JPH0629180A - Correcting method for projection imaging pattern - Google Patents

Abstract

PURPOSE:To efficiently decide a distortion of an imaging pattern with a projec tion exposure by a phase shifting method and an oblique incident illumination system in addition to an ordinary projection exposure by setting a dimensional error amount to a correction amount for data of a mask pattern, and correcting the distortion of the pattern. CONSTITUTION:A dimensional error amount at a slice level is output from symmetrical component and asymmetrical component of a light intensity. In the step, a condition of using a pupil filter is input to optical conditions of a projection optical system, and an amplitude transmittance of the filter of a light source image position to be formed by a light source in a pupil space under the conditions is T. A light intensity value of an imaging pattern obtained without using the filter is standardized to 1.0 by using an entirely transparent white extracted mask as a reference value of the light intensity. When a slice level of the optical conditions of the mask pattern and the filter of the transmittance T is AT, as a value of A, a range of 0.2-0.5 is selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting a projected image formation pattern, and more particularly to a large scale integrated circuit (La
In the projection exposure method of forming a fine pattern on a wafer through a mask on which a required pattern is drawn by a projection optical lens system when manufacturing a rge scale integration (LSI) or the like, the shape of a projected image (hereinafter, also simply referred to as an image shape) ) Is close to a predetermined design shape, a method for correcting a projected image formation pattern.

[0002]

2. Description of the Related Art Generally, in the field of pattern formation by a projection exposure method of this kind, an intensity distribution of a projected image (hereinafter, also simply referred to as an image intensity distribution) corresponding to an arbitrary optical system or pattern condition is used. By simulating
For example, to obtain the design guidelines of the optical system, or to simulate the formation characteristics of the resist pattern based on the simulated image intensity distribution to predict the formation conditions of the fine pattern. The image intensity distribution is widely used and useful.

On the other hand, in the case of a projection exposure apparatus for forming a fine pattern of an LSI or the like on a wafer, a high resolution is usually required for the apparatus itself, which is why it is used in the current projection exposure apparatus. For the projection lens used,
Although a resolution close to the theoretical limit determined by the wavelength of light is given, nevertheless, in order to cope with the recent trend toward miniaturization of LSI patterns, further higher resolution is required. ing.

As one means for satisfying such a demand, recently, a light shielding portion is provided by giving a phase difference close to 180 degrees to a light transmitting portion between adjacent patterns on a mask. A so-called phase shift method has been proposed in which the light intensity at is made as close to 0 as possible.
Attempts have been made to further improve the resolution by this phase shift method. However, in this phase shift method, the so-called L & S pattern (Line & Space Patt
ern), it is possible to achieve the desired high miniaturization effect only when the phase difference of 180 degrees can be easily set in the adjacent light transmitting portions.
In the case of a so-called random pattern other than the S pattern, it is difficult to satisfy such a condition, so that the miniaturization effect is reduced. In other words, in other words, the effect of improving the resolution differs depending on the type of pattern to be formed. Therefore, in the phase shift method here, an effective shifter for a random pattern is used. Placement, and
Technical difficulties such as manufacturing, inspection, and correction of the shifter and disadvantages such as a large increase in reticle manufacturing cost were unavoidable.

On the other hand, the technique of "fine pattern projection exposure apparatus" proposed by Japanese Patent Application No. 3-135317 irradiates the light incident on the mask with an angle corresponding to the numerical aperture of the projection optical system. By irradiating light at an angle from the optical axis, a resolution equivalent to that of the phase shift method is realized, and it is known as a so-called oblique incidence illumination system. Unlike the case of the phase shift method of No. 2, compared to the phase shift method, the effect of improving the resolution can be used regardless of the type of pattern to be formed and the existing mask can be used as it is. And has a great advantage.

The light source in the conventional projection exposure method is
In the normal case, they were arranged in a simple circular shape, and no filter was provided in the entrance pupil. On the other hand, in the above-mentioned oblique incidence illumination method, the light source should be arranged in an annular shape or Accordingly, a plurality of circular or rectangular shapes are arranged, and then a filter is provided in the entrance pupil according to the shape corresponding to such a light source arrangement to give the filter a light transmittance distribution.

[0007]

In the image forming pattern projected by the phase shift method and the grazing incidence illumination method, the ideal pattern image obtained by the mask pattern is usually used. In many cases, the projection shape with a distortion, blurring, etc. is added, and the image-forming distortion in this projection image is the same as that seen in the conventional projection exposure method, for example, for a small pattern close to a large pattern. Since the generation of such image distortion affects the accuracy of the final fine pattern to be formed more and more as the pattern itself becomes finer, under the given mask pattern and optical conditions, etc. A means for accurately determining and correcting whether imaging distortion has occurred is required.

With respect to the means for correcting the image-forming distortion, the image intensity distribution of the projected image-forming pattern is currently obtained by simulation, and at the same time, the presence or absence of the image-forming distortion is visually determined. And
In the case of such a means, in view of the trend of automation in recent years, it is expected that the accuracy of the judgment processing of the image formation distortion in the projected image will be improved by replacing the visual judgment here with the judgment based on the calculation result of the computer. In addition, it is possible to quantitatively obtain the required amount of distortion in the projected image, and when this is used as a correction amount of the mask pattern dimension, as a result, the imaging characteristics are efficiently and effectively obtained. It can be improved.

However, on the other hand, in the automatic measurement of the distortion amount from the image intensity distribution of the projected image, it is technically necessary to have an extremely sophisticated processing means, which significantly speeds up the processing. It raised a new problem that it would hinder it.

Therefore, the object of the present invention is to
In view of such conventional problems, it is possible to efficiently determine and correct the distortion of the image formation pattern in the projection exposure by the phase shift method and the grazing incidence illumination method in addition to the general normal projection exposure. It is an object of the present invention to provide a method of correcting a projected image formation pattern of this kind.

[0011]

In order to achieve the above-mentioned object, in the method of correcting a projected image forming pattern according to the present invention, a symmetric component of the light intensity distribution of the image is opposite to the one-dimensional pattern. The two-dimensional patterns are decomposed, and these decomposed components are used for the determination and correction of the imaging distortion. For a two-dimensional pattern, the attenuation in the real part of the mutual intensity distribution of the imaging is performed. The vibration ratio is used to determine the image distortion.

That is, the present invention is a method for correcting image distortion of a projection pattern when a mask having a required pattern shape is used and a mask image is projected and imaged on a wafer by a projection optical system. A step of inputting a shape, a step of inputting optical conditions of the projection optical system, a step of specifying a plurality of points on the image forming pattern, a step of specifying a slice level of the image forming light intensity, and the specifying The process of the mask pattern contribution to the light intensity of each specified point to give a symmetrical component of the light intensity that is generated by acting symmetrically around one designated point, and to the light intensity of the one designated point. On the other hand, the process in which the contribution of the mask pattern gives an antisymmetric component of the light intensity generated by acting antisymmetrically around the corresponding point, and the symmetry of the light intensity at the plurality of designated points. The step of outputting the dimensional error amount at the slice level from the minute and antisymmetric components, and using the dimensional error amount as the correction amount for the data of the mask pattern to correct the distortion of the imaging pattern. This is a method of correcting a projected image formation pattern that is a feature.

Further, according to the present invention, in the method of correcting the image formation distortion of the projection pattern when the projection optical system projects and forms the image of the mask pattern on the wafer by using the mask having the required pattern shape, The process of subdividing the whole into small regions, and one reference point on the image formation pattern in the arbitrary subdivided small regions, the process of designating a line segment from the reference point in a predetermined direction, and the reference A step of providing a real part of mutual strength between a point and an arbitrary point on the line segment, a step of obtaining a rate of vibration damping as the real part of the mutual strength on the line segment becomes farther from the reference point, A step of comparing whether or not the small region is a region in which distortion correction is required by comparing the ratio of vibration damping according to the distance from the reference point with a reference vibration damping ratio; For small areas that require Te is a method of correcting projection imaging pattern which comprises a step of outputting a correction amount with respect to the mask pattern data.

[0014]

Therefore, in the case of the present invention, for the one-dimensional pattern, the symmetric component and the antisymmetric component of the image light intensity distribution are decomposed, and these decomposed components are used to judge the image distortion.
For the two-dimensional pattern, the ratio of the damping vibration in the real part of the mutual intensity distribution of the image formation is used for the determination of the image formation distortion. In each of the two-dimensional pattern processing, it is possible to efficiently determine whether or not the imaging distortion occurs in the projected image, and the degree thereof. In addition, in the one-dimensional pattern processing, the correction amount for the imaging distortion is also calculated. You can ask.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for correcting a projected image formation pattern according to the present invention will be described in detail below with reference to the accompanying drawings. First, a description will be given of a light intensity expression method of resolution display useful for evaluation of image distortion of a one-dimensional pattern, that is, image shift in the present invention. Generally, the imaging light intensity distribution I
(x) can be expressed as the following formula as an integral of the image intensity created by one point of the light source over the light source surface. Here, the spread of the light source is two-dimensional.

I (x) = (light source integral) | E {Mask-Fourier transform (pupil function-Fourier inverse transform)} | ² ... (1) Then, the value E in the equation (1) is It is given by

E = exp (2πif ₀ x) (2) Here, f ₀ is one variable of the light source integral.

Regarding the value E, it has a role of allocating the image forming light intensity distribution I (x) to each of symmetrical and antisymmetrical components with respect to one point of the mask pattern. Taking the case where the arrangement shape of the corresponding light source has a ring shape with no width and the entrance pupil has no filter as an example, the above formula (1) is specifically obtained as follows.

[0019]

[Equation 1]

Here, A (x ₀ ) is the amplitude transmittance of the one-dimensional mask, and k _s is the wave number of the irradiation light. k _s sin θ = k ₁ sin θ '(4) Here, k ₁ is the maximum wave number of the mask diffraction light that passes through the pupil.

In addition, considering the light intensity at the coordinate x on the image plane in the equation (3), the first of the integrals of the coordinate x _o over the entire surface of the mask that contributes to this The line is
The mask shape collects components that contribute symmetrically around the coordinate x, and the second row collects components that contribute antisymmetry. That is, in this way, the general expression (1) can also be transformed into symmetric and antisymmetric decomposition representations.

Next, how these decomposition components in the image intensity are effective for discriminating the image shift will be concretely described by numerical values by the embodiments shown in FIGS. 3 to 6. In this case, it is assumed that the target mask pattern has a thin line pattern adjacent to a large pattern with an appropriate gap and the gap width and the line width are equal to each other. So, in Figure 3 (a),
The image light intensity distribution when the mask pattern is projected and imaged by the oblique incidence illumination system with the pupil filter, and its symmetric and antisymmetric components are shown.

That is, in FIG. 3 (a), the light intensity indicated by the bold line is the sum of the symmetric and antisymmetric components, and the symmetric component indicated by the thin line is approximately symmetrical with respect to the design pattern. It is clear that the anti-symmetrical components shown by the dotted line, which are distributed and added to this, cause the image shift in this case. The optical conditions in this case are as follows: when the pupil radius is normalized to 1.0, the average radius of the illumination zone is R = 0.7, and the half width of the zone is sd =
0.05, the amplitude transmissivity (filter transmissivity) of the corresponding part of the illumination zone in the pupil is T1 = 0.4, the amplitude transmissivity up to the inner circumference of the pupil outside that is T2 = 0.7, and the defocus amount d
f (defocus amount) is 1.5λ / {2 (NA) ² }. However, here, λ is the wavelength of light, NA is the numerical aperture of the lens,
The horizontal axis is standardized to λ / 2 (NA).

Further, FIG. 3 (b) shows the distributions of the above-mentioned three kinds when a pupil without a filter is used. In this case,
As compared with FIG. 3A, the antisymmetric component is small and the image shift is also small. Similarly, FIG.
(c) shows the result of the conventional projection exposure method,
The spread of the light source is σ = 0.5. And in this case,
This is an example when the method is not applied properly because the symmetric component does not appear symmetrically with respect to the pattern near the resolution limit.

Further, FIG. 3 (d) shows an example of the phase shift method, in which the fine line pattern is provided with a phase difference of 180 degrees, and similarly, the spread of the light source is σ = 0.2. In this case, the image shift at the pattern edge portion is small, even though the antisymmetric component appears largely in the central portion. Indicates that the value in the section must be used.

Next, the means for estimating the dimensional error at the pattern edge from the symmetric and antisymmetric components will be described with reference to FIG. Here, the dimensional error dw that occurs at the light intensity level I _O specified in advance is given by the following equation from the light intensity value I at the edge and its inclination dI / dx (x is the coordinate of the horizontal axis). .

Dw = (Io−I) / (dI / dx) (5)

Further, in the formula (5), (Io-I) is as follows:
From the value Is of the symmetrical component and the value Ia of the antisymmetric component at the edge portion, it is given by the following equation.

Io-I = Io-Is-Ia (6)

Similarly, in the equation (5), the slope of the light intensity dI / d
x can be approximated by the following equation from the value Is of the symmetrical component at the pattern center and the value Is.

DI / dx = (Is-Iso) / (w / 2) (7) where w is the line width.

That is, in the above equation (7), since the symmetrical components are distributed symmetrically with respect to the pattern, a good approximation can be given. Here again, if the slope dI / dx is to be obtained from the light intensity, it is necessary to take fine discrete points for calculating the light intensity. In the case of this embodiment method, the calculation point is the center of the pattern. Therefore, the image shift can be evaluated at high speed, and the dimensional error dw thus obtained can be used as a correction amount for the mask design.

On the other hand, the light intensity level Io for obtaining the dimensional error
Requires that the line width w be changed from a small value to a large value so that the size error is minimized as a whole. Furthermore, the light intensity distribution can be changed into various distribution shapes depending on the pattern size or shape. However, if the projection optical system is provided, it is necessary to set the light intensity level Io to a predetermined value. Further, in the conventional projection exposure method, the image intensity value when using a white mask that allows light to pass through the entire surface is 1.
It is known that when normalized to 0, the light intensity level Io becomes a value around 0.3.

In the phase shift method, when considering that the phase shift is partially applied in the mask, the light intensity level Io similarly becomes a value around 0.3. Further, in the above-mentioned grazing incidence illumination method, when a filter is not used, it may be the same as the conventional projection exposure method, but when a filter is used, it is necessary to reexamine it, and various patterns and optical conditions are required. As a result of studying the case and the simulation, the light intensity level I
It is effective to set o to the following value. That is,
Let T be the amplitude transmittance of the filter at the position of the light source image formed by the light source in the pupil space, and use the blank mask of full transmission as the reference value of the light intensity, and the image formation obtained when the filter is not used. When normalizing the light intensity value to 1.0,
Under the optical condition of the pupil filter having an arbitrary mask pattern and the amplitude transmittance T, the value of AT is selected as the light intensity level Io. Here, the value of A is preferably in the range of 0.2 to 0.5.

Next, FIGS. 5 (a) and 5 (b) show the case where the same pattern as in FIG. 3 is used and the width w of the thin line is changed based on the level setting method. 3 positions of the pattern, that is, the right edge of the large pattern,
And the deviation from the design position of each edge of both ends of the thin line. Here, the broken line represents the right end edge of the large pattern, the dash-dotted line represents the left end edge of the thin line, and the solid line represents the right end edge of the thin line. In addition, the imaging characteristics as designed can be obtained (mask linearity diagram).

FIG. 5 (a) shows the filter amplitude transmittance.
When T1 = 0.4, NA = 0.5, slice level is 0.375 T
1 and FIG. 5 (b) similarly shows T1 = 0.8, NA = 0.4.
In case 5, the slice level is 0.313 T1 and other common optical conditions are wavelength λ = 0.248 μm, R = 0.7, sd
= 0.05, T2 = 1.0, df = 0.75 μm. That is, when comparing FIG. 5 (a) and FIG. 5 (b), the filter value is 1.
It can be seen that the closer to 0, the better the linearity. However, FIG.
In the optical condition of (b), it is necessary to take into consideration the difference in resolution reduction.

FIGS. 6 (a) and 6 (b) compare the effects of the condition R, and FIG. 6 (a) shows the case of R = 0.5 and NA = 0.46, and FIG. ) Indicates the case of R = 0.7, NA = 0.51, and the common condition is that the filter value is T1 = 0.4, T2 =
The slice level is 0.7 and the slice level is 0.3 T1. Others are the same as in the case of FIGS. 5 (a) and 5 (b). That is, in this case, when R is increased, the linearity deteriorates and the line width increases.

Next, FIG. 1 shows a flowchart of a method for correcting an image-forming pattern in a one-dimensional pattern in this embodiment. Here, first, after inputting the one-dimensional mask pattern, then the optical condition, and the intensity level for evaluating the dimension, the symmetric and antisymmetric light intensity distributions at the necessary calculation points are obtained, and finally, The dimensional error is evaluated and this is output as a required correction value.

Next, the case of a two-dimensional pattern will be described. In the case of this two-dimensional pattern, first, when a mask pattern is given, it must be divided into small areas, and then it is necessary to first determine in which small area the image-forming distortion is large. There is. Next, a method for evaluating the image formation distortion will be described. In this evaluation method, the imaging distortion is evaluated using the real part of the mutual intensity distribution of the imaging.

Here, the mutual intensity means that one reference point is set on a two-dimensional pattern, and as the distance from the set reference point is increased, the image is formed in a state of maintaining coherence. Is a quantity that expresses whether or not there is a two-dimensional distribution of complex numbers by arbitrarily scanning between arbitrary points separated from each other, and the mutual strength when the arbitrary point and the reference point coincide with each other. Is represented by a real number and is known to be equal to the light intensity at the point of coincidence (Kusagawa, Yokota Translated by Born, Wolf, "Principles of Optics 1, 2, 3", Tokai University Press).

FIG. 7 shows a small area pattern used for the evaluation. In FIG. 7, light does not pass through the area surrounded by the diagonal lines, and light passes through the white area surrounded by the thick lines. The width of the thin line at the central portion corresponds to w, and the gap width between the two large patterns on both sides is also equal to w. Further, it is assumed that the entire square including the shaded area and the white area is a basic unit that is infinitely repeated in the vertical and horizontal directions. Further, the x mark indicates an upward w from the center of the square.
Points that are distant from each other, and the points marked with X are reference points for calculating the mutual strength.

Further, FIGS. 8A to 8D show an example of the case where the image forming distortion is generated in FIG. 7, where w =
At 0.25 μm, the optical conditions are λ = 0.248 μm, R = 0.74, sd = 0.
05, NA = 0.48, T1 = 0.42, T2 = 0.83, T3 = 0.97, df = 0.75
μm. Note that T3 is the filter amplitude transmittance in the central region of the pupil. FIG. 8 (a) shows contour lines in the light intensity distribution, and FIG. 8 (b) shows the light intensity on the horizontal line marked with a cross in FIG. The intensity level is around 0.125 and the contour level is between the second and third from the bottom. As can be seen from the figure (a), in this case, image distortion occurs at the upper part of the center line. Further, FIG. 8C shows contour lines of the real part in the mutual intensity distribution, and it can be seen that the interference extends from the reference point in the direction in which the large pattern exists. Furthermore, FIG. 8 (d) shows the real part of the intensity distribution on the diagonal line marked with X in FIG. 8 (c), and the curve of (d) is
This represents the characteristic of damping oscillation from the maximum peak in the center to both sides, and the damping is gentle from the center to the left side, which is affected by the large pattern.

Further, FIGS. 9A and 9B show the distortion amount of the imaging pattern in this case in FIG. 7 as a percentage with respect to the w, and the deviation from the design position indicates the design edge. It is shown as a thick solid line that is off. Here, FIG. 9 (a) shows the case of defocus df = 0.0, and FIG. 9 (b) shows the case of df = 0.75 μm. In order to establish a correspondence with FIG. 8 (d), it is necessary to have a case where there is no image distortion as a comparison reference. Subsequently, FIGS. 10 (a) to 10 (d), and FIG. 11 (a),
Each figure in (b) is the same as the figure 8 when w = 0.4 μm.
It is the figure represented corresponding to each figure of (a) thru | or (d), and FIG. 9 (a), (b).

These FIG. 8 (d) and FIG. 10 (d) are compared as follows. Here, the central peak is numbered 0, and the peaks to the left of this are numbered 1, 2, and 3. In this case, regarding the ratio rc2 between the 2nd peak value and the 0th peak value, rc2 = 0.19 on the Fig. 8 (d) side.
Rc2 = 0.19 on the side of FIG. 10 (d), and in the same comparison in the case of df = 0.0 in FIG. 9 (a) and FIG. 11 (a), the former is rc2 = 0.19,
In the latter case, rc2 = 0.19. Then, if the presence or absence of the image-forming distortion is judged at a boundary of, for example, about 10% error of w, in this case, it becomes clear that the boundary is around rc2 = 0.1.

FIG. 12 shows an example of another optical condition. In this case, the optical condition is w = 0.3 μm, R = 0.74,
sd = 0.1, λ = 0.248 μm, NA = 0.48, T1 = 0.42, T2 = 0.8
3, T3 = 0.97, and at df = 0.0 in FIG. 12 (a), rc2 =
At df = 0.75 μm of 0.07, (b), rc2 = 0.04. And in this case, at the upper and lower ends of the central thin line, w
The length is shortened by 10% or more, and the method of this embodiment cannot be applied to the respective portions. And in FIG.
Is an example of the conventional projection exposure method, and the optical conditions in this case are w = 0.3 μm, σ = 0.5, λ = 0.248 μm, NA = 0.4
And df = 0.0 in the figure (a), d in rc2 = 0.08, (b)
At f = 0.75 μm, rc2 = 0.08. Here, the point to be noted when applying the method of this embodiment is that it may not be applicable when the resolution of the pattern is extremely poor.

Further, FIG. 14 shows the result of the phase shift method. The optical conditions at this time are w = 0.25 μm, σ =
0.2, λ = 0.248 μm, NA = 0.31, df = 0.75 μm. In this phase shift method, it can be seen from Fig. 6 (d) that the correlation between the patterns is very strong and the mutual intensity extends to the adjacent region of the repeating unit period. Then, under the same optical conditions, the dimensional error when the pattern dimension is changed to w = 0.3, 0.4 μm is shown in FIGS. 15 and 16, but at this time, the dimension is good only in the case of FIG. That is, the figure
At df = 0.0 in (a), the ratio rc (-1) between the 0th peak and the 1st peak of the mutual intensity is close to 1.0, and in Fig. 14, rc (-
1) is larger than 1.0 and smaller than 1.0 in FIG. What can be inferred from each of these figures is that the mutual intensity spreads over a fairly wide range, so that image distortion is basically unavoidable in this phase shift method. In FIG. 15, the image-forming distortion did not occur.
Under this optical condition, this is an exception when w = 0.3 μm, and it is conjectured that under other optical conditions, imaging distortion may not occur at other dimensions.

Therefore, as described in the above-mentioned two-dimensional embodiment, in order to determine the portion where the image formation distortion occurs in the mask pattern, the resolution of each of the divided small regions is determined. Select the point that seems to be strict as the reference point, specify the direction that the correlation is likely to be strong from the reference point, calculate the real part of the mutual intensity on that line segment, and the number and size of the attenuation peaks. , And the degree of spread can be compared with a prepared criterion.

Here, as in the prior art, in order to determine the image formation distortion from the light intensity of the two-dimensional pattern, it is necessary to calculate the light intensity at the calculation points over the entire surface. In the evaluation of the imaging pattern, since it is sufficient to calculate the real part of the mutual intensity on the line segment, there is an advantage that the calculation amount is substantially small, and it is easy to achieve the processing efficiency. Moreover, even if the light intensity calculation itself is compared, the fineness of the calculation point may be rough, and there is no need to perform the light intensity calculation with two with and without defocus. Sufficient results can be obtained by determining the real part of the mutual intensity distribution without defocusing. Then, if a small area that requires distortion correction is extracted in this way,
The correction of the two-dimensional pattern here can be easily performed by regarding the local as one-dimensional and applying the above-described one-dimensional pattern correction.

Next, FIG. 2 shows a flow chart of a method for evaluating an image formation pattern in a two-dimensional pattern in this embodiment. Here, first, after inputting the optical conditions, the entire mask pattern is divided into small areas, and for each of these small areas, the mask pattern, the reference point for mutual strength calculation, and the real part of mutual strength are calculated. Specify the line segment for calculation and input it to each, calculate the mutual part real part at the required calculation point, and then determine the number and size of the peaks of the damped vibration and the degree of spread to form image distortion. The presence or absence of the distortion is determined by comparing with the judgment criterion of No. 1, and the correction amount is output for the small area for which distortion correction is required, and this is executed for all the small areas. Of.

[0050]

As described above in detail with reference to the embodiments,
According to the method of the present invention, unlike the case of the conventional method,
It is not necessary to calculate the light intensity distribution of the projected image pattern over the entire surface, and in the processing of the one-dimensional pattern, the light intensity distribution of the image pattern at several points related to the design dimension position is symmetrical and antisymmetrical light intensity. It is enough to calculate the distribution, and in the processing of the two-dimensional pattern, it is sufficient to calculate the real part of the mutual intensity distribution on the line segment. As a result, distortion occurs in the imaging pattern. It is possible to significantly reduce the load required for determining whether or not the determination is made, and it is possible to make an efficient determination. In addition, in the processing of the one-dimensional pattern, the dimensional error amount and thus the correction amount for the image-forming distortion are also calculated. It has excellent features such as being easily obtained.

[Brief description of drawings]

FIG. 1 is a flowchart showing an operation of an embodiment method in a one-dimensional pattern of the present invention.

FIG. 2 is a flow chart showing the operation of an embodiment method for a two-dimensional pattern according to the present invention.

FIG. 3 is a graph showing symmetrical and antisymmetrical light intensity distributions in one example regarding the one-dimensional pattern of the present invention.

FIG. 4 is a graph explaining calculation of a dimensional error in the one-dimensional pattern of the same.

FIG. 5 is a diagram of mask linearity comparing effects of filter transmittance performed at the same light intensity level.

FIG. 6 is a diagram of mask linearity comparing the effect of the illumination ring zone radius performed at the same light intensity level.

FIG. 7 is an explanatory diagram showing a two-dimensional mask pattern of the present invention.

FIG. 8 is an explanatory diagram showing a light intensity distribution and a mutual intensity distribution in the case of image distortion in the example in the two-dimensional pattern.

FIG. 9 is an explanatory diagram showing a ratio of distortion occurrence corresponding to (a) of FIG. 8 regarding presence or absence of defocus in the two-dimensional pattern.

FIG. 10 is an explanatory diagram showing the light intensity distribution and the mutual intensity distribution in the case of no image distortion in the example in the two-dimensional pattern.

FIG. 11 is an explanatory diagram showing the rate of distortion occurrence corresponding to (a) of FIG. 10 regarding the presence or absence of defocus in the two-dimensional pattern.

FIG. 12 is an explanatory diagram showing a case in which an image formation distortion is not generated by changing the illumination ring zone width in the two-dimensional pattern.

FIG. 13 is an explanatory diagram showing a state of the conventional two-dimensional pattern projection exposure method.

FIG. 14 is an explanatory diagram showing a light intensity distribution and a mutual intensity distribution in the case where there is imaging distortion in the two-dimensional pattern phase shift method in the same as above.

FIG. 15 is an explanatory diagram showing a state in the case where there is no image distortion in the phase shift method.

FIG. 16 is an explanatory diagram showing a state in which there is image distortion when the pattern size is increased by the phase shift method.

Claims (3)

[Claims] 1. A method of correcting the image formation distortion of a projection pattern when projecting an image of the mask pattern onto a wafer by a projection optical system using a mask having a required pattern shape, and inputting the pattern shape of the mask. A step of inputting optical conditions of the projection optical system, a step of specifying a plurality of points on the image forming pattern, a step of specifying a slice level of the image forming light intensity, and a step of specifying each of the specified points. With respect to the light intensity of each point, the process of the mask pattern contribution giving a symmetrical component of the light intensity produced by acting symmetrically around one designated point, and the light intensity of the one designated point, A process in which the contribution of the mask pattern gives an antisymmetric component of the light intensity generated by acting antisymmetrically around the corresponding point, a symmetric component of the light intensity at the plurality of designated points, and an opposite A step of outputting a dimensional error amount at the slice level from a component, wherein the dimensional error amount is used as a correction amount for mask pattern data to perform distortion correction of the imaging pattern. Image pattern correction method. 2. In the process of outputting the dimensional error amount at the slice level from the symmetric component and the antisymmetric component of the light intensity, the condition for using a pupil filter is input as the optical condition of the projection optical system, Let T be the amplitude transmittance of the pupil filter at the light source image position created in the pupil space by the light source under the conditions, and use a blank mask of full transmission as the reference value of the light intensity, and without using the pupil filter. When the light intensity value of the obtained imaging pattern is normalized to 1.0, and the slice level of the mask pattern and the optical condition of the pupil filter of the amplitude transmittance T is set to the value of AT, the value of A is set to 2. The method for correcting a projected image forming pattern according to claim 1, wherein the range of 0.2 to 0.5 is selected. 3. A method of correcting image distortion of a projection pattern when a mask of a required pattern shape is used to project and image the mask pattern on a wafer by a projection optical system, wherein the entire mask pattern is a small area. The process of subdividing into
And one reference point, a process of designating a line segment in a predetermined direction from the reference point on an image-forming pattern in the subdivided arbitrary small area, and an arbitrary point on the reference point and the line segment. Between the step of giving the real part of the mutual strength, the step of obtaining the rate of vibration damping as the real part of the mutual strength on the line segment moves away from the reference point, and the vibration damping according to the distance from the reference point. A process of determining whether or not the small region is a region requiring distortion correction by comparing the ratio with a reference vibration damping ratio, and for the small region requiring distortion correction, And a step of outputting a correction amount for the mask pattern data.