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Five-Minute Tutorial: Creating An EM Model File

Comments(2)Filed under: power analysis, EPS, EDI, five minute tutorial, rail analysis, iRCX, ict, EM Model, electromigration

One of the least-fun parts of running power and rail analysis has always been coming up with the electromigration (EM) model file. In the past, this involved cracking open the process design rule manual, finding the appropriate equations, and creating a spreadsheet to calculate all the numbers needed for the various metal width and via sizes. Then, this information had to be put in the format of the model file used by Encounter Digital Implementation System (EDI) and Encounter Power System (EPS). This approach was prone to errors and involved some user decisions about what exactly to model. Frustrating, but it worked for the most part.

Now there is an easier way to get this information into an automatically-created EM model file if you are using a TSMC process. You'll need the iRCX file (also referred to as a unified tech file) from TSMC, and you'll need to locate both your extraction installation and your EDI installation.

When you request the iRCX information from TSMC, it may come in a directory that needs to be unzipped and untarred. Ultimately, you're looking for a file that's named something like IRCX_28NM_8M_typical.ircx. Make sure you have the right file for your process, metal stack, and extraction corner.

To locate your extraction installation, type:

>which qrc

To locate your EDI installation, type:

>which encounter

Now, you'll run two translators. The first comes from the extraction installation and is called ircxtoict. This translates the iRCX file into the .ict format:

>/apps/PVE111/11.11.238/bin/ircxtoict -i IRCX_28NM_8M_typical.ict IRCX_28NM_8M_typical.ircx

Now that you have an .ict file, you can use the second translator, which comes from your EDI installation, to create the EM model file. But first, you'll need to create a small text file called conductor.widths (or another name of your choice). It looks something like this, with the order of each line being <metal_layer> <min_width> <max_width>. The width values are in microns:

M1 0.05 4.5
M2 0.05 4.5
M3 0.05 4.5
M4 0.05 4.5
M5 0.05 4.5
M6 0.05 4.5
M7 0.40 12.0
M8 0.40 12.0
AP 2.00 35.0

The metal layer names come from the .ict file, and the min and max widths come from the tech LEF. (Note that the metal layer names may differ between the .ict file and your tech LEF.)

Now we're ready for that second translator, called ict2emfiles. It converts the newly-created .ict file to the EDI/EPS EM model file format:

>/apps/EDI110/11.12.000/share/anls/gift/bin/ict2emfiles -eps -i IRCX_28NM_8M_typical.ict -w conductor.widths

This will result in a file called IRCX_28NM_8M_typical.ict.em_model, which you can then use during the RJ analysis in EDI/EPS.

This method saves a lot of time and removes potential sources of error. I was very happy to be able to create my EM model file this way, and I hope others will find this useful as well.

- Kari Summers


By Jim Lloyd on January 16, 2013
Does this consider the length of the line and how it is terminated?  Is the current assumed average, RMS or maximum? Is Black's law used, anad if so what do you use for a current density?  All this and more matters in electromigration assessments.  Can I get this information?

By Kari on January 17, 2013
Hi Jim, There is lots of information in the Encounter Power System User Guide, in the chapter "Static Power, IR Drop, and EM Analysis". I think you'll find the answers to your questions there.

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