Method and apparatus for pulse electrochemical polishing

A method for pulse electrochemical polishing a wafer, comprising:

• establishing a duty cycle table showing 10,000 or more points on the wafer, a removal thickness corresponding to every point and a duty cycle corresponding to the removal thickness, wherein the step of establishing a duty cycle table further comprises steps of:
• measuring the removal thickness of a number of points on the wafer and then computing the removal thickness of each of the 10,000 or more points on the wafer based on the measured removal thickness;
• obtaining a linear function model of the removal thickness and duty cycle;
• and
• storing the linear function model and converting the removal thickness of each of the 10,000 or more points on the wafer into a corresponding duty cycle according to the linear function model;
• driving a wafer chuck holding and positioning the wafer to move at a preset speed so that a special point on the wafer is right above a nozzle ejecting charged electrolyte onto the wafer;
• looking up the duty cycle table to obtain the removal thickness and the duty cycle corresponding to the special point;
• and
• applying a preset pulse power source to the wafer and the nozzle and the actual polishing power source for polishing the special point being equal to the duty cycle multiplying by the preset power source.