One flaw in the spherical semiconductors. Certian devices are made on the
<100> surface of Si, and others on the <111> surface. When oxidized, the 111
surface has higher surface charged defect density, making it less suitable for
good MOS circuits.
By definition shpere must have multiple crystal orientations on it's surface.
A real fundamental practical problem. I like Dan's stuff on the cheap, slabs-
There is (or was) the multichip module approach (MCM). Bare (no plastic or ceramic chip package) die are bonded to a very high density interconnect. The MCM was made with the same technology as chips a few generations back with thick copper lines of the 10-20 micrometer width range. The market did not really take off and only a few companies are left in it. Micro Module Systems, a spin off from DEC is still credible.
-Jay