Program scheme in 3d nand flash memory

A method for operating a memory device including an array of NAND strings of memory cells, the memory device comprising a plurality of stacks of word lines separated by insulating material, the word lines in the stacks having first vertical sides and second vertical sides opposite the first vertical sides;

• a first plurality of strings disposed on the first vertical sides of the word lines in a particular stack in the plurality of stacks;
• and a second plurality of strings disposed on the second vertical sides of the word lines in the particular stack, the strings in the second plurality of strings being offset from the strings in the first plurality of strings in a direction along which the word lines in the particular stack extend;
• the method comprising:
• executing a first program operation including applying a shielding voltage to a first string in the first plurality of strings, a program voltage to a second string in the second plurality of strings adjacent the first string in the direction along which the word lines in the particular stack extend, the program voltage to a third string in the first plurality of strings, and the shielding voltage to a fourth string in the second plurality of strings adjacent the third string in the direction along which the word lines in the particular stack extend.

A memory device including an array of NAND strings of memory cells, comprising:

• a plurality of stacks of word lines separated by insulating material, the word lines in the stacks having first vertical sides and second vertical sides opposite the first vertical sides;
• a first plurality of strings in the array disposed on the first vertical sides of the word lines in a particular stack in the plurality of stacks;
• a second plurality of strings in the array disposed on the second vertical sides of the word lines in the particular stack, the strings in the second plurality of strings being offset from the strings in the first plurality of strings in a direction along which the word lines in the particular stack extend;
• and
• a controller configured to execute:
• a first program operation including applying a shielding voltage to a first string in the first plurality of strings and a fourth string in the second plurality of strings, applying a program voltage to a second string in the second plurality of strings and a third string in the first plurality of strings;
• and
• a second program operation including applying the program voltage to the first string in the first plurality of strings and the fourth string in the second plurality of strings, and applying the shielding voltage to the second string in the second plurality of strings and the third string in the first plurality of strings,
• wherein in a direction along which the word lines in the particular stack extend, the second string is adjacent the first string, the third string is adjacent the second string, and the fourth string is adjacent the third string.