Fishing – trapping – and vermin destroying
Patent
1992-06-01
1993-07-06
Hearn, Brian E.
Fishing, trapping, and vermin destroying
437193, 437979, H01L 21266
Patent
active
052253627
ABSTRACT:
An electrically erasable programmable read only memory (EEPROM) cell is fabricated by forming first and second first field oxide (FOX1) regions in a P-well in an N-substrate to define a P-type active device region. First and second buried N+ bit lines are formed in the P-well adjacent to the FOX1 regions; bit lines define a P-type channel region therebetween. First and second second field oxide (FOX2) regions are formed adjacent to the FOX1 regions and overlying the buried N+ bit-lines. A layer of gate oxide 300-500.ANG. thick is formed on the P-well between the FOX2 regions. A layer of polysilicon is formed over the gate oxide to extend over only a first portion of the P-type channel region. A tunnel window is defined on the gate oxide over the P-type channel region and overlapping the floating gate edge. The gate oxide is removed from the tunnel window and tunnel oxide about 80-100.ANG. thick is formed. A spacer/contact window is defined over the field oxide and overlapping the floating gate edge on the field oxide. The edge oxide grown on the floating gate during tunnel oxide growth is removed from the spacer/contact window. A polysilicon tunnel spacer is formed over the tunnel oxide and in electrical contact with the floating gate at the spacer/contact window, i.e. at the floating gate edge over field oxide. Oxide is removed from the top of the floating gate plate and substrate over the channel region and adjacent to the floating gate. Then ONO is grown over the floating gate, the poly tunnel spacer and the exposed channel region adjacent the floating gate. Finally, a second layer polysilicon is formed over the ONO to define a control gate of the EEPROM cell.
REFERENCES:
patent: 4924437 (1990-05-01), Paterson et al.
patent: 5021848 (1991-06-01), Chiu
patent: 5108939 (1992-04-01), Manley et al.
patent: 5156991 (1992-10-01), Gill et al.
Chaudhari C.
Hearn Brian E.
National Semiconductor Corporation
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