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
2000-04-26
2002-06-11
Ashton, Rosemary (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
C430S914000, C430S921000
Reexamination Certificate
active
06403280
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a radiation sensitive resin composition and more particularly to a radiation sensitive resin composition which can suitably be used as chemical amplification system of resist which is useful in fine processing with various radiations such as far ultraviolet radiations generated by KrF or ArF excimer lasers, X-rays of synchrotron radiations, charged corpuscular beams such as electron beams.
Recently, there has been required a lithography technique capable of processing to a fine level of 0.20 &mgr;m or less in order to achieve a higher density in the field of fine processing represented by the production of integrated circuit devices.
However, though the prior art lithography process has generally used as radiations near ultraviolet rays such as i-line, it has been said difficult to achieve fine processing to a subquater micron level by using the near ultraviolet rays.
Therefore, an attempt has been made to use of shorter wavelength radiations which make it possible to process to a fineness of 0.20 &mgr;m or less. These shorter wavelength radiations include, for example, a line spectrum of mercury lamp, far ultraviolet rays, X-rays, electron beams and the like. Among them particularly attention has been directed to KrF excimer laser (a wavelength of 248 nm) or ArF excimer laser (a wavelength of 193 nm).
As radiation sensitive resin compositions suitable for exposing with such excimer lasers, there have been proposed a number of compositions which make use of chemical amplification effects by a component having an acid labile function group and a component generating an acid (referred to as “an acid generator” hereinafter) under irradiation with radiations (referred to as “exposure” hereinafter). This type of composition is referred to as “a chemical amplification type of radiation sensitive composition” hereunder.
For example, Japanese Patent Publication Hei 2 (1990)-27660 proposes a composition containing a polymer having a t-butyl carboxylate ester group or a phenol t-butylcarbonate group and an acid generator as a chemical amplification type of radiation sensitive composition. This composition makes use of the phenomenon that the acid generated due to exposure acts to dissociate the t-butylester or the t-butylcarbonate group from the polymer so that the polymer is allowed to have an acidic group comprising a carboxyl group or a phenolic hydroxide group, which makes the exposed area of a resist film coating easily soluble in an alkaline developer solution.
Many of prior art chemical amplification type of radiation sensitive compositions are based on phenolic resins. Such phenolic resins absorb far ultraviolet radiations due to aromatic rings in the resins when far ultraviolet rays are used as radiations. Therefore, they have a drawback that the irradiated far ultraviolet rays can not sufficiently reach the bottom portion of the resist film coatings. This causes an higher amount of exposure in the upper portion and a lower amount in the lower portion of the resist film coatings. After development, the resist has a tapered profile that is thinner at upper position and thicker at lower position. Thus, there has been a problem that no sufficient resolution is achieved. Moreover, in case the resist after development has a tapered profile, the subsequent process, that is, etching and ion implantation can not be performed at a desired size accuracy, which has been also a problem. In addition, if the top configuration of the resist film coatings is other than rectangular, the resist etching rate by dry etching becomes too fast giving a problem that the etching conditions become difficult to control.
On the other hand, the accuracy of the resist pattern can be enhanced by increasing the transmittance to radiation of the resist film coatings. For example, (meth)acrylate resins as represented by polymethyl-methacrylates have a high transparency to far ultraviolet rays and are very preferable resins from the point of view of the transmittance to radiation. For example, Japanese Patent KOKAI Hei 4(1992)-226461 proposes a chemical amplification type of radiation sensitive composition using methacrylate resins. However, this composition has a drawback of a lower durability to dry etching because of having no aromatic ring, though it is excellent in the fine processing performance. In this case, it is also difficult to perform etching at a high accuracy and it can not be said that the composition has both transparency to radiations and durability to dry etching.
As an attempt to improve the durability to dry etching without impairing the transparency to radiation for the resists comprising chemical amplification type of radiation sensitive compositions, a process of introducing alicyclic groups instead of aromatic rings into a resin component in the composition has been known. For example, Japanese Patent KOKAI Hei 7(1995)-234511 describes a chemical amplification type of radiation sensitive composition using (meth)acrylate resins having alicyclic groups.
However, as acid-dissociable functional groups in the resin component, this composition contains relatively easily dissociable groups (eg. acetal functional groups of tetrahydropyranyl groups) with prior acids and less dissociable groups (eg. t-butyl functional groups of t-butylester groups, t-butylcarbonate groups and the like) the dissociation of which can be caused by acids. When the resin component has the former functional groups dissociable with acids, the basic physical properties, especially sensitivity and pattern configuration, of the resist are good, but the composition has an inferior stability during preservation. On the other hand, when the resin component has the latter functional groups dissociable with acids, in contrast, though the composition has a good stability during preservation, it has a drawback that the basic physical properties, especially sensitivity and pattern configuration, of the resist are impaired. Moreover, the incorporation of alicyclic groups into the resin component in the composition makes the resin itself extremely hydrophobic resulting in a poor adhesive property to a substrate.
Thus, there has been a need to develop a chemical amplification type of radiation sensitive resin composition having a high transparency to radiations represented by far ultraviolet rays which is not only excellent in durability to dry etching, sensitivity, resolution, pattern configuration, but also excellent in stability during preservation, and which has sufficient adhesive property to a substrate.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a radiation sensitive resin composition having a high transparency to radiations which is useful for a chemical amplification type of resist sensitive to actinic rays, for example, far ultraviolet rays represented by KrF excimer laser or ArF excimer laser, which is not only excellent in basic physical properties such as durability to dry etching, sensitivity, resolution, pattern configuration, but also excellent in composition stability during preservation, and which has sufficient adhesive property to a substrate.
According to the present invention, the aforementioned object can be achieved by a radiation sensitive resin composition characterized by comprising (A) a resin containing an alkaline insoluble or less soluble group dissociable with acid, said resin being soluble in an alkaline solution when said group is dissociated with acid, selected from the group consisting of copolymers containing a recurring unit (I), a recurring unit (II) and a recurring unit (III-1) represented by the general formula (1) as shown below, and copolymers containing a recurring unit (I), a recurring unit (II) and a recurring unit (III-2) represented by the general formula (2) as shown below, and (B) a radiation sensitive acid-generator:
where in the general formula (1) and the general formula (2), A and B represent independently hydrogen atom, or an acid-dissociable organic group having 20 or less carbon atoms w
Ishii Hiroyuki
Iwanaga Shin-ichiro
Iwasawa Haruo
Murata Kiyoshi
Yamahara Noboru
Ashton Rosemary
JSR Corporation
Kelber Steven B.
Piper Rudnick LLP
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