Semiconductor Back Side Protection via Optical Monitoring
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Solution Overview
Problem
Existing semiconductor devices are vulnerable to physical and optical attacks, particularly on the back side, which can compromise the security of integrated circuits, and existing protection methods fail to effectively detect optical side-channel attacks without harming the device.
Innovation Solution
A semiconductor device with a substrate stack comprising two permanently bonded semiconductor bodies, where one body includes active regions with light emitters and a light absorption region, and the other body is transmissive for light, equipped with light detectors to monitor light intensity changes, providing robust protection against back side attacks and side-channel attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If opaque coating layers or metal grids are used to protect the back side, then physical access to information is blocked, but optical side-channel attacks can still occur and the device complexity increases
Solution Approach 1:
The semiconductor device is divided into two permanently bonded semiconductor bodies (first and second bodies) with a bonding interface between them. This segmentation allows the light emitters to be positioned at the bonding interface in the first body, while light detectors are placed in the second body, creating a distributed optical monitoring system that detects attacks without requiring complex surface coatings or grids.
Solution Approach 2:
The patent replaces mechanical/physical protection methods (opaque coatings, metal grids) with an optical detection system. Instead of blocking light physically, the system uses light emitters and detectors to actively monitor for attacks, substituting a mechanical barrier approach with an optical sensing approach that detects tampering through changes in light transmission.
2Reliability
If light emitters are positioned at the bonding interface, then optical attacks can be detected through light intensity changes, but the device structure becomes more complex
Solution Approach 1:
The patent merges the protection function with the existing bonding interface structure. The light emitters are positioned exactly at the bonding interface between the two semiconductor bodies, utilizing the natural structural feature of the device rather than adding separate protection layers. This integration allows attack detection while minimizing additional structural complexity.
Solution Approach 2:
The bonding interface serves dual purposes: it provides the necessary structural connection between the two semiconductor bodies and simultaneously serves as the optimal location for positioning light emitters to detect attacks. This multi-functionality reduces the need for separate dedicated protection structures, as the bonding interface itself becomes part of the security mechanism.
3Reliability
If permanently bonded semiconductor bodies are used, then structural integrity is enhanced and attacks are detected, but manufacturing precision requirements increase
Solution Approach 1:
The permanent bonding of the two semiconductor bodies is performed during the manufacturing process before the device is put into service. This preliminary action ensures that the bonding interface is established with high precision under controlled manufacturing conditions, rather than attempting to achieve such precision during field operation or through later adjustments.
Solution Approach 2:
The patent uses standard semiconductor wafer bonding techniques that are already established in the industry, copying proven manufacturing processes to create the permanent bond. This approach leverages existing manufacturing precision capabilities rather than requiring entirely new bonding technologies, thereby managing precision requirements through the use of validated 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
The solution effectively detects and prevents attacks on the back side of the semiconductor device, enhancing security without harming the device, and provides additional protection against side-channel attacks, suitable for various applications including smart-cards and military equipment.
Implementation Method 1
an active region with one or more light emitters at the buried bonding interface
Implementation Method 2
a light absorption region, which follows the active region in the depth direction and is opaque for light emitted from the one or more light emitters
Implementation Method 3
at least one light detector at the front side of the substrate stack, which is configured to provide a detector signal indicative of a detected light intensity
Data Source
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AI summary
The invention relates to a semiconductor device (100) comprising: a substrate stack (122) comprising two permanently bonded semiconductor bodies (102, 104), which are stacked in a depth direction that points perpendicularly from a front side (108) towards a back side (110) of the substrate stack, and which share a buried bonding interface (106) that extends at a respective distance from the front and back sides and parallel thereto; wherein: - a first of the two bodies, hereinafter the protection body (104), comprises an active region (113) with one or more light emitters (112) at the buried bonding interface, and a light absorption region (114), which follows the active region in the depth direction and is opaque for light emitted from the one or more light emitters; - a second of the two bodies, hereinafter the circuit body (102), extends from the buried bonding interface to the front side of the substrate stack, is transmissive for the light emitted from the one or more light emitters, and comprises at least one light detector (118, 120) at the front side of the substrate stack, which is configured to provide a detector signal indicative of a detected light intensity of light emitted from the one or more light emitters and transmitted through the circuit body. The semiconductor device further comprises a driver unit that is configured to drive operation of the light emitters using predetermined operation parameters.