Adjustment of vuv emission of a plasma via collisional resonant energy transfer to an energy absorber gas

Abstract

Disclosed are methods of adjusting the emission of vacuum ultraviolet (VUV) radiation from a plasma in a semiconductor processing chamber. The methods may include generating a plasma in the processing chamber which includes a VUV-emitter gas and a collisional energy absorber gas, and adjusting the emission of VUV radiation from the plasma by altering the concentration ratio of the VUV-emitter gas to collisional energy absorber gas in the plasma. In some embodiments, the VUV-emitter gas may be helium and the collisional energy absorber gas may be neon, and in certain such embodiments, adjusting VUV emission may include flowing helium and/or neon into the processing chamber in a proportion so as to alter the concentration ratio of helium to neon in the plasma. Also disclosed are apparatuses which implement the foregoing methods.

1 . A semiconductor processing apparatus, comprising:
 a processing chamber;   a plasma generator;   one or more gas flow inlets configured for flowing a VUV-emitter gas comprising He and a collisional energy absorber gas comprising Ne into the processing chamber; and   a controller comprising machine readable instructions for:   operating the plasma generator to generate a plasma in the processing chamber, the plasma comprising the VUV-emitter gas and the collisional energy absorber gas, the plasma emitting VUV radiation; and   operating the one or more gas flow inlets to adjust the emission of VUV radiation from the plasma by flowing the VUV-emitter gas and/or the collisional energy absorber gas into the processing chamber in a proportion so as to alter the concentration ratio of the VUV-emitter gas to collisional energy absorber gas in the plasma.   
     
     
         2 . The semiconductor processing apparatus of  claim 1 :
 wherein the apparatus further comprises an optical detector; and   wherein the machine readable instructions of the controller further comprise instructions for:   operating the optical detector to measure an emission intensity of an emission band of the plasma; and   operating the one or more gas flow inlets to set the flow rate of the VUV-emitter gas and/or the collisional energy absorber gas into the processing chamber in response to the measured emission intensity.   
     
     
         3 . The semiconductor processing apparatus of  claim 1 :
 wherein the one or more gas flow inlets are further configured for flowing an etchant gas into the processing chamber;   wherein the apparatus further comprises:   a vacuum pump;   a valve-controlled conduit to the vacuum pump; and   a metrology tool for measuring an etch profile of a feature of a semiconductor substrate; and   wherein the machine readable instructions of the controller further comprise instructions for:   operating the one or more gas flow inlets to flow etchant gas into the processing chamber;   setting conditions within the processing chamber such that the etchant adsorbs onto the surface of the semiconductor substrate forming an adsorption-limited layer of etchant;   operating the valve-controlled conduit and vacuum pump to remove unadsorbed and/or desorbed etchant from the volume surrounding the adsorbed etchant;   operating the plasma generator, after absorption of etchant and removal of unadsorbed and/or desorbed etchant, to etch a feature on the semiconductor substrate;   operating the metrology tool to measure an etch profile of the etched feature on the semiconductor substrate; and   operating the one or more gas flow inlets to set the flow rate of the VUV-emitter gas and/or the collisional energy absorber gas into the processing chamber in response to the measured etch profile.   
     
     
         4 . The semiconductor processing apparatus of  claim 1 , wherein the VUV-emitter gas is helium. 
     
     
         5 . The semiconductor processing apparatus of  claim 4 , wherein the collisional energy absorber gas is neon. 
     
     
         6 . The semiconductor processing apparatus of  claim 5 , wherein adjusting the emission of VUV radiation from the plasma comprises flowing helium and/or neon into the processing chamber in a proportion so as to alter the concentration ratio of helium to neon in the plasma. 
     
     
         7 . The semiconductor processing apparatus of  claim 5 , wherein the emission of VUV radiation from the plasma is adjusted upward by flowing helium into the processing chamber so as to increase the ratio of helium to neon in the plasma. 
     
     
         8 . The semiconductor processing apparatus of  claim 5 , wherein the emission of VUV radiation from the plasma is adjusted downward by flowing neon into the processing chamber so as to decrease the ratio of helium to neon in the plasma. 
     
     
         9 . The semiconductor processing apparatus of  claim 5 , wherein the machine readable instructions of the controller further comprise instructions for:
 measuring a property of the plasma and/or the substrate; and   setting the flow of helium and/or neon into the processing chamber in response to the measured property.   
     
     
         10 . The semiconductor processing apparatus of  claim 9 , wherein the property is the emission intensity from an emission band of an excited state species of the plasma. 
     
     
         11 . The semiconductor processing apparatus of  claim 10 , wherein the measured emission band is the emission band of neon centered at 632.8 nm. 
     
     
         12 . The semiconductor processing apparatus of  claim 9 , wherein the property is the profile of an etched feature of a semiconductor substrate measured with a metrology tool, the feature having been etched in the processing chamber. 
     
     
         13 . The semiconductor processing apparatus of  claim 12 , wherein the flow of helium is decreased and/or the flow of neon is increased in response to a measured bowing of the sidewalls of the etched feature. 
     
     
         14 . The semiconductor processing apparatus of  claim 5 , wherein the plasma is a capacitively-coupled plasma. 
     
     
         15 . The semiconductor processing apparatus of  claim 14 , wherein the semiconductor processing chamber in which the plasma is generated is part of a capacitively coupled plasma reactor, the reactor having an upper plate, the reactor configured such that the gap between the upper plate and the substrate is between about 1.5 cm and 2.5 cm. 
     
     
         16 . The semiconductor processing apparatus of  claim 5 , wherein the plasma is an inductively-coupled plasma, wherein the semiconductor processing chamber in which the plasma is generated is part of an inductively coupled plasma reactor having a gap region within which the plasma is generated, and wherein the reactor comprises one or more components located within the gap region which provide a structure against which neon atoms may collide and be collisionally de-excited. 
     
     
         17 . The semiconductor processing apparatus of  claim 16 , wherein the one or more components which provide said structure for the de-excitation of neon comprise a set of concentric cylinders oriented with their central axes perpendicular to the plane of the substrate. 
     
     
         18 . A semiconductor processing apparatus, comprising:
 a processing chamber;   a plasma generator;   one or more gas flow inlets configured for flowing gases into the processing chamber; and   a controller comprising machine readable instructions for etching a feature on a surface of a semiconductor substrate in the processing chamber, comprising:   (a) adsorbing an etchant onto the surface of a semiconductor substrate such that the etchant forms an adsorption-limited layer on the surface;   (b) after (a), removing unadsorbed and/or desorbed etchant from the volume surrounding the adsorbed etchant;   (c) after (b), generating a plasma in the processing chamber, the plasma comprising helium and neon, the plasma emitting VUV radiation;   (d) contacting the adsorbed etchant with the plasma to etch the surface of the substrate; and   (e) repeating (a)-(d) multiple times and adjusting the emission of VUV radiation from the plasma in (d) by altering the concentration ratio of helium to neon in the plasma, thereby altering the anisotropy of the etching of the surface of the substrate.   
     
     
         19 . The semiconductor processing apparatus of  claim 18 , wherein the etchant comprises chlorine. 
     
     
         20 . The semiconductor processing apparatus of  claim 18 , wherein adjusting the emission of VUV radiation from the plasma comprises flowing helium and/or neon into the processing chamber in a proportion so as to alter the concentration ratio of helium to neon in the plasma. 
     
     
         21 . The method of  claim 20 , further comprising:
 measuring the profile of the etched feature of the semiconductor substrate with a metrology tool; and   setting the flow of helium and/or neon into the processing chamber in response to the measured profile.