Radiation imagery chemistry: process – composition – or product th – Visible imaging including step of firing or sintering
Reexamination Certificate
1999-06-01
2001-07-10
Dawson, Robert (Department: 1712)
Radiation imagery chemistry: process, composition, or product th
Visible imaging including step of firing or sintering
C522S065000, C522S099000
Reexamination Certificate
active
06258506
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an ultraviolet-curing silicon-containing resin composition that can be used to fabricate dielectric films in semiconductor devices, and to a method for forming cured silicone patterns using said composition.
Silicone resins are widely used as electrical and electronic materials due to their generally high heat resistance and excellent electrical characteristics. Among these, curable silicone resins are used to coat substrate surfaces. The heat-curing types in general cure through the hydrosilylation reaction, silanol condensation reaction, or siloxane bond-forming reactions based on alcohol, oxime, or acetic acid elimination. UV-curable silicone resins become important when considering factors such as the heat tolerance of the substrate, cure rate, or selective curability.
Cured regions in which crosslinking has been induced by the above-described methods as a general rule have a substantially lower solvent solubility than the uncured regions, and the exploitation of this feature makes imaging possible.
Vinyl- and mercapto-functional silicone can be cured by UV in the presence of oxygen. The technology using the addition of mercaptan to olefin suffers from the odor and corrosivity due to the mercaptan. Air (oxygen) induces cure inhibition where the curing technologies employ the radical polymerization of functional groups as acryloyl, methacryloyl, and so forth. Moreover, the resulting crosslinking moiety has a low thermal stability, and thus the cured products are not robust to use and processing at high temperatures.
The epoxy-functional silicones and vinyl ether-functional silicones are generally cured using a substance that generates acid upon photoexposure. This acid facilitates substrate corrosion while the electrical properties of the cured products are impaired by the ionic impurity.
Silanol-functional silicones and Si—H-functional silicones can be cured through the use of a substance that generates base upon photoexposure, and the resulting cured products thus contain a base. This base also causes various problems, such as impairing the electrical properties of the cured product and causing long-term changes in mechanical properties due to siloxane bond rearrangement. The silanol-functional silicones can also be cured using a substance that generates acid upon photoexposure (Japanese Patent Application Laid Open [Kokai or Unexamined] Number Hei 6-80879 [80,879/1994]). This technology, however, suffers from the same problems as described above for the epoxy-functional silicones and vinyl ether-functional silicones.
Thus, as described above various cure technologies are known for photocurable silicones, but in each case one encounters problems.
It is therefore an object of this invention to provide a storage-stable UV-curable composition whose cure is not inhibited by air or oxygen, which is very efficiently cured by low doses of UV radiation, and which provides a highly heat-resistant cured pattern through the execution of a post-patterning heat treatment.
It is further an object of this invention to provide a method for the formation of cured patterns using the UV-curable composition.
SUMMARY OF THE INVENTION
This invention is a curable composition comprising
(a) 0.001 to 10 wt % based on the total weight of the curable composition of a benzoin ethers (“UV free radical generator”) and
(b) a free-radical polymerizable functional silicone polymer of the general formula
(R
3
SiO
1/2
)
a
(R′
2
SiO
2/2
)
b
(R″SiO
3/2
)
c
(SiO
4/2
)
d
wherein R, R′, and R″ are independently selected from the group consisting of hydrogen and C
1
to C
10
saturated and unsaturated hydrocarbyl. The hydrocarbyl may contain one or more atoms selected from fluorine, oxygen, chlorine, and nitrogen. At least 10% of the total R, R′, and R″ is selected from vinylphenyl, vinylbenzyl, and vinylphenethyl. The sum of subscripts a, b, c, and d=1. The subscripts are each 0 or a positive number and fall into the following ranges:
0.8≧
a≧
0
0.5≧
b≧
0
1.0≧
c≧
0
0.65≧
d≧
0.
At least one of the silicon-bonded divalent oxygen atoms in each R′
2
SiO
2/2
, each R″SiO
3/2
, and each SiO
4/2
is bonded to another silicon to form a siloxane bond while the remaining oxygen in each case can be bonded to another silicon to form a siloxane bond, or can be bonded to methyl or ethyl to form an alkoxy group, or can be bonded to hydrogen to form silanol.
Exposure of this composition to ultraviolet light at particular wavelengths results in an initial cure of the composition in the exposed regions. This process may be carried out in air or under an inert gas blanket such as nitrogen, argon, or others.
THE INVENTION
This invention is a curable composition comprising
(a) 0.001 to 10 wt % based on the total weight of the curable composition of a benzoin ethers (“UV free radical generator”) and
(b) a free-radical polymerizable functional silicone polymer of the general formula
(R
3
SiO
1/2
)
a
(R′
2
SiO
2/2
)
b
(R″SiO
3/2
)
c
(SiO
4/2
)
d
wherein R, R′, and R″ are independently selected from the group consisting of hydrogen and C
1
to C
10
saturated and unsaturated hydrocarbyl wherein the hydrocarbyl may contain one or more atoms selected from fluorine, oxygen, chlorine, and nitrogen; with the proviso that at least 10% of the total R, R′, and R″ is selected from vinylphenyl, vinylbenzyl, and vinylphenethyl; 0.8≧a≧0; 0.5≧b≧0; 1.0≧c≧0; 0.65≧d≧0; and the sum of subscripts a, b, c, and d=1.
The UV free radical generator is a benzoin ethers and is contained at from 0.001 to 10 wt % based on the total weight of the curable composition. The free radicals produced by irradiating the composition function as initiators of the polymerization reaction, and the free radical generator can therefore be added in a catalytic quantity relative to the polymerizable functionality in the subject composition. The addition of too much can lead to fragile physical properties on the part of the composition prior to its cure and can adversely affect the physical properties of the cured composition. Taking into account the cure rate as well as the physical properties of the subject curable composition and the cured product therefrom, the free radical generator is preferably present from 0.01 to 5% based on the total weight of the curable composition.
The free radical generator may exemplified by the 2,2-dialkoxy-1,2-diphenylethan-1-ones with general formula (2) below and by the 2-alkoxy-1,2-diphenylethan-1-ones with general formula (3) below wherein R is independently selected from methyl, ethyl, and propyl.
When considering factors such as ease of acquisition and handling, good photodegradability, and high catalytic activity by the generated free radicals, Irgacure 651™ is optimal among the free radical generators described above. This particular compound is preferably added at from 0.01 to 5 wt % of the composition.
The free radical-polymerizable functional silicone polymer in the curable composition is defined by the following general formula.
(R
3
SiO
1/2
)
a
(R′
2
SiO
2/2
)
b
(R″SiO
3/2
)
c
(SiO
4/2
)
d
.
The R, R′, and R″ in this formula are independently selected from hydrogen and C
1
to C
10
saturated and unsaturated hydrocarbyl. The hydrocarbyl may contain one or more atoms selected from fluorine, oxygen, chlorine, and nitrogen. At least 10% of the total R, R′, and R″ is selected from vinylphenyl, vinylbenzyl, and vinylphenethyl. Subscripts a, b, c, and d in the general formula sum to 1. Subscripts a, b, c, and d are each 0 or a positive number and fall into the following ranges:
0.8≧
a≧
0
0.5≧
b≧
0
1.0≧
c≧
0
0.65≧
d≧
0.
At least one of the silicon-bonded divalent oxygen atoms in each R′
2
SiO
2/2
, at least one of the silicon-bonded divalent oxygen atoms in each R″SiO
3/2
, and at least one of the silicon-bonded divalent oxygen atoms in each
Harkness Brian R.
Tachikawa Mamoru
Takei Kasumi
Aylward D.
Dawson Robert
Dow Corning Asia Ltd.
Gobrogge Roger E.
Streu Rick D.
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