Five-Minute Tutorial: EM Model Files Revisited

 

Back in January, I posted a Five-Minute Tutorial about creating EM Model files. We'll be referencing this previous post a lot, so check it out quickly right now.

That method has worked well for me, but on my most recent project, I hit some snags. As process nodes evolve, the EM models are becoming more complex, and translation scripts are not able to handle all of the cases. So, I had to dig back in and find a new way to get my EM analysis done. I wanted to share this with everyone, since you are likely to hit the same snags that I did, eventually.

Let's assume this is the first time you're trying to create an EM model file for this process. It's worth checking first if your qrcTechFile already contains em_model info:

>Techgen -process_out qrcTechFile

This will result in a human-readable RCGEN.ict file, from which you can then search for the em_model keyword. If the EM info is there, you can go ahead and just use your qrcTechFile by setting the following two switches in your set_rail_analysis_mode command:

set_rail_analysis_mode -process_techgen_em_rules true -extraction_tech_file qrcTechFile

However, I've yet to see a qrcTechFile that included the EM model info, so let's press on. If the EM info was not there, you can create a qrcTechFile that contains the EM info, as long as you have the .ircx file mentioned in the script method from the previous post (keep in mind that this method only applies to TSMC). You'll need to do the first step in the script method, which is to use the ircxtoict script (located in your extraction installation hierarchy) to generate an .ict file: 

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

This file is human-readable and you can check that it has the em_model info.

Next, you will update your qrcTechFile. I recommend making a separate copy to be used just for power analysis, so that we don't inadvertently mess up anything to do with timing. I use the typical RC corner in my examples, but make sure you are using the right one for your flow.

>cp /proj/yourProj/libs/EXTRACTION/typical/qrcTechFile /proj/yourProj/libs/POWER/qrcTechFile.typical

Now use the Techgen utility to update the qrcTechFile with the .ict file previously created (if you have QRC, you should have Techgen in the same install directory):

>Techgen –update_process /proj/yourProj/libs/POWER/qrcTechFile.typical RC_IRCX_CLN28HPM_1P8M+ALRDL_5X2Z_typical.ict

However, you may have some trouble with an error message about layer names or different numbers of sub-vias. Here is how I worked around that:

I dumped out an ict file of my qrcTechfile with: 

>Techgen -process_out /proj/yourProj/libs/POWER/qrcTechFile.typical

This spits out a file called RCGEN.ict. I then copied the em_model sections for each metal and via layer from my RC_IRCX_CLN28HPM_1P8M+ALRDL_5X2Z_typical.ict to the RCGEN.ict file just created. I also had to copy some em_* variables from the top of the file.

Finally, I updated a copy of my qrcTechFile with this RCGEN.ict file: 

>Techgen –update_process /proj/yourProj/libs/POWER/qrcTechFile.typical RCGEN.ict

The set_rail_analysis_mode options are still needed, and make sure that you don't have the -em_model_file switch in the set_rail_analysis_mode command:

set_rail_analysis_mode -process_techgen_em_rules true -extraction_tech_file /proj/yourProj/libs/POWER/qrcTechFile.typical