Wafer inspection method and wafer inspection system

Abstract

A wafer inspection method and a wafer inspection system, said method comprising: acquiring a first light spot position and a second light spot position that are detected by a detector; on the basis of the first light spot position and the second light spot position, adjusting a first inclination of an auxiliary mirror, such that the first light spot position and the second light spot position coincide; adjusting a first axial distance of the auxiliary mirror by means of Michelson interference fringes detected by the detector; introducing a reference objective lens, a measurement objective lens and a third lens into an optical path, and adjusting a second inclination and a first eccentric distance of the reference objective lens by means of detected Linnik interference fringes; and replacing the auxiliary mirror with a reference mirror, the reference mirror and the reference objective lens being fixed on the same mechanical component. By introducing an additional independent auxiliary mirror, which has a higher degree of freedom in adjustment and is not subjected to interference from the reference objective lens, the decoupling of the alignment dimensions between the reference objective lens and the reference mirror can be realized, thereby improving alignment efficiency and accuracy.

Description

Wafer Inspection Methods and Systems

[0001] This application claims priority to Chinese Patent Application No. 2024119335621, filed on December 26, 2024, entitled "A Wafer Inspection Method and Wafer Inspection System", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of wafer inspection technology, such as wafer inspection methods and wafer inspection systems. Background Technology

[0003] In semiconductor manufacturing, wafer inspection systems are frequently used to inspect wafers. These systems consist of a reference optical path (comprised of a reference objective and a reference mirror) and a measurement optical path (comprised of a measurement objective and the wafer under test). The wafer is placed below the measurement objective, and inspection is performed by observing interference fringes generated by the focusing system. In related technologies, the reference mirror is mounted on a mechanical component of the reference objective in the reference optical path. During adjustment, the adjustment dimensions of the reference objective and the reference mirror are coupled, requiring repeated adjustments to both to produce interference fringes. For example, the reference objective might be adjusted first, then the reference mirror, and then back again until interference fringes appear. This process is complex, inefficient, and has low accuracy. Summary of the Invention

[0004] This application provides a wafer inspection method and a wafer inspection system that can decouple the assembly and adjustment dimensions of the reference objective and the reference mirror, thereby improving assembly and adjustment efficiency and accuracy.

[0005] In a first aspect, embodiments of this application provide a wafer inspection method, including:

[0006] When the light source (101), the first lens (102), the beam splitter (103), the wafer under test (105), the second lens (108), and the detector (111) are arranged in the optical path, the position of the first light spot detected by the detector (111) is obtained; and when the light source (101), the first lens (102), the beam splitter (103), the auxiliary reflector (1071), the second lens (108), and the detector (111) are arranged in the optical path, the position of the second light spot detected by the detector (111) is obtained.

[0007] Based on the positions of the first and second light spots, the first tilt angle of the auxiliary reflector (1071) is adjusted so that the positions of the first and second light spots coincide.

[0008] When the light source (101), the first lens (102), the beam splitter (103), the auxiliary mirror (1071), the wafer under test (105), the second lens (108), and the detector (111) are located in the optical path, the first axial distance of the auxiliary mirror (1071) is adjusted by the Michelson interference fringes detected by the detector (111).

[0009] When the light source (101), the first lens (102), the beam splitter (103), the auxiliary mirror (1071), the wafer under test (105), the second lens (108), the detector (111), the reference objective (106), the measuring objective (104), and the third lens (110) are located in the optical path, the second tilt and the first off-center distance of the reference objective (106) are adjusted by the detected Linnicke interference fringes.

[0010] The auxiliary reflector (1071) is replaced with a reference reflector (1072), and the reference reflector (1072) and the reference objective lens (106) are fixed on the same mechanical component.

[0011] In some embodiments of this application, replacing the auxiliary reflector (1071) with the reference reflector (1072) includes:

[0012] After adjusting the first tilt of the auxiliary reflector (1071), light with calibration marks is emitted to the auxiliary reflector (1071) through the autocollimator (113), and the position of the returned calibration marks is recorded;

[0013] Based on the position of the returned calibration mark, the auxiliary reflector (1071) is replaced with the reference reflector (1072) so that the position of the returned calibration mark remains unchanged.

[0014] In some embodiments of this application, when the light source (101), the first lens (102), the beam splitter (103), the auxiliary mirror (1071), the wafer under test (105), the second lens (108), and the detector (111) are located in the optical path, adjusting the first axial distance of the auxiliary mirror (1071) based on the Michelson interference fringes detected by the detector (111) includes:

[0015] When the single-mode laser source (1012), the first lens (102), the beam splitter (103), the auxiliary mirror (1071), the wafer under test (105), the second lens (108), and the detector (111) are located in the optical path, the first axial distance of the auxiliary mirror (1071) is adjusted by the Michelson interference fringes detected by the detector (111) with a first adjustment step.

[0016] The single-mode laser source (1012) is replaced with a white light source (1011), and the first axial distance of the auxiliary reflector (1071) is adjusted by a second adjustment step size based on the Michelson interference fringes detected by the detector (111); the second adjustment step size is smaller than the first adjustment step size.

[0017] In some embodiments of this application, when the light source (101), the first lens (102), the beam splitter (103), the auxiliary mirror (1071), the wafer under test (105), the second lens (108), the detector (111), the reference objective (106), the measuring objective (104), and the third lens (110) are arranged in the optical path, adjusting the second tilt and the first eccentricity distance of the reference objective (106) by detecting the Linnicke interference fringes includes:

[0018] When the surface light source (114), the measuring objective (104), the beam splitter (103), the second lens (108), the third lens (110), and the detector (111) are located in the optical path, the first entrance pupil position detected by the detector (111) is obtained, wherein the measuring objective (104) is located in the optical path between the surface light source (114) and the beam splitter (103), and the third lens (110) is located in the optical path between the beam splitter (103) and the detector (111);

[0019] When the surface light source (114), the reference objective (106), the beam splitter (103), the second lens (108), the third lens (110), and the detector (111) are located in the optical path, the second entrance pupil position detected by the detector (111) is obtained, wherein the reference objective (106) is located in the optical path between the surface light source (114) and the beam splitter (103);

[0020] Based on the first entrance pupil position and the second entrance pupil position, adjust the first eccentricity distance of the reference objective lens (106) so that the first entrance pupil position and the second entrance pupil position coincide;

[0021] When the light source (101), the first lens (102), the beam splitter (103), the reference objective (106), the auxiliary mirror (1071), the measuring objective (104), the wafer under test (105), the second lens (108), the third lens (110), and the detector (111) are located in the optical path, the second tilt and the first eccentricity of the reference objective (106) are adjusted by the detected Linnicke interference fringes.

[0022] In some embodiments of this application, the method further includes:

[0023] When the light with calibration marks emitted by the autocollimator (113) passes through the first lens (102), the beam splitter (103) and the reference objective (106) and is incident on the auxiliary mirror (1071), the second axial distance of the reference objective (106) is adjusted by the focusing sharpness of the calibration marks detected by the detector (111).

[0024] In some embodiments of this application, replacing the auxiliary reflector (1071) with the reference reflector (1072) includes:

[0025] The auxiliary mirror (1071) is replaced with the reference mirror (1072), and the second axial distance of the reference mirror (1072) is adjusted by a third adjustment step based on the focal plane position of the reference objective (106).

[0026] Based on the Linnicke interference fringes detected by the detector (111), the second axial distance is adjusted with a fourth adjustment step size so that the second axial distance is equal to the first axial distance; the fourth adjustment step size is smaller than the third adjustment step size.

[0027] In another aspect, embodiments of this application also provide a wafer inspection system, the system comprising:

[0028] The light source (101), beam splitter (103), measuring objective (104), reference objective (106), and detector (111) are used to split the light emitted by the light source (101) into a measuring beam that propagates into the measuring optical path where the measuring objective (104) is located, and a reference beam that propagates into the reference optical path where the reference objective (106) is located.

[0029] A first lens (102) is disposed in the optical path between the light source (101) and the beam splitter (103);

[0030] The second lens (108) and the third lens (110) are both disposed in the optical path between the beam splitter (103) and the detector (111);

[0031] An auxiliary reflector (1071) is disposed on the light-emitting side of the reference objective (106) for reflecting the reference beam.

[0032] The wafer to be tested (105) is disposed on the light-emitting side of the measuring objective (104) for reflecting the measuring beam;

[0033] The detector (111) is used to detect the interference fringes formed after the reflected measurement beam and the reflected reference beam pass through the beam splitter (103).

[0034] A reference mirror (1072) is fixed on the same mechanical component as the reference objective lens (106) and is used to replace the auxiliary mirror (1071) after the detector (111) detects the interference fringes, so as to inspect the wafer (105) to be tested.

[0035] In some embodiments of this application, the system further includes an autocollimator (113);

[0036] The autocollimator (113) is used to emit light with calibration marks to the auxiliary mirror (1071) after the interference fringes are formed, and to record the position of the returned calibration marks, so that the position of the returned calibration marks remains unchanged after the auxiliary mirror (1071) is replaced with the reference mirror (1072).

[0037] In some embodiments of this application, the light source (101) includes a single-mode laser light source (1012) and a white light light source (1011);

[0038] The single-mode laser source (1012) is used to adjust the first axial distance of the auxiliary reflector (1071) by a first adjustment step size through Michelson interference fringes when emitting laser light;

[0039] The white light source (1011) is used to adjust the first axial distance of the auxiliary reflector (1071) by a second adjustment step size through Michelson interference fringes when emitting white light; the second adjustment step size is smaller than the first adjustment step size.

[0040] In some embodiments of this application, the system further includes:

[0041] An auxiliary beam splitter (109) is disposed between the second lens (108) and the third lens (110);

[0042] An auxiliary detector (112) is used to image the light passing through the auxiliary beam splitter (109).

[0043] This application provides a wafer inspection method and a wafer inspection system. When a light source (101), a first lens (102), a beam splitter (103), a wafer under test (105), a second lens (108), and a detector (111) are configured in an optical path, the system acquires the position of a first light spot detected by the detector (111). When the light source (101), first lens (102), beam splitter (103), auxiliary reflector (1071), second lens (108), and detector (111) are configured in an optical path, the system acquires the position of a second light spot detected by the detector (111). Based on the first and second light spot positions, the system adjusts the first tilt angle of the auxiliary reflector (1071) to make the first and second light spot positions coincide. The system also includes a method for inspecting wafers when the light source (101), first lens (102), beam splitter (103), auxiliary reflector (1071), second lens (108), and detector (111) are configured in an optical path. When the reflector (1071), the wafer under test (105), the second lens (108), and the detector (111) are located in the optical path, the first axial distance of the auxiliary reflector (1071) is adjusted by the Michelson interference fringes detected by the detector (111); when the light source (101), the first lens (102), the beam splitter (103), the auxiliary reflector (1071), the wafer under test (105), the second lens (108), the detector (111), the reference objective (106), the measuring objective (104), and the third lens (110) are located in the optical path, the second tilt and the first eccentric distance of the reference objective (106) are adjusted by the detected Linnicke interference fringes; the auxiliary reflector (1071) is replaced by the reference reflector (1072), and the reference reflector (1072) and the reference objective (106) are fixed on the same mechanical component. In summary, by introducing an additional independent reflector, namely the auxiliary reflector, the auxiliary reflector has greater flexibility in adjustment and is not interfered with by the reference objective. It can determine its own axial position (i.e., the first axial distance) and tilt degree (i.e., the first tilt angle). In addition, it can help adjust the attitude of the reference objective in the future, that is, determine the second tilt angle and the first eccentric distance. In this way, after the auxiliary reflector can help adjust the interference fringes, it can be replaced by the reference reflector, thereby decoupling the adjustment dimensions of the reference objective and the reference reflector, and improving the adjustment efficiency and accuracy. Attached Figure Description

[0044] Figure 1 shows a schematic flowchart of a wafer inspection method provided in an embodiment of this application;

[0045] Figure 2 shows a schematic diagram of an optical path for detecting the position of a first light spot according to an embodiment of this application;

[0046] Figure 3 shows a schematic diagram of an optical path for detecting the position of a second light spot according to an embodiment of this application;

[0047] Figure 4 shows a schematic diagram of the optical path for adjusting an auxiliary reflector according to an embodiment of this application;

[0048] Figure 5 shows a schematic diagram of the optical path for adjusting a reference objective lens according to an embodiment of this application;

[0049] Figure 6 shows a schematic diagram of an optical path for detecting the position of a first entrance pupil according to an embodiment of this application;

[0050] Figure 7 shows a schematic diagram of an optical path for detecting the position of a second entrance pupil according to an embodiment of this application;

[0051] Figure 8 shows a schematic diagram of the optical path for adjusting a reference objective lens according to an embodiment of this application;

[0052] Figure 9 shows a schematic diagram of the optical path for determining the first tilt angle of an auxiliary reflector according to an embodiment of this application.

[0053] Figure 10 shows a schematic diagram of the optical path for adjusting a reference objective lens according to an embodiment of this application.

[0054] Figure 11 shows a schematic diagram of a wafer inspection system provided in an embodiment of this application;

[0055] Figure 12 shows a schematic diagram of another wafer inspection system provided in an embodiment of this application. Detailed Implementation

[0056] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0057] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0058] Secondly, this application provides a detailed description in conjunction with schematic diagrams. When detailing the embodiments of this application, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of this application. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0059] As described in the background section, in related technologies, in the reference optical path, the reference mirror is mounted on the mechanical components of the reference objective. During assembly and adjustment, the assembly and adjustment dimensions of the reference objective and the reference mirror are coupled, requiring repeated adjustments to both to produce interference fringes. For example, the reference objective is adjusted first, then the reference mirror is adjusted, and then the reference objective is adjusted again until interference fringes are produced. This process is complex, inefficient, and has low precision.

[0060] Based on the above technical problems, this application provides a wafer inspection method and a wafer inspection system. By introducing an additional independent reflector, namely an auxiliary reflector, the auxiliary reflector has a higher degree of adjustment freedom and is not interfered with by the reference objective. It can determine its own axial position (i.e., the first axial distance) and tilt degree (i.e., the first tilt angle). In addition, it can also help adjust the attitude of the reference objective, that is, determine the second tilt angle and the first eccentric distance. In this way, after the auxiliary reflector can help adjust the interference fringes, it can be replaced by the reference reflector, thereby decoupling the assembly and adjustment dimensions of the reference objective and the reference reflector, and improving the assembly and adjustment efficiency and accuracy.

[0061] For ease of understanding, the wafer inspection method and wafer inspection system provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0062] Referring to Figure 1, which is a schematic flowchart of a wafer inspection method provided in an embodiment of this application, the method may include the following steps.

[0063] S101, when the light source (101), the first lens (102), the beam splitter (103), the wafer under test (105), the second lens (108) and the detector (111) are arranged in the optical path, the position of the first light spot detected by the detector (111) is obtained, and when the light source (101), the first lens (102), the beam splitter (103), the auxiliary reflector (1071), the second lens (108) and the detector (111) are arranged in the optical path, the position of the second light spot detected by the detector (111) is obtained.

[0064] Specifically, referring to Figure 2, which is a schematic diagram of an optical path for detecting the position of a first light spot according to an embodiment of this application, the optical path includes a light source (101), a first lens (102), a beam splitter (103), a wafer to be tested (105), a second lens (108), and a detector (111).

[0065] The light emitted by the light source (101) is incident on the beam splitter (103) through the first lens (102). The beam splitter (103) has the function of splitting the light, which can cause a part of the light to be incident on the surface of the wafer under test (105). The wafer under test (105) reflects the light. The reflected light passes through the beam splitter (103) and the second lens (108) and is received by the detector (111). The detector (111) can detect the light and record the position of the light spot as the first light spot position.

[0066] Specifically, referring to Figure 3, which is a schematic diagram of an optical path for detecting the position of a second light spot according to an embodiment of this application, the optical path includes a light source (101), a first lens (102), a beam splitter (103), an auxiliary reflector (1071), a second lens (108), and a detector (111).

[0067] The beam splitter (103) allows a portion of the light emitted by the light source (101) to be transmitted and incident on the auxiliary reflector (1071). After the auxiliary reflector (1071) reflects the light, it passes through the beam splitter (103) and the second lens (108) and is received by the detector (111). At this time, the light spot in the detector (111) can be recorded as the position of the second light spot.

[0068] S102, based on the position of the first light spot and the position of the second light spot, adjust the first tilt of the auxiliary reflector (1071) so that the positions of the first light spot and the second light spot coincide.

[0069] Specifically, the first tilt angle can be understood as the angle at which the plane of the auxiliary reflector (1071) deviates from the vertical plane. By adjusting the first tilt angle, the position of the light spot in the detector (111) can be changed, that is, the position of the second light spot can be adjusted.

[0070] Since the position of the first light spot can be understood as the position of the light spot in the measurement optical path, and the position of the second light spot can be understood as the position of the light spot in the reference optical path, by adjusting the first tilt of the auxiliary reflector (1071) to change the position of the second light spot, the first light spot position and the second light spot position coincide, which can indicate that the measurement optical path and the reference optical path are completely coincident. That is, at this time, the tilt of the auxiliary reflector (1071) is consistent with the tilt of the wafer (105) under test. Especially when the plane of the wafer (105) under test is located in the horizontal plane, it can ensure that the mirror surface of the auxiliary reflector (1071) is located in the vertical plane, which facilitates the subsequent adjustment of the interference fringes.

[0071] In actual operation, the position of the first light spot can be detected first, and then the position of the second light spot can be adjusted so that the positions of the two light spots coincide.

[0072] S103, when the light source (101), the first lens (102), the beam splitter (103), the auxiliary mirror (1071), the wafer under test (105), the second lens (108), and the detector (111) are located in the optical path, the first axial distance of the auxiliary mirror (1071) is adjusted by the Michelson interference fringes detected by the detector (111).

[0073] Specifically, referring to Figure 4, which is a schematic diagram of the optical path for adjusting an auxiliary reflector provided in an embodiment of this application, the optical path includes a light source (101), a first lens (102), a beam splitter (103), an auxiliary reflector (1071), a wafer under test (105), a second lens (108), and a detector (111).

[0074] Specifically, after the light emitted by the light source (101) passes through the beam splitter (103), part of the light is incident on the wafer under test (105) for detection, and the other part of the light is incident on the auxiliary reflector (1071). After the two beams of light are reflected by the wafer under test (105) and the auxiliary reflector (1071) respectively, they undergo Michelson interference after passing through the beam splitter (103) and the second lens (108), forming Michelson interference fringes, which are then detected by the detector (111).

[0075] Specifically, the first axial distance of the auxiliary mirror (1071) can be adjusted based on the Michelson interference fringes. The first axial distance can be understood as the distance of the auxiliary mirror (1071) in the direction of light propagation, that is, the distance in the direction of the optical axis. When a zero-order fringe appears in the interference fringes, that is, when a bright fringe or a dark fringe is observed in the detector (111), it indicates that the auxiliary mirror (1071) has been moved to the appropriate position. At this time, the distance between the auxiliary mirror (1071) and the beam splitter (103) is the same as the distance between the wafer under test (105) and the beam splitter (103).

[0076] In one possible implementation, the light source (101) may include a single-mode laser light source (1012) and a white light light source (1011). Then, in S103, when the light source (101), the first lens (102), the beam splitter (103), the auxiliary mirror (1071), the wafer under test (105), the second lens (108), and the detector (111) are located in the optical path, the first axial distance of the auxiliary mirror (1071) is adjusted by the Michelson interference fringes detected by the detector (111). This may specifically include S1031-S1032.

[0077] S1031, when the single-mode laser source (1012), the first lens (102), the beam splitter (103), the auxiliary mirror (1071), the wafer under test (105), the second lens (108) and the detector (111) are located in the optical path, the first axial distance of the auxiliary mirror (1071) is adjusted by the Michelson interference fringes detected by the detector (111) with a first adjustment step.

[0078] Specifically, in order to quickly adjust the first axial distance of the auxiliary reflector (1071), a single-mode laser source (1012) and a white light source (1011) can be used for adjustment. First, a coarse adjustment can be performed using the single-mode laser source (1012), that is, adjustment is performed according to the first adjustment step size, where the first adjustment step size can be understood as the distance the auxiliary reflector (1071) moves in the axial direction, and the moving distance can be relatively large. The light emitted by the single-mode laser source (1012) is split into two beams after passing through the first lens (102) and the beam splitter (103). These two beams undergo Michelson interference, forming interference fringes. Since the coherence length of the single-mode laser is relatively long, it is easier to adjust the interference fringes.

[0079] S1032, replace the single-mode laser source (1012) with a white light source (1011), and adjust the first axial distance of the auxiliary reflector (1071) by the Michelson interference fringes detected by the detector (111) with a second adjustment step.

[0080] Specifically, after using a single-mode laser light source (1012) to generate interference fringes, it can be replaced with a white light source (1011). The white light source (1011) emits white light, and interference fringes are formed between the measuring beam and the reference beam. At this time, the interference fringes are adjusted more finely, that is, adjusted according to the second adjustment step size. The second adjustment step size can also be understood as the axial movement distance of the auxiliary reflector (1071). It is worth noting that the second adjustment step size is smaller than the first adjustment step size. As an example, the second adjustment step size can be a smaller value, that is, the movement distance during fine adjustment can be smaller. When a bright fringe or a dark fringe appears in the detector (111), it indicates that the first axial distance adjustment of the auxiliary reflector (1071) is completed. In this way, the first axial distance of the auxiliary reflector (1071) can be determined as quickly as possible, improving assembly efficiency.

[0081] S104, when the light source (101), first lens (102), beam splitter (103), auxiliary reflector (1071), wafer under test (105), second lens (108), detector (111), reference objective (106), measuring objective (104) and third lens (110) are located in the optical path, the second tilt and first eccentricity of the reference objective (106) are adjusted by the detected Linnicke interference fringes.

[0082] Specifically, referring to Figure 5, which is a schematic diagram of an optical path for adjusting a reference objective lens according to an embodiment of this application, compared with the optical path shown in Figure 4, a reference objective lens (106), a measuring objective lens (104), and a third lens (110) are added to the optical path to form a Linnik interference.

[0083] The light emitted by the light source (101) is split by the beam splitter (103) to form a measurement beam and a reference beam. The measurement beam is incident on the wafer to be measured (105) through the measurement objective (104), and the reference beam is incident on the auxiliary reflector (1071) through the reference objective (106). Then, Linnicke interference occurs between the measurement beam and the reference beam, forming Linnicke interference fringes.

[0084] Since the positions of the measuring objective (104) and the wafer under test (105) remain unchanged, and the position of the auxiliary mirror (1071) in the axial direction has been determined, the interference fringes can be changed by adjusting the reference objective (106).

[0085] The second tilt angle can be understood as the angle at which the plane of the reference objective (106) deviates from the vertical plane, and the first eccentric distance can be understood as the radial distance between the optical axis center of the reference objective (106) and the preset axis. The preset axis can be understood as the direction line of the reference beam generated after the light emitted by the light source (101) passes through the beam splitter (103).

[0086] In short, by adjusting the tilt and eccentricity of the reference objective (106), the position of the reference objective (106) and the position of the measuring objective (104) can be made symmetrical about the beam splitter (103). At this time, interference fringes can be observed in the detector (111) to be broadened to only one bright fringe or only one dark fringe within the field of view, indicating that the reference objective (106) has been properly adjusted.

[0087] In one possible implementation, to improve the adjustment accuracy and efficiency of the reference objective (106), the eccentricity of the reference objective (106) can be coarsely adjusted based on the entrance pupil position, and then the tilt can be adjusted by interference fringes while the eccentricity is finely adjusted. That is, S104, when the light source (101), the first lens (102), the beam splitter (103), the auxiliary mirror (1071), the wafer under test (105), the second lens (108), the detector (111), the reference objective (106), the measuring objective (104), and the third lens (110) are located in the optical path, the second tilt and the first eccentricity distance of the reference objective (106) can be adjusted by the detected Linnicke interference fringes, which can specifically include S1041-S1044.

[0088] S1041, when the surface light source (114), measuring objective lens (104), beam splitter (103), second lens (108), third lens (110) and detector (111) are located in the optical path, the first entrance pupil position detected by the detector (111) is obtained.

[0089] Specifically, referring to Figure 6, which is a schematic diagram of an optical path for detecting the position of the first entrance pupil according to an embodiment of this application, the optical path includes a surface light source (114), a measuring objective lens (104), a beam splitter (103), a second lens (108), a third lens (110), and a detector (111). The measuring objective lens (104) is located on the optical path between the surface light source (114) and the beam splitter (103), and the third lens (110) is located on the optical path between the beam splitter (103) and the detector (111).

[0090] Specifically, the third lens (110) can be located on the back focal plane of the measuring objective (104). The light emitted by the surface light source (114) passes through the measuring objective (104), the beam splitter (103), the second lens (108), and the third lens (110) and is received by the detector (111). A light spot can be observed in the detector (111), and the position of the light spot is the first entrance pupil position. The first entrance pupil position can be understood as the entrance pupil position of the measuring objective (104).

[0091] S1042, when the surface light source (114), reference objective (106), beam splitter (103), second lens (108), third lens (110) and detector (111) are located in the optical path, the second entrance pupil position detected by the detector (111) is obtained.

[0092] Specifically, referring to Figure 7, which is a schematic diagram of an optical path for detecting the position of the second entrance pupil provided in an embodiment of this application, the optical path includes a surface light source (114), a reference objective (106), a beam splitter (103), a second lens (108), a third lens (110), and a detector (111). The reference objective (106) is located on the optical path between the surface light source (114) and the beam splitter (103).

[0093] Specifically, the light emitted by the surface light source (114) passes through the reference objective (106), beam splitter (103), second lens (108), and third lens (110) and is received by the detector (111). The light spot is observed in the detector (111), and the position of the light spot can be used as the second entrance pupil position. The second entrance pupil position can be understood as the entrance pupil position of the reference objective (106).

[0094] S1043, based on the first entrance pupil position and the second entrance pupil position, adjust the first eccentricity distance of the reference objective (106) so that the first entrance pupil position and the second entrance pupil position coincide.

[0095] Specifically, the first eccentricity distance of the reference objective (106) can be adjusted, that is, the reference objective (106) is moved in the vertical direction so that the second entrance pupil position coincides with the first entrance pupil position. At this time, the eccentricity of the reference objective (106) is consistent with the eccentricity of the measuring objective (104). For example, the optical axes of both objectives coincide with the direction of light transmission. In other words, by adjusting the eccentricity of the reference objective (106) through the entrance pupil position, the eccentricity of the reference objective (106) can be quickly adjusted to a suitable range. At this time, it can be considered that the eccentricity of the reference objective (106) has been coarsely adjusted, that is, the vertical movement distance of the reference objective (106) will be larger during adjustment.

[0096] S1044, when the light source (101), first lens (102), beam splitter (103), reference objective (106), auxiliary mirror (1071), measuring objective (104), wafer under test (105), second lens (108), third lens (110) and detector (111) are located in the optical path, the second tilt and first off-center distance of the reference objective (106) are adjusted by the detected Linnicke interference fringes.

[0097] Specifically, referring to Figure 8, which is a schematic diagram of the optical path for adjusting the reference objective provided in another embodiment of this application, the optical path includes a light source (101), a first lens (102), a beam splitter (103), a reference objective (106), an auxiliary mirror (1071), a measuring objective (104), a wafer to be measured (105), a second lens (108), a third lens (110), and a detector (111).

[0098] Specifically, the light emitted by the light source (101) is split into two beams after passing through the first lens (102) and the beam splitter (103), namely the measurement beam and the reference beam. The measurement beam is reflected by the wafer under test (105) after passing through the measurement objective lens (104), and is received by the detector (111) after passing through the beam splitter (103), the second lens (108) and the third lens (110). The reference beam is reflected by the auxiliary mirror (1071) after passing through the reference objective lens (106), and is also received by the detector (111) after passing through the beam splitter (103), the second lens (108) and the third lens (110). Linnicke interference occurs between the reference beam and the measurement beam, and Linnicke interference fringes are observed in the detector (111).

[0099] Specifically, by adjusting the second tilt angle and the first eccentricity distance of the reference objective (106), the Linnicke interference fringes in the detector (111) are broadened to only one bright fringe or only one dark fringe, indicating that the tilt and eccentricity of the reference objective (106) have been adjusted. It is worth noting that the secondary adjustment of the eccentricity of the reference objective (106) at this time is a fine-tuning process, and the vertical movement distance of the reference objective (106) will be smaller.

[0100] In summary, by coarsely adjusting the eccentricity of the reference objective (106) based on the entrance pupil position, it is easier to quickly adjust the Linnicke interference fringes in the future. Furthermore, the tilt of the reference objective (106) can be quickly adjusted based on the Linnicke interference fringes, and the eccentricity of the reference objective (106) can be finely adjusted, thereby improving the efficiency of optical path adjustment.

[0101] S105, the auxiliary reflector (1071) is replaced with a reference reflector (1072), and the reference reflector (1072) and the reference objective lens (106) are fixed on the same mechanical component.

[0102] Specifically, since the reference mirror (1072) needs to be fixed on the same mechanical component as the reference objective (106), after determining the first tilt angle and the first axial distance of the auxiliary mirror (1071), the reference mirror (1072) can be used directly to replace the auxiliary mirror (1071). The reference mirror (1072) is installed according to the first tilt angle and the first axial distance, so that the tilt angle and axial position of the reference mirror (1072) are accurate.

[0103] In summary, due to the coupling of the assembly dimensions of the reference objective and the reference mirror in the relevant technologies, it is not easy to adjust to produce interference fringes, resulting in low assembly efficiency and accuracy. By introducing an additional independent mirror, namely the auxiliary mirror, the adjustment freedom of the auxiliary mirror is increased. It is not interfered with by the reference objective and can determine its own axial position (i.e., the first axial distance) and tilt degree (i.e., the first tilt angle). In addition, it can also help adjust the attitude of the reference objective in the future, that is, determine the second tilt angle and the first eccentricity distance. In this way, after the auxiliary mirror can help adjust to produce interference fringes, it can be replaced with the reference mirror, thereby decoupling the assembly dimensions of the reference objective and the reference mirror and improving the assembly efficiency and accuracy.

[0104] In one possible implementation, S105, the auxiliary reflector (1071) is replaced with the reference reflector (1072), which can be specifically S1051-S1052.

[0105] S1051 After adjusting the first tilt of the auxiliary reflector (1071), light with calibration marks is emitted to the auxiliary reflector (1071) through the autocollimator (113), and the position of the returned calibration marks is recorded.

[0106] Specifically, referring to Figure 9, which is a schematic diagram of the optical path for determining the first tilt angle of an auxiliary reflector according to an embodiment of this application, an autocollimator (113) is added to the optical path. After determining the first tilt angle of the auxiliary reflector (1071), the first tilt angle can be recorded. The autocollimator (113) can emit light with calibration marks, such as cross-shaped light, towards the back of the auxiliary reflector (1071). After being reflected by the auxiliary reflector (1071), the light returns to the autocollimator (113), which can record the position of the returned calibration marks, such as the position of the cross-shaped light.

[0107] S1052, based on the position of the returned calibration mark, replace the auxiliary reflector (1071) with the reference reflector (1072) so that the position of the returned calibration mark remains unchanged.

[0108] Specifically, after replacing the auxiliary reflector (1071) with the reference reflector (1072), in order to confirm that the tilt of the reference reflector (1072) has reached the first tilt, the light emitted from the collimator (113) can be incident on the reference reflector (1072), and the position of the returned calibration mark can be recorded. By adjusting the tilt of the reference reflector (1072), the position of the calibration mark is made to coincide with the previously recorded position, that is, the position of the returned calibration mark remains unchanged, indicating that the tilt of the reference reflector (1072) has reached the first tilt, thereby ensuring that the tilt of the reference reflector (1072) has been confirmed to be accurate.

[0109] In this way, by introducing an autocollimator (113) to record the first tilt of the auxiliary reflector (1071), the tilt of the replaced reference reflector (1072) can be obtained when the reflector is replaced, thereby improving the assembly accuracy of the reference reflector (1072).

[0110] In one possible implementation, the second axial distance of the reference objective (106) can also be adjusted. That is, when the light with the calibration mark emitted from the collimator (113) passes through the first lens (102), the beam splitter (103), and the reference objective (106) and is incident on the auxiliary mirror (1071), the second axial distance of the reference objective (106) is adjusted based on the focusing sharpness of the calibration mark detected by the detector (111).

[0111] Specifically, the second axial distance can be understood as the distance of the reference objective (106) in the direction of light propagation, that is, the distance in the direction of the optical axis. Referring to Figure 10, which is a schematic diagram of the optical path for adjusting the reference objective provided in this application embodiment, an autocollimator (113) can be used to replace the light source (101). Light with calibration marks is incident on the auxiliary reflector (1071), reflected, and enters the detector (111). The detector (111) can record the calibration marks. By adjusting the second axial distance of the reference objective (106), the focusing sharpness of the calibration marks can be changed. When the focusing sharpness reaches the preset requirement, it indicates that the position of the reference objective has been adjusted. At this time, the auxiliary reflector (1071) is located on the focal plane of the reference objective (106), thereby realizing the adjustment of the axial position of the reference objective (106). It can be understood that at this time, the distance between the reference objective (106) and the beam splitter (103) is equal to the distance between the measuring objective (104) and the beam splitter (103). The adjustment of the second axial distance can be made before the second tilt and the first eccentricity.

[0112] In one possible implementation, the auxiliary mirror (1071) is replaced with a reference mirror (1072). Specifically, the auxiliary mirror (1071) is replaced with a reference mirror (1072), and the second axial distance of the reference mirror (1072) is adjusted with a third adjustment step based on the focal plane position of the reference objective (106). Based on the Linnicke interference fringes detected by the detector (111), the second axial distance is adjusted with a fourth adjustment step so that the second axial distance is equal to the first axial distance, and the fourth adjustment step is smaller than the third adjustment step.

[0113] Specifically, the second axial distance can be understood as the distance of the reference mirror (1072) in the direction of light propagation, that is, the distance in the optical axis direction. In order to adjust the axial distance of the reference mirror (1072) more quickly, the reference mirror (1072) can be coarsely adjusted based on the focal plane position of the reference objective (106), that is, the reference objective (106) can be adjusted according to the third adjustment step. The third adjustment step can be understood as the distance the reference objective (106) moves in the axial direction. As an example, the moving distance can be larger at this time, so as to quickly determine the approximate position of the reference mirror (1072) in the axial direction. As an example, the distance between the reference mirror (1072) and the reference objective (106) can be adjusted to the focal length. Furthermore, due to the Linnicke interference between the measuring beam and the reference beam, Linnicke interference fringes are detected in the detector (111). Fine adjustments are then made to the second axial distance, specifically according to the fourth adjustment step. This fourth adjustment step can be understood as the axial movement distance of the reference objective (106). It is worth noting that the fourth adjustment step is smaller than the third adjustment step. For example, the fourth adjustment step can be a smaller value, meaning the movement distance during fine-tuning can be smaller, resulting in only one bright fringe or one dark fringe in the detector (111). This indicates that the second axial distance is equal to the first axial distance, and the position of the reference mirror (1072) completely coincides with the original auxiliary mirror (1071). Thus, through two adjustments—coarse and fine—assembly efficiency is improved, ensuring that the reference mirror (1072) is positioned appropriately along the axial direction.

[0114] Based on the above wafer inspection method, this application embodiment also provides a wafer inspection system. Referring to FIG11, which is a schematic diagram of a wafer inspection system provided in this application embodiment, the wafer inspection system may include a light source (101), a first lens (102), a beam splitter (103), a measuring objective (104), a wafer to be inspected (105), a reference objective (106), an auxiliary reflector (1071), a reference reflector (1072), a second lens (108), a third lens (110), and a detector (111).

[0115] The beam splitter (103) is used to split the light emitted by the light source (101) into a measurement beam that propagates into the measurement optical path where the measurement objective (104) is located, and a reference beam that propagates into the reference optical path where the reference objective (106) is located. The first lens (102) is disposed in the optical path between the light source (101) and the beam splitter (103). The second lens (108) and the third lens (110) are both disposed in the optical path between the beam splitter (103) and the detector (111).

[0116] An auxiliary reflector (1071) is positioned on the light-emitting side of the reference objective (106) to reflect the reference beam in order to form interference fringes. The wafer under test (105) is positioned on the light-emitting side of the measuring objective (104) to reflect the measuring beam in order to form interference fringes.

[0117] The detector (111) is used to detect the interference fringes formed after the reflected measurement beam and the reflected reference beam pass through the beam splitter (103). The reference mirror (1072) and the reference objective (106) are fixed on the same mechanical component and are used to replace the auxiliary mirror (1071) after the detector (111) detects the interference fringes so as to inspect the wafer (105) under test.

[0118] In one possible implementation, the wafer inspection system may further include an autocollimator (113) for emitting light with calibration marks to an auxiliary mirror (1071) after interference fringes are formed, and recording the position of the returned calibration marks, such that the position of the returned calibration marks remains unchanged after the auxiliary mirror (1071) is replaced with a reference mirror (1072).

[0119] In one possible implementation, the light source (101) may include a single-mode laser source (1012) and a white light source (1011). The single-mode laser source (1012) is used to adjust the first axial distance of the auxiliary reflector (1071) with a first adjustment step size by means of Michelson interference fringes when emitting laser light. The white light source (1011) is used to adjust the first axial distance of the auxiliary reflector (1071) with a second adjustment step size by means of Michelson interference fringes when emitting white light. The second adjustment step size is smaller than the first adjustment step size.

[0120] In one possible implementation, the wafer inspection system may further include an auxiliary beam splitter (109) and an auxiliary detector (112), as shown in FIG12, which is a schematic diagram of another wafer inspection system provided in an embodiment of the present application.

[0121] An auxiliary beam splitter (109) is positioned between the second lens (108) and the third lens (110), and an auxiliary detector (112) is used to image the light passing through the auxiliary beam splitter (109). In other words, the interference fringes can also be detected using the auxiliary detector (112), which does not rely on a single detector (111), thereby improving assembly efficiency.

[0122] This application provides a wafer inspection system, which includes a light source, a beam splitter, a measuring objective lens, a reference objective lens, a detector, an auxiliary reflector, a wafer under test, and a reference reflector. The beam splitter splits the light emitted from the light source into a measuring beam that propagates into the measuring optical path of the measuring objective lens and a reference beam that propagates into the reference optical path of the reference objective lens. The auxiliary reflector is disposed on the light-emitting side of the reference objective lens and is used to reflect the reference beam. The wafer under test is disposed on the light-emitting side of the measuring objective lens and is used to reflect the measuring beam. The detector detects the interference fringes formed by the reflected measuring beam and the reflected reference beam after passing through the beam splitter. The reference reflector is fixed to the reference objective lens on the same mechanical component and is used to replace the auxiliary reflector after the detector detects the interference fringes, so as to inspect the wafer under test. In summary, by introducing an additional independent reflector, namely the auxiliary reflector, the auxiliary reflector has greater flexibility in adjustment and is not interfered with by the reference objective. It can determine its own axial position (i.e., the first axial distance) and tilt degree (i.e., the first tilt angle). In addition, it can help adjust the attitude of the reference objective in the future, that is, determine the second tilt angle and the first eccentric distance. In this way, after the auxiliary reflector can help adjust the interference fringes, it can be replaced by the reference reflector, thereby decoupling the adjustment dimensions of the reference objective and the reference reflector, and improving the adjustment efficiency and accuracy.

[0123] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by program instructions in hardware. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps of the above method embodiments. The aforementioned storage medium can be at least one of the following media: read-only memory (ROM), RAM, magnetic disk, or optical disk, etc., and other media capable of storing program code.

[0124] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0125] The above description is merely a preferred embodiment of this application. Although this application has disclosed preferred embodiments above, it is not intended to limit this application. Any person skilled in the art can make many possible variations and modifications to the technical solutions of this application using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of this application. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application shall still fall within the protection scope of the technical solutions of this application.

Claims

1. A wafer inspection method, the method comprising: When the light source (101), the first lens (102), the beam splitter (103), the wafer under test (105), the second lens (108), and the detector (111) are arranged in the optical path, the position of the first light spot detected by the detector (111) is obtained; and when the light source (101), the first lens (102), the beam splitter (103), the auxiliary reflector (1071), the second lens (108), and the detector (111) are arranged in the optical path, the position of the second light spot detected by the detector (111) is obtained. Based on the positions of the first and second light spots, the first tilt angle of the auxiliary reflector (1071) is adjusted so that the positions of the first and second light spots coincide. When the light source (101), the first lens (102), the beam splitter (103), the auxiliary mirror (1071), the wafer under test (105), the second lens (108), and the detector (111) are located in the optical path, the first axial distance of the auxiliary mirror (1071) is adjusted by the Michelson interference fringes detected by the detector (111). When the light source (101), the first lens (102), the beam splitter (103), the auxiliary mirror (1071), the wafer under test (105), the second lens (108), the detector (111), the reference objective (106), the measuring objective (104), and the third lens (110) are located in the optical path, the second tilt and the first off-center distance of the reference objective (106) are adjusted by the detected Linnicke interference fringes. The auxiliary reflector (1071) is replaced with a reference reflector (1072), and the reference reflector (1072) and the reference objective lens (106) are fixed on the same mechanical component.

2. The wafer inspection method according to claim 1, wherein replacing the auxiliary reflector (1071) with the reference reflector (1072) comprises: After adjusting the first tilt of the auxiliary reflector (1071), light with calibration marks is emitted to the auxiliary reflector (1071) through the autocollimator (113), and the position of the returned calibration marks is recorded; Based on the position of the returned calibration mark, the auxiliary reflector (1071) is replaced with the reference reflector (1072) so that the position of the returned calibration mark remains unchanged.

3. The wafer inspection method according to claim 1, wherein when the light source (101), the first lens (102), the beam splitter (103), the auxiliary reflector (1071), the wafer to be inspected (105), the second lens (108), and the detector (111) are arranged in the optical path, adjusting the first axial distance of the auxiliary reflector (1071) based on the Michelson interference fringes detected by the detector (111) includes: When the single-mode laser source (1012), the first lens (102), the beam splitter (103), the auxiliary mirror (1071), the wafer under test (105), the second lens (108), and the detector (111) are located in the optical path, the first axial distance of the auxiliary mirror (1071) is adjusted by the Michelson interference fringes detected by the detector (111) with a first adjustment step. The single-mode laser source (1012) is replaced with a white light source (1011), and the first axial distance of the auxiliary reflector (1071) is adjusted by a second adjustment step using the Michelson interference fringes detected by the detector (111). The second adjustment step size is smaller than the first adjustment step size.

4. The wafer inspection method according to claim 1, wherein when the light source (101), the first lens (102), the beam splitter (103), the auxiliary reflector (1071), the wafer to be inspected (105), the second lens (108), the detector (111), the reference objective (106), the measuring objective (104), and the third lens (110) are arranged in the optical path, adjusting the second tilt and the first offset distance of the reference objective (106) by detecting the Linnicke interference fringes includes: When the surface light source (114), the measuring objective (104), the beam splitter (103), the second lens (108), the third lens (110), and the detector (111) are located in the optical path, the first entrance pupil position detected by the detector (111) is obtained, wherein the measuring objective (104) is located in the optical path between the surface light source (114) and the beam splitter (103), and the third lens (110) is located in the optical path between the beam splitter (103) and the detector (111); When the surface light source (114), the reference objective (106), the beam splitter (103), the second lens (108), the third lens (110), and the detector (111) are located in the optical path, the second entrance pupil position detected by the detector (111) is obtained, wherein the reference objective (106) is located in the optical path between the surface light source (114) and the beam splitter (103); Based on the first entrance pupil position and the second entrance pupil position, adjust the first eccentricity distance of the reference objective lens (106) so that the first entrance pupil position and the second entrance pupil position coincide; When the light source (101), the first lens (102), the beam splitter (103), the reference objective (106), the auxiliary mirror (1071), the measuring objective (104), the wafer under test (105), the second lens (108), the third lens (110), and the detector (111) are located in the optical path, the second tilt and the first eccentricity of the reference objective (106) are adjusted by the detected Linnicke interference fringes.

5. The wafer inspection method according to claim 4, further comprising: When the light with calibration marks emitted by the autocollimator (113) passes through the first lens (102), the beam splitter (103) and the reference objective (106) and is incident on the auxiliary mirror (1071), the second axial distance of the reference objective (106) is adjusted by the focusing sharpness of the calibration marks detected by the detector (111).

6. The wafer inspection method according to any one of claims 1-5, wherein replacing the auxiliary reflector (1071) with the reference reflector (1072) comprises: The auxiliary mirror (1071) is replaced with the reference mirror (1072), and the second axial distance of the reference mirror (1072) is adjusted by a third adjustment step based on the focal plane position of the reference objective (106). Based on the Linnicke interference fringes detected by the detector (111), the second axial distance is adjusted with a fourth adjustment step size so that the second axial distance is equal to the first axial distance; The fourth adjustment step size is smaller than the third adjustment step size.

7. A wafer inspection system, the system comprising: The light source (101), beam splitter (103), measuring objective (104), reference objective (106), and detector (111) are used to split the light emitted by the light source (101) into a measuring beam that propagates into the measuring optical path where the measuring objective (104) is located, and a reference beam that propagates into the reference optical path where the reference objective (106) is located. A first lens (102) is disposed in the optical path between the light source (101) and the beam splitter (103); The second lens (108) and the third lens (110) are both disposed in the optical path between the beam splitter (103) and the detector (111); An auxiliary reflector (1071) is disposed on the light-emitting side of the reference objective (106) for reflecting the reference beam. The wafer to be tested (105) is disposed on the light-emitting side of the measuring objective (104) for reflecting the measuring beam; The detector (111) is used to detect the interference fringes formed after the reflected measurement beam and the reflected reference beam pass through the beam splitter (103). A reference mirror (1072) is fixed on the same mechanical component as the reference objective lens (106) and is used to replace the auxiliary mirror (1071) after the detector (111) detects the interference fringes, so as to inspect the wafer (105) to be tested.

8. The wafer inspection system according to claim 7, wherein the system further comprises an autocollimator (113); The autocollimator (113) is used to emit light with calibration marks to the auxiliary mirror (1071) after the interference fringes are formed, and to record the position of the returned calibration marks, so that the position of the returned calibration marks remains unchanged after the auxiliary mirror (1071) is replaced with the reference mirror (1072).

9. The wafer inspection system according to claim 7, wherein the light source (101) comprises a single-mode laser light source (1012) and a white light light source (1011); The single-mode laser source (1012) is used to adjust the first axial distance of the auxiliary reflector (1071) by a first adjustment step size through Michelson interference fringes when emitting laser light; The white light source (1011) is used to adjust the first axial distance of the auxiliary reflector (1071) by a second adjustment step size through Michelson interference fringes when emitting white light; the second adjustment step size is smaller than the first adjustment step size.

10. The wafer inspection system according to any one of claims 7-9, further comprising: An auxiliary beam splitter (109) is disposed between the second lens (108) and the third lens (110); An auxiliary detector (112) is used to image the light passing through the auxiliary beam splitter (109).

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