Method and apparatus for reduction of voltage potential spike during dechucking

A pneumatic lift mechanism for a plasma reactor wherein lift pins raise and lower a substrate in at least three positions with respect to an upper surface of an electrostatic chuck, the lift mechanism comprising:

• a housing having an upper chamber and a lower chamber;
• an upper piston slidably mounted to move up and down in the upper chamber;
• a lower piston slidably mounted to move up and down in the lower chamber, the lower chamber comprising a hard stop defining an upper limit of travel of the lower piston;
• the at least three positions comprising (1) a lower position at which the upper piston positions the lift pins below the upper surface of the electrostatic chuck, (2) a mid-lift position at which the lower piston is in contact with the hard stop and a shaft of the lower piston raises the upper piston, and (3) an up position at which the upper piston positions the lift pins so the substrate can be removed from the plasma chamber;
• and
• wherein the upper piston and the lower piston are independently pneumatically operated.