Programming methods for three-dimensional memory devices having multi-bit programming, and three-dimensional memory devices programmed thereby
In a method of multiple-bit programming of a three-dimensional memory device having arrays of memory cells that extend in horizontal and vertical directions relative to a substrate, the method comprises first programming a memory cell to be programmed to one among a first set of states. At least one neighboring memory cell that neighbors the memory cell to be programmed to one among the first set of states is then first programmed. Following the first programming of the at least one neighboring memory cell, second programming the memory cell to be programmed to one among a second set of states, wherein the second set of states has a number of states that is greater than the number of states in the first set of states.
1. A method of programming a nonvolatile memory device including strings extending from intersections of first through nth bit lines (n being an integer of 1 or more) and first through mth string selection lines (m being an integer of 4 or more), each string including memory cells formed in a direction perpendicular to a substrate to have multiple layers of cells, wherein the perpendicular direction is a Y-direction, the string lines extend in a Z-direction and the bit lines extend in an X-direction, comprising:
programming memory cells at each layer of an YZ plane with multi-bit data according to a shadow programming method, wherein, where memory cells at an Nth layer (N being an integer of 1 or more) of the YZ plane are programmed, remaining memory cells at an XZ plane corresponding to the Nth layer are programmed before memory cells at another layer of the YZ plane are programmed, wherein the programming comprises:
sequentially performing a first programming operation on first memory cells at a first layer of the YZ plane and defined by a first string selection line and the first through nth bit lines, a second programming operation on second memory cells, defined by a second string selection line and the first through nth bit lines, from among remaining memory cells located at an XZ plane corresponding to the first layer of the YZ plane, a third programming operation on third memory cells, defined by a third string selection line and the first through nth bit lines, from among the remaining memory cells located at the XZ plane corresponding to the first layer of the YZ plane, and a fourth programming operation on fourth memory cells, defined by a fourth string selection line and the first through nth bit lines, from among the remaining memory cells located at the XZ plane corresponding to the first layer of the YZ plane, and
after the first through mth programming operations, programming memory cells at a second layer of the YZ plane.
2. The method of claim 1 , wherein the bit lines are arranged to be vertical to the YZ plane, and when memory cells of the Nth layer of the YZ plane are programmed the bit lines are activated simultaneously.
3. The method of claim 1 , wherein the bit lines are arranged to be vertical to the YZ plane and are divided into a first group and a second group, and when memory cells of the Nth layer of the YZ plane are programmed the bit lines are activated by a group unit.
4. The method of claim 1 , wherein when memory cells of the Nth layer of the YZ plane are programmed, remaining memory cells at an XZ plane corresponding to the Nth layer are programmed by a string selection line unit.
5. The method of claim 1 , wherein the string selection lines are divided into a plurality of groups each formed of two or more string selection lines, and, when memory cells of the Nth layer of the YZ plane are programmed, remaining memory cells at an XZ plane corresponding to the Nth layer are programmed under a condition in which string selection lines in each group are selected in the same order and in turn.
6. The method of claim 1 , wherein layers of the YZ plane are divided into a first group and a second group, and
wherein after memory cells in the first group are programmed, memory cells in the second group are programmed.
7. The method of claim 1 , wherein the strings are divided into four groups on the basis of a string selection line and a layer of the YZ plane, and the groups are programmed independently.
8. The method of claim 1 , wherein the strings are divided into two groups on the basis of a string selection line, and the groups are programmed independently.
9. The method of claim 1 , wherein, in the shadow programming method, before upper bit data is programmed at memory cells at the Nth layer of the YZ plane, memory cells at a (N−1)th layer of the YZ plane are programmed by lower and upper bit data and memory cells at a (N+1)th layer of the YZ plane are programmed by lower bit data.