US 6,723,606 B2 · Aerosol process for fabricating discontinuous floating gate microelectronic devices

Abstract

A process for forming an aerosol of semiconductor nanoparticles includes pyrolyzing a semiconductor material-containing gas then quenching the gas being pyrolyzed to control particle size and prevent uncontrolled coagulation. The aerosol is heated to densify the particles and form crystalline nanoparticles. In an exemplary embodiment, the crystalline particles are advantageously classified by size using a differential mobility analyzer and particles having diameters outside of a pre-selected range of sizes, are removed from the aerosol. In an exemplary embodiment, the crystalline, classified and densified nanoparticles are oxidized to form a continuous oxide shell over the semiconductor core of the particles. The cores include a density which approaches the bulk density of the pure material of which the cores are composed and the majority of the particle cores are single crystalline. The oxidized particles are deposited on a substrate using thermophoretic, electrophoretic, or other deposition means. The deposited particles form a stratum or discontinuous monolayer of oxidized semiconductor particles. In an exemplary embodiment, the stratum is characterized by a uniform particle density on the order of 1012 to 1013 particles/cm2 and a tightly controlled range of particle sizes. A plurality of adjacent particles contact each other, but the oxide shells provide electrical isolation between the particles of the stratum. Clean processing techniques provide a density of foreign atom contamination of less than 1011 atoms/cm2. The stratum is advantageously used as the floating gate in a non-volatile memory device such as a MOSFET. The non-volatile memory device exhibits excellent endurance behavior and long-term non-volatility.

Claims36

Dependent claims

A method for forming a stratum consisting of semiconductor particles, comprising the steps of:

a) forming an original plurality of discrete semiconductor particles from one of a source of semiconductor material and a precursor for said semiconductor material, said original plurality of discrete semiconductor particles entrained in a gas and thereby forming an aerosol, substantially all of said original plurality of discrete semiconductor particles having a diameter less than 20 nanometers;
b) densifying said original plurality of discrete semiconductor particles by heating said aerosol in a substantially oxygen-free environment to a sufficiently high temperature such that substantially all of said particles include a density substantially as great as the bulk density of said semiconductor material and thereby forming a corresponding plurality of densified discrete semiconductor particles entrained in a gas;
c) forming an electrically insulating cover on each of said plurality of densified discrete semiconductor particles, thereby forming a corresponding plurality of insulator-coated densified discrete semiconductor particles;
and
d) depositing said plurality of insulator-coated densified discrete semi-conductor particles on a substrate thereby forming a stratum of discrete, electrically isolated semiconductor particles on said substrate.

2 more elements

Dependencies are inferred from the claim text.

Aerosol process for fabricating discontinuous floating gate microelectronic devices

Life of this patent

Aerosol process for fabricating discontinuous floating gate microelectronic devices

Life of this patent

Abstract

Claims36