Techniques for a 5-V-only 64K EPROM based upon substrate hot-electron injection

A 5-V-only 64K EPROM has been developed, using an HMOS 1 EPROM technology, for the purpose of evaluating the substrate hot-electron (SHE) programming technique. The fully functional device contained all of the circuits normally found on a conventional 64K EPROM plus special circuits associated with the 5-V-only operation and with the SHE approach. The measured data demonstrated that a high injection efficiency was achieved, and that programming with low drain voltage (as low as 5 V) was possible. It was also shown that 5-V-only programming may be accomplished by using the on-chip high-voltage charge pumps, and that this is compatible with the SHE technique, The main disadvantage of the SHE approach (as measured from the device) was the low collection efficiency. This resulted in a programming rate of 1 V/ms. The greatest disadvantage of the SHE technique, as implemented on the test chip, was its complexity which complicated both design and evaluation and required a slightly larger die area.