DRC: radius checking of bends

Tristian

Hi,
I'm writing a DRC script and I want to see if someone can help with this design rule.

Basically, I want to be able to check to see if the bend has a radius less than some value "x". The image I have attached should give you an example of what I'm talking about when I say a bend and the radius that I'm looking to measure.

Any help is greatly appreciated, and I appreciate all help that has been given so far on these forums,
Much appreciated,
Tristian

Matthias

@Tristian I'm afraid this time there is no simple DRC function available. You could go for a maximum bend angle criterion between two edges. But that converts to a minimum radius only for a fixed edge length.

Matthias

Tristian

@Matthias thanks for the help, at the moment, my thinking is to get the distance between two points on the bend that are close together and using this as the arclength, the radius can be assumed to be some max value and then I can get an angle that fits the equation:

radius = arclength / angle

Thanks for the help,
Tristian

Tristian

To continue on this without making a new post.

To try measure the arc length, I'm just measuring the length of smaller segments in the bend but I understand that there is no way to measure the length in the DRC but I'm trying to work around it. I was thinking of using layer.perimeter to get the perimeter, I know the width and so I should be able to get lengths from that, but there is no way to loop through the different segments.

I guess the question I'm asking is, is there a way to loop through all of the polygons within a layer or if there is another way to find the lengths of segments in the bend with different lenghts?

Tristian

Matthias

@Tristian You can loop through the polygons of a layer like this:

layer.data.each_merged do |polygon|
  ...
end

"polygon" will be a RBA::Polygon object that you can analyse further. But I think this solution will be awfully slow.

Matthias

JSS

Hi there!

I was looking for a way to check the minimum radius of bends and then I found this post.
I was wondering if there is a DRC function to check the minimum radius now.

Thanks so much!

Matthias

Hi @JSS,

no, this check is still not available yet.

Roadmap didn't change, but time is an issue.

Matthias

Matthias

There is a kind of workaround using the "unround" feature provided by "extract_rad":

report("Radius check, maybe")

l1 = input(1, 0)

inp = l1.merged

ur = polygons
ur_error = polygons

# Applies "unrounding" - see "extract_rad" documentation
inp.each do |poly|
  x = poly.extract_rad
  if ! x.empty?
    ur.insert(x[0])
  else
    ur_error.insert(poly)
  end
end

# the min. radius to check
rmin = 2.um

# some tolerance to account for segmentation
tol = 10.nm

# compute rounding variants:
# both inner and outer corners rounded
rounded = ur.rounded_corners(rmin, rmin, 64)
# outer corners rounded
rounded_outer = ur.rounded_corners(0, rmin, 64)
# inner corners rounded
rounded_inner = ur.rounded_corners(rmin, 0.um, 64)

# General checks:
# unrounding failed - this can happen for polygons 
# of irregular shape.
ur_error.output("Unrounding failed")
# short edges indicate semicircles with r < rmin for example
ur.edges.with_length(0.0, 2 * rmin).output("Short edges, indicating radius < #{rmin}")

# detect inner corners between unrounded and rounded with rmin
# -> reported as radius < rmin
inner_corners = rounded - rounded_outer
(inner_corners - inp).sized(-tol).output("Inner corner radius < #{rmin}")

# detect outer corners between unrounded and rounded with rmin
# -> reported as radius < rmin
outer_corners = rounded_inner - rounded
(outer_corners & inp).sized(-tol).output("Outer corner radius < #{rmin}")

(this implementation is flat, hence maybe slow)

It reports several classes of errors:

It's not super safe, but maybe useful.

Matthias