METHOD OF PATTERNING A DEVICE

A photoresist layer comprising a fluorinated photoresist material is formed on a device substrate and exposed to patterned radiation. The exposed photoresist layer is contacted with a developing agent to remove a portion of the exposed photoresist layer in accordance with the patterned light, thereby forming a developed structure having a first pattern of photoresist covering the substrate and a complementary second pattern of uncovered substrate corresponding to the removed portion of photoresist, the developing agent comprising a mixture of first and second fluorinated solvents, wherein at least one of the first and second solvents is a hydrofluoroether. The developed structure is treated to form a treated structure. The treated structure is contacted with a stripping agent to remove the first pattern of photoresist, the stripping agent comprising at least the first or second solvent in a concentration different from the developing agent.

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Description
CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/815,465, filed on Apr. 24, 2013, the entire disclosure of which is hereby incorporated herein by reference. This application is also related to U.S. patent application Ser. No. ______ entitled “Method of Patterning a Device,” Attorney Docket No. 16480.0012USU2, filed on even date herewith.

STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with Government support under SBIR Phase II Grant No. 1058509 awarded by the National Science Foundation (NSF). The government may have certain rights in the invention.

BACKGROUND

1. Field of the Invention

The present invention relates to the use of fluorinated solvents and solvent blends for processing fluorinated photoresists. Such solvents and photoresists are particularly useful for patterning organic electronic and biological materials.

2. Discussion of Related Art

Organic electronic devices offer significant performance and price advantages relative to conventional inorganic-based devices. As such, there has been much commercial interest in the use of organic materials in electronic device fabrication. Specifically, organic materials such as conductive polymers can be used to manufacture devices that have reduced weight and drastically greater mechanical flexibility compared to conventional electronic devices based on metals and silicon. Further, devices based on organic materials are likely to be significantly less damaging to the environment than devices made with inorganic materials, since organic materials do not require toxic metals and can ideally be fabricated using relatively benign solvents and methods of manufacture. Thus, in light of these superior weight and mechanical properties, and particularly in light of the lowered environmental impact in fabrication and additionally in disposal, electronic devices based on organic materials are expected to be less expensive than devices based on conventional inorganic materials.

Fabrication of electronic devices, whether from organic or inorganic materials, requires the creation on an industrial scale of precisely defined patterns of the organic or inorganic active materials in these devices, often at a microscopic level. Most commonly, this is accomplished by “photolithography,” in which a light-sensitive “photoresist” film that has been deposited on a substrate is exposed to patterned light. Although this can be done in numerous ways, typically a microscopic pattern of light and shadow created by shining a light through a photographic mask is used to expose the photoresist film, thereby changing the chemical properties of the portions of the photoresist that have been exposed to light. In a “positive” photoresist, the portions of the photoresist that are exposed to light become soluble in the “developer” solution that is then applied to the exposed photoresist, and the light-exposed portions of the photoresist are washed away (“developed”) by the developer solvent to leave a pattern of unexposed photoresist and newly exposed underlying substrate. A “negative” photoresist is treated as for a positive photoresist; however, in a negative photoresist, it is the unexposed rather than the exposed portions of the photoresist that are washed away by the developing step.

In a standard process, the photoresist material is laying on top of an active material layer that is to be patterned. Once the development has taken place, the underlying layer is etched using either a liquid etchant or a reactive ion plasma (RIE) with the appropriate etch chemistry. In either case, the photoresist layer blocks the etching of active material directly beneath it. Once the etching is complete, the resist is typically stripped away, leaving the pattern of active material on the substrate.

Alternatively, the photoresist can be used with a so-called “liftoff” technique. In this case, the resist is processed on a substrate before the active material layer is deposited. After the photoresist pattern is formed, the active material is deposited on both the substrate and the photoresist. In an additional “lift-off” or “stripping” step, remaining photoresist along with an overlying layer of active material is removed via the appropriate solvent to leave the desired patterned active material.

Although the use of photoresists is routine in traditional electronic devices based on inorganic materials, photolithography has been difficult to achieve for devices using organic materials, thereby hindering the development of devices based on these materials. Specifically, organic materials are much less resistant to the solvents that are used for conventional photolithography, as well as to the intense light sources that are sometimes used in these processes, with the result that conventional lithographic solvents and processes tend to degrade organic electronics. Although there have been various attempts to overcome these problems, e.g., by ink jet printing or shadow mask deposition, these alternative methods do not produce the same results as would be obtained with successful photolithography. Specifically, neither ink jet printing nor shadow mask deposition can achieve the fine pattern resolutions that can be obtained by conventional lithography, with ink-jet printing limited to resolutions of approximately 10-20 μm and shadow mask deposition to resolutions of about 25-30 μm.

US 2011/0159252 discloses a useful method for patterning organic electronic materials by an “orthogonal” process that uses fluorinated solvents and fluorinated photoresists. The fluorinated solvents have very low interaction with organic electronic materials. WO 2012/148884 discloses additional fluorinated material sets for orthogonal processing.

Although these disclosures demonstrate good progress, many of the more useful fluorinated solvents can be expensive. Further, the different processing steps (coating, developing and stripping) have very different solvent needs, thereby necessitating the use of multiple fluorinated solvents. The coating solvent must solubilize the photoresist material sufficiently to allow good film formation on a substrate. The developer must discriminate between exposed regions and unexposed regions, i.e., dissolve only one or the other. The stripping solvent must remove the remaining photoresist that the developer solvent left behind. At the same time, they all must not harm the active material (e.g., an organic semiconductor).

To improve manufacturing costs, fluorinated solvents can in theory be recovered and recycled as long as the cost of recycling is not too high. US 2010/0126934 (Nakazato) discloses a method of purifying used fluorine-based solvent solutions using a series of steps including washing, treatment with activated carbon and alumina, and filtration. Distillation is mentioned, but it is noted that sufficient purity is difficult to achieve with distiller sizes typically used in a normal cleaning apparatus. Although the recycling method of Nakazato may help purify the fluorine-based solvents of other materials, it will not separate different fluorinated solvents.

WO2009031731 (Lee) discloses a method for recycling main solvents from conventional photoresist stripper waste. The method uses a first distillation device to remove low boiling point impurities from the photoresist stripper waste solution, a second distillation device to remove high boiling point impurities, and a third distillation device to recycle individual stripper solutions. Lee discloses that it is essential to develop a recycling technique which is capable of recycling stripper waste solutions as highly pure, electronic-grade stripper solutions. There is no disclosure in Lee about also recycling developing solutions or recycling fluorinated solvents.

U.S. Pat. No. 5,994,597 (Bhatt) discloses a multi-step process of recovering low vapor pressure solvent waste, e.g., benzyl alcohol, propylene carbonate, or gamma butyrolactone, from a conventional photoresist line. Bhatt further teaches that, for reuse as a developing agent or stripping agent, it is necessary to recover a purified solvent, i.e., a solvent that is typically 99 or greater weight percent pure. There is no disclosure in Bhatt regarding fluorinated solvents.

U.S. Pat. No. 8,377,626 (Kim) discloses photoresist polymers and processing methods. There is a brief mention that developers may include conventional organic solvents such as ketones, acetates, ethers, and alcohols, and that they may be used alone or in a mixture thereof. There is no disclosure in Kim about fluorinated solvents or recycling developer or stripping solutions.

US20100151395 (Ishiduka) discloses the use of a fluorine-substituted polymer as a protective overcoat on a photoresist for immersion photolithography. Prior to development with a conventional aqueous alkaline developer, the protective overcoat is removed using a hydrofluoroether solvent or solvent mixture. Ishiduka does not disclose using hydrofluoroether solvents as developers nor recycling mixtures of developer and stripping solvents.

In light of the above, there is a need to provide a more cost-effective fluorinated solvent system for use with fluorinated photoresists.

SUMMARY

In accordance with the present disclosure, a method of patterning a device using a fluorinated photoresist comprises:

forming a photoresist layer on a device substrate, the photoresist layer comprising a fluorinated photoresist material;

exposing the photoresist layer to patterned radiation to form an exposed photoresist layer;

contacting the exposed photoresist layer with a developing solution to remove a portion of the exposed photoresist layer in accordance with the patterned radiation, thereby forming a developed structure having a first pattern of photoresist covering the substrate and a complementary second pattern of uncovered substrate corresponding to the removed portion of photoresist, the developing solution comprising a mixture of first and second fluorinated solvents, wherein at least one of the first and second solvents is a hydrofluoroether;

treating the developed structure to form a treated structure; and

contacting the treated structure with a stripping solution to remove the first pattern of photoresist, the stripping solution comprising at least the first or second solvent in a concentration different from the developing solution.

In another aspect of the present disclosure, a photoresist system comprises: a) a developing solution comprising a first solvent and a second solvent, wherein both solvents are fluorinated solvents and at least one is a hydrofluoroether; b) a photoresist coating composition comprising a fluorinated photoresist material and a coating solvent, the coating solvent comprising at least one of the first and second solvents; and c) a stripping solution comprising at least one of the first and second solvents in a concentration different from the developing solution.

In an embodiment, using a mixture of first and second solvents in the developing solution can improve development performance. In an embodiment, using a stripping solution that includes at least the first or second solvent of the developing solution can simplify recycling of such solvents. In an embodiment, using a mixture of first and second solvents in both the developing solution and in the stripping solution (typically in different ratios) can further improve recyclability of processing waste and in some cases improve stripping performance. Enabling relatively simple recycling of solvents from a photolithographic processing waste stream can reduce manufacturing costs and the environmental impact of the process.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow chart depicting the steps in an embodiment of the present invention;

FIG. 2A-2F is a series of cross-sectional views depicting various stages in the formation of a patterned active organic material structure according to an embodiment of the present invention;

FIG. 3A-3D is a series of cross-sectional views depicting various stages in the formation of a patterned active organic material structure according to another embodiment of the present invention; and

FIG. 4 is a representative plot of normalized thickness vs. log (exposure) used to determine photoresist contrast.

 DETAILED DESCRIPTION

It is to be understood that the attached drawings are for purposes of illustrating the concepts of the invention and may not be to scale.

A photoresist includes a light-sensitive material that can be coated to produce a photo-patternable film. Photoresists can be used to pattern devices, e.g., multilayer electronic devices, optical devices, medical devices, biological devices and the like. An embodiment of the present invention is directed to an improved method of processing a fluorinated photoresist using mixtures of fluorinated solvents in the developing solution, and selecting at least one of the solvents from the developing solution for use in the stripping solution. The solvents for the fluorinated photoresist solution, the developing solution and stripping solution are each chosen to have low interaction with other material layers that are not intended to be dissolved or otherwise damaged. Such solvents are collectively termed “orthogonal” solvents. This can be tested by, for example, immersion of a device comprising the material layer of interest into the solvent prior to operation. The solvent is orthogonal if there is no serious reduction in the functioning of the device.

Certain embodiments disclosed in the present disclosure are particularly suited to the patterning of solvent-sensitive, active organic materials. Examples of active organic materials include, but are not limited to, organic electronic materials, such as organic semiconductors, organic conductors, OLED (organic light-emitting diode) materials and organic photovoltaic materials, organic optical materials, medical materials and biological materials. Many of these materials are easily damaged when contacted with organic or aqueous solutions used in conventional photolithographic processes. Active organic materials are often coated to form a layer that may be patterned. For some active organic materials, such coating can be done from a solution using conventional methods. Alternatively, some active organic materials are preferentially coated by vapor deposition, for example, by sublimation from a heated organic material source at reduced pressure. Solvent-sensitive, active organic materials can also include composites of organics and inorganics. For example, the composite may include inorganic semiconductor nanoparticles (quantum dots). Such nanoparticles may have organic ligands or be dispersed in an organic matrix.

Depending on the particular material set and solvation needs of the process, the fluorinated solvent may be selected from a broad range of materials such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), perfluorocarbons (FCs), hydrofluoroethers (HFEs), perfluoroethers, perfluoroamines, trifluoromethyl-substituted aromatic solvents, fluoroketones and the like.

Particularly useful fluorinated solvents include those that are perfluorinated or highly fluorinated liquids at room temperature, which are immiscible with water and many (but not necessarily all) organic solvents. Among those solvents, hydrofluoroethers (HFEs) are well known to be highly environmentally friendly, “green” solvents. HFEs, including segregated HFEs, are preferred solvents because they are non-flammable, have zero ozone-depletion potential, lower global warming potential and show very low toxicity to humans.

Examples of readily available HFEs and isomeric mixtures of HFEs include, but are not limited to, an isomeric mixture of methyl nonafluorobutyl ether and methyl nonafluoroisobutyl ether (HFE-7100), an isomeric mixture of ethyl nonafluorobutyl ether and ethyl nonafluoroisobutyl ether (HFE-7200 aka Novec™ 7200), 3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-trifluoromethyl-hexane (HFE-7500 aka Novec™ 7500), 1,1,1,2,3,3-hexafluoro-4-(1,1,2,3,3,3,-hexafluoropropoxy)-pentane (HFE 7600 aka Novec™ 7600), 1-methoxyheptafluoropropane (HFE-7000), 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-trifluoromethylpentane (HFE-7300 aka Novec™ 7300), 1,3-(1,1,2,2-tetrafluoroethoxy)benzene (HFE-978m), 1,2-(1,1,2,2-tetrafluoroethoxy)ethane (HFE-578E), 1,1,2,2-tetrafluoroethyl-1H,1H,5H-octafluoropentyl ether (HFE-6512), 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (HFE-347E), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE-458E), and 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorooctane-propyl ether (TE6O-C3).

As discussed below, the developing solution comprises a mixture of first and second fluorinated solvents and the stripping solution comprises at least the first or second fluorinated solvent, or optionally both. In a particularly useful embodiment, at least one of the solvents is a hydrofluoroether. In a preferred embodiment, both solvents are hydrofluoroethers. It should be noted that, although either or both of the first and second solvents can each be an isomeric mixture (e.g., HFE-7100, HFE-7200 or any fluorinated solvent comprising multiple stereoisomers), the first and second solvents are not isomeric to each other. If an isomeric mixture is used as the first or second solvent, the isomeric components preferably have the same or similar boiling points, i.e., within a range of 10° C. and more preferably within a range of 5° C. (as measured at atmospheric pressure). In some embodiments, minor amounts of a non-fluorinated solvent may be added to the developing solution or stripping solution. Such non-fluorinated solvents include chlorinated solvents, alcohols and other protic organic solvents, and substituted or unsubstituted hydrocarbons and aromatic hydrocarbons, so long as they are miscible with the fluorinated solvent in the amounts desired for the developing and stripping solutions and maintain orthogonal behavior with respect to active organic materials.

The fluorinated photoresist of the present disclosure is one that includes a fluorinated photoresist material that is at least partially fluorinated, i.e., it contains one or more fluorine atoms. In an embodiment, the weight percentage of fluorine in the fluorinated photoresist material is at least 15%, preferably in a range of 30 to 60%, and more preferably in a range of 35 to 50%. The fluorinated photoresist material should have sufficient solubility or dispersability in a fluorinated solvent or mixture to permit adequate coating and processing. In an embodiment, the fluorinated photoresist material is a polymer or copolymer. The fluorinated photoresist may be a chemically amplified resist. A coatable fluorinated photoresist solution may include a fluorinated photoresist material and a coating solvent, and may optionally further include one or more additional components such as a photo-acid generator, a stabilizer, a light sensitizer, a light filter, an acid scavenger (quencher) or a coating aid. A photoresist layer comprising the fluorinated photoresist material should be sensitive to radiation, e.g., UV or visible light, e-beam, X-ray and the like, so that the solubility properties of the exposed areas are selectively altered to enable development of an image. In a preferred embodiment, the radiation is UV or visible light.

Examples of fluorinated photoresists include, but are not limited to, materials disclosed in application nos. U.S. Ser. No. 12/994,353, PCT/US2011/034145, and PCT/US2012/034748, along with U.S. provisional application Nos. 61/829,523, 61/829,536, 61/829,551, 61/829,556, 61/857,890 and 61/903,450, the entire contents of which are incorporated by reference.

In an embodiment the fluorinated photoresist includes a photopolymer comprising first repeating unit having a fluorine-containing group and a second repeating unit having a solubility-altering reactive group. In an embodiment, the solubility-altering reactive group may be an alcohol-forming precursor group or an acid-forming precursor group such as a carboxylic or sulfonic acid-forming precursor group. The term “repeating unit” is used broadly herein and simply means that there is more than one unit on a polymer chain. The term is not intended to convey that there is necessarily any particular order or structure with respect to the other repeating units unless specified otherwise. The photopolymer may optionally be blended with one or more other polymers, preferably other fluorine-containing polymers. The total fluorine content of the blended polymers may suitably be in a weight range of 15 to 60%, preferably 30 to 55%, relative to the total weight of the blended polymers. The photopolymer may be produced, for example, by co-polymerizing suitable monomers containing the desired repeating units or by functionalizing preformed polymers to attach desired repeating units.

In an embodiment, the fluorine containing group of the first monomer or the first repeating unit is a fluorine-containing alkyl or aryl group that may optionally be further substituted with chemical moieties other than fluorine, e.g., chlorine, a cyano group, or a substituted or unsubstituted alkyl, alkoxy, alkylthio, aryl, aryloxy, amino, alkanoate, benzoate, alkyl ester, aryl ester, alkanone, sulfonamide or monovalent heterocyclic group, or any other substituent that a skilled worker would readily contemplate that would not adversely affect the performance of the fluorinated photopolymer. In a preferred embodiment, the fluorine-containing group is an alkyl group having at least 5 fluorine atoms, or alternatively, at least 10 fluorine atoms. In an embodiment, the alkyl group is a hydrofluorocarbon or hydrofluoroether having at least as many fluorine atoms as carbon atoms. In an embodiment the fluorine-containing group is perfluorinated alkyl or a 1H,1H,2H,2H-perfluorinated alkyl having at least 4 carbon atoms, for example, 1H,1H,2H,2H-perfluorooctyl (i.e., 2-perfluorohexyl ethyl). Throughout this disclosure, unless otherwise specified, any use of the term alkyl includes straight-chain, branched and cyclo alkyls. In an embodiment, the first repeating unit does not contain protic or charged substituents, such as hydroxy, carboxylic acid, sulfonic acid, quaternized amine or the like.

In an embodiment, the solubility-altering reactive group of the second repeating unit is an acid-forming precursor group. Upon exposure to light, the acid-forming precursor group generates a polymer-bound acid group, e.g., a carboxylic or sulfonic acid. This can drastically change its solubility relative to the unexposed regions thereby allowing development of an image with the appropriate solvent. In an embodiment, the developing solution includes a fluorinated solvent that selectively dissolves unexposed areas.

One class of acid-forming precursor groups includes the non-chemically amplified type (i.e., non-acid catalyzed). An example of a second monomer with such a group is 2-nitrobenzyl methacrylate. The non-chemically amplified precursor group may directly absorb light to initiate de-protection of the acid-forming groups. Alternatively, a sensitizing dye may be added to the composition whereby the sensitizing dye absorbs light and forms an excited state capable of directly sensitizing or otherwise initiating the de-protection of acid-forming precursor groups. The sensitizing dye may be added as a small molecule or it may be attached or otherwise incorporated as part of the copolymer. Unlike chemically amplified formulations that rely on generation of an acid (see below), non-chemically amplified photopolymers may sometimes be preferred when a photopolymer is used in contact with an acid-sensitive or acid-containing material. Some active organic materials can be sensitive to the presence of an acid or contain some acid.

A second class of acid-forming precursor groups includes the chemically amplified type. This typically requires addition of a photo-acid generator (PAG) to the photopolymer composition, e.g., as a small molecule additive to the solution. The PAG may function by directly absorbing radiation (e.g. UV light) to cause decomposition of the PAG and release an acid. Alternatively, a sensitizing dye may be added to the composition whereby the sensitizing dye absorbs radiation and forms an excited state capable of reacting with a PAG to generate an acid. The sensitizing dye may be added as a small molecule, e.g., as disclosed in U.S. provisional application No. 61/857,890, which is incorporated herein by reference. The sensitizing dye may be attached to or otherwise incorporated as part of the copolymer, e.g., as disclosed in U.S. provisional application Nos. 61/829,523, 61/829,536, 61/829,551, and 61/829,556, which are incorporated herein by reference. In an embodiment, the sensitizing dye (either small molecule or attached) is fluorinated. In an embodiment, the sensitizing dye may be provided in a range of 0.5 to 10% by weight relative to the total copolymer weight. The photochemically generated acid catalyzes the de-protection of acid-labile protecting groups of the acid-forming precursor. In certain cases, such de-protection may occur at room temperature, but commonly, an exposed chemically amplified photoresist is heated for a short time (“post exposure bake”) to more fully activate de-protection. In some embodiments, chemically amplified photopolymers can be particularly desirable since they enable the exposing step to be performed through the application of relatively low energy UV light exposure (e.g., less than 500 mJ/cm2 or in some embodiments under 100 mJ/cm2). This is advantageous since some active organic materials useful in applications to which the present disclosure pertains may decompose in the presence of too much UV light, and therefore, reduction of the energy during this step permits the photopolymer to be exposed without causing significant photolytic damage to underlying active organic layers. Also, reduced light exposure times improve the manufacturing throughput of the desired devices.

Examples of acid-forming precursor groups that yield a carboxylic acid include, but are not limited to: A) esters capable of forming, or rearranging to, a tertiary cation, e.g., t-butyl ester, 2-methyl-2-adamantyl ester, 1-ethylcyclopentyl ester, 1-ethylcyclohexyl ester, and isobornyl ester; B) esters of lactone, e.g., -butyrolactone-3-yl, -butyrolactone-2-yl, mavalonic lactone, 3-methyl-butyrolactone-3-yl, 3-tetrahydrofuranyl, and 3-oxocyclohexyl; C) acetal esters, e.g., 2-tetrahydropyranyl, 2-tetrahydrofuranyl, and 2,3-propylenecarbonate-1-yl; D) beta-cyclic ketone esters, E) alpha-cyclic ether esters and F) MEEMA (methoxy ethoxy ethyl methacrylate) and other esters which are easily hydrolyzable because of anchimeric assistance. In an embodiment, the second monomer comprises an acrylate-based polymerizable group and a tertiary alkyl ester acid-forming precursor group, e.g., t-butyl methacrylate (“TBMA”) or 1-ethylcyclopentyl methacrylate (“ECPMA”).

In an embodiment, the solubility-altering reactive group is an hydroxyl-forming precursor group (also referred to herein as an “alcohol-forming precursor group”). The hydroxyl-forming precursor includes an acid-labile protecting group and the photopolymer composition typically includes a PAG compound and operates as a “chemically amplified” type of system. Upon exposure to light, the PAG generates an acid (either directly or via a sensitizing dye as described above), which in turn, catalyzes the de-protection of the hydroxyl-forming precursor group, thereby forming a polymer-bound alcohol (hydroxyl group). This significantly changes its solubility relative to the unexposed regions thereby allowing development of an image with the appropriate fluorinated solvent. In an embodiment, the developing solution includes a fluorinated solvent that selectively dissolves unexposed areas.

In an embodiment, the hydroxyl-forming precursor has a structure according to formula

wherein R5 is a carbon atom that forms part of the second repeating unit (or second polymerizable monomer), and R10 is an acid-labile protecting group. Non-limiting examples of useful acid-labile protecting groups include those of formula (AL-1), acetal groups of the formula (AL-2), tertiary alkyl groups of the formula (AL-3) and silane groups of the formula (AL-4).

In formula (AL-1), R11 is a monovalent hydrocarbon group, typically a straight, branched or cyclic alkyl group, of 1 to 20 carbon atoms that may optionally be substituted with groups that a skilled worker would readily contemplate would not adversely affect the performance of the precursor. In an embodiment, R11 may be a tertiary alkyl group. Some representative examples of formula (AL-1) include:

In formula (AL-2), R14 is a monovalent hydrocarbon group, typically a straight, branched or cyclic alkyl group, of 1 to 20 carbon atoms that may optionally be substituted. R12 and R13 are independently selected hydrogen or a monovalent hydrocarbon group, typically a straight, branched or cyclic alkyl group, of 1 to 20 carbon atoms that may optionally be substituted. Some representative examples of formula (AL-2) include:

In formula (AL-3), R15, R16, and R17 represent an independently selected a monovalent hydrocarbon group, typically a straight, branched or cyclic alkyl group, of 1 to 20 carbon atoms that may optionally be substituted. Some representative examples of formula (AL-3) include:

In formula (AL-4), R18, R19 and R20 are independently selected hydrocarbon groups, typically a straight, branched or cyclic alkyl group, of 1 to 20 carbon atoms that may optionally be substituted.

The descriptions of the above acid-labile protecting groups for formulae (AL-2), (AL-3) and (AL-4) have been described in the context of hydroxyl-forming precursors. These same acid-labile protecting groups, when attached instead to a carboxylate group, may also be used to make some of the acid-forming precursor groups described earlier.

Many useful PAG compounds exist that may be added to a photopolymer composition. In the presence of proper exposure and optional sensitization, this photo-acid generator will liberate an acid, which will react with the second monomer portion of the fluorinated photopolymer material to transform it into a less soluble form with respect to fluorinated solvents. The PAG should have some solubility in the coating solvent. The amount of PAG required depends upon the particular system, but generally, will be in a range of about 0.1 to 6% by weight relative to the copolymer. In an embodiment, the presence of a sensitizing dye may substantially reduce the amount of PAG required relative to a composition that does not include a sensitizing dye. In an embodiment, the amount of PAG is in a range of 0.1 to 3% relative to the copolymer. PAGS that are fluorinated or non-ionic or both are particularly useful. Some useful examples of PAG compounds include 2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorene (ONPF) and 2-[2,2,3,3,4,4,4-heptafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-fluorene (HNBF). Other non-ionic PAGS include: norbornene-based non-ionic PAGs such as N-hydroxy-5-norbornene-2,3-dicarboximide perfluorooctanesulfonate, N-hydroxy-5-norbornene-2,3-dicarboximide perfluorobutanesulfonate, and N-hydroxy-5-norbornene-2,3-dicarboximide trifluoromethanesulfonate; and naphthalene-based non-ionic PAGs such as N-hydroxynaphthalimide perfluorooctanesulfonate, N-hydroxynaphthalimide perfluorobutanesulfonate and N-hydroxynaphthalimide trifluoromethanesulfonate.

Some additional classes of PAGs include: triarylsulfonium perfluoroalkanesulfonates, such as triphenylsulfonium perfluorooctanesulfonate, triphenylsulfonium perfluorobutanesulfonate and triphenylsulfonium trifluoromethanesulfonate; triarylsulfonium hexafluorophosphates (or hexafluoroantimonates), such as triphenylsulfonium hexafluorophosphate and triphenylsulfonium hexafluoroantimonate; triaryliodonium perfluoroalkanesulfonates, such as diphenyliodonium perfluorooctanesulfonate, diphenyliodonium perfluorobutanesulfonate, diphenyliodonium trifluoromethanesulfonate, di-(4-tert-butyl)phenyliodonium, perfluorooctanesulfonate, di-(4-tert-butyl)phenyliodonium perfluorobutanesulfonate, and di-(4-tert-butyl)phenyliodonium trifluoromethanesulfonate; and triaryliodonium hexafluorophosphates (or hexafluoroantimonates) such as diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di-(4-tert-butyl)phenyliodonium hexafluorophosphate, and di-(4-tert-butyl)phenyliodonium hexafluoroantimonate. Suitable PAGs are not limited to those specifically mentioned above. Combinations of two or more PAGs may be used as well.

The fluorinated photopolymer composition may optionally include additives such as stabilizers, coating aids, light absorbers, acid scavengers (“quenchers”) and the like.

The fluorinated photopolymer composition of the present disclosure may be applied to a substrate (sometimes referred to herein as a device substrate) using any method suitable for depositing a photosensitive liquid material. For example, the composition may be applied by spin coating, curtain coating, bead coating, bar coating, spray coating, dip coating, gravure coating, ink jet, flexography or the like. The composition may be applied to form a uniform film or a patterned layer of unexposed photopolymer. Alternatively, the photopolymer can be applied to the substrate by transferring a preformed fluorinated photopolymer layer (optionally patterned) from a carrier sheet, for example, by lamination transfer using heat, pressure or both. In such an embodiment, the substrate or the preformed photopolymer layer may optionally have coated thereon an adhesion promoting layer.

In a useful (but non-limiting) embodiment this photoresist can be a copolymer formed from a highly fluorinated alkyl-containing monomer, such as a 1H,1H,2H,2H-perfluoroalkyl methacrylate, and an acid precursor monomer, such as a tert-alkyl methacrylate or a nitrobenzyl methacrylate.

Some specific, but non-limiting, examples include a random copolymer of 1H,1H,2H,2H-perfluorooctyl methacrylate with 2-nitrobenzyl methacrylate (to form “FOMA-NBMA”), a random copolymer of 1H,1H,2H,2H-perfluorooctyl methacrylate with tert-butyl methacrylate (to form “FOMA-TBMA”), a random copolymer of 1H,1H,2H,2H-perfluorodecyl methacrylate with 2-nitrobenzyl methacrylate (to form “FDMA-NBMA”), a random copolymer of 1H,1H,2H,2H-perfluorodecyl methacrylate with tert-butyl methacrylate (to form “FDMA-TBMA”), block copolymers of FOMA-NBMA, FOMA-TBMA, FDMA-NBMA, FDMA-TBMA, derivatives thereof, structurally similar compositions or other polymer photoresist or molecular glass photoresist having sufficient content to permit the photoresist to be dissolved in a fluorinated coating solvent. In certain embodiments, the coating solvent may also need to solublize a photo-acid generator.

A copolymer of FOMA and TBMA may be prepared as follows. A solution of 110.10 g (0.7743 mol) of tert-butyl methacrylate, (TBMA), 330.07 g (0.7636 mol) of 1H,1H,2H,2H-perfluorooctyl methacrylate, (“FOMA”), 874.2 g of Novec™ 7600 and 5.51 g (0.0335 mol) of azobisisobutyronitrile, (“AIBN”) was stirred in a jacketed reaction flask. The flask jacket was connected to a programmable, constant temperature bath (“CTB”) capable of heating and maintaining a set jacket temperature. The solution was sparged with nitrogen at a rate of 0.5 L/minute for 1 hour at ambient temperature. A CTB program was initiated which heated the reaction jacket to 68° C., holds this temperature for 1 hour, heats to 72° C. and holds for 1 hour, and finally heats to 76° C. and holds for 12 hours. When the heating program was completed, the CTB was set to cool the reaction mixture to ambient temperature. The clear, colorless polymer solution obtained was diluted to a viscosity target by the addition of 3.714 kg of Novec™ 7600, and a small sample was removed and dried under vacuum for later characterization. In one embodiment, under yellow lights, 22.0 g of CIBA/BASF CGI-1907 (aka “ONPF”) photo-acid generator (“PAG”) (5% by weight of the original dry weight of TBMA) was dissolved in the remaining photoresist solution. The solution was filtered, and was then ready for use. Many other polymer variations, e.g., having different ratios of monomers, different types of monomers or additional monomers, can be prepared using a similar method.

The FOMA component of the above resist is largely responsible for the general solubility of the copolymer in fluorinated solvents whereas the TBMA groups act as the solubility “switch” as previously described. In certain embodiments, with sufficient fluorine content in the photoresist, the resist can be made both hydrophobic and oleophobic. That is, the resulting material repels or resists both water and many organic solvents, permitting these materials to serve as an in-process encapsulation layers to protect the underlying organic materials from moisture and damage from organic solvents.

As mentioned, the developing solution comprises a mixture of first and second fluorinated solvents and the stripping solution comprises at least the first or second fluorinated solvent, or optionally both. In a particularly useful embodiment, at least one of the solvents is a hydrofluoroether. In a preferred embodiment, both solvents are hydrofluoroethers. A few non-limiting embodiments are discussed below.

General Embodiment 1

In this embodiment, the first solvent is one that has a high degree of discrimination between solubilizing exposed and unexposed regions of the photoresist layer. Typically, the first solvent dissolves the unexposed regions at a moderate rate, but dissolves the exposed (switched) region at a much lower rate, preferably at least 10× lower. This helps produce an image with reasonable contrast and tolerable processing latitude, but an image may take longer than desired to develop appropriately. The second solvent is one that dissolves the unexposed regions at a rate greater than the first solvent rate, and preferably, also dissolves the exposed regions a rate higher than the first solvent rate. That is, the second solvent is generally a stronger solvent than the first solvent for both exposed and unexposed areas. Both should be selected to have a low interaction with sensitive, active organic materials if present during processing. Preferably the first and second solvents are both hydrofluoroethers. In this embodiment, the majority of the volume of the developing solution is typically from the first solvent, but it has been unexpectedly found that a small or moderate amount of the second solvent can significantly increase development rate and improve cleanout of small features without detrimental stripping action. Takt time is reduced and the development of small features is improved. In an embodiment, the developing solution includes the first solvent in a volume range of 75 to 99% and the second solvent in a volume range of 1 to 25%. Alternatively, the developing solution comprises the first solvent in a volume range of 90 to 98% and the second solvent in a volume range of 2 to 10%. The volumes of first and second solvents do not necessarily have to add up to 100%, as small amounts of additional materials may be present in the developing solution. In an embodiment, the first and second solvents comprise at least 97% of the total volume of developing solution. In another embodiment, the first and second solvents comprise at least 99% of the total volume of developing solution. The ratio of solvents can be adjusted to suit the preferred development time, which might depend upon the available processing equipment. The ratio of solvents can also be adjusted to suit the particular fluorinated photoresist system. Although not limiting, useful development times are in a range from 15 sec to 150 sec, or alternatively, 30 sec to 120 sec. Longer times can impact throughput and shorter times can be difficult to control.

In the present General Embodiment 1, the stripping solution typically includes at least the second solvent. Optionally, it may further include the first solvent. In the case of the stripping solution having both first and second solvents, it has been surprisingly found that that the second solvent does not have to be present in the majority, but it is usually at least 30% by volume and may be in a volume range of 30 to 99%. The first solvent can be in a range from 1 to 70%. In an embodiment, the stripping solution includes the second solvent in a volume range of 40 to 97% and first solvent is in a range from 3 to 60%. The volumes of first and second solvents do not necessarily have to add up to 100%, as small amounts of additional materials may be present in the stripping solution. In an embodiment, the first and second solvents comprise at least 90%, alternatively at least 97%, of the total volume of the stripping solution, which may optionally further include up to 10% of a water-soluble, polar or protic solvent such as an alcohol, e.g., IPA. If used, the amount of the protic solvent is preferably in a volume range of 0.001 to 3%. Lower amounts of protic solvents are generally more compatible with a wider array of active organic materials. The ratio of solvents can be adjusted to suit the preferred stripping time, which might depend upon the available processing equipment. The ratio of solvents can also be adjusted to suit the particular fluorinated photoresist system.

General Embodiment 2

Here, the first solvent is one that has a high degree of discrimination between solubilizing exposed and unexposed regions of photoresist layer. Typically, the first solvent dissolves the unexposed regions at a moderate rate, but dissolves the exposed (switched) region at a much lower rate, preferably at least 10× lower. This helps produce an image having reasonable contrast and with good processing latitude, but an image may sometimes take longer than desired to develop appropriately. The second solvent in this embodiment is one that has higher solubilizing power than the first solvent with respect to removing the unexposed regions, but generally lacks sufficient solubilizing power to dissolve the exposed photoresists alone. For example, the first solvent, although it shows some development and good discrimination, may be too slow to be practical on its own. Conversely, the second solvent may be too fast to control, and although it is not capable of stripping the exposed portion, it may lead to some film delamination due to its high strength, making a neat solution of the second solvent unsuitable as either a developing or stripping solution.

It has been found that an appropriate mixture of the first and second solvents can provide rapid development with good contrast. The ratio of first and second solvents in this embodiment depends upon the system, but each solvent is typically be in a volume range of 5 to 95%. In this embodiment, the stripping solution includes at least the first or second solvent and up to 20% by volume of a protic solvent (e.g. an alcohol such as IPA), preferably in a range, 0.05 to 10%. Lower amounts of protic solvents are generally more compatible with a wider array of active organic materials. The stripping solution may optionally have the same ratio of first and second solvents as used in the developing solution, but the overall concentrations are different due to the presence of the protic solvent. Preferably, the stripping solution will have a higher ratio of second solvent to first solvent than the developing solution.

General Embodiment 3

Here, the first solvent generally provides low solubilizing strength with respect to both the exposed and unexposed regions of the photoresist. The second solvent is one that can solubilize both exposed and unexposed portions, but has a higher dissolution rate for the unexposed portions. When sufficient second solvent is added to the first solvent, the developing solution is capable of selectively solubilizing unexposed regions, i.e., dissolving unexposed regions at a rate that is at least 10 times higher than solubilization of the exposed areas. In this embodiment, the volume percentage of the second solvent is in a range from 20 to 80%, preferably 25 to 60%. The stripping solution will include the second solvent, optionally with a small amount of the first solvent or protic solvent or both. The volume of the second solvent in the stripping solution in this embodiment is at least 80%, preferably at least 90%.

An advantage of certain embodiments of the present invention is that by using mixed solvents for the developing solution and at least one common solvent in the stripping solution, inexpensive recycling methods can be used to recover and reuse the solvents. This reduces both the manufacturing cost and environmental impact. If the photoresist coating solution is part of the same waste stream to be recycled, it is preferred that it also uses either the first or second solvent or a combination thereof. This further simplifies recycling.

In an embodiment, the first and second solvents are fluorinated solvents, at least one of which is a hydrofluoroether, and the waste stream from at least the developing and stripping steps are collected and reused using a recycling apparatus. The collected mixture of fluorinated solvents can be reconstituted, e.g., by adding fresh solvent, to provide the correct mixture ratio for use in either the developing or stripping solution. Preferably, prior to reuse, the recycling apparatus separates the solvent mixture from suspended and dissolved solids, e.g., by a flash evaporation step under reduced pressure using a simple roto-evaporating apparatus. Alternatively or in addition to flash evaporation, filtration can be used. Preferably, prior to reuse, the recycling apparatus washes the solvent mixture to remove water soluble components such as protic solvents. Washing and filtering methods disclosed in US 2010/0126934 (the contents of which is incorporated by reference) can optionally be used.

In a further embodiment, the boiling points of the first and second solvents differ by at least 25° C. (measured at atmospheric pressure) and a recycling apparatus is used to achieve at least partial separation of the first and second solvents by distillation. Prior to distillation, suspended and dissolved solids can optionally be removed and the solvent mixture can optionally be washed, as discussed above. Because solvent mixtures are being used for at least the developing solution and optionally the stripping solution, high purity solvent reclamation is not required and a simple distillation column may be used to achieve reasonable levels of solvent separation. Alternatively, a fractional distillation column may be used, but an expensive system should not be required because high purity (>99%) is not necessary. The simple, low-cost recycling apparatus permits on-site recycling and eliminates possible issues regarding shipping wastes from manufacturing sites. The ability to use the mixed waste stream can eliminate the need for multiple solvent recycling stations to handle developing and stripping solutions separately.

At least two fractions are typically recovered by distillation. One recycled solvent mixture is rich in the first solvent and the other recycled solvent mixture is rich in the second solvent. Depending on the needs of the developing and stripping solutions, these may be used directly, or they can be mixed with an appropriate amount of pure solvent to produce the desired ratio. In an embodiment, a recycled solvent mixture is used directly as the stripping solution without the addition of a pure solvent.

Another use for the recycled solvent mixtures is in edge bead removal. Edge bead removal (EBR) is a process whereby a coating of photoresist is removed from an edge area of a substrate where the thickness of the resist is usually larger than desired and where no imaging is needed. This can be done, for example, by directing focused jet or spray of edge bead removal solvent. In embodiments wherein the first and second solvents that both have reasonable solubilizing power for unexposed photoresist, the recycled mixture should provide an inexpensive EBR solvent for photoresists of the present disclosure.

Although not limited, the present invention can be used to form devices having a layer of sensitive, active organic material (see above). Such devices may include electronic devices such as TFTs, touch screens, OLED lighting and displays, e-readers, LCD displays, solar cells, sensors and bioelectronics devices. These devices are typically multilayer structures having numerous other layers such as dielectric layers, optical layers, conductors and a support. Devices may include non-electronic devices such as optical, medical, and biological devices having some patterned active organic material, but that do not require an electrical conductor or semiconductor to operate (e.g., lenses, color filter arrays, down- or up-conversion filters, medical/biological test strips and the like). The device substrate onto which the fluorinated photoresist is provided may include a single layer of a support material or may include a multilayer structure having a support and numerous additional layers. The substrate surface is not necessarily planar. The substrate and support are optionally flexible. Support materials include, but are not limited to, plastics, metals, glasses, ceramics, composites and fabrics.

A flow diagram for an embodiment of the present invention is shown in FIG. 1, and includes the step 2 of forming a photoresist layer on a substrate. This can be accomplished using methods previously described.

In step 4, the photoresist layer is exposed to patterned radiation, e.g. UV light, to form an exposed photoresist layer. The term “radiation” refers to any radiation to which the photoresist is sensitive and can form areas of differential developability due to some chemical or physical change caused by the radiation exposure. Non-limiting examples of radiation include UV, visible and IR light, e-beams and X-rays. Commonly, the radiation is from UV or visible light. Patterned radiation can be produced by many methods, for example, by directing exposing light through a photomask and onto the photoresist layer. Photomasks are widely used in photolithography and often include a patterned layer of chrome that blocks light. The photomask may be in direct contact or in proximity. When using a proximity exposure, it is preferred that the light has a high degree of collimation. Alternatively, the patterned light can be produced by a projection exposure device. In addition, the patterned light can be from a laser source that is selectively directed to certain portions of the photoresist layer.

In step 6, a developed structure is formed that includes a first pattern of photoresist. This can be done by contacting the exposed photoresist layer to a developing solution. As mentioned above, the developing solution includes a mixture of first and second fluorinated solvents, preferably wherein at least one of the first and second solvents is a hydrofluoroether. During development, a portion of the exposed photoresist layer is removed in accordance with the patterned light. Depending on the nature of the chemical or physical change caused by the patterned light, the developing solution may dissolve the unexposed portion (negative working resist) or it may dissolve the exposed portion (positive working resist). Preferably, the developing solution dissolves the unexposed portion. In either case, it leaves behind a developed structure having a first pattern of photoresist that covers the substrate and a complementary second pattern of uncovered substrate corresponding to the removed portion of photoresist. By uncovered substrate, it is meant that the surface of the substrate is substantially exposed or revealed to a degree that it can be subjected to further treatments—a small amount of residual photoresist may be present in some embodiments. Contacting the exposed photoresist layer can be accomplished by immersion into the developing solution or by applying the developing solution in some way, e.g., by spin coating or spray coating. The contacting can be performed multiple times if necessary.

In step 8, a treated structure is formed by treating the developed structure in some way. In an embodiment, the treating includes a chemical or physical etch of the second pattern of uncovered substrate. In this case, the first pattern of photoresist acts as an etch barrier. In another embodiment, the treating includes chemically modifying the surface of the second pattern of uncovered substrate or the first pattern of photoresist. In another embodiment, the treating includes doping the second pattern of uncovered substrate, e.g., to modify its conductivity. In yet another embodiment, the treating includes coating the developed structure with, for example, an active organic material that is deposited both on the surface of the first pattern of photoresist and on the second pattern of uncovered substrate. In any of the above embodiments, the substrate may optionally include an active organic material layer such that the uncovered substrate is the surface of that active organic material layer.

In step 10, the first pattern of photoresist is removed from the treated structure using a stripping solution. As described above, the stripping solution comprises at least the first or second fluorinated solvent, or optionally both. In embodiments wherein the surface of the first pattern of photoresist is covered with another layer of material, e.g., an active organic material layer, that portion is also removed. This is sometimes referred to as a “lift off” process.

Turning now to FIG. 2, there is a series of cross-sectional views depicting the formation of a patterned active organic material structure at various stages according to an embodiment of the present invention. In FIG. 2A, a substrate 20 includes a layer of active organic material 24 provided on a support 22. In FIG. 2B, a negative-type fluorinated photoresist layer 26 is formed on the substrate 20 and in contact with the layer of active organic material 24. Next, as shown in FIG. 2C, photoresist layer 26 is exposed to patterned light by providing a photomask 30 between the photoresist layer 26 and a source of collimated light 28. The exposed photoresist layer 32 includes exposed areas 34 and non-exposed areas 36. The structure is then developed in a developing solution including first and second solvents. In this embodiment the non-exposed areas 36 of the photoresist are selectively dissolved to form a structure having a removed portion of photoresist. As shown in FIG. 2D, developed structure 38 has a first pattern of photoresist 40 covering the substrate, and a complementary second pattern of uncovered substrate 42, in this case the layer of active organic material 24, corresponding to the removed portion of photoresist. Turning now to FIG. 2E, a treated structure 44 is formed by subjecting the developed structure 38 to a chemical or physical etch that selectively removes active organic material from the second pattern of uncovered substrate, thereby forming a patterned layer of active organic material 46 corresponding to the first pattern. By corresponding, it is meant that the patterned layer of active organic material 46 substantially resembles that of the first pattern of photoresist 40, but the two patterns are not necessarily identical. For example, the etching might also etch the sidewalls of the patterned layer of active organic material, thereby making the dimensions slightly smaller than the first pattern. Conversely, etching kinetics or diffusion might be such that the dimensions of the patterned layer of active organic material are slightly larger than the first pattern. Further, the patterned layer of active organic material might not have vertical sidewalls as shown. Rather than rectangular, its cross section could resemble a trapezoid, an inverted trapezoid (undercut), or some other shape, e.g., one having curved sidewalls. Referring to FIG. 2F, treated structure 44 is contacted with a stripping solution that removes the first pattern of photoresist 40, thereby forming patterned active organic material structure 48 having the (now bare) patterned layer of active organic material 46. Patterned active organic material structure 48 may optionally be subjected to additional steps, if necessary, to form a functional device such as an organic TFT array, an OLED display, an e-reader, a solar cell, a bioelectronic device or the like.

FIG. 3 shows a series of cross-sectional views depicting the formation of a patterned active organic material structure at various stages according to another embodiment of the present invention. In FIG. 3A, a negative-type photoresist layer 126 is formed on substrate 120. This structure is then exposed and developed as described above to form developed structure 138, as shown in FIG. 3B. Developed structure 138 has a first pattern of photoresist 140 covering the substrate, and a complementary second pattern of uncovered substrate 142 corresponding to a removed portion of photoresist. Turning now to FIG. 3C, a treated structure 144 is formed by depositing a layer of active organic material 145 over both the first pattern of photoresist and the second pattern of uncovered substrate. In FIG. 3D, the treated structure 144 is then contacted with a stripping solution that removes the first pattern of photoresist and the active organic material deposited over the first pattern of photoresist, thereby forming patterned active organic material structure 148 having a patterned layer of active organic material 146 corresponding to the second pattern. By corresponding, it is meant that the patterned layer of active organic material 146 substantially resembles that of the second pattern of uncovered substrate 142, but the two patterns are not necessarily identical. Patterned active organic material structure 148 may optionally be subjected to additional steps, if necessary, to form a functional device such as an organic TFT array, an OLED display, an e-reader, a solar cell, a bioelectronic device or the like.

EXAMPLES

In the examples below, most of the HFE solvents were purchased from 3M under their “Novec™” brand. For convenience, the solvents are simply referred to by their HFE number. HFE-6512 was purchased from Top Fluorochem Co, LTD.

Example 1

Approximately 1475 g (about 1 L) of combined waste solvents from lithographic testing events was collected from a spin coating bowl. The testing events used a fluorinated photoresist based on FOMA-TBMA, the developing solution included HFE-7300 (b.p.=98° C.) and the stripping solution included HFE-6512 (b.p.=133° C.). The waste further included some amount of IPA. The solvent fraction of the cloudy waste solution was removed in vacuo using a rotary evaporator under full aspirator vacuum (˜28.5 in. Hg) with a bath temperature of 48-60° C. The distillation was stopped when condensate stopped collecting. The pot residue included 37 g of viscous oil, primarily from developed and stripped fluorinated photoresist. The amounts of the IPA, Novec™ 7300 and HFE 6512 after the initial distillation were measured by gas chromatography (GC). The results are shown in Table 1 as “% area” under the GC trace, which approximately corresponds to % volume. The distillate was then washed with 3×250 mL of distilled water and 1×250 mL of saturated NaHCO3 solution. The aqueous fractions were the upper fractions in all of these washes. The washed solution was then dried by stirring over MgSO4, filtered and the solvent amounts were again measured after drying, as shown in Table 1. The mixture was then returned to the rotary evaporator. The bath temperature was set to 40° C. and approximately 500 mL of distillate was collected. This first fraction of recycled solvent mixture was analyzed as shown in Table 1. To make recycled developing solution, 50 mL of this distillate was added to 350 mL of fresh HFE-7300. GC was used to verify the composition which matched the composition of a developing solution prepared from all fresh solvents (Table 1). This recycled developing solution was used in lithographic testing and performed equivalently to developing solution prepared from fresh solvents.

After the preparation of the developing solution, the distillation was resumed with a bath temperature of 53° C. The distillation was continued until no more material remained in the pot and the condensation rate had slowed to a stop. GC was run on this second fraction of recycled solvent mixture (Table 1) and the results were used to calculate the amount of HFE-7300 to add in order to make a recycled stripping solution having 60% vol HFE-7300 and 40% vol HFE-6512. GC was used to verify the adjusted composition after HFE-7300 was added, which matched the composition of a stripping solution prepared from all fresh solvents (Table 1). The recycled stripping solution was used in lithographic tests and performed equivalently to stripper prepared with fresh solvents.

TABLE 1 GC Analysis Result (% area) Sample description IPA* HFE-7300 HFE 6512 Waste solvent solution after initial 5.5 45.6 46.2 distillation Waste solvent solution after water washes n.d. 46.4 50.6 First fraction of recycled solvent n.d. 72.4 25.6 mixture collected at 40° C. Recycled developing solution after adding n.d. 96.4 3.2 Novec ™ 7300 Reference developing solution made with n.d. 96.5 3.2 fresh solvents Second fraction of recycled solvent n.d. 38.6 58.1 mixture collected at 53° C. Recycled stripping solution after adding n.d. 54.8 42.7 Novec ™ 7300 Reference stripping solution made with n.d. 57.3 42.4 fresh solvents *n.d. = none detected

Example 2

A silicon wafer was primed by vapor depositing HMDS. A fluorinated photoresist solution was spin coated onto the silicon wafer and then “soft baked” at 90° C. for 60 seconds. The photoresist layer was about 1.0 to 1.5 μm thick. The photoresist solution included a hydrofluoroether solvent (HFE-7600), a PAG (CGI-1907), and a polymer comprising copolymer of FOMA, TBMA and AMMA (9-anthrylmethyl methacrylate) as sensitizing dye, the polymer having 42.5% by weight of fluorine relative to the polymer. The photoresist was exposed through a reticle to patterned UV radiation (365 nm) with doses ranging from 40 mJ/cm2 to 880 mJ/cm2, followed by post-exposure baking at 90° C. for 60 seconds. The exposed photoresist was then developed to remove the unexposed portion and to form a photoresist pattern on the substrate. Developing solution composition and development times are shown in Table 2. Two applications of developer (approximately 10 mL each) were provided onto the photoresist layer, each forming a “puddle,” and the dwell time of each application was half of the total development time specified in Table 2. The wafer was spun dry at the end of each dwell time. Table 2 shows that even a small amount of a second solvent that is generally used in a stripping solution can significantly reduce development time. Development time can be easily tuned by adjusting the percentage of the second solvent.

TABLE 2 HFE-7300 (% vol) HFE-6512 (% vol) Development Time (sec) 100 0 180 97 3 80 95 5 50 90 10 30

Example 3

An exposed photoresist on a silicon wafer was prepared as described in Example 2. It was developed for a total of 90 sec using two applications of developing solution, each at 45 sec. The developing solution included a 97/3 volume ratio of HFE-7300 to HFE-6512. After development the exposed photoresist was stripped by applying about 10 mL of stripping solution onto the developed photoresist to form a puddle. The time it took to remove (strip) the photoresist images having the highest exposure (880 mJ/cm2) was monitored. The composition of the stripping solutions and stripping times are shown in Table 3. As can be seen, even a relatively large amount of a first solvent commonly used in a developing solution does not seriously increase stripping time. In general, faster stripping is better, but in some systems, it may be advantageous to moderate the rate. Clearly, a wide range of mixtures can effectively strip the photoresist, which makes for a robust system.

TABLE 3 HFE-7300 (% vol) HFE-6512 (% vol) Stripping Time (sec) 0 100 15 20 80 15 30 70 20 40 60 30 50 50 42

Example 4

A developed photoresist sample was prepared as described in Example 3, except the photoresist was from a different synthesis batch and the developing solution used a 97/3 volume ratio of HFE-7300 to HFE-7600 (b.p.=131° C.), rather than HFE-6512. In this example, the stripping time was fixed at 120 sec using two applications of 60 sec each, and the maximum stripping exposure dose wherein stripping was complete was determined. The stripping solution compositions and maximum stripping exposure doses are shown in Table 4. Compared to Example 3, the developed photoresist of this example is apparently more difficult to strip for reasons not fully understood. Regardless, the important point is that the presence of the HFE-7300 (common developer solvent) in combination with either of the HFE-6512 or HFE-7600 stripping solvents did not significantly reduce the maximum stripping exposure dose at a 25% vol ratio. In the case of HFE-6512, addition of 25% HFE-7300 unexpectedly produces an even more effective stripping solution than HFE-6512 alone, and HFE-7300 can be used at higher amounts as well to good effect. In the case of HFE-7600, the presence of 50% HFE-7300 reduced the maximum stripping exposure dose, but stripping was far from shut down and it is clear that the stripping solution can tolerate or even benefit from a wide range of solvent mixtures.

TABLE 4 Maximum Stripping HFE-7300 HFE-6512 HFE-7600 Exposure Dose (% vol) (% vol) (% vol) removed (mJ/cm2) 0 100 n/a 530 25 75 n/a >880 50 50 n/a 859 0 n/a 100 558 25 n/a 75 551 50 n/a 50 243

It was also observed that a small amount of HFE-7300 (e.g. 3% by volume) in HFE-6512 improved the wetting behavior of the stripping solution when applied to the developed photoresist relative to neat HFE-6512. Poor wetting may in some cases increase variability in stripping performance or require a larger volume of stripping solution in order to properly cover the sample.

The contrast of a photoresist system is often an important factor. Higher contrast is typically preferred, as it generally results in straighter sidewalls for imaged areas and overall better discrimination between imaging light and stray light for improved feature resolution. It has been unexpectedly found that certain mixed solvent developers not only speed up development rate, but they also improve the contrast.

To study contrast, the following method was generally used. A subject fluorinated photoresist was spin coated onto a silicon wafer and soft-baked for 1 min at 90° C. The film thickness was generally in a range of about 1 to 1.5 um. An optical 22 step tablet (˜0.15 density units per step) was laid on top of the wafer and the resist was exposed to 365 nm radiation using a 16 W black light lamp. The maximum exposure dose was typically about 175 mJ/cm2. The wafer was post-exposure baked (PEB) for 1 min at 90° C. to activate the switching reaction. The film thickness was then immediately measured in 24 areas (steps). In addition to the 22 areas of the step tablet, the maximum exposure dose was measured just outside of the step tablet area (point 1) as well as a minimum exposure dose area (covered by a metal disc) that received no exposure (point 24).

Five minutes after the PEB, the wafer was contacted with ˜10 mL of a developer solution using the “puddle” method and spin-dried after the target time was reached. The time of each puddle and number of puddles depended on the system. After each puddle, the film thicknesses were measured in the same 24 areas. Film thicknesses after each puddle were normalized to the starting thickness and plotted versus log Exposure (log(E)) to create a set of contrast curves. The contrast between each point was calculated using equation 1:


Contrast=[normalized thickness]/[log(E)]  (Eq. 1)

The highest calculated contrast (the “maximum contrast”) for each curve was determined. FIG. 4 shows an example graph of normalized thickness vs. log(E)—for clarity, only the first 16 points are shown. Other parameters can also be determined as desired such as “0.5 speed point” (exposure dose at normalized density=0.5), “Emax erosion” (normalized thickness loss of the maximum exposure point 1), “time to clear” (time it takes for the minimum exposure to be fully removed), and “time to strip” (time it takes for maximum exposure to be fully removed). For good line shapes, it is desirable that the maximum contrast be at least 1.5, preferably at least 1.9 and more preferably at least 2.1. As discussed earlier, it is also desirable that the contrast be achieved in a processing time in a range of about 15 to 150 sec. It has been unexpectedly found that resist/developer systems of the present disclosure having maximum contrasts higher than about 5 are prone to yield film delamination in regions of moderate exposure. One can try and address this by increasing exposure, but this sometimes results in unwanted line broadening due to light scatter or flare. In particular, image patterns having a variety of feature dimensions and densities become more prone to delamination because small, sparse features may receive significantly less exposure than large/dense feature areas. Surprisingly, by controlling the maximum contrast to a range of about 1.9 to about 5.0, preferably 2.1 to 4.3, the occurrences of delamination can be reduced and the system becomes more robust to variations in exposure across the image. It is particularly desirable if the maximum photopolymer contrast is in the range of about 1.9 to about 5.0 for at least a 15 sec time window within a development contact time period of 15 to 150 seconds. The larger this time window is, the more robust the developer/photoresist system is to variations in the development process.

Example 5

A fluorinated photoresist solution similar to those of Examples 2-4 was spin coated onto the silicon wafer and then “soft baked” at 90° C. for 60 seconds. The photoresist layer was about 1.4 μm thick. The photoresist solution included a HFE-7600 as coating solvent, CGI 1907 as PAG (0.8% wt relative to polymer wt), and a polymer comprising copolymer of FOMA, TBMA and AMMA, the polymer having 42.5% by weight of fluorine relative to the polymer. Contrast curves were measured as described above using HFE-7300 as the developer. The process was then repeated for various mixtures of HFE-7300 and HFE-6512, and various parameters were determined as reported in Table 5. Note that maximum contrast values were only reported if the low exposure regions had fully been removed and when Emax erosion was less than 0.25. Larger erosion levels often make the photoresist system impractical. In Table 5, at HFE-6512 concentrations of 25% or higher, the “time to clear” is reported as “<30” sec. In these cases, 90 to 95% of the polymer in the low exposure region was actually removed in the first 15 sec puddle. For reasons not fully understood, it is often observed that the first puddle, almost independent of puddle time, leaves a small residue of 0.05 to 0.10 of normalized thickness. If shorter puddle times were used, the time to clear would likely be much less than 30 sec. Also, in some cases, the “time to strip” entries are estimates based on simple extrapolations from the available data.

TABLE 5 Solvent Ratio Time to Time to HFE7300/ Clear Max Contrast Emax Erosion Strip HFE6512 (sec) (time, sec) (time, sec) (sec) 100/0  150  1.6 (150) n/a n/a 95/5  60 2.1 (60) n/a 2.0 (90) 0.02 (90) 90/10 30 2.4 (30) n/a 2.4 (60) 1.8 (90) 0.07 (90) 75/25 <30 1.7 (30) 0.16 (30) 180  0.30 (60) (estimate) 0.43 (90) 50/50 <30 n/a 0.36 (30) 60 25/75 <30 n/a 0.95 (30) 35 (estimate) 10/90 <30 n/a 0.95 (30) 35 (estimate)  0/100 <30 n/a 0.94 (30) 35 (estimate)

In Table 5, it is noted that the development rate of this polymer in pure HFE-7300 is very slow. The first “puddle” that was clear in the low exposure area was the puddle corresponding to 150 sec total development time. The contrast was only 1.6 at this time. Perhaps higher contrast could eventually be achieved by extending the development time, but such extended development time can be prohibitive from a practical manufacturing standpoint. However, when 5 or 10% HFE-6512 is added, much better contrasts are achieved in a shorter amount of time. Further, there is a good development time window for achieving these contrasts. At 25% HFE-6512, the Emax is starting to show significant erosion and the mixture has essentially become an effective, albeit slightly slow, stripping solution. By 50% HFE-6512, the stripping rate is much faster. There contrast curves for 75% HFE-6512 and 90% HFE-6512 were not significantly different from 100% HFE-6512, showing that there is a broad range of mixtures that are effective for stripping (consistent with data from Table 4).

Example 6

The same fluorinated photoresist solution used in Example 5 was spin coated onto the silicon wafer and then “soft baked” at 90° C. for 60 seconds. The photoresist layer was about 1.4 μm thick. Contrast curves were measured as described above using HFE-7500 (b.p.=128° C.) as the developer. The process was then repeated for various mixtures with HFE-7200 (b.p.=76° C.). Various parameters were determined and reported in Table 6.

TABLE 6 Solvent Ratio Time to Time to HFE7500/ Clear Max Contrast Emax Erosion Strip HFE7200 (sec) (time, sec) (time, sec) (sec) 100/0  150  1.2 (150) n/a n/a 90/10 90 1.4 (90) n/a n/a  2.4 (150) 80/20 60 1.8 (60) n/a n/a 2.1 (90)  2.6 (150) 20/80 15 2.2 (15) n/a 3.3 (30) 0.03 (30)  0/100 15 2.2 (15) n/a 2.0 (30) 5.8 (60) 0.03 (60) delamination of 51 mJ/cm2 step @ 60 sec 0/100 + 15 n/a 0.64 (15) 30 0.5% vol. IPA 20/80 + 15 n/a 0.30 (15) 60 0.5% vol. IPA 0/100 + 15 1.7 (15) 0.08 (15) 60 0.1% vol. 3.7 (30) 0.10 (30) IPA

Referring to Table 6, it is observed that pure HFE-7500 is similar to HFE-7300 in that it takes 150 sec to clear and the contrast is low. Adding 10 or 20% of HFE-7200 to the developing solution significantly reduces time to clear and improves contrast. Going as far as 80% HFE-7200 produces a very short clear time and slightly better contrasts. HFE-7200 is a much stronger developing solvent than HFE-7500, and when used at 100% it produces a clear time of 15 sec and reasonable contrasts at 2.2 and 2.0, but by 60 sec one of the steps has delaminated (based on debris pattern). Not shown in the table, by 90 sec, more steps have delaminated. Thus, the pure solvent is not as robust as some of the mixtures. It is also noted that HFE-7200 alone is not an effective stripping agent in this system. This example falls into the category of “General Embodiment 2”, and adding just 0.5% by volume of isopropyl alcohol (IPA) makes it a very effective stripping solution. Similarly, 0.5% IPA by volume added to the 20/80 HFE-7500/HFE-7200 blend is also highly effective. Interestingly, adding only 0.1% by volume of IPA to pure HFE-7200 can be made to produce a developing solution having good contrast without delamination, but the development time window is very short. By 30 sec, the only film left was in point 1 (Emax)—all the others had developed away. Shortly thereafter, this step is also removed. Thus, the 0.1% IPA solution is also an effective stripping solution. It appears that there may be an induction period for stripping of Emax, but once it starts, it strips very rapidly. Such as system is not expected to be robust as a developing solution. Not shown, but a pure HFE-7500 with 0.5% IPA is not an effective stripping solution. Thus, it is preferred that the majority of the stripping solution volume comes from the higher activity solvent.

Example 7

A fluorinated photoresist was spin coated onto the silicon wafer and then “soft baked” at 90° C. for 60 seconds. The photoresist layer was about 1.4 μm thick. The photoresist solution included a HFE-6512 as coating solvent, CGI 1907 as PAG (0.8% by wt relative to polymer wt), and a branched polymer comprising copolymer of FOMA, TBMA, ECPMA, EGDMA (ethylene glycol dimethylacrylate) and AMMA in mole ratios of 27.3, 30.4, 37.3, 3, and 2, respectively. The polymer had 28.0% by weight of fluorine relative to the polymer. Contrast curves were measured as described above using HFE-7200 as the developer. The process was then repeated for various mixtures of HFE-7200 and HFE-7600, and various parameters were determined as reported in Table 7. Note that maximum contrast values were only reported if the low exposures had fully been removed and when Emax erosion was less than 0.25. In Table 7, the pure HFE-7600 “time to clear” entry is “<30” sec. In fact, 95% of the polymer in the low exposure region was actually in the first 15 sec puddle. For reasons not fully understood, it is often observed that the first puddle, almost independent of puddle time, leaves a small residue of 0.05 to 0.10 of normalized thickness. If shorter puddle times were used, the time to clear would likely be much less than 30 sec. Interestingly, adding just 10% HFE-7200 eliminates this residual effect. Also, the “time to strip” entries are estimates based on extrapolations from the data.

TABLE 7 Solvent Ratio Time to Time to HFE7200/ Clear Max Contrast Emax Erosion Strip HFE7600 (sec) (time, sec) (time, sec) (sec) 100/0  30 1.2 (30) 0.05 (30) n/a 1.8 (60) 0.09 (60) 2.1 (90) 0.10 (90) 95/5  30 1.9 (30) 0.09 (30) n/a 2.1 (60) 0.11 (60) 2.5 (90) 0.13 (90) 90/10 15 1.3 (15) 0.05 (15) n/a 1.8 (30) 0.13 (30) 3.1 (60) 0.17 (60) 2.4 (90) 0.20 (90) 75/25 15 1.8 (15) 0.10 (15) n/a 1.8 (30) 0.20 (30) 0.27 (60) 0.35 (90) 10/90 15 2.0 (15) 0.21 (15) 105 0.27 (30) (estimate) 0.60 (60) 0.85 (90)  0/100 <30 n/a 0.11 (15) 110 0.34 (30) (estimate) 0.56 (60) 0.82 (90)

It is observed in Table 7 that adding 5 to 10% HFE-7600 to the developing solution can improve contrast and reduce time to clear, relative to pure HFE-7200. Increasing HFE-7600 to 25% or higher results in increased Emax Erosion and the solution becomes a more effect stripping solution than a developing solution. Note that the 10/90 HFE-7200/HFE-7600 mixture is just as effective as the pure HFE-7600 in stripping, and may be slightly advantaged in that the mixture leaves less residual in the first 15 sec puddle.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations, combinations, and modifications can be effected by a person of ordinary skill in the art within the spirit and scope of the invention.

LIST OF REFERENCE NUMBERS USED IN THE DRAWINGS

  • 2 form photoresist layer on substrate step
  • 4 form exposed photoresist layer step
  • 6 form developed structure step
  • 8 form treated structure step
  • 10 remove first pattern of photoresist step
  • 20 substrate
  • 22 support
  • 24 layer of active organic material
  • 26 photoresist layer
  • 28 light
  • 30 photomask
  • 32 exposed photoresist layer
  • 34 exposed areas
  • 36 non-exposed areas
  • 38 developed structure
  • 40 first pattern of photoresist
  • 42 second pattern of uncovered substrate
  • 44 treated structure
  • 46 patterned layer of active organic material
  • 48 patterned active organic material structure
  • 120 substrate
  • 126 photoresist layer
  • 138 developed structure
  • 140 first pattern of photoresist
  • 142 second pattern of uncovered substrate
  • 144 treated structure
  • 145 layer of active organic material
  • 146 patterned layer of active organic material
  • 148 patterned active organic material structure

Claims

1. A method of patterning a device, comprising:

forming on a device substrate a photoresist layer comprising a fluorinated photoresist material;
exposing the photoresist layer to patterned radiation to form an exposed photoresist layer;
contacting the exposed photoresist layer with a developing agent to remove a portion of the exposed photoresist layer in accordance with the patterned radiation, thereby forming a developed structure having a first pattern of photoresist covering the substrate and a complementary second pattern of uncovered substrate corresponding to the removed portion of photoresist, the developing agent comprising a mixture of a first and second fluorinated solvents, wherein at least one of the first and second solvents is a hydrofluoroether;
treating the developed structure to form a treated structure; and
contacting the treated structure with a stripping agent to remove the first pattern of photoresist, the stripping agent comprising at least the first or second solvent in concentrations different from the developing agent.

2. The method of claim 1 wherein both the first and second solvents are hydro fluoro ethers.

3. The method of claim 2 wherein the stripping agent comprises a mixture of first and second solvents in a ratio different from the developing agent.

4. The method of claim 2 wherein at least one of the first and second solvents is a hydrofluoroether selected from the group consisting of an isomeric mixture of methyl nonafluorobutyl ether and methyl nonafluoroisobutyl ether, an isomeric mixture of ethyl nonafluorobutyl ether and ethyl nonafluoroisobutyl ether, 3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-trifluoromethyl-hexane, 1,1,1,2,3,3-hexafluoro-4-(1,1,2,3,3,3,-hexafluoropropoxy)-pentane, 1-methoxyheptafluoropropane, 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-trifluoromethyl-pentane, 1,3-(1,1,2,2-tetrafluoroethoxy)benzene, 1,2-(1,1,2,2-tetrafluoroethoxy)ethane, 1,1,2,2-tetrafluoroethyl-1H,1H,5H-octafluoropentyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorooctane-propyl ether.

5. The method of claim 1 wherein the substrate comprises a support and a layer of active organic material, and wherein the photoresist layer is in contact with the layer of active organic material.

6. The method of claim 5 wherein the treating includes chemical or physical etching of the active organic material in the second pattern of uncovered substrate to form a patterned layer of active organic material corresponding to the first pattern.

7. The method of claim 1 wherein the treating includes providing a layer of active organic material over both the first pattern of photoresist and the second pattern of uncovered substrate, and wherein the stripping further removes active organic material formed over the first pattern of photoresist, thereby forming a patterned layer of active organic material corresponding to the second pattern.

8. The method of claim 1 wherein the developing agent or the stripping agent is obtained at least in part from a recycled mixture of the first and second solvents produced by a recycling apparatus from a waste stream including the developing and the stripping agent.

9. The method of claim 8 wherein the developing agent or the stripping agent is obtained by combining the recycled mixture with a substantially pure source of the first or second agent.

10. The method of claim 8 wherein the recycled mixture is used directly as the stripping agent.

11. The method of claim 1 wherein the stripping agent further comprises a protic solvent in a concentration range of 0.001% to 3% by volume.

12. The method of claim 1 wherein the photoresist layer is formed by depositing a photoresist agent onto the substrate, the photoresist agent comprising a coating solvent and the fluorinated photoresist material, wherein the coating solvent includes the first or second solvent, or a mixture thereof.

13. The method of claim 1 wherein the boiling points of the first and second solvents differ by at least 25° C.

14. The method of claim 13 wherein each of the first and second solvents is selected from the group consisting of an isomeric mixture of methyl nonafluorobutyl ether and methyl nonafluoroisobutyl ether, an isomeric mixture of ethyl nonafluorobutyl ether and ethyl nonafluoroisobutyl ether, 3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-trifluoromethyl-hexane, 1,1,1,2,3,3-hexafluoro-4-(1,1,2,3,3,3,-hexafluoropropoxy)-pentane, 1-methoxyheptafluoropropane, 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-trifluoromethyl-pentane, 1,3-(1,1,2,2-tetrafluoroethoxy)benzene, 1,2-(1,1,2,2-tetrafluoroethoxy)ethane, 1,1,2,2-tetrafluoroethyl-1H,1H,5H-octafluoropentyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorooctane-propyl ether.

15. The method of claim 13 wherein the developing agent comprises the first solvent in a volume range of 75 to 99% and the second solvent in a volume range of 1 to 25%.

16. The method of claim 13 wherein the stripping agent comprises the second solvent in a volume range of 15 to 99% and the first solvent in a volume range of 1 to 85%.

17. The method of claim 2 wherein the fluorinated photoresist material has a fluorine content of 15 to 60% by weight.

18. The method of claim 17 wherein the fluorinated photoresist material comprises a photopolymer including a first repeating unit having a fluorinated alkyl group and a second repeating unit having an acid-forming or alcohol-forming precursor group.

19. The method of claim 1 wherein before exposing the photoresist layer to patterned radiation, photoresist material is removed from an edge area of the device substrate using an edge bead removal solvent comprising one or both of the first and second solvents.

20. The method of claim 1 wherein the device includes an organic thin film transistor, an organic solar cell, an organic light emitting diode, a bioelectronic sensor or an organic conductor-based touch sensor.

21. A photoresist system comprising:

a) a developing agent comprising a first solvent and a second solvent, wherein both solvents are fluorinated solvents and at least one is a hydrofluoroether;
b) a photoresist coating composition comprising a fluorinated photoresist material and a coating solvent, the coating solvent comprising at least one of the first and second solvents; and
c) a stripping agent comprising at least one of the first and second solvents in concentrations different from the developing solution.
Patent History
Publication number: 20140322656
Type: Application
Filed: Apr 24, 2014
Publication Date: Oct 30, 2014
Inventors: Charles Warren Wright (Fairport, NY), Diane Carol Freeman (Pittsford, NY), Frank Xavier Byrne (Webster, NY), John Andrew DeFranco (Rochester, NY)
Application Number: 14/260,666
Classifications
Current U.S. Class: Post Image Treatment To Produce Elevated Pattern (430/325); Finishing Or Perfecting Composition Or Product (430/331)
International Classification: G03F 7/40 (20060101);