Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
1998-12-08
2001-02-06
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S317000
Reexamination Certificate
active
06183938
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to using an organic coating to make very small features. In particular, the present invention relates to using an organic coating and a nitrogen rich material to make sub-lithographic structures.
BACKGROUND ART
In the semiconductor industry, there is a continuing trend toward higher device densities. To achieve these high densities there has been and continues to be efforts toward scaling down the device dimensions on semiconductor wafers. In order to accomplish such high device packing density, smaller and smaller features sizes are required. This includes the width and spacing of interconnecting lines and the surface geometry such as corners and edges of various features. Since numerous interconnecting lines are typically present on a semiconductor wafer, the trend toward higher device densities is a notable concern.
The requirement of small features (and close spacing between adjacent features) requires high resolution photolithographic processes. In general, lithography refers to processes for pattern transfer between various media. It is a technique used for integrated circuit fabrication in which a silicon slice, the wafer, is coated uniformly with a radiation-sensitive film, the resist, and an exposing source (such as optical light, X-rays, or an electron beam) illuminates selected areas of the surface through an intervening master template, the photomask, for a particular pattern. The lithographic coating is generally a radiation-sensitized coating suitable for receiving a projected image of the subject pattern. Once the image is projected, it is indelibly formed in the coating. The projected image may be either a negative or a positive of the subject pattern. Exposure of the coating through the photomask causes a chemical transformation in the exposed areas of the coating thereby making the image area either more or less soluble (depending on the coating) in a particular solvent developer. The more soluble areas are removed in the developing process to leave the pattern image in the coating as less soluble polymer.
Projection lithography is a powerful and essential tool for microelectronics processing. However, lithography is not without limitations. Patterning features having dimensions of about 0.25 &mgr;m or less with acceptable resolution is difficult at best, and impossible in some circumstances. Procedures that increase resolution, improved critical dimension control, and provide small features are therefore desired.
SUMMARY OF THE INVENTION
The present invention provides methods of forming sub-lithographic features. The present invention also provides sub-lithographic features that are particularly useful for subsequent lithographic procedures.
In one embodiment, the present invention relates to a method of making a sub-lithographic structure involving the steps of providing a nitrogen rich film over a portion of a substrate; depositing a photoresist over the nitrogen rich film and the substrate, wherein the photoresist and the nitrogen rich film interact and form a thin desensitized resist layer around an interface between the photoresist and the nitrogen rich film; exposing the photoresist to radiation; developing the photoresist exposing the thin desensitized resist layer; directionally etching a portion of the thin desensitized resist layer; and removing the nitrogen rich film leaving the sub-lithographic structure on the substrate.
In another embodiment, the present invention relates to a method of making a sub-lithographic structure involving the steps of providing a nitrogen rich film over a portion of a substrate, the nitrogen rich film including at least one edge; depositing an acid catalyzed photoresist over the nitrogen rich film and the substrate, wherein the acid catalyzed photoresist and the nitrogen rich film interact and form a thin desensitized resist layer around an interface between the acid catalyzed photoresist and the nitrogen rich film; exposing the acid catalyzed photoresist to radiation; developing the acid catalyzed photoresist exposing the thin desensitized resist layer; directionally etching a portion of the thin desensitized resist layer formed above the nitrogen rich film while maintaining a portion of the thin desensitized resist layer laterally adjacent at least one edge of the nitrogen rich film; and removing the nitrogen rich film leaving the portion of the thin desensitized resist layer laterally adjacent at least one edge of the nitrogen rich film forming the sub-lithographic structure on the substrate, wherein the sub-lithographic structure has a width from about 100 Å to about 2,000 Å and a height from about 300 Å to about 5,000 Å.
In yet another embodiment, the present invention relates to a method of processing a semiconductor substrate, involving the steps of providing a silicon nitride film over a portion of a substrate; depositing an acid catalyzed photoresist over the silicon nitride film and the substrate, wherein the acid catalyzed photoresist and the silicon nitride film interact and form a thin desensitized resist layer having a thickness from about 100 Å to about 2,000 Å around an interface between the acid catalyzed photoresist and the silicon nitride film; exposing the acid catalyzed photoresist to radiation; developing the acid catalyzed photoresist with an aqueous alkaline solution exposing the thin desensitized resist layer; directionally etching a portion of the thin desensitized resist layer; and removing the silicon nitride film leaving a sub-lithographic structure on the substrate.
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patent: 6020269 (2000-02-01), Wang
Lyons Christopher F.
Templeton Michael K.
Advanced Micro Devices , Inc.
Barreca Nicole
Huff Mark F.
Renner, Otto, Boissells & Sklar, LLP
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