Intellectual Property Law

US Patent 7579238 - Multibit nanocrystal nonvolatile memory

Due to the discrete nature of nanocrystals they can be useful to facilitate the storage of multiple bits in semiconductor memory cells. This patent from Freescale Semiconductor teaches a variation of this technique which allows for a larger range of applied voltages making bit erasure possible without damage to the memory cell. Claim 1 reads:

1. A method for forming a multi-bit memory cell using a semiconductor substrate, comprising:

forming a first insulating layer over the semiconductor substrate;

forming a second insulating layer over the first insulating layer;

forming a layer of gate material over the second insulating layer;

patterning the gate material to leave a gate portion of the layer of gate material;

etching the second insulating layer to undercut the gate portion and leave a portion of the second insulating layer between the first insulating layer and the gate portion; and

forming nanocrystals on the first insulating layer wherein a first portion of the nanocrystals is under the gate portion on a first side of the portion of the second insulating layer and a second portion of the nanocrystals is under the gate portion on a second side of the portion of the second insulating layer, whereby the first portion of the nanocrystals are for storing a logic state of a first bit and the second portion is for storing a logic state of a second bit.

Full post as published by TinytechIP on August 27, 2009 (boomark / email).