Method for detecting dislocation of single crystal silicon specimen, method for determining target value of oxygen concentration of single crystal silicon wafer, method for manufacturing single crystal silicon ingot, and method for manufacturing single crystal silicon wafer

Abstract

To provide a novel method for detecting dislocation that is present in a single crystal silicon specimen after a coating is formed thereto.SOLUTION: A method for detecting dislocation of a single crystal silicon specimen includes a step of detecting a part as dislocation that is observed as a bright line in an electronic channeling image that is acquired by irradiating a surface of a single crystal silicon specimen with an electron beam by a scanning electron microscope, where the irradiation with the electron beam includes a step of irradiating one or more crystal planes of the single crystal silicon specimen with the electron beam in an incidence azimuth within a range of satisfying an electronic channeling condition and the one or more crystal planes include a {220} surface.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for detecting dislocations in a single crystal silicon sample, a method for determining a target oxygen concentration of a single crystal silicon wafer, a method for manufacturing a single crystal silicon ingot, and a method for manufacturing a single crystal silicon wafer.

Background Art

[0002] Single crystal silicon wafers are widely used as substrates for semiconductor devices (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In general crystal materials, dislocations already exist in the crystal and move through the crystal or grow in the crystal due to stress generated by an external force. On the other hand, for single crystal silicon wafers, dislocations can occur in the wafer due to stress caused by the difference in the coefficient of thermal expansion between the coating (e.g., insulating film, device structure, etc.) formed on the wafer and the wafer in the device manufacturing process (see paragraph 0007 of Patent Document 1).

[0005] In semiconductor devices, dislocations in the substrate significantly affect the electrical characteristics. Therefore, it is desirable to establish a new method for detecting dislocations present in a single crystal silicon wafer after the coating is formed.

[0006] One aspect of the present invention aims to provide a new method for detecting dislocations present in a single crystal silicon sample after the coating is formed.

Means for Solving the Problems

[0007] One aspect of the present invention is as follows. [1] Detecting a portion observed as a bright line in an electron channeling contrast image obtained by irradiating the surface of a single-crystal silicon sample with an electron beam using a scanning electron microscope as a dislocation, The irradiation of the electron beam includes irradiating the electron beam at an incident orientation within a range that satisfies electron channeling conditions for one or more crystal planes of the single-crystal silicon sample, and The one or more crystal planes include the {220} plane, a method for detecting dislocations in a single-crystal silicon sample. [2] The one or more crystal planes further include the {400} plane, the method for detecting dislocations in a single-crystal silicon sample according to [1]. [3] The one or more crystal planes are the {400} plane and two equivalent {220} planes, the method for detecting dislocations in a single-crystal silicon sample according to [2]. [4] Performing the irradiation of the electron beam after peeling off a coating formed on the surface, the method for detecting dislocations in a single-crystal silicon sample according to any one of [1] to [3]. [5] The coating is silicon nitride, the method for detecting dislocations in a single-crystal silicon sample according to [4]. [6] Performing the irradiation of the electron beam with a coating on a part of the surface, The detected dislocation is a dislocation detected by irradiating the electron beam at a position within a region not covered by the coating on the surface, the method for detecting dislocations in a single-crystal silicon sample according to any one of [1] to [3]. [7] The coating is silicon nitride, the method for detecting dislocations in a single-crystal silicon sample according to [6]. [8] The single-crystal silicon sample is a single-crystal silicon wafer, the method for detecting dislocations in a single-crystal silicon sample according to any one of [1] to [7]. [9] Preparing a plurality of single-crystal silicon samples having different oxygen concentrations, Forming a coating on each of the plurality of single-crystal silicon samples under the same film-forming conditions, Partially removing the coating, and Evaluating the presence or absence of dislocations in the plurality of single-crystalline silicon samples by the method for detecting dislocations in single-crystalline silicon samples described in any one of [1] to [8]. including A method for determining the oxygen concentration target value of a single-crystalline silicon wafer, wherein, as a result of the above evaluation, the oxygen concentration of the single-crystalline silicon sample evaluated as having no dislocations is determined as the oxygen concentration target value of the single-crystalline silicon wafer to be actually manufactured.

[10] The method for determining the oxygen concentration target value of a single-crystalline silicon wafer according to [9], wherein the coating is silicon nitride.

[11] Determining the oxygen concentration target value of a single-crystalline silicon wafer manufactured by the method described in [9] or

[10] , and Growing a single-crystalline silicon ingot under growth conditions in which a single-crystalline silicon having an oxygen concentration within a target range including the determined oxygen concentration target value can be obtained. A method for manufacturing a single-crystalline silicon ingot, including

[12] Manufacturing a single-crystalline silicon ingot by the method described in

[11] , and Cutting out wafers from the manufactured single-crystalline silicon ingot. A method for manufacturing a single-crystalline silicon wafer, including [Effect of the Invention]

[0008] According to one aspect of the present invention, a new method for detecting dislocations in a single-crystalline silicon sample after a coating is formed can be provided. [Brief Description of the Drawings]

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0010] [Method for Detecting Dislocations in a Single-Crystal Silicon Sample] One aspect of the present invention relates to a method for detecting dislocations in a single-crystal silicon sample. The dislocation detection method includes detecting, as dislocations, portions observed as bright lines in an electron channeling contrast image (ECCI: Electron Channeling Contrast Image) obtained by irradiating the surface of a single-crystal silicon sample with an electron beam using a scanning electron microscope (SEM: Scanning Electron Microscope). The irradiation of the electron beam includes irradiating the electron beam at an incident orientation within a range that satisfies electron channeling conditions for one or more crystal planes of the single-crystal silicon sample, and the one or more crystal planes include the {220} plane.

[0011] When an electron beam is irradiated at an incident orientation within a predetermined range and enters a crystal plane, the phenomenon in which the penetration depth of primary electrons changes rapidly is called electron channeling. Details of the incident orientation of the electron beam will be described later. The effect of this electron channeling appears remarkably in the intensity of reflected electrons. Channeling can be interpreted as a result of the change in the probability of interaction between incident electrons and atoms due to the crystal orientation, that is, the difference in the atomic arrangement seen from the electron beam. If the probability of interacting with atoms decreases, as a result, electrons penetrate deeper without losing energy, and the number of reflected electrons jumping out from the surface decreases. By utilizing this electron channeling effect, dislocations can be detected as bright lines. This is because in a reflection electron image, specifically an electron channeling contrast image (ECCI), when there is a lattice distortion such as a dislocation, the channeling condition is locally disrupted at that part, and the probability of interaction increases. For electron channeling and electron channeling contrast image (ECCI), reference can be made to known techniques such as the reference: "Theory and application of electron channelling contrast imaging under controlled diffraction conditions" (Acta Materialia, Vol.75(2014)20-50). In the present invention and in this specification, the "incident orientation within the range satisfying the electron channeling condition" means that in SEM observation by the electron backscattering diffraction (EBSD) method, with the deviation parameter of the incident angle with respect to the crystal plane (irradiated surface) on which the electron beam is incident being w, w is a positive value (i.e., w is greater than 0), and when w is plotted against the intensity difference to the background, this plot is the incident orientation located on the Kikuchi line in the graph of the deviation parameter w and the intensity difference created by the method described in the above reference. An example of the graph is shown in FIG. 4 of the above reference. The deviation parameter w becomes zero when the incident angle with respect to the irradiated surface becomes the Bragg angle. The Bragg angle is the angle θ in Bragg's equation (2d·sinθ = λ). In the Bragg equation, d is the lattice plane spacing and λ is the wavelength of the incident light. Regarding the deviation parameter w, reference can be made to FIG. 2 of the above reference and its description. Also, in the present invention and in this specification, the "maximum channeling incident orientation within the range satisfying the electron channeling condition" means the incident orientation that satisfies the deviation parameter w when the intensity difference from the background is at its minimum value on the Kikuchi line in the above graph.

[0012] As a result of intensive studies by the present inventors, for a single-crystal silicon sample, in an electron channeling contrast image (ECCI) obtained by irradiating an electron beam at an incident orientation within the range satisfying the electron channeling condition for one or more crystal planes including at least the {220} plane, a new finding that bright lines indicating dislocations appear with high contrast, which has not been previously known, was obtained. Therefore, according to the above dislocation detection method, dislocations in a single-crystal silicon sample can be detected as bright lines with high contrast. The high contrast of the bright lines indicating dislocations is desirable from the viewpoint of ease of dislocation detection. Conventionally, the detection of dislocations in a single-crystal silicon sample has been performed by a method of observing the sample after etching (hereinafter referred to as the "etching method") as described in paragraphs 0047 to 0048 of Patent Document 1 (Japanese Patent Application Laid-Open No. 2019-149471), for example. However, in the etching method, dislocations in the extremely surface layer portion of the sample are removed by etching. Therefore, in the etching method, it is difficult to detect dislocations in the extremely surface layer portion of the sample, so there are restrictions on detectable dislocations. In addition, the etching method observes and detects dislocations pitted by etching, but in a single-crystal silicon sample with a low resistivity, pitting of dislocations by etching may not occur. Also in this regard, there are restrictions on the target samples of the etching method. Furthermore, in the etching method, usually, a light etching solution containing harmful chromic acid is used as a chemical solution, so it is necessary to consider the environmental aspect during the treatment of the chemical solution. On the other hand, according to the above dislocation detection method, there are no restrictions on the target sample, and moreover, dislocations in a single-crystal silicon sample can be detected without considering the environmental aspect during the treatment of the chemical solution. However, the dislocations detected by the above dislocation detection method are not limited to the dislocations existing in the extremely surface layer portion of the sample, and the resistivity of the single-crystal silicon sample in which dislocations are detected by the above dislocation detection method is also not limited.

[0013] Hereinafter, the above dislocation detection method will be described in more detail.

[0014] <Single-crystal silicon sample> The dislocation detection target sample in the above dislocation detection method may be any single-crystal silicon sample, and the shape, dimensions, etc. are not limited. As described above, the resistivity of the single-crystal silicon sample is also not limited. In one form, the single-crystal silicon sample can be a single-crystal silicon wafer, can also be a sample cut out from a part of the single-crystal silicon wafer, or can also be a sample cut out from a part of a single-crystal silicon ingot and subjected to mirror etching or polishing treatment.

[0015] An electron channeling contrast image (ECCI) is obtained by irradiating the surface of a single-crystal silicon sample with an electron beam using a scanning electron microscope (SEM) and detecting the reflected electrons. The following are two examples of the surface (irradiated surface) irradiated with the electron beam.

[0016] Example 1: The surface of a single-crystal silicon sample in a state where it has a coating in part Example 2: The surface of a single-crystal silicon sample after a coating is formed on part or the entire surface and then part or all of the coating is peeled off

[0017] For example, if a coating exists on at least part of the surface of a single-crystal silicon sample, dislocations may occur in the single-crystal silicon sample due to the stress caused by this coating. As an example of such dislocations, in a single-crystal silicon sample, dislocations existing in the region located below the coating can be mentioned. When detecting such dislocations, it is preferable to use the surface of the single-crystal silicon sample in Example 2 as the irradiated surface and irradiate an irradiated position within the region that was covered by the coating before the coating was peeled off on the surface of the single-crystal silicon sample with an electron beam. Thereby, the above dislocations can be detected as bright lines in the electron channeling contrast image. Also, as another example of dislocations that may occur due to the above stress, dislocations generated in the single-crystal silicon sample from the stress concentration part occurring near the coating in the region not covered by the coating can be mentioned. When detecting such dislocations, it is preferable to use the surface of the single-crystal silicon sample in Example 1 or the surface of the single-crystal silicon sample after the coating is peeled off in Example 2 as the irradiated surface and irradiate an irradiated position within the region not covered by the coating on the surface of the single-crystal silicon sample with an electron beam. Thereby, the dislocations generated in the single-crystal silicon sample from the above stress concentration part can be detected as bright lines in the electron channeling contrast image.

[0018] The coating is not particularly limited, and examples thereof include various insulating films that can be formed on a semiconductor substrate in a semiconductor device manufacturing process, films that can be formed for device structure fabrication, and the like. As an example of such a coating, silicon nitride (also referred to as "silicon nitride") can be mentioned. The thickness of the coating is not particularly limited. As an example, the coating can be a film having a film thickness in the range of, for example, 50 to 500 nm. The thickness can be measured by a known film thickness measurement method. The method for forming the coating (for example, a film-forming method for forming a film-like coating) is also not particularly limited, and a method known in the semiconductor device manufacturing process can be adopted. Also, after forming a coating on the entire surface of a single-crystalline silicon sample, a single-crystalline silicon sample having a coating on a part of the surface can be produced by partially removing the coating. The method for partially removing the coating is also not particularly limited. Regarding the method for partially removing the coating, a method known in the semiconductor device manufacturing process can be adopted. For example, the coating can be patterned in a strip shape to partially remove the coating. By patterning the coating in a strip shape, a so-called "line and space" can be created on the surface of the single-crystalline silicon sample. As an example of a method for removing a part of the coating, a photolithography method can be mentioned. Also, as an example of a method for peeling the coating, HF treatment can be mentioned. According to HF treatment, the coating on the wafer can be peeled off without etching the single-crystalline silicon wafer. HF treatment can be performed by a known method.

[0019] <Obtaining an Electron Channeling Contrast Image> The scanning electron microscope (SEM) used in the above dislocation detection method is not particularly limited as long as it can acquire an electron channeling contrast image. Preferably, an SEM equipped with an irradiation system capable of precession deflecting the electron beam while fixing the electron beam at a point on the irradiated surface can be used. By using an SEM equipped with such an irradiation system, while fixing the electron beam at a point on the irradiated surface, the electron beam can be precession deflected to achieve incidence from various angles, and at the same time, an electron channeling contrast image (ECCI) including an electron channeling pattern that satisfies a plurality of channeling conditions can be obtained.

[0020] Regarding the irradiation conditions for irradiating the surface (irradiated surface) of a single-crystal silicon sample with an electron beam to obtain an electron channeling contrast image, for example, the energy of the electron beam can be in the range of 10 to 30 keV.

[0021] In the above dislocation detection method, the irradiation of the electron beam for obtaining the electron channeling contrast image of the single-crystal silicon sample is performed at an incident orientation within the range that satisfies the electron channeling conditions for one or more crystal planes of the single-crystal silicon sample irradiated with the electron beam, and at an incident orientation within the range that satisfies the electron channeling conditions for at least the {220} plane. That is, the above one or more crystal planes include the {220} plane. Thereby, as the electron channeling contrast image of the single-crystal silicon sample, it becomes possible to obtain an electron channeling contrast image in which bright lines indicating dislocations are displayed with high contrast. In the present invention and this specification, the "bright line" of the electron channeling contrast image is a linear region that is brightly (in other words, white) displayed in the electron channeling contrast image due to the difference in contrast with other parts. It is not essential for the bright line to be displayed as a completely white region, and it may be a region with higher brightness than the part surrounding this region. Also, the bright line is a region that is visually recognized as a linear region in the electron channeling contrast image, and its shape does not have to be completely straight. For example, a curved portion may be included in part or all of the contour.

[0022] There is at least one of the above crystal planes. When there is only one of the above crystal planes, the crystal plane is the {220} plane. From the viewpoint of obtaining an electron channeling contrast image in which bright lines are displayed with higher contrast, when there are two or more of the above crystal planes, it is preferable that these two or more crystal planes include the {220} plane and the {400} plane. From the above viewpoint, it is preferable that there are three of the above crystal planes, more preferably two of them are the {220} plane and the {400} plane, and still more preferably the three are the {220} plane, the {220} plane (i.e., two equivalent {220} planes) and the {400} plane. Specific examples include the case where the above crystal plane is only the {220} plane, the case of two of the {220} plane and the {400} plane, and the case of three of the above crystal planes being the {220} plane, the {220} plane (i.e., two equivalent {220} planes) and the {400} plane, etc.

[0023] By obtaining the electron channeling contrast image as described above, in this electron channeling contrast image, dislocations present in the single crystal silicon sample after the coating is formed can be detected as bright lines with high contrast.

[0024] [Method for Determining Oxygen Concentration Target Value of Single Crystal Silicon Wafer] One aspect of the present invention relates to a method for determining an oxygen concentration target value of a single crystal silicon wafer. The method for determining the oxygen concentration target value includes preparing a plurality of single crystal silicon samples having different oxygen concentrations, forming a coating on each of the plurality of single crystal silicon samples under the same film formation conditions, partially removing the coating, and evaluating the presence or absence of dislocations in the plurality of single crystal silicon samples by the dislocation detection method. Then, based on the result of the above evaluation, the oxygen concentration of the single crystal silicon sample evaluated as having no dislocations is determined as the oxygen concentration target value of the single crystal silicon wafer to be actually manufactured.

[0025] Regarding a single-crystalline silicon wafer, the occurrence of dislocations after forming a coating is affected by the oxygen concentration of the single-crystalline silicon wafer. The higher the oxygen concentration, the less likely dislocations are to occur. Therefore, in the above oxygen concentration target value determination method, for a plurality of single-crystalline silicon samples with different oxygen concentrations, the presence or absence of dislocations after forming a coating is evaluated by the above dislocation detection method. As a result of such evaluation, the oxygen concentration of the single-crystalline silicon sample evaluated as having no dislocations is determined as the oxygen concentration target value of the single-crystalline silicon wafer to be actually manufactured. For example, by growing a single-crystalline silicon ingot so as to obtain a single-crystalline silicon having an oxygen concentration close to the target value thus determined, and cutting a wafer from this ingot, it becomes possible to manufacture a single-crystalline silicon wafer in which dislocations are less likely to occur after forming a coating during, for example, a semiconductor device manufacturing process, or even if dislocations occur, the degree of dislocation generation is mild.

[0026] Hereinafter, the above oxygen concentration target value determination method will be described in more detail.

[0027] In the present invention and in this specification, the oxygen concentration of a single-crystal silicon sample can be a value determined by a known method. For a plurality of single-crystal silicon samples having different oxygen concentrations, the number of samples and the oxygen concentration are not particularly limited. A coating is formed on each of these plurality of single-crystal silicon samples under the same film-forming conditions. The formation of the coating on the plurality of single-crystal silicon samples, i.e., the film-forming process, may be performed in any of a continuous method, a batch method, and a single-sheet method. Regarding the "same film-forming conditions" in the present invention and in this specification, fluctuations in conditions that can normally occur in the film-forming process are allowed. Thus, a coating is formed on at least a part or the entire surface of at least one of each of the plurality of single-crystal silicon samples. In order to detect dislocations in the single-crystal silicon sample by the above-described dislocation detection method, a part or all of the coating thus formed is peeled off. For the film-forming process and the method of partially removing the coating, reference can be made to the previous description. As described above, an example of the coating can be silicon nitride. As described above, the peeling of the coating may or may not be performed before obtaining an electron channeling contrast image (ECCI).

[0028] For each of the above plurality of single-crystal silicon samples, the presence or absence of dislocations is evaluated by the above-described dislocation detection method. The presence or absence of dislocations may be determined by visually checking an electron channeling contrast image to see if there are bright lines, or may be determined by known image processing such as using commercially available image processing software, with the contrast value as an index to determine the presence or absence of bright lines. If there is only one single-crystal silicon sample that is evaluated as having no dislocations among the above plurality of single-crystal silicon samples, the oxygen concentration of this one single-crystal silicon sample is determined as the oxygen concentration target value of the single-crystal silicon wafer to be actually manufactured. If there are a plurality (i.e., two or more) single-crystal silicon samples that are evaluated as having no dislocations, the oxygen concentration of any one of these plurality of single-crystal silicon samples is determined as the oxygen concentration target value of the single-crystal silicon wafer to be actually manufactured. The oxygen concentration target value thus determined can be used, for example, for the manufacture of a single-crystal silicon ingot described below.

[0029] [Method for manufacturing single crystal silicon ingot] One aspect of the present invention relates to a method for manufacturing a single crystal silicon ingot, which includes determining a target oxygen concentration value of a single crystal silicon wafer actually manufactured by the above-described oxygen concentration target value determination method, and growing a single crystal silicon ingot under growth conditions in which a single crystal silicon having an oxygen concentration within a target range including the determined target oxygen concentration value can be obtained.

[0030] Hereinafter, the method for manufacturing the single crystal silicon ingot will be described in more detail.

[0031] In the method for manufacturing the single crystal silicon ingot, a target oxygen concentration value of a single crystal silicon wafer actually manufactured by the above-described oxygen concentration target value determination method is determined. Growth conditions for obtaining a single crystal silicon are determined such that an oxygen concentration within a target range including the thus determined target oxygen concentration value can be obtained. The above target range only needs to include at least the above target value, and the lower limit value and the upper limit value of the range are not particularly limited, and the range may be set in consideration of the desired quality of the ingot to be manufactured. As a method for growing a single crystal silicon ingot, a known method such as the CZ (Czochralski) method can be adopted. Growth conditions that affect the oxygen concentration of single crystal silicon in each growth method are known. As an example, for the CZ method, the crystal pulling speed, the crucible rotation speed, etc. can be mentioned. Regarding the method for manufacturing the single crystal silicon ingot, it is not essential to confirm by actually measuring the oxygen concentration of the ingot actually manufactured under the growth conditions that it is "growth conditions under which a single crystal silicon having an oxygen concentration within a target range including the determined target oxygen concentration value can be obtained".

[0032] According to the method for manufacturing the single crystal silicon ingot, it is possible to manufacture a single crystal silicon wafer from which a single crystal silicon wafer having a low probability of dislocation generation or a low degree of dislocation generation even if dislocation occurs after forming a coating can be cut out.

[0033] [Method for manufacturing single crystal silicon wafer] One aspect of the present invention relates to a method for manufacturing a single-crystalline silicon wafer, which includes manufacturing a single-crystalline silicon ingot by the method for manufacturing the above single-crystalline silicon ingot and cutting out wafers from the manufactured single-crystalline silicon ingot.

[0034] According to the method for manufacturing the above single-crystalline silicon wafer, it is possible to manufacture a single-crystalline silicon wafer in which dislocations are unlikely to occur after the formation of the coating, or even if they occur, the degree of dislocation generation is mild. For the wafer manufacturing process such as cutting out wafers from the ingot, known techniques related to the manufacturing of semiconductor wafers can be applied.

Examples

[0035] The present invention will be further described below with reference to examples. However, the present invention is not limited to the embodiments shown in the examples.

[0036] The following electron channeling contrast images (ECCI) were obtained at an electron beam energy of 20 keV and an observation magnification of 10,000 to 100,000 times. The SEM used was an SEM equipped with an irradiation system capable of precession deflection of the electron beam while fixing the electron beam at a single point on the irradiated surface.

[0037] [Example of obtaining electron channeling contrast image (ECCI)] Figure 1 shows an electron channeling pattern (ECP) of a single-crystalline silicon wafer with a (100) surface and a diameter of 300 mm obtained by SEM. The ECP shown in Figure 1 was obtained by realizing incidence from various angles by precession deflecting the electron beam while fixing the electron beam at a point on the irradiated surface using the above irradiation system, and is an ECP that satisfies a plurality of electron channeling conditions at the same time. Figure 2 is an example of a partially enlarged view of the ECP shown in Figure 1. The black band-like contrast on the ECP is the part where the intensity of the reflected electrons due to channeling has decreased, and each band corresponds to channeling on each crystal plane. Which crystal plane the channeling pattern is from can be determined from the wavelength of the incident electrons and the camera length to the detector. As an example, Figure 2 shows the electron channeling pattern from the {220} plane and the electron channeling pattern from the {400} plane.

[0038] Figure 3 is another example of a partially enlarged view of the ECP shown in Figure 1. By checking which pattern appears at the center of the field of view of the ECP, it can be confirmed that the incident orientation of the electron beam has been adjusted to satisfy the electron channeling conditions on the desired crystal plane. In Figure 3, the circle in the center is the center of the field of view. In Figure 3(a), the electron beam is incident along the zone axis (perpendicular to the surface ((100) plane)), and in Figure 3(b), the electron channeling conditions of the {220} plane are satisfied. The movement of the pattern within the field of view, that is, the change in the incident orientation, can be performed by rotating and / or tilting the sample. After adjusting to the incident orientation that satisfies the electron channeling conditions of a specific crystal plane, SEM observation is performed at the desired magnification. When there are dislocations in the single crystal under the electron channeling conditions, the electron channeling conditions are disturbed by the strain around the dislocations. This is because the strain, that is, the inclination of the crystal lattice, causes the local substantial incident orientation to deviate from the Bragg angle. As a result, the penetration of the primary electrons becomes shallow around the dislocations, and the intensity of the reflected electrons increases. In this way, the dislocations are observed as contrast (specifically, bright lines) in the reflected electron image. Observations of dislocations in ECCI have already been reported in some polycrystals. In the case of polycrystals, the crystal grains are arranged in various directions. Therefore, when an electron beam is incident on a polycrystal, dislocations in the crystal grains that accidentally satisfy the electron channeling conditions among many crystal grains can be observed. On the other hand, in a single crystal, since the crystal is oriented in the same direction, it is necessary to intentionally adjust the sample to arbitrary electron channeling conditions for dislocation observation. This adjustment can be performed by tilting the sample as described above.

[0039] [Examples of Dislocation Detection] (1) Preparation of Samples Three single-crystal silicon wafers with a diameter of 300 mm and a (100) surface were prepared. After depositing silicon nitride (Si3N4) (film thickness: 280 nm) on the entire surface of each wafer, the silicon nitride film was patterned into strips by photolithography. Thus, Line&Space of the silicon nitride film was formed on the surface of the single-crystal silicon wafer. Specifically, patterning was performed so that Lines with widths of 0.8 μm, 1.2 μm, 1.4 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm, and 10.0 μm were sequentially arranged, and a total of 19 Lines were produced. The interval (i.e., Space) between adjacent Lines was set to 10 μm. Each wafer having Line&Space of the silicon nitride film was heat-treated at 800 °C to generate dislocations. Figure 4 is a transmission electron microscope (TEM) image of a partial cross-section of the sample prepared as described above. A step with a height of 45.9 nm was observed near the Line (patterned silicon nitride film). The position near this stress concentration part (in Figure 4, "Point 1") was used as the electron beam irradiation position in the SEM observation described later.

[0040] (2) Detection of Dislocations The silicon nitride film (Line) of the above sample was peeled off by HF treatment. By this HF treatment, the silicon nitride film can be peeled off without etching the single-crystalline silicon wafer. Figure 5 is an SEM image obtained by observing the above sample by SEM. Figure 5(a) is a backscattered electron image, and Figure 5(b) is a secondary electron image. As shown in Figure 4, since the portion directly under the silicon nitride film of the single-crystalline silicon wafer is slightly raised, that portion appears bright in the SEM image. Figures 5(a) and 5(b) are SEM images of the same portion observed, but the bright line (dislocation) at the position indicated by the arrow in Figure 5(a) is not confirmed in Figure 5(b). From this result, it can be confirmed that the strain of the dislocation that cannot be detected in the secondary electron image can be detected in the backscattered electron image.

[0041] (3) Investigation of incident orientation 1 In the sample after the above HF treatment, with the position shown as "Point 1" in Figure 4 as the electron beam irradiation position, an electron channeling contrast image was obtained by irradiating the electron beam at the incident orientation (specifically, the maximum channeling incident orientation) within the range that satisfies the electron channeling condition for the crystal planes shown in the following Conditions A to F. Condition A: {220}, {400} Condition B: {220} Condition C: {400}, {400} Condition D: {220}, {220}, {400} Condition E: {400} Condition F: {400}

[0042] In the electron channeling pattern (ECP) shown in Figure 6, the black band-like contrast is the portion where the intensity of the backscattered electrons due to channeling has decreased. In Figure 6, it is shown which crystal plane each band corresponds to in terms of channeling. Figure 7 is an electron channeling contrast image (ECCI) obtained by each of Conditions A to F. For each ECCI in Fig. 7, the bright line at the position indicated by the arrow in the ECCI of condition D was set as the dislocation to be detected, and the region within the square frame was averaged to create an intensity profile. As an example, Fig. 8 shows the intensity profile created for the ECCI of condition D in Fig. 7. In the intensity profile, the vertical axis represents intensity and the horizontal axis represents position, both in arbitrary units. I Defect is the maximum intensity value within the bright line, and I background is the minimum intensity value within the observation field of view. For each ECCI in Fig. 7, the luminance contrast C calculated by the following formula was obtained. C = (I Defect - I background ) / I background

[0043] Table 1 shows the luminance contrast C calculated for each ECCI in Fig. 7. As shown in Table 1, since a luminance contrast C exceeding 0.2 was obtained under each of conditions A, B, and D, it can be confirmed that according to the ECCI obtained by irradiating an electron beam at an incident orientation that satisfies the electron channeling condition for at least the {220} plane, dislocations in the single crystal silicon wafer can be detected as bright lines with high contrast. From the fact that a higher luminance contrast C was obtained under each of conditions A and D, it can also be confirmed that it is desirable that the crystal planes satisfying the electron channeling condition further include the {400} plane. Furthermore, since the highest luminance contrast C was obtained under condition D, it can also be confirmed that it is more desirable that the crystal planes satisfying the electron channeling condition are the {220} plane, the {220} plane (i.e., two equivalent {220} planes), and the {400} plane.

[0044]

Table 1

Industrial Applicability

[0045] One aspect of the present invention is useful in the fields of manufacturing single crystal silicon wafers and single crystal silicon ingots.

Claims

1. Detecting a portion observed as a bright line in an electron channeling contrast image obtained by irradiating the surface of a single crystal silicon sample with an electron beam using a scanning electron microscope as a dislocation, wherein the irradiation of the electron beam includes irradiating the electron beam at an incident orientation within a range that satisfies electron channeling conditions for one or more crystal planes of the single crystal silicon sample, and the one or more crystal planes include {220} planes, a method for detecting dislocations in a single crystal silicon sample.

2. The method for detecting dislocations in a single crystal silicon sample according to claim 1, wherein the one or more crystal planes further include {400} planes.

3. The method for detecting dislocations in a single crystal silicon sample according to claim 2, wherein the one or more crystal planes are {400} planes and two equivalent {220} planes.

4. The method for detecting dislocations in a single crystal silicon sample according to claim 1, wherein the irradiation of the electron beam is performed after peeling off a coating formed on the surface.

5. The method for detecting dislocations in a single crystal silicon sample according to claim 4, wherein the coating is silicon nitride.

6. The irradiation of the electron beam is performed with a coating on a part of the surface, and the detected dislocations are dislocations detected by irradiating the electron beam at a position within a region not covered by the coating on the surface, the method for detecting dislocations in a single crystal silicon sample according to claim 1.

7. The method for detecting dislocations in a single crystal silicon sample according to claim 6, wherein the coating is silicon nitride.

8. The method for detecting dislocations in a single crystal silicon sample according to claim 1, wherein the single crystal silicon sample is a single crystal silicon wafer.

9. Preparing a plurality of single crystal silicon samples having different oxygen concentrations, forming a coating on each of the plurality of single crystal silicon samples under the same film formation conditions, partially removing the coating, and evaluating the presence or absence of dislocations in the plurality of single crystal silicon samples by the method for detecting dislocations in a single crystal silicon sample according to claim 1, including determining, as an oxygen concentration target value for a single crystal silicon wafer to be actually manufactured, the oxygen concentration of a single crystal silicon sample evaluated as having no dislocations as a result of the evaluation, a method for determining an oxygen concentration target value for a single crystal silicon wafer.

10. The method for determining an oxygen concentration target value for a single crystal silicon wafer according to claim 9, wherein the coating is silicon nitride.

11. Determining a target oxygen concentration value for a single-crystal silicon wafer to be actually manufactured by the method according to claim 9, and growing a single-crystal silicon ingot under growth conditions in which a single-crystal silicon having an oxygen concentration within a target range including the determined target oxygen concentration value is obtained, A method for manufacturing a single-crystal silicon ingot, comprising:

12. Manufacturing a single-crystal silicon ingot by the method according to claim 11, and cutting out a wafer from the manufactured single-crystal silicon ingot, A method for manufacturing a single-crystal silicon wafer, comprising:

Images