Ellipsometry apparatus and method for obtaining surface information of an object to be measured - Patent Application 20070122997

Abstract

An embodiment of the present disclosure provides an ellipsometry apparatus and a method for obtaining surface information of an object to be measured, wherein the ellipsometry apparatus includes a polarized beam providing device for providing a plurality of parallel polarized beams, a first off-axis parabolic mirror for reflecting the plurality of parallel polarized beams and focusing the plurality of reflected first beams at target points on the surface of the object to be measured, where each polarized beam forms an acute angle with a corresponding first beam, a second off-axis parabolic mirror for reflecting a plurality of second beams formed after the reflected first beam is reflected by the surface of the object to form a plurality of parallel third beams, where each second beam forms an acute angle with a corresponding third beam, and an analyzing device for analyzing the plurality of parallel third beams. The embodiments of the present disclosure can significantly reduce the angle of incidence at which a polarized beam is incident on an off-axis parabolic mirror, thereby effectively guaranteeing the polarization state of the polarized beam.

Description

[Technical Field]

[0001] FIELD Embodiments of the present disclosure relate generally to the field of optical metrology, and more particularly to an ellipsometry device and method for obtaining surface information of an object to be measured. [Background technology]

[0002] Spectroscopic ellipsometry, as an effective optical measurement technique, has been widely applied in fields including, but not limited to, semiconductor manufacturing. FIG. 1 shows a schematic diagram of the local structure of a conventional ellipsometry apparatus 100. The ellipsometry apparatus 100 includes a polarizer 102, a reflector 104, and an analyzer 106. The reflector 104 is an integrally molded parabolic reflector. While the ellipsometry apparatus 100 can avoid problems such as chromatic aberration correction that exist in ellipsometry apparatuses using optical lenses or lens groups, the structure of the reflector 104 requires that the polarized light beam must be incident along an axis A1 parallel to the parabolic surface of the reflector 104. This causes the polarized light beam to be incident at a large angle on the reflector surface, significantly changing the polarization state of the beam, which adversely affects the spectral inversion calculation.

[0003] To summarize the above, in conventional ellipsometry devices, increasing the angle of incidence of a polarized beam significantly changes the original polarization state of the incident polarized beam. Summary of the Invention [Problem to be solved by the invention]

[0004] To address the above-mentioned problems, the embodiments of the present disclosure provide an ellipsometry apparatus and a method for acquiring surface information of a target to be measured. The embodiments of the present disclosure can significantly reduce the incident angle of a polarized beam onto an off-axis parabolic mirror, thereby effectively guaranteeing the polarization state of the polarized beam. [Means for solving the problem]

[0005] According to a first aspect of the present disclosure, there is provided an ellipsometry apparatus comprising: a polarized beam providing device for providing a plurality of parallel polarized beams; a first off-axis parabolic mirror for reflecting the plurality of parallel polarized beams and focusing the plurality of reflected first beams onto a target point on a surface of an object to be measured, wherein an angle between each polarized beam of the plurality of parallel polarized beams and a corresponding first beam of the plurality of reflected first beams is any angle between 20 and 40 degrees; The measurement system includes a second off-axis parabolic mirror for reflecting a plurality of second beams formed after the first beam is reflected by the surface of the object to be measured to form a plurality of parallel third beams, wherein the angle between each second beam of the plurality of second beams and a corresponding third beam of the plurality of parallel third beams is any angle between 20 and 40 degrees, and an analyzing device for analyzing the plurality of parallel third beams.

[0006] In some embodiments, the optical paths corresponding to the plurality of parallel polarized beams and the optical paths corresponding to the plurality of parallel third beams intersect.

[0007] In some embodiments, the polarized beam providing device includes a polarizer for polarizing the incident beam to form a plurality of parallel first polarized beams, and a first planar reflecting mirror for reflecting the plurality of parallel first polarized beams to form the plurality of parallel polarized beams, wherein the angle between each first polarized beam of the plurality of parallel first polarized beams and a corresponding polarized beam of the plurality of parallel polarized beams is any angle between 20 and 40 degrees, and the analyzing device includes a second planar reflecting mirror for reflecting the plurality of parallel third beams to form a plurality of parallel fourth beams, wherein the angle between each fourth beam of the plurality of parallel fourth beams and a corresponding third beam of the plurality of parallel third beams is any angle between 20 and 40 degrees, and an analyzer for analyzing the plurality of parallel fourth beams.

[0008] In some embodiments, the polarizer, the second flat reflecting mirror, and the first off-axis parabolic mirror are located on one side of the target normal plane, and the analyzer, the first flat reflecting mirror, and the second off-axis parabolic mirror are located on the other side of the target normal plane.

[0009] In some embodiments, the height of the first flat reflecting mirror and the second flat reflecting mirror relative to the surface of the object to be measured is greater than the height of the first off-axis parabolic mirror and the second off-axis parabolic mirror relative to the surface of the object to be measured.

[0010] In some embodiments, the lateral distance between the first and second flat reflective mirrors is greater than the lateral distance between the first and second off-axis parabolic mirrors.

[0011] In some embodiments, the first polarized beam and the third beam are parallel, and the fourth beam and the polarized beam are parallel.

[0012] In some embodiments, the polarizer, one of the first and second flat reflecting mirrors, and the first off-axis parabolic mirror are positioned on one side of a target normal plane, which is a normal plane passing through a target point on the object to be measured, and the second off-axis parabolic mirror, the other of the first and second flat reflecting mirrors, and the analyzer are positioned on the other side of the target normal plane.

[0013] In some embodiments, the polarized beam providing device includes a polarizer for polarizing the incident beam to form a plurality of parallel polarized beams, the analyzing device includes an analyzer for analyzing the plurality of parallel third beams, the polarizer and the second off-axis parabolic mirror are positioned on one side of a target normal plane, which is a normal plane passing through a target point of the object to be measured, and the first off-axis parabolic mirror and the analyzer are positioned on the other side of the target normal plane.

[0014] In some embodiments, the angle between each of the plurality of reflected first beams and the normal to the object to be measured is any angle between 60 degrees and 70 degrees.

[0015] In some embodiments, the first off-axis parabolic mirror and the second off-axis parabolic mirror include at least one of a metal off-axis parabolic mirror having a surface accuracy of less than 1 / 10 wavelength and a surface roughness of less than 5 nanometers, and a glass off-axis parabolic mirror having a surface accuracy of less than 1 / 20 wavelength and a surface roughness of less than 1 nanometer.

[0016] In some embodiments, a coating is provided on a surface of each of the first off-axis parabolic mirror, the second off-axis parabolic mirror, the first flat reflecting mirror, and the second flat reflecting mirror, and the coating includes at least one of a metallic reflecting film and a multilayer media film.

[0017] In some embodiments, the metallic off-axis parabolic mirror is fabricated and formed with a single point diamond machining process.

[0018] In some embodiments, the metallic reflective film includes an aluminum reflective layer and a magnesium fluoride protective layer disposed on the surface of the aluminum reflective layer.

[0019] In some embodiments, the first off-axis parabolic mirror and the second off-axis parabolic mirror are positioned opposite each other.

[0020] According to a second aspect of the present disclosure, there is provided a method for obtaining surface information of an object to be measured, the method being realized using the ellipsometry device according to the first aspect of the present disclosure, and the method includes: providing a plurality of parallel polarized beams by a polarized beam providing device; reflecting the plurality of parallel polarized beams by a first off-axis parabolic mirror to focus the plurality of reflected first beams at target points on the surface of the object to be measured; reflecting a plurality of second beams formed after the reflected first beams are reflected by the surface of the object to be measured by a second off-axis parabolic mirror to form a plurality of parallel third beams; and analyzing the plurality of parallel third beams by an analyzing device to obtain surface information of the object to be measured.

[0021] It should be understood that the contents described in this section are not intended to identify key or important features of the embodiments of the present disclosure, and are not intended to limit the scope of protection of the present disclosure. Other features of the present disclosure will be easily understood from the following description. [Brief explanation of the drawings]

[0022] These and other features, advantages, and aspects of the embodiments of the present disclosure will become more apparent from the following detailed description taken in conjunction with the drawings, in which like or similar reference numerals represent like or similar elements. [Figure 1] 1 shows a schematic diagram of the local structure of a conventional ellipsometry device. [Figure 2] 1 shows a structural schematic diagram of an ellipsometry apparatus according to an embodiment of the present disclosure; [Figure 3] 1 shows a structural schematic diagram of an ellipsometry apparatus according to an embodiment of the present disclosure; [Figure 4] 10 shows the measured values ​​of the change in the angle between the phases of P-polarized light and S-polarized light in the ellipsometry device according to the embodiment of the present disclosure and in the conventional ellipsometry device. [Figure 5] 1 shows a schematic diagram of a pupil polarization state distribution of a conventional ellipsometry device. [Figure 6] 1 shows a schematic diagram of a pupil polarization state distribution of an ellipsometry apparatus according to an embodiment of the present disclosure. [Figure 7] 1 shows a schematic diagram of the diffraction-limited on-wafer imaging quality of an ellipsometry apparatus according to an embodiment of the present disclosure. [Figure 8] 1 shows a structural schematic diagram of an ellipsometry apparatus according to an embodiment of the present disclosure; [Figure 9] 1 shows a structural schematic diagram of an ellipsometry apparatus according to an embodiment of the present disclosure; [Figure 10] 1 shows a flowchart of a method for obtaining surface information of an object to be measured according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0023]

[0023] The following description will be made in conjunction with the drawings to illustrate exemplary embodiments of the present disclosure. Various details of the embodiments of the present disclosure are included to facilitate understanding and should be considered merely exemplary. Therefore, those skilled in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present disclosure. Similarly, for the sake of clarity and conciseness, the following description omits descriptions of known functions and structures.

[0024] As used herein, the term "comprises" and variations thereof refer to an open-ended "includes," i.e., "including, but not limited to." Unless otherwise stated, the term "or" refers to "and / or." The term "based on" refers to "based at least in part on." The terms "one exemplary embodiment" and "one embodiment" refer to "at least one exemplary embodiment." The term "another embodiment" refers to "at least one other embodiment." The terms "first," "second," etc. may refer to different or the same object. Other explicit and implicit definitions may also be included below.

[0025] As described above, in conventional ellipsometry devices, increasing the angle of incidence of a polarized beam significantly changes the polarization state of the polarized beam, adversely affecting spectral inversion calculations. As shown in FIG. 1 , a parallel beam Li emitted from a light source (not shown) is polarized after passing through a polarizer 102 to form a polarized beam. The polarized beam is focused by a reflector 104 onto a point P1 on the surface of a semiconductor wafer 108, reflected by the surface of the semiconductor wafer 108, and further reflected by the reflector 104 to an analyzer 106. It should be understood that the reflector 104 is an integrally molded parabolic reflector, and the point P1 is the focus of the paraboloid of the reflector 104. In order to focus the polarized beam at point P1, it is required that the polarized beam must be incident along an axis A1 parallel to the parabolic surface of reflector 104. This restriction imposes a large incident angle on the reflecting surface of reflector 104, and accordingly, the angle between the polarized beam incident on the parabolic surface of reflector 104 and the corresponding reflected beam is obtuse. Such a large incident angle significantly changes the polarization state of the beam passing through the polarizer.

[0026] To at least partially solve one or more of the above problems and other potential problems, exemplary embodiments of the present disclosure provide a solution for an ellipsometry apparatus and a method for acquiring surface information of a target to be measured. In the solution of the present disclosure, the first off-axis parabolic mirror and the second off-axis parabolic mirror are separately installed, and therefore, each polarized beam can be configured to form an acute angle (particularly, any angle between 20 and 40 degrees) between the corresponding first beam and the second beam, and the angle between the corresponding third beam and the second beam can be configured to form an acute angle (particularly, any angle between 20 and 40 degrees). This significantly reduces the incident angle of the polarized beam onto the first off-axis parabolic mirror and the incident angle of the second beam onto the second off-axis parabolic mirror, thereby effectively guaranteeing the polarization states of the beams transmitted by the first off-axis parabolic mirror and the second off-axis parabolic mirror. Furthermore, the optical paths corresponding to the multiple parallel polarized beams and the optical paths corresponding to the multiple parallel third beams intersect, and thus the focal length of the employed off-axis parabolic mirror can be further shortened, thereby significantly improving the NA (Numerical Aperture) and reducing the size of the spot projected onto the wafer.

[0027] The ellipsometry apparatus according to the embodiment of the present disclosure will be described in detail below.

[0028] 2 shows a structural schematic diagram of an ellipsometry apparatus 200 according to an embodiment of the present disclosure. The ellipsometry apparatus 200 includes a polarized beam providing device 210, a first off-axis parabolic mirror 204, a second off-axis parabolic mirror 206, and an analyzing device 220. The polarized beam providing device 210 is for providing a plurality of parallel polarized beams Lp. The first off-axis parabolic mirror 204 is for reflecting the plurality of parallel polarized beams Lp and focusing the plurality of reflected first beams L1 onto a target point P1 on the surface of the object 108 to be measured. An angle (i.e., a first angle θ1) between each polarized beam Lp of the plurality of parallel polarized beams Lp and a corresponding first beam L1 of the plurality of reflected first beams L1 is an acute angle. The second off-axis parabolic mirror 206 is for reflecting the plurality of second beams L2 formed after the reflected first beam L1 is reflected by the surface of the object 108 to be measured to form a plurality of parallel third beams L3, and the angle between each of the plurality of second beams L2 and a corresponding one of the plurality of parallel third beams L3 (i.e., the second angle θ2) is an acute angle. The analyzing device 220 is for analyzing the plurality of parallel third beams L3. Here, the angle between each polarized beam Lp among the multiple parallel polarized beams Lp and the corresponding first beam L1 among the multiple reflected first beams L1 (i.e., the first angle θ1) is any angle between 20 and 40 degrees, and the angle between each second beam L2 among the multiple second beams L2 and the corresponding third beam L3 among the multiple parallel third beams L3 (i.e., the second angle θ2) is any angle between 20 and 40 degrees.

[0029] It should be understood that the first angle θ1 is the sum of the first angle of incidence and the corresponding first angle of reflection, where the first angle of incidence is the angle of incidence of each polarized beam Lp of the plurality of parallel polarized beams Lp on the first off-axis parabolic mirror 204, and the first angle of reflection is the angle of reflection of a corresponding first beam L1 of the plurality of reflected first beams L1 on the first off-axis parabolic mirror 204. The second angle θ2 is the sum of the second angle of incidence and the corresponding second angle of reflection, where the second angle of incidence is the angle of incidence of each second beam L2 of the plurality of parallel third beams L2 on the second off-axis parabolic mirror 206, and the second angle of reflection is the angle of reflection of a corresponding third beam L3 of the plurality of parallel third beams L3 on the second off-axis parabolic mirror 206.

[0030] In some embodiments, the first angle θ1 is any angle between 20 and 40 degrees, and the second angle θ2 is any angle between 20 and 40 degrees.

[0031] In some embodiments, the first angle θ1 is any angle between 20 and 26 degrees, and the second angle θ2 is any angle between 20 and 26 degrees.

[0032] In some embodiments, the optical paths corresponding to the plurality of parallel polarized beams and the optical paths corresponding to the plurality of parallel third beams intersect.

[0033] In some embodiments, the first off-axis parabolic mirror and the second off-axis parabolic mirror are placed opposite each other, i.e., the reflective surface of the first off-axis parabolic mirror and the reflective surface of the second off-axis parabolic mirror face each other, which is different from the method in which the first off-axis parabolic mirror and the second off-axis parabolic mirror are placed back to back.

[0034] In some embodiments, the object 108 to be measured is, for example, a wafer.

[0035] In some embodiments, the polarized beam providing device comprises, for example, a polarizer, and the analyzing device comprises, for example, an analyzer.

[0036] In some embodiments, the polarized beam providing device includes, for example, a polarizer and a first plane reflecting mirror, and the analyzing device includes, for example, an analyzer and a second plane reflecting mirror.

[0037] In some embodiments, the polarizer, one of the first and second flat reflecting mirrors, and the first off-axis parabolic mirror are positioned on one side of a target normal plane, which is a normal plane passing through a target point on the object to be measured, and the second off-axis parabolic mirror, the other of the first and second flat reflecting mirrors, and the analyzer are positioned on the other side of the target normal plane.

[0038] In the above solution, since the first off-axis parabolic mirror 204 and the second off-axis parabolic mirror 206 are installed separately, the angle between each polarized beam Lp and the corresponding first beam L1 can be configured as an acute angle (particularly, any angle between 20 and 40 degrees), and the angle between the second beam L2 and the corresponding third beam L3 can be configured as an acute angle (particularly, any angle between 20 and 40 degrees).This significantly reduces the incident angle at which the polarized beam Lp is incident on the first off-axis parabolic mirror 204, and significantly reduces the incident angle at which the second beam L2 is incident on the second off-axis parabolic mirror 206, thereby effectively guaranteeing the polarization state of the beams transmitted by the first off-axis parabolic mirror 204 and the second off-axis parabolic mirror 206.

[0039] 3 shows a schematic structural diagram of an ellipsometry apparatus 300 according to an embodiment of the present disclosure. The polarized beam providing device includes a polarizer 302 and a first plane reflecting mirror 308. The polarizer 302 polarizes an incident beam to form a plurality of parallel first polarized beams Lp1. The first plane reflecting mirror 308 reflects the plurality of parallel first polarized beams Lp1 to form a plurality of parallel polarized beams Lp, and an angle (i.e., a third angle θ3) between each of the plurality of parallel first polarized beams Lp1 and a corresponding polarized beam Lp among the plurality of parallel polarized beams Lp is an acute angle (particularly, any angle between 20 and 40 degrees).

[0040] The first off-axis parabolic mirror 304 is for reflecting the plurality of parallel polarized beams Lp and focusing the plurality of reflected first beams L1 at a target point P1 on the surface of the object 108 to be measured. An angle (i.e., a first angle θ1) between each polarized beam Lp of the plurality of parallel polarized beams Lp and a corresponding first beam L1 of the plurality of reflected first beams L1 is an acute angle (particularly, any angle between 20 and 40 degrees).

[0041] The second off-axis parabolic mirror 306 is for reflecting the multiple second beams L2 formed after the reflected first beam L1 is reflected by the surface of the object 108 to be measured to form multiple parallel third beams L3, and the angle between each second beam L2 of the multiple second beams L2 and a corresponding third beam L3 of the multiple parallel third beams L3 (i.e., the second angle θ2) is an acute angle (particularly, any angle between 20 and 40 degrees).

[0042] It should be understood that the target point P1 on the surface of the object 108 to be measured is the focus of the first off-axis parabolic mirror 304, and the target point P1 on the surface of the object 108 to be measured is also the focus of the second off-axis parabolic mirror 306.

[0043] The analyzing device includes a second plane reflecting mirror 310 and an analyzer 312. The second plane reflecting mirror 310 is for reflecting the plurality of parallel third beams L3 to form a plurality of parallel fourth beams L4, and a fourth angle θ4 between each fourth beam L4 of the plurality of parallel fourth beams L4 and a corresponding third beam L3 of the plurality of parallel third beams L3 is an acute angle (particularly, any angle between 20 and 40 degrees). The analyzer 312 is for analyzing the plurality of parallel fourth beams L4.

[0044] It should be understood that the third angle θ3 is the sum of the third angle of incidence and the corresponding third angle of reflection, where the third angle of incidence is the angle of incidence of each first polarized beam Lp1 of the plurality of parallel first polarized beams Lp1 on the first flat reflecting mirror 308, and the third angle of reflection is the angle of reflection of a corresponding polarized beam Lp of the plurality of parallel polarized beams Lp on the first flat reflecting mirror 308. The fourth angle θ4 is the sum of the fourth angle of incidence and the corresponding fourth angle of reflection, where the fourth angle of incidence is the angle of incidence of a corresponding third beam L3 of the plurality of parallel third beams L3 on the second flat reflecting mirror 310, and the fourth angle of reflection is the angle of reflection of each fourth beam L4 of the plurality of parallel fourth beams L4 on the second flat reflecting mirror 310.

[0045] It should be understood that the polarizer 302, the first flat reflecting mirror 308, and the first off-axis parabolic mirror 304 are located on one side of the target normal plane Pn, where the target normal plane Pn is a normal plane passing through the target point P1 of the object 108 to be measured. The second off-axis parabolic mirror 306, the second flat reflecting mirror 310, and the analyzer 312 are located on the other side of the target normal plane Pn.

[0046] In this solution, the polarizer 302, the first flat reflecting mirror 308 and the first off-axis parabolic mirror 304 are on the same side of the target normal plane Pn, and the second off-axis parabolic mirror 306, the second flat reflecting mirror 310 and the analyzer 312 are on the same side of the target normal plane Pn. This setting method allows the distance between the polarizer 302, the first flat reflecting mirror 308 and the first off-axis parabolic mirror 304 to be closer, and similarly for the second off-axis parabolic mirror 306, the second flat reflecting mirror 310 and the analyzer 312, thereby reducing the space occupied by the ellipsometry apparatus 300.

[0047] In some embodiments, the angle between each of the reflected first beams L1 and the normal to the object 108 to be measured (i.e., the fifth angle θ5) is any angle between 60 degrees and 70 degrees. It should be understood that the angle between the first beam L1 and the normal to the object 108 to be measured is equal to the angle between the first beam L1 and the target normal plane Pn. In some embodiments, the angle between the central first beam L1 of the reflected first beams L1 and the normal to the object 108 to be measured (i.e., the fifth angle θ5) is 65 degrees.

[0048] In this solution, by setting the first angle θ1 and the second angle θ2 to be acute angles, the influence of the first off-axis parabolic mirror 304 and the second off-axis parabolic mirror 306 on the polarization state of the reflected beam can be significantly reduced, thereby significantly improving the accuracy of the scaling algorithm, significantly reducing the complexity of the scaling process, and significantly improving calculation efficiency. Furthermore, by separately installing the first off-axis parabolic mirror 304 and the second off-axis parabolic mirror 306, the incident angle of the beam on the first off-axis parabolic mirror 304 and the second off-axis parabolic mirror 306 can be easily adjusted, improving the flexibility of the ellipsometry device and making it suitable for a wider range of applications. Furthermore, the ellipsometry device can achieve diffraction-limited spot sizes over a wider polarization wavelength range (including, but not limited to, deep ultraviolet, visible, and near-infrared wavelength ranges).

[0049] In some embodiments, the first off-axis parabolic mirror 304 and the second off-axis parabolic mirror 306 may be metallic off-axis parabolic mirrors. Metallic materials for the metallic off-axis parabolic mirrors include, but are not limited to, aluminum and copper. The metallic off-axis parabolic mirrors are fabricated using a single-point diamond machining process. The surface accuracy of the metallic off-axis parabolic mirrors is less than 1 / 10 wavelength, and the surface roughness of the metallic off-axis parabolic mirrors is less than 5 nanometers. The metallic off-axis parabolic mirrors can significantly improve the reflectivity of the beam.

[0050] In some embodiments, the first off-axis parabolic mirror 304 and the second off-axis parabolic mirror 306 may be glass off-axis parabolic mirrors. Glass materials used for the glass off-axis parabolic mirrors include, but are not limited to, fused silica, crystalline silica, and low-expansion-coefficient microcrystalline glass. The surface accuracy of the glass off-axis parabolic mirrors is less than 1 / 20 wavelength, and the surface roughness of the glass off-axis parabolic mirrors is less than 1 nanometer. The glass off-axis parabolic mirrors can significantly improve the reflectivity of the beam.

[0051] In some embodiments, a coating is provided on the surface of each of the first off-axis parabolic mirror 304, the second off-axis parabolic mirror 306, the first flat reflecting mirror 308, and the second flat reflecting mirror 310. The coating includes at least one of a metal reflecting film and a multilayer medium film. Here, the metal reflecting film includes an aluminum reflecting layer and a magnesium fluoride protective layer provided on the surface of the aluminum reflecting layer. Here, the multilayer medium film has multiple medium layers, each of which has a different refractive index. By matching the refractive indexes of the multiple medium layers, high reflectivity and a high laser damage threshold can be achieved. With regard to the metal reflecting film and the multilayer medium layer, the average reflectivity may be greater than 90% for a beam having a wavelength in the range of 190 to 350 nanometers, and the average reflectivity may be greater than 85% for a beam having a wavelength in the range of 350 to 2500 nanometers.

[0052] FIG. 4 shows the measured values ​​of the change in the phase angle between P-polarized light and S-polarized light for the ellipsometry apparatus 300 according to the embodiment of the present disclosure and a conventional ellipsometry apparatus. Here, Solution 1 corresponds to the ellipsometry apparatus 300 according to the embodiment of the present disclosure shown in FIG. 3, and Solution 2 corresponds to the conventional ellipsometry apparatus 100 shown in FIG. 1. Here, the measured values ​​of the change in the phase angle between P-polarized light and S-polarized light after reflection of polarized light beams of multiple different wavelengths are displayed. As can be seen, the ellipsometry apparatus 300 according to the embodiment of the present disclosure is clearly superior to the conventional ellipsometry apparatus 100.

[0053] FIG. 5 shows a schematic diagram of a pupil polarization state distribution of a conventional ellipsometry apparatus. The conventional ellipsometry apparatus is the conventional ellipsometry apparatus 100 shown in FIG. 1, where an input optical signal (Input) is also shown. FIG. 6 shows a schematic diagram of a pupil polarization state distribution of an ellipsometry apparatus 300 according to an embodiment of the present disclosure. The ellipsometry apparatus according to an embodiment of the present disclosure is the ellipsometry apparatus 300 according to an embodiment of the present disclosure shown in FIG. 3. As can be seen from the comparison, the ellipsometry apparatus 300 according to an embodiment of the present disclosure is clearly superior to the conventional ellipsometry apparatus 100.

[0054] 7 is a schematic diagram illustrating the diffraction-limited imaging quality on the wafer of the ellipsometry apparatus 300 according to the embodiment of the present disclosure. As can be seen, the spot projected on the wafer by the ellipsometry apparatus 300 according to the embodiment of the present disclosure can reach the diffraction limit.

[0055] 8 shows a structural schematic diagram of an ellipsometry apparatus 800 according to an embodiment of the present disclosure. Here, a polarizer 802, a second flat reflecting mirror 810, and a first off-axis parabolic mirror 804 are disposed on one side of a target normal plane Pn. A second off-axis parabolic mirror 806, a first flat reflecting mirror 808, and an analyzer 812 are disposed on the other side of the target normal plane Pn. Therefore, the optical paths corresponding to the multiple parallel polarized beams Lp and the optical paths corresponding to the multiple parallel third beams L3 intersect. It should be understood that the optical path corresponding to the multiple parallel polarized beams Lp is the optical path that the multiple parallel polarized beams Lp take as they propagate along a straight line before being reflected, for example, the optical path that the multiple parallel polarized beams Lp take as they propagate from the first flat reflecting mirror 808 to the first off-axis parabolic mirror 804, and the optical path corresponding to the multiple parallel third beams L3 is the optical path that the multiple parallel third beams L3 take as they propagate along a straight line before being reflected, for example, the optical path that the multiple parallel third beams L3 take as they propagate from the second off-axis parabolic mirror 806 to the second flat reflecting mirror 810.

[0056] The heights of the polarizer 802 and the analyzer 812 relative to the surface of the object 108 to be measured may be the same, for example. The heights of the second flat reflecting mirror 810 and the first flat reflecting mirror 808 relative to the surface of the object 108 to be measured may be the same, for example. The heights of the first off-axis parabolic mirror 804 and the second off-axis parabolic mirror 806 relative to the surface of the object 108 to be measured may be the same, for example. The heights of the polarizer 802, the second flat reflecting mirror 810, and the first off-axis parabolic mirror 804 relative to the surface of the object 108 to be measured are different, and the heights of the second off-axis parabolic mirror 806, the first flat reflecting mirror 808, and the analyzer 812 relative to the surface of the object 108 to be measured are different. In some embodiments, the heights of the polarizer 802, the second flat reflecting mirror 810, and the first off-axis parabolic mirror 804 relative to the surface of the object 108 to be measured decrease sequentially, and the heights of the analyzer 812, the first flat reflecting mirror 808, and the second off-axis parabolic mirror 806 relative to the surface of the object 108 to be measured decrease sequentially.

[0057] In some embodiments, the lateral distance between the first flat reflecting mirror 808 and the second flat reflecting mirror 810 is greater than the lateral distance between the first off-axis parabolic mirror 804 and the second off-axis parabolic mirror 806.

[0058] In this solution, the polarizer 802 and the first off-axis parabolic mirror 804 are installed on one side of the target normal plane Pn, and the first flat reflecting mirror 808 is installed on the other side of the target normal plane Pn, which can facilitate full use of space in the lateral direction, for example, to obtain the smaller third angle θ3 and the smaller first angle θ1. Similarly, the second flat reflecting mirror 810 is installed on one side of the target normal plane Pn, and the second off-axis parabolic mirror 806 and the analyzer 812 are installed on the other side of the target normal plane Pn, which can facilitate full use of space in the lateral direction, for example, to obtain the smaller fourth angle θ4 and the smaller second angle θ2. Therefore, the ellipsometry apparatus 800 can further shorten the focal length of the off-axis parabolic mirror employed compared to the ellipsometry apparatus 300, thereby significantly improving the NA and reducing the size of the spot projected onto the wafer.

[0059] It should be noted that the height of the second flat reflective mirror 810 relative to the surface of the object 108 to be measured is greater than the height of the first off-axis parabolic mirror 804 relative to the surface of the object 108 to be measured, and the height of the first flat reflective mirror 808 relative to the surface of the object 108 to be measured is greater than the height of the second off-axis parabolic mirror 806 relative to the surface of the object 108 to be measured. Therefore, the second flat reflective mirror 810 and the first flat reflective mirror 808 do not occupy the space between the first off-axis parabolic mirror 804 and the second off-axis parabolic mirror 806 in the lateral direction, which can facilitate a closer distance between the first off-axis parabolic mirror 804 and the second off-axis parabolic mirror 806 in some application scenarios. In some embodiments, the polarized beam Lp is parallel to the second beam L2 at the center of the plurality of second beams L2, and the third beam L3 is parallel to the first beam L1 at the center of the plurality of first beams L1.

[0060] In some embodiments, the first polarized beam Lp1 and the third beam L3 are parallel, and the fourth beam L4 and the polarized beam Lp are parallel.

[0061] In some embodiments, the polarizer 802, the second flat reflecting mirror 810, the first off-axis parabolic mirror 804, the second off-axis parabolic mirror 806, the first flat reflecting mirror 808, and the analyzer 812 are stationary relative to each other, that is, in the ellipsometry apparatus 800, the polarizer 802, the second flat reflecting mirror 810, the first off-axis parabolic mirror 804, the second off-axis parabolic mirror 806, the first flat reflecting mirror 808, and the analyzer 812 are not moving parts, which is advantageous for ensuring the stability of the system.

[0062] In some embodiments, the angle formed by each of the plurality of reflected first beams L1 and the normal direction of the object 108 to be measured (i.e., the fifth angle θ5) is any angle between 60 degrees and 70 degrees. In some embodiments, the angle formed by the central first beam L1 of the plurality of reflected first beams L1 and the normal direction of the object 108 to be measured (i.e., the fifth angle θ5) is 65 degrees.

[0063] 9 shows a structural schematic diagram of an ellipsometry apparatus 900 according to an embodiment of the present disclosure. Here, the polarized beam providing device includes a polarizer 902, and the analyzing device includes an analyzer 912. The polarizer 902 and the second off-axis parabolic mirror 906 are disposed on one side of the target normal plane Pn, and the first off-axis parabolic mirror 904 and the analyzer 912 are disposed on the other side of the target normal plane Pn. Therefore, the optical paths corresponding to the multiple parallel polarized beams Lp and the optical paths corresponding to the multiple parallel third beams L3 intersect. It should be understood that the optical paths corresponding to the multiple parallel polarized beams Lp are the optical paths taken by the multiple parallel polarized beams Lp as they propagate along a straight line before being reflected, for example, the optical paths taken by the multiple parallel polarized beams Lp as they propagate from the polarizer 902 to the first off-axis parabolic mirror 904, and the optical paths corresponding to the multiple parallel third beams L3 are the optical paths taken by the multiple parallel third beams L3 as they propagate along a straight line before being reflected, for example, the optical paths taken by the multiple parallel third beams L3 as they propagate from the second off-axis parabolic mirror 906 to the analyzer 912.

[0064] This solution employs fewer optical elements, thereby simplifying the structure of the ellipsometry apparatus 900 and effectively reducing manufacturing costs. Furthermore, compared with the ellipsometry apparatus 800, the ellipsometry apparatus 900 eliminates the need for a flat reflecting mirror, significantly improving the optical efficiency and the system signal-to-noise ratio of the ellipsometry apparatus. For example, in some embodiments, the ellipsometry apparatus 900 is equipped with two reflecting lenses (first off-axis parabolic mirror 904 and second off-axis parabolic mirror 906), while the ellipsometry apparatus 800 is equipped with four reflecting lenses (first off-axis parabolic mirror 804, second off-axis parabolic mirror 806, first flat reflecting mirror 808, and second flat reflecting mirror 810). Therefore, compared to ellipsometry device 800, ellipsometry device 900 employs half the number of reflective lenses (reduced from four to two), thereby doubling the optical efficiency and doubling the system signal-to-noise ratio of the ellipsometry device.

[0065] It should be understood that the size of the spot projected on the wafer is proportional to 1 / NA. Therefore, to achieve a smaller spot size, the NA of the off-axis parabolic mirror needs to be improved. Assuming the beam diameter remains unchanged, the focal length of the off-axis parabolic mirror needs to be shortened. When an optical reflecting mirror (a second flat reflecting mirror and a first flat reflecting mirror) is installed in the horizontal space between the first off-axis parabolic mirror and the second off-axis parabolic mirror, in the process of reducing the size of the spot projected on the wafer, as the horizontal distance between the symmetrically installed first off-axis parabolic mirror and the second off-axis parabolic mirror decreases, the horizontal distance between the second flat reflecting mirror and the first flat reflecting mirror also decreases. As a result, the second flat reflecting mirror and the first flat reflecting mirror may cause serious mechanical interference with each other in space. Therefore, in a solution in which the second flat reflecting mirror and the first flat reflecting mirror are laterally disposed between the first off-axis parabolic mirror and the second off-axis parabolic mirror, the NA of the off-axis parabolic mirror (or the size of the spot projected on the wafer) is limited by the mechanical space size of the flat reflecting mirror and the off-axis parabolic mirror in the lateral direction. In the ellipsometry apparatus 900, since no optical reflecting mirror is disposed in the lateral space between the first off-axis parabolic mirror and the second off-axis parabolic mirror, the distance between the first off-axis parabolic mirror and the second off-axis parabolic mirror can be made closer, thereby satisfying the condition that the incident angle remains small, improving the NA and reducing the spot size. It should be understood that in a solution in which the reflecting mirror is omitted, the optical efficiency can be improved by reducing the number of lenses, and the signal-to-noise ratio can also be improved.

[0066] 10 shows a flowchart of a method 1000 for obtaining surface information of an object to be measured according to an embodiment of the present disclosure. Method 1000 can be implemented using any one of ellipsometry apparatuses 200, 300, 800, and 900. It should be understood that method 1000 may include additional steps not shown and / or omit steps that are shown, and the scope of the present disclosure is not limited in this respect.

[0067] In step 1002, a polarized beam providing device provides a plurality of parallel polarized beams.

[0068] In step 1004, a first off-axis parabolic mirror reflects the plurality of parallel polarized beams to focus the plurality of reflected first beams onto a target point on the surface of the object to be measured.

[0069] In step 1006, a second off-axis parabolic mirror reflects the multiple second beams formed after the reflected first beam is reflected by the surface of the object to be measured to form multiple parallel third beams.

[0070] In step 1008, the plurality of parallel third beams are analyzed by an optical analyzer to obtain surface information of the object to be measured.

[0071] In conjunction with the embodiments of the present disclosure, those skilled in the art can understand the specific implementation details of the method 1000, which will not be further described here.

[0072] Although the embodiments of the present disclosure have been described above, they are illustrative and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical applications, or improvements to technology in the marketplace of each embodiment, or to enable those skilled in the art to understand each embodiment disclosed herein.

[0073] The above are only optional examples of the present disclosure and are not intended to limit the present disclosure, and those skilled in the art can make various modifications and variations to the present disclosure. As long as they do not deviate from the spirit and principle of the present disclosure, any modifications, equivalent changes, improvements, etc. should be included in the protection scope of the present disclosure.

Claims

1. 1. An ellipsometry apparatus comprising: a polarized beam providing device for providing a plurality of parallel polarized beams; a first off-axis parabolic mirror for reflecting the plurality of parallel polarized beams and focusing the plurality of reflected first beams onto a target point on a surface of the object to be measured, wherein each polarized beam of the plurality of parallel polarized beams and a corresponding first beam of the plurality of reflected first beams form an angle between 20 and 40 degrees; a second off-axis parabolic mirror for reflecting a plurality of second beams formed after the reflected first beam is reflected by the surface of the object to be measured to form a plurality of parallel third beams, wherein the angle between each second beam of the plurality of second beams and a corresponding third beam of the plurality of parallel third beams is any angle between 20 and 40 degrees; an analyzing device for performing analysis on the plurality of parallel third beams; The ellipsometry apparatus is characterized in that the optical paths corresponding to the plurality of parallel polarized beams intersect with the optical paths corresponding to the plurality of parallel third beams.

2. The polarized beam providing device a polarizer for polarizing the incident beam to form a plurality of parallel first polarized beams; a first plane reflecting mirror for reflecting the plurality of parallel first polarized beams to form the plurality of parallel polarized beams, wherein an angle formed between each of the plurality of parallel first polarized beams and a corresponding one of the plurality of parallel polarized beams is any angle between 20 and 40 degrees; The detector is a second plane reflecting mirror for reflecting the plurality of parallel third beams to form a plurality of parallel fourth beams, wherein an angle formed between each fourth beam of the plurality of parallel fourth beams and a corresponding third beam of the plurality of parallel third beams is any angle between 20 and 40 degrees; 10. The ellipsometry apparatus of claim 1, further comprising: an analyzer for analyzing the plurality of parallel fourth beams.

3. 3. The ellipsometry apparatus of claim 2, wherein the polarizer, the second flat reflecting mirror, and the first off-axis parabolic mirror are disposed on one side of the target normal plane, and the analyzer, the first flat reflecting mirror, and the second off-axis parabolic mirror are disposed on the other side of the target normal plane.

4. 3. The ellipsometry apparatus according to claim 2, wherein the heights of the first and second flat reflecting mirrors relative to the surface of the object to be measured are greater than the heights of the first and second off-axis parabolic mirrors relative to the surface of the object to be measured.

5. 3. The ellipsometry apparatus according to claim 2, wherein a lateral distance between the first flat reflecting mirror and the second flat reflecting mirror is greater than a lateral distance between the first off-axis parabolic mirror and the second off-axis parabolic mirror.

6. 3. The ellipsometry apparatus of claim 2, wherein the polarized beam and the second beam at the center of the plurality of second beams are parallel, and the third beam and the first beam at the center of the plurality of first beams are parallel.

7. 3. The ellipsometry apparatus of claim 2, wherein the first polarized beam and the third beam are parallel, and the fourth beam and the polarized beam are parallel.

8. The polarized beam providing device a polarizer for polarizing the incident beam to form a plurality of parallel polarized beams; The detector is an analyzer for analyzing the plurality of parallel third beams; 2. The ellipsometry apparatus of claim 1, wherein the polarizer and the second off-axis parabolic mirror are located on one side of a target normal plane, which is a normal plane passing through a target point of the object to be measured, and the first off-axis parabolic mirror and the analyzer are located on the other side of the target normal plane.

9. 2. The ellipsometry apparatus according to claim 1, wherein an angle formed by each of the plurality of reflected first beams and a normal direction of the object to be measured is any angle between 60 degrees and 70 degrees.

10. the first off-axis parabolic mirror and the second off-axis parabolic mirror are metallic off-axis parabolic mirrors having a surface accuracy of less than 1 / 10 wavelength and a surface roughness of less than 5 nanometers; 10. The ellipsometry apparatus according to claim 1, further comprising at least one of: a glass off-axis parabolic mirror having a surface roughness of less than 1 / 20 wavelength and a surface accuracy of less than 1 nanometer.

11. 3. The ellipsometry apparatus of claim 2, wherein a coating is provided on a surface of each of the first off-axis parabolic mirror, the second off-axis parabolic mirror, the first flat reflecting mirror, and the second flat reflecting mirror, and the coating includes at least one of a metal reflecting film and a multilayer medium film.

12. 12. The ellipsometry apparatus according to claim 1, wherein the first off-axis parabolic mirror and the second off-axis parabolic mirror are disposed opposite each other.

13. A method for obtaining surface information of an object to be measured, said method being realized using an ellipsometry apparatus according to any one of claims 1 to 12, said method comprising the steps of: providing a plurality of parallel polarized beams with a polarized beam providing device; reflecting the plurality of parallel polarized beams by a first off-axis parabolic mirror to focus the plurality of reflected first beams onto target points on a surface of the object to be measured; reflecting, by a second off-axis parabolic mirror, a plurality of second beams formed after the reflected first beam is reflected by the surface of the object to be measured, to form a plurality of parallel third beams; and analyzing the plurality of parallel third beams with an optical analyzer to obtain surface information of the object to be measured.

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