JP2000031036A - Exposing method and aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable forming a circuit pattern of complex shape on a wafer, by setting periodical pattern exposure having specified light intensity distribution, pattern exposure and a specified ratio of quantity of lights. SOLUTION: When double exposure of periodical pattern exposure and pattern exposure different from it is performed on a substrate to be exposed, the maximum value of light intensity distribution of periodical pattern is set as I0, and the minimum value is set as I1. An intensity value at a central position of a pattern having the minimum line width of light intensity distribution of pattern exposure is set as (b), an intensity value at a central position between the pattern having the minimum line width and the other pattern having the minimum line width is set as (c), and a light sensitive threshold value of resist formed on the substrate to be exposed is set as Ic. When the ratio l:k of quantity of lights of the periodical pattern exposure and the pattern exposure is properly set, the light intensity distribution and the ratio (k) of quantity of lights are so set that k×b+I0>Ic and k×c+I1<Ic when the resist is a negative type, and that k×b+I1<Ic and k×c+I0>Ic when the resist is a positive type.

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. 19 shows a schematic view of a conventional projection exposure apparatus. In FIG. 19, 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, 1
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
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. 19, and forms an image of a fine pattern on the wafer 198. The substrate stage 199 moves stepwise along the image plane of the projection optical system when a fine pattern is sequentially formed in a plurality of different areas (shot areas: areas forming one or more chips) of the wafer 198. The wafer 198
Are changed 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 the exposure wavelength, and NA is the brightness of the projection optical system 196. The numerical apertures k ₁ and k ₂ on the image side are constants determined by the development process characteristics of the wafer 198 and the like.
The value is about 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 line width of 0.1 mm is formed on a wafer.
A pattern of 5 μm or less can be formed.

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), that is, the brightness of the interference fringes. The width of each part is shown. Β represents an incident angle (absolute value) of each 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.

The above-mentioned US Pat. No. 5,415,835 discloses that a simple fringe pattern (periodic pattern), that is, a binary exposure distribution is given to a wafer (resist) by two-beam interference exposure, and then the resolution range of the exposure apparatus is changed. By performing lithography (exposure) using a mask in which a large opening is formed and giving another binary exposure distribution to the wafer, it is possible to obtain an isolated line (pattern). is suggesting.

However, US Pat. No. 5,415,583 mentioned above.
In the exposure method of No. 5, since only the ordinary binary exposure amount distribution is formed in each of the two exposure methods of the two-beam interference exposure and the normal exposure, it is difficult to obtain a circuit pattern having a more complicated shape. .

Although US Pat. No. 5,415,835 discloses that two exposure methods, two-beam interference exposure and normal exposure, are combined, an exposure apparatus that achieves such a combination will be specifically described. Not in.

According to the present invention, a circuit pattern having a complicated shape is formed on a wafer by using two exposure methods: periodic pattern exposure represented by two-beam interference exposure and normal pattern exposure (normal exposure) not including a periodic pattern. An object is to provide an exposure method and an exposure apparatus which can be formed.

Another object of the present invention is to provide a line width of 0.15 μm.
An exposure method and an exposure apparatus capable of easily obtaining a circuit pattern including the following parts are provided.

Another object of the present invention is to provide an exposure apparatus capable of performing two exposure methods, periodic pattern exposure and normal exposure.

[0024]

According to the present invention, there is provided an exposure method for performing double exposure of a periodic pattern exposure and a different pattern exposure on a substrate to be exposed. Is the maximum value of I ₀ , the minimum value is I ₁ , the intensity value at the center position of the pattern having the minimum line width of the light intensity distribution of the pattern exposure is b, the pattern having the minimum line width and the other minimum line width are When the intensity value at the center position of the pattern is c, the exposure threshold value of the resist provided on the substrate to be exposed is I _c , and the light amount ratio between the periodic pattern exposure and the pattern exposure 1: k is appropriately set. When the resist is a negative type, k × b + I ₀ > I _c k × c + I ₁ <I _{c When the} resist is a positive type, k × b + I ₁ <I _c k × c + I ₀ > I _c Periodic pattern exposure to be distributed;
A feature is that pattern exposure and a light amount ratio k are set.

According to a second aspect of the present invention, in the exposure method of performing double exposure of pattern exposure and periodic pattern exposure on a substrate to be exposed, a part of the pattern is one of the periodic patterns.
The maximum value of the light intensity distribution of the periodic pattern is I ₀ , the minimum value is I _1, and the intensity value of a part of the pattern in the light intensity distribution of pattern exposure is a, When the exposure threshold value of the resist provided on the exposure substrate is set to I _c , and the light intensity ratio between the periodic pattern exposure and the pattern exposure is set to 1: k, when the intensity of the resist pattern forming portion is negative, k × a + I ₀ > I _c k × a + I ₁ > I _{c When the} resist is of a positive type, a periodic pattern exposure having a light intensity distribution such that k × a + I ₁ <I _c k × a + I ₀ <I _c ,
A feature is that pattern exposure and a light amount ratio k are set.

According to a third aspect of the present invention, there is provided an exposure method for performing double exposure of a periodic pattern exposure and a different pattern exposure on a substrate to be exposed, wherein a part of the pattern is one or more of the periodic patterns. The maximum value of the light intensity distribution of the periodic pattern is I ₀ , the minimum value is I _1, and the light intensity distribution of the peripheral portion of the pattern in the light intensity distribution of the pattern exposure is I _s , When the exposure threshold of the resist provided above is I _c and the light amount ratio between the periodic pattern exposure and the pattern exposure is 1: k, the intensity of the portion where the resist pattern is not formed is k × I _s + I ₀ <I _{c When the} resist is of a positive type, a periodic pattern exposure having a light intensity distribution such that k × I _s + I ₁ <I _c ;
A feature is that pattern exposure and a light amount ratio k are set.

According to a fourth aspect of the present invention, in the first, second or third aspect, the illumination method is changed between the periodic pattern exposure and the pattern exposure.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the exposure amount is changed for each exposure so that the light amount ratio between the periodic pattern exposure and the pattern exposure becomes 1: k. And

A sixth aspect of the present invention is characterized in that, in the fourth aspect of the present invention, the periodic pattern exposure makes σ 0.3 or less.

According to a seventh aspect of the present invention, in the fourth aspect of the present invention, the pattern exposure is performed by setting σ to 0.6 or more.

An eighth aspect of the present invention is characterized in that, in the fourth aspect of the present invention, the pattern exposure is performed by using annular illumination in which the inside of the illuminance distribution is lower than the outside.

A ninth aspect of the present invention is characterized in that, in the fifth aspect of the present invention, when the pattern exposure is performed, the exposure amount is about twice that when the periodic pattern is exposed.

According to a tenth aspect of the present invention, when the periodic pattern exposure is σ = 0.3 and the σ of the pattern exposure is smaller than 0.8, the exposure amount of the pattern exposure is reduced by the periodic pattern exposure. It is characterized in that the exposure amount is twice or less.

According to an eleventh aspect of the present invention, when the periodic pattern exposure is σ = 0.3 and the pattern exposure is annular illumination, the pattern is exposed when the width of the annular zone is small. It is characterized in that the exposure amount is at least twice the exposure amount when exposing the periodic pattern.

According to a twelfth aspect of the present invention, in the fifth aspect, when σ of the illumination condition 1 for the periodic pattern exposure is smaller than 0.3, the exposure amount for exposing the pattern is the same as the exposure amount for exposing the periodic pattern. It is characterized by more than twice the amount.

According to a thirteenth aspect of the present invention, in the first, second or third aspect of the present invention, when exposing a periodic pattern, the exposure is performed by rotating the periodic pattern so as to be parallel to the fine pattern direction. Features.

According to a fourteenth aspect of the present invention, there is provided an exposure apparatus according to the first aspect.
13. A pattern on a mask is transferred to a photosensitive substrate by using the exposure method according to any one of (13) to (13).

According to a fifteenth aspect of the invention, there is provided a device manufacturing method, comprising: exposing a pattern on a mask surface to a wafer surface by using the exposure method according to any one of the first to thirteenth aspects; It is characterized in that devices are manufactured through processes.

According to a sixteenth aspect of the invention, there is provided a device manufacturing method, wherein a pattern on a mask surface is exposed on a wafer surface using the exposure apparatus of the fourteenth aspect, and then the wafer is manufactured through a developing process. It is characterized by doing.

[0040]

1 to 9 are explanatory views of an exposure method according to a first embodiment of the present invention. FIG. 1 is a flowchart showing the exposure method of the present invention. FIG. 1 is a block diagram showing a periodic pattern exposure step, a projection exposure step (pattern exposure step, a pattern exposure different from the periodic pattern exposure, hereinafter referred to as "normal pattern exposure"), and a development step which constitute the exposure method of the present invention. The flow is shown. In the figure, the order of the periodic pattern exposure step and the projection exposure step may be reversed, and when one of the steps includes a plurality of exposure steps, each step may be performed alternately. Also, between each exposure step. Although there is a step of performing precise alignment, the illustration is omitted here.

An exposure method and an exposure apparatus according to the present invention are characterized in that a substrate to be exposed (photosensitive substrate) is subjected to double exposure of periodic pattern exposure and normal exposure.

Here, the normal pattern exposure is an exposure in which the resolution is lower than that of the periodic pattern exposure, but the exposure can be performed in an arbitrary pattern. As a typical example, the projection optical system shown in FIG. Exposure.

The pattern (normal pattern) exposed by the normal pattern exposure includes a fine pattern having a resolution equal to or less than the resolution. The periodic pattern exposure forms a periodic pattern having substantially the same line width as the fine pattern. A large pattern having a resolution equal to or larger than the resolution of the normal pattern exposure is not limited to the line width of the periodic pattern exposure, but an integer multiple is effective.

Normally, the pattern exposure has an arbitrary shape and may be oriented in various directions. Generally, an IC pattern has two directions, one direction and the direction perpendicular to the other.
In many cases, it is oriented in a direction, and the finest pattern is often limited to only one specific direction.

When performing periodic pattern exposure by double exposure, it is important to match the direction of the periodic pattern with the direction of the finest pattern of the normal pattern.

Further, the exposure is performed such that the center of the peak of the periodic pattern coincides with the center of a fine pattern having a resolution lower than the resolution of the normal pattern.

The double exposure in the present invention means a double exposure of a periodic pattern exposure and a normal pattern exposure. The periodic pattern exposure is repeated several times in parallel with the direction of the finest pattern of the normal pattern exposure. Exposure.

Each of the periodic pattern exposure and the normal pattern exposure of the exposure method and exposure apparatus of the present invention comprises one or a plurality of exposure steps. Different exposure dose distributions are given to the photosensitive substrate.

When exposure is performed according to the flow of FIG.
First, the wafer (photosensitive substrate) is exposed in a periodic pattern as shown in FIG. The numbers in FIG. 2 represent the exposure amounts. The hatched portions in FIG. 2A indicate the exposure amount 1 (actually arbitrary) and the white portions indicate the exposure amount 0.

When developing only such a periodic pattern after exposure, usually, the exposure threshold value E of the resist on the photosensitive substrate is used.
th is set between the exposure amounts 0 and 1 as shown in the lower graph of FIG. The upper part of FIG. 2B shows a finally obtained lithography pattern (concavo-convex pattern).

FIG. 3 shows the relationship between the exposure amount dependency of the film thickness after development and the exposure threshold value of the resist on the photosensitive substrate in this case, that is, the positive resist (hereinafter, referred to as “positive”) and the negative resist. Each of the resists (hereinafter referred to as “negative type”) is shown. In the case of the positive type, when the exposure threshold value Eth or more, and in the case of the negative type, the exposure threshold value Eth or less,
The film thickness after development becomes zero.

FIG. 4 is a schematic diagram showing a state in which a lithography pattern is formed through the development and etching processes in the case of performing such exposure, for a negative type and a positive type.

In this embodiment, unlike the normal exposure sensitivity setting, FIGS. 5 (same as FIG. 2A) and FIG.
As shown in the figure, when the central exposure amount in the periodic pattern exposure is 1, the exposure threshold value Eth of the resist on the exposed substrate is 1
It is set larger than. When the exposure pattern (exposure amount distribution) obtained by performing only the base pattern exposure shown in FIG. 2 is developed on the photosensitive substrate, the exposure amount becomes insufficient. Does not occur, and no lithography pattern is formed by etching. This can be regarded as the disappearance of the periodic pattern (note that the present invention will be described using an example using a negative type, but the present invention can also be implemented in a positive type).

In FIG. 6, the upper part shows the lithography pattern (nothing can be done), and the lower part shows the relationship between the exposure amount distribution and the exposure threshold value. Incidentally, E ₁ according to bottom the exposure amount in the periodic pattern exposure, E ₂ represents an exposure amount in the conventional projection exposure.

The feature of this embodiment is that a high-resolution exposure pattern, which is apparently lost only by periodic pattern exposure, is fused with an exposure pattern of an arbitrary shape including a pattern having a size equal to or smaller than the resolution of an exposure apparatus by ordinary projection exposure. And selectively exposing only the desired area to the exposure threshold or more of the resist,
Finally, a desired lithography pattern can be formed.

FIG. 7A shows an exposure pattern by normal projection exposure (normal pattern exposure), which is a fine pattern and cannot be resolved, and the intensity distribution on the object to be exposed is blurred and wide. . In the present embodiment, a fine pattern having a paper width of about half the resolution of normal projection exposure is used.

The projection exposure for forming the exposure pattern shown in FIG. 7A is performed after the periodic pattern exposure shown in FIG.
Assuming that the exposure is performed on the same region of the same resist, the total exposure distribution on the resist surface is as shown in the lower graph of FIG. 7B. Here, 1 is the ratio of the exposure amount E ₂ of the exposure amount E ₁ and the projection exposure of the periodic pattern exposure: 1, the exposure amount exposed threshold Eth is resist E ₁ (= 1) and the exposure amount E ₁ projection Since the exposure amount is set between the sum (= 2) of the exposure amounts E ₂ , the lithography pattern shown in the upper part of FIG. 7B is formed.

At this time, the center of the normal pattern is made to coincide with the peak of the periodic pattern. Also, the direction of the normal pattern and the direction of the periodic pattern are matched.

The isolated line pattern shown in the upper part of FIG. 7B has a resolution of periodic pattern exposure and has no simple periodic pattern. Therefore, a high-resolution pattern higher than the resolution that can be realized by ordinary projection exposure is obtained.

Here, suppose that the projection exposure for forming the exposure pattern shown in FIG. 8 (the line width twice as large as the exposure pattern in FIG. 5 and the exposure threshold or more (here, the exposure amount twice as large as the threshold)). 5) is superimposed on the same region of the same resist without the development step after the periodic pattern exposure of FIG. At this time, by making the center of the normal pattern coincide with the peak position of the periodic pattern exposure, the symmetry of the superposed pattern is good, and a good pattern image can be obtained.

The total exposure distribution of this resist is shown in FIG.
As shown in (B), the exposure pattern of the two-beam interference exposure (periodic pattern exposure) disappears, and finally only the lithography pattern by the projection exposure is formed.

As shown in FIG. 9, the principle is the same when the exposure is performed with a line width three times as large as that of the exposure pattern shown in FIG. 5. For an exposure pattern with a line width four times or more, basically two times as large. From the combination of the line width exposure pattern and the triple line width exposure pattern, the line width of the finally obtained lithography pattern is obvious, and all the lithography patterns that can be realized by projection exposure are also formed in this embodiment. It is possible.

By adjusting the exposure amount distribution (absolute value and distribution) and the resist threshold value of the photosensitive substrate by each of the periodic pattern exposure and the projection exposure briefly described above,
The minimum line width is composed of a combination of various patterns as shown in FIGS. 6, 7B, 8B, and 9B, and the minimum line width is the resolution of the periodic pattern exposure (of FIG. 7B). A circuit pattern serving as a pattern can be formed.

The principles of the above-described exposure methods can be summarized as follows: (A-1) A pattern area that is not subjected to projection exposure (normal pattern exposure), that is, a periodic exposure pattern equal to or less than the exposure threshold of a resist disappears by development.

(A-2) Regarding the pattern area of the projection exposure performed with the exposure amount equal to or less than the exposure threshold value of the resist, the exposure pattern having the resolution of the periodic pattern exposure determined by the combination of the projection exposure and the periodic pattern exposure is used. It is formed.

(A-3) In the pattern area of the projection exposure performed with the exposure amount equal to or more than the exposure threshold value, a fine pattern (corresponding to a mask) which is not resolved only by the projection exposure is similarly formed. It turns out that. Further, as an advantage of the exposure method, if the periodic pattern exposure having the highest resolution is performed by two-beam interference exposure, a much larger depth of focus can be obtained as compared with normal exposure.

In the above description, the order of the periodic pattern exposure and the projection exposure is the order of the periodic pattern exposure, but is not limited to this order.

Next, a second embodiment of the present invention will be described.

The present embodiment is directed to a so-called gate type pattern shown in FIG. 10 as a circuit pattern (lithography pattern) obtained by exposure.

The gate pattern of FIG. 10 has a minimum line width of 0.1 μm in the horizontal direction, that is, the direction of AA ′ in the figure, whereas it has a minimum line width of 0.2 μm or more in the vertical direction. According to the present invention, it is possible to obtain a high resolution only in such a one-dimensional direction.
For two-dimensional patterns, two-beam interference exposure (periodic pattern exposure) may be performed only in one-dimensional directions that require such high resolution.

In this embodiment, an example of a combination of two-beam interference exposure only in one-dimensional direction and ordinary projection exposure will be described with reference to FIG.

FIG. 11A shows a periodic exposure pattern by two-beam interference exposure only in one-dimensional direction. The period of this exposure pattern is 0.2 μm, and this exposure pattern corresponds to a line width of 0.1 μmL & S pattern. Numerical values in the lower part of FIG. 11 represent exposure amounts.

As an exposure apparatus for realizing such two-beam interference exposure, an exposure apparatus having an interferometer-type demultiplexing / multiplexing optical system using a laser 151, a half mirror 152, and a plane mirror 153 as shown in FIG. , As shown in FIG.
There is a projection exposure apparatus in which a mask and an illumination method are configured as shown in FIG. 17 or FIG.

The exposure apparatus shown in FIG. 15 will be described.

In the exposure apparatus shown in FIG. 15, as described above, each of the two multiplexed light beams is obliquely incident on the wafer 154 at an angle θ, and the line width of the interference fringe pattern (exposure pattern) that can be formed on the wafer 154 is as described in (3) above. It is expressed by an equation. The relationship between the angle θ and the NA on the image plane side of the demultiplexing / multiplexing optical system is NA = sin θ. The angle θ is a pair of flat mirrors 153 (153a, 15a).
3b) can be arbitrarily adjusted and set by changing each angle. If the value of the angle θ is set to be large with a pair of plane mirrors, the line width of each interference fringe pattern becomes small.
For example, when the wavelength of the two light beams is 248 nm (KrF excimer), an interference fringe pattern having a line width of about 0.1 μm can be formed even at θ = 38 degrees. In this case, NA = sin θ
= 0.62. If the angle θ is set to be larger than 38 degrees, it goes without saying that higher resolution can be obtained.

Next, the exposure apparatus shown in FIGS. 16 to 18 will be described.

The exposure apparatus shown in FIG. 16 is, for example, a projection exposure apparatus using a normal step-and-repeat type or step-and-scan type reduction projection optical system (comprising a large number of lenses), and currently has an exposure wavelength of 248 nm. On the other hand, there are those having NA of 0.6 or more.

In FIG. 16, reference numeral 161 denotes a mask; 162, object-side exposure light which emerges from the mask 161 and enters the optical system 163; 163, a projection optical system; 164, an aperture stop; 165, a wafer which emerges from the projection optical system 163; Image-side exposure light 166 incident on the wafer 166 indicates a wafer serving as a photosensitive substrate.
FIG. 9 is an explanatory diagram showing the position of a light beam on the pupil plane corresponding to the circular opening of the stop 164 by a pair of black dots. FIG. 16 is a schematic diagram showing a state in which the two-beam interference exposure is performed. Both the object-side exposure light 162 and the image-side exposure light 165 are different from the normal projection exposure in FIG. Consists only of

In order to perform two-beam interference exposure (periodic pattern exposure) in a normal projection exposure apparatus as shown in FIG. 16, the mask 161 and its illumination method may be set as shown in FIG. 17 or FIG. Hereinafter, these three examples will be described.

FIG. 17A shows a Levenson-type phase shift mask 173, in which a light shielding portion 17 made of chrome is used.
The pitch P _{0 of} 1 is 0 in the equation (4), and the pitch P _0s of the phase shifter 172 is the mask represented by the equation (5).

P ₀ = P / M = 2R / M = λ / M (2NA) (4) P _0s = 2P ₀ = λ / M (NA) (5) where M is the projection optical system 163. The projection magnification, λ indicates the exposure wavelength, and NA indicates the numerical aperture of the projection optical system 163 on the image side.

On the other hand, a mask 174 shown in FIG. 17B is a shifter-edge type phase shift mask made of chrome without a light-shielding portion, and is similar to the Levenson type.
The pitch P _0s of 5 is configured to satisfy the above equation (5).

In order to perform two-beam interference exposure using the phase shift masks shown in FIGS. 17A and 17B, these masks are subjected to so-called coherent illumination with σ = 0 (or a value close to 0). Specifically, as shown in FIG.
The mask 170 is irradiated with a parallel light beam from a direction perpendicular to the mask (a direction parallel to the optical axis).

Here, σ = numerical aperture of the illumination optical system / numerical aperture of the projection optical system.

When such illumination is performed, the phase shifter 172 (175) cancels out the 0th-order transmitted diffracted light exiting in the vertical direction from the mask 170 because the phase difference between the adjacent transmitted lights becomes π. The two parallel light beams of ± 1st-order transmitted diffraction light are generated symmetrically from the mask 170 with respect to the optical axis of the projection optical system 163, and the two object-side exposures 165 in FIG. I do. Also 2
The higher-order diffracted light of higher order is transmitted through the aperture stop 1 of the projection optical system 163.
Since it does not enter the aperture 64, it does not contribute to imaging.

The mask 180 shown in FIG. 18 is a mask in which the pitch P ₀ of the light-shielding portion 181 made of chrome is represented by the following equation (6) similar to the equation (4).

P ₀ = P / M = 2R / M = λ / M (2NA) (6) where M is the projection magnification of the projection optical system 163, λ is the exposure wavelength, and NA is the image of the projection optical system 163. The numerical aperture on the side is shown.

The mask having no phase shifter shown in FIG. 18 is subjected to oblique incidence illumination using one or two parallel light beams. In this case, the incident angle θ of the parallel light beam to the mask 180
₀ is set to satisfy Expression (7). When two parallel light fluxes are used, the mask is illuminated with parallel light fluxes inclined by θ _{0 in} opposite directions with respect to the optical axis.

[0089] _{sinθ 0 = M / NA ... (} 7) again, M is the projection magnification, NA of the projection optical system 163 represents a numerical aperture on the image side of the projection optical system 163.

When obliquely illuminating a mask having no phase shifter shown in FIG. 18 with a parallel light beam satisfying the above equation (7), the mask 180 outputs an angle θ with respect to the optical axis.
_0- order transmitted diffracted light that travels straight at 0, and travels along an optical path symmetrical with respect to the optical path of the 0-order transmitted diffracted light and the optical axis of the projection optical system (travels at an angle -θ ₀ with respect to the optical axis) —first-order transmission Two light beams of the diffracted light are generated as two object-side exposure light beams 162 in FIG. 16, and these two light beams enter the opening of the aperture stop 164 of the projection optical system 163 to form an image.

In the present invention, such oblique incidence illumination using one or two parallel light beams is also treated as "coherent illumination".

The technique for performing two-beam interference exposure using an ordinary projection exposure apparatus has been described above. The illumination optical system of the ordinary projection exposure apparatus as shown in FIG. 19 is configured to perform partial coherent illumination. 19, the aperture stop (not shown) corresponding to 0 <σ <1 of the illumination optical system in FIG. 19 can be replaced with a special aperture stop corresponding to σ ≒ 0, etc. It can be configured to provide coherent illumination.

Returning to the description of the second embodiment shown in FIGS. In the present embodiment, a normal projection exposure (normal pattern exposure) (for example, an apparatus of FIG. 19 that performs partial coherent illumination on a mask) subsequent to the two-beam interference exposure (periodic pattern exposure) described above is used in FIG. Exposure is performed on the gate pattern shown in FIG. The upper part of FIG. 11C shows the relative positional relationship with the exposure pattern by two-beam interference exposure and the exposure amount in the area of the exposure pattern of normal projection exposure, and the lower part of FIG. The exposure amount of the resist on the wafer is mapped vertically and horizontally with a resolution of a pitch of a minimum line width.

The exposure amount distribution shown in the lower part of FIG. 11 shows an intensity distribution for exposing the wafer with the light intensity incident from the mask as 1.

By exposure of the periodic pattern shown in FIG.
Exposure distribution should ideally be a square wave of 1s and 0s
Uses the line width near the resolution limit of two-beam interference exposure
Therefore, it becomes a sine wave formed only by the zero-order light and the first-order light.
I have. The maximum value of the sin wave is I ₀, The minimum value is I₁And
You. At this time, I₀And I₁Is the value of
Is determined.

The exposure amount distribution by the normal projection exposure in FIG. 11B shows typical values in each part. The minimum line width portion of the exposure pattern by this projection exposure is blurred and widened without resolution, and the value of the light intensity at each store decreases. The exposure amount is roughly set to b at the center of the pattern, d at both sides, and c at the center where blurred images from both sides of the pattern come. The line width twice as large as the minimum line width is larger than the values of the exposure amounts b, c and d. However, since the line width is near the resolution limit of the projection exposure, the value of the exposure amount a is slightly blurred. These values of a, b, c, and d change depending on the lighting conditions.

The exposure amount distribution of FIG.
This is obtained as a result of adding the exposure amounts of the exposure pattern of FIG. 11A and the exposure pattern of FIG.

The light amount ratio in each of the two-beam interference exposure and the projection exposure differs depending on the illumination conditions of each exposure. The light amount ratio in each exposure in the addition is set as two-beam interference exposure: projection exposure = 1: k as the illuminance ratio of the illumination system, and the value of k is obtained as follows.

The exposure distribution shown in FIG. 11C can be expressed by the following equation using the above exposure distribution and light amount ratio.

When the resist is a negative resist, a ′ = k × a + I ₀ a ″ = k × a + I ₁ b ′ = k × b + I ₀ c ′ = k × c + I ₁ d ′ = to obtain k × d + I ₁ desired gate pattern, obtaining a relational expression of the threshold I _c of the photosensitive resist. for example, the resist is negative-working, is as follows.

A ′> I _C a ″> I _C b ′> I _C c ′ <I _C d ′ <I _C a ′, a ″, b ′ is preferably smaller, and c ′ and especially b ′
It is desirable to have a difference with By solving these equations, the optimum light amount ratio under each illumination condition can be obtained.

In the case where the resist is a negative type, it is particularly related to a fine pattern. The following two equations are important.

K × b + I ₀ > I _C k × c + I ₁ <I _C FIG. 25 shows a case where the resist is of a positive type, similarly to FIG.

When the resist is a positive type, a '= k × a + I ₁ <I _c a ″ = k × a + I ₀ <I _c b ′ = k × b + I ₁ <I _c c ′ = k _{× c + I 0> I c} d '= k × d + I 0> I c , and the following two equations are important.

K × b + I₁<I_C k × c + I₀> I_C If the resist is positive, the magnitude relationship of the exposure distribution is inverted
And the resist threshold I _cThe inequality sign is reversed.
Thus, the optimum light quantity ratio is required.

The manner in which the fine circuit pattern of FIG. 12 is formed by combining two different illumination methods of the two-beam interference exposure and the ordinary projection exposure described above will be described. In this embodiment, there is no developing process between the two-beam interference exposure and the normal projection exposure. Therefore, the exposure amount in the region where the exposure pattern of each exposure overlaps is added, and a new exposure pattern is generated by the added exposure amount (distribution).

FIG. 12, FIG. 13 and FIG. 14 show K at a wavelength of 248 nm.
This is a specific example using an rF excimer stepper.

As shown in FIG. 12, a gate pattern having a minimum line width of 0.12 μm is normally exposed, and a periodic pattern is overlapped with a Levenson-type phase shift mask so as to overlap the minimum line width.

The NA of the projection lens was 0.6, and the σ of the illumination system was 0.3 in exposure using a Levenson mask. At the time of normal mask exposure, σ = 0.3, 0.6, 0.8 and annular illumination.

In the case of exposing a periodic pattern by two-beam interference such as a phase shift mask, coherent illumination is σ
Is zero or a value close to it, but if it is too small, the amount of exposure per unit time will be small and the time required for exposure will be long, which is not practical.

In the case of periodic pattern exposure, σ is desirably 0.3 or less, and the maximum σ = 0.3 in exposure using a Levenson mask.

In normal exposure, partial coherent illumination is generally used. However, when σ is increased, reproducibility of a complicated shape is improved and the depth is increased. In a so-called annular illumination in which the illuminance distribution is lower on the inner side than on the outer side, this tendency is remarkable, but there is a disadvantage that the contrast is reduced.

As shown in FIG. 13A, the σ of the normal exposure
Is set to 0.3 which is the same as σ of the periodic pattern exposure, and the double exposure is performed under the same illumination condition, the gate pattern is defocused to 0.
Although the resolution is within the range of ± 0.2 μm, the line pattern portion is undulating, and the narrow portion causes disconnection, which is not preferable.

In the case of normal pattern exposure, it is preferable that σ = 0.6 or more. As shown in FIG. 13B, when σ of the normal exposure is set to 0.6, the gate pattern can be resolved within the range of defocus 0 ± 0.4 μm, and the undulation of the line pattern is eliminated. Set the exposure amount ratio between normal exposure and periodic pattern exposure to normal exposure: periodic pattern exposure = 1.5:
It was set to 1.

As shown in FIG. 14A, the σ of the normal exposure
When is increased to 0.8, the reproducibility of a complicated shape is slightly improved. The exposure amount ratio between normal exposure and periodic pattern exposure was set to normal pattern exposure: periodic pattern exposure = 2: 1. In the case of normal pattern exposure, the exposure amount is preferably twice or more as compared with the periodical pattern exposure.

FIG. 14 (B) shows a two-dimensional intensity distribution when the normal exposure is annular illumination, the illuminance from 0.6 inside the ring to 0.8 outside is 1 and the illuminance below 0.6 inside the ring is 0. . The exposure amount ratio between the normal exposure and the periodic pattern exposure was set to normal exposure: periodic pattern exposure = 2.5: 1.

In the annular illumination, the reproducibility of a complex shape is improved and the depth is increased as compared with when σ is 0.8. A good image was obtained with a defocus of ± 0.4 μm or less.

The fine circuit pattern is formed by double exposure with periodic pattern exposure. Normally, the fine pattern of the exposure pattern is not normally resolved because the light intensity is low and the contrast is low. Become imaged.

On the other hand, even a large pattern having a resolution equal to or higher than the resolution of the normal exposure pattern is superimposed on the intensity of the periodic pattern exposure to enhance the contrast. According to the exposure method of the present invention, a circuit pattern having a fine line width of 0.12 μm can be formed by using a projection exposure apparatus having an illumination optical system capable of switching illumination conditions such as changing σ or a light amount ratio of illuminance. And

The optimum value of the light amount ratio between the periodic pattern exposure and the normal pattern exposure was determined by the above-mentioned formula based on the combination of the illumination conditions.

The following is a case where the resist is a negative resist.

Illumination condition 1 Periodic pattern exposure is σ = 0.
3. Normal pattern exposure: σ = 0.3 Exposure amount distribution by periodic pattern exposure shown in the lower part of FIG.
The exposure distribution (best focus) by the normal projection exposure shown in the lower part of (B) is shown below.

I ₀ = 0.80 I ₁ = 0.23 a = 1.31 b = 0.34 c = 0.61 d = 0.09 It is optimal when k = 1.0, and a ′ = 2.11 a ″ = 1.54 b ′ = 1.21 c ′ = 0.89 d ′
= 0.32 although peripheral gate patterns exist next intensity distribution, in the _{k × I s + I 0 k} × I s + I 1, but showing the periphery intensity of I _S is usually patterns, I _S
Since = 0, they are I ₀ and I ₁ respectively. In the case of a negative resist, high strength I ₀ is a problem.

For later comparison, the maximum value a 'is normalized by 1 as follows.

A '= 1.0 a "= 0.73 b' = 0.57 c '
= 0.42 d '= 0.15 Maximum intensity I ₀ = 0.38 remaining around the periphery Illumination condition 2 σ = 0.3 for periodic pattern exposure, σ = 0.6 I ₀ = 0.80 I ₁ = 0.23 for normal pattern exposure a = 1.25 b = 0.44 c = Optimal when 0.53 d = 0.13 k = 1.5, a '= 2.68 a "= 2.11 b' = 1.46 c '= 1.03 d'
= 0.43, and for the later comparison, the maximum value a 'is normalized by 1 as follows.

A ′ = 1.0 a ″ = 0.79 b ′ = 0.55 c ′
= 0.38 d '= 0.16 I ₀ = 0.30 Illumination condition 3 σ = 0.3 for periodic pattern exposure, σ = 0.8 for normal pattern exposure I ₀ = 0.80 I ₁ = 0.23 a = 1.20 b = 0.48 c = 0.47 d = Optimal when 0.16 k = 2.0, a '= 3.20 a "= 2.63 b' = 1.76 c '= 1.17 d'
= 0.55, and the maximum value a 'is normalized by 1 as follows.

A '= 1.0 a "= 0.82 b' = 0.55 c '
= 0.37 d '= 0.17 I ₀ = 0.25 Illumination condition 4 Periodic pattern exposure is σ = 0.3, normal pattern exposure is σ = 0.8, and annular illumination is used.
The illuminance distribution of σ0.6 or less was set to zero.

I ₀ = 0.80 I ₁ = 0.23 a = 1.10 b = 0.47 c = 0.36 d = 0.19 k = 2.5 Optimum, a '= 3.55 a "= 2.98 b' = 1.98 c '= 1.13 d'
= 0.71 and the maximum value a 'is normalized by 1 as follows.

A '= 1.0 a "= 0.84 b' = 0.56 c '
= 0.32 d '= 0.20 I ₀ = 0.23 In the discussion so far, the resist threshold value was 1.5 when the maximum exposure amount was 3, and therefore, when normalized with the maximum exposure amount, the resist threshold value may be set to 0.5. Looking at this normalized exposure distribution, a ', a ", b ' is greater than the resist threshold 0.5, which is standardized, c ', d', near the maximum intensity I ₀ is less than the threshold .

Since a portion where the exposure amount is larger than the resist threshold value by the development is exposed, only the exposure amount a ′, a ″, and b ′ remains as a pattern after the development.
The part shown in gray at the bottom of (C) is the shape after development.

Next, an optimum light amount ratio is obtained for a case where the resist is a positive resist. When the positive resist is developed, the light transmitting portion disappears and the light shielded portion remains. In order to leave the pattern portion of the resist after the development, exposure may be performed using a reticle that transmits light around the pattern and shields the pattern portion from light. In such a reticle, the light intensity around the pattern is 1 and the light intensity at the pattern portion is 0. Therefore, in the light amount distribution after the normal exposure as shown in FIG. 25, it can be considered that the light intensity around the pattern is 1.

In the case of a positive resist, assuming that the intensity distribution of the composite image is the maximum value I ₀ and the minimum value I ₁ of the periodic pattern, a ′ = k × a + I ₁ a ″ = k × a + I ₀ b '= K × b + I ₁ c' = k × c + I ₀ d '= k × d + I _{0 The} pattern peripheral intensity is k × I _s + I ₀ k × I _s + I ₁ , but the peripheral intensity of the normal pattern I2max the I maximum value, when I2min the minimum value of the pattern around the strength, I2max = k × 1 + I 0 = I 2 I2min = k × 1 + I 1 = I 3 Figure 25 I ₂ is the map of the intensity distribution of the (C), I ₃ and shown. here, the strength of the portion to be left as a pattern is set to be _{a '<I c a "<} I c b'<I c c '> I c d'> I c.

FIGS. 26 and 27 are explanatory diagrams of the gate pattern of the positive resist and the illumination conditions, and correspond to the illumination conditions of the gate pattern of the negative resist in FIGS. Next, an illumination condition when a positive resist is used will be described with reference to FIGS.

The exposure amount distribution by the exposure of the periodic pattern shown in the lower part of FIG. 25A and the exposure amount distribution (best focus) by the normal projection exposure shown in the lower part of FIG. 25B are shown below.

Illumination condition 1 Periodic pattern exposure is σ = 0.
3. For normal pattern exposure, σ = 0.3 I ₀ = 0.80 I ₁ = 0.23 a = 0.03 b = 0.27 c = 0.21 d = 0.58 When k = 1.5 a ′ = 0.28 a ″ = 0.85 b ′ = 0.64 c ′ = 1.12. d '
= 1.67 I2min = 0.28, and the result is normalized by dividing by (k × 1 + 1) so that the peripheral intensity becomes 1 as follows.

A '= 0.11 a "= 0.34 b' = 0.23 c '
= 0.45 d '= 0.67 I2min = 0.69 normalized resist threshold I _c is, a' = k × a + I 1 <I c a "= k × a + I 0 <I c b '= k × b + I 1 <I c pattern since the periphery of the other I do not want to leave a pattern c '= k × c + I 0> I c I2min = k × 1 + I 1> do not have to be I _c, 0.34 <Ic and 0.45 <Ic where I2min = k × 1 + I ₁ is the peripheral intensity distribution of the normal pattern I _s
In this case, I _s = 1 in I 2 min = k × I _s . Intensity distribution I _s of the peripheral portion of the normal pattern (gate pattern) is equivalent to 1, d, c, etc. in FIG. 25 (B).

Illumination condition 2 The exposure of the periodic pattern is σ = 0.
3. For normal pattern exposure, σ = 0.6 I ₀ = 0.80 I ₁ = 0.23 a = 0.04 b = 0.26 c = 0.23 d = 0.58 When k = 2.0 a ′ = 0.31 a ″ = 0.88 b ′ = 0.75 c ′ = 1.26 d '
= 1.96 I2min = 2.23, and the result is normalized by dividing by (k × 1 + 1) so that the peripheral intensity becomes 1 as follows.

A '= 0.10 a "= 0.29 b' = 0.25 c '
= 0.42 d '= 0.65 I2min = 0.74 normalized resist threshold I _c is, 0.29 <I _c and 0.42> I _c illumination condition 3 exposed periodic pattern is sigma = 0.3, usually pattern exposure σ = 0.8 I ₀ = 0.80 I ₁ = 0.23 a = 0.05 b = 0.26 c = 0.27 d = 0.59 When k = 2.5 a '= 0.36 a "= 0.93 b' = 0.88 c '= 1.48 d'
= 2.28 I2min = 2.73, and normalization by dividing by (k × 1 + 1) so that the surrounding intensity is 1 is as follows.

A '= 0.10 a "= 0.26 b' = 0.25 c '
= 0.42 d '= 0.65 I2min = 0.78 normalized resist threshold I _c is, 0.26 <I _c <0.42 illumination condition 4 exposed periodic pattern is sigma = 0.3, usually pattern exposure and annular illumination with sigma = 0.8, Inside (inside the ring zone)
The illuminance distribution with σ = 0.6 or less was set to zero.

I ₀ = 0.80 I ₁ = 0.23 a = 0.06 b = 0.26 c = 0.35 d = 0.62 When k = 3.0 a ′ = 0.41 a ″ = 0.98 b ′ = 1.01 c ′ = 1.85 d ′
= 2.66 I2min = 3.23, and normalization by dividing by (k × 1 + 1) so that the peripheral intensity is 1 is as follows.

A '= 0.10 a "= 0.25 b' = 0.25 c '
= 'Is = 0.67 I2min = 0.81 normalized resist threshold I _c, 0.25 <when I _c <0.46 normalized resist threshold is in the range of the, a' 0.46 d, a " , b ' of the The intensity of the normalized exposure distribution is smaller than the threshold, and c ′, d ′, and I2min are larger than the threshold.

Since a portion where the exposure amount is smaller than the resist threshold value remains due to the development, only the exposure amount distribution of a ', a ", and b' remains after development as a pattern. The shaded portion at the bottom is the shape after development.

The intensity distribution shown in the embodiment is standardized on the assumption that the amount of light incident on the reticle is equal to the amount of light emitted on the wafer surface. The light amount ratio shown here is calculated based on this intensity distribution, and the optimum light amount ratio is near the light amount ratio described under each illumination condition.

Actually, the amount of light incident on the reticle is not equal to the amount of light emitted on the wafer surface. For example, the ratio between the amount of incident light and the amount of emitted light changes depending on differences in the reticle, illumination conditions, and other conditions. Strictly speaking, the optimum light intensity ratio may be different, but the optimum light intensity ratio can be obtained from the above-described formula from the respective intensity distributions of the normal exposure and the periodic pattern exposure that provides a high contrast.

That is, by adjusting the respective exposure amounts, an optimum light amount ratio is obtained, and the exposure amount distribution of the composite image satisfies the magnitude relationship in the above-described calculation formula with the resist threshold value. Things are important.
The exposure distribution changes depending on the illumination conditions as described in the embodiment, and also changes depending on the size of the pattern.

The actual resist threshold value is obtained by proportionally multiplying the normalized resist threshold value. The synthesized image and the actual exposure dose distribution in each exposure are also obtained by the standardized exposure dose. The distribution is proportionally multiplied.

The actual exposure amount distribution is adjusted so that the integrated exposure amount becomes an appropriate exposure amount while maintaining the optimum light amount ratio of the multiple exposure according to the actual resist threshold value.

In other words, the pattern shape after development is determined by the magnitude relationship between the actual integrated exposure amount distribution and the actual resist threshold value. Is left, the pattern is obtained by adjusting the exposure amount distribution of the portion to be left as a pattern so that the exposure amount is smaller than the resist threshold value.

In general, when exposing a normal exposure pattern, an exposure amount that is about twice as large as that for exposing a periodic pattern is appropriate.
There is an optimum exposure amount ratio depending on a combination of illumination conditions when exposing the periodic pattern, and it can be obtained by the above-described formula.

As a result of calculating various combinations of the lighting conditions from the above-mentioned formula, the following was shown. In the case of periodic pattern exposure, σ = 0.3 and the illumination condition σ of normal pattern exposure
Is smaller than 0.8, the exposure amount when exposing a normal pattern is 2 times larger than the exposure amount when exposing a periodic pattern.
It is good to make it twice or less.

In the case of a periodic pattern, when σ = 0.3 and the illumination condition for exposing the normal pattern is annular illumination, when the width of the annular zone is small, the exposure amount for exposing the normal pattern exposes the periodic pattern. It is preferable that the exposure amount is twice or more than the exposure amount at that time.

Illumination condition σ when exposing periodic pattern
Is smaller than 0.3, the exposure amount for exposing the normal pattern should be at least twice the exposure amount for exposing the periodic pattern.

FIG. 20 is a schematic view showing an example of an exposure apparatus for two-beam interference exposure according to the present invention.
Reference numeral 201 denotes an optical system for two-beam interference exposure.
This is the same as the optical system No. 5. 202 is a KrF or ArF excimer laser, 203 is a half mirror, 204 (20
4a, 204b) are plane mirrors, 205 is an optical system 201
Observing the two-beam interference alignment mark on the wafer 206 with an off-axis type alignment optical system in which the positional relationship with is fixed or can be appropriately detected as a baseline (amount),
The position is detected. 206 is a wafer which is a photosensitive substrate,
Reference numeral 207 denotes a plane orthogonal to the optical axis of the optical system 201 and an XYZ stage movable in the optical axis direction. The position of the XYZ stage is accurately controlled using a laser interferometer or the like. Since the configurations and functions of the apparatus 205 and the XYZ stage 207 are well known, a specific description is omitted.

FIG. 21 is a schematic view showing a high-resolution exposure apparatus comprising the two-beam interference exposure apparatus of the present invention and a normal projection exposure apparatus.

In FIG. 21, reference numeral 212 denotes a two-beam interference exposure apparatus including the optical system 201 and the apparatus 205 shown in FIG. 20, and 213 denotes an illumination optical system (not shown), a reticle positioning optical system 214, and a wafer positioning optical system. (Off-Axis Positioning Optical System) A projection optical system 216 for reducing and projecting the circuit pattern of the mask 215 and the mask 215 onto the wafer 218.
This is a normal projection exposure apparatus including:

The reticle positioning optical system 214 observes the positioning mark on the mask 215 and detects the position. The wafer alignment optical system 217 observes an alignment mark for projection exposure or dual light beam interference on the wafer 206 and detects its position. Optical systems 214 and 21
6, 217, the configuration and function of which are well-known, and thus a detailed description is omitted.

In FIG. 21, reference numeral 219 denotes a two-beam interference exposure apparatus 2
12 is one XYZ stage shared by the projection exposure apparatus 213, and this stage 219
A plane orthogonal to each optical axis 13 and the optical axis can be moved in the optical axis direction, and its position in the XY directions is accurately controlled using a laser interferometer or the like.

Stage 219 holding wafer 218
21 is sent to the position (1) in FIG. 21 and the position is accurately measured. Based on the measurement result, the light is sent to the exposure position of the device 212 indicated by the position (2) and the two-beam interference exposure is performed on the wafer 218. The device 213 is then fed into position (3) and its position is accurately measured and indicated by position (4).
And the wafer 218 is subjected to projection exposure.

In the apparatus 213, instead of the off-axis alignment optical system 217, a TTL alignment optical system (not shown) for observing the alignment mark of the wafer 218 via the projection optical system 216 and detecting the position is detected. System and
A TTR alignment optical system (not shown) for observing an alignment mark on the wafer 218 via the projection optical system 216 and the mask (reticle) 215 and detecting the position can also be used.

FIG. 22 is a schematic view showing a high-resolution exposure apparatus according to the present invention which can perform both two-beam interference exposure and normal projection exposure.

In FIG. 22, 221 denotes KrF or Ar
F excimer laser, 222 is an illumination optical system, 223 is a mask (reticle), 224 is a mask stage, 227 is a projection optical system for reducing and projecting the circuit pattern of the mask 223 onto the wafer 228, and 225 is a mask (reticle) changer. To selectively supply a normal reticle and the aforementioned Levenson phase shift mask (reticle), edge shifter type mask (reticle), or periodic pattern mask (reticle) having no phase shifter to the stage 224. It is provided.

The mask stage has a function of rotating the mask based on information previously drawn on a bar code or the like in order to make the direction of the fine pattern parallel to the direction of the periodic pattern. .

Reference numeral 229 in FIG. 22 denotes one XYZ stage shared by the two-beam interference exposure and the projection exposure. The stage 229 is movable in a plane orthogonal to the optical axis of the optical system 227 and in the optical axis direction. The position in the XY directions is accurately controlled using a laser interferometer or the like.

The apparatus shown in FIG. 22 includes a reticle positioning optical system (not shown) and a wafer positioning optical system (off-axis positioning optical system, TTL positioning optical system, and TTR positioning optical system described with reference to FIG. 21). And

The illumination optical system 222 of the exposure apparatus shown in FIG. 22 is configured to be able to switch between partially coherent illumination and coherent illumination. In the case of coherent illumination, the above-described (1a) or (1a) shown in the block 230 is used. (1b)
Is supplied to one of the above-mentioned Levenson-type phase shift reticles or edge shifter-type reticles or one of the periodic pattern reticles having no phase shifter, and in the case of partial coherent illumination, is illustrated in block 230 (2a). ) Is supplied to a desired reticle. Switching from partial coherent illumination to coherent illumination or annular illumination is performed by using an aperture stop, which is usually placed immediately after the fly-eye lens of the optical system 222, with a coherent illumination stop having an aperture diameter sufficiently smaller than the aperture stop. Just replace it.

The exposure method and exposure apparatus of the present invention
When the second exposure is a projection exposure, the exposure wavelength of the first exposure and the second exposure in the double exposure is 400 nm or less, and preferably 250 nm or less. 250n
In order to obtain light having an exposure wavelength of less than m, a KJrF excimer laser (about 248 nm) or an ArF excimer laser (about 193 nm) is used.
nm).

In the present invention, the term "projection exposure" refers to exposure in which three or more parallel light beams from an arbitrary pattern formed on a mask are incident on an image plane at various angles different from each other. Things.

The exposure apparatus of the present invention has a projection optical system for projecting a mask pattern onto a wafer, and a mask illumination optical system capable of performing both partial coherent illumination and coherent illumination. By performing normal exposure and performing two-beam interference exposure by coherent illumination, it is characterized by periodic pattern exposure.
“Partial coherent illumination” is illumination in which the value of σ = (numerical aperture of the illumination optical system / numerical aperture of the projection optical system) is greater than zero and less than 1, and “coherent illumination” means that the value of σ is zero. Or a value close thereto, which is considerably smaller than σ of the partially coherent illumination.

In coherent illumination in periodic pattern exposure, σ is set to 0.3 or less. Partial coherent illumination during normal exposure makes σ 0.6 or more. σ = 0.8 is desirable. Furthermore, it is still more effective to use annular illumination in which the illuminance distribution is lower on the inside than on the outside.

The exposure wavelength of this exposure apparatus is 400 nm or less, preferably 250 nm or less. 250n
In order to obtain light having an exposure wavelength of less than m, a KrF excimer laser (about 248 nm) or an ArF excimer laser (about 193 nm)
m).

In the embodiments of the present invention, an optical system which can switch between partially coherent illumination and coherent illumination is disclosed as a mask illumination optical system.

The exposure apparatus of the present invention has a two-beam interference exposure apparatus and a moving stage for holding a substrate to be exposed (photosensitive substrate), which is shared by both apparatuses.

The exposure wavelength of this exposure apparatus is also 400 nm or less, preferably 250 nm or less. 250n
In order to obtain light having an exposure wavelength of less than m, a KrF excimer laser (about 248 nm) or an ArF excimer laser (about 193 n) is used.
m).

Using the above-described exposure method and exposure apparatus, various devices such as semiconductor chips such as ICs and LSIs, display elements such as liquid crystal panels, detection elements such as magnetic heads, and image pickup elements such as CCDs can be manufactured. .

The present invention is not limited to the embodiments described above, and can be variously modified without departing from the gist of the present invention. In particular, the number of exposures and the number of exposure steps in each step of the two-beam interference exposure and the normal exposure can be appropriately selected, and the exposure can be appropriately adjusted such that the exposure is superimposed and shifted. By performing such an adjustment, variations in circuit patterns that can be formed increase.

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

FIG. 23 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.

On the other hand, in step 3 (wafer manufacturing), 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 produced 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. 24 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 (developing), 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.

[0186]

As described above, the present invention provides (a-1) periodic pattern exposure represented by two-beam interference exposure and normal pattern exposure not including the periodic pattern (normal exposure)
An exposure method and an exposure apparatus capable of forming a circuit pattern having a complicated shape on a wafer by using the two exposure methods.

(A-2) An exposure method and an exposure apparatus capable of easily obtaining a circuit pattern having a portion having a line width of 0.15 μm or less.

(A-3) An exposure apparatus capable of performing two exposure methods, periodic pattern exposure and normal exposure. Can be achieved.

In particular, according to the present invention, (a-4) a complex pattern having a fine line width of, for example, 0.15 μm or less can be obtained by fusing two-beam interference exposure with ordinary exposure.

[Brief description of the drawings]

FIG. 1 is a flowchart of an exposure method according to the present invention.

FIG. 2 is an explanatory view showing an exposure pattern by two-beam interference exposure.

FIG. 3 is an explanatory diagram showing exposure sensitivity characteristics of a resist.

FIG. 4 is an explanatory view showing pattern formation by development.

FIG. 5 is an explanatory view showing an exposure pattern by ordinary two-beam interference exposure.

FIG. 6 is an explanatory view showing an exposure pattern by two-beam interference exposure in the present invention.

FIG. 7 is an explanatory view showing an example of an exposure pattern (lithography pattern) that can be formed in the first embodiment of the present invention.

FIG. 8 is an explanatory view showing another example of an exposure pattern (lithography pattern) that can be formed in the first embodiment of the present invention.

FIG. 9 is an explanatory view showing another example of an exposure pattern (lithography pattern) that can be formed in the first embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a gate pattern according to a second embodiment of the present invention.

FIG. 11 is an explanatory view showing a second embodiment of the present invention.

FIG. 12 illustrates a gate pattern.

FIG. 13 is an explanatory diagram of a formed gate pattern.

FIG. 14 is an explanatory diagram of a formed gate pattern.

FIG. 15 is a schematic view showing an example of a conventional two-beam interference exposure apparatus.

FIG. 16 is a schematic diagram illustrating an example of a projection exposure apparatus that performs two-beam interference exposure.

FIG. 17 is an explanatory view showing an example of a mask and an illumination method used in the apparatus of FIG.

FIG. 18 is an explanatory view showing another example of a mask and an illumination method used in the apparatus in FIG. 16;

FIG. 19 is a schematic view showing a conventional projection exposure apparatus.

FIG. 20 is a schematic view showing an example of a two-beam interference exposure apparatus of the present invention.

FIG. 21 is a schematic view showing an example of a high-resolution exposure apparatus of the present invention.

FIG. 22 is a schematic view showing an example of a high-resolution exposure apparatus of the present invention.

FIG. 23 is a flowchart of a device manufacturing method of the present invention.

FIG. 24 is a flowchart of a device manufacturing method of the present invention.

FIG. 25 is an explanatory diagram of Embodiment 3 of the present invention.

FIG. 26 is an explanatory diagram of a formed gate pattern.

FIG. 27 is an explanatory diagram of a formed gate pattern.

[Explanation of symbols]

221 Excimer laser 222 Illumination optical system 223 Mask (reticle) 224 Mask (reticle) stage 225 2 Light flux interference mask and mask for normal projection exposure 226 Mask (reticle) changer 227 Projection optical system 228 Wafer 229 XYZ stage

Claims (16)

[Claims] 1. An exposure method for performing double exposure of a periodic pattern exposure and a different pattern exposure on a substrate to be exposed, wherein a maximum value of a light intensity distribution of the periodic pattern is I ₀ , a minimum value is I ₁ , The intensity value at the center position of the pattern having the minimum line width in the light intensity distribution of the pattern exposure is represented by b, and the intensity value at the center position of the pattern having the minimum line width and the other pattern having the minimum line width are represented by c. When the exposure threshold value of the resist provided on the exposure substrate is appropriately set to I _c , and the light amount ratio between the periodic pattern exposure and the pattern exposure 1: k is appropriately set, when the resist is a negative type, k × b + I ₀ > I _c k × c + I ₁ <I _{c When the} resist is of a positive type, a periodic pattern exposure having a light intensity distribution such that k × b + I ₁ <I _c k × c + I ₀ > I _c ;
An exposure method, wherein a pattern exposure and a light amount ratio k are set. 2. An exposure method for performing a double exposure of a pattern exposure and a periodic pattern exposure on a substrate to be exposed, wherein a part of the pattern extends over one or more of the periodic patterns, and the light intensity distribution of the periodic pattern is The maximum value is I ₀ , the minimum value is I ₁ , the intensity value of a part of the pattern in the light intensity distribution of the pattern exposure is a, and the photosensitive threshold value of the resist provided on the substrate to be exposed is I _c. When the light intensity ratio between the periodic pattern exposure and the pattern exposure is set to 1: k, and the intensity of the resist pattern forming portion is negative, k × a + I ₀ > I _c k × a + I ₁ > I _c When the resist is of a positive type, periodic pattern exposure having a light intensity distribution such that k × a + I ₁ <I _c k × a + I ₀ <I _c ;
An exposure method, wherein a pattern exposure and a light amount ratio k are set. 3. An exposure method for performing double exposure of a periodic pattern exposure and a different pattern exposure on a substrate to be exposed, wherein a part of the pattern extends over one or more of the periodic patterns. The maximum value of the light intensity distribution is I ₀ , the minimum value is I _1, and among the light intensity distributions of the pattern exposure, the light intensity distribution at the periphery of the pattern is I _s , and the sensitivity of the resist provided on the substrate to be exposed is increased. When the threshold value is I _c and the light amount ratio between the periodic pattern exposure and the pattern exposure is 1: k,
If the strength of the formed parts not resist pattern resist is a negative type, if _{k × I s + I 0 <} I c resist of a positive type, such that _{k × I s + I 1 <} I c, and the light intensity distribution Periodic pattern exposure,
An exposure method, wherein a pattern exposure and a light amount ratio k are set. 4. The exposure method according to claim 1, wherein an illumination method is changed between the periodic pattern exposure and the pattern exposure. 5. The exposure method according to claim 1, wherein an exposure amount is changed for each exposure so that a light amount ratio between the periodic pattern exposure and the pattern exposure becomes 1: k. 6. The exposure method according to claim 4, wherein in the periodic pattern exposure, σ is set to 0.3 or less. 7. The exposure method according to claim 4, wherein in the pattern exposure, σ is set to 0.6 or more. 8. The exposure method according to claim 4, wherein in the pattern exposure, the annular illumination is lower inside the illuminance distribution than outside. 9. The exposure method according to claim 5, wherein the amount of exposure in pattern exposure is about twice as large as that in exposure of a periodic pattern. 10. When the periodic pattern exposure is .sigma. = 0.3 and the .sigma. Of the pattern exposure is smaller than 0.8, the exposure amount of the pattern exposure is set to twice or less than the exposure amount of the periodic pattern exposure. 6. The exposure method according to claim 5, wherein 11. When the periodic pattern exposure is σ = 0.3 and the pattern exposure is annular illumination, when the width of the annular zone is small, the exposure amount for exposing the pattern is the exposure amount for exposing the periodic pattern. 6. The exposure method according to claim 5, wherein the amount is at least twice the amount. 12. When σ of the illumination condition 1 for periodic pattern exposure is smaller than 0.3, the exposure amount for exposing the pattern is at least twice as large as the exposure amount for exposing the periodic pattern. The exposure method according to claim 5, wherein 13. The exposure method according to claim 1, wherein, when exposing the periodic pattern, the exposure is performed so that the periodic pattern is rotated so as to be parallel to the direction of the fine pattern. 14. An exposure apparatus, wherein a pattern on a mask is transferred to a photosensitive substrate using the exposure method according to claim 1. Description: 15. After the pattern on the mask surface is exposed on the wafer surface by using the exposure method according to claim 1, a device is manufactured through the developing process of the wafer. A method for manufacturing a device, comprising: 16. A device according to claim 14, wherein after the pattern on the mask surface is exposed on the wafer surface using the exposure apparatus according to claim 14, the wafer is subjected to a developing process to produce a device. Production method.