High step coverage tungsten deposition

A method comprising:

• providing a substrate including a feature having an opening in a top surface, a sidewall and a bottom in a chamber;
• and
• depositing a tungsten nucleation layer in the feature by performing multiple cycles of:
• flowing a boron-containing reducing agent pulse in the chamber, wherein the boron-containing reducing agent is adsorbed to the feature sidewall and feature bottom,
• purging the chamber,
• flowing a tungsten-containing precursor pulse in the chamber to react with the adsorbed boron-containing reducing agent, and
• purging the chamber;
• and wherein depositing the nucleation layer further comprises at least one cycle of:
• flowing a silane pulse in the chamber;
• purging the chamber;
• flowing a tungsten-containing precursor pulse in the chamber wherein no hydrogen is flowed during the tungsten-containing precursor pulse;
• and purging the chamber.

A method comprising:

• providing a substrate including a feature having an opening in a top surface, a sidewall and a bottom in a chamber;
• and
• depositing a tungsten nucleation layer in the feature by performing multiple cycles of:
• flowing a boron-containing reducing agent pulse in the chamber, wherein the boron-containing reducing agent pulse in the chamber is flowed into the chamber with an inert gas and the boron-containing reducing agent is adsorbed to the feature sidewall and feature bottom,
• purging the chamber,
• flowing a tungsten-containing precursor pulse in the chamber to react with the adsorbed boron-containing reducing agent, and
• purging the chamber,
• wherein hydrogen (H2) is flowed during the boron-containing reducing agent pulse and no H2 is flowed during the tungsten-containing precursor pulse.