Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/022—Quinonediazides
  • G03F7/0226—Quinonediazides characterised by the non-macromolecular additives

Definitions

• This invention relates to a photoresist system and is more particularly concerned with light-sensitive photoresist compositions which can be employed to produce negative relief images and with processes for preparing such images.
• positive resist systems generally comprise a base-soluble polymer such as a novolak resin and a photosensitizer containing diazo and keto groups on adj acent positions in a benzenoid structure .
• Exposure o f the compos ition to actinic radiation serves to convert the diazo-keto configuration of the sensitizer to a ⁇ arboxyl group thereby rendering the exposed composition soluble in alkaline developers .
• negative resist systems In con ⁇ trast , negative resist systems generally comprise a polymer in association with a sensitizer which initiates cross -linking of the polymer upon exposure to actinic rad i at ion .
• the exposed image is thereby rendered insoluble in developer solvents and is developed by dissolving away the unexposed portions of the resist system.
• photores ist systems More recently, photores ist systems have been described which are capable of being processed in the negative as well as the positive modes.
• Kaplan et al. U.S. Patent 4,007,047 describes a process by which a negative image can be produced using a system based on an alkali-soluble resin and a diazo-ketone sensitizer which normally is employed in the positive mode.
• a layer of the composition is exposed imagewise to actinic radiation to convert the diazo-keto sensitizer to an alkali soluble carboxyli ⁇ acid
• the exposed image is treated with mild aqueous acid (which treatment apparently converts the alkali soluble form of the sensitizer to an alkali-insoluble form by decarboxyl- ation)
• the layer so treated is subject to a blanket exposure which converts the sensitizer in the previously unexposed portions of the layer to the carboxylic acid form.
• the negative image is then developed using an alkaline developer which removes the originally unexposed portions of the photosensitive layer which have been rendered alkali soluble by the blanket exposure.
• Stahlhofen U.S. Patent 4,581,321 describes a vari ⁇ ation of the above process in which the material in the exposed image layer is rendered insoluble in alkaline developer by a post exposure bake of the image after which the previously unexposed portions of tlie photo ⁇ sensitive layer are blanket exposed to radiation as in the previous process and the negative image developed using alkaline developers.
• a hexamethylmelamine ether is included in the composition employed in the process and its function is said to be that of a cross-linker for the polymeric resin in the composition.
• the cross-linking takes place during the post-exposure bake and is said to be catalyzed by the acid generated in the portion of the photosensitive layer which has been exposed to the actinic radiation.
• Spak et al. Seventh International Technical Conference on Photopolyaers, Ellenville, New York, October, 1985, pp. 247-269 describe the properties of, and theoretical background relating to operation of, a typical image reversal system based on a diazo keto sensitizer and a novolak resin, which system is avail ⁇ able commercially under the name AZ R 5214.
• the description given by Spak et al. of the procedure for use of this system in the negative mode corresponds to that set forth in the aforesaid '321 with the exception that no mention is specifically made of the need for a second blanket exposure prior to development of the negative image.
• the system is basically designed to operate in the positive mode. It is not yet known whether it can be utilized satisfactorily in the negative mode without the need for a second blanket exposure and or other process or formulation modifica- tions.
• the invention in one embodiment, comprises an improved process for producing a negative image on a substrate comprising the steps of: coating said substrate with a layer of a lightsensitive composition comprising in admixture
• b) a 1,2-quinonediazide sensitizer exposing said light-sensitive layer imagewise to actinic radiation; heating said layer, after said exposure, to a temperature and for a time sufficient to render said imagewise exposed portions of said layer insoluble in alkaline developer; and thereafter dissolving the unexposed portions of said layer in an alkaline developer; wherein the improvement comprises incorporating in said light-sensitive composition at least one organic solubilizing agent in an amount sufficient to render soluble in alkaline developer the portions of said layer which have not been exposed to actinic radiations.
• the invention also comprises a l ight-sensitive im a g e r ev e r s i b l e ph o to re s i st compos it i on wh i ch comprises , in admixture , (a) at least one novolak resin , (b ) a 1 , 2-quinonediazide sensitizer, and (c) at least one organic solubili z ing agent present in an amount sufficient to render said total composition soluble in alkaline developer.
• image reversible photoresist composi ⁇ tion means a light-sensitive composition which can be employed in either the positive or negative image mode .
• the light-sensitive image reversible photoresist compositions of the invention in the broadest embodiment thereof comprise a phenolic resin, a 1,2-quinonediazide sensitizer, and, as the novel component, at least one organic solubilizing agent.
• organic solubilizing agent is meant an organic compound, or a mixture of two or more such compounds, which serves to render soluble in alkaline developers the total combined components of the photosensitive compositions of the invention when the latter are present in the areas of a coating of the same which have not been exposed to actinic radiation but have been subjected to a post-image bake as herein ⁇ after discussed.
• solubilizing agents employed in the compositions of the invention are compatible with the other components of the compositions, i.e., do not enter into chemical reaction therewith or interfere in any way with the desired operation of the photosensitive composition other than to render it soluble in the unexposed state in alkaline developers, and are stable on storage in admixture with the other components.
• solubilizing agents render the compositions of the invention alkali soluble is con ⁇ sidered adequate if the total composition, without exposure to actinic radiation but after being subjected to a post-image bake, is completely soluble in conven ⁇ tional alkaline developers in a reasonable length of time, i.e., up to about five minutes but preferably from 1 to 2 minutes in the case of a layer of the composition having an average thickness up to about 10 microns.
• organic solubilizing agents are compounds which contain phenolic and or carboxylic groups.
• the latter compounds are inclusive.of -organic compounds which contain (a) at least one phenolic group and preferably two or more phenolic groups in a benze- noid ring or rings or (b) at least one, and preferably two or more, carboxylic acid groups or (c) at least one phenolic group and at least one carboxylic group in the molecule.
• phenolic compounds such as mono, di, and trihydroxybenzophenone, resor ⁇ inol, 1,3 ,4-xylenol, hydroquinone, catechol, pyrogallol, phloroglu ⁇ inol, polymeric phenolic resins such as poly(vinylphenol), orcinol, 1,2,4-benzentriol, 4-methylcate ⁇ hol, 2-methylresorcinol, 2,2*4,4'-tetra- hydroxybenzophenone, picric acid, coniferyl alcohol, and the like; weak carboxylic acids such as abietic acid, cinnamic acid, 9-anthroic acid, 3-methyladipic acid, pimelic acid, 1-methyl-l-cyclohexane carboxylic acid, linolenic acid, and the like, and compounds containing both carboxylic and phenolic groups such as salicylic, protocatechuic, m-hydroxybenzoic, vanillic, p-hydroxy
• solubilizing agents employed in the composi ⁇ tions of the invention also include diazoles and triazoles particularly benzotriazole and substituted benzotriazoles, such as l,2,3,4tetrachlorobenzotriazole, 1,2,3-trichlorobenzotrazole, 1,2dichlorobenzotriazole, 1-chlorobenzotriazole and the like.
• Preferred compounds for use in the compositions of the invention are poly (vinylphenols) , polyhydroxybenzophenone, abietic acid, benzotriazole and mixtures of two or more such compounds.
• the amount of the organic solubilizing agent employed, singly or in mixtures of two or more, in the compositions of the invention is at least such that, when employed as a thin coating (up to about 10 microns) , the total composition without exposure to actinic radiation is rendered completely soluble in a reasonable length of time in conventional alkaline developers such as aqueous sodium or potassium hydroxide solution, sodium meta silicate, sodium orthophosphate, sodium hydrogen phosphate, and the like.
• the actual amount of the organic solubilizing agent or agents which is necessary to achieve the desired rate of solubilization of the composition will depend principally, in any given instance, upon the particular mode, i.e., positive or negative image, in which the composition is to be employed.
• the exposed image and the unexposed photo ⁇ resist composition are both soluble to different degrees in aqueous alkaline developer.
• the rate of dissolution of the exposed image in the developer must be significantly greater than the rate of dissolution of the unexposed material in the same developer.
• This difference in rates is generally referred to as development contrast and can be measured in any given instance simply by measuring the percentage of the film coating loss in the areas which remain after the more soluble areas have been removed entirely.
• the develop ⁇ ment contrast is advantageously such that the percentage of film coating remaining in the unexposed areas, when the exposed area has been completely removed, can be as high as about 50 percent.
• the amount of film coating remaining in the unexposed areas is of the order of about 70 percent.
• concentration of the organic solubilizing agent or agents, which is present in the compositions of the invention in order to achieve development contrast in the above range will obviously depend to some degree on the particular solubilizing agent or agents employed but can be determined readily in any given instance by a process of trial and error.
• the total amount of such agent or agents employed in the compositions of the invention is of the order of about 1 to about 20 percent by weight based on weight of phenolic resin present in the compositions.
• the compositions of the invention are employed in the negative mode the requirement that there be development contrast still holds but in this case, as will be discussed in more detail below, the exposed image has been rendered substantially insoluble in the alkaline developers. Accordingly, in this mode, it is only necessary that the amount of organic solubilizing agent or agents be sufficient to render the unexposed areas of the composition completely soluble in conven ⁇ tional alkaline developers within a reasonable period of time, advantageously about 10 seconds to about 5 minutes and preferably about 1 minute for a thickness of film of the order of about 1 - 5 microns.
• concentration of the above solubilizing agent or agents necessary to achieve such a degree of solubility can be readily determined in any given instance by a process of trial and error.
• solubilizing agent or the total amount if two or more agents are used, is of the order of about 2 to about 20 percent by weight based on weight of phenolic resin present in the total composition.
• phenolic resins convention ⁇ ally employed in positive photoresist compositions can be employed in the compositions of the invention.
• Such resins are generally prepared by acid condensation of formaldehyde and phenol or an alkylsubstituted phenol under conditions described, for example, in Chemistry and Application of Phenolic Resins, Knop et al.. Chapter 4, Springer Verlag, New York, 1979.
• a particularly preferred group of resins for use in the compositions of the invention is the group of novolak resins derived from m-cresol alone or from a mixture of phenols in which m-cresol is the major component, i.e., is present in an amount greater than 50 percent and preferably greater than about 90 percent by weight.
• the resins employed, including the preferred group have average molecular weights in the range of about 600 to about 1600 and preferably from about 800 to about 1500.
• the 1,2-quinonediazide sensitizers employed in the compositions of the invention can be any of those conven ⁇ tionally employed in positive photoresist compositions available in the art.
• Such sensitizers comprise the esters and amides of naphthoquinone-(1,2)-diazide-(2)-4- sulfonic acid and naphthoquinone- (1,2)-diazide-(2)-5- sulfoni ⁇ acid.
• the esters are generally those derived from polyhydric phenols such as 2,3,4 trihydroxybenzo- phenone, 2,4-dihydroxybenzophenone, 4-decanoylresor ⁇ in- ol, 4,4-bis(4-hydroxyphenyl)valeric acid butyl ester and the like.
• a preferred group of such esters are the esters of the above two acids with 2,3,4-trihydroxy- benzophenone.
• the amides of the above two acids which can be employed in the compositions of the invention are those derived from long chain aliphatic primary amines or from aromatic primary amines.
• the proportion of such sensitizers employed in the compositions of the invention is advantageously of the order of about 2 percent to about 20 percent by weight and preferably about 2 to about 8 percent by weight, based on weight of total constituents of the composi ⁇ tions other than solvents.
• the optimum proportion to employ in any given instance can be determined readily by a process of trial, and error.
• the proportion of phenolic resin employed in the compositions of the invention is advantageously of the order of about 2 percent to about 45 percent by weight, and preferably about 2 to about 20 percent by weight, based on weight of total constituents of the composition other than solvents.
• the compositions of the invention generally also comprise a solvent or a mixture of solvents.
• the solvent or solvents employed are generally selected based on compatibility, volatility, inertness with respect to the components of the photoresist and like considerations.
• ketones such as methylethylketone, methylisopropylke- tone, diethylketone and the like; chlorinated hydro ⁇ carbons such as trichloroethylene, 1,1,1-trichloroethane and the like; aliphatic alcohols such as ethanol, n-propyl alcohol, n-butyl alcohol, n-hexyl alcohol and the like; aliphatic esters such as n-butyl acetate, n-hexyl acetate, cellosolve acetate and the like; glycol ethers such as ethylene glycol monomethyl ether, propy- lene glycol monomethyl ether and esters thereof such as the acetates, propionates and the like; and aromatic hydrocarbons such as toluene, xylene and the like.
• ketones such as methylethylketone, methylisopropylke- tone, diethylketone and the like
• a preferred group of solvents are the aliphatic alcohols, aliphatic esters, glycol ether esters and aromatic hydrocarbons and mixtures of two or more such solvents.
• the amount of solvent or mixture of solvents employed is generally such as to represent from about 50 to about 80 percent by weight, and preferably from about 60 to about 70 percent by weight, based on total weight of the compo ⁇ sitions of the invention.
• the compositions of the invention may also com ⁇ prise other optional components conventionally employed in the art such as surfactants, adhesion-promoters, finely-divided pigments and the like.
• compositions of the invention also comprise one or more cross-linking agents such as hexamethylolmelamine alkyl ethers, 2 , 6-bis (hydroxyl- ethyl) -4methylphenol, resoles, epoxy resins, and the like.
• crosslinking agents may be employed in a concentration of about 0.5 to about 20 percent by weight, and preferably in a concentration of about 1 to about 10 percent by weight, based on total components other than solvents present in the 'compositions of the invention.
• the optimum concentration for use in any given instance can be readily determined by a process of trial and error.
• the substrate is coated with a layer of a photosensitive composition of the invention using any of the coating techniques conventional in the art. Illustrative of such techniques are spin-coating, spraying, dipping, roller coating and the like.
• the substrate can be metallic such as aluminum, copper and the like or non- metallic such as reinforced epoxy resins, silicon wafers and the like.
• the surface of the substrate is generally chemically pretreated, depending on the substrate material, by use of appropriate compositions such as hexamethyl disilizane and the like compositions conventionally employed in the art.
• the thickness of the coating applied to the substrate is generally in the order of about 0.5 to about 10 microns but higher or lower thicknesses can be employed in any given instance.
• the layer of photo ⁇ sensitive composition applied to the substrate in the above manner is then treated to remove the solvent present in the layer in any conventional manner. Generally speaking this step is achieved by baking the coated substrate at a temperature less than that which would result in decomposition of the sensitizer. A temperature of the order of about 90 to llO'Cis usually satisfactory and reduced pressures can be employed if desired in order to facilitate removal of solvent.
• the resulting coated substrate is then exposed imagewise to actinic radiation. If the composition is being employed in the positive resist mode the image is then developed using aqueous alkaline developer until the exposed material has been completely removed. Any of the alkaline developers commonly employed in the art, such as those exemplified above, can be used. Prefer ⁇ ably the developer has a pH within the range of about 11 to about 14. If the composition coated on the substrate is being used in the negative mode, the coated substrate, after imagewise exposure to actinic radiation but prior to development, is subjected to a post-exposure bake. This step is conducted at a temperature and for a time such that the exposed image portions of the coating are rendered insoluble in alkaline developer.
• the bake temperature necessary to achieve this result is gener ⁇ ally within the range of about 115'C to about 140°C and preferably within the range of about 120"C to about 135"C.
• the temperature is chosen preferably to avoid any significant decomposition of the sensitizer present in the unexposed portions of the light-sensitive layer.
• the time required to achieve the desired result, i.e., insolubilization of the exposed image will vary depend- ing upon the particular composition which is being employed and the heating mode used. In general the time required is of the order of about 5 to about 60 minutes in an oven and 1 to 3 minutes when a hot plate is used. The optimum time required in any given instance can be readily determined by a process of trial and error.
• the process which takes place in the exposed image portions of the photosensitive layer during the exposure and subsequent post-exposure baking is believed to be as follows.
• the exposure of the sensitizer to actinic radiation is believed to result in conversion of the diazo-keto function of the sensitizer to an indene carboxylic acid illustrated schematically as follows:
• the acid function of the indene carboxylic acid produced in situ as shown above s believed to serve to catalyze cross-linking of the novolak resin in the exposed image portions of the photosensitive coating.
• the cross-linking is facilitat ⁇ ed by the presence of the cross-linking agent or agents in the photosensitive compositions of the invention.
• the unexposed portions of the photosensitive layer do not undergo cross-linking since no carboxylic acid has been produced in situ therein during imagewise exposure of the layer to actinic radiation. Accordingly, the unexposed portions of the photosensitive layer remain solubl e in alkal ine developer whereas the exposed portions become insoluble due to the exposure followed by post exposure baking.
• the negative image is produced by dissolving out the unexposed portions of the l ayer using alkaline developers as hereinbefore described. It is to be understood that the above theory is offered for purposes of explanation only and is not to be construed as limiting the scope of the invention in any manner whatsoever. • As will be understood by one skilled in the art, the composition and process of the invention represent significant advances over those hitherto available in the art since the omission of the second flood or blanket exposure, hitherto necessary in the compositions and processes employed in the art, is not required. Elimination of this step results in the elimination of one or more work stations with attendant savings in space, equipment and labor. Further the compositions of the invention give rise to markedly improved aspect ratio and resulting definition of the image produced and are also characterized by outstanding performance in the various steps of the processes of the invention.
• a composition in accordance with the invention was prepared by dissolving the following components in the proportions shown in the solvent shown.
• the resulting layer was baked at 80"C for
• Example 1 The process described in Example 1 is repeated us ⁇ ing a composition in accordance with the invention which had been prepared by dissolving the following components in the proportions shown in the solvent shown.
• novolak resin 1 sensitizer 2
• Example 3 The process . described in Example 1 is repeated using "a compos ition in accordance with the invention which had been prepared by dissolving the following components in the proportions shown in the solvent shown '
• a composition in accordance with the invention was prepared by dissolving the following components in the amounts shown in 71 parts by weight of a mixture of propylene glycol monomethyl ether acetate, n-butanol, p-butylacetate and xylene.
• Example 5 A composition of the invention was prepared in the same manner and using the same ingredients as in Example 4 with the exception that the amount of sensitizer was increased to 5 parts by weight.
• Example 6 This Example illustrates the use of a typical composition of the invention to fabricate a positive resist image.
• a silicon wafer was spin-coated at 5000 rpm with a layer of the composition of Example 4.
• the average thickness of the coating was 1.35 microns.
• the result ⁇ ing layer was baked at 110*C for 50 seconds on a hot plate to evaporate solvents before being cooled and exposed imagewise to UV light in a broad band contact exposure mode (150mJ/cm 2 ) using an Oriel printer.
• the image was developed using a positive photoresist alka ⁇ line developer [MF-62: MacDermid Inc., Waterbury, Ct.] which had been diluted with water to 20 percent of the original concentration. The time required for complete clearing of the non-image areas was observed and the average loss in layer thickness of the image was measured after development was completed.
• This example illustrates the use of a typical composition of the invention to fabricate a negative resist image employing a silicon wafer as a substrate.
• the wafer was coated, baked, cooled, and exposed using the composition and method described in Example 6. After exposure, the wafer was baked at 130 ⁇ C for 20 minutes in an oven. The wafer was then developed by immers ion for one minute in an alkaline developed [MF- 62 ; diluted with water to 35% of the original concentration] . The resulting image was well-defined.

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• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• General Physics & Mathematics (AREA)
• Photosensitive Polymer And Photoresist Processing (AREA)
• Materials For Photolithography (AREA)
• Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
• Image Processing (AREA)

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• 1987
  • 1987-10-16 JP JP62506919A patent/JPH01501176A/ja active Pending
  • 1987-10-16 WO PCT/US1987/002743 patent/WO1988002878A1/en not_active Ceased
  • 1987-10-16 AU AU81734/87A patent/AU8173487A/en not_active Abandoned
  • 1987-10-16 EP EP19870907391 patent/EP0288533A4/de not_active Withdrawn

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