Manufacturing method of epitaxial silicon wafer

Abstract

To manufacture an epitaxial silicon wafer in which generation of an epitaxial defect is suppressed, and hydrogen remains at a high concentration in a modified layer.SOLUTION: In a first step, a cluster ion 12 containing carbon and hydrogen on a front surface 10A of a silicon wafer 10 is irradiated, and a modified layer 14 in which a constituent element of the cluster ion 12 is solidly dissolved is formed onto a front layer part of the silicon wafer 10. After that, in a second step, a laser anneal processing is performed to the silicon wafer 10. After that, a silicon epitaxial layer 16 is formed onto the modified layer 14 to obtain an epitaxial silicon wafer 100. In the first step, a carbon dosage amount is 1.0*1015 atoms / cm2 or more, and the step is performed under a condition that an amorphous region 14A that reaches the front surface of the modified layer is formed for the modified layer 14. The second step is performed under the condition that the amorphous region 14A is recrystallization by a solid phase epitaxial growth by a laser beam radiated to the modified layer 14.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing an epitaxial silicon wafer. [Background technology]

[0002] Epitaxial silicon wafers, which have an epitaxial layer of single crystal silicon 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) type CISs (CMOS Image Sensors).

[0003] Here, if the epitaxial layer is contaminated with heavy metals, the dark current of the CIS increases, and defects called white defects occur, which are factors that degrade the characteristics of the semiconductor device. Therefore, in order to suppress such heavy metal contamination, there is a technology that forms gettering sites in the silicon wafer to capture heavy metals. One known method is to implant ions into the silicon wafer and then form the epitaxial layer. In this method, the ion-implanted region functions as the gettering site.

[0004] In Patent Document 1 and Patent Document 2, C is added to the surface of a silicon wafer. 3 H 5 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 a higher gettering ability than an ion-implanted region obtained by implanting carbon monomer ions. 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 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.

[0006] However, if the dose is too high, the crystallinity of the surface of the modified layer (i.e., the surface of the silicon wafer on which the epitaxial layer is formed) is disturbed, which causes epitaxial defects in the epitaxial layer formed later. This problem is particularly noticeable when an amorphous region that reaches the surface of the modified layer is formed by irradiation with a high dose of cluster ions.

[0007] To solve this problem, a technique is known in which a heat treatment is performed on the silicon wafer after the irradiation of cluster ions and before the formation of an epitaxial layer in order to recover the crystallinity of the modified layer. Patent Document 2 also describes a recovery heat treatment performed by RTA (Rapid Thermal Annealing) or the like at 900°C to 1200°C for 10 seconds to 1 hour.

[0008] Here, hydrogen is a lighter element than carbon, and therefore hydrogen is more easily diffused than carbon injected into the modified layer by cluster ion irradiation, and is more likely to diffuse and be desorbed from the modified layer by heat treatment during the formation of the epitaxial layer. However, a large amount of defects (damage) are formed in the modified layer by the irradiation of cluster ions, and hydrogen trapped in these defects remains in the modified layer (i.e., directly below the epitaxial layer) even after epitaxial growth. The hydrogen remaining in the modified layer diffuses into the epitaxial layer by heat treatment during the device formation process for forming a semiconductor device on the epitaxial layer, and inactivates (passivates) the interface state defects in the epitaxial layer, thereby contributing to improving device characteristics such as reducing leakage current. This is referred to in this specification as the "passivation effect by hydrogen."

[0009] However, when a heat treatment is performed to recover the crystallinity of the modified layer in order to suppress the occurrence of epitaxial defects, the amount of defects in the modified layer is reduced, making it difficult to leave a high concentration of hydrogen in the modified layer after the formation of the epitaxial layer. Thus, when irradiating the layer with a high dose of cluster ions from the viewpoint of improving the gettering ability, it seems that it is difficult to achieve both the suppression of the occurrence of epitaxial defects and the leaving of a high concentration of hydrogen in the modified layer, which are mutually exclusive.

[0010] Here, Patent Document 3 describes that by performing a low-temperature, short-time recovery heat treatment in which "the temperature of the silicon wafer is raised at a heating rate of 10°C / s or more, and the maximum temperature reached is held at 350°C or more and 700°C or less for 1 second or more and 100 seconds or less," using heating by RTA or resistance heating in a batch furnace, it is possible to suppress the occurrence of epitaxial defects and allow hydrogen to remain at a high concentration in the modified layer when irradiated with a high dose of cluster ions. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 2012 / 157162 [Patent Document 2] International Publication No. 2015 / 104965 [Patent Document 3] JP 2020-170794 A Summary of the Invention [Problem to be solved by the invention]

[0012] However, according to the inventors' investigations, it was found that even if the recovery heat treatment is performed under the conditions described in Patent Document 3, the effect of leaving hydrogen in the modified layer after epitaxial growth is limited, and there is a problem in this regard that there is room for improvement.

[0013] In view of the above problems, an object of the present invention is to provide a method for producing an epitaxial silicon wafer, which is capable of producing an epitaxial silicon wafer in which hydrogen remains at a higher concentration in a modified layer while suppressing the occurrence of epitaxial defects when irradiated with a high dose of cluster ions from the viewpoint of improving gettering ability. [Means for solving the problem]

[0014] In order to solve the above problems, the present inventors have conducted extensive research and obtained the following findings. That is, by applying a laser annealing treatment as the recovery heat treatment, it is possible to perform a heat treatment for an extremely short time of sub-milliseconds, and it is possible to recover the crystallinity of the modified layer while suppressing the diffusion of hydrogen during the recovery heat treatment. As a result, it is possible to increase the amount of hydrogen retained in the modified layer after the recovery heat treatment, and therefore it is possible to allow a higher concentration of hydrogen to remain in the modified layer even after epitaxial growth.

[0015] In this case, it is important to perform the laser annealing treatment at a low energy density (laser output) so that the amorphous region formed on the surface of the modified layer is recrystallized by solid-phase epitaxial growth without melting the surface of the modified layer. If the laser annealing treatment is performed at a high energy density, the surface of the modified layer will melt, (i) the surface of the modified layer will not completely recrystallize after the laser annealing treatment and some parts will remain amorphous, or even if it does recrystallize, it will not become a single crystal but will become polycrystal, making it impossible to form an epitaxial layer on the modified layer, and (ii) hydrogen will diffuse from the modified layer during the laser annealing treatment, significantly reducing the amount of hydrogen held by the modified layer after the laser annealing treatment.

[0016] The present invention, which has been completed based on the above findings, has the following essential features. [1] A first step of irradiating a surface of a silicon wafer with cluster ions containing carbon and hydrogen as constituent elements to form a modified layer in a surface layer portion of the silicon wafer, in which the constituent elements of the cluster ions are dissolved; Thereafter, a second step of subjecting the silicon wafer to a laser annealing treatment; Thereafter, a third step of forming a silicon epitaxial layer on the modified layer of the silicon wafer; having In the first step, the carbon dose is 1.0×10 15 atoms / cm 2 The above-mentioned process is carried out under conditions in which an amorphous region is formed in the modified layer, the amorphous region reaching the surface of the modified layer. the second step is performed under conditions in which the amorphous region is recrystallized by solid phase epitaxial growth using a laser beam irradiated onto the modified layer; 1. A method for producing an epitaxial silicon wafer comprising the steps of:

[0017] [2] The method for producing an epitaxial silicon wafer according to [1] above, wherein the second step is performed under conditions such that a ratio of crystalline regions on the surface of the modified layer is 0.8 or more.

[0018] [3] The method for producing an epitaxial silicon wafer according to the above [1] or [2], wherein the second step is performed for a treatment time of 0.001 milliseconds or more and 100 milliseconds or less.

[0019] [4] In the first step, the hydrogen dose is 1.0 × 10 15 atoms / cm 2 The method for producing an epitaxial silicon wafer according to any one of the above [1] to [3], which is carried out under the above conditions. Effect of the Invention

[0020] According to the method for producing an epitaxial silicon wafer of the present invention, when irradiated with a high dose of cluster ions from the viewpoint of improving the gettering ability, it is possible to produce an epitaxial silicon wafer in which hydrogen remains in the modified layer at a higher concentration while suppressing the occurrence of epitaxial defects. [Brief description of the drawings]

[0021] [Figure 1] 1A to 1C are schematic cross-sectional views illustrating a method for producing an epitaxial silicon wafer 100 according to an embodiment of the present invention. [Diagram 2] FIG. 11 is a schematic cross-sectional view illustrating the state of crystallinity recovery of the modified layer 14 when laser annealing is performed at a high laser output and when it is performed at a low laser output after irradiation with cluster ions. [Diagram 3] FIG. 1 is a flow chart showing the experimental procedure in the examples. [Figure 4] (A) is a cross-sectional TEM image including a modified layer of a silicon wafer immediately after irradiation with cluster ions, and (B) is a planar TEM image of the surface of the silicon wafer in (A) (surface of the modified layer). [Diagram 5] FIG. 13 is a diagram for explaining curve fitting of a Si2p photoelectron spectrum performed to obtain the ratio of a crystalline region (crystallization rate) on the surface of a modified layer. [Figure 6]Graph (A) shows the relationship between the laser output in the laser annealing treatment and the crystallization rate on the surface of the modified layer, and graph (B) shows the relationship between the heat treatment temperature in the RTA treatment and the crystallization rate on the surface of the modified layer. [Figure 7] (A) to (C) are cross-sectional TEM images (upper) and hydrogen concentration profiles (lower) of silicon wafers including modified layers after heat treatment under various recovery heat treatment conditions. [Figure 8] 8 is a graph showing the amount of hydrogen retained in the implantation region under each of the conditions of the recovery heat treatment shown in FIG. 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] (Method of manufacturing epitaxial silicon wafers) Hereinafter, a method for manufacturing an epitaxial silicon wafer 100 according to an embodiment of the present invention will be described with reference to the drawings. For convenience of explanation, the thicknesses of the modified layer 14 and the silicon epitaxial layer 16 are shown in an exaggerated manner with respect to the silicon wafer 10, unlike the actual thickness ratios.

[0023] 1, a method for producing an epitaxial silicon wafer 100 according to an embodiment of the present invention includes a first step (steps A and B in FIG. 1) of irradiating a surface 10A of a silicon wafer 10 with cluster ions 12 containing carbon and hydrogen as constituent elements to form a modified layer 14 in which the constituent elements of the cluster ions 12 are dissolved in a solid solution in a surface layer portion of the silicon wafer 10, a second step (steps C and D in FIG. 1) of subjecting the silicon wafer 10 to a laser annealing treatment as a recovery heat treatment, and a third step (step E in FIG. 1) of forming 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 producing semiconductor elements such as a BSI type CIS.

[0024] [1st step] The silicon wafer 10 may be, for example, a bulk single crystal silicon wafer that does not have an epitaxial layer on the surface 10A that is the irradiated surface. Such a single crystal silicon wafer can be obtained by slicing a single crystal silicon ingot grown by the Czochralski method (CZ method) or the floating zone melting method (FZ method) with a wire saw or the like. In order to obtain a higher gettering ability, carbon and / or nitrogen may be added to the silicon wafer 10. Furthermore, any dopant may be added to the silicon wafer 10 at a predetermined concentration to make it n-type or p-type.

[0025] 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. In this case, the surface of the silicon epitaxial layer becomes the surface 10A of the silicon wafer 10 as the irradiated surface. The silicon epitaxial layer can be formed under general conditions by a CVD method. The silicon epitaxial layer preferably has a thickness in the range of 0.1 to 20 μm, more preferably in the range of 0.2 to 10 μm.

[0026] As described above, in the first step (steps A and B in FIG. 1), the surface 10A of the silicon wafer 10 is irradiated with cluster ions 12 containing carbon and hydrogen as constituent elements. The "cluster ions" in this specification are obtained by bombarding gaseous molecules with electrons to dissociate the bonds of the gaseous molecules to form atomic aggregates with various numbers of atoms, fragmenting the atomic aggregates to ionize them, and performing mass separation on the ionized atomic aggregates with various numbers of atoms to extract ionized atomic aggregates with specific mass numbers. That is, the "cluster ions" in this specification are ionized clusters formed by aggregating multiple atoms and giving them a positive or negative charge, and are clearly distinguished from monoatomic ions such as carbon ions and monomolecular ions such as carbon monoxide ions. The number of constituent atoms of a cluster ion is usually about 5 to 100. For example, CLARIS (registered trademark) manufactured by Nissin Ion Equipment Co., Ltd. can be used as a cluster ion implantation device using such a principle.

[0027] When the silicon wafer 10 is irradiated with cluster ions 12 containing carbon and hydrogen, the silicon instantaneously reaches a high temperature of about 1350 to 1400°C due to the irradiation energy, and melts. After that, the silicon is rapidly cooled, and carbon and hydrogen are dissolved in the silicon wafer near the surface. That is, the "modified layer" in this specification means a layer in which carbon and hydrogen, which are constituent elements of the irradiated cluster ions, are dissolved in interstitial positions or substitution positions of the crystals in the surface layer of the silicon wafer. The modified layer is specified as a region in which the concentration of at least one element is detected to be higher than the background in the concentration profile of carbon and hydrogen in the depth direction of the silicon wafer. After the implantation of cluster ions and before the formation of the epitaxial layer, the surface layer of the silicon wafer is generally 500 nm or less from the surface. After the epitaxial layer is formed, carbon diffuses from the surface of the silicon wafer to the inside to some extent, so that a surface layer of about 2 to 4 μm from the surface of the silicon wafer (the interface between the epitaxial layer and the silicon wafer) becomes a modified layer.

[0028] The elements irradiated in the form of cluster ions behave differently depending on the type of element, but some degree of thermal diffusion occurs during the formation process of the silicon epitaxial layer 16 described below. However, carbon is an element that is relatively difficult to diffuse. Therefore, when carbon is included in the constituent elements of the cluster ions, carbon can be locally dissolved in the modified layer 14 at a high concentration. It is believed that this local carbon solid solution region becomes a strong gettering site, thereby obtaining a high gettering ability.

[0029] On the other hand, hydrogen injected into the modified layer 14 is likely to diffuse. The purpose of this embodiment is to suppress the diffusion of hydrogen dissolved in the modified layer 14 during the recovery heat treatment and the formation of the epitaxial layer 16, to cause hydrogen to remain in the modified layer 14 at a higher concentration, and to enhance the passivation effect of hydrogen.

[0030] The irradiation conditions of the cluster ions 12 include the cluster size, the dose amount, the acceleration voltage, and the beam current value.

[0031] The cluster size can be appropriately set to 2 to 100, preferably 60 or less, more preferably 50 or less. In this specification, "cluster size" means the number of atoms constituting one cluster. The cluster size can be adjusted by adjusting the pressure of the gas ejected from the nozzle, the pressure of the vacuum vessel, the voltage applied to the filament during ionization, etc. The cluster size can be determined by determining the cluster number distribution by mass spectrometry using a quadrupole high-frequency electric field or time-of-flight mass spectrometry, and calculating the average value of the cluster numbers.

[0032] The constituent elements of the cluster ions 12 are not particularly limited as long as they include carbon and hydrogen, but as an example, they are made of carbon and hydrogen. It is also preferable that the constituent elements of the cluster ions 12 include elements other than hydrogen and carbon. In particular, it is preferable that the constituent elements of the cluster ions 12 include one or more elements selected from the group consisting of boron, phosphorus, arsenic, and antimony, in addition to hydrogen and carbon. Since the type of metal that can be efficiently gettered varies depending on the type of element to be dissolved, a wider range of metal contamination can be dealt with by dissolving a plurality of elements in a solid solution. For example, in the case of carbon, nickel (Ni) can be efficiently gettered, and in the case of boron, copper (Cu) and iron (Fe) can be efficiently gettered.

[0033] The gaseous molecules that are the source of cluster ions are not particularly limited as long as they can produce cluster ions of the desired size. For example, cyclohexane (C 6 H 12 ) as the source gas, cluster ions consisting of carbon and hydrogen can be generated and extracted. In addition, pyrene (C 16 H 10 ), dibenzyl (C 14 H 14 ) Cluster C generated from n H m (3≦n≦16, 3≦m≦10, n and m are both integers) is preferably used because it is easy to control a small-sized cluster ion beam.

[0034] The dose of the cluster ions can be adjusted by controlling the ion irradiation time. The dose of each element constituting the cluster ions depends on the cluster ion species (cluster size) and the dose of the cluster ions (ions / cm 2 Therefore, the dose of the cluster ions may be appropriately set according to the type of cluster ions so that the dose of each element has a desired value.

[0035] In this embodiment, the dose of carbon is set to 1.0×10 15 atoms / cm 2 More preferably, it is 2.0×10 15 atoms / cm 2 2, an amorphous region 14A reaching the surface is formed in the modified layer 14 immediately after the cluster ion irradiation (before the recovery heat treatment). On the other hand, the dose of carbon is set to 1.0×10 16 atoms / cm 2 It is preferable that the surface of the modified layer 14 is equal to or less than 1 / 2 mm. In this case, referring to Fig. 2, the surface of the modified layer 14 immediately after the cluster ion irradiation (before the recovery heat treatment) is not completely amorphous, but is in a state in which the remaining crystalline regions 14B and the discretely formed amorphous regions 14A are mixed. However, even if the epitaxial layer 16 is formed on the modified layer 14 in this state, the occurrence of epitaxial defects is unavoidable, so a heat treatment is required to recover the crystallinity of the modified layer 14.

[0036] The dose of hydrogen is preferably 1.0×10 to 1.5×10 s in order to inject hydrogen into the modified layer 14 at a high concentration and to allow hydrogen to remain in the modified layer 14 at a high concentration even after the epitaxial layer is formed. 15 atoms / cm 2 More preferably, it is 1.7×10 15 atoms / cm 2 More preferably, it is 2.8×10 15 atoms / cm 2 More preferably, it is 3.3×10 15 atoms / cm 2 On the other hand, the dose of hydrogen is set to 2.0×10 so as not to cause significant damage to the surface of the epitaxial layer. 16 atoms / cm 2 It is preferable that:

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

[0038] The beam current value of the cluster ions is not particularly limited, but is preferably appropriately determined from the range of 50 μA or more and 5000 μA or less. It is preferable to set the beam current value of the cluster ions to 50 μA or more, irradiate the silicon wafer surface with hydrogen in a relatively short time, and increase the damage in the modified layer. By setting the beam current value to 50 μA or more, the damage increases, and hydrogen tends to remain in the modified layer at a high concentration even after the subsequent epitaxial layer is formed. It is more preferable to set the beam current value of the cluster ions to 100 μA or more, and even more preferable to set it to 300 μA or more. On the other hand, if the beam current value becomes too large, there is a risk that epitaxial defects will be excessively generated in the epitaxial layer, so it is preferable to set the beam current value to 5000 μA or less. 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] After the first step, a second step (steps C and D in FIG. 1) is performed in which the silicon wafer 10 is subjected to a laser annealing treatment as a recovery heat treatment. By applying the laser annealing treatment as the recovery heat treatment, it is possible to perform a heat treatment for an extremely short time of sub-milliseconds, and it is possible to recover the crystallinity of the modified layer 14 while suppressing the diffusion of hydrogen during the recovery heat treatment. As a result, it is possible to increase the amount of hydrogen retained in the modified layer 14 after the recovery heat treatment, so that a higher concentration of hydrogen can remain in the modified layer 14 even after epitaxial growth. This makes it possible to obtain a more sufficient passivation effect by hydrogen.

[0040] 2, when laser annealing is performed with a high energy density (laser output), the surface layer of the modified layer 14 melts, and the melted portion recrystallizes by liquid phase epitaxial growth. In this case, the surface layer of the modified layer 14 does not completely recrystallize after the laser annealing, and some parts remain amorphous, or even if it does recrystallize, it does not become a single crystal but becomes polycrystal, and an epitaxial layer cannot be formed on the modified layer 14. Furthermore, hydrogen diffuses from the modified layer 14 during the laser annealing, and the amount of hydrogen held by the modified layer 14 after the laser annealing is significantly reduced.

[0041] Therefore, it is essential that the laser annealing process is performed under conditions where the amorphous region 14A is recrystallized by solid-phase epitaxial growth using the laser light irradiated onto the modified layer 14. Specifically, the laser annealing process is performed at a low energy density (laser output). In this case, recrystallization of the amorphous region 14A proceeds by solid-phase epitaxial growth from the interface between the amorphous region 14A and the crystalline region 14B present in the modified layer 14. Therefore, the surface of the modified layer 14 after the laser annealing process is sufficiently single-crystallized. In addition, the diffusion of hydrogen from the modified layer 14 during the laser annealing process is suppressed, and the amount of hydrogen held by the modified layer 14 after the laser annealing process can be secured to be large. In this way, the laser output required for the amorphous region 14A to be recrystallized by solid-phase epitaxial growth without melting the surface layer portion of the modified layer 14 depends on the type and spot diameter of the laser, and can be determined accordingly.

[0042] On the other hand, if the energy density (laser output) in the laser annealing process is too low, the recrystallization of the amorphous regions 14A becomes insufficient, and many amorphous regions 14A remain on the surface of the modified layer 14, so that the occurrence of epitaxial defects cannot be sufficiently suppressed. Therefore, it is preferable that the laser annealing process is performed under conditions in which the ratio of the crystalline regions 14B on the surface of the modified layer 14 (hereinafter referred to as the "crystallization ratio") is 0.8 or more. The laser output that satisfies such conditions depends on the type and spot diameter of the laser, and can be determined accordingly.

[0043] Here, the crystallization rate on the surface of the modified layer 14 is determined by the following method using X-ray photoelectron spectroscopy (XPS) with reference to FIG. 5. First, a Si2p photoelectron spectrum of the silicon wafer surface (perfect crystal) before cluster ion implantation is obtained. This spectrum corresponds to the spectrum of an ideal crystalline component, and typically has a Si2p 1 / 2 and Si2p 3 / 2Next, an excessive dose of cluster ions is implanted, and the Si2p photoelectron spectrum of the modified layer surface (completely amorphous) in which the entire surface of the modified layer becomes an amorphous region is obtained. This spectrum corresponds to the spectrum of an ideal amorphous component, and is typically Si2p 1 / 2 and Si2p 3 / 2 The two peaks disappear and one broad peak appears. Next, the Si2p photoelectron spectrum (original spectrum in FIG. 5) of the surface of the modified layer for which the crystallization rate is to be determined is obtained. Then, curve fitting is performed so that the composite spectrum of the completely crystalline spectrum and the completely amorphous spectrum matches the original spectrum. Then, the spectrum of the crystalline component and the spectrum of the amorphous component after curve fitting are identified, and the crystallization rate on the surface of the modified layer 14 is calculated based on the following formula: Crystallinity ratio = integral value of spectrum of crystalline component / (integral value of spectrum of crystalline component + integral value of spectrum of amorphous component)

[0044] The type of laser and the wavelength of the laser light used in the laser annealing treatment are not particularly limited, but a blue laser that irradiates blue light with a wavelength in the range of 430 to 490 nm, a UV laser that irradiates ultraviolet light with a wavelength in the range of 200 to 400 nm, etc. can be suitably used. The oscillation mode of the laser light may be continuous oscillation or pulse oscillation.

[0045] The laser spot diameter (scan width) is not particularly limited, but is preferably within the range of, for example, 0.4 mm to 30.0 mm. If the spot diameter (scan width) is 0.4 mm or more, the number of scans will not be excessive, and if the spot diameter (scan width) is 30.0 mm or less, the uniformity within the irradiation range will not decrease.

[0046] If the processing time of the laser annealing process is too short, the crystallinity of the modified layer 14 is not sufficiently restored, and the occurrence of epitaxial defects cannot be sufficiently suppressed. Therefore, the processing time of the laser annealing process is preferably 0.001 milliseconds or more, more preferably 0.01 milliseconds or more, and even more preferably 0.1 milliseconds or more. On the other hand, if the processing time of the laser annealing process is too long, the crystallinity of the modified layer 14 is sufficiently restored, but hydrogen diffuses from the modified layer 14, and the hydrogen retention amount of the modified layer 14 after the laser annealing process cannot be maintained large. Therefore, the processing time of the laser annealing process is preferably 100 milliseconds or less, more preferably 10 milliseconds or less, and even more preferably 1 millisecond or less. The "processing time" of the laser annealing process means the time during which each part of the surface of the modified layer 14 is irradiated with laser light, and can be controlled by the scanning speed of the laser light.

[0047] The laser output may be appropriately determined according to the type of laser and the spot diameter so as to satisfy the above-mentioned conditions. For example, when a blue laser that irradiates blue light having a wavelength in the range of 430 to 490 nm is used and the spot diameter is set to 0.4 to 30.0 mm, the laser output required for the amorphous region 14A to be recrystallized by solid phase epitaxial growth without melting the surface layer of the modified layer 14 is 400 W / cm. 2 may be less than 390 W / cm 2 It can be less than 380 W / cm 2 The laser output required for the crystallization rate on the surface of the modified layer 14 to be 0.8 or more is 250 W / cm 2 It could be more than that.

[0048] The atmosphere in which the laser annealing treatment is performed is not particularly limited, and may be, for example, nitrogen gas (N 2 ) or argon gas (Ar). 3 It is also preferable to perform flash lamp annealing treatment in a .

[0049] The apparatus for performing the laser annealing treatment is not particularly limited, and any known apparatus can be used.

[0050] [3rd step] After the second step, a third step (step E in FIG. 1) is performed in which a silicon epitaxial layer 16 is formed on the modified layer 14 of the silicon wafer 10. In this manner, an epitaxial silicon wafer 100 in which the silicon epitaxial layer 16 is formed on the modified layer 14 can be obtained.

[0051] The silicon epitaxial layer 16 can be formed under general conditions. For example, hydrogen is used as a carrier gas, and a source gas such as dichlorosilane or trichlorosilane is introduced into a chamber. Although the growth temperature varies depending on the source gas used, the silicon epitaxial layer 16 can be epitaxially grown on the modified layer 14 of the silicon wafer 10 by a CVD method at a temperature in the range of about 1000 to 1200°C. The thickness of the silicon epitaxial layer 16 is preferably in the range of 1 to 15 μm. If the thickness is less than 1 μm, the resistivity of the silicon epitaxial layer 16 may change due to outward diffusion of dopants from the silicon wafer 10, and if the thickness exceeds 15 μm, the spectral sensitivity characteristics of the CIS may be affected.

[0052] According to the manufacturing method of the present embodiment described above, when cluster ions are irradiated at a high dose from the viewpoint of improving the gettering ability, it is possible to manufacture an epitaxial silicon wafer in which hydrogen remains in the modified layer at a higher concentration while suppressing the occurrence of epitaxial defects.

[0053] (Method of manufacturing semiconductor devices) A method for manufacturing a semiconductor device according to an 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. This manufacturing method can suppress the occurrence of epitaxial defects while ensuring gettering capability, and furthermore, can cause hydrogen to remain in the modified layer at a higher concentration, thereby more fully obtaining the passivation effect by hydrogen.

[0054] The semiconductor device formed on the silicon epitaxial layer 16 is not particularly limited, and examples thereof include MOSFETs, DRAMs, power transistors, and BSI type CISs. EXAMPLES

[0055] The following examples will be described along the experimental procedure shown in FIG.

[0056] [C 3 H 5 Cluster ion implantation] A p-type silicon wafer (diameter: 300 mm, thickness: 775 μm, dopant type: boron, resistivity: 20 Ω cm) obtained from a CZ single crystal silicon ingot was prepared. Next, a cluster ion generator (manufactured by Nissin Ion Equipment Co., Ltd., CLARIS (registered trademark)) was used to generate cyclohexane (C 6 H 12 ) to C 3 H 5 Cluster ions were generated and extracted, and irradiated onto the surface of a silicon wafer under irradiation conditions of an acceleration voltage of 80 keV / Cluster. The dose of cluster ions was 1.0×10 15 ions / cm 2 That is, the carbon dose was 3.0×10 15 atoms / cm 2 and the hydrogen dose is 5.0×10 15 atoms / cm 2The beam current of the cluster ions was set to 850 μA. The temperature of the silicon wafer during the cluster ion irradiation was set to room temperature, and the tilt angle and twist angle during the cluster ion irradiation were both set to 0°.

[0057] The carbon and hydrogen concentration profiles in the depth direction from the surface of the silicon wafer after irradiation with cluster ions were measured using secondary ion mass spectrometry (SIMS), and a modified layer was identified at a depth of approximately 350 nm in the surface layer of the silicon wafer.

[0058] [Cross-sectional TEM and surface planar TEM observations] The silicon wafer after the cluster ion irradiation was observed by a transmission electron microscope (TEM). Figure 4(A) is a cross-sectional TEM image including the modified layer of the silicon wafer immediately after the cluster ion irradiation, and (B) is a planar TEM image of the surface of the silicon wafer (surface of the modified layer). The sample thickness in the planar TEM image was 10 nm from the surface of the silicon wafer. In Figures 4(A) and (B), the black parts are crystalline regions of the modified layer that are particularly heavily damaged, and the white parts are amorphous regions. As shown in Figure 4(B), the surface of the modified layer immediately after the cluster ion irradiation is a mixture of remaining crystalline regions (black parts) and discretely formed amorphous regions (white parts). From Figure 4(A), amorphous regions were observed in the range of depths from 20 nm to 80 nm from the surface of the silicon wafer. In Figure 4(A), the area from the surface of the silicon wafer to 20 nm is observed to be a heavily damaged crystalline region (black area), but Figure 4(B) shows that there are discrete amorphous regions in this area as well. This is thought to be because cross-sectional TEM images are the sum of information in the thickness direction of the sample, and so the discrete amorphous regions are cancelled out and the crystalline regions are displayed as the dominant region.

[0059] [Laser annealing / RTA treatment] The silicon wafer after the cluster ion irradiation was subjected to laser annealing as a recovery heat treatment. A blue laser with a wavelength of 445 nm was used. The laser irradiation was performed in continuous oscillation mode. The laser spot diameter (scan width) was 0.46 mm, and the treatment time was 0.1 ms. The laser output was 100 W / cm. 2 , 150W / cm 2 , 200W / cm 2 , 240W / cm 2 , 250W / cm 2 , 300W / cm 2 , 355W / cm 2 , and 400 W / cm 2 The eight conditions were:

[0060] In addition, as a comparative experiment, silicon wafers after cluster ion irradiation were subjected to RTA treatment using a halogen lamp as a recovery heat treatment. The heat treatment time (lamp irradiation time) was 1 second, and the heat treatment temperatures (silicon wafer temperatures) were 550°C, 575°C, 600°C, 625°C, and 700°C.

[0061] [Evaluation of surface crystallinity by X-ray photoelectron spectroscopy] The surface crystallinity (recrystallization behavior) of the modified layer after the recovery heat treatment under each condition was evaluated by XPS. The Si2p photoelectron spectrum of the modified layer surface of the silicon wafer under each condition was obtained by XPS, and the crystallization rate on the modified layer surface was calculated by the method explained using Figure 5.

[0062] FIG. 6(A) shows the relationship between the laser output and the crystallization rate on the surface of the modified layer in the laser annealing process. As the laser output increases, recrystallization in the surface of the modified layer progresses, and the crystallization rate increases. 2 Up to 250W / cm, the crystallization rate was low at 0.5 or less, and recrystallization was insufficient, so there was concern about the occurrence of epitaxial defects after the formation of the epitaxial layer. 2 Under the above conditions, the crystallization rate was 0.8 or more, and it can be seen that recrystallization had progressed sufficiently. And, when the laser output was 355 W / cm2 It can be seen that the surface of the modified layer is almost completely recrystallized. However, when the laser output is 400 W / cm 2 In the case of , the surface of the modified layer melted and recrystallized by liquid phase epitaxial growth, and the formation of crystal grains was confirmed on the surface of the silicon wafer, as shown in Figure 7(C) below. 2 In the case of , the recrystallized region becomes polycrystalline and contains grain boundaries, which is thought to result in a decrease in the crystallization rate.

[0063] Figure 6(B) shows the relationship between the heat treatment temperature in the RTA treatment and the crystallization rate on the surface of the modified layer. As the heat treatment temperature increases, recrystallization of the surface of the modified layer progresses, and the crystallization rate increases. At a heat treatment temperature of 700°C, the crystallization rate is 0.9 or more, and it can be seen that almost the entire surface of the modified layer is recrystallized.

[0064] [Cross-sectional TEM observation, SIMS analysis] Cross-sectional TEM images including the modified layer of the silicon wafer after the recovery heat treatment under each condition were obtained. In addition, the hydrogen concentration profile in the depth direction from the surface of the silicon wafer after the recovery heat treatment under each condition was measured by SIMS. The peak area obtained from the obtained hydrogen concentration profile was calculated as the "hydrogen retention amount in the implanted region."

[0065] Representative conditions were: (1) laser annealing (laser output: 355 W / cm 2 , processing time: 0.1 ms), (2) RTA treatment (heat treatment temperature: 700°C, heat treatment time: 1 s), and (3) laser annealing treatment (laser output: 400 W / cm 2 The results for three conditions (1: 1, 2: 1, 3: 1, 4: 1, 5: 2, 6: 3, 7: 4, 8: 5, 9: 6, 10: 7, 11: 8, 12: 9, 13: 14, 14: 15, 15: 16, 16: 17, 17: 18, 19: 19

[0066] Figure 7 shows a cross-sectional TEM image (top) and hydrogen concentration profile (bottom) of the silicon wafer including the modified layer after the recovery heat treatment under the above three conditions. From Figures 7(A) and (B), it can be seen that in both the laser annealing treatment and the RTA treatment, the amorphous region formed in the modified layer recrystallized from both the surface side and the inside side by solid-phase epitaxial growth, and defects (black areas) due to crystal misfit were formed at the meeting points of the recrystallization. Also, from Figure 7(C), it can be seen that when the laser output was 400 W / cm 2 In the case of (a), the surface portion of the modified layer melted and recrystallized by liquid phase epitaxial growth, so that the formation of crystal grains was confirmed on the surface of the silicon wafer and the surface roughness was deteriorated.

[0067] Figure 8 shows the amount of hydrogen retained in the implanted region after the recovery heat treatment under the above three conditions. The amount of hydrogen retained in the RTA treatment was 2.9 × 10 21 atoms / cm 2 In contrast, the laser annealing process, which is a solid-phase epitaxial growth process, is 4.1 × 10 21 atoms / cm 2 It can be seen that the recrystallization of the modified layer was achieved while maintaining a high concentration of hydrogen in the implanted region. On the other hand, it was confirmed that the hydrogen in the implanted region was diffused in the laser annealing process, which melts the surface of the modified layer. [Industrial Applicability]

[0068] According to the method for producing an epitaxial silicon wafer of the present invention, when irradiated with a high dose of cluster ions from the viewpoint of improving the gettering ability, it is possible to produce an epitaxial silicon wafer in which hydrogen remains in the modified layer at a higher concentration while suppressing the occurrence of epitaxial defects.

[0069] Epitaxial silicon wafers are essential to support our lives as a core material of semiconductor devices. In particular, CIS is a core component of the camera function of digital cameras and smartphones, and is an essential technology for acquiring images and videos. This invention makes it possible to manufacture high-quality epitaxial silicon wafers and provide high-quality, highly accurate images, which can contribute to sustainable activities such as improving the quality and efficiency of medical care in the medical field, improving the health and welfare of society as a whole (Sustainable Development Goals (SDGs) Goal 3 "Ensure healthy lives and promote well-being for all at all ages"), and improving social safety and security through the sophistication of surveillance systems and security systems, such as crime prevention and disaster countermeasures (Sustainable Development Goals (SDGs) Goal 11 "Make cities inclusive, safe, resilient and sustainable"). [Explanation of symbols]

[0070] 100 Epitaxial Silicon Wafers 10. Silicon Wafer 10A Silicon Wafer Surface 12 Cluster ions 14 Modification layer 14A Amorphous region 14B Crystal region 16 Silicon epitaxial layer

Claims

1. a first step of irradiating a surface of a silicon wafer with cluster ions containing carbon and hydrogen as constituent elements to form a modified layer in a surface layer portion of the silicon wafer, in which the constituent elements of the cluster ions are dissolved; A second step of thereafter subjecting the silicon wafer to a laser annealing treatment; Thereafter, a third step of forming a silicon epitaxial layer on the modified layer of the silicon wafer; having In the first step, the carbon dose is 1.0×10 １５ atoms / cm ２ The above-mentioned process is carried out under conditions in which an amorphous region is formed in the modified layer, the amorphous region reaching the surface of the modified layer. the second step is performed under conditions in which the amorphous region is recrystallized by solid phase epitaxial growth using a laser beam irradiated onto the modified layer; 1. A method for producing an epitaxial silicon wafer comprising the steps of:

2. 2. The method for producing an epitaxial silicon wafer according to claim 1, wherein the second step is performed under conditions such that a ratio of a crystalline region on a surface of the modified layer is 0.8 or more.

3. 3. The method for producing an epitaxial silicon wafer according to claim 1, wherein the second step is performed for a treatment time of 0.001 milliseconds or more and 100 milliseconds or less.

4. In the first step, the hydrogen dose is 1.0×10 １５ atoms / cm ２ 3. The method for producing an epitaxial silicon wafer according to claim 1 or 2, which is carried out under the above conditions.

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