Patents Assigned to STMicrolelectronics, Inc.
  • Patent number: 5885871
    Abstract: A memory cell for an EEPROM memory is fabricated to provide increased oxide thickness at the edge of the tunnel oxide and under the edges of the polysilicon capacitor plate in order to improve the dielectric integrity of the capacitor structure. In one embodiment using a silicided polysilicon process, the oxide is made thicker at the edge of the tunnel oxide by reoxidizing the silicon at the corner of the polysilicon capacitor plate and the underlying substrate surface by exposing the device to a short duration oxidation step after having deposited a 200 .ANG. to 500 .ANG. thick porous oxide over the device to protect the silicide from excessivie exposure to the oxidizing ambient. In another embodiment the tunnel oxide is grown in a window in the gate oxide layer, which is about four times thicker than the tunnel oxide, so that the gate oxide completely surrounds the tunnel oxide, and the polysilicon capacitor plate extends beyond the edge of the tunnel oxide terminating at a point above the gate oxide.
    Type: Grant
    Filed: July 31, 1997
    Date of Patent: March 23, 1999
    Assignee: STMicrolelectronics, Inc.
    Inventors: Tsiu Chiu Chan, Pervez H. Sagarwala, Loi Nguyen