Thermal atomic layer etch with rapid temperature cycling

Abstract

Disclosed are apparatuses and methods for performing atomic layer etching. A method may include supporting and thermally floating a substrate in a processing chamber, modifying one or more surface layers of material on the substrate by chemical adsorption, without using a plasma, while the substrate is maintained at a first temperature, and removing the one or more modified surface layers by desorption, without using a plasma, while the substrate is maintained at a second temperature, the first temperature being different than the second temperature. An apparatus may include a processing chamber and support features configured to support and thermally float a substrate in the chamber, a process gas unit configured to flow a first process gas onto the substrate, a substrate heating unit configured to heat the substrate, and a substrate cooling unit configured to actively cool the substrate.

What is claimed is: 
     
         1 . An apparatus for semiconductor processing, the apparatus comprising:
 a processing chamber that includes chamber walls that at least partially bound a chamber interior, and substrate positioning features configured to support and thermally float a substrate in the chamber interior;   a process gas unit configured to flow a first process gas into the chamber interior and onto the substrate in the chamber interior;   a substrate heating unit configured to heat the substrate in the chamber interior;   a substrate cooling unit configured to actively cool the substrate in the chamber interior; and   a controller with instructions that are configured to:   (a) cause the substrate heating unit to heat a substrate positioned on the substrate positioning features to a first temperature,   (b) cause the process gas unit to flow the first process gas to the substrate in the chamber interior, wherein the first process gas is configured to modify one or more surface layers of material on the substrate by chemical adsorption without using a plasma while the substrate is maintained at the first temperature, and   (c) cause the substrate heating unit to maintain the substrate at a second temperature, wherein the one or more modified surface layers on the substrate are removed by desorption without using a plasma while the substrate is maintained at the second temperature.   
     
     
         2 . The apparatus of  claim 1 , wherein:
 the second temperature is higher than the first temperature, and   the controller further includes instructions that are configured to:   (d) cause, after (b), the substrate heating unit to heat the substrate to the second temperature.   
     
     
         3 . The apparatus of  claim 2 , wherein the controller further includes instructions that are configured to:
 (e) cause, after (d), the substrate cooling unit to actively cool the substrate to the first temperature, and   (f) repeat, after (e), (a) through (e).   
     
     
         4 . The apparatus of  claim 1 , wherein:
 the second temperature is lower than the first temperature, and   the controller further includes instructions that are configured to:   (g) cause, after (b), the substrate cooling unit to actively cool the substrate to the second temperature.   
     
     
         5 . The apparatus of  claim 4 , wherein the controller further includes instructions that are configured to:
 (h) repeat, after (g), (a) through (g).   
     
     
         6 . The apparatus of  claim 1 , wherein the first process gas comprises an oxidizing gas or a halogenating gas. 
     
     
         7 . The apparatus of  claim 1 , wherein:
 the substrate heating unit is configured to: heat the substrate from a bottom direction, heat the substrate from a top direction, and heat the substrate from both the top and the bottom directions, and   the substrate cooling unit is configured to: cool the substrate from a bottom direction, cool the substrate from a top direction, and cool the substrate from both the top and the bottom directions.   
     
     
         8 . The apparatus of  claim 1 , wherein the substrate heating unit includes at least one of: one or more lamps, one or more gradient-index (“GRIN”) lenses connected to a light source, a laser, a convective heating unit, and a plasma heating unit. 
     
     
         9 . The apparatus of  claim 8 , wherein:
 the processing chamber further comprises a window that partially bounds the chamber interior and is configured to allow radiation to be transmitted into the chamber interior,   the substrate heating unit is positioned outside the chamber interior such that at least a portion of the window is interposed between the chamber interior and the substrate heating unit,   the substrate heating unit includes at least one of: one or more lamps, one or more GRIN lenses connected to a light source, and a laser, and   the substrate heating unit is configured to emit radiation through the window and into the chamber interior to heat a substrate in the chamber interior.   
     
     
         10 . The apparatus of  claim 9 , further comprising a plasma generator configured to generate a plasma in the chamber interior, wherein the plasma generator is one of: a capacitively coupled plasma, an inductively coupled plasma, an upper remote plasma, and a lower remote plasma. 
     
     
         11 . The apparatus of  claim 10 , wherein:
 the plasma generator is a capacitively coupled plasma,   an RF electrode of the plasma generator is comprised of a metal or a doped silicon, and   the substrate heating unit includes a plurality of GRIN lenses that are positioned within the RF electrode or the ground plate.   
     
     
         12 . The apparatus of  claim 10 , wherein:
 the plasma generator is a capacitively coupled plasma,   an RF electrode of the plasma generator comprises the window, and   the substrate heating unit includes at least one of: one or more lamps, one or more GRIN lenses connected to a light source, and a laser.   
     
     
         13 . The apparatus of  claim 12 , wherein the window is a transparent indium tin oxide (“ITO”) window that is grounded or powered. 
     
     
         14 . The apparatus of  claim 10 , wherein:
 the plasma generator is an inductively coupled plasma,   an antenna of the plasma generator is positioned outside the chamber interior,   the substrate heating unit includes a plurality of GRIN lenses that are positioned within the window, and   the window is interposed between the antenna and the chamber interior.   
     
     
         15 . The apparatus of  claim 10 , wherein:
 the plasma generator is an upper remote plasma configured to flow a plasma into the chamber interior, and   the substrate heating unit includes a plurality of GRIN lenses connected to a light source that are positioned within the window.   
     
     
         16 . The apparatus of  claim 10 , wherein:
 the plasma generator is a lower remote plasma that includes an antenna vertically interposed between the substrate positioning features and a bottom of the chamber interior, and   the substrate heating unit includes one of: one or more lamps, one or more GRIN lenses, and a laser.   
     
     
         17 . The apparatus of  claim 8 , wherein the substrate heating unit includes a plurality of lamps that are positioned inside the chamber interior. 
     
     
         18 . The apparatus of  claim 1 , wherein the substrate cooling unit includes at least one of:
 a cooling fluid supply configured to cool a cooling fluid to 0° C. or less and flow the cooling fluid into the chamber interior and onto the substrate, and   a laser.   
     
     
         19 . The apparatus of  claim 18 , further comprising one or more nozzles fluidically connected to the cooling fluid supply, wherein the one or more nozzles are configured to flow the cooling fluid into the chamber interior. 
     
     
         20 . The apparatus of  claim 1 , wherein the processing chamber does not include a pedestal.