Process for producing a calibrated resistance element
First Claim
1. A process for producing a calibrated resistance element on a substrate, comprising the steps of:
- (a) depositing a dielectric layer attackable by a chemical agent on said substrate;
(b) topping said dielectric layer with a coating of a different material resistant to attack by said agent;
(c) destroying part of said coating to leave a residue with at least one exposed lateral edge;
(d) subjecting said dielectric layer to an isotropic attack by said agent with resulting reduction in the thickness of said layer except for a pedestal supporting said residue and with erosion of the periphery of said pedestal underneath said exposed edge whereby an elongate undercut is formed in said periphery;
(e) forming a conductive deposit of predetermined resistivity on said dielectric layer at least to the level of said residue with penetration of said undercut by a filiform portion of said deposit; and
(f) removing said deposit at least along said edge while leaving intact the filiform portion thereof accumulated in said undercut.
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Accused Products
Abstract
Filiform elements of predetermined resistivity, e.g. selectively destructible leads of an electrically programmable read-only memory, are formed on a semiconductor substrate such as a silicon body by first depositing thereon a layer of dielectric material such as SiO2 and topping that layer with a conductive or nonconductive coating which is resistant to a chemical such as hydrofluoric acid capable of attacking the dielectric layer. Next, the top coating is partly destroyed by photolithographic treatment to leave at least one substantially rectangular patch. Thereafter, the dielectric layer is isotropically attacked by the aforementioned chemical with resulting reduction to about half its original thickness and concurrent lateral erosion of a patch-supporting pedestal of that layer whereby channels of generally semicylindrical concavity are formed around the periphery of this pedestal. The patch, if composed of conductive or semiconductive material, is then clad in an insulating envelope whereupon the dielectric layer and the patch are covered with a deposit of the desired electrical conductivity which could consist of doped polycrystalline silicon or of metal. Finally, this deposit is removed by chemical or ionic etching except in the channels of the pedestal and along a pair of parallel strips adjoining opposite pedestal sides whereby these strips remain electrically interconnected by filiform inserts left in the undercuts of the other two sides.
8 Citations
10 Claims
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1. A process for producing a calibrated resistance element on a substrate, comprising the steps of:
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(a) depositing a dielectric layer attackable by a chemical agent on said substrate; (b) topping said dielectric layer with a coating of a different material resistant to attack by said agent; (c) destroying part of said coating to leave a residue with at least one exposed lateral edge; (d) subjecting said dielectric layer to an isotropic attack by said agent with resulting reduction in the thickness of said layer except for a pedestal supporting said residue and with erosion of the periphery of said pedestal underneath said exposed edge whereby an elongate undercut is formed in said periphery; (e) forming a conductive deposit of predetermined resistivity on said dielectric layer at least to the level of said residue with penetration of said undercut by a filiform portion of said deposit; and (f) removing said deposit at least along said edge while leaving intact the filiform portion thereof accumulated in said undercut. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification