Memory device with charge isolation to reduce injection type of program disturb
AssigneeSanDisk Technologies LLC
InventorsHong-Yan Chen, Wei Zhao
Life of this patent
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Abstract
Techniques are described for reducing an injection type of program disturb in a memory device. A charge isolation region is created in a channel of a NAND string on the source side of the selected word line, WLn, and spaced apart from WLn by one or more other word lines, when the program voltage is increased to a program voltage (Vpgm). The isolation region is created by applying 0 V or other low voltage to an isolation word line. The isolation region is maintained for a first portion of a time period in which Vpgm is applied. The charge isolation region can be modified based on factors associated with a risk of program disturb including the magnitude of Vpgm, the position of WLn in a set of word lines and an ambient temperature.
Claims20
An apparatus, comprising:
- a set of memory cells arranged in NAND strings, the set of memory cells comprises memory cells connected to a selected word line and memory cells connected to unselected word lines, the unselected word lines comprise an isolation word line which is on a source side of the selected word line and separated from the selected word line by at least one other word line, and the unselected word lines also comprise additional unselected word lines;
- and
- a control circuit, the control circuit, to program the selected memory cells in one program loop, is configured to concurrently increase a voltage on the selected word line and the additional unselected word lines from an initial voltage to a pass voltage, and subsequently increase the voltage on the selected word line from the pass voltage to a program voltage and maintain the voltage on the selected word line at the program voltage for a period of time, and increase a voltage on the isolation word line from an initial voltage to the pass voltage before an end of the period of time, and after a delay from the increase of the voltage on the selected word line from the pass voltage to the program voltage.
A method, comprising:
- increasing a voltage on unselected word lines in a block from an initial voltage to a pass voltage;
- increasing the voltage on a selected word line to a program voltage and maintaining the voltage on the selected word line at the program voltage for a period of time;
- and
- increasing a voltage on an isolation word line from the initial voltage to the pass voltage before an end of the period of time, and after a delay from the increase of the voltage on the selected word line to the program voltage, wherein the isolation word line is on a source side of the selected word line and separated from the selected word line by at least one other word line.
An apparatus, comprising:
- a set of memory cells arranged in NAND strings, the NAND strings are connected to a selected word line and to unselected word lines, the unselected word lines comprise a first isolation word line which is on a source side of the selected word line and separated from the selected word line by at least one other word line, and the unselected word lines also comprise additional unselected word lines;
- and
- a control circuit configured to concurrently increase a voltage on the selected word line and the additional unselected word lines from an initial voltage to a pass voltage, subsequently increase the voltage on the selected word line from the pass voltage to a program voltage and maintain the voltage on the selected word line at the program voltage for a period of time, and increase a voltage on the first isolation word line from the initial voltage to the pass voltage before an end of the period of time, and after a delay from the increase of the voltage on the selected word line from the pass voltage to the program voltage.
Dependencies are inferred from the claim text.