Evaluation procedures for semiconductor wafers and semiconductor wafers

Abstract

Method for evaluating a semiconductor wafer having a polished surface using a laser surface inspection device comprising incident and light reception systems, wherein the method comprises evaluating the semiconductor wafer by detecting, as a light spot defect, an irregularity selected from the group consisting of a manufacturing defect and a foreign body adhering to the surface, present on the polished surface of the semiconductor wafer, based on measurement result 1, obtained by directing incident light onto the polished surface of the semiconductor wafer from an incident system, and receiving, with a first light receiving system, radiant light which was emitted by the incident light that was reflected or scattered by the polished surface, Measurement result 2, obtained by receiving the radiant light with a second light receiving system, as well as Measurement result 3, obtained by receiving the radiant light with a third light receiving system, and at least one, selected from the group consisting of a light reception angle and a polarization selectivity, differs between the first light reception system, the second light reception system and the third light reception system; In one of the three light reception systems, one light reception system receives undirected light, while each of the other two light reception systems selectively receives polarized light with different azimuthal angles.

Description

Technical field

[0001] The present invention relates to an evaluation method for semiconductor wafers having a polished surface.

[0002] The present invention further relates to a semiconductor wafer which has a polished surface and has been evaluated by the above evaluation method. State of the art

[0003] A commonly used method for evaluating defects in semiconductor wafers or foreign bodies adhering to the surface of a semiconductor wafer is based on a light spot defect (LPD) detected by a laser surface inspection device (see, for example, Japanese patent JP 5 509 581 B2). In this method, light is directed onto the surface of a semiconductor wafer to be evaluated, and the radiant light emanating from this surface (scattered and reflected light) is detected to assess the presence or absence and / or size of a defect / foreign body in the semiconductor wafer.

[0004] Furthermore, US 8,169,613 B1 describes how a polarization device can be used with a sample inspection system that has one or more collection systems which receive scattered radiation from an area on a sample surface and direct it to a detector. The polarization device is configured to direct scattered radiation from defects to the detector and prevent noise from background sources that do not share properties with the scattered radiation from the defects from reaching the detector, while maximizing a detection rate for the defects on the detector with a less than optimal signal-to-noise ratio. Summary of the invention

[0005] Among semiconductor wafers, a polished wafer is a semiconductor wafer manufactured through various steps, including polishing, and its surface (the top surface) is polished. Here, "polished surface" refers to a surface that has been polished to a high gloss (also called mirror polishing). Foreign particles and defects (hereinafter referred to as "manufacturing defects") may be present on the surface (polished surface) of a polished wafer, created by high-gloss polishing and / or various steps performed before or after high-gloss polishing.If these surface-adherent foreign bodies and manufacturing defects can be detected, a polished wafer with few manufacturing defects / surface-adherent foreign bodies can be provided by controlling the manufacturing process, such as by removing the causes of the surface-adherent foreign body and the manufacturing defect, based on the result of the detection.

[0006] One aspect of the present invention provides a new evaluation method for evaluating a semiconductor wafer with a polished surface by detecting manufacturing defects / foreign bodies adhering to the surface.

[0007] A laser surface inspection device includes an (optical) incident light system and a light receiving system. In this context, patent literature 1 (Japanese patent no. JP 5 509 581 B2) describes an approach for detecting defects and foreign bodies introduced during the polishing step using a laser surface inspection device provided with two types of incident light systems. In contrast, the present inventor, as a result of repeated intensive studies, has developed the following evaluation method, which uses incident light from an incident light system: A method for evaluating a polished-surface semiconductor wafer using a laser surface inspection device, including incident and light-receiving systems, which includes the evaluation of the semiconductor wafer by detection, as a light spot defect, of an irregularity selected from the group consisting of a manufacturing defect and a foreign body adhering to the surface, present on the polished surface of the semiconductor wafer, based on measurement result 1, obtained by directing incident light onto the polished surface of the semiconductor wafer from an incident system and receiving, with a first light-receiving system, of radiant light emitted by the incident light that was reflected or scattered by the polished surface, measurement result 2, obtained by receiving the radiant light with a second light-receiving system, and measurement result 3.The light is obtained by receiving the radiant light with a third light-receiving system, wherein at least one of these systems, selected from the group consisting of a light-receiving angle and a polarization selectivity, differs from the first, second, and third light-receiving systems. Among the three light-receiving systems, one receives omnidirectional light, while each of the other two selectively receives polarized light with a different azimuthal angle.

[0008] This means that with the above evaluation method it is possible to detect the above irregularities based on three types of measurement results obtained by a laser surface inspection device, including an incident system and three types of light reception systems, among which at least one, selected from the group consisting of a light reception angle and a polarization selectivity, differs from each other.

[0009] In one embodiment, the light reception angle of the light receiving system that receives the omnidirectional light is a larger angle than the light reception angles of the other two light receiving systems.

[0010] In one embodiment, if the azimuthal angle of the polarized light received by one of the above two other light receiving systems is designated Θ1°, and the azimuthal angle of the polarized light received by another is designated Θ2°, 0° ≤ 0°, 0° ≤ 90° and 90° ≤ Θ2° ≤ 180° are satisfied.

[0011] In one embodiment, the first light receiving system receives omnidirectional light, The second light reception system receives polarized light with an azimuthal angle Θ1°, and the third light receiving system receives polarized light with an azimuthal angle of Θ2°, where The light reception angle of the first light receiving system is a larger angle than the light reception angle of the second and third light receiving systems, and Based on the determination criteria, selected from the group consisting of the presence or absence of detection and detection quantity in measurement result 1, the presence or absence of detection and detection quantity in measurement result 2, and the presence and absence of detection and detection quantity in measurement result 3, it is determined whether the detected irregularity is a manufacturing defect or a foreign body adhering to the surface.

[0012] In one embodiment, the above determination is carried out according to the determination criteria listed in Table 1 described later.

[0013] The above criteria are met if 1.0 < X ​​< 2.0. In one embodiment, 1.3 < X < 1.6 is met.

[0014] In one embodiment, the angle of incidence of the above incident light is greater than 0° and less than 90° if all directions horizontal to the polarized surface of a semiconductor wafer are defined as 0° and the direction perpendicular to the polished surface is defined as 90°.

[0015] One aspect of the present invention relates to a semiconductor wafer which has a polished surface and has been evaluated according to the above evaluation method.

[0016] According to one aspect of the present invention, various types of irregularities can be detected in a semiconductor wafer with a polished surface. Brief description of the drawings Fig. Figure 1 illustrates an example (diagram of a schematic setup) of a laser surface testing device. Fig.Figure 2 illustrates different types of irregularities (SEM images) observed with a scanning electron microscope on the polished surface of a polished wafer, which was evaluated in the examples. Fig. Figure 3 is a graph illustrating the results of the evaluation of a polished wafer using a laser surface inspection device in the examples. Fig. Figure 4 is a graph illustrating the results of the evaluation of a polished wafer using a laser surface inspection device in the examples. Procedures for carrying out the invention; method for evaluating a semiconductor wafer

[0017] One aspect of the present invention relates to a method (hereinafter also referred to as the "evaluation method") for evaluating a semiconductor wafer with a polished surface using a laser surface inspection device, including incident and light-receiving systems. The above evaluation method includes evaluating the semiconductor wafer by detecting, as a light spot defect, an irregularity selected from the group consisting of a manufacturing defect and a foreign body adhering to the surface, in this case on the polished surface of the semiconductor wafer, based on measurement result 1, obtained by directing incident light onto the polished surface of the semiconductor wafer from an incident system, and receiving, with a first light-receiving system, radiant light emitted by the incident light, which has been reflected or scattered by the polished surface, measurement result 2.The first light receiving system is obtained by receiving the radiant light with a second light receiving system, and the third measurement result is obtained by receiving the radiant light with a third light receiving system, and at least one of these, selected from the group consisting of a light reception angle and a polarization selectivity, differs between the first light receiving system, the second light receiving system, and the third light receiving system. Among the three light receiving systems, one light receiving system receives omnidirectional light, while each of the other two light receiving systems selectively receives polarized light with different azimuthal angles.

[0018] The evaluation procedure described above is explained in more detail below. A semiconductor wafer with a polished surface will also be referred to as a polished wafer in the following text. Laser surface testing device

[0019] A laser surface inspection device (hereinafter simply referred to as the "surface inspection device") used in the above evaluation procedure includes: an attack system; and three light reception systems (first light reception system, second light reception system and third light reception system), among which at least one, selected from the group consisting of a light reception angle and a polarization selectivity, differs from each other.

[0020] In such a surface inspection device, the radiant light emitted by the light incident on the polished surface of the semiconductor wafer being evaluated, which is reflected or scattered at various points on the polished surface, is received by the three light receiving systems mentioned above. The direction in which the radiant light is emitted (specifically the reflection angle of reflected light or the scattering angle of scattered light) and the polarization properties can vary in various ways if a manufacturing defect and / or a foreign body is present on the surface.The presenting inventor assumes that by receiving different types of radiation, exhibiting different radiation directions and polarization properties, through the three light reception systems, at least one of which is selected from the group consisting of a light reception system and a polarization selectivity, a manufacturing defect and / or a foreign body adhering to the surface can be detected as a light spot defect. An example (diagram of a schematic setup) of a laser surface inspection device 10, which includes such an incident light system and a light reception system, is shown in . Fig. 1 shown. Fig.1 The direction of incidence and direction of radiation shown in the figure are exemplary, although incident light is schematically represented by a solid arrow and radiated light is schematically represented by a dotted arrow, and are not intended to limit the present invention in any way.

[0021] A surface testing device 10, shown in Fig. 1, includes: as an incident system and light receiving systems, a laser light source 100; and Light receivers 101, 102 on the small angle side and light receiver 201 on the large angle side, which receive the radiant light emitted by the light incident from the laser light source 100, which is scattered or reflected by the surface (polished surface) of a polished wafer 1.

[0022] Although the surface testing device 10, shown in Fig.1. While the surface inspection device 10 includes one light receiver 201 on the large-angle side and two light receivers 101, 102 on the small-angle side, it is not limited to such a configuration and can include two light receivers 201 on the large-angle side and one light receiver 101, 102 on the small-angle side. The light reception angles of the two light receivers 101, 102 on the small-angle side can be the same or different. This can also be the case where there are two light receivers 201 on the large-angle side. Among these three light receivers 101, 102, 101, at least one, selected from the group consisting of a light reception angle and a polarization selectivity, differs from the others. This point will be described in more detail later. In the case of the Fig.In the surface inspection device 10 shown, the light receivers 101 and 102 on the wide-angle side receive the radiated light in the entire area above a stage 11, however, their construction is not based on those in Fig. 1 shown, limited, provided it is capable of receiving radiant light.

[0023] The surface inspection device 10 further includes a rotary motor 12 to make the stage 11, on which the polished wafer 1 is to be placed, rotatable, and movable means (not shown) to make the stage 11 movable in the horizontal direction so that the irradiation position of the light incident from the respective laser light source 100 can be changed. Thus, it is possible to irradiate (scan) a specific area to be evaluated or the entire surface of the polished wafer 1 with light in succession and to detect an irregularity in the area to be evaluated or on the entire surface.

[0024] The surface inspection device 10 further includes a controller 13, configured to control the rotation and horizontal movement of the object stage 11, and a computer 14, configured to calculate the detection magnitude of a detected irregularity based on information about the radiation detected by the respective light receivers 101, 102, 201. Furthermore, a PC (personal computer) 15 receives position information about the illuminated area from the controller 13 and transmits a signal to move the object stage 11 to illuminate an unilluminated area.

[0025] Furthermore, the PC 15 is able to receive information from the computer 14 about the detection size of a detected irregularity and to generate measurement result 1, measurement result 2 and measurement result 3.

[0026] However, the design of the surface testing device 10, which is shown in Fig. 1 outlines, by way of example. In the above evaluation procedure, the surface testing device is not limited to one with the in Fig. The setup shown in Figure 1, and various types of surface inspection devices can be used, provided that each is a surface inspection device that includes an incidence system and three light reception systems (first light reception system, second light reception system, and third light reception system), at least one of which differs from the others, selected from the group consisting of a light reception angle and a polarization selectivity. For example, the Surfscan Series SP5, manufactured by KLA TENSOR Corporation, can be used as a surface inspection device that includes an incidence system and the three light reception systems mentioned above. Irregularity to be detected

[0027] The object to be detected in the above evaluation procedure is an irregularity selected from the group consisting of a manufacturing defect and a foreign body adhering to the surface, in this case on the polished surface of a semiconductor wafer. These irregularities are detected as light spot defects in a light receiving system by directing light from an incident system onto the polished surface of the wafer being evaluated, as well as by the light emitted (scattered or reflected) from the polished surface. By detecting the light spot defect, the computer of the surface inspection device can calculate the size (detection size) of an irregularity that causes the light spot defect, based on the size of the detected light spot defect and the size of a standard particle.The calculation of the detection size based on the size of a standard particle can be performed using calculation aids with a commercially available surface inspection device or by a known calculation method.

[0028] A surface-adherent foreign body is a foreign body that has attached itself to polished wafers during the manufacturing process and / or the like, and is usually referred to as a particle.

[0029] In contrast, a manufacturing defect is introduced into a polished wafer due to chemical or mechanical processing during the polished wafer manufacturing process. Examples of manufacturing defects include: PID (polishing-induced defect), a linear, convex defect introduced by polishing, such as high-gloss polishing or coarse polishing (e.g., lapping), which is usually done before high-gloss polishing; Short PID, a relatively short, island-shaped PID among PIDs; and flat spot, a relatively smooth, concave-shaped defect. Special implementation of the evaluation procedure

[0030] Next, a specific embodiment of the above evaluation procedure will be described. Ingress system

[0031] The wavelength of the incident light, which falls from an incident system onto the polished surface of a polished semiconductor wafer to be evaluated, is not specifically limited. In one embodiment, the incident light is ultraviolet light, but it can be visible light or another type of light. Here, in the present invention, ultraviolet light denotes light with a wavelength range of less than 400 nm, while visible light denotes light with a wavelength range of 400 to 600 nm.

[0032] The angle of incidence of the incident light, which falls from an incidence system onto the polished surface of a polished wafer to be evaluated, can be equal to or greater than 0° and equal to or less than 90°, and is preferably greater than 0° and less than 90° if all directions horizontal to the polished surface are defined as 0°, the direction perpendicular to the polished surface is defined as 90°, and the angle of incidence is defined as a range from a minimum of 0° to a maximum of 90°. Light reception system

[0033] As described above, the surface inspection device used in the evaluation method of the present invention includes three light reception systems, at least one of which is selected from the group consisting of a light reception angle and a polarization selectivity. In one embodiment, one light reception system is a wide-angle light reception system which receives the radiant light from the polished surface of a polished wafer to be evaluated on the wide-angle side, while the other two light reception systems are small-angle light reception systems which receive the aforementioned radiant light on the small-angle side. The light reception angles of the two small-angle light reception systems can be the same or different.Here, the large-angle side / small-angle side, relative to the light reception angle, is determined based on a relationship between one angular side and another, and no specific angle is restricted. In one embodiment, if the angle, as with the previously described angle of incidence, is defined based on the polished surface of a polished wafer to be evaluated, the light reception on the large-angle side can refer to light reception with an angle of incidence in the range of greater than 80° to equal to or less than 90°, and the light reception on the small-angle side can refer to light reception with an angle of incidence in the range of 0° to 80°. Furthermore, in another embodiment, two light reception systems can be large-angle light reception systems, and one light reception system can be a small-angle light reception system.In this case, the light reception angles of two wide-angle light reception systems can be the same or different.

[0034] At least one of the three light-receiving systems selected from the group consisting of a light-receiving angle and a polarization selectivity differs from the others. The light-receiving angle is as described above. On the other hand, "polarization selectivity differs" means that at least one of the following properties differs among the light-receiving systems: a property of selecting and receiving polarized light (i.e., exhibiting polarization selectivity), a property of receiving non-polarized light (i.e., not exhibiting polarization selectivity), and a property of selectively receiving polarized light, exhibiting a specific azimuthal angle (or range) under polarized light. Means of imparting polarization selectivity to a light-receiving system are well known.For example, a light receiving system with polarization selectivity can be formed by incorporating a polarization filter into the light receiving system, and a property of selectively receiving polarized light which has a special azimuthal angle (or an azimuthal angle in a special range) can be imparted to the light receiving system according to the type of polarization filter.

[0035] In the surface inspection device described above, one light receiving system receives omnidirectional light, while the other two light receiving systems receive selectively polarized light. Furthermore, one light receiving system receives omnidirectional light, while the other two light receiving systems each receive selectively polarized light with different azimuthal angles. For two light receiving systems that receive selectively polarized light, if the azimuthal angle of the polarized light received by one of the light receiving systems is denoted as Θ1° and the azimuthal angle of the polarized light received by the other is denoted as Θ2°, then 0° ≤ Θ1° ≤ 90° and 90° ≤ Θ2° ≤ 180° can be satisfied.Furthermore, in a preferred specific embodiment, the light reception angle of the light receiving system that receives the undirectional light can be a larger angle than the light reception angle of the light receiving system that receives polarized light. Undirectional light is also referred to as unpolarized light and is light that is not polarized. In contrast, polarized light is light that has a specific directional property (azimuth angle).

[0036] A more preferred, special embodiment of the light receiving system is the following: the first light reception system receives undirected light, The second light receiving system receives the polarized light, exhibiting an azimuthal angle Θ1°, The third light receiving system receives the polarized light, exhibiting an azimuthal angle Θ2°, and The light reception angle of the first light receiving system is a larger angle than the light reception angles of the second and third light receiving systems.

[0037] This means that the first light-receiving system, which receives the omnidirectional light, is a wide-angle light-receiving system, while the second and third light-receiving systems, which receive polarized light, are narrow-angle light-receiving systems. Furthermore, the azimuthal angles Θ1° and Θ2° of the polarized light received by two polarized light-receiving systems (the second and third light-receiving systems) satisfy Θ1° < Θ2°.

[0038] The object to be detected in the above evaluation procedure is an irregularity selected from the group consisting of a manufacturing defect and a surface-adherent foreign body, in this case on a polished surface. Among these irregularities, the surface-adherent foreign body (usually referred to as a "particle") tends to scatter the incident light isotropically compared to the manufacturing defect. In other words, a manufacturing defect tends to scatter the incident light anisotropically compared to the surface-adherent foreign body.The presenting inventor believes that, taking such inclination into account, in a surface inspection device with the light reception system according to the preferred special embodiment described above, the second light reception system, which receives polarized light and has a smaller azimuthal angle, can suppress the reflected light component from a polished wafer surface (polished surface) and can easily detect the scattered light from the foreign body adhering to the surface, which scatters light isotropically.In contrast, the presenting inventor believes that the third light receiving system, which receives polarized light with a larger azimuthal angle, is less effective than the second light receiving system at suppressing the portion of light reflected from a polished wafer surface, but can detect with high sensitivity the scattered light from a manufacturing defect that scatters light anisotropically. Furthermore, the presenting inventor suggests that by combining the aforementioned second light receiving system and the third light receiving system with the first light receiving system, which receives the non-directional light at a larger angle than these two systems, the detection sensitivity for various types of irregularities can be further increased.Thus, the presenting inventor believes that both the manufacturing defect and the foreign body adhering to the surface can be detected with high sensitivity. However, the above discussion includes the present inventor's assumption and is not intended to limit the present invention in any way.

[0039] As previously described, since the causes of the manufacturing defect and the surface-adherent foreign matter differ, the means of reducing this manufacturing defect and the surface-adherent foreign matter can also differ. For example, the surface-adherent foreign matter can usually be removed by washing. Accordingly, the washing process can be improved to reduce surface-adherent foreign matter. On the other hand, since the manufacturing defect is introduced by polishing or the like, as described above, modifying the various conditions of the manufacturing process is desirable in order to reduce manufacturing defects.Accordingly, when evaluating a polished wafer, a desirable distinction can be made between foreign matter adhering to the surface and manufacturing defects, and these can be detected. This is because, by distinguishing and detecting, the number of occurrences and / or the presence state (distribution) of each of the foreign matter adhering to the surface and manufacturing defects can be recorded, and thus suitable means of reduction can be selected according to the number of occurrences and / or the distribution. In this context, where the surface inspection device is provided with the light reception system according to the preferred embodiment above, it can be determined whether a detected irregularity is a manufacturing defect or a foreign matter adhering to the surface, based on the determination criteria selected from the group consisting of: the presence or absence of detection and detection quantity in measurement result 1, obtained by light reception with the first light reception system, which receives the undirected light on the wide-angle side; the presence or absence of detection and detection quantity in measurement result 2, obtained by light reception with the second light reception system, which receives the polarized light with the azimuthal angle Θ1° on the small-angle side; and the presence or absence of detection and detection quantity in measurement result 3, obtained by the light reception with the third light reception system, which receives the polarized light with the azimuthal angle Θ2◦ on the small-angle side (here: Θ1° < Θ2°).

[0040] The presenting inventor believes that the reason such a determination is possible is that the manufacturing defect and the foreign body adhering to the surface each exhibit different behavior in scattering and reflecting light due to a difference in shape and the like, caused by a difference in the causes, and therefore the presence or absence of detection and / or detection magnitude differs among the light receiving systems, each of which has a different light reception angle and / or polarization selectivity.

[0041] Since the surface inspection device is provided with the light reception system according to the preferred embodiment described above, it can be determined more preferably, based on the criteria shown in Table 1 below, whether a detected irregularity is a foreign body adhering to the surface or a manufacturing defect. In Table 1 below, X 1.0 < X ​​< 2.0.The presenting inventor believes that the reason why manufacturing defects and surface-adherent foreign bodies can be distinguished by an X that satisfies 1.0 < X ​​< 2.0 of a relational formula below, and the criteria below based on the presence or absence of detection in a specific light-receiving system, lies in a difference in the light reception angle and / or the polarization selectivity of the respective light-receiving system, and furthermore in a difference in the scattering and reflection of light between a manufacturing defect and a surface-adherent foreign body. This point is a novel insight obtained through intensive study by the presenting inventor and is not conventionally known in any way. Table 1 Type of irregularity Determination criteria foreign body adhering to the surface detected only in measurement result 2 and not detected in measurement result 1 and measurement result 3, satisfies (detection quantity in measurement result 3) / (detection quantity in measurement result 2) < X or satisfies (detection quantity in measurement result 1) / (detection quantity in measurement result 2) < X manufacturing defect detected in at least one of measurement result 1 and measurement result 3, and not detected in measurement result 2, satisfies (detection quantity in measurement result 3) / (detection quantity in measurement result 2) ≥ X or satisfies (detection quantity in measurement result 1) / (detection quantity in measurement result 2) ≥ X

[0042] X satisfies 1.0 < X ​​< 2.0 and preferably 1.3 <X < 1,6. Als Beispiel wird beispielsweise X = 1,4 angeführt.

[0043] A more specific embodiment of the above evaluation method will be described later using examples. The above evaluation method allows for various types of assessments regarding irregularities, such as the presence or absence of an irregularity on the surface of a polished wafer and the number and / or position (distribution) of irregularities.

[0044] The evaluation can be carried out using the evaluation procedure described above, and subsequently, based on the evaluation results obtained, process changes and / or maintenance work (for example, a change in the manufacturing conditions, replacement of manufacturing equipment, washing, improvement of the quality of chemical liquids, and the like) can be carried out in the manufacturing process of polished wafers in order to reduce the various types of irregularities, so that a high-quality polished wafer with fewer irregularities can subsequently be provided in the form of a product wafer.

[0045] Furthermore, before being shipped as a product, a polished wafer can be evaluated using the above assessment procedure. A polished wafer for which it has been confirmed that the number of different types of irregularities present falls within a defined permissible range (equal to or less than a threshold) can be shipped as a product wafer, thus ensuring the stable delivery of a high-quality polished wafer. The threshold is not specifically limited and can be appropriately determined according to the application and other requirements of the product wafer.

[0046] This means that the above evaluation method can be used for process control and / or quality control of polished wafers. Polished wafers

[0047] Another aspect of the present invention relates to a semiconductor wafer (polished wafer) which has a polished surface and has been evaluated using the above evaluation method. Such a polished wafer can be one for which it has been confirmed that the number of different types of irregularities present, by evaluation based on the above evaluation results, is within a defined permissible range (equal to or less than a threshold). Examples

[0048] The present invention will be further explained below using examples. However, the present invention is not limited to the embodiments shown in the examples. 1. Detection of light spot defects (LPD) and calculation of the size of irregularities

[0049] A wafer for evaluation was fabricated and a light spot defect was detected using a Surfscan Series SP5, manufactured by KLA TENCOR Corporation, as a surface inspection device. The Surfscan Series SP5, manufactured by KLA TENCOR Corporation, includes, as an incident light system, a UV light source to cause the incident light to strike the surface of the wafer at an oblique angle, and includes three light receiving systems: DNO (Dark-Field Narrow Oblique), DW1O (Dark-Field Wide 1 Oblique), and DW2O (Dark-Field Wide 2 Oblique). DNO is a light receiving system that receives non-directional light (i.e., without polarization selectivity) and is a light receiving system on the wide-angle side, relative to the DW1O channel and the DW2O channel.On the other hand, the DW1O and DW2O channels are small-angle receiving systems relative to the DNO channel and possess polarization selectivity. The azimuthal angle of the polarized light received by the DW1O channel is smaller than the azimuthal angle of the polarized light received by the DW2O channel. Specifically, the azimuthal angle of the polarized light received by the DW1O channel is equal to or greater than 0° and equal to or less than 90°, while the azimuthal angle of the polarized light received by the DW2O channel is equal to or greater than 90° and equal to or less than 180°.

[0050] Using the Surfscan SP5 series surface inspection device manufactured by KLA TENSOR Corporation, the entire polished surface of a polished wafer under evaluation was scanned with incident light to detect any irregularity as a light spot defect (LPD). Subsequently, the detected size of the irregularity (detection size) was calculated by a computer within the surface inspection device based on the size of the light spot defect. The lower limit (lower limit of detection) of the size of a light spot defect detected in the respective light receiving system of the surface inspection device is 36 nm in the DNO channel, 19 nm in the DW1O channel, and 31 nm in the DW2O channel. 2. Observation of irregularities using a scanning electron microscope

[0051] The polished surface of the wafer evaluated under point 1 above was observed with a scanning electron microscope (SEM). Any irregularity present at the location of the light spot defect detected by the surface inspection device above was classified as a foreign body (particle) adhering to the surface and as various types of manufacturing defects (PID, short PID, and flat spot) based on the observed shape. An example (SEM image) of each irregularity observed with the SEM is shown in Fig. 2 shown. Fig. 2(a), Fig. 2(b), Fig. 2(c) and Fig. 2(d) are SEM images of irregularities that were classified as particles, PID, short PID and flat spots respectively. 3. Investigation of the calculated size and type of irregularity (1) Comparison between the result obtained in the DW1O channel and the result obtained in the DW2O channel

[0052] Fig. Figure 3 illustrates a graph showing the size of each irregularity, classified based on the SEM observation in point 2 above. This size is calculated from the size detected as a light spot defect in the DW1O channel, and it is calculated from the size detected as a light spot defect in the DW2O channel, both shown in point 1 above. In this graph, irregularities plotted on the x-axis are those detected only in the DW1O channel and not in the DW2O channel, while LPDs plotted on the y-axis are those detected only in the DW2O channel and not in the DW1O channel.

[0053] The following trends can be derived from the in Fig. This can be confirmed by the 3 graphs shown. (i) Particle becomes: detected only in the DW1O channel (not detected in the DW2O channel), or The size ratio DW2O / DW1O is approximately 1 (present mainly on the line of y = x or in its vicinity); (ii) PID, short PID and flat spot become: detected only in the DW2O channel (not detected in the DW1O channel), or The size ratio DW2O / DW1O is approximately 2 (present mainly on the line of y = 2x or in its vicinity). (2) Comparison between the result obtained in the DW1O channel and the result obtained in the DW2O channel

[0054] Fig.Figure 4 shows a graph in which, for each irregularity classified based on the SEM observation in point 2 above, the size of the irregularity is shown, calculated from the size detected as a light spot defect in the DW1O channel, as well as the size of the irregularity calculated from the size detected as a light spot defect in the DNO channel, both in point 1 above. In this graph, irregularities plotted on the x-axis are those detected only in the DW1O channel and not in the DNO channel, while irregularities plotted on the y-axis are LPDs detected only in the DNO channel and not in the DW1O channel.

[0055] The following trends can be confirmed from the in Fig. 4 graphs shown. (i) Particle becomes: detected only in the DW1O channel (not detected in the DNO channel), or The size ratio DNO / DW1O is approximately 1 (present mainly on the line of y = x or in its vicinity); (ii) PID, short PID and flat spot become: detected only in the DNO channel (not detected in the DW1O channel), or The size ratio DNO / DW1O is approximately 2 (present mainly on the line of y = 2x or in its vicinity).

[0056] As in Fig. 3 and Fig. As shown in Figure 4, there is a size difference between the different types of irregularities, calculated from the size of the detected light spot defect in the three light reception systems above and / or in the presence or absence of detection.

[0057] Subsequently, based on the results above, the conditions for distinguishing the irregularities shown in Table 2 were established. Since the particle size ratio DW₂O / DW₁O and the particle size ratio DNO / DW₁O are approximately 1, and the manufacturing defects, such as PID, have a size ratio of approximately 2, it was assumed that the threshold values ​​for the particle size ratios DW₂O / DW₁O and DNO / DW₁O should ideally be set greater than 1.0 and less than 2.0 to differentiate between particles and the manufacturing defect. Therefore, they were provisionally set to 1.4. The differentiation was performed using the criteria for determining irregularities listed in Table 2, and the validity of these criteria was confirmed by the results of the SEM observation described in section 2 above.As a result, there were extremely few irregularities that did not match the irregularity criteria listed in Table 2, and the agreement rate, calculated as “Agreement rate (%) = [Number of matching irregularities / (Number of matching irregularities + Number of non-matching irregularities)] × 100”, was greater than 90%, as shown in Table 2. Table 2 Criteria for identifying irregularities Determination Number of irregularities, consistent with the determining criteria Number of irregularities not in accordance with the determination criteria Correlation Detected only in the DW1O channel (not detected in the DW2O and DNO channels), size ratio DW2O / DW1O < 1.4, size ratio DNO / DW1O < 1.4 Particles 199 2 99 % Detected in the DW2O channel and / or DNO channel (not detected in the DW1O channel) Size ratio DW2O / DW1O ≥ 1.4 Size ratio DNO / DW1O ≥ 1.4 PID Short PID Flat Spot 53 2 96 %

[0058] One aspect of the present invention is applicable in the field of manufacturing polished wafers.

Claims

[1] Method for evaluating a semiconductor wafer having a polished surface using a laser surface inspection device comprising incident and light reception systems, wherein the method comprises evaluating the semiconductor wafer by detecting, as a light spot defect, an irregularity selected from the group consisting of a manufacturing defect and a foreign body adhering to the surface, present on the polished surface of the semiconductor wafer, based on measurement result 1, obtained by directing incident light onto the polished surface of the semiconductor wafer from an incident system, and receiving, with a first light receiving system, radiant light which was emitted by the incident light that was reflected or scattered by the polished surface, Measurement result 2, obtained by receiving the radiant light with a second light receiving system, as well as Measurement result 3, obtained by receiving the radiant light with a third light receiving system, and at least one, selected from the group consisting of a light reception angle and a polarization selectivity, differs between the first light reception system, the second light reception system and the third light reception system; In one of the three light reception systems, one light reception system receives undirected light, while each of the other two light reception systems selectively receives polarized light with different azimuthal angles. [2] Method for evaluation according to claim 1, wherein the light reception angle of the light receiving system which receives the omnidirectional light is a larger angle than the light reception angles of the two other light receiving systems. [3] Method for evaluation according to claim 1 or 2, wherein, if the azimuthal angle of the polarized light received by one of the other two light receiving systems is designated as T1° and the azimuthal angle of the polarized light received by another is designated as T2°, 0° ≤ Θ1° ≤ 90° and 90° ≤ Θ2° ≤ 180° are satisfied. [4] Method for evaluation according to claim 3, wherein the first light receiving system receives omnidirectional light, the second light receiving system receives polarized light, having an azimuthal angle of T1°, the third light reception system receives polarized light, exhibiting an azimuthal angle of T2°, The light reception angle of the first light receiving system is a larger angle than the light reception angles of the second and third light receiving systems, and the procedure which includes determining whether the detected irregularity is a manufacturing defect or a foreign body adhering to the surface, based on determination criteria which are selected from the group consisting of the presence or absence of detection and detection quantity in measurement result 1, the presence or absence of detection and detection quantity in measurement result 2 and the presence or absence of detection and detection quantity in measurement result 3. [5] Method for evaluation according to claim 4, comprising carrying out the determination according to the following criteria: Table 1 Type of irregularity Determination criteria foreign body adhering to the surface detected only in measurement result 2 and not detected in measurement result 1 and measurement result 3, satisfies (detection quantity in measurement result 3) / (detection quantity in measurement result 2) < X or satisfies (detection quantity in measurement result 1) / (detection quantity in measurement result 2) < X manufacturing defect detected in at least one of measurement result 1 and measurement result 3, and not detected in measurement result 2, satisfies (detection quantity in measurement result 3) / (detection quantity in measurement result 2) ≥ X or satisfies (detection quantity in measurement result 1) / (detection quantity in measurement result 2) ≥ X where 1.0 < X ​​< 2.0 is satisfied. [6] Method for evaluation according to claim 5, wherein X 1.3 < X < 1.6 is satisfied. [7] Method for evaluation according to any one of claims 1 to 6, where the angle of incidence of the incident light is greater than 0° and less than 90°, if all directions horizontal to the polished surface of the semiconductor wafer are defined as 0° and one direction perpendicular to the polished surface is defined as 90°. [8] Semiconductor wafer having a polished surface and having been evaluated by the evaluation method according to any one of claims 1 to 7.

Images