A laser detection system for observing non-transparent sample particles or defects

Abstract

The present application relates to a kind of laser detection systems for observing non-transparent sample particles or defects, belong to laser measuring instrument technical field.The present application is combined by setting up including two light transmission holes and the light collection lens of symmetrical layout conical hole with excitation light source, light collimation system, reflector, one aspect can let laser focusing light beam complete irradiation and focusing to sample surface through two conical holes, avoid laser into lens and affect weak scattered light signal, another aspect can let normal incidence excitation light beam sequentially pass through reflector, light collection lens converge on sample surface, through the refraction light generated by excitation light to particle or defect on sample, make that refraction light is emitted after being reflected four times in light collection lens by the light collection lens of special structure convergence, and there is light collimation system capture, to make that overall optical path system length is effectively shortened, solve the problem of large equipment volume, complex structure, can also realize large numerical aperture light energy collection simultaneously.

Description

Technical Field

[0001] This invention relates to a laser detection system for observing particulate matter or defects in non-transparent samples, belonging to the field of laser measurement instrument technology. Background Technology

[0002] When a tiny object (such as sample particles or defects on a sample surface) is illuminated, its scattered light is emitted in all directions. The smaller the object, the lower the scattered energy, and the wider the scattering energy distribution angle; this is referred to as wide-channel scattered light. For a scattered light collection system, it is necessary to collect as much wide-channel scattered light as possible to acquire sufficient scattered signals from tiny objects in order to measure and identify the characteristics of the tiny objects or other information of interest.

[0003] In existing technologies, light energy harvesting devices with a large light-gathering range (i.e., large numerical aperture NA) are often used to collect scattered light energy, such as CN119804392A and CN110426326A. These devices use ellipsoidal reflectors to collect light energy. However, the amount of light energy collected by an ellipsoidal reflector is closely related to the distance between the two focal points of the ellipsoid. The longer the distance, the larger the angle that can be collected. Such a design inevitably results in a large structural size, making the equipment structure complex and hindering the installation, debugging, stability, and cost control of the equipment.

[0004] In addition, for example, CN118732248A and CN119620341A use two folded optical paths to shorten the overall length, and the reflex mirror assembly used to collect light energy consists of three separate optical elements, which also makes the equipment structure more complicated, which is not conducive to the installation, debugging, stability and cost control of the equipment.

[0005] Therefore, in order to address the above problems, there is an urgent need to find a laser measurement and detection device that can collect as much excitation light energy as possible while simplifying the size and structure of the device. Summary of the Invention

[0006] To address the above problems, this invention proposes a laser detection system for observing particulate matter or defects in non-transparent samples, comprising:

[0007] The excitation light source can emit a focused laser beam;

[0008] The light-collecting lens has two opposing optical surfaces, namely surface S1 and surface S2. Surface S1 has curvature and a first light-transmitting hole at its center, the first light-transmitting hole being coated with a reflective film. Surface S2 is planar and has a second light-transmitting hole at its center, the second light-transmitting hole also being coated with a reflective film. The light-collecting lens has a first conical hole and a second conical hole symmetrically arranged and penetrating the lens on both sides of the optical axis, with the larger diameter ends of the first and second conical holes located on the side surfaces of the light-collecting lens.

[0009] A light collimation system having positive optical power and positioned on the optical axis extension line of the light-collecting lens;

[0010] A reflector with an inclination angle of 45 degrees is provided between the light-collecting lens and the light collimation system;

[0011] The sample is placed on the side of the light-collecting lens where the S2 surface is located. An obliquely incident excitation beam generated by the excitation source passes through the light-collecting lens through the first conical hole to illuminate the sample. After being reflected by the sample, it exits the light-collecting lens through the second conical hole. Another normally incident excitation beam is incident on the reflector in a direction perpendicular to the optical axis. After being reflected by the reflector, the normally incident excitation beam passes through the light-collecting lens and converges on the sample surface, causing particles or defects on the sample to be excited and thus generating scattered light. The scattered light can enter the light-collecting lens through the second light-transmitting hole and undergo four reflections between the two optical surfaces of the light-collecting lens before exiting from the first light-transmitting hole. The outgoing light rays converge at a convergence point F2 on the outer optical axis of the light-collecting lens, and the convergence point coincides with the focal point of the light collimation system. After passing through the light collimation system, the outgoing light rays will be emitted as parallel rays.

[0012] Furthermore, the scattered light can enter the light-receiving lens through the second light-transmitting hole at a scattering angle of α to β, wherein the minimum scattering angle α = 5° and the maximum scattering angle β = 71.8°.

[0013] Furthermore, the scattered light undergoes sequential reflections of r1, r2, r3, and r4 on surfaces S1 and S2 within the light-receiving lens, with r1 and r3 on surface S1 and r2 and r4 on surface S2. In other words, the scattered light is reflected four times within the light-receiving lens before exiting through the first light-transmitting hole.

[0014] Furthermore, the relationship between the diameter D1 of the first light-transmitting hole and the diameter D2 of the second light-transmitting hole is 0.8≤D1 / D2≤1.2.

[0015] Furthermore, the diameter D3 of the light-collecting lens is related to the diameter D1 of the first light-transmitting hole and the diameter D2 of the second light-transmitting hole in the following relationship: D1 / D3≤1 / 3, D2 / D3≤1 / 3.

[0016] Furthermore, in the four reflections of the light-receiving lens entering from the S2 surface with the minimum scattering angle α, the distance L2 from the optical axis O of the light-receiving lens at the fourth reflection point r4b is greater than 0.5*D2; when the light-receiving lens enters from the S2 surface with the maximum scattering angle β, the distance L1 from the transmission position from the S1 surface after the fourth reflection to the optical axis O of the light-receiving lens is less than 0.5*D1.

[0017] Furthermore, a negative lens is provided between the light-collecting lens and the reflector. The negative lens can reduce the convergence angle of the outgoing light rays exiting the light-collecting lens and converge them to a convergence point F3 on the outer optical axis of the light-collecting lens. The convergence point coincides with the focal point of the light collimation system, thereby reducing the image-side NA value. The center of the negative lens is provided with a through hole for the positively incident excitation beam to pass through.

[0018] Furthermore, the diameter of the negative lens is Df, the diameter of the through hole is Dt, and Dt / Df≤0.5.

[0019] The beneficial effects of this invention are:

[0020] This invention combines a light-collecting lens with two light-transmitting holes and a symmetrically arranged conical aperture with an excitation source, a light collimation system, and a reflector. On the one hand, it allows the laser focused beam to irradiate and focus on the sample surface through the two conical apertures, avoiding the laser from entering the lens and affecting the weak scattered light signal. On the other hand, it allows the normally incident excitation beam to pass sequentially through the reflector and the light-collecting lens to converge on the sample surface, forming excitation in both oblique and normal directions. The excitation light excites particles or defects on the sample and generates refracted light. The specially structured light-collecting lens reflects the refracted light four times before it is emitted and converged, and the light collimation system captures it. This effectively shortens the overall optical path length, solving the problems of large device size and complex structure, while also enabling large numerical aperture light energy collection. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of Embodiment 1 of the present invention (without a negative lens).

[0022] Figure 2 This is a schematic diagram of the overall structure (with a negative lens) of Embodiment 2 of the present invention.

[0023] Figure 3 This is a schematic diagram of the light-collecting lens of the present invention.

[0024] Figure 4 This is a point diagram showing the light rays converged by a light-collecting lens in Embodiment 1 of the present invention.

[0025] Figure 5 This is a point diagram showing the light rays converged by the light-collecting lens in Embodiment 2 of the present invention.

[0026] In the figure, 1 is the normally incident excitation beam; 2 is the light-collecting lens; 3 is the light collimation system; 4 is the reflecting mirror; 5 is the sample; 6 is the obliquely incident excitation beam; 7 is the negative lens; 2A is the first conical aperture; 2B is the second conical aperture. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0028] In this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] In this invention, the terms "first" and "second" are used only to distinguish similar components / parts in different positions or with different characteristics, and have no other limiting meaning; "upper" refers to the direction in which each component is away from the ground, and "lower" refers to the direction in which each component is away from the ground.

[0030] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0031] Example 1

[0032] like Figure 1 As shown, this invention proposes a laser detection system for observing particulate matter or defects in non-transparent samples, including an excitation source, a light-collecting lens, and a light collimation system. Sample 5 is selected as a silicon wafer, wherein:

[0033] Excitation source 1 is a light source component capable of emitting a focused laser beam. Figure 1 In the example, the emitted beam is a normal incident excitation beam from bottom to top;

[0034] The light-collecting lens 2 has two opposing optical surfaces, namely surface S1 and surface S2. Surface S1 has curvature (aspherical) and a first light-transmitting hole at its center, with a reflective film coated on the outside of the first light-transmitting hole. Surface S2 is planar and has a second light-transmitting hole at its center, also coated with a reflective film. The light-collecting lens has a first conical hole 2A and a second conical hole 2B symmetrically arranged and penetrating the lens on both sides of the optical axis. The large-diameter ends of the first conical hole 2A and the second conical hole 2B are located on the side of the light-collecting lens 2. An obliquely incident excitation beam 6 can pass through the first conical hole 2A through the entire light-collecting lens 2 and reach the surface of sample 5 on one side of surface S2. After being reflected by the surface of sample 5, it exits the light-collecting lens 2 through the second conical hole 2B.

[0035] Preferably, the diameter of the first light-transmitting hole is D1 = 12 mm, and the diameter of the second light-transmitting hole is D2 = 14 mm. The diameter of the light-receiving lens is D3 = 58 mm, the thickness is 22.926 mm, and the working wavelength is 0.266 μm.

[0036] The specific parameters of the light-collecting lens 2 are shown in Table 1:

[0037] Table 1

[0038]

[0039] The light collimation system, which has positive optical power and is located on the optical axis extension line of the light-collecting lens 2, can collect and converge light from the left end and emit parallel light from the right end to achieve the light collimation effect, so as to facilitate the subsequent processing and analysis of the collected signal using various optical elements;

[0040] On one hand, the sample 5 is placed on the side of the S2 surface of the light-collecting lens. The obliquely incident excitation beam 6 passes through the first conical hole 2A and irradiates the sample through the light-collecting lens 2. After being reflected by the sample, it exits the light-collecting lens 2 through the second conical hole 2B, thus avoiding the laser from entering the light-collecting lens 2 and affecting the signal of the weak scattered light.

[0041] On the other hand, in this embodiment, a downward-tilting reflector 4 with an inclination angle of 45 degrees is provided between the light-collecting lens 2 and the light collimation system 3; a normally incident excitation beam 1 is also provided to be incident from bottom to top in a direction perpendicular to the optical axis to the reflector. After being reflected by the reflector, the normally incident excitation beam passes through the light-collecting lens and converges on the surface of the sample 5, so that the particles or defects on the sample 5 are excited to generate scattered light. The scattered light can enter the light-collecting lens 2 through the second light-transmitting hole and undergo four reflections between the two optical surfaces of the light-collecting lens 2 before exiting from the first light-transmitting hole. The outgoing light rays will converge at a convergence point F2 on the outer optical axis of the light-collecting lens 2, and the convergence point coincides with the focal point of the light collimation system 3. After passing through the light collimation system 3, the outgoing light rays will be emitted as parallel rays, which is conducive to the subsequent processing and analysis of the collected signals using various optical elements.

[0042] Furthermore, such as Figure 3 As shown, the scattered light can enter the receiving lens 2 through the second light-transmitting aperture at scattering angles of α to β, where the minimum scattering angle α = 23° and the maximum scattering angle β = 71.8°. The scattered light undergoes sequential reflections (r1, r2, r3, r4) on surfaces S1 and S2 within the receiving lens 2, with r1 and r3 on surface S1 and r2 and r4 on surface S2. That is, the scattered light exits through the first light-transmitting aperture after four reflections within the receiving lens 2, thus effectively shortening the overall optical path system length.

[0043] Furthermore, in the four reflections of the light-collecting lens 2 entering from the S2 surface with the minimum scattering angle α, the distance L2 = 6.3 mm from the optical axis O of the light-collecting lens at the fourth reflection point r4b; when the light-collecting lens 2 enters from the S2 surface with the maximum scattering angle β, the distance L2 = 6.3 mm from the transmission position from the S1 surface after the fourth reflection to the optical axis O of the light-collecting lens after the fourth reflection.

[0044] Light rays with scattering angles between α and β are collected by the light-collecting lens 2, and ultimately converge to a point F2 on the outer optical axis O of the light-collecting lens, such as... Figure 4 As shown, the RMS radius of the converging spot is 0.403 μm, indicating a good focusing effect.

[0045] Example 2

[0046] Based on the structure of Embodiment 1, a negative lens 7 is provided between the light-collecting lens 2 and the reflecting mirror 4, such as... Figure 2 As shown, the negative lens 7 can reduce the convergence angle of the outgoing light rays from the light-collecting lens 2 and converge them to a convergence point F3 on the outer optical axis of the light-collecting lens 2. The convergence point coincides with the focal point of the light collimation system 3, thereby reducing the image-side NA value. The NA of the light collimation system 3 only needs to be greater than 0.28 to collect all the light rays. The negative lens 7 has a through hole at its center for the positively incident excitation beam to pass through.

[0047] Unlike Embodiment 1, this embodiment adjusts the relevant parameters of the light-collecting lens: the diameter of the first light-transmitting aperture D1 = 16 mm, and the diameter of the second light-transmitting aperture D2 = 14.7 mm. The diameter of the light-collecting lens D3 = 70 mm, the thickness is 28.82 mm, and the working wavelength is 0.266 μm. Specific parameters of the light-collecting lens 2 are shown in Table 2.

[0048] Table 2

[0049]

[0050] Furthermore, the distance between the light-receiving lens 2 and the negative lens 7 is 2 mm. Preferably, the diameter of the negative lens 7 is Df, the diameter of the through hole is Dt, and Dt / Df ≤ 0.5. Specific parameters of the negative lens 7 are shown in Table 3.

[0051] Table 3

[0052]

[0053] Furthermore, in the four reflections of the light-receiving lens entering from the S2 surface with the minimum scattering angle α, the distance L2 = 6.8 mm from the optical axis O of the light-receiving lens at the fourth reflection point r4b; when entering from the S2 surface with the maximum scattering angle β, the distance L1 = 5.8 mm from the transmission position from the S1 surface after the fourth reflection to the optical axis O of the light-receiving lens after the fourth reflection.

[0054] On one hand, the sample 5 is placed on the side of the S2 surface of the light-collecting lens. The obliquely incident excitation beam 6 passes through the first conical hole 2A and irradiates the sample through the light-collecting lens. After being reflected by the sample, it exits the light-collecting lens 2 through the second conical hole 2B, thus avoiding the laser from entering the light-collecting lens 2 and affecting the signal of the weak scattered light.

[0055] On the other hand, a positively incident excitation beam 1 is directed upwards from below in a direction perpendicular to the optical axis to the reflector 4. After being reflected by the reflector 4, the positively incident excitation beam passes sequentially through the through hole of the negative lens 7, the first and second light-transmitting holes of the light-collecting lens 2, and converges on the surface of the sample 5. This excites the particles or defects on the sample 5, thereby generating scattered light. The scattered light can enter the light-collecting lens 2 through the second light-transmitting hole and undergo four reflections between the two optical surfaces of the light-collecting lens 2 before exiting through the first light-transmitting hole. The outgoing light rays converge at a convergence point F3 on the outer optical axis of the light-collecting lens 2, and the convergence point coincides with the focal point of the light collimation system 3. After passing through the light collimation system 3, the outgoing light rays will emit parallel light rays, which is beneficial for subsequent processing and analysis of the collected signals using various optical elements.

[0056] Similarly, such as Figure 3As shown, the scattered light can still enter the receiving lens 2 through the second light-transmitting aperture at scattering angles of α to β, where the minimum scattering angle α = 18° and the maximum scattering angle β = 71.8°. The scattered light undergoes sequential reflections (r1, r2, r3, r4) on surfaces S1 and S2 within the receiving lens 2, with r1 and r3 on surface S1 and r2 and r4 on surface S2. That is, the scattered light exits through the first light-transmitting aperture after four reflections within the receiving lens 2, thus effectively shortening the overall optical path system length.

[0057] Light rays with scattering angles between α and β are collected by the light-collecting lens 2, and ultimately converge to a point F2 on the outer optical axis O of the light-collecting lens, such as... Figure 5 As shown, the RMS radius of the converging spot is 0.07µm, indicating good focusing effect.

[0058] Example 3

[0059] Depending on the actual needs, either Example 1 or Example 2 laser detection system can be reasonably selected for sample defect detection and measurement. The specific method is as follows:

[0060] Step 1: Place the surface of the sample 5 to be tested at the focal point on one side of the light-collecting lens 2, and use the positive incident excitation beam 1 to shoot out towards the reflecting mirror 4. After reflection, it is focused onto the surface of the sample 5 to be tested by the light-collecting lens 2 (or by passing through the negative lens 7 and the light-collecting lens 2 in sequence); or, the oblique incident excitation beam 6 can be used to focus onto the sample through the first conical hole 2A.

[0061] Step 2: Move sample 5 along a certain path. For example, for a circular sample, move it outward in a spiral shape starting from the center of the sample, or for a square sample, move it along an "arch" path.

[0062] Step 3: During the movement, if there are particles or defects on the sample surface, the incident laser will be scattered. The smaller the size of the particles or defects, the wider the angle of the scattered light energy distribution. This scattered light energy enters the light-collecting lens with a large numerical aperture through the second light-transmitting hole and is collected into the lens. After four reflections between the S1 and S2 surfaces in front of and behind the lens, it is transmitted out of the light-collecting lens 2 through the first light-transmitting hole and converges at a convergence point F2 or F3 on the outer optical axis of the light-collecting lens 2.

[0063] Step 4: After passing through point F2 or F3, the light rays enter the collimation system 3 and will exit in a collimated state;

[0064] Step 5: The beam collimated by the collimation system 3 is parallel light, providing ample space for various optical devices and processing. For example, filters can be used to obtain wavelengths of interest, and polarizers can be used to obtain polarized light of interest. Finally, these rays are incident on a photoelectric conversion device and converted into electrical signals. The presence, strength, corresponding wavelength, and occurrence time of the electrical signals characterize the presence, size, composition, and location of particles, thus enabling the detection of particles or defects using laser technology.

[0065] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A laser detection system for observing particulate matter or defects in non-transparent samples, characterized in that, include: Excitation light source, capable of emitting excitation beams in any direction; The light-collecting lens has two opposing optical surfaces, namely surface S1 and surface S2. Surface S1 has curvature and a first light-transmitting hole at its center, the first light-transmitting hole being coated with a reflective film. Surface S2 is flat and has a second light-transmitting hole at its center, the second light-transmitting hole also being coated with a reflective film. The light-collecting lens has a first conical hole and a second conical hole symmetrically arranged and penetrating the lens on both sides of the optical axis, with the larger diameter ends of the first and second conical holes located on the side surfaces of the light-collecting lens. A light collimation system having positive optical power and positioned on the optical axis extension line of the light-collecting lens; A reflector with an inclination angle of 45 degrees is provided between the light-collecting lens and the light collimation system; The sample is placed on the side of the light-collecting lens where the S2 surface is located. An obliquely incident excitation beam generated by the excitation source passes through the light-collecting lens through the first conical hole to illuminate the sample. After being reflected by the sample, it exits the light-collecting lens through the second conical hole. Another normally incident excitation beam is incident on the reflector in a direction perpendicular to the optical axis. After being reflected by the reflector, the normally incident excitation beam passes through the light-collecting lens and converges on the sample surface, causing particles or defects on the sample to be excited and thus generating scattered light. The scattered light can enter the light-collecting lens through the second light-transmitting hole and undergo four reflections between the two optical surfaces of the light-collecting lens before exiting from the first light-transmitting hole. The outgoing light rays converge at a convergence point F2 on the outer optical axis of the light-collecting lens, and the convergence point coincides with the focal point of the light collimation system. After passing through the light collimation system, the outgoing light rays will be emitted as parallel rays.

2. The laser detection system according to claim 1, characterized in that, The scattered light can enter the light-receiving lens through the second light-transmitting hole at a scattering angle of α to β, wherein the minimum scattering angle α = 5° and the maximum scattering angle β = 71.8°.

3. The laser detection system according to claim 2, characterized in that, The scattered light undergoes sequential reflections of r1, r2, r3, and r4 on surfaces S1 and S2 within the light-receiving lens, with r1 and r3 on surface S1 and r2 and r4 on surface S2. In other words, the scattered light is reflected four times within the light-receiving lens before exiting through the first light-transmitting hole.

4. The laser detection system according to claim 3, characterized in that, The relationship between the diameter D1 of the first light-transmitting hole and the diameter D2 of the second light-transmitting hole is 0.8≤D1 / D2≤1.2; the relationship between the diameter D3 of the light-receiving lens and the diameters D1 and D2 of the first light-transmitting hole is D1 / D3≤1 / 3, D2 / D3≤1 / 3.

5. The laser detection system according to claim 4, characterized in that, In the four reflections of the light-receiving lens entering from the S2 surface with the minimum scattering angle α, the distance L2 from the optical axis O of the light-receiving lens at the fourth reflection point r4b is greater than 0.5*D2; when the light-receiving lens enters from the S2 surface with the maximum scattering angle β, the distance L1 from the transmission position from the S1 surface after the fourth reflection to the optical axis O of the light-receiving lens is less than 0.5*D1.

6. The laser detection system according to claim 5, characterized in that, A negative lens is also provided between the light-collecting lens and the reflector. The negative lens can reduce the convergence angle of the light rays emitted from the light-collecting lens and converge them to a convergence point F3 on the outer optical axis of the light-collecting lens. The convergence point coincides with the focal point of the light collimation system, thereby reducing the image-side NA value. A through hole is provided at the center of the negative lens for the positively incident excitation beam to pass through.

7. The laser detection system according to claim 6, characterized in that, The diameter of the negative lens is Df, the diameter of the through hole is Dt, and Dt / Df≤0.5.

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