Patent
1979-07-19
1981-06-09
Edlow, Martin H.
357 54, 357 59, H01L 2978
Patent
active
042727740
ABSTRACT:
A floating gate memory cell has its control gate self-aligned to the floating gate in the source to drain direction and its floating gate self-aligned to the channel region in that direction and the direction transverse thereto without overlaying the field oxide. The cell may be manufactured by the following method: forming insulation such as silicon oxide over the substrate to serve as gate oxide; forming a conductor such as polysilicon over the insulation; etching the polysilicon to a patterned mask and using the mask to dissolve the unprotected oxide to leave a future floating gate of polysilicon overlaying and coextensive with the future channel region in the direction transverse to the source-to-drain region; overlaying insulation such as a further oxide and then overlaying a second conductor such as polysilicon, which is thus insulated from the floating gate; patterning this second polysilicon, which will serve as a control gate, with a photo resist mask to etch the second conductor to form a control gate, and to preferentially remove enough oxide to expose the unmasked portion of the future floating gate, and etching this unmasked portion. Thus, the floating gate is self-aligned to the channel in the source-to-drain direction, as well as in the direction transverse to the source-to-drain direction. The remaining insulation may now be dissolved using the gates as masks to expose the source and drain regions.
REFERENCES:
patent: 3984822 (1976-10-01), Simko
patent: 3996657 (1976-12-01), Simko
patent: 4004159 (1977-01-01), Rai
patent: 4104784 (1978-08-01), Klein
patent: 4142926 (1979-03-01), Morgan
Edlow Martin H.
National Semiconductor Corporation
Sheridan James A.
Woodward Gail W.
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