3D - PROGRAM AND READ OPERATIONS FOR 3D NON-VOLATILE MEMORY BASED ON MEMORY HOLE DIAMETER

摘要

Techniques are provided for programming and reading memory cells in a 3D non-volatile memory device by compensating for variations in memory hole diameter. The diameter of the memory hole at the bottom of the stack, which causes more severe read disturbance, is smaller. To compensate, the programming of memory cells in the lower wordline layers is modified. In one approach, the threshold voltage (Vth) distributions of one or more data states during programming are narrowed so that a lower read pass voltage can be used for subsequent sensing operations. Sufficient spacing is maintained between the read tail voltage and the upper tail of the highest data state. The Vth distributions can also be downshifted. In another method, the read pass voltage is not lowered and the least programmed state is upshifted to provide an interval from the erased top tail.