Semiconductor wafer evaluation method

Abstract

The present invention provides a method for evaluating a semiconductor wafer using a laser surface inspection device. The semiconductor wafer has a cover layer on a semiconductor substrate, and the laser surface inspection device has: a first incident system; a second incident system that causes light to be incident on the irradiated surface at an incident angle higher than the incident angle of light incident on the irradiated surface by the first incident system; a first light receiving system; a second light receiving system; and a third light receiving system. The three light receiving systems have at least one different light receiving angle selected from the group consisting of a light receiving angle and a polarization selectivity for receiving light emitted from the irradiated surface. The method includes evaluating the semiconductor chip on the surface of the covering layer in the following manner: based on multiple measurement results including three low-incident-angle measurement results and at least one high-incident-angle measurement result, detecting a defect type selected from the group consisting of attached matter and non-attached convex defects present on the surface of the covering layer as a bright spot, wherein the three low-incident-angle measurement results are obtained by respectively receiving, by the three light receiving systems, radiated light emitted by reflection or scattering of light incident from a first incident system on the surface, and the at least one high-incident-angle measurement result is obtained by receiving, by at least one of the three light receiving systems, radiated light emitted by reflection or scattering of light incident from a second incident system on the surface.

Description

[0001] Cross-references of related applications

[0002] This application claims the benefit of priority from Japanese Patent Application No. 2020-099230, filed on June 8, 2020, the entire contents of which are expressly incorporated herein by reference. Technical Field

[0003] The present invention relates to a method for evaluating a semiconductor wafer, and more particularly, to a method for evaluating a semiconductor wafer having a cover layer on a semiconductor substrate. Background Art

[0004] In recent years, as a method for evaluating defects in semiconductor wafers and foreign matter attached to the surface, a method based on a bright spot (LPD; Light Point Defect) detected by a laser surface inspection device has been widely used (for example, see Japanese Patent Publication No. 2005-43277 (the entire description of which is hereby incorporated by reference as a special disclosure)). In this method, light is incident on the surface of a semiconductor wafer to be evaluated, and by detecting the radiated light (scattered light or reflected light) from the surface, the presence and size of defects and foreign matter in the semiconductor wafer are evaluated.

[0005] Japanese Patent Publication No. 2005-43277 discloses a method for classifying convex defects and concave defects and evaluating the state of a semiconductor wafer on which a film has been deposited using a laser surface inspection device having an incident system and two receiving systems (a second embodiment described in paragraphs 0024 to 0026 of Japanese Patent Publication No. 2005-43277).

[0006] On a semiconductor wafer after the covering layer is formed, there may be surface defects such as attachments and non-attached convex defects on the surface of the covering layer. Attachments are foreign matter that attaches to the covering layer from the external environment during and / or after the film forming process. In contrast, non-attached convex defects are local protrusions on the surface of the covering layer, which are usually defects that are centered on defects on the surface of the wafer before film formation and are enlarged due to film formation. Since the attachments can be removed by cleaning, the impact on subsequent processes is small. In contrast, non-attached convex defects may cause abnormal operation during, for example, subsequent wiring processes, which may lead to a reduction in yield, but cannot be removed by cleaning. As described above, since the countermeasures for reducing attachments and non-attached convex defects are different, it is desirable to detect both separately. Summary of the invention

[0007] One embodiment of the present invention provides a novel evaluation method for evaluating a semiconductor wafer having a cover layer by detecting attached matter and / or non-attached convex defects on the surface of the cover layer.

[0008] One embodiment of the present invention is a method for evaluating a semiconductor wafer (hereinafter also simply referred to as an "evaluation method"), wherein a semiconductor wafer (hereinafter also simply referred to as a "wafer") is evaluated using a laser surface inspection apparatus.

[0009] The semiconductor wafer has a cover layer on the semiconductor substrate.

[0010] The above-mentioned laser surface inspection device has:

[0011] First incident system;

[0012] a second incident system for causing light to be incident on the illuminated surface at an incident angle higher than the incident angle of the light incident on the illuminated surface by the first incident system;

[0013] The first light receiving system;

[0014] a second light receiving system; and

[0015] The third light receiving system,

[0016] The three light receiving systems are different in one or more selected from the group consisting of a light receiving angle and a polarization selectivity of receiving light emitted from the illuminated surface.

[0017] The evaluation method of the semiconductor wafer includes evaluating the semiconductor wafer on the surface of the above-mentioned covering layer in the following manner: based on multiple measurement results including three low-incident angle measurement results and at least one high-incident angle measurement result, a defect type selected from the group consisting of attached objects and non-attached convex defects present on the surface of the above-mentioned covering layer is detected as a bright spot, the above-mentioned three low-incident angle measurement results are obtained by the above-mentioned three light receiving systems respectively receiving the radiated light emitted by the light incident from the first incident system on the above-mentioned surface, or by scattering, and the above-mentioned at least one high-incident angle measurement result is obtained by at least one of the above-mentioned three light receiving systems receiving the radiated light emitted by the light incident from the second incident system on the above-mentioned surface, or by scattering.

[0018] In one embodiment, one of the three light receiving systems can receive omnidirectional light, and the other two light receiving systems can selectively receive polarized light having different azimuth angles.

[0019] In one embodiment, the light receiving angle of the light receiving system that receives the omnidirectional light may be higher than the light receiving angles of the other two light receiving systems.

[0020] In one embodiment, the azimuth angle of polarized light selectively received by one of the other two light receiving systems may be set to θ1°, and the azimuth angle of polarized light selectively received by the other light receiving system may be set to θ2°, where 0°≤θ1°≤90°, and 90°≤θ2°≤180°.

[0021] In one embodiment, the at least one high incident angle measurement result may include a measurement result obtained by receiving, by at least one of the other two light receiving systems, radiated light emitted by light incident from the second incident system reflected or scattered on the surface.

[0022] In one embodiment, the evaluation method may be:

[0023] The first light receiving system receives omnidirectional light.

[0024] The second light receiving system selectively receives polarized light with an azimuth angle of θ1°.

[0025] The third light receiving system selectively receives polarized light having an azimuth angle θ2° different from the azimuth angle θ1°.

[0026] 0°≤θ1°≤90°and 90°≤θ2°≤180°,

[0027] The light receiving angle of the first light receiving system is an angle higher than the light receiving angle of the second light receiving system and the light receiving angle of the third light receiving system, including the light receiving angle selected from

[0028] The presence or absence of detection and the detection size in the measurement result 1 obtained by combining the first incident system and the first receiving system,

[0029] The presence or absence of detection and the detection size in the measurement result 2 obtained by combining the first incident system and the second light receiving system,

[0030] The presence or absence of detection and the detection size in the measurement result 3 obtained by combining the first incident system and the third light receiving system, and

[0031] The presence or absence of detection and the detection size in the measurement result 4 obtained by combining the second incident system with the second light receiving system or the third light receiving system

[0032] The determination criteria of the constituted group is to determine whether the defect type detected as the bright spot is an attached substance or a non-attached convex defect.

[0033] In one embodiment, the above-mentioned determination can be performed according to the determination criteria shown in Table 1 described later.

[0034] In one embodiment, in Table 1, X may be in the range of 1.30 to 1.50.

[0035] In one embodiment, in Table 1, Y may be in the range of 0.60 to 0.80.

[0036] In one embodiment, in Table 1, Z may be in the range of 0.80 to 0.85.

[0037] In one embodiment, the cover layer may be a deposited layer in which a film-forming material is deposited.

[0038] In one embodiment, the semiconductor substrate may be a single crystal silicon substrate.

[0039] Effects of the invention:

[0040] According to one embodiment of the present invention, by detecting adhered matter and / or non-adhered convex defects on the surface of the cover layer, a semiconductor wafer having a cover layer on a semiconductor substrate can be evaluated. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 An example of a laser surface inspection device (schematic configuration diagram) is shown.

[0042] Figure 2 An example (SEM image) of non-adherent protruding defects and adhered matter observed by SEM on the surface of the cover layer of the semiconductor wafer in the Example is shown.

[0043] Figure 3 This is a graph showing the detection size distribution of the DW10 channel and the DW20 channel used in the determination of (2) and (3) shown in Table 2 in the Example.

[0044] Figure 4 This is a graph showing the detection size distribution of the DW10 channel and the DNO channel used in the determination of (4) shown in Table 2 in the example.

[0045] Figure 5 This is a graph showing the detection size distribution of the DW10 channel and the DWN channel used in the determinations (5) and (6) shown in Table 2 in the example.

[0046] Figure 6 This is a graph showing the detection size distribution of the DW10 channel and the DW20 channel used in the determination (7) shown in Table 2 in the Examples. DETAILED DESCRIPTION

[0047] Next, the above-mentioned evaluation method will be described in more detail.

[0048] [Semiconductor wafer to be evaluated]

[0049] The semiconductor wafer to be evaluated in the above evaluation method is a semiconductor wafer having a cover layer on a semiconductor substrate. The above semiconductor substrate may be various semiconductor substrates such as a single crystal silicon substrate.

[0050] The cover layer on the semiconductor substrate may be any of various cover layers formed by a known film forming method, and specific examples of the cover layer include an oxide layer, a nitride layer, a polysilicon layer, an amorphous silicon layer, and a metal layer.

[0051] In one embodiment, the cover layer may be a deposition layer in which a film-forming material is deposited on a semiconductor substrate. As a film-forming method for forming the deposition layer, various film-forming methods can be cited that can deposit a film-forming material on a semiconductor substrate by a vapor phase growth method, such as a CVD (Chemical Vapor Deposition) method, an ALD (Atomic Layer Deposition) method, etc. The thickness of the cover layer may be, for example, in the range of 5 to 500 nm, but is not limited to this range.

[0052] There may be attachments and non-attached convex defects on the surface of the covering layer on the semiconductor substrate. These types of defects can be detected according to the evaluation method described in detail below. In addition, both attachments and non-attached convex defects exist on the surface of the covering layer in a convex shape, and usually have a wide range of size distribution and exist on the surface of the covering layer. Therefore, it is difficult to distinguish between the two in the evaluation based solely on the size of the bright spot detected by the laser surface inspection device. In contrast, according to the evaluation method described in detail below, attachments and non-attached convex defects can be distinguished.

[0053] [Laser surface inspection device]

[0054] The laser surface inspection device (hereinafter also simply referred to as “surface inspection device”) used in the above evaluation method comprises:

[0055] Two incident systems, the incident angles of light incident on the illuminated surface are different; and

[0056] The three light receiving systems (a first light receiving system, a second light receiving system, and a third light receiving system) are different from each other in at least one selected from the group consisting of a light receiving angle and a polarization selectivity.

[0057] In the above-mentioned surface inspection device, different light receiving systems receive radiated light emitted by reflection or scattering of light incident from different incident systems on the surface of the covering layer of the semiconductor wafer to be evaluated (i.e., the irradiated surface) at various locations on the irradiated surface. The direction of radiated light emission (in detail, the reflection angle of reflected light or the scattering angle of scattered light) and polarization characteristics may change in various ways depending on the presence of attached matter or non-attached convex defects in the covering layer formed on the semiconductor substrate. The inventors of the present invention speculate that by receiving these different various radiated lights by at least one of the above-mentioned three different light receiving systems selected from the group consisting of light receiving angle and polarization selectivity, the above-mentioned attached matter and non-attached convex defects can be detected as bright spots. Figure 1 An example of a surface inspection device having such an incident system and a light receiving system is shown (schematic structure diagram). Figure 1 In the figure, the incident light is schematically represented by a solid arrow, and the radiated light is schematically represented by a dotted arrow. However, the incident direction and the radiated direction shown in the figure are examples and do not limit the present invention in any way. In addition, the radiated light received by each light receiving system may include one or both of reflected light and scattered light.

[0058] Figure 1 The surface inspection device 10 shown in the figure has a low-angle side laser light source 100 as a first incident system. A second incident system that causes light to be incident on the irradiated surface at an incident angle higher than the incident angle of the light incident on the irradiated surface by the first incident system is composed of a high-angle side laser light source 101a and a reflector 101b. The light emitted from the high-angle side laser light source 101a is reflected by the reflector 101b, and its emission direction is changed and incident on the surface of the cover layer (not shown) of the wafer 1.

[0059] Figure 1 The surface inspection device 10 shown includes a high-angle side light receiver 201 , a low-angle side light receiver 202 , and a low-angle side light receiver 203 as three types of light receiving systems. Figure 1 The surface inspection device 10 shown has a structure with one high-angle side light receiver and two low-angle side light receivers. However, the surface inspection device used in the above evaluation method is not limited to the above structure, and may also be a structure with two high-angle side light receivers and one low-angle side light receiver. In addition, the light receiving angles of the two low-angle side light receivers may be the same or different. This aspect is also the same when there are two high-angle side light receivers. At least one of the three light receivers selected from the group consisting of light receiving angles and polarization selectivity is different. This aspect will be further described later. In addition, in Figure 1In the surface inspection device 10 shown in FIG. 1 , the low-angle side light receivers 202 and 203 have a structure for receiving the radiated light all around the stage 11. However, the light receiving system of the surface inspection device is not limited to any structure as long as it has a structure capable of receiving the radiated light. Figure 1 The structure shown.

[0060] Furthermore, the surface inspection device 10 is provided with a rotating motor 12 capable of rotating the stage 11 on which the wafer 1 is mounted, and a movable unit (not shown) capable of moving in the horizontal direction, so that the irradiation position of the light incident from the above-mentioned respective laser light sources can be changed. Thus, the area to be evaluated or the entire surface area of ​​the cover layer of the wafer 1 can be sequentially irradiated (i.e., scanned) with light, and the defect type can be detected in the area to be evaluated or the entire surface area.

[0061] In addition, the surface inspection device 10 includes: a control unit 13 that controls the rotation and horizontal movement of the stage 11; and a calculation unit 14 that calculates the detection size of the detected defect type based on the information of the radiated light received by each of the above-mentioned light receivers. In addition, the PC (Personal Computer) 15 receives the position information of the position where the light is irradiated from the control unit 13, and sends a signal to move the stage 11 in order to irradiate the light to the non-irradiated position. Furthermore, the PC 15 can receive information related to the detection size of the detected defect type from the calculation unit 14, and generate various measurement results described in detail later.

[0062] but, Figure 1 The structure of the surface inspection device schematically shown in the figure is an example. In the above evaluation method, as long as the surface inspection device has two incident systems with different incident angles of light incident on the irradiated surface, and at least one of three different light receiving systems (first light receiving system, second light receiving system and third light receiving system) selected from the group consisting of light receiving angle and polarization selectivity, it is not limited to Figure 1 As the surface defect device of the structure shown, various surface inspection devices can be used. As specific device names, for example, Surfscan series SP5 and the same series SP7 manufactured by KLA can be cited.

[0063] [Types of defects to be inspected]

[0064] The detection object of the surface inspection device in the above-mentioned evaluation method is a defect type selected from the group consisting of attached objects and non-attached convex defects existing on the surface of the covering layer formed on the semiconductor substrate in the semiconductor wafer. The light is respectively incident on the surface of the covering layer of the wafer of the evaluation object through the above-mentioned two incident systems, and the light is radiated (scattered or reflected) from the surface of the above-mentioned covering layer, and these defect types are detected as bright spots in the light receiving system. By detecting the bright spots, the size (detection size) of the defect type causing the bright spots can be calculated in the calculation unit of the surface inspection device according to the size of the detected bright spots and based on the size of the standard particles. The calculation of the detection size based on the size of the standard particles can be performed by a calculation unit possessed by a commercially available surface inspection device or a known calculation method.

[0065] The attached matter is a foreign matter that is attached to the surface of the cover layer from the external environment during and / or after the film formation process for forming the cover layer on the semiconductor substrate.

[0066] In contrast, the non-adhesive convex defect is different from the above-mentioned defect caused by adhesion and is a local protrusion on the surface of the coating layer. The above-mentioned non-adhesive convex defect is usually a defect that has a defect existing on the wafer surface before film formation as a core and expands due to film formation.

[0067] In the above evaluation method, on the surface of the cover layer of the wafer, a defect type selected from the group consisting of attached matter and non-attached convex defects existing on the surface of the cover layer of the wafer can be detected as a bright spot based on a plurality of measurement results including three low-incident angle measurement results obtained by receiving, by the three light receiving systems, respectively, radiated light emitted by light incident from a first incident system (i.e., a low-angle side incident system) reflected or scattered on the surface, and at least one high-incident angle measurement result obtained by receiving, by at least one of the three light receiving systems, radiated light emitted by light incident from a second incident system (i.e., a high-angle side incident system) reflected or scattered on the surface. The inventors of the present invention believe that since the properties of radiating the incident light from the two incident systems are different in attached matter and non-attached convex defects, by using a plurality of measurement results in the above manner, attached matter and non-attached convex defects can be distinguished and detected as bright spots.

[0068] [Specific implementation of the evaluation method]

[0069] Next, a specific aspect of the above-mentioned evaluation method will be described.

[0070] <Incident System>

[0071] The wavelength of the incident light incident on the surface of the cover layer of the wafer from the first incident system and the second incident system is not particularly limited. In one embodiment, the incident light may be ultraviolet light, but may also be visible light or other light. Here, ultraviolet light in the present invention and this specification refers to light in a wavelength region of less than 400 nm, and visible light refers to light in a wavelength region of 400 to 600 nm.

[0072] Regarding the above two incident systems, relative to the incident angle, high angle (side) / low angle (side) refers to the angle determined relatively by the relationship between one side and the other side, and the specific angle is not limited. In one embodiment, if all directions horizontal to the above-mentioned covering layer surface are set to 0°, and the direction perpendicular to the covering layer surface is set to 90°, and the incident angle is specified from a minimum of 0° to a maximum of 90°, then the incident angle of the incident light incident from the first incident system (i.e., the low-angle side incident system) to the covering layer surface of the wafer of the evaluation object can be 0° or more and 60° or less, preferably in the range of more than 0° and less than 30°. On the other hand, as the incident angle specified in the same way as above, the incident angle of the incident light incident from the second incident system (i.e., the high-angle side incident system) to the covering layer surface of the wafer of the evaluation object can be more than 60° and less than 90°, preferably more than 80° and less than 90°.

[0073] <Light receiving system>

[0074] The surface inspection device used in the above evaluation method has three light receiving systems, and at least one of the three light receiving systems selected from the group consisting of light receiving angle and polarization selectivity is different. In one embodiment, one light receiving system can be a high-angle side light receiving system that receives the radiated light from the surface of the cover layer of the wafer of the evaluation object on the high angle side, and the other two light receiving systems can be low-angle side light receiving systems that receive the above-mentioned radiated light on the low angle side. The light receiving angles of the two low-angle side light receiving systems can be the same or different. Here, with respect to the light receiving angle, high angle (side) / low angle (side) is an angle determined relatively by the relationship between one side and the other side, and the specific angle is not limited. In one embodiment, when the angle is specified based on the surface of the cover layer of the wafer of the evaluation object as the incident angle described above, the light receiving on the high angle side can refer to the light receiving at a light receiving angle exceeding 80° and below 90°, and the light receiving on the low angle side can refer to the light receiving at a light receiving angle of 0° or above and below 80°. In another embodiment, two light receiving systems may be high-angle side light receiving systems, and one light receiving system may be low-angle side light receiving system. In this case, the light receiving angles of the two high-angle side light receiving systems may be the same or different.

[0075] The above three light receiving systems are different from each other in at least one of the group consisting of the light receiving angle and the polarization selectivity. The light receiving angle is as described above. On the other hand, "different polarization selectivity" means that the light receiving system has at least one different property of selecting polarized light and receiving light (i.e., having polarization selectivity), receiving omnidirectional light (i.e., having no polarization selectivity), and selectively receiving polarized light with a specific (or a specific range of) azimuth angle in polarized light. Methods for imparting polarization selectivity to a light receiving system are well known. For example, by providing a polarization filter in the light receiving system, a light receiving system with polarization selectivity can be constructed, and the light receiving system can be endowed with the property of selectively receiving polarized light with a specific (or a specific range of) azimuth angle according to the type of polarization filter.

[0076] In one embodiment, the surface inspection device may be a light receiving system that receives omnidirectional light, and the other two light receiving systems that selectively receive polarized light. In addition, in a specific embodiment, one light receiving system may receive omnidirectional light, and the other two light receiving systems may selectively receive polarized light of different azimuth angles. Regarding the two light receiving systems that selectively receive polarized light, the azimuth angle of the polarized light received by one light receiving system may be set to θ1°, and the azimuth angle of the polarized light received by the other light receiving system may be set to θ2°, 0°≤θ1°≤90° and 90°≤θ2°≤180°. In addition, in a preferred specific embodiment, the light receiving angle of the light receiving system that receives omnidirectional angles may be an angle higher than that of the light receiving system that selectively receives polarized light. In addition, omnidirectional light is also called non-polarized light, which refers to unpolarized light. In contrast, polarized light refers to light with a specific directionality (azimuth angle).

[0077] A more preferred specific embodiment of the light receiving system is as follows.

[0078] The first light receiving system receives omnidirectional light.

[0079] The second light receiving system receives polarized light with an azimuth angle of θ1°.

[0080] The third light receiving system receives polarized light with an azimuth angle of θ2°.

[0081] The light receiving angle of the first light receiving system is higher than the light receiving angles of the second light receiving system and the third light receiving system. That is, the first light receiving system that receives all angles is a high-angle side light receiving system, and the second light receiving system and the third light receiving system that receive polarized light are low-angle side light receiving systems. In addition, the azimuth angle of the polarized light received by the two light receiving systems (the second light receiving system and the third light receiving system) that receive polarized light is θ1°<θ2°.

[0082] In a surface inspection device having a light receiving system of a more preferred specific mode described above, it can be considered that the second light receiving system that receives polarized light with a smaller azimuth angle can suppress the reflected light component from the surface of the cover layer of the wafer, and can easily detect scattered light from defect types that scatter isotropically. In contrast, the inventors believe that the third light receiving system that receives polarized light with a larger azimuth angle has a lower suppression effect on the reflected light component from the surface of the cover layer of the wafer than the second light receiving system, but can detect scattered light from defect types that scatter anisotropically with high sensitivity. In addition, the inventors speculate that by combining the first light receiving system that receives omnidirectional light at a higher angle side than these two light receiving systems with the second light receiving system and the third light receiving system, the detection sensitivity of various defect types can be further improved. As a result, the inventors believe that it is possible to detect both attached objects and non-attached convex defects with high sensitivity. However, the above includes the inventors' speculations and does not limit the present invention in any way.

[0083] In the above evaluation method, on the surface of the cover layer of the wafer to be evaluated, a defect type selected from the group consisting of attached matter and non-attached convex defects existing on the surface of the cover layer of the wafer is detected as a bright spot based on a plurality of measurement results including three low-incident-angle measurement results obtained by receiving, by the three light receiving systems, respectively, radiated light emitted by reflection or scattering of light incident from a first incident system (i.e., a low-angle side incident system), and at least one high-incident-angle measurement result obtained by receiving, by at least one of the three light receiving systems, radiated light emitted by reflection or scattering of light incident from a second incident system (i.e., a high-angle side incident system) on the surface of the cover layer. From the viewpoint of further improving the detection sensitivity of attached matter and / or non-attached convex defects, the above high-incident-angle measurement results preferably include measurement results obtained by receiving, by at least one of the two light receiving systems capable of selectively receiving polarized light, radiated light emitted by reflection or scattering of light incident from the second incident system on the surface of the cover layer of the wafer to be evaluated. In one embodiment, the high incident angle measurement result can be a measurement result obtained by receiving, by any one of the two light receiving systems capable of selectively receiving polarized light, radiated light emitted by reflection or scattering of light incident from the second incident system on the surface of the covering layer of the wafer to be evaluated.

[0084] However, as described above, since the causes of attachments and non-attached convex defects are different, the methods used to reduce them are also different. For example, attachments can be easily removed by general cleaning. Therefore, in order to reduce attachments, for example, it is sufficient to strengthen the cleaning conditions. Specifically, as a method for reducing attachments, increasing the number of cleaning times, extending the cleaning time, using a cleaning agent with higher cleaning power, etc. can be cited. Or as an example of a method for reducing attachments, it can be cited that the attachment of foreign matter to the surface of the covering layer during and / or after the film forming process is suppressed by re-examining the film forming process. On the other hand, non-attached convex defects cannot be removed by cleaning after the covering layer is formed. Therefore, as a method for reducing non-attached convex defects, it can be cited that the manufacturing process of semiconductor wafers and non-attached convex defects can be removed by cleaning, such as strengthening the cleaning conditions of the semiconductor substrate before the film forming process of the covering layer, and removing foreign matter on the surface of the semiconductor substrate that may become the core of the formation of non-attached convex defects. Therefore, in the evaluation of wafers with a covering layer, it is expected to be able to distinguish and detect attachments and non-attached convex defects. By distinguishing and detecting, the occurrence number and existence state (distribution) of each of the attached matter and the non-attached convex defect can be understood, and an appropriate reduction method can be selected according to the occurrence number and distribution.

[0085] In the above aspect, according to the surface inspection device having two incident systems with different incident angles and a light receiving system in one more preferred specific embodiment, based on the light receiving system selected from

[0086] The presence or absence of detection and the detection size in the measurement result 1 obtained by combining the first incident system and the first receiving system,

[0087] The presence or absence of detection and the detection size in the measurement result 2 obtained by combining the first incident system and the second light receiving system,

[0088] The presence or absence of detection and the detection size in the measurement result 3 obtained by combining the first incident system and the third light receiving system, and

[0089] The presence or absence of detection and the detection size in the measurement result 4 obtained by combining the second incident system with the second light receiving system or the third light receiving system

[0090] At least one discrimination criterion of the constituted group can discriminate whether the defect type detected as a bright spot in the surface inspection device is an attached object or a non-attached convex defect. The inventors believe that the reason for such discrimination is that the attached objects and non-attached convex defects existing on the surface of the cover layer of the wafer are different in shape and the like due to different causes of generation, thereby making the light scattering / reflection behavior different. Therefore, the presence or absence of detection in the light receiving system and the detection size are different according to the different incident angles of light incident on the surface of the cover layer of the wafer, the different light receiving angles of the light receiving system, and the different polarization selectivity.

[0091] According to a surface inspection device having two incident systems with different incident angles and a light receiving system of the above-mentioned more preferred specific mode, it is more preferred that, according to the criteria shown in the following Table 1, the type of defect detected can be more accurately determined as an attached object or a non-attached convex defect.

[0092] [Table 1]

[0093]

[0094] In Table 1, X, Y, and Z are each independently greater than 0. In one embodiment, X may be in the range of 1.30 to 1.50, Y may be in the range of 0.60 to 0.80, and Z may be in the range of 0.80 to 0.85.

[0095] The upper detection limit size in the above (1) is determined according to the surface inspection device used for evaluation. For example, regarding the detection size in the surface inspection device, the upper detection limit size of measurement result 1 can be greater than 300nm, the upper detection limit size of measurement result 2 can be greater than 100nm, and the upper detection limit size of measurement result 3 can be greater than 200nm.

[0096] A more specific method of the above evaluation method is described later based on an embodiment. Through the evaluation based on the above evaluation method, various evaluations can be performed on the types of defects (attached matter and / or non-attached convex defects) on the surface of the covering layer formed on the semiconductor substrate of the semiconductor wafer, the number of defect types, the location (distribution) of the defect types, etc.

[0097] Based on the evaluation results obtained by the evaluation method described above, in the manufacturing process of the semiconductor chip, by performing process changes and maintenance (such as changes in manufacturing conditions, replacement of manufacturing equipment, cleaning, improvement of the quality of the chemical solution, etc.) to suppress the types of defects (adherent matter and / or non-adherent convex defects) generated on the surface of the covering layer, it is possible to provide high-quality semiconductor chips with fewer types of the above defects as product chips.

[0098] In addition, by evaluating semiconductor wafers before shipment as products using the above evaluation method, semiconductor wafers that have been confirmed to have the number of surface defect types of the cover layer within a predetermined allowable range (below a threshold value) are shipped as product wafers, thereby enabling the stable provision of high-quality semiconductor wafers. In addition, the threshold value is not particularly limited and can be appropriately set according to the purpose of the product wafer, etc.

[0099] That is, the above-mentioned evaluation method can be used for process management and quality management of a semiconductor wafer having a cover layer on a semiconductor substrate.

[0100] [Example]

[0101] 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. 1. Detection of bright spot (LPD) and calculation of defect size

[0102] As the semiconductor wafers to be evaluated, three semiconductor wafers having a nitride layer (silicon nitride layer) formed by CVD on a single crystal silicon substrate were prepared. The thickness of the nitride layer of the three semiconductor wafers was 10 nm, 50 nm, and 100 nm, respectively.

[0103] Bright spots were detected on the surfaces of the nitride layers of the three semiconductor wafers using Surfscan series SP7 manufactured by KLA as a surface inspection apparatus.

[0104] In the Surfscan series SP7 manufactured by KLA,

[0105] As the incident system has:

[0106] an oblique laser light source (ultraviolet light source) that causes incident light to obliquely enter the surface of the cover layer of the wafer to be evaluated; and

[0107] A vertical laser light source (ultraviolet light source) is used to allow incident light to be vertically incident on the surface of the cover layer of the wafer to be evaluated via a reflecting mirror.

[0108] The surface inspection device has the following channels as a combination of the incident system and the light receiving system:

[0109] DW1O (Dark-Field Wide1 Oblique) channel;

[0110] DW2O (Dark-Field Wide2 Oblique) channel;

[0111] DNO (Dark-Field Narrow Oblique) channel;

[0112] DWN (Dark-Field Wide Normal) channel; and

[0113] DNN (Dark-Field Narrow Normal) channel.

[0114] In addition, in this evaluation, the DNN pipeline was not used.

[0115] The photoreceivers of the DW1O channel and the DW2O channel are photoreceivers located at a low angle relative to the photoreceiver of the DNO channel and have polarization selectivity. The azimuth angle of polarized light received by the DW1O channel is smaller than the azimuth angle of polarized light received by the DW2O channel. The azimuth angle of polarized light received by the DW1O channel is within the range of 0° to 90°, and the azimuth angle of polarized light received by the DW2O channel is within the range of 90° to 180°. The detection result of the DW1O channel is equivalent to "Measurement Result 2" in Table 1. The detection result of the DW2O channel is equivalent to "Measurement Result 3" in Table 1.

[0116] The light receiver of the DWN channel is the same as that of the DW10 channel. The detection result of the DWN channel is equivalent to "Measurement Result 4" in Table 1.

[0117] The DNO channel light receiver is a light receiver that receives omnidirectional light (i.e., does not have polarization selectivity) and is located at a higher angle than the light receivers of the DW1O and DW2O channels. The detection result of the DNO channel is equivalent to "Measurement Result 1" in Table 1.

[0118] Using the surface inspection device, incident light was scanned over the entire surface area of ​​the nitride layer of each of the three semiconductor wafers to detect the defect type as a bright spot (LPD), and based on the size of the bright spot, the size of the detected defect type (detection size) was calculated in the calculation unit of the surface inspection device. In addition, the lower limit of the size of the bright spot detected in each light receiving system of the surface inspection device (detection lower limit size) was 40 nm for the DNO channel, 20 nm for the DW1O channel, 30 nm for the DW2O channel, and 50 nm for the DWN channel.

[0119] In addition, in the above-mentioned surface inspection device, as the detection result of the DCO (Dark-Field Composite Oblique) channel, the result of adding the detection results of the DW1O channel, the DW2O channel and the DNO channel is obtained. In the DCO channel, when a bright spot is detected in more than two channels of the DW1O channel, the DW2O channel and the DNO channel at the same position, the larger size is used as the size of the bright spot. In addition, in the DCO channel, when the size is displayed as "200000μm", "200000μm" is only a value displayed for convenience, which means that in at least one of the DW1O channel, the DW2O channel and the DNO channel, the detection size exceeds the upper detection limit size. The upper detection limit size of the DW1O channel is 100nm, the upper detection limit size of the DW2O channel is 200nm, and the upper detection limit size of the DNO channel is 300nm.

[0120] 2. Observation of defect types using a scanning electron microscope

[0121] The surface of the nitride layer of the semiconductor wafer evaluated in 1. above was observed using a scanning electron microscope (SEM), and based on the observation results, the types of defects present at the bright spot positions detected by the surface inspection device were classified into deposits and non-deposited convex defects. Figure 2 An example of each defect type observed by SEM (SEM image) is shown. Figure 2 (a) is a SEM image of a defect type classified as a non-adhesive convex defect. Figure 2 (b) is a SEM image of a defect type classified as an attachment.

[0122] 3. Determination of defect types

[0123] Based on the detection results of 1. above, the detected bright spots are classified as attached objects or non-attached convex defects according to the algorithm of the following Table 2 according to the previously shown Table 1.

[0124] Figure 3 Graph showing the detection size distribution of the DW1O channel and the DW2O channel used for the determination of (2) and (3) above.

[0125] Figure 4 It is a graph showing the detection size distribution of the DW10 channel and the DNO channel used for the determination in (4) above.

[0126] Figure 5 It is a graph showing the detection size distribution of the DW10 channel and the DWN channel used for the above-mentioned determinations (5) and (6).

[0127] Figure 6 It is a graph showing the detection size distribution of the DW1O channel and the DW2O channel used for the above-mentioned determination (7).

[0128] The above-mentioned graphs also show the classification results of defect types based on the SEM observation in 2. above.

[0129] The defect classification results obtained in the above manner were compared with the SEM observation results in 2. above, and the number of defect types corresponding to the discrimination criteria was obtained, and the results were the values ​​shown in Table 2. Based on these results, the probability that the discrimination results based on the discrimination criteria shown in Table 2 and the classification results based on the SEM observation results are consistent, that is, the correspondence rate, was calculated, and the results were the values ​​shown in Table 2, confirming that the defect types can be discriminated and evaluated with high accuracy without relying on the thickness of the covering layer.

[0130] [Table 2]

[0131]

[0132]

[0133] One embodiment of the present invention is useful in the field of semiconductor wafer manufacturing.

Claims

1. A method for evaluating a semiconductor wafer using a laser surface inspection device, characterized in that: The semiconductor wafer has a cover layer on a semiconductor substrate, The laser surface inspection device comprises: First incident system; a second incident system for causing light to be incident on the illuminated surface at an incident angle higher than the incident angle of the light incident on the illuminated surface by the first incident system; The first light receiving system; The second light receiving system; as well as The third light receiving system, The three light receiving systems have at least one selected from the group consisting of a light receiving angle and polarization selectivity for receiving light emitted from the illuminated surface, which are different from each other. The semiconductor wafer evaluation method includes evaluating the semiconductor wafer on the surface of the cover layer in the following manner: detecting a defect type selected from the group consisting of attached matter and non-attached convex defects existing on the surface of the cover layer as a bright spot based on a plurality of measurement results including three low-incident-angle measurement results obtained by receiving, by the three light receiving systems, respectively, radiated light radiated by reflection or scattering of light incident from a first incident system on the surface, and at least one high-incident-angle measurement result obtained by receiving, by at least one of the three light receiving systems, radiated light radiated by reflection or scattering of light incident from a second incident system on the surface; and, including based on the choice of The presence or absence of detection and the detection size in the measurement result 1 obtained by combining the first incident system and the first receiving system, The presence or absence of detection and the detection size in the measurement result 2 obtained by combining the first incident system and the second light receiving system, The presence or absence of detection and the detection size in the measurement result 3 obtained by combining the first incident system and the third light receiving system, and The presence or absence of detection and the detection size in the measurement result 4 obtained by combining the second incident system with the second light receiving system or the third light receiving system A determination criterion for the group of components to determine whether the defect type detected as the bright spot is an attached object or a non-attached convex defect; The first light receiving system receives omnidirectional light. The second light receiving system selectively receives polarized light with an azimuth angle of θ1°. The third light receiving system selectively receives polarized light having an azimuth angle θ2° different from the azimuth angle θ1°. 0°≤θ1°≤90°and 90°≤θ2°≤180°, The light receiving angle of the first light receiving system is an angle higher than the light receiving angles of the second light receiving system and the light receiving angles of the third light receiving system; The above determination is performed according to the criteria shown in Table 1 below. [Table 1] X, Y, and Z are each independently greater than 0.

2. The semiconductor wafer evaluation method according to claim 1, wherein: X is in the range of 1.30 to 1.50, Y is in the range of 0.60 to 0.80, and Z is in the range of 0.80 to 0.

85.

3. The semiconductor wafer evaluation method according to claim 1 or 2, characterized in that: The capping layer is a deposition layer on which a film-forming material is deposited.

4. The semiconductor wafer evaluation method according to claim 1 or 2, characterized in that: The semiconductor substrate is a single crystal silicon substrate.

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