1. POLY FUSE a n EW STANDARD OF CIRCUIT PROTECTION
BY- TARUN SHARMA

2. 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

3. 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.

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

5. 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.

6. 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.

7. 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).

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

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

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

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

12. 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 µs µs

13. 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

14. 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

15. 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

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

17. 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

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

19. 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)

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

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

22. 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