Low leakage, low threshold voltage, split-gate flash cell operation
View Patent ↗A method of reading a memory device having rows and columns of memory cells formed on a substrate, where each memory cell includes spaced apart first and second regions with a channel region therebetween, a floating gate disposed over a first portion of the channel region, a select gate disposed over a second portion of the channel region, a control gate disposed over the floating gate, and an erase gate disposed over the first region. The method includes placing a small positive voltage on the unselected source lines, and/or a small negative voltage on the unselected word lines, during the read operation to suppress sub-threshold leakage and thereby improve read performance.
1. A method of reading a memory device having rows and columns of memory cells formed on a substrate of semiconductor material having a first conductivity type:
wherein each of the memory cells comprises:
spaced apart first and second regions formed in the substrate and having a second conductivity type different than the first conductivity type, wherein a channel region of the substrate is disposed between the first and second regions,
a floating gate disposed over and insulated from a first portion of the channel region,
a select gate disposed over and insulated from a second portion of the channel region,
a control gate disposed over and insulated from the floating gate, and
an erase gate disposed over and insulated from the first region;
wherein the memory device further comprises:
a plurality of word lines each electrically connecting together a row of the select gates,
a plurality of bit lines each electrically connecting together a column of the second regions,
a plurality of source lines each electrically connecting together a row of the first regions,
a plurality of control gate lines each electrically connecting together a row of the control gates, and
a plurality of erase gate lines each electrically connecting together a row of the erase gates;
wherein the method of reading the memory device comprises:
applying a positive voltage to one of the word lines which is associated with a target memory cell, and applying a zero voltage to all the other word lines;
applying a positive voltage to one of the bit lines which is associated with the target memory cell, and applying a zero voltage to all the other bit lines; and
applying a zero voltage to one of the source lines which is associated with the target memory cell, and applying a positive voltage to all the other source lines.
2. The method of claim 1 , further comprising:
applying a zero or positive voltage to one of the control gate lines which is associated with the target memory cell, and applying a zero or positive voltage to all the other control gate lines; and
applying a zero or positive voltage to one of the erase gate lines which is associated with the target memory cell, and applying a zero voltage to all the other erase gate lines.
3. The method of claim 1 , wherein:
the positive voltage applied to the word line associated with the target memory cell is 1.2 to 3.7 volts;
the positive voltage applied to the bit line associated with the target memory cell is 0.5 to 1.5 volts;
the positive voltage applied to the all other source lines is 0.1 to 0.5 volts.
4. The method of claim 3 , wherein:
the positive voltage applied to the word line associated with the target memory cell is substantially 1.2 volts;
the positive voltage applied to the bit line associated with the target memory cell is substantially 0.6 volts; and
the positive voltage applied to the all other source lines is substantially 0.2 volts.
5. The method of claim 4 , further comprising:
applying substantially 2.5 volts to the control gate lines.
6. The method of claim 5 , further comprising:
applying a zero voltage to the erase gate lines.
7. A method of reading a memory device having rows and columns of memory cells formed on a substrate of semiconductor material having a first conductivity type:
wherein each of the memory cells comprises:
spaced apart first and second regions formed in the substrate and having a second conductivity type different than the first conductivity type, wherein a channel region of the substrate is disposed between the first and second regions,
a floating gate disposed over and insulated from a first portion of the channel region,
a select gate disposed over and insulated from a second portion of the channel region,
a control gate disposed over and insulated from the floating gate, and
an erase gate disposed over and insulated from the first region;
wherein the memory device further comprises:
a plurality of word lines each electrically connecting together a row of the select gates,
a plurality of bit lines each electrically connecting together a column of the second regions,
a plurality of source lines each electrically connecting together a row of the first regions,
a plurality of control gate lines each electrically connecting together a row of the control gates, and
a plurality of erase gate lines each electrically connecting together a row of the erase gates;
wherein the method of reading the memory device comprises:
applying a positive voltage to one of the word lines which is associated with a target memory cell, and applying a negative voltage to all the other word lines;
applying a positive voltage to one of the bit lines which is associated with the target memory cell, and applying a zero voltage to all the other bit lines; and
applying a zero voltage to the source lines; and
applying a zero or positive voltage to one of the control gate lines which is associated with the target memory cell, and applying a positive voltage to all the other control gate lines.
8. The method of claim 7 , further comprising:
applying a zero or positive voltage to one of the erase gate lines which is associated with the target memory cell, and applying a zero voltage to all the other erase gate lines.
9. The method of claim 7 , wherein:
the positive voltage applied to the word line associated with the target memory cell is 1.2 to 3.7 volts;
the positive voltage applied to the bit line associated with the target memory cell is 0.5 to 1.5 volts;
the negative voltage applied to the all other word lines is −0.1 to −0.5 volts.
10. The method of claim 9 , wherein:
the positive voltage applied to the word line associated with the target memory cell is substantially 1.2 volts;
the positive voltage applied to the bit line associated with the target memory cell is substantially 0.6 volts; and
the negative voltage applied to the all other word lines is substantially −0.2 volts.
11. The method of claim 10 , further comprising:
applying substantially 2.5 volts to the control gate lines.
12. The method of claim 11 , further comprising:
applying a zero voltage to the erase gate lines.
13. A method of reading a memory device having rows and columns of memory cells formed on a substrate of semiconductor material having a first conductivity type:
wherein each of the memory cells comprises:
spaced apart first and second regions formed in the substrate and having a second conductivity type different than the first conductivity type, wherein a channel region of the substrate is disposed between the first and second regions,
a floating gate disposed over and insulated from a first portion of the channel region,
a select gate disposed over and insulated from a second portion of the channel region,
a control gate disposed over and insulated from the floating gate, and
an erase gate disposed over and insulated from the first region;
wherein the memory device further comprises:
a plurality of word lines each electrically connecting together a row of the select gates,
a plurality of bit lines each electrically connecting together a column of the second regions,
a plurality of source lines each electrically connecting together a row of the first regions,
a plurality of control gate lines each electrically connecting together a row of the control gates, and
a plurality of erase gate lines each electrically connecting together a row of the erase gates;
wherein the method of reading the memory device comprises:
applying a positive voltage to one of the word lines which is associated with a target memory cell, and applying a negative voltage to all the other word lines;
applying a positive voltage to one of the bit lines which is associated with the target memory cell, and applying a zero voltage to all the other bit lines; and
applying a zero voltage to one of the source lines which is associated with the target memory cell, and applying a positive voltage to all the other source lines.
14. The method of claim 13 , further comprising:
applying a zero or positive voltage to one of the control gate lines which is associated with the target memory cell, and applying a zero or positive voltage to all the other control gate lines; and
applying a zero or positive voltage to one of the erase gate lines which is associated with the target memory cell, and applying a zero voltage to all the other erase gate lines.
15. The method of claim 13 , wherein:
the positive voltage applied to the word line associated with the target memory cell is 1.2 to 3.7 volts;
the positive voltage applied to the bit line associated with the target memory cell is 0.5 to 1.5 volts;
the negative voltage applied to the all other word lines is −0.1 to −0.5 volts; and
the positive voltage applied to the all other source lines is 0.1 to 0.5 volts.
16. The method of claim 15 , wherein:
the positive voltage applied to the word line associated with the target memory cell is substantially 1.2 volts;
the positive voltage applied to the bit line associated with the target memory cell is substantially 0.6 volts;
the negative voltage applied to the all other word lines is substantially −0.2 volts; and
the positive voltage applied to the all other source lines is substantially 0.2 volts.
17. The method of claim 16 , further comprising:
applying substantially 2.5 volts to the control gate lines.
18. The method of claim 17 , further comprising:
applying a zero voltage to the erase gate lines.