Double verify method with soft programming to suppress read noise

摘要

Memory cells which have read noise are identified during a programming pass and an amount of programming is increased for noisy memory cells compared to non-noisy cells. The read noise is indicated by a decrease in the threshold voltage of a cell when the cell is repeatedly read. During the programming pass, a cell enters a temporary lockout state when it passes a first verify test. In this state, the cell is subject to one or more additional verify tests. If the one or more additional verify tests indicate that the threshold voltage of a cell has decreased, the cell is noisy and is soft programmed before being permanently locked out. In contrast, programming of a non-noisy cell is concluded after the first verify test without further programming.

主权项

1. A method for programming a set of memory cells connected to a word line, comprising:
performing one or more program-verify iterations in a programming pass, two or more memory cells of the set of memory cells are programmed by the one or more program-verify iterations until the two or more memory cells pass a first verify test; in response to the two or more memory cells passing the first verify test, performing one or more program-verify iterations in the programming pass in which the two or more memory cells are temporarily locked out from programming, the two or more memory cells are subject to one or more additional verify tests while the two or more memory cells are temporarily locked out from programming; based on a result of the one or more additional verify tests, determining that the two or more memory cells comprise a noisy memory cell and a non-noisy memory cell; performing one or more program-verify iterations in the programming pass in which the noisy memory cell is further programmed; and permanently locking out the non-noisy memory cell from programming in the programming pass without performing further programming of the non-noisy memory cell.