Method for evaluating semiconductor wafer and method for manufacturing semiconductor wafer

Abstract

The present application provides a kind of evaluation method of semiconductor wafer, it includes: the film thickness range of the coating film that the intensity of scattered light obtained by defect inspection device is determined to be above specified intensity;Form the coating film that makes the defect existing on the surface of the evaluation object semiconductor wafer expand in the film thickness above the above-mentioned film thickness range;LPD determination is carried out by checking the surface of the above-mentioned coating film by defect inspection device;Based on the coordinate data obtained by the above-mentioned LPD determination, determine the position of the observation object LPD, by using scanning electron microscope to observe the position, determine whether the above-mentioned observation object LPD is the coating film protrusion of the above-mentioned coating film protrusion;And carry out evaluation related to the above-mentioned coating film protrusion.

Description

Related applications

[0001] This application claims priority to Japanese Patent Application No. 2024-055694, filed on March 29, 2024, the entire contents of which are incorporated herein by special disclosure. Technical Field

[0002] This invention relates to a method for evaluating semiconductor wafers and a method for manufacturing semiconductor wafers. Background Technology

[0003] As an evaluation method for semiconductor wafers, the method based on the detection of bright spots (LPD: Light Point Defect) by a defect inspection device is widely used (see, for example, Patent Document 1 and Patent Document 2, the entire contents of which are incorporated herein by reference as special disclosure).

[0004] Patent Document 1: Japanese Patent No. 6414801 Specification Patent Document 2: Japanese Patent Application Publication No. 2023-061116 Summary of the Invention

[0005] Defects may exist on the surface of a semiconductor wafer. Among these defects may be minute defects smaller than the detection limit size of a defect inspection device. If an evaluation can be performed on the semiconductor wafer that may contain such minute defects, then, for example, based on the evaluation results, by changing the manufacturing conditions of the semiconductor wafer to suppress the generation of minute defects, it is possible to manufacture a high-quality semiconductor wafer with fewer minute defects.

[0006] One objective of this invention is to provide a novel evaluation method capable of evaluating defects present on the surface of a semiconductor wafer.

[0007] For example, as described in Japanese Patent No. 6414801 (Patent Document 1) and Japanese Unexamined Patent Publication No. 2023-061116 (Patent Document 2), in order to evaluate a semiconductor wafer, a coating is formed on the surface of the semiconductor wafer to be evaluated, causing defects existing on that surface to expand. If the coating surface is observed by a defect inspection device after such a coating is formed, the LPD detection size can be increased compared to before the coating is formed. This is preferred for evaluating semiconductor wafers that may contain tiny defects smaller than the detection limit size of the defect inspection device. Therefore, the inventors of the present invention have repeatedly conducted in-depth research on evaluation methods for semiconductor wafers including forming the above-mentioned coating on the surface of the semiconductor wafer to be evaluated. As a result, the inventors of the present invention have discovered a new evaluation method, which includes: setting the film thickness of the coating formed on the surface of the semiconductor wafer to be evaluated within a film thickness range where the scattered light intensity obtained by the defect inspection device is above a predetermined intensity; and observing the coating surface using a scanning electron microscope to classify the types of LPDs.

[0008] That is, one aspect of the present invention is as described below.

[0009] [1] A method for evaluating semiconductor wafers (hereinafter also referred to as "the first evaluation method") Determine the range of film thicknesses for which the intensity of scattered light obtained by the defect inspection device is above a specified intensity; A coating is formed on the surface of the semiconductor wafer being evaluated, with a film thickness within the aforementioned range, to propagate defects present on that surface. LPD measurement is performed by inspecting the surface of the above-mentioned coating using a defect inspection device. Based on the coordinate data obtained through the LPD measurement described above, the location of the LPD of the observed object is determined. This location is then observed using a scanning electron microscope (SEM) to determine whether the LPD of the observed object is a coating protrusion of the aforementioned coating elevation; and An evaluation related to the aforementioned membrane protrusions was conducted.

[0010] [2] According to the evaluation method for semiconductor wafers described in [1], determining the film thickness range of the above-mentioned coating includes: Prepare multiple wafers for experimental use; LPD measurements were performed by inspecting the surfaces of the aforementioned experimental wafers using a defect inspection device. A coating of different thickness is formed on each of the aforementioned surfaces of the plurality of experimental wafers; LPD measurements were performed by inspecting the surface of the coating on the aforementioned multiple experimental wafers using a defect inspection device. For each of the above-mentioned multiple experimental wafers, the position of the LPD of the object under observation is determined based on the coordinate data obtained by measuring the LPD after the above-mentioned coating is formed. The LPD of the object under observation is determined by observing the position using a scanning electron microscope to determine whether the LPD of the object under observation is a coating protrusion of the above-mentioned coating. For each of the aforementioned experimental wafers identified as having coated protrusions in its LPD, the ratio of the LPD detection size obtained by LPD measurement before coating formation to the LPD detection size obtained by LPD measurement after coating formation is calculated; and The film thickness range is determined based on the ratio calculated above.

[0011] [3] The evaluation method for semiconductor wafers according to [1] or [2], wherein the coating is a nitride film.

[0012] [4] The evaluation method of a semiconductor wafer according to any one of [1] to [3], wherein the above-mentioned defect is a particle.

[0013] [5] The evaluation method for a semiconductor wafer according to any one of [2] to [4], wherein the coating is a nitride film and the defect is a particle.

[0014] [6] A method for evaluating a semiconductor wafer (hereinafter also referred to as "the second evaluation method"), comprising: A coating is formed on the surface of the semiconductor wafer being evaluated with a film thickness ranging from 70 nm to 140 nm to propagate defects present on that surface. LPD measurement is performed by inspecting the surface of the above-mentioned coating using a defect inspection device. Based on the coordinate data obtained through the LPD measurement described above, the position of the LPD of the observed object is determined. This position is then observed using a scanning electron microscope to determine whether the LPD of the observed object is a coating protrusion of the aforementioned coating elevation; and An evaluation related to the aforementioned membrane protrusions was conducted.

[0015] [7] According to the evaluation method for semiconductor wafers described in [6], wherein the coating is a nitride film.

[0016] [8] The evaluation method for semiconductor wafers according to [6] or [7], wherein the above-mentioned defects are particles.

[0017] [9] The evaluation method for semiconductor wafers according to [7] or [8], wherein the above-mentioned defects are particles.

[0018]

[10] The evaluation method for a semiconductor wafer according to any one of [1] to [9] further includes determining the quality of the semiconductor wafer to be evaluated based on the evaluation results related to the above-mentioned coating protrusions.

[0019]

[11] A method for manufacturing a semiconductor wafer, comprising: Manufacturing semiconductor wafers under the manufacturing conditions of the object being evaluated; The semiconductor wafer manufactured above was evaluated using the evaluation method described in

[10] ; Based on the results of the above evaluation, the manufacturing conditions under which changes were imposed on the evaluated object will be determined as the subsequent manufacturing conditions, or the manufacturing conditions of the evaluated object will be determined as the manufacturing conditions to be continued; and Semiconductor wafers are manufactured under the manufacturing conditions specified above.

[0020] According to one aspect of the present invention, a new evaluation method is provided that can evaluate defects present on the surface of a semiconductor wafer. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of size expansion based on the lens effect.

[0022] Figure 2 Specific examples are shown, including SEM images of the coated protrusions and the particles after film formation.

[0023] Figure 3 In this embodiment, for four experimental wafers, a graph is obtained by plotting the LPD detection dimensions before film deposition on the X-axis and the LPD detection dimensions after film deposition on the Y-axis.

[0024] Figure 4 The number of coating protrusions determined for the five levels of the evaluation object wafer is shown in the embodiment. Detailed Implementation

[0025] Evaluation methods for semiconductor wafers In this specification, both the first evaluation method and the second evaluation method are referred to together as "evaluation method for semiconductor wafers" or simply "evaluation method". Unless otherwise specified, descriptions relating to the first evaluation method also apply to the second evaluation method, and vice versa.

[0026] <Evaluation Object: Semiconductor Wafers> The term "semiconductor wafer being evaluated" is also used. Regarding the types of semiconductor wafers, various semiconductor wafers generally used as semiconductor substrates can be cited as examples of semiconductor wafers evaluated using the above evaluation method. For example, various silicon wafers can be cited as specific examples of semiconductor wafers. Silicon wafers can be, for example, single-crystal silicon wafers cut from single-crystal silicon ingots and processed through various steps, polished wafers with a polished surface due to grinding, epitaxial wafers with an epitaxial layer formed, etc. The diameter of the semiconductor wafer being evaluated is, for example, 200 mm or less, or 200 mm or more (e.g., 200 mm, 300 mm, or 450 mm), but is not particularly limited.

[0027] Defects exist on the surface of the semiconductor wafer being evaluated. These defects can be protruding defects. A specific example of a protruding defect is a particle. A particle is a foreign object that adheres to the wafer surface during the wafer manufacturing process.

[0028] <LPD Measurement Based on Defect Inspection Device> In the above evaluation method, the LPD measurement of the coated surface is performed at least after the coating is formed, as described later. Alternatively, the LPD measurement of the semiconductor wafer surface can be performed before the coating is formed. Hereinafter, the LPD measurement of the coated surface after coating formation will be referred to as "post-coating LPD measurement of the wafer under evaluation" or "post-coating LPD measurement," and the LPD measurement of the wafer surface before coating formation will be referred to as "pre-coating LPD measurement of the wafer under evaluation" or "pre-coating LPD measurement."

[0029] As a defect inspection device, a known defect inspection device can be used that can incident light onto the surface of the object to be inspected and detect the scattered light from that surface. Such defect inspection devices are generally also called light scattering defect inspection devices, surface inspection machines, etc. A specific example of a defect inspection device is a laser defect inspection device. Laser defect inspection devices typically use a laser to scan the surface of the object to be inspected, and use the scattered light to detect protrusions on the surface of the object as light spots (LPDs). Furthermore, by measuring the scattered light from the LPD, the position (specifically, coordinate points) of the protrusions on the surface of the object to be inspected and the size detected by the LPD (LPD detection size) can be determined. The LPD detection size is output by the resolution unit of the defect inspection device by comparing the intensity of the scattered light from the LPD with the intensity of the scattered light from standard particles such as silica particles. As a laser, ultraviolet light, visible light, etc., can be used, and the wavelength is not particularly limited. Ultraviolet light refers to light in the wavelength region of less than 400 nm, and visible light refers to light in the wavelength region of 400 nm to 600 nm. The resolution unit of a laser defect inspection device is typically capable of acquiring two-dimensional position coordinates (X and Y coordinates) on the surface of the object being inspected for each of the multiple detected LPDs, and creating an LPD map representing the in-plane distribution of LPDs on the surface of the object being inspected based on the acquired two-dimensional position coordinate information. Specific examples of commercially available laser defect inspection devices include the KLA-TENCOR Surfscan series SP1, SP2, SP3, SP5, and SP7. However, these devices are merely examples, and various other defect inspection devices can also be used. In both post-film deposition LPD measurement and pre-film deposition LPD measurement of the wafer being evaluated, the inspection area based on the defect inspection device can be the entire in-plane area or a portion of the in-plane area of ​​the wafer surface. In post-film deposition LPD measurement of the wafer being evaluated, the inspection area on the wafer surface is preferably the same area as the inspection area in the pre-film deposition LPD measurement, or an area containing the same area as the inspection area in the pre-film deposition LPD measurement. Therefore, LPDs detected in pre-film deposition LPD measurements of the wafer being evaluated can also be detected in post-film deposition LPD measurements of the wafer being evaluated. Using the defect inspection apparatus, scattered light intensity (specifically, the LPD detection size calculated based on the scattered light intensity as described above) and coordinate data can be obtained for LPDs within the inspection area. For example, if an LPD is detected in post-film deposition LPD measurements at the same coordinates as the LPD detected in pre-film deposition LPD measurements of the wafer being evaluated, it can be determined that a defect exceeding the detection limit size of the defect inspection apparatus exists at that location on the surface of the wafer being evaluated.If the LPD coordinate is not detected in the LPD measurement before film deposition of the wafer being evaluated, but is detected in the LPD measurement after film deposition of the wafer being evaluated, then it is determined that there is a defect smaller than the detection limit size of the defect inspection device at that coordinate position on the surface of the wafer being evaluated.

[0030] <Formation of the coating> As a coating formed on the surface of a semiconductor wafer being evaluated, various coatings formed by known film-forming methods can be cited. Specific examples of such coatings include nitride films, oxide films, polycrystalline silicon films, amorphous silicon films, and metal films.

[0031] In one embodiment, the aforementioned coating can be a deposited film of film-forming material deposited on the surface of a semiconductor wafer. Examples of film-forming methods for forming the deposited film include various methods that deposit film-forming materials on the surface of a semiconductor wafer using vapor phase growth methods, such as CVD (Chemical Vapor Deposition) and ALD (Atomic Layer Deposition). Examples of CVD methods include LP (Low Pressure) CVD and plasma CVD.

[0032] Regarding the film thickness of the coating, in the first evaluation method, the film thickness range where the scattered light intensity obtained by the defect inspection device is above a specified intensity is determined. Hereinafter, the process of performing the above determination will be described as the "film thickness determination process". In the second evaluation method, a coating with a thickness in the range of 70 nm to 140 nm is formed on the surface of the semiconductor wafer being evaluated. The film thickness range of 70 nm to 140 nm can be the film thickness range where the scattered light intensity obtained by the defect inspection device is above a specified intensity. In this invention and this specification, the film thickness can be a value obtained by a known film thickness measurement method, or it can be a set film thickness set in the film deposition apparatus.

[0033] In the second evaluation method, from the viewpoint of maximizing the intensity of scattered light obtained by the defect inspection device, the film thickness of the coating formed on the surface of the semiconductor wafer being evaluated is 70 nm or more, preferably 80 nm or more, and more preferably 90 nm or more, 100 nm or more, and 110 nm or more. Furthermore, from the above viewpoint, in the second evaluation method, the film thickness of the coating formed on the surface of the semiconductor wafer being evaluated is 140 nm or less, preferably 130 nm or less.

[0034] In the first evaluation method, the film thickness of the coating formed on the surface of the semiconductor wafer to be evaluated is only required to be within a range where the intensity of scattered light obtained by the defect inspection device is above a specified intensity. For the second evaluation method, the thickness can be outside or within this range. In one embodiment, in the first evaluation method, the film thickness of the coating formed on the surface of the semiconductor wafer to be evaluated is preferably 70 nm or more, more preferably 80 nm or more, and further preferably 90 nm or more, 100 nm or more, and 110 nm or more, respectively. Furthermore, in another embodiment, in the first evaluation method, the film thickness of the coating formed on the surface of the semiconductor wafer to be evaluated is preferably 140 nm or less, more preferably 130 nm or less.

[0035] The aforementioned coating enables the expansion of defects present on the surface of a semiconductor wafer. Through this "expansion," a protrusion larger than the size of a defect on the surface of the semiconductor wafer is formed on the surface of the coating. This is based on the so-called "lens effect." The "lens effect" refers to the phenomenon where, originating from a protrusion, a coating protrusion with a diameter several times larger than the protrusion itself forms on the coating surface directly above it. In this invention and this specification, "coating protrusion" refers to a portion of the coating surface that is raised due to the presence of a protruding defect directly below it.

[0036] Figure 1 This is a schematic diagram of size expansion based on the lens effect. In Figure 1 In the example shown, coatings of different thicknesses (T1 < T2 < T3) are formed on the surface of each wafer.

[0037] The defect inspection device incident light onto the surface of the object being inspected and receives the scattered light from the surface as a signal from the protrusion, thereby detecting the LPD. The intensity of the scattered light is mainly based on Rayleigh scattering as shown in equation (1).

[0038] [Mathematical Expression 1] Equation (1) (In Equation (1), Is: scattered light intensity, λ: wavelength of light incident on the surface of the object being inspected, Ii: incident intensity, r: distance between the scatterer and the detector, d: diameter of the scatterer (defect), n: complex refractive index (including attenuation coefficient), θ: scattering angle (angle between the incident direction and the detector)) The larger the diameter of the sphere acting as a scatterer, the greater the intensity of Rayleigh scattering. Defect inspection devices also follow this rule: the larger the scatterer, the easier the detection becomes. For example, ... Figure 1As shown, compared to the case of film thickness T1, the coating protrusions become larger at film thickness T2, thus increasing the intensity of scattered light. However, it can be considered that the scattering characteristics differ when the shape of the scatterer is significantly different from that of a sphere. Because the coating thickness increases, the shape of the coating protrusions becomes smoother, resulting in a shape significantly different from that of a sphere, thus reducing the amount of scattered light. For example, as... Figure 1 As shown, compared with the case of film thickness T2, the intensity of scattered light is weaker when the film thickness is T3, making it difficult to detect as LPD.

[0039] Based on the above, if a film with a thickness within the range where the intensity of scattered light obtained by the defect inspection device is above a specified intensity is formed on the surface of the semiconductor wafer being evaluated, then LPD detection becomes easier. In the first evaluation method, such a film thickness range is determined in the film thickness determination step.

[0040] <Film Thickness Determination Process> The film thickness determination process in the first evaluation method may include: Prepare multiple wafers as experimental wafers (hereinafter referred to as "Experimental Wafer Preparation Process"); The LPD measurement was performed by inspecting the surface of the above-mentioned multiple experimental wafers using a defect inspection device (hereinafter referred to as "LPD measurement of experimental wafers before film formation" or "LPD measurement before film formation"). A coating of different thickness is formed on each of the aforementioned surfaces of the plurality of experimental wafers (hereinafter referred to as "film formation process of experimental wafers"). The LPD measurement was performed by inspecting the surface of the coating of the above-mentioned multiple experimental wafers using a defect inspection device (hereinafter referred to as "LPD measurement of experimental wafers after film formation" or "LPD measurement after film formation"). For each of the aforementioned experimental wafers, the position of the LPD of the object to be observed is determined based on the coordinate data obtained by measuring the LPD after the coating is formed. The LPD of the object to be observed is determined by observing the position using a scanning electron microscope to determine whether the LPD of the object to be observed is a coating protrusion of the coating (hereinafter referred to as "LPD classification process of experimental wafers"). For each of the aforementioned experimental wafers identified as having a coated protrusion, the ratio of the LPD detection size obtained through the LPD measurement prior to coating formation to the LPD detection size obtained through the LPD measurement after coating formation is calculated (hereinafter referred to as the "ratio calculation process"); and The film thickness range is determined based on the ratio calculated above (hereinafter referred to as the "film thickness range determination process").

[0041] The various processes described above will be explained in turn below.

[0042] (Preparation process for experimental wafers) Regarding the experimental wafers, please refer to the preceding descriptions related to the semiconductor wafers to be evaluated. However, the experimental wafers do not need to be the same type of wafer as the wafer to be evaluated, nor do they need to be wafers of the same diameter. Epitaxial wafers tend to have fewer types of defects on their surface (specifically, the surface of the epitaxial layer) than polished wafers. Therefore, when comparing polished wafers and epitaxial wafers, it is preferable to use epitaxial wafers as experimental wafers. However, polished wafers may also be used as experimental wafers. Furthermore, the number of experimental wafers is not limited to wafers cut from the same ingot. The number of experimental wafers can be 2 or more, or 3 or more, or 4 or less. In addition, the number of experimental wafers can be, for example, 8 or less, 7 or less, 6 or less, or 5 or less. However, the number of experimental wafers is not limited to the above ranges. It is preferable that the multiple experimental wafers are wafers that have undergone cleaning treatment under the same cleaning conditions, because there is little or no difference in the types of defects on the wafer surface among the multiple experimental wafers. In this invention and in this specification, "the same cleaning conditions" is not limited to being exactly the same, but also allows for variations that are normally possible (such as changes in the concentration of the cleaning solution over time) and / or variations caused by the operator or the equipment.

[0043] (LPD measurement of the wafer before film formation in the experiment) LPD (Limited Potential Damage) measurements are performed by inspecting the surfaces of the aforementioned multiple experimental wafers using a defect inspection device. For details regarding LPD measurements, please refer to the preceding description related to LPD measurements of the semiconductor wafers being evaluated. When inspecting the surfaces of multiple experimental wafers using the defect inspection device, the inspection area may be the same or different. As described later, for the purpose of single-pass production, it is preferable to inspect multiple LPDs on the surface of each experimental wafer. The number of LPDs inspected may be 2 or more, or 3 or more, 5 or more, 10 or more, 20 or more, 30 or more, 40 or more, or 50 or more; alternatively, it may be 100 or less, 90 or less, or 80 or less.

[0044] (Film deposition process for experimental wafers) Next, for the aforementioned experimental wafers, a coating was formed on the surface after LPD measurement was performed prior to film formation. The thickness of the coating formed here is different for each of the aforementioned experimental wafers. The types of coatings formed on the surfaces of the aforementioned experimental wafers may be the same or different. Furthermore, the types of coatings formed on the surfaces of the multiple experimental wafers may be the same as or different from the coatings formed on the surface of the semiconductor wafer of the evaluation object. Regarding the formation of the coating, please refer to the preceding description related to the formation of coatings on the semiconductor wafer of the evaluation object.

[0045] (LPD measurement of the wafer after film formation in the experiment) After coatings are formed on the surfaces of the aforementioned experimental wafers, LPD (Limited Potential) measurements are performed by inspecting the coating surfaces using a defect inspection device. In the post-coating LPD measurement of the experimental wafers, the inspection area on the coating surface of each experimental wafer is preferably the same area as the inspection area in the pre-coating LPD measurement, or an area that includes the same area as the pre-coating LPD measurement. Therefore, LPD detected in the pre-coating LPD measurement can also be detected in the post-coating LPD measurement of the experimental wafers. For information on LPD measurement, please refer to the preceding description related to the LPD measurement of the semiconductor wafers being evaluated.

[0046] (LPD sorting process for experimental wafers) For each of the aforementioned experimental wafers, the location of the LPD (Liquidity Diode) of the observed object is determined based on the coordinate data obtained from the LPD measurement after film deposition, and this location is observed using a scanning electron microscope (SEM). Through this SEM-based morphological observation, it is possible to determine whether the LPD detected by the defect inspection device at the observed location is a coating protrusion (a portion of the coating surface that is raised due to a protruding defect directly below it). Foreign matter (i.e., post-coating particles) adhering to the coating surface after coating formation and coating protrusions can be easily classified through SEM-based morphological observation. SEM observation can be performed using methods commonly used for semiconductor wafers.

[0047] (Ratio calculation process) For each of the aforementioned experimental wafers and its corresponding coated protrusions, the ratio of the LPD detection size obtained by the pre-filming LPD measurement (hereinafter also referred to as "pre-filming LPD detection size") to the LPD detection size obtained by the post-filming LPD measurement (hereinafter also referred to as "post-filming LPD detection size") is calculated. The LPD to which this ratio is calculated can be a portion or all of the LPDs identified as coated protrusions. This ratio can be "post-filming LPD detection size / pre-filming LPD detection size" or "pre-filming LPD detection size / post-filming LPD detection size," preferably "post-filming LPD detection size / pre-filming LPD detection size." Hereinafter, "post-filming LPD detection size / pre-filming LPD detection size" will also be referred to as "size magnification." Size magnification can be calculated, for example, as follows.

[0048] For each of the aforementioned experimental wafers, for each of the LPDs identified as coated protrusions, the LPD detection dimensions before film formation are plotted on the X-axis, and the LPD detection dimensions after film formation are plotted on the Y-axis. A straight line Y=aX is fitted using a known fitting method. The slope "a" of this straight line is taken as the dimensional magnification.

[0049] (Process for determining film thickness range) Regarding the measurement lower limit value set in the defect inspection apparatus, it is preferable to set the measurement lower limit value for the LPD detection size when performing LPD measurement on a coating formed on the wafer surface (post-coating LPD measurement) to be higher (i.e., a larger value) than the measurement lower limit value for the LPD detection size when performing LPD measurement on the wafer surface before coating formation (pre-coating LPD measurement). This is because, generally, the coating surface is rougher and has higher hapticity compared to the wafer surface. When the measurement lower limit value in post-coating LPD measurement is set to "A" and the measurement lower limit value in pre-coating LPD measurement is set to "B" (A > B), since smaller LPDs can be detected by increasing the intensity of scattered light, the size magnification is preferably "A / B" or higher. Therefore, for example, by using the above-mentioned "A / B" value as an indicator, it is possible to determine "the range of coating thicknesses where the scattered light intensity obtained by the defect inspection apparatus is above a specified intensity". For example, among multiple experimental wafers, the smallest coating thickness within the range of dimensional magnification of "A / B" or higher can be used as the lower limit of the aforementioned film thickness range, and the largest coating thickness within the range of dimensional magnification of "A / B" or higher can be used as the upper limit of the aforementioned film thickness range. In the first evaluation method, for example, a coating with a thickness within such a determined film thickness range can be formed on the surface of the semiconductor wafer to be evaluated. As an example, the same film thickness as the coating of the experimental wafer with the largest dimensional magnification within the aforementioned film thickness range can be determined as the film thickness formed on the surface of the semiconductor wafer to be evaluated, but this is only an example, and the first evaluation method is not limited to the above example.

[0050] <LPD Classification Related to the Semiconductor Wafers Being Evaluated> In the above evaluation method, for the semiconductor wafer being evaluated, the location of the LPD (Limited Partial Damage) is determined based on coordinate data obtained from LPD measurement after coating formation, and this location is observed using a scanning electron microscope (SEM). Through this SEM-based morphological observation, it is possible to determine whether the LPD detected by the defect inspection device at the observed location is a coating protrusion (a portion of the coating surface that is raised due to a protruding defect directly below it). For details on SEM observation, please refer to the preceding description.

[0051] <Evaluation and quality assessment of coating protrusions on semiconductor wafers being evaluated> In the above evaluation method, for example, it is possible to determine one or more of the following: the LPD detection size, number, and in-plane distribution (in-plane number distribution, in-plane size distribution, etc.) of the LPDs classified as coated protrusions according to the above LPD classification. Furthermore, one or more of these can be used as indicators to determine the quality of the semiconductor wafer being evaluated. Alternatively, based on the LPD detection size and size magnification of the coated protrusions, it is possible to estimate the size of the LPD defect on the wafer surface before film deposition, which is the LPD whose detection size is determined by LPD measurement after film deposition. For an example of the calculation method used for the above estimation, please refer to the description of the embodiments described later. For example, the defect size calculated in this way can also be used as an indicator for quality determination. The threshold for quality determination can be set according to the desired quality of the product wafer. For specific examples of quality determination, please refer to the description related to the semiconductor wafer manufacturing method described later.

[0052] According to the above evaluation methods (i.e., the first evaluation method and the second evaluation method), through the expansion based on the coating (lens effect), it is possible to detect and evaluate tiny protruding defects that cannot be detected by the defect inspection device on the surface of the semiconductor wafer.

[0053] [Semiconductor wafer manufacturing methods] One aspect of the present invention relates to a method for manufacturing a semiconductor wafer, comprising: manufacturing a semiconductor wafer under manufacturing conditions for an evaluation object; evaluating the manufactured semiconductor wafer using the semiconductor wafer evaluation method; determining, based on the evaluation results, manufacturing conditions under which changes were imposed on the manufacturing conditions for the evaluation object as subsequent manufacturing conditions, or determining the manufacturing conditions for the evaluation object as manufacturing conditions to be continued; and manufacturing the semiconductor wafer under the determined manufacturing conditions.

[0054] As a specific example of the above manufacturing method, the following methods can be cited.

[0055] Semiconductor wafers are manufactured under manufacturing conditions A.

[0056] In addition, semiconductor wafers are manufactured under manufacturing conditions B, which are different from manufacturing conditions A.

[0057] The manufacturing conditions of the evaluated object are referred to as "Manufacturing Condition B".

[0058] Evaluation wafers were extracted from wafer sets manufactured under manufacturing conditions A and B, respectively, and evaluated using the evaluation method described above.

[0059] For example, if the evaluation result shows that the total number of coating protrusions determined by the evaluation method described above is less than the number of evaluation wafers drawn from the wafer set manufactured under manufacturing condition A compared to the number of evaluation wafers drawn from the wafer set manufactured under manufacturing condition B, then manufacturing condition A can be determined as a manufacturing condition that makes it difficult to generate defects on the semiconductor wafer surface compared to manufacturing condition B. In this case, manufacturing condition B can be modified to be closer to manufacturing condition A, and the modified manufacturing condition can be used as improved manufacturing condition B for subsequent semiconductor wafer manufacturing.

[0060] Furthermore, for example, if the evaluation result is that the in-plane distribution (in-plane size distribution, in-plane number distribution, etc.) of the coating protrusions obtained by the evaluation method described above deviates more from the desired in-plane distribution of the product from the evaluation wafer drawn from the wafer set manufactured under manufacturing condition B than from the evaluation wafer drawn from the wafer set manufactured under manufacturing condition A, then manufacturing condition A can be determined as a better manufacturing condition compared to manufacturing condition B. In this case, manufacturing condition B can be changed to be closer to manufacturing condition A, and the manufacturing condition with the aforementioned change can be used as improved manufacturing condition B for subsequent semiconductor wafer manufacturing. In the above example, the manufacturing condition is determined by comparing two manufacturing conditions (manufacturing conditions A and B), but the manufacturing conditions compared can also be three or more.

[0061] Furthermore, the following methods can also be cited as specific examples of the above manufacturing methods.

[0062] In order to determine the manufacturing conditions (hereinafter referred to as "actual manufacturing conditions") used to manufacture semiconductor wafers that are actually shipped as products, the test manufacturing conditions are first determined.

[0063] Semiconductor wafers are manufactured under these test manufacturing conditions.

[0064] Semiconductor wafers manufactured under test manufacturing conditions are evaluated using the evaluation methods described above.

[0065] Based on the evaluation results, the manufacturing conditions that have been modified from the test manufacturing conditions can be identified as the actual manufacturing conditions, or the test manufacturing conditions themselves can be identified as the actual manufacturing conditions. Then, semiconductor wafers can be manufactured under the identified actual manufacturing conditions.

[0066] For example, the evaluation result is that, in a semiconductor wafer manufactured under test manufacturing conditions, if the total number of coating protrusions determined by the evaluation method described above exceeds a predetermined target value, the manufacturing conditions under which changes were made to the test manufacturing conditions to suppress the generation of defects on the wafer surface can be determined as the actual manufacturing conditions.

[0067] Furthermore, for example, the evaluation results show that even if the in-plane distribution (in-plane size distribution, in-plane number distribution, etc.) of the coating protrusions obtained by the evaluation method described above deviates significantly from the desired in-plane distribution in a semiconductor wafer manufactured under test manufacturing conditions, the manufacturing conditions under which the test manufacturing conditions were modified to suppress the generation of defects on the wafer surface can be determined as the actual manufacturing conditions.

[0068] Regarding the manufacturing processes of semiconductor wafers, such as the manufacturing process of polishing wafers, the process can be carried out by a manufacturing process that includes cutting the wafer from a semiconductor ingot such as a single-crystal silicon ingot (slicing), chamfering, rough grinding (e.g., polishing), etching, mirror polishing (fine grinding), and cleaning processes performed between or after the above processing steps. Particles, which are a form of protruding defect on the surface of a semiconductor wafer, are foreign matter attached to the wafer surface and can therefore be removed by cleaning. Therefore, in one approach, the modified manufacturing conditions described above can be cleaning conditions. To reduce particles, for example, simply strengthening the cleaning conditions is sufficient. Specifically, as means of reducing particles, examples include increasing the number of cleaning cycles, extending the cleaning time, and using cleaning agents with higher cleaning power.

[0069] Example

[0070] The present invention will be further described below based on embodiments. However, the present invention is not limited to the embodiments shown in the examples.

[0071] The defect inspection device used below is the KLA-TENCOR Surfscan SP7 series. In the LPD measurement before film formation, the lower limit of measurement for SP7 was set to 15 nm, and in the LPD measurement after film formation, the lower limit of measurement for SP7 was set to 24 nm.

[0072] The film thicknesses described below are set film thicknesses in the film forming apparatus.

[0073] [Measurements related to experimental wafers] <Experimental wafer preparation process> Four single-crystal silicon wafers (epitaxy wafers) that underwent cleaning treatment under the same cleaning conditions were prepared as experimental wafers.

[0074] <LPD Measurement of Experimental Wafers Before Film Formation> The LPD (Latent Light Dispersion) measurement was performed on the entire in-plane area of ​​one surface of each of the four experimental wafers using a defect inspection device. For all detected LPDs, the LPD detection size (scattered light intensity) and coordinate data were obtained.

[0075] <Film deposition process for experimental wafers> After performing LPD measurement before film formation, in the same LP-CVD film formation apparatus, nitride films (silicon nitride films) of different thicknesses (20nm, 70nm, 120nm, 140nm) were formed on the surfaces of the four experimental wafers after LPD measurement using the same film formation material.

[0076] <LPD Measurement of Experimental Wafers After Film Formation> The LPD (Laminated Light Density) measurement was performed on the entire in-plane area of ​​the coating (nitride film) formed on the surface of each of the four experimental wafers using a defect inspection device. For all detected LPDs, the LPD detection size (scattered light intensity) and coordinate data were obtained.

[0077] <LPD sorting process for experimental wafers> All LPDs detected in the entire in-plane region of the coating surface formed on the surfaces of the four experimental wafers were subjected to SEM-based morphological observation. Specifically, using coordinate data obtained from the post-film-forming LPD measurements, protrusions were observed to acquire secondary electron images. Based on the shape of the secondary electron images, coating protrusions and post-film-forming particles on the coating surface were classified. Figure 2 Specific examples are shown, including SEM images of the coated protrusions and the particles after film formation.

[0078] <Calculation of Size Magnification> Using LPD measurements of all LPDs detected at the same locations in pre-film deposition LPD measurements, identified as coating protrusions through SEM observation, the dimensional magnification of LPDs before and after film deposition was calculated. Specifically, for the four experimental wafers mentioned above, the pre-film deposition LPD measurement dimensions were plotted on the X-axis, and the post-film deposition LPD measurement dimensions were plotted on the Y-axis. The resulting curves are plotted as follows: Figure 3 For each experimental wafer, the straight line Y=aX was fitted using the least squares method. The value of "a" obtained in this way was used as the size magnification.

[0079] <Determination of film thickness range> As previously described, the lower limit of SP7 measurement was set at 15 nm in pre-film deposition LPD measurement and at 24 nm in post-film deposition LPD measurement. Therefore, if the value "1.6" calculated as "24 nm / 15 nm = 1.6" is used as the threshold for dimensional magnification, it is below the threshold when the film thickness is 20 nm, and above the threshold when the film thickness is 70 nm, 120 nm, and 140 nm. From the above results, the range of "70 nm or more and 140 nm or less" is defined as "the range of film thicknesses where the scattered light intensity obtained by the defect inspection device is above a specified intensity." As the film thickness for the film deposited on the surface of the evaluation wafer described later, the film thickness of 120 nm, formed on the surface of the experimental wafer with the largest dimensional magnification among the four experimental wafers mentioned above, was adopted.

[0080] according to Figure 3 The slope 'a' of each straight line Y=aX shown can estimate the size of the LPD defect on the wafer surface before film deposition, from which the LPD detection size is determined by LPD measurement after film deposition. For example, in the case of forming a coating with a film thickness of 120 nm, the dimensional magnification is 2.9 (refer to...). Figure 3 Therefore, the LPD detection size of 24 nm, which is set as the detection lower limit in the post-film deposition LPD measurement, can be calculated as "24 nm / 2.9 = 8.3 nm". Based on the above calculation results, it can be confirmed that by post-film deposition LPD measurement, defects with sizes lower than the detection lower limit in the pre-film deposition LPD measurement can be detected as LPD.

[0081] [Measurements and evaluations related to the wafer being evaluated] <Preparation of the chip to be evaluated> For the semiconductor wafers to be evaluated, five levels of single-crystal silicon wafers (epitaxy wafers) with different cleaning conditions were prepared (levels A, B, C, D, and E).

[0082] <Forming a coating on the surface of the wafer being evaluated> For each of the five wafer levels mentioned above, a 120 nm thick silicon nitride film was formed on the surface of the epitaxial layer. The same film-forming apparatus and the same film-forming material were used in the film-forming process of the experimental wafer.

[0083] <Post-film deposition LPD measurement of the evaluation wafer> The LPD (Latent Light Dispersion) measurement is performed on the entire in-plane area of ​​the coating surface formed on the surface of each of the five evaluation target wafers at the above-mentioned levels using a defect inspection device. For all detected LPDs, the LPD detection size (scattered light intensity) and coordinate data are obtained.

[0084] <LPD Classification Related to the Evaluation Object Chip> For all LPDs detected in the entire in-plane region of the coating surface formed on the respective surfaces of the evaluation object wafers at the five levels mentioned above, SEM-based morphological observation was performed. Specifically, using coordinate data obtained through the post-film-forming LPD measurement, protrusions were observed to obtain secondary electron images. Based on the shape of the secondary electron images, coating protrusions and post-film-forming particles on the coating surface were classified.

[0085] <Evaluation related to membrane protrusions> Figure 4 The table shows the number of coating protrusions obtained from the evaluation of the wafers at the above five levels. For example... Figure 4 As shown, level D has the most membrane protrusions, while level E has the fewest.

[0086] Based on the above results, for example, the cleaning conditions at level E can be determined to be capable of removing even small particles and can be adopted as actual manufacturing conditions. Furthermore, for example, it can be determined that the cleaning conditions at level D are preferably modified for use as actual manufacturing conditions.

[0087] According to one aspect of the present invention, a high-quality semiconductor wafer with few tiny particles can be provided. For example, this high-quality semiconductor wafer with few tiny particles can be used as a semiconductor substrate in a front-end logic device. This front-end logic device, for example, is mounted in a smartphone, enabling the smartphone to achieve multifunctionality and high performance. For example, according to the front-end logic device, multiple applications can be executed simultaneously, or graphics processing capabilities can be improved to smoothly process high-resolution images and / or moving images. As described above, one aspect of the present invention can manufacture high-performance logic semiconductors, enriching people's lives.

[0088] One aspect of the present invention is useful in the manufacture of various semiconductor wafers, such as silicon wafers.

Claims

1. A method for evaluating semiconductor wafers, characterized in that, The evaluation method includes: Determine the range of film thicknesses for which the intensity of scattered light obtained by the defect inspection device is above a specified intensity; A coating is formed on the surface of the semiconductor wafer being evaluated, with a thickness within the specified range, to propagate defects present on that surface. LPD measurement is performed by inspecting the surface of the coating using a defect inspection device. Based on the coordinate data obtained through the LPD measurement, the position of the LPD of the observed object is determined. This position is then observed using a scanning electron microscope to determine whether the LPD of the observed object is a coating protrusion of the coating elevation; and An evaluation related to the coating protrusions was conducted.

2. The evaluation method for semiconductor wafers according to claim 1, characterized in that, Determining the film thickness range of the coating includes: Prepare multiple wafers for experimental use; LPD measurements were performed by inspecting the surfaces of the multiple experimental wafers using a defect inspection device. A coating of different thickness is formed on each of the surfaces of the plurality of experimental wafers; LPD measurements are performed by inspecting the surface of the coating on the plurality of experimental wafers using a defect inspection device. For each of the plurality of experimental wafers, the position of the LPD of the object under observation is determined based on the coordinate data obtained by measuring the LPD after the coating is formed. The LPD of the object under observation is then observed using a scanning electron microscope to determine whether it is a coating protrusion of the coating. For each LPD identified as a coated protrusion on one of the plurality of experimental wafers, the ratio of the LPD detection size obtained by LPD measurement before coating formation to the LPD detection size obtained by LPD measurement after coating formation is calculated; and The film thickness range is determined based on the calculated ratio.

3. The evaluation method for semiconductor wafers according to claim 1, characterized in that, The coating is a nitrided film.

4. The evaluation method for semiconductor wafers according to claim 1, characterized in that, The defect is a particle.

5. The evaluation method for semiconductor wafers according to claim 2, characterized in that, The coating is a nitrided film, and the defect is a particle.

6. A method for evaluating semiconductor wafers, characterized in that, The evaluation method includes: A coating is formed on the surface of the semiconductor wafer being evaluated with a film thickness ranging from 70 nm to 140 nm to propagate defects present on that surface. LPD measurement is performed by inspecting the surface of the coating using a defect inspection device. Based on the coordinate data obtained through the LPD measurement, the position of the LPD of the observed object is determined. This position is then observed using a scanning electron microscope to determine whether the LPD of the observed object is a coating protrusion of the coating elevation; and An evaluation related to the coating protrusions was conducted.

7. The evaluation method for semiconductor wafers according to claim 6, characterized in that, The coating is a nitrided film.

8. The evaluation method for semiconductor wafers according to claim 6, characterized in that, The defect is a particle.

9. The evaluation method for semiconductor wafers according to claim 7, characterized in that, The defect is a particle.

10. The method for evaluating a semiconductor wafer according to any one of claims 1 to 9, characterized in that, Also includes: Based on the evaluation results related to the coating protrusions, the quality of the semiconductor wafer being evaluated is determined.

11. A method for manufacturing a semiconductor wafer, characterized in that, The manufacturing method includes: Manufacturing semiconductor wafers under the manufacturing conditions of the object being evaluated; The manufactured semiconductor wafer is evaluated using the evaluation method described in claim 10; Based on the evaluation results, the manufacturing conditions under which changes were imposed on the evaluated object are determined to be the subsequent manufacturing conditions, or the manufacturing conditions of the evaluated object are determined to be the manufacturing conditions to be continued; and Semiconductor wafers are manufactured under the defined manufacturing conditions.

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