density error in calibre

Hello i did my layout in cadence virtuoso.. I had no DRC errors. I am learning calibre. When i run calibre DRC i am getting the following errors as in the image. All have got to do with density.

Can anyone tell me what is this density error and how to correct it pls. Wer can change the settings wer i can change density accordingly? In the fig i have pointed a part with arrow. For all the errors i choose in calibre it is pointing to that same part of the layout. Pls help!!!

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Hi i found online that "The density of a layer in any particular region is the total area covered by the drawn features on that layer divided by the area of the region".
E.g. if the total area of your cellview is 10um2 ("um2" means micro-metre square) and you only a single piece of M1 metal with area 1um2, then it means that your M1 density is 100% * 1/10 = 10% and hence your cell fails the requirement of 30%.
So does that mean i am supposed to increase the width and length dimensions of the poly, metal1, metal 2 and 3 so that it meets the density requirement??? Is this the way to correct the error??? So like all empty spaces in the layout i just need to fill it with metals right? But wat abt for poly density error. When i place an poly rectangle in an empty space i am getting the error of floating poly... Pls let me know if i am right about the correction.. Thank you!!!

If there is a option of placing dummy metal layer, you can use it. While fabrication, those dummy layers will be filled with corresponding metal layers, but beware of parasitics.

Thank you for the reply... Pls check this image below. This layout has a lot of dummy metals covering the entire empty space below. But still i am getting the density error in calibre DRC. I have no empty space to fill so still in this case if density error occurs how to correct it? My colleague said this was a tested chip. So wen i am running the DRC i am finding these errors. So are these errors negligible???

I'm assuming the dummy metal fill is on a different layer (or even layers) than the non-fill metal. At some point, you need to combine the dummy and design layers that will be on the same physical layer so that the density check sees them both. There are several different ways to do this, and your group probably has a preferred method so that the "golden rules" don't have to be modified.

Thank you for the reply!!! But i don't understand what you mean by dummy metal is on a different layer. The layout design and the dummies are all on the same p-substrate right??? pls correct me if wrong... Like what does it mean to combine design layers and the dummy???

Usually the physical layers are mapped to more than one logical layer in the layout database (GDS, OASIS, various other proprietary formats). Designers do this for various reasons -- keeping straight which geometries came from IP/internally developed blocks/interconnect, for example, or which are central to the design versus a place holder like dummy fill that could be changed out with (hopefully!) minimal effect.

In the case you have, where you have a shape you care about and you know there will be fill added at a later stage so you use dummy fill, it is easier for everyone if they are on separate GDS/OASIS layers. Somewhere you need to tell the DRC checks, though, that the two layer numbers represent the same physical layer.

So say you called the layers "metal1" on layer 10 for the part you drew, and "m1_fill" on layer 120 for the dummy fill. To feed both of them to the density check, which checks m1, you might have an SVRF statement like "m1 = OR metal1 m1_fill". Other options would be modifying the density check, using a Layer statement that maps both layer numbers to metal1 (I think that would be LAYER metal1 10 120), or probably a few other techniques.

Perhaps you are using GDS layer types to separate shapes by function on a "single" layer? If the dummy fill went on a new layer type, you'll still want to check the layer definition in the SVRF file to make sure that metal1 includes the dummy fill's layer type.