Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
1999-01-21
2001-09-18
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S125000, C528S167000, C528S403000, C528S410000, C528S422000, C528S480000, C528S494000, C528S503000, C525S390000, C428S411100
Reexamination Certificate
active
06291628
ABSTRACT:
BACKGROUND
1. Field of the Invention
This application relates generally to low dielectric constant polymer materials and more particularly to solvent systems for use with arylene ether based polymer materials.
2. Description of the Related Art
As the dimension of the interconnect design rules for integrated circuits (IC) undergoes progressive shrinkage to sub-quarter micron metal spacing, the use of organic polymer dielectrics to minimize capacitance and reduce power consumption and cross talk, while increasing signal propagation speed becomes a necessity. The organic dielectrics must possess dielectric constants no higher than 3.0 and should have dielectric constants as low as possible toward a theoretical limit of 1.0. The practical expectation for polymer dielectrics is in the range of 2.2 to 3.0. The organic dielectrics must have glass transition temperatures above 300° C. and as high as possible toward 450° C., a value determined by the thermal stability of organic polymers. The organic dielectrics should also be easily processed, preferably, by standard spin-bake-cure processing techniques. The organic dielectrics should also be free from moisture and out-gassing problems, in addition to having expected adhesive and gap-filling qualities, and dimensional stability towards thermal cycling, etching, and chemical mechanical polishing processes.
Arylene ether polymers, such as poly(arylene ether) (PAE), poly(arylene ether ether ketone) (PAEEK), poly(arylene ether ether acetylene) (PAEEA), poly(arylene ether ether acetylene ether ether ketone) (PAEEAEEK), poly(arylene ether ether acetylene ketone) (PAEEAK), and poly(naphthylene ether) (PNE) comprising different polymer designs that include homopolymers, block or random copolymers, polymer blends, interpenetrating polymer networks (IPNs), and semi-interpenetrating polymer networks (SIPNs), are materials that have been identified as organic dielectrics.
Taking advantage of the low dielectric property of these organic materials requires the IC industry to make a significant shift in its processing paradigm. New processing approaches, such as the use of spin-coating, require selection of appropriate solvents for formulation of the spin-on polymer solution, cleaning, edge-bead removal, and wafer backside rinsing. Desirable formulations will provide spin-coated polymer dielectric films with excellent uniformity, a wide thickness range from hundreds of angstroms to hundreds of microns, very low out-gassing at high temperature, excellent gap-filling to 0.1 micron, excellent local, regional and global planarization, and ease of wafer edge bead removal and wafer backside rinsing. In addition, the spin-on dielectric polymer solution should be easily filtered to minimize its manufacturing cost. Finally, the solution must be environmentally acceptable.
While conventional alcoholic solvents media used for spin-on glasses, familiar to IC engineers, are obvious solvent candidates, they cannot necessarily be applied to organic materials. Their environmental benevolence, in many cases, ease in clean up, and low viscosity features are much desired. Ketonyl and other aprotic solvents have been used for photoresists and polymer dielectrics. These solvents include methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, &ggr;-butyrolactone, N-methylpyrrolidinone, N-cyclohexylpyrrolidinone and N,N-dimethylacetamide. Among them, cyclic ketonyl solvents are commonly used as solvents for arylene ether dielectrics. However, cyclic ketones normally are not as miscible with most arylene ether polymer dielectrics as would be desired and the spin-on solutions formulated from these solvents usually yield some extent of striation on the spin-coated film, especially for films with thicknesses greater than 1.5 micron. Serious striation could cause inadequate gap-filling, problems in adhesion of the dielectric film with a substrate and other problems. Additionally, cyclic ketonyl solvents have varying degrees of moisture, pH, and photosensitivities, often exacerbated by heat. Users need to be cognizant of these potential difficulties. For example, cyclopentanone is significantly more sensitive than first thought toward low pH, in addition to its well-known sensitivity toward light, moisture, and high pH. Cyclohexanone is more stable than cyclopentanone and has been a fair solvent for photoresists in the industry. However, cyclohexanone is still sensitive to light and low pH. Furthermore, cyclohexanone is considered to be barely tolerable by the industry due to its very low exposure limit.
To summarize, as knowledge in the application and processing of organic dielectric materials expands, shortcomings among the currently-used cyclic ketonyl solvents are becoming more recognized. It would be desirable to provide process compatible and benign solvents for arylene ether polymer dielectrics. In particular, it would be desirable to provide a family of extremely useful high-boiling point solvents for formulation of spin-on dielectric polymer solutions, edge bead removal of these dielectric films, and wafer backside and spin-coater rinsing.
SUMMARY
In accordance with this invention, there is provided a new family of high boiling point solvents, namely aromatic aliphatic ethers, which are utilized in the formation of spin-on dielectric polymer solutions as well as in the spin-coating process of such materials. The chemical structures of this family of ethers is presented below. Several significant examples of this family are anisole (C
6
H
5
OCH
3
, n=1, m=0) and phenetole (C
6
H
5
OC
2
H
5
, n=2, m=0) with a boiling point of 155 and 170° C., respectively, and 2-, 3-, or 4-methylanisole with a boiling point in the range of 170° C. to 175° C. This solvent family is most appropriately applied to the arylene ether dielectric polymers including poly(arylene ether) (PAE), poly(arylene ether ether ketone) (PAEEK), poly(arylene ether ether acetylene) (PAEEA), poly(arylene ether ether acetylene ether ether ketone) (PAEEAEEK), poly(arylene ether ether acetylene ketone) (PAEEAK) and their block or random copolymers and blends. Mixtures of one or more of these solvents may be employed in this invention.
Solvent
R
R
1
to R
5
C
n
H
2n+1
n = 1 to 6
C
m
H
2m+1
m = 0 to 3
According to another embodiment of the present invention, a process for producing low dielectric films on semiconductor substrates uses a spin-coating solution of a low dielectric constant polymer dissolved in an aromatic aliphatic ether solvent. The films produced by this process advantageously have high thickness uniformity and do not exhibit striation.
DETAILED DESCRIPTION
Aromatic aliphatic ether solvents, such as anisole, methylanisole, and phenetole, have been found to highly dissolve arylene ether polymers. As described above, arylene ether polymers have been identified as useful for forming low dielectric constant organic films.
An example of such a polymer is FLARE™ poly(arylene ether) of AlliedSignal Inc. These polymers have flexible structural moieties built into the uncured structures thereby maintaining the polymers' flexibility and low melt viscosity, which allows them to be formulated for spin-coating. After being spun onto the surface of a wafer, the polymers are thermally activated to undergo a cross-linking reaction and cured to give rise to a T
g
value above 250° C. and typically in the range of 300° C. to 450° C., without additional assistance from cross-linking additives.
The chemical structures shown below are two examples of poly(arylene ethers) which may be used as dielectric materials in the IC industry. The dielectric constant for arylene ether polymers typically falls between 2.5 to 3.0, which meets the requirement of next generation dielectrics for ultra large scale integration (ULSI).
In formula 1 above, y is between 0 and 1. In both formulas 1 and 2, x is typically between about 2 and about 200. Preferably, x is between about 2 and about 100.
The polymer represented by formula
Chen Tian-An
Lau Kreisler S. Y.
Zhao Qiang
Allied Signal Inc.
Fish Robert D.
Fish & Associates, LLP
Truong Duc
LandOfFree
Solvent systems for low dielectric constant polymeric materials does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Solvent systems for low dielectric constant polymeric materials, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Solvent systems for low dielectric constant polymeric materials will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2447958