Wafer profiling for etching system

Abstract

A substrate etching system includes a support to hold a wafer in a face-up orientation, a dispenser arm movable laterally across the wafer on the support, the dispenser arm supporting a delivery port to selectively dispense a liquid etchant onto a portion of a top face of the wafer, and a monitoring system comprising a probe movable laterally across the wafer on the support.

What is claimed is: 
     
         1 . A substrate etching system, comprising:
 a rotatable spindle;   a support on the rotatable spindle to hold a wafer in a face-up orientation;   a dispenser arm movable laterally across the wafer on the support, the dispenser arm supporting a delivery port to selectively dispense a liquid etchant onto a portion of a top face of the wafer; and   an optical monitoring system comprising a light source, a detector, and an optical fiber to carry light from the light source to the wafer and carry reflected light from the wafer to the detector, wherein an end of the optical fiber is secured to the dispenser arm such that the end of the optical fiber is movable laterally across the wafer on the support with the dispenser arm; and   a controller configured to cause the dispenser arm to move laterally across the wafer such that the optical monitoring system generates measurements at a plurality of different radial positions on the wafer, and to determine, before starting dispensing of liquid etchant, whether the wafer placed on the support is misaligned or whether there is a tilt of the wafer using a magnitude of the reflected light.   
     
     
         2 . The system of  claim 1 , wherein the controller is configured to determine whether the wafer has a tilt. 
     
     
         3 . The system of  claim 2 , wherein the controller is configured to compare a magnitude of the reflected light to an expected magnitude. 
     
     
         4 . The system of  claim 3 , wherein the controller is configured to indicate that the wafer is titled if the magnitude of the reflected light is less than the expected magnitude by a prescribed threshold. 
     
     
         5 . The system of  claim 1 , wherein the controller is configured to determine whether the wafer is misaligned. 
     
     
         6 . The system of  claim 5 , wherein the controller is configured to compare two reflectance measurements from two opposing edges of the wafer. 
     
     
         7 . The system of  claim 6 , wherein the controller is configured to indicate that the wafer is misaligned if a difference between the two reflectance measurements is larger than a prescribed threshold. 
     
     
         8 . The system of  claim 1 , wherein the controller is configured to determine if an improper wafer type is placed on the support. 
     
     
         9 . The system of  claim 8 , wherein the controller is configured to indicate the improper wafer type if a reflectance measurement is outside of an expected range of reflectance. 
     
     
         10 . The system of  claim 1 , wherein the detector comprises a spectrometer. 
     
     
         11 . The system of  claim 10 , wherein the controller is configured determine an etching rate from a plurality of spectral measurement, and to detect a variation in the etching rate from a target etch rate. 
     
     
         12 . The system of  claim 11 , wherein the controller is configured to at least one of indicate an alert to change an etchant bath or adjust a processing parameter of the etchant bath in a reservoir to reduce a variation of etching rate from the target rate. 
     
     
         13 . The system of  claim 12 , wherein the processing parameter comprises a concentration of etchant. 
     
     
         14 . The system of  claim 11 , wherein the controller is configured determine an etching rate profile from a plurality of spectral measurements at a plurality of different positions across the substrate, to detect variations in the etching rate profile from a target etch rate profile, and adjust a dwell time of the port or a flow rate of the etchant to reduce variations in the etching rate from the target etch rate profile. 
     
     
         15 . A substrate etching system, comprising:
 a rotatable spindle;   a support on the rotatable spindle to hold a wafer in a face-up orientation;   a dispenser arm movable laterally across the wafer on the support, the dispenser arm supporting a delivery port extending downwardly below the top edge of the sidewall to selectively dispense a liquid etchant onto a portion of a top face of the wafer;   an optical monitoring system comprising a light source, a spectrometer, and an optical fiber to carry light from the light source to the wafer and carry reflected light from the wafer to the spectrometer, wherein an end of the optical fiber is secured to the dispenser arm adjacent the delivery port such that the end of the optical fiber is movable laterally across the wafer on the support with the dispenser arm, and wherein the end of the optical fiber is arranged adjacent the delivery port and oriented to direct light onto the wafer substantially normal to the surface of the wafer; and   a controller configured to:
 cause the probe to move laterally across the wafer such that the optical monitoring system generates measurements at a plurality of different radial positions on the wafer, receive a measurement of a spectrum reflected from the wafer, 
 select annular zones for the measurements based on positions of the arm at times of the measurements, 
 determine an etching rate from the measurements; 
 detect variations in the etching rate from a target etch rate profile, and to adjust a dwell time of the port or a flow rate of the etchant to reduce variations in the etching rate from the target etch rate profile. 
   
     
     
         16 . The system of  claim 15 , comprising a housing including a floor and a sidewall extending upwardly from the floor, wherein the rotatable spindle extends through the floor, wherein the support is positioned above the floor of the housing to hold the wafer in a volume enclosed by the housing and below a top edge of the sidewall, wherein the delivery port and the end of the optical fiber extend downwardly below the top edge of the sidewall. 
     
     
         17 . The system of  claim 15 , wherein the controller is configured to determine whether a processing endpoint has been reached for each zone of the annular zones based on measurements from radial positions within the zone, and to cause the dispenser to stop dispensing of the liquid etchant from the delivery port upon determining that endpoint has been reached for all of the zones.