Optical detection system

Abstract

The utility model provides an optical detection system. The optical detection system comprises: a vacuum chamber in which a sample to be detected is placed, the top of which is provided with a window; the plane mirror is arranged at the window to seal the window; the microscope is arranged outside the vacuum chamber; and the aberration compensation device is arranged between the microscope and the sample to be detected, comprises a first lens structure positioned above the plane mirror and a second lens structure positioned below the plane mirror, and is configured to reduce or eliminate aberration introduced by the plane mirror. According to the optical detection system provided by the utility model, aberration introduced by the plane mirror of the vacuum chamber window can be reduced or eliminated, and the detection precision and the detection efficiency of the optical detection system are improved; the device eliminates the limitation of the working distance of the objective lens on the thickness of the window plane mirror, is suitable for objective lenses with various working distances, and enlarges the application range.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of semiconductor detection, especially to an optical detection system. BACKGROUND

[0002] The surface detection of semiconductor wafers is crucial in the semiconductor industry, and the rapid development of the semiconductor industry has also put forward higher requirements for semiconductor wafer detection technology. Among them, the optical detection system plays a key role in wafer detection, which determines the precision and efficiency of semiconductor wafer detection.

[0003] In the prior art, in order to avoid the interference of other factors, the wafer usually needs to be placed in a vacuum environment. However, the general microscope objective does not have vacuum compatibility, and there is a risk of air leakage and damage to the objective lens in a vacuum, so the main body of the optical detection system is often set outside the vacuum chamber, and the optical image is transmitted through the vacuum window mirror to isolate the vacuum and the atmosphere. However, the prior art has the problem of low detection quality and detection precision for wafer optical detection. UTILITY MODEL CONTENT

[0004] One object of the utility model is to reduce or eliminate the aberration introduced by the plane mirror of the vacuum chamber window, and to improve the detection precision and efficiency of the optical detection system.

[0005] A further object of the utility model is to eliminate the restriction of the working distance of the objective lens on the thickness of the window plane mirror, which is suitable for objective lenses of various working distances, and expands the application range 。

[0006] In particular, the utility model provides an optical detection system, which comprises: a vacuum chamber, which internally places a sample to be detected, and has a window opened at the top; a plane mirror, which is arranged at the window to close the window; a microscope, which is arranged outside the vacuum chamber; and an aberration compensation device, which is arranged between the microscope and the sample to be detected, and comprises a first lens structure above the plane mirror and a second lens structure below the plane mirror, and is configured to reduce or eliminate the aberration introduced by the plane mirror.

[0007] Optionally, the optical detection system further comprises: an image acquisition device, which is arranged above the microscope system and is configured to acquire the image of the sample to be detected; and a light source, which is configured to emit a light beam, and the light beam is reflected after reaching the sample to be detected, and the reflected light enters the microscope after passing through the aberration compensation device, and finally forms an image on the image acquisition device to obtain a clear image.

[0008] Optionally, the microscope comprises: an objective lens and an eyepiece, wherein the image acquisition device, the eyepiece and the objective lens are arranged in sequence from top to bottom, and the numerical aperture of the aberration compensation device is greater than or equal to the numerical aperture of the objective lens.

[0009] The imaging position of the optical imaging generated by the aberration compensation device is higher than the upper surface of the sample to be detected, so as to match the working distance of the objective lens.

[0010] Optionally, the first lens structure is a single lens or a lens group composed of multiple lenses; and the second lens structure is a single lens or a lens group composed of multiple lenses.

[0011] Optionally, the first lens structure and the second lens structure are both single aspheric lenses, and the first lens structure and the second lens structure are placed in a symmetrical and conjugate manner with the plane in which the plane mirror is located as a symmetrical plane.

[0012] Optionally, there is a clearance between the aberration compensation device and the sample to be detected and the microscope.

[0013] Optionally, the material of the plane mirror is BK7 glass or fused quartz.

[0014] Optionally, the image acquisition device is a CCD camera.

[0015] Optionally, the optical detection system further comprises a light splitting prism arranged between the objective lens and the eyepiece, and the light beam emitted by the light source reaches the sample to be detected after passing through the light splitting prism.

[0016] The optical detection system of the utility model, including: vacuum chamber, its inside places have sample to be detected, its top is provided with window, plane mirror, set up in window place, to close window, microscope, set up vacuum chamber outside, and aberration compensation device, set up between microscope and sample to be detected, it includes first lens structure located plane mirror above and second lens structure located plane mirror below, through setting aberration compensation device, can reduce or eliminate the aberration introduced by the plane mirror of the window of the vacuum chamber, improve the detection precision and detection efficiency of the optical detection system.

[0017] Further, the optical detection system of the utility model, the microscope comprises: an objective lens and an eyepiece, wherein the image acquisition device, the eyepiece and the objective lens are sequentially arranged from top to bottom, and the numerical aperture of the aberration compensation device is greater than or equal to the numerical aperture of the objective lens; the imaging position of the optical imaging generated by the aberration compensation device is higher than the upper surface of the sample to be detected, so as to match the working distance of the objective lens, which can eliminate the limitation of the working distance of the objective lens on the thickness of the window plane mirror, is suitable for objective lenses of various working distances, and expands the application range.

[0018] The above and other objects, advantages and features of the utility model will be more apparent from the following detailed description of the specific embodiments thereof, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0019] Some specific embodiments of the present application will be described in detail below with reference to the accompanying drawings, which are presented by way of illustration and not of limitation. The same reference numbers in the drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that the drawings are not necessarily drawn to scale. In the drawings:

[0020] Figure 1 is a structural schematic diagram of an optical detection system according to an embodiment of the present application; and

[0021] Figure 2 is a structural schematic diagram of an aberration compensation device of an optical detection system according to an embodiment of the present application. DETAILED DESCRIPTION

[0022] In the prior art, the optical detection system detects the wafer, and the wafer usually needs to be arranged in a vacuum environment, and the main body of the optical detection system is usually arranged outside the vacuum chamber, and the optical image is transmitted through the vacuum window mirror to isolate the vacuum and the atmosphere. However, the optical detection of the wafer in the prior art has the problems of low detection quality and detection precision, mainly including: first, the resolution and the working distance of the microscope objective are negatively correlated, and the resolution and the magnification of the long working distance microscope objective are not enough; second, the oblique light passing through the vacuum window mirror will introduce a large optical aberration, resulting in a decrease in image resolution and image distortion; third, the custom of long working distance objective or vacuum compatible objective has a long cycle and poor economic benefit, and the resolution and detection precision are limited.

[0023] The embodiment provides an optical detection system, which can reduce or eliminate the aberration introduced by the plane mirror of the vacuum chamber window, improve the detection precision and detection efficiency of the optical detection system, eliminate the limitation of the working distance of the objective lens on the thickness of the window plane mirror, and be suitable for objective lenses of various working distances, thereby expanding the application range. Figure 1 is a structural schematic diagram of an optical detection system 100 according to an embodiment of the present application, Figure 2 is a structural schematic diagram of an aberration compensation device 140 of the optical detection system 100 according to an embodiment of the present application.

[0024] As Figure 1 and Figure 2As shown, the optical detection system 100 of the embodiment can generally include a vacuum chamber 110, a plane mirror 120, a microscope 130, and an aberration compensation device 140. The vacuum chamber 110 has a sample 200 to be detected placed inside, and a window 111 is formed on the top of the vacuum chamber 110. In a specific embodiment, the optical detection system 100 can further include a displacement table 180 configured to carry the sample 200 to be detected and adjust the up-and-down position of the sample 200 to be detected. More specifically, the optical detection system 100 can further include a driving mechanism (not shown in the figure). The driving mechanism is connected with the displacement table 180 and configured to adjust the up-and-down position of the displacement table 180, so as to adjust the up-and-down position of the sample 200 to be detected. In a specific embodiment, the driving mechanism can be a motor, and the sample 200 to be detected can be a wafer.

[0025] The plane mirror 120 is arranged at the window 111 to close the window 111. By completely closing the window 111 with the plane mirror 120, the vacuum condition can be achieved inside the vacuum chamber 110, and interference from other factors can be avoided. The microscope 130 is arranged outside the vacuum chamber 110 and above the sample 200 to be detected. By arranging the microscope 130 outside the vacuum chamber 110, the problem of non-vacuum compatibility of the microscope 130 can be solved.

[0026] The aberration compensation device 140 includes a first lens structure 141 above the plane mirror 120 and a second lens structure 142 below the plane mirror 120, and is configured to reduce or eliminate the aberration introduced by the plane mirror 120. Since the plane mirror 120 is arranged at the window 111 on the top of the vacuum chamber 110, the first lens structure 141 above the plane mirror 120 is outside the vacuum chamber 110, and the second lens structure 142 below the plane mirror 120 is inside the vacuum chamber 110.

[0027] It should be noted that the first lens structure 141 is a single lens or a lens group composed of multiple lenses, and the second lens structure 142 is a single lens or a lens group composed of multiple lenses. In a preferred embodiment, the first lens structure 141 and the second lens structure 142 are both single aspheric lenses, and the first lens structure 141 and the second lens structure 142 are placed in a symmetrical plane conjugate symmetry with the plane where the plane mirror 120 is located as the symmetrical plane.

[0028] In other embodiments, the first lens structure 141 and the second lens structure 142 can both be lens groups composed of multiple lenses. Each lens group is formed by combining multiple independent lenses, and the specific arrangement can make the first lens structure 141 and the second lens structure 142 achieve a similar optical path function as the single aspheric lens described above.

[0029] It should be noted that the microscope 130, the plane mirror 120, the aberration compensation device 140 and the sample to be detected 200 are on the same vertical optical axis, which effectively ensures the smooth implementation of the optical detection of the sample to be detected 200. Specifically, the microscope 130, the first lens structure 141, the plane mirror 120, the second lens structure 142 and the sample to be detected 200 are sequentially arranged from top to bottom.

[0030] In a specific embodiment, the optical detection system 100 can further include an image acquisition device 150 and a light source 160. The image acquisition device 150 is arranged above the microscope 130 system and is configured to acquire an image of the sample to be detected 200. In a preferred embodiment, the image acquisition device 150 is a CCD camera. As a digital camera with a charge-coupled device image sensor, the CCD camera has the advantages of high image quality, wide dynamic range, low noise, high color restoration degree, etc., and is very suitable for the application scenario of acquiring the image of the sample to be detected 200 in the embodiment.

[0031] The light source 160 is configured to emit a light beam, and the light beam is reflected after reaching the sample to be detected 200. The reflected light passes through the aberration compensation device 140 and enters the microscope 130, and finally forms an image on the image acquisition device 150, obtaining a clear image. Since the plane mirror 120 will introduce a large optical aberration when the light passes through it, resulting in a decrease in image resolution and image distortion, the aberration compensation device 140 is arranged in the embodiment to reduce or eliminate the aberration introduced by the plane mirror 120 of the window 111 of the vacuum chamber 110, so as to obtain a high-definition high-resolution image, thereby improving the detection accuracy and detection efficiency of the optical detection system 100.

[0032] In a specific embodiment, the light source 160 can adopt a halogen lamp light source, a laser light source or an LED light source. It should be noted that the halogen lamp light source has low light efficiency, generates large heat dissipation, has poor light collimation, needs a special light condensing and collimating system to shape the light beam, has low illumination efficiency, and has a short service life, which needs to be frequently replaced and re-calibrated.

[0033] The laser light source adopts a collimating and expanding beam method, so that the laser has a large beam diameter and a low divergence angle. Then, the annular diaphragm is used to block the invalid area of the light beam, so that the effective area of the light beam passes through the dark field channel of the microscope objective lens and is aggregated to irradiate the detection area of the sample. After the laser is expanded, the annular diaphragm blocks and absorbs the center area with the largest energy density, and the part close to the edge with small energy density passes through. As a result, the actual illumination efficiency is very low, and a large power laser and a large aperture expander are needed to improve the illumination efficiency to a certain extent. Moreover, a large part of the light energy absorbed by the diaphragm may generate heat.

[0034] Therefore, in a preferred embodiment, an LED light source can be used to emit the light beam. Although the LED light source has a very large divergence angle and needs a special shaping system to correct the light beam, and the LED lighting has high requirements for the driving device, the LED light source and its driving device have the advantages of high integration, high brightness, long service life, small attenuation, good economy, etc., which are suitable for the application scenarios of the present embodiment.

[0035] In a specific embodiment, the microscope 130 includes an objective lens 131 and an eyepiece 132, wherein the image acquisition device 150, the eyepiece 132 and the objective lens 131 are arranged in sequence from top to bottom. More specifically, the optical detection system 100 can further include a beam splitter prism 170 arranged between the objective lens 131 and the eyepiece 132, and the light beam emitted by the light source 160 reaches the sample to be detected 200 after passing through the beam splitter prism 170.

[0036] The transmission-reflection ratio of the beam splitter prism 170 can be set according to actual conditions. The direction of the light beam emitted by the light source 160 is perpendicular to the optical axis of the microscope 130. After the light beam is reflected by the beam splitter prism 170, part of the light rays reach the sample to be detected 200 along the optical axis, and after being reflected by the sample to be detected 200, they enter the objective lens 131, the beam splitter prism 170, the eyepiece 132 and the image acquisition device 150 in sequence, and finally form an image in the image acquisition device 150.

[0037] In a specific embodiment, the aberration compensation device 140 has a clearance distance with the sample to be detected 200 and the microscope 130. This can ensure the safe arrangement of the components and prevent damage caused by collision and extrusion. The clearance distance between the aberration compensation device 140 and the sample to be detected 200 can actually refer to the minimum gap between the lower surface of the second lens structure 142 and the upper surface of the sample to be detected 200. The clearance distance between the aberration compensation device 140 and the microscope 130 can actually refer to the minimum gap between the upper surface of the first lens structure 141 and the lower surface of the objective lens 131 of the microscope 130.

[0038] In a preferred embodiment, the material of the plane mirror 120 is BK7 glass or fused quartz. The BK7 optical glass has the advantages of high transmittance, low absorption, good weather resistance, easy processing, etc. The fused quartz has the advantages of high purity, excellent physical and chemical properties, good thermal stability, etc. The specific parameters of the first lens structure 141 and the second lens structure 142 can be set according to actual needs, such as the surface shape, material and optical parameters of the lens.

[0039] However, it is emphasized that the numerical aperture of the aberration compensation device 140 composed of the first lens structure 141 and the second lens structure 142 is greater than or equal to the numerical aperture of the objective lens 131. The imaging position of the optical imaging generated by the aberration compensation device 140 is higher than the upper surface of the sample to be detected 200, thereby matching the working distance of the objective lens 131, so that the limitation on the length of the working distance of the objective lens 131 can be avoided.

[0040] In summary, the optical detection system 100 of the embodiment includes: a vacuum chamber 110, in which the sample to be detected 200 is placed, and a window 111 is opened at the top of the vacuum chamber 110; a plane mirror 120 is arranged at the window 111 to close the window 111; a microscope 130 is arranged outside the vacuum chamber 110; and an aberration compensation device 140 is arranged between the microscope and the sample to be detected, which includes a first lens structure 141 above the plane mirror 120 and a second lens structure 142 below the plane mirror 120. By arranging the aberration compensation device 140, the aberration introduced by the plane mirror 120 of the window 111 of the vacuum chamber 110 can be reduced or eliminated, and the detection accuracy and detection efficiency of the optical detection system 100 can be improved.

[0041] Further, the optical detection system 100 of the embodiment, the microscope 130 includes: an objective lens 131 and an eyepiece 132, wherein the image acquisition device 150, the eyepiece 132 and the objective lens 131 are arranged in sequence from top to bottom, and the numerical aperture of the aberration compensation device 140 is greater than or equal to the numerical aperture of the objective lens 131; the imaging position of the optical imaging generated by the aberration compensation device 140 is higher than the upper surface of the sample to be detected 200, thereby matching the working distance of the objective lens 131, which can eliminate the limitation of the thickness of the window 111 plane mirror 120 on the working distance of the objective lens 131, and is suitable for objective lenses 131 of various working distances, thereby expanding the application range.

[0042] Those skilled in the art should understand that, in the absence of special instructions, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", "clockwise", "counterclockwise" and the like used to indicate the orientation or positional relationship in the technical scheme of the utility model are only for the convenience of description and understanding of the utility model, and are not intended to indicate or imply that the devices or components referred to must have a particular orientation, so it cannot be understood as a limitation on the utility model.

[0043] The terms "first", "second", etc. are used only for descriptive purposes and do not connote or imply relative importance or an ordered or prioritized order to the indicated technical features. Thus, the use of "first", "second", etc. to describe a particular feature can mean one or more of the features being so described and can be used either explicitly or implicitly in this specification. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined. When a certain feature is "included", "comprises" or "comprised of" a certain component, unless otherwise specifically described, it means that the feature can include the component and can further include other components, unless otherwise specifically described.

[0044] Unless otherwise defined, the terms "mounting", "connected", "connecting", "fixed", and the like, are to be construed as broad terms, for example, can be fixed connection, can be detachable connection, or integral; can be mechanical connection, can be electrical connection; can be direct connection, can be indirect connection through an intermediate medium, can be internal connection of two elements or interaction relationship between two elements, unless otherwise specifically defined. Those skilled in the art should be able to understand the specific meaning of the above terms in the present application according to the specific circumstances.

[0045] In addition, in the description of the present embodiment, the first feature "above" or "below" the second feature can include that the first and second features are in direct contact, or can include that the first and second features are not in direct contact but are in contact through another feature between them. That is, in the description of the present embodiment, the first feature "above", "over", and "on" the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the first feature is higher in horizontal height than the second feature. The first feature "below", "under", or "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or only indicates that the first feature is lower in horizontal height than the second feature.

[0046] In the description of the present embodiment, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0047] Up to now, the person skilled in the art should recognize that, although the multiple exemplary embodiments of the utility model have been shown and described in detail herein, many other variants or modifications conforming to the principles of the utility model can still be directly determined or deduced according to the content disclosed by the utility model without departing from the spirit and scope of the utility model. Therefore, the scope of the utility model should be understood and recognized as covering all these other variants or modifications.

Claims

1. An optical detection system, characterized in that The optical detection system comprises: a vacuum chamber, in which a sample to be detected is placed, and a window is formed on the top of the vacuum chamber; a plane mirror, which is arranged at the window to close the window; a microscope, which is arranged outside the vacuum chamber; and an aberration compensation device, which is arranged between the microscope and the sample to be detected, and comprises a first lens structure above the plane mirror and a second lens structure below the plane mirror, and is configured to reduce or eliminate the aberration introduced by the plane mirror. The optical detection system further comprises:

2. The optical detection system of claim 1, wherein, an image acquisition device, which is arranged above the microscope system and is configured to acquire an image of the sample to be detected; and a light source, which is configured to emit a light beam, and the light beam is reflected after reaching the sample to be detected, and the reflected light enters the microscope after passing through the aberration compensation device, and finally forms an image on the image acquisition device to obtain a clear image.

3. The optical detection system according to claim 2, wherein the microscope comprises an objective lens and an ocular lens, and the image acquisition device, the ocular lens and the objective lens are arranged in sequence from top to bottom, and the numerical aperture of the aberration compensation device is greater than or equal to the numerical aperture of the objective lens.

4. The optical detection system according to claim 3, wherein the imaging position of the optical imaging generated by the aberration compensation device is higher than the upper surface of the sample to be detected, so as to match the working distance of the objective lens.

5. The optical detection system according to claim 1, wherein the first lens structure is a single lens or a lens group composed of multiple lenses, and the second lens structure is a single lens or a lens group composed of multiple lenses.

6. The optical detection system according to claim 5, wherein the first lens structure and the second lens structure are both single aspherical lenses, and the first lens structure and the second lens structure are placed in symmetrical conjugate positions with the plane in which the plane mirror is arranged as the symmetrical plane.

7. The optical detection system according to claim 1, wherein there is a clearance between the aberration compensation device and the sample to be detected and the microscope.

8. The optical detection system according to claim 1, wherein the material of the plane mirror is BK7 glass or fused quartz.

9. The optical detection system according to claim 2, wherein the image acquisition device is a CCD camera. The optical detection system further comprises: a light splitting prism, which is arranged between the objective lens and the ocular lens, and the light beam emitted by the light source reaches the sample to be detected after passing through the light splitting prism. ​ ​ ​ ​ ​ ​ ​ ​ ​ 10. The optical detection system of claim 3, wherein, ​ ​

Images