Controlling Radical Lifetimes in a Remote Plasma Chamber

Abstract

Remote-plasma treatments of surfaces, for example in semiconductor manufacture, can be improved by preferentially exposing the surface to only a selected subset of the plasma species generated by the plasma source. The probability that a selected species reaches the surface, or that an unselected species is quenched or otherwise converted or diverted before reaching the surface, can be manipulated by introducing additional gases with selected properties either at the plasma source or in the process chamber, varying chamber pressure or flow rate to increase or decrease collisions, or changing the dimensions or geometry of the injection ports, conduits and other passages traversed by the species. Some example processes treat surfaces preferentially with relatively low-energy radicals, vary the concentration of radicals at the surface in real time, or clean and passivate in the same unit process.

What is claimed is: 
     
         1 . A method of plasma-treating a surface of a substrate, the method comprising:
 positioning the substrate in a process chamber;   creating a plurality of plasma activated species;   selecting a species from the plurality of the plasma activated species while leaving another species unselected; and   preferentially exposing the surface to the selected species by modifying at least one of a relative concentration of the selected species and the unselected species, an expected lifetime of the unselected species, or an expected travel time from a plasma generating source to the surface.   
     
     
         2 . The method of  claim 1 , wherein the selected species comprises a radical. 
     
     
         3 . The method of  claim 3 , wherein the selected species comprises a nitrogen radical. 
     
     
         4 . The method of  claim 3 , wherein the selected species comprises an oxygen radical or a hydrogen radical. 
     
     
         5 . The method of  claim 1 , wherein the selected species is selected for low energy dissipation. 
     
     
         6 . The method of  claim 5 , wherein the surface comprises a layer formed by atomic layer deposition. 
     
     
         7 . The method of  claim 6 , wherein the layer is less than about 10 nm thick. 
     
     
         8 . The method of  claim 5 , wherein the surface comprises germanium, germanium oxide, a III-V material, or a III-V material oxide. 
     
     
         9 . The method of  claim 1 , wherein the relative concentration of the selected species and the unselected species is modified at the plasma generating source. 
     
     
         10 . The method of  claim 9 , wherein modifying the relative concentration comprises introducing an inert gas. 
     
     
         11 . The method of  claim 10 , wherein the inert gas comprises argon or helium. 
     
     
         12 . The method of  claim 9 , wherein modifying the relative concentration comprises introducing a reactive gas. 
     
     
         13 . The method of  claim 12 , wherein the reactive gas comprises oxygen or hydrogen. 
     
     
         14 . The method of  claim 12 , wherein the reactive gas preferentially quenches the unselected species compared to the selected species. 
     
     
         15 . The method of  claim 1 , wherein modifying the expected lifetime or the expected travel time comprises adjusting a composition, flow rate, pressure, or temperature of a buffer gas. 
     
     
         16 . The method of  claim 1 , wherein modifying the expected lifetime or the expected travel time comprises adjusting a composition, flow rate, pressure, or temperature of a plasma at the plasma generating source. 
     
     
         17 . The method of  claim 1 , wherein modifying the expected lifetime or the expected travel time comprises changing a gas conductance of the plasma generation source, a showerhead body, a showerhead, or a chamber interior. 
     
     
         18 . The method of  claim 1 , wherein modifying the expected lifetime or the expected travel time comprises changing a gas conductance of a showerhead by changing the size, position, or geometry of an injection port in the showerhead. 
     
     
         19 . The method of  claim 1 , further comprising measuring an effect of the plasma activated species on the surface by a method comprising one of:
 a sheet resistance of a film over or under the surface;   a line resistance of a feature on the surface;   an I-V curve of a diode created by depositing a conductive film on the surface;   a C-V curve of a capacitor structure created on the surface;   a characteristic of an atomic-layer-deposition film on the surface   a Fourier transform infrared spectrum taken near the surface; or   an optical emission spectrum of the plasma generating source.   
     
     
         20 . A method of cleaning a surface of a substrate, comprising:
 positioning the substrate in a process chamber;   pre-conditioning by removing trapped water from the substrate and from the process chamber; and   exposing the surface to an alternating sequence of O* and H* radicals from a plasma generating source until the surface is clean;   wherein higher-energy species than the O* and H* radicals are generated by the plasma generating source but are prevented from reaching the surface.