Flash memory array of floating gate-based non-volatile memory cells
View Patent ↗A flash memory array comprises a plurality of memory cells organized in a matrix of rows and columns. Each of the memory cells includes a floating gate memory transistor having a source region and a drain region, and a coupling capacitor electrically connected to the memory transistor. A plurality of word lines are each electrically connected to the capacitor in each of the memory cells in a respective row. A first set of bit lines are each electrically connected to the drain region of the memory transistor in each of the memory cells in a respective column. A plurality of high voltage access transistors are each electrically connected to a bit line in the first set of bit lines. A second set of bit lines are each electrically connected to the source region of the memory transistor in each of the memory cells in a respective column. Various combinations of voltages can be applied to the word lines and the first and second sets of bit lines in operations to erase, program, inhibit, or read the logic state stored by the memory transistor in one or more of the memory cells.
1. A method of erasing a single bit in a memory cell of a flash memory array, the method comprising:
providing a flash memory array comprising a plurality of memory cells organized in a matrix of rows and columns, each of the memory cells comprising:
a floating gate memory transistor;
a program terminal electrically connected to the memory transistor;
a coupling capacitor electrically connected to the memory transistor; and
a capacitor terminal electrically connected to the coupling capacitor;
wherein a plurality of word lines are each electrically connected to the coupling capacitor in each of the memory cells in a respective row, and a first set of bit lines are each electrically connected to the memory transistor in each of the memory cells in a respective column;
wherein a plurality of high voltage access transistors are each electrically connected to a bit line in the first set of bit lines, and a control terminal is electrically connected to each access transistor;
wherein a second set of bit lines are each electrically connected to the program terminal in each of the memory cells in a respective column;
grounding the capacitor terminal of the memory cell to be erased;
applying a first voltage to the program terminal of the memory cell to be erased;
applying a second voltage to capacitor terminals not connected to the memory cell to be erased, the second voltage being less than the first voltage;
grounding the control terminal of the access transistor electrically connected to a bit line, in the first set of bit lines, connected to the memory transistor of the memory cell to be erased; and
applying a third voltage to program terminals not connected to the memory cell to be erased, the third voltage being less than the first voltage.
2. The method of claim 1 , wherein the second voltage is about one-half of the first voltage.
3. The method of claim 1 , wherein the third voltage is about one-half of the first voltage.
4. The method of claim 1 , wherein erasing of the single bit is carried out by Fowler-Nordheim tunneling.
5. A method of erasing a single bit in a memory cell of a flash memory array, the method comprising:
grounding a word line connected to the memory cell to be erased;
applying a first voltage to a bit line connected to a source region of a memory transistor in the memory cell to be erased;
applying a second voltage to word lines not connected to the memory cell to be erased, the second voltage being less than the first voltage;
grounding a bit line connected to a drain region of the memory transistor in the memory cell to be erased; and
applying a third voltage to bit lines connected to source regions of memory transistors not connected to the memory cell to be erased, the third voltage being less than the first voltage.
6. The method of claim 5 , wherein the second voltage is about one-half of the first voltage.