Integrated metrology chamber for transparent substrates

Abstract

The embodiments of the invention relate to a method and apparatus for measuring the etch depth between etching for an alternate phase shift photomask in a semiconductor photomask processing system. The apparatus for measuring the etch depth of a substrate in an etch processing system comprises a measurement cell coupled to a mainframe of the etch processing system, and an etch depth measurement tool coupled to the bottom of the measurement cell, wherein an opening at the bottom of the measurement cell allows light beams to pass between the etch depth measurement tool and the substrate. The embodiments of the invention also relate to the method of preparing an alternate phase shift mask by partially etching the quartz substrate to an initial etch depth, followed by measuring the etch depth with an integrated measurement tool. The substrate is then etched and measured repeatedly until the targeted etch depth has been reached.

1 . An apparatus for measuring the etch depth of a substrate in an etch processing system, comprising: 
 a measurement cell coupled to a mainframe of the etch processing system; and    an etch depth measurement tool coupled to the bottom of the measurement cell, wherein an opening at the bottom of the measurement cell allows light beams to pass between the etch depth measurement tool and the substrate.    
   
   
       2 . The apparatus of  claim 1 , further comprising: 
 a substrate transfer robot placed in the mainframe to transfer the substrate to the measurement cell, wherein the substrate transfer robot having a robot blade to hold a substrate and the robot blade having an opening to allow light beam to be shined on the substrate backside.    
   
   
       3 . The apparatus of  claim 1 , wherein the opening at the bottom of the measurement cell is circular.  
   
   
       4 . The apparatus of  claim 2 , wherein the opening of the robot blade is a square.  
   
   
       5 . The apparatus of  claim 2 , wherein the robot blade comprises a calibration pad used to calibrate the etch depth measurement tool.  
   
   
       6 . The apparatus of  claim 2 , wherein the robot blade has roll and tilt function to position the surface of the substrate to be perpendicular to the light beam emitted from the etch depth measurement tool.  
   
   
       7 . The apparatus of  claim 1 , wherein the measurement cell can be under vacuum.  
   
   
       8 . The apparatus of  claim 2 , wherein the depth measurement tool is configured to test a substrate having an optically transparent layer.  
   
   
       9 . An apparatus for measuring the etch depth of a substrate in an etch processing system, comprising: 
 a measurement cell coupled to a mainframe of the etch processing system;    an etch depth measurement tool coupled to the bottom of the measurement cell, wherein an opening at the bottom of the measurement cell allows light beams to pass between the etch depth measurement tool and the substrate; and    a substrate transfer robot placed in the mainframe to transfer substrate to the measurement cell, wherein the substrate transfer robot having a robot blade to hold a substrate and the robot blade having an opening to allow light beam to be shined on the substrate backside.    
   
   
       10 . The apparatus of  claim 9 , wherein the opening at the bottom of the measurement cell is circular.  
   
   
       11 . The apparatus of  claim 9 , wherein the opening of the robot blade is a square.  
   
   
       12 . The apparatus of  claim 9 , wherein the robot blade comprises a calibration pad used to calibrate the etch depth measurement tool.  
   
   
       13 . The apparatus of  claim 12 , wherein the calibration pad comprises a bare silicon.  
   
   
       14 . The apparatus of  claim 9 , wherein the robot blade has roll and tilt function to position the surface of the substrate to be perpendicular to the light beam emitted from the etch depth measurement tool.  
   
   
       15 . The apparatus of  claim 9 , wherein the measurement cell can be under vacuum.  
   
   
       16 . The apparatus of  claim 9 , wherein the depth measurement tool is configured to test a substrate having an optically transparent layer.  
   
   
       17 . A method of preparing an alternate phase shift mask, comprising: 
 a) placing a substrate in an etch processing chamber, wherein the substrate is made of an optically transparent material and has a first patterned opaque layer and a second patterned photoresist layer on the optically transparent material;    b) etching the quartz to a first etch depth;    c) transferring the substrate to a measurement cell coupled to a substrate transfer chamber;    d) measuring the etch depth from the substrate backside by a etch depth measurement tool coupled to the bottom of the measurement cell to determine the etch time of next etch;    e) placing the substrate back to the etch processing chamber;    f) etching for the etch time determined by the etch depth measurement;    g) transferring the substrate to the measurement cell;    h) measuring the etch depth from the substrate backside by a etch depth measurement tool coupled to the bottom of the measurement cell to determine the etch time of next etch; and    i) repeating “e” to “h” until a targeted etch depth has been reached.    
   
   
       18 . The method of  claim 17 , wherein the etch depth measurement is performed by collecting reflected light beams from the backside of the substrate.  
   
   
       19 . An apparatus for measuring the etch depth of a substrate in an etch processing system, comprising: 
 a measurement cell coupled to a mainframe of the etch processing system;    an etch depth measurement tool coupled to the bottom of the measurement cell, wherein an opening at the bottom of the measurement cell that allows light beams to pass between the etch depth measurement tool and the substrate;    a CD measurement tool coupled to the top of the measurement cell, wherein an opening at the top of the measurement cell allows light beams to pass between the CD measurement tool and the substrate; and    a substrate transfer robot placed in the mainframe to transfer the substrate to the measurement cell, wherein the substrate transfer robot having a robot blade to hold the substrate and the robot blade having an opening to allow light beam to be shined on the substrate.