Programming of a memory with discrete charge storage elements
View Patent ↗A non volatile memory ( 100 ) includes an array ( 102 ) of transistors ( 30 ) having discrete charge storage elements ( 40 ). The transistors are programmed by using a two step programming method ( 60 ) where a first step ( 68 ) is hot carrier injection (HCl) programming with low gate voltages. A second step ( 78 ) is selectively utilized on some memory cells to modify the injected charge distribution to enhance the separation of charge distribution between each memory bit within the transistor memory cell. The second step of programming is implemented without adding significant additional time to the programming operation. In one example, the first step injects electrons and the second step injects holes. The resulting distribution of the two steps removes electron charge in the central region of the storage medium.
1. A method for programming at least one portion of a memory cell with a first programmed value, the method comprising:
injecting charge having a first polarity into a first plurality of discrete charge storage elements within the memory cell;
injecting charge having a second polarity into a portion of the first plurality of discrete charge storage elements; and
using the first plurality of discrete charge storage elements to represent the first programmed value.
2. A method as in claim 1 , wherein the charge having the first polarity is injected by electrons and wherein the charge having the second polarity is injected by holes.
3. A method as in claim 1 , further comprising:
before said step of injecting charge having a first polarity, determining if a present logic state of the at least one portion of the memory cell is different than the first programmed value.
4. A method as in claim 1 , wherein the first programmed value is one of a logic state one and a logic state zero.
5. A method as in claim 1 , further comprising providing a plurality of memory cells in a memory that is a non-volatile memory.
6. A method as in claim 5 , further comprising implementing the memory as an electrically erasable programmable memory.
7. A method as in claim 1 , wherein the memory cell has a first portion and a second portion, and wherein the first plurality of discrete charge storage elements are located in the first portion of the memory cell.
8. A method as in claim 7 , further comprising:
determining if a present logic state of the first portion of the memory cell is different than the first programmed value;
if the present logic state of the first portion of the memory cell is different than the first programmed value, performing said step of injecting charge having a first polarity;
determining if a second programmed value to be programmed into the second portion of the memory cell is different than the first programmed value; and
if the second programmed value is different than the first programmed value, performing said step of injecting charge having a second polarity.
9. A method as in claim 7 , further comprising:
injecting charge having a first polarity into a second plurality of discrete charge storage elements within the second portion of the memory cell;
injecting charge having a second polarity into a portion of the second plurality of discrete charge storage elements; and
using the second plurality of discrete charge storage elements to represent a second programmed value.
10. A method as in claim 1 , further comprising:
providing the memory cell in an erased state before said step of injecting charge having a first polarity.
11. A memory, comprising:
means for injecting charge having a first polarity into a first plurality of discrete charge storage elements within a portion of the memory;
means for injecting charge having a second polarity into a portion of the first plurality of discrete charge storage elements; and
means for retrieving a programmed value from the first plurality of discrete charge storage elements.
12. A memory as in claim 11 , wherein the means for injecting charge having the second polarity can concurrently inject charge to a plurality of memory cells within a row of the memory.
13. A memory as in claim 11 , wherein the means for injecting charge having the second polarity can concurrently inject charge to a plurality of memory cells within a column of the memory.
14. A memory, comprising:
a memory cell having a first portion and a second portion, said first portion having a first state and said second portion having a second state;
a sense amplifier coupled to said memory cell wherein said sense amplifier senses the first state of said first portion and second state of said second portion; and
program circuitry coupled to said sense amplifier, whereby based on a comparison of the first state and second state, charge is selectively injected into at least one of said first portion and said second portion.
15. A memory as in claim 14 , wherein said charge is selectively injected during programming of at least one portion of the memory cell.
16. A memory as in claim 14 , wherein said charge comprises holes which are selectively injected during programming of at least one portion of the memory cell.
17. A memory as in claim 16 , wherein said memory cell is located within a row of memory cells, and wherein said charge is injected into a plurality of memory cells within the row based on logic states stored in the plurality of memory cells.
18. A memory as in claim 14 , wherein said charge is selectively injected when the first state and said second state are of opposite states.
19. A memory as in claim 14 , wherein said charge comprises electrons.
20. A memory as in claim 14 , wherein the memory is a non-volatile memory.
21. A memory as in claim 14 , wherein the memory is an electrically erasable programmable memory.