Non-volatile memory and program method thereof

A non-volatile memory, comprising:

• a plurality of word lines, each of the word lines coupled to at least one memory cell string;
• a plurality of word line drivers, coupled to the word lines, configured to adjust voltages on the word lines;
• and
• a controller, coupled to the word line drivers, configured to:
• set one of the word lines to be a program word line, set the word lines except the program word line to be a plurality of unselected word lines;
• raise a voltage on the program word line from a reference voltage to a first program voltage during a first sub-time period of a program time period;
• raise the voltage on the program word line from the first program voltage to a second program voltage during a second sub-time period of the program time period, wherein the second program voltage is greater than the first program voltage;
• and
• raise voltages on at least part of the unselected word lines from the reference voltage to a pass voltage during the second sub-time period,
• wherein the first sub-time period is before the second sub-time period.