Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Forming nonplanar surface
Reexamination Certificate
2000-01-05
2003-03-25
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Forming nonplanar surface
C430S322000, C430S270100, C430S281100, C430S286100
Reexamination Certificate
active
06537735
ABSTRACT:
The present specification relates to methods of forming a desired pattern on a substrate which has coated on it a coating comprising a positive working radiation sensitive composition. The invention further relates to novel positive working radiation sensitive compositions per se, and to novel compounds used therein, and to the preparation thereof. The compositions are suitable for making lithographic printing forms or fine resist patterns of electronic parts such as printed circuits. The invention relates further to such lithographic printing forms and electronic parts per se, and to their production.
The art of lithographic printing is based on the immiscibility of ink, generally an oily formulation, and water, wherein in the traditional method the ink is preferentially retained by the image or pattern area and the water or fountain solution is preferentially retained by the non-image or non-pattern area. When a suitably prepared surface is moistened with water and an ink is then applied, the background or non-image area retains the water whilst the image area accepts ink and repels the water. The ink on the image area is then transferred to the surface of a material upon which the image is to be reproduced, such as, paper, cloth and the like. Commonly the ink is transferred to an intermediate material called the blanket which in turn transfers the ink to the surface of the material upon which the image is to be reproduced.
New types of “waterless” lithographic printing employ only an oily ink material and preferentially ink-accepting image areas and ink-repelling non-image areas on the printing form.
A generally used type of lithographic printing form precursor (by which we mean a coated printing form prior to exposure and development) has a light sensitive coating applied to an aluminium base support. Negative working lithographic printing form precursors have a radiation sensitive coating which when imagewise exposed to radiation of a suitable wavelength hardens in the exposed areas. On development the non-exposed areas of the coated composition are removed leaving the image. On the other hand positive working lithographic printing form precursors have a radiation sensitive coating, which after imagewise exposure to radiation of a suitable wavelength becomes more soluble in the exposed areas than in the non-exposed areas, in a developer. In both cases only the image area on the printing form itself is ink-receptive.
The differentiation between image and non-image areas is made in the exposure process where a film is applied to the printing form precursor with a vacuum to ensure good contact. The printing form precursor is then exposed to a light source, comprising UV radiation. In the case where a positive form precursor is used, the area of the film that corresponds to the image in the printing form precursor is opaque so that no light will strike the printing form precursor, whereas the area on the film that corresponds to the non-image area is clear and permits the transmission of light to the coating which becomes more soluble and is removed.
The photoresists used in pattern forming methods for electronic parts such as printed circuits are also classified into two types negative working and positive working. After exposure to radiation and development, the resist pattern is used as a mask for forming the patterns onto the underlying electronic elements—for example by etching an underlying copper foil. Due to the high resolution demands and the requirements of high resistance to etching techniques, positive working systems are widely used. In particular, there have in the main been used alkali developable positive working photoresists composed of alkali-soluble novolak resins as disclosed in J. C. Streiter, Kodak Microelectronics Seminar Proceedings, 1979, p. 116. The primary active component of such positive working compositions, both in the context of lithographic printing forms and electronic parts, is a naphthoquinonediazide (NQD) derivative.
The types of electronic parts whose manufacture may use a photoresist include printed wiring boards (PWBs), thick- and thin-film circuits, comprising passive elements such as resistors, capacitors and inductors; multichip devices (MDCs); and integrated circuits (ICs). These are all classified as printed circuits.
Imageable compositions may also be applied to masks. The required pattern is formed on the mask, which is then used as a screen in a later processing step, in forming a pattern on, for example, a printing or electronic part substrate.
Common to virtually all commercial applications of positive working systems over several decades have been compositions comprising alkali soluble phenolic resins and NQD derivatives. However, the role of the NQD derivatives in the compositions, in inhibiting developer resistance of the resin and increasing dissolution after exposure, is not well understood several decades after the effect was discovered by O. Süs (ref. Annalen 1944, 556, 65; German Patent 879,204).
The nature of the pure resin dissolution process has been studied in detail (Templeton et. al. SPIE Vol. 711 Advances in Resist Technology and Processing IV (1987), p. 136) and the effects of resin structure and developer components investigated. Phenolic resin dissolution is controlled by primary structural properties, such as bridging groups, substitution positions and steric effects of phenyl ring substituents, which significantly affect intra and intermolecular bonding of the resin chains, the so-called resin secondary structure. This secondary structure forms channels of hydrophilic sites through the resin which act so as to promote dissolution in the developer.
A number of complementary mechanisms have been proposed as to the nature of the solubility inhibition of the resins brought about by the use of NQD compounds, by a number of workers (Koshiba et. al., Regional Technical Conference of the SPE, Ellenville, N.Y., 1988, p. 235; Reiser et. al., Agnew. Chem. Ind. Engl. 1996, 35, p. 2428-2540; Honda et. al., SPIE Vol. 1262, Advances in Resist Technology and Processing VII, 1990, p. 493). Key mechanisms proposed have been: the presence of hydrophobic NQD in the resin matrix retarding penetration by aqueous developer; the alkali developer promoting a crosslinking, insolubilising reaction between the resin and the NQD at the interface between the resin and the developer; resin molecules being preferentially extracted from the thin interface layer into the developer causing a concentration build up of developer-insoluble NQD at the surface retarding further development; and a macromolecular structure formed between the hydrophilic sites of the resin and the polar groups of the NQD whereby the NQD acts to cap, or block, access of developer components to the hydrogen bonded secondary structure of the resin, thus preventing dissolution. The latter mechanism is generally regarded as the primary factor whilst the other mechanisms are regarded as making more minor contributions.
Also, the increased dissolution of the coatings after exposure has for decades been considered a result of the formation of an indene carboxylic acid, increasing alkali solubility. More recently Reiser et. al. have proposed that the exothermic degradation of the NQD breaks down the macromolecular structure which causes the initial inhibition. This is as a result of the loss of co-ordinating sites on the NQD and a heat pulse assisting in dispersing the structure of the resin previously imposed by the NQD.
All of the literature work on such NQD systems has concentrated on the use of simple NQD compounds in admixture with resins. However, it has been common practice for many years in the lithographic industry to utilise almost exclusively positive working systems whereby the photoactive NQD has been chemically attached to the resin itself, by esterification of the resin with an NQD sulphonyl chloride, to make a so-called NQD resin ester. These systems were developed primarily as a solution to crystallisation and/or migration of simple NQD compounds within coa
Bayes Stuart
McCullough Christopher David
Monk Alan Stanley Victor
Ray Kevin Barry
Spowage Mark John
Baxter Janet
Faigre & Benson LLP
Kodak Polychrome Graphics LLC
Thornton Yvette C.
LandOfFree
Pattern-forming methods and radiation sensitive materials does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pattern-forming methods and radiation sensitive materials, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pattern-forming methods and radiation sensitive materials will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3073545