JPH09280954A - Object inspecting instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a detection of foreign matters disturbing exposure simultaneously with the inspection of a defect in the difference of phase by inspecting the defect in the difference of phase over the entire area of a shifter within a binary reticle in a short time. SOLUTION: Two lights EO and OE adjusted in phase difference by a polarizer 10 and a 1/4 wavelength plate 12 out of the lights supplied from a lighting means is refracted by a condenser 16 with the optical axis thereof relatively sheared by a Nomarski prism 14 to be irradiated to an object to be observed. The light passing through the object is transmitted through an objective lens 18 to be synthesized by a Nomarski prism 20 and is divided by a half mirror 22 to be admitted into a polarized beam splitters 24 and 28. As a result, a plurality of interference components are extracted to inspect the object by performing a computation utilizing the squaring of two interference images involved and other interference images.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object observing apparatus, and more specifically to an object inspecting apparatus suitable for inspecting a reticle or mask for defects.

[0002]

BACKGROUND OF THE INVENTION As an apparatus for inspecting a phase shift amount defect of a shifter of a binary reticle,
For example SPIE, Proceedings series Volume 2254, `` Photom
Ask and X-Ray Mask technology ”, p.294-301. This is a device that measures the phase amount of the phase shifter on the reticle. The phase shifter part to be inspected in the reticle is positioned in the visual field of the optical microscope, and the phase of one sampled phase in the visual field is measured. A phase shift amount measuring device for a reticle with a phase shifter that measures the amount. Therefore, one inspection can obtain only the inspection result of one sampled point in the phase shifter. For this reason, it is not suitable for inspecting the presence or absence of defects in all parts of the reticle.

Further, as the defects of the reticle with the phase shifter, there are defects such as adhesion of foreign matter in addition to the above-mentioned defects relating to the phase. Therefore, as an object inspection device,
It is preferable that various kinds of defects can be comprehensively inspected. However, the above-mentioned phase shift amount measuring device only inspects for defects of the amount of phase difference and cannot inspect for the presence or absence of other foreign matter at the same time.

The present invention has been made in view of such circumstances, and an object thereof is to inspect defects of the phase difference amount in the entire area of the shifter in the binary reticle in a short time. Another object is to detect the foreign matter that interferes with the exposure simultaneously with the inspection of the phase difference amount defect. Yet another purpose is
An object inspection apparatus that can be used as a foreign matter inspection apparatus for a reticle without a shifter is provided.

[0005]

In order to achieve the above-mentioned object, the present invention provides an illumination means (50, 54) for supplying light for illuminating an object;
Phase difference adjusting means (10, 12, 14, 20) for adjusting the phase difference between the light beams of the first and second polarization directions which are orthogonal to each other; A light separating means (14) for irradiating an object to be observed by relatively shearing the optical axes of the light in the second polarization direction; the light in the first polarization direction and the second polarization transmitted or reflected by the object. Light combining means (20) for combining light in different directions; coherent from light supplied from the light combining means in a first direction, a second direction, and a third direction parallel to either the first direction or the second direction. Filter means (24, 26, 28) for extracting respective polarized light components to obtain first, second and third interference images; the first, second and third interference images obtained thereby Inspection means (70,78,82,86,72,74,88,90,9209
4,66); are provided.

According to another invention, coherent polarization components in the first direction, the second direction, and the third and fourth directions orthogonal to each other are extracted from the light supplied from the light combining means, respectively. The inspection target is inspected by utilizing the first, second, third and fourth interference images obtained by this.

The inspection means includes the first, second and third inspection means.
Of the interference image corresponding to the phase difference between the interference components and another one of the interference images, the inspection is performed by considering the optical characteristics of the inspection target. To do. Alternatively, of the first, second, third and fourth interference images,
The square of the difference between the interference images corresponding to the phase difference between the interference components,
The inspection is performed by performing the operation considering the optical characteristics of the inspection target with respect to the differential signal obtained by performing the operation considering the additional phase difference of the rays other than the principal ray on the other two interference images. I do.

According to a main aspect, there is provided branching means for branching the light supplied from the light combining means into first and second light, and the filter means comprises first and second light from the branched first light. It is characterized by including first filter means for obtaining the second interference image and second filter means for obtaining the third and fourth interference images from the branched second light.

The phase difference adjusting means includes, for example, (1) a rotatable polarizer and a quarter-wave plate, (2) a liquid crystal whose refractive index can be controlled by a voltage, and (3) the light in the direction crossing the optical axis. It comprises a separating means and a means for moving at least one of the photosynthetic means.

According to still another aspect, at least one of the light separating means and the light combining means is constituted by a birefringent prism, and the filter means is constituted by a polarization beam splitter. Further, the illuminating means includes a laser light source and a scanning means for scanning a laser beam outputted from the laser light source. The illuminating means is arranged in an optical path of light transmitted through or reflected by an object, and is conjugate with an object point. A pinhole is provided at the position.

The main aspects of the present invention are as follows. (1) An inspection device for inspecting a reticle for defects, wherein a laser light source that emits a first light beam and a first light beam are two linearly polarized lights 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 combining the two linearly polarized light rays refracted by the lens into a second light ray having a third polarization state, and two linearly polarized light rays having the first and second polarization states of the second light ray. The relative components of the rays of First phase difference adjusting means for adjusting a first phase difference which is a general phase difference amount, a half mirror for amplitude-dividing the second light ray into a third light ray and a fourth light ray, and the third light ray. Is separated into two linearly polarized light beams having fourth and fifth polarization states, and the fourth light beam is divided into two linearly polarized light beams having sixth and seventh polarization states. Between the second polarized light splitting means for splitting into a third polarized light component and a component of the third light ray, which is a linearly polarized light component parallel to the first polarization state and a linearly polarized light component parallel to the second polarization state. A second phase difference adjusting means for adjusting the second phase difference which is the relative phase difference amount of

The difference between the signal intensities of the photoelectric conversion signals of the first to fourth photoelectric conversion elements for photoelectrically converting the light rays of the fourth to seventh polarization states and the signal intensity of the photoelectric conversion signals of the first and second photoelectric conversion elements. First difference signal generating means for generating a certain first difference signal, and first signal strength adjustment for adjusting and outputting the relative strength of the signal strength of the photoelectric conversion signals of the third and fourth photoelectric conversion elements. Means, a second difference signal generating means for generating a second difference signal which is a difference between the two signal strengths after the relative strength is adjusted by the first signal strength adjusting means, and the first difference signal generating means. Signal strength squaring means for squaring the signal strength of the difference signal and outputting it as a square signal, and second signal strength adjusting means for adjusting and outputting the relative strength of the squared signal and the second difference signal. And the two after the relative intensity is adjusted by the second signal intensity adjusting means. Is the difference between the No. intensity and the error signal calculation means for calculating an error signal, binarizing the error signal, 2
An apparatus for inspecting a reticle, which has a binarizing means for outputting a binarized signal, and judges that there is a defect based on the binarized signal.

(2) An object 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 a reflection direction from a light-reflecting reticle, and a first half mirror for reflecting the first light beam toward the objective lens. A light ray separating means for separating the first light ray reflected by the first half mirror into two linearly polarized light rays having first and second polarization states and traveling in mutually different directions. , The objective lens collects the two linearly polarized light rays and outputs them in a first area of the reticle.
Two linearly polarized light beams having the first and second polarization states, which form two beam spots and travel in mutually different directions, pass through the objective lens, strike the reticle, are reflected, and are reflected again. The light is re-incident on the objective lens and the light beam splitting means, becomes a second light beam having a third polarization state, exits the light beam splitting means, and is transmitted through the first half mirror,
Further, a scanning means for two-dimensionally scanning the two beam spots in the first area and a relative phase difference amount between two linearly polarized light rays in the first and second polarization states. A first phase difference adjusting means for adjusting one phase difference, a second half mirror for amplitude-dividing the second light ray into third and fourth light rays, and a third light ray And a first polarization splitting means for splitting into two linearly polarized light rays of a fifth polarization state, and a fourth splitting means for splitting the fourth light ray into two linearly polarized light rays of a sixth and a seventh polarization state. A second polarization splitting means, and a relative component between the components of the third light ray, the components of the linearly polarized light parallel to the first polarization state and the components of the linearly polarized light parallel to the second polarization state. Second phase difference adjusting means for adjusting the second phase difference is the amount of phase difference,

The difference between the signal intensities of the photoelectric conversion signals of the first to fourth photoelectric conversion elements for photoelectrically converting the light rays of the fourth to seventh polarization states and the photoelectric conversion signals of the first and second photoelectric conversion elements. First difference signal generating means for generating a certain first difference signal, and first signal strength adjustment for adjusting and outputting the relative strength of the signal strength of the photoelectric conversion signals of the third and fourth photoelectric conversion elements. Means, a second difference signal generating means for generating a second difference signal which is a difference between the two signal strengths after the relative strength is adjusted by the first signal strength adjusting means, and the first difference signal generating means. It is the difference between the two signal intensities after the relative intensity is adjusted by the signal intensity squaring unit that squares the signal intensity of the difference signal and outputs it as a squared signal, and the second signal intensity adjusting unit. Error signal calculating means for calculating an error signal, and binarizing the error signal It has a binarizing means for outputting a binary signal, the inspection system of the reticle, characterized in that to determine that there is a defect on the basis of the 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. Alternatively, the reticle inspection device described in (2). (4) 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, (1) to (3) ) The reticle inspection device described above. (5) The first light ray 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. Reticle inspection device.

(6) The reticle inspection apparatus according to any one of (1) to (5) above, wherein one or both of the light beam splitting means and the light beam combining means is a birefringent prism. (7) The reticle according to (1) to (6), wherein the first phase difference adjusting means is a combination of a quarter-wave plate and a polarizer rotatable about an optical axis. Inspection equipment. (8) The reticle inspection apparatus according to any one of (1) to (7), wherein the second phase difference adjusting means is a quarter wavelength plate. (9) The first phase difference adjusting means is capable of adjusting 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. A reticle inspection apparatus according to any one of (1) to (6) above.

(10) The reticle inspection apparatus according to any one of (1) to (9), wherein the first and second polarization separation means are polarization beam splitters. (11) The fourth to seventh polarization states are linearly polarized light and are 4 with respect to the plane of polarization of the linearly polarized light in the first polarization state.
The reticle inspection apparatus according to (1) to (11), wherein the reticle inspection apparatus has an angle of 5 °. (12) The reticle inspection apparatus according to (1) to (11), wherein the plane of polarization of the linearly polarized light having the first polarization state and the plane of polarization of the linearly polarized light having the second polarization state are orthogonal to each other.

According to the present invention, of the light supplied from the illumination means, the phase difference between the light in the first and second polarization directions orthogonal to each other is adjusted by the phase difference adjusting means. The adjusted optical axes of the light of the first polarization direction and the light of the second polarization direction are applied to the object to be observed while being relatively sheared by the light separating means. The light of the first polarization direction and the light of the second polarization direction transmitted or reflected by the object are combined by the light combining means, and further coherent in the first to third different directions or the first to fourth different directions. The polarization component is extracted by the filter means. In the inspection means, for the interference image based on the obtained interference polarization component, two interference images corresponding to the phase difference between the interference components, for example, the difference between the interference images in which the absolute values of the phase difference between the interference components are equal to each other, The object is inspected by performing calculations using the square and other interference images.

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

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to Examples.

[0021]

[Basic Mode 1] First, the first basic mode will be described with reference to FIG. It should be noted that, with respect to each element in the figure, Cartesian coordinates (X1, Y1) to (X8, Y8)
Are orthogonal to the optical axis AX and have the same orientation, that is, the coordinates are set so that the coordinate axes overlap. Hereinafter, those directions will be simply expressed as (x, y). Also,
For ease of understanding, only the chief ray is used in the following description. Further, due to space limitations, the optical axis AX is divided into two and displayed, and the points A and A'are originally connected.

A light ray i00 for illumination emitted from a light source (not shown) is rotatable with a polarizer 10 and a quarter-wave plate 1
2. The light passes through the Nomarski prism 14 in order and enters the condenser lens 16. The polarizer 10 is a polarization direction of the transmitted light with an azimuth angle θ1 with respect to the x-axis, and this angle θ1 can be changed by rotating the polarizer 10. The quarter-wave plate 12 has a fast axis ne as an optical axis and a slow axis no orthogonal to the optical axis ne. The azimuth angle of the fast axis ne is 45 ° with respect to the x axis, and the azimuth angle of the slow axis no is x.
It is set at -45 ° to the axis. Of the incident light
The linear polarization component of the plane of polarization parallel to the slow axis no is fast axis ne
1/4 wavelength (9
0 °) phase delay occurs. The rays that have passed through the quarter-wave plate 12 are rays EO and OE that are 2δ sheared on the (X3, Y3) coordinate plane that is the object plane S by the Nomarski prism 14 and the condenser lens 16. Ray EO
Is a linearly polarized light with a plane of polarization parallel to the Y3 axis, and the ray OE
Is a linearly polarized light having a plane of polarization parallel to the X3 axis.

For example, the azimuth angle θ1 of the polarizer 10 is 1
When it coincides with the fast axis ne of the / 4 wave plate 12, the polarized light in the fast axis ne direction of the light ray i00 is transmitted as it is. The azimuth angle θ1 of the polarizer 10 is a quarter wave plate 12
Of the ray i00, the polarized light in the slow axis no direction of the ray i00 is 90% by the ¼ wavelength plate 12.
Transmitted after phase delay. In this way, the Polarizer 1
By the action of the 0 and 1/4 wavelength plates 12, the phase difference between the two linearly polarized light components EO and OE orthogonal to each other can be arbitrarily adjusted. Specifically, the relative phase difference α between the light rays EO and OE can be changed as shown in Expression (2) described below by changing the polarizer angle θ1.

Next, the light rays transmitted through the object on the object surface S are again combined into one light ray by the action of the objective lens 18 and the Nomarski prism 20. When the object is a perfect parallel plate having no phase difference, the Nomarski prism is adjusted so that the phase difference given between the illumination lights EO and OE between the two Nomarski prisms 14 and 20 is an integral multiple of 2π. The positions of 14 and 20 are adjusted in the direction crossing the optical axis AX.

The Nomarski prism 20 again sets 1
The combined rays enter the half mirror 22. Then, 50% of the total amplitude of light passes through the half mirror 22 and further reaches the polarization beam splitter (analyzer) 24. On the other hand, the remaining 50% of the light beam incident on the half mirror 22 passes through the quarter-wave plate 26, travels along the optical axis AX2, and reaches the polarization beam splitter 28.

The quarter-wave plate 26 has a fast axis ne as 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.

Next, of the rays reaching the polarization beam splitter 24, the component of the plane of polarization parallel to the azimuth of θ2 = 45 ° with respect to the x-axis is transmitted and becomes a ray i1, and θ3 = with respect to the x-axis. The component of the plane of polarization parallel to the azimuth of 135 ° is reflected to form a light ray i2, which travels along the optical axis AX1. As a result, interference components are extracted from the illumination lights OE and EO, and a differential interference image is obtained from the difference between them.

On the other hand, of the light rays reaching the polarization beam splitter 28, the component of the plane of polarization parallel to the azimuth of θ4 = 45 ° with respect to the x-axis is transmitted and becomes a light ray i11, and θ5 = 135 with respect to the x-axis. The component of the plane of polarization parallel to the azimuth angle is reflected and becomes a ray i22, which travels along the optical axis AX3. As a result, interference components are extracted from the illumination lights OE and EO, and a differential interference image is obtained from the difference between them. In addition,
The arrows shown in the Cartesian coordinates (X4, Y4) to (X7, Y7) indicate the directions of the planes of polarization.

Next, assuming that the influence of the OTF of the lens is not considered, the intensity of the differential interference image by the light rays i1, i2, i11, i22 at the step position of the object, for example, the reticle 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. Although the actual optical system is two-dimensional, in the following discussion, 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.

In addition, this embodiment has a structure of a laser scanning microscope which follows the optical system of the differential interference microscope. Therefore, the Nomarski prism 14 which is the light beam separating means
Amplitude and phase information of the two beams on the object generated by the above are stored in one light beam generated by the interference of the two light waves in the Nomarski prism 20, which is the 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. Therefore, the installation position of the imaging unit (for example, the photoelectric conversion element) for obtaining the interference image may be any position after the light beam combining unit.

One image point obtained by the differential interference microscope shown in FIG. 1 corresponds to two object points which are separated from each other by the interval 2δ due to the shear of the Nomarski prism 14. If these are O (+ δ) and O (−δ) and the relative phase difference between them is Ψ, the following equation (1) is obtained.
The expression (1) is a complex representation, where a and b represent amplitude components and exp (jΨ) represent phase components. “J” is an imaginary unit.

[0032]

[Equation 1]

Assuming that the phase difference added by the differential interference microscope is α1, α2, α11, α22, the relationship with the azimuth angle θ1 of the polarizer 10 is given by the following equation (2). Then, the interference image intensities Ii1 (x, α1), Ii2 (x, α) in the ideal optical system corresponding to the light rays i1, i2, i11, i22.
2), Ii11 (x, α11) and Ii22 (x, α22) are expressed by the following equation (3) with C as a constant.

[0034]

[Equation 2]

(Equation 3)

Here, the azimuth angle of the polarizer 10 is θ1 = π
By rearranging it as / 4, the following equation (4) is obtained. At this time, the light beam emitted from the quarter-wave plate 12 is linearly polarized light and has the same plane of polarization as that before the incidence on the quarter-wave plate 12, and no phase modulation is performed. Therefore, when θ1 = π / 4, the quarter wave plate 12 may be omitted. More generally, when θ1 is an integral multiple of π and π / 4 is added, 1
The quarter wave plate 12 may be omitted.

Further, in FIG. 1, polarized light other than linearly polarized light is assumed as the light source, and the linearly polarized light having an arbitrary polarization plane direction can be taken out by the polarizer 10. However, as in the embodiment described above, a laser light source is used. When used, linearly polarized light is emitted directly from the laser light source, so the polarizer 1
0 is not necessary. In this case, in order to rotate the plane of polarization, for example, a rotatable half-wave plate is provided instead of the polarizer 10, and this is rotated to rotate the plane of polarization by an angle corresponding to twice the angle of the polarizer. You can

[0037]

(Equation 4)

Here, the differential output S + (x) is given by the following (5
A) It is defined like the formula. In general, α11 = -α2
When 2, the above equation (5A) becomes equation (5B). Then, in the expression (5B), α11 = π / 2 + nπ (n = 0,1,2,3,
……), S + (x) becomes maximum like (5A), but it is not always necessary. Further, for this differential output, the error signal Se is defined by the following equation (6) with k being a constant.

[0039]

(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 S + (x) and the image signal Ii2 (x, α2 = π) are all at the step portion. Only has a non-zero value. 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. However, differential output S +
The sign of (x) changes at the rise and fall of the step. The squared image signal is completely similar to the image signal Ii2 (x, α2 = π). On the other hand, considering the case of performing defect detection by a simple binarization process, it is desirable to obtain the error signal Se 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 Se
For all steps and flat parts of the reticle with no defects,
In other words, it is possible to make all parts zero.

[0042]

(Equation 7)

(Equation 8)

It should be noted that the error signal Se in the equation (6) can be made completely zero by the coefficient shown in the equation (8), that is,
Transfer characteristics of optical system (numerical aperture, coherent illumination, in-
It has been confirmed by computer simulation that it can be realized without depending on the conditions such as coherent illumination). Therefore, if the error signal Se 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.

Although it has been assumed above that the objective lens 18 is ideal and the image signal Ii2 (x, α12 = π) becomes zero in the flat portion of the object, it does not become completely zero in the actual objective lens. On the other hand, the differential output S + (x) becomes completely zero in the flat part of the object. Image signal Ii2 (x, α12
= Π) does not become zero in the flat portion of the object, which is an obstacle to the purpose of making the error signal Se zero in all steps and flat portions (that is, all portions) of the defect-free portion of the reticle. Below, the method of overcoming this is demonstrated.

For example, in a transmission illumination type differential interference microscope,
By reducing the aperture stop of the illumination system when no object is present, only the chief rays are caused to interfere with each other, and the image signal Ii2 (x, α2 = π) of the equation (4) can be made almost zero. However, as the aperture stop is opened, the phenomenon that the background gradually becomes brighter can be observed experimentally. This is because the additional phase difference due to the objective lens remains in the rays other than the principal ray.

The additional phase difference of the rays other than the remaining principal ray is considered as the phase object O0 which does not depend on the position of the object, and is defined as in the following equation (9). In this formula,
“A0” indicates the amplitude of the illumination light, and γ is the average value of the additional phase difference of the rays other than the principal ray. It should be noted that “j” is an imaginary unit as in the equation (1).

[0047]

[Equation 9]

The additional phase difference of the rays other than the chief ray is not actually a single value, but varies depending on the position on the pupil plane of the objective lens 18 as it passes through the pupil plane.
Therefore, even if the phase difference is adjusted by the Nomarski prism 20 or the like, the image signal Ii2 (x, α2 = π) when there is no object in the state where the aperture stop is opened cannot be made completely zero. However, since the additional phase difference of rays other than the principal ray is generally a small value, it may be represented by an average value. Therefore, the intensity when the phase object O0 is observed with an ideal optical system, that is, the background intensity image signals Ii2 (O0, x), Ii1 (O
0, x) is obtained by the following equations (10) and (11). These are obtained by substituting the amplitude and phase of the equation (9) into the equation (4).

[0049]

(Equation 10)

[Equation 11]

Next, the differential output S0 of the background intensity is defined by the following equation (12) with kb being a constant. By substituting the equations (7) and (8) into the equation (12), the following equation (13) is obtained. Then, when the constant kb is set to the value of the following expression (14), S0 = 0, and the differential output related to the background can be completely zero. In this way, it is possible to obtain an image equivalent to the fact that the additional phase difference of the rays other than the principal ray is eliminated.

[0051]

(Equation 12)

(Equation 13)

[Equation 14]

Next, when observing the object represented by the equation (1) with the aperture stop open, if the object in consideration of the average value γ of the additional phase difference is expressed as Or, the following ( It becomes like the formula 15). At this time, the differential signal Sr corresponding to the equation (12) is given by the following (16) by the same constant kb as the equation (12).
It is shown by the formula.

[0053]

(Equation 15)

(Equation 16)

On the other hand, by substituting the equation (15) into the equation (4), the following equations (17) and (18) are obtained. By substituting these into the equation (16), the following equation (19) is obtained. The approximation of the equation (19) is accurately established, since the average value γ of the additional phase difference due to the objective lens 18 or the like is usually about 1 to 2 °. Therefore, according to the above observation method, the rotation of the phase remaining in the optical system is satisfactorily erased, and even if the aperture stop is opened, the ideal interference image Ii2 of the optical system shown by the equation (4) is obtained. An image equivalent to (x, α2 = π) can be obtained.

[0055]

[Equation 17]

(Equation 18)

[0056]

[Equation 19]

That is, when calculating the error signal Se of the equation (6), the differential signal Sr of the equations (16) and (19) is used instead of the image signal Ii2 (x, α2 = π) of the equation (4). Using, the expression (6) can be made completely zero by the coefficient according to the expression (8) in the flat part of the reticle, regardless of the actual characteristics of the objective lens 18, that is, the transfer characteristic of the optical system, that is, the numerical aperture or It can be realized regardless of conditions such as coherent illumination or in-coherent illumination.

[0058]

[Basic Form 2] 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 16 and the objective lens 18 are shared by the objective lens 34,
The Nomarski prisms 14 and 20 also become one Nomarski prism 32. Also, the reflected light from the object is extracted by the half mirror 30 in a direction different from the optical axis AX0 of the illumination optical system.

More specifically, the light ray i00 is transmitted by the polarizer 10
Is linearly polarized in the plane of polarization having an azimuth angle θ1 with respect to the x (X1) axis, passes through the quarter-wave plate 12, and undergoes phase modulation. Then, the light travels along the optical axis AX0 and enters the half mirror 30. The light beam reflected by the half mirror 30 travels along the optical axis AX and passes through the Nomarski prism 32 and the objective lens 34 in order. By the actions of the Nomarski prism 24 and the objective lens 26, the illumination light EO, OE which is 2δ sheared on the object plane S which is the (X3, Y3) coordinate plane is obtained. Illumination light EO is Y3
The linearly polarized light having the plane of polarization parallel to the axis and the illumination light OE are the linearly polarized light having the plane of polarization parallel to the X3 axis. Similarly, the illumination light EO, O
The relative phase difference α between E is the azimuth angle θ of the polarizer 10.
It can be changed by changing 1 (see the above formula (2)).

The illumination light reflected by the object on the object surface S is again combined into one light beam by the action of the objective lens 34 and the Nomarski prism 32. When the object is a perfect mirror surface having no phase difference, the phase difference of the Nomarski prism 32 is adjusted so that the phase difference given between the illumination light EO and OE between the object and the Nomarski prism 32 becomes an integral multiple of 2π. The position is adjusted across the optical axis AX. The rays that have been combined again by the Nomarski prism 32 enter the half mirror 30. Then, the light ray that has passed through this enters the half mirror 22. The subsequent operation is similar to that of the above-described first embodiment.

[0061]

[Example of Simulation] Next, referring to FIGS. 3 to 6, one-dimensional simulation results when an ideal objective lens for a main signal is assumed will be described. Various conditions are as follows. (1) Wavelength of illumination light: 488 nm, (2) Illumination condition: Epi-illumination of coherent illumination, (3) Numerical aperture NA of objective lens; 0.4, (4) Object to be inspected; 50 nm chromium on reticle Imagine a membrane. There is a 5 μm wide chrome-free portion in the chrome film, and the glass is exposed here. In addition, the phase difference ψ due to the step of the film is 2 × (50 nm / 488 nm)
× 360 ° = 73.77 °. The intensity reflectance of the chrome portion is 48%, and the intensity reflectance of the glass portion is 4%.

The main signals obtained by performing the simulation calculation under such conditions are shown in the graphs of FIGS. In each case, the horizontal axis represents the one-dimensional position on the reticle, and the unit is μm. The vertical axis of FIG. 3 represents intensity or reflectance, and “1” corresponds to reflectance of 100%. The vertical axis of FIG. 4 represents the normalized intensity. In FIG. 3, the image signal Ii2 (x, α2 = π) and the differential output S + (x) are shown.
The graph of the bright field image IM observed when the analyzer of the differential interference microscope is removed is also shown. In the bright field image IM, although the image is somewhat uneven due to the influence of the Nomarski prism, it shows almost the reflectance distribution of the pattern on the reticle. Therefore, the portion where the bright-field image IM changes greatly corresponds to the stepped portion of the pattern.

FIG. 4 shows the image signal Ii2 (x, shown in FIG.
α2 = π), the result of performing a constant calculation on the differential output S + (x) is shown. That is, the constant k is set so that the error signal Se of the equation (6) is minimized (to satisfy the equation (8)) when the phase difference is 73.7 °, and then the right side of the equation (6) is calculated. Two graphs normalized by multiplying the first and second terms by a coefficient k1 and the error signal S corresponding to the difference between them
A total of three graphs obtained by multiplying e by a coefficient k1 are drawn.
As is apparent from FIG. 4, the graph of the first term and the graph of the second term on the right side of the equation (6) completely overlap. Therefore, the error signal Se, which is the difference between the two, becomes completely zero.

Next, FIG. 5 shows the result of calculation of how the error signal Se changes when the value of the constant k determined previously is fixed and the chrome film thickness is changed. ing. The vertical axis and the horizontal axis are the same as in FIG. The chrome film thickness corresponds to the phase difference, and the phase difference ψ = 60 ° (= 73.7
7-13.7 °) and 90 ° (= 73.77 + 16.3 °) were calculated. As shown in the figure, as the phase difference increases, the signal strength increases at the step portion.

Here, for example, if the signal is detected at the slice level th, it is not detected when ψ = 73.77 °, but it is detected when ψ = 60 ° and 90 °. The difference between the two is 73.77-60 = 13.77 °. This value is 13.77 ° / 360 ° × 488, considering that it is the result of giving twice the optical path difference to the epi-illumination light in the round trip.
This corresponds to a very small step variation of nm / 2 = 9.33 nm (= λ / 52). As described above, according to the present invention, even a very small step change can be easily detected.

Further, FIG. 6 shows the vertical axis of FIG. 5 magnified 100 times or more. As is clear from this graph, the error signal Se when the phase difference ψ = 73.77 ° is completely zero. Therefore, depending on the setting of the slice level th for signal detection, it is possible to detect even a minute step change.

As described above, according to the present invention, by eliminating the signal of a defect-free step, that is, a step of a specific normal height (film thickness) or reflectance, a step having a defect, that is, an abnormal step. It is possible to satisfactorily detect steps in height and reflectance,
Abnormalities in the amount of phase shift, such as phase shifters, can be easily detected, as well as foreign matter on the reticle. In addition, it is possible to completely erase an image of a defect-free step. Therefore, the resolution limit of the objective lens (= λ / NA (coherent illumination)
It is possible to favorably detect an abnormality in height or reflectance even with respect to a step of an object of about λ / 2NA (in-coherent illumination).

[0068]

[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. 7, the light beam emitted from the laser light source 50 is linearly polarized light having a polarization plane 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 16
It enters the Nomarski prism 14 located in the vicinity of the pupil position. After passing through the Nomarski prism 14, it is separated into two linearly polarized lights whose polarization directions are orthogonal to each other and which make a slight relative angle, and the condenser lens 16
Incident on. Each light beam refracted by the condenser lens 16 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 14. These spots
By the action of the XY scanning unit 54, the pattern 62 is one-dimensionally scanned in the X direction. When performing an object inspection by optical scanning and driving of a stage, the optical scanning means in the apparatus as shown in FIG.
It is not particularly necessary to perform two-dimensional scanning, and one-dimensional scanning may be used. However, when it is desired to observe a defective portion at an arbitrary position from the inspection result, it is more convenient to perform two-dimensional optical scanning and display the two-dimensional image with the stage 59 stationary.

The light beam that has passed through the binary reticle 60 is incident on the objective lens 18, is refracted, passes through the Nomarski prism 20 located near the pupil position of the objective lens 18, and is incident on the half mirror 22. A part of the total amplitude passes through the half mirror 22 and reaches the polarization beam splitter 24. The light ray i1 transmitted through the polarization beam splitter 24 is
It becomes a linearly polarized light having an azimuth of 45 ° with respect to the x axis. The light ray i2 reflected by the polarization beam splitter 24 becomes linearly polarized light having an azimuth of 135 ° with respect to the x-axis.

On the other hand, the light beam reflected by the half mirror 22 passes through the quarter-wave plate 26 and reaches the polarization beam splitter 28. The light ray i11 transmitted through the polarization beam splitter 28 becomes linearly polarized light having an azimuth of 45 ° with respect to the x-axis. The light ray i22 reflected by the polarization beam splitter 28 becomes a linearly polarized light having an azimuth of 135 ° with respect to the x-axis.

With respect to the azimuth angle with respect to the x-axis centering on the optical axis AX of each of the above-mentioned optical elements, assuming that the y-axis direction is positive, the optical axis of the quarter-wave plate 26 is 0 °, the Nomarski prism 14, The direction of the wedge of 20 is 0 °, the analyzer angle (θ2) of the polarization beam splitter 24 is + 45 °, and the analyzer angle (θ4) of the polarization beam splitter 28 is + 45 °. 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 above two beams, for example, in the case of a parallel plate, the initial phase difference given to the two rays between the two Nomarski prisms 14 and 20. The position of the Nomarski prism 14 is adjusted by the actuator 64 in the direction crossing the optical axis AX so that the value becomes an integral multiple of 2π. The actuator 64 is controlled by the computer 66.

The ray i1 is refracted by the lens 68,
A video signal is output after being photoelectrically converted by a photoelectric conversion element 70 composed of a CCD or the like. The video signal is input to the attenuator (multiplier) 72, multiplied by the constant kb shown in the equation (14), and input to the differential amplifier 74. This constant kb is a fixed value determined for each optical system, and once set, it need not be changed for all inspection objects.

On the other hand, the light ray i2 is refracted by the lens 76 and photoelectrically converted by the photoelectric conversion element 78 to output a video signal. This video signal is input to the differential amplifier 74, and the differential signal is output from the differential amplifier 74.

The ray i11 is refracted by the lens 80,
A video signal is output after being photoelectrically converted by the photoelectric conversion element 82. The light ray i22 is refracted by the lens 84, photoelectrically converted by the photoelectric conversion element 86, and a video signal is output. These video signals are input to the differential amplifier 88, and the differential signal is output from the differential amplifier 88.

The outputs of the differential amplifiers 74 and 88 described above are
The error signal Se is supplied to the subtractor 90, and the error signal Se is calculated by the subtractor 90 based on the equation (6). For this operation,
An operation of squaring the output value of the differential amplifier 88 is also included. The amplification factor with respect to the output of the subtractor 90 can be controlled by the computer 66. By registering this amplification factor by the operator, the detection sensitivity of the reticle defect can be changed. The coefficient k in the equation (6) is determined prior to the defect inspection so as to minimize the error signal Se by utilizing the defect-free step portion in the circuit pattern on the reticle. Alternatively, as another method, the coefficient k may be determined by the equation (8).

Therefore, the computer 66 controls the actuator 64 to finely adjust the Nomarski prism 14 to set the initial phase difference amount of the microscope before the inspection is started, and the operator's necessary work for the coefficient k of the equation (6). The computer 66 can be programmed so as to automate only the act of registering a defect-free portion in the reticle 60.

The error signal Se which is the subtraction result is input to the signal processing circuit 92 which has a window comparator circuit which is a binarizing circuit having two slice levels on the plus side and the minus side. In the signal processing circuit 92, the binarized signal of the error signal is obtained, the value of the binarized signal, the error signal Se, the values of the two differential signals, etc. are output to the synchronizer 94, and further to the computer 66. Supplied.

The two slice levels on the plus side and the minus side of the window comparator circuit of the signal processing circuit 92 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 from the outside via the interface 96 and the computer 66. In the synchronizer 94, the XY scanning unit 54 that is performing the inspection and the X-
The Y stage 59 is synchronously controlled. The XY scanning unit 54 is driven via the actuator 98. X-
The Y stage 59 is driven via the actuator 99.

The computer 66 creates a defect map based on the binarized signal indicating the presence of a defect and the position information from the synchronizer 94 indicating the position of the defect and displays it on the display unit 100. Further, the degree of the defect detected by the binarization circuit is approximately proportional to the error signal Se before being binarized, the output values of the two differential amplifiers, etc. It may be displayed on 100. That is, 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 is generated and displayed on the display unit 100.

Next, according to the present embodiment, the XY stage 5
9 allows any area on the reticle 60 to be inspected. This will be described below with reference to FIG. The operator designates a part of the area on the reticle 60 as the inspection area D, for example. On the other hand, the device of this embodiment shown in FIG. 7 is supposed to be able to observe the inside of the visual field FV, for example. In this case, the reticle 60 is moved at a constant speed by the XY stage 59.
For example, while moving in the Y direction, reciprocal optical scanning of the light rays EO and OE in the X direction is performed. In the illustrated example, the rays EO,
The shear direction of the OE coincides with the optical scanning direction, and both are in the X direction. Therefore, since the shear amount 2δ exists, the scanning distance L becomes 2δ shorter than the diameter of the visual field FV at the maximum. Of course, the shear direction does not necessarily have to match the optical scanning direction. The area to be inspected by one-time optical scanning is an area indicated by SI that is scanned by any light beam of EO and OE. As a result, the presence or absence of defects is inspected in the hatched region S.

The width W of the band-shaped area S is continuously expanded or reduced in the Y direction, or the reticle 60 is stepwise moved in the X direction to expand the area S in the X direction. You may proceed. Further, from the sampling theorem, it is desirable that the feeding speed of the reticle 60 in the Y direction be equal to or less than 1/2 of the resolution limit of the microscope. By doing so, all resolvable information of the microscope can be captured as image information. Similarly, when converting an image signal into time-series digital data, the resolution limit of 1
It is preferable to take in with a fineness of / 2 or less.

Further, as described above, the Nomarski prism 14 (or 20) can be finely adjusted by the control of the actuator 64 by the computer 66, whereby the setup before the start of the inspection can be automatically performed. At the time of this setup, for example, a reticle that is defect-free and has no circuit pattern is used. In addition, the interface 96 is a computer 6 operated by an external operator.
It is also used to input the inspection sensitivity, the inspection area, the initial setting of the apparatus, the execution of the inspection, etc.

As described above, according to the present embodiment, the conventional reticle of the circuit pattern made of the chrome light shielding film and the halftone reticle in 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.

[0086]

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 30 in the direction along the optical axis AX, and enters the Nomarski prism 32. After passing through the Nomarski prism 32, 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 34. Each light beam refracted by the objective lens 34 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 32. 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 34 and is refracted, and the objective lens 3
After passing through the Nomarski prism 32 located near the pupil position 4 again, the light enters the half mirror 30. A part of the total amplitude passes through the half mirror 30 and enters the half mirror 22. Then, the light beam transmitted through the half mirror 22 reaches the polarization beam splitter 24. On the other hand, the light beam reflected by the half mirror 22 reaches the polarization beam splitter 28 via the quarter-wave plate 26. The subsequent operation is similar to that of the first embodiment described above, the error signal Se is generated in the subtractor 90, and the binary reticle 60 is inspected.

[0089]

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 arranged so as to pass through the XY scanning unit 54 once again, which is an optical configuration of a so-called confocal microscope.

Therefore, the photoelectric conversion elements 70, 78, 8
The luminous fluxes incident on 2,86 are always stationary regardless of the two-dimensional scanning of the laser beam on the binary reticle 60. Therefore, light is condensed by the lenses 68, 76, 80, 84, 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. The resolution of the confocal microscope is equivalent to that of the imaging type microscope of incoherent illumination, and the resolution limit is halved as compared with the case without the aperture. Moreover, the influence of objects other than the focal plane can be reduced.

[0091]

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) The above embodiment is an example of a laser scanning microscope, but the apparatus may be constructed by using an imaging microscope using a halogen lamp or a mercury lamp. In this case, unlike the beam spot of the laser, the illumination light collectively illuminates the objective lens. Therefore,
An image sensor having a plurality of pixels is used as a photoelectric conversion element, and this is arranged at an image forming position conjugate with an object.

(4) In the above-mentioned 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 apparatuses 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.

[0095]

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 perspective view showing a first basic form of the present invention.

FIG. 2 is a perspective view showing a second basic form of the present invention.

FIG. 3 is a graph showing an example of a simulation of a main signal according to the above embodiment.

FIG. 4 is a graph showing an example of a simulation of a main signal according to the above embodiment.

FIG. 5 is a graph showing an example of a simulation of a main signal according to the above embodiment.

FIG. 6 is a graph showing an example of a simulation of a main signal according to the above embodiment.

FIG. 7 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 8 is a diagram showing how a reticle is inspected in the first embodiment.

FIG. 9 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a third embodiment of the present invention.

[Explanation of symbols]

 10 ... Polarizer 12 ... Quarter wave plate 14, 20, 32 ... Nomarski prism 16 ... Condenser lens 18, 34 ... Objective lens 22, 30 ... Half mirror 24, 28 ... Polarization beam splitter (analyzer) 50 ... Laser light source 52 ... Beam expander 54 ... XY scanning unit 56, 58 ... Relay lens 59 ... XY stage 60 ... Binary reticle 62 ... Pattern 64, 98, 99 ... Actuator 66 ... Computer 68, 76, 80, 84 ... Lens 70 , 78, 82, 86 ... Photoelectric conversion element 72 ... Attenuator 74, 88 ... Differential amplifier 90 ... Subtractor 92 ... Signal processing circuit 94 ... Synchronizing device 96 ... Interface 100 ... Display unit 102 ... Pupil projection lens 110, 112, 114, 116 ... Pinhole D, S ... Inspection area FV ... Field of view L ... Scan Away W ... inspection range

Claims (12)

[Claims] 1. Illumination means for supplying light for illuminating an object; first of the lights supplied thereby orthogonal to each other
And a phase difference adjusting means for adjusting the phase difference between the light in the second polarization direction; and the optical axes of the light in the first polarization direction and the light in the second polarization direction, the phase differences of which are adjusted by the phase difference adjusting means. Light separating means for irradiating an object to be observed after shearing; light combining means for combining the light of the first polarization direction and the light of the second polarization direction transmitted or reflected by the object; supplied from the light combiner From the light, coherent polarization components in the first direction, the second direction, and the third direction parallel to either the first direction or the second direction are extracted, and the first, second, and third interference images are extracted. An object inspecting device, comprising: a filter unit for obtaining an inspection target; an inspection unit that inspects an inspection target by using the first, second, and third interference images obtained thereby. 2. The inspection means is configured to square the difference between the interference images corresponding to the phase difference between the interference components of the first, second and third interference images and another interference image. The object inspection apparatus according to claim 1, wherein the inspection is performed by performing a calculation in consideration of the optical characteristics of the inspection target. 3. Illumination means for supplying light for illuminating an object; first of the lights supplied thereby orthogonal to each other
And a phase difference adjusting means for adjusting the phase difference between the light in the second polarization direction; and the optical axes of the light in the first polarization direction and the light in the second polarization direction, the phase differences of which are adjusted by the phase difference adjusting means. Light separating means for irradiating an object to be observed after shearing; light combining means for combining the light of the first polarization direction and the light of the second polarization direction transmitted or reflected by the object; supplied from the light combiner From the light, the first direction, the second direction, the third orthogonal
And filter means for respectively extracting coherent polarization components in the fourth and fourth directions to obtain first, second, third, and fourth interference images; the first, second, and second filters thus obtained. An object inspection apparatus, comprising: an inspection means for inspecting an inspection object using the third and fourth interference images. 4. The inspection means includes the first, second, and third
In the fourth interference image, the square of the difference between the interference images corresponding to the phase difference between the interference components and the additional phase difference of the rays other than the chief ray with respect to the other two interference images are considered. 4. The inspection is performed by performing an operation in consideration of the optical characteristics of the inspection target on the differential signal obtained by performing the above operation.
The object inspection device described. 5. A branching unit that branches the light supplied from the light combining unit into first and second lights, and the filter unit includes first and second interferences from the branched first light. A first filtering means for obtaining an image and a second branched one
5. The object observing apparatus according to claim 1, further comprising a second filter means for obtaining third and fourth interference images from the light. 6. The object observation apparatus according to claim 1, wherein the phase difference adjusting means includes a rotatable polarizer and a quarter-wave plate. 7. The object observing apparatus according to claim 1, wherein the phase difference adjusting means is a liquid crystal whose refractive index is controllable by a voltage. 8. The phase difference adjusting means is means for moving at least one of the light separating means and the light combining means in a direction crossing an optical axis.
The object observation device according to 2, 3, 4 or 5. 9. The object observing apparatus according to claim 1, wherein at least one of the light separating means and the light synthesizing means is a birefringent prism. 10. The filter means comprises a polarization beam splitter, 1, 2, 3, 4, 4.
The object observation device according to 5, 6, 78 or 9. 11. The illuminating means includes a laser light source and a scanning means for scanning a laser beam output from the laser light source, 1, 2, 3, 4, 5, 6, 7, 7.
The object observation device according to 8, 9, or 10. 12. The object observing apparatus according to claim 10, wherein the scanning means is arranged in an optical path of light transmitted or reflected by the object, and a pinhole is provided at a position conjugate with an object point. .