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EM Rules Specification

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This section contains information about the EM rule requirements in Voltus-Fi-XL.

EM Rule File Requirements in Voltus-Fi-XL

Before running EMIR analysis in Voltus-Fi-XL, you need to specify the EM reliability rules. EM rules are defined in the technology files. The Voltus-Fi - Spectre EMIR solution supports the following technology file formats:

• The Quantus technology file (qrcTechFile)
• The ICT, ICT-EM (EM Rules only) file
• Interoperable interconnect extraction (iRCX) file
• The EM data file (emDataFile).
  
  The emDataFile support is provided only for backward compatibility. It is recommended that you convert your emDataFile into an ICT file to specify the EM rules for performing EM analysis.

The ICT file contains the process information for the design and information about the EM rules. This is a text-based file that can be edited using any text editor. You can either specify the ICT file directly as an input for EM analysis or use the information in the ICT file to update the qrcTechFile.

Related Topics

• Conversion of EM Data File into ICT File
• Parameters for Limit-Based EM Analysis in Voltus-Fi-XL
• Supported Current Density Keywords in Voltus-Fi-XL

Parameters for Limit-Based EM Analysis in Voltus-Fi-XL

Voltus-Fi-XL supports parameters for only limit-based EM analysis. The following parameters can be used to specify EM rules in the ICT EM file. The EM rules might also be embedded in the ICT file or the qrcTechFile.

Related Topics

• Supported Current Density Keywords in Voltus-Fi-XL
• EM Rule File Requirements in Voltus-Fi-XL

Supported Current Density Keywords in Voltus-Fi-XL

The table below lists the Current Density (JMAX) keywords that can be specified in the ICT EM file.

Where star ‘*’ implies that ‘_w’ and ‘_n’ rules are also supported.

For example,

• em_jmax_ac_peak_w is an optional parameter that is essentially the same as em_jmax_ac_peak, with the exception that it is specified for wide wires (as defined by em_W_n).
• em_jmax_ac_peak_n is an optional parameter that is essentially the same as em_jmax_ac_peak, with the exception that it is specified for narrow wires (as defined by em_W_n).

Related Topics

• EM Rule File Requirements in Voltus-Fi-XL
• Parameters for Limit-Based EM Analysis in Voltus-Fi-XL

EM Model Syntax

em_model {

# Width Independent parameters are not affected by width or area

[em_vcwidth <value>]

[em_W_n <value>]

[em_recover <value>]

# Parameters applying specifically to narrow or wide wires

[em_jmax_ac_avg_n <value>]

     [jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[em_jmax_ac_avg_w <value>]

     [jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[em_jmax_ac_peak_n <value>]

     [jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[em_jmax_ac_peak_w <value>]

     [jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[em_jmax_ac_rms_n <value>]

     [jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[em_jmax_ac_rms_w <value>]

     [jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[em_jmax_ac_rec_n <value>]

     [jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[em_jmax_ac_rec_w <value>]

     [jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[em_jmax_dc_avg_n <value>]

     [jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[em_jmax_dc_avg_w <value>]

     [jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[em_jmax_dc_peak_n <value>]

     [jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[em_jmax_dc_peak_w <value>]

     [jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[em_jmax_dc_rms_n <value>]

     [jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[em_jmax_dc_rms_w <value>]

     [jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

# Width dependent parameters for a conductor or diffusion layer

[em_jmax_ac_avg <value> | <value_1> <width_1> [...] | EQU <fn(E)> ]

[jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[jmax_life <life1> <scale1> [<life2> <scale2>.....]

[via_range <value>]

[em_jmax_ac_peak <value> | <value_1> <width_1> [...] | EQU <fn(E)> ]

[jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[jmax_life <life1> <scale1> [<life2> <scale2>.....]

[via_range <value>]

[em_jmax_ac_rms <value> | <value_1> <width_1> [...] | EQU <fn(E)> ]

[jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[jmax_life <life1> <scale1> [<life2> <scale2>.....]

[via_range <value>]

[em_jmax_ac_rec <value> | <value_1> <width_1> [...] | EQU <fn(E)> ]

[jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[jmax_life <life1> <scale1> [<life2> <scale2>.....]

[via_range <value>]

[em_jmax_dc_avg <value> | <value_1> <width_1> [...] | EQU <fn(E)> ]

[jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[jmax_life <life1> <scale1> [<life2> <scale2>....]

[via_range <value>] [L < | <= | > | >= <value in microns>]

     [W < | <= | > | >= <value in microns>]

[em_jmax_dc_peak <value> | <value_1> <width_1> [...] | EQU <fn(E)> ]

[jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[jmax_life <life1> <scale1> [<life2> <scale2>.....]

[via_range <value>] [L < | <= | > | >= <value in microns>]

     [W < | <= | > | >= <value in microns>]

[em_jmax_dc_rms <value> | <value_1> <width_1> [...] | EQU <fn(E)> ]

[jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[jmax_life <life1> <scale1> [<life2> <scale2>....]

[via_range <value>] [L < | <= | > | >= <value in microns>]

     [W < | <= | > | >= <value in microns>]

# Area dependent parameters for a via layer

[em_jmax_ac_avg <value> | <value_1> <area_1> [...] | EQU <fn(E)>]

[jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[jmax_life <life1> <scale1> [<life2> <scale2>.....]

[current_direction up|down|both] [via_range <value>]

[em_jmax_ac_peak <value> | <value_1> <area_1> [...] | EQU <fn(E)>]

[jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[jmax_life <life1> <scale1> [<life2> <scale2>.....]

[current_direction up|down|both] [via_range <value>]

[em_jmax_ac_rms <value> | <value_1> <area_1> [...] | EQU <fn(E)>]

[jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[jmax_life <life1> <scale1> [<life2> <scale2>.....]

[current_direction up|down|both] [via_range <value>]

[em_jmax_ac_rec <value> | <value_1> <area_1> [...] | EQU <fn(E)>]

[jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[jmax_life <life1> <scale1> [<life2> <scale2>.....]

[current_direction up|down|both] [via_range <value>]

[em_jmax_dc_avg <value> | <value_1> <area_1> [...] | EQU <fn(E)>]

[jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[jmax_life <life1> <scale1> [<life2> <scale2>....]

[current_direction up|down|both] [via_range <value>]

[L < | <= | > | >= <value in microns>]

     [W < | <= | > | >= <value in microns>]

[em_jmax_dc_peak <value> | <value_1> <area_1> [...] | EQU <fn(E)>]

[jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[jmax_life <life1> <scale1> [<life2> <scale2>....]

[current_direction up|down|both] [via_range <value>]

[L < | <= | > | >= <value in microns>]

     [W < | <= | > | >= <value in microns>]

[em_jmax_dc_rms <value> | <value_1> <area_1> [...] | EQU <fn(E)>]

[jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[jmax_life <life1> <scale1> [<life2> <scale2>.......]

[current_direction up|down|both] [via_range <value>]

[L < | <= | > | >= <value in microns>]

     [W < | <= | > | >= <value in microns>]

}

Special Variables in ICT-EM File

The following list of special variables are defined by Cadence. You must not define these variables as custom variables in the ICT-EM file. It is recommended to contact your Cadence representative if you wish to use these variables in the file.

Rules for Defining EM Parameters in Voltus-Fi-XL

An example of the EM rule for defining the em_jmax_dc_avg parameter is provided below:

[em_jmax_dc_avg <value> | <value_1> <area_1/width_1> [...] | EQU <fn(E)>]

[jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]]

[jmax_life <life1> <scale1> [<life2> <scale2>.......]]

[current_direction up | down | both]

[via_range <value>]

[conditions]

[single]

[power_rail/power_grid    ]

[priority==<priority no.>]

[device==”<device model names>”]

[sub_conductor=="<subconductor names>"]

[color=="<list of color no.>"]

[mask==<mask no.>]

All other EM parameters are defined with the same structure but apply to different characteristics of the em_model (peak current versus average for instance). The following rules apply to all the limit-based em_model parameters:

• Single Value Current Density
  Specifying a single value or an equation is an enhancement for width or area dependent parameters (such as em_jmax_ac_avg).
  
  For narrow/wide wire parameters (such as em_jmax_ac_avg_n or em_jmax_ac_avg_w) you can only specify a single value. It will not accept either a PWL table or an equation.
• Piece-wise Linear (PWL) Interpolation
  In a width-dependent model for a conductor layer, or for an area-dependent model for a via layer, PWL interpolation uses a series of data points that are points on a graph of X versus Y, where X can be either a value or an expression and Y is a value. For example, current density value and area <value1> <area1>, current density value and width <value1> <width1>, current density expression and area <expression1> <area1>, or current density expression and width <expression1> <width1>.
  The following syntax are supported:

  em_jmax_dc_avg PWL <value1> <area1/width1> <value2> <area1/width1>

  em_jmax_dc_avg PWL (<value1> <area1/width1> <value2> <area1/width1>)

  em_jmax_dc_avg PWL (<expression1> <area1/width1> <expression2> < area1/width1>)

  For example:

  em_jmax_dc_avg PWL 0.3582 0.001444 0.5694 0.003364 0.7164 0.0038

  em_jmax_dc_avg PWL (0.3582 0.001444 0.5694 0.003364 0.7164 0.0038)

  em_jmax_dc_avg PWL (0.05*0.5 0.002 0.1*0.5 0.004 0.2*0.5 0.008)

• Equations in EM Model
  The EQU keyword denotes the definition of an equation for current density.
  An EOL or one of the qualifiers (jmax_factor, current_direction,or single) marks the end of an equation specifying the Current Density limit. If the equation resolves into two separate equations, then this will result in an error.
  For EQU, the following operators (not case-sensitive) are supported:
  • SQRT
  • LOG
  • EXP
  • * / + -
  • ()
  • e
  • ^
  • expr1? expr2: expr3
  
  Where, expr1 is a conditional expression. If expr1 evaluates to true, then expr2 is evaluated, else expr3 is evaluated.
  For example:
  Life_factor= ((A < 5 and B > 2)? 3:4)
em_jmax_dc_avg EQU 3.0*w * Life_factor jmax_factor 50 1.1 110 1.0 125 0.92 L > 5
  
  Square brackets ‘[]’ are not supported. A comma ‘,’ implies multiple equations, and results in an error. The period ‘.’ is ambiguous and should not be used to indicate multiplication (use * instead).
  Spaces are permitted to make an equation more readable.
  Variables within equations will be populated by the analysis tool at run-time. Use the em_variables parameter in the process definition to globally declare variables that are used within the various em_models. List of supported variables are provided below:
  • a: area of the resistor
  • w: width
  • l: length
  • La: length of pseudo via
  • La_x: length of pseudo via along the x-axis
  • La_y: length of pseudo via along the y-axis
  • N: number of vias
  • delta_T: rise in temperature in degree Celsius
  • r: duty ratio
  • Tref: refers to em_tref, the nominal temperature for EM analysis defined in the process section of the ICT file. If em_tref is not defined, then default value(110C) is set.
  • cdf_percentage: This variable lets you use the value specified using the keyword cdf_percentage in the emir config file or command file, in the EM rules. For example,
    

    conductor "m1" {

        min_spacing         0.3

        min_width           0.3

        height              1.05

        thickness           0.53

        resistivity         0.1

        gate_forming_layer  false

        thermal_conductivity 0.39

        em_model {

          cxyz=exp(normsinv(cdf_percentage*10.0))

          em_jmax_dc_avg  EQU 2*w*cxyz L >  5

          em_jmax_dc_avg  EQU 3*w*cxyz L <= 5

        }

    } 

  • Tlife: This variable provides the value of lifetime at which EM analysis is performed. This value can be specified in hours or years.
    The value of lifetime can be specified in the config file as follows:

    emirutil Tlife = "20000 hours"

    It can also be specified in techfile in the process block section as follows:

    em_lifetime 20000

    
    
    The lifetime value specified in the techfile gets priority over the value specified in the config file. If the value is not specified in either of these files, the default value of “10 years” is used.
  • jmax_factor_multiplier: This variable provides the value of jmax_factor for the resistor.
  • jmax_life_multiplier: This variable provides the value of jmax_life for the resistor.
    For example:

    derate = jmax_factor_multiplier * jmax_life_multiplier

    em_jmax_dc_avg  EQU 3.0*derate   jmax_factor   50 1.1  110  1.0  125 0.92 L >  5

    The equation definition ends when reaching the end of line (EOL) or another keyword (jmax_factor, current_direction, or single).
  
  The following are supported for equations in the ICT EM file:
  • Support for min max functions: The min and max functions accepts two arguments:
    

    min(a,b) => It returns the smallest value of a and b

    max(a,b) => It returns the largest value of a and b

    Nested min and max functions are also supported as shown below:

    min(a, max(b, c))

    max(max(a, b), c)

    min(min(a, b), max(c, d))

    max(min(a, b), max(c, d))

  • Support for defining the normsinv function: The normsinv function accepts a single argument. It returns the value by taking the inverse normal distribution of the fraction x. The value of x must always be between 0 to 1.
    

    normsinv(x) 

  • Support for defining variables: Variables can be defined to be used in equations specifying the current density limit. An example of how these are specified in the ICT file is shown below. In the below equation, s1, s2, s3 and s4 are variables.
    

    em_model {

     s1 = 2.0*w

     s2 = s1*1.0

     s3 = 3.0*w

     s4 = s3

     em_jmax_dc_avg EQU s2*4 jmax_factor 50 1.1 110 1.0 125 0.92 L> 5

     em_jmax_dc_avg EQU s4*2 jmax_factor 50 1.1 110 1.0 125 0.92 L<=5

    }

    
    
    A variable needs to be defined before it is used.
  • Support for keyword “cond” and logical operator “not”: The keyword “cond” can be used to group multiple conditions logically for EM rules. for example:
    

    em_jmax_dc_avg EQU 0.1*w     cond (L <=0.024 and L>=0.026)

    em_jmax_dc_avg EQU 0.2*w     cond (((L == 0.020) or (L == 0.030))and (W < 0.01))

    em_jmax_dc_avg EQU 0.2*w     cond ( not(L == 0.020 or L == 0.030))

  • Support for jmax_factor_dc_avg and jmax_factor_ac_avg: These are specified for defining the jmax_factor information at the layer level.
    jmax_factor_dc_avg: specifies the jmax_factor information for the DC avg EM rules at the layer level.
    jmax_factor_ac_avg: specifies the jmax_factor information for the AC avg EM rules at the layer level.
    For example:

    conductor "M1" {

       em_model {

              jmax_factor_dc_avg 85 3 90 2 100 1 110 0.6 120 0.2 125 0.1

              jmax_factor_ac_avg 85 3 90 2 100 1 110 0.6 120 0.2 125 0.1            

              em_jmax_dc_avg EQU 2 * w     L < 0.5 

              em_jmax_ac_avg EQU 2 * w     L < 0.5

              em_jmax_dc_avg EQU 1.5 * w   L >= 0.5 

              em_jmax_ac_avg EQU 1.5 * w   L >= 0.5  

        }

    }

    
    
    For EM rules that have jmax_factor construct, jmax_factor will be calculated from the rule jmax_factor information instead of the layer-level construct jmax_factor_dc_avg or jmax_factor_ac_avg.
  • Support for jmax_life_dc_avg and jmax_life_ac_avg: These are specified for defining the jmax_life information at the layer level.
    jmax_life_dc_avg: specifies the jmax_life information for the DC avg EM rules at the layer level.
    jmax_life_ac_avg: specifies the jmax_life information for the AC avg EM rules at the layer level.
    When the lifetime has an exact match in the PWL, jmax_life gets the corresponding value from the PWL. If not, then the expression in the below syntax is evaluated to get the value of jmax_life.

    jmax_life_dc_avg <life1> <scale1> <life2> <scale2> <life3> <scale3>  jmax_life_equ <expression>

    jmax_life_ac_avg <life1> <scale1> <life2> <scale2> <life3> <scale3>  jmax_life_equ <expression>

    For example:

    jmax_life_dc_avg PWL 43800 1.8 52560 1.5  61320 1.3 70080 1.2  78840 1.1  87600 1 131400 0.6 175200 0.5  jmax_life_equ  (10/Tlife)^0.9

    jmax_life_ac_avg 43800 1.8 52560 1.5  61320 1.3 70080 1.2  78840 1.1  87600 1 131400 0.6 175200 0.5  jmax_life_equ  (10/Tlife)^0.9

    
    
    For EM rules that have jmax_life construct, jmax_life will be calculated from the rule jmax_life information instead of the layer-level construct jmax_life_dc_avg or jmax_life_ac_avg.
• Order Dependency
  The actual Current Density limit (value, piece-wise linear or PWL pairs, or equation) should follow immediately after the Current Density keyword (em_jmax_dc_avg). Any of the qualifiers (jmax_factor, current_direction, or single) will come after that. The order of the qualifiers is not important.
• Units of Values
  The unit should be specified in accordance with the setting defined by the em_conductor_unit, em_via_unit, and em_via_area_unit parameters defined in the process definition. Units are specified as:
  • For a single value or an equation:
    • A/cm2 or mA for metal layers (width based)
    • A/via or mA for via layers (per via)
  • For a PWL table:
    • A/cm2 or mA, with width specified in microns for metal layers
    • A/cm2 or mA, with area specified in square microns for via layers
• JMAX Factor
  jmax_factor <temp1> <scale1> [<temp2> <scale2> ...]
jmax_factor is the optional scaling factor to use at different temperatures compared to the reference temperature (defined by em_tref in the process definition). The temperature for jmax_factor should be specified in degrees Celsius.
  Scaling factor is a positive integer: >1 to scale up, <1 to scale down, or 1 for no scale effect.
  If the specified temperature, T, falls between the defined minimum and maximum temperatures, the software will calculate a new scale factor (RT) using the formula, TTF=A*J^(-n)*exp(Ea/kT).
  For example:

  RT = RT1*exp((Ea/kT)*(1/T-1/T1))

  where

  Ea/kT=(T1*T2/(T1-T2))*ln(RT2/RT1)

  
  Note:
  
  • The temperatures T, T1, and T2 mentioned in the above formula are in Kelvin.
  • If the specified temperature, T, is either below or above the defined minimum and maximum temperatures, the software will use the minimum and maximum temperature for calculating the scale factor, respectively.
  • When setting scale factors for multiple temperatures, they should be specified in an ascending sequence to enable interpolation.
• Format of the Conditions
  Condition = [L/W/Lu/Wu/Lb/Wb/Lv2v/Sv/Td/r/a/N < | <= | > | >= | == | != <value in microns/micro seconds> | ground_net | supply_net | Vu_current_direction {up | down}] | [Itolerance < | <= | > | >= | == | != <value in percentage> ]
  Conditions = [condition]*
  The L parameter specifies the length-based jmax values in microns.
  The W parameter specifies the width-based jmax values in microns.
  L and W are applicable for both metals and vias.
  Lu, Lb, Wu, and Wb are applicable for vias only.
  Lv2v and Itolerance are applicable only for the power_rail rule.
  Where,
  L = length W = Width Lu = Upper metal length Lb = Bottom metal length Wu = Upper metal width Wb = Lower metal width Lv2v = Distance between terminal vias Sv = Distance between the two top vias enclosing a metal/via. For metals, it indicates the distance between the immediate top vias across a metal. For via, it indicates the distance between two neighboring vias with the same current direction. Vu_current_direction {up | down} = Current direction of the top vias across a metal/via. For metal, it indicates the current direction of the immediate top vias across a metal layer. For via, it indicates the current direction of the immediate top vias across a particular via. supply_net = specifies that the EM rule is applicable only to the supply net ground_net = specifies that the EM rule is applicable only to the ground net Itolerance = Difference in the current values of terminal vias. For example, if a difference of up to 5 percent is acceptable, then specify 'Itolerance <= 0.05'. Td = Time duration in micro second or total ‘On Time” period r = Duty ratio a = Area of the single cut in the via or in the via array N = Number of vias in the via array
  Voltus-Fi-XL supports metal length/width rules above and below vias, where, the dimensions to be checked for the rules are different for the metal above and the metal below. In this case, Lu/Wu refers to dimensions of the metal above the via and Lb/Wb refers to dimensions of the metal below the via.
• Single
  The keyword, single can be specified to differentiate between a single square cut via and square viaarray. The following example shows how to use the single keyword:

  em_jmax_dc_avg PWL 0.022  0.01  jmax_factor 105 1.1  110 1.0 115

  0.9 120 0.8 125 0.7 130 0.6 140 0.5 150 0.4  current_direction up

  Lb > 4 Wb >= 0.05  current_direction up single

• JMAX Life
  The keyword, jmax_life provides the ability to set the scaling factor that applies to the Current Density limits for different lifetimes. The syntax is as follows:

  jmax_life <life1> <scale1> [<life2> <scale2>.......]

  
  
  The software will take the unit of lifetime from the em_lifetime_units parameter specified in the process section of the ICT file. In case the specified life value does not match any of the life values provided using jmax_life, the software performs linear interpolation to calculate the Tlife factor.
• rating_factor
  The keyword, rating_factor specifies the temperature derating factor for different lifetimes using the rating factor table. The table is used along with the global lifetime factor table that lists the lifetime variables for different lifetimes. These variables can be used in the EM equation. For example,

  em_model {

       GLOBAL_LIFETIME_FACTOR  =   (
       ( LIFETIME    HOURS   LF0 LF1 )

       ( 3_YEAR    26280   5.0 6.0 )

       ( 4_YEAR    35040   7.0 8.0 )

       ( DEFAULT   100000  9.0 10.0 )

       )

       RATING_FACTOR   =   (

       ( LIFETIME    100 105 110 115 120 125 130 140 150 )

       ( 3_YEAR  2.0 1.7 1.3 1.0 0.9 0.8 0.7 0.6 0.5 )

       ( 4_YEAR  2.0 1.6 1.4 1.2 1.0 0.4 0.3 0.2 0.1 )

       ( DEFAULT 1.8 1.7 1.6 1.4 1.1 0.9 0.5 0.4 0.3 )

       )

         em_jmax_dc_avg  EQU 2.0*w*1.0*LF0   rating_factor L >  5
         em_jmax_dc_avg  EQU 2.0*w*3.0*LF1   rating_factor

   }

  Where,
  The different lifetimes, 3 years, 4 years..., are specified in the rating_factor table and the lifetime variables for these lifetimes, LFO, LFI, are specified in the global lifetime factor table.
  
  The rating factor is only applied to EM rules that have the rating_factor keyword.
• Length
  [L < | <= | > | >= <value in microns>]
  The L parameter specifies the length-based jmax values in microns.
• Width
  [W < | <= | > | >= <value in microns>]
  Similar to the L parameter, the W parameter specifies the width-based jmax values in microns.
• Current Direction
  current_direction [up | down | both] can be specified for via current direction. The syntax of current_direction is:
  • up - means the direction of the current is from bottom to top and specifies to use the length and width of the metal below Lb/Wb for the VIA Jmax factor
  • down - means the direction of the current is from top to bottom and specifies to use the length and width of the metal above Lu/Wu for VIA Jmax factor
  • both - This rule is applicable only when the direction of the current is uncertain. This rule is unlikely to be applied since the software calculates the current direction
• Via Range
  via_range <value>
via_range is an optional parameter which can be used with the via layers. The value of via_range denotes the number of vias for which the calculated limits are valid.
  via_range is specified as a positive integer.
• Power Rail/Power Grid
  The keyword power_rail or power_grid can be specified to enable the particular EM rule for power-rail analysis. When power-rail analysis is enabled, an EM rule with the power_rail or power_grid keyword will have a higher priority than any other rule.

  em_jmax_dc_avg PWL 0.022 0.01 jmax_factor 105 1.1 110 1.0 115

  0.9 120 0.8 125 0.7 130 0.6 140 0.5 150 0.4 

  Lb > 4 Wb >= 0.05 current_direction up  

  power_rail  Lv2v <= 5 Itolerance <= 0.05

• ApplyR
  The keyword applyR can be used to modify the threshold value of ratio “r” in AC-Peak analysis. The default value of this parameter is 0.05. Modifying this parameter is useful in scenarios where the value of “r” is very small. A small “r” value results in an unreasonable increase in the Ipeak_ac limit. You can avoid such scenarios by resetting the value of “r” in the ICT file. For example:

  em_jmax_ac_peak EQU 4.0 r < 0.01 applyR 0.01

• Priority
  Specifies the priority of a rule. It is an integer number. Currently the only value that is supported is 1. The syntax is as follows:

  priority==<integer no.>

  
  
  The rule with priority==1 is only enabled when the variable 'powerRailRules=n10_special' is set and when the power_grid and power_rail keywords are also specified.
• Device
  This keyword is used to specify different EM rules for device resistors, which are subsets of other layers. The syntax is as follows:

  device=="device model names"

  For example, the following keyword specifies that the particular EM rule is applicable only to device with the model names, “devRA devRB”.

  device=="devRA devRB"

• Subconductor
  This keyword is used to specify different EM rules for subconductors, which are subsets of poly or other layers. The syntax is as follows:
  sub_conductor=="subconductor names"
  For example, the following keyword specifies that the particular EM rule is applicable only to subconductor layers, pploy and gpoly.
  sub_conductor=="ppoly gpoly"
• bridge_via
  This keyword is used to specify that the particular EM rule will apply only to bridge vias.
• Color
  This keyword is used to specify that the particular EM rule is applicable only to the resistor with the specified color number.
  For example,
  color==”2 4 5” specifies that the particular EM rule is applicable only to the resistor with property, $M=2 OR $M=4 OR $M=5.
• Masks
  This keyword is used to specify that the particular EM rule is applicable only to the resistor with the specified mask number.
  For example,
  mask==2 specifies that the particular EM rule is applicable only to the resistor with property, $M=2.
• hi_em
  This keyword is used to specify that the particular EM rule is applicable only to the design resistor with the specified value of hi_em parameter.
  For example,
  hi_em==1 specifies that the particular EM rule is applicable only to the design resistor with the property, hi_em=1.
  
  The Sh keyword is not supported in the EM rules condition. It is ignored if specified in the EM rules condition inside the techfile.

Rules for Specifying Via Area

You can specify PWL in either one of the following ways:

• Provide PWL for a specific area:
  

  em_jmax_* PWL Value_1 area_1 … Value_N areaN

  For example,

  em_jmax_* PWL 1.3 2.0 1.7 3.0 

• Provide PWL for a specified area range:
  

  em_jmax_* EQU <equation with 'a'> conditions

  For example,

  em_jmax_* EQU (1.3 * a)/2.0  a>=0.0 a<2.5 

  em_jmax_* EQU (1.7 * a)/3.0  a>=2.5 N>=3

  em_jmax_* EQU (1.9 * a)/3.0  a>=2.5 N<3 

Rules for Specifying the EM Analysis Type for Power and Ground Nets

Set the variable, splitACDCRules, to true for specifying different rules for EM analysis of power and signal nets. You can set this variable in the following ways:

• setenv VOLTUSFI_SPLIT_ACDC_RULES true
set_variable splitACDCRules true When this variable is specified using the set_variable command, it takes priority over the setenv variable.
• Set the variable, splitACDCRules, to true in the Variables form. You can open this form from the EM tab of the IR/EM Results form.

The table below shows the rules for power and signal nets both when the variable is set and not set.

EM Rule Selection Priority

This section details the order of priority in which the EM rules are applied by Voltus-Fi-XL based on the specified keywords. The order of priority of keywords in descending order is provided below:

1. device --> highest priority
2. sub_conductor
3. bridge_via
4. priority
5. power_grid/power_rail
6. color
7. mask
8. current_direction
9. Conditions
10. Area matching in case of PWL
11. Base rule
12. Optimistic/pessimistic rules --> lowest priority

These are detailed below.

• device
  When a device is specified in the EM rule file, the software first looks for the device keyword and applies the EM rules to the specified device.
  For example, for a device with model name, devRA, if the following rules are specified in the ICT file:

  1. em_jmax* …   device==“devRA”

  2. em_jmax* …   device==“devRB”

  3. em_jmax* …

  Then the software follows the order of priority provided below:
  • Match rule 1 because it has a matching device keyword
  • Match rule 3 if rule 1 does not match
  • Skip rule 2 because it is for device, devRB
• sub_conductor
  When a sub conductor is specified in the EM rule file, the software first looks for the sub_conductor keyword and applies the EM rules to the specified sub conductor.
  For example, for a resistor on layer, ppoly, if the following rules are specified in the ICT file:

  1. em_jmax* …   sub_conductor==“ppoly”

  2. em_jmax* …   sub_conductor==“gpoly”

  3. em_jmax* …

  Then the software follows the order of priority provided below:
  • Match rule 1 because it has a matching sub_conductor keyword
  • Match rule 3 if rule 1 does not match
  • Skip rule 2 because it is for sub conductor, gpoly
• bridge_via
  When a bridge_via is specified in the EM rule file, the software first looks for the bridge_via keyword and applies the EM rules having bridge_via keyword for the bridge via. In case, the via is not bridge via, rules having bridge_via keyword will be ignored.
  For example, for a bridge via, if the following rules are specified in the ICT file:

  1. em_jmax* … bridge_via

  2. em_jmax* … 

  Then the software follows the order of priority provided below:
  • Match rule 1 because it is a bridge via
  • Match rule 2 if rule 1 does not match
  
  In case, the via is not bridge via, then the software will match rule 2.
• priority
  When a priority is specified in the EM rule file, in the following manner:

  1. em_jmax* …   priority==1    

  2. em_jmax* …

  Then the software follows the order of priority provided below:
  • Match rule 1 when powerRailRules=n10_special is set
  • Match rule 2 if rule 1 does not match
• power_rail/power_grid
  When the power_rail/power_grid keyword is specified in the EM rule file, in the following manner:

  1. em_jmax* …   power_grid    

  2. em_jmax* …

  Then the software follows the order of priority provided below:
  • Match rule 1 when the power grid analysis is enabled
  • Match rule 2 if rule 1 does not match
• color
  When the color keyword is specified in the EM rule file, in the following manner:

  1. em_jmax* …   color==”1 3 5” 

  2. em_jmax* …

  For example, if a resistor has color number 5, specified using $M=5, then the software follows the order of priority provided below:
  • Match rule 1 for the specified color number
  • Match rule 2 if rule 1 does not match
• mask
  When the mask keyword is specified in the EM rule file, in the following manner:

  1. em_jmax* …   mask==2 

  2. em_jmax* …

  For example, if a resistor has mask number 2, specified using $M=2, then the software follows the order of priority provided below:
  • Match rule 1 for the specified mask number
  • Match rule 2 if rule 1 does not match
• current_direction
  When the current_direction keyword is specified in the EM rule file, in the following manner:

  1. em_jmax* …   current_direction up

  2. em_jmax* …   current_direction down

  3. em_jmax* …

  Then, for a resistor with current_direction up, the software follows the order of priority provided below:
  • Match rule 1 because it has a matching current_direction keyword
  • Match rule 3 if rule 1 does not match
  • Skip rule 2 because the current direction is not matching
• Conditions
  When conditions are specified in the EM rule file, in the following manner:

  1. em_jmax* …   L <=5

  2. em_jmax  …   L > 5

  3. em_jmax* …

  Then the software follows the order of priority provided below:
  • Match rules 1 and 2 because conditions are specified
  • Match rule 3 if rules 1 and 2 are not matching
• Area Matching from the PWL
  When the PWL for specific via areas are specified in the EM rule file, in the following manner:

  1. em_jmax* …   PWL VAL_1   AREA_1   VAL_2   AREA_2    L <=5 

  2. em_jmax  …   PWL VAL_3   AREA_3   VAL_4   AREA_4   L <=5

  Then the software follows the order of priority provided below:
  • Match the exact areas provided in the rule file
  • The software does not interpolate for unmatched areas (other than AREA_1, AREA_2, AREA_3, and AREA_4 in above example)
• Base Rule Selection
  When the PWL for specific via area is specified in the EM rule file, without any conditions in the following manner:

  em_jmax* …   PWL VAL_1   AREA_1   VAL_2   AREA_2 

  Then the software follows the order of priority provided below:
  • Match the exact areas from the base rule
  • The software does not interpolate for unmatched areas (other than AREA_1 and AREA_2 in above example)
• Optimistic/Pessimistic Rule Selection
  When multiple rules are selected after all conditions match, the software selects the optimistic/pessimistic value based on whether the variable, optimisticEMRuleSelection, is set to true or false.
  By default, the software selects the pessimistic value.
  For example, when the following rule set is provided:

  1. em_jmax*   EQU   1.5    …

  2. em_jmax*   EQU   3.5    …

  3. em_jmax*   EQU   2.5    …

  • Rule 1 is selected by default because it is more pessimistic as compared to rules 2 and 3
  • When the variable, optimisticEMRuleSelection, is set to true, then rule 2 is selected because it is more optimistic as compared to the other rules
  • Rule 2 is skipped because it is neither the most pessimistic nor the most optimistic

Example

Consider the two scenarios provided below for EM rule selection.

The given rule set is as follows:

1. em_jmax*… current_direction up L>=5

2. em_jmax*… current_direction up L<5

3. em_jmax*… current_direction down L>=5

4. em_jmax*… L<5

Case 1: EM rule selection for a resistor with current direction “up” and with L==3 will be as follows:

• The tool will select rules 1 and 2 because they match the current direction “up”
• Of the two selected rules, the tool will discard rule 1 because of the non-matching condition, L>=5 and it will select rule 2 because of the condition, L==3, which matches the condition L<5

The final rule selection in Case 1 will be rule 2.

Case 2: EM rule selection for a resistor with current direction “down” and L==2 will be as follows:

• The tool will first select rule 3 as it matches the current direction “down”
• The tool will then discard the selected rule 3 because of the non-matching condition, L>=5
• The tool will then select rule 4 from the remaining rules, as rule 4 does not have any current direction condition but it matches the condition, L<5

The final rule selection in Case 2 will be rule 4.

Process

process "name" {

# Specify silicon based erosion tables

use_silicon_density true

background_dielectric_constant value

layout_scale value

temp_reference value

# EM_Model parameters

[em_tref <value>]

[em_output_wlt <silicon|drawn>]

[em_variables <variable1> [<variable2> [ ...]]]

[em_conductor_unit A/cm^2 | mA/um | mA]

[em_via_unit A | mA ]

[em_via_area_unit A/cm^2 | mA ]

[em_lifetime_units hours | years]

}

The process command specifies key characteristics of the device, such as background dielectric constant, reference temperature, and overall scale.

Arguments

EM Data File in Voltus-Fi-XL

An EM data file specifies the technology information, such as current density limits, and provides a mapping between the layers for highlighting. The EM data file syntax is case-sensitive. The file must start with parenthesis.

Following is a sample EM data file.

(

; this file is case sensitive

routingLayers = ("Poly" "Metal1" "Metal2" "Metal3" "Metal4" "Metal5" "Metal6")

viaLayers = ("Cont" "Nimp" "Pimp" "Via1" "Via2" "Via3" "Via4" "Via5")

viaWidthList = (("Nimp" 0.2) ("Pimp" 0.2) ("Cont" 0.2) ("Via1" 0.2)

("Via2" 0.2) ("Via3" 0.2) ("Via4" 0.2) ("Via4" 0.2))

xrefLayers = (

( "POLYcont" ("Cont" "Cont"))

( "NSDcont" ("Nimp" "Nimp"))

( "PSDcont" ("Pimp" "Pimp"))

( "poly" ("Poly" "Poly"))

( "mt1" ("Metal1" "Metal1"))

( "mt2" ("Metal2" "Metal2"))

( "mt3" ("Metal3" "Metal3"))

( "mt4" ("Metal4" "Metal4"))

( "mt5" ("Metal5" "Metal5"))

( "mt6" ("Metal6" "Metal6"))

( "Via2NoCapInd" ("Via2" "Via2"))

( "Via2" ("Via2" "Via2"))

)

avgCurrentDensSpecList = (

(nil layer "Poly" minW 0.0 maxW -1.0 minL 0 maxL 5 currentDensity ((1.0 , 110)))

(nil layer "Metal1" minW 0.0 maxW -1.0 currentDensity ((1.1 , 110)))

(nil layer "Metal2" minW 0.0 maxW -1.0 currentDensity ((1.2 , 110)))

(nil layer "Metal3" minW 0.0 maxW -1.0 currentDensity ((1.3 , 110)))

(nil layer "Metal4" minW 0.0 maxW -1.0 currentDensity ((1.4 , 110)))

(nil layer "Metal5" minW 0.0 maxW -1.0 currentDensity ((1.5 , 110)))

(nil layer "Metal6" minW 0.0 maxW -1.0 currentDensity ((1.6 , 110)))

(nil layer "Cont" minW 0.0 maxW -1.0 res 1.0 currentDensity ((2.0 , 110)))

(nil layer "Nimp" minW 0.0 maxW -1.0 res 1.1 currentDensity ((2.1 , 110)))

(nil layer "Pimp" minW 0.0 maxW -1.0 res 1.2 currentDensity ((2.2 , 110)))

(nil layer "Via1" minW 0.0 maxW -1.0 res 1.3 currentDensity ((2.3 , 110)))

(nil layer "Via2" minW 0.0 maxW -1.0 res 1.4 currentDensity ((2.4 , 110)))

(nil layer "Via3" minW 0.0 maxW -1.0 res 1.5 currentDensity ((2.5 , 110)))

(nil layer "Via4" minW 0.0 maxW -1.0 res 1.6 currentDensity ((2.6 , 110)))

(nil layer "Via5" minW 0.0 maxW -1.0 res 1.7 currentDensity ((2.7 , 110)))

)

peakCurrentDensSpecList = (

(nil layer "Poly" minW 0.0 maxW -1.0 currentDensity ((1.1 , 110)))

(nil layer "Metal1" minW 0.0 maxW -1.0 currentDensity ((1.2 , 110)))

(nil layer "Metal2" minW 0.0 maxW -1.0 currentDensity ((1.3 , 110)))

(nil layer "Metal3" minW 0.0 maxW -1.0 currentDensity ((1.4 , 110)))

(nil layer "Metal4" minW 0.0 maxW -1.0 currentDensity ((1.5 , 110)))

(nil layer "Metal5" minW 0.0 maxW -1.0 currentDensity ((1.6 , 110)))

(nil layer "Metal6" minW 0.0 maxW -1.0 currentDensity ((1.7 , 110)))

(nil layer "Cont" minW 0.0 maxW -1.0 res 1.0 currentDensity ((2.1 , 110)))

(nil layer "Nimp" minW 0.0 maxW -1.0 res 1.1 currentDensity ((2.2 , 110)))

(nil layer "Pimp" minW 0.0 maxW -1.0 res 1.2 currentDensity ((2.3 , 110)))

(nil layer "Via1" minW 0.0 maxW -1.0 res 1.3 currentDensity ((2.4 , 110)))

(nil layer "Via2" minW 0.0 maxW -1.0 res 1.4 currentDensity ((2.5 , 110)))

(nil layer "Via3" minW 0.0 maxW -1.0 res 1.5 currentDensity ((2.6 , 110)))

(nil layer "Via4" minW 0.0 maxW -1.0 res 1.6 currentDensity ((2.7 , 110)))

(nil layer "Via5" minW 0.0 maxW -1.0 res 1.7 currentDensity ((2.8 , 110)))

)

iRCX Files for EM analysis

Voltus-Fi supports interoperable interconnect extraction (iRCX) files as an input for running EM analysis. This file contains process and EM model information for EM analysis and is provided by the foundry.

The iRCX file is further divided into two separate files, iRCX-RC and iRCX-EM. The iRCX-RC file is an encrypted file that contains confidential technology information of the foundry, whereas the iRCX-EM file is a plain text file that contains EM model information. The iRCX-EM file can further be converted into the ICT-EM file.

The iRCX-EM file is supported in both the qrcTechFile flow and the emDataFile flow. However, the qrcTechFile flow is the recommended flow to be used in Voltus-Fi-XL.

Set the following parameters in the EMIR control file (emir.conf) to directly use an iRCX file in Voltus-Fi-XL:

emirutil rcIrcxFile=[./RC_your_file.ircx]

emirutil emirIrcxFile=[./EMIR_your_file.ircx]

Support of iRCX Files in the qrcTechFile Flow

When you get a new iRCX or ICT-EM file from the foundry, you must update the qrcTechFile with the updated EM model information using the Techgen utility.

You can use one of the following ways to update the qrcTechFile using Techgen:

• Use the following recommended option for advanced nodes:
  

  Techgen –update_em <qrcTechFile> <RC.iRCX EM.iRCX| ICT-EM>

• Use the following option if a single iRCX file contains both RC and EM information:
  

  Techgen –update_em <qrcTechFile> <iRCX | ICT-EM>

• Use the following option for a non-encrypted ICT or iRCX file:
  

  Techgen -process_out <qrcTechFile>

  It dumps the RCGEN.ict file containing EM model information. However, it works only when the qrcTechFile is compiled with the openprocess option.

  ircxtoict –i <ICT output> –em_update <ICT with/without EM> <iRCX file>

  It updates the ICT file with the EM models specified in the iRCX file.

  Techgen –update_process <qrcTechFile> <ICT from ircxtoict>

  It updates the qrcTechFile with the EM models specified in the ICT file.

• If the qrcTechFile is encrypted, contact the foundry to get the original ICT file that was used to compile the encrypted qrcTechFile.
• It is recommended not to generate an ICT file from scratch using the ircxtoict utility and the iRCX file. It is strongly recommended to start from an ICT file dumped out of an existing qrcTechFile for updating the EM model information.

Support of iRCX Files in the emDataFile Flow

When you get a new iRCX file, you must convert it to the ICT format using the ircxtoict utility and then generate an emDataFile using the ict2emfiles utility.

Do the following:

1. Use the following command to convert the iRCX file to the ICT format with EM rules:
   

   ircxtoict –i <ICT output> <iRCX file>

2. Use the following command to generate the emDataFile:
   

   ict2emfiles -i <ict_file> <-eps|-ic|-both> [-im <mapping_file>] [–w <width_file> OR –l <lef_technology_file> -lm <lefdef_layer_map>]

Conversion of EM Data File into ICT File

Voltus-Fi-XL supports the conversion of an EM data file (emDataFile) into an interconnect technology (ICT) file in batch mode. The converted ICT file can then be used, both in batch and GUI modes, to perform EM analysis in Voltus-Fi-XL.

To convert an EM data file into an ICT file, perform the following step:

• Provide information about the convert_emdatafile_to_ict command in the command file, which is specified using the vfibatch command.
  

  vfibatch -cmd cmd-file-name

  The convert_emdatafile_to_ict command converts the specified EM data file into an ICT file.

convert_emdatafile_to_ict

convert_emdatafile_to_ict
-emDataFile emDataFile_path \
[-ictfile converted_ict_file] \
[-cmdfile additional_cmd_file] \
-extracted_lib_name lib_name \
-extracted_cell_name cell_name \
-extracted_view_name view_name 

Converts the specified EM data file into an ICT file to be used for performing EM analysis in Voltus-Fi-XL.

Parameters

Example

In the following example, the emDataFile.txt file in the amsPLL/vco/layout cellview is converted into the myict.ict file. The command file, mycmd.cmd, is generated from the emDataFile.txt file.

convert_emdatafile_to_ict \

-emDataFile emDataFile.txt \

-ictfile myict.ict \

-cmdfile mycmd.cmd \

-extracted_lib_name amsPLL \

-extracted_cell_name vco \

-extracted_view_name layout

Supported EM Rules for Converting EM Data File into ICT File

The following EM rules are supported in the conversion of an EM data file into an ICT file:

(nil layer "M1" minW 0.09 maxW 12.0 currentDensity 

recoveryFactor=<value>

I (avg) = max( I+, I- ) - (recovery factor)* min( I+, I-)

recoveryFactorList=(("Via1" 0.7)("mt1" 0.3))

routingLayers=("poly1" "m1" "m2" "m3" "m4" "m5" "m6" "m7" "m8" "m9" "MD")

( Metal1      Cont            Poly)//the via layer is Cont

viaLayers=("cw" "v1" "v2" "v3" "v4" "v5" "v6" "v7" "v8")

(("QuantusName" ("currentDensityName" "DFIIName"))

(("LayerName" ("upperMetalLayerName" "bottomMetalLayerName"))

viaWidthList=(("Cont" 0.2)("Via1" 0.2))

extViaWidthList=(("extCont" 0.2)("extVia1" 0.2))

DesignResistors = ("CellName1" "CellName2" "CellName3")
DesignResistors = ("CellName.*")

Unsupported EM Rules for Converting EM Data File into ICT File

The following EM rules are not supported in the conversion of an EM data file (emDataFile) into an ICT file: