WO2015089062A1 - Patterning functional materials - Google Patents

Abstract

A method of patterning a functional material layer in an electronic device is disclosed. An etch barrier layer is provided in a first pattern over a layer of functional material, thereby forming an intermediate structure having a second pattern of uncovered functional material. The intermediate structure is contacted with an etch fluid having a siloxane compound to selectively dissolve the second pattern of uncovered functional material, thereby forming a patterned functional material layer corresponding to the first pattern.

Description

PATTERNING FUNCTIONAL MATERIALS

CROSS REFERENCE TO RELATED APPLICATIONS

This application is being filed on 9 December 2014, as a PCT International patent application, and claims priority to U.S. Provisional Patent Application No. 61/913,655, filed December 9, 2013, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

The present disclosure relates to patterning of electronic materials, in particular, organic electronic materials.

Electronic devices typically include patterned layers of functional materials that serve some purpose in the operation of the device. For example, the patterned functional material might be a conductor, a semiconductor, an insulator, an optical layer or the like. Although there has been some adoption of using printing technologies to pattern functional material layers, the electronics industry primarily relies on lithographic patterning. One very common method of using lithography involves applying a photoresist layer over a target material, patterning the photoresist by exposure to light and development of an image, and using the remaining imaged photoresist as an etch barrier. That is, the structure is subjected to an etching treatment (e.g., a solution or a reactive ion gas) to selectively remove the functional material in the uncovered areas.

Relative to reactive ion etching, solution or "wet" etching can have throughput advantages in manufacturing, e.g., by enabling batch-mode processing. However, it can be difficult to find a wet etchant that is compatible with the resist, effectively etches the functional material and does not otherwise damage the device. Organic functional materials are particularly problematic because many of the useful etchants are organic solvents that also dissolve or compromise the resist, which typically is also organic in nature. SUMMARY

In accordance with the present disclosure, a method of patterning a functional material layer in an electronic device includes: providing a layer of a functional material; providing an etch barrier layer in a first pattern over the layer of functional material, thereby forming an intermediate structure having a second pattern of uncovered functional material; and contacting the intermediate structure with an etch fluid having a siloxane compound to selectively dissolve the second pattern of uncovered functional material, thereby forming a patterned functional material layer corresponding to the first pattern.

Siloxane-based etching fluids of the present disclosure provide an effective medium for the selective removal of functional materials in conjunction with an etch barrier pattern. In an embodiment, the functional material is an organic

semiconductor, the etch barrier is a fluorinated photopolymer and the etch fluid includes a disiloxane compound.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow chart depicting the steps in an embodiment of the present disclosure; FIG. 2 is a flow chart depicting the steps in another embodiment of the present disclosure;

FIG. 3A - 3F is a series of cross-sectional views depicting various stages in the formation of a patterned functional material structure according to an embodiment of the present disclosure.

FIG. 4A - 4D is a series of cross-sectional views depicting various stages in the formation of a patterned functional material structure according to another embodiment of the present disclosure.

FIG. 5A - 5D is a series of cross-sectional views depicting several OTFT structures each having a patterned organic semiconductor layer.

DETAILED DESCRIPTION

Methods and materials of the present disclosure may be used in the fabrication of many types of electronic devices including, but not limited to, displays (e.g., OLED, LCD, electrophoretic), lighting (e.g., OLED, LED), photovoltaic (e.g., organic PV), sensors, microprocessors, bioelectronic devices, MEMS and the like.

Electronic devices of the present disclosure include a layer of patterned functional material. The functional material may be a conductor, a semiconductor, an insulator, or an optical material. In an embodiment, the functional material has a molecular weight of less than 1000 daltons. In an embodiment, the functional material is non-polymeric. In an embodiment, the functional material has at least one aliphatic carbon. In an embodiment, the functional material includes an alkyl silane, alkyl germane or a tertiary alkyl group. In the present disclosure, the term "alkyl silane" refers to a group having at least one alkyl carbon-silicon bond, but the silicon may optionally further have one or more non-alkyl carbon bonds such as a silicon-oxygen bond (silyl ethers, siloxanes and the like) or an aryl carbon-silicon bond.

In an embodiment, the functional material is an organic semiconductor or conductor that may be used in an organic TFT, an OLED or an organic PV device. Preferred organic semiconductors are non-polymeric. The organic semiconductor may be n-type, p-type or have both n-type and p-type properties (ambipolar). Some non-limiting classes of non-polymeric organic semiconductors include polycyclic aromatic or heteroaromatic hydrocarbons, fullerenes and metal complexes (e.g., of Ga, Al, Ir, Re, Ru, Au, Pt, Ag or Os). The organic semiconductor may be a mixture, e.g., of a host material and a dopant material. In an embodiment the non-polymeric organic semiconductor includes an alkyl silane, an alkyl germane or a tertiary alkyl group. In an OLED structure, the organic semiconductor may serve the function of hole injection, hole transport, light emission, electron transport, electron injection, hole blocking or electron blocking.

In an embodiment, the functional material has a structure according to formula (1):

wherein a and a' are independently selected 0 to 4, one or both of X and X' are independently selected monovalent alkyl, alkenyl, alkynyl, aryl, heteroaryl, alkoxy or aryloxy that may optionally be further substituted, or one or both of X and

X' represent an independently selected fused aliphatic, aromatic or heterocyclic ring structure that may optionally be further substituted, Z and Z' are independently selected alkyl, alkenyl, alkynyl, aryl, heteroaryl, alkoxy, aryloxy that may optionally be further substituted. In an embodiment, Z and Z' are independently selected alkynyl having a structure according to formula (la):

wherein R¹, R² and R³ are independently selected alkyl, alkenyl, aryl, or heteroaryl that may optionally be further substituted and Q is carbon, germanium or silicon. Some examples of structures according to formula (1) are shown below.

Some non-limiting examples of useful organic semiconductors can be found in US7385221 , US6690029, US8404844B2, WO2013039842A1 , US8212243B2, and US7981719B2 the contents of which are incorporated herein by reference.

In an embodiment, the functional material comprises an inorganic conductive or semiconductive nanoparticle comprising, e.g., Au, Ag, (II/VI) compounds, (III/V) compounds, Si, and the like. Preferably, the nanoparticle includes an outer layer comprising an organic ligand, an organic coating, an alkyl silane group, an alkyl germane group or a tertiary alkyl group.

In an embodiment, a layer of functional material may be coated by applying a solution using conventional methods (spin coating, ink jet, gravure, flexography, curtain coating, bead coating, dip coating and the like). The functional material may alternatively be coated by vapor deposition, for example, by sublimation from a heated organic material source at reduced pressure. The functional material layer may be provided by transfer from a donor sheet, e.g., thermal transfer.

Etch barriers of the present disclosure are those that may be applied over the functional material without causing significant damage to the functional material and also withstand the etch fluid comprising the siloxane compound. The etch barrier is preferably an organic polymer. It may be pattern-applied directly using inkjet printing, flexographic printing, thermal transfer from a donor sheet or the like. In an embodiment, the etch barrier is formed from a photosensitive resin that may be patterned by exposure to light and development of an image using a developing agent. The photosensitive resin may be positive working (where portions exposed to light are developed away) or negative working (where unexposed portions are developed away).

In a preferred embodiment, the etch barrier comprises a patterned fluoropolymer. In an embodiment, the fluoropolymer is a fluorinated photosensitive resin (photopolymer). In another embodiment, the fluoropolymer is provided in a multilayer system wherein a fluoropolymer having low or no photosensitivity is first applied over a target substrate followed by application of another layer comprising a photosensitive resin, for example, a fluorinated or non-fluorinated photoresist.

In an embodiment, the patterned fluoropolymer may optionally be removed (stripped). In an embodiment, the patterned fluoropolymer may remain as part of a device. In an embodiment fluorinated solvents are used to coat, develop and optionally strip the fluoropolymer. Such solvents are 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 problematic reduction in the functioning of the device.

Certain embodiments of the present disclosure are particularly suited to patterning devices having solvent-sensitive, organic functional materials. Examples of such functional 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, and organic optical materials. Many of these materials are easily damaged when contacted with organic or aqueous solutions used in conventional photolithographic processes.

The fluoropolymer may be applied using any method suitable for depositing a liquid material. For example, a fluoropolymer 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 fluoropolymer. Alternatively, the fluoropolymer can be applied to the substrate by transferring a preformed fluoropolymer 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 fluoropolymer layer may optionally have coated thereon an adhesion promoting layer.

The etch fluid of the present disclosure comprises a siloxane compound. In a preferred embodiment, the etch fluid is a liquid having a melting point less than 15 °C and a boiling point greater than 50 °C. In an embodiment, the etch fluid may include a single siloxane compound. In another embodiment, the etch fluid may be a mixture of two or more siloxane compounds, e.g., wherein one siloxane is a more active etchant than the other. Alternatively, the etch fluid may include a mixture of one or more siloxane compounds with a non-siloxane solvent. In an embodiment, the weight percent of the siloxane(s) in such mixtures is greater than the weight percent of the non-siloxane. In an embodiment, the etch fluid is an azeotrope of a siloxane with a non-siloxane solvent, e.g., an alcohol, an ester, or an ether. A few non-limiting examples of azeotropes include 2-methyl-pentanol, ethyl lactate, isopropyl lactate, 1 -methoxy-2-propanol, n-propyl acetate, 1 -n-propyloxy-2- propanol, dipropyleneglycol monomethyl ether, dipropyleneglycol monoethyl ether, 1 -hexanol, and 2-methylcyclohexanol. In an embodiment, the etch fluid includes a surfactant. In an embodiment, in addition to etching a target functional material, the etch fluid assists in removing water from the substrate by water displacement drying.

The etch fluid is selected so that it can selectively dissolve or otherwise remove areas of functional material not covered by the etch barrier, but does not significantly dissolve the etch barrier or otherwise negatively impact the device structure. In an embodiment, the etch fluid may also act as a developing agent for a photopolymer-based etch barrier. For example, the etch fluid may comprise a fluorinated solvent along with a siloxane compound and the etch fluid may be used to develop a fluorinated photopolymer and the functional material in a common step.

In an embodiment, the siloxane compound has a structure according to formula 4a or 4b:

wherein R¹ through R¹⁴ are independently selected, substituted or unsubstituted alkyl, aryl or heteroaryl groups, n = 0 to 8, and m = 1 to 4. Preferred alkyl groups have 8 or fewer carbon atoms, and more preferably, 4 or fewer carbon atoms. Preferred aryl groups have 14 or fewer carbon atoms, and more preferably, is a phenyl group. In a preferred embodiment, the siloxane has at least one alkyl group. Some non-limiting examples of useful siloxanes in the present disclosure include hexamethyldisiloxane (HMDSO), hexaethyldisiloxane,

octamethyltrisiloxane, octamethylcyclotetrasiloxane, decamethyltetrasiloxane, decamethylcyclopentasiloxane, and tetramethyltetraphenyltrisiloxane. In an embodiment, when etching a functional material having at least one aliphatic carbon, the siloxane should have at least as many alkyl groups as aryl groups. In an embodiment, when etching a functional material having no aliphatic carbons, the siloxane should have at least as many aryl groups as alkyl groups. In an

embodiment, the siloxane compound is a disiloxane.

In some cases, the etching rate can be controlled to a target etch time by diluting a more active siloxane compound with a less active siloxane (or with a less active non-siloxane solvent). By "more active", it is meant that the removal rate of a target functional material is at least 30% higher than the comparative, less active siloxane or non-siloxane solvent. Preferably, such removal rate is at least 50% higher. In an embodiment, the etch fluid comprises HMDSO provided as a mixture in a less active siloxane such that the volume percent of HMDSO is 10 to 90% relative to the total etch fluid volume, preferably 25 to 75%.

A flow diagram for an embodiment of the present disclosure is shown in FIG. 1 , and includes the Step 2 of providing a layer of functional material. Non- limiting examples of functional materials are discussed above. This is followed by Step 4 of providing an etch barrier layer in a first pattern over the layer of functional material thereby forming an intermediate structure. In Step 6, the intermediate structure is contacted with an etch fluid to form a patterned functional material layer having a pattern corresponding to the first pattern. In optional Step 8, the etch barrier layer is removed.

As previously mentioned, the patterned etch barrier layer may optionally be provided by a fluorinated photopolymer, e.g., by following the Steps 4a, 4b and 4c in FIG. 2. In Step 4a, a fluorinated photopolymer is provided over the layer of functional material layer, e.g., by spin-coating from a solution to form a layer of the photopolymer. In Step 4b, the layer of fluorinated photopolymer is exposed to pattern radiation, e.g., UV or visible light (depending on the spectral sensitivity of the photopolymer). This is followed by Step 4c, wherein the exposed photopolymer is developed to form an intermediate structure having an imaged photopolymer (etch barrier) in a first pattern that remains over a portion of the functional material layer. The other steps are the same as described for FIG. 1 . As mentioned previously, in an embodiment, the etch fluid may also act as a developing agent for a

photopolymer-based etch barrier. In that case, Step 4c and Step 6 are basically combined into a single step and the intermediate structure is transiently formed.

FIG. 3 shows a series of cross-sectional views depicting the formation of a patterned functional material structure at various stages according to an embodiment of the present disclosure. In FIG. 3A, a substrate 20 includes a layer of functional material 24 provided on a support 22. Support 22 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. In FIG. 3B, a negative-type fluorinated photopolymer layer 26 is formed on the substrate 20 and in contact with the layer of functional material 24. Next, as shown in FIG. 3C, fluorinated photopolymer layer 26 is exposed to patterned light by providing a photomask 30 between the photopolymer layer 26 and a source of collimated light 28. The exposed fluorinated photopolymer layer 32 includes exposed areas 34 and non-exposed areas 36. The structure is then developed in a developing agent including a fluorinated solvent. The non-exposed areas 36 of the fluorinated photopolymer are selectively dissolved to form an intermediate structure. As shown in FIG. 3D, intermediate structure 38 has a first pattern of fluorinated photopolymer 40 covering a portion of the layer of functional material 24, and a complementary second pattern of uncovered functional material 42 corresponding to the removed portion of fluorinated photopolymer. Turning now to FIG. 3E, a treated structure 44 is formed by subjecting the intermediate structure 38 to an etch fluid comprising a siloxane compound that selectively removes functional material from the second pattern of uncovered substrate, thereby forming a patterned layer of functional material 46 corresponding to the first pattern. By corresponding, it is meant that the patterned layer of functional 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 functional 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 functional material are slightly larger than the first pattern. Further, the patterned layer of functional 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. 3F, treated structure 44 is contacted with a stripping agent that removes the first pattern of photoresist 40, thereby forming patterned functional material structure 48 having the (now bare) patterned layer of functional material 46. Such stripping agent preferably includes a fluorinated solvent.

Patterned functional material structure 48 may optionally be subjected to additional steps, if necessary, to form a device such as an organic TFT array, an OLED display, an e-reader, a solar cell, a bioelectronic device or the like. In another embodiment, the patterned etch barrier is provided using a multilayer system such as disclosed in US Patent Publication 2010/0289019. An embodiment is shown in FIG. 4. In FIG. 4A, a layer of an initially non-patterned fluoropolymer 160 is applied over a functional material layer 124, e.g., by coating from a solution or by dry film transfer from a donor sheet. In this embodiment, the fluoropolymer is soluble in one or more fluorinated solvents that do not interact significantly with functional material layer. Next, a layer of a photosensitive second polymer 161 (e.g., a photoresist) is provided over the non-patterned fluoropolymer 160 to form an unpatterned bilayer structure. The photosensitive second polymer 161 may, for example, be coated from an organic or aqueous solution in which the underlying non-patterned fluoropolymer is not soluble. The photosensitive second polymer 161 may be a photosensitive fluoropolymer coated from a fluorinated solvent that does not significantly dissolve or impact the underlying non-patterned fluoropolymer 160. The photosensitive second polymer 161 may alternatively be any conventional photoresist or photopolymer that can be coated and developed using aqueous or non-fluorinated organic solvents that do not deleteriously interact with the underlying fluoropolymer layer. The developed photosensitive second polymer should also have low solubility in fluorinated solvents used to pattern the underlying fluoropolymer layer (see below). In an embodiment, the photosensitive second polymer has a total fluorine content by weight of less than 30%, alternatively less than 15%. In an embodiment, the photosensitive second polymer has a total fluorine content of less that 1% by weight.

Referring now to FIG. 4B, a photomask 62 is provided between radiation source emitting radiation 61 (e.g., UV light) and the layer of photosensitive second polymer (e.g., that is sensitive to the UV light), thereby forming an exposed layer of photosensitive second polymer 163 having a pattern 164 of exposed photosensitive second polymer and a pattern 165 of unexposed photosensitive second polymer. In FIG. 4C, the exposed layer of photosensitive second polymer 163 is then contacted with a second polymer developing agent to selectively remove unexposed areas of the photosensitive second polymer (a negative tone photopolymer in this embodiment) thereby forming a partially patterned bilayer structure 168 including a patterned layer 166 of second polymer over the non-patterned fluoropolymer layer 160. The non-patterned fluoropolymer 160 is not highly soluble in the second polymer developing agent and is not removed at this point. The photosensitive second polymer could instead be a positive tone material, in which case, the patterned layer of second polymer would correspond to the unexposed areas. In an alternative embodiment, the patterned layer 166 of second polymer may be formed by printing.

The partially patterned bilayer structure 168 is contacted with a developing agent including a fluorinated solvent in which the fluoropolymer has some solubility, but not the second polymer. As shown in FIG. 4D, this results in selective removal of the fluoropolymer in areas not covered by the second polymer, thereby forming an intermediate structure having a bilayer structure 169 including a layer of fluoropolymer in a pattern 66 and the patterned layer 166 of second polymer. A pattern of uncovered functional material 142 is also formed in this step corresponding to the removed portion of fluorinated photopolymer. It should be noted that the solubility of the fluoropolymer in the fluorinated solvent may lead to some harmless undercutting (not shown), but this can be controlled through selection of time, temperature, choice of fluorinated solvents, agitation and the like. In some embodiments, the undercutting is desirable. If the contacting with the fluorinated solvent is done under conditions too aggressive, this may result in lift-off of the second polymer. This is not desired at this point, but may be desirable later on after etching. Areas of uncovered functional material 142 can be removed by contact with an etch fluid as described in FIG. 3 to form a patterned functional material layer (not shown). The bilayer structure 169 can optionally be removed, preferably by contact with a stripping or lift-off agent comprising a fluorinated solvent that dissolves or otherwise removes the patterned fluoropolymer.

In an embodiment, methods of the present disclosure are used to fabricate an organic TFT device, wherein the functional material is an organic semiconductor which is patterned so that each OTFT or display pixel/sub-pixel has its own discrete and separate organic semiconductor material. General materials and methods for making and operating OTFT devices are known to the skilled artisan, and some non- limiting examples can be found in US 7029945, US 8404844, US 8334456, US 841 1489 and US 7858970, the entire contents of which are incorporated by reference. FIG. 5 illustrates a few of the numerous possible OTFT embodiments, but in general, an OTFT is formed on a substrate 210 and has an organic semiconductor material layer 212, a gate dielectric material layer 214, a source electrode 216, a drain electrode 218 and a gate electrode 220. FIG. 5A shows a bottom gate / bottom contact OTFT, FIG. 5B shows a bottom gate / top contact OTFT, FIG. 5C shows a top gate / bottom contact OTFT, and FIG. 5D shows a top gate / top contact OTFT. In an embodiment, a fluoropolymer is used as both the etch barrier and also as a dielectric in a top gate OTFT device, e.g., the

fluoropolymer may be a photo-crosslinking type of polymer. Although not shown in the figures, gate dielectric material layer 14 may be photopatterned as needed, for example, to provide open areas for making electrical contacts or building via structures.

In an embodiment, organic semiconductor patterning system or kit can be produced including an etch fluid composition including a siloxane compound and either a) a coatable semiconductor composition including an organic semiconductor material provided in a coating solvent, or b) a coatable resist composition including a fluoropolymer and a fluorinated solvent, or both (a) and (b). The coatable resist composition can be used to form a patterned etch barrier and the system or kit may further include other processing solvents for patterning the etch barrier such as developers or strippers. The fluoropolymer may optionally be a photosensitive fluoropolymer. The compositions of such kits can be individually adjusted to ensure good patterning performance without unnecessary experimentation by an end user.

In an embodiment, a method of patterning a fluoropolymer includes use of a fluoropolymer developing agent having a mixture of a hydrofluoroether solvent and a siloxane compound.

As mentioned above, certain processing steps of the present disclosure may include the use of a fluorinated solvent. When fluorinated solvents are used, they may be used in some embodiments as mixtures or solutions with non-fluorinated materials, but typically such mixtures include at least 50% by volume of a fluorinated solvent, preferably at least 90% by volume. 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 (PFCs), hydrofluoroethers (HFEs), perfluoroethers, perfluoroamines,

trifluoromethyl-substituted aromatic solvents, fiuoroketones and the like.

Particularly useful fluorinated solvents include those that are perfiuorinated or highly fluorinated liquids at room temperature, which are immiscible with water and many 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 than PFCs 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-l, l , l ,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-(l , 1 ,2,3,3,3,- hexafluoropropoxy)-pentane (HFE-7600 aka PF7600(from 3M)), 1 - methoxyheptafluoropropane (HFE-7000), l ,l , l,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), l ,2-(l,l ,2,2-tetrafluoroethoxy)ethane

(HFE-578E), l ,l ,2,2-tetrafluoroethyl-l H, l H,5H-octafiuoropentyl ether (HFE-6512), l ,l ,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (HFE-347E), 1 , 1 ,2,2- tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE-458E), 2,3,3,4,4- pentafluorotetrahydro-5-methoxy-2,5-bis[l ,2,2,2-tetrafluoro-l -(trifluoromethyl) ethyl]-furan (HFE-7700 aka Novec™ 7700) and 1, 1 , 1 ,2,2,3,3,4,4,5,5,6,6- tridecafluorooctane-propyl ether (TE60-C3).

Mixtures of fluorinated solvents may optionally be used, e.g., as disclosed in US patent applications nos. 14/260,666 and 14/260,705, the entire contents of which are incorporated by reference herein.

The term "fluoropolymer" herein includes not only high molecular weight, long chain fluorinated materials, but also lower molecular weight oligomers, macrocyclic compounds such as fluorinated calixarene derivatives and other highly fluorinated hydrocarbons having at least 15 carbon atoms. In an embodiment, the molecular weight of the fluoropolymer is at least 750. In an embodiment, the fluoropolymer is soluble in one or more fluorinated solvents. Fluoropolymers preferably have a total fluorine content by weight in a range of 15% to 75%, or alternatively 30% to 75%, or alternatively 30% to 55%.

When the fluoropolymer is provided as a layer that is not inherently photosensitive (used in a multilayer configuration mentioned above), the fluorine content by weight is preferably in a range of 40% to 75%. Some non-limiting coatable examples of such polymers include Teflon AF (copolymer of

tetrafluoroethylene with 2,2'-bis(trifluoromethyl)-4,5-difluoro-l ,3-dioxole) and Cytop (a cyclic polymer formed from F₂C=CFCF₂OCF=CF2). In an embodiment, the non-inherently photosensitive fluoropolymer is a copolymer comprising a fluorine-containing group (see below for examples) and a non-photosensitive functional group. The non-photosensitive functional group may improve film adhesion, improve coatability, adjust dissolution rate, absorb light, improve etch resistance and the like. In an embodiment, the non-photosensitive functional group is a non-fluorine-containing aromatic or aliphatic hydrocarbon that may optionally be substituted, for example, with oxygen-containing groups such as ethers, alcohols, esters, and carboxylic acids.

Photosensitive fluoropolymers can be provided, e.g., by coating a photosensitive fluoropolymer composition (also referred to herein as a fluorinated photopolymer composition) that includes a fluorinated solvent, a fluorinated photopolymer material, and optionally additional materials such as sensitizing dyes, photo-acid generator compounds, stabilizers, and the like. In an embodiment, the fluorinated photopolymer material includes a copolymer comprising at least two distinct repeating units, including a first repeating unit having a fluorine-containing group and a second repeating unit having a solubility-altering reactive group. In an embodiment using a fluorinated photopolymer that is a copolymer, the copolymer has a total fluorine content of at least 10%, preferably at least 15%. In an embodiment, the total fluorine content is in a range of 15% to 60%, alternatively 30 to 60%, or alternatively 35 to 55%. The copolymer is suitably a random copolymer, but other copolymer types may be used, e.g., block copolymers, alternating copolymers, and periodic copolymers. The term "repeating unit" is used broadly herein and simply means that there is more than one unit. 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. When a repeating unit represents a low mole % of the combined repeating units, there may be only one such unit on a polymer chain. The copolymer may be optionally blended with one or more other polymers, preferably other fluorine-containing polymers. The fluoropolymer may optionally be branched, which may in certain embodiments enable lower fluorine content, faster development and stripping rates, or incorporation of groups that otherwise may have low solubility in a fluorinated polymer. Non-limiting examples of photosensitive fluoropolymer compositions are described in US Patent Publication 201 1/0159252, US Patent Application Nos. 14/1 13,408, 14/291 ,692, 14/335,476, US Provisional Patent Application Nos.

61/990,966, and 61/937, 122, the contents of which are incorporated by reference.

In an embodiment, at least one of the specified repeat units is formed via a post-polymerization reaction. In this embodiment, an intermediate polymer (a precursor to the desired copolymer) is first prepared, said intermediate polymer comprising suitably reactive functional groups for forming one of more of the specified repeat units. For example, an intermediate polymer containing pendant carboxylic acid moieties can be reacted with a fluorinated alcohol compound in an esterification reaction to produce the specified fluorinated repeating unit. Similarly, a precursor polymer containing an alcohol can be reacted with a suitably derivatized glycidyl moiety to form an acid-catalyzed cross-linkable (epoxy-containing) repeating unit as the solubility-altering reactive group. In another example, a polymer containing a suitable leaving group such as primary halide can be reacted with an appropriate compound bearing a phenol moiety to form the desired repeat unit via an etherification reaction. In addition to simple condensation reactions such as esterification and amidation, and simple displacement reactions such as etherification, a variety of other covalent-bond forming reactions well-known to practitioners skilled in the art of organic synthesis can be used to form any of the specified repeat units. Examples include palladium-catalyzed coupling reactions, "click" reactions, addition to multiple bond reactions, Wittig reactions, reactions of acid halides with suitable nucleophiles, and the like.

In an alternative embodiment, the first and second repeating units of the copolymer are formed directly by polymerization of two (or more) appropriate monomers, rather than by attachment to an intermediate polymer. Although many of the embodiments below refer to polymerizable monomers, analogous structures and ranges are contemplated wherein one or more of the first and second repeating units are formed by attachment of the relevant group to an intermediate polymer as described above.

In an embodiment, the fluorinated photopolymer material includes a copolymer formed at least from a first monomer having a fluorine-containing group and a second monomer having a solubility-altering reactive group. Additional monomers may optionally be incorporated into the copolymer. The first monomer is one capable of being copolymerized with the second monomer and has at least one fluorine-containing group. In an embodiment, at least 70% of the fluorine content of the copolymer (by weight) is derived from the first monomer. In another embodiment, at least 85% of the fluorine content of the copolymer (by weight) is derived from the first monomer.

The first monomer includes a polymerizable group and a fluorine-containing group. Some non-limiting examples of useful polymerizable groups include acrylates (e.g. acrylate, methacrylate, cyanoacrylate and the like), acrylamides, vinylenes (e.g., styrenes), vinyl ethers and vinyl esters. The fluorine-containing group of the first monomer or the first repeating unit is preferably an 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. Throughout this disclosure, unless otherwise specified, any use of the term alkyl includes straight-chain, branched and cyclo alkyls. In an embodiment, the first monomer does not contain protic or charged substituents, such as hydroxy, carboxylic acid, sulfonic acid or the like. In an embodiment, the first monomer has a structure according to formula

(2):

In formula (2), Ri represents a hydrogen atom, a cyano group, a methyl group or an ethyl group. R₂ represents a fluorine-containing group, in particular, a substituted or unsubstituted alkyl group having at least 5 fluorine atoms, preferably at least 10 fluorine atoms. In an embodiment, the alkyl group is a cyclic or non-cyclic hydrofluorocarbon or hydrofluoroether having at least as many fluorine atoms as carbon atoms. In a preferred embodiment R₂ represents a perfluorinated alkyl or a 1 H, 1 H,2H,2H-perfluorinated alkyl having at least 4 carbon atoms. An example of the latter is 1 H, 1 H,2H,2H-perfluorooctyl methacrylate ("FOMA").

A combination of multiple first monomers or first repeating units having different fluorine-containing groups may be used. The total mole ratio of first monomers relative to all of the monomers of the copolymer may be in a range of 5 to 80%, or alternatively 10 to 70%, or alternatively 20 to 60%.

The second monomer is one capable of being copolymerized with the first monomer. The second monomer includes a polymerizable group and a solubility- altering reactive group. Some non-limiting examples of useful polymerizable groups include those described for the first monomer.

In an embodiment, the solubility-altering reactive group of the second monomer or 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 agent includes a fluorinated solvent that selectively dissolves unexposed areas. In an alternative embodiment, the developing agent includes a polar solvent that selectively dissolves the exposed areas. In an embodiment, a carboxylic acid-forming precursor is provided from a monomer in a weight percentage range of 4 to 40% relative to the copolymer, or alternatively in a weight percentage range of 10 to 30%. 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.

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 US Patent Application No. 14/335,476, 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 US Patent Application Nos. 14/291 ,692 and 14/291,767, 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 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. This is advantageous since some active organic materials useful in applications to which the present disclosure pertains may decompose in the presence of 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, t-amyl ester, 2-methyl-2-adamantyl ester, 1- ethylcyclopentyl ester, and 1 -ethylcyclohexyl ester; B) esters of lactone, e.g., γ- butyrolactone-3-yl, y-butyrolactone-2-yl, mevalonic lactone, 3-methyl-7- butyrolactone-3-yl, 3-tetrahydrofuranyl, and 3-oxocyclohexyl; C) acetal esters, e.g., 2-tetrahydropyranyl, 2-tetrahydrofuranyl, and 2,3-propylenecarbonate-l-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 deprotection 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 solvent (typically fluorinated). In an embodiment, the developing agent includes a fluorinated solvent that selectively dissolves unexposed areas. In an alternative embodiment, the developing agent includes a polar solvent that selectively dissolves the exposed areas. In an embodiment, an hydroxyl- forming precursor is provided from a monomer in a weight percentage range of 4 to 40 % relative to the copolymer. In an embodiment, the hydroxyl-forming precursor has a structure according to formula (3):

R5 R10 (3)

wherein R₅ is a carbon atom that forms part of the second repeating unit or second monomer, and Rio 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).

^■Si— R19

I

R20 (AL-4)

In formula (AL-1), Rn 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,

may be a tertiary alkyl group. Some representative examples of formula (AL-1) include:

1 -3

In formula (AL-2), RM is a monovalent hydrocarbon group, typically a straight, branched or cyclic alkyl group, of 1 to 20 carbon atoms that may optionally be substituted. Ri₂ and R₎₃ 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:

AL-2-3

AL-2-6

In formula (AL-3), R15, i6, 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.

In an embodiment, the solubility-altering reactive group is a cross-linkable group, e.g., an acid-catalyzed cross-linkable group or a photo cross-linkable (non- acid catalyzed) group. Photo cross-linkable groups typically have at least one double bond so that when the group forms an excited state (either by direct absorption of light or by excited state transfer from a sensitizing dye), sets of double bonds from adjacent polymer chains crosslink. In an embodiment, the photo cross- linkable group (not catalyzed) comprises a cinnamate that may optionally further include fluorine-containing substituents, as described in US Provisional Application No. 61/937, 122. Some non-limiting examples of polymerizable monomers including such cinnamates are shown below.



(C-9)

Compositions comprising such materials may optionally further include a sensitizing dye. Some non-limiting examples of useful sensitizing dyes for cinnamate cross-linking groups include diaryl ketones (e.g., benzophenones), arylalkyl ketones (e.g., acetophenones), diaryl butadienes, diaryl diketones (e.g. benzils), xanthones, thioxanthones, naphthalenes, anthracenes, benzanthrone, phenanthrenes, crysens, anthrones, 5-nitroacenapthene, 4-nitroaniline, 3- nitrofluorene, 4-nitromethylaniline, 4-nitrobiphenyl, picramide, 4-nitro-2,6- dichlorodimethylaniline, Michler's ketone, N-acyl-4-nitro-l -naphthylamine.

Examples of acid-catalyzed cross-linkable groups include, but are not limited to, cyclic ether groups and vinyloxy groups. In an embodiment, the cyclic ether is an epoxide or an oxetane. The photopolymer composition including an acid- catalyzed cross-linkable group typically includes a PAG compound and operates as a "chemically amplified" type of system in a manner described above. Upon exposure to light, the PAG generates an acid (either directly or via a sensitizing dye as described above), which in turn, catalyzes the cross-linking of the acid-catalyzed cross-linkable groups. This significantly changes its solubility relative to the unexposed regions thereby allowing development of an image with the appropriate fluorinated solvent. Usually, cross-linking reduces solubility. In an embodiment, the developing agent includes a fluorinated solvent that selectively dissolves unexposed areas. In an embodiment, a cross-linkable group is provided from a monomer in a weight percentage range of 4 to 40 % relative to the copolymer.

Some non-limiting examples of some acid-catalyzed cross- linkable groups include the following wherein (*) refers to an attachment site to the polymer or the polymerizable group of a monomer:

In an embodiment, the solubility-altering reactive groups are ones that, when the photopolymer composition or layer is exposed to light, undergo a bond-breaking reaction to form a material with higher solubility in fluorinated solvents. For example, the solubility-altering reactive groups could be cross-linked and the links are broken upon exposure to light thereby forming lower molecular weight materials. In this embodiment, a fluorinated solvent may be selected to selectively remove exposed areas, thereby acting as a positive photopolymer system.

A combination of multiple second monomers or second repeating units having different solubility-altering reactive groups may be used. For example, a fluorinated photopolymer may comprise both acid-forming and an alcohol-forming precursor groups.

The copolymer may optionally include additional repeating units having other functional groups or purposes. For example, the copolymer may optionally include a repeating unit that adjusts some photopolymer or film property (e.g., solubility, Tg, light absorption, sensitization efficiency, adhesion, surface wetting, etch resistance, dielectric constant, branching and the like).

Many useful PAG compounds exist that may be added to a photopolymer composition. In the presence of proper exposure and 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 needs to 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 0.1 to 6% by weight relative to the copolymer. In an embodiment, the amount of PAG is in a range of 0.1 to 2% relative to the copolymer. Fluorinated PAGs are generally preferred and non-ionic PAGs are particularly useful. Some useful examples of PAG compounds include 2-

[2,2,3,3,4,4,5, 5-octafluoro- l-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorene (ONPF) and 2- [2,2,3,3,4,4,4-heptafluoro-l-(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. Suitable PAGs are not limited to those specifically mentioned above and some ionic PAGs can work, too. Combinations of two or more PAGs may be used as well.

EXAMPLES

Example 1

A number of etching fluids were tested for their ability to etch diF-TEG-

ADT (structure 1-2) and TIPS-pentacene (structure 1-3), two known organic semiconductors (OSC). A diF-TEG-ADT solution was prepared at 2% by weight in chlorobenzene, and a TIPS-pentacene solution was prepared at 2% by weight in toluene. The test solution was deposited onto clean glass using a spin coater, ramped up to 1000 rpm over 20 seconds. Each of the following siloxane compounds were tested as etch fluids: hexamethyldisiloxane (HMDSO),

decamethyltetrasiloxane, decamethylcyclopentasiloxane (DMCPSO),

octamethyltrisiloxane and octamethylcyclotetrasiloxane. In each case, the coated glass sample was dipped into the etch fluid for a controlled amount of time and observations were made about the removal or non-removal of the OSC. The color of the coated samples (red for diF-TEG-ADT and blue for TIPS-pentacene) made it evident when the organic material had been removed. Table 1 summarizes the observations for diF-TEG-ADT and shows that hexamethyldisiloxane is the strongest etchant for this material, while the other tested siloxane solvents are slower. To adjust the etch rate to achieve a target etch time, one can optionally dilute a more active siloxane etchant (e.g., HMDSO) in a less active siloxane etchant (e.g., DMCPSO).

Table 1 - Etch Fluid test for diF-TEG-ADT

Table 2 summarizes the observations for TIPS-pentacene and shows that hexamethyldisiloxane and octamethylcyclotetrasiloxane are relatively strong etchants for TIPS pentacene, while the other tested siloxane solvents are slower. As mentioned, etching time can be adjusted by varying combinations of these solvents to achieve the desired rate.

Table 2 - Etch Fluid Test for TIPS-Pentacene

Note that the etching times will vary with the crystallinity of the organic material, so etching times can be adjusted according to specific processes. In addition to the OSC materials tested above, other useful electronic/optical materials were found to have some solubility in HMDSO such as fluorene, coumarin 6, and various anthracene derivatives, especially those with aliphatic carbons.

Tetramethyltetraphenyltrisiloxane was found also to solubilize useful

electronic/optical materials and in some embodiments is preferred when the functional material has no aliphatic carbons.

Example 2

A glass substrate was prepared having a bottom (gate) layer of patterned silver, a polymer dielectric, and a top (source/drain) layer of patterned silver - a configuration similar to FIG. 5A. The silver contacts were treated with a thiol- containing self-assembled monolayer, and coated with the 2% w/w solution of diF- TEG-ADT in chlorobenzene. The solution was deposited using a spin coater, ramped up to 1000 rpm over 20 seconds. The OSC material formed reddish crystals over the structure upon drying of the chlorobenzene.

The barrier layer used in this example was OSCoR 4000 fluorinated photoresist. OSCoR 4000 is a photosensitive fluorinated photopolymer provided in a hydrofluoroether solvent along with a fluorinated non-ionic PAG. The fluorine content of the photosensitive fluoropolymer was about 42% by weight and the polymer included a carboxylic acid-forming precursor group. The resist was coated at 1000 rpm on a spin coater, and baked at 90 °C for 60 seconds. The sample was then exposed through a photomask to 365 nm light providing a dose of

approximately 108 mJ/cm². The sample was then post-exposure baked at 90 °C for 60 seconds. The sample was developed using two (2) 45 sec puddles and one (1) 20 sec puddle of Orthogonal Developer 103 (includes a hydrofluoroether solvent that is different from the OSCoR 4000 coating solvent), each followed by spin dry step. The patterned resist (720 μηι x 460 μιη) covered the silver contact regions and the portion in between, leaving the remaining OSC uncovered.

The etchant used in this example was 1 : 1 v/v hexamethyldisiloxane / decamethyltetrasiloxane. The etchant was puddled on the sample for two (2) 60 sec puddles and spun dry. The crystals in the resist-covered areas were visibly unchanged whereas the diF-TEG-ADT was almost completely removed in other portions. Microscope images showed no obvious undercutting of the etching solution under the patterned resist. In other experiments it has been found that there is a large window for etch times (robust process) because the rate of undercutting is very low with the siloxane etch fluid. The patterned resist was removed with two (2) 60 sec puddles of Orthogonal Stripper 900 (includes another HFE solvent) thereby forming a patterned organic semiconductor having a structure similar to that shown in FIG. 5A. The OSC material was compatible with all of the fluorinated solvents used, and the photoresist was not attacked by the etchant.

Comparison 1.

A sample was prepared as in Example 2, but instead of using the siloxane- based etching fluid, etching was carried out using toluene for 30 sec. The toluene rapidly undercut and completely dissolved the diF-TEG-ADT and partially lifted off the photoresist. Although toluene is an effective solvent for diF-TEG-ADT, it is a very poor etch fluid in this system.

Example 3

Example 3 was similar to Example 2 except that the etchant was 1 : 1 v/v hexamethyldisiloxane / decamethylcyclopentasiloxane. In this example, the etchant was puddled on the sample for three (3) 60 sec puddles and spun dry. The crystals in the resist-covered areas were visibly unchanged whereas the diF-TEG-ADT was almost completely removed in other portions. Microscope images showed no obvious undercutting of the etching solution under the patterned resist. The patterned resist was removed with two (2) 60 sec puddles of Orthogonal Stripper 900 (includes another HFE solvent) thereby forming a patterned organic

semiconductor having a structure similar to that shown in FIG. 5A. The OSC material was compatible with all of the fluorinated solvents used, and the photoresist was not attacked by the etchant.

Example 4

Example 4 was similar to Example 2 except that the etchant was 1 : 1 v/v hexamethyldisiloxane / octamethylcyclotetrasiloxane. In this example, the etchant was puddled on the sample for three (3) 60 sec puddles and spun dry. The crystals in the resist-covered areas were visibly unchanged whereas the diF-TEG-ADT was almost completely removed in other portions. Microscope images showed no obvious undercutting of the etching solution under the patterned resist. The patterned resist was removed with two (2) 60 sec puddles of Orthogonal Stripper 900 (includes another HFE solvent) thereby forming a patterned organic

semiconductor having a structure similar to that shown in FIG. 5A. The OSC material was compatible with all of the fluorinated solvents used, and the photoresist was not attacked by the etchant.

Example 5

Example 5 was similar to Example 2 except that the OSC was TIPS- pentacene (provided from a 2% w/w solution in toluene) and the etchant was 2: 1 v/v hexamethyldisiloxane / octmethylcyclotetrasiloxane. In this example, the etchant was puddled on the sample for two (2) 60 sec puddles and spun dry. The crystals in the resist-covered areas were visibly unchanged whereas the TIPS-pentacene was almost completely removed in other portions. Microscope images showed no obvious undercutting of the etching solution under the patterned resist. The patterned resist was removed with two (2) 60 sec puddles of Orthogonal Stripper 900 (includes another HFE solvent) thereby forming a patterned organic

semiconductor having a structure similar to that shown in FIG. 5A. The OSC material was compatible with all of the fluorinated solvents used, and the photoresist was not attacked by the etchant.

Comparison 2

A TIPS-pentacene film was provided over a silicon substrate. Over the TIPS-pentacene was coated a commercial negative photoresist (nLOF 2020 from AZ Electronic Materials). It was visibly evident that TIPS-pentacene layer was compromised. The photoresist was stripped using AZ Remover 100 and no TIPS- pentacene was present. The conventional solvents used in the photoresist and stripper dissolved the TIPS-pentacene and were therefore unsuitable.

Example 6

The etch barrier should not be attacked by the etch fluid. An exposed, negative-tone fluorinated photopolymer (OSCoR 4000) was tested by contact with the same etch fluids used in the Table 1 above. There was no measurable dissolution or obvious physical change in the fluorinated photopolymer when contacted with any of the etch fluids. Thus, these fluoropolymers are compatible with siloxane-containing etch fluids.

Example 7

As an etch fluid, a 1 : 1 volume mixture of HMDSO and HFE-7300 was prepared by diluting 5 mL of HMDSO to 10 mL with HFE-7300. A film of TIPS- pentacene was coated on a glass slide by spin coating a 2% w/w solution in toluene at 500 rpm. The OSC did not coat uniformly over the bare glass, but was nevertheless useful for the purposes of this experiment. The TIPS-pentacene film was treated with three (3) 30 sec puddles of the 1 : 1 HMDSO/HFE-7300 mixture, each followed by a spin dry step. In each puddle, dissolution of the TIPS-pentacene was clearly observed based on the blue color of the etch fluid. After the three puddles, thin areas of TIPS-pentacene were gone and thick areas were reduced in optical density. Treatment of a TIPS-pentacene film with HFE-7300 alone produced no sign of dissolution. The mixture, however, is a good etching fluid for OSC materials.

Example 8

In another test, thin films of OSCoR 4000 and OSCoR 3313 (both from Orthogonal, Inc.) were prepared on silicon chips by spin coating at 1000 rpm for 30 sec followed by a soft bake at 90 °C for 1 min. OSCoR 4000 has been previously described. OSCoR 3313 is a photosensitive fluorinated photopolymer provided in a hydrofluoroether solvent along with a fluorinated non-ionic PAG. The fluorine content of the photosensitive fluoropolymer was about 41 % by weight and the polymer included both a carboxylic acid-forming precursor group and an alcohol- forming precursor group. Half of the chip was exposed on a Pluvex 1410 UV exposure unit to a dose of -250 mJ/cm² as measured at 365 nm, followed by a 1 min post exposure bake at 90 °C. Film thicknesses were measured in both the exposed and unexposed areas using a Filmetrics F20 thin-film analyzer. The film thickness in the unexposed portion was approximately 1.9 μιη for OSCoR 3313 and 1.7 μι^η for OSCoR 4000. Three minutes after the post exposure bake, a sample was treated with a developing agent for a period of time (by applying a puddle) and spun dry. In the case of OSCoR 4000, the development time was 15 sec whereas for OSCoR 3313, the development time was 10 sec. Three different developing agents were used including neat HMDSO, neat HFE-7300 and the 1 : 1 v/v mixture of HMDSO / HFE-7300 described in Example 7. The exposed portions of the photosensitive fluoropolymers did not dissolve in any of the developing agents. The unexposed portions partially dissolved in HFE-7300 and the 1 : 1 mixture, but HMDSO alone did not dissolve any of the unexposed fluoropolymers. With one or two more additional puddles, the HFE-7300 and 1 : 1 mixture fully removed both unexposed fluoropolymer. Thus, HFE-7300 and the 1 : 1 mixture of HMDSO/HFE-7300 are effective developing agents, but HMDSO alone is not. Dissolution rates were measured for the unexposed areas and they are reported in Table 3.

Table 3

When taken with Example 7, Example 8 demonstrates that a mixture of a siloxane compound with a hydrofluoroether solvent can be used as a developing agent for a fluoropolymer and as an etchant for functional materials. Further, Example 8 shows an unexpected result that such mixtures can provide faster dissolution (development) rates of fluoropolymers than pure HFE alone, even though the pure siloxane has virtually no solubilizing power on its own.

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 Provide Layer of Functional Material step

4 Provide Etch Barrier Layer in First Pattern Over Layer of Functional Material to Form Intermediate Structure step 4a Provide Fluorinated Photopolymer Layer over Layer of Functional Material step

4b Expose Fluorinated Photopolymer Layer to Patterned Radiation step

4c Develop Exposed Fluorinated Photopolymer Layer to Form Intermediate Structure Having an Etch Barrier Layer in a First Pattern step 6 Contact Intermediate Structure with Etch Fluid to form Patterned Functional Material Layer step

8 Optionally Remove Etch Barrier Layer step

20 substrate

22 support

24 layer of functional material

26 fluorinated photopolymer layer

28 light

30 photomask

32 exposed fluorinated photopolymer layer

34 exposed areas

36 non-exposed areas

38 intermediate structure

40 first pattern of fluorinated photopolymer

42 second pattern of uncovered functional material

44 treated structure

46 patterned layer of functional material

48 patterned functional material structure

61 radiation

62 photomask

66 patterned layer of fiuoropolymer

124 functional material layer

142 pattern of uncovered functional material 160 non-patterned fluoropolymer

161 photosensitive second polymer

163 exposed layer of photosensitive second polymer

164 pattern of exposed photosensitive second polymer

165 pattern of unexposed photosensitive second polymer

166 patterned layer of second polymer

168 partially patterned bi layer structure

169 bilayer structure

210 substrate

212 organic semiconductor material layer

214 gate dielectric material layer

216 source electrode

218 drain electrode

220 gate electrode

Claims

1. A method of patterning a functional material layer in an electronic device, comprising:

providing a layer of a functional material;

providing an etch barrier layer in a first pattern over the layer of functional material, thereby forming an intermediate structure having a second pattern of uncovered functional material; and

contacting the intermediate structure with an etch fluid comprising a siloxane compound to selectively dissolve the second pattern of uncovered functional material, thereby forming a patterned functional material layer corresponding to the first pattern.

2. The method of claim 1 wherein the functional material is a conductor or semiconductor.

3. The method according to claims 1 or 2 wherein the functional material is organic and has a molecular weight of less than 1000 daltons.

4. The method according to any of claims 1 - 3 wherein the functional material is non-polymeric.

5. The method according to any of claims 1 - 4 wherein the functional material has at least one aliphatic carbon.

6. The method according to any of claims 1 - 5 wherein the functional material includes an alkyl silane, alkyl germane or a tertiary alkyl group.

7. The method according to any of claims 1 - 6 wherein the functional material includes an inorganic nanoparticle having an outer layer comprising an organic ligand, an organic coating, an alkyl silane group, an alkyl germane group or a tertiary alkyl group.

8. The method according to any of claims 1 - 7 wherein the etch barrier is an organic polymer.

9. The method according to any of claims 1 - 8 wherein the etch barrier is formed from a photosensitive resin.

10. The method according to any of claims 1 - 9 wherein the etch barrier is formed in the first pattern by applying a photopolymer layer from a coating solvent, exposing the photopolymer layer to patterned radiation, and developing the exposed photopolymer layer in a developing agent comprising a developing solvent.

1 1 . The method according to claim 10 wherein the photopolymer, the coating solvent and the developing solvent are fluorinated.

12. The method according to claim 10 or 1 1 wherein the developing agent is also the etch fluid.

13. The method according to any of claims 1 - 8 wherein the etch barrier is pattern-applied by ink jet printing, flexographic printing or thermal transfer from a donor sheet.

14. The method according to any of claims 1 - 13 wherein the etch fluid has a melting point less than 15 °C and a boiling point greater than 50 °C.

15. The method according to any of claims 1 - 14 wherein the etch fluid comprises a mixture of two or more siloxane compounds, wherein one siloxane compound is a more active etchant than the other siloxane compound(s).

16. The method according to any of claims 1 - 15 wherein at least one siloxane compound has at least one alkyl group.

17. The method according to any of claims 1 - 16 wherein at least one siloxane compound is selected from the group consisting of hexamethyldisiloxane, hexaethyldisiloxane, octamethyltrisiloxane, octamethylcyclotetrasiloxane, decamethyltetrasiloxane, decamethylcyclopentasiloxane, and

tetramethyltetraphyltrisiloxane.

18. The method according to any of claims 1 - 17 wherein the functional material has at least one aliphatic carbon and at least one siloxane compound has at least as many alkyl groups as aryl groups.

19. The method according to any of claims 1 - 17 wherein the functional material has no aliphatic carbon atoms and at least one siloxane compound has at least as many aryl groups as alkyl groups.

20. The method according to any of claims 1 - 18 wherein at least one siloxane compound is a disiloxane.

21 . The method according to any of claims 1 - 20 wherein the etch fluid further comprises a non-siloxane solvent.

22. The method according to any of claims 1 - 21 wherein the etch fluid is an azeotrope of a siloxane compound and a non-siloxane solvent.

23. The method according to any of claims 1 - 22 wherein the etch fluid further comprises a hydrofluoroether solvent.

24. An organic semiconductor patterning system comprising:

an etch fluid composition comprising a siloxane compound; and either a) a coatable semiconductor composition comprising an organic semiconductor material provided in a coating solvent, or b) a coatable resist composition comprising a fluoropolymer and a fluorinated solvent, or both (a) and (b).

25. The patterning system of claim 24 wherein the fluoropolymer is a photosensitive fluoropolymer.