CN119375150A - Wafer detection method and wafer detection system - Google Patents
Wafer detection method and wafer detection system Download PDFInfo
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- CN119375150A CN119375150A CN202411933562.1A CN202411933562A CN119375150A CN 119375150 A CN119375150 A CN 119375150A CN 202411933562 A CN202411933562 A CN 202411933562A CN 119375150 A CN119375150 A CN 119375150A
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Abstract
The application provides a wafer detection method and a wafer detection system, which are used for acquiring a first light spot position and a second light spot position detected by a detector, adjusting a first inclination of an auxiliary reflector based on the first light spot position and the second light spot position so as to enable the first light spot position and the second light spot position to coincide, adjusting a first axial distance of the auxiliary reflector by Michelson interference fringes detected by the detector, adding a reference objective lens, a measuring objective lens and a third lens into a light path, adjusting a second inclination and a first eccentric distance of the reference objective lens by the detected Michelson interference fringes, and replacing the auxiliary reflector with the reference reflector, wherein the reference reflector and the reference objective lens are fixed on the same mechanical part. By additionally introducing an independent auxiliary reflector, the auxiliary reflector has higher degree of freedom of adjustment, cannot be interfered by the reference objective, and can realize decoupling of the adjustment dimension of the reference objective and the reference reflector, thereby improving the adjustment efficiency and accuracy.
Description
Technical Field
The present application relates to the field of wafer inspection, and in particular, to a wafer inspection method and a wafer inspection system.
Background
In semiconductor manufacturing processes, it is often necessary to inspect a wafer using a wafer inspection system that includes a reference optical path composed of a reference objective and a reference mirror, and a measurement optical path composed of a measurement objective and a wafer to be measured. And placing the wafer to be detected under the measuring objective lens, and detecting the wafer by observing interference fringes generated by the focusing system. In the related art, on a reference optical path, a reference mirror is mounted on a mechanical part of a reference objective, when the reference objective and the reference mirror are assembled and adjusted, the adjustment dimension of the reference objective and the adjustment dimension of the reference mirror are coupled, and interference fringes can be adjusted only by repeatedly adjusting the reference objective and the reference mirror back and forth, for example, the reference objective is adjusted first, then the reference mirror is adjusted, and then the reference objective is adjusted again until the interference fringes are adjusted, so that the assembly and adjustment complexity is high, and the assembly and adjustment efficiency and the adjustment precision are lower.
Disclosure of Invention
Accordingly, the present application is directed to a wafer inspection method and a wafer inspection system, which can realize decoupling of the adjustment dimensions of the reference objective and the reference mirror, and improve the adjustment efficiency and accuracy. The specific scheme is as follows:
in one aspect, the present application provides a wafer inspection method, the method comprising:
Acquiring a first spot position detected by a detector (111) when a light source (101), a first lens (102), a beam splitter (103), a wafer (105) to be tested, a second lens (108) and the detector (111) are arranged in an optical path, and acquiring a second spot position detected by the detector (111) when the light source (101), the first lens (102), the beam splitter (103), an auxiliary mirror (1071), the second lens (108) and the detector (111) are arranged in the optical path;
-adjusting a first tilt of the auxiliary mirror (1071) based on the first and second spot positions such that the first and second spot positions coincide;
When the light source (101), the first lens (102), the beam splitter (103), the auxiliary reflector (1071), the wafer (105) to be tested, the second lens (108) and the detector (111) are arranged in a light path, a first axial distance of the auxiliary reflector (1071) is adjusted through 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 to be tested (105), the second lens (108), the detector (111), the reference objective lens (106), the measuring objective lens (104) and the third lens (110) are arranged in a light path, the second inclination and the first eccentric distance of the reference objective lens (106) are adjusted through the detected Linkey interference fringes;
the auxiliary mirror (1071) is replaced by a reference mirror (1072), the reference mirror (1072) and the reference objective (106) being fixed on the same machine.
In particular, the replacement of the auxiliary mirror (1071) with a reference mirror (1072) comprises:
After the first inclination of the auxiliary mirror (1071) is adjusted, emitting light with a calibration mark to the auxiliary mirror (1071) through an auto-collimator (113), and recording the position of the returned calibration mark;
-replacing the auxiliary mirror (1071) with the reference mirror (1072) based on the position of the returned calibration mark, so that the position of the returned calibration mark is unchanged.
Specifically, when the light source (101), the first lens (102), the beam splitter (103), the auxiliary mirror (1071), the wafer (105) to be measured, the second lens (108), and the detector (111) are disposed in an optical path, the first axial distance of the auxiliary mirror (1071) is adjusted by michelson interference fringes detected by the detector (111), including:
When a single-mode laser light source (1012), the first lens (102), the beam splitter (103), the auxiliary reflector (1071), the wafer (105) to be tested, the second lens (108) and the detector (111) are arranged in a light path, a first axial distance of the auxiliary reflector (1071) is adjusted by a first adjustment step length through Michelson interference fringes detected by the detector (111);
The single-mode laser light source (1012) is replaced by a white light source (1011), and the Michelson interference fringes detected by the detector (111) are used for adjusting the first axial distance of the auxiliary reflector (1071) by a second adjustment step length, wherein the second adjustment step length is smaller than the first adjustment step length.
Specifically, when the light source (101), the first lens (102), the beam splitter (103), the auxiliary mirror (1071), the wafer (105) to be tested, the second lens (108), the detector (111), the reference objective lens (106), the measurement objective lens (104) and the third lens (110) are arranged in the light path, the second inclination and the first eccentric distance of the reference objective lens (106) are adjusted by the detected linn-nike interference fringes, including:
Acquiring a first entrance pupil position detected by the detector (111) when a surface light source (114), the measuring objective (104), the beam splitter (103), the second lens (108), a third lens (110) and the detector (111) are arranged in an optical path, wherein the measuring objective (104) is positioned on the optical path between the surface light source (114) and the beam splitter (103), and the third lens (110) is positioned on the optical path between the beam splitter (103) and the detector (111);
acquiring a second entrance pupil position detected by 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 arranged in an optical path, wherein the reference objective (106) is positioned on the optical path between the surface light source (114) and the beam splitter (103);
Adjusting the first eccentric position of the reference objective (106) based on the first and second entrance pupil positions such that the first and second entrance pupil positions 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 (105) to be measured, the second lens (108), the third lens (110) and the detector (111) are arranged in a light path, the second inclination and the first eccentric distance of the reference objective (106) are adjusted through the detected linrnike interference fringes.
Specifically, the method further comprises:
When light with a calibration mark emitted by an autocollimator (113) passes through the first lens (102), the beam splitter (103) and the reference objective lens (106) and is incident on the auxiliary mirror (1071), the second axial distance of the reference objective lens (106) is adjusted by the focusing definition of the calibration mark detected by the detector (111).
In particular, the replacement of the auxiliary mirror (1071) with the reference mirror (1072) comprises:
-replacing the auxiliary mirror (1071) with the reference mirror (1072), adjusting the second axial distance of the reference mirror (1072) with a third adjustment step based on the focal plane position of the reference objective (106);
And based on the Linked interference fringes detected by the detector (111), adjusting the second axial distance by a fourth adjustment step length to make the second axial distance equal to the first axial distance, wherein the fourth adjustment step length is smaller than the third adjustment step length.
In yet another aspect, an embodiment of the present application further provides a wafer inspection system, including:
the device comprises a light source (101), a beam splitter (103), a measuring objective lens (104), a reference objective lens (106) and a detector (111), wherein the beam splitter (103) is used for dividing light emitted by the light source (101) into a measuring light beam which propagates into a measuring light path where the measuring objective lens (104) is positioned and a reference light beam which propagates into a reference light path where the reference objective lens (106) is positioned;
A first lens (102) disposed on an optical path between the light source (101) and the beam splitter (103);
a second lens (108) and a third lens (110), both disposed on an optical path between the beam splitter (103) and the detector (111);
an auxiliary mirror (1071) provided on the light outgoing side of the reference objective lens (106) for reflecting the reference beam;
The wafer to be measured (105) is arranged on the light emitting side of the measuring objective lens (104) and is used for reflecting the measuring light beam;
The detector (111) is used for detecting interference fringes formed after the reflected measuring beam and the reflected reference beam pass through the beam splitter (103);
and the reference reflector (1072) and the reference objective lens (106) are fixed on the same mechanical part, and the reference reflector (1072) is used for replacing the auxiliary reflector (1071) after the detector (111) detects the interference fringes so as to detect the wafer (105) to be detected.
In particular, the system further comprises an autocollimator (113);
The autocollimator (113) is used for emitting light with a calibration mark to the auxiliary mirror (1071) after the interference fringes are formed and recording the position of the returned calibration mark so that the position of the returned calibration mark is unchanged after the auxiliary mirror (1071) is replaced by the reference mirror (1072).
Specifically, the light source (101) includes a single-mode laser light source (1012) and a white light source (1011);
the single-mode laser light source (1012) is used for adjusting the first axial distance of the auxiliary reflector (1071) by a first adjustment step length through Michelson interference fringes when laser is emitted;
the white light source (1011) is configured to adjust a first axial distance of the auxiliary mirror (1071) by a michelson interference fringe by a second adjustment step when emitting white light, the second adjustment step being smaller than the first adjustment step.
Specifically, the system further comprises:
An auxiliary beam splitter (109) disposed between the second lens (108) and the third lens (110);
-an auxiliary detector (112) for imaging light passing through the auxiliary beam splitter (109).
The embodiment of the application provides a wafer detection method and a wafer detection system, wherein when a light source (101), a first lens (102), a beam splitter (103), a wafer (105) to be detected, a second lens (108) and a detector (111) are arranged in a light path, a first light spot position detected by the detector (111) is acquired, and when the light source (101), the first lens (102), the beam splitter (103), an auxiliary reflector (1071), the second lens (108) and the detector (111) are arranged in the light path, a second light spot position detected by the detector (111) is acquired, the first inclination of the auxiliary reflector (1071) is adjusted based on the first light spot position and the second light spot position so that the first light spot position and the second light spot position coincide, when the light source (101), the first lens (102), the beam splitter (103), the auxiliary reflector (1071), the wafer (105) to be detected, the second lens (108) and the detector (111) are arranged in the light path, the interference fringes detected by the detector (111) are adjusted, the first axial distance of the auxiliary reflector (1071), the first lens (107), the second lens (108) and the auxiliary reflector (1071) are arranged, the first axial distance of the light source (101), the auxiliary reflector (1071) is adjusted, and the second axial distance of the auxiliary reflector (1071) is arranged between the first light spot position and the first lens (102) and the second light spot position is equal to the second light spot position When the measuring objective lens (104) and the third lens (110) are positioned in the light path, the second inclination and the first eccentric distance of the reference objective lens (106) are adjusted through the detected Linkey interference fringes, the auxiliary reflecting mirror (1071) is replaced by the reference reflecting mirror (1072), and the reference reflecting mirror (1072) and the reference objective lens (106) are fixed on the same mechanical piece. In a word, by additionally introducing an independent reflecting mirror, namely an auxiliary reflecting mirror, the allocation freedom degree of the auxiliary reflecting mirror is higher, the auxiliary reflecting mirror cannot be interfered by the reference objective lens, the axial position (namely the first axial distance) and the inclination degree (namely the first inclination) of the auxiliary reflecting mirror can be determined, and in addition, the posture of the reference objective lens can be adjusted in a follow-up manner, namely the second inclination and the first eccentric distance are determined, so that the auxiliary reflecting mirror can be replaced by the reference reflecting mirror after the auxiliary reflecting mirror has been used for helping to adjust interference fringes, and therefore decoupling of the adjustment dimensions of the reference objective lens and the reference reflecting mirror is realized, and the adjustment efficiency and accuracy are improved.
Drawings
In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are some embodiments of the application and that other drawings may be obtained from these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic flow chart of a wafer inspection method according to an embodiment of the present application;
Fig. 2 is a schematic diagram of an optical path for detecting a first light spot according to an embodiment of the present application;
FIG. 3 is a schematic diagram of an optical path for detecting a second light spot according to an embodiment of the present application;
FIG. 4 is a schematic view of an optical path of an adjustment auxiliary mirror according to an embodiment of the present application;
Fig. 5 shows a schematic optical path diagram of an adjustment reference objective according to an embodiment of the present application;
FIG. 6 is a schematic diagram of an optical path for detecting a first entrance pupil position according to an embodiment of the present application;
FIG. 7 is a schematic view of an optical path for detecting a second entrance pupil position according to an embodiment of the present application;
FIG. 8 is a schematic view of an optical path of another reference objective according to an embodiment of the present application;
FIG. 9 is a schematic view of an optical path for determining a first tilt of an auxiliary mirror according to an embodiment of the present application;
FIG. 10 is a schematic view of an optical path of another reference objective according to an embodiment of the present application;
FIG. 11 is a schematic diagram of a wafer inspection system according to an embodiment of the present application;
fig. 12 is a schematic diagram of another wafer inspection system according to an embodiment of the present application.
Detailed Description
In order that the above objects, features and advantages of the application will be readily understood, a more particular description of the application will be rendered by reference to the appended drawings.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, but the present application may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present application is not limited to the specific embodiments disclosed below.
In the following detailed description of the embodiments of the present application, reference is made to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration only, and in which is shown by way of illustration only, and in which the scope of the application is not limited for ease of illustration. In addition, the three-dimensional dimensions of length, width and depth should be included in actual fabrication.
As described in the background art, in the related art, in the reference optical path, the reference mirror is mounted on a mechanical part of the reference objective, and when the reference objective and the reference mirror are assembled and adjusted, the adjustment dimension of the reference objective and the adjustment dimension of the reference mirror are coupled, and the adjustment is required to be repeatedly performed to adjust the two to adjust the 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 the interference fringes are adjusted, so that the assembly and adjustment complexity is high, and the assembly and adjustment efficiency and the adjustment precision are lower.
Based on the above technical problems, the embodiment of the application provides a wafer detection method and a wafer detection system, by additionally introducing an independent reflector, namely an auxiliary reflector, the allocation freedom degree of the auxiliary reflector is higher, the auxiliary reflector cannot be interfered by a reference objective lens, the axial position (namely a first axial distance) and the inclination degree (namely a first inclination) of the auxiliary reflector can be determined, in addition, the posture of the reference objective lens, namely the second inclination and the first eccentric distance, can be adjusted in a subsequent manner, so that the auxiliary reflector can be replaced by the reference reflector after the interference fringes are adjusted, and the decoupling of the adjustment dimensions of the reference objective lens and the reference reflector is realized, and the adjustment efficiency and the adjustment accuracy are improved.
For easy understanding, a wafer inspection method and a wafer inspection system according to embodiments of the present application are described in detail below with reference to the accompanying drawings.
Referring to fig. 1, a flow chart of a wafer inspection method according to an embodiment of the application is shown, and the method may include the following steps.
S101, when the light source (101), the first lens (102), the beam splitter (103), the wafer (105) to be tested, the second lens (108) and the detector (111) are arranged in the light path, acquiring a first light spot position detected by the detector (111), 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 light path, acquiring a second light spot position detected by the detector (111).
Specifically, referring to fig. 2, an optical path schematic diagram for detecting a first light spot position according to an embodiment of the present application includes a light source (101), a first lens (102), a beam splitter (103), a wafer (105) to be tested, a second lens (108), and a detector (111).
Light emitted by the light source (101) is incident to the beam splitter (103) through the first lens (102), the beam splitter (103) has a beam splitting function, a part of light can be incident to the surface of the wafer (105) to be detected, the wafer (105) to be detected reflects the light, the reflected light is received by the detector (111) after passing through the beam splitter (103) and the second lens (108), the detector (111) can detect the light, and the light spot position is recorded as a first light spot position.
Specifically, referring to fig. 3, an optical path schematic diagram for detecting a second light spot position according to an embodiment of the present application is provided, where the optical path includes a light source (101), a first lens (102), a beam splitter (103), an auxiliary mirror (1071), a second lens (108), and a detector (111).
The beam splitter (103) can enable a part of light emitted by the light source (101) to transmit and enter the auxiliary reflector (1071), the auxiliary reflector (1071) reflects the light and then receives the light through the beam splitter (103) and the second lens (108) by the detector (111), and a light spot of the light in the detector (111) can be marked as a second light spot position.
S102, adjusting the first inclination of the auxiliary reflector (1071) based on the first light spot position and the second light spot position so that the first light spot position and the second light spot position are overlapped.
In particular, the first inclination is understood as the angle of the plane of the auxiliary mirror (1071) from the vertical plane, by adjusting the first inclination the spot position of the light in the detector (111) can be changed, i.e. an adjustment of the second spot position can be achieved.
Since the first light spot position can be understood as the light spot position in the measuring light path, the second light spot is located at the light spot position which can be understood as the light spot position in the reference light path, the second light spot position is changed by adjusting the first inclination of the auxiliary reflector (1071), and the first light spot position and the second light spot position are coincident, so that the measuring light path and the reference light path can be completely coincident, namely, at the moment, the inclination of the auxiliary reflector (1071) is consistent with the inclination of the wafer (105) to be measured, and particularly, when the plane of the wafer (105) to be measured is located in the horizontal plane, the mirror surface of the auxiliary reflector (1071) can be ensured to be located in the vertical plane, so that the interference fringes can be conveniently adjusted subsequently.
In the actual operation process, the first light spot position can be detected first, and then the second light spot position can be adjusted so that the two light spot positions are overlapped.
S103, when the light source (101), the first lens (102), the beam splitter (103), the auxiliary reflector (1071), the wafer (105) to be tested, the second lens (108) and the detector (111) are arranged in the light path, the first axial distance of the auxiliary reflector (1071) is adjusted through Michelson interference fringes detected by the detector (111).
Specifically, referring to fig. 4, a schematic diagram of an optical path for adjusting an auxiliary mirror according to an embodiment of the present application is provided, where the optical path includes a light source (101), a first lens (102), a beam splitter (103), an auxiliary mirror (1071), a wafer to be measured (105), a second lens (108), and a detector (111).
Specifically, after light emitted by the light source (101) passes through the beam splitter (103), a part of light is incident on the wafer (105) to be detected, the other part of light is incident on the auxiliary reflector (1071), after the two light beams are respectively reflected by the wafer (105) to be detected and the auxiliary reflector (1071), michelson interference occurs after passing through the beam splitter (103) and the second lens (108), michelson interference fringes are formed, and the Michelson interference fringes are detected by the detector (111).
In particular, the first axial distance of the auxiliary mirror (1071) can be adjusted in accordance with michelson interference fringes, which can be understood as the distance of the auxiliary mirror (1071) in the light propagation direction, i.e. in the optical axis direction. When the interference fringes show zero-order fringes, i.e. a bright or a dark fringe is observed in the detector (111), it is indicated that the auxiliary mirror (1071) has been moved into 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 105 to be measured and the beam splitter 103.
In one possible implementation, the light source (101) may include a single-mode laser light source (1012) and a white light source (1011), then S103, when the light source (101), the first lens (102), the beam splitter (103), the auxiliary mirror (1071), the wafer (105) to be tested, the second lens (108), and the detector (111) are configured to be located in the optical path, the first axial distance of the auxiliary mirror (1071) is adjusted by michelson interference fringes detected by the detector (111), and S1031-S1032 may specifically include.
S1031, when a single-mode laser light source (1012), a first lens (102), a beam splitter (103), an auxiliary reflector (1071), a wafer (105) to be tested, a second lens (108) and a detector (111) are arranged in an optical path, a first axial distance of the auxiliary reflector (1071) is adjusted by a first adjustment step length through Michelson interference fringes detected by the detector (111).
Specifically, in order to be able to adjust the first axial distance of the auxiliary mirror (1071) as quickly as possible, the adjustment can be performed with a single-mode laser light source (1012) and a white light source (1011). First, coarse adjustment, i.e. adjustment according to a first adjustment step, can be performed with the single-mode laser light source (1012), wherein the first adjustment step can be understood as the movement distance of the auxiliary mirror (1071) in the axial direction, which can be larger. Light emitted by a single-mode laser light source (1012) is divided into two beams of light through a first lens (102) and a beam splitter (103), and the two beams of light are subjected to Michelson interference to form interference fringes.
S1032, replacing the single-mode laser light source (1012) with a white light source (1011), and adjusting the first axial distance of the auxiliary reflector (1071) with a second adjustment step size through Michelson interference fringes detected by the detector (111).
Specifically, after the single-mode laser light source (1012) is utilized to call out the interference fringes, the single-mode laser light source (1012) can be replaced by a white light source (1011), the white light source (1011) emits white light, and the interference fringes are formed between the measuring beam and the reference beam, at this time, the interference fringes are more finely adjusted, namely, the interference fringes are adjusted according to a second adjustment step length, which can also be understood as a moving distance of the auxiliary mirror (1071) in the axial direction, and is obviously smaller than the first adjustment step length, as an example, the second adjustment step length can take a smaller value, namely, the moving distance during fine adjustment can be smaller, and when a bright fringe or a dark fringe appears in the detector (111), the first axial distance adjustment of the auxiliary mirror (1071) is indicated. In this way, the first axial distance of the auxiliary mirror (1071) can be determined as soon as possible, and the assembly efficiency can be improved.
S104, when the light source (101), the first lens (102), the beam splitter (103), the auxiliary reflector (1071), the wafer (105) to be tested, the second lens (108), the detector (111), the reference objective (106), the measuring objective (104) and the third lens (110) are arranged in the light path, the second inclination and the first eccentric distance of the reference objective (106) are adjusted through the detected Linkey interference fringes.
Specifically, referring to fig. 5, a schematic optical path diagram of an adjusting reference objective according to an embodiment of the present application is provided, and compared with the optical path shown in fig. 4, a reference objective (106), a measuring objective (104) and a third lens (110) are added in the optical path, so as to form Linnik interference.
Light emitted by the light source (101) is split by the beam splitter (103) to form a measuring beam and a reference beam, the measuring beam is incident on the wafer (105) to be measured by the measuring objective lens (104), the reference beam is incident on the auxiliary reflector (1071) by the reference objective lens (106), and then the measuring beam and the reference beam are subjected to Linnike interference to form Linnike interference fringes.
Since the positions of the measuring objective (104) and the wafer (105) to be measured remain unchanged all the time 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).
The second inclination may be understood as an angle of the plane of the reference objective (106) deviating from the vertical plane, and the first eccentric distance may be understood as a radial distance of the optical axis center of the reference objective (106) with respect to a preset axis, wherein the preset axis may be understood as a direction line of a reference beam generated by the light emitted by the light source (101) after passing through the beam splitter (103).
In short, by adjusting the tilt degree and the decentering distance of the reference objective (106), the position of the reference objective (106) and the position of the measuring objective (104) can be made symmetrical with respect to the beam splitter (103), at which time, in the detector (111), it can be observed that the interference fringes spread to only one bright fringe or only one dark fringe within the field of view, indicating that the reference objective (106) has been adjusted.
In one possible implementation, to improve the accuracy and efficiency of the adjustment of the reference objective (106), the decentration of the reference objective (106) may be first coarsely adjusted based on the entrance pupil position, and then the tilt may be adjusted by the interference fringes while the decentration 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 (105) to be tested, the second lens (108), the detector (111), the reference objective lens (106), the measurement objective lens (104) and the third lens (110) are disposed in the optical path, the second inclination and the first decentering distance of the reference objective lens (106) are adjusted by the detected linn interference fringes, and may specifically include S1041-S1044.
S1041, when 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) are arranged in the light path, acquiring a first entrance pupil position detected by the detector (111).
Specifically, referring to fig. 6, an optical path schematic diagram for detecting a first entrance pupil position according to an embodiment of the present application includes a surface light source (114), a measurement objective lens (104), a beam splitter (103), a second lens (108), a third lens (110), and a detector (111). The measuring objective (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).
Specifically, the third lens (110) may be located on a back focal plane of the measurement objective lens (104), light emitted by the surface light source (114) is received by the detector (111) after passing through the measurement objective lens (104), the beam splitter (103), the second lens (108) and the third lens (110), a light spot can be observed in the detector (111), the position of the light spot is a first entrance pupil position, and the first entrance pupil position can be understood as an entrance pupil position of the measurement objective lens (104).
S1042, when a surface light source (114), a reference objective lens (106), a beam splitter (103), a second lens (108), a third lens (110) and a detector (111) are arranged in the optical path, a second entrance pupil position detected by the detector (111) is acquired.
Specifically, referring to fig. 7, an optical path schematic diagram for detecting a second entrance pupil position according to an embodiment of the present application includes a surface light source (114), a reference objective lens (106), a beam splitter (103), a second lens (108), a third lens (110), and a detector (111), where the reference objective lens (106) is located on an optical path between the surface light source (114) and the beam splitter (103).
Specifically, light emitted by the surface light source (114) passes through the reference objective (106), the beam splitter (103), the second lens (108) and the third lens (110) and is received by the detector (111), a light spot is observed in the detector (111), the position of the light spot can be used as a second entrance pupil position, and the second entrance pupil position can be understood as the entrance pupil position of the reference objective (106).
S1043, adjusting a first eccentric position of the reference objective (106) based on the first and second entrance pupil positions so that the first and second entrance pupil positions coincide.
Specifically, the first eccentric position of the reference objective (106) may 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 position, at this time, the eccentric condition of the reference objective (106) coincides with the eccentric condition of the measurement objective (104), for example, the optical axes of both objective lenses coincide with the light transmission direction, that is, the eccentric of the reference objective (106) is adjusted by the entrance pupil position, so that the eccentric of the reference objective (106) may be quickly adjusted to be within a suitable range, at this time, it may be considered that coarse adjustment is performed on the eccentric of the reference objective (106), that is, the moving distance of the reference objective (106) in the vertical direction may be larger during the adjustment.
S1044, when the light source (101), the first lens (102), the beam splitter (103), the reference objective lens (106), the auxiliary reflector (1071), the measuring objective lens (104), the wafer (105) to be measured, the second lens (108), the third lens (110) and the detector (111) are arranged in the light path, the second inclination and the first eccentric distance of the reference objective lens (106) are adjusted through the detected Linkey interference fringes.
Specifically, referring to fig. 8, a schematic optical path diagram of still another reference objective lens for adjusting according to an embodiment of the present application is provided, in which an optical path includes a light source (101), a first lens (102), a beam splitter (103), a reference objective lens (106), an auxiliary mirror (1071), a measurement objective lens (104), a wafer to be measured (105), a second lens (108), a third lens (110), and a detector (111).
Specifically, light emitted by the light source (101) is divided into two beams, namely a measuring beam and a reference beam after passing through the first lens (102) and the beam splitter (103), the measuring beam is reflected by the wafer (105) to be measured after passing through the measuring objective lens (104), the measuring beam 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 reflector (1071) after passing through the reference objective lens (106), the measuring beam is received by the detector (111) after passing through the beam splitter (103), the second lens (108) and the third lens (110), and the Linnik interference occurs between the reference beam and the measuring beam, so that Linnik interference fringes are observed in the detector (111).
Specifically, by adjusting the second tilt of the reference objective (106), and the first decentration distance, the Linkey interference fringes are stretched in the detector (111) to only one bright fringe or only one dark fringe, indicating that the tilt and decentration of the reference objective (106) has been adjusted at this time. It is noted that the distance of the reference objective (106) moving in the vertical direction is smaller in the fine adjustment process when the eccentricity of the reference objective (106) is secondarily adjusted.
In a word, through this kind of coarse adjustment is carried out reference objective (106) eccentric based on the entrance pupil position, conveniently follow-up can be faster adjustment out Lin's interference fringe, and then can be quick adjust the slope of reference objective (106) and fine adjustment reference objective (106) eccentric based on Lin's interference fringe, improved light path adjustment efficiency.
S105, replacing the auxiliary mirror (1071) with the reference mirror (1072), wherein the reference mirror (1072) and the reference objective lens (106) are fixed on the same mechanical piece.
Specifically, since the reference mirror (1072) needs to be fixed on the same mechanical piece as the reference objective (106), after the first inclination and the first axial distance of the auxiliary mirror (1071) are determined, the reference mirror (1072) can be directly used to replace the auxiliary mirror (1071), and the reference mirror (1072) is mounted according to the first inclination and the first axial distance, so that the inclination degree and the axial position of the reference mirror (1072) are accurate.
In summary, in the related art, since coupling exists between the assembly dimensions of the reference objective lens and the reference mirror, interference fringes are not easy to adjust, the adjustment efficiency and accuracy are relatively low, and an independent mirror, namely the auxiliary mirror, is additionally introduced, so that the adjustment freedom degree of the auxiliary mirror is higher, the auxiliary mirror cannot be interfered by the reference objective lens, the axial position (namely the first axial distance) and the inclination degree (namely the first inclination) of the auxiliary mirror can be determined, and in addition, the posture of the reference objective lens can be adjusted in a follow-up manner, namely the second inclination and the first eccentric distance can be determined, so that the auxiliary mirror can be replaced by the reference mirror after the interference fringes can be adjusted, the decoupling of the adjustment dimensions of the reference objective lens and the reference mirror is realized, and the adjustment efficiency and accuracy are improved.
In one possible implementation, S105, the auxiliary mirror (1071) is replaced by a reference mirror (1072), which may be embodied as S1051-S1052.
S1051, after the first inclination of the auxiliary reflector (1071) is adjusted, the light with the calibration mark is emitted to the auxiliary reflector (1071) through the auto-collimator (113), and the position of the returned calibration mark is recorded.
Specifically, referring to fig. 9, a schematic optical path diagram for determining a first inclination of an auxiliary mirror according to an embodiment of the present application is shown, in which an auto-collimator (113) is added. After the first tilt of the auxiliary mirror (1071) is determined, the first tilt may be recorded. The autocollimator (113) can emit light with a calibration mark to the back surface of the auxiliary reflector (1071), for example, the light can be cross-shaped, and after the light is reflected by the auxiliary reflector (1071), the light can return to the autocollimator (113), and the autocollimator (113) can record the position of the returned calibration mark, for example, the position of the cross-shaped light.
S1052, based on the position of the returned calibration mark, the auxiliary mirror (1071) is replaced with the reference mirror (1072) so that the position of the returned calibration mark is unchanged.
Specifically, after the auxiliary mirror (1071) is replaced by the reference mirror (1072), in order to confirm that the inclination degree of the reference mirror (1072) reaches the first inclination, light emitted by the autocollimator (113) can be made to enter the reference mirror (1072) and the position of the returned calibration mark is recorded, and the position of the calibration mark is overlapped with the position recorded before by adjusting the inclination degree of the reference mirror (1072), namely, the position of the returned calibration mark is unchanged, so that the inclination degree of the reference mirror (1072) reaches the first inclination degree, and the accuracy of the inclination of the reference mirror (1072) is ensured.
In this way, the first inclination of the auxiliary mirror (1071) is recorded by introducing the autocollimator (113), so that the first inclination of the replaced reference mirror (1072) can be obtained when the mirror replacement is performed, and the assembly precision of the reference mirror (1072) is improved.
In one possible implementation, the second axial distance of the reference objective (106) may also be adjusted. That is, when light having a calibration mark emitted from the collimator (113) is incident on the auxiliary mirror (1071) through the first lens (102), the beam splitter (103), and the reference objective lens (106), the second axial distance of the reference objective lens (106) is adjusted by the focus sharpness of the calibration mark detected by the detector (111).
In particular, the second axial distance can be understood as the distance of the reference objective (106) in the direction of propagation of the light, i.e. in the direction of the optical axis. Referring to fig. 10, a schematic diagram of an optical path of another reference objective lens for adjustment according to an embodiment of the present application may be provided, in which an auto-collimator (113) is used to replace the light source (101), light with a calibration mark is incident on the auxiliary mirror (1071), reflected and enters the detector (111), the calibration mark may be recorded in the detector (111), the second axial distance of the reference objective lens (106) may be adjusted, the focal resolution of the calibration mark may be changed, and when the focal resolution reaches a preset requirement, it indicates that the position of the reference objective lens has been adjusted, and at this time, the auxiliary mirror (1071) is located on the focal plane of the reference objective lens (106), thereby implementing adjustment of the axial position of the reference objective lens (106). It will be appreciated that at this point the distance between the reference objective (106) and the beam splitter (103) and the distance between the measurement objective (104) and the beam splitter (103) are equal. Wherein the adjustment of the second axial distance may be performed before the second inclination and the first eccentric distance.
In one possible implementation, the auxiliary mirror (1071) is replaced by a reference mirror (1072), and specifically, the auxiliary mirror (1071) is replaced by a reference mirror (1072), 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 lens (106), and the second axial distance is adjusted by a fourth adjustment step based on the Linnik interference fringes detected by the detector (111) 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.
In particular, the second axial distance may be understood as the distance of the reference mirror (1072) in the direction of propagation of the light, i.e. in the direction of the optical axis. For faster adjustment of the axial distance of the reference mirror (1072), the reference mirror (1072) may be first coarsely adjusted based on the focal plane position of the reference objective (106), i.e. the reference objective (106) is adjusted according to a third adjustment step, which may be understood as the distance of movement of the reference objective (106) in the axial direction, which may be larger, as an example, so that the approximate position of the reference mirror (1072) in the axial direction may be quickly determined. As an example, it is sufficient to adjust the distance between the reference mirror (1072) and the reference objective (106) to be the focal length. Further, since the linn-nice interference occurs between the measuring beam and the reference beam, the detector (111) detects the linn-nice interference fringe, and the second axial distance is further finely adjusted, i.e. according to a fourth adjustment step, the fourth adjustment step can also be understood as a moving distance of the reference objective lens (106) in the axial direction, and it is worth noting that the fourth adjustment step is smaller than the third adjustment step, and as an example, the fourth adjustment step can take a smaller value, i.e. the moving distance during fine adjustment can be smaller, so that only one bright fringe or only one dark fringe in the detector (111) indicates that the second axial distance is equal to the first axial distance at this time, and the position of the reference mirror (1072) is completely coincident with the original auxiliary mirror (1071). In this way, by adjusting both coarse and fine adjustments, assembly efficiency can be improved such that the reference mirror (1072) is located at a proper axial position.
Based on the above wafer inspection method, the embodiment of the present application further provides a wafer inspection system, and referring to fig. 11, a schematic diagram of the wafer inspection system provided in the embodiment of the present application may include a light source (101), a first lens (102), a beam splitter (103), a measurement objective lens (104), a wafer to be inspected (105), a reference objective lens (106), an auxiliary mirror (1071), a reference mirror (1072), a second lens (108), a third lens (110), and a detector (111).
The beam splitter (103) is used for dividing light emitted by the light source (101) into a measuring light beam which propagates into a measuring light path where the measuring objective lens (104) is located and a reference light beam which propagates into a reference light path where the reference objective lens (106) is located, the first lens (102) is arranged on the light path between the light source (101) and the beam splitter (103), and the second lens (108) and the third lens (110) are both arranged on the light path between the beam splitter (103) and the detector (111).
The auxiliary reflector (1071) is arranged on the light-emitting side of the reference objective lens (106) and is used for reflecting the reference light beam so as to form interference fringes, and the wafer (105) to be measured is arranged on the light-emitting side of the measuring objective lens (104) and is used for reflecting the measuring light beam so as to form interference fringes.
The detector (111) is used for detecting interference fringes formed by the reflected measuring light beam and the reflected reference light beam after passing through the beam splitter (103), and the reference reflector (1072) and the reference objective lens (106) are fixed on the same mechanical piece and used for replacing the auxiliary reflector (1071) after the detector (111) detects the interference fringes so as to detect the wafer (105) to be detected.
In one possible implementation, the wafer inspection system may further include an auto-collimator (113), the auto-collimator (113) configured to emit light with the calibration marks to the auxiliary mirror (1071) after forming the interference fringes, and record the positions of the returned calibration marks such that the positions of the returned calibration marks are unchanged after replacing the auxiliary mirror (1071) with the reference mirror (1072).
In one possible implementation, the light source (101) may include a single-mode laser light source (1012) and a white light source (1011), the single-mode laser light source (1012) being configured to adjust the first axial distance of the auxiliary mirror (1071) by a michelson interference fringe by a first adjustment step when lasing, the white light source (1011) being configured to adjust the first axial distance of the auxiliary mirror (1071) by a michelson interference fringe when lasing by a second adjustment step when white light is emitted, the second adjustment step being smaller than the first adjustment step.
In one possible implementation, the wafer inspection system may further include an auxiliary beam splitter (109) and an auxiliary detector (112), and referring to fig. 12, a schematic diagram of another wafer inspection system according to an embodiment of the present application is shown.
An auxiliary beam splitter (109) is arranged between the second lens (108) and the third lens (110), an auxiliary detector (112) for imaging the light passing through the auxiliary beam splitter (109). That is, the interference fringes can be detected by the auxiliary detector (112), not only depending on one detector (111), thereby improving the assembly efficiency.
The embodiment of the application provides a wafer detection system, which comprises a light source, a beam splitter, a measuring objective lens, a reference objective lens, a detector, an auxiliary reflector, a wafer to be detected and a reference reflector, wherein the beam splitter is used for dividing light emitted by the light source into measuring light beams which propagate in a measuring light path where the measuring objective lens is located and reference light beams which propagate in a reference light path where the reference objective lens is located, the auxiliary reflector is arranged on the light emitting side of the reference objective lens and used for reflecting the reference light beams, the wafer to be detected is arranged on the light emitting side of the measuring objective lens and used for reflecting the measuring light beams, the detector is used for detecting interference fringes formed by the reflected measuring light beams and the reflected reference light beams after passing through the beam splitter, and the reference reflector and the reference objective lens are fixed on the same mechanical piece and used for replacing the auxiliary reflector after the interference fringes are detected by the detector so as to detect the wafer to be detected. In a word, by additionally introducing an independent reflecting mirror, namely an auxiliary reflecting mirror, the allocation freedom degree of the auxiliary reflecting mirror is higher, the auxiliary reflecting mirror cannot be interfered by the reference objective lens, the axial position (namely the first axial distance) and the inclination degree (namely the first inclination) of the auxiliary reflecting mirror can be determined, and in addition, the posture of the reference objective lens can be adjusted in a follow-up manner, namely the second inclination and the first eccentric distance are determined, so that the auxiliary reflecting mirror can be replaced by the reference reflecting mirror after the auxiliary reflecting mirror has been used for helping to adjust interference fringes, and therefore decoupling of the adjustment dimensions of the reference objective lens and the reference reflecting mirror is realized, and the adjustment efficiency and accuracy are improved.
It will be appreciated by those of ordinary skill in the art that all or part of the steps of implementing the above-described method embodiments may be implemented by program instruction hardware, and the above-described program may be stored in a computer readable storage medium, where the program performs the steps including the above-described method embodiments when executed, and the above-described storage medium may be at least one of a Read-only Memory (ROM), a RAM, a magnetic disk, or an optical disk, etc. various media in which program codes may be stored.
In this specification, each embodiment is described in a progressive manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments. In particular, for system embodiments, since they are substantially similar to method embodiments, the description is relatively simple, with reference to the description of method embodiments in part.
The foregoing is merely a preferred embodiment of the present application, and the present application has been disclosed in the above description of the preferred embodiment, but is not limited thereto. Any person skilled in the art can make many possible variations and modifications to the technical solution of the present application or modifications to equivalent embodiments using the methods and technical contents disclosed above, without departing from the scope of the technical solution of the present application. Therefore, any simple modification, equivalent variation and modification of the above embodiments according to the technical substance of the present application still fall within the scope of the technical solution of the present application.
Claims (10)
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