Control of steam generation for chemical mechanical polishing

Abstract

A chemical mechanical polishing system includes a steam generator with a heating element to apply heat to a vessel to generate steam, an opening to deliver steam onto a polishing pad, a first valve in a fluid line between the opening and the vessel, a sensor to monitor a steam parameter, and a control system. The control system causes the valve to open and close in accordance with a steam delivery schedule in a recipe, receive a measured value for the steam parameter from the sensor, receive a target value for the steam parameter, and perform a proportional integral derivative control algorithm with the target value and measured value as inputs so as to control the first valve and/or a second pressure release valve and/or the heating element such that the measured value reaches the target value substantially just before the valve is opened according to the steam delivery schedule.

What is claimed is: 
     
         1 . A computer program product, comprising a computer-readable medium having instructions to cause one or more processors to:
 access a polishing process recipe stored as data in a non-transitory storage device;   cause a first valve between an outlet of a steam generation device and an opening to open and close in accordance with the steam delivery schedule that alternates between a recuperation phase in which the first valve is closed and a dispense phase in which the first valve is open;   receive from a sensor a measured value for a steam parameter of steam in the steam generation device;   receive a target value for the steam parameter,   control a second pressure release valve and/or the heating element based on the target value and measured value such that the measured value reaches the target value substantially just before the valve is opened according to the steam delivery schedule, and   open the first valve during a dispense phase of a cycle and configured to close the first valve during a recuperation phase of the cycle.   
     
     
         2 . The computer program product of  claim 1 , wherein the steam parameter is steam temperature, the measured value is a measured steam temperature value, and the target value is a target steam temperature value. 
     
     
         3 . The computer program product of  claim 1 , wherein the steam parameter is steam pressure, the measured value is a measured steam pressure value, and the target value is a target steam pressure value. 
     
     
         4 . The computer program product of  claim 1 , comprising instructions to control the second pressure release valve such that the measured value reaches the target value substantially just before the valve is opened. 
     
     
         5 . The computer program product of  claim 1 , comprising instructions to control the heater such that the measured value reaches the target value substantially just before the valve is opened 
     
     
         6 . The computer program product of  claim 1 , comprising instructions to control the second pressure release valve and/or the heating element based such that the measured value reaches the target value less than  10  seconds before the first valve is opened. 
     
     
         7 . The computer program product of  claim 1 , comprising instructions to control the second pressure release valve and/or the heating element based such that the measured value reaches the target value less than  3  seconds before the first valve is opened. 
     
     
         8 . The computer program product of  claim 1 , comprising instructions to control the second pressure release valve and/or the heating element based such that the measured value reaches the target value less than  1  seconds before the first valve is opened. 
     
     
         9 . The computer program product of  claim 1 , comprising instructions to receive a signal from a water level sensor and to modify a flow rate of water through the water inlet based on the signal from the water level sensor to keep a water level in the vessel above the heating element and below the outlet. 
     
     
         10 . The computer program product of  claim 9 , wherein each cycle corresponds to polishing of a single substrate. 
     
     
         11 . The computer program product of  claim 9 , wherein each cycle consists of a single dispense phase and a single recuperation phase. 
     
     
         12 . The computer program product of  claim 1 , comprising instructions to receive a signal representing the temperature of the polishing pad from a sensor and to set the target value for the steam parameter based on the signal. 
     
     
         13 . The computer program product of  claim 12 , comprising instructions to set the target value on a cycle-by-cycle basis. 
     
     
         14 . The computer program product of  claim 12 , comprising instructions to set the target value on a continuous basis through a cycle.