A continuous zoom laser interferometer endpoint detection system

Abstract

The present invention discloses a continuous zoom laser interference endpoint detection system for semiconductor etching and thin film process endpoint detection, comprising: an illumination module, a laser interference module and an imaging module; the laser interference module comprises a laser, a beam splitter, a beam splitter cube, a lens and a detector, the laser beam emitted by the laser is focused to the area to be detected on the surface of the wafer after passing through the beam splitter, the beam splitter cube and the lens, and the wafer surface reflects the laser to the detector for detection; the focal length of the lens is continuously adjustable; the illumination module comprises a light source, which is arranged on one side of the lens, and the illumination beam emitted by the light source is used to illuminate the area to be detected on the surface of the wafer; the imaging module comprises a camera, which is arranged on one side of the lens, and is used to record and output image information of the area to be detected on the surface of the wafer. The present invention realizes high-definition imaging and precise detection of etching and thin film process endpoints at long working distances through continuous zoom and large numerical aperture of the lens.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor detection equipment, and in particular to a continuous zoom laser interference endpoint detection system. Background Art

[0002] LEP uses the principle of monochromatic laser interference to detect the endpoint of semiconductor etching and the deposition rate and thickness. The optical probe is installed vertically just above the detection position. By adjusting the coordinate position of the laser spot, the process focus area is quickly located, and the thickness and rate values ​​of the process film etching or epitaxial growth are provided in real time. The imaging module and the horizontal motion adjustment module can provide clear wafer surface image information and the XY direction can be automatically adjusted.

[0003] In the prior art, the working distance of the lens of the detection system can be adjusted in a small range. When the working distance changes greatly, different lenses need to be replaced. Therefore, the adjustable compatibility of the detection system for different working distances is limited. At the same time, the entrance pupil diameter of the lens in the detection system is small, and the imaging resolution of the lens at different working distances is low, which affects the detection accuracy.

[0004] Therefore, it is necessary to provide a continuous zoom laser interferometer endpoint detection system to solve the above-mentioned deficiencies in the prior art. Summary of the invention

[0005] The object of the present invention is to provide a continuous zoom laser interference endpoint detection system, which is used to detect the laser interference endpoint and can achieve a lens working distance of 360-800mm and continuous zoom of the lens.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A continuous zoom laser interference endpoint detection system is used for semiconductor etching and thin film process endpoint detection, including: an illumination module, a laser interference module and an imaging module;

[0008] The laser interference module includes a laser, a beam splitter, a beam splitter cube, a lens and a detector. The laser beam emitted by the laser passes through the beam splitter, the beam splitter cube and the lens and is focused to the area to be detected on the surface of the wafer. The wafer surface reflects the laser to the detector for detection.

[0009] The focal length of the lens is adjustable, and the focal length range of the lens is 60-152mm, the working distance of the detection system is 360-800mm, the numerical aperture range is 0.01~0.05, and the entrance pupil diameter is 30mm;

[0010] The lighting module comprises a light source, which is arranged on one side of the beam splitter cube and away from the optical axis of the lens in a direction perpendicular to the optical axis of the lens, and the lighting beam emitted by the light source is used to illuminate the area to be inspected on the surface of the wafer;

[0011] The imaging module includes a camera, which is arranged on a side of the beam splitter cube away from the lens and is used to record and output image information of the area to be inspected on the surface of the wafer;

[0012] In the working state, the focal length of the lens is adjusted to detect wafers at different working distances, and the area to be detected on the surface of the wafer reflects the laser beam to the imaging module, and the imaging module records and outputs image information.

[0013] By adopting the above technical solution, the laser, beam splitter, beam splitter cube, lens and detector cooperate to enable the laser emitted by the laser to be focused on the area to be detected on the surface of the wafer. At the same time, since the focal length range of the lens is 360-800mm, the laser interference module can achieve continuous zoom within the range of 360-800mm, so an ultra-long-distance microscope system can be realized, which is convenient for position detection of laser interference end points at different distances.

[0014] Optionally, the lens comprises a second fixed group, a zoom group and a first fixed group which are sequentially arranged along the optical axis;

[0015] The interval between the second fixing group and the first fixing group is 50-76 mm;

[0016] The zoom group moves between the second fixed group and the first fixed group to adjust the focal length of the lens, and the interval between the zoom group and the second fixed group is 14-31 mm;

[0017] In the working state, the laser beam emitted by the laser passes through the beam splitter and the beam splitter cube, and then sequentially passes through the first fixed group, the zoom group and the second fixed group to be focused on the area to be detected on the surface of the wafer.

[0018] By adopting the above technical solution, the interval between the zoom group and the second fixed group is 14-31 mm. By moving the position of the zoom group, the laser beam passing through the lens can be focused at different distances to achieve a working distance of 360-800 mm.

[0019] Optionally, the first fixed group includes a third lens and a fourth lens sequentially arranged along an optical axis from the image side to the object side;

[0020] The third lens is a concave-planar lens with a focal length of f3, and the focal length f3 of the third lens is in the range of -21mm≤f3≤-14mm;

[0021] The fourth lens is a concave-convex lens with a focal length of f4. The focal length f4 of the fourth lens is in the range of 28mm≤f4≤42mm.

[0022] By adopting the above technical solution, the third lens and the fourth lens in the first fixed group cooperate to correct the field curvature during the working process.

[0023] Optionally, the zoom group includes a No. 5 lens, the No. 5 lens is a biconcave lens with a focal length of f5, and the focal length f5 of the No. 5 lens ranges from -84mm≤f5≤-56mm; the interval between the No. 5 lens and the No. 4 lens is 10-20mm.

[0024] By adopting the above technical solution, the focal length f5 of the fifth lens is in the range of -84mm≤f5≤-56mm. The movement of the fifth lens makes the focal length of the system change in the range of 60-152mm, thereby achieving a working distance of 360-800mm for the lens.

[0025] Optionally, the second fixed group includes a sixth lens and a cemented group;

[0026] The sixth lens is a plano-convex lens with a focal length of f6, and the focal length f6 of the sixth lens is in the range of 211 mm ≤ f6 ≤ 316 mm;

[0027] The glued group is a double-glued double-convex lens with a focal length of f. The focal length f of the glued group ranges from 94 mm ≤ f ≤ 141 mm.

[0028] By adopting the above technical solution, the No. 6 lens and the cemented group are coordinated to correct the chromatic aberration and spherical aberration during the working process and achieve a working distance of 360-800mm for the lens.

[0029] Optionally, the beam splitter has a transmission surface and a reflection surface, and the detector is arranged on one side of the reflection surface;

[0030] In the working state, the laser beam emitted by the laser passes through the transmission surface and irradiates the area to be detected on the surface of the wafer, and then the reflected light of the area to be detected is reflected back by the reflection surface and reaches the detector.

[0031] By adopting the above technical solution, the beam splitter has a transmission surface and a reflection surface. When the light beam enters the beam splitter from different positions, it passes through the beam splitter or is reflected by the beam splitter. When the laser beam is reflected by the beam splitter, it reaches the detector to achieve detection.

[0032] Optionally, the beam splitter cube includes a first beam splitter cube and a second beam splitter cube which are coaxially arranged in sequence;

[0033] The light source is disposed on one side of the first beam splitter cube, and the first beam splitter cube is used to deflect the illumination light beam emitted by the light source;

[0034] The laser interference module is arranged on one side of the second beam splitter cube, and the second beam splitter cube is used to deflect the laser beam emitted by the laser and deflect the reflected light on the surface of the wafer;

[0035] In working state,

[0036] The laser beam emitted by the laser is deflected by the second beam splitter cube to the area to be detected on the surface of the wafer, the illumination beam emitted by the light source is deflected by the first beam splitter cube and passes through the second beam splitter cube to reach the area to be detected on the surface of the wafer, the laser beam reflected by the area to be detected of the wafer and the illumination beam emitted by the light source pass through the second beam splitter cube and the first beam splitter cube in turn and are focused on the photosensitive surface of the camera, and the laser beam reflected by the area to be detected of the wafer is deflected by the second beam splitter cube and is focused on the detector.

[0037] By adopting the above technical solution, the light source, the laser, the first beam splitter cube and the second beam splitter cube cooperate to focus the laser beam reflected by the wafer to be inspected area onto the detector.

[0038] Optionally, the emitting end of the laser is provided with a single-mode optical fiber, and the core of the single-mode optical fiber is 4-6 μm.

[0039] By adopting the above technical solution, single-mode optical fiber only allows a single mode of light to pass through, which reduces mode dispersion, makes the output light beam higher in quality, and has better phase and amplitude stability; at the same time, it ensures the clarity and integrity of the signal.

[0040] Optionally, a temperature control component is provided on the detector, and the temperature control component includes a semiconductor refrigerator, and the semiconductor refrigerator is connected to the detector to control the temperature at the detector.

[0041] By adopting the above technical solution, the semiconductor refrigerator is connected to the detector to control the temperature at the detector, so that the temperature at the detector is stable, which facilitates the detection process.

[0042] Optionally, the temperature control component also includes an isolating member, one end of which is connected to the semiconductor refrigerator, and the other end is connected to the detector. The isolating member is made of PEEK, and the isolating member and the semiconductor refrigerator cooperate to control the temperature at the detector.

[0043] By adopting the above technical solution, the isolating element and the semiconductor cooler cooperate to isolate the hot end and the cold end of the semiconductor cooler from heat transfer, thereby ensuring the temperature stability at the detector.

[0044] Optionally, the temperature control range of the temperature control component is 10-30°C, and the temperature control accuracy is higher than 0.5°C.

[0045] By adopting the above technical solution, the temperature control accuracy is higher than 0.5°C, which minimizes the impact of temperature changes on the test results.

[0046] The beneficial effects of the continuous zoom laser interferometer endpoint detection system provided by the present invention include at least:

[0047] 1. The lens has the ability to achieve 360-800mm continuous zoom of the system, realize fast and accurate positioning of the area to be inspected at a long working distance, and detect the etching depth, etching rate or film growth thickness and growth rate data in real time.

[0048] 2. The imaging system cooperates with illumination and laser interferometry technology to improve the imaging resolution and clarity of groove etching, small aperture ratio process and multi-layer process. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of the main structure of an embodiment of the present invention;

[0050] Figure 2 A schematic diagram of a lens assembly method according to an embodiment of the present invention;

[0051] Figure 3 This is a schematic diagram of the structure of a temperature control component according to an embodiment of the present invention;

[0052] Figure 4 : This is the MTF curve at a working distance of 360 mm in an embodiment of the present invention, wherein the X-axis represents the spatial frequency in lines / mm, and the Y-axis represents the contrast;

[0053] Figure 5 : The MTF curve at a working distance of 800 mm in an embodiment of the present invention, wherein the X-axis represents the spatial frequency in lines / mm, and the Y-axis represents the contrast;

[0054] Figure 6 This is a spot diagram at a working distance of 360 mm in an embodiment of the present invention;

[0055] Figure 7 It is a spot diagram at a working distance of 800 mm in an embodiment of the present invention;

[0056] Figure 8 : is an axial chromatic aberration diagram at a working distance of 360 mm in an embodiment of the present invention, wherein the X-axis represents the axial aberration in mm, the Y-axis represents the normalized radius, the blue line in the figure represents a wavelength of 0.486 microns, the green line represents a wavelength of 0.588 microns, and the red line represents a wavelength of 0.656 microns;

[0057] Fig. 9 800mm working distance in the embodiment of the present invention, wherein the X-axis represents the axial aberration in mm, the Y-axis represents the normalized radius, the blue line in the figure represents the wavelength of 0.486 microns, the green line represents the wavelength of 0.588 microns, and the red line represents the wavelength of 0.656 microns;

[0058] Fig.10 3 is a field curvature and distortion diagram at a working distance of 360 mm in an embodiment of the present invention, wherein the X-axis in A1 represents the field curvature amount, and the Y-axis represents different fields of view, the X-axis in B1 represents the distortion, and the Y-axis represents different fields of view, and in the figure, the blue line represents a wavelength of 0.486 microns, the green line represents a wavelength of 0.588 microns, and the red line represents a wavelength of 0.656 microns;

[0059] Fig.11 3 is a field curvature and distortion diagram at a working distance of 800 mm in an embodiment of the present invention, wherein the X-axis in A1 represents the field curvature, and the Y-axis represents different fields of view; the X-axis in B1 represents the distortion, and the Y-axis represents different fields of view; in the figure, the blue line represents a wavelength of 0.486 microns, the green line represents a wavelength of 0.588 microns, and the red line represents a wavelength of 0.656 microns.

[0060] Reference numerals:

[0061] 100, lighting module; 200, laser interference module; 210, laser; 220, beam splitter; 230, lens; 240, detector; 300, imaging module; 400, temperature control component; 410, semiconductor refrigerator; 420, isolation member; 430, first heat conducting member; 440, second heat conducting member; G1, beam splitter cube; L1, first beam splitter cube; S1, left surface of first beam splitter cube; S2, right surface of first beam splitter cube; L2, second beam splitter cube; S3, left surface of second beam splitter cube; S4, right surface of second beam splitter cube; G2, first fixed group; L3, third lens Mirror; S5, left surface of lens No. 3; S6, right surface of lens No. 3; L4, lens No. 4; S7, left surface of lens No. 4; S8, right surface of lens No. 4; G3, zoom group; L5, lens No. 5; S9, left surface of lens No. 5; S10, right surface of lens No. 5; G4, second fixed group; L6, lens No. 6; S11, left surface of lens No. 6; S12, right surface of lens No. 6; L7, lens No. 7; S13, left surface of lens No. 7; S14, right surface of lens No. 7; L8, lens No. 8; S15, left surface of lens No. 8; S16, right surface of lens No. 8; S17, aperture. DETAILED DESCRIPTION

[0062] In order to make the purpose, 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 part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be understood by people with general skills in the field to which the present invention belongs. "Including" and similar words used in this article mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0063] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0064] Reference Figure 1-11 . An embodiment of the present invention provides a continuous zoom laser interference endpoint detection system, which is used for semiconductor etching and thin film process endpoint detection, wherein the etching and thin film process endpoint detection includes an illumination module 100, a laser interference module 200 and an imaging module 300. During operation, the illumination module 100, the laser interference module 200 and the imaging module 300 cooperate with each other to achieve semiconductor etching and thin film process endpoint detection; wherein the laser interference module 200 includes a laser 210, a beam splitter 220, a beam splitter cube G1, a lens 230 and a detector 240. During operation, the laser beam emitted by the laser 210 passes through the beam splitter 220, the beam splitter cube G1 and the lens 230 in sequence and then focuses on the area to be detected on the surface of the wafer, and the wafer surface reflects the laser to the detector 240 for detection.

[0065] Reference Figure 1-11The beam splitter cube G1 includes a first beam splitter cube L1 and a second beam splitter cube L2, and the first beam splitter cube L1 and the second beam splitter cube L2 are sequentially arranged along the optical axis direction. In this embodiment, the first beam splitter cube L1, the second beam splitter cube L2 and the lens 230 are sequentially arranged along the optical axis direction, and the laser 210 is arranged on one side of the second beam splitter cube L2. The second beam splitter cube L2 is used to deflect the laser beam emitted by the laser 210 and deflect the reflected light on the surface of the wafer; the lighting module 100 includes a light source, and the light source is used to emit an illumination beam to illuminate the area to be detected on the surface of the wafer. In this embodiment, the lighting module 100 is arranged on one side of the beam splitter cube G1, away from the optical axis of the lens 230 in a direction perpendicular to the optical axis of the lens 230. Specifically, the lighting module 100 is arranged on one side of the first beam splitter cube L1, and the lighting module 1 00 and the laser 210 are arranged on the same side of the beam splitter cube G1, and the first beam splitter cube L1 is used to deflect the illumination light beam emitted by the illumination module 100; at the same time, the imaging module 300 includes a camera, which is arranged on the side of the beam splitter cube G1 away from the lens 230. Specifically in this embodiment, the imaging module 300, the first beam splitter cube L1 and the second beam splitter cube L2 are arranged in sequence along the optical axis direction, so that the light beam passes through the left surface S1 of the first beam splitter cube, the right surface S2 of the first beam splitter cube, the left surface S3 of the second beam splitter cube and the right surface S4 of the second beam splitter cube in sequence. The area to be detected on the surface of the wafer can reflect the laser beam to the imaging module 300, and the imaging module 300 records and outputs image information. Specifically, the laser beam reflected by the area to be detected on the surface of the wafer passes through the second beam splitter cube L2 and the first beam splitter cube L1 in sequence and then reaches the camera.

[0066] In order to enable the first beam splitter cube L1 and the second beam splitter cube L2 to reflect the laser beam and transmit the laser beam at the same time, refer to Figure 1-11The shapes of the first beam splitter cube L1 and the second beam splitter cube L2 are both square, wherein the first beam splitter cube L1 and the second beam splitter cube L2 both have a light passing surface for passing or reflecting light, and the light passing surface is coated with a 400-1100nm anti-reflection film, so that the reflectivity R=50% and the transmittance T=50% of the light passing surface. In the working state, the light passing surfaces of the first beam splitter cube L1 and the second beam splitter cube L2 can reflect part of the light beam and transmit part of the light beam, so that in the lighting module 100, the lighting beam emitted by the light source is reflected by the light passing surface of the first beam splitter cube L1 and passes through the light passing surface of the second beam splitter cube L2. The light surface enters the lens 230, thereby irradiating the area to be detected on the surface of the wafer; the laser beam emitted by the laser 210 is reflected by the light passing surface of the second beam splitter cube L2, enters the lens 230, and irradiates the area to be detected on the surface of the wafer; the light passing surface of the first beam splitter cube L1 and the light passing surface of the second beam splitter cube L2 are inclined at an angle of 45° relative to the laser beam emission path of the laser 210, which is convenient for the deflection of the laser beam and the illumination beam; the area to be detected on the surface of the wafer reflects the laser beam, and the laser beam passes through the light passing surface of the second beam splitter cube L2 and the light passing surface of the first beam splitter cube L1 in sequence and then enters the camera, The imaging module 300 is capable of recording and outputting image information; in addition, the side length range of the first beam splitter cube L1 is required to be 15mm-25mm. Specifically, in this embodiment, the side length of the first beam splitter cube L1 is 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; the side length range of the second beam splitter cube L2 is required to be 15mm-25mm. In this embodiment, the side length of the second beam splitter cube L2 is specifically selected to be 25mm, the refractive index is required to be 1.45-1.6, and the Abbe number is required to be 50-70; in addition, the focal length range of the lens 230 is 60-1 52mm, the numerical aperture range is 0.01~0.05, and the entrance pupil diameter is 30mm. Specifically, the numerical aperture range is 0.01875~0.04163. During operation, by adjusting the focal length of the lens 230, wafers at different positions can be detected, and the area to be detected on the surface of the wafer reflects the laser beam to the imaging module 300, and the imaging module 300 records and outputs image information. By adjusting the focal length of the lens 230, the continuous zoom laser interferometer endpoint detection system can meet the working distance of 360-800mm, thereby realizing the ultra-long working distance of the continuous zoom laser interferometer endpoint detection system.

[0067] In order for the lens 230 to achieve a zoom range of 60-152 mm, refer to Figure 1-11The lens 230 includes a second fixed group G4, a zoom group G3, a first fixed group G2 and an aperture S17. The second fixed group G4, the zoom group G3 and the first fixed group G2 are sequentially arranged along the optical axis, and the interval between the first fixed group G2 and the second fixed group G4 is 50-76 mm; the zoom group G3 can move between the first fixed group G2 and the second fixed group G4 along the optical axis to adjust the focal length of the lens 230. In addition, the interval between the zoom group G3 and the first fixed group G2 is 14-31 mm, that is, the zoom group G3 is located between the first fixed group G2 and the second fixed group G4. Between G2 and the second fixed group G4, the adjustment is performed within a specific range of 14-31mm with the first fixed group G2 along the optical axis direction, thereby adjusting the focal length of the lens 230, so that the continuous zoom laser interferometric endpoint detection system can meet the working distance of 360-800mm; the light beam at the beam splitter cube G1 can be focused to the area to be detected on the wafer surface after passing through the first fixed group G2, the zoom group G3, the second fixed group G4 and the aperture S17 in sequence; the side close to the wafer along the optical axis direction is defined as the right side, and the side close to the beam splitter cube G1 along the optical axis direction is defined as the left side;

[0068] The first fixed group G2 includes a third lens L3 and a fourth lens L4, which are arranged in sequence along the optical axis so that the light beam at the beam splitter cube G1 can pass through the third lens L3 and the fourth lens L4 in sequence;

[0069] The third lens L3 is a concave-planar lens, that is, the left surface S5 of the third lens is a concave surface, the right surface S6 of the third lens is a plane, the focal length of the third lens L3 is f3, and the range of the focal length f3 of the third lens L3 is -21mm≤f3≤-14mm. In this embodiment, the focal length f3 is selected to be -16.4mm; the refractive index and Abbe number of the third lens L3 are n3 and v3 respectively; the refractive index range of the third lens L3 is 1.4≤n3≤1.8; the Abbe number range of the third lens L3 is 51≤v3≤64;

[0070] The fourth lens L4 is a concave-convex lens, that is, the left surface S7 of the fourth lens is concave, and the right surface S8 of the fourth lens is convex. The focal length of the fourth lens L4 is f4, and the range of the focal length f4 of the fourth lens L4 is 28mm≤f4≤42mm. In this embodiment, the focal length f4 is 37.9mm. The refractive index and Abbe number of the fourth lens L4 are n4 and v4 respectively. The refractive index range of the fourth lens L4 is 1.4≤n4≤1.8. The Abbe number range of the third lens L3 is 51≤v4≤64.

[0071] The third lens L3 and the fourth lens L4 make the optical power of the first fixed group G2 negative.

[0072] The zoom group G3 includes lens No. 5 L5, which is a double concave lens. The left surface S9 of the lens No. 5 is concave, and the right surface S10 of the lens No. 5 is concave. The focal length of lens No. 5 is f5, and the range of the focal length f5 of lens No. 5 is -84mm≤f5≤-56mm. In the present embodiment, the focal length f5 is -63.1mm. The refractive index and Abbe number of lens No. 5 are n5 and v5, and the refractive index and Abbe number of lens No. 5 satisfy the following value range: 1.4≤n5≤1.8, 60≤v5≤74. Meanwhile, the interval between lens No. 5 L5 and lens No. 4 L4 is 10-20mm, that is, lens No. 5 is moved within the range of 10-20mm from lens No. 4 L4 along the optical axis, so that the continuous zoom laser interference endpoint detection system can meet the working distance of 360-800mm.

[0073] The second fixed group G4 includes a sixth lens L6 and a cemented group, wherein the sixth lens L6 is a plano-convex lens, the left surface S11 of the sixth lens is a plane, the right surface S12 of the sixth lens is a convex surface, the focal length of the sixth lens L6 is f6, and the range of the focal length f6 of the sixth lens L6 is 211mm≤f6≤316mm. In this embodiment, the focal length f6 is selected to be 271.4mm; meanwhile, the refractive index and Abbe number of the sixth lens L6 are n6 and v6; the refractive index and Abbe number of the sixth lens L6 respectively satisfy the following value ranges: 1.5≤n6≤1.9, 27≤v6≤60;

[0074] The glued group is a double glued double convex lens, with a focal length of f, and the focal length f of the glued group ranges from 94mm≤f≤141mm. Specifically, the glued group includes lens No. 7 L7 and lens No. 8 L8. Lens No. 7 L7 is a double convex lens, the left surface S13 of lens No. 7 is a convex surface, and the right surface S14 of lens No. 7 is a convex surface; lens No. 8 L8 is a concave-planar lens, the left surface S15 of lens No. 8 is a concave surface, and the right surface S16 of lens No. 8 is a plane; the object side surface of lens No. 7 L7 is glued to the image side surface of lens No. 8 L8; at the same time, the focal length of lens No. 7 L7 is f7, and the focal length range of lens No. 7 L7 is -130mm≤f7≤-87mm. In this embodiment, In the embodiment, the focal length f7 is selected to be -108.1 mm, the refractive index and Abbe number of the seventh lens L7 are n7 and v7 respectively, and the refractive index and Abbe number of the seventh lens L7 respectively satisfy 1.4≤n7≤1.6, 80≤v7≤95; the focal length of the eighth lens L8 is f8, and the focal length range of the eighth lens L8 is 73 mm≤f8≤109 mm. In the present embodiment, the focal length f8 is selected to be 90.6 mm, the refractive index and Abbe number of the eighth lens L8 are n8 and v8 respectively, and the refractive index and Abbe number of the eighth lens L8 respectively satisfy 1.5≤n8≤1.75, 40≤v8≤65; the cemented group is mainly used to correct chromatic aberration and spherical aberration;

[0075] Among them, the first beam splitter cube L1, the second beam splitter cube L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7 and the eighth lens L8 are arranged in sequence along the optical axis from the image side to the object side; the optical focal length of the combination of the zoom group G3 and the second fixed group G4 is positive, and the first fixed group G2, the second fixed group G4 and the zoom group G3 cooperate to achieve a larger system focal length with a smaller combination size; during operation, the zoom group G3 moves along the axial direction of the optical axis in a direction away from the first fixed group G2 to achieve continuous zoom of the lens 230, so that the continuous zoom laser interferometer endpoint detection system can meet 360 -800mm working distance; specifically in this embodiment, when the working distance is 360mm, the combined focal length of the zoom group G3 and the second fixed group G4 is 70-100mm; when the working distance is 800mm, the combined focal length of the zoom group G3 and the second fixed group G4 is 120-145mm; that is, during the continuous zooming process, the combined focal length of the zoom group G3 and the second fixed group G4 zooms from the range of 70-100mm to the range of 120-145mm, and the focal length range of the first fixed group G2 is -50mm-(-20)mm, thereby achieving a system focal length range of 60-152mm, which meets the working distance of 360-800mm.

[0076] In order to facilitate the detector 240 to receive the light beam reflected by the area to be detected on the wafer surface, refer to Figure 1-11 , the beam splitter 220 is arranged between the laser 210 and the second beam splitter cube L2, and the beam splitter 220 has a transmission surface and a reflection surface, and the detector 240 is arranged on the reflection surface side of the beam splitter 220. In the working state, the laser beam emitted by the laser 210 passes through the transmission surface to irradiate the second beam splitter cube L2, and is reflected by the second beam splitter cube L2 to the area to be detected on the surface of the wafer; the area to be detected on the surface of the wafer reflects the laser beam, and the reflected laser beam is reflected to the beam splitter 220 at the second beam splitter cube L2, and is reflected by the reflection surface of the beam splitter 220 to reach the detector 240, that is, the reflected light of the area to be detected is reflected back through the reflection surface to reach the detector 240, so that the detector 240 receives the laser beam reflected by the area to be detected on the surface of the wafer;

[0077] That is, the overall working mode of the system is that the laser beam emitted by the laser 210 is deflected to the area to be detected on the surface of the wafer after passing through the second beam splitter cube L2, the illumination beam emitted by the light source is deflected by the first beam splitter cube L1 and reaches the area to be detected on the surface of the wafer after passing through the second beam splitter cube L1, the laser beam reflected by the area to be detected of the wafer and the illumination beam emitted by the light source are focused on the photosensitive surface of the camera after passing through the second beam splitter cube L2 and the first beam splitter cube L1 in turn, and the laser beam reflected by the area to be detected of the wafer is focused on the detector 240 after being deflected by the second beam splitter cube L2, so as to facilitate the working process; in addition, the emitting end of the laser 210 is provided with a single-mode optical fiber, and the core of the single-mode optical fiber is 4-6μm, so that the laser spot projected onto the wafer through the lens 230 is small, which is convenient for improving the detection accuracy; based on the above, some parameters are as follows:

[0078]

[0079] When the working distance is 360mm, the distance between the zoom group G3 and the second fixed group G4 (i.e., the distance between the right surface S10 of the fifth lens and the left surface S11 of the sixth lens) is 42mm; the distance between the first fixed group G2 and the zoom group G3 (i.e., the distance between the right surface S8 of the fourth lens and the left surface S9 of the fifth lens) is 14mm;

[0080] When the working distance is 800mm, the distance between the zoom group G3 and the second fixed group G4 (i.e. the distance between the right surface S10 of the fifth lens and the left surface S11 of the sixth lens) is 25mm. The distance between the first fixed group G2 and the zoom group G3 (i.e. the distance between the right surface S8 of the fourth lens and the left surface S9 of the fifth lens) is 31mm.

[0081] Among them, the distance between the first fixed group G2 and the second fixed group G4 (that is, the distance between the right surface S8 of the fourth lens and the left surface S11 of the sixth lens) is 63mm; the thickness of the fifth lens L5 is 7mm, so 42+14+7=63mm corresponds to the distance between the first fixed group G2 and the second fixed group G4.

[0082] In addition, according to the Rayleigh criterion: the Rayleigh criterion defines the resolution limit in a diffraction-limited system, and distinguishes or resolves two light points from each other. Rayleigh proposed such a distance resolution standard: when the edge of one Airy disk coincides with the center of another Airy disk, the corresponding two object points can be just resolved by the human eye or optical instrument, as follows:

[0083]

[0084] in That is, it is the minimum distance between two points that the system can distinguish. F is the system object-side F number, often recorded as Fno. or F / #, F#=f / D, which is a parameter that represents the light-transmitting ability of the lens, also called the aperture number. NA is the system object-side numerical aperture, and the corresponding units of the left and right dimensions are um.

[0085] It can be seen that the system's ultimate resolution is determined by the imaging wavelength used and the system lens NA. The LEP optical system has a resolution of 9.8um at a working distance of 3600mm and a resolution of 20um at a working distance of 800mm. The system uses a 6.3-megapixel COMS camera with a single pixel size of 2.4umx2.4um.

[0086] This makes imaging clearer in applications such as trench etching, small aperture ratio processes, and multi-layer etching.

[0087] In order to facilitate the stability of the detector detection data, refer to Figure 1-11 , a temperature control component 400 is arranged on the detector 240, and the temperature control component 400 includes a semiconductor refrigerator 410 and an isolating member 420, wherein the semiconductor refrigerator 410 is connected to the detector 240 to control the temperature at the detector 240, so that the temperature at the detector 240 is maintained at a stable state; the isolating member 420 is arranged between the semiconductor refrigerator 410 and the detector 240, one end of the isolating member 420 is connected to the semiconductor refrigerator 410, and the other end is connected to the detector 240, and the material of the isolating member 420 is PEEK, and the isolating member 420 and the semiconductor refrigerator 410 cooperate to control the temperature at the detector 240; at the same time, the upper end of the semiconductor refrigerator 410 is also fixedly provided with a first heat conducting member 430 and a second heat conducting member 440 in sequence, and the fixing method thereof is a clamping fixing method, and the first heat conducting member 430 and the second heat conducting member 440 are both made of brass. In this embodiment, the upper surface of the semiconductor refrigerator 410 is the hot end, The lower surface is the cold end, and the heat of the hot end is quickly conducted to the optical machine main structure through the first heat conductor 430 and the second heat conductor 440. The optical machine main structure has a large heat capacity. In addition, the isolation member 420 can prevent the heat generated by the hot end from being conducted to the detector 240, so that the temperature accuracy at the detector 240 is relatively high. At the same time, in this embodiment, the temperature control range of the temperature control component 400 is 10-30°C, and the temperature control accuracy is higher than 0.5°C. Furthermore, through the structural design of the temperature control component 400 in this embodiment, a temperature control accuracy of 0.01°C is achieved, thereby reducing the impact of temperature changes on the detection results and improving the detection accuracy. At the same time, the lens 230 has the advantages of a long working distance, a large depth of field and a high resolution. A 6.3 million pixel COMS camera with a single pixel size of 2.4umx2.4um is used, which is combined with the system optical machine to form an ultra-long-distance microscope system. The imaging system can detect the morphology of the etched chip in real time and detect the interference end position of the laser 210.

[0088] In this embodiment, the zoom lens 230 refers to a lens whose focal length continuously changes within a certain range while the image plane remains stationary. When the image plane is fixed, different working distances are obtained by continuous focusing, thereby replacing a plurality of fixed magnification lenses 230; wherein the magnification of the optical system is:

[0089]

[0090] Where y is the object height, y' is the image height, the magnification is 1.25 when the working distance is 360mm, and the object line field of view is 7.14mm, and the working distance is 800mm, the magnification is 0.54, and the object line field of view is 16.61mm; the system entrance pupil diameter is 30mm, so the F# number at each working distance can be calculated, F / #=f' / D, where f' is the system focal length, D is the entrance pupil, and the system F# number ranges from 1.3-4.

[0091] In addition, the rear focal length remains unchanged during the zooming process of the optical system to ensure that the image quality is close to that of the fixed-focus optical system, so the requirements for aberration correction are higher. It is also necessary to ensure that the image plane position is the same within the continuous focal length change range, and the image quality at each focal length is close to the diffraction limit. Therefore, higher requirements for aberration correction are required; so it is necessary to correct on-axis spherical aberration, off-axis astigmatism, positional chromatic aberration, and magnification chromatic aberration. Field curvature and distortion are also aberrations that concern the imaging quality, but considering the small field of view of the system, the field curvature and distortion can be within the required range.

[0092] The second fixed group G4 is composed of a cemented group with positive optical power and lens No. 6 L6, where the Abbe number represents the relative dispersion of the material, and the higher the Abbe number, the smaller the dispersion; lens No. 7 L7 in the cemented group has a low refractive index and a high Abbe number; lens No. 8 L8 has a high refractive index and a low Abbe number. In addition to changing the object distance, the second fixed group G4 also corrects the high-order aberrations of the system. The first fixed group G2 is used to correct the last remaining paraxial aberrations such as spherical aberration in the system; that is, when the system is at a working distance of 360mm, it can be seen from the axial chromatic aberration diagram that the axial chromatic aberration of the 0.707 band has been eliminated, and the secondary spectrum is less than 0.4um; the axial chromatic aberration at a working distance of 800mm is less than 0.5um; at a working distance of 360mm, the meridian and sagittal field curvatures are less than 0.5um, and the distortion is less than 0.3%. At a working distance of 800mm, the meridian and sagittal field curvatures are less than 0.7um, and the distortion is less than 0.3%; therefore, light of different wavelengths can be well converged on the same focus, reducing color distortion; at the same time, the flatness and geometric accuracy of the image in the entire field of view are guaranteed, ensuring that the entire optical system can provide high-resolution, low-distortion imaging performance at different working distances.

[0093] The implementation principle of a continuous zoom laser interference endpoint detection system in the embodiment of the present application is that by adjusting the position of the zoom group G3 between the first fixed group G2 and the second fixed group G4, the lens 230 can continuously zoom and adapt to the long working distance detection of 360-800mm, so as to accurately lock the target process to be detected area, and obtain the etching depth, etching rate or thin film growth thickness, growth rate data in real time. In addition, the high integration of the imaging system with the lighting module 100 and the laser interference module 200 significantly improves the imaging resolution of the film thickness and groove depth in the etching and thin film process, especially optimizes the imaging quality of the small aperture ratio process and the multi-film thickness process, and ensures the accurate detection of the etching and thin film process endpoints.

[0094] Although the embodiments of the present invention are described in detail above, it is obvious 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 are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A continuous zoom laser interferometer endpoint detection system, characterized in that: Used for semiconductor etching and thin film process endpoint detection, including: lighting module, laser interferometer module and imaging module; The laser interference module includes a laser, a beam splitter, a beam splitter cube, a lens and a detector. The laser beam emitted by the laser passes through the beam splitter, the beam splitter cube and the lens and is focused to the area to be detected on the surface of the wafer. The wafer surface reflects the laser to the detector for detection. The focal length of the lens is adjustable, and the focal length range of the lens is 60-152mm, the working distance of the detection system is 360-800mm, the numerical aperture range is 0.01~0.05, and the entrance pupil diameter is 30mm; The lighting module comprises a light source, which is arranged on one side of the beam splitter cube and away from the optical axis of the lens in a direction perpendicular to the optical axis of the lens, and the lighting beam emitted by the light source is used to illuminate the area to be inspected on the surface of the wafer; The imaging module is arranged on a side of the beam splitter cube away from the lens, and is used to record and output image information of the area to be inspected on the surface of the wafer; In the working state, the focal length of the lens is adjusted to detect wafers at different working distances, and the area to be detected on the surface of the wafer reflects the laser beam to the imaging module, and the imaging module records and outputs image information.

2. The continuous zoom laser interferometer endpoint detection system according to claim 1, characterized in that: The lens comprises a first fixed group, a zoom group and a second fixed group which are sequentially arranged along the optical axis; The interval between the first fixing group and the second fixing group is 50-76 mm; The zoom group moves between the first fixed group and the second fixed group to adjust the focal length of the lens, and the interval between the zoom group and the first fixed group is 14-31 mm; In the working state, the laser beam emitted by the laser passes through the beam splitter and the beam splitter cube, and then sequentially passes through the first fixed group, the zoom group and the second fixed group to be focused on the area to be detected on the surface of the wafer.

3. The continuous zoom laser interferometer endpoint detection system according to claim 2, characterized in that: The first fixed group includes a third lens and a fourth lens arranged in sequence along the optical axis from the image side to the object side; The third lens is a concave-planar lens with a focal length of f3, and the focal length f3 of the third lens is in the range of -21mm≤f3≤-14mm; The fourth lens is a concave-convex lens with a focal length of f4. The focal length f4 of the fourth lens is in the range of 28mm≤f4≤42mm.

4. The continuous zoom laser interferometry endpoint detection system according to claim 3, characterized in that: The zoom group includes a No. 5 lens, which is a biconcave lens with a focal length of f5. The focal length f5 of the No. 5 lens ranges from -84mm≤f5≤-56mm; and the interval between the No. 5 lens and the No. 4 lens is 10-20mm.

5. The continuous zoom laser interferometer endpoint detection system according to claim 2, characterized in that: The second fixed group includes a sixth lens and a cemented group; The sixth lens is a plano-convex lens with a focal length of f6, and the focal length f6 of the sixth lens is in the range of 211 mm ≤ f6 ≤ 316 mm; The glued group is a double-glued double-convex lens with a focal length of fclose. The focal length fclose of the glued group ranges from 94mm≤fclose≤141mm.

6. The continuous zoom laser interferometer endpoint detection system according to claim 1, characterized in that: The beam splitter has a transmission surface and a reflection surface, and the detector is arranged on one side of the reflection surface; In the working state, the laser beam emitted by the laser passes through the transmission surface and irradiates the area to be detected on the surface of the wafer, and then the reflected light of the area to be detected is reflected back by the reflection surface and reaches the detector.

7. The continuous zoom laser interferometry endpoint detection system according to claim 1, characterized in that: The imaging module includes a camera, and the beam splitter cube includes a first beam splitter cube and a second beam splitter cube which are coaxially arranged in sequence; The light source is disposed on one side of the first beam splitter cube, and the first beam splitter cube is used to deflect the illumination light beam emitted by the light source; The laser interference module is arranged on one side of the second beam splitter cube, and the second beam splitter cube is used to deflect the laser beam emitted by the laser and deflect the reflected light on the surface of the wafer; In working state, The laser beam emitted by the laser is deflected by the second beam splitter cube to the area to be detected on the surface of the wafer, the illumination beam emitted by the light source is deflected by the first beam splitter cube and passes through the second beam splitter cube to reach the area to be detected on the surface of the wafer, the laser beam reflected by the area to be detected of the wafer and the illumination beam emitted by the light source pass through the second beam splitter cube and the first beam splitter cube in turn and are focused on the photosensitive surface of the camera, and the laser beam reflected by the area to be detected of the wafer is deflected by the second beam splitter cube and is focused on the detector.

8. The continuous zoom laser interferometry endpoint detection system according to claim 1, characterized in that: The emitting end of the laser is provided with a single-mode optical fiber, and the core of the single-mode optical fiber has a diameter of 4-6 μm.

9. The continuous zoom laser interferometry endpoint detection system according to claim 1, characterized in that: A temperature control component is arranged on the detector, and the temperature control component comprises a semiconductor refrigerator. The semiconductor refrigerator is connected to the detector to control the temperature at the detector.

10. The continuous zoom laser interferometer endpoint detection system according to claim 9, characterized in that: The temperature control component also includes an isolating member, one end of which is connected to the semiconductor refrigerator, and the other end is connected to the detector. The isolating member is made of PEEK, and the isolating member and the semiconductor refrigerator cooperate to control the temperature at the detector.

11. The continuous zoom laser interferometer endpoint detection system according to claim 9, characterized in that: The temperature control range of the temperature control component is 10-30°C, and the temperature control accuracy is higher than 0.5°C.

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