Dan Moy

Electrically Programmable Fuse (eFUSE): From Memory Redundancy to Autonomic Chips

Electrical fuse (eFUSE) has become a popular choice to enable memory redundancy, chip identification and authentication, analog device trimming, and other applications. We will review the evolution and applications of electrical fuse solutions for 180 nm to 45 nm technologies at IBM, and provide some insight into future uses in 32 nm technology and beyond with the eFUSE as a building block for the autonomic chip of the future.

A Compact eFUSE Programmable Array Memory for SOI CMOS

Demonstrating a >10X density increase over traditional VLSI fuse circuits, a compact eFUSE programmable array memory configured as a 4 Kb one-time programmable ROM (OTPROM) is presented using a 6.2 mum2 NiSix silicide electromigration ITIR cell in 65 nm SOI CMOS. A 20 mus programming time at 1.5 V is achieved by asymmetrical scaling of the fuse and a shared differential sensing scheme. Having zero process cost adder, eFUSE is fully compatible with standard VLSI manufacturing.

Reliability investigation of NiPtSi electrical fuse with different programming mechanisms

The reliability of NiPtSi/p-poly Si electrical fuses with different programming mechanisms, i.e., electromigration and thermal rupture, was investigated in terms of fuse resistance stability and fuse array functionality for the 65-nm technology node. The resistance of the fuses programmed within the electromigration programming window was found to be very stable; resistance shift was only observed on fuses programmed in the underprogrammed mode, which results in incomplete electromigration. For fuses programmed with the thermal rupture mechanism, both resistance shift and functional sensing fails were observed. Furthermore, a guard band was defined for fuses programmed with an electromigration mechanism to ensure sufficient margins for fuse reliability. However, a guard band cannot be defined for fuses programmed with a rupture mode due to the unpredictable nature of the rupture programming mechanism. The unprogrammed fuse elements were shown to be stable through extensive reliability evaluations.

The Application of Deep UV Phase Shifted-Single Layer Halftone Reticles to 256 Mbit Dynamic Random Access Memory Cell Patterns

We have applied deep UV (DUV) halftone reticles, with a single layer absorptive shifter consisting of silicon nitride, to 256 Mbit dynamic random access memory (DRAM) critical levels, and have evaluated the resolution in those cell patterns. For the periodic line levels, halftone reticles were combined with off-axis illumination (OAI) techniques. Resolution capabilities were characterized not only with stepper exposures but also with direct aerial image measurement. For hole levels such the Storage Node and Bitline Contact, halftone reticles offered clear improvement with standard illumination as compared to conventional reticles. For line levels such the Isolation, Wordline and Bitline, dramatic improvement was obtained with the combination of halftone reticles and off-axis illumination.

Highly selective sputtering of silicon from TiSi2 at elevated temperature

We demonstrate almost 100% selective sputtering of silicon from TiSi2 using a combination of low energy ion bombardment and elevated temperature. TiSi2 was prepared by annealing 1000‐A‐thick Ti on (100)Si in He at 635 °C for 30 min to produce 2300‐A thick TiSi2. Ion beam etching was carried out using 300 eV argon with a flux of 0.27 mA/cm2 at temperatures from 33 to 700 °C. In situ sheet resistance measurements were used to monitor the decrease in silicide thickness as a function of time. Near room temperature, ion etching causes normal sputtering of the silicide. However, at temperatures of 500–700 °C, the sheet resistance remains almost unchanged during ion beam etching. Analysis by Rutherford backscattering, with and without Xe markers, shows that Si atoms sputtered from the surface of these high‐temperature samples are continuously replaced by Si diffusing from beneath the silicide layer. The thickness and composition of the silicide remain almost unchanged, but the dramatic change in sputtering behav...