High selectivity slurry delivery system

A slurry delivery system, comprising:

• a first flow controller having a first fluid input coupled to a source of slurry additive, the slurry additive enabling chemical mechanical polishing of a film selectively to another film;
• a second flow controller having a second fluid input coupled to a source of slurry;
• a controller for generating an output signal to and thereby controlling discharges from the first and second flow controllers;
• a variable resistor coupled between an output of the controller and an input of the second flow controller;
• and
• whereby the output signal of the controller and the resistance of the variable resistor may be selected to selectively control discharge of slurry additive from the first flow controller and slurry from the second flow controller.

A chemical mechanical polishing system, comprising:

• a platen for engaging a semiconductor workpiece;
• a first flow controller having a first fluid input coupled to a source of slurry additive, the slurry additive enabling chemical mechanical polishing of a film of the semiconductor workpiece selectively to another film of the semiconductor workpiece;
• a second flow controller having a second fluid input coupled to a source of slurry;
• a manifold coupled to respective fluid outputs of the first and second flow controllers and having an output for delivering discharges from the first and flow controllers to the platen;
• a controller for generating an output signal to and thereby controlling discharges from the first and second flow controllers to the platen;
• a variable resistor coupled between an output of the controller and an input of the second flow controller;
• and
• whereby the output signal of the controller and the resistance of the variable resistor may be selected to selectively control discharge of slurry additive from the first flow controllers and slurry from the second flow controller to the platen.

A method of delivering a liquid for performing a process, comprising:

• delivering a first fluid to a first flow controller;
• delivering a second fluid to a second flow controller;
• generating an output signal to the first and second flow controllers to control respective discharges therefrom;
• passing a portion of the output signal through a variable resistor coupled between an output of the controller and an input of the second flow controller;
• and
• whereby the output signal may be selected to selectively control discharge of the first fluid from the first flow controller and the resistance of the variable resistor may be selected selectively control discharge of the second fluid from the second flow controller.