Method and apparatus for nitride spacer etch process implementing in situ interferometry endpoint detection and non-interferometry endpoint monitoring

Abstract

An in situ dual-stage etch endpoint detection system is disclosed. The system includes an etch chamber, an interferometry endpoint monitoring system, and a non-IEP endpoint monitoring system. The etch chamber includes an electrostatic chuck (ESC), a top electrode, and a bottom electrode. The ESC is designed to support a wafer having a spacer layer formed over a gate structure. The interferometry endpoint (IEP) monitoring system is designed to monitor an interference photon beam reflected by the top of spacer layer and the reflection beam on interface of bottom of spacer during a first etch operation. The non-IEP endpoint monitoring system monitors a second etch operation by monitoring an etch time. A first etch operation implementing the IEP monitoring system is discontinued, leaving a thin spacer layer to be etched during the second etch operation.

1 . An in situ dual-stage etch endpoint detection system, the system comprising: 
 an etch chamber configured to include an electrostatic chuck (ESC), a top electrode, and a bottom electrode, the ESC being configured to support a wafer having a spacer layer formed over a gate structure;    an interferometry endpoint (IEP) monitoring system configured to monitor a photon beam reflected by the spacer layer during a first etch operation; and    a non-IEP endpoint monitoring system configured to monitor a second etch operation by monitoring an etch time;    wherein a first etch operation implementing the IEP monitoring system is configured to be discontinued so as to leave a thin spacer layer to be etched during the second etch operation.    
   
   
       2 . The system of  claim 1 , wherein the non-IEP etch endpoint monitoring system is configured to implement optical emission spectroscopy (OES) to monitor the second etch operation.  
   
   
       3 . The system of  claim 1 , wherein the IEP monitoring system is configured to monitor a photon beam reflected by the spacer layer so as to determine the thickness of an etch depth during the first etch operation implementing the distance between consecutive maximum intensities.  
   
   
       4 . The method of  claim 1 , wherein the first etch operation implements a etchant gas configured to be one of a combination of C 2 F 6 , CH 2 F 2 , and O 2 , a combination of CF 4 , CH 2 F 2 , and O 2 , and a combination of CF 4 , HBr, and O 2  and the second etch operation implements a second etchant gas configured to be one of a combination of C 2 F 6 , CH 2 F 2 , and O 2  and a combination of O 2 , HBr, and SF 6 .