Intelligent fill pattern and extraction methodology for sensitive RF/analog or SoC products

Distribution of mask pattern density of isolating or conducting, layers of the die, such as active, poly, or metals, impacts product voltage tolerance and frequency response. At active level, nonuniform pattern density lowers punch-through or breakdown voltages. At metal levels, planarity issues give rise to high via resistances and variations of inter-layer capacitive coupling. Devices required to build an SoC product such as precision resistors, inductors, RF FETs, and capacitors, have diversified geometry characteristics. Usually, the differences in pattern density they cause over the die cannot be mitigated at design stage. Therefore, die pattern density has to be made uniform at die integration stage, by global addition of fill features (waffles). This presents significant challenge as the criteria for this addition are often contradictory or difficult to meet. The basic, but time consuming way of equalizing pattern density calls for manual adding of dummy features. In comparison, a simplistic, automated geometric approach is to add fill pattern of fixed density, which would then become target pattern density of the die. However, it may not be possible to equalize pattern density over all the regions even allowing for some changes in the die architecture in the course of either manual or automated waffling process. In addition, the approach tends to add dummy features even if unnecessary, creating local extremes of pattern density. Such outcome is not always preferred by the product RF/analog applications, which can be compromised by capacitive coupling through the waffles. In our methodology proposed in this work, the die pattern density is first analyzed, followed by the adjustable, intelligent fill of dynamic density. This way, it is possible to keep the original pattern density and work only on the areas of small density. We also propose to adjust the standard cell methodology in order to enable pre-die level modifications of pattern density and its extraction and ensure that all the required blocks could be placed on the product with their parasitics accounted for.