Atomic layer removal process with higher etch amount

Abstract

Higher overall etch rate and throughput for atomic layer removal (ALR) is achieved. The reaction is a self-limiting process, thus limiting the total amount of material that may be etched per cycle. By pumping down the process station between reacting operations, the reaction is partially “reset.” A higher overall etch rate is achieved by a multiple exposure with pump down ALR process.

1 - 20 . (canceled) 
     
     
         21 . A method comprising:
 (a) reacting a film on a substrate with one or more reactants to form a solid reaction product, the solid reaction product having a greater specific volume than the film consumed to form the solid reaction product, the substrate being in a processing station;   (b) reducing a pressure in the processing station;   (c) reacting the film with the one or more reactants to form additional solid reaction product while substantially all the solid reaction product of operation (a) remains on the substrate; and   (d) removing the solid reaction product, wherein a reduced pressure in operation (b) is maintained for a period less than or equal to a duration of operation (d).   
     
     
         22 . The method of  claim 21 , further comprising transferring the substrate to a second processing station after operation (c). 
     
     
         23 . The method of  claim 21 , further comprising repeating operations (b) and (c). 
     
     
         24 . The method of  claim 21 , further comprising repeating operations (a) though (d). 
     
     
         25 . The method of  claim 21 , wherein operation (a) comprises exposing the substrate to at least two reactants concurrently, and wherein operation (c) comprises exposing the substrate to at least two reactants concurrently. 
     
     
         26 . The method of  claim 21 , wherein the one or more reactants comprise a fluorine source and a nitrogen source. 
     
     
         27 . The method of  claim 26 , wherein the nitrogen source comprises one or more of ammonia (NH 3 ) and atomic nitrogen (N*). 
     
     
         28 . The method of  claim 26 , wherein the fluorine source comprises at least one of hydrogen fluoride (HF), fluorine (F 2 ), nitrogen trifluoride (NF 3 ), atomic fluorine (F*), ammonium fluoride (NH 4 F), and ammonium bifluoride (NH 4 F:HF). 
     
     
         29 . The method of  claim 26 , wherein the fluorine source is hydrogen fluoride and the nitrogen source is ammonia, and wherein a flow rate ratio of hydrogen fluoride to ammonia is about 1 to 1 to about 3 to 1. 
     
     
         30 . The method of  claim 21 , wherein during operation (a), a reactant partial pressure is about 1 mTorr to about 100 mTorr. 
     
     
         31 . The method of  claim 21 , wherein operation (a) is performed at a first processing station pressure and operation (c) is performed at a second processing station pressure. 
     
     
         32 . The method of  claim 21 , wherein operation (a) is performed at a first processing station pressure and operation (c) is performed at the first processing station pressure. 
     
     
         33 . The method of  claim 21 , wherein removing the solid reaction product comprises sublimating the solid reaction product at an elevated substrate temperature. 
     
     
         34 . The method of  claim 33 , wherein the inert gas is heated to a temperature above 25° C. 
     
     
         35 . The method of  claim 21 , wherein the pressure in operation (b) is reduced to between about 0.01 mTorr and about 50 mTorr. 
     
     
         36 . The method of  claim 21 , wherein the pressure in operation (b) is reduced to less than about 10 mTorr. 
     
     
         37 . The method of  claim 21 , wherein a reduced pressure in operation (b) is maintained for a period of between about 1 second and 60 seconds. 
     
     
         38 . The method of  claim 21 , further comprising:
 depositing a fill material in a recessed feature on a surface of a substrate and on the surface of the substrate, the feature having a bottom and sidewalls, wherein the depositing forms a cusp structure on the sidewalls of the feature near the surface of the substrate;   wherein the film in operations (a) and (c) comprises the fill material;   wherein during operations (a) and (c) the fill material at the bottom of the feature is substantially protected from the one or more reactants; and   wherein operation (d) results in exposure of unreacted fill material toward the bottom of the feature.   
     
     
         39 . The method of  claim 38 , wherein the fill material comprises silicon oxide, and wherein the one or more reactants in each of operations (a) and (c) comprise a fluorine source and a nitrogen source. 
     
     
         40 . A method comprising:
 (a) reacting a film on a substrate with one or more reactants to form a solid reaction product, the solid reaction product having a greater specific volume than the film consumed to form the solid reaction product, the substrate being in a processing station;   (b) reducing a pressure in the processing station;   (c) reacting the film with the one or more reactants to form additional solid reaction product while substantially all the solid reaction product of operation (a) remains on the substrate, wherein a reaction rate at the beginning of operation (c) is higher than a reaction rate at the end of operation (a); and   (d) removing the solid reaction product, wherein a reduced pressure in operation (b) is maintained for a period less than or equal to a duration of operation (d).