Laser Attack Protection via Impurity Trapping Zone in IC Chips
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Solution Overview
Problem
Integrated circuit chips are vulnerable to laser attacks, which can inject faults into memory cells and compromise sensitive information, with existing protection methods being either ineffective or increasing chip complexity and silicon area.
Innovation Solution
A method involving the formation of an impurity trapping zone under the active layer of the chip, using metallic impurities like iron at specific concentrations, to disperse and attenuate laser beams, preventing them from reaching sensitive components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional protection methods (integrity tests, temperature sensors) are implemented, then attack detection capability is improved, but device complexity and silicon area increase
Solution Approach 1:
The patent introduces metallic impurities (such as iron) into the substrate that normally would be considered defects or contaminants. These impurities serve as laser beam absorbers, converting the harmful laser attack into detectable thermal energy or optical absorption signals, thereby protecting the chip without adding complex detection circuits
Solution Approach 2:
The metallic impurities act as an intermediary layer between the laser attack and the chip components. Instead of directly detecting laser attacks on the chip circuits, the impurities absorb and concentrate the laser energy, making the attack detectable through their optical or thermal properties without requiring complex sensors on the chip itself
2Illumination intensity
If substrate thinning is performed to improve laser attack efficiency, then laser beam penetration is improved, but chip structural integrity and manufacturing complexity worsen
Solution Approach 1:
Instead of uniformly thinning the entire substrate which compromises structural integrity, the patent introduces metallic impurities at specific locations and depths within the substrate. This creates localized laser absorption zones that protect critical areas without requiring overall substrate thinning, maintaining both structural strength and laser attack detectability
3Object-affected harmful factors
If metallic impurities are introduced to absorb laser beams, then laser attack resistance is improved, but manufacturing precision requirements worsen
Solution Approach 1:
The patent specifies optimal concentration ranges for metallic impurities (e.g., iron at 10^17 to 10^19 atoms/cm³) that balance laser absorption effectiveness with manufacturing feasibility. By defining parameter ranges rather than exact values, the solution accommodates normal manufacturing variations while maintaining protection effectiveness
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 solution significantly increases the power required for a laser attack to inject faults, making it easier to detect before sensitive information is compromised, without modifying the chip or manufacturing process, and without increasing silicon area.
Implementation Method 1
introducing into the substrate diffusing metallic impurities adapted to be retained in the trapping zone at a concentration of between 10^17 and 10^19 per cm³, in particular iron
Implementation Method 2
dispers e and attenuate laser beams, preventing them from reaching sensitive components
Data Source
Figure 1~3
Figure 4
AI summary
The method involves forming an impurities trapping zone (23) extended below an active part (5), in a semiconductor substrate (3) by introducing inert gas i.e. helium, in the semiconductor substrate, where an upper limit of the trapping zone is at a depth ranging from 5 to 50 micrometer, from an upper face of the semiconductor substrate. Diffusing metal impurities with concentration ranging between 10power17 and 10power18 atoms per cubic centimeter, are introduced in the semiconductor substrate, where the impurities are retained in the trapping zone. The trapping zone is formed by precipitation of oxygen. The metal impurities contain iron atoms. An independent claim is also included for an integrated circuit chip comprising an active part.