Focusing and leveling sensor and ambient light noise elimination method
By designing the modulation slit plate and the detection slit plate in the focus leveling sensor, and using the detector to receive ambient light and signal light respectively, the measurement error problem under the influence of ambient light is solved, and high-precision defocus detection is achieved.
Patent Information
- Application Number
- CN202411990385.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-03-18
AI Technical Summary
The existing focus leveling sensors are easily affected by ambient light when detecting the defocus amount, resulting in an increase in measurement error and unstable ambient light intensity, making it difficult to effectively reduce the error.
A focus leveling sensor is designed, including a light source, a modulation slit plate, a projection lens assembly, a detection lens assembly, a detection slit plate and a detector. By modulating the design of the slit plate and the detection slit plate, the detector receives ambient light and signal light respectively, and ambient light noise is eliminated by subtracting the light intensity measured by the detector that only receives ambient light.
Effectively eliminate ambient light noise, improve the accuracy of system defocus detection, and reduce measurement errors.
Smart Images
Figure CN119644686A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of semiconductor processing and manufacturing technology, and in particular to a focusing and leveling sensor and an ambient light noise elimination method. Background Art
[0002] Photolithography plays an important role in the mass production of integrated circuits. With the rapid development of the integrated circuit industry, the requirements for the performance of photolithography machines are getting higher and higher. With the development of related technologies, the exposure wavelength of photolithography technology has gradually decreased, and the numerical aperture of the projection lens has also gradually increased. The smaller the exposure wavelength and the larger the numerical aperture, the higher the photolithography resolution, but at the same time it will cause the depth of focus to become smaller.
[0003] In exposure equipment, a focusing and leveling system is required to control the wafer surface within the focal depth range. As the focal depth decreases, the accuracy requirements for the focusing and leveling sensors become higher and higher.
[0004] Existing focusing and leveling sensors introduce ambient light when detecting defocus, but the introduction of ambient light will increase the defocus detection error, and the intensity of ambient light is not constant. Therefore, effectively detecting the intensity of ambient light incident on the detector target surface is extremely important to reduce the measurement error of the focusing and leveling sensor.
[0005] Based on this, a new technical solution is needed. Summary of the invention
[0006] In view of this, an embodiment of the present specification provides a focusing and leveling sensor and an ambient light noise elimination method.
[0007] The embodiments of this specification provide the following technical solutions:
[0008] The embodiment of the present specification provides a focusing and leveling sensor, which can eliminate ambient light noise, including a light source, a modulating slit plate, a projection lens assembly, a detection lens assembly, a detection slit plate and a detector; the light source emits parallel light to the modulating slit plate, and the parallel light passes through the slit of the modulating slit plate to form a slit image; the projection lens assembly receives the formed slit image, and the projection lens assembly projects the slit image to the surface of a wafer; the detection lens assembly detects the slit image on the surface of the wafer, and the detection lens assembly transmits the detected slit image to the detection slit plate; a part of the slits of the detection slit plate passes the transmitted slit image as signal light; the slit of the detection slit plate passes ambient light; the slits of the detection slit plate and the detector are correspondingly arranged; the detectors corresponding to a part of the slits of the detection slit plate respectively receive ambient light and signal light, and the detectors corresponding to another part of the slits of the detection slit plate respectively receive ambient light.
[0009] Preferably, the slits on the modulation slit plate are arranged in one-to-one correspondence with a part of the slits on the detection slit plate; and the slits on the detection slit plate are arranged in one-to-one correspondence with the detectors.
[0010] Preferably, on the detection slit plate, the slit that transmits the ambient light and the signal light is arranged adjacent to the slit that transmits only the ambient light.
[0011] Preferably, on the detection slit plate, slits that transmit the ambient light and the signal light are arranged around the slit that transmits only the ambient light.
[0012] Preferably, on the detection slit plate, slits that transmit only ambient light are arranged around slits that transmit ambient light and signal light.
[0013] Preferably, on the detection slit plate, slits that transmit the ambient light and the signal light and slits that transmit only the ambient light are alternately arranged.
[0014] Preferably, the slits on the detection slit plate are arranged in a spaced array.
[0015] Preferably, a rotating reflector is installed in the detection lens assembly; the rotating reflector is used to modulate the position of the transmitted slit image relative to a part of the slit of the detection slit plate, and detect the defocus amount of each slit image corresponding to the position according to the change of the detector light intensity.
[0016] Preferably, the sensor further comprises a focusing lens; the focusing lens focuses the ambient light and the signal light passing through the detection slit plate.
[0017] The embodiment of this specification also provides a method for eliminating ambient light noise, using a focusing and leveling sensor, comprising the following steps:
[0018] Optical path transmission steps: a light source emits parallel light to a modulated slit plate, and the parallel light passes through the slit of the modulated slit plate to form a slit image; a projection lens assembly receives the formed slit image, and the projection lens assembly projects the slit image to the wafer surface; a detection lens assembly detects the slit image on the wafer surface, and the detection lens assembly transmits the detected slit image to the detection slit plate; a part of the slits of the detection slit plate passes the transmitted slit image as signal light; the slit of the detection slit plate passes ambient light; the slits of the detection slit plate and the detector are correspondingly arranged; the detectors corresponding to a part of the slits of the detection slit plate respectively receive ambient light and signal light, and the detectors corresponding to another part of the slits of the detection slit plate respectively receive ambient light; a processing step: the light intensity measured by the detector receiving ambient light and signal light is subtracted from the light intensity measured by the detector receiving only ambient light to eliminate ambient light noise.
[0019] Compared with the prior art, the at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects:
[0020] The present invention designs different styles of modulation slit plates and detection slit plates. The number of slits on the modulation slit plate is less than that on the detection slit plate. Each slit on the detection slit plate corresponds to a detector for light intensity detection. The detector without signal light is used for ambient light detection, and the detector with signal light is used for defocus detection at the corresponding position. The detectors for ambient light detection and the detectors for defocus detection are placed alternately. It can be considered that the ambient light intensity reaching the ambient light detection detector and the defocus detection detector is consistent, which can most accurately filter out the influence of ambient light and effectively improve the system defocus detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0022] Figure 1 This is a schematic diagram of the structure of a focusing and leveling sensor based on a rotating reflector in this application;
[0023] Figure 2 This is a schematic diagram of the slit distribution of the detection slit plate in this application;
[0024] Figure 3 This is a schematic diagram of the slit distribution of the modulated slit plate in this application;
[0025] Figure 4 This is a schematic diagram of the distribution of the slit image array on the wafer surface in this application;
[0026] Figure 5 A schematic diagram of a photodetector for eliminating the influence of ambient light noise in this application;
[0027] Figure 6 Schematic diagram of the slit distribution of the modulated slit plate in another embodiment of the present application.
[0028] Figure numerals: 1, light source; 2, modulation slit plate; 3, projection lens front group; 4, projection reflector; 5, projection lens rear group; 6, wafer; 7, detection lens front group; 8, scanning reflector; 9, detection lens rear group; 10, detection slit plate; 11, focusing lens; 12, array detector; 1001, one slit; 1002, another slit; 1201, one detector; 1202, another detector; 13, ambient light in one slit; 14, ambient light in another slit; 15, signal light in another slit. DETAILED DESCRIPTION
[0029] The embodiments of the present application are described in detail below with reference to the accompanying drawings.
[0030] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.
[0031] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspect described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.
[0032] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The drawings only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.
[0033] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the examples can be practiced without these specific details.
[0034] In view of this, the applicant has conducted in-depth research and improvement on the focus and leveling sensor and the defocus detection, and found that: the focus and leveling sensor based on the rotating reflector mainly includes a light source 1 ( Figure 1 ), modulation slit plate 2 ( Figure 1 ), imaging lens, rotating mirror, detection slit plate 10 ( Figure 1 The slit image is modulated by rotating the reflector to achieve high-precision defocus detection. Combined with multi-point defocus, wafer 6 ( Figure 1(shown in Figure 2) deflection angle detection (Rx, Ry). Rx is the rotation in the X direction, and Ry is the rotation in the Y direction, which are specifically two of the six degrees of freedom of an object. However, in the focus and leveling detection system, the ambient light will directly change the light intensity detected by the system detector, resulting in errors in the defocus detection, that is, the introduction of ambient light will increase the defocus detection error, and the intensity of the ambient light does not remain constant. Therefore, it is extremely important to effectively detect the intensity of ambient light incident on the detector target surface to reduce the measurement error of the focus and leveling sensor.
[0035] Based on this, the technical solutions provided by the embodiments of the present application are described below in conjunction with the accompanying drawings.
[0036] An embodiment of this specification proposes a focusing and leveling sensor, such as Figure 1 As shown, it includes a light source 1, a modulation slit plate 2, a projection lens assembly, a detection lens assembly, a detection slit plate 10 and a detector.
[0037] The light source 1 emits parallel light to the modulating slit plate 2, and the parallel light passes through the slit of the modulating slit plate 2 to form a slit image; the projection lens assembly receives the formed slit image, and the projection lens assembly projects the slit image to the surface of the wafer 6; the detection lens assembly detects the slit image on the surface of the wafer 6, and the detection lens assembly transmits the detected slit image to the detection slit plate 10; a part of the slits of the detection slit plate 10 transmits the transmitted slit image as signal light; the slit of the detection slit plate 10 transmits ambient light; the slits and detectors of the detection slit plate 10 are set correspondingly; the detectors corresponding to a part of the slits of the detection slit plate 10 respectively receive ambient light and signal light, and the detectors corresponding to another part of the slits of the detection slit plate 10 respectively receive ambient light. The light intensity measured by the detector receiving ambient light and signal light is subtracted from the light intensity measured by the detector receiving only ambient light, so as to filter out the influence of ambient light and effectively improve the accuracy of the system defocus detection.
[0038] In one embodiment, the slits on the modulation slit plate 2 are arranged in one-to-one correspondence with a part of the slits on the detection slit plate 10; the slits on the detection slit plate 10 are arranged in one-to-one correspondence with the detectors. There are multiple slits on the modulation slit plate 2, multiple slits on the detection slit plate 10, and multiple detectors, and the slits on the detection slit plate 10 are more than the slits on the modulation slit plate 2. The present application realizes the monitoring of ambient light by adopting different styles of modulation slit plates 2 and detection slit plates 10. The number of slits on the modulation slit plate 2 is less than the number of slits on the detection slit plate 10, and a detector is installed behind the slit of each detection slit plate 10. The detector without slit images on the detection slits is used to detect ambient light in real time.
[0039] In one embodiment, on the detection slit plate 10, the slit that transmits ambient light and signal light is arranged adjacent to the slit that only transmits ambient light, and then the detector for ambient light detection and the detector for defocus detection are arranged adjacent to each other. It can be considered that the ambient light intensity reaching the ambient light detection detector and the defocus detection detector is consistent, thereby improving the accuracy of filtering out ambient light and further improving the system defocus detection accuracy.
[0040] In one embodiment, the slits that transmit ambient light and signal light are arranged around the slit that transmits only ambient light on the detection slit plate 10. The defocus detection detector can detect the deflection angle of the wafer 6 by detecting the defocus amounts at multiple positions.
[0041] In one embodiment, the slits on the detection slit plate 10 are arranged in an array according to intervals. The slit positions of the detection slit plate 10 corresponding to the modulation slit plate 2 and the positions without slits are arranged in an array according to the detection slit plate 10. A plurality of detector arrays are arranged as array detectors 12. Alternatively, it can be said that both the modulation slit plate 2 and the detection slit plate 10 are slit arrays arranged at certain intervals. Figure 2 As shown, the slit distribution of the slit plate 10 is detected, and the slit distribution is 5×7, with a total of 35 slits. Figure 3 As shown, the distribution of slits on the modulation slit plate 2 is shown. The solid line part is the slit corresponding to the detection slit plate 10 and has light transmission capability. The dotted line part is the slit position corresponding to the detection slit plate 10 but no slit is set, that is, the dotted line part has no light transmission capability. The number of slits on the modulation slit plate 2 is 29. The slit images on the detection slit plate 10 correspond one-to-one to the detectors on the array detector 12. Therefore, there are 6 detectors on the array detector 12 without detection light incident, which are used for ambient light intensity detection. There are 29 detectors on the array detector 12 for detecting the defocus amount on the surface of the wafer 6.
[0042] In one embodiment, the projection lens assembly includes a projection lens front group 3, a projection lens rear group 5, and a projection reflector 4. The array slit image on the modulation slit plate 2 is imaged on the wafer 6 after passing through the projection lens front group 3, the projection reflector 4, and the projection lens rear group 5. The array slit image formed on the wafer 6 is as shown in FIG. Figure 4 As shown in FIG. 1 , the number of slit images on the surface of wafer 6 is 29.
[0043] In one embodiment, a rotating reflector is installed in the detection lens assembly; the rotating reflector is used to modulate the position of the transmitted slit image relative to a part of the slit of the detection slit plate 10, and the defocus amount detection of each slit image corresponding to the position is performed according to the change of the detector light intensity. The detection lens assembly includes a detection lens front group 7, a detection lens rear group 9 and a scanning reflector 8, and the scanning reflector 8 can be a rotating reflector. The array slit image on the wafer 6 is imaged on the surface of the detection slit plate 10 after passing through the detection lens front group 7, the scanning reflector 8 and the detection lens rear group 9. A rotating reflector is installed in the detection lens, which is used to modulate the position of the slit image array relative to the detection slit plate 10. The defocus amount detection of each slit image corresponding to the position can be realized according to the change of the detector light intensity, and the defocus amount of multiple positions can be combined to realize the detection of the deflection angle of the wafer 6.
[0044] In one embodiment, the sensor further includes a focusing lens 11; the focusing lens 11 may be a focusing lens. The focusing lens 11 focuses the ambient light and signal light passing through the detection slit plate 10, and then the detector receives the focused ambient light and signal light, that is, the detector corresponding to a part of the slits of the detection slit plate 10 receives the focused ambient light and signal light, and the detector corresponding to another part of the slits of the detection slit plate 10 receives the focused ambient light. That is, the array slit image on the surface of the detection slit plate 10 passes through the slits on the surface of the detection slit plate 10, and then passes through the focusing lens 11 and is received by the array detector 12.
[0045] The light source 1 emits parallel light that is incident on the modulation slit plate 2, which is a slit array arranged at a certain interval. The projection lens projects the slit array image onto the surface of the wafer 6. The slit image on the surface of the wafer 6 is imaged on the detection slit plate 10 after passing through the detection lens. The detection slit plate 10 is a slit array arranged at a certain interval, and the number of slits is greater than the number of slits in the modulation slit plate 2. There are a focusing lens and an array detector 12 behind the detection slit plate 10. The detection surface on the array detector 12 corresponds one-to-one to the slits on the detection slit plate 10, and is used to detect the intensity of light passing through each slit on the detection slit plate 10.
[0046] The present application is for a focusing and leveling sensor, which can effectively filter out the influence of ambient light on the detection results. By designing different styles of modulation slit plates 2 and detection slit plates 10, detectors for ambient light detection and detectors for defocus detection are alternately distributed, thereby effectively filtering out the influence of ambient light on the detection accuracy of the focusing and leveling sensor.
[0047] Another embodiment of the present invention further provides a focusing and leveling sensor, such as Figure 6 As shown, the difference from the above embodiment is that, on the detection slit plate 10, the slits that only transmit the ambient light are arranged around the slits that transmit the ambient light and the signal light.
[0048] In one embodiment, on the detection slit plate 10, slits that transmit ambient light and signal light and slits that transmit only ambient light are alternately arranged. Figure 6 The slit distribution on the modulation slit plate 2 shown in the figure has 17 slits, which is about half the number of the detection slit plate 10. Each detector for detecting signal light is surrounded by four detectors for monitoring ambient light, which can effectively filter out the influence of ambient light on the detection signal.
[0049] The embodiment of the present specification also provides a method for eliminating ambient light noise, which uses the focusing and leveling sensor described in any of the above embodiments, and includes the following steps:
[0050] The light path transmission steps are as follows: the light source 1 emits parallel light to the modulating slit plate 2, and the parallel light passes through the slit of the modulating slit plate 2 to form a slit image; the projection lens assembly receives the formed slit image, and the projection lens assembly projects the slit image to the surface of the wafer 6; the detection lens assembly detects the slit image on the surface of the wafer 6, and the detection lens assembly transmits the detected slit image to the detection slit plate 10; a part of the slits of the detection slit plate 10 passes the transmitted slit image as signal light; the slit of the detection slit plate 10 passes ambient light; the slits and detectors of the detection slit plate 10 are correspondingly arranged; the detectors corresponding to a part of the slits of the detection slit plate 10 respectively receive ambient light and signal light, and the detectors corresponding to another part of the slits of the detection slit plate 10 respectively receive ambient light.
[0051] Processing steps: The light intensity measured by the detector receiving the ambient light and the signal light is subtracted from the light intensity measured by the detector receiving only the ambient light to eliminate the ambient light noise.
[0052] like Figure 5 As shown, it is a photoelectric detector for filtering out the influence of ambient light. By detecting one slit 1001 and the other slit 1002 of two adjacent slits on the slit plate 10, the light of one slit 1001 and the other slit 1002 are detected by one detector 1201 and the other detector 1202 in the corresponding adjacent detectors on the array detector 12 in turn. One detector 1201 only detects the ambient light 13 in one slit, and the other detector 1202 detects the ambient light 14 in the other slit and the signal light 15 in the other slit. Since one slit 1001 and the other slit 1002 are two adjacent slits on the detection slit plate 10, and the distance is very close, it can be considered that the intensity of the ambient light 13 in one slit and the intensity of the ambient light 14 in the other slit are equal. Therefore, the light intensity measured by the other detector 1202 minus the light intensity measured by the one detector 1201 can filter out the influence of ambient light noise, and achieve high-precision defocus detection.
[0053] In this specification, the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the embodiments described later, the description is relatively simple, and the relevant parts can be referred to the partial description of the previous embodiments.
[0054] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.
Claims
1. A focusing and leveling sensor capable of eliminating ambient light noise, characterized in that: It includes a light source, a modulation slit plate, a projection lens assembly, a detection lens assembly, a detection slit plate and a detector; The light source emits parallel light to the modulating slit plate, and the parallel light passes through the slit of the modulating slit plate to form a slit image; The projection lens assembly receives the formed slit image, and the projection lens assembly projects the slit image onto the wafer surface; The detection lens assembly detects the slit image on the surface of the wafer, and the detection lens assembly transmits the detected slit image to the detection slit plate; A part of the slits of the detection slit plate transmits the slit image as signal light; The slit of the detection slit plate transmits ambient light; The slits of the detection slit plate and the detectors are arranged correspondingly; the detectors corresponding to a part of the slits of the detection slit plate respectively receive ambient light and signal light, and the detectors corresponding to another part of the slits of the detection slit plate respectively receive ambient light.
2. The focusing and leveling sensor according to claim 1, characterized in that: The slits on the modulation slit plate are arranged in one-to-one correspondence with a portion of the slits on the detection slit plate; The slits on the detection slit plate are arranged in one-to-one correspondence with the detectors.
3. The focusing and leveling sensor according to claim 2, characterized in that: On the detection slit plate, the slit that transmits the ambient light and the signal light is arranged adjacent to the slit that transmits only the ambient light.
4. The focusing and leveling sensor according to claim 3, characterized in that: On the detection slit plate, the slits that transmit the ambient light and the signal light are arranged around the slit that transmits only the ambient light.
5. The focusing and leveling sensor according to claim 3, characterized in that: On the detection slit plate, the slits that transmit only the ambient light are arranged around the slits that transmit the ambient light and the signal light.
6. The focusing and leveling sensor according to claim 5, characterized in that: On the detection slit plate, slits that transmit ambient light and signal light and slits that transmit only ambient light are arranged alternately and at intervals.
7. The focusing and leveling sensor according to claim 3, characterized in that: The slits on the detection slit plate are arranged in an interval array.
8. The focusing and leveling sensor according to claim 2, characterized in that: A rotating reflector is installed in the detection lens assembly; The rotating reflector is used to modulate the position of the transmitted slit image relative to a portion of the slits of the detection slit plate, and to detect the defocus amount of each corresponding position of the slit image according to the change of the detector light intensity.
9. The focusing and leveling sensor according to claim 1, characterized in that: The sensor also includes a focusing lens; The focusing lens focuses the ambient light and the signal light that pass through the detection slit plate.
10. A method for eliminating ambient light noise, characterized in that: Using the focusing and leveling sensor described in any one of claims 1 to 9 comprises the following steps: Optical path transmission step: the light source emits parallel light to the modulating slit plate, and the parallel light passes through the slit of the modulating slit plate to form a slit image; the projection lens assembly receives the formed slit image, and the projection lens assembly projects the slit image to the wafer surface; the detection lens assembly detects the slit image on the wafer surface, and the detection lens assembly transmits the detected slit image to the detection slit plate; a part of the slits of the detection slit plate transmits the transmitted slit image as signal light; the slit of the detection slit plate transmits ambient light; the slit of the detection slit plate and the detector are correspondingly arranged; the detectors corresponding to a part of the slits of the detection slit plate respectively receive ambient light and signal light, and the detectors corresponding to another part of the slits of the detection slit plate respectively receive ambient light; Processing steps: The light intensity measured by the detector receiving the ambient light and the signal light is subtracted from the light intensity measured by the detector receiving only the ambient light to eliminate the ambient light noise.