Finding substrate notch on substrate in a chemical mechanical polishing system

Abstract

A polishing apparatus has a polishing station, a notch finding station, and a substrate handling system to move a substrate therebetween. The substrate handling system includes a carrier to hold a substrate at the notch finding station. The notch finding station includes a housing including floor and sidewalls that form an open-topped reservoir, the sidewalls having a lower portion and an upper portion having an upper edge that is thinner than the lower portion, a passage to introduce a liquid into the open-topped reservoir to form a liquid column extending to the substrate, and an optical fiber extending through a floor of the housing and positioned to direct a light beam through the liquid column onto the substrate when held by the carrier at the notch finding station and to receive reflections of the light beam from the substrate.

What is claimed is: 
     
         1 . A polishing apparatus, comprising: 
 a polishing station;    a notch finding station; and   a substrate handling system to move a substrate between the polishing station and the notch finding station and including a carrier hold a substrate at the notch finding station;   
       wherein the notch finding station includes 
       a housing including floor and sidewalls that form an open-topped reservoir, the sidewalls having a lower portion and an upper portion having an upper edge that is thinner than the lower portion,  
       a passage to introduce a liquid into the open-topped reservoir to form a liquid column extending to the substrate, and 
       an optical fiber extending through a floor of the housing and positioned to direct a light beam through the liquid column onto the substrate when held by the carrier at the notch finding station and to receive reflections of the light beam from the substrate. 
     
     
         2 . The polishing apparatus of  claim 1 , wherein the sidewalls include an angularly tapered portion. 
     
     
         3 . The polishing apparatus of  claim 2 , wherein the sidewalls taper such that an outer surface of the sidewalls is angled. 
     
     
         4 . The polishing apparatus of  claim 3 , wherein the lower portion and the upper portion have a continuous vertical inner surface. 
     
     
         5 . The polishing apparatus of  claim 1 , wherein the upper portion has a uniform thickness along a vertical axis.  
     
     
         6 . The polishing apparatus of  claim 5 , wherein an outer surface of the upper portion is recessed relative to an outer surface of the lower portion. 
     
     
         7 . The polishing apparatus of  claim 6 , wherein the lower portion and the upper portion have a continuous vertical inner surface. 
     
     
         8 . The polishing apparatus of  claim 5 , wherein the upper portion projects 3-5 mm above the lower portion. 
     
     
         9 . The polishing apparatus of  claim 1 , wherein the floor and sidewalls form a cylindrical cup. 
     
     
         10 . The polishing apparatus of  claim 9 , wherein an inner diameter of the cylindrical cup is 10-20 mm. 
     
     
         11 . The polishing apparatus of  claim 1 , wherein the carrier is configured to hold the substrate at a height of no more than 10 mm above the upper edge of the upper portion. 
     
     
         12 . The polishing apparatus of  claim 1 , further comprising a lens positioned on an end of the optical fiber in the housing. 
     
     
         13 . The polishing apparatus of  claim 1 , further comprising a controller configured to  
       cause an actuator to position the carrier such that the substrate is positioned at the notch finding station such that sensing region of a sensor is at an edge of the substrate, 
       cause a motor to rotate the carrier such that a sensing region of the sensor scans along a circumference of the substrate, and 
       detect an angular position of a notch in an edge of the substrate based on a signal from the sensor. 
     
     
         14 . A polishing apparatus, comprising: 
 a polishing station;    a notch finding station;    a substrate handling system to move a substrate between the polishing station and the notch finding station and including a carrier hold a substrate at the notch finding station;   wherein the notch finding station includes   a housing including floor and sidewalls that form an open-topped reservoir,    a passage to introduce a liquid into the open-topped reservoir to form a liquid column extending to the substrate, and   an optical fiber extending through a floor of the housing and positioned to direct a light beam through the liquid column onto the substrate when held by the carrier at the notch finding station and to receive reflections of the light beam from the substrate;    a liquid source to supply the liquid; and   a controller configured to cause the liquid source to flow the liquid at a first flow rate when the notching finding station is operating to detect a notch and at a second reduced non-zero flow rate when the notching finding station is idling.   
     
     
         15 . The polishing apparatus of  claim 14 , wherein during a start-up the controller configured to ramp up a flow rate of the liquid from zero to the second reduced non-zero flow rate at a first ramp-up rate during a start-up operation of the notch finding station and to ramp up the flow rate of the liquid from the second reduced non-zero flow rate to the first flow rate at a second ramp-up rate during operation of the notch finding station, and wherein the second ramp-up rate is greater than the first ramp-up rate. 
     
     
         16 . The polishing apparatus of  claim 14 , wherein the first flow rate is 0.8-2 liters per minute. 
     
     
         17 . The polishing apparatus of  claim 14 , wherein the second reduced non-zero flow rate is 0.1 to 1LPM. 
     
     
         18 . The polishing apparatus of  claim 14 , wherein the liquid is water. 
     
     
         19 . The polishing apparatus of  claim 15 , wherein the carrier is configured to hold the substrate at a height of 3-6 mm above an upper edge of an upper portion.