maxFloatingArea (oacMaxFloatingArea)

Description

Some fabs have maximum area rules for floating metal shapes that are not connected to a diffusion or polysilicon-gate. In concept it is similar to process antenna rules because the rule applies to only the current layer and any lower layers (e.g. all the layers that have been fabricated up to the layer of interest), but it is slightly different from the process antenna rules.

The basic form of this rule requires that floating shapes on the routing layers between minRoutingLayer and maxRoutingLayer must have a total area >= maxArea.

Floating metal (typically this rule is defined for metal routing layers) is defined as metal on the current layer that cannot trace a path to diffusion or polysilicon-gate using only same-layer or lower-layer metal connections.

Grounded metal is defined as metal that can connect to a diffusion connection or polysilicon-gate using only same-layer or lower-layer connections. The area rule need not be met if all of the shapes that comprise the area meet a minimum spacing rule (specified by minSpacing) or a parallel-run length spacing rule (specified by minParSpacing, minParallelLength) on the layers specified.

The rule can be applied in the following ways:

singleConnected: the rule applies to each individual floating metal shape on any routing layer between minRoutingLayer and maxRoutingLayer inclusive. Each shape must have an area >= maxArea or meet the min-spacing to other grounded shapes.

Connected: the rule applies to the area of floating metal shapes connected together on each layer between minRoutingLayer and maxRoutingLayer inclusive. Just as with the singleConnected case, the connected area on a current layer must be >= maxArea and meet the min-spacing to other grounded shapes on this layer. In addition, all shapes connected to this shape on the lower layers must also meet the min-spacing rule.

allConnected: Means the rule applies to the connected area of floating metal shapes connected together on each layer between minRoutingLayer and maxRoutingLayer inclusive. The total connected area on the current and lower layers must be >= maxArea or meet the min-spacing to other grounded shapes on this layer and all lower connected layer shapes. minRoutingLayer and maxRoutingLayer must be the names of two previously defined routing layers.

Constraint at a Glance

Constraint type:	oaSimpleConstraint
Value types:	oaFltValue
Database types:	oaDesign, oaTech
Object types:	oaAppObject

Values

The following value types are supported by this constraint:

oaFltValue
This value represents the max area converted to dbu squared.

Units: DBU Square

Parameters

The following parameters are supported by this constraint:

Name

Value Type

Units

Default

Description

floatingMetal
oacFloatingMetalConstraintParamType

oaIntValue

Enum

(Required)

This parameter stores the inclusive list of routing layers between range of routing layers to which the constraint applies. This parameter can take one of the following values: SingleLayerType, ConnectedType, and AllConnectedType.

This parameter is represented by an oaConnectLayerType enumeration:

Value	Name
oacSingleConnectLayerType	single
oacConnectedConnectLayerType	connected
oacAllConnectedConnectLayerType	allConnected

routingLayers
oacRoutingLayersConstraintParamType

oaLayerArrayValue

Layer Number

(Required)

This parameter stores the inclusive range of oaLayerValue values that correspond to the layers implied by the range of minRoutingLayer to maxRoutinglayer.

floatingAreaSpacing
oacFloatingAreaSpacingConstraintParamType

oaIntDualIntArrayTblValue

DBU

(Required)

This parameter stores pairs of minimum spacings and minimum parallel spacings for a given layer. The index of the table corresponds to the index of the layer in the oaLayerArrayConstraint. The oaDualIntValue is represented as ((minSpacing 0)(minParSpacing minParallelLength)...)

Examples

Manufacturing Reasons

This rule is intended to avoid shorts between floating and non-floating metal wires caused by arcing due to charge build-up during some steps of processing. This construct is defined at a global level, and can optionally specify the min-spacing required to avoid a max floating area violation.