Alastair Reynolds wrote some great books which touch on this concept - the Perfect series has a AI character who originally started out as a fatal brain scan of a person who eventually escaped...
The most revelatory idea for me in it was the idea of how a human being could plausibly become a near god-like entity.
This isn't even the real premise of the book but a brief detour over a few pages where the author expounds this idea.
The man, Valmik, starts off as a human much like any other.
As the first stage in his metamorphosis he replaces his brain neuron by neuron, with mechanical parts.
Once this is done he no longer needs his body.
This now frees him from his mortal shell which he discards. He now lives purely as an electro-mechanical device for centuries. He shuns all his human contacts since they are unable to keep up with him.
At this point he starts adding more artificial neurons till his count surpasses several orders of magnitude of his starter human brain.
But he realises that he is still subject to the vicissitudes of the planet that the machine that's him is located in.
This he couldn't abide by.
At this next stage, the already superhuman intelligence formerly known as Valmik sets off on a space faring vehicle.
The endlessness of space is no bother to this entity, because he has no bounds on his longevity.
And so he travels the cosmos for millennia in this state, free from the erstwhile shackles binding him to Earth.
But he realises that even this is not enough. Just one well aimed shot would destroy him.
Not good enough for an immortal.
So he transforms each of his neurons into an independent self-sustaining machine. Each of these machines communicates with each other via light/EM beams.
The formerly comet sized machine that housed his consciousness was now split across these self sustaining machines.
These machines can now drift apart. As far apart as he wanted.
His brain was now a cloud consciousness that could span the size of solar systems.
But this expansion came at a cost.
The cost was this: transmission between his independent neuron nodes, now each far apart from one another, took time, limited by the speed of light.
Thoughts that would formerly take him micro seconds would now consume days. But that was no matter to this entity that had left all his companions behind and only needed to talk to himself.
And thus, Valmik, once man, now a cloud consciousness came to disperse himself all across the Oort cloud.
