A catadioptric laser interferometry endpoint detection system

Abstract

This invention discloses a catadioptric laser interferometry endpoint detection system, relating to the field of semiconductor technology. The system includes a first fixed lens group, a second fixed lens group, and a third fixed lens group arranged sequentially along the optical path. A first reflector is movably positioned around the first fixed lens group along the optical path, and a second reflector is positioned between the third fixed lens group and the wafer. Both the first and second reflectors have an arc-shaped structure, and the second reflector has a blocking ratio of 0.04-0.08. A light source includes a light-emitting element and a microlens. The light source is positioned on one side of the optical path to emit illumination light. The microlens divides the illumination light into multiple sub-beams, which sequentially pass through the first, second, and third fixed lens groups and are reflected by the second and first reflectors before being superimposed onto the wafer, thus spreading the contaminants from the light source onto the target surface. This invention enables high-magnification, long-working-distance, high-definition imaging.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a system for detecting the endpoint of catadioptric laser interferometry. Background Technology

[0002] In semiconductor manufacturing, dry etching is one of the key processes for forming the microstructure of devices. Its precision directly determines the critical dimensions and morphological quality of key components such as transistors, capacitors, and interconnects. As integrated circuit technology nodes continue to shrink to the nanometer and even sub-nanometer level, the requirements for controlling various parameters in the etching process are becoming increasingly stringent. Therefore, real-time and accurate determination of the etching endpoint is of paramount importance in the process flow. Among these, precise control of etching depth is particularly critical, as it not only affects the electrical performance of devices but also directly relates to the isolation effect between devices, gate integrity, and the reliability of multilayer interconnect structures. Any deviation in etching depth, whether over-etching or under-etching, can lead to device performance degradation, reduced yield, and even subsequent failures in subsequent processes.

[0003] In existing technologies, the limited internal space of the detection device affects the arrangement of the lens group, thus impacting the working distance of the detection device. Simultaneously, contamination at the light source can affect the imaging effect and detection results of the imaging unit. Firstly, with the increasing integration of semiconductor devices, the installation space inside the reaction chamber and the detection module is severely limited. This spatial constraint significantly affects the rational arrangement and optimization of the lens group in the detection optical system, making it difficult for the system to achieve an ideal long working distance. An excessively short working distance not only increases the risk of optical components being contaminated by process byproducts but also limits its applicability in certain complex reaction chambers. Secondly, during long-term process operations, the light source window of the detection device inevitably accumulates polymer or other byproduct contaminants generated by process gases. These contaminants significantly attenuate the intensity of the incident laser and scatter the laser beam, leading to a decrease in the signal-to-noise ratio reaching the imaging unit. This deteriorates the contrast of the interference fringes, drastically reducing the sensitivity and accuracy of endpoint determination, and even making it impossible to capture weak endpoint signals in advanced processes.

[0004] Therefore, it is necessary to provide a new catadioptric laser interferometry endpoint detection system to solve the above-mentioned problems existing in the prior art. Summary of the Invention

[0005] The technical problem to be solved by this application is how to provide a high-magnification, long-working-distance, high-definition imaging system for detecting the endpoint of catadioptric laser interferometry.

[0006] To address the aforementioned technical problems, according to embodiments of this application, a catadioptric laser interferometry endpoint detection system is provided, comprising:

[0007] A first fixed lens group, a second fixed lens group, and a third fixed lens group are arranged sequentially along the optical path;

[0008] The reflecting unit includes a first reflecting mirror and a second reflecting mirror; the first reflecting mirror is movably arranged around the first fixed lens group and along the optical path, and the second reflecting mirror is disposed between the third fixed lens group and the wafer; both the first and second reflecting mirrors have an arc-shaped structure, and the obstruction ratio of the second reflecting mirror is 0.04-0.08; resulting in a system working distance of 212-417 mm, a numerical aperture range of 0.01-0.06, and a magnification of 2.9. -1.62 ;

[0009] The detection unit, located on one side of the optical path, is used to emit detection light rays;

[0010] An imaging unit is located on the side of the first fixed lens group away from the wafer, and is used to record and output image information of the wafer;

[0011] The light source includes a light-emitting element and a microlens; the light source is disposed on one side of the optical path, the light-emitting element is used to emit illumination light, and the microlens is used to divide the illumination light into multiple sub-beams, so that the illumination light emitted by the light-emitting element is divided into multiple sub-beams by the microlens and then passes sequentially through the first fixed lens group, the second fixed lens group and the third fixed lens group, and is reflected by the second reflector and the first reflector and then superimposed on the wafer, so as to spread the stains of the light source onto the target surface.

[0012] According to an embodiment of this application, both the first reflector and the second reflector protrude toward the imaging unit to form an arc-shaped structure.

[0013] According to embodiments of this application, both the first reflector and the second reflector satisfy the following formula:

[0014]

[0015] Where z represents the height difference from the vertex of the mirror to the radius of a certain point; c is the curvature of the vertex of the mirror; r is the horizontal distance from the optical axis of the mirror to a certain point; and k is the conic constant.

[0016] According to an embodiment of this application, the curvature of the first reflecting mirror for,

[0017]

[0018] in, Let be the radius of curvature of the first reflecting mirror, 200 ≤ ≤250.

[0019] According to an embodiment of this application, the curvature of the second reflector for,

[0020]

[0021] in, Let be the radius of curvature of the second reflecting mirror, 50 ≤ ≤100.

[0022] According to an embodiment of this application, it further includes a first beam splitter; the first beam splitter is disposed between the first fixed lens group and the imaging unit; the illumination light emitted by the light source is reflected by the first beam splitter and passes through the first fixed lens group, the second fixed lens group and the third fixed lens group in sequence before illuminating the wafer.

[0023] According to an embodiment of this application, the light source further includes a collimating lens; the collimating lens is disposed between the light-emitting element and the microlens, so that the illumination light emitted by the light-emitting element is collimated after passing through the collimating lens and irradiates the microlens.

[0024] According to an embodiment of this application, the microlens has an incident surface and an exit surface, so that light rays pass sequentially through the incident surface and the exit surface;

[0025] The curvature c3 of the incident surface ranges from 0.7 to 0.8; the curvature c4 of the exit surface ranges from (-0.75) to (-0.85).

[0026] According to an embodiment of this application, the microlens includes multiple lens units, and the height h1 between the highest and lowest points of each lens unit is ≤0.5um; the peak-to-valley value h2 between two adjacent lens units is ≤0.5um.

[0027] According to an embodiment of this application, the detection unit includes a detection component and a second beam splitter;

[0028] The second beam splitter is disposed between the first fixed lens group and the imaging unit, and the detection component is used to emit laser light to the wafer and receive laser light reflected from the wafer for detection.

[0029] According to an embodiment of this application, the detection component includes a transmitter, a detector, and a third beam splitter;

[0030] The third beam splitter is disposed between the second beam splitter and the transmitter;

[0031] The transmitter is used to emit laser light so that the laser light is reflected by the second beam splitter after passing through the third beam splitter and enters the first fixed lens group;

[0032] The detector is located on one side of the third beam splitter so that the laser light reflected by the wafer is reflected by the second beam splitter and then illuminates the third beam splitter, and is received by the detector after being reflected by the third beam splitter.

[0033] By employing the above technical solution, and by setting microlenses in the light source, the illumination light is divided into multiple sub-beams. Each sub-beam can be laid flat on the surface of the wafer, thereby effectively eliminating the speckle effect caused by lens stains, dust, and metal debris on imaging. At the same time, through the first and second reflecting mirrors, a wider wavelength band is achieved, namely the visible light imaging band and the near-infrared laser band (e.g., 1550nm), thus realizing high-magnification, long-working-distance, high-definition imaging. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of a catadioptric laser interferometry endpoint detection system according to an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the structure of a first fixed lens group, a second fixed lens group, and a third fixed lens group according to an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram showing the position and structure of a microlens according to an embodiment of the present invention;

[0037] Figure 4 The figure shows the MTF curve at a working distance of 212mm in this embodiment of the invention, where the X-axis represents spatial frequency in lines / mm, and the Y-axis represents contrast. The red line in the figure represents a wavelength of 0.486 micrometers, the green line represents a wavelength of 0.588 micrometers, and the blue line represents a wavelength of 0.656 micrometers.

[0038] Figure 5 This is a dot plot of a 212mm working distance in an embodiment of the present invention; in the figure, red dots represent wavelengths of 0.486 micrometers, green dots represent wavelengths of 0.588 micrometers, and blue dots represent wavelengths of 0.656 micrometers.

[0039] Figure 6 This is an axial color difference diagram with a working distance of 212mm in an embodiment of the present invention, where the X-axis represents the axial aberration in mm, the Y-axis represents the normalized radius, the red line in the diagram represents a wavelength of 0.486 micrometers, the green line represents a wavelength of 0.588 micrometers, and the blue line represents a wavelength of 0.656 micrometers.

[0040] Figure 7The figure shows the MTF curve at a working distance of 417mm in this embodiment of the invention, where the X-axis represents spatial frequency in lines / mm, and the Y-axis represents contrast. The red line in the figure represents a wavelength of 0.486 micrometers, the green line represents a wavelength of 0.588 micrometers, and the blue line represents a wavelength of 0.656 micrometers.

[0041] Figure 8 This is a dot plot of a 417mm working distance in an embodiment of the present invention; in the figure, red dots represent wavelengths of 0.486 micrometers, green dots represent wavelengths of 0.588 micrometers, and blue dots represent wavelengths of 0.656 micrometers.

[0042] Figure 9 This is an axial chromatic aberration diagram at a working distance of 417mm in an embodiment of the present invention, where the X-axis represents the axial aberration in mm, the Y-axis represents the normalized radius, the red line in the diagram represents a wavelength of 0.486 micrometers, the green line represents a wavelength of 0.588 micrometers, and the blue line represents a wavelength of 0.656 micrometers.

[0043] Figure label:

[0044] 110, First reflecting mirror; 120, Second reflecting mirror; 210, Detection component; 211, Emitter; 212, Detector; 213, Third beam splitter; 220, Second beam splitter; 300, Imaging unit; 400, Light source; 410, Light-emitting element; 420, Microlens; 421, Incident surface; 422, Exit surface; 430, Collimating lens; 500, Wafer; G, Lens group; G1, First fixed lens group; G2, Second fixed lens group; G 3. Third fixed lens group; L1, Lens 1; S1, Left surface of Lens 1; S2, Right surface of Lens 1; L2, Lens 2; S3, Left surface of Lens 2; S4, Cemented surface 2; S5, Right surface of Lens 2; L3, Lens 3; S6, Left surface of Lens 3; S7, Cemented surface 3; S8, Right surface of Lens 3; L4, Lens 4; S9, Left surface of Lens 4; S10, Cemented surface 4; S11, Right surface of Lens 4. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects.

[0046] The following is in conjunction with the appendix Figure 1-9 The specific embodiments of the present invention will be further described in detail below.

[0047] An embodiment of the present invention provides a catadioptric laser interferometry endpoint detection system, comprising:

[0048] A first fixed lens group G1, a second fixed lens group G2, and a third fixed lens group G3 are arranged sequentially along the optical path;

[0049] The reflecting unit includes a first reflecting mirror 110 and a second reflecting mirror 120; the first reflecting mirror 110 is arranged around the first fixed lens group G1, and the second reflecting mirror 120 is arranged between the third fixed lens group G3 and the wafer 500; both the first reflecting mirror 110 and the second reflecting mirror 120 have an arc-shaped structure, and the blocking ratio of the second reflecting mirror 120 is 0.04-0.08;

[0050] The detection unit, located on one side of the optical path, is used to emit detection light rays;

[0051] The imaging unit 300 is located on the side of the first fixed lens group G1 away from the wafer 500, and is used to record and output image information of the wafer 500.

[0052] The light source 400 includes a light-emitting element 410 and a microlens 420. The light source 400 is disposed on one side of the optical path. The light-emitting element 410 is used to emit illumination light, and the microlens 420 is used to divide the illumination light into multiple sub-beams. After the illumination light emitted by the light-emitting element 410 is divided into multiple sub-beams by the microlens 420, it passes through the first fixed lens group G1, the second fixed lens group G2 and the third fixed lens group G3 in sequence, and is reflected by the second reflector 120 and the first reflector 110 and then superimposed on the wafer 500 to spread the stains of the light source 400 onto the target surface.

[0053] In some embodiments, the catadioptric laser interferometry endpoint detection system is used for semiconductor etching and thin film process endpoint detection. The system includes a first fixed lens group G1, a second fixed lens group G2, and a third fixed lens group G3 arranged sequentially along the optical path. It also includes a detection unit, an imaging unit 300, and a light source 400. The imaging unit 300 is positioned on the side of the first fixed lens group G1 away from the wafer 500; that is, the first fixed lens group G1, the second fixed lens group G2, the third fixed lens group G3, and the imaging unit 300 are placed on the same vertical optical path. Simultaneously, the light source 400 and the detection unit are both positioned on one side of the optical path. The light source 400 is used to emit illumination light, and the detection unit is used to emit detection light. During operation, the illumination light emitted by the light source 400 and the detection light emitted by the detection unit can be reflected to the first fixed lens group G1 (described in detail below). After passing through the first fixed lens group G1, the illumination light and / or the detection light pass through the second fixed lens group G2 and the third fixed lens group G3 in sequence and are focused onto the surface of the wafer 500. The surface of the wafer 500 reflects the light, and the reflected light passes through the third fixed lens group G3, the second fixed lens group G2 and the first fixed lens group G1 in sequence before entering the imaging unit 300. The imaging unit 300 records and outputs the image information of the wafer 500.

[0054] In some embodiments, the first fixed lens group G1 includes a first lens L1 and a second lens L2, which are arranged sequentially along the optical axis so that the light beam can pass through the first lens L1 and the second lens L2 sequentially.

[0055] In some embodiments, the second fixed lens group G2 includes a third lens L3.

[0056] In some embodiments, the third fixed lens group G3 includes a fourth lens L4.

[0057] In some specific embodiments, the first fixed lens group G1 includes a first lens L1 and a second lens L2, which are arranged sequentially along the optical axis so that the light beam can pass through the first lens L1 and the second lens L2 in sequence.

[0058] In some more specific embodiments, lens L1 is a biconvex lens, that is, the left surface S1 of lens L1 is convex and the right surface S2 of lens L1 is convex. The focal length of lens L1 is f1, and the range of focal length f1 is 60mm≤f1≤80mm. In this embodiment, the focal length f1 is 70mm. The radius of curvature of the left surface S1 of lens L1 is 40-60mm. In this embodiment, the radius of curvature of the left surface S1 of lens L1 is 50mm. The radius of curvature of the right surface S2 of lens L1 is (-30)-(-20)mm. In this embodiment, the radius of curvature of the right surface S2 of lens L1 is -24mm. The refractive index and Abbe number of lens L1 are N1 and V1, respectively. The range of refractive index of lens L1 is 1.4≤N1≤1.8. The range of Abbe number of lens L1 is 51≤V1≤64.

[0059] In some more specific embodiments, the second lens L2 is a concave-convex lens, which is formed by cementing two lenses together, namely, it includes the left surface S3 of the second lens, the cemented surface S4 of the second lens, and the right surface S5 of the second lens; wherein the left surface S3 of the second lens is concave, and the right surface S5 of the second lens is convex; the focal length f2 of the lens of the second lens L2 closer to the first lens L1 is in the range of -28mm≤f2≤-42mm, and in this embodiment, the focal length f2 is selected as -30mm; the focal length f3 of the lens of the second lens L2 farther from the first lens L1 is in the range of 60mm≤f3≤70mm, and in this embodiment, the focal length f3 is selected as 65mm; the radius of curvature of the left surface S3 of the second lens is (-20)-(-10)mm, and in this embodiment, the radius of curvature is selected as (-20)-(-10)mm. The radius of curvature of the left surface S3 of lens 2 is -15mm; the radius of curvature of the cemented surface S4 of lens 2 is 15-20mm, and in this embodiment, the radius of curvature of the cemented surface S4 of lens 2 is 17mm; the radius of curvature of the right surface S5 of lens 2 is (-50)-(-40)mm, and in this embodiment, the radius of curvature of the right surface S5 of lens 2 is -46mm; the refractive index and Abbe number of the lens closer to lens 1 in lens 2 L2 are N21 and V21 respectively; where 1.4≤N21≤1.8; 51≤V21≤64; the refractive index and Abbe number of the lens farther from lens 1 in lens 2 L2 are N22 and V22 respectively; where 1.4≤N22≤1.8; 45≤V21≤55.

[0060] In some more specific embodiments, lens L1 and lens L2 make the optical power of the first fixed lens group G1 negative.

[0061] In some more specific embodiments, the second fixed lens group G2 includes a third lens L3, which is a plano-concave lens comprising two cemented lenses. Specifically, the third lens L3 includes a left surface S6, a cemented surface S7, and a right surface S8. The left surface S6 is planar, and the right surface S8 is concave. The focal length f4 of the lens closer to the second lens L2 in the third lens L3 ranges from -125mm to -100mm; in this embodiment, a focal length f4 of -115mm is selected. The focal length f5 of the lens farther from the second lens L2 in the third lens L3 ranges from -25mm to -15mm; in this embodiment, a focal length f5 of -21mm is selected. The radius of curvature of the left surface S6 of the third lens is (-235) to (-225)mm; in this embodiment, a radius of curvature of (-235) to (-225)mm is selected. The radius of curvature of the left surface S6 of lens 3 is -231mm; the radius of curvature of the cemented surface S7 of lens 3 is (-20)-(-15)mm, and in this embodiment, the radius of curvature of the cemented surface S7 of lens 3 is -16mm; the radius of curvature of the right surface S8 of lens 3 is 10-20mm, and in this embodiment, the radius of curvature of the right surface S8 of lens 3 is 17mm; the refractive index and Abbe number of the lens in lens 3 L3 closest to lens 2 L2 are N31 and V31, and their refractive index and Abbe number satisfy the following range: 1.4≤N31≤1.8, 50≤V31≤60; the refractive index and Abbe number of the lens in lens 3 L3 far from lens 2 L2 are N32 and V32, and their refractive index and Abbe number satisfy the following range: 1.4≤N32≤1.8, 20≤V32≤30.

[0062] In some more specific embodiments, the third fixed lens group G3 includes a fourth lens L4, which comprises two lenses cemented together, namely, the fourth lens L4 includes a left surface S9, a cemented surface S10, and a right surface S11; the focal length f6 of the lens closer to the third lens L3 in the fourth lens L4 ranges from -40mm to f6 to -20mm, and in this embodiment, the focal length f6 is -30mm; the focal length f7 of the lens farther from the third lens L3 in the fourth lens L4 ranges from 20mm to f7 to 30mm, and in this embodiment, the focal length f7 is 24mm; the radius of curvature of the left surface S9 of the fourth lens is (-20) to (-10)mm, and in this embodiment, the radius of curvature of the left surface S9 of the fourth lens is -16mm; the radius of curvature of the cemented surface S10 is... The radius is (-80)-(-60) mm. In this embodiment, the radius of curvature of the fourth cemented surface S10 is -70 mm; the radius of curvature of the right surface S11 of the fourth lens is (-70)-(-50) mm. In this embodiment, the radius of curvature of the right surface S11 of the fourth lens is -60 mm; the refractive index and Abbe number of the lens closest to the third lens L3 in the fourth lens L4 are N41 and V41, and their refractive index and Abbe number satisfy the following range: 1.4≤N41≤1.8, 50≤V41≤60; the refractive index and Abbe number of the lens furthest from the third lens L3 in the fourth lens L4 are N42 and V42, and their refractive index and Abbe number satisfy the following range: 1.4≤N42≤1.8, 40≤V42≤50; the fourth lens L4 is mainly used to correct chromatic aberration and spherical aberration. In summary, some parameters are as follows:

[0063]

[0064] The aforementioned thickness / spacing refers to the distance between the two surfaces of two adjacent lenses, or the thickness between the two surfaces of a single lens. For example, a thickness / spacing of 3mm on the left surface S1 of lens 1 means that the thickness from the left surface S1 to the right surface S2 of lens 1 is 3mm. A thickness / spacing of 4.7mm on the right surface S2 of lens 1 means that the distance from the right surface S2 of lens 1 to the left surface S3 of lens 2 is 4.7mm.

[0065] The refractive index Nd represents the refractive index of the corresponding lens. For example, the refractive index corresponding to the left surface S1 of lens 1 is the refractive index of lens 1 L1. The refractive index corresponding to the left surface S3 of lens 2 is the refractive index of the lens closer to lens 1 L1 in the cemented lens 2 L2. The refractive index corresponding to the cemented surface S4 of lens 2 is the refractive index of the lens farther from lens 1 L1 in the cemented lens 2 L2. Similarly, the refractive index corresponding to the cemented surface S7 of lens 3 is the refractive index of the lens farther from lens 2 L2 in the cemented lens 3 L3; and the refractive index corresponding to the cemented surface S10 of lens 4 is the refractive index of the lens farther from lens 3 L3 in the cemented lens 4 L4.

[0066] The Abbe number Vd is the refractive index of the corresponding lens. For example, the Abbe number corresponding to the left surface S3 of lens number 2 is the Abbe number of the lens closest to lens number 1 L1 in the cemented lens number 2 L2. The Abbe number corresponding to the cemented surface S4 is the Abbe number of the lens furthest from lens number 1 L1 in the cemented lens number 2 L2.

[0067] The focal length refers to the focal length of the corresponding lens. For example, the focal length corresponding to the left surface S3 of lens number two is the focal length of the lens closer to lens number one L1 in the cemented lens number two L2. The focal length corresponding to the cemented surface S4 of lens number two is the focal length of the lens farther away from lens number one L1 in the cemented lens number two L2.

[0068] In some embodiments, to achieve high-magnification, long-working-distance high-definition imaging and to ensure that the laser focal point diameter is as close as possible to the diffraction limit, a reflection unit is provided in the catadioptric laser interferometry endpoint detection system. Specifically, a first reflecting mirror 110 is arranged around a first fixed lens group G1. The first reflecting mirror 110 has a mounting hole through which the first fixed lens group G1 passes, so that the first reflecting mirror 110 circumferentially surrounds the first fixed lens group G1. A second reflecting mirror 120 is disposed between a third fixed lens group G3 and the wafer 500, allowing light passing through the third fixed lens group G3 to illuminate the surface of the second reflecting mirror 120. Specifically, both the first reflector 110 and the second reflector 120 are arc-shaped. The middle part of the first reflector 110 protrudes along the optical path in a direction away from the second fixed lens group G2 and closer to the imaging unit 300, and the middle part of the second reflector 120 protrudes along the optical path in a direction away from the second fixed lens group G2 and closer to the imaging unit 300. This ensures that after passing through the first fixed lens group G1, the second fixed lens group G2, and the third fixed lens group G3 in sequence, the light rays reach the second reflector 120 and are reflected by it. The light rays reflected by the second reflector 120 then reach the first reflector 110, are reflected by it, and are focused onto the surface of the wafer 500. Since the second reflector 120 is positioned between the first reflector 110 and the wafer 500, the blocking ratio of the second reflector 120 is set to 0.04-0.08 to ensure that the light rays reflected by the first reflector 110 are focused onto the wafer 500 without being blocked by the second reflector 120. The ratio of the obstruction area of ​​the second reflector 120 to the area of ​​the first reflector 110 is 0.04–0.08. When the obstruction ratio is less than 0.04, the diameter of the second reflector 120 becomes too small, requiring it to be very close to the wafer 500 to completely reflect the beam, which contradicts the required long working distance. Additionally, the mirror body of the second reflector 120 becomes too thin, making it prone to deformation during manufacturing. When the obstruction ratio is greater than 0.08, the broadening of the diffraction peak and the decrease in contrast caused by central obstruction become apparent, and the diameter of the laser focal point deviates significantly. Therefore, an obstruction ratio range of 0.04–0.08 is selected for the second reflector 120 to achieve a long working distance, high resolution, and low energy loss. This minimizes energy loss caused by central obstruction while maintaining a high signal-to-noise ratio for the imaging unit 300, all while ensuring a long working distance.

[0069] In some specific embodiments, the first reflector 110 can move along the optical path direction, that is, the first reflector 110 can move toward the direction closer to the wafer 500 or away from the wafer 500, thereby adjusting the distance between the first reflector 110 and the second reflector 120. By moving the first reflector 110, the distance between the first reflector and the wafer 500 can be adjusted, thereby realizing the adjustment of the light focusing position to adjust the focal length.

[0070] In some specific embodiments, the imaging band range of the catadioptric laser interferometry endpoint detection system with the first reflecting mirror 110 and the second reflecting mirror 120 is 400-700mm, which can be 400mm, 500mm, 600mm, or 700mm, etc.; the laser band range is 405nm, 670nm, 905nm, 980nm, or 1550nm; and the magnification is 2.9. -1.62 The focal length range of lens group G (first fixed lens group G1, second fixed lens group G2, and third fixed lens group G3) is 225 mm to 318 mm; the system's working distance is 212 mm to 417 mm. That is, lens group G achieves a zoom range of 225 mm to 318 mm, corresponding to an object-side working distance range of 212 mm to 417 mm, and a magnification of 2.9. ~1.62 (Magnification of detector 212 from object side to receiving image side), therefore the system has the performance of high magnification over long working distance.

[0071] In some specific embodiments, both the first reflector 110 and the second reflector 120 protrude toward the imaging unit 300 to form an arc-shaped structure. In order to facilitate the reflection of the detection light and / or illumination light passing through the third fixed lens group G3, both the first reflector 110 and the second reflector 120 are arranged in an arc shape. The middle part of the first reflector 110 protrudes toward the imaging unit 300, and the middle part of the second reflector 120 protrudes toward the imaging unit 300, so that the light passing through the third fixed lens group G3 can be reflected by the arc-shaped second reflector 120 to the first reflector 110, and then focused onto the surface of the wafer 500 after passing through the arc-shaped first reflector 110.

[0072] In some specific embodiments, since both the first reflector 110 and the second reflector 120 are arc-shaped, the arc angles of the first reflector 110 and the second reflector 120 must meet certain conditions during the reflection process so that light can be reflected between the first reflector 110 and the second reflector 120 and focused onto the wafer 500. Specifically, both the first reflector 110 and the second reflector 120 satisfy the following formula:

[0073]

[0074] Among them, z is the surface sagittal height, that is, z represents the height difference from the vertex of the mirror surface to a certain point on the radius, and is used to judge the degree of "concavity" or "convexity" of the mirror surface; c is the curvature of the vertex of the mirror surface; r is the horizontal distance from the optical axis of the mirror surface to a certain point; k is the conic constant, which is used to describe the "conic type" of the mirror surface shape; when -k = 0, it is a spherical surface; when -k < -1, it is a hyperbolic surface; when -k = -1, it is a parabolic surface; when -1 < k < 0, it is an ellipsoidal surface (the long axis is in the optical axis direction); when -k > 0, it is an ellipsoidal surface (the short axis is in the optical axis direction).

[0075] In some specific embodiments, the curvature of the first reflector 110 is

[0076]

[0077] Among them, is the radius of curvature of the first reflector 110, 200 ≤ ≤ 250.

[0078] In some more specific embodiments, is selected to be 230.

[0079] That is, it can be understood that:

[0080]

[0081] Among them, is the surface sagittal height of the first reflector 110, that is represents the height difference from the vertex of the mirror surface of the first reflector 110 to a certain point on the radius; is the curvature of the vertex of the mirror surface of the first reflector 110; is the horizontal distance from the optical axis of the mirror surface of the first reflector 110 to a certain point; k is -0.06.

[0082] In some specific embodiments, the curvature of the second reflector 120 is

[0083]

[0084] Among them, is the radius of curvature of the second reflector 120, 50 ≤ ≤ 100.

[0085] In some more specific embodiments, is selected to be 88.

[0086] That is, it can be understood that:

[0087]

[0088] in, The surface sagitta of the second reflecting mirror 120 is, i.e. To represent the height difference from the vertex of the second reflecting mirror 120 to a point at a certain radius; Let be the curvature of the vertex of the second reflecting mirror 120; Let k be the horizontal distance from the optical axis of the second reflecting mirror 120 to a certain point; k is 1.04.

[0089] In some specific embodiments, the light source 400 includes a light-emitting element 410 and a microlens 420. The light-emitting element 410 is used to emit illumination light and can be selected as an LED or other light-emitting device. During the detection process, when the lens of the light-emitting element 410 becomes contaminated, the contaminant is projected onto the surface of the wafer 500, thereby forming a light spot on the imaging unit 300, affecting the imaging output and detection results. Therefore, in order to improve the impact of contaminants on the lens on detection and imaging, a microlens 420 is provided on the lens of the light-emitting element 410. Specifically, the light source 400 is placed on one side of the optical path, that is, the light-emitting element 410 and the microlens 420 are both placed on the same side of the optical path. The illumination light emitted by the light source enters the first fixed lens group G1 through reflection by the beam splitter, as described in detail later. More specifically, the light-emitting element 410 is used to emit illumination light, and the microlens 420 is used to divide the illumination light into multiple sub-beams. During operation, after the illumination light is divided into multiple sub-beams, it passes through the first fixed lens group G1, the second fixed lens group G2, and the third fixed lens group G3 in sequence, and is reflected by the second reflector 120 and the first reflector 110 in sequence before being superimposed on the wafer 500. Specifically, each sub-beam can be laid on the surface of the wafer 500, thereby spreading the dirt at the lens of the light-emitting element 410 on the surface of the wafer 500, so that the dirt forms a background on the imaging unit 300, thereby reducing the impact of the dirt of the light source 400 on the detection results.

[0090] In some embodiments, the microlens 420 has an incident surface 421 and an exit surface 422, such that light passes through the incident surface 421 and the exit surface 422 in sequence.

[0091] The curvature c3 of the incident surface 421 ranges from 0.7 to 0.8; the curvature c4 of the exit surface 422 ranges from (-0.75) to (-0.85).

[0092] In some specific embodiments, the illumination light emitted by the light-emitting element 410 enters the microlens 420 from the incident surface 421 and shines onto the outside of the microlens 420 from the exit surface 422; that is, the illumination light passes through the incident surface 421 and the exit surface 422 in sequence; wherein, both the incident surface 421 and the exit surface 422 are arc-shaped; specifically, the curvature c3 of the incident surface 421 is in the range of 0.7-0.8, which can be 0.7, 0.75 or 0.8, and here it is preferred that the curvature c3 of the incident surface 421 is 0.8; the curvature c4 of the exit surface 422 is in the range of (-0.75)-(-0.85), which can be -0.75, -0.8 or -0.85, and here it is preferred that the curvature c4 of the exit surface 422 is -0.8.

[0093] In some more specific embodiments, the refractive index of the microlens 420 is 1.3-1.6; in this embodiment, the refractive index of the microlens 420 is preferably 1.47.

[0094] In some embodiments, the microlens 420 includes multiple lens units, where the height h1 between the highest and lowest points of each lens unit is ≤0.5 μm; and the peak-to-valley value h2 between two adjacent lens units is ≤0.5 μm. Specifically, the microlens 420 includes multiple lens units, each of which is arc-shaped. These multiple lens units divide the illumination light into multiple sub-beams, meaning each lens unit can form a beam; thereby segmenting and spreading the stain to form a background.

[0095] In some specific embodiments, the PV of the arcuate spherical surface of a single lens unit is ≤0.5µm, and the surface shape difference PV between the arcuate spherical surfaces of adjacent lens units in multiple lens units is ≤0.5µm; that is, the height difference between the highest and lowest points of the arcuate spherical surface of a single lens unit does not exceed 0.5µm, which can reflect the maximum local deviation of the spherical surface shape. The peak-to-valley value of the surface shape difference (i.e., the deviation of one spherical surface relative to another) between the arcuate spherical surfaces of adjacent lens units in multiple lens units also does not exceed 0.5µm, which can be used to assess consistency or repeatability.

[0096] In some embodiments, in order for the illumination light emitted by the light source 400 to illuminate the first fixed lens group G1, the catadioptric laser interference endpoint detection system further includes a first beam splitter; wherein, the first beam splitter is disposed between the first fixed lens group G1 and the imaging unit 300; the illumination light emitted by the light source 400 is reflected by the first beam splitter and passes through the first fixed lens group G1, the second fixed lens group G2 and the third fixed lens group G3 in sequence before illuminating the wafer 500.

[0097] In some specific embodiments, the first beam splitter has a light-passing surface for transmitting light. The light-passing surface is coated with a 400-1100nm anti-reflection film, making the reflectivity R of the light-passing surface R=50%. The transmitted light is reflected by the light-passing surface of the first beam splitter and enters the first fixed lens group G1, thereby illuminating the surface of the wafer 500. Specifically, the first beam splitter is an inclined surface in the first beam-splitting cube, thereby forming the light-passing surface. The first beam-splitting cube is rectangular, and the first beam-splitting cube and its material are existing technologies and will not be described in detail here. The side length of the first beam-splitting cube is required to be in the range of 15mm-25mm. In this specific embodiment, the side length of the first beam-splitting cube is selected to be 25mm, the refractive index is required to be in the range of 1.45-1.6, and the Abbe number is required to be in the range of 50-70.

[0098] In some embodiments, since the detection unit is also located on one side of the optical path, a beam splitter is also required in order for the detection light emitted by the detection unit to enter the first fixed lens group G1. Specifically, the detection unit includes a detection component 210 and a second beam splitter 220;

[0099] The second beam splitter 220 is disposed between the first fixed lens group G1 and the imaging unit 300. The detection component 210 is used to emit laser light to the wafer 500 and to receive the laser light reflected by the wafer 500 for detection.

[0100] In some specific embodiments, the second beam splitter 220 has a light-passing surface for transmitting light. This light-passing surface is coated with a 400-1100nm anti-reflection film, resulting in a reflectivity R of 50%. Transmitted light is reflected by the light-passing surface of the second beam splitter 220 and enters the first fixed lens group G1, thereby illuminating the surface of the wafer 500. Specifically, the second beam splitter 220 is a sloping surface within a second beam-splitting cube, forming the light-passing surface. The second beam-splitting cube is rectangular, and its material is existing technology and will not be described in detail here. The side length of the second beam-splitting cube is required to be between 15mm and 25mm, specifically 25mm. The refractive index is required to be between 1.45 and 1.6, and the Abbe number is required to be between 50 and 70. The laser emitted by the detection unit 210 irradiates the light-passing surface of the second beam splitter 220 and is reflected back to the first fixed lens group G1.

[0101] In some more specific embodiments, the second beam splitter 220 is placed between the first beam splitter and the imaging unit 300. The laser emitted by the detection component 210 illuminates the light-passing surface of the second beam splitter 220 and passes through the first beam splitter to illuminate the first fixed lens group G1.

[0102] In some embodiments, the detection component 210 includes a transmitter 211, a detector 212, and a third beam splitter 213; specifically, the third beam splitter 213 is disposed between the second beam splitter 220 and the transmitter 211; wherein the parameters and structure of the third beam splitter 213 are the same as those of the first beam splitter and the second beam splitter 220, and will not be described in detail here. The transmitter 211 is used to emit detection light, specifically a laser, so that the laser passes through the third beam splitter 213 and is reflected by the second beam splitter 220, and then enters the first fixed lens group G1. Specifically, the laser emitted by the transmitter 211 passes through the light-passing surface of the third beam splitter 213 and illuminates the light-passing surface of the second beam splitter 220. It is reflected by the light-passing surface of the second beam splitter 220, passes through the light-passing surface of the first beam splitter, and then passes through the first fixed lens group G1, the second fixed lens group G2, and the third fixed lens group G3 in sequence before illuminating the second reflector 120. After being reflected by the second reflector 120 and the first reflector 110 in sequence, it illuminates the surface of the wafer 500, thereby cooperating with the illumination light to achieve detection.

[0103] In some specific embodiments, the detector 212 is located on one side of the third beam splitter 213, so that the laser light reflected by the wafer 500 is reflected by the second beam splitter 220 and then illuminates the third beam splitter 213, and is then reflected by the third beam splitter 213 and received by the detector 212. Specifically, the light light reflected by the wafer 500 illuminates the first reflecting mirror 110, is reflected sequentially by the first reflecting mirror 110 and the second reflecting mirror 120, enters the third fixed lens group G3, and passes sequentially through the third fixed lens group G3, the second fixed lens group G2 and the first fixed lens group G1, passes through the light-passing surface of the first beam splitter, is reflected by the light-passing surface of the second beam splitter 220 to the third beam splitter 213, and is then reflected by the light-passing surface of the third beam splitter 213 to the detector 212 for reception.

[0104] In some embodiments, the light source 400 further includes a collimating lens 430; the collimating lens 430 is disposed between the light-emitting element 410 and the microlens 420, so that the illumination light emitted by the light-emitting element 410 is collimated after passing through the collimating lens 430 and then illuminates the microlens 420; specifically, a collimated beam of light illuminates the microlens 420, thereby causing the microlens 420 to split this collimated beam of light into multiple sub-beams. This facilitates reducing the impact of dirt on the lens of the light source 400 on the detection.

[0105] The implementation principle of the catadioptric laser interferometry endpoint detection system in this application is as follows: by setting a microlens 420 on the light source 400, the illumination light is divided into multiple sub-beams, each of which can be laid flat on the surface of the wafer 500, thereby effectively eliminating the influence of lens stains, dust, and metal debris on the imaging of ghosting. At the same time, through the first reflector 110 and the second reflector 120, a wider wavelength band is achieved, namely the visible light imaging band and the near-infrared laser band (e.g., 1550nm), thereby realizing high-magnification, long working distance, and high-definition imaging.

[0106] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A catadioptric laser interferometric end-point detection system, characterized in that, The application relates to a wafer cleaning device. The device comprises a first fixed lens group, a second fixed lens group and a third fixed lens group arranged in sequence along an optical path; A reflecting unit comprises a first mirror and a second mirror; The first mirror is movably arranged around the first fixed lens group and along the light path, and the second mirror is arranged between the third fixed lens group and the wafer; the first mirror and the second mirror are both in arc-shaped structure, and the obscuration ratio of the second mirror is 0.04-0.08; so that the system working distance is 212-417mm, the numerical aperture range is 0.01-0.06, and the magnification is 2.9 -1.62 ; A detecting unit is arranged on one side of the optical path and used for emitting detecting light; An imaging unit is arranged on the side of the first fixed lens group away from the wafer and used for recording and outputting image information of the wafer; A light source comprises a light emitting element and a microlens; the light source is arranged on one side of the optical path; the light emitting element is used for emitting illuminating light; and the microlens is used for dividing the illuminating light into multiple sub-beams so that the illuminating light emitted by the light emitting element is divided into multiple sub-beams by the microlens, sequentially passes through the first fixed lens group, the second fixed lens group and the third fixed lens group, is reflected by the second mirror and the first mirror, and is superimposed on the wafer to spread stains of the light source on a target surface.

2. The catadioptric laser interference end point detection system of claim 1, wherein, The first mirror and the second mirror are both convex and form arc structures towards the imaging unit.

3. The catadioptric laser interference end point detection system of claim 1, wherein, The first mirror and the second mirror both satisfy the following formula: Wherein, z represents a height difference from a mirror vertex to a point at a radius; c represents a curvature of the mirror vertex; r represents a horizontal distance from an optical axis of the mirror to a point; and k represents a conic constant.

4. The catadioptric laser interference end point detection system of claim 3, wherein, Curvature of the first mirror is, wherein is the radius of curvature of the first mirror, 200 ≤ ≤ 250.

5. The catadioptric laser interference end point detection system of claim 3, wherein, Curvature of the second mirror is, wherein is the radius of curvature of the second mirror, 50 ≤ ≤ 100.

6. The catadioptric laser interference end point detection system of claim 1, wherein, The device further comprises a first beam splitter; the first beam splitter is arranged between the first fixed lens group and the imaging unit; and the illuminating light emitted by the light source is reflected by the first beam splitter and irradiated to the wafer after sequentially passing through the first fixed lens group, the second fixed lens group and the third fixed lens group.

7. The catadioptric laser interference end point detection system of claim 6, wherein, The light source further comprises a collimating lens; the collimating lens is arranged between the light emitting element and the microlens so that the illuminating light emitted by the light emitting element becomes collimating light after passing through the collimating lens and is irradiated to the microlens.

8. The catadioptric laser interference end point detection system of claim 1, wherein, The microlens has an incident surface and an exit surface so that light sequentially passes through the incident surface and the exit surface; The curvature c3 of the incident surface ranges from 0.7 to 0.8; and the curvature c4 of the exit surface ranges from (-0.75) to (-0.85).

9. The catadioptric laser interference end-point detection system of claim 1, wherein, The microlens comprises multiple lens units; a height h1 between a highest point and a lowest point of each lens unit is less than or equal to 0.5 um; and a peak valley value h2 between two adjacent lens units is less than or equal to 0.5 um.

10. The catadioptric laser interference end-point detection system of claim 1, wherein, The detecting unit comprises a detecting component and a second beam splitter; The second beam splitter is arranged between the first fixed lens group and the imaging unit; the detecting component is used for emitting laser to the wafer; and the detecting component receives the laser reflected by the wafer to perform detection.

11. The catadioptric laser interference end point detection system of claim 10, wherein, The detecting component comprises an emitter, a detector and a third beam splitter; The third beam splitter is arranged between the second beam splitter and the emitter; The emitter is used for emitting laser so that the laser passes through the third beam splitter and is reflected by the second beam splitter and enters the first fixed lens group; The detector is arranged on one side of the third beam splitter so that the laser reflected by the wafer is reflected by the second beam splitter, irradiated to the third beam splitter, reflected by the third beam splitter and received by the detector.

Images