Hidden Shared Contact in Integrated Circuit
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Solution Overview
Problem
Existing integrated circuits with shared contacts between substrate zones and polysilicon regions on insulating zones occupy a larger volume, making them easily detectable in reverse engineering, which is a security concern.
Innovation Solution
Incorporating a strip at the base of the polysilicon region to reduce the volume of shared contacts and make them indistinguishable from other contacts by matching their cross-sectional dimensions, thereby complicating reverse engineering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shared contact is made between substrate zones and polysilicon regions, then electrical connection is established, but the contact occupies greater volume and becomes easily detectable
Solution Approach 1:
The patent introduces a vertical dimension by extending the conductive pad through the isolating zone to contact the polysilicon region at its base, rather than making contact at the top surface. This dimensional change allows the contact to be hidden within the isolating zone, reducing its detectable volume while maintaining electrical connectivity between the substrate zone and polysilicon region.
2Reliability
If a shared contact is made between substrate zones and polysilicon regions, then electrical connection is established, but the contact becomes easily detectable in reverse engineering
Solution Approach 1:
The isolating zone serves as an intermediary medium that conceals the conductive pad and shared contact. By routing the contact through this dielectric layer to reach the polysilicon region at its base, the invention hides the contact path from external observation, making reverse engineering significantly more difficult while preserving the electrical connection function.
3Reliability
If the contact cross section is made larger to ensure good electrical contact, then connection reliability improves, but the contact volume increases and becomes more detectable
Solution Approach 1:
The conductive pad is nested within the isolating zone, with the polysilicon region extending down to contact the pad through the dielectric layer. This nesting arrangement allows the contact structure to be embedded within existing circuit elements, minimizing the overall volume occupied while ensuring reliable electrical connection through the silicided interface between the pad and polysilicon.
Data Source
AI summary
An integrated circuit includes a substrate and an interconnect. A substrate zone is delineated by an insulating zone. A polysilicon region extends on the insulating zone and includes a strip part. An isolating region is situated between the substrate and the interconnect and covers the substrate zone and the polysilicon region. A first electrically conductive pad passes through the isolating region and has a first end in electrical contact with both the strip part and the substrate zone. A second end of the electrically conductive pad is in electrical contact with the interconnect. A second electrically conductive pad also passes through the isolating region to make electrical contact with another region. The first and second electrically conductive pads have equal or substantially equal cross sectional sizes, within a tolerance.