CA2238833A1 - Photosensitive composition - Google Patents
Photosensitive composition Download PDFInfo
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- CA2238833A1 CA2238833A1 CA002238833A CA2238833A CA2238833A1 CA 2238833 A1 CA2238833 A1 CA 2238833A1 CA 002238833 A CA002238833 A CA 002238833A CA 2238833 A CA2238833 A CA 2238833A CA 2238833 A1 CA2238833 A1 CA 2238833A1
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/004—Photosensitive materials
- G03F7/039—Macromolecular compounds which are photodegradable, e.g. positive electron resists
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/36—Sulfur-, selenium-, or tellurium-containing compounds
- C08K5/41—Compounds containing sulfur bound to oxygen
- C08K5/42—Sulfonic acids; Derivatives thereof
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/004—Photosensitive materials
- G03F7/0045—Photosensitive materials with organic non-macromolecular light-sensitive compounds not otherwise provided for, e.g. dissolution inhibitors
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/0073—Masks not provided for in groups H05K3/02 - H05K3/46, e.g. for photomechanical production of patterned surfaces
- H05K3/0076—Masks not provided for in groups H05K3/02 - H05K3/46, e.g. for photomechanical production of patterned surfaces characterised by the composition of the mask
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/02—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding
- H05K3/06—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding the conductive material being removed chemically or electrolytically, e.g. by photo-etch process
- H05K3/061—Etching masks
- H05K3/064—Photoresists
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- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Spectroscopy & Molecular Physics (AREA)
- General Physics & Mathematics (AREA)
- Medicinal Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Materials For Photolithography (AREA)
- Manufacturing Of Printed Circuit Boards (AREA)
- Acyclic And Carbocyclic Compounds In Medicinal Compositions (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
The invention relates to photosensitive compositions capable of being developed as positives. Conventional compositions are either insufficiently photosensitive or unsuitable for use on copper surfaces such as those in printed circuit boards, since the exposed regions of the composition layer cannot be completely removed during development and create problems in the subsequent metal-coating or etching operations. These drawbacks are not found with the claimed photosensitive compositions. Various compositions are described containing photo-acid generators and a polymer resin containing acid-cleavable side groups and formed by polymerisation of at least three different acrylate or methacrylate monomers.
Description
CA 02238833 1998-0~-27 .
Photosensitive Composition Specification:
The invention reiates to photosensitive compositions and their use as etching orgalvano resist in the structuring of metal coatings on electrical circuit-substrates.
In order to structure metal coatings, for example copper coatings on circuit board laminates, photosensitive lacquers or foils are used preferably, which cover thecopper coatings during etching, so that the latter can be protected with respect to the etching solutions (Panel-Plating-Process, Print-and-Etch Process).
In this case these resists serve as etching protection. For this purpose, the circuit board surfaces or the laminates which serve as the circuit board inner coatings are coated with the resist film, then exposed with the conductive pattern, developed and the uncovered copper surfaces removed by etching. Subsequently the resist which is being used as an etching mask can be removed again.
In another type of method (Pattern-Plating-Process) the resists are applied, before the further metal application, on to the substrates which are to be coated (galvano resists) and then exposed with the conductive pattern and developed. After that,further metal can be deposited on to the uncovered copper surfaces.
In the past, in the construction of circuit conductor track structures, resist types were predominantly used which were developed after exposure with the metal structure about to be produced by means of organic solvents. In this process solvents, which besides water included esters, organic carbonates, ethers or acetates, were preferably used. Recently resist types have been introduced which can be developed by means of aqueous-alkaline solutions, since these developing solutions are easier to handle in effluent treatment. Moreover, they also offer advantages with respect to the protection of personnel since no volatile organic compounds, which are harmful to health, are contained in the solutions.
As a rule so-called negative resists are used, which are hardened by exposure sothat after subsequent developing the resist regions, which were not exposed, can be CA 02238833 1998-0~-27 .
removed. The disadvantage of negative resists lies in the fact that the protective effect of the resists only occurs after photo-hardening. For example, dust particles can prevent the photo-hardening during exposure at certain places, with the result that holes occur in the resist surface in these places during development. This susceptibility to error can be avoided by using larger resist coating thicknesses.
Admittedly, the photographic resoiution of the resist, for example, reduces thenbecause of light seattering in the resist coating. Another possibility for avoiding the probiem consists of increasing the purity of the ambient air. However this uses a lot of resources and is therefore costly. Therefore a certain proportion of circuit boards, which are produced with a negative resist, must be examined for error, possibly even within the manufacturing process after exposure and developing of the resist, inorder to expose defects of this type.
Furthermore, negative resists for use in the Panel-Plating-Process are used only as foil and therefore protect the holes, which are contained in the circuit boards, against the copper etching solutions such that the resist foil covers the hole entrances(Tenting Process). An alternative type of method, in which the negative resist is deposited on to the hole walls directly and remains there for the protection of the copper coatings, even during the subsequent copper etching procedure, is by comparison not practicable, since the resist which is in the holes for this purpose would need to be exposed. This is however not possible on a reliable basis, particularly not in smallish holes with rough hole walls. In the Tenting Process it is essential that the resist foil regions which cover the holes, have an adequately large supporting area round the hole entrances for a copper ring to be placed round the hole entrances at these points even during subsequent etching, said copper ring however occupying unnecessary space on the circuit board.
When using a positive resist, in which the film, which is deposited on the surfaces about to be constructed, is at first insoluble in the developing solutions and only converted into a soluble state by exposure, the problems which have been mentioned exist to a far lesser extent.
In particular, it is possible by means of positive resists to metallise holes in circuit -CA 02238833 1998-0~-27 .
boards using the Panel-Plating-Process without residual rings being left round the hole entrances. In this way considerably finer circuit patterns are made possible.
Furthermore, it has emerged that, with positive resists, a better photographic resolution can be obtained by means of more precise definition of the structure edges.
The effect of negative and positive resists is depicted in greater detail in W. M.
Moreau, Semiconductor Lithography, Plenum Press, 1988.
Typical positive photoresists normally contain novolaks as polymers. For example, resists of this type are described in US-PS 52 66 440.
These photoresists are however not particularly light sensitive, so that long exposure times or high light intensities must be accepted. For example, in order to expose circuit boards which are coated with traditional positive resists, light intensities of about 350 mJ/cm2are required, while, when using negative resists, normally values of about 100 mJ/cm2 suffice (c.f. Nakahara, Electronic Packaging & Production, 1992, pp. 66 ff).
In recent times positive resists are described, the photosensitivity of which depends on light-induced proton splitt-off in certain organic acids and consequent acid cleavage of side groups of the polymer consisting the resist generating soluble compounds in aqueous-alkaline solutions. The photosensitivity of these resist types is considerably higher that that of the previously mentioned types.
The principle of these resists described as "Photoresiste mit chemischer Verstarkung" (Amplifikation- "chemically amplified photoresists") is described in G.
M. Wallraff et.al., "Designing tomorrow's photoresists", Chemtech, 1993, pp. 22 to 30. According to this, organic onium salts, for example, diphenyliodonium-hexafluoroantimonate are used as acid generators which are split by UV radiation.
Polyacrylates are used preferably as acid-cleavable polymers, said polyacrylatescontaining tert.-butyl-groups as carbon acid ester side groups which are split off by acid catalysis. In this process polar carbon acid side groups emerge, which cause CA 02238833 1998-0~-27 .
the higher solubility of the polymer in an aqueous solution.
In US-PS 44 91 628, a resist composition operating according to the previously mentioned principle is shown, said resist composition containing, as well as the acid generator, an acid-cleavable polymer. As a polymer, compounds with phenols or styrenes with tert.-butylester-groups, for example poly-(tert.-butoxycarbonyloxystyrene) are suggested. As acid generators, diaryliodonium- andtriarylsulfonium- metal halogenides are used.
In EP O 445 058 A1 photoresists are described, which are catalysed by acid cleavage and which, besides an acid generator, contain acid-cleavable polymers for example polystyrenes with tert.-butoxycarbonyloxy-groups. Organic onium salts for example aryldiazonium-, diaryliodonium-, and triarylsulfonium- metal halogenides are suggested as acid generators.
In EP O 568 827 A2, a pattern-forming composition is described which can also bedeposited electrica!ly and which, besides an acid generator, also contains polystyrenes as acid-cleavable polymers, namely phenolic resins, for example novolaks with tert.-butoxycarbonyloxy-groups.
In US-PS 52 72 042 positive resists are described, which likewise contain polystyrenes with tert.-butoxycarbonyl-groups, as well as those which contain, as acid-cleavable polymers, polyacrylates with tert.-butoxycarbonyl-groups as side groups. N-hydroxyamides and N-hydroxyimides, for example N-trifluoromethyl sulfonyloxynaphthalimide are used as acid generators. In order to make the photoresist sensitive to visible light as well, an anthracene derivative is also used as a photosensitizer, for example 9,10-bis-(trimethylsilytethinyl)-anthracene.
In US-PS 50 71 730 a positive resist is likewise described which, besides an acid generator, (aryldiazonium-, diaryliodonium-, triarylsulfonium- metal halogenide), and photosensitisers (pyrene, perylene) contains an acid-cleavable polymer. A
polyacrylate, which is formed from three different acrylates, namely tert.-butylacrylate or tert.-butylmethacrylate, methylacrylate or methylmethacrylate and acryl- or CA 02238833 1998-0~-27 .
methacryl- acid is suggested as a polymer.
In US-PS 50 45 431 a composition is shown which is very similar to the previously mentioned resist, the polymer of which is formed likewise from acrylate compounds and contains ethylacrylate or butylacrylate as possible additional acrylate units in the polymer chain.
In US-PS 52 30 984 there is a resin composition, serving to form a depositable photoresist by means of electrophoresis, said resin composition consisting of acryl-or methacryl- acid, also tert.-alkylacryiate or tert.-alkylmethacrylate and also a monomer which can be polymerised, the latter as a homopolymer having a glass transition temperature of 0~C or lower. Among others, ethyl acrylate, propylacrylate, iso-butylacrylate and higher homologues are mentioned as monomers of this type.
As photo acid generators, phosphonium-, sulphonium-, diazonium-, iodonium- saltsand oxazole derivatives among others are suggested.
It has emerged, that the known positive resists, which are applied to the coppersurfaces of circuit boards, cannot be removed from the copper surfaces without leaving residues during developing of the exposed regions. Even after an extended exposure time or increased light intensity during exposure, residues on the copper surfaces cannot be entirely removed, at least not when the resist film is treated during exposure within the parameters which are required for achieving a satisfactory exposure result (exposure time, light intensity). In particular, a resist coating Iying directly on the copper surface during developing cannot be removedentirely and with assurance, so that, in the subsequent etching during the Panel-Plating-Process or in the subsequent electrolytic plating Pattern-Plating-Process, problems arise. The residues which cannot be removed lead to defective adhesion of the subsequently deposited metal coating to the copper surfaces or to unsatisfactory etching results, since the residues impede the etching process. In a particularly unfortunate scenario, no further metal coatings at all are deposited in these places or the copper coating is not attacked at all in the etching process.
Problems of this sort do not occur in the structoring of semiconductor substrates.
-CA 02238833 1998-0~-27 Furthermore, the contrast between exposed and unexposed places in traditional photoresists is only partly insufficiently small, with the result that the contour definition is not adequate. In addition, known resist coatings do not have sumcient resistance to chemicals, above all against acid etching solutions, since often a compromise between adequate ease of developing in alkaline solutions and resistance to chemicals must be found. Moreover, known resists also suffer from an increased susceptibility to the effects of dust and other impurities which are deposited on the resist coatings during exposure and thus prevent exposure. In positive resists, contaminations of this type normally lead to undeveloped places in the exposed regions, so that, in the production of circuit boards, metal deposition cannot proceed in these regions. In the production of semiconductor circuits this increased defect frequency does not play a highly significant part, since the procedure is done in any case in highly purified air.
The highest requirements in the purity of the air during production of circuit boards cannot however be met.
The problem underlying the present invention resides thus in avoiding the disadvantages of the known methods and particularly in making available a resist composition, which can be removed from the copper surfaces, for example of a circuit board, without leaving any residues during developing, so that the further treatment steps can be carried out without any impairment caused by residues from the photo resist. Furthermore, it must also be guaranteed that the photo resist coating adheres sumciently well to the copper surfaces. In particular, the unexposed resist coating which is not removed CA 02238833 1998 - 0~ - 27 during the subsequent developing process must also withstand further chemical treatment steps without damage, must have a good contrast between exposed and unexposed areas, and must be as unreceptive as possible to contamination during developing.
The problem is solved by photosensitive compositions according to Patent claims 1, 4, 5, 6, 7 and 12. Advantageous embodiments of the invention are indicated in the sub-claims.
The resist variants according to the invention, in addition to at least one photoacid generator, contain at least one polymer with acid-cleavable side groups, and which is converted into a soluble condition by the acid of the photoacid generator released during exposure.
The polymer, preferably copolymer, is formed from various monomers in order to fulfil the object according to the invention. The polymer is formed from the following fractions of monomers, relative to the polymer:
1 st Variant:
A - Monomers selected from the group of compounds acrylic acid and methacrylic acid, with a fraction of 8 mol-% to 20 mol-%.
B - Monomers selected from the group of compounds tert.-butacrylate and tert.-butylmethacrylate, with a fraction of 19 CA 02238833 1998-0~-27 7a mol-% to 70 mol-% and C - Monomers selected from the group of compounds hydroxyethylmethacrylate, hydroxypropylmethacrylate, hydroxyphenylmethacrylate, hydroxyethylacrylate, hydroxypropylacrylate and hydroxyphenylacrylate with a fraction of 1% by mol to 30% by mol.
The acid-cleavable polymer can contain in addition to the previously mentioned monomers, D- Monomers selected from the group of compounds methylacrylate and methylmethacrylate with a fraction of 10% by mol to 60% by mol.
Moreover, the acid-cleavable polymer, can further contain in addition to the previously mentioned monomers A, B, C and D
E- Monomers selected from the group of compounds wth the general formula CH2=CR1-COOR2, where R1 is a hydrogen atom or a methyl group and R2 is a linear or branched alkyl group with at least three carbon atoms, with a fraction of 3% by mol to 35% by mol.
CA 02238833 1998-0~-27 .
2nd Variant:
A- Monomers selected from the group of compounds acrylic acid and methacrylic acid, with a fraction of 10% by mol to 25% by mol, B- Monomers selected from the group of compounds tert.-butylacrylate and tert.-butylmethacrylate with a fraction of 17% by mol to 40% by mol, D- Monomers, selected from the group of compounds methylacrylate and methylmethacrylate with a fraction of 20% by mol to 60% by mol and E- Monomers selected from the group of compounds with the general formula CH2= CR'-COOR2, where R' is a hydrogen atom or a methyl group and R2 is a linear or branched alkyl group with at least five carbon atoms, with a fraction of 1% by mol to 35% by mol.
3rd Variant:
A- Monomers selected from the group of compounds acrylic acid and methacrylic acid, with a fraction of 14% by mol to 20% by mol, B- Monomers selected from the group of compounds tert.-butylacrylate and tert.-butylmethacrylate with a fraction of 20% by mol to 32% by mol, D- Monomers, selected from the group of compounds methylacrylate and methylmethacrylate with a fraction of 30% by mol to 50% by mol and E- Monomers selected from the group of compounds with the general formula CH2= CR'-COOR2, where R' is a hydrogen atom or a methyl group and R2 is a linear or branched alkyl group with two to four carbon atoms with a fraction of 10% by mol to 40% by mol CA 02238833 1998-0~-27 4th Variant:
A- Monomers selected from the group of compounds acrylic acid and methacrylic acid, with a fraction of 14% by mol to 19% by mol, B- Monomers selected from the group of compounds tert.-butylacrylate and tert.-butylmethacrylate with a fraction of 26% by mol to 40% by mol, D- Monomers, selected from the group of compounds methylacrylate and methylmethacrylate with a fraction of 40% by mol to 55% by mol, preferably from 50% by mol to 55% by mol, 5th Variant:
A- Monomers selected from the group of compounds acrylic acid and methacrylic acid, with a fraction of 13% by mol to 15% by mol, B- Monomers selected from the group of compounds tert.-butylacrylate and tert.-butylmethacrylate with a fraction of 22.5% by mol to 30% by mol, D- Monomers, selected from the group of compounds methylacrylate and methylmethacrylate with a fraction of 50% by mol to 65% by mol.
With the previously mentioned compositions, which include, besides the photo acid generator, at least one of the described polymers, photoresists are obtained with the following characteristics:
a. In an exposed state, the resist coating can be removed with no problem from the underlying copper coating by using developing solutions. No residues remain on the copper surface. Since the polymer contains tert.-butylacrylate and/or tert.-butylmethacrylate, the solubility of the resist coating increases in aqueous developing solutions during exposure.
b. In the unexposed state the resists withstand the treating solutions which arenormally used in an electroplating process. In particular the resist coating has a high CA 02238833 1998-0~-27 .
adhesion to the copper coating of a circuit board. Because of the carbon acid proportion in the polymer, namely the proportion of acrylic acid and methacrylic acid, the adhesion of the resist on to the copper surface increases, by means of which the danger of chemicals undercutting the resist coating is reduced. On the other hand, the solubility of the resist in aqueous developing solutions is reduced when theproportion of carbon acid in the polymer is reduced.
By using hydrophobic monomer components in the monomer, which contain at least three carbon atoms in the side chain of the acrylate according to the 1st polymer variant, the resistance of the unexposed composition to chemical treating medium(aqueous treating solutions with pH values of 0 to 13) is increased. The same adaptation of the exposed and unexposed regions in the photoresist according to the invention can furthermore be achieved by adjusting the balance between the content of hydrophilic and hydrophobic components (also side chains with at least two carbon atoms) in the polymer with further monomers. By means of the polymersaccording to the invention, an increased contrast of the resists during exposure is achieved and also an exceptionally high chemical resistance of the developed coatings. For example, a developed coating of the resist according to the invention on a circuit board covered with a copper lamination can even withstand being situated for several hours in a hydrochloric acid / copper-(ll)-chloride solution which is normally used for etching copper. Admittedly, undercuts are formed in this situation on the flanks of the developed structures, which result from sideways corrosion from the etching medium on to the copper lamination. However, the resist coating adheres moreover to the copper lamination without defect.
c. In addition, a substantially smaller defect rate is attained than with traditional resists, said defect rate being caused by dust contamination and other impurities on the resist surface during developing.
d. Furthermore, the unexposed resist coating can be removed again from the substrate surface by appropriate solutions (strippers).
e. The resists have a high light sensitivity. The polymers according to the invention CA 02238833 1998-0~-27 furthermore have the advantage of a high transparency, with the result that light in the resist coating is only scattered a little. For this reason, a high contour definition is achieved during exposure and subsequent developing, which leads to outstanding definition and excellent photographic resolution capability. The contrast increases with the proportion of tert.-butylacrylate or tert.-butylmethacrylate during development of the resist.
f. By means of appropriate composition of the polymer from certain monomers, it is possible to make polymers with an appropriate glass transition temperature T~
between 40~C and 1 50~C. Since the photosensitive composition according to the invention is heated during the application process on the surfaces about to be structured, the resulting coatings can be formed by partial softening as uniformly thick films, which are free of air bubbles, inclusions or other interfering impurities.
Moreover, by means of a glass temperature in the given range, a resist coating is made possible which is mechanically capable of resistance in a cold state and which is flexible in a warm state.
The glass transition temperatures of the resist coatings Iying within the given range further make possible an unproblematic transfer of the resist coatings, which are deposited on polymer carrier films, on to the substrate surface for use as dry resists.
Too low a glass transition temperature would lead further to the composition delivering unusable images. Too high a temperature would lead to greater strength of the resist coating and also to very high transfer temperatures (transfer of the resist coating from a carrier on to the substrate) and glazing temperatures.
g. The resist coatings formed from the compositions according to the invention can be developed with aqueous-alkaline solutions or completely removed. Organic solvents are not required, in particular no chlorinated hydrocarbons.
The photosensitive polymers have average molecular weight Mw of 30,000 to 90,000, preferably 35,000 to 82,000.
The molecular weight distribution of the polymers can be described by a poly-CA 02238833 1998-0~-27 .
molecularity index Pl, which gives the ratio of the average molecular weight Mw of the polymer to the number average of the molecular weight M". The poly-molecularity index Pl describes the range of the molecular weight distribution (c.f. also for this M.Hoffmann, H. ~Croner, R. Kuhn in Polymeranalytik 1, p. 34, G. Thieme Verlag, Deutschland, 1977). The poly-molecularity index Pl of the polymers according to the invention has a value of 1.6 to 3.1, preferably 2.1 to 3Ø
These characteristics are influenced by a large number of reaction parameters, for example by the choice of solvent, the choice of reaction temperature and the type of reaction initiator (for example of the peroxide compound) in the polymerisation of monomer mixtures according to the invention. An indication of the mechanism for controlling the poly-molecularity index Pl is given in H. G. Glas, Makromolekule, p.
487, Huthig-Verlag, Deutschland, 1990. Small values for poly-molecularity index Pl reflect a narrow molecular weight distribution.
The normal compounds may be used as photo acid generators, for example N-trifluoromethylsulfonyloxynaphthalimide (NIT) F~ F
O' ~0 O~, N ~O
~3 and other trifluoromethylsulfonyloxyimide derivatives such as xF
Fo,S~' O ,~
~1~1 ~~
further, triiluoromethylsulphonyloxy-bicyclo[2.2. 1 ]-hept-5-en-2,3-dicarboximide (MDT), naphthoquinone-1,2-diazide-4-sulphonic acid ester, for example 1-naphthalinesulphonic acid-3-diazo-3,4-dihydro4-oxoester with phenyl-(2,3,4-trihydroxypheny)-methanone. Further N-trifluormethylsulfonyloxyimide derivativesare given in J.M.J. Fréchet, Pure and Appl. Chem., 64, pp. 1239-1248 also in US-PS 52 72 042, for example, o XN~
~--s=c~
A o DNQ, with A = aromatic residue and .
a ~N
~ ~ <~
[3~ 3~=
o--s--a N
,~, CNQ-P.
Furthermore, 1,2,3-benzene-tris-(sulphonic acid trifluoromethylester), 1,2,3-benzene-tris-(sulphonic acid methylester), 6,7-bis-(trifluoromethylsulphonyloxy)-coumarin, 2,3,4-tris-(fiuoromethylsulphonyloxy)-benzophenone are suitable as photo acid generators as well as those photo acid generators described in EP-A 0 489 560.
The synthesis of photo acid generators is amongst others described in EP-A 0 058638 as well as in J.M.J. Fréchet, Pure and Appl.Chem., 64, pp.1239 to 1248.
The content of photo acid generators in the photosensitive composition is 1 % byweight to 25% by weight, preferably 2% by weight to 20% by weight, relating to the weight of the polymer in the composition.
CA 02238833 1998-0~-27 .
In the photosensitive composition, further components are included besides the photo acid generators and the polymer:
In order to also make the composition sensitive to light with a certain spectraldistribution of intensity, preferably in the visible range (330nm to 440nm) one or a plurality of photo sensitisers are added to the composition. The main concern here is polycyclic aromatic compounds for example anthracene, 9-anthracene methanol, 1,4-dimethoxyanthracene, 9,10-diethylanthracene, 9-phenoxymethylanthracene and 9,10-bis-(ethinyl)-anthrancenes, such forexample as 9,10-bis-(trimethylsilylethinyl)-anthracene, by means of which the light sensitivity of the photosensitive compositions, preferably to red light, is greatly increased.
These photosensitisers are used preferably in concentrations of 1% by weight to 6%
by weight, preferably of 2% by weight to 4% by weight, reiating to the weight of the polymer in the composition.
Furthermore, the compositions according to the invention can also contain dyes, to improve the perceptibility of the resist, even in a thin coating on the substrate which is about to be structured, and also contain further components which are normal for photoresist materials.
The compositions which can be used as resists are used for example as liquid formulations. For this purpose, they are mixed with appropriate solvents, for example ethers, ether alcohols or ether esters. For example, propylene glycol monomethylether acetate, 1-methoxy-2-propanol, ethyl lactate, 3-ethoxypropionate, ethylene glycol monoethyl ether acetate, methoxybutanol, diethylene glycol monoalkylether and propylene glycol monobutylether are used as solvents.
The liquid composition is deposited on the surfaces which are to be coated for example by spinning-on (Spin-coating). Another deposition technique is the roller coating procedure in which the composition first of all moistens a first roller with a thin coating, the liquid being deposited by means of wringers on to the roller at a defined thickness. From this roller the coating is conveyed next, through direct -CA 02238833 1998-0~-27 contact of the roller with the substrate on to the latter. In this way, a uniformly thick film can also be formed on large-surface flat substrate surfaces. Normally coating thicknesses of the composition of 3,um to 20,um are used.
The roller coating procedure has the advantage that unproblematically defined coating thicknesses of the resist can be used on plate-shaped substrates, for example circuit boards. Moreover, the substrates can be conveyed in a horizontalposition and direction through the coating unit. Coating units of this type can be connected furthermore with other horizontal units for the further treatment steps in producing the metal structures with the result that the substrates can be handled more easily with the possibility of automation.
Furthermore, the liquid composition can be deposited on the substrate also by submerging it. There is a problem however here in that coating thicknesses are set which are variable and not controllable at the edges.
The compositions according to the invention can be deposited however, for use inthe dry film technique also, on to a polymer carrier film, for example on to a polyester foil. From the latter, the composition can be conveyed by direct contact of the photosensitive coating, which is deposited on the foil, to the substrate which is to be structured, for example by pressing.
AKer coating the substrate with the composition, the resist coating which is formed is dried by the effect of heat, for example in a forced-air oven or by means of infra-red radiation. AKer that, the coating is coated with the template, then heated again, to accelerate the formation of the latent pattern (Reheating)1 and subsequently thecoated regions in the resist coating are dissolved away during developing. For this purpose spraying units are used preferably, by means of which the developing solution is sprayed on to the substrate surfaces via jets. Aqueous-alkaline solutions are preferably used as developing solutions, for example sodium carbonate solution.
The photosensitive compositions can be used as etching or galvanoresists for making metal coatings, for example for producing electrical circuit carriers. The CA 02238833 1998-0~-27 .
further processes for producing the desired metal structures endorse the mentioned procedural steps, for example etching processes or further electrolytic metal deposition procedures, in which, in the resist channels which are formed, the uncovered metal surfaces are removed by etching processes or are constructed further by means of electrolytic deposition procedures.
A further use of the photosensitive compositions resides in their use as an galvanoresist in the additive process, preferably for the photo-structuring of substrates from epoxy resins, acrylonitrile-butadiene-styrene-copolymers (ABS) and polyimide. Metal structures are thus produced by means of electroless plating baths in the resist channels, which are fommed by exposure and developing.
After completion of the structuring method the resist coating is removed again from the substrate surfaces preferably by means of aqueous-alkaline solutions, for example a caustic soda solution.
The compositions according to the invention are used for making metal coatings on electric circuit carriers, for example on epoxy resin-, polyimide- laminates or their composites as well as for decorative purposes on metal and plastic material substrates. In a preferred application, the compositions are used for producing circuit boards provided with copper surfaces and inner layerlaminates to be used for circuit boards.
The following examples serve to explain the invention:
Example 1 ( Polymer synthesis for producing a dry substance):
In order to produce the acrylate polymers according to the invention, tetrahydrofuran (THF) and azo-bis-isobutyronitrile (AIBN) were first placed in a double-necked flask.
Then the monomers were added. The reaction mixture was kept hermetically sealed during the entire duration of the reaction. The ratios of the amounts used for producing a polymer according to the invention are given in the following table CA 02238833 1998-0~-27 .
Component Quantity in parts by weight AIBN 1 .956 methacrylic acid 64.2 tert.-butylmethacrylate 1 28.4 methylmethacrylate 1 28.4 butylacrylate 1 34.7 hydroxypropylmethacrylate 33.3 At the start of the polymerisation reaction the mixture was heated. The mixture was refluxed for 24 hours, the conversion was 100% after the reaction was finished.
AKer completion of the reaction the polymer was precipitated with petroleum benzene. After separation, a colourless powder was obtained, which was dried in a vacuum for 48 hours at 60~C to 70~C.
The polymers given in Table 1 were also produced, furthermore, using the presently described method.
Example 2 (Polymer synthesis for the direct use of the reaction solution as photoresist base):
The procedure was as in Example 1. However propylene glycol monomethylether acetate (PGMEA) was used as solution medium instead of THF. The following ratiosof the amounts of individual components were used to produce the polymer.
CA 02238833 1998-0C,-27 Component Quantity in parts by weight AIBN 0.652 methacrylic acid 21.4 tert.-butylmethacrylate 42.8 Methylmethacrylate 42.8 butylacrylate 44.9 hydroxypropylmethacrylate 11 . 1 At the start of the polymerisation reaction the mixture was heated to 100~ C. The mixture was heated for 26 hours, the conversion was 100%. A polymer with the same composition as the polymer produced using the method according to Example 1 was obtained. The polymers given in Table 1 were also produced, using the presently described method.
Instead of the solvents used in Examples 1 and 2, in polymerisation, dioxane, cyclohexanone or heptane were used as selvents. Instead of azo-bis-isobutyronitrile (AIBN), benzoyl-peroxide or other radical initiators can be used. The completeness of the reaction is thus dependent on the solvent used, on the reaction temperature, on the type of initiator and the duration of the reaction.
Example 3 (Production of a liquid photoresist composition, photosensitive resist):
In the yellow-light area 30 parts by weight N-trifluoromethylsulfonyloxynaphthalimide (NIT) as acid generator and 20 parts by weight 9-anthracenemethanol (AM) as sensitiser were mixed with 1000 parts by weight of a solution of polymer, obtained according to Example 1 in propylene glycol monomethylether acetate, with a solution having a solids content of approx. 25% by weight (20 to 30% by weight).
In another embodiment, a polymer solution with 20% by weight and 30% by weight, resp., was used instead of a polymer solution with 25% by weight.
CA 02238833 1998-0~-27 .
In a further experiment, 200 parts by weight 4-diazonaphthoquinone sulphonicacidester was used instead of NIT and AM.
Furthermore, appropriate polymer soiutions, which were obtained by dissolving the polymer dry substance, obtained according to Example 1, in 1-methoxy-2-propanol with the same solids contents, were used to produce the liquid photopolymer compositions.
Example 4 (Use of the photoresist composition according to Example 3 for structuring circuit boards):
A circuit board base material was used which was made by the company Allied Signal Norplex Oak, USA with the type designation ED 130, which had on both sides a 18 I~m.thick copper laminate (corresponding to the US Military specihcation MIL S 13949). The base material was treated according to the following procedure:
1. Pre-treatment: a- etch cleaning with Scheretch M
(Product of company Atotech Deutschland GmbH, Berlin, DE) 20-25~C
b- Rinsing with water 25~C
c- Pickling with HzSO4 25~C
d- Rinsing with water 25~C
e- compressed-air drying f- drying in circulated-air oven (5 min) 80~C
Photosensitive Composition Specification:
The invention reiates to photosensitive compositions and their use as etching orgalvano resist in the structuring of metal coatings on electrical circuit-substrates.
In order to structure metal coatings, for example copper coatings on circuit board laminates, photosensitive lacquers or foils are used preferably, which cover thecopper coatings during etching, so that the latter can be protected with respect to the etching solutions (Panel-Plating-Process, Print-and-Etch Process).
In this case these resists serve as etching protection. For this purpose, the circuit board surfaces or the laminates which serve as the circuit board inner coatings are coated with the resist film, then exposed with the conductive pattern, developed and the uncovered copper surfaces removed by etching. Subsequently the resist which is being used as an etching mask can be removed again.
In another type of method (Pattern-Plating-Process) the resists are applied, before the further metal application, on to the substrates which are to be coated (galvano resists) and then exposed with the conductive pattern and developed. After that,further metal can be deposited on to the uncovered copper surfaces.
In the past, in the construction of circuit conductor track structures, resist types were predominantly used which were developed after exposure with the metal structure about to be produced by means of organic solvents. In this process solvents, which besides water included esters, organic carbonates, ethers or acetates, were preferably used. Recently resist types have been introduced which can be developed by means of aqueous-alkaline solutions, since these developing solutions are easier to handle in effluent treatment. Moreover, they also offer advantages with respect to the protection of personnel since no volatile organic compounds, which are harmful to health, are contained in the solutions.
As a rule so-called negative resists are used, which are hardened by exposure sothat after subsequent developing the resist regions, which were not exposed, can be CA 02238833 1998-0~-27 .
removed. The disadvantage of negative resists lies in the fact that the protective effect of the resists only occurs after photo-hardening. For example, dust particles can prevent the photo-hardening during exposure at certain places, with the result that holes occur in the resist surface in these places during development. This susceptibility to error can be avoided by using larger resist coating thicknesses.
Admittedly, the photographic resoiution of the resist, for example, reduces thenbecause of light seattering in the resist coating. Another possibility for avoiding the probiem consists of increasing the purity of the ambient air. However this uses a lot of resources and is therefore costly. Therefore a certain proportion of circuit boards, which are produced with a negative resist, must be examined for error, possibly even within the manufacturing process after exposure and developing of the resist, inorder to expose defects of this type.
Furthermore, negative resists for use in the Panel-Plating-Process are used only as foil and therefore protect the holes, which are contained in the circuit boards, against the copper etching solutions such that the resist foil covers the hole entrances(Tenting Process). An alternative type of method, in which the negative resist is deposited on to the hole walls directly and remains there for the protection of the copper coatings, even during the subsequent copper etching procedure, is by comparison not practicable, since the resist which is in the holes for this purpose would need to be exposed. This is however not possible on a reliable basis, particularly not in smallish holes with rough hole walls. In the Tenting Process it is essential that the resist foil regions which cover the holes, have an adequately large supporting area round the hole entrances for a copper ring to be placed round the hole entrances at these points even during subsequent etching, said copper ring however occupying unnecessary space on the circuit board.
When using a positive resist, in which the film, which is deposited on the surfaces about to be constructed, is at first insoluble in the developing solutions and only converted into a soluble state by exposure, the problems which have been mentioned exist to a far lesser extent.
In particular, it is possible by means of positive resists to metallise holes in circuit -CA 02238833 1998-0~-27 .
boards using the Panel-Plating-Process without residual rings being left round the hole entrances. In this way considerably finer circuit patterns are made possible.
Furthermore, it has emerged that, with positive resists, a better photographic resolution can be obtained by means of more precise definition of the structure edges.
The effect of negative and positive resists is depicted in greater detail in W. M.
Moreau, Semiconductor Lithography, Plenum Press, 1988.
Typical positive photoresists normally contain novolaks as polymers. For example, resists of this type are described in US-PS 52 66 440.
These photoresists are however not particularly light sensitive, so that long exposure times or high light intensities must be accepted. For example, in order to expose circuit boards which are coated with traditional positive resists, light intensities of about 350 mJ/cm2are required, while, when using negative resists, normally values of about 100 mJ/cm2 suffice (c.f. Nakahara, Electronic Packaging & Production, 1992, pp. 66 ff).
In recent times positive resists are described, the photosensitivity of which depends on light-induced proton splitt-off in certain organic acids and consequent acid cleavage of side groups of the polymer consisting the resist generating soluble compounds in aqueous-alkaline solutions. The photosensitivity of these resist types is considerably higher that that of the previously mentioned types.
The principle of these resists described as "Photoresiste mit chemischer Verstarkung" (Amplifikation- "chemically amplified photoresists") is described in G.
M. Wallraff et.al., "Designing tomorrow's photoresists", Chemtech, 1993, pp. 22 to 30. According to this, organic onium salts, for example, diphenyliodonium-hexafluoroantimonate are used as acid generators which are split by UV radiation.
Polyacrylates are used preferably as acid-cleavable polymers, said polyacrylatescontaining tert.-butyl-groups as carbon acid ester side groups which are split off by acid catalysis. In this process polar carbon acid side groups emerge, which cause CA 02238833 1998-0~-27 .
the higher solubility of the polymer in an aqueous solution.
In US-PS 44 91 628, a resist composition operating according to the previously mentioned principle is shown, said resist composition containing, as well as the acid generator, an acid-cleavable polymer. As a polymer, compounds with phenols or styrenes with tert.-butylester-groups, for example poly-(tert.-butoxycarbonyloxystyrene) are suggested. As acid generators, diaryliodonium- andtriarylsulfonium- metal halogenides are used.
In EP O 445 058 A1 photoresists are described, which are catalysed by acid cleavage and which, besides an acid generator, contain acid-cleavable polymers for example polystyrenes with tert.-butoxycarbonyloxy-groups. Organic onium salts for example aryldiazonium-, diaryliodonium-, and triarylsulfonium- metal halogenides are suggested as acid generators.
In EP O 568 827 A2, a pattern-forming composition is described which can also bedeposited electrica!ly and which, besides an acid generator, also contains polystyrenes as acid-cleavable polymers, namely phenolic resins, for example novolaks with tert.-butoxycarbonyloxy-groups.
In US-PS 52 72 042 positive resists are described, which likewise contain polystyrenes with tert.-butoxycarbonyl-groups, as well as those which contain, as acid-cleavable polymers, polyacrylates with tert.-butoxycarbonyl-groups as side groups. N-hydroxyamides and N-hydroxyimides, for example N-trifluoromethyl sulfonyloxynaphthalimide are used as acid generators. In order to make the photoresist sensitive to visible light as well, an anthracene derivative is also used as a photosensitizer, for example 9,10-bis-(trimethylsilytethinyl)-anthracene.
In US-PS 50 71 730 a positive resist is likewise described which, besides an acid generator, (aryldiazonium-, diaryliodonium-, triarylsulfonium- metal halogenide), and photosensitisers (pyrene, perylene) contains an acid-cleavable polymer. A
polyacrylate, which is formed from three different acrylates, namely tert.-butylacrylate or tert.-butylmethacrylate, methylacrylate or methylmethacrylate and acryl- or CA 02238833 1998-0~-27 .
methacryl- acid is suggested as a polymer.
In US-PS 50 45 431 a composition is shown which is very similar to the previously mentioned resist, the polymer of which is formed likewise from acrylate compounds and contains ethylacrylate or butylacrylate as possible additional acrylate units in the polymer chain.
In US-PS 52 30 984 there is a resin composition, serving to form a depositable photoresist by means of electrophoresis, said resin composition consisting of acryl-or methacryl- acid, also tert.-alkylacryiate or tert.-alkylmethacrylate and also a monomer which can be polymerised, the latter as a homopolymer having a glass transition temperature of 0~C or lower. Among others, ethyl acrylate, propylacrylate, iso-butylacrylate and higher homologues are mentioned as monomers of this type.
As photo acid generators, phosphonium-, sulphonium-, diazonium-, iodonium- saltsand oxazole derivatives among others are suggested.
It has emerged, that the known positive resists, which are applied to the coppersurfaces of circuit boards, cannot be removed from the copper surfaces without leaving residues during developing of the exposed regions. Even after an extended exposure time or increased light intensity during exposure, residues on the copper surfaces cannot be entirely removed, at least not when the resist film is treated during exposure within the parameters which are required for achieving a satisfactory exposure result (exposure time, light intensity). In particular, a resist coating Iying directly on the copper surface during developing cannot be removedentirely and with assurance, so that, in the subsequent etching during the Panel-Plating-Process or in the subsequent electrolytic plating Pattern-Plating-Process, problems arise. The residues which cannot be removed lead to defective adhesion of the subsequently deposited metal coating to the copper surfaces or to unsatisfactory etching results, since the residues impede the etching process. In a particularly unfortunate scenario, no further metal coatings at all are deposited in these places or the copper coating is not attacked at all in the etching process.
Problems of this sort do not occur in the structoring of semiconductor substrates.
-CA 02238833 1998-0~-27 Furthermore, the contrast between exposed and unexposed places in traditional photoresists is only partly insufficiently small, with the result that the contour definition is not adequate. In addition, known resist coatings do not have sumcient resistance to chemicals, above all against acid etching solutions, since often a compromise between adequate ease of developing in alkaline solutions and resistance to chemicals must be found. Moreover, known resists also suffer from an increased susceptibility to the effects of dust and other impurities which are deposited on the resist coatings during exposure and thus prevent exposure. In positive resists, contaminations of this type normally lead to undeveloped places in the exposed regions, so that, in the production of circuit boards, metal deposition cannot proceed in these regions. In the production of semiconductor circuits this increased defect frequency does not play a highly significant part, since the procedure is done in any case in highly purified air.
The highest requirements in the purity of the air during production of circuit boards cannot however be met.
The problem underlying the present invention resides thus in avoiding the disadvantages of the known methods and particularly in making available a resist composition, which can be removed from the copper surfaces, for example of a circuit board, without leaving any residues during developing, so that the further treatment steps can be carried out without any impairment caused by residues from the photo resist. Furthermore, it must also be guaranteed that the photo resist coating adheres sumciently well to the copper surfaces. In particular, the unexposed resist coating which is not removed CA 02238833 1998 - 0~ - 27 during the subsequent developing process must also withstand further chemical treatment steps without damage, must have a good contrast between exposed and unexposed areas, and must be as unreceptive as possible to contamination during developing.
The problem is solved by photosensitive compositions according to Patent claims 1, 4, 5, 6, 7 and 12. Advantageous embodiments of the invention are indicated in the sub-claims.
The resist variants according to the invention, in addition to at least one photoacid generator, contain at least one polymer with acid-cleavable side groups, and which is converted into a soluble condition by the acid of the photoacid generator released during exposure.
The polymer, preferably copolymer, is formed from various monomers in order to fulfil the object according to the invention. The polymer is formed from the following fractions of monomers, relative to the polymer:
1 st Variant:
A - Monomers selected from the group of compounds acrylic acid and methacrylic acid, with a fraction of 8 mol-% to 20 mol-%.
B - Monomers selected from the group of compounds tert.-butacrylate and tert.-butylmethacrylate, with a fraction of 19 CA 02238833 1998-0~-27 7a mol-% to 70 mol-% and C - Monomers selected from the group of compounds hydroxyethylmethacrylate, hydroxypropylmethacrylate, hydroxyphenylmethacrylate, hydroxyethylacrylate, hydroxypropylacrylate and hydroxyphenylacrylate with a fraction of 1% by mol to 30% by mol.
The acid-cleavable polymer can contain in addition to the previously mentioned monomers, D- Monomers selected from the group of compounds methylacrylate and methylmethacrylate with a fraction of 10% by mol to 60% by mol.
Moreover, the acid-cleavable polymer, can further contain in addition to the previously mentioned monomers A, B, C and D
E- Monomers selected from the group of compounds wth the general formula CH2=CR1-COOR2, where R1 is a hydrogen atom or a methyl group and R2 is a linear or branched alkyl group with at least three carbon atoms, with a fraction of 3% by mol to 35% by mol.
CA 02238833 1998-0~-27 .
2nd Variant:
A- Monomers selected from the group of compounds acrylic acid and methacrylic acid, with a fraction of 10% by mol to 25% by mol, B- Monomers selected from the group of compounds tert.-butylacrylate and tert.-butylmethacrylate with a fraction of 17% by mol to 40% by mol, D- Monomers, selected from the group of compounds methylacrylate and methylmethacrylate with a fraction of 20% by mol to 60% by mol and E- Monomers selected from the group of compounds with the general formula CH2= CR'-COOR2, where R' is a hydrogen atom or a methyl group and R2 is a linear or branched alkyl group with at least five carbon atoms, with a fraction of 1% by mol to 35% by mol.
3rd Variant:
A- Monomers selected from the group of compounds acrylic acid and methacrylic acid, with a fraction of 14% by mol to 20% by mol, B- Monomers selected from the group of compounds tert.-butylacrylate and tert.-butylmethacrylate with a fraction of 20% by mol to 32% by mol, D- Monomers, selected from the group of compounds methylacrylate and methylmethacrylate with a fraction of 30% by mol to 50% by mol and E- Monomers selected from the group of compounds with the general formula CH2= CR'-COOR2, where R' is a hydrogen atom or a methyl group and R2 is a linear or branched alkyl group with two to four carbon atoms with a fraction of 10% by mol to 40% by mol CA 02238833 1998-0~-27 4th Variant:
A- Monomers selected from the group of compounds acrylic acid and methacrylic acid, with a fraction of 14% by mol to 19% by mol, B- Monomers selected from the group of compounds tert.-butylacrylate and tert.-butylmethacrylate with a fraction of 26% by mol to 40% by mol, D- Monomers, selected from the group of compounds methylacrylate and methylmethacrylate with a fraction of 40% by mol to 55% by mol, preferably from 50% by mol to 55% by mol, 5th Variant:
A- Monomers selected from the group of compounds acrylic acid and methacrylic acid, with a fraction of 13% by mol to 15% by mol, B- Monomers selected from the group of compounds tert.-butylacrylate and tert.-butylmethacrylate with a fraction of 22.5% by mol to 30% by mol, D- Monomers, selected from the group of compounds methylacrylate and methylmethacrylate with a fraction of 50% by mol to 65% by mol.
With the previously mentioned compositions, which include, besides the photo acid generator, at least one of the described polymers, photoresists are obtained with the following characteristics:
a. In an exposed state, the resist coating can be removed with no problem from the underlying copper coating by using developing solutions. No residues remain on the copper surface. Since the polymer contains tert.-butylacrylate and/or tert.-butylmethacrylate, the solubility of the resist coating increases in aqueous developing solutions during exposure.
b. In the unexposed state the resists withstand the treating solutions which arenormally used in an electroplating process. In particular the resist coating has a high CA 02238833 1998-0~-27 .
adhesion to the copper coating of a circuit board. Because of the carbon acid proportion in the polymer, namely the proportion of acrylic acid and methacrylic acid, the adhesion of the resist on to the copper surface increases, by means of which the danger of chemicals undercutting the resist coating is reduced. On the other hand, the solubility of the resist in aqueous developing solutions is reduced when theproportion of carbon acid in the polymer is reduced.
By using hydrophobic monomer components in the monomer, which contain at least three carbon atoms in the side chain of the acrylate according to the 1st polymer variant, the resistance of the unexposed composition to chemical treating medium(aqueous treating solutions with pH values of 0 to 13) is increased. The same adaptation of the exposed and unexposed regions in the photoresist according to the invention can furthermore be achieved by adjusting the balance between the content of hydrophilic and hydrophobic components (also side chains with at least two carbon atoms) in the polymer with further monomers. By means of the polymersaccording to the invention, an increased contrast of the resists during exposure is achieved and also an exceptionally high chemical resistance of the developed coatings. For example, a developed coating of the resist according to the invention on a circuit board covered with a copper lamination can even withstand being situated for several hours in a hydrochloric acid / copper-(ll)-chloride solution which is normally used for etching copper. Admittedly, undercuts are formed in this situation on the flanks of the developed structures, which result from sideways corrosion from the etching medium on to the copper lamination. However, the resist coating adheres moreover to the copper lamination without defect.
c. In addition, a substantially smaller defect rate is attained than with traditional resists, said defect rate being caused by dust contamination and other impurities on the resist surface during developing.
d. Furthermore, the unexposed resist coating can be removed again from the substrate surface by appropriate solutions (strippers).
e. The resists have a high light sensitivity. The polymers according to the invention CA 02238833 1998-0~-27 furthermore have the advantage of a high transparency, with the result that light in the resist coating is only scattered a little. For this reason, a high contour definition is achieved during exposure and subsequent developing, which leads to outstanding definition and excellent photographic resolution capability. The contrast increases with the proportion of tert.-butylacrylate or tert.-butylmethacrylate during development of the resist.
f. By means of appropriate composition of the polymer from certain monomers, it is possible to make polymers with an appropriate glass transition temperature T~
between 40~C and 1 50~C. Since the photosensitive composition according to the invention is heated during the application process on the surfaces about to be structured, the resulting coatings can be formed by partial softening as uniformly thick films, which are free of air bubbles, inclusions or other interfering impurities.
Moreover, by means of a glass temperature in the given range, a resist coating is made possible which is mechanically capable of resistance in a cold state and which is flexible in a warm state.
The glass transition temperatures of the resist coatings Iying within the given range further make possible an unproblematic transfer of the resist coatings, which are deposited on polymer carrier films, on to the substrate surface for use as dry resists.
Too low a glass transition temperature would lead further to the composition delivering unusable images. Too high a temperature would lead to greater strength of the resist coating and also to very high transfer temperatures (transfer of the resist coating from a carrier on to the substrate) and glazing temperatures.
g. The resist coatings formed from the compositions according to the invention can be developed with aqueous-alkaline solutions or completely removed. Organic solvents are not required, in particular no chlorinated hydrocarbons.
The photosensitive polymers have average molecular weight Mw of 30,000 to 90,000, preferably 35,000 to 82,000.
The molecular weight distribution of the polymers can be described by a poly-CA 02238833 1998-0~-27 .
molecularity index Pl, which gives the ratio of the average molecular weight Mw of the polymer to the number average of the molecular weight M". The poly-molecularity index Pl describes the range of the molecular weight distribution (c.f. also for this M.Hoffmann, H. ~Croner, R. Kuhn in Polymeranalytik 1, p. 34, G. Thieme Verlag, Deutschland, 1977). The poly-molecularity index Pl of the polymers according to the invention has a value of 1.6 to 3.1, preferably 2.1 to 3Ø
These characteristics are influenced by a large number of reaction parameters, for example by the choice of solvent, the choice of reaction temperature and the type of reaction initiator (for example of the peroxide compound) in the polymerisation of monomer mixtures according to the invention. An indication of the mechanism for controlling the poly-molecularity index Pl is given in H. G. Glas, Makromolekule, p.
487, Huthig-Verlag, Deutschland, 1990. Small values for poly-molecularity index Pl reflect a narrow molecular weight distribution.
The normal compounds may be used as photo acid generators, for example N-trifluoromethylsulfonyloxynaphthalimide (NIT) F~ F
O' ~0 O~, N ~O
~3 and other trifluoromethylsulfonyloxyimide derivatives such as xF
Fo,S~' O ,~
~1~1 ~~
further, triiluoromethylsulphonyloxy-bicyclo[2.2. 1 ]-hept-5-en-2,3-dicarboximide (MDT), naphthoquinone-1,2-diazide-4-sulphonic acid ester, for example 1-naphthalinesulphonic acid-3-diazo-3,4-dihydro4-oxoester with phenyl-(2,3,4-trihydroxypheny)-methanone. Further N-trifluormethylsulfonyloxyimide derivativesare given in J.M.J. Fréchet, Pure and Appl. Chem., 64, pp. 1239-1248 also in US-PS 52 72 042, for example, o XN~
~--s=c~
A o DNQ, with A = aromatic residue and .
a ~N
~ ~ <~
[3~ 3~=
o--s--a N
,~, CNQ-P.
Furthermore, 1,2,3-benzene-tris-(sulphonic acid trifluoromethylester), 1,2,3-benzene-tris-(sulphonic acid methylester), 6,7-bis-(trifluoromethylsulphonyloxy)-coumarin, 2,3,4-tris-(fiuoromethylsulphonyloxy)-benzophenone are suitable as photo acid generators as well as those photo acid generators described in EP-A 0 489 560.
The synthesis of photo acid generators is amongst others described in EP-A 0 058638 as well as in J.M.J. Fréchet, Pure and Appl.Chem., 64, pp.1239 to 1248.
The content of photo acid generators in the photosensitive composition is 1 % byweight to 25% by weight, preferably 2% by weight to 20% by weight, relating to the weight of the polymer in the composition.
CA 02238833 1998-0~-27 .
In the photosensitive composition, further components are included besides the photo acid generators and the polymer:
In order to also make the composition sensitive to light with a certain spectraldistribution of intensity, preferably in the visible range (330nm to 440nm) one or a plurality of photo sensitisers are added to the composition. The main concern here is polycyclic aromatic compounds for example anthracene, 9-anthracene methanol, 1,4-dimethoxyanthracene, 9,10-diethylanthracene, 9-phenoxymethylanthracene and 9,10-bis-(ethinyl)-anthrancenes, such forexample as 9,10-bis-(trimethylsilylethinyl)-anthracene, by means of which the light sensitivity of the photosensitive compositions, preferably to red light, is greatly increased.
These photosensitisers are used preferably in concentrations of 1% by weight to 6%
by weight, preferably of 2% by weight to 4% by weight, reiating to the weight of the polymer in the composition.
Furthermore, the compositions according to the invention can also contain dyes, to improve the perceptibility of the resist, even in a thin coating on the substrate which is about to be structured, and also contain further components which are normal for photoresist materials.
The compositions which can be used as resists are used for example as liquid formulations. For this purpose, they are mixed with appropriate solvents, for example ethers, ether alcohols or ether esters. For example, propylene glycol monomethylether acetate, 1-methoxy-2-propanol, ethyl lactate, 3-ethoxypropionate, ethylene glycol monoethyl ether acetate, methoxybutanol, diethylene glycol monoalkylether and propylene glycol monobutylether are used as solvents.
The liquid composition is deposited on the surfaces which are to be coated for example by spinning-on (Spin-coating). Another deposition technique is the roller coating procedure in which the composition first of all moistens a first roller with a thin coating, the liquid being deposited by means of wringers on to the roller at a defined thickness. From this roller the coating is conveyed next, through direct -CA 02238833 1998-0~-27 contact of the roller with the substrate on to the latter. In this way, a uniformly thick film can also be formed on large-surface flat substrate surfaces. Normally coating thicknesses of the composition of 3,um to 20,um are used.
The roller coating procedure has the advantage that unproblematically defined coating thicknesses of the resist can be used on plate-shaped substrates, for example circuit boards. Moreover, the substrates can be conveyed in a horizontalposition and direction through the coating unit. Coating units of this type can be connected furthermore with other horizontal units for the further treatment steps in producing the metal structures with the result that the substrates can be handled more easily with the possibility of automation.
Furthermore, the liquid composition can be deposited on the substrate also by submerging it. There is a problem however here in that coating thicknesses are set which are variable and not controllable at the edges.
The compositions according to the invention can be deposited however, for use inthe dry film technique also, on to a polymer carrier film, for example on to a polyester foil. From the latter, the composition can be conveyed by direct contact of the photosensitive coating, which is deposited on the foil, to the substrate which is to be structured, for example by pressing.
AKer coating the substrate with the composition, the resist coating which is formed is dried by the effect of heat, for example in a forced-air oven or by means of infra-red radiation. AKer that, the coating is coated with the template, then heated again, to accelerate the formation of the latent pattern (Reheating)1 and subsequently thecoated regions in the resist coating are dissolved away during developing. For this purpose spraying units are used preferably, by means of which the developing solution is sprayed on to the substrate surfaces via jets. Aqueous-alkaline solutions are preferably used as developing solutions, for example sodium carbonate solution.
The photosensitive compositions can be used as etching or galvanoresists for making metal coatings, for example for producing electrical circuit carriers. The CA 02238833 1998-0~-27 .
further processes for producing the desired metal structures endorse the mentioned procedural steps, for example etching processes or further electrolytic metal deposition procedures, in which, in the resist channels which are formed, the uncovered metal surfaces are removed by etching processes or are constructed further by means of electrolytic deposition procedures.
A further use of the photosensitive compositions resides in their use as an galvanoresist in the additive process, preferably for the photo-structuring of substrates from epoxy resins, acrylonitrile-butadiene-styrene-copolymers (ABS) and polyimide. Metal structures are thus produced by means of electroless plating baths in the resist channels, which are fommed by exposure and developing.
After completion of the structuring method the resist coating is removed again from the substrate surfaces preferably by means of aqueous-alkaline solutions, for example a caustic soda solution.
The compositions according to the invention are used for making metal coatings on electric circuit carriers, for example on epoxy resin-, polyimide- laminates or their composites as well as for decorative purposes on metal and plastic material substrates. In a preferred application, the compositions are used for producing circuit boards provided with copper surfaces and inner layerlaminates to be used for circuit boards.
The following examples serve to explain the invention:
Example 1 ( Polymer synthesis for producing a dry substance):
In order to produce the acrylate polymers according to the invention, tetrahydrofuran (THF) and azo-bis-isobutyronitrile (AIBN) were first placed in a double-necked flask.
Then the monomers were added. The reaction mixture was kept hermetically sealed during the entire duration of the reaction. The ratios of the amounts used for producing a polymer according to the invention are given in the following table CA 02238833 1998-0~-27 .
Component Quantity in parts by weight AIBN 1 .956 methacrylic acid 64.2 tert.-butylmethacrylate 1 28.4 methylmethacrylate 1 28.4 butylacrylate 1 34.7 hydroxypropylmethacrylate 33.3 At the start of the polymerisation reaction the mixture was heated. The mixture was refluxed for 24 hours, the conversion was 100% after the reaction was finished.
AKer completion of the reaction the polymer was precipitated with petroleum benzene. After separation, a colourless powder was obtained, which was dried in a vacuum for 48 hours at 60~C to 70~C.
The polymers given in Table 1 were also produced, furthermore, using the presently described method.
Example 2 (Polymer synthesis for the direct use of the reaction solution as photoresist base):
The procedure was as in Example 1. However propylene glycol monomethylether acetate (PGMEA) was used as solution medium instead of THF. The following ratiosof the amounts of individual components were used to produce the polymer.
CA 02238833 1998-0C,-27 Component Quantity in parts by weight AIBN 0.652 methacrylic acid 21.4 tert.-butylmethacrylate 42.8 Methylmethacrylate 42.8 butylacrylate 44.9 hydroxypropylmethacrylate 11 . 1 At the start of the polymerisation reaction the mixture was heated to 100~ C. The mixture was heated for 26 hours, the conversion was 100%. A polymer with the same composition as the polymer produced using the method according to Example 1 was obtained. The polymers given in Table 1 were also produced, using the presently described method.
Instead of the solvents used in Examples 1 and 2, in polymerisation, dioxane, cyclohexanone or heptane were used as selvents. Instead of azo-bis-isobutyronitrile (AIBN), benzoyl-peroxide or other radical initiators can be used. The completeness of the reaction is thus dependent on the solvent used, on the reaction temperature, on the type of initiator and the duration of the reaction.
Example 3 (Production of a liquid photoresist composition, photosensitive resist):
In the yellow-light area 30 parts by weight N-trifluoromethylsulfonyloxynaphthalimide (NIT) as acid generator and 20 parts by weight 9-anthracenemethanol (AM) as sensitiser were mixed with 1000 parts by weight of a solution of polymer, obtained according to Example 1 in propylene glycol monomethylether acetate, with a solution having a solids content of approx. 25% by weight (20 to 30% by weight).
In another embodiment, a polymer solution with 20% by weight and 30% by weight, resp., was used instead of a polymer solution with 25% by weight.
CA 02238833 1998-0~-27 .
In a further experiment, 200 parts by weight 4-diazonaphthoquinone sulphonicacidester was used instead of NIT and AM.
Furthermore, appropriate polymer soiutions, which were obtained by dissolving the polymer dry substance, obtained according to Example 1, in 1-methoxy-2-propanol with the same solids contents, were used to produce the liquid photopolymer compositions.
Example 4 (Use of the photoresist composition according to Example 3 for structuring circuit boards):
A circuit board base material was used which was made by the company Allied Signal Norplex Oak, USA with the type designation ED 130, which had on both sides a 18 I~m.thick copper laminate (corresponding to the US Military specihcation MIL S 13949). The base material was treated according to the following procedure:
1. Pre-treatment: a- etch cleaning with Scheretch M
(Product of company Atotech Deutschland GmbH, Berlin, DE) 20-25~C
b- Rinsing with water 25~C
c- Pickling with HzSO4 25~C
d- Rinsing with water 25~C
e- compressed-air drying f- drying in circulated-air oven (5 min) 80~C
2. Coating: Spin Coating spun-on layer thickness: 2,5"um to 4,5 ,um 3. Drying: On the heater plate (2 min) 100~C
or in circulated-air oven (5 min) 80~C or 1 00~C
or in circulated-air oven (5 min) 80~C or 1 00~C
4. Exposure: Exposer of company FSL, United Kingdom, Type T 5000 CA 02238833 1998-0~-27 .
Wavelength 365 nm (i-line) Light intensity 20 mJ/cm2 to 60 mJ/cm2 Layout: resolution line test-mask No. 31 of company Haidenhain, Germany 5.Reheating: On heater plate or in circulated-air oven 3 min to 20 min 80-120~C
Wavelength 365 nm (i-line) Light intensity 20 mJ/cm2 to 60 mJ/cm2 Layout: resolution line test-mask No. 31 of company Haidenhain, Germany 5.Reheating: On heater plate or in circulated-air oven 3 min to 20 min 80-120~C
6. Developing: In a spray installation with a 1% by weight Na2C03-solution (1 min to 3 min) 30~C
7. Copper Etching: Acidic iron-(lll)-chloride etching solution (105 sec to 3 min) 40~C
8. Layer Removal: In a spray installation with a 1,8% by weight NaOH solution 5~~C
While using a resist produced according to Example 3 with polymer compositions given in Table 1, a photographic resolution according to table 2 was achieved. In the channels in the photoresist structure, which resulted after developing, no residues could be seen. After etching the uncovered copper surfaces (procedural step 7.) and after the subsequent removal of the resist coating (procedural step 8.), a copper template with highly resolved structures was obtained.
Example 5:
The same result was achieved with resists with compositions according to Table 1, which were produced from the reaction solution according to Example 2. For this purpose a polymer solution was produced respectively according to Example 2 and mixed according to Example 3 with NIT and AM to form a photoresist composition.
CA 02238833 1998-0~-27 .
Under the conditions of the procedure according to example 4, in which the exposed resist coating was reheated for 20 minutes at 80~C, a very good photographic resolution of the structures which were formed was likewise obtained. After developing, there were no resist residues left in the channels.
.
Comparative test V1:
With a polymer of the composition 17.6% by mol methylacrylacid, A
21.4% by mol tert.-butylmethacrylate, B
61% by mol methylmethacrylate D
a liquid photoresist composition was produced with 30 parts by weight NIT and 20parts by weight AM respectively per 1000 parts by weight of polymer solution being dissolved in a 25% by weight polymer solution in propylene glycol monomethyl ether.
The photoresist was deposited on a circuit board base material using the procedure according to Example 4 and structured. After developing, a continuous thin resist coating was found in the resist channels. For that reason, the underlying copper could not be or only very imperfectly be removed by the etching solution.
This firmly adhering resist film could be penetrated at least partly only after extending the developing time, using a stronger concentration of developing solution, increasing the developing temperature or with a combination of these measures. However the etching result was unsatisfactory even in this situation, since the etching solution could not corrode the copper without hindrance because of the parts of the resist coatings which were left behind. Moreover, the copper surfaces in the resist channels were partly passivated by the more intensive corrosion of the developing solution with the result that the copper surfaces were also for that reason harder to etch.
The test was repeated with polymers having the following compositions:
1. 2.1% by mol acrylic acid, CA 02238833 1998-0~-27 .
30.7% by mol tert.-butylmethacrylate, 33.6% by mol methylmethacrylate, 33.6% by mol ethylacrylate;
2. 20.5% by mol methacrylic acid, 31.0% by mol tert.-butylmethacrylate, 48.5% by mol methylmethacrylate.
In those cases there were no sufficiently good results obtained while developing the resist coatings: it emerged that residues of the resist were left behind in the resist channels and that said resists could not be completely removed during development.
Example 6 (Roller deposition method for the photoresist):
By means of a roller deposition device, liquid photoresist compositions, which were produced according to Example 3, from the polymers C, J and P (also see table 1), were applied to the copper surfaces of circuit board base material blanks ( 25cm X
37.5cm)-For this purpose 1 .5mm thick FR 4-plates from the Circuit-Foil company, USA and1.0mm thick plates from the Fukada company, Japan were used. Both types had 17.5,um thick copper laminations on both sides.
The procedure for treating circuit boards is shown in the following:
1. Pre-treatment: a- etch cleaning with a solution of Na2S208 and H2S04 (0.5 min) 25~C
b- Rinsing with water (0.5 min) 25~C
c- drying in air (ca. 1 min) 2. Coating: Roller coating or Spin Coating layer thickness 4,um to 6 ,um CA 02238833 1998-0~-27 .
3. Drying: In circulated-air oven (5 min) 100~C
4. Exposure: Exposer of company Tamarack, ~ wavelength 365 nm (i-line) Light intensity 10 mJ/cm2 to 150 mJ/cm2 5. Reheating: In circulated-air oven 5 min to 20 min 80 - 120~C
6. Developing: In a spray installation with a 1% by weight Na2C03solution (2 min) 30~C
7. Copper Etching:
a- acidic copper-(ll)-chloride etching solution (70 sec) 50~C
b- acidic rinsing c- rinsing with water (0,5 min) 8. Layer Removal: In a spray installation with a 1.8% by weight NaOH-solution (1,5 min) 55~C
The results shown in Table 3 were obtained. Highly resolved structures were attained after developing the resist. In the resist channels there were no residues of the resist left behind.
Comparative test V2:
The test from Example 6 was repeated. Instead of the resists used there however,resists from comparative Test V1 were used with a polymer formed from 17.6% by mol methacryl acid, 21.4% by mol tert.-butylmethacrylate, 61.0% by mol methylmethacrylate, In Table 4, the test conditions are given.
CA 02238833 1998-0~-27 .
No acceptable results could be obtained. In the resist channels, produced duringdevelopment, there were still resist residues left, which, even with a more intensive development process, could not be removed.
Example 7 (Additive Technique):
A photoresist combination, according to the invention, formed from 20% by weight of the polymer J, 0.6% by weight N-trifluoromethylsulfonyloxynaphthalimide (NIT) as an acid generator and 0.4% by weight 9-anthracene methanol (AM) as photosensitizer in propylene glycol monomethylether acetate was spun on to a plastic part made fromacrylnitrile-butadiene-styrene-copolymer (ABS) which had previously been treatedwith a chrome/sulphuric acid pickling solution, then activated with an activator(Noviganth ~AK 1 from the company Atotech Deutschland GmbH) and fixed with the solution Noviganth~AK 11 from the companyAtotech Deutschland GmbH. The photo composition was alternatively applied also on to the ABS-part using a roller coating technique. The thickness of the resist coating lay between 3,um to 20 ,um.
Next the resist coating was exposed through a photomask with a light intensity of 71 mJ/cm2 to 94mJ/cm2 and after that reheated in a forced air oven for 10 minutes at a temperature of 1 00~C. The sample part was developed with a 1% by weight Na2CO3 solution at 30~C.
In the 100 ,um wide structures in the resist coating, a nickel coating was deposited from an electroless nickel bath (Noviganth ~TC from the company Atotech Deutschland GmbH) on to the palladium gemms formed with the Noviganth~ activator in the space of 3 to 4 minutes at 45aC to 50~.
A tin-lead alloy coating was further deposited electrolytically within 5 to 6 minutes at 35~C on the nickel coating (Sulfolyt ~TC from the company Atotech Deutschland GmbH).
Subsequently, the resist coating was again removed completely from the ABS part by means of a 5% by weight potassium hydroxide solution. In order to accelerate theremoval of the coating, butyldiglycol was added to the potassium hydroxide solution.
Table 1:
Test 1.Comp. (A) 2.Comp. (B) 3.Comp.(D) 4.Comp. (E) 5.Comp.(C) T~ Mn Mw Pl [Mol-%] [Mol-%] [Mol-%] [Mol-%] [Mol-%] l~C] [9/Mol] [g/mol]
A 14.2 (MM) 23.6 (TBMA) 62.2 (MMA) - - 150 23.900 50.000 2.1 B 17.6 (MM) 21.4 (TBMA) 30.5 (MMA) 30.5 (BA) - 116 22.000 52.700 2.4 C 17.6 (MM) 21.4 (TBMA) 50.0 (MMA) 11 (2EHA) - 122.1 28.600 63.400 2.2 D 17.6 (MM) 21.4 (BMA) 41.0 (MMA) 20 (ANON) - 109.9 30.000 63.900 2.1 E 14 (MM) 24 (TBMA) 41 (MMA)20 (BA) - 40 15.800 34.700 2.2 D
F 14 (MM) 24 (TBMA) 41 (MMA)21 (BA) - 18.630 56.920 3.1 G 18 (MM) 22.9 (TBMA) 39.1 (MMA) 20 (BA) - 22.880 67.130 3.0 H 17.6 (MM) 21.4 (TBMA) 50.0 (MMA) - 11.0 (HPMA) 145.8 33.700 82.600 2.4 J 17.6 (MM) 21.4 (TBMA) 30.5 (MMA) 25 (BA) 5.5 (HPMA) 98.5 22.300 60.500 2.7 MM: methacrylic acid BA: butyl acrylate HPMA: hydroxypropylmethacrylate ul TBMA: tert.-butylmethacrylic acid 2EHA: 2-ethylhexylacrylate '' ANON: nonylacrylate MMA: methylmethacrylate Continuation of Table 1:
Test l.Comp.(A) 2.Comp.(B) 3.Comp.(D) 4;Comp.(E) 5.Comp.(C) T~ M" Mw Pl [Mol-%) [Mol-%] [Mol-%] [Mol-%] [Mol-%] [~C] [g/mol] [glMol]
K 17.6 (MM) 21.4 (TBMA) 30.5 (MMA) 25 (BA) 5.5 (HEMA) L 17.0 (MM) 20.8 (TBMA) 29.9 (MMA) 24.4 (BA) 8.0 (HPMA) M 19.0(MM) 21.0(TBMA) 30.1 (MMA) 24.7(BA) 5.2(HPMA) N 17.6 (MM) 31.9 (TBMA) 30.5 (MMA) 20.0 (BA) - 110.5 24.500 56.000 2.3 D
0 17.6 (MM) 31.4 (TBA) 51.0 (MMA) - - 118.9 21.000 53.200 2.5 P 17.6 (MM) 21.4 (TBMA) 30.5 (MMA) 30.5 (BA) - 92 MM: methacrylic acid BA: butylacrylate HEMA: hydroxyethylmethacrylate TBMA: tert.-butylmethacrylic acid MMA: methylmethacrylate HPMA: hydroxypropylmethacrylate ~n TBA: tert.-butylacrylate ANON: nonylacrylate CA 02238833 1998-0~-27 .
Table 2 (Photographic resolution after development of the photoresist layers spun on by spin coating):
The optical resolution values were obtained on test samples with a line/interspace ratio of 1:1.
Test Exposure Reheating Development Photographic Energy2~ensity Temp. Trtmt.time Trtmt.time Resolution [mJ/cm ~ [~C] [min] [min] [I~m]
Resist A:
Resist B:
Resist C:
Resist D:
CA 02238833 1998-0~-27 .
Continuation of Table 2:
Test Exposure Reheating Development Photographic Energydensity Temp. Trtmt.time Trtmt.time Resolution [m.~/~m2] [~C] [min] [min] [,um]
Resist E:
Resist F:
F1 16 80 20 2.5 25 F2 30 80 20 2.5 32 Resist G
G 1 16 80 20 2.5 25 G2 30 80 20 2.5 40 Resist H:
Resist J:
Resist K:
K1 16 80 20 2.5 20 K2 30 80 20 2.5 32 K3 40 80 20 2.5 40 .
Further Continuation of Table 2:
Test Exposure Reheating Development Photographic Energydensity Temp. Trtmt.time Trtmt.time Resolution [mJ/cm2] [~C] [min] [min] [,um]
Resist L:
L1 30 80 20 2.5 25 L2 40 80 20 2.5 40 Resist M:
M1 16 80 20 2.5 60 M2 30 80 20 2.5 20 Resist N:
N6 40 80 20 2.5 32 Resist 0:
.
Table 3: (Photographic resolution aKer development of the photoresist layers applied by means of the roller coating method):
Test Exposure Reheating Photographic Energy density Temp. Trtmt.time Resolution [mJ/cm2] [~C] [minj [~m]
Resist C:
Resist J:
J1 37 80 10 6.3 J2 55 80 10 6.3 J6 18 100 5 6.3 Resist P.
.
Table 4 (Photographicresolution after development of the photoresist layers according to Comparative Test V2, applied by the roller coating method):
Test Exposure Reheating Photographic Energydensity Temp. Trtmt.time Resolution [mJ/cm2] [~C] [min] [~m]
37 80 20 no image Il 55 100 10 6.3/notetchable lll 147 100 20 16/not etchable
While using a resist produced according to Example 3 with polymer compositions given in Table 1, a photographic resolution according to table 2 was achieved. In the channels in the photoresist structure, which resulted after developing, no residues could be seen. After etching the uncovered copper surfaces (procedural step 7.) and after the subsequent removal of the resist coating (procedural step 8.), a copper template with highly resolved structures was obtained.
Example 5:
The same result was achieved with resists with compositions according to Table 1, which were produced from the reaction solution according to Example 2. For this purpose a polymer solution was produced respectively according to Example 2 and mixed according to Example 3 with NIT and AM to form a photoresist composition.
CA 02238833 1998-0~-27 .
Under the conditions of the procedure according to example 4, in which the exposed resist coating was reheated for 20 minutes at 80~C, a very good photographic resolution of the structures which were formed was likewise obtained. After developing, there were no resist residues left in the channels.
.
Comparative test V1:
With a polymer of the composition 17.6% by mol methylacrylacid, A
21.4% by mol tert.-butylmethacrylate, B
61% by mol methylmethacrylate D
a liquid photoresist composition was produced with 30 parts by weight NIT and 20parts by weight AM respectively per 1000 parts by weight of polymer solution being dissolved in a 25% by weight polymer solution in propylene glycol monomethyl ether.
The photoresist was deposited on a circuit board base material using the procedure according to Example 4 and structured. After developing, a continuous thin resist coating was found in the resist channels. For that reason, the underlying copper could not be or only very imperfectly be removed by the etching solution.
This firmly adhering resist film could be penetrated at least partly only after extending the developing time, using a stronger concentration of developing solution, increasing the developing temperature or with a combination of these measures. However the etching result was unsatisfactory even in this situation, since the etching solution could not corrode the copper without hindrance because of the parts of the resist coatings which were left behind. Moreover, the copper surfaces in the resist channels were partly passivated by the more intensive corrosion of the developing solution with the result that the copper surfaces were also for that reason harder to etch.
The test was repeated with polymers having the following compositions:
1. 2.1% by mol acrylic acid, CA 02238833 1998-0~-27 .
30.7% by mol tert.-butylmethacrylate, 33.6% by mol methylmethacrylate, 33.6% by mol ethylacrylate;
2. 20.5% by mol methacrylic acid, 31.0% by mol tert.-butylmethacrylate, 48.5% by mol methylmethacrylate.
In those cases there were no sufficiently good results obtained while developing the resist coatings: it emerged that residues of the resist were left behind in the resist channels and that said resists could not be completely removed during development.
Example 6 (Roller deposition method for the photoresist):
By means of a roller deposition device, liquid photoresist compositions, which were produced according to Example 3, from the polymers C, J and P (also see table 1), were applied to the copper surfaces of circuit board base material blanks ( 25cm X
37.5cm)-For this purpose 1 .5mm thick FR 4-plates from the Circuit-Foil company, USA and1.0mm thick plates from the Fukada company, Japan were used. Both types had 17.5,um thick copper laminations on both sides.
The procedure for treating circuit boards is shown in the following:
1. Pre-treatment: a- etch cleaning with a solution of Na2S208 and H2S04 (0.5 min) 25~C
b- Rinsing with water (0.5 min) 25~C
c- drying in air (ca. 1 min) 2. Coating: Roller coating or Spin Coating layer thickness 4,um to 6 ,um CA 02238833 1998-0~-27 .
3. Drying: In circulated-air oven (5 min) 100~C
4. Exposure: Exposer of company Tamarack, ~ wavelength 365 nm (i-line) Light intensity 10 mJ/cm2 to 150 mJ/cm2 5. Reheating: In circulated-air oven 5 min to 20 min 80 - 120~C
6. Developing: In a spray installation with a 1% by weight Na2C03solution (2 min) 30~C
7. Copper Etching:
a- acidic copper-(ll)-chloride etching solution (70 sec) 50~C
b- acidic rinsing c- rinsing with water (0,5 min) 8. Layer Removal: In a spray installation with a 1.8% by weight NaOH-solution (1,5 min) 55~C
The results shown in Table 3 were obtained. Highly resolved structures were attained after developing the resist. In the resist channels there were no residues of the resist left behind.
Comparative test V2:
The test from Example 6 was repeated. Instead of the resists used there however,resists from comparative Test V1 were used with a polymer formed from 17.6% by mol methacryl acid, 21.4% by mol tert.-butylmethacrylate, 61.0% by mol methylmethacrylate, In Table 4, the test conditions are given.
CA 02238833 1998-0~-27 .
No acceptable results could be obtained. In the resist channels, produced duringdevelopment, there were still resist residues left, which, even with a more intensive development process, could not be removed.
Example 7 (Additive Technique):
A photoresist combination, according to the invention, formed from 20% by weight of the polymer J, 0.6% by weight N-trifluoromethylsulfonyloxynaphthalimide (NIT) as an acid generator and 0.4% by weight 9-anthracene methanol (AM) as photosensitizer in propylene glycol monomethylether acetate was spun on to a plastic part made fromacrylnitrile-butadiene-styrene-copolymer (ABS) which had previously been treatedwith a chrome/sulphuric acid pickling solution, then activated with an activator(Noviganth ~AK 1 from the company Atotech Deutschland GmbH) and fixed with the solution Noviganth~AK 11 from the companyAtotech Deutschland GmbH. The photo composition was alternatively applied also on to the ABS-part using a roller coating technique. The thickness of the resist coating lay between 3,um to 20 ,um.
Next the resist coating was exposed through a photomask with a light intensity of 71 mJ/cm2 to 94mJ/cm2 and after that reheated in a forced air oven for 10 minutes at a temperature of 1 00~C. The sample part was developed with a 1% by weight Na2CO3 solution at 30~C.
In the 100 ,um wide structures in the resist coating, a nickel coating was deposited from an electroless nickel bath (Noviganth ~TC from the company Atotech Deutschland GmbH) on to the palladium gemms formed with the Noviganth~ activator in the space of 3 to 4 minutes at 45aC to 50~.
A tin-lead alloy coating was further deposited electrolytically within 5 to 6 minutes at 35~C on the nickel coating (Sulfolyt ~TC from the company Atotech Deutschland GmbH).
Subsequently, the resist coating was again removed completely from the ABS part by means of a 5% by weight potassium hydroxide solution. In order to accelerate theremoval of the coating, butyldiglycol was added to the potassium hydroxide solution.
Table 1:
Test 1.Comp. (A) 2.Comp. (B) 3.Comp.(D) 4.Comp. (E) 5.Comp.(C) T~ Mn Mw Pl [Mol-%] [Mol-%] [Mol-%] [Mol-%] [Mol-%] l~C] [9/Mol] [g/mol]
A 14.2 (MM) 23.6 (TBMA) 62.2 (MMA) - - 150 23.900 50.000 2.1 B 17.6 (MM) 21.4 (TBMA) 30.5 (MMA) 30.5 (BA) - 116 22.000 52.700 2.4 C 17.6 (MM) 21.4 (TBMA) 50.0 (MMA) 11 (2EHA) - 122.1 28.600 63.400 2.2 D 17.6 (MM) 21.4 (BMA) 41.0 (MMA) 20 (ANON) - 109.9 30.000 63.900 2.1 E 14 (MM) 24 (TBMA) 41 (MMA)20 (BA) - 40 15.800 34.700 2.2 D
F 14 (MM) 24 (TBMA) 41 (MMA)21 (BA) - 18.630 56.920 3.1 G 18 (MM) 22.9 (TBMA) 39.1 (MMA) 20 (BA) - 22.880 67.130 3.0 H 17.6 (MM) 21.4 (TBMA) 50.0 (MMA) - 11.0 (HPMA) 145.8 33.700 82.600 2.4 J 17.6 (MM) 21.4 (TBMA) 30.5 (MMA) 25 (BA) 5.5 (HPMA) 98.5 22.300 60.500 2.7 MM: methacrylic acid BA: butyl acrylate HPMA: hydroxypropylmethacrylate ul TBMA: tert.-butylmethacrylic acid 2EHA: 2-ethylhexylacrylate '' ANON: nonylacrylate MMA: methylmethacrylate Continuation of Table 1:
Test l.Comp.(A) 2.Comp.(B) 3.Comp.(D) 4;Comp.(E) 5.Comp.(C) T~ M" Mw Pl [Mol-%) [Mol-%] [Mol-%] [Mol-%] [Mol-%] [~C] [g/mol] [glMol]
K 17.6 (MM) 21.4 (TBMA) 30.5 (MMA) 25 (BA) 5.5 (HEMA) L 17.0 (MM) 20.8 (TBMA) 29.9 (MMA) 24.4 (BA) 8.0 (HPMA) M 19.0(MM) 21.0(TBMA) 30.1 (MMA) 24.7(BA) 5.2(HPMA) N 17.6 (MM) 31.9 (TBMA) 30.5 (MMA) 20.0 (BA) - 110.5 24.500 56.000 2.3 D
0 17.6 (MM) 31.4 (TBA) 51.0 (MMA) - - 118.9 21.000 53.200 2.5 P 17.6 (MM) 21.4 (TBMA) 30.5 (MMA) 30.5 (BA) - 92 MM: methacrylic acid BA: butylacrylate HEMA: hydroxyethylmethacrylate TBMA: tert.-butylmethacrylic acid MMA: methylmethacrylate HPMA: hydroxypropylmethacrylate ~n TBA: tert.-butylacrylate ANON: nonylacrylate CA 02238833 1998-0~-27 .
Table 2 (Photographic resolution after development of the photoresist layers spun on by spin coating):
The optical resolution values were obtained on test samples with a line/interspace ratio of 1:1.
Test Exposure Reheating Development Photographic Energy2~ensity Temp. Trtmt.time Trtmt.time Resolution [mJ/cm ~ [~C] [min] [min] [I~m]
Resist A:
Resist B:
Resist C:
Resist D:
CA 02238833 1998-0~-27 .
Continuation of Table 2:
Test Exposure Reheating Development Photographic Energydensity Temp. Trtmt.time Trtmt.time Resolution [m.~/~m2] [~C] [min] [min] [,um]
Resist E:
Resist F:
F1 16 80 20 2.5 25 F2 30 80 20 2.5 32 Resist G
G 1 16 80 20 2.5 25 G2 30 80 20 2.5 40 Resist H:
Resist J:
Resist K:
K1 16 80 20 2.5 20 K2 30 80 20 2.5 32 K3 40 80 20 2.5 40 .
Further Continuation of Table 2:
Test Exposure Reheating Development Photographic Energydensity Temp. Trtmt.time Trtmt.time Resolution [mJ/cm2] [~C] [min] [min] [,um]
Resist L:
L1 30 80 20 2.5 25 L2 40 80 20 2.5 40 Resist M:
M1 16 80 20 2.5 60 M2 30 80 20 2.5 20 Resist N:
N6 40 80 20 2.5 32 Resist 0:
.
Table 3: (Photographic resolution aKer development of the photoresist layers applied by means of the roller coating method):
Test Exposure Reheating Photographic Energy density Temp. Trtmt.time Resolution [mJ/cm2] [~C] [minj [~m]
Resist C:
Resist J:
J1 37 80 10 6.3 J2 55 80 10 6.3 J6 18 100 5 6.3 Resist P.
.
Table 4 (Photographicresolution after development of the photoresist layers according to Comparative Test V2, applied by the roller coating method):
Test Exposure Reheating Photographic Energydensity Temp. Trtmt.time Resolution [mJ/cm2] [~C] [min] [~m]
37 80 20 no image Il 55 100 10 6.3/notetchable lll 147 100 20 16/not etchable
Claims (15)
1. Photo sensitive composition, which can be converted by exposure in developingsolutions from an insoluble to a soluble state, containing I- at least one photo acid generator and II- polymers which are formed from the following fractions of monomers, relative to the polymer:
A- monomers, selected from the group of compounds acrylic acid and methacrylic acid with a fraction of 8% by mol to 20% by mol, B- monomers selected from the group of compounds tert.-butylacrylate and tert.-butylmethacrylate with a fraction of 19% by mol to 70% by mol and C- monomers selected from the group of compounds hydroxyethylmethacrylate, hydroxypropylmethacrylate, hydroxyphenylmethacrylate, hydroxyethylacrylate, hydroxypropylacrylate and hydroxyphenylacrylate with a fraction of 1% by mol to 30% by mol.
A- monomers, selected from the group of compounds acrylic acid and methacrylic acid with a fraction of 8% by mol to 20% by mol, B- monomers selected from the group of compounds tert.-butylacrylate and tert.-butylmethacrylate with a fraction of 19% by mol to 70% by mol and C- monomers selected from the group of compounds hydroxyethylmethacrylate, hydroxypropylmethacrylate, hydroxyphenylmethacrylate, hydroxyethylacrylate, hydroxypropylacrylate and hydroxyphenylacrylate with a fraction of 1% by mol to 30% by mol.
2. Composition according to Claim 1, characterised by D- Additional monomers selected from the group of compounds methylacrylate and methylmethacrylate with a fraction of 10% by mol to 60% by mol.
3. Composition according to Claim 2, characterised by E- Additional monomers selected from the group of compounds with the general formula CH2= CR1-COOR2, where R1 is a hydrogen atom or a methyl group and R2 is a linear or branched alkyl group with at least three carbon atoms, with a fraction of 3% by mol to 35% by mol.
4. Photo sensitive composition, which can be converted by exposure in developingsolutions from an insoluble to a soluble state, containing I- at least one photo acid generator and II- polymers which are formed from the following fractions of monomers, relative to the polymer A- monomers selected from the group of compounds acrylic acid and methacrylic acid, with a fraction of 10% by mol to 25% by mol, B- monomers selected from the group of compounds tert.-butylacrylate and tert.-butylmethacrylate with a fraction of 17% by mol to 40% by mol, D- monomers, selected from the group of compounds methylacrylate and methylmethacrylate with a fraction of 20% by mol to 60% by mol and E- monomers selected from the group of compounds with the general formula CH2=CR1-COOR2, where R1 is a hydrogen atom or a methyl group and R2 is a linear or branched alkyl group with at least five carbon atoms with a fraction of 1% by mol to 35% by mol.
5. Photo sensitive composition, which can be converted by exposure in developingsolutions from an insoluble to a soluble state, containing I- at least one photo acid generator and II- polymers which are formed from the following fractions of monomers, relative to the polymer A- monomers selected from the group of compounds acrylic acid and methacrylic acid, with a fraction of 14% by mol to 20% by mol, B- monomers selected from the group of compounds tert.-butylacrylate and tert.-butylmethacrylate with a fraction of 20% by mol to 32% by mol, D- monomers, selected from the group of compounds methylacrylate and methylmethacrylate with a fraction of 30% by mol to 50% by mol and E- monomers selected from the group of compounds with the general formula CH2=CR1-COOR2, where R1 is a hydrogen atom or a methyl group and R2 is a linear or branched alkyl group with at least five carbon atoms with a fraction of 10%
by mol to 40% by mol.
by mol to 40% by mol.
6. Photosensitive composition, which can be converted by exposure in developing solutions from an insoluble to a soluble state, said composition containing no phenol polymers and no novolacks, containing I - at least one photoacid generator and II - polymers formed from the following fractions of monomers relative to the polymer:
A - monomers selected from the group of compounds acrylic acid and methacrylic acid, with a fraction of 14% by mol to 19% by mol.
B - monomers selected from the group of compounds tert.-butylacrylate and tert.-butylmethacrylate, with a fraction of 26%
by mol to 40% by mol and D - monomers selected from the group methylacrylate and methylmethacrylate, with a fraction of 40% by mol to 55% by mol.
A - monomers selected from the group of compounds acrylic acid and methacrylic acid, with a fraction of 14% by mol to 19% by mol.
B - monomers selected from the group of compounds tert.-butylacrylate and tert.-butylmethacrylate, with a fraction of 26%
by mol to 40% by mol and D - monomers selected from the group methylacrylate and methylmethacrylate, with a fraction of 40% by mol to 55% by mol.
7. Photo sensitive composition, which can be converted by exposure in developing solutions from an insoluble to a soluble state, containing I- at least one photo acid generator and II- polymers which are formed from the following fractions of monomers, relative to the polymer A- monomers selected from the group of compounds acrylic acid and methacrylic acid, with a fraction of 13% by mol to 15% by mol, B- monomers selected from the group of compounds tert.-butylacrylate and tert.-butylmethacrylate with a fraction of 22.5% by mol to 30% by mol, D- monomers, selected from the group of compounds methylacrylate and methylmethacrylate with a fraction of 50% by mol to 65% by mol.
8. Composition according to one of the preceding claims, characterised by an average molecular weight Mw of the polymers from 30,000 to 90,000 preferably from 35,000 to 82,000 and with a polymolecularity index Pl of 1.6 to 3.1, preferably of 2.1 to 3Ø
9. Composition according to one of the preceding claims, characterised by a content of the photo acid generator from 1% by weight to 25% by weight, preferably of 2% by weight to 20% by weight, relative to the weight of the polymer in the composition.
10. Composition according to one of the preceding claims, characterised by one or several additionally included photo-sensitisers.
11. Composition according to one of the preceding claims, characterised by a content of photosensitisers from 1% by weight to 6% by weight preferably of 2% by weight to 4% by weight, relative to the weight of the polymer in the composition.
12. Use of the composition according to one of the claims 1 to 11 as an etching- or galvano-resist for structuring metal coatings.
13. Use according to claim 12, characterised by circuit boards provided with copper surfaces or for inner layer laminates to be used for circuit boards as well as polyimide/copper laminates used as electrical circuit carrier.
14. Photo sensitive composition, which can be converted by exposure in developing solutions from an insoluble to a soluble state, characterised by individual or all new features or a combination of shown features.
15. Use of the photo sensitive composition according to Claim 13, characterised by individual or all new features or combinations of shown features.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19546140.1 | 1995-11-28 | ||
| DE19546140A DE19546140C2 (en) | 1995-11-28 | 1995-11-28 | Photosensitive composition |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2238833A1 true CA2238833A1 (en) | 1997-06-05 |
Family
ID=7779769
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002238833A Abandoned CA2238833A1 (en) | 1995-11-28 | 1996-11-27 | Photosensitive composition |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0864119B1 (en) |
| JP (1) | JP3789137B2 (en) |
| AT (1) | ATE199187T1 (en) |
| CA (1) | CA2238833A1 (en) |
| DE (2) | DE19546140C2 (en) |
| ES (1) | ES2154849T3 (en) |
| TW (1) | TW495647B (en) |
| WO (1) | WO1997020254A1 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6800422B2 (en) * | 2001-05-11 | 2004-10-05 | Shipley Company, L.L.C. | Thick film photoresists and methods for use thereof |
| GR1004058B (en) * | 2001-05-31 | 2002-11-15 | Photoresists processable under biocompatible conditions for multi-biomolecule patterning | |
| JP2006145853A (en) * | 2004-11-19 | 2006-06-08 | Jsr Corp | Radiation-sensitive resin composition and manufacturing method of product formed by plating |
| EP3182203A1 (en) * | 2015-12-18 | 2017-06-21 | Heraeus Precious Metals North America Daychem LLC | A combination of nit derivatives with sensitizers |
| JP7402015B2 (en) * | 2019-11-05 | 2023-12-20 | 東京応化工業株式会社 | Chemically amplified positive photosensitive resin composition, photosensitive dry film, method for producing a photosensitive dry film, method for producing a patterned resist film, method for producing a substrate with a mold, and method for producing a plated object |
| TWI849024B (en) * | 2018-12-26 | 2024-07-21 | 日商東京應化工業股份有限公司 | Chemically amplified positive photosensitive resin composition, photosensitive dry film, method for manufacturing photosensitive dry film, method for manufacturing patterned resist film, method for manufacturing cast-on substrate, and method for manufacturing coated structure |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5045431A (en) * | 1990-04-24 | 1991-09-03 | International Business Machines Corporation | Dry film, aqueous processable photoresist compositions |
| JPH0539444A (en) * | 1990-11-30 | 1993-02-19 | Hitachi Chem Co Ltd | Positive type photosensitive anionic electrodeposition coating compound resin composition, electrdeposition coating bath using the same composition, electrodeposition coating and production of printed circuit board |
| US5372912A (en) * | 1992-12-31 | 1994-12-13 | International Business Machines Corporation | Radiation-sensitive resist composition and process for its use |
| US5374500A (en) * | 1993-04-02 | 1994-12-20 | International Business Machines Corporation | Positive photoresist composition containing photoacid generator and use thereof |
-
1995
- 1995-11-28 DE DE19546140A patent/DE19546140C2/en not_active Expired - Fee Related
-
1996
- 1996-11-23 TW TW085114470A patent/TW495647B/en not_active IP Right Cessation
- 1996-11-27 AT AT96941630T patent/ATE199187T1/en not_active IP Right Cessation
- 1996-11-27 ES ES96941630T patent/ES2154849T3/en not_active Expired - Lifetime
- 1996-11-27 DE DE59606441T patent/DE59606441D1/en not_active Expired - Lifetime
- 1996-11-27 WO PCT/EP1996/005313 patent/WO1997020254A1/en active IP Right Grant
- 1996-11-27 CA CA002238833A patent/CA2238833A1/en not_active Abandoned
- 1996-11-27 JP JP52018897A patent/JP3789137B2/en not_active Expired - Fee Related
- 1996-11-27 EP EP96941630A patent/EP0864119B1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| TW495647B (en) | 2002-07-21 |
| DE19546140A1 (en) | 1997-06-05 |
| EP0864119A1 (en) | 1998-09-16 |
| DE19546140C2 (en) | 1998-08-06 |
| JP3789137B2 (en) | 2006-06-21 |
| ES2154849T3 (en) | 2001-04-16 |
| EP0864119B1 (en) | 2001-02-14 |
| DE59606441D1 (en) | 2001-03-22 |
| JP2000500883A (en) | 2000-01-25 |
| ATE199187T1 (en) | 2001-02-15 |
| WO1997020254A1 (en) | 1997-06-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |