Optical emission spectroscopy (oes) for remote plasma monitoring

Abstract

Methods and systems for etching substrates using a remote plasma are described. Remotely excited etchants are formed in a remote plasma and flowed through a showerhead into a substrate processing region to etch the substrate. Optical emission spectra are acquired from the substrate processing region just above the substrate. The optical emission spectra may be used to determine an endpoint of the etch, determine the etch rate or otherwise characterize the etch process. A weak plasma may be present in the substrate processing region. The weak plasma may have much lower intensity than the remote plasma. In cases where no bias plasma is used above the substrate in an etch process, a weak plasma may be ignited near a viewport disposed near the side of the substrate processing region to characterize the etchants.

1 . A substrate processing chamber, the substrate processing chamber comprising:
 a remote plasma region, wherein the remote plasma region is configured to receive a fluorine-containing precursor and form a remote plasma from the fluorine-containing precursor;   a remote plasma power supply configured to apply a remote plasma power to the remote plasma region and configured to form the remote plasma;   a substrate processing region;   a showerhead disposed between the remote plasma region and the substrate processing region, wherein the substrate processing region is fluidly coupled to the remote plasma region by through-holes in the showerhead;   a pedestal configured to support a substrate;   a flange attached to the substrate processing chamber, wherein the flange forms a vacuum seal with the substrate processing chamber;   a viewport attached to the flange forming a vacuum seal with the flange, wherein the viewport is optically transmissive in a near infrared spectrum; and   an optical emission spectrometer configured to receive optical radiation after the optical radiation passes through the viewport, wherein the optical emission spectrometer is disposed on an exterior of the viewport and the optical radiation originates from above the substrate.   
     
     
         2 . The substrate processing chamber of  claim 1  further comprising a local plasma power supply configured to form a local plasma in the substrate processing region, wherein the local plasma has a local plasma power less than 10% of the remote plasma power. 
     
     
         3 . The substrate processing chamber of  claim 1  further comprising a fiber optic cable configured to guide the optical radiation from the viewport to the optical emission spectrometer. 
     
     
         4 . The substrate processing chamber of  claim 1  further comprising an electrode proximal to the viewport, wherein the electrode is disposed on the exterior of the viewport. 
     
     
         5 . The substrate processing chamber of  claim 4  further comprising a plasma power supply configured to apply a plasma power to the electrode. 
     
     
         6 . The substrate processing chamber of  claim 4  further comprising a second electrode configured to apply a plasma power to the electrode, wherein the electrode is electrically insulated from the second electrode. 
     
     
         7 . An optical emission spectrometer assembly, the optical emission spectrometer assembly comprising:
 a flange configured to attach to a substrate processing chamber, wherein the flange is configured to form a vacuum seal with the substrate processing chamber;   a planar viewport attached to the flange forming a vacuum seal with the flange, wherein the planar viewport is optically transmissive in a near infrared spectrum;   an electrode proximal to the planar viewport, wherein the electrode is disposed on an external side of the planar viewport;   an optical emission spectrometer configured to receive optical radiation after the optical radiation passes through the planar viewport, wherein the optical emission spectrometer is disposed on the external side of the planar viewport; and   a plasma power supply configured to apply a plasma power to the electrode.   
     
     
         8 . The optical emission spectrometer assembly of  claim 7  further comprising a fiber optic cable configured to guide infrared light from the planar viewport to the optical emission spectrometer. 
     
     
         9 . The optical emission spectrometer assembly of  claim 7  wherein the plasma power supply is configured to apply the plasma power between the electrode and the substrate processing chamber. 
     
     
         10 . The optical emission spectrometer assembly of  claim 7  further comprising a second electrode proximal to the planar viewport, wherein the electrode is electrically insulated from the second electrode. 
     
     
         11 . The optical emission spectrometer assembly of  claim 10  wherein the plasma power supply is configured to apply the plasma power between the electrode and the second electrode.