🚀 go-pugleaf

In article <RAJE.91May9115209@lattice.stanford.edu> raje@lattice.stanford.edu (Prasad Raje) writes:
>The cell size must get smaller, but the cell capacitance cannot.
>Why? 
>You need a large enough cell capacitance to guard against soft errors due
>to radiation. That is you need to store at some minimum number of electrons
>per cell. These days this number is in the few tens of thousands of electrons.

An interesting note: Don Speck, in his paper at the '91 Santa Cruz
VLSI conference had a paper about a DRAM design that he built for the
MOSIAC project at Caltech.  He did a bit of investigation of radiation
effects, and found evidence indicating that this argument might not be
correct.  

The idea is that the radiation hit creates some number of
electron-hole pairs that could corrupt the state of the capacitor.
However, the charged-pair creation happens below the surface of the
chip, so that by the time they diffuse up, they've also spread.  So
the amount of corrupting charge becomes a function of the area of the
capacitor (since the diffused area is much larger than a capacitor).

As the size of the cell decreases, the amount of the charge on the
cell decrease, but so does the amount of charge intercepted.

It was a nice paper.  I'd recommend it.