Flash memory device and fabrication process thereof, method of forming a dielectric film
View Patent ↗A fabrication process of a flash memory device includes microwave excitation of high-density plasma in a mixed gas of Kr and an oxidizing gas or a nitriding gas. The resultant atomic state oxygen O* or hydrogen nitride radicals NH* are used for nitridation or oxidation of a polysilicon electrode surface. It is also disclosed the method of forming an oxide film and a nitride film on a polysilicon film according to such a plasma processing.
1. A method of fabricating a flash memory device, wherein the flash memory device comprising a silicon substrate, a first electrode formed on said silicon substrate with an insulation film interposed therebetween, and a second electrode formed on the first electrode with an inter-electrode insulation film interposed therebetween, the inter-electrode insulation film comprising at least one silicon oxide film and at least one silicon nitride film, the method comprising:
forming the least one silicon nitride film of the inter-electrode insulation film, wherein forming the at least one silicon nitride film comprises:
maintaining the temperature of the silicon substrate at a temperature exceeding 400° C;
introducing a mixture of a gas into a processing chamber, wherein the mixture of gas containing one of NH 3 or nitrogen and hydrogen, the mixture of gas also contains Ar gas or Kr gas;
making hydrogen nitride radicals NH * by exciting plasma in the mixture of gas; and
forming the at least one silicon nitride film using the hydrogen nitride radicals NH * .
2. The method according to claim 1 , wherein the plasma is excited by a microwave.
3. The method according to claim 2 , wherein the microwave having a frequency between 900 MHz and 10 Ghz.
4. The method according to claim 1 , wherein the inter-electrode insulation film includes a first silicon nitride film, a first silicon oxide film, a second silicon nitride film and a second silicon oxide film.
5. The method according to claim 1 , wherein the inter-electrode insulation film includes a silicon oxide film and a silicon nitride film.
6. The method according to claim 1 , further comprising:
depositing a polysilicon film on the silicon substrate as the first electrode.
7. The method acording to claim 6 , wherein the one of the at least one silicon nitride film of the inter-electrode insulation film is formed by exposing a surface of the polysilicon film to the hydrogen nitride radicals NH * .
8. The method according to claim 1 , wherein the at least one silicon nitride film is formed by a CVD process.
9. The method according to claim 1 , wherein silicon substrate is maintained at temperature of at least 500° C.
10. The method according to claim 1 , wherein the plasma has a diversity of approximately 1 x 10 12 cm −3 .