Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2000-11-06
2001-08-14
Ashton, Rosemary E. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S270100, C430S327000
Reexamination Certificate
active
06274289
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to improving lithography by using a coating containing a cleaving compound to reduce the thickness of a resist layer. In particular, the present invention relates to using a coating containing a cleaving compound to controllably decrease the thickness of a resist layer.
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. Patterning small features with a high degree of critical dimension control is also very difficult. Procedures that increase resolution, improved critical dimension control, and provide small features are therefore desired.
In an effort to increase resolution, improved critical dimension control, and provide small features, relatively thin photoresists are employed. However, there are problems associated with employing thin photoresist. For example, one problem is that the pinhole density is typically quite high when forming a thin photoresist layer. Pinholes lead to defects in pattern formation. Another problem is that it is difficult to planarize a thin photoresist. This is important because a non-planar photoresist layer tends not lead to a uniform patterned resist.
SUMMARY OF THE INVENTION
The present invention provides chemical resist thickness reduction processes, methods of forming thin resists, and methods of treating resists. The present invention also provides thin resist features that are particularly useful for subsequent semiconductor processing procedures. The methods of forming thin resists are conducted in a controllable manner whereby a specified or desired thickness of the resist may be achieved. As a result of the present invention, a relatively thin resist layer having a reduced pinhole density is provided. The thin resists of the present invention facilitate the use of small wavelengths that typically have difficulty in deeply penetrating resist layers.
In one embodiment, the present invention relates to a method of treating a resist layer involving the steps of providing the resist layer having a first thickness, the resist layer comprising a polymer having a labile group; contacting a coating containing at least one cleaving compound with the resist layer to form a deprotected resist layer at an interface between the resist layer and the coating; and removing the coating and the deprotected resist layer leaving a resist having a second thickness, wherein the second thickness is smaller than the first thickness.
In another embodiment, the present invention relates to a chemical resist thickness reduction process involving the steps of forming a resist layer having a first thickness, the resist layer comprising a polymer having an acid labile pendent group; depositing an acid containing coating over the resist layer, the acid containing coating comprising at least one acid and a coating material, thereby forming a deprotected resist layer at an interface between the resist layer and the acid containing coating; and removing the acid containing coating and the deprotected resist layer thereby providing a resist layer having a second thickness, the first thickness greater than the second thickness.
In yet another embodiment, the present invention relates to a method of decreasing the thickness of a resist, involving the steps of providing a chemically amplified resist having a first thickness on a substrate; depositing an acid containing coating on the chemically amplified resist thereby forming a deprotected resist layer within the chemically amplified resist; and removing the acid containing coating and the deprotected resist layer leaving a chemically amplified resist having a second thickness, wherein the second thickness is at least about 10% smaller than the first thickness.
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“0.1um Level Contact Hole Pattern Formation with KrF Lithography by Resolution Enhancement Lithography Assisted by Chemical Shrink (RELACS),” T. Toyoshima, et al., Advanced Technology R&D Center, Mitsubishi Electric Corp., IEDM IEEE 1998, pp. 98-333-336.
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Quinto Ursula Q.
Rangarajan Bharath
Subramanian Ramkumar
Templeton Michael K.
Advanced Micro Devices , Inc.
Amin & Turocy LLP
Ashton Rosemary E.
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