Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Combined with the removal of material by nonchemical means
Reexamination Certificate
2001-05-10
2003-07-15
Karlsen, Ernest (Department: 2829)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Combined with the removal of material by nonchemical means
C438S690000, C438S758000, C438S778000, C438S780000
Reexamination Certificate
active
06593249
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of forming a metal pattern on a dielectric substrate coated with a layer of metal, preferably with a copper film.
2. Brief Description of the Related Art
In the past, many different methods of producing circuit patterns on electric circuit carriers have been proposed. In the panel plating process, a layer of copper that completely covers the drilled printed circuit board material is first produced in the thickness required for the circuit structures. Then, those regions of the outer sides of the printed circuit boards are covered with a layer of resist that correspond to the circuit structures to be formed so that these regions are protected during the subsequent etching process, thus being preserved. In the pattern plating process but a thin copper film is at first formed on the printed circuit board material. A layer of photoresist is for example applied there onto and the copper film is led bare again by photostructuring at the places that correspond to the circuit structures to be formed. A layer of galvanoresist is applied to the bare copper regions. Then, the layer of photoresist is removed and the bare copper film is removed by etching, the layer of galvanoresist protecting the layer of metal located underneath against the etching agent. In the subcase of the metal resist process, a layer of metal resist, a layer of terne metal for example, is applied as a galvanoresist layer.
These methods and other known methods present considerable disadvantages. More specifically, it is not possible to manufacture under manufacturing conditions circuit structures of widths of less than 100 &mgr;m in a reproducible way. Numerous attempts have been made to achieve this goal. With the help of some complicated methods and basic materials, such circuits could finally be produced. Such methods however are not suited for mass production since they are too expensive and complex and/or require very expensive basic materials. These methods are not suited to produce circuits with lines having a structure width of less than 50 micrometers though.
DE-A-18 113 77 discloses a method of manufacturing printed circuit boards with circuit lines applied on both sides thereof, in which an etch resist layer, more specifically a layer of tin, is exclusively applied to the copper film in the bores of the printed circuit boards that have been contacted through and in which the desired delineation pattern is made by etching. For this purpose, the outer sides of the boards are provided with a layer of varnish extending as far as the brinks of the bores prior to applying the etch resist layer.
DE 37 32 249 A1 indicates a method of manufacturing three-dimensional printed circuit boards in subtractive/semi-additive technique with image transmission on an insulating substrate in which the substrate coated with a copper film is at first coated all over with a tin metal resist that may be electroless plated and/or electrolytically deposited and the metal resist is then selectively exposed to laser irradiation without using a mask so that the circuit pattern created is a negative. The copper regions that have been laid bare may then be removed by etching.
EP 0 062 300 A2 also describes a method of producing printed circuit boards in which one copper film is applied on at least one side of a plastic substrate, the circuit pattern being then formed in the copper film in that a metallic etch resist layer is deposited onto the copper film, the etch resist layer being selectively evaporated according to the desired circuit pattern by means of a laser beam and the remaining copper film being removed by etching as far as the surface of the plastic substrate at the places removed by way of the laser treatment.
In Derwent Abstracts to JP-A-59227186 a method is outlined in which a photoresist is applied to the outer sides only of a printed circuit board that has been contacted through, then a metallic layer of etch resist, among others of solder metal or tin, is deposited on the walls of the bores, whereupon the photoresist with the delineation pattern is exposed to light and developed prior to finally removing by etching the copper that has been laid bare.
EP 0 757 885 B1 indicates a method of forming metallic circuit patterns on electrically isolating substrates in which at first a layer of metal is applied to the substrate prior to applying thereupon an organic protective layer with an electrophoretic dip coat. Then. , the protective layer is removed in the regions of the circuit patterns to be formed by means of laser irradiation. An etch resistant layer of metal is deposited onto the metal surface that has been laid bare. Then, the organic protective layer is cleared off in the regions adjacent the future circuit pattern by means of laser irradiation and the layer of metal that has been laid bare is also removed in these regions by means of an etching process. Laser irradiation is generated by an Nd-YAG-laser.
DE 41 31 065 A1 discloses still another method of manufacturing printed circuit boards, in which at first a layer of metal and then a metallic or an organic layer of etch resist is applied onto a substrate. It suggests using as a metallic layer of etch resist a layer of an alloy of tin or of terne metal and as an organic layer of etch resist a layer that may be produced by electrophoretic enameling or electrostatic coating. In the regions directly adjacent the future circuit pattern, the layer of etch resist is then removed by etching by means of electromagnetic irradiation, by means of laser irradiation for example, in such a way that the circuit pattern and islands of the layer of metal that are electrically isolated from the pattern by etching grooves remain on the substrate. Laser irradiation is generated by an Nd-YAG-laser. The document indicates that etching grooves of 150 &mgr;m width are produced with this method, the undercut of the layers of metal on each flank of the etching grooves amounting to 35 &mgr;m.
EP 0 469 635 A1 also describes a method of producing printed circuit boards in which a layer of metal and then an organic layer of etch resist are applied onto a substrate. The organic etch resist layer used is an electrophoretic dip coating. Subsequently, the layer of etch resist in the regions directly adjacent the future circuit pattern is cleared off by way of an Nd-YAG-laser and the thus laid bare layer of metal is removed by etching.
EP 0 489 560 A1 describes a composition of resin for forming a positive photoresist which is used as an anaphoretic varnish for manufacturing printed circuit boards. The resin composition is obtained by copolymerization of the following compounds: a) acrylic acid and methacrylic acid, b) compounds that are unstable in acids, for example tert.-butyl acrylate and tert.-butyl methacrylate and also c) a polymerizable monomer with which a homopolymer can be obtained that has a glass transition temperature T
g
of 0° C. or less, e.g. ethyl acrylate, iso-propyl acrylate, n-propyl acrylate, iso-butyl acrylate, 2-ethyl hexyl acrylate, n-hexyl methacrylate, n-octyl methacrylate and n-decyl methacrylate. The resist also contains a photoacid generator, e.g. a phosphonium, sulphonium, diazonium and iodonium salt. For structuring, the resist is exposed to light and developed, the regions being altered by the exposure in such a way that they are soluble in the processing solution.
The known methods either are extremely sophisticated and thus expensive or it is not possible to manufacture very fine structures with a width of 50 &mgr;m and less in a reproducible way. The only known possibility to produce such fine structures consists in starting from a material being provided with a copper film of no more than 5 &mgr;m thick. But it is extraordinarily complicated and thus expensive to manufacture such materials with this process. In using the customary materials with a thick copper film (usually 17 &mgr;m), it has been found that, on account of considerable undercut, the circuit structures often
Grieser Udo
Meyer Heinrich
Atotech Deutschland GmbH
Geyer Scott B.
Karlsen Ernest
Paul & Paul
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