Chip Rear Face Embrittlement Structure for Attack Detection
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Solution Overview
Problem
The rear face of electronic chips lacks effective protection against various attack methods, such as thinning and chemical etching, which can compromise the security of the chip's electronic circuit.
Innovation Solution
An embrittlement structure with blind holes of non-circular cross-sections having a surface area greater than π times the radius squared is implemented on the rear face, combined with a resistive element and conductive vias, to enhance mechanical strength and detect attacks, while maintaining protection against thinning and chemical etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If blind holes with circular cross-section are used in the embrittlement structure, then the manufacturing process is simpler, but the mechanical strength and resistance to thinning attacks are reduced
Solution Approach 1:
The patent applies asymmetry by replacing circular cross-sections with non-circular cross-sections (such as square, rectangular, or polygonal shapes) in the embrittlement structure. This asymmetric geometry increases the moment of inertia and section modulus, thereby enhancing mechanical strength and resistance to thinning attacks while maintaining manufacturing feasibility through standard semiconductor fabrication processes.
Solution Approach 2:
The patent utilizes curvature principles by optimizing the rounded corners of non-circular cross-sections. The rounded corners with specific radius values stress concentration points, improving the embrittlement effect while maintaining structural integrity. This controlled curvature enhances mechanical strength without significantly increasing manufacturing complexity.
2Reliability
If the blind holes are made deeper to improve embrittlement, then the protection against thinning attacks increases, but the manufacturing precision requirements increase
Solution Approach 1:
The non-circular cross-sections provide increased structural efficiency per unit depth, allowing achieving the same or higher embrittlement effect with shallower holes compared to circular sections. This reduces the aspect ratio and consequently lowers the etching precision requirements while maintaining reliable protection.
Solution Approach 2:
The embrittlement structure is designed and fabricated during the standard CMOS manufacturing process before the chip is subjected to thinning attacks. The non-circular cross-sections are pre-formed with optimized dimensions to provide sufficient embrittlement at reduced depths, ensuring protection reliability is established in advance without requiring ultra-precise deep etching.
3Reliability
If multiple protection elements are added to the rear face, then the security against attacks improves, but the device complexity increases
Solution Approach 1:
The embrittlement structure with non-circular cross-sections serves multiple functions simultaneously: it provides mechanical strength enhancement, creates stress concentration for embrittlement, and offers resistance to chemical etching. This multi-functionality achieves improved security reliability without proportionally increasing device complexity, as a single structural feature accomplishes multiple protective roles.
Solution Approach 2:
The patent merges the embrittlement function with the existing blind hole structure used in standard chip fabrication. By integrating the protective embrittlement features into the常规 manufacturing process and combining multiple protection mechanisms (mechanical embrittlement, chemical resistance) into a unified structure, the security reliability is enhanced while minimizing the increase in device complexity.
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
The embrittlement structure provides substantial mechanical strength and resistance to thinning attacks, while the resistive element helps detect and respond to potential threats, effectively securing the chip's rear face without compromising its primary functions.
Implementation Method 1
the zones of maximum stress are located at the blind holes of smaller diameter. When the electronic chip includes the embrittlement structure and it is subject to flexural stress, cracks appear precisely at the zones where the maximum stress is located
Implementation Method 2
A difference in depth between the electrically conductive vias and the blind holes is obtained using the ARDE (Aspect Ratio Dependent Etching) phenomenon whereby a greater etching depth is obtained for the wider patterns during a single etching step
Data Source
AI summary
An electronic chip includes at least an electronic circuit disposed on a front face of a substrate; and an embrittlement structure comprising at least blind holes, each extending through a rear face of the substrate and a portion of the thickness of the substrate and each having a section, in a plane parallel to the rear face of the substrate, of surface area S and having a closed outer contour, the shape of which includes at least one radius of curvature R, such that S>π·R2.