Evaporation cell for vacuum evaporation chamber and associated evaporation method

An evaporation cell for a vacuum evaporation chamber, the evaporation cell comprising:

• a crucible configured to receive a solid or liquid material to be sublimated or evaporated;
• heating resistances configured to heat the material in the crucible;
• a nozzle disposed at an open end of the crucible, the nozzle comprising
• a frustoconical portion having an opening defined for passage of a flow of evaporated or sublimated material towards the vacuum evaporation chamber,
• two bottom plates each comprising at least one opening, the openings of the two bottom plates being disposed in a zig zag form, and
• a cylindrical wall connecting the two bottom plates to the frustoconical portion of the nozzle, a gap being defined between the cylindrical wall and the crucible, the cylindrical wall including radially-directed openings connected to the gap between the cylindrical wall and the crucible;
• and
• a cover disposed on the nozzle, the cover having an opening disposed about the frustoconical portion of the nozzle, the cover including
• at least one support portion,
• at least one frustoconical portion, and
• at least one annular portion connecting the at least one support portion to the at least one frustoconical portion,
• the at least one frustoconical portion of the cover extending from the opening of the cover in the at least one annular portion toward a same direction and along a same axis as the frustoconical portion of the nozzle, the at least one frustoconical portion of the cover being disposed about the frustoconical portion of the nozzle, the cover forming a thermal barrier between the crucible and the vacuum evaporation chamber,
• wherein the nozzle is configured such that the flow of evaporated or sublimated material passes through the first and second bottom plates or through the radially-directed openings of the cylindrical wall, and
• wherein the heating resistances comprise
• a first heating area disposed about a lower portion of the crucible, and
• a second heating area disposed about the nozzle.