Crosstalk Reasons

Reasons

1. High Density of standard cells

2. High Routing Density

Crosstalk comes into picture due to coupling capacitance, below figure may help you to understand the coupling capacitance,

so, we can deduce one direct reason of cross-talk is spacing

for same area, if density of standard cells is high than more cross-talk

if compare, 0.25um (older mobile chips) vs 0.1um below chips, have density difference due to functionality addition in latest chips, so, it has high density due to transistor size and more functionality which make transistor placement very near to other transistor

3. Increase in number of metal layers, increase lateral capacitance

In higher technology node like 0.25um and above,
metal cross section area = w * t
where, w = metal net width and t = metal net thickness
so, At higher node technology, standard cells placed far apart form each other cells, and have enough space for routing, so, routing is possible on same metal area.
here, due to higher width of metal, inter layer capacitance became more n more dominant factor

while in lower node, for same area, number of standards cell increase, but routing method cant be same as higher node, due to higher complexity, routing cant be on same layer. and in other side, metal net width is also less, so, effective inter layer capacitance is not dominant
but, lateral capacitance comes into picture, as net routes very near to each others, and complexity is also high so, number of net routing is also very high, due to that at lower node lateral capacitance is major parasitic s while designing chips

4. Supply voltage

..will be updated soon