Spectrometer and measurement system

Abstract

To provide a spectrometer and a metrology system that are capable of improving spectral performance.SOLUTION: A spectrometer 1 according to an embodiment includes: a collimator lens 21 that converts, into parallel light, light that has passed through an incident slit 10; a dispersive optical element 30 that disperses, at different angles according to wavelengths, the light converted into the parallel light by the collimator lens 21; a focusing lens 41 that focuses the dispersed light; and a reflective SLM that has a reflective plane to reflect the light focused by the focusing lens 41. The light reflected by the SLM is output from an output slit 60 through the focusing lens 41 and the dispersive optical element 30. If a first plane, which includes optical paths of the light dispersed at different angles, and a second plane, which is perpendicular to the first plane and includes an optical axis 21A of the collimator lens 21 and an optical axis 41A of the focusing lens 41, are defined, then on the second plane the incident slit 10, the output slit 60, and the reflective plane have a conjugate relationship.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a spectrometer and a measurement system. [Background technology]

[0002] In the semiconductor manufacturing process, optical measuring instruments based on principles such as SR (Spectroscopic Reflectometry) and SE (Spectroscopic Ellipsometry) are widely used to measure with high precision the dimensions, such as film thickness, and optical constants, such as refractive index, of semiconductor circuit structures formed on Si substrates. These are called OCD (Optical Critical Dimension) measuring instruments, and are commonly used to determine the dimensions of semiconductor circuit structures and the optical constants of their constituent materials by comparing and fitting the measurement results with the results of a simulation using a model of the semiconductor circuit structure.

[0003] Over the past decade or so, semiconductor circuit structures have become increasingly three-dimensional and complex, with FinFETs in logic semiconductors and 3D-NAND in memory. As the target structure becomes more complex, the number of floating parameters required for fitting increases. For example, current FinFET OCD measurement equipment requires the use of around 20-30 floating parameters.

[0004] To find a solution for the dimensions, a minimum of more measurements than the number of floating parameters is required for fitting to a model. This requires measuring reflectance in the case of SR, and Ψ and Δ in the case of SE, at multiple wavelengths. Furthermore, there is a problem known as "coupling," in which the fitting converges on a combination of floating parameters that differs from the actual dimensions. To avoid this, SR and SE are often performed at more than 100 wavelengths. Despite these demands for measurement accuracy, OCD measurements in the semiconductor manufacturing process require extremely short measurements. For example, the allowable measurement time per wafer is a few tens of seconds at most, and in such a short time, only a very limited area on the wafer can be measured.

[0005] There are two main methods for measuring multiple wavelengths in OCD measurement devices. One is to transmit light emitted from a light source through a monochromator to illuminate the object in a monochromatic form. The other is to illuminate the object with light in a wide wavelength range, and then use a spectrometer to measure the reflected light and measure each wavelength. The latter method allows for faster measurements because it can measure multiple wavelengths simultaneously, but there are also many cases where the former monochromator is required, such as for wide-field image measurement, pupil reflectance measurement, and ellipsometry measurement.

[0006] Generally, a monochromator is configured to rotate a diffraction grating or dispersion prism, and wavelength switching requires several tens of milliseconds or more due to the time used to accelerate and decelerate the rotation stage. When the number of wavelengths to be switched exceeds 100, the switching time alone requires several seconds or more, which is a major factor in reducing the throughput of the entire OCD measurement device.

[0007] Patent Document 1 describes a spectrometer that uses a double monochromator configuration using two dispersive elements and has a movable slit located near the intermediate image in order to reduce the mechanical drive time. Based on the configuration of Patent Document 1, a method of switching wavelengths using a Spatial Light Modulator (SLM) has been proposed.

[0008] The basic configuration of a Digital Micro Mirror Device (DMD) is described in Patent Document 2. Many attempts have been made to put DMDs such as those described in Patent Document 2 into practical use.

[0009] Patent Documents 3 and 4 propose methods for switching wavelengths using a DMD. In Patent Document 4, an SLM (DMD) is used for spectral analysis within a laser resonator that can amplify by switching wavelengths. Specifically, within the laser resonator of Patent Document 4, light of a specific wavelength reflected by the SLM (DMD) is amplified by traveling back and forth multiple times along the same optical path. When the configuration of Patent Document 4 is applied to a monochromator, there is a problem in that the extraction efficiency of the spectrally dispersed light is significantly reduced.

[0010] In order to solve the problems of Patent Document 4, Patent Document 5 describes a configuration in which mirrors are placed before and after reflection on the SLM (DMD), so that the light incident on the SLM (DMD) and the reflected light do not travel the same optical path, thereby improving the light extraction efficiency.

[0011] Patent Documents 6 and 7 describe a configuration in which an SLM is arranged so that light is incident on it at an angle and pupil division is performed, making it possible to extract light without a mirror. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] U.S. Patent No. 4,575,243 [Patent Document 2] U.S. Patent No. 5,061,049 [Patent Document 3] U.S. Patent No. 5,504,575 [Patent Document 4] U.S. Patent No. 7,256,885 [Patent Document 5] U.S. Patent No. 6,870,619 [Patent Document 6] US Patent Application Publication No. 2007 / 296969 [Patent Document 7] US Patent Application Publication No. 2010 / 245818 Summary of the Invention [Problem to be solved by the invention]

[0013] In spectrometers using a reflective SLM (DMD), Patent Documents 5 to 7, among others, propose a configuration in which the SLM surface is tilted to extract the dispersed light. These configurations are valid as long as the mirrors of each pixel on the SLM are parallel to the SLM surface. However, in devices with a micro-mirror array (MMA) structure, such as the DMD, which allows for high-speed operation and dispersion over a wide wavelength range, the mirrors of each pixel are tilted relative to the entire DMD surface in both the ON and OFF states. Therefore, in the configurations described in the examples in Patent Documents 5 to 7, among others, light incident on the DMD is not reflected toward the focusing optical system. Furthermore, if the DMD is tilted so that the mirror surface of each DMD pixel is perpendicular to the optical axis of the focusing optical system, the light is reflected toward the focusing optical system. However, with this configuration, dispersed light is focused only near the center of the DMD, and defocusing occurs outside the DMD's center, preventing improved spectral performance.

[0014] The present invention has been made to solve such problems, and provides a spectrometer and a measurement system that can improve the light utilization efficiency and improve the spectroscopic performance. [Means for solving the problem]

[0015] In one embodiment, the spectrometer comprises a collimator lens that converts light that has passed through an entrance slit into parallel light, a dispersive optical element that disperses the light converted into parallel light by the collimator lens at different angles depending on the wavelength, a focusing lens that converges the dispersed light, and a reflective SLM having a reflective surface that reflects the light converged by the focusing lens, wherein the light reflected by the SLM exits from an exit slit via the focusing lens and the dispersive optical element, and when a first surface is defined that includes the optical paths of the light dispersed at different angles, and a second surface that includes the optical axis of the collimator lens and the optical axis of the focusing lens and is perpendicular to the first surface, the entrance slit, the exit slit, and the reflective surface are in a conjugate relationship on the second surface.

[0016] In the above spectrometer, the SLM may be a DMD including a plate-shaped substrate and a plurality of pixel mirrors arranged in a matrix on the surface of the substrate, each pixel mirror having a mirror surface that reflects the light and a rotation axis extending in a direction perpendicular to the second surface, and each pixel mirror may be in a first state in which the mirror surface is inclined at a first angle with respect to the substrate surface, and a second state in which the mirror surface is inclined at a second angle with respect to the surface.

[0017] In the above spectrometer, the DMD may set an extraction wavelength array including a plurality of the pixel mirrors along a direction perpendicular to the first surface, and may emit the light including a predetermined wavelength band from the exit slit by setting each pixel mirror of the extraction wavelength array to the first state.

[0018] In the above spectrometer, the DMD may set a plurality of extracted wavelength rows and cause the light including a plurality of the wavelength bands to exit from the exit slit by setting each pixel mirror of the plurality of extracted wavelength rows to the first state.

[0019] In the above spectrometer, the DMD may randomly change each pixel mirror of the extracted wavelength array to the first state or the second state, and set a plurality of pixel mirrors other than the extracted wavelength array to the second state.

[0020] In the above spectrometer, the central axis of the light incident on the second mirror surface may be perpendicular to the mirror surface.

[0021] In the above spectrometer, at the second surface, an incident angle of the central axis of the light incident on the mirror surface may be equal to a reflection angle of the central axis of the light reflected by the mirror surface.

[0022] In the above spectrometer, the optical axis of the focusing lens may be arranged parallel to the optical axis of the collimator lens at a position shifted from the optical axis of the collimator lens.

[0023] In the above spectrometer, the optical axis of the focusing lens may be inclined with respect to the optical axis of the collimator lens, and at the second surface, the angle of incidence of the central axis of the light incident on the mirror surface may be equal to the angle of reflection of the central axis of the light reflected by the mirror surface.

[0024] The above spectrometer may further include an optical member disposed between the collimator lens and the dispersive optical element, for splitting the light and providing an optical path difference to the split light.

[0025] In the above spectrometer, the optical member may include a stepped prism.

[0026] In the above spectrometer, the light may include laser light emitted from a fiber, and the entrance slit may include an end face of the fiber.

[0027] A measurement system in one embodiment includes the above-described spectrometer and a semiconductor measurement device that inspects or measures a semiconductor using the light emitted from the spectrometer.

[0028] In the above measurement system, spectroscopic ellipsometry may be used as the principle.

[0029] In the above measurement system, the semiconductor measurement device may inspect or measure the semiconductor by independently using the light including a plurality of wavelengths emitted from the spectrometer.

[0030] In the above measurement system, ellipsometry measurement may be performed from interference fringes formed by interference between light of different polarization components reflected from the semiconductor, and information on the light of the plurality of wavelengths may be separated from the frequency components of the interference fringes. [Effects of the Invention]

[0031] According to the present invention, it is possible to provide a spectrometer and a measurement system that can improve the efficiency of use of light that has passed through an entrance slit and improve spectroscopic performance. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a diagram illustrating a spectroscope according to a first embodiment. [Figure 2] FIG. 1 is a diagram illustrating a spectroscope according to a first embodiment. [Figure 3] 2 is a cross-sectional view illustrating a DMD in the spectrometer according to the first embodiment. FIG. [Figure 4] 2 is a cross-sectional view illustrating a DMD in the spectrometer according to the first embodiment. FIG. [Figure 5] 2 is a perspective view illustrating a DMD in the spectrometer according to the first embodiment. FIG. [Figure 6] 2 is a perspective view illustrating a pixel mirror of a DMD in the spectrometer according to the first embodiment. FIG. [Figure 7] 2 is a cross-sectional view illustrating a pixel mirror of a DMD in the spectrometer according to the first embodiment, showing a cross section perpendicular to the rotation axis of the pixel mirror. FIG. [Figure 8] 3A and 3B are diagrams illustrating images of an entrance slit formed on a DMD at different positions depending on wavelength in the spectrometer according to the first embodiment. [Figure 9] 3A and 3B are diagrams illustrating images of an entrance slit formed on a DMD at different positions depending on wavelength in the spectrometer according to the first embodiment. [Figure 10] FIG. 10 is a diagram illustrating a spectroscope according to a comparative example. [Figure 11] FIG. 10 is a diagram illustrating a spectroscope according to a comparative example. [Figure 12] FIG. 10 is a diagram illustrating a measurement system according to a modified example of the first embodiment. [Figure 13] FIG. 10 is a diagram illustrating a spectroscope according to a second embodiment. [Figure 14] FIG. 10 is a diagram illustrating a spectroscope according to a second embodiment. [Figure 15] 10 is a cross-sectional view illustrating a DMD in a spectrometer according to a second embodiment. FIG. [Figure 16] 10 is a cross-sectional view illustrating a DMD in a spectrometer according to a second embodiment. FIG. [Figure 17] FIG. 10 is a diagram illustrating a spectroscope according to a third embodiment. [Figure 18] FIG. 10 is a diagram illustrating a spectroscope according to a third embodiment. [Figure 19] 10 is a cross-sectional view illustrating a DMD in a spectrometer according to a third embodiment. FIG. [Figure 20] 10 is a cross-sectional view illustrating a DMD in a spectrometer according to a third embodiment. FIG. [Figure 21] FIG. 10 is a diagram illustrating a spectroscope according to a fourth embodiment. [Figure 22] FIG. 10 is a diagram illustrating a spectroscope according to a fourth embodiment. [Figure 23] FIG. 10 is a diagram illustrating a measurement system according to a fifth embodiment. [Figure 24] FIG. 10 is a configuration diagram illustrating a polarization optical element, an analyzer, and an image detector in a measurement system according to a fifth embodiment. [Figure 25] 13 is a diagram illustrating linearly polarized light transmitted through an analyzer in the measurement system according to the fifth embodiment. FIG. [Figure 26]10 is a diagram illustrating an example of the wavefront of each linearly polarized light contained in reflected light incident on an image detector in the measurement system according to the fifth embodiment. FIG. [Figure 27] 13 is a diagram illustrating an example of interference fringes of reflected light that has interfered on an image detector in the measurement system according to the fifth embodiment. FIG. [Figure 28] FIG. 11 is a diagram illustrating ellipsometry coefficients determined from interference fringes on an image detector in the measurement system according to the fifth embodiment. [Figure 29] 13 is a diagram illustrating interference fringes of reflected light that has interfered on an image detector in a measurement system 5 according to another example of the fifth embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0033] For clarity of explanation, the following description and drawings have been omitted and simplified as appropriate. In addition, the same elements in each drawing are given the same reference numerals, and duplicate explanations have been omitted as necessary.

[0034] (Embodiment 1) A spectrometer according to embodiment 1 will be described. The spectrometer of embodiment 1 is a spectrometer (monochromator) that switches the wavelength of light used in a semiconductor measurement device such as a semiconductor inspection device or a semiconductor measurement device. Specifically, the spectrometer is used in an optical inspection device or an optical measurement device that measures the dimensions, distortion, and physical properties of a circuit structure formed on a sample such as a semiconductor wafer or detects defects in the semiconductor manufacturing process. Note that the spectrometer of embodiment 1 may also be used in devices other than semiconductor measurement devices.

[0035] 1 and 2 are diagrams illustrating a spectrometer according to embodiment 1. Here, for convenience of explanation of the spectrometer, an XYZ Cartesian coordinate system is introduced. The XY plane is a plane containing light dispersed at different angles according to wavelength by a dispersive optical element, which will be described later. FIG. 1 shows the arrangement of each component in the XY plane as viewed from the Z-axis direction. FIG. 2 shows the arrangement of each component in the XZ plane as viewed from the Y-axis direction. The solid lines, wavy lines, and dotted lines indicating light in FIG. 1 indicate differences in wavelength.

[0036] 1 and 2, the spectrometer 1 includes an entrance slit 10, a collimator optical system 20, a dispersive optical element 30, a focusing optical system 40, a DMD 50, and an exit slit 60. The spectrometer 1 includes the DMD 50 as a reflective SLM. Note that the reflective SLM of the spectrometer 1 is not limited to the DMD 50, and may be an SLM using liquid crystal.

[0037] The entrance slit 10 is formed in, for example, a plate-shaped entrance slit portion 11. The entrance slit 10 may be an exit port at the end face of a fiber that guides light. The entrance slit 10 passes light generated by the light source and guides it to the collimator optical system 20.

[0038] The collimator optical system 20 includes, for example, a collimator lens 21, a beam splitter 22, and a collimator lens 23. The collimator lens 21 converts the light that has passed through the entrance slit 10 into parallel light. The light converted into parallel light by the collimator lens 21 enters the beam splitter 22.

[0039] On the outgoing path of the light in the +X-axis direction, the beam splitter 22 transmits a portion of the incident parallel light and guides it to the dispersion optical element 30. On the returning path of the light in the −X-axis direction, the beam splitter 22 reflects a portion of the light that has transmitted through the dispersion optical element 30 to the collimator lens 23. The collimator lens 23 collects the light reflected by the beam splitter 22 and passes it through the exit slit 60.

[0040] The dispersive optical element 30 disperses light. Specifically, the dispersive optical element 30 disperses the light converted into parallel light by the collimator lens 21 at different angles depending on the wavelength. That is, the dispersive optical element 30 disperses light at different angles for each wavelength. The dispersive optical element 30 includes a diffraction grating or a prism. The dispersive optical element 30 disperses light transmitted through the beam splitter 22 for each wavelength, turning it into light traveling at different angles, as shown by the dotted line, wavy line, and solid line in FIG. 1, for example. The Y-axis direction in which the dispersive optical element 30 disperses light is called the dispersion direction.

[0041] The focusing optical system 40 includes a focusing lens 41. The focusing lens 41 converges the dispersed light. For example, in FIG. 1 , in the XY plane including the dispersion direction, the focusing lens 41 is arranged so that the dispersion optical element 30 is located at the focal position on the −X axis direction side. The focusing lens 41 is arranged so that the DMD 50 is located at the focal position on the +X axis direction side. As a result, in the XY plane, an image of the entrance slit 10 dispersed for each wavelength is formed on the DMD 50.

[0042] As shown in FIG. 2, in the XZ plane, the optical axis 41A of the focusing lens 41 is shifted from the optical axis 21A of the collimator lens 21 and is disposed parallel to the optical axis 21A of the collimator lens 21. For example, the optical axis 41A of the focusing lens 41 is shifted in the +Z-axis direction from the optical axis 21A of the collimator lens 21. The DMD 50 is disposed on the optical axis 41A of the focusing lens 41. In FIG. 2, the focusing lens 41 is configured by cutting out a portion from the entire lens. The shape before cutting is represented by a dotted line. Whether the focusing lens 41 is actually cut out may depend on the product specifications. Light transmitted through the dispersive optical element 30 is focused toward the intersection of the optical axis 41A of the focusing lens 41 and the DMD 50. Therefore, an angle is formed between the chief ray (the central axis of light) and the optical axis 41A of the focusing lens 41.

[0043] As shown in FIG. 1, in the XY plane including the dispersion direction, an image of the entrance slit 10, into which light enters, is formed on the DMD 50 for each wavelength. The light reflected by the DMD 50 is transmitted again through the same dispersion optical element 30, thereby canceling out the wavelength dispersion. Therefore, the image of the entrance slit 10 is formed at the same position independent of wavelength. Therefore, the exit slit 60 is positioned at the position where the image of the entrance slit 10 is formed. Meanwhile, as shown in FIG. 2, in the XZ plane perpendicular to the dispersion direction, the DMD 50 is positioned on the optical axis 41A of the focusing lens 41, which is positioned so as to be shifted from the optical axis 21A of the collimator lens 21.

[0044] The XY plane, which includes the optical paths of the light dispersed at different angles, is defined as the first plane. The XZ plane, which includes the optical axis 21A of the collimator lens 21 and the optical axis 41A of the focusing lens 41 and is perpendicular to the first plane, is defined as the second plane. When the first and second planes are defined in this way, the surface 19 of the entrance slit 10, the surface 69 of the exit slit 60, and the reflecting surface 59 of the DMD 50 are in a conjugate relationship on the second plane. In addition, a dispersive optical element 30 is disposed at a pupil position 39.

[0045] 3 and 4 are cross-sectional views illustrating the DMD 50 in the spectrometer 1 according to the first embodiment. FIG. 3 shows a cross-sectional view perpendicular to the Z-axis direction. FIG. 4 shows a cross-sectional view perpendicular to the Y-axis direction. FIG. 5 is a perspective view illustrating the DMD 50 in the spectrometer 1 according to the first embodiment. FIG. 6 is a perspective view illustrating the pixel mirror 53 of the DMD 50 in the spectrometer 1 according to the first embodiment. FIG. 7 is a cross-sectional view illustrating the pixel mirror 53 of the DMD 50 in the spectrometer 1 according to the first embodiment, showing a cross section perpendicular to the rotation axis 55 of the pixel mirror 53.

[0046] As shown in FIGS. 3 to 5, the DMD 50 has a reflective surface that reflects light converged by the focusing lens 41. The DMD 50 includes a plate-shaped substrate 51 and a plurality of pixel mirrors 53. The surface of the substrate 51 on the −X-axis direction side is called the substrate surface 52. The plurality of pixel mirrors 53 are arranged in a matrix on the substrate surface 52 of the substrate 51. Each pixel mirror 53 has a mirror surface 54 that reflects light. Therefore, the mirror surface 54 is a reflective surface that reflects the light converged by the focusing lens 41.

[0047] As shown in Figure 3, in a cross section of the XY plane including the dispersion direction, the cutting line of the substrate surface 52 of the substrate 51 and the cutting line of the mirror surface 54 of the pixel mirror 53 are parallel. These cutting lines are perpendicular to the chief ray of the incident light (the central axis of the light). With this arrangement, the focal point of light for all dispersed wavelengths coincides with the mirror surface 54 in the XY plane. This allows for improved spectral performance.

[0048] 4, in the cross section of the XZ plane perpendicular to the dispersion direction, the substrate surface 52 of the substrate 51 and the optical axis 41A of the focusing lens 41 are perpendicular to each other. The mirror surface 54 of each pixel mirror 53 is perpendicular to the chief ray (central axis of light) of the incident light. Therefore, in the XZ plane, the central axis of light incident on the DMD 50 is perpendicular to the mirror surface 54. With this arrangement, the focal point of light for all dispersed wavelengths in the XZ plane coincides with the mirror surface 54. This can improve light utilization efficiency and spectral performance.

[0049] As shown in FIGS. 6 and 7 , each pixel mirror 53 has a rotation axis 55. The rotation axis 55 extends, for example, in the Y-axis direction. Therefore, the rotation axis 55 extends in the dispersion direction. Each pixel mirror 53 rotates around the rotation axis 55. The mirror surface 54 of each pixel mirror 53 is at a predetermined angle with respect to the substrate surface 52 of the substrate 51. For example, each pixel mirror 53 is in an ON state in which the mirror surface 54 is tilted at a predetermined first angle with respect to the substrate surface 52, and an OFF state in which the mirror surface 54 is tilted at a predetermined second angle with respect to the substrate surface 52. In this way, each pixel mirror 53 can be switched between two states. However, the mirror surface 54 of each pixel mirror 53 is not parallel to the substrate surface 52 of the substrate 51 of the DMD 50 in either the ON state or the OFF state.

[0050] 5 to 7, in both the ON state and the OFF state, the DMD 50 is disposed so that a plane including the normal to each mirror surface 54 and the normal to the substrate surface 52 of the substrate 51 is perpendicular to the direction of dispersion of light by the dispersion optical element 30. With this configuration, the entire surface of the DMD 50 has a conjugate relationship with the entrance slit 10, thereby achieving high wavelength resolution and improving light utilization efficiency.

[0051] When the spectrometer 1 is used in a semiconductor measurement device, for example, only the pixel mirrors 53 of the DMD 50 that correspond to the wavelengths of light desired to be used in the semiconductor measurement device are turned on. Then, the light reflected by the pixel mirrors 53 that are turned on is returned toward the focusing optical system 40. For example, the DMD 50 sets an extraction wavelength array including multiple pixel mirrors 53 along the Z-axis direction. The Z-axis direction is perpendicular to the dispersion direction.

[0052] 8 and 9 are diagrams illustrating images of the entrance slit 10 formed on the DMD 50 and positioned differently depending on the wavelength in the spectrometer 1 according to the first embodiment. In FIGS. 8 and 9, white portions indicate pixel mirrors 53 in the extracted wavelength array 56, and black portions indicate pixel mirrors 53 other than those in the extracted wavelength array 56. The DMD 50 can emit light containing a predetermined wavelength band from the exit slit 60 by turning on each pixel mirror in the extracted wavelength array 56. Note that the DMD 50 may have multiple extracted wavelength arrays 56. The DMD 50 may also emit light containing multiple wavelength bands from the exit slit 60 by turning on each pixel mirror in the multiple extracted wavelength arrays 56.

[0053] Furthermore, as shown in FIG. 8, when a white laser such as a supercontinuum laser (hereinafter referred to as an SC laser) is used, the high spatial coherency of the white laser may cause a granular light intensity distribution called speckle. Therefore, as shown in FIG. 9, the DMD 50 randomly switches each pixel mirror 53 of the extracted wavelength array 56 between the ON and OFF states. In this way, randomly switching the ON and OFF states of a large number of pixel mirrors 53 in the wavelength band being used can reduce speckle. Meanwhile, the DMD 50 turns OFF multiple pixel mirrors 53 other than those of the extracted wavelength array 56.

[0054] The light reflected by the DMD 50 passes through the focusing lens 41 and the dispersive optical element 30 and exits from the exit slit 60. Specifically, the light passes through the focusing lens 41 and the dispersive optical element 30, passes through the beam splitter 22 and collimator lens 23 of the collimator optical system 20, and the exit slit 60, and is then exited from the monochromator. In this way, the spectrometer 1 of this embodiment has a retro configuration.

[0055] (Comparative Example) Next, a spectrometer according to a comparative example will be described. Figures 10 and 11 are diagrams illustrating a spectrometer according to a comparative example. As shown in Figures 10 and 11, a spectrometer 101 according to the comparative example includes an entrance slit 110, a collimator optical system 120, a dispersive optical element 130, a focusing optical system 140, an SLM 150, and an exit slit 160. The entrance slit 110 passes light generated by the light source and guides it to the collimator optical system 120.

[0056] The collimator optical system 120 includes a collimator lens 121 and a collimator lens 123. The collimator lens 121 converts the light that has passed through the entrance slit 110 into parallel light. The light that has been converted into parallel light by the collimator lens 121 enters the dispersive optical element 130.

[0057] The dispersive optical element 130 disperses the light converted into parallel light by the collimator lens 121 at different angles depending on the wavelength.

[0058] The focusing optical system 140 includes a focusing lens 141. For example, in the XY plane including the dispersion direction in Fig. 10, the focusing lens 141 is arranged so that the dispersion optical element 130 is located at the focal position on the -X axis direction side. The focusing lens 141 is arranged so that the SLM 150 is located at the focal position on the +X axis direction side. As a result, an image of the entrance slit 110 dispersed according to wavelength is formed on the SLM 150 in the XY plane.

[0059] 11 , in the XZ plane, the optical axis 141A of the focusing optical system 140 is disposed parallel to but shifted from the optical axis 121A of the collimator lens 121. For example, the optical axis 141A of the focusing lens 141 is shifted in the −Z-axis direction from the optical axis 121A of the collimator lens 121. The SLM 150 is disposed on the optical axis 141A of the focusing optical system 140. The light transmitted through the dispersive optical element 130 is focused toward the intersection of the optical axis 141A of the focusing optical system 140 and the SLM 150.

[0060] In the comparative example, the reflecting surface of SLM 150 is conjugate with entrance slit 110 and exit slit 160, and is arranged perpendicular to optical axis 141A of focusing lens 141. However, in spectrometer 101, dispersed light is focused only when reflected near the center of SLM 150. On the other hand, dispersed light reflected elsewhere than near the center of SLM 150 is defocused. Therefore, the comparative example has the problem that the spectroscopic performance cannot be improved due to the defocusing.

[0061] Next, the effects of this embodiment will be described. Compared to the comparative example shown in Figures 10 and 11, the spectrometer 1 of embodiment 1 can focus light on the entire surface of the DMD 50 and make light perpendicular to the mirror surface 54 of each pixel mirror 53 of the DMD 50. Therefore, light transmitted through the entrance slit 10 can be dispersed with high resolution. This allows the spectrometer 1 to improve light utilization efficiency and spectroscopic performance.

[0062] Furthermore, the spectrometer 1 of this embodiment can realize a practical spectrometer 1 using a DMD 50. Specifically, wavelength switching is more than 1,000 times faster than conventional spectrometers that mechanically rotate a diffraction grating or a dispersion prism. Furthermore, switching to wavelengths that are 100 nm or more apart can be more than 10,000 times faster. Furthermore, it is possible to transmit multiple wavelengths simultaneously, and the measurement time using an image detector can be significantly reduced (by more than two times). These factors can improve the throughput of measurement systems that include semiconductor measurement devices.

[0063] (Variation) Next, as a modified example, an example will be described in which the spectrometer 1 of embodiment 1 is applied to a measurement system including a semiconductor measurement device such as a semiconductor inspection device and a semiconductor measurement device. Fig. 12 is a diagram illustrating a measurement system according to a modified example of embodiment 1. As shown in Fig. 12, the measurement system 1a includes a light source LS, a spectrometer 1, a semiconductor measurement device 80, and a processing device 90. The measurement system 1a of this embodiment may use spectroscopic ellipsometry as its principle.

[0064] The light source LS is, for example, an SC laser. The light source LS is connected to a single-mode fiber SFB. Light generated by the light source LS passes through the single-mode fiber SFB and is emitted from a single-mode fiber end face SFBT. The single-mode fiber end face SFBT typically has a diameter of 4 to 5 μm. The single-mode fiber end face SFBT may also serve as the entrance slit 10 of the spectrometer 1. In this way, the light may include laser light emitted from the fiber, and the entrance slit 10 may include the end face of the fiber.

[0065] The spectrometer 1 disperses the incident light and emits light of a desired wavelength as output light from an output slit 60. The light output from the spectrometer 1 is incident on the multimode fiber MFB. Note that the multimode fiber end face MFBT, which is the entrance of the multimode fiber MFB, may also serve as the output slit 60 of the spectrometer 1. The light that has been dispersed and incident on the multimode fiber end face MFBT is incident on an optical system 81 in a semiconductor measurement device 80 via the multimode fiber MFB. It is then used for the required measurement or inspection.

[0066] The semiconductor measuring device 80 inspects or measures a sample 89 using light emitted from the spectrometer 1. The sample 89 is, for example, a semiconductor such as a semiconductor substrate or a semiconductor circuit. Note that the sample 89 may be a material other than a semiconductor. The semiconductor measuring device 80 includes an optical system 81, a base 82, an isolator 83, an optical surface plate 84, a frame 85, a stage 86, a wafer holder 87, and an image detector 88. In the semiconductor measuring device 80, the optical surface plate 84 is disposed on the base 82 with the isolator 83 sandwiched therebetween. A frame 85, to which the optical system 81 is attached, is fixed on the optical surface plate 84. A stage 86 is disposed directly below the optical system 81 on the optical surface plate 84. The sample 89, held by the wafer holder 87, is disposed on the stage 86. The semiconductor measuring device 80 uses the optical system 81 to capture an image of the sample 89 with the image detector 88. This allows the sample 89 to be inspected or measured.

[0067] The processing device 90 includes, for example, an information processing device such as a computer 91. In addition to the computer 91, the processing device 90 also includes, for example, a DMD control unit 92, an image detector control unit 93, and a stage control unit 94. The DMD control unit 92 controls the operation of the DMD 50. The image detector control unit 93 controls the operation of the image detector 88. The stage control unit 94 controls the operation of the stage 86.

[0068] The semiconductor measuring device 80 may inspect or measure the sample 89 independently using light containing multiple wavelengths emitted from the spectrometer 1. The semiconductor measuring device 80 may also perform ellipsometry measurement from interference fringes formed by interference between light of different polarization components reflected from the sample 89. The semiconductor measuring device 80 may then perform ellipsometry measurement by separating information on light of multiple wavelengths from the frequency components of the interference fringes. This will be described later.

[0069] (Embodiment 2) Next, a spectrometer according to a second embodiment will be described. In the spectrometer of this embodiment, the optical paths of the incident light and the outgoing light are separated by pupil division within the XZ plane. The mirror surface 54 of each pixel mirror 53 of the DMD 50 is arranged so that the angle of incidence of the central axis of the incident light is equal to the angle of emergence of the central axis of the outgoing light. This eliminates the need to use a beam splitter 22 in the collimator optical system 20, thereby further improving light utilization efficiency.

[0070] 13 and 14 are diagrams illustrating a spectrometer according to embodiment 2. FIG. 13 is a diagram viewed from the Z-axis direction perpendicular to the XY plane, showing the arrangement of each component in the XY plane. FIG. 14 is a diagram viewed from the Y-axis direction, showing the arrangement of each component in the XZ plane. FIGS. 15 and 16 are cross-sectional views illustrating a DMD 50 in the spectrometer according to embodiment 2. FIG. 15 shows a cross-sectional view perpendicular to the Z-axis direction. FIG. 16 shows a cross-sectional view perpendicular to the Y-axis direction.

[0071] As shown in FIGS. 13 to 16, in the spectrometer 2 of this embodiment, the angle of incidence of the central axis of light incident on the mirror surface is equal to the angle of reflection of the central axis of light reflected by the mirror surface in the XZ plane.

[0072] The entrance slit 10 passes light generated by the light source and guides it to the collimator optical system 20. In the spectrometer 2 of this embodiment, the collimator optical system 20 includes a collimator lens 21 and a collimator lens 23. The collimator optical system 20 of this embodiment does not have a beam splitter 22. The collimator lens 21 converts the light that has passed through the entrance slit 10 into parallel light. The light converted into parallel light by the collimator lens 21 enters the dispersive optical element 30.

[0073] The dispersion optical element 30 disperses the light converted into parallel light by the collimator lens 21 at different angles depending on the wavelength. The focusing optical system 40 includes a focusing lens 41. The focusing lens 41 converges the dispersed light. For example, as shown in FIG. 13 , in the XY plane including the dispersion direction, the focusing lens 41 converges the light dispersed according to the wavelength onto the DMD 50. As shown in FIG. 14 , in the XZ plane, the focusing lens 41 converges the light transmitted through the dispersion optical element 30 onto the DMD 50. In this embodiment, the incident light is incident so that the central axis of the incident light has an angle of incidence. This makes the angle of incidence of the central axis of the light incident on the mirror surface 54 of the DMD 50 equal to the angle of reflection of the central axis of the light reflected by the mirror surface 54.

[0074] As shown in Figure 15, in a cross section of the XY plane including the dispersion direction, the cutting line of the substrate surface 52 of the substrate 51 and the cutting line of the mirror surface 54 of the pixel mirror 53 are parallel. These cutting lines are arranged perpendicular to the central axis of the incident light. With this arrangement, the focal points of all dispersed wavelengths coincide with the mirror surface 54. This allows for improved spectral performance.

[0075] 16, in the cross section of the XZ plane perpendicular to the dispersion direction, the substrate surface 52 of the substrate 51 and the optical axis 41A of the focusing optical system 40 are perpendicular to each other. In the XZ plane, the angle of incidence of the central axis of light incident on the mirror surface 54 of each pixel mirror 53 is equal to the angle of reflection of the central axis of the light reflected by the mirror surface 54. With this arrangement, the focal point coincides with the mirror surface 54 of the pixel mirror 53 even in this plane. This makes it possible to improve light utilization efficiency and spectral performance.

[0076] The light reflected by the DMD 50 passes through the focusing lens 41 and the dispersive optical element 30 and exits from the exit slit 60. Specifically, the light passes through the focusing lens 41 and the dispersive optical element 30, passes through the collimator lens 23 and the exit slit 60, and is then exited from the spectrometer 2. However, the optical axis 23A of the collimator lens 23 is shifted in the -Z-axis direction from the optical axis 21A of the collimator lens 21. Therefore, the light that passes through the collimator lens 23 follows an optical path that is shifted in the -Z-axis direction from the incident light that passes through the collimator lens 21 and travels through the dispersive optical element 30 and the focusing lens 41. Even in this case, the spectrometer 2 of this embodiment is configured in a Retro configuration.

[0077] As shown in Figure 15, within the XY plane including the dispersion direction, an image of the entrance slit 10, into which light enters, is formed on the DMD 50 for each wavelength. The light reflected by the DMD 50 is transmitted again through the same dispersive optical element 30, thereby canceling out the wavelength dispersion. Therefore, the image of the entrance slit 10 is formed at the same position independent of wavelength. Therefore, the exit slit 60 is placed at the position where the image of the entrance slit 10 is formed.

[0078] 16, in the XZ plane perpendicular to the dispersion direction, the DMD 50 is disposed on the optical axis 41A of the focusing lens 41, which is disposed so as to be shifted from the optical axis 21A of the collimator lens 21. Therefore, the optical axis 41A of the focusing lens 41 and the substrate surface 52 of the DMD 50 are perpendicular to each other.

[0079] In the spectrometer 2 of this embodiment, the focal point of the light dispersed according to wavelength also coincides with the mirror surface 54. This improves spectroscopic performance. Furthermore, the beam splitter 22 can be eliminated in the collimator optical system 20. Other configurations and effects are included in the description of the first embodiment.

[0080] (Embodiment 3) Next, a spectrometer according to embodiment 3 will be described. In the spectrometer of this embodiment, the optical axis 41A of the focusing lens 41 is tilted instead of being shifted from the optical axis 21A of the collimator lens 21. Even with this configuration, the focal point of the light dispersed according to wavelength coincides with the mirror surface 54.

[0081] 17 and 18 are diagrams illustrating a spectrometer according to embodiment 3. FIG. 17 is a diagram viewed from the Z-axis direction perpendicular to the XY plane, showing the arrangement of each component in the XY plane. FIG. 18 is a diagram viewed from the Y-axis direction, showing the arrangement of each component in the XZ plane. FIGS. 19 and 20 are cross-sectional views illustrating a DMD 50 in the spectrometer according to embodiment 3. FIG. 19 shows a cross-sectional view perpendicular to the Z-axis direction. FIG. 20 shows a cross-sectional view perpendicular to the Y-axis direction.

[0082] 17 to 20, the optical axis 41A of the focusing lens 41 is inclined with respect to the optical axis 21A of the collimator lens 21. Specifically, the optical axis 41A of the focusing lens 41 and the optical axis 21A of the collimator lens 21 are positioned in the XZ plane. The optical axis 41A of the focusing lens 41 and the optical axis 21A of the collimator lens 21 intersect in the XZ plane. Furthermore, in the XZ plane, the angle of incidence of the central axis of light incident on the mirror surface 54 is equal to the angle of reflection of the central axis of the light reflected by the mirror surface 54.

[0083] The entrance slit 10 passes light generated by the light source and guides it to the collimator optical system 20. The collimator lens 21 of the collimator optical system 20 converts the light that has passed through the entrance slit 10 into parallel light. The light that has been converted into parallel light by the collimator lens 21 enters the dispersive optical element 30.

[0084] The dispersive optical element 30 disperses the light converted into parallel light by the collimator lens 21 at different angles depending on the wavelength. The focusing lens 41 of the focusing optical system 40 converges the dispersed light. For example, as shown in FIG. 17 , in the XY plane including the dispersion direction, the focusing lens 41 converges the light dispersed according to the wavelength onto the DMD 50. Also, as shown in FIG. 18 , in the XZ plane, the focusing lens 41 converges the light transmitted through the dispersive optical element 30 onto the DMD 50. The angle of incidence of the central axis of the light incident on the DMD 50 is equal to the angle of reflection of the central axis of the light reflected by the mirror surface 54.

[0085] As shown in Figure 19, in a cross section of the XY plane including the dispersion direction, the cutting line of the substrate surface 52 of the substrate 51 and the cutting line of the mirror surface 54 of the pixel mirror 53 are parallel. These cutting lines are perpendicular to the chief ray of the incident light (the central axis of the light). With this arrangement, the focal points of all dispersed wavelengths coincide with the mirror surface 54. This allows for improved spectral performance.

[0086] 20, in the cross section of the XZ plane perpendicular to the dispersion direction, the substrate surface 52 of the substrate 51 and the optical axis 41A of the focusing optical system 40 are perpendicular to each other. In the XZ plane, the angle of incidence of the central axis of light incident on the mirror surface 54 of each pixel mirror 53 is equal to the angle of reflection of the central axis of the light reflected by the mirror surface 54. With this arrangement, the focal point coincides with the mirror surface 54 of the pixel mirror 53 of the DMD 50 even in this plane. This makes it possible to improve light utilization efficiency and spectral performance.

[0087] The light reflected by the DMD 50 passes through the focusing lens 41 and the dispersive optical element 30 and exits from the exit slit 60. Specifically, the light passes through the focusing lens 41 and the dispersive optical element 30, passes through the collimator lens 23 of the collimator optical system 20 and the exit slit 60, and is then emitted from the monochromator. However, the light passes through an optical path that is shifted in the -Z axis direction from the incident light that passes through the collimator lens 21 and proceeds through the dispersive optical element 30 and the focusing lens 41. Even in this case, the spectrometer 3 of this embodiment is configured in a retro configuration.

[0088] In this embodiment, too, the substrate surface 52 of the substrate 51 and the optical axis 41A of the focusing optical system 40 are perpendicular to each other. Furthermore, the angle of incidence of the central axis of light incident on the mirror surface 54 of each pixel mirror 53 is equal to the angle of reflection of the central axis of the light reflected by the mirror surface 54. Therefore, the focal points of all dispersed wavelengths of light coincide with the mirror surface 54. This makes it possible to improve light utilization efficiency and spectral performance. Other configurations and effects are included in the descriptions of the first and second embodiments.

[0089] (Embodiment 4) Next, a description will be given of a spectroscope according to embodiment 4. In the spectroscope of this embodiment, a step-shaped prism is disposed between the collimator optical system 20 and the dispersion optical element 30.

[0090] 21 and 22 are diagrams illustrating a spectrometer according to embodiment 4. Fig. 21 is a diagram viewed from the Z-axis direction perpendicular to the XY plane, showing the arrangement of each component in the XY plane. Fig. 22 is a diagram viewed from the Y-axis direction, showing the arrangement of each component in the XZ plane.

[0091] 21 and 22, the spectrometer 4 of this embodiment has an optical element 25 disposed between the collimator optical system 20 and the dispersive optical element 30. The optical element 25 is a component that splits incident light and provides an optical path difference to the split light. The optical element 25 includes, for example, a stepped prism.

[0092] The spectrometer 4 of this embodiment has an optical member 25 that provides an optical path difference. Therefore, even when a light source with high spatial coherency, such as an SC laser, is used, the spatial coherency can be reduced by providing an optical path difference that is equal to or greater than the distance at which interference occurs in the light split by the optical member 25.

[0093] Furthermore, in the operation of the spectrometer 4, instead of switching all pixel mirrors 53 on the substrate surface 52 of the DMD 50 that reflect the incident light to the ON state, only about half of the pixel mirrors 53 are randomly arranged to reflect the incident light, and the DMD 50 is driven so that this random arrangement changes over time. That is, as shown in FIG. 9, the DMD 50 randomly switches each pixel mirror 53 of the extracted wavelength array 56 to the ON or OFF state. This operation is realized through software in the computer 91 and the DMD control unit 92 shown in FIG. 12. This reduces speckle generation when a white laser such as an SC laser is used as a light source, thereby improving the quality of the illumination light used in the semiconductor measurement device 80. Other configurations and effects are included in the description of embodiments 1 to 3.

[0094] (Embodiment 5) Next, a description will be given of a spectrometer according to embodiment 5. This embodiment is a measurement system in which any one of the spectrometers 1 to 4 described above is applied to a semiconductor measurement device 80 based on the principle of self-interference ellipsometry.

[0095] Fig. 23 is a diagram illustrating a measurement system according to embodiment 5. As shown in Fig. 23, the measurement system 5 includes a light source LS such as an SC laser, one of the spectrometers 1 to 4, a semiconductor measurement device 80, and a processing device 90. The measurement system 5 receives reflected light R1 formed when illumination light L1 is reflected by a sample 89, and measures the ellipsometry coefficients Ψ and Δ.

[0096] The optical system 81 includes an illumination lens 81a, a polarizer 81b, a beam splitter 81c, an objective lens 81d, relay lenses 81e and 81f, a polarization optical element 81g, an analyzer 81h, and an image detector 88. The analyzer 81h is, for example, a polarizing plate. The image detector 88 is, for example, a camera.

[0097] The optical system 81 illuminates a sample 89 such as a semiconductor with illumination light L1 including linearly polarized light. The optical system 81 also collects reflected light R1 resulting from the illumination light L1 being reflected by the sample 89. Specifically, the illumination lens 81a irradiates the illumination light L1 onto a polarizer 81b. For example, the illumination lens 81a converts the illumination light L1 emitted from the multi-fiber MFB into parallel light. The parallel illumination light L1 is then incident on the polarizer 81b.

[0098] The polarizer 81b transmits illumination light L1 containing linearly polarized light in one direction. For example, the polarizer 81b outputs linearly polarized illumination light L1, the polarization direction of which is tilted 45° with respect to the plane of the paper, to the beam splitter 81c. The beam splitter 81c reflects a portion of the incident illumination light L1 and transmits the other portion. The beam splitter 81c reflects a portion of the incident illumination light L1 toward the objective lens 81d. The illumination light L1 reflected by the beam splitter 81c enters the objective lens 81d.

[0099] The objective lens 81d illuminates the specimen 89 with illumination light L1 including linearly polarized light. The objective lens 81d focuses the illumination light L1 reflected by the beam splitter 81c into a point shape to illuminate the specimen 89. The objective lens 81d then transmits reflected light R1 formed by the illumination light L1 being reflected by the specimen 89. In the measurement system 5 of this embodiment, the optical axis C of the illumination light L1 incident on the specimen 89 and the optical axis C of the reflected light R1 reflected by the specimen 89 are perpendicular to the measurement surface of the specimen 89.

[0100] The illumination light L1 that illuminates the sample 89 contains linearly polarized light in one direction. Such illumination light L1 containing linearly polarized light in one direction is condensed and incident on the measurement surface of the sample 89. Therefore, if the illumination light L1 is fully polarized and linearly polarized, and the optical axis C is perpendicular to the measurement surface of the sample 89, then the illumination light L1 will contain both P-polarized and S-polarized light depending on the direction of incidence on the measurement surface. The S-polarized portion of the illumination light L1 is reflected as S-polarized light. The P-polarized portion of the illumination light L1 is reflected as P-polarized light.

[0101] The objective lens 81d transmits reflected light R1, which is illumination light L1 reflected by the measurement surface of the sample 89, and causes the reflected light R1 to enter the beam splitter 81c. The beam splitter 81c transmits a portion of the incident reflected light R1. For example, the reflected light R1 that has passed through the beam splitter 81c enters the relay lens 81e. The relay lens 81e condenses the reflected light R1 that has passed through the beam splitter 81c, forms an image, and then causes the light to enter the relay lens 81f. The relay lens 81f transmits the incident reflected light R1 and causes it to enter the polarization optical element 81g.

[0102] Fig. 24 is a configuration diagram illustrating a polarization optical element 81g, an analyzer 81h, and an image detector 88 in a measurement system 5 according to the fifth embodiment. As shown in Fig. 24, the polarization optical element 81g separates reflected light R1, which is illumination light L1 including linearly polarized light and reflected by a sample 89, into two linearly polarized lights polarized in directions perpendicular to each other and outputs the separated light. The polarization optical element 81g is, for example, a Nomarski prism.

[0103] The polarization directions that are orthogonal to each other and separated by the polarizing optical element 81g are defined as the α direction and the β direction. In this case, the plane formed by the α direction and the β direction is orthogonal to the optical axis of the reflected light R1. The polarizing optical element 81g then separates the light into linearly polarized light in the α direction and linearly polarized light in the β direction. The polarizing optical element 81g then deflects the separated linearly polarized light in the α direction and linearly polarized light in the β direction so that they converge to the same point on the image detector 88, and emits the light. Note that the polarizing optical element 81g is not limited to a Nomarski prism, and may include a Wollaston prism or a Rochon prism.

[0104] FIG. 25 is a diagram illustrating linearly polarized light passing through an analyzer in the measurement system 5 according to the fifth embodiment. As shown in FIG. 25, the analyzer 81h transmits linearly polarized light components in the α-direction polarization direction and the β-direction polarization direction separated by the polarization optical element 81g, and in a direction tilted by 45 degrees. Therefore, the analyzer 81h transmits the polarization component tilted by 45 degrees from the α-direction among the linearly polarized light polarized in the α-direction. Furthermore, the analyzer 81h transmits the polarization component tilted by 45 degrees from the β-direction among the linearly polarized light polarized in the β-direction. Therefore, the two linearly polarized light beams that are orthogonal to each other pass through the analyzer 81h and are output as polarization components polarized in the same direction (a direction tilted by 45 degrees). The reflected light R1 including the polarization components output from the analyzer 81h is incident on the image detector 88.

[0105] The image detector 88 receives the incident reflected light R1. The image detector 88 is disposed at a pupil conjugate position 19b that is conjugate with the pupil position 19a of the objective lens 81d. The reflected light R1 contains polarization components of two linearly polarized lights that are orthogonal to each other and polarized in the same direction. Therefore, the reflected light R1 interferes on the image detector 88. As a result, interference fringes are formed on the image detector 88. The image detector 88 detects the interference fringes of each polarization component that has passed through the analyzer 81h.

[0106] Fig. 26 is a diagram illustrating the wavefronts of each linearly polarized light contained in the reflected light incident on the image detector 88 in the measurement system 5 according to the fifth embodiment. Fig. 27 is a diagram illustrating interference fringes of the reflected light that has interfered on the image detector 88 in the measurement system 5 according to the fifth embodiment. As shown in Figs. 26 and 27, the reflected light R1, which includes two linearly polarized light beams R1α and R1β separated by the polarization optical element 81g, passes through the analyzer 81h and forms interference fringes on the image detector 88.

[0107] The processing device 90 calculates the ellipsometry coefficients Ψ and Δ from the interference fringes detected by the image detector 88. For example, the processing device 90 calculates the ellipsometry coefficients Ψ and Δ by fitting the intensity distribution Ifringe of the reflected light R1 in the interference fringes to the following equation (1). Here, the intensity distribution Ifringe is a function of the position on the image detector 88.

[0108]

number

[0109] Here, the ellipsometry coefficient Ψ is calculated from equation (2).

number

[0110] Fig. 28 is a diagram illustrating ellipsometry coefficients determined from interference fringes on the image detector 88 in the measurement system 5 according to the fifth embodiment. As shown in Fig. 28, when the intensity ratio (Ψ) and phase difference (Δ) of the two polarized lights are changed, the intensity of the reflected light R1 that forms the interference fringes changes at each position on the image detector 88. Using this relationship, the ellipsometry coefficients Ψ and Δ can be determined from the interference fringes.

[0111] For example, for reflected light R1 having the intensity variation indicated by the thick line, the intensity ratio E1:E2 of the two polarized lights is 1:1, and the phase difference Δ is 0. For reflected light R1 having the intensity variation indicated by the dotted line, the intensity ratio E1:E2 of the two polarized lights is 1:1, and the phase difference Δ is π / 4. For reflected light R1 having the intensity variation indicated by the thin line, the intensity ratio E1:E2 of the two polarized lights is 2:1, and the phase difference Δ is 0. Thus, optical system 81 transmits the linearly polarized light in each of the separated polarization directions (α direction and β direction) through an analyzer with a transmission axis tilted by 45 degrees, causing the two linearly polarized light components to interfere, and calculates ellipsometry coefficients Ψ and Δ from the interference fringes on image detector 88.

[0112] 29 is a diagram illustrating interference fringes of reflected light that has interfered on the image detector 88 in a measurement system 5 according to another example of the fifth embodiment. As shown in Fig. 29, in the DMD 50, the pixel mirrors 53 of the extraction wavelength array 56 corresponding to two wavelengths I and II may be turned on to guide light including wavelengths I and II to the semiconductor measuring device 80. In this case, the interference fringes are a combination of the interference fringes at wavelength I and the interference fringes at wavelength II.

[0113] The obtained interference fringes are subjected to Fourier transform to obtain information on the amplitude and phase of specific frequency components, and the surface condition of sample 89 is analyzed. When two wavelengths are incident simultaneously, setting window functions in two places during Fourier transform makes it possible to simultaneously analyze the interference fringes from the two wavelengths.

[0114] Next, the effects of this embodiment will be described. The measurement system 5 of this embodiment uses a polarization optical element 81g in measuring the ellipsometry coefficients Ψ and Δ. The polarization optical element 81g separates the reflected light R1 reflected by the sample 89 into two linearly polarized light beams R1α and R1β with orthogonal polarization directions, and forms interference fringes on the image detector 88 from the two separated linearly polarized light beams. The ellipsometry coefficients Ψ and Δ, which are two independent parameters, are directly measured from the measurement results of the contrast and phase of the interference fringes. This eliminates the need to measure the light intensity of at least four polarization components in a time series using a rotating polarizer or compensator, which was previously required for measuring the ellipsometry coefficients Ψ and Δ.

[0115] Furthermore, in conventional measurements of the ellipsometry coefficients Ψ and Δ, Stokes parameters are calculated from the light intensities of light in a plurality of different polarization states, and the ellipsometry coefficients Ψ and Δ are then calculated from the calculated Stokes parameters. In this embodiment, the ellipsometry coefficients Ψ and Δ can be calculated directly from a single image. Therefore, measurements can be performed in a short time, improving the throughput of OCD measurements.

[0116] Furthermore, compared to conventional ellipsometers, the absence of moving parts allows for more stable measurements of the ellipsometry coefficients Ψ and Δ.

[0117] Furthermore, in many ellipsometers used in OCD measurement devices, the angle of incidence of illumination light L1 incident on the surface of sample 89 is fixed at the Brewster angle. However, in this embodiment, by placing image detector 42 at a pupil-conjugate position conjugate to the pupil position of large NA objective lens 17, it becomes possible to measure ellipsometry coefficients Ψ and Δ at any incident angle and incident direction. Such a configuration cannot be easily realized with the configuration of conventional ellipsometers that rotate an analyzer or the like.

[0118] As a result, for example, measurement results under a wider range of conditions can be used when fitting a microstructure model on a wafer. This also reduces the coupling between different dimensions, a common problem with OCD measurement systems. This is expected to improve accuracy, particularly in measuring semiconductor structures, which are becoming increasingly three-dimensional. Furthermore, the illumination area of ​​the sample 89 illuminated by the illumination light L1 can be reduced from approximately φ30 μm to φ1 μm or less, enabling evaluation of the dimensional distribution within a chip with higher position resolution. These measurement results can be reflected in lithography, film deposition, and etching processes, enabling appropriate process control in semiconductor manufacturing. This will improve yield and productivity in semiconductor manufacturing.

[0119] Furthermore, in logic circuits, the test patterns for measuring ellipsometry coefficients placed within semiconductor chips can be reduced from the previous size of several tens of microns squared to a few microns squared or less, which increases the area available for circuits within the semiconductor chip and contributes to reducing the cost of semiconductor devices.

[0120] The present invention is not limited to the above-described embodiments, and can be modified as appropriate without departing from the spirit of the present invention. For example, the configurations of the first to fifth embodiments can be combined with each other. [Explanation of symbols]

[0121] 1, 2, 3, 4 spectrometer 1a, 5 Measurement system 10 Entrance slit 11 Entrance slit section 19 sides 20 Collimator optical system 21 Collimator lens 21A optical axis 22 Beam Splitter 23 Collimator lens 25 Optical Components 30 Dispersive optical element 40 Focusing Optical System 41 Focusing Lens 41A optical axis 50 DMD 51 PCB 52 Substrate surface 53 pixel mirror 54 Mirror Surface 55 Rotation axis 56 Extracted wavelength sequence 59 Reflective surface 60 Exit slit 69 sides 80 Semiconductor measurement equipment 81 Optical system 81a Lighting lens 81b Polarizer 81c Beam Splitter 81d objective lens 81e, 81f relay lenses 81g Polarized Optical Element 81h analyzer 82 Foundation 83 Isolator 84 Optical Surface Plate 85 frames 86 Stages 87 Wafer Holder 88 Image Detector 89 samples 90 Processing equipment 91 Computer 92 DMD control section 93 Image detector control unit 94 Stage control section 101 Spectrometer 110 Entrance slit 120 Collimator Optical System 121 Collimator Lens 121A optical axis 123 Collimator Lens 130 Dispersive Optical Elements 140 Focusing Optical System 141 Focusing Lens 141A optical axis 150 SLM 160 Exit slit LS light source MFB Multimode Fiber MFBT multimode fiber end face SFB Single Mode Fiber SFBT single mode fiber end face

Claims

1. a collimator lens that converts the light that has passed through the entrance slit into parallel light; a dispersion optical element that disperses the light converted into parallel light by the collimator lens at different angles depending on the wavelength; a focusing lens that converges the dispersed light; an SLM having a reflective surface that reflects the light converged by the focusing lens; Equipped with the light reflected by the SLM passes through the focusing lens and the dispersion optical element and exits from an exit slit; When a first surface including optical paths of light dispersed at different angles and a second surface including an optical axis of the collimator lens and an optical axis of the focusing lens and perpendicular to the first surface are defined, the entrance slit, the exit slit, and the reflecting surface are in a conjugate relationship on the second surface, the SLM is a DMD including a plate-shaped substrate and a plurality of pixel mirrors arranged in a matrix on a surface of the substrate, The DMD is driven to change the tilt state of only about half of the pixel mirrors on the substrate surface where the incident light is reflected over time to adopt a random arrangement, The optical element is further provided with an optical member that is disposed between the collimator lens and the dispersion optical element, and that splits the light and provides an optical path difference of at least a distance at which interference occurs in the split light. Spectrometer.

2. each pixel mirror has a mirror surface that reflects the light and a rotation axis that extends in a direction perpendicular to the second surface; Each of the pixel mirrors has, as the tilt state, a first state in which the mirror surface is tilted at a first angle with respect to the substrate surface, and a second state in which the mirror surface is tilted at a second angle with respect to the substrate surface.

10. The spectrometer of claim 1.

3. the DMD sets an extraction wavelength array including a plurality of the pixel mirrors along a direction perpendicular to the first surface, and causes the light including a predetermined wavelength band to be output from the output slit by setting each pixel mirror of the extraction wavelength array to the first state; 3. The spectrometer of claim 2.

4. the DMD sets a plurality of extracted wavelength arrays, and causes each pixel mirror of the plurality of extracted wavelength arrays to be in the first state, thereby causing the light including the plurality of wavelength bands to be output from the output slit; 4. The spectrometer of claim 3.

5. On the second surface, the central axis of the light incident on the mirror surface is perpendicular to the mirror surface. The spectrometer according to any one of claims 2 to 4.

6. On the second surface, an incident angle of the central axis of the light incident on the mirror surface is equal to a reflection angle of the central axis of the light reflected on the mirror surface. The spectrometer according to any one of claims 2 to 4.

7. The optical axis of the focusing lens is shifted from the optical axis of the collimator lens and is arranged parallel to the optical axis of the collimator lens. The spectrometer according to any one of claims 1 to 6.

8. the optical axis of the focusing lens is inclined with respect to the optical axis of the collimator lens; On the second surface, an incident angle of the central axis of the light incident on the mirror surface is equal to a reflection angle of the central axis of the light reflected on the mirror surface. The spectrometer according to any one of claims 2 to 4.

9. The optical element includes a stepped prism.

10. The spectrometer of claim 1.

10. the light includes laser light emitted from a fiber, the entrance slit includes an end face of the fiber; The spectrometer according to any one of claims 1 to 9.

11. A spectroscope according to any one of claims 1 to 10; a semiconductor measurement device that inspects or measures a semiconductor using the light emitted from the spectrometer; A measurement system equipped with

12. Using spectroscopic ellipsometry as a principle, The measurement system of claim 11.

13. the semiconductor measurement device inspects or measures the semiconductor by independently using the light including the plurality of wavelengths emitted from the spectrometer; The measurement system according to claim 11 or 12.

14. performing ellipsometry measurement from interference fringes caused by interference between light beams having different polarization components among the light beams reflected from the semiconductor; Separating information of the light of multiple wavelengths from the frequency components of the interference fringes; The measurement system according to any one of claims 11 to 13.

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