial layer was identified as a modified layer formed in the surface layer of the silicon wafer.

[0061] The amount of carbon after epitaxial growth for each example was determined by integrating the carbon concentration profile from the surface of the epitaxial layer to the end of the modified layer (the position where the carbon concentration profile becomes flat), and is shown in Table 2. As is clear from Figure 3(a), in the carbon concentration profile of No. 5, a gentle first peak exists across the silicon epitaxial layer and the modified layer. Furthermore, a steep second peak branched off from this gentle first peak and appeared at a position near the interface between the modified layer and the epitaxial layer. Such a second peak was also confirmed in Nos. 3 to 9.

[0062] As is clear from Fig. 3(b), in the hydrogen concentration profile of No. 5, the peak concentration was 1.0 × 10 near the interface between the reformed layer and the epitaxial layer. 16 atoms / cm 3 The above peaks appeared. Such peaks were also confirmed in Nos. 3 to 9. The peak concentrations of these peaks are shown in Table 2 as "hydrogen peak concentrations."

[0063] [Cross-sectional TEM observation] The cross section of the modified layer (near the interface with the epitaxial layer) of each epitaxial silicon wafer was observed by TEM. Figure 4 shows TEM images (magnification: 200,000 times) obtained for (a) No. 9, (b) No. 6, and (c) No. 4. In the TEM image of No. 9, black dot-like micro-defects with a diameter of about 5 nm were observed. These were aggregates of carbon, and were characterized by the C2H y It is known that these defects are caused by ion implantation. On the other hand, in Nos. 4 and 6, in addition to micro-defects, stacking faults (EOR defects) with a maximum width of 50 to 250 nm were observed. This is due to the SiH x These defects are presumed to be caused by ion implantation. For each example, the microdefect density and EOR defect density were determined using the method described above. Table 2 shows the microdefect density and EOR defect density for each example.

[0064] [Evaluation of passivation effect] To evaluate the passivation effect of hydrogen, an oxide film was formed on each epitaxial silicon wafer at 800°C for 4 hours (25 nm), and then an additional heat treatment was performed at 700°C for 30 minutes to prepare samples. The samples after the additional heat treatment were measured using the QSCV method, and the interface state density D was calculated from the obtained capacitance value. it was calculated.

[0065] The method for calculating the interface state density using the QSCV method is explained below. Figure 5 shows the equivalent circuits of the MOS structure during (a) low-frequency CV measurement and (b) high-frequency CV measurement. ox is the gate oxide capacitance, C it is the capacitance of the interface state, C s is the capacitance on the silicon substrate side and represents the sum of the depletion layer capacitance and the inversion layer capacitance. From this equivalent circuit, the minimum capacitance C of the MOS capacitor during low-frequency CV measurement is LF is expressed by the following equation (1). Furthermore, the interface state density D it is expressed by the following equation (2).

number

number

[0066] In addition, C in equation (2) ox C LF / (C ox -C LF ) is the measured substrate capacitance. The substrate capacitance C of an ideal MOS structure s There are two ways to calculate C: either from a theoretical formula or from high frequency CV measurements. s was calculated using the results of high-frequency CV measurements.

[0067] Figure 6 shows No. 3, 4, and 6 D it The calculation results are shown below. it From the calculation results, D in the midgap of each example it The value of D at the midgap of each example is shown in Table 2. it The value of D at midgap is shown. it When comparing the results of each example, the D it It can be seen that the value is lower than that of the comparative example. x ions and CH y It can be seen that implanting cluster ions containing hydrogen ions provides a higher passivation effect than conventional epi-wafers implanted with hydrogen molecule ions.

[0068] [Considerations from the evaluation results] Considering the evaluation results, it is assumed that the following phenomenon occurred in the invention example. C2H y Micro-defects are formed due to ion implantation, and further SiH x EOR defects are formed due to the implantation of ions. As the carbon implantation amount decreases, the density of micro-defects also decreases, so it is thought that limiting the carbon implantation amount will also reduce the concentration of hydrogen trapped by micro-defects. However, since micro-defects consisting of carbon aggregates are thought to have a high hydrogen trapping ability (adsorption reaction), it is thought that the amount of hydrogen re-trapped in the hydrogen adsorption / desorption reaction will be reduced due to the low micro-defect density. Furthermore, SiH xThe simultaneous implantation of ions increases the density of point defects (vacancies and interstitial silicon) in the mixed molecular ion implanted region, which increases the hydrogen diffusion rate. As a result, the hydrogen recapture rate decreases and the hydrogen diffusion rate increases, which is thought to increase the amount of hydrogen that reaches the SiO2 / Si interface, leading to an improved passivation effect by hydrogen. [Industrial Applicability]

[0069] According to the present invention, it is possible to provide an epitaxial silicon wafer having a high passivation effect by hydrogen and a method for manufacturing the same. [Explanation of symbols]

[0070] 100 epitaxial silicon wafers 10 Silicon wafers 10A Silicon wafer surface 12 Cluster ions 12A SiH x ion 12B C2H y ion 14 Modified layer 16 Silicon epitaxial layer

Claims

1. On the surface of the silicon wafer, SiH ｘ (x is one or more selected from integers of 1 to 3) and C ２ H ｙ (y is one or more ions selected from integers of 2 to 5) to form a modified layer in a surface layer portion of the silicon wafer, in which constituent elements of the cluster ions are dissolved; a second step of forming a silicon epitaxial layer on the modified layer of the silicon wafer; and The total dose of the cluster ions irradiated in the first step is 6.00×10 １３ ions / cm ２ Above 1.00 x 10 １５ ions / cm ２ is as follows: The C irradiated in the first step ２ H ｙ The ion dose is 1.00×10 １４ ions / cm ２ Over 3.00 x 10 １４ ions / cm ２ is as follows: a ratio of the number of Si atoms to the number of C atoms implanted in the first step, [Si / C], of 0.3 to 1.6;

2. The C irradiated in the first step ２ H ｙ The ion dose is 1.25×10 １４ ions / cm ２ The method for producing an epitaxial silicon wafer according to claim 1 .

3. A silicon wafer; a modified layer formed on a surface layer portion of the silicon wafer, the modified layer containing a solid solution of at least one of carbon and hydrogen; a silicon epitaxial layer formed on the modified layer; and In defect evaluation of the modified layer using a cross-sectional TEM image, the modified layer had 1.00×10 microdefects consisting of carbon aggregates with a size of 3 nm or more and 10 nm or less. １６ pieces / cm ２ Above 8.00 x 10 １６ pieces / cm ２ and the number of EOR defects having a maximum width of 50 nm or more and 250 nm or less is 2.00×10 ７ pieces / cm ２ Above 5.00 x 10 ７ pieces / cm ２ A second defect region is observed to be present at a density of less than The amount of carbon distributed in the silicon epitaxial layer and the modified layer is 2.00×10 １４ atoms / cm ２ Over 6.00 x 10 １４ atoms / cm ２ is as follows: In the SIMS hydrogen concentration profile in the depth direction of the modified layer, the peak concentration is 5.00×10 １６ atoms / cm ３ Above 1.00 x 10 １８ atoms / cm ３ An epitaxial silicon wafer characterized by:

4. In the defect evaluation of the modified layer using a cross-sectional TEM image, the EOR defects were 2.50×10 ７ pieces / cm ２ The above is 4.50 x 10 ７ pieces / cm ２ 4. The epitaxial silicon wafer of claim 3, wherein the epitaxial silicon wafer is present at a density of:

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

6. The method for producing an epitaxial silicon wafer according to claim 1 or 2; forming a semiconductor device in the silicon epitaxial layer of the epitaxial silicon wafer; A method for manufacturing a semiconductor device comprising:

7. A method for manufacturing a semiconductor device, comprising forming a semiconductor device in the silicon epitaxial layer of the epitaxial silicon wafer according to claim 3 or 4.

8. A method for manufacturing a semiconductor device, comprising forming a semiconductor device in the silicon epitaxial layer of the epitaxial silicon wafer according to claim 5.

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