Patent Application
20100099046
The priority of Korean patent application No. 10-2008-0103325 filed Oct. 21, 2008, the disclosure of which is hereby incorporated in its entirety by reference, is claimed.
The present invention relates to a method for manufacturing a semiconductor device that comprises forming a protective film over a photoresist pattern to improve the residual ratio of the photoresist pattern.
A semiconductor is a material that could be made to be conductive or non-conductive depending on whether or not it is doped with impurities. The semiconductor is used to produce a semiconductor device such as a transistor by adding impurities to the semiconductor and forming source and drain regions thereon. As the semiconductor device becomes high-integrated, a semiconductor chip size becomes smaller. Improved fabrication processes continually needed to make the chips smaller and smaller.
A semiconductor memory device includes a volatile memory and a non-volatile memory. The volatile memory requires continuous power to retain data. The non-volatile memory does not require power to retain data.
In order to obtain high integration and high yield, much research has been done on improving to photolithography processes to push the limits of the cell structure and the physical properties of a line-forming material and an insulating-film-forming material. The photolithography process is used to form patterns and contact holes on a substrate and form semiconductor devices having multi-layered structures. The limits of the cell structure size cannot be pushed without improving the photolithography process.
The photolithography process utilizes the material called photoresist that experiences physical property changes based on whether or not it is exposed to light. In a typical photolithography process, light is selectively irradiated on a photoresist layer provided over a semiconductor substrate using a mask having a pattern. The pattern defined on the mask is transferred onto the photoresist. This patterned photoresist is transfer the pattern to an underlying material thereto.
As the semiconductor device is made smaller and smaller, a finer and finer pattern is required. However, as the pattern becomes smaller, the residual ratio of the photoresist pattern becomes lower. The residual ratio refers to the stability of the photoresist pattern in the etching process. When an underlying layer exposed by the photoresist pattern is etched, a portion of the photoresist film is also etched. If the thickness of the photoresist pattern is thinner, an etching margin for stably etching a lower layer may be insufficient. One method used to improve the residual ratio of the photoresist pattern is to increase the thickness of the photoresist layer when it is initial formed over a substrate. However, when the photoresist layer is thicker and its patterns are thicker, the resolution and the focus margin are degraded so that it is difficult to form a fine pattern using the photolithography process.
In order to obtain the fine pattern, an organic bottom antireflective coating film is provided below the photoresist film during the photolithography process using a light source having a wavelength less than 248 nm. The bottom antireflective film reduces the reflectivity of the light during the exposure process and increase the light transmissivity. If the light transmissivity is increased by the bottom antireflective coating film in the exposure process, the amount of light reflected to the photoresist film is reduced so that the photoresist film may be patterned to be finer. However, it is difficult to secure an etching selectivity in the photoresist film or the bottom antireflective film that includes a hydrocarbon compound as a main component. As a result, a significant amount of the photoresist pattern is etched away when the lower bottom antireflective coating film is etched with the photoresist pattern as a mask.
For example, when a pattern including the bottom antireflective coating film having a thickness of 24 nm and the photoresist pattern having a thickness of 50 nm is formed, the photoresist pattern experiences a significant loss in order to etch away the exposed bottom antireflective coating film. That is, the thickness of the photoresist pattern becomes significantly thinner. As a result, the residual ratio of the photoresist pattern is degraded so that it may be difficult to etch a layer provided below the bottom antireflective coating film using the remaining photoresist pattern.
Various embodiments of the invention are directed to providing a method for manufacturing a semiconductor device that comprises forming a protective film over a photoresist pattern to improve the residual ratio of the photoresist pattern.
According to an embodiment of the present invention, a method for manufacturing a semiconductor device comprises: forming a photoresist pattern over an underlying layer; and forming a protective pattern on an upper portion and sidewalls of the photoresist pattern.
Preferably, the method further comprises forming an antireflection coating film between the underlying layer and the photoresist pattern.
Preferably, the forming-a-protective-pattern includes: forming a protective film over the resulting structure including the photoresist pattern; and etching the protective film to expose the underlying layer.
Preferably, the protective film is etched by a plasma process or an etch-back process.
Preferably, the protective film includes one selected from the group consisting of an oxide film, a nitride film and combinations thereof.
Preferably, the protective film is deposited at a temperature ranging from 0 to 250° C.
Preferably, the protective film is formed to be thicker over the photoresist pattern than the underlying layer.
Preferably, the method further comprises etching the underlying layer with the protective pattern as a mask to obtain a fine pattern after forming the protective pattern.
a to 1f are cross-sectional diagrams illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention.
a to 1f are cross-sectional diagrams illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention.
a illustrates an underlying layer 110 (or target layer) formed over a semiconductor substrate 100, and an antireflection coating film 120 is deposited over the underlying layer 110.
A photoresist film is coated over the antireflection coating film 120 (
A protective film 140 is formed over the resulting structure including the photoresist pattern 130 (
In one embodiment, the protective film 140 includes an upper portion 142 formed over the photoresist pattern 130 and a lower portion 144 formed over the antireflection coating film 120. The upper portion 142 is formed to be thicker than the lower portion 144 in the present embodiment.
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As described above, the method of the present invention comprises forming the protective film over the photoresist pattern, thereby preventing cutting and collapse phenomena of the photoresist pattern due to the thickness loss of the photoresist pattern when the underlying layer is etched. Particularly, the protective film increases the residual ratio of the photoresist pattern so that the fine pattern may be stably formed while the underlying layer is etched, thereby improving yield of the semiconductor device.
The above embodiments of the present invention are illustrative and not limitative. Various alternatives and equivalents are possible. The invention is not limited by the type of deposition, etching polishing, and patterning steps describe herein. Nor is the invention limited to any specific type of semiconductor device. For example, the present invention may be implemented in a dynamic random access memory (DRAM) device or non volatile memory device. Other additions, subtractions, or modifications are obvious in view of the present disclosure and are intended to fall within the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2008-0103325 | Oct 2008 | KR | national |
