JP3392708B2 - Image forming characteristic measuring apparatus, exposure apparatus, and methods thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming characteristic measuring apparatus, an exposure apparatus and a method, and more particularly to an image forming characteristic measuring apparatus and an exposure apparatus suitable for measuring an image forming characteristic of an exposure apparatus used for manufacturing a semiconductor element or the like. And method.

[0002]

2. Description of the Related Art An exposure apparatus such as a stepper used in a lithographic process is indispensable for manufacturing semiconductor elements and liquid crystal display panels. In the exposure apparatus, Koehler illumination is performed from an illumination system to a mask such as a reticle, and light transmitted through this reticle further passes through a projection optical system to expose a reticle image on the wafer surface. .

In such an exposure apparatus, it is necessary to project and expose a reticle image or the like onto a minute area on a wafer with high precision, so it is extremely important to investigate what image forming characteristics the projection optical system has.

Conventionally, such a measurement is carried out by placing a measuring plate coated with a photosensitive material on a stage and checking the diameter of a circular photosensitive portion obtained by changing the height position of the stage. ing.

As the imaging characteristics, the numerical aperture (NA) of the projection optical system and the coherence factor (σ) are measured. In this type of projection system, the image is formed such that the image of the secondary light source surface is included within the effective diameter of the pupil. Here, the numerical aperture (NA) of the projection optical system means the numerical aperture from the object plane on the wafer mounted on the stage to the pupil of the projection optical system, and NA = n · sin θ (here, n Is the refractive index of the medium, and θ is the angle (the maximum cone angle θ) stretched with respect to the radius of the pupil.

On the other hand, the coherence factor σ is the diameter (Si) of the image of the secondary light source surface formed on the pupil of the projection optical system without the reticle R, and the effective diameter (Sp) of the pupil.
(Si / Sp), that is, the ratio of the numerical aperture of the illumination system to the reticle and the numerical aperture of the projection optical system.

The coherence factor σ is 1 of the illumination condition.
It is treated as one factor. When the σ value is as close to zero as possible, it is called coherence illumination, and the σ value is 1
Is called incoherent illumination, and values in between are called partial coherent. The simplest method for setting this σ value is to change the aperture size of the illumination system diaphragm in the figure.

Now, in order to measure the numerical aperture NA and the coherence factor σ using a measuring plate coated with a photosensitive material, first place a diffusion plate at the position of the reticle.
The light diffused by the diffusion plate reaches the entire effective system of the pupil of the projection optical system, and the irradiation light corresponding to the pupil reaches the measurement plate. Therefore, if the height position of the wafer is changed and the radius of the photosensitive portion is examined, the cone angle θ is obtained and the NA can be calculated.

On the other hand, if the diffusing plate is not placed at the reticle position, an image corresponding to the pupil of the illumination system will be obtained on the pupil of the projection optical system, and the light that reaches the measuring plate by this image will be illuminated. It corresponds to the pupil of the system. Therefore,
The numerical aperture NA of the illumination system can be measured in the same manner as the numerical aperture NA of the projection optical system, and the coherence factor σ can be obtained.

[0010]

However, the above-mentioned conventional image-forming characteristic measuring method has the following problems. First, in order to measure the numerical aperture NA of the projection optical system, it is necessary to expose the measurement plate to light, but this is a complicated task. Furthermore, the coherence factor σ
In order to measure (1), it is necessary to obtain the numerical aperture of the illumination system, and thus the same exposure work is required. As described above, in the conventional method, at least two exposures are required to measure a series of imaging characteristics, and in addition, it is necessary to replace the measurement plate and insert / remove the diffusion plate in each work. It is also necessary to perform measurement work on the exposed portion after measurement. Further, when a photosensitive material is used, it is necessary to adjust the intensity of incident light with respect to the photosensitivity of the material, and in order to do this, it is necessary to repeat exposure and repeat trial and error.

As described above, in the conventional method, it is necessary to repeat the complicated work only by measuring the image forming characteristic of the projection optical system corresponding to one point on the reticle. In addition, with the further miniaturization of devices in recent years, it has become necessary to consider the distribution of the imaging characteristics in the exposureable area corresponding to the exposure area. Specifically, the numerical aperture N of the exposure optical system
A and the coherence factor σ may differ at any point in the exposure area due to the influence of the aberration of the optical system. At this time, the problem that the device pattern size to be exposed differs depending on the position in the exposure region cannot be ignored. Therefore, it is necessary to check not only the image forming characteristic corresponding to one point in the exposureable area by the projection optical system but also the image forming characteristic corresponding to each position in the exposureable area.

However, in the conventional method, it is necessary to perform extremely complicated work even by measuring the image forming characteristic of one point as described above, and the distribution of the image forming characteristic of a plurality of points can be performed with high accuracy and efficiency. It is virtually impossible to investigate.

The present invention has been made in consideration of such a situation, and its first object is to form an image forming characteristic of a projection optical system which can be easily measured with high accuracy. To provide a measuring device and method.

A second object of the present invention is to provide an image-forming characteristic measuring device capable of measuring the distribution of the image-forming characteristic of the projection optical system at a plurality of points in the exposureable area simply, with high accuracy, and efficiently. To provide a method.

A third object of the present invention is to provide an exposure apparatus capable of automatically and automatically adjusting the image forming characteristic to an optimum or desired value and an image forming characteristic adjusting method thereof.

[0016]

The essence of the present invention is to create a pinhole on the mask surface and illuminate it, and shift the mask position or the wafer surface position in the optical axis direction from the position of the mask / wafer surface in an image forming relationship. When observing the pinhole image with light, the light intensity distribution of the pinhole image becomes a distribution divided into two stages due to the diffraction of the illumination light in the pinhole.
By measuring the size of each distribution in the diametrical direction, the numerical aperture (NA), coherence factor σ, etc. of the projection optical system of the exposure apparatus can be measured with high accuracy and quantitatively.

More specifically, the solution of the above-mentioned problems is realized by the following solution means. First, the invention according to claim 1 irradiates an illumination light from a light source to a mask through an illumination optical system and measures an image forming characteristic of an optical system in which an image of a pattern of the mask is formed by a projection optical system. Bei the apparatus, the mask, the opening of the micro is provided with a plurality, the light intensity measuring means for measuring the light intensity of the image formed by using merge projection optical system corresponding to the opening of the small
In the image to be formed, it passes directly through a minute aperture.
Illumination light and a projection optical system
Diffracted light that passes and the respective light intensity distributions corresponding to
Based on the imaging characteristics, the numerical aperture and coherence of the projection optical system
This is a device for measuring an imaging characteristic, which calculates a lens factor corresponding to each minute aperture .

Since such means is provided in the present invention,
The distribution of the imaging characteristics of the optical system at multiple points in the exposure area can be measured easily and with high accuracy, and each imaging characteristic corresponding to multiple apertures can be measured at one time, making it efficient. It is possible to measure it.

[0019]

Further, according to the present invention, the numerical aperture and the coherence factor of the projection optical system can be obtained as the imaging characteristics. In addition, both NA and σ can be measured with one measurement, which enables efficient measurement.

Further, the invention corresponding to claim 2 is
In the invention corresponding to claim 1 , the light intensity measuring means is:
It is a measuring device of image forming characteristics which is a measuring means for converting light into an electric signal.

Since such means is provided in the present invention,
In the detection of the light intensity distribution, the adjustment work by adjusting the gain and level is easy, and since the adjustment can be performed during or after the measurement of the light intensity, the adjustment in the measurement is better than that in the case of using the photosensitive material. The labor can be significantly reduced.

The invention corresponding to claim 3 is the claim
In the invention corresponding to 1 or 2 , the image-forming characteristic is provided with a moving mechanism capable of moving the image-forming target so that an arbitrary position on the image-forming surface formed by the projection optical system can be measured by the light intensity measuring means. It is a measuring device.

As described above, the present invention is characterized in that the means for measuring the imaging characteristic has the moving mechanism capable of measuring at any position in the exposure area. With such a mechanism, it is possible to measure the numerical aperture and the coherent factor at any position within the exposure area.

Next, the invention corresponding to claim 4, claim
An imaging characteristic measuring device corresponding to any one of 1 to 3 and an imaging of the projection optical system by deforming the diaphragm into an isotropic shape or an anisotropic shape and / or enlarging or reducing the diaphragm. The diaphragm mechanism for changing the characteristics and the diaphragm mechanism so that the imaging characteristics obtained by the measuring apparatus for the imaging characteristics fall within a predetermined range, or the optimum imaging characteristics out of a finite number of changes of the imaging characteristics. And an aperture stop adjusting unit for adjusting the image forming characteristics of the projection optical system by controlling the.

Since such means is provided in the present invention,
The imaging characteristics can be adjusted automatically and to an optimum or desired value. In addition, since the diaphragm shape can be deformed to an isotropic shape or an anisotropic shape, even if the measured imaging characteristics are anisotropically distributed in the imaging plane, the diaphragm shape can be deformed. The distribution can be corrected anisotropically in the image plane so that uniform image formation characteristics can be obtained in the plane.

The invention according to claim 5 irradiates the mask with the illumination light from the light source through the illumination optical system and forms an image of the pattern of the mask by the projection optical system. In the method of measuring the characteristics, the mask has
Opening of the minute is provided with a plurality, measured imaging characteristics of the optical system by measuring the light intensity of the image formed by using merge projection optical system corresponding to the opening of this small, the image formed To
The direct illumination light that passes through the minute aperture,
Diffracted light generated at the aperture of and passing through the projection optical system,
Based on each light intensity distribution corresponding to
The projection optical system numerical aperture and coherence factor.
This is a method of measuring the image formation characteristic calculated corresponding to a minute aperture .

Since such means is provided in the present invention,
It is Ru can <br/> to the same advantages as the invention corresponding to claim 1.

[0029] is found in addition, the invention corresponding to claim 6,
In the invention corresponding to claim 5 , there is provided a method for measuring an image forming characteristic, wherein the light intensity is measured by means of converting light into an electric signal.

Since such means is provided in the present invention,
It is possible to obtain the same operational effect as the invention corresponding to claim 2 . Next, the invention corresponding to claim 7 is the same as claim 5 or
In the invention corresponding to 6 , the light intensity of the image is a method of measuring an image forming characteristic which enables measurement at an arbitrary position on the image forming surface by the projection optical system.

Since such means is provided in the present invention,
It is possible to measure the image forming characteristics at any position on the image forming surface. Meanwhile, invention corresponding to claim 8, claim
If the image forming characteristic obtained by the image forming characteristic measuring method according to any one of 5 to 7 is not within the predetermined range, a characteristic changing step of changing the image forming characteristic of the projection optical system, and The new imaging characteristics of the projection optical system according to claim 5,
Repeat the characteristic measurement step of measuring by the imaging characteristic measuring method according to any one of the above, the characteristic changing step and the characteristic measuring step, and finally, in a state where the imaging characteristic falls within a predetermined range, or repeatedly. And a characteristic adjusting step of adjusting the image forming characteristic of the projection optical system so as to obtain the optimum image forming characteristic during the finite number of times. Since such means is provided in the present invention, the image forming characteristic of the exposure apparatus can be automatically and optimally adjusted to a desired value.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. (First Embodiment of the Invention) FIG. 1 is a schematic configuration diagram showing an example of a projection type exposure apparatus to which a measuring apparatus of an image forming characteristic according to a first embodiment of the present invention is applied.

In this projection type exposure apparatus (stepper), the illumination optical system 3 is composed of a light quantity adjusting section such as an illumination system diaphragm 2 and an illuminance equalizing means for exposing the exposure light using a mercury lamp or an excimer laser beam as a light source 1. The reticle 4 is illuminated by the Koehler with a uniform illuminance.

A pattern 5 is formed on one surface of the reticle 4 with a chrome layer or a phase shift layer, and light passing through this pattern 5 enters a bi-telecentric projection optical system 6 and the projection optical system. A pattern image of the reticle 4 is formed on the wafer 8 after passing through the projection optical system diaphragm 7 in the inside 6.

A photosensitive material (not shown) is provided on the wafer 8 and serves as a measuring plate whose portion is exposed in response to the irradiated light. The stage 9 on which the wafer 8 is placed can be moved in the vertical and horizontal directions by the stage driving device 10. For example, the stage 9 is moved by a distance L, and the intensity distribution of the irradiation light is measured at a plurality of height positions. it can.

The reticle 4 used in this embodiment has a pinhole 11 in order to investigate the image forming characteristics of the projection optical system 6.
And the pattern 5 has a pinhole 1
In a part other than the part 1, the pattern is such that the light passing through the illumination optical system 3 is blocked.

The projection optical system 6 has a projection lens (objective lens) composed of a plurality of lenses. Although not shown in FIG. 1, there is a pupil (pupil of the projection lens) corresponding to the wafer 8 which is the object plane.

Now, the relationship between the pupil of the illumination system and the pupil of the projection lens will be described. In the present embodiment, as described above, the Koehler illumination method in which the image of the secondary light source surface is formed as an aerial image on the pupil of the projection lens is adopted. Since the pupil of the projection lens has a finite diameter, only the light that passes through this pupil
And reaches an image forming light flux. Therefore, the effective diameter of the pupil of the projection lens determines the NA (numerical aperture) of the projection lens.

On the other hand, the image of the secondary light source surface formed as an aerial image on the pupil of the projection lens corresponds to the pupil of the illumination system. Therefore, it is possible to measure the NA (numerical aperture) of the illumination system on the wafer 8 corresponding to the size of the image on the pupil of the projection lens. This relationship will be described in more detail with reference to FIG.

FIG. 2 is a view for explaining the measuring principle of the image forming characteristic measuring apparatus of this embodiment. As shown in the figure, the illumination light from the pupil plane 21 of the illumination system passes through the reticle 4 with the maximum cone angle θ1 ′ spread by the pinhole 11. The light that has directly passed through the pinhole 11 is light of high brightness and will be referred to as direct illumination light 22 for convenience.

Further, when the illumination light passes through the pinhole 11, it is diffracted so that the diffracted light having a low lightness is projected onto the projection optical system 6.
Is incident on. Of this diffracted light, the light that emerges from the projection optical system 6 and is at the outermost position is the light that passes through the outermost periphery of the pupil plane 24 of the projection optical system. Hereinafter, of the diffracted light, the light that passes inside the outermost circumference of the pupil plane 24 of the projection optical system is referred to as diffracted light 23.

Therefore, the light applied to the wafer 8 is
It is composed of the direct illumination light 22 having high brightness and the diffracted light 23 having low brightness. Here, as shown in FIG. 2, the direct illumination light 22 is incident on the wafer surface at the maximum cone angle θ1, and the diffracted light 23 is incident on the wafer surface at the maximum cone angle θ2. The spot diameters on the wafer 8 corresponding to these are the diameters r1 and r2 shown in FIG.

FIG. 3 is a diagram showing the image intensity distribution of the irradiation light on the wafer surface in this embodiment. The image intensity distribution by irradiation in the figure is obtained when the wafer position 8a is shifted by the distance L to the wafer position 8b when the reticle 4 and the wafer 8 are in an image forming relationship with each other. In this distribution curve, the light intensity formed from the diffracted light 23 and the direct illumination light 22 is shown.

When the diameters r1 and r2 shown in the figure are measured, sin θ1 = r1 / (2L), sin θ2 = r
From 2 / (2L), the maximum cone angles θ1 and θ2 can be obtained. Here, since the outside of the intensity distribution curve of the diffracted light 23 represents the NA of the projection optical system, from NA = n · sin θ2,
The NA of the projection optical system is obtained. On the other hand, the bright part inside the intensity distribution curve shows the NA of the illumination system. Actually, the NA of the illumination system is represented by n · sin θ1 ′, but since the relationship between θ1 and θ1 ′ can be known from the characteristics of the projection optical system, the NA of the illumination system is the same as in the case of the projection optical system. You will be asked. Since the coherent factor σ is the ratio of the illumination system NA and the projection optical system NA, it can be obtained from these.

In practice, by providing appropriate threshold levels corresponding to both, it is possible to obtain the size of each part exposed on the measuring plate, the inner bright part and the outer dark part. Note that, in the case shown in FIGS. 2 and 3, for the purpose of exemplifying explanation, the case where the light from the reticle 4 is projected onto the object along the central axis thereof is explained, but in the present embodiment, the projection optics is used. Since the system 6 is bi-telecentric, even when the optical axis in the projection optical system 6 deviates from the central axis, the calculation of the imaging characteristics NA and σ of the projection optical system 6
It can be considered as above.

As described above, in the apparatus and method for measuring the image formation characteristic according to the embodiment of the present invention, the reticle 4 is provided with the pinhole 11, and the direct illumination light passing through the pinhole 11 and the pinhole 11 are used. Since the imaging characteristics are calculated based on the respective light intensity distributions corresponding to the diffracted light generated in 11 and passing through the projection optical system 6, the imaging characteristics of the projection optical system are simple and high. It can be measured with accuracy. Specifically, it is possible to easily measure the numerical aperture and coherence factor of the projection optical system, which have been difficult to measure conventionally.

Further, both NA and σ can be measured by one measurement, which enables efficient measurement. (Second Embodiment of the Invention) In this embodiment, the wafer is moved in the horizontal direction to efficiently investigate the image forming characteristics at a plurality of points in the exposure area, and the light is not measured by the photosensitive material. A case where the imaging characteristic measurement is performed by means of converting into an electric signal will be described.

FIG. 4 is a schematic configuration diagram showing an example of a projection type exposure apparatus to which the image-forming characteristic measuring apparatus according to the second embodiment of the present invention is applied. The same reference numerals are given and the description thereof is omitted, and only different parts will be described here.

In the imaging characteristic measuring apparatus of this embodiment, a plurality of pinholes 11 are provided on the reticle 4, and the light intensity distribution at the wafer position 8b in FIG. 2 is converted into an electric signal instead of a photosensitive material. The configuration is similar to that of the first embodiment, except that the measuring means is used.

In this apparatus for measuring the image-forming characteristic, the folding mirror 31 is provided on the wafer 8 and the projection optical system 6 is used.
The irradiation light from is reflected by the mirror 31 and measured by the intensity distribution measuring element 32.

As the intensity distribution measuring element 32, for example, a CCD camera or a line sensor camera can be used. In the case of the present embodiment, a two-dimensional image forming characteristic distribution in the exposure possible area will be obtained. Therefore, a CCD camera is used.

The output from the intensity distribution measuring element 32 is input to the image forming characteristic calculating section 33, and the image forming characteristic NA of the projection optical system 6 is corresponded to each pinhole 11 of the reticle 4 by the intensity distribution measuring element 32. , Σ is calculated.

Further, in this embodiment, the folding mirror 31 and the measuring element 32 on the wafer 8 are provided with a horizontal moving mechanism capable of moving arbitrarily in a direction parallel to the wafer 8. This moving mechanism is specifically composed of the stage 9 and its stage driving device 10 shown in FIG. By this XY movement of the stage, NA and σ of the exposure optical system can be obtained at all positions within the exposure area.

In calculating the image forming characteristics NA and σ, the light corresponding to each pinhole 11 when the wafer 8 is displaced from the position where the reticle 4 and the light receiving surface of the intensity distribution measuring element 32 form an image forming relationship with each other. The intensity distribution is similar to that shown in FIG. Therefore, the threshold # 1 and the threshold # 2 are provided to the output of this light intensity distribution to provide the diameters r1 and r, respectively.
After measuring 2, the NA and σ of the projection optical system can be calculated in the same manner as in the first embodiment.

In FIG. 5, the bright portion by the direct illumination light and the dark portion by the diffracted light 23 in this embodiment are the intensity distribution measuring element 3.
It is a figure which shows typically a mode that it arises on the 2 light-receiving surface. As shown in the figure, by distributing the pinholes 11 on the reticle 4 on a two-dimensional plane, the bright portions 34 corresponding to the pinholes 11 are distributed.
And the dark portion 35 are also two-dimensionally distributed, NA and σ of the projection optical system are calculated from each, and the two-dimensional imaging characteristic distribution of the projection optical system in the exposure possible area can be easily obtained by one measurement. Becomes

As described above, the apparatus and method for measuring the imaging characteristics according to the embodiment of the present invention have the same structure as that of the first embodiment, and also have a plurality of pinholes 11 on the reticle 4. Therefore, the same effect as that of the first embodiment can be obtained, and in addition, the distribution of the imaging characteristics of the optical system at a plurality of points in the exposure area can be measured easily and with high accuracy.

Further, since the measuring element can be moved to an arbitrary position by the horizontal movement mechanism, each image forming characteristic corresponding to the plurality of pinholes 11 can be measured at one time. In addition, since the intensity distribution measuring element 32 that electrically expresses the light intensity, such as a CCD element, is used for measuring the light intensity distribution, adjustment work by gain and level adjustment is simple, and the light intensity measurement is performed. The adjustment can be performed at the time or after the measurement, and the adjustment labor in the measurement can be significantly reduced as compared with the case where the photosensitive material is used. Therefore, the imaging characteristics can be measured with high accuracy, quantitatively and with good reproducibility. (Third Embodiment of the Invention) In each of the above-described embodiments, the stage 9 on which the wafer 8 is placed is moved up and down,
Although the distance L is shifted from the position where the reticle 4 and the wafer 8 are in an image-forming relationship with each other, such optical shift can also be performed by vertically moving the reticle 4. In the present embodiment, a case will be described in which the reticle 4 is moved up and down to calculate the NA and σ of the projection optical system.

FIG. 6 is a diagram illustrating a state in which the reticle position is moved up and down in the image forming characteristic measuring apparatus according to the third embodiment of the present invention, and is the same as FIG. 1, FIG. 2, and FIG. Are denoted by the same reference numerals and description thereof will be omitted, and only different portions will be described here.

In the figure, a driving device 41 is provided so that a table 42 on which the reticle 4 is placed can be driven up and down. The NA or σ of the projection optical system is calculated in the first or second
The same idea as in the embodiment is used.

FIG. 7 is a diagram illustrating a method of changing the reticle vertical position without using the driving means. Figure 7 (a)
Shows the position of the normal reticle 4. At this time, the pattern 5 of the reticle 4 is on the lower side, that is, on the projection optical system 6 side.

FIG. 7B shows a case where the reticle 4 is turned over and the pattern 5 is on the upper side, that is, on the side of the illumination optical system 3. In FIG. 7A, if the reticle 4 and the wafer 8 are adjusted to a position where they form an image with each other, the reticle 4 can be turned over in this way to shift the optical position by that thickness. it can.

FIG. 7C shows a case where a spacer 43 is inserted between the reticle 4 and the table 42. By using such a spacer 43, it is possible to shift the optical position by the thickness thereof.

In this embodiment as well, since the projection optical system 6 is bi-telecentric, even if the reticle 4 having a plurality of pinholes 11 is moved up and down, no particular problem occurs in the measurement of the imaging characteristics.

As described above, the apparatus and method for measuring the image forming characteristic according to the embodiment of the present invention are provided with the same configuration as that of the first or second embodiment, and additionally, the reticle 4 and the measurement position. Since the optical position is shifted by changing the position of the reticle, the same effect as that of the first or second embodiment can be obtained, and the image forming characteristic can be changed by a means different from the operation of the stage 9 in FIG. The optical position for the measurement can be changed. (Fourth Embodiment of the Invention) In the present embodiment, an exposure apparatus using the measuring apparatus for the image forming characteristics described in the first to third embodiments will be described.

That is, the exposure apparatus of the present embodiment simultaneously performs optical characteristic adjustment of the exposure apparatus while feeding back the results of the imaging characteristics NA and σ measured by the means for converting light into an electric signal shown in FIG. Is something that
The optimum NA and σ are obtained from the measured NA and σ values.

The exposure apparatus of the present embodiment includes a second exposure apparatus main body including the illumination optical system 3 and the projection optical system 6 shown in FIG.
Alternatively, it is configured as a system provided with the image-forming characteristic measuring device of the third embodiment.

The exposure apparatus main body is provided with a diaphragm mechanism for adjusting the image forming characteristics NA and σ separately from the illumination optical system 3 and / or the projection optical system 6 or these optical systems 3 and 6. There is.

Further, in this diaphragm mechanism, the degree of the diaphragm is controlled by the diaphragm adjusting device on the basis of the image forming characteristics NA and σ of the image forming characteristic calculator 33 shown in FIG. Also,
The diaphragm mechanism is capable of not only enlarging and reducing the diaphragm but also anisotropically deforming (for example, deforming between a circle and an ellipse).

FIG. 8 is a view showing how the diaphragm is enlarged / reduced and deformed by the diaphragm mechanism of the exposure apparatus according to the fourth embodiment of the present invention. In the same figure, a circular and elliptical shape is shown as the deformation pattern of the diaphragm, but the diaphragm mechanism can be modified into other shapes. By performing the anisotropic deformation in this way, the XY difference in the in-plane distribution of NA and σ can be corrected.

Further, the diaphragm adjusting device includes an image forming characteristic calculating section 33.
Based on the in-plane measurement results of NA and σ according to, the diaphragm is enlarged or reduced or deformed according to a predetermined rule.
That is, N is calculated by statistically processing each NA and σ.
The entire in-plane measurement results of A and σ are evaluated, and the diaphragm is enlarged or reduced or deformed, and new NA and σ are evaluated.

By repeating this, the new NA and σ are sequentially adjusted in the direction of higher evaluation. Then, when the NA and σ values of the set range are reached, or when the aperture adjustment of a predetermined pattern is performed and evaluated, or when the aperture enlargement / reduction or deformation and evaluation of a predetermined number of times are repeated,
End the evaluation work.

The diaphragm adjusting device adjusts the diaphragm mechanism to the diaphragm state that gives the best NA and σ values in the final evaluation of the imaging characteristics. As described above, the exposure apparatus and the image forming characteristic adjusting method therefor according to the embodiment of the present invention are the second or the third.
In addition to providing a configuration similar to that of the embodiment, the exposure apparatus main body is provided with an aperture mechanism and an aperture adjustment unit that controls the aperture mechanism,
Since the diaphragm adjustment is performed based on the in-plane measurement results of NA and σ by the imaging characteristic calculation unit 33, the imaging characteristics of the exposure apparatus can be automatically and optimally or desired adjusted. it can.

Further, since the diaphragm shape can be transformed into an isotropic shape or an anisotropic shape, even if the measured image forming characteristics are anisotropically distributed in the image forming plane, the diaphragm shape can be changed. The deformation can correct the distribution anisotropically in the image plane so that uniform image formation characteristics can be obtained in the plane. The present invention is not limited to the above-mentioned embodiments, and can be variously modified without departing from the scope of the invention.

[0074]

As described in detail above, according to the present invention, it is possible to provide an image forming characteristic measuring apparatus and method capable of measuring the image forming characteristic of a projection optical system easily and with high accuracy. it can.

Further, according to the present invention, the distribution of the image forming characteristics of the projection optical system at a plurality of points in the exposureable area can be measured easily, with high accuracy, and more efficiently, and the image forming characteristics can be measured. An apparatus and method can be provided.

Further, according to the present invention, it is possible to provide an exposure apparatus and an image forming characteristic adjusting method thereof capable of automatically adjusting the image forming characteristic to an optimum or desired value.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a projection type exposure apparatus to which an image forming characteristic measuring apparatus according to a first embodiment of the present invention is applied.

FIG. 2 is a view for explaining the measurement principle of the imaging characteristic measuring apparatus of the same embodiment.

FIG. 3 is a view showing an image intensity distribution of irradiation light on a wafer surface in the same embodiment.

FIG. 4 is a schematic configuration diagram showing an example of a projection type exposure apparatus to which the measuring apparatus for image formation characteristics according to the second embodiment of the present invention is applied.

FIG. 5 is a diagram schematically showing how a bright portion due to direct illumination light and a dark portion due to diffracted light occur on the light receiving surface of the intensity distribution measuring element in the same embodiment.

FIG. 6 is a diagram exemplifying a state in which a reticle position is moved up and down in an image formation characteristic measuring apparatus according to a third embodiment of the present invention.

FIG. 7 is a diagram illustrating a method for changing the reticle vertical position without using a driving unit.

FIG. 8 is a diagram showing a state in which an aperture mechanism is enlarged, reduced, or deformed by an aperture mechanism in an exposure apparatus according to a fourth embodiment of the present invention.

[Explanation of symbols]

1 ... Light source 2. Illumination system diaphragm 3 ... Illumination optical system 4 ... Reticle 5 ... Pattern 6 ... Projection optical system 7: Projection optical system diaphragm 8 ... Wafer 9 ... Stage 10 ... Stage drive device 11 ... Pinhole 31 ... Folding mirror 32 ... Intensity distribution measuring element 33 ... Imaging characteristic calculation unit 41 ... Drive device 42 ... stand 43 ... Spacer

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Keita Asanuma Keita Asanuma, Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa 8 Yokohama Co., Ltd. (56) Reference JP-A-59-94032 (JP, A) JP-A-2 -50417 (JP, A) JP-A-8-97116 (JP, A) JP-A-6-29179 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 7/20 521

Claims (8)

(57) [Claims] 1. An apparatus for measuring image formation characteristics of an optical system, wherein an illumination light from a light source is applied to a mask through an illumination optical system and an image of a pattern of the mask is formed by a projection optical system. the opening of the micro is provided with a plurality, comprising a light intensity measuring means for measuring the light intensity of the image formed by using merge the projection optical system corresponding to the opening of the micro, the image to be the focused At, passing through the minute opening
Direct illumination light, and generated by the minute aperture and
Diffracted light that passes through the projection optical system, and
Based on the light intensity distribution, the projection optics as the imaging characteristic
The numerical aperture and coherence factor of the system are set for each small aperture.
Measuring device for imaging characteristics, which is characterized by corresponding calculation . 2. The apparatus for measuring an image forming characteristic according to claim 1 , wherein the light intensity measuring means is a measuring means for converting light into an electric signal. The wherein any position of the focal plane by the projection optical system, characterized by comprising a moving mechanism that can move the imaging subject so as to be measured by the light intensity measuring means according Item 1. An apparatus for measuring image forming characteristics according to item 1 or 2 . 4. A measuring device for image formation characteristics according to claim 1 , wherein the diaphragm is deformed into an isotropic shape or an anisotropic shape and / or the diaphragm is enlarged or reduced. A diaphragm mechanism for changing the image forming characteristic of the projection optical system and an image forming characteristic obtained by a measuring device for the image forming characteristic are within a predetermined range, or an optimum image forming is performed among a finite number of image forming characteristic changes. And a diaphragm adjusting unit that controls the diaphragm mechanism so as to adjust the image forming characteristics of the projection optical system so as to obtain a characteristic. 5. A method for measuring image forming characteristics of an optical system, wherein an illumination light from a light source is applied to a mask through an illumination optical system and an image of a pattern of the mask is formed by a projection optical system. the opening of the micro is provided with a plurality, measured imaging characteristics of the optical system by measuring the light intensity of an image formed by the corresponding one one the projection optical system to the opening of the small , Passing through the minute aperture in the formed image
Direct illumination light, and generated by the minute aperture and
Diffracted light that passes through the projection optical system, and
Based on the light intensity distribution, the projection optics as the imaging characteristic
The numerical aperture and coherence factor of the system are set for each small aperture.
Method of measuring the imaging characteristic you and calculates correspondingly. 6. The method for measuring an image formation characteristic according to claim 5 , wherein the light intensity is measured by means of converting light into an electric signal. 7. The method according to claim 5 , wherein the light intensity of the image can be measured at any position on the image plane formed by the projection optical system. 8. The image forming characteristic of the projection optical system when the image forming characteristic obtained by the image forming characteristic measuring method according to any one of claims 5 to 7 is not within a predetermined range. And a characteristic measuring step of measuring a new image forming characteristic of the changed projection optical system by the image forming characteristic measuring method according to any one of claims 6 to 9. Repeating the characteristic changing step and the characteristic measuring step, finally, in a state in which the image forming characteristic falls within a predetermined range, or in a state in which the image forming characteristic becomes an optimum image forming characteristic during a finite number of times, And a characteristic adjusting step for adjusting an image forming characteristic of a projection optical system.