Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Electron beam imaging
Reexamination Certificate
2000-06-08
2002-01-22
Young, Christopher G. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Electron beam imaging
C430S017000, C430S311000, C430S326000, C430S328000, C430S330000, C430S942000
Reexamination Certificate
active
06340556
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for decreasing the linewidth and contact hole diameters of photoresist images which are suitable for use in the production of microelectronic devices such as integrated circuits. More particularly, the invention provides a process for decreasing the linewidth and contact hole diameters of images produced from positive working 193 nm sensitive photoresists.
2. Description of the Related Art
As feature sizes in the production of integrated circuits approach 100 nm, problems of packing density become increasingly difficult to overcome. The major problem is lithographic exposure tool resolution for exposure of photoresists. Photoresists are well known in the art. These light sensitive materials are applied as a thin film coating to a suitable substrate. Upon imagewise exposure of the coated substrate to actinic radiation, the difference in solubility rates between exposed and unexposed areas produces an image on the substrate after development. The uncovered substrate is thereafter subjected to an etching process. Frequently, this involves a plasma etching against which the resist coating must be sufficiently stable. For a positive tone photoresist, the coating protects those areas of the substrate from the etchant which were covered during the exposure, and thus the etchant is only able to etch the areas which were uncovered. The photoresist coating protects the covered areas of the substrate from the etchant and thus the etchant is only able to etch the uncovered areas of the substrate. Thus, a pattern can be created on the substrate which corresponds to the pattern of the mask or template that was used to create selective exposure patterns on the coated substrate prior to development.
The ability to reproduce very small dimensions, is extremely important in the production of large scale integrated circuits on silicon chips and similar components. As the integration degree of semiconductor devices becomes higher, finer photoresist film patterns are required. One way to increase circuit density on such a chip is by increasing the resolution capabilities of the resist. Positive photoresists have been found to be capable of much higher resolution and have almost universally replaced negative resists for this purpose.
The optimally obtainable microlithographic resolution is essentially determined by the radiation wavelengths used for the selective irradiation. However the resolution capacity that can be obtained with conventional deep UV microlithography (i.e. 248 nm) has its limits. In order to be able to sufficiently resolve optically small structural elements, e.g. features of 0.18 &mgr;m and smaller, radiation with a wavelength of 193 nm, in particular, the radiation of argon fluoride excimer lasers, which has a wavelength of 193 nm has been employed.
Chemical amplification resist films have been developed, which have been found to have superior resolution. A typical chemical amplification photoresist film comprises a polymer, a photoacid generator, and other optional additives. The polymer is required to be soluble in the chosen developer solution, and have high thermal stability and low absorbance to the 193 nm exposure wavelength in addition to having excellent etch resistance. 193 nm photoresists are based on chemically amplified deprotection. With this mechanism, a molecule of photogenerated acid catalyzes the breaking of bonds in a protecting group of a polymer. During the deprotecting process, another molecule of the same acid is created as a byproduct, and continues the acid-catalytic deprotection cycle. The chemistry of a 193 nm photoresist is based on polymers such as, but not limited to, acrylates, cyclic olefins, acrylates with pendant alicyclic groups, and hybrids of the aforementioned polymers which lack aromatic rings, which contribute to opacity at 193 nm. It has thus been known to utilize photoresists based on methacrylate resins for the production of microstructures by means of 193 nm radiation.
However, depending on the imaging configuration, and type of chemically amplified resist, sometimes even chemically amplified resist films are not able to adequately resolve integrated circuit lines having a thickness in the 100-200 nm range. It has now been found according to the present invention, that by subjecting a developed photoresist having lines having a thickness in the 100-200 nm range to electron beam irradiation, that it is possible to reduce the linewidth of the lines produced in the resist image while still imparting sufficient integrity to permit plasma etching without intolerable resist profile degradation. The present invention therefore provides a process for reducing the linewidth of 100-200 nm photoresist lines by from about 5 to about 50% while maintaining sufficient line integrity to permit plasma etching.
SUMMARY OF THE INVENTION
The invention provides a process for reducing the linewidth of a photoresist image which comprises:
(a) coating and drying a photosensitive composition onto a substrate, which photosensitive composition comprises
(i) at least one water insoluble, acid decomposable polymer, wherein said polymer is present in the photosensitive composition in an amount sufficient to form a uniform film of the composition components when it is coated on a substrate and dried;
(ii) at least one photosensitive compound capable of generating an acid upon exposure to sufficient activating energy, said photosensitive compound being present in an amount sufficient to substantially uniformly photosensitize the photosensitive composition;
(b) imagewise exposing the photosensitive composition to sufficient activating energy to cause the photosensitive compound to generate sufficient acid to decompose the polymer in the imagewise exposed areas of the photosensitive composition and produce a latent pattern of lines having a linewidth of from about 100 nm to about 200 nm;
(c) developing the photosensitive composition to thereby remove the exposed nonimage areas and leaving the unexposed image areas of the photosensitive composition in the form of a pattern of lines having a linewidth of from about 100 nm to about 200 nm;
(d) controllably irradiating the image areas of the photosensitive composition to sufficient electron beam radiation to thereby reduce the linewidth by an amount of from about 5% to about 50%.
The invention also provides a process for producing a microelectronic device image which comprises:
(a) coating and drying a photosensitive composition onto a substrate, which substrate comprises a material selected from the group consisting of silicon, aluminum, lithium niobate, polymeric resins, silicon dioxide, doped silicon dioxide, gallium arsenide, Group III/V compounds, oxides, oxynitrides, silicon nitride, titanium, titanium nitride, tantalum, tantalum nitride, copper, polysilicon, ceramics, aluminum/copper mixtures and combinations thereof, and which photosensitive composition comprises
(i) at least one water insoluble, acid decomposable polymer, wherein said polymer is present in the photosensitive composition in an amount sufficient to form a uniform film of the composition components when it is coated on a substrate and dried;
(ii) at least one photosensitive compound capable of generating an acid upon exposure to sufficient activating energy, said photosensitive compound being present in an amount sufficient to substantially uniformly photosensitive the photosensitive composition;
(b) imagewise exposing the photosensitive composition to sufficient activating energy to cause the photosensitive compound to generate sufficient acid to decompose the polymer in the imagewise exposed areas of the photosensitive composition and produce a latent pattern of lines having a linewidth of from about 100 nm to about 200 nm;
(c) developing the photosensitive composition to thereby remove the exposed nonimage areas and leaving the unexposed image areas of the photosensitive composition in the form of a pattern of lines having a linewidth of from about 1
Electron Vision Corporation
Roberts & Mercanti LLP
Young Christopher G.
LandOfFree
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