Array of non-volatile memory cells including embedded local and global reference cells and system
View Patent ↗An array of memory cells has a first side adjacent to a first column, a second side opposite the first side, a third side adjacent to a first row, and a fourth side opposite the third side. Each memory cell is connected to a bit line, a high voltage source, and a low voltage source. Reference cells, substantially the same as the memory cells, evenly spaced apart, are embedded in the array. A high voltage decoder is on the first side, connected to the memory cells and reference cells in the same row. A low voltage row decoder is on the second side, connected to the memory cells and reference cells in the same row. Sense amplifiers are on the third side, connected to the memory cells and to the reference cells.
1. A non-volatile memory device comprising:
an array of non-volatile memory cells arranged in a plurality of rows and columns, with each memory cell having a first region of a first conductivity type in a substrate of a second conductivity type, a second region of the first conductivity type spaced apart from the first region forming a channel region therebetween, a floating gate positioned over a portion of the channel region and insulated therefrom and adjacent to the first region, a control gate positioned over another portion of the channel region, and insulated therefrom, and adjacent to the floating gate and insulated therefrom, a top gate positioned over the floating gate, insulated therefrom, and an erase gate positioned over the first region, insulated therefrom, and adjacent to the floating gate; a bit terminal for connection to a bit line, wherein the bit terminal is said second region, and a source terminal for connection to a source line, wherein the source terminal is the first region;
said array having a first side adjacent to a first column of memory cells, and a second side opposite the first side, a third side adjacent to a first row of memory cells, and a fourth side opposite the third side;
a plurality of columns of reference memory cells embedded in said memory array, with a plurality of reference cells in each row of said array of non-volatile memory cells, substantially evenly spaced apart from one another; each of said reference memory cells, substantially the same as the non-volatile memory cells;
a plurality of sense amplifiers positioned on said third side, with each sense amplifier connected to the bit terminal of one column of non-volatile memory cells and to the bit terminal of a column of reference memory cells; and
resistance circuitry replicating the resistance of the source line containing the selected memory cells;
wherein the control gate and the top gate are connected to low voltage terminals, and the erase gate and top gate and the first region are connected to high voltage terminals.
2. The memory device of claim 1 wherein each sense amplifier is connected to the bit terminal of one column of a plurality of columns of memory cells and to the bit terminal of a column of reference memory cells.
3. The memory device of claim 1 further comprising a metal line for strapping to the first region of each of the memory cells and the reference cells in the same row.
4. The memory device of claim 1 further comprising a source line connected to the first region of the memory cells in the same row, with a plurality of pull down transistors connected to the source line.
5. The memory device of claim 1 wherein each memory cell is programmed incrementally until a threshold is reached.
6. The memory device of claim 1 wherein each memory cell is erased incrementally until a threshold is reached.
7. The memory device of claim 1 wherein each of the reference memory cells is located spaced apart from the first side, second side, third side and fourth side.
8. The memory device of claim 3 wherein each of the reference memory cells is located spaced apart from metal line for strapping to the first region.
9. The memory device of claim 1 further comprising circuitry for choosing selected reference memory cells from a column of memory cells for connection to the plurality of sense amplifiers.