JP2001085327A - Semiconductor device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a monochromatic microcircuit pattern which is located on a mask and different from a pattern that is transferred onto a substrate to be very accurately checked by a method wherein a first pattern is formed on a wafer, and then a second mask with a phase shifter is irradiated with an excimer laser beam for light exposure, and the wafer is etched. SOLUTION: A first mask pattern is projected onto a wafer for light exposure, a first pattern is formed on the wafer by etching, a second mask with a phase shifter is irradiated with an excimer laser beam to project a second mask pattern onto the wafer for exposure, and a pattern is formed on the wafer by etching. At least, a part of O-order diffracted light is shielded with a light shielding plate (image formation spatial filter 3302) on a diffraction image plane, by which only diffracted light inverted in phase reaches to an image-formation plane, so that it appears that a phase film is formed on the mask from a viewpoint of an image-formation plane. As a result, a circuit pattern is transferred onto a wafer the same as a phase shifter method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention eliminates the influence of interference light generated in an extremely fine circuit pattern formed on a mask and forms an image on a substrate with a high resolution using an excimer laser beam through a projection lens. The present invention relates to an excimer or other exposure method and apparatus, and an excimer or other exposure method and a mask circuit pattern inspection method.

[0002]

2. Description of the Related Art In LSI manufacturing, a circuit pattern on a mask is exposed and transferred onto a wafer to form a fine circuit pattern on the wafer. However, in order to meet the needs for high integration of LSIs, circuit patterns transferred onto wafers have become extremely fine and have reached the resolution limit of the imaging optical system.

Therefore, various techniques have been developed to transfer an extremely fine circuit pattern.

For example, there is a method of exposing using X-rays such as SOR (Synchrotron Organized Resonance) light.

There is also a method using EB (electron beam, electron beam exposure machine).

[0006] Further, since the exposure throughput is fast and the handling is relatively simple, "Excimer laser stepper for sub-half micron lithography, Akikazu Tanimoto, SPIIE No. 1088"
Optical Laser Microlithography 2 (198
9) "" Excimer Laser Stepper for Sub-halfMicron Li
thography, Akikazu Tanimoto, SPIE Vol. 1088 Opti
cal Laser Microlithography 2 (1989) "
There is a method using an excimer laser disclosed in JP-A-7-198631.

A phase shifter method is known from Japanese Patent Publication No. Sho 62-50811 in which the resolution is improved by devising a mask. This phase shifter method increases the resolution by interfering light from an adjacent pattern, and provides a film (phase shifter) whose phase is alternately shifted by π so that the phase of an adjacent pattern is inverted. Realize.

[0008] Further, as a document introducing a theoretical analysis of partial coherent imaging, "Optical (1), (2),
(3), (4) ”(Optical Technology Contact, Vol.27, No.12, p.
p. 762-771, Vol. 28, No. 1, pp. 59-67, Vol. 28, No.
2.pp.108-119, Vol.28, No.3, pp.165-175).

An example in which the resolution is improved by using a spatial filter is described in Japanese Patent Application Laid-Open No. 27516/1991.

[0010]

SUMMARY OF THE INVENTION The above Japanese Patent Publication No. Sho 62-50
The conventional technique disclosed in Japanese Patent Application Laid-Open No. 811 has a problem that it is difficult to dispose a phase shifter and it is difficult to manufacture a mask provided with the phase shifter.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to make it possible to transfer an extremely fine black and white circuit pattern formed on a mask onto a substrate with a resolution equal to or higher than that of a phase shifter. And an exposure method therefor.

Another object of the present invention is to provide an exposure system such as an excimer, which can simulate and confirm data of a transfer pattern onto a substrate which is actually transferred by an exposure apparatus by a calculation process.

Further, an object of the present invention is to provide a method for forming an extremely fine circuit pattern formed on a mask with high accuracy even when a very fine circuit pattern formed on a mask is different from a pattern transferred on a substrate. An object of the present invention is to provide a mask circuit pattern inspection system capable of performing inspection.

[0014]

SUMMARY OF THE INVENTION According to the present invention, there is provided illumination means for emitting light, such as excimer laser light, which maintains coherence to some extent;
Imaging means for forming an image of light illuminating a mask (including a reticle) on the wafer by the illuminating means, and light shielding means for shielding at least a part of the zero-order diffracted light among the light transmitted or reflected by the mask; An exposing device or an exposing method such as an excimer is provided, and can solve the above problem.

The present invention is also an exposure apparatus such as an excimer, wherein the spatial filter is formed of a device which shields an area corresponding to NA of the illuminating means.

Further, the present invention is an exposure apparatus such as an excimer, which has an integrator and a spatial filter as the illumination means.

Further, the present invention is the excimer exposure apparatus, wherein the mask has a circuit pattern formed with a line width of approximately の of the imaging resolution.

According to the present invention, there is provided an illumination means for applying an annular diffuse illumination formed from a large number of virtual point light sources to a mask substantially uniformly in an exposure area, and an illumination means for applying the illumination light to the mask substantially uniformly. Has an optical pupil for blocking at least a part of the 0th-order diffracted light or the low-order diffracted light among the light transmitted through the mask diffusely illuminated, and the circuit pattern formed on the mask in the exposure area is formed on the substrate. And a method for step-and-repeat and sequentially reducing a circuit pattern formed on a mask on a substrate.

Further, according to the present invention, there is provided an image forming means for illuminating a mask on which a circuit pattern is formed, and shielding at least a part of the zero-order diffracted light from the light transmitted or reflected by the illuminated mask circuit pattern. An exposing method for excimer or the like, wherein the image is formed and transferred onto a substrate.

Further, the present invention is an exposure method for excimer or the like, wherein the minimum line width of the circuit pattern on the mask is formed in conformity with the imaging resolution of the imaging means.

The present invention is also an excimer or other exposure method, characterized in that the mask has a circuit pattern formed with a line width of approximately 1/2 of the imaging resolution.

Further, according to the present invention, the circuit pattern on the mask is formed with a line width of about 1/2 of the imaging resolution, and a wide circuit pattern transferred onto the substrate is transmitted through the mask. Is approximately 1 / of the imaging resolution
An excimer or other exposure method characterized by being formed in a line and space or lattice pattern with a pitch of 2 to 1/3.

The present invention is also directed to an excimer or the like, which is characterized in that a fine pattern portion and a large pattern portion of a circuit pattern formed on a mask are divided and imaged by an image forming means and transferred onto a substrate. Exposure method.

According to the present invention, there is provided a mask data converting means for converting and generating mask data from wiring data, and mask data obtained from the mask data converting means.
Calculating means for performing an arithmetic process based on a transfer function substantially equivalent to imaging means for transferring the circuit pattern formed on the mask onto the substrate using excimer laser light, and calculating data of a transfer pattern on the substrate; And an exposure method such as an excimer.

According to the present invention, there is provided a mask data converting means for converting and generating mask data from wiring data, and mask data obtained from the mask data converting means.
The circuit pattern formed on the mask is subjected to arithmetic processing based on a transfer function substantially equivalent to an image forming means for transferring the circuit pattern onto the substrate using light such as excimer laser light to calculate data of the transfer pattern on the wafer. Calculating means, illuminating means for illuminating the mask with excimer laser light or the like, forming an image of light transmitted or reflected by the mask illuminated by the illuminating means at the detection position, and a transfer function substantially equivalent to the imaging means. An inspection apparatus having an imaging means having a light receiving means for receiving an imaging circuit pattern imaged at the detection position to obtain an image signal; and an image signal obtained from the light receiving means of the inspection apparatus and the calculation means. The mask circuit pattern inspection system includes a comparison unit for comparing the calculated data of the transfer pattern onto the wafer with the calculated data.

[0026]

In an exposure apparatus using light such as an excimer laser beam, the cause of lowering the contrast of a circuit pattern transferred onto a substrate is that diffracted light cannot be sufficiently taken in the aperture (pupil) of the imaging means. Meanwhile, light is diffracted from the circuit pattern on the mask according to the wavelength used and the dimensions of the circuit pattern. At this time, when the circuit pattern becomes extremely fine with respect to the exposure wavelength, the diffraction angle increases, and the intensity of the diffracted light also increases. As a result, light does not enter the aperture of the imaging means (projection lens) used for transfer, which causes a reduction in resolution.

In order to prevent the diffracted light from being missed as much as possible, the wavelength can be shortened to reduce the diffraction component as in an excimer laser stepper, or by increasing the NA of the imaging means (projection lens). Something that captures more light is conceivable.

On the other hand, according to the present invention, while the diffracted light from the circuit pattern on the mask has a small amount of components taken into the image forming means (projection lens), the diffracted light from the circuit pattern on the mask (0 Of the light necessary for image formation, only the 0th-order diffracted light is taken into the image forming means (projection lens) in a large amount, and the image forming means (projection lens) is relatively absorbed. ) Focuses on the fact that a small amount of the diffracted light component is taken in, and shields at least a part of the 0th-order diffracted light so that the balance between the amount of diffracted light emitted from the imaging means (projection lens) and the 0th-order diffracted light can be balanced Achieves high-resolution exposure by improving the contrast of the ultrafine circuit pattern formed on the mask through the imaging means (projection lens) and transferring it onto the substrate. It is those intoxicated to.

Further, in order to efficiently realize the shielding of the zero-order diffracted light, it is necessary to increase the coherency of the illumination light of the mask. In addition, in the projection exposure apparatus, the spatial coherence degree (sigma, σ) of the illumination system is increased in order to provide the remodeling ability to a high spatial frequency. These two conditions seemingly contradict each other, but can be simultaneously achieved by using an annular illumination light source used in a phase contrast microscope or the like.

Further, since the annular light source can increase the coherence, the depth of focus of the optical system can be increased.

In particular, the present invention provides an illumination means for applying, to a mask, an annular diffused illumination formed from a large number of virtual point light sources almost uniformly in an exposure region, and an illumination means for applying the illumination light to the mask. Among the light transmitted through the diffusely illuminated mask, the optical pattern has an optical pupil that blocks at least a part of the 0th-order diffracted light or the low-order diffracted light, and a circuit pattern formed on the mask in the exposure region is formed on a substrate. By providing a reduction projection lens that forms an image, it is possible to achieve high resolution exposure by improving the contrast in which an extremely fine circuit pattern formed on a mask is transferred onto a substrate through the reduction projection lens. Can be.

It is apparent that the present invention is not necessarily limited to the projection type exposure method using excimer laser light.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the principle of the present invention will be described with reference to FIGS.

That is, in the present invention, the circuit pattern on the mask is transferred with an improved contrast rather than faithfully transferred onto the substrate by the imaging means (projection lens). That is, in the projection exposure, it is not always necessary to “transfer the circuit pattern accurately”, but it is based on a new technical idea that “the circuit pattern desired to be obtained on the substrate (wafer) should be transferred with high contrast”.

FIG. 1 (a) shows a glass substrate 10
FIG. 2 is a cross-sectional view of the mask 100 on which a mask circuit pattern 104 is formed by chrome 102 on 1; A waveform 301 in FIG. 1B is a strong signal intensity distribution of an imaging pattern formed on the substrate (wafer) 200 by the projection exposure apparatus 3000 shown in FIGS. 4 to 6 for the mask circuit pattern 104. This waveform 301 is considered separately into a waveform 302 due to the zero-order diffracted light and a waveform 303 due to the high-order diffracted light.
When the mask circuit pattern 104 is a fine circuit pattern 105 as shown in FIG. 1A, the waveform 301 detected by the higher-order diffracted light is smaller than the waveform 302 generated by the 0th-order diffracted light. AV
Becomes smaller. Here, since the component of the waveform 302 can be removed by blocking the 0th-order diffracted light, the detected waveform is the waveform 3
A high contrast like 02 is obtained.

Further, another principle of the present invention will be described below. That is, in the present invention, the phase of an adjacent circuit pattern on the mask is intended to be inverted (ie, to be shifted by π) without using a phase film. As shown in FIGS. 2 and 3, when the light-shielding portion between the circuit patterns 321 (A) and 323 (B) adjacent to the mask (reticle) 100 is narrow, a completely complementary figure is formed, and the light-shielding is performed. If the parts have a finite width, they will be approximately complementary. The circuit patterns 321 (A) and 323 (B) adjacent to the mask (reticle) 100 are applied to the diffraction image plane 3203 by the imaging optical system (projection lens) 3201 so that the Babinet (Ba)
In the Fraunhofer diffraction image, the light intensity is equal and the phase is shifted by π except for the central point (zero-order diffracted light) according to the principle of “Binet”. This diffraction image plane 320
In 3, the light from the adjacent circuit patterns 321 (A) and 323 (B) in the diffraction pattern other than the 0th-order diffracted light has the phase inverted (shifted by π), and is blocked on the diffraction pattern (diffraction image plane). Plate 324 (imaging spatial filter 3302)
By blocking a small part of the 0th-order diffracted light, the light to be imaged on the surface of the substrate 200 (imaging surface) is as if light from an adjacent pattern in which the phase is inverted (shifted by π). It is equivalent to forming an image, and a very fine circuit pattern of high contrast on the substrate 200 (a fine circuit pattern of about 0.1 μm or less on the wafer).
Can be transcribed. That is, as shown in FIG. 2 or FIG. 3, the light-shielding plate 324 (the
Since at least a part of the 0th-order diffracted light is shielded by 302), only the diffracted light whose phase is inverted reaches the image forming surface, so that as viewed from the image forming surface, it is as if a phase film is formed on the mask. appear. As a result, the same circuit pattern as in the phase shifter method is imaged on the wafer,
With respect to the intensity distribution of the image forming surface, an extremely fine circuit pattern with high contrast is obtained on the wafer 200 as compared with the case of the conventional reduced projection exposure shown in FIG. FIG. 7 is a diagram for explaining the case of the conventional reduced projection exposure, in which the images of the adjacent fine circuit patterns 321 and 323 have low contrast on the image forming surface. In short, in the case of the reduced projection exposure according to the present invention, as shown in FIGS. 2 and 3, an extremely fine circuit pattern having a higher contrast on the image forming surface as compared with the case of the conventional reduced projection exposure shown in FIG. (Extra fine circuit pattern of about 0.1 μm or less on the wafer) is transferred and exposed.

Hereinafter, the example shown in FIG. 4 will be described using mathematical expressions. In the example of FIG. 4, light emitted from the mercury lamp 3101 is condensed on the light source spatial filter 3301 by the condenser lens 3103, and the mask 100 is illuminated by the condenser lens 3106.

A part of the light transmitted through the mask is shielded by the image forming spatial filter 3302, and the light is transmitted through the image forming lens 3201.
Thus, an image is formed on the wafer 200. The shape of the light source spatial filter 3301 is l (u, v), the shape of the pattern on the mask 100 is f (x, y), and the shape of the imaging spatial filter 3302 is
Assuming that a (u, v), the intensity gp (x, y) of the image on the wafer 200 is calculated by the following (Equation 1).

[0039]

(Equation 1)

In equation (1), the light source spatial filter 31
Light emitted from each (u, v) on 03 does not interfere with each other, and is integrated after calculating the intensity on the imaging plane. According to Kubota, Wave Optics (Iwanami Shoten), the resolution of an optical system is generally determined by the response function of the optical system or the optical transfer function (OTF).
Can be considered. The response function H (u, v) in the example of FIG. 4 is expressed by the following equation (2) using the pattern f (x, y) on the object plane and the intensity gp (x, y) of the image. Is calculated.

[0041]

(Equation 2)

FIG. 32 shows the calculated response function of the optical system in a curve 351. The horizontal axis indicates the spatial frequency s, and the numerical aperture (NA = 0.3) of the corresponding imaging lens for reference.
8). The vertical axis indicates the response function normalized by the zero-order component. Here, the position of the point 355 indicates the size of the aperture of the imaging lens. Curve 352
Is a conventional optical system, that is, a light source spatial filter 3301.
And a response function when the imaging spatial filter 3302 is not used, a curve 353 shows an apparent response function by the phase shift method, and a curve 354 shows a response function when coherent light such as a laser is used for reference. Is shown. The response function 352 of the conventional method extends to a position s1 indicated by the following equation (3).

[0043]

(Equation 3)

The method according to the present invention is the same as the conventional method in that the response function extends to the position shown in the above equation (Equation 3).
It has a stable shape up to the position. Further, in the present invention, the response function of the entire system of the present invention is reduced by a curve 35 by reducing the response function of the low-frequency component by devising the shape of the mask pattern as described later.
6 shape. Curve 357 is shown as normalized.
And has a stable response function over a wide band from low frequency components to high frequency components. This indicates that a fine pattern can be imaged with high contrast according to the present invention. Specifically, for example, 0.3
The μm line and space is at point 358,
This contrast is C1 in the conventional method, but is as high as C2 in the present invention. In the present invention, the shapes of the light source spatial filter 3301 and the imaging spatial filter 3302 are determined so as to optimize the response function calculated using the above (Equation 1). As described above, according to the present invention, the value of the response function of the high frequency component can be relatively increased by reducing the response function of the low frequency component.

Further, by using the annular light source spatial filter, the response function can be extended up to the band defined by the above equation (3). Light source space filter-33
01 and the size and width of the imaging spatial filter 3302 can be optimized by calculating a response function using the above (Equation 2).

A method of calculating the state of image formation on the wafer 200 by simulation and confirming the mask shape will be described later. However, since the equation (1) cannot be solved analytically,
It is calculated by numerical calculation based on the above-mentioned (Equation 1).
In addition, when a response function that can be calculated by the above equation (2) is obtained and calculated by the following equation (4), the calculation time can be reduced.

[0047]

(Equation 4)

FIGS. 33 to 38 show light source spatial filters 3.
A method for determining the shapes of the image 301 and the imaging spatial filter 3302 will be described. The optical system of the present invention is a so-called partial coherence imaging optical system, and cannot be sufficiently explained by a so-called response function. The optical system of the partial coherence imaging is described in “Optics of Stepper” (Optical Technology Contact, Vol. 27, No. 12, pp. 762-771). Using this concept, the imaging characteristics of the optical system using the annular light source and the annular spatial filter of the present invention are calculated.

The imaging characteristics of this partial coherence imaging indicate the relationship between the shape of the light source and the shape of the pupil plane of the detection optical system.
Using the concept of Transmission Cross-Coefficient, T (x1, x2), it is calculated by the following (Equation 5). Further, according to the above-mentioned "optical system of the stepper", the imaging characteristic (OTF, Optical Transfer Function) of this optical system is approximately determined by the lowest-order Transmission Cross-Coefficient, T (x, 0). T (x, 0) is represented by a correlation function between the shape of the light source and the shape of the pupil plane.

[0050]

(Equation 5)

That is, the characteristic of the partial coherent imaging represented by the complicated equation (5) is a geometrical problem of a correlation function between the light source shape and the pupil plane shape. FIG. 33 shows a light transmitting portion 3305 of the light source spatial filter 3301 and a light shielding portion 3306 of the imaging spatial filter 3302. The correlation function between the light source and the pupil plane at the coordinate x is indicated by the area of the hatched portion 364 in FIG. Similarly, a correlation function between a light source and a pupil plane according to the related art is shown by a hatched portion 365 in FIG.

The correlation function in the case of FIG. 33, that is, TransmissionCross-Coefficien, is shown in the curve 367 of FIG.
The calculated values of t and T (x, 0) are shown. Compared to the correlation function curve 366 in the conventional case shown in FIG. 34, the value is larger in the high frequency region. That is, the contrast increases. This FIG. A. = 0.38, σ = 0.
9 was calculated. The horizontal axis of FIG. 37 indicates that each N.D. A.
Is shown as the minimum pattern size. (For example, 0.3
Means 0.3 microns line and space. )
It can be seen that the 0.3 micron OTF is about twice that of the conventional example.

FIGS. 36 and 37 show the light source spatial filter 3301 and the imaging spatial filter 3302, respectively.
A diagram for deepening the intuitive understanding of the shape setting and assisting the setting is shown. A hatched portion A in FIG. 35A shows a correlation function between the outer diameter of the light source and the light shielding portion 3306, and a hatched portion B in FIG. 35B shows a correlation function between the inner diameter of the light source and the light shielding portion 3306. Further, a hatched portion C in FIG. 35C indicates a correlation function between the transmission portion 3305 of the light source and the maximum pupil of the optical system. The correlation function between the final light source shape and the spatial filter is represented by the shaded area 36 in FIG.
7, which is determined by CA-B above.
By determining the correlation function in this manner, the effect of the spatial filter or the annular illumination can be intuitively understood, and on the contrary, it is helpful in determining these shapes. Specifically, the value of the high frequency region 382 becomes larger than that of the medium frequency region 381 by the annular illumination. In addition, the low frequency region 383
Is too large, the effect of the spatial filter is printed by the route A and B, thereby further reducing the value in the low frequency region. Thus, the effects of the annular illumination and the spatial filter were intuitively described.

Of course, the shape of the light source and the shape of the spatial filter should be evaluated on the basis of equation (5). It is.

Further, since the annular light source can increase the coherence, the depth of the optical system can be increased. Here, the narrower the band width of the annular light source, the higher the coherence of the light source, so that the focal depth increases. The larger the diameter of the annular band of the annular light source, the higher the spatial coherence degree, the higher the resolution. .

FIG. 39 illustrates the effects of the annular light source and the annular spatial filter used in the present invention. FIG.
9A, a pupil 3301 of the imaging lens, a light source image 3305a (zero-order diffracted light) formed on the pupil, and the mask 1
A pattern (circuit pattern) formed in the y direction on 00
3305b and 3305c of the light source are shown.

FIG. 39 (a) shows a case where the light source has a ring shape, and FIG. 39 (b) shows a case where the light source is circular.

A filter for shielding the 0th-order diffracted light is indicated by a shaded portion 371. The hatched portion 371 also shields 372 which is a part of the diffracted light 3305b and 3305c of the light source at the same time. In the case of (a), only 10% to 20% is shielded, but (b) If, 4
0% or more is shielded from light. That is, the objective of efficiently shielding only the 0th-order diffracted light is more effectively achieved by the annular light source shown in FIG. In other words, the performance of the annular light source is higher. Here, the smaller the width of the annular light source, the smaller the ratio of the diffracted light that is blocked.

In the present invention, in order to block a part of the zero-order diffracted light, a spatial filter 330 having a ring width of about 30% of the ring width of the light source as shown in FIG.
40 is used, it is only necessary to shield a part of the 0th-order diffracted light. Therefore, the annular zone width as shown in FIG. % May be used. Of course, the width of the annular zone may be smaller than that of the image of the light source, and the transmittance may be lower than 70%. Further, although the case where the light-shielding ratio of the 0th-order diffracted light is set to approximately 30% is shown here, the light-shielding ratio is not limited to 30% as described later. Further, in order to block a part of the zero-order diffracted light, a phase plate may be used in which the spatial filter 3306 has a transmittance of 100% and a phase shift of π at the used wavelength by π. Such a filter is also a filter that substantially blocks a part of the zero-order diffracted light. Further, light may be shielded by using polarized light and a polarizing plate.

Further, as shown in FIG. 50, the ring width of the filter having the transmittance of about 70% may be larger than the ring width of the light source. With such a configuration, 0
Not only the second-order diffracted light but also a part of the low-order diffracted light can be shielded, and the MTF curve can be further improved. Also, the example shown in FIG. 40A is configured to block a part of the low-order diffracted light as in the example of FIG.

As described above, in order to efficiently block the 0th-order diffracted light, an annular light source is effective, and the effect becomes greater when the width of the annular zone is reduced. Here, the annular light source can be considered as small light sources arranged in an annular shape. That is, it can be considered as a set of coherent point light sources. Therefore, as shown in FIG. 41, the spatial coherence degree close to the point light source is 0.1 to 0.3.
The object of the present invention can be achieved even if a light-shielding plate 376 smaller than the light source 375 is installed at a position corresponding to the set of light sources 375 of the same degree. It goes without saying that a light-shielding plate 376 having a reduced transmittance may be used. In FIG. 41 (a),
An example of arrangement in a ring shape is shown. Further, if this concept is advanced, the shielding of the 0th-order diffracted light can be achieved even if it does not have an annular shape as shown in FIG. At the same time, FIG.
As shown in (c), such a light source and a light-shielding plate may be arranged in several layers. Further, as shown in FIG. 41D, in order to shield a part of the zero-order diffracted light, a light-shielding plate may be provided only for a part of the corresponding light source.

FIGS. 42A and 42B show the light intensity distribution of the light source and the transmittance of the spatial filter in the radial direction, respectively. Here, FIG. 42 shows a rectangular distribution for both the light intensity distribution and the transmittance distribution, but there is no problem if it shows a gentle distribution as shown in FIG.
This can be understood by considering that the OTF is represented by these correlation functions. That is, since the correlation function is obtained by integrating weights with respect to the overlapping portion, the value of the correlation function does not change significantly even if a gentle distribution is shown. In each case, radially equal distribution,
It is a concentric distribution, which is important.

The fact that the light source described here may have a distribution as shown in FIG.
It is shown that the intensity of the light source shown in (c) and (d) may be reduced as the intensity becomes the center. In such an embodiment, there is an effect that a light source having less coherency can be produced and the low frequency component can be further reduced.

As described above, according to the present invention, it is a means for effectively solving a part of the zero-order diffracted light by the exposure apparatus or other image forming optical systems to solve the objects of improving resolution and depth of focus. It is. However, in order to efficiently block the 0th-order diffracted light, the 0th-order diffracted light and the diffracted light need to be separated and not overlapped on the Fourier transform plane where the spatial filter is arranged. Coherency must be high. That is, it is desirable to be close to a point light source. On the other hand, in order to improve the resolution of the imaging optical system, it is desirable to increase the spatial coherence degree of the light source, that is, the σ value. That is, a large light source is desirable. In other words, it is necessary to balance the contradiction of a point light source and a large light source.

It is the annular light source and the spatial filter of the present invention that make these conflicts compatible.

To efficiently satisfy this, it is one measure to use an aggregate of small light sources. Furthermore, if this assembly is arranged in a large annular shape, the condition of a large light source is satisfied. That is, if the width of the orbicular zone is reduced, coherency is increased and the depth of focus is improved, and if the radius of the orbicular zone is increased, the degree of spatial coherence is increased and the resolution is improved.

Therefore, if the radius of the annular zone is increased while blocking a part of the above-mentioned zero-order diffracted light, there is a condition that the diameter of the spatial filter 3306 becomes as large as the pupil of the optical system. I do. This condition is a condition in which a part of the zero-order diffracted light is shielded and the size of the annular light source is maximized. That is, the condition for obtaining the maximum resolution is obtained for a certain reduction projection lens. 44 (a), (b), and (c),
This embodiment will be described. In each case, the size of the light source is larger than the lens pupil. In general, it has been considered that when the size of the light source is increased, the depth of focus becomes shallower and cannot be used for lithography. However, since the depth of focus can be increased by using the annular light source as described above, a light source larger than the pupil as shown in FIG. 44 can be used. Each of the embodiments has a configuration in which a part 377 of the zero-order diffracted light is shielded. OTF of this configuration
Is also represented by a correlation function. Thus, there is an effect that the cutoff frequency of the OTF is longer than when the size of the light source is smaller than the pupil. Another advantage of this configuration is that a large projection lens is used without using a reduction projection lens that requires high accuracy. A. There is a point that the resolution can be improved only by the improvement of the illumination system which is easy to realize. In this embodiment, the N.N. A. A pattern of approximately 0.2 μm can be transferred by i-line using a 0.4 lens.

What is important in these imaging systems for shielding the 0th-order diffracted light is that the OTF curve gradually decreases monotonically. FIG. 45 shows the OTF 378 of the present invention. Where O
When the TF is not gentle and undulates like 379, the contrast becomes low near the minimum point of the wave, and the pattern is not correctly transferred in an actual LSI pattern having various spatial frequency components. However, a special pattern formed only of a specific spatial frequency component is not limited to this, and the contrast may be increased only for a specific spatial frequency. That is, the MTF curve needs to be within the range of the specific width Wb. This Wb is to be calculated from a transfer result calculated by a transfer simulator described later.

Therefore, even when the light source shown in FIG. 44 is large, the OTF that gradually decreases monotonously becomes necessary. Therefore, when an actual LSI pattern is transferred, as shown in FIG. 44, the difference between the inner diameter of the light source and the pupil diameter of the reduction projection lens, and the difference between the outer diameter of the light source and the pupil diameter of the reduction projection lens are almost equal. Desirably equal. In order to obtain a realistic depth of focus, it is desirable that the ratio between the pupil diameter and the inner diameter of the reduction projection lens be 0.6 or more.

In the example of FIG. 44A, a filter having an appropriate transmittance may be arranged in a portion 380 corresponding to the zero-order diffracted light of the light source in the pupil of the reduction projection lens.
In this case, the width of the portion 377 outside the light source pupil can be reduced, and thus the size of the light source can be reduced. Conversely, the width of the portion 380 in the pupil of the reduction projection lens can be made larger than 377. In this case, effects such as easy maintenance of stable contrast in a wide band in which the light intensity is easy to increase are produced.

Further, even if the outer diameter of the light source of the annular zone is the same as the outer diameter of the pupil of the reduction projection lens, the object of the present invention can be achieved to some extent. However, the configuration shown in FIG. 44 (a) can cut a part of the zero-order diffracted light without inserting a spatial filter in the pupil of the reduction projection lens, so that the configuration is simple and easy to implement. Having.

Further, as shown in FIG. 47, by disposing the annular light source 378 further outside the light source of FIG. 44, the resolution is further improved. FIG. 48 shows an example in which the light source shown in FIG. 47 is implemented. Thus, N. A. The laser light source 31 is difficult because the
21, beam scanning means 3122, ring-shaped mirror 312
3, 3124 are used. In the case of this embodiment, the N.I. A. 0.15μ using 0.4 lens
m can be resolved.

In this embodiment, there is no difference from the basic idea of the present invention in that a part of the zero-order diffracted light is shielded.

Next, an embodiment of a pattern transfer system (reduced projection exposure optical system) 3000 according to the present invention will be described with reference to FIGS. That is, in the pattern transfer system (reduction projection exposure optical system) 3000, out of the light from the Hg lamp 3101, the i-line having a wavelength of 365 nm is filtered by the color filter 31.
02 and selectively condensed on the surface of the integrator 3104 by the condenser lens 3103. Light incident on each element 3107 (FIG. 9) in the integrator 3104 individually exits at an exit angle α, and illuminates the mask 100 with a condenser lens 3106.
Here, the integrator 3104 will be described later.
The integrator 310 is formed as a light source spatial filter 3301 in the form of an annular shape in which a large number of virtual point light sources are arranged.
4 near the output end.

Then, a mask circuit pattern 104 on the mask 100 (for example, shown in FIG. 20).

The light transmitted and diffracted by the light source passes through an imaging lens (reduction projection lens) 3201 and an imaging spatial filter 3302 installed near the pupil of the imaging lens 3201, and is then projected onto a wafer (substrate) 200200. The image is transferred as a wafer circuit pattern 204 having a contrast (for example, as shown in FIG. 18).

By the way, the image of the light source spatial filter 3301 formed in a ring shape in which a large number of virtual point light sources are arranged is formed in a ring shape by the condenser lens 3106 and the imaging lens (reduction projection lens) 3201. An image is formed at the position of the image forming spatial filter 3302. 13 and 14 show the imaging relationship between the light source spatial filter 3301 and the imaging spatial filter 3302 in the present embodiment.
Shown in Both the light source spatial filter 3301 and the imaging spatial filter 3302 have an annular shape.

The light source spatial filter 3301 has an outer diameter DL
O, the light source of the orbicular zone 3305 having the inner diameter DLI is formed, and both the inside and the outside of the orbicular zone 3305 are shielded from light.

The imaging spatial filter 3302 has an outer diameter DL
O, the orbicular zone 3306 of the inner diameter DLI is shielded from light, and both inside and outside of the orbicular zone 3306 are configured to transmit light. Note that an imaging lens (reduction projection lens) 3201
The incident portion is denoted by 3205, and the output portion is denoted by 3206.

Here, the imaging spatial filter 3302 is located at the front position 3202 of the imaging lens 3201, at the rear position 3204 of the imaging lens, and at the pupil position 3203 in the imaging lens. It may be. The position 3203 has the best effect on the design, and the position 3204 has the lowest cost and the sufficient effect. In FIG. 11, the imaging spatial filter 33 is located at a position 3204.
FIG. 2 shows a perspective view of an imaging lens 3201 on which an image sensor 02 is mounted. Since the imaging spatial filter 3302 is formed of a metal plate, it is supported by the support bar 3311. It goes without saying that the smaller and thinner the support rod 3311 is, the better. FIG. 12 shows an image forming spatial filter 33 formed by forming a light shielding film 3313 on a glass substrate 3312.
02 is shown. In this case, the support rod 3311 is unnecessary, but it is necessary to design the imaging lens 3201 in consideration of the aberration due to the glass substrate 3312.

Here, assuming that the imaging magnification between the light source spatial filter 3301 and the imaging spatial filter 3302 is M,
As shown in FIG. 13, DLI is the outer diameter of the light source spatial filter 3301, DIO is the outer diameter of the imaging spatial filter 3302, and D is the inner diameter of the imaging spatial filter 3302.
The relationship between II will be described later. In short, if part or all of the zero-order diffracted light is shielded, a fine circuit pattern on the mask can be formed on the wafer with high contrast.

As described above, the light source spatial filter 3301
DLO, DLI, as well as the imaging spatial filter 33
02 DIO and DII can be configured as a variable spatial filter such as a liquid crystal display device, or a plurality of spatial filters having different dimensions can be exchanged to control the annular shape of the spatial filter. It is.

Next, an embodiment of the entire projection exposure system of the present invention will be described with reference to FIGS.

First, the pattern data generation system 1000 will be described.

In the pattern data generation system 1000,
The wiring data creation unit 1102 forms wafer pattern shape data 1103 to be formed on the substrate (wafer) 200 based on wiring drawing data 1101 such as design data. The pattern conversion unit 1104 generates a mask (reticle) based on the wafer pattern shape data 1103.
Mask pattern shape data 110 to be formed on
Convert to 5. At this time, the pattern transfer simulator 11
08 is the mask 1 converted by the pattern conversion unit 1104
The wiring pattern creation unit 1102
Pattern data 1103 formed by
And setting conditions such as the outer diameter DLO and the inner diameter DLI of the orbicular zone 3305 of the light source spatial filter 3301, and the outer and outer diameters DIO and D of the orbicular zone 3306 of the imaging spatial filter 3302.
Based on the setting conditions such as II, it is checked whether or not the actual pattern transfer optical system 3000 approximately matches the wafer pattern shape data 1103 when the substrate 200 is exposed, and is fed back to the pattern conversion unit 1104. The corrected and wafer pattern shape data 11
Optimal shape of the spatial filter (ring zone 330
5, the outer diameter DIO, the inner diameter DLI, etc., the outer diameter DIO, the inner diameter DII, etc. of the orbicular zone 3306), and the result is transmitted to the light source spatial filter control unit (adjustment unit) 3303 via the spatial filter control system 3305 and the imaging. It is guided to a spatial filter control unit (adjustment unit) 3304 to control (adjust) the shapes of the light source spatial filter 3301 and the imaging spatial filter 3302. The pattern generation unit 1106 includes a pattern conversion unit 110
4 is the mask pattern shape data 110 converted
5 is converted into EB data 1107 suitable for the electron beam drawing apparatus 2103.

Next, the mask manufacturing system 2000 will be described. That is, in the mask manufacturing system 2000, the film forming apparatus 2101 forms the metal chromium, chromium oxide, or a plurality of stacked films 202 of metal chromium and chromium oxide on the mask substrate 101.

The coating apparatus 2101 includes a resist film 20 on the mask substrate 101 formed by the film forming apparatus 2101.
3 is applied. Then, the electron beam drawing apparatus 2103 generates the EB data 110 generated by the pattern generation unit 1106.
7, the same circuit pattern as the mask pattern shape data 1105 is drawn and formed. Thereafter, the developing device 2
By 104, the circuit pattern on the mask substrate 201 is developed to complete the mask 100. Completed mask 100
The pattern inspection is performed by comparing the image data detected by the pattern inspection apparatus 2106 with the data from the mask pattern data 1103 or the wafer pattern data 1105 or the data from the transfer simulator 1108. Pattern correction device 21
05, and finally mask 1
Inspect foreign objects on 00. Cleaning device 21 if foreign matter is present
Wash with 08. Here, the mask 100 according to the present invention
Since, for example, as shown in FIG. 20, since it can be formed with a single layer film 102, it has a feature that it is cheaper to clean than a phase shifter mask. Further, the mask 100 can be easily manufactured as compared with a mask of a phase shifter. Also,
In the pattern inspection apparatus 2105, the detected image data may be compared with any of the mask pattern data 1103, the wafer pattern data 1105, and the data from the transfer simulator 1108. However, it is most effective to make the light source and the imaging optical system of the pattern inspection apparatus 2105 equivalent to the pattern transfer system (reduced projection exposure system) 3000 according to the present invention, and to compare and inspect the wafer pattern data 1105. That is, the pattern inspection device 210
Reference numeral 5 denotes an optical system equivalent to a pattern transfer system (reduction projection exposure system) 3000, in which a mask 100 to be inspected is set on a mask stage 3401, and a light receiving element is placed at a position where a wafer (substrate) 200 is set. What is necessary is just to arrange and to detect the image formed on the light receiving element. By configuring the pattern inspection apparatus 2105 in this manner, the same circuit pattern as the very fine circuit pattern actually projected and exposed on the wafer (an extremely fine circuit pattern of about 0.1 μm or less on the wafer) can be used. Without being affected by the interference of light, the image signal can be detected as a high-contrast image signal from the light receiving element.
By comparing and inspecting with 105, even a fine circuit pattern can be inspected accurately.

Next, a pattern transfer system (reduced projection exposure optical system) 3000 which is an important component of the present invention will be described. That is, in the pattern transfer system 3000, the Hg lamp 3
Of the light from the light 101, the i-line having a wavelength of 365 nm is selectively transmitted by the color filter 3102,
03, the light is focused on the surface of the integrator 3104. Each element 3107 in the integrator 3104
(FIG. 9) are individually emitted as emission angles α, and are illuminated on the mask 100 by the condenser lens 3106. Here, the configurations of different embodiments of the integrator 3104 are shown in FIGS. 9 and 10, respectively. FIG. 9 shows a case where the cross section of the integrator 3104 is annular. In FIG. 10, the annular shape is shown as a light shielding plate 310.
5 shows an embodiment of the integrator 3104 formed by the fifth embodiment. In short, it is clear that other configurations may be used as long as they serve as a spatial filter, that is, as long as they have a light shielding function in an annular shape. The DLI of the light source spatial filter 3301 configured as described above,
The DLO is configured as a variable spatial filter or provided with a plurality of spatial filters having different dimensions, and can be controlled by exchanging them. The DLO is controlled or adjusted by a command from a light source spatial filter control unit (adjustment unit) 3303. It is desirable to be able to do so. Otherwise, you will be very restricted.

Here, in this embodiment, when a light-shielding plate is placed on the light source surface, the total exposure amount is reduced. Therefore,
It is necessary to increase the light intensity of the light source. However, it has been difficult for conventional lamps to increase the light intensity. A strobe light source for fiber lighting is disclosed in "Applied Physics Society Academic Lecture 11p-ZH-8", Yamamoto et al. The strobe light source as disclosed herein has not been used in an exposure apparatus. However, it is effective to use such a lamp in the present invention in which it is necessary to obtain a sufficient light intensity.

Further, this light source is suitable for the present invention because of its large diameter.

In the embodiment shown in FIG. 44 of the present invention,
An intagrator using an optical fiber as shown in FIG. 49 is effective. The integrator using this optical fiber is obtained by bundling many optical fibers 380. The light introduction surface 3131 is circular so that light from the light source 3101 is condensed and cheap, and the bundle of optical fibers is bundled again so that the light emission surface becomes annular.
By using an optical fiber in this way, a ring-shaped light source can be efficiently created using a light source having a circular light source shape such as a mercury lamp. Furthermore, since the integrator 3104 can be made flexible by using an optical fiber, there is an effect that the light source, which is a heat source, can be installed away from the apparatus main body requiring temperature control.

Here, it is preferable that the bundle of fibers shown in FIG. 49 be separated without being fixed, so that the outer diameter and the inner diameter can be made variable. Such a variable mechanism is controlled by the light source spatial filter control mechanism 3303.

The light transmitted and diffracted through the mask pattern 104 (FIG. 15) on the mask 100 is applied to the imaging lens 3.
An image is formed as a wafer pattern 204 (for example, as shown in FIG. 18) on the wafer 200 through the 201 and the imaging spatial filter 3302.

Here, the imaging spatial filter 3302 is located at the front position 3202 of the imaging lens 3201, at the rear position 3204 of the imaging lens, and at the pupil position 3203 in the imaging lens. It may be. The position 3203 has the best effect in terms of design, and the position 3204 has the lowest cost and the highest effect. In FIG. 11, the imaging spatial filter 33 is located at a position 3204.
FIG. 2 shows a perspective view of an imaging lens 3201 on which an image sensor 02 is mounted. Since the imaging spatial filter 3302 is formed of a metal plate, it is supported by the support bar 3311. It goes without saying that the smaller and thinner the support rod 3311 is, the better. FIG. 12 shows an image forming spatial filter 33 formed by forming a light shielding film 3313 on a glass substrate 3312.
02 is shown. In this case, the support rod 3311 is unnecessary, but it is necessary to design the imaging lens 3201 in consideration of the aberration due to the glass substrate 3312.

Here, the image of the light source spatial filter 3301 is formed at the position of the image spatial filter 3302 by the condenser lens 3106 and the image forming lens 3201. Light source spatial filter 3301 in this embodiment
13 and 14 show the image forming relationship of the image forming spatial filter 3302. Both the light source spatial filter and the imaging spatial filter have an annular shape, and the light source spatial filter 3301 includes an annular portion 330 having an outer diameter DLO and an inner diameter DLI.
5 and both the inside and outside of the annular zone 3305 are shielded from light. In the imaging spatial filter 3302, the orbicular zone 3306 having the outer diameter DIO and the inner diameter DII is shielded from light, and the orbicular zone 33
Both the inside and the outside of 06 are configured to transmit light.
Light source spatial filter 3301, imaging spatial filter 33
Assuming that the imaging magnification between 02 is M, DLO, DLI, DI
The following equation (Equation 6) holds between O and DII.

[0096]

DIO = M · δ · DLO DII = M · ε · DLI M · DLI ≦ DII ≦ DIO ≦ M · DLO (Equation 6) where δ and ε are coefficients, and (Equation 6) is satisfied.

[0097]

0.7 ≤ δ ≤ 1.0 1.0 ≤ ε ≤ 1.3 (Equation 7) Note that when these coefficients satisfy the above expression (Equation 7), the effect of the present invention is obtained. Appears most prominently. However, it is not always necessary to satisfy these formulas, and it is only necessary that part or all of the zero-order diffracted light be shielded.

In setting δ and ε, the values of δ and ε of the spatial filter having the highest contrast are selected by the pattern transfer simulator 1108.

FIG. 23 shows the contrast when the values of δ and ε are changed. According to this figure, δ is 0.8ε and 1.
When the value is 1, the best contrast is obtained. However, it is apparent from FIG. 23 that good contrast cannot be obtained only at this value.

Here, an imaging lens (reduction projection optical system) 32
The numerical aperture of the injection side 3204 of 00 is NAO, and the same
The numerical aperture of the projection of the image of the light source at the position is denoted by NAL. Here, NAL / NAO is defined as a spatial coherence degree σ. FIG. 24 shows the relationship between σ and contrast. The best contrast is obtained when σ is about 0.9. However, high contrast can be obtained even if σ is slightly shifted from 0.9.

The object of the present invention is most remarkably achieved when the light source spatial filter 3301 and the imaging spatial filter 3302 shown in FIG. 13 are used. Since this is achieved by shielding part or all of the light, the high contrast circuit pattern can be imaged on the wafer by using the spatial filters shown in FIGS. In the spatial filters shown in FIGS. 14 to 17, the shaded portions shown in the figures are the light shielding portions.

The pattern transfer system 3000 includes an Hg lamp 3101, a color filter 3102, and a condenser lens 31.
03, integrator 3104 and condenser lens 3
106, a light source unit 3100, and an imaging lens 3
An imaging optical system 3200 including the light source spatial filter 3301, an imaging spatial filter 3302, a light source spatial filter control unit (adjustment unit) 3303 for controlling the light source spatial filter 3301, and an imaging spatial filter 330
Imaging spatial filter control unit (adjustment unit) 330 for controlling
4, a light source spatial filter control unit (adjustment unit) 3303, an imaging spatial filter control unit (adjustment unit) 3304, and a positioning mark detection unit based on command signals such as DLO, DLI, DIO, and DII obtained from the pattern transfer simulator 1108. A spatial filter control system (adjustment system) 3300 including an overall control unit 3305 that sends a control signal to 3403 to control the whole, a mask stage 3401 on which the mask 100 is mounted, and a wafer stage 3402 on which the wafer 200 is mounted A positioning mark detecting unit 3403 for detecting a positioning mark on the wafer, a mask stage control system 3404 for controlling the mask stage 3304 by a command from the positioning mark detecting unit 3403, and a wafer stage 3402 controlled by a command from the positioning mark detecting unit 3403. Wafer stay It composed of a positioning portion 3400 composed of di-control system 3405.

The following operation is performed by the above configuration. That is, the mask 100 manufactured by the mask manufacturing system 2000
Is mounted on the mask stage 3401 and the light source unit 310
Illuminated by 0. Light transmitted from mask 100, light source 3
A part of the 0th-order diffracted light from the light source spatial filter 3301 in 100 is shielded by the imaging spatial filter 3302, and a part of the high-order diffracted light and a part of the 0th-order diffracted light pass through the imaging optical system (reduction projection lens) 3200 to the wafer 200. An image of a circuit pattern is formed thereon.

Here, as shown in FIG. 13, an annular filter formed by arranging a large number of virtual point light sources is used as the spatial filter in order to provide the light source with coherence. . There are two types of coherence, temporal and spatial. The temporal coherence is the band of the wavelength of the light source, and the light having the shorter band has higher coherence. Spatial coherence is
The size of the light source, which corresponds to the size of the light source spatial filter 3301 in the present invention. However, when the size of the light source is reduced in order to increase the coherence, the light intensity of the light source is reduced, so that the exposure time becomes longer, and the exposure throughput is reduced.

Therefore, the annular light source spatial filter 33 is used.
When 01 is used, the image of the light source spatial filter 3301 formed at this image forming position is a 0th-order diffracted light. That is, by using the annular filter 3301, it is possible to realize a light source having high intensity and coherence. This is the same as using a ring-shaped spatial filter to obtain coherent light from white light in a phase contrast microscope, and is shown in Kubota, Wave Optics (Iwanami Shoten).

The light source spatial filter 3301 has an annular shape for another reason. As described above, there is a relationship as shown in the figure between the dimension of the pattern on the wafer to be transferred and the degree of spatial coherence of the light source that transfers the pattern of the dimension with the highest contrast. Therefore, if the spatial coherence degree is determined according to the dimension (pitch) of the pattern to be transferred, the effect of the present invention will be remarkably exhibited. By forming the light source spatial filter 3301 and the imaging spatial filter 3302 on the annular zone, the degree of spatial coherence, that is, the size of the annular zone can be controlled and the cost can be reduced. However, it goes without saying that the greater the radius of the annular zone (spatial coherence degree) between the annular zone light source and the spatial filter, the better the resolution.

In the present invention, both the annular light source and the spatial filter are concentric circles. With the concentric shape, the circuit pattern to be transferred by the MTF can have no directivity. When transferring an LSI circuit pattern having circuit patterns in various directions, it is important that the MTF has no directionality. Further, the concentric filter is different from the non-concentric filter shown in FIG.
This has the effect that complicated aberrations hardly enter the lens.

The above effects can be achieved by balancing the intensities of the zero-order diffracted light and the high-order diffracted light. Therefore, the imaging spatial filter 3302 is omitted, and the light source spatial filter 3301
Only slightly lower can be achieved. Conversely, the light source spatial filter 3301 is omitted, and the imaging spatial filter 3
The effect described above can be attained with a slightly lower level by using only 302.

Next, a method of forming a pattern will be described more specifically with reference to FIGS. That is, as described above, the object of the present invention is to provide a light source spatial filter 3
The effects of the present invention can be further improved by devising the mask pattern 104 as described below, which can be achieved by using the image forming apparatus 301 and the imaging spatial filter 3302.

FIG. 25 shows a line width (light transmission) of a line space pattern of equal pitch formed on the mask 100.
9 shows the contrast of the circuit pattern projected on the wafer 200 by the imaging optical system 3200 when the image pattern is changed. As shown in FIG. 25, the contrast increases as the line width decreases. That is, the line width may be reduced. Here, when the line width is reduced, the light intensity decreases, so that it is necessary to increase the exposure time. Therefore, the line width of the circuit pattern formed on the mask 100 is determined by the balance between the contrast required to transfer the circuit pattern and the exposure time.

Therefore, in the exposure method according to the present invention, it is desirable that the line width for forming the mask pattern 104 is constant. Therefore, the wide wafer pattern 204
If you want to form, there is a device. Here, if the line width cannot be made constant and becomes wider, the light intensity on the image plane becomes larger than that of a pattern having a constant peripheral line width, and the shape of the transfer pattern after resist development is originally obtained. It will be far away from the circuit pattern. This is considered to be due to the influence of light circulating from a circuit pattern having a large light intensity in a part.

In order to correctly form this wide circuit pattern, it is necessary to form the light intensity at the same light intensity as the peripheral circuit pattern having a constant line width. A method for forming this wide circuit pattern will be described with reference to the drawings. When a circuit pattern is transferred using the imaging optical system 3200, a circuit pattern sufficiently smaller than the resolution of the imaging optical system cannot be resolved and is formed as a uniform image. This phenomenon is used when imaging the wide circuit pattern. That is, a fine pattern having a resolution lower than the resolution of the present optical system is shown in FIGS.
As shown by reference numeral 08 in FIG.
As shown in FIGS.
Can be transferred on top.

FIG. 26 shows the contrast when the pitch of the line space pattern is changed. FIG.
The contrast decreases as the pitch decreases.

That is, there is a position 331 where the contrast becomes almost 0 when the pitch is reduced. When it is desired to make the entire surface of a wide circuit pattern white, a pattern having a pitch of 331 may be used. Specifically, a pattern of about 1/2 of the pitch of the pattern to be resolved is best. At this pitch, the light intensity of the wide circuit pattern is almost equal to the light intensity of the minimum pattern.

More specifically, in order to obtain the wafer pattern 204 as shown in FIG. 18, a mask pattern as shown in FIG. 20 is manufactured and a negative resist is used or as shown in FIG. What is necessary is just to produce a suitable mask pattern and use a positive resist. In this case, the patterns 105, 106, 107, and 108 through which light is to be transmitted are shown in FIG.
2 is formed by a pattern with a small pitch. In addition, these 105, 106, 107, 108
The mask pattern 104 for transmitting light over a wide range as described above is automatically generated by the pattern conversion unit 1104, and the pattern transfer simulator 110
8 simulated.

Here, the half pitch pattern may be a half pitch only in one of the X direction and the Y direction.
Of course, it goes without saying that the X and Y directions may be a lattice pattern having a 1/2 pitch. Further, the pitch does not necessarily have to be １ ／, and may be another pitch that makes the light intensity on the wafer pattern 204 necessary and sufficient.

According to the above-described method, even in the case of a mask in which an extremely fine circuit pattern and a large circuit pattern are mixed, it is possible to perform transfer by one reduction projection exposure. However, when transferring an extremely fine circuit pattern and a large circuit pattern by two or more reduction projection exposures, the above method is not necessary, and the pattern 104 can be formed only by a pattern having a constant line width. In this case, there is an effect that a system such as the pattern conversion unit 1104 becomes unnecessary.

As described above, in the method according to the present invention, there is no need to dispose a phase shifter, so that the processing in the pattern conversion unit 1104 is simple, time is saved, and errors are reduced.

In this embodiment, the mask pattern is converted based on a circuit pattern having a constant line width.
In the case of a circuit pattern having many repetitive parts such as a memory, a mask pattern 104 that can obtain an optimal wafer pattern 204 may be obtained while performing a simulation with the transfer simulator 1108. That is, the mask pattern 104 is obtained by the transfer simulator 1108 for each memory cell.

Next, the transfer mechanism of the mask pattern on the wafer will be described with reference to FIGS. 1, 2 and 3.
FIG. 1A is a cross-sectional view of a mask 100 in which a mask pattern 104 is formed by chrome 102 on a glass substrate 101. A waveform 301 in FIG. 1B is a strong signal intensity distribution of the image forming pattern of the mask pattern 104. Waveform 3
01 is considered to be divided into a waveform 302 due to the zero-order diffracted light and a waveform 303 due to the high-order diffracted light. In the case where the mask pattern 104 is a fine pattern 105 as shown in the figure, the waveform 302 due to the 0th-order diffracted light is different from the waveform 303 due to the high-order diffracted light
Is small, the detected waveform 301 has a contrast AM
/ AV becomes smaller. Here, since the component of the waveform 302 can be removed by blocking the 0th-order diffracted light, the detected waveform has a high contrast like the waveform 302.

According to Babinet's principle, in a diffraction pattern other than the zero-order diffraction light, light from an adjacent pattern appears as if the phase of the adjacent pattern is inverted (shifted by π). . In other words, if the 0th-order diffracted light is shielded on the diffraction pattern, the light that forms an image on the wafer surface is formed by light from an adjacent pattern whose phase is inverted (shifted by π). Is equivalent to Based on this technical idea, as shown in FIGS. 2 and 3, at least a part of the 0th-order diffracted light is shielded by the light shielding plate 324 (imaging spatial filter 3302) on the diffraction image plane as shown in FIGS. Since only the diffracted light whose phase is inverted reaches the imaging plane, the intensity distribution on the imaging plane has a high contrast.

Next, the contrast improving mechanism will be described. That is, as an example, FIG. 28 shows a transfer result of a circuit pattern formed on the mask shown in FIG.
FIG. 29 shows a change in contrast when the pitch PIT is changed. In the conventional reduction projection exposure method, the contrast sharply decreases as the pattern size becomes extremely fine as indicated by 342, whereas in the reduction projection exposure method according to the present invention, the contrast does not decrease as indicated by 341. I understand.

FIG. 30 shows an evaluation example of the depth of focus of the reduction projection exposure method according to the present invention. According to the present invention, as shown at 343, the contrast is about 80 in the range of ± 1.5 μm.
% Is shown. In the conventional reduction projection exposure method, as indicated by 344, the contrast sharply drops due to defocus. This indicates that the present invention can cope with a resist having a large resist film thickness, and consequently can form a wafer pattern using the resist with a high aspect ratio. As a result, it is possible to form a pattern having a good aspect ratio and a high aspect ratio during etching.

Similarly, FIG. 38 shows the depth of focus 362 of the present invention.
And the depth of focus 363 of the phase shifter method. Both are almost the same, and the depth of focus 362 of the present invention shows sufficiently good results as compared with the depth of focus 361 of the conventional method.

FIG. 31 shows an embodiment of a so-called excimer stepper using an excimer laser having a wavelength shorter than i-line as a light source. According to this embodiment, the light source spatial filter 33
The effect of the light source spatial filter 3301 can be achieved by scanning the position of 01 with the excimer laser light so as to have an annular shape. According to this embodiment, the shape of the light source spatial filter 3301 can be easily controlled by controlling the scanning unit. That is, in this embodiment, the light source unit 3100 of the embodiment shown in FIG.
This is an example in which an excimer laser using a gas such as (krypton fluoride) is used. By using light having a shorter wavelength, a finer circuit pattern can be transferred. In this embodiment, it goes without saying that a laser of another wavelength may be used. Light source section 310 of this embodiment
0 is an excimer laser 3111, a shutter 3108,
Beam expander 3112, X galvanometer mirror 311
3, Y galvanometer mirror 3114, integrator 310
4. Integrator cooling means 3120, condenser lens 3106, spatial filter unit 3300
Is composed of a scanning control system 3311, a liquid crystal display element 3312, and a liquid crystal control system 3313. The light source spatial filter adjustment system 3303 of the embodiment shown in FIG.
13, Y galvanometer mirror 3114, scanning control system 3311
Hit. Here, the integrator cooling means 3120
Is intended to prevent the temperature of the integrator from rising due to the light of the excimer laser being concentrated on the integrator.Specifically, even if it circulates cooling water or blows nitrogen gas for cooling, etc. Good. Other components are in accordance with the embodiment shown in FIG. That is,
In this embodiment, the position of the light source spatial filter 3301 is the position of the integrator 3104, and the X-gavano mirror 3113 and the Y galvano mirror 3114 in the light source spatial filter adjustment unit 3303 are scanned to form an annular zone having the same shape as the light source spatial filter 3301. Make a light source.
Also, as described in the embodiment shown in FIG. 8, the imaging spatial filter 3302 has a liquid crystal control system 3313 in which a ring-shaped light shielding portion is formed on the liquid crystal display element 3312 so as to shield part or all of the zero-order diffracted light. It is formed. Accordingly, the resolution of the liquid crystal display element 3303 needs to have a necessary and sufficient precision to form the above-mentioned annular shape. Further, it is only necessary to be able to form an imaging spatial filter. Even if it is not a liquid crystal display element, for example, even if it is a metal plate formed so as to shield light in a ring shape from the beginning, it is possible to form a ring on glass. May be formed.

Further, in this embodiment, the excimer laser light is focused on one point on the imaging spatial filter 3302. Only by scanning on the orbicular zone on the light source spatial filter will it be in an orbicular shape on the imaging spatial filter. Therefore, according to the scanning on the light source spatial filter, if only the light is shielded on each point on the imaging spatial filter,
The object of the present invention can be achieved. Accordingly, since the light is not blocked too much, there is an effect that the exposure time can be shortened and the throughput can be increased. By the way, the mask 10
0 is placed on the mask stage 3401, and the mask stage 3401 is controlled by the mask stage control system 3404 to position the mask 100 at the reference position. Thereafter, the position of the alignment mark on the wafer 100 is determined by the positioning mark detection unit 3403. The wafer stage 3402 is controlled by the wafer stage control system 3405 based on the detected signal, and the mask 100 and the wafer 200 are aligned. After the alignment, the shutter 3108 is opened, and the annular light source is formed by the light source space filter adjusting unit 3303, so that the mask 100 is illuminated and the mask pattern is transferred onto the wafer 200 to form a wafer pattern.

In this embodiment, the excimer laser 3111
Since the light from the light source has strong coherence, it is necessary to reduce the coherence to an appropriate value. By forming a ring-shaped light source on the light source spatial filter 3301, there is also an effect that it can be achieved at the same time.

In particular, in the present invention, uniform illumination within the exposure field (in the exposure area) is sufficient, and it is not always necessary to simultaneously illuminate annular illumination formed by arranging a large number of virtual point light sources. It is apparent that the above-described embodiment may be realized by time-sharing or by scanning as in the above-described embodiment. Also, it is obvious that the annular illumination formed by arranging a large number of point light sources may be realized by being divided into a plurality.

As described above, according to the present invention, a large circuit pattern portion and a small circuit pattern portion can be exposed twice. Further, a mask in which a phase shifter is arranged at least partially (partly or entirely) of the circuit pattern on the mask can be used. in this case,
By using the annular light source, the central value of the incident angle of the illumination light incident on the reticle becomes large, and therefore, in order to set the phase shift by the phase shifter to π, the thickness of the phase shifter needs to be slightly reduced. . This value is calculated using the incident angle θ.

(2m + 1) π = (d / cos θ) · (n / λ) · 2π (Equation 8) where m is an integer, d is the thickness of the phase shifter, n is the refractive index of the phase shifter, and λ is the exposure. Wavelength.

As described above, the present invention produces a new effect such that various circuit patterns can be handled by using the conventional exposure apparatus or the phase shifter in combination.

In practicing the present invention, the incident angle of light applied to the reticle becomes large, so that the thickness of the circuit pattern such as chrome on the mask becomes a problem.
That is, depending on the irradiation angle, a shadow due to the thickness of the circuit pattern such as chrome on the mask may be formed.
Therefore, in the practice of the present invention, in order to obtain accurate transfer pattern dimensions, it is desirable that the thickness of the circuit pattern such as chrome on the mask be thin. Therefore, when the thickness of the circuit pattern of chrome or the like is dm and the allowable value of the transfer pattern is pc, it is necessary to satisfy Expression (9).

Dm ≦ pc / l (Equation 9) where l is the reduction ratio of the reduction projection lens.

To achieve this, it is necessary to pattern the mask with another material having a lower transmittance than chromium. However, if the size of the circuit pattern of the mask is determined in consideration of the dimensional change due to the incident angle of illumination, the above problem can be reduced.

Further, if the transmission portion of the mask is coated so as to maximize the transmittance of the light beam incident at the incident angle used, the exposure amount increases, and the time required for exposure can be shortened. it can.

Further, since the present invention utilizes the wave nature as described above, it is apparent that the present invention can be applied to an exposure apparatus using an electron beam or X-ray.

[0137]

According to the present invention, when transferring the mask pattern, it is possible to avoid imbalance between the light intensity of the 0th-order diffracted light and the diffracted light. There is an effect that exposure can be performed with the same or higher resolution.

[Brief description of the drawings]

FIG. 1 is a diagram showing a light diffraction phenomenon by a circuit pattern formed on a mask for explaining the principle of the present invention.

FIG. 2 is a diagram for explaining the principle of the present invention.

FIG. 3 is a diagram for explaining the principle of the present invention, similarly to FIG. 2;

FIG. 4 is a schematic configuration perspective view showing an embodiment of an exposure system in a reduction projection exposure apparatus according to the present invention.

FIG. 5 is a sectional view showing an arrangement relationship between a light source spatial filter and an imaging spatial filter in the exposure system according to the present invention.

6 is a cross-sectional view showing an arrangement relationship of an imaging spatial filter in the exposure system according to the present invention, similarly to FIG.

FIG. 7 is a diagram showing an image forming relationship of a circuit pattern on a mask in a conventional reduction projection exposure apparatus.

FIG. 8 is a configuration diagram showing one embodiment of the entire exposure system according to the present invention.

FIG. 9 is a perspective view showing a first embodiment of an integrator having a light source spatial filter in an exposure system according to the present invention.

FIG. 10 is a perspective view showing a second embodiment of an integrator having a light source spatial filter in an exposure system according to the present invention.

FIG. 11 is a perspective view showing a first embodiment of an imaging lens having an imaging spatial filter in an exposure system according to the present invention.

FIG. 12 is a perspective view showing a second embodiment of the imaging lens having the imaging spatial filter in the exposure system according to the present invention.

FIG. 13 is a plan view showing the relationship between the light source spatial filter of the first embodiment and the imaging spatial filter of the first embodiment according to the present invention.

FIG. 14 is a plan view showing a relationship between a light source spatial filter according to a second embodiment of the present invention and an imaging spatial filter according to the second embodiment.

FIG. 15 is a plan view showing a light source spatial filter according to a third embodiment of the present invention and an imaging spatial filter according to the third embodiment;

FIG. 16 is a plan view showing a light source spatial filter according to a fourth embodiment of the present invention and an imaging spatial filter according to the fourth embodiment;

FIG. 17 is a plan view showing a relationship between a light source spatial filter according to a fifth embodiment of the present invention and an imaging spatial filter according to the fifth embodiment;

FIG. 18 is a plan view and a cross-sectional view illustrating an example of a wafer pattern transferred onto a wafer according to the present invention.

FIG. 19 is a plan view and a cross-sectional view showing another example of a wafer pattern transferred onto a wafer according to the present invention.

20 is a plan view and a cross-sectional view showing an example of a mask pattern for obtaining the wafer pattern shown in FIG. 18 according to the present invention.

21 is a plan view and a cross-sectional view showing an example of a mask pattern for obtaining the wafer pattern shown in FIG. 19 according to the present invention.

FIG. 22 is a view showing various forms of a mask pattern according to the present invention.

FIG. 23 is a diagram showing a relationship between δ and ε related to a spatial filter of the present invention and contrast on a wafer.

FIG. 24 is a diagram showing a relationship between σ related to the spatial filter of the present invention and contrast on a wafer.

FIG. 25 is a diagram showing a relationship between a line width of a circuit pattern on a mask and a contrast on a wafer according to the present invention.

FIG. 26 is a diagram showing a relationship between a pitch of a circuit pattern on a mask and a contrast on a wafer according to the present invention.

FIG. 27 is a plan view showing an example of a circuit pattern on a mask according to the present invention.

FIG. 28 is a diagram showing a transfer result of a circuit pattern in FIG. 27 according to the present invention.

FIG. 29 is a diagram showing a relationship between a pitch of an extremely fine circuit pattern formed on a mask according to the present invention and a contrast on a wafer.

FIG. 30 is a diagram showing the relationship between the depth of focus and the contrast according to the present invention.

FIG. 31 is a configuration diagram showing another embodiment of the entire exposure system according to the present invention.

FIG. 32 shows a response function of the system according to the present invention.

FIG. 33 is an explanatory diagram of a correlation function between a light source and a spatial filter according to the present invention.

FIG. 34 is an explanatory diagram of a correlation function between a light source and a spatial filter in a conventional example.

FIG. 35 is an explanatory diagram of a calculation method of a correlation function between a light source and a spatial filter.

FIG. 36 is an explanatory diagram of a calculation method of a correlation function between a light source and a spatial filter.

FIG. 37 is a diagram showing a calculation result of the OTF of the present invention.

FIG. 38 is a diagram showing the depth of focus of the present invention.

FIG. 39 is a diagram illustrating the effects of the annular light source and the annular filter.

FIG. 40 is a view showing an annular filter.

FIG. 41 is a diagram showing an embodiment of an annular light source and an annular filter.

FIG. 42 is a diagram showing an example of the intensity distribution of the annular light source and the annular filter.

FIG. 43 is a diagram showing another example of the intensity distribution of the annular light source and the annular filter.

FIG. 44 is a view showing another embodiment of an annular light source and an annular filter.

FIG. 45 is a diagram showing an MTF curve.

FIG. 46 is a diagram showing an MTF curve.

FIG. 47 is a view showing another embodiment of an annular light source and an annular filter.

FIG. 48 is a diagram showing a block diagram of an embodiment of the light source in FIG. 47.

FIG. 49 is a diagram illustrating an example of an integrator.

FIG. 50 is a view showing another embodiment of an annular light source and an annular filter.

[Explanation of symbols]

1000: Pattern generation system, 2000: Mask production system, 3000: Exposure system 3101: Hg lamp, 3104: Integrator, 3301: Light source spatial filter (annular shape) 100: Mask, 3201: Imaging lens, 3302: Imaging spatial filter , 200 ... wafer

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[Procedure amendment]

[Submission date] August 23, 2000 (2008.2
3)

[Procedure amendment 1]

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[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention eliminates the influence of interference light generated in an extremely fine circuit pattern formed on a mask and forms an image with high resolution on a substrate through a projection lens using excimer laser light or the like. The present invention relates to a semiconductor device having a circuit pattern formed by exposure to light and a method of manufacturing the same.

[Procedure amendment 2]

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[0014]

In order to achieve the above object, according to the present invention, a pattern of a first mask is exposed on a wafer by irradiating a first light source to a first mask.
After the first pattern is formed on the wafer by etching, the pattern of the second mask is exposed on the wafer by irradiating an excimer laser to a second mask having a phase shift, and the wafer is etched. A semiconductor device characterized in that a pattern is formed on the semiconductor device.

[Procedure amendment 3]

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[Correction contents]

According to the present invention, in the method of manufacturing a semiconductor device, the pattern of the first mask is exposed on the wafer by irradiating the first light source to the first mask, and the wafer is etched. After forming the first pattern, the pattern of the second mask is exposed on the wafer by irradiating the second mask having a phase shift with an excimer laser, and the pattern is formed on the wafer by etching. did.

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──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/30 527 (72) Inventor Yoshitada Oshida 292 Yoshidacho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd. Inside the Research Institute of Production Technology (72) Inventor Masataka Shiba 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd. Inside Hitachi, Ltd. Production Technology Laboratory (72) Inventor Makoto Murayama 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Hitachi, Ltd. Production Technology Laboratory

Claims (6)

[Claims] A first light source that irradiates a first mask with a first light source to irradiate the first mask with a pattern on the wafer;
After forming a first pattern on the wafer by etching, the pattern of the second mask is exposed on the wafer by irradiating an excimer laser to a second mask having a phase shift, and etching is performed. A semiconductor device, wherein a pattern is formed on the wafer. 2. A pattern of the first mask is exposed on a wafer by irradiating a first light source to the first mask,
A first step of forming a first pattern on the wafer by etching, and exposing a pattern of the second mask on the wafer by irradiating an excimer laser to a second mask having a phase shift And a second step of forming a pattern on the wafer by etching. 3. A pattern of the first mask is exposed on a wafer by irradiating a first light source to the first mask,
After forming a first pattern on the wafer by etching, the pattern of the second mask is exposed on the wafer by irradiating an excimer laser to a second mask having a phase shift at a desired angle. And forming a pattern on the wafer by etching. 4. A pattern of the first mask is exposed on a wafer by irradiating a first light source to the first mask,
After forming a first pattern on the wafer by etching, the second mask having a phase shift is irradiated with light of annular illumination formed using an excimer laser on the wafer to form a second pattern on the wafer. A semiconductor device wherein a pattern is formed on the wafer by exposing and etching a pattern of a second mask. 5. A pattern of the first mask is exposed on a wafer by irradiating a first light source to the first mask,
After forming a first pattern on the wafer by etching, the second mask having a phase shift is irradiated with an excimer laser for forming annular illumination at a desired angle on the wafer to form a first pattern on the wafer. A semiconductor device, wherein a pattern having a pattern having a line width of 0.2 μm or less is formed on the wafer by exposing and etching the pattern of the second mask. 6. A filter formed between a light source and the mask is selected according to the spatial frequency of a pattern formed on the mask, and the mask is irradiated with exposure light through the selected filter. Forming a pattern having a line width of 0.2 micrometers or less on the wafer by exposing a pattern formed on the mask on the wafer by exposure light emitted from the mask. .