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Use of spacers as floating gates in EEPROM with doubled storage efficiency

  • US 5,760,435 A
  • Filed: 04/22/1996
  • Issued: 06/02/1998
  • Est. Priority Date: 04/22/1996
  • Status: Expired due to Term
First Claim
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1. A method of forming side-by-side, double floating gates in an electrically erasable programmable read only memory (EEPROM) with doubled storage efficiency comprising the steps of:

  • providing a semiconductor substrate having a layer of silicon oxide;

    providing a layer of polycrystalline silicon deposited over said silicon oxide;

    patterning said polycrystalline silicon and silicon oxide layers to form a control gate;

    doping said control gateion-implanting said substrate using said control gate;

    as a mask;

    depositing three layers of dielectric over said substrate;

    etching said dielectric layers;

    growing a tunnel oxide over said dielectric layers;

    depositing a second layer of polycrystalline silicon over said substrate;

    etching back said polycrystalline silicon layer to form side-by-side double floating gates adjacent to said control gate;

    ion-implanting said floating gates; and

    ion-implanting said substrate to complete a lightly doped drain (LDD) structure.

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