Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-06-21
2003-08-26
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S170000, C528S172000, C528S173000, C528S174000, C528S188000, C528S189000, C528S272000, C528S353000, C522S164000, C430S283100, C430S325000, C430S326000, C525S420000
Reexamination Certificate
active
06610815
ABSTRACT:
This application is the national phase under 35 U.S.C. § 371 of PCT International Application No. PCT/JP00/00302, which has an International filing date of Jan. 21, 2000, which designated the United States of America and was not published in English.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polyamide ester. More particularly, the present invention is concerned with a polyamide ester which comprises a plurality of specific amide ester recurring units including, in a specific ratio, recurring units containing a tetravalent benzene group and recurring units containing a tetravalent diphenyl ether group, and which is adapted to be converted to a polyimide in a coating form by heat-curing, wherein the polyimide coating exhibits a residual stress of 33 MPa or less as measured with respect to a 10 &mgr;m-thick polyimide coating formed on a silicon substrate. By the use of the polyamide ester of the present invention, it has become possible to prepare a photosensitive composition having excellent storage stability, wherein, for example, the change in viscosity of the composition during the storage thereof is suppressed. Further, the use of such a photosensitive composition enables not only the formation of a polyimide coating which simultaneously exhibits a low residual stress, a high chemical resistance, a high heat resistance and a high adhesiveness to a substrate, but also the formation of a polyimide pattern with a high resolution and a high precision. Therefore, the polyamide ester of the present invention can be advantageously used in the production of electric or electronic parts, such as a semiconductor device and a multilayer circuit board. Further, the present invention is also concerned with a polyamide ester composition having the same excellent effects as mentioned above in connection with the polyamide ester of the present invention.
2. Prior Art
Polyimide resins have excellent thermal and chemical stabilities, a low dielectric constant and a planation or planarization ability. Therefore, polyimide resins have been drawing attention as materials for use in fields related to microelectronics and, in fact, have been widely used as a material for a surface-protective film for a semiconductor, a material for an insulator layer used in a multilayer circuit structure, a material for a multichip module, and the like.
Generally, in the process for forming a polyimide resin coating in a desired pattern on a semiconductor device, a polyimide resin coating is first formed on a substrate and then, a desired pattern is formed on the polyimide resin coating by a lithographic technique. In this case, the desired pattern is formed through an indirect procedure. Specifically, a polyimide resin pattern is formed by a process in which a photoresist pattern (corresponding to a desired polyimide resin pattern) is formed on a polyimide resin coating using a photoresist and a photomask, followed by etching to obtain a polyimide resin pattern. This process has problems in that it requires complicated operations (wherein a photoresist pattern serving as a mask for a subsequent etching operation is first formed on a polyimide resin coating and, then, the polyimide resin is etched, and, finally, the photoresist pattern, which no longer is necessary, is removed), and that, since the desired pattern is formed through an indirect procedure, the resolution is low. In addition, this process has a problem of safety, since this process requires the use of a poisonous substance, such as hydrazine, as a solvent for etching.
In recent years, for solving the above-mentioned problems, studies have been made on a method using a polyimide precursor containing a photopolymerizable photosensitive group. In this method a desired pattern is directly formed in a polyimide precursor coating. For example, there has been proposed a method which comprises: forming on a substrate a coating of a photosensitive composition (comprising a polyimide precursor composed of a polyamide acid derivative having bonded thereto a double bond-containing compound through an ester linkage, an amide linkage, an ionic linkage or the like, and a photoinitiator); exposing the coating through a photomask (having an image corresponding to a desired pattern), so that the polyimide precursor present in the exposed area of the coating becomes insoluble to a developer, thereby forming a latent pattern image in the coating; subjecting the resultant coating to a developing treatment, thereby obtaining a desired pattern of the polyimide precursor; and heating the obtained pattern to remove photosensitive group-containing components (such as the above-mentioned double bond-containing compound and the photoinitiator), thereby converting the polyimide precursor to a polyimide having heat stability (Yamaoka and Omote, “Pori fairu (Polyfile)”, Vol. 27, No. 2, pages 14 to 18, 1990). This method is generally called a photosensitive polyimide technique. By this technique, the above-mentioned problems accompanying the conventional processes using a non-photosensitive polyimide have been overcome. Therefore, the above-mentioned photosensitive polyimide technique has been put into wide use in the formation of a polyimide pattern.
However, in recent years, demands for higher resolution in the formation of a polyimide pattern used in a semiconductor device and the like have increased. In the processes using a non-photosensitive polyimide (which were developed prior to the development of the above-mentioned photosensitive polyimide technique), the resolution is low, and such low resolution is taken into consideration when the semiconductor devices per se and the production processes for semiconductor devices are designed. Therefore, the degree of circuit integration of the semiconductor devices and the precision of the semiconductor devices are necessarily low. On the other hand, by the use of the photosensitive polyimide, it is possible to achieve a high resolution in the formation of a polyimide pattern and, hence, semiconductor devices having a high degree of circuit integration and a high precision can be produced. On this point, an explanation is made below. For example, in the production of a memory device etc., in order to increase productivity, commonly employable circuits are first formed and, after examination of the memory device etc., unnecessary circuit portions are cut-off. In conventional processes using a non-photosensitive polyimide, this cutting step is conducted before forming the polyimide patterns. On the other hand, in the processes using a photosensitive polyimide, it has become possible to obtain high resolution patterning of the polyimide. Therefore, in forming polyimide patterns on circuits, appropriate holes are first formed in the polyimide pattern film, so that cutting of unnecessary circuit portions can be performed through the holes after the formation of the polyimide pattern film. The cutting-off of unnecessary circuit portions after forming polyimide patterns enables the yield of products to be improved, since the timing of the cutting-off of the unnecessary circuit portions is close to the completion of the final products, as compared to the case of the conventional processes using a non-photosensitive polyimide.
In the above-mentioned process in which the cutting of unnecessary circuit portions is performed through the holes after the formation of polyimide patterns, it is desired that the holes be as small as possible so as to achieve a high degree of circuit integration of the device. Accordingly, the demand for photosensitive polyimide precursors capable of forming a pattern with an improved resolution has increased. When such a photosensitive polyimide precursor is used, it becomes possible to achieve a wide process margin which is necessary for efficiently producing a semiconductor device having a high degree of circuit integration and a high precision. (A process having a “wide process margin” means a process in which the employable ranges of conditions (e.g., time and temp
Hata Keiko
Matsuoka Yoshio
Tanizaki Yoko
Asahi Kasei Kabushiki Kaisha
Hampton-Hightower P.
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