Electronic Chip Rear Face Anti-Tamper Protection
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Solution Overview
Problem
Existing electronic chips lack effective protection for their rear faces, making them vulnerable to attacks such as thinning, polishing, and focused ion probe (FIB) attacks, which can compromise the security of the chip's electronic circuit.
Innovation Solution
The electronic chip incorporates a resistive element with a serpentine pattern and two overlapping parts on its rear face, along with an embrittlement structure of blind holes, where the blind holes and electrically conductive vias have similar external dimensions, making it difficult for attackers to distinguish between them, and the resistive element's complex pattern prevents easy identification or replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the blind holes and electrically conductive vias are made with the same external dimensions, then it becomes difficult for attackers to distinguish between them, but the manufacturing precision required to achieve this increases
Solution Approach 1:
The patent applies asymmetry in the internal structure rather than external appearance. The blind holes and electrically conductive vias have the same external dimensions and positioning to confuse attackers, but differ internally: blind holes are filled with insulating material while vias contain conductive material. This asymmetric internal design provides security without compromising manufacturing precision.
Solution Approach 2:
The patent uses local quality by filling different holes with different materials based on their function. The blind holes are filled with insulating material (such as epoxy resin or oxide) while the electrically conductive vias are filled with conductive material (such as copper or aluminum). This localized differentiation achieves security through material properties rather than dimensional asymmetry.
2Reliability
If the resistive element is made with a complex serpentine pattern, then it becomes difficult for attackers to locate and replace, but the device complexity increases
Solution Approach 1:
The patent uses a serpentine (curved/winding) pattern for the resistive element instead of a straight line. This curved path makes it significantly more difficult for attackers to locate the exact start and end points of the resistive element on the rear face, thereby preventing easy replacement or tampering. The complexity is confined to the geometric pattern rather than the functional structure.
3Ease of manufacture
If the resistive element is made with larger dimensions, then it becomes easier to manufacture, but it becomes easier for attackers to locate and access
Solution Approach 1:
The patent resolves the dimensional conflict by adding a vertical dimension through overlapping parts. The resistive element consists of multiple parts at different heights (first part at a first height, second part at a second height), creating a three-dimensional structure. This vertical stacking provides security against attacks while maintaining manufacturability through standard multi-layer fabrication processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the security of the rear face by making it difficult for attackers to locate and access the resistive element, thereby preventing unauthorized access and ensuring the chip's integrity is maintained, even under mechanical or chemical attacks.
Implementation Method 1
a difference in depth between the TSVs and the blind holes is obtained by using the phenomenon of ARDE ('Aspect Ratio Dependent Etching') according to which a greater etching depth is obtained for the patterns greater width during a single etching step
Implementation Method 2
a resistive element arranged on the side of a rear face of the substrate and plumb with at least part of the electronic circuit; two electrically conductive vias, or TSVs, passing through the substrate and extending between the front and rear faces of the substrate, each electrically connected to the electronic circuit and to one of at least two ends of the resistive element such that the value of the electrical resistance of the resistive element can be measured
Data Source
Figure 1~2
Figure 3~4
AI summary
Electronic chip (100) comprising: - an electronic circuit (108); - a resistive element (116) disposed on a rear face (114) of a substrate (104); - two conductive vias (126) passing through the substrate, each connected to the electronic circuit and to one end of the resistive element, and masked by the resistive element; and comprising a weakening structure formed of blind holes (130) such that each of the blind holes has a section, at the rear face, of shape and external dimensions similar to those of the conducting vias, and has a portion (132) of the substrate masked by the resistive element, and/or in which the resistive element has first and second parts (118, 122) spaced apart, arranged one above the other, electrically connected to each other and together forming a serpentine pattern and/or several alternating, intertwined, coiled or interlaced patterns.