JP2000021762A - Method of exposure and aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of exposure and an aligner in which arbitrary high-resolution patterns are produced by double exposure which is obtained with a periodic pattern exposure and an ordinary exposure. SOLUTION: In a method of exposure, in which illumination light from an illumination optics system having a light source means 11 illuminates the region of a prescribed form to be illuminated and patterns of a mask 14 placed in the region to be illuminated is projected onto a photoreceptive substrate through a projection optics system 18, the mask 14 has repeated patterns of light transmitting parts arranged by repetition of a basic pattern, the neighboring transmitting parts of the basic pattern mutually have an optical phase difference of approximately 180 deg., and the photoreceptive substrate is exposed plural number times by changing the illumination conditions of the illumination optics system 12 and the light transmission condition at the pupil plane of the projection optics system 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposing method and an exposing apparatus, and more particularly, to exposing a photosensitive substrate with a fine circuit pattern, for example, a semiconductor chip such as an IC or LSI, a display element such as a liquid crystal panel, a magnetic head, and the like. It is suitable for use in the manufacture of various devices such as a detection device and an imaging device such as a CCD.

[0002]

2. Description of the Related Art Conventionally, when devices such as ICs, LSIs, and liquid crystal panels are manufactured using photolithography technology, circuits formed on the surface of a photomask or reticle (hereinafter, referred to as "mask"). A projection exposure method and projection in which a pattern is projected onto a photosensitive substrate such as a silicon wafer or a glass plate (hereinafter, referred to as a “wafer”) coated with a photoresist or the like by a projection optical system, and transferred (exposed) there. An exposure apparatus is used.

In recent years, in response to the higher integration of the above devices, there has been a demand for miniaturization of a pattern to be transferred to a wafer, that is, higher resolution and larger area of one chip on the wafer. Therefore, even in the above-described projection exposure method and projection exposure apparatus that form the center of microfabrication technology for wafers,
In order to form an image (circuit pattern image) having a dimension (line width) of 0.5 / μm or less over a wide range, improvement in resolution and enlargement of an exposure area have been attempted.

FIG. 20 shows a schematic view of a conventional projection exposure apparatus. In FIG. 20, 191 is an excimer laser as a light source for far ultraviolet exposure, 192 is an illumination optical system, 193 is illumination light emitted from the illumination optical system 192, 194 is a mask,
Reference numeral 95 denotes an optical system (projection optical system) 19 which exits from the mask 194.
Reference numeral 196 denotes an object-side exposure light, reference numeral 196 denotes a reduction type projection optical system, reference numeral 197 denotes an image-side exposure light which exits from the projection optical system 196 and enters a substrate 198, reference numeral 198 denotes a wafer which is a photosensitive substrate,
Reference numeral 99 denotes a substrate stage for holding a photosensitive substrate.

[0005] The laser light emitted from the excimer laser 191 is guided to the illumination optical system 192 by the routing optical systems (190a, 190b), and the illumination optical system 192 provides a predetermined light intensity distribution, light distribution, and opening angle (Sekiguchi). The mask 19 is adjusted so as to have the illumination light 193 having several NA) or the like.
Light 4 On the mask 194, a pattern having a size obtained by reciprocally multiplying (for example, 2 times, 4 times, or 5 times) the fine pattern formed on the wafer 198 by a projection magnification of the projection optical system 196 is formed on a quartz substrate by chrome or the like. And illumination light 1
93 is transmitted and diffracted by the fine pattern of the mask 194, and becomes the object side exposure light 195. The projection optical system 196 includes:
The object-side exposure light 195 is converted into image-side exposure light 197 that forms a fine pattern of the mask 194 on the wafer 198 at the above-described projection magnification and with sufficiently small aberration. Image side exposure light 19
Reference numeral 7 converges on the wafer 198 at a predetermined numerical aperture NA (= Sin (θ)) as shown in the enlarged view at the bottom of FIG. 20, and forms an image of a fine pattern on the wafer 198. The substrate stage 199 has a plurality of different areas (shot areas: areas to be one or more chips) of the wafer 198.
When sequentially forming a fine pattern, the wafer 19 is moved stepwise along the image plane of the projection optical system.
8 with respect to the projection optical system 196.

A projection exposure apparatus using the above-described excimer laser as a light source has a high projection resolution, but it is technically difficult to form a pattern image of, for example, 0.15 μm or less.

[0007] The projection optical system 196 has a resolution limit due to a trade-off between the optical resolution due to (exposure) wavelength and the depth of focus. The resolution R of the resolution pattern and the depth of focus DOF by the projection exposure apparatus are expressed by the following Rayleigh formulas (1) and (2).

R = k ₁ = (λ / NA) ‥‥‥ (1) DOF = k ₂ = (λ / NA ² ) ‥‥‥ (2) where λ is an exposure wavelength, and NA is a projection optical system 196. Are the image side numerical apertures, k ₁ and k _{2, which} are constants determined by the development process characteristics of the wafer 198.
The value is about 5 to 0.7. From the equations (1) and (2), it is apparent that the numerical aperture N
There is "higher NA" to increase A. However, in actual exposure, the depth of focus DOF of the projection optical system 196 needs to be set to a certain value or more, so that it is difficult to increase the NA to a certain value or more. It is understood that "short wavelength" for reducing the wavelength λ is required.

However, as the exposure wavelength becomes shorter, a serious problem arises. It is the projection optical system 196
Is that the glass material of the lens that constitutes is lost. The transmittance of most glass materials is close to 0 in the deep ultraviolet region,
Using a special manufacturing method for exposure equipment (exposure wavelength about 248
nm), fused quartz exists as a glass material.
The transmittance of the fused quartz also sharply decreases for an exposure wavelength of 193 nm or less. It is very difficult to develop a practical glass material in a region having an exposure wavelength of 150 nm or less corresponding to a fine pattern having a line width of 0.15 μm or less. In addition, the glass material used in the deep ultraviolet region must satisfy various conditions such as durability, uniformity of refractive index, optical distortion, workability, etc. in addition to transmittance. Existence is at stake.

As described above, in the conventional projection exposure method and projection exposure apparatus, it is necessary to reduce the exposure wavelength to about 150 nm or less in order to form a pattern having a line width of 0.15 μm or less on a wafer. On the other hand, at present, there is no practical glass material in this wavelength region, so that a pattern having a line width of 0.15 μm or less cannot be formed on the wafer.

US Pat. No. 5,415,835 discloses a technique for forming a fine pattern by two-beam interference exposure. According to the two-beam interference exposure, a pattern having a line width of 0.15 μm or less is formed on a wafer. be able to.

The principle of two-beam interference exposure will be described with reference to FIG. In the two-beam interference exposure, a laser beam L151 having coherence from a laser 151 and being a parallel beam is converted into laser beams L151a and L151 by a half mirror 152.
The two laser light beams (coherent parallel light beams) are divided from larger than 0 to 9 by being split into two light beams of ab and reflecting the split two light beams by the plane mirrors 153a and 153b, respectively.
An interference fringe is formed at the intersection by intersecting at an angle of less than 0 degree on the surface of the wafer 154. By exposing and exposing the wafer 154 with (the light intensity distribution of) the interference fringes, a fine periodic pattern corresponding to the light intensity distribution of the interference fringes is formed on the wafer 154.

The two light beams L151a and L151b are
In the case where the wafer intersects with the perpendiculars formed on the 54 surfaces in a state inclined at the same angle in the opposite directions to each other on the wafer surface, the resolution R in the two-beam interference exposure is expressed by the following equation (3).

R = λ / (4 sin θ) = λ / 4NA = 0.25 (λ / NA) (3) where R is the width of each L & S (line and space), ie, interference fringes. The width of each of the light and dark portions is shown. Β represents the incident angle (absolute value) of the two light beams with respect to each image plane, and NA = Sin θ.

Comparing equation (1), which is the equation for resolution in normal projection exposure, and equation (3), which is the equation for resolution in two-beam interference exposure, the resolution R of two-beam interference exposure is expressed by equation (1). Since this corresponds to the case where k ₁ = 0.25, it is possible to obtain a resolution twice or more as high as that of a normal projection exposure in which k ₁ = 0.5 to 0.7 in two-beam interference exposure. .

Although not disclosed in the above US patent, for example, when λ = 0.248 nm (KrF excimer) and NA =
At 0.6, R = 0.10 μm is obtained.

[0017]

In the two-beam interference exposure, basically, only a simple fringe pattern corresponding to the light intensity of the interference fringes (exposure amount distribution) can be obtained. Difficult to form.

In the above-mentioned US Pat. No. 5,415,835, a simple fringe pattern (periodic pattern), that is, a binary exposure amount distribution is given to a wafer (resist) by two-beam interference exposure, and then the resolution of the exposure apparatus is increased. Obtaining an isolated line (pattern) by performing normal lithography (exposure) using a mask in which an opening having a size within the range is formed and giving another binary exposure distribution to the wafer Has been proposed.

However, US Pat. No. 5,415,583 mentioned above.
The exposure method disclosed in Japanese Patent Application Laid-Open No. 5-205
In each of the two exposure methods, only a normal binary exposure amount distribution is formed, so that it is difficult to obtain a circuit pattern having a more complicated shape.

The above-mentioned US Pat. No. 5,415,835 discloses that two exposure methods, two-beam interference exposure and normal exposure, are combined. An exposure apparatus which achieves such a combination is specifically shown. Not.

As described above, the two-beam interference exposure method has a fundamental problem that an arbitrary pattern such as a circuit pattern of a semiconductor element cannot be exposed. That is, 2
In the exposure by the light beam interference, only the pattern having the same pitch over the entire intersection area can be substantially exposed. To improve this, for example, an aperture is set near the image plane to limit the exposure area. For example, several line and space patterns required as a pattern are sequentially moved while changing the direction, and the exposure area is reduced to a sufficiently small area. At the same time that a small stop is provided in an attempt to limit the light intensity, the light intensity distribution changes due to the diffraction of each light beam itself, so that effective interference fringes cannot be formed.

As described above, in the two-beam interference exposure, 0.15 μm is used.
Although a resolution of m or less can be achieved, the pattern is limited to those having the same pitch, and there has been a problem that a circuit pattern of a type required for an actual element cannot be exposed.

A technique utilizing the principle of the resolution of the two-beam interference exposure is a Levenson type phase shift mask as shown in FIG. In this phase shift mask 173, 1: 1
A phase shifter 172 for giving not only transmittance but also a phase change is arranged as shown in FIG. 22 on a mask having a periodic pattern or the like having a line width of, so that the light beam transmitted through the mask becomes two substantially parallel light beams. ing.

Reference numeral 171 denotes a light shielding portion made of chrome. Po is the pitch of the light shielding portion 171, and Pos is the pitch of the phase shifter 172.

FIG. 23 is a schematic view of a main part of an exposure apparatus using the Levenson-type phase shift mask 173 of FIG.

In FIG. 23, 173 is a Levenson-type phase shift mask, 162 is a projection optical system 1
Reference numeral 163 denotes an object-side exposure light which enters the projection optical system 43;
Numeral 64 denotes an aperture stop, 165 denotes an image-side exposure light coming out of the projection optical system 163 and entering the wafer 166, 166 denotes a wafer which is a photosensitive device, and 167 denotes a light beam on a pupil plane corresponding to a circular aperture of the stop 164 FIG. 4 is an explanatory diagram showing the position of the black spot by a pair of black dots. FIG. 23 is a schematic diagram showing a state in which the two-beam interference exposure is being performed. Both the object-side exposure light 162 and the image-side exposure light 165 are composed of only two parallel light beams.

These two substantially parallel light beams become the outermost two points on the aperture stop surface (pupil surface) 164, and become two light beams again before the image-defining surface, and have the finest period that can be resolved by this projection optical system. Re-image the pattern. The Levenson-type phase shift mask 173 can be formed with a pattern other than the periodic pattern. However, the effect is weak for an arbitrary pattern other than the periodic pattern having a line width of 1: 1. There was also. For this reason, it was not possible to obtain a sufficient resolution and a sufficient pattern type when applied to a general circuit pattern.

According to the present invention, there is provided an exposure method in which the above-described high resolution can be obtained by changing the illumination conditions, the aperture stop, and the like to a small extent without adding a special exposure device such as separately providing a two-beam interference device. And an exposure apparatus.

A further object of the present invention is to provide an exposure method capable of forming a pattern having a line width of 0.15 μm or less by an exposure method using an appropriately set phase mask and multiple exposure, and a line using the same. It is an object of the present invention to provide an exposure apparatus capable of exposing an actual circuit pattern having a width of 0.15 μm or less.

In the present invention, the Levenson-type phase mask is defined as:
By using it for patterns other than the 1L & S periodic pattern (exposure with a Levenson mask other than the 1: 1 L & S periodic pattern is less effective as described above), the illumination conditions of the illumination optical system and the aperture stop of the projection optical system are controlled. And an exposure apparatus capable of performing exposure with a resolution close to that obtained when a fine L & S periodic pattern is exposed using a Levenson mask by performing multiple exposures, and without deteriorating the shape of other arbitrary pattern portions. It is an object.

[0031]

An exposure method according to the present invention comprises: (1-1) illuminating an illumination area of a predetermined shape by an illumination optical system with exposure light from a light source means, and a mask pattern provided in the illumination area. In an exposure method of projecting a photosensitive substrate with a projection optical system, the mask has a repetitive pattern in which a plurality of basic patterns composed of light transmitting portions are repeatedly arranged,
Adjacent transmissive portions of the repeating pattern are approximately 18
It has an optical phase difference of 0 degrees, and the exposure condition of the illumination optical system and the light transmission condition on the pupil plane of the projection optical system are changed by the pattern of the mask to perform multiple exposure on the photosensitive substrate. It is characterized by:

In particular, (1-1-1) the basic pattern includes a pair of transmission patterns, and the corresponding light transmission portions of the pair of transmission patterns have an optical phase difference of about 180 degrees from each other. .

(1-1-2) As one of the illumination conditions, substantially coherent illumination with a small effective light source is used.

(1-1-3) One of the light transmission conditions on the pupil plane of the projection optical system is to limit the transmission area by using an aperture stop having a long opening in the direction of high pattern resolution on the mask. That is to do.

(1-1-4) The aperture stop has a plurality of movable light shielding plates, and the light shielding plates are inserted into the projection optical system when the multiple exposure is switched.

(1-1-5) Switching of multiple exposure using an illumination stop holding means configured so that one of a plurality of illumination stops can be inserted into and removed from the optical path of the illumination optical system. The lighting conditions are sometimes changed.

(1-1-6) A light-shielding plate rotation control comprising a light-shielding plate having one or more openings and holding means for the light-shielding plate, wherein the light-shielding plate is rotated in the illumination optical system when the multiple exposure is switched. Means for changing the lighting conditions. And so on.

The exposure apparatus of the present invention is characterized in that (2-1) the pattern on the mask is transferred to a photosensitive substrate by using the exposure method of the constitution (1-1).

The method for manufacturing a device according to the present invention comprises the following steps: (3-1) After exposing a pattern on a mask surface onto a wafer surface using the exposure method of the constitution (1-1), the wafer is subjected to a developing process. The device is manufactured via

(3-2) After the pattern on the mask surface is exposed on the wafer surface using the exposure apparatus of the constitution (2-1), the wafer is subjected to a developing process to manufacture a device. It is characterized by.

In the present invention, "multiple exposure" refers to "exposing the same area on a photosensitive substrate with different light patterns without passing through a developing process".

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a main part of a first embodiment of an exposure apparatus according to the present invention. The exposure apparatus shown in FIG. 1 has a projection optical system 18 for projecting a pattern of a mask (phase shift mask) 14 onto a wafer, and an illumination optical system 12 capable of performing both partial coherent illumination and coherent illumination. A predetermined pattern on the mask 14 is projected and exposed by performing rough exposure using partial coherent illumination and performing fine line exposure using coherent illumination.

Here, "partially coherent illumination" means σ
= (Numerical aperture of the illumination optical system 12 / numerical aperture of the projection optical system 18) is an illumination that is larger than zero and smaller than 1.
The term “coherent illumination” means that the value of σ is zero or a value close thereto, and is considerably smaller than σ of partially coherent illumination. The details of the configuration in FIG. 1 will be described later.

The principle of the exposure method according to the present invention is that the spatial frequency component of the Levenson-type mask and the control of the spatial frequency spectrum of the projection optical system are combined by controlling the spatial frequency spectrum of the Levenson type mask and the projection optical system. Is extracted, and a very fine line pattern which cannot be resolved by the normal exposure included in the mask is independently exposed under the most preferable nearly two-beam interference condition, and this is superimposed as a latent image by the normal exposure, and then the integrated latent image is exposed. Development is performed based on the image to obtain a pattern image.

According to the present invention, various patterns included in one mask can be exposed by using the limit capability of the exposure apparatus by the multiple exposure, and the capability of the projection exposure apparatus which is limited by a simple single exposure can be reduced. I have pulled out to the maximum.

As described above, according to the present invention, for example, NA
It is also possible to expose a 0.1 μm pattern with a 0.6 KrF excimer laser exposure apparatus, which has about twice the resolution of a 0.2 μm pattern, which is usually regarded as a limit. Furthermore, there are effects such as uniformity of the fine line portion and expansion of the depth of focus.

Furthermore, in the present invention, only one mask is required for performing multiple exposure, and the cost of the mask itself and the work of lowering the throughput such as mask replacement and associated alignment are omitted.

FIG. 2 is a flowchart of the exposure method of the present invention. FIG. 2 shows a rough exposure step for projecting and exposing a pattern having a relatively large line width, a fine line exposure step for projecting and exposing a pattern having a small line width, and a developing step, which constitute the exposure method of the present invention. It is.

Here, the rough exposure step and the fine line exposure step do not have to be in the order shown in this figure, the fine line exposure step may be performed first, and when the exposure is performed a plurality of times, they can be performed alternately.

Further, an alignment step or the like can be appropriately inserted in each exposure step to improve image forming accuracy, and the present invention is not limited to this step configuration by this figure.

Next, the principle of how the effects of the present invention are realized by these steps will be described. When the flow of FIG. 2 is used, first, rough exposure is performed to expose a mask image of a desired pattern on a photosensitive substrate.

In the present invention, since the exposure is performed with a resolution equal to or less than the limit line width that can be resolved by the projection optical system, the desired pattern formed on the mask includes a pattern having a size equal to or smaller than the limit line width.

FIG. 3 shows an example of a pattern formed on such a mask surface. In FIG. 3, 33 is a basic pattern, and 31 and 32 are light transmitting portions (lines). The basic pattern 33 is repeatedly arranged to form a repeated pattern.

This pattern is an ASIC for a semiconductor device.
This is a so-called gate pattern (basic pattern) used for the above.

In the figure, the gate line 31 is a main part for controlling the switching, and the line width is desired to be extremely fine. On the other hand, the 32 wiring contact portions require a certain area and have a larger pattern than the gate lines. In such a pattern, a fine line and a pattern larger than the fine line are mixed. Further, as shown in FIG. 4, since it is preferable from the viewpoint of the function of the IC that the gate patterns are integrated as much as possible, the gap 9 between the patterns may be the same as the width a of the fine line pattern.

FIG. 5 is a schematic view of a mask M used in the present invention. The mask M utilizes the fact that the gate pattern 33 is composed of a pair of patterns, and the phase difference of light equivalent to the pair of patterns is approximately π (180
Degree). Also in the figure, there is a phase difference of 180 degrees between the transparent portion and the hatched portion.

Further, the upper and lower rows of the gate patterns (upper and lower sides of the paper) are formed so that the phase difference between adjacent patterns is also π. By forming in this way, the effect of improving the resolution of the pattern image is obtained by weakening the light due to the phase difference at the boundary between the adjacent patterns.

However, in the rough exposure step alone, even if such a Levenson mask is used, a fine line having a width smaller than the limit line width such as the gate line portion is not completely resolved, and the depth of focus is shallow. Here, approximately 180 degrees means 180 degrees ± 10 degrees.

Next, as a second step, fine lines are exposed on the photosensitive substrate after the rough exposure prior to the fine line exposure. No development has yet been performed.

In the fine line exposure, the position of the mask M is kept at the same position as the rough exposure, and the exposure is performed after adjusting the illumination conditions of the illumination optical system 12 and the aperture stop of the projection optical system 18.

FIG. 6 is a schematic view of the exposure conditions of the present invention and the pattern obtained by each exposure. Illumination conditions for fine line exposure are as follows.
And a small σ illumination (illumination similar to so-called coherent illumination) as shown on the right side of the figure, and an aperture stop provided on the pupil plane of the projection optical system has a rectangular aperture as shown in the middle of the right side of the figure. . The mask M is the same as in FIG.

The x-axis and y-axis in the figure are aligned with the x-axis and y-axis shown in the gate pattern shown in FIG.

FIG. 7 is an explanatory diagram of the light intensity distribution of the pattern when the exposure shown in FIG. 6 is performed. FIG. 8 shows FIG.
FIG. 4 is a graph of light intensity distribution showing the same light intensity distribution with respect to the gate line portion (AA ′ in the figure) of the gate pattern shown in FIG. 3.

These figures show the results of negative exposure, and show the results of integrating the rough exposure step, the fine line exposure step, and the double exposure thereof from the left.

As is clear from FIG. 7, in the rough exposure, the fine line portion is not resolved but is a blurred image, and the light intensity is lower than the intensity of the contact portion. The fine line exposure portion has a good resolution of the gate line portion, and a better point is that light is concentrated on a portion where the gate line exists even in the gate line direction.

The light intensity integrated by the multiple exposure is shown in the right figure, and it can be seen that the target pattern image is well reproduced.

Further, as shown in FIG. 8, the width (margin) of the allowable exposure amount capable of forming a gate line is small in the rough exposure, while the light of the gate line pattern portion having a large contrast is obtained by the fine line exposure in the double exposure integration. It can be seen that by integrating the intensity distributions, the width of the allowable exposure amount is approximately doubled.

As described above, according to the present invention, a pattern image having a higher resolution than the normal exposure limit can be stably obtained by using multiple exposures in which the mask, illumination conditions, aperture stop, etc. are adjusted as described above. Projection exposure.

FIG. 9 is a schematic view showing the effect of exposure using a Levenson mask (Levenson-type phase mask) used in the fine line exposure of this embodiment. In the figure, (A) shows the state of use of the limit resolution of the normal exposure apparatus, (B) shows the case where an attempt is made to expose a pattern at twice the pitch of the limit resolution in the state of normal use, and (C) shows the state of the book. It is a schematic diagram which shows a mode that the pattern of 2 times pitch is exposed by the Levenson mask of an Example.

171 is a light-shielding portion made of chromium, P1, P2
Is the pitch of the periodic pattern.

Hereinafter, each case will be described.
FIG. 9A shows a state where the first-order diffracted light (angle θ) corresponding to the line pitch P1 on the mask M just enters the object side NA of the projection optical system. That is, the light that passes through the projection optical system and contributes to the image formation is three light beams of 0-order light and ± 1st-order light.

In FIG. 9B, the pitch P2 of the line pattern on the mask M is twice the pitch P1. In this case, the angle θ2 of the first-order diffracted light diffracted by the mask is shown in FIG.
The angle is twice as large as the angle θ1 in the case of (A).

Therefore, only the 0th-order light enters the object side NA of the projection optical system, that is, only the 0th-order light that passes through the projection optical system and contributes to the image formation is obtained. The image is not resolved.

FIG. 9C is the same as FIG. 9B as in FIG.
A pattern having a pitch P2 twice that of (A) is used, but the mask M is a Levenson mask. In this case, as shown in the figure, the 0th and ± 1st-order lights are shifted obliquely, and as a result, the 0th-order light and the + 1st-order light (or the 0th-order light and the -1st-order light) are shifted in the object side NA of the projection optical system. , That is, transmitted through the projection optical system and contributes to image formation.

This is two-beam interference. In this case, the angle (NA) formed by the image plane of the 0th-order light and the + 1st-order light is twice the angle (NA) of the three-beam interference in the case of normal illumination, and therefore the resolution is twice.

The above description is a one-dimensional view. If the mask is a one-dimensional periodic pattern dedicated to fine line exposure, fine lines can be exposed only by the above-mentioned Levenson mask. When a pattern other than the fine line is included, the pattern on the mask is also two-dimensional, and the aperture stop is also two-dimensional.
Due to the three-dimensional aperture, the diffracted light is 2
Even if a Levenson mask is used, the image is two-dimensionally mixed with various angles (NA), and the resolution of the two-beam interference mentioned above cannot be doubled. From this, it can be understood that the above configuration cannot completely achieve the object with respect to the object of the present invention in which the fine line pattern included in the pattern is exposed at twice the resolution.

Therefore, in this embodiment, as described above,
By arranging an aperture stop having a rectangular aperture on the aperture stop surface of the projection optical system, a two-dimensional light beam mixed with various angles is limited to one dimension for fine line resolution, and Achieved the purpose by realizing one-dimensional approximately two-beam imaging corresponding to

Next, a schematic view of one embodiment of the exposure apparatus of the present invention shown in FIG. 1 will be described.

In the figure, reference numeral 11 denotes an exposure light source, which comprises a KrF or ArF excimer laser. 12 is an illumination optical system, and 13 is a schematic diagram of an illumination mode.
2 shows a state of a light beam emitted from the light emitting device 2. Reference numeral 14 denotes a mask which is formed by repeating the basic pattern 33 as shown in FIG. 5, for example, and has a pattern having an optical phase difference of 180 degrees between adjacent transmission regions. Reference numeral 15 denotes a diaphragm exchange unit of the illumination optical system 12, and reference numeral 16 denotes various exchange diaphragms. The diaphragms are exchanged to change the shape of the effective light source. 17
Denotes a reticle stage, which holds a mask 14.
Reference numeral 18 denotes a projection optical system, and 19 denotes an aperture stop, which is provided on a pupil plane of the projection optical system 18. Reference numeral 20 denotes an aperture stop changing unit that makes the aperture stops 85 and 86 replaceable. 21 is a wafer (photosensitive substrate) 22 is a wafer stage.

In this exposure apparatus, when performing rough exposure for projecting and exposing a rough pattern having a relatively large line width of the pattern formed on the mask 14, as shown in FIG. That is, a partially coherent illumination having a relatively large effective light source σ (approximately 0.6 to 0.8) is used. The aperture stop 19 used for the projection optical system 18 does not have any special shape.
Exposure is performed at approximately the maximum NA of the projection optical system. It goes without saying that annular illumination or the like can also be used as appropriate.

Next, in this exposure apparatus, a fine line pattern having a small line width of the pattern formed on the mask 14 is projected and exposed. When performing fine line exposure, the effective light source 63 in FIG.
, Small σ illumination (illumination close to so-called coherent illumination) is used. As the aperture stop used in the projection exposure system 18, a rectangular aperture stop 85 having a length in the direction perpendicular to the gate line, that is, in the high resolution direction is used.

For switching between rough exposure and fine line exposure, the aperture 16 is exchanged by the aperture exchange means 15 for the illumination optical system 12, and the aperture stop 19 by the aperture aperture exchange means 20 for the aperture stop 19 in the projection optical system 18. Replace 19.

Here, the diaphragm exchange means 1 of the illumination optical system 12
As 5, as shown in FIG. 10, two apertures (aperture filters) of a rough exposure aperture 64 and a fine line exposure aperture 63 are fixed to one holder 61, and the holder 61 is orthogonal to the optical axis. And a plurality of diaphragms 73 to 77 are replaced by a slide 71 as shown in FIG. It is also possible to appropriately use a device which is fixed to the lens and rotated and similarly arranged at the stop position 72 in the illumination optical system 12.

The aperture stop changing means 20 is as follows.
As shown in FIG. 12, an aperture stop 85 is inserted and arranged at a predetermined position in the projection optical system 18 at the time of fine line exposure by sliding the aperture stop 85 in parallel to a plane orthogonal to the optical axis. On the other hand, at the time of rough exposure, similarly, the aperture stop 85 is slid and retracted, and the aperture stop 86 is inserted. As shown in FIG. At the same time, a device or the like that slides in parallel to a predetermined position, inserts and arranges, and forms a rectangular opening at the center can be used as appropriate.

Further, in order to change the orientation of an asymmetric opening such as a rectangle for the purpose of matching a rough pattern or a fine pattern, the light shielding plate and the insertion / retraction means are made rotatable. The one provided with the plate and the insertion / retraction means can be applied. Further, a mechanism for rotating the aperture stop 101 having a rectangular aperture as shown in FIG. 14 after insertion may be used.

Next, another configuration of the embodiment of the present invention will be described.

The present embodiment is an exposure method suitable for a case where the pattern integration as shown in FIG. 3 is further advanced and the separation of the patterns in the gate line direction (the y direction in the figure) becomes a limit. .

In this embodiment, as shown in FIG. 15, triple exposure of rough exposure and fine line exposure 1 and 2 is performed. As the fine line exposure, in addition to the fine line exposure 1 in the center of the figure (the same as the fine line exposure in FIG. 6), the fine line exposure 2 is performed using an aperture stop in which the opening direction of the aperture stop 85 differs by 90 degrees. The effect of enhancing the separation boundary between basic gate patterns is obtained.

As shown in the figure, the fine line exposure 2
It is similar to the fine line exposure 1 in that spatial frequency adjustment by illumination and an aperture stop is performed, but the direction of the rectangular aperture of the aperture stop is rotated by 90 degrees. In this way, the resolution in the y direction (up and down on the paper surface), for which the resolution is required due to integration, is increased, and exposure is performed in an overlapping manner to facilitate separation of basic patterns in the gate line direction.

The present invention is not limited to the embodiment described above, and the sequence flow and the like can be variously changed without departing from the spirit of the present invention.

In particular, the illumination conditions of the illumination optical system and the shape of the aperture stop of the projection optical system can be appropriately selected in accordance with the intended pattern and can be subjected to multiple exposure. As fine line exposure, various illuminations such as annular illumination, quadrupole illumination, elliptical aperture stop, and quadrupole aperture stop can be used. FIG. 16 shows an example of a variation of the aperture stop.

In addition, the shape of the gate pattern on the mask can be partially changed from the intended pattern as appropriate in order to enhance the separation between the basic gate patterns and to correct the line width and shape. . FIG. 17 is an explanatory view of a mask for the purpose of separating gate patterns according to the present invention.

In the figure, the opening indicated by oblique lines gives a phase difference of 180 degrees (π) to the transmitted light with respect to the other openings.

FIG. 24 is an explanatory view of one embodiment of a specific optical system in the exposure apparatus of the present invention.

This embodiment shows a case where the present invention is applied to a step-and-repeat type or step-and-scan type exposure apparatus for lithography of submicron or quarter micron or less.

In the figure, a laser beam from a laser light source 201 is enlarged in beam diameter by a beam shaping unit 205 and is incident on an incident surface 206 a of an optical integrator 206. The optical integrator 206 is configured by two-dimensionally arranging a plurality of minute lenses (fly-eye lenses) 6-i (i = 1 to N) having a quadrangular or cylindrical cross section at a predetermined pitch. A secondary light source image is formed near the exit surface 206b.

The light amount control means 217 is disposed near the incident surface 206a of the optical integrator 206.
A plane (XY) perpendicular to the optical axis La of the optical system 205 (illumination system)
(Plane), in the direction of the optical axis La, and in a predetermined angle direction with respect to the optical axis La.

The light amount control means 217 controls the amount of light transmitted through at least one of the plurality of minute lenses of the optical integrator 206 by means of a light amount adjusting section comprising an ND filter and a light shielding member. 218
Denotes a drive mechanism, which is a masking blade 210 described later.
Alternatively, based on a signal from an illuminance distribution measurement unit (not shown) for measuring the illuminance on the reticle (mask) 212 or the wafer 215 surface, the light amount control unit 217 is set to a plane perpendicular to the optical axis,
The illuminance distribution on the illuminated surface (masking blade) 210 is adjusted by moving in the optical axis direction and at a predetermined angle with respect to the optical axis.

Reference numeral 217 denotes an aperture, which is the exchange aperture 16 shown in FIG.
And the shape of the secondary light source is determined. The aperture 217 can be switched by an aperture exchange mechanism (actuator) 216 so that various apertures 7a and 7b are positioned in the optical path according to the illumination conditions. As the stop 207, for example, a stop having a normal circular aperture, the projection lens 2
13, an annular illumination stop, a quadrupole illumination stop, a small σ-value illumination stop, etc., for changing the light intensity distribution on the pupil plane 214 of the thirteenth pupil plane 214. Has been placed.

In this embodiment, by using various apertures 207, the light flux incident on the condenser lens 208 is changed variously, and the light intensity distribution on the pupil plane 214 of the projection optical system 213 is appropriately controlled. The condensing lens 208 includes a plurality of lenses 2 near the exit surface 206 b of the optical integrator 206.
A plurality of light beams emitted from the next light source and transmitted through the stop 207 are condensed, reflected by the mirror 209 and superposed on the surface of the masking blade 210 as a surface to be irradiated, and the surface is uniformly irradiated. The masking blade 210 is composed of a plurality of movable light shielding plates so that an arbitrary opening shape is formed.

Reference numeral 211 denotes an image forming lens which transfers the shape of the opening of the masking blade 210 onto a reticle (mask) 212 as a surface to be irradiated, and uniformly illuminates a required area on the reticle 212.

Reference numeral 213 denotes a projection optical system (projection lens) which reduces and projects a circuit pattern on the reticle 217 surface onto a wafer (substrate) 215 surface mounted on a wafer chuck. Reference numeral 214 denotes a pupil plane of the projection optical system 213. On the pupil plane 214, the various aperture stops 19 shown in FIG.

In the optical system according to the present embodiment, the light emitting section 2
01a, the second focal point 204, the incident surface 206a of the optical integrator 206, the masking blade 210, the reticle 212, and the wafer 215 have a conjugate relationship with each other. Also, the stop 207a and the pupil plane 2 of the projection optical system 213
14 has a substantially conjugate relationship.

In the present embodiment, with the above configuration,
The pattern on the reticle 212 surface is subjected to reduced projection exposure on the wafer 215 surface. The device (semiconductor element) is manufactured through a predetermined development process.

In the present embodiment, as described above, a stop having a different aperture shape is selected and used on the pupil plane 214 of the projection optical system 213 according to the pattern shape on the target reticle 212 surface. The light intensity distribution is varied.

In the present invention, (a) as an illumination method of an illumination optical system, it is applicable to illuminate a mask pattern with light from a KrF excimer laser, an ArF excimer laser or an F2 excimer laser.

(B) Refraction system, reflection
It is applicable to project the mask pattern by a projection optical system composed of either a refraction system or a reflection system.

(C) As the exposure apparatus, a step-and-repeat type reduction projection exposure apparatus having the exposure method of the present invention as an exposure mode, a step-and-scan type reduction projection exposure apparatus having the exposure method of the present invention as an exposure mode, etc. are applied. It is possible.

Next, an embodiment of a method of manufacturing a semiconductor device using the above-described projection exposure apparatus will be described.

FIG. 18 shows a flow of manufacturing a semiconductor device (a semiconductor chip such as an IC or an LSI, or a liquid crystal panel or a CCD).

In step 1 (circuit design), a circuit of a semiconductor device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design.

In step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. Step 4
The (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer.

The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer prepared in step 4, and includes an assembly process (dicing and bonding) and a packaging process (chip encapsulation). And the like.

In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 19 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface.

In step 13 (electrode formation), electrodes are formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the above-described exposure apparatus to print and expose the circuit pattern of the mask onto the wafer.

In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist are removed. In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of this embodiment, it is possible to easily manufacture a highly integrated semiconductor device which has conventionally been difficult to manufacture.

[0119]

As described above, according to the present invention, (a-1) there is no need to add a special exposure device such as separately providing a two-beam interference device, and it is possible to improve the illumination conditions, switch the aperture stop, and to a small extent. By performing the above, it is possible to achieve an exposure method and an exposure apparatus capable of obtaining the high resolution described above.

(A-2) By the exposure method using multiple exposure,
An exposure method capable of forming a pattern with a line width of 0.15 μm or less and an exposure apparatus capable of exposing a real circuit pattern with a line width of 0.15 μm or less using the same can be achieved.

(A-3) Levenson type phase mask is 1: 1L
By using it for patterns other than the & S periodic pattern (exposure with a Levenson mask other than the 1: 1 L & S periodic pattern is less effective as described above), the illumination conditions of the illumination optical system and the aperture stop of the projection optical system are controlled. To achieve an exposure method and an exposure apparatus capable of performing exposure with a resolution close to that obtained when a fine L & S pattern is exposed using a Levenson mask by performing multiple exposures without exacerbating the shape and the like of other arbitrary pattern portions. be able to.

[Brief description of the drawings]

FIG. 1 is a view showing an example of an exposure apparatus of the present invention.

FIG. 2 is a diagram showing an example of a flow of an exposure method of the present invention.

FIG. 3 is a schematic diagram showing a gate pattern shape.

FIG. 4 is a schematic diagram showing an integrated gate chart shape.

FIG. 5 is a schematic view showing an example of a Levenson mask according to the present invention.

FIG. 6 is a schematic diagram illustrating exposure conditions and image intensity according to the first embodiment of the present invention.

FIG. 7 is a schematic diagram showing a light intensity distribution of a pattern image according to the first embodiment of the present invention.

FIG. 8 is a schematic diagram illustrating a fine line portion intensity distribution and exposure latitude according to the first embodiment of the present invention.

FIG. 9 is a schematic view illustrating the effect of a Levenson mask.

FIG. 10 is a schematic diagram showing another example of the illumination condition control means according to the present invention.

FIG. 11 is a schematic diagram showing another example of the illumination condition control means according to the present invention.

FIG. 12 is a schematic diagram illustrating an example of an aperture stop control unit of the projection optical system.

FIG. 13 is a schematic view showing another example of the aperture stop control unit of the projection optical system.

FIG. 14 is a schematic view showing an example of a rotation unit of an aperture stop of the projection optical system.

FIG. 15 is a schematic diagram illustrating exposure conditions and image intensity according to a third embodiment of the present invention.

FIG. 16 is a schematic view showing another embodiment of the present invention.

FIG. 17 is a schematic view showing another example of the mask of the present invention.

FIG. 18 is a flowchart of a device manufacturing method according to the present invention.

FIG. 19 is a flowchart of a device manufacturing method according to the present invention.

FIG. 20 is a schematic view showing a conventional projection exposure apparatus.

FIG. 21 is a schematic view showing an example of a conventional two-beam interference exposure apparatus.

FIG. 22 is an explanatory diagram of a Levenson-type phase shift mask.

FIG. 23 is a schematic view showing an example of a conventional two-beam interference exposure apparatus.

FIG. 24 is an explanatory diagram of an optical system of the exposure apparatus of the present invention.

[Explanation of symbols]

 Reference Signs List 11 excimer laser 12 illumination optical system 14 mask (reticle) M, 17 mask (reticle) stage 15 mask (reticle) changer 18 projection optical system 21 wafer 22 XYZ stage 16, 63, 64 illumination diaphragm 19, 85, 86 aperture diaphragm 173 Phase shift type mask 94,95 Light shielding part 33 Basic pattern 171 Chrome (light shielding part) 172 Phase shift 173 Levenson type phase shift mask

Claims (10)

[Claims] An exposure method for illuminating an illumination area having a predetermined shape with an illumination optical system with exposure light from a light source means and projecting a mask pattern provided in the illumination area onto a photosensitive substrate with a projection optical system. Has a repeating pattern in which a plurality of basic patterns composed of light transmitting portions are repeatedly arranged, and adjacent transmitting portions of the repeating pattern have an optical phase difference of about 180 degrees from each other, and An exposure method, wherein the photosensitive substrate is subjected to multiple exposure by changing illumination conditions of an illumination optical system and light transmission conditions on a pupil plane of a projection optical system in a pattern. 2. The basic pattern according to claim 1, wherein a corresponding light transmitting portion of the pair of transmitting patterns has an optical phase difference of about 180 degrees. Exposure method. 3. The exposure method according to claim 1, wherein as one of the illumination conditions, substantially coherent illumination with a small effective light source is used. 4. One of the light transmission conditions on the pupil plane of the projection optical system is to limit a transmission area by using an aperture stop having a long opening in a direction of high pattern resolution on the mask. The exposure method according to claim 1, wherein: 5. The exposure method according to claim 4, wherein the aperture stop has a plurality of movable light shielding plates, and the light shielding plates are inserted into the projection optical system when the multiple exposure is switched. 6. An illumination stop holding unit configured so that one of a plurality of illumination stops can be inserted into and removed from the optical path of the illumination optical system, and the illumination condition is changed when switching between multiple exposures. 2. The exposure method according to claim 1, wherein the exposure method is changed. 7. A light-shielding plate having one or more openings and holding means for the light-shielding plate, wherein the light-shielding plate rotation control means for rotating the light-shielding plate in the illumination optical system when the multiple exposure is switched is used. 2. The exposure method according to claim 1, wherein illumination conditions are changed. 8. An exposure apparatus, wherein a pattern on a mask is transferred to a photosensitive substrate by using the exposure method according to claim 1. 9. After exposing a pattern on a mask surface to a wafer surface using the exposure method according to claim 1, the device is manufactured through a development process on the wafer. A method for manufacturing a device, comprising: 10. A device according to claim 8, wherein after the pattern on the mask surface is exposed on the wafer surface using the exposure apparatus according to claim 8, the wafer is subjected to a developing process to produce a device. Production method.