Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Chip mounted on chip
Patent
1996-01-17
1998-01-20
Jackson, Jerome
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Chip mounted on chip
257724, 257792, 257113, H01L 2348
Patent
active
057104638
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
A high-voltage breakover diode is described in German Patent Application No. DE 40 32 131, in which a multiplicity of series-connected breakover diodes constitute a high-voltage breakover diode. In this case, the individual semiconductor elements are stacked one above the other in a cascade circuit and the periphery of this semiconductor stack is subsequently covered with a translucent insulator. High voltages can be switched with great precision by means of such a high-voltage breakover diode, with the result that this high-voltage breakover diode can be used as an ignition voltage distributor for solid-state high-voltage distribution. In this case, the pn junctions situated at the periphery of the cascade form light-sensitive zones, which are driven by light-emitting elements in such a way that they switch through at a predetermined point in time.
SUMMARY OF THE INVENTION
The arrangement according to the present invention has the advantage that conventional breakover diode chips produced using planar technology can be used for the production of the breakover diode cascade. Moreover, this arrangement has the advantage that the pn junctions with a high blocking capacity are not exposed at the periphery of the breakover diode stack but are passivated with silicon oxide (SiO.sub.2) on the top of the chips and, consequently, it is not possible for undesired switching of the breakover diode to take place due to undefined surface conditions at the edge, which may result from sawing damage, as a result of which a high yield from the silicon wafer and a high switching accuracy of each breakover diode chip are provided. The insulation between the breakover diode chips by means of an electrically insulating plastic layer and the mechanical connection and electrical contact-making by means of a connecting layer provide additional mechanical strength, even with a small cathode surface area. It is thus possible to use breakover diode chips having a small chip surface area, resulting in lower chip costs, and at the same time to ensure a high mechanical strength.
It is particularly advantageous that the electrically insulating plastic layer can be photopatterned, and that it can be applied using the screen printing process and the necessary recesses in the region of the electrodes and of the sawing trenches can subsequently be produced by photolithography. Moreover, it is advantageous to use a polyimide layer as the electrically insulating plastic layer. It is thus possible to ensure the conduction of light from the periphery of the high-voltage breakover diode to the light-sensitive pn junctions, which are in each case exposed on the top of the breakover diode chips.
It is further advantageous that, for the production of a high-voltage breakover diode, a silicon wafer having a multiplicity of individual breakover diodes can firstly be produced and then individual wafers are stacked one above the other to form a stack, with the result that the high-voltage breakover diode can be produced very cost-effectively and easily by simply sawing it out.
Furthermore, it is advantageous to produce the mechanical connection and to make electrical contact between the individual breakover diode wafers by means of a conductive adhesive, for example a polyimide adhesive containing metal, it being advantageous to use a precurable adhesive since this can be applied using the screen printing process and is precured for better handling, with the result that this adhesive only has to be cured after the connection of the individual breakover diode chips.
Finally, a soldered connection can also be provided for the mechanical and electrical connection of the individual breakover diode chips, the soldered connection under certain circumstances being more cost-effective than the adhesive.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the basic structure of an ignition system using a high-voltage breakover diode.
FIG. 2 shows a detail of a structured silicon wafer having individual breakover diodes.
FIG. 3 show
REFERENCES:
patent: 3363150 (1968-01-01), Whitman et al.
patent: 3373335 (1968-03-01), Rosenberg
patent: 3416046 (1968-12-01), Dickson, Jr. et al.
patent: 4535350 (1985-08-01), Goodrich et al.
patent: 4989063 (1991-01-01), Kolesar, Jr.
patent: 5245412 (1993-09-01), Clark et al.
Goebel Herbert
Herden Werner
Konrad Johann
Spitz Richard
Vogel Manfred
Jackson Jerome
Kelly Nathan K.
Robert & Bosch GmbH
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