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LEF Syntax - Layer (Implant)

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This chapter contains information about the following topics:

• Layer (Implant)
  • Defining Implant Layer Properties to Create 32/28 nm and Smaller Nodes Rules
  • Area Rule
  • Core Edge Length Rule
  • Corner Spacing Rule
  • Min Enclosed Area Rule
  • Min Step Rule
  • Spacing Rule
  • Width Rule

Layer (Implant)

LAYER layerName
TYPE IMPLANT ;
[MANUFACTURINGGRID value ;]
[MASK maskNum ;]
[WIDTH minWidth ;]
[SPACING minSpacing [LAYER layerName2]   ;] ...
[PROPERTY propName propVal ;] ...
[PROPERTY LEF_CDN_AREA 
   "AREA minArea
   ; " ;]
[PROPERTY LEF_CDN_COREEDGELENGTH
   "COREEDGELENGTH minLength 
       [EXCEPTADJACENTLENGTH 
          {exactEdgeLength adjLength [EXACTADJACENTLENGTH]}...]
   ; " ;]
[PROPERTY LEF_CDN_CORNERSPACING 
   "CORNERSPACING spacing [ALIGNEDONLY]
       [CHECKIMPLANTGROUPONLY]
   ; " ;]
[PROPERTY LEF_CDN_MINENCLOSEDAREA
   "MINENCLOSEDAREA area 
   ; " ;]
[PROPERTY LEF_CDN_MINSTEP
   "MINSTEP minStepLength MINADJACENTLENGTH minAdjLength
   ; " ;]
[PROPERTY LEF_CDN_SPACING
   "SPACING minSpacing [LAYER layerName2] 
       [HORIZONTAL|VERTICAL PRL prl ][EXCEPTABUTTED]
            [EXCEPTCORNERTOUCH] [LENGTH length]
            [INTERSECTLAYERS layerNameList...]
   ; " ;]
[PROPERTY LEF_CDN_WIDTH
   "WIDTH minWidth [LAYER {layerName2 | ANY}]
       [ZEROPRL [MAXWIDTH maxWidth]] [EXCEPTCORNERTOUCH]
       [LENGTH length] [CHECKIMPLANTGROUP groupName]
   ; " ;]

END layerName 

Defines implant layers in the design. Each layer is defined by assigning it a name and simple spacing and width rules. These spacing and width rules only affect the legal cell placements. These rules interact with the library methodology, detailed placement, and filler cell support. You must define implant layers separately, with their own layer statements.

Example 3-1 Implant Layer

Typically, you define high-drive cells on one implant layer and low-drive cells on another implant layer. The following example defines high-drive cells on implant1 and low-drive cells on implant2. Both implant layers cover the entire cell. The placer and filler cell creation attempt to legalize the cell overlaps in abutting rows to ensure that the minimum width and spacing values are met.

LAYER implant1         #high-drive implant layer

TYPE IMPLANT ; 

WIDTH 0.50 ;       #implant rectangles must be >=0.50 microns wide

SPACING 0.50 ;     #implant rectangles must be >=0.50 microns apart 

END implant1

LAYER implant2         #low-drive implant layer

   TYPE IMPLANT ; 

   WIDTH 0.50 ;    #implant rectangles must be >=0.50 microns wide

   SPACING 0.50 ;  #implant rectangles must be >=0.50 microns apart

END implant2

Assume that the high-drive cells and low-drive cells are completely covered by their respective implant layers. Because there is no spacing between implant1 and implant2 specified, you might see a placement like that illustrated in Figure 3-1.

Figure 3-1

Note that you can correct A, C, D, and E by putting in filler cells with the appropriate implant type. However, B cannot be corrected by a filler cell—either the placer must avoid it, or you must allow the filler cell or post-process command to move cells or modify the implant layer to correct the error.

Defining Implant Layer Properties to Create 32/28 nm and Smaller Nodes Rules

You can include implant layer properties in your LEF file to create DRC rules that currently are not supported by existing LEF syntax. The properties are specified inside the LAYER IMPLANT statements, where they can be seen with other rules.

Before you can reference them, properties must be defined at the beginning of the LEF file in the PROPERTYDEFINITIONS statement, immediately before the first LAYER statement.

• Properties belong to the LAYER object and have a type of STRING.
• The property names used for these rules all start with LEF_CDN_.

All properties use the following syntax within the LEF PROPERTYDEFINITIONS statement:

PROPERTYDEFINITIONS 
LAYER propName STRING ["stringValue"] ; 

END PROPERTYDEFINITIONS 

The property definitions for the implant layer properties are as follows:

PROPERTYDEFINITIONS

LAYER LEF_CDN_AREA STRING ;

LAYER LEF_CDN_COREEDGELENGTH STRING ;

LAYER LEF_CDN_CORNERSPACING STRING ;

LAYER LEF_CDN_MINENCLOSEDAREA STRING ;

LAYER LEF_CDN_MINSTEP STRING ;

LAYER LEF_CDN_SPACING STRING ;

LAYER LEF_CDN_WIDTH STRING ;

END PROPERTYDEFINITIONS

Area Rule

An area rule can be used to specify the minimum area on the implant layer.

You can use the following property definition:

PROPERTY LEF_CDN_AREA 
"AREA minArea
; " ;

Where:

Core Edge Length Rule

A core edge length rule can be used to indicate that the edge length of an implant shape of a CORE (standard) cell must be greater than or equal to the specified minimum length.

You can create a core edge length rule by using the following property definition:

PROPERTY LEF_CDN_COREEDGELENGTH
 "COREEDGELENGTH minLength 
     [EXCEPTADJACENTLENGTH 
        {exactEdgeLength adjLength [EXACTADJACENTLENGTH]}…]
  ; " ;

Where:

Figure 3-2 Example of Core Edge Length Rule

Corner Spacing Rule

A corner spacing rule can be used to specify the spacing between two corner touch points.

You can create a corner spacing rule by using the following property definition:

PROPERTY LEF_CDN_CORNERSPACING 
   "CORNERSPACING spacing [ALIGNEDONLY]
       [CHECKIMPLANTGROUPONLY]
   ; " ;

Where:

Corner Spacing Rule Examples

Figure 3-3 Illustration of Corner Spacing Rule

• The following example illustrates a corner spacing rule with CHECKIMPLANTGROUPONLY:
  

  PROPERTYDEFINITIONS

  LIBRARY LEF_CDN_IMPLANTGROUP STRING "

        IMPLANTGROUP IPG1 LAYER IP1 IP2 BASEDLAYER IP1 ;";

  END PROPERTYDEFINITIONS

  On layer IP1:

  PROPERTY LEF_CDN_CORNERSPACING "

        CORNERSPACING 0.15 ALIGNEDONLY 

            CHECKIMPLANTGROUPONLY ; " ;

  
  Figure 3-4 Example of the Corner Spacing Rule with CHECKIMPLANTGROUPONLY
  

Min Enclosed Area Rule

A min enclosed area rule can be used to specify the minimum area that is enclosed by shapes on the current implant layer.

You can create a min enclosed area rule by using the following property definition:

PROPERTY LEF_CDN_MINENCLOSEDAREA
 "MINENCLOSEDAREA area 
  ; " ;

Where:

Figure 3-5 Example of the Min Enclosed Area Rule

Min Step Rule

You can create a min step rule by using the following property definition:

PROPERTY LEF_CDN_MINSTEP
   "MINSTEP minStepLength MINADJACENTLENGTH minAdjLength
   ; " ;

Where:

Figure 3-6 Illustration of the Min Step Rule

Spacing Rule

A spacing rule can be used to specify the spacing requirements for the current implant layer. You can create a spacing rule by using the following property definition:

PROPERTY LEF_CDN_SPACING
   "SPACING minSpacing [LAYER layerName2] 
       [HORIZONTAL|VERTICAL PRL prl ][EXCEPTABUTTED]
            [EXCEPTCORNERTOUCH] [LENGTH length]
            [INTERSECTLAYERS layerNameList...]
       ; " ;

Where:

Spacing Rule Examples

Figure 3-7 Illustration of the Spacing Rule

Figure 3-8 Illustration of the Spacing Rule

Width Rule

A width rule can be used to specify the width requirements for the current implant layer. You can create a spacing rule by using the following property definition:

[PROPERTY LEF_CDN_WIDTH
   "WIDTH minWidth [LAYER {layerName2 | ANY}]
       [ZEROPRL [MAXWIDTH maxWidth]] [EXCEPTCORNERTOUCH]
       [LENGTH length] [CHECKIMPLANTGROUP groupName]
       ]; " ;

Where:

Width Rule Examples

• The following example illustrates a Width rule with EXCEPTCORNERTOUCH:
  Figure 3-9 Example of the Width Rule with EXCEPTCORNERTOUCH
  
• The following example illustrates a Width rule with CHECKIMPLANTGROUP:
  

  PROPERTYDEFINITIONS

  LIBRARY LEF_CDN_IMPLANTGROUP STRING "

        IMPLANTGROUP IPG1 LAYER IP1 IP2 IP3 BASEDLAYER IP1 ;

        IMPLANTGROUP IPG2 LAYER IP1 IP4 BASEDLAYER IP1 ; " ;

  END PROPERTYDEFINITIONS

  On layer IP1:

  PROPERTY LEF_CDN_WIDTH  "

        WIDTH 0.15 LAYER IP2 ZEROPRL 

            CHECKIMPLANTGROUP IPG1 ; " ;

  
  Figure 3-10 Example of the Width Rule with CHECKIMPLANTGROUP
  
• The following example illustrates a Width rule with MAXWIDTH:
  On layer IP1:

  PROPERTY LEF58_WIDTH  "

        WIDTH 0.15 ZEROPRL MAXWIDTH 0.4 ;

        WIDTH 0.15 LAYER IP2 ZEROPRL MAXWIDTH 0.4 ; " ;

  
  Figure 3-11 Example of the Width Rule with MAXWIDTH