Simultaneous control of deposition time and temperature of multi-zone furnaces

Abstract

The present invention facilitates multi-zone furnace ( 102 ) based deposition processes by iteratively adjusting deposition time and zonal setpoint temperatures to mitigate deviations from desired target thickness(es). Coupled feedback loops are employed to update the deposition time ( 520 ) and the zonal setpoint temperatures ( 510 ) lot to lot and batch to batch while mitigating deviations fro the desired target thickness(es). Error checking is performed by computing an error metric ( 506 ) and only updating the setpoint temperatures on the error metric being within an acceptable value ( 508 ). Additionally, an excitation parameter ( 512 ) is determined that indicates variations in furnace operation.

1 . A system comprising: 
 a multi-zone furnace having a plurality of temperature zones and a central temperature zone; and    a controller that receives a number of thickness measurements from the multi-zone furnace as feedback and iteratively adjusts zone temperature setpoints for the plurality of temperature zones and deposition times of the multizone furnace according to a thermal model and the received measurements.    
   
   
       2 . The system of  claim 1 , wherein the thermal model includes deposition rates for the plurality of zones according to deviations in temperature from the central temperature zone.  
   
   
       3 . The system of  claim 1 , wherein the controller additionally controls pressure of the multi-zone furnace and gas flow into the furnace of a deposition material source.  
   
   
       4 . The system of  claim 1 , further comprising a metrology tool that provides deposition process parameters to the controller, wherein the controller initially sets the zone temperature setpoints for the plurality of temperature zones and the central temperature zone at least in part according to the provided deposition process parameters.  
   
   
       5 . The system of  claim 4 , wherein the deposition process parameters include one or more target thicknesses.  
   
   
       6 . The system of  claim 1 , wherein the multi-zone furnace includes a number of slots throughout the plurality of temperature zones and the central temperature zone.  
   
   
       7 . The system of  claim 6 , wherein the number of slots are filled with monitor wafers, product wafers, and dummy wafers.  
   
   
       8 . The system of  claim 7 , further comprising probes that obtain the thickness measurements from selected product wafers and provide the thickness measurements to the controller.  
   
   
       9 . The system of  claim 1 , wherein the controller determines an error metric according to the thermal model and the received measurements that indicate model error.  
   
   
       10 . The system of  claim 1 , wherein the controller determines an error metric according to sub-sampling error and adjusts the zone temperature setpoints on the error metric being above a dead zone value.  
   
   
       11 . The system of  claim 1 , wherein the controller builds the thermal model of deposition rates for the plurality of zones from thickness measurements.  
   
   
       12 . The system of  claim 1 , wherein the controller determines an excitation value according to the thickness measurements that indicates presence of information available in the thickness measurements.  
   
   
       13 . The system of  claim 12 , wherein the controller determines the excitation value by tracking changes processes performed by the furnace.  
   
   
       14 . The system of  claim 12 , wherein the controller adjusts the deposition times at least in part according to the excitation value.  
   
   
       15 . A furnace controller comprising: 
 a thermal model that provides changes in deposition rates according to temperature changes in a number temperature zones;    a filter that recursively determines adjustments to deposition time according to deposition rates in the multiple temperature zones;    an update component that receives a number of thickness measurements, employs the thermal model to determine setpoint temperature values for the number of temperature zones, determines deposition rates from the number of thickness measurements, and employs the filter to obtains updates to the deposition time.    
   
   
       16 . The furnace controller of  claim 15 , wherein the number of measurements is at least equal to the number of temperature zones.  
   
   
       17 . The furnace controller of  claim 15 , wherein the update component identifies erroneous thickness measurements.  
   
   
       18 . The furnace controller of  claim 15 , wherein the update component adjusts the number of thickness measurements according to variations in a present furnace load and a previous furnace load on which the thermal model is based.  
   
   
       19 . The furnace controller of  claim 15 , wherein the filter is a Kalman filter.  
   
   
       20 . A method of controlling a furnace during deposition comprising: 
 obtaining a number of thickness measurements;    determining an error metric according to the number of thickness measurements that indicates subsampling error;    on the error metric being acceptable, using a thermal model to determine adjusted setpoint temperatures for a number of zones of the furnace according to the thermal model, the number of thickness measurements, and one or more target thicknesses;    determining an excitation value according to batch to batch variations in furnace operation;    adjusting one or more parameters of a filter based on the determined excitation value; and    adjusting a deposition time according to the filter.    
   
   
       21 . The method of  claim 20 , wherein building the thermal model comprises determining adjustments in deposition rate per slot of the furnace according to temperature changes in the number of zones of the furnace.  
   
   
       22 . The method of  claim 19 , wherein the one or more target thicknesses include an isolation layer target thickness and a sidewall target thickness.  
   
   
       23 . The method of  claim 20 , further comprising building a thermal model that estimates deposition rate change according to temperature change.  
   
   
       24 . The method of  claim 20 , further comprising selecting a number production wafers located in associated slots to provide the thickness measurements.  
   
   
       25 . The method of  claim 24 , wherein the error metric is further determined according to locations of the associated slots that provide the thickness measurements.  
   
   
       26 . The method of  claim 20 , wherein a subset of the one or more parameters are updated on the excitation value being above a threshold value and remaining parameters of the one or more parameters are maintained at previous values.  
   
   
       27 . The method of  claim 20 , wherein the excitation value is determined according to changes in batch to batch thickness targets.