Organohydridosiloxane resins with high organic content

Details Organohydridosiloxane resins with high organic content Organohydridosiloxane resins with high organic content

2000-06-30

2003-01-28

Dawson, Robert (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From silicon reactant having at least one...

C528S031000

Reexamination Certificate

active

06512071

ABSTRACT:

BACKGROUND
1. Field of the Invention
The present invention relates generally to siloxane-based resins, and more specifically to the synthesis of novel siloxane based resins and the low dielectric constant films formed therefrom.
2. Related Art
Semiconductor devices often have one or more arrays of patterned interconnect levels that serve to electrically couple the individual circuit elements thus forming an integrated circuit (IC). These interconnect levels are typically separated by an insulating or dielectric film. Previously, a silicon oxide film formed using chemical vapor deposition (CVD) or plasma enhanced CVD (PECVD) techniques was the most commonly used material for such dielectric films. However, as the size of circuit elements and the spaces between such elements decreases, the relatively high dielectric constant of such silicon oxide films is problematic.
In order to provide a lower dielectric constant than that of silicon oxide, dielectric films formed from siloxane based resins are becoming widely used. One such family of films formed from siloxane based resins are the films derived from hydrogen silsesquioxane (HSQ) resins (See, U.S. Pat. No. 3,615,272, Oct. 19, 1971, Collins et al.; and U.S. Pat. No. 4,756,977, Jul. 12, 1988, Haluska et al.) However, while such films do provide lower dielectric constants than CVD or PECVD silicon oxide films and also provide other benefits such as enhanced gap filling and surface planarization, it has been found that typically the dielectric constants of such films are limited to approximately 3.0 or greater (See, U.S. Pat. No. 5,523,163, Jun. 4, 1996, Ballance et al.).
As known, the dielectric constant of such insulating films is an important factor where IC's with low power consumption, cross-talk, and signal delay are required. As IC dimensions continue to shrink, this factor increases in importance. As a result, siloxane based resin materials, and methods for making such materials, that can provide insulating films with dielectric constants below 3.0 are very desirable. In addition, it would be desirable to have siloxane-based resins, and method for making the resins, that provide such low dielectric constant films and which additionally have a high resistance to cracking. It would also be desirable for such films to have low stress when formed in thicknesses of approximately 1.0 micron (&mgr;m) or greater. Additionally, it would be desirable for such siloxane-based resins, and methods for making, to provide low dielectric constant films via standard processing techniques. In this manner curing processes that require an ammonia or ammonia derivative type of atmosphere (See, U.S. Pat. No. 5,145,723, Sep. 8, 1992, Ballance et al.), an ozone atmosphere (See, U.S. Pat. No. 5,336,532, Haluska et al.), or other non-standard type of semiconductor process, are avoided.
SUMMARY
In accordance with the present invention, organohydridosiloxane resins, and methods for making such resins, are provided. Solutions of such organohydridosiloxane resins are employed for forming caged siloxane polymer films useful in the fabrication of a variety of microelectronic devices, particularly semiconductor integrated circuits.
The organohydridosiloxane resins of the present invention have one of the four general formulae:
(HSiO
1.5
)
n
(RSiO
1.5
)
m
  Formula 1
(H
0.4−1.0
SiO
1.5−1.8
)
n
(R
0.4−1.0
SiO
1.5−1.8
)
m
  Formula 2
(H
0−1.0
SiO
1.5−2.0
)
n
(RSiO
1.5
)
m
  Formula 3
wherein:
the sum of n and m is from about 8 to about 5000 and m is selected such that the organic substituent is present to about 40 Mole percent (Mol %) or greater;
(HSiO
1.5
)
x
(RSiO
1.5
)
y
(SiO
2
)
z
  Formula 4
wherein:
the sum of x, y and z is from about 8 to about 5000 and y is selected such that the organic substituent is present to about 40 mole percent (Mol %) or greater; and
R is selected from substituted and unsubstitued groups including normal and branched alkyl groups, cycloalkyl groups, aryl groups, and mixtures thereof;
wherein the specific Mol % of organic or carbon containing substituents is a function of the ratio of the amounts of starting materials.
Polymers in accordance with the present invention have a caged structure with a polymer backbone encompassing alternate silicon and oxygen atoms. In particular, each backbone silicon atom is bonded to at least three backbone oxygen atoms. In contrast with previously known organosiloxane resins, polymers of the present invention have essentially no hydroxyl or alkoxy groups bonded to backbone silicon atoms. Rather, each silicon atom, in addition to the aforementioned backbone oxygen atoms, is bonded only to hydrogen atoms and/or the ‘R’ groups defined in Formulae 1, 2, 3 and 4. By attaching only hydrogen and/or ‘R’ groups directly to backbone silicon atoms in the polymer, the shelf life of organohydridosiloxane resin solutions in accordance with the present invention is enhanced as compared to solutions of previously known organosiloxane resins.
In accordance with the methods of this invention, the synthesis of the organohydridosiloxane compositions of this invention include a dual phase solvent system using a catalyst. In some embodiments of the present invention, the starting materials encompass trichlorosilane and one or more organotrichlorosilanes, for example either an alkyl or an aryl substituted trichlorosilane.
In some embodiments, the methods of this invention include mixing a solution of at least one organotrihalosilane and hydridotrihalosilane to form a mixture; combining the mixture with a dual phase solvent which includes both a non-polar solvent and a polar solvent; adding a catalyst to the dual phase solvent and trihalosilane mixture, thus providing a dual phase reaction mixture; reacting the dual phase reaction mixture to produce an organohydridosiloxane; and recovering the organohydridosiloxane from the non-polar portion of the dual phase solvent system.
In some embodiments, additional steps may include washing the recovered organohydridosiloxane to remove any low molecular weight species, and fractionating the organohydridosiloxane product to thereby classify the product according to molecular weight.
In some embodiments, the catalyst is a phase transfer catalyst including, but not limited to, tetrabutylammonium chloride and benzyltrimethylammonium chloride. In other embodiments the catalyst is a solid phase catalyst, such as Amberjet 4200 or Amberlite I-6766 ion exchange resin (Rohm and Haas Company, Philadelphia, Pa.).
In some embodiments of the present invention, the amount of organotrihalosilane monomer present is an amount sufficient to provide an as-cured dielectric film having an organic content of at least approximately 40 Mol % carbon containing substituents. Such dielectric films formed in accordance with the present invention advantageously provide low dielectric constants, typically less than 2.7. Additionally, dielectric films in accordance with the organohydridosiloxane compositions of this invention exhibit thermal stability permitting cure temperatures of about 425 degrees Centigrade (° C.) or greater.
DETAILED DESCRIPTION
As the present invention is described with reference to various embodiments thereof, it will be understood that these embodiments are presented as examples and not limitations of this invention. Thus, various modifications or adaptations of the specific materials and methods may become apparent to those skilled in the art. All such modifications, adaptations or variations that rely upon the teachings of the present invention as illustrated by the embodiments herein, are considered to be within the spirit and scope of the present invention. For example, while the embodiments herein typically use a chlorinated silane monomer, other monomers such as trifluorosilane, tribromosilane, organotrifluorosilane, and organotribromosilane can also be employed.
The organohydridosiloxane resins of the present invention have one of the four general formulae:
(HSiO
1.5
)
n
(RSiO
1.5
)
m
 &emsp

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