JP2003234274A - Near-field light exposure method by mask multiple exposure - Google Patents

Abstract

[57] [Summary] [PROBLEMS] To solve the problem by using near-field light which is not limited by the light source wavelength
Provided is a low-cost near-field light exposure method capable of exposing a fine pattern of 00 nm or less. A second resist layer is irradiated with near-field light by an exposure mask that receives irradiated light to generate near-field light, and the resist layer is developed to form a diffraction grating pattern, which is used as an etching mask. In the near-field light exposure method in which the first resist layer is dry-etched to form a pattern on the substrate, the complicated pattern 4 is divided into slit patterns 5 and 6 arranged in one direction, and the divided slit patterns are divided. A plurality of exposure masks 2 and 3 are prepared and exposed under optimum exposure conditions to form a complex pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to near-field lithography in which a mask and a photoresist are in close contact with each other and a mask pattern is transferred to the resist by near-field light, and more particularly to a near-field exposure method having a complicated mask pattern. is there.

[0002]

2. Description of the Related Art Conventional photolithography technology has been supported by advances in reduction projection exposure technology and resist technology. The performance of the reduction projection exposure technique is mainly determined by two basic quantities, resolution and depth of focus. In order to increase the resolution of lithography, it is important to reduce the exposure wavelength and increase the numerical aperture of the projection lens. However, increasing the numerical aperture increases resolution, but the depth of focus is inversely proportional to the square of the numerical aperture. As a result of miniaturization, it has become necessary to reduce the wavelength. Therefore, the exposure wavelength is shortened from the g-line (436 nm) to the i-line (365 nm), and the excimer laser (248 nm.1) is further added.
93 nm).

However, in optical lithography, the diffraction limit of light becomes the limit of resolution. Therefore, even if an F2 excimer laser with a wavelength of 248 nm is used, miniaturization with a line width of 100 nm is a limit of lithography using a lens array optical system. It is said. Further, in order to obtain the nanometer-order resolution beyond that, it is necessary to use electron beam or X-ray (in particular, SOR light: synchrotron radiation light) lithography technology.
Electron beam lithography can control pattern formation on the order of nanometers with high precision, and can obtain a considerably deeper depth of focus than an optical system. Besides, it has an advantage that it can be directly written on a wafer without a mask, but has a drawback that it is far from the mass production level because of its low throughput and high cost. Further, although X-ray lithography can improve the resolution and accuracy by about one digit as compared with the excimer laser exposure, it has a drawback in that it is difficult to make a mask and difficult to realize, and the cost of the apparatus is high.

As a method for solving these problems, for example, as disclosed in Japanese Patent Application Laid-Open No. 13-15427, "Method for forming fine pattern", the proximity that exudes from an opening having a diameter sufficiently smaller than the wavelength of the light to be irradiated is used. Near-field photolithography has been developed, which is optimal for the technique of creating a diffraction grating (grating) of a DBR laser or DFB laser, which forms a fine pattern by exposing a resist using a field light as a light source and developing it. ing. FIG. 6 is a diagram showing a process of a conventional fine pattern forming method.
As shown in (a), a first resist film 102 made of an organic polymer and a second resist layer 103 made of a photosensitive material are sequentially applied on a substrate 101 by a spin coating method or a spray method to form a two-layer resist layer. Forming 103 '.
Next, as shown in FIG. 6B, a minute opening pattern 10 of metal is formed on the mask substrate 105 made of a dielectric material such as glass.
The exposure mask 104 on which No. 6 is formed is brought into close contact with the two-layer resist 103, and the i-line (365n
When the exposure is performed by the near-field light 107 that exudes from the opening where the metal of the exposure mask 104 is not formed by the light irradiation such as m), the exposed portion of the resist is exposed as shown in FIG. 6C. To do. Next, as shown in FIG. 6D, the exposed portion is made soluble in a developing solvent by developing the second resist layer 103 with a developing solution to form a positive pattern. After that, as shown in FIG. 6E, the first resist layer 102 is dry-etched by O ₂ plasma using the pattern of the second resist layer 103 as a mask, and the aspect ratio as shown in FIG. To form a fine pattern with high quality. Finally, the two-layer resist layer 103 '
After the substrate is processed by etching, vapor deposition or the like according to the pattern, the two-layer resist is peeled off to complete.

In this case, in the step of bringing the exposure mask 104 and the two-layer resist 103 'into close contact with each other, as shown in FIG. 7, the wafer in which the two-layer resist layer 103' is applied on the substrate 101 before the exposure is mounted on the base of the exposure apparatus. 7A, the mask 104 is mounted in close proximity thereto, and as shown in FIG. 7A, N ₂ gas is constantly flowed between the mask 104 and the resist 103 in the apparatus, and when exposure, As shown in FIG. 7B, a vacuum is drawn between the mask 104 and the resist 103 to bring the mask 104 into close contact with the resist 103. As described above, in near-field photolithography using near-field light and a two-layer resist, the resist is exposed and developed by near-field light exuding from a pattern having a line width sufficiently smaller than the wavelength of the light to be irradiated, and It has become possible to form a fine pattern of 100 nm or less, which has been a limit in optical lithography, with a high aspect ratio and low cost. Moreover, the resolution of the conventional lithography was mainly determined by the wavelength of the light source, but since the wavelength of the light source that generates the near-field light can be any, it is not necessary to develop a new light source, and there is a constraint on pattern miniaturization. Since it can be mitigated, a significant cost reduction can be expected.

[0006]

However, in the above-mentioned conventional example, the near-field optical lithography developed as a method for forming a shape having a size smaller than the wavelength of light is
When the exposure mask 104 that generates near-field light is brought into close contact with the photosensitive resist material 103 ′ to transfer near-field light having a fine distribution of wavelength or less, as shown in FIG. i) The polarization direction of L (for example, P polarization) is
As shown by the solid line arrow in FIG.
4 is parallel to the direction of the slit 110 (direction perpendicular to the paper surface in FIG. 8), the near-field light 107 exudes locally and normally, but as shown in FIG. When the deflection direction indicated by the solid arrow of L is perpendicular to the direction of the slit 110, there is a problem that the transfer pattern becomes different from the slit pattern due to "line width thickening" or the like.

Therefore, according to the present invention, when the slit pattern formed on the exposure mask is not limited to one direction but has a complicated shape, the pattern is decomposed into several elements to perform multiple exposure. It is an object of the present invention to provide a near-field light exposure method by mask multiple exposure capable of accurately transferring a fine pattern.

[0008]

To achieve the above object, the invention according to claim 1 is characterized in that only a first resist layer which can be removed by dry etching on a substrate and only a portion irradiated or not irradiated by light irradiation is developed. The recording material, in which a second resist layer having a photosensitive dry etching resistance which is soluble in a solvent is laminated in this order, is applied to a recording material by a generating means such as an exposure mask which receives irradiation light to generate near-field light. Two
The resist layer is irradiated with near-field light in a desired pattern to develop the resist layer to form a diffraction grating pattern, and the first resist layer is dry-etched using the resist layer pattern as an etching mask. In the near-field light exposure method of forming a pattern on the substrate of the recording material by this, the complicated pattern for generating the near-field light is divided into slit patterns arranged in one direction, and each divided slit pattern is divided. It is characterized in that a means for performing multiple exposure under the optimum exposure condition is provided. By doing so, the polarized light is controlled under optimal conditions for each divided slit pattern to generate near-field light, and a desired complicated fine pattern is faithfully formed by multiple exposure in which each divided slit pattern is exposed. There is an effect that it is possible to perform exposure for

Further, in the invention according to claim 2, the means for performing the multiple exposure prepares a plurality of exposure masks each having a pattern formed for each of the divided slit patterns, and the exposure masks are sequentially adhered to the resist layer. Then, multiple exposure is performed to form a complicated pattern by performing exposure under the respective optimum exposure conditions. By doing this, it is possible to perform multiple exposure to form a desired fine pattern by creating an exposure mask for each of the divided slit patterns and performing exposure under optimal conditions that match the polarization direction and the slit direction. There is an effect that.

According to a third aspect of the present invention, in the means for performing the multiple exposure, only a desired portion of the complicated pattern for generating the near-field light is irradiated with the light via the spatial light modulator. In addition, multiple exposure is performed by exposing each of the desired portions under optimum exposure conditions. By doing so, it is possible to perform multiple exposure under optimal conditions by changing the irradiation region of polarized light on one exposure mask, and it is possible to form a desired fine pattern.

The invention according to claim 4 is characterized in that the spatial light modulator is of a liquid crystal type. By doing so, it becomes possible to construct a spatial light modulator having a fine array structure and perform light irradiation for generating near-field light that can locally and faithfully expose a fine pattern in each divided slit pattern region. Has the effect of becoming

According to a fifth aspect of the present invention, the spatial light modulator is a MEMS type (Micro Electro).
-Mechanical System). By doing so, the UV light can be used and there is no loss due to the polarization system, so that a spatial light modulation element having high utilization efficiency is configured to generate near-field light capable of exposing a fine pattern for each divided slit pattern region. There is an effect that light irradiation becomes possible.

In addition, according to the present invention, when the pattern of the exposure mask is composed of a set of straight lines extending in one direction under the optimum exposure conditions, the linear polarization direction of the exposure light and the direction of the straight line of the pattern of the exposure mask are set. It is characterized by matching. Furthermore, the present invention is characterized in that, under the optimum exposure condition, the ratio of the component linearly polarized in the direction perpendicular to the desired linearly polarized light component is 25% or less, preferably 15% or less. By doing so, the exposed "line width thickening" expressed by the ratio to the mask pattern line width exceeding the line width of the mask pattern overlaps adjacent patterns when the line and space ratio is 1: 1. 50% that can prevent
The ratio of the vertical component (S-polarized light) to the linearly polarized light component (P-polarized light) is reduced from 25% to 1
If it is reduced to 5% or less, the numerical value capable of preventing pattern overlap can be suppressed to about 30% or less, and it is possible to obtain an extremely fine pattern by suppressing the thickening of the exposed line width.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a mask pattern of a near-field light exposure method by mask multiple exposure according to a first embodiment of the present invention. FIG. 2 is a conceptual diagram of multiple exposure using the mask pattern shown in FIG.
In FIG. 1, 1 is, for example, an exposure mask having the same circular shape as a wafer, and 4 is an original mask pattern formed on the exposure mask 1, which is finer than a light wavelength written by an electron beam or the like ( It is a complicated pattern having an opening pattern (slit pattern) of 100 nm or less) in the X and Y2 directions. At the time of exposure, the same polarized wave can only be set parallel to the slit in one direction, so Y (vertical)
Exposure mask 2 having only slits 5 in the direction X,
Exposure mask 3 having only slits 6 in the (horizontal) direction
Then, the exposure mask is divided into two and created.

Next, the operation will be described with reference to FIG. First, in the case of exposure of the exposure mask 2, the exposure mask 2 held on the mask carrier using a wafer transfer system or the like (not shown) is transferred to the exposure apparatus similar to that of FIG. The exposure mask 2 and the second resist layer 7 on the substrate are brought into close contact with each other by vacuuming. Next, the exposure mask 2 is irradiated with light L such as g or i rays from a mercury lamp light source to generate near-field light, and the pattern 5 is transferred to the second resist layer.

After the exposure of the exposure mask 2 is completed, N ₂ gas or the like is blown between the exposure mask 2 and the second resist layer 7 in the exposure apparatus to separate the exposure mask 2 and the second resist layer 7, and again. The exposure mask 2 is returned to the mask carrier by the wafer transfer system. Next, the exposure mask 3 is conveyed and set in the exposure apparatus, and is brought into close contact with the second resist layer 7 by vacuuming. Then, the exposure mask 3 is irradiated with light L such as g-line to generate near-field light, and the pattern 6 is formed on the second resist layer 7.
Transfer to. When the exposure of the pattern 6 of the exposure mask 3 is completed, N ₂ gas or the like is blown into the exposure apparatus to expose the exposure mask 3
Then, the second resist layer 7 is peeled off, the exposure mask 3 is returned into the mask carrier, and the complex pattern 4 of the exposure mask 1 is transferred to the second resist layer 7 by multiple exposure.

Here, the light L such as g or i rays of a mercury lamp is used.
When generating the near-field light by irradiating with, the direction of the linearly polarized light of the irradiating light L and the direction of the straight line of the slit pattern of the exposure mask 2 or 3 need to match. Polarizing plate (not shown) for polarization
Etc. are inserted between the light source and the exposure mask to control, for example, P-polarized light so as to match the linear direction of the slit pattern. For the linearly polarized light component of the exposure light (for example, P-polarized light) that matches the direction of the straight line of this slit pattern,
The ratio of the linearly polarized light component (for example, S-polarized light) in the vertical direction is 25% or less, and is preferably 15% or less. This can prevent the exposed line width from becoming thick. When a polarized laser wave is used as the light source, the light source itself may be rotated so as to match the slit pattern.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a conceptual diagram of a spatial light modulator of a near-field light exposure method by mask multiple exposure according to the second embodiment of the present invention. FIG. 4 is a diagram in which the spatial light modulator shown in FIG. 1 is made of liquid crystal. FIG. 5 is a diagram in which the spatial light modulator shown in FIG. 1 is configured by MEMS.
In FIG. 3, 8 is a ferroelectric liquid crystal or MEMS (Mi
cro Electro-Mechanical Sy
This is a conceptual representation of a spatial light modulation element using a device such as a system). Reference numeral 9 is a pattern area of the exposure mask 1 in the X (horizontal) direction, and 10 is a pattern area of the exposure mask 1 in the Y (vertical) direction.

Next, the operation will be described. In the second embodiment shown in FIG. 3, the exposure region is limited by using the spatial light modulator 8 that exhibits selective light transmission characteristics, and a desired (for example, X direction: FIG. 3A, or The near-field photolithography is configured by multiple exposure in which the light L is applied only to the slit pattern region in the Y direction: only one slit pattern in FIG. 3B) direction. First, the liquid crystal switching element at a position corresponding to the slit pattern area 9 in the X direction of the spatial light modulation element 8 is ON-controlled, and linearly polarized light L whose direction is matched with the slit pattern is irradiated to the slit pattern 9 so as to approach them. Perform field exposure. Then X
The liquid crystal switching element corresponding to the slit pattern in the Y direction is turned off, and the liquid crystal switching element corresponding to the slit pattern area 10 in the Y direction is turned on, and linearly polarized light whose direction is aligned with the slit pattern is irradiated to irradiate the liquid crystal in the Y direction. Near-field light exposure of slit pattern is performed and X / Y2
Multiple exposure is performed by controlling the direction of exposure division.

With respect to the actual configuration of the spatial light modulation element, as shown in FIG. 4, a liquid crystal type in which a MOS-FET for ON / OFF driving a ferroelectric liquid crystal as a switching element is integrally configured. A polarization beam splitter (PBS) 22 is arranged on the opposite transparent substrate side of the spatial light modulation element 21, and the light L from the light source 23 is reflected by the PBS 22 as an S polarized wave and enters the spatial light modulation element 21 to enter the liquid crystal layer. The reflected light is incident on the PBS 22 again, and only the P-polarized component of the reflected light is transmitted through the PBS 22 and becomes output light. The spatial light modulators are arranged in an array type matrix and liquid crystal
The output light is modulated and controlled by performing N / OFF control.

Next, in an actual MEMS example, the DMD
(Digital Micromirror Device
(c), etc., such as an element that performs optical modulation in accordance with a change in the incident angle of an array of miniature mirrors, or, for example, an electromechanical operation of a diaphragm, as shown in FIG. 5, to perform optical modulation. There is a spatial light modulator, etc. The spatial light modulation element MEMS 30 shown in FIG. 5 emits light from the UV lamp 33b provided on the side of the flat light source unit 33a from the upper surface of the flat light source unit 33a, and below the diaphragm (mechanical operation part) 32. The dielectric multilayer mirror 35 and the dielectric multilayer mirror 36 on the substrate 31 are arranged so as to face each other with a predetermined gap. Here, when a control voltage is applied to the electrodes on the substrate, the gap 37 between the dielectric multilayer mirrors is reduced due to the deformation of the diaphragm 32, the incident angle of light is changed, and the incident light is transmitted and emitted. The MEMS are arranged in an array type matrix to perform optical modulation. This is a MEMS that applies the Fabry-Perot interference, but one that applies the light guide diffusion function and other MEMS.
But it doesn't matter.

[0022]

As described above, according to the first aspect of the invention, only the first resist layer which can be removed by dry etching on the substrate and the portion irradiated or not irradiated by light irradiation can be used as the developing solvent. A second resist layer of the recording material is formed by a generating means such as an exposure mask that generates near-field light by receiving irradiation light on a recording material in which a second resist layer having a photosensitive dry etching resistance that is dissolved is laminated in this order. By forming a diffraction grating pattern by irradiating the resist layer with a desired pattern in a near-field pattern to form a diffraction grating pattern, and dry-etching the first resist layer using the resist layer pattern as an etching mask. In a near-field light exposure method for forming a pattern on a substrate of a recording material, a slit pattern in which a complicated pattern for generating near-field light is arranged in one direction is used. Since there is a means for performing multiple exposure under optimum exposure conditions for each divided slit pattern, it controls polarization under the optimum conditions for each divided slit pattern to generate near-field light, and The multiple exposure in which each slit pattern is exposed has an effect that it becomes possible to perform exposure for faithfully forming a desired complicated fine pattern.

According to a second aspect of the present invention, the means for performing multiple exposure is to prepare a plurality of exposure masks each having a pattern formed for each of the divided slit patterns, and bring each exposure mask into close contact with the resist layer in sequence. , Multiple exposure is performed under each optimum exposure condition to form a complicated pattern, so an exposure mask is created for each divided slit pattern, and the exposure is performed under the optimum condition to match the polarization direction with the slit direction. This has the effect of enabling multiple exposure to form a desired fine pattern.

According to the third aspect of the present invention, the means for performing multiple exposure is such that light is irradiated to only a desired portion of a complicated pattern for generating near-field light via the spatial light modulator. Then, since multiple exposure is performed by exposing each desired portion under optimum exposure conditions, it is possible to perform multiple exposure under optimum conditions by changing the irradiation area of polarized light on one exposure mask. There is an effect that a fine pattern can be formed.

Further, according to the invention described in claim 4, since the spatial light modulator is composed of liquid crystal, a spatial light modulator having a fine array structure is constituted and localized in each divided slit pattern region. There is an effect that light irradiation that generates a near-field light that can faithfully expose a fine pattern with

According to a fifth aspect of the invention, the spatial light modulator is a MEMS (Micro Electro Microscope).
-Mechanical System), UV light can be used and there is no loss due to the polarization system. Therefore, a spatial light modulator with high utilization efficiency can be configured, and near-field light that can expose a fine pattern for each divided slit pattern area can be generated. There is an effect that it is possible to irradiate the generated light.

[Brief description of drawings]

FIG. 1 is a diagram showing a mask pattern of a near-field light exposure method by mask multiple exposure according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram of multiple exposure using the mask pattern shown in FIG.

FIG. 3 is a conceptual diagram of a spatial light modulator of a near-field light exposure method by mask multiple exposure according to a second embodiment of the present invention.

FIG. 4 is a diagram in which the spatial light modulator shown in FIG. 3 is made of liquid crystal.

5 is a diagram in which the spatial light modulator shown in FIG. 3 is configured by MEMS.

FIG. 6 is a diagram showing a conventional fine pattern forming method.

FIG. 7 is a diagram showing an exposure apparatus having the pattern shown in FIG.

FIG. 8 is an explanatory diagram of polarized light of the exposure apparatus shown in FIG.

[Explanation of symbols] 1 exposure mask Two or three division exposure mask 4 complex patterns 5, 6 division pattern 7 Two-layer resist layer 8 Spatial light modulator 9,10 pattern area 21 Spatial light modulator using liquid crystal 22 PBS 23 Light source 30 MEMS 31 substrate 32 diaphragm 33 UV lamp 35, 36 Dielectric multilayer mirror

Claims (5)

[Claims] 1. A first resist layer which can be removed by dry etching on a substrate and a second resist layer having a photosensitive dry etching resistance in which only a portion irradiated or not irradiated by light irradiation is soluble in a developing solvent. The second resist layer of the recording material is irradiated with the desired pattern in a desired pattern by a generating means such as an exposure mask that receives the irradiation light to generate the near-field light. In the near-field light exposure method, a diffraction grating pattern is formed by developing, and the first resist layer is dry-etched using the resist layer pattern as an etching mask to form a pattern on the substrate of the recording material. The complex pattern for generating the near-field light is divided into slit patterns arranged in one direction, and the divided slit pattern Near-field light exposure method using the mask multiple exposure and performing multiple exposure by the optimal exposure conditions. 2. The means for performing multiple exposure prepares a plurality of exposure masks each having a pattern formed for each of the divided slit patterns, and sequentially brings the respective exposure masks into close contact with the resist layer, according to respective optimum exposure conditions. The near-field light exposure method by mask multiple exposure according to claim 1, wherein multiple exposure is performed to form a complicated pattern by exposing. 3. The means for performing the multiple exposure is such that light is irradiated to only a desired portion of the complicated pattern for generating the near-field light via a spatial light modulator, and each of the desired portions is exposed. 2. The near-field light exposure method by mask multiple exposure according to claim 1, wherein the multiple exposure is performed by exposing to the optimum exposure conditions. 4. The near-field light exposure method by mask multiple exposure according to claim 3, wherein the spatial light modulator is of a liquid crystal type. 5. The spatial light modulator is a MEMS (Mi
cro Electro-Mechanical Sy
4. The near-field light exposure method by mask multiple exposure according to claim 3, wherein the method is a type).