Systems And Methods For Read Disturb Management In Non-Volatile Memory
First Claim
1. A method of reading non-volatile storage, comprising:
- applying a set of read voltages to a selected word line as part of reading data from a set of non-volatile storage elements coupled to the selected word line, the set of read voltages including a first read voltage, a second read voltage, and a third read voltage;
applying to a first unselected word line that is adjacent to the selected word line a first set of state-dependent pass voltages, the first set of state-dependent pass voltages including a first pass voltage that is applied while applying the first read voltage, a second pass voltage that is applied while applying the second read voltage, and a third pass voltage that is applied while applying the third read voltage, the first pass voltage is greater than the second pass voltage and the second pass voltage is greater than the third pass voltage; and
applying to a second unselected word line a fourth pass voltage corresponding to the set of read voltages, the fourth pass voltage being less than the first pass voltage and the second pass voltage, the fourth pass voltage being less than or equal to the third pass voltage.
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Abstract
Non-volatile memory and methods of reading non-volatile memory are provided for managing and reducing read related disturb. Techniques are introduced to reduce read disturb using state-dependent read pass voltages for particular word lines during a read operation. Because of their proximity to a selected word line, adjacent word lines can be biased using state-dependent pass voltages while other unselected word lines are biased using a standard or second set of pass voltages. Generally, each state-dependent pass voltage applied to a word line adjacent to the selected word line is larger than the second set of pass voltages applied to other unselected word lines, although this is not required. Other word lines, may also be biased using state-dependent pass voltages. System-level techniques are provided with or independently of state-dependent pass voltages to further reduce and manage read disturb. Techniques may account for data validity and memory write and erase cycles.
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Citations
22 Claims
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1. A method of reading non-volatile storage, comprising:
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applying a set of read voltages to a selected word line as part of reading data from a set of non-volatile storage elements coupled to the selected word line, the set of read voltages including a first read voltage, a second read voltage, and a third read voltage; applying to a first unselected word line that is adjacent to the selected word line a first set of state-dependent pass voltages, the first set of state-dependent pass voltages including a first pass voltage that is applied while applying the first read voltage, a second pass voltage that is applied while applying the second read voltage, and a third pass voltage that is applied while applying the third read voltage, the first pass voltage is greater than the second pass voltage and the second pass voltage is greater than the third pass voltage; and applying to a second unselected word line a fourth pass voltage corresponding to the set of read voltages, the fourth pass voltage being less than the first pass voltage and the second pass voltage, the fourth pass voltage being less than or equal to the third pass voltage. - View Dependent Claims (2, 3, 4, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 20, 21)
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5. A method according to claim 5, wherein applying the second set of state-dependent pass voltages comprises:
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applying a fifth pass voltage to the third unselected word line while applying the first pass voltage to the second unselected word line, the fifth pass voltage being less than the first pass voltage; applying a sixth pass voltage to the third unselected word line while applying the second pass voltage to the second unselected word line, the sixth pass voltage being less than the second pass voltage; and applying a seventh pass voltage to the third unselected word line while applying the third pass voltage to the second unselected word line, the seventh pass voltage being less than or equal to the third pass voltage.
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6. A method according to claim 6, further comprising:
applying an eighth pass voltage to a fourth unselected word line that is adjacent to the third unselected word line while applying the second set of one or more pass voltages, the eighth pass voltage being less than or equal to the third pass voltage.
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14. A non-volatile storage device, comprising:
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a plurality of strings of serially-connected non-volatile storage elements; a plurality of word lines, each word line is coupled to one non-volatile storage element of each of the plurality of strings; and a controller in communication with the plurality of strings and the plurality of word lines, the controller biases a selected word line during reading using a first read voltage, a second read voltage, and a third read voltage, the controller biases a first unselected word line that is adjacent to the selected word line using a first pass voltage that is applied while applying the first read voltage, a second pass voltage that is applied while applying the second read voltage, and a third pass voltage that is applied while applying the third read voltage, the controller biases a second unselected word line using a fourth pass voltage that is applied while applying the first read voltage, the second read voltage, and the third read voltage, the fourth pass voltage is less than the first pass voltage and the second pass voltage, the fourth pass voltage is less than or equal to the third pass voltage.
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19. A method of operating non-volatile storage, the non-volatile storage including a plurality of strings of serially-connected non-volatile storage elements, the method comprising:
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applying a first read voltage and a second read voltage to a selected word line, the selected word line is coupled to a selected non-volatile storage element on a first of the plurality of strings, the second read voltage is greater than the first read voltage; applying a first pass voltage to a first unselected word line adjacent to the selected word line while applying the first read voltage to the selected word line and applying a second pass voltage to the first unselected word line while applying the second read voltage to the selected word line, the first unselected word line is coupled to a first unselected non-volatile storage element on the first string, the second pass voltage is less than the first pass voltage; and applying a third pass voltage to a second unselected word line adjacent to the first unselected word line while applying the first pass voltage to the first unselected word line and the second read compare voltage to the selected word line, the second unselected word line is coupled to a second unselected non-volatile storage element on the first string, the third pass voltage is less than the first pass voltage and is less than or equal to the second pass voltage. - View Dependent Claims (22)
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Specification