You can use cell bloating to insert whitespace (increased cell spacing) during the
place_design step. This leads to a lower density of cells in a given area of the die, which can reduce congestion by increasing available routing. This technique is particularly effective in small, congested areas of relatively high-performance logic.
To use cell bloating, apply the CELL_BLOAT_FACTOR property to hierarchical cells and set the value to LOW, MEDIUM, or HIGH. When working with smaller modules of several hundred cells, HIGH is the recommended setting.
If the device already uses too many routing resources, cell bloating is not recommended. In addition, using cell bloating on larger cells might force placed cells to be too far apart.