Antifuse Link Programming via Electromigration
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Solution Overview
Problem
Current antifuse structures face challenges such as high programming voltage requirements, potential damage to other circuits, unreliable reproducibility, substantial capacitance, and storage time degradation due to high leakage currents, especially in CMOS manufacturing processes.
Innovation Solution
An antifuse structure comprising an anode, cathode, and link with specific semiconductor and silicide materials, where the link has a silicided and unsilicided portion, allowing for programming with low voltage and current, and employing electromigration to reduce resistance, with shallow trench isolation and dielectric material masking for enhanced reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high programming voltage (above 6 volts) is used to break down the insulating layer in traditional antifuse structures, then the antifuse can be programmed reliably, but other circuits on the chip may be damaged and operation at lower voltages becomes unreliable
Solution Approach 1:
The patent changes the material parameters of the link from insulating to conductive semiconductor material (polysilicon, silicon-germanium alloy, or silicon-carbon alloy), allowing programming at low voltages (5V or less) while maintaining reliable operation. This material transformation eliminates the need for high voltage breakdown while achieving the desired resistance change for programming.
Solution Approach 2:
The patent utilizes phase transition or structural transformation of the semiconductor link material during programming. The conductive link material undergoes a resistance state change when exposed to programming current, enabling reliable programming without high voltage breakdown of insulating layers, thus avoiding damage to other circuits.
2Reliability
If a dielectric layer is used to separate conductive regions in traditional antifuses, then insulation is provided, but substantial capacitance is introduced which slows circuit operation
Solution Approach 1:
The patent extracts and removes the dielectric layer from the antifuse structure, replacing it with a conductive semiconductor link material. This elimination of the dielectric layer removes the source of substantial capacitance, thereby speeding up circuit operation while maintaining proper electrical isolation through the inherent properties of the semiconductor link structure.
3Manufacturing precision
If low pressure chemical vapor deposition is used to deposit the dielectric layer with high uniformity, then film composition and thickness uniformity is improved, but hillocks form in the first metallic layer
Solution Approach 1:
The patent removes the dielectric layer entirely from the structure, thereby eliminating the process step of low pressure chemical vapor deposition. This extraction of the problematic layer and its deposition process prevents the formation of hillocks in the metallic layer while still achieving the necessary electrical isolation through the semiconductor link design.
4Use of energy by moving object
If amorphous silicon is used as an interlayer between metal layers to reduce programming voltage, then programming voltage is reduced, but extremely high leakage currents occur which cause controllability and storage time problems
Solution Approach 1:
The patent changes the material parameters by using lightly doped or intrinsic semiconductor materials (polysilicon, silicon-germanium alloy, or silicon-carbon alloy) with controlled doping levels instead of amorphous silicon. This material selection and doping control achieves low programming voltage requirements while maintaining low leakage currents, thereby ensuring controllability and long-term storage reliability.
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 antifuse structure can be reliably programmed with low heat generation and high reliability, achieving a significant resistance reduction, improving manufacturing yield and reducing the risk of circuit damage, while maintaining controllability and long-term performance.
Implementation Method 1
The method comprises the steps of electromigrating a silicide containing material into the unsilicided portion of the link; and reducing the resistance of the antifuse.
Data Source
AI summary
An antifuse having a link including a region of unsilicided semiconductor material may be programmed at reduced voltage and current and with reduced generation of heat by electromigration of metal or silicide from a cathode into the region of unsilicided semiconductor material to form an alloy having reduced bulk resistance. The cathode and anode are preferably shaped to control regions from which and to which material is electrically migrated. After programming, additional electromigration of material can return the antifuse to a high resistance state. The process by which the antifuse is fabricated is completely compatible with fabrication of field effect transistors and the antifuse may be advantageously formed on isolation structures.