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US 7,924,619 B2Granted
Programming method to reduce word line to word line breakdown for NAND flash
AssigneeMicron Technology, Inc.
InventorSeiichi Aritome
Life of this patent
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Abstract
A NAND architecture non-volatile memory device and programming process programs the various cells of strings of non-volatile memory cells by the application of differing word line pass voltages (Vpass) to the unselected word lines adjacent to the selected word line and memory cell being programmed in order to reduce voltage differences between the word lines of the memory cell string or array during a programming cycle. This allows the word line to word line voltage differential to be reduced and thus decreases the likelihood of breakdown or punch through of the insulator materials placed between the adjacent word lines.
Claims22
A method of programming a selected memory cell of a NAND string of non-volatile memory cells where each memory cell is coupled to a word line, the method comprising:
- applying a programming voltage to a selected word line wherein the selected word line is coupled to the selected memory cell;
- applying a first pass voltage to a first set of word lines, wherein a first word line of the first set of word lines is adjacent to the selected word line and is interposed between the selected word line and a source line connection to the NAND string and a second word line of the first set of word lines is adjacent to the selected word line and is interposed between the selected word line and a bit line connection to the NAND string;
- applying a second pass voltage to a second set of word lines, wherein a first word line of the second set of word lines is adjacent to the first word line of the first set of word lines and is interposed between the first word line of the first set of word lines and the source line connection to the NAND string and a second word line of the second set of word lines is adjacent to the second word line of the first set of word lines and is interposed between the second word line of the first set of word lines and the bit line connection to the NAND string;
- and
- applying a third pass voltage to a third set of one or more word lines;
- wherein the first pass voltage is less than the programming voltage and where the first pass voltage is greater than the second pass voltage and the third pass voltage.
3 more elements
A method of programming a selected memory cell of a NAND string of non-volatile memory cells where each memory cell is coupled to a word line, the method comprising:
- applying a programming voltage to a selected word line wherein the selected word line is coupled to the selected memory cell;
- biasing each of two or more first unselected word lines sequentially adjacent to the selected word line and located between the selected word line and a first end of the NAND string with a respective one of a sequence of decreasing pass voltages so that a first unselected word line of the two or more first unselected word lines that is closest to the selected word line is biased with the greatest pass voltage of the sequence of decreasing pass voltages and a first unselected word line of the two or more first unselected word lines that is furthest from the selected word line is biased with the smallest pass voltage of the sequence of decreasing pass voltages;
- and
- biasing each of two or more second unselected word lines sequentially adjacent to the selected word line and located between the selected word line and a second end of the NAND string with a respective one of the sequence of decreasing pass voltages so that a second unselected word line of the two or more second unselected word lines that is closest to the selected word line is biased with the greatest pass voltage of the sequence of decreasing pass voltages and a second unselected word line of the two or more second unselected word lines that is furthest from the selected word line is biased with the smallest pass voltage of the sequence of decreasing pass voltages;
- wherein the programming voltage is greater than each pass voltage of the sequence of decreasing pass voltages.
2 more elements
A method of programming a selected memory cell of a NAND string of non-volatile memory cells having a first end of the NAND string coupled to a bit line and a second end of the NAND string coupled to a source line and where each memory cell is coupled to a word line, the method comprising:
- applying a programming voltage to a selected word line wherein the selected word line is coupled to the selected memory cell;
- biasing a first pair of unselected word lines to first pass voltage that is less than the programming voltage, wherein a first unselected word line of the first pair of unselected word lines is located between the selected word line and the first end of the NAND string and a second unselected word line of the first pair of unselected word lines is located between the selected word line and the second end of the NAND string;
- and
- biasing a second pair of unselected word lines to second pass voltage that is less than the first pass voltage, wherein a first unselected word line of the second pair of unselected word lines is located between the first unselected word line of the first pair of unselected word lines and the first end of the NAND string and a second unselected word line of the second pair of unselected word lines is located between the second unselected word line of the first pair of unselected word lines and the second end of the NAND string.
1 more element
A memory device, comprising:
- an array of memory cells arranged in rows and in columns where each memory cell of each row is coupled to a word line, wherein at least one column comprises a string of series coupled memory cells;
- and
- control circuitry, wherein the control circuitry is configured to:
- apply a programming voltage to a selected word line, wherein the selected word line is coupled to a selected memory cell of the string of series coupled memory cells;
- bias each of two or more first unselected word lines sequentially adjacent to the selected word line and located between the selected word line and a first end of the string of series coupled memory cells with a respective one of a sequence of decreasing pass voltages so that a first unselected word line of the two or more first unselected word lines that is closest to the selected word line is biased with the greatest pass voltage of the sequence of decreasing pass voltages and a first unselected word line of the two or more first unselected word line that is furthest from the selected word line is biased with the smallest pass voltage of the sequence of decreasing pass voltages;
- and
- bias each of two or more second unselected word lines sequentially adjacent to the selected word line and located between the selected word line and a second end of the string of series coupled memory cells with a respective one of the sequence of decreasing pass voltages so that a second unselected word line of the two or more second unselected word lines that is closest to the selected word line is biased with the greatest pass voltage of the sequence of decreasing pass voltages and a second unselected word line of the two or more second unselected word lines that is furthest from the selected word line is biased with the smallest pass voltage of the sequence of decreasing pass voltages;
- wherein the programming voltage is greater than each pass voltage of the sequence of decreasing pass voltages.
5 more elements
Dependencies are inferred from the claim text.