Good for tessellation only if chips are also hexagons. Arguably chips themselves could be hexagons for better pin density and potentially thermal properties. Surprised nobody has tried this before.
You cannot cut straight lines trough hexagons. Triangles would work but would be even more inconvenient to design cut and process into normal chips. So squares it is.
Water jet cutters or EDM cutters could both be used on silicon and there is no need for either to cut straight lines.
When silicon area is expensive and performance can be maximised by reducing average on-die wire length, hexagons sound like they might make sense.
Obviously current layout tools prefer X-Y area splits, so a lot of tooling would have to be redesigned to make use of a probably rather small performance gain.
No you can't. Anyone whose spent any time breaking glass into specific shapes knows how difficult it is. Glass can't handle the force required to break it in one go. Multiple perfect passes have to be made in order to do it with reasonable yield. Having corners inside your fault lines is asking for trouble. Chips arent that much different.
It isn’t a question of cutting at an angle, it is a question of cutting in a specific direction all the way across the water. Hexagons demand that you change directions multiple times while cutting at chip level precision across a wafer you are trying to hold in place with the same amount of accuracy.