Anti-fuse Cell Using Metal Silicide Diffusion for Low-Voltage Programming
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Solution Overview
Problem
Existing one-time programmable cells, such as fuses and anti-fuses, require high voltages for programming, are limited to in-wafer programming, have high resistance when closed, and lack verification mechanisms, making them unsuitable for many applications and prone to errors in decision-making.
Innovation Solution
An anti-fuse cell with a MOS transistor and a metal silicide layer, surrounded by a resistive track that can be programmed with low voltage after packaging, featuring a high resistance in the un-programmed state and low resistance in the programmed state, with a method that includes forming wider insulating field regions and a conductive track around the transistor for simultaneous manufacturing with standard MOS transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high voltage is applied for programming existing fuses and anti-fuses, then programming can be achieved, but special voltage supply sources and non-standard devices are required
Solution Approach 1:
The patent changes the programming mechanism from high-voltage electrical breakdown to thermal diffusion process. By applying current through the resistive track to heat the metal silicide layer, the metal diffuses across the junction to create a permanent low-resistance connection, eliminating the need for high-voltage supply circuits
Solution Approach 2:
The patent replaces the electrical field-based programming mechanism (high voltage breakdown) with a thermal field-based mechanism (heat-induced diffusion). The resistive track serves as a heating element that thermally activates metal diffusion, substituting electrical breakdown with thermal processing
2Ease of manufacture
If non-electrically programmable fuses are used, then programming can be done at manufacturing site, but programming is only possible while integrated circuits are in wafer form and cannot be performed after packaging
Solution Approach 1:
The patent enables the anti-fuse cell to be programmed independently after packaging by using standard voltage sources already present in the integrated circuit. The resistive track and metal silicide structure allow the cell to self-program through controlled heating without requiring external specialized equipment
Solution Approach 2:
The patent creates a universal programming mechanism that works both during manufacturing and after packaging. The same thermal diffusion process can be initiated at any time by applying voltage to the resistive track, making the cell adaptable to different programming timelines and locations
3Reliability
If generally known anti-fuses are used, then programming can be achieved, but they present relatively high resistance when closed, excluding them from many applications
Solution Approach 1:
The patent creates a localized low-resistance path by having metal from the silicide layer diffuse specifically across the drain or source junction into the substrate. This localized metal accumulation forms a low-resistance shunt path that bypasses the normal channel, achieving resistance less than ten ohms in the programmed state
Solution Approach 2:
The patent uses a composite structure combining metal silicide layer with the semiconductor substrate. The diffusion of metal atoms from the silicide into the silicon substrate creates a composite region with tailored electrical properties, achieving the desired low resistance characteristic
4Reliability
If fusing process is used to break connections, then programming can be achieved, but the surrounding layers are liable to be damaged significantly and the break is sometimes unreliable
Solution Approach 1:
The patent converts the potentially harmful high current that could damage surrounding layers into a beneficial heating mechanism. By directing the current through the resistive track to heat only the metal silicide layer locally, the harmful thermal effect is confined and converted into useful metal diffusion, eliminating damage to surrounding structures
Solution Approach 2:
The patent segments the current path and heating zone by using a specifically designed resistive track that directs current flow only to the metal silicide layer. This spatial segmentation ensures that thermal energy is concentrated where needed (at the metal layer) while surrounding sensitive structures remain unaffected
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
Enables reliable programming with low voltage, post-packaging, and verification of programming decisions, reducing the risk of errors and improving resistance characteristics, making the cells suitable for a wider range of applications.
Implementation Method 1
adapted to pass a heating current such that the metal of said metal silicide diffuses across drain and/or source junctions
Implementation Method 2
adapted to pass a heating current such that the metal of said metal silicide diffuses
Data Source
AI summary
An anti-fuse cell includes a standard MOS transistor of an integrated circuit, with source and drain regions covered with a metal silicide layer and at least one track of a resistive layer at least partially surrounding the MOS transistor, and adapted to pass a heating current such that the metal of said metal silicide diffuses across drain and/or source junctions.