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Semiconductor Chip Insulation by Anodic Oxidation

IP.com Disclosure Number: IPCOM000096052D
Original Publication Date: 1964-Nov-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Lehman, HS: AUTHOR

Abstract

These semiconductor chips have their lateral surfaces coated with an oxide insulating material. When the chip is attached to a substrate having a printed circuit on it, the oxide insulation prevents the chip from short circuiting to the conductors on the surface of the substrate. The anodic oxide is applied to the chip surface by a method which produces a plurality of insulated chips.

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Semiconductor Chip Insulation by Anodic Oxidation

These semiconductor chips have their lateral surfaces coated with an oxide insulating material. When the chip is attached to a substrate having a printed circuit on it, the oxide insulation prevents the chip from short circuiting to the conductors on the surface of the substrate. The anodic oxide is applied to the chip surface by a method which produces a plurality of insulated chips.

Semiconductor wafer 10 is coated with protecting film 14, typically wax. A series of grooves 16 are cut along the surface of wafer 10. Anode electrode 18 is connected to wafer 10 which is deposited in electrolyte bath 12 of methyl acetamide. Electrolyte 12 also includes a small amount, typically 1% of potassium nitrate. Cathode electrode 20 is extended into electrolyte 12 to complete the apparatus for coating the lateral surfaces of wafer 10.

When a suitable voltage is applied between an anode and cathode for thirty minutes at a constant current of ten milliamps with the voltage gradually increased up to 350 volts so as to maintain the current level, anodic oxidation 22 occurs along the lateral surfaces of wafer 10. Typical oxide thicknesses for the anodic process are 1000 to 1500 angstroms (approximately. 004 to. 006 mils). Wafer 10 is removed from electrolyte 12 and anode 18 is disconnected. Wafer 10 is further cut in the notches to fabricate a plurality of individual semiconductor chips. Each chip is coated with an anodic oxidatio...