Semiconductor wafer evaluation method, semiconductor wafer manufacturing method, and semiconductor wafer

Abstract

To provide a new evaluation method capable of evaluating minute protruding defects present on the surface of a semiconductor wafer.SOLUTION: A semiconductor wafer evaluation method includes forming a film on the surface of a semiconductor wafer for expanding protruding defects existing on the surface, inspecting the surface of the film using a surface defect inspection device, and evaluating protruding defects present on the surface of the semiconductor wafer on the basis of the results of the inspection, and the film is made of a material having a light attenuation coefficient of 4 or more at a wavelength of 266 nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a semiconductor wafer evaluation method, a semiconductor wafer manufacturing method, and a semiconductor wafer. [Background technology]

[0002] As a method for evaluating defects in semiconductor wafers, a method based on light point defects (LPDs) detected by a surface defect inspection device is widely used (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-212009 Summary of the Invention [Problem to be solved by the invention]

[0004] Protrusion-like defects may exist on the surface of a semiconductor wafer. Specific examples of protrusion-like defects are particles and PIDs (Process Induced Defects). Particles are foreign matter that adheres to the wafer surface during the wafer manufacturing process. PIDs are processing-induced defects that occur due to processing performed in the wafer manufacturing process, and are defects that occur mainly due to polishing. These protrusion-like defects may include minute defects that are below the detection limit size of a surface defect inspection device. If it becomes possible to evaluate such minute defects, it will be possible to manufacture high-quality semiconductor wafers with fewer minute defects, for example, by changing the manufacturing conditions of semiconductor wafers based on the evaluation results to suppress the occurrence of minute defects.

[0005] An object of one aspect of the present invention is to provide a new evaluation method capable of evaluating minute protruding defects present on the surface of a semiconductor wafer. [Means for solving the problem]

[0006] The aforementioned Japanese Patent Application Laid-Open No. 2016-212009 (Patent Document 1) discloses that in order to expand protruding defects present on the wafer surface, a nitride film is formed on the wafer surface, and the protruding portions formed on the surface of this nitride film are detected using a surface defect inspection device (see claims 1, 5, etc. of Japanese Patent Application Laid-Open No. 2016-212009). In response to this, the present inventors have conducted extensive research and have newly discovered that a coating made of a material with an attenuation coefficient of light at a wavelength of 266 nm of 4 or more is suitable as a coating for expanding protruding defects present on the wafer surface. This point will be explained in further detail below.

[0007] A surface defect inspection device irradiates light onto the surface of an evaluation object and detects light emitted from this surface (scattered light or reflected light). This allows the surface defect inspection device to detect protrusions present on the surface of the evaluation object as light point defects (LPDs). However, through extensive research, the inventors discovered that the nitride film described in JP 2016-212009 A (Patent Document 1) has high surface haze, and therefore the measurement sensitivity of the surface defect inspection device is low for the nitride film surface. The reason for the high surface haze of the nitride film is thought to be primarily due to the optical properties of the film itself. Specifically, because nitride films have a small attenuation coefficient (physical property) for light irradiated from a surface defect inspection device (the attenuation coefficient of silicon nitride Si3N4 at a wavelength of 266 nm is 0.013), much of the light incident on the nitride film passes through the nitride film, reaches the interface between the nitride film and the semiconductor wafer, and is reflected at the interface. As a result, the reflected light from the interface is scattered inside and on the surface of the nitride film, which is presumably the reason for the high surface haze of the nitride film. In contrast, if the coating is made of a material with an attenuation coefficient of 4 or greater for light at a wavelength of 266 nm, it is possible to suppress or reduce the reflection of light incident from a surface defect inspection device at the interface between the coating and the semiconductor wafer after passing through the coating. As a result, surface haze caused by light reflected from the interface can be reduced, making it possible to reduce the minimum detectable size of the light-receiving unit of the surface defect inspection device. Therefore, it is believed that high-sensitivity measurement by a surface defect inspection device is possible if the surface of the coating is made of a material with an attenuation coefficient of 4 or greater for light at a wavelength of 266 nm. As described above, the present inventors have completed the present invention as a result of extensive research focusing on the attenuation coefficient inherent to the film. Note that the term "attenuation coefficient" used in this specification and the present invention refers to a coefficient that represents the degree to which emitted light is attenuated by absorption and / or scattering as it travels through a medium.

[0008] That is, one aspect of the present invention is as follows. [1] Forming a coating on the surface of a semiconductor wafer (also simply referred to as a "wafer") to expand protruding defects present on the surface; Inspecting the surface of the coating using a surface defect inspection device; and evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection; Including, A method for evaluating a semiconductor wafer (also simply referred to as "evaluation method"), wherein the coating is a coating made of a material having an attenuation coefficient of light at a wavelength of 266 nm of 4 or more. [2] The semiconductor wafer evaluation method according to [1], wherein the material is amorphous silicon. [3] forming a coating on the surface of a semiconductor wafer; Inspecting the surface of the coating using a surface defect inspection device; and evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection; and The method for evaluating a semiconductor wafer, wherein the coating is an amorphous silicon film. [4] The method for evaluating a semiconductor wafer according to any one of [1] to [3], wherein the surface of the coating has an average haze of 0.5 ppm or less. [5] The method for evaluating a semiconductor wafer according to any one of [1] to [4], wherein the thickness of the coating is 15 nm or more and 500 nm or less. [6] Evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection, The method for evaluating a semiconductor wafer according to any one of [1] to [5], comprising regarding the number of LPDs detected by the inspection as the number of protrusion-like defects present on the surface of the semiconductor wafer, and evaluating the number of protrusion-like defects present on the surface of the semiconductor wafer. [7] Evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection, The method for evaluating a semiconductor wafer according to any one of [1] to [6], comprising measuring the height of a protrusion on the surface of the coating at a position where an LPD is detected by the inspection using an atomic force microscope, regarding the measured height value as the size of a protrusion-like defect present on the surface of the semiconductor wafer directly below the protrusion, and evaluating the size of the protrusion-like defect present on the surface of the semiconductor wafer. [8] The evaluation of the size of the protruding defects present on the surface of the semiconductor wafer is as follows: evaluating the size distribution of protrusion-like defects present on the surface of the semiconductor wafer based on height distribution information created based on measurement values ​​of heights of the plurality of protrusions on the surface of the coating; The semiconductor wafer evaluation method according to [7], comprising: [9] The method for evaluating a semiconductor wafer according to any one of [1] to [8], wherein the protruding defects present on the surface of the semiconductor wafer are defects selected from the group consisting of particles and PIDs.

[10] The method for evaluating a semiconductor wafer according to any one of [1] to [9], wherein the semiconductor wafer is a silicon wafer.

[11] The material is amorphous silicon, the surface of the coating has an average haze of 0.5 ppm or less; The thickness of the coating is 15 nm or more and 500 nm or less, The protruding defects present on the surface of the semiconductor wafer are defects selected from the group consisting of particles and PIDs, the semiconductor wafer is a silicon wafer, and The method for evaluating a semiconductor wafer according to [1], wherein evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection includes at least one of the following (1) and (2). (1) The number of LPDs detected by the inspection is regarded as the number of protrusion-like defects present on the surface of the semiconductor wafer, and the number of protrusion-like defects present on the surface of the semiconductor wafer is evaluated. (2) The height of the protrusion on the coating surface at the position where the LPD was detected by the inspection is measured using an atomic force microscope, and the measured height value is regarded as the size of the protrusion-like defect present on the semiconductor wafer surface directly below the protrusion, and the size of the protrusion-like defect present on the semiconductor wafer surface is evaluated.

[12] The evaluation of the size of the protruding defects present on the surface of the semiconductor wafer is as follows: evaluating the size distribution of protrusion-like defects present on the surface of the semiconductor wafer based on height distribution information created based on measurement values ​​of heights of the plurality of protrusions on the surface of the coating; The semiconductor wafer evaluation method according to

[11] , comprising:

[13] Manufacturing semiconductor wafers under the manufacturing conditions to be evaluated; Evaluating the manufactured semiconductor wafer by the semiconductor wafer evaluation method according to any one of [1] to

[12] . Based on the results of the evaluation, determine the manufacturing conditions obtained by modifying the manufacturing conditions to be evaluated as the manufacturing conditions to be used subsequently, or determine the manufacturing conditions to be evaluated as the manufacturing conditions to be used continuously; and manufacturing a semiconductor wafer under the determined manufacturing conditions; A method for manufacturing a semiconductor wafer (also simply referred to as "manufacturing method"), comprising:

[14] A semiconductor wafer in which, when the semiconductor wafer is evaluated using the semiconductor wafer evaluation method described in any one of [1] to

[12] , the number of LPDs detected by inspecting the surface of the coating using a surface defect inspection device is 15 or less per wafer. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to evaluate minute protruding defects present on the surface of a semiconductor wafer. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of size expansion due to the lens effect. [Figure 2] The results of comparing the LPD detection size before and after the formation of an amorphous silicon film are shown. [Figure 3] 1 shows the average haze measured on the surface of an amorphous silicon film and a silicon nitride film. [Figure 4] For Example 1, the number of LPDs found on the wafer surface before film formation is shown. [Figure 5] Specific examples of SEM images of protrusions and adhered particles after film formation are shown below. [Figure 6] For Example 1, the number of LPDs (post-deposition protrusions) found on the surface of the amorphous silicon film after film formation is shown. [Figure 7] The numbers of LPDs found on the wafer surface after film formation for Comparative Example 1 and Example 2 are shown. [Figure 8] 1 shows the number distribution (height distribution information) obtained by measuring the heights of all protrusions on the surface of the amorphous silicon film by AFM for one of the wafers after LPD measurement after film formation in Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0011] The above evaluation methods and production methods will be described in more detail below.

[0012] [Semiconductor wafer evaluation method] <Semiconductor wafer to be evaluated> The semiconductor wafer evaluated by the above evaluation method can be any of various semiconductor wafers commonly used as semiconductor substrates. Specific examples of semiconductor wafers include various silicon wafers. Silicon wafers can be, for example, silicon single crystal wafers that have been cut from a silicon single crystal ingot and then subjected to various processing steps, such as polished wafers that have been polished to have a polished surface, or epitaxial wafers on which an epitaxial layer has been formed. The diameter of the semiconductor wafer to be 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.

[0013] The semiconductor wafer surface to be evaluated has protruding defects, which can be particles and / or PIDs.

[0014] <Coating formation> In the evaluation method, a coating is formed on the surface of a semiconductor wafer. The coating is made of a material with an attenuation coefficient (also simply referred to as "attenuation coefficient") of 4 or more for light at a wavelength of 266 nm. As described in detail above, a coating made of a material with an attenuation coefficient of 4 or more can reduce the surface haze of the coating, thereby contributing to improved measurement sensitivity. Examples of materials with an attenuation coefficient of 4 or more include amorphous silicon and silicon germanium. While the present invention employs 266 nm as the wavelength for defining the attenuation coefficient, this is to identify the attenuation coefficient as a physical property inherent to the material. The wavelength of light irradiated by the surface defect inspection device used in the evaluation method is not limited to 266 nm. The attenuation coefficients of various materials are publicly known in the literature or can be measured by publicly known methods. For example, see "Edward D. Parik, 'Handbook of Optical Constants of Solids,' Academic Press, 1985." For example, the attenuation coefficient of amorphous silicon is 4.426, and the attenuation coefficient of silicon nitride Si3N4 is 0.013.

[0015] For the above reasons, the attenuation coefficient of the material constituting the coating is 4 or more, and can be, for example, 4,000 or more, 4,100 or more, 4,200 or more, or 4,300 or more. From the viewpoint of improving measurement sensitivity, there is no particular upper limit on the attenuation coefficient. Since sufficient measurement sensitivity can be obtained if the material constituting the coating has an attenuation coefficient of 4 or more, it is not necessary to use a material with an excessively high attenuation coefficient. From this viewpoint, the attenuation coefficient of the material constituting the coating can be, for example, 10 or less, 8 or less, 6 or less, 6,000 or less, 5,500 or less, or 5,000 or less.

[0016] The coating can be formed using a known film-forming apparatus such as a low-pressure chemical vapor deposition (LP-CVD), plasma CVD, or atomic layer deposition (ALD) apparatus.

[0017] A specific example of the material for the coating is amorphous silicon. Hereinafter, a coating made of amorphous silicon will also be referred to as an "amorphous silicon film." Known methods can be used to form an amorphous silicon film. For example, an amorphous silicon film can be formed on the surface of a semiconductor wafer by forming a seed layer using aminosilane gas on the surface of the semiconductor wafer and then depositing a silane gas with a smaller molecular weight than the aminosilane used to form the seed layer. The seed layer serves as the starting point for the growth of amorphous silicon. Among silane-based gases that serve as source gases for amorphous silicon films, depositing an aminosilane gas with a larger molecular weight is preferred from the perspective of forming a highly smooth film surface. For specific processes for forming amorphous silicon films, see, for example, Japanese Patent Application Laid-Open Nos. 2011-249764 and 2014-127693.

[0018] Forming an amorphous silicon film as the coating is preferable from the following viewpoint. During nitride film deposition, ammonium chloride, a reaction by-product, generates dust, resulting in a large amount of foreign matter (adhered particles) adhering to the nitride film surface. Evaluations using a surface defect inspection system cannot distinguish between protrusions (hereinafter also referred to as "post-deposition protrusions"), which are raised portions of the coating surface due to the presence of protrusion-like defects directly below the surface, and adhered particles. Therefore, a defect discrimination process using a scanning electron microscope (SEM) or similar must be performed to distinguish between post-deposition protrusions and adhered particles. Therefore, it is difficult to accurately evaluate the difference in the level of protrusion-like defects on the semiconductor wafer surface located below the nitride film from the results of inspection of the nitride film surface using a surface defect inspection system. In contrast, deposition of an amorphous silicon film generates fewer attached particles. Therefore, it is possible to accurately evaluate the difference in the levels of protrusion-like defects on the surface of the semiconductor wafer located below the amorphous silicon film based on the inspection results of the amorphous silicon film surface using a surface defect inspection device, without performing a defect discrimination process using an SEM or the like. However, it is also possible to perform a defect discrimination process using an SEM or the like on the amorphous silicon film surface and exclude protrusions determined to be attached particles from subsequent evaluation.

[0019] As described above, a coating made of a material with an attenuation coefficient of 4 or more at a wavelength of 266 nm is preferred because it has low surface haze. An example of a surface haze index is average haze. In the present invention and this specification, "average haze" refers to the DW1O (Dark-field Wide-1 Oblique) Haze Average measured using a KLA-Tencor Surfscan Series SP7. In the above evaluation method, the coating formed on the surface of a semiconductor wafer can have an average haze of 0.5 ppm or less measured on the coating surface. Figure 3 shows the average haze measured on the surface of an amorphous silicon film and a silicon nitride film. Figure 3 also shows the measurement results of the average haze of an amorphous silicon film and a silicon nitride film. Specifically, Figure 3 shows the DW1O Haze Average values ​​measured using a KLA-Tencor Surfscan Series SP7 for a 120 nm-thick amorphous silicon film and a 120 nm-thick silicon nitride film. In Figure 3, "SiN" is an abbreviation for silicon nitride film, and "a-Si" and "amorphous Si film" are abbreviations for amorphous silicon film. The amorphous silicon film has an average haze of 0.5 ppm or less, confirming low surface haze. For example, when the average haze is 0.042, the sensitivity set by the 95% Capture Rate of the SEMI standard (SEMI M50-1101) is 19 nm as the sensitivity (minimum detectable size of the light receiving element) of the DW10 channel of the KLA-Tencor Surfscan series SP7. In contrast, when the average haze is 2.067 for a silicon nitride film, the sensitivity (minimum detectable size of the light receiving element) of the DW10 channel of the KLA-Tencor Surfscan series SP7, which is set in the same way, is 29 nm. Thus, a coating with low surface haze is preferable from the viewpoint of increasing the measurement sensitivity of a surface defect inspection device.

[0020] The coating can expand protruding defects present on the semiconductor wafer surface. By "expanding," protrusions larger in size than the protruding defects on the semiconductor wafer surface are formed on the coating surface. This is due to the so-called "lens effect." The "lens effect" is a phenomenon in which, starting from a protrusion, a post-film-deposition protrusion with a diameter several times larger than the protrusion is formed on the coating surface directly above it. Figure 1 is a schematic diagram of size expansion due to the lens effect. In the example shown in Figure 1, the post-deposition protrusion on the coating surface directly above a protrusion with diameter D has a diameter X that is several times larger than the diameter D of the protrusion. Furthermore, the post-deposition protrusion formed by the lens effect is a defect that rises by the same size as the protruding defect on the semiconductor wafer surface directly below it. Therefore, in the example shown in Figure 1, the height of the post-deposition protrusion on the coating surface is the same value as the diameter D of the protrusion. Evaluation utilizing this point will be described in detail later.

[0021] By forming the above coating on the surface of the semiconductor wafer, a protrusion larger in size than a protrusion-like defect on the surface of the semiconductor wafer can be formed on the surface of the coating immediately above the defect. Thus, for example, for a protrusion-like defect on the surface of the semiconductor wafer that is minute in size below the detection limit of a surface defect inspection device, a protrusion that is detectable by a surface defect inspection device and has a size equal to or larger than the detection limit can be formed on the surface of the coating immediately above the defect. As a specific example, Figure 2 shows a comparison of the LPD detection size before and after the deposition of an amorphous silicon film. Figure 2 also shows a comparison of the LPD detection size on the semiconductor wafer surface before the deposition of amorphous silicon films with thicknesses of 20 nm, 40 nm, 70 nm, and 140 nm, with the LPD detection size on the surface of the amorphous silicon film after the deposition. A KLA-Tencor Surfscan Series SP7 was used as the surface defect inspection system. The results shown in Figure 2 confirm that the formation of a coating can enlarge protruding defects on the semiconductor wafer surface. For example, in the example shown in Figure 2, where a 140 nm thick coating was formed, the LPD detection size is approximately three times larger than the LPD detection size before the coating. According to the lens effect, the thicker the deposited coating, the larger the protrusion size detected on the coating surface directly above a protruding defect on the semiconductor wafer surface. In a surface defect inspection device, the larger the defect size, the easier it is to detect the defect as an LPD. Furthermore, it is preferable that the thickness of the coating be thicker than the size of the protrusion-like defect to be evaluated. From the above perspective, it is preferable that the thickness of the coating formed on the semiconductor wafer surface be 15 nm or more. For example, in the case of the KLA-Tencor Surfscan Series SP7, the undetectable size is less than 15 nm, so it is preferable to form a coating of 15 nm or more. The thickness of the coating can be, for example, 500 nm or less, 200 nm or less, or 140 nm or less.

[0022] <Surface inspection using a surface defect inspection device> The surface defect inspection device may be a known surface defect inspection device capable of irradiating the surface of an object to be inspected with light and detecting radiant light (scattered light or reflected light) from the surface. Such surface defect inspection devices are generally referred to as light-scattering surface defect inspection devices, surface inspection machines, etc. A specific example of a surface defect inspection device is a laser surface defect inspection device. A laser surface defect inspection device typically scans the surface of an object to be inspected with a laser beam and detects protrusions on the surface of the object to be inspected as bright spots (LPDs) using the radiant light (scattered light or reflected light). Furthermore, by measuring the radiant 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 as an LPD (LPD detection size) can be determined. The LPD detection size is typically output by an analysis unit of the surface defect inspection device by comparing the intensity of the radiant light from the LPD with the radiant light intensity of standard particles such as silica particles. Ultraviolet light, visible light, etc., can be used as the laser beam, and its wavelength is not particularly limited. Ultraviolet light refers to light in a wavelength range of less than 400 nm, and visible light refers to light in a wavelength range of 400 to 600 nm. The analysis unit of a laser surface defect inspection device typically acquires information on the two-dimensional position coordinates (X and Y coordinates) on the surface of the object to be inspected for each of the detected LPDs, and can create an LPD map showing the in-plane distribution of LPDs on the surface of the object to be inspected from the acquired two-dimensional position coordinate information. Specific examples of commercially available laser surface defect inspection devices include the Surfscan series SP1, SP2, SP3, SP5, and SP7 manufactured by KLA-Tencor. However, these devices are merely examples, and various other surface defect inspection devices can also be used.

[0023] <Evaluation of protruding defects on the surface of semiconductor wafers> In the above evaluation method, protruding defects present on the surface of the semiconductor wafer located below the coating are evaluated based on the results of inspection of the surface of the coating using a surface defect inspection device. Specific examples of such evaluations include the following evaluations (1) and (2). For example, of evaluations (1) and (2), only evaluation (1) or evaluation (2) may be performed, or both evaluations (1) and (2) may be performed.

[0024] (1) The number of LPDs detected by the above inspection is regarded as the number of protrusion-like defects present on the surface of the semiconductor wafer, and the number of protrusion-like defects present on the surface of the semiconductor wafer is evaluated. (2) At the position where the LPD was detected by the above inspection, the height of the protrusion on the coating surface is measured using an atomic force microscope, and the measured height value is regarded as the size of the protrusion-like defect present on the semiconductor wafer surface directly below the protrusion, and the size of the protrusion-like defect present on the semiconductor wafer surface is evaluated.

[0025] According to evaluation (1), the expansion (lens effect) of the coating makes it possible to evaluate the number of minute protrusion-like defects that cannot be detected by inspecting the surface of a semiconductor wafer using a surface defect inspection device.

[0026] Next, evaluation (2) will be explained in more detail.

[0027] As shown in Figure 1, a post-film formation protrusion formed on the coating surface due to the lens effect is a defect that rises by the same size as the protrusion-like defect on the semiconductor wafer surface directly below it. Therefore, the height of a post-film formation protrusion can be considered to be the size of the protrusion-like defect that exists on the semiconductor wafer surface directly below the protrusion. For example, the height of a protrusion measured on the coating surface can be considered to be the diameter of a particle on the semiconductor wafer surface, or the height of a PID on the semiconductor wafer surface. The height of a protrusion on the coating surface can be measured using a known measuring device, for example, an atomic force microscope (AFM).

[0028] Furthermore, as a specific embodiment of evaluation (2), the size distribution of protrusion-like defects present on the surface of a semiconductor wafer can be evaluated based on height distribution information created based on measurement values ​​of the heights of multiple protrusions on the surface of the coating. According to the above evaluation method, the size of minute protrusion-like defects that cannot be detected by inspecting the semiconductor wafer surface with a surface defect inspection device due to the expansion (lens effect) of the coating can also be determined as the height of the protrusions on the surface of the coating. This makes it possible to evaluate the size distribution of protrusion-like defects present on the surface of a semiconductor wafer more accurately than when inspecting the semiconductor wafer surface with a surface defect inspection device.

[0029] For specific examples of evaluation (1) and evaluation (2), see the examples described below.

[0030] [Semiconductor wafer manufacturing method] One aspect of the present invention relates to a method for manufacturing a semiconductor wafer, including manufacturing a semiconductor wafer under manufacturing conditions to be evaluated, evaluating the manufactured semiconductor wafer using the semiconductor wafer evaluation method, determining, based on the results of the evaluation, manufacturing conditions obtained by modifying the manufacturing conditions to be evaluated as subsequent manufacturing conditions, or determining the manufacturing conditions to be evaluated as manufacturing conditions to be continued, and manufacturing a semiconductor wafer under the determined manufacturing conditions.

[0031] Specific examples of the above-mentioned production method include the following. Semiconductor wafers are manufactured under manufacturing conditions A. Separately, semiconductor wafers are manufactured under manufacturing conditions B which are different from manufacturing conditions A. The manufacturing conditions to be evaluated are referred to as "manufacturing conditions B." Evaluation wafers are sampled from each of the group of wafers manufactured under manufacturing conditions A and the group of wafers manufactured under manufacturing conditions B, and are evaluated by the evaluation method described above. For example, if the evaluation results show that the total number of protrusion-like defects on the semiconductor wafer surface, as determined by the evaluation method described above, is smaller in evaluation wafers sampled from a group of wafers manufactured under manufacturing conditions A than in evaluation wafers sampled from a group of wafers manufactured under manufacturing conditions B, then manufacturing conditions A can be determined to be manufacturing conditions that make protrusion-like defects less likely to occur on the semiconductor wafer surface compared to manufacturing conditions B. In this case, manufacturing conditions B can be changed to approach manufacturing conditions A, and the manufacturing conditions with such changes can be designated as improved manufacturing conditions B, and subsequent semiconductor wafer manufacturing can be carried out. Furthermore, for example, if the evaluation results show that the size distribution of protrusion-like defects on the semiconductor wafer surface, determined by the evaluation method described above, is more deviated from the size distribution desired for the product in an evaluation wafer sampled from a group of wafers manufactured under manufacturing condition B than in an evaluation wafer sampled from a group of wafers manufactured under manufacturing condition A, then manufacturing condition A can be determined to be a more desirable manufacturing condition than manufacturing condition B. In this case, manufacturing condition B can be changed to approach manufacturing condition A, and the manufacturing conditions with such changes can be designated as improved manufacturing condition B, and subsequent semiconductor wafer manufacturing can be carried out.

[0032] Further, specific examples of the above-mentioned production method include the following. In order to determine the manufacturing conditions for manufacturing semiconductor wafers that will actually be shipped as products (hereinafter referred to as "actual manufacturing conditions"), test manufacturing conditions are first determined. Semiconductor wafers are manufactured under these test manufacturing conditions. The semiconductor wafers manufactured under the test manufacturing conditions are evaluated by the evaluation method described above. Based on the evaluation results, the manufacturing conditions obtained by modifying the test manufacturing conditions can be determined as the actual manufacturing conditions, or the test manufacturing conditions themselves can be determined as the actual manufacturing conditions. Then, semiconductor wafers can be manufactured under the determined actual manufacturing conditions. For example, if the evaluation results show that the total number of protrusion-like defects on the surface of a semiconductor wafer manufactured under test manufacturing conditions, as determined by the evaluation method described above, exceeds a predetermined target value, manufacturing conditions obtained by modifying the test manufacturing conditions so as to suppress the occurrence of protrusion-like defects can be determined as actual manufacturing conditions. Furthermore, for example, even if the evaluation results show that the size distribution of protrusion-like defects on the surface of the semiconductor wafer, as determined by the evaluation method described above, in a semiconductor wafer manufactured under test manufacturing conditions is significantly different from the desired size distribution, manufacturing conditions obtained by modifying the test manufacturing conditions so as to suppress the occurrence of protrusion-like defects can be determined as actual manufacturing conditions.

[0033] Regarding the manufacturing process of semiconductor wafers, for example, the manufacturing process of polished wafers can be carried out by a manufacturing process including cutting (slicing) wafers from semiconductor ingots such as silicon single crystal ingots, chamfering, rough polishing (e.g., lapping), etching, mirror polishing (finish polishing), and cleaning processes performed between or after the above processing steps. PIDs, which are a type of protruding defect, are defects that can occur during the polishing process. Therefore, in one embodiment, the manufacturing conditions to which the above-mentioned changes are made can be the polishing process conditions of the semiconductor wafer surface. Specific examples include changes in various polishing conditions, such as changing the polishing slurry, changing the polishing slurry composition, changing the polishing pad, changing the type of polishing pad, and changing the operating conditions of the polishing apparatus.

[0034] Furthermore, particles, which are one type of protruding defects on the surface of a semiconductor wafer, are foreign matter adhering to the wafer surface and can be removed by cleaning. Therefore, in one embodiment, the manufacturing conditions to which the above-mentioned changes are made can be cleaning conditions. In order to reduce particles, for example, cleaning conditions can be strengthened. Specifically, measures for reducing particles include increasing the number of cleanings, lengthening the cleaning time, and using a cleaner with stronger cleaning power. [Example]

[0035] The present invention will be further described below based on examples, although the present invention is not limited to the embodiments shown in the examples.

[0036] The surface defect inspection device used below is a Surfscan series SP7 manufactured by KLA-Tencor Corporation.

[0037] [Example 1] (1) LPD measurement before film formation As the semiconductor wafers to be evaluated, 300 mm diameter epitaxial wafers (epitaxial wafers in which a silicon epitaxial layer is formed on a silicon single crystal wafer) were prepared, which were fabricated under different process conditions (process condition A, process condition B) that had significant differences in the number of protrusion defects. The wafers fabricated under process condition A are referred to as A1 to A6, and the wafers fabricated under process condition B are referred to as B1 to B6. The surface of the wafer to be evaluated was inspected using a surface defect inspection device, and LPD detection sizes and coordinate data were obtained over the entire surface.

[0038] Figure 4 shows the number of LPDs found on the surface of the wafer under evaluation using the DW10 channel of the KLA-Tencor Surfscan Series SP7. The sensitivity (minimum detectable size) set by the 95% Capture Rate of the SEMI standard (SEMI M50-1101) was 15 nm.

[0039] (2) Film formation process For the wafers to be evaluated, an amorphous silicon film was formed on the surface that had been subjected to the LPD measurement in (1) above using an LP-CVD device. Specifically, a seed layer was formed on the wafer surface using aminosilane gas, and then a silane gas with a smaller molecular weight than the aminosilane used to form the seed layer was deposited to form an amorphous silicon film with a thickness of 120 nm.

[0040] (3) LPD measurement after film formation The surface of the amorphous silicon film of the wafer to be evaluated was inspected using a surface defect inspection device, and LPD detection size and coordinate data were obtained over the entire surface.

[0041] (4) SEM observation The surface of the amorphous silicon film on the wafer to be evaluated was observed using an SEM. Specifically, the coordinate data obtained by the LPD measurement in (3) above was used to observe the protrusions and obtain secondary electron images. Based on the shape of the secondary electron images, the amorphous silicon film surface was classified into post-deposition protrusions and adhered particles. Figure 5 shows specific examples of SEM images of post-deposition protrusions and adhered particles. Since the number of adhered particles on the amorphous silicon film surface was very small, it was confirmed that protrusion-like defects on the semiconductor wafer surface could be evaluated from the LPD measurement results of the protrusions on the amorphous silicon film surface without excluding the adhered particles.

[0042] Figure 6 shows the number of LPDs found on the surface of the amorphous silicon film of the wafer being evaluated using the DW10 channel of the KLA-Tencor Surfscan Series SP7. Figure 6 also shows the results for LPDs determined to be post-film formation protrusions in (4) above. The sensitivity (minimum defect size) set by the 95% Capture Rate of the SEMI standard (SEMI M50-1101) was 19 nm.

[0043] As shown in Figure 4, before film deposition, no significant difference was observed in the number of LPDs between the wafers fabricated under process condition A and the wafers fabricated under process condition B. In contrast, as shown in Figure 6, after the amorphous silicon film was deposited, a significant difference was observed in the number of LPDs between the wafers fabricated under process condition A and the wafers fabricated under process condition B.

[0044] [Example 2, Comparative Example 1] The semiconductor wafers to be evaluated were polished wafers (silicon single crystal wafers) with a diameter of 300 mm, fabricated under different process conditions (process conditions C and D) that resulted in significant differences in the number of protrusion defects. The wafers fabricated under process condition C are designated C1 to C4, and the wafers fabricated under process condition D are designated D1 to D8. Process condition C was a process condition that employed single-wafer cleaning using hydrofluoric acid and ozone water, while process condition D was a process condition that employed batch cleaning using SC-1 (Standard Cleaning-1) cleaning or the like.

[0045] In Example 2, an amorphous silicon film was formed on the surface of the wafer to be evaluated using an LP-CVD apparatus. Specifically, a seed layer was formed on the wafer surface using aminosilane gas, and then a silane gas with a smaller molecular weight than the aminosilane used to form the seed layer was deposited to form an amorphous silicon film with a thickness of 120 nm. In Comparative Example 1, a silicon nitride film having a thickness of 120 nm was formed on the surface of the wafer to be evaluated using dichlorosilane gas (H2SiCl2) and ammonia (NH3) in an LP-CVD apparatus.

[0046] FIG. 7 shows the number of LPDs found on the surface of each of the above coatings (silicon nitride film or amorphous silicon film) for Comparative Example 1 and Example 2 using the DW10 channel of the Surfscan series SP7 manufactured by KLA-Tencor Corporation. In Comparative Example 1, no significant difference was observed in the number of LPDs between the wafers fabricated under process conditions C and D. In contrast, in Example 2, a significant difference was observed in the number of LPDs between wafers produced under process condition C and wafers produced under process condition D, and it was confirmed that wafers C1 to C4 produced under process condition C, which employed single-wafer cleaning using hydrofluoric acid and ozone water, were able to achieve the required number of LPDs of 15 or less on the surface of the coating. The above results show that, since the number of particles adhering to the surface of an amorphous silicon film that cause disturbance is small, the difference between levels can be evaluated without carrying out a defect discrimination process using an SEM.

[0047] As described above, according to one aspect of the present invention, it is possible to provide a semiconductor wafer in which, when evaluated by the semiconductor wafer evaluation method, the number of LPDs detected by inspecting the surface of the coating using a surface defect inspection device is 15 or less per wafer (i.e., 15 or less per wafer). The number of LPDs per wafer can be, for example, 0 to 15 or 1 to 15.

[0048] For one of the wafers after LPD measurement after film formation in Example 2, the heights of all protrusions on the surface of the amorphous silicon film were measured using AFM, and the number distribution (height distribution information) shown in FIG. 8 was obtained. As described above, the post-film formation protrusions formed on the coating surface due to the lens effect are defects that rise by the same size as the protrusion-like defects on the semiconductor wafer surface directly below. Therefore, the height of the post-film formation protrusions (protrusions on the coating surface) can be considered to be the size of the protrusion-like defects present on the semiconductor wafer surface directly below the protrusions. Therefore, the above number distribution (height distribution information) can be considered to be the size distribution of the protrusion-like defects present on the wafer surface located below the amorphous silicon film. [Industrial Applicability]

[0049] One aspect of the present invention is useful in the field of manufacturing various semiconductor wafers such as silicon wafers.

Claims

1. forming a coating on a surface of a semiconductor wafer for expanding protruding defects present on the surface; Inspecting the surface of the coating with a surface defect inspection device; and evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection; Including, The coating is made of a material having an attenuation coefficient of 4 or more for light at a wavelength of 266 nm, and Evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection includes: a method for evaluating a semiconductor wafer, comprising: measuring the height of a protrusion on the coating surface at a position where an LPD is detected by the inspection using an atomic force microscope; regarding the measured height value as the size of a protrusion-like defect present on the semiconductor wafer surface directly below the protrusion; and evaluating the size of the protrusion-like defect present on the semiconductor wafer surface.

2. 2. The semiconductor wafer evaluation method according to claim 1, wherein the material is amorphous silicon.

3. 2. The method for evaluating a semiconductor wafer according to claim 1, wherein the surface of the coating has an average haze of 0.5 ppm or less.

4. 2. The semiconductor wafer evaluation method according to claim 1, wherein the coating has a thickness of 15 nm or more and 500 nm or less.

5. Evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection includes:

2. The semiconductor wafer evaluation method according to claim 1, further comprising: regarding the number of LPDs detected by the inspection as the number of protrusion-like defects present on the surface of the semiconductor wafer, and evaluating the number of protrusion-like defects present on the surface of the semiconductor wafer.

6. The evaluation of the size of protruding defects present on the surface of the semiconductor wafer is carried out by: evaluating the size distribution of protrusion-like defects present on the surface of the semiconductor wafer based on height distribution information created based on measurement values ​​of the heights of the plurality of protrusions on the surface of the coating; The semiconductor wafer evaluation method according to claim 1 , comprising:

7. 2. The semiconductor wafer evaluation method according to claim 1, wherein the protruding defect present on the surface of the semiconductor wafer is a defect selected from the group consisting of a particle and a PID.

8. The semiconductor wafer evaluation method according to claim 1 , wherein the semiconductor wafer is a silicon wafer.

9. the material is amorphous silicon, the surface of the coating has an average haze of 0.5 ppm or less; The thickness of the coating is 15 nm or more and 500 nm or less, The protruding defect present on the surface of the semiconductor wafer is a defect selected from the group consisting of particles and PIDs, the semiconductor wafer is a silicon wafer; and 2. The semiconductor wafer evaluation method according to claim 1, wherein evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection further includes the following (1): (1) The number of LPDs detected by the inspection is regarded as the number of protrusion-like defects present on the surface of the semiconductor wafer, and the number of protrusion-like defects present on the surface of the semiconductor wafer is evaluated.

10. The evaluation of the size of protruding defects present on the surface of the semiconductor wafer is carried out by: evaluating the size distribution of protrusion-like defects present on the surface of the semiconductor wafer based on height distribution information created based on measurement values ​​of the heights of the plurality of protrusions on the surface of the coating; The semiconductor wafer evaluation method according to claim 9 , comprising:

11. forming a coating on a surface of a semiconductor wafer; Inspecting the surface of the coating with a surface defect inspection device; and evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection; Including, the coating is an amorphous silicon film; and Evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection includes: a method for evaluating a semiconductor wafer, comprising: measuring the height of a protrusion on the coating surface at a position where an LPD is detected by the inspection using an atomic force microscope; regarding the measured height value as the size of a protrusion-like defect present on the semiconductor wafer surface directly below the protrusion; and evaluating the size of the protrusion-like defect present on the semiconductor wafer surface.

12. The surface of the coating has an average haze of 0.5 ppm or less, and 12. The semiconductor wafer evaluation method according to claim 11, wherein the coating has a thickness of 15 nm or more and 500 nm or less.

13. The semiconductor wafer evaluation method according to claim 11, wherein the protruding defect present on the surface of the semiconductor wafer is a defect selected from the group consisting of a particle and a PID.

14. Evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection includes:

12. The semiconductor wafer evaluation method according to claim 11, further comprising: regarding the number of LPDs detected by the inspection as the number of protrusion-like defects present on the surface of the semiconductor wafer, and evaluating the number of protrusion-like defects present on the surface of the semiconductor wafer.

15. manufacturing semiconductor wafers under the manufacturing conditions to be evaluated; Evaluating the manufactured semiconductor wafer by the semiconductor wafer evaluation method according to any one of claims 1 to 14; Based on the results of the evaluation, determining the manufacturing conditions obtained by modifying the manufacturing conditions to be evaluated as the subsequent manufacturing conditions, or determining the manufacturing conditions to be evaluated as the manufacturing conditions to be continuously adopted; and manufacturing a semiconductor wafer under the determined manufacturing conditions; A method for manufacturing a semiconductor wafer, comprising:

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