Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
2002-11-12
2004-08-10
Ashton, Rosemary (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S314000, C430S325000
Reexamination Certificate
active
06773867
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resist composition, and more specifically it relates to a chemical amplification resist composition that can be developed by a basic aqueous solution after exposure. The invention further relates to a negative resist pattern forming method employing the resist composition. The resist composition of the-invention can be used to form intricate negative resist patterns that have practical sensitivity without swelling. Furthermore, the present invention relates to electronic devices including semiconductor devices such as LSI and VLSI and magnetic recording heads such as MR heads, and the production process thereof.
2. Description of the Related Art
Higher integration of semiconductor integrated circuits has progressed to the current situation in which LSIs and VLSIs are feasible, and the minimal wiring widths of wiring patterns have reached the range of 0.2 Am and smaller. This has rendered essential the establishment of microworking techniques, and in the field of lithography the demand has largely been met by shifting the ultraviolet wavelengths of light exposure sources to shorter wavelengths in the far ultraviolet range; it has been predicted that light exposure techniques employing light sources with wavelengths in the deep ultraviolet range will soon be implemented in mass production processes. At the same time, development has been rapidly progressing with resist materials that exhibit lower light absorption of the aforementioned shorter wavelengths, have satisfactory sensitivity and also exhibit high dry etching resistance.
In recent years much research has been conducted in the field of photolithography employing as the exposure light sources krypton fluoride excimer lasers (wavelength: 248 nm, here under abbreviated to KrF), as a new light exposure technique for manufacture of semiconductor devices, and they are being widely used for mass production. H. Ito et al. of IBM, U.S.A. have already developed resist compositions based on the concept of “chemical amplification”, as resists with high sensitivity and high resolution that are suitable for such short wavelength light exposure. (See, for example, J. M. J. Frechet et al.,
Proc. Microcircuit Eng.,
260(1982), H. Ito et al., Digest of Technical Papers of 1982 Symposium on VLSI Technology, 86(1983), H. Ito et al., “Polymers in Electronics”, ACS Symposium Series 242, T. Davidson ed., ACS, 11(1984), and U.S. Pat. No. 4,491,628). As is readily understood from these publications, the fundamental concept of chemical amplification resist compositions is based on higher sensitivity through an improved apparent quantum yield achieved by a catalytic reaction in the resist film.
There may be cited the very widely used and researched chemical amplification resist type that comprises t-butoxycarbonyl polyvinylphenol (t-BOCPVP) and further contains a Photo Acid Generator (PAG), which has the function of generating an acid upon light exposure; “post exposure baking” (PEB) of the exposed sections of the resist results in loss of the t-BOC groups to give isobutene and carbon dioxide. The proton acid produced upon loss of t-BOC serves as a catalyst promoting a deprotection chain reaction, which greatly alters the polarity of the exposed sections. With this type of resist, an appropriate developer can be selected to match the large change in polarity of the exposed sections, to easily form an intricate resist pattern with no swelling.
Incidentally, one of the high-resolution techniques widely used in recent years is a method employing a mask that alters the phase of light, known as a phase-shift mask or Levenson mask, and it holds promise as a method that can give resolution below the exposure light wavelength and an adequate focal depth. When such masks are used, negative resists are usually appropriate due to restrictions of the mask pattern, and this has created a strong demand for provision of negative resists. When KrF is used as the light source, these masks are considered for applications in which resolution of under 0.20 &mgr;m is required, and this has led to spurring development of high performance resists that can resolve intricate patterns without swelling, as mentioned above. There has also been abundant research in the field of lithography using argon fluoride excimer lasers (wavelength: 193 nm, hereunder abbreviated to ArF) and electron beam (EB) sources, with even shorter wavelengths than KrF, and it is an essential technique for formation of patterns of less than 0.13 &mgr;m. The development of a negative resist that can be used for ArF, EB and the like on which more advanced microworking depends, will therefore provide many industrial advantages.
Alkali-developable negative resists for KrF and EB include those based on polar reaction caused by an acid-catalyzed reaction [for example, H. Ito et al., Proc. SPIE, 1466, 408(1991), S. Uchino et al., J. Photopolym. Sci. Technol., 11(4), 553-564(1998), etc.] and those based on acid catalyzed crosslinking reaction [for example, J. W. Thackeray et al., Proc. SPIE, 1086, 34(1989), M. T. Allen et al., J. Photopolym. Sci. Technol., 7, 4(3), 379-387(1991), Liu H. I., J. Vac. Sci. Technol., B6, 379(1988), etc.]. Crosslinkable types of negative resists for ArF are also known [for example, A. Katsuyama et al., Abstracted Papers of Third International Symposium on 193 nm Lithography, 51(1997), K. Maeda et al., J. Photopolym. Sci. Technol., 11(4), 507-512(1998), etc.]
However, despite the strong demand for a high performance negative resist that can be used for high resolution techniques employing the aforementioned phase-shift masks or Levenson masks and that can be applied for KrF, ArF and EB, the existing negative resists that are practical for use consist of only the crosslinkable types mentioned above. Crosslinkable negative resists accomplish patterning by utilizing a crosslinking reaction to increase the molecular weight at the exposed sections, thus producing a difference in solubility in the developing solution with respect to the unexposed sections; it is therefore difficult to increase contrast, and unlike resists based on polar reaction caused by an acid-catalyzed reaction, it is impossible to circumvent the limitations on microworking due to pattern swelling.
As described above, when negative chemical amplification resists are examined, they are found to be largely classified as types that contain in the resist an alkali-soluble base resin, a photoacid generator that decomposes upon absorption of image-forming radiation to release an acid and a substance that causes a polarity change due to the acid-catalyzed reaction, and types that contain in the resin an alkali-soluble base resin, a photoacid generator that decomposes upon absorption of image-forming radiation to release an acid and a substance that can cause crosslinking reaction within the resin. The former chemical amplification resists that utilize a polar reaction typically make use of a pinacol transfer reaction as disclosed, for example, in R. Sooriyakumaran et al., SPIE, 1466, 419(1991) and S. Uchino et al., SPIE, 1466, 429(1991). The acid-catalyzed reaction in such a resist proceeds in the following manner.
That is, the alkali-soluble pinacol is affected by the acid and heat, being rendered alkali-insoluble. However, such chemical amplification resists have a problem in terms of resolution. Although the pinacol itself is rendered alkali-insoluble by the acid-catalyzed reaction as explained above, the alkali-soluble base resin itself does not react and it is therefore impossible to achieve a sufficient dissolution rate difference.
Chemical amplification resists are also disclosed in Japanese Unexamined Patent Publications (Kokai) Nos. 4-165359, 7-104473, 11-133606, and elsewhere. For example, Japanese Unexamined Patent Publication (Kokai) No. 4-165359 discloses a radiation-sensitive composition characterized by containing an alkali-soluble polymer compound, a secondary or tertiary alcohol with a
Kon Junichi
Kozawa Miwa
Namiki Takahisa
Nozaki Koji
Yano Ei
Armstrong Kratz Quintos Hanson & Brooks, LLP
Ashton Rosemary
Fujitsu Limited
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