Dual-NA compact broadband light source and wafer metrology system

Abstract

The application provides a double-NA compact broadband light source and a wafer quantity detection system, and belongs to the field of light sources of industrial vision. The double-NA compact broadband light source comprises a laser pumping module, a light beam shaping module, a light source chamber, a glass ellipsoidal mirror for light splitting, a bulb, a spherical mirror, a high-voltage driving module and a light source output window. The glass ellipsoidal mirror for light splitting adopts optical glass as an ellipsoidal mirror base and the mirror surface is coated with a spectrum selective medium film. The application utilizes the spectrum splitting characteristics of the medium film to realize a light splitting working mechanism with high reflection of pumping laser and high transmission of target broadband light. The ellipsoidal mirror is provided with a spherical mirror behind the ellipsoidal mirror to construct a return light collecting channel, thereby forming a global double-path light collecting system of forward straight-through + backward return, and realizing super-large NA pumping and super-large NA global light collecting. The scheme has high adaptability and can be used in semiconductor precision quantity detection, sensor high-precision calibration, embedded integrated detection equipment, biochemical spectrum analysis and other types of scenes, and has stronger engineering practicability.

Description

Technical Field

[0001] This invention belongs to the field of industrial vision light sources, especially the field of laser-driven plasma light source technology, and specifically relates to a dual-NA compact broadband light source and wafer quantity detection system. Background Technology

[0002] In fields such as semiconductor testing, optical calibration, precision optical testing, and biochemical spectroscopy analysis, there is an urgent need for wide-bandwidth, high-brightness, and high-stability laser-driven light sources. Laser-driven light sources possess advantages such as an ultra-wide continuous spectrum from ultraviolet to visible to infrared, good stability, and long lifespan, and have gradually replaced traditional lamp light sources, finding widespread application in high-precision optical testing scenarios. As testing equipment continues to evolve towards miniaturization and integration, the industry demands that light sources, while retaining features such as large NA pumping, high laser utilization, high saturation threshold, and high brightness output, further improve overall compactness, reduce light output height, and enhance spatial adaptability.

[0003] Current mainstream high-brightness laser-driven light sources generally adopt large numerical aperture pumping and large-angle light collection structure, which effectively improves laser focusing efficiency, energy utilization and light source saturation threshold, and solves the defects of insufficient brightness and low light efficiency of traditional small NA light sources, and can meet the basic light emission requirements of high-precision detection.

[0004] However, the existing large NA light source optical path structure design is fixed. In order to ensure large-angle pumping and large solid angle light collection effect, a large structural redundancy and device installation spacing are required. The optical layout is loose and the space utilization rate is low, resulting in a large overall size, low integration and high light output window height. It is difficult to adapt to miniaturized embedded devices and narrow space integration scenarios, which greatly limits the application range of the light source.

[0005] Existing compact light source solutions mostly achieve miniaturization by reducing the pump angle and sacrificing the pump NA. Although the overall size of the machine is reduced, it will cause problems such as decreased laser utilization, lower saturation threshold, insufficient plasma excitation, and decreased output brightness. It cannot meet the multiple requirements of large NA pump, large NA light collection, high brightness and small compact structure.

[0006] In summary, the industry currently lacks a laser drive source that can fully retain the advantages of high-efficiency pumping with a large NA, high-efficiency light collection with a large solid angle, high saturation threshold, and high brightness output, while also possessing a highly compact optical path, low light output height, and wide applicability. This makes it difficult to meet the development needs of high-end miniaturized and integrated detection equipment. Therefore, developing this type of novel compact high-brightness laser drive source has significant engineering application value and market significance. Summary of the Invention

[0007] To address the technical bottleneck of traditional large-NA laser-driven light sources, which struggle to simultaneously achieve lossless pumping across the entire range, ultra-wide-angle full-range light collection, and an extremely compact structure, this invention proposes a technical solution for a dual-NA compact broadband light source and a wafer quantity measurement system.

[0008] Design Principle: This invention retains the characteristics of large numerical aperture pumping, large solid angle light collection, high laser utilization, high saturation threshold, and compact optical path layout. It also features a novel optimized design of the material and optical film system of the core pumping and focusing device, the ellipsoidal mirror. This eliminates the need for opening holes in the ellipsoidal mirror or adding additional folding light collection structures, enabling simultaneous ultra-large NA laser pumping and ultra-large NA broad-spectrum light collection. This further simplifies the optical path structure, improves the output brightness of the light source and the structural integration, and effectively solves the technical pain point of existing technologies that cannot simultaneously achieve high pumping performance, high light collection efficiency, and a minimalist and compact structure.

[0009] A compact broadband light source with dual laser emitters (NAs) based on a dielectric film beam-splitting ellipsoidal mirror is disclosed. The compact broadband light source includes a laser pumping module, a beam shaping module, a light source chamber, a beam-splitting glass ellipsoidal mirror, a lamp, a spherical reflector, a high-voltage driving module, and a light source output window. The beam-splitting glass ellipsoidal mirror uses optical glass as the substrate and has a spectrally selective dielectric film coated on its surface. The front of the beam-splitting glass ellipsoidal mirror faces the lamp for focusing, and the spherical reflector is positioned behind the beam-splitting glass ellipsoidal mirror, thereby constructing a dual-path light-receiving system with forward direct access and backward reflection. This system achieves both ultra-large NA pumping and ultra-large NA global light collection simultaneously without any pump NA loss or mirror openings.

[0010] Furthermore, the laser pumping module includes a laser and an optical path coupling mirror assembly for supplying a laser beam into the light source cavity.

[0011] Furthermore, the beam shaping module includes diffractive optical elements, apertures, spatial light modulators, and micromirror arrays.

[0012] Furthermore, the spectrally selective medium film of the beam-splitting glass ellipsoid is configured such that the laser beam output after beam shaping by the beam shaping module is totally reflected and converged to the central region of the bulb; the effective wavelength light in one of the plasma emission paths of the bulb is directly transmitted through the beam-splitting glass ellipsoid, and the light is reflected back along the original path by the spherical reflector on the rear side, and then exported from the light source output window on the front side after passing through the beam-splitting glass ellipsoid again.

[0013] Furthermore, the lateral receiving angle of the beam-splitting glass ellipsoid is 180°.

[0014] Furthermore, the bulb is a high-pressure sealed bulb, and the bulb is filled with working gas.

[0015] Furthermore, the high-voltage drive module is connected to the two electrodes of the bulb, and applies high voltage to the inside of the bulb through the electrodes, causing the working gas filled in the center of the bulb to be pre-ionized to form a plasma light-emitting region; the pump laser focused out by the beam-splitting glass ellipsoid mirror continuously excites the plasma, causing the plasma to generate a broad spectrum of continuous light covering the ultraviolet, visible and infrared bands.

[0016] Furthermore, an output window is embedded in the output window of the light source chamber, and the output window is made of flat glass or curved glass. An anti-reflective coating is deposited on the glass surface of the output window.

[0017] The present invention also provides a wafer quantity inspection system, including a wafer stage, an optical inspection station and a processor, wherein the light source of the optical inspection station adopts the aforementioned dual-NA compact broadband light source.

[0018] Compared to existing technologies, this application innovatively uses a glass-based spectrally selective dielectric film ellipsoidal mirror to replace the traditional metal-plated aluminum mirror, breaking through the limitation of traditional mirrors that can only reflect pump light. Utilizing the spectral frequency division characteristics of the dielectric film, it achieves a beam splitting mechanism that enables high reflectivity of the pump laser and high transmittance of the target's broad spectrum. This invention eliminates the need for openings in the ellipsoidal mirror, fully preserving its ultra-large angle receiving range and ensuring lossless ultra-large NA throughout the pump light path. Simultaneously, it utilizes the light transmission characteristics of the ellipsoidal mirror in conjunction with a rear spherical mirror to construct a folding light receiving path, forming a full-domain dual-path light receiving system with forward direct access and backward folding. Without increasing the complexity of the optical path structure, it maximizes both the pump NA and the collecting NA, resolving the inherent contradiction of traditional structures that either sacrifice pump performance for light receiving efficiency or have limited brightness due to limited light receiving angle. Compared to existing technologies, this invention possesses significant structural innovation and performance improvement, with the following specific beneficial effects.

[0019] First, this invention employs a glass substrate + selective dielectric film ellipsoidal mirror structure, completely eliminating the single-function limitations of traditional metal-plated aluminum mirrors. While fully retaining the core performance of ultra-large NA laser pumping, high laser utilization, high saturation threshold, and high pump brightness, it endows the ellipsoidal mirror with broad-spectrum light transmission capability, enabling optical path splitting and multiplexing, and significantly improving the utilization rate of optical devices. Simultaneously, compared to traditional metal substrate aluminum-plated film structures, the glass substrate combined with the dielectric film achieves ultra-high reflectivity for the pump laser wavelength, effectively reducing pump laser reflection loss and further improving laser energy utilization efficiency. Moreover, this coating process technology is mature, has high mass production stability, and possesses excellent cost competitiveness, making it suitable for large-scale industrial production.

[0020] Secondly, the elimination of the need for an ellipsoidal mirror aperture design avoids the problems caused by aperture structures, such as pump beam distortion, reduced effective reflection area, local energy loss, and difficulty in optical path adjustment, resulting in higher pump optical path integrity and stability.

[0021] Third, by using a back-transmitting light + spherical mirror reversal structure, the ineffective light rays emitted by the plasma in the back direction are fully recovered. Combined with forward direct light collection, three-dimensional full-area light collection is achieved, which greatly improves the numerical aperture of the collection optical path and the overall luminous flux of the light source, and significantly improves the output brightness of the light source and the detection signal-to-noise ratio.

[0022] Fourth, the present invention has a high degree of optical path integration, a very simple and compact structure, no redundant structures, small overall size, simple assembly, and good mass production consistency. While retaining the high performance of dual full-size NA, it greatly improves the miniaturization and space adaptability of the equipment. It can be widely adapted to various scenarios such as semiconductor precision detection, high-precision sensor calibration, embedded integrated detection equipment, and biochemical spectral analysis, with a wider range of applications and stronger engineering practicality. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the dual-NA compact broadband light source based on a dielectric film beam-splitting ellipsoidal mirror according to this application; Figure 2 for Figure 1 A schematic diagram of the optical path for collection; Figure 3 This is a schematic diagram of the laser pupil distribution after passing through the beam shaping module; Figure 4 This is a schematic diagram illustrating the working principle of a laser-driven light source.

[0024] In the diagram, 1. Beam-splitting glass ellipsoid; 2. Bulb; 3. Output window; 4. Source cavity; 5. Laser beam; 6. Output beam; 7. Spherical mirror; 8. Beam shaping module; 9. Laser. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] A compact broadband light source with dual nanometers based on a dielectric film beam-splitting ellipsoidal mirror, see [link to relevant documentation]. Figures 1-4 The dual-NA compact broadband light source includes a laser pump module, a beam shaping module 8, a light source chamber 4, a beam-splitting glass ellipsoid mirror 1, a bulb 2, a spherical reflector 7, a high-voltage drive module, and a light source output window.

[0027] In this design, the beam-splitting glass ellipsoid 1 uses optical glass as the ellipsoidal reflector substrate and has a spectrally selective medium film coated on the mirror surface. The front of the beam-splitting glass ellipsoid 1 faces the bulb 2 for focusing light, while the spherical reflector 7 is positioned behind it. This constructs a dual-path light-receiving system with forward direct access and backward reflection, achieving both ultra-large NA pumping and ultra-large NA full-domain light collection without any pump NA loss or mirror aperture. The core difference between this solution and the traditional metal-coated aluminum ellipsoidal mirror optical path structure lies in its use of optical glass as the ellipsoidal reflector substrate and the coating of a spectrally selective medium film on the mirror surface, replacing the traditional metal-based aluminum-coated structure. In this field, the ultra-large NA index value aperture NA is ≥0.9.

[0028] The laser pumping module includes a laser 9 and an optical path coupling mirror assembly, which is used to provide a laser beam 5 into the light source cavity 4.

[0029] The beam shaping module 8 includes diffractive optical elements, an aperture, a spatial light modulator, and a micromirror array.

[0030] The spectrally selective medium film of the beam-splitting glass ellipsoid 1 is configured to: totally reflect and converge the laser beam 5 output by the beam shaping module 8 to the central region of the bulb 2; and directly transmit the selected effective wavelength light in the plasma emission of the bulb 2 (in this example, the selected effective wavelength optical selection is a wavelength of 260nm-450nm in one path) through the beam-splitting glass ellipsoid 1, and then reflect this part of the light back along the original path through the spherical reflector 7 on the rear side, and then send it out from the light source output window on the front side after passing through the beam-splitting glass ellipsoid 1 again.

[0031] Specifically, the lateral receiving angle of the beam-splitting glass ellipsoid 1 is 180°.

[0032] Among them, bulb 2 is a high-pressure sealed bulb, and the bulb is filled with working gas. The high-pressure drive module is connected to the two electrodes of bulb 2. The high pressure is applied to the inside of bulb 2 through the electrodes, so that the working gas filled in the center of the bulb is pre-ionized to form a plasma light-emitting region. The pump laser focused out by the beam-splitting glass ellipsoid 1 continuously excites the plasma, so that the plasma generates a broad spectrum of continuous light covering the ultraviolet, visible and infrared bands.

[0033] An output window 3 is embedded in the light source output window of the light source chamber 4. The output window 3 is made of flat glass or curved glass. Further, in an optional example, an anti-reflective coating is deposited on the glass surface of the output window 3.

[0034] For the core working principle of the light source of this invention, please refer to [link / reference]. Figure 4As shown: A high-power laser is coupled into the light source cavity 4, and after being shaped and focused by the pump optical path, it is converged into the interior of the high-pressure sealed bulb; the working gas inside the bulb 2 is pre-ionized by the high-voltage excitation of the electrodes to form a stable plasma; the high-energy laser continuously pumps and excites the plasma to generate a broad spectrum of light covering ultraviolet, visible and infrared light; finally, the broad spectrum of light is efficiently captured and output by the large solid angle collection optical path, realizing a stable light source output with high brightness and high luminous flux.

[0035] In the specific operation, the pump laser output from laser 9 is optically coupled into the source cavity 4 and then first enters the beam shaping module 8. The beam shaping module 8 precisely shapes the laser pupil distribution and beam profile, ensuring that the output beam shape and spot size perfectly match the effective reflecting surface of the beam-splitting glass ellipsoidal mirror 1 (i.e., the glass ellipsoidal reflector). This guarantees that the pump laser is incident on the ellipsoidal mirror surface at full aperture and high efficiency, preventing beam deviation and energy waste. The shaped pupil distribution is as follows: Figure 3 As shown in the illustration, the example is a semi-circular shape.

[0036] like Figure 1 As shown, the shaped pump laser is incident on a beam-splitting glass ellipsoidal mirror 1 coated with a dielectric film. Utilizing the ultra-high reflectivity of the dielectric film to the pump laser wavelength, the incident laser is precisely focused and concentrated onto the central region of a high-pressure sealed bulb using a large numerical aperture. High-voltage excitation of the electrodes pre-ionizes the working gas inside the bulb, forming a stable high-temperature plasma emitter. The continuously focused high-energy laser pumps the plasma, generating a broad-spectrum continuous light spectrum covering ultraviolet, visible, and infrared light. The glass substrate combined with the dielectric film structure used in this embodiment has a higher laser reflectivity than traditional metal-coated aluminum mirrors, significantly reducing pump laser reflection loss and effectively improving the overall laser utilization efficiency. Furthermore, the process is mature, production costs are controllable, and it is suitable for mass production applications.

[0037] like Figure 2 As shown, plasma emission achieves efficient collection and output through two optical paths: one is direct forward light collection, where the broad-spectrum light radiated by the plasma toward the output window directly penetrates the chamber and is output to the outside through the output window; the other is back-reflection light collection, where the 260-450nm effective wavelength light radiated by the plasma toward the ellipsoidal mirror can directly pass through the glass ellipsoidal mirror and the dielectric film layer, and be incident on the spherical reflector arranged on the rear side. The spherical reflector 7 accurately reflects this part of the light back along the original path, and after passing through the ellipsoidal mirror optical path again, it is exported from the front output window as the output beam 6.

[0038] This embodiment eliminates the need for openings in the ellipsoidal mirror, fully preserving its 180° large-angle receiving characteristics and maintaining ultra-large NA high-efficiency pumping performance throughout. Simultaneously, the dual-path light-collecting structure maximizes the capture of plasma divergent light, effectively improving the optical path's numerical aperture and the light source's output luminous flux. The overall optical path structure is extremely simple and compact, easy to assemble, and exhibits good mass production consistency. While maintaining high laser utilization, high saturation threshold, and ultra-high luminous brightness, it significantly reduces the overall size of the device, enhancing its spatial adaptability. It can effectively adapt to various high-precision applications such as miniaturized integrated detection equipment, semiconductor precision detection, high-precision optical calibration, and biochemical spectroscopy detection.

[0039] In an application example, the present invention also provides a wafer quantity inspection system, including a wafer stage, an optical inspection station and a processor, wherein the light source of the optical inspection station adopts the aforementioned dual-NA compact broadband light source.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A compact broadband light source with dual nano-fields based on a dielectric film beam-splitting ellipsoidal mirror, characterized in that, The dual-NA compact broadband light source includes a laser pump module, a beam shaping module (8), a light source chamber (4), a beam-splitting glass ellipsoid mirror (1), a bulb (2), a spherical reflector (7), a high-voltage drive module, and a light source output window; The beam-splitter glass ellipsoid (1) uses optical glass as the substrate of the ellipsoidal reflector and a spectrally selective medium film is coated on the mirror surface. The front side of the beam-splitter glass ellipsoid (1) faces the bulb (2) to concentrate light, and the spherical reflector (7) is set on the rear side of the beam-splitter glass ellipsoid (1), thereby constructing a dual light-receiving optical path with forward direct passage and backward reflection, realizing ultra-large NA pumping and ultra-large NA global light collection.

2. The dual-NA compact broadband light source according to claim 1, characterized in that, The laser pumping module includes a laser (9) and an optical path coupling mirror assembly for supplying a laser beam (5) into the light source chamber (4).

3. The dual-NA compact broadband light source according to claim 1, characterized in that, The beam shaping module (8) includes diffractive optical elements, apertures, spatial light modulators and micromirror arrays.

4. The dual-NA compact broadband light source according to claim 1, characterized in that, The spectrally selective medium film of the beam splitter glass ellipsoid (1) is configured such that the laser beam (5) output after beam shaping by the beam shaping module (8) is totally reflected and converged to the central region of the bulb (2); the selected effective wavelength light in the plasma emission of the bulb (2) is directly transmitted through the beam splitter glass ellipsoid (1), and the light is reflected back along the original path by the spherical reflector (7) on the rear side, and then exported from the light source output window on the front side after passing through the beam splitter glass ellipsoid (1) again.

5. The dual-NA compact broadband light source according to claim 1, characterized in that, The lateral receiving angle of the beam-splitting glass ellipsoid (1) is 180°.

6. The dual-NA compact broadband light source according to claim 1, characterized in that, The bulb (2) is a high-pressure sealed bulb, and the bulb is filled with working gas.

7. The dual-NA compact broadband light source according to claim 1, characterized in that, The high-voltage drive module is connected to the two electrodes of the bulb (2). The electrodes apply high voltage to the inside of the bulb (2), causing the working gas filled in the center of the bulb to be pre-ionized to form a plasma light-emitting area. The pump laser focused out by the beam splitter glass ellipsoid (1) continuously excites the plasma, causing the plasma to generate a broad spectrum of continuous light covering the ultraviolet, visible and infrared bands.

8. The dual-NA compact broadband light source according to claim 1, characterized in that, An output window (3) is embedded in the light source output window of the light source chamber (4), and the output window (3) is made of flat glass or curved glass.

9. A wafer metrology system, comprising a wafer stage, an optical inspection station, and a processor, characterized in that: The light source of the optical inspection station adopts the dual-NA compact broadband light source as described in any one of claims 1-8.

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