| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | September 14, 2004 |
| PATENT TITLE |
Low dielectric constant polymers having good adhesion and toughness and articles made with such polymers |
| PATENT ABSTRACT | A cured polyphenylene polymer having a glass transition temperature no greater than 465.degree. C. An integrated circuit article having a fracture toughness as determined by the modified edge liftoff test of at least 0.3 MPa-m.sup.1/2. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | April 29, 2002 |
| PATENT REFERENCES CITED |
Allada, "Low K Adhesion Issues in Cu/Low K Integration," IEEE Proceedings from the IITC (San Francisco, CA), pp. 161-163 (1999). Hayashi et al., 1996 Symposium on VLSI Technology Digest of Technical Papers, pp. 88-89 (1996). Kumar et al., "Hybrid Polyimide-Polyphenylenes by the Diels-Alder Polymerization Between Biscyclpentadienones and Ethynyl-Terminated Imides," Microelectrics Technology Chapter 34, pp. 518-526 (1995). Nelb, "Diels-Alder Polymerizations: Investigations into the synthesis of minimally phenylated polyphenylenes and the crosslinking of aromatic polymers by a cyclotrimerization reaction," Chemistry, Polymer, p. 2288 (1976). Shaffer II et al., "Designing Reliable Polymer Coatings," Polymer Engineering and Science, vol. 36, No. 18, pp. 2375-2381 (1996). Shaffer II et al., "Adhesion energy measurements of multilayer low-K dielectric materials for ULSI applications," Low-Dielectirc Constant Materials III Symposium (1998)--Abstract Only. Shaffer II et al., "Adhesion energy measurements of multilayer low-K dielectric materials for ULSI applications," Low-Dielectric Constant Materials IV Symposium (1998)--Abstract Only. Simonyi et al., "Characterization of spin-on glasses by microindentation," Low Dielectric Constant Materials IV Symposium (Apr. 16-18, 1998)--Abstract Only. Wrasidlo et al., "Preparation of Poly(Octaphenyl-Tetraphenylene)," Polymer Letters, vol. 7, pp. 519-523 (1969). |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. In a method for making an integrated circuit article which comprises providing a substrate containing transistors, forming an electrical interconnect structure comprising a pattern of metal lines, solution coating a curable polyphenylene oligomer composition, cross-linking the curable polyphenylene oligomer, and chemically mechanical polishing, the improvement wherein the polyphenylene oligomer composition is preselected to provide a fracture toughness as measured by the modified Edge Liftoff Test of at least 0.3 MPa-m.sup.1/2. 2. The method of claim 1 wherein the cross-linked polyphenylene has a glass transition temperature of less than 465.degree. C. 3. The method of claim 1 wherein the polyphenylene oligomer composition comprises an adhesion promoter. 4. In a method for making an integrated circuit article which comprises providing a substrate containing transistors, forming an electrical interconnect structure comprising a pattern of metal lines, applying an adhesion promoter, solution coating a curable polyphenylene oligomer composition, cross-linking the curable polyphenylene oligomer, and chemically mechanically polishing, the improvement wherein the adhesion promoter and the polyphenylene oligomer composition are preselected to provide a fracture toughness as measured by the modified Edge Liftoff Test of at least 0.3 MPa-m.sup.1/2. 5. In a method for making an article which comprises providing a substrate, solution coating a curable polyphenylene oligomers composition, and cross-linking the curable polyphenylene oligomer, the improvement wherein the polyphenylene oligomer composition and an optional adhesion promoter are preselected to provide a fracture toughness as measured by the modified edge liftoff test of at least 0.3 MPa-m.sup.1/2. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
FIELD OF THE INVENTION This invention relates to polyphenylene oligomers and polymers that display excellent toughness. The invention also relates to integrated circuit articles having good fracture toughness and made using polyphenylene dielectrics. BACKGROUND-OF THE INVENTION Polymer dielectrics may be used as insulating layers between various circuits and layers within circuits in microelectronic devices, such as integrated circuits, multichip modules, and laminated circuit boards. The microelectronics fabrication industry is moving toward smaller geometries in its devices to enable lower power and faster speeds. As the conductor lines become finer and more closely packed, the requirements of the dielectrics between such conductors become more stringent. While polymer dielectrics often provide lower dielectric constants than inorganic dielectrics, such as silicon dioxide, they often present challenges to process integration during fabrication. For example, to replace silicon dioxide as a dielectric in integrated circuits, the dielectric must be able to withstand processing temperatures during metallization and annealing steps of the process. Preferably, the dielectric material should have a glass transition temperature greater than the processing temperature. The dielectric must also retain the desirable properties under device use conditions. For example, the dielectric should not absorb water which may cause an increase in the dielectric constant and potential corrosion of metal conductors. WO 98/11149, incorporated herein by reference, discloses a dielectric polymer, which is the reaction product of a cyclopentadienone functional compound and an acetylene functional compound and is useful for microelectronics fabrication. SUMMARY OF THE INVENTION The inventors have discovered that an integrated circuit article requires a fracture toughness of greater than about 0.3 in order to withstand manufacturing processes. Thus, according to a first embodiment, the invention is an integrated circuit article comprising an active substrate containing transistors and a pattern of metal lines forming an electrical interconnect structure wherein the metal lines are at least partially separated by a polyphenylene material. This integrated circuit article has a fracture toughness as defined, for example, by the modified Edge Liftoff Test of greater than about 0.3, preferably greater than 0.32 MPa-m.sup.1/2. Fracture toughness refers to both the cohesive and adhesive toughness of the components of the article and all interfaces between those components. By the term polyphenylene, we mean a material which comprises predominately aromatic rings directly bonded to other aromatic rings. These aromatic rings may be phenyl rings; substituted phenyl rings; fused aromatic systems such as naphthalene, anthracene, phenanthrene, fluorene, and the like; and substituted fused aromatic systems. There may be linking groups in the polyphenylene polymer chain, such as oxygen, sulfur, sulfones, sulfoxides, amines, phosphorous, silicon, aliphatic carbon groups, carbonyl, carboxylate, etc., separating some of these aromatic rings. Substituent groups on the aromatic rings may be essentially inert or may be reactive species which can further react and link two or more polyphenylene polymer chains together. To obtain the desired adhesion and toughness, it is preferred that the glass transition temperature, Tg, of the cured polyphenylene composition be less than 465.degree. C., but preferably greater than 350.degree. C. in order to withstand processing temperatures. Thus, according to a second embodiment, this invention is a polyphenylene having a glass transition temperature of less than 465.degree. C., preferably less than 450.degree. C. and preferably greater than 350.degree. C., more preferably greater than 400.degree. C. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plot of glass transition temperature versus mole ratio of certain trifunctional components in a polymer. FIGS. 2 and 3 are plots of adhesion versus glass transition temperature of a polymer. DETAILED DESCRIPTION OF THE INVENTION The polyphenylenes preferably are the reaction product of a compound having two or more diene functional reactive groups and a compound having two or more dienophile functional reactive groups. The preferred polyphenylenes are cross-linked materials, therefore, at least some of the compounds must have three or more reactive groups. The preferred polyphenylenes (including precursor b-staged, curable oligomers) may have the formula: [A].sub.w [B].sub.z [EG].sub.v wherein A has the structure: ##STR1## and B has the structure: ##STR2## wherein EG are end groups having one or more of the structures: ##STR3## wherein R.sup.1 and R.sup.2 are independently H or an unsubstituted or inertly-substituted aromatic moiety and Ar.sup.1, Ar.sup.2 and Ar.sup.3 are independently an unsubstituted aromatic moiety or inertly-substituted aromatic moiety, M is a bond, and y is an integer of three or more, p is the number of unreacted acetylene groups in the given mer unit, r is one less than the number of reacted acetylene groups in the given mer unit and p+r=y-1, z is an integer from 1 to 1000; w is an integer from 0 to 1000 and v is an integer of 2 or more. Such oligomers and polymers can be prepared by reacting a biscyclopentadienone, an aromatic acetylene containing three or more acetylene moieties and, optionally, a polyfunctional compound containing two aromatic acetylene moieties. Such a reaction may be represented by the reaction of compounds of the formulas: (a) a biscyclopentadienone of the formula: ##STR4## (b) a polyfunctional acetylene of the formula: ##STR5## (c) and, preferably, a diacetylene of the formula: ##STR6## wherein R.sup.1, R.sup.2, Ar.sup.1, Ar.sup.2, Ar.sup.3 and y are as previously defined. The definition of aromatic moiety includes phenyl, polyaromatic and fused aromatic moieties. Inertly-substituted means the substituent groups are essentially inert to the cyclopentadienone and acetylene polymerization reactions and do not readily react under the conditions of use of the cured polymer in microelectronic devices with environmental species, such as water. Such substituent groups include, for example, F, Cl, Br, --CF.sub.3, --OCH.sub.3, --OCF.sub.3, --O--Ph and alkyl of from 1 to 8 carbon atoms, and cycloalkyl of from 3 to 8 carbon atoms. For example, the moieties which can be unsubstituted or inertly-substituted aromatic moieties include: ##STR7## ##STR8## wherein Z can be: --O--, --S--, alkylene, --CF.sub.2 --, --CH.sub.2 --, --O--CF.sub.2 --, perfluoroalkyl, perfluoroalkoxy, ##STR9## wherein each R.sup.3 is independently --H, --CH.sub.3, --CH.sub.2 CH.sub.3, --(CH.sub.2).sub.2 CH.sub.3 or Ph. Ph is phenyl. Another group of preferred polyphenylene oligomers and polymers may be represented by the formula: ##STR10## wherein P represents the growing branching oligomer/polymer chain and has the repeat structure: ##STR11## and wherein G are the end-groups filling the valencies where oligomer/polymer growth has not occurred and have the structure: ##STR12## wherein R.sup.1 and R.sup.2 are independently H or unsubstituted or inertly substituted aromatic moieties, Ar.sup.4 is an aromatic moiety or an inertly substituted aromatic moiety, i and j are integers greater than or equal to 1 with the proviso that i+j is greater than or equal to 3, n and m are integers greater than or equal to 0 with the proviso that n+m is greater than or equal to 1. Such a polymer may be prepared by the reaction of the cyclopentadienone functionality and the acetylene functionality of a polyfunctional compound of the general formula: ##STR13## wherein R.sup.1, R.sup.2, and Ar.sup.4 are as defined previously. A polyfunctional compound containing two or more aromatic cyclopentadienone moieties may be made by the condensation of benzils with benzyl ketones using conventional methods. Exemplary methods are disclosed in Kumar, et al. Macromolecules, 1995, 28, 124-130; Ogliaruso, et al., J. Org. Chem., 1965, 30, 3354; Ogliaruso, et al., J. Org. Chem., 1963, 28, 2725; and U.S. Pat. No. 4,400,540. A polyfunctional compound containing two or more aromatic acetylene moieties may be made by conventional methods. An aromatic compound may be halogenated and then reacted with the appropriate substituted acetylene in the presence of an aryl ethynylation catalyst to replace the halogen with the substituted acetylene compound. The polymerization steps may occur as taught in WO 98/11149. The polyphenylenes may be applied to the integrated circuit device according to any known process, such as solution deposition, liquid-phase epitaxy, screen printing, melt-spinning, dip coating, roll coating, spinning, brushing (for example, as a varnish), spray coating, powder coating, plasma-deposition, dispersion-spraying, solution-casting, slurry-spraying, dry-powder-spraying, fluidized bed techniques, welding, explosion methods including the Wire Explosion Spraying Method and explosion bonding, press bonding with heat, plasma polymerization, dispersion in a dispersion media with subsequent removal of dispersion media, pressure bonding, heat bonding with pressure, gaseous environment vulcanization, extruding molten polymer, hot-gas welding, baking, coating, and sintering. Mono- and multilayer films can also be deposited onto a substrate using a Langmuir-Blodgett technique at an air-water or other interface. Preferably, the curable polyphenylene oligomer solution is spin coated onto the substrate from an organic solvent. Suitable organic solvents include mesitylene, pyridine, triethylamine, N-methylpyrrolidinone (NMP), methyl benzoate, ethyl benzoate, butyl benzoate, cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, cyclohexylpyrrolidinone, and ethers or hydroxy ethers, such as dibenzylethers, diglyme, triglyme, diethylene glycol ethyl ether, diethylene glycol methyl ether, dipropylene glycol methyl ether, dipropylene glycol dimethyl ether, propylene glycol phenyl ether, propylene glycol methyl ether, tripropylene glycol methyl ether, toluene, xylene, benzene, dipropylene glycol monomethyl ether acetate, dichlorobenzene, propylene carbonate, naphthalene, diphenyl ether, butyrolactone, dimethylacetamide, dimethylformamide and mixtures thereof. The preferred solvents are mesitylene, N-methylpyrrolidinone (NMP), gamma-butyrolactone, diphenylether, cyclohexanone, and mixtures thereof. After coating, the oligomer or polymer is preferably exposed to temperatures sufficient to advance the oligomer or polymer to a higher molecular weight, and in the most preferred examples, to a cross-linked polymer with the desired glass transition temperature. The integrated circuit article of this invention may be made according any known method in the art, such as those fabricated with silicon or gallium arsenide. An integrated circuit would, typically, have multiple layers of metal conductors separated by one or more insulating materials. The polyphenylene can be used as insulation between discrete metal conductors in the same layer, and/or between conductor levels of the interconnect structure. The polyphenylene can also be used in combination with other materials, such as SiO.sub.2 or Si.sub.3 N.sub.4, in a composite interconnect structure. For example, integrated circuit devices may be made as taught in U.S. Pat. No. 5,550,405; U.S. Pat. No. 5,591,677 and Hayashi, et al., 1996 Symposium on VLSI Technology Digest of Technical Papers, pg. 88-89, and WO098/11149. The integrated circuit articles can be made by any known process such as either a "damascene" metal inlay or subtractive metal patterning scheme. Processes for fabricating damascene lines and vias are known in the art. See, for example, U.S. Pat. Nos. 5,262,354 and 5,093,279. Patterning of the material may be done with typical reactive ion etch procedures using oxygen, argon, nitrogen, helium, carbon dioxide, fluorine-containing compounds, or mixtures of these and other gases, using a photoresist "softmask", such as an epoxy novolac, or a photoresist in combination with an inorganic "hardmask" such as SiO.sub.2, Si.sub.3 N.sub.4, or metal. The polyphenylene may be used in conjunction with Al, Al alloys, Cu, Cu alloys, gold, silver, W, and other common metal conductor materials (for conductive lines and plugs) deposited by physical vapor deposition, chemical vapor deposition, evaporation, electroplating, electroless deposition, and other deposition methods. Additional metal layers to the basic metal conductors, such as tantalum, titanium, tungsten, chromium, cobalt, their alloys, or their nitrides, may be used to fill holes, enhance metal fill, enhance adhesion, provide a barrier, or modify metal reflectivity. Depending on the fabrication architecture, either metal or the dielectric material of this invention may be removed or planarized using chemical-mechanical polishing techniques. The inventors have discovered that, for integrated circuit articles, a fracture toughness, K.sub.c, of no less than about 0.3, preferably no less than about 0.32, MPa-m.sup.1/2, as measured by the modified edge liftoff test, is needed in order for the articles to consistently withstand the manufacturing processes. Fracture toughness refers to the cohesive toughness and adhesive toughness of all materials and interfaces comprising the integrated circuit article. The modified Edge Liftoff Test (m-ELT) is described, for example, in the article by E. O. Shaffer II, et al., Poly. Sci. & Eng, 36 (18) 2381 (1996), incorporated herein by reference. According to the test, a thick backing material, such as an epoxy, is applied to the test structure (i.e., the article to be tested). The test structure has a rigid substrate with one or more additional materials coated on the substrate. The backing material must have a known-stress-temperature profile, have higher fracture toughness than the test structure, and have excellent adhesion to the test structure. The test structure is diced into squares so that 90.degree. edges to the substrate are formed. The sample is then cooled until failure in the article is observed. Failure may be debonding at the interfaces or some other fracture in the article. The applied fracture intensity or fracture toughness is K.sub.app =.sigma..sub.o h/2 where .sigma..sub.o is the residual stress in the backing layer at the failure temperature, and h is the thickness of the backing layer. The applied fracture intensity approximates the critical fracture energy, K.sub.c, at the locus of the failure, which can be either adhesive or cohesive. The inventors have determined that there are a variety of ways to achieve the required fracture toughness. The glass transition temperature of the cured polymer has been found to affect the adhesion and fracture toughness. While a high glass transition temperature is desirable from the standpoint of being able to withstand high temperature processing steps, a lower glass transition temperature provides improved adhesion and fracture toughness. Therefore, the inventors have determined that the cured resin should have a glass transition temperature of less than 465.degree. C., preferably less than 450.degree. C., and preferably greater than 350.degree. C., more preferably greater than 380.degree. C., and most preferably greater than 400.degree. C. As one means of adjusting the glass transition temperature and/or the fracture toughness of the material, the inventors have reacted a bifunctional diene compound (preferably a biscyclopentadienone), a bifunctional dienophile (preferably a bisacetylene), and a tri or higher functional dienophile (preferably a trisacetylene). Adjusting the molar ratios of monomers leads to variations in the glass transition temperatures of the resultant cured resin. Alternatively, the glass transition temperature of the cured resin and/or the fracture toughness may be adjusted via addition of monofunctional monomers or by modification of the system before or during cure to adjust the number of reactive groups available for cure reactions. For example, if the polyphenylene is the reaction product of a di-cyclopentadienone functional compound and a tris-acetylene compound, raising the ratio of cyclopentadienone functional compound to acetylene compound improves fracture toughness. Cure conditions, such as temperature, time of cure and atmosphere, may also have an effect on toughness. For instance, the Tg is related to the cure temperature and in some instances can be limited to the cure temperature, if the cure temperature is not sufficient to allow the cross-linking reactions to go to completion. As a result, the glass-transition temperature can be artificially controlled by varying the cure temperature. That is, lower cure temperatures can lead to lower glass-transition temperature. If cure temperature is used to control glass transition temperature, preferably, the cure temperature is no greater than 425.degree. C., more preferably, no greater than 410.degree. C. As an example, certain samples of the highest Tg resin (Tg>500.degree. C.) cured at 450.degree. C. have adhesion of 0.18 MPa-m.sup.1/2, whereas, samples of the same formulation cured at 400.degree. C. can have adhesion in excess of 0.38 MPa-m.sup.1/2. The oligomers or polymers of the invention adhere directly to many materials, such as compatible polymers, polymers having a common solvent, metals, particularly textured metals, silicon or silicon dioxide, especially etched silicon or silicon oxides, glass, silicon nitride, aluminum nitride, alumina, gallium arsenide, quartz, and ceramics. However, in order to meet the required fracture toughness of 0.3 MPa-m.sup.1/2, adhesion promoters may be useful or necessary. Adhesion promoters, such as those based on silane chemistry, may be applied to the substrate prior to the application of the polyphenylene oligomer or polymer solution, or added directly to the solution. Representative examples of such adhesion promoting materials are silanes, preferably organosilanes such as alkoxy silanes (e.g., trimethoxyvinylsilane, triethoxyvinylsilane, tetraethoxysilane), acetoxysilanes (e.g., vinyltriacetoxysilane), hexamethyldisilazane [(CH.sub.3).sub.3 --Si--NH--Si(CH.sub.3).sub.3 ], or an aminosilane coupler such as .gamma.-aminopropyltriethoxysilane, or a chelate such as aluminum monoethylacetoacetatedi-isopropylate [((isoC.sub.3 H.sub.7 O).sub.2 Al(OCOC.sub.2 H.sub.5 CHCOCH.sub.3))]. In some cases, the adhesion promoter is applied from 0.01 weight percent to 5 weight percent solution, excess solution is removed, and then the polyphenylene applied. In other cases, for example, a chelate of aluminum monoethylacetoacetatedi-isopropylate, can be incorporated onto a substrate by spreading a toluene solution of the chelate on a substrate and then baking the coated substrate at 350.degree. C. for 30 minutes in oxygen to form a very thin (for example, 5 nanometer) adhesion promoting layer of aluminum oxide on the surface. Other means for depositing aluminum oxide are likewise suitable, such as the use of aluminum alkoxides. Alternatively, the adhesion promoter, in an amount of, for example, from 0.05 weight percent to 5 weight percent based on the weight of the b-staged material, can be blended with the b-staged material before application to the substrate, negating the need for formation of an additional layer. Adhesion can also be enhanced by surface preparation, such as texturizing (for example, scratching, etching, plasma treating, or buffing) or cleaning (for example, degreasing or sonic cleaning); otherwise treating (for example, plasma, solvent, SO.sub.3, plasma glow discharge, corona discharge, sodium, wet etching, or ozone treatments) the substrate's surface or using electron beam techniques such as 6 MeV fluorine ions; electrons at intensities of 50 to 2000V; hydrogen cations at 0.2 to 500 ev to 1 MeV; helium cations at 200 KeV to 1 MeV; fluorine or chlorine ions at 0.5 MeV; neon at 280 KeV; oxygen enriched flame treatment; or an accelerated argon ion treatment. |
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