JPH09281401A - Object inspecting instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously inspect, in a short time, the defect of the phase shift amount of a main area at the inside of reticle and foreign matter such as contaminant or the like hindering exposure. SOLUTION: A light beam for illumination i00 is made illuminating light beams EO and OE sheared by a Nomarski prism 10 and an objective lens 12. Light passing through an object surface S is synthesized by the objective lens 14 and the Nomarski prism 16, and is made incident on a half mirror 18. The interference components of transmitted light are taken out in different polarization directions by a 1/4 wavelength plate 20 and a polarizing beam splitter 22, and the intensity component of the illuminating light EO and OE of reflected light is taken out by the polarizing beam splitter 24. The inspection of the defect of an object is performed by an error signal obtained by performing the intensity adjustments of respective components.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object inspection apparatus, for example, an object inspection apparatus suitable for defect inspection of a reticle (or mask) having a phase shifter.

[0002]

BACKGROUND ART A defect inspection apparatus for a reticle having a phase shifter includes, for example,
"SPEI, Proceeding Series Volume 2254, Photoma
sk and X-Ray Mask Technology, "P.294〜301""has a shifter phase shift measuring device. In this apparatus, the phase shifter portion to be inspected in the reticle is adjusted so as to be located within the visual field of the optical microscope. Then, the phase amount of one sampled point in the field of view is measured. This operation is repeated for each sampling point.

Therefore, according to this background art, only the inspection result for each sampled point can be obtained for each measurement. Therefore, it is completely unsuitable for inspecting all the defects in the reticle. Further, in the case of a reticle of a type having a light-shielding portion made of chromium or the like in addition to the phase shifter, it is convenient as a defect inspection apparatus because it is possible to simultaneously detect foreign matters in addition to defects of the phase shift amount.

In view of the above circumstances, the present invention can inspect defects in the amount of phase shift in the main area of the reticle in a short time, and in addition, inspect foreign matters such as contaminants that interfere with exposure. It is an object of the present invention to provide an object inspection device that can be used as a foreign matter inspection device for a reticle without a shifter by performing the above.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to illumination means (50, 54) for providing light in first and second orthogonal polarization directions for illumination; first and second orthogonal light sources obtained therefrom. (10) for irradiating an object to be observed by relatively shearing the optical axes of the light in the polarization directions of (1); Photosynthesis for combining the light in the first and second polarization directions transmitted or reflected by the object Means (16); Phase difference adjusting means (10) for adjusting the phase difference between the light in the first and second polarization directions; Light in the first and second polarization directions from the light combined by the light combining means Intensity component detection means (24,76,8
0); from the light synthesized by the photosynthetic means, the first
And an interference component detecting means (22, 66, 70) for detecting an interference component in the second polarization direction; an inspection means for inspecting an object from the detection results of the intensity component detecting means and the interference component detecting means ( 72,82,88,90,86);

According to a main aspect, at least one of the light splitting means and the main light combining means comprises a birefringent prism. Further, the phase difference adjusting means moves at least one of the light separating means or the light combining means in a direction crossing the optical axis, a rotatable polarizer and a quarter wavelength plate, and a refractive index can be controlled by a voltage. Composed of any liquid crystal.

According to another aspect of the invention, the inspection means includes an image pickup means (66, 70, 7) for photoelectrically converting the detection component obtained by the intensity component detection means or the interference component detection means.
6,80); computing means (72,82) for obtaining an amplitude differential image and an intensity differential image from the respective detection signals obtained thereby; adjusting the intensity based on the amplitude differential image and the intensity differential image thus obtained. Error signal generation means (8
8, 90); are provided.

According to another aspect, at least one of the intensity component detecting means and the interference component detecting means includes a polarization beam splitter (22, 24). Further, the illumination means includes a laser light source and a scanning means (54) for scanning the laser beam output from the laser light source. The scanning means is arranged in an optical path through which light rays on the forward path and the backward path with respect to the object pass.
Further, the shear amount of the optical axis by the light separating means is variable.

The main aspects of the present invention include the following. (1) A defect inspection device for inspecting a reticle for defects, which comprises a laser light source for emitting a first light beam and a first light beam with two linearly polarized light of a first polarization state and a second polarization state. And a condenser lens for condensing the two linearly polarized light rays and forming two beam spots in a first region in the reticle, Scanning means for two-dimensionally scanning two beam spots in the first region, an objective lens capable of condensing light rays generated in the transmission direction from the light transmissive reticle, and an objective lens that transmits the reticle Ray combining means for synthesizing the two linearly polarized rays refracted by the lens into a second ray having a third polarization state; and a second ray state having a first polarization state and a second polarization state. Two linearly polarized rays A first phase difference adjusting means for adjusting a first phase difference which is a relative phase difference amount, a half mirror for amplitude-dividing the second light ray into a third light ray and a fourth light ray, A first polarization splitting means for splitting the third light ray into two linearly polarized light rays having a fourth polarization state and a fifth polarization state, and the fourth light ray having a sixth polarization state and a sixth polarization state. A second polarization splitting means for splitting the light into two linearly polarized light beams having a seven polarization state; and a linearly polarized light component that is a component of the third light beam and is parallel to the first polarization state, and a second Second phase difference adjusting means for adjusting the second phase difference which is the relative phase difference amount between the components of the linearly polarized light parallel to the polarization state of,

The photoelectric conversion elements for photoelectrically converting the light rays of the fourth to seventh polarization states, the first photoelectric conversion element, and the photoelectric conversion elements of the second photoelectric conversion element, respectively. Generating a first difference signal that is a difference in signal strength of the converted signal, a first difference signal generation unit, the third photoelectric conversion element, and the photoelectric conversion signal of each of the fourth photoelectric conversion element A second difference signal generating means for generating a second difference signal which is a difference in signal strength, a signal strength adjusting means for adjusting the signal strength of the second difference signal and outputting as a third signal, The error signal calculating means for calculating an error signal which is a difference between the first difference signal and the third signal, and the binarizing means for binarizing the error signal and outputting the binarized signal are provided. An object inspection apparatus characterized by determining that there is a defect based on a binarized signal.

(2) A defect inspection apparatus for inspecting a reticle for defects, which comprises a laser light source for emitting a first light beam,
An objective lens arranged along an optical axis capable of condensing a light beam generated in the reflection direction from the light-reflecting reticle, and the first light beam to the objective lens arranged along the optical axis. A first half-mirror for reflecting the first half-mirror and a first light ray reflected by the first half-mirror in two directions of linearly polarized light having a first polarization state and a second polarization state, which are different from each other. The objective lens collects the two linearly polarized light beams to form two beam spots in a first region in the reticle, 2 of polarization state and second polarization state
Rays of two linearly polarized lights traveling in different directions pass through the objective lens and strike the reticle,
It is reflected, then again enters the objective lens, then enters the light beam separating means again, becomes a second light beam having a third polarization state, exits the light beam separating means, and passes through the first half mirror. Further, a scanning means for two-dimensionally scanning the two beam spots in the first region, and a relative phase difference between two linearly polarized light rays of the first polarization state and the second polarization state. A first phase difference adjusting means for adjusting the first phase difference which is an amount, a second half mirror for amplitude-dividing the second light ray into a third light ray and a fourth light ray, and the third A first polarization splitting means for splitting the light beam into two linearly polarized light beams having a fourth polarization state and a fifth polarization state; and the fourth light beam having a sixth polarization state and a seventh polarization state. A second polarization splitting means for splitting into two linearly polarized light rays of A second phase difference for adjusting a second phase difference which is a relative phase difference amount between the linearly polarized light component parallel to the first polarization state and the linearly polarized light component parallel to the second polarization state. Adjusting means,

The first to fourth photoelectric conversion elements for photoelectrically converting the light rays in the fourth to seventh polarization states, the first photoelectric conversion element, and the photoelectric conversion elements of the second photoelectric conversion element, respectively. A first difference signal generating unit that generates a first difference signal that is a difference in signal intensity of the converted signal, the third photoelectric conversion element, and a signal of the photoelectric conversion signal of each of the fourth photoelectric conversion elements. A second difference signal generating means for generating a second difference signal which is a difference in strength, a signal strength adjusting means for adjusting the signal strength of the second difference signal and outputting the third signal as the third signal, The error signal calculating means for calculating an error signal which is a difference between the difference signal and the third signal, and the binarizing means for binarizing the error signal and outputting a binarized signal are provided. An object inspection apparatus characterized by determining that there is a defect based on a binary signal.

(3) The first phase difference is an integral multiple of π, and the second phase difference is a value obtained by adding π / 2 to an integral multiple of π. 1) The object inspection device described above. (4) The above-mentioned (1), wherein the second phase difference is an integral multiple of π, and the first phase difference is a value obtained by adding π / 2 to an integral multiple of π Object inspection device.

(5) The object inspection apparatus according to (1), wherein the sixth polarization state is a linear polarization having a plane of polarization parallel to the linear polarization of the first polarization state. (6) The object inspection device according to (1), wherein one or both of the light beam splitting unit and the light beam combining unit is a birefringent prism.

(7) The first phase difference adjusting means is 1 /
The object inspection apparatus according to (1) above, which is a combination of a four-wave plate and a polarizer that can rotate about an optical axis. (8) The object inspection device according to (1), wherein the second phase difference adjusting means is a quarter-wave plate.

(9) The first phase difference adjusting means can adjust the phase difference by moving one or both of the light beam separating means and the light beam combining means in a direction crossing the optical axis. The object inspection apparatus according to (1) above. (10) The object inspection apparatus according to (1) above, wherein one or both of the first and second polarization separation means is a polarization beam splitter.

(11) The first polarization state is linearly polarized light and forms an angle of 45 ° with respect to the plane of polarization of the linearly polarized light in the first polarization state. Object inspection device. (12) The object inspection according to (1), wherein the fifth polarization state is linearly polarized light and forms an angle of 45 ° with the plane of polarization of the linearly polarized light in the first polarization state. apparatus.

(13) Microscope means capable of independently forming an amplitude differential image and an intensity differential image, and photoelectric conversion for independently photoelectrically converting the amplitude differential image and the intensity differential image to generate an amplitude differential signal and an intensity differential signal. Means, and an intensity adjusting means capable of adjusting a relative intensity ratio of the amplitude differential signal and the intensity differential signal,
After adjusting the relative strength by the strength adjusting means,
An object inspection apparatus characterized by calculating an error signal which is a difference between signal strengths of the two and performing a defect inspection based on the error signal.

According to the present invention, an intensity differential image (intensity) and an amplitude differential image (interference image) are detected on the reflection side or the transmission side of an object by using two sheared light rays. And
An error signal whose intensity is adjusted with respect to these differential images is calculated to inspect the object.

The above and other objects, features and advantages of the present invention will be apparent from the following detailed description and the accompanying drawings.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. To facilitate an understanding of the present invention, the basic form and operation will be described first, and then some preferred embodiments will be described.

[0022]

[First Basic Form] First, the first basic structure and operation of the present invention will be described with reference to FIG. The configuration of FIG. 1 is of a transmission type, and includes both an amplitude differential interference microscope and an intensity differential interference microscope on the transmission side of illumination light.

For each element in the figure, the orthogonal coordinates (X1, Y1) to (X7, Y7) are orthogonal to the optical axis AX and have the same orientation, that is, each coordinate axis. Set the coordinates so that they overlap. Hereinafter, those directions will be simply expressed as (x, y). Further, in order to facilitate understanding, only the chief ray is used in the following description. In addition, the optical axis AX is divided into two and displayed due to space limitations.
A'is originally connected.

In the figure, a light ray i00 output from a light source (not shown) has an azimuth angle θ1 = 4 with respect to the x axis (X1 axis).
It is a linearly polarized laser beam with a polarization plane of 5 °. This ray i00 travels along the optical axis AX, and by the action of the Nomarski prism 10 and the objective lens 12, (X2, Y
2) Illumination light E that is 2δ sheared on the object plane S that is the coordinate plane
O and OE. The illumination light EO is linearly polarized light having a plane of polarization parallel to the y-axis, and the illumination light OE is linearly polarized light having a plane of polarization parallel to the x-axis.

On the object plane S, for example, a reticle (not shown) to be inspected is arranged, and the illumination light transmitted through this is the objective lens 14 and the Nomarski prism 16.
Is combined again into one ray by the action of. When the object is, for example, a perfect parallel plate having no circuit pattern or phase difference, the phase difference provided between the illumination lights EO and OE between the two Nomarski prisms 10 and 16 is an integral multiple of 2π. Further, the position of the Nomarski prism 26 is adjusted in the direction crossing the optical axis AX.

1 again by the Nomarski prism 16.
The combined rays enter the half mirror 18. Then, 50% of the total amplitude of light passes through the half mirror 18, and further through the quarter wavelength plate 20, and reaches the polarization beam splitter (analyzer) 22. On the other hand, the remaining 50% of the light rays incident on the half mirror 18 are reflected by the half mirror 18 and travel along the optical axis AX2,
It reaches the polarization beam splitter 24.

The quarter-wave plate 20 has a fast axis ne, which is an optical axis, and a slow axis no orthogonal to the optical axis ne. The slow axis no has an azimuth parallel to the x axis and the fast axis ne has an azimuth y axis. It is set to be parallel to. Therefore, the linear polarization component of the plane of polarization parallel to the x-axis has a phase difference (π / 2 of −π / 2 (1/4 wavelength, 90 °)) with respect to the linear polarization component of the plane of polarization parallel to the y-axis. Phase delay) occurs. In this embodiment, the polarization direction of the illumination light EO is parallel to the y axis, and the polarization direction of the illumination light OE is parallel to the x axis. Therefore, the illumination light OE has a 1/4 wavelength phase delay with respect to the illumination light EO.

The light beam having such a phase difference is incident on the polarization beam splitter 22. Of the light rays reaching the polarization beam splitter 22, θ2 = 45 with respect to the x-axis
The component of the plane of polarization parallel to the azimuth is transmitted and becomes the ray i1, and the component of the plane of polarization parallel to the azimuth of θ3 = 135 ° with respect to the x-axis is reflected and becomes the ray i2, along the optical axis AX1. proceed. As a result, the amplitude interference components are extracted from the illumination lights OE and EO, and an amplitude differential image (interference image) is obtained from the difference between the two, as will be described later.

On the other hand, the light beam reflected by the half mirror 18 enters the polarization beam splitter 24. Of the rays reaching the polarization beam splitter 24, the component of the plane of polarization parallel to the azimuth of θ4 = 0 ° with respect to the x-axis is transmitted and becomes a ray i11, which is parallel to the azimuth of θ5 = 90 ° with respect to the x-axis. The component of the plane of polarization is reflected to form the ray i22, and the optical axis AX2
Proceed along. As a result, intensity components are extracted from the illumination lights OE and EO, respectively, and an intensity differential image is obtained from the difference between the two, as will be described later. The Cartesian coordinates (X3,
The arrows shown in (Y3) to (X7, Y7) indicate the directions of the planes of polarization.

As described above, the interference (amplitude) component and the intensity component of the illumination lights EO and OE transmitted through the object are extracted by the optical system shown in FIG.

Next, assuming that the influence of the OTF of the lens is not considered, the light ray i at the step position of the reticle which is the object is
The intensity of the differential image of 1, ray i2, ray i11, and ray i22 is obtained. Since the step of the object to be observed is basically a one-dimensional structure, the following analysis will be performed in all one-dimensional including the optical system. The actual optical system is two-dimensional, but in the following discussion, the one-dimensional assumption is perfectly acceptable. Further, in the following description, the intensity of the point image on the image plane of the image-forming differential interference microscope will be described. However, except that the depth of focus also differs depending on the differential interference microscope of the laser scanning optical system, the image-forming differential Σ of the illumination system in the interference microscope
Since the same differential interference contrast image can be obtained by setting the values appropriately, it is basically applicable to the scanning type.

Further, the present embodiment has a structure of a laser scanning microscope which follows the optical system of the differential interference microscope. For this reason, the Nomarski prism 12 which is a light beam separating means.
Amplitude and phase information of the two beams on the object caused by is stored in one light beam generated by the interference of the two light waves in the Nomarski prism 16 which is a light beam combining means. Therefore, the differential interference contrast image can be obtained also by a photoelectric conversion element installed at a position other than the image plane, for example, near the pupil conjugate plane. The image pickup means (for example, a photoelectric conversion element) for obtaining the interference image may be installed at any position after the light beam combining means.

One image point obtained by the differential interference microscope corresponds to two object points separated from each other by the interval 2δ due to the shear of the Nomarski prism 12. If these are O (x + δ) and O (x−δ) and the relative phase difference between them is ψ, the following equation (1) is obtained. “J” is an imaginary unit.

[0034]

[Equation 1]

Differential interference microscope (mainly 1/4 wave plate 2
0) the phase difference added by α1 and α2, the intensity I at the image point corresponding to the rays i1, i2, i11 and i22
i1 (x, α1), Ii2 (x, α2), Ii11 (x), Ii22
(X) is expressed by the following equation (2) with C as a constant.
Here, the amplitude differential output Sa and the intensity differential output Si are defined by the following equation (3).

[0036]

[Equation 2]

(Equation 3)

Substituting the equation (2) into the equation (3),
The following equations (4) and (5) are obtained. Here, the error signal Sr
Is defined by the following equation (6), where k is a constant.

[0038]

(Equation 4)

(Equation 5)

(Equation 6)

By the way, when observing a circuit pattern on a defect-free binary reticle by transmitted illumination, the amplitude differential output Sa and the intensity differential output Si both have a value other than zero only at the step portion. That is, in the portion other than the step, the same phase change is imparted to the two sheared light rays by the reticle, so that their differential outputs become zero. However, in the step portion, since one light ray impinges on the step, different phase differences are given between the two, and as a result, the differential output has a value other than zero in the step portion. On the other hand, considering the case of performing defect detection by a simple binarization process, it is desirable to obtain an error signal Sr that is the minimum (or zero) when the circuit pattern on the binary reticle is defect-free.

There are two possible cases of the complex amplitude transmittance distribution showing the step of the circuit pattern on the defect-free binary reticle. The first is the step at the boundary between the glass portion and the phase shifter portion, and the second is the step at the boundary between the glass portion and the chromium light shielding film. These are all expressed in the form of the following equation (7), and only the values of the constants a0, b0 and Ψ0 change. Therefore, if the type of reticle to be inspected is determined, the values of the constants a0, b0, Ψ0 are determined, and if the constant k is calculated from the following equation (8) based on these values, the error signal Sr
For all steps and flat parts of the reticle with no defects,
In other words, it is possible to make all parts zero.

[0041]

(Equation 7)

(Equation 8)

Therefore, if the error signal Sr is binarized at an appropriate slice level, it becomes possible to detect contaminants such as defects and foreign matters in the phase shift amount of the phase shifter portion at the same time. When the constants a0, b0, Ψ0 are unknown, the constant k may be experimentally determined so that the error signal in the defect-free portion becomes zero.

[0043]

[Second Basic Form] Next, the second basic form will be described with reference to FIG. In this mode, the above-described first mode is implemented by an epi-illumination method. In this epi-illumination method, the condenser lens 12
And the objective lens 14 are shared by the objective lens 32, and the Nomarski prisms 10 and 16 also become one Nomarski prism 30. Also, the reflected light from the object is
It is extracted by the half mirror 28 in a direction different from the optical axis AX0 of the illumination optical system.

More specifically, the light ray i00 output from a light source (not shown) has an azimuth angle θ1 = 45 with respect to the x axis (X1 axis).
It is a linearly polarized laser beam with a polarization plane of °. For extracting such specific polarized light, for example, the polarizer 26
You can use. The light ray i00 travels along the optical axis AX0, is reflected by the half mirror 28, and is reflected in the direction of the Nomarski prism 30 along the optical axis AX.
The reflected light rays become illumination light EO, OE which is 2δ sheared on the object plane S which is the (X2, Y2) coordinate plane by the action of the Nomarski prism 30 and the objective lens 32.

A reticle (not shown) to be inspected is arranged on the object surface S, and the illumination light reflected by this is the objective lens 32 and the Nomarski prism 3.
By the action of 0, they are combined into one ray again. When the object is a perfect mirror surface with no phase difference, the phase difference given between the illumination light EO and OE between the object and the Nomarski prism 30 is an integral multiple of 2π so that the Nomarski prism 30 has a phase difference. The position is adjusted across the optical axis AX.

1 again by the Nomarski prism 30
The combined light rays sequentially enter the half mirrors 28 and 18. Then, the light rays that have passed through them pass through the quarter-wave plate 18 and reach the polarization beam splitter 20. The light beam reflected by the half mirror 16 enters the polarization beam splitter 22. The subsequent operation is the same as that of the first embodiment described above, and the interference (amplitude) component and the intensity component of the illumination light EO, OE reflected by the object are respectively extracted by the optical system of FIG.

[0047]

[Embodiment 1] Next, an embodiment of the present invention will be described with reference to FIG. The basic structure is the same as that shown in FIG. In FIG. 3, the light beam emitted from the laser light source 50 is a linearly polarized light having a plane of polarization of 45 ° on the paper surface. This light beam is converted into parallel light by the beam expander 52, is reflected by the reflection mirror 53, and is reflected by the XY scanning unit 5.
4 is incident. The light beam is spatially scanned and deflected by the XY scanning unit 54. The light beam after scanning is the first relay lens 56,
After passing through the second relay lens 58, the condenser lens 12
It is incident on the Nomarski prism 10 located near the pupil position of. After passing through the Nomarski prism 10, it is separated into two linearly polarized lights whose polarization directions are orthogonal to each other and which have a slight relative angle, and the condenser lens 12
Incident on. Each light beam refracted by the condenser lens 12 forms a beam spot on the binary reticle 60 on which the circuit pattern 62 is drawn.

On the binary reticle 60, two spots, which are slightly displaced from each other, are formed close to each other by the action of the Nomarski prism 10. These spots
The pattern 62 is two-dimensionally scanned by the action of the XY scanning unit 54.

The light beam that has passed through the binary reticle 60 enters the objective lens 14 and is refracted, passes through the Nomarski prism 16 located in the vicinity of the pupil position of the objective lens 14, and enters the half mirror 18. A part of the total amplitude passes through the half mirror 18, passes through the quarter wavelength plate 20, and reaches the polarization beam splitter 22. The light ray i1 transmitted through the polarization beam splitter 22 becomes linearly polarized light having an azimuth of 45 ° with respect to the x-axis. The light ray i2 reflected by the polarization beam splitter 22 becomes linearly polarized light having an azimuth of 135 ° with respect to the x-axis.

The ray i1 is refracted by the lens 64,
A video signal is output after being photoelectrically converted by a photoelectric conversion element 66 composed of a CCD or the like. The light ray i2 is refracted by the lens 68 and photoelectrically converted by the photoelectric conversion element 70 to output a video signal. These video signals are
It is input to the differential amplifier 72, and an amplitude differential signal is output from the differential amplifier 72. An amplitude differential image is obtained by this differential output.

On the other hand, the light beam reflected by the half mirror 18 reaches the polarization beam splitter 24. The light ray i11 transmitted through the polarization beam splitter 24 becomes a linearly polarized light having an azimuth of 0 ° with respect to the x axis. The light ray i22 reflected by the polarization beam splitter 24 becomes a linearly polarized light having an azimuth of 90 ° with respect to the x-axis.

The ray i11 is refracted by the lens 74,
The video signal is output after being photoelectrically converted by the photoelectric conversion element 76. The light ray i22 is refracted by the lens 78 and photoelectrically converted by the photoelectric conversion element 80 to output a video signal. These video signals are input to the differential amplifier 82, and an intensity differential signal is output from the differential amplifier 82. An intensity differential image is obtained by this differential output.

The azimuth angle of each of the above optical elements with respect to the x axis about the optical axis AX is positive in the y axis direction, the optical axis of the quarter wavelength plate 20 is 0 °, the Nomarski prism 10, The direction of the wedge of 16 is 0 °, the analyzer angle (θ2) of the polarization beam splitter 22 is + 45 °, and the analyzer angle (θ4) of the polarization beam splitter 24 is 0 °. Note that these are the same as those in FIG.

Further, as described above, the binary reticle 60
When there is no circuit pattern that causes a phase difference between the two beams above, for example, in the case of a parallel plate, the initial phase difference given to the two rays between the two Nomarski prisms 10 and 16 The position of the Nomarski prism 10 is adjusted by the actuator 84 in the direction crossing the optical axis AX so that the value becomes an integral multiple of 2π. The actuator 84 is controlled by the computer 86.

The outputs of the differential amplifiers 72 and 82 described above are
The error signal Sr is supplied to the subtractor 88, and the error signal Sr is calculated by the subtractor 88 based on the equation (6). The calculation result has 2 slice levels on the plus side and the minus side.
It is input to the signal processing circuit 90 having a window comparator circuit which is a binarization circuit. In the signal processing circuit 90,
The binarized signal of the error signal is obtained, and the value of the binarized signal and the value of the differential signal are output to the synchronizer 92.

The two slice levels on the plus side and the minus side of the window comparator circuit of the signal processing circuit 90 are set to a level at which a pseudo defect does not occur due to optical noise or electrical noise. The slice levels can be set externally via the interface 94 and the computer 86.

In the synchronizer 92, synchronization control of the XY scanning section 54 and the XY stage 59 during inspection is performed. The XY scanning unit 54 is driven via the actuator 96. The XY stage 59 includes the actuator 9
8 is driven. The computer 86 generates a map showing the position of the defect in the binary reticle 60 and the signal amount of the error signal Sr or the amplitude differential output Sa at the defect position, and this map is displayed on the display unit 100.

As described above, the Nomarski prism 10 includes the actuator 8 operated by the computer 86.
It is possible to make fine adjustments by the control of No. 4, which allows automatic setup before the start of inspection. At the time of this setup, for example, a reticle that is defect-free and has no circuit pattern is used. Also, interface 9
The external operator 4 is also used by the external operator to input the inspection sensitivity, the inspection area, the initial setting of the apparatus, the execution of the inspection, etc. to the computer 86.

As described above, according to the present embodiment, the conventional reticle for the circuit pattern made of the chrome light-shielding film and the halftone reticle for which the circuit pattern is drawn only by the phase shifter made of the light transmissive thin film are used. However, it is possible to simultaneously inspect whether or not the phase shift amount of the phase shifter portion is abnormal and whether or not a foreign object is attached to the optically transparent phase object.

[0060]

Second Embodiment Next, a second embodiment will be described with reference to FIG. The second embodiment is an example in which the first embodiment is configured by the epi-illumination method, and corresponds to the second basic form. In the figure, the light beam emitted from the laser light source 50 becomes parallel light by the beam expander 52, and is further spatially scanned and deflected by the XY scanning unit 54. The light beam after scanning enters the pupil projection lens 102 through the first relay lens 56 and the second relay lens 58. The light beam refracted by the pupil projection lens 102 is reflected by the half mirror 28 in the direction along the optical axis AX, and enters the Nomarski prism 30. After passing through the Nomarski prism 30, the two linearly polarized lights whose polarization directions are orthogonal to each other are separated into light beams having a slight relative angle, and are incident on the objective lens 32. Each light beam refracted by the objective lens 32 forms a beam spot on the binary reticle 60.

On the binary reticle 60, two spots, which are slightly displaced from each other, are formed close to each other by the action of the Nomarski prism 30. These spots
The pattern 62 is two-dimensionally scanned by the action of the XY scanning unit 54.

The light beam reflected by the binary reticle 60 enters the objective lens 32 and is refracted, and the objective lens 3
It passes through the Nomarski prism 30 located near the pupil position of No. 2 again and enters the half mirror 28. A part of the total amplitude passes through the half mirror 28 and enters the half mirror 18. Then, the light beam transmitted through the half mirror 18 passes through the quarter wavelength plate 20 and reaches the polarization beam splitter 22. On the other hand, the light beam reflected by the half mirror 18 reaches the polarization beam splitter 24. The operation thereafter is similar to that of the above-described first embodiment, and the differential amplifier 72,
At 82, an amplitude differential image and an intensity differential image are obtained respectively. Then, using them, an error signal is similarly generated, and the binary reticle 60 is inspected.

[0063]

Third Embodiment Next, a third embodiment will be described with reference to FIG. The third embodiment is almost the same as the second embodiment, but the position of the XY scanning unit 54 is different in the present embodiment. That is, the reflected light from the binary reticle 60 is
It is arranged to pass the XY scanning unit 54 again,
It has a so-called confocal microscope optical configuration.

Therefore, the photoelectric conversion elements 66, 70, 7
The light fluxes incident on 6, 80 always stand still regardless of the two-dimensional scanning of the laser beam on the binary reticle 60. Therefore, the light is condensed by the lenses 64, 68, 74, and 78, and pinholes 110, 112, 114, 116 are provided at the condensing points (points conjugate with the binary reticle) to eliminate unnecessary light such as flare. Is decreasing.

[0065]

Other Embodiments The present invention has many embodiments and can be variously modified based on the above disclosure. For example, the following is also included. (1) In the above-described embodiment, the means for adjusting the phase difference between the two sheared beams is constituted by a mechanism for moving the Nomarski prism in and out in the direction crossing the optical axis.
The same effect can be obtained by a quarter wavelength plate and a rotatable polarizer. Alternatively, the phase difference may be adjusted using an element such as a liquid crystal having a variable refractive index. The shear amounts of the two beams may be variable.

(2) Although a two-dimensional image pickup device such as a CCD is used in the above embodiment, any image pickup means may be used. Further, the output of the polarization beam splitter may be optically observed. In addition, a relay optical system or a mirror may be used if necessary.

(3) In the above-described embodiment, the present invention is mainly applied to the defect inspection of the reticle, but the present invention can be applied to all surface inspection devices for objects. For example, it is also effective for measuring the step of an object, inspecting a defect of a magnetic head, a wafer, etc., and measuring the position in consideration of the surface shape of the object.

[0068]

As described above, according to the present invention,
Both defects of the phase shift amount in the phase shifter pattern in the reticle and foreign matter of the light-transmissive phase object can be simultaneously inspected in a short time. It has the effect that it can also be used.

[Brief description of drawings]

FIG. 1 is a diagram showing a first basic configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a second basic configuration of the embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a third embodiment of the present invention.

[Explanation of symbols]

 10, 16 ... Nomarski prism 14, 32 ... Objective lens 18, 28 ... Half mirror 20 ... Quarter wave plate 22, 24 ... Polarization beam splitter (analyzer) 50 ... Laser light source 52 ... Beam expander 54 ... XY scanning 56, 58 ... Relay lens 59 ... XY stage 60 ... Binary reticle 62 ... Pattern 64, 68, 74, 78 ... Lens 66, 70, 76, 80 ... Photoelectric conversion element 72, 82 ... Differential amplifier 84, 96, 98 ... Actuator 86 ... Computer 88 ... Subtractor 90 ... Signal processing circuit 92 ... Synchronization device 94 ... Interface 100 ... Display unit 102 ... Pupil projection lens 110, 112, 114, 116 ... Pinhole

Claims (10)

[Claims] 1. Illumination means for supplying light of orthogonal first and second polarization directions for illumination; relative optical axes of the light of orthogonal first and second polarization directions obtained therefrom. And a light separating means for irradiating the object to be observed; a light combining means for combining the light having the first and second polarization directions transmitted or reflected by the object; the phase difference between the lights having the first and second polarization directions. Phase difference adjusting means for adjusting the intensity component; intensity component detecting means for detecting intensity components of light in the first and second polarization directions from the light combined by the light combining means; Interference component detecting means for detecting interference components in the first and second polarization directions; inspection means for inspecting an object from the detection results of the intensity component detecting means and the interference component detecting means; Characteristic object inspection device. 2. The object inspection apparatus according to claim 1, wherein at least one of the light separating means and the light combining main means includes a birefringent prism. 3. The object inspection apparatus according to claim 1, wherein the phase difference adjusting unit is a unit that moves at least one of the light separating unit and the light combining unit in a direction traversing the optical axis. . 4. The object inspection apparatus according to claim 1, wherein the phase difference adjusting unit includes a rotatable polarizer and a quarter-wave plate. 5. The phase difference adjusting means is a liquid crystal whose refractive index is controllable by a voltage.
Or the object inspection device according to 2. 6. The inspecting means is an imaging means for photoelectrically converting the detection component obtained by the intensity component detecting means or the interference component detecting means; an amplitude differential image and an intensity differential image from each detection signal obtained by the image sensing means. 5. An error signal generating means for generating an error signal whose intensity is adjusted based on the amplitude differential image and the intensity differential image obtained by the calculation means; 4. The object inspection device according to 4 or 5. 7. The object inspection apparatus according to claim 1, wherein at least one of the intensity component detection means and the interference component detection means includes a polarization beam splitter. 8. The object according to claim 1, wherein the illuminating means includes a laser light source and a scanning means for scanning a laser beam output from the laser light source. Inspection device. 9. The object inspection apparatus according to claim 8, wherein the scanning means is arranged in an optical path through which light rays of an outward path and a backward path of the object pass. 10. The shear amount of the optical axis by the light separating means is variable.
The object inspection device according to 5, 6, 7, 8 or 9.