Method for evaluating semiconductor wafers and method for manufacturing semiconductor wafers

Abstract

To provide an evaluation method capable of highly sensitively evaluating minute, protruding defects present on the surface of a semiconductor wafer. [Solution] A method for evaluating a semiconductor wafer, comprising: depositing a silicon nitride film on the surface of a semiconductor wafer to expand protruding defects present on the surface, with the raw material gas flow rate ratio introduced into the reactor of a CVD apparatus being 0.820 or less; inspecting the surface of the silicon nitride film with a defect inspection device; and evaluating the protruding defects present on the surface of the semiconductor wafer based on the results of the inspection. The raw material gas flow rate ratio is the ratio of the nitrogen source gas flow rate to the total flow rate of the silicon source gas flow rate and the nitrogen source gas flow rate [nitrogen source gas / (silicon source gas + nitrogen source gas)].

Description

Technical Field

[0006]

[0001] The present invention relates to a method for evaluating a semiconductor wafer and a method for manufacturing a semiconductor wafer.

Background Art

[0002] As a method for evaluating defects in a semiconductor wafer, a method based on light point defects (LPD) detected by a defect inspection apparatus is widely used (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the surface of a semiconductor wafer, protrusion-shaped defects may exist. Among these defects, there may be minute defects smaller than the detection lower limit size of a defect inspection apparatus. By evaluating a semiconductor wafer that may include such minute protrusion-shaped defects, for example, based on the evaluation results, the manufacturing conditions of the semiconductor wafer can be changed so that the generation of minute protrusion-shaped defects is suppressed, thereby making it possible to manufacture a semiconductor wafer with fewer minute protrusion-shaped defects. Further, if the size of evaluable defects can be made smaller, that is, if the detection sensitivity of defects can be increased, it becomes possible to manufacture a high-quality semiconductor wafer with even fewer minute protrusion-shaped defects.

[0005] One aspect of the present invention aims to provide an evaluation method capable of highly sensitively evaluating minute protrusion-shaped defects present on the surface of a semiconductor wafer.

Means for Solving the Problems

[0006] For example, as described in Japanese Patent Publication No. 2016-212009 (Patent Document 1), in order to evaluate semiconductor wafers, a coating is formed on the surface of the semiconductor wafer to be evaluated to enlarge the protruding defects present on this surface. If the surface of the coating is observed with a defect inspection device after such a coating has been formed, the LPD detection size can be increased compared to before the coating was formed. This is advantageous when evaluating semiconductor wafers that may contain minute protruding defects below the detection limit size of the defect inspection device. Therefore, the inventors have diligently studied semiconductor wafer evaluation methods that include forming such a coating on the surface of the semiconductor wafer to be evaluated. As a result, the inventors have newly discovered that when forming a silicon nitride film as a coating by the CVD method, by setting the flow rate ratio of the nitrogen source gas and the silicon source gas within a predetermined range, even minute protruding defects can be detected as LPDs. While Japanese Patent Publication No. 2016-212009 (Patent Document 1) describes the deposition of a silicon nitride film (referred to as a silicon nitride film in Patent Document 1) as a coating on the surface of a semiconductor wafer, it does not mention anything about the flow rate ratio of the nitrogen source gas and the silicon source gas.

[0007] That is, one aspect of the present invention is as follows. [1] A silicon nitride film is deposited on the surface of a semiconductor wafer to expand the protruding defects present on the surface, with the raw material gas flow rate ratio introduced into the reactor of a CVD (Chemical Vapor Deposition) apparatus being 0.820 or less. The surface of the silicon nitride film is inspected using a defect inspection device, and Based on the results of the above inspection, evaluate the protruding defects present on the surface of the semiconductor wafer. Includes, The above raw material gas flow rate ratio is the ratio of the nitrogen source gas flow rate to the total flow rate of silicon source gas and nitrogen source gas [nitrogen source gas / (silicon source gas + nitrogen source gas)], in a method for evaluating semiconductor wafers. [2] The semiconductor wafer evaluation method according to [1], wherein the film deposition temperature in the above-mentioned reactor is 700°C or higher and 800°C or lower. [3] The semiconductor wafer evaluation method according to [1] or [2], wherein the CVD apparatus is an LP (Low Pressure)-CVD apparatus. [4] The above nitrogen source gas is ammonia gas, the semiconductor wafer evaluation method according to any one of [1] to [3]. [5] The silicon source gas is one or more silicon source gases selected from the group consisting of dichlorosilane gas, silane gas, trichlorosilane gas, and silicon tetrachloride gas, the semiconductor wafer evaluation method according to any one of [1] to [4]. [6] The above-mentioned protruding defects are particles, a method for evaluating a semiconductor wafer according to any one of [1] to [5]. [7] The semiconductor wafer is a silicon wafer, and the method for evaluating a semiconductor wafer is as described in any of [1] to [6]. [8] The film formation temperature in the above reactor is 700°C or higher and 800°C or lower. The above CVD apparatus is an LP-CVD apparatus. The above nitrogen source gas is ammonia gas. The above silicon source gas is one or more silicon source gases selected from the group consisting of dichlorosilane gas, silane gas, trichlorosilane gas, and silicon tetrachloride gas. The above-mentioned protruding defects are particles, and The above semiconductor wafer is a silicon wafer, and the method for evaluating a semiconductor wafer is as described in any of [1] to [7]. [9] A method for evaluating a semiconductor wafer according to any one of [1] to [8], further comprising determining whether the semiconductor wafer is good or bad based on the evaluation results of the above-mentioned protruding defects.

[10] Manufacturing semiconductor wafers under the manufacturing conditions under evaluation, The manufactured semiconductor wafer shall be evaluated by any of the evaluation methods described in [1] to [9] above. Based on the results of the above evaluation, either the manufacturing conditions modified from the evaluated manufacturing conditions will be decided as the subsequent manufacturing conditions, or the manufacturing conditions that were evaluated will be decided as the manufacturing conditions to be continued, and To manufacture semiconductor wafers under the above-determined manufacturing conditions, A method for manufacturing semiconductor wafers containing [the specified material]. [Effects of the Invention]

[0008] According to one aspect of the present invention, an evaluation method capable of highly sensitively evaluating minute defects present on the surface of a semiconductor wafer can be provided. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram illustrating size expansion due to the lens effect. [Modes for carrying out the invention]

[0010] [Methods for evaluating semiconductor wafers] One aspect of the present invention relates to a method for evaluating a semiconductor wafer, comprising: depositing a silicon nitride film on the surface of a semiconductor wafer to expand protruding defects present on the surface, with a raw material gas flow rate ratio of 0.820 or less introduced into the reactor of a CVD apparatus; inspecting the surface of the silicon nitride film with a defect inspection device; and evaluating the protruding defects present on the surface of the semiconductor wafer based on the results of the inspection. The raw material gas flow rate ratio is the ratio of the nitrogen source gas flow rate to the total flow rate of the silicon source gas flow rate and the nitrogen source gas flow rate [nitrogen source gas / (silicon source gas + nitrogen source gas)]. The evaluation method described above will be explained in more detail below.

[0011] <Semiconductor wafers to be evaluated> The semiconductor wafers to be evaluated using the above evaluation method include various types of semiconductor wafers commonly used as semiconductor substrates. For example, specific examples of semiconductor wafers include various types of silicon wafers. Silicon wafers can include, for example, silicon single-crystal wafers that have undergone various processing steps after being cut from a silicon single-crystal ingot, polished wafers that have been polished to have a polished surface, and epitaxial wafers that have an epitaxial layer formed on them. The diameter of the semiconductor wafer to be evaluated is, for example, 200 mm or less, or 200 mm or more (for example, 200 mm, 300 mm, or 450 mm), but is not particularly limited.

[0012] The semiconductor wafer being evaluated has protruding defects on its surface. A specific example of a protruding defect is particles. Particles are foreign matter that adheres to the wafer surface during the wafer manufacturing process, etc.

[0013] <Deposition of silicon nitride films> In the above evaluation method, the formation of the silicon nitride film on the surface of the semiconductor wafer to be evaluated is performed by the CVD method. According to the CVD method, a raw material gas is introduced into the reactor of the CVD apparatus in which the film formation target is disposed inside, and a chemical vapor reaction is allowed to proceed in the reactor to form a film on the surface of the film formation target. The CVD apparatus is classified into an "AP (Atmospheric Pressure)-CVD apparatus" and a "LP-CVD apparatus" as classification by process pressure. In the AP-CVD apparatus, CVD is performed under atmospheric pressure without controlling the pressure inside the reactor, whereas in the LP-CVD apparatus, CVD is performed with the inside of the reactor in a reduced pressure state lower than atmospheric pressure. The formation of the silicon nitride film in the above evaluation method can be performed in an AP-CVD apparatus or an LP-CVD apparatus. The LP-CVD method has a higher film formation rate and better film uniformity of the film to be formed than the AP-CVD method. From these points, it is preferable to perform the formation of the silicon nitride film in the above evaluation method in an LP-CVD apparatus. When the ambient temperature inside the reactor of the CVD apparatus during film formation is referred to as the "film formation temperature", the film formation temperature can be, for example, 700°C or higher and 800°C or lower. In the present invention and this specification, the "film formation temperature" refers to the set value set in the CVD apparatus.

[0014] As the raw material gas for the formation of the silicon nitride film, a nitrogen source gas and a silicon source gas are used. By the chemical vapor reaction of the nitrogen source gas and the silicon source gas, a silicon nitride film can be formed on the surface of the semiconductor wafer to be evaluated. The silicon source gas is a gas of a substance containing silicon (Si) as a constituent element. As the silicon source gas, for example, one or more gases selected from the group consisting of dichlorosilane gas (SiH2Cl2), silane gas (SiH4), trichlorosilane gas (SiHCl3), and silicon tetrachloride gas (SiCl4) can be used. The silicon source gas may be used alone or two or more kinds may be used. When two or more kinds of silicon source gases are used, the flow rate of the silicon source gas refers to the total flow rate of two or more kinds of silicon source gases. The above points are the same for the nitrogen source gas. The nitrogen source gas is a gas of a substance containing nitrogen (N) as a constituent element. Specific examples of the nitrogen source gas include ammonia gas (NH3).

[0015] In the CVD apparatus, the source gases discharged from each of the plurality of source gas containers are introduced into the reactor from separate flow paths, or they merge at a merging point provided upstream of the reactor and are introduced into the reactor as a merged gas. The "nitrogen source gas source flow rate" and "silicon source gas flow rate" in the present invention and this specification refer to set values set in the CVD apparatus, and usually, the flow rates of the respective gases are controlled by a flow rate control mechanism provided near the discharge port of the source gas container filled with each gas.

[0016] In the present invention and this specification, the "source gas flow rate ratio" is the ratio of the nitrogen source gas flow rate to the total flow rate of the silicon source gas flow rate and the nitrogen source gas flow rate [nitrogen source gas / (silicon source gas + nitrogen source gas)]. The formation of the silicon nitride film in the above evaluation method is performed with the source gas flow rate ratio being 0.820 or less. According to the silicon nitride film formed with the source gas flow rate ratio being 0.820 or less, it has newly been found as a result of the intensive study by the present inventor that even more minute protrusion-like defects existing on the surface of the semiconductor wafer can be detected as LPD. The source gas flow rate ratio is 0.820 or less, and from the viewpoint of making even more minute protrusion-like defects detectable as LPD, it is preferably 0.815 or less, more preferably 0.800 or less, 0.780 or less, 0.760 or less, 0.740 or less, 0.720 or less, 0.700 or less, 0.650 or less, 0.600 or less, 0.550 or less, 0.500 or less, 0.450 or less, 0.400 or less, 0.350 or less, 0.300 or less in this order. The source gas flow rate ratio can be, for example, 0.100 or more, 0.150 or more, 0.200 or more, or 0.250 or more. The inventors speculate that by setting the raw material gas flow rate ratio to 0.820 or less, a silicon nitride film with low surface haze can be formed, which may be the reason why even minute protruding defects can be detected as LPDs. However, the present invention is not limited to the speculation described herein. The surface haze of the silicon nitride film can be, for example, between 0.100 ppm and 1.830 ppm as the "DW1O (Dark-field Wide-1 Oblique) Haze Average" measured by a KLA-TENCOR Surfscan series SP7, but is not limited to this range.

[0017] From the viewpoint of increasing the intensity of scattered light obtained by the defect inspection device, the thickness of the silicon nitride film deposited in the CVD apparatus is preferably 70 nm or more, and more preferably 80 nm or more, 90 nm or more, 100 nm or more, and 110 nm or more, in that order. From the above viewpoint, the thickness of the silicon nitride film is preferably 140 nm or less, and more preferably 130 nm or less. In the present invention and this specification, the thickness of the silicon nitride film may be a value obtained by a known film thickness measurement method, or it may be a set film thickness set in the film deposition apparatus. The stoichiometric composition of silicon nitride is Si3N4, but the composition of silicon nitride in the silicon nitride film deposited in the CVD apparatus may be a stoichiometric composition or a non-stoichiometric composition.

[0018] <Inspection using defect detection equipment> In the evaluation method described above, the surface of the silicon nitride film deposited as described above is inspected using a defect inspection device. As the defect inspection device, a known surface defect inspection device capable of detecting the synchrotron radiation (scattered and / or reflected light) from the surface of the object to be inspected by irradiating it with light can be used. Such a surface defect inspection device is generally also called a light scattering type surface defect inspection device or surface inspection device. A specific example of a surface defect inspection device is a laser surface defect inspection device. A laser surface defect inspection device usually scans the surface of the object to be inspected with laser light and detects protrusions on the surface of the object to be inspected as bright spots (LPDs) using synchrotron radiation (scattered and / or reflected light). Furthermore, by measuring the synchrotron radiation from the LPDs, the position (specifically, the coordinate point) of the protrusions on the surface of the object to be inspected and the size detected as LPDs (LPD detection size) can be determined. This LPD detection size is usually output by the analysis unit of the surface defect inspection device by comparing the intensity of the synchrotron radiation from the LPDs with the synchrotron radiation intensity of standard particles such as silica particles. The laser light used can be ultraviolet light, visible light, etc., and its wavelength is not particularly limited. Ultraviolet light refers to light in the wavelength range of less than 400 nm, and visible light refers to light in the wavelength range of 400 to 600 nm. The analysis unit of the laser surface defect inspection device can usually acquire information on the two-dimensional position coordinates (X and Y coordinates) on the surface of the object being inspected for each of the multiple LPDs detected, and can create an LPD map showing the in-plane distribution state of the LPD on the surface of the object being inspected from the acquired two-dimensional position coordinate information. Specific examples of commercially available laser surface defect inspection devices include the KLA-TENCOR Surfscan series SP1, SP2, SP3, SP5, SP7, etc. However, these devices are examples, and various other types of defect inspection devices can also be used.

[0019] The silicon nitride film described above can expand protruding defects present on the surface of a semiconductor wafer. By "expanding" them, protrusions larger than the size of the protruding defects on the semiconductor wafer surface are formed on the surface of the silicon nitride film. This is due to the so-called "lens effect." The "lens effect" is a phenomenon in which a protrusion several times larger in diameter than the original protrusion (also referred to as a "post-deposition protrusion") is formed on the surface of the film directly above it, starting from the original protrusion. 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 film surface directly above the protrusion of 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 has risen by the size of 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 film surface is the same as the diameter D of the protrusion. Details of evaluation using this point will be described later. In the above evaluation method, as described above, by forming a silicon nitride film, the minimum size of LPD detectable by the defect inspection device can be reduced. Therefore, according to the above evaluation method, by inspecting the surface of the silicon nitride film with a defect inspection device, it becomes possible to detect even minute protruding defects as LPDs.

[0020] <Quality Determination of Semiconductor Wafers> The above evaluation method allows for the evaluation of protruding defects present on the surface of the semiconductor wafer located beneath the silicon nitride film, based on the results of inspecting the surface of the silicon nitride film with a defect inspection device. Specific examples of such evaluations include the following evaluations (1) and (2). For example, evaluation (1) or evaluation (2) alone may be performed, or both evaluations (1) and (2) may be performed.

[0021] (1) The number of LPDs detected by the above inspection is considered to be the number of protruding defects present on the surface of the semiconductor wafer, and the number of protruding defects present on the surface of the semiconductor wafer is evaluated. (2) At the location where LPD is detected by the above inspection, the height of the protrusion on the silicon nitride film surface is measured using a measuring device, and the measured height value is considered to be the size of the protruding defect located directly beneath the protrusion on the semiconductor wafer surface, and an evaluation of the size of the protruding defect present on the semiconductor wafer surface is performed.

[0022] According to evaluation (1), the expansion (lens effect) by the silicon nitride film makes it possible to evaluate the number of defects on the semiconductor wafer surface, including the number of minute protrusion-like defects that cannot be detected by inspecting the semiconductor wafer surface with a defect inspection device.

[0023] For example, the quality of a semiconductor wafer can be determined by setting a threshold for determining whether it is good or bad based on the number of protruding defects on the surface of the semiconductor wafer obtained by evaluation (1). If the number of defects is below or equal to the threshold, it is determined to be a good product, and if it is above or equal to the threshold, it is determined to be a defective product.

[0024] Next, we will explain evaluation (2) in more detail.

[0025] As shown in Figure 1, the post-deposition protrusions formed on the film surface due to the lens effect are defects that are raised by the size of the protruding defects on the semiconductor wafer surface directly beneath them. Therefore, the height of the post-deposition protrusions can be considered as the size of the protruding defects on the semiconductor wafer surface directly beneath them. For example, the height of a protrusion measured on the silicon nitride film surface can be considered as the diameter of a particle on the semiconductor wafer surface. The height of protrusions on the silicon nitride film surface can be measured using known measuring devices, such as an atomic force microscope (AFM).

[0026] For example, the quality of a semiconductor wafer can be determined by defining a threshold for determining whether a defect is good or bad based on the size of the protruding defect (e.g., minimum size, maximum size, or average size) located directly beneath the protrusion on the semiconductor wafer surface obtained by evaluation (2). If the size is below or equal to the threshold, the wafer is deemed good, and if it is above or equal to the threshold, the wafer is deemed defective.

[0027] Furthermore, as a specific embodiment of evaluation (2), the size distribution of protruding defects present on the semiconductor wafer surface can be evaluated based on height distribution information created from measured heights of multiple protrusions on the silicon nitride film surface. According to the above evaluation method, even minute protruding defects that cannot be detected by inspecting the semiconductor wafer surface with a defect inspection device due to expansion (lens effect) by the silicon nitride film can be determined as the height of the protrusions on the silicon nitride film surface. This makes it possible to evaluate the size distribution of protruding defects present on the semiconductor wafer surface with greater accuracy compared to inspecting the semiconductor wafer surface with a defect inspection device. For example, regarding the size distribution, a threshold value for an index related to the distribution (e.g., standard deviation) can be set, and the quality of the semiconductor wafer can be determined by judging that a product is good if it is below or less than the threshold, and a product is defective if it is above or greater than the threshold.

[0028] For example, as shown in the example above, the quality of a semiconductor wafer can be determined based on the evaluation results of protruding defects. The various thresholds used for quality determination are not particularly limited and can be arbitrarily set by methods such as conducting preliminary experiments, determining them empirically, or calculating them from theoretical formulas.

[0029] [Method for manufacturing semiconductor wafers] One aspect of the present invention relates to a method for manufacturing a semiconductor wafer, which includes manufacturing a semiconductor wafer under manufacturing conditions to be evaluated; evaluating the manufactured semiconductor wafer using a semiconductor wafer evaluation method; determining, based on the results of the evaluation, to modify the manufacturing conditions to be evaluated as subsequent manufacturing conditions, or to determine that the manufacturing conditions to be evaluated will continue to be used as manufacturing conditions; and manufacturing a semiconductor wafer under the determined manufacturing conditions.

[0030] The following are examples of specific forms of the above manufacturing method. Semiconductor wafers are manufactured under manufacturing condition A. Separately, semiconductor wafers are manufactured under manufacturing conditions B, which are different from manufacturing conditions A. The manufacturing conditions to be evaluated are designated as "Manufacturing Condition B". Evaluation wafers are selected from the group of wafers manufactured under manufacturing condition A and the group of wafers manufactured under manufacturing condition B, respectively, and evaluated according to the evaluation method described above. For example, if the evaluation results show that the number of protruding defects determined by the evaluation method described above is less in an evaluation wafer sampled from a group of wafers manufactured under manufacturing condition A than in an evaluation wafer sampled from a group of wafers manufactured under manufacturing condition B, then manufacturing condition A can be determined to be a manufacturing condition that is less likely to cause protruding 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 designated as improved manufacturing condition B for subsequent semiconductor wafer manufacturing. Furthermore, for example, if the in-plane distribution of protruding defects (in-plane size distribution, in-plane number distribution, etc.) obtained by the evaluation method described above is further from the desired in-plane distribution for the product in an evaluation wafer sampled from a group of wafers manufactured under manufacturing condition B, compared to 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 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.

[0031] In the example above, the manufacturing conditions are determined by comparing two manufacturing conditions (manufacturing conditions A and B), but there may be three or more manufacturing conditions to compare.

[0032] Furthermore, the following are examples of specific forms of the above manufacturing method. In order to determine the manufacturing conditions for producing semiconductor wafers that will actually be shipped as products (hereinafter referred to as "actual manufacturing conditions"), we first determine the test manufacturing conditions. Semiconductor wafers are manufactured under these test manufacturing conditions. Semiconductor wafers manufactured under test manufacturing conditions are evaluated using the evaluation method described above. Based on the evaluation results, the manufacturing conditions can be modified from the test manufacturing conditions to determine 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 number of protruding defects in a semiconductor wafer manufactured under test manufacturing conditions exceeds a predetermined threshold, the manufacturing conditions modified to suppress the occurrence of protruding defects on the wafer surface can be determined as the actual manufacturing conditions. Furthermore, for example, if the evaluation results show that the in-plane distribution of protruding defects (in-plane size distribution, in-plane number distribution, etc.) obtained by the evaluation method described above for semiconductor wafers manufactured under test manufacturing conditions deviates significantly from the desired in-plane distribution, the manufacturing conditions modified from the test manufacturing conditions to suppress the occurrence of protruding defects on the wafer surface can be determined as the actual manufacturing conditions.

[0033] Regarding the manufacturing process of semiconductor wafers, for example, the manufacturing process for polished wafers can be carried out by a manufacturing process that includes cutting (slicing), chamfering, rough polishing (e.g., lapping), etching, mirror polishing (finish polishing), and cleaning processes performed between or after the above processing steps. Particles, which are a form of protruding defects on the surface of a semiconductor wafer, are foreign matter adhering to the wafer surface and can therefore be removed by cleaning. Thus, the manufacturing conditions to which the above modifications are made can, in one form, be cleaning conditions. To reduce particles, for example, cleaning conditions can be strengthened. Specifically, means of reducing particles include increasing the number of cleaning cycles, increasing the cleaning time, and using a cleaning agent with higher cleaning power. [Examples]

[0034] The present invention will be further described below based on examples. However, the present invention is not limited to the embodiments shown in the examples.

[0035] <Preparation of wafers to be evaluated> Nine silicon single-crystal wafers (epitaxial wafers) were prepared for evaluation, each having undergone the same cleaning process. It is presumed that minute particles that could not be removed by the cleaning process are present on the surface of these wafers.

[0036] <Deposition of silicon nitride films> In each of Examples 1 to 4 and Comparative Examples 1 to 5, a silicon nitride film was formed on one surface of the wafer to be evaluated under the film formation conditions shown below. (Film formation conditions) Film formation apparatus: LP-CVD apparatus Film formation temperature: 725 °C Nitrogen source gas: Ammonia gas (NH3) Silicon source gas: Dichlorosilane gas (hereinafter referred to as "DCS"). Raw material gas flow rate ratio (NH3 / (DCS + NH3)): Refer to Table 1 Set film thickness: 120 nm

[0037] [Table 1]

[0038] <Inspection by defect inspection apparatus> For each of Examples 1 to 4 and Comparative Examples 1 to 5, the surface of the silicon nitride film on the wafer to be evaluated was inspected by a defect inspection apparatus (Surfscan series SP7 manufactured by KLA-TENCOR).

[0039] <Surface haze> For each of Examples 1 to 4 and Comparative Examples 1 to 5, as the inspection result by the defect inspection apparatus, DW1O Haze Average shown in Table 2 was obtained.

[0040] [Table 2]

[0041] <LPD inspection apparatus detection lower limit value> For each of Examples 1 to 4 and Comparative Examples 1 to 5, by inspection with a defect inspection apparatus, 95% CR (Capture Rate), which is the SEMI standard (SEMI M50-1101), was measured, and the detection lower limit size value was determined. The obtained detection lower limit size value is shown in Table 3 as "SP7 minimum particle size".

[0042] [Table 3]

[0043] The detection sensitivity of the inspection device described in paragraph 0042 of Japanese Patent Publication No. 2016-212009 (Patent Document 1) is 25 nm. Therefore, for the results shown in Table 3, 23 nm was set as the threshold for the minimum SP7 particle size, which is sufficiently smaller than 25 nm. If a minimum SP7 particle size of 23 nm or less was achieved, it was determined that the protruding minute defects present on the semiconductor wafer surface could be detected with high sensitivity. From the results shown in Table 3, it can be confirmed that in Examples 1 to 4, the protruding minute defects present on the semiconductor wafer could be detected with high sensitivity.

[0044] According to one aspect of the present invention, it is possible to provide high-quality semiconductor wafers with fewer minute particles. For example, high-quality semiconductor wafers with fewer minute particles can be used as semiconductor substrates in state-of-the-art logic devices. State-of-the-art logic devices can be incorporated into, for example, smartphones, enabling the multi-functionality and high performance of smartphones. For example, state-of-the-art logic devices can enable the simultaneous execution of multiple applications and improve graphics processing capabilities to smoothly process high-resolution images and / or videos. As described above, one aspect of the present invention enables the manufacture of high-performance logic semiconductors, which can enrich people's lives. [Industrial applicability]

[0045] One aspect of the present invention is useful in the field of manufacturing various semiconductor wafers, such as silicon wafers.

Claims

1. A silicon nitride film is deposited on the surface of a semiconductor wafer to expand protruding defects present on the surface, with the raw material gas flow rate ratio introduced into the reactor of the CVD apparatus being 0.820 or less. The surface of the silicon nitride film is inspected using a defect inspection device, and Based on the results of the inspection, evaluate the protruding defects present on the surface of the semiconductor wafer. Includes, A method for evaluating semiconductor wafers, wherein the aforementioned raw material gas flow rate ratio is the ratio of the nitrogen source gas flow rate to the total flow rate of the silicon source gas flow rate and the nitrogen source gas flow rate [nitrogen source gas / (silicon source gas + nitrogen source gas)].

2. The semiconductor wafer evaluation method according to claim 1, wherein the film deposition temperature in the reactor is 700°C or higher and 800°C or lower.

3. The semiconductor wafer evaluation method according to claim 1, wherein the CVD apparatus is an LP-CVD apparatus.

4. The semiconductor wafer evaluation method according to claim 1, wherein the nitrogen source gas is ammonia gas.

5. The semiconductor wafer evaluation method according to claim 1, wherein the silicon source gas is one or more silicon source gases selected from the group consisting of dichlorosilane gas, silane gas, trichlorosilane gas, and silicon tetrachloride gas.

6. The method for evaluating a semiconductor wafer according to claim 1, wherein the aforementioned protruding defects are particles.

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

8. The film formation temperature in the aforementioned reactor is 700°C or higher and 800°C or lower. The CVD apparatus is an LP-CVD apparatus, The nitrogen source gas is ammonia gas. The silicon source gas is one or more silicon source gases selected from the group consisting of dichlorosilane gas, silane gas, trichlorosilane gas, and silicon tetrachloride gas. The aforementioned protruding defects are particles, and The semiconductor wafer evaluation method according to claim 1, wherein the semiconductor wafer is a silicon wafer.

9. A method for evaluating a semiconductor wafer according to any one of claims 1 to 8, further comprising determining whether the semiconductor wafer is good or bad based on the evaluation results of the aforementioned protruding defects.

10. Manufacturing semiconductor wafers under the manufacturing conditions being evaluated, The manufactured semiconductor wafer is evaluated by the evaluation method described in claim 9. Based on the results of the evaluation, the manufacturing conditions modified from the evaluation subject will be determined as the subsequent manufacturing conditions, or the manufacturing conditions from the evaluation subject will be determined as the manufacturing conditions to be continued, and To manufacture semiconductor wafers under the aforementioned determined manufacturing conditions, A method for manufacturing semiconductor wafers containing [the specified material].

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