Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
2000-02-04
2002-05-28
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S314000, C430S003000, C427S058000, C428S338000
Reexamination Certificate
active
06395454
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention lies in the semiconductor technology field. More specifically, the invention relates to a process for the production of an integrated electrical circuit, in which one or more dielectric layers and one or more structured semiconductor layers as well as at least one metal plane are applied on a substrate. A monomolecular film, made up of molecules which contain at least one anchoring group, is applied as a passivation layer to the metal plane by wetting the metal plane with a solution. Metal wires are connected to the metal plane.
It is known in the art that integrated electrical circuits, which contain a metal plane, can be protected against corrosion and mechanical damage by providing the metal plane with a passivation layer.
Dielectrics (e.g. silicon nitride: Si
3
N
4
) and metal passivations (e.g. titanium, tantalum, aluminum, palladium) have to date been used as diffusion and oxidation barriers.
In order to buffer against mechanical stresses, it has been found effective to provide these passivation layers with an additional organic layer, in particular a polymer layer. The thickness of the polymer layer is at least one micron (1 &mgr;m). Other organic protective layers also have a defined minimum thickness of preferably more than 200 nm.
The prior art passivation layers are used in the large-scale fabrication of integrated circuits. In prolonged operation or under high operating temperatures, however, instabilities occur which may lead to a rupture of the passivation layer. A further disadvantage of these passivation layers is the impediment caused by them when making contact with the metal plane using connection wires. It is hence necessary, before making contact, to apply a mask (by depositing resist, exposing and developing), and subsequently to treat the contact locations using anisotropic metal etching.
Japanese patent application JP-A-6041183 discloses a metal surface of a biosensor. A surface of the biosensor is covered with a monomolecular layer.
Such monomolecular layers are used as passivation layers for integrated semiconductor circuits. U.S. Pat. No. 5,264,731 discloses an integrated semiconductor circuit whose surface is first covered with a monomolecular passivation layer and then enclosed with a synthetic resin.
SUMMARY OF THE INVENTION
The object of the invention is to provide a process for the production of an integrated electrical circuit which overcomes the above-noted deficiencies and disadvantages of the prior art devices and methods of this kind, and in which, on the one hand, the passivation layer is produced in the simplest and most cost-effective way and, on the other hand, the passivation layer does not impede the connection of metal wires to the metal plane. It is a further object to render it possible for the application of the passivation layer to be integrated in the process sequence for the production of the integrated electrical circuit.
With the above and other objects in view there is provided, in accordance with the invention, a method of producing an integrated electrical circuit, which comprises:
forming one or more dielectric layers, one or more structured semiconductor layers, and at least one metal plane on a substrate;
wetting the metal plane with a solution for applying a passivation layer on the metal in the form of a monomolecular film made up of molecules containing an anchoring group; and
subsequently connecting a metal wire to the metal plane with a pressure sufficient to pierce the monomolecular film.
In other words, the passivation layer is applied before the metal wires are connected to the metal plane, and the metal wires are connected to the metal plane using a pressure which is sufficient to pierce the monomolecular film.
In accordance with an added feature of the invention, the metal plane is formed of copper, silver, or gold.
In accordance with another feature of the invention, the anchoring group of the molecules of the monomolecular film is a thiol. In a preferred embodiment, the molecules of the monomolecular film are alkanethiol molecules.
In accordance with an additional feature of the invention, the anchoring group of the molecules of the monomolecular film is a sulfide or a disulfide.
With the above and other objects in view there is also provided, in accordance with an alternative feature of the invention, a method of producing an integrated electrical circuit, which comprises:
forming one or more dielectric layers, one or more structured semiconductor layers, and at least one metal plane on a substrate;
wetting the metal plane with a solution for applying thereon a passivation layer in the form of a monomolecular film made up of molecules containing an anchoring group; and
subsequently connecting a metal wire to the metal plane by performing the following steps:
energizing the monomolecular film at locations defined for connection to the metal wires in a controlled manner using electromagnetic radiation with an energy great enough for a bonding of the molecules to the metal to be weakened at the locations; and
connecting the metal wires to the metal plane at the locations.
In other words, the alternative mode of connecting the wires to the metal layer includes the following process steps:
energy is delivered to the monomolecular film at the locations intended for connection to the metal wires in a controlled way using electromagnetic radiation. The energy is great enough for the bonding of the molecules to the metal to be weakened at these locations; and
the metal wires are connected to the metal plane at these “weakened-bond” locations.
In accordance with an added feature of the invention, prior to connecting the metal wires to the metal plane, a solution is applied that has a solvent power sufficient to dissolve the molecules whose bonding to the metal has been weakened in the energizing step.
In accordance with again an added feature of the invention, the film is washed with high-purity deionized water and subsequently dried with nitrogen.
In accordance with again an additional feature of the invention, the film at the specified locations is radiated with UV light.
In accordance with an alternative feature of the invention, the energizing step comprises exposing with an extra-high-pressure mercury lamp.
In accordance with a concomitant feature of the invention, the energizing step comprises exposing with a laser.
In once more summarizing the invention, a film is provided in direct contact with the surface of the metal to act as a passivation layer. Because the film consists of molecules whose adhesion to the metal surface is very strong, it is not possible for any further substances to be taken up. A monomolecular protective film is hence provided.
Such a protective film is distinguished in that it can be formed straightforwardly by dipping the electrical circuit in a solution. It is hence possible to provide more than 100 integrated electrical circuits with the passivation layer in one solvent simultaneously.
Further layers, for example an additional protective film, may be applied to the monomolecular film, although, just the monomolecular film itself is actually sufficient to obtain the desired properties of the passivation layer.
In contrast to the passivations known in the prior art, which have as large a passivation layer thickness as possible, the invention hence proposes that the passivation layer be formed in such a way that it has a minimal thickness and can bond in an ideal way conformally to the surface of the metal.
Such a bond between the metal surface and the film is obtained, according to a particularly advantageous embodiment, in that the monomolecular film consists of molecules which contain an anchoring group. The electrons of this anchoring group can interact with the metal surface. Relevant inter-action mechanisms include both physical adsorption processes as well as covalent and ionic forces.
The effect of the exothermic interaction of the anchoring group with the metal surface is that the molecules contained in solution
Barreca Nicole
Greenberg Laurence A.
Huff Mark F.
Infineon - Technologies AG
Lerner Herbert L.
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