This U.S. non-provisional patent application claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2020-0140658, filed on Oct. 27, 2020, in the Korean Intellectual Property Office, the entire contents of which are hereby incorporated by reference.
The present disclosure relates to an exposure apparatus and a method of fabricating a semiconductor device using the same, and in particular, to a photomask, an exposure apparatus, and a method of fabricating a three-dimensional semiconductor memory device using the same.
In general, a photolithography process includes a photoresist coating step, an exposing step, and a developing step. The exposing step is a step of transferring an image pattern onto a photoresist layer, which is coated on a flat substrate. As an integration density of a semiconductor device increases, it may be necessary to reduce a wavelength of light used in the exposing step and to increase a numerical aperture of a lens. However, in this case, a depth of focus may be reduced, and it may be necessary to apply an extreme-level planarization technology to the photoresist layer.
An embodiment of the inventive concept provides a photomask, which is configured to locally change a focal point of light, and an exposure apparatus including the same.
According to an embodiment of the inventive concept, a photomask may include a mask substrate, a first mask pattern on the mask substrate, and an optical path modulation substrate including a first region on a portion of the first mask pattern, and a second region on another portion of the first mask pattern, wherein the second region has a thickness that is less than a thickness of the first region.
According to an embodiment of the inventive concept, an exposure apparatus may include a stage configured to receive a substrate thereon, a light source configured to generate light to be provided onto the substrate on the stage, an objective lens disposed between the light source and the stage and configured to concentrate the light onto the substrate, and a photomask disposed between the objective lens and the light source. The photomask is configured to project a pattern onto the substrate. The photomask may include a mask substrate, a first mask pattern on the mask substrate, and an optical path modulation substrate including a first region on a portion of the first mask pattern, and a second region provided on another portion of the first mask pattern, wherein the second region has a thickness that is less than a thickness of the first region.
According to an embodiment of the inventive concept, a method of fabricating a three-dimensional semiconductor memory device may include forming a layered structure including insulating layers and horizontal layers, which are alternately stacked on a substrate having a cell array region and a connection region, forming a first photoresist pattern exposing a portion of the layered structure on the connection region, forming dummy pad patterns having a stepped shape on the connection region, using etching and trimming processes, in which the first photoresist pattern is used as an etch mask, forming a second photoresist pattern locally exposing the dummy pad patterns, using an exposure apparatus with a photomask, and forming dummy additional layers on the dummy pad patterns. The photomask may include a mask substrate, a first mask pattern on the mask substrate, and an optical path modulation substrate including a first region on a portion of the first mask pattern, and a second region on another portion of the first mask pattern, wherein the second region has a thickness that is less than a thickness of the first region.
Example embodiments will be more clearly understood from the following brief description taken in conjunction with the accompanying drawings. The accompanying drawings represent non-limiting, example embodiments as described herein.
Example embodiments of the inventive concepts will now be described more fully with reference to the accompanying drawings, in which example embodiments are shown.
Referring to
The stage 110 may be configured to load a substrate W thereon. The stage 110 may also be configured to move the substrate W in a horizontal direction. The substrate W may have a stepped top surface, as illustrated in
The light source 120 may be provided on the stage 110. The light source 120 may be configured to produce light 122 and to provide the light 122 to the substrate W. The light 122 may include an excimer laser or a deep ultraviolet light. For example, the light 122 may have a wavelength of 193 nm (ArF), 248 nm (KrF), 365 nm (i-line), or 436 nm (G-line).
The optical system 130 may be provided between the light source 120 and the stage 110. The optical system 130 may include, for example, a lens. The optical system 130 may be configured to project the light 122 onto the photomask 150 in an enlargement and/or reduction manner. Alternatively, the optical system 130 may include a mirror, but the inventive concept is not limited to this example. In an embodiment, the optical system 130 may be configured to change a propagation path of the light 122 and/or to collimate the light 122.
The objective lens 140 may be provided between the stage 110 and the optical system 130. The objective lens 140 may be configured to concentrate the light 122 onto a specific region of the substrate W. The objective lens 140 may include, for example, at least one convex lens.
The photomask 150 may be provided between the objective lens 140 and the optical system 130. As an example, the photomask 150 may be a transmission-type photomask. The photomask 150 may be used to project the light 122 onto a specific region of the substrate W. The photomask 150 may be configured to cause a spatial variation in optical path of the light 122. For example, the photomask 150 may shift a focal length of the objective lens 140 to locate a focal point 142 of the light 122 on the stepped top surface of the substrate W.
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The mask substrate 152 may be a transparent substrate. For example, the mask substrate 152 may be formed of or include quartz. Alternatively, the mask substrate 152 may be formed of or include glass, but the inventive concept is not limited to this example.
The first mask pattern 154 may be disposed on the mask substrate 152. The first mask pattern 154 may absorb and block a portion of the light 122, which is provided to the mask substrate 152. The light 122, which is made by the first mask pattern 154, may be projected onto the substrate W. An intensity of the light 122 may be variable. For example, the first mask pattern 154 may be formed of or include a metallic material (e.g., chromium).
The supporting portion 156 may be provided on an edge of the mask substrate 152 that is located outside the first mask pattern 154. The supporting portion 156 may be provided between the mask substrate 152 and the optical path modulation substrate 158. The supporting portion 156 may be configured to fasten the optical path modulation substrate 158 to the mask substrate 152. In an embodiment, the supporting portion 156 may be formed of or include at least one of, for example, sealants or adhesives. In an embodiment, the supporting portion 156 may be formed of or include a polymeric material, but the inventive concept is not limited to this example.
The optical path modulation substrate 158 may be disposed on the first mask pattern 154 and the supporting portion 156. The optical path modulation substrate 158 may be transparent to light 122, and thus, light 122 may be incident into the mask substrate 152 through the optical path modulation substrate 158. The optical path modulation substrate 158 may be formed of or include the same material as the mask substrate 152. For example, the optical path modulation substrate 158 may be formed of or include quartz. The optical path modulation substrate 158 may be configured to locally change the focal point 142 of the light 122, which is incident into the objective lens 140. As an example, the optical path modulation substrate 158 may have an edge region 151, a flat first region 153, and a non-flat second region 155, as illustrated in
The edge region 151 may be disposed outside the flat first region 153 and the non-flat second region 155, as illustrated in
The flat first region 153 may be provided on a portion of the first mask pattern 154 (i.e., as illustrated in
The non-flat second region 155 may be provided on another portion of the first mask pattern 154. The non-flat second region 155 may be thinner than the flat first region 153, as illustrated in
The recess 157 may be provided adjacent to the first mask pattern 154. The recess 157 may be provided on the bottom surface of the optical path modulation substrate 158. The top surface of the optical path modulation substrate 158 may be flat. The recess 157 may have a curvature radius R. When the stepped top surface of the substrate W has the height difference 12 of about 1 μm to about 10 μm, the curvature radius R may range from about 160 cm to 1400 cm. The recess 157 may locally change an optical path of light through the optical path modulation substrate 158, and thus, the focal point 142 of the light 122 may be shifted.
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The second mask pattern 160 may remove distortion of the light 122, which occurs when the light 122 passes through the optical path modulation substrate 158. The second mask pattern 160 may be formed of or include a metallic material (e.g., chromium). The second mask pattern 160 may be provided in the optical path modulation substrate 158.
The optical path modulation substrate 158 may have a trench 159, and the second mask pattern 160 may be provided in the trench 159. For example, the second mask pattern 160 may have a triangular crosssection, as illustrated in
The mask substrate 152, the first mask pattern 154, and the supporting portion 156 may be configured to have substantially the same features as the embodiment of
Referring to
The mask substrate 152, the first mask pattern 154, the supporting portion 156, and the optical path modulation substrate 158 may have substantially the same features as the embodiment of
Hereinafter, a method of fabricating a three-dimensional semiconductor memory device using the exposure apparatus 100 will be described in more detail.
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Thereafter, the first photoresist pattern PR1 may be removed by an ashing or cleaning process.
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Although not shown, channel holes and channel structures, which are provided in the channel holes, may be formed in the cell array region 202.
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Thereafter, the horizontal layers 214, the dummy pad patterns 220, and the dummy additional layers 230, which are exposed through the line-cut trench 242, may be removed (in S80). The horizontal layers 214, the dummy pad patterns 220, and the dummy additional layers 230 may be removed by a wet etching method.
Next, word lines WL and pad patterns 222 may be formed in regions, which are formed by removing the horizontal layers 214, the dummy pad patterns 220, and the dummy additional layers 230 (in S90). The word lines WL and the pad patterns 222 may be formed on the insulating layers 212 by an atomic layer deposition method. The word lines WL and the pad patterns 222 may be formed of or include at least one of metallic materials (e.g., tungsten). The pad patterns 222 may be formed at ends of the word lines WL to have a stepped shape.
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Although not shown, an interconnection layer may be formed on the contact plugs 260.
Thus, in the method of fabricating a three-dimensional semiconductor memory device according to an embodiment of the inventive concept, the photomask 150 may be configured to cause a local variation of a focal length of the light 122, and in this case, the photomask 150 may be used to form the dummy pad patterns 220 and the dummy additional layers 230 in a stepped shape and to form the pad patterns 222 in a stepped shape on ends of the word lines WL.
According to an embodiment of the inventive concept, a photomask may include an optical path modulation substrate with a recessed portion, and this substrate may be used to realize a local variation in a focal point of light to be incident into the photomask.
While example embodiments of the inventive concept have been particularly shown and described, it will be understood by one of ordinary skill in the art that variations in form and detail may be made therein without departing from the scope of the attached claims.
Number | Date | Country | Kind |
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10-2020-0140658 | Oct 2020 | KR | national |