«SPECIFICATION PATENT EUROPEAN © (§) Date of publication of patent spécification: 02.10.85 (§) Int. Cl.4: G 03 F 7/10, G 03 F 7 / 2 6, G 03 C ...»
J E u r o pEuropean e Patent Office
âisch s (ÏÏ) Publication number:
Office européen des brevets
(§) Date of publication of patent spécification: 02.10.85 (§) Int. Cl.4: G 03 F 7/10, G 03 F 7 / 2 6, G 03 C 1/00, G 03 C 1/72, ~ ® APP|ication number: 81300617.8 G 03 C 1/94, G 03 C 5 / 2 4 ® Dateoffiling: 13.02.81 (54) Photographie System and photographie material for use therein.
(§) Priority: 15.02.80 BG 46640/80 (73) Proprietor: Zlafop-Ban Quartal Geo Milev Block V-2 Sofia (BG) (43) Date of publication of application:
26.08.81 Bulletin 81/34 (§) Inventor: Konstantinov, Ivan Teofilov 13, St.Peshev Street (4§) Publication of the grant of the patent: Sofia (BG) 02.10.85 Bulletin 85/40 Inventor: Mednikarov, Borisiav Dimitrov 65, Vitosha Street Sofia (BG) (S) Designated Contracting States: Inventor: Sahatchiev, Maria Andreeva BECH DE FRGB Ll NL 27, San-Stefano Street Sofia (BG) Inventor: Burov, Atanas Tzvetanov (§) Références cited: 53, LKaravelov Street US-A-3 762 325 Sofia (BG) Représentative: Silverman, Warren et al OÛ HASELTINE LAKE & CO. Hazlitt House 28 Southampton Buildings Chancery Lane
co Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1 ) European patent convention).
LU Courier Press, Leamington Spa, England.
This invention relates to a photographic system for use in photolithography, for use for example in the production of microelectronic circuits and the production of sensitizing and printing elements in offset printing formes and to photographic materials for use therein.
As used herein, a photographic system denotes a combination of materials to be used together, namely a combination of a photographic material comprising a photosensitive layer of the type to be described herein and an alkaline developing agent to be used on the photosensitive layer after exposure thereof to radiation, to obtain a visible photographic image.
It is known that some inorganic photosensitive substances, such as arsenous sulphide undergo changes in some of their physical and chemical properties after exposure to radiation of various types. If only partial or imagewise exposure to radiation of such substances takes place, it has been found that the change in chemical properties on irradiation includes an increase in the rate of dissolution in certain solvents in those areas of the photosensitive substance which have been irradiated as compared to the non-irradiated areas. The solvents generally employed are alkaline solutions. These inorganic photosensitive substances are nevertheless stable to some chemical reagents, for example acids, thereby enabling acid to be employed to etch out metal exposed on dissolution of exposed photosensitive substance leaving a metal image corresponding to the subject originally photographed on removal of the residual undissolved photosensitive layer. Such a procedure for use of the photographic material of the aforementioned type in the production of photoresist materials, for example for use in the production of microelectronic printed circuits is described by Nogai. H, Yoshikawa. A, Toyoshima. Y, Ochi. 0 and Mizushima. Y in Applied Physics Letters 28, 145 (1976) and in Applied Physics Letters 29, 677 (1976). The capacity for inking of the materials resulting from dissolution of imagewise exposed photosensitive material renders them suitable, in principle, for use in the production of offset printing formes (U.S. Patent No. 3,762,325). Notwithstanding the advantages given in the first two aformentioned references of such a photographic system for use in the production of photoresist material, as compared to the previously widely used photolacquers, namely exceptionally high resolution, the possibility of depositing the photosensitive layer on a substrate by evaporation in a vacuum, thereby achieving excellent uniformity and impurity-free preparation conditions, very good adhesion, thereby allowing the more intricate processes of etching of the substrate or an intermediate layer to be carried out successfully, nevertheless such photographic materials have not hitherto found practical application. The main reason for this is the low ratio between the rates of disssolution of imagewise exposed and unexposed photosensitive substance in the presence of the usual alkaline solutions employed for such purpose. This ratio may be termed photoselectivity of dissolution. This ratio increases on increasing the extent of exposure, but even when exposure is at the maximum practical, the alkaline development procedure does not provide sufficient photoselectivity of dissolution. Moreover, the photographic material is generally insufficiently sensitive to the comparatively high exposure required to achieve the maximum photoselectivity of dissolution.
Hence the following two disadvantages of the aforementioned type of photographic system may be
1. Low sensitivity in comparsion to organic photolacquers hitherto used.
2. Very poor tolerance during the duration of the alkaline development, i.e. development to the critical extent is difficult to achieve.
The critical character of the alkaline development results from the low photoselectivity of dissolution which results, on complete removal of exposed inorganic photosensitive substance, in unexposed areas being affected to some extent depending upon the amount of exposure and on the activity of the alkaline developer as a solvent for the photosensitive substance, the pH of the developer being of particular importance here. Because of the way in which the two aforementioned disadvantages are inter-related, there has not hitherto been described any photographic system which simultaneously solves both problems.
Experiments carried out by the inventors have revealed two further disadvantages in such photographic systems. The first is the appearance of pinholes in the photosensitive layer after alkaline development and treatment with an acid etching solution, for example an acid ceric ion-containing solution for chromium. The second disadvantage is the increase in the number and size of these pinholes which takes place when these photographic materials undergo storage over a period of time before processing.
This ageing process makes the exposed photographic materials unusable as photoresists after a certain storage time, or even immediately after their production when particularly high standards are placed on the photoresists, as for example in the production of microelectronic printed circuits. Bearing in mind the characteristic advantages of a photographic system of the aforementioned type, it will therefore be appreciated how the overcoming of the aforementioned disadvantages would yield a product capable of wide application in photolithographic processes.
It is an object of this invention to produce a photographic material or photographic system of the aforementioned type, the photographic material comprising a photosensitive substance and the photographic system comprising an alkaline developer to be used thereon after imagewise exposure, which shows good photo-selectivity of dissolution after exposure to radiation.
It is a further object of the invention to provide methods for the production of such photographic systems and photographic materials for use therein which lead to the productioin of a photographic material which is stable on storage and which because of the photoselectivity of dissolution on development will provide high photographic sensitivity, thereby enabling use of the developed photographic material for photolithographic purposes.
According to the present invention, there is provided a photographic material for use in photolithography, which material is capable of yielding, on imagewise exposure to radiation, a latent positive image, which material comprises a carrier base and on the carrier base, optionally with interposition therebetween and the carrier base of an intermediate layer having adhesive and/or insulating and/or hydrophilic properties, a thin homogenous vapour deposited or heterogeneous photosensitive layer comprising at least one photosensitive substance selected from chalcogenides of phosphorous, arsenic, germanium and metals belonging to Groups Ib, Ilb, Illa, IVa and Va of the Periodic System of the Elements, which photosensitive substance is capable upon exposure to radiation of exhibiting photoselective capacity for dissolution in an alkaline developer which is an aqueous solution of an alkaline developing agent, the photographic material being optionally in association with a said alkaline developer for use on the photographic material after exposure to radiation, thereby forming a photographic system, characterised in that the photographic system, characterised in that the photographic material or the alkaline developer when in association therewith in a said system, contains at least one organic compound selected from dyestuffs having the capacity for dyeing tannined cotton, dyestuffs having the capacity for dyeing synthetic fibres, compounds capable of acting as accelerators, antioxidants or age resistors in the vulcanization of elastomers and developing agents effective in the development of silver halide-based photographic materials.
The carrie base of a photographic material, either embodying the invention or used in association with an alkaline developer in a photographic system embodying the invention, can be of any one of a wide variety of materials, for example, plastics, paper, cardboard, glass, ceramic material or metal. The size, shape and contours of the surface of the carrier base to which the photosensitive layer is to be applied can be selected in accordance with the intended use of the photographic material to be produced. In some cases, it may be necessary for there to be between the carrier base and the photosensitive layer, an intermediate layer which does not react with the photosensitive layer when the latter is exposed to radiation and which is formed, for example, of rubber, lacquer, plastics, metal, for example chromium or aluminium, dielectric materials used in the production of thin films for optical purposes etc., or a combination of several such layers applied in turn. Depending on the properties thereof, the intermediate layer or layers serve to improve the adhesion of the photosensitive layer to the carrier base and/or the isolation of the photosensitive layer from the carrier base when the latter might otherwise react with the photosensitive substance during exposure and/or to render the carrier base hydrophilic as for example when it is to be used in the production of offset printing formes. The provision of metal intermediate layers will be of particular value when preparing photoresist materials.
The photosensitive layer comprises an inorganic photosensitive substance which, after exposure to radiation, undergoes photoselective dissolution on treatment with an alkaline developer. Such inorganic photosensitive substances may be deposited pure or doped with halogen and will be sulphides, selenides and tellurides of one or more elements selected from phosphorous, arsenic, germanium and certain metals, being metals belonging to groups Ib, Ilb, Illa, IVa and Va of the Periodic Table of the elements, being especially antimony (III), cadmium and bismuth, as in for example antimonous, cadmium and bismuth sulphides. Another preferred material is phosphorous sulphide. The photosensitive materials are preferably amorphous substances, for example arsenous sulphides and mixtures of a number of the aforementioned elements, in particular arsenic, sulphur, germanium and selenium. From the foregoing, it will be appreciated that the photosensitive substances are not ncessarily simple compounds but may contain the respective elements in other than an exact stoichiometric ratio.
The development of the photographic material in discrete areas to obtain a latent positive image is carried out using an alkaline developer, that is an aqueous alkaline solution. For this purpose it-is possible to employ, for example, salts of strong bases and weak acids, for example lithium, sodium, potassium and ammonium carbonates, phosphates, sulphides, polyphosphates or borates, hydroxide solutions, for example alkaline metal hyroxides and aqueous ammonia, solutions of organic compounds which undergo alkaline reaction, for example aliphatic amines, diamines, polyamines, and quaternary phosphonium oxides.
Both the inorganic photosensitive substance and the alkaline developing agent may contain mixtures of substances as aforementioned.
The organic compounds employed according to the present invention in the photographic material itself or in the developing agent for use therewith in order to improve the properties and photographic characteristics of the photographic material after processing may be selected from three fundamental classes of materials.
Thus, it is possible to employ an organic dyestuff which may be a dyestuff suitable for use in the dyeing of tannined cotton. Examples of dyestuffs which may be used for this purpose and in the aforementioned photographic materials are xanthine, acridine, azine, oxazine, thiazine, diphenylmethane, triphenylmethane, cyanine and basic azodyes. It is also possible to employ dyestuffs suitable for use in the dyeing of synthetic fibres, especially polyacrylonitrile and acrylic fibres in general. Dyestuffs of such type are the commercially available dyes known as Basacryl, Sandocryl, Astrazon, Deorlin, Maxilon and Setacyl dyestuffs depending upon the manufacturer thereof. Although each of these dyestuff names is a trade mark, these trade marks have come to be accepted in the art as the common names by which the dyestuffs are known.
A second group of organic compounds which may be employed are those used in the vulcanization of
elastomers as accelerators, antioxidants or age resistors. Examples of these compounds are the following:
1. dithiocarbamates and derivatives thereof having e.g. the general formula: