POLY FUSE a n EW STANDARD OF CIRCUIT PROTECTION BY- TARUN SHARMA http://www.scribd.com/doc/59911050/POLY-FUSE-2010 0814331052

OUTLOOK INTRODUCTION HISTORY AND BASICS MODERN POLY FUSE PRINCIPLE ELECTRONIC CIRCUIT PROGRAMMING FEATURES AND CHARACTERISTICS CROSS SECTION RELIABILITY INVESTIGATION PROCESS CONTROL DESIGN ISSUE DESIGN REQUIREMENT APPLICATION CONCLUSION REFERENCES

INTRODUCTION A Polyfuse is a one-time-programmable memory component used in semiconductor circuits for storing unique data like chip identification numbers or memory repair data. Polyfuses were developed as a replacement of laser fuses.

Polyfuse used as an OTP base element Poly Silicon with Tungsten Silizide Low ohmic standard resistance (<100W) High ohmic after programming (>10kW)

HISTORY AND BASICS The first polyfuses consisted of a polysilicon line, which was programmed by applying a high (10V- 15V) voltage across the device. The resultant current physically alters the device and results in an increase in electrical resistance. This change in resistance can be detected and registered as a logical one.

An unprogrammed Polyfuse would be registered as a logical zero. These early devices had severe drawbacks like a high programming voltage and unreliability of the programmed devices.

MODERN POLYFUSE Modern polyfuses consist of a siliced polysilicon line, which is also programmed by applying a voltage across the device. the resultant current physically alters the device and results in an increase in resistance. The silicide layer covering the polysilicon line reduces its resistance (before programming), allowing the use of much lower programming voltages (1.8V-3.3V).

Polyfuses have been shown to reliably store programmed data and can be programmed at high speed. Programming speeds of 100ns have been reported

PRINCIPLE ELECTRONIC CIRCUIT Principle schematic have: Polyfuse Element Programming Transistor Current Mirror Testmodes

Principle Layout PROM Storage RAM Access LOADing Mode PROGramming Mode Optional Parallel Out

PROGRAMMING FEATURES Programming in standard CMOS process Current programming Infield programming possible

PROGRAMMING CHARACTERISTICS Ilinear: Linear resistor characteristics Iheat: Temp. is raising Imelt: Tungsten Silicide is melting Imax: Maximum current of minimum resistance Imin: Local current min. Iosc: Oscillation because of break Ialloy: No autonomous current pinch off Iprog mA Vprog V tprog 0µs 1µs 2µs 3µs

CROSS SECTION Typical Current Programmed Poly Fuse Local break of a few nm Minimal lifetime drift of the resistance value Typical Current Programmed Poly Fuse Active PolyFuse region no longer has Tungsten included High ohmic stable alloy Substrate Field Oxide Poly Silicon Tungsten Silicide Tungsten Plug approx. 40nm

Low Current Programmed Poly Fuse Low ohmic resistor Lifetime drift to higher resistor values Low Current Programmed Poly Fuse Inhomogenious temperature gradient during programming Tungs Tungsten Plug Tungsten Plug Tungsten Plug Tungsten Plug Field Oxide Tungsten Silicide Tungsten Silicide Poly Silicon Poly Silicon Field Oxide Substrate

Higher Current Programmed Poly Fuse High energy is forcing the Tungsten seperation Break before Tungsten completely removed Relatively high ohmic resistor Lifetime drift to lower resistor values possible Tungsten Plug Tungsten HALO Field Oxide Tungsten Plug Tungsten Silicide Tungsten Silicide Poly Silicon Poly Silicon Tungsten Field Oxide Substrate

RELIABILITY INVESTIGATIONS Lifetime Drift over Time 2000h BurnIn@125 °C HTOL Test JESD22-108 Lifetime Drift Investigated for typical current programmed PolyFuses low current programmed PolyFuses high current programmed PolyFuses

DESIGN ISSUE IP Blocks with PolyFuses Designed 32 bit 128bit Optimized Programming Path PolyFuse Related programming transistor Special Test Function to guarantee lifetime stability for infield programming

PROCESS CONTROL WAT Structure Measurements PolyFuse Element Burning NMOS Transistor Measurements Resistor of unprogrammed PolyFuse Resistor of programmed PolyFuse Current of Burning Transistor

DESIGN REQUIREMENT Requirements For Lifetime Stability A programmed PolyFuse resistance must be larger than 10kW after programming The resistance of a programmed PolyFuse is checked at 1kW during lifetime operation This margin ensures proper operation of programmed PolyFuses over lifetime Requirement for Infield Programming Testmode to measure the unprogrammed PolyFuse resistance (<100W)

APPLICATION Used in : Automobiles Batteries Computers Peripherals Industrial control Consumer electronics Medical electronics Lightening Security and fire alarm system Telecommunication equipment

CONCLUSION Reliable Programming Conditions Programmable over whole Process Range Lifetime Stability High Programming Yield Process Control Infield Programming Option

REFERENCES Mochizuki; Semiconductor devices having fuses; United States Patent 4,413,272; November 1983 M. Alavi, M. Bohr, J.Hicks; A PROM Element based on Salicide Agglomeration of Poly Fuses in a CMOS Logic Process; IEEE International Electron Device Meeting; December 1997 W.R. Tonti, J.A. Fifield, J. Higgins, W.H. Guthrie, W. Bery,C. Narayan; Product Specific Sub-Micron E-Fuse Reliability and Design Qualification; IEEE 2003 IRW Final Report J.Simader; Entwicklung von Polyfuses als PROM Element für den CSD (0,35 μm CMOS) Prozess; Diploma Thesys, September 2002 Research Institute for Electron Microscopy and Fine Structure Research (FELMI); TU-Graz