JP2001141428A - Inspecting device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inspect microstructure patterns such as circuit patterns formed in semiconductor wafers speedily and appropriately. SOLUTION: An ultraviolet laser beam from an ultraviolet solid-state laser 2 is shone on the L/S pattern 101 of a semiconductor wafer 100, which is an object to be inspected, and the reflected light is subjected to Fourier transform by a Fourier-transform lens 17. Then the Fourier-transform image of the L/S pattern 101 is picked up by a COD image pickup element 18. The state of the L/S pattern 101 is inspected on the basis of the Fourier-transform image of the picked-up L/S pattern 101.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an inspection apparatus used for inspecting a device having a fine pattern such as a semiconductor integrated circuit and an inspection method for inspecting a device having a fine pattern.

[0002]

2. Description of the Related Art In recent years, with the progress of digitization in the electric industry, the integration of semiconductor integrated circuits has been actively improved. How to efficiently provide such a highly integrated semiconductor integrated circuit at low cost is an important issue that will influence the development of the digital electric industry in the future.

In order to efficiently produce a semiconductor integrated circuit at low cost, it is important to quickly and accurately detect a problem occurring during a manufacturing process. For this reason, there is an increasing demand for an inspection device capable of inspecting a fine pattern with high accuracy.

[0004] In addition to semiconductor integrated circuits, such an inspection apparatus is very important for efficiently producing devices requiring fine processing such as magnetic heads used in hard disk drives at low cost. is there.

As an inspection apparatus having a high resolution, a scanning electron microscope (SEM) is available.
e) and Atomic Force Microsco (AFM)
Those using pe) are known. However, these scanning electron microscopes and atomic force microscopes are inconvenient to handle because a vacuum is required for inspection, and have a problem that it takes time to inspect the entire device.

On the other hand, an inspection apparatus using an optical microscope has an advantage that inspection can be performed in a non-destructive and non-contact manner without requiring a vacuum. In recent years, a solid-state laser that emits ultraviolet light by wavelength conversion such as a YAG laser using a nonlinear optical crystal has been developed. The solid-state laser is used as an illumination light source, and an illumination optical system is configured using a high NA objective lens. If this is the case, the optical microscope is expected to have a resolution as thin as that of a scanning electron microscope or the like.

[0007]

The patterns of semiconductor integrated circuits and the like to be inspected have been increasingly miniaturized in recent years, and the dimensions of the fine structures have reached the same level as the wavelength of illumination light. ing.

When such a fine structure is irradiated with illumination light, diffraction occurs in the illumination light. When the light having this diffraction is observed on the image plane, an intensity distribution of a predetermined pattern is obtained according to the degree of the diffraction, that is, the diffraction efficiency with respect to the illumination light of the fine structure.

The diffraction efficiency of a fine structure to be inspected changes according to the variation of the pattern of the fine structure. Specifically, for example, when the microstructure is a concavo-convex pattern in which concave portions and convex portions are lined up at a predetermined period, the diffraction efficiency of the fine structure is changed in accordance with a change in the width of the convex portion, a change in the depth of the concave portion, and the like. change.
When the diffraction efficiency of the fine structure changes, the intensity distribution of the pattern observed on the image plane changes. Therefore, it is possible to detect a change in the pattern of the fine structure from a change in the intensity distribution of the pattern observed on this image plane.

As described above, if the fluctuation of the pattern of the fine structure is detected from the change of the intensity distribution of the pattern observed on the image plane of the diffracted light, the resolution exceeding the resolution of the optical microscope can be greatly improved. Since a fine pattern variation can be detected, it is very useful as an inspection device.

However, when such a fine structure is irradiated with partially coherent light as illumination light,
The relationship between the pattern observed on the image plane and the fine structure pattern is not linear. Even if the partial coherence is considered, the scalar imaging theory can normally handle only objects whose microstructure dimensions are about three to five times the wavelength of the illumination light. Because Kirchhoff's boundary condition does not hold for objects with finer structures,
This is because Maxwell's equations must be solved for boundary conditions.

In particular, when the diffraction efficiency of the fine structure exceeds a predetermined value, the intensity distribution of the pattern observed on the image plane of the fine structure contains a frequency component twice as large as the spatial frequency of the pattern of the fine structure. Come to appear. Therefore, when obtaining information about the pattern of the fine structure from the intensity distribution of the pattern observed on the image plane of the fine structure, it is necessary to determine such a double frequency component. Processing for inspecting a pattern of a fine structure is complicated, which is a factor that hinders quickness of the inspection.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an inspection apparatus and an inspection method capable of quickly and appropriately inspecting a fine structure pattern. .

[0014]

According to the present invention, there is provided an inspection apparatus for illuminating an inspection object by irradiating an inspection object having an uneven pattern with a predetermined period with illumination light, and the illumination means. Fourier transform means for performing Fourier transform of reflected light or transmitted light from the object illuminated by the above, and Fourier transform of the inspected object by detecting reflected light or transmitted light of the object which has been Fourier transformed by the Fourier transform means. Imaging means for imaging the converted image. In this inspection apparatus, the state of the inspection object is inspected based on the Fourier transform image of the inspection object captured by the imaging unit.

Specifically, in this inspection apparatus, for example,
Fluctuations in the uneven pattern of the object to be inspected are inspected from changes in the amount of light of the Fourier transform image of the object to be inspected due to changes in the diffraction efficiency of the uneven pattern of the object to be inspected.

That is, when illuminating light is irradiated from the illuminating means onto the concave / convex pattern of the inspection object, the reflected light or transmitted light is diffracted. At this time, if a pattern variation such as a variation in the width of the concave portion or the convex portion occurs in the concave / convex pattern, the diffraction efficiency of the concave / convex pattern changes according to the pattern variation.

Then, when the reflected light or transmitted light from the inspection object on which the diffraction has occurred is Fourier-transformed by the Fourier transformation means, and the Fourier-transformed image of the inspection object is imaged by the imaging means, it appears in the imaged Fourier-transformed image. The light quantity of each diffraction order light changes according to the diffraction efficiency of the concavo-convex pattern.

Therefore, if a change in the amount of light of each diffraction order light appearing in the captured Fourier transform image is detected, a change in the concavo-convex pattern of the object to be inspected, for example, a change in the width of a concave portion or a convex portion is detected. be able to.

According to the inspection apparatus of the present invention, as described above, the state of the inspection object is inspected based on the Fourier transform image of the inspection object captured by the imaging means. The inspection can be performed quickly and appropriately.

In this inspection apparatus, it is desirable that the illumination means include an incident angle varying means for varying an incident angle of the illumination light with respect to the inspection object. As described above, when the illumination unit includes the incident angle variable unit that varies the incident angle of the illumination light with respect to the inspection object, for example, the incident angle of the illumination light with respect to the inspection object is set to an optimum angle according to the inspection object. By setting the incident angle, the inspection of the inspection object can be performed effectively, and a plurality of Fourier transform images of the inspection object illuminated at the respective incident angles while changing the incident angle of the illumination light. It is possible to inspect the state of the inspection object based on the above, and the inspection of the inspection object can be performed more appropriately.

In this inspection apparatus, it is desirable that the illuminating means irradiates the object to be inspected with ultraviolet laser light as illumination light. In this way, when the illuminating means irradiates the object to be inspected with ultraviolet laser light, which is light having a very short wavelength, as illumination light, compared with the case where visible light is illuminated as illumination light, Inspection of an inspection object having a finer pattern can be appropriately performed.

When the illuminating means irradiates the inspection object with an ultraviolet laser beam which is coherent light as illumination light, speckle noise is generated. It is desirable to provide a speckle averaging means for canceling speckle noise in the optical path.

The inspection apparatus further includes polarization separation means for polarizing and separating the reflected light or transmitted light from the object to be inspected, and the imaging means individually detects the polarized components separated by the polarization separation means. Then, it is desirable to individually capture the Fourier transform images of the inspection object. As described above, the reflected light or the transmitted light from the inspection object is polarization-separated by the polarization separation unit, the polarization-separated polarization components are individually detected by the imaging unit, and the Fourier transform images of the inspection object are respectively detected. In the case where individual images are taken, it becomes possible to perform multifaceted inspection by utilizing the polarization dependence of the inspection object,
The inspection of the inspection object can be performed more appropriately.

Further, another inspection apparatus according to the present invention includes an illuminating means for illuminating the inspection object by irradiating the inspection object with an ultraviolet laser beam as illumination light, and an inspection apparatus illuminated by the illumination means. Fourier transform means for Fourier transforming reflected light or transmitted light from the object, and imaging for detecting the reflected light or transmitted light of the inspected object Fourier-transformed by the Fourier transform means to capture a Fourier transformed image of the inspected object Means. In this inspection apparatus, the state of the inspection object is inspected based on the Fourier transform image of the inspection object captured by the imaging unit.

According to this inspection apparatus, the state of the inspection object is inspected based on the Fourier transform image of the inspection object imaged by the imaging means, so that the inspection of the inspection object can be performed quickly and appropriately. Can be. Further, in this inspection apparatus, since the illumination unit illuminates the inspection object by irradiating ultraviolet laser light as illumination light, the inspection object having a finer pattern than in the case of irradiating visible light as illumination light. Inspection can be performed appropriately.

In this inspection apparatus, since the illumination means irradiates the inspection object with ultraviolet laser light, which is coherent light, as illumination light, speckle noise occurs in the illuminated image of the inspection object. . Therefore, in this inspection apparatus, in the optical path of the ultraviolet laser light irradiated on the inspection object,
It is desirable to provide a speckle averaging means for canceling speckle noise.

In this inspection apparatus, it is desirable that the illuminating means include an incident angle varying means for varying an incident angle of the ultraviolet laser light to the inspection object. As described above, when the illumination unit includes the incident angle changing unit that changes the incident angle of the ultraviolet laser light with respect to the inspection object, for example, the incident angle of the ultraviolet laser light with respect to the inspection object is set according to the inspection object. By setting the optimum angle of incidence, it is possible to effectively inspect the object to be inspected.Also, while changing the angle of incidence of the ultraviolet laser light, a plurality of objects to be inspected illuminated at each angle of incidence can be obtained. The state of the inspection object can be inspected based on the Fourier transform image, and the inspection of the inspection object can be performed more appropriately.

The inspection apparatus further includes a polarization separation unit that separates the reflected light or the transmitted light from the object to be inspected, and the imaging unit individually detects each polarized light component separated by the polarization separation unit. Then, it is desirable to individually capture the Fourier transform images of the inspection object. As described above, the reflected light or the transmitted light from the inspection object is polarization-separated by the polarization separation unit, the polarization-separated polarization components are individually detected by the imaging unit, and the Fourier transform images of the inspection object are respectively detected. In the case where individual images are taken, it becomes possible to perform multifaceted inspection by utilizing the polarization dependence of the inspection object,
The inspection of the inspection object can be performed more appropriately.

Further, the inspection method according to the present invention illuminates an inspection object having a concavo-convex pattern with a predetermined period with illumination light, and performs Fourier transform on reflected light or transmitted light from the inspection object illuminated with the illumination light. Then, a Fourier-transformed image of the object to be inspected is detected by detecting the reflected light or transmitted light of the object to be Fourier-transformed, and the state of the object to be inspected is determined based on the Fourier-transformed image of the object to be inspected. It is characterized by inspecting.

According to this inspection method, the state of the inspection object is inspected based on the captured Fourier transform image of the inspection object, so that inspection of the inspection object can be performed quickly and appropriately.

In this inspection method, it is desirable to illuminate the inspection object while setting the incident angle of the illumination light to the inspection object to an optimum value according to the inspection object. As described above, by illuminating the inspection object while setting the incident angle of the illumination light to the inspection object to an optimum value according to the inspection object,
The inspection of the inspection object can be performed more effectively.

In this inspection method, the Fourier transform images of the object illuminated at the respective incident angles are respectively taken while changing the incident angles of the illumination light to the object, and the imaged inspection object is taken. It is desirable to inspect the state of the inspection object based on a plurality of Fourier transform images of the object. As described above, by illuminating the inspection object while changing the incident angle of the illumination light, and inspecting the state of the inspection object based on a plurality of Fourier transform images of the inspection object, the inspection object can be inspected. Inspection of an object can be performed more appropriately.

In this inspection method, it is desirable that the object to be inspected is illuminated with ultraviolet laser light. As described above, when an object to be inspected is irradiated with an ultraviolet laser beam, which is a light having a very short wavelength, an object having a finer pattern is illuminated than when the object to be inspected is irradiated with visible light. The inspection of the inspection object can be performed appropriately.

In another inspection method according to the present invention, an object to be inspected is illuminated with an ultraviolet laser beam, and reflected light or transmitted light from the object illuminated by the ultraviolet laser beam is subjected to Fourier transform, and Fourier transform is performed. Detecting reflected light or transmitted light of the inspected object and imaging a Fourier transform image of the inspected object, and inspecting the state of the inspected object based on the captured Fourier transform image of the inspected object. Features.

According to this inspection method, the state of the inspection object is inspected based on the captured Fourier transform image of the inspection object, so that the inspection of the inspection object can be performed quickly and appropriately. In addition, according to this inspection method, the object to be inspected is illuminated with ultraviolet laser light, which is light having a very short wavelength, so that the object to be inspected is finer than when irradiating the object with visible light. The inspection of the inspection object having the pattern can be appropriately performed.

In this inspection method, it is desirable to illuminate the inspection object while setting the incident angle of the ultraviolet laser light to the inspection object to an optimum value according to the inspection object. In this way, the inspection of the inspection object is performed more effectively by illuminating the inspection object while setting the incident angle of the ultraviolet laser light to the inspection object to an optimum value according to the inspection object. Can be.

In this inspection method, the Fourier transform images of the object illuminated at the respective incident angles are respectively taken while changing the incident angles of the ultraviolet laser light to the object, and the imaged object is taken. It is desirable to inspect the state of the inspection object based on a plurality of Fourier transform images of the inspection object. By illuminating the inspection object while changing the incident angle of the ultraviolet laser light and inspecting the state of the inspection object based on a plurality of Fourier transform images of the inspection object as described above, The inspection of the inspection object can be performed more appropriately.

[0038]

Embodiments of the present invention will be described below in detail with reference to the drawings. Here, an example will be described in which the inspection apparatus according to the present invention is used to inspect a semiconductor wafer on which a circuit pattern such as a semiconductor integrated circuit is formed, but the inspection apparatus according to the present invention is limited to this example. It can be widely applied to inspection of fine patterns, for example, it is also effective for inspection of magnetic heads used in hard disk drives, inspection of flat panel displays on which fine patterns are formed, etc. is there.

The inspection apparatus according to the present invention illuminates a circuit pattern formed on a semiconductor wafer with illumination light, Fourier-transforms transmitted light or reflected light, and observes a Fourier-transformed image of the circuit pattern. The state of the circuit pattern formed on the semiconductor wafer is inspected. That is, in the Fourier transform image of the circuit pattern to be inspected, a distribution in which the transmittance or the reflectance of the semiconductor wafer, the phase of the circuit pattern, or the like is Fourier transformed with respect to the spatial frequency appears. The inspection apparatus according to the present invention detects the distribution appearing in the Fourier transform image and inspects the state of the circuit pattern formed on the semiconductor wafer based on the distribution.

The circuit pattern formed on the semiconductor wafer has a concave / convex pattern (L / S pattern: Line and Space P) in which concave portions and convex portions are arranged at predetermined intervals in the vertical or horizontal direction.
The inspection apparatus according to the present invention is particularly suitable as an inspection apparatus for inspecting the state of such an L / S pattern.

The principle of inspecting the state of the L / S pattern formed on the semiconductor wafer by the inspection device according to the present invention will be described with reference to FIG.

The L / L of the semiconductor wafer 100 to be inspected is
When the S pattern 101 is irradiated with illumination light, the L / S pattern 101 functions as a diffraction grating, and diffraction occurs in the illumination light. Then, the transmitted light or the reflected light of the illumination light having undergone the diffraction is Fourier-transformed using the Fourier-transform lens 102, and the Fourier-transformed image of the L / S pattern 101 formed on the Fourier image plane is observed. Has L / S
A distribution is obtained in which each diffraction order light of the illumination light diffracted by the pattern 101 is concentrated at a specific point.

Here, the intensity of each diffraction order light of the illumination light appearing in the Fourier transform image of the L / S pattern 101 depends on the diffraction efficiency of the L / S pattern 101 and the L / S pattern 10
When the diffraction efficiency 1 changes, the intensity of each diffraction order light of the illumination light appearing in the Fourier transform image changes. Also, L / S
The diffraction efficiency of the pattern 101 depends on the shape of the L / S pattern 101, and when the shape of the L / S pattern 101 changes, the diffraction efficiency also changes. Therefore, by detecting the intensity of each diffraction order light of the illumination light appearing in the Fourier transform image of the L / S pattern 101, the L / S pattern 10
1 can obtain information about the shape change.

In the inspection apparatus to which the present invention is applied, the L / S formed on the semiconductor wafer 100 is
An image of the Fourier transform image of the pattern 101 is taken, and for example, the taken Fourier transform image and the correct L / S
The defective L / S pattern 101 can be determined by comparing the Fourier transform image of the pattern 101 with the Fourier transform image.

FIG. 2 shows an example of the configuration of an inspection apparatus to which the present invention is applied. The inspection apparatus 1 shown in FIG. 2 irradiates an L / S pattern 101 of a semiconductor wafer 100 to be inspected with ultraviolet laser light as illumination light, performs a Fourier transform on the reflected light, and forms an image on a Fourier surface. L / S pattern 10
The imaging apparatus is configured to take one Fourier transform image and inspect the L / S pattern 101 based on the Fourier transform image.

This inspection apparatus 1 uses an ultraviolet solid-state laser 2 as a light source of illumination light for illuminating an L / S pattern 101 of a semiconductor wafer 100 to be inspected. This ultraviolet solid laser 2 converts the wavelength of a solid laser such as a YAG laser using a nonlinear optical crystal.
An ultraviolet laser beam of about 66 nm is emitted.

The inspection capability of the inspection apparatus depends on the wavelength of the illumination light to be irradiated on the inspection object. A shorter wavelength of the illumination light enables inspection of a finer structure. In the inspection apparatus 1 to which the present invention is applied, since the ultraviolet solid laser 2 is used as a light source of the illumination light and the L / S pattern 101 of the semiconductor wafer 100 is illuminated with a short wavelength ultraviolet laser light, The inspection of the L / S pattern 101 having a simple structure can be appropriately performed. In particular, the semiconductor wafer 100
In recent years, the L / S pattern 101 formed on the substrate has been increasingly miniaturized, and the width of the convex portion (hereinafter, referred to as line width) is 0.1 mm.
It has been reduced to about 18 μm. And this L /
The S pattern 101 tends to be further miniaturized in the future. In the inspection apparatus 1 to which the present invention is applied, by using a short-wavelength ultraviolet laser beam as illumination light, it is possible to appropriately inspect even the L / S pattern 101 which is extremely miniaturized in this way. .

If the illumination light has a short wavelength, the Fourier transform image of the object illuminated by the illumination light can be observed in a wide spatial frequency band.
L / S formed on semiconductor wafer 100 to be inspected
Inspection apparatus 1 for observing Fourier transform image of pattern 101
In this case, it is very effective to use a short wavelength ultraviolet laser as illumination light. Also, L / L for the wavelength of the illumination light
As the ratio of the depth of the concave portion of the S pattern 101 or the ratio of the line width variation of the L / S pattern 101 to the wavelength of the illumination light increases, the change in the diffraction efficiency of the L / S pattern 101 increases.
Since it becomes sensitive to a change in the shape of the pattern 101, L
In the inspection apparatus 1 for inspecting a change in the shape of the L / S pattern 101 based on a change in the Fourier transform image depending on a change in the diffraction efficiency of the / S pattern 101, an ultraviolet laser beam having a short wavelength may be used as illumination light. Very effective.

Further, the ultraviolet solid-state laser 2 is excellent in handling such that the apparatus itself is small and does not require water cooling, and is optimal as a light source of illumination light in the inspection apparatus 1.

In the inspection apparatus according to the present invention, the light source of the illuminating light is not limited to the ultraviolet solid-state laser 2 described above. For example, an InGaN-based blue semiconductor laser or the like may be used. Good.

In the inspection apparatus 1, the ultraviolet solid-state laser 2
Illumination light (ultraviolet laser light) emitted from is guided by the condenser lens 3 and the ultraviolet light fiber 4, and is condensed on the rotary diffusion plate 6 via the lens 5.

Since the inspection apparatus 1 uses laser light having good coherence as illumination light, speckle noise is generated. The inspection apparatus 1 cannot properly observe the Fourier transform image of the L / S pattern 101 unless the speckle noise is canceled. Therefore, in the inspection apparatus 1, the rotating diffuser 6 is disposed in the optical path of the illumination light as speckle averaging means for canceling speckle noise. The illumination light is transmitted through the rotating diffusion plate 6 to cancel the speckle noise.

In the inspection apparatus according to the present invention, the speckle averaging means is not limited to the rotating diffusion plate 6 as described above, and for example, a fiber bundle or the like may be used.

In the inspection apparatus 1, the illumination light transmitted through the rotary diffusion plate 6 is incident on the first beam splitter 8 via the condenser lens 7.

The first beam splitter 8 separates the optical path of illumination light for irradiating the L / S pattern 101 of the semiconductor wafer 100 to be inspected with the optical path of light reflected by the L / S pattern 101. It is for separation. Then, in the inspection apparatus 1, the illumination light reflected by the first beam splitter 8 is applied to the L / S pattern 101 of the semiconductor wafer 100 via the objective lens 9.

The semiconductor wafer 100 is placed on the inspection stage 1
0. The inspection stage 10 supports the semiconductor wafer 100 and
It has a function of moving 0 in a horizontal direction or a vertical direction and positioning it at a predetermined inspection position. This inspection stage 1
Numeral 0 is connected to a control computer 11 for controlling the operation of each mechanism of the inspection apparatus 1, and is mounted on the inspection stage 10 based on a control signal supplied from the control computer 11. The semiconductor wafer 100 is moved and positioned at a predetermined inspection position. This inspection device 1
As described above, the L / L of the semiconductor wafer 100 positioned at the predetermined inspection position by the inspection stage 10 as described above.
The S pattern 101 is irradiated with an ultraviolet laser from the ultraviolet solid-state laser 2 as illumination light.

Here, the L / S pattern 101 to which the illumination light is applied is a concavo-convex pattern in which the concave portions and the convex portions are arranged at a predetermined cycle, as described above.
The illumination light applied to the light source 1 is diffracted by the L / S pattern 101.

The illumination light applied to the semiconductor wafer 100 is reflected by the semiconductor wafer 100, and the reflected light enters the first beam splitter 8 again via the objective lens 9. Then, the first beam splitter 8
The reflected light transmitted through the second beam splitter 12 enters the second beam splitter 12. Note that, as the objective lens 9, for example, a lens having a high numerical aperture of about 0.9 is used. The objective lens 9 is held by an actuator 20 so as to be movable in a direction to approach and separate from the semiconductor wafer 100 mounted on the inspection stage 10, and based on a control signal from a control computer 11, The automatic focus control of the objective lens 9 is performed by the actuator 20 moving the objective lens 9 in the direction of moving toward and away from the semiconductor wafer 100.

The second beam splitter 12 splits the optical path of the light reflected by the semiconductor wafer 100 into two. Then, in the inspection apparatus 1, of the reflected light that has entered the second beam splitter 12, the light reflected by the second beam splitter 12 is transmitted through the first imaging lens 13 to the first light. CCD (ch
An image is formed on an image sensor 14 (arge-coupled device). Therefore, in this inspection device 1,
The L / S pattern 1
Thus, an image of the entire portion irradiated with the 01 illumination light is captured. The image of the L / S pattern 101 imaged by the first CCD image sensor 14 is an L / S pattern 1
11 is an image having an intensity distribution according to the diffraction efficiency of No. 01.

In the inspection apparatus 1, the first CCD image pickup device 14 is connected to the control computer 11, and the first CCD image pickup device 14 picks up the L image picked up by the first CCD image pickup device 14.
The image of the / S pattern 101 can be taken into the control computer 11. In the inspection device 1, the L image picked up by the first CCD
The image of the / S pattern 101 is processed by the control computer 11 to obtain various information. For example, when the semiconductor wafer 100 to be inspected is shifted from a predetermined inspection position, the inspection stage 10 is driven. In order to perform an appropriate inspection such as moving the semiconductor wafer 100 to a predetermined inspection position and, when the focal position of the objective lens 9 is deviated, moving the objective lens 9 to focus. The required mechanisms are controlled.

In the inspection apparatus 1, of the reflected light incident on the second beam splitter 12, the light transmitted through the second beam splitter 12 is converted into the second image forming lens 15, the variable aperture 16, Fourier transform lens 17
The image is formed on the second CCD image pickup device 18 through the.

The variable aperture 16 is for extracting only the reflected light from the portion to be observed in the L / S pattern 101 illuminated by the illumination light. That is, the variable aperture 16 transmits only the reflected light from the portion to be observed in the L / S pattern 101 illuminated by the illumination light, and blocks the other portions. The variable aperture 16 is connected to the control computer 11 so that the portion through which the reflected light is transmitted can be arbitrarily changed under the control of the control computer 11. Note that, of the L / S pattern 101 illuminated by the illumination light, the means for extracting only the reflected light from the portion to be observed is not limited to the variable aperture 16 as described above. A mask may be prepared in advance, and this mask may be switched and used. When it is desired to observe the entire portion of the L / S pattern 101 irradiated with the illumination light, such a unit may not be provided.

The Fourier transform lens 17 is for Fourier transforming the reflected light transmitted through the variable aperture 16. In the inspection device 1, the reflected light of the illumination light applied to the L / S pattern 101 is Fourier-transformed by the Fourier transform lens 17, and the Fourier-transformed image of the L / S pattern 101 is subjected to the second CCD imaging device 18. An image is taken.

In the inspection apparatus 1, the second CCD image sensor 18 is connected to the control computer 11, and performs Fourier transform of the L / S pattern 101 imaged by the second CCD image sensor 18. An image can be taken into the control computer 11. In the inspection device 1, the second CCD image pickup device 1
The control computer 11 processes the Fourier-transformed image of the L / S pattern 101 captured by the controller 8 to inspect the L / S pattern 101. Specifically, the inspection device 1 is, for example, a second CCD.
The defective L / S pattern 101 is determined by comparing the Fourier transform image of the L / S pattern 101 captured by the image sensor 18 with the Fourier transform image of the correct L / S pattern 101 obtained in advance. I have to.

As described above, in the Fourier transform image of the L / S pattern 101, a distribution is obtained in which each diffraction order light of the illumination light diffracted by the L / S pattern 101 is concentrated at a specific point. Then, since the intensity of each diffraction order light becomes an intensity corresponding to the diffraction efficiency that changes according to the shape change of the L / S pattern 101, the L / S
The shape change of the pattern 101 can be estimated.

The factor that causes a change in the diffraction efficiency of the L / S pattern 101 is as follows.
1 line width fluctuation and concave part depth fluctuation, L / S pattern 1
In addition to a shape change such as a change in the spatial frequency of 01, various factors such as a change in the refractive index of the material of the semiconductor wafer 100 can be considered. Therefore, when the plurality of factors fluctuate at the same time, it is not possible to uniquely detect the fluctuation of a specific factor from the Fourier transform image of the L / S pattern 101.

However, in inspecting a defect in a specific process in a process of manufacturing a circuit pattern of a semiconductor integrated circuit or the like, the factors that cause a defect in the process are limited to some extent. It is possible to detect a change in a specific factor in the process. For example, in a certain process, L / S pattern 1
Assuming that the line width of the L / S pattern 101 may fluctuate and the fluctuations of other factors can be ignored, the inspection apparatus 1 uses the line of the L / S pattern 101 based on the Fourier transform image of the L / S pattern 101. It is possible to detect a variation in width.

More specifically, in the lithography process, when defocusing and aberrations occur to deteriorate the imaging state, the effect mainly appears as a variation in the line width of the L / S pattern 101. That is, the line width of the L / S pattern 101 increases due to blurring caused by the deterioration of the imaging state. As described above, due to the deterioration of the imaging state, L /
When the line width of the S pattern 101 increases, the diffraction efficiency of the L / S pattern 101 changes, and the second CC of the inspection apparatus 1
L / S pattern 101 imaged by D image sensor 18
Will change in the intensity of each diffraction order light appearing in the Fourier transform image of. Therefore, in this case, it is possible to detect a change in the line width of the L / S pattern 101 by monitoring the intensity change of each diffraction order light appearing in the Fourier transform image of the L / S pattern 101.

In the inspection apparatus 1 to which the present invention is applied,
As described above, the L of the semiconductor wafer 100 to be inspected is
The reflected light from the / S pattern 101 is Fourier transformed by the Fourier transform lens 17, and the Fourier transformed image of the L / S pattern 101 is captured by the second CCD image sensor 18, and is captured by the second CCD image sensor 18. Based on the Fourier transform image of the L / S pattern 101
Since the state of the L / S pattern 101 is inspected, for example, L / S
/ S pattern 101 can be inspected quickly and appropriately.

Specifically, in the conventional inspection apparatus, L
When inspecting the line width of the / S pattern 101, an image of the L / S pattern 101 that has not been subjected to Fourier transform, that is,
First CCD imaging device 1 of inspection apparatus 1 to which the present invention is applied
4, an averaging process is performed on a cross section in a direction perpendicular to the pattern, based on the image of the L / S pattern 101, and the line width of the L / S pattern 101 is inspected. However, in this method, the signal and noise for each pixel of the CCD image sensor are integrated simultaneously, and there is a problem from the viewpoint of the S / N ratio.

On the other hand, in the inspection apparatus 1 to which the present invention is applied, the Fourier transform image of the L / S
Image is taken by the CCD image pickup device 18, the necessary information is concentrated and appears in some pixels of the second CCD image pickup device 18, and the conversion from light to an electric signal is performed in such a manner that only the signal is integrated. Is performed. Therefore, the inspection apparatus 1 can detect a signal having a high S / N ratio, and can inspect the state of the L / S pattern 101 extremely appropriately.

Further, in the Fourier transform image of the L / S pattern 101, as described above, a distribution is obtained in which each diffraction order light of the illumination light diffracted by the L / S pattern 101 is concentrated at a specific point. . Therefore, this L / S pattern 101
In the inspection apparatus 1 for inspecting the state of the L / S pattern 101 from the Fourier transform image of the above, the image processing algorithm is simplified as compared with comparing an image of a complicated inspection object with an image of an ideal object. Therefore, it is possible to improve the accuracy of the inspection and to speed up the processing.

In the Fourier transform image of the L / S pattern 101, a distribution is obtained in which each diffraction order light of the illumination light diffracted by the L / S pattern 101 is concentrated at a specific point. From the Fourier transform image of the S pattern 101, L
In the inspection apparatus 1 for inspecting the state of the / S pattern 101,
Even if the amount of the ultraviolet laser light as the illumination light is reduced, the inspection can be appropriately performed. Therefore, the inspection apparatus 1 can appropriately inspect, for example, a resist before etching, which is likely to be destructed by exposure to ultraviolet laser light, without causing destruction.

In the inspection apparatus 1 described above, the ultraviolet laser light, which is the illumination light, is irradiated perpendicularly to the L / S pattern 101 of the semiconductor wafer 100. L / S pattern 101 to be inspected
When the L / S pattern 101 is set to an optimum value according to
The change in the diffraction efficiency to the change in the shape of the L / S pattern 101 becomes the most sensitive, and the change in the shape of the L / S pattern 101 can be inspected more appropriately. Here, the optimum incident angle of the illumination light has different values depending on the L / S pattern 101 to be inspected. Therefore, as the inspection device 1,
A means for changing the incident angle of the illumination light is provided, and the inspection L /
It is desirable that the inspection is performed by changing the incident angle of the illumination light according to the S pattern 101 and setting the optimum incident angle according to the L / S pattern 101.

Further, if the inspection apparatus 1 is provided with means for varying the incident angle of the illumination light, the L / S illuminated at each incident angle is changed while changing the incident angle of the illumination light with respect to the L / S pattern 101. The inspection result is corrected by imaging the Fourier transform image of the S pattern 101 with the second CCD image sensor 18 and inspecting the state of the L / S pattern 101 based on the obtained plural Fourier transform images. While
It is also possible to more appropriately inspect the state of the L / S pattern 101.

An example of a method of arbitrarily changing the incident angle of the illumination light will be described with reference to FIGS. The light emitted from the light source 110 is diffracted by the grating 111 and passes through the condenser lens 112 and the objective lens 113.
L / S pattern 1 of semiconductor wafer 100 to be inspected
Consider an illumination optical system that irradiates the light at 01. At this time, for example, the + 1st-order light or the -1st-order light diffracted by the grating 111 is filtered and the L / S pattern 10
By irradiating the light onto the L / S pattern 101, so-called oblique incidence illumination, in which illumination light is obliquely incident on the L / S pattern 101, is possible.

Then, when the grating 111 is moved from the first position p1 shown in FIG. 3 to the second position p2 shown in FIG. The virtual images 110a and 110b are
Therefore, the incident angle of the + 1st-order light or the -1st-order light used as the illumination light on the inspection target 134 increases.

As described above, in the illumination optical system described above, the incident angle of the illumination light with respect to the L / S pattern 101 can be arbitrarily changed by moving the grating 111 in the optical axis direction. .

Using the above principle, the inspection apparatus 1 arranges the grating 111 on the optical axis of the ultraviolet laser light emitted from the ultraviolet solid-state laser 2 as shown in FIG. Means 114 for moving the laser beam in the direction of the optical axis of the ultraviolet laser beam (Z direction in FIG. 5).
Is provided, the L / L of the ultraviolet laser light, which is the illumination light,
The incident angle with respect to the S pattern 101 can be made variable, for example, the L / S pattern 10 of the ultraviolet laser light.
Inspection is performed by setting the angle of incidence with respect to 1 to an optimum value according to the L / S pattern 101, or L is determined at a different angle of incidence.
By inspecting a plurality of times by illuminating the / S pattern 101 and correcting the obtained inspection result, the state of the L / S pattern 101 can be more appropriately inspected.

In the above, an example in which the grating 111 is moved in the optical axis direction of the ultraviolet laser light by the moving means 114 so that the incident angle of the ultraviolet laser light on the L / S pattern 101 is made variable. However, the method of making the incident angle of the ultraviolet laser light on the L / S pattern 101 variable is not limited to the above example. For example, a plurality of gratings having different lattice constants are prepared, and the plurality of gratings are prepared. May be selectively arranged on the optical axis of the ultraviolet laser light while switching the gratings.

Further, in order to inspect the L / S pattern 101 more appropriately, the inspection apparatus 1 needs to be configured as shown in FIG.
The polarization beam splitter 19 is disposed in the optical path of the reflected light from the / S pattern 101, and the polarization beam splitter 1
It is effective to individually capture the Fourier transform images of the respective polarization components separated by the polarization in step 9 and inspect the L / S pattern 101 based on the obtained plurality of Fourier transform images.

In the inspection apparatus 1 shown in FIG. 6, each polarized component separated by the polarization beam splitter 19 is
The imaging lenses 15a, 15b and the variable aperture 16a,
The light is incident on the Fourier transform lenses 17a and 17b via the light guide 16b. Then, the Fourier transform images subjected to Fourier transform by the Fourier transform lenses 17a and 17b are individually captured by the CCD image sensors 18a and 18b, respectively.

As described above, the reflected light from the L / S pattern 101 is polarized and separated, a Fourier transform image of each polarized component is captured, and the L / S pattern 101 is inspected based on this. Then, the inspection apparatus 1 performs multi-face inspection using the polarization dependence of the L / S pattern 101, and
/ S pattern 101 can be more appropriately inspected.

In the above, an example has been described in which the reflected light from the L / S pattern 101 is polarized and separated by using the polarizing beam splitter 19, but the reflected light from the L / S pattern 101 is polarized and separated. The means is not limited to the above example. For example, the reflected light from the L / S pattern 101 may be polarized and separated using a Wollaston prism or the like.

[0085]

As described above in detail, according to the inspection apparatus of the present invention, the reflected light or the transmitted light from the inspection object illuminated by the illumination light is Fourier transformed by the Fourier transform means, and Since the Fourier transform image of the inspection object is captured by the imaging unit and the state of the inspection object is inspected based on the image, the inspection of the inspection object can be performed quickly and appropriately.

Further, the inspection apparatus according to the present invention illuminates the object to be inspected by irradiating the object to be inspected by irradiating ultraviolet laser light, which is light having a very short wavelength, as illumination light, compared with the case of using visible light as illumination light. Thus, the inspection of the inspection object having a finer pattern can be appropriately performed.

Further, in the inspection method according to the present invention, the reflected light or the transmitted light from the inspection object illuminated by the illumination light is Fourier-transformed, and a Fourier-transformed image of the inspection object is taken. Since the state of the inspection object is inspected based on the Fourier transform image of the inspection object, the inspection of the inspection object can be performed quickly and appropriately.

Further, in the inspection method according to the present invention, if the ultraviolet laser light, which is light having a very short wavelength, is used as the illumination light and the ultraviolet laser light illuminates the inspection object, the inspection object can be inspected. Inspection of an inspection object having a finer pattern can be appropriately performed as compared with the case of irradiating visible light.

[Brief description of the drawings]

FIG. 1 is a view for explaining the principle of inspecting the state of an L / S pattern formed on a semiconductor wafer by an inspection apparatus according to the present invention.

FIG. 2 is a schematic diagram showing one configuration example of an inspection device according to the present invention.

FIG. 3 is a diagram illustrating an example of a method of arbitrarily changing an incident angle of illumination light, and is a diagram illustrating a state where a grating is at a first position.

FIG. 4 is a diagram illustrating an example of a method of arbitrarily changing an incident angle of illumination light, and is a diagram illustrating a state where a grating is at a second position.

FIG. 5 is a schematic diagram showing another configuration example of the inspection device according to the present invention.

FIG. 6 is a schematic diagram showing still another configuration example of the inspection device according to the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 inspection apparatus, 2 ultraviolet solid laser, 6 rotating diffuser, 9 objective lens, 10 inspection stage, 11 control computer, 14 first CCD imaging device, 17
Fourier transform lens, 18 second CCD image sensor,
19 polarizing beam splitter, 100 semiconductor wafer,
101 L / S pattern, 111 grating, 1
13 Transportation

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 2F065 AA49 BB02 BB18 CC19 CC25 DD04 DD06 EE00 FF42 FF48 FF49 GG04 GG22 HH12 HH13 HH15 HH18 JJ03 JJ05 JJ09 JJ26 LL04 LL10 LL30 LL37 LL42 Q12 NN42 Q09 AA01 BA05 DB02 DB04 DB08 DB12 DB13 DB14 DB30 DJ04 DJ05

Claims (20)

[Claims] An illumination unit that illuminates the inspection object by irradiating the inspection object with an uneven pattern having a predetermined period with illumination light; and reflected light from the inspection object illuminated by the illumination unit. Or Fourier transform means for performing Fourier transform of transmitted light, and imaging means for detecting reflected light or transmitted light of the test object subjected to Fourier transform by the Fourier transform means and capturing a Fourier transform image of the test object. An inspection apparatus for inspecting a state of the inspection object based on a Fourier transform image of the inspection object captured by the imaging unit. 2. A light quantity change of a Fourier transform image of the object to be inspected due to a change in diffraction efficiency of the uneven pattern,
2. The inspection apparatus according to claim 1, wherein the inspection apparatus inspects a variation in the uneven pattern of the inspection object. 3. A light amount change of a Fourier transform image of the object to be inspected due to a change in diffraction efficiency of the concavo-convex pattern,
3. The inspection apparatus according to claim 2, wherein a variation in the width of a concave portion or a convex portion of the concave / convex pattern of the inspection object is inspected. 4. An inspection apparatus according to claim 1, wherein said illuminating means includes an incident angle varying means for varying an incident angle of illumination light with respect to said inspection object. 5. The inspection apparatus according to claim 1, wherein the illumination means irradiates the inspection object with ultraviolet laser light as illumination light. 6. The inspection apparatus according to claim 5, further comprising a speckle averaging means for canceling speckle noise in an optical path of the ultraviolet laser light applied to the inspection object. 7. A polarized light separating means for polarizing and separating reflected light or transmitted light from the object to be inspected, wherein the imaging means individually detects each polarized light component which has been polarized and separated by the polarized light separating means. 2. The inspection apparatus according to claim 1, wherein a Fourier transform image of the inspection object is individually captured. 8. An illumination means for irradiating the inspection object with ultraviolet laser light as illumination light to illuminate the inspection object, and reflecting light or transmitted light from the inspection object illuminated by the illumination means. Fourier transform means for performing Fourier transform, and imaging means for detecting reflected light or transmitted light of the test object subjected to Fourier transform by the Fourier transform means and imaging a Fourier transform image of the test object, the imaging means An inspection apparatus for inspecting a state of the inspection object based on a Fourier transform image of the inspection object captured by the method. 9. An inspection apparatus according to claim 8, wherein said illuminating means includes an incident angle varying means for varying an incident angle of the ultraviolet laser light with respect to the inspection object. 10. The inspection apparatus according to claim 8, further comprising speckle averaging means for canceling speckle noise in an optical path of the ultraviolet laser light applied to the inspection object. 11. A polarized light separating means for polarizing and separating reflected light or transmitted light from the object to be inspected, wherein the image pickup means individually detects each polarized light component separated by the polarized light separating means. 9. The inspection apparatus according to claim 8, wherein the Fourier transform images of the inspection object are individually captured. 12. An object having an irregular pattern having a predetermined period is illuminated with illumination light, and reflected light or transmitted light from the object illuminated by the illumination light is subjected to Fourier transform. Detecting reflected light or transmitted light of the inspected object to capture a Fourier transform image of the inspected object, and inspecting a state of the inspected object based on the captured Fourier transformed image of the inspected object; An inspection method characterized by the following. 13. The method according to claim 12, wherein a change in the uneven pattern of the object is inspected based on a change in a light amount of a Fourier transform image of the object caused by a change in diffraction efficiency of the uneven pattern. Inspection method. 14. A method for inspecting a variation in a width of a concave portion or a convex portion of the concave-convex pattern of the object to be inspected from a change in a light amount of a Fourier transform image of the object to be inspected due to a change in diffraction efficiency of the irregular pattern. 14. The inspection method according to claim 13, wherein: 15. The inspection according to claim 12, wherein the inspection object is illuminated while an incident angle of the illumination light to the inspection object is set to an optimum value according to the inspection object. Method. 16. A Fourier transform image of the inspection object illuminated at each incident angle while changing an incident angle of the illumination light to the inspection object, and changing the incident angle of the illumination light to the inspection object. 13. The inspection method according to claim 12, wherein a state of the inspection object is inspected based on a plurality of Fourier transform images. 17. The inspection method according to claim 12, wherein the inspection object is illuminated with an ultraviolet laser beam. 18. An object to be inspected is illuminated by an ultraviolet laser beam, and reflected light or transmitted light from the object illuminated by the ultraviolet laser light is Fourier-transformed, and the Fourier-transformed reflected light of the object to be inspected. An inspection method for detecting a transmitted light, capturing a Fourier transform image of the inspection object, and inspecting a state of the inspection object based on the captured Fourier transform image of the inspection object. . 19. The device according to claim 18, wherein the object to be inspected is illuminated while an incident angle of the ultraviolet laser light to the object to be inspected is set to an optimum value according to the object to be inspected. Inspection methods. 20. Fourier transform images of the inspected object illuminated at the respective incident angles while changing the incident angle of the ultraviolet laser beam to the inspected object, and the imaged inspected object 19. The inspection method according to claim 18, wherein the state of the inspection object is inspected based on the plurality of Fourier transform images.