Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
2002-05-28
2003-10-21
Duda, Kathleen (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S330000, C427S096400
Reexamination Certificate
active
06635410
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
In microelectronics, metallic conductors are produced, inter alia, by chemical or electrochemical deposition methods. There is a continuous trend toward more reliable and more economical methods. The metallic conductor tracks of an integrated circuit (IC) or of a multichip module (MCM) consist of, for example, copper. The conductor tracks are insulated using an organic or inorganic dielectric,: such as polyimide or silica. For so-called rewiring of the outer contacts of ICs, simple and selective methods are required for increasing the performance and for reducing the costs. The methods customarily used at present are generally complex and expensive because they consist of numerous individual processes, and also in part, because they include expensive vacuum processes (cf. for example: H. Eigler, W. Beyer “Moderne Produktionsprozesse der Elektrotechnik, Elektronik und Mikrosystemtechnik: Entwurf—Optimierung—Technologietransfer” (Modern production processes of electrical engineering, electronics and Microsystems technology: Design—optimization-technology transfer), expert-Verlaq, 1996, pages 304 to 309).
Thus, for example, applying a thin metal layer, i.e. an electroplating starting layer, to the dielectric using a vacuum process is known. A photoresist is then applied to this metal layer by spin-coating and the photoresist is exposed to light and developed. As a result of the lithographic structuring, specific parts of the surface are bared and the bare metal surface is then metallized by electroplating. After the photoresist has been stripped, a thin electroplating starting layer is etched (cf. for example: W. Menz, P. Bley “‘Mikrosystemtechnik für Ingenieure” (Microsystems technology for engineers), VCH Verlagsgesellschaft mbH, 1993, pages 192 to 194, 198 to 199 and 251). However, such a procedure is complicated and expensive.
Published German Patent Application DE 198 51 101 A1 discloses a method for the selective deposition of a metal layer on the surface of a plastics substrate. Those parts of the surface that are to be coated are exposed to electromagnetic radiation, such that chemical bonds are cleaved and functional groups are created as reactive centers. The irradiation is effected in particular using UV radiation at wavelengths of <320 nm, preferably 222 nm. After the irradiation, which is effected using a mask or using a writing laser beam, a noble metal compound is fixed at the reactive functional groups of the surface. For this purpose, the plastics part is either immersed in a swelling solution, for example, in a 5 molar aqueous NaOH solution, or brought into direct contact with a solution containing the substance to be deposited, i.e. with a seed solution. The metal layer is then deposited in a currentless metallization bath.
Such a procedure is not feasible in microelectronics since high-energy radiation, in particular having a wavelength of 222 nm, is required for cleaving the chemical bonds. However, there are no sufficiently powerful lamps of this wavelength. Therefore, the exposure times are substantially longer (factor of >10) than in the case of standard exposures to light. As a result, however, the throughput of seedable substrates is greatly limited and moreover the required excimer UV lamps are very expensive. In addition, low molecular weight fragments that may soil expensive masks are liberated during the cleavage of the bonds. A further disadvantage of the known process is that it is only positive-working, i.e. only the parts exposed to light can be seeded. A procedure in the negative mode, whereby the unexposed parts are seeded, is not possible. This may entail high additional costs for new masks when only negative masks are required, for example, for existing processes.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for metallizing dielectrics which overcomes the above-mentioned disadvantages of the prior art methods of this general type.
In particular, it is an object of the invention to provide a method that is suitable for selectively metallizing dielectrics and that can be used, in particular, in microelectronics. It is necessary to fulfill the requirement for compatibility with the conditions of existing process lines.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for metallizing dielectrics that includes steps of: applying a photosensitive dielectric including a photosensitive polymer precursor to a substrate; and performing either a first process sequence or a second process sequence. The first process sequence includes exposing the photosensitive polymer precursor to light through a mask, seeding the photosensitive polymer precursor with a metal, and subjecting the photosensitive polymer precursor to a thermal treatment. The second process sequence includes seeding the photosensitive polymer precursor with a metal, exposing the photosensitive polymer precursor to light through a mask, and removing excess seeding material. After performing either the first process sequence or the second process sequence, the photosensitive polymer precursor is chemically metallized.
In accordance with an added feature of the invention, the step of applying the photosensitive dielectric includes: applying the photosensitive polymer precursor, which is in a form selected from the group consisting of a dissolved form and a pasty form, to the substrate, and then drying the photosensitive polymer precursor.
In accordance with an additional feature of the invention, the photosensitive polymer precursor is treated with a metal-containing seed solution or an emulsion.
In accordance with another feature of the invention, the photosensitive polymer precursor is exposed to light through a mask having narrow valley structures and narrow hole structures.
In accordance with a further feature of the invention, the photosensitive polymer precursor has a high chemical and thermal stability.
In accordance with a further feature of the invention, the photosensitive polymer precursor is seeded with a noble metal compound.
In accordance with a further added feature of the invention, the seeding material includes a metal of oxidation state 0.
In accordance with yet an added feature of the invention, the seeding material includes a photosensitive metal complex.
The objects of the invention are achieved by a procedure in which a photosensitive dielectric is applied to a substrate. The dielectric is exposed to light through a mask, the dielectric is seeded with a metal, the dielectric is subjected to a thermal treatment, and the dielectric is then chemically metallized. Alternatively after being applied to the substrate, the dielectric can first be seeded with a metal and can then be exposed to light through a mask. Thereafter, excess seeding material is removed and the dielectric is chemically metallized.
The inventive method thus takes place in a manner such that a photosensitive dielectric is first applied to a substrate. The dielectric is preferably, applied in dissolved or pasty form to the substrate, i.e. in a more or less liquid phase, and is then dried. Thereafter, the dielectric is exposed to light through a mask and is selectively seeded. “Seeding” is understood here as meaning the binding of seeds to the surface and the chemical activation of the seeds. Thereafter, the dielectric is subjected to a thermal treatment, i.e. heated, and chemically metallized. The heating is effected in general at a temperature of 90 to 450° C.
In an alternative procedure, seeding material is first adsorbed onto the total surface of the dielectric. The selective anchoring and activation of the seeds is then affected by exposing them to light through a mask. Thereafter, excess seeding material is removed and the dielectric is chemically metallized. The seeding material is removed, in general, by washing it away with water or with a solvent.
In both cases, the seeding (with a metal) is preferably effected by treating the dielectric with
Haussmann Joerg
Lowack Klaus
Radlik Wolfgang
Schmid Guenter
Sezi Recai
Duda Kathleen
Greenberg Laurence A.
Infineon - Technologies AG
Locher Ralph E.
Stemer Werner H.
LandOfFree
Metallizing method for dielectrics does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Metallizing method for dielectrics, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Metallizing method for dielectrics will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3167432