JP2024035995A - Semiconductor wafer evaluation method, semiconductor wafer manufacturing method, and semiconductor wafer - Google Patents

Abstract

An object 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. [Solution] Forming a coating on the surface of a semiconductor wafer to expand protruding defects existing on the surface, inspecting the surface of the coating using a surface defect inspection device, and results of the inspection. evaluating the protrusion-like defects present on the surface of the semiconductor wafer based on the semiconductor wafer, wherein the coating is a coating made of a material having a light attenuation coefficient of 4 or more at a wavelength of 266 nm. Evaluation method. [Selection diagram] None

Description

The present invention relates to a semiconductor wafer evaluation method, a semiconductor wafer manufacturing method, and a semiconductor wafer.

As a method for evaluating defects in semiconductor wafers, a method based on light point defects (LPD) detected by a surface defect inspection device is widely used (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 2016-212009

Protrusion-like defects may exist on the surface of a semiconductor wafer. Specific examples of protruding defects are particles and PIDs (Process Induced Defects). Particles are foreign substances that adhere to the wafer surface during the wafer manufacturing process. PID is a process-induced defect that occurs due to processing performed in the wafer manufacturing process, and is a defect that mainly occurs due to polishing. These protruding defects may include minute defects that are smaller than the detection limit size of the surface defect inspection device. If it becomes possible to evaluate such micro defects, for example, based on the evaluation results, it is possible to reduce the number of micro defects by changing the manufacturing conditions of semiconductor wafers to suppress the occurrence of micro defects. It becomes possible to manufacture high quality semiconductor wafers.

An object of one aspect of the present invention is to provide a new evaluation method that can evaluate minute protruding defects present on the surface of a semiconductor wafer.

The above-mentioned Japanese Unexamined Patent Publication No. 2016-212009 (Patent Document 1) discloses that a nitride film is formed on the wafer surface, and a nitride film is formed on the surface of this nitride film in order to expand the protruding defects existing on the wafer surface. It has been disclosed that a surface defect inspection device detects the protrusions that have been formed (see claims 1, 5, etc. of JP-A No. 2016-212009).
On the other hand, as a result of extensive studies, the present inventors found that a coating for expanding the protruding defects existing on the wafer surface is made of a material with an optical attenuation coefficient of 4 or more at a wavelength of 266 nm. It has been newly discovered that a coating is suitable. This point will be explained in more detail below.

A surface defect inspection device makes light incident on a surface to be evaluated and detects emitted light (scattered light or reflected light) from this surface. Thereby, according to the surface defect inspection apparatus, the protrusion present on the surface of the evaluation target can be detected as a bright point defect (LPD). However, as the inventors of the present invention conducted extensive studies, we discovered that the nitride film described in JP-A No. 2016-212009 (Patent Document 1) has a high surface haze, so the surface haze of the nitride film cannot be measured using a surface defect inspection device. It was found that the sensitivity was low. The reason why the surface haze of the nitride film becomes high is thought to be mainly due to the optical properties of the film itself.
Specifically, since nitride film has a small attenuation coefficient (physical property value) for light irradiated from a surface defect inspection device (attenuation coefficient of light at a wavelength of 266 nm for silicon nitride Si ₃ N ₄ : 0.013), nitride film Most of the incident light 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, it is presumed that the reason why the surface haze of the nitride film is high is that the reflected light from the interface is scattered inside and on the surface of the nitride film.
On the other hand, if the coating is made of a material with a light attenuation coefficient of 4 or more at a wavelength of 266 nm, the light incident from the surface defect inspection device will pass through the coating and be reflected at the interface between the coating and the semiconductor wafer. can be suppressed or reduced. As a result, the surface haze caused by the reflected light from the interface can be reduced, making it possible to reduce the minimum detection size of the light receiving section of the surface defect inspection device. Therefore, if the surface of a coating is made of a material with a light attenuation coefficient of 4 or more at a wavelength of 266 nm, it is considered that high-sensitivity measurement using a surface defect inspection device is possible. As described above, the present inventors have completed the present invention as a result of intensive studies focusing on the attenuation coefficient specific to the membrane. Note that the term "attenuation coefficient" used in the present invention and this specification refers to a coefficient representing the degree to which emitted light is attenuated by absorption and/or scattering while traveling through a medium.

That is, one embodiment of the present invention is as follows.
[1] Forming a film on the surface of a semiconductor wafer (also simply referred to as "wafer") for expanding protrusion-like defects existing on this 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 an "evaluation method"), wherein the film is a film made of a material having a light attenuation coefficient of 4 or more at a wavelength of 266 nm.
[2] The method for evaluating a semiconductor wafer according to [1], wherein the material is amorphous silicon.
[3] Forming a film on the surface of the 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 film 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 the protruding defects present on the surface of the semiconductor wafer based on the results of the above inspection includes:
Evaluating the number of protruding defects present on the surface of the semiconductor wafer by regarding the number of LPDs detected by the inspection as the number of protruding defects present on the surface of the semiconductor wafer, [ The method for evaluating a semiconductor wafer according to any one of [1] to [5].
[7] Evaluating the protruding defects present on the surface of the semiconductor wafer based on the results of the above inspection includes:
The height of the protrusion on the surface of the coating is measured using an atomic force microscope at the position where LPD is detected by the above inspection, and the measured height value is used to determine the height of the protrusion on the surface of the semiconductor wafer, which is located directly below the protrusion. The method for evaluating a semiconductor wafer according to any one of [1] to [6], which includes evaluating the size of the protruding defect present on the surface of the semiconductor wafer, regarding the size of the protruding defect as being the size of the protruding defect.
[8] Evaluation regarding the size of the protruding defects present on the surface of the semiconductor wafer is as follows:
Evaluating the size distribution of the protrusion-like defects present on the semiconductor wafer surface based on height distribution information created based on the measured values of the heights of the plurality of protrusions on the surface of the film;
The method for evaluating a semiconductor wafer according to [7], comprising:
[9] The method for evaluating a semiconductor wafer according to any one of [1] to [8], wherein the protruding defect present on the surface of the semiconductor wafer is a defect selected from the group consisting of particles and PID.
[10] The semiconductor wafer evaluation method according to any one of [1] to [9], wherein the semiconductor wafer is a silicon wafer.
[11] The above 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 PID,
The semiconductor wafer is a silicon wafer, and evaluating the 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). The method for evaluating a semiconductor wafer according to [1].
(1) Evaluating the number of protruding defects present on the surface of the semiconductor wafer by regarding the number of LPDs detected by the above inspection as the number of protruding defects present on the surface of the semiconductor wafer.
(2) Measure the height of the protrusion on the surface of the film using an atomic force microscope at the position where LPD was detected by the above inspection, and set the measured height value directly below the protrusion on the surface of the semiconductor wafer. The size of the protruding defects present on the surface of the semiconductor wafer is evaluated by regarding the size of the protruding defects present on the surface of the semiconductor wafer.
[12] Evaluation regarding the size of the protruding defects present on the surface of the semiconductor wafer is as follows:
Evaluating the size distribution of the protrusion-like defects present on the semiconductor wafer surface based on height distribution information created based on the measured values of the heights of the plurality of protrusions on the surface of the film;
The method for evaluating a semiconductor wafer according to [11], comprising:
[13] Manufacturing a semiconductor wafer under the manufacturing conditions to be evaluated;
Evaluating the semiconductor wafer manufactured above by the semiconductor wafer evaluation method according to any one of [1] to [12];
Based on the results of the above evaluation, the manufacturing conditions that have been modified from the manufacturing conditions to be evaluated are determined as the subsequent manufacturing conditions, or the manufacturing conditions to be evaluated are determined as the manufacturing conditions that will continue to be adopted; ,
manufacturing a semiconductor wafer under the manufacturing conditions determined above;
A method for manufacturing a semiconductor wafer (also simply referred to as a "manufacturing method").
[14] When a semiconductor wafer is evaluated by the semiconductor wafer evaluation method according to any one of [1] to [12], the number of LPDs detected by inspecting the surface of the coating with a surface defect inspection device is Semiconductor wafers of 15 pieces/wafer or less.

According to one aspect of the present invention, it is possible to evaluate minute protruding defects present on the surface of a semiconductor wafer.

FIG. 3 is a schematic diagram of size expansion due to a lens effect. The comparison result of the LPD detection size before and after film formation of an amorphous silicon film is shown. The average haze measured on the surfaces of an amorphous silicon film and a silicon nitride film is shown. Regarding Example 1, the number of LPDs determined on the wafer surface before film formation is shown. A specific example of a SEM image of protrusions and attached particles after film formation is shown. In Example 1, the number of LPDs (post-deposition protrusions) determined on the surface of the amorphous silicon film after film formation is shown. For Comparative Example 1 and Example 2, the number of LPDs determined on the wafer surface after film formation is shown. The number distribution (height distribution information) obtained by measuring the heights of all protrusions on the surface of the amorphous silicon film using AFM for one of the wafers after the LPD measurement after film formation in Example 2 was performed. show.

Hereinafter, the above evaluation method and the above manufacturing method will be explained in more detail.

[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. For example, specific examples of semiconductor wafers include various silicon wafers. Silicon wafers 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 subjected to polishing treatment and have a polished surface on their surfaces, epitaxial wafers that have epitaxial layers formed, etc. can be. The diameter of the semiconductor wafer to be evaluated is, for example, 200 mm or less and 200 mm or more (for example, 200 mm, 300 mm, or 450 mm), but is not particularly limited.

A protruding defect exists on the surface of the semiconductor wafer to be evaluated. Such defects can be particles and/or PIDs.

<Formation of film>
In the above evaluation method, a film is formed on the surface of a semiconductor wafer. As the above-mentioned coating, a coating made of a material having a light attenuation coefficient (also simply referred to as "attenuation coefficient") of 4 or more at a wavelength of 266 nm is formed. If the coating is made of a material with an attenuation coefficient of 4 or more, the surface haze of the coating can be reduced as described in detail above, which can contribute to improving measurement sensitivity. Examples of materials having an attenuation coefficient of 4 or more include amorphous silicon and silicon germanium. In addition, in the present invention, 266 nm is adopted as the wavelength for defining the attenuation coefficient, but this is because the attenuation coefficient is specified as a physical property value specific to the material, and the surface defect inspection device used in the above evaluation method irradiates. The wavelength of light is not limited to 266 nm. The attenuation coefficients of various materials are values known in literature, or can be measured by known methods. An example is described in "Edward D. Parik, "Handbook of Optical Constants of Solid" Academic press, 1985". For example, the damping coefficient of amorphous silicon is 4.426 and the damping coefficient of silicon nitride Si ₃ N ₄ is 0.013.

The attenuation coefficient of the material constituting the coating is 4 or more for the above reasons, 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, the upper limit of the attenuation coefficient is not particularly limited. If the material constituting the coating has an attenuation coefficient of 4 or more, sufficient measurement sensitivity can be obtained, so there is no need to use a material with an excessively high attenuation coefficient. From this point of view, 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.

The film can be formed using a known film forming apparatus such as LP-CVD (Low Pressure Chemical Vapor Deposition), plasma CVD, or ALD (Atomic Layer Deposition) apparatus.

A specific example of the material of the film is amorphous silicon. In the following, a film made of amorphous silicon will also be referred to as an "amorphous silicon film." A known method can be used to form the amorphous silicon film. For example, an amorphous silicon film is formed on the semiconductor wafer surface by forming a seed layer on the semiconductor wafer surface using aminosilane gas and depositing a silane gas with a smaller molecular weight than the aminosilane used to form the seed layer. I can do it. The seed layer serves as a starting point for the growth of amorphous silicon. Among silane-based gases that serve as source gases for the amorphous silicon film, it is preferable to deposit aminosilane gas having a large molecular weight from the viewpoint of forming a highly smooth film-forming surface. For a specific film formation process of an amorphous silicon film, reference can be made to, for example, JP-A No. 2011-249764 and JP-A No. 2014-127693.

Forming an amorphous silicon film as the above-mentioned film is also preferable from the following viewpoints.
In the formation of a nitride film, ammonium chloride, which is a reaction by-product, reduces dust generation, which increases the number of foreign substances (attached particles) that adhere to the surface of the nitride film. In the evaluation using a surface defect inspection device, on the surface of the film, the part where the film surface is raised due to the presence of a protruding defect directly below (protrusion (hereinafter also referred to as "post-film protrusion")) is Cannot be distinguished from attached particles. Therefore, in order to classify protrusions and attached particles after film formation, a defect discrimination process using a scanning electron microscope (SEM) or the like must be performed. Therefore, it is difficult to accurately evaluate the difference between the levels of protruding defects on the semiconductor wafer surface located under the nitride film from the inspection results of the nitride film surface using the surface defect inspection apparatus.
On the other hand, when forming an amorphous silicon film, fewer adhering particles are generated. Therefore, the difference between the levels of protrusion-like defects on the semiconductor wafer surface located under the amorphous silicon film can be detected based on the inspection results of the amorphous silicon film surface using a surface defect inspection device, without performing a defect discrimination process using SEM or the like. It can be evaluated with high accuracy. However, of course, it is also possible to perform a defect determination process using SEM or the like on the surface of the amorphous silicon film, and to exclude protrusions determined to be attached particles from subsequent evaluation.

As described above, a coating made of a material having an attenuation coefficient of 4 or more at a wavelength of 266 nm is preferable because it has a low surface haze. Average haze can be cited as an index of surface haze. In the present invention and this specification, "average haze" refers to DW1O (Dark-field Wide-1 Oblique) Haze Average measured with Surfscan series SP7 manufactured by KLA-TENCOR. The coating formed on the surface of the semiconductor wafer in the above evaluation method can have an average haze measured on the coating surface of 0.5 ppm or less.
FIG. 3 shows the average haze measured on the surfaces of the amorphous silicon film and the silicon nitride film. FIG. 3 shows the measurement results of the average haze of an amorphous silicon film and a silicon nitride film. Specifically, FIG. 3 shows the values of DW1O Haze Average measured with Surfscan series SP7 manufactured by KLA-TENCOR for each of a 120 nm thick amorphous silicon film and a 120 nm thick silicon nitride film. . In FIG. 3, "SiN" is an abbreviation for silicon nitride film, and "a-Si" and "amorphous Si film" are abbreviation for amorphous silicon film. The average haze of the amorphous silicon film is 0.5 ppm or less, which confirms that the surface haze is low.
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 the sensitivity of the DW1O channel of the Surfscan series SP7 manufactured by KLA-TENCOR (minimum detection of the light receiving part). The size) is 19 nm. On the other hand, in the case of a silicon nitride film with an average haze of 2.067, the sensitivity (minimum detection size of the light receiving part) of the DW1O channel of the Surfscan series SP7 manufactured by KLA-TENCOR, which is similarly set, is 29 nm. As described above, a film with a low surface haze is preferable from the viewpoint of increasing measurement sensitivity in a surface defect inspection device.

The above coating can expand protruding defects existing on the surface of a semiconductor wafer. By "expanding", protrusions larger in size than the protrusion-like defects on the semiconductor wafer surface are formed on the surface of the coating. This is due to the so-called "lens effect." The "lens effect" is a phenomenon in which, after film formation, a protrusion starting from a protrusion and having a diameter several times larger than the protrusion is formed on the coating surface directly above the protrusion.
FIG. 1 is a schematic diagram of size expansion due to lens effect. In the example shown in FIG. 1, the protrusion after film formation on the coating surface directly above the protrusion of diameter D has a diameter X that is several times larger than the diameter D of the protrusion. Further, the post-film-forming protrusion formed by the lens effect is a defect that is raised by the size of the protrusion-like defect on the surface of the semiconductor wafer directly below. Therefore, in the example shown in FIG. 1, the height of the protrusion after film formation on the coating surface has the same value as the diameter D of the protrusion. Details of evaluation using this point will be described later.

By forming the above film on the surface of the semiconductor wafer, it is possible to form protrusions larger in size than the defects on the surface of the film directly above the protrusion-like defects on the surface of the semiconductor wafer. Therefore, for example, on the surface of a semiconductor wafer, a microscopic protruding defect that is smaller than the detection limit size of a surface defect inspection device can be detected by a surface defect inspection device that has a size larger than the detection limit size on the coating surface directly above it. It is possible to form a protrusion.
As a specific example, FIG. 2 shows a comparison result of the LPD detection size before and after the formation of an amorphous silicon film. Figure 2 shows the LPD detection size on the semiconductor wafer surface and the coordinate points where LPD was detected on the semiconductor wafer surface before forming an amorphous silicon film with a thickness of 20 nm, 40 nm, 70 nm, and 140 nm. Comparison results with the LPD detection size detected on the surface of the amorphous silicon film after film formation are shown. As the surface defect inspection device, Surfscan series SP7 manufactured by KLA-TENCOR was used. From the results shown in FIG. 2, it can be confirmed that the protrusion-like defects on the surface of the semiconductor wafer can be expanded by forming the film. For example, in the example shown in FIG. 2 in which a film with a thickness of 140 nm is formed, the LPD detection size is about three times the LPD detection size before film formation. According to the lens effect, the thicker the deposited film, the larger the size of the protrusion detected on the film surface directly above the protrusion-like defect on the semiconductor wafer surface. In a surface defect inspection apparatus, generally, the larger the defect size, the easier it is to detect the defect as an LPD. Further, it is preferable that the thickness of the coating is greater than the size of the protruding defect to be evaluated. From the above viewpoint, the thickness of the coating formed on the surface of the semiconductor wafer is preferably 15 nm or more. For example, in the Surfscan series SP7 manufactured by KLA-TENCOR, the undetectable size is less than 15 nm, so it is preferable to form a film with a thickness 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.

<Surface inspection using surface defect inspection device>
As the surface defect inspection device, a known surface defect inspection device that can make light enter the surface of the inspection target and detect emitted light (scattered light or reflected light) from this surface can be used. Such a surface defect inspection device is generally also called a light scattering type surface defect inspection device, a surface inspection device, or the like. A specific example of the 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 laser light, and detects protrusions on the surface of the object as bright spots (LPD) using emitted light (scattered light or reflected light). Furthermore, by measuring the emitted light from the LPD, the position (specifically, the coordinate point) of the protrusion on the surface of the inspection target and the size detected as the LPD (LPD detection size) can be determined. Such an LPD detection size is usually output by an analysis section of a surface defect inspection device by comparing the intensity of emitted light from the LPD with the intensity of emitted light of standard particles such as silica particles. As the laser light, ultraviolet light, visible light, etc. can be used, and the wavelength thereof 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 the laser surface defect inspection device usually acquires information on the two-dimensional position coordinates (X coordinate and Y coordinate) on the surface of the inspection target for each of the plurality of detected LPDs, and calculates the acquired two-dimensional position. An LPD map showing the in-plane LPD distribution state on the surface of the inspection target can be created from the coordinate information. Specific examples of commercially available laser surface defect inspection devices include 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.

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

(1) The number of LPDs detected by the above inspection is regarded as 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) Measure the height of the protrusion on the surface of the film using an atomic force microscope at the position where LPD was detected by the above inspection, and place the measured height value directly below the protrusion on the semiconductor wafer surface. The size of the protrusion-like defects present on the semiconductor wafer surface is evaluated by regarding the size of the protrusion-like defects as being the size of the protrusion-like defects present.

According to evaluation (1), due to the expansion (lens effect) caused by the film, it is possible to evaluate the number of minute protruding defects that cannot be detected by inspecting the surface of a semiconductor wafer with a surface defect inspection device.

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

As shown in FIG. 1, the post-film-forming protrusion formed on the surface of the film due to the lens effect is a defect that is raised by the size of the protrusion-like defect on the surface of the semiconductor wafer directly below. Therefore, the height of a protrusion after film formation can be regarded as the size of a protrusion-like defect existing directly below the protrusion on the semiconductor wafer surface. For example, the height of a protrusion measured on the coating surface can be regarded as the particle diameter for particles on the semiconductor wafer surface, and can be regarded as the PID height for the PID on the semiconductor wafer surface. The height of the protrusions on the surface of the coating can be measured using a known measuring device, such as an atomic force microscope (AFM).

In addition, as a specific embodiment of evaluation (2), the size of a protrusion-like defect existing on the semiconductor wafer surface is determined based on height distribution information created based on the measured values of the heights of a plurality of protrusions on the surface of the film. The distribution can be evaluated. According to the above evaluation method, due to the expansion (lens effect) caused by the coating, the size of minute protrusion-like defects that cannot be detected by inspecting the semiconductor wafer surface with a surface defect inspection device can be measured as the height of the protrusions on the coating surface. You can ask for it. This makes it possible to evaluate the size distribution of protruding defects present on the semiconductor wafer surface with higher accuracy than when the semiconductor wafer surface is inspected using a surface defect inspection device.

For specific examples of evaluation (1) and evaluation (2), refer to Examples described below.

[Method for manufacturing semiconductor wafers]
One aspect of the present invention is to manufacture a semiconductor wafer under manufacturing conditions to be evaluated, to evaluate the manufactured semiconductor wafer using the semiconductor wafer evaluation method described above, and to evaluate the semiconductor wafer based on the result of the evaluation. Determine the manufacturing conditions with changes to the manufacturing conditions as the subsequent manufacturing conditions, or determine the manufacturing conditions to be evaluated as the manufacturing conditions that will continue to be adopted, and semiconductor wafers under the determined manufacturing conditions. The present invention relates to a method of manufacturing a semiconductor wafer, including manufacturing a semiconductor wafer.

Specific examples of the above manufacturing method include the following.
Semiconductor wafers are manufactured under manufacturing conditions A.
Separately, semiconductor wafers are manufactured under manufacturing conditions B that are different from manufacturing conditions A.
The manufacturing conditions to be evaluated are referred to as "manufacturing conditions B."
Wafers for evaluation are extracted from each of the wafer group manufactured under manufacturing condition A and the wafer group manufactured under manufacturing condition B, and evaluated by the evaluation method described above.
For example, as a result of the evaluation, the total number of protrusion-like defects on the surface of the semiconductor wafer determined by the evaluation method described above is higher than the total number of protruding defects on the surface of the semiconductor wafer in the evaluation wafer selected from the group of wafers manufactured under manufacturing condition A. If the number is smaller than the number of evaluation wafers extracted from a group of wafers manufactured under B, it can be determined that manufacturing condition A is a manufacturing condition in which protruding defects are less likely to occur on the semiconductor wafer surface compared to manufacturing condition B. In this case, manufacturing conditions B can be changed to be closer to manufacturing conditions A, and subsequent semiconductor wafers can be manufactured using the modified manufacturing conditions as improved manufacturing conditions B.
For example, as a result of the evaluation, the size distribution of protruding defects on the surface of the semiconductor wafer determined by the evaluation method described above may be , compared to the evaluation wafer extracted from a group of wafers manufactured under manufacturing condition A, if the size distribution is further away from the desired product size distribution, manufacturing condition A is more desirable than manufacturing condition B. It can be determined that it is a condition. In this case, manufacturing conditions B can be changed to be closer to manufacturing conditions A, and subsequent semiconductor wafers can be manufactured using the modified manufacturing conditions as improved manufacturing conditions B.

Moreover, the following can also be exemplified as a specific form of the above manufacturing method.
In order to determine manufacturing conditions for manufacturing semiconductor wafers to be actually 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.
Semiconductor wafers manufactured under test manufacturing conditions are evaluated by the evaluation method described above.
Based on the evaluation results, manufacturing conditions obtained by adding changes to 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, as a result of evaluation, in semiconductor wafers manufactured under test manufacturing conditions, if the total number of protruding defects on the semiconductor wafer surface determined by the evaluation method described above exceeds a preset target value. In this case, manufacturing conditions obtained by adding changes to the test manufacturing conditions so as to suppress the occurrence of protruding defects can be determined as actual manufacturing conditions.
For example, as a result of evaluation, the size distribution of protrusion-like defects on the semiconductor wafer surface determined by the evaluation method described above in semiconductor wafers manufactured under test manufacturing conditions deviates significantly from the desired size distribution. Even in the case where the test manufacturing conditions are changed so as to suppress the occurrence of protruding defects, it is possible to determine the manufacturing conditions as the actual manufacturing conditions.

Regarding the manufacturing process of semiconductor wafers, for example, the manufacturing process of polished wafers includes cutting (slicing), chamfering, rough polishing (e.g. lapping), etching, and mirror polishing (finish polishing) of the wafer from a semiconductor ingot such as a silicon single crystal ingot. ), it can be manufactured by a manufacturing process including a cleaning process performed between or after the above processing steps. PID, which is a type of protruding defect, is a defect that can occur during polishing processing. Therefore, in one form, the manufacturing conditions to which the above changes are made can be polishing processing conditions for the surface of a semiconductor wafer. Specifically, various polishing conditions can be changed, such as replacing the polishing slurry, changing the composition of the polishing slurry, replacing the polishing pad, changing the type of polishing pad, and changing the operating conditions of the polishing apparatus.

Furthermore, particles, which are a form of protruding defects on the surface of a semiconductor wafer, are foreign matter attached to the surface of the wafer, and therefore can be removed by cleaning. Therefore, in one form, the manufacturing conditions to which the above changes are made can be cleaning conditions. In order to reduce particles, for example, cleaning conditions may be strengthened. Specifically, measures for reducing particles include increasing the number of times of cleaning, lengthening the cleaning time, and using a cleaning agent with higher cleaning power.

The present invention will be further explained below based on Examples. However, the present invention is not limited to the embodiments shown in Examples.

The surface defect inspection device used below is Surfscan series SP7 manufactured by KLA-TENCOR.

[Example 1]
(1) LPD measurement before film formation The semiconductor wafer to be evaluated is an epitaxial wafer with a diameter of 300 mm manufactured under different process conditions (process condition A, process condition B) with a significant difference in the number of protruding defects. (an epitaxial wafer in which a silicon epitaxial layer was formed on a silicon single crystal wafer) was prepared. Wafers manufactured under process condition A are designated as A1 to A6, and wafers manufactured under process condition B are designated as B1 to B6.
The surface of the wafer to be evaluated was inspected using a surface defect inspection device, and the LPD detection size and coordinate data were obtained over the entire surface area.

FIG. 4 shows the number of LPDs determined by the DW1O channel of the Surfscan series SP7 manufactured by KLA-TENCOR on the surface of the wafer to be evaluated. The sensitivity (minimum detection size) set by the 95% Capture Rate of the SEMI standard (SEMI M50-1101) was 15 nm.

(2) Film Formation Process Regarding the above-mentioned evaluation target wafer, an amorphous silicon film was formed on the surface where the LPD measurement was performed in the above (1) using an LP-CVD apparatus. Specifically, an amorphous silicon film with a thickness of 120 nm was formed by forming a seed layer on the wafer surface using aminosilane gas and depositing a silane gas having a lower molecular weight than the aminosilane used to form the seed layer.

(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 the LPD detection size and coordinate data were obtained over the entire in-plane area.

(4) SEM Observation The surface of the amorphous silicon film of the wafer to be evaluated was observed using SEM. Specifically, the protrusions were observed using the coordinate data obtained by the LPD measurement in (3) above, and a secondary electron image was obtained. Based on the shape of the secondary electron image, post-forming protrusions and attached particles on the surface of the amorphous silicon film were classified. FIG. 5 shows a specific example of a SEM image of protrusions and attached particles after film formation. It was confirmed that there were very few particles attached to the surface of the amorphous silicon film, and that it was possible to evaluate the protrusion-like defects on the surface of the semiconductor wafer from the LPD measurement results of the protrusions on the surface of the amorphous silicon film without excluding the attached particles.

FIG. 6 shows the number of LPDs determined by the DW1O channel of Surfscan series SP7 manufactured by KLA-TENCOR on the surface of the amorphous silicon film of the wafer to be evaluated. FIG. 6 shows the results of LPD that was determined to be a protrusion after film formation in (4) above. The sensitivity (minimum defect size) set by the 95% Capture Rate of the SEMI standard (SEMI M50-1101) was 19 nm.

As shown in FIG. 4, before film formation, there was no significant difference in the number of LPDs between the wafers manufactured under process conditions A and wafers manufactured under process conditions B. On the other hand, as shown in FIG. 6, after the amorphous silicon film was formed, there was a significant difference in the number of LPDs between the wafers manufactured under process condition A and the wafers manufactured under process condition B. It was seen.

[Example 2, Comparative Example 1]
The semiconductor wafers to be evaluated were polished wafers (silicon single crystal wafers) with a diameter of 300 mm that were manufactured under different process conditions (process conditions C and process conditions D) that had a significant difference in the number of protruding defects. Got ready. Wafers manufactured under process conditions C are designated as C1 to C4, and wafers manufactured under process conditions D are designated as D1 to D8. Process condition C is a process condition that employs single wafer cleaning using hydrofluoric acid and ozone water, and process condition D is a process condition that employs batch cleaning using SC-1 (Standard Cleaning-1) cleaning, etc. It is.

In Example 2, an amorphous silicon film was formed on the surface of the wafer to be evaluated using an LP-CVD apparatus. Specifically, an amorphous silicon film with a thickness of 120 nm was formed by forming a seed layer on the wafer surface using aminosilane gas and depositing a silane gas having a lower molecular weight than the aminosilane used to form the seed layer.
For Comparative Example 1, a silicon nitride film with a thickness of 120 nm was formed on the surface of the evaluation target wafer using dichlorosilane gas (H ₂ SiCl ₂ ) and ammonia (NH ₃ ) in an LP-CVD apparatus. .

FIG. 7 shows the number of LPDs determined by the DW1O channel of Surfscan series SP7 manufactured by KLA-TENCOR on the surface of each film (silicon nitride film or amorphous silicon film) for Comparative Example 1 and Example 2.
In Comparative Example 1, there was no significant difference in the number of LPDs between the wafers manufactured under process conditions C and the wafers manufactured under process conditions D.
On the other hand, in Example 2, there was a significant difference in the number of LPDs between the wafers manufactured under process conditions C and wafers manufactured under process conditions D. It was confirmed that in the wafers C1 to C4 manufactured under process condition C employing single-wafer cleaning using a wafer, the required number of LPDs on the surface of the film was 15 or less.
The above results indicate that the difference between levels can be evaluated without performing a defect determination process using SEM because the number of attached particles that cause disturbance is small on the surface of an amorphous silicon film.

As described above, according to one aspect of the present invention, when evaluated by the semiconductor wafer evaluation method, the number of LPDs detected when the surface of the coating is inspected by a surface defect inspection device is 15 or less per wafer. (That is, 15 or less per wafer) can be provided. The number of LPDs per wafer can be, for example, 0 to 15 or 1 to 15.

For one of the wafers subjected to LPD measurement after film formation in Example 2, the heights of all protrusions on the surface of the amorphous silicon film were measured by AFM, and the number distribution (height distribution information) shown in FIG. )was gotten.
As described above, the post-film formation protrusions formed on the film surface due to the lens effect are defects that are raised by the size of the protrusion-like defects on the surface of the semiconductor wafer directly below. Therefore, the height of a protrusion after film formation (a protrusion on the surface of a film) can be regarded as the size of a protrusion-like defect existing directly below the protrusion on the semiconductor wafer surface. Therefore, the above-mentioned number distribution (height distribution information) can be regarded as the size distribution of protruding defects present on the surface of the wafer located under the amorphous silicon film.

One embodiment of the present invention is useful in the field of manufacturing various semiconductor wafers such as silicon wafers.

Claims (18)

forming a coating on the surface of a semiconductor wafer for expanding protrusion-like defects existing 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;
The method for evaluating a semiconductor wafer, wherein the coating is a coating made of a material having a light attenuation coefficient of 4 or more at a wavelength of 266 nm. The semiconductor wafer evaluation method according to claim 1, wherein the material is amorphous silicon. 2. The semiconductor wafer evaluation method according to claim 1, wherein the surface of the coating has an average haze of 0.5 ppm or less. The method for evaluating a semiconductor wafer according to claim 1, wherein the thickness of the coating is 15 nm or more and 500 nm or less. Evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection includes:
A claim comprising evaluating the number of protruding defects present on the surface of the semiconductor wafer by regarding the number of LPDs detected by the inspection as the number of protruding defects present on the surface of the semiconductor wafer. Item 1. The method for evaluating a semiconductor wafer according to Item 1. Evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection includes:
The height of the protrusion on the surface of the film is measured using an atomic force microscope at the position where the LPD is detected by the inspection, and the measured height value is calculated as the height of the protrusion on the surface of the semiconductor wafer. 2. The method for evaluating a semiconductor wafer according to claim 1, comprising evaluating the size of the protruding defect present on the surface of the semiconductor wafer by regarding the size of the protruding defect as being the size of the protruding defect. The evaluation regarding the size of the protruding defects existing on the semiconductor wafer surface is as follows:
evaluating the size distribution of protrusion-like defects present on the semiconductor wafer surface based on height distribution information created based on measured values of the heights of the plurality of protrusions on the surface of the coating;
The semiconductor wafer evaluation method according to claim 6, comprising: 2. The method for evaluating a semiconductor wafer according to claim 1, wherein the protruding defect existing on the surface of the semiconductor wafer is a defect selected from the group consisting of particles and PID. The semiconductor wafer evaluation method according to claim 1, wherein the semiconductor wafer is a silicon wafer. 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 PID,
The semiconductor wafer is a silicon wafer, and evaluating the protruding defects present on the surface of the semiconductor wafer based on the inspection results includes at least one of the following (1) and (2). The method for evaluating a semiconductor wafer according to claim 1.
(1) Evaluating the number of protruding defects present on the surface of the semiconductor wafer by regarding the number of LPDs detected by the inspection as the number of protruding defects present on the surface of the semiconductor wafer.
(2) The height of the protrusion on the surface of the film is measured using an atomic force microscope at the position where LPD is detected by the inspection, and the measured height value is set directly below the protrusion on the surface of the semiconductor wafer. evaluating the size of the protruding defects present on the surface of the semiconductor wafer. The evaluation regarding the size of the protruding defects existing on the semiconductor wafer surface is as follows:
evaluating the size distribution of protrusion-like defects present on the semiconductor wafer surface based on height distribution information created based on measured values of the heights of the plurality of protrusions on the surface of the coating;
The method for evaluating a semiconductor wafer according to claim 10, comprising: forming a film 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 film is an amorphous silicon film. The method for evaluating a semiconductor wafer according to claim 12, wherein the surface of the coating has an average haze of 0.5 ppm or less, and the thickness of the coating is 15 nm or more and 500 nm or less. 13. The method for evaluating a semiconductor wafer according to claim 12, wherein the protruding defect present on the surface of the semiconductor wafer is a defect selected from the group consisting of particles and PID. Evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection includes:
A claim comprising evaluating the number of protruding defects present on the surface of the semiconductor wafer by regarding the number of LPDs detected by the inspection as the number of protruding defects present on the surface of the semiconductor wafer. Item 13. The method for evaluating a semiconductor wafer according to item 12. Evaluating protruding defects present on the surface of the semiconductor wafer based on the results of the inspection includes:
The height of the protrusion on the surface of the film is measured using an atomic force microscope at the position where the LPD is detected by the inspection, and the measured height value is calculated as the height of the protrusion on the surface of the semiconductor wafer. 13. The method for evaluating a semiconductor wafer according to claim 12, comprising evaluating the size of the protruding defect present on the surface of the semiconductor wafer by regarding the size of the protruding defect as being the size of the protruding defect. 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 16;
Based on the results of the evaluation, determining manufacturing conditions with changes to the manufacturing conditions to be evaluated as subsequent manufacturing conditions, or determining manufacturing conditions to continue to adopt the manufacturing conditions to be evaluated; and ,
manufacturing a semiconductor wafer under the determined manufacturing conditions;
A method for manufacturing a semiconductor wafer, including: When a semiconductor wafer is evaluated by the semiconductor wafer evaluation method according to any one of claims 1 to 16, the number of LPDs detected when the surface of the coating is inspected by a surface defect inspection device is 15/ A semiconductor wafer that is smaller than a wafer.