Ellipsometer and semiconductor device inspection device

Abstract

To provide an ellipsometer which can improve a throughput for measuring ellipsometry coefficients Ψ and Δ, and an inspection device of a semiconductor device.SOLUTION: An ellipsometer 1 according to an embodiment comprises: a polarization optical element unit 30 which separates two polarization components in the polarization directions orthogonal to each other in reflection light R1 obtained with reflection on a measurement surface of a sample 50 of illumination light L1 including at least one of linearly polarized light, circularly polarized light and elliptically polarized light in the radiation direction with an optical axis C of an optical system of the reflection light R1 as a center; an analyzer unit 41 which makes the two polarization components pass through components in the direction different from each polarization direction and interfere with each other to form a concentric circular interference fringe; an image detector 42 which detects the interference fringe; and an analysis device 43 which calculates ellipsometry coefficients Ψ and Δ from the detected interference fringe.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an ellipsometer and an inspection device for semiconductor devices. [Background technology]

[0002] Since Aspnes et al. made automatic measurement possible in 1975, ellipsometry has significantly reduced measurement time and improved accuracy, and spectroscopic ellipsometry, which measures using multiple wavelengths, has also been put to practical use. Since then, ellipsometry has been widely used in the semiconductor manufacturing process, taking advantage of its characteristic of being able to measure dimensions such as film thickness and optical constants such as refractive index with high precision in non-destructive measurements of thin films and fine structures. Even today, ellipsometry is used as a complementary measurement SEM (Scanning Electron-beam Microscope) and AFM (Atomic Force Microscope) as an OCD (Optical Critical Dimension) measurement device that measures the dimensions of fine structures with line widths of circuit patterns on wafers of 10 nm or less.

[0003] In the past 10 years, semiconductor circuit structures have become more complex with the advancement of three-dimensionality, such as FinFET (Fin Field-Effect Transistor) in logic semiconductors and 3D-NAND in memory. Many OCDs use spectroscopic ellipsometry as their measurement principle, and in order to obtain the dimensions of the semiconductor circuit structure to be measured and the optical constants of the constituent materials, a model is created, and the dimensions and optical constants of the object to be measured are treated as floating parameters, and the model is fitted to the measurement results to obtain a solution. Therefore, as the structure of the object to be measured becomes more complex, the number of floating parameters increases. For example, the measurement of a FinFET using OCD currently requires the use of about 20-30 floating parameters. In ellipsometry, two values, Ψ and Δ, are generally obtained as the ellipsometry coefficients, which are the measurement results, and both the ellipsometry coefficients Ψ and Δ are wavelength dependent. Therefore, in the case of spectroscopic ellipsometry, the ellipsometry coefficients Ψ and Δ can be expressed as Ψ(λ) and Δ(λ).

[0004] In order to find a solution for Dimension, it is necessary at a minimum to measure and obtain a number of ellipsometry coefficients Ψ and Δ that is greater than the number of floating parameters in order to fit the model. However, when the number of floating parameters is large, a problem occurs in which the fitting converges to a combination of floating parameters that is different from the actual Dimension. This is a problem called coupling, and to avoid this, it is effective to measure and fit ellipsometry coefficients Ψ and Δ that have different dependencies on the floating parameters. Therefore, it is desirable to perform ellipsometry measurements at different angles of incidence and directions of incidence in addition to wavelengths, and to use ellipsometry coefficients Ψ and Δ that have more different dependencies on the floating parameters for fitting the model.

[0005] In terms of measurement sensitivity, the Brewster angle, where the reflectance of P-polarized light is zero for the illumination light on a semiconductor wafer, is the most sensitive. For this reason, ellipsometry measurements are often performed with the Brewster angle as the angle of incidence. This angle of incidence corresponds to approximately 60° to 75° in semiconductor circuit structures. When performing measurements with such oblique incidence, spectroscopic ellipsometry measurements are often performed using an oblique incidence optical system specialized for a single angle of incidence and orientation. However, in order to avoid the above-mentioned coupling problem, there is a growing demand for an optical system that can handle multiple angles of incidence and orientations of incidence.

[0006] To meet this demand, if the optical system or the semiconductor wafer is moved for each measurement, the measurement time will be very long. Therefore, an objective lens with a large NA, such as the Brewster angle mentioned above, is used to simultaneously introduce measurement light from a wide range of incident angles and incident directions. Then, the reflected light from the semiconductor wafer is guided onto the exit pupil of the objective lens to perform ellipsometry measurement. This combination of the pupil image measurement optical system and ellipsometry measurement is ideal. However, even in this case, in a configuration that combines a rotating compensator and a rotating analyzer, which are general ellipsometry measurement methods, the measurement time for each wavelength is more than one second due to the limit of the pupil image transfer speed to be acquired. Furthermore, if spectroscopic ellipsometry measurement is performed using illumination light with more than 100 wavelengths, the measurement time becomes unrealistic for an OCD measurement device in the semiconductor manufacturing process. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-085698 [Patent Document 2] U.S. Pat. No. 5,596,411 [Patent Document 3] U.S. Patent No. 7,616,323 [Patent Document 4] U.S. Pat. No. 5,953,137 [Patent Document 5] U.S. Patent No. 6,856,384 [Patent Document 6] Japanese Patent Application Publication No. 62-197706 [Patent Document 7] JP 2010-002846 A [Patent Document 8] JP 2000-331927 A [Patent Document 9] JP 2003-279854 A Summary of the Invention [Problem to be solved by the invention]

[0008] Ellipsometers used in OCD measurement devices in semiconductor manufacturing processes typically require a measurement time of one to several seconds per point. Due to the time allocated for measurement, only a few to several dozen points on a wafer can usually be measured, and there are cases where yield deterioration due to partial film thickness changes or line width changes in the wafer is overlooked. The main reasons for this are that a large number of measurement points are required in synchronization with modulation by a rotating compensator or phase modulation element, that in the case of spectroscopic measurement, the amount of light split into each wavelength by a dispersive element such as a diffraction grating must be measured with a high S / N ratio, and that in the case of Mueller matrix ellipsometry, measurement must be performed while switching between several types of polarization states in the illumination light.

[0009] On the other hand, in order to increase the number of measurement points on the wafer and shorten the time required for ellipsometry measurement, it is necessary to increase the speed of moving parts such as the rotating compensator. However, stability, heat generation, etc. are bottlenecks, making it difficult to improve the throughput of ellipsometry coefficient measurement for OCD measurement, etc.

[0010] Fig. 1 is a block diagram illustrating an ellipsometer according to a comparative example. As shown in Fig. 1, the comparative ellipsometer 101 described in Patent Document 1 was devised to solve the above-mentioned problems, and uses a Nomarski prism 131 to cause two orthogonal polarized components to interfere on an image detector 142. An analyzer 143 then finds Ψ and Δ from the amplitude and phase of the generated interference fringes. With this method, it is expected that an OCD device that realizes high throughput in the semiconductor manufacturing process and has high stability due to the absence of moving parts will be put to practical use.

[0011] The illumination optical system 110 includes a light source 111, a spectrometer 112, a fiber 113, an illumination lens 114, a polarizer 115, a beam splitter 116, and an objective lens 117, and illuminates the sample 50 with illumination light L1. The light collecting optical system 120 includes the objective lens 117, the beam splitter 116, and relay lenses 121 and 122, and collects reflected light R1 reflected by the sample 50. The polarization optical element 130 includes a Nomarski prism 131, and the light receiving optical system 140 includes an analyzer 141, an image detector 142, and an analyzer 143.

[0012] This method can obtain Ψ and Δ from one image without obtaining the Stokes parameters that are common in ellipsometry measurements. This makes the measurement efficient, and spectroscopic ellipsometry is also possible when combined with a high-speed spectrometer. By applying this measurement principle to pupil image measurement using a large NA objective lens 117, it is possible to simultaneously obtain ellipsometry information for multiple angles of incidence and orientations of incidence, achieving ideal performance as a measurement device in semiconductor manufacturing.

[0013] 2 is a diagram illustrating interference fringes on an image detector 142 according to a comparative example. FIG. 2 shows a graph in which the horizontal axis represents the position of the image detector 142 and the vertical axis represents the intensity of light forming the interference fringes, corresponding to the interference fringes. As shown in FIG. 2, the ellipsometer 101 of the comparative example forms vertical interference fringes on the image detector 142 by, for example, causing interference between X-polarized light and Y-polarized light. On a vertical line passing through the center of the image detector 142, the optical path length difference between the X-polarized light and the Y-polarized light is zero. If the wavelength width is wide, the contrast of the interference fringes on both sides decreases.

[0014] In this way, because partially coherent light is used as the illumination light L1, when the number of interference fringes formed on the pupil is increased, the contrast of the interference fringes decreases in the left and right regions where the optical path length difference between the two interfering polarization components is large in principle, as shown in Figure 2. The phenomenon in which the contrast of the interference fringes decreases in regions where the optical path length difference is large means that there is an upper limit to the number of usable interference fringes.

[0015] FIG. 3 is a diagram illustrating interference fringes when the wavelength width is the same for long-, medium-, and short-wavelength illumination lights according to a comparative example. As shown in FIG. 3, when the wavelength width is the same, the number of interference fringes is greater for short wavelengths, so the contrast of the interference fringes is lower for shorter wavelengths. To avoid this problem, it is necessary to reduce the polarization separation angle of the Nomarski prism 131 or narrow the wavelength width when measuring at short wavelengths. However, in the former case, the fringe spacing becomes wider especially on the long-wavelength side, so the measurement resolution on the pupil decreases. In the latter case, a side effect occurs in that the amount of light at short wavelengths is reduced.

[0016] The present invention has been made to solve such problems, and provides an ellipsometer and a semiconductor device inspection apparatus that can suppress a decrease in resolution caused by a wide fringe spacing and a decrease in light quantity caused by narrowing the wavelength width of the spectrometer, even when measurement is performed using a combination of a light source and a spectrometer having a wide wavelength range, and can improve the throughput of measuring the ellipsometry coefficients Ψ and Δ. [Means for solving the problem]

[0017] Linearly polarized light is transmitted through the objective lens to illuminate the measurement sample simultaneously from multiple angles and orientations of incidence, and the light reflected by the measurement sample is incident on the objective lens, passes through a relay lens and a polarizing optical element, and is then received by an image detector positioned at the pupil conjugate position of the objective lens.

[0018] The polarization analysis unit is composed of at least two uniaxial birefringent crystals (e.g., magnesium fluoride) and a linear polarizer. The uniaxial birefringent crystals are combined so that their crystal optical axes are perpendicular to each other and to the optical axis. When reflected by the sample, the light is split into two polarized components in the radial direction centered on the optical axis.

[0019] This uniaxial birefringent crystal is a sphere with at least one convex or concave surface, and has no refractive power when two crystals are combined. The two polarized light components separated by the crystal through a linear polarizer (analyzer) located just before the image detector interfere with each other on the image detector, forming concentric interference fringes. The contrast and phase information of the obtained interference fringe image are processed to obtain the ellipsometry measurement results Ψ and Δ.

[0020] An ellipsometer in one embodiment includes a polarization optical element unit that separates two polarization components having mutually orthogonal polarization directions, of reflected light obtained by reflecting illumination light, which includes at least one of linearly polarized light, circularly polarized light, and elliptically polarized light, off a measurement surface of a sample, into radial directions centered on an optical axis of an optical system of the reflected light; an analyzer unit that transmits components of the two polarization directions different from the polarization directions of the two polarization components to cause interference and form concentric interference fringes; an image detector that detects the interference fringes; and an analyzer that calculates ellipsometry coefficients Ψ and Δ from the detected interference fringes.

[0021] In one embodiment, the ellipsometer includes a polarization optical element unit that separates illumination light including linear polarization, reflected by a measurement surface of a sample, into two linearly polarized components having polarization directions perpendicular to each other, an analyzer unit that transmits the two linearly polarized components in directions different from the polarization directions, causing them to interfere with each other and form interference fringes, an image detector that detects the interference fringes, and an analyzer that calculates ellipsometry coefficients Ψ and Δ from the detected interference fringes, and the fringe pitch of the interference fringes has the same value for a plurality of wavelengths of the illumination light.

[0022] Furthermore, an inspection apparatus for a semiconductor device according to one embodiment includes the above-described ellipsometer. Effect of the Invention

[0023] According to the present invention, it is possible to provide an ellipsometer and a semiconductor device inspection apparatus capable of improving the throughput in measuring the ellipsometry coefficients Ψ and Δ. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a configuration diagram illustrating an ellipsometer according to a comparative example. [Diagram 2] 11 is a diagram illustrating interference fringes on an image detector according to a comparative example. [Diagram 3] 11 is a diagram illustrating interference fringes when long-wavelength, medium-wavelength, and short-wavelength illumination light have the same wavelength width according to a comparative example. [Figure 4] 1 is a configuration diagram illustrating an ellipsometer according to a first embodiment. [Diagram 5] 4 is a diagram illustrating linearly polarized light transmitted through an analyzer unit in the ellipsometer according to the first embodiment. FIG. [Figure 6] 4 is a diagram illustrating interference fringes of reflected light that has interfered on an image detector in the ellipsometer according to the first embodiment. FIG. [Figure 7] 5A to 5C are diagrams illustrating a method of analyzing interference fringes of reflected light that has interfered on the image detector according to the first embodiment. [Figure 8]5A to 5C are diagrams illustrating a method of analyzing interference fringes of reflected light that has interfered on the image detector according to the first embodiment. [Figure 9] 5A to 5C are diagrams illustrating a method of analyzing interference fringes of reflected light that has interfered on the image detector according to the first embodiment. [Figure 10] 4 is a diagram illustrating interference fringes of reflected light that has interfered on an image detector in the ellipsometers according to the first embodiment and the comparative example. FIG. [Figure 11] 1 is a perspective view illustrating an example of the arrangement of an illumination optical system, a focusing optical system, and a pupil plane according to the first embodiment. [Figure 12] 4 is a diagram illustrating an example of the relationship between the position on the pupil plane and the incident angle and incident direction of light to a sample according to the first embodiment. FIG. [Figure 13] FIG. 13 is a configuration diagram illustrating an inspection device for a semiconductor device according to a modified example of the first embodiment. [Figure 14] FIG. 11 is a configuration diagram illustrating an ellipsometer according to a second embodiment. [Figure 15] 11 is a diagram illustrating an example of interference fringes, radial polarization, and azimuth polarization of reflected light that has interfered on an image detector in the ellipsometer according to the second embodiment. FIG. [Figure 16] 11 is a diagram illustrating a polarizing optical element portion according to a second embodiment. FIG. [Figure 17] FIG. 11 is a configuration diagram illustrating an ellipsometer according to a third embodiment. [Figure 18] 13 is a diagram illustrating interference fringes, radial polarization, and azimuth polarization of reflected light that has interfered on an image detector in the ellipsometer according to the third embodiment. FIG. [Figure 19] 11 is a diagram illustrating a polarizing optical element portion according to a third embodiment. FIG. [Figure 20] 13 is a diagram illustrating a polarizing optical element portion according to Modification 1 of Embodiment 3. FIG. [Figure 21] 13 is a diagram illustrating a polarizing optical element portion according to Modification 2 of Embodiment 3. FIG. [Figure 22] 13 is a diagram illustrating a polarizing optical element portion according to Modification 3 of Embodiment 3. FIG. [Figure 23]13 is a diagram illustrating a polarizing optical element portion according to Modification 4 of Embodiment 3. FIG. [Figure 24] FIG. 11 is a configuration diagram illustrating an ellipsometer according to a fourth embodiment. [Diagram 25] 13 is a diagram illustrating an example of interference fringes of reflected light, X-polarized light, and Y-polarized light that have interfered on an image detector in the ellipsometer according to the fourth embodiment. FIG. [Figure 26] 1 is a graph illustrating the wavelength dependence of birefringence in each material of a birefringent crystal, where the horizontal axis indicates wavelength and the vertical axis indicates birefringence. [Figure 27] 11 is a diagram illustrating a polarizing optical element according to a fourth embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In addition, in each drawing, the same elements are given the same reference numerals, and duplicate explanations are omitted as necessary.

[0026] (Embodiment 1) An ellipsometer according to the embodiment 1 will be described. Fig. 4 is a configuration diagram illustrating the ellipsometer according to the embodiment 1. As shown in Fig. 4, the ellipsometer 1 includes an illumination optical system 10, a focusing optical system 20, a polarizing optical element unit 30, and a light receiving optical system 40. The ellipsometer 1 receives reflected light R1 that is illumination light L1 reflected by a sample 50, and obtains ellipsometry coefficients Ψ and Δ.

[0027] The illumination optical system 10 illuminates a sample 50 with illumination light L1 including linearly polarized light. The illumination optical system 10 includes a light source 11, a spectrometer 12, a fiber 13, an illumination lens 14, a polarizer unit 15, a beam splitter 16, and an objective lens 17.

[0028] The light source 11 generates illumination light L1. The illumination light L1 generated by the light source 11 may include light of a wide band of wavelengths. The illumination light L1 is, for example, white light. Note that the illumination light L1 generated by the light source 11 is not limited to white light, and may be monochromatic light having a specific wavelength or light having a specific wavelength range. The illumination light L1 generated by the light source 11 is incident on the spectroscope 12.

[0029] The spectroscope 12 extracts and outputs light of a specific wavelength range from the incident illumination light L1. For example, the spectroscope 12 outputs light with a central wavelength of 400 nm having a wavelength range of 10 nm. The illumination light L1 output from the spectroscope 12 is input to a fiber 13.

[0030] The fiber 13 is a cable-like light guide member having one end and the other end. The illumination light L1 that enters one end of the fiber 13 exits from the other end of the fiber 13. The illumination light L1 that exits from the other end of the fiber 13 enters an illumination lens 14.

[0031] The illumination lens 14 is, for example, a convex lens. The illumination lens 14 changes the angular distribution of the incident illumination light L1, and irradiates the illumination light L1 onto the polarizer unit 15. For example, the illumination lens 14 converts the illumination light L1 emitted from the other end of the fiber 13 into parallel light. Then, the illumination lens 14 causes the parallel illumination light L1 to be incident on the polarizer unit 15.

[0032] The polarizer unit 15 receives illumination light L1 generated by the light source 11. The polarizer unit 15 includes, for example, a linear polarizer H1 that generates linearly polarized light. Thus, the polarizer unit 15 transmits illumination light L1 that includes linearly polarized light in one direction. For example, the polarizer unit 15 outputs to the beam splitter 16 linearly polarized illumination light L1 whose polarization direction is inclined 45° with respect to the paper surface.

[0033] The beam splitter 16 reflects a portion of the incident illumination light L1 and transmits a portion of it. The beam splitter 16 reflects a portion of the incident illumination light L1 toward the objective lens 17. The illumination light L1 reflected by the beam splitter 16 is incident on the objective lens 17.

[0034] The objective lens 17 illuminates the sample 50 with illumination light L1 including linearly polarized light. The objective lens 17 condenses the illumination light L1 reflected by the beam splitter 16 into a point shape to illuminate the sample 50. The objective lens 17 has an NA. The objective lens 17 illuminates the sample 50 from all angles and all directions within the NA. The NA of the objective lens is desirably a value including the Brewster's angle with respect to the sample 50 (e.g., 0.95) or more.

[0035] The objective lens 17 transmits the illumination light L1 and also transmits reflected light R1 that is the illumination light L1 reflected by the measurement surface of the sample 50. In the ellipsometer 1 of this embodiment, the optical axis C of the illumination light L1 incident on the sample 50 and the optical axis C of the reflected light R1 reflected by the sample 50 are perpendicular to the measurement surface of the sample 50.

[0036] Here, an XYZ orthogonal coordinate system is introduced for the convenience of explanation of the ellipsometer 1. The Z-axis direction is defined as the optical axis C. Two directions that are perpendicular to the Z-axis direction and perpendicular to each other are defined as the X-axis direction and the Y-axis direction.

[0037] The illumination light L1 that illuminates the sample 50 contains linearly polarized light in one direction. Such illumination light L1 containing linearly polarized light in one direction is incident on the measurement surface of the sample 50 while being condensed. Therefore, if the illumination light L1 is completely polarized and linearly polarized, and the optical axis C is perpendicular to the measurement surface of the sample 50, the illumination light L1 will have both P-polarized and S-polarized parts depending on the direction of incidence on the measurement surface. The P-polarized part of the illumination light L1 is reflected as P-polarized light. The S-polarized part of the illumination light L1 is reflected as S-polarized light.

[0038] The focusing optical system 20 focuses the reflected light R1 of the illumination light L1 reflected by the sample 50. The focusing optical system 20 includes an objective lens 17, a beam splitter 16, and relay lenses 21 and 22. The objective lens 17 is a member of the illumination optical system 10 and also a member of the focusing optical system 20. The reflected light R1 reflected by the sample 50 passes through a pupil position 23 of the objective lens 17. The pupil position 23 is re-imaged on the image detector 42 by the relay lenses 21 and 22. In this manner, the focusing optical system 20 focuses the exit pupil of the objective lens 17 on the image detector 42. The objective lens 17 transmits the reflected light R1 of the illumination light L1 reflected by the sample 50, causing it to enter the beam splitter 16.

[0039] The beam splitter 16 transmits a part of the reflected light R1 that is incident thereon. For example, the reflected light R1 that is transmitted through the beam splitter 16 is incident on a relay lens 21.

[0040] The relay lens 21 condenses the reflected light R1 that has passed through the beam splitter 16, forms an image, and then causes the light to enter a relay lens 22. The relay lens 22 transmits the incident reflected light R1 and causes it to enter a polarizing optical element unit 30.

[0041] The polarization optical element unit 30 separates two linearly polarized components having mutually orthogonal polarization directions from the reflected light R1, which is the illumination light L1 including linear polarization and is reflected by the measurement surface of the sample 50, into radial directions centered on the optical axis C of the focusing optical system 20 of the reflected light R1. The polarization optical element unit 30 includes, for example, a Wollaston lens. The polarization optical element unit 30 may include a plurality of Wollaston lenses W10 and W20. The Wollaston lens W10 includes two birefringent crystals W11 and W12. The Wollaston lens W20 includes two birefringent crystals W21 and W22.

[0042] The birefringent crystal W11 includes a uniaxial birefringent crystal. The birefringent crystal W11 has a plane entrance surface and a concave spherical exit surface. The birefringent crystal W11 has a crystal optical axis in the X-axis direction. The birefringent crystal W12 includes a uniaxial birefringent crystal. The birefringent crystal W12 has a convex spherical entrance surface and a plane exit surface. The birefringent crystal W12 has a crystal optical axis in the Y-axis direction. Thus, the Wollaston lens W10 includes two uniaxial birefringent crystals having spherical shapes that fit together. The crystal optical axes of the uniaxial birefringent crystals of the Wollaston lens W10 are perpendicular to the optical axis C of the focusing optical system 20 and perpendicular to each other.

[0043] The birefringent crystal W21 includes a uniaxial birefringent crystal. The birefringent crystal W21 has a plane entrance surface and a concave spherical exit surface. The birefringent crystal W21 has a crystal optical axis in the Y-axis direction. The birefringent crystal W22 includes a uniaxial birefringent crystal. The birefringent crystal W22 has a convex spherical entrance surface and a plane exit surface. The birefringent crystal W22 has a crystal optical axis in the X-axis direction. Thus, the Wollaston lens W20 includes two uniaxial birefringent crystals having spherical shapes that fit together. The crystal optical axes of the uniaxial birefringent crystals of the Wollaston lens W20 are perpendicular to the optical axis C of the focusing optical system 20 and perpendicular to each other.

[0044] Each of the birefringent crystals W11, W12, W21, and W22 may include any of quartz, magnesium fluoride, sapphire, calcite, and αBBO as a material. In the polarizing optical element unit 30, the Wollaston lens W10 and the Wollaston lens W20 have a refractive power of 0. Therefore, the polarizing optical element unit 30 does not need to collect or diffuse the reflected light R1.

[0045] In the Wollaston lens W10, the crystal optical axis of the birefringent crystal W11 and the crystal optical axis of the birefringent crystal W12 are arranged so as to be perpendicular to each other and orthogonal to the optical axis C. For example, the crystal optical axis of the birefringent crystal W11 is in the X-axis direction, and the crystal optical axis of the birefringent crystal W12 is in the Y-axis direction. As a result, two mutually perpendicular polarized lights (X-polarized light and Y-polarized light in FIG. 1) are radially separated from the optical axis C and travel in different directions. For example, the X-polarized light is separated outward, farther from the optical axis C than the Y-polarized light. The Y-polarized light is separated inward, closer to the optical axis C than the X-polarized light.

[0046] The polarizing optical element section 30 further includes another pair of Wollaston lenses W20. In the Wollaston lens W20, the crystal optical axis of the birefringent crystal W21 and the crystal optical axis of the birefringent crystal W22 are arranged so as to be perpendicular to each other and perpendicular to the optical axis C. However, in the Wollaston lens W20, the crystal optical axis of each birefringent crystal is opposite to the crystal optical axis of each birefringent crystal of the Wollaston lens W10. For example, the crystal optical axis of the birefringent crystal W21 is in the Y-axis direction, and the crystal optical axis of the birefringent crystal W22 is in the X-axis direction. As a result, the two pairs of Wollaston lenses W10 and W20 are designed in terms of their arrangement and curvature radius so that they separate the respective polarized lights in opposite directions and the two polarized lights are again at the same point on the image detector 42. Therefore, the two polarized components of the reflected light R1 transmitted through the polarizing optical element section 30 and the analyzer section 41 are detected at the same point on the image detector 42.

[0047] The light receiving optical system 40 receives the reflected light R1 and calculates the ellipsometry coefficients Ψ and Δ. The light receiving optical system 40 has an analyzer unit 41, an image detector 42, and an analyzer 43. The analyzer unit 41 includes, for example, a linear polarizer H2 that transmits a linearly polarized component in a predetermined direction.

[0048] FIG. 5 is a diagram illustrating linearly polarized light transmitted through the analyzer unit 41 in the ellipsometer 1 according to the first embodiment. As shown in FIG. 5, the analyzer unit 41 transmits linearly polarized light components in the X-direction polarization direction and the Y-direction polarization direction separated by the polarization optical element unit 30 and inclined by 45 degrees. Thus, the analyzer unit 41 transmits the polarization component inclined by 45 degrees from the X-direction among linearly polarized light having the X-direction polarization direction. The analyzer unit 41 also transmits the polarization component inclined by 45 degrees from the Y-direction among linearly polarized light having the Y-direction polarization direction. In this way, the analyzer unit 41, such as the linear polarizer H2, is also disposed between the Wollaston lens W20 and the image detector 42. The transmission axis direction of this linear polarizer H2 is disposed in an orientation that is midway (45 degrees) between the optical axes of the two uniaxial birefringent crystals that form the Wollaston lenses W10 and W20. Therefore, the analyzer unit 41 transmits components of two mutually orthogonal polarized light segments in directions different from the polarization direction, causing them to interfere with each other and form concentric interference fringes. That is, by transmitting through the analyzer unit 41, the two polarized light segments are emitted as polarized components polarized in the same direction (a direction tilted by 45 degrees) and interfere with each other.

[0049] The image detector 42 receives the reflected light R1. The image detector 42 is disposed at a pupil conjugate position 24 that is conjugate with the pupil position 23 of the objective lens 17. The reflected light R1 contains polarization components in the same direction of two linearly polarized lights that are orthogonal to each other. Therefore, the reflected light R1 interferes on the image detector 42. As a result, concentric interference fringes are formed on the image detector 42. The image detector 42 detects the interference fringes of each polarization component that has passed through the analyzer unit 41.

[0050] FIG. 6 is a diagram illustrating interference fringes of reflected light that has interfered on the image detector 42 in the ellipsometer 1 according to the first embodiment. As shown in FIG. 6, the interference fringes on the image detector 42 have a concentric shape. In this embodiment, such concentric interference fringes are called Wollaston lens interference fringes. The Wollaston lens interference fringes are formed by the interference of X-polarized light and Y-polarized light. In the Wollaston lens interference fringes, the fringe spacing is large near the center, and the fringe spacing is small at the edge of the pupil corresponding to the light incident at the Brewster angle. The Wollaston lens interference fringes have a circular shape in the peripheral region of the image detector 42, and have a position where the optical path length difference between the X-polarized light and the Y-polarized light is 0.

[0051] 7 to 9 are diagrams illustrating a method of analyzing the interference fringes of the reflected light R1 that has interfered on the image detector 42 according to the first embodiment. As shown in FIG. 7, the analysis device 43 acquires an image detected on the image detector 42. Then, the analysis device 43 converts the acquired image including the point-symmetric concentric interference fringes into polar coordinates so that the center of the concentric circle becomes the coordinate origin. Next, the analysis device 43 expresses the image after the coordinate conversion in two-dimensional coordinates with the radius (radius vector) and the azimuth (deflection angle) of the polar coordinate system as axes. The analysis device 43 performs a two-dimensional Fourier transform on the plane of the two-dimensional coordinates, and trims the converted frequency space image by dividing it into a DC component and an AC component.

[0052] Next, as shown in FIG. 8, the analysis device 43 performs an inverse Fourier transform on the DC component after shifting the peak position to the coordinate origin. Also, as shown in FIG. 9, the analysis device 43 performs an inverse Fourier transform on the AC component after shifting the peak position to the coordinate origin. The analysis device 43 further obtains an AC component (amplitude) which is an amplitude component and an AC component (phase) which is a phase component from the AC component. The obtained AC component (phase) directly corresponds to Δ of the ellipsometry measurement. Ψ of the ellipsometry measurement is expressed by the following formula (1). Here, DC indicates the DC component, and AC amplitude indicates the AC component (amplitude). In this way, the analysis device 43 calculates the ellipsometry coefficients Ψ and Δ from the detected interference fringes based on the result of the inverse Fourier transform.

[0053] Ψ=tan -1 [DC / AC amplitude ±√{(DC / AC amplitude) 2 -1}] (1)

[0054] Next, the effect of this embodiment will be described. Fig. 10 is a diagram illustrating interference fringes of reflected light R1 that has interfered on the image detector 42 in the ellipsometers 1 and 101 according to the first embodiment and the comparative example. As shown in Fig. 10, the ellipsometers 1 and 101 that use interference fringes use light that is partially coherent in time and space for measurement. Therefore, in a place where the optical path length difference between the two interfering polarized lights becomes large, the contrast of the interference fringes is significantly reduced. Therefore, there is an upper limit to the number of interference fringes formed in the pupil, depending on the wavelength width and the field of view.

[0055] As shown in FIG. 10, in order to compare the concentric interference fringes formed by the ellipsometer 1 of this embodiment with the interference fringes formed by the ellipsometer 101 of the comparative example, the number of fringes is set to be the same for both, for example, about five. In this case, the interference fringes of the comparative example are equally spaced within the pupil. In contrast, the interference fringes of the present embodiment are sparse near the center and dense near the periphery. Also, the width including the same five interference fringes is the pupil diameter in the comparative example, whereas it is the pupil radius in this embodiment. Thus, in the ellipsometer 1 of this embodiment, the interference fringes can be arranged twice as densely as in the ellipsometer 101 of the comparative example. In particular, the interference fringes can be formed several to ten times denser near the periphery of the pupil.

[0056] Here, the importance on the pupil in ellipsometry measurement is considered. FIG. 11 is a perspective view illustrating an example of the arrangement of the illumination optical system 10, the condensing optical system 20, and the pupil plane according to the first embodiment. It is a diagram illustrating the relationship between the position on the pupil plane and the incidence angle and incidence direction of light on the sample 50. Light that is perpendicularly incident on the sample 50 reaches the vicinity of the center on the pupil. On the other hand, light that is incident on the sample 50 at a large incidence angle reaches the vicinity of the periphery of the sample 50. In ellipsometry measurement, the latter oblique incidence light is more important. In particular, ellipsometry measurement using illumination light L1 with an incidence angle of 60° to 75°, which is close to the Brewster angle, has the highest sensitivity. In addition, illumination light L1 with such an incidence angle has a large incidence angle dependency and incidence direction dependency, so that it can be measured with high resolution.

[0057] 12 is a diagram illustrating the relationship between the position on the pupil plane and the angle and direction of incidence of light on the sample 50 according to the first embodiment. NA=0.95, which is the upper limit of the NA of a general objective lens 17, corresponds to an angle of incidence of 72°, which almost includes the Brewster angle. NA=0.7 corresponds to an angle of incidence of 45°. The ellipsometer 1 of this embodiment can form dense interference fringes near the more important periphery on the pupil. Therefore, for example, this has a great advantage in high-precision measurements in semiconductor manufacturing.

[0058] In this way, the ellipsometer 1 of this embodiment has a characteristic measurement principle of calculating Ψ and Δ from concentric interference fringes formed by two different polarized lights. In particular, when performing spectroscopic ellipsometry measurement by combining a broadband light source with a spectrometer, it is possible to improve the resolution on the pupil and increase the amount of light, which is expected to reduce the measurement time. Therefore, it is possible to improve the measurement accuracy and throughput.

[0059] (Modification) Next, a modified example of the first embodiment will be described. This modified example is an example in which the above-mentioned ellipsometer 1 is applied to an inspection device for a semiconductor device. FIG. 13 is a configuration diagram illustrating an inspection device for a semiconductor device according to a modified example of the first embodiment. As shown in FIG. 13, the inspection device 1A includes an ellipsometer 1, a base 80, an isolator 81, an optical surface plate 82, a stage 83, a wafer holder 84, a frame 85, an environmental chamber 86, a temperature controller unit 87, and an automatic substrate transport device 88. The ellipsometer 1 includes a light source 11, a spectrometer 12, an illumination optical system 10, a focusing optical system 20, a polarizing optical element unit 30, and a light receiving optical system 40.

[0060] The base 80 is a base. The isolator 81 provided on the base 80 isolates vibrations from the floor. The optical table 82 is provided on the isolator 81. The stage 83 and the frame 85 are arranged on the optical table 82. The stage 83 is placed on the sample 50, such as a Si wafer attached to a wafer holder 84. The frame 85 fixes the optical system. The environmental chamber 86 isolates some components of the ellipsometer 1, such as the base 80, the isolator 81, the optical table 82, the stage 83, the wafer holder 84, the frame 85, etc., from the external environment. The temperature controller unit 87 maintains the inside of the environmental chamber 86 at a predetermined temperature. The automatic substrate transport device 88 transports the sample 50.

[0061] The analysis device 43 of the ellipsometer 1 captures an image from the image detector 42 such as a camera and processes the ellipsometry measurement. The analysis device 43 may include a control unit 91 such as a computer, a grabber board 92 that captures and processes the image from the image detector 42, a stage controller 93 that controls the stage 83 on which the sample 50 is mounted, and a light source / spectroscope controller 94 that controls the light source 11 and the spectrometer 12.

[0062] The semiconductor device inspection device 1A of this modification includes the ellipsometer 1 described above. Therefore, it is possible to improve the measurement accuracy in the inspection of the semiconductor device and increase the throughput. For example, in the CD measurement and overlay evaluation in the semiconductor manufacturing process, the measurement of several points in one wafer can be performed up to the distribution evaluation in the shot, chip, and memory cell on the wafer. This contributes to the improvement of the yield and productivity in the manufacture of semiconductor devices, and also leads to the cost reduction of the semiconductor devices. Other configurations and effects are included in the description of the first embodiment.

[0063] (Embodiment 2) Next, an ellipsometer according to a second embodiment will be described. The ellipsometer of this embodiment uses illumination light L1 including circularly polarized light. FIG. 14 is a configuration diagram illustrating an ellipsometer according to the second embodiment. As shown in FIG. 14, the ellipsometer 2 of this embodiment has a polarizer unit 18 instead of the polarizer unit 15. The polarizer unit 18 includes a circular polarizer that generates circularly polarized light that rotates left or right around the optical axis of the illumination light L1. The circular polarizer includes a linear polarizer H1 and a λ / 4 wave plate H3.

[0064] Moreover, the ellipsometer 2 of this embodiment has an analyzer unit 44 instead of the analyzer unit 41. The analyzer unit 44 includes a circular polarizer that transmits a circularly polarized light component that rotates either left or right. The circular polarizer includes a linear polarizer H2 and a λ / 4 wave plate H4.

[0065] Further, the ellipsometer 2 of this embodiment has a polarizing optical element section 31 instead of the polarizing optical element section 30. The polarizing optical element section 31 includes a birefringent crystal F1. The birefringent crystal F1 is disposed in a position in the focusing optical system 20 where the reflected light R1 is focused or diffused. For example, the birefringent crystal F1 is disposed in a position between the relay lens 21 and the relay lens 22 where the reflected light R1 is diffused. The birefringent crystal F1 has a parallel plate shape. Therefore, the birefringent crystal F1 has two parallel plate surfaces. The birefringent crystal F1 is a uniaxial birefringent crystal. The crystal optical axis of the birefringent crystal F1 is disposed in a direction perpendicular to the plate surface. The birefringent crystal F1 is disposed so that the plate surface is perpendicular to the optical axis. Therefore, the crystal optical axis of the birefringent crystal F1 is parallel to the optical axis C of the focusing optical system 20. The birefringent crystal F1 includes, for example, αBBO as a material. The birefringent crystal F1 may include any of quartz crystal, magnesium fluoride, sapphire, and calcite.

[0066] In the ellipsometer 2 of this embodiment, the illumination light L1 converted into parallel light by the illumination lens 14 passes through the linear polarizer H1 and contains linearly polarized light. The illumination light L1 containing linearly polarized light then passes through a λ / 4 wave plate H3 to become illumination light L1 containing circularly polarized light. Note that the illumination light L1 may contain elliptically polarized light.

[0067] The illumination light L1 passes through the objective lens 17 via the beam splitter 16. This allows the sample 50 to be illuminated from all angles and all directions within the NA of the objective lens 17. In this case, it is desirable for the NA of the objective lens 17 to be equal to or greater than a value that includes the Brewster angle of the sample 50.

[0068] The reflected light R1 reflected by the sample 50 contains radially polarized light and azimuthally polarized light. The reflected light R1 passes through a pupil position 23 of the objective lens 17. A pupil conjugate position 24 conjugate to the pupil position 23 is imaged on the image detector 42 by relay lenses 21 and 22.

[0069] FIG. 15 is a diagram illustrating the interference fringes, radial polarization, and azimuth polarization of the reflected light R1 that has interfered on the image detector 42 in the ellipsometer 2 according to the second embodiment. As shown in FIG. 15, consider the action of the radial polarization and azimuth polarization contained in the reflected light R1 when they are transmitted through the birefringent crystal F1. First, the azimuth polarization is always perpendicular to the crystal optical axis of the birefringent crystal F1. Therefore, the azimuth polarization is ordinary light. On the other hand, the radial polarization has a polarization direction inclined with respect to the optical axis C except for the optical axis C. Therefore, it includes extraordinary light in which the crystal optical axis of the birefringent crystal F1 is parallel to the electric field.

[0070] FIG. 16 is a diagram illustrating a polarizing optical element unit 31 according to the second embodiment. In FIG. 16, the linear polarizer H2 and the λ / 4 wave plate H4 of the analyzer unit 44 are omitted in order to explain the propagation state of radial polarization and azimuth polarization. As shown in FIG. 16, in the polarizing optical element unit 31 of this embodiment, the radial polarization and azimuth polarization transmitted through the birefringent crystal F1 have relatively different traveling directions and phases due to the difference in refractive index. That is, the radial polarization including extraordinary light spreads and travels in a direction away from the optical axis C more than the azimuth polarization including ordinary light. On the other hand, after transmitting through the birefringent crystal F1, the radial polarization and the azimuth polarization travel in a shifted parallel manner to each other.

[0071] After passing through the relay lens 22, the radial polarization and the azimuth polarization return to the same point on the image detector 42 (on the pupil). It is important to note that the phase difference between the two polarizations is also delayed by different amounts. On the optical axis C, the radial polarization and the azimuth polarization have the same phase, but the phase differs as they approach the periphery of the image detector 42 (on the pupil).

[0072] Between the image detector 42 and the relay lens 22, an analyzer section 44 including a λ / 4 wave plate H4 and a linear polarizer H2 is disposed. The analyzer section 44 transmits only the common polarization components of the radial polarization and the azimuth polarization. As a result, the radial polarization and the azimuth polarization transmitted through the analyzer section 44 become interferable and form concentric interference fringes on the image detector 42. Here, the radial polarization corresponds to the P polarization on a sample 50 such as a semiconductor wafer, and the azimuth polarization corresponds to the S polarization on the sample 50. Thus, the ellipsometer 2 of this embodiment is configured to enable ellipsometry measurement of the P polarization and the S polarization in all directions, and can perform highly sensitive measurement independent of the structure of the measurement target due to its symmetry. Other configurations and effects are included in the description of the first embodiment and the modified examples.

[0073] (Embodiment 3) Next, an ellipsometer according to embodiment 3 will be described. In the above-mentioned embodiment 2, the position where the optical path length difference between radial polarization and azimuth polarization is zero is on the optical axis C of the focusing optical system 20. In contrast, in this embodiment, the position where the optical path length difference between radial polarization and azimuth polarization is zero is arranged more peripherally on the pupil. This allows the number of interference fringes to be densely measured.

[0074] FIG. 17 is a configuration diagram illustrating an ellipsometer according to the third embodiment. As shown in FIG. 17, the ellipsometer 3 of this embodiment has a polarizing optical element section 32 instead of the polarizing optical element section 31. The polarizing optical element section 32 includes a birefringent crystal F2 in addition to the birefringent crystal F1. The birefringent crystal F2 is disposed between the relay lens 22 and the analyzer section 44. The birefringent crystal F2 is a plate having an incident surface and an exit surface, and the incident surface has a concave conical shape and the exit surface has a convex conical shape. The birefringent crystal F2 has a so-called double-sided axicon lens shape. The birefringent crystal F2 includes a uniaxial birefringent crystal. The crystal optical axis of the birefringent crystal F2 is parallel to the optical axis C of the focusing optical system 20.

[0075] The birefringent crystal F2 has a birefringence opposite to that of the birefringent crystal F1. Specifically, the birefringent crystal F1 and the birefringent crystal F2 have a refractive index n 0 (Hereinafter, n 0 ) < the refractive index of extraordinary light n e (Hereinafter, n e ), and n 0 >n e For example, if the birefringent crystal F1 is a negative crystal (n 0 >n e ), then the birefringent crystal F2 is a positive crystal (n 0 <n e ) The birefringent crystal F1 is a positive crystal (n 0 <n e ), the birefringent crystal F2 is a negative crystal (n 0 >n e ).

[0076] Fig. 18 is a diagram illustrating the interference fringes, radial polarization, and azimuth polarization of the reflected light that has interfered on the image detector 42 in the ellipsometer 3 according to the third embodiment. Fig. 19 is a diagram illustrating the polarization optical element unit 32 according to the third embodiment. As shown in Figs. 18 and 19, by adding a birefringent crystal F2 to the birefringent crystal F1, the position of the optical path length difference of 0 between the radial polarization and the azimuth polarization on the image detector 42 can be moved to a position outside the optical axis C. Note that in Fig. 19, the linear polarizer H2 and the λ / 4 wave plate H4 of the analyzer unit 44 are omitted in order to explain the propagation state of the radial polarization and the azimuth polarization.

[0077] (Variations 1 to 4) Next, modified examples 1 to 4 of embodiment 3 will be described. Fig. 20 to Fig. 23 are diagrams illustrating polarization optical element sections 33 to 36 according to modified examples 1 to 4 of embodiment 3. As shown in Fig. 20 to Fig. 23, even if the polarization optical element sections 33 to 36 have a configuration different from that of the polarization optical element section 32, concentric interference fringes of radial polarization and azimuth polarization can be formed on the image detector 42 based on the same principle as the polarization optical element section 32.

[0078] As shown in FIG. 20, the polarizing optical element section 33 of the first modification includes a birefringent crystal F1 and a birefringent crystal F3. Specifically, the polarizing optical element section 33 of the first modification is configured in such a manner that the birefringent crystal F2 is omitted from the configuration of the polarizing optical element section 32 of the third embodiment, and the birefringent crystal F3 is disposed between the birefringent crystal F1 and the relay lens 22. Thus, the birefringent crystal F3 is disposed in a region where the reflected light R1 of the focusing optical system 20 is focused or diffused. The birefringent crystal F3 includes a uniaxial birefringent crystal having a parallel plate shape. The birefringent crystal F3 has two parallel plate surfaces. The crystal optical axis of the birefringent crystal F3 is perpendicular to the plate surfaces. The birefringent crystal F3 is disposed so that the plate surfaces are perpendicular to the optical axis C of the focusing optical system 20. The crystal optical axis of the birefringent crystal F3 is parallel to the optical axis C.

[0079] The birefringent crystal F3 has a birefringence opposite to that of the birefringent crystal F1. Specifically, the birefringent crystal F1 and the birefringent crystal F3 have a birefringence of n 0 <n e and n 0 >n e For example, if the birefringent crystal F1 is a negative crystal (n 0 >n e ), then the birefringent crystal F3 is a positive crystal (n 0 <n e ) The birefringent crystal F1 is a positive crystal (n 0 <n e ), the birefringent crystal F3 is a negative crystal (n 0 >n e ).

[0080] As shown in FIG. 21, the polarizing optical element section 34 of the modified example 2 includes a birefringent crystal F2 having a double-sided axicon lens shape and a birefringent crystal F4 having a meniscus lens shape. Specifically, the polarizing optical element section 34 of the modified example 2 includes a birefringent crystal F4 arranged between the relay lens 21 and the relay lens 22 instead of the birefringent crystal F1 in the configuration of the polarizing optical element section 32 of the embodiment 3. Thus, the birefringent crystal F4 is arranged in a region where the reflected light R1 of the focusing optical system 20 is focused or diffused. The birefringent crystal F4 has an entrance surface and an exit surface. The birefringent crystal F4 has a concave spherical entrance surface and a convex spherical exit surface. The birefringent crystal F4 includes a uniaxial birefringent crystal. The crystal optical axis of the birefringent crystal F4 is arranged to be parallel to the optical axis C of the focusing optical system 20.

[0081] The birefringent crystal F4 has a birefringence opposite to that of the birefringent crystal F2. Specifically, the birefringent crystal F2 and the birefringent crystal F4 have a birefringence of n 0 <n e and n 0 >n e For example, if the birefringent crystal F2 is a negative crystal (n 0 >n e ), then the birefringent crystal F4 is a positive crystal (n 0 <n e ) The birefringent crystal F2 is a positive crystal (n 0 <n e ), the birefringent crystal F4 is a negative crystal (n 0 >n e ).

[0082] As shown in FIG. 22, the polarizing optical element section 35 of the modified example 3 includes a birefringent crystal F1, a birefringent crystal F5, and axicon lenses 25 and 26. Specifically, the polarizing optical element section 35 of the modified example 3 has a configuration in which a parallel plate-shaped birefringent crystal F5 is sandwiched between concave and convex axicon lenses 25 and 26 instead of the double-sided axicon lens-shaped birefringent crystal F2 in the configuration of the embodiment 3. The birefringent crystal F5 includes a uniaxial birefringent crystal in a parallel plate shape. The birefringent crystal F5 has two parallel plate surfaces. The crystal optical axis of the birefringent crystal F5 is perpendicular to the plate surfaces. The birefringent crystal F5 is arranged so that the plate surfaces are perpendicular to the optical axis C of the focusing optical system 20. The crystal optical axis of the birefringent crystal F5 is parallel to the optical axis C.

[0083] The axicon lens 25 is disposed between the relay lens 22 and the birefringent crystal F5. Therefore, the axicon lens 25 is disposed on the incident surface side of the birefringent crystal F5. The axicon lens 25 includes, for example, glass as a material. The axicon lens 25 has an incident surface with a concave conical shape and an exit surface with a flat shape.

[0084] The axicon lens 26 is disposed between the birefringent crystal F5 and the analyzer unit 44. Therefore, the axicon lens 26 is disposed on the exit surface side of the birefringent crystal F5. The axicon lens 26 includes, for example, glass as a material. The axicon lens 26 has a flat entrance surface and a convex conical exit surface.

[0085] The birefringent crystal F5 has a birefringence opposite to that of the birefringent crystal F1. Specifically, the birefringent crystal F1 and the birefringent crystal F5 have a birefringence of n 0 <n e and n 0 >n e For example, if the birefringent crystal F1 is a negative crystal (n 0 >n e ), the birefringent crystal F5 is a positive crystal (n 0 <n e ) The birefringent crystal F1 is a positive crystal (n 0 <n e), the birefringent crystal F5 is a negative crystal (n 0 >n e ).

[0086] As shown in FIG. 23, the polarizing optical element section 36 of the modified example 4 includes a birefringent crystal F2, a birefringent crystal F6, and a birefringent crystal F7. Specifically, the polarizing optical element section 36 of the modified example 4 includes a birefringent crystal F6 and a birefringent crystal F7 instead of the birefringent crystal F1 in the configuration of the embodiment 3. Therefore, the birefringent crystal F6 and the birefringent crystal F7 are arranged in a region where the reflected light R1 of the focusing optical system 20 is focused or diffused. The birefringent crystal F6 and the birefringent crystal F7 include uniaxial birefringent crystals having a parallel plate shape. The birefringent crystal F6 and the birefringent crystal F7 each have two parallel plate surfaces. The crystal optical axis of the birefringent crystal F6 and the crystal optical axis of the birefringent crystal F7 are parallel to the plate surfaces. The birefringent crystal F6 and the birefringent crystal F7 are arranged so that the plate surfaces are perpendicular to the optical axis C of the focusing optical system 20. The crystal optical axis of the birefringent crystal F6 and the crystal optical axis of the birefringent crystal F7 are perpendicular to the optical axis C of the focusing optical system 20 and are mutually perpendicular.

[0087] The birefringent crystal F6 and the birefringent crystal F7 have birefringence opposite to that of the birefringent crystal F2. 0 <n e and n 0 >n e For example, the birefringent crystal F6 and the birefringent crystal F7 have negative birefringence (n 0 >n e ), then the birefringent crystal F2 is a positive crystal (n 0 <n e ) The birefringent crystals F6 and F7 are positive crystals (n 0 <n e ), the birefringent crystal F2 is a negative crystal (n 0 >n e In this way, in the third embodiment and the first to fourth modifications, the polarization optical element units 32 to 36 are n 0 <n e , and n 0 >n eThe birefringent crystals have mutually opposite birefringence. Other configurations and effects are included in the description of the first and second embodiments and the modified examples.

[0088] (Embodiment 4) Next, an ellipsometer according to the fourth embodiment will be described. Fig. 24 is a configuration diagram illustrating an ellipsometer according to the fourth embodiment. As shown in Fig. 24, in the ellipsometer 4, the polarizer section 15 includes a linear polarizer H1, and the analyzer section 41 includes a linear polarizer H2. The polarizing optical element section 37 includes Nomarski prisms 131 and 132. The polarizing optical element section 37 includes n 0 <n e A uniaxial birefringent crystal having a positive birefringence of n 0 >n e The polarizing optical element 37 includes a Nomarski prism 131 including a uniaxial birefringent crystal having negative birefringence, and a Nomarski prism 132 including a uniaxial birefringent crystal having positive birefringence and a uniaxial birefringent crystal having negative birefringence. Thus, the polarizing optical element 37 separates the reflected light R1, which is the illumination light L1 including linear polarization and reflected by the measurement surface of the sample 50, into two linearly polarized components having mutually orthogonal linear polarization directions. The analyzer 41 transmits the two linearly polarized components in a direction different from each polarization direction, causing them to interfere with each other and form interference fringes. The image detector 42 detects the interference fringes. The analyzer 43 calculates the ellipsometry coefficients Ψ and Δ from the detected interference fringes.

[0089] FIG. 25 is a diagram illustrating the interference fringes of the reflected light R1 that has interfered on the image detector 42, and the X-polarized light and the Y-polarized light in the ellipsometer 4 according to the fourth embodiment. FIG. 25 also illustrates the interference fringes of the reflected light R1 that has interfered on the image detector 142 in the ellipsometer 101 of the comparative example. The ellipsometer 4 of this embodiment, unlike the first to third embodiments, forms the interference fringes of the X-polarized light and the Y-polarized light in a one-dimensional vertical stripe on the pupil. However, by using two or more types of crystals with different birefringence, the separation angle of the two polarized lights is changed for each wavelength. More specifically, the Nomarski prisms 131 and 132 are arranged so that the separation angle of the two polarized lights just before the image detector 42 is larger on the long wavelength side and smaller on the short wavelength side. Therefore, in this embodiment, by including the achromatic Nomarski prism 132, it is possible to suppress the decrease in contrast at both ends in the X-axis direction compared to the comparative example. In this way, the change in the interval between the interference fringes due to the difference in wavelength is reduced. Therefore, even in measurements using a broadband light source, it is possible to narrow the spacing between interference fringes and widen the wavelength width compared to previous methods.

[0090] FIG. 26 is a graph illustrating the wavelength dependence of birefringence in each material of birefringent crystal, where the horizontal axis indicates wavelength and the vertical axis indicates birefringence. In FIG. 0 -n e ) / {(n 0 +n e ) / 2} is normalized to 1 when the wavelength is 400 nm, and αBBO, quartz, magnesium fluoride (MgF 2 ), Sapphire (Al 2 O 3 This figure shows the wavelength dependence of the polarization separation angle when Nomarski prisms are made from each of the materials magnesium fluoride and calcite. As shown in Figure 26, magnesium fluoride has a relatively small wavelength dependence of the polarization separation angle, while calcite has a large wavelength dependence. The fringe pitch of the interference fringes is the same value for multiple wavelengths of illumination light.

[0091] Fig. 27 is a diagram illustrating a polarizing optical element section 37 according to the fourth embodiment. As shown in Fig. 27, if the Nomarski prism 132 is made of calcite and the Nomarski prism 131 is made of magnesium fluoride, the polarization separation angle immediately before the image detector 42 is large on the long wavelength side and small on the short wavelength side. By designing in this way, it is possible to reduce the wavelength dependency of the interval between interference fringes. Other configurations and effects are included in the descriptions of the first to third embodiments and the modified examples.

[0092] The present invention is not limited to the above-mentioned embodiment, and can be modified as appropriate without departing from the spirit of the present invention. For example, the configurations of the first to fourth embodiments and the modifications can be combined with each other. In addition, an inspection device for a semiconductor device equipped with an ellipsometer according to the first to fourth embodiments and the modifications is also included in the technical idea of ​​the present embodiment. [Explanation of symbols]

[0093] 1, 2, 3, 4 Ellipsometer 1A Inspection equipment 10 Illumination optical system 11 Light source 12 Spectrometer 13. Fiber 14 Lighting lens 15, 18 Polarizer section 16 Beam splitter 17 Objective Lens 20 Light collecting optical system 21, 22 Relay lens 23 Pupil position 24 Pupil conjugate position 25, 26 Axicon Lens 30, 31, 32, 33, 34, 35, 36, 37 Polarizing optical element section 40 Light receiving optical system 41, 44 Analyzer section 42 Image detector 43 Analyzer 50 samples 80 Bases 81 Isolator 82 Optical Surface Plate 83 Stage 84 Wafer Holder 85 frames 86 Environmental Chamber 87 Temperature Controller Unit 88 Automatic substrate transfer device 91 Control Unit 92 Grabber Board 93 Stage Controller 94 Light source / spectrometer controller 101 Ellipsometer 110 Illumination optical system 111 Light source 112 Spectrometer 113 Fiber 114 Lighting Lens 115 Polarizer 116 Beam splitter 117 Objective Lens 120 Condensing optical system 121, 122 Relay lens 130 Polarizing Optical Elements 131, 132 Nomarski prism 140 Light receiving optical system 141 Analyzer 142 Image detector 143 Analysis equipment C optical axis H1, H2 linear polarizer H3, H4 λ / 4 wave plate F1, F2 birefringent crystals L1 illumination light R1 Reflected light W10, W20 Wollaston lens

Claims

1. a polarizing optical element unit that separates two polarized components having mutually orthogonal polarization directions of reflected light, which is obtained by reflecting illumination light including at least one of linearly polarized light, circularly polarized light, and elliptically polarized light off a measurement surface of a sample, into radial directions centered on an optical axis of an optical system of the reflected light; an analyzer unit that transmits components of the two polarized components in directions different from the polarization directions of the two polarized components, thereby causing interference and forming concentric interference fringes; an image detector for detecting the interference fringes; an analyzer for calculating ellipsometry coefficients Ψ and Δ from the detected interference fringes; An ellipsometer equipped with

2. A light source that generates the illumination light; a polarizer unit to which the illumination light generated by the light source is incident and which transmits the illumination light including at least one of the linearly polarized light, the circularly polarized light, and the elliptically polarized light; an objective lens that transmits the illumination light and transmits the reflected light that is reflected by the measurement surface of the sample from the illumination light; a focusing optical system for imaging an exit pupil of the objective lens onto the image detector; 10. The ellipsometer of claim 1 further comprising:

3. The polarizer unit includes a linear polarizer that generates linearly polarized light, The analyzer unit includes a linear polarizer that transmits a linearly polarized component in a predetermined direction.

3. The ellipsometer of claim 2.

4. the polarizer unit includes a circular polarizer that generates circularly polarized light that rotates left or right around an optical axis of the illumination light, The analyzer unit includes a circular polarizer that transmits a circularly polarized component that rotates either left or right.

3. The ellipsometer of claim 2.

5. Each of the circular polarizers includes a linear polarizer and a λ / 4 wave plate.

5. The ellipsometer of claim 4.

6. the polarizing optical element portion includes a Wollaston lens, The Wollaston lens includes two uniaxial birefringent crystals having interdigitated spherical shapes; The crystal optical axis of each of the uniaxial birefringent crystals is perpendicular to the optical axis of the optical system and perpendicular to each other.

4. The ellipsometer of claim 3.

7. The polarizing optical element portion further includes another Wollaston lens, the two polarized components of the reflected light transmitted through the polarizing optical element unit and the analyzer unit are detected at the same point on the image detector; 7. The ellipsometer of claim 6.

8. the polarization optical element unit includes a first birefringent crystal having a parallel plate shape arranged at a position in the optical system where the reflected light is condensed or diffused, the first birefringent crystal is a uniaxial birefringent crystal, The crystal optical axis of the first birefringent crystal is parallel to the optical axis of the optical system.

6. An ellipsometer according to claim 4 or 5.

9. The polarizing optical element unit is a first birefringent crystal having a parallel plate shape arranged at a position in the optical system where the reflected light is focused or diffused; a second birefringent crystal having a concave conical entrance surface and a convex conical exit surface; Including, the first birefringent crystal and the second birefringent crystal are uniaxial birefringent crystals, a crystal optical axis of the first birefringent crystal and a crystal optical axis of the second birefringent crystal are parallel to an optical axis of the optical system; 6. An ellipsometer according to claim 4 or 5.

10. The polarizing optical element unit is a first birefringent crystal having a parallel plate shape arranged at a position in the optical system where the reflected light is focused or diffused; a third birefringent crystal having a parallel plate shape arranged at a position in the optical system where the reflected light is focused or diffused; Including, the first birefringent crystal and the third birefringent crystal are uniaxial birefringent crystals, a crystal optical axis of the first birefringent crystal and a crystal optical axis of the third birefringent crystal are parallel to an optical axis of the optical system; 6. An ellipsometer according to claim 4 or 5.

11. The polarizing optical element unit is a fourth birefringent crystal that is disposed in the optical system at a position where the reflected light is condensed or diffused, the fourth birefringent crystal having an incident surface that is a concave spherical shape and an exit surface that is a convex spherical shape; a second birefringent crystal having a concave conical entrance surface and a convex conical exit surface; Including, the second birefringent crystal and the fourth birefringent crystal are uniaxial birefringent crystals, a crystal optical axis of the second birefringent crystal and a crystal optical axis of the fourth birefringent crystal are parallel to an optical axis of the optical system; 6. An ellipsometer according to claim 4 or 5.

12. The polarizing optical element unit is a first birefringent crystal having a parallel plate shape arranged at a position in the optical system where the reflected light is focused or diffused; a fifth birefringent crystal having the parallel plate shape; a first glass substrate disposed on the incident surface side of the fifth birefringent crystal, the first glass substrate having an incident surface in a concave conical shape and an exit surface in a planar shape; a second glass substrate disposed on the exit surface side of the fifth birefringent crystal, the second glass substrate having an entrance surface in a planar shape and an exit surface in a convex cone shape; Including, the first birefringent crystal and the fifth birefringent crystal are uniaxial birefringent crystals, The crystal optical axis of the first birefringent crystal and the crystal optical axis of the fifth birefringent crystal are parallel to the optical axis of the optical system.

6. An ellipsometer according to claim 4 or 5.

13. The polarizing optical element unit is a sixth birefringent crystal having a parallel plate shape and arranged at a position in the optical system where the reflected light is focused or diffused; a seventh birefringent crystal having a parallel plate shape and arranged at a position in the optical system where the reflected light is focused or diffused; a second birefringent crystal having a concave conical entrance surface and a convex conical exit surface; Including, the second birefringent crystal, the sixth birefringent crystal, and the seventh birefringent crystal are uniaxial birefringent crystals; a crystal optical axis of the second birefringent crystal is parallel to an optical axis of the optical system; The crystal optical axis of the sixth birefringent crystal and the crystal optical axis of the seventh birefringent crystal are perpendicular to the optical axis of the optical system and perpendicular to each other.

6. An ellipsometer according to claim 4 or 5.

14. The polarizing optical element has a refractive index n ０ <Refractive index of extraordinary light n ｅ , and the refractive index of normal light n ０ > Refractive index of extraordinary light n ｅ The birefringent crystals have mutually opposite birefringences of The ellipsometer according to any one of claims 9 to 13.

15. a polarization optical element unit that separates the reflected light, which is illumination light including linear polarization and is reflected by a measurement surface of a sample, into two linearly polarized components having polarization directions perpendicular to each other; an analyzer unit that transmits the two linearly polarized components in directions different from the polarization directions, causes them to interfere with each other, and forms interference fringes; an image detector for detecting the interference fringes; an analyzer for calculating ellipsometry coefficients Ψ and Δ from the detected interference fringes; Equipped with the fringe pitch of the interference fringes is the same for a plurality of wavelengths of the illumination light; Ellipsometer.

16. The polarizing optical element unit is Refractive index of ordinary light n ０ <Refractive index of extraordinary light n ｅ A uniaxial birefringent crystal having a positive birefringence, and a refractive index of ordinary light n ０ > Refractive index of extraordinary light n ｅ A first Nomarski prism including a uniaxial birefringent crystal having a negative birefringence, a second Nomarski prism including the uniaxial birefringent crystal having the positive birefringence and the uniaxial birefringent crystal having the negative birefringence; Including, 16. The ellipsometer of claim 15.

17. the first Nomarski prism and the second Nomarski prism are arranged such that a separation angle of the two polarized lights immediately before the image detector is large on the long wavelength side and small on the short wavelength side; 17. The ellipsometer of claim 16.

18. The birefringent crystal includes any one of quartz, magnesium fluoride, sapphire, calcite, and αBBO; The ellipsometer according to any one of claims 6 to 14 and 16 to 17.

19. The analysis device includes: The image including the concentric interference fringes is transformed into polar coordinates so that the center of the concentric circle becomes the coordinate origin; A two-dimensional Fourier transform is performed on a two-dimensional coordinate plane having the radius and the deviation angle of the polar coordinates as axes; In the frequency space image after the two-dimensional Fourier transform, a DC component and an AC component are separated and trimmed; Ψ and Δ are calculated based on the results of the inverse Fourier transform of the trimmed area. The ellipsometer according to any one of claims 1 to 14.

20. An ellipsometer comprising the ellipsometer according to any one of claims 1 to 19. Inspection equipment for semiconductor devices.

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