JP2021085698A - Ellipsometer and device for inspecting semiconductor device - Google Patents

Abstract

To provide an ellipsometer and a device for inspecting a semiconductor device that can increase the throughput for measuring an ellipsometry coefficient.SOLUTION: An ellipsometer 1 includes: a polarization optical element 30 for separating a reflection light R1 formed by reflection of an illumination light L1 including a linear polarization by a sample 50 into two linear polarizations of polarization directions perpendicular to each other; and a light receiving optical system 40 for causing an interference of components of two linear polarizations in directions different from the separated polarization directions and calculating an ellipsometry coefficient from a formed interference fringe.SELECTED DRAWING: Figure 1

Description

The present invention relates to an ellipsometer and an inspection device for a semiconductor device.

Since ellipsometry became possible for automatic measurement by Aspines et al. In 1975, the measurement time has been significantly shortened and the accuracy has been greatly improved, and spectroscopic ellipsometry for measuring with multiple wavelengths has also been put into practical use. .. Since then, in non-destructive measurement of thin films and fine structures, it has been widely used in semiconductor manufacturing processes by taking advantage of its characteristic of being able to measure dimensions such as film thickness and optical constants such as refractive index with high accuracy. Even now, as an OCD (Optical Critical Distance) measuring device for measuring the dimension of a fine structure in which the line width of a circuit pattern on a wafer is 10 nm or less, a length measuring SEM (Scanning Electron-beam Microscope) or an AFM (Atomic Force) is used. It is used as a complement to Force Microscope).

In the last 10 years or so, semiconductor circuit structures such as FinFETs for logic semiconductors and 3D-NAND for memories have become more three-dimensional and become more complicated. Many OCDs use spectroscopic ellipsometry as a measurement principle, and in order to obtain the dimensions of the semiconductor circuit structure to be measured and the optical constants of the constituent materials, a model is created and the dimensions and optical constants to be measured are floated. As a parameter, a method is adopted in which a model is fitted to the measurement result to obtain a solution. Therefore, when the structure of the target to be sought becomes complicated, the number of Floating parameters increases. For example, in the current OCD measurement of FinFET, it is necessary to use about 20 to 30 Floating parameters. Ellipsometry generally obtains two values of Ψ and Δ as measurement result ellipsometry coefficients, but both Ψ and Δ are wavelength-dependent. Therefore, in the case of spectroscopic ellipsometry, the ellipsometry coefficients can be expressed as Ψ (λ) and Δ (λ).

In order to find the solution of the dimension, it is necessary to obtain the number of ellipsometry coefficients by measurement, which is larger than the number of floating parameters, in order to fit the model, but it occurs when the number of floating parameters is large. As a problem, the fitting may converge with a combination of flooring parameters different from the actual dimension. This is a problem called coupling, and in order to avoid this, it is effective to measure and perform fitting by measuring the ellipsometry coefficient that has different dependence on the floating parameters. Therefore, ellipsometry measurement is performed under conditions in which the incident angle and the incident direction are different in addition to the wavelength, and the ellipsometry coefficient having a different dependence on the floating parameter is used for fitting the model.

For these reasons, the spectroscopic ellipsometry used in the OCD measuring device in the semiconductor manufacturing process is strongly expected to be able to measure the ellipsometry coefficient in a shorter time and under more measurement conditions.

U.S. Pat. No. 5,596,411 U.S. Pat. No. 7667841 U.S. Pat. No. 6,856,384 U.S. Pat. No. 8,908,180

The spectroscopic ellipsometry used in the OCD measuring device in the semiconductor manufacturing process requires a measurement time of 1 second to several seconds to measure one point. The reason for this is that a large number of measurement points are generally required within the modulation cycle of the Rotating compensator or phase modulation element used in the ellipsometer. Further, since it is a spectroscopic measurement, it is necessary to measure the amount of light divided into each wavelength by a dispersion element such as a diffraction grating with a high S / N ratio. Therefore, in order to inspect all the wafers in the manufacturing process, only a few to several tens of points can be measured in the wafer, and in order to evaluate the entire surface of the wafer, it is necessary to combine it with a film thickness measuring device or a macro inspection device. There is.

In order to shorten the measurement of spectroscopic ellipsometry for the purpose of increasing the number of measurement points in the wafer, it is necessary to increase the speed of moving parts such as rotation compensators, but stability and heat generation become bottlenecks. , It is difficult to improve the throughput of ellipsometry coefficient measurement for OCD measurement and the like.

The present invention has been made to solve such a problem, and provides an ellipsometer and a semiconductor device inspection device capable of improving the throughput for measuring the ellipsometry coefficient for OCD measurement and the like.

The basic method of conventional ellipsometry measurement is to "measure the intensity of light in a single polarized state under a plurality of conditions", but in the present invention, "the intensity of light in two polarized states" is used. It is based on a different approach: "The ratio and phase difference are determined by measuring the interference fringes." For this measurement, the sample is illuminated with coherent and fully polarized illumination light, the reflected light from the sample is divided into two linearly polarized lights, and the same light beam before the division of the reflected light is emitted on the image detector. The optical system should be such that it overlaps again. A nomarski prism is ideal as a polarizing element that realizes this, but a wollaston prism or a lotion prism depends on the difference in the illumination region on the sample and the spatial coherence of the light source. It is also possible to use (rochon prism).

As a more specific configuration, a combination of a white light source and a monochromometer, or light from a monochromatic light source is used as illumination light, and the illumination light is transmitted through a polarizer or a wave plate to make the illumination light a straight line of completely polarized light. Polarized or elliptically polarized light. The illumination light on the sample is focused in dots, and the spatial coherence changes depending on the size of the illumination area at this time. After the illumination light is reflected by the sample, it becomes parallel light near the pupil of the light receiving optical system, is divided by a Nomalski prism or the like so that the two linearly polarized light components travel at different angles, and is again at the same point on the image detector. Overlap. Immediately before the image detector, a polarizing plate having a transmission axis intermediate between the polarization directions of the two divided linearly polarized light is installed, and the two linearly polarized light become coherent after being transmitted through the polarizing plate, and on the image detector. Form interference fringes.

This polarizing plate is placed in front of the detector like the detector of a conventional ellipsometer, but its role is to allow linearly polarized light whose two polarization directions are orthogonal to each other, and the purpose is completely different. ..

In general ellipsometers, the illumination optical system and the light receiving optical system are often configured differently. The advantages of this configuration are that the wavelength range can be widened and that the polarizer and the analyzer can be arranged between the sample and the optical system, so that they are not easily affected by birefringence by the lens. However, since only one incident angle and incident direction can be measured at the same time, it cannot be said that the configuration is optimal as a measurement and inspection device in semiconductor manufacturing in which throughput is very important.

On the other hand, an ellipsometer that uses an objective lens with a large NA and arranges an image detector at the pupil conjugate position of the objective lens can measure multiple incident angles and directions at the same time, which is an advantage as a semiconductor inspection device. is there. One of the advantages of the ellipsometer of the present invention is measurement in a short time, and the latter combination with the optical system configuration can be most effective.

Furthermore, when a white light source is used, it is possible to obtain Ψ and Δ of each wavelength from a single image by Fourier transforming the interference fringes on the image detector, and it can also be used as a spectroscopic ellipsometer. It will be possible.

The semiconductor device inspection device according to the present invention includes the ellipsometer described above.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide an ellipsometer and a semiconductor device inspection device capable of improving the throughput for measuring the ellipsometry coefficient.

It is a block diagram which exemplifies the ellipsometer according to Embodiment 1. FIG. 5 is a configuration diagram illustrating a polarizing optical element and a light receiving optical system in the ellipsometer according to the first embodiment. FIG. 5 is a diagram illustrating linearly polarized light transmitted through an analyzer in the ellipsometer according to the first embodiment. FIG. 5 is a diagram illustrating the wavefront of each linearly polarized light contained in the reflected light incident on the image detector in the ellipsometer according to the first embodiment. FIG. 5 is a diagram illustrating interference fringes of reflected light that interfered on an image detector in the ellipsometer according to the first embodiment. It is a figure exemplifying the ellipsometry coefficient obtained from the interference fringes on an image detector in the ellipsometer according to the first embodiment. It is a block diagram which illustrated the ellipsometer which concerns on Embodiment 2. In the ellipsometer according to the second embodiment, it is a figure exemplifying a plurality of division pieces of a Nomalski prism and a direction in which each division piece separates into two linearly polarized light. FIG. 5 is a diagram illustrating interference fringes of reflected light that interfered on an image detector in the ellipsometer according to the second embodiment. It is a figure which illustrated the interference fringe on the image detector in the ellipsometer which concerns on Embodiment 2, and shows the intensity of the AA line and the BB line of FIG. It is a block diagram which illustrated the ellipsometer which concerns on Embodiment 3. FIG. 5 is a diagram illustrating interference fringes of reflected light that interfered on an image detector in the ellipsometer according to the third embodiment. FIG. 5 is a graph illustrating the result of Fourier transforming the intensity and phase contained in the interference fringes of the reflected light that interfered on the image detector with respect to the wavelength of the reflected light in the ellipsometer according to the third embodiment. It is a block diagram which illustrated the ellipsometer which concerns on Embodiment 4. FIG. FIG. 5 is a diagram illustrating interference fringes of reflected light that interfered on two image detectors in the ellipsometer according to the fourth embodiment. In the ellipsometer according to the fourth embodiment, each component is illustrated when the polarization directions reflected and transmitted by the polarization beam splitter are shifted from 45 [deg] with respect to the two linear directions separated by the polarizing optical elements. is there. It is a block diagram which illustrated the ellipsometer which concerns on Embodiment 5. It is a block diagram which illustrated the ellipsometer which concerns on Embodiment 6. It is a block diagram which illustrated the ellipsometer which concerns on Embodiment 7. It is a block diagram which illustrated the ellipsometer which concerns on Embodiment 8. FIG. 5 is a configuration diagram illustrating a polarizing optical element and a light receiving optical system in the ellipsometer according to the eighth embodiment.

In order to clarify the explanation, the following description and drawings have been omitted or simplified as appropriate. Further, in each drawing, the same elements are designated by the same reference numerals, and duplicate explanations are omitted as necessary.

(Embodiment 1)
The ellipsometer according to the first embodiment will be described. FIG. 1 is a configuration diagram illustrating an ellipsometer according to the first embodiment. As shown in FIG. 1, the ellipsometer 1 includes an illumination optical system 10, a condensing optical system 20, a polarizing optical element 30, and a light receiving optical system 40. The ellipsometer 1 receives the reflected light R1 reflected by the sample 50 by the illumination light L1 and measures the ellipsometry coefficients Ψ and Δ.

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

The light source 11 generates the illumination light L1. The illumination light L1 generated by the light source 11 is, for example, white light. The illumination light L1 generated by the light source 11 is not limited to white light, but may be monochromatic light having a specific wavelength. The illumination light L1 generated from the light source 11 is incident on the monochromator 12.

The monochromator 12 extracts monochromatic light having a specific wavelength from the incident illumination light L1 and emits it. The illumination light L1 emitted from the monochromator 12 is monochromatic light and is incident on the fiber 13.

The fiber 13 is a cable-shaped light guide member having one end and the other end. The illumination light L1 incident on one end of the fiber 13 is emitted from the other end of the fiber 13. The illumination light L1 emitted from the other end of the fiber 13 is incident on the illumination lens 14.

The illumination lens 14 is, for example, a convex lens. The illumination lens 14 changes the angular distribution of the incident illumination light L1 and irradiates the polarizer 15 with the illumination light L1. For example, the illumination lens 14 converts the illumination light L1 emitted from the other end of the fiber 13 into parallel light. Then, the illumination light L1 made into parallel light is incident on the polarizer 15.

Illumination light L1 generated from the light source 11 is incident on the polarizer 15. The polarizer 15 transmits the illumination light L1 including linearly polarized light in one direction. For example, the polarizer 15 emits linearly polarized illumination light L1 whose polarization direction is tilted by 45 ° with respect to the paper surface to the beam splitter 16.

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

The objective lens 17 illuminates the sample 50 with the illumination light L1 including linearly polarized light. The objective lens 17 illuminates the sample 50 by condensing the illumination light L1 reflected by the beam splitter 16 in a point shape. Then, the objective lens 17 transmits the reflected light R1 reflected by the illumination light L1 on the sample 50. In the ellipsometer 1 of the present embodiment, the optical axis C of the illumination light L1 incident on the sample 50 and the optical axis C of the reflected light R1 reflected by the sample 50 are orthogonal to the measurement surface of the sample 50.

The illumination light L1 that illuminates the sample 50 contains linearly polarized light in one direction. The illumination light L1 containing such unidirectional linearly polarized light is incident on the measurement surface of the sample 50 while being condensed. Therefore, when the illumination light L1 is completely polarized and linearly polarized, when the optical axis C is orthogonal to the measurement surface of the sample 50, the illumination light L1 also has a P-polarized part depending on the orientation incident on the measurement surface. If there is, there is also an S-polarized part. The S-polarized part in the illumination light L1 is reflected as S-polarized light. The P-polarized part in the illumination light L1 is reflected as P-polarized light.

The condensing optical system 20 condenses the reflected light R1 reflected by the illumination light L1 on the sample 50. The condensing optical system 20 includes an objective lens 17, a beam splitter 16, and relay lenses 21 and 22. The objective lens 17 is also a member of the illumination optical system 10 and a member of the condensing optical system 20. The objective lens 17 transmits the reflected light R1 reflected by the sample 50 by the illumination light L1 and causes the illumination light L1 to enter the beam splitter 16.

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

The relay lens 21 collects the reflected light R1 transmitted through the beam splitter 16 and causes the reflected light R1 to be incident on the relay lens 22 after forming an image. The relay lens 22 transmits the incident reflected light R1 and causes the incident light R1 to enter the polarizing optical element 30.

FIG. 2 is a configuration diagram illustrating a polarizing optical element and a light receiving optical system in the ellipsometer according to the first embodiment. As shown in FIG. 2, the polarizing optical element 30 separates the reflected light R1 reflected by the illumination light L1 including linearly polarized light on the sample 50 into two linearly polarized lights in the polarization directions orthogonal to each other and emits them. The polarizing optical element 30 is, for example, a Nomalski prism 31.

The polarization directions orthogonal to each other from which the polarization optical elements 30 are separated are defined as the X direction and the Y direction. In this case, the plane formed by the X and Y directions and the optical axis of the reflected light R1 are orthogonal to each other. Then, the Nomalski prism 31 is separated into linearly polarized light in the X direction and linearly polarized light in the Y direction. Then, the Nomalski prism 31 deflects the separated linearly polarized light in the X direction and the linearly polarized light in the Y direction so as to be at the same point again on the image detector, and emits the polarized light. The polarizing optical element 30 is not limited to the Nomalski prism 31, and may include a Wollaston prism or a lotion prism.

The light receiving optical system 40 receives the reflected light R1 and calculates ellipsometry coefficients Ψ and Δ. The light receiving optical system 40 includes an analyzer 41, an image detector 42, and an image processing unit 43. The analyzer 41 is, for example, a polarizing plate.

FIG. 3 is a diagram illustrating linearly polarized light transmitted through an analyzer in the ellipsometer according to the first embodiment. As shown in FIG. 3, the analyzer 41 transmits the components of linearly polarized light in the polarization direction in the X direction and the polarization direction in the Y direction separated by the polarizing optical element 30 and in the direction inclined by 45 [deg]. Therefore, the detector 41 transmits a polarized light component tilted by 45 [deg] with respect to the X direction among the linearly polarized light having the polarization direction in the X direction. Further, the detector 41 transmits a polarized light component tilted by 45 [deg] with respect to the Y direction among linearly polarized light having a polarization direction in the Y direction. Therefore, the two linearly polarized light orthogonal to each other are emitted as polarized light components polarized in the same direction (45 [deg] tilted direction) by passing through the analyzer 41. The reflected light R1 including the polarization component emitted from the detector 41 is incident on the image detector 42.

The image detector 42 receives the incident reflected light R1. The image detector 42 is arranged at the pupil conjugate position 19b conjugate with the pupil position 19a of the objective lens 17. The reflected light R1 contains polarization components in the same direction in two linearly polarized light orthogonal to each other. Therefore, the reflected light R1 interferes with the image detector 42. As a result, interference fringes are formed on the image detector 42. The image detector 42 detects the interference fringes of each polarization component transmitted through the analyzer 41.

FIG. 4 is a diagram illustrating the wavefront of each linearly polarized light contained in the reflected light incident on the image detector in the ellipsometer according to the first embodiment. FIG. 5 is a diagram illustrating interference fringes of reflected light that interfered on the image detector in the ellipsometer according to the first embodiment. As shown in FIGS. 4 and 5, the reflected light R1 including the two linearly polarized light R1X and R1Y separated by the polarizing optical element 30 passes through the analyzer 41 and forms interference fringes on the image detector 42. ..

The image processing unit 43 is, for example, a PC. The image processing unit 43 calculates the ellipsometry coefficients Ψ and Δ from the interference fringes detected by the image detector 42. For example, the image processing unit 43 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 42.

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

FIG. 6 is a diagram illustrating the ellipsometry coefficient obtained from the interference fringes on the image detector in the ellipsometer according to the first embodiment. As shown in FIG. 6, when the ratio (Ψ) and the phase difference (Δ) of the intensities of the two polarized lights are changed, the intensities of the reflected light R1 forming interference fringes at each position of the image detector 42. Changes. Using this relationship, the ellipsometry coefficients Ψ and Δ can be obtained from the interference fringes.

For example, for the reflected light R1 having the intensity change indicated by the thick line, the intensity ratios E1: E2 of the two polarized lights are 1: 1 and the phase difference Δ is 0. Further, for the reflected light R1 having the intensity change 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. Further, for the reflected light R1 having the intensity change 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. In this way, the light receiving optical system 40 transmits the separated linearly polarized light in each polarization direction (X direction and Y direction) through an detector having a transmission axis inclined by 45 [deg], thereby transmitting two straight lines. The polarized light components are made to interfere with each other, and the ellipsometry coefficients Ψ and Δ are calculated from the interference fringes on the image detector 42.

Next, the effect of this embodiment will be described. The ellipsometer 1 of the present embodiment utilizes the polarizing optical element 30 in the measurement of the ellipsometry coefficients Ψ and Δ. The polarizing optical element 30 separates the reflected light R1 reflected by the sample 50 into two linearly polarized light R1X and R1Y in the polarization directions orthogonal to each other, and forms interference fringes on the image detector 42 from the two separated linearly polarized light. To do. From the measurement results of the contrast and phase of the interference fringes, the ellipsometry coefficients Ψ and Δ, which are two independent parameters, are directly measured. This eliminates the need to measure the amount of light of at least four polarization components in the time series using a rotating polarizer or compensator, which was necessary for the conventional measurement of ellipsometry coefficients Ψ and Δ.

Further, in the previous measurements of the ellipsometry coefficients Ψ and Δ, the Stokes parameters are obtained from the amount of light of light in a plurality of different polarized states, and the ellipsometry coefficients Ψ and Δ are obtained from the obtained Stokes parameters. In this embodiment, the ellipsometry coefficients Ψ and Δ can be obtained directly and from a single image. Therefore, since the measurement can be performed in a short time, the throughput of OCD measurement can be improved.

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

Further, in many ellipsometers used in the OCD measuring device, the incident angle of the illumination light L1 incident on the surface of the sample 50 is fixed at the Brewster angle. However, in the present embodiment, the ellipsometry coefficients Ψ and Δ are measured at an arbitrary incident angle and incident direction by arranging the image detector 42 at a pupil conjugate position conjugated to the pupil position of the objective lens 17 having a large NA. Is possible. Such a configuration cannot be easily realized by the conventional ellipsometer configuration for rotating an analyzer or the like.

As a result, for example, in fitting to a microstructure model on a wafer, measurement results under more conditions can be used, and coupling of different dimensions, which is often a problem in OCD measuring devices, can be reduced. Since they are connected, it is expected to improve the accuracy especially in the measurement of the current semiconductor structure, which has been made three-dimensional. Further, the illumination region of the sample 50 by the illumination light L1 can be reduced from about φ30 [μm] to φ1 [μm] or less, and the distribution of the dimension in the chip can be evaluated with higher position resolution. Is possible. These measurement results can be reflected in the lithography, film formation, and etching processes to appropriately control the process of semiconductor manufacturing. As a result, the yield and productivity in semiconductor manufacturing can be improved.

Further, in the logic, the test pattern for measuring the ellipsometry coefficient arranged in the semiconductor chip can be reduced from several tens [μm] squares to several [μm] squares or less. it can. Therefore, the area that can be used for the circuit in the semiconductor chip increases, which can contribute to the cost reduction of the semiconductor device.

(Embodiment 2)
Next, the ellipsometer according to the second embodiment will be described. In the ellipsometer 2 of the present embodiment, the polarizer 18, the Nomalski prism 32, and the analyzer 44 are divided into four parts. FIG. 7 is a configuration diagram illustrating an ellipsometer according to the second embodiment. As shown in FIG. 7, the ellipsometer 2 differs from the ellipsometer 1 of the first embodiment in the polarizer 18, the Nomalski prism 32, and the analyzer 44.

FIG. 8 is a diagram illustrating the direction in which the plurality of divided pieces of the Nomalski prism and each divided piece are separated into two linearly polarized light in the ellipsometer according to the second embodiment. As shown in FIG. 8, the Nomalski prism 32 is divided into four in a plane orthogonal to the optical axis C of the reflected light R1.

360 [deg] centered on the optical axis C is equally divided. For example, the Nomalski prism 32 is divided into four fan-shaped divided pieces 32a to 32d having a central angle of 90 [deg]. Each of the divided pieces 32a to 32d separates two linearly polarized light in a direction orthogonal to the bisector of the central angle.

Therefore, the directions in which the divided pieces 32a and 32c facing each other across the optical axis C are separated are parallel, and the directions in which the divided pieces 32b and 32d are separated are parallel. The direction in which the divided pieces 32a to 32d are separated is orthogonal to the direction in which the adjacent divided pieces 32a to 32d are separated. That is, the direction in which the divided pieces 32a and 32c are separated is orthogonal to the direction in which the divided pieces 32b and 32d are separated.

The analyzer 44 is also divided into divided pieces 44a to 44d as the Nomalski prism 32 is divided. The detector 44 includes a plurality of fan-shaped divided pieces having a central angle obtained by equally dividing the rotation angle of one rotation around the optical axis C in a plane orthogonal to the optical axis C of the transmitted reflected light R1. There is. Specifically, the analyzer 44 is divided into four fan-shaped divided pieces 44a to 44d having a central angle of 90 [deg].

The divided pieces 44a to 44d correspond to the divided pieces 32a to 32d. The reflected light R1 transmitted through the divided pieces 32a to 32d is incident on the divided pieces 44a to 44d. Therefore, each of the divided pieces 44a to 44d transmits the two linearly polarized light separated by the divided pieces 32a to 32d and the reflected light R1 in the polarization direction inclined by 45 degrees.

The polarizer 18 also includes a plurality of fan-shaped divided pieces having a central angle obtained by equally dividing the rotation angle of one rotation around the optical axis C in a plane orthogonal to the optical axis C direction of the transmitted illumination light L1. I'm out. Specifically, the polarizer 18 is divided into four fan-shaped dividing pieces 18a to 18d having a central angle of 90 [deg]. The divided pieces 18a to 18d correspond to the divided pieces 32a to 32d. The reflected light R1 transmitted through the divided pieces 18a to 18d and reflected by the sample 50 is incident on the divided pieces 32a to 32d.

In the pupil plane on the image detector 42, the central portion is the reflected light R1 when the illumination light L1 is incident perpendicularly to the sample 50. On the other hand, on the pupil surface, the peripheral portion is the reflected light R1 when the illumination light L1 is incident on the sample 50 at an angle. In the measurement by the ellipsometer 2, when the incident angle of the illumination light L1 with respect to the sample 50 changes, the ellipsometry coefficients Ψ and Δ also change.

Therefore, in the present embodiment, the Nomalski prism 32 is divided into four so that the separation direction is orthogonal to the bisector of the central angle of each of the divided pieces 32a to 32d. As a result, the separation direction has a portion that is tangential to the cylinder centered on the optical axis C. When fitting the above equation (1) to the interference fringes of the reflected light R1, the equation (1) is fitted to a profile in a certain range. In that case, in order to make the incident angle of the illumination light L1 constant, it is preferable to use a profile of interference fringes along the tangential direction of the cylinder centered on the optical axis C.

FIG. 9 is a diagram illustrating interference fringes of reflected light that interfered on the image detector in the ellipsometer according to the second embodiment. FIG. 10 is a diagram illustrating interference fringes on the image detector in the ellipsometer according to the second embodiment, and shows the intensities of the AA line and the BB line of FIG.

As shown in FIGS. 9 and 10, in the ellipsometer 2 of the present embodiment, the direction in which the interference fringes of the four divided pieces 32a to 32d are lined up is the optical axis C as shown by the AA line and the BB line of FIG. It has a portion along the tangential direction of the cylinder as the central axis. Then, as shown in FIG. 10, it is possible to fit the reflected light having a substantially constant incident angle at which the illumination light L1 is incident on the sample 50. Therefore, the ellipsometry coefficients Ψ and Δ can be measured accurately.

As shown in FIG. 10, the phase difference (Δ) is obtained from the position of the interference fringes. Further, the intensity ratio (Ψ) can be obtained from the AC / DC ratio of the interference fringes. In the present embodiment, the Nomalski prism 32 and the like are divided into four, but the present invention is not limited to this, and the Nomalski prism 32 and the like may be divided into eight or sixteen. Other configurations and effects are included in the description of Embodiment 1.

(Embodiment 3)
Next, the ellipsometer according to the third embodiment will be described. FIG. 11 is a configuration diagram illustrating an ellipsometer according to the third embodiment. As shown in FIG. 11, the ellipsometer 3 does not include a monochromator. Other configurations are the same as the configuration of the ellipsometer 2 of the second embodiment.

In the ellipsometer 3 of the present embodiment, the illumination light L1 is white light. When the illumination light L1 is monochromatic light as in the ellipsometers of the first and second embodiments, the interference fringes having the same phase are measured. On the other hand, when the illumination light L1 is white light, the contrast becomes stronger only where the phases are aligned.

FIG. 12 is a diagram illustrating interference fringes of reflected light that interfered on the image detector in the ellipsometer according to the third embodiment. The lower part of FIG. 12 shows the intensity along the AA'line. FIG. 13 shows, in the ellipsometer according to the third embodiment, Fourier transform the intensity distribution of the interference fringes of the reflected light that interfered on the image detector, divide the frequency into a real part representing the amplitude and an imaginary part representing the phase, and divide the frequency into the illumination light. It is a graph which illustrated the result associated with the wavelength of L1.

As shown in FIG. 12, for example, the interference fringes along the tangential direction of the cylinder centered on the optical axis C have a large contrast in the central portion where the optical path difference between the two interfering linearly polarized light components is small. The contrast is small at both ends. In the present embodiment, the image processing unit 43 Fourier transforms the interference fringes and calculates the ellipsometry coefficient from the Fourier transformed interference fringes.

The illumination light L1 of the present embodiment is white light and includes various wavelengths. The period of the interference fringes also changes depending on the wavelength contained in the white light. Therefore, as shown in FIG. 13, the intensity of the component of each wavelength and the phase of each wavelength are extracted by the Fourier transform by the Fourier transform. As a result, the ellipsometry coefficients Ψ and Δ are obtained for each wavelength.

According to this embodiment, the monochromator 12 can be eliminated. Therefore, the device can be simplified and the cost can be reduced. In addition, it is not necessary to switch the monochromator when measuring at various wavelengths. Therefore, the measurement time can be shortened. Other configurations and effects are included in the description of embodiments 1 and 2.

(Embodiment 4)
Next, the ellipsometer according to the fourth embodiment will be described. In the ellipsometer of the present embodiment, the polarizing beam splitter 45 is arranged in place of the analyzer 41 in the light receiving optical system 40. Hereinafter, description will be made with reference to the drawings.

FIG. 14 is a configuration diagram illustrating an ellipsometer according to the fourth embodiment. As shown in FIG. 14, the light receiving optical system 40 of the ellipsometer 4 includes a polarization beam splitter 45 and two image detectors 42a and 42b.

The analyzer 41 of the above-described first embodiment interferes by transmitting the 45 [deg] components of two linearly polarized light separated in the polarization directions of 0 [deg] and 90 [deg] by, for example, the polarizing optical element 30. It is something that makes you. In this case, the analyzer 41 absorbs or reflects the 135 [deg] component.

On the other hand, the polarization beam splitter 45 of the present embodiment is arranged so as to reflect the 45 [deg] component and transmit the 135 [deg] component. In this way, the polarization beam splitter 45 reflects two linearly polarized light components in a direction different from each polarization direction and transmits two linearly polarized light components in a direction orthogonal to the different directions. Specifically, of the linearly polarized light separated by the polarizing optical element 30, the linearly polarized light in the direction tilted by 45 [deg] is reflected, and the linearly polarized light in the direction tilted by 135 [deg] is transmitted.

The image detector 42 includes image detectors 42a and 42b. The image detector 42a detects interference fringes of each polarization component (in the 45 [deg] direction) reflected by the polarization beam splitter 45. The image detector 42b detects interference fringes of each polarization component (in the 135 [deg] direction) transmitted through the polarization beam splitter 45.

FIG. 15 is a diagram illustrating the interference fringes of the reflected light R1 that interfered on the two image detectors in the ellipsometer according to the fourth embodiment. As shown in FIG. 15, interference fringes having a phase inverted by 180 [deg] are formed on the image detectors 42a and 42.

FIG. 16 shows each component when the polarization directions reflected and transmitted by the polarization beam splitter are shifted from 45 [deg] with respect to the two linear directions separated by the polarizing optical element in the ellipsometer according to the fourth embodiment. It is an illustrated figure.

As shown in FIG. 16, a case where the strength of the component in the X direction and the strength of the component in the Y direction are different, for example, the case where the strength of the component in the X direction is 2 and the strength of the component in the Y direction is 1, is examined. When the polarization directions reflected and transmitted by the polarizing beam splitter 45 are shifted from 45 [deg] to 40 [deg] with respect to the two linear directions separated by the polarizing optical element 30, the component in the X direction becomes large. , The component in the Y direction becomes smaller. Therefore, the difference between the component in the X direction and the component in the Y direction becomes larger and larger, and the contrast decreases.

On the other hand, when it is shifted from 135 [deg] to 130 [deg], the component in the X direction becomes small and the component in the Y direction becomes large. Therefore, the difference between the component in the X direction and the component in the Y direction becomes small, and the contrast increases. In the first embodiment, when the intensity of one of the two linearly polarized light separated by the polarizing optical element 30 decreases, the contrast decreases. In this case, it is not possible to measure which linearly polarized light is reduced. However, in the present embodiment, it is possible to determine which linearly polarized light is reduced.

In FIG. 14, the reflected light R1 reflected and transmitted by the polarizing beam splitter 45 travels in two directions in a plane parallel to the paper surface, but actually travels in a direction tilted by 45 [deg]. Other configurations and effects are included in the description of Embodiments 1-3.

(Embodiment 5)
Next, the ellipsometer according to the fifth embodiment will be described. The ellipsometer of the present embodiment uses a polarization beam splitter in which two triangular prisms are joined instead of the polarization beam splitter of the fourth embodiment.

FIG. 17 is a configuration diagram illustrating an ellipsometer according to the fifth embodiment. As shown in FIG. 17, in the ellipsometer 5 of the fifth embodiment, the light receiving optical system 40 has a polarization beam splitter in which two triangular prisms 46 and 47 are joined. The two triangular prisms 46 and 47 bottom a right triangle. The triangular prism 46 has two side surfaces 46a and 46c that sandwich the right-angled edge, and side surfaces 46b that face the edge, and the angles of the vertices other than the right angle are 30 [deg] and 60 [deg]. The triangular prism 47 has two side surfaces 47a and 47c sandwiching a right-angled edge and side surfaces 47b facing the edge, and is line-symmetrical with the triangular prisms 46 and 47a as axes. The side surface 46a of the triangular prism 46 and the side surface 47a of the triangular prism 47 are joined. Of the linearly polarized light separated by the polarizing optical element 30, the side surfaces 46a and 47a, which are the joining surfaces, reflect, for example, the linearly polarized light in the direction inclined by 45 [deg], and the linearly polarized light in the direction inclined by 135 [deg]. To be transparent.

The reflected light R1 is incident from the side surface 46b of the triangular prism 46. When incident, the polarizing beam splitter is installed so that the optical axis C of the reflected light R1 is orthogonal to the side surface 46b. The incident reflected light R1 is reflected and transmitted on the side surfaces 46a and 47a which are the joint surfaces. The reflected reflected light R1 is reflected by the side surface 46b of the triangular prism. In this case, if the glass material of the triangular prism 46 is appropriately selected, the reflected light R1 is totally reflected on the side surface 46b. The reflected light R1 reflected by the side surface 46b is emitted from the side surface 46c of the triangular prism 46.

The reflected light R1 transmitted through the side surfaces 46a and 47a, which are the joint surfaces, is reflected by the side surface 47b of the triangular prism 47. Also in this case, by appropriately selecting the glass material of the triangular prism 47, the reflected light R1 is totally reflected on the side surface 47b. The reflected light R1 reflected by the side surface 47b is emitted from the side surface 47c of the triangular prism 47.

As described above, the polarized beam splitter of the present embodiment reflects two linearly polarized light components in a direction different from each polarization direction (for example, 45 [deg] direction) and is orthogonal to each direction (for example, 135). [Deg]) allows the two linearly polarized light components to pass through. Then, the polarization beam splitter emits each reflected component and each transmitted component onto the pupil surface of the same image detector 42. For example, a polarizing beam splitter emits each reflected component and each transmitted component in the same direction.

With such a configuration, the reflected light R1 reflected and transmitted by the polarizing beam splitter is emitted from the side surfaces 46c and 47c of the two triangular prisms 46 and 47. Therefore, one image detector 42 can receive the reflected light R1.

Further, as in the fourth embodiment, when the polarization directions reflecting and transmitting the polarizing beam splitter are deviated from 45 [deg] with respect to the two linear directions separated by the polarizing optical element 30, the two linear directions The intensity ratio of can be easily obtained. Therefore, it is possible to measure which linearly polarized light is lowered. Other configurations and effects are included in the description of Embodiments 1 to 4.

(Embodiment 6)
Next, the ellipsometer according to the sixth embodiment will be described. The ellipsometer of the present embodiment obliquely incident the illumination light. Then, the sample is point-illuminated, and the image detector is placed at the pupil position of the objective lens.

FIG. 18 is a configuration diagram illustrating an ellipsometer according to the sixth embodiment. As shown in FIG. 18, the ellipsometer 6 of the present embodiment includes an illumination optical system 10, a condensing optical system 20, a polarizing optical element 30, and a light receiving optical system 40.

The illumination optical system 10 illuminates the sample 50 with illumination light L1 including linearly polarized light. The illumination optical system 10 includes a light source 11, a monochromator 12, a fiber 13, an illumination lens 14, and a polarizer 15. Unlike the first embodiment, it does not have a beam splitter 16 and an objective lens 17. Further, the optical axis C of the illumination light L1 incident on the sample 50 is inclined with respect to the sample 50.

The illumination light L1 generated from the light source 11 is incident on the monochromator 12. The monochromator 12 extracts monochromatic light having a specific wavelength from the incident illumination light L1 and emits it to the fiber 13. The monochromator 12 selects and emits monochromatic light having a predetermined wavelength in the range from ultraviolet light to infrared light as the illumination light L1. The illumination light L1 incident on one end of the fiber 13 is emitted from the other end of the fiber 13. The illumination light L1 emitted from the other end of the fiber 13 is incident on the illumination lens 14.

The illumination lens 14 illuminates the sample 50 by condensing the incident illumination light L1 in a point shape through the polarizing element 15. The polarizer 15 receives the illumination light L1 generated from the light source 11 and transmits the illumination light L1 including linearly polarized light in one direction. Therefore, the illumination lens 14 spot-illuminates one point of the sample 50 with the illumination light L1 including linearly polarized light.

The condensing optical system 20 includes a condensing lens 23. The condenser lens 23 transmits the reflected light R1 reflected by the sample 50 by the illumination light L1 and causes the illumination light L1 to enter the polarizing optical element 30. The optical axis C of the reflected light reflected by the sample 50 is inclined with respect to the measurement surface of the sample 50. The image detector 42 is arranged at the pupil conjugate position 19b of the condenser lens 23. The other configurations of the polarizing optical element 30 and the light receiving optical system 40 are the same as those in the first embodiment.

According to the ellipsometer 6 of the present embodiment, the ellipsometry coefficients Ψ and Δ can be directly measured even in the oblique incident configuration often seen in a general ellipsometer. Other configurations and effects are included in the description of embodiments 1-5.

(Embodiment 7)
Next, the ellipsometer according to the seventh embodiment will be described. The ellipsometer of the present embodiment is an illumination lens that irradiates a surface and measures a region having a spread on a sample. FIG. 19 is a configuration diagram illustrating an ellipsometer according to the seventh embodiment.

As shown in FIG. 19, in the ellipsometer 7 of the present embodiment, the illumination lens 14 does not spot-irradiate the sample 50, but surface-irradiates the sample 50. That is, the illumination lens 14 illuminates the region having a predetermined spread in the sample 50 with the illumination light L1. For example, the illumination lens 14 illuminates the sample 50 with the illumination light L1 as parallel light. The image detector 42 is not arranged at the pupil position, but at the image position 52 formed by the condenser lens 23 of the sample 50. For example, the image detector 42 is arranged at an angle with respect to the optical axis C so as to satisfy the conditions of Scheimpflug. The image detector 42 measures a wide area on the sample 50.

In the ellipsometer 7 of the present embodiment, since the incident angle at which the illumination light L1 is incident on the sample 50 is constant, the image detector 42 arranged at the image position 52 can detect the interference fringes as an image. Other configurations and effects are included in the description of embodiments 1-6.

(Embodiment 8)
Next, the ellipsometer according to the eighth embodiment will be described. In the ellipsometer of the present embodiment, instead of arranging the Nomalski prism in the pupil space, a beam displacer is arranged in the image space. The pupil space is a space in which the reflected light of the illumination light illuminating one point on the sample 50 is parallel, and the image space is a space in which the reflected light is condensed / diffused.

FIG. 20 is a configuration diagram illustrating an ellipsometer according to the eighth embodiment. FIG. 21 is a configuration diagram illustrating a polarizing optical element and a light receiving optical system in the ellipsometer according to the eighth embodiment. As shown in FIGS. 20 and 21, in the ellipsometer 8 of the eighth embodiment, the polarizing optical element 30 is a beam displacer 33.

The beam displacer 33 is arranged in the image space between the relay lens 21 and the relay lens 22. Specifically, the beam displacer 33 is arranged between the focal point of the relay lens 22 and the relay lens 22. Therefore, it is arranged in the region where the reflected light R1 is emitted.

The beam displacer 33 separates the reflected light R1 reflected by the illumination light L1 including linearly polarized light in the sample 50 into two linearly polarized light in the polarization directions orthogonal to each other. Then, when the beam displacer 33 emits two separated linearly polarized light, one linearly polarized light is shifted in parallel and emitted. The reflected light R1 including the two linearly polarized light emitted from the beam displacer 33 is incident on the relay lens 22.

The relay lens 22 collects the incident reflected light R1 on the image detector 42 via the analyzer 41. Specifically, the relay lens 22 emits the separated linearly polarized light in the X direction and the linearly polarized light in the Y direction so as to be at the same point again on the image detector.

The detector 41 transmits two linearly polarized light components in the polarization direction in the X direction and the polarization direction in the Y direction separated by the beam displacer 33, and in the direction tilted by 45 [deg]. Therefore, the two linearly polarized light orthogonal to each other are emitted as polarized light components polarized in the same direction (45 [deg] tilted direction) by passing through the analyzer 41. The reflected light R1 including the polarization component emitted from the detector 41 is incident on the image detector 42.

According to the ellipsometer 8 of the present embodiment, the beam displacer 33 can be used as the polarizing optical element 30. Therefore, the polarizing optical element 30 can be arranged in the image space instead of being arranged in the pupil space. Other configurations and effects are included in the description of embodiments 1-7.

(Embodiment 9)
Next, the semiconductor device inspection device according to the ninth embodiment will be described. The semiconductor device inspection device of the present embodiment includes the ellipsometer according to the first to eighth embodiments. Therefore, the semiconductor device inspection device of the present embodiment can shorten the time required for the semiconductor device inspection. Moreover, the inspection accuracy can be improved. Furthermore, it contributes to the reduction of the size of the semiconductor device. Other configurations and effects are included in the description of embodiments 1-8.

The present invention is not limited to the above-described embodiment, and can be appropriately modified without departing from the spirit. For example, the configurations of embodiments 1-9 can be combined with each other.

1, 2, 3, 4, 5, 6, 7, 8 Ellipsometer 10 Illumination optics 11 Light source 12 Monochrome meter 13 Fiber 14 Illumination lens 15, 18 Polarizer 18a, 18b, 18c, 18d Split piece 16 Beam splitter 17 Objective lens 19a Eye position 19b Eye conjugate position 20 Condensing optical system 21, 22 Relay lens 23 Condensing lens 30 Polarizing optical element 31, 32 Nomalski prism 32a, 32b, 32c, 32d Divided piece 33 Beam displacer 40 Light receiving optical system 41, 44 Photons 42, 42a, 42b Image detector 43 Image processing unit 44a, 44b, 44c, 44d Divided piece 45 Polarized beam splitter 46, 47 Triangular prism 46a, 46b, 46c, 47a, 47b, 47c Side 50 Sample 52 Image position L1 Illumination light R1 reflected light

Claims (20)

A polarized optical element that separates the reflected light reflected by the sample from the illumination light including linearly polarized light into two linearly polarized light in the polarization directions orthogonal to each other.
A light receiving optical system that calculates an ellipsometry coefficient from interference fringes in which the two linearly polarized light components interfere with each other in a direction different from the polarization direction.
Ellipsometer with. A light source that produces illumination light and
A polarizer in which the illumination light generated from the light source is incident and transmits the illumination light including linearly polarized light in one direction.
An objective lens that illuminates the sample with the illumination light containing the linearly polarized light and transmits the reflected light reflected by the sample.
With more
The light receiving optical system is
An image detector that detects the interference fringes and
An image processing unit that calculates the ellipsometry coefficient from the interference fringes,
Have,
The ellipsometer according to claim 1. The optical axis of the illumination light incident on the sample and the optical axis of the reflected light reflected by the sample are orthogonal to the sample.
The ellipsometer according to claim 2. The objective lens illuminates the sample by condensing the illumination light in a point shape.
The image detector was arranged at a pupil conjugate position conjugate with the pupil position of the objective lens.
The ellipsometer according to claim 2 or 3. A light source that produces illumination light and
A polarizer in which the illumination light generated from the light source is incident and transmits the illumination light including linearly polarized light in one direction.
An illumination lens that illuminates the sample with the illumination light containing the linearly polarized light,
A condenser lens that transmits the reflected light reflected by the sample and the illumination light.
With more
The light receiving optical system is
An image detector that detects the interference fringes and
An image processing unit that calculates the ellipsometry coefficient from the interference fringes,
Have,
The ellipsometer according to claim 1. The optical axis of the illumination light incident on the sample and the optical axis of the reflected light reflected by the sample were inclined with respect to the sample.
The ellipsometer according to claim 5. The illumination lens illuminates the sample by condensing the illumination light in a point shape.
The image detector was arranged at the pupil position of the condenser lens.
The ellipsometer according to claim 5 or 6. The illumination lens illuminates the sample by condensing the illumination light on a region having a predetermined spread in the sample.
The image detector was placed at the image position of the sample.
The ellipsometer according to claim 5 or 6. The light-receiving optical system further includes an analyzer that transmits the two linearly polarized light components in each of the polarization directions and a direction tilted by 45 [deg].
The image detector detects the interference fringes of each of the components that have passed through the analyzer.
The ellipsometer according to any one of claims 2 to 8. The light receiving optical system has a polarization beam splitter that reflects the two linearly polarized light components in a direction different from each polarization direction and transmits the two linearly polarized light components in a direction orthogonal to the different directions. ,
The image detector
A first image detector that detects the interference fringes of each of the components reflected by the polarization beam splitter, and
A second image detector that detects the interference fringes of each of the components transmitted through the polarization beam splitter, and
including,
The ellipsometer according to any one of claims 2 to 8. The light receiving optical system has a polarization beam splitter that reflects the two linearly polarized light components in a direction different from each polarization direction and transmits the two linearly polarized light components in a direction orthogonal to the different directions. ,
The polarization beam splitter emits each reflected component and each transmitted component onto the same image detector.
The ellipsometer according to any one of claims 2 to 8. The polarizing optical element is a Nomalski prism.
The ellipsometer according to any one of claims 1 to 11. The Nomalski prism includes a plurality of fan-shaped divided pieces having a central angle obtained by equally dividing the rotation angle of one rotation around the optical axis in a plane orthogonal to the optical axis of the reflected light.
Each of the divided pieces separates the two linearly polarized light in a direction orthogonal to the bisector of each of the central angles.
The ellipsometer according to claim 12. The polarizing optical element includes a Wollaston prism or a lotion prism.
The ellipsometer according to any one of claims 1 to 11. The polarized optical element is a beam displacer that shifts one linearly polarized light in parallel and emits it when emitting the two separated linearly polarized light.
The ellipsometer according to any one of claims 1 to 11. The illumination light is monochromatic light.
The ellipsometer according to any one of claims 1 to 15. The illumination light is white light.
The light receiving optical system is
An image detector that detects the interference fringes and
An image processing unit that Fourier transforms the interference fringes and calculates the ellipsometry coefficient from the Fourier transformed interference fringes.
Have,
The ellipsometer according to any one of claims 1 to 15. The illumination light including the linearly polarized light is fully polarized linearly polarized light.
The ellipsometer according to any one of claims 1 to 17. The illumination light including the linearly polarized light is completely polarized elliptically polarized light.
The ellipsometer according to any one of claims 1 to 17. An inspection device for a semiconductor device including the ellipsometer according to any one of claims 1 to 19.

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