US 5,191,213 AGranted

Integrated circuit structure analysis

AssigneeOlivetti Systems & Networks S.r.l.

InventorsHaroon Ahmed, Simon Blythe, Beatrice Fraboni

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Abstract

The structure of a multilayered integrated circuit is determined by removing successive layers of the circuit. Following removal of each layer, the revealed surface is scanned by an electron beam. The intensity of backscattered or secondary electrons is detected by a first or second detector respectively. From the detected electron intensities, image processing circuitry derives a representation of the integrated circuit surface scanned. Where the surface of the integrated circuit is a flat layer of semiconductor substrate material having implanted doped areas, the surface is covered with a metallisation layer providing a Schottky barrier junction with the doped areas. Electron beam scanning of the metallisation layer induces a current at this junction which is monitored and processed to derive a representation of the outline of the doped implanted areas.

Claims64

Dependent claims

Apparatus for determining the structure of an integrated circuit of the type comprising different layers, including metallic and non-metallic features, and a body including at least one region with a higher type-p or type-n dopant concentration with respect to adjacent regions, said apparatus comprising:

an electron beam source;
means for focussing an electron beam from said source and for controllably scanning said electron beam over a surface of said integrated circuit;
a first detector responsive to backscattered electrons from the surface of said integrated circuit to represent said metallic features;
a second detector responsive to secondary electrons emitted by said surface to represent said non-metallic features;
and
processing means coupled to each of said first and second detectors and operable to derive a representation of said metallic and non-metallic features of said layers from signals from said first and second detectors;
the improvement comprising means for representing said one region with the higher type-p or type-n dopant concentration as induced at a Schottky barrier junction in said one region, said means comprising:
a third detector connected with a metallisation layer of one of a first type of metal or a second type of metal to define the Schottky barrier junction with said region with respecitve ones of the higher type-p dopant concentration or type-n dopant concentration, and
current sensing means connected with said third detector for sensing a current arising from said Schottky barrier junction as said electron beam scans said metallisation layer;
and
wherein said processing means are also coupled to said third detector and are operable to derive a representation of said at least one region with the higher type-p doped or type-n doped concentration from signals from said third detector.

8 more elements

A method of determining the location, in a surface of a body of semiconductor material, of first and second regions of said body having higher dopant concentration of type-p dopant and type-n dopant, respectively, with respect to contiguous portions of said body, said method comprising the steps of:

depositing a metallisation layer of a first type on said surface so as to form a first Schottky barrier junction with one of the first and second regions of said body;
controllably scanning said metallisation layer of a first type with a focussed electron beam;
sensing the current arising from said first Schottky barrier junction as said beam scans said metallisation layer to represent said one of the first and second regions in said surface;
removing said metallisation layer of a first type and replacing it with a metallisation layer of a second type so as to form a second Schottky barrier junction with another of the first and second regions of said body;
controllably scanning said metallisation layer of a second type with a focussed electron beam;
sensing the current arising from said second Schottky barrier junction as said beam scans said metallisation layer of a second type to represent said other of the first and the second regions in said surface;
and
providing a derived representation of said surface in response to the current arising from said first and second Schottky barriers.

5 more elements

Dependencies are inferred from the claim text.