KR20220169377A - Spectrosmeter, metrology systems and semiconductor inspection methods - Google Patents

Abstract

Provided are a spectrometer and measurement system capable of improving spectrum performance. The spectrometer regarding to an embodiment is equipped with a collimator lens, a focusing lens, and an SLM, wherein a light reflected by the SLM is emitted from an exit slit through the focusing lens and a dispersion optical element, and the entrance slit, exit slit, and reflective surface are related to conjugation in a second surface orthogonal to a first surface comprising a light path of the light dispersed at different angles.

Description

Spectrosmeter, metrology systems and semiconductor inspection methods}

The present invention relates to a spectrometer, metrology system, and semiconductor inspection method.

In a semiconductor manufacturing process, optical measuring instruments using spectroscopic reflectometry (SR), spectroscopic ellipsometry (SE), and the like are widely used. The optical measuring device can measure optical constants such as refractive index or dimensions such as film thickness of a semiconductor circuit structure formed on a silicon substrate with high precision. Such an optical measuring device is also referred to as an OCD (Optical Critical Dimension) measuring device, and the measurement result is compared with a simulation result using a semiconductor circuit structure model, and by fitting, the dimension of the semiconductor circuit structure or the optical constant of the constituent material is measured. yield

In the last 10 years or so, semiconductor circuit structures such as FinFETs of logic semiconductor devices and 3D-NAND flash memories of memory semiconductor devices have been 3-dimensionalized and become more complex structures. If the structure of the object to be requested becomes complex, the number of floating parameters is increased by fitting. For example, in the current FinFET OCD measuring device measurement, it is necessary to use about 20 to 30 floating parameters.

In fitting a model, it is necessary to obtain a number of measurements greater than the number of floating parameters in order to obtain a dimension value. For example, SR requires a reflectance spectrum, and SE requires a spectrum of Ψ and a spectrum of Δ. In model fitting, there is a coupling problem in which the fitting converges by a combination of floating parameters different from actual dimensions. In order to avoid coupling, in many cases SR or SE is implemented for 100 or more wavelengths. In spite of such demands on measurement accuracy, very short time measurement is required for OCD measurement in a semiconductor manufacturing process. For example, the permissible measurement time per wafer is about several tens of seconds at most, and therefore measurement is limited to a very small portion of the wafer.

Measurement of multiple wavelengths in the OCD measuring device is roughly divided into two types. One is a method of monochromating light emitted from a light source through a monochromator to illuminate the light. Another is a method of measuring the reflected light by illuminating with light of a wide wavelength band by spectroscopy for each wavelength. Spectroscopic measurement using a spectrometer enables high-speed measurement because it can measure multiple wavelengths simultaneously, but a monochromator is required due to factors such as image measurement with a wide field of view, reflectance on the pupil, and ellipsometry measurement. There are many cases.

In general, a monochromator has a structure in which a diffraction grating or a dispersion prism is rotated, and depending on the time used for acceleration and deceleration of the rotation stage, it takes several ten milliseconds or more for wavelength conversion. When the number of wavelengths to be switched is 100 or more, it takes several seconds or more for only the switching time, which is a major deterioration factor in the throughput of the entire OCD measuring device.

Patent Document 1 describes a spectrometer having a structure of a double monochromator using two dispersing elements and a movable slit disposed near the middle image in order to reduce the mechanical driving time. Based on the configuration of Patent Literature 1, a method of performing wavelength conversion using an SLM (Spatial Light Modulator) has been proposed.

Patent Document 2 describes the basic configuration of a Digital Micro Mirror Device (DMD), which is an example of an SLM. Many attempts have been made to put DMD such as Patent Document 2 into practical use.

In Patent Document 3 and Patent Document 4, a method of performing wavelength conversion using an SLM (eg, DMD) is proposed. In Patent Document 4, an SLM (e.g., DMD) is used for spectroscopy in a laser resonator that can be amplified by changing the wavelength. Specifically, in the laser resonator of Patent Document 4, the light is amplified by reciprocating the light of a specific wavelength reflected from the SLM (e.g., DMD) several times on the same optical path. When the structure of Patent Document 4 is applied to a monochromator, there is a problem that the extraction efficiency of the spectral light is remarkably lowered.

In Patent Document 5, in order to solve the problem of Patent Document 4, mirrors are arranged before and after reflection on the SLM (eg DMD) so that the light incident on the SLM (eg DMD) and the reflected light have different optical paths. A configuration in which light extraction efficiency is improved is described.

Patent Literature 6 and Patent Literature 7 describe configurations in which light can be extracted even without a mirror by configuring an optical system so that light is obliquely incident on the SLM and then performing pupil division.

Patent Document 1: Specification of US Patent No. 4575243 Patent Document 2: Specification of US Patent No. 5061049 Patent Document 3: Specification of US Patent No. 5504575 Patent Document 4: Specification of US Patent No. 7256885 Patent Document 5: Specification of US Patent No. 6870619 Patent Document 6: Specification of US Patent Application Publication No. 2007/296969 Patent Document 7: Specification of US Patent Application Publication No. 2010/245818

In a spectrometer using a reflective Spatial Light Modulator (SLM) (e.g., Digital Micro Mirror Device (DMD)), configurations in which the surface of the SLM is inclined in order to extract the split light have been proposed in Patent Documents 5 to 7 and the like. This configuration is established if the mirrors of each pixel on the SLM are parallel to the SLM surface. However, starting with the DMD, in a device having a Micro-Mirror-Array (MMA) structure capable of high-speed driving and spectroscopy in a wide wavelength range, the mirror of each pixel covers the entire surface of the DMD both on and off. inclined towards Therefore, in the arrangements described in Examples such as Patent Documents 5 to 7, the light incident on the DMD is not reflected toward the focusing optical system. In addition, when the DMD is inclined so that the mirror surface of each pixel of the DMD is perpendicular to the optical axis of the focusing optical system, light is reflected toward the focusing optical system. However, in this arrangement, light scattered outside the vicinity of the center of the DMD is out of focus, and the spectral performance cannot be improved due to defocusing except near the center of the DMD.

The present invention has been made to solve these problems, and provides a spectrometer and a measurement system capable of improving light utilization efficiency and spectroscopic performance.

According to exemplary embodiments for solving the above technical problem, a spectrometer is provided. The spectrometer includes a collimator lens configured to generate collimated light by collimating the light passing through the entrance slit; a dispersive optical element configured to generate dispersed light by dispersing the collimated light at different angles according to wavelengths; a focusing lens configured to generate focused light by focusing the scattered light; and a Spatial Light Modulator (SLM) configured to generate reflected light by reflecting the focused light by the focusing lens, wherein the reflected light passes through the focusing lens and the dispersion optical element and is emitted through an exit slit. The entrance slit, the exit slit, and the reflective surface are in a conjugate relationship on a second surface orthogonal to the first surface, the first surface includes an optical path of the scattered light, and the second surface The plane includes an optical axis of the collimator lens and an optical axis of the focusing lens.

According to example embodiments, a metrology system is provided. The system includes a spectrometer configured to generate inspection light; and a semiconductor measurement device configured to inspect a semiconductor using the inspection light emitted from the spectrometer, wherein the spectrometer includes: a collimator lens configured to generate parallel light by collimating light passing through an incident slit; a dispersive optical element configured to generate dispersed light by dispersing the collimated light at different angles according to wavelengths; a focusing lens configured to generate focused light by focusing the scattered light; and a Spatial Light Modulator (SLM) configured to generate reflected light by reflecting the focused light by the focusing lens, wherein the SLM includes: a plate-shaped substrate; and a plurality of pixel mirrors arranged in a matrix on a substrate surface of the substrate, wherein a normal of the substrate surface and an optical axis of the focusing lens are parallel, and a mirror surface of each of the plurality of pixel mirrors and the substrate surface are oblique. And, the optical axis of the collimator lens and the optical axis of the focusing lens are oblique.

According to exemplary embodiments, a spectrometer is provided. The collimator includes a collimator lens configured to produce collimated light by collimating light passing through an entrance slit; a dispersive optical element configured to generate dispersed light by dispersing the collimated light at different angles according to wavelengths; a focusing lens configured to generate focused light by focusing the scattered light; and a DMD configured to generate reflected light by reflecting the focused light by the focusing lens, wherein the DMD comprises: a plate-shaped substrate; and a plurality of pixel mirrors arranged in a matrix on the substrate surface of the substrate, each of the plurality of pixel mirrors having a mirror surface reflecting the light and a rotation axis extending in a dispersion direction of the dispersion optical element.

According to exemplary embodiments, a semiconductor inspection method is provided. The method may include generating inspection light using a spectrometer including a DMD; radiating the inspection light to the semiconductor and detecting the inspection light reflected by the semiconductor, wherein the DMD comprises: a plate-shaped substrate; and a plurality of pixel mirrors arranged in a matrix on a substrate surface of the substrate, each of the plurality of pixel mirrors having a mirror surface reflecting the light and a rotation axis extending in a dispersion direction of the dispersion optical element; The generating of the inspection light may include setting an extraction wavelength train including those of the plurality of pixel mirrors arranged along a direction perpendicular to the dispersion direction, so as to set a wavelength band corresponding to the extraction wavelength train among the focused lights. It is configured to reflect only a part of

According to the present invention, it is possible to provide a spectrometer and a measurement system capable of improving the utilization efficiency of light passing through an incident slit and improving spectroscopic performance.

1 illustrates a spectrometer according to Embodiment 1.
2 illustrates a spectrometer according to Embodiment 1.
3 is a cross-sectional view illustrating a DMD in the spectrometer according to Embodiment 1;
4 is a cross-sectional view illustrating a DMD in the spectrometer according to the first embodiment.
5 is a perspective view illustrating a DMD in the spectrometer according to Embodiment 1;
6 illustrates a pixel mirror of a DMD (Digital Micro Mirror Device) in the spectrometer according to the first embodiment.
Fig. 7 is a cross-sectional view illustrating a pixel mirror of a DMD in the spectrometer according to Embodiment 1, and shows a cross-section orthogonal to the rotation axis of the pixel mirror.
8 illustrates an image of an incident slit formed on a DMD having different positions according to wavelengths in the spectrometer according to Embodiment 1. FIG.
Fig. 9 illustrates an image of an incident slit formed on a DMD having different positions according to wavelengths in the spectrometer according to Embodiment 1.
10 illustrates a spectrometer according to a comparative example.
11 illustrates a spectrometer according to a comparative example.
12 illustrates a measurement system according to a modified example of Embodiment 1.
13 illustrates a spectrometer according to Embodiment 2.
14 illustrates a spectrometer according to Embodiment 2.
15 is a cross-sectional view illustrating a DMD in the spectrometer according to the second embodiment.
16 is a cross-sectional view illustrating a DMD in the spectrometer according to the second embodiment.
17 illustrates a spectrometer according to Embodiment 3.
18 illustrates a spectrometer according to Embodiment 3.
Fig. 19 is a cross-sectional view illustrating a DMD in the spectrometer according to Embodiment 3;
Fig. 20 is a cross-sectional view illustrating a DMD in the spectrometer according to Embodiment 3;
21 illustrates a spectrometer according to Embodiment 4.
22 illustrates a spectrometer according to Embodiment 4.
23 illustrates the measurement system according to the fifth embodiment.
24 is a configuration diagram illustrating a polarization optical element, an analyzer, and an image detector in the measurement system according to the fifth embodiment.
Fig. 25 illustrates linearly polarized light transmitted through an analyzer in the measurement system according to Embodiment 5.
26 illustrates the wavefront of each linearly polarized light included in the reflected light incident on the image detector in the measurement system according to the fifth embodiment.
27 illustrates an interference fringe of reflected light interfering on the image detector in the measurement system according to the fifth embodiment.
28 illustrates ellipsometry coefficients obtained from interference fringes on an image detector in the measurement system according to the fifth embodiment.
29 illustrates an interference fringe of reflected light interfering on an image detector in the measurement system according to another example of the fifth embodiment.

For clarity of explanation, the following descriptions and drawings are appropriately omitted and simplified. In addition, in each figure, the same code|symbol is attached|subjected to the same element, and overlapping description is abbreviate|omitted as needed.

(Embodiment 1)

The spectrometer according to Embodiment 1 will be described. The spectroscope of Embodiment 1 is a spectroscope (monochrometer) that converts the wavelength of light used in, for example, a semiconductor measuring device such as a semiconductor inspection device or a semiconductor measuring device. Specifically, the spectrometer is used in an optical inspection device or an optical measurement device for measuring dimensions, distortions, and physical property values of a circuit structure formed on a sample such as a semiconductor wafer or the like in a semiconductor manufacturing process, or detecting a defect. Also, the spectrometer of Embodiment 1 may be used other than the semiconductor measurement device.

1 and 2 are diagrams illustrating the spectrometer according to the first embodiment. Here, for convenience of description of the spectrometer, an XYZ Cartesian coordinate axis system is introduced. A plane containing light dispersed at different angles depending on the wavelength by a dispersing optical element described later is referred to as an XY plane. Fig. 1 - shows the arrangement of each component in the XY plane as viewed in the Z-axis direction (i.e., perpendicular to the Z-axis). Figure 2 shows the arrangement of each component in the XZ plane viewed in the direction of the +Y axis (i.e., perpendicular to the Y axis). Solid lines, broken lines and dotted lines in Fig. 1 are used to distinguish different wavelength lights.

In the drawing, +X axis direction, +Y axis direction, +Z axis direction, -X axis direction, -Y axis direction, and -Z axis direction are shown, but for convenience of explanation, ±X axis direction is simply referred to as X direction. The ±Y axis direction may be referred to as the Y direction, and the ±Z axis direction may be referred to simply as the Z direction.

1 and 2, the spectrometer 1 includes an incident slit 10, a collimator optical system 20, a dispersive optical element 30, a focusing optical system 40, and a digital micro mirror device (DMD) 50. , and an exit slit 60. The spectrometer 1 includes a DMD 50 which is a reflective Spatial Light Modulator (SLM). Note that the spectrometer 1 is a reflective SLM, and is not limited to the DMD 50, and may be an SLM using liquid crystal.

The incident slit plate 11 may include an incident slit 10 . Also, the incident slit 10 may be a cross-sectional exit port of a fiber that guides light. The incident slit 10 passes the light generated by the light source and guides it to the collimator optical system 20 .

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 passing through the incident slit 10 into parallel light. The collimated light generated by the collimator lens 21 is incident to the beam splitter 22 .

The beam splitter 22 transmits a part of the incident parallel light in the outward path of the light in the +X-axis direction and guides it to the dispersion optical element 30. Further, the beam splitter 22 reflects a part of the light transmitted through the dispersing optical element 30 to the collimator lens 23 in the return path of the light in the -X-axis direction. The collimator lens 23 condenses the light reflected by the beam splitter 22 and passes it through the output slit 60 .

The dispersing optical element 30 disperses the light. Specifically, the dispersion optical element 30 disperses the light converted into parallel light by the collimator lens 21 at different angles according to wavelengths. The collimated light scattered by the dispersing optical element 30 may also be referred to as alternatively scattered light.

That is, the dispersion optical element 30 disperses at different angles for each wavelength. Dispersive optical element 30 includes a diffraction grating or prism. The dispersion optical element 30 disperses the light transmitted through the beam splitter 22 so that the light transmitted through the beam splitter 22 travels at different angles depending on the wavelength, as shown in dotted lines, broken lines, and solid lines in FIG. 1 . can make it That is, in FIG. 1 , dotted lines, broken lines, and solid lines indicate paths of light having different wavelengths. The Y-axis direction in which the dispersion optical element 30 disperses light is called a dispersion direction.

The focusing optical system 40 includes a focusing lens 41 . The focusing lens 41 condenses the scattered light. For example, in FIG. 1 , in the XY plane including the dispersion direction, the focusing lens 41 may be arranged such that the dispersion optical element 30 is located at a focal position on the -X-axis direction side of the focusing lens 41 . The focusing lens 41 may be disposed so that the DMD 50 is located at a focal position of the focusing lens 41 on the +X-axis direction side. In other words, the dispersion optical element 30 is positioned at the focal position of the focusing lens 41 on the -X-axis direction side, and the DMD 50 is positioned at the focal position of the focusing lens 41 on the +X-axis direction side. Accordingly, an image of the incident slit 10 dispersed according to the wavelength in the XY plane is formed on the DMD 50.

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, the optical axis 21A of the collimator lens 21 ) are placed parallel to each other. For example, the optical axis 41A of the focusing lens 41 is shifted from the optical axis 21A of the collimator lens 21 in the +Z-axis direction. That is, the extension of the optical axis 41A of the focusing lens 41 and the extension of the optical axis 41A of the focusing lens 41 may be spaced apart from each other in one direction (eg, in the ±Z direction). The DMD 50 may be disposed on the optical axis 41A of the focusing lens 41 .

In Fig. 2, the focusing lens 41 has a structure in which a part is cut out from the entire lens. The shape of the cut out part is indicated by a dotted line. Whether to actually cut the focusing lens 41 may be determined according to product specifications. Dispersed light passing through the dispersion optical element 30 may be focused toward an intersection of the optical axis 41A of the focusing lens 41 and the DMD 50 . That is, the focusing lens 41 may generate focused light based on the scattered light. For this reason, it can be oblique with respect to the principal ray (central axis of light) and the optical axis 41A of the focusing lens 41.

As shown in FIG. 1, in the XY plane including the dispersion direction, an image of each wavelength of the incident slit 10 through which light is incident is formed in the DMD 50. The light reflected from the DMD 50 cancels the wavelength dispersion by transmitting back through the same dispersive optical element 30. Accordingly, an image of the incident slit 10 is formed at the same position independent of the wavelength (ie, the same position for each of the lights of different wavelengths). Therefore, the exit slit 60 is disposed at a position where the image of the entrance slit 10 is formed. On the other hand, as shown in FIG. 2, in the XZ plane perpendicular to the dispersion direction, the DMD 50 is on the optical axis 41A of the focusing lens 41 shifted from the optical axis 21A of the collimator lens 21. are placed

A dispersion plane, that is, an XY plane including optical paths of light scattered at different angles is defined as the first plane. An XZ plane orthogonal to the first plane including the optical axis 21A of the collimator lens 21 and the optical axis 41A of the focusing lens 41 is defined as the second plane. When the first surface and the second surface are defined in this way, on the second surface, the surface 19 of the entrance slit 10, the surface 69 of the exit slit 60, and the reflection surface 59 of the DMD 50 ) is a conjugate relation to the optical system of the spectrometer 1. In addition, a dispersing optical element 30 is disposed at the pupil position 39 .

3 and 4 are cross-sectional views illustrating the DMD 50 in the spectrometer 1 according to the first embodiment. 3 shows a cross-sectional view orthogonal to the Z-axis direction. 4 shows a cross-sectional view orthogonal to the Y-axis direction. 5 is a perspective view illustrating a DMD 50 in the spectrometer 1 according to the first embodiment. 6 is a perspective view illustrating a plurality of pixel mirrors 53 of the DMD 50 in the spectrometer 1 according to the first embodiment. 7 is a cross-sectional view illustrating the pixel mirror 53 of the DMD 50 in the spectrometer 1 according to Embodiment 1, showing a cross-section perpendicular to the rotational axis 55 of the plurality of pixel mirrors 53. indicate

As shown in FIGS. 3 to 5 , the DMD 50 has a reflective surface that reflects the light focused by the focusing lens 41 . The DMD 50 may include a plate-shaped substrate 51 and a plurality of pixel mirrors 53 . The substrate surface 52 is a surface of the substrate 51 on the -X-axis direction side. A plurality of pixel mirrors 53 may be arranged in a matrix on the substrate surface 52 of the substrate 51 . Each of the plurality of pixel mirrors 53 has a mirror surface 54 that reflects light. Accordingly, the mirror surface 54 is a reflection surface of each of the plurality of pixel mirrors 53 that reflect the light focused by the focusing lens 41 .

As shown in FIG. 3, on the cross section of the XY plane including the dispersing direction, (cutting line of) the substrate surface 52 of the substrate 51 and the mirror surface 54 (of each of the plurality of pixel mirrors 53) The cutting line of) is parallel. This substrate surface 52 (cut line) and mirror surface 54 (cut line) are substantially perpendicular to the chief ray of incident light (the central axis of the light). With this arrangement, on the XY plane, the focus of light at all the wavelengths of dispersion coincides with the mirror surface 54. Therefore, the spectral performance can be improved.

As shown in Fig. 4, the substrate surface 52 of the substrate 51 and the optical axis 41A of the focusing lens 41 are perpendicular to each other in the cross section of the XZ plane perpendicular to the dispersion direction. The mirror surface 54 of each of the plurality of pixel mirrors 53 is perpendicular to the principal ray of the incident light (the central axis of the light). Accordingly, on the XZ plane, the central axis of light incident on the DMD 50 is incident perpendicularly to the mirror surface 54. By this arrangement, in the XZ plane, the focus of light at all wavelengths that are scattered coincides with the mirror plane 54. Therefore, light utilization efficiency and spectral performance can be improved.

As shown in FIGS. 6 and 7 , each of the plurality of pixel mirrors 53 may have a rotation axis 55 . The rotating shaft 55 may extend, for example, in the Y-axis direction. Thus, the axis of rotation 55 can extend in the dispersion direction. Each of the plurality of pixel mirrors 53 rotates around a rotation axis 55 . The mirror surfaces 54 of the plurality of pixel mirrors 53 take a predetermined angle with respect to the substrate surface 52 of the substrate 51 . For example, each pixel mirror 53 has an ON state in which the mirror surface 54 is inclined at a first predetermined angle with respect to the substrate surface 52 and an ON state in which the mirror surface 54 is inclined at a predetermined second angle with respect to the substrate surface 52. Take the OFF state inclined at an angle. In this way, each pixel mirror 53 can switch 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 both the ON state and the OFF state.

As shown in FIGS. 5 to 7, in each of the ON state and the OFF state, the surface including the normal of each mirror surface 54 and the normal of the substrate surface 52 of the substrate 51 (namely, the XZ plane) It is arranged so as to be perpendicular to the dispersion direction of light by this dispersion optical element 30. According to this configuration, since the entire surface of the DMD 50 has a conjugate relationship with the incident slit 10, the wavelength resolution is high and light utilization efficiency can be improved.

When the spectrometer 1 is used in a semiconductor measurement device, for example, among the pixel mirrors 53 of the DMD 50, only the pixel mirror 53 corresponding to the light of the wavelength to be used in the semiconductor measurement device is turned ON. . Then, the reflected light reflected by the pixel mirror 53 in the ON state is returned to the focusing optical system 40 again . For example, the DMD 50 sets an extraction wavelength train including a plurality of pixel mirrors 53 along the Z-axis direction. The Z-axis direction is orthogonal to the dispersion direction.

8 and 9 illustrate the images of the incident slit 10 formed on the DMD 50 and having different positions depending on the wavelength in the spectrometer 1 according to the first embodiment. In Figs. 8 and 9, the white portion indicates the pixel mirror 53 of the extracted wavelength column 56, and the black portion indicates the pixel mirror 53 other than the extracted wavelength column 56. The DMD 50 can emit light including a predetermined wavelength band through the emission slit 60 by turning on each pixel mirror of the extraction wavelength column 56 in an ON state. In addition, the DMD 50 can set a plurality of extraction wavelength trains 56. Then, the DMD 50 can emit light including a plurality of wavelength bands from the emission slit 60 by turning on each pixel mirror of the plurality of extraction wavelength columns 56 in an ON state.

In addition, as shown in FIG. 8, when a white laser such as a supercontinuum laser (hereinafter referred to as an SC laser) is used, the white laser speckles due to high spatial coherency. ), there is a case where a particle shaped light quantity distribution occurs. Therefore, as shown in Fig. 9, the DMD 50 randomly changes each pixel mirror 53 of the extraction wavelength string 56 to an ON state or an OFF state. In this way, in the wavelength band to be used, if the ON state and the OFF state of the plurality of pixel mirrors 53 are randomly switched, the speckle can be reduced. On the other hand, the DMD 50 turns off a plurality of pixel mirrors 53 other than the extraction wavelength column 56.

The light reflected by the DMD 50 is emitted from the exit slit 60 through the focusing lens 41 and the dispersing optical element 30 . More specifically, the light reflected from the DMD 50 passes through the focusing lens 41 and the dispersing optical element 30, and the beam splitter 22 and the collimator lens 23 of the collimator optical system 20, and the exit slit (60) and exits from the monochromator. In this way, the spectrometer 1 of the present embodiment may include a retro arrangement.

(Comparative example)

Next, a spectrometer according to a comparative example will be described. 10 and 11 illustrate a spectrometer according to a comparative example. 10 and 11, the spectrometer 101 of the comparative example includes an entrance slit 110, a collimator optical system 120, a dispersing optical element 130, a focusing optical system 140, an SLM 150, an exit slit ( 160) is provided. The incident slit 110 passes the light generated by the light source and guides it to the collimator optical system 120 .

The collimator optical system 120 includes a collimator lens 121 and a collimator lens 123 . The collimator lens 121 converts light passing through the incident slit 110 into parallel light. The light converted into collimated light by the collimator lens 121 is incident to the dispersion optical element 130 .

The dispersion optical element 130 disperses the light converted into parallel light by the collimator lens 121 at different angles according to wavelengths.

The focusing optical system 140 includes a focusing lens 141 . For example, in the XY plane including the dispersion direction of FIG. 10 , the focusing lens 141 is arranged so that the dispersion optical element 130 is located at the focus position on the -X-axis direction side of the focusing lens 141 . The focusing lens 141 is arranged so that the SLM 150 is located at a focal point on the +X-axis direction side of the focusing lens 141 . Accordingly, an image of the incident slits 110 dispersed according to the wavelength is formed on the SLM 150 in the XY plane.

11, in the XZ plane, the optical axis 141A of the focusing optical system 140 is arranged parallel to the optical axis 121A of the collimator lens 121 at a shifted position. For example, the optical axis 141A of the focusing lens 141 shifts from the optical axis 121A of the collimator lens 121 in the -Z-axis direction. The SLM 150 is disposed on the optical axis 141A of the focusing optical system 140. The light transmitted through the dispersion optical element 130 is condensed toward the intersection of the optical axis 141A of the focusing optical system 140 and the SLM 150 .

In the comparative example, the reflection surface of the SLM 150 is in conjugate relationship with the entrance slit 110 and the exit slit 160, and is arranged so as to be perpendicular to the optical axis 141A of the focusing lens 141. However, in the spectrometer 101, the scattered light is focused only when it is reflected near the center of the SLM 150. On the other hand, scattered light reflected from the vicinity of the center of the SLM 150 is out of focus. Therefore, in the Comparative Example, there is a problem that the spectral performance cannot be improved by defocusing.

Next, the effect of this embodiment is demonstrated. Compared to the comparative example shown in FIGS. 10 and 11, the spectrometer 1 of Embodiment 1 focuses the scattered light on the entire surface of the DMD 50, and the mirror of each pixel mirror 53 of the DMD 50. Light may be incident perpendicularly to the surface 54 . Accordingly, the light passing through the incident slit 10 can be separated with high resolution. Accordingly, the spectrometer 1 can improve light utilization efficiency and spectral performance.

Further, according to the spectrometer 1 of the present embodiment, a practical spectrometer 1 using the DMD 50 can be realized. Specifically, the wavelength conversion is 1000 times or more faster than conventional spectrometers in which a diffraction grating or a dispersion prism is mechanically rotated. Further, in conversion to a wavelength separated by 100 nm or more, a speed-up of 10,000 times or more can be achieved. In addition, a plurality of wavelengths can be simultaneously transmitted, and the measurement time using an image detector can be significantly reduced (by two times or more). Through this, throughput in a measurement system including a semiconductor measurement device can be improved.

(modified example)

Next, as a modified example, an example in which the spectrometer 1 of the first embodiment is applied to a measurement system including semiconductor measurement devices such as a semiconductor inspection device and a semiconductor measurement device will be described. 12 illustrates 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 can use spectroscopic ellipsometry as a principle.

The light source LS is, for example, an SC laser. The light source LS is connected to a single mode fiber SFB. The light generated by the light source LS is emitted from the single mode fiber end face SFBT through the single mode fiber SFB. The single mode fiber cross-section (SFBT) is typically φ4 μm to φ5 μm. A single mode fiber cross-section (SFBT) can 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 incident slit 10 may include a cross section of the fiber.

The spectrometer 1 disperses the incident light and emits light of a desired wavelength from the output slit 60 as output light. Light emitted from the spectrometer 1 is incident on a multi-mode fiber (MFB). In addition, the multi-mode fiber end face (MFBT) serving as an inlet of the multi-mode fiber (MFB) may serve as the output slit 60 of the spectrometer 1. The light incident on the multi-mode fiber end face (MFBT) and after being split is incident to the optical system 81 in the semiconductor measurement device 80 through the multi-mode fiber (MFB). And, it is used for necessary measurement or inspection.

The semiconductor measuring device 80 inspects or measures the 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. Also, the sample 89 may be a member other than a semiconductor. The semiconductor measuring device 80 includes an optical system 81 and an image detector 88 . The semiconductor measurement device 80 may further include a base, an isolator, an optical support plate, a frame, a stage, and a wafer holder.

The optical system 81 may be mounted on a frame, and the frame may be fixed to an optical platform. A suspension surface plate may be placed on the base. An isolator may be disposed between the optical surface plate and the base. The stage can drive a wafer holder supporting the sample 89 . A wafer holder holding the sample 89 may be placed on the stage. The stage may be disposed under the optics 81. The semiconductor measuring device 80 uses an optical system 81 to capture an image of a sample 89 with an image detector 88 . Accordingly, the sample 89 is inspected or measured.

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 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 section 93 controls the operation of the image detector 88. The stage controller 94 controls the operation of the stage 86.

The semiconductor measuring device 80 may inspect or measure the sample 89 by independently using light including a plurality of wavelengths emitted from the spectrometer 1 . In addition, the semiconductor measuring device 80 may perform ellipsometry measurement from interference fringes obtained by interfering light of different polarization components among light reflected from the specimen 89 . In addition, the semiconductor measurement device 80 may perform ellipsometry measurement by separating optical information of a plurality of wavelengths from the frequency components of the interference fringes. This will be described later.

(Embodiment 2)

Next, the spectrometer according to Embodiment 2 illustrated in FIGS. 13 and 14 will be described. In the spectrometer of this embodiment, the optical path of incident light and outgoing light is divided by pupil division in the XZ plane. In addition, the center-axis incident angle of the incident light and the central-axis exit angle of the outgoing light are the same on the mirror surface 54 of each pixel mirror 53 of the DMD 50 . Accordingly, in the collimator optical system 20 , light utilization efficiency can be further improved without using the beam splitter 22 .

13 and 14 illustrate the spectrometer according to Embodiment 2. Fig. 13 is a view in the Z-axis direction orthogonal to the XY plane, and shows the arrangement of each component in the XY plane. Fig. 14 is a view in the Y-axis direction, showing the arrangement of each component in the XZ plane. 15 and 16 are cross-sectional views illustrating the DMD 50 in the spectrometer according to the second embodiment. 15 is a cross-sectional view orthogonal to the Z-axis direction. 16 is a cross-sectional view orthogonal to the Y-axis direction.

As shown in Figs. 13 to 16, in the spectrometer 2 of the present embodiment, on the XZ plane, the central axis incident angle of light entering the mirror surface 54 is equal to the central axis reflection angle of the light reflected from the mirror surface 54. Do.

The incident slit 10 passes the 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 the beam splitter 22 . The collimator lens 21 converts the light passing through the incident slit 10 into parallel light. The light converted into collimated light by the collimator lens 21 is incident to the dispersion optical element 30 .

The dispersion optical element 30 disperses the light converted into collimated light by the collimator lens 21 at different angles according to wavelengths. The focusing optical system 40 includes a focusing lens 41 . The focusing lens 41 focuses the scattered light. For example, as shown in FIG. 13, the focusing lens 41 focuses the light dispersed according to the wavelength onto the DMD 50 in the XY plane including the dispersion direction. Further, as shown in Fig. 14, in the XZ plane, the focusing lens 41 focuses the light transmitted through the dispersion optical element 30 onto the DMD 50.

In this embodiment, the focusing lens 41 makes the incident light incident on the DMD 50 such that the central axis of the incident light has an incident angle with respect to the mirror surface 54 of the DMD 50 . Accordingly, the center axis angle of incidence of the light incident on the mirror surface 54 of the DMD 50 is equal to the central axis reflection angle of the light reflected from the mirror surface 54 .

As shown in FIG. 15 , in the cross section of the XY plane including the dispersion direction, the cutting line of (the cutting line of) the substrate surface 52 of the substrate 51 and the mirror surface 54 of the pixel mirror 53 ) is parallel. This substrate surface 52 (cut line) and mirror surface 54 (cut line) may be substantially perpendicular to the central axis of the incident light. By this arrangement, the focal point coincides with the mirror surface 54 at all wavelengths scattered on the XY plane. Therefore, the spectral performance can be improved.

As shown in Fig. 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. The mirror surface of the pixel mirror 53 and the chief ray of incident light may be perpendicular to each other. Accordingly, on the XZ plane, the central axis incident angle of light incident on the mirror surface 54 of each pixel mirror 53 is equal to the central axis reflection angle of light reflected from the mirror surface 54 . With this arrangement, the focal point coincides with the mirror surface 54 of the pixel mirror 53 even within the XZ plane. Therefore, light utilization efficiency and spectral performance can be improved.

The light reflected by the DMD 50 is emitted from the exit slit 60 through the focusing lens 41 and the dispersing optical element 30 . Specifically, it passes through the focusing lens 41 and the dispersing optical element 30, passes through the collimator lens 23 and the output slit 60, and is emitted from the spectrometer 2. However, the optical axis 23A of the collimator lens 23 is shifted from the optical axis 21A of the collimator lens 21 in the -Z-axis direction. Accordingly, the light passing through the collimator lens 23 is spaced apart from the light of the incident light passing through the collimator lens 21 and traveling through the dispersing optical element 30 and the focusing lens 41 in the -Z-axis direction. Also in this case, the spectrometer 2 of this embodiment is retro-arranged.

As shown in FIG. 15, in the XY plane including the dispersion direction, an image of each wavelength of the incident slit 10 through which light is incident is formed in the DMD 50. The light reflected from the DMD 50 cancels the wavelength dispersion by transmitting back through the same dispersive optical element 30. Therefore, an image of the incident slit 10 is formed at the same position independent of the wavelength. Therefore, the exit slit 60 is disposed at a position where the image of the entrance slit 10 is formed.

As shown in Fig. 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 arranged so as to be shifted with the optical axis 21A of the collimator lens 21. there is. Accordingly, the optical axis 41A of the focusing lens 41 is perpendicular to the substrate surface 52 of the DMD 50.

In the spectrometer 2 of this embodiment, the focal point of the light dispersed according to the wavelength also coincides with the mirror surface 54. Therefore, the spectral performance can be improved. In addition, in the collimator optical system 20, the beam splitter 22 may not be required. Other configurations and effects are included in the description of Embodiment 1.

(Embodiment 3)

Next, a spectrometer according to Embodiment 3 illustrated in FIGS. 17 and 18 will be described. In the spectroscope of this embodiment, instead of shifting the optical axis 41A of the focusing lens 41 from the optical axis 21A of the collimator lens 21, the focusing lens 41 transmits parallel light passing through the optical element 30. are placed at an angle to In the structure of Embodiment 3, the focal point of the light dispersed according to the wavelength coincides with the mirror surface 54.

17 and 18 illustrate the spectrometer according to Embodiment 3. Fig. 17 is a view in the Z-axis direction orthogonal to the XY plane, and shows the arrangement of each component in the XY plane. Fig. 18 is a view as viewed from the Y-axis direction, showing the arrangement of each component in the XZ plane. 19 and 20 are cross-sectional views illustrating the DMD 50 in the spectrometer according to the third embodiment. 19 is a cross-sectional view orthogonal to the Z-axis direction. 20 is a cross-sectional view orthogonal to the Y-axis direction.

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 located 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. Further, on 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 light reflected from the mirror surface 54.

The incident slit 10 passes the 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 light passing through the incident slit 10 into parallel light. The collimated light generated by the collimator lens 21 is incident to the dispersive optical element 30 .

The dispersion optical element 30 disperses the light converted into collimated light by the collimator lens 21 at different angles according to wavelengths. The focusing lens 41 of the focusing optical system 40 focuses the scattered light. For example, as shown in Fig. 17, the focusing lens 41 focuses the light dispersed according to the wavelength onto the DMD 50 in the XY plane including the dispersion direction. Further, as shown in Fig. 18, in the XZ plane, the focusing lens 41 focuses the light transmitted through the dispersion optical element 30 onto the DMD 50. The center axis angle of incidence of light incident on the DMD 50 is equal to the center axis reflection angle of light reflected from the mirror surface 54 .

As shown in Fig. 19, on 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. The cut line and the principal ray of incident light (the central axis of light) are arranged vertically. With this arrangement, the focal point coincides with the mirror surface 54 at all scattered wavelengths. Therefore, the spectral performance can be improved.

As shown in Fig. 20, 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 cross section of the XZ plane perpendicular to the dispersion direction. On the XZ plane, the central axis angle of incidence of light incident on the mirror surface 54 of each pixel mirror 53 is equal to the central axis reflection angle of light reflected from the mirror surface 54 . With the arrangement of Embodiment 3, the focal point coincides with the mirror surface 54 of the pixel mirror 53 of the DMD 50 even within the XZ plane. Therefore, light utilization efficiency and spectral performance can be improved.

The light reflected by the DMD 50 is emitted from the exit slit 60 through the focusing lens 41 and the dispersing optical element 30 . Specifically, the light passes through the focusing lens 41 and the dispersion optical element 30, passes through the collimator lens 23 of the collimator optical system 20 and the output slit 60, and is emitted from the monochromator. However, the optical path of the emitted light is separated from the incident light passing through the collimator lens 21 and traveling through the dispersion optical element 30 and the focusing lens 41 in the -Z-axis direction. Also in this case, the spectrometer 3 of this embodiment is retro-arranged.

Also in this embodiment, 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 addition, the center axis angle of incidence of light incident on the mirror surface 54 of each pixel mirror 53 is equal to the central axis reflection angle of light reflected from the mirror surface 54 . Thus, the focus of all scattered wavelengths of light coincides on the mirror surface 54 . Therefore, light utilization efficiency and spectral performance can be improved. Other configurations and effects are included in the description of Embodiments 1 and 2.

(Embodiment 4)

Next, a spectrometer according to Embodiment 4 illustrated in FIGS. 21 and 22 will be described. In the spectrometer of this embodiment, a stepped prism is disposed between the collimator optical system 20 and the dispersive optical element 30.

21 and 22 illustrate the spectrometer according to Embodiment 4. Fig. 21 is a view in the Z-axis direction orthogonal to the XY plane, and shows the arrangement of each component in the XY plane. Fig. 22 is a view as viewed from the Y-axis direction, showing the arrangement of each component in the XZ plane.

21 and 22, in the spectrometer 4 of this embodiment, an optical member 25 is disposed between the collimator optical system 20 and the dispersing optical element 30. The optical member 25 is a member that divides the incident light and gives an optical path difference to the divided light. The optical member 25 may also be referred to as a spatial retarder. One example of the optical member 25 includes a stepped prism.

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, spatial coherency can be reduced by providing an optical path difference greater than or equal to the distance at which interference occurs in the light split by the optical member 25. .

In addition, in the operation of the spectrometer 4, not all of the pixel mirrors 53 of the portion where the incident light incident on the substrate surface 52 of the DMD 50 is reflected are turned ON, but about half of the pixel mirrors. In addition to reflecting only (53) in a random arrangement (eg, switching to an ON state), the DMD 50 is driven so that the random arrangement changes with time. That is, as shown in Fig. 9, the DMD 50 randomly changes each pixel mirror 53 in the extraction wavelength string 56 to an ON state or an OFF state. These operations are realized through the software of the computer 91 in FIG. 12 and the DMD control unit 92. Accordingly, when a white laser such as an SC laser is used as a light source, it is possible to reduce the generation of speckles and improve the quality of light used in the semiconductor measurement device 80 as illumination light. Other configurations and effects are included in the description of Embodiments 1 to 3.

(Embodiment 5)

Next, the spectrometer according to Embodiment 5 will be described. This embodiment is a measurement system in the case where any one of the spectrometers 1, 2, 3, and 4 described above is applied to the semiconductor measurement device 80 based on self-interference ellipsometry.

23 illustrates the measurement system according to the fifth embodiment. As shown in FIG. 23, the measurement system 5 includes a light source LS such as an SC laser, any one of the spectrometers 1, 2, 3, and 4, a semiconductor measurement device 80, and a processing device 90. are doing The measurement system 5 receives the reflected light R1 reflected from the specimen 89 by the illumination light L1 and measures the ellipsometry coefficients Ψ and Δ.

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, An image detector 88 is included. The analyzer 81h is, for example, a polarizing plate. The image detector 88 is, for example, a camera.

The optical system 81 illuminates the sample 89, such as a semiconductor, with illumination light L1 containing linearly polarized light. In addition, the optical system 81 collects the reflected light R1 of the illumination light L1 reflected by the sample 89 . Specifically, the illumination lens 81a irradiates the illumination light L1 to the polarizer 81b. For example, the illumination lens 81a converts the illumination light L1 emitted from the multi-fiber MFB into parallel light. Then, the illumination light L1 converted into parallel light is made incident on the polarizer 81b.

The polarizer 81b transmits the illumination light L1 including linearly polarized light in one direction. For example, the polarizer 81b emits linearly polarized illumination light L1 whose polarization direction is inclined at 45 degrees with respect to the ground to the beam splitter 81c. The beam splitter 81c reflects part of the incident illumination light L1 and transmits part of it. The beam splitter 81c reflects part of the incident illumination light L1 toward the objective lens 81d. The illumination light L1 reflected by the beam splitter 81c is incident on the objective lens 81d.

The objective lens 81d illuminates the specimen 89 with illumination light L1 containing linearly polarized light. The objective lens 81d condenses the illumination light L1 reflected by the beam splitter 81c into a dot shape to illuminate the sample 89. Then, the objective lens 81d transmits the reflected light R1 in which the illumination light L1 is reflected from the sample 89. In the measurement system 5 of this embodiment, the optical axis C of the illumination light L1 incident on the sample 89 and the optical axis C of the reflected light R1 reflected from the sample 89 are It is orthogonal to the measurement plane.

The illumination light L1 illuminating the sample 89 includes linearly polarized light in one direction. The illumination light L1 including linearly polarized light in one direction is incident on the measurement surface of the sample 89 while being condensed. Therefore, when the illumination light L1 is completely polarized and linearly polarized, and the optical axis C is orthogonal to the measurement plane of the sample 89, depending on the direction incident on the measurement plane, the illumination light L1 is a P polarization component and It may contain an S polarization component. 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.

The objective lens 81d transmits the reflected light R1 reflected from the measurement surface of the specimen 89 by the illumination light L1 and enters the beam splitter 81c. The beam splitter 81c transmits a part of the incident reflected light R1. For example, the reflected light R1 transmitted through the beam splitter 81c is incident to the relay lens 81e. The relay lens 81e condenses the reflected light R1 transmitted through the beam splitter 81c, forms an image, and then makes it incident to the relay lens 81f. The relay lens 81f transmits the incident reflected light R1 and makes it incident to the polarization optical element 81g.

Fig. 24 is a configuration diagram illustrating the polarization optical element 81g, the analyzer 81h, and the image detector 88 in the measurement system 5 according to the fifth embodiment. As shown in FIG. 24, the polarization optical element 81g separates the reflected light R1 of the illumination light L1 including linearly polarized light reflected from the sample 89 into two linearly polarized light with mutually orthogonal polarization directions, and emits the light. let it The polarization optical element 81g is, for example, a Nomarsky prism.

The mutually orthogonal polarization directions separated by the polarization optical element 81g are the α direction and the β direction. In this case, the plane formed by the α and β directions and the optical axis of the reflected light R1 are orthogonal. Then, the polarization optical element 81g separates linearly polarized light in the α-direction and linearly polarized light in the β-direction. Then, the polarization optical element 81g deflects the separated linearly polarized light in the α-direction and the linearly polarized light in the β-direction to the same point again on the image detector 88 and emits them. In addition, the polarization optical element 81g is not limited to a Nomarsky prism, and may include a Wollaston prism or a Lotion prism.

Fig. 25 illustrates linearly polarized light passing through the analyzer in the measurement system 5 according to the fifth embodiment. As shown in Fig. 25, the analyzer 81h transmits the component of linearly polarized light separated by the polarization optical element 81g in the direction inclined at 45 [deg] from the polarization direction of the α direction and the polarization direction of the β direction. Accordingly, the analyzer 81h transmits a polarized component at an angle of 45 [deg] to the α direction among linearly polarized light having a polarization direction of the α direction. In addition, the analyzer 81h transmits a polarized component at an angle of 45 [deg] to the β direction among linearly polarized light having a polarization direction in the β direction. Accordingly, the two linearly polarized light orthogonal to each other pass through the analyzer 81h and are emitted as polarized components polarized in the same direction (45 [deg] inclined direction). The reflected light R1 including the polarization component emitted from the analyzer 81h is incident on the image detector 88.

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 includes polarization components in the same direction of two linearly polarized lights orthogonal to each other. Accordingly, 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 an interference fringe of each polarization component transmitted through the analyzer 81h.

26 illustrates the wave surface of each linearly polarized light included in the reflected light incident on the image detector 88 in the measurement system 5 according to the fifth embodiment. 27 illustrates an interference fringe of reflected light interfering on the image detector 88 in the measurement system 5 according to the fifth embodiment. 26 and 27, the reflected light R1 comprising two linearly polarized lights R1α and R1β separated by the polarization optical element 81g passes through the analyzer 81h and detects an image detector 88 ) form an interference fringe.

The processing device 90 calculates 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 fringe to the following equation (1). Here, the intensity distribution Ifringe is a function of the position on the image detector 88.

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

28 illustrates ellipsometry coefficients obtained 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 ratio (Ψ) of the intensity of the two polarizations and the phase difference (Δ) are changed, the intensity of the reflected light R1 forming the interference fringe at each position of the image detector 88. is changed Using this relationship, the ellipsometry coefficients Ψ and Δ can be obtained from the interference fringes.

For example, for reflected light R1 having an intensity change indicated by a thick line, the intensity ratio E1:E2 of two polarizations is 1:1, and the phase difference Δ is zero. In addition, for the reflected light R1 having an intensity change indicated by a dotted line, the intensity ratio E1:E2 of the two polarizations is 1:1, and the phase difference Δ is π/4. In addition, for the reflected light R1 having an intensity change indicated by the thin line, the intensity ratio E1:E2 of the two polarizations is 2:1, and the phase difference Δ is zero. In this way, the optical system 81 transmits the separated linearly polarized light in each polarization direction (α direction and β direction) through an analyzer having a transmission axis tilted by 45 [deg], thereby interfering with components of the two linearly polarized light, and detecting an image detector. Calculate the ellipsometry coefficients Ψ and Δ from the interference fringes on (88).

29 illustrates an interference fringe of reflected light that has interfered on the image detector 88 in the measurement system 5 according to another example of the fifth embodiment. As shown in Fig. 29, in the DMD 50, the pixel mirror 53 of the extraction wavelength column 56 corresponding to the two wavelengths I and II is turned ON, and the light containing the wavelengths I and II is turned on. can be guided to the semiconductor measurement device 80. In this case, the interference pattern is a combination of the interference pattern of wavelength I and the interference pattern of wavelength II.

The surface state of the sample 89 is analyzed by obtaining information on the amplitude and phase of a specific frequency component by Fourier transform from the obtained interference fringes. When the lights of two wavelengths are simultaneously incident, it is possible to simultaneously analyze the interference fringes of the lights of the two wavelengths by providing window functions at two locations during Fourier transformation.

Next, the effect of this embodiment is demonstrated. The measurement system 5 of this embodiment uses the polarization optical element 81g in measuring the ellipsometry coefficients Ψ and Δ. The polarization optical element 81g separates the reflected light R1 reflected from the specimen 89 into two linearly polarized rays (R1α and R1β) of polarization directions orthogonal to each other, and generates interference fringes from the separated two linearly polarized light into an image detector. Form on (88). From the measurement results of the contrast and phase of the interference fringe, ellipsometry coefficients (Ψ and Δ), which are two independent parameters, are directly measured. Accordingly, it is unnecessary to measure the amount of light of at least four polarization components in time series using a rotating polarizer or a compensator necessary for measuring the ellipsometry coefficients (Ψ and Δ) so far.

In addition, in the measurement of the ellipsometry coefficients (Ψ and Δ) so far, a Stokes parameter is obtained from the light quantity of light in a plurality of different polarization states, and the ellipsometry coefficients (Ψ and Δ) are obtained from the obtained Stokes parameters. is looking for In this embodiment, the ellipsometry coefficients Ψ and Δ can be obtained directly and from a single image. Therefore, since measurement can be performed in a short time, the throughput of OCD measurement can be improved.

In addition, compared to conventional ellipsometers, since there are no moving parts, more stable ellipsometry coefficients (Ψ and Δ) can be measured.

In addition, in many ellipsometers used in OCD measuring devices, the angle of incidence of the illumination light L1 incident on the surface of the sample 89 was fixed to a brewster angle. However, in the present embodiment, by arranging the image detector 42 at a pupil conjugate position that is conjugate to the pupil position of the large NA (Numerical Aperture) objective lens 17, ellipsometry at an arbitrary angle of incidence and direction of incidence is achieved. Allows measurement of tree coefficients (Ψ and Δ). Such a configuration cannot be easily realized with conventional ellipsometer configurations in which an analyzer or the like is rotated.

As a result, for example, in fitting to a microstructure model on a wafer, measurement results under more conditions can be used, and coupling reduction in other dimensions, which is a problem in OCD measuring devices, is also reduced. In particular, an improvement in precision is expected in the measurement of current semiconductor structures where three-dimensionalization has advanced. In addition, the illumination area of the sample 89 by the illumination light L1 can be reduced from about φ30 [μm] up to now to φ1 [μm] or less, and evaluation of the dimensional distribution within the chip is also performed with higher positional resolution. it is possible These measurement results are reflected in lithography, film formation, and etching processes, and process control in semiconductor manufacturing can be appropriately performed. Accordingly, product yield and productivity in semiconductor manufacturing can be improved.

Further, in logic, test patterns for measuring ellipsometry coefficients arranged in a semiconductor chip can be reduced from several tens [μm] squares to several [μm] squares or less. For this reason, the area usable for the circuit in a semiconductor chip increases, and it can also contribute to cost reduction of a semiconductor device.

The present invention is not limited to the above embodiment, and appropriate changes are possible within a range not departing from the gist. For example, each configuration of Embodiments 1 to 5 can be combined with each other.

1, 2, 3, 4 spectrographs
1a, 5 measurement system
10 entrance slits
11 entrance slit part
19 sides
20 collimator optics
21 collimator lens
21A optical axis
22 beam splitter
23 collimator lens
25 optical elements
30 Dispersive Optical Elements
40 focusing optics
41 focusing lens
41A optical axis
50 DMD
51 substrate
52 board surface
53 pixel mirror
54 mirror face
55 axis of rotation
56 take-out wavelength train
59 reflector
60 exit slits
69 sides
80 Semiconductor Measuring Device
81 Optics
81a lighting lens
81b polarizer
81c beam splitter
81d objective lens
81e, 81f relay lens
81g polarized optical element
81h Analyzer
82 expectations
83 Isolator
84 optical table
85 frames
86 stage
87 wafer holder
88 image detector
89 samples
90 processing unit
91 computer
92 DMD Control
93 image detector control unit
94 stage control
101 Spectrograph
110 entrance slit
120 collimator optics
121 collimator lens
121A optical axis
123 collimator lens
130 Dispersive Optics
140 focusing optics
141 Focusing Lens
141A optical axis
150 SLM
160 exit slits
LS light source
MFB multimode fiber
MFBT multimode fiber cross section
SFB singlemode fiber
SFBT singlemode fiber cross section

Claims (10)

a collimator lens configured to generate collimated light by collimating the light passing through the entrance slit;
a dispersive optical element configured to generate dispersed light by dispersing the collimated light at different angles according to wavelengths;
a focusing lens configured to generate focused light by focusing the scattered light; and
A Spatial Light Modulator (SLM) having a reflective surface configured to generate reflected light by reflecting the focused light by the focusing lens;
The reflected light passes through the focusing lens and the dispersing optical element and exits through an exit slit;
The entrance slit, the exit slit, and the reflective surface have a conjugate relationship on a second surface orthogonal to the first surface,
The first surface includes an optical path of the scattered light, and
The second surface comprises an optical axis of the collimator lens and an optical axis of the focusing lens. According to claim 1,
The optical axis of the focusing lens is shifted from the optical axis of the collimator lens. According to claim 1,
The light includes laser light emitted from the fiber,
Wherein the incident slit comprises a cross section of the fiber. According to claim 1,
and an optical member disposed between the collimator lens and the dispersing optical element, splitting the collimated light and causing an optical path difference in the divided collimated light. According to claim 4,
The optical member is a spectrometer that includes a stepped prism. According to claim 1,
The SLM is a DMD (Digital Micro Mirror Device) including a plate-shaped substrate and a plurality of pixel mirrors arranged in a matrix on the substrate surface of the substrate,
wherein each of the plurality of pixel mirrors has a mirror surface reflecting the light and a rotation axis extending in a direction orthogonal to the second surface. According to claim 6,
A central axis of the focused light incident on the mirror surface on the second surface is perpendicular to the mirror surface. According to claim 6,
On the second surface, an incident angle of a central axis of the focused light incident on the mirror surface is equal to a reflection angle of the central axis of the light reflected from the mirror surface. According to claim 6,
An optical axis of the focusing lens is inclined with respect to an optical axis of the collimator lens;
On the second surface, an incident angle of a central axis of the focused light incident on the mirror surface is equal to a reflection angle of a central axis of the reflected light reflected from the mirror surface. According to claim 6,
Each of the plurality of pixel mirrors is in any one of 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 substrate surface. collimator.

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