Sandisk Technologies Inc.

Rajan Paudel

Jagdish Sabde

Sagar Magia

Daniel Joseph Linnen

Grishma Shah

Kirubakaran Periyannan

Mrinal Kochar

Khanh Vinh Nguyen

Dongxiang Liao

Avinash Rajagiri

Srikar Peesari

Shantanu Gupta

Deepak Bharadwaj

Navkiran Kaur Sandhu

An apparatus includes control circuits configured to connect to word lines that are coupled to NAND strings. The control circuits are configured to detect a defective word line, apply single word line erase voltages to the word lines to erase memory cells of the defective word line and, with the memory cells of the defective word line in an erased state, read data from neighboring memory cells of the NAND strings.

Data recovery in nonvolatile memory with defective word line

Techniques are presented for testing the high-speed data path between the IO pads and the read/write buffer of a memory circuit without the use of an external test device. In an on-chip process, a data test pattern is transferred at a high data rate between the read/write register and a source for the test pattern, such as register for this purpose or the read/write buffer of another plane. The test data after the high-speed transfer is then checked against its expected, uncorrupted value, such as by transferring it back at a lower speed for comparison or by transferring the test data a second time, but at a lower rate, and comparing the high transfer rate copy with the lower transfer rate copy at the receiving end of the transfers.

High-speed data path testing techniques for non-volatile memory

Techniques are provided for operating a memory device which detect word line short circuits, such as short circuits between adjacent word lines. In an example implementation, during a programming operation, the number of program loops used to complete programming or reach another programming milestone for WLn are counted. If the number of program loops exceeds a loop count limit, the memory cells of WLn+1 are evaluated to determine whether a short circuit is present. The evaluation involves a read operation which counts erased state memory cells in the upper tail of the Vth distribution of WLn+1. If the count exceeds a bit count limit, it is concluded that a short circuit exits between WLn and WLn+1, and a corrective action is taken. The loop count limit is adjusted lower as the number of program-erase cycles increases.

Word line look ahead read for word line to word line short detection

A method is provided for programming a memory cell connected to a selected word line in a memory device. The method includes performing one programming pass of a multi-pass programming operation for the memory cell, wherein a first set of program pulses is applied to the selected word line during the one programming pass, determining a number of the program pulses applied to the selected word line during the one programming pass, determining a difference between the determined number of program pulses applied to the selected word line during the one programming pass and a predetermined number of program pulses, adjusting a parameter of a second set of program pulses for the another programming pass based on the determined difference, and performing the another programming pass for the set of memory cells, wherein the second set of program pulses is applied to the selected word line during the another programming pass.

Adaptive multi-page programming methods and apparatus for non-volatile memory

Techniques are provided for erasing a memory device. In one aspect, different zones of a block can be separately erased and subject to a verify test. Erase parameters can be optimized for each zone, so that endurance is improved. If one zone is found to be too slow to erase, it can be marked as being bad while other zones remain available for use. In another aspect, the zone-based erase occurs after a block based erased when a criterion is met, such as the block-based erase being too slow or failing to complete within an allowable number of program loops. The zone-based erase can occur after the block-based erase in the same erase operation, or in a subsequent, new erase operation.

Block and zone erase algorithm for memory

A stress mode for use in testing non-volatile memory arrays for a number of types of defects is described. More specifically, a multi-word line select option for a given block can be used for a group of selected word lines to be set to the a programming or other high voltage, while the unselected word lines of the block are set to a pass voltage to minimize electric field differences in order to avoid disturb. For example, a group of selected word lines could number 4, 8 or 16. The multi-word line option can be applied to one block per plane, so that if there are two memory planes, for example, two such blocks can be selected simultaneously for the multi-word line option for those blocks.

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Fremont, CA, United States of America

Rajan Paudel