Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
1999-10-19
2001-01-16
Nguyen, Nam (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S192120, C205S118000, C205S135000, C216S041000, C438S703000
Reexamination Certificate
active
06174416
ABSTRACT:
BACKGROUND INFORMATION
1. Field of the Invention
The present invention relates to a micromechanical component, which is composed of multiple layers, for example electrically conductive and non-conductive layers or areas, or layers or areas made of metallic and non-metallic materials, and a method for its production.
2. Background Information
In a component used as a microvalve and described in German Patent Application No. 39 19 876, individual layers are processed by micromechanical production methods in the construction of the microvalve. For example, the surface of a silicon wafer is patterned by photolithography and predetermined areas partially removed in a subsequent etching step, thus forming the mechanical elements by processing these layers in a three-dimensional pattern.
Conventional production methods include UV gravure lithography for patterning the non-conductive areas and multilayer electroplating for producing metallic, conductive areas. In this case, a conductive start layer for later electrodeposition with the application of external current in the proper areas is also needed on non-conductive carrier layers.
Conductive metal layers applied as carrier layers to the entire surface of non-conductive substrates are known as metallic start platings. These start layers can be applied by resist-coating (spraying, dipping, spinning, etc.) or with the aid of various wet-chemical methods or PVD (physical vapor deposition) methods (vaporization, sputtering, etc.). They either have an intrinsic electrical conductivity that is sufficient for electroplating with the application of external current or are used as the nucleation layer for deposition of a metal layer without the application of external current, which, in turn, serves as the start layer for subsequent multilayer electroplating with the application of external current.
Wet-chemical methods (DMS-E methods) for patterning surfaces are also known from p.c. board technology discribed in European Patent Application No. 0 206 133), for example, in order to make the holes drilled into the p.c. board conductive. In this case, a start layer is patterned or applied selectively to the non-conductive areas of the p.c. board surface, thus making the entire surface electrically conductive. However, these processing methods are incompatible with the processes of UV gravure lithography and multilayer electroplating because they lack the necessary precision.
Methods which allow two metal layers on an intermediate layer to be separated are also known. To do this, the intermediate layer is selectively removed from the remaining materials in the form of a sacrificial layer by etching or stripping. This method leaves gaps measuring several &mgr;m thick between the layers to be separated, which is disadvantageous especially when tight-fitting surfaces need to be produced which will also be used as sealing surfaces.
SUMMARY OF THE INVENTION
In one embodiment, a method for producing a micromechanical component according to the present invention has the advantage that, in carrying out the multilayer electroplating step, metallic start platings are applied which are compatible with the other processes and materials used in UV gravure lithography and multilayer electroplating. The metallic start plating according to the present invention makes it possible to deposit the new electroplated layer so that it adheres well to the layer beneath it, thus providing three-dimensionally patterned components in a layered structure.
The method according to the present invention for producing the micromechanical components has a particular advantage over previously known processes, especially with regard to the metallic start plating of a substrate that has electrically conductive and non-conductive areas, for the following reasons:
1: It is possible to use sputtering processes at substrate temperatures below 100° C., or wet-chemical processes in a pH range below pH 8.5 (very slightly alkaline or acidic values) which are compatible with the materials and production processes used in UW gravure lithography. The resists in the non-conductive areas thus continue to adhere to the substrate during the production steps and can be removed as needed at the end of the process chain using the Conventional.
2: The metallic surfaces of the conductive areas are chemically passivated by the individual process steps only to the extent that, prior to the application of each new plating, they can be reactivated as needed using standard methods, so that they can accept additional metal layers. This is the only way to ensure that the metallic electroplated layers deposited upon one another will adhere firmly to each other.
3. The sputtered layer is patterned by etching the lower electroplated layer. This ensures that the nucleation or start layer covers the non-conductive areas very precisely, leaving the metallic areas of the substrate unchanged. The adhesion between the electroplated layers can therefore be as strong as the adhesion between two unpatterned electroplated layers deposited upon one another.
According to another embodiment, the metallic start plating is designed so that one poorly adhering layer is provided in the form of a start layer in certain areas of the substrate. In these areas, the upper electroplated layer can be lifted away from the lower one, and moveable components can be created with as narrow a clearance as desired between their contact surfaces. Examples include sealing elements for fluid applications and normally closed switching elements.
The production method according to the present invention makes it possible to further develop the manufacturing methods using UV gravure lithography and multilayer electroplating in order to produce components with three-dimensional patterns and recesses. This is achieved with the use of the electrically conductive intermediate layers, which allow metals to be deposited electrolytically, i.e., with the application of external current, to surfaces that have metallic patterns and electrically insulating plastic. The metallic areas in the surface of the layers are generally composed of a lower electroplated layer, and the insulating areas are composed of a photopatterned resist (such as polyimide, AZ resist (photoresist) or solid resists).
Applications of the component according to the present invention are three-dimensional microcomponents made of metal with recesses, such as turbulent flow nozzles for fuel-air mixing in spark-ignition engines as well as microsensors or components which have additional movable structures such as microvalves, microrelays, microswitches, or micromotors.
REFERENCES:
patent: 5080763 (1992-01-01), Baigetsu
patent: 5194402 (1993-03-01), Ehrfeld et al.
patent: 5387495 (1995-02-01), Lee et al.
patent: 5755947 (1998-05-01), McElhanon et al.
patent: 6030851 (2000-02-01), Grandmont et al.
patent: 39 19 876 (1990-12-01), None
patent: 0 206 133 (1986-12-01), None
Minami et al., “Fabrication of Distributed Electronic Micro Actuator (DEMA)”, Journal of Microelectromechanical Systems, Bd. 2, Nr. 3, pp. 121-127.
Glas Ronald
Glock Armin
Jauernig Alexandra
Krauss Elke
Magenau Horst
Kenyon & Kenyon
Nguyen Nam
Robert & Bosch GmbH
Ver Steeg Steven H.
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