Automated Design for Micromachining

# Fillet

## Introduction

This parameterized cell is used to create a fillet for the corners of a polygon whose exterior angle is less than 180°. From the angle of the corner and the radius of curvature, this cell will construct the necessary arc and fill the corner in.

Combined with the circle parameterized cell, a fillet for any corner can be easily constructed.

## Theory

### Tolerance

Please refer to the same section in the documentation for the circle parameterized cell.

## Parameters

Any parameter may be modified, if necessary, to meet design rules. Typically, this involves increasing parameters that specify distances, so that minimum line width and minimum line spacing rules will not be violated. This has been extended to the convention of specifying a zero for some parameters to obtain an instance of the minimum size.

In addition to the parameters listed below, several technology parameters also influence the implementation of parameterized cells. This data must be present in the technology library.

Table 1: Parameters for the 'donut' parameterized cell.
Name Description Range Units
layer This must be one of the drawing layers in the technology, and specifies the layer onto which the circle will be drawn. dwg layers -
radius This parameter specifies the radius of curvature for the fillet. any design rules. [0,∞) um
angle This parameters specifies the angle of the fillet. This is the exterior angle of the shape's polygon. (0,180] degrees
rotation Cadence does not natively support rotations by increments other than 90°. To overcome this limitation, a rotation of up to 45° can be specified. Combined with the reflections about X and Y axes, any arc in any position can be drawn. [0,45) degrees
tolerance This parameter specifies the upper limit on which the polygon generated to approximate the inside and outisde arc (or portion thereof) can deviate from a true circle. While a value of zero can be specified, if the tolerance is less than half of the technology's manufacturing grid, it will be increased before the donut will be approximated. [0,inner radius] um
include guide If true, the parameterized cell will draw (using the TMP drawing layer, which must therefore be present), a circle indicating the full extent of the circle representing the fillet. true/false -

## References

The documentation for this parameterized cell does not contain any references.