Esmat Z. Hamdy

Dielectric based antifuse for logic and memory ICs

The authors describe a programmable low-impedance circuit element (PLICE), which is a dielectric-based antifuse for use in both logic and memory ICs. The antifuse element offers significant size and performance improvement compared to other programmable cells. A simple thermal model has been developed to predict the antifuse resistance. Each antifuse occupies an area of 1.5- mu m/sup 2/ using 1.2- mu m technology. It can be programmed within 1 ms and has a tight resistance distribution centered around 500 Omega . The reliability of both the programmed and unprogrammed states is demonstrated to be better than 40 years. The antifuse was used in the design of the first family of desktop-configurable channeled gate arrays and a 64 K PROM (programmable read-only memory) device.<<ETX>>

Characterization and modeling of a highly reliable metal-to-metal antifuse for high-performance and high-density field-programmable gate arrays

The reliability of a new amorphous silicon/dielectric antifuse is characterized and modeled. Unprogrammed antifuse leakage and time-to-breakdown are functions not only of applied voltage but also of stressing polarity and temperature. Both breakdown and leakage criteria are used to investigate their effects on time-to-fail. A thermal model incorporates the effects of programming and stress currents, ambient temperature, and variation of antifuse resistance with temperature. The measured temperature dependence of antifuse resistance is used for the first time to derive key physical parameters in the model.

An electro-thermal model for metal-oxide-metal antifuses

In this paper, a complete electro-thermal analysis is presented for the metal-oxide-metal antifuses. The application of the Wiedemann-Franz Law and the thin film effect on thermal and electrical conductivities of metal films were also discussed. Several key parameters for tungsten-oxide-tungsten antifuse were extracted. The reaction temperature between tungsten and oxide was estimated to be around 1300/spl deg/C. The core resistivity was found to be around 250 /spl mu//spl Omega//spl middot/cm. This model can be readily extended to the other metal-dielectric-metal systems. >

Oxide-nitride-oxide antifuse reliability

Compact, low-resistance oxide-nitride-oxide (ONO) antifuses are studied for time-dependent dielectric breakdown (TDDB), program disturb, programmed antifuse resistance stability, and effective screen. ONO antifuses are superior to oxide antifuses. No ONO antifuse failures were observed in 1.8 million accelerated burn-in device-hours accumulated on 1108 product units. This is in agreement with the 1/E field acceleration model.<<ETX>>

Metal-to-metal antifuses with very thin silicon dioxide films

Antifuse samples with very thin insulating oxide were fabricated using a technique of two-step PECVD oxide deposition. Dielectric strength as high as 13 MV/cm was obtained for our samples. Defect density and uniformity have been improved in this way. The on-state resistance of the programmed antifuses shows a stronger dependence on the oxide thickness when it was programmed at the lower current than when it was programmed at the higher current.<<ETX>>

Characteristic voltage of programmed metal-to-metal antifuses

The characteristic voltage V/sub f/ of different programmed metal-to-metal antifuses was measured and found to be nearly independent of the electrode materials. An electrothermal model, used previously to predict programmed silicon-electrode antifuse resistance, was extended to explain the above phenomenon. The metal-to-metal antifuse resistance vs. the programming current is governed by the Wiedeman-Franz Law.<<ETX>>

On-state reliability of amorphous silicon antifuses

A unified model of the on-state reliability of a-Si antifuses is presented. This physical model accounts for both thermal activation and electromigration. Temperature at the conductive link is the temperature at which the antifuse is stressed and is controlled by the stress current, not the ambient. To ensure a 10 year lifetime, a-Si antifuses should be operated at a current value less than 60% of its programming current value.

Reliable metal-to-metal oxide antifuses

This paper presents a new high performance, reliable metal-to-metal antifuse. The problem of switch-off in the programmed antifuses is avoided by using metals with low thermal conductivity and thin oxide.<<ETX>>

A Novel 65 nm Radiation Tolerant Flash Configuration Cell Used in RTG4 Field Programmable Gate Array

The newly introduced radiation-tolerant flash-based FPGA, RTG4, uses a novel configuration cell design composed of a NMOS switch controlled by a totem pole p-channel flash and n-channel flash construction. Its radiation tolerance is far superior to that in the present available Flash-based FPGA. This paper describes the radiation hardening by design (RHBD) process for the new flash-based configuration cell. A subtle and unique retention issue was found and resolved through studying physical mechanisms and conducting experiments.

Clock buffer circuit soft errors in antifuse-based field programmable gate arrays

Three-dimensional mixed-mode device simulation is used to investigate the clock upset in an antifuse FPGA device. Two versions of the clock circuit were simulated, the original and the redesigned with improved SEU hardness. The threshold LET of each version was simulated both at static and during transition. Compared to the test data, the simulated results consistently underestimate the LET/sub th/. The difference between LET/sub th/ at static and during transition is relatively small. This disagrees with the previous speculation that the clock upset is due to heavy-ion strikes very close to the clock edge. Efforts were also made to optimize the simulation methodology to reduce the simulation time for practicality.