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Fuse simulation (Read 6289 times)
deff0
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Fuse simulation
Mar 29th, 2009, 1:58am
 
Hello everybody!

I'm trying to simulate fuse for 180nm process using CFD software.
Fuse is a piece of Al wire created with top metal and passivation opening above.
I apply power dissipation to it and calculate time-temperature chart.

The problem is that I can't determine the point when my fuse is blown up.
Any solutions on this?

Thanks in advance.
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rf-design
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Reiner Franke

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Re: Fuse simulation
Reply #1 - Mar 29th, 2009, 4:05am
 
First I am not an expert on that but have heart some comments about the right layout for a fuse. That gives reasons for a more complicated behaviour than it seems first.

1. Passivation opening
Required to give the poly a way out in the stage from going from liquid to vapor.

2. Right angle and distant from the much wider supporting poly which supplies current but also drain heath. Poly's conductivity is 140x oxide's.

3. Electric field which fires gas discharge at the transistion from vapor phase.


I think that will be very complicated simulation with a huge number of physical effects. I have doubts that you can get without experimentation a high yield fuse. Concider circuit configurations with redundancy. Otherwise fuse yield could dominate.
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deff0
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Re: Fuse simulation
Reply #2 - Mar 29th, 2009, 7:45am
 
Unfortunately, we can't use poly as a fuse. Technology we use doesn't allow us to make opening through all the layers. That's why the only source for our fuse is a top metal and pad window above.

This fuse prototype will be well tested on test wafer and only then may go to production stage.
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salty
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Re: Fuse simulation
Reply #3 - May 26th, 2009, 2:44pm
 
You can always add some extra fuses and then pass them through an ECC block of logic.  Hamming codes are very easy to implement in logic and will give you protection/correction if some fuses do not blow properly.
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Colbhaidh
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Re: Fuse simulation
Reply #4 - Jul 21st, 2009, 4:03am
 
For simulating a fuse, assuming your CFD is properly simulating the temperature of the metal line, then the point it fuses is when the temperature causes the metal to flow (melt). This depends on the metal, the metal stack (e.g. for aluminium track, it will be composed of for example 20nm Ti/ 45nm TiN/ 0.6um Al-Cu/ 45nm TiN).
The simulator will not simulate the actual fusing of the track so you need to find out the critical temperature for your metal line.

By the way, you do not need an opening above a poly fuse. The poly will melt while contained by the dielectric and still fuse reliably. The only thing not to do with a poly fuse is run metal over the top of it.
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