Multiple deposition for integration of spacers in pitch multiplication process

Abstract

Pitch multiplication is performed using a two step process to deposit spacer material on mandrels. The precursors of the first step react minimally with the mandrels, forming a barrier layer against chemical reactions for the deposition process of the second step, which uses precursors more reactive with the mandrels. Where the mandrels are formed of amorphous carbon and the spacer material is silicon oxide, the silicon oxide is first deposited by a plasma enhanced deposition process and then by a thermal chemical vapor deposition process. Oxygen gas and plasma-enhanced tetraethylorthosilicate (TEOS) are used as reactants in the plasma enhanced process, while ozone and TEOS are used as reactants in the thermal chemical vapor deposition process. The oxygen gas is less reactive with the amorphous carbon than ozone, thereby minimizing deformation of the mandrels caused by oxidation of the amorphous carbon.

1 . A process for forming an integrated circuit, comprising:
 depositing a first layer of spacer material over a plurality of vertically-extending and spaced-apart mandrels;   subsequently depositing a second layer of spacer material over the mandrels, wherein the first layer reduces deformation of the mandrels relative to depositing the second spacer layer directly on the mandrels; and   selectively removing the mandrels relative to the spacer material of the first and second layers;   wherein the first layer is denser than the second layer.   
     
     
         2 . The process of  claim 1 , wherein the first and second layers comprise the same material. 
     
     
         3 . The process of  claim 1 , wherein depositing the first layer comprises performing a different deposition process than subsequently depositing the second layer. 
     
     
         4 . The process of  claim 3 , wherein depositing the first layer comprises exposing the mandrel to excited reactive species. 
     
     
         5 . The process of  claim 4 , wherein depositing the second layer comprises exposing the first layer to non-radical species. 
     
     
         6 . The process of  claim 1 , wherein the mandrel is formed of amorphous carbon and wherein depositing the first layer and subsequently depositing the second layer of spacer material comprise silicon oxide. 
     
     
         7 . The process of  claim 1 , further comprising subjecting the first and the second layers to an anisotropic etch to form spacers on sidewalls of the mandrels after subsequently depositing the second layer and before selectively removing the mandrels. 
     
     
         8 . The process of  claim 7 , wherein removing the mandrels forms a pattern of standalone spacers, further comprising successively transferring the pattern to a plurality of hard mask layers before transferring the pattern to an underlying substrate. 
     
     
         9 . The process of  claim 8 , wherein successively transferring the pattern to a plurality of hard mask layers comprises transferring the pattern to an amorphous carbon hard mask layer. 
     
     
         10 . A method for defining patterns in a material, comprising:
 providing a plurality of laterally separated sacrificial features over a substrate;   blanket depositing a spacer material on the sacrificial features, the spacer material deposited by performing a plurality of deposition processes, wherein later deposition processes have a higher propensity to deform the sacrificial features than earlier deposition processes;   preferentially etching the spacer material to expose a copy of the sacrificial features.   
     
     
         11 . The method of  claim 10 , wherein blanket depositing comprises performing a chemical vapor depositing process. 
     
     
         12 . The method of  claim 11 , wherein the chemical vapor deposition process is a plasma enhanced chemical vapor deposition or a thermal chemical vapor deposition. 
     
     
         13 . The method of  claim 10 , further comprising etching the substrate through a mask comprising the spacers. 
     
     
         14 . The method of  claim 10 , further comprising:
 transferring a pattern defined by the spacers to an underlying hard mask layer; and   removing the spacers before etching the substrate through the hard mask layer.   
     
     
         15 . The method of  claim 10 , wherein the spacer material is silicon oxide. 
     
     
         16 . The method of  claim 10 , wherein the sacrificial features are formed of amorphous carbon. 
     
     
         17 . A method for forming masks, comprising:
 providing a plurality of mandrels, each mandrel having sidewalls;   blanket depositing a first layer of masking material on the sidewalls, the first layer extending continuously between neighboring mandrels;   blanket depositing a second layer of masking material on the first layer; and   using a single first etch chemistry to selectively remove a portion of the first and second layers relative to the mandrels, thereby exposing the mandrels.   
     
     
         18 . The method of  claim 17 , further comprising removing the mandrel to form a pattern defined by vertically-extending remnants of the first and second layers. 
     
     
         19 . The method of  claim 18 , wherein removing the mandrel comprises using a single second etch chemistry to selectively etch the mandrels relative to the first and second layers. 
     
     
         20 . The method of  claim 19 , further comprising using a single third etch chemistry to selectively etch an underlying layer of hard mask material relative to the first and second layers. 
     
     
         21 . The method of  claim 19 , wherein the first etch chemistry is an anisotropic etch chemistry. 
     
     
         22 . The method of  claim 21 , wherein the first etch chemistry comprises a fluorocarbon etch. 
     
     
         23 . The method of  claim 17 , wherein the mandrel is disposed over a semiconductor substrate. 
     
     
         24 . The method of  claim 17 , wherein the first and the second layers are formed of a same material. 
     
     
         25 . The method of  claim 24 , wherein the first and the second layers are formed of silicon oxide.