JP2001297976A - Method of exposure and aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method of exposure and an aligner by which a high- resolution pattern can be formed in an arbitrary shape by double exposure consisting of exposure of periodic patterns and normal pattern exposure. SOLUTION: Several mask patterns having different patterns are composed by an optical composition member and the same region on a wafer surface is scanned and exposed through the several mask patterns in sequence or simultaneously and in the same way by a projection optical system with synchronism between the several mask patterns and the wafer.

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. 24 shows a schematic view of a conventional projection exposure apparatus. In FIG. 24, 191 is an excimer laser as a light source for exposure to far ultraviolet rays, 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
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. 24, 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 the exposure wavelength, and NA is the 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 from the equations (1) and (2) 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, with 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.

On the other hand, in JP-A-6-20916,
Without using a photomask having a two-layer structure using both the phase shifter film and the light shielding film, two separate photos having only a single-layer pattern of one of the phase shifter film and the light shielding film are used. A projection exposure method and a projection exposure apparatus that can achieve the same effect as the phase shift method using a mask are disclosed.

As a specific configuration of the projection exposure apparatus proposed in the publication, a light source for generating light having a coherent component and a one-layer structure of one of a phase shifter film and a light-shielding film are provided. First and second having a pattern of
Individual photomask elements, mounting the substrate at a predetermined position, means for positioning, with light from the light source,
Optical means for projecting the pattern of the first photomask element and the pattern of the second photomask element onto the substrate so that a combined pattern of both patterns is formed on the substrate; A first portion of the light for projecting a pattern of a photomask element onto the substrate;
So that the second part of the light that projects the pattern of the photomask element onto the substrate has a predetermined phase difference,
A phase control unit for controlling a phase of at least one of the first light portion and the second light portion.

[0019]

The above-mentioned U.S. Pat.
In the multiple exposure method disclosed in Japanese Patent No. 5835, since a wafer is placed in an exposure apparatus for two-beam interference exposure, exposure is performed, and then the wafer is replaced in another exposure apparatus for normal exposure to perform exposure. There was a problem that it took. In addition, Japanese Unexamined Patent Publication
The exposure apparatus proposed in Japanese Patent No. 20916 needs to provide a phase control means in one optical path, and the apparatus tends to be complicated.

An object of the present invention is to provide an exposure method and an exposure apparatus capable of easily performing multiple exposures in a relatively short time.

According to the present invention, two exposures, a periodic pattern exposure typified by two-beam interference exposure and a normal pattern exposure (normal exposure) not including the periodic pattern, are simultaneously performed in the same area on the surface of the photosensitive substrate (wafer). Accordingly, an object of the present invention is to provide an exposure method and an exposure apparatus capable of forming a circuit pattern on a wafer with high throughput.

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.

It is another object of the present invention to provide an exposure method and an exposure apparatus capable of simultaneously performing two exposure methods of periodic pattern exposure and normal exposure using different illumination methods.

In addition, according to the present invention, a plurality of masks having different patterns formed thereon are illuminated under different optimum illumination conditions, and a pattern based on the plurality of masks is synthesized by a light synthesizing means to form the same pattern on the wafer surface. It is an object of the present invention to provide an exposure apparatus capable of transferring a finer pattern by simultaneously projecting and exposing regions, and capable of manufacturing a device with a high degree of integration at a high throughput, and a method of manufacturing a device using the same. I do.

[0025]

According to an exposure method of the present invention, a plurality of mask patterns having different patterns are synthesized by a photosynthesis member, and the same area on a wafer surface is sequentially or simultaneously projected by a projection optical system. It is characterized in that the plurality of mask patterns and the wafer are scanned and exposed in synchronization with each other and are exposed by projection.

A second aspect of the present invention is characterized in that, in the first aspect of the present invention, the plurality of different mask patterns are formed on separate substrates.

According to a third aspect of the present invention, in the first aspect of the present invention, the different mask patterns are formed on a common substrate.

According to a fourth aspect of the present invention, in the first aspect of the present invention, one of the plurality of different mask patterns is provided.
One is characterized by a line and space pattern.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the plurality of different mask patterns are illuminated by a plurality of illumination systems having different illumination conditions.

According to a sixth aspect of the present invention, in the first aspect of the present invention, two mask patterns forming the plurality of mask patterns are simultaneously scanned in mutually opposite directions.

According to a seventh aspect of the present invention, in the first aspect, the illumination condition is coherent illumination or partial coherent illumination.

An eighth aspect of the present invention is characterized in that, in the first aspect of the present invention, the illumination condition is σ (sigma).

In a ninth aspect of the present invention, in the first aspect, the illumination condition is NA (numerical aperture).

According to a tenth aspect, in the first aspect, the illumination condition is an incident angle of illumination light.

According to an eleventh aspect of the present invention, there is provided an exposure apparatus having the exposure method according to any one of the first to tenth aspects as an exposure mode.

According to a twelfth aspect of the invention, an exposure apparatus of the step-and-repeat reduction projection type has the exposure method according to any one of the first to tenth aspects as an exposure mode.

According to a thirteenth aspect of the present invention, an exposure apparatus of the step-and-scan reduction projection type has the exposure method according to any one of the first to tenth aspects as an exposure mode.

According to a fourteenth aspect of the present invention, there is provided a method of manufacturing a device, comprising the steps of exposing a wafer to a device pattern using the exposure apparatus of the eleventh, twelfth, or thirteenth aspect and developing the exposed wafer. And

[0039]

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.

FIG. 1 shows that both the two-beam interference exposure using the first illumination system and the normal projection exposure using the second illumination system are the same on the surface of the wafer 228 by the projection optical system 227 via the beam splitter 226. 1 shows a high-resolution exposure apparatus that simultaneously multiple-exposes an area.

The mask 1 is, for example, an FM mask. A periodic pattern without a phase shifter, a Levenson phase shift mask, an edge shifter type mask (fine pattern) and the like are formed on the mask 1 as described later. ing.

The mask 2 is, for example, an RM mask, on which a circuit pattern (normal pattern) is formed as described later, and is mounted on the mask stage 2. Note that the masks 1 and 2 may be mounted on a common mask stage instead of the independent mask stages 1 and 2.

The first illumination system and the second illumination system are, for example, KrF
A laser or an ArF laser is used as a light source. As will be described later, a first illumination system is coherent illumination, and a second illumination system is partially coherent illumination. Illuminates the area. Note that the illumination ranges of the first illumination system and the second illumination system may be different depending on the mask.

An equal-magnification image-forming optical system is formed in the optical path of the mask 1, and the projected image of the mask 1 is inverted to form a projection optical system 227.
Is incident on.

Reference numeral 240 denotes a mask stage guide. The mask is a projection optical system, and the patterns of the masks 1 and 2 are combined by using mirrors (241, 242, 243), the two optical paths are combined by a beam splitter-226, and the patterns are superimposed to form the same area on the surface of the wafer 228. Projection exposure. In this way, multiple exposures (double exposures) of different patterns on the same area on the wafer surface are performed without passing through the developing process.

Reference numeral 229 denotes an XYZ stage. This stage 229 is movable in a plane perpendicular to the optical axis of the optical system 227 and in the direction of the optical axis, and its position in the XY direction can be accurately determined using a laser interferometer or the like. Controlled.

The apparatus shown in FIG. 1 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). Note that the beam splitter-226 may be a polarization beam splitter, and the masks 1 and 2 may be illuminated by changing the polarization state of the light beams from the first illumination system and the second illumination system, respectively. The number of illumination systems is not limited to two, and three or more illumination systems may be provided, and masks on which different patterns are formed may be illuminated under different illumination conditions to perform multiple exposure on the wafer 228 surface.
Further, the exposure of the pattern of the mask 1 and the mask 2 onto the surface of the wafer 228 may be selectively performed by using a shutter in one optical path.

FIG. 2 is an explanatory diagram of the FM mask of the mask 1, and FIG. 3 is an explanatory diagram of the RM mask of the mask 2.

The FM mask shown in FIG. 2 is composed of a periodic pattern FMP in which fine patterns that cannot be resolved by ordinary projection exposure are periodically arranged. R shown in FIG.
The M mask is composed of a normal circuit pattern (eg, a gate pattern) RMP having a line width that can be resolved by projection exposure. 2 and 3 show cross sections of each mask, and show a case where the FM pattern in FIG. 2 is formed of a phase type pattern.

The projection pattern image F of the FM mask and the projection pattern image R of the RM mask are overlapped by the beam splitter-226, and the same area on the surface of the photosensitive substrate (wafer) 228 is subjected to step exposure or scan exposure, and multiple exposure. (Double exposure). In the case of scan exposure, the mask stage 1 on which the FM mask is mounted, the mask stage 2 on which the RM mask is mounted, and the wafer stage 229 are synchronized with each other to correspond to the magnification ratio of the projection optical system. Scan (move) in the direction perpendicular to the optical axis 227a of the system 227
are doing. At this time, it is preferable to provide an optical attenuator in at least one of the optical paths so that the scanning speeds of the two masks 1 and 2 are the same and the exposure amount is the same.

An image rotator composed of a prism is inserted in place of the equal-magnification optical system for entering the light that has passed through the mask 1 shown in FIG. 1, and a parallel flat plate having the same optical path length as the image rotator is inserted in the optical path of the mask 2. The projection optical system 227 can be configured so that the best imaging performance can be obtained in the inserted state.

When the pattern of one of the two masks is symmetric with respect to the scanning direction, the mask stage having the symmetric pattern is opposed to the scanning direction of the other mask stage. According to this, the stage driving reaction force is canceled, no vibration occurs, and high-speed, high-precision scanning can be performed.

The exposure wavelength in the multiple exposure in the exposure method and the exposure apparatus of the present invention is 400 nm or less, preferably 250 nm or less. To obtain light having an exposure wavelength of 250 nm or less, use a KrF excimer laser (about 248 nm).
m) or an ArF excimer laser (about 193 nm).

In the present invention, "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 includes a projection optical system for projecting a mask pattern onto a wafer, and a mask (RM mask) 2.
And a first illumination system for coherently illuminating the mask (FM mask) 1, and performing exposure of the normal pattern of the FM mask on the surface of the wafer 228 by partial coherent illumination. By performing two-beam interference exposure with coherent illumination,
It is characterized in that periodic pattern exposure of the RM mask is performed simultaneously. “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.

FIGS. 4 and 5 show an embodiment of the present invention.
FIG. 2 is an explanatory diagram of an optical system of coherent illumination and partial coherent illumination of a first illumination system and a second illumination system. Each of the illumination systems forms a secondary light source and uses a light beam therefrom.
Of these, the first illumination system in FIG. 4 shows a part of the light beam that coherently illuminates the FM mask. Second in FIG.
In the illumination system, a part of the light beam that partially coherently illuminates the RM mask is shown.

In FIG. 4 and FIG. 5, reference numeral 50 denotes light source means for guiding exposure light to the fly-eye lens 51. Fly-eye lens (optical integrator) 51
Has a plurality of secondary light sources formed on its exit surface. FIG.
In FIG. 5, the fly-eye lens 51 uses light beams from a plurality of fly-eye lenses 51a in a central region, and FIG. 5 uses light beams from a plurality of fly-eye lenses 51b in a peripheral region. A light beam from the secondary light source on the exit surface of the fly-eye lens 51a (51b) passes through the stop 52, and is condensed on the surface of the stop 54 by the condenser lens 53.

Reference numeral 55 denotes a condenser lens, which illuminates the FM mask (RM mask) of the mask M with a light beam passing through the openings 54a (54b) of the diaphragm 54. Here, FIG. 4 constitutes a small σ illumination system, and FIG. 5 constitutes a large σ (ring zone) illumination system.

In the first illumination system and the second illumination system shown in FIGS. 4 and 5, a light amount adjusting means (ND filter or the like) for adjusting the illumination intensity of the FM mask and the RM mask is provided in one optical path. Is good.

FIG. 6 is an explanatory diagram showing the relationship between the effective light source and the mask in the illumination system shown in FIGS. FIG. 6A shows the case of the small σ illumination system of FIG. 4, and FIG. 6B shows the case of the large σ illumination system of FIG.

The projected state of the pattern of the FM mask illuminated by the illumination system of FIG. 4 will be described with reference to FIGS.

In FIG. 7, reference numeral 161 denotes a mask; 162, object-side exposure light exiting from the mask 161 and entering the optical system 163;
Reference numeral 163 denotes a projection optical system, 164 denotes an aperture stop, 165 denotes an image-side exposure light emitted from the projection optical system 163 and incident on the wafer 166, 166 denotes a wafer serving as a photosensitive substrate, and 167 corresponds to a circular aperture of the stop 164. FIG. 5 is an explanatory diagram showing a position of a light beam on a pupil plane by a pair of black dots. FIG. 7 is a schematic view showing a state where the two-beam interference exposure is being performed.
And the image side exposure light 165, unlike normal projection exposure, consist of only two parallel light beams.

In order to perform two-beam interference exposure (periodic pattern exposure) in a normal projection exposure apparatus as shown in FIG. 7, the mask 161 and its illumination method may be set as shown in FIG. 8 or FIG. Hereinafter, these three examples will be described.

FIG. 8A shows a Levenson-type phase shift mask 173, in which a light shielding portion 171 made of chrome is used.
The pitch P ₀ of the phase shifter 172 is 0 in the expression (a1), and the pitch P _0S of the phase shifter 172 is the mask expressed in the expression (a2).

P ₀ = MP = 2MR = Mλ / (2NA) ‥‥‥ (a1) P _0S = 2P ₀ = Mλ / (NA) ‥‥‥ (a2) where M is the projection magnification of the projection optical system 163. , 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, the mask 174 shown in FIG. 8B is a shifter edge type phase shift mask made of chromium without a light-shielding portion, and is the same as the Levenson type.
_Is configured to satisfy the above equation (a2).

In order to perform two-beam interference exposure using the phase shift masks of FIGS. 8A and 8B, these masks are subjected to so-called coherent illumination with σ = 0 (or a value close to 0). Specifically, as shown in FIG. 8, the mask 170 is irradiated with a parallel light beam from a direction perpendicular to the mask surface 170 (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 zero-order transmitted diffracted light exiting in the vertical direction from the mask 170, since the phase difference between adjacent transmitted lights becomes π. The two parallel light beams of ± 1st-order transmitted diffracted light are generated from the mask 170 symmetrically with respect to the optical axis of the projection optical system 163, and the two object-side exposures 165 in FIG. I do. The second-order or higher-order diffracted light passes through the aperture stop 16 of the projection optical system 163.
Since the light does not enter the aperture No. 4, it does not contribute to the image formation.

The mask 180 shown in FIG. 9 is a mask in which the pitch P ₀ of the light shielding portions 181 made of chrome is represented by the following equation (a3) similar to the equation (a1).

P ₀ = MP = 2MR = Mλ / (2NA) ‥‥‥ (a3) where M is the projection magnification of the projection optical system 163, λ is the exposure wavelength, and NA is the aperture on the image side of the projection optical system 163. Indicates a number.

The mask without the phase shifter shown in FIG. 9 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 so as to satisfy the expression (a4). 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.

Sin θ ₀ = M / NA ‥‥‥ (a4) Here, M is the projection magnification of the projection optical system 163, and NA is the image-side numerical aperture of the projection optical system 163.

When a mask having no phase shifter shown in FIG. 9 is subjected to oblique incidence illumination with a parallel light beam satisfying the above equation (a4), 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 by one or two parallel light beams is also treated as "coherent illumination".

The technique for performing two-beam interference exposure using a normal projection exposure apparatus has been described above, and the illumination optical system of the normal projection exposure apparatus is configured as described above. The projection exposure apparatus can be configured to perform substantially coherent illumination, for example, by replacing an aperture stop (not shown) corresponding to <σ <1 with a special aperture stop corresponding to σ ≒ 0.

FIG. 10 is a schematic view of a main part when the exposure apparatus of FIG. 1 is used as a scanning type exposure apparatus. In the figure, the mask 1 (mask 2) mounted on the mask stage 1 (mask stage 2) is moved as shown by an arrow using a linear motor actuator 32 and a linear motor stator 33 to move the mask 1 on the wafer surface. A mechanism for simultaneously scanning and exposing the same area with the patterns of the mask 1 and the mask 2 is shown.

In the scanning exposure apparatus of the present embodiment,
Double exposure is simultaneously performed with two masks, and the two masks are mounted on respective mask stages having substantially the same mass. Then, the scanning movement directions are opposed to each other, and one mask 2 and the wafer are in a projection relationship via a projection optical system.
The other mask 1 is a mask that is symmetrical in the scanning direction, such as a repetitive pattern.

If the two masks 1 and 2 are mounted on the respective mask stages 1 and 2 and are symmetrical in the scanning direction such as a repetitive pattern, driving in the opposite direction cancels the driving reaction force, and the high acceleration Since vibration does not occur even when driven, high speed and high accuracy can be achieved. Further, when the original is not symmetrical in the scanning direction, driving in the same direction increases the degree of freedom of the original.

As described above, in the present embodiment, it is possible to transfer a fine pattern using two masks.

FIG. 11 is a schematic view of a main part of the second embodiment of the present invention. This embodiment is different from the first embodiment in FIG.
The difference is that the optical axes 1a and 2a of the illumination system and the second illumination system are arranged so as to be substantially orthogonal to the optical axis 227a of the projection optical system mask, and the other configurations are the same.

In this embodiment, the patterns of the mask 1 and the mask 2 are combined by the beam splitter 226, and the same area on the surface of the wafer 228 is subjected to multiple exposure by the projection lens 227. Also, when performing scanning exposure, the mask stage 1,
2 is moved in a direction parallel to the optical axis 227a of the projection optical system 227.

FIG. 12 is a schematic view of a main part of a third embodiment of the present invention. This embodiment is different from the second embodiment in FIG. 11 in that a reflective mask is used as one of the masks, and the other configuration is the same.

The reflection type mask 1 is arranged at an angle of 45 degrees with respect to the optical axis 227a of the projection optical system 227. The light beam from the reflective mask 1 illuminated with the light beam from the first illumination system is combined with the light beam from the pattern of the mask 2 by the beam splitter 226 via the relay system 245 for correcting the optical path length.

The pattern of the reflective mask 1 and the pattern of the mask 2 are subjected to multiple exposure on the same area of the wafer 228 by the projection optical system 227. During scanning exposure, the reflective mask 1 and the mask 2 are moved as shown by arrows, and the wafer is also moved synchronously.

That is, in this embodiment, one of the two masks 1 is constituted by a reflection mask, the illumination light and the optical axis of the projection optical system are arranged at right angles, and the illumination mask is used to bend the light beam by this reflection mask. 4 with respect to the optical axis of light and the projection optical system
5 °, and the scanning direction is parallel to the reflection mask. The other mask 2 is perpendicular to the optical axis of the projection optical system 227, and the scanning direction is parallel to the mask.

FIGS. 13 to 21 are explanatory diagrams of the exposure method according to the first embodiment of the present invention. FIG. 13 is a flowchart showing the exposure method of the present invention. FIG. 13 shows each block of a periodic pattern using an FM mask, a simultaneous exposure step of a normal pattern using an RM mask, and a developing step, which constitute the exposure method of the present invention, and the flow thereof.

In the figure, there is a step or the like for precise alignment between each exposure step, but it is not shown here.

The exposure method and the exposure apparatus according to the present invention are characterized in that periodic pattern exposure and normal pattern exposure are simultaneously performed on each chip region of a substrate to be exposed (photosensitive substrate), and this is repeated in the step direction.

Here, the normal pattern exposure is an exposure which has a lower resolution than the periodic pattern exposure but can perform exposure in an arbitrary pattern.

The pattern (normal pattern) exposed by the normal pattern exposure includes a fine pattern having a resolution equal to or less than the resolution, and 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 that the direction of the periodic pattern matches the direction of the finest pattern of the normal pattern.

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

In the present invention, double exposure means simultaneous exposure of periodic pattern exposure and normal pattern exposure.

The case of performing exposure according to the flow of FIG. 13 will be described. The periodic pattern exposure and the normal pattern exposure are performed simultaneously. First, the periodic pattern exposure will be described.

The wafer (photosensitive substrate) is exposed in a periodic pattern as shown in FIG. The numbers in FIG. 14 represent the exposure amounts. The hatched portions in FIG. 14A 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. 14B shows a lithography pattern (concavo-convex pattern) finally obtained.

FIG. 15 shows the dependency of the film thickness after development on the amount of exposure and the exposure threshold value of the resist on the photosensitive substrate in this case, as a positive resist (hereinafter referred to as "positive") and a negative resist. Each of the resists (hereinafter referred to as “negative type”) is shown. If the case of a positive type or exposure threshold E _th, the case of a negative if: the exposure threshold E _th, the film thickness after development becomes 0.

FIG. 16 is a schematic diagram showing a state in which a lithography pattern is formed through 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, as shown in FIGS. 17 (same as FIG. 14A) and FIG. 18, when the central exposure amount in the periodic pattern exposure is 1, , The exposure threshold E _th of the resist on the exposed substrate
Is set to be larger than 1. This photosensitive substrate is shown in FIG.
In the case of developing an exposure pattern (exposure amount distribution) in which only the base pattern exposure shown in (2) is developed, the exposure amount is insufficient. No lithography pattern is formed. This can be regarded as the disappearance of the periodic pattern. (Here, the present invention will be described using an example in which a negative type is used, but the present invention can also be implemented in a positive type.)

In FIG. 18, the upper part shows a lithography pattern (no pattern image can be formed), and the lower part shows the relationship between the exposure distribution and the exposure threshold.
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. 19A 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.

Assuming that the projection exposure for forming the exposure pattern shown in FIG. 19A is performed on the same region of the same resist simultaneously with the periodic pattern exposure shown in FIG. 17, the total exposure amount distribution on the resist surface is as shown in FIG. It becomes like the graph at the bottom of 19 (B). Here, the exposure amount E of the periodic pattern exposure
₁ and the ratio of the exposure amount E ₂ of the projection exposure is 1: 1, the exposure threshold E _th of the resist exposure E ₁ (= 1) and the exposure amount sum of the exposure amount E ₂ of E ₁ and the projection exposure (= Since it is set between 2),
The lithography pattern shown in the upper part of FIG. 19B 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. 19B has a resolution of a 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. 20 (projection exposure with a line width twice the exposure pattern in FIG. 17 and an exposure threshold or more (here, an exposure amount twice the threshold)) is performed. ) Is superimposed on the same region of the same resist simultaneously with the periodic pattern exposure in 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.

Also, as shown in FIG. 21, the principle is the same when the exposure is performed with a line width three times the exposure pattern of FIG.
With an exposure pattern having a line width of four times or more, the line width of a finally obtained lithography pattern is obvious from a combination of an exposure pattern having a double line width and an exposure pattern having a triple line width. All the lithography patterns that can be realized by projection exposure can also be formed in the present embodiment.

By adjusting the exposure amount distribution (absolute value and distribution) and the threshold value of the resist on the photosensitive substrate by each of the periodic pattern exposure and the projection exposure briefly described above,
18, 19 (B), 20 (B), and 21.
The minimum line width is composed of a combination of various types of patterns as shown in FIG.
A circuit pattern serving as the pattern (B) can be formed.

The principles of the above exposure method can be summarized as follows: (A-1) A pattern area 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 pattern 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 not less 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.

In the present invention, (a-1) as an illumination method of the 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-2) In an exposure apparatus, a refraction system and reflection
It is applicable to project the mask pattern by a projection optical system composed of either a refraction system or a reflection system.

(A-3) 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. Is applicable.

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

FIG. 22 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 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. 23 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.

[0128]

According to the present invention, it is possible to achieve (c-1) an exposure method and an exposure apparatus capable of easily performing multiple exposures in a relatively short time.

(C-2) Two exposures, a periodic pattern exposure typified by two-beam interference exposure and a normal pattern exposure (normal exposure) not including the periodic pattern, are simultaneously performed on the same area on the surface of the photosensitive substrate (wafer). This makes it possible to achieve an exposure method and an exposure apparatus capable of forming a circuit pattern on a wafer with high throughput.

(C-3) An exposure method and an exposure apparatus which can easily obtain a circuit pattern having a portion having a line width of 0.15 μm or less can be achieved.

(C-4) It is possible to achieve an exposure method and an exposure apparatus that can simultaneously perform two exposure methods, that is, a periodic pattern exposure and a normal exposure using different illumination methods.

(C-5) A plurality of masks on which different patterns are formed are illuminated under different optimum illumination conditions, and a pattern based on the plurality of masks is synthesized by photosynthesis means to form the same area on the wafer surface. By simultaneously projecting and exposing, an exposure apparatus capable of transferring a finer pattern and capable of manufacturing a highly integrated device with high throughput and a device manufacturing method using the same can be achieved. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a main part of an exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of the mask of FIG. 1;

FIG. 3 is an explanatory view of the mask of FIG. 1;

FIG. 4 is an explanatory diagram when a part of the optical path in FIG. 1 is developed.

FIG. 5 is an explanatory diagram when a part of the optical path in FIG. 1 is developed.

FIG. 6 is an explanatory diagram of exposure conditions of the exposure apparatus of FIG.

FIG. 7 is an explanatory view of a part of the exposure apparatus of FIG. 1;

8 is an explanatory view of a part of the exposure apparatus of FIG.

FIG. 9 is an explanatory view of a part of the exposure apparatus of FIG. 1;

FIG. 10 is an explanatory view of a part of FIG. 1;

FIG. 11 is a schematic diagram of a main part of an exposure apparatus according to a second embodiment of the present invention.

FIG. 12 is a schematic view of a main part of an exposure apparatus according to a third embodiment of the present invention.

FIG. 13 is a flowchart of an exposure method according to the present invention.

FIG. 14 is an explanatory view showing an exposure pattern by two-beam interference exposure

FIG. 15 is an explanatory diagram showing exposure sensitivity characteristics of a resist.

FIG. 16 is an explanatory view showing pattern formation by development.

FIG. 17 is an explanatory view showing an exposure pattern by ordinary two-beam interference exposure.

FIG. 18 is an explanatory view showing an exposure pattern by two-beam interference exposure in the present invention.

FIG. 19 is an explanatory diagram showing an example of an exposure pattern (lithography pattern) that can be formed in the first embodiment of the present invention.

FIG. 20 is an explanatory view showing another example of the exposure pattern (lithography pattern) that can be formed in the first embodiment of the present invention.

FIG. 21 is an explanatory diagram showing another example of the exposure pattern (lithography pattern) that can be formed in the first embodiment of the present invention.

FIG. 22 is a flowchart of a device manufacturing method of the present invention.

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

FIG. 24 is a schematic view showing a conventional projection exposure apparatus.

FIG. 25 is a schematic view showing an example of a conventional two-beam interference exposure apparatus.

[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 (14)

[Claims] A plurality of mask patterns having different patterns are synthesized by a photosynthesis member, and the same area on a wafer surface is sequentially or simultaneously synchronized with the plurality of mask patterns and the wafer by a projection optical system. An exposure method, wherein the simultaneous exposure is performed by projection exposure. 2. The exposure method according to claim 1, wherein the plurality of different mask patterns are formed on separate substrates. 3. The exposure method according to claim 1, wherein the different mask patterns are formed on a common substrate. 4. The exposure method according to claim 1, wherein one of the plurality of different mask patterns is a line and space pattern. 5. The exposure method according to claim 1, wherein the plurality of different mask patterns are illuminated by a plurality of illumination systems having different illumination conditions. 6. The exposure method according to claim 1, wherein two mask patterns forming the plurality of mask patterns are simultaneously scanned in directions opposite to each other. 7. The exposure method according to claim 1, wherein the illumination condition is coherent illumination or partial coherent illumination. 8. The exposure method according to claim 1, wherein the illumination condition is σ (sigma). 9. The exposure method according to claim 1, wherein the illumination condition is NA (numerical aperture). 10. The exposure method according to claim 1, wherein the illumination condition is an incident angle of illumination light. 11. An exposure apparatus having the exposure method according to claim 1 as an exposure mode. 12. An exposure apparatus of a step-and-repeat reduction projection type, comprising the exposure method according to claim 1 as an exposure mode. 13. An exposure apparatus of a step-and-scan reduction projection type, comprising the exposure method according to claim 1 as an exposure mode. 14. Exposure of a wafer with a device pattern using the exposure apparatus according to claim 11, 12, or 13.
Developing the exposed wafer.