A METALLIC BUILDING ELEMENT FOR OPTOELECTRONICS

Abstract: The present invention relates to a method of patterning metallic building elements, and also to a metallic building element, where the measuring accuracy achieved can lie in the sub-micrometer range. Starting from a silicon master or original that can be etched to sub-micrometer precision and then plated with a metal, such as nickel (3), on the silicon surface, there can be produced a nickel shim where precision and surface fineness can lie in the sub-micrometer range. Subsequent to removal of the silicon master, a photo-sensitive material (5) can be used in liquid form or in film form to create mould cavities (9) that reach down to the nickel shim. These cavities can then be metal-plated to provide a building element (8) of higher precision in three dimensions.

Description: A METALLIC BUILDING ELEMENT FOR OPTOELECTRONICS FIELD OF INVENTION The present invention relates to a method of patterning metallic building elements and to a patterned metallic building element, said building element being produced in accordance with the method of patterning metallic building elements, wherein the measurement accuracy obtained can lie in the sub-micrometer range. The building elements produced in accordance with the method may be used, among other things, as carriers for optoelectrical and electrical components, and fibres and waveguides. The metallic building elements may also be used as micromechanical building blocks or as parts of a mould cavity for injection moulding or compression moulding purposes. BACKGROUND ART The technique at present used for mounting optoelectric laser chips in low-cost applications most often includes soldering of a chip to a ceramic or silicon carrier. Alignment between the optical active part of a laser and the core of a fibre can be achieved by virtue of the possibilities of etching silicon with great precision and the use of a technique in which the laser is firmly soldered and aligned with the aid of the surface tension forces present in a solder melt. Some sort of gluing technique is normally used, for instance, to fasten pin diodes to a carrier. Optical mirrors produced by etching in silicon and metallising the surface are often used to reflect light from a fibre to a pin diode. When an optoelectric laser chip is to be mounted on a ceramic carrier or a silicon carrier, there often arises the problem of dissipating heat generating in the chip. Varying chip temperature can, in operation, influence the transmitted wavelength. An excessively high operating temperature can also shorten the useful life of the chip. Furthermore, ceramic and silicon carriers often demand a high price, due to the relatively complicated manufacturing processes involved. SUMMARY OF THE INVENTION The technique described in accordance with the invention enables the cost-effective production of building elements that can be used either free-standing or as a substantial, pattern-creating part in a mould cavity intended for injection moulding or compression moulding purposes. The technique can be used to create metallic carriers that have low thermal resistance and good electrical conductivity, with the intention of preventing damage to electrical and optoelectrical chips, such as lasers, due to high or varying temperatures . With a starting point from a silicon original or master, which can be etched to sub-micrometer precision and then plated with a metal, such as nickel, on the silicon surface, it is possible to produce a nickel shim with a precision and a surface fineness that will still lie in the sub-micrometer range. If necessary, the rear side of the shim can then be made flat prior to separating silicon from nickel. Subsequent to removing the silicon master, a photo-sensitive material, in liquid form or in film-form, can be used to create cavities that reach down to the nickel shim. These cavities can then be metallised, to form three-dimensional building elements of high precision. These metal precision elements can then be used, for instance, for effectively conducting away heat from lasers or other heat-generating chips. The precision, surface fineness and measurement accuracy that can be achieved with the method also enable optoelectrical components, such as, e.g., lasers with optical single-mode fibres and sharp optical mirrors to be aligned. The method also provides building elements that can conduct electric current, which enables three-dimensional electric conductors and electrodes to be produced to a specified thickness. The template or form produced in accordance with the aforedescribed method can also be used repeatedly in plating cycles, therewith contributing to low- cost production of the plated building elements. The invention will now be described in more detail with reference to a preferred embodiment thereof and also with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure la is a cross-sectional view of a micro-worked silicon plate . Figure lb is a cross-sectional view of the patterned silicon plate covered with a thin metal film. Figure lc is a cross-sectional view of the coated silicon plate coated with a further metal layer. Figure Id is a cross-sectional view of the coated silicon plate where the metal layer coating in Figure lc has been levelled or smoothed-off . Figure le is a cross-sectional view of metallic layers that remain subsequent to the removal of the silicon plate. Figure If is a cross-sectional view of the remaining metal layers covered with a separation layer. Figure lg is a cross-sectional view of the remaining metallic layers with the separation layer laminated with a photosensitive material. Figure lh is a cross-sectional view of the metallic layers according to Figure lg exposed to light with the aid of a photomask. Figure li is a cross-sectional view of the metallic layers according to Figure lh with dissolved parts. Figure lj is a cross-sectional view of the metallic layers according to Figure li with metal-filled cavities. Figure Ik is a cross-sectional view of the metallic layers according to Figure lj with remaining photosensitive material etched away. Figure 11 is a cross-sectional view of various separated, released and therewith formed building elements. Figure lm is a cross-sectional view of remaining metallic layers that can be reused as moulds or templates according to Figure lg. DESCRIPTION OF PREFERRED EMBODIMENTS Figure la illustrates a micro-worked silicon plate 1. The resultant pattern can be obtained in one or more of the following ways: dry etching, wet etching, laser processing or spark processing. Figure lb shows how a thin metal layer 2, a so-called start layer, has been sputtered or vaporised on the patterned silicon plate 1 to enable subsequent initiation of a plating process . Figure lc shows how a metal 3, and then preferably nickel, has been plated on the thin metal layer 2 on the silicon plate 1, to provide a so-called nickel shim on the start layer. Figure Id shows how the nickel shim 3 firmly seated on the silicon plate 1 has been levelled or smoothed by some mechanical process, for instance by smooth grinding or polishing. Figure le shows how the silicon plate 1 and the nickel shim 3 have been separated from one another after being reversed. Figure If shows how the nickel shim 3 has been coated with a separation layer 4 on the existing start layer 2, said separation layer enabling separation in a later stage, as described hereinafter with reference to Figure 11, but does not prevent plating, see hereinafter with reference to Figure lj . Figure lg shows how the nickel shim 3 with layers 2 and 4 has been laminated with a photo-sensitive material 5. Figure lh shows how selective parts of the photo-sensitive material 5 have been exposed to light, with the aid of a so- called photomask 6. Figure li shows how the photo-sensitive material has been developed, wherewith those parts that have been exposed to light have been dissolved in a developer to form cavities 9, leaving parts of non-exposed photo-sensitive material 7. If a negative photo-sensitive material has been used, non-exposed parts will dissolve in the developer. Figure lj shows the mould cavities plated with a selected metal, to form building elements 8. Figure Ik shows how remaining non-exposed photo-sensitive material has been dissolved with the aid of a chemical suitable to this end, therewith leaving building elements on the separation layer of the nickel shim. Figure 11 shows how the individual, plated building elements have been released with the aid of the earlier provided separation layer. Figure lm shows how the individual, plated building elements 8 have been released from the nickel shim 3 with the aid of the separation layer 4. The nickel shim can now be reused and coated with photo-sensitive material, as indicated with the arrow marking from Figure lm to Figure lg. Etching away of the photo-sensitive material 7 to free the created building elements, as described above with reference to Figure Ik, can be excluded in certain applications, and a production cycle may run in accordance with the arrow marking from the state in Figure lm to the state in Figure li, where renewed plating can take place. Plated electrical parts, so- called electrodes, can be created on the plated basic structures, by using a slightly different sequence of operations than that described, but with the same basic content . It will be understood that the invention is not restricted to the aforedescribed, illustrated embodiments thereof, and that modifications can be made within the scope of the following Claims .

Claims: CLAIMS 1. A method of providing building elements with patterns, such as carriers with patterns, for instance optofibre accommodating grooves, characterised by metal plating a patterned silicon plate; etching away the silicon plate; coating the formed metal pattern with a photosensitive material; delimiting the metal pattern with a photomask and light energy, therewith to form cavities; metal plating the formed cavities, such as to form metallic building elements that include patterns, such as grooves; wherein said building elements are separable from the metal pattern for individual use as optofibre carriers or micromechanical building elements, and wherein said cavities can be recreated and reused to form new building elements. 2. A patterned building element, such as a patterned carrier, for instance patterned with optofibre accommodating grooves, characterised in that from a metal plated and patterned silicon plate (1) there is provided by etching away a metal pattern (3) from which there have been delimited with a photomask (6) and like energy cavities (9) for metal plating such as to form individual metal building elements (8) which present the same pattern as that presented by the silicon plate, wherein said cavities can be recreated and reused to form new building elements. 3. A building element according to Claim 2, characterised in that the patterned surface of said silicon plate has a thin metal layer (2) which enables initiation of a plating process . 4. A building element according to Claim 3, characterised in that the metal layer (2) has been coated with a separation layer (4) .

Inventors: BLOM CLAES, LARSSON OLLE, VIEIDER CHRISTIAN, BLOM, CLAES, LARSSON, OLLE, VIEIDER, CHRISTIAN
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
Application year: 1999
Main classification: G02B6
IPC codes: C25D1, G02B6