SUMITOMO BAKELITE CO., LTD. (Headquarters: at 2-5-8 Higashi Shinagawa, Shinagawa
ward, Tokyo; Tsuneo Moriya, President) has developed CRA-9000 series low-k
interlayer dielectrics having a dielectric constant of less than2.2, required
for semiconductor devices stipulated by the future design rule of 0.1ƒÊm or finer
devices emerging thereafter.
This was achieved by using a specific material
of oxazole resin having a heat resistance of higher than 4000C, and
by establishing a process for forming a porous structure with ultra fine pores
of several nano microns scale, a technology unattainable so far out of organic
materials.
It possesses uniform film characteristics and superior adhesive
quality as well as mechanical strength despite the porous structure of the
material taking advantage of its ultra-fine pores.
We are further exploring
the level of 1.5 of dielectric constant required in the 0.7ƒÊm design rule and
thereafter. A presentation was given on this result of study at the Multi-layer
Wiring Technology Congress of the Semicon Europe 2001 held in Munich, Germany,
from April 24.
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| Societal Background |
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In semiconductor devices the requirement for higher-speed
operational processing has been fulfilled by higher precision of circuit wiring,
but as the level of the precision is getting closer to the design rule of 0.1ƒÊm,
it is pointed out that the signal delay due to the increase of capacitance
stored between wires in proximity is serious enough to cancel the expected
high-speed effect. A key solution to this problem is the low-k interlayer
dielectric technology. An interlayer dielectric having dielectric constant of
less than 2.2 is needed for the design rule of 0.1ƒÊm. The most prospective
approach to attain the value is to take in and confine air, whose dielectric
constant is as low as 1.0. Thus, many material makers are working for the
development of porous films for use in the interlayer dielectric.
As for a
candidate of the porous-type interlayer dielectric attempts have been made to
use inorganic silica-family materials, which in fact have brought preceding
results of research and study, however, the dielectric constant of silica itself
is as high as 4.1, wherein to obtain the value of 2.2 more than 50 % of the
volume must be pores, which are liable to become continuous big pores to result
in the poor mechanical strength as well as contamination of foreign matters
stored thein during the fabrication of the mutilayer circuits.
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| Description of the nano-porous oxazole
resin interlayer dielectric. |
The technology we have developed employs oxazole, an
organic material as the skeletal structure. The dielectric constant of the
material itself can be reduced to about 2.6, which allowed to decrease the pore
content in the total volume down to 30% to lower accordingly the dielectric
constant equal to or below 2.2.
Moreover, our proprietary molecular designing
technology allowed to form independent pores of several micron meters in size.
The material used for this technology is soluble in solvents and supplied as a
varnish. It is applied to wafers by spin coating followed by simple heating to
achieve the nano-porosity.. We used the simple process and general-purpose spin
coater in view of the future development of lower-k materials based on the same
basic concept to utilize the existing equipment or processing lines and
know-how.
We are shipping samples of the products to a number of
semiconductor manufacturers who are currently conducting the evaluation for
their practical use.
We are aiming to make this product the de facto
standard material of multi-layered interlayer
dielectrics.
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| Technology Features |
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| 1. |
Superior adhesive quality and mechanical strength are
ensured by the ultra-fine pores of the material in a size of several nanometers,
where the thickness of the dielectric is far smaller than the distances between
wirings stipulated even in the design rules of 0.1ƒÊm or that of thereafter
maintaining uniform characteristics. |
| 2. |
Free from hazardous outgassing even when
heated up to 4000C owing to its high heat
resistance. |
| 3. |
Excellent mechanical strength secured by
restraining the porous ratio in an organic, heat-resistant resin format with a
very low dielectric constant value. |
| 4. |
An insulating film dielectric can be formed
through a simple process of coating, heating and curing the
resin. |
| 5. |
An existing conventional process line of
spin coater can be used for processing a material of this category even in the
coming requirement of a lower-k
age. |
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| Effects by adoption of the nano-porous
oxazole resin interlayer dielectrics. |
| It is a preventive measure of signal delay due to the
increase of capacitance stored between routed wires which is liable to take
place very often in higher-speed operational processing of semiconductor
devices. |
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Thank you.
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