JP2002075857A - Resist pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a micropattern having pitches and the line width of between two thirds and a half of conventional ones. SOLUTION: The patterns in the exposure field are divided into two groups of patterns and a two-layer resist composed of a lower resist film and an upper resist film is used. The upper resist film is exposed to an exposure light beam with a band of wavelengths by which only the upper resist film is sensed into a shape corresponding to the divided first group of patterns. After the upper resist pattern is formed by development, parts of the lower resist film exposed between the traces of the upper resist pattern are exposed to an exposure light beam with short wavelengths which can hardly pass through the upper resist pattern and senses the lower resist pattern into a pattern shape corresponding to the divided second group of patterns and development is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a fine resist pattern used in manufacturing a semiconductor integrated circuit or the like.

[0002]

2. Description of the Related Art Conventionally, a fine pattern of a semiconductor integrated circuit or the like is manufactured based on a resist pattern obtained by transferring a fine pattern on an original substrate such as a reticle or a mask to a resist formed on a substrate to be exposed such as a semiconductor wafer. I do. That is, the original drawing substrate is illuminated with exposure light such as short-wavelength visible light, ultraviolet light, far ultraviolet light, vacuum ultraviolet light, and extreme ultraviolet light, and is exposed to light by various exposure means such as projection exposure, proximity exposure, and contact exposure. The resist film formed on the substrate is exposed to a fine pattern shape on the original substrate or a shape correlated with the fine pattern shape. After the exposure, when the resist film is subjected to a developing treatment, a part of the resist film is removed according to the exposure intensity distribution, and a desired resist pattern is obtained. The process of forming a resist pattern by combining exposure and development in this way is called lithography.

The minimum size of a pattern of a semiconductor integrated circuit, a semiconductor device, an optoelectronic device, a micro component for a micromachine, and the like is determined by how fine a resist pattern formed by lithography can be. Therefore, in order to miniaturize the patterns of the above-mentioned circuits, elements and components, it is necessary to minimize the resist pattern dimensions that can be formed by lithography.

[0004] In particular, in the formation of patterns for semiconductor integrated circuits and semiconductor elements for which miniaturization of patterns is urgently required, lenses, mirrors, or projection exposure optical systems combining them are used to form fine patterns on the original drawing substrate. A projection exposure method of projecting and exposing a pattern on a substrate to be exposed is mainly used. The main factor that determines the minimum dimension of a resist pattern that can be transferred by the projection exposure method, that is, the resolution, is the numerical aperture N of the projection exposure optical system of the exposure apparatus used for projection exposure.
A and the exposure wavelength λ.

Assuming a projection exposure optical system having no aberration, the resolution R is proportional to the exposure wavelength λ and inversely proportional to the numerical aperture NA of the projection exposure optical system. Therefore, the shorter the wavelength, the more exposure
In addition, the higher the exposure is made by using a projection exposure optical system having a large numerical aperture, the higher the resolution becomes, and a finer pattern is transferred.

However, it is technically very difficult to shorten the exposure wavelength λ or increase the numerical aperture NA of the projection exposure optical system, and each of them has reached the limit of the current technology.

To realize a projection exposure optical system with low aberration,
A projection exposure optical system using a lens is preferable.
There are few stable and inexpensive lens materials that have high transmittance for light having a wavelength of less than m. On the other hand, a projection exposure optical system using a mirror limits the number of surfaces that can be used due to restrictions when spatially arranged, and the device becomes large, so that a practical low aberration that can transfer an extremely fine resist pattern can be used. Projection exposure optics have not been developed yet. Therefore, there is a limit to shorten the exposure wavelength λ, and at present, the limit has been almost reached.

Further, assuming that the exposure field has a practical size, it is necessary to increase the aperture of the projection exposure optical system in order to increase the numerical aperture NA, and it becomes difficult to correct aberrations. It is also difficult to greatly increase the numerical aperture, and at present, the highest possible numerical aperture has already been achieved.

In contrast, in proximity exposure or close contact exposure, when the exposure wavelength is λ and the gap between the original substrate and the substrate to be exposed is z, the resolution R is proportional to the square root of λz. That is, in the case of proximity exposure or contact exposure, the exposure wavelength λ and the original substrate
The exposed substrate gap z is the main factor that determines the resolution.

Therefore, in order to increase the resolution, the exposure wavelength λ may be shortened to reduce the gap z between the original substrate and the substrate to be exposed. However, in proximity exposure or close contact exposure, since only a fine pattern having the same dimensions as the original substrate can be transferred, it is becoming difficult to form an ultra-fine pattern on the original substrate. In addition, when the exposure wavelength λ is shortened, the exposure light transmittance of the original substrate decreases, and the expansion and contraction of the original substrate due to light absorption becomes a problem. Further, when the gap z between the original substrate and the substrate to be exposed is reduced or the two are brought into contact or in close contact with each other, contamination of the original substrate or damage to the resist film formed on the substrate to be exposed may be caused. Therefore, it is practically very difficult to significantly improve the exposure wavelength λ and the gap z between the original substrate and the substrate to be exposed.

On the other hand, in addition to ordinary reticles and masks having a light shielding portion and a transmitting portion, phase shift masks in which various phase shifters are appropriately arranged have been developed. The use of the phase shift mask improves the light / dark contrast of the light intensity distribution of the light beam for exposing the resist film, and achieves a high resolution with respect to the same numerical aperture NA, the same exposure wavelength λ, and the same original substrate / substrate gap z. Is obtained. This method has also been gradually adopted, and is an effective measure for achieving high resolution. However, even if the phase shift mask is applied, the resolution is still insufficient, and there is a situation where further improvement in the resolution is required.

Also, attempts have been made to improve the resolution by devising a method of forming a resist pattern, a structure and a material of a resist film, etc. for the same contrast of the light intensity distribution. Resist thinning, surface reaction resist process, multilayer resist, contrast enhancement layer (hereinafter C
Recorded as EL. ) Is a typical example.

When the film thickness of the resist is reduced, the optical path length when the exposure light beam passes between the film thicknesses is shortened, and the light intensity distribution of the resist substrate can be made not so different from the light intensity distribution of the resist surface. At the time of projection exposure, the entire resist thickness can be kept within the depth of focus. For this reason, even if the light-intensity distribution of the light beam for exposing the resist film is low in contrast to the case where the resist film thickness is large, the image is resolved.

In the surface reaction resist process, only the surface of the resist is reacted at the time of exposure, and the shape of the portion where only the surface has reacted is transferred to a material provided under the surface reaction layer by using silylation or the like. The way to go. Since only the surface of the resist is required to be exposed at the time of exposure, the light can be resolved even if the contrast of the light intensity distribution of the light beam for exposing the resist film is low.

The multi-layer resist is formed by coating the resist in two or more layers so as to make the uppermost resist thinner so that the uppermost resist has a shape corresponding to the fine pattern on the original drawing substrate even with a low contrast light intensity distribution. Resolution. Then, using the upper resist pattern as a mask, the resist film thereunder is sequentially etched from the uppermost layer, and finally, the pattern of the lowermost resist required for the subsequent process is formed.

The multi-layer resist is constituted by a two-layer resist,
A method of exposing the lower resist film using the upper resist pattern as a light-shielding portion without using etching, developing after exposure, and transferring the shape of the upper resist pattern to the lower resist film as it is, for example, Journal of Vacuum Sci.
ence and Technology Vol. 1
6, p. 1620 (1979). However, according to the disclosed method, the entire area within the field is collectively irradiated at the time of exposing the lower resist film, so that the shape of the upper resist pattern is simply transferred to the lower resist. Therefore, the pitch of the pattern finally obtained by exposing and developing the lower resist film is the same as that of the upper resist pattern, and it is impossible to form a resist pattern having a pitch much smaller than the pitch of the upper resist pattern.

In the method using CEL, a CEL film is formed on a resist film, and the resist is exposed to light by increasing the difference in light intensity between light and dark. Since the transmittance of the CEL film increases in the exposed portion by exposure, the exposure ratio of the exposed portion and the unexposed portion is improved. Therefore, the resolution is improved as compared with the case where CEL is not used.

The method of devising these resist processes is a method of forming a pattern corresponding to the light intensity distribution at the time of first exposing the material of the uppermost layer or the uppermost part. Alternatively, the pattern shape formed on the uppermost material is merely used for the purpose of increasing the resistance to the subsequent etching or the like and recreating the pattern. Therefore, the resolution is almost determined by the light intensity distribution for exposing the uppermost layer or uppermost material. Further, since the light intensity distribution itself for exposing the material of the uppermost layer or the uppermost portion is not improved, the state of improvement in resolution is generally at most one.
It is about 0 to 20%, which is not very noticeable.

As yet another resolution improving method, there is a method in which a pattern in an exposure field is divided into two groups of patterns, and each of the divided patterns is exposed twice.
stof Papers, Micro Process
'94, pp. 4-5. This method
Usually, the resist is exposed in proportion to the light intensity, and the solubility in the developer changes according to the exposure intensity, whereas the photosensitivity and the solubility in the developer change in proportion to the square of the exposure intensity. This is a method using a two-photon resist. If two groups of patterns divided by using a two-photon absorption resist are sequentially exposed, even if the light-dark contrast of the light intensity distribution at the time of exposure of each pattern group is low, the contrast of the squared distribution becomes sufficiently high. By synthesizing the patterns subjected to the divided exposure, it is possible to form a pattern having a narrower pitch than the conventional one. However, in this method, a resist having the above-mentioned special characteristics is indispensable, whereas a required practical two-photon absorption resist has not yet been developed after the disclosure of the technology.

[0020]

As described above, there are many methods for improving the resolution, but each has various restrictions, and a desired resolution can be obtained even if various methods are used as much as possible. Therefore, a new method capable of greatly improving the degree of integration and fineness has been demanded. It is needless to say that a new method for forming a fine pattern is preferably a method which can be applied together with the conventional high resolution method described above, and which can produce an effect synergistically. .

[0021]

According to the present invention, the integration field and the fineness are greatly improved, and many of the conventional high resolution means can be applied simultaneously with the present invention. Is divided into two groups of patterns, and the steps of exposing and developing the divided patterns of each group are sequentially performed.
A two-step pattern forming process is included.

In the first resist pattern forming step, a two-layer resist composed of a lower resist film and an upper resist film formed on a substrate or a substrate with a coating is used, and the lower resist film is not exposed and the upper resist film is not exposed. Exposing the upper resist film to a shape corresponding to the divided first pattern group by an exposure light beam in a wavelength band to which only
After the exposure, development is performed to form an upper resist pattern corresponding to the first pattern group.

In the second resist pattern forming step, the upper resist pattern formed in the first resist pattern forming step is hardly penetrable, and the lower resist film is exposed to light to form the first resist pattern forming step. By the exposure light beam having a shorter wavelength band than the exposure light beam used in the step, the lower resist film exposed between an arbitrary pattern in the upper resist pattern and a pattern adjacent to the arbitrary pattern is divided into the second resist film. Exposure is performed in a pattern shape corresponding to the pattern group, and after the exposure, development is performed to form a lower resist pattern immediately below the upper resist pattern and in a dark portion of the pattern shape exposure corresponding to the second pattern group. I do.

When the pattern is divided into two groups of patterns, every other pattern is divided into two groups of patterns so that the center line of the resist pattern formed in the first resist pattern forming step is formed. Is set to be 3.5 times or more the minimum line width of the resist pattern, and the interval between the center lines of the resist pattern formed by the reticle or the mask in the second resist pattern forming step is set to the minimum line width of the resist pattern. 3.5 times or more.

Further, in the first resist pattern forming step and / or the second resist pattern forming step, a projection exposure method of illuminating the original substrate with an illumination secondary light source whose peripheral light intensity is higher than the central light intensity is provided. To form a pattern.

In the first resist pattern forming step and / or the second resist pattern forming step, a resist pattern is formed using a shifter edge type phase shift mask.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings.

FIG. 1 is an explanatory view of a method for forming a resist pattern according to the present invention. First, as shown in FIG. 1A, a lower resist film 2 is formed on a substrate 1 such as a semiconductor wafer, and an upper resist film 3 is formed thereon. In order to form such a resist composition, for example, after modifying the substrate 1 with a surfactant such as hexamethylzine lazan so that the coatability of the resist is improved, the lower resist film 2 is formed using a spin coater. Apply and bake. Then, an upper resist film 3 is applied thereon and baked again. The treatment for improving the adhesiveness of the resist by the surfactant may be omitted if the lower resist film 2 can be applied without any problem and the peeling of the resist or uneven development is not caused in a developing step described later.

Incidentally, an arbitrary coating may be formed on the substrate 1. A resist is often applied on the substrate 1 only when a test for forming a resist pattern is performed. However, when a semiconductor integrated circuit or the like is manufactured, not only the purpose of making a resist pattern by lithography but also the purpose of the resist. In many cases, the purpose is to process a film under the resist by performing etching using a pattern as a mask. Therefore, in such a case, an insulating film, a metal film, a semiconductor film, or the like, which is a film to be processed, is often formed on the substrate 1, but the substrate 1 with such a coating may be used. Needless to say, the substrate may be a substrate from which a part of the coating is removed in an arbitrary pattern shape, that is, a substrate with an arbitrary pattern.

If reflection of exposure light from the surface of the substrate 1 becomes a problem, an antireflection film is formed on the substrate 1, a lower resist film 2 is formed thereon, and an upper resist film is formed thereon. The films 3 may be formed in layers.

When forming the upper resist film 3 on the lower resist film 2, the lower resist film 2 is a resist film whose photosensitive wavelength band exists on the longer wavelength side than the photosensitive wavelength band of the upper resist film 3. 3 is a resist film that is not exposed to exposure light for exposure.

As a specific example, a resist film for exposing a KrF excimer laser having a wavelength of 248 nm or a resist film for exposing to a deep ultraviolet ray having a wavelength of about 210 to 270 nm is used as the lower resist film 2, and a resist film having a wavelength of 36 nm is used as the upper resist film 3.
5nm i-line exposure resist or 436nm wavelength g
A resist for line exposure is used. The lower resist film 2 is a resist film for 193 nm wavelength ArF excimer laser exposure, and the upper resist film 3 is a 248 nm wavelength KrF excimer laser exposure resist film or 210 to 270 n.
m deep UV exposure resist film or wavelength 365nm
Or a resist for g-ray exposure with a wavelength of 436 nm. The lower resist film 2 has a wavelength of 15
7mm fluorine excimer laser exposure resist film,
The upper resist film 3 is formed of a 193 nm wavelength KrF excimer laser exposure resist film, a 248 nm wavelength KrF excimer laser exposure resist film, or a wavelength range of 210 to 270 n.
m deep UV exposure resist film or wavelength 365nm
Or a resist for g-ray exposure with a wavelength of 436 nm.

After the upper resist film 3 is formed on the lower resist film 2, the upper resist film 3 is formed into a pattern by using an exposure light beam in which only the upper resist film 3 is exposed and the lower resist film 2 is not exposed. Expose. At this time, the pattern for exposing the upper resist film 3 is one pattern group in which the pattern in the exposure field is divided into two groups in advance.

As described above, if the upper resist film 3 is exposed to the shape of one of the divided groups of patterns, development is subsequently performed to form the upper resist pattern 4 as shown in FIG. I do. In the upper resist pattern 4, the distance p between the center lines of the resist pattern is set to 3.5 times or more the minimum line width w of the resist pattern. Whether or not a fine pattern can be transferred to the upper resist film 3 is also affected by the fineness of the line width of the pattern, but in a dense pattern, the pattern cycle is the largest determining factor. Therefore, if the minimum distance between the center lines of the resist pattern to be formed is sufficiently large, the line width of the pattern itself can be transferred even smaller than 3.5 times the minimum distance between the center lines.

When the sensitivity and resolution depend on the post-exposure bake before development, ie, post-bake, such as when the upper resist film 3 is a chemically amplified resist, post-bake and development are performed as necessary. Upper resist pattern 4
To form

In order to make the line width of the pattern left on the lower resist film 2 as the upper resist pattern 4 as narrow as possible, a lens, a mirror, or a projection exposure optical system combining them is used to reduce the fine pattern on the original substrate. Projection exposure is performed on the substrate to be exposed. As shown in the example of FIG. 2, a projection exposure using a secondary illumination light source whose peripheral light intensity is higher than the central light intensity is used as a secondary illumination light source for illuminating the original substrate using the projection exposure method. It is valid. In FIG. 2, a hatched portion indicates the light emitting unit 5 of the secondary light source. FIG.
(A) is annular illumination or annular illumination, and the width of the annular or annular zone is arbitrary. (B) and (c) show four-point illumination, and the size and shape are arbitrary. (D) Illumination by a secondary light source having a continuous light intensity distribution, (e),
(F) is a two-point illumination and a two-division illumination, and the size and shape are also arbitrary here. It goes without saying that the light intensity at the center may be 0 in the case of (d).

When an illumination secondary light source whose peripheral light intensity is higher than the central light intensity is used, the original substrate is illuminated by obliquely incident light, and only one of the primary diffracted light is taken into the projection exposure optical system. For this reason, the Japanese Journal
of Applied Physics, Vol. 3
3, No. 12B, pp. As disclosed in US Pat. No. 6,823,830, when a periodic pattern is projected and exposed, a light intensity distribution formed by two-beam interference is generated, and a light-shielding pattern portion is formed as compared with the case of using a normal secondary light source with uniform intensity. Have a small line width. In the present invention, it is necessary to set the minimum interval between the center lines of the resist pattern to be formed to be at least 3.5 times the minimum line width of the resist pattern, and to make the pattern line width smaller than the space width. Therefore, the projection exposure method using the secondary illumination light source in which the light intensity at the periphery is higher than the light intensity at the center where the line width of the light-shielding pattern portion is easily formed is particularly effective.

In order to minimize the line width of the pattern left on the lower resist film 2 as the upper resist pattern 4, a shifter edge type phase shift reticle or a phase shift reticle shown in FIG. It is also effective to apply a shift mask. FIG.
In the phase shift reticle or the phase shift mask shown in (a), a phase shifter 7 for substantially inverting the phase of an exposure light beam is provided on a reticle or a mask substrate 6.
At the edge of, light passing through both sides interfere with each other to reduce the light intensity. In addition, the phase shift reticle or the phase shift mask shown in FIG. 3B digs the reticle or the mask substrate 6 instead of attaching the phase shifter 7, and substantially reverses the phase of the exposure light beam. Further, as shown in FIGS. 3C and 3D, it is more effective to dispose a thin light-shielding pattern 8 on the shifter edge of FIG. 3A or 3B. The distance between the center lines of the resist pattern to be formed, that is, the width of the phase shifter 7 in FIGS. 3A to 3D or the width p of the dug portion for giving a phase shift is determined by the minimum line width of the resist pattern to be formed. If it is 3.5 times or more, the distance between the shifter edges is sufficiently large, so that the shifter edge can be used as a very thin light shielding portion.

Next, the entire lower resist film 2 is baked again at a prebaking temperature. The re-bake may be performed as necessary, and may be omitted when the re-bake of the lower resist film 2 softens the upper resist pattern 4.

Thereafter, the lower resist film 2 is exposed using an exposure light beam which exposes the lower resist film, and is subsequently developed to form a lower resist pattern 5 as shown in FIG. 1C. . At this time, the pattern for exposing the lower resist film 2 was the other pattern group in which the pattern in the exposure field was divided into two groups in advance, and was not formed as the upper resist pattern 4 formed alternately, for example. The other alternate patterns are formed so as to complement the space between the upper resist patterns 4. Of the lower resist pattern 5, a pattern obtained by exposing the lower resist film 2 exposed between an arbitrary pattern in the upper resist pattern 4 and a pattern adjacent to the arbitrary pattern is, as shown in FIG. The distance p between the center lines of the pattern is set to 3.5, which is the minimum line width w of the pattern.
More than double.

In order to expose the lower resist film 2 locally, as in the case of exposing the upper resist film 3, projection exposure, proximity exposure, contact exposure and the like may be performed using a reticle or mask as an original substrate. In the case where the lower resist film 2 is a chemically amplified resist and the sensitivity and resolution depend on the post-exposure bake before development, that is, post-bake, post-bake is performed as necessary, and then the lower resist pattern is developed. 5 is formed.

Also in this case, in order to form the remaining resist pattern as small as possible as the lower resist pattern 5, a fine pattern on the original substrate is formed on the substrate to be exposed by using a lens, a mirror, or a projection exposure optical system combining them. As a secondary light source for illuminating the original substrate using the projection exposure method, the peripheral light intensity previously shown for forming the upper resist pattern 4 is higher than the central light intensity.
It is particularly effective to use projection exposure using a secondary light source.

It is also effective to apply the shifter edge type phase shift reticle or phase shift mask previously shown for forming the upper resist pattern 4 as the original substrate.

At this time, the materials of the lower resist film 2 and the upper resist film 3 are selected so that the light beam for exposing the lower resist film 2 can hardly pass through the upper resist pattern 4 formed previously. For example, when an i-line exposure resist having a wavelength of 365 nm or a g-line exposure resist having a wavelength of 436 nm is used as the upper resist film 3,
When a resist using a novolak resin as a base resin is used as the i-line exposure resist or the g-line exposure resist, the transmittance of exposure light having a wavelength of about 250 nm or less can be extremely reduced. When a resist film for KrF excimer laser exposure with a wavelength of 248 nm or a resist film for deep ultraviolet exposure with a wavelength of 210 to 270 nm is used as the upper resist film 3, a resist using polyhydroxystyrene as a base resin is used as the resist. For example, the transmittance of exposure light having a wavelength of 200 nm or less can be extremely reduced. Further, the upper resist film 3 is set to a wavelength of 193n.
When the resist film for ArF excimer laser exposure of m is used, the transmittance of exposure light having a wavelength of 157 nm or less can be extremely reduced by using an acrylic or norbornene-based polymer as a base resin and using a resist having an alicyclic structure. it can.

If the light beam for exposing the lower resist film 2 is hardly transmitted through the upper resist pattern 4 previously formed, the portion where the upper resist pattern 4 exists is shielded from light. Lower resist film 2
A pattern having a shape obtained by synthesizing the light-shielding pattern portion of the original substrate used for exposing the lower resist film 2 and the pattern shape of the upper resist pattern 4 is formed. That is, the required pattern is finally formed.

Although FIG. 1 is drawn assuming a positive resist in which exposed portions of the resist film are removed by development, the lower resist film 2 and / or the upper resist film may be used as necessary. Needless to say, 3 may be a negative resist film.

If the upper resist pattern 4 is partially left on the lower resist pattern 5, when etching is performed after the pattern is formed, the etching resistance differs between the place where the upper resist pattern 4 is present and the place where it is not. Even if the resist pattern is apparently uniform, the pattern line width obtained after etching may vary. Also,
The light wraps around the back side of the upper resist pattern 4 by diffraction, and the line width of the lower resist pattern 5 may have an error even though the desired line width is formed by observation from above. In some cases, the pattern line width varies. Therefore, it is often preferable that the upper resist pattern 4 does not remain before the etching is performed after the pattern is formed.

In such a case, when the upper resist film 3 is a posi-type resist film, after forming the lower resist pattern 5, the entire surface of the substrate is exposed to an exposure light beam for exposing the upper resist, and then again. Alternatively, development may be performed to remove the upper resist pattern 4. However, the condition is that the lower resist pattern 5 is not damaged by the development.

It is needless to say that if there is a stripping solution of the upper resist pattern 4 which does not damage the lower resist pattern 5, it may be used.

When the lower resist pattern 5 is formed, an exposure light beam for exposing the upper resist film 3 is mixed with an exposure light beam for exposing the lower resist film 2 so that the upper resist pattern 4 is dissolved and removed during development. Is also good. In this case, the developing solution for the upper resist film 3 and the developing solution for the lower resist film 2 must be common, but it is possible if the upper resist film 3 and the lower resist film 2 using a standard alkali developing solution are selected and used. is there.

In the above description, the upper resist pattern 4 is formed directly on the upper resist film 3. However, it is clear that any multilayer resist process may be used when forming the upper resist pattern 4.

For example, an upper resist pattern 4 is formed of a two-layer resist, a pattern is formed on the upper layer of the two-layer resist, and the lower layer is dry-etched using the pattern as a mask to form an upper resist pattern 4. May be.

Another resist film is formed under the lower resist film 2 and the another resist film is etched using the lower resist pattern 5 as an etching mask.
The resist pattern formed by the etching may be finally formed on the substrate 1 or the substrate 1 on which the coating is formed.

In FIG. 1 used in the above description, the upper resist pattern 4 and the lower resist pattern 5
Are drawn as patterns uniformly arranged periodically. However, it is needless to say that the upper resist pattern 4 and the lower resist pattern 5 do not need to be patterns arranged regularly uniformly, and may be arbitrary patterns.

[0055]

As described above, according to the present invention, the finally required pattern is divided into two original drawing substrates, and every other pattern is alternately arranged, so that the center line of the resist pattern to be transferred is obtained. Is the minimum line width of the resist pattern.
In order to make it 5 times or more, for example, the conventional Digest of
Papers, Micro Process '94,
pp. As in the method disclosed in 4-5, without using a special resist such as a two-photon absorption resist, the arrangement pitch of the original pattern in both the upper resist pattern 4 and the lower resist pattern 5 can be made about twice as large as that in the related art.

In the case of forming a fine pattern such as a semiconductor integrated circuit, the resolution is mainly determined by the pattern pitch of the pattern dense portion. If the pattern pitch is large, the pattern line width can be considerably reduced by adjusting the exposure amount. Further, a finer pattern can be formed by applying a projection exposure using a secondary illumination light source whose peripheral light intensity is higher than the central light intensity or a phase shift mask using a shifter edge. Therefore, for example, if a pattern having a line width of 1/4 of the pattern pitch is formed at the time of forming the upper resist pattern 4 and the lower resist pattern 5, for example, the lower resist pattern 4 is finally obtained. In addition, a fine pattern having a pitch twice the pattern pitch on the original substrate at the time of exposing the lower resist film 2 can be obtained.

The limit of the pattern line width that can be formed is the limit dimension at which the pattern can be formed when the upper resist pattern 4 and the lower resist pattern 5 are formed. In general, a pattern having the same pattern line width and space width and being half the pitch is most difficult to form, and if there is a sufficient pitch, it is relatively easy to form a fine resist pattern. In the present invention, since the minimum interval between the center lines of the resist pattern to be formed is set to be 3.5 times or more the minimum line width of the resist pattern, approximately 2/3 or more of the case where a pattern having a half pitch exists. A pattern having a line width of about 1/2 can be formed.

When the minimum interval between the center lines of the resist pattern is set to four times the minimum line width of the resist pattern, a dense pattern having a half pitch can be formed as the lower resist pattern 5. Therefore, the minimum pattern line width and space width of the dense pattern that can be transferred are 2/3 as compared with the case where the dense pattern corresponding to 1/2 of the pitch is simultaneously transferred.
Or it can be reduced to half.

Therefore, if the present invention is applied to the manufacture of semiconductor integrated circuits and optoelectronic devices, the degree of integration can be greatly improved, and the performance can be greatly improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a method for forming a resist pattern according to the present invention.

FIG. 2 is an example of a secondary illumination light source shape effective for the present invention.

FIG. 3 is a configuration example of a shifter edge type phase shift mask effective for the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Lower resist film 3 Upper resist film 4 Upper resist pattern 5 Lower resist pattern

Claims (4)

[Claims] 1. A resist pattern forming method including a two-step pattern forming step of dividing a pattern in an exposure field into two groups of patterns, and sequentially exposing and developing the divided groups of patterns. Using a two-layer resist consisting of a lower resist film and an upper resist film formed on a substrate or a substrate with a coating, the upper resist film is exposed to light in a wavelength band in which the lower resist film is not exposed and only the upper resist film is exposed. A first resist pattern forming step of exposing to a shape corresponding to the divided first pattern group, performing development after the exposure, and forming an upper resist pattern corresponding to the first pattern group. However, the upper resist pattern formed in the first resist pattern forming step hardly penetrates, and the lower resist film is exposed,
The lower resist film exposed between an arbitrary pattern in the upper resist pattern and a pattern adjacent to the arbitrary pattern by the exposure light in a shorter wavelength band than the exposure light used in the first resist pattern forming step is used. Exposure is performed in a pattern shape corresponding to the divided second pattern group, and after the exposure, development is performed.
A second resist pattern forming step of forming a lower resist pattern in a dark portion at the time of pattern shape exposure corresponding to the above pattern group. 2. The method according to claim 1, wherein the distance between the center lines of the resist pattern formed in the first resist pattern forming step is at least 3.5 times the minimum line width of the resist pattern, and the reticle or the reticle is formed in the second resist pattern forming step. 2. The method according to claim 1, wherein the distance between the center lines of the resist pattern formed by the mask is at least 3.5 times the minimum line width of the resist pattern. 3. A first resist pattern forming step of forming an upper resist pattern by using a projection exposure method of illuminating an original substrate with an illumination secondary light source whose peripheral light intensity is higher than the central light intensity and / or a peripheral resist pattern. 2. The method according to claim 1, further comprising a second resist pattern forming step of forming a lower resist pattern using a projection exposure method of illuminating the original substrate with an illumination secondary light source having a light intensity higher than the central light intensity.
And a method for forming a resist pattern according to claim 2. 4. A first resist pattern forming step of forming an upper resist pattern using a shifter edge type phase shift mask and / or a second resist pattern forming step of forming a lower resist pattern using a shifter edge type phase shift mask. 2. The method according to claim 1, wherein
And a method for forming a resist pattern according to claim 2.