Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Reexamination Certificate
2000-10-27
2003-01-28
Chu, John S. (Department: 1752)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
C528S129000, C528S148000, C430S192000, C430S193000, C210S634000
Reexamination Certificate
active
06512087
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention provides a process for separating low molecular weight oligomers of a film forming resin utilizing the combination of a static mixer and a liquid—liquid centrifuge. The low molecular weight oligomers are useful in enhancing the photospeed of a photoresist composition. Furthermore, derivatives of these low molecular weight oligomers (such as esterified products of the oligomers with diazonaphthaquinone compounds) are themselves photoactive and can be used in a photoresist composition. As such, the present invention also provides a process for producing a photoresist composition comprising said low molecular oligomers or derivatives of said low molecular weight oligomers. The present invention also provides a process for producing a semiconductor device by forming an image on a substrate utilizing the foregoing low molecular oligomers or their derivatives.
Fractionation reduces the overall yield of a resin by removing low molecular weight materials (such as unreacted monomers, dimers, trimers and intermediate oligomers). Depending upon the functional properties needed for the final resist, many fractionation techniques can be devised for the general removal of a broad range of these lower molecular weight fractions and intermediate oligomers. Economically, the cost of the raw material is directly related to the yield of useful resin obtained from the fractionation steps. It would be desirable to selectively remove those fractions that are known in a particular technical application to affect functional properties of a final resist composition without substantial lowering the overall yields of the film forming resin. The present invention affords such a process for selective removal of oligomeric fractions of a film forming resin. For example, in the preparation of microelectronic devices, multiple high temperature baking steps may be used to a) remove solvents immediately after spin coating the liquid resist composition onto a semi-conductor substrate and a post development bake after the wafer is imaged through a photomask. Other heat treatment steps may be optionally applied to further remove entrained solvents or to facilitate heat activated chemical changes in the coated film. Serious defects can occur in some of these heat treatment steps when low molecular weight oligomers of a film forming resin, such as dimers and trimers of a novolak resin, volatilize, and either affect film integrity or, more commonly, sublime on the inside of the processing equipment. It would be desirable to remove substantial portions of the low molecular oligomers of a film forming resin, such as dimers/trimers of a novolak resin, while retaining a high yield of the remaining film forming resin. The present invention affords a method for the selective removal of such dimers and trimer fractions of the film forming resin. While distillation methods can be used to remove volatile materials such as low molecular weight oligomers, these methods are batch processes and require long set-up times and cleaning steps, and the yield of the resulting fractionated resin is also low. These disadvantages are lacking in the present invention. In the present invention, by the combined use of a static mixer and liquid/liquid centrifuge fractionation process, one can continuously remove low molecular weight oligomeric fractions, such as dimers and trimers of a film forming resin, while maintaining a high yield of the desired fractionated film forming resin.
Photoresist compositions are used in microlithography processes for making miniaturized electronic components, such as in the fabrication of computer chips and integrated circuits. Generally, in these processes, a thin coating of a film of a photoresist composition is first applied to a substrate material, such as silicon wafers used for making integrated circuits. The coated substrate is then baked to evaporate any solvent in the photoresist composition and to fix the coating onto the substrate. The baked coated surface of the substrate is next subjected to an image-wise exposure to radiation.
This radiation exposure causes a chemical transformation in the exposed areas of the coated surface. Visible light, ultraviolet (UV) light, electron beam and X-ray radiant energy are radiation types commonly used today in microlithographic processes. After this image-wise exposure, the coated substrate is treated with a developer solution to dissolve and remove either the radiation-exposed or the unexposed areas of the coated surface of the substrate.
There are two types of photoresist compositions, negative-working and positive-working. When negative-working photoresist compositions are exposed image-wise to radiation, the areas of the resist composition exposed to the radiation become less soluble to a developer solution (e.g. a cross-linking reaction occurs) while the unexposed areas of the photoresist coating remain relatively soluble to such a solution. Thus, treatment of an exposed negative-working resist with a developer causes removal of the non-exposed areas of the photoresist coating and the creation of a negative image in the coating thereby uncovering a desired portion of the underlying substrate surface on which the photoresist composition was deposited.
On the other hand, when positive-working photoresist compositions are exposed image-wise to radiation, those areas of the photoresist composition exposed to the radiation become more soluble to the developer solution (e.g. a rearrangement reaction occurs) while those areas not exposed remain relatively insoluble to the developer solution. Thus, treatment of an exposed positive-working photoresist with the developer causes removal of the exposed areas of the coating and the creation of a positive image in the photoresist coating. Again, a desired portion of the underlying substrate surface is uncovered.
After this development operation, the now partially unprotected substrate may be treated with a substrate-etchant solution or plasma gases and the like. The etchant solution or plasma gases etch that portion of the substrate where the photoresist coating was removed during development. The areas of the substrate where the photoresist coating still remains are protected and, thus, an etched pattern is created in the substrate material which corresponds to the photomask used for the image-wise exposure of the radiation. Later, the remaining areas of the photoresist coating may be removed during a stripping operation, leaving a clean etched substrate surface. In some instances, it is desirable to heat treat the remaining photoresist layer, after the development step and before the etching step, to increase its adhesion to the underlying substrate and its resistance to etching solutions.
Positive working photoresist compositions are currently favored over negative working resists because the former generally have better resolution capabilities and pattern transfer characteristics. Photoresist resolution is defined as the smallest feature which the resist composition can transfer from the photomask to the substrate with a high degree of image edge acuity after exposure and development. In many manufacturing applications today, resist resolution on the order of less than one micron are necessary. In addition, it is almost always desirable that the developed photoresist wall profiles be near vertical relative to the substrate. Such demarcations between developed and undeveloped areas of the resist coating translate into accurate pattern transfer of the mask image onto the substrate.
U.S. Pat. No. 6,121,412 and International Publication WO 00/33137 disclose a method for producing a film forming, fractionated novolak resin, by: a) condensing formaldehyde with one or more phenolic compounds, and thereby producing a novolak resin; b) adding a photoresist solvent, and optionally a water soluble organic polar solvent; c) feeding the mixture into a liquid/liquid centrifuge and feeding a C
5
-C
8
alkane, water or aromatic hydrocarbon solvent into the liquid/liquid centrifuge
Rahman M. Dalil
Wanat Stanley F.
Xiang Zhong
Banerjee Krishna G.
Chu John S.
Clariant Finance (BVI) Limited
LandOfFree
Fractionation of resins using a static mixer and a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fractionation of resins using a static mixer and a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fractionation of resins using a static mixer and a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3019958