Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-07-18
2003-05-06
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S502000
Reexamination Certificate
active
06559215
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to spin-on-dielectric compositions which have additives, which reduce striations and/or broaden the processing window and, especially, to polyarylene compositions, which include such additives and are useful in making microelectronic devices.
BACKGROUND OF THE INVENTION
Spin-on-dielectrics include organic polymeric materials, which may be spin coated to form very thin layers useful in microelectronics applications. See, e.g., CYCLOTENE™ benzocyclobutene based resins from The Dow Chemical Company; WO 97/10193; WO 98/11149 (disclosing polyarylenes) and EP 0 755 957 B1, Jun. 5, 1999; N. H. Hedricks and K. S. Y. Liu,
Polym. Prepr
. (Am. Chem. Soc., Div. Polym. Chm.), 1996, 37(1), pp. 150-151; also, J. S. Drage, et al.,
Material Res. Soc., Symp. Proc
., (1997), Volume 476, (Low Dielectric Constant Materials III), pp. 121-128 (disclosing polyarylene ethers). In many of these microelectronics applications, such as interlayer dielectric, passivation, etc., the coating quality and uniformity are very important.
Unfortunately, some compositions are extremely difficult to spin coat without experiencing coating defects, such as striations and cracking. Therefore, compositions are desired that can be coated with minimal defects and/or which have a broader processing window for spin speed and environmental conditions, such as temperature and humidity.
Various types of materials have been taught to generally facilitate coating. For example, resins, such as acrylics, ureas, melamines, cellulose acetobutyrates, and polyvinyl butyrals, at typical addition levels between 0.5 and 2.0 percent, have been taught to control surface flow. Silicones and fluorocarbons and other surfactants have also been taught to be useful. See
Handbook of Coating Additives
, Ch. 5, Leveling and Flow Control, by Horst Vltavsky, pp. 129-131, Ed. Leonard J. Calbo, Marcel Dekker Inc. (1987).
An article in
SPIE
, Vol. 631, Advances in Resist Technology and Processing III, (1986),
Surface Tension Effects in Microlithography—Striations
by B. Daniels, et al. mentions that for photoresists used in lithography as little as 0.005 percent of an unidentified surface leveling agent can eliminate striations in a Novolak diazoquinone resist but suffered from a negative cratering effect.
SUMMARY OF THE INVENTION
Applicants have discovered spin-on-dielectric formulations that have a broader processing window and limited or no observable striations with only very low levels of polymeric coating additives. Preferably, these additives are free or substantially free of silicon and fluorine as these materials are perceived as being detrimental in integrated circuit manufacture.
This invention is a composition comprising (a) an oligomer or polymer dispersible in an organic solvent, (b) at least one organic solvent and (c) less than 1000 parts by weight of a polymeric coating additive per million parts by weight of total composition (ppm). Component (a) is preferably present in amounts less than 40 percent, preferably less than 30 percent and more preferably less than 20 percent by weight based on total weight of the composition. This oligomer or polymer is preferably curable to form a cured polymer characterized by a dielectric constant less than 4.0, preferably less than 3.0. If said polymer is not curable, the dielectric constant of the polymer itself is less that 4.0, preferably less than 3.0. While a single organic solvent may be used, the solvent system preferably comprises at least a first and second solvent. The polymeric coating additive is preferably used in an amount less than 500 parts by weight, more preferably less than about 200 parts by weight per million parts by weight of the total composition.
The polymeric additive is characterized in that it is miscible with component (a) and the solvent system but becomes incompatible with the mixture of component (a) and solvent during the coating process. In other words, as the solvent is removed during the spin coating process, the additive will become incompatible with the remainder of the composition (i.e., component (a) and what remains of the solvent) and, therefore, will migrate to surface interfaces.
According to one preferred embodiment, the additive is characterized in that it has a total Hansen solubility parameter, &dgr;
t
, that differs from, and is preferably less than, the solubility parameter of component (a) by at least 1 MPa
½
. More preferably, the solubility parameter of component (c) differs from, and is most preferably less than, the solubility parameter of component (a) by at least 1.5 MPa
½
. Note, however, that molecular weights of the polymeric components also have an effect and high molecular weight polymers require lower additive levels to be effective and/or may function with a smaller difference in solubility parameter. Note, also, that if the polymeric coating additive (c) is too soluble in the solvents, the incompatibility may not be sufficient to resolve the striation problem, even if the difference in solubility parameters between component (a) and (c) would seem to be sufficient.
Thus, according to a second preferred embodiment, the solvent system comprises at least a first solvent and a second solvent, wherein the first solvent has a higher vapor pressure than the second solvent (or stated alternatively, the first solvent has a lower boiling point than the second solvent) and the coating additive is characterized in that it is soluble in the first solvent but phase separates to form a substantially contiguous fluid phase in the second solvent.
According to a third preferred embodiment, the resin is selected from the group consisting of polybutene, polyisoprene, acrylate polymers and copolymers.
According to a fourth preferred embodiment, this invention is a method of spin coating the formulation of any of the previous formulations onto a substrate resulting in a film of the curable polymer or oligomer, which is free of striations.
This invention is also a process using the previous compositions to form a film of a polymer having a low dielectric constant, said film being substantially free of striations.
DETAILED DESCRIPTION OF THE INVENTION
The curable polymers or oligomers of this invention are materials, which when cured, form a polymer having dielectric constants of less than 4.0, preferably less than 3.0. Preferred materials are benzocyclobutene based polymers, such as CYCLOTENE™ 5021 from The Dow Chemical Company, the bisorthodiacetylene based polymers as disclosed, for example, in WO 97/10193. These polymers are made by the reaction of precursor compounds of the formula:
(R—C═C—)
n
—Ar—L[—Ar(—C═C—R)
m
]
q
wherein each Ar is an aromatic group or inertly-substituted aromatic group and each Ar comprises at least one aromatic ring; each R is independently hydrogen, an alkyl, aryl or inertly-substituted alkyl or aryl group; L is a covalent bond or a group which links one Ar to at least one other Ar; preferably a substituted or unsubstituted alkyl group, n and m are integers of at least 2; and q is an integer of at least 1, and wherein at least two of the ethynylic groups on one of the aromatic rings are ortho to one another. Alternatively, polyarylenes as disclosed, for example, in WO 98/11149, and polyarylene ethers, such as, for example, PAE resins—Air Products, are described in EP 0 755 957 B1, Jun. 5, 1999 and/or the FLARE™ resins made by Honeywell International, Inc. (see N. H. Hedricks and K. S. Y. Liu,
Polym. Prepr
. (Am. Chem. Soc., Div. Polym. Chm.), 1996, 37(1), pp. 150-151; also J. S. Drage, et al.,
Material Res. Soc., Symp. Proc
., (1997), Volume 476 (Low Dielectric Constant Materials III), pp. 121-128 may be used. Thermosetting materials are especially desirable for interlayer dielectric applications.
Preferably, the oligomers and polymers and corresponding starting monomers of the present invention are:
I. Oligomers and polymers of the general formula:
[A]
w
[B]
z
[EG]
v
wherein A has the structure:
and B has the st
Dominowski JoLee M.
Foster Kenneth L.
Hahn Stephen F.
Mills Lynne K.
Rose Gene D.
Cain Edward J.
Dow Global Technologies Inc.
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