CN111458837A - Broadband low-dispersion lens - Google Patents
Broadband low-dispersion lens Download PDFInfo
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- CN111458837A CN111458837A CN202010272718.1A CN202010272718A CN111458837A CN 111458837 A CN111458837 A CN 111458837A CN 202010272718 A CN202010272718 A CN 202010272718A CN 111458837 A CN111458837 A CN 111458837A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/02—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of crystals, e.g. rock-salt, semi-conductors
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Abstract
The invention discloses a broadband low-dispersion lens, which comprises field beam restraint lenses L sequentially arranged from an object space to an image space1A first correcting lens group L2And a second corrective lens group L3First corrective lens L2And a second corrective lens group L3Used for correcting chromatic aberration on the axis and the size of a light spot and controlling the working distance. The working wavelength range of the lens is from 210nm to 900nm, and the lens covers the deep ultraviolet to near infrared wave bands; paraxial diffuse speckles are optimized to within the allium spot range while compressing the number of lens lenses and reducing chromatic aberration.
Description
Technical Field
The invention relates to the field of optics, in particular to semiconductor measuring equipment based on optical reflection, optical scattering and optical ellipsometry principles.
Background
The birth of the first transistor in 1947 marked the beginning of the semiconductor industry, from which semiconductor design, fabrication, inspection and applications became more and more widespread. From the beginning of wafer growth to the end of chip packaging, measurement equipment is an indispensable part of the semiconductor industry chain.
At present, the core and key technology of semiconductor measuring equipment are mainly mastered by some large-scale equipment manufacturers abroad, and the development of the domestic industry depends heavily on imported equipment, so that the development of the semiconductor measuring equipment with independent intellectual property rights becomes a high and new industry which is rapidly developed in China, and the inspirations fill the blank in China.
The non-contact optical measuring equipment becomes the main force of semiconductor measuring equipment, with the continuous improvement of industrial technology, the line width is from 14nm to 7nm to 5nm, and the film layer is from dozens of layers to hundreds of layers. The existing film thickness measuring equipment requires a wider spectrum, a smaller light spot and higher corresponding speed, and does not have higher requirements on the measuring equipment.
At present, the spectral range of the domestic ellipsometry measuring equipment is mostly concentrated on near ultraviolet to near infrared wave bands (350nm-800nm), the measuring light spot is larger than 45um, and the measurement cannot be carried out if thinner or smaller etching patterns are required to be tested. The existing solution generally adopts a multi-light-path system to separately measure, but has the defects of precision loss, speed reduction, complex system structure, poor stability, cost improvement and the like.
Disclosure of Invention
1. Objects of the invention
The invention provides a broadband low-dispersion lens for improving the measurement precision and expanding the application range in the prior art.
2. The technical scheme adopted by the invention
The lens design adopts 3 lenses as initial structure collocation, and provides a broadband low dispersion lens, including the restraint lens, the first correction lens group and the second correction lens group of the visual field light beam that arrange in proper order from the object space to the image space, first correction lens group, second correction lens group are used for correcting on-axis chromatic aberration and facula and are used for and control working distance.
The low refractive index and high Abbe number calcium fluoride materials are used as a constraint lens, namely a first lens group, so that the generation of chromatic aberration is reduced; then, performing compensation optimization by using the first correction lens group and the second correction lens group; the materials adopt fused quartz and calcium fluoride which can penetrate 210nm wave band; the first lens group constraint lens is made of calcium fluoride material, the first correction lens group is made of fused quartz material, and the second correction lens group is made of calcium fluoride.
Preferably, the paraxial magnification is adjusted by using both finite distance conjugation and infinite distance conjugation.
Preferably, the stop position is provided at the incident end, between the constraint lens and the first correction lens group, or between the first correction lens and the second correction lens group.
Preferably, the focal length f of the lens is constrained1Satisfies 0.4f<f1<0.9f。
Preferably, the focal length f2 of the first corrective lens group satisfies-0.4 f<f2<-0.15f。
Preferably, the focal length f3 of the second correction lens group satisfies 0.4f<f3<0.8f。
Preferably, infinite conjugation is adopted, and the diaphragm is positioned between the first correction lens and the second correction lens group;
preferably, the wavelength range is 210nm-900 nm.
Preferably, a first space ring is arranged between the constraint lens and the first correction lens, and a second space ring is arranged between the first correction lens and the second correction lens group.
Preferably, the incident end of the lens is fixed by a pressing ring; the external connecting part of the lens is matched with an external thread structure, a coaxial or flange adjusting structure.
3. Advantageous effects adopted by the present invention
(1) The invention provides improvement aiming at the spectrum range in the prior semiconductor measuring equipment technology and focusing light spots, so that the wide band is compatible with 210nm-900nm, the working band covers ultraviolet and near infrared bands, and the measuring range of the equipment is widened.
(2) According to the lens, the axial chromatic aberration and the light spot are within the diffraction limit, and the axial chromatic aberration is within the diffraction limit, so that a small light spot measuring system can be realized, and the energy is concentrated.
(3) The number of the lenses of the invention is reduced to 3, thus effectively reducing the energy loss of the reflecting surface and effectively improving the measuring precision and speed under the condition of less number of lenses.
Drawings
FIG. 1 is a schematic diagram of an infinity lens configuration according to the present invention;
FIG. 2 is an internal structure view of an infinity lens according to the present invention;
FIG. 3 is a diagram of the diffuse spot diameter of the infinity lens according to the present invention;
FIG. 4 is a diagram of chromatic aberration on an infinity lens axis according to the present invention;
FIG. 5 is a block diagram of the limited distance lens according to the present invention;
FIG. 6 is an internal structure view of a limited distance lens according to the present invention;
FIG. 7 is a finite distance lens diffuse spot diameter of the present invention;
FIG. 8 is a diagram of chromatic aberration on the limited distal lens axis of the present invention;
FIG. 9 is a schematic view of the numbering of the lenses of the invention.
Detailed Description
The technical solutions in the examples of the present invention are clearly and completely described below with reference to the drawings in the examples of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without inventive step, are within the scope of the present invention.
The present invention will be described in further detail with reference to the accompanying drawings.
The invention provides a wide-band, small-spot and low-chromatic aberration lens, which comprises field beam restriction lenses L arranged in sequence from an object space to an image space1A first correcting lens group L2And a second corrective lens group L3First corrective lens L2And a second corrective lens group L3For correcting on-axis chromatic aberration and controlling working distance, and system aperture can be set at the constraint lens L1A first correcting lens group L2And a second corrective lens group L3The lens can be designed into two modes of finite distance conjugate and infinite distance conjugate, can freely adjust paraxial magnification, and can be matched with various systems for use, and the constraint lens L1And a first corrective lens L2A first space ring is arranged betweenFirst corrective lens L2And a second corrective lens group L3A second space ring arranged between them, and a constraint lens L1Focal length f of1Satisfies 0.5f<f1<0.9f, a first corrective lens L2Focal length f of2Satisfies-0.4 f<f2<0.15f, a second corrective lens group L3Focal length f of3Satisfies 0.4f<f3<0.8 f; wherein f is the focal length of the lens. The incident end of the lens is fixed by a pressing ring. The external connecting part of the lens is matched by an external thread structure and a coaxial or flange adjusting structure; the materials should be fused quartz and calcium fluoride which can penetrate 210nm wave band; the lens is fixedly connected with low-stress or stress-free glue inside the lens.
The lens adopts two pieces of calcium fluoride and one piece of fused quartz as initial structure collocation, and adopts low refractive index and high Abbe number calcium fluoride material as constraint lens L1High Abbe number can reduce the generation of chromatic aberration and lay a foundation for later correction, and then a first correction lens L is used2And a second corrective lens group L3Focal length f of3Satisfies 0.4f<f3<0.8f, where f is the focal length of the lens, and the second correction lens L3 is optimized to compensate for the first correction lens L2Using fused silica material, part of the chromatic aberration is corrected while the second correction lens L is adjusted3The thickness and curvature of the (calcium fluoride) can further optimize the light spot and the chromatic aberration.
The lens has compact structure, the number of the lenses is reduced to 3, the design optimization wave band is 210nm-900nm, the ultraviolet wave band is considered, and the selection on materials is very limited. Meanwhile, in the selectable materials, the refractive indexes of calcium fluoride and fused silica are very similar, and the number of the lenses needs to be reduced as much as possible, so that the matching and combination in design are particularly important.
Example 1
In an infinite embodiment of the present invention, as shown in FIG. 1, the lens has a bullet shape with a fixed thread at the tail, a total mechanical length of 36mm and a mechanical outer diameter of 15mm, and the second corrective lens group L is mounted3A first correcting lens group L2And a containment lens L1Sequentially arranged at the tail part, provided with a space ring in the middle,the tail part is fixed by a pressing ring.
Referring to fig. 2 and table 1 below, the lens design parameters of the lens assembly are shown in table 1, the first lens group constraint lens L1 of the lens assembly is arranged in sequence from left to right, the focal length of the lens assembly is defined as f, and the maximum outer diameter of the lens assembly is 6.0 mm.
TABLE 1 lens parameters
| Noodle numbering | Radius of curvature R | Thickness-spacing H | Half caliber D/2 | Glass material |
| S1 | 0.59f | 0.08f | 2.8 | Caf2 |
| S2 | -0.52f | 0.012f | 2.7 | / |
| S3 (diaphragm) | -0.72f | 0.18f | 2.6 | F_silica |
| S4 | 0.23f | 0.015f | 2.2 | / |
| S5 | 0.32f | 0.57f | 2.3 | Caf2 |
| S6 | -0.82f | 0.66f | 1.7 |
Fig. 3 shows paraxial diffuse spots in the full-band of the lens according to the infinity-related embodiment of the present invention. The designed wave band is 210nm-900nm, the full-wave band diffuse spots are all in the Airy spot range, the paraxial point light spot is very small, the geometric radius is 3.7um, and the small-spot measuring system is suitable for the requirement of the small-spot measuring system.
Fig. 4 shows a lens barrel according to an infinite embodiment of the present invention. The maximum focal shift change of the full-wave band 210nm-900nm is 76.2um, which is smaller than the diffraction limit change of 82.9um, and the method is suitable for the requirement of a small light spot measuring system.
Example 2
Fig. 5 is a view showing an outline of the finite distance lens according to the present invention. The appearance structure is the same as the infinite structure.
Referring to fig. 6 and table 2 below, the lens design parameters of the lens according to the limited distance embodiment of the present invention are shown in table 2, the first lens group of the lens is arranged in order from left to right, and the limited distance entrance lens group restraining lens L1Design value of300mm, the focal length of the lens is defined as f, and the maximum outer diameter of the lens is 6.0 mm.
TABLE 2 lens parameters
| Noodle numbering | Radius of curvature R | Thickness-spacing H | Half caliber D/2 | Glass material |
| S1 (diaphragm) | 0.52f | 0.34f | 2.8 | Caf2 |
| S2 | -0.27f | 0.015f | 2.3 | / |
| S3 | -0.22f | 0.22f | 2.2 | F_silica |
| S4 | 0.24f | 0.015f | 2.0 | / |
| S5 | 0.22f | 0.55f | 2.1 | Caf2 |
| S6 | -0.58f | 0.52f | 1.5 |
FIG. 7 shows paraxial diffuse speckles in the full-band of the lens according to the limited distance embodiment of the present invention. The designed wave band is 210nm-900nm, the full-wave band diffuse spots are all in the Airy spot range, the paraxial point light spot is very small, the geometric radius is 4.29um, and the small-spot measuring system is suitable for the requirement of the small-spot measuring system.
FIG. 8 shows a lens according to a limited distance embodiment of the present invention. The maximum focal shift change of the full-wave band 210nm-900nm is 70.9um, which is less than the diffraction limit change of 72.1um, and the method is suitable for the requirement of a small light spot measuring system.
The two lenses of the example realize the design of low chromatic aberration and small light spots of wide wave bands (from ultraviolet to near infrared bands of 210nm to 900 nm). Two kinds of camera lenses all adopt the project organization of 3 lenses, have reduced lens use quantity in the very big degree, have promoted the system transmittance. Meanwhile, two modes of finite distance and infinite distance conjugation can be selected, various measuring light paths can be matched, and the optical performance of the ellipsometry measuring equipment in the conventional semiconductor measuring equipment is optimized.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A broadband low dispersion lens is characterized in that: the device comprises a constraint lens, a first correction lens group and a second correction lens group which are sequentially arranged from an object side to an image side, wherein the constraint lens reduces chromatic aberration, and the first correction lens group and the second correction lens group are used for correcting axial chromatic aberration and light spots and controlling working distance.
2. The broadband low dispersion lens of claim 1, wherein: the lens group adopts fused quartz and calcium fluoride materials; the first lens group, namely the constraint lens, is made of calcium fluoride material, the first correction lens group is made of fused quartz material, and the second correction lens group is made of calcium fluoride.
3. The broadband low dispersion lens of claim 1, wherein: and adjusting the paraxial magnification by adopting two modes of finite distance conjugation and infinite distance conjugation.
4. The broadband low dispersion lens of claim 1, wherein: the stop position is provided at the incident end, between the constraint lens and the first correction lens group, or between the first correction lens and the second correction lens group.
5. The broadband low dispersion lens of claim 1, wherein: confining the lens focal length f1Satisfies 0.4f<f1<0.9f。
6. The broadband low dispersion lens of claim 1, wherein: focal length f of first correction lens group2Satisfies-0.4 f<f2<-0.15f。
7. The broadband low dispersion lens of claim 1, wherein: focal length f of the second correction lens group3Satisfies 0.4f<f3<0.8f。
8. The broadband low dispersion lens of claim 1, wherein: the working wave band ranges from 210nm to 900 nm.
9. The broadband low dispersion lens of claim 1, wherein: a first space ring is arranged between the constraint lens and the first correction lens, and a second space ring is arranged between the first correction lens and the second correction lens.
10. The broadband low dispersion lens of claim 1, wherein: the incident end of the lens is fixed by a pressing ring; the external connecting part of the lens is matched with an external thread structure, a coaxial or flange adjusting structure.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010272718.1A CN111458837B (en) | 2020-04-09 | 2020-04-09 | Broadband low-dispersion lens |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010272718.1A CN111458837B (en) | 2020-04-09 | 2020-04-09 | Broadband low-dispersion lens |
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| CN111458837A true CN111458837A (en) | 2020-07-28 |
| CN111458837B CN111458837B (en) | 2022-07-01 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114217451A (en) * | 2021-12-10 | 2022-03-22 | 中国科学院光电技术研究所 | Lens system |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20090303614A1 (en) * | 2008-06-09 | 2009-12-10 | Astrium Gmbh | Apochromatic lens |
| CN103837974A (en) * | 2014-02-26 | 2014-06-04 | 中国科学院上海光学精密机械研究所 | Optical system of microscope lens with infinite tube length |
| CN105181604A (en) * | 2015-05-11 | 2015-12-23 | 福州大学 | Multi-angle incident single shot ellipsometry measurement method |
| CN108732723A (en) * | 2018-08-07 | 2018-11-02 | 舜宇光学(中山)有限公司 | telecentric lens |
| CN108761746A (en) * | 2018-08-07 | 2018-11-06 | 卓外（上海）医疗电子科技有限公司 | Big depth of field wide-angle laparoscope/thoracic cavity lens head |
-
2020
- 2020-04-09 CN CN202010272718.1A patent/CN111458837B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20090303614A1 (en) * | 2008-06-09 | 2009-12-10 | Astrium Gmbh | Apochromatic lens |
| CN103837974A (en) * | 2014-02-26 | 2014-06-04 | 中国科学院上海光学精密机械研究所 | Optical system of microscope lens with infinite tube length |
| CN105181604A (en) * | 2015-05-11 | 2015-12-23 | 福州大学 | Multi-angle incident single shot ellipsometry measurement method |
| CN108732723A (en) * | 2018-08-07 | 2018-11-02 | 舜宇光学(中山)有限公司 | telecentric lens |
| CN108761746A (en) * | 2018-08-07 | 2018-11-06 | 卓外（上海）医疗电子科技有限公司 | Big depth of field wide-angle laparoscope/thoracic cavity lens head |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114217451A (en) * | 2021-12-10 | 2022-03-22 | 中国科学院光电技术研究所 | Lens system |
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Address after: 201306 building C, No. 888, Huanhu West 2nd Road, Lingang New District, China (Shanghai) pilot Free Trade Zone, Pudong New Area, Shanghai Patentee after: Jiangling Technology (Shanghai) Co.,Ltd. Address before: 215500 building 10-1, 1150 southeast Avenue, Southeast street, Changshu City, Suzhou City, Jiangsu Province Patentee before: Jiangsu Jiangling Semiconductor Co.,Ltd. |
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