JP3977093B2 - Near-field light exposure method by mask multiple exposure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to near-field lithography in which a mask and a photoresist are in close contact 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.
[0002]
[Prior 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 of 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 the resolution, but the depth of focus is inversely proportional to the square of the numerical aperture. Therefore, as the trend of miniaturization, it is required to reduce the wavelength.
Therefore, the exposure wavelength is shortened from the g-line (436 nm) to the i-line (365 nm), and further shifted to an excimer laser (248 nm.193 nm).
[0003]
However, in optical lithography, the diffraction limit of light becomes the limit of resolution, so even if an F2 excimer laser with a wavelength of 248 nm is used, miniaturization with a line width of 100 nm is said to be the limit of lithography using a lens array optical system. Yes. Furthermore, if it is going to obtain | require the resolution | decomposability of the nanometer order ahead of that, it is necessary to use the electron beam and X-ray (especially SOR light: synchrotron radiation light) lithography technique. Electron beam lithography can control pattern formation on the order of nanometers with high accuracy, and can provide a considerably deeper depth of focus than an optical system. In addition, there is an advantage that direct writing can be performed on a wafer without a mask, but there is a disadvantage that it is far from mass production because of low throughput and high cost. In addition, X-ray lithography can improve the resolution and accuracy by an order of magnitude compared to excimer laser exposure, but has the disadvantages that it is difficult to create a mask and difficult to implement, and the cost of the apparatus is high.
[0004]
As a method for solving these problems, for example, near-field light that oozes out from an opening having a diameter sufficiently smaller than the wavelength of light to be irradiated as disclosed in Japanese Patent Application Laid-Open No. 13-15427 “Method for forming a fine pattern”. Near-field lithography has been developed which is optimal for a technique for producing a diffraction grating (grating) of a DBR laser or a DFB laser, in which a resist is exposed as a light source and developed to form a fine pattern.
FIG. 6 is a diagram showing a process of a conventional fine pattern forming method. As shown in FIG. 6A, a first resist film 102 made of an organic polymer and a second resist made of a photosensitive material are formed on a substrate 101. The layer 103 is sequentially applied by spin coating or spraying to form a two-layer resist layer 103 ′. Next, as shown in FIG. 6B, an exposure mask 104 in which a minute opening pattern 106 of metal is formed on a mask substrate 105 made of a dielectric material such as glass is brought into close contact with the two-layer resist 103. When exposure is performed with near-field light 107 that exudes from an opening in which the metal of the exposure mask 104 is not formed by light irradiation such as i-line (365 nm) from the back surface, exposure is performed as shown in FIG. A portion of the resist is exposed.
Next, as shown in FIG. 6D, by developing the second resist layer 103 with a developer, the exposed portion becomes soluble in a developing solvent and forms a positive pattern. Thereafter, 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 to obtain an aspect ratio as shown in FIG. A high fine pattern is formed.
Finally, the substrate is processed by etching or vapor deposition according to the pattern of the two-layer resist layer 103 ′, and then the two-layer resist is removed to complete.
[0005]
In this case, as shown in FIG. 7, the step of bringing the exposure mask 104 and the two-layer resist 103 ′ into close contact is performed by mounting a wafer coated with the two-layer resist layer 103 ′ on the substrate 101 on the stage of the exposure apparatus before exposure. Then, a mask 104 is mounted in close proximity thereto, and as shown in FIG. 7 (a), N ₂ gas is always allowed to flow between the mask 104 and the resist 103 in the apparatus. ), The mask 104 is brought into close contact with the resist 103 by evacuating the mask 104 and the resist 103.
As described above, in the near-field light lithography using the near-field light and the two-layer resist, the resist is exposed and developed by the near-field light that exudes from the pattern having a line width sufficiently smaller than the wavelength of the irradiation light. It has become possible to form a fine pattern of 100 nm or less, which is a limit in optical lithography, at a high aspect ratio and at a low cost.
In addition, the resolution of conventional lithography was mainly determined by the wavelength of the light source. However, any wavelength of the light source that generates near-field light can be used, eliminating the need to develop a new light source and restricting pattern miniaturization. Since it can be mitigated, significant cost reductions can be expected.
[0006]
[Problems to be solved by the invention]
However, in the above-described conventional example, the exposure mask 104 that generates near-field light is brought into close contact with the photosensitive resist material 103 ′ by near-field photolithography developed as a method for creating a shape having a size smaller than the wavelength of light. In the case of transferring near-field light having a fine distribution below the wavelength, as shown in FIG. 8, the polarization direction (for example, P-polarized light) of the irradiation light (g, i, etc.) L is as shown in FIG. As shown by the solid line arrows in FIG. 8, when the exposure mask 104 is parallel to the direction of the slit 110 (the direction perpendicular to the paper surface in FIG. 8), the oozing of the near-field light 107 is localized and normal. As shown in FIG. 8B, when the deflection direction indicated by the solid arrow of the irradiation light L is perpendicular to the direction of the slit 110, the transfer pattern is different from the slit pattern due to “thickening of the line width” or the like. Question There was.
[0007]
Therefore, the present invention is not limited to the slit pattern formed on the exposure mask in one direction, and even in the case of a complicated shape pattern, a fine pattern is obtained by decomposing the pattern into several elements and performing multiple exposure. It is an object of the present invention to provide a near-field light exposure method by mask multiple exposure that can accurately transfer the image.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the near field light exposure method of the present invention is characterized in that only the first resist layer that can be removed by dry etching on the substrate and the irradiated or non-irradiated portion by light irradiation can be used as a developing solvent. A recording material in which a second resist layer having a photosensitive dry etching resistance to be dissolved is laminated in this order is applied to the second resist layer of the recording material by means of generating an exposure mask that receives irradiation light and generates near-field light. A diffraction grating pattern is formed by irradiating near-field light in a desired pattern and developing the resist layer, and the first resist layer is dry-etched using the resist layer pattern as an etching mask, thereby recording material a near-field light exposure method for forming a pattern on a substrate, a single exposure mask having a complicated pattern for generating the near field light For example, to classify complex patterns of the exposure mask for each slit pattern arranged in one direction, the near-field light exposure method for performing multiple exposure by the optimal exposure condition for each slit pattern classification, is disposed opposite to the exposure mask a matrix of spatial light modulator element, and a light source for irradiating light to the spatial light modulator is irradiated with light from the light source to the spatial light modulator, said spatial light modulator for each of the pattern A portion corresponding to the pattern of the exposure mask is exposed to near-field light with the light emitted from the spatial light modulation element selected by selective control.
[0013]
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 matched. It is characterized by.
Furthermore, the present invention is characterized in that, under the optimum exposure conditions, the ratio of the component linearly polarized in the direction perpendicular to the desired linearly polarized component is 25% or less, preferably 15% or less.
In this way, the exposed "line width thickening" expressed by the ratio to the mask pattern line width exceeding the line width of the mask pattern overlaps the adjacent pattern when the line and space ratio is 1: 1. If the ratio of the vertical component (S-polarized light) to the linearly polarized light component (P-polarized light) is reduced from 25% to 15% or less, pattern overlap can be prevented. It is possible to suppress the numerical value that can be reduced to about 30% or less, and there is an effect that an extremely fine pattern can be obtained by suppressing the thickness of the exposed line width.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a view showing a mask pattern of a near-field light exposure method by mask multiple exposure according to the 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 smaller in size than the 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.
Since the same polarized wave can be set parallel to only one direction slit at the time of exposure, the exposure mask 2 in which only the Y (vertical) direction slit 5 is formed and the exposure mask in which only the X (lateral) direction slit 6 is formed. 3 and the exposure mask is divided into two.
[0015]
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 and set to an exposure apparatus similar to that of FIG. Then, the exposure mask 2 and the second resist layer 7 of the substrate are brought into close contact with each other by evacuation.
Next, the exposure mask 2 is irradiated with light L such as g or i line from a mercury lamp light source to generate near-field light, and the pattern 5 is transferred to the second resist layer.
[0016]
When 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 wafer transport system To return the exposure mask 2 to the mask carrier.
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 evacuation.
Subsequently, the exposure mask 3 is irradiated with light L such as g-line to generate near-field light, and the pattern 6 is transferred to the second resist layer 7.
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, the exposure mask 3 and the second resist layer 7 are peeled off, the exposure mask 3 is returned into the mask carrier, and the second resist The complex pattern 4 of the exposure mask 1 is transferred to the layer 7 by multiple exposure.
[0017]
Here, when generating near-field light by irradiating light L such as g or i line of a mercury lamp, the direction of linearly polarized light of the irradiated light L and the direction of the straight line of the slit pattern of the exposure mask 2 or 3 In order to linearly polarize the light L of the mercury lamp, a polarizing plate (not shown) or the like is inserted between the light source and the exposure mask, for example, so that the P-polarized light is directed in the linear direction of the slit pattern. Control to match.
The ratio of the linearly polarized light component (for example, S-polarized light) in the vertical direction to the linearly polarized light component (for example, P-polarized light) of the exposure light that matches the direction of the straight line of the slit pattern is 15%, with 25% or less as a guide. The following is desirable. As a result, the exposed line width can be prevented from being increased.
When a polarized laser wave is used as the light source, it may be matched with the slit pattern by a method such as rotationally controlling the light source itself.
[0018]
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 using 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.
FIG. 5 is a diagram in which the spatial light modulation element shown in FIG. 1 is configured by MEMS.
In FIG. 3, reference numeral 8 conceptually represents a spatial light modulation element using a ferroelectric liquid crystal, MEMS (Micro Electro-Mechanical System) or the like. Reference numeral 9 denotes a pattern region in the X (horizontal) direction of the exposure mask 1, and reference numeral 10 denotes a pattern region in the Y (vertical) direction of the exposure mask 1.
[0019]
Next, the operation will be described.
In the second embodiment shown in FIG. 3, the exposure area is limited by using the spatial light modulation element 8 exhibiting selective light transmission characteristics, and a desired (for example, X direction: FIG. 3A), or In the Y-direction (only one slit pattern in FIG. 3B), light L is irradiated only in the slit pattern region in the direction, and near-field optical lithography is configured by multiple exposure that is combined.
First, the liquid crystal switching element at a position corresponding to the slit pattern region 9 in the X direction of the spatial light modulator 8 is controlled to be ON, and the linearly polarized light L whose direction coincides with the slit pattern is irradiated to the slit pattern 9 to approach the liquid crystal switching element. Perform field light exposure.
Next, the liquid crystal switching element corresponding to the slit pattern in the X direction is turned off, the liquid crystal switching element corresponding to the slit pattern area 10 in the Y direction is turned on, and the linearly polarized light whose direction coincides with the slit pattern is irradiated. Then, near-field light exposure of the slit pattern in the Y direction is performed, and multiple exposure is performed by exposure division control in the X and Y2 directions.
[0020]
As for the actual configuration of the spatial light modulation element, as shown in FIG. 4, a liquid crystal type spatial light modulation in which a MOS-FET that is ON / OFF driven using a ferroelectric liquid crystal as a switching element is integrated. A polarization beam splitter (PBS) 22 is disposed on the opposite transparent substrate side of the element 21, and the light L from the light source 23 reflects the S-polarized wave by the PBS 22, enters the spatial light modulation element 21, and is reflected by the liquid crystal layer. Then, it enters the PBS 22 again, and only the P-polarized component of the reflected light passes through the PBS 22 and becomes output light. The spatial light modulators are arranged in an array matrix, and the output light is modulated and controlled by ON / OFF control of the liquid crystal.
[0021]
Next, in an actual MEMS example, elements such as DMD (Digital Micromirror Device) that perform light modulation according to the change in the incident angle of the minimal mirror configured in an array, or as shown in FIG. For example, there is a spatial light modulation element or the like in which the diaphragm is electromechanically operated to perform light modulation.
A spatial light modulation element MEMS 30 shown in FIG. 5 emits light from a UV lamp 33b provided on the side of the planar light source unit 33a from the upper surface of the planar light source unit 33a, and below the diaphragm (machine operating unit) 32, The dielectric multilayer mirror 35 is disposed opposite to the dielectric multilayer mirror 36 on the substrate 31 with a predetermined interval.
Here, when a control voltage is applied to the electrode on the substrate, the gap 37 between the dielectric multilayer mirrors is reduced due to the deformation of the diaphragm 32, and the incident angle of the light changes to transmit and emit the incident light. Optical modulation is performed by arranging the MEMS in an array matrix. This is a MEMS that applies the Fabry-Perot interference, but a MEMS that applies a light guide diffusion action or other MEMS may be used.
[0022]
【The invention's effect】
As described above, according to the first aspect of the present invention, the first resist layer that can be removed by dry etching on the substrate and the photosensitivity in which only the irradiated or non-irradiated portion by light irradiation is soluble in the developing solvent. The near-field light is applied to the second resist layer of the recording material by a generating means such as an exposure mask that receives the irradiation light and generates near-field light on the recording material in which the second resist layer having dry etching resistance is laminated in this order. A diffraction grating pattern is formed by developing the resist layer by irradiating it in a desired pattern, and the first resist layer is dry-etched using the resist layer pattern as an etching mask to form a substrate on the recording material. In the near-field light exposure method for forming a pattern on the surface, a complex pattern that generates near-field light is divided into slit patterns arranged in one direction. Since each divided slit pattern is provided with means for performing multiple exposure under optimum exposure conditions, near-field light is generated by controlling polarization under optimum conditions for each divided slit pattern, and exposure is performed for each divided slit pattern. The multiple exposure has an effect that exposure for faithfully forming a desired complicated fine pattern becomes possible.
[0023]
According to the second aspect of the present invention, the means for performing multiple exposure prepares a plurality of exposure masks each having a pattern formed for each divided slit pattern, and sequentially adheres each exposure mask to the resist layer. Since multiple exposure is performed to form a complex pattern by exposing under optimal exposure conditions, by creating an exposure mask for each divided slit pattern and performing exposure under optimal conditions to match the polarization direction and slit direction, There is an effect that multiple exposure for forming a desired fine pattern becomes possible.
[0024]
According to the invention of claim 3, the means for performing multiple exposure is such that only a desired portion of a complex pattern that generates near-field light is irradiated with light through the spatial light modulator, Multiple exposure is performed by exposing each desired portion under optimum exposure conditions, so that multiple exposure under optimum conditions can be performed by changing the irradiation area of polarized light on one exposure mask, and a desired fine pattern can be obtained. There is an effect that it can be formed.
[0025]
According to the invention described in claim 4, since the spatial light modulator is made of liquid crystal, a spatial light modulator having a fine array structure is formed, and the divided slit pattern regions are localized and faithful. There is an effect that light irradiation that generates near-field light that can expose a fine pattern becomes possible.
According to the invention described in claim 5, since the spatial light modulation element is configured by MEMS (Micro Electro-Mechanical System), it can use UV light and there is no loss due to the polarization system, so that the spatial light with high utilization efficiency. There is an effect that it is possible to irradiate light that generates a near-field light capable of exposing a fine pattern for each divided slit pattern region by configuring a modulation element.
[Brief description of 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.
FIG. 3 is a conceptual diagram of a spatial light modulator of a near-field light exposure method using mask multiple exposure according to a second embodiment of the present invention.
4 is a diagram in which the spatial light modulation element shown in FIG. 3 is composed of liquid crystals.
FIG. 5 is a diagram in which the spatial light modulation element shown in FIG. 3 is configured by MEMS.
FIG. 6 is a diagram showing a conventional fine pattern forming method.
7 is a view showing an exposure apparatus for the pattern shown in FIG. 1. FIG.
8 is an explanatory view of polarized light of the exposure apparatus shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Exposure mask 2, 3 Division | segmentation exposure mask 4 Complex pattern 5, 6 Division | segmentation pattern 7 Two-layer resist layer 8 Spatial light modulation element 9, 10 Pattern area | region 21 Spatial light modulation element 22 using liquid crystal PBS
23 Light source 30 MEMS
31 Substrate 32 Diaphragm 33 UV lamp 35, 36 Dielectric multilayer mirror

Claims (1)

A first resist layer which can be removed by dry etching and a second resist layer having a photosensitive dry etching resistance in which only an irradiated portion or non-irradiated portion by light irradiation is soluble in a developing solvent are laminated in this order on the substrate. By diffracting the resist layer by irradiating the second resist layer of the recording material with a desired pattern by an exposure mask generating means for generating the near-field light upon receiving the irradiation light on the recording material. A near-field light exposure method for forming a pattern on a substrate of a recording material by forming a lattice pattern and dry-etching the first resist layer using the pattern of the resist layer as an etching mask ,
A single exposure mask having a complex pattern that generates the near-field light is provided, the complex pattern of the exposure mask is classified into slit patterns arranged in one direction, and an optimum exposure condition is determined for each classified slit pattern. In the near-field light exposure method for performing multiple exposure ,
Comprising a matrix of spatial light modulator that is disposed to face the exposure mask, and a light source for irradiating light to the spatial light modulator is irradiated with light from the light source to the spatial light modulator, the pattern for each The near-field light is characterized in that a portion corresponding to the pattern of the exposure mask is exposed to near-field light with light emitted from the selected spatial light-modulating element by selectively controlling the spatial light-modulating element. Exposure method.

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