Dielectric Reflector Layout for Laser-Programmable Fuse Protection
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Solution Overview
Problem
The use of laser-programmable fuses in integrated circuits results in damage to underlying circuitry due to laser light spillover, necessitating lateral spacing that occupies valuable chip real estate and reduces circuit density.
Innovation Solution
Incorporation of a dielectric reflector with alternating high and low refractive index layers to reflect laser light away from circuitry, allowing fuses to be positioned adjacent to circuit elements and reducing the need for lateral spacing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If circuitry is spaced laterally from fuses to avoid laser damage, then circuitry is protected from laser light spillover, but chip real estate is wasted and circuit density is reduced
Solution Approach 1:
A dielectric reflector layer is introduced as an intermediary component between the fuse and the underlying circuitry. This reflector layer redirects laser light away from the circuitry, allowing the fuse to be positioned directly over the circuitry without causing damage. The reflector acts as a mediator that enables close proximity positioning while maintaining circuit safety.
Solution Approach 2:
The solution moves the protective function from the lateral dimension to the vertical dimension by stacking the dielectric reflector layer beneath the fuse in the vertical direction. This allows the fuse and circuitry to be positioned adjacent to each other in the lateral direction without requiring lateral spacing, effectively utilizing the vertical dimension to resolve the spatial conflict.
2Reliability
If circuitry is spaced laterally from fuses to avoid laser damage, then circuitry is protected from laser light spillover, but circuit density is reduced
Solution Approach 1:
The dielectric reflector layer serves as a protective intermediary that enables higher circuit density by allowing fuses to be positioned adjacent to circuitry without lateral spacing. This mediator eliminates the need for protective spacing while maintaining circuit safety, thereby increasing the number of circuits that can be integrated on the chip.
3Area of stationary object
If fuses are positioned over circuitry to maximize space utilization, then chip real estate is efficiently used, but circuitry is damaged by laser light during programming
Solution Approach 1:
The dielectric reflector layer is positioned between the fuse and the circuitry to act as a protective intermediary. It reflects laser light away from the circuitry while allowing the fuse to be positioned directly over the circuitry, thus maximizing space utilization without exposing the circuitry to harmful laser light during programming.
Solution Approach 2:
The dielectric reflector layer converts the potentially harmful laser light into a beneficial reflected path that redirects away from the circuitry. By utilizing the optical reflection property, the harmful laser energy is redirected to serve the beneficial purpose of programming the fuse while protecting the underlying circuitry.
4Ease of manufacture
If lateral spacing is provided between fuses and circuitry, then manufacturing is simplified without complex protective structures, but valuable chip space is lost
Solution Approach 1:
The dielectric reflector layer is formed using standard semiconductor manufacturing processes that are already part of the fabrication sequence. It serves multiple functions: protecting circuitry from laser damage, enabling closer fuse positioning, and maintaining compatibility with existing manufacturing flows, thus achieving space efficiency without significantly complicating the manufacturing process.
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
Protects circuitry from laser damage, enabling more efficient use of chip space and allowing for denser circuit integration by placing fuses closer to circuit elements.
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
Implementation Method 2
The dielectric reflector has a plurality of alternating high and low refractive index dielectric layers
Data Source
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.