EM analysis

What are the EM model-supported formats and in which order are they honored by Voltus?

EM_model_formats.png

1. Text-based EM model

When -process_techgen_em_rules false and -em_models are used together, the tool uses EM rules from the EM-based text file only.

Text-based_EM_model_file.png

2. ICT-EM file

When -process_techgen_em_rules is set to 'true', the tool uses EM rules are picked in the following priority:

1. ICT-EM file provided using -ict_em_models ICTEM.txt
2. qrcTechFile provided using -extraction_tech_file qrcTechFile
3. qrcTechFile from Tech PGV provided using -power_grid_library

EM Modeling using QRC Technology File

In addition to the set_rail_analysis_config -em_models file command parameter,
you can use the QRC Techfile for EM model specification.
The set_rail_analysis_config -process_techgen_em_rules true parameter
specifies to process the EM models in the ICT section of the qrcTechFile.

Important
The -process_techgen_em_rules and -em_models parameters of the
set_rail_analysis_config command are mutually exclusive. If none of these
parameters are specified, rj analysis will not be performed.

when -process_techgen_em_rules is specified with -extraction_tech_file, the
extraction technology file will be processed.f -process_techgen_em_rules is
specified without -extraction_tech_file, the .cl model will be processed.

set_rail_analysis_mode \
  -method static \
  -em_models textEM_model.txt \
  -process_techgen_em_rules true \
  -ict_em_models ICTEM.txt \
  -extraction_tech_file qrcTechFile \
  -power_grid_library \
    {tech.cl cells.cl} \
  -em_temperature 125 \
  -em_threshold 0.8

1. Text-based EM model
    When '-process_techgen_em_rules false' and '-em_models' are used together, the tool uses EM rules from the EM-based text file only.
2. ICT-EM file 
    When '-process_techgen_em_rules is set to 'true', the tool uses EM rules are picked in the following priority:

    1. ICT-EM file provided using -ict_em_models ICTEM.txt 
    2. qrcTechFile provided using -extraction_tech_file qrcTechFile
    3. qrcTechFile from Tech PGV provided using -power_grid_library 

Note: When '-process_techgen_em_rules is set to 'false'(default)and the '-em_models' option is also not used, EM analysis will be disabled.

Terminologies used in the calculation.

Current_density_terminology.png

Example: 
Current : 6.327329e-03mA. (Tool calculated)
Current density(J):  = I/Metal area 
                     = I/(width*thickness)
                     = 6.327329e-03mA / (0.18um*0.15um)
                     = 6.327329e-03mA / (0.18e-04cm * 0.15e-04cm)
                     = 2.343455e+04 (A/cm2)
Max current density (Jmax) from file, = max current density *Jmax_factor 
                                      = 8e+05*1
                                      = 8e+05 (A/cm2)
Max current (Ilimit) = Jmax * metal area = 8e+05 (A/cm2) * (0.18um*0.15um)
                                         = 2.16e-01mA
I/Ilimit = 6.327329e-03mA / 2.16e-01mA
         = 0.0292932
Note: J/Jmax = I/Ilimit. 
Current density(J) / Max current density (Jmax) = 2.343455e+04 (A/cm2)/8e+05 (A/cm2) = 0.0292932

Understanding and validating Power EM report generated using "analyze_rail" command

./era_run_no_scale/vdd_d_25C_avg_1/Reports/vdd_d/vdd_d.rj.avg.rpt

The /Reports//.rj.avg.rpt report captures the related parameters used to check the reliability of metal/via on Power network.
# The current or EM limit at via layer is reported as the value per cut for a via cluster
# EM Reporting Threshold: 0.9
# Total Violations: 223                     
#
# Report format:
# Short (Blech) Length with N/A indicates a loop in layout, and benefit factor would be 1.0.

# I/Ilimit  I(mA)      Ilimit(mA)       Layer          Location                              ShortLength     Width      ViaArea        Via        Fix Width/      Current        Benefit     J(A/cm^2)    Jmax(A/cm^2)  ResistorID 
#                                                   {X1 Y1 X2 Y2}                               (um)         (um)        (nm^2)        Cuts         Via           Direction      Factor  
#
  2.97901  5.958016e+00  2.000000e+00   MET4      {6153.6200  890.6800  6153.6200  896.6300}     N/A          2           N/A          N/A         5.95802         N/A            1.00      2.979008e+05  1.000000e+05  141466  

I(mA) :
    This current value (4.708982e-02)that flows through the Metal/Via resistor is calculated by the tool.    
Ilimit (mA):
    This is the current limit(2.992880e-02)whose value is provided by the foundry depending upon its width and thickness.   
    1. For Metal layers Ilimit calculation:
        If the -ict_em_models option is used, refer to the article #20466998.
        If the -em_models is used, refer to the article #20467159.
    2. For Via layer Ilimit calculation:
        If  the -ict_em_models option is used, refer to the article #20466988.
        If the-em_models option is used, refer to the article #11141402.
Current Direction:
    Current Direction is applicable only to via layers where 'D" denotes down, "U" denotes up.