can someone expert explain what is quantum problems and why it so much harder to go smaller into 7nm ?
Yeah, explaining quantum mechanics in a forum comment...
There are different quantum effects making problems in transistors, but IMO the easiest one to understand is quantum tunneling (or at least the general idea).
I'll skip the whole probability theory, waves, potentials and so on...
Basically, you have to remember that the world around you is not corpuscular (solid, made of small particles that collide). It's made of interacting "points".
In other words: particles are points (no size), but since they repel each other, they create a structure which has dimensions (just like a triangle is defined by 3 points).
So you have your typical macro-scale wire and there's an electric current inside, like this:
-----------------------------------------
outside....inside....outside
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............|-|....e....|-|................
-----------------------------------------
It's isolated by some walls |-|, so you can hold it and so on. In the scale you're looking at them with naked eye, they seem solid.
But as you zoom to nanometres (e.g. single transistors), the walls can't be treated as solid anymore.
Particles that create the walls repel electrons inside, but - as the walls become thinner and thinner - repelling becomes weak. As a result, sometimes an electron gets through the wall.
In other words: if you could "measure electricity" on a nano scale, you would also get some reading outside the walls as well:
-----------------------------------------------------------------------
outside.........wall.........inside........wall........outside
-----------------------------------------------------------------------
........e'........|----------|........e........|----------|......e'.......
-----------------------------------------------------------------------
wierdness.
