Figure A-5 Planar Dielectric Syntax

The syntax for conformal dielectric contains the following parameters:

· conformal true

Specifies that the dielectric is conformal. This field is required.

· height value

Specifies the layer's height above the substrate.

· dielectric_constant value

Specifies the dielectric constant for this material.

· delta_height value

Specifies the layer's height relative to the top of another layer.

· delta_layer value

Specifies the reference layer for delta_height. It must be a layer that was already defined before RCgen parsed the dielectric definition. A reference layer can be a conducting layer or a dielectric layer.

· upto value

Specifies the layer's top surface height above the substrate. This value is equal to the height plus the thickness. You only need to specify two of the three parameters (height (or {delta_height, delta_layer}), thickness, upto) to complete the geometrical definition of a dielectric layer.

· thickness value

Specifies the bottom thickness of the conformal dielectric. Figure A-7 illustrates this thickness. The syntax of this option is the same as that of the thickness parameter for the planar dielectric.

· airgap {

base_thickness [value|[value spacing]+]

roof_thickness [value|[value spacing]+]

separation [value|[value spacing]+]

elevation [value|[value spacing]+]

pinch_off value

dielectric_constant value

}

Allows air gaps in the conformal dielectric layer. Conformal dielectrics with slanted side walls may form air gaps if the spacing of the conductors is below a certain threshold. These gaps alter the effective dielectric constant of the material and therefore have an impact on the amount of capacitive coupling.

The term "air gaps" refers to explicit air gaps. That is, the existence, shape, and location of these air gaps is entirely defined as part of the process file. They are not implicitly derived by emulating the manufacturing process.

It is assumed that the shape of the air gaps can be approximated by a symmetric pentagon defined by the following required keywords:

o base_thickness [value|[value spacing]+]

Defines the thickness of the lower rectangle of the pentagon (see Figure A-6). The thickness may depend on the spacing of the conductors, which you can specify by providing a sequence of value-spacing pairs. The value of the thickness for intermediate spacings is interpolated linearly between value-spacing pairs. The values associated with the minimal and maximal spacings, respectively, are used for spacings outside any value-spacing pair. A single value is a shortcut for the constant function.

Figure A-6 Air Gaps in Fire & Ice QX

o roof_thickness [value|[value spacing]+]

Defines the thickness of the upper triangle of the pentagon (see Figure A-6) as a function of spacing.

o separation [value|[value spacing]+]

Specifies the distance between the air gap and the conductor as a function of spacing.

o elevation [value|[value spacing]+]

Specifies the delta height of the air gap with respect to the previous metal or dielectric layer as a function of spacing.

Two additional keywords are necessary to complete the definition of air gaps:

o pinch_off value

Specifies the threshold below which an air gap forms.

o dielectric_constant value

Specifies the dielectric constant of the material inside the air gap. This value is generally equal to 1.0.

Date: 2016-01-14; view: 841