Method of Forming a Polymer on a Substrate

This invention relates to materials used to provide isolation of conductive layers in microelectronic circuitry. In particular, it relates to polymeric materials which can be photopolymerized so that dielectric layers can be formed where desired in multilayer structures. Such layers must be excellent insulators, have good chemical resistance and, of course, must adhere to the substrate on which they are placed.

Polyimides have been used for such dielectrics since they have superior temperature and chemical resistance compared to many other polymers. Literature and patents disclosing of the use of polyimides are extensively discussed in U.S. Pat. No. 4,908,096 by one of the present inventors and incorporated herein by reference. The disadvantages of the polyimides are discussed, namely, that they release large amounts of volatiles during curing, absorb moisture, have poor adhesion, and have a relatively high coefficient of expansion. The patent discloses and claims the use of other polymers as interlevel dielectrics having improved properties, namely, vinyl benzyl or alkyl ethers of the condensation products of dialdehydes and phenols.

The present invention relates to other polymers which have been found to provide useful interlevel dielectrics.

In U.S. Pat. No. 4,855,375 one of the present inventors has disclosed oligomers which are ethers of bisphenols and formaldehyde which may be fluorinated and which have application to making laminated boards for electronic applications. The patent is incorporated by reference herein. Such fluorinated polymers have been found to be useful as interlevel dielectrics, as will be seen in the discussion below.

This invention comprises a method of forming a predetermined pattern from a polymer on a substrate and the thus-created dielectric layers which may be used in an electronic interconnect structure.

Such patterns are created by coating onto the substrate a prepolymer and then irradiating the exposed portions of a masking pattern to render the prepolymer insoluble, then selectively dissolving the non-irradiated masked portions of the coating leaving the insoluble irradiated prepolymer, and curing the irradiated prepolymer to form an infusible glassy solid in the predetermined pattern.

The prepolymer is an ether of the oligomeric condensation product of a dihydric phenol and formaldehyde having the formula ##STR2## where the recurring unit Q has the structure, ##STR3## and n is an integer from 1 to 10;

s is 1;

each X is C(CF.sub.3).sub.2 ;

each R.sub.1 and R.sub.2 is independently selected from the group consisting of hydrogen, alkyl and alkoxy moieties containing 1 to 10 carbon atoms, phenyl and phenoxy;

a and b are independently 0 or integers from 1 to 4;

Z is Cl or Br;

E is selected from the group consisting of the vinyl-benzyl moiety, alkyl moieties containing 1 to 10 carbon atoms, or benzyl, subject to the constraint that at least 50% of all E's are the vinylbenzyl moiety.

In a preferred embodiment, E is at least 70% vinyl benzyl and the remaining E's are propyl.

In U.S. Pat. No. 4,855,375, one of the present inventors disclosed the preparation and use of the ethers of the oligomeric condensation products of a dihydric phenol and formaldehyde and their use in composites, especially laminated boards for electronic uses. It has now been found that these compositions can be used as interlevel dielectrics, where they have the advantages of low water absorption, low dielectric constant, low coefficient of thermal expansion, high glass transition temperature, high thermal stability, high solids coating concentrations, and are photochemically curable, thermally curable, and generate little or no volatiles during the curing process.

The prepolymers used in forming a pattern have the formula ##STR4##

They result from the etherification of oligomers which are the condensation product of a dihydric phenol and formaldehyde. The product will be a mixture of oligomers with varying molecular weight. The number, n, of recurring units Q generally will vary from 1 to 10. Preferably, n is 1 or an integer from 1 to 6 and the number average of n is about 3.

The recurring unit Q itself has the structure, ##STR5## Note that the condensation may occur either on the same ring, as in the right hand structure, or in different rings, as in the left hand structure. The aromatic rings in the recurring unit Q are separated by an intervening moiety X. That is, S is 1. Each of the moieties X is hexafluoroisopropylidene [C(CF.sub.3).sub.2 ].

Each of the aromatic rings may bear substituents or may be completely unsubstituted. Thus, R.sub.1 and R.sub.2 are independently selected from moieties such as hydrogen, alkyl moieties containing from 1 to 10 carbon atoms, the phenyl moiety, alkoxy moieties containing from 1 to 10 carbon atoms, and phenoxy, C.sub.6 H.sub.5 O. Examples of suitable alkyl moieties include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptl, octyl, nonyl, and decyl moieties. The methyl and tertbutyl butyl groups are preferred alkyl moieties, although the variant where R.sub.1 =R.sub.2 =H is quite desirable.

The basic resins can be modified to be flame retardant by incorporating halogen atoms into the aromatic rings. Thus, Z may be a halogen atom, especially bromine, and where the aromatic ring is halogenated a and b are integers from 1 to 4. Polyhalogenated materials are preferred as flame retardants, and thus a and b are recommended to be 2, 3, or 4.

The oligomeric condensation products have a multiplicity of phenolic hydroxyl groups substantially all of which are end-capped as ether groups in our interlevel dielectric resins. The best case results where the ether portion, E, is a vinylbenzyl moiety, that is, of the structure. ##STR6## which may be either the meta- or para-isomer, and which usually is a mixture of the meta- and para-isomers. Although it is desirable to have all the phenolic hydroxyls end-capped with vinylbenzyl moieties, there is a cost advantage when fewer than all of the ether groups are vinylbenzyl, but usually at the expense of a somewhat lower dielectric constant. At least 50% of the E moieties should be a vinylbenzyl moiety, but better performance characteristics result when from 70 to 100% of the ether groups are vinylbenzyl, and the best prepolymer product results when 95 to 100% of such groups are vinylbenzyl. However, for many applications less than complete end-capping with vinyl benzyl groups is acceptable, but all of the hydroxyl groups should be capped.

Where the ether groups include other than vinylbenzyl, then E is an alkyl group containing from 1 to 10 carbons or a benzyl group. Where E is an alkyl group, the primary alkyl groups are preferred, especially the primary lower alkyl groups containing from 1 to 4 carbon atoms. Thus, the most desirable alkyl groups consist of methyl, ethyl, 1-propyl, 1-butyl, and 1-methyl-1-propyl. Other alkyl groups are represented by 1-pentyl, 1-hexyl, 1-heptyl, 1-octyl, 1-nonyl, 1-decyl, 2-methyl-1-butyl, 3-methyl-1-butyl, 2,3-dimethyl-1-buty1,3,3-dimethyl-1-butyl, 2-methyl-1-pentyl, and so forth.

In a preferred embodiment, E is at least 70% vinyl benzyl and the remaining E's are propyl. The prepolymers may be prepared by acid catalyzed condensation of dihydric phenols with formaldehyde followed by end-capping substantially all the phenolic hydroxyls by converting them to ethers. Acid catalyzed condensation is preferred to avoid the formation of terminal hydroxyl methylene groups, -CH.sub.2 OH. End-capping by ether formation can be effected by any suitable means, such as by reacting the phenolic condensation product with an alkyl or benzyl halide in a basic medium.

The resulting thermosetting oligomers may be polymerized with attendant crosslinking by a variety of curing means. When curing is effected by thermal means, it generally is autoinitiated by heating the oligomer resin in air at a temperature between about 100.degree. and 300.degree. C., and more particularly between about 120.degree. and 300.degree. C. Curing also may be brought about by chemical means using a free radical initiator such as azo-bis-isobutyronitrile, benzoyl peroxide, di-t-butyl peroxide, etc. In the present invention curing is begun by irradiation, especially by ultraviolet light in the presence or absence of a sensitizer or photoinitiator, followed by thermal curing to produce an infusible, insoluble glassy solid.

The oligomers may be used as a passivant, as an interlevel dielectric, as a means of providing device deep dielectric isolation (insulator isolating trenches), as a high temperature solder mask, a photoresist, etc. Although much of what follows describes its use primarily as an interlevel dielectric, the skilled worker will recognize from this description how to use the materials of the invention in other applications as well.

The oligomers are applied as a coating to a suitable substrate. Preferably the coating will have a thickness of 2 to 15 .mu.m, most preferably 5 to 10 .mu.m. For the most part the substrates used will be a silicon wafer, a silicon chip of an integrated circuit, a printed circuit board or a ceramic substrate. The photosensitive oligomers may be applied by spin coating, spray coating, by use of a doctor knife, or any other conventional techniques known in the art to obtain a uniform coating. Where the viscosity is too high, a solution of the resin in a suitable solvent may be used. The oligomers are soluble in a broad class of solvents including polar aprotic solvents, aromatic hydrocarbons, halogenated hydrocarbons, ketones, ester, and so forth. Examples of solvents which may be employed in the practice of our invention include dimethylformamide (DMF), hexamethylphosphoramide (HMPA), N-methylacetamide (NMAc), dimethylsulfoxide (DMSO), N-methylpyrrolidone (NMP), benzene, toluene, xylene, dichloromethane, chloroform, carbon tetrachloride, chlorobenzene, tetrachloroethane, tetrachloroethylene, trichloroethane, gamma-butyrolactone, methyl ethyl ketone, diethyl ketone, hexanone, heptanone, octanone, methyl acetate, ethyl acetate, methoxy ethanol, ethoxy ethanol, and so forth. The solvent should be unreactive with both the substrate and the photosensitive oligomers and able to dissolve the resins to provide at least about a 10 weight-volume percent solution. Since the solvent is typically removed prior to further processing, it is also preferable that as low boiling a solvent as possible be used consistent with the foregoing considerations.

Although the oligomers may be photopolymerized directly, a photosensitizer or photoinitiator may be used and may be useful to decrease irradiation time. Where a photosensitizer or photoinitiator is used it will be added with the oligomers at the coating stage and will be present in an amount from about 0.001 to about 5.0 weight percent relative to the oligomerics. Examples of photosensitizers or photoinitiators which may be successively used in the practice of this invention include such materials as benzophenone, 4,4'-bis(dimethylamino)benzophenone, xanthone, acetophenone, 4-trifluoromethyl-acetophenone, triphenylene, thioxanthone, anthraquinone, 4-phenylbenzophenone, naphthalene, 2-acetonaphthalene, 1-acetonaphthalene, chrysene, anthracene, 9,10-dichloroanthracene, pyrene, triphenylene,l-fluoronaphthalene, 1-chloronaphthalene, 1-bromonaphthalene, 1-iodonaphthalene, 1,3-dicyanobenzene, dimethyl isophthalate, diethyl isophthalate, methyl 3-cyano-benzoate, ethyl 3-cyano-benzoate, phenyl 3-cyano-benzoate, 2,2-dimethoxyacetophenone, 2,2-diethoxyacetophenone, 2,2'-dimethoxy-2-phenylacetophenone, 2,2'-diethoxy-2-phenylacetophenone, benzoin methyl ether, and 1-phenyl-1,2-propanedione-2-0-benzoyloxime. Preferred sensitizers include benzophenone, 4,4'-bis(dimethylamino)benzophenone, 1,3-dicyanobenzene, dimethyl isophthalate, diethyl isophthalate, methyl 3-cyano-benzoate, and phenyl 3-cyano-benzoate.

Where the photosensitive oligomers have been applied as a solution to the substrate the solvent used must be removed prior to irradiation. Consequently, it is conventional to heat the coated substrate for a time sufficient to remove essentially all of the solvent present, if any, prior to irradiation, a stage known as the "softbake." It is for this reason that the use of a low boiling solvent is preferred. It is acceptable to use enough heat to provide a semicured coating, especially since the oligomers may begin to cure at temperatures as low as about 110.degree. C. The softbake can be carried out in vacuum, under an inert atmosphere (e.g., nitrogen, helium, argon, etc.) or in air.

A mask containing the desired pattern or image is placed on or adjacent to the coated substrate and the oligomeric coating is then irradiated through the mask by x-ray, electron beam, ion beam, ultraviolet, or visible radiation. For reasons of economy and ease of fabrication it is preferred to use radiation in the range from about 200 to about 800 nanometers. Since lower wave length radiation tends to afford better resolution, irradiation in the 200-500nm range is preferred. With this treatment the irradiated portion of the coating becomes crosslinked so that the photocrosslinked oligomer is rather insoluble in the same solvent in which the original photosensitive oligomers remain quite soluble.

Irradiation may be done in either the presence or absence of oxygen. Exposure time necessary for adequate photocrosslinking to afford the differential solubility characteristic sought depends upon the wavelength of the light used, its intensity, the presence or absence of a photosensitizer or photoinitiator, and so forth, with a variation from a few seconds up through several minutes. For production purposes the shorter exposure times are highly preferred. One desirable characteristic of the photosensitive oligomers of this invention is that they photochemically crosslink throughout the thickness of the film. Therefore, the pattern shows no or minimal undercutting upon development.

The selective pattern appears upon development with the solvent. As mentioned above, upon irradiation the photosensitive oligomeric resin becomes extensively crosslinked with a subsequent large differential solubility between the crosslinked, or irradiated, and non-crosslinked, or non-irradiated, portions of the oligomers. The solvents used in the development are in general the same ones used in preparing a solution of the oligomers for coating purposes. Thus, classes of solvents include aprotic solvents, aromatic hydrocarbons, halogenated hydrocarbons, ketones, esters, the Carbitols, and mixtures of solvents.

Upon development selective patterns appear where the elevated portions correspond to the photochemically crosslinked oligomers. These relief structures are then thermally cured to afford a highly crosslinked, infusible, glassy solid highly resistant to elevated temperatures, chemical degradation, ion transport, and which serves as an effective protective layer and dielectric insulator. Curing is attended by crosslinking of the vinyl groups and may be effected either thermally, chemically, or photochemically, with thermal curing preferred. Thermal curing is generally done in the temperature range between about 100.degree. C. and about 300.degree. C., and often is done in stages. So, for example, curing may first be effected at a temperature between about 150.degree. C. and about 200.degree. C. for 0.5-5 hours with postcuring at about 180.degree. C.-300.degree. C. for about 0.5-24 hours. Curing also may be brought about using a free radical initiator, such as azo-bis-isobutyronitrile, benzoyl peroxide, di-t-butylperoxide, and so on.

The oligomers of the invention have been found particularly useful in photodefinable applications since they may be coated as solutions with high solids levels and thus less solvent must be evaporated. Also, since no volatile by-products are generated during curing the shrinkage of the films is minimized.

The substrate (i.e., ceramic, alumina, silicon, printed wiring board, etc.) may be cleaned with conventional cleaning solvents (e.g., methylene chloride, chloroform, Genesolv.RTM., trichloroethylene, ethanol, methanol, sodium bisulfite, sodium sulfite, potassium sulfite, etc.) employing normal cleaning processes as known in the art. In addition, the substrate may contain circuitry already deposited upon it. The substrate may be utilized after the cleaning process or may be surface treated to promote adhesion between the substrate and the metals and/or polymer dielectric layer.

If used, an adhesion promoter between the substrate and the dielectric layer may be chosen from a range of surface silylating agents containing reactive groups capable of reacting with the polymers of the invention. Examples of surface silylating agents which can be employed are: vinylmethyldimethoxysilane, vinyltrimethoxysilane, vinylmethyldiethoxysilane, vinyltriethoxysilane, d i e t h o x y m e t h y l v i n y l p h e n e t h y l s i l a n e , d i m e t h o x y m e t h y l v i n y l p h e n e t h y l s i l a n e , t r i e t h o x y v i n y l p h e n e t h y l s i l a n e , trimethoxyvinylphenethylsilane, etc. Preferred silylating agents are vinylmethyldimethoxysilane, v i n y l m e t h y l d i e t h o x y s i l a n e , diethoxymethylvinylphenethylsilane, and dimethoxymethylvinylphenethylsilane. The surface silylating agent would be applied to the substrate via dipping, spin coating, or other techniques from an alcohol-water solution. For example, a 1 to 10 wt.% solution of the silylating agent is dissolved in 85 to 98 wt.% of alcohol (e.g., methanol, ethanol, isopropanol, etc.) and 1 to 13 wt.% of water. The substrate is dipped in this solution for 15 seconds to 5 m-nutes, air dried for 1 minute to 5 hours, and then soft baked for 1 minute to 5 hours at 60.degree. to 100.degree. C. either in a convection oven, vacuum oven or hot plate.

The cleaned and/or surface treated substrate will be covered with a metal pattern before being covered with the dielectric layer of the invention. For example, a 500 to 1000 .ANG. layer of chromium, 8000 to 20000 .ANG. layer of copper and a 500 to 1000 .ANG. layer of chromium may be sputtered onto the surface. Then, the metal layer is coated with a commercial photoresist and processed according to the recommended processing scheme utilizing a spin coat, soft bake, imaging, developing, and hard bake cycle. This exposes portions of the metal layer to be removed by etching to create the pattern. The metals are etched utilizing standard wet techniques, for example: The top chromium layer is etched with a 1 to 30 % hydrochloric acid solution activated with aluminum for 10 seconds to 5 minutes; the copper layer is etched with a sodium persulfate solution for 10 seconds to 10 minutes; the bottom chromium layer is etched with a 1 to 30 % hydrochloric acid solution activated with aluminum for 10 seconds to 5 minutes; and finally the etched substrate is washed with deionized water for 10 to 60 seconds. Then the remaining photoresist is stripped from the metal pattern as per the processing technique recommended for the photoresist. Finally the cleaned substrate is dried prior to the next processing step.

The dielectric layer is coated onto the substrate and its metal pattern and processed as follows: The prepolymer (e.g., 10 to 80 wt. %) solution in an appropriate solvent (toluene, NMP, DMF, etc.) is spin coated onto the substrate at a speed of 500 to 2500 rpm for 30 to 90 seconds; the prepolymer coated substrate is soft baked at a temperature of 25 to 60.degree. C. for 15 minutes to 24 hours in a vacuum oven with or without a nitrogen bleed; the soft-baked coating is then imaged with a UV light source (220-320 nm range) for 15 seconds to 30 minutes employing a mask of desired design for vias and the like; the photocured polymer is then developed with an appropriate solvent system (e.g., toluene, toluene/hexane, toluene/ethanol, cyclohexane, etc.) at 25.degree. to 35.degree. C. with or without ultrasonics or via spraying for 15 to 120 seconds; the developed substrate can then be exposed to a stop or rinse bath or solvent spray based upon a solvent system miscible with the developing solvent but a poor solvent for the polymer system (for example hexane, pentane, ethanol, etc.) (optional step); the vias are then cleaned with a plasma or wet etch; and finally the dried substrate is hard baked in vacuum or under an inert atmosphere (nitrogen, argon, etc.) with a preferred cure cycle including a ramp from 25.degree. to 300.degree. C. for 30 minutes to 10 hours, a hold at 300.degree. C. for 5 hours and then a cool down from 300.degree. to 25.degree. C. with a 10 minute to 3 hour ramp.

The process is repeated as required in order to form an electronic interconnect structure of desired electrical and dielectric levels.

Hexafluorobisphenol-A formaldehyde (BPAF6-F) was prepared as follows: 336.24 g (1.00 mole) of hexafluorobisphenol-A, 30.00 g (1.00 mole of formaldehyde functionality) of paraformaldehyde, and 250 mL of ethanol were charged into a 2000 mL 3-neck flask equipped with a mechanical stirrer, thermometer, Therm-0-Watch, condenser, addition funnel and nitrogen purge. The reaction mixture was heated to 60.degree. C., 1.00 mL of concentrated sulfuric acid was added dropwise over a 30 minute interval. The reaction was maintained at 60.degree. C. for 3 days. The solvent was distilled from the reaction mixture and then the resin was dissolved in NMP and coagulated into water, the resin was dried in a vacuum oven at 60.degree. C., yielding 130.0 g of resin, Mn =280, Mw=660, dispersity of 2.4.

126.60 grams of the above BPAF6-F was dissolved in 250 mL of N-methylpyrrolidinone (NMP) in a 1000 mL 3-neck round bottom flask equipped with mechanical stirrer, addition funnel, condenser, thermometer, nitrogen purge and Therm-0-Watch. To this reaction mixture was added 120.0 g (0.786 moles) of vinylbenzylchloride (60/40 para/meta isomer ratio) and 0.40 g of 2,6-di-tert-butyl-p-cresol (BHT). The reaction mixture was heated to 60.degree. C. and 45.0 g (0.802 moles) of potassium hydroxide in 130 mL of methanol was added dropwise over a 45 minute interval. The reaction was maintained at 60.degree. C. for 19 hrs with stirring under a nitrogen purge. After cooling to room temperature the reaction mixture was transferred to a separatory funnel, and 2.0 Liters of toluene added and then washed thrice with 4 Liters of water, dried over magnesium sulfate, filtered and concentrated under vacuum. Infrared analysis after workup indicated incomplete capping of the hydroxyl groups; the resin was transferred to 1000 mL 3-neck reaction flask (equipped as above) with 250 mL of NMP. To this reaction mixture was added 57.88 g (0.471 moles) of n-propylbromide was added to the reaction mixture and heated with stirring under purge to 60.degree. C. To this reaction mixture was then added 26.41 g (0.471 moles) of potassium hydroxide in 65 mL of methanol over a 40 minute interval. The reaction was maintained at 60.degree. C. for 24 hours and then allowed to cool to room temperature. The reaction mixture was then transferred to a separatory funnel, and 2.0 Liters of toluene added and then washed thrice with 2 Liters of water and once with saturated sodium chloride solution, dried over magnesium sulfate, filtered and concentrated under vacuum, yielding a red resinous product; Mn=700, Mw=980, dispersity 1.4.

Hexafluorobisphenol-A formaldehyde (BPAF6-F) was prepared as follows: 336.24 g (1.00 mole) of hexafluorobisphenol-A, 45.00 g (1.50 mole of formaldehyde functionality) of paraformaldehyde, and 250 mL of ethanol were charged into a 2000 mL 3-neck flask equipped with a mechanical stirrer, thermometer, Therm-0-Watch, condenser, addition funnel and nitrogen purge. The reaction mixture was heated to 80.degree. C., 2.00 mL of concentrated sulfuric acid was added dropwise over a 30 minute interval. The reaction was maintained at 60.degree. C. for 1 day. The solvent was distilled from the reaction mixture with the reactor equipped with a Dean-Stark trap and then the resin was dissolved in NMP and coagulated into water, the resin was dried in a vacuum oven at 60.degree. C., yielding 211.0 g of resin, Mn=570, Mw =790, dispersity of 1.39.

211.00 grams of the above BPAF6-F was dissolved in 350 mL of N-methylpyrrolidinone (NMP) in a 2000 mL 3-neck round bottom flask equipped with mechanical stirrer, addition funnel, condenser, thermometer, nitrogen purge and Therm-O-Watch. To this reaction mixture was added 134.0 g (0.878 moles) of vinylbenzylchloride (60/40 para/meta isomer ratio) and 0.10 g of 2,6-di-tert-butyl-p-cresol (BHT). The reaction mixture was heated to 60.degree. C. and 54.2 g (0.966 moles) of potassium hydroxide in 150 mL of methanol was added dropwise over a 1.2 hr interval. The reaction was maintained at 60.degree. C. for 19 hrs with stirring under a nitrogen purge. 57.5 g (0.467 moles) of n-propylbromide was added to the reaction mixture, to this reaction mixture was then added 26.4 g (0.471 moles) of potassium hydroxide in 8o mL of methanol over a 2 hr. interval, the reaction was maintained at 60.degree. C. for 18 hrs. After cooling to room temperature the reaction mixture was transferred to a separatory funnel, 2 Liters of toluene was added and then washed thrice with 2 Liters of water, dried over magnesium sulfate and stripped under vacuum. IR indicates presence of residual hydroxyl moieties; resin transferred to 2000 mL 3-neck round bottom flask (as equipped above) with 350 mL of NMP. 57.5 g (0.467 moles) of n-propylbromide was added to reaction mixture and then heated with stirring under nitrogen purge to 60.degree. C. To this reaction mixture was added 26.4 g (0.471 moles) of potassium hydroxide in 80 mL of methanol over a 2 hour period and the reaction was maintained at 60.degree. C. for 18 hrs. Upon cooling the reaction mixture was transferred to a separatory funnel with 2 Liters of toluene, and then washed twice with 2 Liters of water and once with saturated ammonium chloride solution, dried over sodium sulfate, filtered and then concentrated under vacuum, yielding 236.0 g of resin; Mn=1600, Mw=7200, dispersity of 4.5.

Hexafluorobisphenol-A formaldehyde (BPAF6-F) was prepared as follows: 336.24 g (I.00 mole) of hexafluorobisphenol-A, 30.00 g (1.00 mole of formaldehyde functionality) of paraformaldehyde, and 125 mL of ethanol were charged into a 2000 mL 3-neck flask equipped with a mechanical stirrer, thermometer, Therm-O-Watch, condenser, addition funnel and nitrogen purge. The reaction mixture was heated to 80.degree. C., 2.00 mL of concentrated sulfuric acid was added dropwise over a 30 minute interval. The reaction was maintained at 80.degree. C. for 1 day. The solvent was distilled from the reaction mixture with the reactor equipped with a Dean-Stark trap and then the resin was dissolved in NMP and coagulated into water. The resin was dried in a vacuum oven at 60.degree. C., yielding 167.2 g of resin; Mn=620, Mw =790, dispersity of 1.27.

167.2 grams of the above BPAF6-F was dissolved in 550 mL of N-methylpyrrolidinone (NMP) in a 2000 mL 3-neck round bottom flask equipped with mechanical stirrer, addition funnel, condenser, thermometer, nitrogen purge and Therm-O-Watch. To this reaction mixture Was added 106.28 g (0.696 moles) of vinylbenzylchloride (60/40 para/meta isomer ratio) and 0.20 g of 2,6-di-tert-butyl-p-cresol (BHT). The reaction mixture was heated to 60.degree. C. and 42.98 g (0.760 moles) of potassium hydroxide in 120 mL of methanol was added dropwise over a 1.0 hr interval. The reaction was maintained at 60.degree. C. for 19 hrs with stirring under a nitrogen purge. 40.05 g (0.326 moles) of n-propylbromide was added to the reaction mixture, to this reaction mixture was then added 18.17 g (0.323 moles) of potassium hydroxide in 80 mL of methanol over a 2 hr. interval and the reaction was maintained at 60.degree. C. for 4 hrs. After cooling to room temperature the reaction mixture was transferred to a separatory funnel, 2 Liters of toluene was added and then washed thrice with 2 Liters of water, dried over sodium sulfate and stripped under vacuum. IR indicates presence of residual hydroxyl moieties; the resin was transferred to 2000 mL 3-neck round bottom flask (as equipped above) with 700 mL of NMP. 40.05 g (0.326 moles) of n-propylbromide, and 0.10 g of BHT was added to reaction mixture, and then heated with stirring under nitrogen purge to 60.degree. C. To this reaction mixture is then added 18.17 g (0.323 moles) of potassium hydroxide in 80 mL of methanol over a 2 hour period and the reaction was maintained at 60.degree. C. for 4 hrs. Upon cooling the reaction mixture was transferred to a separatory funnel with 2 Liters of toluene, and then washed twice with 2 Liters of water and once with saturated ammonium chloride solution, dried over sodium sulfate, filtered and then concentrated under vacuum, IR indicates presence of hydroxyl groups; resin transferred to 2000 mL 3-neck round bottom flask (as equipped above) with 700 mL of NMP. 40.05 g (0.326 moles) of n-propylbromide, and 0.10 g of BHT was added to reaction mixture, and then heated with stirring under nitrogen purge to 60.degree. C. To this reaction mixture was added 18.17 g (0.323 moles) of potassium hydroxide in 80 mL of methanol over a 2 hour period and the reaction was maintained at 60.degree. C. for 4 hrs. Upon cooling the reaction mixture was transferred to a separatory funnel with 2 Liters of toluene, then washed twice with 2 Liters of water and once with saturated ammonium chloride solution, dried over sodium sulfate, filtered and then concentrated under vacuum, yielding 96.72 g of resin; Mn=1300, Mw=6900, dispersity of 5.2.

Hexafluorobisphenol-A formaldehyde (BPAF6-F) was prepared as follows: 336.24 g (1.00 mole) of hexafluorobisphenol-A, 22.50 g (0.750 mole of formaldehyde functionality) of paraformaldehyde, and 125 mL of ethanol were charged into a 2000 mL 3-neck flask equipped with a mechanical stirrer, thermometer, Therm-O-Watch, condenser, addition funnel and nitrogen purge. The reaction mixture was heated to 80.degree. C., 2.00 mL of concentrated sulfuric acid was added dropwise over a 30 minute interval. The reaction was maintained at 80.degree. C. for 1 day. The solvent was distilled from the reaction mixture with the reactor equipped with a Dean-Stark trap and then the resin was dissolved in NMP and coagulated into water, the resin was dried in a vacuum oven at 60.degree. C., yielding 180.78 g of resin.

180.78 grams of the above BPAF6-F was dissolved in 400 mL of N-methylpyrrolidinone (NMP) in a 2000 mL 3-neck round bottom flask equipped with mechanical stirrer, addition funnel, condenser, thermometer, nitrogen purge and Therm-O-Watch. To this reaction mixture was added 114.88 g (0.753 moles) of vinylbenzylchloride (60/40 para/meta isomer ratio) and 0.10 g of 2,6-di-tert-butyl-p-cresol (BHT). The reaction mixture was heated to 60.degree. C. and 52.79 g (0.941 moles) of potassium hydroxide in 150 mL of methanol was added dropwise over a 1.2 hr interval. The reaction was maintained at 60.degree. C. for 19 hrs with stirring under a nitrogen purge. 43.64 g (0.355 moles) of n-propylbromide was added to the reaction mixture, and then was added 24.88 g (0.443 moles) of potassium hydroxide in 75 mL of methanol over a 2 hr. interval and the reaction was maintained at 60.degree. C. for 18 hrs. After cooling to room temperature the reaction mixture was transferred to a separatory funnel, 2 Liters of toluene was added and then washed thrice with 1 Liter of water, dried over magnesium sulfate and stripped under vacuum, yielding a red resinous product; Mn=660, Mw=970, dispersity of 1.5.

Hexafluorobisphenol-A formaldehyde (BPAF6-F) was prepared as follows: 1029.7 g (3.062 mole) of hexafluorobisphenol-A, 68.90 g (2.30 mole of formaldehyde functionality) of paraformaldehyde, and 380 mL of ethanol were charged into a 3000 mL 3-neck flask equipped with a mechanical stirrer, thermometer, Therm-O-Watch, condenser, addition funnel and nitrogen purge. The reaction mixture was heated to 80.degree. C., 6.00 mL of concentrated sulfuric acid was added dropwise over a 30 minute interval. The reaction was maintained at 80.degree. C. for 1 day. The solvent was distilled from the reaction mixture with the reactor equipped with a Dean-Stark trap and then the resin was dissolved in NMP and coagulated into water, the resin was dried in a vacuum oven at 105.degree. C., yielding 908.0 g of resin.

900.0 grams of the above BPAF6-F was dissolved in 2000 mL of N-methylpyrrolidinone (NMP) in a 5000 mL 3-neck round bottom flask equipped with mechanical stirrer, addition funnel, condenser, thermometer, nitrogen purge and Therm-O-Watch. To this reaction mixture was added 572.0 g (3.748 moles) of vinylbenzylchloride (60/40 para/meta isomer ratio) and 0.50 g of 2,6-di-tert-butyl-p-cresol (BHT). The reaction mixture was heated to 60.degree. C. and 263.0 g (4.687 moles) of potassium hydroxide in 500 mL of methanol was added dropwise over a 2.0 hr interval. The reaction was maintained at 60.degree. C. for 19 hrs with stirring under a nitrogen purge. 299.0 g (2.431 moles) of n-propylbromide was added to the reaction mixture, to this reaction mixture was then added 135.0 g (2.406 moles) of potassium hydroxide in 250 mL of methanol over a 2 hr. interval, the reaction was maintained at 60.degree. C. for 4 hrs. After cooling to room temperature the reaction mixture was transferred to a separatory funnel, 4 Liters of toluene was added and then washed thrice with 4 Liters of water, dried over magnesium sulfate and stripped under vacuum, yielding a red resinous product; Mn=490, Mw=1200, dispersity of 2.5.

1138.4 g (3.386 mole) of hexafluorobisphenol-A, 76.18 g (2.539 mole of formaldehyde functionality) of paraformaldehyde, and 430 mL of ethanol were charged into a 5000 mL 3-neck flask equipped with a mechanical stirrer, thermometer, Therm-O-Watch, condenser, addition funnel and nitrogen purge. The reaction mixture was heated to 60.degree. C., 7.00 mL of concentrated sulfuric acid was added dropwise over a 30 minute interval. The reaction was maintained at 60.degree. C. for 1 day. The solvent was distilled from the reaction mixture with the reactor equipped with a Dean-Stark trap. The BPAF6-F Resin was dissolved in 1500 mL of N-methylpyrrolidinone (NMP). To this reaction mixture was added 723.42 g (4.740 moles) of vinylbenzylchloride (60/40 para/meta isomer ratio) and 0.50 g of 2,6-di-tert-butyl-p-cresol (BHT). The reaction mixture was heated to 60.degree. C. and 292.55 g (5.214 moles) of potassium hydroxide in 650 mL of methanol was added dropwise over a 2.5 hr interval. The reaction was maintained at 60.degree. C. for 19 hrs with stirring under a nitrogen purge. 333.12 g (2.708 moles) of n-propylbromide was added to the reaction mixture, to this reaction mixture was then added 151.97 g (2.708 moles) of potassium hydroxide in 350 mL of methanol over a 2 hr. interval, the reaction was maintained at 60.degree. C. for 4 hrs. After 4 hrs. a small (50 mL) sample of the reaction mixture was worked up and analyzed, the sample showed residual hydroxyl groups. 150.0 g (1.220 moles) of n-propylbromide was added to the reaction mixture at 60.degree. C., and then 75.0 g (1.337 moles) of potassium hydroxide in 180 mL of methanol was added over a 1 hr interval and then heated at 60.degree. C. for 18 hrs. A small sample (50 mL) of the reaction mixture was worked up and analyzed, once again residual hydroxyl groups were found. 75.0 g (0.610 moles) of n-propylbromide was added to the reaction mixture and then heated to 60.degree. C. with stirring under a nitrogen purge, 75.0 g (1.337 moles) of potassium hydroxide in 180 of methanol was added to the reaction mixture over a 1 hour interval, the reaction was maintained at 60.degree. C. for 4 hour. Upon cooling to room temperature the reaction mixture was transferred to a separatory funnel, 4.5 Liters of toluene was added and then washed twice with 2 Liters of water, and once with saturated ammonium chloride solution, dried over sodium sulfate and stripped under vacuum, yielding a red resinous product; Mn=3300, Mw=5000, dispersity of 1.5.

795.6 g (2.366 mole) of hexafluorobisphenol-A, 35.4 g (1.180 mole of formaldehyde functionality) of paraformaldehyde, and 300 mL of ethanol were charged into a 5000 mL 3-neck flask equipped with a mechanical stirrer, thermometer, Thermo-O-Watch, condenser, addition funnel and nitrogen purge. The reaction mixture was heated to 80.degree. C., 5.00 mL of concentrated sulfuric acid was added dropwise over a 30 minute interval. The reaction was maintained at 80.degree. C. for 1 day. The solvent was distilled from the reaction mixture with the reactor equipped with a Dean-Stark trap. The BPAF6-F Resin was dissolved in 1600 mL of N-methylpyrrolidinone (NMP). To this reaction mixture was added 505.6 g (3.313 moles) of vinylbenzylchloride (60/40 para/meta isomer ratio) and 0.25 g of 2,6-di-tert-butyl-p-cresol (BHT). The reaction mixture was heated to 60.degree. C. and 185.89 g (3.313 moles) of potassium hydroxide in 400 mL of methanol was added dropwise over a 2.0 hr interval. The reaction was maintained at 60.degree. C. for 18 hrs with stirring under a nitrogen purge. 290.99 g (2.365 moles) of n-propylbromide was added to the reaction mixture, to this reaction mixture was then added 132.75 g (2.366 moles) of potassium hydroxide in 280 mL of methanol over a 1 hr. interval, the reaction was maintained at 60.degree. C. for 24 hrs. Upon cooling to room temperature the reaction mixture was transferred to a separatory funnel, 4.0 Liters of toluene was added and then washed twice with 2 Liters of water, and once with saturated ammonium chloride solution, dried over sodium sulfate and stripped under vacuum, yielding 864.7 g of resin; Mn=480, Mw=700, dispersity of 1.5.

2131.9 g (6.340 mole) of hexafluorobisphenol-A, 142.80 g (4.760 mole of formaldehyde functionality) of paraformaldehyde, and 1200 mL of ethanol were charged into a 12000 mL 3-neck flask equipped with a mechanical stirrer, thermometer, Therm-O-Watch, condenser, addition funnel and nitrogen purge. The reaction mixture was heated to 60.degree.C., 15.00 mL of concentrated sulfuric acid was added dropwise over a 44 minute interval. The reaction was maintained at 60.degree. C. for 1 day. The solvent was distilled from the reaction mixture with the reactor equipped with a Dean-Stark trap. The BPAF6-F Resin was dissolved in 3700 mL of N-methylpyrrolidinone (NMP). To this reaction mixture was added 1390.3 g (9.110 moles) of vinylbenzylchloride (60/40 para/meta isomer ratio) and 1.30 g of 2,6-di-tert-butyl-p-cresol (BHT). The reaction mixture was heated to 60.degree. C. and 622.5 g (11.094 moles) of potassium hydroxide in 1200 mL of methanol was added dropwise over a 2.0 hr interval. The reaction was maintained at 60.degree. C. for 46 hrs with stirring under a nitrogen purge. 833.0 g (6.772 moles) of n-propylbromide was added to the reaction mixture, and then was added 355.8 g (6.341 moles) of potassium hydroxide in 900 mL of methanol over a 45 minute interval, the reaction was maintained at 60.degree. C. for 20 hrs. Upon cooling, a small (50 mL) sample of the reaction mixture was worked up and analyzed, the sample showed residual hydroxyl groups. 320.0 g (2.602 moles) of n-propylbromide was added to the reaction mixture and then heated with stirring under a nitrogen purge to 60.degree. C. Then 146.0 g (2.602 moles) of potassium hydroxide in 300 mL of methanol was added over a 30 minute interval and maintained at 60.degree. C. for 18 hrs. Upon cooling to room temperature the reaction mixture was transferred to a separatory funnel, 6.0 Liters of toluene was added and then washed twice with 4 Liters of water, and once with saturated ammonium chloride solution, dried over magnesium sulfate and stripped under vacuum, IR indicates small residual hydroxyl group. Resin taken up in 3000 mL of NMP and recharged into 12000 mL reactor as equipped above. 1.2 g of BHT, and 300.0 g (2.439 moles) of n-propylbromide was added to the reaction mixture and then heated with stirring under a nitrogen purge to 60.degree. C. Then 136.0 g (2.424 moles) of potassium hydroxide in 300 mL of methanol was added over a 2 hour interval and maintained at 60.degree. C. for 18 hrs. Upon cooling to room temperature the reaction mixture was transferred to a separatory funnel, 6.0 Liters of toluene was added and then washed twice with 4 Liters of water, and once with saturated ammonium chloride solution, dried over magnesium sulfate, filtered, and concentrated under vacuum, yielding a red resinous product; Mn=810, Mw=12500, dispersity of 15.0.

2164.0 g (6.436 mole) of hexafluorobisphenol-A, 144.95 g (4.832 mole of formaldehyde functionality) of paraformaldehyde, and 1200 mL of ethanol were charged into a 12000 mL 3-neck flask equipped with a mechanical stirrer, thermometer, Therm-O-Watch, condenser, addition funnel and nitrogen purge. The reaction mixture was heated to 80.degree. C., 15.00 mL of concentrated sulfuric acid was added dropwise over a 40 minute interval. The reaction was maintained at 80.degree. C. for 1 day. The solvent was distilled from the reaction mixture with the reactor equipped with a Dean-Stark trap. The BPAF6-F Resin was dissolved in 4600 mL of N-methylpyrrolidinone (NMP). To this reaction mixture was added 1178.7 g (7.723 moles) of vinylbenzylchloride (60/40 para/meta isomer ratio) and 1.13 g of 2,6-di-tert-butyl-p-cresol (BHT). The reaction mixture was heated to 60.degree. C. and 541.7 g (9.654 moles) of potassium hydroxide in 1000 mL of methanol was added dropwise over a 4.25 hr interval. The reaction was maintained at 60.degree. C. for 18 hrs with stirring under a nitrogen purge. 791.6 g (6.436 moles) of n-propylbromide was added to the reaction mixture, to this reaction mixture was then added 361.12 g (6.436 moles) of potassium hydroxide in 800 mL of methanol over a 2.5 hr. interval, the reaction was maintained at 60.degree. C. for 44 hrs. Upon cooling, a small (50 mL) sample of the reaction mixture was worked up and analyzed, the sample showed residual hydroxyl groups. 316.65 g (2.574 moles) of n-propylbromide was added to the reaction mixture and then heated with stirring under a nitrogen purge to 60.degree. C. Then, 144.45 g (2.574 moles) of potassium hydroxide in 300 mL of methanol was added over a 2 hr. interval and maintained at 60.degree. C. for 18 hrs. Upon cooling to room temperature the reaction mixture was transferred to a separatory funnel, 8.0 Liters of toluene was added and then washed twice with 4 Liters of water, twice with 7 Liters of water, and twice with saturated ammonium chloride solution, dried over magnesium sulfate, filtered, and then concentrated under vacuum, yielding 2724.1 g of resin; Mn=750, Mw =1300, dispersity of 1.7.

A series of styrene terminated hexafluorobisphenol-A formaldehydes (STBPAF6-F) (STBPAF6-F) (samples 1, 2, 3, and 4 below) prepared in Examples 5, 3, 2, and 9, respectively, were cured via the following cure cycle 2 hrs. at 80.degree. C., 16 hrs. at 100.degree. C; 4 hrs. at 120.degree. C; 16 hrs. at 160.degree. C., 2 hrs. at 200.degree. C. and 1 hr. at 225.degree. C. and their properties measured. The results are summarized in the following table.

A series of coating solutions were prepared and used to coat silicon surfaces. The solution concentrations were between 55.0 and 61.5 wt. % STBPAF6-F (Example 5) in toluene. The solutions were applied by spin coating at 900-950 rpm for 60 seconds. The coated discs were soft backed at 25.degree. C. for 18 hours under vacuum. Then, they were exposed for 3 minutes to UV irradiation with a 300 watt mercury vapor lamp with a quartz/water filter. The irradiated coatings were then exposed to various solvents and the amount of cured resin dissolved was measured. The results are shown in the following tables.

Tables B and C may be compared with the results of Tables D and E below in which only the soft bake was carried out and no curing by UV radiation was done.

The following tables, F and G, make a similar comparison using another solvent system and in which the effect of UV radiation on the resin is demonstrated.

STBPAF6-F resin of Example 7 was dissolved in toluene to yield a solution of composition 58.9% STBPAF6-F and 41.1% toluene. This solution was spin coated onto a silicon surface utilizing spin coating rates from 600 rpm to 2000 rpm for 60 seconds; and soft baked for 24 hours at 25.degree. C. under vacuum. The samples were then exposed for 3 minutes of UV irradiation with a 300 watt mercury lamp employing an USAF Test Pattern and a quartz/water filter. The photocured polymer was then developed with toluene for 1 minute at 25.degree. C. The air dried substrate was hard baked employing a cure cycle under vacuum of 25.degree. C. to 238.degree. C. ramp in 1 hour, held at 238.degree. C. for 2.5 hours and then cooled to room temperature.

The film thickness and sidewall angle of the photocured polymer was analyzed utilizing a Sloan Technology Corporation Dektak 3030 profilometer.

STBPA6-F resin of Example 7 was dissolved in toluene to yield a solution of composition ranging from 41.7% to 72.0% STBPAF6-F and 28.0% to 58.3% toluene. These solutions were spin coated onto a silicon surface utilizing spin coating rates from 700 rpm to 1500 rpm for 60 seconds; soft baked for 24 hours at 25.degree. C. under vacuum. The samples were then exposed for 3 minutes to UV irradiation with a 300 watt mercury lamp employing an USAF Test Pattern and a quartz/water filter. The photocured polymer was then developed with toluene for 1 minute at 25.degree. C. The air dried substrate was hard baked employing a cure cycle under vacuum of 25.degree. C. to 220.degree. C. ramp in 1 hour, held at 220.degree. C. for 2.5 hours and then cooled to room temperature.

The film thickness of the photocured polymer was analyzed employing a Taylor-Hobson Talysurf 10 profilometer.

STBPAF6-F resin of Example 7 was dissolved in toluene to yield a solution of composition ranging from 41.7% to 72.0% STBPAF6-F and 28.0% to 58.3% toluene. This solution was spin coated onto a silicon substrate (surface) utilizing spin coating rates from 700 rpm to 1500 rpm for 60 seconds; soft baked for 24 hours at 25.degree. C. under vacuum. The samples were then exposed for 3 minutes to UV irradiation with a 300 watt mercury lamp employing an USAF Test Pattern and a quartz/water filter. The photocured polymer was then developed with toluene for 1 minute at 25.degree. C. The air dried substrate was hard baked employing a cure cycle under vacuum of 25.degree. C. to 220.degree. C. ramp in 1 hour, held at 220.degree. C. for 2.5 hours and then cooled to room temperature. The samples were then metallized via ion-beam sputtering to yield a metal film of thickness 5000 to 10000.ANG..

The adhesion was evaluated via a calibrated "Scotch-Tape" adhesion test before and after thermal shock cycling. A thermal shock cycle encompasses the following thermal cycling of the sample: hold at -55.degree. C. for 10 minutes, -55.degree. C. to 125.degree. C. over a rapid ramp, hold at 125.degree. C. for 10 minutes. In the following tables the ratio given means that of 25 squares of the metal, some to all of them were not removed by the tape. That is, 25/25 means that all of the squares remained adhered to the dielectric polymer while 5/25 means that 20 squares of metal were removed.

STBPAF6-F resin of Example 5 was dissolved in toluene to yield a solution of composition 58.95% STBPAF6-F and 41.1% toluene. This solution was spin coated onto an alumina or silicon substrate (surface) utilizing spin coating rate of 1000 rpm for 60 seconds; soft baked for 1 hour at 60.degree. C. under nitrogen. The polymer was hard baked employing a cure cycle under nitrogen of 25.degree. C. to 220.degree. C. ramp in 3 hours, held at 220.degree. C. for 2.0 hours and then ramped from 220.degree. C. to 25.degree. C. in 4 hours.

The adhesion was evaluated via a calibrated "Scotch-Tape" adhesion test before and after thermal shock cycling. A thermal shock cycle encompasses the following thermal cycling of the sample: hold at -55.degree. C. for 10 minutes, -55.degree. C. to 125.degree. C. over a rapid ramp, hold at 125.degree. C. for 10 minutes.

STBPA6-F resin of Example 5 was dissolved in toluene to yield a solution of composition 58.9% STBPAF6- F and 41.1% toluene. This solution was spin coated onto an alumina substrate (surface) onto which had been ion-sputtered with a metal film of thickness 5000 .ANG., utilizing spin coating rate of 1000 rpm for 60 seconds; soft baked for 1 hour at 60.degree. C. under nitrogen. The polymer was hard baked employing a cure cycle under nitrogen of 25.degree. C. to 220.degree. C. ramp in 3 hours, held at 220.degree. C. for 2.0 hours and then ramped from 220.degree. C. to 25.degree. C. in 4 hours.

The adhesion was evaluated via a calibrated "Scotch-Tape" adhesion test before and after thermal shock cycling. A thermal shock cycle encompasses the following thermal cycling of the sample: hold at -55.degree. C. for 10 minutes, -55.degree. C. to 125.degree. C. over a rapid ramp, hold at 125.degree. C. for 10 minutes.

As can be seen in the above Examples 14-16 chromium adhered particularly well to the dielectric polymers and thus can serve as a suitable base for copper layers which provide conductive patterns in the multilevel structures.