Tungsten feature fill

Abstract

Described herein are methods of filling features with tungsten and related systems and apparatus. The methods include inside-out fill techniques as well as conformal deposition in features. Inside-out fill techniques can include selective deposition on etched tungsten layers in features. Conformal and non-conformal etch techniques can be used according to various implementations. The methods described herein can be used to fill vertical features, such as in tungsten vias, and horizontal features, such as vertical NAND (VNAND) word lines. Examples of applications include logic and memory contact fill, DRAM buried word line fill, vertically integrated memory gate/word line fill, and 3-D integration with through-silicon vias (TSVs).

1 . (canceled) 
     
     
         2 . A method comprising:
 performing multiple cycles of a feature fill process to fill a feature on substrate, wherein each cycle comprises a) conformally depositing a boron layer in the feature, the boron layer having a thickness of at least 1.5 nm and b) converting the boron layer in the feature to tungsten.   
     
     
         3 . The method of  claim 1 , wherein the feature is completely filled with tungsten. 
     
     
         4 . The method of  claim 1 , wherein the boron layer in at least one cycle of the multiple cycles has a thickness of at least 3 nm. 
     
     
         5 . The method of  claim 1 , wherein the boron layer in at least one cycle of the multiple cycles has a thickness of at least 5 nm. 
     
     
         6 . The method of  claim 1 , wherein (b) comprises volumetric expansion of material in the feature. 
     
     
         7 . The method of  claim 1 , wherein the feature includes a titanium nitride layer. 
     
     
         8 . A method comprising:
 providing a substrate including a feature;   conformally depositing a reducing agent layer in the feature;   converting a portion of the boron layer in the feature to tungsten, leaving a remaining boron layer in the feature;   selectively etching the tungsten with respect to the remaining boron layer; and   converting the remaining boron layer to tungsten.   
     
     
         9 . The method of  claim 8 , wherein the reducing agent layer has a lower etch rate than the tungsten in an etch chemistry and conditions employed to selectively etch the tungsten. 
     
     
         10 . The method of  claim 8 , wherein the reducing agent layer is deposited in the feature prior to any tungsten deposition in the feature. 
     
     
         11 . The method of  claim 8 , wherein the reducing agent layer is deposited in the feature after initial tungsten deposition in the feature. 
     
     
         12 . The method of  claim 8 , wherein the reducing agent layer is a boron layer. 
     
     
         13 . The method of  claim 12 , wherein selectively etching the tungsten with respect to the remaining boron layer comprises exposing the tungsten to a fluorine-based remote plasma. 
     
     
         14 . The method of  claim 8 , wherein reducing agent layer is a silicon-containing layer, a phosphorous-containing layer, a boron-containing layer, or a germanium-containing layer. 
     
     
         15 . A method comprising:
 providing a substrate including a feature having one or more feature openings, feature sidewalls, and a feature interior,   conformally depositing a fluorine-free tungsten nitride layer in the feature, wherein the fluorine-free tungsten nitride layer is deposited using a fluorine-free tungsten precursor; and   converting the fluorine-free tungsten nitride layer to a fluorine-free tungsten layer.   
     
     
         16 . The method of  claim 15 , wherein depositing the fluorine-free tungsten nitride layer further comprises sequentially pulsing a nitrogen-containing compound and the fluorine-free tungsten precursor into a chamber containing the substrate. 
     
     
         17 . The method of  claim 15 , wherein depositing the fluorine-free tungsten nitride layer further comprises sequentially pulsing, in any order, the fluorine-free tungsten precursor, the nitrogen-containing compound, and a reducing agent into a chamber containing the substrate. 
     
     
         18 . The method of  claim 15 , wherein the fluorine-free tungsten precursor is an organo-tungsten precursor. 
     
     
         19 . The method of  claim 15 , further comprising depositing a first tungsten layer in the feature from a fluorine-containing tungsten precursor, wherein the fluorine-free tungsten nitride layer is deposited on the first tungsten layer.