NAND structure with tier select gate transistors
First Claim
1. An apparatus, comprising:
- a first portion of a NAND string connected to a bit line;
a second portion of the NAND string connected to a source line;
an isolation transistor configured to electrically disconnect the first portion of the NAND string from the second portion of the NAND string during a memory operation, the isolation transistor comprises a first channel length and the first portion of the NAND string comprises a second transistor with a second channel length different from the first channel length; and
a control circuit configured to detect that a programmed data state stored within memory cell transistors of the second portion of the NAND string is greater than a particular threshold voltage and cause the isolation transistor to electrically disconnect the first portion of the NAND string from the second portion of the NAND string during the memory operation in response to detection that the programmed data state is greater than the particular threshold voltage.
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Accused Products
Abstract
Systems and methods for improving performance of a non-volatile memory by utilizing one or more tier select gate transistors between different portions of a NAND string are described. A first memory string tier may comprise a first set of memory cell transistors that may be programmed to store a first set of data and a second memory string tier may comprise a second set of memory cell transistors that are arranged above the first set of transistors and that may be programmed to store a second set of data. Between the first set of memory cell transistors and the second set of memory cell transistors may comprise a tier select gate transistor in series with the first set of memory cell transistors and the second set of memory cell transistors. The tier select gate transistor may comprise a programmable transistor or a non-programmable transistor.
42 Citations
18 Claims
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1. An apparatus, comprising:
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a first portion of a NAND string connected to a bit line; a second portion of the NAND string connected to a source line; an isolation transistor configured to electrically disconnect the first portion of the NAND string from the second portion of the NAND string during a memory operation, the isolation transistor comprises a first channel length and the first portion of the NAND string comprises a second transistor with a second channel length different from the first channel length; and a control circuit configured to detect that a programmed data state stored within memory cell transistors of the second portion of the NAND string is greater than a particular threshold voltage and cause the isolation transistor to electrically disconnect the first portion of the NAND string from the second portion of the NAND string during the memory operation in response to detection that the programmed data state is greater than the particular threshold voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An apparatus, comprising:
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a first set of memory cell transistors associated with a NAND string; a second set of memory cell transistors associated with the NAND string; an isolation device arranged between the first set of memory cell transistors and the second set of memory cell transistors, the isolation device configured to electrically isolate the first set of memory cell transistors from the second set of memory cell transistors during a memory operation, the isolation device comprises a first transistor with a first channel length and the first set of memory cell transistors comprises a second transistor with a second channel length less than the first channel length; and a control circuit configured to detect that a programmed data state stored within memory cell transistors of the second set of memory cell transistors is less than a particular threshold voltage and cause the isolation device to electrically isolate the first set of memory cell transistors from the second set of memory cell transistors during the memory operation in response to detection that the programmed data state is less than the particular threshold voltage. - View Dependent Claims (14, 15, 16, 17)
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18. A method, comprising:
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setting a tier select gate transistor arranged between a first set of memory cell transistors of a NAND string and a second set of memory cell transistors of the NAND string into a non-conducting state during a memory operation; detecting that a programmed data state stored within memory cell transistors of the first set of memory cell transistors of the NAND string is greater than a particular threshold voltage and setting the tier select gate transistor into the non-conducting state during the memory operation in response to detecting that the programmed data state is greater than the particular threshold voltage; applying a selected word line voltage to a second memory cell transistor of the second set of memory cell transistors during the memory operation, the tier select gate transistor comprises a non-programmable transistor, the tier select gate transistor comprises a first channel length and the first set of memory cell transistors comprises a first transistor of a second channel length less than the first channel length; setting the tier select gate transistor arranged between the first set of memory cell transistors of the NAND string and the second set of memory cell transistors of the NAND string into a conducting state during a second memory operation; and applying a second selected word line voltage to the second memory cell transistor of the second set of memory cell transistors during the second memory operation.
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Specification