Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Forming nonplanar surface
Reexamination Certificate
2002-06-28
2004-07-06
Barreca, Nicole (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Forming nonplanar surface
C430S324000, C430S325000, C430S330000, C430S331000, C430S401000, C430S414000, C430S428000, C430S432000, C430S925000
Reexamination Certificate
active
06759184
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a process for the post-exposure amplification of structured resists as used in the production of microelectronic components.
In order to increase the computational speed of processors, the storage volume of memory elements, and to reduce the costs of the components, chips that have increasingly small structures and hence an increasingly high density of components are being developed in the semiconductor industry. A particular challenge is the reduction of the minimum structure size. In optical lithography, reducing wavelengths has reduced the minimum structure size. At a structure size of 100 to 70 nm, the processes known to date, which use wavelengths down to 193 nm, have reached the limit of their resolution. Therefore, the development of novel processes is necessary. Optical lithography has particularly good prospects for potential industrial use, a radiation having a wavelength of 157 nm being used for exposure since the chip manufacturers can in this case continue to use their extensive knowledge in optical lithography. A substantial difficulty in using an exposure radiation having a wavelength of 157 nm is the unsatisfactory transparency of the materials used to date. For industrial use, the base polymer in these high-resolution resists must have a transparency that is as high as possible, while the photosensitive chemicals with which, for example, an acid is produced in the resist must have a high quantum yield.
Some of the resists currently used for the manufacture of microchips operate with so-called chemical amplification. Exposure in a photochemical reaction changes the chemical structure of the photoresist. In the case of a positive-working, chemically-amplified resist (for example, a strong acid which affects catalytic conversion or cleavage of the resist) is produced by the exposure. This chemical reaction dramatically changes the solubility of the polymer in a developer so that a substantial differentiation between exposed and unexposed parts is possible.
The structured photoresist can be used as a mask for further processes, for example, dry etching processes. If the photoresist is used to structure an organic chemical medium underneath, for example in two-layer resists, the photoresist disposed as the uppermost layer must have high etch resistance. For this purpose, the photoresist can either have corresponding groups in the polymer chain, for example, silicon-containing groups, or it is amplified in a step that follows the structuring of the photoresist. For this purpose, reactive groups must be present as anchor groups in the polymer. These then react with a suitable reactive group of an amplification reagent, which group acts as a linking group, with formation of a chemical bond. In this way, silicon-containing or aromatic groups can be subsequently introduced into the polymer. The etch resistance of aromatic and organosilicon compounds in oxygen plasma is substantially higher compared with aliphatic organic hydrocarbon compounds. Particularly for resist structures having a very small layer thickness, post-exposure amplification of the resist structures is therefore advantageous. The reaction for incorporating organosilicon compounds is often silylation, and the incorporation of aromatic compounds is referred to as aromatization.
A process for the post-exposure amplification of resist structures is described, for example, in European Patent EP 0 395 917 B1, which corresponds to U.S. Pat. Nos. 5,234,794 and 5,234,793. According to those patents, the photoresists used for exposure wavelengths of 248 and 193 nm are structured and then chemically amplified in their etch resistance by the incorporation of organosilicon groups and thus form a sufficiently stable etch resist. For this purpose, the film-forming polymer of the etch resist includes reactive groups: for example, anhydride groups. These anhydride groups react with basic groups of the silylating solution that contains, for example, bifunctional aminosiloxanes, amide bonds being formed between polymer and silylating reagent with crosslinking of the resist structure. Finally, excess silylating reagent is washed away with a suitable wash solution. Resists to be exposed to radiation having a wavelength of 248 or 193 nm permit layer thicknesses in the range from 140 to 200 nm. During the silylation, the amplification agent increases a volume in the horizontal and vertical direction. A narrowing of the valleys of the resist structure and hence an improvement in the resolution are therefore possible.
As already mentioned, the low transparency of the known photoresists at a wavelength of 157 nm is a substantial difficulty in the development of 157 nm technology. With the currently known photoresists, layer thicknesses of more than 50 nm can be realized. At present, photoresists having a high degree of fluorination are being developed. This makes it possible substantially to increase the transparency of the polymer at a wavelength of 157 nm. Nevertheless, these polymers have about 50 times higher absorption than the currently customary polymers in the industrially used resists for exposure to radiation having a wavelength of 193 or 248 nm. Even with these highly fluorinated polymers, only layer thicknesses of up to 200 nm are achieved. This creates problems with the structuring of the underlying material. Therefore, attempts have been made to increase substantially the layer thickness of the already structured photoresist. However, if the abovementioned processes of European Patent EP 0 395 917 B1 are used for this purpose, only unsatisfactory results are obtained.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide an amplification of resist structures of fluorinated resist polymers by structural-growth of the structures by targeted chemical bonding of fluorinated oligomers that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that provides a process for the post-exposure amplification of resist structures. The process can increase the layer thickness of an already structured photoresist for the 157 nm technology.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a process for post-exposure amplification of structured resists. The first step of the process is applying a chemically amplified photoresist to a substrate. The photoresist includes an at least partially fluorinated film-forming polymer having acid-labile groups and hindered anchor groups for linking amplification agents. The acid-labile groups are eliminatable by acid and used for liberating polar groups to increase solubility of the polymer in polar developers The photoresist also includes polar groups attached to the polymer, a photo acid generator, and a solvent. The next step is drying the photoresist to yield a photoresist film. The next step is exposing section-by-section the photoresist film to produce an exposed resist containing a latent image. The next step is heating the exposed resist to a first temperature to convert the latent image into a chemical profile by liberating the polar groups on the polymer. The next step is developing the resist with a polar developer by detaching parts of the chemical profile containing liberated polar groups being detached from the substrate to yield a structured resist. The next step is applying an amplification agent to the structured resist. The amplification agent is at least partially fluorinated and has at least one linkage group for reacting with the anchor group of the polymer to link the amplification agent to the polymer. The next step is removing excess amplification agent.
A process for the post-exposure amplification of structured resists achieves the object. The process includes the following steps:
(a) applying a chemically amplified photoresist to a substrate; the photoresist including the following components:
an at least partially fluorinated polymer including acid-labile groups
Eschbaumer Christian
Herbst Waltraud
Hohle Christoph
Rottstegge Jörg
Sebald Michael
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