Photodefineable compositions

Details Photodefineable compositions Photodefineable compositions

2001-07-20

2004-04-27

Weiner, Laura (Department: 1745)

Radiation imagery chemistry: process, composition, or product th

Imaging affecting physical property of radiation sensitive...

Radiation sensitive composition or product or process of making

C430S281100, C430S919000, C430S923000, C522S065000, C522S172000, C522S057000

Reexamination Certificate

active

06727038

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to photodefineable polymers.
U.S. patent application Ser. No. 290,197, filed Aug. 15, 1994; which is a continuation-in-part of U.S. patent application Ser. No. 805,395, filed Dec. 10, 1991; and which corresponds to PCT Application No. 92/10,649, filed Dec. 10, 1992 and published as 93/12,055, Jun. 24, 1993; U.S. patent application Ser. No. 224,203, filed Apr. 14, 1994; which is a continuation-in-part of U.S. patent application Ser. No. 54,999, filed Apr. 29, 1993; and which corresponds to PCT Application No. 94/04,535, filed Apr. 25, 1994 and published as 94/25,903, Nov. 10, 1994; Moyer et al.,
Proceedings, IEPS
, Austin, 1992, p. 37 and Rutter et al.,
Proceedings, ISHM/IEPS
, Denver, April 1992, p. 394 disclose a DVS resin that is rendered photo-curable by the addition of at least one photosensitive agent in an amount sufficient to convert the mixture to an organic-insoluble solid upon exposing the mixture to photon radiation. All of these references are incorporated herein by reference.
These DVS resin compositions are useful as thin film dielectrics in electronic applications such as multichip modules, integrated circuits and printed circuit boards.
These references disclose that a polymer of a monomer of the formula:
may be rendered photo-cureable by the addition of a photosensitive agent such as a bis azide.
The depictions of this monomer herein should not be construed to define any particular geometric isomer or spatial orientation about the ethenylene double bonds. Compositions made by the processes disclosed herein contain positional isomers about these double bonds as well as other compounds. This monomer will be hereinafter referred to as DVS bis BCB. A partially polymerized DVS bis BCB monomer will be hereinafter referred to as DVS resin.
The DVS bis BCB monomer can be prepared by methods disclosed in U.S. Pat. Nos. 4,812,588; 5,136,069; 5,138,081; and 5,264,646.
Following one of the disclosed procedures for making the most preferred DVS bis BCB monomer, one will obtain a mixture containing as a major component divinyltetramethyldisiloxane-bis-benzocyclobutene monomer. This monomer is partially polymerized or B-staged prior to addition of a photosensitive agent.
The most preferred group of photosensitive agents disclosed to render a DVS resin photodefineable is the azides. The azides disclosed in preparing the photodefineable polymers correspond to the formula:
Q—(N
3
)
x
wherein
Q is an x-valent organic moiety, and
x is an integer of 2 or more.
Bis azides of the formulae:
among others are disclosed.
2,6-Bis(4-azidobenzylidene)-4-methylcyclohexanone (BAC-M) is exemplified as the most preferred photosensitive agent.
The formulation containing these components is not only sensitive to photon radiation but is also unstable at room temperature. The bis azide reacts to form species which will no longer render the polymer photodefineable. At room temperature, substantial changes in the formulation properties occur in as little as three days. Because of this, the formulation is stored under refrigeration. A precipitate was found after storing the formulation under refrigeration. Upon analysis, this precipitate was found to consist largely of the BAC-M bis azide. Precipitation of a formulation component is unacceptable for many users of the formulation who require consistent and predictable behavior from the formulation.
SUMMARY OF THE INVENTION
This invention is a photodefineable, organic-soluble mixture comprising DVS resin as its major resin component dissolved in mesitylene and at least 2,6-bis (4-azidobenzylidene)-4-ethylcyclohexanone as a photosensitive agent in an amount sufficient to convert the mixture to an organic-insoluble solid upon exposing the mixture to photon radiation.
The mixture of this invention may be exposed to photon radiation to form an organic-insoluble solid polymer which may be patterned by masking portions of the mixture from the photon radiation. These photo-crosslinked polymers may then be subjected to thermal curing. These photo/thermally cured polymers are useful in many applications such as thin film dielectrics in integrated circuits, multichip modules, printed circuit boards and other microelectronic devices, as passivation or overcoat layers in microelectronics, as planarization layers in flat panel displays, as binders for conductive adhesives and the like.
A feature of this invention is that the photodefineable mixture contains DVS resin as its major resin component dissolved in mesitylene and at least 2,6-bis(4-azidobenzylidene)-4-ethylcyclohexanone as a photosensitive agent.
An advantage of this invention is that the photodefineable mixture may go for months at lower temperatures to preserve the consistency of performance of the formulation and not form a precipitate.
DETAILED DESCRIPTION OF THE INVENTION
The DVS resin used in the mixture of the invention is described in the hereinbefore cited references. The DVS resin-containing portion of the formulation may be oligomerized or B-staged prior to use to improve handling, processing, and performance characteristics.
It is most preferred to have the highest molecular weight possible while maintaining a high solubility level. This will result in the maximum solubility difference between the exposed and unexposed areas of the polymer film covering the wafer or substrate.
One may obtain a DVS resin which readily crosslinks to an insoluble gel by B-staging the DVS bis BCB monomer neat and dissolving in a miscible solvent and then precipitating out the desired higher molecular weight species as disclosed in PCT publication 93/12,055, published Jun. 24, 1993. Or, one may obtain a DVS resin which readily crosslinks to an insoluble gel by B-staging the DVS bis BCB monomer dissolved in mesitylene at a concentration of 25 weight percent DVS bis BCB monomer as disclosed in PCT publication 94/25,903, published Nov. 10, 1994.
The required bis azide has the formula:
is a known material having CAS# 114391-97-8.
One may wish to use other bis azides in conjunction with BAC-E depending on the thickness of the layer of DVS resin to be patterned. BAC-E absorbs light at 365 nm. In thicker layers, this may prevent the photon radiation from penetrating the full depth of the film. BAC-E used as the sole bis azide is a good choice for thin layers such as 5 microns or less. In thicker layers such as 10 microns, one may wish to use BAC-E in conjunction with another bis azide that does not absorb at such a wavelength. Preferred second bis azides include 4,4′- or 3,3′-diazidophenyl sulfone, 4,4′- or 3,3′-diazidophenyl ether, 2,2-bis[4-(4-azidophenoxy) phenyl] propane or 2,2-bis[4-(3-azidophenoxy) phenyl)] propane. Most preferred is 2,2-bis[4-(4-azidophenoxy) phenyl] propane. The mixture containing BAC-E and 2,2-bis [4-(4-azidophenoxy) phenyl] propane may have a longer pot life at room temperature than a mixture containing BAC-M and 4,4′- or 3,3′-diazidophenyl sulfone. The mixture of the invention preferably contains no other bis azide substituted cyclohexanones.
The amounts of DVS resin and BAC-E employed in preparing the photodefineable mixture of this invention can vary. Suitable amounts are those which contain DVS resin as the major component and provide a photodefineable mixture from which photodefined organic-insoluble polymers can be prepared. A suitable amount of BAC-E is that which provides sufficient curing in the photon-exposed portion of the mixture to render it insoluble in the developing solvent. A preferred weight percent range of photosensitive agent(s) is about 0.1 to about 20 based on the sum of the weights of the photosensitive agent and the DVS resin. A more preferred weight percent range of photosensitive agent is about 1 to about 6. The most preferred weight percent range of photosensitive agent is about 2 to about 4. A preferred weight percent range of the DVS resin is about 80 to about 99.9 based on the sum of the weights of the photosensitive agent and the

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