Laser Fuse Reflector Stack for Protecting Underlying IC Circuitry
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Solution Overview
Problem
In integrated circuits, programmable fuses require laser programming, which can damage underlying circuitry, leading to inefficient use of chip space due to the need for lateral spacing to protect the circuitry from laser light.
Innovation Solution
A dielectric reflector with alternating high and low refractive index layers is used adjacent to the fuses and circuitry to reflect laser light away from the circuitry, allowing fuses to be placed closer to circuitry and optimizing chip space usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If circuitry is placed below the fuses to optimize chip space, then area utilization is improved, but the circuitry is damaged by laser light during fuse programming
Solution Approach 1:
A dielectric reflector layer is introduced as an intermediary component between the fuses and the underlying circuitry. This reflector layer has high reflectivity to laser light and redirects the laser energy away from the circuitry while allowing the fuse programming to proceed. The reflector thus mediates the interaction between laser light and circuitry, protecting the circuitry from damage while enabling space-efficient layout with fuses positioned over circuitry regions.
2Object-affected harmful factors
If lateral spacing is maintained between fuses and circuitry to protect from laser damage, then circuitry is protected from laser light, but chip space is wasted
Solution Approach 1:
The dielectric reflector serves as a protective intermediary that eliminates the need for lateral spacing between fuses and circuitry. By placing the reflector directly beneath the fuses and above the circuitry, it provides localized protection exactly where needed, allowing maximum space utilization without compromising circuitry protection.
Solution Approach 2:
The solution applies protection locally rather than globally. The dielectric reflector is positioned specifically in the region where laser light would cause damage (between fuses and underlying circuitry), while other regions of the chip can be used for additional circuitry. This localized approach optimizes space usage by protecting only the necessary areas.
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 dielectric reflector protects circuitry from laser damage, reduces laser light fluence needed for programming, and enables placement of circuitry beneath the fuses, enhancing space utilization on the integrated circuit.
Implementation Method 1
The dielectric reflector has a plurality of alternating high and low refractive index dielectric layers configured to reflect at least a portion of the laser light incident thereto away from the circuitry adjacent to the dielectric reflector
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
An integrated circuit has fuses that are selectively configurable by laser light having a wavelength incident on the fuses. A substrate of the integrated circuit has circuitry thereon. Fuses are disposed vertically above at least a portion of the circuitry. A dielectric reflector is disposed vertically above and laterally covers at least a portion of the circuitry. The dielectric reflector has a plurality of alternating dielectric layers of different refractive indices and is disposed adjacent to the fuses. The dielectric reflector is configured to reflect at least a portion of the laser light at the wavelength incident thereto.