Spectroscopic ellipsometer

Abstract

To reduce a measurement time required for thickness measurement of a semiconductor wafer, and more accurately measure optical characteristics of reduced regions.SOLUTION: A spectroscopic ellipsometer according to the invention comprises: a mounting table on which a sample is placed; a light source; irradiation means for irradiating at least two or more target areas provided on the sample with inspection light using light from the light source; and a photodetector splitting and receiving the inspection light reflected on the at least two or more target areas. The irradiation means preferably is a transmission type mask including a plurality of transmission surfaces corresponding to the at least two or more target areas, in addition to a reflection type mask or a reflecting mirror including a plurality of reflection surfaces corresponding respectively to the at least two or more target areas.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a spectroscopic ellipsometer for measuring, for example, the thickness and optical properties of a thin film on the surface of a semiconductor wafer.

Background Art

[0002] Conventionally, ellipsometry (polarization analysis technique) is known as a technique for measuring the optical properties of substances. Ellipsometry measures the change in the polarization state when the inspection light is reflected by a substance, and determines the optical properties of the substance from the measured change in the polarization state. The change in the polarization state is measured as the ratio (amplitude reflection coefficient ratio) ρ of the amplitude reflection coefficient rp of p-polarized light to the amplitude reflection coefficient rs of s-polarized light. The ratio ρ of the amplitude reflection coefficient rp of p-polarized light to the amplitude reflection coefficient rs of s-polarized light is expressed as ρ = tan(Ψ)·exp(iΔ) by using two ellipsometry angles Ψ and Δ. The two ellipsometry angles Ψ and Δ depend on the optical properties of individual substances. Therefore, an ellipsometer using ellipsometry is used for measuring the optical properties and film thickness of thin films in, for example, the semiconductor field (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, semiconductor wafers require the formation of thin films of single materials or compound materials while maintaining their purity on a high-purity silicon (Si) substrate, for example, in a vacuum. Therefore, if minute dust or contaminating gases are present in the space that should be a vacuum when the thin film is deposited on the substrate, the semiconductor wafer obtained through the deposition process will be treated as a defective product. Thus, in the semiconductor wafer inspection process, in addition to checking the operation of semiconductor circuits formed in each of the multiple regions used as a semiconductor chip, the film thickness of multiple test pads provided in each of the regions used as a semiconductor chip is measured. This film thickness measurement requires measuring each test pad for each region. Here, the test pads mentioned above are, for example, 50 × 50 μm in size, but with the advancement of semiconductor chips, there is a demand for smaller test pads. Therefore, there is a need for technology to accurately measure film thickness using smaller test pads.

[0005] This invention has been made in view of the above problems, and its objective is to provide a technology that shortens the measurement time for measuring the film thickness of a semiconductor wafer and enables more accurate measurement of optical properties in a reduced area. [Means for solving the problem]

[0006] To solve the above problems, the spectroscopic ellipsometer of the present invention is characterized by comprising: a mounting stage on which a sample is placed; a light source; an irradiation means for irradiating the sample with inspection light directed toward at least two or more target areas using light from the light source; and a photodetector for spectrally detecting and receiving the inspection light reflected from the at least two or more target areas.

[0007] Furthermore, the irradiation means is characterized by being a reflective mask or mirror having a plurality of reflective surfaces corresponding to each of the at least two target regions. Here, the inspection light is reflected off the mask or mirror and projected onto the sample. When the inspection light is irradiated onto the sample from an oblique angle, in order to focus the inspection light onto the surface of the sample, the arrangement of the reflective surfaces of the mask or mirror and the surface of the sample must satisfy the shine-proof condition. In this case, it is preferable that the reflective mask or mirror is positioned such that the at least two target regions and the reflective surfaces corresponding to each of the at least two target regions are in a conjugate relationship, and that the projection magnification of the inspection light onto the surface of the sample is equal.

[0008] Furthermore, the irradiation means is characterized by being a transmissive mask having a transmissive surface corresponding to each of the at least two target regions. In this case, it is preferable that the transmissive mask is positioned such that the at least two target regions and the transmissive surface corresponding to each of the at least two target regions are in a conjugate relationship, and that the projection magnification of the inspection light onto the surface of the sample is equal.

[0009] Furthermore, the sample is a semiconductor wafer, and the target region is characterized by being a plurality of test pads provided within a region corresponding to a semiconductor chip provided on the semiconductor wafer.

[0010] Furthermore, the photodetector is characterized by having a collimator lens that passes through the intersection of a conjugate plane, which is in a conjugate relationship with the surface of the sample, and the optical axis of the inspection light reflected from the sample, and has an optical axis perpendicular to the conjugate plane, and emits the incident inspection light as parallel light.

[0011] Furthermore, the photodetector comprises a collimator lens that emits the inspection light as parallel light, and a prism that spectrally separates the inspection light from the collimator lens, wherein the collimator lens is positioned such that its image field curvature characteristics align with a conjugate plane that is conjugate to the surface of the sample, and the optical axis of the collimator lens is offset from the optical axis of the inspection light.

[0012] Furthermore, the photodetector comprises a concave mirror that emits the inspection light as parallel light, and a prism that spectrally separates the inspection light from the concave mirror, wherein the optical axis of the concave mirror is offset from the optical axis of the inspection light, such that the image field curvature characteristics of the concave mirror are aligned with a conjugate surface that is conjugate to the surface of the sample. [Effects of the Invention]

[0013] This method allows for a reduction in the measurement time required for measuring the film thickness of semiconductor wafers, and enables more accurate measurement of optical properties in a reduced area. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram showing an example of the configuration of an ellipsometer in the first embodiment. [Figure 2] This is an explanatory diagram showing an example of the arrangement of reflective surfaces provided on a mask. [Figure 3] This is a plan view of a semiconductor wafer in which multiple chip regions are formed in a two-dimensional manner. [Figure 4] (a) is an example of the arrangement of a chip region and test pads provided on a semiconductor wafer, (b) is an example of a chip region in which one of the test pads arranged in the X-axis direction is offset in the Y-axis direction, and (c) is an explanatory diagram showing an example of a chip region in which one of the test pads is positioned offset in both the X-axis and Y-axis directions. [Figure 5] This is a schematic diagram showing an example of the configuration of a photodetector. [Figure 6] This is an explanatory diagram showing an example of collimator lens arrangement when the optical axis of the collimator lens is perpendicular to the conjugate plane and the optical axis of the collimator lens passes through the intersection of the conjugate plane and the optical axis of the reflected light. [Figure 7] This is an explanatory diagram showing an example of collimator lens arrangement when the optical axis of the collimator lens is perpendicular to the conjugate plane and the center of the collimator lens is located at [location]. [Figure 8]FIG. 0 is a diagram showing an example of a photodetector in which a collimator lens is arranged with its optical axis shifted from the optical axis of inspection light along the image plane curvature characteristic on a conjugate plane in conjugate relation with the surface of a sample. [Figure 9] FIG. 3 is a diagram showing an example of a photodetector in which a concave mirror is arranged with its optical axis shifted from the optical axis of inspection light along the image plane curvature characteristic on a conjugate plane in conjugate relation with the surface of a sample. [Figure 10] FIG. 6 is a diagram showing that inspection light emitted from mask 16 is irradiated obliquely onto a 1×2 mm area of the surface of sample S. [Figure 11] FIG. 9 is a diagram showing the streak ratio when light beams emitted from points P1 to P9 are focused on a light receiving surface when using each inspection light with wavelengths λ = 365, 436, 588, 656, 707, 1014 nm, in a case where a collimator lens is arranged with its optical axis shifted from the optical axis of inspection light along the image plane curvature characteristic of the collimator lens on a conjugate plane in conjugate relation with the surface of a sample, and the irradiation angle θ at which the inspection light irradiates the surface of the sample is θ = 50°. [Figure 12] FIG. 12 is a diagram showing the streak ratio when light beams emitted from points P1 to P9 are focused on a light receiving surface when using each inspection light with wavelengths λ = 365, 436, 588, 656, 707, 1014 nm, in a case where a collimator lens is arranged with its optical axis shifted from the optical axis of inspection light along the image plane curvature characteristic of the collimator lens on a conjugate plane in conjugate relation with the surface of a sample, and the irradiation angle θ at which the inspection light irradiates the surface of the sample is θ = 55°. [Figure 13] FIG. 15 is a diagram showing the streak ratio when light beams emitted from points P1 to P9 are focused on a light receiving surface when using each inspection light with wavelengths λ = 365, 436, 588, 656, 707, 1014 nm, in a case where a collimator lens is arranged with its optical axis shifted from the optical axis of inspection light along the image plane curvature characteristic of the collimator lens on a conjugate plane in conjugate relation with the surface of a sample, and the irradiation angle θ at which the inspection light irradiates the surface of the sample is θ = 60°. [Figure 14]This is a diagram showing the streak ratio when the light beams emitted from point P1 to point P9 are focused on the light-receiving surface when using each inspection light with wavelengths λ = 365, 436, 588, 656, 707, 1014 nm, in a case where a collimator lens is arranged with its optical axis shifted from the optical axis of the inspection light in a form along the image surface curvature characteristic of the collimator lens on a conjugate surface in conjugate relation with the surface of the sample, and the irradiation angle θ at which the inspection light irradiates the surface of the sample is θ = 65°. [Figure 15] This is a diagram showing the streak ratio when the light beams emitted from point P1 to point P9 are focused on the light-receiving surface when using each inspection light with wavelengths λ = 365, 436, 588, 656, 707, 1014 nm, in a case where a collimator lens is arranged with its optical axis shifted from the optical axis of the inspection light in a form along the image surface curvature characteristic of the collimator lens on a conjugate surface in conjugate relation with the surface of the sample, and the irradiation angle θ at which the inspection light irradiates the surface of the sample is θ = 70°. [Figure 16] This is a diagram showing the streak ratio when the light beams emitted from point P1 to point P9 are focused on the light-receiving surface when using each inspection light with wavelengths λ = 365, 436, 588, 656, 707, 1014 nm, in a case where a concave mirror is arranged with its optical axis shifted from the optical axis of the inspection light in a form along the image surface curvature characteristic of the concave mirror on a conjugate surface in conjugate relation with the surface of the sample, and the irradiation angle θ at which the inspection light irradiates the surface of the sample is θ = 50°. [Figure 17] This is a diagram showing the streak ratio when the light beams emitted from point P1 to point P9 are focused on the light-receiving surface when using each inspection light with wavelengths λ = 365, 436, 588, 656, 707, 1014 nm, in a case where a concave mirror is arranged with its optical axis shifted from the optical axis of the inspection light in a form along the image surface curvature characteristic of the concave mirror on a conjugate surface in conjugate relation with the surface of the sample, and the irradiation angle θ at which the inspection light irradiates the surface of the sample is θ = 55°. [Figure 18]This figure shows the Strehr ratio when the light beam emitted from point P1 to point P9 is focused onto the light-receiving surface, when the optical axis of the concave mirror is offset from the optical axis of the inspection light, and the irradiation angle θ at which the inspection light is irradiated onto the surface of the sample is θ = 60°, and inspection light wavelengths λ = 365, 436, 588, 656, 707, 1014 nm are used. [Figure 19] This figure shows the Strehr ratio when the light beam emitted from point P1 to point P9 is focused onto the light-receiving surface, when the optical axis of the concave mirror is offset from the optical axis of the inspection light, and the irradiation angle θ at which the inspection light is irradiated onto the surface of the sample is θ = 65°, and inspection light with wavelengths λ = 365, 436, 588, 656, 707, and 1014 nm is used. [Figure 20] This figure shows the Strehr ratio when the light beam emitted from point P1 to point P9 is focused onto the light-receiving surface, when the optical axis of the concave mirror is offset from the optical axis of the inspection light, and the irradiation angle θ at which the inspection light is irradiated onto the surface of the sample is θ = 70°, and inspection light with wavelengths λ = 365, 436, 588, 656, 707, and 1014 nm is used. [Modes for carrying out the invention]

[0015] The following describes a spectroscopic ellipsometer to which the present invention is applied, based on the drawings. Since the present invention concerns the device configuration of a spectroscopic ellipsometer, the explanation of ellipsometry (polarization analysis technique) will be omitted.

[0016] A spectroscopic ellipsometer is a device that measures the change in polarization state of the inspection light incident on the surface of an object and the change in polarization state of the inspection light reflected from the surface of the object, thereby measuring the optical properties of the object's surface and the thickness of a thin film on the object's surface. Hereafter, the object to be measured with a spectroscopic ellipsometer will be referred to as the sample. The following explanation will describe the measurement of the thickness of a thin film on the surface of a sample using a spectroscopic ellipsometer as an example.

[0017] As shown in Figure 1, the spectroscopic ellipsometer 10 includes a light source 15, a mask 16, an incident optical system 17, a mounting stage 18, an exit optical system 19, and a photodetector 20.

[0018] The light source 15 emits, for example, white light. Examples of the light source 15 include xenon lamps, incandescent bulbs, and halogen lamps.

[0019] The mask 16 is, for example, a reflective mask or a transmissive mask. The following description will explain the case where a reflective mask is used as the mask 16. The mask 16 reflects a portion of the white light emitted by the light source 15 at each of the multiple reflective surfaces RS. The white light reflected by the reflective surfaces RS is incident on the incident optical system 17 as inspection light. Although not shown in the diagram, the mask 16 is formed by stacking a reflective layer and a light-absorbing layer on the surface of the substrate in that order, and exposing a portion of the reflective layer to the outside to form the reflective surfaces RS.

[0020] As shown in Figure 2, multiple reflective surfaces RS are arranged in the X-axis direction in Figure 2, and each of the multiple reflective surfaces RS corresponds to each of the test pads TP(n) provided in the chip region A(x,y) of the semiconductor wafer 30. In other words, the number n of the multiple reflective surfaces RS (for example, n=1,2,...) is set to be the same as the number of test pads TP(n) provided in each of the chip regions A(x,y). Hereafter, the reflective surfaces will be referred to as RS(n). Although the mask 16 and the sample S are in a conjugate relationship, the shape and area of ​​the reflective surfaces are set so that when the reflective surfaces RS are projected onto the surface of the sample S, the image of the reflective surfaces RS(n) does not extend beyond the test pads TP(n). Here, the X-axis direction in Figure 2 is the same direction as the X-axis direction shown in Figure 1.

[0021] Returning to Figure 1, the incident optical system 17 includes a collimator lens 25, a polarizer 26, and a condenser lens 27. The collimator lens 25 makes the inspection light from the mask 16 into parallel light. The polarizer 26 polarizes the inspection light that has passed through the collimator lens 25. The condenser lens 27 focuses the inspection light polarized by the polarizer 26 toward the surface of the sample S on the mounting stage 18.

[0022] The spectroscopic ellipsometer 10 sets the magnification (hereinafter referred to as projection magnification) at which the inspection light from the mask 16 is projected onto the surface of the sample S to, for example, 1x. The spectroscopic ellipsometer 10 directs the inspection light onto the sample S at an oblique angle. When the position of the surface of the mask 16 that reflects the inspection light and the position of the surface of the sample S that is irradiated by the inspection light reflected from the mask 16 satisfy the Scheinproof condition, the inspection light reflected from the mask 16 is projected as an image that is focused on the surface of the sample S.

[0023] The mounting stage 18 holds and supports the sample S. Here, the surface of the sample S placed on the mounting stage 18 and the surface of the mask 16 are in a conjugate relationship. The mounting stage 18 has a moving mechanism (not shown in the figure) that allows the sample S placed on the mounting stage 18 to be moved on the XY plane in Figure 1.

[0024] The sample S held on the mounting stage 18 is, for example, a semiconductor wafer. As shown in Figure 3, the semiconductor wafer 30 is, for example, disc-shaped. The semiconductor wafer 30 has a plurality of chip regions A divided in two dimensions. Chip regions A are regions used as semiconductor chips when the semiconductor wafer 30 is cut. Hereinafter, the chip region A at the x-th row and y-th column will be referred to as A(x,y). Here, the X-axis direction shown in Figure 3 and the X-axis direction shown in Figure 1 are the same direction. The Y-axis direction shown in Figure 3 and the Y-axis direction shown in Figure 1 are the same direction.

[0025] As shown in Figure 4(a), the chip region A(x,y) includes, for example, a semiconductor circuit (not shown) and a plurality of test pads TP. Multiple test pads TP are arranged, for example, along the X-axis. The number of test pads TP is set to be the same as the number of reflective surfaces RS set by the mask 16. Hereinafter, the test pads will be referred to as TP(n).

[0026] Returning to Figure 1, the output optical system 19 includes a compensator 35, an analyzer 36, and a condenser lens 37. The compensator 35 rotates the inspection light about the optical axis L2 of the inspection light reflected from the surface of the sample S as its center of rotation, thereby shifting the phase of the inspection light reflected from the surface of the sample S. The analyzer 36 allows the inspection light that has undergone a phase shift by the compensator 35 to pass through, specifically the inspection light polarized at a particular angle. The condenser lens 37 focuses the inspection light that has passed through the analyzer 36 and directs it into the photodetector 20.

[0027] In this embodiment, the compensator 35 describes a case in which the inspection light reflected from the surface of the sample S is rotated around the optical axis L2 of the inspection light as the center of rotation to shift the phase of the inspection light. However, it is also possible to shift the phase of the inspection light in the analyzer 36 by rotating the inspection light reflected from the surface of the sample S around the optical axis L2 of the inspection light as the center of rotation. Furthermore, it is also possible to shift the phase of the inspection light by arranging a photoelastic modulator instead of the compensator 35.

[0028] The photodetector 20 detects the inspection light emitted from the output optical system 19. As shown in Figure 5, the photodetector 20 has a spectral optical system 41 and a light receiving unit 42. The spectral optical system 41 includes, for example, a collimator lens 45, a spectral prism 46, and an imaging lens 47. The collimator lens 45 makes the inspection light emitted from the condenser lens 37 of the output optical system 19 into parallel light. Alternatively, instead of using a collimator lens 45, a collimating mirror may be used to reflect the inspection light emitted from the condenser lens 37 toward the subsequent spectral prism 46. The spectral prism 46 spectrally separates and emits the inspection light emitted from the condenser lens 37. The imaging lens 47 images the inspection light emitted from the spectral prism 46 onto the light receiving unit 42.

[0029] The light-receiving unit 42 receives the inspection light spectrally separated by the spectral prism 46. The light-receiving unit 42 outputs a signal based on the received inspection light to an analysis device (not shown). Examples of the light-receiving unit 42 include a photodiode array in which photodiodes are arranged in a two-dimensional manner, and a CCD (Charge Coupled Device). In addition, the light-receiving unit 42 can also be a photodiode array in which multiple photodiodes are arranged in one direction, or a line CCD, which can be arranged in the same direction as the arrangement direction of the test pads TP on the semiconductor wafer 30 (for example, the X-axis direction in Figure 1).

[0030] The operation of the spectroscopic ellipsometer 10 will now be described. The spectroscopic ellipsometer 10 measures the optical properties of test pads TP(n) provided in each of the two-dimensionally arranged chip regions A(x,y) of a semiconductor wafer 30 placed on a mounting stage 18. For example, the spectroscopic ellipsometer 10 performs measurements on test pads TP(1) to TP(n) provided in the first row, first column chip region A(1,1). When the light source 15 emits white light, the emitted white light is reflected by each of the multiple reflective surfaces RS(n) provided on the mask 16. The reflected white light is incident on the incident optical system 17 as inspection light. The inspection light incident on the incident optical system 17 is polarized by the polarizer 26 of the incident optical system 17 and then incident on the surface of the semiconductor wafer 30, which is the sample S. That is, multiple test pads TP provided in the first row, first column chip region A(1,1) can be measured simultaneously.

[0031] As described above, the surface of the mask 16 and the surface of the semiconductor wafer 30 are conjugate, and the projection magnification of the incident inspection light is set to 1x. Also, the size of each reflective surface RS and the test pad TP are the same. Therefore, the light reflected from each reflective surface RS of the mask 16 is accurately projected onto each of the test pads TP(n) provided in the first row chip region A(1,1) of the semiconductor wafer 30.

[0032] The inspection light incident on the test pads TP(1) to TP(n) provided in the chip region A(1,1) of the semiconductor wafer 30 is reflected by the test pads TP(1) to TP(n) provided in the first row of chip region A(1,1) of the semiconductor wafer 30 and incident on the output optical system 19.

[0033] The inspection light incident on the output optical system 19 undergoes a phase transition by the compensator 35, and only the inspection light polarized to a specific angle by the analyzer 36 is incident on the photodetector 20. The photodetector 20 spectrally analyzes the incident inspection light and receives the light. As described above, the inspection light reflected from the semiconductor wafer 30 is the inspection light reflected from the test pads TP(1) to TP(n) provided in the chip region A(1,1) of the semiconductor wafer 30. Therefore, the light receiving unit 42 of the photodetector 20 receives the inspection light reflected from each of the test pads TP(1) to TP(n) provided in each of the chip regions A(1,1) of the semiconductor wafer 30. The light receiving unit 42 outputs a signal based on the received inspection light to an analysis device (not shown). As a result, the optical characteristics (including film thickness) of each of the test pads TP(1) to TP(n) are analyzed in the analysis device.

[0034] Once measurements have been completed on the test pads TP(1) to TP(n) located in the first row, first column chip region A(1,1) of the semiconductor wafer 30, the mounting stage 18 moves a predetermined amount, for example, in the Y-axis direction in Figure 1, to perform measurements on the test pads TP(1) to TP(n) located in the first row, second column chip region A(1,2). Once measurements have been completed on all test pads TP(n) located in the same row chip region A(1,y), the mounting stage 18 moves in the X-axis and Y-axis directions to perform measurements on the test pads TP(1) to TP(n) located in the second row, first column chip region A(2,1). In other words, among the multiple chip regions A(x,y) arranged in two dimensions, measurements are performed on the chip region A(x,y) located in the same row, then on the chip region A(x,y) located in the adjacent row, until measurements are performed on all chip regions A(x,y).

[0035] As described above, the spectroscopic ellipsometer 10 can simultaneously measure multiple test pads TP(n) located in a single chip region A(x,y), thus shortening the measurement time for a single chip region A(x,y). As described above, the spectroscopic ellipsometer 10 in this embodiment measures multiple test pads TP(n) located in the chip region A(x,y) to be measured while switching between the chip regions A(x,y) being measured, thus significantly shortening the measurement time for the entire semiconductor wafer.

[0036] While the procedure currently involves measuring the test pad TP(n) in chip area A(x,y) located in the same row, followed by measuring the test pad TP(n) in the adjacent row, it is also possible to measure the test pad TP(n) in chip area A(x,y) located in the same column, followed by measuring the test pad TP(n) in the adjacent column. Furthermore, it is also possible to measure the test pad TP(n) in chip area A(x,y) located in the same column all at once.

[0037] In this embodiment, the chip region A(x,y) shown represents a case where multiple test pads TP(n) provided in the chip region A(x,y) are arranged along the X-axis. However, as shown in Figure 4(b), among the multiple test pads TP(n) provided in the chip region A(x,y), for example, test pads TP(2) and TP(4) may be positioned offset in the Y-axis direction relative to the other test pads TP(n). Even in such cases, as long as the positions of the surface of the mask 16 and the surface of the sample S satisfy the shine-proof conditions, the inspection light reflected by the reflective surface RS will focus on the corresponding test pad TP(n), and measurement can be performed in a similar manner.

[0038] Furthermore, as shown in Figure 4(c), some of the multiple test pads TP(n) may be arranged in a two-dimensional manner. In such cases, measurements are performed using one or more masks on which reflective surfaces RS corresponding to the test pads TP(n) provided in each chip region A of the semiconductor wafer 30 are arranged. As shown in Figure 4(c), for example, among the test pads TP(n) arranged in chip region A(x,y), measurements are performed on test pads TP(5) arranged along the X-axis direction, and then measurements are performed on test pads TP(1) arranged in a two-dimensional manner, and then on test pads TP(4). At this time, the mask used when measuring from test pad TP(5) to test pad TP(n) is switched from the mask used when measuring from test pad TP(1) to test pad TP(4). Also, when switching masks, the mounting stage 18 is moved by a predetermined amount in the Y-axis direction. In this case, since two or more of the multiple test pads TP(n) provided in chip region A(x,y) can be measured simultaneously, the measurement time for the semiconductor wafer 30 can be shortened.

[0039] In the embodiment described above, a reflective mask 16 with multiple reflective surfaces RS arranged in one direction (the X-axis direction in Figure 2) is used to irradiate the test pad TP(n) provided on the chip region A(x,y) on the semiconductor wafer 30 with inspection light from the light source 15. However, instead of using the mask 16, it is also possible to use a DMD (Digital Mirror Device) with multiple micromirrors arranged in two dimensions.

[0040] DMD switches each of multiple micromirrors arranged in a two-dimensional pattern between an "on" position, where light is reflected toward the sample, and an "off" position, where light is reflected to a different location from the sample. In other words, when using DMD, the operation is performed to switch the micromirrors corresponding to each test pad TP(n) located in the chip region A(x,y) on the semiconductor wafer 30 from the off position to the on position. In this case, it becomes unnecessary to create a mask 16 that matches the position of the test pad TP(n), thus reducing the cost of measurement.

[0041] In the spectroscopic ellipsometer 10 described above, the surface of the mask 16 and the surface of the sample S are described as being in a conjugate relationship, but it is preferable that the surface of the sample S and the light-receiving surface of the light-receiving unit 42 are also in a conjugate relationship. Incidentally, in the spectroscopic ellipsometer 10 described above, the inspection light is incident on the surface of the sample S from obliquely above, reflected from the surface of the sample S, and then travels obliquely upward. Here, if the collimator lens 45 is positioned so that its optical axis coincides with the optical axis L2 of the inspection light, there is a risk that some of the inspection light emitted from the collimator lens 45 will not be parallel light, but rather diffuse light or focused light. Therefore, as a method to make the inspection light emitted from the collimator lens 45 parallel light, for example, the image plane of the collimator lens 45 and the conjugate plane CS can be set parallel to each other.

[0042] As shown in Figure 6, the conjugate plane CS is located on the optical axis L2 of the inspection light emitted from the condenser lens 37 of the output optical system 19. Therefore, the collimator lens 45 of the spectroscopic optical system 41 is positioned such that the optical axis L3 of the collimator lens 45 is perpendicular to the conjugate plane CS and passes through the intersection point E1 between the optical axis L2 of the inspection light and the conjugate plane CS. At this time, the collimator lens 45 is positioned on the optical path of the inspection light so that the inspection light is incident on the collimator lens 45. That is, the collimator lens 45 is positioned with its optical axis L3 tilted with respect to the optical axis L2 of the inspection light. As a result, the inspection light emitted from the collimator lens 45 is incident on the spectroscopic prism 46 as parallel light.

[0043] Furthermore, as shown in Figure 7, it is also possible to position the collimator lens 45 of the spectroscopic optical system 41 such that its optical axis L3 is parallel to a straight line L4 that passes through the intersection point E2 of the conjugate plane CS and the optical axis L2 of the inspection light, and that the center E3 of the collimator lens 45 is located on the optical axis L2 of the inspection light. In this case as well, the collimator lens 45 of the spectroscopic optical system 41 is positioned such that its optical axis L3 is tilted with respect to the optical axis L2 of the inspection light. As a result, the inspection light emitted from the collimator lens 45 is incident on the spectroscopic prism 46 as parallel light.

[0044] In measuring a test pad TP(n) located in the chip region A(x,y) of a semiconductor wafer 30, if the film being measured is thick or a complex multilayer film, measurements are performed using multiple incident angles. In other words, when the incident angle is changed, the tilt angle of the conjugate plane CS with respect to the optical axis L2 changes, so it is also necessary to adjust the tilt angle of the collimator lens 45 in accordance with the change in the tilt angle of the conjugate plane CS with respect to the optical axis L2.

[0045] In the spectroscopic ellipsometer 10, the incident angle at which the inspection light emitted from the incident optical system 17 enters the sample S is 50 to 70°. Therefore, if the optical axis L3 of the collimator lens 45 is tilted with respect to the optical axis L2 of the inspection light, the angles of the inspection light entering the collimator lens 45 and the inspection light emitted from the collimator lens 45 become large, making it difficult to correct aberrations in the collimator lens and to adjust the layout and position (angle) of the spectroscopic optical system 41 in the photodetector 20.

[0046] Generally, lenses have field curvature characteristics. Field curvature is the property that the image plane of light transmitted through a lens is not a plane perpendicular to the optical axis of the lens, but rather a curved surface that is located closer to the output surface of the lens as it moves away from the optical axis (center) of the lens. Therefore, it is possible to position a collimator lens installed in a photodetector so that the field curvature characteristics of the collimator lens are aligned with a conjugate plane that is conjugate to the surface of the sample, with the optical axis of the collimator lens offset from the optical axis of the inspection light.

[0047] Figure 8 shows an example of a photodetector used in a spectroscopic ellipsometer. As shown in Figure 8, the photodetector 51 includes a spectroscopic optical system 52 and a light-receiving unit 53. The spectroscopic optical system 52 also includes a collimator lens 54, a spectroscopic prism 55, and an imaging lens 56. The collimator lens 54 is positioned such that its image field curvature characteristics align with a conjugate plane CS1 that is conjugate to the surface of the sample S, with the optical axis L5 of the collimator lens 54 offset from the optical axis L2 of the inspection light. More specifically, the collimator lens 54 is positioned such that the conjugate plane CS1 is located on the image plane 58 based on the image field curvature characteristics of the collimator lens 54. By positioning the collimator lens 54 in this way, the inspection light transmitted through the collimator lens 54 is affected by the image field curvature characteristics of the collimator lens 54 and enters the spectroscopic prism 55 as parallel light.

[0048] In addition, some photodetectors use a concave mirror instead of a collimator lens. As shown in Figure 9, for example, the photodetector 61 includes a spectroscopic optical system 62 and a light-receiving unit 63. The spectroscopic optical system 62 includes a concave mirror 64, a spectroscopic prism 65, and an imaging lens 66.

[0049] Here, even when the concave mirror 64 is used instead of the collimator lens, the same as when the collimator lens is used, the optical axis L6 of the concave mirror 64 is offset from the optical axis L2 of the inspection light so that the image field curvature characteristics of the concave mirror 64 are aligned with the conjugate plane CS2 which is conjugate to the surface of the sample S. More specifically, the concave mirror 64 is positioned so that the conjugate plane CS2 is located on the image plane 68 based on the image field curvature characteristics of the concave mirror 64. By positioning the concave mirror 64 in this way, the light reflected from the concave mirror 64 is affected by the image field curvature characteristics of the concave mirror 64 and enters the spectral prism 65 as parallel light.

[0050] Below, we will describe the simulation results of the case where the collimator lens 54 is positioned such that its image field curvature characteristics align with the conjugate plane CS1 which is conjugate to the surface of the sample S, and the optical axis L5 of the collimator lens 54 is offset from the optical axis L2 of the inspection light, as Example 1.

[0051] <Example 1> Table 1 shows the specifications (optical characteristics in the optical system, etc.) of the spectroscopic ellipsometer 10 shown in Example 1. In the spectroscopic ellipsometer 10 shown in Example 1, Figure 8 shows the collimator lens 54 as a single lens, but the collimator lens 54 is composed of, for example, six lenses (not shown). The six lenses constituting the collimator lens 54 will be referred to below as lens G1, lens G2, lens G3, lens G4, lens G5, and lens G6, starting from the sample S side. Lenses G1 to G6 have spherical incident and exit surfaces. Lenses G1 to G5 are arranged on the optical axis of the exit optical system 19, while lens G6 is eccentric or inclined with respect to the optical axis of the exit optical system 19.

[0052] [Table 1]

[0053] In the simulation, the mask 16 is considered the object surface, and the angle θ (see Figure 1) between the optical axis of the inspection light and the surface of the sample S is defined as the irradiation angle θ. It is assumed that the inspection light emitted from each object height on the surface of the mask 16 at θ = 50°, 55°, 60°, 65°, and 70° is irradiated onto a 1 × 2 mm area on the surface of the sample S, as shown in Figure 10. Note that for each object height of the mask 16, points symmetrical along the Y axis are omitted, and the points are designated as points P1 to P9. In Figure 10, the points on the surface of the sample S that are conjugate to points P1 to P9 are designated as points P1' to P9'.

[0054] Tables 2 to 6 show the surface data when the irradiation angle θ is set to θ = 50°, 55°, 60°, 65°, and 70°. Tables 7 to 11 show the positions of points P1 to P9 when the irradiation angle θ is set to θ = 50°, 55°, 60°, 65°, and 70°. As described above, in the spectroscopic ellipsometer 10 shown in Example 1, light from the mask 16 is irradiated onto the sample S from obliquely above. Therefore, for example, if points P1' to P9' on the sample S are used as a reference, the Y-axis positions of points P4 to P6 and P7 to P9 on the mask 16 are y × cosθ.

[0055] [Table 2]

[0056] [Table 3]

[0057] [Table 4]

[0058] [Table 5]

[0059] [Table 6]

[0060] [Table 7]

[0061] [Table 8]

[0062] [Table 9]

[0063] [Table 10]

[0064] [Table 11]

[0065] As described above, the inspection light emitted from each point P1 to P9 passes through the incident optical system 17, is reflected from the surface of the sample S, and enters the exit optical system 19. The inspection light that enters the exit optical system 19 has its phase shifted by the compensator 35, then exits the exit optical system 19 and enters the photodetector 51. The inspection light that enters the photodetector 51 becomes parallel light by the collimator lens 54, is spectrally separated by the spectral prism 55, and is imaged by the imaging lens 56 in the light receiving unit 53.

[0066] In Example 1, since the incident optical system 17 and the exit optical system 19 are paraxial lenses, the image of the mask 16 on the conjugate plane CS1 is aberration-free. Furthermore, the collimation property of the collimator lens 54 is confirmed by using a paraxial lens for the imaging lens 56, and by making the focal length of the imaging lens 56 equal to the distance between the imaging lens 56 and the light-receiving unit 53, and then calculating the Strehl ratio at the light-receiving unit 53. Optical design simulation software was used to calculate the Strehl ratio.

[0067] For example, when the irradiation angle θ mentioned above is θ = 50°, as shown in Figure 11, even when using any of the wavelengths λ = 365, 436, 583, 656, 707, or 1014 nm for the inspection light wavelength λ, the Strehr ratio in the fields of view (fields of view 1 to 9) corresponding to any of the points P1 to P9 is generally 0.8 or higher (more specifically, 0.89 or higher), which is almost aberration-free. In other words, when the irradiation angle θ = 50°, when the collimator lens 54 is positioned such that its field curvature characteristics align with the conjugate plane CS1 which is conjugate to the surface of the sample S, and the optical axis L5 of the collimator lens 54 is offset from the optical axis L2 of the inspection light, highly collimable inspection light can be incident on the spectral prism 55.

[0068] Furthermore, for example, when the irradiation angle θ is θ = 55°, as shown in Figure 12, even when using any of the wavelengths λ = 365, 436, 583, 656, 707, or 1014 nm for the inspection light wavelength λ, the Strehr ratio is generally 0.8 or higher (more specifically, 0.9 or higher) for the light beam emitted from any of the points P1 to P9, which is nearly aberration-free. In other words, when the irradiation angle θ = 55°, when the collimator lens 54 is positioned such that its image field curvature characteristics align with the conjugate plane CS1 which is conjugate to the surface of the sample S, and the collimator lens 54's optical axis L5 is offset from the optical axis L2 of the inspection light, highly collimable inspection light can be incident on the spectral prism 55.

[0069] Furthermore, when the irradiation angle θ is θ = 60°, as shown in Figure 13, even when using any of the wavelengths λ = 365, 436, 583, 656, 707, or 1014 nm for the inspection light wavelength λ, the Strehr ratio is generally 0.8 or higher (more specifically, 0.9 or higher) for the light beam emitted from any of the points P1 to P9, which is nearly aberration-free. In other words, even when the irradiation angle θ = 60°, when the collimator lens 54 is positioned such that its image field curvature characteristics align with the conjugate plane CS1 which is conjugate to the surface of the sample S, and the collimator lens 54's optical axis L5 is offset from the optical axis L2 of the inspection light, highly collimable inspection light can be incident on the spectral prism 55.

[0070] Furthermore, when the irradiation angle θ is θ = 65°, as shown in Figure 14, even when using any of the wavelengths λ = 365, 436, 583, 656, 707, or 1014 nm for the inspection light wavelength λ, the Strehr ratio is generally 0.8 or higher (specifically, 0.86 or higher), which is nearly aberration-free, for the light beam emitted from any of the points P1 to P9. In other words, even when the irradiation angle θ = 65°, when the collimator lens 54 is positioned such that its image field curvature characteristics align with the conjugate plane CS1 which is conjugate to the surface of the sample S, and the collimator lens 54's optical axis L5 is offset from the optical axis L2 of the inspection light, highly collimable inspection light can be incident on the spectral prism 55.

[0071] Furthermore, when the irradiation angle θ is θ = 70°, as shown in Figure 15, even when using any of the wavelengths λ = 365, 436, 583, 656, 707, or 1014 nm for the inspection light wavelength λ, the Strehr ratio is generally 0.8 or higher (specifically, 0.82 or higher) for the light beam emitted from any of the points P1 to P9, which is nearly aberration-free. In other words, even when the irradiation angle θ = 70°, when the collimator lens 54 is positioned such that its image field curvature characteristics align with the conjugate plane CS1 which is conjugate to the surface of the sample S, and the collimator lens 54's optical axis L5 is offset from the optical axis L2 of the inspection light, highly collimable inspection light can be incident on the spectral prism 55.

[0072] Thus, when the irradiation angle of the inspection light emitted from the incident optical system 17 irradiates the surface of the sample S is in the range of 50° to 70°, the image field curvature characteristics of the collimator lens 54 are aligned with the conjugate plane CS1 which is conjugate to the surface of the sample S. When the collimator lens 54 is positioned with its optical axis L5 offset from the optical axis L2 of the inspection light, it is possible to irradiate the spectral prism 55 with highly collimated inspection light.

[0073] Next, as Example 2, we will describe the results of a simulation in a spectroscopic ellipsometer 10 using a photodetector 61 in which the optical axis L6 of the concave mirror 64 is offset from the optical axis L2 of the inspection light, such that the image field curvature characteristics of the concave mirror 64 are aligned with the conjugate plane CS2 which is in a conjugate relationship with the surface of the sample S.

[0074] <Example 2> Table 12 shows the specifications (optical characteristics in the optical system, etc.) for the spectroscopic ellipsometer 10 shown in Example 2. Note that if the optical surface is aspherical, the sign * is added to the right of the surface number. The aspherical shape is defined as follows, where x is the displacement from the surface vertex in the optical axis direction, h is the height from the optical axis perpendicular to the optical axis, R is the radius of paraxial curvature, k is the cone constant, and A4, A6, A8, A10, A12 are the aspherical coefficients of their respective orders. x=( h 2 / R) / [1+{1-(1+k)(h / R) 2} 1 / 2 ]+A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 It is expressed as follows. Note that k is the cone constant, and Table 13 shows an example for A4, A6, A8, A10, and A12. In Table 13, "E±XX" for each aspheric coefficient A4, A6, A8, A10, and A12 is "×10 ±XX This means "[...]." A detailed explanation of the specifications of the spectroscopic ellipsometer 10 will be omitted.

[0075] [Table 12] [Table 13]

[0076] The simulation in Example 2 is similar to the simulation in Example 1, assuming that the mask 16 is the object surface, the angle θ (see Figure 1) between the optical axis of the inspection light and the surface of the sample S is the irradiation angle θ, and that the inspection light emitted from each object height on the surface of the mask 16 at θ = 50°, 55°, 60°, 65°, and 70° is irradiated onto a 1 × 2 mm area on the surface of the sample S, as shown in Figure 10. Note that for each object height of the mask 16, points symmetrical along the Y axis are omitted and referred to as points P1 to P9, and in Figure 10, points P1' to P9' are the conjugate points of points P1 to P9 on the surface of the sample S.

[0077] Tables 13 to 17 show the surface data when the irradiation angle θ is set to θ = 50°, 55°, 60°, 65°, and 70°. Tables 18 to 22 show the positions of points P1 to P9 when the irradiation angle θ is set to θ = 50°, 55°, 60°, 65°, and 70°. As described above, in the spectroscopic ellipsometer 10 shown in Example 2, light from the mask 16 is irradiated onto the sample S from obliquely above. Therefore, for example, if points P1' to P9' on the sample S are used as a reference, the Y-axis positions of points P4 to P6 and points P7 to P9 on the mask 16 are y × cosθ.

[0078] [Table 14]

[0079] [Table 15]

[0080] [Table 16]

[0081] [Table 17]

[0082] [Table 18]

[0083] [Table 19]

[0084] [Table 20]

[0085] [Table 21]

[0086] [Table 22]

[0087] [Table 23]

[0088] In this case as well, the inspection light emitted from each point P1 to P9 passes through the incident optical system 17, is reflected from the surface of the sample S, and enters the exit optical system 19. The inspection light that enters the exit optical system 19 has its phase shifted by the compensator 35, then exits the exit optical system 19 and enters the photodetector 61. The inspection light that enters the photodetector 61 becomes parallel light by the concave mirror 64, is spectrally separated by the spectral prism 65, and is imaged by the imaging lens 66 in the light receiving unit 63.

[0089] Similar to Example 1, the incident optical system 17 and the exit optical system 19 are paraxial lenses, so the image of the mask 16 on the conjugate plane CS2 is aberration-free. Furthermore, the collimation property of the concave mirror 64 is confirmed by using a paraxial lens for the imaging lens 66, and by making the focal length of the imaging lens 66 equal to the distance between the imaging lens 66 and the light-receiving section 63, and then calculating the Strehr ratio on the light-receiving surface.

[0090] For example, when the irradiation angle θ is θ = 50°, as shown in Figure 16, even when using a wavelength λ of 365, 436, 583, 656, 707, or 1014 nm as the wavelength λ of the inspection light, the Strehl ratio is generally 0.8 or higher (more specifically, 0.90 or higher) for the light beam emitted from any of the points P1 to P9, which is almost aberration-free. In other words, when the irradiation angle θ = 50°, when the concave mirror 64 is positioned such that its image field curvature characteristics align with the conjugate plane CS2 which is conjugate to the surface of the sample S, and the optical axis L6 of the concave mirror 64 is offset from the optical axis L2 of the inspection light, highly collimable inspection light can be incident on the spectral prism 65.

[0091] For example, when the irradiation angle θ is θ = 55°, as shown in Figure 17, even when using a wavelength λ of 365, 436, 583, 656, 707, or 1014 nm as the wavelength λ of the inspection light, the Strehl ratio is generally 0.8 or higher (more specifically, 0.95 or higher) for the light beam emitted from any point P1 to P9, which is nearly aberration-free. In other words, when the irradiation angle θ = 55°, when the concave mirror 64 is positioned such that its image field curvature characteristics align with the conjugate plane CS2 which is conjugate to the surface of the sample S, and the optical axis L6 of the concave mirror 64 is offset from the optical axis L2 of the inspection light, highly collimable inspection light can be incident on the spectral prism 65.

[0092] Furthermore, for example, when the irradiation angle θ is θ = 60°, as shown in Figure 18, even when using any of the wavelengths λ = 365, 436, 583, 656, 707, or 1014 nm for the inspection light wavelength λ, the Strehr ratio is generally 0.8 or higher (more specifically, 0.9 or higher) for the light beam emitted from any of the points P1 to P9, which is nearly aberration-free. In other words, even when the irradiation angle θ = 60°, when the concave mirror 64 is positioned such that its image field curvature characteristics align with the conjugate plane CS1 which is conjugate to the surface of the sample S, and the optical axis L6 of the concave mirror 64 is offset from the optical axis L2 of the inspection light, highly collimable inspection light can be incident on the spectral prism 65.

[0093] Furthermore, for example, when the irradiation angle θ is θ = 65°, as shown in Figure 19, even when using a wavelength of λ = 365, 436, 583, 656, 707, or 1014 nm as the wavelength λ of the inspection light, the Strehl ratio is generally 0.8 or higher (specifically, 0.94 or higher), which is almost aberration-free, for the light beam emitted from any point from point P1 to point P9. In other words, even when the irradiation angle θ = 65°, when the concave mirror 64 is positioned such that its image field curvature characteristics align with the conjugate plane CS2 which is conjugate to the surface of the sample S, and the optical axis L6 of the concave mirror 64 is offset from the optical axis L2 of the inspection light, highly collimable inspection light can be incident on the spectral prism 65.

[0094] Furthermore, for example, when the irradiation angle θ is θ = 70°, as shown in Figure 20, even when using a wavelength λ of 365, 436, 583, 656, 707, or 1014 nm as the wavelength λ of the inspection light, the Strehl ratio is generally 0.8 or higher (specifically, 0.92 or higher), which is almost aberration-free, for the light beam emitted from any of the points P1 to P9. In other words, even when the irradiation angle θ = 70°, when the concave mirror 64 is positioned such that its image field curvature characteristics align with the conjugate plane CS2 which is conjugate to the surface of the sample S, and the optical axis L6 of the concave mirror 64 is offset from the optical axis L2 of the inspection light, highly collimable inspection light can be incident on the spectral prism 65.

[0095] Thus, when the irradiation angle of the inspection light emitted from the incident optical system 17 irradiates the surface of the sample S is in the range of 50° to 70°, the image field curvature characteristics of the collimator lens 54 are aligned with the conjugate plane CS2 which is conjugate to the surface of the sample S. When the concave mirror 64 is positioned with its optical axis L6 offset from the optical axis L2 of the inspection light, a highly collimable inspection light can be incident on the spectral prism 65.

[0096] <Regarding the effects> The spectroscopic ellipsometer 10 of the present invention is characterized by comprising: a mounting stage 18 on which a sample S is placed; a light source 15; an irradiation means that uses the light emitted from the light source 15 to irradiate an inspection light onto at least two or more test pads TP(n) provided on the sample S; and a photodetector 20 that spectrally analyzes and receives the reflected light reflected by at least two or more test pads TP(n).

[0097] This allows for the measurement of film thickness or optical properties for test pads TP(n) at multiple locations, thus reducing the measurement time compared to measuring film thickness or optical properties for a single test pad TP(n).

[0098] Furthermore, the irradiation means is a reflective mask 16 or a reflector (mirror) having multiple reflective surfaces corresponding to multiple test pads TP.

[0099] According to this, the inspection light reflected from each reflective surface of the mask is irradiated onto each corresponding test pad TP(n). In other words, with a simple configuration, light from the light source can be reliably irradiated onto the test pad TP(n). Furthermore, if a digital mirror device is used as the mirror, which reflects the inspection light towards the sample S by switching the reflection direction of micromirrors arranged in a two-dimensional manner for each mirror, the reflection direction can be switched for each micromirror, eliminating the need to create a mask 16 that matches the position of the test pad TP(n) for each sample S, thereby reducing measurement costs.

[0100] Furthermore, the reflective mask 16 or mirror is positioned such that multiple reflective surfaces RS(n) and multiple test pads TP(n) are in a conjugate relationship, and the projection magnification of the inspection light onto the surface of the sample S is equal.

[0101] According to this, the inspection light illuminates each of the corresponding test pads TP(n). At this time, since the multiple reflective surfaces RS and the multiple test pads TP(n) are positioned in a conjugate relationship, the inspection light reliably illuminates the test pads TP(n) without illuminating the periphery of the test pads TP(n). As a result, the inspection light detected by the photodetector 20 does not contain any component of light that reflects off the periphery of the test pads TP(n), and only contains the component of light that illuminates the test pads TP, so the optical properties of the thin film on the test pads TP(n) can be accurately measured.

[0102] Furthermore, the irradiation means is a transmissive mask having a transmissive surface corresponding to each of the multiple test pads TP(n).

[0103] According to this method, the inspection light reflected from each of the mask's transparent surfaces is directed onto each of the corresponding test pads TP(n). In other words, a simple configuration can be used to reliably direct light from the light source onto the test pads TP(n).

[0104] Furthermore, the transmissive mask is positioned such that multiple transmissive surfaces and multiple test pads TP(n) are in a conjugate relationship, and the projection magnification of the inspection light onto the surface of the sample S is equal.

[0105] According to this, the inspection light illuminates each of the corresponding test pads TP(n). At this time, since the multiple transmission surfaces and multiple test pads TP(n) are positioned in a conjugate relationship, the inspection light reliably illuminates the test pads TP(n) without illuminating the periphery of the test pads TP(n). As a result, the inspection light detected by the photodetector 20 does not contain any component of light that reflects off the periphery of the test pads TP(n), and only contains the component of light that illuminates the test pads TP(n), so the optical properties of the thin film on the test pads TP(n) can be accurately measured.

[0106] Furthermore, the sample S is a semiconductor wafer 30, and multiple test pads are provided within the chip region A corresponding to the semiconductor chips provided on the semiconductor wafer 30.

[0107] According to this, the test pad TP(n) provided within the chip region A of the semiconductor wafer 30 can be accurately illuminated with inspection light, making it possible to accurately measure the optical properties of the thin film relative to the test pad TP(n).

[0108] Furthermore, the photodetector 20 has a collimator lens 45 that passes through the intersection point E1 (or E3) of the conjugate plane CS, which is in a conjugate relationship with the surface of the sample S, and the optical axis L2 of the inspection light reflected from the sample S, and has an optical axis L3 that is perpendicular to the conjugate plane CS, and emits the incident inspection light as parallel light.

[0109] According to this, in the photodetector 20, the inspection light reflected from the sample S is incident on the spectral prism 46 in the form of parallel light, so the inspection light can be accurately spectrally separated.

[0110] Furthermore, the photodetector 51 includes a collimator lens 54 that makes the inspection light incident on the photodetector 51 into parallel light, and a spectral prism 55 that spectrally separates the inspection light from the collimator lens 54. The collimator lens 54 is positioned such that its image field curvature characteristics are aligned with a conjugate plane CS1 that is conjugate to the surface of the sample S, and the optical axis L5 of the collimator lens 54 is offset from the optical axis L2 of the inspection light.

[0111] According to this, even if the inspection light reflected from the sample S passes through the collimator lens 54, the influence of the image field curvature characteristics of the collimator lens 54 on the inspection light is suppressed, and the inspection light that has passed through the collimator lens 54 is incident on the spectral prism 55 in a parallel light state. As a result, the inspection light can be spectrally separated more accurately.

[0112] Furthermore, the photodetector 61 includes a concave mirror 64 that emits inspection light as parallel light, and a spectral prism 65 that spectrally separates the inspection light from the concave mirror 64. The concave mirror 64 is positioned such that its image field curvature characteristics align with a conjugate plane CS2 that is conjugate to the surface of the sample S, and its optical axis L6 is offset from the optical axis L2 of the inspection light.

[0113] According to this, when the inspection light reflected from the sample S is reflected by the concave mirror 64, the influence of the image field curvature characteristics of the concave mirror 64 on the inspection light is suppressed, and the inspection light reflected from the concave mirror 64 is incident on the spectral prism 65 in a parallel light state. As a result, the inspection light can be spectrally separated more accurately. [Explanation of Symbols]

[0114] 10…Spectroscopic ellipsometer 15...Light source 16… Mask 18… Mounting platform 20…Photodetector 26… Polarizer 36… Photometer 30… Semiconductor wafers 54...Collimator lens 55, 65... Spectroscopic prism 56, 66… imaging lenses 64…Concave mirror RS(n)…Reflecting surface S... Sample TP(n)...Test pad

Claims

1. A mounting platform on which the sample is placed, Light source and An irradiation means that uses light from the light source to irradiate the sample with inspection light directed towards at least two or more target areas, A photodetector that spectrally analyzes and receives the inspection light reflected from at least two of the aforementioned target regions, Equipped with, The irradiation means is a reflective mask or mirror having multiple reflective surfaces corresponding to each of the at least two target areas. A spectroscopic ellipsometer characterized by the following features.

2. In the spectroscopic ellipsometer according to Claim 1, The reflective mask or mirror is positioned such that the at least two target regions and the reflective surfaces corresponding to each of the at least two target regions are in a conjugate relationship. The projection magnification of the inspection light onto the surface of the sample is equal to 1x. A spectroscopic ellipsometer characterized by the following features.

3. A mounting platform for placing a sample, Light source and An irradiation means that uses light from the light source to irradiate the sample with inspection light directed towards at least two or more target areas, A photodetector that spectrally analyzes and receives the inspection light reflected from at least two of the aforementioned target regions, Equipped with, The irradiation means is a transmissive mask having a transmissive surface corresponding to each of the at least two target regions. A spectroscopic ellipsometer characterized by the following features.

4. In the spectroscopic ellipsometer according to claim 3, The transparent mask is positioned such that the at least two target regions and the transparent surfaces corresponding to each of the at least two target regions are in a conjugate relationship. The projection magnification of the inspection light onto the surface of the sample is equal to 1x. A spectroscopic ellipsometer characterized by the following features.

5. In a spectroscopic ellipsometer according to any one of claims 1 to 4, The aforementioned sample is a semiconductor wafer, The spectroscopic ellipsometer is characterized in that the target region is a plurality of test pads provided within a region corresponding to a semiconductor chip on a semiconductor wafer.

6. A mounting platform for placing a sample, Light source and An irradiation means that uses light from the light source to irradiate the sample with inspection light directed towards at least two or more target areas, A photodetector that spectrally analyzes and receives the inspection light reflected from at least two of the aforementioned target regions, Equipped with, The aforementioned photodetector is The collimator lens has an optical axis that passes through the intersection of a conjugate plane, which is conjugate to the surface of the sample, and the optical axis of the inspection light reflected from the sample, and is perpendicular to the conjugate plane, and emits the incident inspection light as parallel light. A spectroscopic ellipsometer characterized by the following features.

7. A mounting platform for placing a sample, Light source and An irradiation means that uses light from the light source to irradiate the sample with inspection light directed towards at least two or more target areas, A photodetector that spectrally analyzes and receives the inspection light reflected from at least two of the aforementioned target regions, Equipped with, The aforementioned photodetector is A collimator lens that emits the aforementioned inspection light as parallel light, A prism for spectrally separating the inspection light from the collimator lens, It has, The collimator lens is positioned such that its image field curvature characteristics align with a conjugate plane that is conjugate to the surface of the sample, and the optical axis of the collimator lens is offset from the optical axis of the inspection light. A spectroscopic ellipsometer characterized by the following features.

8. A mounting platform for placing a sample, Light source and An irradiation means that uses light from the light source to irradiate the sample with inspection light directed towards at least two or more target areas, A photodetector that spectrally analyzes and receives the inspection light reflected from at least two of the aforementioned target regions, Equipped with, The aforementioned photodetector is A concave mirror that emits the aforementioned inspection light as parallel light, A prism for spectrally separating the inspection light from the concave mirror, It has, The concave mirror is positioned such that its image field curvature characteristics align with a conjugate plane that is conjugate to the surface of the sample, with the optical axis of the concave mirror offset from the optical axis of the inspection light. A spectroscopic ellipsometer characterized by the following features.

Images